研究者詳細 - 紺谷　浩

論文 - 紺谷　浩

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Intrinsic spin and orbital Hall effects in d- and f-electron systems

Kontani H., Tanaka T., Naito M., Hirashima D. S., Yamada K., Inoue J.

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 巻頁： 275-277 2008年1月

Giant Intrinsic Spin and Orbital Hall Effects in Sr2MO4 (M=Ru,Rh,Mo) 査読有り

H. Kontani, T. Tanaka, D.S. Hirashima, K. Yamada, J. Inoue

Physical Review Letters 100 巻頁： 096601 2008年

*Intrinsic spin Hall effect and orbital Hall effect in 4d and 5d transition metals 査読有り

T. Tanaka, H. Kontani, M. Naito, T. Naito, D. S. Hirashima, K. Yamada, and J. Inoue

Physical Review B 77 巻頁： 165117 2008年

記述言語：英語

We study the intrinsic spin Hall conductivity (SHC) in various 5d transition metals (Ta, W, Re, Os, Ir, Pt, and Au) and 4d transition metals (Nb, Mo, Tc, Ru, Rh, Pd, and Ag) based on the Naval Research Laboratory tight-binding model, which enables us to perform quantitatively reliable analysis. In each metal, the obtained intrinsic SHC is independent of resistivity in the low resistive regime (ρ<50 μΩ cm) whereas it decreases in proportion to ρ−2 in the high resistive regime. In the low resistive regime, the SHC takes a large positive value in Pt and Pd, both of which have approximately nine d electrons per ion (nd=9). On the other hand, the SHC takes a large negative value in Ta, Nb, W, and Mo, where nd<5. In transition metals, a conduction electron acquires the trajectory-dependent phase factor that originates from the atomic wave function. This phase factor, which is reminiscent of the Aharonov–Bohm phase, is the origin of the SHC in paramagnetic metals and that of the anomalous Hall conductivity in ferromagnetic metals. Furthermore, each transition metal shows huge and positive d-orbital Hall conductivity (OHC), independent of the strength of the spin-orbit interaction. Since the OHC is much larger than the SHC, it will be possible to realize an orbitronics device made of transition metals.

Intrinsic spin Hall effect in graphene: Numerical calculations in a multiorbital model 査読有り

S. Onari, Y. Ishikawa, H. Kontani, and J. Inoue

Physical Review B 78 巻頁： 121403R 2008年

Unconventional pairing originating from the disconnected Fermi surfaces of superconducting LaFeAsO1-xFx 査読有り

K. Kuroki, S. Onari, R. Arita, H. Usui, Y. Tanaka, H. Kontani and H. Aoki

Physical Review Letters 101 巻頁： 087004 2008年

Magnetotransport properties governed by antiferromagnetic fluctuations in the heavy-fermion superconductor CeIrIn5 査読有り

Y. Nakajima, H. Shishido, H. Nakai, T. Shibauchi, M. Hedo, Y. Uwatoko, T. Matsumoto, R. Settai, Y. Onuki, H. Kontani, and Y. Matsuda

Physical Review B 77 巻頁： 0214504 2008年

Theory of ac anomalous Hall conductivity in d -electron systems 査読有り

T. Tanaka and H. Kontani

Physical Review B 77 巻頁： 195129 2008年

s-wave superconductivity due to Suhl-Kondo mechanism in NaxCoO2⋅yH2O: Effect of Coulomb interaction and trigonal distortion 査読有り

K. Yada and H. Kontani

Physical Review B 77 巻頁： 184521 2008年

*Anomalous Transport Phenomena in Fermi Liquids with Strong Magnetic Fluctuations 招待有り査読有り

Hiroshi Kontani

Reports on Progress in Physics 71 巻頁： 026501 2008年

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

In many strongly correlated electron systems, remarkable violation of the relaxation time approximation (RTA) is observed. The most famous example would be high-Tc superconductors (HTSCs), and similar anomalous transport phenomena have been observed in metals near their antiferromagnetic (AF) quantum critical point (QCP). Here, we develop a transport theory involving resistivity and Hall coefficient on the basis of the microscopic Fermi liquid theory, by considering the current vertex correction (CVC). In nearly AF Fermi liquids, the CVC accounts for the significant enhancements in the Hall coefficient, magnetoresistance, thermoelectric power, and Nernst coefficient in nearly AF metals. According to the numerical study, aspects of anomalous transport phenomena in HTSC are explained in a unified way by considering the CVC, without introducing any fitting parameters; this strongly supports the idea that HTSCs are Fermi liquids with strong AF fluctuations. In addition, the striking \omega-dependence of the AC Hall coefficient and the remarkable effects of impurities on the transport coefficients in HTSCs appear to fit naturally into the present theory. The present theory also explains very similar anomalous transport phenomena occurring in CeCoIn5 and CeRhIn5, which is a heavy-fermion system near the AF QCP, and in the organic superconductor \kappa-(BEDT-TTF).

Study of intrinsic spin and orbital Hall effects in Pt based on a (6s, 6p, 5d) tight-binding model 査読有り

H. Kontani, M. Naito, D.S. Hirashima, K. Yamada and J. Inoue

Journal of the Physical Society of Japan 76 巻頁： 103702 2007年10月

Study of intrinsic spin and orbital hall effects in pt based on a (6s, 6p, 5d) tight-binding model

Kontani Hiroshi, Naito Masayuki, Hirashima Dai S., Yamada Kosaku, Inoce Jun-Ichiro

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 巻 ( 10 ) 2007年10月

Striking similarities between HTSC and quasi-2D HFCeRIn5

Izawa Koichi, Nakajima Y., Kasahara Y., Bel R., Behnia K., Shishido H., Settai R., Onuki Y., Kontani H., Matsuda Y.

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460 巻頁： 145 - 148 2007年9月

Unusual Hall effect in quasi two-dimensional strongly correlated metal CeCoIn5

Nakajima Y., Shishido H., Izawa K., Matsuda Y., Kontani H., Hedo H., Uwatoko Y., Matsumoto T., Settai R., Onuki Y.

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460 巻頁： 680 - 681 2007年9月

Robustness of s-wave superconductivity against Coulomb interactions in NaxCoO2

Yada Keiji, Kontani Hiroshi

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 460 巻頁： 483-484 2007年9月

Theory of thermal conductivity in high-T-c superconductors below T-c: Comparison between hole- and electron-doped systems

Hara Hideyuki, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 巻 ( 7 ) 2007年7月

Theory of Thermal Conductivity in High-Tc Superconductors below Tc: Comparison between Hole- and Electron-Doped Systems 査読有り

Hideyuki Hara, Hiroshi Kontan

Journal of the Physical Society of Japan 76 巻 ( 18 ) 頁： 184416 2007年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

In hole-doped high-Tc superconductors, thermal conductivity κ increases drastically just below Tc, which has been considered as a hallmark of a nodal gap. In contrast, such a coherence peak in κ is not visible in electron-doped compounds, which may indicate a full-gap state such as a d+is-wave state. To settle this problem, we study κ in the Hubbard model using the fluctuation-exchange (FLEX) approximation, which predicts that the nodal d-wave state is realized in both hole- and electron-doped compounds. The contrasting behavior of κ in both compounds originates from the differences in the hot/cold spot structure. In general, a prominent coherence peak in κ appears in line-node superconductors only when the cold spot exists on the nodal line.

Theory of Infrared Hall Conductivity Based on the Fermi Liquid Theory: Analysis of High-Tc Superconductors 査読有り

76 巻頁： 074707 2007年7月

Theory of Thermal Conductivity in High-Tc Superconductors below Tc: Comparison between Hole- and Electron-Doped Systems 査読有り

Hideyuki Hara, and Hiroshi Kontani

Journal of the Physical Society of Japan 76 巻頁： 073705 2007年7月

Theory of Infrared Hall Conductivity Based on the Fermi Liquid Theory: Analysis of High-Tc Superconductors 査読有り

H. Kontani

Journal of the Physical Society of Japan 76 巻 ( 07 ) 頁： 074707 2007年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

We study optical Hall conductivity for high-Tc superconductors on the basis of microscopic Fermi liquid theory. Current vertex corrections (CVCs) are correctly taken into account to satisfy the conservation laws, and are performed for the first time for optical conductivities based on the fluctuation-exchange (FLEX) approximation. We find that (I) the CVC emphasizes the ω-dependence of σxy(ω) significantly when the antiferromagnetic (AF) fluctuations are strong. For this reason, the relation σxy(ω)∼{σxx(ω)}2, which is satisfied in the extended Drude model given by the relaxation time approximation (RTA), is completely violated for a wide range of frequencies. Consequently, (II) the optical Hall coefficient RH(ω) strongly depends on ω below infrared frequencies, which is consistent with experimental observations. Interestingly, although σxx(ω) does not follow a simple Drude form due to the ω-dependence of the relaxation time τ, θH(ω) and σxy(ω) follow approximate simple Drude forms since the ω-dependences of τ and CVC almost cancel each other out. In conclusion, anomalous optical transport phenomena in high-Tc superconductors, which had been frequently assumed to be as evidence of the breakdown of the Fermi liquid state, can be well explained in terms of the nearly AF Fermi liquid once the CVC is taken into account.

Theory of infrared hall conductivity based on the fermi liquid theory: Analysis of high-T-c superconductors

Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 巻 ( 7 ) 2007年7月

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