二维非共线磁体Tc$_2$Cl$_2$O和Tc$_2$Br$_2$O中的镜像陈绝缘体
Mirror Chern insulators in two-dimensional altermagnetic Tc$_2$Cl$_2$O and Tc$_2$Br$_2$O
浏览论文内容
中文总结 AI 辅助
本研究通过第一性原理计算，确定二维非共线磁体Tc₂Cl₂O和Tc₂Br₂O为镜像陈绝缘体，建立非共线磁性与镜像陈拓扑的关联，为探索相关拓扑现象提供了新平台。
中文摘要 AI 辅助
非共线磁有序与晶体能带拓扑的相互作用，为实现具有独特自旋依赖特性的非常规拓扑相提供了一条引人入胜的途径。本文基于第一性原理计算与理论分析，确定单层Tc$_2$X$_2$O（X=Cl、Br）为一类二维非共线磁镜像陈绝缘体。在无自旋轨道耦合（SOC）时，两种单层结构均表现出稳定的非共线磁性，具备镜面对称-自旋耦合特性，且在费米能级附近的每个自旋通道中存在两个对称性保护的外尔点；相反自旋通道中的外尔点带有不同的镜面对称本征值m_z=±i。引入自旋轨道耦合后，外尔点打开能隙，两个镜面对称区获得相反的陈数，即C_+=1和C_-=-1，从而产生非零的镜像陈数C_m=1。低能k·p模型可描述外尔点的对称性保护机制，并阐明其自旋轨道耦合诱导的质量能隙与拓扑特性。此外，形成的镜像陈绝缘相在体带隙内具有螺旋边缘态，且呈现出量子化的自旋霍尔电导率。本工作建立了非共线磁性与镜像陈拓扑之间的直接关联，为在二维非共线磁材料中探索非常规拓扑及自旋依赖现象提供了有前景的平台。
英文摘要
The interplay between altermagnetism and crystalline band topology provides an intriguing avenue for realizing unconventional topological phases with distinctive spin-dependent properties. Here, based on first-principles calculations and theoretical analysis, we identify monolayer $\mathrm{Tc}_2X_2\mathrm{O}$ ($X$ = Cl, Br) as a family of two-dimensional altermagnetic mirror Chern insulators. In the absence of spin--orbit coupling (SOC), both monolayers exhibit robust altermagnetism with mirror-spin coupling and host two symmetry-protected Weyl points in each spin channel near the Fermi level. The Weyl points in opposite spin channels carry distinct mirror-symmetry eigenvalues, $m_z=\pm i$. Upon inclusion of SOC, the Weyl points are gapped, and the two mirror sectors acquire opposite Chern numbers, ${\cal {C}}_{+}=1$ and ${\cal {C}}_{-}=-1$, resulting in a nonzero mirror Chern number ${\cal {C}}_m=1$. A low-energy $k\cdot p$ model captures the symmetry protection of the Weyl points and elucidates their SOC-induced mass gaps and topological character. Furthermore, the resulting mirror Chern insulating phases host helical edge states within the bulk band gap and exhibit a quantized spin Hall conductivity. Our work establishes a direct connection between altermagnetism and mirror Chern topology and provides a promising platform for exploring unconventional topological and spin-dependent phenomena in two-dimensional altermagnetic materials.
