Effects of Weak Intersite Repulsion and Negative Diagonal Transfer on Superconductivity and Antiferromagnetism in Hubbard Model

Withcuprate superconductors in mind, we study the effects of intersite repulsion V and diagonal transfer on antiferromagnetism (AF) and superconductivity (SC) inthe Hubbard model on a squarelattice, using a variational Monte Carlo method. In the trial wave function, essential factors for Mott physics and band renormalization are included. It is foundthat the effect of small V generally suppresses SC, but makesthe range of doping rate unstable toward phase separation narrower.The effect of also extends thearea stable against charge inhomogeneity, and, in particular,removesthe area of a coexistent state of SC and AF.