Exciton Transport and Andreev Reflection in a Bilayer Quantum Hall System

TL;DR

This paper reveals that neutral excitons enable counterflowing electrical currents to traverse the bulk of a bilayer quantum Hall system through an Andreev reflection process, despite the inability of charged excitations to do so.

Contribution

It introduces a novel mechanism where neutral excitons facilitate bulk transport in a bilayer quantum Hall system via Andreev reflection.

Findings

Counterflowing currents are transported by neutral excitons.

Excitons are emitted and absorbed at boundaries via Andreev reflection.

Bulk transport occurs despite charged excitations being immobile.

Abstract

We demonstrate that counterflowing electrical currents can move through the bulk of the excitonic quantized Hall phase found in bilayer two-dimensional electron systems (2DES) even as charged excitations cannot. These counterflowing currents are transported by neutral excitons which are emitted and absorbed at the inner and outer boundaries of an annular 2DES sample via an Andreev reflection process.