S-S-ASTERISK-D-WAVE SUPERCONDUCTOR ON A SQUARE LATTICE AND ITS BCS PHASE-DIAGRAM

We study an extended Hubbard model with on-site repulsion and nearest- neighbors attraction which tries to mimic some of the experimental fea tures of doped cuprates in the superconducting state. We draw and disc uss the phase diagram as a function of the effective interactions amon g electrons for a wide range of doping concentrations. We locate the r egion which is relevant for the cuprates setting some constraints on t he parameters which may be used in this kind of effective model. We al so study the effects of temperature and orthorombicity on the symmetry and magnitude of the gap function, and map the model onto a simpler l inearized Hamiltonian, which produces similar phase diagrams.