  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.
