Proximity Effect Enhancement Induced by Roughness of SN Interface

TL;DR

This paper investigates how roughness at the superconductor-normal metal interface enhances the proximity effect, significantly affecting the critical temperature reduction in layered superconductors with anisotropic properties.

Contribution

It introduces the concept that interface roughness can substantially increase the proximity effect, leading to greater critical temperature reduction in layered superconductors.

Findings

Rough SN interface increases electron penetration into the superconductor.

Enhanced proximity effect results in larger $ riangle T_c$ compared to smooth interfaces.

Effect is pronounced in highly anisotropic layered superconductors.

Abstract

Critical temperature reduction $\Delta T_c$ is considered for a thin film of a layered superconductor (S) with a rough surface covered by a thick layer of a normal metal (N). The roughness of the SN interface increases the penetration of electrons from the normal metal into the superconductor and leads to an enhancement of the proximity effect. The value of $\Delta T_c$ induced by the roughness of the SN interface can be much higher than $\Delta T_c$ for a film with a plain surface for an extremely anisotropic layered superconductor with the coherence lengths $\xi_a,\xi_b\gg\xi_c$.