Observation of backscattering induced by magnetism in a topological edge state
Observation of backscattering induced by magnetism in a topological edge state
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DOI：
10.1073/pnas.2005071117
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发表时间：
2020-07-14
影响因子：
11.1
通讯作者：
Yazdani, Ali
中科院分区：
文献类型：
--
作者：
Jack, Berthold;Xie, Yonglong;Yazdani, Ali
拓扑绝缘体的边界模被非平凡的体电子态的对称性所保护。除非这些对称性被打破，否则它们可能会产生新的现象，例如一维(1D)拓扑边缘态中的量子自旋霍尔效应，其中准粒子的后向散射被时间反转对称性(TRS)抑制。在这里，我们研究了在没有TRS的情况下，铋的一维拓扑边态的性质，其中预测了发生后向散射的情况。利用扫描隧道显微镜的光谱成像和自旋极化测量，我们比较了发生在原始的双互穿双层膜边缘状态的准粒子干涉(QPI)和发生在双层薄膜边缘状态的准粒子干涉(QPI)，双层薄膜的边缘状态被破坏TRS的铁磁性铁团簇终止。我们在装饰的双层边缘上的实验揭示了一个额外的QPI分支，它可以与时间反转带对之间跨越Brioullin区中心的自旋反转散射有关。观测到的QPI特征与拓扑边缘态的理论预期完全匹配，具有一对Kramer带。综上所述，我们的结果为铋的非平凡性质提供了进一步的证据，特别是证明了在破裂的TRS通过局域磁性诱导的螺旋拓扑边缘态内的后向散射。
The boundary modes of topological insulators are protected by the symmetries of the nontrivial bulk electronic states. Unless these symmetries are broken, they can give rise to novel phe-nomena, such as the quantum spin Hall effect in one-dimensional (1D) topological edge states, where quasiparticle backscattering is suppressed by time-reversal symmetry (TRS). Here, we investi-gate the properties of the 1D topological edge state of bismuth in the absence of TRS, where backscattering is predicted to occur. Using spectroscopic imaging and spin-polarized measurements with a scanning tunneling microscope, we compared quasiparticle interference (QPI) occurring in the edge state of a pristine bis-muth bilayer with that occurring in the edge state of a bilayer, which is terminated by ferromagnetic iron clusters that break TRS. Our experiments on the decorated bilayer edge reveal an additional QPI branch, which can be associated with spin-flip scattering across the Brioullin zone center between time-reversal band partners. The observed QPI characteristics exactly match with theoretical expectations for a topological edge state, having one Kramer's pair of bands. Together, our results provide further evidence for the nontrivial nature of bismuth and in particular, demonstrate backscattering inside a helical topological edge state induced by broken TRS through local magnetism.