Fluctations and noise in time-resolved light scattering experiments : measuring temporally heterogeneous dynamics

TL;DR

This paper employs Time Resolved Correlation (TRC) to analyze fluctuations in light scattering experiments, revealing that slow dynamics in soft glasses are temporally heterogeneous, with implications for understanding glassy material behavior.

Contribution

It introduces the use of TRC to quantify temporal heterogeneity in soft glass dynamics, providing new insights into their fluctuation characteristics.

Findings

Fluctuations in correlation functions are significant in jammed materials.

Soft glasses exhibit temporally heterogeneous slow dynamics.

Comparison with Brownian samples highlights distinct fluctuation patterns.

Abstract

We use Time Resolved Correlation (TRC), a recently introduced light scattering method, to study the dynamics of a variety of jammed, or glassy, soft materials. The output of a TRC experiment is cI(t,tau), the time series of the degree of correlation between the speckle patterns generated by the light scattered at time t and t+tau. We characterize the fluctuations of cI by calculating their Probability Density Function, their variance as a function of the lag tau, and their time autocorrelation function. The comparison between these quantities for a Brownian sample and for jammed materials indicate unambiguously that the slow dynamics measured in soft glasses is temporally heterogeneous. The analogies with recent experimental, numerical and theoretical work on temporal heterogeneity in the glassy dynamics are briefly discussed.