Search for Superconductivity in an Extended Hubbard Model.

Extensions of the Gutzwiller variational method are used to study whether substantial nearest-neighbor repulsion between holes on a copper-oxygen lattice in two dimensions leads to simple s-wave superconductivity. Although such a repulsion promotes double occupation on oxygen atoms, the simplest one parameter s-wave superconducting wavefunctions do not lower the energy with respect to the normal state.