Theory of the proximity effect between normal metals

Abstract

An analysis is made of the AC electrical conductivity of a thin metal film of relatively short electronic mean free path deposited on a pure metal substrate, assuming such good contact that a proportion of the electrons approaching the interface cross over to the other side without being scattered. An approximate but selfconsistent method is developed for combining Maxwell's equations with the solution to the Boltzmann transport equation. The results show how the effective conductivity of the film and the surface impedance of the film-substrate combination vary with the film thickness, the electric mean free path in each medium, the frequency of the applied field and the probability of electron cross over. The effect analysed is the classical analogue of the proximity effect between superconducting and normal metals.