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arXiv · 2410.14780

Strong photon coupling to high-frequency antiferromagnetic magnons via topological surface states

Henrik T. Kaarbø·Henning G. Hugdal·Sol H. Jacobsen
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Abstract

We show strong coupling between antiferromagnetic magnons and microwave cavity photons at both high and externally controllable magnon frequencies. Using the fully quantum mechanical path-integral method, we study an antiferromagnetic insulator (AFM) interfaced with a topological insulator (TI), taking Bi$_2$Se$_3$--MnSe as a representative example. We show that the mutual coupling of the spin-polarized surface states of the TI to both the squeezed magnons and the circularly polarized cavity photons results in a Chern-Simons term that activates the stronger electric, rather than magnetic, dipole coupling. Moreover, a squeezing-mediated enhancement of the coupling is achieved due to the unequal interfacial exchange coupling to the AFM sublattices, resulting in a coupling strength up to several orders stronger than for direct magnon-photon coupling. While direct cavity-AFM coupling has so far been limited in its applicability due to weak or low frequency coupling, this result may advance the utilization of high-frequency cavity magnonics and enable its incorporation into quantum information technology.

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Henrik T. Kaarbø, Henning G. Hugdal, Sol H. Jacobsen. 2024-10-18. Strong photon coupling to high-frequency antiferromagnetic magnons via topological surface states. https://doi.org/10.1103/9sxt-6749

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