Liu Jieyi, Singh Angadjit, Liu Yu Yang Fredrik, Ionescu Adrian, Achinuq Barat, Barnes Crispin H W, Hesjedal Thorsten
Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Nano Lett. 2020 Jul 8;20(7):5315-5322. doi: 10.1021/acs.nanolett.0c01666. Epub 2020 Jun 24.
Magnetic doping and proximity coupling can open a band gap in a topological insulator (TI) and give rise to dissipationless quantum conduction phenomena. Here, by combining these two approaches, we demonstrate a novel TI superlattice structure that is alternately doped with transition and rare earth elements. An unexpected exchange bias effect is unambiguously confirmed in the superlattice with a large exchange bias field using magneto-transport and magneto-optical techniques. Further, the Curie temperature of the Cr-doped layers in the superlattice is found to increase by 60 K compared to a Cr-doped single-layer film. This result is supported by density-functional-theory calculations, which indicate the presence of antiferromagnetic ordering in Dy:BiTe induced by proximity coupling to Cr:SbTe at the interface. This work provides a new pathway to realizing the quantum anomalous Hall effect at elevated temperatures and axion insulator state at zero magnetic field by interface engineering in TI heterostructures.
磁性掺杂和近邻耦合可以在拓扑绝缘体（TI）中打开一个带隙，并产生无耗散量子传导现象。在这里，通过结合这两种方法，我们展示了一种交替掺杂过渡元素和稀土元素的新型TI超晶格结构。利用磁输运和磁光技术，在具有大交换偏置场的超晶格中明确证实了意外的交换偏置效应。此外，发现超晶格中Cr掺杂层的居里温度比Cr掺杂单层膜提高了60K。这一结果得到了密度泛函理论计算的支持，该计算表明在界面处与Cr:SbTe近邻耦合诱导的Dy:BiTe中存在反铁磁有序。这项工作为通过TI异质结构中的界面工程在高温下实现量子反常霍尔效应和在零磁场下实现轴子绝缘体状态提供了一条新途径。
