Ultrafast photocurrents in MoSe${}_2$ probed by terahertz spectroscopy

Abstract

We use the terahertz (THz) emission spectroscopy to study femtosecond photocurrent dynamics in the prototypical 2D semiconductor, transition metal dichalcogenide MoSe${}_2$. We identify several distinct mechanisms producing THz radiation in response to an ultrashort ($30$fs) 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 $23$THz in the emission from the BL sample. We attribute the oscillations to quantum beats between two excitonic states with energetic separation of $\sim 100$meV.

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

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Cited by in corpus (4)

• Spintronic THz emitters based on transition metals and semi-metals/Pt multilayers
• Terahertz emission from transient currents and coherent phonons in layered MoSe${}_2$ and WSe${}_2$
• Probing the formation of dark interlayer excitons via ultrafast photocurrent
• Quantum beats of coherent 1s 2s excitons in two dimensional transition metal