Temperature-controlled elastic wave transport in topological ferroelectric phononic crystal plates

Thermally tunable elastic wave transport with controllable topological properties in a thin plate is investigated. For the prior plate-type phononic crystals designed with passive materials, the working frequencies are fixed once manufactured. However, meta-devices are always desired to be tuned at will. Therefore, we use ferroelectric ceramics to design topologically protected elastic waveguide devices by temperature variation, leading to the manipulation of band properties and working frequencies. The initial configuration of the unit periodic cell is comprised of a thin plate sandwiched by two snowflake prisms. The polarization of elastic waves in thin plates is utilized to distinguish the wave modes. By further tuning the geometric parameter, the snowflake prisms are changed to A-shaped prisms. Consequently, the mirror symmetry is broken to open a new bandgap for A0 Lamb mode. Then, the topological phase transition is observed by analyzing the mode shapes and the valley Chern number. To further capture the topologically protected interface mode, we design an interface between two arrays of unit cells controlled by different symmetry-broken geometries. It is found that the topological phononic crystal plate with A-shaped prisms realizes broadband interface modes with high quality factors compared to the structures with other geometrically tuning parameters. Based on the interface mode, the controllable waveguide paths are numerically demonstrated and a novel elastic whisper-gallery mode is realized. Via temperature control, the system can be easily tuned to work in a wider frequency range. The results obtained in this manuscript can further promote the practical application of controllable elastic wave transport in thin plates.