Theory of disorder-induced increase and degradation of superconductingTc

For a recent strong coupling theory for dirty superconductors, the leading disorder dependence of $T_c$ is calculated exactly within a jellium model, and found to be linear in the resistivity ρ. Due to competition between attractive and repulsive effective electron-electron interactions, ${\mathrm{dT}}_c$/dρ changes sign as a function of the clean-limit temperature $T_c^0$. This explains the experimental fact that low-$T_c$ superconductors show an increase of $T_c$ with disorder, while high-$T_c$ materials show a $T_c$ degradation. Analysis of experiments on many very different materials shows that this correlation is surprisingly well pronounced. Comparison of the model calculation with the experimental results yields satisfactory agreement.