Symmetry-protected Spoof Localized Surface Plasmonic Skyrmion

TL;DR

This paper demonstrates the creation of electromagnetic skyrmions, specifically spoof plasmonic skyrmions, in planar microwave resonators using symmetry principles, with potential applications in microwave technology and broad-spectrum EM devices.

Contribution

It introduces the first experimental realization of spoof plasmonic skyrmions in planar microwave resonators and explains their symmetry origin using group theory.

Findings

Successfully constructed a spoof plasmonic skyrmion with hedgehog-like electric field configuration.

Proved the existence of skyrmions in any planar EM resonator with rotational and mirroring symmetries.

The symmetry-based design principle is independent of dimensions and operating frequencies.

Abstract

Electromagnetic (EM) skyrmions are an EM analogue of the skyrmions in condensed matter physics, which offer new degrees of freedom to structure light and manipulate light matter interactions and thus promise various groundbreaking applications in optics and photonics. Recently, there is a growing interest in composing EM skyrmions based on different field vectors of EM waves. Here, we realize an EM skyrmion, i.e., a spoof plasmonic skyrmion, using the electric field vectors of spoof localized surface plasmons (spoof LSPs) in a planar microwave resonator with rotational and mirroring symmetries. We construct the spoof plasmonic skyrmion, which holds a hedgehog-like configuration in its electric field vectors, by synthesizing a scalar vortex with a topological charge 0 in the out-of-plane component of the fields, and a polarization vortex with a topological charge 1 in the in-plane component of the fields. Besides an experimental demonstration of this skyrmion, we employ group representation theory and pinpoint the symmetry origin of the skyrmion. Such an investigation demonstrates the ubiquity of the existence of the skyrmion in any planar EM resonator holding rotational and mirroring symmetries, regardless the dimensions and the operating frequencies. The designed skyrmion not only promises novel microwave applications for sensing, processing, storing and transferring information, but also lays down a general guideline for devising skyrmions operating over a broad range in the EM spectra owing to the fact that the conducted symmetry investigation is independent of specific dimension or frequency.