Describing the dispersion of hyperbolic metamaterials by elementary excitation coupling

Hyperbolic metamaterials are extremely anisotropic materials with iso-frequency surfaces shaped as hyperboloids, unlike natural materials. These metamaterials are interesting for many applications thanks to the large density of states and the extreme confinement of light they provide. We show that the dispersion of metamaterials made of square or rectangular metal nanorods in a 2D lattice can be understood via the coupling of elementary excitations, which often turn out to be the plasmons supported by the nanorod corners. Depending on the size of the nanorods, coupling occurs mainly through the dielectric or through the metal