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<p>Manipulating the spin and valley degrees of freedom of electrons is crucial for next-generation information technologies. Altermagnets, as an emerging magnetic phase, provide a quantum platform with intrinsic spin-valley locking, enabling multi-state manipulation of both spin and valley. Here, we propose a Janus monolayer CaCoFeN<sub>2</sub>, achieved through in situ substitution of magnetic transition metal atoms in the two-dimensional (2D) altermagnet Ca(CoN)<sub>2</sub> [<Emphasis Type="Underline">Phys. Rev. Lett. 133, 056401 (2024)</Emphasis>]. Our first-principles calculations identify CaCoFeN<sub>2</sub> as an anisotropic spin-plasmon ferrovalley semiconductor, with a large valley splitting of 273 meV solely through crystal symmetry breaking, without any involvement of spin-orbit coupling (SOC). Furthermore, its anisotropic electronic structures facilitate highly directional spin plasmon propagation. Carrier-type switching (<i>n</i>-type ↔ <i>p</i>-type) reverses the anisotropy along orthogonal axes, yielding open equi-frequency contours in <i>n</i>-type CaCoFeN<sub>2</sub>. The integration of spontaneous spin and valley polarization within a single material without SOC, offers new opportunities for advancements in spintronics and valleytronics.</p>

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Giant valley splitting and tunable anisotropic spin plasmons in a Janus ferrovalley monolayer

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月26日

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  • Zhihua Zhang,
  • Haotian Sun,
  • Mimi Dong,
  • Yiyi Guo,
  • Mingwen Zhao

摘要

Manipulating the spin and valley degrees of freedom of electrons is crucial for next-generation information technologies. Altermagnets, as an emerging magnetic phase, provide a quantum platform with intrinsic spin-valley locking, enabling multi-state manipulation of both spin and valley. Here, we propose a Janus monolayer CaCoFeN2, achieved through in situ substitution of magnetic transition metal atoms in the two-dimensional (2D) altermagnet Ca(CoN)2 [Phys. Rev. Lett. 133, 056401 (2024)]. Our first-principles calculations identify CaCoFeN2 as an anisotropic spin-plasmon ferrovalley semiconductor, with a large valley splitting of 273 meV solely through crystal symmetry breaking, without any involvement of spin-orbit coupling (SOC). Furthermore, its anisotropic electronic structures facilitate highly directional spin plasmon propagation. Carrier-type switching (n-type ↔ p-type) reverses the anisotropy along orthogonal axes, yielding open equi-frequency contours in n-type CaCoFeN2. The integration of spontaneous spin and valley polarization within a single material without SOC, offers new opportunities for advancements in spintronics and valleytronics.