Physics Institute II, University of Cologne, Zülpicher Str. 77, 50937, Köln, Germany.
Institute for Theoretical Physics, University of Cologne, Zülpicher Str. 77, 50937, Köln, Germany.
Nat Commun. 2017 Nov 7;8(1):1340. doi: 10.1038/s41467-017-01474-8.
A prominent feature of topological insulators (TIs) is the surface states comprising of spin-nondegenerate massless Dirac fermions. Recent technical advances have made it possible to address the surface transport properties of TI thin films by tuning the Fermi levels of both top and bottom surfaces. Here we report our discovery of a novel planar Hall effect (PHE) from the TI surface, which results from a hitherto-unknown resistivity anisotropy induced by an in-plane magnetic field. This effect is observed in dual-gated devices of bulk-insulating Bi Sb Te thin films, where the field-induced anisotropy presents a strong dependence on the gate voltage with a characteristic two-peak structure near the Dirac point. The origin of PHE is the peculiar time-reversal-breaking effect of an in-plane magnetic field, which anisotropically lifts the protection of surface Dirac fermions from backscattering. The observed PHE provides a useful tool to analyze and manipulate the topological protection of the TI surface.
拓扑绝缘体的一个显著特点是其表面态包含自旋非简并的无质量狄拉克费米子。最近的技术进步使得通过调节顶部和底部表面的费米能级来研究拓扑绝缘体薄膜的表面输运性质成为可能。在这里，我们报告了一种来自拓扑绝缘体表面的新型平面霍尔效应（PHE）的发现，该效应源自平面磁场引起的未知电阻各向异性。这种效应在体绝缘 BiSbTe 薄膜的双栅器件中被观察到，其中场诱导各向异性与栅极电压强烈相关，在狄拉克点附近呈现出双峰结构。PHE 的起源是平面磁场的反常时间反演破坏效应，它各向异性地破坏了表面狄拉克费米子免受背散射的保护。所观察到的 PHE 为分析和操纵拓扑绝缘体表面的拓扑保护提供了有用的工具。
