Effects of off-site Coulomb interaction in a Hubbard model on a triangular lattice

• Published in: The Journal of physics and chemistry of solids Vol. 69; no. 12; pp. 3372 - 3374
• Main Authors: Watanabe, Tsutomu, Yokoyama, Hisatoshi, Tanaka, Yukio, Inoue, Jun-ichiro
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 01.12.2008; Elsevier
• Subjects: A. Organic compounds; A. Superconductors; Condensed matter: electronic structure, electrical, magnetic, and optical properties; D. Electrical properties; D. Magnetic properties; D. Superconductivity; Exact sciences and technology; Organic superconductors; Pairing symmetries; Physics; Superconducting materials (excluding high-tc compounds); Superconductivity; Theory and models of superconducting state; 74.70.−b; D. Magnetic properties; A. Superconductors; 74.20.Rp; D. Superconductivity; 74.20.−z; A. Organic compounds; D. Electrical properties; Antiferromagnetism; Organic superconductors; Charge ordering; Hubbard model; Mott transition; Coulomb interaction; Monte Carlo methods; Triangular lattices; Anisotropy; BEDT-TTF; 74.20.-z; 74.70.-b; Magnetic structure; Pairing
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2008.06.089

Half-filled-band extended Hubbard models on anisotropic triangular lattices are studied using a variational Monte Carlo method, with κ -(BEDT-TTF) 2X in mind. Mott transitions are always observed at certain U. For the isotropic case, an antiferromagnetic (AF) order with 120° spin structure becomes dominant in the insulating regime. Introduction of intersite Coulomb interaction ( V) only slightly affects the AF order, but a threefold charge order appears when V / U ≳ 1 3 . As for superconductivity, d 2 -, d xy -, and f 2 -wave pairing states, which form pairs on next-nearest-neighbor sites, are stabilized with respect to the normal state for large V.