Superconducting gap symmetry from repulsive interactions in the spin-singlet state

We obtained the superconducting gap equation in terms of the effective T-sc attering matrix. We considered the gap symmetry in both singlet and triplet states as well as in charge and spin channels, We show that the supercondu cting gap for the repulsive interactions in the spin-singlet state exists i n the charge channel only, and the gap has s-wave symmetry (l = 0, where l is the orbital quantum number of a pair) or d-wave (l = 2) symmetry. We als o show that in the 2D case, the strongly anisotropic s-wave gap might have nodes in the direction of the nesting wave vector and may resemble the d(x2 -y2) gap symmetry. We show that there is a gap for the attractive interacti ons in the spin channel only. Such a gap indicates the phase transition int o superfluid state which is similar to liquid He-3. The gap due to pairing instability for the attractive interactions in the spin channel has p-wave symmetry (l = 1) for the spin-triplet state with m(s) = +/-1 or p-wave symm etry (l = 1) for the spin-triplet state with m(s) = 0. (C) 2001 Elsevier Sc ience B,V. All rights reserved.