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Description:

Mobile electrons in the semiconductor monolayer-MoS2 form a ferromagnetic state at low temper- ature. The Fermi sea consists of two circles, one at the K-point, the other at the K ̃-point, both with the same spin. Here, we present an optical experiment on gated MoS2 at low electron-density in which excitons are injected with known spin and valley quantum numbers. The resulting trions are identified using a model which accounts for the injection process, the formation of antisymmetrized trion states, electron-hole scattering from one valley to the other, and recombination. The results are consistent with a complete spin polarization. From the splittings between different trion states, we measure the exchange energy, Σ, the energy required to flip a single spin within the ferromagnetic state, as well as the intervalley Coulomb exchange energy, J. We determine Σ = 11.2 meV and J = 5 meV at n = 1.5 × 1012 cm−2, and find that J depends strongly on the electron density, n.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Ferromagnetic state, excitons, Coulomb exchange

Date published: 2024-07-08

Publisher: American Physical Society (APS)

Journal:

• Physical Review Letters (ISSN: 00319007) vol. 133 issue. 2 026501

Funding:

• Universität Basel
• Swiss Nanoscience Institute
• Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung P500PT_206917
• Japan Society for the Promotion of Science 21H05233
• Japan Society for the Promotion of Science 23H02052
• Ministry of Education, Culture, Sports, Science and Technology
• World Premier International Research Center Initiative
• Georg H. Endress Foundation

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

MDR DOI:

First published URL: https://doi.org/10.1103/physrevlett.133.026501

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Updated at: 2025-02-05 12:31:55 +0900

Published on MDR: 2025-02-05 12:31:55 +0900