Faculty Profiles - KOBAYASHI Tatsuo

Papers - KOBAYASHI Tatsuo

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Structural and Superconducting Properties of Bi₂Rh₃(Se_1–xS_x)₂ (x = 0–1.0) Reviewed

Zhiyan Zhang, Wanli Pan, Masaki Utsumi, Yuki Yamamoto, Hidenori Goto, Ryusuke Kondo, Takayoshi Yokoya, Ryota Goban, Tomoki Higashikawa, Ritsuko Eguchi, Yasuhiro Takabayashi, Koichi Hayashi, Hirofumi Ishii, Tatsuo C. Kobayashi, Yoshihiro Kubozono

Inorganic Chemistry 63 ( 45 ) 21531 - 21540 2024.10

Ferrimagnetic structure in the high-pressure phase of α−Mn Reviewed

Shingo Araki, Kaisei Iwamoto, Kazuto Akiba, Tatsuo C. Kobayashi, Koji Munakata, Koji Kaneko, Toyotaka Osakabe

Physical Review B 2024.9

Realization of nodal-ring semimetal in pressurized black phosphorus Reviewed

Kazuto Akiba, Yuichi Akahama, Masashi Tokunaga, Tatsuo C. Kobayashi

Physical Review B 109 ( 20 ) 2024.5

Zero-Field NMR of α-Mn up to 5GPa Reviewed

Go Fujita, Fumiya Kawanabe, Hideto Fukazawa, Tetsuo Ohama, Yoh Kohori, Kentaro Kitagawa, Kaisei Iwamoto, Shingo Araki, Tatsuo C. Kobayashi

Journal of the Physical Society of Japan 93 ( 2 ) 2024.2

Publishing type：Research paper (scientific journal)

We performed zero-field nuclear magnetic resonance (ZF NMR) measurements of the antiferromagnetic and pressure-induced magnetically ordered phases of α-Mn at high pressures using a piston cylinder cell and an opposed-anvil high-pressure cell. We found that 55Mn internal magnetic fields disappeared discontinuously at 4.2–4.3 GPa. This suggests a first-order phase transition.

DOI： 10.7566/JPSJ.93.023707

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Pressure Dependence of the Structural and Superconducting Properties of the Bi-Based Superconductor Bi₂Pd₃Se₂ Reviewed

Zhiyan Zhang, Mitsuki Ikeda, Masaki Utsumi, Yuki Yamamoto, Hidenori Goto, Ritsuko Eguchi, Yen-Fa Liao, Hirofumi Ishii, Yasuhiro Takabayashi, Koichi Hayashi, Ryusuke Kondo, Tatsuo C. Kobayashi, Yoshihiro Kubozono

Inorganic Chemistry 63 ( 5 ) 2553 - 2561 2024.1

Superconductivity in a ferroelectric-like topological semimetal SrAuBi Reviewed

Hidefumi Takahashi, Tomohiro Sasaki, Akitoshi Nakano, Kazuto Akiba, Masayuki Takahashi, Alex H. Mayo, Masaho Onose, Tatsuo C. Kobayashi, Shintaro Ishiwata

npj Quantum Materials 8 ( 1 ) 2023.12

Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

Given the rarity of metallic systems that exhibit ferroelectric-like transitions, it is apparently challenging to find a system that simultaneously possesses superconductivity and ferroelectric-like structural instability. Here, we report the observation of superconductivity at 2.4 K in a layered semimetal SrAuBi characterized by strong spin–orbit coupling (SOC) and ferroelectric-like lattice distortion. Single crystals of SrAuBi have been successfully synthesized and found to show a polar-nonpolar structure transition at 214 K, which is associated with the buckling of Au-Bi honeycomb lattice. On the basis of the band calculations considering SOC, we found significant Rashba-type spin splitting and symmetry-protected multiple Dirac points near the Fermi level. We believe that this discovery opens up new possibilities of pursuing exotic superconducting states associated with the semimetallic band structure without space inversion symmetry and the topological surface state with the strong SOC.

DOI： 10.1038/s41535-023-00612-4

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Other Link： https://www.nature.com/articles/s41535-023-00612-4

Phonon-mediated superconductivity in the Sb square-net compound LaCuSb₂ Reviewed

Kazuto Akiba, Tatsuo C. Kobayashi

Phys. Rev. B 107 245117 2023.6

NMR Study of α-Mn Exhibiting Anomalous Hall Effect under High Pressure Reviewed

H. Fukazawa, G. Fujita, N. Shioda, T. Ohama, Y. Kohori, K. Iwamoto, S. Araki, T. C. Kobayashi

Proceedings of the 29th International Conference on Low Temperature Physics (LT29) 2023.5

Effect of High Pressure on the Electrical Resistivity of Electric Toroidal Ordering Candidate Ca₅Ir₃O₁₂ Reviewed

Kazuto Akiba, Tatsuo C. Kobayashi, Momoka Hayashida, Kazuyuki Matsuhira

Journal of the Physical Society of Japan 92 ( 3 ) 2023.3

Superconductivity in a Magnetic Rashba Semimetal EuAuBi Reviewed

Hidefumi Takahashi, Kazuto Akiba, Masayuki Takahashi, Alex H. Mayo, Masayuki Ochi, Tatsuo C. Kobayashi, Shintaro Ishiwata

Journal of the Physical Society of Japan 92 ( 1 ) 2023.1

Site Split of Antiferromagnetic α-Mn Revealed by ⁵⁵Mn Nuclear Magnetic Resonance Reviewed

Masahiro Manago, Gaku Motoyama, Shijo Nishigori, Kenji Fujiwara, Katsuki Kinjo, Shunsaku Kitagawa, Kenji Ishida, Kazuto Akiba, Shingo Araki, Tatsuo C. Kobayashi, Hisatomo Harima

Journal of the Physical Society of Japan 91 ( 11 ) 2022.11

Observation of superconductivity and its enhancement at the charge density wave critical point in LaAgSb2 Reviewed

Kazuto Akiba, Nobuaki Umeshita, Tatsuo C. Kobayashi

PHYSICAL REVIEW B 106 ( 16 ) 2022.10

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

We discover superconductivity (SC) in LaAgSb2 at ambient pressure and its close correlation with a charge density wave (CDW) under pressure. The superconducting transition temperature (Tc) exhibits a sharp peak at a CDW critical pressure of 3.2 GPa. We demonstrate that the carriers inhabiting the Sb-square net are crucial not only in the formation of CDW but also in SC for their relatively strong electron-phonon coupling (EPC). Furthermore, theoretical EPC strength in pristine LaAgSb2 cannot explain the observed peak with Tc - 1 K, which indicates that an additional mechanism reinforces SC only around the CDW critical pressure.

DOI： 10.1103/PhysRevB.106.L161113

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Solid and Liquid Oxygen under Ultrahigh Magnetic Fields Reviewed

Toshihiro Nomura, Yasuhiro H. Matsuda, Tatsuo C. Kobayashi

Oxygen 2 ( 2 ) 152 - 163 2022.5

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI AG

Oxygen is a unique molecule that possesses a spin quantum number S=1. In the condensed phases of oxygen, the delicate balance between the antiferromagnetic interaction and van der Waals force results in the various phases with different crystal structures. By applying ultrahigh magnetic fields, the antiferromagnetic coupling between O2 molecules breaks, and novel high-field phases can appear. We have investigated the physical properties of condensed oxygen under ultrahigh magnetic fields and have found that the stable crystal structure of solid oxygen changes around 100 T. Even in liquid oxygen, we observed a strong acoustic attenuation, which indicates the fluctuation of local molecular arrangements. These results demonstrate that magnetic fields can modulate the packing structure of oxygen through spin-lattice coupling. Our study implies the possibility of controlling oxygen-related (bio-)chemical processes by using an external magnetic field.

DOI： 10.3390/oxygen2020013

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Magnetotransport studies of the Sb square-net compound LaAgSb2 under high pressure and rotating magnetic fields Reviewed

Kazuto Akiba, Nobuaki Umeshita, Tatsuo C. Kobayashi

Physical Review B 105 ( 3 ) 2022.1

Physical properties of liquid oxygen under ultrahigh magnetic fields Reviewed

T. Nomura, A. Ikeda, M. Gen, A. Matsuo, K. Kindo, Y. Kohama, Y. H. Matsuda, S. Zherlitsyn, J. Wosnitza, H. Tsuda, T. C. Kobayashi

Physical Review B 104 ( 22 ) 2021.12

Spin-gap formation due to spin-Peierls instability in π-orbital-ordered NaO2 Reviewed International journal

Mizuki Miyajima, Fahmi Astuti, Takahito Fukuda, Masashi Kodani, Shinsuke Iida, Shinichiro Asai, Akira Matsuo, Takatsugu Masuda, Koichi Kindo, Takumi Hasegawa, Tatsuo C. Kobayashi, Takehito Nakano, Isao Watanabe, Takashi Kambe

Physical Review B 104 ( 14 ) 2021.10

Successive destruction of charge density wave states by pressure in LaAgSb2 Reviewed

Kazuto Akiba, Hiroaki Nishimori, Nobuaki Umeshita, Tatsuo C. Kobayashi

Physical Review B 103 ( 8 ) 2021.2

Domain Control by Adjusting Anisotropic Stress in Pyrochlore Oxide Cd2Re2O7 Reviewed

Satoshi Tajima, Daigorou Hirai, Yuto Kinoshita, Masashi Tokunaga, Kazuto Akiba, Tatsuo C. Kobayashi, Hishiro T. Hirose, Zenji Hiroi

Journal of the Physical Society of Japan 89 ( 11 ) 114711 - 114711 2020.11

Anomalous Hall effect triggered by pressure-induced magnetic phase transition in α -Mn Reviewed

Kazuto Akiba, Kaisei Iwamoto, Takaaki Sato, Shingo Araki, Tatsuo C. Kobayashi

Physical Review Research 2 ( 4 ) 2020.10

Two Qualitatively Different Superconducting Phases under High Pressure in Single-Crystalline CeNiGe3 Reviewed

Shunsaku Kitagawa, Shingo Araki, Tatsuo C. Kobayashi, Yoichi Ikeda

Journal of the Physical Society of Japan 89 ( 6 ) 063702 - 063702 2020.6

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

We have measured the temperature dependence of resistivity in single-crystalline CeNiGe3 under hydrostatic pressure in order to establish the characteristic pressure-temperature phase diagram. The transition temperature to AFM-I phase T-N1 = 5.5 K at ambient pressure initially increases with increasing pressure and has a maximum at similar to 3.0GPa. Above 2.3 GPa, a clear zero-resistivity is observed (SC-I phase) and this superconducting (SC) state coexists with AFM-I phase. The SC-I phase suddenly disappears at 3.7 GPa simultaneously with the appearance of an additional kink anomaly corresponding to the phase transition to AFM-II phase. The AFM-II phase is continuously suppressed with further increasing pressure and disappears at similar to 6.5 GPa. In the narrow range near the critical pressure, an SC phase reappears (SC-II phase). A large initial slope of upper critical field mu H-0(c2) and non-Fermi liquid behavior indicate that the SC-II phase is mediated by antiferromagnetic fluctuations. On the other hand, the robust coexistence of the SC-I phase and AFM-I phase is unusual on the contrary to superconductivity near a quantum critical point on most of heavy-fermion compounds.

DOI： 10.7566/jpsj.89.063702

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Papers - KOBAYASHI Tatsuo