论文标题
在非热米 - 米勒模型中的投影性拓扑特殊点
Projectively topological exceptional points in non-Hermitian Rice-Mele model
论文作者
论文摘要
我们研究了耦合的非米尔米米尔链，由Su-Schrieffer-Heeger（SSH）链系统组成，具有交错的现场假想电位。在二维（2D）热力学极限中，表现出特殊点（EP）具有拓扑特征：EPS对应于K空间中真实的辅助2D矢量场的拓扑缺陷，该缺陷是从非赫米特式汉密尔顿的Bloch状态获得的。作为拓扑不变的，通过绕组编号计算获得的EPS的拓扑费用为$ \ pm $ 1/2。值得注意的是，我们发现这种拓扑表征仍然存在有限数量的耦合链，甚至是单个链，其中一个方向的动量是离散的。它表明，准1D系统中的EPS仍然具有拓扑特性，并且可以成为具有对称受保护的EPS的2D系统的删节版本，这些EPS在扰动方面具有鲁棒性，这证明了准式不变性的拓扑不变性可以从它的相应2D限制系统的投影中提取。
We study coupled non-Hermitian Rice-Mele chains, which consist of Su-Schrieffer-Heeger (SSH) chain system with staggered on-site imaginary potentials. In two dimensional (2D) thermodynamic limit, the exceptional points (EPs) are shown to exhibit topological feature: EPs correspond to topological defects of a real auxiliary 2D vector field in k space, which is obtained from the Bloch states of the non-Hermitian Hamiltonian. As a topological invariant, the topological charges of EPs can be $\pm$1/2, obtained by the winding number calculation. Remarkably, we find that such a topological characterization remains for a finite number of coupled chains, even a single chain, in which the momentum in one direction is discrete. It shows that the EPs in the quasi-1D system still exhibit topological characteristics and can be an abridged version for a 2D system with symmetry protected EPs that are robust in perturbations, which proves that topological invariants for a quasi-1D system can be extracted from the projection of the corresponding 2D limit system on it.
