Aging and ultra-slow equilibration in concentrated colloidal hard spheres

TL;DR

This paper investigates the slow aging dynamics of concentrated colloidal hard spheres, revealing prolonged non-equilibrium states and unusual aging behavior using light scattering techniques.

Contribution

It provides new insights into the ultra-slow equilibration process and aging phenomena in concentrated colloidal systems, highlighting dynamics lasting much longer than previously observed.

Findings

Equilibrium takes a very long time to reach, up to three orders of magnitude longer than the relaxation time.

The system exhibits non-monotonic evolution of relaxation time with sample age.

The intermediate scattering function decays faster than exponential during aging.

Abstract

We study the dynamic behaviour of concentrated colloidal hard spheres using Time Resolved Correlation, a light scattering technique that can detect the slow evolution of the dynamics in out-of-equilibrium systems. Surprisingly, equilibrium is reached a very long time after sample initialization, the non-stationary regime lasting up to three orders of magnitude more than the relaxation time of the system. Before reaching equilibrium, the system displays unusual aging behaviour. The intermediate scattering function decays faster than exponentially and its relaxation time evolves non-monotonically with sample age.