Cavity-mediated coupling of antiferromagnetic spin waves

TL;DR

This paper demonstrates that two antiferromagnetic oscillators inside an electromagnetic cavity can couple via terahertz modes, forming hybrid magnon-polariton modes, with potential applications in quantum and communication technologies.

Contribution

It provides the first systematic experimental and theoretical study of cavity-mediated coupling of antiferromagnetic spin waves in hematite crystals.

Findings

Coupling observed between two hematite oscillators via cavity modes

Hybrid magnon-polariton modes formed and characterized

Coupling strength depends on temperature and separation distance

Abstract

Coupling of space-separated oscillators is interesting for quantum and communication technologies. In this work, it is shown that two antiferromagnetic oscillators placed inside an electromagnetic cavity couple cooperatively to its terahertz modes and, in effect, hybridized magnon-polariton modes are formed. This is supported by a systematic study of reflection spectra from two parallel-plane slabs of hematite ($\alpha$-Fe$_2$O$_3$), measured as a function of their temperatures and separation distance, and modeled theoretically. The mediating cavity was formed by the crystals themselves and the experiment was performed in a practical distance range of a few millimetres and above room temperature. Cavity-mediated coupling allows for engineering of complex resonators controlled by their geometry and by sharing properties of their components.