论文标题

Floquet拓扑绝缘阶段中的反传播边缘状态

Counter-propagating edge states in Floquet topological insulating phases

论文作者

Umer, Muhammad, Bomantara, Raditya Weda, Gong, Jiangbin

论文摘要

已知由于周期性驾驶而引起的非平衡浮部拓扑阶段,它们表现出丰富而有趣的特征,没有静态类似物。通常建议表征静态拓扑系统的各种已知的拓扑不变性通常无法完全表征Floquet拓扑阶段。这一事实激发了对浮雕拓扑阶段的广泛研究,以更好地了解非平衡拓扑阶段并探索其可能的应用。在这里,我们提出了一个理论上简单的浮雕拓扑系统,该系统可能具有任意数量的反传播手性边缘状态。对我们系统的进一步研究通过调整相同的系统参数集,即几乎平坦(无分散)边缘模式的出现来揭示另一个相关功能。特别是,我们采用两末端电导和动态绕组数来表征反向传播的手性边缘状态。我们进一步证明了这种边缘状态防止对称性保存障碍的鲁棒性。最后,我们在布里渊区的某些子主流区域中确定了一个新兴的手性对称性,可以解释几乎平坦的边缘模式的存在。我们的结果在Floquet拓扑问题上暴露了更多有趣的可能性。

Nonequilibrium Floquet topological phases due to periodic driving are known to exhibit rich and interesting features with no static analogs. Various known topological invariants usually proposed to characterize static topological systems often fail to fully characterize Floquet topological phases. This fact has motivated extensive studies of Floquet topological phases to better understand nonequilibrium topological phases and to explore their possible applications. Here we present a theoretically simple Floquet topological insulating system that may possess an arbitrary number of counter-propagating chiral edge states. Further investigation into our system reveals another related feature by tuning the same set of system parameters, namely, the emergence of almost flat (dispersionless) edge modes. In particular, we employ two-terminal conductance and dynamical winding numbers to characterize counter-propagating chiral edge states. We further demonstrate the robustness of such edge states against symmetry preserving disorder. Finally, we identify an emergent chiral symmetry at certain sub-regimes of the Brillouin zone that can explain the presence of almost flat edge modes. Our results have exposed more interesting possibilities in Floquet topological matter.

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