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Ellipticity-Controlled Bright-Dark Coherence Transition in Monolayer WSe_{2}
Kang Lan1, Xiangji Cai2, Zhongxiao Man1
1Qufu Normal University, School of Physics and Physical Engineering, 273165, Qufu, China.
Physical Review Letters
|July 31, 2026
Summary
Researchers demonstrate that light polarization ellipticity controls exciton valley coherence in WSe2. This method allows selective generation and manipulation of bright and dark coherence, even with magnetic fields.
Area of Science:
- Condensed Matter Physics
- Quantum Optics
- Materials Science
Background:
- Exciton valley coherence is crucial for quantum information processing.
- Traditionally, linearly polarized (LP) light is used to generate coherence, while circularly polarized (CP) light is ineffective.
- Understanding the role of different exciton species (bright and dark) is key to controlling valley coherence.
Purpose of the Study:
- To develop a theoretical framework for controlling exciton valley coherence using light polarization.
- To investigate the selective generation of bright and dark coherence.
- To explore magnetic field effects on dark coherence manipulation.
Main Methods:
- Development of a unified, microscopically grounded open-quantum-system framework.
- Utilized a five-level model incorporating bright-dark exciton interactions in monolayer WSe2.
- Analyzed the impact of excitation field polarization ellipticity on valley coherence.
Main Results:
- Demonstrated that polarization ellipticity selectively controls bright and dark exciton coherence.
- LP light generates bright coherence, while CP light generates dark coherence.
- An out-of-plane magnetic field suppresses coherence decay, and an in-plane field enables optical readout of dark coherence.
Conclusions:
- Ellipticity-driven coherence transfer provides a powerful mechanism for accessing hidden dark exciton states.
- This work establishes a new pathway for harnessing bright-dark valley-coherence transitions in quantum control.
- The findings offer a novel approach to manipulating quantum states in 2D materials.
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