Dc Electrical Current Generated by Upstream Neutral Modes

TL;DR

This paper demonstrates that neutral modes in quantum Hall systems can generate a measurable dc electrical current at the drain when biased, revealing their ability to carry nonlocal charge information.

Contribution

It introduces a novel protocol to detect neutral modes via dc current generation, applicable to quantum Hall and other systems with neutral modes.

Findings

Neutral modes can induce a dc current at the drain under bias.

Backscattering between counter-propagating modes is essential.

The protocol is applicable beyond quantum Hall systems.

Abstract

Quantum Hall phases are gapped in the bulk but support chiral edge modes, both charged and neutral. Here we consider a circuit where the path from the source of electric current to the drain necessarily passes through a segment consisting solely of neutral modes. We find that upon biasing the source, a dc electric current is detected at the drain, provided there is backscattering between counter-propagating modes under the contacts placed in certain locations. Thus, neutral modes carry information that can be used to nonlocally reconstruct a dc charge current. Our protocol can be used to detect any neutral mode that counterpropagates with respect to all charge modes. Our protocol applies not only to the edge modes of a quantum Hall system, but also to systems that have neutral modes of non-quantum Hall origin. We conclude with a possible experimental realization of this phenomenon.