Resonances in small scatterers with impedance boundary

TL;DR

This paper demonstrates the existence of strong, subwavelength resonances in small spheres with impedance boundaries, revealing their characteristics and similarities to plasmonic and dielectric resonances through analytical and numerical methods.

Contribution

It introduces the analytical and numerical analysis of resonances in small impedance-boundary spheres, highlighting their properties and relation to known plasmonic and dielectric resonances.

Findings

Resonances are damped and shifted with size and impedance.

Electric and magnetic resonances exhibit inductive and capacitive behavior.

Resonances resemble plasmonic and dielectric resonances in small scatterers.

Abstract

With analytical (generalized Mie scattering) and numerical (integral-equation-based) considerations we show the existence of strong resonances in the scattering response of small spheres with lossless impedance boundary. With increasing size, these multipolar resonances are damped and shifted with respect to the magnitude of the surface impedance. The electric-type resonances are inductive and magnetic ones capacitive. Interestingly, these subwavelength resonances resemble plasmonic resonances in small negative-permittivity scatterers and dielectric resonances in small high-permittivity scatterers. The fundamental dipolar mode is also analyzed from the point of view of surface currents and the effect of the change of the shape into a non-spherical geometry.