Phononic band calculations and experimental imaging of topological boundary modes in a hexagonal flexural wave machine

Abstract

We construct a two-dimensional mechanical wave machine based on a hexagonal lattice to investigate low-frequency flexural plate waves whose propagation mimicks a topological quantum valley Hall system. We thereby demonstrate “mechanical graphene” by extension of the one-dimensional Shive wave machine to two dimensions. Imaging experiments, backed up by simulations, reveal the presence of boundary modes along a topological interface. This work provides an alternative route for the investigation of topological phononic crystals, and should lead to new insights into the design and observation of artificial phononic structures.

Keywords

• phononic crystals
• mechanical metamaterials
• topological boundary modes
• wave machine
• quantum valley Hall effect
• Berry curvature