Bending sound around sharp corners without using topological edge states

TL;DR

This paper introduces a novel anisotropic metamaterial framework for guiding acoustic waves around sharp corners without backscattering, offering advantages over topological edge states and validated through experiments with spoof surface acoustic waves.

Contribution

It presents a new theoretical approach using anisotropic metamaterials for backscattering-immune waveguides, distinct from topological methods, with experimental validation.

Findings

Exact condition for one-way wave propagation derived

Advantages over topological waveguides identified

Experimental validation with spoof surface acoustic waves

Abstract

Routing and guiding acoustic waves around sharp corners without backscattering losses is of great interest in the acoustics community. Sonic crystals have been primarily utilized to design backscattering-immune waveguides. While conventional approaches use defects to guide waves, a considerably more sophisticated and robust approach was recently developed based on topological edge states. In this paper, we propose a radically different theoretical framework based on extremely anisotropic metamaterials for engineering backscattering-immune waveguides. We theoretically derived the exact condition for one-way wave propagation in zigzag paths, and identified a number of key advantages of the current design over topologically protected waveguides. While the theoretical underpinning is universal and is applicable to acoustic and electromagnetic waves, the experimental validation was conducted using spoof surface acoustic waves. The proposed metamaterial could open up new possibilities for wave manipulation and lead to applications in on-chip devices and noise control.