Breaking time reversal symmetry in a topological insulator may lead to quantum anomalous Hall effect and axion insulator phase. MnBi₄Te₇ is a recently discovered antiferromagnetic topological insulator with T_N ∼ 12.5 K, which is composed of an alternatively stacked magnetic layer (MnBi₂Te₄) and nonmagnetic layer (Bi₂Te₃). By means of scanning tunneling spectroscopy, we clearly observe the electronic state present at a step edge of a magnetic MnBi₂Te₄ layer but absent at nonmagnetic Bi₂Te₃ layers at 4.5 K. Furthermore, we find that as the temperature rises above T_N the edge state vanishes, while the point defect induced state persists upon an increase in temperature. These results confirm the observation of magnetism-induced edge states. Our analysis based on an axion insulator theory reveals that the nontrivial topological nature of the observed edge state.

中文翻译：

---

反铁磁拓扑绝缘体 MnBi4Te7 中磁致拓扑边缘态的观察

破坏拓扑绝缘体中的时间反转对称性可能导致量子反常霍尔效应和轴子绝缘体相。MnBi ₄ Te ₇是最近发现的一种反铁磁拓扑绝缘体，T _N ∼ 12.5 K，由交替堆叠的磁性层(MnBi ₂ Te ₄ )和非磁性层(Bi ₂ Te ₃ )组成。通过扫描隧道谱，我们清楚地观察到磁性 MnBi ₂ Te ₄层阶梯边缘处存在的电子态，而非磁性 Bi ₂ Te _{3层中不存在的电子态}层在 4.5 K。此外，我们发现当温度升高到T _N以上时，边缘状态消失，而点缺陷诱导状态在温度升高时持续存在。这些结果证实了对磁感应边缘状态的观察。我们基于轴子绝缘体理论的分析揭示了观察到的边缘状态的非平凡拓扑性质。