Berlin 2018 – scientific programme

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DS: Fachverband Dünne Schichten

DS 12: 2D Materials: Session II (joint session DS/CPP/HL)

DS 12.8: Talk

Tuesday, March 13, 2018, 11:30–11:45, H 2032

Thickness dependent electronic and optical properties of TMDCs within many-body perturbation theory — •Philipp Marauhn, Peter Krüger, and Michael Rohlfing — Institut für Festkörpertheorie, Westfälische Wilhelms-Universität, 48149 Münster, Germany

Experimental studies have shown that the spectrum of MoS₂ and other TMDC materials strongly depends on the number of layers of the system. With increasing thickness of a system, the optical absorption spectrum is generally shifted to lower energies.

In this talk we address this behaviour from a theoretical point of view. To investigate the excited electronic states of the TMDCs, we perform three consecutive steps: (i) DFT (ii) GW (iii) BSE (Bethe-Salpeter equation). Our results show that both the fundamental quasiparticle gap and the exciton binding energy are significantly reduced when the number of layers is increased. These two effects do not perfectly compensate each other, but lead to an effective shift of the excitation energies towards lower energy. This redshift with increasing number of layers is in agreement with experimental differential reflectance measurements [1]. We also find significant changes in the wave function of some exciton resonances with increasing sample thickness. In multilayer systems, excitons may be composed from electrons and holes situated on different layers, which can be considered as interlayer excitons [2].

[1] Y. Niu et. al., submitted

[2] A. Arora et. al., Nat. Commun., 8(1), 639 (2017)