Arrays of core-shell nanospheres as 3d isotropic broadband ENZ and highly absorbing metamaterials

Making use of homogenization techniques, core-shell particle nanocomposites have been considered to estimate the efficiency of the effective permittivity nulling and enhanced absorption in terms of bandwidth. Core-shell metallodielectric spheres are shown to hold promise as building blocks for the design of metamaterials with the real part of the effective permittivity close to zero, as well as with a high absorption over a frequency band. In the former case, the imaginary part of the effective permittivity remains relatively high over the band, in particular, due to strong electron scattering at the shell boundaries. In the latter case, ultrabroadband metamaterial absorbtion can be realized which is resulted from individual absorption band overlapping.