Superconducting phases in the presence of Coulomb interaction: From weak to strong correlations

We study the evolution of the superconducting phases in a model with compet ing short-range attractive (W) and on-site repulsive (U) interactions. The influence of the correlations on the phase diagram of s- and d-wave superco nductors is studied by means of various approximations. The knowledge of th e normal state correlation effects allows the tracking of the influence of U on the superconductivity in correlated systems. We have found the qualita tively different response of the superconducting phases in systems with W<U -cr, when the system ceases to superconduct for large enough U, and in the limit of strong W>U-cr, when the system remains superconducting for arbitra rily large U. [S0163-1829(99)07701-2].