Topological magnon-photon interaction for cavity magnonics

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. Reaching the strong coupling regime in cavity magnonics is impaired by quantum decoherence effects introduced by a large size of magnet required. By mediating it via a topological insulator, the authors propose an indirect coupling mechanism to enhance the magnon-photon interaction strength.

Automated summary

The study investigates the possibility of combining cavity magnonics and topological insulators by exploring hybrid cavity systems incorporating a ferromagnet and a topological insulator. The researchers find that the topological surface state efficiently mediates the coupling between the spin of the ferromagnet and the electric field of the cavity, which is different from the conventional magnetic dipole coupling. They refer to this coupling as topological magnon-photon interaction and show that it is significantly stronger than the conventional magnon-photon coupling. The proposed device has the potential to scale down and control the cavity system using electronics.