Specific heat discontinuity of a proximity-effect sandwich system containing Kondo impurities

Abstract

The theoretical work of Matsuura, Ichinose, and Nagaoka on the Kondo effect in superconductors and McMillan's tunneling model are applied to a proximity-effect sandwich system containing Kondo impurities. Analytic expressions for the renormalized Green's functions of superconducting and normal-metal electrons are given as functions of the system composition. It is found that as the thicknesses become large, the specific heat discontinuity changes continuously from the Müller-Hartmann-Zittartz value for the magnetic cases to the Ichinose value for the nonmagnetic ones. For small values of the layer thickness, and with the films in proximity, our results can be used to calculate the specific heat jump at the transition temperature numerically. © 1983 Plenum Publishing Corporation.