Long-range transport of 2D excitons with acoustic waves

TL;DR

This paper demonstrates that surface acoustic waves can effectively drive long-range, directional transport of interlayer excitons in 2D semiconductors, surpassing diffusion limits and enabling excitonic device applications.

Contribution

It introduces a contact-free method using acoustic waves to control and extend exciton transport in 2D materials, surpassing previous diffusion constraints.

Findings

SAW-driven excitonic transport reaches 20 mm at 100 K

Transport distance exceeds diffusion length by at least ten times

Transition from diffusion-limited to acoustic field-driven regime with temperature

Abstract

Excitons are elementary optical excitation in semiconductors. The ability to manipulate and transport these quasiparticles would enable excitonic circuits and devices for quantum photonic technologies. Recently, interlayer excitons in 2D semiconductors have emerged as a promising candidate for engineering excitonic devices due to their long lifetime, large exciton binding energy, and gate tunability. However, the charge-neutral nature of the excitons leads to weak response to the in-plane electric field and thus inhibits transport beyond the diffusion length. Here, we demonstrate the directional transport of interlayer excitons in bilayer WSe2 driven by the propagating potential traps induced by surface acoustic waves (SAW). We show that at 100 K, the SAW-driven excitonic transport is activated above a threshold acoustic power and reaches 20 mm, a distance at least ten times longer than the diffusion length and only limited by the device size. Temperature-dependent measurement reveals the transition from the diffusion-limited regime at low temperature to the acoustic field-driven regime at elevated temperature. Our work shows that acoustic waves are an effective, contact-free means to control exciton dynamics and transport, promising for realizing 2D materials-based excitonic devices such as exciton transistors, switches, and transducers up to room temperature.