Symmetry-Related Large-Area Corner Mode with a Tunable Mode Area and Stable Frequency

Emergent collective modes in lattices give birth to many intriguing physical phenomena in condensed matter physics. Among these collective modes, large-area modes typically feature small-level spacings, while a mode with stable frequency tends to be spatially tightly confined. In this Letter, we theoretically propose and experimentally demonstrate a symmetry-related large-area topological corner mode with a tunable mode area and stable frequency. This mode emerges from the hybridization of the homogeneous Dirac point mode and in-gap topological corner modes. Remarkably, this hybridized mode possesses unique chirality related to the chiral symmetry. We experimentally observe such hybridized mode in a two-dimensional (2D) photonic system and demonstrate its robustness by introducing disorders in the structure. Our findings advance the frontier of higher-order topology research, transitioning it from single-lattice systems to hybridized multilattice systems. These results may support promising potential applications, particularly in vertical-cavity surface-emitting lasers.