Resonant metal-semiconductor nanostructures as building blocks of low-loss negative- and zero-index metamaterials

Abstract

Here we propose a 2D isotropic metamaterial with negative electric and magnetic responses in the optical regime, based on hybrid metallo-dielectric core-shell nanowires. The magnetic response stems from the lowest magnetic resonance of the dielectric shell with high refractive index (i.e., lossless semiconductor), and can be tuned to coincide with the plasmon resonance of the metal core, responsible for the electric response. Also, the same metamaterial design is shown to yield zero refractive index for a different spectral regime (in connection with overlapping resonances), exhibiting in turn an impedance close to that of vacuum.