Tuning of Electromagnetic Topological States via Staggered Bianisotropy

Electromagnetic topological states uncover a broad assortment of promising tools for light manipulation allowing for extraordinary robustness of wave propagation and localization to disorder and perturbations. Basically, tailoring of topological states relies on the external fields introduction or lattice symmetry adjustment, which both restrict their performance and tunability. Here, we propose a novel strategy to implement electromagnetic topological states exploiting on-site degree of freedom of a single scatterer - bianisotropy, which is manifested in a spatial-inversion-symmetry broken meta-atom. In this case, the effective coupling between two meta-atoms is controlled by their mutual orientation and, therefore, can be easily tuned. We demonstrate topological phase transitions in 1D arrays of bianisotropic particles (split-ring resonators) in full-wave numerical simulations. The proposed approach opens an alternative route of photonic topological states engineering which potentially can be generalized to higher dimensions and higher-order topological states on plasmonic as well as all-dielectric platform.