Degenerate zero-energy-line symmetric topological disclination modes in photonic crystals
Phys. Rev. Applied 24, 034066 – Published 24 September, 2025
DOI: https://doi.org/10.1103/6qqt-9fg9
Abstract
Topological disclination (TD) serves as an ideal platform for trapping localized zero-dimensional modes and has been extensively studied in classical wave systems. Due to the unconventional bulk-disclination correspondence in topological materials, TDs are robust against local lattice perturbations. However, most TD states lack chiral symmetry protection, which complicates the confinement of these modes near or at the midgap, particularly in photonic systems. In this work, we propose a confined Mie-resonance photonic lattice with rotational symmetries that supports an enlarged bandgap, and construct a two-dimensional metamaterial with a TD core that preserves chiral symmetry. This configuration ensures the confinement of degenerate TD states between the zero-energy line, preventing them from merging into bulk bands. Experimental results demonstrate that two pairs of degenerate TD modes are symmetrically located near the midgap. Our work provides a alternate perspective for realizing robust TD states in 2D photonic materials, releasing possibilities for the fabrication of topological optical devices.
