We report the experimental and numerical realization of a pseudospin-dependent acoustic topological insulator based on two sonic crystals constructed by the same regular hexagonal rods. Based on the zone folding mechanism, we obtain double Dirac cones with a four-fold deterministic degeneracy in the sonic crystal, and realize a band inversion and topological phase transition by rotating the rods. We observe the topologically protected one-way sound propagation of pseudospin-dependent edge states in a designed topological insulator composed of two selected sonic crystals with different rotation angles of the rods. Furthermore, we experimentally demonstrate the robustness of topological sound propagation against two types of defects, in which the edge states are almost immune to backscattering, and remain pseudospin-dependent characteristics. Our work provides a diverse route for designing tunable topological functional sound devices.

We report a numerical study of a reconfigurable topological waveguide based on honeycomb-lattice elastic phononic crystals (EPCs) which consist of two kinds of cavities filled with water. We can realize the EPCs with different symmetries by adjusting the water depth of the cavities, and obtain a Dirac cone for the EPCs composed of the cavities with the same water depth, in which the Dirac frequency can be modulated by adjusting the water depth. When the water depths of the cavities are different, the inversion symmetry of the EPC is broken, destroying the two-fold degeneracy of the Dirac point, and opening an omnidirectional bandgap. Based on EPC-I and EPC-II with opposite valley Hall phases, we design a valley topological waveguide of elastic wave, and obtain valley edge states in the domain wall. Importantly, by adjusting the water depths, we can achieve the conversion between EPC-I and EPC-II, and realize arbitrary domain walls for the propagations of elastic waves in the topological waveguide. Finally, we discuss an interesting application of a path-selective waveguide based on a linear interference mechanism. The designed reconfigurable topological waveguide provides an effective method to manipulate valley topological transports of elastic waves, and a theoretical basis for designing advanced topological devices.