arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2202.07655cond-mat.mes-hall
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多重交联Su-Schrieffer-Heeger链的拓扑结构

Topology of multiple cross-linked Su-Schrieffer-Heeger chains

A. Sivan, M. Orenstein

摘要:

在聚合物科学中,与一维组成链相比,聚合物链的交联产生了实质上改性的系统,这是由于维度的增加和缺陷(交联位点)的有效播种。受这一概念的启发,我们分析了一个广义拓扑网格的单位细胞的拓扑特征,包括通过一个单一的网站交联的几个一维苏-施里弗-海格尔(SSH)晶格。耦合网站的功能作为一个缺陷与保护状态的平凡制度,也诱导边缘内的散装与保护本地化的国家围绕它的拓扑制度。当两个以上的晶格耦合的缺陷,即,一个图维数大于1,交叉链支持两种类型的本地化的缺陷周围的本征态。一种类型是高度可控的,通过修改交联强度,使广泛的调谐本征能被淹没在体带成为高度隔离和保护。我们发现,这些独特的功能可以解释由上述系统的SSH链耦合noncurrently到外部水库的等价物,产生一个独特的赝光谱的体积和本地化的状态,空间对称的本征态。应用非厄米性通过增加增益和损失的交替网站,相关的,例如可能实现的拓扑耦合激光织物,我们观察到一个突然的过渡的拓扑保护的中间间隙状态从反本地化到本地化附近的缺陷。通过改变增益-损耗参数,我们观察到级联的空间对称性破缺的支持状态的特殊点,奇偶时间对称性被打破,本地化和散装状态,表现出各种新颖的相位。

英文摘要:

In polymer science, cross-linking of polymer chains yields a substantially modified system compared to the one-dimensional constituent chains, due to the increase of dimensionality and effective seeding by defects (cross-linking sites). Inspired by this concept, we analyze topological features of a unit cell of a generalized topological mesh comprised of several one-dimensional Su-Schrieffer-Heeger (SSH) lattices cross-linked via a single site. The coupling site functions as a defect with protected states in the trivial regime and also induces edges inside the bulk with protected localized states centered around it in the topological regime. When more than two lattices are coupled by the defect, namely, a graph-dimensionality larger than one, the crossed chains support two types of localized eigenstates around the defect. One type is highly controllable by modifying the cross-linking strength, enabling broad tuning of eigenenergies from being submerged in the bulk band to becoming highly isolated and protected. We show that these unique features can be explained by an equivalence of the aforementioned system to an SSH chain coupled nonreciprocally to an external reservoir, yielding a unique pseudospectrum for both the bulk and localized states, with spatially symmetric eigenstates. Applying non-Hermiticity by adding gain and loss to alternating sites, relevant for example to a possible realization of topological coupled-laser fabric, we observe an abrupt transition of the topologically protected mid-gap state from anti-localized to localized near the defect. By changing the gain-loss parameters, we observe a cascaded spatial symmetry breaking of the supported states at exceptional points where parity-time symmetry is broken, for both the localized and the bulk states, exhibiting various novel phases.

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