The intricate interplay between non-trivial topology and magnetism in two-dimensional materials can lead to the emergence of interesting phenomena such as the quantum anomalous Hall effect. Here we investigate the quantum transport of both bulk crystal and exfoliated MnBi₂Te₄ flakes in a field-effect transistor geometry. For the six septuple-layer device tuned into the insulating regime, we observe a large longitudinal resistance and zero Hall plateau, which are characteristics of an axion insulator state. The robust axion insulator state occurs in zero magnetic field, over a wide magnetic-field range and at relatively high temperatures. Moreover, a moderate magnetic field drives a quantum phase transition from the axion insulator phase to a Chern insulator phase with zero longitudinal resistance and quantized Hall resistance h/e², where h is Planck’s constant and e is electron charge. Our results pave the way for using even-number septuple-layer MnBi₂Te₄ to realize the quantized topological magnetoelectric effect and axion electrodynamics in condensed matter systems.

二维材料中非平凡拓扑和磁性之间复杂的相互作用可能导致有趣现象的出现，例如量子反常霍尔效应。在这里，我们研究了块状晶体和剥离的 MnBi ₂ Te _{4的量子传输}场效应晶体管几何结构中的薄片。对于调谐到绝缘状态的六七层器件，我们观察到大的纵向电阻和零霍尔平台，这是轴子绝缘体状态的特征。坚固的轴子绝缘体状态发生在零磁场、宽磁场范围和相对较高的温度下。此外，中等磁场驱动从轴子绝缘体相到具有零纵向电阻和量子化霍尔电阻h / e ²的陈绝缘体相的量子相变，其中h是普朗克常数，e是电子电荷。我们的结果为使用偶数七层 MnBi ₂ Te铺平了道路₄实现凝聚态系统中的量子化拓扑磁电效应和轴子电动力学。