All-dielectric photonic higher-order topological insulator induced by a staggered bianisotropy

In this paper, we introduce a two-dimensional all-dielectric photonic higher-order topological insulator that is driven by the bianisotropic responses of electromagnetic fields. The nontrivial topology originates from staggered bianisotropy effects, which result in modulated coupling between neighbor sites under a fixed lattice constant. This model is generalized from an analogous Su-Schrieffer-Heeger model in one dimension and we show that it realizes a second-order photonic topological insulator with robust symmetry-protected corner modes in two dimensions. We also demonstrate that the topological property of such a model can be characterized by a quantized quadrupolar moment. Our paper introduces a different platform for studying higher-order topological photonics via bianisotropy, as well as a distinct method to engineer all-dielectric topological photonic meta-atoms.