Anomalous Bloch oscillation and electrical switching of edge magnetization in bilayer graphene nanoribbon

TL;DR

This paper reports an anomalous Bloch oscillation in topological edge bands of bilayer graphene nanoribbons, enabling electrical switching of edge magnetization through a novel electron oscillation mechanism.

Contribution

It introduces a new type of Bloch oscillation in topological edge states and demonstrates its potential for electrical control of edge magnetization in bilayer graphene.

Findings

Observation of anomalous Bloch oscillation in edge bands

Electron oscillation between edges of different configurations

Electrical switching of edge magnetization achieved

Abstract

Graphene features topological edge bands that connect the pair of Dirac points through either sectors of the 1D Brillouin zone depending on edge configurations (zigzag or bearded). Because of their flat dispersion, spontaneous edge magnetisation can arise from Coulomb interaction in graphene nanoribbons, which has caught remarkable interest. We find an anomalous Bloch oscillation in such edge bands, in which the flat dispersion freezes electron motion along the field direction, while the topological connection of the bands through the bulk leads to electron oscillation in the transverse direction between edges of different configurations on opposite sides/layers of a bilayer ribbon. Our Hubbard-model mean-field calculation shows that this phenomenon can be exploited for electrical switching of edge magnetisation configurations.