Rainbow trapping and concentration of surface waves on broad waveguide

In recent years, topological insulators have been widely designed to manipulate various types of classical waves. The topological edge states characterized by defect and backscattering immunity show great application potential in energy harvesting. This work reports a spin-locked topological surface wave channel, which consists of concrete-filled steel tubes (CFST) placed on foundation soil. Here, the distance between the lattice and the center of the CFST controls the hopping strength between adjacent atoms, determining the topological phase transition. Introducing the surface wave crystal with Dirac cones in the interface, then the robust broad waveguide modes of phononic heterostructure are explored. Notably, incorporating the rainbow effect allows for precise regulation and reliable concentration within the broad waveguide. The proposed broad waveguide surpasses traditional waveguides by simultaneously focusing and segregating energy, enabling applications in low-frequency energy harvesting, sensing, and logic gates. Our work will provide an efficient recovery platform for daily vibration energy, especially for vehicle loads.