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

Abstract

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-Fröhlich (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.

16 pages, 4 figures

References in corpus (8)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material
• Tuning Electronic and Magnetic Properties of Early Transition Metal Dichalcogenides via Tensile Strain
• Phonon Sidebands in Transition Metal Dichalcogenides
• Exciton-phonon coupling strength in single-layer MoSe2 at room temperature
• Efficient phonon cascades in hot photoluminescence of WSe${}_2$ monolayers
• Electron-phonon interaction and transport properties of metallic bulk and monolayer transition metal dichalcogenide TaS${}_2$
• Group Theory analysis of phonons in two-dimensional Transition Metal Dichalcogenides

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