Faculty Profiles - KONTANI, Hiroshi

Papers - KONTANI, Hiroshi

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Theory of anisotropic s-wave superconductivity with point-node-like gap minima: Analysis of (Y,Lu)Ni2B2C

Kontani H

PHYSICAL REVIEW B Vol. 70 ( 5 ) 2004.8

Generalized Kadowaki-Woods Relation in Heavy Fermion Systems with Orbital Degeneracy Reviewed

Hiroshi Kontani

Journal of Physical Society of Japan Vol. 73 ( 3 ) 2004.3

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

We present a theoretical study of the Kadowaki-Woods relation in the orbitally degenerate periodic Anderson model. Based on the Fermi liquid theory, we derive the generalized Kadowaki-Woods relationin the strong coupling limit, Aγ-2 \approx 10-5 /½ N(N-1) [µΩ cm (mol·K/mJ)2], where A is the coefficient of the T2 term in the resistivity, γ is the T-linear specific heat coefficient, and N is the f-orbital degeneracy. This result naturally explains the remarkably smaller value of Aγ-2 in various orbitally degenerate (mainly Yb-based) heavy Fermion systems, reported by Tsujii et al. [J. Phys.: Condens. Matter 15 (2003) 1993].

Generalized Kadowaki-Woods relation in heavy fermion systems with orbital degeneracy

Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 73 ( 3 ) page： 515 - 518 2004.3

Normal-state Hall Angle and Magnetoresistance in Quasi-2D Heavy Fermion CeCoIn5 near a Quantum Critical Point Reviewed

Y. Nakajima, K. Izawa, Y. Matsuda, S. Uji, T. Terashima, H. Shishido, R. Settai, Y. Onuki and H. Kontani

Journal of Physical Society of Japan Vol. 73 ( 1 ) page： 5-8 2004.1

Language：English Publishing type：Research paper (scientific journal)

The normal-state Hall effect and magnetoresisitance (MR) have been measured in the quasi two dimensional (2D) heavy fermion superconductor CeCoIn5. In the non-Fermi liquid region where the reistivity ρxx exhibits an almost perfect T-linear dependence, the Hall angle varies as cot θH ∝ T2 and MR displays a strong violation of Kohler's rule. We demonstrate a novel relation between the MR and the Hall conductivity, Δ ρxx/ρxx∝ (σxyρxx)2. These results bear a striking resemblance to the normal-state properties of high-Tc cuprates, indicating universal transport properties in the presence of quasi-2D antiferromagnetic fluctuations near a quantum critical point.

Phase Diagram of β'-(BEDT-TTF)2ICl2 under High Pressure Based on the First-Principles Electronic Structure Reviewed

Hiori Kino, Hiroshi Kontani and Tsuyoshi Miyazaki

Journal of Physical Society of Japan Vol. 73 ( 1 ) page： 25-28 2004.1

Language：English Publishing type：Research paper (scientific journal)

We present a theoretical study on the superconductivity of β'-(BEDT-TTF)2ICl2 at Tc=14.2 K under a high hydrostatic pressure recently found, which is the highest among organic superconductors. In the present work, we study an effective model using the fluctuation-exchange (FLEX) approximation based on the results of first-principles calculation. In the obtained phase diagram, the superconductivity with dxy-like symmetry is realized next to the antiferromagnetic phase, as a result of the one-dimensional to two-dimensional crossover driven by the pressure.

Phase diagram of beta '-(BEDT-TTF)(2)ICl2 under high pressure based on the first-principles electronic structure

Kino H, Kontani H, Miyazaki T

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 73 ( 1 ) page： 25 - 28 2004.1

Normal-state hall angle and magnetoresistance in Quasi-2D heavy fermion CeCoIn5 near a quantum critical point

Nakajima Y, Izawa K, Matsuda Y, Uji S, Terashima T, Shishido H, Settai R, Onuki Y, Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 73 ( 1 ) page： 5 - 8 2004.1

高温超伝導体の以上金属相における輸送現象の理論 ─フェルミ液体論に基づく統一的理論─ Invited Reviewed

紺谷浩

日本物理学会誌 Vol. 58 ( 7 ) page： 524-527 2003.7

Origin of superconductivity in beta(')-(BEDT-TTF)(2)ICl2 under high pressure and in beta-(BEDT-TTF)(2)X at atmospheric pressure

Kontani H

PHYSICAL REVIEW B Vol. 67 ( 18 ) 2003.5

Theory of Nernst coefficient in high-T-c cuprates: the role of vertex corrections

Kontani H

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Vol. 388 page： 68 - 69 2003.5

Nernst coefficient in high-T-c superconductors: The role of superconducting fluctuations

Kontani H

ACTA PHYSICA POLONICA B Vol. 34 ( 2 ) page： 799 - 802 2003.2

General formula for the thermoelectric transport phenomena based on Fermi liquid theory: Thermoelectric power, Nernst coefficient, and thermal conductivity

Kontani H

PHYSICAL REVIEW B Vol. 67 ( 1 ) 2003.1

Nernst coefficient and magnetoresistance in high-T-c superconductors: The role of superconducting fluctuations

Kontani H

PHYSICAL REVIEW LETTERS Vol. 89 ( 23 ) 2002.12

Nernst Coefficient and Magnetoresistance in High-Tc Superconductors: The Role of Superconducting Fluctuations Reviewed

Hiroshi Kontani

Physical Review Letter Vol. 89 ( 23 ) page： 237003(4p) 2002.11

Language：English Publishing type：Research paper (scientific journal)

In high-Tc cuprates, the Nernst coefficient (ν) as well as the magnetoresistance (Δρ/ρ) increases drastically below the pseudogap temperature, T*, which attracts much attention as a key phenomenon in the pseudogap region. We study these transport phenomena in terms of the fluctuation-exchange+T–matrix approximation. In this present theory, the d-wave superconducting (SC) fluctuations, which are mediated by antiferromagnetic (AF) correlations, become dominant below T*. We especially investigate the vertex corrections both for the charge current and the heat one to keep the conservation laws. As a result, the mysterious behaviors of ν and Δρ/ρ are naturally explained as the reflection of the enhancement of the SC fluctuation, without assuming thermally excited vortices. The present result suggests that the pseudogap phenomena are well described in terms of the Fermi liquid with AF and SC fluctuations.

Theory of magnetoresistance in correlated electron systems: modified Kohler rule in high-T-c superconductors

Kontani H

PHYSICA B-CONDENSED MATTER Vol. 312 page： 25 - 27 2002.3

Theory of Thermoelectric Power in High-Tc Superconductors Reviewed

Hiroshi Kontani

Journal of the Physical Society of Japan Vol. 2001 ( 6 ) page： 2840-2843 2001.10

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

We present a microscopic theory for the thermoelectric power (TEP) in high-Tc cuprates. Based on the general expression for the TEP, we perform the calculation of the TEP for a two-dimensional Hubbard model including all the vertex corrections necessary to satisfy the conservation laws. In the present study, characteristic anomalous temperature and doping dependences of the TEP in high-Tc cuprates, which have been a long-standing problem in high-Tc cuprates, are well reproduced for both hole- and electron-doped systems, except for the heavily under-doped case. According to the present analysis, the strong momentum and energy dependences of the self-energy due to the strong antiferromagnetic fluctuations play an essential role in reproducing experimental anomalies of the TEP.

Theory of thermoelectric power in high T-c superconductors

Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 70 ( 10 ) page： 2840 - 2843 2001.10

General formula for the magnetoresistance on the basis of Fermi liquid theory

Kontani H

PHYSICAL REVIEW B Vol. 64 ( 5 ) 2001.8

General formula for the magnetoresistance on the basis of Fermi liquid theory Reviewed

Hiroshi Kontani

Physical Review B. Vol. 64 ( 5 ) page： 054413(19p) 2001.8

Magnetoresistance in High-Tc Superconductors: The Role of Vertex Corrections Reviewed

Hiroshi Kontani

Journal of the Physical Society of Japan Vol. 70 ( 7 ) page： 1873-1876 2001.7

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

In high-Tc cuprates, the orbital magnetoresistance in plane (Δρ/ρ) is anomalously enhanced at lower tempemeratures compared with conventional Fermi liquids, and thus Kohler's rule is strongly violated. Moreover, it should be noted that an intimate relation between Δρ/ρ and the Hall coefficient (RH), Δρ/ρ ∝ (RH/ρ)2, holds well experimentally, and is called the “modified Kohler's rule". In this letter, we study this long-standing problem in terms of the nearly antiferromagnetic (AF) Fermi liquid. We analyze the exact expression for Δρ/ρ by including the vertex corrections (VC's) to keep the conservation laws, and find the approximate relation Δρ/ρ ∝ ξAF4 ρ-2 · H2 (ξAF being the AF correlation length) in the presence of AF fluctuations. The factor ξAF4, which comes from the VC's for the current, gives the additional temperature dependence. By taking account of the relation RH ∝ ξAF2 [Kontani et al.: Phys. Rev. B 59 (1999) 14723], we can naturally explain the modified Kohler's rule. In conclusion, based on the Fermi liquid theory, the famous seemingly non-Fermi liquid behaviors of RH and Δρ/ρ in high-Tc cuprates are naturally understood on an equal footing.

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Papers - KONTANI, Hiroshi