Andreev reflection at high magnetic fields: Evidence for electron and hole transport in edge states

TL;DR

This paper investigates Andreev reflection at high magnetic fields in InAs/AlGaSb heterostructures, revealing evidence for electron and hole transport in edge states through magnetotransport measurements.

Contribution

It provides experimental evidence of Andreev reflection involving edge states in the quantum Hall regime at high magnetic fields.

Findings

Observation of strong magnetoresistance oscillations exceeding Shubnikov-de Haas oscillations.

Detection of higher longitudinal resistance in the superconducting state above a certain magnetic field.

Evidence for electron and hole transport via edge channels with Andreev reflection.

Abstract

We have studied magnetotransport in arrays of niobium filled grooves in an InAs/AlGaSb heterostructure. The critical field of up to 2.6 T permits to enter the quantum Hall regime. In the superconducting state, we observe strong magnetoresistance oscillations, whose amplitude exceeds the Shubnikov-de Haas oscillations by a factor of about two, when normalized to the background. Additionally, we find that above a geometry-dependent magnetic field value the sample in the superconducting state has a higher longitudinal resistance than in the normal state. Both observations can be explained with edge channels populated with electrons and Andreev reflected holes.