Ultrafast electron localization and screening in a transition metal dichalcogenide

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....

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2023-04, Vol.120 (15), p.e2221725120-e2221725120
Main Authors: Schumacher, Z, Sato, S A, Neb, S, Niedermayr, A, Gallmann, L, Rubio, A, Keller, U
Format: Article
Language:English
Subjects:
Absorption spectroscopy
Chalcogenides
Conduction bands
Current carriers
Electromagnetic absorption
Electronic properties
Electrons
Localization
Metals
Molybdenum
Physical Sciences
Selenium
Semiconductors
Titanium
Transition metal compounds
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Summary: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 MoSe , 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 , , 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.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2221725120