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Abstract Strong many-body interaction in two-dimensional transitional metal dichalcogenides provides a unique platform to study the interplay between different quasiparticles, such as prominent phonon replica emission and modified valley-selection rules. A large out-of-plane magnetic field is expected to modify the exciton-phonon interactions by quantizing excitons into discrete Landau levels, which is largely unexplored. Here, we observe the Landau levels originating from phonon-exciton complexes and directly probe exciton-phonon interaction under a quantizing magnetic field. Phonon-exciton interaction lifts the inter-Landau-level transition selection rules for dark trions, manifested by a distinctively different Landau fan pattern compared to bright trions. This allows us to experimentally extract the effective mass of both holes and electrons. The onset of Landau quantization coincides with a significant increase of the valley-Zeeman shift, suggesting strong many-body effects on the phonon-exciton interaction. Our work demonstrates monolayer WSe2as an intriguing playground to study phonon-exciton interactions and their interplay with charge, spin, and valley.
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Electric-field-tunable intervalley excitons and phonon replicas in bilayer WSe2
We report the direct observation of intervalley exciton between the Q conduction valley and Γ valence valley in bilayer WSe2 by photoluminescence. The QΓ exciton lies at ~18 meV below the QK exciton and dominates the luminescence of bilayer WSe2. By measuring the exciton spectra at gate-tunable electric field, we reveal different interlayer electric dipole moments and Stark shifts between QΓ and QK excitons. Notably, we can use the electric field to switch the energy order and dominant luminescence between QΓ and QK excitons. Both QΓ and QK excitons exhibit pronounced phonon replicas, in which two-phonon replicas outshine the one-phonon replicas due to the existence of (nearly) resonant exciton-phonon scatterings and numerous two-phonon scattering paths. We can simulate the replica spectra by comprehensive theoretical modeling and calculations. The good agreement between theory and experiment for the Stark shifts and phonon replicas strongly supports our assignment of QΓ and QK excitons.
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- Award ID(s):
- 1945660
- PAR ID:
- 10286161
- Date Published:
- Journal Name:
- ArXivorg
- ISSN:
- 2331-8422
- Page Range / eLocation ID:
- arXiv:2101.11161
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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