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Spin-valley coupling enhanced high-TC ferromagnetism in a non-van der Waals monolayer Cr2Se3 on graphene

Author

Listed:
  • C.-W. Chuang

    (Tohoku University)

  • T. Kawakami

    (Tohoku University)

  • K. Sugawara

    (Tohoku University
    Tohoku University
    Japan Science and Technology Agency (JST))

  • K. Nakayama

    (Tohoku University)

  • S. Souma

    (Tohoku University
    Tohoku University)

  • M. Kitamura

    (High Energy Accelerator Research Organization (KEK)
    National Institutes for Quantum Science and Technology (QST))

  • K. Amemiya

    (High Energy Accelerator Research Organization (KEK))

  • K. Horiba

    (National Institutes for Quantum Science and Technology (QST))

  • H. Kumigashira

    (Tohoku University)

  • G. Kremer

    (Université de Lorraine)

  • Y. Fagot-Revurat

    (Université de Lorraine)

  • D. Malterre

    (Université de Lorraine)

  • C. Bigi

    (L’Orme des Merisiers)

  • F. Bertran

    (L’Orme des Merisiers)

  • F. H. Chang

    (National Synchrotron Radiation Research Center)

  • H. J. Lin

    (National Synchrotron Radiation Research Center)

  • C. T. Chen

    (National Synchrotron Radiation Research Center)

  • T. Takahashi

    (Tohoku University)

  • A. Chainani

    (National Synchrotron Radiation Research Center)

  • T. Sato

    (Tohoku University
    Tohoku University
    Tohoku University
    Tohoku University)

Abstract

Spin-valley magnetic ordering is restricted to layered van der Waals type transition-metal dichalcogenides with ordering temperatures below 55 K. Recent theoretical studies on non-van der Waals structures have predicted spin-valley polarization induced semiconducting ferromagnetic ground states, but experimental validation is missing. We report high-Curie temperature (TC ~ 225 K) metallic ferromagnetism with spontaneous spin-valley polarization in monolayer Cr2Se3 on graphene. Angle-resolved photoemission spectroscopy (ARPES) reveals systematic temperature-dependent energy shifts and splitting of localized Cr 3 d↑-t2g bands, accompanied by occupancy of the itinerant Cr 3d-eg valleys. The t2g-eg spin-valley coupling at the K/K’ points of hexagonal Brillouin zone leads to ferromagnetic ordering. Circular dichroism in ARPES shows clear evidence of spin-valley polarized states. Comparison with bilayer and trilayer Cr2Se3 reveals the crucial role of valley carrier density in enhancing TC and provides a guiding principle to realize 2D ferromagnetism at higher temperatures in non-van der Waals materials.

Suggested Citation

  • C.-W. Chuang & T. Kawakami & K. Sugawara & K. Nakayama & S. Souma & M. Kitamura & K. Amemiya & K. Horiba & H. Kumigashira & G. Kremer & Y. Fagot-Revurat & D. Malterre & C. Bigi & F. Bertran & F. H. Ch, 2025. "Spin-valley coupling enhanced high-TC ferromagnetism in a non-van der Waals monolayer Cr2Se3 on graphene," Nature Communications, Nature, vol. 16(1), pages 1-8, December.
    • Handle: RePEc:nat:natcom:v:16:y:2025:i:1:d:10.1038_s41467-025-58643-3
    DOI: 10.1038/s41467-025-58643-3
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