Regensburg 2022 – scientific programme

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O: Fachverband Oberflächenphysik

O 48: 2D Materials 1: Electronic Structure of Transition Metal Dichalcogenides

O 48.3: Talk

Wednesday, September 7, 2022, 15:30–15:45, S052

Structural, electronic and optical properties of strained MoS₂ — •Jan-Hauke Graalmann and Michael Rohlfing — Institute of Solid State Theory, University of Münster, 48149 Münster, Germany

Experimental and theoretical studies have shown that the spectrum of MoS₂ changes when the system gets strained. Stretching a monolayer leads to a shift of the optical absorption spectrum to lower energies. In case of the bilayer under hydrostatic stress, the interlayer interaction plays a major role.

In this talk we investigate the behaviour of a MoS₂ monolayer and bilayer theoretically using DFT, GdW and the Bethe-Salpeter equation. Our results show a transition of the monolayer from a direct semiconductor to an indirect one when the in-plane lattice constant is increased. Furthermore, the fundamental gap at the K point is reduced while the binding energies of the A and B excitons remain approximately constant. These effects lead to an effective shift of the excitation energies of both excitons towards lower energy with similar gauge factors.

We also find a significant influence of interlayer interaction within the bilayer. The effect of a decreasing gap by biaxial shrinking of each single layer under an external hydrostatic pressure gets counterbalanced by the reduction of the interlayer distance.