Hole Density Dependence of the Critical Temperature and Coupling Constant in the Cuprate Superconductors

Abstract

A bond valence sum (BVS) analysis was performed for the p-type cuprate superconductors. The superconducting critical temperature T_c versus in-plane Cu-O BVS correlation for copper is grouped into classes and subclasses. Only within a class or subclass for which the nonelectronic effect is constant does the variation of the in-plane Cu-O BVS reflect the corresponding change in the hole density n_H of the CuO₂ layers. This study strongly suggests that the T_c for every class or subclass of the superconductors is an inverted parabolic function of n_H, and so is the coupling constant λ for Cooper pair formation.