Regensburg 2019 – scientific programme

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O: Fachverband Oberflächenphysik

O 53: 2D Materials II: Transition Metal Dichalcogenides

O 53.9: Talk

Wednesday, April 3, 2019, 12:30–12:45, H16

A many-body view on electronic excitations in TMDCs — •Philipp Marauhn, Peter Krüger, and Michael Rohlfing — Institut für Festkörpertheorie, Westfälische Wilhelms-Universität, 48149 Münster, Germany

Semiconducting transition metal dichalcogenides (TMDCs) have remarkable physical properties. Their two-dimensional nature in the monolayer limit leads to high exciton binding energies of several hundreds of milli-electronvolt. In this talk we discuss effects on the excited states that arise when stacking monolayers into multilayer or bulk systems.

To investigate electronic excitations in TMDCs we employ ab-initio many-body perturbation theory. Notably we solve the Bethe-Salpeter equation on the basis of a preceding LDA+GdW calculation, which is a simplified version of the GW method. Our results show that screening is a crucial ingredient when describing the optical spectra of TMDCs. Stacking layers on top of each other results in an enhanced screening environment shifting exciton resonances towards lower energy. This redshift is in agreement with experimental differential reflectance measurements [1]. Another effect of stacking is the admixture of pure intralayer excitons with charge transfer configurations.

[1] Y. Niu et al., Nanomaterials, 8, 725 (2018)