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

IF 14.7 1区综合性期刊 Q1 MULTIDISCIPLINARY SCIENCES

Nature Communications Pub Date : 2025-04-18 DOI:10.1038/s41467-025-58643-3

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

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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 (T_C ~ 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^↑-t_2g bands, accompanied by occupancy of the itinerant Cr 3d-e_g valleys. The t_2g-e_g 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 T_C and provides a guiding principle to realize 2D ferromagnetism at higher temperatures in non-van der Waals materials.

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自旋谷磁性有序仅限于有序温度低于 55 K 的层状范德华型过渡金属二钴化物。最近关于非范德华结构的理论研究预测了自旋谷极化诱导的半导体铁磁基态，但缺乏实验验证。我们报告了石墨烯上单层 Cr2Se3 自发自旋valley 极化的高居里温度（TC ~ 225 K）金属铁磁性。角度分辨光发射光谱 (ARPES) 揭示了局部 Cr 3 d↑-t2g 带随温度变化的系统能量移动和分裂，同时还发现了流动 Cr 3d-eg 谷。六方布里渊区 K/K' 点的 t2g-eg 自旋谷耦合导致了铁磁有序化。ARPES 中的圆二色性显示了自旋valley 极化态的明显证据。与双层和三层 Cr2Se3 的比较揭示了谷载流子密度在增强 TC 方面的关键作用，并为非范德华材料在更高温度下实现二维铁磁性提供了指导原则。

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来源期刊

Nature Communications Biological Science Disciplines-

CiteScore

24.90

自引率

2.40%

发文量

6928

审稿时长

3.7 months

期刊介绍： Nature Communications, an open-access journal, publishes high-quality research spanning all areas of the natural sciences. Papers featured in the journal showcase significant advances relevant to specialists in each respective field. With a 2-year impact factor of 16.6 (2022) and a median time of 8 days from submission to the first editorial decision, Nature Communications is committed to rapid dissemination of research findings. As a multidisciplinary journal, it welcomes contributions from biological, health, physical, chemical, Earth, social, mathematical, applied, and engineering sciences, aiming to highlight important breakthroughs within each domain.