Effects of impurities on Andreev reflection in an N-S bilayer

Abstract

We calculate the effects of impurities in the normal layer of an N-S contact on the beam of Andreev reflected electrons. We find oscillations in the intensity of the beam which are superimposed on the classical exponential decay. This effect is interpreted as oscillations in the impurity cross section which come from the quantum interference of electrons and Andreev reflected holes. This kind of particle-hole interference is a typical feature of the traditional BCS picture of superconductivity. Its observation in high T c superconductors would be an indication for a traditional type of superconductivity in these materials.