Manipulation of elastic wave by reconfigurable elastic topological waveguide

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 (DW). Importantly, by adjusting the water depths, we can achieve the conversion between EPC-I and EPC-II, and realize arbitrary DWs 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.