Dynamic Mechanical\nModulation of WS<sub>2</sub> Monolayer\nby Standing Surface Acoustic Waves

Surface\nacoustic waves (SAWs) propagating on piezoelectric materials\ncarry large out-of-plane mechanical strain and strong in-plane electromagnetic\nfields, providing a fascinating hybrid platform for the manipulation\nof excitons in active media. The interaction of SAWs with two-dimensional\n(2D) semiconducting transition-metal dichalcogenide (TMD) monolayers\nhas recently garnered significant attention due to their extreme sensitivity\nto strain and electromagnetic near-fields, resulting in exciton ionization\nin lithium niobate (LiNbO<sub>3</sub>) based delay lines. In this\nstudy, we demonstrate an innovative approach to manipulate the optomechanical\nproperties of a tungsten disulfide (WS<sub>2</sub>) monolayer, based\non the excitation of standing SAWs in an acoustic resonator defined\non gallium arsenide (GaAs), a weak piezoelectric material. In contrast\nto previous reports on LiNbO<sub>3</sub> delay lines, our platform\nexhibits a resonant enhancement of the monolayer’s photoemission\ntogether with the imprinting of a discernible spatial structuring\nof the WS<sub>2</sub> luminescence in a one-dimensional (1D) periodic\npattern. By imaging a large monolayer flake driven at the resonator\nfrequency, we demonstrate that this optical modulation arises from\na periodic detachment of the monolayer from the substrate surface\ndue to the robust mechanical oscillations induced by the standing\nSAW pattern in high quality factor resonators. Our work establishes\nSAW resonators as an alternative paradigm to locally and reversibly\ntuning the optical and structural properties of TMD monolayers at\nroom temperature by micro/nanoscale control of mechanical fields.\nThis approach holds substantial potential for applications in the\nfield of optics and nanophotonics with tunable light-matter interactions.