Breaking the symmetry of a Brownian motor with symmetric potentials

TL;DR

This paper explores how symmetric potentials can produce directed transport in Brownian motors by introducing various asymmetries such as potential depths, frictions, or temperatures, expanding the understanding of non-equilibrium noise effects.

Contribution

It demonstrates that asymmetry in a two-state Brownian motor can be achieved through multiple parameters beyond transfer rates, including potential depths, frictions, and temperatures.

Findings

Asymmetries in potential depths, frictions, or temperatures can induce directed transport.

Thermal noise effects depend on the specific asymmetry mechanism.

Symmetric potentials can produce directed motion with appropriate parameter inequalities.

Abstract

The directed transport of Brownian particles requires a system with an asymmetry and with non-equilibrium noise. We here investigate numerically alternative ways of fulfilling these requirements for a two-state Brownian motor, realised with Brownian particles alternating between two phase-shifted, symmetric potentials. We show that, besides the previously known spatio-temporal asymmetry based on unequal transfer rates between the potentials, inequalities in the potential depths, the frictions, or the equilibrium temperatures of the two potentials also generate the required asymmetry. We also show that the effects of the thermal noise and the noise of the transfer's randomness depend on the way the asymmetry is induced.