Theory of the "universal" degradation ofTcin high-temperature superconductors

Abstract

The superconducting $T_c$ decreases similarly with disorder (as measured by resistivity $\rho$) for all systems with high $T_c$. We propose that this is a localization effect. For strong disorder, electron diffusion is slow and strongly scale dependent. This increases the effective Coulomb repulsion. Model calculations with realistic parameters describe well the experimental $T_c-\mathrm{vs}-\rho$ curves. Explanations are suggested for the relatively large critical conductance found.