Superconductivity and a Mott transition in a Hubbard model on an anisotropic triangular lattice

Tsutomu Watanabe; Hisatoshi Yokoyama; Yukio Tanaka; Jun Ichiro Inoue

doi:10.1143/JPSJ.75.074707

Superconductivity and a Mott transition in a Hubbard model on an anisotropic triangular lattice

Tsutomu Watanabe, Hisatoshi Yokoyama, Yukio Tanaka, Jun Ichiro Inoue

SCI - Physics

Research output: Contribution to journal › Article › peer-review

88 Citations (Scopus)

Abstract

A half-filled-band Hubbard model on an anisotropic triangular lattice (t in two bond directions and t′ in the other) is studied using an optimization variational Monte Carlo method, to consider a Mott transition and superconductivity arising in κ-(BEDT-TTF)₂X. Adopting wave functions with doublon-holon binding factors, we reveal that a first-order Mott (conductor-to-nonmagnetic insulator) transition takes place at U = U _c, approximately of the bandwidth, for a wide t′=t range. This transition is not directly connected to magnetism. Robust d-wave superconductivity appears in a restricted parameter range: immediately below U_c and the moderate strength of frustration (0.4 ≲ t′/t ≲ 0.7), where short-range antiferromagnetic correlation sufficiently develops but does not come to a long-range order. The relevance to experiments is also discussed.

Original language	English
Article number	074707
Journal	Journal of the Physical Society of Japan
Volume	75
Issue number	7
DOIs	https://doi.org/10.1143/JPSJ.75.074707
Publication status	Published - 2006 Jul

Keywords

Anisotropic triangular lattice
Antiferromagnetic correlation
D wave
Hubbard model
Mott transition
Superconductivity
Variational Monte Carlo method
κ-(BEDT-TTF)X

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10.1143/JPSJ.75.074707

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title = "Superconductivity and a Mott transition in a Hubbard model on an anisotropic triangular lattice",

abstract = "A half-filled-band Hubbard model on an anisotropic triangular lattice (t in two bond directions and t′ in the other) is studied using an optimization variational Monte Carlo method, to consider a Mott transition and superconductivity arising in κ-(BEDT-TTF)2X. Adopting wave functions with doublon-holon binding factors, we reveal that a first-order Mott (conductor-to-nonmagnetic insulator) transition takes place at U = U c, approximately of the bandwidth, for a wide t′=t range. This transition is not directly connected to magnetism. Robust d-wave superconductivity appears in a restricted parameter range: immediately below Uc and the moderate strength of frustration (0.4 ≲ t′/t ≲ 0.7), where short-range antiferromagnetic correlation sufficiently develops but does not come to a long-range order. The relevance to experiments is also discussed.",

keywords = "Anisotropic triangular lattice, Antiferromagnetic correlation, D wave, Hubbard model, Mott transition, Superconductivity, Variational Monte Carlo method, κ-(BEDT-TTF)X",

author = "Tsutomu Watanabe and Hisatoshi Yokoyama and Yukio Tanaka and Inoue, {Jun Ichiro}",

note = "Funding Information: This work is partly supported by Grant-in-Aid from the Ministry of Education, etc. Japan, from the Supercomputer Center, ISSP, Univ. of Tokyo, from NAREGI Nanoscience Project and for the 21st Century COE “Frontiers of Computational Science”.",

year = "2006",

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AU - Watanabe, Tsutomu

AU - Yokoyama, Hisatoshi

AU - Tanaka, Yukio

AU - Inoue, Jun Ichiro

N1 - Funding Information: This work is partly supported by Grant-in-Aid from the Ministry of Education, etc. Japan, from the Supercomputer Center, ISSP, Univ. of Tokyo, from NAREGI Nanoscience Project and for the 21st Century COE “Frontiers of Computational Science”.

PY - 2006/7

Y1 - 2006/7

N2 - A half-filled-band Hubbard model on an anisotropic triangular lattice (t in two bond directions and t′ in the other) is studied using an optimization variational Monte Carlo method, to consider a Mott transition and superconductivity arising in κ-(BEDT-TTF)2X. Adopting wave functions with doublon-holon binding factors, we reveal that a first-order Mott (conductor-to-nonmagnetic insulator) transition takes place at U = U c, approximately of the bandwidth, for a wide t′=t range. This transition is not directly connected to magnetism. Robust d-wave superconductivity appears in a restricted parameter range: immediately below Uc and the moderate strength of frustration (0.4 ≲ t′/t ≲ 0.7), where short-range antiferromagnetic correlation sufficiently develops but does not come to a long-range order. The relevance to experiments is also discussed.

AB - A half-filled-band Hubbard model on an anisotropic triangular lattice (t in two bond directions and t′ in the other) is studied using an optimization variational Monte Carlo method, to consider a Mott transition and superconductivity arising in κ-(BEDT-TTF)2X. Adopting wave functions with doublon-holon binding factors, we reveal that a first-order Mott (conductor-to-nonmagnetic insulator) transition takes place at U = U c, approximately of the bandwidth, for a wide t′=t range. This transition is not directly connected to magnetism. Robust d-wave superconductivity appears in a restricted parameter range: immediately below Uc and the moderate strength of frustration (0.4 ≲ t′/t ≲ 0.7), where short-range antiferromagnetic correlation sufficiently develops but does not come to a long-range order. The relevance to experiments is also discussed.

KW - Anisotropic triangular lattice

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KW - Mott transition

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KW - Variational Monte Carlo method

KW - κ-(BEDT-TTF)X

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Superconductivity and a Mott transition in a Hubbard model on an anisotropic triangular lattice

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