Topological phononic switch based on reconfigurable symmetry-broken crystals with rotatable scatterers

This study introduces a novel square lattice of steel scatterers embedded in an air matrix, providing a flexible and tunable platform for designing topological phononic crystals. With their reconfigurability, these crystals can be switched between on or off states easily by rotating the scatterers without modifying the lattice arrangement. This rotation disrupts the mirror symmetry, resulting in the emergence of a new bandgap. The stability of these topological phononic crystals against various defects has been demonstrated numerically. Leveraging this property, two topological switch designs with two inputs and two outputs were proposed and experimentally implemented. These switches feature different symmetry-broken geometries that support topologically protected edge states. The switching performance at the outputs, including on and off states, has been verified through both simulations and experimental tests. The first proposed topological switch achieves switching by rotating 12 controllable scatterers, whereas the second one requires the rotation of only a single scatterer to perform the switching operation.