Enhanced Superconductivity in Layered Metallic Films

Abstract

We have observed large increases in the transition temperature ${T}_{c}$ of thin, quenched composite films consisting of alternating layers of dissimilar metals. We estimate the regions of the film which experience the greatest increase to be within a few monolayers of the metal-vacuum or metal-metal surfaces. A possible explanation for the increased ${T}_{c}'\mathrm{s}$ is the shift in the electron-phonon coupling to larger values due to the lowering of the phonon frequencies.