论文标题

Hofstadter蝴蝶的万花筒和Aharonov-bohm笼子,$ 2^n $ - root toutepology在装饰方形晶格中

Kaleidoscopes of Hofstadter Butterflies and Aharonov-Bohm caging from $2^n$-root topology in decorated square lattices

论文作者

Marques, A. M., Mögerle, J., Pelegrí, G., Flannigan, S., Dias, R. G., Daley, A. J.

论文摘要

Square-root拓扑描述了模型,其拓扑特性可以在平方的哈密顿量时揭示,该模型产生了各自的父母拓扑绝缘子。该概念最近已被推广到$ 2^n $ - root拓扑,表征了模型,其中$ n $ squaring操作必须应用于汉密尔顿人,以便到达模型的拓扑来源。在本文中,我们分析了准阶数(准1D)和二维(2D)$ 2^n $ - 根模型的霍夫史塔特制度,后者的型号(SL)(SL)(SL)(SL)(以Hofstadter butterfly而闻名)。我们表明,在增加模型的根测度后,出现多个磁通量不敏感的平坦带,并通过分析确定相应的本征态。这些可以重铸为紧凑的局部状态(CLS),占据了晶格的有限区域。对于有限的通量,这些CLS对应于同一Aharonov-Bohm(AB)笼中包含的不同谐波。此外,随着根度的增加,蝴蝶的万花筒出现在霍夫史塔特图中,每个蝴蝶构成了原始SL的拓扑相等的复制品。因此,索引$ n $唯一地标识了该模型的根数,可以将其视为其Hofstadter图中存在的$ 2^n $ root模型的附加分形维度。我们讨论如何在超电原子的实验中实现这些动力学,并通过Bragg光谱或通过观察最初定位的原子在量子气体显微镜中的动力学进行测量。

Square-root topology describes models whose topological properties can be revealed upon squaring the Hamiltonian, which produces their respective parent topological insulators. This concept has recently been generalized to $2^n$-root topology, characterizing models where $n$ squaring operations must be applied to the Hamiltonian in order to arrive at the topological source of the model. In this paper, we analyze the Hofstadter regime of quasi-one-dimensional (quasi-1D) and two-dimensional (2D) $2^n$-root models, the latter of which has the square lattice (SL) (known for the Hofstadter Butterfly) as the source model. We show that upon increasing the root-degree of the model, there appear multiple magnetic flux insensitive flat bands, and analytically determine corresponding eigenstates. These can be recast as compact localized states (CLSs) occupying a finite region of the lattice. For a finite flux, these CLSs correspond to different harmonics contained within the same Aharonov-Bohm (AB) cage. Furthermore, as the root-degree increases, a kaleidoscope of butterflies is seen to appear in the Hofstadter diagram, with each butterfly constituting a topologically equivalent replica of the original one of the SL. As such, the index $n$, which uniquely identifies the root-degree of the model, can be seen as an additional fractal dimension of the $2^n$-root model present in its Hofstadter diagram. We discuss how these dynamics could be realized in experiments with ultracold atoms, and measured by Bragg spectroscopy or through observing dynamics of initially localized atoms in a quantum gas microscope.

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