Acoustic Modulation of Excitonic Complexes in hBN/WSe2/hBN Heterostructures

The interaction of high-frequency surface acoustic waves (SAWs) and excitons in van der Waals heterostructures (vdWHs) offers challenging opportunities to explore novel quantum effects and functionalities. We probe the interaction of neutral excitons, trions, and biexcitons with SAWs in a hBN/WSe₂/hBN vdWH. We show that neutral excitons respond weakly to the SAW stimulus at 5 K. The remaining excitonic complexes, because of their lower binding energy or charged character, interact much more efficiently with the SAW piezoelectric field, particularly intra- and intervalley trions. At room temperature, the SAW can play a dual role (sometimes dissociating excitons and sometimes increasing the vdWH local doping density) which depends of the laser-induced photodoping of the vdWH prior to the SAW generation and the role of metastable energy states in the SAW-induced carrier dynamics. Our results shed light in the unexplored biexciton modulation with SAWs, important for 2D materials-based optoelectronic and energy harvesting devices.