Coherent terahertz magnon-phonon three-wave mixing in a layered antiferromagnet

TL;DR

This study demonstrates direct observation of coherent magnon-phonon three-wave mixing in a layered antiferromagnet using terahertz spectroscopy, revealing nonlinear interactions crucial for quantum control.

Contribution

It provides the first direct measurement of coherent magnon-phonon three-wave mixing in a 2D antiferromagnetic insulator, highlighting nonlinear couplings in the terahertz regime.

Findings

Resolved second- and third-order nonlinear responses of magnons.

Identified sum- and difference-frequency generation between magnons and phonons.

Established a foundation for quantum control of magnetic and vibrational excitations.

Abstract

The coherent nonlinear dynamics between collective excitations, such as magnons and phonons, drive emergent phenomena in quantum materials, yet their direct observation remains a central challenge. Here, using double-terahertz-pump optical-probe spectroscopy, we report the direct observation of coherent magnon-phonon three-wave mixing in the layered antiferromagnetic insulator FePS$_{3}$. We resolve both second- and third-order nonlinear responses of antiferromagnetic magnons and identify a suite of nonlinear couplings in two-dimensional (2D) coherent spectra, including definitive sum- and difference-frequency generation between magnons and phonons. These results lay the groundwork for exploiting coherent nonlinearities to entangle magnetic and vibrational excitations, opening avenues for quantum control and hybrid quantum technologies in the terahertz regime.