Radiative Toroidal Dipole and Anapole Excitations in Collectively Responding Arrays of Atoms

K. E. Ballantine and J. Ruostekoski
Phys. Rev. Lett. 125, 063201 – Published 4 August 2020
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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 nonradiating, 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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  • Received 12 May 2020
  • Accepted 17 July 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.063201

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Authors & Affiliations

K. E. Ballantine* and J. Ruostekoski

  • Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom

  • *k.ballantine@lancaster.ac.uk
  • j.ruostekoski@lancaster.ac.uk

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Issue

Vol. 125, Iss. 6 — 7 August 2020

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