Jamming and Clogging Transitions for Systems with Quenched Disorder

Jamming can occur in systems consisting of collections of
particles. It appears as a transition from a fluid like state that can
easily flow to a state that acts like a solid. For example, a loose
collection of grains flows readily at low densities, but as the
density increases there is a transition to a jammed state at a density
termed Point J. Liu and Nagel have proposed that there may be a
universal jamming phase diagram as a function of density, load, or
temperature [1]. Here we propose adding a new axis to the jamming
phase diagram in the form of the density of fixed obstacles or
quenched disorder that can cause the system to jam at densities below
Point J and can strongly influence the dynamics. We find that as the
obstacle density increases, there is a crossover to a behavior which
we term clogging rather than jamming. The clogged states are highly
heterogeneous and fragile, and they exhibit memory effects. These
results are relevant to particle flow in porous media as well as
de-pinning transitions in systems such as vortices in type-II
superconductors. I will describe other systems we have been studying
beyond granular matter that exhibit jamming or clogging behaviors,
including vortices in type-II superconductors with funnel geometries,
active matter such as swarming bacteria, and dislocation pileup
formation in materials.

[1] A.J. Liu and S.R. Nagel, Nature 396, 21 (1998)