Properties of Superconducting Alloys Containing Paramagnetic Impurities with Local States within the Gap

Abstract

Using the Green's function given by Shiba or Rusinov, we have calculated several properties of superconducting alloys containing paramagnetic impurities and having local states within the gap. At temperatures equal to zero, near zero, and near T_c, the analytic expressions for the order parameter and various thermal properties are given. For various values of ε₀ (the normalized position of a local state with a single impurity), the dependence of the zero temperature order parameter and the zero temperature critical field on the inverse spin-flip collision time are computed. Further, for various values of ε₀, the impurity-concentration dependence of the zero temperature order parameter, the transition temperature, the zero temperature critical field, and the jump in specific heat at T_c are computed. Some of our results would also apply to superconducting Kondo systems.