Magnetic corner states in a two-dimensional gyromagnetic photonic crystal

Abstract

Recently discovered higher-order states extensively enrich the study of topological phases, allowing one to manipulate wave propagating or localizing in more than one dimension lower than the bulk. To date, vast higher-order topological phases have been demonstrated in photonics, acoustics, mechanics, and electronics; however, these are usually in magnetic-free scenarios. Here, we report our realization of magnetic corner states in a two-dimensional honeycomb lattice gyromagnetic photonic crystal. By simultaneously breaking both time-reversal and parity symmetries with one-sublattice magnetic bias, we elaborately gap the native gapless chiral edge states of the quantum-Hall phase. In the complete band gaps, we experimentally observe a pair of unconventional corner states originating from the hybridization of two Wannier centers to shape symmetrical and antisymmetrical modes. Furthermore, we can switch on (off) the corner field localizations solely by adding (removing) the magnetic fields of the corner sites without changing other configurations.