Zheng Guolin, Wang Ning, Yang Jiyong, Wang Weike, Du Haifeng, Ning Wei, Yang Zhaorong, Lu Hai-Zhou, Zhang Yuheng, Tian Mingliang
High Magnetic Field Laboratory, the Chinese Academy of Sciences, Hefei 230031, the People's Republic of China; University of Science and Technology of China, Hefei 230026, The People's Republic of China.
Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, The People's Republic of China.
Sci Rep. 2016 Feb 19;6:21334. doi: 10.1038/srep21334.
Many exotic physics anticipated in topological insulators require a gap to be opened for their topological surface states by breaking time reversal symmetry. The gap opening has been achieved by doping magnetic impurities, which however inevitably create extra carriers and disorder that undermine the electronic transport. In contrast, the proximity to a ferromagnetic/ferrimagnetic insulator may improve the device quality, thus promises a better way to open the gap while minimizing the side-effects. Here, we grow thin single-crystal Sb1.9Bi0.1Te3 micro flakes on insulating ferrimagnet BaFe12O19 by using the van der Waals epitaxy technique. The micro flakes show a negative magnetoresistance in weak perpendicular fields below 50 K, which can be quenched by increasing temperature. The signature implies the weak localization effect as its origin, which is absent in intrinsic topological insulators, unless a surface state gap is opened. The surface state gap is estimated to be 10 meV by using the theory of the gap-induced weak localization effect. These results indicate that the magnetic proximity effect may open the gap for the topological surface attached to BaM insulating ferrimagnet. This heterostructure may pave the way for the realization of new physical effects as well as the potential applications of spintronics devices.
拓扑绝缘体中预期的许多奇异物理现象需要通过打破时间反演对称性来为其拓扑表面态打开能隙。通过掺杂磁性杂质已经实现了能隙的打开，然而这不可避免地会产生额外的载流子和无序，从而破坏电子输运。相比之下，接近铁磁/亚铁磁绝缘体可能会提高器件质量，因此有望提供一种更好的方法来打开能隙，同时将副作用降至最低。在此，我们利用范德华外延技术在绝缘亚铁磁体BaFe12O19上生长了薄的单晶Sb1.9Bi0.1Te3微片。这些微片在低于50 K的弱垂直磁场中表现出负磁阻，该负磁阻可通过升高温度而被淬灭。这一特征表明其起源为弱局域化效应，而在本征拓扑绝缘体中不存在这种效应，除非打开表面态能隙。利用能隙诱导的弱局域化效应理论，估计表面态能隙为10 meV。这些结果表明，磁近邻效应可能会为附着在BaM绝缘亚铁磁体上的拓扑表面打开能隙。这种异质结构可能为实现新的物理效应以及自旋电子器件的潜在应用铺平道路。
