VAN-HOVE SCENARIO AND THE 8-BAND MODEL FOR HIGH-T-C SUPERCONDUCTORS

We investigate the doping dependence of the superconducting transition temperature T-c for the cuprate superconductors on the basis of a sem iphenomenological description of pairing and the eight-band model for their electronic structure in the normal state. We find, in agreement with experiments, that T-c rises and then falls steeply as the number of holes increases from underdoping to overdoping. We identify the cha racteristic saddle points of the eight-band model as the cause of this behavior. Because our description of pairing is semiphenomenological, we shed new light on the physical mechanism of pairing only indirectl y, nevertheless we present new evidence that the above Van Hove-like s cenario is an essential feature of superconductivity in these, materia ls. [S0163-1829(98)03025-2].