Observation of nonreciprocal wave propagation in a dynamic phononic lattice

TL;DR

This paper demonstrates experimentally and numerically that a dynamically modulated phononic crystal with time-dependent elastic properties exhibits nonreciprocal wave propagation, enabling potential phononic diode applications.

Contribution

It introduces a novel experimental setup of a time-modulated phononic crystal showing nonreciprocal wave behavior, which was not previously demonstrated.

Findings

Time modulation breaks time-reversal symmetry.

A directional band gap is observed in the dispersion relation.

Nonreciprocal wave propagation enables phononic diode functionalities.

Abstract

Acoustic waves in a linear time-invariant medium are generally reciprocal; however, reciprocity can break down in a time-variant system. In this Letter, we report on an experimental demonstration of nonreciprocity in a dynamic one-dimensional phononic crystal, where the local elastic properties are dependent on time. The system consists of an array of repelling magnets, and the on-site elastic potentials of the constitutive elements are modulated by an array of electromagnets. The modulation in time breaks time-reversal symmetry and opens a directional band gap in the dispersion relation. As shown by experimental and numerical results, nonreciprocal mechanical systems like the one presented here offer opportunities to create phononic diodes that can serve for rectification applications.