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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Keywords
A Simple Brownian Heat Engine