Retarded long-range interaction in split-ring-resonator square arrays
M. Decker, N. Feth, C.M. Soukoulis, S. Linden, and M. Wegener
Phys. Rev. B
We systematically investigate the optical extinction spectra of planar gold split-ring-resonator square arrays operating at ∼200-THz frequency versus the lattice constant and versus angle of incidence. We find a strong dependence of the resonance damping on the in-plane wave vector, namely, the resonance damping increases (decreases) versus the in-plane wave vector for small lattice constants (large lattice constants). By comparison with two simple one-dimensional models as well as with more complete numerical calculations, this behavior is interpreted in terms of a long-range retarded interaction among the split-ring resonators. In contrast, the assumptions of only nearest-neighbor interaction and/or of an instantaneous interaction lead to a striking disagreement with the overall experimental facts.