THEORY OF HOLE SUPERCONDUCTIVITY IN HIGH-TC SUPERCONDUCTORS - BCS-GORKOV FORMALISM IN EXTENDED HUBBARD-MODEL

A theory of superconductivity in high T(c) oxide superconductors is developed including on site Hubbard interaction and off diagonal Coulomb correlations which give rise to a modified hopping. We have used a recently proposed model Hamiltonian for describing this system and have obtained the energy spectrum in the presence of Coulomb correlations. BCS pairing in this modified energy spectrum has been considered to obtain the superconducting gap function which has explicit dependence on carrier concentration. Calculation of T(c) using this gap function confirms to the experimental variation of T(c) with carrier (hole) concentration.