Layer dependent electronic structure changes in transition metal dichalcogenides- The microscopic origin

Abstract

We have examined the electronic structure evolution in transition metal dichalcogenides MX${}_2$, where M=Mo,W and X=S,Se and Te. These are generally referred to as van der Waals heterostructures on the one hand, yet one has band gap changes as large as 0.6 eV with thickness in some instances. This does not seem to be consistent with a description where the dominant interactions are van der Waals interactions. Mapping onto a tight binding model allows us to quantify the electronic structure changes which are found to be dictated solely by interlayer hopping interactions. Different environments that an atom encounters could change the Madelung potential and therefore the onsite energies. This could happen while going from monolayer to bilayer as well as in cases where the stackings are different from what is found in 2H structures. These effects are quantitatively found to be negligible, enabling us to quantify the thickness dependent electronic structure changes as arising from interlayer interactions alone.

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• Band tail formation in mono and multilayered transition metal dichalcogenides: A detailed assessment and a quick-reference guide
• The deep-acceptor nature of the chalcogen vacancies in 2D transition-metal dichalcogenides
• On the importance of electron-electron and electron-phonon scatterings and energy renormalizations during carrier relaxation in monolayer transition-metal dichalcogenides
• Ab-initio study of the energy competition between Γand K valleys in bilayer transition metal dichalcogenides
• Nonlinear effects in many-body van der Waals interactions