Electromagnetic duality symmetry and helicity conservation for the macroscopic Maxwell's equations (previously "Experimental demonstration of electromagnetic duality symmetry breaking")

TL;DR

This paper explores the restoration of electromagnetic duality symmetry in macroscopic Maxwell's equations and demonstrates its implications for light-matter interactions, with experimental evidence showing enhanced helicity transformations in nanoapertures.

Contribution

It introduces a framework linking electromagnetic duality and helicity conservation, showing symmetry restoration at the macroscopic level and experimentally investigating helicity transformations.

Findings

Symmetry can be restored in macroscopic Maxwell's equations despite microscopic symmetry breaking.

Helicity transformations are significantly enhanced by surface mode coupling in nanoapertures.

Electromagnetic duality symmetry provides a new tool for studying light-matter interactions.

Abstract

Modern physics is largely devoted to study conservation laws, such as charge, energy, linear momentum or angular momentum, because they give us information about the symmetries of our universe. Here, we propose to add the relationship between electromagnetic duality and helicity to the toolkit. Generalized electromagnetic duality symmetry, broken in the microscopic Maxwell's equations by the empirical absence of magnetic charges, can be restored for the macroscopic Maxwell's equations. The restoration of this symmetry is shown to be independent of the geometry of the problem. These results provide a simple and powerful tool for the study of light-matter interactions within the framework of symmetries and conservation laws. We apply such framework to the experimental investigation of helicity transformations in cylindrical nanoapertures, and we find that the transformation is significantly enhanced by the coupling to surface modes, where electromagnetic duality is strongly broken.