Ultrathin films of intrinsic magnetic topological insulator MnBi₂Te₄ exhibit fascinating quantum properties such as the quantum anomalous Hall effect and the axion insulator state. In this work, we systematically investigate the evolution of the electronic structure of MnBi₂Te₄ thin films. With increasing film thickness, the electronic structure changes from an insulator type with a large energy gap to one with in-gap topological surface states, which is, however, still in drastic contrast to the bulk material. By surface doping of alkali-metal atoms, a Rashba split band gradually emerges and hybridizes with topological surface states, which not only reconciles the puzzling difference between the electronic structures of the bulk and thin-film MnBi₂Te₄ but also provides an interesting platform to establish Rashba ferromagnet that is attractive for (quantum) anomalous Hall effect. Our results provide important insights into the understanding and engineering of the intriguing quantum properties of MnBi₂Te₄ thin films.

中文翻译：

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超薄 MnBi2Te4 薄膜电子结构的演变

本征磁性拓扑绝缘体MnBi ₂ Te ₄的超薄膜表现出迷人的量子特性，例如量子反常霍尔效应和轴子绝缘体状态。_{在这项工作中，我们系统地研究了 MnBi 2} Te ₄的电子结构的演变。薄膜。随着薄膜厚度的增加，电子结构从具有大能隙的绝缘体类型变为具有能隙内拓扑表面态的类型，然而，这仍然与块状材料形成鲜明对比。通过碱金属原子的表面掺杂，Rashba 分裂带逐渐出现并与拓扑表面态杂化，这不仅调和了体和薄膜 MnBi ₂ Te ₄的电子结构之间令人费解的差异，而且提供了一个有趣的平台建立对（量子）异常霍尔效应具有吸引力的 Rashba 铁磁体。_{我们的研究结果为理解和设计 MnBi 2} Te ₄的有趣量子特性提供了重要的见解薄膜。