Local Thermometry of Neutral Modes on the Quantum Hall Edge

TL;DR

This study demonstrates local thermometry of quantum Hall edge modes, revealing that charge transport is unidirectional while heat can flow upstream, indicating complex edge structures related to fractional quantum Hall states.

Contribution

It introduces a method to measure local temperature and chemical potential along quantum Hall edges, uncovering heat transport upstream despite charge moving downstream.

Findings

Charge is transported exclusively downstream.

Heat can be transported upstream in certain edge states.

Edge structure reveals fractional quantum Hall physics.

Abstract

A system of electrons in two dimensions and strong magnetic fields can be tuned to create a gapped 2D system with one dimensional channels along the edge. Interactions among these edge modes can lead to independent transport of charge and heat, even in opposite directions. Measuring the chirality and transport properties of these charge and heat modes can reveal otherwise hidden structure in the edge. Here, we heat the outer edge of such a quantum Hall system using a quantum point contact. By placing quantum dots upstream and downstream along the edge of the heater, we can measure both the chemical potential and temperature of that edge to study charge and heat transport, respectively. We find that charge is transported exclusively downstream, but heat can be transported upstream when the edge has additional structure related to fractional quantum Hall physics.