Moon Jisoo, Kim Jinwoong, Koirala Nikesh, Salehi Maryam, Vanderbilt David, Oh Seongshik
Department of Physics and Astronomy , Rutgers, The State University of New Jersey , Piscataway , New Jersey 08854 , United States.
Department of Materials Science and Engineering , Rutgers, The State University of New Jersey , Piscataway , New Jersey 08854 , United States.
Nano Lett. 2019 Jun 12;19(6):3409-3414. doi: 10.1021/acs.nanolett.8b03745. Epub 2019 May 2.
The anomalous Hall effect (AHE) is a nonlinear Hall effect appearing in magnetic conductors, boosted by internal magnetism beyond what is expected from the ordinary Hall effect. With the recent discovery of the quantized version of the AHE, the quantum anomalous Hall effect (QAHE), in Cr- or V-doped topological insulator (TI) (Sb,Bi)Te thin films, the AHE in magnetic TIs has been attracting significant interest. However, one of the puzzles in this system has been that while Cr- or V-doped (Sb,Bi)Te and V-doped BiSe exhibit AHE, Cr-doped BiSe has failed to exhibit even ferromagnetic AHE, the expected predecessor to the QAHE, though it is the first material predicted to exhibit the QAHE. Here, we have successfully implemented ferromagnetic AHE in Cr-doped BiSe thin films by utilizing a surface state engineering scheme. Surprisingly, the observed ferromagnetic AHE in the Cr-doped BiSe thin films exhibited only a positive slope regardless of the carrier type. We show that this sign problem can be explained by the intrinsic Berry curvature of the system as calculated from a tight-binding model combined with a first-principles method.
反常霍尔效应（AHE）是出现在磁性导体中的一种非线性霍尔效应，由内部磁性增强，超出了普通霍尔效应的预期。随着最近在Cr或V掺杂的拓扑绝缘体（TI）（Sb，Bi）Te薄膜中发现了AHE的量子化版本，即量子反常霍尔效应（QAHE），磁性拓扑绝缘体中的AHE引起了极大的关注。然而，该系统中的一个谜题是，虽然Cr或V掺杂的（Sb，Bi）Te以及V掺杂的BiSe表现出AHE，但Cr掺杂的BiSe甚至未能表现出预期的QAHE前身——铁磁反常霍尔效应，尽管它是首个被预测会表现出QAHE的材料。在此，我们通过利用一种表面态工程方案，成功在Cr掺杂的BiSe薄膜中实现了铁磁反常霍尔效应。令人惊讶的是，在Cr掺杂的BiSe薄膜中观察到的铁磁反常霍尔效应无论载流子类型如何都仅表现出正斜率。我们表明，这个符号问题可以通过结合第一性原理方法的紧束缚模型计算出的系统固有贝里曲率来解释。
