Inapplicability of the Anderson theorem to elastic scattering in superconducting proximity effect sandwiches

It is shown that the Anderson theorem does not apply to elastic s-wave scattering in the N metal layer of a proximity effect NS sandwich. For a thin N metal, a consequence of this fact is that the pair potential in the N-metal obeys an equation which is mathematically identical to the equation it satisfies in the phenomenological McMillan tunneling model of the proximity effect. The tunneling density of states for our model differs significantly from the McMillan model predictions, however. (orig.)