Coherence and Nonequilibrium Steady State of a simple Brownian Heat Engine

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Date

2005-06

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Addis Ababa University

Abstract

Overdamped motion of a Brownian particle in a ratchet potential with space dependent temperature is studied. Explicit analytic expressions for particle steady state velocity, diffusion coefficient and Peciet number which characterizes the transport are derived. Their dependencies on temperature profile, tilting force, the shape of the potential and barrier height are analyzed. We show that the asymmetry parameter of the potential along with temperature profile can enhance or suppress effective diffusion coefficient compared to that of free diffusion. The Peciet number is also shown to be very sensitive to temperature profile and asymmetry of the potential. At moderate values of asymmetry parameter an optimized transport with respect to temperature profile and barrier height is observed. We show that our model exhibits a pronounced coherence in a wide range of model parameters. We also propose a systematic way of studying the mobility of a particie described by Langevin equation with nonuniform temperature in the absence of bias. It is shown that for a symmetric potential, mobility increases monotonically and saturates to one for large values of temperature profile. Based on our formulation, we also study the effective temperature of the model. It is shown that for a symmetric potential, the effective temperature of the system is greater than that of the temperature of the cold region of the ratchet potential

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A Simple Brownian Heat Engine

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