Carrier-mediated optomechanical forces in semiconductor nanomembranes with coupled quantum wells

In the majority of optomechanical experiments, the interaction between light and mechanical motion is mediated by radiation pressure, which arises from momentum transfer of reflecting photons. This is an inherently weak interaction, and optically generated carriers in semiconductors have been predicted to be the mediator of different and potentially much stronger forces. Here we demonstrate optomechanical forces induced by electron-hole pairs in coupled quantum wells embedded into a free-free nanomembrane. We identify contributions from the deformation-potential and piezoelectric coupling and observe optically driven motion more than 500 times larger than expected from radiation pressure. The amplitude and phase of the driven oscillations are controlled by an applied electric field, which tunes the carrier lifetime to match the mechanical period. Our work opens perspectives for not only enhancing the optomechanical interaction in a range of experiments, but also for interfacing mechanical objects with complex macroscopic quantum objects, such as excitonic condensates.