YRLG Workshop: Correlation and Topology in magnetic materials, July 16th - 18th 2024
Geoffrey Diederich
The nonlinear dynamics of collective excitations offer both intriguing fundamental phenomena and significant practical applications. A prime illustration is the field of nonlinear optics, where diverse frequency mixing processes are central to advancing communication, sensing, imaging, and photonic technologies. In this talk, I will demonstrate the creation of exciton floquet states in the near infrared by coupling to abundant magnon modes generated by extreme magnon nonlinearities in the microwave regime in the layered antiferromagnetic semiconductor CrSBr. Launching the coherent magnon with an above-gap pump laser pulse, we observe a series of magnon sidebands with respect to the exciton resonance in transient optical reflectivity signals. Remarkably, over 20 harmonics (or over 600 GHz in frequency) of the optical side bands are observed, resulting from high-harmonic magnon generation. By the application of symmetry breaking magnetic fields, we then create two optically bright magnon modes. These two magnon modes produce sum and difference frequency generation (SFG & DFG), manifesting again as optical side bands. The DFG mode can be largely tuned by rotating the symmetry-breaking magnetic field. This tuning allows us to push the DFG mode into resonance with one of the fundamental magnons, and thus controllably induce parametric amplification. These findings herald a new paradigm in opto-nonlinear magnonic coupling for hybrid quantum magnonics.