Mesoscopic model of temporal and spatial heterogeneity in aging colloids (original) (raw)

A model of dense hard sphere colloids building on simple notions of particle mobility and spatial coherence is presented and shown to reproduce results of experiments and simulations for key quantities such as the intermediate scattering function, the particle mean-square displacement and the χ4 mobility correlation function. All results are explained by two emerging and interrelated dynamical properties: i) a rate of intermittent events, quakes, which decreases as the inverse of the system age t, leading to µq(tw, t) ∝ log(t/tw) as the average number of quakes occurring between the 'waiting time' tw and the current time t; ii) a length scale characterizing correlated domains, which increases linearly in log t. This leads to simple and accurate scaling forms expressed in terms of the single variable, t/tw, preferable to the established use of tw and of the lag time τ = t − tw as variables in two-point correlation functions. Finally, we propose to use χ4 (tw, t) experimentally to extract the growing length scale of an aging colloid and suggest that a suitable scaling of the probability density function of particle displacement can experimentally reveal the rate of quakes.