Shin Dongbin, Sato Shunsuke A, Hübener Hannes, De Giovannini Umberto, Kim Jeongwoo, Park Noejung, Rubio Angel
Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea.
Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany.
Proc Natl Acad Sci U S A. 2019 Mar 5;116(10):4135-4140. doi: 10.1073/pnas.1816904116. Epub 2019 Feb 14.
Materials can be classified by the topological character of their electronic structure and, in this perspective, global attributes immune to local deformations have been discussed in terms of Berry curvature and Chern numbers. Except for instructional simple models, linear response theories have been ubiquitously used in calculations of topological properties of real materials. Here we propose a completely different and versatile approach to obtain the topological characteristics of materials by calculating physical observables from the real-time evolving Bloch states: The cell-averaged current density reveals the anomalous velocities that lead to the conductivity quantum. Results for prototypical cases are shown, including a spin-frozen valley Hall and a quantum anomalous Hall insulator. The advantage of this method is best illustrated by the example of a quantum spin Hall insulator: The quantized spin Hall conductivity is straightforwardly obtained irrespective of the non-Abelian nature in its Berry curvature. Moreover, the method can be extended to the description of real observables in nonequilibrium states of topological materials.
材料可以根据其电子结构的拓扑特性进行分类,从这个角度来看,已根据贝里曲率和陈数讨论了对局部变形免疫的全局属性。除了用于教学的简单模型外,线性响应理论已被广泛用于计算实际材料的拓扑性质。在此,我们提出一种完全不同且通用的方法,通过从实时演化的布洛赫态计算物理可观测量来获得材料的拓扑特征:元胞平均电流密度揭示了导致电导率量子化的反常速度。展示了典型案例的结果,包括自旋冻结的谷霍尔和量子反常霍尔绝缘体。量子自旋霍尔绝缘体的例子最能说明这种方法的优势:无论其贝里曲率中的非阿贝尔性质如何,都能直接获得量子化的自旋霍尔电导率。此外,该方法可以扩展到描述拓扑材料非平衡态中的实际可观测量。