Fate of the Mollow triplet in strongly-coupled atomic arrays

Subwavelength arrays of quantum emitters have emerged as an interesting platform displaying prominent collective effects. Here we study such arrays under coherent driving, realizing an open quantum many-body problem in a strongly non-linear regime. We show that the combination of dipolar interactions and regular geometry have a dramatic effect on the spectrum of emitted light: the famous Mollow triplet characterizing the emission of a single atom develops a structured broadening with flat sidebands, with a bandwidth determined by the dipolar interactions. This emission spectrum characterizes atomic arrays and distinguishes them from disordered ensembles as well as non-interacting emitters. Our predictions are based on a novel dynamical mean-field theory (DMFT) approach to the problem, paving the way for further studies of these systems.