Interference-induced surface superconductivity: Enhancement by tuning the Debye energy

Abstract

In the usual perception, surface superconductivity is associated with the surface nucleation of a superconducting condensate above the upper critical field in type-II superconductors or with a rearrangement of phonon properties and the electron-phonon coupling near surfaces/interfaces. Recently, it has been found that there is another example when the surface superconducting temperature is increased up to 20-25% as compared to the bulk one due to constructive interference of superconducting pair states. In the present work, we demonstrate that in fact, such an interferenceinduced enhancement can be much more pronounced, up to nearly 70%. Furthermore, here it is shown that such an interference enhancement persists over a wide range of microscopic parameters.

Effect of Material-Dependent Boundaries on the Interference Induced Enhancement of the Surface Superconductivity Temperature

“…For r s ≳ 3.5 the dependence of the surface ordering effect on the coupling g and on the Debye window ϵ D ≡ ℏω D is also of importance. 60 According to how the system temperature ratio responds to a change in the coupling constant, two trends can be distinguished. In the case of a narrow Debye window, an Moreover, the growth is enhanced at lower densities beyond the minimum point.…”