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Low dimensionality has non-trivial effects on Coulomb interaction. One attractive platform to investigate 2D-Coulomb interaction is the excitons in monolayer transition metal dichalcogenides (1L-TMDs). 1L-TMD excitons are known to have non-hydrogenic level structures. However, no empirical rule that universally describes exciton level structures in various 1L-TMD systems has been obtained from experiments. Here, we conducted sum frequency generation spectroscopies on four 1L-MX2 (M=Mo, W, X=S, Se) thin films encapsulated by hBN, and simultaneously observed s-series and p-series exciton levels. From the obtained energies, we extracted excitonic parameters, such as binding energies and average radii, with help of numerical calculations considering dielectric screening in 2D and band structure. We found a simple and non-trivial power-law scaling between obtained excitonic parameters. The power-law scaling is understood as an approximate form of the virial theorem which strictly holds for 3D hydrogen models. This result indicates that dielectric screening of hBN is the main factor that governs 1L-TMD exciton level structure.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Excitons, sum frequency generation spectroscopy, dielectric screening

Date published: 2024-11-08

Publisher: Springer Science and Business Media LLC

Journal:

• Scientific Reports (ISSN: 20452322) vol. 14 issue. 1 27286

Funding:

• Japan Society for the Promotion of Science JP17H06124
• Japan Society for the Promotion of Science JP21H05233
• Japan Society for the Promotion of Science JP20H02573
• Japan Science and Technology Agency JPMJMI17F2
• Japan Science and Technology Agency JPMJCR17I5
• Ministry of Education, Culture, Sports, Science and Technology JPMXS0118067634

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

MDR DOI:

First published URL: https://doi.org/10.1038/s41598-024-77625-x

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Updated at: 2025-02-05 12:30:34 +0900

Published on MDR: 2025-02-05 12:30:34 +0900