ENERGY-BAND OVERLAPPING IN HIGH-T-C SUPERCONDUCTORS

Multi-band superconductors are analyzed and the relevance of overlappi ng energy bands to the high-T-c of these materials is studied. Within the BCS framework, a two band model with generalized Fermi surface top ologies is developed. Values of the overlapped occupancy parameters fo r typical cuprate superconductors are obtained as a function of the ra tio R and the effective coupling constant, lambda, in the weak-couplin g limit. The overlap scale is of the order or lower than the cutoff (D ebye) energy. The typical behavior of the isotope effect is obtained. As these superconductors have transition temperatures above the phonon barrier, the results of this approach are important to the generic un derstanding of the high-T-c superconducting mechanism.