Title: Observation of Fully Flat Bands in a Photonic Dipolar Kagome Lattice Show Chinese title

Title: 光子偶极 Kagome 晶格中完全平坦带的观察

Abstract: Flat bands, characterized by zero group velocity and strong energy localization, enable interaction-enhanced phenomena across both quantum and classical systems. Existing photonic flat-band implementations were limited to evanescent-wave systems, specific lattice symmetries, or complex supercell modulations. A simple, universal, and efficient approach to realizing flat bands without dedicated source excitation is to be explored. Here, inspired by geometrically frustrated configurations, we theoretically proposed and experimentally demonstrated threefold-degenerate flat bands by integrating orbital and rotational degrees of freedom in a photonic dipolar kagome lattice. By rotating the dipole orientation, the system exhibits a band flip transition at which point all bands achieve complete flatness and degeneracy across the entire Brillouin zone. In contrast to conventional s-orbital kagome lattices with only a single flat band, our approach flattens the entire band structure, eliminating dispersive modes and enabling compatibility with arbitrary excitations. These results establish a new mechanism for flat-band engineering, offering a tunable strategy for enhancing light-matter interactions and may have applications in compact photonic devices and energy-efficient information processing. Show Chinese abstract

Abstract: 平带的特点是零群速度和强能量局域化，这使得在量子和经典系统中都能实现增强的相互作用现象。 现有的光子平带实现方法仅限于倏逝波系统、特定的晶格对称性或复杂的超胞调制。 需要探索一种简单、通用且高效的实现平带的方法，而无需专门的源激励。 在此，受几何受挫构型的启发，我们理论上提出了并通过实验展示了通过在光子偶极kagome晶格中整合轨道和旋转自由度来实现三重简并的平带。 通过旋转偶极方向，系统在某一时刻表现出带翻转转变，此时所有带在整个布里渊区都达到完全平直和简并。 与传统s轨道kagome晶格仅有一个平带不同，我们的方法使整个能带结构变平，消除了色散模式，并实现了与任意激发的兼容性。 这些结果建立了一种新的平带工程机制，提供了一种可调制的策略来增强光-物质相互作用，可能在紧凑的光子器件和节能的信息处理中具有应用。