Using hyperbolic metamaterials to strengthen microwave-magnon coupling in van der Waals antiferromagnet CrSBr

The van der Waals antiferromagnet CrSBr offers exciting opportunities due to its highly tunable magnons and strong magnon-exciton-photon coupling. We characterize the microwave response of CrSBr, showing the tunability of CrSBr magnons with an applied magnetic field. To enhance this microwave coupling we propose the use of a hyperbolic metamaterial cavity to realize broadband enhancement in the density of states for microwave photons. We layer metal and dielectric into a frustum pyramid and demonstrate its microwave absorption over a broad GHz range. Finally, we characterize the enhanced microwave response of CrSBr when placed on top of this hyperbolic structure. Results of microwave and optical characterization will be presented.