Evolution of the quantum Hall bulk spectrum into chiral edge states

TL;DR

This study uses advanced spectroscopy on a GaAs quantum wire to directly observe the evolution of quantum Hall edge states from low to high magnetic fields, confirming the bulk-edge correspondence and revealing complex many-body effects.

Contribution

It provides the first detailed experimental visualization of the continuous evolution of chiral edge states with magnetic field, supported by analytical and numerical models.

Findings

Direct evidence of bulk-edge correspondence in quantum Hall systems

Observation of Fermi level pinning and exchange-enhanced spin splitting

Signatures of edge-state reconstruction beyond single-particle models

Abstract

One of the most intriguing and fundamental properties of topological materials is the correspondence between the conducting edge states and the gapped bulk spectrum. So far, it has been impossible to access the full evolution of edge states with critical parameters such as magnetic field due to poor resolution, remnant bulk conductivity, or disorder. Here, we use a GaAs cleaved edge quantum wire to perform momentum-resolved tunneling spectroscopy. This allows us to probe the evolution of the chiral quantum Hall edge states and their positions from the sample edge with unprecedented precision from very low magnetic fields all the way to high fields where depopulation occurs. We present consistent analytical and numerical models, inferring the edge states from the well known bulk spectrum, finding excellent agreement with the experiment -- thus providing direct evidence for the bulk to edge correspondence. In addition, we observe various features beyond the single-particle picture, such as Fermi level pinning, exchange-enhanced spin splitting and signatures of edge-state reconstruction.