Regensburg 2022 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 15: 2D Materials 3 (joint session HL/CPP/DS)
HL 15.3: Vortrag
Dienstag, 6. September 2022, 10:15–10:30, H36
Optical nonlinearities in the excited carrier density of 2d TMDs — •Daniel Erben1, Alexander Steinhoff1, Michael Lorke1,2, and Frank Jahnke1 — 1Institute for Theoretical Physics, University of Bremen — 2Bremen Center for Computational Materi- als Science, University of Bremen
The prospects of using 2d transition metal dichalcogenides (TMDs) in future optoelectronic device application requires insight in the excitation dynamics of photoexcited charge carriers and the resulting optical nonlinearities. Utilizing ab-initio electronic-state calculations combined with many-body treatment of optical excitation, we calculate the excited carrier dynamics and the nonlinear absorption in MoS2, MoSe2, WS2, and WSe2 under various excitation conditions.
We find, that the increase of the carrier density with excitation strength deviates from a linear behaviour. Based on this, the validity range of a linear approximation for the excited carrier density as function of the pump fluence is determined. The use of a linear absorption coefficient of the unexcited system can significantly underestimate the achievable carrier density for strong pump fields. Furthermore, we study the excitation-induced many-body effects of excited charge carriers like band-gap renormalization, dephasing, screening, and scattering processes, that are mediated by the strong Coulomb interaction. Additional contributions to optical nonlinearities originate from phase space filling.