Superconductivity in the fcc negative-U Hubbard model: From two to three dimensions

We evaluate the s-wave pairing correlation in the negative-U Hubbard model on the fcc lattice as the system evolves from a two-dimensional thin film to a three-dimensional bulk structure. Exact-diagonalization techniques and a simple interpolation scheme connecting the film and the bulk structure are employed. The dependence of the pairing correlation on band filling and dimensionality has been systematically studied. Indications of superconductivity at different band fillings with changing dimensionality and interaction strength have been found and discussed