Spin Berry phase in anisotropic topological insulators
Spin Berry phase in anisotropic topological insulators
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DOI：
10.1103/physrevb.84.195406
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发表时间：
2011-11-02
影响因子：
3.7
通讯作者：
Tanaka, Akihiro
中科院分区：
文献类型：
--
作者：
Imura, Ken-Ichiro;Takane, Yositake;Tanaka, Akihiro
三维拓扑绝缘体的特征是存在受保护的无间隙自旋螺旋表面态。在真实采样中，这些曲面状态从一个曲面延伸到另一个曲面，覆盖整个采样。通常，在拓扑绝缘体的曲面上，处于表面态的电子获得自旋Berry相，作为有效表面自旋必须遵循真实空间几何的切面的约束的表达。当电子环绕时，例如在圆柱体周围一次时，这样的Berry相加起来为pi。现实的拓扑绝缘体化合物通常也是层状的，即各向异性的。我们明确地证明了这种pi-Berry相的存在和不存在(由于晶体的各向异性)的柱状对称性，也就是说，无论是否满足自旋到表面的锁定条件。利用pi-通量管穿透的拓扑绝缘体纳米线的紧束缚模型实现，数值验证了自旋Berry相pi对柱对称破缺的稳健性。
Three-dimensional topological insulators are characterized by the presence of protected gapless spin helical surface states. In realistic samples these surface states are extended from one surface to another, covering the entire sample. Generally, on a curved surface of a topological insulator an electron in a surface state acquires a spin Berry phase as an expression of the constraint that the effective surface spin must follow the tangential surface of real space geometry. Such a Berry phase adds up to pi when the electron encircles, e.g., once around a cylinder. Realistic topological insulators compounds are also often layered, i.e., are anisotropic. We demonstrate explicitly the existence of such a pi Berry phase in the presence and absence (due to crystal anisotropy) of cylindrical symmetry, that is, regardless of fulfilling the spin-to-surface locking condition. The robustness of the spin Berry phase pi against cylindrical symmetry breaking is confirmed numerically using a tight-binding model implementation of a topological insulator nanowire penetrated by a pi-flux tube.