Title: Critical temperature enhancement in a composite superconductor

Abstract:

Increasing superconductors' critical temperature has been a long standing goal in material science. In order to do so, both a high Cooper-pairing energy and a large phase coherence of the pairs are required. However, these two necessary ingredients tend to compete with each other. It has been suggested that it is possible to overcome this competition by coupling a superconductor to a metallic layer. We consider a model of such a composite system, and determine the critical temperature using a combination of analytic and Monte Carlo methods. The maximal critical temperature is bound from above when the pairing is strong, and scales like a fraction of the zero temperature pairing gap when the pairing is weak. In this weak pairing regime the critical temperature seems to exceed that of a homogeneous model of the same pairing energy.