Anisotropic pairing on a three-band Fermi surface for A3C60.

We study a model for anisotropic singlet pairing in A3C60, using a realistic model for the Fermi surface in a hypothesized orientationally-ordered doped crystal. Anisotropic solutions are studied by combining numerical solutions to the gap equation in the low-temperature phase with a Landau expansion near the mean field critical temperature. We focus on a class of three-dimensional nodeless d-wave solutions to the model, which exhibit a fully developed gap everywhere on the Fermi surface, but non-BCS temperature dependence of the order parameter in the condensed state, a relatively large value of the low-temperature gap, 2∆/kTc , and non-BCS structure in the quasiparticle spectrum near the gap.