Second-Order Topological Phases in Non-Hermitian Systems
Second-Order Topological Phases in Non-Hermitian Systems
复制标题
非厄米系统中的二阶拓扑相
DOI：
10.1103/physrevlett.122.076801
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发表时间：
2019-02-20
影响因子：
8.6
通讯作者：
Nori, Franco
中科院分区：
文献类型：
--
作者：
Liu, Tao;Zhang, Yu-Ran;Nori, Franco
d维二阶拓扑绝缘体（SOTI）可以承载拓扑保护的（d - 2）维无带隙边界模式。在这里，我们表明，一个二维非厄米SOTI可以主机零能量模式在其角落。与厄米的情况相反，这些零能量模式只能局限在一个角落。一个3D非厄米SOTI示出支持二阶边界模式，这是本地化的不是沿着铰链，但在一个角落里的恶意。在二阶2D（3D）非厄米系统中，通常的体角（铰链）对应被打破。基于复波矢量的缠绕数（陈数）被用来表征二维（三维）的二阶拓扑相位。还讨论了超冷原子的一种可能的实验情况。我们的工作奠定了基石，探索非厄米特系统中的高阶拓扑现象。
A d-dimensional second-order topological insulator (SOTI) can host topologically protected (d - 2)-dimensional gapless boundary modes. Here, we show that a 2D non-Hermitian SOTI can host zero-energy modes at its corners. In contrast to the Hermitian case, these zero-energy modes can be localized only at one corner. A 3D non-Hermitian SOTI is shown to support second-order boundary modes, which are localized not along hinges but anomalously at a corner. The usual bulk-corner (hinge) correspondence in the second-order 2D (3D) non-Hermitian system breaks down. The winding number (Chern number) based on complex wave vectors is used to characterize the second-order topological phases in 2D (3D). A possible experimental situation with ultracold atoms is also discussed. Our work lays the cornerstone for exploring higher-order topological phenomena in non-Hermitian systems.