Broadband and controllable topological interface state of longitudinal wave in pillared phononic crystal beams

We design one-dimensional broadband and controllable pillared phononic crystal (PC) beams composed of magnetic pillars deposited on an Aluminum beam to realize the tunable topological interface state of longitudinal wave. Relying on the adjustable geometrical parameters in a unit cell (i.e., the distance between magnetic pillars and the number of magnetic pillars), the topological transition point can be easily generated and tuned, the controllable topological interface state of longitudinal wave can be obtained within band gap and at the interface of two pillared PC beams with different topological phases. The localization of topological interface state decreases gradually through increasing the number of magnetic pillars. The topological interface state has also been experimentally verified in the proposed PC systems. This work provides presents a simple method to flexibly control the topological interface state, further facilitating the potential applications of elastic topological systems such as energy harvesters, wave filters and switches.