Article Interactions and ultrafast dynamics of exciton complexes in a monolayer semiconductor with electron gas

Aleksander Rodek ; Kacper Oreszczuk ; Tomasz Kazimierczuk ; James Howarth ; Takashi Taniguchi SAMURAI ORCID (National Institute for Materials Science) ; Kenji Watanabe SAMURAI ORCID (National Institute for Materials Science) ; Marek Potemski ; Piotr Kossacki

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Aleksander Rodek, Kacper Oreszczuk, Tomasz Kazimierczuk, James Howarth, Takashi Taniguchi, Kenji Watanabe, Marek Potemski, Piotr Kossacki. Interactions and ultrafast dynamics of exciton complexes in a monolayer semiconductor with electron gas. Nanophotonics. 2024, 13 (4), 487-497.
SAMURAI

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(abstract)

We present femtosecond pump-probe measurements of neutral and charged exciton optical response in monolayer MoSe2 to resonant photoexcitation of a given exciton state in the presence of 2D electron gas. We show that creation of charged exciton (X−) population in a given K,K’ valley requires the capture of available free carriers in the opposite valley and reduces the interaction of neutral X with the Fermi sea. We also observe spectral broadening of X transition line with the increasing X− population caused by efficient scattering and excitation induced dephasing. From the valley-resolved analysis of the observed effects we are able to extract the spin-valley relaxation times of free carriers as a function of carrier density. Moreover, we analyze the oscillator strength and energy shift of X in the Fermi sea regime under resonant excitation. From this we can observe the process of X decay by radiative recombination paired with trion formation effect. We demonstrate an increase of neutral exciton relaxation rate with the introduction of Fermi sea of electrons. We ascribe the observed effect to the increased efficiency of trion formation channel, as well as the radiative decay caused by the screening of disorder by the free carriers.

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Keyword: Pump-probe measurements, exciton optical response, MoSe2

Date published: 2024-02-21

Publisher: Walter de Gruyter GmbH

Journal:

  • Nanophotonics (ISSN: 21928614) vol. 13 issue. 4 p. 487-497

Funding:

  • European Union Graphene Flagship
  • Fundacja na rzecz Nauki Polskiej IRA-MAB/2018/9 Grant
  • Fundacja na rzecz Nauki Polskiej SG 0P Program of the EU
  • Narodowe Centrum Nauki 2020/39/B/ST3/03251
  • Narodowe Centrum Nauki 2021/41/N/ST3/04240

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1515/nanoph-2023-0913

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Updated at: 2025-02-15 12:30:26 +0900

Published on MDR: 2025-02-15 12:30:26 +0900

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