Super Scatterers Based on Artificial Localized Magnon Resonances

Abstract

The interaction between electromagnetic waves and objects is strongly affected by the shape and material composition of the latter. Artificially created materials, formed by a subwavelength structuring of their unit cells, namely metamaterials, can exhibit peculiar responses to electromagnetic radiation and provide additional powerful degrees of freedom to the scatterer design. In particular, negative material susceptibilities give rise to strong resonant interactions with deeply subwavelength particles. While the negative electrical permittivity of natural noble metals manifests itself in localized plasmon resonant oscillations, negative magnetic permeability is virtually non-existent in nature. Here the concept of artificial magnon resonance in subwavelength objects with effective negative permeability, designed based on the metamaterial approach, is demonstrated. Strong localized oscillations of the magnetic fields within an array of split ring resonators, forming a sphere, hybridize in a collective mode of the structure. As a result, extremely high scattering cross section, exceeding that of a steel sphere with the same radius by four orders of magnitude, was demonstrated. Furthermore, the scattering cross section of subwavelength metamaterial-based sphere was shown to be comparable to the low frequency (MHz) radar signature of a big military aircraft. Super scatterers, based on tunable resonances within artificially created materials, can find use in a broad range of electromagnetic applications, including wireless communications, radars, RFID, internet of things hardware and many others.