发表机构
Tsinghua University; Shanghai Jiao Tong University（清华大学; 上海交通大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文揭示表面缺陷通过降低静电势使拓扑表面态离域并抑制交换作用，从而闭合MnBi$_2$Te$_4$的表面磁隙；提出利用电场或界面场恢复磁隙并调控拓扑性，为稳健量子化输运提供位移场工程方案。
AI 中文摘要
本征磁性拓扑绝缘体MnBi$_2$Te$_4$中量子化反常输运的广泛实验实现受到其难以捉摸的表面磁隙的阻碍。揭示无隙态的起源对于获取其拓扑性质至关重要。在此我们表明，表面缺陷降低静电势，驱动拓扑表面态进入亚表面层，抑制交换相互作用，从而闭合磁隙。通过外部电场或范德华异质结构中的界面场调节表面静电势，可恢复预期的磁隙并实现对其拓扑性的控制。这一结论得到模型计算证实，并在与极性绝缘体界面的缺陷MnBi$_2$Te$_4$薄膜中得到验证，解释了近期实验中观察到的在AlO$_x$覆盖下增强的量子反常霍尔效应。我们的理论将静电驱动的表面态离域识别为磁隙抑制的一个竞争性起源，并提出位移场工程以实现稳健的量子化输运。
英文摘要
A widespread experimental realization of quantized anomalous transport in the intrinsic magnetic topological insulator MnBi$_2$Te$_4$ is hindered by its elusive surface magnetic gap. Uncovering the origin of the gapless states is essential for accessing its topological properties. Here we show that surface defects lower the electrostatic potential, drive topological surface states into subsurface layers, suppress exchange interactions, thereby closing the gap. Tuning the surface electrostatic potential via external electric fields or interfacial fields in van der Waals heterostructures restores the expected gap and enables control of its topology. This is confirmed by model calculations and validated in defective MnBi$_2$Te$_4$ films interfaced with polar insulators, explaining the enhanced quantum anomalous Hall effect under AlO$_x$ capping observed in recent experiments. Our theory identifies electrostatically driven surface-state delocalization as a competitive origin of gap suppression and proposes displacement-field engineering for robust quantized transport.
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