Enhanced Exciton Drift Transport through Suppressed Diffusion in One-Dimensional Guides

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Investigating exciton dynamics is crucial for understanding energy transport in low-dimensional materials.
• Room-temperature operation is essential for practical applications of excitonic devices.
• Strain engineering offers a method to control quantum phenomena in 2D materials.

Purpose of the Study:

• To investigate the drift-diffusion dynamics of excitons in a 1D WSe2 monolayer at room temperature.
• To explore the impact of spatial energy modulation via local strain on exciton transport.
• To analyze deviations from the Einstein relation and the role of defect interactions.

Main Methods:

• Fabrication of a 1D exciton guide in a WSe2 monolayer using local strain.
• Measurement of exciton transport properties under varying potential gradients.
• Analysis of exciton temperature, diffusion, and drift velocity at different exciton densities.

Main Results:

• Observed a massive deviation from the Einstein relation, attributed to exciton capture by defects.
• Demonstrated enhanced drift transport visibility (38%) due to defect-mediated confinement.
• Estimated exciton mobility at room temperature to be 169 ± 39 cm^2/(eV s).
• Found that exciton drift velocity increases with exciton density due to many-body effects.

Conclusions:

• Spatial strain engineering effectively controls exciton transport and confinement in WSe2 monolayers.
• Exciton capture by defects significantly alters diffusion dynamics and enhances drift visibility.
• Exciton mobility and drift velocity exhibit distinct dependencies on exciton density at room temperature.