Defying Disorder: Surprising Order in Active Systems

In classical condensed matter systems, quenched disorder—time-independent disorder—disrupts long-range order. Given this understanding in equilibrium systems, one might expect quenched disorders to similarly affect the coordinated motion of far-from-equilibrium agents.To explore this, we conduct numerical simulations of active particles navigating through randomly distributed defects. We demonstrate that, at sufficiently high densities, active agents can exhibit an ordered, coherently moving phase even in the presence of such obstacles in two dimensions. This behavior sharply contrasts with equilibrium systems with defects, which fail to sustain long-range order even in three dimensions. Our study offers insights into designing obstacles that enhance cooperation among active agents and may be relevant for the coordinated motion of robots on a substrate.