Anomalous Interlayer Exciton Diffusion in WS₂/WSe₂ Moiré Heterostructure.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Van der Waals heterostructures offer tunable electronic properties through controlled stacking.
• Exciton transport in these materials is crucial for optoelectronic applications.
• Understanding exciton dynamics in moiré potentials is key to device design.

Purpose of the Study:

• Investigate exciton diffusion in WS2/WSe2 van der Waals heterostructures.
• Explore the temperature dependence of exciton transport.
• Elucidate the role of moiré potentials and lattice dynamics in exciton diffusion.

Main Methods:

• Fabrication of WS2/WSe2 van der Waals heterostructures.
• Spatially and temporally resolved photoluminescence spectroscopy (30–250 K).
• Ab initio theory and molecular dynamics simulations.

Main Results:

• Observed distinct interlayer excitons for parallel and antiparallel stacking.
• Measured exciton diffusivity decreases with temperature but plateaus below 90 K.
• Classical models failed to explain the observed anomalous diffusion.

Conclusions:

• Low-energy phonons (phasons) in moiré heterostructures are critical for anomalous exciton diffusion.
• The moiré potential landscape is dynamic even at low temperatures.
• Phason modes facilitate efficient energy transport via excitons.