Theory of Andreev reflection in a junction with a strongly disordered semiconductor

TL;DR

This paper develops a theoretical model for Andreev reflection in a junction with a strongly disordered semiconductor, predicting a sharp zero-bias conductance peak that persists without Schottky barriers, relevant for experimental heterostructures.

Contribution

It provides a novel theoretical analysis of Andreev reflection in strongly disordered semiconductors, highlighting the persistence of zero-bias conductance peaks without additional barriers.

Findings

Zero-bias conductance peak predicted at V=0

Peak persists without Schottky barrier

Zero-bias conductance is comparable to normal state conductance

Abstract

We study the conduction of a {\sl N~-~Sm~-~S} junction, where {\sl Sm} is a strongly disordered semiconductor. The differential conductance $dI/dV$ of this {\sl N~-~Sm~-~S} structure is predicted to have a sharp peak at $V=0$. Unlike the case of a weakly disordered system, this feature persists even in the absence of an additional (Schottky) barrier on the boundary. The zero-bias conductance of such a junction $G_{NS}$ is smaller only by a numerical factor than the conductance in the normal state $G_N$. Implications for experiments on gated heterostructures with superconducting leads are discussed.