Non-Equilibrium Edge Channel Spectroscopy in the Integer Quantum Hall Regime

TL;DR

This paper introduces a new spectroscopy method to analyze energy transport in quantum Hall edge channels, testing the presence of additional gapless modes and confirming the quantum optics analogy in heat transport.

Contribution

It provides a novel technique to measure energy distributions in out-of-equilibrium edge channels, clarifying the nature of gapless modes in the integer quantum Hall regime.

Findings

No evidence of additional gapless edge modes carrying energy.

Validates the quantum optics analogy for quantum point contacts.

Opens new avenues for heat transport studies in mesoscopic systems.

Abstract

Heat transport has large potentialities to unveil new physics in mesoscopic systems. A striking illustration is the integer quantum Hall regime, where the robustness of Hall currents limits information accessible from charge transport. Consequently, the gapless edge excitations are incompletely understood. The effective edge states theory describes them as prototypal one-dimensional chiral fermions - a simple picture that explains a large body of observations and calls for quantum information experiments with quantum point contacts in the role of beam splitters. However, it is in ostensible disagreement with the prevailing theoretical framework that predicts, in most situations, additional gapless edge modes. Here, we present a setup which gives access to the energy distribution, and consequently to the energy current, in an edge channel brought out-of-equilibrium. This provides a stringent test of whether the additional states capture part of the injected energy. Our results show it is not the case and thereby demonstrate regarding energy transport, the quantum optics analogy of quantum point contacts and beam splitters. Beyond the quantum Hall regime, this novel spectroscopy technique opens a new window for heat transport and out-of-equilibrium experiments.