Acoustic Pseudospin Transport in Dual‐Layer Topological Insulators with Multiple Topological Phases

Abstract Pseudospin‐dependent acoustic topological insulators (ATIs) with high‐robustness edge states have recently attracted as surge of interest owing to their potential applications, such as one‐way sound transport and acoustic communications. Despite the rapid development of pseudospin‐dependent ATIs, most existing efforts are limited to monolayer, restricting degree of freedoms to achieve novel physical phenomena and device applications. Here, a series of pseudospin‐dependent ATIs composed of dual‐layer honeycomb‐lattice sonic crystals is experimentally proposed. By introducing the layer degree of freedom, the dual‐layer ATIs have four distinct topological phases and can be used to construct six types of domain walls, exhibiting different transport behavior, such as layer‐mixed, layer‐polarized, and single‐layer propagation characteristics. This further enables to experimentally realize interlayer converters for functional sound devices that are otherwise impossible for single‐layer ATIs. This work may find various acoustic applications in layer‐selective emitters and splitters, multi‐path topological sorting, and multifunctional information processing.