拓扑绝缘体锐边表面上的Dirac电子
Dirac Electrons on a Sharply Edged Surface of Topological Insulators
摘要：
在强拓扑绝缘体（STI）表面出射的未成对无隙狄拉克电子受到体-面对应的保护，并被认为不受后向散射的影响。然而，当表面由多个具有不同取向的小平面组成时（通常形成阶梯状结构），这种无间隙狄拉克态是否在整个表面上平滑地延伸，这就不那么明显了，而且还有待明确地验证。在我们考虑的现实情况下，样品的各向异性导致在每个这样的小平面中不同的群速度。在这里，我们建议，可以通过研究STI的双曲线表面上的电子态来获得关于这个问题的更多见解。通过显式地构造表面有效哈密顿量，我们证明了没有后向散射发生在一个凹$90^\circ$台阶边缘。一个强大的重整化的速度在附近的台阶边缘也建议。
英文摘要：
An unpaired gapless Dirac electron emergent at the surface of a strong topological insulator (STI) is protected by the bulk-surface correspondence and believed to be immune to backward scattering. It is less obvious, however, and yet to be verified explicitly whether such a gapless Dirac state is smoothly extended over the entire surface when the surface is composed of more than a single facet with different orientations in contact with one another at sharp corner edges (typically forming a steplike structure). In the realistic situation that we consider, the anisotropy of the sample leads to different group velocities in each of such facets. Here, we propose that much insight on this issue can be obtained by studying the electronic states on a hyperbolic surface of an STI. By explicitly constructing the surface effective Hamiltonian, we demonstrate that no backward scattering takes place at a concave $90^\circ$ step edge. A strong renormalization of the velocity in the close vicinity of the step edge is also suggested.
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