Imaging Coulomb Islands in a Quantum Hall Interferometer

TL;DR

This paper uses scanning gate microscopy to visualize and analyze Coulomb islands within a quantum Hall interferometer, revealing their spatial structure and evolution with magnetic field, which explains complex magnetoresistance oscillations.

Contribution

It provides the first direct imaging of quantum Hall Coulomb islands and demonstrates their role in transport phenomena within a quantum Hall interferometer.

Findings

Electron islands are spatially mapped using scanning gate microscopy.

Active electron islands evolve continuously with magnetic field.

The results clarify the origin of complex magnetoresistance oscillations.

Abstract

In the Quantum Hall regime, near integer filling factors, electrons should only be transmitted through spatially-separated edge states. However, in mesoscopic systems, electronic transmission turns out to be more complex, giving rise to a large spectrum of magnetoresistance oscillations. To explain these observations, recent models put forward that, as edge states come close to each other, electrons can hop between counterpropagating edge channels, or tunnel through Coulomb islands. Here, we use scanning gate microscopy to demonstrate the presence of quantum Hall Coulomb islands, and reveal the spatial structure of transport inside a quantum Hall interferometer. Electron islands locations are found by modulating the tunneling between edge states and confined electron orbits. Tuning the magnetic field, we unveil a continuous evolution of active electron islands. This allows to decrypt the complexity of high magnetic field magnetoresistance oscillations, and opens the way to further local scale manipulations of quantum Hall localized states.