ORCID Profile
0000-0003-3712-371X
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Publisher: IOP Publishing
Date: 16-02-2023
Abstract: Excitons in thin layers of semiconducting transition metal dichalcogenides are highly subject to the strongly modified Coulomb electron-hole interaction in these materials. Therefore, they do not follow the model system of a two-dimensional hydrogen atom. We investigate experimentally and theoretically excitonic properties in both the monolayer (ML) and the bilayer (BL) of MoSe 2 encapsulated in hexagonal BN. The measured magnetic field evolutions of the reflectance contrast spectra of the MoSe 2 ML and BL allow us to determine g -factors of intralayer A and B excitons, as well as the g -factors of the interlayer exciton. We explain the dependence of g -factors on the number of layers and excitation state can be explained using first principles calculations. Furthermore, we demonstrate that the experimentally measured ladder of excitonic s states in the ML can be reproduced using the k·p approach with the Rytova-Keldysh potential that describes the electron-hole interaction. In contrast, the analogous calculation for the BL case require taking into account the out-of-plane dielectric response of the MoSe 2 BL.
Publisher: Springer Science and Business Media LLC
Date: 23-08-2021
DOI: 10.1038/S41598-021-95700-5
Abstract: Two-dimensional layered materials offer the possibility to create artificial vertically stacked structures possessing an additional degree of freedom— the interlayer twist . We present a comprehensive optical study of artificially stacked bilayers (BLs) MoS $$_2$$ 2 encapsulated in hexagonal BN with interlayer twist angle ranging from 0 $$^{\\circ }$$ ∘ to 60 $$^{\\circ }$$ ∘ using Raman scattering and photoluminescence spectroscopies. It is found that the strength of the interlayer coupling in the studied BLs can be estimated using the energy dependence of indirect emission versus the A $$_\\text {1g}$$ 1g –E $$_\\text {2g}^1$$ 2g 1 energy separation. Due to the hybridization of electronic states in the valence band, the emission line related to the interlayer exciton is apparent in both the natural (2H) and artificial (62 $$^\\circ $$ ∘ ) MoS $$_2$$ 2 BLs, while it is absent in the structures with other twist angles. The interlayer coupling energy is estimated to be of about 50 meV. The effect of temperature on energies and intensities of the direct and indirect emission lines in MoS $$_2$$ 2 BLs is also quantified.
Location: China
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