标题： 连续体中的束缚态产生的平带用于轨道角动量局域化 显示英文标题

标题： Flatbands from Bound States in the Continuum for Orbital Angular Momentum Localization

摘要： 一种平坦带材料是一种具有零色散能带的系统，允许波函数在实空间中紧密局域化。这种紧密局域化显著增强了粒子间相关性和光-物质相互作用，导致了诸如凝聚态系统中的分数陈绝缘体和光子学中的平坦带激光器等显著进展。以前的平坦带平台，包括扭曲双层石墨烯和人工kagome/Lieb晶格，通常专注于非简并平坦带，缺乏访问可以促进轨道角动量（OAM）局域化的高简并度。在这里，我们提出了一种通用框架，从连续态中的束缚态（BICs）构建高度简并的平坦带——这一概念起源于量子理论，但在近年来的光子学和声学中得到了显著发展。平坦带的简并度由晶格中每个原胞内的BIC数量决定。我们在二维（2D）和三维（3D）声学晶体中实验验证了这种方法，分别展示了四重和十二重简并的平坦带。高简并度提供了足够的内部自由度，使得可以在任何位置以任何方向选择性地激发局域化的OAM。我们的结果为探索由BIC构建的平坦带及其局域化特性铺平了道路。 显示英文摘要

摘要： A flatband material is a system characterized by energy bands with zero dispersion, allowing for the compact localization of wavefunctions in real space. This compact localization significantly enhances inter-particle correlations and light-matter interactions, leading to notable advancements such as fractional Chern insulators in condensed matter systems and flat-band lasers in photonics. Previous flatband platforms, including twisted bilayer graphene and artificial kagome/Lieb lattices, typically focused on nondegenerate flatbands, lacking access to the high degeneracy that can facilitate the localization of orbital angular momentum (OAM). Here, we propose a general framework to construct highly degenerate flatbands from bound states in the continuum (BICs)--a concept originating from quantum theory but significantly developed in photonics and acoustics in recent years. The degeneracy of flatbands is determined by the number of BICs within each unit cell in a lattice. We experimentally validate this approach in two-dimensional (2D) and three-dimensional (3D) acoustic crystals, demonstrating flatbands with 4-fold and 12-fold degeneracies, respectively. The high degeneracy provides sufficient internal degrees of freedom, enabling the selective excitation of localized OAM at any position in any direction. Our results pave the way for exploring BIC-constructed flatbands and their localization properties.