Updated on 2024/02/03

写真a

 
KITTAKA Shunichiro
 
Organization
Faculty of Science and Engineering Associate Professor
Other responsible organization
Physics Course of Graduate School of Science and Engineering, Master's Program
Physics Course of Graduate School of Science and Engineering, Doctoral Program
Contact information
The inquiry by e-mail is 《here
External link

Degree

  • 博士(理学) ( 京都大学 )

  • 修士(理学) ( 京都大学 )

Education

  • 2010.3
     

    Kyoto University   doctor course   completed

  • 2007.3
     

    Kyoto University   master course   completed

  • 2005.3
     

    Kyoto University   Faculty of Science   graduated

Research History

  • 2020.4 - Now

    Chuo University   Faculty of Science and Engineering   Associate Professor

  • 2010.4 - 2020.3

    The University of Tokyo   The Institute for Solid State Physics   Assistant Professor

Professional Memberships

  • THE PHYSICAL SOCIETY OF JAPAN

Research Interests

  • 磁性

  • 超伝導

Research Areas

  • Natural Science / Magnetism, superconductivity and strongly correlated systems

Papers

  • Random singlets in the s=5/2 coupled frustrated cubic lattice Lu3Sb3Mn2O14

    Chanhyeon Lee, Suheon Lee, Heung-Sik Kim, Shunichiro Kittaka, Yoshimitsu Kohama, Toshiro Sakakibara, Ki Hoon Lee, J. van Tol, Denis I. Gorbunov, Seung-Hwan Do, Sungwon Yoon, Adam Berlie, Kwang-Yong Choi

    Physical Review B   2023.6

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    DOI: 10.1103/PhysRevB.107.214404

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  • Modulation vector of the Fulde-Ferrell-Larkin-Ovchinnikov state in CeCoIn5 revealed by high-resolution magnetostriction measurements Reviewed

    Shunichiro Kittaka, Yohei Kono, Kaito Tsunashima, Daisuke Kimoto, Makoto Yokoyama, Yusei Shimizu, Toshiro Sakakibara, Minoru Yamashita, Kazushige Machida

    Phys. Rev. B   107   L220505   2023.6

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    DOI: 10.1103/PhysRevB.107.L220505

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  • Anomalous electromagnetic response in the spin-triplet superconductor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>UTe</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:math>

    Yusei Shimizu, Shunichiro Kittaka, Yohei Kono, Toshiro Sakakibara, Kazushige Machida, Ai Nakamura, Dexin Li, Yoshiya Homma, Yoshiki J. Sato, Atsushi Miyake, Minoru Yamashita, Dai Aoki

    Physical Review B   106 ( 21 )   2022.12

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevb.106.214525

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.106.214525/fulltext

  • Piezomagnetic switching of anomalous Hall effect in an antiferromagnet at room temperature Reviewed

    M. Ikhlas, S. Dasgupta, F. Theuss, T. Higo, Shunichiro Kittaka, B. J. Ramshaw, O. Tchernyshyov, C. W. Hicks, S. Nakatsuji

    Nature Physics   18   2022.8

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    DOI: 10.1038/s41567-022-01645-5

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  • Anisotropic field response of specific heat for a ferromagnetic superconductor UCoGe in magnetic fields

    Shota Nakamura, Shunichiro Kittaka, Kazushige Machida, Yusei Shimizu, Ai Nakamura, Dai Aoki, Toshiro Sakakibara

    PHYSICAL REVIEW B   106 ( 3 )   2022.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER PHYSICAL SOC  

    Magnetic-field-angle-resolved specific heat and magnetization measurements were conducted on a ferromagnetic superconductor UCoGe with remarkable anisotropic upper critical field Hc2. Although Hc2 reaches a high magnetic field (-20 T) along the b axis, it is small (-0.6 T) when a magnetic field is applied along the magnetic easy c axis. This study indicates that the specific heat is abruptly suppressed when the magnetic field is applied toward the c axis from the a and b axes in the ferromagnetic state. The field response of density of states (DOS) is anisotropic, relative to the c axis, and its angle dependence is slightly singular. The Ising-type magnetic anisotropy of the ferromagnetic state is dominant even in the anisotropic reinforced superconducting state. These facts indicate that the suppression of DOS may closely relate to the superconducting state. We theoretically analyze these findings together with URhGe and UTe2 by highlighting the common and distinctive features among three compounds.

    DOI: 10.1103/PhysRevB.106.035152

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  • Nature of field-induced antiferromagnetic order in Zn-doped CeCoIn5 and its connection to quantum criticality in the pure compound

    Yokoyama, Makoto, Honma, Yutoku, Oshima, Yoshiki, Rahmanto, Suzuki, Kohei, Tenya, Kenichi, Shimizu, Yusei, Aoki, Dai, Matsuo, Akira, Kindo, Koichi, Nakamura, Shota, Kono, Yohei, Kittaka, Shunichiro, Sakakibara, Toshiro

    Physical Review B   2022

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    DOI: 10.1103/PHYSREVB.105.054515

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  • Development of high-resolution capacitive Faraday magnetometers for sub-Kelvin region

    Yusei Shimizu, Yohei Kono, Tomoyoshi Sugiyama, Shunichiro Kittaka, Yasuyuki Shimura, Atsushi Miyake, Dai Aoki, Toshiro Sakakibara

    Review of Scientific Instruments   92 ( 12 )   2021.12

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    High-sensitivity capacitive Faraday magnetometers were developed for static DC magnetization measurements in a sub-Kelvin region that can be used with 3He-4He dilution refrigerators (∼50 mK) and 3He refrigerators (∼0.28 K). For high-resolution magnetization measurements, the background magnetization of the force-sensing capacitor should be as small as possible, compared with the magnetization value of a measured specimen. In this study, we succeeded in reducing the background of the capacitor in both low- and high-field regions by compensating for the diamagnetic response of a thin quartz plate, making use of Pauli-paramagnetic alloys and Van Vleck paramagnets as a counter magnetization for a diamagnetic signal. Having established an ultra-high-sensitivity capacitor, we achieved a resolution of 10-5 (∼10-5-10-6) emu in the low- (high-) field region below (above) 1 T. In particular, the newly developed capacitors with a Van Vleck paramagnet Pr0.1La0.9Be13 and paramagnetic MgAl alloys are demonstrated to be very useful for high-resolution magnetization measurements at milli-Kelvin temperatures in low and high magnetic fields, respectively.

    DOI: 10.1063/5.0067759

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  • Gapped ground state in a spin- 12 frustrated square lattice

    H. Yamaguchi, N. Uemoto, T. Okubo, Y. Kono, S. Kittaka, T. Sakakibara, T. Yajima, S. Shimono, Y. Iwasaki, Y. Hosokoshi

    Physical Review B   104 ( 6 )   2021.8

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    Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    We present a model compound with a spin-1/2 frustrated square lattice, in which three ferromagnetic (F) interactions and one antiferromagnetic (AF) compet. Considering the effective spin-1 formed by the dominant F dimer, this square lattice can be mapped to a spin-1 spatially anisotropic triangular lattice. The magnetization curve exhibits gapped behavior indicative of a dominant one-dimensional (1D) AF correlation. In the field-induced gapless phase, the specific heat and magnetic susceptibility show a phase transition to an ordered state with 2D characteristics. These results indicate that the spin-1 Haldane state is extended to the 2D system. We demonstrate that the gapped ground state observed in the present spin-1/2 frustrated square lattice originates from the one-dimensionalization caused by frustration.

    DOI: 10.1103/physrevb.104.l060411

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.104.L060411/fulltext

  • Field-angle-resolved landscape of non-fermi-liquid behavior in the Quasi-Kagome Kondo lattice CeRhSn

    Shunichiro Kittaka, Yohei Kono, Suguru Tsuda, Toshiro Takabatake, Toshiro Sakakibara

    Journal of the Physical Society of Japan   90 ( 6 )   2021.6

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    We have employed a magnetic field angle as a tuning parameter in a comprehensive measurement of the specific heat, magnetocaloric effect, and magnetization for the quasi-kagome Kondo lattice CeRhSn, which is considered to exhibit zero-field quantum criticality driven by geometrical frustration. By constructing the field-angle-resolved landscape of the entropy, we unexpectedly revealed that the non-Fermi-liquid nature survives up to a metamagnetic crossover field of roughly 3 T in the very narrow field-orientation range, close to the direction parallel to the quasi-kagome plane. We propose that spin fluctuations along the hexagonal c axis are the dominant driving force for the non-Fermi-liquid behavior because it is strongly suppressed by a magnetic-field component along the c axis. The multidimensional entropy landscape, which directly reflects the degeneracy of ground states, opens a new route for uncovering the nature of exotic phases in anisotropic systems.

    DOI: 10.7566/JPSJ.90.064703

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  • Magnetic phase transitions of the 4f skyrmion compound EuPtSi studied by magnetization measurements

    Toshiro Sakakibara, Shota Nakamura, Shunichiro Kittaka, Masashi Kakihana, Masato Hedo, Takao Nakama, Yoshichika Ōnuki

    Journal of the Physical Society of Japan   90 ( 6 )   2021.6

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    In this study, we measure the magnetic field and temperature variations of the magnetization MðH;TÞ of the cubic chiral compound EuPtSi and extensively investigate the magnetic phase transitions in a wide temperature range down to 60mK. The incommensurate–commensurate transition at TN ’ 2:5K in the helical state, which has not been observed in transport or thermodynamic measurements, is exclusively detected in M(T) for H ∥ 〈111〉. TN shows a rapid decrease in H. For H ∥ [100] and [111], M(H) at T < 100mK showed that the helical q vectors are depinned from the preferred orientations at H ≳ 10kOe and gradually rotate toward the field directions as H increases. The skyrmion lattice phase (A-phase) field-induced in H ∥ 〈111〉 only above 0.4K in equilibrium conditions can be created at 60mK under field cooling, with a sharp tilted plateau structure developing in M(H) of the A-phase. A similar metastable state is also created below 100mK for the AA phase induced by H ∥ 〈100〉 at T ≳ 0:3K in equilibrium conditions. The magnetic phase diagrams established for the three directions [111], [110], and [100] are highly anisotropic and discussed herein on the basis of the q vectors rather strongly pinned to the lattice and transform under the lattice symmetry operations.

    DOI: 10.7566/JPSJ.90.064701

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  • Thermal Hall Effects of Spins and Phonons in Kagome Antiferromagnet Cd-Kapellasite

    Masatoshi Akazawa, Masaaki Shimozawa, Shunichiro Kittaka, Toshiro Sakakibara, Ryutaro Okuma, Zenji Hiroi, Hyun-Yong Lee, Naoki Kawashima, Jung Hoon Han, Minoru Yamashita

    PHYSICAL REVIEW X   10 ( 4 )   2020.12

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    We investigate the thermal-transport properties of the kagome antiferromagnet Cd-kapellasite (Cd-K). We find that a field-suppression effect on the longitudinal thermal conductivity K-xx, sets in below approximately 25 K. This field-suppression effect at 15 T becomes as large as 80% at low temperatures, suggesting a large spin contribution K-xx(sp) in K-xx. We also find clear thermal Hall signals in the spin liquid phase in all Cd-K samples. The magnitude of the thermal Hall conductivity K-xy shows a significant dependence on the sample's scattering time, as seen in the rise of the peak K-xy value in almost linear fashion with the magnitude of K-xx. On the other hand, the temperature dependence of K-xy is similar in all Cd-K samples; K-xy shows a peak at almost the same temperature of the peak of the phonon thermal conductivity ex which is estimated by K-xx, at 15 T. These results indicate the presence of a dominant phonon thermal Hall K-xy at 15 T. In addition to e y , we find that the field dependence of K-xy at low fields turns out to be nonlinear at low temperatures, concomitantly with the appearance of the field suppression of K-xx, indicating the presence of a spin thermal Hall K-xy(sp) at low fields. Remarkably, by assembling the K-xx dependence of ex K-xy(sp) data of other kagome antiferromagnets, we find that, whereas K-xy(sp) stays a constant in the low-K-xx region, K-xy(sp) starts to increase as K-xx does in the high-K-xx region. This K-xx dependence of K-xy(sp) indicates the presence of both intrinsic and extrinsic mechanisms in the spin thermal Hall effect in kagome antiferromagnets. Furthermore, both K-xy(ph) and K-xy(sp), disappear in the antiferromagnetic ordered phase at low fields, showing that phonons alone do not exhibit the thermal Hall effect. A high field above approximately 7 T induces K-xy(ph), concomitantly with a field-induced increase of K-xx and the specific heat, suggesting a coupling of the phonons to the field-induced spin excitations as the origin of K-xy(ph).

    DOI: 10.1103/PhysRevX.10.041059

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  • Kitaev Spin Liquid Candidate OsxCl3 Comprised of Honeycomb Nano-Domains Reviewed

    Kota Kataoka, Daigoro Hirai, Takeshi Yajima, Daisuke Nishio-Hamane, Rieko Ishii, Kwang-Yong Choi, Dirk Wulferding, Peter Lemmens, Shunichiro Kittaka, Toshiro Sakakibara, Hajime Ishikawa, Akira Matsuo, Koichi Kindo, Zenji Hiroi

    Journal of the Physical Society of Japan   89 ( 11 )   114709-1 - 114709-9   2020.10

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    © 2020 The Physical Society of Japan. An osmium chloride with the chemical formula of OsxCl3 (x = 0.81) was synthesized and its crystal structure and thermodynamic properties were investigated. OsxCl3 crystallizes in a layered CdCl2-type structure with the triangular lattice partially occupied by Os ions on average. However, on microscopic length scales, the triangular lattice is composed of nano-domains with a honeycomb arrangement of Os ions, as observed by electron microscopy and Raman scattering experiments. Magnetization and heat capacity measurements revealed an absence of magnetic long-range order down to 0.08 K, while a broad peak in heat capacity at 0.15K may indicate a short-range order in the local honeycomb lattice. OsxCl3 may exhibit certain aspects of the Kitaev spin liquid that are expected for a perfect honeycomb lattice of osmium trichloride.

    DOI: 10.7566/jpsj.89.114709

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  • Evidence for nematic superconductivity of topological surface states in PbTaSe2 Reviewed

    Tian Le, Yue Sun, Hui-Ke Jin, Liqiang Che, Lichang Yin, Jie Li, Guiming Pang, Chunqiang Xu, Lingxiao Zhao, Shunichiro Kittaka, Toshiro Sakakibara, Kazushige Machida, Raman Sankar, Huiqiu Yuan, Genfu Chen, Xiaofeng Xu, Shiyan Li, Yi Zhou, Xin Lu

    Science Bulletin   65 ( 16 )   1349 - 1355   2020.8

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    Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.scib.2020.04.039

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  • Orientation of point nodes and nonunitary triplet pairing tuned by the easy-axis magnetization in UTe2 Reviewed

    Shunichiro Kittaka, Yusei Shimizu, Toshiro Sakakibara, Ai Nakamura, Dexin Li, Yoshiya Homma, Fuminori Honda, Dai Aoki, Kazushige Machida

    Physical Review Research   2 ( 3 )   2020.7

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    The gap structure of a novel uranium-based superconductor UTe2, situated in the vicinity of ferromagnetic quantum criticality, has been investigated via specific-heat C(T, H, Omega) measurements in various field orientations. Its angular Omega(phi, theta) variation shows a characteristic shoulder anomaly with a local minimum in H parallel to a at moderate fields rotated within the ab and ac planes. Based on theoretical calculations, these features can be attributed to the presence of point nodes in the superconducting gap along the a direction. Under the field orientation along the easy-magnetization a axis, an unusual temperature dependence of the upper critical field at low fields together with a convex downward curvature in C(H) were observed. These anomalous behaviors can be explained on the basis of a nonunitary triplet state model with equal-spin pairing whose T-c is tuned by the magnetization along the a axis. From these results, the gap symmetry of UTe2 is most likely described by a vector order parameter of d(k) = (b + ic)(k(b) + ik(c)).

    DOI: 10.1103/physrevresearch.2.032014

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevResearch.2.032014/fulltext

  • Fully gapped superconductivity without sign reversal in the topological superconductor PbTaSe2 Reviewed

    Yue Sun, Shunichiro Kittaka, Toshiro Sakakibara, Kazushige Machida, R. Sankar, Xiaofeng Xu, Nan Zhou, Xiangzhuo Xing, Zhixiang Shi, Sunseng Pyon, Tsuyoshi Tamegai

    PHYSICAL REVIEW B   102 ( 2 )   2020.7

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    We investigate the superconducting gap function of the topological superconductor PbTaSe2. The temperature, magnetic field, and three-dimensional (3D) field-angle dependences of the specific heat prove that the superconductivity of PbTaSe2 is fully gapped, with two isotropic s-wave gaps. The pair-breaking effect is probed by systematically increasing nonmagnetic disorders through H+ irradiation. The superconducting transition temperature T-c is found to be robust against disorders, which suggests that the pairing should be sign preserved rather than sign reversed.

    DOI: 10.1103/PhysRevB.102.024517

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.102.024517/fulltext

  • Magnetic properties of a spin-2 antiferromagnet with metal-radical hybrid spins Reviewed

    Y. Iwasaki, T. Okabe, N. Uemoto, Y. Kono, Y. Hosokoshi, S. Nakamura, S. Kittaka, T. Sakakibara, M. Hagiwara, T. Kawakami, H. Yamaguchi

    Physical Review B   101 ( 17 )   2020.5

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    DOI: 10.1103/physrevb.101.174412

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.101.174412/fulltext

  • Synthesis and Magnetic Properties of M2+Ti4+ Substituted Ba12Fe28Ti15O84 Reviewed

    N. Yasuda, S. Kittaka, Y. Kono, T. Sakakibara, K. Kakizaki, K. Kamishima

    Journal of the Magnetics Society of Japan   44 ( 3 )   70 - 74   2020.5

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    Publishing type:Research paper (scientific journal)   Publisher:The Magnetics Society of Japan  

    DOI: 10.3379/msjmag.2005r004

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  • Field-Orientation Effect on Ferro-Quadrupole Order in PrTi2Al20 Reviewed

    Shunichiro Kittaka, Takanori Taniguchi, Kazumasa Hattori, Shota Nakamura, Toshiro Sakakibara, Masashi Takigawa, Masaki Tsujimoto, Akito Sakai, Yosuke Matsumoto, Satoru Nakatsuji

    Journal of the Physical Society of Japan   89 ( 4 )   043701 - 043701   2020.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Physical Society of Japan  

    Ferro-quadrupole (FQ) order in the non-Kramers Gamma(3) doublet system PrTi2Al20 has been investigated via angle-resolved measurements of the specific heat, rotational magnetocaloric effect, and entropy, under a rotating magnetic field within the (1 (1) over bar0) plane. The FQ transition occurring at 2K is robust when the magnetic field B is applied precisely along the [111] direction or in low fields below 1 T. By contrast, the magnetic field of larger than 1 T tilted away from the [111] direction sensitively changes the FQ transition to a crossover. The energy gap between the ground and first-excited states in the FQ order increases remarkably with the magnetic field in B parallel to [001], but hardly depends on the magnetic-field strength, at least up to 5 T, in the field orientation between the [111] and [110] axes. These features can be reproduced by using a phenomenological model for FQ order assuming an anisotropic field-dependent interaction between quadrupoles, which has been recently proposed to explain the field-induced first-order phase transition in PrTi2Al20. The present study demonstrates the great potential of the field-angle-resolved measurements for evaluating possible scenarios for multipole orders.

    DOI: 10.7566/jpsj.89.043701

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  • Heavy Fermion State of YbNi2Si3 without Local Inversion Symmetry Reviewed

    Shota Nakamura, Kazushi Hyodo, Yuji Matsumoto, Yoshinori Haga, Hitoshi Sato, Shigenori Ueda, Kojiro Mimura, Katsuyoshi Saiki, Kosei Iso, Minoru Yamashita, Shunichiro Kittaka, Toshiro Sakakibara, Shigeo Ohara

    Journal of the Physical Society of Japan   89 ( 2 )   024705 - 024705   2020.2

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    DOI: 10.7566/JPSJ.89.024705

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  • Magnetic properties of a spin-1/2 honeycomb lattice antiferromagnet Reviewed

    Y. Kono, T. Okabe, N. Uemoto, Y. Iwasaki, Y. Hosokoshi, S. Kittaka, T. Sakakibara, H. Yamaguchi

    Phys. Rev. B   101   014437-1 - 014437-6   2020.1

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    DOI: 10.1103/PhysRevB.101.014437

    DOI: 10.1103/physrevb.101.014437

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  • Superconductivity in PtSbS with a Noncentrosymmetric Cubic Crystal Structure Reviewed

    Mizutani Ryosuke, Okamoto Yoshihiko, Nagaso Hayate, Yamakawa Youichi, Takatsu Hiroshi, Kageyama Hiroshi, Kittaka Shunichiro, Kono Yohei, Sakakibara Toshiro, Takenaka Koshi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   88 ( 9 )   2019.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PHYSICAL SOC JAPAN  

    We report the synthesis, electronic properties, and electronic structure of ullmannite-type PtSbS, which has a cubic crystal structure without space inversion symmetry. Electrical resistivity and magnetization measured at low temperatures suggested that this compound is a bulk superconductor with a superconducting transition temperature of T-c = 0.15 K. First principles calculations indicated that Fermi surfaces of PtSbS include strongly nested hole pockets, which can make this compound interesting if they contribute to the emergence of superconductivity.

    DOI: 10.7566/JPSJ.88.093709

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  • Emergent critical phenomenon in spin-1/2 ferromagnetic-leg ladders: Quasi-one-dimensional Bose―Einstein condensate Reviewed

    Y. Kono, S. Kittaka, H. Yamaguchi, Y. Hosokoshi, T. Sakakibara

    Phys. Rev. B   100   054442-1 - 054442-8   2019.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physical Society  

    DOI: 10.1103/PhysRevB.100.054442

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    Other Link: http://orcid.org/0000-0001-7613-3721

  • Fluctuation-Induced First-Order Transition and Tricritical Point in EuPtSi Reviewed

    Sakakibara Toshiro, Nakamura Shota, Kittaka Shunichiro, Kakihana Masashi, Hedo Masato, Nakama Takao, Onuki Yoshichika

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   88 ( 9 )   093701-1 - 093701-5   2019.7

  • Quasiparticle Evidence for the Nematic State above T-c in SrxBi2Se3 Reviewed

    Sun Yue, Kittaka Shunichiro, Sakakibara Toshiro, Machida Kazushige, Wang Jinghui, Wen Jinsheng, Xing Xiangzhuo, Shi Zhixiang, Tamegai Tsuyoshi

    PHYSICAL REVIEW LETTERS   123 ( 2 )   027002-1 - 027002-6   2019.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER PHYSICAL SOC  

    In the electronic nematic state, an electronic system has a lower symmetry than the crystal structure of the same system. Electronic nematic states have been observed in various unconventional superconductors such as cuprate, iron-based, heavy-fermion, and topological superconductors. The relation between nematicity and superconductivity is a major unsolved problem in condensed matter physics. By angle-resolved specific heat measurements, we report bulk quasiparticle evidence of nematicity in the topological superconductor SrxBi2Se3. The specific heat exhibited a clear twofold symmetry despite the threefold symmetric lattice. Most importantly, the twofold symmetry appeared in the normal state above the superconducting transition temperature. This is explained by the angle-dependent Zeeman effect due to the anisotropic density of states in the nematic phase. Such results highlight the interrelation between nematicity and unconventional superconductivity.

    DOI: 10.1103/PhysRevLett.123.027002

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  • S=1/2 ferromagnetic Heisenberg chain in a verdazyl-based complex Reviewed

    N. Uemoto, Y. Kono, S. Kittaka, T. Sakakibara, T. Yajima, Y. Iwasaki, S. Miyamoto, Y. Hosokoshi, H. Yamaguchi

    PHYSICAL REVIEW B   99 ( 9 )   094418-1 - 094418-6   2019.3

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    We present a model compound for the S = 1/2 ferromagnetic Heisenberg chain composed of the verdazyl-based complex [Zn(hfac)(2)][4-Cl-o-Py-V-(4-F)(2)]. Ab initio MO calculations indicate a predominant ferromagnetic interaction forming an S = 1/2 ferromagnetic chain. The magnetic susceptibility and specific heat indicate a phase transition to an antiferromagnetic (AF) order due to the finite interchain couplings. We explain the magnetic susceptibility and magnetization curve above the phase-transition temperature based on the S = 1/2 ferromagnetic Heisenberg chain. The magnetization curve in the ordered phase is described by a conventional AF two-sublattice model. Furthermore, the obtained magnetic specific heat reproduces the almost temperature-independent behavior of the S = 1/2 ferromagnetic Heisenberg chain. In the low-temperature region, the magnetic specific heat exhibits a root T dependence, which is attributed to the energy dispersion in the ferromagnetic chain.

    DOI: 10.1103/PhysRevB.99.094418

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  • Anisotropic magnetic-field response of quantum critical fluctuations in Ni-doped CeCoIn5 Reviewed

    Makoto Yokoyama, Kohei Suzuki, Kenichi Tenya, Shota Nakamura, Yohei Kono, Shunichiro Kittaka, Toshiro Sakakibara

    Physical Review B   2019.2

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    DOI: 10.1103/physrevb.99.054506

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  • Unconventional Field-Induced Spin Gap in an S=1/2 Chiral Staggered Chain. Reviewed International journal

    J Liu, S Kittaka, R D Johnson, T Lancaster, J Singleton, T Sakakibara, Y Kohama, J van Tol, A Ardavan, B H Williams, S J Blundell, Z E Manson, J L Manson, P A Goddard

    Physical review letters   122 ( 5 )   057207 - 057207   2019.2

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    We investigate the low-temperature magnetic properties of the molecule-based chiral spin chain [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O (pym=pyrimidine). Electron-spin resonance, magnetometry and heat capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation spectrum, a staggered susceptibility, and a spin gap that opens on the application of a magnetic field. These phenomena are reminiscent of those previously observed in nonchiral staggered chains, which are explicable within the sine-Gordon quantum-field theory. In the present case, however, although the sine-Gordon model accounts well for the form of the temperature dependence of the heat capacity, the size of the gap and its measured linear field dependence do not fit with the sine-Gordon theory as it stands. We propose that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure of [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O, particularly a uniform Dzyaloshinskii-Moriya coupling and a fourfold periodic staggered field.

    DOI: 10.1103/PhysRevLett.122.057207

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  • Synthesis and physical properties of Kitaev spin liquid candidate OsCl3

    Kataoka K., Hirai D., Yajima T., Hamane D., Kittaka S., Sakakibara T., Hiroi Z.

    Meeting Abstracts of the Physical Society of Japan   74.1   2313 - 2313   2019

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    DOI: 10.11316/jpsgaiyo.74.1.0_2313

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  • Field-induced quantum magnetism in the verdazyl-based charge-transfer salt [o-MePy-V-(p-Br)2]FeCl4 Reviewed

    Y. Iwasaki, T. Kida, M. Hagiwara, T. Kawakami, Y. Kono, S. Kittaka, T. Sakakibara, Y. Hosokoshi, H. Yamaguchi

    PHYSICAL REVIEW B   98 ( 22 )   224411-1 - 224411-7   2018.12

  • Low-Temperature Magnetization Measurements with Precise Two-Axis Alignment of the Sample Orientation Reviewed

    Shota Nakamura, Akira Kasahara, Shunichiro Kittaka, Yohei Kono, Yoshichika Ōnuki, Toshiro Sakakibara

    Journal of the Physical Society of Japan   87   114001   2018.11

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  • Magnetization study on the ising ferromagnet URhGe with high-precision angle-resolved magnetic field near the hard axis Reviewed

    Nakamura S, Sakakibara T, Shimizu Y, Kittaka S, Kono Y, Haga Y, Pospíšil J, Yamamoto E

    Progress in Nuclear Science and Technology   5   123 - 127   2018.11

  • Metamagnetic crossover in the quasikagome Ising Kondo-lattice compound CeIrSn Reviewed

    S. Tsuda, C. L. Yang, Y. Shimura, K. Umeo, H. Fukuoka, Y. Yamane, T. Onimaru, T. Takabatake, N. Kikugawa, T. Terashima, H. T. Hirose, S. Uji, S. Kittaka, T. Sakakibara

    PHYSICAL REVIEW B   98 ( 15 )   155147-1 - 155147-7   2018.10

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    © 2018 American Physical Society. The Ce atoms in CeIrSn form a quasikagome lattice in the hexagonal c plane. Our single-crystal x-ray diffraction analysis has confirmed the absence of superstructure in the ZrNiAl-type structure. Motivated by the recent observation of quantum critical behaviors in the isostructural and isoelectronic compound CeRhSn, we have studied low-temperature properties of single-crystalline samples of CeIrSn by measuring the electrical resistivity, magnetic susceptibility χ, magnetization M, and specific heat C down to 0.05 K. Our study does not show evidence of a long-range magnetic ordering down to the lowest temperature. The χ(T) data show an Ising character, χc a, and power-law behaviors at low temperatures: χcT-0.8 and χaT-0.6. When external field B is applied along the a axis, both M(B) and C(B)/T exhibit metamagnetic anomalies at 5.5 T, which resemble those observed in CeRhSn at 3.5 T. We attribute the metamagnetic crossover under in-plane magnetic fields to the alleviation of magnetic frustration inherent in the quasikagome Ising Kondo lattice.

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  • Investigation of the tricritical point of the ising ferromagnet URhGe by angle-resolved measurements Reviewed

    Nakamura Shota, Kittaka Shunichiro, Sakakibara Toshiro, Shimizu Yusei, Kono Yohei, Haga Yoshinori, Pospisil Jiri, Yamamoto Etsuji

    AIP ADVANCES   8 ( 10 )   101305-1 - 101305-5   2018.10

  • Searching for Gap Zeros in Sr2RuO4 via Field-Angle-Dependent Specific-Heat Measurement Reviewed

    Shunichiro Kittaka, Shota Nakamura, Toshiro Sakakibara, Naoki Kikugawa, Taichi Terashima, Shinya Uji, Dmitry A. Sokolov, Andrew P. Mackenzie, Koki Irie, Yasumasa Tsutsumi, Katsuhiro Suzuki, Kazushige Machida

    Journal of the Physical Society of Japan   87   093703   2018.9

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  • Field-enhanced quantum fluctuation in an S=1/2 frustrated square lattice Reviewed

    Yamaguchi H, Sasaki Y, Okubo T, Yoshida M, Kida T, Hagiwara M, Kono Y, Kittaka S, Sakakibara T, Takigawa M, Iwasaki Y, Hosokoshi Y

    PHYSICAL REVIEW B   98 ( 9 )   094402-1 - 094402-6   2018.9

  • Disorder-sensitive nodelike small gap in FeSe Reviewed

    Yue Sun, Shunichiro Kittaka, Shota Nakamura, Toshiro Sakakibara, Peng Zhang, Shik Shin, Koki Irie, Takuya Nomoto, Kazushige Machida, Jingting Chen, Tsuyoshi Tamegai

    Physical Review B   98   064505   2018.8

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    DOI: 10.1103/physrevb.98.064505

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  • Field-rotational Magnetocaloric Effect: A New Experimental Technique for Accurate Measurement of the Anisotropic Magnetic Entropy Reviewed

    Shunichiro Kittaka, Shota Nakamura, Hiroaki Kadowaki, Hiroshi Takatsu, Toshiro Sakakibara

    Journal of the Physical Society of Japan   87   073601   2018.7

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  • Superconducting symmetries and magnetic responses of uranium heavy-fermion systems UBe13 and UPd2Al3 Reviewed

    Yusei Shimizu, Shunichiro Kittaka, Toshiro Sakakibara, Dai Aoki

    Physica B: Condensed Matter   536   553 - 557   2018.5

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    Low-temperature thermodynamic investigation for UBe13 and UPd2Al3 were performed in order to gain insight into their unusual ground states of 5f electrons. Our heat-capacity data for the cubic UBe13 strongly suggest that nodal quasiparticles are absent and its superconducting (SC) gap is fully open over the Fermi surface. Moreover, two unusual thermodynamic anomalies are also observed in UBe13 at ∼ 3 T and ∼ 9 T
    the lower-field anomaly is seen only in the SC mixed state by dc magnetization M(H) as well as heat-capacity C(H), while the higher-field anomaly appears for C(H) in the normal phase above the upper critical field. On the other hand, field-orientation dependence of the heat capacity in the hexagonal UPd2Al3 shows a significantly anisotropic behavior of C(H)∝H1/2, reflecting the nodal gap structure of this system. Our result strongly suggests the presence of a horizontal line node on the Fermi surface with heavy effective mass in UPd2Al3.

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  • Quasi-one-dimensional Bose-Einstein condensation in the spin-1/2 ferromagnetic-leg ladder 3-I-V Reviewed

    Y. Kono, S. Kittaka, H. Yamaguchi, Y. Hosokoshi, T. Sakakibara

    Physical Review B   97 ( 10 )   100406(R)-1 - 100406(R)-5   2018.3

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    Quantum criticality of the spin-1/2 ferromagnetic-leg ladder 3-I-V [=3-(3-iodophenyl)-1,5-diphenylverdazyl] has been examined with respect to the antiferromagnetic to paramagnetic phase transition near the saturation field Hc. The phase boundary Tc(H) follows the power-law Tc(H) Hc-H for a wide temperature range. This characteristic behavior is discussed as a quasi-one-dimensional (quasi-1D) Bose-Einstein condensation, which is predicted theoretically for weakly coupled quasi-1D ferromagnets. Thus, 3-I-V provides the first promising candidate for this attractive prediction.

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  • Gap structure of FeSe determined by angle-resolved specific heat measurements in applied rotating magnetic field Reviewed

    Yue Sun, Shunichiro Kittaka, Shota Nakamura, Toshiro Sakakibara, Koki Irie, Takuya Nomoto, Kazushige Machida, Jingting Chen, Tsuyoshi Tamegai

    Physical Review B   96   2200505   2017.12

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  • Magnetic properties and magnetic phase diagrams of trigonal DyNi3Ga9 Reviewed

    Hiroki Ninomiya, Yuji Matsumoto, Shota Nakamura, Yohei Kono, Shunichiro Kittaka, Toshiro Sakakibara, Katsuya Inoue, Shigeo Ohara

    Journal of the Physical Society of Japan   86 ( 12 )   2017.12

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    We report the crystal structure, magnetic properties, and magnetic phase diagrams of single crystalline DyNi3Ga9 studied using X-ray diffraction, electrical resistivity, specific heat, and magnetization measurements. DyNi3Ga9 crystallizes in the chiral structure with space group R32. The dysprosium ions, which are responsible for the magnetism in this compound, form a two-dimensional honeycomb structure on a (0001) plane. We show that DyNi3Ga9 exhibits successive phase transitions at TN = 10K and TN0 ¼ 9K. The former suggests quadrupolar ordering, and the latter is attributed to the antiferromagnetic order. It is considered that DyNi3Ga9 forms the canted-antiferromagnetic structure below TN0 owing to a small hysteresis loop of the low-field magnetization curve. We observe the strong easy-plane anisotropy, and the multiple-metamagnetic transitions with magnetization-plateaus under the field applied along the honeycomb plane. For H k ½2110 , the plateau-region arises every 1=6 for saturation magnetization. The magnetic phase diagrams of DyNi3Ga9 are determined for the fields along principal-crystal axes.

    DOI: 10.7566/JPSJ.86.124704

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  • Randomness-induced quantum spin liquid on honeycomb lattice Reviewed

    Hironori Yamaguchi, Masataka Okada, Yohei Kono, Shunichiro Kittaka, Toshiro Sakakibara, Toshiki Okabe, Yoshiki Iwasaki, Yuko Hosokoshi

    SCIENTIFIC REPORTS   7   16144-1 - 16144-6   2017.11

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    Quantum entanglement in magnetic materials is expected to yield a quantum spin liquid (QSL), in which strong quantum fluctuations prevent magnetic ordering even at zero temperature. This topic has been one of the primary focuses of condensed-matter science since Anderson first proposed the resonating valence bond state in a certain spin-1/2 frustrated magnet in 1973. Since then, several candidate materials featuring frustration, such as triangular and kagome lattices, have been reported to exhibit liquid-like behavior. However, the mechanisms that stabilize the liquid-like states have remained elusive. Here, we present a QSL state in a spin-1/2 honeycomb lattice with randomness in the exchange interaction. That is, we successfully introduce randomness into the organic radialbased complex and realize a random-singlet (RS) state (or valence bond glass). All magnetic and thermodynamic experimental results indicate the liquid-like behaviors, which are consistent with those expected in the RS state. Our results suggest that the randomness or inhomogeneity in the actual systems stabilize the RS state and yield liquid-like behavior.

    DOI: 10.1038/s41598-017-16431-0

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  • Quasiparticle excitations and evidence for superconducting double transitions in monocrystalline U0.97Th0.03Be13 Reviewed

    Y. Shimizu, S. Kittaka, S. Nakamura, T. Sakakibara, D. Aoki, Y. Homma, A. Nakamura, K. Machida

    Physical Review B   96   100505   2017.9

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  • Wing structure in the phase diagram of the Ising ferromagnet URhGe close to its tricritical point investigated by angle-resolved magnetization measurements Reviewed

    Shota Nakamura, Toshiro Sakakibara, Yusei Shimizu, Shunichiro Kittaka, Yohei Kono, Yoshinori Haga, Jiri Pospisil, Etsuji Yamamoto

    PHYSICAL REVIEW B   96 ( 9 )   094411-1 - 094411-9   2017.9

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    High-precision angle-resolved dc magnetization and magnetic torque studies were performed on a singlecrystalline sample of URhGe, an orthorhombic Ising ferromagnet with the c axis being the magnetization easy axis, in order to investigate the phase diagram around the ferromagnetic (FM) reorientation transition in a magnetic field near the b axis. We have clearly detected a first-order transition in both the magnetization and the magnetic torque at low temperatures, and determined detailed profiles of the wing structure of the three-dimensional T-Hb-Hc phase diagram, where H-c and H-b denote the field components along the c and the b axes, respectively. The quantum wing critical points are located at mu H-0(c) similar to +/- 1.1 T and mu H-0(b) similar to 13.5 T. Two second-order transition lines at the boundaries of the wing planes rapidly tend to approach each other with increasing temperature up to similar to 3 K. Just at the zero conjugate field (H-c = 0), however, a signature of the first-order transition can still be seen in the field derivative of the magnetization at similar to 4 K, indicating that the tricritical point exists in a rather high temperature region above 4 K. This feature of the wing plane structure is consistent with the theoretical expectation that three second-order transition lines merge tangentially at the tricritical point.

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  • Fully gapped superconductivity with no sign change in the prototypical heavy-fermion CeCu2Si2 Reviewed

    Takuya Yamashita, Takaaki Takenaka, Yoshifumi Tokiwa, Joseph A. Wilcox, Yuta Mizukami, Daiki Terazawa, Yuichi Kasahara, Shunichiro Kittaka, Toshiro Sakakibara, Marcin Konczykowski, Silvia Seiro, Hirale S. Jeevan, Christoph Geibel, Carsten Putzke, Takafumi Onishi, Hiroaki Ikeda, Antony Carrington, Takasada Shibauchi, Yuji Matsuda

    SCIENCE ADVANCES   3 ( 6 )   e1601667-1 - e1601667-7   2017.6

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    In exotic superconductors, including high-T-c copper oxides, the interactions mediating electron Cooper pairing are widely considered to have a magnetic rather than a conventional electron-phonon origin. Interest in this exotic pairing was initiated by the 1979 discovery of heavy-fermion superconductivity in CeCu2Si2, which exhibits strong antiferromagnetic fluctuations. A hallmark of unconventional pairing by anisotropic repulsive interactions is that the superconducting energy gap changes sign as a function of the electron momentum, often leading to nodes where the gap goes to zero. We report low-temperature specific heat, thermal conductivity, and magnetic penetration depth measurements in CeCu2Si2, demonstrating the absence of gap nodes at any point on the Fermi surface. Moreover, electron irradiation experiments reveal that the superconductivity survives even when the electron mean free path becomes substantially shorter than the superconducting coherence length. This indicates that superconductivity is robust against impurities, implying that there is no sign change in the gap function. These results show that, contrary to long-standing belief, heavy electrons with extremely strong Coulomb repulsions can condense into a fully gapped s-wave superconducting state, which has an on-site attractive pairing interaction.

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  • Thermodynamic properties of quadrupolar states in the frustrated pyrochlore magnet Tb2Ti2O7 Reviewed

    H. Takatsu, T. Taniguchi, S. Kittaka, T. Sakakibara, H. Kadowaki

    Journal of Physics: Conference Series   828 ( 1 )   012007-1 - 012007-6   2017.4

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    The low-temperature thermodynamic properties of the frustrated pyrochlore Tb2+xTi2-xO7+y have been studied using the single crystal of x = 0.005 sitting in a long range ordered phase in the x-T phase diagram. We observed that the specific heat exhibits a minimum around 2 K and slightly increases on cooling, similar to a Schottky-like anomaly for canonical spin ices. A clear specific-heat peak observed at Tc = 0.53 K is ascribable to the phase transition to a quadrupolar state, which contributes to a relatively large change in entropy, S ≃ 2.7 J K-1mol-1. However, it is still smaller than R ln 2 for the ground state doublet of the Tb ions. The entropy release persists to higher temperatures, suggesting strong fluctuations associated with spin ice correlations above Tc. We discuss the field dependence of the entropy change for H ∥ [111] and H ∥ [001].

    DOI: 10.1088/1742-6596/828/1/012007

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  • Nodal gap structure of the heavy-fermion superconductor URu2Si2 revealed by field-angle-dependent specific-heat measurements Reviewed

    Shunichiro Kittaka, Yusei Shimizu, Toshiro Sakakibara, Yoshinori Haga, Etsuji Yamamoto, Yoshichika O'Nuki, Yasumasa Tsutsumi, Takuya Nomoto, Hiroaki Ikeda, Kazushige Machida

    Journal of Physics: Conference Series   807 ( 5 )   052001-1 - 052001-6   2017.4

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    URu2Si2 is a promising candidate for a chiral d-wave superconductor whose gap is composed of a horizontal line node at equator and point nodes at the north and south poles. However, previous measurements of the specific heat and the thermal conductivity did not detect quasiparticle excitations from a horizontal line node in heavy-mass bands. Here, we have provided strong evidence for the presence of a horizontal line node from field-angle-dependent specific-heat measurements by using a high-quality single crystal of URu2Si2. We observed the behavior of the specific heat at low fields which does not depend on inplane field angle φ but shows a shoulder-like anomaly in the polar-angle θ dependence around θ ∼ 45°. This feature is more clearly seen at lower temperatures, suggesting the detection of low-energy quasiparticle excitations reflecting the gap structure. From theoretical analyses based on microscopic calculations, we have demonstrated that this anomaly can be explained by the existence of a horizontal line node at kz = 0. Thus, the gap structure of URu2Si2 matches well with the Eg chiral kz(kx + iky) symmetry.

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  • Structural, Magnetic, and Superconducting Properties of Caged Compounds ROs2Zn20 ( R = La, Ce, Pr, and Nd) Reviewed

    Kazuhei Wakiya, Takahiro Onimaru, Keisuke T. Matsumoto, Yu Yamane, Naohiro Nagasawa, Kazunori Umeo, Shunichiro Kittaka, Toshiro Sakakibara, Yoshitaka Matsushita, Toshiro Takabatake

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   86 ( 3 )   034707-1 - 034707-6   2017.3

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    The electrical resistivity, magnetization, and specific heat of the caged compounds ROs2Zn20 ( R = La, Ce, Pr, and Nd) have been measured to study their structural, magnetic, and superconducting properties. These measurements indicate that the compounds undergo structural transitions at T-s = 151, 109, 87, and 62 K, respectively. The decrease in Ts along with the lanthanoid contraction suggests that the high-temperature phase is more stable for a smaller lattice volume. Analysis of the lattice specific heat of LaOs2Zn20 reveals that the Zn atom at the 16c site encapsulated in the R2Zn12 cage vibrates at a low energy of 3meV. For CeOs2Zn20, the small magnetic susceptibility with a broad maximum indicates the valence-fluctuating state of the Ce ions. In PrOs2Zn20, the crystalline electric field ground state of the 4f(2) state of the Pr3+ ion remains in a non-Kramers doublet at T &gt; T-s, which is lifted by symmetry lowering of the Pr site at T &lt; T-s. Thereby, the quadrupolar degrees of freedom are quenched, avoiding the long-range quadrupole order. PrOs2Zn20 and LaOs2Zn20 exhibit superconducting transitions at 0.06 and 0.07 K, respectively.

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  • Thermodynamic Investigation of Metamagnetic Transitions and Partial Disorder in the Quasi-Kagome Kondo Lattice CePdAl Reviewed

    Kenji Mochidzuki, Yusei Shimizu, Akihiro Kondo, Shota Nakamura, Shunichiro Kittaka, Yohei Kono, Toshiro Sakakibara, Yoichi Ikeda, Yosikazu Isikawa, Koichi Kindo

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   86 ( 3 )   034709-1 - 034709-5   2017.3

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    Low-temperature (T) thermodynamic properties of the quasi-Kagome antiferromagnet CePdAl ( T-N = 2.7 K) in magnetic fields (B) were studied by magnetization and specific-heat C(T, B) measurements. The unusual magnetic phase diagram, including three thermodynamic phases I-III and crossover anomalies, has been obtained. In the low-field phase I, the existence of the partial Kondo screening state on one-third of the Ce sites is supported from the following thermodynamic view points: (i) the appearance of a paramagnetic moment with one-third of the full moment around 3 T and (ii) the occurrence of an entropy release of similar to 0.3R ln 2 around the observed crossover. On the other hand, a strong enhancement of C/T was found around the point where T-N( B) meets the boundary of phase III, indicating the possible presence of a tricritical point. Furthermore, it is suggested that the three metamagnetic transitions at B-mi (i = 1, 2. 3) originate from successive increments of the Ising-type magnetic moment along the c-axis. In the high-field region above 20 T, the behavior of f electrons can be roughly described by the crystal-electric-field model.

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  • <講義ノート>磁場角度回転比熱測定による超伝導研究 (J-Physics 若手夏の学校 2016年8月8日~12日:テキスト)

    橘高 俊一郎

    物性研究・電子版   6 ( 1 )   85 - 125   2017.2

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  • Magnetic properties of the S=1/2 honeycomb lattice antiferromagnet 2-Cl-3,6-F-2-V Reviewed

    Toshiki Okabe, Hironori Yamaguchi, Shunichiro Kittaka, Toshiro Sakakibara, Toshio Ono, Yuko Hosokoshi

    PHYSICAL REVIEW B   95 ( 7 )   075120-1 - 075120-6   2017.2

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    We successfully synthesized single crystals of the verdazyl radical 2-Cl-3,6-F-2-V [=3-(2-chloro-3,6-difluorophenyl)-1,5-diphenylverdazyl], which is a rare model compound with an S = 1/2 Heisenberg antiferromagnetic (HAF) honeycomb lattice. Ab initio molecular orbital calculations indicate two dominant AF interactions, forming a slightly distorted honeycomb lattice. We explain the magnetic susceptibility and the magnetization curve up to the saturation field based on the expected spin model using the quantum Monte Carlo method. In the low-temperature regions, we found a phase transition to an AF ordered state at about 0.77 K for the zero field and obtained the magnetic field-temperature phase diagram from the magnetic susceptibility and the specific heat for various magnetic fields. Through the analysis considering the effect of lattice distortion on magnetic behavior, we confirm that the lattice distortion of the present model is small enough that it does not affect the intrinsic behavior of the uniform S = 1/2 HAF honeycomb lattice.

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  • Angle-resolved heat capacity of heavy fermion superconductors Reviewed

    Toshiro Sakakibara, Shunichiro Kittaka, Kazushige Machida

    REPORTS ON PROGRESS IN PHYSICS   79 ( 9 )   094002-1 - 094002-19   2016.9

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    Owing to a strong Coulomb repulsion, heavy electron superconductors mostly have anisotropic gap functions which have nodes for certain directions in the momentum space. Since the nodal structure is closely related to the pairing mechanism, its experimental determination is of primary importance. This article discusses the experimental methods of the gap determination by bulk heat capacity measurements in a rotating magnetic field. The basic idea is based on the fact that the quasiparticle density of states in the vortex state of nodal superconductors is field and direction dependent. We present our recent experimental results of the field-orientation dependence of the heat capacity in heavy fermion superconductors CeTIn5 (T = Co, Ir), UPt3, CeCu2Si2, and UBe13 and discuss their gap structures.

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  • Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2 Reviewed

    Shunichiro Kittaka, Yuya Aoki, Yasuyuki Shimura, Toshiro Sakakibara, Silvia Seiro, Christoph Geibel, Frank Steglich, Yasumasa Tsutsumi, Hiroaki Ikeda, Kazushige Machida

    PHYSICAL REVIEW B   94 ( 5 )   054514-1 - 054514-9   2016.8

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    This paper presents the results of specific-heat and magnetization measurements, in particular their field-orientation dependence, on the first discovered heavy-fermion superconductor CeCu2Si2 (T-c similar to 0.6K). We discuss the superconducting gap structure and the origin of the anomalous pair-breaking phenomena, leading, e.g., to the suppression of the upper critical field H-c2, found in the high-field region. The data show that the anomalous pair breaking becomes prominent below about 0.15 K in any field direction, but occurs closer to H-c2 for H parallel to c. The presence of this anomaly is confirmed by the fact that the specific-heat and magnetization data satisfy standard thermodynamic relations. Concerning the gap structure, field-angle dependencies of the low-temperature specific heat within the ab and ac planes do not show any evidence for gap nodes. From microscopic calculations in the framework of a two-band full-gap model, the power-law-like temperature dependencies of C and 1/T-1, reminiscent of nodal superconductivity, have been reproduced reasonably. These facts further support multiband full-gap superconductivity in CeCu2Si2.

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  • Quadrupole-driven non-Fermi-liquid and magnetic-field-induced heavy fermion states in a non-Kramers doublet system Reviewed

    T. Onimaru, K. Izawa, K. T. Matsumoto, T. Yoshida, Y. Machida, T. Ikeura, K. Wakiya, K. Umeo, S. Kittaka, K. Araki, T. Sakakibara, T. Takabatake

    PHYSICAL REVIEW B   94 ( 7 )   075134-1 - 075134-8   2016.8

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    Orbital degrees of freedom in condensed matter could play important roles in forming a variety of exotic electronic states by interacting with conduction electrons. In 4f-electron systems, because of strong intra-atomic spin-orbit coupling, an orbitally degenerate state inherently carries quadrupolar degrees of freedom. The present work has focused on a purely quadrupole-active system PrIr2Zn20 showing superconductivity in the presence of an antiferroquadrupole order at T-Q = 0.11 K. We observed non-Fermi-liquid (NFL) behaviors emerging in the electrical resistivity rho and the 4f contribution to the specific heat, C-4f, in the paramagnetic state at T &gt; T-Q. Moreover, in magnetic fields B &lt;= 6 T, all data sets of rho(T) and C-4f (T) are well scaled with characteristic temperatures T-0's. This observation of the NFL state in the nonmagnetic quadrupole-active system has an origin intrinsically different from that observed in the vicinity of the conventional quantum critical point. It implies possible formation of a quadrupole Kondo lattice resulting from hybridization between the quadrupoles and the conduction electrons with an energy scale of k(B)T(0). At T &lt;= 0.13 K, rho(T) and C-4f (T) exhibit anomalies as B approaches 5 T. This is the manifestation of a field-induced crossover toward a Fermi-liquid ground state in the quadrupole Kondo lattice.

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  • Comparison With Ground States of Frustrated Quantum Spin Chain Systems A(2)Cu(2)Mo(3)O(12) (A = Rb and Cs) Reviewed

    Akio Fujimura, Yukio Yasui, Yudai Yanagisawa, Ichiro Terasaki, Yohei Kono, Shunichiro Kittaka, Toshiro Sakakibara

    IEEE TRANSACTIONS ON MAGNETICS   52 ( 7 )   1100503-1 - 1100503-3   2016.7

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    We have measured the magnetic and thermal properties below 2 K of a quasi-1-D frustrated spin-1/2 system Cs2Cu2Mo3O12 called CuO2 ribbon chain systems in order to investigate its magnetic ground state. In the temperature dependence of the specific heat divided by temperature, C/T-T, we found a sharp peak structure at T-N = 1.85 K, which indicates the existence of a phase transition. Considering the behavior of the magnetization and specific heat, it is found that Cs2Cu2Mo3O12 exhibits an antiferromagnetic transition at TN = 1.85 K, and its magnetic ground state is an antiferromagnetic long-range ordered one. The determined ground state of Cs2Cu2Mo3O12 significantly contrasts with a nonmagnetic ground state of isostructural compound Rb2Cu2Mo3O12. We discuss the origins of difference of the magnetic ground states between Rb2Cu2Mo3O12 and Cs2Cu2Mo3O12.

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  • Omnidirectional Measurements of Angle-Resolved Heat Capacity for Complete Detection of Superconducting Gap Structure in the Heavy-Fermion Antiferromagnet UPd2Al3 Reviewed

    Yusei Shimizu, Shunichiro Kittaka, Toshiro Sakakibara, Yasumasa Tsutsumi, Takuya Nomoto, Hiroaki Ikeda, Kazushige Machida, Yoshiya Homma, Dai Aoki

    PHYSICAL REVIEW LETTERS   117 ( 3 )   037001-1 - 037001-5   2016.7

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    Quasiparticle excitations in UPd2Al3 were studied by means of heat-capacity (C) measurements under rotating magnetic fields using a high-quality single crystal. The field dependence shows C(H) proportional to H-1/2-like behavior at low temperatures for both two hexagonal crystal axes, i. e., H parallel to[0001] (c axis) and H parallel to[1120] (a axis), suggesting the presence of nodal quasiparticle excitations from heavy bands. At low temperatures, the polar-angle (theta) dependence of C exhibits a maximum along H parallel to[0001] with a twofold symmetric oscillation below 0.5 T, and an unusual shoulder or hump anomaly has been found around 30 degrees-60 degrees from the c axis in C(theta) at intermediate fields (1 less than or similar to mu(0) less than or similar to 2 T). These behaviors in UPd2Al3 purely come from the superconducting nodal quasiparticle excitations, and can be successfully reproduced by theoretical calculations assuming the gap symmetry with a horizontal linear line node. We demonstrate the whole angle-resolved heat-capacity measurements done here as a novel spectroscopic method for nodal gap determination, which can be applied to other exotic superconductors.

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  • Quadrupole Order in the Frustrated Pyrochlore Tb2+xTi2-xO7+y Reviewed

    H. Takatsu, S. Onoda, S. Kittaka, A. Kasahara, Y. Kono, T. Sakakibara, Y. Kato, B. Fak, J. Ollivier, J. W. Lynn, T. Taniguchi, M. Wakita, H. Kadowaki

    PHYSICAL REVIEW LETTERS   116 ( 21 )   217201-1 - 217201-6   2016.5

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    A hidden order that emerges in the frustrated pyrochlore Tb2+xTi2-xO7+y with T-c = 0.53 K is studied using specific heat, magnetization, and neutron scattering experiments on a high-quality single crystal. Semiquantitative analyses based on a pseudospin-1/2 Hamiltonian for ionic non-Kramers magnetic doublets demonstrate that it is an ordered state of electric quadrupole moments. The elusive spin liquid state of the nominal Tb2Ti2O7 is most likely a U(1) quantum spin-liquid state.

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  • Ferromagnetic ordered phase of quantum spin ice system Yb2Ti2O7 under [001] magnetic field Reviewed

    Noriaki Hamachi, Yukio Yasui, Koji Araki, Shunichiro Kittaka, Toshiro Sakakibara

    AIP ADVANCES   6 ( 5 )   055707-1 - 055707-6   2016.5

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    Measurements of magnetization (M) and specific heat (C) under a [001] magnetic field were carried out on a single crystal of a quantum spin ice system Yb2Ti2O7 in order to investigate a feature of the transition occurred at T-C similar to 0.2 K. As a result of applying the magnetic field mu H-0 &lt; 0.1 T, the C/T-T curve structure and transition temperature barely changed. On the other hand, applying the more than 0.1 T magnetic field, the C/T-T curve structure drastically change from sharp peak structure to broad peak one, and the broad peak temperature of C/T-T curves linearly increases with increasing magnetic field (H). In the magnetic field mu H-0 &lt; 0.1 T, the magnetization drastically increases around T-C similar to 0.2 K with decreasing T, and a thermal hysteresis loop of the M-T curve is observed. With increasing H, the thermal hysteresis loop of the M-T curves disappears above mu H-0(C) = 0.1 T. We can understand these results, where Yb2Ti2O7 exhibits a first-order ferromagnetic transition associated with the latent heat corresponding to the energy of mu H-0(C) = 0.1 T. Basis of the H-T phase diagram along [001] magnetic field, the feature of the transition occurred at T-C similar to 0.2 K in quantum spin ice system Yb2Ti2O7 is discussed. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

    DOI: 10.1063/1.4944337

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  • Unconventional S=2 alternating chain realized by a metal-radical hybrid-spin approach Reviewed

    H. Yamaguchi, Y. Shinpuku, Y. Kono, S. Kittaka, T. Sakakibara, M. Hagiwara, T. Kawakami, K. Iwase, T. Ono, Y. Hosokoshi

    PHYSICAL REVIEW B   93 ( 11 )   115145-1 - 115145-7   2016.3

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    We demonstrate an advanced spin-system design using a hybrid spin consisting of a strongly coupled metal ion and verdazyl radical. Ab initio calculation, magnetization, and ESR measurements evidenced the first realization of an S = 2 ferromagnetic-antiferromagnetic alternating chain with Ising anisotropy in a Mn-verdazyl complex [Mn(hfac)(2)]center dot(o-Py-V) [hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate; o-Py-V = 3-(2-pyridyl)-1,5-diphenylverdazyl]. Furthermore, we find an anomalous change in magnetization at 1/4 of the saturation value, which is probably a manifestation of the quantum nature of the system.

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  • Evidence for Chiral d-Wave Superconductivity in URu2Si2 from the Field-Angle Variation of Its Specific Heat Reviewed

    Shunichiro Kittaka, Yusei Shimizu, Toshiro Sakakibara, Yoshinori Haga, Etsuji Yamamoto, Yoshichika Onuki, Yasumasa Tsutsumi, Takuya Nomoto, Hiroaki Ikeda, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   85 ( 3 )   033704-1 - 033704-4   2016.3

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    Low-energy quasiparticle (QP) excitations in the heavy-fermion superconductor URu2Si2 were investigated by specific-heat C(T, H, phi, theta) measurements of a high-quality single crystal. The occurrence of QP excitations due to the Doppler-shift effect was detected regardless of the field direction in C(H) of the present clean sample, which is in sharp contrast to a previous report. Furthermore, the polar-angle-dependent C(theta) measured under a rotating magnetic field within the ac plane exhibits a shoulder-like anomaly at theta similar to 45 degrees and a sharp dip at theta = 90 degrees (H || a) in the moderate-field region. These features are supported by theoretical analyses based on microscopic calculations assuming the gap symmetry of k(z)(k(x) + ik(y)), whose gap structure is characterized by a combination of a horizontal line node at the equator and point nodes at the poles. The present results have settled the previous controversy over the gap structure of URu2Si2 and have authenticated its chiral d-wave superconductivity.

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  • Heat capacity measurements on UB13 in rotated magnetic fields: Anisotropic response in the normal state and absence of nodal quasiparticles Reviewed

    Yusei Shimizu, Shunichiro Kittaka, Toshiro Sakakibara, Yoshinori Haga, Etsuji Yamamoto, Hiroshi Amitsuka, Yasumasa Tsutsumi, Kazushige Machida

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   400   52 - 55   2016.2

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    In order to gain insight into the superconducting (SC) gap of UBe13, we studied its quasiparticle excitations by means of heat-capacity measurements. Quite unexpectedly, we found the isotropic C(H) alpha H behavior in low fields at low temperatures, implying the absence of nodal quasiparticle excitations. This result indicates that the SC gap in UBe13 is fully open over the Fermi surfaces. Furthermore, we observed a characteristic oscillation of heat capacity both in the SC and non-Fermi-liquid normal states above similar to 2 T, and the angular variation of heat capacity possibly originates from anisotropic magnetic response of the heavy-electron state. Our result regarding the low-energy quasiparticle excitations in the SC and normal states will be a clue to understand the unusual nature of UBe13. (C) 2015 Elsevier BY. All rights reserved.

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  • Possible observation of highly itinerant quantum magnetic monopoles in the frustrated pyrochlore Yb2Ti2O7 Reviewed

    Y. Tokiwa, T. Yamashita, M. Udagawa, S. Kittaka, T. Sakakibara, D. Terazawa, Y. Shimoyama, T. Terashima, Y. Yasui, T. Shibauchi, Y. Matsuda

    NATURE COMMUNICATIONS   7   10807-1 - 10807-6   2016.2

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    The low-energy elementary excitations in frustrated quantum magnets have fascinated researchers for decades. In frustrated Ising magnets on a pyrochlore lattice possessing macroscopically degenerate spin-ice ground states, the excitations have been discussed in terms of classical magnetic monopoles, which do not contain quantum fluctuations. Here we report unusual behaviours of magneto-thermal conductivity in the disordered spin-liquid regime of pyrochlore Yb2Ti2O7, which hosts frustrated spin-ice correlations with large quantum fluctuations owing to pseudospin-1/2 of Yb ions. The analysis of the temperature and magnetic field dependencies shows the presence of gapped elementary excitations. We find that the gap energy is largely suppressed from that expected in classical monopoles. Moreover, these excitations propagate a long distance without being scattered, in contrast to the diffusive nature of classical monopoles. These results suggests the emergence of highly itinerant quantum magnetic monopole, which is a heavy quasiparticle that propagates coherently in three-dimensional spin liquids.

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  • First-order superconducting transition of Sr2RuO4 investigated by magnetization and magnetic torque Reviewed

    Shunichiro Kittaka, Akira Kasahara, Toshiro Sakakibara, Daisuke Shibata, Shingo Yonezawa, Yoshiteru Maeno, Kenichi Tenya, Kazushige Machida

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   400   81 - 83   2016.2

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    The first-order superconducting transition, recently discovered in a long-standing candidate for a spin-triplet chiral-p-wave superconductor Sr2RuO4, is mysterious because it is not expected within the present scenario of spin-triplet superconductivity. To uncover its mechanism, we have measured the magnetization and the magnetic torque using an ultra-clean single crystal of Sr2RuO4 down to 0.1 K. In this study, the magnetic-field orientation has been controlled with a high precision within the accuracy of 0.01 degrees. We observed a sharp magnetization jump of as large as 0.01 emu/g with a field hysteresis of 100 Oe at 0.1 K. With increasing temperature, this magnetization jump decreases and diminishes above 0.8 K. The magnetic torque indicates that the first-order transition occurs only when the magnetic field is applied close to the ab plane within 2 degrees deviation. These features of the first-order transition provide the keystone issues whose resolution is crucial in uncovering a "hidden" pair-breaking mechanism within the triplet-pairing scenario, or might urge the reconsideration of the order parameter in Sr2RuO4. (C) 2015 Elsevier B.V. All rights reserved.

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  • Field-induced phase transitions and magnetoferroelectricity in the perfect triangular lattice antiferromagnet RbFe(MoO4)(2) in a vertical magnetic field Reviewed

    Hiroyuki Mitamura, Ryuta Watanuki, Norimichi Onozaki, Yuta Amou, Yohei Kono, Shunichiro Kittaka, Yasuyuki Shimura, Isao Yamamoto, Kazuya Suzuki, Toshiro Sakakibara

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   400   70 - 72   2016.2

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    We performed electric polarization P, dielectric constant epsilon and magnetization M measurements on the perfect triangular-lattice antiferromagnet RbFe(MoO4)(2) in high magnetic fields B applied along the c-axis. Whereas M(B) at T=1.5 K monotonically increases with B up to the saturation at B-s = 21 T, P(B) disappears about 14 T, far below the saturation point. In a field range 13 &lt;= B &lt;= 14T, the temperature variation of e shows a double peak structure below 2.8 K, indicating two successive transitions. These results strongly suggest the presence of a new high-field phase; the magnetic structure changes from a low-field conical state having chirality to a high-field coplanar non-collinear structure without chirality. The obtained phase diagram is in agreement with a theoretical prediction on XY-like Heisenberg spin triangular lattice antiferromagnets. (C) 2015 Elsevier B.V. All rights reserved.

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  • The heavy fermion state in hexagonal Ce2Pt6Ga15

    Matsumoto Yuji, Ueda Takuya, Ohara Shigeo, Kono Yohei, Nakamura Shota, Kittaka Shunichiro, Sakakibara Toshiro, Uwatoko Yoshiya

    Meeting Abstracts of the Physical Society of Japan   71   2208 - 2208   2016

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  • 21aBD-11 Field-induced Quantum Critical Phenomena in Spin-1/2 Organic Ferro-leg Ladders

    Kono Y., Kittaka S., Yamaguchi H., Hosokoshi Y., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   71   1229 - 1229   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_1229

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  • 20pPSB-25 Development of the apparatus to measure the field-angle-resolved specific heat under pressure for the study of superconducting gap structure

    Kittaka S., Matsubayashi K., Uwatoko Y., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   71   2128 - 2128   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_2128

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  • 22pBM-3 Specific heat of Sr_2RuO_4 under uniaxial pressure

    Yamazaki T., Kittaka S., Ito A., Sakakibara T., Yaguchi H.

    Meeting Abstracts of the Physical Society of Japan   71   2460 - 2460   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_2460

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  • 19aPS-42 Magnetic Behavior and Magnetic Structure of CuO_2 Ribbon System A_2Cu_2Mo_3O_<12>(A=Rb, Cs)

    Fujimura A., Yasui Y., Kono Y., Kittaka S., Sakakibara T., Igawa N., Matsukawa T., Yoshida Y., Hoshikawa A., Ishigaki T.

    Meeting Abstracts of the Physical Society of Japan   71   1049 - 1049   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_1049

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  • 19aPS-56 Low temperature physical property of honeycomb lattice antiferromagnetic 2-Cl-3,6-F_2-V

    Okabe T., Yamaguchi H., Ono T., Hosokoshi Y., Kittaka S., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   71   1063 - 1063   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_1063

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  • 19aBL-6 Low-temperature heat capacity in the heavy-fermion superconductor Ube_<13> under high magnetic fields

    Shimizu Y., Kittaka S., Kono Y., Sakakibara T., Haga Y., Yamamoto E., Amitsuka H., Machida K.

    Meeting Abstracts of the Physical Society of Japan   71   1963 - 1963   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_1963

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  • 19aPS-70 Magnetic property of quantum spin ice system Yb_2Ti_2O_7

    Hamachi N., Yasui Y., Kono Y., Kittaka S., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   71   1076 - 1076   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_1076

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  • Low-temperature high-sensitivity magnetization for the non-Fermi-liquid heavy-fermion superconductor UBe13

    Shimizu Y., Kono Y., Kittaka S., Haga Y., Yamamoto E., Amitsuka H., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   71   1754 - 1754   2016

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  • Field-angle-dependent specific heat of a superconductor Zr2Co

    Kittaka Shunichiro, Sakakibara Toshiro, Kakihana Masashi, Teruya Atsushi, Hedo Masato, Nakama Takao, Onuki Yoshichika

    Meeting Abstracts of the Physical Society of Japan   71   2236 - 2236   2016

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  • Magnetization Measurements of URhGe in Magnetic Feilds along the Hard Axis

    Nakamura Shota, Kono Yohei, Kittaka Shunichiro, Sakakibara Toshiro, Shimizu Yusei, Haga Yoshinori, Pospíšil Jiří, Yamamoto Etsuji

    Meeting Abstracts of the Physical Society of Japan   71   1759 - 1759   2016

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  • High-sensitivity dc magnetization study for the heavy-fermion antiferromagnetic superconductor UPd2Al3 at very low temperatures

    Shimizu Y., Kittaka S., Kono Y., Nakamura S., Sakakibara T., Aoki D.

    Meeting Abstracts of the Physical Society of Japan   71   1753 - 1753   2016

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  • Study of superconducting gap structure in the heavy fermion superconductor CeCu2Si2 by thermal conductivity measurements and pair breaking effect

    Onishi Takafumi, Terazawa Daiki, Yamashita Takuya, Tokiwa Yoshi, Kittaka Shunichiro, Sakakibara Toshiro, Jeevan H. S., Ceibel C., Konczykowski M., Haga Yoshinori, Mizukami Yuta, Shibauchi Takasada, Terashima Takahito, Matsuda Yuji

    Meeting Abstracts of the Physical Society of Japan   71   2006 - 2006   2016

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  • Quadrupole order in the frustrated pyrochlore magnet Tb2Ti2O7 Reviewed

    H. Takatsu, T. Taniguchi, S. Kittaka, T. Sakakibara, H. Kadowaki

    TMU INTERNATIONAL SYMPOSIUM ON NEW QUANTUM PHASES EMERGING FROM NOVEL CRYSTAL STRUCTURE   683   012022-1 - 012022-6   2016

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    We have studied the hidden long-range order (LRO) of the frustrated pyrochlore magnet Tb2Ti2O7 by means of specific-heat experiments and Monte-Carlo (MC) simulations, which has been discussed as the LRO of quadrupole moments inherent to the non-Kramers ion of Tb3+. We have found that the sharp specific-heat peak is collapsed into a broad hump by magnetic fields above 0.3 T for H//[001]. This result, qualitatively reproduced by MC simulations, suggests that a field-induced magnetic state overcomes the quadrupolar LRO state, as a similar case of a classical spin ice. The present results support the interpretation that Tb2+xTi2-xO7+y is a unique material in the boundary between the quadrupolar (x &gt;= x(c) = -0.0025) and spin-liquid (x &lt;= x(c)) states, where the magnetic field along the [001] axis is a tuning parameter which induces the magnetic ordered state.

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  • Experimental Realization of a Quantum Pentagonal Lattice Reviewed

    Hironori Yamaguchi, Tsuyoshi Okubo, Shunichiro Kittaka, Toshiro Sakakibara, Koji Araki, Kenji Iwase, Naoki Amaya, Toshio Ono, Yuko Hosokoshi

    SCIENTIFIC REPORTS   5   15327-1 - 15327-6   2015.10

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    Geometric frustration, in which competing interactions give rise to degenerate ground states, potentially induces various exotic quantum phenomena in magnetic materials. Minimal models comprising triangular units, such as triangular and Kagome lattices, have been investigated for decades to realize novel quantum phases, such as quantum spin liquid. A pentagon is the second-minimal elementary unit for geometric frustration. The realization of such systems is expected to provide a distinct platform for studying frustrated magnetism. Here, we present a spin-1/2 quantum pentagonal lattice in the new organic radical crystal alpha-2,6-Cl-2-V [=alpha-3-(2,6-dichlorophenyl)-1,5-diphenylverdazyl]. Its unique molecular arrangement allows the formation of a partially corner-shared pentagonal lattice (PCPL). We find a clear 1/3 magnetization plateau and an anomalous change in magnetization in the vicinity of the saturation field, which originate from frustrated interactions in the PCPL.

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  • First-Order Ferromagnetic Transition of Quantum Spin Ice System Yb2Ti2O7 Reviewed

    Yukio Yasui, Noriaki Hamachi, Yohei Kono, Shunichiro Kittaka, Toshiro Sakakibara

    SPIN   5 ( 2 )   1540002-1 - 1540002-6   2015.6

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    The neutron diffraction and measurements of specific heat and magnetization were carried out on single crystals of a quantum spin ice system Yb2Ti2O7. The thermal hysteresis loops of temperature dependence of the magnetization and neutron diffraction intensity indicate a first-order ferromagnetic transition, where the used single crystals are confirmed to have a sharp peak structure in the specific heat (C)-temperature (T) curve at T-C similar to 0.2 K. The magnetic structure analysis of neutron diffraction results revealed that the Yb3+ moments have a ferromagnetic collinear structure along [001] directions with ordered moment value 1.1 +/- 0.1 mu(B) at 0.03 K. The mechanism of ferromagnetic transition of Yb2Ti2O7 will be discussed.

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  • Field-Orientation Dependence of Low-Energy Quasiparticle Excitations in the Heavy-Electron Superconductor UBe13 Reviewed

    Yusei Shimizu, Shunichiro Kittaka, Toshiro Sakakibara, Yoshinori Haga, Etsuji Yamamoto, Hiroshi Amitsuka, Yasumasa Tsutsumi, Kazushige Machida

    PHYSICAL REVIEW LETTERS   114 ( 14 )   147002-1 - 147002-6   2015.4

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    Low-energy quasiparticle excitations in the superconducting (SC) state of UBe13 were studied by means of specific-heat (C) measurements in a rotating field. Quite unexpectedly, the magnetic-field dependence of C(H) is linear in H with no angular dependence at low fields in the SC state, implying that the gap is fully open over the Fermi surfaces, in stark contrast to previous expectations. In addition, a characteristic cubic anisotropy of C(H) was observed above 2 T with a maximum (minimum) for H parallel to[001] ([111]) within the (1 (1) over bar0) plane, in the normal as well as in the SC states. This oscillation possibly originates from the anisotropic response of the heavy quasiparticle bands, and might be a key to understand the unusual properties of UBe13

    DOI: 10.1103/PhysRevLett.114.147002

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  • Quantum phase near the saturation field in the S=1/2 frustrated spin ladder Reviewed

    H. Yamaguchi, H. Miyagai, Y. Kono, S. Kittaka, T. Sakakibara, K. Iwase, T. Ono, T. Shimokawa, Y. Hosokoshi

    PHYSICAL REVIEW B   91 ( 12 )   125104-1 - 125104-5   2015.3

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    We present low-temperature specific heat and magnetization measurements of the S = 1/2 organic spin ladder 3-I-V [3-(3-iodophenyl)-1,5-diphenylverdazyl]. Ab initio molecular orbital calculations indicate the existence of an intraladder diagonal interaction J(diag) and three types of interladder interactions. The ferromagnetic J(diag) induces frustration in the spin ladder, which has an essential contribution to the ground state. The obtained phase diagram exhibits a low-field three-dimensional order and a nontrivial phase near the saturation field. The absence of successive phase transition with decreasing temperature and the anomalous behavior of the magnetization curve near the saturation field suggest that these two phases are longitudinal spin-density-wave and spin-multipolar orders, respectively.

    DOI: 10.1103/PhysRevB.91.125104

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  • S=1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain in a zinc-verdazyl complex Reviewed

    Hironori Yamaguchi, Yasuhiro Shinpuku, Tokuro Shimokawa, Kenji Iwase, Toshio Ono, Yohei Kono, Shunichiro Kittaka, Toshiro Sakakibara, Yuko Hosokoshi

    PHYSICAL REVIEW B   91 ( 8 )   085117-1 - 085117-6   2015.2

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    We successfully synthesized the zinc-verdazyl complex [Zn(hfac)(2)]center dot(o-Py-V) [hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate; o-Py-V = 3-(2-pyridyl)-1,5-diphenylverdazyl], which is an ideal model compound with an S = 1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain (F-AF AHC). Ab initio molecular-orbital (MO) calculations indicate that two dominant interactions J(F) and J(AF) form the S = 1 2 F-AF AHC in this compound. The magnetic susceptibility and magnetic specific heat of the compound exhibit thermally activated behavior below approximately 1 K. Furthermore, its magnetization curve is observed up to the saturation field and directly indicates a zero-field excitation gap of 0.5 T. These experimental results provide evidence for the existence of a Haldane gap. We successfully explain the results in terms of the S = 1 2 F-AF AHC through quantum Monte Carlo calculations with vertical bar J(AF)/J(F)vertical bar = 0.22. The ab initio MO calculations also indicate a weak AF interchain interaction J' and that the coupled F-AF AHCs form a honeycomb lattice. The J' dependence of the Haldane gap is calculated, and the actual value of J' is determined to be less than 0.01 vertical bar J(F)vertical bar.

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  • 16aDA-5 Quasiparticle Excitations of the Antiferromagnetic Heavy-Fermion Superconductor UPd_2Al_3 Probed by Specific-Heat Measurements

    Shimizu Y., Kittaka S., Sakakibara T., Tsutsumi Y., Machida K., Homma Y., Aoki D.

    Meeting Abstracts of the Physical Society of Japan   70   1668 - 1668   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_1668

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  • 16aPS-51 Low-temperature physical properties of new metal-verdazyl complexs

    Okada M., Yamaguchi H., Ono T., Hosokoshi Y., Kono Y., Kittaka S., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   70   756 - 756   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_756

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  • 16aDA-2 Low-temperature specific heat of a clean single crystal URu_2Si_2 under magnetic field

    Kittaka S., Shimizu Y., Sakakibara T., Haga Y., Yamamoto E., Onuki Y., Tsutsumi Y., Machida K.

    Meeting Abstracts of the Physical Society of Japan   70   1665 - 1665   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_1665

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  • 17aDA-10 Study of superconducting gap structure in the heavy fermion superconductor CeCu_2Si_2 by thermal conductivity measurements

    Terazawa D., Yamashita T., Tokiwa Y., Kittaka S., Sakakibara T., JEEVAN H. S., GEIBEL C., Haga Y., Terashima T., Matsuda Y.

    Meeting Abstracts of the Physical Society of Japan   70   1771 - 1771   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_1771

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  • 21pPSA-52 Low temperature physical property of charge-transfer complex consisting of verdazyl radical and TCNQ

    Sasaki Y., Yamaguchi H., Ono T., Hosokoshi Y., Kono Y., Kittaka S., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   70   1122 - 1122   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_1122

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  • 22aPS-118 Singlet ground state in tetragonal PrZn_<11>

    Ninomiya Hiroki, Sato Takaaki, Matsumoto Yuji, Ohara Shigeo, Kono Yohei, Kittaka Shunichiro, Sakakibara Toshiro

    Meeting Abstracts of the Physical Society of Japan   70   2207 - 2207   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_2207

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  • 24aBE-11 Magnetic Response of the Heavy-Electron Compound UBe_<13> : Normal-State Magnetization in High-Field Region and Magnetic Anomaly in Superconducting Mixed State

    Shimizu Y., Kono Y., Sakakibara T., Kittaka S., Haga Y., Yamamoto E., Amitsuka H.

    Meeting Abstracts of the Physical Society of Japan   70   2350 - 2350   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_2350

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  • 21aBB-2 Temperature dependences of the specific heat and the nuclear relaxation rate in heavy-fermion superconductors CeCu_2Si_2 and UBe_<13> : Evaluation of multiband full-gap superconductivity

    Kittaka S., Tsutsumi Y., Shimizu Y., Sakakibara T., Ikeda H., Machida K.

    Meeting Abstracts of the Physical Society of Japan   70   1947 - 1947   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_1947

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  • 24aBJ-11 Investigation of the long-range order of Tb_<2+x>Ti_<2-x>O_<7+y> by means of magnetization measurements

    Takatsu H., Wakita M., Taniguchi T., Kadowaki H., Kasahara A., Kono Y., Kittaka S., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   70   1240 - 1240   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_1240

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  • 21aAH-1 Magnetic phase diagrams of Cs_2Cu_2Mo_3O_<12> below 2K with CuO_2 ribbon chains

    Fujimura A., Yasui Y., Igawa N., Yoshida Y., Ishigaki T., Kono Y., Kittaka S., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   70   967 - 967   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_967

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  • Low Temperature Magnetic Properties of a New Quasi-one-dimensional Organic Magnet alpha-2-Cl-4-F-V Reviewed

    Yohei Kono, Shunichiro Kittaka, Hironori Yamaguchi, Yuko Hosokoshi, Toshiro Sakakibara

    20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015   75   679 - 686   2015

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    We examine low-temperature magnetic properties of a new verdazyl radical crystal alpha-2-Cl-4-FV. Molecular orbital calculations predict that this material is a spin-1/2 quasi-one-dimensional antiferromagnet; the exchange interaction is strongest in the chains along the b axis, whereas there are three interchain coupling parameters, the ratio of which are 0.06 similar to 0.14 to the intrachain. The magnetization curve at 0.1 K shows gapless behavior like conventional one-dimensional quantum spin systems and saturates at about 5 T. A peak is observed in the temperature dependence of the heat capacity at 0 T, indicating that a three-dimensional ordering occurs at about 0.2 K. On the other hand, the temperature dependence of the magnetization at various magnetic fields shows an anomaly similar to that observed in many of gapped spin systems. This behavior is attributed to the highly frustrated nature of the interchain interactions.

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  • Antiferromagnetic transition of the caged compound TmTi2Al20 Reviewed

    Naoki Kase, Yasuyuki Shimura, Shunichiro Kittaka, Toshiro Sakakibara, Satoru Nakatsuji, Tomohito Nakano, Naoya Takeda, Jun Akimitsu

    INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS 2014 (SCES2014)   592   012052-1 - 012052-5   2015

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    We examined the low temperature magnetic properties of a single crystal of TmTi2Al20, a hole analogue of PrTi2Al20, by means of specific heat C(T) and magnetization M(T, H) measurements. At low field, an anomaly that can be ascribed to an antiferromagnetic ordering is observed in M(T) at T-N = 0.7 K. C(T) shows a very sharp lambda-type anomaly at 0.7 K, confirming the phase transition. From the calculated magnetic entropy S(T), we found that the ground state of TmTi2Al20 is likely to be a magnetic Gamma(5) triplet in the J = 6 multiplet.

    DOI: 10.1088/1742-6596/592/1/012052

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  • 16aPS-45 Study of Quantum Criticality in Ferro-leg Ladders of Verdazyl Radical Crystals

    Kono Y., Kittaka S., Yamaguchi H., Hosokoshi Y., Sakakibara T.

    Meeting Abstracts of the Physical Society of Japan   70   750 - 750   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_750

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  • Sharp magnetization jump at the first-order superconducting transition in Sr2RuO4 Reviewed

    Shunichiro Kittaka, Akira Kasahara, Toshiro Sakakibara, Daisuke Shibata, Shingo Yonezawa, Yoshiteru Maeno, Kenichi Tenya, Kazushige Machida

    PHYSICAL REVIEW B   90 ( 22 )   220502(R)-1 - 220502(R)-5   2014.12

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    The magnetization and magnetic torque of a high-quality single crystal of Sr2RuO4 have been measured down to 0.1 K under precise control of the magnetic-field orientation. When the magnetic field is applied exactly parallel to the ab plane, a sharp magnetization jump 4 pi delta M of (0.74 +/- 0.15) G at the upper critical field H-c2,H-ab similar to 15 kOe with a field hysteresis of 100 Oe is observed at low temperatures, evidencing a first-order superconducting-normal transition. A strong magnetic torque appearing when H is slightly tilted away from the ab plane confirms an intrinsic anisotropy Gamma = xi(a)/xi(c) of as large as 60 even at 100 mK, in contrast with the observed H-c2 anisotropy of similar to 20. The present results raise fundamental issues in both the existing spin-triplet and spin-singlet scenarios, providing, in turn, crucial hints toward the resolution of the superconducting nature of Sr2RuO4.

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  • Spin-Chirality-Driven Ferroelectricity on a Perfect Triangular Lattice Antiferromagnet Reviewed

    H. Mitamura, R. Watanuki, K. Kaneko, N. Onozaki, Y. Amou, S. Kittaka, R. Kobayashi, Y. Shimura, I. Yamamoto, K. Suzuki, S. Chi, T. Sakakibara

    PHYSICAL REVIEW LETTERS   113 ( 14 )   147202-1 - 147202-5   2014.10

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    Magnetic field (B) variation of the electrical polarization P-c (parallel to c) of the perfect triangular lattice antiferromagnet RbFe(MoO4)(2) is examined up to the saturation point of the magnetization for B perpendicular to c.P-c is observed only in phases for which chirality is predicted in the in-plane magnetic structures. No strong anomaly is observed in P-c at the field at which the spin modulation along the c axis, and hence the spin helicity, exhibits a discontinuity to the commensurate state. These results indicate that the ferroelectricity in this compound originates predominantly from the spin chirality, the explanation of which would require a new mechanism for magnetoferroelectricity. The obtained field-temperature phase diagram of ferroelectricity agree well with those theoretically predicted for the spin chirality of a Heisenberg spin triangular lattice antiferromagnet.

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  • Anisotropic Superconductivity of the Caged Compound Y5Rh6Sn18 with Unusual Normal-State Electrical Resistivity Reviewed

    Kase Naoki, Kittaka Shunichiro, Sakakibara Toshiro, Akimitsu Jun

    JPS CONFERENCE PROCEEDINGS   3   015042-1 - 015042-5   2014.6

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    DOI: 10.7566/JPSCP.3.015042

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  • Field-induced incommensurate phase in the strong-rung spin ladder with ferromagnetic legs Reviewed

    H. Yamaguchi, H. Miyagai, M. Yoshida, M. Takigawa, K. Iwase, T. Ono, N. Kase, K. Araki, S. Kittaka, T. Sakakibara, T. Shimokawa, T. Okubo, K. Okunishi, A. Matsuo, Y. Hosokoshi

    PHYSICAL REVIEW B   89 ( 22 )   220402(R)-1 - 220402(R)-5   2014.6

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    We report magnetization, specific heat, and NMR measurements of 3-Br-4-F-V [=3-(3-bromo-4-fluorophenyl)-1,5-diphenylverdazyl], a strong-rung S = 1/2 Heisenberg spin ladder with ferromagnetic leg interactions. We explain the magnetic and thermodynamic properties based on the strong-rung regime. Furthermore, we find a field-induced successive phase transition in the specific heat and the nuclear spin-lattice relaxation rate 1/T-1. F-19-NMR spectra for higher-and lower-temperature phases indicate partial magnetic order and incommensurate long-range order, respectively, evidencing the presence of frustration due to weak interladder couplings.

    DOI: 10.1103/PhysRevB.89.220402

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  • Fine-Tuning of Magnetic Interactions in Organic Spin Ladders Reviewed

    Hironori Yamaguchi, Hirotsugu Miyagai, Tokuro Shimokawa, Kenji Iwase, Toshio Ono, Yohei Kono, Naoki Kase, Koji Araki, Shunichiro Kittaka, Toshiro Sakakibara, Takashi Kawakami, Kouichi Okunishi, Yuko Hosokoshi

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   83 ( 3 )   033707-1 - 033707-4   2014.3

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    We have succeeded in synthesizing two types of new organic radical crystals 3-I-V [= 3-(3-iodophenyl)-1,5-diphenylverdazyl] and 3-Br-4-F-V [= 3-(3-bromo-4-fluorophenyl)-1,5-diphenylverdazyl]. Their crystal strucutures are found to be isomorphous to that of previously reported spin ladder 3-Cl-4-F-V. Through the quantitative analysis of their molecular arrangements and magnetic properties, we confirm that these materials form ferromagnetic chain-based spin ladders with slightly modulated magnetic interactions. These results present the first quantitative demonstration of the fine-tuning of magnetic interactions in the molecular-based materials.

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  • Spin-Orbital Entanglement and the Breakdown of Singlets and Triplets in Sr2RuO4 Revealed by Spin- and Angle-Resolved Photoemission Spectroscopy Reviewed

    C. N. Veenstra, Z. -H. Zhu, M. Raichle, B. M. Ludbrook, A. Nicolaou, B. Slomski, G. Landolt, S. Kittaka, Y. Maeno, J. H. Dil, I. S. Elfimov, M. W. Haverkort, A. Damascelli

    PHYSICAL REVIEW LETTERS   112 ( 12 )   127002-1 - 127002-5   2014.3

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    Spin-orbit coupling has been conjectured to play a key role in the low-energy electronic structure of Sr2RuO4. By using circularly polarized light combined with spin-and angle-resolved photoemission spectroscopy, we directly measure the value of the effective spin-orbit coupling to be 130 +/- 30 meV. This is even larger than theoretically predicted and comparable to the energy splitting of the d(xy) and d(xz,yz) orbitals around the Fermi surface, resulting in a strongly momentum-dependent entanglement of spin and orbital character in the electronic wavefunction. As demonstrated by the spin expectation value &lt;(S-k) over arrow.(S-k) over arrow &gt; calculated for a pair of electrons with zero total momentum, the classification of the Cooper pairs in terms of pure singlets or triplets fundamentally breaks down, necessitating a description of the unconventional superconducting state of Sr2RuO4 in terms of these newly found spin-orbital entangled eigenstates.

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  • Multiband Superconductivity with Unexpected Deficiency of Nodal Quasiparticles in CeCu2Si2 Reviewed

    Shunichiro Kittaka, Yuya Aoki, Yasuyuki Shimura, Toshiro Sakakibara, Silvia Seiro, Christoph Geibel, Frank Steglich, Hiroaki Ikeda, Kazushige Machida

    PHYSICAL REVIEW LETTERS   112 ( 6 )   067002-1 - 067002-5   2014.2

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    Superconductivity in the heavy-fermion compound CeCu2Si2 is a prototypical example of Cooper pairs formed by strongly correlated electrons. For more than 30 years, it has been believed to arise from nodal d-wave pairing mediated by a magnetic glue. Here, we report a detailed study of the specific heat and magnetization at low temperatures for a high-quality single crystal. Unexpectedly, the specific-heat measurements exhibit exponential decay with a two-gap feature in its temperature dependence, along with a linear dependence as a function of magnetic field and the absence of oscillations in the field angle, reminiscent of multiband full-gap superconductivity. In addition, we find anomalous behavior at high fields, attributed to a strong Pauli paramagnetic effect. A low quasiparticle density of states at low energies with a multiband Fermi-surface topology would open a new door into electron pairing in CeCu2Si2.

    DOI: 10.1103/PhysRevLett.112.067002

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  • Thermodynamic Study of Nodal Structure and Multiband Superconductivity of KFe2As2 Reviewed

    Shunichiro Kittaka, Yuya Aoki, Naoki Kase, Toshiro Sakakibara, Taku Saito, Hideto Fukazawa, Yoh Kohori, Kunihiro Kihou, Chul-Ho Lee, Akira Iyo, Hiroshi Eisaki, Kazuhiko Deguchi, Noriaki K. Sato, Yasumasa Tsutsumi, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   83 ( 1 )   13704-1 - 13704-4   2014.1

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    The temperature, field, and field-orientation dependences of the electronic specific heat C-e of the iron-pnictide superconductor KFe2As2 have been investigated. Thermodynamic evidence of the presence of line nodes is obtained from the T and root H linear dependences of C-e/T in the low-T and low-H region. Under a magnetic field rotated within the tetragonal ab-plane, a fourfold oscillation is observed in C-e with a sign change at 0.08T(c). On the basis of the Dopplershift analysis, the observed C-e minima in H parallel to [100] at low T indicate the presence of line nodes somewhere on the Fermi surface where the Fermi velocity is parallel to the [100] direction; this is consistent with the octet-line-node scenario proposed recently by a photoemission experiment. In addition, the low-T C-e/T exhibits an unusual upturn on cooling at moderate fields only for H parallel to ab, which is understood in terms of the strong Pauli paramagnetic effect on multiband superconductivity.

    DOI: 10.7566/JPSJ.83.013704

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  • Verification of anisotropic s-Wave superconducting gap structure in CeRu2 from low-temperature field-Angle-Resolved specific heat measurements Reviewed

    Shunichiro Kittaka, Toshiro Sakakibara, Masato Hedo, Yoshichika Onuki, Kazushige Machida

    Journal of the Physical Society of Japan   82 ( 12 )   123706-1 - 123706-4   2013.12

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    The field-angle-resolved specific heat C(T,H,Ø) of the f -electron superconductor CeRu2 (Tc=6.3 K) has been measured at low temperatures down to 90mK on two single crystals of slightly different qualities. We reveal that the C(Ø) oscillation in a rotating magnetic field, originating from the gap anisotropy, diminishes at low temperatures below the characteristic field H*, as expected for an anisotropic gap without nodes. We also observe the suppression of H* by decreasing the gap anisotropy ratio Δmin/Δmax, a behavior that has been predicted from a microscopic theory for anisotropic s-wave superconductors. The present technique is established as a powerful tool for investigating minimum-gap structures as well as nodal structures. © 2013 The Physical Society of Japan.

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  • Quasi-one-dimensional S=1/2 Heisenberg antiferromagnetic chain consisting of the organic radical p-Br-V Reviewed

    Kenji Iwase, Hironori Yamaguchi, Toshio Ono, Yuko Hosokoshi, Tokuro Shimokawa, Yohei Kono, Shunichiro Kittaka, Toshiro Sakakibara, Akira Matsuo, Koichi Kindo

    PHYSICAL REVIEW B   88 ( 18 )   184431-1 - 184431-5   2013.11

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    We have succeeded in synthesizing single crystals of an organic radical p-Br-V [3-(4-bromophenyl)-1,5-diphenylverdazyl]. The dominant intermolecular interactions forming a one-dimensional spin chain are deduced from the molecular packing in the crystal, and the ab initio molecular orbital calculation also indicates such an exchange network. We analyzed the magnetic susceptibility, magnetization curve, and magnetic specific heat through the quantum Monte Carlo method and successfully explained them as being attributed to an S = 1/2 Heisenberg antiferromagnetic chain. Furthermore, we have found an unexpected successive phase transition in the specific heats, which indicates the formation of a noncollinear magnetic structure induced by frustration.

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  • Various regimes of quantum behavior in an S=1/2 Heisenberg antiferromagnetic chain with fourfold periodicity Reviewed

    H. Yamaguchi, T. Okubo, K. Iwase, T. Ono, Y. Kono, S. Kittaka, T. Sakakibara, A. Matsuo, K. Kindo, Y. Hosokoshi

    PHYSICAL REVIEW B   88 ( 17 )   174410-1 - 174410-5   2013.11

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    We have succeeded in synthesizing single crystals of the verdazyl radical beta-3-(2,6-dichlorophenyl)-1,5-diphenylverdazyl. The ab initio molecular orbital calculation indicates the formation of an S = 1/2 Heisenberg antiferromagnetic chain with fourfold magnetic periodicity consisting of three types of exchange interactions. We successfully explain the magnetic and thermodynamic properties based on the expected spin model by using the quantum Monte Carlo method. Furthermore, we reveal that the alternating and unique Ising ferromagnetic chains become effective in the specific field regions and observe a cooperative phenomenon caused by the magnetic order and quantum fluctuations. These results demonstrate that the verdazyl radical could form an unconventional spin model with interesting quantum behavior and provide a way to study a variety of quantum spin systems.

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  • Singlet-triplet crossover in the two-dimensional dimer spin system YbAl3C3 Reviewed

    Shunichiro Kittaka, Tomoyoshi Sugiyama, Yasuyuki Shimura, Toshiro Sakakibara, Saori Matsuda, Akira Ochiai

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY   62 ( 12 )   2088 - 2092   2013.7

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    Low-temperature magnetization (M) measurements down to 0.1 K have been performed in magnetic fields up to 14.5 T for a single piece of a tiny single-crystalline sample (similar to 0.2 mg weight) of the spin-gap system YbAl3C3. At the base temperature of 0.1 K, several metamagnetic transitions were clearly observed for H aEuro- c in the range 6 T &lt; A mu (0) H &lt; 9 T whereas only two transitions were observed, one at 4.8 T and the other at 6.6 T, for H aEuro- a. At fields above 9 T, the magnetization becomes almost saturated for both H aEuro- a and H aEuro- c. The present results indicate that a singlet-triplet crossover occurs in a relatively narrow field range, suggesting a rather weak interdimer interaction in spite of the nearly triangular lattice of Yb ions.

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  • Unconventional magnetic and thermodynamic properties of S=1/2 spin ladder with ferromagnetic legs Reviewed

    H. Yamaguchi, K. Iwase, T. Ono, T. Shimokawa, H. Nakano, Y. Shimura, N. Kase, S. Kittaka, T. Sakakibara, T. Kawakami, Y. Hosokoshi

    Physical Review Letters   110 ( 15 )   157205-1 - 157205-5   2013.4

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    We have succeeded in synthesizing single crystals of a new organic radical 3-Cl-4-F-V [3-(3-chloro-4-fluorophenyl)-1,5-diphenylverdazyl]. Through the ab initio molecular orbital calculation and the analysis of the magnetic properties, this compound was confirmed to be the first experimental realization of an S=1/2 spin-ladder system with ferromagnetic leg interactions. The field-temperature phase diagram indicated that the ground state is situated very close to the quantum critical point. Furthermore, we found an unexpected field-induced successive phase transition, which possibly originates from the interplay of low dimensionality and frustration. © 2013 American Physical Society.

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  • Determining the surface-to-bulk progression in the normal-state electronic structure of Sr2RuO4 by angle-resolved photoemission and density functional theory Reviewed

    C. N. Veenstra, Z. H. Zhu, B. Ludbrook, M. Capsoni, G. Levy, A. Nicolaou, J. A. Rosen, R. Comin, S. Kittaka, Y. Maeno, I. S. Elfimov, A. Damascelli

    Physical Review Letters   110 ( 9 )   097004-1 - 097004-5   2013.3

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    We revisit the normal-state electronic structure of Sr2RuO 4 by angle-resolved photoemission spectroscopy with improved data quality, as well as ab initio band structure calculations in the local-density approximation with the inclusion of spin-orbit coupling. We find that the current model of a single surface layer (√2×√2)R45 reconstruction does not explain all detected features. The observed depth-dependent signal degradation, together with the close quantitative agreement with the slab calculations based on the surface crystal structure as determined by low-energy electron diffraction, reveal that - at a minimum - the subsurface layer also undergoes a similar although weaker reconstruction. This model accounts for all features - a key step in understanding the electronic structure - and indicates a surface-to-bulk progression of the electronic states driven by structural instabilities. Finally, we find no evidence for other phases stemming from either topological bulk properties or, alternatively, the interplay between spin-orbit coupling and the broken symmetry of the surface. © 2013 American Physical Society.

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  • Anomalous field-angle dependence of the specific heat of heavy-fermion superconductor UPt3 Reviewed

    Shunichiro Kittaka, Koji An, Toshiro Sakakibara, Yoshinori Haga, Etsuji Yamamoto, Noriaki Kimura, Yoshichika Onuki, Kazushige Machida

    Journal of the Physical Society of Japan   82 ( 2 )   024707-1 - 024707-5   2013.2

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    We have investigated the field-angle variation of the specific heat C(H, φ, θ) of the heavy-fermion superconductor UPt3 at low temperatures T down to 50 mK, where φ and θ denote the azimuthal and polar angles of the magnetic field H, respectively. For T = 88 mK, C(H, θ = 90°) increases proportionally to √H up to nearly the upper critical field Hc2, indicating the presence of line nodes. By contrast, C(H, θ = 0°) deviates upward from the √H dependence for √H/Hc2 ≥ 0.5. This behavior can be related to the suppression of Hc2 along the c direction, whose origin has not been resolved yet. Our data show that the unusual Hc2 limit becomes marked only when θ is smaller than 30°. In order to explore the possible vertical line nodes in the gap structure, we measured the ′ dependence of C in wide T and H ranges. However, we did not observe any in-plane angular oscillation of C within the accuracy of ΔC/C ~ 0.5%. This result implies that field-induced excitations of the heavy quasiparticles occur isotropically with respect to ′, which is apparently contrary to the recent finding of a twofold thermal-conductivity κ(′) oscillation. Copyright © 2013 The Physical Society of Japan.

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  • Superconducting gap structure of the cage compound Sc5Rh6Sn18 Reviewed

    Naoki Kase, Shunichiro Kittaka, Toshiro Sakakibara, Jun Akimitsu

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   81   SB016-1 - SB016-4   2012.12

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    We report on the superconducting properties of the cage compound Sc5Rh6Sn18 with T-c = 5 K determined by magnetic susceptibility, electrical resistivity, and specific heat measurements. Measurements in magnetic fields indicate type-II superconductivity with the upper critical field mu H-0(c2)(0) = 7.24 T. H-c2( T) shows a clear enhancement over the Werthamer-Helfand-Hohenberg prediction, suggesting a strong electron-phonon coupling. Specific heat data reveal that Sc5Rh6Sn18 is indeed a strong-coupling BCS superconductor having an isotropic superconducting gap.

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  • Field dependence of the specific heat in a heavy-fermion superconductor CeIrIn5 Reviewed

    Yuya Aoki, Shunichiro Kittaka, Toshiro Sakakibara, Akito Sakai, Satoru Nakatsuji, Yasumasa Tsutsumi, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   81   SB014-1 - SB014-4   2012.12

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    We investigated temperature, field, and field-orientation dependences of the specific heat of CeIrIn5. The upper critical field H-c2 was determined down to 80 mK from the specific heat measurements and exhibits a slight suppression at low temperatures. We revealed that the specific heat at 80 mK increases proportional to the square root of H up to nearly H-c2 for both H parallel to ab and H parallel to c, implying the presence of line nodes and a weak contribution of the Pauli paramagnetic pair-breaking effect. Furthermore, we revealed that the specific heat shows a fourfold oscillation under a rotating magnetic field in the ab plane. This result indicates that CeIrIn5 has fourfold symmetry around the c axis in its gap amplitude.

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  • Simultaneous superconducting and antiferroquadrupolar transitions in PrRh2Zn20 Reviewed

    T. Onimaru, N. Nagasawa, K. T. Matsumoto, K. Wakiya, K. Umeo, S. Kittaka, T. Sakakibara, Y. Matsushita, T. Takabatake

    PHYSICAL REVIEW B   86 ( 18 )   184426-1 - 184426-7   2012.11

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    Superconducting and antiferroquadrupolar (AFQ) transitions in a Pr-based compound PrRh2Zn20 have been found to occur simultaneously at T-c = T-Q = 0.06 K. The superconducting transition manifests itself by zero resistance and large diamagnetic susceptibility. The specific heat exhibits a Schottky anomaly peaking at 14 K, and magnetization curves measured at 2 K show anisotropic behaviors. The analysis of these data indicates that the crystalline electric field ground state of the trivalent Pr ion is the non-Kramers Gamma(3) doublet with the quadrupolar degrees of freedom. A sharp peak in the specific heat at 0.06 K has been attributed not to the superconducting transition but to the AFQ transition because the ordering temperature T-Q decreases in B parallel to [100] but increases in B parallel to [110] and B parallel to [111] with increasing B up to 6 T. This anisotropic behavior of T-Q(B) can be well explained by a two-sublattice mean-field calculation, which corroborates the AFQ ordered state below T-Q. The entropy release at TQ is only 10% of R ln 2 expected for the Gamma(3) doublet, suggesting possible interplay between the quadrupolar degrees of freedom and the superconductivity.

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  • Nonmagnetic ground states and phase transitions in the caged compounds PrT2Zn20 (T=Ru, Rh and Ir) Reviewed

    T. Onimaru, K. T. Matsumoto, N. Nagasawa, Y. F. Inoue, K. Umeo, R. Tamura, K. Nishimoto, S. Kittaka, T. Sakakibara, T. Takabatake

    JOURNAL OF PHYSICS-CONDENSED MATTER   24 ( 29 )   294207-1 - 294207-5   2012.7

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    We performed electrical resistivity rho, magnetic susceptibility chi, specific heat C and electron diffraction measurements on single-crystalline samples of PrT2Zn20 (T = Ru, Rh and Ir). The three compounds show the Van Vleck paramagnetic behavior, indicating the nonmagnetic crystalline electric field (CEF) ground states. A Schottky-type peak appears at around 14 K, irrespective of the T element, which can be moderately reproduced by a doublet-triplet model. For T = Ru, a structural transition occurs at T-s = 138 K, below which no phase transition appears down to 0.04 K. On the other hand, for T = Ir, antiferroquadrupole (AFQ) ordering arising from the nonmagnetic 03 doublet takes place at T-Q = 0.11 K. For T = Rh, despite a structural transition between 170 and 470 K, the CEF ground state is still the non-Kramers Gamma(3) doublet. However, no phase transition due to the Gamma(3) doublet was observed even down to 0.1 K.

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  • Superconducting gap structure of CeIrIn5 from field-angle-resolved measurements of its specific heat Reviewed

    Shunichiro Kittaka, Yuya Aoki, Toshiro Sakakibara, Akito Sakai, Satoru Nakatsuji, Yasumasa Tsutsumi, Masanori Ichioka, Kazushige Machida

    PHYSICAL REVIEW B   85 ( 6 )   060505(R)-1 - 060505(R)-5   2012.2

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    In order to identify the gap structure of CeIrIn5, we measured field-angle-resolved specific heat C(phi) by conically rotating the magnetic field H around the c axis at low temperatures down to 80 mK. We revealed that C(phi) exhibits a fourfold angular oscillation, whose amplitude decreases monotonically by tilting H out of the ab plane. Detailed microscopic calculations based on the quasiclassical Eilenberger equation confirm that the observed features are uniquely explained by assuming the d(x2-y2)-wave gap. These results strongly indicate that CeIrIn5 is a d(x2-y2)-wave superconductor and suggest the universal pairing mechanism in CeMIn5 (M = Co, Rh, and Ir).

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  • Evaluation of Spin-Triplet Superconductivity in Sr2RuO4 Reviewed

    Yoshiteru Maeno, Shunichiro Kittaka, Takuji Nomura, Shingo Yonezawa, Kenji Ishida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   81 ( 1 )   011009-1 - 011009-29   2012.1

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    This review presents a summary and evaluations of the superconducting properties of the layered ruthenate Sr2RuO4 as they are known in the autumn of 2011. This paper appends the main progress that has been made since the preceding review by Mackenzie and Maeno was published in 2003. Here, special focus is placed on the critical evaluation of the spin-triplet, odd-parity pairing scenario applied to Sr2RuO4. After an introduction to superconductors with possible odd-parity pairing, accumulated evidence for the pairing symmetry of Sr2RuO4 is examined. Then, significant recent progress on the theoretical approaches to the superconducting pairing by Coulomb repulsion is reviewed. A section is devoted to some experimental properties of Sr2RuO4 that seem to defy simple explanations in terms of currently available spin-triplet scenario. The next section deals with some new developments using eutectic boundaries and micro-crystals, which reveals novel superconducting phenomena related to chiral edge states, odd-frequency pairing states, and half-fluxoid states. Some of these properties are intimately connected with the properties as a topological superconductor. The article concludes with a summary of knowledge emerged from the study of Sr2RuO4 that are now more widely applied to understand the physics of other unconventional superconductors, as well as with a brief discussion of relatively unexplored but promising areas of ongoing and future studies of Sr2RuO4.

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  • Field-temperature phase diagram of superconductivity in Sr2RuO4-Ru under out-of-plane uniaxial pressure Reviewed

    H. Taniguchi, S. Kittaka, S. Yonezawa, H. Yaguchi, Y. Maeno

    INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011)   391   012108-1 - 012108-5   2012

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    One of the interesting issues on the spin-triplet superconductor Sr2RuO4 (T-c = 1.5 K) is the origin of the T-c enhancement up to about 3 K in the eutectic system Sr2RuO4-Ru. We have recently revealed a striking fact that T-c of pure Sr2RuO4 is also enhanced up to 3.2 K by uniaxial pressure along the c axis (P-parallel to c). When P-parallel to c is applied to Sr2RuO4-Ru, there is a crossover at P-parallel to c* similar to 0.4 GPa from behavior attributable to interfacial superconductivity (SC) to behavior similar to that in pure Sr2RuO4 under P-parallel to c. We focus on the field-temperature phase diagrams of Sr2RuO4-Ru above and below P-parallel to c*. We revealed that the H-T curves of Sr2RuO4-Ru both above and below P-parallel to c* are concave-up. This fact suggests that the P-parallel to c-originated SC above P-parallel to c*c as well as the interfacial SC below P-parallel to c*c are granular-like. We also found that the H-T curves of these SCs do not scale with T-c's, which is possibly related to a difference in the spatial distribution of superconducting regions.

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  • Probing Spin Chirality of the Equilateral Triangular-Lattice Antiferromagnet RbFe(MoO4)(2) through Multiferroicity Reviewed

    H. Mitamura, R. Watanuki, N. Onozaki, Y. Shimura, S. Kittaka, T. Sakakibara, K. Suzuki

    INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011)   391   012099-1 - 012099-4   2012

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    Ferroelectricity was studied in magnetic fields up to 14 T on the XY-like perfect-triangular-lattice antiferromagnet RbFe(MoO4)(2), which exhibits a magnetically induced ferroelectric polarization along the c axis in the low-field 120 degrees structure phases P1 and P2. We have experimentally confirmed that the high-field P4/P5 phases of RbFe(MoO4)(2) for B parallel to a are nonferroelectric. The results favor the scenario that the ferroelectricity in the low-field phases of this system is driven by the in-plane spin chirality.

    DOI: 10.1088/1742-6596/391/1/012099

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  • Searching for the in-plane anisotropy of the specific heat of UPt3 in rotating fields Reviewed

    S. Kittaka, K. An, T. Sakakibara, Y. Haga, E. Yamamoto, N. Kimura, Y. O. Nuki, K. Machida

    INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES 2011)   391   012031-1 - 012031-4   2012

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    In order to identify the gap structure of a spin-triplet superconductor UPt3, we performed field-angle-resolved specific heat (C-phi) measurements in a magnetic field rotated around the [0001] axis. Although various theories predict fourfold symmetry of the gap in the superconducting C phase, we observed no angular variation in C-phi in a temperature range down to 88 mK (similar to 0.17T(c)). This absence of the variation in C-phi implies that the field-angle-dependent quasiparticle excitations, reflecting the gap anisotropy, are averaged out in the bulk of UPt3.

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  • Uniaxial pressure effect on the superconductivity in the Sr3Ru2O7 region of the Sr3Ru2O7-Sr2RuO4 eutectic system Reviewed

    Shunichiro Kittaka, Hiroshi Yaguchi, Yoshiteru Maeno, Rosalba Fittipaldi, Antonio Vecchione

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470   S728 - S729   2010.12

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    In the Sr3Ru2O7 region of the Sr3Ru2O7-Sr2RuO4 eutectic system, multiple superconducting (SC) transitions are observed with onset temperatures of 1.3 and 1 K. Based on various experimental results, the SC transition at 1.3 K is attributable to thin Sr2RuO4 layers embedded in the Sr3Ru2O7 region as stacking faults. In this study, in order to clarify the origin of the SC transition at 1 K we have investigated its uniaxial pressure effect along the c axis. We revealed that, although Sr3Ru2O7 exhibits ferromagnetism under the uniaxial pressure along the c axis above 0.3 GPa, the onset temperature of the SC transition at 1 K is almost invariant or increases slightly under the uniaxial pressure up to 0.4 GPa. This result suggests that this SC transition is not strongly related to the electronic state of Sr3Ru2O7 and it is consistent with the scenario that the 1-K transition also originates from the embedded thin Sr2RuO4 layers whose thickness is thinner than that of the 1.3-K transition. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2009.11.038

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  • Higher-Tc superconducting phase in Sr2RuO4 induced by uniaxial pressure Reviewed

    Shunichiro Kittaka, Haruka Taniguchi, Shingo Yonezawa, Hiroshi Yaguchi, Yoshiteru Maeno

    PHYSICAL REVIEW B   81 ( 18 )   180510(R)-1 - 180510(R)-4   2010.5

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    We have investigated uniaxial pressure effect on superconductivity of pure Sr2RuO4, whose intrinsic superconducting transition temperature T-c is 1.5 K. It is revealed that a very low uniaxial pressure along the c axis, only 0.2 GPa, induces superconductivity with the onset T-c above 3 K. The present results indicate that pure Sr2RuO4 has two superconducting phases with T-c=1.5 K and with varying T-c up to 3.2 K. The latter phase exhibits unusual features and is attributable to anisotropic crystal distortions beyond the elastic limit.

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  • Angular dependence of the upper critical field of Sr2RuO4 Reviewed

    S. Kittaka, T. Nakamura, Y. Aono, S. Yonezawa, K. Ishida, Y. Maeno

    PHYSICAL REVIEW B   80 ( 17 )   174514-1 - 174514-6   2009.11

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    One of the remaining issues concerning the spin-triplet superconductivity of Sr2RuO4 is the strong limit of the in-plane upper critical field H-c2 at low temperatures. In this study, we clarified the dependence of H-c2 on the angle theta between the magnetic field and the ab plane at various temperatures, by precisely and accurately controlling the magnetic field direction. We revealed that, although the temperature dependence of H-c2 for vertical bar theta vertical bar &gt;= 5 degrees is well explained by the orbital pair-breaking effect, H-c2(T) for vertical bar theta vertical bar &lt; 5 degrees is clearly limited at low temperatures. We also revealed that the H-c2 limit for vertical bar theta vertical bar &lt; 5 degrees is present not only at low temperatures but also at temperatures close to T-c. These features may provide additional hints for clarifying the origin of the H-c2 limit. Interestingly, if the anisotropic ratio in Sr2RuO4 is assumed to depend on temperature, the observed angular dependence of H-c2 is reproduced better at lower temperature with an effective-mass model for an anisotropic three-dimensional superconductor. We discuss the observed behavior of H-c2 based on existing theories.

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  • Large Enhancement of 3-K Phase Superconductivity in the Sr2RuO4-Ru Eutectic System by Uniaxial Pressure Reviewed

    Shunichiro Kittaka, Hiroshi Yaguchi, Yoshiteru Maeno

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   78 ( 10 )   103705-1 - 103705-4   2009.10

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    While the superconducting transition temperature T-c of Sr2RuO4 is 1.5 K. its onset T-c is enhanced as high as 3 K in the Sr2RuO4-Ru eutectic system, which is often referred to as the 3-K phase. We have investigated effects of uniaxial pressure on the non-bulk Superconductivity in the 3-K. phase. While T-c of pure Sr2RuO4 is known to be suppressed by hydrostatic pressure, a large enhancement of the superconducting volume fraction of the 3-K phase was observed for both out-of-plane and in-plane uniaxial pressures. Especially, under the in-plane pressure, the shielding fraction at 1.8 K of only less than 0.5% at 0 GPa exceeds 40% at 0.4 GPa. Such a large shielding fraction suggests that under the uniaxial pressure interfacial 3-K phase superconductivity penetrates deep into the bulk of Sr2RuO4. The present finding provides a significant implication to the unresolved origin of the enhancement of T-c to 3 K in the Sr2RuO4-Ru eutectic system.

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  • Atomic structure of functional interfaces in Sr2RuO4/Sr3Ru2O7 eutectic crystals Reviewed

    R. Ciancio, H. Pettersson, J. Borjesson, S. Lopatin, R. Fittipaldi, A. Vecchione, S. Kittaka, Y. Maeno, S. Pace, E. Olsson

    APPLIED PHYSICS LETTERS   95 ( 14 )   142507-1 - 142507-3   2009.10

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    Sr2RuO4/Sr3Ru2O7 eutectic system is investigated by transmission electron microscopy (TEM) and high angle annular dark field scanning TEM (STEM). The Sr2RuO4/Sr3Ru2O7 lamellar structure allows studying tunneling and proximity effects between spin-triplet superconductor Sr2RuO4 and metamagnetic normal metal Sr3Ru2O7. Our analyses reveal two typologies of interfaces within the eutectic: interfaces parallel to the growth direction are sharp and defect-free whereas interfaces perpendicular to the growth direction appear wavy and decorated with Ru precipitates. These results indicate that interfaces parallel to the growth direction are the best candidates for Sr2RuO4/Sr3Ru2O7 natural junctions to study the unusual superconductivity of Sr2RuO4. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3243691]

    DOI: 10.1063/1.3243691

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  • Toward intrinsic functionalities of bilayered ruthenate Sr3Ru2O7 Reviewed

    R. Ciancio, J. Borjesson, H. Pettersson, R. Fittipaldi, D. Zola, A. Vecchione, M. Polichetti, S. Kittaka, Y. Maeno, S. Pace, E. Olsson

    PHYSICAL REVIEW B   80 ( 5 )   054110-1 - 054110-7   2009.8

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    Polymorphic materials are known for being prone to intergrowth. Remarkable examples are strontium ruthenates whose properties are dramatically tuned by impurities and disorder. In particular, Sr3Ru2O7 shows a strong variation in transport and magnetic properties depending on synthesis process. It is therefore crucial to correlate atomic structure and properties to identify the functionalities of individual nanostructural constituents. We report a comparative study between Sr3Ru2O7 crystals grown as single phase and in Sr3Ru2O7-Sr2RuO4 eutectics. Our analysis by transmission electron microscopy reveals that Sr3Ru2O7 domains of the eutectic have a significantly lower level of impurities compared to Sr3Ru2O7 single-phase crystals, where intergrowths of Sr4Ru3O10 and SrRuO3 phase are seen. This is confirmed by magnetic measurements. These results identify the eutectic solidification as a fruitful way to grow highly pure crystals of polymorphic materials which, in combination with recent technological developments allowing the extraction of embedded features of crystals, opens a pathway for understanding of their physical properties and applications.

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  • Spatial Development of Superconductivity in the Sr2RuO4-Ru Eutectic System Reviewed

    Shunichiro Kittaka, Taketomo Nakamura, Hiroshi Yaguchi, Shingo Yonezawa, Yoshiteru Maeno

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   78 ( 6 )   064703-1 - 064703-6   2009.6

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    We have clarified how the enhanced superconductivity, often referred to as the 3-K phase superconductivity, develops in the Sr2RuO4-Ru eutectic system. From the detailed ac and dc Susceptibility measurements on well-characterized crystals, we revealed strongly anisotropic shielding, governed by the direction of the screening current dominated within the RuO2 plane rather than by the orientation of the Ru lamellae. The onset temperature of the 3-K phase superconductivity probed by diamagnetic screening is as high as 3.5 K. The temperature dependence of the diamagnetic shielding above around 2 K is well ascribed by (he interfacial screening around each Ru lamella. Below around 2 K, the rapid development of the shielding fraction as well as its peculiar response to ac and dc magnetic fields are explained by the formation of the Josephson network consisting of inter-lamellar supercurrents.

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  • Superconducting behaviour via percolation in Sr2RuO4-Sr3Ru2O7 eutectic crystals Reviewed

    R. Fittipaldi, M. Cuoco, V. Granata, C. Noce, S. Pace, D. Stornaiuolo, D. Born, F. Tafuri, S. Kittaka, Y. Maeno, A. Vecchione

    25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 5   150   052056-1 - 052056-4   2009

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    We report on super conducting behavior of Sr3Ru2O7 macrodomain taken out from Sr2RuO4-Sr3Ru2O7 eutectic crystals. Transport measurements performed down to 300 mK provide evidence of a supercurrent owing through the whole sample. Structural and compositional analyses are used to estimate the percentage of possible Sr2RuO4 inclusions. On the base of a model that describes the system as a proximity network made of superconducting Sr2RuO4 grains dispersed in the normal Sr3Ru2O7 matrix we determine the conditions for having a percolating superflow through the system.

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  • Unusual temperature dependence of the in-plane critical field in Sr(2)RuO(4) Reviewed

    S. Kittaka, T. Nakamura, Y. Aono, S. Yonezawa, K. Ishida, Y. Maeno

    25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 5   150   052112-1 - 052112-4   2009

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    We have studied the upper critical field H(c2) of the spin-triplet superconductor Sr(2)RuO(4). For H parallel to c, H(c2) increases linearly with decreasing temperature down to well below T(c) = 1.5 K, consistent with the orbital depairing effect. However, for H parallel to ab, the increase of H(c2) is strongly suppressed below 1 K. The origin of this in-plane H(c2) limit has been actively discussed, but its mechanism is still unclear. In the present study, we performed ac susceptibility measurements in the applied fields with higher accuracy than in previous studies to obtain the field-temperature phase diagrams for H parallel to c and H parallel to ab. We revealed that H(c2 parallel to ab)(T) does not exhibit a linear temperature dependence even above 1 K, which indicates that the H(c2) suppression is operative even close to T(c). In addition, we found that the H(c2) anisotropy ratio H(c2 parallel to ab)/H(c2 parallel to c) decreases monotonically from 60 to 20 with decreasing temperature.

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  • Evidence for the Sr2RuO4 intercalations in the Sr3Ru2O7 region of the Sr3Ru2O7 - Sr2RuO4 eutectic system Reviewed

    S. Kittaka, S. Yonezawa, H. Yaguchi, Y. Maeno, R. Fittipaldi, A. Vecchione, J. -F. Mercure, A. Gibbs, R. S. Perry, A. P. Mackenzie

    25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 5   150   052113-1 - 052113-5   2009

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    Although Sr3Ru2O7 has not been reported to exhibit superconductivity so far, ac susceptibility measurements revealed multiple superconducting transitions occurring in the Sr3Ru2O7 region cut from Sr3Ru2O7 - Sr2RuO4 eutectic crystals. Based on various experimental results, some of us proposed the scenario in which Sr2RuO4 thin slabs with a few layers of the RuO2 plane are embedded in the Sr3Ru2O7 region as stacking faults and multiple superconducting transitions arise from the distribution of the slab thickness. To examine this scenario, we measured the resistivity along the ab plane (rho(ab)) using a Sr3Ru2O7-region sample cut from the eutectic crystal, as well as along the c axis (rho(c)) using the same crystal. As a result, we detected resistance drops associated with superconductivity only in rho(ab), but not in rho(c). These results support the Sr2RuO4 thin-slab scenario. In addition, we measured the resistivity of a single crystal of pure Sr3Ru2O7 with very high quality and found that pure Sr3Ru2O7 does not exhibit superconductivity down to 15 mK.

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  • Enhancement of Interfacial Superconductivity in the Eutectic System Sr(2)RuO(4)-Ru by Uniaxial Pressure Reviewed

    Hiroshi Yaguchi, Shunichiro Kittaka, Yoshiteru Maeno

    25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PT 5A   150 ( 5a )   052285-1 - 052285-4   2009

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    We have investigated effects of uniaxial pressure on superconductivity in the 3-K phase in the eutectic system Sr(2)RuO(4)-Ru. We have found a large enhancement of 3-K phase superconductivity particularly in volume fraction for both in-plane pressure P parallel to ab and the c-axis pressure P parallel to c in contrast to expectations for the 1.5-K phase in pure Sr(2)RuO(4). Surprisingly, the effect of the in-plane pressure is even greater than that of the c-axis pressure. This could be related to the origin of the 3-K phase.

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  • Multiple superconducting transitions in the Sr(3)Ru(2)O(7) region of Sr(3)Ru(2)O(7)-Sr(2)RuO(4) eutectic crystals Reviewed

    S. Kittaka, S. Fusanobori, S. Yonezawa, H. Yaguchi, Y. Maeno, R. Fittipaldi, A. Vecchione

    PHYSICAL REVIEW B   77 ( 21 )   214511-1 - 214511-9   2008.6

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    We report the superconducting properties of Sr(3)Ru(2)O(7)-Sr(2)RuO(4) eutectic crystals, which consist of the spin-triplet superconductor Sr(2)RuO(4) with a monolayer stacking of RuO(2) planes and the metamagnetic normal metal Sr(3)Ru(2)O(7) with a bilayer stacking. Although Sr(3)Ru(2)O(7) so far has not been reported to exhibit superconductivity, our ac susceptibility measurements revealed multiple superconducting transitions that occur in the Sr(3)Ru(2)O(7) region of the eutectic crystals. The diamagnetic shielding essentially reached the full fraction at low ac fields parallel to the c axis. However, both the shielding fraction and the onset temperature are easily suppressed by ac fields larger than 0.1 mT rms and no anomaly was observed in the specific heat. Moreover, the critical field curves of these transitions have a positive curvature near zero fields, which is different from the upper critical field curve of the bulk Sr(2)RuO(4). These facts suggest that the superconductivity observed in the Sr(3)Ru(2)O(7) region is not a bulk property. To explain these experimental results, we propose the scenario that stacking RuO(2) planes, which are the building blocks of superconducting Sr(2)RuO(4), are contained in the Sr(3)Ru(2)O(7) region as stacking faults.

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  • Superconductivity in Sr(2)RuO(4)-Sr(3)Ru(2)O(7) eutectic crystals Reviewed

    R. Fittipaldi, A. Vecchione, R. Ciancio, S. Pace, M. Cuoco, D. Stornaiuolo, D. Born, F. Tafuri, E. Olsson, S. Kittaka, H. Yaguchi, Y. Maeno

    EPL   83 ( 2 )   27007-1 - 27007-5   2008

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    Superconducting behavior has been observed in the Sr(2)RuO(4)-Sr(3)Ru(2)O(7) eutectic system as grown by the flux-feeding floating-zone technique. A supercurrent flows across a single interface between Sr(2)RuO(4) and Sr(3)Ru(2)O(7) areas at distances that are far beyond those expected in a conventional proximity effect. The current-voltage characteristics within the Sr(3)Ru(2)O(7) macrodomain, as extracted from the eutectic, exhibit signatures of superconductivity in the bilayered Sr(3)Ru(2)O(7) region. Detailed microstructural, morphological and compositional analyses address issues on the concentration and the size of Sr(2)RuO(4) inclusions within the Sr(3)Ru(2)O(7) matrix. We speculate on the possibility of inhomogeneous superconductivity in the eutectic Sr(3)Ru(2)O(7) and exotic pairing induced by the Sr(2)RuO(4) inclusions. Copyright (C) EPLA, 2008.

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  • Structure, morphology and composition of superconducting Sr2RuO4-Sr3Ru2O7 eutectic crystals Reviewed

    R. Fittipaldi, S. Fusanobori, S. Kittaka, H. Yaguchi, J. Hooper, A. Vecchione, Y. Maeno

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   460   524 - 525   2007.9

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    We report a study of morphological, compositional and structural aspects of SrRuO4-Sr3Ru2O7 cutectic crystals to check the stoichiometry of the phases that compose the crystals and how the two phases match each other in the same crystal. This knowledge is also a necessary prerequisite for the understanding of the experimental results on the superconducting behaviour reported. (C) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2007.03.178

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  • AC susceptibility of Sr2RuO4-Sr3Ru2O7 eutectics: Dependence on AC field strength and frequency Reviewed

    S. Fusanobori, S. Kittaka, H. Yaguchi, R. Fittipaldi, A. Vecchione, Y. Maeno

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   310 ( 2 )   643 - 644   2007.3

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    The low-field AC susceptibility of a eutectic crystal of the Sr2RuO4-Sr3Ru2O7 system exhibits superconducting transition features at three temperatures. We investigate the dependence on AC field strength from 0.021 to 2.1 Oe-rms and frequency from 17 to 3 kHz. The two lower-temperature peaks in the imaginary part originate in the Sr3Ru2O7 part. The lowest-temperature peak is exceedingly sensitive to the. eld amplitude and shifts to lower temperatures with increasing amplitude. By contrast, it slightly shifts to higher temperatures with increasing frequency. These results support that the sensitive features involve weak links forming the screening paths. (c) 2006 Published by Elsevier B.V.

    DOI: 10.1016/j.jmmm.2006.10.103

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  • ハニカム格子系における特異な内部磁場と磁場誘起量子物性

    岩崎義己, 山口博則, 細越裕子, 川上貴資, 河野洋平, 橘高俊一郎, 榊原俊郎, 木田孝則, 萩原政幸

    日本物理学会講演概要集(CD-ROM)   74 ( 1 )   ROMBUNNO.14aS‐PS‐43   2019.3

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  • Kitaevスピン液体候補物質OsCl3の合成と物性

    片岡亨太, 平井大悟郎, 矢島健, 浜根大輔, 橘高俊一郎, 榊原俊郎, 広井善二

    日本物理学会講演概要集(CD-ROM)   74 ( 1 )   2019

  • 重い電子系U1-xThxBe13の極低温電気抵抗・比熱における非フェルミ液体的性質

    清水悠晴, 橘高俊一郎, 中村翔太, 榊原俊郎, 青木大, 佐藤芳樹, 本間佳哉, 仲村愛, MAURYA Arvind, LI D. X, 本多史憲

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   ROMBUNNO.23pK504‐9   2018.3

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  • S=2ハニカム格子磁性体[Mn(hfac)2][o‐Py‐V‐p‐F2]の低温物性

    岡部俊輝, 山口博則, 細越裕子, 萩原政幸, 松尾昌, 中村翔太, 橘高俊一郎, 榊原俊郎

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   ROMBUNNO.22pPSA‐13 - 990   2018.3

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    DOI: 10.11316/jpsgaiyo.73.1.0_990

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  • URhGeのb軸方向近傍の極低温比熱・磁気熱量効果測定

    中村翔太, 橘高俊一郎, 河野洋平, 榊原俊郎, 清水悠晴, 芳賀芳範, POSPISIL Jiri, 山本悦嗣

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   ROMBUNNO.23pK504‐3   2018.3

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  • スピンアイス物質Dy2Ti2O7の磁場角度分解エントロピー測定

    橘高俊一郎, 門脇広明, 高津浩, 中村翔太, 榊原俊郎

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   ROMBUNNO.24pK504‐13   2018.3

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  • CsFe(MoO4)2およびKFe(MoO4)2におけるスピンカイラリティ起源の強誘電性

    綿貫竜太, 橋本真里子, 依光雄也, 三田村裕幸, 中村翔太, 橘高俊一郎, 榊原俊郎

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   ROMBUNNO.23aPS‐17   2018.3

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  • Ce(Co1-xNix)In5における量子臨界揺らぎ

    鈴木康平, 横山淳, 大島佳樹, 天谷健一, 近藤晃弘, 金道浩一, 中村翔太, 橘高俊一郎, 榊原俊郎

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   ROMBUNNO.24pK504‐6   2018.3

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  • 強磁性超伝導体UCoGeにおける極低温磁場回転比熱測定

    中村翔太, 橘高俊一郎, 清水悠晴, 清水悠晴, 河野洋平, 榊原俊郎, 青木大, 青木大, 仲村愛, 本多史憲, FLOUQUET Jacques

    日本物理学会講演概要集(CD-ROM)   72 ( 2 )   ROMBUNNO.21aF21‐4   2017.9

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  • 磁場角度回転比熱測定による超伝導研究

    橘高 俊一郎

    物性研究・電子版   6 ( 1 )   061204   2017

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  • UCoGeの容易軸方向磁場下における磁化と比熱の測定

    中村翔太, 河野洋平, 清水悠晴, 橘高俊一郎, 榊原俊郎, 青木大, 青木大, 仲村愛, 本多史憲, FLOUQUET Jacques

    日本物理学会講演概要集(CD-ROM)   71 ( 1 )   ROMBUNNO.20PBL‐3 - 2061   2016.3

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    DOI: 10.11316/jpsgaiyo.71.1.0_2061

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  • 21aAL-5 Anomalous-logT dependence of Specific heat NdO_<1-x>F_xBiS_2 Superconductor

    Mita M, Asano T, Kono Y, Nakamura S, Kittaka S, Sakakibara T, Higashinaka R, Matsuda T. D, Aoki Y

    日本物理学会講演概要集   71 ( 1 )   2158 - 2158   2016.3

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    DOI: 10.11316/jpsgaiyo.71.1.0_2158

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  • 21pBM-5 Single crystal growth and physical properties of heavy fermion antiferromagnet YbNi_2Si_2

    Matsumoto Y, Nakamura Y, Ohara S, Haga Y, Fisk Zachary, Kono Y, Nakamura S, Kittaka S, Sakakibara T

    Meeting Abstracts of the Physical Society of Japan   71 ( 0 )   2301 - 2301   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_2301

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  • 20pPSB-27 Specific heat in magnetic field of heavy-fermion antiferromagnet YbNi_2Si_2

    Nakamura Y, Matsumoto Y, Ohara S, Kono Y, Nakamura S, Kittaka S, Sakakibara T, Haga Y, Fisk Zachary

    Meeting Abstracts of the Physical Society of Japan   71 ( 0 )   2130 - 2130   2016

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    DOI: 10.11316/jpsgaiyo.71.1.0_2130

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  • Recent progress on the study of heavy-fermion superconductivity : Gap symmetry probed by field-angle-resolved specific heat measurements

    51 ( 8 )   411 - 427   2016

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  • 18pPSB-19 Magnetization measurements of Bi single crystal at very low temperatures

    Nakamura S, Kono Y, Kittaka S, Sakakibara T, Behnia K

    Meeting Abstracts of the Physical Society of Japan   70 ( 0 )   1127 - 1127   2015

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    DOI: 10.11316/jpsgaiyo.70.2.0_1127

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  • 21aPS-110 μSR measurement of quantum spin ice system Yb_2Ti_2O_7

    Hamachi N, Yasui Y, Kono Y, Kittaka S, Sakakibara T, Chang L. J, Onoda S, Watanabe I

    Meeting Abstracts of the Physical Society of Japan   70 ( 0 )   1038 - 1038   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_1038

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  • 22pBC-9 Superconducting gap structure of the caged compound of Y_5Tr_6Sn_<18>(Tr: Transition metal)

    Kase N., Kittaka S., Sakakibara T., Terui Y., Nakano T., Takeda N., Akimitsu J.

    Meeting Abstracts of the Physical Society of Japan   70 ( 0 )   2243 - 2243   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_2243

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  • 8aPS-105 Superconducting Symmetry, Magnetic Anomaly, and Non-Fermi-Liquid State of Heavy-Electron Compound UBe_<13>

    Shimizu Y., Kittaka S., Kono Y., Sakakibara T., Haga Y., Yamamoto E., Amitsuka H., Tsutsumi Y., Machida K.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   382 - 382   2014.8

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  • 7aBJ-11 Spin-Chirality-Driven Ferroelectricity on a Perfect Triangular Lattice Antiferromagnet RbFe(MoO_4)_2

    Watanuki R., Mitamura H., Kaneko K., Onozaki N., Amou Y., Kittaka S., Kobayashi R., Shimura Y., Yamamoto I., Suzuki K., Chi Songxue, Sakakibara T.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   328 - 328   2014.8

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  • 8pBC-10 Low-temperature Properties of a New Spin-ladder Organic Antiferromagnet α-2-Cl-4-F-V

    Kono Y., Kittaka S., Sakakibara T., Yamaguchi H., Hamada R., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   295 - 295   2014.8

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  • 9pBC-7 Hidden order and field-induced magnetic order of Tb_<2+x>Ti_<2-x>O_<7+y> investigated by low-temperature specific heat experiments

    Takatsu H., Taniguchi T., Kadowaki H., Kittaka S., Sakakibara T.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   307 - 307   2014.8

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  • 8aPS-35 Development of the apparatus to measure the low-temperature specific heat under uniaxial pressure and its application to CeCoIn_5

    Kittaka S., Sakakibara T., Yokoyama M.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   365 - 365   2014.8

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  • 9aBA-8 Low-temperature physical property of a frustrated pentagonal lattice

    Yamaguchi H., Ono T., Hosokoshi Y., Okubo T., Kittaka S., Sakakibara T., Araki K., Kawakami T.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   298 - 298   2014.8

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  • 7aPS-127 Low-Temperature physical property of S=2 Mn Complex o-Py-V・Mn(hfac)_2

    Shimpuku Y., Yamaguchi H., Ono T., Hosokoshi Y., Kono Y., Kittaka S., Sakakibara T., Kawakami T.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   261 - 261   2014.8

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  • 7pBK-1 Field-orientation dependence of the specific heat of non-centrosymmetric superconductor CePt_3Si

    Kittaka S., Kono Y., Sakakibara T., Bauer Ernst

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   343 - 343   2014.8

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  • 9aPS-55 Magnetostriction and thermal expansion measurements of Cd_2Os_2O_7

    Mitamura H., Yamaura J., Kono Y., Kittaka S., Sakakibara T., Hiroi Z.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   416 - 416   2014.8

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  • 10aBJ-4 Low-Temperature Magnetization and Torque Measurements of the Superconductor Sr_2RuO_4 with a Fine-Tuned Field Orientation

    Kasahara A., Kittaka S., Sakakibara T., Shibata D., Yonezawa S., Maeno Y., Tenya K., Machida K.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   456 - 456   2014.8

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  • 9pBK-1 Quadrupole Kondo effect in PrIr_2Zn_<20> with a nonmagnetic doublet ground state studied by specific heat measurements in magnetic field

    Onimaru T., Matsumoto K. T., Umeo K., Kittaka S., Araki K., Sakakibara T., Takabatake T.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   444 - 444   2014.8

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  • 28aPS-116 Low-Temperature Magnetization Measurements of the Superconductor Sr_2RuO_4 with a Fine-Tuned Field Orientation

    Kasahara A., Kittaka S., Sakakibara T., Shibata D., Yonezawa S., Maeno Y., Tenya K., Machida K.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   619 - 619   2014.3

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  • 28aAY-12 Low-temperature physical properties of ferromagnetic chain-based spin ladder 3-I-V

    Yamaguchi H., Miyagai H., Ono T., Kono Y., Kittaka S., Sakakibara T., Shimokawa T., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   515 - 515   2014.3

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  • 30aCM-11 Substituted effect of anisotropic superconducting gap of Y_5Tr_6Sn_<16>(Tr=Rh,Ir)

    Kase N., Kittaka S., Sakakibara T., Akimitsu J.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   676 - 676   2014.3

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  • 28pAY-6 The formation of the honeycomb lattice by the metal complex with verdazyl radical

    Shimpuku Y., Yamaguchi H., Ono T., Shimokawa T., Kawakami T., Kono Y., Kittaka S., Sakakibara T., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   520 - 520   2014.3

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  • 29pBE-5 Superconducting gap structure and anomalous normal state of UBe_<13> investigated by specific-heat measurements in magnetic fields

    Kittaka S., Shimizu Y., Sakakibara T., Amitsuka H., Haga Y., Yamamoto E., Tsutsumi Y., Machida K.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   646 - 646   2014.3

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  • 27aPS-82 New quantum phase of a spin-ladder material with ferromagnetic interactions

    Miyagai H., Yamaguchi H., Ono T., Shimokawa T., Yoshida M., Takigawa H., Kono Y., Kittaka S., Sakakibara T., Okunishi K., Okubo T., Kawakami T., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   494 - 494   2014.3

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  • 27aPS-90 Magnetic phase diagrams of triangular antiferromagnets Ba_3MTa_2O_9 (M=Ni & Co)

    Ono T., Tominaga H., Yamaguchi H., Kono Y., Kittaka S., Sakakibara T., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   496 - 496   2014.3

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  • 28aPS-133 Study on the d-electron-based ferromagnetic superconductor Y_9Co_7 (II)

    Kunikata S., Imura K., Deguchi K., Kittaka S., Sakakibara T., Sato N. K.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   623 - 623   2014.3

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  • 27aPS-108 Magnetic phase diagram and novel magnetic transition of quantum spin ice system Yb_2Ti_2O_7

    Hamachi N, Yasui Y, Kittaka S, Sakakibara T, Onoda S

    Meeting Abstracts of the Physical Society of Japan   69 ( 0 )   500 - 500   2014

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  • 10aBK-8 Superconducting state of the caged compound Sc_5Tr_6Sn_<18> (Tr = Co, Rh, Ir)

    Kase N., Terui Y., Nakano T., Takeda N., Kittaka S., Sakakibara T., Akimitsu J.

    Meeting Abstracts of the Physical Society of Japan   69 ( 0 )   460 - 460   2014

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    DOI: 10.11316/jpsgaiyo.69.2.3.0_460_3

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  • PrIr2Zn20の超伝導と四極子秩序に対するLa置換効果

    松本圭介, 鬼丸孝博, 大林容子, 長澤直裕, 脇舎和平, 梅尾和則, 高畠敏郎, 橘高俊一郎, 榊原俊郎

    日本物理学会講演概要集   68 ( 2 )   493   2013.8

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  • Low-temperature physical property of a new one-dimensional chain with four-fold magnetic periodicity

    Yamaguchi H, Ono T, Kida T, Hagiwara M, Okubo T, Matuso A, Kindo K, Kono Y, Kittaka S, Sakakibara T, Shimokawa T, Hosokoshi Y

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   431 - 431   2013.8

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  • Anisotropic superconducting gap of Y_5Tr_6Sn_<18>(Tr=Rh,Ir) with strong intrinsic disorder

    Kase N., Kittaka S., Sakakibara T., Akimitsu J.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   568 - 568   2013.8

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  • Low-temperature physical properties of a new spin-ladder material with ferromagnetic interactions

    Miyagai H., Yamaguchi H., Iwase K., Ono T., Shimokawa T., Kono Y., Kittaka S., Sakakibara T., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   385 - 385   2013.8

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  • A novel magnetic phase of a perfect triangular lattice antiferromagnet RbFe(MoO_4)_2 in high magnetic fields

    Mitamura H., Kono Y., Watanuki R., Amou Y., Onozaki N., Kittaka S., Shimura Y., Sakakibara T., Suzuki K.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   373 - 373   2013.8

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  • Criteria for the presence of the spin-chirality-driven ferroelectricity on a perfect triangular lattice antiferromagnet

    Mitamura H., Watanuki R., Amou Y., Onozaki N., Kittaka S., Kono Y., Shimura T., Sakakibara T., Suzuki K.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   450 - 450   2013.8

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  • Heavy-fermion superconductivity in CeCu_2Si_2 investigated by low-temperature magnetization and specific-heat measurements

    Kittaka S., Aoki Y., Shimura Y., Sakakibara T., Seiro S., Geibei C., Steglich Y., Ikeda H., Machida K.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   592 - 592   2013.8

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  • Low-Temperature Magnetization Mesurements with a Fine-Tuned Field Orientation

    Kasahara A., Kittaka S., Mitamura H., Sakakibara T.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   397 - 397   2013.8

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  • Superconducting and Antiferro-quadrupolar Transitions in PrIr_2Zn_<20>

    Matsumoto K.T., Onimatu T., Obayashi Y., Nagasawa N., Wakiya K., Umeo K., Takabatake T., Kittaka S., Sakakibara T.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   493 - 493   2013.8

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  • 29aXB-1 Identification of the superconducting gap symmetry of CeCu_2Si_2 by specific heat measurements in magnetic field

    Kittaka S., Aoki Y., Shimura Y., Sakakibara T., Geibel C., Steglich F., Ikeda H., Machida K.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   685 - 685   2013.3

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  • 27aPS-20 Low-Temperature Specific Heat and Magnetization of Heavy-Fermion Superconductor CeCu_2Si_2 Magnetic Fields

    Aoki Y., Kittaka S., Shimura Y., Sakakibara T., Geibel C., Steglich F., Ikeda H., Machida K.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   614 - 614   2013.3

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  • 26pXW-1 Low-temperature physical property of new spin-ladder material with ferromagnetic legs

    Yamaguchi H., Iwase K., Ono T., Shimokawa T., Kawakami T., Shimura Y., Kase N., Araki K., Kittaka S., Sakakibara T., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   531 - 531   2013.3

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  • 27aPS-73 Low temperature measurements of the cage compound TmTr_2Al_<20>

    Kase N., Shimura Y., Kittaka S., Sakakibara T., Nakatsuji S., Akimitsu J.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   627 - 627   2013.3

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  • 26aPS-72 Novel Magnetic Transition of Quantum Spin Ice system Yb_2Ti_2O_7

    Yasui Y, Araki K, Kittaka S, Sakakibara T, Onoda S

    Meeting Abstracts of the Physical Society of Japan   68 ( 0 )   515 - 515   2013

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  • 非磁性基底二重項を持つ立方晶PrT2Zn20(T=Rh,Ir)の反強四極子秩序と四極子近藤効果

    鬼丸孝博, 長澤直裕, 大林容子, 脇舎和平, 松本圭介, 梅尾和則, 橘高俊一郎, 榊原俊郎, 高畠敏郎

    日本物理学会講演概要集   67 ( 2 )   491 - 491   2012.8

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  • 18aPSA-61 Criteria for the presence of the spin driven ferroelectricity on a perfect triangular lattice antiferromagnet

    Mitamura H., Watanuki R., Amou Y., Onozaki N., Shimura Y., Kittaka S., Sakakibara T., Yamamoto I., Suzuki K.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   392 - 392   2012.8

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  • 19pCD-7 Electric polarization measurement of the perfect triangular lattice antiferromagnet RbFe(MoO_4)_2 in pulsed high magnetic fields

    Mitamura H., Watanuki R., Amou Y., Onozaki N., Shimura Y., Kittaka S., Sakakibara T., Yamamoto I., Suzuki K.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   420 - 420   2012.8

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  • 18aPSA-53 Low-temperature physical properties of a new honeycomb-lattice material with vsrdazyl monoradical

    Yamaguchi H., Iwase K., Ono T., Shimura Y., Kase N., Kittaka S., Sakakibara T., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   390 - 390   2012.8

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  • 19pHC-6 Low temperature measurements of the cage compound TmTi_2Al_<20>

    Kase N., Shimura Y., Kittaka S., Sakakibara T., Nakatsuji S., Akimitsu J.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   492 - 492   2012.8

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  • 19aFF-2 Gap structure of anisotropic s-wave superconductor CeRu_2 probed by the specific heat measurements in rotating magnetic fields

    Kittaka S., Sakakibara T., Hedo M., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   471 - 471   2012.8

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  • 25aYH-1 Superconducting gap structures of Y_5T_6Sn_<18>(T=Rh,Ir) determined by angle-resolved specific heat measurements

    Kase N., Kittaka S., Sakakibara T., Akimitsu J.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   593 - 593   2012.3

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  • 27aYB-12 Magnetization Measurements of a Single Crystal of YbAl_3C_3 Using a Very High Sensitivity Capacitive Faraday Magnetometer (II)

    Sugiyama T., Kittaka S., Shimura Y., Sakakibara T., Matsuda S., Ochiai A.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   682 - 682   2012.3

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  • 26pYA-7 Phase transition in a nonmagnetic doublet ground state of PrRh_2Zn_<20> with a caged structure

    Onimaru T., Nagasawa N., Matsumoto K. T., Umeo K., Kittaka S., Sakakibara T., Takabatake T.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   663 - 663   2012.3

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  • 25pPSB-41 Multipolar phase transition attributed to a nonmagnetic doublet ground state of a caged compound PrRh_2Zn_<20>

    Nagasawa N., Matsumoto K. T., Onimaru T., Umeo K., Kittaka S., Sakakibara T., Takabatake T.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   654 - 654   2012.3

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  • 25aPS-85 Magnetic Field Variation of the Specific Heat of Iron-based Superconductor KFe_2As_2 : Sample Dependences

    Aoki Y., Kittaka S., Kase N., Sakakibara T., Saito T., Fukazawa H., Kohori Y., Kiho K., Lee C. H., Iyo A., Eisaki H.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   612 - 612   2012.3

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  • 24pPSB-37 Low-temperature specific heat of a heavy-fermion superconductor CeRu_2 in magnetic fields

    Kittaka S., Sakakibara T., Hedo M., Onuki Y.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   572 - 572   2012.3

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  • 24aSA-9 Low-temperature magnetic state of new spin-ladder material with verdazyl monoradical

    Yamaguchi H., Iwase K., Ono T., Shimokawa T., Nakano H., Shimura Y., Kase N., Kittaka S., Sakakibara T., Hosokoshi Y.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   474 - 474   2012.3

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  • Superconducting gap structure of CeIrIn 5 from field-angle-resolved measurements of its specific heat

    Shunichiro Kittaka, Yuya Aoki, Toshiro Sakakibara, Akito Sakai, Satoru Nakatsuji, Yasumasa Tsutsumi, Masanori Ichioka, Kazushige Machida

    Physical Review B - Condensed Matter and Materials Physics   85 ( 6 )   2012.2

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    In order to identify the gap structure of CeIrIn 5, we measured field-angle-resolved specific heat C(φ) by conically rotating the magnetic field H around the c axis at low temperatures down to 80 mK. We revealed that C(φ) exhibits a fourfold angular oscillation, whose amplitude decreases monotonically by tilting H out of the ab plane. Detailed microscopic calculations based on the quasiclassical Eilenberger equation confirm that the observed features are uniquely explained by assuming the d x2-y2-wave gap. These results strongly indicate that CeIrIn 5 is a d x2-y2-wave superconductor and suggest the universal pairing mechanism in CeMIn 5 (M=Co, Rh, and Ir). © 2012 American Physical Society.

    DOI: 10.1103/PhysRevB.85.060505

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  • Superconducting gap structure of the cage compound Sc₅Rh₆Sn₁₈ (Proceedings of International Workshop on Heavy Fermions : TOKIMEKI 2011)

    KASE Naoki, KITTAKA Shunichiro, SAKAKIBARA Toshiro

    Journal of the Physical Society of Japan   81   SB016 - 1-4   2012

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  • 角度分解磁場中比熱測定から切り拓く重い電子系の超伝導

    橘高 俊一郎

    新学術領域研究「重い電子系の形成と秩序化」News letter   4 ( 2 )   1 - 3   2012

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  • 24aGE-1 Anisotropic Superconducting Gap of Y_5T_6Sn_<18> (T=Rh, Ir) Studied by Specific Heat Measurements in Magnetic Fields

    Kase N., Kittaka S., Sakakibara T., Akimitsu J.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   637 - 637   2011.8

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  • 21pGD-3 Superconducting gap structure of CeIrIn_5 probed by the specific heat measurements in rotating magnetic fields

    Kittaka S., Aoki Y., Sakakibara T., Sakai A., Nakatsuji S., Tsutsumi Y., Machida K.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   479 - 479   2011.8

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  • 24pGC-4 Low temperature specific heat of PrRh_2Zn_<20> with Γ_3 doublet ground state.

    Nagasawa N., Matsumoto K. T., Onimaru T., Umeo K., Kittaka S., Sakakibara T., Takabatake T.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   649 - 649   2011.8

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  • 22aGM-8 Field-Angle-Resolved Specific Heat and Superconducting gap structure of Iron-Pnictide Superconductor KFe_2As_2

    Aoki Y., Kittaka S., Sakakibara T., Saito T., Fukazawa H., Kohori Y., Kiho K., Lee C. H., Iyo A., Eisaki H.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   504 - 504   2011.8

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  • 23aPS-63 Improvement in Sensitivity of the Faraday Force Magnetrometer and Magnetization Measurements of YbAl_3C_3 Microcrystal (2)

    Sugiyama T., Kittaka S., Shimura Y., Sakakibara T., Matsuda S., Ochiai A.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   592 - 592   2011.8

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  • 22aPS-76 Dielectric polarization measurements of RbFe(MoO_4)_2 in magnetic fields

    Mitamura H., Watanuki R., Onozaki N., Shimura Y., Kittaka S., Sakakibara T., Suzuki K.

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   527 - 527   2011.8

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  • 25aEC-1 Dependence of the specific heat of UPt_3 on the magnetic-field direction

    Kittaka S., An K., Sakakibara T., Haga Y., Yamamoto E., Kimura N., Onuki Y., Machida K.

    Meeting abstracts of the Physical Society of Japan   66 ( 1 )   517 - 517   2011.3

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  • 27pPSB-3 Gap Structure of the Heavy Electron Superconductor UPt_3 Probed by the Angle Resolved Specific Heat Measurement in Magnetic Fields III

    An K., Kittaka S., Sakakibara T., Haga Y., Yamamoto E., Kimura N., Onuki Y., Machida K.

    Meeting abstracts of the Physical Society of Japan   66 ( 1 )   650 - 650   2011.3

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  • 25aPS-68 Improvement in Sensitivity of the Faraday Force Magnetrometer and Magnetization Measurements of YbAl_3C_3 Microcrystal

    Sugiyama T., Kittaka S., Shimura Y., Sakakibara T., Matsuda S., Ochiai A.

    Meeting abstracts of the Physical Society of Japan   66 ( 1 )   472 - 472   2011.3

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  • 23pPSA-3 Gap Structure of the Heavy Electron Superconductor UPt_3 Probed by the Angle Resolved Specific Heat Measurement in Magnetic Fields II

    An K., Kittaka S., Sakakibara T., Haga Y., Yamamoto E., Kimura N., Onuki Y., Machida K.

    Meeting abstracts of the Physical Society of Japan   65 ( 2 )   512 - 512   2010.8

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  • 23aXP-2 Low temperature magnetization of spin gap system YbAl_3C_3

    Kittaka S., Shimura Y., Sakakibara T., Matsuda S., Ochiai A.

    Meeting abstracts of the Physical Society of Japan   65 ( 2 )   457 - 457   2010.8

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  • 25aPS-80 Development of High-Sensitivity Low Temperature Magnetrometer Using a Microcantilever

    Sugiyama T., Kittaka S., Mitamura H., Sakakibara T.

    Meeting abstracts of the Physical Society of Japan   65 ( 2 )   417 - 417   2010.8

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  • 20pGE-11 Enhancement of Superconducting Onset Temperature in Sr_2RuO_4 by Uniaxial Pressure

    Taniguchi H., Kittaka S., Yonezawa S., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   558 - 558   2010.3

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  • 20pPSA-29 Diamagnetic domain in spin-triplet superconductor Sr_2RuO_4

    Karaki Y., Nema H., Kubota M., Uwatoko Y., Kittaka S., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   65 ( 1 )   571 - 571   2010.3

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  • 26aPS-31 Low temperature magnetization measurement of Sr_2RuO_4

    Karaki Y., Nema H., Kubota M., Uwatoko Y., Kittaka S., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   64 ( 2 )   485 - 485   2009.8

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  • 25aRK-12 Uniaxial Pressure Effect on Superconducting Transition Temperature of Sr_2RuO_4

    Taniguchi H., Kittaka S., Yonezawa S., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   64 ( 2 )   410 - 410   2009.8

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  • 29pTL-2 Uniaxial pressure effect on the multiple superconducting transitions in the Sr_3Ru_2O_7-Sr_2RuO_4 eutectic system

    Kittaka S., Yaguchi H., Maeno Y., Fittipaldi R., Vecchione A.

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   636 - 636   2009.3

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  • 30pTD-9 Superconductive properties of Ternary Transition Metal Silicide CaIrSi_3

    Eguchi G., Peets Darren, Kriener Markus, Takatsu H., Kittaka S., Yonezawa S., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   666 - 666   2009.3

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  • 23aQC-1 Superconducting network in the Sr_2RuO_4-Ru eutectic system

    Nakamura T., Kittaka S., Yaguchi H., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   63 ( 2 )   567 - 567   2008.8

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  • 23aQC-2 Accurate and precise examination of the dependence of the upper critical field in Sr_2RuO_4 on the magnetic-field direction

    Kittaka S., Nakamura T., Aono Y., Yonezawa S., Ishida K., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   63 ( 2 )   567 - 567   2008.8

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  • 21aPS-71 Superconductivity of Sintered Crystals of Sr_2RuO_4

    Nakamura T., Kittaka S., Murakawa H., Yaguchi H., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   533 - 533   2007.8

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  • 24aXJ-9 Syntheses and low temperature properties of ACu_3Ru_4O_<12> (A=Na, Ca, La)

    Tanaka S., Shimazui N., Onuma K., Takatsu H., Kittaka S., Yonezawa S., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   62 ( 2 )   658 - 658   2007.8

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  • 19pWF-4 Field-Temperature phase diagram of the superconductivity observed in the Sr_3Ru_2O_7 region of Sr_2RuO_4-Sr_3Ru_2O_7 eutectic crystals.

    Kittaka S., Yaguchi H., Maeno Y., Fittipaidi R., Vecchione A.

    Meeting abstracts of the Physical Society of Japan   62 ( 1 )   589 - 589   2007.2

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  • 24pZL-3 Superconducting proximity effects in eutectic systems containing Sr_2RuO_4

    Kittaka S., Kusaba S., Yaguchi H., Yonezawa S., Maeno Y., Fittipaldi R., Vecchione A.

    Meeting abstracts of the Physical Society of Japan   61 ( 2 )   470 - 470   2006.8

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  • 24pZL-4 Effects of uni-axial pressure on superconductivity in eutectic containing Sr_2RuO_4

    Yaguchi H., Kittaka S., Takizawa K., Fusanobori S., Maeno Y., Fittipaldi R., Vecchione A., Hooper J.

    Meeting abstracts of the Physical Society of Japan   61 ( 2 )   471 - 471   2006.8

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  • 27aTC-3 Weak superconductivity observed in Sr_3Ru_2O_7 regions of Sr_2RuO_4-Sr_3Ru_2O_7 eutectic system

    Kittaka S., Fusanobori S., Yaguchi H., Yonezawa S., Maeno Y., Fittipaldi R., Vecchione A.

    Meeting abstracts of the Physical Society of Japan   61 ( 1 )   507 - 507   2006.3

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  • 21aYJ-2 Superconductivity of Sr_2RuO_4-Sr_3Ru_2O_7 Eutectic

    Fusanobori S., Kittaka S., Yaguchi H., Yonezawa S., Maeno Y., Fittipaldi R., Vecchione A.

    Meeting abstracts of the Physical Society of Japan   60 ( 2 )   478 - 478   2005.8

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  • 21aYJ-1 Interface superconductivity in Sr_2RuO_4-Ru under uniaxial pressure

    Yagudhi H., Kittaka S., Takizawa K., Maeno Y.

    Meeting abstracts of the Physical Society of Japan   60 ( 2 )   478 - 478   2005.8

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Presentations

  • 角度回転比熱測定からの超伝導ギャップ構造(領域8,領域4シンポジウム:新奇重い電子超伝導体UTe2の研究の現状)

    橘高 俊一郎

    日本物理学会2020年秋季大会  2020.9 

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  • 磁場角度の効果から探るPrTi2Al20とPrIr2Zn20の多極子秩序相

    橘高 俊一郎

    J-Physics地域研究会・本郷  2019.6 

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  • Thermodynamic study of the pairing symmetry in Sr2RuO4 Invited International conference

    Shunichiro Kittaka

    Strontium Ruthenate - 25 years of a puzzling superconductor  2019.5 

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  • 幾何学フラストレーションを持つ重い電子系反強磁性体CePdAlとその置換系における極低温精密磁化測定

    清水悠晴, 中村翔太, 望月健生, 河野洋平, 橘高俊一郎, 榊原俊郎, 池田陽一, 石川義和

    日本物理学会第74回年次大会  2019.3 

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  • 擬カゴメ近藤格子CeRhSnにおける量子臨界性の磁場角度依存性

    橘高 俊一郎, 河野 洋平, 津田 研, 高畠 敏郎, 榊原 俊郎

    日本物理学会第74回年次大会  2019.3 

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  • CeCoIn5のNi置換系における異方的量子臨界揺らぎ

    横山淳, 鈴木康平, 天谷健一, 中村翔太, 河野洋平, 橘高俊一郎, 榊原俊郎

    日本物理学会第74回年次大会  2019.3 

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  • Kitaevスピン液体候補物質OsCl3の合成と物性

    片岡亨太, 平井大悟郎, 矢島健, 浜根大輔, 橘高俊一郎, 榊原俊郎, 広井善二

    日本物理学会第74回年次大会  2019.3 

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  • PrTi2Al20における高圧下交流比熱測定

    星竜二, 元山史都, 桑田凌, 曽我部尚希, 磯前貴央, 酒井明人, 中辻知, 橘高俊一郎, 上床美也, 北川健太郎, 松林和幸

    日本物理学会第74回年次大会  2019.3 

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  • 新しいYb系化合物Yb2Rh3Si5の極低温磁化と比熱測定

    中村翔太, 成瀬淳基, 兵藤一志, 河野洋平, 橘高俊一郎, 榊原俊郎, 大原繁男

    日本物理学会第74回年次大会  2019.3 

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  • 擬カゴメ近藤格子化合物CeTSn (T=Rh, Ir)の磁気フラストレーションとLaIrSnの超伝導

    津田研, 楊崇立, 志村恭通, 山根悠, 梅尾和則, 鬼丸孝博, 高畠敏郎, 福岡宏, 菊川直樹, 寺嶋太一, 廣瀬陽代, 宇治進也, 橘高俊一郎, 榊原俊郎

    日本物理学会第74回年次大会  2019.3 

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  • フェルダジル系金属錯体を用いたスピンモデル設計

    上本菜央, 山口博則, 細越裕子, 河野洋平, 橘高俊一郎, 榊原俊郎

    日本物理学会第74回年次大会  2019.3 

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  • ハニカム格子系における特異な内部磁場と磁場誘起量子物性

    岩﨑義己, 山口博則, 細越裕子, 川上貴資, 木田孝則, 萩原政幸, 河野洋平, 橘高俊一郎, 榊原俊郎

    日本物理学会第74回年次大会  2019.3 

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  • Field-orientation effect on the hidden-order transition in URu2Si2 International conference

    Shunichiro Kittaka

    Symposium:TPFC 2019  2019.2 

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  • Multiband full-gap superconductivity in heavy-fermion superconductor CeCu2Si2 revealed by specific-heat measurements Invited International conference

    Shunichiro Kittaka

    Plasma 2019 Workshop  2019.1 

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  • Sr2RuO4の超伝導ギャップ構造の検証:回転磁場下での比熱測定から Invited

    橘高 俊一郎, 中村 翔太, 榊原 俊郎, 菊川 直樹, 寺嶋 太一, 宇治 進也, Dmitry A. Sokolov, Andrew, P. Mackenzie, 入江 光輝, 堤 康雅, 鈴木 雄大, 町田 一成

    つくば-柏-本郷 超伝導かけはしプロジェクト ワークショップ(2)  2019.1 

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  • Thermodynamic study of Sr2RuO4: identification of the superconducting gap structure Invited International conference

    S. Kittaka, S. Nakamura, T. Sakakibara, N. Kikugawa, T. Terashima, S. Uji, D. A. Sokolov, A. P. Mackenzie, K. Irie, Y. Tsutsumi, K. Suzuki, K. Machida

    International Workshop on j-Fermion Physics and Materials  2018.12 

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  • 磁場角度分解比熱・エントロピー測定からみたPrTi2Al20の四極子秩序

    橘高 俊一郎, 谷口 貴紀, 中村 翔太, 榊原 俊郎, 瀧川 仁, 辻本 真規, 酒井 明人, 松本 洋介, 中辻 知

    日本物理学会2018年秋季大会  2018.9 

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  • 圧力下における交流法比熱測定装置の開発

    星竜二, 橘高俊一郎, 上床美也, 松林和幸

    日本物理学会2018年秋季大会  2018.9 

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  • 重い電子系化合物YbNi2Si3の極低温比熱と磁化

    中村翔太, 兵頭一志, 橘高俊一郎, 榊原俊郎, 大原繁男

    日本物理学会2018年秋季大会  2018.9 

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  • フェルダジルラジカル系スピン1/2フェロレッグラダーにおける量子臨界現象の普遍性

    河野洋平, 橘高俊一郎, 山口博則, 細越裕子, 榊原俊郎

    日本物理学会2018年秋季大会  2018.9 

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  • スピンアイスDy2Ti2O7の気相液相転移再考

    元木大介, 河野洋平, 橘高俊一郎, 榊原俊郎, 高津浩, 門脇広明

    日本物理学会2018年秋季大会  2018.9 

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  • 幾何学フラストレーションを持つ重い電子系反強磁性体CePdAlにおける極低温精密磁化測定

    清水悠晴, 中村翔太, 望月健生, 河野洋平, 橘高俊一郎, 榊原俊郎, 池田陽一, 石川義和

    日本物理学会2018年秋季大会  2018.9 

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  • 擬カゴメ近藤格子系CeIrSnの磁気フラストレーション

    津田研, 楊崇立, 山根悠, 梅尾和則, 志村恭通, 鬼丸孝博, 高畠敏郎, 福岡宏, 菊川直樹, 寺嶋太一, 廣瀬陽代, 宇治進也, 橘高俊一郎, 榊原俊郎

    日本物理学会2018年秋季大会  2018.9 

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  • CeCoIn5のNi置換系における量子臨界揺らぎの磁気異方性

    鈴木康平, 横山淳, 大島佳樹, 天谷健一, 中村翔太, 河野洋平, 橘高俊一郎, 榊原俊郎

    日本物理学会2018年秋季大会  2018.9 

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  • S=1/2ハニカム格子系の低温物性

    上本菜央, 山口博則, 細越裕子, 河野洋平, 橘高俊一郎, 榊原俊郎

    日本物理学会2018年秋季大会  2018.9 

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  • Full-gap superconductivity of Cd2Re2O7 investigated by field-angle-resolved measurement of its specific heat

    S. Kittaka, D. Hirai, Z. Hiroi, T. Sakakibara

    B01 D01トピカルミーテイング ものづくりシリーズ第3回「物質探索最前線」  2018.8 

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  • Quasi-one-dimensional Bose-Einstein Condensation in Spin- 1/2 Ferromagnetic-leg Ladder Organic Magnets International conference

    Y. Kono, S. Kittaka, H. Yamaguchi, Y. Hosokoshi, T. Sakakibara

    International Conference on Magnetism 2018 (ICM2018)  2018.7 

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  • Non-Fermi-liquid behavior in heavy-fermion compound CeCo1-xNixIn5 International conference

    K. Suzuki, M. Yokoyama, Y. Oshima, T. Hasegawa, K. Tenya, S. Nakamura, S. Kittaka, T. Sakakibara, I. Kawasaki, W. Higemoto, I. Watanabe

    International Conference on Magnetism 2018 (ICM2018)  2018.7 

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  • Magnetic Behavior of Quasi-One-dimensional Frustrated Quantum spin systems (Rb,Cs)2Cu2Mo3O12 International conference

    Y. Yasui, S. Iguchi, S. Nakamura, Y. Kono, S. Kittaka, T. Sakakibara

    International Conference on Magnetism 2018 (ICM2018)  2018.7 

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  • Investigation of the Wing-Structure of the Ising Ferromagnet URhGe by Angle-Resolved Measurements International conference

    S. Nakamura, S. Kittaka, T. Sakakibara, Y. Shimizu, Y. Kono, Y. Haga, E. Yamamoto

    International Conference on Magnetism 2018 (ICM2018)  2018.7 

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  • Towards identification of the superconducting gap structure of Sr2RuO4: evidence for a horizontal line node gap from field-angle dependence of its specific heat International conference

    S. Kittaka, S. Nakamura, T. Sakakibara, N. Kikugawa, T. Terashima, S. Uji, D. A. Sokolov, A. P. Mackenzie, K. Irie, Y. Tsutsumi, K. Suzuki, K. Machida

    International Conference on Magnetism 2018 (ICM2018)  2018.7 

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  • Novel quantum phases of conductive multipole systems studied by field-angle-resolved measurements of specific heat and entropy

    橘高 俊一郎

    J-Physics平成30年度領域全体会議  2018.5 

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  • スピンアイス物質Dy2Ti2O7の磁場角度分解エントロピー測定

    橘高 俊一郎, 門脇 広明, 高津 浩, 中村 翔太, 榊原 俊郎

    日本物理学会第73回年次大会  2018.3 

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  • Ce(Co1-xNix)In5における量子臨界揺らぎ

    鈴木 康平, 横山 淳, 大島 佳樹, 天谷 健一, 近藤 晃弘, 金道 浩一, 中村 翔太, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第73回年次大会  2018.3 

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  • CsFe(MoO4)2およびKFe(MoO4)2におけるスピンカイラリティ起源の強誘電性

    綿貫 竜太, 橋本 真里子, 依光 雄也, 三田村 裕幸, 中村 翔太, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第73回年次大会  2018.3 

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  • URhGeのb方向近傍の極低温比熱・磁気熱量効果測定

    中村 翔太, 橘高 俊一郎, 河野 洋平, 榊原 俊郎, 清水 悠晴, 芳賀 芳範, Posp??il, 山本 悦嗣

    日本物理学会第73回年次大会  2018.3 

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  • 重い電子系U1-xThxBe13の極低温電気抵抗・比熱における非フェルミ液体的性質

    清水 悠晴, 橘高 俊一郎, 中村 翔太, 榊原 俊郎, 青木 大, 佐藤 芳樹, 本間 佳哉, 仲村 愛, Maurya Arvin, 李 徳新, 本多 史憲

    日本物理学会第73回年次大会  2018.3 

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  • Gap structure and paring mechanism of non-centrosymmetric superconductor PbTaSe2

    Y. Sun, S. Kittaka, T. Sakakibara, S. Pyon, T. Tamegai

    日本物理学会第73回年次大会  2018.3 

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  • S=2ハニカム格子磁性体[Mn(hfac)2][o-Py-V-p-F2]の低温物性

    岡部 俊輝, 山口 博則, 細越 裕子, 萩原 政幸, 中村 翔太, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第73回年次大会  2018.3 

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  • Field-orientation dependence of a ferroquadrupole order in PrTi2Al20 investigated by thermal measurements

    S. Kittaka, T. Taniguchi, S. Nakamura, T. Sakakibara, M. Takigawa, M. Tsujimoto, A. Sakai, Y. Matsumoto, S. Nakatsuji

    J-Physics平成29年度領域全体会議  2018.3 

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  • 精密磁場中比熱測定による重い電子系超伝導体CeCu2Si2の研究 Invited

    橘高 俊一郎

    東京大学物性研究所所長賞授与式  2018.3 

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  • Gap structure of uranium superconductors studied by specific heat Invited International conference

    橘高 俊一郎

    Physics of Uranium-based Unconventional superconductors  2017.9 

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  • Investigation of the Wing-Structure Phase Diagram of the Ising Ferromagnet URhGe by Angle-Resolved Magnetization Measurements International conference

    S. Nakamura, T. Sakakibara, Y. Shimizu, Y. Kono, S. Kittaka, Y. Haga, J. Posp??il, E. Yamamoto

    J-Physics 2017: International Workshop on Multipole Physics and Related Phenomena  2017.9 

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  • 磁場角度分解比熱測定によるSr2RuO4の超伝導ギャップ構造の再検証

    橘高 俊一郎, 中村 翔太, 榊原 俊郎, 菊川 直樹, 寺嶋 太一, 宇治 進也, Dmitry Sokolov, Andrew, P. Mackenzie, 入江 光輝, 堤 康雅, 町田 一成

    日本物理学会2017年秋季大会  2017.9 

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  • CsFe(MoO4)2の磁性と強誘電性

    橋本真里子, 依光雄也, 鈴木和也, 中村翔太, 橘高 俊一郎, 榊原俊郎, 三田村裕幸, 綿貫竜太

    日本物理学会2017年秋季大会  2017.9 

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  • Disorder-sensitive node-like small gap in FeSe

    Y. Sun, S. Kittaka, T. Sakakibara, J. Chen, T. Tamegai, K. Machida

    日本物理学会2017年秋季大会  2017.9 

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  • CeCo(In1-xZnx)5の低温高磁場相における磁化測定

    大島佳樹, 横山淳, 鈴木康平, 益子寛明, 天谷健一, 中村翔太, 橘高 俊一郎, 榊原俊郎

    日本物理学会2017年秋季大会  2017.9 

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  • 強磁性超伝導体UCoGeにおける極低温磁場回転比熱測定

    中村翔太, 橘高 俊一郎, 清水悠晴, 河野洋平, 榊原俊郎, 青木大, 仲村愛, 本多史憲, Jacques Flouquet

    日本物理学会2017年秋季大会  2017.9 

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  • 重い電子系超伝導体U0.97Th0.03Be13における極低温精密磁化測定

    清水悠晴, 中村翔太, 河野洋平, 橘高 俊一郎, 榊原俊郎, 青木大, 本間佳哉, 仲村愛, 町田一成

    日本物理学会2017年秋季大会  2017.9 

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  • スピン1/2有機フェロレッグラダー物質の磁気熱量効果測定

    河野洋平, 橘高 俊一郎, 山口博則, 細越裕子, 榊原俊郎

    日本物理学会2017年秋季大会  2017.9 

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  • ハニカム格子を形成するフェルダジル系金属錯体の低温物性

    岡部俊輝, 山口博則, 小野俊雄, 細越裕子, 中村翔太, 橘高 俊一郎, 榊原俊郎

    日本物理学会2017年秋季大会  2017.9 

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  • Superconducting gap symmetries and magnetic responses in the uranium heavy-fermion systems UBe13 and UPd2Al3 International conference

    Y. Shimizu, S. Kittaka, T. Sakakibara, D. Aoki

    International Conference on Strongly Correlated Electron Systems 2017 (SCES2017)  2017.7 

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  • Quadrupole order and quantum spin liquid states in Tb2+xTi2-xO7+y International conference

    H. Takatsu, H. Kadowaki, S. Onoda, S. Kittaka, A. Kasahara, Y. Kono, T. Sakakibara, Y. Kato, B. Fak, J. Ollivier, J. W. Lynn, T. Taniguchi, M. Wakita, H. Kageyama

    International Conference on Strongly Correlated Electron Systems 2017 (SCES2017)  2017.7 

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  • Superconducting gap structure of Sr2RuO4 revisited by the field-angle-dependent specific heat at very low temperatures International conference

    S. Kittaka, S. Nakamura, T. Sakakibara, N. Kikugawa, T. Terashima, S. Uji, D. Sokolov, A. P. Mackenzie, K. Irie, Y. Tsutsumi, K. Machida

    International Conference on Strongly Correlated Electron Systems 2017 (SCES2017)  2017.7 

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  • Hard-Axis Magnetization Study on the Ising Ferromagnet URhGe with High-Precision in-situ Alignment of the Magnetic Field International conference

    S. Nakamura, Y. Shimizu, Y. Kono, S. Kittaka, T. Sakakibara, Y. Haga, J. Pospíšil, E. Yamamoto

    International Conference on Strongly Correlated Electron Systems 2017 (SCES2017)  2017.7 

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  • Field-angle-resolved Specific Heat of Uranium Superconductors Invited International conference

    S. Kittaka, Y. Shimizu, T. Sakakibara

    ACTINIDES2017  2017.7 

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  • 準粒子励起構造から探るSr2RuO4のノード構造と対称性 Invited

    橘高 俊一郎

    基研研究会 「超伝導研究の最先端:多自由度、非平衡、電子相関、トポロジー、人工制御」  2017.6 

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  • (シンポジウム講演) 比熱測定から見た重い電子系超伝導体のギャップ構造 Invited

    橘高 俊一郎

    日本物理学会第72回年次大会  2017.3 

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  • (若手奨励賞) 磁場方位制御下の精密比熱測定による重い電子系超伝導の研究 Invited

    橘高 俊一郎

    日本物理学会第72回年次大会  2017.3 

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  • Gap structure of FeSe determined by field-angle-resolved specific heat measurements

    Y. Sun, S. Kittaka, T. Sakakibara, J. Chen, T. Tamegai, K. Machida

    日本物理学会第72回年次大会  2017.3 

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  • 極低温におけるSr2RuO4の磁場角度分解比熱

    橘高 俊一郎, 中村 翔太, 榊原 俊郎, 菊川 直樹, 寺嶋 太一, 宇治 進也, Dmitry Sokolov, Andrew, P. Mackenzie, 堤 康雅, 町田 一成

    日本物理学会第72回年次大会  2017.3 

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  • URhGeの磁化困難軸方向近傍の極低温磁化測定

    中村翔太, 河野洋平, 橘高 俊一郎, 榊原俊郎, 清水悠晴, 芳賀芳範, J. Posp??i, 山本悦嗣

    日本物理学会第72回年次大会  2017.3 

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  • 重い電子系超伝導体U0.97Th0.03Be13における極低温比熱測定

    清水悠晴, 橘高 俊一郎, 中村翔太, 榊原俊郎, 青木大, 本間佳哉, 仲村愛, 町田一成

    日本物理学会第72回年次大会  2017.3 

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  • 反強磁性ハニカム格子磁性体2-Cl-3,6-F2-Vの低温物性II

    岡部俊輝, 山口博則, 小野俊雄, 細越裕子, 橘高 俊一郎, 榊原俊郎

    日本物理学会第72回年次大会  2017.3 

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  • Searching for Gap Nodes in the Heavy-fermion Superconductor CeCu2Si2 from Specific-heat Measurement International conference

    S. Kittaka, Y. Aoki, Y. Shimura, T. Sakakibara, S. Seiro, C. Geibel, F. Steglich, Y. Tsutsumi, H. Ikeda, K. Machida

    29th International Symposium on Superconductivity (ISS2016)  2016.12 

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  • 超伝導体Zr2Coの磁場角度分解比熱

    橘高 俊一郎, 榊原 俊郎, 垣花 将司, 照屋 淳志, 辺土 正人, 仲間 隆男, 大貫 惇睦

    日本物理学会2016年秋季大会  2016.9 

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  • 六方晶Ce2Pt6Ga15の重い電子状態

    松本裕司, 植田拓也, 大原繁男, 河野洋平, 中村翔太, 橘高 俊一郎, 榊原俊郎, 上床美也

    日本物理学会2016年秋季大会  2016.9 

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  • 熱伝導率測定および対破壊効果からみた重い電子系超伝導体CeCu2Si2の超伝導ギャップ構造

    大西隆史, 寺澤大樹, 山下卓也, 常盤欣文, 橘高 俊一郎, 榊原俊郎, H.S.Jeevan, C.Geibel, M. Konczykowski, 芳賀芳範, 水上雄太, 芝内孝禎, 寺嶋孝仁, 松田祐司

    日本物理学会2016年秋季大会  2016.9 

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  • 重い電子系超伝導体UPd2Al3における極低温精密磁化測定

    清水悠晴, 橘高 俊一郎, 河野洋平, 中村翔太, 榊原俊郎, 青木大

    日本物理学会2016年秋季大会  2016.9 

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  • 重い電子系化合物UBe13の超伝導・非フェルミ液体状態における極低温精密磁化測定

    清水 悠晴, 河野 洋平, 橘高 俊一郎, 芳賀 芳範, 山本 悦嗣, 網塚 浩, 榊原 俊郎

    日本物理学会2016年秋季大会  2016.9 

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  • URhGeの磁化困難軸方向の極低温磁化測定

    中村翔太, 河野洋平, 橘高 俊一郎, 榊原俊郎, 清水悠晴, 芳賀芳範, J. Posp??i, 山本悦嗣

    日本物理学会2016年秋季大会  2016.9 

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  • Thermal conductivity of exotic elementary excitations in quantum spin ice International conference

    Y. Tokiwa, T. Yamashita, D. Terazawa, M. Udagawa, Y. Yasui, S. Kittaka, T. Sakakibara, K. Kimura, M. Halim, S. Nakatsuji, T. Terashima, T. Shibauchi, Y. Matsuda

    International Conference on Strongly Correlated Electron Systems 2016 (SCES2016)  2016.5 

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  • Nodal gap structure of the heavy-fermion superconductor URu2Si2 revealed by field-angle-dependent specific-heat measurements International conference

    S. Kittaka, Y. Shimizu, T. Sakakibara, Y. Haga, E. Yamamoto, Y. Onuki, Y. Tsutsumi, T. Nomoto, H. Ikeda, K. Machida

    International Conference on Strongly Correlated Electron Systems 2016 (SCES2016)  2016.5 

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  • Single crystal growth and physical properties of heavy fermion antiferromagnet YbNi2Si2 International conference

    Y. Matsumoto, Y. Nakamura, S. Ohara, Y. Haga, Z. Fisk, Y. Kono, S. Nakamura, S. Kittaka, T. Sakakibara

    International Conference on Strongly Correlated Electron Systems 2016 (SCES2016)  2016.5 

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  • 極低温熱伝導率測定からみた重い電子系超伝導体CeCu2Si2の超伝導ギャップ構造

    大西 隆史, 寺澤 大樹, 山下 卓也, 笠原 裕一, 常盤 欣文, 橘高 俊一郎, 榊原 俊郎, H. S.Jeevan, C. Geibel, M. Konczykowski, 芳賀 芳範, 芝内 孝禎, 寺嶋 孝仁, 松田 祐司

    日本物理学会第71回年次大会  2016.3 

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  • Sr2RuO4の一軸性圧力下比熱

    山崎 照夫, 橘高 俊一郎, 伊藤 温海, 榊原 俊郎, 矢口 宏

    日本物理学会第71回年次大会  2016.3 

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  • スピン1/2有機フェロレッグラダー物質の磁場誘起量子臨界現象

    河野 洋平, 橘高 俊一郎, 山口 博則, 細越 裕子, 榊原 俊郎

    日本物理学会第71回年次大会  2016.3 

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  • 重い電子系反強磁性体YbNi2Si2の単結晶育成と磁性

    松本 裕司, 中村 友紀, 大原 繁男, 芳賀 芳範, Zachary Fisk, 河野 洋平, 中村 翔太, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第71回年次大会  2016.3 

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  • 超伝導ギャップ構造の解析に適した圧力下角度分解磁場中比熱測定装置の開発

    橘高 俊一郎, 松林 和幸, 上床 美也, 榊原 俊郎

    日本物理学会第71回年次大会  2016.3 

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  • UCoGeの容易軸方向磁場下における磁化と比熱の測定

    中村 翔太, 河野 洋平, 清水 悠晴, 橘高 俊一郎, 榊原 俊郎, 青木 大, 仲村 愛, 本多 史憲, Jacques Flouquet

    日本物理学会第71回年次大会  2016.3 

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  • 重い電子系反強磁性体YbNi2Si2の磁場中比熱

    中村 友紀, 松本 裕司, 大原 繁男, 河野 洋平, 中村 翔太, 橘高 俊一郎, 榊原 俊郎, 芳賀 芳範, Zachary Fisk

    日本物理学会第71回年次大会  2016.3 

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  • 重い電子系超伝導体UBe13における極低温高磁場中比熱

    清水 悠晴, 橘高 俊一郎, 河野 洋平, 榊原 俊郎, 芳賀 芳範, 山本 悦嗣, 網塚 浩, 町田 一成

    日本物理学会第71回年次大会  2016.3 

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  • CuO2リボン鎖を持つA2Cu2Mo3O12 (A=Rb, Cs)の磁気的挙動と磁気構造

    藤村 明央, 安井 幸夫, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, 井川 直樹, 松川 健, 吉田 幸彦, 星川 晃範, 石垣 徹

    日本物理学会第71回年次大会  2016.3 

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  • 反強磁性ハニカム格子磁性体2-Cl-3,6-F2-Vの低温物性

    岡部 俊輝, 山口 博則, 小野 俊雄, 細越 裕子, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第71回年次大会  2016.3 

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  • 量子スピンアイス系Yb2Ti2O2の磁気特性

    濱地 紀彰, 安井 幸夫, 河野 洋平, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第71回年次大会  2016.3 

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  • 重い電子系における超伝導研究の新展開 ~磁場角度分解比熱測定からみたギャップ対称性~

    橘高 俊一郎

    日本学術会議公開シンポジウム 「物性物理学・一般物理学分野の展開と大型研究計画」  2016.3 

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  • 単結晶Biの極低温磁化測定

    中村 翔太, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, Kamran Behnia

    日本物理学会2015年秋季大会  2015.9 

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  • 熱伝導率測定による重い電子系超伝導体CeCu2Si2のギャップ構造の解明

    寺澤 大樹, 山下 卓也, 常盤 欣文, 橘高 俊一郎, 榊原 俊郎, H. S. Jeeva, C. Geibel, 芳賀 芳範, 寺嶋 孝仁, 松田 祐司

    日本物理学会2015年秋季大会  2015.9 

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  • 六方晶R2Pt6Ga15(R:希土類元素)の磁性

    植田 拓也, 松本 裕司, 大原 繁男, 河野 洋平, 中村 翔太, 橘高 俊一郎, 榊原 俊郎

    日本物理学会2015年秋季大会  2015.9 

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  • URu2Si2純良単結晶の極低温磁場中比熱

    橘高 俊一郎, 清水 悠晴, 榊原 俊郎, 芳賀 芳範, 山本 悦嗣, 大貫 惇睦, 堤 康雅, 町田 一成

    日本物理学会2015年秋季大会  2015.9 

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  • 比熱測定から見た重い電子系反強磁性超伝導体UPd2Al3の超伝導準粒子励起構造

    清水 悠晴, 橘高 俊一郎, 榊原 俊郎, 本間 佳哉, 青木 大

    日本物理学会2015年秋季大会  2015.9 

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  • フェルダジルラジカル系物質を用いた強磁性鎖からなるスピンラダーの量子臨界性の研究

    河野 洋平, 橘高 俊一郎, 榊原 俊郎, 山口 博則, 細越 裕子

    日本物理学会2015年秋季大会  2015.9 

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  • フェルダジルラジカルを用いた新規金属錯体の低温物性

    岡田 将孝, 山口 博則, 小野 俊雄, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, 細越 裕子

    日本物理学会2015年秋季大会  2015.9 

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  • Recent progress on the gap determination of heavy-fermion superconductors Invited International conference

    橘高 俊一郎

    Electron correlation in nanostructures  2015.9 

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  • First-order superconducting transition of Sr2RuO4 investigated by magnetization and magnetic torque International conference

    S. Kittaka, A. Kasahara, T. Sakakibara, D. Shibata, S. Yonezawa, Y. Maeno, K. Tenya, K. Machida

    The 20th International Conference on Magnetism (ICM2015)  2015.7 

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  • Low Temperature Magnetic Properties of a New Quasi-one-dimensional Organic Magnet α-2-Cl-4-F-V International conference

    Y. Kono, S. Kittaka, T. Sakakibara, H. Yamaguchi, Y. Hosokoshi

    The 20th International Conference on Magnetism (ICM2015)  2015.7 

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  • Field-induced phase transitions and magnetoferroelectricity in the perfect triangular lattice antiferromagnet RbFe(MoO4)2 in a vertical magnetic field International conference

    H. Mitamura, R. Watanuki, N. Onozaki, Y. Amou, Y. Kono, S. Kittaka, Y. Shimura, I. Yamamoto, K. Suzuki, T. Sakakibara

    The 20th International Conference on Magnetism (ICM2015)  2015.7 

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  • Correlation between ferromagnetism and superconductivity in Y9Co7 International conference

    S. Kunikata, A. Takeda, K. Imura, K. Deguchi, N. K. Sato, S. Kittaka, T. Sakakibara

    The 20th International Conference on Magnetism (ICM2015)  2015.7 

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  • Heat capacity measurements on UBe13 in rotated magnetic fields: anisotropic response in the normal state and the absence of nodal quasiparticles International conference

    Y. Shimizu, S. Kittaka, T. Sakakibara, Y. Haga, E. Yamamoto, H. Amitsuka, Y. Tsutsumi, K. Machida

    The 20th International Conference on Magnetism (ICM2015)  2015.7 

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  • 重い電子系化合物UBe13の高磁場常伝導状態及び超伝導相内における磁気異常の磁気応答

    清水 悠晴, 河野 洋平, 榊原 俊郎, 橘高 俊一郎, 芳賀 芳範, 山本 悦嗣, 網塚 浩

    日本物理学会第70回年次大会  2015.3 

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  • 低温磁化測定によるTb2+xTi2-xO7+yの長距離秩序の起源の検証

    高津 浩, 脇田 美香, 谷口 智洋, 門脇 広明, 笠原 聡, 河野 洋平, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第70回年次大会  2015.3 

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  • 正方晶PrZn11の一重項基底状態

    二宮 博樹, 佐藤 嵩晃, 松本 裕司, 大原 繁男, 河野 洋平, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第70回年次大会  2015.3 

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  • カゴ状構造を有するY5Tr6Sn18 (Tr:遷移金属)の超伝導ギャップ構造の研究

    加瀬 直樹, 橘高 俊一郎, 榊原 俊郎, 照井 祐輔, 中野 智仁, 武田 直也, 秋光 純

    日本物理学会第70回年次大会  2015.3 

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  • CeCu2Si2とUBe13における比熱と核磁気緩和率の温度依存性:多バンドフルギャップ超伝導の検証

    橘高 俊一郎, 堤 康雅, 清水 悠晴, 榊原 俊郎, 池田 浩章, 町田 一成

    日本物理学会第70回年次大会  2015.3 

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  • CuO2リボン鎖を持つCs2Cu2Mo3O12の磁気相図と磁気構造

    藤村 明央, 安井 幸夫, 井川 直樹, 吉田 幸彦, 石垣 徹, 河野 洋平, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第70回年次大会  2015.3 

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  • 量子スピンアイス系Yb2Ti2O7のμSR測定

    濱地 紀彰, 安井 幸夫, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, L. J. Chang, 小野田 繁樹, 渡邊 功雄

    日本物理学会第70回年次大会  2015.3 

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  • フェルタジルラジカルとTCNQから成る新規電荷移動錯体の低温物性

    佐々木 裕太, 山口 博則, 小野 俊雄, 細越 裕子, 河野 洋平, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第70回年次大会  2015.3 

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  • 完全三角格子反強磁性体RbFe(MoO4)2におけるスピンカイラリティ起源の強誘電性

    綿貫 竜太, 三田村 裕幸, 金子 耕士, 小林 理気, 天羽 祐太, 小野崎 紀道, 山本 勲, 鈴木 和也, 志村 恭通, 橘高 俊一郎, 榊原 俊郎

    日本物理学会2014年秋季大会  2014.9 

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  • S = 2 Mn錯体o-Py-V?Mn(hfac)2の低温物性

    新福 泰弘, 山口 博則, 小野 俊雄, 細越 裕子, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, 川上 貴資

    日本物理学会2014年秋季大会  2014.9 

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  • 重い電子系化合物UBe13における超伝導対称性と磁気異常及び非フェルミ液体状態

    清水 悠晴, 橘高 俊一郎, 榊原 俊郎, 芳賀 芳範, 網塚 浩, 町田 一成

    日本物理学会2014年秋季大会  2014.9 

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  • 新規スピンラダー有機磁性体α-2-Cl-4-F-Vの低温物性

    河野 洋平, 橘高 俊一郎, 榊原 俊郎, 山口 博則, 濱田 領平, 細越 裕子

    日本物理学会2014年秋季大会  2014.9 

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  • 五角形から成るフラストレート系物質の低温物性

    山口 博則, 小野 俊雄, 細越 裕子, 大久保 毅, 橘高 俊一郎, 榊原 俊郎, 荒木 幸治, 川上 貴資

    日本物理学会2014年秋季大会  2014.9 

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  • Cd2Os2O7の磁歪・熱膨張

    三田村 裕幸, 山浦 淳一, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, 廣井 善二

    日本物理学会2014年秋季大会  2014.9 

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  • 極低温比熱測定からみたTb2+xTi2-xO7+yにおける“隠れた秩序”と磁場誘起相転移

    高津 浩, 谷口 智洋, 門脇 広明, 橘高 俊一郎, 榊原 俊郎

    日本物理学会2014年秋季大会  2014.9 

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  • 非磁性基底二重項をもつPrIr2Zn20の磁場中比熱測定による四極子近藤効果の検証

    鬼丸 孝博, 松本 圭介, 梅尾 和則, 橘高 俊一郎, 荒木 幸治, 榊原 俊郎, 高畠 敏郎

    日本物理学会2014年秋季大会  2014.9 

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  • 超伝導体Sr2RuO4の磁場方向を精密制御した極低温磁化測定及び磁気トルク測定

    笠原 聡, 橘高 俊一郎, 榊原 俊郎, 柴田 大輔, 米澤 進吾, 前野 悦輝, 天谷 健一, 町田 一成

    日本物理学会2014年秋季大会  2014.9 

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  • カゴ状構造を有する Sc5Tr6Sn18(Tr = Co, Rh, Ir)の超伝導特性

    加瀬 直樹, 照井 祐輔, 中野 智仁, 武田 直也, 橘高 俊一郎, 榊原 俊郎, 秋光 純

    日本物理学会2014年秋季大会  2014.9 

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  • 一軸性圧力下での極低温磁場中比熱測定装置の開発とCeCoIn5への応用

    橘高 俊一郎, 榊原 俊郎, 横山 淳

    日本物理学会2014年秋季大会  2014.9 

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  • 比熱測定から調べた空間反転対称性の破れた超伝導体CePt3Siの磁場方位依存性

    橘高 俊一郎, 河野 洋平, 榊原 俊郎, rnst Bauer

    日本物理学会2014年秋季大会  2014.9 

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  • Low temperature magnetic properties of the cage compound TmTr2Al20(Tr = Ti, V) International conference

    N. Kase, Y. Shimura, S. Kittaka, T. Sakakibara, S. Nakatsuji, T. Nakano, N. Takeda, J. Akimitsu

    International Conference on Strongly Correlated Electron Systems 2014 (SCES2014)  2014.7 

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  • Magnetic field induced quantum critical phenomena in a non-Kramers doublet system PrIr2Zn20 International conference

    T. Onimaru, K. T. Matsumoto, K. Umeo, S. Kittaka, T. Sakakibara, T. Takabatake

    International Conference on Strongly Correlated Electron Systems 2014 (SCES2014)  2014.7 

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  • Y5Tr6Sn18(Tr=Rh, Ir)の置換効果に対する異方的超伝導ギャップへの影響

    加瀬 直樹, 橘高 俊一郎, 榊原 俊郎, 秋光 純

    日本物理学会第69回年次大会  2014.3 

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  • 磁場中比熱測定から見たUBe13の超伝導ギャップ構造と異常な常伝導状態

    橘高 俊一郎, 清水 悠晴, 榊原 俊郎, 網塚 浩, 芳賀 芳範, 山本 悦嗣, 堤 康雅, 町田 一成

    日本物理学会第69回年次大会  2014.3 

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  • 強磁性鎖から成るスピンラダー3-I-Vの低温物性

    山口 博則, 宮外 浩嗣, 小野 俊雄, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, 下川 統久朗, 細越 裕子

    日本物理学会第69回年次大会  2014.3 

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  • 超伝導体Sr2RuO4の磁場方向を精密制御した低温磁化測定

    笠原 聡, 橘高 俊一郎, 榊原 俊郎, 柴田 大輔, 米澤 進吾, 前野 悦輝, 天谷 健一, 町田 一成

    日本物理学会第69回年次大会  2014.3 

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  • フェルダジルラジカルを用いた金属錯体によるハニカム格子の形成

    新福 泰弘, 山口 博則, 小野 俊雄, 下川 統久朗, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, 細越 裕子

    日本物理学会第69回年次大会  2014.3 

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  • 強磁性相互作用を含む梯子格子磁性体における新奇量子相

    宮外 浩嗣, 山口 博則, 小野 俊雄, 下川 統久朗, 吉田 誠, 瀧川 仁, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, 奥西 巧一, 大久保 毅, 川上 貴資, 細越 裕子

    日本物理学会第69回年次大会  2014.3 

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  • 三角格子反強磁性体Ba3MTa2O9 (M=Ni & Co)の磁気相図

    小野 俊雄, 富永 紘基, 山口 博則, 河野 洋平, 橘高 俊一郎, 榊原 俊郎, 細越 裕子

    日本物理学会第69回年次大会  2014.3 

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  • 量子スピンアイス系Yb2Ti2O7の新奇な強磁性転移と磁気相図

    濱地 紀彰, 安井 幸夫, 橘高 俊一郎, 榊原 俊郎, 小野田 繁樹

    日本物理学会第69回年次大会  2014.3 

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  • 極低温磁化・比熱測定から見たCeCu2Si2の重い電子系超伝導

    橘高 俊一郎, 青木 優也, 志村 恭通, 榊原 俊郎, S. Seiro, C. Geibel, F. Steglich, 池田 浩章, 町田 一成

    日本物理学会2013年秋季大会  2013.9 

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  • 4倍周期磁気構造を持つ新規一次元磁性体の低温物性

    山口 博則, 小野 俊雄, 木田 孝則, 萩原 政幸, 大久保 毅, 松尾 晶, 金道 浩一, 荒木 幸治, 橘高 俊一郎, 榊原 俊郎, 細越 裕子

    日本物理学会2013年秋季大会  2013.9 

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  • 不純物散乱の強い系で実現するY5Tr6Sn18(Tr=Rh,Ir)の異方的超伝導

    加瀬 直樹, 橘高 俊一郎, 榊原 俊郎, 秋光 純

    日本物理学会2013年秋季大会  2013.9 

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  • PrIr2Zn20の超伝導と四極子秩序に対するLa置換効果

    松本 圭介, 鬼丸 孝博, 大林 容子, 長澤 直裕, 脇舎 和平, 梅尾 和則, 高畠 敏郎, 橘高 俊一郎, 榊原 俊郎

    日本物理学会2013年秋季大会  2013.9 

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  • 完全三角格子反強磁性体におけるスピンカイラリティ由来の強誘電性の発生条件

    三田村 裕幸, 綿貫 竜太, 天羽 祐太, 小野崎 紀道, 橘高 俊一郎, 河野 洋平, 志村 恭通, 榊原 俊郎, 鈴木 和也

    日本物理学会2013年秋季大会  2013.9 

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  • 完全三角格子反強磁性体RbFe(MoO4)2の高磁場新規磁気相

    三田村 裕幸, 綿貫 竜太, 河野 洋平, 橘高 俊一郎, 志村 恭通, 天羽 祐太, 小野崎 紀道, 榊原 俊郎, 鈴木 和也

    日本物理学会2013年秋季大会  2013.9 

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  • 磁場方向を精密制御した極低温磁化測定装置の開発

    笠原 聡, 橘高 俊一郎, 三田村 裕幸, 榊原 俊郎

    日本物理学会2013年秋季大会  2013.9 

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  • Field-orientation dependence of the specific heat of nodal superconductor KFe2As2 International conference

    S. Kittaka, Y. Aoki, N. Kase, T. Sakakibara, T. Saito, H. Fukazawa, Y. Kohori, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki

    International Conference on Strongly Correlated Electron Systems 2013 (SCES2013)  2013.8 

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  • Anisotropic superconducting gap of caged compound Y5Rh6Sn18 with strong intrinsic disorder International conference

    N. Kase, S. Kittaka, T. Sakakibara, J. Akimitsu

    International Conference on Strongly Correlated Electron Systems 2013 (SCES2013)  2013.8 

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  • Superconducting and Antiferroquadrupolar Transitions in Isoelectronic Caged Compounds PrT2Zn20 (T=Co, Rh, and Ir) International conference

    T. Onimaru, K. T. Matsumoto, N. Nagasawa, K. Wakiya, Y. Obayashi, Y. Shimada, Y. Inoue, K. Umeo, S. Kittaka, T. Sakakibara, Y. Karaki, K. Minoru, Y. Matsushita, T. Takabatake

    International Conference on Strongly Correlated Electron Systems 2013 (SCES2013)  2013.8 

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  • UPt3の磁場中比熱

    橘高 俊一郎

    「対称性の破れた凝縮系におけるトポロジカル量子現象」第12回集中連携研究会「Sr2RuO4の超伝導対称性とトポロジカル超伝導」  2013.6 

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  • 磁場中比熱測定によるCeCu2Si2の超伝導対称性の検証

    橘高 俊一郎, 青木 優也, 志村 恭通, 榊原 俊郎, S. Seiro, C. Geibel, F. Steglich, 池田 浩章, 町田 一成

    日本物理学会第68回年次大会  2013.3 

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  • カゴ状物質TmTr2Al20(Tr:遷移金属)の低温物性

    加瀬 直樹, 志村 恭通, 橘高 俊一郎, 榊原 俊郎, 中辻 知, 秋光 純

    日本物理学会第68回年次大会  2013.3 

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  • 重い電子系超伝導体CeCu2Si2の低温磁場中における比熱・磁化測定

    青木 優也, 橘高 俊一郎, 志村 恭通, 榊原 俊郎, C. Geibel, F. Steglich, 町田 一成

    日本物理学会第68回年次大会  2013.3 

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  • 強磁性鎖から成る新規梯子格子磁性体の低温物性

    山口 博則, 宮外 浩嗣, 小野 敏雄, 下川 統久朗, 川上 貴資, 志村 恭通, 加瀬 直樹, 荒木 幸治, 橘高 俊一郎, 榊原 俊郎, 細越 裕子

    日本物理学会第68回年次大会  2013.3 

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  • 量子スピンアイス系Yb2Ti2O7の新奇な磁気転移

    安井 幸夫, 小野田 繁樹, 橘高 俊一郎, 榊原 俊郎

    日本物理学会第68回年次大会  2013.3 

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  • 鉄系超伝導体KFe2As2の磁場中比熱と試料依存性

    青木 優也, 橘高 俊一郎, 加瀬 直樹, 榊原 俊郎, 斉藤 拓, 深澤 英人, 小堀 洋, 木方 邦宏, 李 哲虎, 伊豫 彰, 永崎 洋

    日本物理学会第67回年次大会  2013.3 

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  • Specific heat study of the heavy-fermion superconductor UPt3 Invited International conference

    S. Kittaka, K. An, T. Sakakibara, Y. Haga, E. Yamamoto, N. Kimura, Y. Onuki, K. Machida

    The IMR-ASRC 3rd REIMEI International Workshop  2013.2 

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  • 磁場中比熱・磁化測定からみたCeCu2Si2の超伝導対称性

    橘高 俊一郎

    「重い電子系の形成と秩序化」第4回研究会  2013.1 

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  • 重い電子系超伝導体CeCu2Si2の磁場中比熱

    橘高 俊一郎

    第6回物性科学領域横断研究会  2012.11 

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  • Field-angle-resolved specific heat measurements on anisotropic superconductors Invited International conference

    橘高 俊一郎

    Quantum Science Symposium-2012  2012.11 

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  • 回転磁場中比熱測定から見た異方的s波超伝導体CeRu2のギャップ構造

    橘高 俊一郎, 榊原 俊郎, 辺土 正人, 大貫 惇睦

    日本物理学会2012年秋季大会  2012.9 

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  • カゴ状物質TmTi2Al20の低温磁化、比熱測定

    加瀬 直樹, 志村 恭通, 橘高 俊一郎, 榊原 俊郎, 中辻 知, 秋光 純

    日本物理学会2012年秋季大会  2012.9 

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  • 非磁性基底二重項を持つ立方晶PrT2Zn20 (T=Rh, Ir)の反強四極子秩序と四極子近藤効果

    鬼丸 孝博, 長澤 直裕, 大林 容子, 脇舎 和平, 松本 圭介, 梅尾 和則, 橘高 俊一郎, 榊原 俊郎, 高畠 敏郎

    日本物理学会2012年秋季大会  2012.9 

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  • 完全三角格子反強磁性体RbFe(MoO4)2のパルス磁場中誘電分極測定

    三田村 裕幸, 綿貫 竜太, 天羽 祐太, 小野崎 紀道, 志村 恭通, 橘高 俊一郎, 榊原 俊郎, 鈴木 和也, 山本 勲

    日本物理学会2012年秋季大会  2012.9 

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  • 完全三角格子反強磁性体における磁性由来強誘電性の発生条件

    三田村 裕幸, 綿貫 竜太, 天羽 祐太, 小野崎 紀道, 志村 恭通, 橘高 俊一郎, 榊原 俊郎, 鈴木 和也, 山本 勲

    日本物理学会2012年秋季大会  2012.9 

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  • フェルダジルラジカルを用いた新規ハニカム格子磁性体の低温物性

    山口 博則, 岩瀬 賢治, 小野 俊雄, 志村 恭通, 加瀬 直樹, 橘高 俊一郎, 榊原 俊郎, 細越 裕子

    日本物理学会2012年秋季大会  2012.9 

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  • Singlet-triplet crossover in the two-dimensional dimer spin system YbAl3C3 International conference

    S. Kittaka, T. Sugiyama, Y. Shimura, T. Sakakibara, S. Matsuda, A. Ochiai

    The 19th International Conference on Magnetism with Strongly Correlated Electron Systems (ICM2012)  2012.7 

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  • Multipolar phase transition of the 4f2 nonmagnetic doublet in a caged compound PrRh2Zn20 International conference

    N. Nagasawa, K. T. Matsumoto, K. Wakiya, T. Onimaru, K. Umeo, S. Kittaka, T. Sakakibara, T. Takabatake

    The 19th International Conference on Magnetism with Strongly Correlated Electron Systems (ICM2012)  2012.7 

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  • Superconducting, antiferroquadrupolar, and structural transitions in caged compounds PrT2Zn20 (T=Ru, Rh, and Ir) International conference

    T. Onimaru, K. T. Matsumoto, N. Nagasawa, Y. F. Inoue, K. Umeo, S. Kittaka, T. Sakakibara, Y. Karaki, M. Kubota, T. Takabatake

    The 19th International Conference on Magnetism with Strongly Correlated Electron Systems (ICM2012)  2012.7 

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  • 高感度化したキャパシタンス式ファラデー法によるYbAl3C3微結晶の磁化測定(II)

    杉山 友理, 橘高 俊一郎, 志村 恭通, 榊原 俊郎, 松田 沙織, 落合 明

    日本物理学会第67回年次大会  2012.3 

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  • カゴ状化合物PrRh2Zn20の非磁性基底二重項と低温相転移

    鬼丸 孝博, 長澤 直裕, 松本 圭介, 梅尾 和則, 橘高 俊一郎, 榊原 俊郎, 高畠 敏郎

    日本物理学会第67回年次大会  2012.3 

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  • Pr内包カゴ状化合物PrRh2Zn20の非磁性基底二重項と多極子秩序

    長澤 直裕, 松本 圭介, 鬼丸 孝博, 梅尾 和則, 橘高 俊一郎, 榊原 俊郎, 高畠 敏郎

    日本物理学会第67回年次大会  2012.3 

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  • 回転磁場中比熱測定によるY5T6Sn18の超伝導ギャップ構造の研究

    加瀬 直樹, 橘高 俊一郎, 榊原 俊郎, 秋光 純

    日本物理学会第67回年次大会  2012.3 

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  • 重い電子系超伝導体CeRu2の極低温磁場中比熱

    橘高 俊一郎, 榊原 俊郎, 辺土 正人, 大貫 惇睦

    日本物理学会第67回年次大会  2012.3 

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  • フェルダジルラジカルを用いた新規梯子格子磁性体の低温磁気状態

    山口 博則, 岩瀬 賢治, 小野 俊雄, 下川 統久朗, 中野 博生, 志村 恭通, 加瀬 直樹, 橘高 俊一郎, 榊原 俊郎, 細越 裕子

    日本物理学会第67回年次大会  2012.3 

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  • UPt3の極低温回転磁場中比熱

    橘高 俊一郎

    「重い電子系の形成と秩序化」ワークショップ ~超伝導、多極子の物理における最近の話題~  2012.1 

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  • Superconducting Gap Structures of the Cage Compounds R5Rh6Sn18 (R = Sc, Y, Lu) International conference

    N. Kase, S. Kittaka, T. Sakakibara, J. Akimitsu

    International workshop on heavy fermion TOKIMEKI 2011  2011.11 

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  • Field Dependence of the Specific Heat in a Heavy-Fermion Superconductor CeIrIn5 International conference

    Y. Aoki, S. Kittaka, T. Sakakibara, A. Sakai, S. Nakatsuji, Y. Tsutsumi, K. Machida

    International workshop on heavy fermion TOKIMEKI 2011  2011.11 

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  • 回転磁場中比熱測定から明らかにする重い電子系超伝導体CeIrIn5のノード構造

    橘高 俊一郎

    第2回重い電子系若手秋の学校  2011.9 

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  • 比熱測定によるY5Rh6Sn18 (T = Rh, Ir)の異方的超伝導ギャップ構造の決定

    加瀬 直樹, 橘高 俊一郎, 榊原 俊郎, 秋光 純

    日本物理学会2011年秋季大会  2011.9 

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  • キャパシタンス式ファラデー法の高感度化及びYbAl3C3微結晶の磁化測定(2)

    杉山 友理, 橘高 俊一郎, 志村 恭通, 榊原 俊郎, 松田 沙織, 落合 明

    日本物理学会2011年秋季大会  2011.9 

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  • 鉄ヒ素系超伝導体KFe2As2における比熱の回転磁場依存性と超伝導ギャップ構造

    青木 優也, 橘高 俊一郎, 加瀬 直樹, 榊原 俊郎, 斉藤 拓, 深澤 英人, 小堀 洋, 木方 邦宏, 李 哲虎, 伊豫 彰, 永崎 洋

    日本物理学会2011年秋季大会  2011.9 

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  • 非磁性Γ3二重項をもつPrRh2Zn20の低温比熱

    長澤 直裕, 松本 圭介, 鬼丸 孝博, 梅尾 和則, 橘高 俊一郎, 榊原 俊郎, 高畠 敏郎

    日本物理学会2011年秋季大会  2011.9 

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  • RbFe(MoO4)2の磁場中誘電分極測定III

    三田村 裕幸, 綿貫 竜太, 小野崎 紀道, 志村 恭通, 橘高 俊一郎, 榊原 俊郎, 鈴木 和也

    日本物理学会2011年秋季大会  2011.9 

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  • 回転磁場中比熱測定によるCeIrIn5の超伝導ギャップ構造の研究

    橘高 俊一郎, 青木 優也, 榊原 俊郎, 酒井 明人, 中辻 知, 堤 康雅, 町田 一成

    日本物理学会2011年秋季大会  2011.9 

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  • Uniaxial Pressure Effects on Sr2RuO4 and Ca2RuO4 International conference

    H. Taniguchi, R. Ishikawa, S. Kittaka, S. Yonezawa, F. Nakamura, S. Goh, Y. Maeno

    International Conference on Strongly Correlated Electron Systems 2011 (SCES2011)  2011.9 

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  • Anisotropy of the superconducting properties of UPt3 studied by the specific heat in rotating fields International conference

    S. Kittaka, K. An, T. Sakakibara, Y. Haga, E. Yamamoto, N. Kimura, Y. Onuki, K. Machida

    International Conference on Strongly Correlated Electron Systems 2011 (SCES2011)  2011.8 

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  • Probing Spin Chirality of the Equilateral Triangular-Lattice Antiferromagnet RbFe(MoO4)2 Through Multiferroicity International conference

    H. Mitamura, R. Watanuki, N. Onozaki, S. Kittaka, Y. Shimura, T. Sakakibara, K. Suzuki

    International Conference on Strongly Correlated Electron Systems 2011 (SCES2011)  2011.8 

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  • 重い電子系超伝導体UPt3およびCeIrIn5の角度分解磁場中比熱

    橘高 俊一郎

    「重い電子系の形成と秩序化」第3回研究会  2011.6 

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  • UPt3の角度分解磁場中比熱測定による超伝導ギャップ構造の観測(3)

    安 幸治, 橘高 俊一郎, 榊原 俊郎, 芳賀 芳範, 山本 悦嗣, 木村 憲昭, 大貫 惇睦, 町田 一成

    日本物理学会第66回年次大会  2011.3 

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  • ウラン系超伝導体UPt3における比熱の磁場方位依存性

    橘高 俊一郎, 安 幸治, 榊原 俊郎, 芳賀 芳範, 山本 悦嗣, 木村 憲彰, 大貫 惇睦, 町田 一成

    日本物理学会第66回年次大会  2011.3 

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  • キャパシタンス式ファラデー法の高感度化及びYbAl3C3微結晶の磁化測定

    杉山 友理, 橘高 俊一郎, 志村 恭通, 榊原 俊郎, 松田 沙織, 落合 明

    日本物理学会第66回年次大会  2011.3 

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  • マイクロカンチレバーを用いた高感度極低温磁化測定装置の開発

    杉山 友理, 橘高 俊一郎, 三田村 裕幸, 榊原 俊郎

    日本物理学会2010年秋季大会  2010.9 

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  • スピンギャップ系YbAl3C3の極低温磁化

    橘高 俊一郎, 志村 恭通, 榊原 俊郎, 松田 沙織, 落合 明

    日本物理学会2010年秋季大会  2010.9 

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  • UPt3の角度分解磁場中比熱測定による超伝導ギャップ構造の観測(2)

    安幸治, 橘高 俊一郎, 榊原 俊郎, 芳賀 芳範, 山本 悦嗣, 木村 憲昭, 大貫 惇睦, 町田 一成

    日本物理学会2010年秋季大会  2010.9 

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  • Sr2RuO4の超伝導オンセット温度の一軸性圧力による上昇

    谷口 晴香, 橘高 俊一郎, 米澤 進吾, 前野 悦輝

    日本物理学会第65回年次大会  2010.3 

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  • Sr2RuO4の反磁性的な超伝導ドメイン

    柄木 良友, 根間 裕史, 久保 田実, 上床 美也, 橘高 俊一郎, 前野 悦輝

    日本物理学会第65回年次大会  2010.3 

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  • Enhancement of Tc to 3 K by applying uniaxial pressure to Sr2RuO4 International conference

    S. Kittaka, H. Taniguchi, S. Yonezawa, H. Yaguchi, Y. Maeno

    International Symposium on Physics of New Quantum Phases in Superclean Materials (PSM2010)  2010.3 

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  • Sr2RuO4の極低温磁化測定

    柄木 良友, 根間 裕史, 久保田 実, 上床 美也, 橘高 俊一郎, 前野 悦輝

    日本物理学会2009年秋季大会  2009.9 

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  • Sr2RuO4の超伝導転移温度の一軸性圧力効果

    谷口 晴香, 橘高 俊一郎, 米澤 進吾, 前野 悦輝

    日本物理学会2009年秋季大会  2009.9 

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  • Uniaxial pressure effect on the superconductivity observed in the Sr3Ru2O7 region of the Sr3Ru2O7-Sr2RuO4 eutectic system International conference

    S. Kittaka, H. Yaguchi, Y. Maeno, R. Fittipaldi, A. Vecchione

    The 9th International Conference on Materials and Mechanisms of Superconductivity (M2S-IX)  2009.9 

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  • Accurate and precise examination of the angular dependence of the upper critical field of Sr2RuO4 International conference

    S. Kittaka, T. Nakamura, Y. Aono, S. Yonezawa, K. Ishida, Y. Maeno

    Novel Spin Pairing 2009 (NSP2009)  2009.9 

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  • Uniaxial pressure effect on the eutectic systems containing spin-triplet superconductor Sr2RuO4

    S. Kittaka, H. Yaguchi, Y. Maeno

    「スーパークリーン物質で実現する新しい量子相の物理」A03,A04合同研究会  2009.4 

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  • 三元系遷移金属ケイ化合物の超伝導特性

    江口 学, Darren Peets, Markus Kriener, 高津 浩, 橘高 俊一郎, 米澤 進吾, 前野 悦輝

    日本物理学会第64回年次大会  2009.3 

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  • Sr3Ru2O7-Sr2RuO4共晶系における 多段階超伝導転移の一軸性圧力効果

    橘高 俊一郎, 矢口 宏, 前野 悦輝, R. Fittipaldi, A. Vecchione

    日本物理学会第64回年次大会  2009.3 

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  • 広がる超伝導の世界 ~電子が彩る量子現象~

    橘高 俊一郎

    理学系異分野交流会「自然科学縦横無尽2008」  2008.11 

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  • 磁場方向精密制御下におけるSr2RuO4の上部臨界磁場角度依存性

    橘高 俊一郎, 中村 壮智, 青野 有造, 米澤 進吾, 石田 憲二, 前野 悦輝

    日本物理学会2008年秋季大会  2008.9 

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  • Sr2RuO4-Ru共晶系における超伝導ネットワーク

    中村 壮智, 橘高 俊一郎, 矢口 宏, 前野 悦輝

    日本物理学会2008年秋季大会  2008.9 

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  • スピン三重項超伝導体Sr2RuO4で観測される異常な上部臨界磁場の振る舞い

    橘高 俊一郎, 中村 壮智, 青野 有造, 米澤 進吾, 石田 憲二, 前野 悦輝

    「スーパークリーン特定・若手夏の学校」  2008.8 

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  • Enhancement of interfacial superconductivity in the eutectic system Sr2RuO4-Ru by uniaxial presure International conference

    H. Yaguchi, S. Kittaka, Y. Maeno

    The 25th International Conference on Low Temperature Physics (LT25)  2008.8 

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  • Evidence for the Sr2RuO4 intercalations in the Sr3Ru2O7 region of the Sr3Ru2O7-Sr2RuO4 eutectic system International conference

    S. Kittaka, S. Yonezawa, H. Yaguchi, Y. Maeno, R. Fittipaldi, A. Vecchione, J. -F. Mercure, A. Gibbs, R. S. Perry, A. P. Mackenzie

    The 25th International conference on Low Temperature Physics (LT25)  2008.8 

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  • Unusual temperature dependence of in-plane critical field in Sr2RuO4 International conference

    S. Kittaka, T. Nakamura, Y. Aono, S. Yonezawa, K. Ishida, Y. Maeno

    The 25th International conference on Low Temperature Physics (LT25)  2008.8 

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  • Nature of superconducting behavior in the Sr3Ru2O7 domain of Sr2RuO4-Sr3Ru2O7 eutectic crystals International conference

    M. Cuoco, R. Fittipaldi, D. Zola, R. Ciancio, M. Polichetti, S. Pace, E. Olsson, D. Stornaiuolo, D Born, F. Tafuri, S. Kittaka, Y. Maeno, A. Vecchione

    The 25th International Conference on Low Temperature Physics (LT25)  2008.8 

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  • Anisotropy of the upper critical field in Sr2RuO4 International conference

    S. Kittaka, T. Nakamura, Y. Aono, S. Kusaba, S. Yonezawa, K. Ishida, Y. Maeno

    Kalvi Institute for Theoretical Physics Miniprogram: Sr2RuO4 and Chiral p-wave Superconductivity  2007.12 

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  • Search for the origin of multiple superconducting transitions observed in the Sr3Ru2O7 region of Sr3Ru2O7-Sr2RuO4 eutectic crystals International conference

    S. Kittaka, H. Yaguchi, Y. Maeno, R. Fittipaldi, A. Vecchione, J.-F. Mercure, A. Gibbs, A. P. Mackenzie

    International Symposium on Physics of New Quantum Phases in Superclean Materials  2007.10 

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  • Two distinct superconducting transitions in the Sr3Ru2O7 region of Sr2RuO4-Sr3Ru2O7 eutectic crystals International conference

    S. Kittaka, S. Fusanobori, H. Yaguchi, S. Yonezawa, Y. Maeno, R. Fittipaldi, A. Vecchione

    Quantum Materials Program Meeting  2007.5 

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  • ACu3Ru4O12(A=Na, Ca, La)の合成と低温物性

    田中 壮太郎, 島居 宣博, 小沼 圭介, 高津 浩, 橘高 俊一郎, 米澤進吾, 前野悦輝

    日本物理学会第62回年次大会  2007.3 

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  • Sr2RuO4-Ruの粉砕単結晶粒からなる焼結体の超伝導接合特性

    中村 壮智, 橘高 俊一郎, 村川 寛, 矢口 宏, 前野 悦輝

    日本物理学会第62回年次大会  2007.3 

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  • Sr2RuO4-Sr3Ru2O7共晶体中のSr3Ru2O7領域で観測される超伝導の温度磁場相図

    橘高 俊一郎, 矢口 宏, 前野 悦輝, R. Fittipaldi, A. Vecchione

    日本物理学会2007年春季大会  2007.3 

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  • Granular superconductivity in the Sr3Ru2O7 region of Sr2RuO4-Sr3Ru2O7 eutectic crystals

    S. Kittaka, S. Fusanobori, H. Yaguchi, S. Yonezawa, Y. Maeno, R. Fittipaldi, A. Vecchione

    「スーパークリーン物質で実現する新しい量子相の物理」平成18年度研究成果発表会  2006.12 

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  • Sr2RuO4を含む共晶系における超伝導近接効果

    橘高 俊一郎, 草場 壽一, 矢口 宏, 米澤 進吾, 前野 悦輝, R. Fittipaldi, A. Vecchione

    日本物理学会2006年秋季大会  2006.9 

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  • Sr2RuO4を含む共晶系の超伝導性における一軸性圧力の効果

    矢口 宏, 橘高 俊一郎, 滝沢 恵一, 房登 真司, 前野 悦輝, R. Fittipaldi, A. Vecchione

    日本物理学会2006年秋季大会  2006.9 

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  • AC Susceptibility of Sr2RuO4-Sr3Ru2O7 Eutectics: Dependence on AC Field Strength and Frequency International conference

    S. Fusanobori, S. Kittaka, H. Yaguchi, S. Yonezawa, Y. Maeno, R. Fittipaldi, A. Vecchione

    The 17th International Conference on Magnetism (ICM2006)  2006.8 

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  • Sr2RuO4-Sr3Ru2O7共晶系のSr3Ru2O7領域で観測される弱い超伝導

    橘高 俊一郎, 房登 真司, 矢口 宏, 米澤 進吾, 前野 悦輝, R. Fittipaldi, A. Vecchione

    日本物理学会第61回年次大会  2006.3 

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  • Sr2RuO4-Sr3Ru2O7共晶の超伝導性

    房登 真司, 橘高 俊一郎, 矢口 宏, 米澤 進吾, 前野 悦輝, R. Fittipaldi, A. Vecchione

    日本物理学会2005年秋季大会  2005.9 

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  • 一軸性圧力下におけるSr2RuO4-Ru共晶体の界面超伝導

    矢口 宏, 橘高 俊一郎, 滝沢 恵一, 前野 悦輝

    日本物理学会2005年秋季大会  2005.9 

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Awards

  • The Young Scientists’ Prize, The Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology

    2020.4  

  • JPSJ Most Cited Articles in 2019 from Vol. 87 (2018)

    2020  

  • 14th Condensed-Matter Science Prize

    2019.11  

  • 第15回ISSP学術奨励賞

    2018  

    橘高 俊一郎

  • JPSJ Most Cited Articles in 2017 since Vol. 1 (1946)

    2018  

    橘高 俊一郎

  • PRB Editors' Suggestion(1)

    2017  

  • JPSJ Most Cited Articles in 2016 since Vol. 1 (1946)

    2017  

  • 第11回日本物理学会若手奨励賞(領域8)

    2017  

    橘高 俊一郎

  • PRB Editors' Suggestion(2)

    2017  

  • PRL Editors' Suggestion

    2016  

  • JPSJ Papers of Editors' Choice

    2016  

  • JPSJ Most Cited Articles in 2013 from Vol. 81 (2012)

    2014  

    橘高 俊一郎

  • JPSJ Most Cited Articles in 2013 since Vol. 1 (1946)

    2014  

    橘高 俊一郎

  • JPSJ Papers of Editors' Choice

    2013  

  • PRB Editors' Suggestion

    2012  

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Research Projects

  • Exploring Novel Functionalities in Asymmetric Quantum Matters through Precise Measurements

    Grant number:23H04868  2023.4 - 2028.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Transformative Research Areas (A)  Hokkaido University

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    Grant amount: \187200000 ( Direct Cost: \144000000 、 Indirect Cost: \43200000 )

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  • 磁場方位制御可能なサブピコメートル膨張計の開発と新奇超伝導相の研究

    Grant number:20K20893  2020.7 - 2023.3

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)  挑戦的研究(萌芽)  中央大学

    橘高 俊一郎

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    Grant amount: \6370000 ( Direct Cost: \4900000 、 Indirect Cost: \1470000 )

    本年度は、昨年度までに開発した自作のキャパシタンス式のサブピコメートル膨張計を用いて主に重い電子系超伝導体CeCoIn5の磁歪測定を行った。CeCoIn5は超伝導1次相転移を伴う強いパウリ常磁性効果を示し、ab面方向の磁場下ではFFLO超伝導の実現が有力視されている。一方、c軸方向の磁場下においては、ab面と同様に強いパウリ常磁性効果が観測されるが、FFLO超伝導の実現可能性は未だ明らかになっていない。そこで、本研究では開発した自作の膨張計をCeCoIn5の研究に応用し、c軸方向の磁場下における磁歪測定を0.12 Kの極低温まで行った。その結果、c軸方向の磁場下で履歴を伴う超伝導1次相転移の観測に成功し、さらに極低温では1次相転移点近傍で磁歪が微弱ではあるが多段構造を示すことを明らかにした。本結果により、CeCoIn5のc軸磁場下において超伝導内部相転移が起きている可能性が示唆される。一方、測定は1つの単結晶試料に集中して行っているため、多段の超伝導1次相転移が試料不均一性に伴う現象である可能性は否定できていない。今後、別の単結晶試料を準備して磁歪の再現性を検証する必要がある。本年度は並行して、昨年度までに行った非従来型超伝導体Sr2RuO4の磁歪測定結果の考察や量子臨界現象を示すYbRh2Si2の磁場角度依存性の研究を進めた。また、膨張計の更なる高感度化・小型化を目指して、膨張計のデザイン改良にも引き続き取り組んだ。

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  • Development of apparatus for measuring field-angle-resolved entropy and its application to frustrated magnetic materials

    Grant number:18H01161  2018.4 - 2021.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B) 

    Kittaka Shunichiro

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    Grant amount: \18200000 ( Direct Cost: \14000000 、 Indirect Cost: \4200000 )

    We have developed an innovative experimental method to measure the field-angle dependence of the entropy by taking advantage of the field-rotational magnetocaloric effect. By using this technique, we made the field-angle-resolved entropy landscape and succeeded in detecting the well-known spin-flip transition in the spin-ice compound Dy2Ti2O7 under a rotating magnetic field within the (1-10) plane. We also studied the quasi-kagome Kondo lattice CeRhSn and revealed that the high-entropy state survives up to a relatively high magnetic field when the field is applied precisely along the quasi-kagome plane. Thus, we have established a new experimental technique which is useful to investigate various phenomena in anisotropic systems.

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  • Exotic quantum phases in conductive multipole systems studied by field-angle-resolved specific heat and entropy

    Grant number:18H04306  2018.4 - 2020.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)  The University of Tokyo

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount: \8970000 ( Direct Cost: \6900000 、 Indirect Cost: \2070000 )

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  • Experimental technique for the low-temperature magnetization measurements with a precise tuning of he field direction and its application to strongly correlated systems with strong anisotropy

    Grant number:15H03682  2015.4 - 2018.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)  The University of Tokyo

    Sakakibara Toshiro, KITTAKA Shunichiro

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    Grant amount: \14040000 ( Direct Cost: \10800000 、 Indirect Cost: \3240000 )

    Experimental technique for the low-temperature magnetization measurements with a fine tuning of the field orientation has been developed. Using this technique, we studied a field-induced quantum phase transition of the itinerant Ising ferromagnet URhGe and obtained the detailed structure of the wing phase diagram below the tricritical point. We also examined the liquid-gas transition of spin ice Dy2Ti2O7 in a magnetic field by precisely tuning the field direction along the [111] axis. We confirmed that the first-order transition occurring near 0.9T has an intrinsic width of about 0.5T even at very low temperatures. The results suggest the presence of some spatial structure in the monopole crystallization transition.

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  • Pairing mechanism of multiband full-gap superconductivity in heavy-electron systems

    Grant number:15K05158  2015.4 - 2018.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)  The University of Tokyo

    Kittaka Shunichiro, SAKAKIBARA Toshiro

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount: \4550000 ( Direct Cost: \3500000 、 Indirect Cost: \1050000 )

    Pairing mechanism of heavy-fermion superconductivity has attracted much attention because the first discovered heavy-fermion superconductor CeCu2Si2 has been unexpectedly revealed to be a multiband full-gap superconductor. In this study, we have examined the gap symmetry of CeCu2Si2 and those of various exotic superconductors, in order to deepen understanding of their exotic pairing mechanisms. Furthermore, we developed an apparatus for measuring field-angle-dependent specific heat under pressure to study the pressure effect on the gap structure.

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  • Heavy-fermion superconductivity probed by field-angle-resolved specific heat measurement under uniaxial pressure

    Grant number:25800186  2013.4 - 2015.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)  Grant-in-Aid for Young Scientists (B)  The University of Tokyo

    KITTAKA Shunichiro

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount: \4160000 ( Direct Cost: \3200000 、 Indirect Cost: \960000 )

    Identification of the superconducting gap structure, which is closely related to the pairing interaction, is crucial to resolve the pairing mechanism of unconventional superconductivity. One of the powerful methods to determine the gap anisotropy is field-angle-resolved specific heat measurement. In this project, we have developed the apparatus to measure the field-angle-resolved specific heat under uniaxial pressure in order to uncover exotic features of heavy-fermion superconductivity. Furthermore, gap structures of various heavy-fermion superconductors have been investigated by this method at ambient pressure.

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  • Low-temperature high-sensitivity magnetization measurements on tiny single crystals of quantum magnet systems

    Grant number:24340075  2012.4 - 2015.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)  The University of Tokyo

    SAKAKIBARA Toshiro, MITAMURA Hiroyuki, KITTAKA Shunichiro

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    Grant amount: \17940000 ( Direct Cost: \13800000 、 Indirect Cost: \4140000 )

    Low-dimensional quantum spin systems and strongly correlated electron systems can quite often be obtained only as tiny single-crystalline samples. In this project, sensitivity of the low-temperature magnetometer, which the present principal investigator has been developed, is improved by a factor of 100 to be able to measure those tiny crystals. Some selected achievements: (1) Field and temperature variations of the magnetization of a spin 1/2 one dimensional Heisenberg antiferromagnet CuPzN are confirmed to precisely follow the predictions of the exact solutions. (2) Magnetization of a high-quality single crystal of Sr2RuO4 in a magnetic field applied exactly parallel to the c plane exhibits a sharp magnetization jump at the upper critical field at low temperatures, evidencing a first-order superconducting-normal transition. The results provide an important clue for elucidating its pairing symmetry.

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  • 角度分解磁場中比熱測定から切り拓く重い電子系の超伝導

    Grant number:23102705  2011.4 - 2013.3

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)  新学術領域研究(研究領域提案型)  東京大学

    橘高 俊一郎

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount: \7540000 ( Direct Cost: \5800000 、 Indirect Cost: \1740000 )

    超伝導ギャップ構造の決定は超伝導発現メカニズムを解明する上で重要な役割を果たす。本研究では、方位を精密制御した磁場中で様々な重い電子系超伝導体の比熱を極低温まで測定し、それぞれの超伝導ギャップにおけるノード構造を決定することを目的としている。平成24年度には、前年度までに行ったCeIrIn5とUPt3に関する角度分解磁場中比熱測定の結果を論文にまとめて公表し、国際ワークショップなど2件の招待講演の依頼を頂いた。特にUPt3に関しては、c軸から30度以内の磁場角度範囲で超伝導が異常に壊れやすくなっていることを見出し、さらに最近有力視される2回対称性を有する超伝導ギャップが比熱では奇妙なことに検出されないことを明らかにした。これらの結果は、UPt3超伝導の謎を解明する上で重要な手掛かりになると期待され、本研究成果をまとめた論文はJPSJ注目論文に選定された。
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    本年度は加えて異方的s波超伝導体CeRu2、重い電子系超伝導体CeCu2Si2について角度分解磁場中比熱測定を行った。CeRu2は純度の異なる2つの試料について測定を行い、回転磁場中比熱の相対振動振幅がギャップ極小の大きさに対応した磁場下で温度とともにゼロに減衰することを明らかにした。この結果は、微視的理論計算から予測される振る舞いと良く一致しており、本手法が異方的s波ギャップの評価にも有用であることを示している。CeCu2Si2に関しては現在も研究が進行中であり、超伝導対称性に関する重要な知見が得られつつある。
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    他にも一軸性圧力下極低温比熱測定装置の開発を進め、一軸性圧力下での比熱測定からCeIrIn5の超伝導転移(Tc=0.4 K)を観測することに成功した。これにより今後、一軸性圧力下比熱という新たなアプローチから超伝導研究を行うことが可能となった。

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  • スピン三重項超伝導体ルテニウム酸化物とそれを含む共晶体の一軸性圧力効果

    2008.4 - 2010.3

    平成20年度日本学術振興会特別研究員 DC2 

    橘高 俊一郎

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    Authorship:Principal investigator  Grant type:Competitive

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  • ウラン系超伝導体の超伝導ギャップ構造の決定

    Grant number:22840013  2010    

    日本学術振興会  科学研究費助成事業 研究活動スタート支援  研究活動スタート支援  東京大学

    橘高 俊一郎

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    Grant amount: \3120000 ( Direct Cost: \2400000 、 Indirect Cost: \720000 )

    本研究課題では、角度分解磁場中比熱測定からウラン系超伝導体のギャップ異方性を検出し、その超伝導対称性を解明することを目的としている。比熱からギャップ異方性を明らかにするためには熱励起による影響を抑えた上で測定を行う必要があり、超伝導転移温度(T_c)の10分の1程度の極低温まで比熱測定を行うことが重要となってくる。しかし、ウラン系超伝導体の多くは比較的低い現(~0.5K)を持っており、それらのギャップ構造の研究にはこれまでに確立していた準断熱法による比熱測定装置(最低到達温度100mK程度)では不十分であった。
    そこで本年度は、熱浴との断熱性を比較的悪くした上で比熱を精度良く測定できる新たなセルの開発を行った。試行錯誤の結果、50mK以下の極低温まで比熱を測定することに成功し、ウラン系超伝導体の研究を行う態勢を整えた。
    開発したセルを用いて、スピン三重項超伝導体の有力候補であるUPt_3(T_c~0.5K)の角度分解磁場中比熱測定を行った。c軸中心に回転させた磁場中で比熱測定を行った結果、理論予測に反して50mKの低温まで比熱に磁場方位依存性が現れないことが分かった。さらに、a軸中心に回転させた磁場中でも比熱測定を行い、c軸から30度以内の磁場方向でのみ強い対破壊効果が働いていることを突き止めた。これらの結果は日本物理学会にて発表を行った。極低温で比熱測定を行う態勢が整ったため、今後は他のウラン系超伝導体についても角度分解磁場中比熱測定を進めていく予定である。

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  • スピン三重項超伝導体ルテニウム酸化物とそれを含む共晶体の一軸性圧力効果

    Grant number:08J00959  2008 - 2009

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費  京都大学

    橘高 俊一郎

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    Grant amount: \1200000 ( Direct Cost: \1200000 )

    Sr_2RuO_4-Ru共晶体では、Sr_2RuO_4の超伝導転移温度T_c(=1.5K)より約2倍高い3Kから界面超伝導を示すが、そのメカニズムは長年未解明であった。我々は、Sr_2RuO_4の異方的な結晶歪みがT_cの上昇に寄与していると考え、様々な方向の一軸性圧力下でSQUID磁束計(MPMS、最低到達温度1.8K)を用いてSr_2RuO_4-Ru共晶体の磁化測定を行った。その結果、静水圧力下ではSr_2RuO_4のT_cは減少するにもかかわらず、一軸性圧力を印加した共晶体ではいずれの方向においても1.8Kでのマイスナー信号が上昇し、その上昇は面内方向の圧力下で最も大きいことを明らかにした。一方、純粋なSr_2RuO_4はT_cが低いために、SQUID磁束計ではその超伝導転移は検出不可能であった。そこで、0.3Kの低温まで交流帯磁率を一軸性圧力下で測定可能な実験手法を開発し、純粋なSr_2RuO_4における超伝導の一軸性圧力効果を調べた。その結果、驚くべきことにSr_2RuO_4のc軸方向に0.2GPaの弱い一軸性圧力を印加することで、オンセットT_cが3.2Kの超伝導が誘起されることを発見した。この効果は、バンド計算やEhrenfestの関係式からこれまでに予想されていたSr_2RuO_4の一軸性圧力効果と質的・量的に異なっており、Sr_2RuO_4が異方的結晶歪みの有無によりT_c=1.5KとT_c~3Kという2つの超伝導相を元来有していることを示唆している。本研究により、長年研究されているSr_2RuO_4超伝導の新たな一面を見出すことに成功した。

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  • 2023   半導体物理学   Department

  • 2023   卒業研究Ⅰ   Department

  • 2023   卒業研究Ⅱ   Department

  • 2023   教育実習Ⅰ(事前・事後指導を含む)   Department

  • 2023   教育実習Ⅱ   Department

  • 2023   熱力学・電磁気学   Department

  • 2023   物理実験   Department

  • 2023   物理1   Department

  • 2023   量子力学及演習1   Department

  • 2023   凝縮系物理学特論第一   Graduate school

  • 2023   凝縮系物理学特論第二   Graduate school

  • 2023   物理学特殊論文研修Ⅰ   Graduate school

  • 2023   物理学特殊論文研修Ⅱ   Graduate school

  • 2023   物理学特殊論文研修Ⅲ   Graduate school

  • 2023   物理学特殊論文研修Ⅳ   Graduate school

  • 2023   物理学特殊論文研修Ⅴ   Graduate school

  • 2023   物理学特殊論文研修Ⅵ   Graduate school

  • 2023   物理学特論   Graduate school

  • 2023   物理学論文研修第一   Graduate school

  • 2023   物理学論文研修第三   Graduate school

  • 2023   物理学論文研修第二   Graduate school

  • 2023   物理学論文研修第四   Graduate school

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Committee Memberships

  • 2023.3 - Now

    日本物理学会   第79~80期代議員  

  • 2022.4 - 2023.3

    日本物理学会   領域8運営委員