Faculty Profiles - KONTANI, Hiroshi

Papers - KONTANI, Hiroshi

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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.

Possible appearance of superconductivity on Si(100) surface

Kino H, Kontani H

SURFACE SCIENCE Vol. 482 page： 501 - 506 2001.6

Theory of the Hall coefficient and resistivity for the layered organic superconductors kappa-(BEDT-TTF)(2)X

Kontani H, Kino H

PHYSICAL REVIEW B Vol. 63 ( 13 ) 2001.4

Comment on "Charge-orbital stripe structure in La1-xCaxMnO3 (x=1/2, 2/3)" - Reply

Mutou T, Kontani H

PHYSICAL REVIEW LETTERS Vol. 86 ( 11 ) page： 2479 - 2479 2001.3

Comment on "Charge-orbital stripe structure in La1-xCaxMnO3 (x=1/2, 2/3)"

Hotta T, Dagotto E, Koizumi H, Takada Y

PHYSICAL REVIEW LETTERS Vol. 86 ( 11 ) page： 2478 - 2478 2001.3

Hall effect in high-T-c superconductors

Kontani H, Kanki K, Ueda K

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS Vol. 62 ( 1-2 ) page： 83 - 87 2001

Possible appearance of superconductivity on Si(001) surface

Kino H, Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 69 ( 7 ) page： 1962 - 1965 2000.7

Origin of the charge-ordered stripe with the orbital ordering in manganese oxides

Mutou T, Kontani H

PHYSICA B Vol. 281 page： 531 - 533 2000.6

Anomalous behaviors of the transport phenomena in high-T-c superconductors

Kontani H, Kanki K, Ueda K

PHYSICA B Vol. 281 page： 808 - 809 2000.6

Charge-orbital stripe structure in La1-xCaxMnO3 (x=1/2, 2/3)

Mutou T, Kontani H

PHYSICAL REVIEW LETTERS Vol. 83 ( 18 ) page： 3685 - 3688 1999.11

Effects of spin fluctuations and superconductivity in quasi-one-dimensional organic conductors

Kino H, Kontani H

JOURNAL OF LOW TEMPERATURE PHYSICS Vol. 117 ( 3-4 ) page： 317 - 321 1999.11

Hall effect and resistivity in high-Tc superconductors: The conserving approximation Reviewed

H. Kontani, K. Kanki, and K. Ueda

Physical Review B. Vol. 59 ( 22 ) page： 14723-14739 1999.7

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

The Hall coefficient RH in high-Tc cuprates in the normal state shows the striking non-Fermi-liquid behavior: RH follows a Curie-Weiss type temperature dependence and |RH|≫1/|ne| at low temperatures in the underdoped compounds. Moreover, RH is positive for hole-doped compounds and negative for electron-doped ones, although each of them has a similar holelike Fermi surface. In this paper, we give the explanation of this long-standing problem from the standpoint of the nearly antiferromagnetic (AF) Fermi liquid. We consider seriously the vertex corrections for the current which are indispensable to satisfy the conservation laws, which are violated within the conventional Boltzmann transport approximation. The obtained total current Jk takes an enhanced value and is no longer perpendicular to the Fermi surface due to the strong AF fluctuations. By virtue of this mechanism, the anomalous behaviors of RH in high-Tc cuprates are naturally explained. Both the temperature and the (electron, hole) doping dependences of RH in high-Tc cuprates are reproduced well by numerical calculations based on the fluctuation-exchange approximation, applied to the single-band Hubbard model with a holelike Fermi surface. We also discuss the singular temperature dependence of RH in other nearly AF metals, e.g., V2O3, κ-BEDT-TTF organic superconductors, and heavy fermion systems close to the AF phase boundary.

Hall effect and resistivity in high-T-c superconductors: The conserving approximation

Kontani H, Kanki K, Ueda K

PHYSICAL REVIEW B Vol. 59 ( 22 ) page： 14723 - 14739 1999.6

Theory of Hall effect and electrical transport in high-T-c cuprates: Effects of antiferromagnetic spin fluctuations

Kanki K, Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 68 ( 5 ) page： 1614 - 1624 1999.5

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Papers - KONTANI, Hiroshi