Bulletin of the American Physical Society
APS March Meeting 2024
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session F55: Collective Excitations and Exciton Dynamics
8:00 AM–11:00 AM,
Tuesday, March 5, 2024
Room: 204AB
Sponsoring
Unit:
DLS
Chair: Hanyu Zhu, RICE UNIVERSITY
Abstract: F55.00011 : Disentangling many-body effects in the coherent optical response of a 2D Semiconductor
10:00 AM–10:12 AM
Presenter:
Chiara Trovatello
(Columbia University)
Authors:
Chiara Trovatello
(Columbia University)
Florian Katsch
(TU Berlin)
Qiuyang Li
(University of Michigan)
Xiaoyang Zhu
(Columbia University)
Andreas Knorr
(TU Berlin)
Giulio Cerullo
(Politecnico di Milano)
Stefano Dal Conte
(Politecnico di Milano)
In this work, we measure the transient optical response of 1L-WS2 on SiO2 across the A and B excitonic resonances. The sample is photoexcited on- and out-of-resonance with the A exciton, and at variable pump fluences below the exciton-Mott transition. We disentangle absorption reduction, energy shift and broadening of the excitonic peak from the transient optical response, using Kramers-Kronig constrained variational analysis. From the measured transient reflectivity (ΔR/R) of 1L-WS2 we retrieve the absorbance spectrum as a function of pump-probe delay. All the spectra are well reproduced by a fitting function made by the sum of two Lorentz oscillators on top of a polynomial background. The transient energy shift persists over a timescale much longer than the temporal overlap of pump and probe pulses, excluding the possibility that it originates from optical Stark effect.
Microscopic calculations based on excitonic Heisenberg equations of motion quantitatively reproduce the non-linear absorbance spectra of the material[4].
In conclusion, our combined experimental and theoretical studies give important insights into the complex interplay between many-body correlations and excitonic interactions determining the non-equilibrium response of 1L-TMDs[4].
[1] Chernikov, A. et al. Phys. Rev. Lett. 113, 076802 (2014).
[2] Moody, G. et al., J. Opt. Soc. Am. B 33, C39–C49 (2016).
[3] Katsch, F., et al., Phys. Rev. Lett. 124, 257402 (2020).
[4] Trovatello, C. et al., Nano Letters, 22, 5322-5329 (2022).
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