Tunable topological valley transport in acoustic topological metamaterials

Valley Hall topological insulators (VHTIs) in condensed matter physics have been recently extended to acoustic systems and have attracted great attention. However, the current acoustic topological insulators (ATIs) are mainly based on the mechanism of Bragg scattering in phononic crystals. Their demonstration and application are limited by factors, such as non-tunable structure and lattice-scale size. Here, we propose and engineer a tunable ATI by using a metamaterial structure to realize topologically valley-projected edge states. The topological metamaterial consists of a honeycomb lattice array of 2D triple split ring (TSR) based on local resonance mechanism. We numerically demonstrate the robustness of edge sound transport and flexible manipulation of sound propagation paths in the proposed topological metamaterial. Theoretical analysis, numerical simulation and experimental measurement all confirm the existence of edge states. This study may enrich the design of ATIs with tunability and have potential applications in flexible manipulation of sound propagation.