Two-time correlations for probing the aging dynamics of glassy colloids

Abstract

We present results for the aging dynamics of a jammed 2D colloidal system obtained with molecular dynamics simulations. We performed extensive simulations to gather detailed statistics about rare rearrangement events. With a simple criterion for identifying irreversible events based on Voronoi tessellations, we find that the rate of those events decelerates hyperbolically. We track the probability density function for particle displacements, the van-Hove function, with sufficient statistics as to reveal its two-time dependence that is indicative of aging. Those displacements, measured from a waiting time tw after the quench up to times t = tw +∆t, exhibit a data collapse as a function of ∆t/tw. These findings can be explained comprehensively as manifestations of "record dynamics", i.e., a relaxation dynamic driven by record-breaking fluctuations. We show that an on-lattice model of a colloid that was built on record dynamics indeed reproduces the experimental results in great detail.arXiv:1802.05350v1 [cond-mat.soft]

Dynamics of dense hard sphere colloidal systems: A numerical analysis

“…We find that both distributions are age independent, and that the weight of the exponential tail is a function of the ratio of the lag time and the system age. This extends a result recently obtained [30] for a 2D HSC system and is akin to the behavior of heat transfer in a spin glass model [36].…”

“…Recall that σ is the average particle diameter. This result concurs with the estimate obtained from 2D simulations [30], which suggest ". .…”

“…[36] to describe heat transfer in a spin-glass model and its results concur broadly with those of Ref. [6] and precisely with those of a more recent simulational study of 2D HSC [30] which obtains a data collapse by scaling the lag time with the system age, as we presently do.…”

“…Summarizing, our analysis of the self part of the Van Hove function indicates that cage-breakings occur at a rate which decreases with the inverse of the system age, see [28] and [30] for corroborating experimental and simulational evidence. Consequently, the number of these events increases logarithmically with time.…”

“…For all other volume fractions, the MSD grows, after a short transient, as the logarithm of time for more than four decades of simulation. For similar results, see [24,30].…”