We have observed for very narrow tin films a depression of the superconducting transition temperature below that of wider portions of the same films. We propose a model which accounts for this depression and also suggests a condition on the maximum microwave enhancement of critical current in narrow thin-film bridges as observed by Wyatt et al.

• Received 16 January 1967

DOI:https://doi.org/10.1103/PhysRevLett.18.551