Chiral symmetry-preserving coupling method for topological acoustic metamaterials

Acoustic crystals have emerged as a versatile platform for studying topological phases, showcasing their universality and diversity. The properties of topological insulators and their boundary states depend on the space dimension and symmetries of materials, as evidenced by the periodic table of topological invariants. Studying and observing different topological classes require precise enforcement of topological symmetries and this poses a big challenge for acoustic metamaterials. In this paper, we propose and demonstrate an effective experimental coupling strategy for acoustic crystals, while maintaining the integrity of chiral symmetry. We employed the SSH model for testing purposes to ascertain whether various types of connections support topologically edge and interface modes. We observed that a modular platform, where the resonators are coupled through the bottom, provides support for topologically protected edge and interface states. This platform exhibits exceptional versatility, including reconfigurability, as well as preservation of chiral symmetry.