Activity-driven Fluidization and Jamming of Dense Particulate Systems: The Extreme Active Limit*

Simulations of dense, athermal assemblies of self-propelled soft particles with infinite persistence time display intriguing mechanical properties as a function of the strength of the active propulsion force and the packing fraction of the system. Applying active propulsion to an initial, passively-jammed state results in unjamming and subsequent flow of the system. We find that there is a threshold force above which the system fluidizes indefinitely but below which the system experiences dynamical arrest, and that this threshold force increases as the density of the system is increased.

We analyze various mechanical and network properties in the final jammed states as well as over time series of such systems to illuminate the differences between packings formed with passive and active constituents, as well as understand the underlying mechanisms of dynamical arrest in this extreme active limit. We also investigate the scaling behavior of system quantities such as the contact force distribution and pair correlation function in the jammed states, appropriately accounting for the active force.