The critical temperature of s + d-wave superconductors with impurities

The authors study the critical temperature of s + d-wave superconductors as a function of impurity concentration using a s + d-wave model which is based on anisotropic Eliashberg equations. A spin fluctuation spectrum is responsible for the d-wave coupling, while a simple Einstein spectrum is used to describe the s-wave coupling. It is also possible to study within this model how the two pairing mechanisms influence each other. The results are in good qualitative agreement with experiment