Magnon-polarons in van der Waals antiferromagnet FePS3

TL;DR

This study demonstrates the formation of magnon-polarons in FePS3, a van der Waals antiferromagnet, revealing strong magnon-phonon hybridization with potential applications in antiferromagnetic optospintronics.

Contribution

It reports the observation of magnon-phonon hybridization and magnon polarons in FePS3, highlighting their tunability and interaction with terahertz photons, advancing understanding of light-matter coupling in 2D antiferromagnets.

Findings

Observation of avoided crossing indicating magnon-phonon hybridization

Detection of magnon polarons via Raman scattering

Coupling of magnon polarons to terahertz photons

Abstract

The hybridization of magnons (spin waves) with phonons, if sufficiently strong and comprising long wavelength excitations, may offer a new playground when manipulating the magnetically ordered systems with light. Applying a magnetic field to a quasi-2D antiferromagnet, FePS3, we tune the magnon-gap excitation towards coincidence with the initially lower-in-energy phonon modes. Hybrid magnon-phonon modes, the magnon polarons are unveiled with demonstration of a pronounced avoided crossing between the otherwise bare magnon and phonon excitations. The magnon polarons in FePS3 are primary traced with Raman scattering experiments, but, as we show, they also couple directly to terahertz photons, what evokes their further explorations in the domain of antiferromagnetic optospintronics.