Electrostatically confined Quantum Rings in bilayer Graphene

TL;DR

This paper introduces a novel electrostatically confined quantum ring system in bilayer graphene, revealing unique magnetic field-dependent energy spectra with non-symmetric and complex features.

Contribution

It presents a new method to create quantum rings in bilayer graphene with distinctive magnetic field responses, expanding the understanding of graphene-based quantum confinement.

Findings

Energy levels depend uniquely on magnetic field B0.

Eigenvalues are not symmetric under B0 inversion.

Spectra exhibit anti-crossings due to state overlaps.

Abstract

We propose a new system where electron and hole states are electrostatically confined into a quantum ring in bilayer graphene. These structures can be created by tuning the gap of the graphene bilayer using nanostructured gates or by position-dependent doping. The energy levels have a magnetic field ($B_{0}$) dependence that is strikingly distinct from that of usual semiconductor quantum rings. In particular, the eigenvalues are not invariant under a $B_0 \to -B_0$ transformation and, for a fixed total angular momentum index $m$, their field dependence is not parabolic, but displays two minima separated by a saddle point. The spectra also display several anti-crossings, which arise due to the overlap of gate-confined and magnetically-confined states.