Dual-band selective rainbow trapping in two-dimensional gradient valley phononic crystals

The realization of topological rainbow trapping provides significant potential for applications in energy storage and recovery, signal sensing, and related fields. Most studies focus on the first bandgap of valley phononic crystals, which presents a challenge for developing multi-band topological acoustic devices. This study designs a three-legged circular rod valley phononic crystal, where spatial symmetry is broken through rotation to open two Dirac cones. It observes topological edge states within the ranges of the original two bandgaps by combining two valley phononic crystals with different topological phases. In addition, the magnitude of the group velocity is calculated in the supercells at different rod lengths, revealing points with a group velocity of zero at different frequencies, thus realizing rainbow trapping in…