Origin of Superconductivity in Cuprate Oxide –Quantitative Analysis on the Basisofd-pModel–

The origin of superconductivity in cuprate oxide systems is studied from the first principle starting with the d - p model Hamiltonian. We derive the Dyson-Gor'kov equations which include the second order terms with respect to Coulomb repulsion U between d-electrons both in normal and anomalous self-energy parts, and solve them completely in due consideration of full momentum and energy structures in the equations. We obtain the superconducting transition temperature T c by treating both the attractive interaction and the damping effect on an equal footing. As a result, it is shown that d -wave superconductivity is possible under a suitable condition, though T c is suppressed by the damping effect. The possibility of obtaining high T c by including higher order terms in U is discussed in connection with the experimental results on Tl-systems.