Reference : Time-Dependent Screening Explains the Ultrafast Excitonic Signal Rise in 2D Semiconductors
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Physics
Physics and Materials Science; Computational Sciences
Time-Dependent Screening Explains the Ultrafast Excitonic Signal Rise in 2D Semiconductors
Smejkal, Valerie [> >]
Libisch, Florian [> >]
Molina-Sanchez, Alejandro [> >]
Trovatello, Chiara [> >]
Wirtz, Ludger mailto [University of Luxembourg > Faculty of Science, Technology and Medicine (FSTM) > Department of Physics and Materials Science (DPHYMS)]
Marini, Andrea [> >]
ACS Nano
American Chemical Society
Yes (verified by ORBilu)
[en] exciton-phonon coupling ; time-dependent spectroscopy ; ab-initio many-body perturbation theory
[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.
Fonds National de la Recherche - FnR ; H2020 ; MINECO, Spain ; TU Wien
FnR ; FNR13376969 > Ludger Wirtz > ACCEPT > Anharmonic And Exchange Interactions In Phonon Spectra > 01/01/2020 > 30/06/2024 > 2018

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