Tcdegradation by the Coulomb interaction in anisotropic disordered superconductors

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Abstract
The authors calculate the depression of Tc caused by the effect of a short mean free path on the Coulomb repulsion, for the special case of a very anisotropic superconductor. Specifically, they consider the linear chain model for A15 superconductors with a large difference between the in-chain and inter-chain scattering rates. Previous work based on the McMillan equation for Tc gave a large reduction in Tc. In this work they find Tc numerically from the Eliashberg equations. They find that the reduction of Tc due to this effect is about 25% to 30%, which is considerably less than observed experimentally. The effective Coulomb term is retarded, and as a result is frequency dependent. It is affected by the disorder mainly at small frequencies ( approximately 10 meV).