Universal Relation Connecting Fermi Surface to Symmetry of the Gap Function in BCS-Like Superconductors

Abstract

A universal relation connecting Fermi surface (FS) to the symmetry of the gap function in BCS-like superconductors is derived. It is found that the shape of the FS can be deduced directly from the symmetry of the superconducting gap function, and is also influenced by the next nearest-neighbor overlapping. The application of this relation to cuprate superconductors is discussed. There is observed an interesting property that Luttinger's theorem perfectly holds for the tight-binding band while it is violated by inclusion of the next nearest-neighbor overlapping integral.