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.