Quantized Anomalous Hall Effect in Magnetic Topological Insulators
Quantized Anomalous Hall Effect in Magnetic Topological Insulators
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磁拓扑绝缘体中的量子化反常霍尔效应
DOI：
10.1126/science.1187485
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发表时间：
2010-07-02
期刊：
影响因子：
56.9
通讯作者：
Fang, Zhong
中科院分区：
文献类型：
--
作者：
Yu, Rui;Zhang, Wei;Fang, Zhong
除了霍尔效应之外，铁磁体还表现出反常霍尔效应，这种效应通常与它们的磁化成正比，与磁场的存在无关。霍尔效应表现为导体对外部磁场的电压变化。这种效应在一个多世纪前首次被观察到，但还没有以量子化的形式实现。Yu等人（第61页，6月3日在线发表）提出了一种通过磁性掺杂三维拓扑绝缘体薄膜来实现量子反常霍尔系统的方法，并计算了各种掺杂剂和薄膜厚度的影响。由此产生的绝缘体预计具有长程铁磁有序，有可能加入稀磁半导体作为自旋电子应用的候选者。磁掺杂拓扑绝缘体被预测为铁磁性并表现出量子反常霍尔效应。反常霍尔效应是固体中由自旋轨道耦合引起的一种基本输运过程。在量子反常霍尔绝缘体中，自发磁矩和自旋轨道耦合结合产生拓扑上的非平凡电子结构，导致没有外部磁场的量子化霍尔效应。基于第一性原理计算，我们预测，当掺杂过渡金属元素（Cr或Fe）时，四钛矿半导体Bi2Te3、Bi2Se3和Sb2Te3形成磁有序绝缘体，而传统的稀磁半导体则需要自由载流子来调节磁耦合。在二维薄膜中，这种磁序产生了以有限陈恩数为特征的拓扑电子结构，霍尔电导量子化单位为e2/h（其中e是电子的电荷，h是普朗克常数）。
Quantum Anomalous Hall Effect In addition to the Hall effect, which appears as a voltage change in conductors in response to an external magnetic field, ferromagnets exhibit the anomalous Hall effect, which is often proportional to their magnetization and independent of the presence of the magnetic field. This effect, first observed more than a century ago, has not been realized in its quantized form. Yu et al. (p. 61, published online 3 June) propose a realization of a quantum anomalous Hall system by magnetically doping thin films of three-dimensional topological insulators and calculate the effects of various dopants and film thicknesses. The resulting insulators are predicted to have long-range ferromagnetic order, potentially joining dilute magnetic semiconductors as candidates for spintronic applications. Magnetically doped topological insulators are predicted to be ferromagnetic and exhibit the quantum anomalous Hall effect. The anomalous Hall effect is a fundamental transport process in solids arising from the spin-orbit coupling. In a quantum anomalous Hall insulator, spontaneous magnetic moments and spin-orbit coupling combine to give rise to a topologically nontrivial electronic structure, leading to the quantized Hall effect without an external magnetic field. Based on first-principles calculations, we predict that the tetradymite semiconductors Bi2Te3, Bi2Se3, and Sb2Te3 form magnetically ordered insulators when doped with transition metal elements (Cr or Fe), in contrast to conventional dilute magnetic semiconductors where free carriers are necessary to mediate the magnetic coupling. In two-dimensional thin films, this magnetic order gives rise to a topological electronic structure characterized by a finite Chern number, with the Hall conductance quantized in units of e2/h (where e is the charge of an electron and h is Planck’s constant).