ANISOTROPIC SUPERCONDUCTIVITY IN THE 2D HUBBARD-MODEL - GAP FUNCTION AND INTERACTION WEIGHT

A potential d(x2-y2) pairing state in the 2D Hubbard model is investig ated within a conserving extension of Hartree-Fock theory known as the fluctuation exchange approximation. The self-consistent field equatio ns are solved with the aid of a recently developed renormalization gro up approach for general models which lack a Migdal theorem. The calcul ations yield an anisotropic gap which saturates rapidly below T(c) to a peak value of 2DELTA(k)/kT(c) approximately 10-12 for k along the k( x) and k(y) axes.