Magnetoelectric-field helicities and reactive power flows

TL;DR

This paper investigates the unique topological helicity properties of magnetoelectric fields generated by ferrite particles, revealing their complex helicity states and conservation laws, which differ from traditional electromagnetic fields.

Contribution

It introduces the concept of complex helicity in ME fields and analyzes their conservation laws, highlighting differences from classical electromagnetic helicity.

Findings

Helicity density relates to the imaginary part of complex power flow.

ME field helicity can be a complex value.

Topologically protected quantum-like helicity states.

Abstract

The dual symmetry between the electric and magnetic fields underlies Maxwell's electrodynamics. Due to this symmetry one can describe topological properties of an electromagnetic field in free space and obtain the conservation law of optical (electromagnetic) helicity. What kind of the field helicity one can expect to see when the electromagnetic-field symmetry is broken? The near fields originated from small ferrite particles with magnetic dipolar mode (MDM) oscillations are the fields with the electric and magnetic components, but with broken dual (electric-magnetic) symmetry. These fields, called magnetoelectric (ME) fields, have topological properties different from such properties of electromagnetic fields. The helicity states of ME fields are topologically protected quantum like states. In this paper, we study the helicity properties of ME fields. We analyze conservation laws of the ME-field helicity and show that the helicity density is related to an imaginary part of the complex power flow density. We show also that the helicity of ME fields can be a complex value.