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Moiré potential impedes interlayer exciton diffusion in van der Waals heterostructures
Junho Choi1, Wei-Ting Hsu1, Li-Syuan Lu2
1Department of Physics, Complex Quantum Systems, and Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA.
Science Advances
|September 24, 2020
Summary
Exciton diffusion in van der Waals heterostructures is tunable. Varying twist angles in WSe2/MoSe2 systems control exciton localization and diffusion, impacting energy transport in transition metal dichalcogenides.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Van der Waals heterostructures exhibit tunable properties due to moiré superlattices.
- Exciton diffusion is a key energy transport mechanism in transition metal dichalcogenides (TMDs).
- Previous studies suggested long exciton diffusion, but localization is also possible.
Purpose of the Study:
- To experimentally investigate the diverse phenomena of interlayer exciton diffusion in WSe2/MoSe2 heterostructures.
- To explore the influence of moiré superlattices and twist angles on exciton behavior.
- To understand energy transport dynamics in TMD heterobilayers.
Main Methods:
- Fabrication of WSe2/MoSe2 heterostructures using chemical vapor deposition and mechanical stacking.
- Accurate control and variation of twist angles between the constituent layers.
- Experimental characterization of interlayer exciton diffusion and localization phenomena.
Main Results:
- Demonstrated that interlayer excitons can be localized in large moiré supercells.
- Showed that reduced moiré periods (larger twist angles) enable exciton tunneling and longer diffusion.
- Observed the longest diffusion in commensurate heterostructures lacking a moiré superlattice.
Conclusions:
- The twist angle in TMD heterostructures critically controls interlayer exciton diffusion and localization.
- Tailoring moiré superlattices offers a pathway to engineer energy transport in van der Waals materials.
- This work reveals rich exciton dynamics crucial for optoelectronic applications.
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