Consequences of Anomalous Diffusion in Disordered Systems under Cyclic Forcing

We study the particle scale response of a 2D frictionless disk system to bulk forcing via cyclic shear with reversal amplitude gamma(r). We find a subdiffusive gamma(r)-dependent regime, which is consistent with models of anomalous diffusion with scale-invariant cage dynamics, and a crossover to diffusive grain motion at high gamma(r). Analysis of local displacements of a particle relative to its cage of neighbors reveals a key distinction from thermal systems. Particles are moved by fluctuations of their cage of neighbors rather than rattling in their cage, indicating a distinct cage-breaking mechanism.