RVB mean-field analysis of the Heisenberg model on the quasi-one-dimensional triangular lattice Original Research Article

Stimulated by recent experiments on an organic conductor κκ-(BEDT-TTF)2Cu2 (CN)3, we investigate the View the MathML sourceS=12 Heisenberg model on the triangular lattice with quasi-one-dimensional anisotropy. This model is equivalent to the one-dimensional (1D) chains coupled with frustrated zigzag bonds. Using the resonating valence bond mean-field approximation, we calculate one-particle excitation spectra of this system. By changing the anisotropy parameter J′/JJ′/J from the decoupled 1D chains (J′/J=0J′/J=0) to the isotropic triangular lattice (J′/J=1J′/J=1), we find almost gapless excitations in the wide range from the 1D limit. Relations to the observed “gapless” spin excitation in κκ-(BEDT-TTF)2Cu2(CN)3 are discussed.