Analysis of tunnelling experiments on normal metal backed by Nb

Abstract
Analysis of recent tunnelling experiments (E.L. Wolf et al., Phys. Rev. B, 1980) on Al:Nb samples reveals that the Eliashberg function alpha 2F is much closer to a Nakagawa-Woods spectrum than previously realised. The role of a thin disordered surface layer in bringing about 'proximity effect' behaviour is discussed.