Exciton–Plasmon Coupling in 2D Semiconductors Accessed by Surface Acoustic Waves

• Published in: ACS photonics Vol. 8; no. 6; pp. 1698 - 1704
• Main Authors: Fandan, Rajveer, Pedrós, Jorge, Calle, Fernando
• Format: Journal Article
• Language: English
• Published: American Chemical Society 16-06-2021
• Subjects: plexciton; black phosphorus; strong coupling; MoS2; surface acoustic wave; exciton−plasmon polariton
• ISSN: 2330-4022; 2330-4022
• DOI: 10.1021/acsphotonics.1c00173

We theoretically demonstrate the strong coupling between excitons in 2D semiconductors and surface plasmons in a thin metal film forming exciton–plasmon polaritons (or plexcitons) that can be optically accessed by means of a surface acoustic wave (SAW). The strain field of the SAW creates a dynamic diffraction grating, providing the momentum match for the surface plasmons, whereas the piezoelectric field that could dissociate the excitons is canceled out by the metal. This is exemplified for monolayer MoS2 and mono- and few-layer black phosphorus on top of a thin silver layer on a LiNbO3 piezoelectric substrate, providing Rabi splittings of 100–150 meV. Thus, we demonstrate that SAWs are powerful tools to modulate the optical properties of supported 2D semiconductors by means of the high-frequency localized deformations tailored by the acoustic transducers, that can serve as electrically switchable launchers of propagating plexcitons suitable for active high-speed nanophotonic applications.