Realization of a tunable surface Dirac gap in Sb-doped MnBi2Te4
Realization of a tunable surface Dirac gap in Sb-doped MnBi2Te4
复制标题
掺锑表面可调狄拉克能隙的实现
DOI：
10.1103/physrevb.103.l121112
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发表时间：
2021-03-17
影响因子：
3.7
通讯作者：
Liu, Chang
中科院分区：
文献类型：
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作者：
Ma, Xiao-Ming;Zhao, Yufei;Liu, Chang
最近在化学计量比反铁磁拓扑绝缘体MnBi2Te4薄膜中观察到量子反常霍尔效应和轴子电动力学的特征。轴离子绝缘体的体拓扑磁电响应的直接证据需要在其拓扑表面态(TSS)处有能隙。然而，独立的光谱实验显示，这样的表面间隙比之前认为的要小得多。在这里，我们利用角分辨光电子能谱和密度泛函理论计算证明，在Sb掺杂的MnBi2Te4中意外地存在一个相当大的TSS能隙，其中体相系统在拓扑上保持不平凡。这一能隙对体相变不敏感，但随着Sb浓度的增加而增大，使得费米能级和TSS能隙大小同时可调(最高可达&gT；100 meV)。我们的工作表明，Sb掺杂不仅可以控制MnBi2Te4的费米能级，还可以引起可调的表面带隙，为观察高温轴子-绝缘体相的关键特性提供了潜在的平台。
Signatures of both the quantum anomalous Hall effect and axion electrodynamics have been recently observed to exist in thin films of MnBi2Te4, a stoichiometric antiferromagnetic topological insulator. Direct evidence of the bulk topological magnetoelectric response in an axion insulator requires an energy gap at its topological surface state (TSS). However, independent spectroscopic experiments revealed that such a surface gap is much smaller than previously thought. Here we utilize angle resolved photoemission spectroscopy and density functional theory calculations to demonstrate that a sizable TSS gap unexpectedly exists in Sb-doped MnBi2Te4 where the bulk system remains topologically nontrivial. This gap is found to be insensitive to the bulk antiferromagnetic-paramagnetic transition, while it enlarges along with increasing Sb concentration, enabling simultaneous tunability of the Fermi level and the TSS gap size (up to >100 meV). Our work shows that Sb dopants in MnBi2Te4 can not only control the Fermi level but also induce a tunable surface gap, providing a potential platform to observe the key features of the high-temperature axion-insulator phase.