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 [T. Watanabe, H. Yokoyama, Y. Tanaka, and J. Inoue, J. Phys. Soc. Jpn. 75, 074707 (2006)]. We introduce two new trial states: (i) A coexisting state of Psi(co)(Q)-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 degrees 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 (pi,pi)-AF order survives up to t(')/t similar to 0.9 (U/t=12), and a 120 degrees-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.