Dynamic Screening of Quasiparticles in WS2 Monolayers
- PC Online Talk
- Date: Mar 18, 2021
- Time: 11:00 AM (Local Time Germany)
- Speaker: Stefano Calati
- FHI Department PC
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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