Shiba-Rusinov theory of magnetic impurities in anisotropic superconductors: Eliashberg formalism

Abstract

The effect of paramagnetic impurities in anisotropic superconductors is investigated with use of the Shiba-Rusinov theory for the impurities and the Eliashberg formalism for the host superconductor. The analytical expressions for the transition temperature Tc and the specific-heat jump C are derived with the use of the square-well model for the electron-phonon interaction. Considered as a function of the spin-flip scattering rate ±, the quantities TcTc0 and CC0 depend on the microscopic parameters , D, and μ* of the host material. The dependence on the material parameters becomes insignificant if the above properties are plotted versus ±cr or if CC0 versus TcTc0 is studied. (Tc0 and C0 are values of Tc and C, respectively, in the absence of impurities, cr is the value of for which Tc becomes zero, is electron-phononinteraction parameter, D is the Debye frequency, and μ* is the Coulomb pseudopotential.) © 1984 The American Physical Society.