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Hot excitons are usually neglected in optical spectroscopy in 2D semiconductors for the sake of momentum conservation, as the majority of hot excitons are out of light cones. In this letter, we elaborate the contribution of hot excitons to optical properties in monolayer transition metal dichalcogenides (TMDs) with photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy. With the intensity-dependent PL, temperature-dependent PL and PLE experiments combined with the simulations, we experimentally distinguish the influences of the exciton temperature and the lattice temperature in the PL spectrum. It is concluded that the acoustic phonon assisted photoluminescence accounts for the non-Lorentzian high energy tail of the PL spectrum and the hot exciton effect is significant even at linear optical properties of TMDs. Besides, the effective exciton temperature is found to be several tens of Kelvin higher than the lattice temperature at non-resonant optical excitation which may indicate that the exciton temperature needs to be carefully taken into account when considering the exciton related strong correlated phenomenon such as exciton condensation. Finally, we found the effective exciton temperature can be well tuned by excitation energy.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Hot excitons, photoluminescence spectroscopy, transition metal dichalcogenides

Date published: 2022-11-29

Publisher: Wiley

Journal:

• Natural Sciences (ISSN: 26986248) vol. 3 issue. 1 e20220035

Funding:

• Glaucoma Research Foundation 17300520

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1002/ntls.20220035

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Updated at: 2025-03-01 12:30:11 +0900

Published on MDR: 2025-03-01 12:30:12 +0900