Phenomenological model for long wavelength optical modes in transition-metal dichalcogenide monolayer

Transition metal dichalcogenides (TMDs) are an exciting family of 2D materials; a member of this family, MoS\(_2\), became the first measured monolayer semiconductor. In this article, a generalized phenomenological continuum model for the optical vibrations of the monolayer TMDs valid in the long-wa...

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Bibliographic Details
Published in:arXiv.org 2021-04
Main Authors: Trallero-Giner, C, Menéndez-Proupin, E, E Suárez Morell, Pérez-Alvarez, R, Santiago-Pérez, Darío G
Format: Article
Language:English
Subjects:
Atomic properties
Brillouin zones
Chalcogenides
Continuum modeling
Coupled modes
Deformation effects
Differential equations
Dispersion curve analysis
Electric fields
Mathematical models
Monolayers
Oscillations
Perturbation theory
Phonons
Polarons
Transition metal compounds
Two dimensional materials
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Summary:Transition metal dichalcogenides (TMDs) are an exciting family of 2D materials; a member of this family, MoS\(_2\), became the first measured monolayer semiconductor. In this article, a generalized phenomenological continuum model for the optical vibrations of the monolayer TMDs valid in the long-wavelength limit is developed. Non-polar oscillations involve differential equations for the phonon displacement vector that describe phonon dispersion up to a quadratic approximation. On the other hand, the polar modes satisfy coupled differential equations for the displacement vectors and the inner electric field. The two-dimensional phonon dispersion curves for in-plane and out-of-plane oscillations are thoroughly analyzed. This model provides an efficient approach to obtain the phonon dispersion curves at the \(\Gamma\)-point of the Brillouin zone of the whole family of TMD monolayers. The model parameters are fitted from density functional perturbation theory calculations. A detailed evaluation of the intravalley Pekar-Fr\"ohlich (P-F) and the \(A_1\)-homopolar mode deformation potential (Dp) coupling mechanisms is performed. The effects of metal ions and chalcogen atoms on polaron mass and binding energy are studied, considering these two contributions, the short-range Dp and P-F. It is argued that both mechanisms must be considered for a correct analysis of the polaron properties.
ISSN:2331-8422
DOI:10.48550/arxiv.2103.14942