论文标题

带有混合边缘的浮光拓扑绝缘子

Floquet topological insulators with hybrid edges

论文作者

Ren, Boquan, Kartashov, Yaroslav V., Wang, Hongguang, Li, Yongdong, Zhang, Yiqi

论文摘要

拓扑边缘状态在周期性材料的边缘形成,其模态光谱中具有特定的归化性,例如狄拉克点,在破坏系统某些对称性的效果的作用下。特别是,由于基础晶格电位的动态调制,在浮雕拓扑绝缘子中,单向边缘状态出现在有效的时反转对称性时。但是,通常报告了某些简单的晶格终止,例如在蜂窝晶格中的锯齿形或胡须边缘。在这里,我们表明,基于螺旋波导的阵列和杂种边缘的阵列,涉及交替的锯齿形和扶手椅段的混合边缘,即使后者很长,也可能存在非常规的拓扑边缘状态。这样的边缘状态出现在第一个布里鲁因区域的最大部分,并在通过缺陷的情况下显示出拓扑保护。在材料的非线性存在下,混合边缘处的拓扑状态持续存在。我们的结果可以扩展到其他晶格类型和物理系统,它们取消了与晶格终止相关的一些约束,这些终止可能在没有破坏系统的时间反向对称性的情况下可能不支持边缘状态,并扩大了可以构建拓扑绝缘子的几何形状的多样性。

Topological edge states form at the edges of periodic materials with specific degeneracies in their modal spectra, such as Dirac points, under the action of effects breaking certain symmetries of the system. In particular, in Floquet topological insulators unidirectional edge states appear upon breakup of the effective time-reversal symmetry due to dynamical modulations of the underlying lattice potential. However, such states are usually reported for certain simple lattice terminations, for example, at zigzag or bearded edges in honeycomb lattices. Here we show that unconventional topological edge states may exist in Floquet insulators based on arrays of helical waveguides with hybrid edges involving alternating zigzag and armchair segments, even if the latter are long. Such edge states appear in the largest part of the first Brillouin zone and show topological protection upon passage through the defects. Topological states at hybrid edges persist in the presence of focusing nonlinearity of the material. Our results can be extended to other lattice types and physical systems, they lift some of the constraints connected with lattice terminations that may not support edge states in the absence of effects breaking time-reversal symmetry of the system and expand the variety of geometrical shapes in which topological insulators can be constructed.

扫码加入交流群

加入微信交流群

微信交流群二维码

扫码加入学术交流群,获取更多资源