We use the terahertz (THz) emission spectroscopy to study femtosecond photocurrent dynamics in the prototypical 2D semiconductor, transition metal dichalcogenide MoSe2. We identify several distinct mechanisms producing THz radiation in response to an ultrashort (30fs) optical excitation in a bilayer (BL) and a multilayer (ML) sample. In the ML, the THz radiation is generated at a picosecond timescale by out-of-plane currents due to the drift of photoexcited charge carriers in the surface electric field. The BL emission is generated by an in-plane shift current. Finally, we observe oscillations at about 23THz in the emission from the BL sample. We attribute the oscillations to quantum beats between two excitonic states with energetic separation of ∼100meV.
@article{arxiv.2008.12203,
title = {Ultrafast photocurrents in MoSe$_2$ probed by terahertz spectroscopy},
author = {Denis Yagodkin and Lukas Nadvornik and Oliver Gueckstock and Cornelius Gahl and Tobias Kampfrath and Kirill I. Bolotin},
journal= {arXiv preprint arXiv:2008.12203},
year = {2020}
}
Comments
This is the Accepted Manuscript version of an article accepted for publication in 2D Materials. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/2053-1583/abd527 7 pages, 9 figures