Primordial Media: The Shrouded Realm of Composite Materials

Electromagnetic composites (metamaterials) recently underwent explosive growth fueled in part by advances in nanofabrication. It is commonly believed that as the size of the components decreases, the behavior of a composite converges to the response of a homogeneous material (recent research indicates that in the limit of nanoscale composites, the constituent parameters of nanostructures may be quantitatively affected by nonlocal corrections). Here we show that this intuitive understanding of the electromagnetic response of composite media is fundamentally flawed, even at the qualitative level. In contrast to the well-understood (local) effective medium response, the properties of nanostructured composites can be dominated, not simply corrected, by electromagnetic nonlocality. We demonstrate that in composites, the interplay between the nonlocality and the structural inhomogeneity introduces two fundamentally new electromagnetic regimes: primordial metamaterials and homogenizable nonlocality. We develop an analytical description of these regimes and show that the behavior of metamaterials in the limits of vanishing nonlocality and of vanishing component size does not commute. Our work opens a new dimension in the design space of nanostructured electromagnetic composites.