TRANSITION-TEMPERATURES IN CUPRATE SUPERCONDUCTORS ON THE BASIS OF D-P MODEL

On the basis of d-p model, both normal and anomalous self-energies are calculated perturbatively up to third order with respect to the Coulomb repulsion U between d-electrons at a Cu site. The superconducting transition temperature T-c is obtained as a function of d- and p-hole numbers by the solution of the Dyson-Gor'kov equation. In the over-doped region, T-c decreases with the increase of the total hole number delta. This experimentally obtained behavior of T-c is successfully reproduced. In the under-doped region, T-c decreases rapidly with the decrease of delta experimentally. Such a rapid change of T-c is not obtained in our calculation, but it is found that T-c is almost independent of delta by the suppression due to the vertex corrections.