Topological disclination mode in photonic Chern insulators

Abstract

Topological defects in topological materials offer novel routes for creating topological modes and probing bulk topology. Disclination, a class of topological defects, has been recently shown to host fractional charges in topological crystalline insulators with well-defined Wannier centers. Here, we study the effects of disclinations in gyromagnetic photonic crystals with non-zero Chern numbers that prohibit the Wannier center picture. We find the emergence of topological disclination modes carrying orbital angular momentum from the interplay between the Chern-type topology and the effective flux induced by the disclination. When the Chern number changes its sign, the chirality of the disclination mode also flips, revealing the bulk-disclination correspondence. Furthermore, we perform numerical experiments to probe the disclination mode. Our results expand the study of disclination physics in photonic crystals to time-reversal-broken systems.