Dual-frequency layer-polarized topological interface states of shear horizontal guided wave in one-dimensional bilayer phononic crystals

In this paper, we investigate the existence of double interface states and layer polarization phenomena in one-dimensional (1D) topological bilayer phononic crystal plate (PCP). By constructing a bilayer PCP based on the double Su–Schrieffer–Heeger (DSSH) model, it is found that the dual-frequency topological interface states of shear horizontal (SH) wave can be realized in one common topological bandgap. Notably, we discover that by controlling gliding symmetry of the topological interfaces, the double topological interface states with two frequencies of 91.03 and 95.28 kHz are obtained in one common bandgap, both of which exhibit the fascinatingly layer-polarized phenomena. Compared with previous researches, this study achieved the generation of two interface states with different layer polarization at the same interface. Based on the obtained dual-frequency topological interface states, the dual-frequency rainbow trapping of the SH wave is successfully realized, in which the SH wave energy can be selectively captured in the upper or lower layer of PCP. This study provides a new perspective for the design of topological filtering devices and has potential applications in multi-frequency acoustic sensing and layer-polarized couplers.