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

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

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88 Citations (Scopus)


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.

Original languageEnglish
Article number074707
JournalJournal of the Physical Society of Japan
Issue number7
Publication statusPublished - 2006 Jul


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


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