Direct measurement of the coherence length of edge states in the Integer Quantum Hall Regime

TL;DR

This paper measures the coherence length of edge states in the Integer Quantum Hall Effect regime using Mach-Zehnder interferometers, revealing an exponential decay of visibility with temperature and establishing a precise value for the coherence length.

Contribution

It provides the first accurate measurement of the coherence length of edge states in the IQHE regime through temperature-dependent interference experiments.

Findings

Coherence length inversely proportional to temperature

Maximum coherence length at the edge of the quantum Hall plateau

Visibility decays exponentially with temperature

Abstract

We have determined the finite temperature coherence length of edge states in the Integer Quantum Hall Effect (IQHE) regime. This was realized by measuring the visibility of electronic Mach-Zehnder interferometers of different sizes, at filling factor 2. The visibility shows an exponential decay with the temperature. The characteristic temperature scale is found inversely proportional to the length of the interferometer arm, allowing to define a coherence length $\l_\phi$. The variations of $\l_\phi$ with magnetic field are the same for all samples, with a maximum located at the upper end of the quantum hall plateau. Our results provide the first accurate determination of $\l_\phi$ in the quantum Hall regime.