Competition between Superconductivity and Antiferromagnetism in the Extended Hubbard Model

Abstract

We investigate a mean-field theory of the extended Hubbard model for the coexistence of antiferromagnetism (AF) and superconductivity (SC) in high-temperature homogeneous superconductive materials. We calculate the ordering parameter and the critical temperature as a function of filling. It is concluded that the superconducting state is destroyed when the antiferromagnetic state develops. For weak Coulomb correlation we show that the superconducting d-wave ordering parameter, which by itself has a maximum in the limit of a half-filled Hubbard band, goes to zero in the presence of antiferromagnetic ordering. Our phase diagram of antiferromagnetic and d-wave superconductivity critical temperatures as a function of filling resembles the experimental evidence.