MXene Fe$_2$C 中的轨道分辨超交换与拓扑磁振子能带

中文摘要 AI 辅助

磁性 MXene 因其引人入胜的性质，被认为是未来自旋电子学的有前景候选材料。然而，磁振子能带的拓扑性质及超交换机制仍相对未被充分探索。在本工作中，我们利用线性自旋波方法计算了 MXene Fe$_2$C 的自旋波色散，其中交换耦合参数来自第一性原理计算。由于两个 Fe 子晶格的交错堆叠，层间交换耦合消除了铁磁磁振子模式的简并。在磁振子能带的 $K$ 点识别出一个狄拉克点。我们进一步通过一个两带模型计算了磁振子能带的拓扑性质，包括贝里曲率、谷陈数和边缘态。我们还推导了一个有效哈密顿量来解释磁振子拓扑，该拓扑受 $C_{3v}$ 旋转对称性保护。为了理解支配磁振子能带的交换耦合的微观起源，我们随后构建了一个整合了微扰理论和紧束缚方法的精细模型。铁磁超交换耦合是通过两个不同 Fe 位点的 d 轨道经由桥接 C 位点的一对正交 p 轨道的虚跃迁来介导的。具体而言，层内交换耦合由面内的 $p_x$ 和 $p_y$ 轨道主导，而面外的 $p_z$ 轨道负责层间交换耦合。我们的结果建立了磁性 MXene Fe$_2$C 中轨道分辨的各向异性超交换与磁振子能带拓扑性质之间的直接联系，为未来的自旋电子学应用提供了理论指导。

英文摘要

Magnetic MXenes are promising candidates for future spintronics due to their intriguing properties. Nevertheless, the topological properties of magnon bands and superexchange mechanism remain relatively underexplored. In this work, we have calculated the spin wave dispersions for MXene Fe$_2$C using the linear spin wave method, with the exchange coupling parameters obtained from first-principles calculations. Owing to the staggered stacking of two Fe sub-lattices, the interlayer exchange coupling lifts the degeneracy of the ferromagnetic magnon modes. A Dirac point is identified in the magnon bands at the $K$ point. The topological properties of magnon bands, including Berry curvature, valley Chern number and edge states, are further computed by means of a two-band model. We also derive an effective Hamiltonian to explain the magnonic topology, which is protected by the $C_{3v}$ rotational symmetry. To understand the microscopic origin of the exchange couplings that govern the magnon bands, we then construct a refined model integrating perturbation theory and the tight-binding approach. The ferromagnetic superexchange coupling is mediated by the virtual hopping between the d orbitals of two distinct Fe sites via a pair of orthogonal p orbitals at the bridging C site. In detail, the intralayer exchange coupling is governed by the in-plane $p_x$ and $p_y$ orbitals, while the out-of-plane $p_z$ orbital is responsible for the interlayer exchange coupling. Our results establish a direct link between the orbital-resolved anisotropic superexchange and topological properties of the magnon bands in magnetic MXene Fe$_2$C, providing theoretical guidance for future spintronics applications.

发表机构

• School of Science, Shenyang University of Technology（沈阳工业大学理学院）
• Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences（中国科学院金属研究所沈阳材料科学国家实验室）
• College of Physics and Electronic Engineering, Chongqing Normal University（重庆师范大学物理与电子工程学院）
• Suzhou Laboratory（苏州实验室）

机构由 AI 辅助整理，请以论文原文为准。

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3figures, 37 pages