Limiting responses of extreme-parameter particles in composites

Helsinki University of Technology, Department of Radio Science and Engineering, P.O. Box 3000, 02015 TKK, Finland

Corresponding author: ari.sihvola@tkk.fi

Received: 9 April 2009
Accepted: 10 June 2009
Published online: 3 February 2010

Abstract

In this article polarizability properties of spheres and ellipsoids are analyzed. For limiting shapes (disks and needles), the polarizability values can theoretically become extremely large. In the limiting process, however, the sequence is crucial in which the geometric parameters and the permittivity magnitude approach infinity. This article determines the levels of the achievable polarizability, which levels dictate the limits of the effective parameters of the composite to be made of such components. Furthermore, the plasmonic details in the negative permittivity domain are connected with the positive-permittivity behavior. Particular geometries carry over the plasmonic response to ENZ (epsilon-near-zero) materials, which brings forth interesting perspectives for material design with extreme parameters. These singularities are carefully analyzed in the present paper for non-magnetic and non-chiral particles.