Impurity effects on the anisotropic s-wave superconductor of the interlayer pair tunneling mechanism.

Abstract

We study the effects of nonmagnetic impurities in the interlayer pair tunneling mechanism for an anisotropic s-wave (ASW) superconductor proposed by Anderson et al. using the self-consistent T-matrix approximation. We found that the impurity effects on this particular model are quite different from those of the conventional ASW model of the BCS-type pairing. It shows a much stronger suppression of ${\mathit{T}}_{\mathit{c}}$ upon doping with nonmagnetic impurities than in the conventional ASW pairing state. Moreover, the minimum-energy gap does not monotonically grow with increasing impurity concentration but instead it quickly shrinks. We also show that the temperature dependence of the gap anisotropy ratio, R(T)=${\mathrm{\ensuremath{\Delta}}}_{\mathrm{max}}$(T)/${\mathrm{\ensuremath{\Delta}}}_{\mathrm{min}}$(T) increases with increasing temperature which has a similar trend with a recent experiment by Ma et al.