Reconfigurable valley acoustic phononic crystals based on a fluidic system

Abstract

Valley serves as a new degree of freedom in controlling wave dynamics. Here, we present a design of valley acoustic phononic crystals (PCs) composed of a hybrid channel-cavity structure. Valley states for both waveguide and surface acoustic modes can be realized, and the mode transition is enabled by adjusting the channel height. Reconfigurable valley Hall phase transition in a wide range of frequencies is allowed by tuning the cavity sizes based on a fluidic system. By injecting/withdrawing fluid into/out of the cavities, the dispersion relation, phase transition, and edge states can be controlled conveniently in the two-dimensional PCs. Frequency-dependent acoustic routing, tunable refraction, topological switching, wave splitting, and reconfigurable acoustic pathways with suppressed backscattering are demonstrated both numerically and experimentally through acoustic field scanning. The reconfigurable valley PCs can serve as a versatile platform for exploring valley-related physics and achieving tunable wideband acoustic devices.