Chiral edge plasmons in quantum anomalous Hall insulators

TL;DR

This paper demonstrates that Berry curvature causes chiral edge plasmons in quantum anomalous Hall insulators, with their properties tunable by external fields and wave vector, providing insights for topological plasmonics.

Contribution

It reveals how Berry curvature induces unidirectional edge plasmons in quantum anomalous Hall insulators and explains recent experimental observations.

Findings

Berry curvature splits edge plasmons propagating in opposite directions.

Unidirectional edge plasmon can be controlled by external fields.

Group velocity of edge plasmons can change sign at large wave vectors.

Abstract

We find that the Berry curvature splits the edge plasmons propagating along the opposite directions in quantum anomalous Hall insulators even with vanishing Chern number. When the bulk is insulating, only one unidirectional edge plasmon mode survives whose direction can be changed by external fields. The unidirectional edge plasmon in the long-wavelength limit is acoustic and essentially determined by the anomalous Hall conductivity. The group velocity of the chiral edge plasmon would change its sign for a large wave vector, which originates from the k-quadratic correction to the effective mass. The impacts of the Fermi level and the wave vector on the bulk and edge plasmons are discussed. Our work provides a well quantitative explanation of the recent observation of the chiral edge plasmon in quantum anomalous Hall insulators and some insight into the application of realistic topological materials in chiral plasmonics.