Enhanced cavity magnonics with easy-axis ferromagnet and topological insulators*

Cavity magnonic systems have emerged as a promising setup to control and probe magnons using their coherent interaction with cavity photons. The main challenge of this approach is that magnetic interaction between the cavity photon and the magnet is typically weak. In this talk, we present schemes to engineer the enhanced magnon-photon coupling strength beyond the typical strategy of collective enhancement either by using the intrinsic property of the magnet or by creating a heterostructure. The first strategy is to use magnetic anisotropy of the easy-axis ferromagnet [1]. Here, we demonstrate that the magnon squeezing and the magnon-photon coupling strength can be critically enhanced by tuning a static magnetic field to induce a magnonic superradiant phase transition. The second strategy is to use a heterostructure of a topological insulator and a ferromagnet [2]. In this setup, the topological insulator acts as a glue that strongly couples the magnon to the electric field of the cavity photons, resulting in an order of magnitude increase in the coupling strength compared to the conventional magnetic dipole coupling. Our work paves the way to develop unique capabilities of cavity magnonics by engineering magnetic devices.

 

[1] J. M. Lee, H.-W. Lee, and M. -J. Hwang, Cavity magnonics with easy-axis ferromagnet: critically enhanced magnon squeezing and light-matter interaction, arXiv:2305.08119

[2] J. M. Lee, M. -J. Hwang, and H.-W. Lee, Topological magnon-photon interaction for cavity magnonics, Communications Physics, 6, 194 (2023)