SKM 2023 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 23: Optical Properties (joint session HL/CPP)
CPP 23.10: 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.