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Interlayer Coupling and Gate-Tunable Excitons in Transition Metal Dichalcogenide Heterostructures
Shiyuan Gao1, Li Yang1,2, Catalin D Spataru3
1Department of Physics, Washington University in St. Louis , St. Louis, Missouri 63136, United States.
Nano Letters
|November 23, 2017
Summary
Bilayer van der Waals heterostructures exhibit tunable interlayer excitons. Applying a gate field significantly alters exciton properties like oscillator strength and lifetime, paving the way for advanced 2D optoelectronic devices.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Quantum Chemistry
Background:
- Bilayer van der Waals (vdW) heterostructures, such as MoS2/WS2 and MoSe2/WSe2, are of significant interest.
- These materials feature type II band alignments and form interlayer excitons as the lowest-energy excitonic state.
Purpose of the Study:
- To investigate the electronic and optical properties of bilayer vdW heterostructures.
- To reveal the influence of interlayer coupling on excited-state properties, including band alignment and excitonic behavior.
- To explore the tunability of interlayer excitons using external gate fields.
Main Methods:
- First-principles calculations using the GW+Bethe-Salpeter Equation (BSE) method.
- Analysis of electronic band structure and optical properties.
- Development of a simplified physical model for tunability.
Main Results:
- Interlayer coupling plays a crucial role in determining excited-state properties.
- Low-energy excitons in these heterostructures are widely tunable via a vertical gate field.
- Dipole oscillator strength and radiative lifetime of the lowest energy exciton can be modulated by over an order of magnitude with practical gate fields.
Conclusions:
- The study clarifies the physical picture of interlayer excitons in bilayer vdW heterostructures.
- A simple model effectively captures the physics of gate-field tunability.
- The findings predict a broad range of gate-tunable excited-state properties for 2D optoelectronic devices.
Keywords:
first-principles calculationinterlayer excitontransition metal dichalcogenidesvan der Waals heterostructureMore Related Videos
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