4.8 Article

Time-Dependent Screening Explains the Ultrafast Excitonic Signal Rise in 2D Semiconductors

Journal

ACS NANO
Volume 15, Issue 1, Pages 1179-1185

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acsnano.0c08173

Keywords

transition-metal dichalcogenides; screening; excitons; ultrafast spectroscopy; time-dependent many-body perturbation theory

Funding

  1. European Union [676598, 824143, 654360]
  2. TU Wien
  3. IMPRS-APS program of the MPQ (Germany)
  4. Ramon y Cajal programme (MINECO, Spain) [RYC2018-024024-I]
  5. FNR (Fond National de Recherche, Luxembourg) [INTER/19/ANR/13376969/ACCEPT]

Ask authors/readers for more resources

The study investigates 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, finding that the delayed buildup of the signal is caused by coordinated carrier dynamics and its influence on screening.
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 Bexciton, 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.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.8
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available