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Control of the Bright-Dark Exciton Splitting Using the Lamb Shift in a Two-Dimensional Semiconductor
1Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077 Toulouse, France.
Physical Review Letters
|September 29, 2023
Summary
We tuned exciton fine structure in WSe2 van der Waals heterostructures by controlling optical modes. This Lamb shift, influenced by vacuum fluctuations, alters bright-dark exciton splitting and linewidth.
Area of Science:
- Condensed Matter Physics
- Quantum Optics
- Materials Science
Background:
- Exciton fine structure in 2D materials is crucial for optoelectronic applications.
- Van der Waals heterostructures offer tunable properties.
- Vacuum fluctuations significantly impact quantum systems.
Purpose of the Study:
- Investigate exciton fine structure in WSe2 heterostructures.
- Tune the energy splitting between bright and dark excitons.
- Understand the role of vacuum fluctuations and optical modes.
Main Methods:
- Photoluminescence spectroscopy to measure energy splitting (Δ).
- Fabrication of WSe2-based van der Waals heterostructures.
- Tuning the density of optical modes at the semiconductor monolayer.
Main Results:
- Demonstrated tunable bright-dark exciton energy splitting (Δ) by a few meV.
- Observed significant Lamb shift of the optically active exciton due to vacuum fluctuations.
- Measured strong variations in bright exciton radiative linewidth via the Purcell effect.
Conclusions:
- Excitons exhibit strong sensitivity to local vacuum field fluctuations.
- A classical electrodynamical model accurately describes the observed phenomena.
- Bright-dark splitting control in weak light-matter coupling is achievable and broadly applicable to semiconductor structures.
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