Coexistence of Chiral and Antichiral Edge States in Photonic Crystals

This study reports a modified Haldane model that supports transitions between valley and Chern topological phases in photonic crystals. Berry curvatures of this system can be flexibly diffused, converged, or flipped by endowing different model parameters, thus exhibiting exotic topological interface/edge behaviors, such as topological bound states with ideally zero dispersion. Importantly, the coexistence of chiral and antichiral edge states preserved simultaneously by valley and Chern topological phases is achieved by splicing together two kinds of topological structures as an entirety. It further employs a honeycomb lattice comprising gyromagnetic and ceramic cylinders at microwave frequencies, where inversion and time-reversal symmetries can be flexibly manipulated. Topological interface transport is demonstrated, including two opposite signs of group velocities jointly protected by topologically distinct regimes. These results bridge the gap between valley and Chern topological physics and shed light on developing reconfigurable integrated device applications for classical (quantum) information processing and photonic computing. The coexistence of chiral and antichiral edge states is proposed for photonic crystals by a modified Haldane model. Berry curvatures of this system can be flexibly diffused, converged, or flipped by endowing different parameters, exhibiting exotic topological interface/edge behaviors, such as topological bound states with ideally zero dispersion. This demonstrates promising applications in information processing and photonic computing.image