Antichiral one-way edge states in a gyromagnetic photonic crystal
Jianfeng Chen, Wenyao Liang, Zhi‐Yuan Li
Abstract
We propose and show that antichiral edge states can be realized in a gyromagnetic photonic crystal (GPC) with a honeycomb lattice consisting of two interpenetrating triangular sublattices $A$ and $B$. When sublattices $A$ and $B$ are immersed in opposite external magnetic fields respectively, the band structure of the GPC tilts and antichiral edge states emerge. These special edge states propagate in the same direction at the two opposite parallel zigzag boundaries of the GPC, which are completely distinguished from the well-studied topological edge states in chiral photonic systems where the edge states transport in opposite directions at the opposite two parallel zigzag boundaries. We show that these unique antichiral edge states originate from the overall coupling effects of the counterclockwise energy flux vortexes of sublattice $A$ and clockwise energy flux vortexes of sublattice $B$, so that two copropagating one-way transport channels are created on the boundaries. We further demonstrate that these antichiral edge states are also strongly robust against backscattering from the obstacles at the zigzag edges. Our findings clearly indicate that deeply digging into the GPC systems can help to find rich novel and significant topological physics. Antichiral edge states are of significance not only in basic physics, but also in offering useful insights and routines to design novel electromagnetic and optical functional devices, such as the compact multichannel one-way waveguide.