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Creating anomalous Floquet Chern insulators with magnetic quantum walks

机译:利用磁量子游走创建异常的Floquet Chern绝缘子

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摘要

We propose a realistic scheme to construct anomalous Floquet Chern topological insulators using spin-1/2 particles carrying out a discrete-time quantum walk in a two-dimensional lattice. By Floquet engineering the quantum-walk protocol, an Aharonov-Bohm geometric phase is imprinted onto closed-loop paths in the lattice, thus realizing an Abelian gauge field, the analog of a magnetic flux threading a two-dimensional electron gas. We show that in the strong-field regime, when the flux per plaquette is a sizable fraction of the flux quantum, magnetic quantum walks give rise to nearly flat energy bands featuring nonvanishing Chern numbers. Furthermore, we find that because of the nonperturbative nature of the periodic driving, a second topological number, the so-called RLBL invariant, is necessary to fully characterize the anomalous Floquet topological phases of magnetic quantum walks and to compute the number of topologically protected edge modes expected at the boundaries between different phases. In the second part of this paper, we discuss an implementation of this scheme using neutral atoms in two-dimensional spin-dependent optical lattices, which enables the generation of arbitrary magnetic-field landscapes, including those with sharp boundaries. The robust atom transport, which is observed along boundaries separating regions of different field strength, reveals the topological character of the Floquet Chern bands.
机译:我们提出了一个现实的方案,使用自旋1/2粒子在二维晶格中执行离散时间的量子游走,来构造异常的Floquet Chern拓扑绝缘体。通过Floquet工程公司的量子行走协议,将Aharonov-Bohm几何相位印在晶格中的闭环路径上,从而实现了阿贝尔规范场,该磁场类似于磁通量二维电子气的模拟。我们显示出,在强场状态下,当每块弹丸的通量是通量量子的相当大的一部分时,磁量子步态会产生具有不消失的Chern数的几乎平坦的能带。此外,我们发现由于周期性驱动的非扰动性质,第二个拓扑数,即所谓的RLBL不变量,对于充分表征磁量子行走的异常Floquet拓扑相并计算拓扑保护边的数量是必需的在不同阶段之间的边界处期望的模式。在本文的第二部分中,我们讨论了在二维自旋相关的光学晶格中使用中性原子实现此方案的方法,该方法可以生成任意磁场,包括边界清晰的磁场。沿分开不同场强区域的边界观察到的稳健原子传输揭示了Floquet Chern能带的拓扑特征。

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  • 来源
    《Physical review》 |2019年第21期|214303.1-214303.19|共19页
  • 作者单位

    Univ Bonn, Inst Angew Phys, Wegelerstr 8, D-53115 Bonn, Germany;

    Univ Bonn, Inst Angew Phys, Wegelerstr 8, D-53115 Bonn, Germany|Hungarian Acad Sci, Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary;

    Univ Bonn, Inst Angew Phys, Wegelerstr 8, D-53115 Bonn, Germany;

    Leibniz Univ Hannover, Inst Theoret Phys, Appelstr 2, D-30167 Hannover, Germany;

    Univ Bonn, Inst Angew Phys, Wegelerstr 8, D-53115 Bonn, Germany;

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