SKM 2023 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 18: Optical Properties (joint session HL/CPP)

HL 18.10: Talk

Tuesday, March 28, 2023, 12:15–12:30, POT 112

Excitons in MoS₂ bilayers under pressure — •Jan-Hauke Graalmann¹, Paul Steeger², Robert Schmidt², Steffen Michaelis de Vasconcellos², Rudolf Bratschitsch², and Michael Rohlfing¹ — ¹Institute of Solid State Theory, University of Münster, 48149 Münster, Germany — ²Institute of Physics, University of Münster, 48149 Münster, Germany

Theoretical and experimental studies have shown that the optical spectrum of the MoS₂ bilayer changes under pressure.

Our theoretical investigations are based on DFT, GdW and the Bethe-Salpeter equation. For the specific stress conditions of the experiment, our calculations show an effective shift of the excitation energies of the A exciton towards higher energies with increasing pressure. This behaviour can be explained with an approximately constant direct band gap at the K point while the binding energy decreases. Due to a growing valence band splitting for increasing pressures, the interlayer exciton shows a smaller shift. These results are substantiated by measurements using a piston type diamond anvil cell (DAC) to create pressures in the GPa range.

The reason for only small changes of the fundamental band gap is a significant influence of interlayer interaction. The effect of a decreasing gap by biaxial lateral shrinking of each single layer under an external pressure gets counterbalanced by the reduction of the interlayer distance. Furthermore, the real space distribution shows an increased interlayer character for the A and interlayer exciton under pressure.