Ultrafast electron localization and screening in a transition metal dichalcogenide
Abstract
The coupling of light to electrical charge carriers in semiconductors is the foundation of many technological applications. Attosecond transient absorption spectroscopy measures simultaneously how excited electrons and the vacancies they leave behind dynamically react to the applied optical fields. In compound semiconductors, these dynamics can be probed via any of their atomic constituents with core-level transitions into valence and conduction band. Typically, the atomic species forming the compound contribute comparably to the relevant electronic properties of the material. One therefore expects to observe similar dynamics, irrespective of the choice of atomic species via which it is probed. Here, we show in the two-dimensional transition metal dichalcogenide semiconductor MoSe2, that through a selenium-based core-level transition we observe charge carriers acting independently from each other, while when probed through molybdenum, the collective, many-body motion of the carriers dominates. Such unexpectedly contrasting behavior can be explained by a strong localization of electrons around molybdenum atoms following absorption of light, which modifies the local fields acting on the carriers. We show that similar behavior in elemental titanium metal [M. Volkov et al., Nat. Phys.15, 1145-1149 (2019)] carries over to transition metal-containing compounds and is expected to play an essential role for a wide range of such materials. Knowledge of independent particle and collective response is essential for fully understanding these materials. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000608044Publication status
publishedExternal links
Journal / series
Proceedings of the National Academy of Sciences of the United States of AmericaVolume
Pages / Article No.
Publisher
National Academy of SciencesSubject
ultrafast dynamics ; 2D materials ; ultrafast spectroscopy; transition metal dichalcogenide ; screeningOrganisational unit
03371 - Keller, Ursula / Keller, Ursula
08733 - Gallmann, Lukas (Tit.-Prof.) / Gallmann, Lukas (Tit.-Prof.)
Funding
200416 - High repetition rate attosecond pulse generation (SNF)
801459 - Fellowship Program of the NCCR MUST (National Competence Center for Research in Molecular Ultrafast Science and Technology) and the Cluster of Excellence RESOLV (EC)
Related publications and datasets
Is supplemented by: https://doi.org/10.3929/ethz-b-000604259
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