Faculty Profiles - KONTANI, Hiroshi

Papers - KONTANI, Hiroshi

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Drastic magnetic-field-induced chiral current order and emergent current-bond-field interplay in kagome metals Reviewed

Rina Tazai, Youichi Yamakawa, Hiroshi Kontani

Proceedings of the National Academy of Sciences Vol. 121 page： e2303476121 2024.1

Charge-loop current order and Z3 nematicity mediated by bond order fluctuations in kagome metals Reviewed

Tazai, R; Yamakawa, Y; Kontani, H

NATURE COMMUNICATIONS Vol. 14 ( 1 ) 2023.11

Unconventional density waves and superconductivities in Fe-based superconductors and other strongly correlated electron systems Invited Reviewed

Hiroshi Kontani, Rina Tazai, Youichi Yamakawa, Seiichiro Onari

Advances in Physics Vol. 3 page： 355 - 443 2023.1

Real-space Loop Current Pattern in Time-reversal-symmetry Breaking Phase in Kagome Metals Reviewed

Koki Shimura, Rina Tazai, Youichi Yamakawa, Seiichiro Onari, and Hiroshi Kontani

Journal of the Physical Society of Japan Vol. 93 page： 033704 2024.2

Evidence for an odd-parity nematic phase above the charge-density-wave transition in a kagome metal Reviewed International coauthorship

T. Asaba, A. Onishi, Y. Kageyama, T. Kiyosue, K. Ohtsuka, S. Suetsugu, Y. Kohsaka, T. Gaggl, Y. Kasahara, H. Murayama, K. Hashimoto, R. Tazai, H. Kontani, B. R. Ortiz, S. D. Wilson, Q. Li, H. -H. Wen, T. Shibauchi, and Y, Matsuda

Nature Physics Vol. 20 page： 40 - 46 2024.1

Low temperature phase transitions under CDW state in kagome metals AV3Sb5 (A=Cs,Rb,K): Significance of mix-type Fermi surface electron correlations Reviewed

Jianxin Huang, Rina Tazai, Youichi Yamakawa, Seiichiro Onari, Hiroshi Kontani

Physical Review B 2024.1

Three-dimensional bond-order instability in infinite-layer nickelates due to nonlocal quantum interference Invited Reviewed

Seiichiro Onari and Hiroshi Kontani

Physical Review B Vol. 108 page： L241119 2023.12

Rigorous formalism for unconventional symmetry breaking in Fermi liquid theory and its application to nematicity in FeSe Reviewed

Tazai Rina, Matsubara Shun, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 107 ( 3 ) 2023.1

Correlation-driven electronic nematicity in the Dirac semimetal BaNiS2 Reviewed

Butler Christopher John, Kohsaka Yuhki, Yamakawa Youichi, Bahramy Mohammad Saeed, Onari Seiichiro, Kontani Hiroshi, Hanaguri Tetsuo, Shamoto Shinichi

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Vol. 119 ( 49 ) 2022.11

Diverse Exotic Orders and Fermiology in Fe-Based Superconductors: A Unified Mechanism for B1g/B2g Nematicity in FeSe/(Cs,Rb)Fe2As2 and Smectic Order in BaFe2As2 Invited Reviewed

Seiichiro Onari and Hiroshi Kontani

Frontiers in Physics Vol. 10 page： 915619 2022.7

Mechanism of exotic density-wave and beyond-Migdal unconventional superconductivity in kagome metal AV(3)Sb(5) (A = K, Rb, Cs) Reviewed

Tazai Rina, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

SCIENCE ADVANCES Vol. 8 ( 13 ) 2022.4

SU(4) Valley + Spin Fluctuation Interference Mechanism for Nematic Order in Magic-Angle Twisted Bilayer Graphene: The Impact of Vertex Corrections Reviewed

Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW LETTERS Vol. 128 ( 6 ) 2022.2

d- and p-wave Quantum Liquid Crystal Orders in Cuprate Superconductors, Kappa-(BEDT-TTF)(2)X, and Coupled Chain Hubbard Models: Functional-renormalization-group Analysis Invited Reviewed

Tazai Rina, Yamakawa Youichi, Tsuchiizu Masahisa, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 90 ( 11 ) 2021.11

Discovery of mesoscopic nematicity wave in iron-based superconductors Reviewed

Shimojima T., Motoyui Y., Taniuchi T., Bareille C., Onari S., Kontani H., Nakajima M., Kasahara S., Shibauchi T., Matsuda Y., Shin S.

SCIENCE Vol. 373 ( 6559 ) page： 1122 - + 2021.9

Unconventional orbital charge density wave mechanism in the transition metal dichalcogenide 1T-TaS2 Reviewed

Hirata Toru, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW RESEARCH Vol. 3 ( 3 ) 2021.8

Pressure-induced reconstitution of Fermi surfaces and spin fluctuations in S-substituted FeSe Reviewed

Kuwayama T., Matsuura K., Gouchi J., Yamakawa Y., Mizukami Y., Kasahara S., Matsuda Y., Shibauchi T., Kontani H., Uwatoko Y., Fujiwara N.

SCIENTIFIC REPORTS Vol. 11 ( 1 ) 2021.8

Generation of odd-frequency surface superconductivity with spontaneous spin current due to the zero-energy Andreev bound state

Matsubara Shun, Tanaka Yukio, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 103 ( 24 ) 2021.6

Development of Spin Fluctuations under the Presence of d-wave Bond Order in Cuprate Superconductors

Ando Satoshi, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 90 ( 6 ) 2021.6

Prediction of pseudogap formation due to d-wave bond-order in organic superconductor kappa-(BEDT-TTF)(2)X

Tazai Rina, Yamakawa Youichi, Tsuchiizu Masahisa, Kontani Hiroshi

PHYSICAL REVIEW RESEARCH Vol. 3 ( 2 ) 2021.5

Emergence of charge loop current in the geometrically frustrated Hubbard model: A functional renormalization group study

Tazai Rina, Yamakawa Youichi, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 103 ( 16 ) 2021.4

Odd-parity spin-loop-current order mediated by transverse spin fluctuations in cuprates and related electron systems

Kontani Hiroshi, Yamakawa Youichi, Tazai Rina, Onari Seiichiro

PHYSICAL REVIEW RESEARCH Vol. 3 ( 1 ) 2021.2

Spin-fluctuation-driven B-1g and B-2g Bond Order and Induced In-plane Anisotropy in Magnetic Susceptibility in Cuprate Superconductors: Impact of Hot-/Cold-spot Structure on Bond-order Symmetry

Kawaguchi Kouki, Onari Seiichiro, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 89 ( 12 ) 2020.12

Hidden antiferronematic order in Fe-based superconductor BaFe2As2 and NaFeAs above T-S

Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW RESEARCH Vol. 2 ( 4 ) 2020.10

Non-Fermi liquid transport in the vicinity of the nematic quantum critical point of superconducting FeSe1-xSx

Huang W. K., Hosoi S., Culo M., Kasahara S., Sato Y., Matsuura K., Mizukami Y., Berben M., Hussey N. E., Kontani H., Shibauchi T., Matsuda Y.

PHYSICAL REVIEW RESEARCH Vol. 2 ( 3 ) 2020.9

Doping effects on electronic states in electron-doped FeSe: Impact of self-energy and vertex corrections

Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 102 ( 8 ) 2020.8

Emergence of d +/- ip-wave superconducting state at the edge of d-wave superconductors mediated by ferromagnetic fluctuations driven by Andreev bound states

Matsubara Shun, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 101 ( 23 ) 2020.6

Emergence of strongly correlated electronic states driven by the Andreev bound state in d-wave superconductors

Matsubara Shun, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 101 ( 7 ) 2020.2

Multipole fluctuation theory for heavy fermion systems: Application to multipole orders in CeB6

Tazai Rina, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 100 ( 24 ) 2019.12

Origin of diverse nematic orders in Fe-based superconductors: 45 degrees rotated nematicity in AFe(2)As(2) (A=Cs, Rb)

Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 100 ( 2 ) 2019.7

Hexadecapole Fluctuation Mechanism for s-wave Heavy Fermion Superconductor CeCu2Si2: Interplay between Intra- and Inter-Orbital Cooper Pairs

Tazai Rina, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 88 ( 6 ) 2019.6

Pressure-induced quantum critical point in the heavily hydrogen-doped iron-based superconductor LaFeAsO

Takeuchi Masayoshi, Fujiwara Naoki, Kuwayama Takanori, Nakagawa Satoshi, Iimura Soshi, Matsuishi Satoru, Yamakawa Youichi, Kontani Hiroshi, Hosono Hideo

PHYSICAL REVIEW B Vol. 99 ( 17 ) 2019.5

Fully gapped s-wave superconductivity enhanced by magnetic criticality in heavy-fermion systems

Tazai Rina, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 98 ( 20 ) 2018.11

Self-energy driven resonancelike inelastic neutron spectrum in the s(++)-wave state in Fe-based superconductors

Takeuchi Lisa, Yamakawa Youichi, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 98 ( 16 ) 2018.10

Pairing mechanism for nodal s-wave superconductivity in BaFe2(As, P)(2): Analysis beyond Migdal-Eliashberg formalism

Nakaoka Hironori, Yamakawa Youichi, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 98 ( 12 ) 2018.9

Edge-induced Strongly Correlated Electronic States in Two-dimensional Hubbard Model: Enhancement of Magnetic Correlations and Self-energy Effects

Matsubara Shun, Yamakawa Youichi, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 87 ( 7 ) 2018.7

Multistage electronic nematic transitions in cuprate superconductors: A functional-renormalization-group analysis

Tsuchiizu Masahisa, Kawaguchi Kouki, Yamakawa Youichi, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 97 ( 16 ) 2018.4

Abrupt change of the superconducting gap structure at the nematic critical point in FeSe1-xSx

Sato Yuki, Kasahara Shigeru, Taniguchi Tomoya, Xing Xiangzhuo, Kasahara Yuichi, Tokiwa Yoshifumi, Yamakawa Youichi, Kontani Hiroshi, Shibauchi Takasada, Matsuda Yuji

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Vol. 115 ( 6 ) page： 1227-1231 2018.2

Nematicity, magnetism, and superconductivity in FeSe under pressure: Unified explanation based on the self-consistent vertex correction theory

Youichi Yamakawa, Hiroshi Kontani

Phys. Rev. B Vol. 96 ( 14 ) page： 144509 2017.10

In-plane anisotropy of transport coefficients in electronic nematic states: Universal origin of nematicity in Fe-based superconductors

Phys. Rev. B Vol. 96 ( 9 ) page： 094527 2017.9

Superconductivity without a hole pocket in electron-doped FeSe: Analysis beyond the Migdal-Eliashberg formalism

Phys. Rev. B Vol. 96 ( 4 ) page： 043130 2017.7

Plain s-Wave Superconductivity near Magnetic Criticality: Enhancement of Attractive Electron-Boson Coupling Vertex Corrections

Tazai Rina, Yamakawa Youichi, Tsuchiizu Masahisa, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 86 ( 7 ) 2017.7

Competing Unconventional Charge-Density-Wave States in Cuprate Superconductors: Spin-Fluctuation-Driven Mechanism

Kawaguchi Kouki, Yamakawa Youichi, Tsuchiizu Masahisa, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 86 ( 6 ) 2017.6

High-Tc Superconductivity in FeSe at High Pressure: Dominant Hole Carriers and Enhanced Spin Fluctuations

Phys. Rev. Lett. Vol. 118 ( 14 ) page： 147004 2017.4

Unusual nodal behaviors of the superconducting gap in the iron-based superconductor Ba(Fe0.65Ru0.35)(2)As-2: Effects of spin-orbit coupling

Liu L., Okazaki K., Yoshida T., Suzuki H., Horio M., Ambolode L. C. C. II, Xu J., Ideta S., Hashimoto M., Lu D. H., Shen Z. -X., Ota Y., Shin S., Nakajima M., Ishida S., Kihou K., Lee C. H., Iyo A., Eisaki H., Mikami T., Kakeshita T., Yamakawa Y., Kontani H., Uchida S., Fujimori A.

PHYSICAL REVIEW B Vol. 95 ( 10 ) 2017.3

Functional renormalization group study of orbital fluctuation mediated superconductivity: Impact of the electron-boson coupling vertex corrections

Rina Tazai, Youichi Yamakawa, Masahisa Tsuchiizu, Hiroshi Kontani

Physical Review B Vol. 94 ( 11 ) page： 115155 2016.9

Theoretical prediction of nematic orbital-ordered state in the Ti oxypnictide superconductor BaTi2(As,Sb)(2)O

Nakaoka Hironori, Yamakawa Youichi, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 93 ( 24 ) 2016.6

Nematicity and magnetism in FeSe and other families of Fe-based superconductors

Youichi Yamakawa, Seiichiro Onari, Hiroshi Kontani

Physical Review X Vol. 6 ( 2 ) page： 021032 2016.6

Sign-reversing orbital polarization in the nematic phase of FeSe due to the $C_2$ symmetry-breaking in the self-energy

Seiichiro Onari, Youichi Yamakawa, Hiroshi Kontani

Physical Review Letters Vol. 116 ( 22 ) page： 227001 2016.6

p-orbital density wave with d symmetry in high-T-c cuprate superconductors predicted by renormalization-group plus constrained RPA theory

Tsuchiizu Masahisa, Yamakawa Youichi, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 93 ( 15 ) 2016.4

Superconductivity pairing mechanism from cobalt impurity doping in FeSe: Spin (s(+/-)) or orbital (s(++)) fluctuation

Urata T., Tanabe Y., Huynh K. K., Yamakawa Y., Kontani H., Tanigaki K.

PHYSICAL REVIEW B Vol. 93 ( 1 ) 2016.1

Momentum-dependent sign inversion of orbital order in superconducting FeSe

Suzuki Y., Shimojima T., Sonobe T., Nakamura A., Sakano M., Tsuji H., Omachi J., Yoshioka K., Kuwata-Gonokami M., Watashige T., Kobayashi R., Kasahara S., Shibauchi T., Matsuda Y., Yamakawa Y., Kontani H., Ishizaka K.

PHYSICAL REVIEW B Vol. 92 ( 20 ) 2015.11

Revisiting orbital-fluctuation-mediated superconductivity in LiFeAs: Nontrivial spin-orbit interaction effects on the band structure and superconducting gap function

Saito Tetsuro, Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 92 ( 13 ) 2015.10

$p$-orbital density wave with $d$ symmetry in high-$T_c$ cuprate superconductors predicted by the renormalization-group + constrained RPA theory Reviewed

Masahisa Tsuchiizu, Youichi Yamakawa, Hiroshi Kontani

Physical Review B Vol. 93 page： 155148 2015.7

Quasiparticle Interference in Fe-based Superconductors Based on a Five-Orbital Tight-Binding Model Reviewed

Youichi Yamakawa, Hiroshi Kontani

Physical Review B Vol. 92 page： 045124 2015.6

Spin-Fluctuation-Driven Nematic Charge-Density Wave in Cuprate Superconductors: Impact of Aslamazov-Larkin Vertex Corrections

Youichi Yamakawa and Hiroshi Kontani

Physical Review Letters Vol. 114 ( 25 ) page： 257001 2015.6

Spin-triplet superconductivity in Sr2RuO4 due to orbital and spin fluctuations: Analyses by two-dimensional renormalization group theory and self-consistent vertex-correction method

Masahisa Tsuchiizu, Youichi Yamakawa, Seiichiro Onari, Yusuke Ohno, and Hiroshi Kontani

Physical Review B Vol. 91 ( 15 ) page： 2015 2015.4

Quantum critical behavior in heavily doped LaFeAsO$_{1-x}$H$_x$ pnictide superconductors analyzed using nuclear magnetic resonance

R. Sakurai, N. Fujiwara, N. Kawaguchi, Y. Yamakawa, H. Kontani, S. Iimura, S. Matsuishi, H. Hosono

Physical Review B Vol. 91 ( 6 ) page： 064509 2015.2

Orbital plus Spin Multimode Fluctuation Theory in Iron-based Superconductors

Onari Seiichiro, Kontani Hiroshi

IRON-BASED SUPERCONDUCTIVITY Vol. 211 page： 331-376 2015

Anisotropy of the superconducting gap in the iron-based superconductor BaFe2(As1-xPx)(2)

Yoshida T., Ideta S., Shimojima T., Malaeb W., Shinada K., Suzuki H., Nishi I., Fujimori A., Ishizaka K., Shin S., Nakashima Y., Anzai H., Arita M., Ino A., Namatame H., Taniguchi M., Kumigashira H., Ono K., Kasahara S., Shibauchi T., Terashima T., Matsuda Y., Nakajima M., Uchida S., Tomioka Y., Ito T., Kihou K., Lee C. H., Iyo A., Eisaki H., Ikeda H., Arita R., Saito T., Onari S., Kontani H.

SCIENTIFIC REPORTS Vol. 4 2014.12

Linear Response Theory for Shear Modulus $C_{66}$ and Raman Quadrupole Susceptibility: Significant Evidence for Orbital Nematic Fluctuations in Fe-Based Superconductors

Hiroshi Kontani, and Youichi Yamakawa

Phys. Rev. Lett. Vol. 113 ( 4 ) page： 047001 (5p) 2014.7

Reproduction of experimental gap structure in LiFeAs based on orbital-spin fluctuation theory: s(++)-wave, s(+/-)-wave, and hole-s(+/-)-wave states

Saito Tetsuro, Onari Seiichiro, Yamakawa Youichi, Kontani Hiroshi, Borisenko Sergey V., Zabolotnyy Volodymyr B.

PHYSICAL REVIEW B Vol. 90 ( 3 ) 2014.7

High-Tc Superconductivity near the Anion Height Instability in Fe-Based Superconductors

Seiichiro Onari, Youichi Yamakawa, and Hiroshi Kontani

Phys. Rev. Lett. Vol. 112 ( 18 ) page： 187001 (5p) 2014.5

NMR Study on a Pnictide Superconductor LaFeAsO1-x H (x) in a H-Overdoped Regime: Revival of Antiferromagnetic Fluctuations

Fujiwara N., Iimura S., Matsuishi S., Hosono H., Yamakawa Y., Kontani H.

JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM Vol. 27 ( 4 ) page： 933-936 2014.4

Microstructural Analysis of Low-cycle Fatigue Damage Process of Sn-Ag-Cu Solder Joint

Kontani Hiroyuki, Kariya Yoshiharu, Fumikura Tomoya

PROCEEDINGS OF THE ASME INTERNATIONAL TECHNICAL CONFERENCE AND EXHIBITION ON PACKAGING AND INTEGRATION OF ELECTRONIC AND PHOTONIC MICROSYSTEMS, 2013, VOL 1 2014

Infrared anomalous Hall effect in CaxSr1-xRuO3 films

Kim M. -H., Tanaka T., Ellis C. T., Mukherjee A., Acbas G., Ohkubo I., Christen H., Mandrus D., Kontani H., Cerne J.

PHYSICAL REVIEW B Vol. 88 ( 15 ) 2013.10

Orbital Nematic Instability in Two-Orbital Hubbard Model: Renormalization-Group + Constrained RPA Analysis Reviewed

Yusuke Ohno, Masahisa Tsuchiizu, Seiichiro Onari, Hiroshi Kontani

Physical Review Letters Vol. 111 page： 057003 2013.9

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

Motivated by the nematic electronic fluid phase in Sr_{3}Ru_{2}O_{7}, we develop a combined scheme of the renormalization-group method and the random-phase-approximation-type method, and analyze orbital susceptibilities of the (d_{xz},d_{yz})-orbital Hubbard model with high accuracy. It is confirmed that the present model exhibits a ferro-orbital instability near the magnetic or superconducting quantum criticality, due to the Aslamazov-Larkin-type vertex corrections. This mechanism of orbital nematic order presents a natural explanation for the nematic order in Sr_{3}Ru_{2}O_{7}, and is expected to be realized in various multiorbital systems, such as Fe-based superconductors.

Zigzag Chain Structure Transition and Orbital Fluctuations in Ni-Based Superconductors

Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 82 ( 9 ) 2013.9

Detection of antiferromagnetic ordering in heavily doped LaFeAsO1-xHx pnictide superconductors using nuclear-magnetic-resonance techniques

N. Fujiwara, S. Tsutsumi, S. Iimura, S. Matsuishi, H. Hosono, Y. Yamakawa, and H. Kontani

Phys. Rev. Lett. Vol. 111 ( 9 ) page： 097002 (4p) 2013.8

Orbital Nematic Instability in Two-Orbital Hubbard Model: Renormalization-Group + Constrained RPA Analysis

Masahisa Tsuchiizu, Yusuke Ohno, Seiichiro Onari, Hiroshi Kontani

Physical Review Letters Vol. 111 ( 5 ) page： 057003 2013.7

Phase diagram and superconducting states in LaFeAsO1-xHx based on the multiorbital extended Hubbard model

Yamakawa Y., Onari S., Kontani H., Fujiwara N., Iimura S., Hosono H.

PHYSICAL REVIEW B Vol. 88 ( 4 ) 2013.7

Nodal gap structure in Fe-based superconductors due to the competition between orbital and spin fluctuations

Saito Tetsuro, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 88 ( 4 ) 2013.7

Effect of realistic finite-size impurities on T-c in Fe-based superconductors based on the five-orbital tight-binding model

Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 87 ( 19 ) 2013.5

Spin-Fluctuation-Driven Orbital Nematic Order in Ru-Oxides: Self-Consistent Vertex Correction Analysis for Two-Orbital Model

Ohno Yusuke, Tsuchiizu Masahisa, Onari Seiichiro, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 82 ( 1 ) 2013.1

Extrinsic Spin Hall Effect Due to Transition-Metal Impurities

Tanaka Takuro, Kontani Hiroshi

PROGRESS OF THEORETICAL PHYSICS Vol. 128 ( 5 ) page： 805-828 2012.11

Self-consistent Vertex Correction Analysis for Iron-based Superconductors: Mechanism of Coulomb Interaction-Driven Orbital Fluctuations

Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW LETTERS Vol. 109 ( 13 ) 2012.9

Spin Hall effect in iron-based superconductors: A Dirac-point effect

Pandey Sudhakar, Kontani Hiroshi, Hirashima Dai S., Arita Ryotaro, Aoki Hideo

PHYSICAL REVIEW B Vol. 86 ( 6 ) 2012.8

Effect of inelastic scattering on the nuclear magnetic relaxation rate 1/T1T in iron-based superconductors

Yamakawa Youichi, Onari Seiichiro, Kontani Hiroshi

SUPERCONDUCTOR SCIENCE & TECHNOLOGY Vol. 25 ( 8 ) 2012.8

Superconductivity suppression of Ba(0.5)K(0.5)Fe2-2xM2xAs(2) single crystals by substitution of transition metal (M = Mn, Ru, Co, Ni, Cu, and Zn)

Li J., Guo Y. F., Zhang S. B., Yuan J., Tsujimoto Y., Wang X., Sathish C. I., Sun Y., Yu S., Yi W., Yamaura K., Takayama-Muromachiu E., Shirako Y., Akaogi M., Kontani H.

PHYSICAL REVIEW B Vol. 85 ( 21 ) 2012.6

Impurity-induced electronic nematic state and C-2-symmetric nanostructures in iron pnictide superconductors

Inoue Yoshio, Yamakawa Youichi, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 85 ( 22 ) 2012.6

Self-consistent Vertex Correction Analysis for Iron-based Superconductors: Mechanism of Coulomb Interaction-Driven Orbital Fluctuations Reviewed

S. Onari and H. Kontani

Phys. Rev. Lett. Vol. 109 page： 137001 2012.6

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

We study the mechanism of orbital/spin fluctuations due to multiorbital Coulomb interaction in iron-based superconductors, going beyond the random-phase-approximation. For this purpose, we develop a self-consistent vertex correction (SC-VC) method, and find that multiple orbital fluctuations in addition to spin fluctuations are mutually emphasized by the "multimode interference effect" described by the VC. Then, both the antiferro-orbital and ferro-orbital (=nematic) fluctuations simultaneously develop for $J/U \sim 0.1$, both of which contribute to the s-wave superconductivity. Especially, the ferro-orbital fluctuations give the orthorhombic structure transition as well as the softening of shear modulus $C_{66}$.

Non-Fermi-liquid transport phenomena and superconductivity driven by orbital fluctuations in iron pnictides: Analysis by fluctuation-exchange approximation

Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 85 ( 13 ) 2012.4

Orbital fluctuation theory in iron-based superconductors: s++-wave superconductivity, structure transition, and impurity-induced nematic order Invited Reviewed

H. Kontani, I. Yoshio. T. Saito, Y. Yamakawa and S. Onari

Solid State Communications Vol. 152 page： 718-727 2012.4

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

The main features in iron-based superconductors would be (i) the orthorhombic transition accompanied by remarkable softening of shear modulus, (ii) high-Tc superconductivity close to the orthorhombic phase, and (iii) nematic transition in the tetragonal phase. In this paper, we present a unified explanation for them, based on the orbital fluctuation theory, considering both the e-ph and the Coulomb interaction. It is found that a small e-ph coupling constant ($\lambda ~ 0.2$) is enough to produce large orbital (=charge quadrupole $O_{xz/yz}$) fluctuations, which causes the s-wave superconductivity without sign reversal ($s_{++}$-wave state). The derived orbital fluctuations also cause the instability toward the structure transition due to the bound state formation of two orbitons with opposite momenta, which is called the "two-orbiton process". Moreover, impurity-induced non-local orbital order with $C_2$-symmetry is obtained when the orbital fluctuations are strong. This "impurity-induced nematic state" explains the in-plane anisotropy of resistivity in detwinned samples. We stress that (i)-(iii) are reproducible only when orbital fluctuations with respect to $O_{xz}$ and $O_{yz}$ charge quadrupoles are the most divergent. This fact ensures the reliability of the present model Hamiltonian and calculation.

Orbital fluctuation theory in iron-based superconductors: s(++)-wave superconductivity, structure transition, and impurity-induced nematic order

Kontani Hiroshi, Inoue Yoshio, Saito Tetsuro, Yamakawa Youichi, Onari Seiichiro

SOLID STATE COMMUNICATIONS Vol. 152 ( 8 ) page： 718-727 2012.4

Study of non-Fermi-liquid-like state and pairing symmetry in iron pnictides based on the multiorbital Hubbard-Holstein model

Onari S., Kontani H.

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Vol. 471 ( 21-22 ) page： 670-674 2011.11

Extremely strong-coupling superconductivity in artificial two-dimensional Kondo lattices

Mizukami Y., Shishido H., Shibauchi T., Shimozawa M., Yasumoto S., Watanabe D., Yamashita M., Ikeda H., Terashima T., Kontani H., Matsuda Y.

NATURE PHYSICS Vol. 7 ( 11 ) page： 849 - 853 2011.11

Neutron inelastic scattering peak by dissipationless mechanism in the s(++)-wave state in iron-based superconductors

Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 84 ( 14 ) 2011.10

Linear decrease of critical temperature with increasing Zn substitution in the iron-based superconductor BaFe1.89-2xZn2xCo0.11As2

Li Jun, Guo Yanfeng, Zhang Shoubao, Yu Shan, Tsujimoto Yoshihiro, Kontani Hiroshi, Yamaura Kazunari, Takayama-Muromachi Eiji

PHYSICAL REVIEW B Vol. 84 ( 2 ) 2011.7

Origin of orthorhombic transition, magnetic transition, and shear-modulus softening in iron pnictide superconductors: Analysis based on the orbital fluctuations theory

Kontani Hiroshi, Saito Tetsuro, Onari Seiichiro

PHYSICAL REVIEW B Vol. 84 ( 2 ) 2011.7

Comment on "Violation of Anderson's Theorem for the Sign-Reversing s-Wave State of Iron-Pnictide Superconductors" Reply

Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW LETTERS Vol. 106 ( 25 ) 2011.6

Indication of intrinsic spin Hall effect in 4d and 5d transition metals

Morota M., Niimi Y., Ohnishi K., Wei D. H., Tanaka T., Kontani H., Kimura T., Otani Y.

PHYSICAL REVIEW B Vol. 83 ( 17 ) 2011.5

Comment on "Orbital Order, Structural Transition and Superconductivity in Iron Pnictides" [J. Phys. Soc. Jpn. 79 (2010) 123707]

Kontani Hiroshi, Onari Seiichiro

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 80 ( 5 ) 2011.5

Emergence of fully gapped s(++)-wave and nodal d-wave states mediated by orbital and spin fluctuations in a ten-orbital model of KFe2Se2

Saito Tetsuro, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 83 ( 14 ) 2011.4

Emergence of Fully-Gapped s++-wave and Nodal d-wave States Mediated by Orbital- and Spin-Fluctuations in Ten-Orbital Model for KFe2Se2 Reviewed

T. Saito, S. Onari, and H. Kontani

Phys. Rev. B Vol. 83 page： 140512 2011

Extremely strong-coupling superconductivity in artificial two-dimensional Kondo lattices Reviewed

Y. Mizukami, H. Shishido, T. Shibauchi, M. Shimozawa, S. Yasumoto, D. Watanabe, M.Yamashita, H. Ikeda, T. Terashima, H. Kontani, and Y. Matsuda

Nature Physics Vol. 7 page： 849 2011

Neutron inelastic scattering peak by dissipationless mechanism in the s++-wave state in iron-based superconductors Reviewed

S. Onari and H. Kontani

Phys. Rev. B Vol. 84 page： 144518 2011

Linear decrease of critical temperature with increasing Zn substitution in the iron-based superconductor Reviewed

Jun Li, Y. Guo, S. Zhang, S. Yu, Y. Tsujimoto, H. Kontani, K. Yamaura, and E. Takayama-Muromachi

Phys. Rev. B Vol. 84 page： 020513 2011

Origin of Orthorhombic Transition, Magnetic Transition, and Shear Modulus Softening in Iron Pnictide Superconductors: Analysis based on the Orbital Fluctuation Theory Reviewed

H. Kontani, T. Saito, and S. Onari

Phys. Rev. B Vol. 84 page： 024528 2011

Indication of intrinsic spin Hall effect in 4d and 5d transition metals Reviewed

M. Morota, Y. Niimi, K. Ohnishi, T. Tanaka, H. Kontani, T. Kimura, Y. Otani

Phys. Rev. B Vol. 83 page： 174405 2011

Nonmagnetic impurity effects and neutron scattering spectrum in iron pnictides

Onari S., Kontani H.

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Vol. 470 ( 20 ) page： 1007-1009 2010.11

Orbital fluctuation theory in iron pnictides: Effects of As-Fe-As bond angle, isotope substitution, and Z(2)-orbital pocket on superconductivity

Saito Tetsuro, Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 82 ( 14 ) 2010.10

Orbital fluctuation theory in iron pnictides: Effects of As-Fe-As bond angle, isotope substitution, and Z2-orbital pocket on superconductivity Reviewed

Tetsuro Saito, Seiichiro Onari, Hiroshi Kontani

Physical Review B Vol. 82 ( 14 ) page： 144510 2010.10

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

We study the pairing mechanism in iron pnictide superconductors based on the five-orbital Hubbard-Holstein model. Due to Fe-ion oscillations, the s-wave superconducting (SC) state without sign reversal (s++-wave state) is induced by orbital fluctuations by using realistic model parameters. The virtue of the present theory is that the famous empirical relation between Tc and the As-Fe-As bond angle is automatically explained since the electron-phonon coupling that creates the orbital fluctuations is the strongest when the As4 tetrahedron is regular. The negative iron isotope effect is also reproduced. In addition, the magnitude of the SC gap on hole pockets is predicted to be rather insensitive to the corresponding d orbital (xz/yz or z2 orbital), which is consistent with the recent bulk-sensitive angle-resolved photoemission spectroscopy (ARPES) measurement for (Ba,K)Fe2As2 and BaFe2(As,P)2. These obtained results indicate that the orbital fluctuation mediated s++-wave state is a plausible candidate for iron pnictides.

Terahertz Hall measurements on optimally doped single-crystal Bi2Sr2CaCu2O8+x

Jenkins G. S., Schmadel D. C., Sushkov A. B., Gu G. D., Kontani H., Drew H. D.

PHYSICAL REVIEW B Vol. 82 ( 9 ) 2010.9

Anomalous Hall effect due to noncollinearity in pyrochlore compounds: Role of orbital Aharonov-Bohm effect

Tomizawa Takeshi, Kontani Hirhoshi

PHYSICAL REVIEW B Vol. 82 ( 10 ) 2010.9

Anomalous Hall effect due to noncollinearity in pyrochlore compounds: Role of orbital Aharonov-Bohm effect Reviewed

Takeshi Tomizawa, Hirhoshi Kontani

physical Review B Vol. 82 ( 10 ) page： 104412 2010.9

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

To elucidate the origin of spin structure-driven anomalous Hall effect (AHE) in pyrochlore compounds, we construct the t2g-orbital kagome lattice model and analyze the anomalous Hall conductivity (AHC). We reveal that a conduction electron acquires a Berry phase due to the complex d-orbital wave function in the presence of spin-orbit interaction. This orbital Aharonov-Bohm (AB) effect produces the AHC that is drastically changed in the presence of noncollinear spin structure. In both ferromagnetic compound Nd2Mo2O7 and paramagnetic compound Pr2Ir2O7, the AHC given by the orbital AB effect totally dominates the spin-chirality mechanism and succeeds in explaining the experimental relation between the spin structure and the AHC.

Intrinsic spin and orbital Hall effects in heavy-fermion systems

Tanaka T., Kontani H.

PHYSICAL REVIEW B Vol. 81 ( 22 ) 2010.6

Tight-binding study of anomalous Hall effect in ferromagnetic 3d transition metals

Naito T., Hirashima D. S., Kontani H.

PHYSICAL REVIEW B Vol. 81 ( 19 ) 2010.5

Orbital-Fluctuation-Mediated Superconductivity in Iron Pnictides: Analysis of the Five-Orbital Hubbard-Holstein Model

Kontani Hiroshi, Onari Seiichiro

PHYSICAL REVIEW LETTERS Vol. 104 ( 15 ) 2010.4

Orbital-Fluctuation-Mediated Superconductivity in Iron Pnictides: Analysis of the Five-Orbital Hubbard-Holstein Model Reviewed

Hiroshi Kontani, Seiichiro Onari

Physical Review Letters Vol. 104 ( 15 ) page： 157001 2010.4

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

In iron pnictides, we find that the moderate electron-phonon interaction due to the Fe-ion oscillation can induce the critical d-orbital fluctuations, without being prohibited by the Coulomb interaction. These fluctuations give rise to the strong pairing interaction for the s-wave superconducting (SC) state without sign reversal (s++-wave state), which is consistent with experimentally observed robustness of superconductivity against impurities. When the magnetic fluctuations due to Coulomb interaction are also strong, the SC state shows a smooth crossover from the s-wave state with sign reversal (s±-wave state) to the s++-wave state as impurity concentration increases.

Tuning the Dimensionality of the Heavy Fermion Compound CeIn3

Shishido H., Shibauchi T., Yasu K., Kato T., Kontani H., Terashima T., Matsuda Y.

SCIENCE Vol. 327 ( 5968 ) page： 980-983 2010.2

Structure of Neutron-Scattering Peak in both s++ wave and s+- wave states of an Iron pnictide Superconductor Reviewed

Seiichiro Onari, Hiroshi Kontani, Masatoshi Sato

physical Review B Vol. 81 ( 6 ) page： 060504(R) 2010.2

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

We study the neutron-scattering spectrum in iron pnictides based on the random-phase approximation in the five-orbital model for fully gapped s-wave states with sign reversal (s±) and without sign reversal (s++). In the s++-wave state, we find that a prominent hump structure appears just above the spectral gap by taking account of the quasiparticle damping γ due to strong electron-electron correlation: as the superconductivity develops, the reduction in γ gives rise to the large overshoot in the spectrum above the gap. The obtained hump structure looks similar to the resonance peak in the s±-wave state, although the height and weight of the peak in the latter state is much larger. In the present study, experimentally observed broad spectral peak in iron pnictides is naturally reproduced by assuming the s++-wave state.

Structure of neutron-scattering peaks in both s(++)-wave and s(+/-)-wave states of an iron pnictide superconductor

Onari Seiichiro, Kontani Hiroshi, Sato Masatoshi

PHYSICAL REVIEW B Vol. 81 ( 6 ) 2010.2

Origin of the anomalous Hall effect in the overdoped n-type superconductor Pr(2-x)Ce(x)Cuo(4): Current-vertex corrections due to antiferromagnetic fluctuations

Jenkins G. S., Schmadel D. C., Bach P. L., Greene R. L., Bechamp-Laganiere X., Roberge G., Fournier P., Kontani Hiroshi, Drew H. D.

PHYSICAL REVIEW B Vol. 81 ( 2 ) 2010.1

Violation of Anderson's Theorem for the Sign-Reversing s-Wave State of Iron-Pnictide Superconductors

Onari Seiichiro, Kontani Hiroshi

PHYSICAL REVIEW LETTERS Vol. 103 ( 17 ) 2009.10

*Violation of Anderson's Theorem for the Sign-Reversing s-Wave State of Iron-Pnictide Superconductors Invited Reviewed

Seiichiro Onari and Hiroshi Kontani

Physical Review Letters Vol. 103 page： 177001 2009.10

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

Based on the five-orbital model, we study the effect of local impurity in iron pnictides, and find that the interband impurity scattering is promoted by the d-orbital degree of freedom. This fact means that the fully gapped sign-reversing s-wave state, which is predicted by spin fluctuation theories, is very fragile against impurities. In the BCS theory, only 1% impurities with intermediate strength induce huge pair breaking, resulting in the large in-gap state and prominent reduction in Tc, contrary to the prediction based on simple orbital-less models. The present study provides a stringent constraint on the pairing symmetry and the electronic states in iron pnictides.

Anomalous Hall effect in the t2g orbital kagome lattice due to noncollinearity: Significance of the orbital Aharonov-Bohm effect Reviewed

Takeshi Tomizawa and Hiroshi Kontani

Physical Review B Vol. 80 page： 100401 2009.9

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

A mechanism of spin structure-driven anomalous Hall effect (AHE) in tilted ferromagnetic metals is proposed by taking account of the d-orbital degree of freedom. We find that a conduction electron acquires a Berry phase due to the complex d-orbital wave function, in the presence of noncollinear spin structure and the spin-orbit interaction. The AHE driven by this orbital-derived Berry phase is much larger than the AHE induced by spin chirality, and it naturally explains the salient features of spin structure-driven AHE in pyrochlore Nd2Mo2O7. Since the proposed AHE can occur even for coplanar spin orders (Mz=0), it is expected to emerge in other interesting geometrically frustrated systems.

Anomalous Hall effect in the t2g orbital kagome lattice due to noncollinearity: Significance of the orbital Aharonov-Bohm effect

Tomizawa Takeshi, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 80 ( 10 ) 2009.9

Anomalous and spin Hall effects in magnetic granular films

Inoue Jun-ichiro, Tanaka Takuro, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 80 ( 2 ) 2009.7

Impurity-induced in-gap state and T-c in sign-reversing s-wave superconductors: analysis of iron oxypnictide superconductors

Senga Yuko, Kontani Hiroshi

NEW JOURNAL OF PHYSICS Vol. 11 2009.3

Unconventional Pairing Originating from the Disconnected Fermi Surfaces of Superconducting LaFeAsO1-xFx (vol 101, 087004, 2008)

Kuroki Kazuhiko, Onari Seiichiro, Arita Ryotaro, Usui Hidetomo, Tanaka Yukio, Kontani Hiroshi, Aoki Hideo

PHYSICAL REVIEW LETTERS Vol. 102 ( 10 ) 2009.3

Unconventional pairing originating from disconnected Fermi surfaces in the iron-based superconductor

Kuroki Kazuhiko, Onari Seiichiro, Arita Ryotaro, Usui Hidetomo, Tanaka Yukio, Kontani Hiroshi, Aoki Hideo

NEW JOURNAL OF PHYSICS Vol. 11 2009.2

Intrinsic Spin Hall Effect in the s-Wave Superconducting State: Analysis of the Rashba Model

Kontani H., Goryo J., Hirashima D. S.

PHYSICAL REVIEW LETTERS Vol. 102 ( 8 ) 2009.2

Intrinsic Spin Hall Effect in the s-Wave Superconducting State: Analysis of the Rashba Model Reviewed

H. Kontani, J. Goryo, and D. S. Hirashima

Physical Review Letters Vol. 102 page： 086602 2009.2

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

A general expression for spin Hall conductivity (SHC) in the s-wave superconducting state at finite temperatures is derived. Based on the expression, we study SHC in a two-dimensional electron gas model in the presence of Rashba spin-orbit interaction (SOI). SHC is zero in the normal state, whereas it takes a large negative value as soon as the superconductivity occurs, due to the change in the quasiparticle contributions. Since this remarkable behavior is independent of the strength of the SOI, it will be widely observed in thin films of superconductors with surface-induced Rashba SOI, or in various noncentrosymmetric superconductors.

Giant extrinsic spin Hall effect due to rare-earth impurities

Tanaka T., Kontani H.

NEW JOURNAL OF PHYSICS Vol. 11 2009.1

Giant Orbital Hall Effect in Transition Metals: Origin of Large Spin and Anomalous Hall Effects

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

PHYSICAL REVIEW LETTERS Vol. 102 ( 1 ) 2009.1

*Giant Orbital Hall Effect in Transition Metals: Origin of Large Spin and Anomalous Hall Effects Invited Reviewed

Vol. 102 page： 016601 2009.1

Minimal model for study on Superconductivity in LaFeAsO1-xFx based on ab-initio downfolding

Arita Ryotaro, Onari Seiichiro, Usui Hidetomo, Kuroki Kazuhiko, Tanaka Yukio, Kontani Hiroshi, Aoki Hideo

25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 5 Vol. 150 2009

Non-Fermi liquid behavior in the magnetotransport of quasi two-dimensional heavy Fermion compounds CeMIn5

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

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS Vol. 69 ( 12 ) page： 3261 - 3264 2008.12

Spin Hall effect in Sr2RuO4 and transition metals (Nb,Ta)

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

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS Vol. 69 ( 12 ) page： 3250-3252 2008.12

Impurity Effects in Sign-Reversing Fully Gapped Superconductors: Analysis of FeAs Superconductors

Senga Yuko, Kontani Hiroshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 77 ( 11 ) 2008.11

Unconventional superconductivity originating from disconnected Fermi surfaces in the iron-based oxypnictide

Kuroki Kazuhiko, Onari Seiichiro, Arita Ryotaro, Usui Hidetomo, Tanaka Yukio, Kontani Hiroshi, Aoki Hideo

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 77 page： 96-98 2008.11

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

Onari Seiichiro, Ishikawa Yasuhito, Kontani Hiroshi, Inoue Jun-ichiro

PHYSICAL REVIEW B Vol. 78 ( 12 ) 2008.9

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

Kuroki Kazuhiko, Onari Seiichiro, Arita Ryotaro, Usui Hidetomo, Tanaka Yukio, Kontani Hiroshi, Aoki Hideo

PHYSICAL REVIEW LETTERS Vol. 101 ( 8 ) 2008.8

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

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

PHYSICAL REVIEW B Vol. 77 ( 21 ) 2008.6

s-wave superconductivity due to Suhl-Kondo mechanism in Na(x)CoO(2)center dot yH(2)O: Effect of Coulomb interaction and trigonal distortion

Yada Keiji, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 77 ( 18 ) 2008.5

Theory of ac anomalous Hall conductivity in d-electron systems

Tanaka T., Kontani H.

PHYSICAL REVIEW B Vol. 77 ( 19 ) 2008.5

Intrinsic spin Hall effect and orbital Hall effect in 4d and 5d transition metals

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

PHYSICAL REVIEW B Vol. 77 ( 16 ) 2008.4

Giant intrinsic spin and orbital hall effects in Sr2MO4 (M=Ru, Rh, Mo)

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

PHYSICAL REVIEW LETTERS Vol. 100 ( 9 ) 2008.3

Spin-Dependent Mass Enhancement under Magnetic Field in the Periodic Anderson Model Reviewed

S. Onari, H. Kontani and Y. Tanaka,

Journal of the Physical Society of Japan Vol. 77 page： 023703 2008.2

Anomalous transport phenomena in Fermi liquids with strong magnetic fluctuations

Kontani Hiroshi

REPORTS ON PROGRESS IN PHYSICS Vol. 71 ( 2 ) 2008.2

Spin-dependent mass enhancement under a magnetic field in the periodic Anderson model

Onari Seiichiro, Kontani Hiroshi, Tanaka Yukio

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 77 ( 2 ) 2008.2

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 Vol. 77 page： 275-277 2008.1

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

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

Physical Review Letters Vol. 100 page： 096601 2008

*Intrinsic spin Hall effect and orbital Hall effect in 4d and 5d transition metals Reviewed

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

Physical Review B Vol. 77 page： 165117 2008

Language：English

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 Reviewed

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

Physical Review B Vol. 78 page： 121403R 2008

Unconventional pairing originating from the disconnected Fermi surfaces of superconducting LaFeAsO1-xFx Reviewed

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

Physical Review Letters Vol. 101 page： 087004 2008

Magnetotransport properties governed by antiferromagnetic fluctuations in the heavy-fermion superconductor CeIrIn5 Reviewed

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 Vol. 77 page： 0214504 2008

Theory of ac anomalous Hall conductivity in d -electron systems Reviewed

T. Tanaka and H. Kontani

Physical Review B Vol. 77 page： 195129 2008

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

K. Yada and H. Kontani

Physical Review B Vol. 77 page： 184521 2008

*Anomalous Transport Phenomena in Fermi Liquids with Strong Magnetic Fluctuations Invited Reviewed

Hiroshi Kontani

Reports on Progress in Physics Vol. 71 page： 026501 2008

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

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 Reviewed

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

Journal of the Physical Society of Japan Vol. 76 page： 103702 2007.10

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 Vol. 76 ( 10 ) 2007.10

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 Vol. 460 page： 145 - 148 2007.9

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 Vol. 460 page： 680 - 681 2007.9

Robustness of s-wave superconductivity against Coulomb interactions in NaxCoO2

Yada Keiji, Kontani Hiroshi

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS Vol. 460 page： 483-484 2007.9

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 Vol. 76 ( 7 ) 2007.7

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

Hideyuki Hara, Hiroshi Kontan

Journal of the Physical Society of Japan Vol. 76 ( 18 ) page： 184416 2007.7

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

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 Reviewed

Vol. 76 page： 074707 2007.7

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

Hideyuki Hara, and Hiroshi Kontani

Journal of the Physical Society of Japan Vol. 76 page： 073705 2007.7

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

H. Kontani

Journal of the Physical Society of Japan Vol. 76 ( 07 ) page： 074707 2007.7

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

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 Vol. 76 ( 7 ) 2007.7

Intrinsic anomalous Hall effect in ferromagnetic metals studied by the multi-d-orbital tight-binding model

Kontani Hiroshi, Tanaka Takuro, Yamada Kosaku

PHYSICAL REVIEW B Vol. 75 ( 18 ) 2007.5

Infrared Hall conductivity in optimally doped Bi2Sr2CaCu2O8+δ : Drude behavior examined by experiment and fluctuation-exchange-model calculations Reviewed

D.C. Schmadel, G. S. Jenkins, J.J. Tu, G.D. Gu, H. Kontani, and H. D. Drew

Physical Review B Vol. 75 ( 14 ) page： 140506R (4p) 2007.4

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

The temperature dependence of the Hall conductivity is reported at mid- and far-IR frequencies for cleaved single crystals. A nearly simple Drude behavior is observed with a scattering rate that is linear in temperature and nearly frequency independent. The Hall data are in good agreement with calculations based on the fluctuation-exchange interaction when current vertex corrections are included. The σxy quasiparticle spectral weight is suppressed to 0.09 times the band value, compared with 0.33 times the band value for σxx.

Infrared Hall conductivity in optimally doped Bi2Sr2CaCu2O8+delta: Drude behavior examined by experiment and fluctuation-exchange-model calculations

Schmadel D. C., Jenkins G. S., Tu J. J., Gu G. D., Kontani Hiroshi, Drew H. D.

PHYSICAL REVIEW B Vol. 75 ( 14 ) 2007.4

Hall effect in the quasi two-dimensional strongly correlated metal CeMIn5 (M = Co, Rh)

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

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Vol. 310 ( 2 ) page： 334 - 336 2007.3

Anomalous transport phenomena in CeCoIn5 close to quantum critical point

Onari S., Kontani H., Tanaka Y.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Vol. 310 ( 2 ) page： 359-361 2007.3

Nonlocal effect of local nonmagnetic impurity in high-T-c superconductors: Induced local moment and huge residual resistivity

Kontani Hiroshi, Ohno Masanori

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Vol. 310 ( 2 ) page： 483-485 2007.3

Renormalization of Coulomb interactions in s-wave superconductor NaxCoO2

Yada Keiji, Kontani Hiroshi

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Vol. 310 ( 2 ) page： 684 - 686 2007.3

Non-fermi liquid behavior in the magnetotransport of CeMln(5) (M : Co and Rh): Striking similarity between quasi two-dimensional heavy fermion and high-T-c cuprates

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 76 ( 2 ) 2007.2

Non-Fermi Liquid Behavior in the Magnetotransport of CeMIn5 (M: Co and Rh): Striking Similarity between Quasi Two-Dimensional Heavy Fermion and High-Tc Cuprates Reviewed

Y. Nakajima, H. Shishido, H. Nakai, T. Shibauchi, K. Behnia, K. Izawa, M. Hedo, Y. Uwatoko, T. Matsumoto, R. Settai, Y. Ōnuki, H. Kontani, and Y. Matsuda

Journal of the Physical Society of Japan Vol. 76 ( 02 ) page： 024703 2007.2

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

We present a systematic study of the dc-resistivity, Hall effect, and magnetoresistance in the normal state of quasi two-dimensional (2D) heavy fermion superconductors CeMIn5 (M: Rh and Co) under pressure. Here the electronic system evolves with pressure from an antiferromagnetic (AF) metal, through a highly unconventional non-Fermi liquid, and finally into a Fermi-liquid state. The novelty of these materials is best highlighted when compared with LaMIn5, a system with similar electronic structures, which shows a nearly temperature independent Hall coefficient and a magnetoresisitance which is well described by the classical Kohler's rule. In sharp contrast, in CeMIn5, the amplitude of the Hall coefficient increases dramatically with decreasing temperature, reaching at low temperatures a value significantly larger than 1/ne, where n is the carrier number. Furthermore, the magnetoresistance is characterized by T- and H-dependence which clearly violate Kohler's rule. We found that the cotangent of the Hall angle cot ΘH varies as T2, and the magnetoresistance is well scaled by the Hall angle as Δρxx/ρxx∝tan 2ΘH. These non-Fermi liquid properties in the electron transport are remarkably pronounced when the AF fluctuations are enhanced in the vicinity of the quantum critical point. We lay particular emphasis on the striking resemblance of these anomalous magnetotransport with those of the high-Tc cuprates. We argue that features commonly observed in quasi 2D heavy fermion and cuprates very likely capture universal features of strongly correlated electron systems in the presence of strong AF fluctuations, holding the promise of bridging our understanding of heavy fermion systems and high-Tc cuprates.

Degeneracy dependence of the Kadowaki-Woods relation in heavy-fermion systems

Tsujii Naohito, Kontani Hiroshi, Yoshimura Kazuyoshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 76 page： 174-177 2007.1

Intrinsic anomalous Hall effect in ferromagnetic metals studied by the multi- d -orbital tight-binding model Reviewed

Hiroshi Kontani, Takuro Tanaka, and Kosaku Yamada

Physical Review B Vol. 75 ( 18 ) page： 184416 2007

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

To elucidate the origin of anomalous Hall effect (AHE) in ferromagnetic transition metals, we study the intrinsic AHE based on a multiorbital (dxz,dyz) tight-binding model. We find that a large anomalous velocity comes from the off-diagonal (interorbital) hopping. For this reason, the present model shows a large intrinsic anomalous Hall conductivity (AHC) which is compatible with typical experimental values in ferromagnets (102–103 Ω−1 cm−1), without the necessity to assume a special band structure at the Fermi level. In good metals where ρ is small, the intrinsic AHC is constant (dissipationless) as found by Karplus and Luttinger. In bad metals, however, we find that the AHC is proportional to ρ−2 when ℏ∕2τ is larger than the minimum band splitting measured from the Fermi level Δ. This crossover behavior of the intrinsic AHE, which was derived in J. Phys. Soc. Jpn. 63, 2627 (1994), was recently observed in various ferromagnetic metals universally by Asamitsu We also stress that the present (dxz,dyz) tight-binding model shows a huge spin Hall effect in a paramagnetic state.

Optical conductivity of bad metals: Shift of the Drude peak

T. Mutou and H. Kontani

Physical Review B Vol. 74 ( 11 ) page： 115107 (6p) 2006.12

Theoretical study of the phase diagram of beta '-(BEDT-TTF)(2)AuCl2 at hydrostatic pressure

Kino Hiori, Kontani Hiroshi, Miyazaki Tsuyoshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 75 ( 10 ) 2006.10

Optical conductivity of bad metals: Shift of the Drude peak

Mutou Tetsuya, Kontani Hiroshi

PHYSICAL REVIEW B Vol. 74 ( 11 ) 2006.9

Effect of a nonmagnetic impurity in a nearly antiferromagnetic Fermi liquid: Magnetic correlations and transport phenomena

Kontani Hiroshi, Ohno Masanori

PHYSICAL REVIEW B Vol. 74 ( 1 ) 2006.7

Transport phenomena in a three-dimensional system close to the magnetic quantum critical point: The conserving approximation with current vertex corrections, Reviewed

S. Onari, H. Kontani, and Y. Tanaka,

Physical Review B Vol. 74 ( 22 ) page： 224434 (10p) 2006.6

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

It is known that various transport coefficients strongly deviate from conventional Fermi-liquid behaviors in many electron systems which are close to antiferromagnetic (AF) quantum critical points (QCP). For example, Hall coefficients and Nernst coefficients in three-dimensional heavy fermion CeCoIn5 and CeCu6–xAux increase strikingly at low temperatures, whose overall behaviors are similar to those in high-Tc cuprates. These temperature dependencies are too strong to explain in terms of the relaxation time approximation. To elucidate the origin of these anomalous transport phenomena in three-dimensional systems, we study the current vertex corrections (CVC) based on the fluctuation exchange approximation, and find out the decisive role of the CVC. The main finding of the present paper is that the Hall coefficient and the Nernst coefficient strongly increase thanks to the CVC in the vicinity of the AF QCP, irrespective of dimensionality. We also study the relaxation time of quasiparticles, and find that "hot points" and "cold lines" are formed in general three-dimensional systems due to strong AF fluctuations.

Effect of a nonmagnetic impurity in a nearly antiferromagnetic Fermi liquid: Magnetic correlations and transport phenomena Reviewed

H. Kontani and M. Ohno

Physical Review B Vol. 74 ( 01 ) page： 014406 (21p) 2006.6

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

In nearly antiferromagnetic (AF) metals such as high-Tc superconductors (HTSCs), a single nonmagnetic impurity frequently causes nontrivial widespread change of the electronic states. To elucidate this long-standing issue, we study a Hubbard model with a strong onsite impurity potential based on an improved fluctuation-exchange (FLEX) approximation, which we call the GVI-FLEX method. This model corresponds to the HTSC with dilute nonmagnetic impurity concentration. We find that (i) both local and staggered susceptibilities are strongly enhanced around the impurity. By this reason, (ii) the quasiparticle lifetime as well as the local density of states are strongly suppressed in a wide area around the impurity (like a Swiss cheese hole), which causes the "huge residual resistivity" beyond the s-wave unitary scattering limit. We stress that the excess quasiparticle damping rate caused by impurities has strong k-dependence due to non-s-wave scatterings induced by many-body effects, so the structure of the "hot spot/cold spot" in the host system persists against impurity doping. This result could be examined by the ARPES measurements. In addition, (iii) only a few percent of impurities can cause a "Kondo-like" upturn of resistivity (d/dT<0) at low T when the system is very close to the AF quantum critical point. The results (i)–(iii) obtained in the present study, which cannot be derived by the simple FLEX approximation, naturally explain the main impurity effects in HTSCs. We also discuss the impurity effect in heavy fermion systems and organic superconductors.

Transport phenomena in a three-dimensional system close to the magnetic quantum critical point: The conserving approximation with current vertex corrections

Onari Seiichiro, Kontani Hiroshi, Tanaka Yukio

PHYSICAL REVIEW B Vol. 73 ( 22 ) 2006.6

Grand Kadowaki-Woods relation of heavy-fermion systems with degeneracy

Tsujii N., Kontani H., Yoshimura K.

PHYSICA B-CONDENSED MATTER Vol. 378-80 page： 730 - 731 2006.5

Electron-Phonon Mechanism for Superconductivity in Na0.35CoO2: Valence-Band Suhl-Kondo Effect Driven by Shear Phonons Reviewed

K. Yada and H. Kontai

Journal of the Physical Society of Japan Vol. 75 ( 3 ) page： 033705 (4p) 2006.3

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

To study the possible mechanism of superconductivity in Na0.35CoO2, we examine the interaction between all the relevant optical phonons (breathing and shear phonons) and t2g (a1g+eg') electrons of Co ions, and study the transition temperature for s-wave superconductivity. The obtained Tc is very low when the eg' valence bands are far below the Fermi level. However, Tc is strongly enhanced when the top of the eg' valence bands is close to the Fermi level (e.g., -50 meV), thanks to the interband hopping of Cooper pairs caused by shear phonons. This “valence-band Suhl–Kondo mechanism" due to shear phonons is important in understanding the superconductivity in Na0.35CoO2. By the same mechanism, the kink structure of the band dispersion observed by angle-resolved photoemission spectroscopy (ARPES) measurements, which indicates the strong mass enhancement (m*/m∼3) due to optical phonons, is also explained.

Theoretical Study of the Phase Diagram of β'-(BEDT-TTF)2AuCl2 at Hydrostatic Pressure Reviewed

Journal of the Physical Society of Japan Vol. 75 ( 10 ) page： 104702 (4) 2006.3

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

We study the electronic structure of β'-(BEDT-TTF)2AuCl2 under hydrostatic pressures of up to 20 GPa. We employ the effective single-band Hubbard model, the band structure of which is based on the first-principles result, and apply the FLEX approximation to take into account of the effective on-site Coulomb interaction. We examine magnetic and superconducting instabilities to find that the resulting theoretical phase diagram shows that the Néel temperature is high under hydrostatic pressure. In contrast to β'-(BEDT-TTF)2ICl2, β'-(BEDT-TTF)2AuCl2 is expected to show no superconducting state.

Electron-phonon mechanism for superconductivity in Na0.35CoO2: Valence-band Suhl-Kondo effect driven by shear phonons

Yada K, Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 75 ( 3 ) 2006.3

Evolution of Hall coefficient in two-dimensional heavy fermion CeCoIn5

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 75 ( 2 ) 2006.2

Evolution of Hall Coefficient in Two-Dimensional Heavy Fermion CeCoIn5 Reviewed

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

Journal of the Physical Society of Japan Vol. 2006 ( 1 ) page： 023705(4p) 2006.1

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

We report on the pressure dependence of the Hall coefficient RH in quasi-2D heavy fermion CeCoIn5. At ambient pressure, below a temperature associated with the emergence of non-Fermi liquid properties, RH is anomalously enhanced. We found that the restoration of the Fermi liquid state with applied pressure leads to a gradual suppression of this dramatic enhancement. Moreover, the enhancement in RH was found to be confined to an intermediate temperature window, where inelastic electron-electron scattering is dominant. Our results strongly support the presence of cold and hot spots on the Fermi surface probably due to anisotropic scattering by antiferromagnetic fluctuations, which may also prove relevant for the debate on the anomalous normal-state properties of high-Tc cuprates.

Optical Conductivity and Hall Coefficient in High-Tc Superconductors: Significant Role of Current Vertex Corrections Reviewed

Hiroshi Kontani

Journal of the Physical Society of Japan Vol. 75 ( 1 ) page： 013703(4p) 2006.1

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

We study AC conductivities in high-Tc cuprates, which offer us significant information to determine the true ground states. We take the current vertex correction (CVC) into account correctly to satisfy the conservation laws in terms of the fluctuation-exchange (FLEX) approximation. The significant role of the CVC on the optical Hall conductivity [σxy(ω)] is confirmed in the presence of strong antiferromagnetic (AF) fluctuations. This fact leads to the failure of the relaxation time approximation (RTA). As a result, experimental highly unusual behaviors, (i) prominent ω and temperature dependences of the optical Hall conductivity and the optical Hall coefficient [RH(ω)], and (ii) a simple Drude form of the optical Hall angle [θH(ω)] for a wide range of ω, are satisfactorily reproduced. In conclusion, both DC and AC transport phenomena in (slightly under-doped) high-Tc cuprates can be explained comprehensively in terms of a nearly AF Fermi liquid, without assuming an exotic ground state.

Optical conductivity and hall coefficient in high-T-c superconductors: Significant role of current vertex corrections

Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 75 ( 1 ) 2006.1

Physical meaning of the current vertex corrections: DC and AC transport phenomena in high-T-c superconductors

Kontani Hiroshi

Low Temperature Physics, Pts A and B Vol. 850 page： 565-566 2006

Spin fluctuations and weak pseudogap behaviors in Na0.35CoO2: Renormalization of band structure

Yada Keiji, Kontani Hiroshi

LOW TEMPERATURE PHYSICS, PTS A AND B Vol. 850 page： 707-+ 2006

軌道縮退を有する重い電子系のGrand Kadowaki-Woods則 Invited Reviewed

辻井直人、紺谷浩、吉村一良

日本物理学会誌 Vol. 60 ( 11 ) page： 872-875 2005.11

Origin of Weak Pseudogap Behaviors in Na0.35CoO2: Absence of Small Hole Pockets Reviewed

Keiji Yada and Hiroshi Kontani

Journal of the Physical Society of Japan Vol. 74 ( 8 ) page： 2161-2164 2005.8

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

We analyze the normal electronic states of Na0.35CoO2 based on the effective d- p model with a full d-orbital freedom using the fluctuation-exchange (FLEX) approximation. The electronic states sensitively depend on the topology of Fermi surfaces, which changes with the crystalline electric splitting (CES) due to the trigonal deformation. We succeed in reproducing the weak pseudogap behaviors in the density of states (DOS) and in the uniform magnetic susceptibility below 300 K, assuming that six small hole pockets predicted by LDA band calculations are absent. If these pockets exist, on the contrary, “anti-pseudogap behaviors" should inevitably appear. Thus, the present study strongly supports the absence of the small hole pockets in Na0.35CoO2, as reported by recent ARPES measurements. A large Fermi surface around the Γ-point would account for the superconductivity in water-intercalated samples.

Origin of weak pseudogap behaviors in Na0.35CoO2: Absence of small hole pockets

Yada K, Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 74 ( 8 ) page： 2161 - 2164 2005.8

Generalized Kadowaki-Woods relation in Er- and Sm-based heavy fermion systems

Kontani H

PHYSICA B-CONDENSED MATTER Vol. 359 page： 202-204 2005.4

Universality in heavy fermion systems with general degeneracy

Tsujii N, Kontani H, Yoshimura K

PHYSICAL REVIEW LETTERS Vol. 94 ( 5 ) 2005.2

*Universality in Heavy Fermion Systems with General Degeneracy Reviewed

N. Tsujii, H. Kontani, and K. Yoshimura

Physical Review Letter Vol. 94 ( 11 ) page： 057201(4p) 2005.2

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

We discuss the relation between the T2 coefficient of electrical resistivity A and the T-linear specific-heat coefficient γ for heavy-fermion systems with general N, where N is the degeneracy of quasiparticles. A set of experimental data reveals that the Kadowaki-Woods relation, A/γ2=1×10-5  μΩ cm(K mol/mJ)2, collapses remarkably for large-N systems, although this relation has been regarded to be commonly applicable to the Fermi liquids. Instead, based on the Fermi-liquid theory we propose a new relation, A˜/γ˜2=1×10-5 with A˜=A/1/2N(N-1) and γ˜=γ/1/2N(N-1). This new relation exhibits an excellent agreement with the data for the whole range of degenerate heavy fermions.

From Kondo Effect to Fermi Liquid Invited Reviewed

Hiroshi Kontani and Kosaku Yamada

Journal of the Physical Society of Japan Vol. 74 ( 1 ) page： 155-166 2005.1

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

The Kondo effect has been playing an important role in strongly correlated electon systems. The important point is that the magnetic impurity in metals is a typical example of the Fermi liquid. In the system the local spin is conserved in the ground state and continuity with respect to Coulomb repulsion U is satisfied. This nature is satisfied also in the periodic systems as far as the systems remain as the Fermi liquid. This property of the Fermi liquid is essential to understand the cuprate high-Tc superconductors (HTSC). On the basis of the Fermi liquid theory we develop the transport theory such as the resistivity and the Hall coefficient in strongly correlated electron systems, such as HTSC, organic metals and heavy Fermion systems. The significant role of the vertex corrections for total charge- and heat-currents on the transport phenomena is explained. By taking the effect of the current vertex corrections into account, various typical non-Fermi-liquid-like transport phenomena in systems with strong magnetic and/or superconducting flucutations are explained within the Fermi liquid theory.

Magnetic-Field-induced Antiferromagnetism in Two-dimensional Hubbard Model: Analysis of CeRhIn5 Reviewed

Keitaro Sakurazawa, Hiroshi Kontani and Tetsuro Saso

Journal of the Physical Society of Japan Vol. 74 ( 1 ) page： 271-274 2005.1

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

We propose a mechanism for the magnetic-field-induced antiferromagnetic (AF) state in a two-dimensional Hubbard model in the vicinity of the AF quantum critical point (QCP), using the fluctuation-exchange (FLEX) approximation by taking the Zeeman energy due to the magnetic field B into account. In the vicinity of the QCP, we find that the AF correlation perpendicular to B is enhanced, whereas that parallel to B is reduced. This fact means that the finite magnetic field increases TN, with the AF order perpendicular to B. The increment of TN can be understood in terms of the reduction of both quantum and thermal fluctuations due to the magnetic field, which is caused by the self-energy effect within the FLEX approximation. The present study naturally explains the increment of TN in CeRhIn5 under the magnetic field found recently. We will also discuss a relation to some organic metals.

From Kondo effect to Fermi liquid

Kontani H, Yamada K

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 74 ( 1 ) page： 155 - 166 2005.1

Magnetic-field-induced antiferromagnetism in two-dimensional Hubbard model: Analysis of CeRhIn5

Sakurazawa K, Kontani H, Saso T

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 74 ( 1 ) page： 271 - 274 2005.1

Generalized Kadowaki-Woods relation in Er- and Sm-based Heavy Fermion Systems, Invited Reviewed

Hiroshi Kontani

Physica B. Vol. 359-361 page： 202-204 2005

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

H. Kontani

Physical Review B Vol. 70 ( 5 ) page： 054507(13p) 2004.8

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

Recent intensive experimental studies revealed that (Y,Lu)Ni2B2C is an extremely anisotropic s-wave superconductor. In addition, its gap function possesses deep point minima, whose ratio of the gap anisotropy is more than 10. On the theoretical side, however, it is nontrivial to understand the origin of such a peculiar superconductivity. In the present paper, we propose a mechanism of the s-wave superconductivity with deep gap minima, based on the theoretical model where strong electron-phonon coupling as well as the moderate magnetic fluctuations coexist. By analyzing the strong coupling Eliashberg equation, we find that s-wave superconducting gap function owing to the electron-phonon coupling becomes highly anisotropic as the magnetic fluctuations increase. The set of model parameters for realizing the strong gap anisotropy in the present model will be appropriate for (Y,Lu)Ni2B2C. According to the present mechanism, (groups of) pairs of gap minima appear at points on the Fermi surface which are connected by the nesting vector Q, in both cases of s-wave superconductors and non-s-wave ones. We briefly discuss other superconductors with highly anisotropic gap function, e.g., PrOs4Sb12 and Na0.33CoO2.

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.

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

Effects of spin fluctuations in quasi-one-dimensional organic superconductors

Kino H, Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 68 ( 5 ) page： 1481 - 1484 1999.5

Anomalous Hall effect in Sr2RuO4

Miyazawa M, Kontani H, Yamada E

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 68 ( 5 ) page： 1625 - 1631 1999.5

Phase diagram of superconductivity on the anisotropic triangular lattice Hubbard model: An effective model of kappa-(BEDT-TTF) salts

Kino H, Kontani H

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 67 ( 11 ) page： 3691 - 3694 1998.11

Phase Diagram of Superconductivity on the Anisotropic Triangular Lattice Hubbard Model: An Effective Model of κ-(BEDT-TTF) Salts Reviewed

Hiori Kino and Hiroshi Kontani

Journal of the Physical Society of Japan Vol. 1998 ( 7 ) page： 3691-3694 1998.7

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

We study the electronic states of the anisotropic triangular lattice Hubbard model at half-filling, which is a simple effective model for the organic superconducting κ-BEDT-TTF compounds. We treat the effect of the Coulomb interaction by the fluctuation exchange (FLEX) method, and obtain the phase diagram of this model for various sets of parameters. It is shown that d-wave superconductivity is realized in a wide region of the phase diagram, next to the antiferromagnetic states. The obtained phase diagram explains well the characteristics of the experimental results.

Electronic properties of the trellis-lattice Hubbard model: Pseudogap and superconductivity

Kontani H, Ueda K

PHYSICAL REVIEW LETTERS Vol. 80 ( 25 ) page： 5619 - 5622 1998.6

Theory of anomalous Hall effect in a heavy fermion system with a strong anisotropic crystal field

Kontani H, Miyazawa M, Yamada K

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 66 ( 8 ) page： 2252 - 2255 1997.8

Electronic state and magnetic susceptibility in orbitally degenerate (J=5/2) periodic Anderson model

Kontani H, Yamada K

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 66 ( 8 ) page： 2232 - 2235 1997.8

Quantum fluctuations and frustration of the collinear phase in CaV3O7

Kontani H, Zhitomirsky ME, Ueda K

PHYSICA B Vol. 230 page： 752 - 755 1997.2

Plaquette resonating-valence-bond ground state of CaV4O9

Ueda K, Troyer M, Kontani H, Sigrist M, Lee PA

JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. 29 page： S128 - S130 1996.8

Plaquette resonating-valence-bond ground state of CaV4O9 (vol 76, pg 1932, 1996)

Ueda K, Kontani H, Sigrist M, Lee PA

PHYSICAL REVIEW LETTERS Vol. 76 ( 24 ) page： 4650 - 4650 1996.6

Effect of quantum fluctuations on magnetic ordering in CaV3O7

Kontani H, Zhitomirsky ME, Ueda K

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 65 ( 6 ) page： 1566 - 1569 1996.6

Phase diagram of depleted Heisenberg model for CaV4O9

Troyer M, Kontani H, Ueda K

PHYSICAL REVIEW LETTERS Vol. 76 ( 20 ) page： 3822 - 3825 1996.5

Plaquette resonating-valence-bond ground state of CaV4O9

Ueda K, Kontani H, Sigrist M, Lee PA

PHYSICAL REVIEW LETTERS Vol. 76 ( 11 ) page： 1932 - 1935 1996.3

Magnetic Susceptibility of the Orbitally Degenerate ( J = 5/2) Periodic Anderson Model - Analysis on the Basis of the Fermi Liquid Theory - Reviewed

Hiroshi Kontani and Kosaku Yamada

Journal of the Physical Society of Japan Vol. 65 ( 1 ) page： 172-188 1996.1

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

In the orbitally degenerate (J= 5/2) Periodic Anderson Model, the magnetic susceptibility is composed of both the Pauli term and the Van Vleck term, as is well known. The former is strongly enhanced by the strong correlation between f-electrons. But, for the latter, the influence of the strong correlation has been obscure for years. In this paper we give the solution of the longstanding problem. With the aid of the d=∞ approximation, we study this problem on the basis of the Fermi liquid theory with degenerate orbitals, taking account of all the vertex corrections in a consistent way. As a result, we obtain the simple expression for the magnetic susceptibility, and show unambiguously that the Van Vleck term is also highly enhanced in the strong correlation regime. This fact explains naturally the enhanced magnetic susceptibility observed in many insulating systems (i.e., Kondo insulator). Moreover, we show that the Wilson ratio takes a value around 1 in the metallic system, in good agreement with experiments.

Plaquette resonating-valence-bond ground state of CaV4O9

Kontani H, Troyer M, Ueda K, Sigrist M, Lee PA

CZECHOSLOVAK JOURNAL OF PHYSICS Vol. 46 page： 1903 - 1904 1996

Theory of Anomalous Hall Effect in Heavy Fermion System Reviewed

Hiroshi Kontani and Kosaku Yamada

Journal of the Physical Society of Japan Vol. 1994 ( 7 ) page： 2627-2652 1994.7

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

The theory of the anomalous Hall effect in the heavy fermion system in the coherent regime is developed on the basis of the periodic Anderson Hamiltonian with degenerate orbitals. The anomalous Hall conductivity arises from the skew-scattering due to the orbital momenta of f-electrons in the presence of magnetic field. By a newly developed analysis based on the phase factor of the f-electron wavefunction in x-y plane, a simple expression for the Hall conductivity σ xy is derived. It makes possible to understand clearly the mechanism and to estimate the sign and the magnitude of the anomalous Hall coefficient. Our theory explains well experimental results in the heavy fermion systems. Finally, we discuss the extension of this theory to explain the temperature dependence of the Hall coefficient in the cuprate high-T c superconductors.

ANOMALOUS HALL-COEFFICIENT IN HEAVY-ELECTRON SYSTEMS

YAMADA K, KONTANI H, KOHNO H, INAGAKI S

PROGRESS OF THEORETICAL PHYSICS Vol. 89 ( 6 ) page： 1155 - 1166 1993.6

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