Coexistence of antiferromagnetism and superconductivity in a mean-field theory of high-T_{c} superconductors

Abstract

We investigate a mean-field theory of the Hubbard model in the large on-site correlation limit, allowing for the possibility of a commensurate spin-density wave together with s- and d-wave-like superconductivity. As a function of t/U and band filling, the resulting phase diagram exhibits phases which are simultaneously superconducting and antiferromagnetic. We show that the superconducting order parameter goes to zero in the limit of a 1/2-filled Hubbard band. We comment on the possible relevance of these results to the newly discovered high-${T}_{c}$ superconductors.