Free-energy formula for a superconducting alloy with localized states in the energy gap: Eliashberg formalism

Abstract

We give a derivation of the formula for calculating the free-energy difference between the superconducting and the normal states of a weak-coupling superconductor with localized states within the energy gap (induced by magnetic impurities) by using the technique of coupling-constant integration. We use the Eliashberg formalism and the square-well model of the electron-phonon interaction. © 1988 The American Physical Society.