Mobility and Diffusion of a Tagged Particle in a Driven Colloidal Suspension

Abstract

We study numerically the influence of density and strain rate on the diffusion and mobility of a single tagged particle in a sheared colloidal suspension. We determine independently the time-dependent velocity autocorrelation functions and, through a novel method, the response functions with respect to a small force. While both the diffusion coefficient and the mobility depend on the strain rate the latter exhibits a rather weak dependency. Somewhat surprisingly, we find that the initial decay of response and correlation functions coincide, allowing for an interpretation in terms of an 'effective temperature'. Such a phenomenological effective temperature recovers the Einstein relation in nonequilibrium. We show that our data is well described by two expansions to lowest order in the strain rate.

submitted to EPL

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• The modified Langevin description for probes in a nonlinear medium
• Crystallization in a sheared colloidal suspension
• Effective Confinement as Origin of the Equivalence of Kinetic Temperature and Fluctuation-Dissipation Ratio in a Dense Shear Driven Suspension
• Active velocity processes with suprathermal stationary distributions and long-time tails
• Tagged particle in a sheared suspension: effective temperature determines density distribution in a slowly varying external potential beyond linear response