Interplay between antiferromagnetism and superconductivity in the Hubbard model with frustration

Abstract: Coexistence of and competition between antiferromagnetism (AF) and d-wave superconductivity (SC) are studied for a Hubbard model on the square lattice with a diagonal transfer , using a variational Monte Carlo method. The following improvements are introduced into the trial function: (1) Coexistence of AF and d-wave singlet gaps that allows a continuous description of their interplay, (2) band renormalization effect, and (3) refined doublon–holon correlation factors. Optimizing this function for a strongly correlated value of , we construct a phase diagram in the (doping rate)- space, and find that for a coexisting state is realized, whose range of extends as increases. In contrast, for , AF and SC states are mutually exclusive, and a coexisting state does not appear. In connection with the “two-gap” problem, we confirm even for the present refined function that the gradient of momentum distribution function at the antinodal point mainly dominates the magnitude of the d-wave SC correlation function. [Copyright &y& Elsevier]