Local invariants identify topology in metals and gapless systems
Local invariants identify topology in metals and gapless systems
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DOI：
10.1103/physrevb.106.064109
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发表时间：
2022-08-30
影响因子：
3.7
通讯作者：
Loring, Terry A.
中科院分区：
文献类型：
--
作者：
Cerjan, Alexander;Loring, Terry A.
尽管拓扑能带理论已被用于发现和分类绝缘和半金属系统中的各种新型拓扑相，但它并不适合于识别金属或无间隙系统中的拓扑现象。在这里，我们基于系统的光谱定位器和相关的Clifford伪光谱开发了拓扑金属理论，该理论既可以确定系统是否在存在简并体带的情况下表现出边界局域化状态，也可以在没有体带隙的情况下提供这些状态的拓扑保护措施。我们在两个晶格系统中证明了这种方法在对称类上的通用性，一个陈氏金属和一个高阶拓扑金属，并证明了这些系统的拓扑对相对强的扰动具有鲁棒性。定义金属和无间隙系统的不变量的能力使得在广泛的自然、光子和其他人工材料中发现拓扑现象成为可能，而这些现象以前是无法探索的。
Although topological band theory has been used to discover and classify a wide array of novel topological phases in insulating and semimetal systems, it is not well suited to identifying topological phenomena in metallic or gapless systems. Here, we develop a theory of topological metals based on the system's spectral localizer and associated Clifford pseudospectrum, which can both determine whether a system exhibits boundary-localized states despite the presence of degenerate bulk bands and provide a measure of these states' topological protection even in the absence of a bulk band gap. We demonstrate the generality of this method across symmetry classes in two lattice systems, a Chern metal and a higher-order topological metal, and prove the topology of these systems is robust to relatively strong perturbations. The ability to define invariants for metallic and gapless systems allows for the possibility of finding topological phenomena in a broad range of natural, photonic, and other artificial materials that could not be previously explored.