Tunable interactions between excitons and hybridized magnons in a layered semiconductor

The interaction between distinct excitations in solids is of both fundamental interest and technological importance. One such interaction is the coupling between an exciton, a Coulomb bound electron-hole pair, and a magnon, a collective spin excitation. The recent emergence of van der Waals magnetic semiconductors provides a platform for exploring these exciton-magnon interactions and their fundamental properties, such as strong correlation, as well as their photo-spintronic and quantum transduction applications. In this talk, I will demonstrate precise control of coherent exciton-magnon interactions in the layered magnetic semiconductor CrSBr. I will show how varying the direction of an applied magnetic field relative to the crystal axes breaks the rotational symmetry of the magnetic system. Thereby, one can tune not only the exciton coupling to the bright magnon, but also to an optically dark mode via magnon-magnon hybridization. Further, I will show how we modulated the exciton-magnon coupling and the associated magnon dispersion curves through the application of uniaxial strain. At the critical strain, a dispersionless dark magnon band emerges. The results I will present demonstrate unprecedented control of the opto-mechanical-magnonic coupling, and a step towards the predictable and controllable implementation of hybrid quantum magnonics.