论文标题
在拓扑磁铁MNBI2TE4中，抗铁磁和铁磁阶的抗铁磁序之间的明显磁性间隙
Distinct magnetic gaps between antiferromagnetic and ferromagnetic orders driven by surface defects in the topological magnet MnBi2Te4
论文作者
论文摘要
磁性绝缘体MNBI $ _2 $ te $ _4 $，在薄膜传输中显示了零磁场（抗磁场，AFM）的金属行为，与垂直分辨的光效率光谱观察到无间隙的表面状态，同时可以在较大的6 t t t the fireromag上观察到的光效率光谱，同时可以成为Chern Insulator。因此，曾经据推测，零场表面磁磁与散装AFM相有所不同。然而，最近的磁力显微镜通过检测表面上的持续AFM顺序来反驳这一假设。在这项工作中，我们提出了一种与表面缺陷有关的机制，该机制可以使这些矛盾的观察结果合理化，在不同的实验中。我们发现，在范德华层中换成Mn和Bi原子的共抗性可以在AFM相中强烈抑制磁间隙，而无需违反磁性顺序，但在FM相中保留了磁性间隙。 AFM和FM相之间的不同差距大小是由缺陷引起的表面电荷重新分布引起的。该理论可以通过未来表面光谱测量的位置和田间依赖性差距来验证。我们的工作建议在样品中抑制相关的缺陷，以实现零场处的量子异常绝缘子或轴突绝缘子。
The magnetic topological insulator, MnBi$_2$Te$_4$, shows metallic behavior at zero magnetic fields (antiferromagnetic phase, AFM) in thin film transport, which coincides with gapless surface states observed by angle-resolved photoemission spectroscopy, while it can become a Chern insulator at field larger than 6 T (ferromagnetic phase, FM). Thus, the zero-field surface magnetism was once speculated to be different from the bulk AFM phase. However, recent magnetic force microscopy refutes this assumption by detecting persistent AFM order on the surface. In this work, we propose a mechanism related to surface defects that can rationalize these contradicting observations in different experiments. We find that co-antisites (exchanging Mn and Bi atoms in the surface van der Waals layer) can strongly suppress the magnetic gap down to several meV in the AFM phase without violating the magnetic order but preserve the magnetic gap in the FM phase. The different gap sizes between AFM and FM phases are caused by the defect-induced surface charge redistribution among top two van der Waals layers. This theory can be validated by the position- and field-dependent gap in future surface spectroscopy measurements. Our work suggests suppressing related defects in samples to realize the quantum anomalous Hall insulator or axion insulator at zero fields.
