Dirac cones and chiral selection of elastic waves in a soft strip

TL;DR

This paper investigates elastic wave propagation in a soft strip, revealing Dirac cones, negative wave velocity, and chiral wave selection, supported by experiments and models, highlighting unique wave phenomena in soft materials relevant to biological tissues.

Contribution

It demonstrates the existence of Dirac cones and chiral wave control in soft elastic strips through experimental and theoretical analysis, a novel finding in soft matter physics.

Findings

Evidence of Dirac cones in soft elastic strips

Observation of negative wave velocity and ZGV phenomena

Successful chiral wave selection through source manipulation

Abstract

We study the propagation of in-plane elastic waves in a soft thin strip; a specific geometrical and mechanical hybrid framework which we expect to exhibit Dirac-like cone. We separate the low frequencies guided modes (typically 100 Hz for a centimetre wide strip) and obtain experimentally the full dispersion diagram. Dirac cones are evidenced together with other remarkable wave phenomena such as negative wave velocity or pseudo-zero group velocity (ZGV). Our measurements are convincingly supported by a model (and numerical simulation) for both Neumann and Dirichlet boundary conditions. Finally, we perform one-way chiral selection by carefully setting the source position and polarization. Therefore, we show that soft materials support atypical wave-based phenomena, which is all the more interesting as they make most of the biological tissues.