  We report on a particle-based numerical study of sheared amorphous solids in
the dense slow flow regime. In this framework, deformation and flow are
accompanied by critical fluctuation patterns associated with the macroscopic
plastic response and single particle kinematics. The former is commonly
attributed to the collective slip patterns that relax internal stresses within
the bulk material and give rise to an effective mechanical noise governing the
latter particle-level process. In this work, the avalanche-type dynamics
between plastic events is shown to have a strong relevance on the
self-diffusion of tracer particles in the Fickian regime. As a consequence,
strong size effects emerge in the effective diffusion coefficient that is
rationalized in terms of avalanche size distributions and the relevant temporal
occurrence.
