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Origin of magnetic inhomogeneity in Cr- and V-doped topological insulators

机译：CR-和V掺杂拓扑绝缘体中磁性不均匀性的起源

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The quantum anomalous Hall effect (QAHE) has been experimentally observed in magnetically doped topological insulators at ultralow temperatures. Inhomogeneous ferromagnetism is considered to be one of the main factors that lead to the unexpected low QAHE observation temperature. Dopant-induced disorder is usually the origin of the inhomogeneous ferromagnetism. Here, our systematic first-principles calculations demonstrate that inhomogeneous mixing of Bi and Sb in a (Bi, Sb)_2Te_3 system is the intrinsic origin of inhomogeneous ferromagnetism. Different from diluted magnetic semiconductors, the mixing energy of Cr and Ⅴ in Bi_2Se_3, Sb_2Te_3, and (Bi, Sb)_2Te_3 topological insulators clearly show that magnetic dopants are homogeneously distributed even in the presence of naturally formed crystalline defects. Surprisingly, our study shows that the mixing energies of Sb and Bi in a (Bi, Sb)_2Te_3 system are all positive in the whole range of doping concentration, indicating that Bi elements in a (Bi, Sb)_2Te_3 system are inhomogeneously distributed. Moreover, the formation energies of Cr and Ⅴ suggest that they are relatively easy to substitute Bi sites in Bi inhomogeneously distributed (Bi, Sb)_2Te_3 systems, which leads to inhomogeneous ferromagnetism of the experimental QAHE system. The influence of the inhomogeneous distribution of Bi on the electronic structures of bulk (Bi, Sb)_2Te_3 systems is also analyzed. We believe that our finding of the intrinsic origin of magnetic inhomogeneity should be beneficial for the experimental enhancement of the QAHE observation temperature in magnetically doped topological insulators.
机译：在超级温度下，在磁掺杂拓扑绝缘体中已经通过实验观察量子异常霍尔效应（QAHE）。不均匀的铁磁性被认为是导致意外低QAHE观察温度的主要因素之一。掺杂剂诱导的疾病通常是不均匀铁磁性的起源。这里，我们的系统的第一原理计算表明，Bi和Sb的非均匀混合（Bi，Sb）_2Te_3系统是非均匀铁磁性的内在起源。与稀释的磁半导体不同，Cr和ⅴ中的混合能量在Bi_2Se_3，Sb_2Ste_3和（Bi，Sb）_2Te_3拓扑绝缘体中清楚地表明即使在天然形成的晶体缺陷存在下也均匀地分布。令人惊讶的是，我们的研究表明，在A（Bi，Sb）_2Te_3系统中的Sb和Bi的混合能量在整个掺杂浓度范围内都是正的，表明（Bi，Sb）_2te_3系统中的BI元素是不均匀分布的。此外，CR和Ⅳ的形成能量表明它们相对容易替代Bi Inohomeneply分布（Bi，Sb）_2Te_3系统中的BI位点，这导致实验性QAHE系统的不均匀铁磁性。还分析了BI的非均匀分布对散装（BI，SB）_2TE_3系统的电子结构的影响。我们认为，我们的发现磁性不均匀性的内在原点应该有利于磁掺杂拓扑绝缘体中的QAHE观察温度的实验性提升。

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  • 来源
    《Physical review》 |2020年第24期|241407.1-241407.6|共6页
  • 作者

    Shifei Qi; Zheng Liu; Maozhi Chang; Ruiling Gao; Yulei Han; Zhenhua Qiao;

  • 作者单位

    College of Physics Hebei Normal University Shijiazhuang Hebei 050024 China ICQD Hefei National Laboratory for Physical Sciences at Microscale CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics and Department of Physics University of Science and Technology of China Hefei Anhui 230026 China;

    ICQD Hefei National Laboratory for Physical Sciences at Microscale CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics and Department of Physics University of Science and Technology of China Hefei Anhui 230026 China;

    Institute of Materials Science Shand Normal University Linfen Shanxi 041004 China;

    Institute of Materials Science Shand Normal University Linfen Shanxi 041004 China College of Physics Hebei Normal University Shijiazhuang Hebei 050024 China;

    ICQD Hefei National Laboratory for Physical Sciences at Microscale CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics and Department of Physics University of Science and Technology of China Hefei Anhui 230026 China;

    ICQD Hefei National Laboratory for Physical Sciences at Microscale CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics and Department of Physics University of Science and Technology of China Hefei Anhui 230026 China;

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