McMillan's tunneling theory of the proximity effect has been applied to results on gold-aluminum-oxide-aluminum thin-film sandwiches. Measurements of the transition temperature and minimum energy gap give consistent agreement with the theory and indicate that the interaction parameter in gold is 0.072×0.004.

• Received 31 January 1972

DOI:https://doi.org/10.1103/PhysRevLett.28.959