Emergence of spontaneous order in driven and undriven arrays of atoms coupled to one-dimensional reservoirs

We present our results on the transient and steady-state many-body behavior of an atomic array coupled to a waveguide. Collective dissipation into the waveguide imprints memory onto the atoms, which gives rise to emergent order in the emission direction. For transient (undriven) dynamics, this results in photon avalanches where (shot-to-shot) the mirror symmetry is spontaneously broken as the atoms emit most photons in one direction. For incoherently driven systems, order also emerges spontaneously above a certain driving strength, leading to line narrowing and the emission of coherent light. Our work advances the understanding of how order emerges in quantum systems with multiple competing decay channels, and paves the way towards the development of cavity-less superradiant lasers.