Extreme Spatial Dispersion in Nonlocally-Resonant Elastic Metamaterials

TL;DR

This paper introduces a novel class of elastic metamaterials that utilize zero-energy modes to achieve extreme spatial dispersion and anomalous wave properties at subwavelength scales, validated through simulations and experiments.

Contribution

It presents a new design principle for elastic metamaterials based on zero-energy modes, enabling anomalous dispersion without bandwidth limitations.

Findings

Demonstrated anomalous dispersion cones at 0 Hz

Achieved subwavelength control of wave properties

Validated designs through simulations and experiments

Abstract

To date, the vast majority of architected materials have leveraged two physical principles to control wave behavior, namely Bragg interference and local resonances. Here, we describe a third path: structures that accommodate a finite number of delocalized zero-energy modes, leading to anomalous dispersion cones that nucleate from extreme spatial dispersion at 0 Hz. We explain how to design such zero-energy modes in the context of elasticity and show that many of the landmark wave properties of metamaterials can also be induced at an extremely subwavelength scale by the associated anomalous cones, without suffering from the same bandwidth limitations. We then validate our theory through a combination of simulations and experiments. Finally, we present an inverse design method to produce anomalous cones at desired locations in momentum space.