Twisted pillared phononic crystal plates

Recent discoveries in twisted heterostructure materials have opened research directions in classical wave systems. This Letter investigates a family of double-sided pillared phononic crystal plates as the elastodynamic analog of bilayer graphene, including twisted bilayer graphene. The phononic crystal plate design is first validated by studying the basic AA- and AB-stack configurations under weak interlayer coupling. A specific commensurate twist angle giving rise to the sublattice exchange even symmetry is then studied to examine the twist-modulated band structure. Finally, this study demonstrates that the same twist angle, in concert with an ultra-strong interlayer coupling, can collectively create valley-dependent edge states that have not been previously observed in electronic bilayer graphene.