Fate of the Mollow triplet in strongly-coupled atomic arrays

Abstract: Subwavelength arrays of quantum two-level emitters have emerged as an interesting platform displaying prominent collective effects that can be harnessed for applications. Here we study such arrays under strong coherent driving, realizing an open quantum many-body problem in a strongly non-linear regime. For this we introduce a novel approach to this problem in terms of a Dynamical Mean Field Theory (DMFT), paving the way for further studies. We show that the spectrum of scattered light, characterized by the famous Mollow triplet for a single atom, develops a characteristic lineshape with flat sidebands determined by dipolar interactions and relevant for experiments. Remarkably, this is to some extent independent of the specific geometry, but is sensitive to the ordered arrangement of the atoms. This lineshape therefore characterizes atomic arrays and distinguishes them from disordered ensembles and non-interacting emitters.