| Riassunto: | Diatomic metamaterials, whose properties can be easily tailored, are studied with the aid of split ring resonator elements. Two different types are shown to exist depending on the coupling within a unit cell being larger or smaller than that between the unit cells. The freedom to adjust the coupling coefficients is used to construct a chain in which coupling alternates between electric and magnetic, between positive and negative. The resulting dispersion characteristics are shown to be radically different from the classical acoustic and optical branches: the upper branch is a forward wave and the lower branch is a backward wave, and even the gap between the two pass bands may disappear yielding infinite phase, finite group-velocity wave. The theory is confirmed both by simulations and experiments. © 2011 American Physical Society.
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