Avalanches and Clogging in Active Matter Systems

Jamming and clogging have been extensively studied in passive soft matter systems such as granular matter or colloids moving through disordered environments such as obstacle arrays. Here we consider a system of disks moving through a random obstacle array and examine the transition to a clogged state as function of obstacle density as we go from the passive particle limit to an active matter limit. In the passive case, for a fixed disk density there is a well defined obstacle density above which the system reaches a clogged state. As the activity is increased, the disks can become mobile again when the activity breaks up the clogs; however, for large activity, which corresponds to long run times in a run-or-tumble system, the disks undergo intermittent clogging and we find that above a certain activity level, the unclogging events exhibit a power law distribution. We argue that the activity induced clustering brings the system into a critical state associated with local regions that have reached the jamming density known as point J. For infinite run times or the ballistic active matter limit, the system can reach a completely clogged state with no avalanches for disk densities that are much lower than those at which clogging is observed for passive particles.