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

A bond valence sum (BVS) analysis was performed for the -type cuprate superconductors. The superconducting critical temperature {Tc} versus in-plane Cu-O BVS correlation for copper is grouped into classes and subclasses. Only within a class of 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{sub H} of the CuO{sub 2} layers. This study strongly suggests that the {Tc} for every class or subclass of the superconductors is an inverted parabolic function of n{sub H}, and so is the coupling constant {lambda} for Cooper pair formation. 43 refs., 4 figs., 2 tabs.