Locally Polarized Wave Propagation through Metamaterials' Crystallinity

TL;DR

This paper demonstrates how crystalline metamaterials can be used to control wave propagation and routing at subwavelength scales, emulating solid-state physics phenomena with microwaves.

Contribution

It introduces a method to induce and manipulate wave propagation with angular momentum in crystalline metamaterials, inspired by the Quantum Valley-Hall Effect.

Findings

Wave propagation with angular momentum observed in wire-based metamaterials

Interface modes enable directional wave routing

Crystalline structure emulates solid-state physics phenomena

Abstract

Wave propagation control is of fundamental interest in many areas of Physics. It can be achieved with wavelength-scaled photonic crystals, hence avoiding low frequency applications. By contrast, metamaterials are structured on a deep-subwavelength scale, and therefore usually described through homogenization, neglecting the unit-cell structuration. Here, we show with microwaves that, by considering their inherent crystallinity, we can induce wave propagation carrying angular momenta within a subwavelength-scaled collection of wires. Then, inspired by the Quantum Valley-Hall Effect in condensed matter physics, we exploit this bulk circular polarization to create modes propagating along particular interfaces. The latter also carry an edge angular momentum whose conservation during the propagation allows wave routing by design in specific directions. This experimental study not only evidences that crystalline metamaterials are a straightforward tabletop platform to emulate exciting solid-state physics phenomena at the macroscopic scale, but it also opens the door to crystalline polarized subwavelength waveguides.