Acoustic topological insulator combining hybrid tunable double elements

In this paper, we obtain acoustic topological insulators with acoustic pseudospin and topological boundary states by breaking the symmetry of lattice structure with local and global rotating elements respectively. When the local triangular component carrier is rotated ±30° around the center, the quadruple degenerate states are separated and realizing a topological phase transition. Furthermore, without changing the structural parameters of the bi-component elements, band inversion can also be achieved by simply rotating the bi-component elements as a whole, and the relative band of its nontrivial band gap is broadened by a factor of 3. Finally, the numerical simulation of its acoustic transmission characteristics is carried out by using the finite element method, and the robustness of the topological boundary state is verified. The results of this study can provide ideas and methods for designing multi-form tunable acoustic topological devices by using multi-component phononic crystals.