Most natural and artificial materials have crystalline structures from which abundant topological phases emerge^1,2,3,4,5,6. However, the bulk–edge correspondence—which has been widely used in experiments to determine the band topology from edge properties—is inadequate in discerning various topological crystalline phases^{7,8,9,10,11,12,13,14,15,16}, leading to challenges in the experimental classification of the large family of topological crystalline materials^4,5,6. It has been theoretically predicted that disclinations—ubiquitous crystallographic defects—can provide an effective probe of crystalline topology beyond edges^17,18,19, but this has not yet been confirmed in experiments. Here we report an experimental demonstration of bulk–disclination correspondence, which manifests as fractional spectral charge and robust bound states at the disclinations. The fractional disclination charge originates from the symmetry-protected bulk charge patterns—a fundamental property of many topological crystalline insulators (TCIs). Furthermore, the robust bound states at disclinations emerge as a secondary, but directly observable, property of TCIs. Using reconfigurable photonic crystals as photonic TCIs with higher-order topology, we observe these hallmark features via pump–probe and near-field detection measurements. It is shown that both the fractional charge and the localized states emerge at the disclination in the TCI phase but vanish in the trivial phase. This experimental demonstration of bulk–disclination correspondence reveals a fundamental phenomenon and a paradigm for exploring topological materials.

大多数天然和人造材料具有晶体结构，从中出现丰富的拓扑相^1,2,3,4,5,6。然而，体-边对应关系——已广泛用于实验中从边缘特性确定能带拓扑——不足以识别各种拓扑结晶相^{7、8、9、10、11、12、13、14、15， 16}，导致拓扑晶体材料大族的实验分类面临挑战^4,5,6。理论上已经预测，向错（普遍存在的晶体缺陷）可以有效探测边缘以外的晶体拓扑结构^17,18,19, 但这尚未在实验中得到证实。在这里，我们报告了体向旋对应的实验演示，其表现为向错处的分数光谱电荷和稳健的束缚态。分数向错电荷源于对称保护的体电荷模式——许多拓扑晶体绝缘体 (TCI) 的基本特性。此外，向错处的稳健束缚态作为 TCI 的次要但可直接观察到的属性出现。使用可重构光子晶体作为具有高阶拓扑的光子 TCI，我们通过泵浦探针和近场检测测量观察到这些标志性特征。结果表明，分数电荷和局域态都出现在 TCI 相的向错处，但在平凡相中消失。