Design and optimization of dual-band sonic topological insulators based on genetic algorithm

The 2D sonic topological insulators (STIs), which can support topological edge states and corner states, provide a platform for acoustic manipulation. We utilize genetic algorithm (GA) to optimize the C4v symmetric square lattices to achieve dual-band STIs, and the center frequency of the second topological bandgap is twice that of the first one. The topological properties of the optimized lattice are investigated based on the parities at the high symmetry points. In a further way, dual-band topological edge states and double corner states are verified by finite element method simulation in the domain wall and bending structures, respectively. A GA optimization is also used for optimizing the nearest two unit cells at the domain wall, and the bandwidths of edge states are widened. Our work provides an efficient way for achieving the frequency-doubled topological acoustic wave manipulation and multiband acoustic topological cavities.