Topological magnon-photon interaction for cavity magnonics

TL;DR

This paper introduces a novel topological magnon-photon interaction in cavity systems combining ferromagnets and topological insulators, showing it is stronger and more controllable than conventional methods, opening new avenues for quantum device engineering.

Contribution

It proposes and analyzes a new topological magnon-photon coupling mediated by surface electrons, which surpasses traditional magnetic dipole coupling in strength and controllability.

Findings

Topological surface states mediate electric dipole coupling.

The coupling is an order of magnitude stronger than conventional.

Sign of the coupling can be manipulated electronically.

Abstract

The study of cavity magnonics and topological insulators has made significant advances over the past decade, however the possibility of combining the two fields is still unexplored. Here, we explore such connection by investigating hybrid cavity systems that incorporate both a ferromagnet and a topological insulator. We find that electrons in the topological surface state efficiently mediate the effective electric dipole coupling between the spin of the ferromagnet and the electric field of the cavity, in contrast with the conventional cavity magnonics theory based on magnetic dipole coupling. We refer to this coupling as topological magnon-photon interaction, estimating it one order of magnitude stronger than the conventional magnon-photon coupling, and showing that its sign can be manipulated. We discuss the potential of our proposed device to allow for scaling down and controlling the cavity system using electronics. Our results provide solid ground for exploring the functionalities enabled by merging cavity magnonics with topological insulators.