Acoustic topological circuitry in square and rectangular phononic crystals

TL;DR

This paper demonstrates the design and experimental realization of topological phononic circuits using square and rectangular lattice structures, enabling robust acoustic wave manipulation over a broad frequency range.

Contribution

It introduces a novel approach to creating topological phononic circuits in square and rectangular lattices, distinct from hexagonal systems, with experimental validation and numerical simulations.

Findings

Observation of topological edge states in square and rectangular phononic crystals

Successful experimental demonstration of acoustic wave routing at domain walls

Numerical simulations confirming the robustness and resolution of edge modes

Abstract

We systematically engineer a series of square and rectangular phononic crystals to create experimental realisations of complex topological phononic circuits. The exotic topological transport observed is wholly reliant upon the underlying structure which must belong to either a square or rectangular lattice system and not to any hexagonal-based structure. The phononic system chosen consists of a periodic array of square steel bars which partitions acoustic waves in water over a broadband range of frequencies (~0.5 MHz). An ultrasonic transducer launches an acoustic pulse which propagates along a domain wall, before encountering a nodal point, from which the acoustic signal partitions towards three exit ports. Numerical simulations are performed to clearly illustrate the highly resolved edge states as well as corroborate our experimental findings. To achieve complete control over the flow of energy, power division and redirection devices are required. The tunability afforded by our designs, in conjunction with the topological robustness of the modes, will result in their assimilation into acoustical devices.