Honeycomb or triangular lattices were extensively studied and thought to be proper platforms for realizing quantum anomalous Hall effect (QAHE), where magnetism is usually caused by d orbitals of transition metals. Here we propose that square lattice can host three magnetic topological states, including the fully spin polarized nodal loop semimetal, QAHE and topologically trivial ferromagnetic semiconductor, in terms of the symmetry and k · p model analyses that are materials-independent. A phase diagram is presented. We further show that the above three magnetic topological states can be indeed implemented in two-dimensional (2D) materials ScLiCl5, LiScZ5 (Z=Cl, Br), and ScLiBr5, respectively. The ferromagnetism in these 2D materials is microscopically revealed from p electrons of halogen atoms. This present study opens a door to explore the exotic topological states as well as quantum magnetism from p-orbital electrons by means of the materials-independent approach.

中文翻译：

---

方形晶格上的 P 轨道磁拓扑态

蜂窝或三角形晶格被广泛研究并被认为是实现量子反常霍尔效应 (QAHE) 的合适平台，其中磁性通常由过渡金属的 d 轨道引起。在这里，我们提出方形晶格可以承载三种磁性拓扑状态，包括完全自旋极化的节点环半金属、QAHE 和拓扑平凡的铁磁半导体，就对称性和与材料无关的 k·p 模型分析而言。给出了相图。我们进一步表明，上述三种磁性拓扑状态确实可以分别在二维（2D）材料 ScLiCl5、LiScZ5（Z=Cl、Br）和 ScLiBr5 中实现。这些 2D 材料中的铁磁性从卤素原子的 p 电子显微镜下可以看出。