  We theoretically analyze the experimental observations of a spectral line
collapse in a metamaterial array of asymmetric split ring resonators [Fedotov
et al., Phys. Rev. Lett. 104, 223901 (2010)]. We show that the ensemble of
closely-spaced resonators exhibits cooperative response, explaining the
observed system-size dependent narrowing of the transmission resonance
linewidth. We further show that this cooperative narrowing depends sensitively
on the lattice spacing and that significantly stronger narrowing could be
achieved in media with suppressed ohmic losses.
