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<p>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 (<i>T</i><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 <i>d</i><sup>↑</sup>-<i>t</i><sub>2<i>g</i></sub> bands, accompanied by occupancy of the itinerant Cr 3<i>d</i>-<i>e</i><sub><i>g</i></sub> valleys. The <i>t</i><sub><i>2g</i></sub>-<i>e</i><sub><i>g</i></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 <i>T</i><sub>C</sub> and provides a guiding principle to realize 2D ferromagnetism at higher temperatures in non-van der Waals materials.</p>

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

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年4月18日

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  • 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. Chang,
  • H. J. Lin,
  • C. T. Chen,
  • T. Takahashi,
  • A. Chainani,
  • T. Sato

摘要

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.