Ageing dynamics of colloidal hard sphere glasses

TL;DR

This study investigates the aging behavior of colloidal hard sphere glasses using dynamic light scattering, revealing a power-law approach to an aged state and non-stationary dynamics across different volume fractions.

Contribution

It provides detailed measurements of the intermediate scattering function and characterizes the aging process in colloidal glasses, highlighting the algebraic decay and non-stationarity of dynamics.

Findings

Aging follows a power-law decay towards a stable glass state.

Coupling between fast and slow decay processes decreases algebraically with waiting time.

Non-stationarity persists even in the fastest detectable processes.

Abstract

We report results of dynamic light scattering measurements of the coherent intermediate scattering function (ISF) of glasses of hard spheres for several volume fractions and a range of scattering vectors around the primary maximum of the static structure factor. The ISF shows a clear crossover from an initial fast decay to a slower non-stationary decay. Ageing is quantified in several different ways. However, regardless of the method chosen, the perfect "aged" glass is approached in a power-law fashion. In particular, the coupling between the fast and slow decays, as measured by the degree of stretching of the ISF at the crossover, also decreases algebraically with waiting time. The non-stationarity of this coupling implies that even the fastest detectable processes are themselves non-stationary.