Self-consistent T-matrix approximation to the negative-U Hubbard model: numerical results

Abstract

The authors consider the negative-U Hubbard model on a square lattice in the self-consistent T-matrix approximation. They investigate the influence of the Fermi sea on the bound states which always occur in two spatial dimensions in the presence of an attractive interaction. As long as the binding energy is smaller than the Fermi energy, these bound states are found to be broadened sufficiently that Fermi liquid behaviour is restored. Only in the limit of large binding energy does one expect coexisting stable Bose pairs and dissociated fermions leading to a breakdown of Fermi liquid theory.