Effects of Diagonal Hopping on Stability of Antiferromagnetic State

Intrinsic stability as to phase separation of an antiferromagnetic state is studied for a strongly correlated Hubbard model with frustration (t-t'-U model) near half filling, using a variational Monte Carlo method. In the Hartree-Fock (one-body) part of the many-body trial state, band-renormalization effect, which is necessary for partly recovering the nesting condition, is introduced up to three-step hopping distance. As a result, a doped AF state for has a low energy but is unstable toward phase separation, which is consistent with previous studies. In contrast, the AF state becomes stable against phase separation for, owing to the contribution of hopping energy in diagonal directions. The doped AF states are metallic for the two values of, but exhibit contrastive behavior in the momentum distribution function in the nodal and antinodal regions.