Anisotropic superconductivity in the 2D Hubbard model: Gap function and interaction weight

A potential dₓ²-y² pairing state in the 2D Hubbard model is investigated within a conserving extension of Hartree-Fock theory known as the fluctuation exchange approximation. The self-consistent field equations are solved with the aid of a recently developed renormalization group approach for general models which lack a Migdal theorem. The calculations yield an anisotropic gap which saturates rapidly below Tc to a peak value of 2Δₖ/kTc{~}10--12 for k along the kₓ and ky axes.