Symmetry Breaking via Buckling in a Soft Piezoelectric Phononic Crystal

A soft phononic crystal can be the basis for a two state phononic device, as under compression the crystal will buckle and come to a second geometric state with new crystal symmetry and therefore new phononic properties. There are many interesting applications and extensions to this system that can be explored for more exotic device functionalities. Piezoelectric phononic crystals (PPCs) are of interest for their ability to have surface acoustic waves actuated by transducers embedded in the crystal, and soft PPCs may have some unique properties under deformation but are relatively unexplored.

We simulated compression of a soft PPC using the arc-length method to investigate large, nonlinear deformations. The simulations explore the relationship between the symmetry group of the crystal, the group of the electric field caused by the piezoelectric response, and the properties of the piezoelectric modulus itself. We also explore the inverse problem, attempting to generate different buckled crystals by varying the piezoelectric modulus and the applied electric field instead of applying a force to directly compress the crystal. The various buckling geometries cause distinct phonon propagation properties due to the changed symmetry of the crystal.