Band-renormalization effect in coexistent state of d-wave superconducting and antiferromagnetic orders for Hubbard model

Abstract

In view of cuprate superconductors, we apply a variational Monte Carlo method to a strongly correlated square-lattice Hubbard (t-t′-U) model. As a one-body part in a trial wave function, we use a coexistent state of antiferromagnetic (AF) and d-wave superconducting (SC) orders for each of which band-renormalization effect (BRE) is considered independently. We focus on t′/t and doping-rate (δ) dependence of properties of this state. It is found that the BRE for the AF order causes expansion of the AF area up to δ ∼ 0.2 for a large |t′/t|. For t′/t=0 (−0.3), the AF and SC orders are coexistent (mutually exclusive), and the state is unstable toward (stable against) phase separation. This feature of coexistence or exclusion depends on the position of the Fermi surface in the underlying pure AF state, and indicates that antinodal Fermi surfaces are crucial for forming d-wave SC.