SELF-CONSISTENT SOLUTION OF THE BOND-ASYMMETRIC 2-BAND MODEL FOR A CU-O BASED HIGH-TC SUPERCONDUCTOR

To describe high-T(c) superconductivity the hole-occupation number-constrained BCS equation is self-consistently solved for the quasi-2 D bond-asymmetric two-band model with weak coupling pairing interaction. The model is characterized by the splitted two oxygen bands and hole transfer interactions among nearest and next nearest neighbour O-sites. Since the self-consistent mean field induced by the Coulomb repulsion in the O-site is dependent on the hole-occupation numbers in the oxygen site O(a)(O(b)), n(a) (n(b)), behaviour of the square-root singularities in the state density is determined by the total hole-occupation number, x = n(a) + n(b). The self-consistent solution to the extended BCS equation describes x-dependence of physical properties and shows substantial quenching of the isotope effect in association with the superconducting phase realized only in a limited range of x. These results are displayed for some typical sets of interaction strengths.