Exciton Dressing by Extreme Nonlinear Magnons in a Layered Semiconductor

TL;DR

This paper demonstrates nonlinear coupling between excitons and magnons in a layered magnetic semiconductor, enabling tunable optical sidebands and magnon amplification, with potential applications in magnonics and quantum technologies.

Contribution

It introduces the observation of exciton states dressed by multiple magnon harmonics and tunable frequency generation in a layered antiferromagnetic semiconductor, advancing opto-magnonic device capabilities.

Findings

Exciton states dressed by up to 20 magnon harmonics.

Tunable optical sidebands via sum- and difference-frequency generation.

Resonance tuning leads to magnon parametric amplification.

Abstract

Collective excitations presenting nonlinear dynamics are fundamental phenomena with broad applications. A prime example is nonlinear optics, where diverse frequency mixing processes are central to communication, sensing, wavelength conversion, and attosecond physics. Leveraging recent progress in van der Waals magnetic semiconductors, we demonstrate nonlinear opto-magnonic coupling by presenting exciton states dressed by up to 20 harmonics of magnons, resulting from their nonlinearities, in the layered antiferromagnetic semiconductor CrSBr. We also create tunable optical side bands from sum- and difference-frequency generation between two optically bright magnon modes under symmetry breaking magnetic fields. Moreover, the observed difference-frequency generation mode can be continuously tuned into resonance with one of the fundamental magnons, resulting in parametric amplification of magnons. These findings realize the modulation of the optical frequency exciton with the extreme nonlinearity of magnons at microwave frequencies, which could find applications in magnonics and hybrid quantum systems, and provide new avenues for implementing opto-magnonic devices.