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Probing a Nonequilibrium Einstein Relation in an Aging Colloidal Glass

2004; American Physical Society; Volume: 93; Issue: 16 Linguagem: Inglês

10.1103/physrevlett.93.160603

1092-0145

Bérengère Abou, François Gallet,

Advanced Thermodynamics and Statistical Mechanics

We present a direct experimental measurement of an effective temperature in a colloidal glass of laponite, using a micrometric bead as a thermometer. The nonequilibrium fluctuation-dissipation relation, in the particular form of a modified Einstein relation, is investigated with diffusion and mobility measurements of the bead embedded in the glass. We observe an unusual nonmonotonic behavior of the effective temperature: starting from the bath temperature, it is found to increase up to a maximum value, and then decrease back, as the system ages. We show that the observed deviation from the Einstein relation is related to the relaxation times previously measured in dynamic light scattering experiments.