TC ENHANCEMENT DUE TO ANISOTROPY IN THE PAIRING INTERACTION

We give a simple demonstration that anisotropy (of arbitrary strength) in the pairing interaction (of arbitrary origin) always enhances the superconducting temperature T(c), thanks to a general theorem in matrix theory. Moreover, such an anisotropic interaction also gives rise to different partial-wave pairings than in the corresponding isotropic cases. A particular example, treated rigorously in the weak-coupling regime, explicitly exhibits, depending on the anisotropy parameters, either singlet pairing (as an admixture of s (l = 0) and d (l = 2) waves), or triplet (l = 1) pairings. We discuss the possible implications of our results for actual physical systems as well as their plausible link with d-wave pairing often invoked for high-T(c) materials.