Light-Matter Interactions in Two-Dimensional Transition Metal Dichalcogenides: Dominant Excitonic Transitions in mono- and few-layer MoX${}_2$ and Band Nesting

Abstract

We report ab initio calculations of the dielectric function of six mono- and bilayer molybdenum dichalcogenides based in a Bethe Salpether equation+G${}_0$W${}_0$ ansatz, focussing on the excitonic transitions dominating the absorption spectrum up to an excitation energy of 3\,eV. Our calculations suggest that switching chalcogen atoms and the strength of interlayer interactions should affect the detailed composition of the high 'C' peaks in experimental optical spectra of molybdenum dichalcogenides and cause a significant spin-orbit-splitting of the contributing excitonic transitions in monolayer MoSe${}_2$ and MoTe${}_2$. This can be explained through changes in the electronic dispersion around the Fermi energy along the chalcogen series S$\to$Se$\to$Te that move the van-Hove singularities in the density of states of the two-dimensional materials along the \textit{$\Gamma$}-\textit{K} line in the Brillouin zone. Further, we confirm the distinct interlayer character of the '\textsl{C}' peak transition in few-layer MoS${}_2$ that was predicted before from experimental data and show that a similar behaviour can be expected for MoSe${}_2$ and MoTe${}_2$ as well.

Submitted manuscript + supplementary material

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• Interlayer excitons in MoSe${}_2$/WSe${}_2$ heterostructures from first-principles
• Flat-Bands-Enabled Triplet Excitonic Insulator in a Di-atomic Kagome Lattice
• Phonon dispersion of MoS${}_2$
• Resonance profiles of valley polarization in single-layer MoS${}_2$ and MoSe${}_2$
• Stacking-Dependent Optical Properties in Bilayer WSe2
• First-Principles Mapping of the Electronic Properties of Two-Dimensional Materials for Strain-Tunable Nanoelectronics
• Critical assessment of $G_0{W}_0$ calculations for 2D materials: the example of monolayer MoS${}_2$
• Excitonic Absorption Signatures of Twisted Bilayer WSe${}_2$ by Electron Energy-Loss Spectroscopy
• Interlayer excitonic spectra of vertically stacked MoSe${}_2$/WSe${}_2$ heterobilayers
• Surfactant-Free Polar-to-Non-Polar-Phase Transfer of Exfoliated MoS2 Two-Dimensional Colloids
• Interlayer Raman modes in twisted bilayer TMDCs
• Excitonic effect on two-photon absorption of two-dimensional semiconductors: Theory and applications to MoS2 and WS2 monolayers
• Wannier-Function-Based Approach to Coupled Exciton-Phonon-Photon Dynamics in Two-Dimensional Semiconductors
• Deciphering the Intense Post-Gap Absorptions of Monolayer Transition Metal Dichalcogenides
• Efficient $GW$ band structure calculations using Gaussian basis functions and application to atomically thin transition-metal dichalcogenides