Dependence of band structure and exciton properties of encapsulated WSe 2 monolayers on the hBN-layer thickness

I.C. Gerber (1) , Xavier Marie (1)

1 LPCNO - Laboratoire de physique et chimie des nano-objets

The optical properties of two-dimensional transition-metal dichalcogenide monolayers, such as MoS 2 or WSe 2 are dominated by excitons, Coulomb bound electron-hole pairs. Screening effects due to the presence of hexagonal-boron nitride (hBN) surrounding layers have been investigated by solving the Bethe-Salpeter equation on top of GW wave functions in density functional theory calculations. We have calculated the dependence of both the quasiparticle gap and the binding energy of the neutral exciton ground-state E b as a function of the hBN-layer thickness. This paper demonstrates that the effects of screening at this level of theory are more short ranged than is widely believed. The encapsulation of a WSe 2 monolayer by three sheets of hBN (∼1 nm) already yields a 20% decrease in E b , whereas the maximal reduction is 27% for thick hBN. We have performed similar calculations in the case of a WSe 2 monolayer deposited on stacked hBN layers. These results are compared to the recently proposed quantum electrostatic heterostructure approach.

Mots clés: Valleytronics; First-principles calculations; Excitons; Electronic structure; Physical Systems 2-dimensional systems; Monolayer films; Transition-metal dichalcogenide Techniques; All-electron density functional calculations

Domaines: Autre

I.C. Gerber, Xavier Marie. Dependence of band structure and exciton properties of encapsulated WSe 2 monolayers on the hBN-layer thickness. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2018, 98 (24), ⟨10.1103/physrevb.98.245126⟩. ⟨hal-01999602⟩