Making waves with excitons and magnons

Ziel

Van der Waals magnetic semiconductors were recently found to host strongly bound optical quasiparticles (excitons) and long-lived magnetic excitations (magnons). With their interactions, this project is going to make WAVES, a new experiment designed for the study of coupled quasiparticles in solids. By smartly combining optical lasers with microwaves and magnetic fields, WAVES is able to control excitons and magnons with remarkable precision: Since microwave antennas are used to excite propagating magnon waves with coherence far greater than the typical size of an optically generated exciton distribution, spatially structured light fields turn excitons into fully programmable scattering landscapes for magnons. A new stroboscopic imaging technique is introduced to show that many hallmark experiments of quantum physics can be recreated in this new experiment. Having demonstrated, for instance, diffraction of magnons at exciton double slits or their confinement inside exciton cavities, WAVES draws inspiration from cold atomic gases and photonics when studying magnons in excitonic lattices with variable symmetry and topology. Efforts in parallel employ ultrafast microscopy and the emission of excitons to trace exciton transport into unexplored regimes. The focus lies on ultrathin samples where broken reciprocity could materialize novel connections between excitons, magnons, and transport phenomena related to quantum metric and altermagnetism. Finally, in a holistic approach, both quasiparticles will be measured in space and time to demonstrate novel interaction effects, such as the recoil of excitons scattered by magnon waves. Overall, WAVES' opportunities for discovery at the frontiers of semiconductor physics, magnetism, and optics are as exceptional as their potential for opening new pathways for quasiparticles in solids.