Unconventional Flatband Line States in Photonic Lieb Lattices
Unconventional Flatband Line States in Photonic Lieb Lattices
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光子 Lieb 晶格中的非常规平带线态
DOI：
10.1103/physrevlett.121.263902
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发表时间：
2018
影响因子：
8.6
通讯作者：
Zhigang Chen
中科院分区：
文献类型：
--
作者：
Shiqi Xia;Ajith Ramach;ran;Shiqiang Xia;Denghui Li;Xiuying Liu;Liqin Tang;Yi Hu;Daohong Song;Jingjun Xu;Daniel Leykam;Sergej Flach;Zhigang Chen
由于与无色散能带相关的布洛赫波函数的破坏性干涉和宏观简并，平带系统通常具有“紧凑局域态”（CLS）。使用光子Lieb晶格（LL），发现这种传统的局域平带状态本质上是不完整的，缺失模式表现为在整个晶格周围形成不可收缩环路的延伸线状态。实验上，我们开发了一种连续波激光写入技术，以建立具有特殊定制边界的有限尺寸光子LL，从而直接观察异常扩展的平坦带线状态。这种非常规的线态不能表示为先前观察到的边界无关体CLS的线性组合，而是来自于非平凡的实空间拓扑。讨论了线路状态对不完全激励条件的鲁棒性，并说明了它们的潜在应用。
Flatband systems typically host “compact localized states” (CLS) due to destructive interference and macroscopic degeneracy of Bloch wave functions associated with a dispersionless energy band. Using a photonic Lieb lattice (LL), such conventional localized flatband states are found to be inherently incomplete, with the missing modes manifested as extendedline statesthat form noncontractible loops winding around the entire lattice. Experimentally, we develop a continuous-wave laser writing technique to establish a finite-sized photonic LL with specially tailored boundaries and, thereby, directly observe the unusually extended flatband line states. Such unconventional line states cannot be expressed as a linear combination of the previously observed boundary-independent bulk CLS but rather arise from the nontrivial real-space topology. The robustness of the line states to imperfect excitation conditions is discussed, and their potential applications are illustrated.