Regensburg 2022 – scientific programme
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O: Fachverband Oberflächenphysik
O 16: Poster Monday: Ultrafast Processes 1
O 16.10: Poster
Monday, September 5, 2022, 18:00–20:00, P4
Influence of the static dielectric permittivity on ultrafast quasiparticles dynamics in WS2 monolayers — •Subhadra Mohapatra1,2, Stefano Calati1,2, Quiyang Li3, Xiaoyang Zhu3, and Julia Stähler1,2 — 1Humboldt-Universität zu Berlin, Institut für Chemie,Berlin,Germany — 2Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abt. Physikalische Chemie, Berlin, Germany — 3Columbia University, New York City, New York
In our recent fluence-and photon energy-dependent studies [1,2] of quasiparticle dynamics in WS2 monolayers on fused silica (FS) and Si-SiO2 substrates, we observed that excitonic screening solely reduces the binding energy of the excitons, leading to a transient blue-shift of the exciton resonance while quasi free carrier screening effectively shows a red shift, as the carrier-induced screening leads to a larger band gap renormalization than binding energy reduction. Further investigation of such fluence-dependent quasiparticle dynamics studies using a higher dielectric permittivity of a sapphire substrate, we found that scattering rates, relaxation time constants, and band gap renormalization are not influenced by the dielectric permittivity. On the contrary, the ratio of dynamic screening parameter of the excitons and their Bohr radius is approximately 4 times higher in sapphire than for FS, which must be a direct consequence of the increased dielectric permittivity likely leading to more localized excitons.
References:
[1] Calati et al. PCCP 23(39) (2021).
[2] Calati et al. arXiv:2204.02125 (2022).