Exciton-Plasmon Coupling in 2D Semiconductors by Surface Acoustic Waves

TL;DR

This paper theoretically shows how surface acoustic waves can enable strong coupling between excitons in 2D semiconductors and surface plasmons, creating tunable plexcitons for advanced nanophotonic devices.

Contribution

It introduces a novel method using surface acoustic waves to achieve strong exciton-plasmon coupling in 2D materials, with potential for high-speed optoelectronic applications.

Findings

Achieved Rabi splittings of 100-150 meV in modeled systems.

Demonstrated dynamic diffraction grating via SAWs for momentum matching.

Proposed electrically switchable plexciton launchers for nanophotonics.

Abstract

We theoretically demonstrate the coupling between excitons in 2D semiconductors and surface plasmons in a thin metal film by means of a surface acoustic wave (SAW), proving that the generated exciton-plasmon polaritons (or plexcitons) are in the strong coupling regime. 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 cancelled out by the metal. This is exemplified for monolayer MoS$\mathrm{_{2}}$ and mono- and few-layer black phosphorus on top of a thin silver layer on a LiNbO$\mathrm{_{3}}$ 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.