Density of states and reflectionless tunneling in NS junction with a barrier

TL;DR

This paper investigates how barriers influence the proximity effect in normal-superconductor junctions, revealing that both conductance enhancement and density of states modifications originate from the same physical mechanism.

Contribution

It provides a general criterion for barrier transparency and links reflectionless tunneling with density of states changes in NS junctions.

Findings

Barrier transparency criterion derived

Reflectionless tunneling explained by barrier effects

Density of states affected similarly to conductance

Abstract

The effect of the barrier on the proximity effect in normal-superconductor junction is analyzed. A general criterion for the barrier, though large, to be effectively transparent, is given. This criterion is applied to both the conductance of a disordered NS junction (reflectionless tunneling) and the density of states across it, showing that both phenomena stem from the same physical effect.