Physikalische Chemie - Direktor: Prof. Dr. Martin Wolf
PC Online Talk
Chair: Julia Stähler

Thursday, March 18, 2021, 11:00 am
Seminar Link
Stefano Calati
FHI Department PC
Dynamic Screening of Quasiparticles in WS2 Monolayers
The low dimensional nature of TMDCs and the resulting reduced screening influence their non-equilibrium optical properties, as dynamic screening by photoexcited quasiparticles governs the transient response. Here, we investigate the respective roles of excitons and quasi-free carriers on the dynamic response of WS2 monolayers on SiO2. We find drastic changes in the reflectivity/transmittance contrast upon photoexcitation. The main observation is a pump photon energy-dependent blue/red shifts of the neutral exciton. Based on a phenomenological model, we disentangle the different impact of excitons and free carriers on the renormalization of the quasi-free-particle band gap and exciton binding energy. This work unravels and quantifies the competition and interplay of the multiple electronic and thermal processes contributing to the recovery of the system upon photoexcitation.

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