研究者詳細 - 小林　達生

論文 - 小林　達生

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Magnetotransport properties of tellurium under extreme conditions 査読

Kazuto Akiba, Kaya Kobayashi, Tatsuo C. Kobayashi, Ryo Koezuka, Atsushi Miyake, Jun Gouchi, Yoshiya Uwatoko, Masashi Tokunaga

Physical Review B 101 ( 24 ) 2020年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Physical Society (APS)

This study investigates the transport properties of a chiral elemental semiconductor tellurium (Te) under magnetic fields and pressure. Application of hydrostatic pressure reduces the resistivity of Te, while its temperature dependence remains semiconducting up to 4 GPa, contrary to recent theoretical and experimental studies. Application of higher pressure causes structural as well as semiconductor-metal transitions. The resulting metallic phase above 4 GPa exhibits superconductivity at 2 K along with a noticeable linear magnetoresistance effect. On the other hand, at ambient pressure, we identified metallic surface states on the as-cleaved (10 (1) over bar0) surfaces of Te. The nature of these metallic surface states has been systematically studied by analyzing quantum oscillations observed in high magnetic fields. We clarify that a well-defined metallic surface state exists not only on chemically etched samples that were previously reported, but also on as-cleaved ones.

DOI： 10.1103/physrevb.101.245111

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.101.245111/fulltext

Variation in Superconducting Symmetry Against Pressure on Noncentrosymmetric Superconductor Cd2Re2O7 Revealed by 185/187Re Nuclear Quadrupole Resonance 査読

Shunsaku Kitagawa, Kenji Ishida, Tatsuo C. Kobayashi, Yasuhito Matsubayashi, Daigorou Hirai, Zenji Hiroi

Journal of the Physical Society of Japan 89 ( 5 ) 053701 - 053701 2020年5月

Pressure-Temperature Phase Diagram of alpha-Mn 査読国際誌

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

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019) 30 011030-1 - 011030-6 2020年3月

Helimagnetic Structure and Heavy-Fermion-Like Behavior in the Vicinity of the Quantum Critical Point in Mn3P 査読

Hisashi Kotegawa, Masaaki Matsuda, Feng Ye, Yuki Tani, Kohei Uda, Yoshiki Kuwata, Hideki Tou, Eiichi Matsuoka, Hitoshi Sugawara, Takahiro Sakurai, Hitoshi Ohta, Hisatomo Harima, Keiki Takeda, Junichi Hayashi, Shingo Araki, Tatsuo C. Kobayashi

Physical Review Letters 124 ( 8 ) 2020年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Physical Society (APS)

Antiferromagnet Mn3P with Neel temperature T-N = 30 K is composed of Mn tetrahedrons and zigzag chains formed by three inequivalent Mn sites. Due to the nearly frustrated lattice with many short Mn-Mn bonds, competition of the exchange interactions is expected. We here investigate the magnetic structure and physical properties including pressure effect in single crystals of this material, and reveal a complex yet well-ordered helimagnetic structure. The itinerant character of this materials is strong, and the ordered state with small magnetic moments is easily suppressed under pressure, exhibiting a quantum critical point at similar to 1.6 GPa. The remarkable mass renormalization, even in the ordered state, and an incoherent-coherent crossover in the low-temperature region, characterize an unusual electronic state in Mn3P, which is most likely effected by the underlying frustration effect.

DOI： 10.1103/physrevlett.124.087202

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その他リンク： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevLett.124.087202/fulltext

High magnetic field x-ray diffraction study of the α phase of solid oxygen: Absence of giant magnetostriction 査読

Yasuhiro H. Matsuda, Ayumi Shimizu, Akihiko Ikeda, Toshihiro Nomura, Takeshi Yajima, Toshiya Inami, Kohki Takahashi, Tatsuo C. Kobayashi

Physical Review B 100 ( 21 ) 2019年12月

Interplay between unconventional superconductivity and heavy-fermion quantum criticality: CeCu2Si2 versus YbRh2Si2 査読

M. Smidman, O. Stockert, J. Arndt, G. M. Pang, L. Jiao, H. Q. Yuan, H. A. Vieyra, S. Kitagawa, K. Ishida, K. Fujiwara, T. C. Kobayashi, E. Schuberth, M. Tippmann, L. Steinke, S. Lausberg, A. Steppke, M. Brando, H. Pfau, U. Stockert, P. Sun, S. Friedemann, S. Wirth, C. Krellner, S. Kirchner, E. M. Nica, R. Yu, Q. Si, F. Steglich

Philosophical Magazine 98 ( 32 ) 2930 - 2963 2018年11月

Pyrochlore Oxide Superconductor Cd2Re2O7Revisited 査読

Zenji Hiroi, Jun-ichi Yamaura, Tatsuo C. Kobayashi, Yasuhito Matsubayashi, Daigorou Hirai

Journal of the Physical Society of Japan 87 ( 2 ) 024702 - 024702 2018年2月

Magnetostriction studies up to megagauss fields using fiber Bragg grating technique

Akihiko Ikeda, Yasuhiro H. Matsuda, Daisuke Nakamura, Shojiro Takeyama, Hiroshi Tsuda, Kazuya Nomura, Ayumi Shimizu, Akira Matsuo, Toshihiro Nomura, Tatsuo C. Kobayashi, Takeshi Yajima, Hajime Ishikawa, Zenji Hiroi, Masahiko Isobe, Touru Yamauchi, Keisuke Sato

2018 16TH INTERNATIONAL CONFERENCE ON MEGAGAUSS MAGNETIC FIELD GENERATION AND RELATED TOPICS (MEGAGAUSS) 98 - 106 2018年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

We here report magnetostriction measurements under pulsed megagauss fields using a high-speed 100 MHz strain monitoring system devised using fiber Bragg grating (FBG) technique with optical filter method. The optical filter method is a detection scheme of the strain of FBG, where the changing Bragg wavelength of the FBG reflection is converted to the intensity of reflected light to enable the 100 MHz measurement. In order to show the usefulness and reliability of the method, we report the measurements for solid oxygen, spin-controlled crystal, and volborthite, a deformed Kagome quantum spin lattice, using static magnetic fields up to 7 T and non-destructive millisecond pulse magnets up to 50 T. Then, we show the application of the method for the magnetostriction measurements of CaV4O9, a two-dimensional antiferromagnet with spin-halves, and LaCoO3, an anomalous spin-crossover oxide, in the megagauss fields.

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Pressure-Induced Superconductivity from Doping-Induced Antiferromagnetic Phase of 112-type Ca1−xLaxFeAs2 査読

Shunsaku Kitagawa, Taishi Sekiya, Yo Fujiyoshi, Shingo Araki, Tatsuo C. Kobayashi, Naoki Nishimoto, Tasuku Mizukami, Satoshi Ioka, Kazunori Fujimura, Kazutaka Kudo, Minoru Nohara

Journal of the Physical Society of Japan 86 ( 11 ) 113705 - 113705 2017年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physical Society of Japan

The effects of pressure on antiferromagnetic (AFM) and superconducting phase transitions of 112-type Ca1-xLaxFeAs2 were studied, and the in-plane electrical resistivity rho(ab) was measured with an indenter-type pressure cell. The AFM phase transition temperatures of T-N = 47, 63, and 63 K at ambient pressure for x = 0.18, 0.21, and 0.26 was suppressed by applying pressure P, with superconductivity emerging at critical pressures of P-c similar or equal to 0, 1.5, and 3.4 GPa, respectively. Correspondingly, the slope of T-N against P decreased as dT(N)/P similar or equal to -15 and -2K/GPa for x = 0.21 and 0.26, respectively. Thus, although the AFM phase was stabilized with La doping x, the AFM phase was suppressed by pressure, and superconductivity eventually emerged.

DOI： 10.7566/jpsj.86.113705

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H−T phase diagram of solid oxygen 査読

T. Nomura, Y. H. Matsuda, T. C. Kobayashi

Physical Review B 96 ( 5 ) 2017年8月

alpha-beta and beta-gamma phase boundaries of solid oxygen observed by adiabatic magnetocaloric effect 査読

Toshihiro Nomura, Yoshimitsu Kohama, Yasuhiro H. Matsuda, Koichi Kindo, Tatsuo C. Kobayashi

Phys Rev B 5 104420 2017年3月

Successive spatial symmetry breaking under high pressure in the spin-orbit-coupled metal Cd2Re2O7 査読

Jun-ichi Yamaura, Keiki Takeda, Yoichi Ikeda, Naohisa Hirao, Yasuo Ohishi, Tatsuo C. Kobayashi, Zenji Hiroi

PHYSICAL REVIEW B 95 ( 2 ) 163 - 170 2017年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

The 5d-transition-metal pyrochlore oxide Cd2Re2O7, which was recently suggested to be a prototype of the spin-orbit-coupled metal [Phys. Rev. Lett. 115, 026401 (2015)], exhibits an inversion-symmetry-breaking (ISB) transition at 200 K and a subsequent superconductivity below 1 K at ambient pressure. We study the crystal structure at high pressures up to 5 GPa by means of synchrotron x-ray powder diffraction. A rich structural phase diagram is obtained, which contains at least seven phases, and is almost consistent with the electronic phase diagram determined by previous resistivity measurements. Interestingly, the ISB transition vanishes at similar to 4 GPa where the enhancement of the upper critical field was observed in resistivity. Moreover, it is shown that the point groups at 8 K, probably kept in the superconducting phases, sequentially transform into piezoelectric, ferroelectric, and centrosymmetric structures on the application of pressure.

DOI： 10.1103/PhysRevB.95.020102

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Chemical analysis of superconducting phase in K-doped picene 査読

Takashi Kambe, Saki Nishiyama, Huyen L. T. Nguyen, Takahiro Terao, Masanari Izumi, Yusuke Sakai, Lu Zheng, Hidenori Goto, Yugo Itoh, Taiki Onji, Tatsuo C. Kobayashi, Hisako Sugino, Shin Gohda, Hideki Okamoto, Yoshihiro Kubozono

JOURNAL OF PHYSICS-CONDENSED MATTER 28 ( 44 ) 2016年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

Potassium-doped picene (K(3.0)picene) with a superconducting transition temperature (TC) as high as 14 K at ambient pressure has been prepared using an annealing technique. The shielding fraction of this sample was 5.4% at 0 GPa. The TC showed a positive pressure-dependence and reached 19 K at 1.13 GPa. The shielding fraction also reached 18.5%. To investigate the chemical composition and the state of the picene skeleton in the superconducting sample, we used energy-dispersive x-ray (EDX) spectroscopy, MALDI-time-of-flight (MALDI-TOF) mass spectroscopy and x-ray diffraction (XRD). Both EDX and MALDI-TOF indicated no contamination with materials other than K-doped picene or K-doped picene fragments, and supported the preservation of the picene skeleton. However, it was also found that a magnetic K-doped picene sample consisted mainly of picene fragments or K-doped picene fragments. Thus, removal of the component contributing the magnetic quality to a superconducting sample should enhance the volume fraction.

DOI： 10.1088/0953-8984/28/44/444001

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Irreversible Heating Measurement with Microsecond Pulse Magnet: Example of the alpha-theta Phase Transition of Solid Oxygen 査読

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 85 ( 9 ) 2016年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

Dissipation inevitably occurs in first-order phase transitions, leading to irreversible heating. Conversely, the irreversible heating effect may indicate the occurrence of the first-order phase transition. We measured the temperature change at the magnetic-field-induced alpha-theta phase transition of solid oxygen. A significant temperature increase from 13 to 37 K, amounting to 700 J/mol, due to irreversible heating was observed at the first-order phase transition. We argue that the hysteresis loss of the magnetization curve and the dissipative structural transformation account for the irreversible heating. The measurement of irreversible heating can be utilized to detect the first-order phase transition in combination with an ultrahigh magnetic fields generated in a time of mu s order.

DOI： 10.7566/JPSJ.85.094601

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Characteristic Fermi surfaces and charge density wave in SrAl4 and related compounds with the BaAl4-type tetragonal structure 査読

Ai Nakamura, Taro Uejo, Hisatomo Harima, Shingo Araki, Tatsuo C. Kobayashi, Miho Nakashima, Yasushi Amako, Masato Hedo, Takao Nakama, Yoshichika Onuki

JOURNAL OF ALLOYS AND COMPOUNDS 654 290 - 299 2016年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

We succeeded in growing single crystals of SrAl4 and related compounds with the BaAl4-type tetragonal structure by the self-flux method, and measured the electrical resistivity, magnetic susceptibility, Hall coefficient, thermoelectric power, and de Haas-van Alphen (dHvA) effect. A plausible characteristic feature of the charge density wave (CDW) was observed below T-CDW = 243 K in SrAl4. We also studied an effect of pressure on the electronic state in SrAl4 by measuring the electrical resistivity and thermoelectric power. T-CDW is found to decrease with increasing pressure, with a rate of dT(CDW)/dP = -12.5 K/GPa. To clarify the Fermi surface nesting, we studied the Fermi surface in SrAl4, which is found to be different from the Fermi surfaces of the similar compounds SrGa4, BaGa4, and BaAl4 without CDW. The Fermi surfaces in these compounds were determined from the dHvA experiments, together with the energy band calculations. (C) 2015 Published by Elsevier B.V.

DOI： 10.1016/j.jallcom.2015.08.193

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Hall Effect in CeIn3 under High Pressure 査読

Shingo Araki, Taiki Onji, Shunsaku Kitagawa, Tatsuo C. Kobayashi, Takashi Kambe

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 84 ( 12 ) 123702-1-123702-4 2015年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

The temperature dependence of the Hall coefficient of CeIn3 under high pressure has been investigated. The absolute value of the Hall coefficient shows an anomalous increase below T* similar to 80K at ambient pressure. The increase in T* with increasing pressure is similar to the pressure dependence of the characteristic temperature where the resistivity reaches its maximum. The temperature variations below T* at various pressures are well scaled on a single curve that is the formula based on the two-fluid model. No effect of the antiferromagnetic fluctuations observed in CeTIn5 (T = Co, Rh, and Ir) is observed above 2K even near the critical pressure where antiferromagnetic ordering disappears.

DOI： 10.7566/JPSJ.84.123702

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Suppression of Nonmagnetic Insulating State by Application of Pressure in Mineral Tetrahedrite Cu12Sb4S13 査読

Shunsaku Kitagawa, Taishi Sekiya, Shingo Araki, Tatsuo C. Kobayashi, Kenji Ishida, Takashi Kambe, Takumi Kimura, Naoki Nishimoto, Kazutaka Kudo, Minoru Nohara

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 84 ( 9 ) 093701-1-093701-4 2015年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

The mineral tetrahedrite Cu12Sb4S13 exhibits a first-order metal-insulator transition (MIT) at T-MI = 85K and ambient pressure. We measured the 63Cu-NMR at ambient pressure and the resistivity and magnetic susceptibility at high pressures. Cu-63-NMR results indicate a nonmagnetic insulating ground state in this compound. The MIT is monotonically suppressed by pressure and disappears at similar to 1.0 GPa. Two other anomalies are observed in the resistivity measurements, and the pressure-temperature phase diagram of Cu12Sb4S13 is constructed.

DOI： 10.7566/JPSJ.84.093701

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Phase boundary of θ phase of solid oxygen in ultrahigh magnetic fields 査読

T. Nomura, Y. H. Matsuda, S. Takeyama, A. Matsuo, K. Kindo, T. C. Kobayashi

Physical Review B - Condensed Matter and Materials Physics 92 ( 6 ) 2015年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：American Physical Society

The phase diagram of solid oxygen in the magnetic-field-temperature (B-T) plane is revealed by magnetization and magnetotransmission measurements. The high-field phase of solid oxygen, which we term the θ phase, is induced at the temperature below 42 K. The transition fields at the α-θ and β-θ transitions are almost temperature independent, with the phase boundary being very steep. This phase boundary indicates that the entropy change is very small at the α-θ and β-θ transitions, in contrast to the entropy-driven β-γ transition at zero field. We argue that the θ phase differs from the high-temperature γ phase in terms of entropy
the molecular rotation is inhibited in the θ phase, whereas permitted in the γ phase. This finding consolidates the novelty of the θ phase.

DOI： 10.1103/PhysRevB.92.064109

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Emergence of double-dome superconductivity in ammoniated metal-doped FeSe 査読

Masanari Izumi, Lu Zheng, Yusuke Sakai, Hidenori Goto, Masafumi Sakata, Yuki Nakamoto, Huyen L. T. Nguyen, Tomoko Kagayama, Katsuya Shimizu, Shingo Araki, Tatsuo C. Kobayashi, Takashi Kambe, Dachun Gu, Jing Guo, Jing Liu, Yanchun Li, Liling Sun, Kosmas Prassides, Yoshihiro Kubozono

SCIENTIFIC REPORTS 5 9477-1-9477-7 2015年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

The pressure dependence of the superconducting transition temperature (T-c) and unit cell metrics of tetragonal (NH3)(y)Cs0.4FeSe were investigated in high pressures up to 41 GPa. The T-c decreases with increasing pressure up to 13 GPa, which can be clearly correlated with the pressure dependence of c (or FeSe layer spacing). The T-c vs. c plot is compared with those of various (NH3)(y)MxFeSe (M: metal atoms) materials exhibiting different T-c and c, showing that the T-c is universally related to c. This behaviour means that a decrease in two-dimensionality lowers the T-c. No superconductivity was observed down to 4.3 K in (NH3)(y)Cs0.4FeSe at 11 and 13 GPa. Surprisingly, superconductivity re-appeared rapidly above 13 GPa, with the T-c reaching 49 K at 21 GPa. The appearance of a new superconducting phase is not accompanied by a structural transition, as evidenced by pressure-dependent XRD. Furthermore, T-c slowly decreased with increasing pressure above 21 GPa, and at 41 GPa superconductivity disappeared entirely at temperatures above 4.9 K. The observation of a double-dome superconducting phase may provide a hint for pursuing the superconducting coupling-mechanism of ammoniated/non-ammoniated metal-doped FeSe.

DOI： 10.1038/srep09477

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Pressure-Temperature-Field Phase Diagram in the Ferromagnet U3P4 査読

Shingo Araki, Minami Hayashida, Naoto Nishiumi, Hiroki Manabe, Yoichi Ikeda, Tatsuo C. Kobayashi, Keizo Murata, Yoshihiko Inada, Piotr Wisniewski, Dai Aoki, Yoshichika Onuki, Etsuji Yamamoto, Yoshinori Haga

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 84 ( 2 ) 024705-1-024705-8 2015年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

The pressure-temperature-field phase diagram and quantum fluctuation effect were investigated in the itinerant ferromagnet U3P4 by resistivity, ac susceptibility, and Hall effect measurements under high pressure. The zero-temperature ferromagnetic-to-paramagnetic transition is located at P-c similar to 4.0 GPa. The tricritical point exists at P* = 3.8 GPa and T* = 32 K, where the ferromagnetic transition changes from second- to first-order. As a quantum fluctuation effect, the low-temperature resistivity at P-c follows T-5/3 dependence, which was theoretically described in the case of a three-dimensional ferromagnet. This result indicates that the ferromagnetic-to-paramagnetic transition at P-c may be considered as weakly first-order. Another critical behavior, the huge enhancement of rho(0) observed at P-c, cannot be interpreted as the ferromagnetic fluctuation effect. The Hall effect measurements suggest that the magnetic structure in the ordered state changes under high pressure.

DOI： 10.7566/JPSJ.84.024705

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