Spin-valley coupling enhanced high-TC ferromagnetism in a non-van der Waals monolayer Cr2Se3 on graphene
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 (T<sub>C</sub> ~ 225 K) metallic ferromagnetism with spontaneous spin-valley polarization in monolayer Cr<sub>2</sub>Se<sub>3</sub> on graphene. Angle-resolved photoemission spectroscopy (ARPES) reveals systematic temperature-dependent energy shifts and splitting of localized Cr 3 d<sup>↑</sup>-t<sub>2g</sub> bands, accompanied by occupancy of the itinerant Cr 3d-e<sub>g</sub> valleys. The t<sub>2g</sub>-e<sub>g</sub> 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 Cr<sub>2</sub>Se<sub>3</sub> reveals the crucial role of valley carrier density in enhancing T<sub>C</sub> and provides a guiding principle to realize 2D ferromagnetism at higher temperatures in non-van der Waals materials.
Authors
- T. Takahashi (ORCID: https://orcid.org/0000-0001-7717-6512)
- Tappei Kawakami (ORCID: https://orcid.org/0000-0003-4643-2805)
- H. J. Lin (ORCID: https://orcid.org/0000-0002-7195-9628)
- Geoffroy Kremer (ORCID: https://orcid.org/0000-0003-1753-3471)
- A. Chainani (ORCID: https://orcid.org/0000-0002-5639-5393)
- Y. Fagot‐Révurat (ORCID: https://orcid.org/0000-0002-3302-5736)
- S. Souma (ORCID: https://orcid.org/0000-0003-2460-4602)
- Hiroshi Kumigashira (ORCID: https://orcid.org/0000-0003-4668-2695)
- Chien‐Te Chen (ORCID: https://orcid.org/0000-0002-1881-2600)
- C. W. Chuang (ORCID: https://orcid.org/0000-0003-0403-2723)
- Chiara Bigi (ORCID: https://orcid.org/0000-0003-0977-3993)
- Kenta Amemiya (ORCID: https://orcid.org/0000-0003-2415-6686)
- T. Sato (ORCID: https://orcid.org/0000-0002-4544-5463)
- K. Sugawara (ORCID: https://orcid.org/0000-0003-2926-9436)
- K. Nakayama (ORCID: https://orcid.org/0000-0003-2462-2253)
- F. Bertran (ORCID: https://orcid.org/0000-0002-2416-0514)
- Koji Horiba (ORCID: https://orcid.org/0000-0002-1124-0451)
- D. Malterre
- M. Kitamura
- F. H. Chang
Institutions
- High Energy Accelerator Research Organization (JP)
- Tohoku University (JP)
- Synchrotron soleil (FR)
- Japan Science and Technology Agency (JP)
- National Synchrotron Radiation Research Center (TW)
- Advanced Institute of Materials Science (JP)
- National Institutes for Quantum Science and Technology (JP)
- Institut Jean Lamour (FR)
- Université de Lorraine (FR)
Publication Details
- Journal
- Nature Communications
- Published
- 2025-04-18
- DOI
- https://doi.org/10.1038/s41467-025-58643-3
- Citations
- 5
- Primary Topic
- 2D Materials and Applications
- Type
- article
- Field-Weighted Citation Impact
- 2.59
Funders
- National Science and Technology Council
- Japan Society for the Promotion of Science
- Core Research for Evolutional Science and Technology