Recent experimental work identified a reversible to irreversible transition in sheared colloidal systems [D.J. Pine et al., Nature 438, 998 (2005)]. This is an example of a nonequilibrium phase transition from a fluctuating state to an absorbed state in which the fluctuations vanish and the system becomes trapped. We demonstrate that the results from the colloidal system can be generalized to a much wider class of systems of driven particle systems with quenched disorder undergoing plastic flow. In these systems, the transient times to reach steady state behavior show a power law divergence consistent with a nonequilibrium phase transition. We provide evidence that the transition falls into the class of directed percolation, and make clear predictions for the behavior of the velocity noise under cycling that can be used to identify the reversible-irreversible transition in a system which cannot be imaged directly. We also propose that plastic depinning is a true phase transition which falls into the class of absorbing phase transitions, and possibly into the class of directed or conserved directed percolation.
We examine an assembly of repulsive disks interacting with a random obstacle array under a periodic drive, and find a transition from reversible to irreversible dynamics as a function of drive amplitude or disk density. At low densities and drives, the system rapidly forms a reversible state where the disks return to their exact positions at the end of each cycle. In contrast, at high amplitudes or high densities, the system enters an irreversible state where the disks exhibit normal diffusion. Between these two regimes, there can be a glassy irreversible state where most of the system is reversible, but localized irreversible regions are present that are prevented from spreading through the system due to a screening effect from the obstacles. We also find states that we term combinatorial reversible states in which the disks return to their original positions after multiple driving cycles. In these states, individual disks exchange positions but form the same configurations during the subcycles of the larger reversible cycle.
Last modified Jan 7, 2019