Andreev reflection and cyclotron motion at superconductor -- normal-metal interfaces

TL;DR

This paper develops a microscopic theory of Andreev reflection at superconductor--2DES interfaces in magnetic fields, revealing how Zeeman splitting and screening currents influence conductance and edge state formation.

Contribution

It introduces a detailed Bogoliubov--de Gennes based model incorporating Zeeman effects and screening currents to analyze Andreev reflection at superconductor--2DES interfaces.

Findings

Zeeman splitting causes a double-step feature in conductance.

Screening currents shift conductance steps to larger filling factors.

Andreev edge state formation is suppressed below a critical filling factor.

Abstract

We investigate Andreev reflection at the interface between a superconductor and a two--dimensional electron system (2DES) in an external magnetic field such that cyclotron motion is important in the latter. A finite Zeeman splitting in the 2DES and the presence of diamagnetic screening currents in the superconductor are incorporated into a microscopic theory of Andreev edge states, which is based on the Bogoliubov--de Gennes formalism. The Andreev--reflection contribution to the interface conductance is calculated. The effect of Zeeman splitting is most visible as a double--step feature in the conductance through clean interfaces. Due to a screening current, conductance steps are shifted to larger filling factors and the formation of Andreev edge states is suppressed below a critical filling factor.