Properties of a two-dimensional D-wave superconductor from phenomenological susceptibility

Using fast-Fourier-transform techniques, we calculated several properties of a two-dimensional D-wave superconductor directly from the phenomenological form of the magnetic susceptibility suggested by Millis, Monien, and Pines. A BCS-type formalism is employed, but no assumptions are made about the exact form of the gap anisotropy. The results for the gap exhibit D-wave symmetry and go beyond the usual cosine minus cosine model. The results obtained are compared with those obtained from the simpler and much used separable model