论文标题

Floquet拓扑绝缘子中的异常悬浮和an灭

Anomalous levitation and annihilation in Floquet topological insulators

论文作者

Liu, Hui, Fulga, Ion Cosma, Asboth, Janos K.

论文摘要

安德森(Anderson)在二维拓扑绝缘子中的定位是通过所谓的悬浮和歼灭过程进行的。随着疾病的增加,携带相反拓扑不变的扩展散装状态在能量方面相互朝向彼此,减少了拓扑间隙的大小,最终会遇到和本地化。这导致了拓扑的安德森绝缘子。在这里,我们介绍了异常的悬浮和歼灭,这是一个定期驱动或Floquet系统独有的过程。由于准谱系的周期性,我们发现拓扑间隙可能会随着无序力量的函数而增加。因此,毕竟所有散装状态都已经定位,该系统在拓扑上仍然是不平凡的,形成了异常的浮雕安德森绝缘子(AFAI)阶段。我们展示了此过程的具体示例,通过现场潜在的“踢”为Chern绝缘子模型增加了障碍。通过更改两次踢的周期,我们可以调节系统中发生哪种类型的(常规或异常)悬浮。我们希望我们的结果适用于通用的Floquet拓扑系统,并提供一种可访问的方法来实验实现AFAI,而无需多步驾驶方案。

Anderson localization in two-dimensional topological insulators takes place via the so-called levitation and pair annihilation process. As disorder is increased, extended bulk states carrying opposite topological invariants move towards each other in energy, reducing the size of the topological gap, eventually meeting and localizing. This results in a topologically trivial Anderson insulator. Here, we introduce the anomalous levitation and pair annihilation, a process unique to periodically-driven, or Floquet systems. Due to the periodicity of the quasienergy spectrum, we find it is possible for the topological gap to increase as a function of disorder strength. Thus, after all bulk states have localized, the system remains topologically nontrivial, forming an anomalous Floquet Anderson insulator (AFAI) phase. We show a concrete example for this process, adding disorder via onsite potential "kicks" to a Chern insulator model. By changing the period between kicks, we can tune which type of (conventional or anomalous) levitation-and-annihilation occurs in the system. We expect our results to be applicable to generic Floquet topological systems and to provide an accessible way to realize AFAIs experimentally, without the need for multi-step driving schemes.

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