Generalized Einstein Relation in an aging colloidal glass

TL;DR

This study investigates the validity of the Generalized Einstein Relation in an aging colloidal glass, revealing deviations linked to changes in relaxation times as the glass ages, through combined experimental and theoretical analysis.

Contribution

It provides a novel experimental and theoretical analysis of the GER in out-of-equilibrium aging colloidal glasses, highlighting how deviations relate to relaxation time changes.

Findings

Deviations from GER increase with aging time.

Deviations are frequency-dependent and linked to relaxation times.

Experimental data matches theoretical predictions.

Abstract

We present an experimental and theoretical investigation of the Generalized Einstein Relation (GER), a particular form of a fluctuation-dissipation relation, in an out-of-equilibrium visco-elastic fluid. Micrometer beads, used as thermometers, are immersed in an aging colloidal glass to provide both fluctuation and dissipation measurements. The deviations from the Generalized Einstein Relation are derived as a function of frequency and aging time. The observed deviations from GER are interpreted as directly related to the change in the glass relaxation times with aging time. In our scenario, deviations are observed in the regime where the observation time scale is of the order of a characteristic relaxation time of the glass.