Plasmon-magnon interactions in two-dimensional honeycomb magnets

TL;DR

This paper develops a microscopic theory for plasmon-magnon interactions in doped 2D honeycomb ferromagnets, revealing potential for novel charge-spin coupling phenomena in these materials.

Contribution

It introduces a double random phase approximation-based theory for plasmon-magnon interactions in 2D honeycomb magnets, a novel approach in this context.

Findings

The theory predicts energy and momentum matching conditions for plasmon-magnon interactions.

Potential to observe these interactions in materials like Cr2Ge2Te6.

Highlights the role of optical spin-wave and plasmon modes in 2D magnets.

Abstract

Two-dimensional honeycomb ferromagnets offer the unprecedented opportunity to study interactions between collective modes that in standard bulk ferromagnets do not cross paths. Indeed, they harbor an optical spin-wave branch, i.e. a spin wave which disperses weakly near the Brillouin zone center. When doped with free carriers, they also host the typical gapless plasmonic mode of 2D itinerant electron/hole systems. When the plasmon branch meets the optical spin-wave branch, energy and momentum matching occurs, paving the way for interactions between the charge and spin sector. In this Letter we present a microscopic theory of such plasmon-magnon interactions, which is based on a double random phase approximation. We comment on the possibility to unveil this physics in recently isolated 2D honeycomb magnets such as ${\rm Cr}_2{\rm Ge}_2{\rm Te}_6$.