Space-coiling metamaterials with double negativity and conical dispersion

TL;DR

This paper introduces a novel geometric method to create acoustic and microwave metamaterials with negative and zero indices by coiling space, demonstrating negative refraction and conical dispersion without resonant elements.

Contribution

It presents the first experimental realization of space-coiled metamaterials with conical dispersion and double negativity for acoustic and microwave applications.

Findings

Demonstrated negative refraction in acoustic metamaterials with airborne sound.

Achieved tunable extreme dispersion by coiling space, avoiding resonant losses.

Designed double-negative metamaterials for microwaves using the same geometric principle.

Abstract

Metamaterials are effectively homogeneous materials that display extraordinary dispersion. Negative index metamaterials, zero index metamaterials and extremely anisotropic metamaterials are just a few examples. Instead of using locally resonating elements that may cause undesirable absorption, there are huge efforts to seek alternative routes to obtain these unusual properties. Here, we experimentally demonstrate an alternative approach for constructing metamaterials with extreme dispersion by simply coiling up space with curled channels. Such a geometric approach has the advantage that the ratio between the wavelength and the lattice constant in achieving a negative or zero index is easily tunable. It allows us to construct for the first time an acoustic metamaterial with conical dispersion, leading to a clear demonstration of negative refraction from an acoustic metamaterial with airborne sound. We also design and realize a double-negative metamaterial for microwaves under the same principle.