IMPURITY EFFECTS ON THE ANISOTROPIC S-WAVE SUPERCONDUCTOR OF THE INTERLAYER PAIR TUNNELING MECHANISM

We study the effects of nonmagnetic impurities in the interlayer pair tunneling mechanism for an anisotropic s-wave (ASW) superconductor proposed by Anderson ct 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 T-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) = Delta(max)(T)/Delta(min)(T), increases with increasing temperature which has a similar trend with a recent experiment by Ma et al.