Aharonov-Bohm oscillations and magnetic focusing in ballistic graphene rings

TL;DR

This study demonstrates phase-coherent transport, Aharonov-Bohm oscillations, and magnetic focusing in ballistic graphene rings, supported by tight-binding calculations, revealing complex quantum interference effects at various magnetic field regimes.

Contribution

It provides the first detailed observation of AB oscillations in graphene rings across different regimes, including the quantum Hall regime, with theoretical support for the experimental findings.

Findings

Observation of $h/e$, $h/2e$, and $h/3e$ conductance oscillations.

Detection of magnetic focusing effects at small magnetic fields.

AB oscillations in the quantum Hall regime with up to 0.7% visibility.

Abstract

We present low-temperature magnetotransport measurements on graphene rings encapsulated in hexagonal boron nitride. We investigate phase-coherent transport and show Aharonov-Bohm (AB) oscillations in quasi-ballistic graphene rings with hard confinement. In particular, we report on the observation of $h/e$, $h/2e$ and $h/3e$ conductance oscillations. Moreover we show signatures of magnetic focusing effects at small magnetic fields confirming ballistic transport. We perform tight binding calculations which allow to reproduce all significant features of our experimental findings and enable a deeper understanding of the underlying physics. Finally, we report on the observation of the AB conductance oscillations in the quantum Hall regime at reasonable high magnetic fields, where we find regions with enhanced AB oscillation visibility with values up to $0.7$%. These oscillations are well explained by taking disorder into account allowing for a coexistence of hard and soft-wall confinement.