Tang Chi, Chang Cui-Zu, Zhao Gejian, Liu Yawen, Jiang Zilong, Liu Chao-Xing, McCartney Martha R, Smith David J, Chen Tingyong, Moodera Jagadeesh S, Shi Jing
Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521, USA.
Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Sci Adv. 2017 Jun 23;3(6):e1700307. doi: 10.1126/sciadv.1700307. eCollection 2017 Jun.
The quantum anomalous Hall effect (QAHE) that emerges under broken time-reversal symmetry in topological insulators (TIs) exhibits many fascinating physical properties for potential applications in nanoelectronics and spintronics. However, in transition metal-doped TIs, the only experimentally demonstrated QAHE system to date, the QAHE is lost at practically relevant temperatures. This constraint is imposed by the relatively low Curie temperature () and inherent spin disorder associated with the random magnetic dopants. We demonstrate drastically enhanced by exchange coupling TIs to TmFeO, a high- magnetic insulator with perpendicular magnetic anisotropy. Signatures showing that the TI surface states acquire robust ferromagnetism are revealed by distinct squared anomalous Hall hysteresis loops at 400 K. Point-contact Andreev reflection spectroscopy confirms that the TI surface is spin-polarized. The greatly enhanced , absence of spin disorder, and perpendicular anisotropy are all essential to the occurrence of the QAHE at high temperatures.
在拓扑绝缘体（TI）中，时间反演对称性破缺时出现的量子反常霍尔效应（QAHE）展现出许多迷人的物理特性，在纳米电子学和自旋电子学中有潜在应用。然而，在过渡金属掺杂的TI中，这是迄今为止唯一通过实验证明的QAHE系统，在实际相关温度下QAHE会消失。这种限制是由相对较低的居里温度（）以及与随机磁性掺杂剂相关的固有自旋无序所导致的。我们通过将TI与具有垂直磁各向异性的高磁性绝缘体TmFeO进行交换耦合，证明了居里温度大幅提高。在400 K时，独特的平方反常霍尔磁滞回线揭示了TI表面态获得强铁磁性的特征。点接触安德烈夫反射光谱证实了TI表面是自旋极化的。居里温度的大幅提高、自旋无序的消除以及垂直各向异性对于高温下QAHE的出现都是必不可少的。
