Subwavelength path-switchable wave routing and topological corner states for a higher-order topological insulator

Abstract

Wave manipulation has always been popular research subject due to its striking physical phenomena and promising real-life engineering applications. Recently, the birth of topological insulators carved a new way for wave control because of the capabilities of such insulators in confining wave propagation along specific directions. However, routing such wave guiding path with a flexible approach and further exploration about higher-order topological insulators are still very immature. In this regard, we wish to tackle this issue by introducing anisotropy into a local resonance plate with C4v symmetry. Through comprehensive theoretical and numerical research, we reveal the whole picture of bandgaps and topological properties by tuning the distance between resonators. Distinct topological edge states along different directions can be enabled by purposely designing anisotropy and controlling phase confliction. Based on this phenomenon, a path-switchable wave-guiding topological insulator is designed where the wave transmission path can be flexibly tuned by changing the operating frequency. Subsequently, we design a higher-order topological insulator which exhibits remarkable energy concentration at corners due to the topological corner states. Regarding these properties, our research provides an eligible candidate for achieving wave filtering, wave routing, and we also offer possible solutions for next generation integrated solid-state phononic circuits.