We employed Surface Acoustic Waves (SAWs) to manipulate excitonic states in MoSe2 and MoS2 monolayers (MLs), as illustrated in the figure below. By transferring the MLs to high dielectric constant LiNbO3 substrates, we have shown how the SAW strain and piezoelectric field modifies the light emission of neutral and negatively charged excitonic states (trions). As the SAW in-plane piezoelectric field increases, excitons and trions are efficiently dissociated, leading to a strong photoluminescence quenching. In particular, we have observed for the first time the red-shift of the exciton emission lines induced by the SAW piezoelectric field, the so-called Stark effect (see the figure below). The experimental results were complemented by finite element simulations, which allowed us to experimentally determine the in-plane polarizability of neutral and negatively charged excitons in MoSe2 MLs.
This work has been published in ACS Nano under the title “Acoustically driven Stark effect in transition metal dichalcogenide monolayers“. To view the whole manuscript click HERE.