论文标题
来自光子硼苯晶格中部分平坦带的不合理的循环状态
Noncontractible loop states from a partially flat band in a photonic borophene lattice
论文作者
论文摘要
平面条带系统通常与平坦的特征态在平坦带能量的宏观变性产生的紧凑局部局部状态（CLS）相关。如果有奇异的平坦频带，已经发现这些常规的局部平面状态是不完整的，导致存在具有非平凡的真实空间拓扑的所谓不缩回环状状态（NLSS）。在这里，我们通过实验和分析表明，2D光子硼苯格晶格可以在没有CLS的情况下托管NLSS，因为仅沿高对称线和沿其他频带沿高对称线和分散性均固定。因此，我们消除了传统的观点，即由于宽大的对应关系，NLSS必然与稳健边界模式相关。 NLSS源自受频段平面性保护的带触摸，在研究平坦带系统的基本物理学中起着关键作用。我们的结果确实改变了当前对平坦带的理解，并且可以很容易地以硼原子的平面薄片的形式转移到2D材料中。
Flat band systems are usually associated to compact localized states (CLSs) resulting from the macroscopic degeneracy of eigenstates at the flat band energy. In case of singular flat bands, these conventional localized flat band states have been found to be incomplete leading to the existence of so-called noncontractible loop states (NLSs) with nontrivial real space topology. Here, we experimentally and analytically demonstrate that a 2D photonic borophene lattice can host NLSs without a CLS counterpart because of a band that is flat only along high-symmetry lines and dispersive along others. We hence dispel the conventional wisdom that NLSs are necessarily linked to robust boundary modes due to a bulk-boundary correspondence. Originating from band touching protected by the band flatness, NLSs play a key role in studying the fundamental physics of flat band systems. Our results truly transform the current understanding of flat bands and could readily be transferred to a 2D material in the form of a planar sheet of boron atoms.
