Radiative toroidal dipole and anapole excitations in collectively responding arrays of atoms

Kyle E. Ballantine; Janne Ruostekoski

doi:10.1103/physrevlett.125.063201

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arXiv · 2005.05918

Radiative toroidal dipole and anapole excitations in collectively responding arrays of atoms

Kyle E. Ballantine·Janne Ruostekoski

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Abstract

A toroidal dipole represents an often overlooked electromagnetic excitation distinct from the standard electric and magnetic multipole expansion. We show how a simple arrangement of strongly radiatively coupled atoms can be used to synthesize a toroidal dipole where the toroidal topology is generated by radiative transitions forming an effective poloidal electric current wound around a torus. We extend the protocol for methods to prepare a delocalized collective excitation mode consisting of a synthetic lattice of such toroidal dipoles and a non-radiating, yet oscillating charge-current configuration, dynamic anapole, for which the far-field radiation of a toroidal dipole is identically canceled by an electric dipole.

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Kyle E. Ballantine, Janne Ruostekoski. 2020-07-28. Radiative toroidal dipole and anapole excitations in collectively responding arrays of atoms. https://doi.org/10.1103/physrevlett.125.063201

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