Origin of the anapole condition as revealed by a simple expansion beyond the toroidal multipole

Shi-Qiang Li; Kenneth B Crozier

Journal article

Origin of the anapole condition as revealed by a simple expansion beyond the toroidal multipole

Shi-Qiang Li, Kenneth B Crozier

PHYSICAL REVIEW B | AMER PHYSICAL SOC | Published : 2018

DOI: 10.1103/PhysRevB.97.245423

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Abstract

Toroidal multipoles are a topic of increasing interest in the nanophotonics and metamaterials communities. In this paper, we separate out the toroidal multipole components of multipole expansions in polar coordinates (two- and three-dimensional) by expanding the Bessel or spherical Bessel functions. We discuss the formation of the lowest order of magnetic anapoles from the interaction between the magnetic toroidal dipole and the magnetic dipole. Our method also reveals that there are higher order current configurations other than the electric toroidal multipole that have the same radiation characteristics as the pure electric dipole. Furthermore, we find that the anapole condition requires t..

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University of Melbourne Researchers

Kenneth Crozier Author Physics

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Awarded by Australian Research Council

Funding Acknowledgements

This work was supported by the Australian Research Council (DP150103736, DP180104141, and FT140100577) and by the Victorian Endowment for Science, Knowledge and Innovation (VESKI). The authors thank Ramon Paniagua-Dominguez from the Data Storage Institute of the Agency for Science, Technology and Research (A*STAR) in Singapore, Dr. Patrick Grahn from COMSOL Inc., and Prof. John B. Ketterson from Northwestern University for helpful discussion.