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Twist Angle-Dependent Interlayer Exciton Lifetimes in van der Waals Heterostructures
Junho Choi1, Matthias Florian2, Alexander Steinhoff2
1Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, Texas 78712, USA.
Physical Review Letters
|February 12, 2021
Summary
Twist angle in transition metal dichalcogenide bilayers controls exciton dynamics. Varying twist angles significantly alters interlayer exciton lifetimes, offering new avenues for "twistronics" applications.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Optics
Background:
- Van der Waals (vdW) heterostructures, formed by stacking transition metal dichalcogenide monolayers, exhibit tunable exciton properties.
- Exciton dynamics in these systems are influenced by vertical and lateral confinement, with twist angle emerging as a key control parameter.
Purpose of the Study:
- To investigate the impact of twist angle on exciton dynamics in MoSe_{2}/WSe_{2} twisted bilayers (TBLs).
- To elucidate the mechanisms governing interlayer exciton radiative lifetimes and their dependence on twist angle.
Main Methods:
- Experimental measurements of interlayer exciton lifetimes in MoSe_{2}/WSe_{2} TBLs across varying twist angles (1° to 3.5°).
- Theoretical modeling using a low-energy continuum model to separate contributions to exciton lifetimes.
Main Results:
- Interlayer exciton lifetimes in MoSe_{2}/WSe_{2} TBLs varied by an order of magnitude with twist angle.
- Identified momentum space shifts to indirect transitions and moiré potential modulation as key factors influencing exciton lifetimes.
- Predicted distinct temperature dependencies of exciton lifetimes for different twist angles, with partial experimental validation.
Conclusions:
- The twist angle is a critical parameter for controlling exciton dynamics in vdW heterostructures.
- Understanding twist angle-dependent exciton lifetimes expands the scope of
- twistronics
- beyond ground states to optically excited states.
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