Dielectric Engineering for Manipulating Exciton Transport in Semiconductor Monolayers

Area of Science:

• Condensed Matter Physics
• Materials Science
• Optoelectronics

Background:

• Atomically thin transition metal dichalcogenides (TMDs) exhibit unique optoelectronic properties.
• Exciton dynamics in TMDs are sensitive to their surrounding dielectric environment.
• Disordered dielectric media can significantly influence defect energy levels.

Purpose of the Study:

• Investigate the impact of dielectric screening from disordered media on exciton transport in WSe2 monolayers.
• Identify the cause of anomalous exciton diffusion in WSe2.
• Demonstrate control over exciton transport by engineering the dielectric environment.

Main Methods:

• Studied WSe2 monolayers with various dielectric environments.
• Analyzed exciton diffusion and energy dynamics.
• Engineered dielectric environment using graphene/hexagonal boron nitride (h-BN) moiré superlattice.

Main Results:

• Attributed anomalous exciton diffusion to modified defect state energy distributions.
• Successfully manipulated exciton transport by engineering the dielectric environment.
• Observed enhanced dielectric disorder effects at high excitation fluences, contributing to phonon drag.

Conclusions:

• Dielectric screening in disordered media is crucial for understanding exciton behavior in TMDs.
• Engineering the dielectric environment provides a pathway for controlling exciton transport.
• These findings are vital for developing advanced opto-excitonic devices.