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. 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 by electromagnetic nonlocality. We demonstrate that the interplay between the nonlocality and the structural inhomogeneity introduces two fundamentally new electromagnetic regimes, primordial metamaterials and nonlocal effective medium. 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 do not commute. Our work opens a new dimension in the design space of nanostructured electromagnetic composites.