Optomagnonics in dispersive media: magnon-photon coupling enhancement at the epsilon-near-zero frequency

TL;DR

This paper proposes a new platform using epsilon-near-zero media to achieve strong coupling between magnons and photons, enabling potential quantum device applications through enhanced optomagnonic interactions.

Contribution

It introduces a phenomenological model for magnon-photon coupling in dispersive epsilon-near-zero media and predicts conditions for reaching the single-magnon strong coupling regime.

Findings

Coupling can be comparable to magnon frequency in epsilon-near-zero media.

Single-magnon strong coupling regime is achievable with current technology.

Nonlinear energy spectrum can be observed via magnon sidebands in photon spectra.

Abstract

Reaching strong light-matter coupling in solid-state systems has been long pursued for the implementation of scalable quantum devices. Here, we put forward the concept of a platform capable of achieving strong coupling between magnetic excitations (magnons) and optics based in an epsilon-near-zero medium, that's it, a medium in which the permittivity is close to zero. We adopt a phenomenological approach to quantize the electromagnetic field inside a dispersive magnetic medium and obtain a Hamiltonian describing the interaction between photons and magnons and the frequency-dependent coupling. We predict that, in the epsilon-near-zero regime, the single-magnon photon optomagnonic coupling can be comparable to the uniform magnon's frequency for small magnetic volumes. For state-of-the-art illustrative values, this would correspond to achieving the single-magnon strong coupling regime, where the coupling rate is larger than all the decay rates. Finally, we show that the non-linear energy spectrum intrinsic to this coupling regime regime can be probed via the characteristic multiple magnon sidebands in the photon power spectrum.