Article (Scientific journals)
Time-Dependent Screening Explains the Ultrafast Excitonic Signal Rise in 2D Semiconductors
Smejkal, Valerie; Libisch, Florian; Molina-Sanchez, Alejandro et al.
2021In ACS Nano, 15 (1), p. 1179--1185
Peer reviewed
 

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Keywords :
exciton-phonon coupling; time-dependent spectroscopy; ab-initio many-body perturbation theory
Abstract :
[en] We calculate the time evolution of the transient reflection signal in an MoS2 monolayer on a SiO2/Si substrate using first-principles out-of-equilibrium real-time methods. Our simulations provide a simple and intuitive physical picture for the delayed, yet ultrafast, evolution of the signal whose rise time depends on the excess energy of the pump laser: at laser energies above the A- and B-exciton, the pump pulse excites electrons and holes far away from the K valleys in the first Brillouin zone. Electron–phonon and hole–phonon scattering lead to a gradual relaxation of the carriers toward small Active Excitonic Regions around K, enhancing the dielectric screening. The accompanying time-dependent band gap renormalization dominates over Pauli blocking and the excitonic binding energy renormalization. This explains the delayed buildup of the transient reflection signal of the probe pulse, in excellent agreement with recent experimental data. Our results show that the observed delay is not a unique signature of an exciton formation process but rather caused by coordinated carrier dynamics and its influence on the screening.
Disciplines :
Physics
Author, co-author :
Smejkal, Valerie
Libisch, Florian
Molina-Sanchez, Alejandro
Trovatello, Chiara
Wirtz, Ludger ;  University of Luxembourg > Faculty of Science, Technology and Medicine (FSTM) > Department of Physics and Materials Science (DPHYMS)
Marini, Andrea
External co-authors :
yes
Language :
English
Title :
Time-Dependent Screening Explains the Ultrafast Excitonic Signal Rise in 2D Semiconductors
Publication date :
2021
Journal title :
ACS Nano
ISSN :
1936-0851
Publisher :
American Chemical Society
Volume :
15
Issue :
1
Pages :
1179--1185
Peer reviewed :
Peer reviewed
Focus Area :
Physics and Materials Science
Computational Sciences
FnR Project :
FNR13376969 - Anharmonic And Exchange Interactions In Phonon Spectra, 2018 (01/01/2020-30/06/2024) - Ludger Wirtz
Funders :
FNR - Fonds National de la Recherche [LU]
H2020
MINECO, Spain
TU Wien
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since 28 March 2022

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