Negative refraction in split-ring-resonator stack at normal incidence

Metamaterials building blocks, from microwave to optical range are mainly based on metal-dielectric composite. In almost all structures with true negative index (not coming from losses) two kind of meta-atoms (electric and magnetic) are mixed in order to drive simultaneously the effective permittivity and permeability to negative values and thus to obtain a negative index of refraction. In this paper we show that two coupled structures with localized plasmons modes (e.g. Cut wires or Split-Ring-Resonators) can exhibit negative refractive index by their own, by appropriately controlling the hybridization scheme of the so called plasmons modes. As a result, the metallic filling factor is drastically reduced and low losses especially at optical frequencies may allow realistic applications of metamaterials.