Predominant magnetic states in the Hubbard model on anisotropic triangular lattices

By using an optimization variational Monte Carlo method, we study the half-filled-band Hubbard model on anisotropic triangular lattices, as a continuation of the preceding study. We introduce two new trial states: (i) A coexisting state of ΨQ co -antiferromagnetic (AF) and a d -wave singlet gaps, in which we allow for a band renormalization effect, and (ii) a state with an AF order of 120° spin structure. In both states, a first-order metal-to-insulator transition occurs at smaller U/t than that of the pure d -wave state. In insulating regimes, magnetic orders always exist; an ordinary (π,π) -AF order survives up to t′/t∼0.9 (U/t=12), and a 120°-AF order becomes dominant for t′/t. The regimes of the robust superconductor and of the nonmagnetic insulator the preceding study proposed give way to these magnetic domains.