Strategy for designing epsilon-near-zero nanostructured metamaterials over a frequency range

In terms of the effective medium theory, we propose a general solution to such a fundamental problem as designing nanostructured materials with the very low permittivity (epsilon-near-zero metamaterials) over a frequency range. We show, in particular, that this can be accomplished for a columnar metal-dielectric composite consisting of parallel cylinders with varied thickness that resembles a forest of identical stems. The applicability of our method and some limitations are also discussed. Whilst the corresponding production procedure does not appear to be very simple, it nevertheless is realizable.