Bright and dark singlet excitons via linear and two-photon spectroscopy in monolayer transition metal dichalcogenides
- Princeton Univ., Princeton, NJ (United States)
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Columbia Univ., New York, NY (United States)
We discuss the linear and two-photon spectroscopic selection rules for spin-singlet excitons in monolayer transition-metal dichalcogenides. Our microscopic formalism combines a fully k-dependent few-orbital band structure with a many-body Bethe-Salpeter equation treatment of the electron-hole interaction, using a model dielectric function. We show analytically and numerically that the single-particle, valley-dependent selection rules are preserved in the presence of excitonic effects. Furthermore, we definitively demonstrate that the bright (one-photon allowed) excitons have s-type azimuthal symmetry and that dark p-type excitons can be probed via two-photon spectroscopy. Thus, the screened Coulomb interaction in these materials substantially deviates from the 1/ε₀r form; this breaks the “accidental” angular momentum degeneracy in the exciton spectrum, such that the 2p exciton has a lower energy than the 2s exciton by at least 50 meV. We compare our calculated two-photon absorption spectra to recent experimental measurements.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC00112704; SC0012704
- OSTI ID:
- 1213377
- Alternate ID(s):
- OSTI ID: 1209848
- Report Number(s):
- BNL-108047-2015-JA; R&D Project: 16068; KC0403020
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 92, Issue 8; ISSN 1098-0121
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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