Brownian motors: current fluctuations and rectification efficiency

TL;DR

This paper examines how fluctuations in noise-induced current affect the efficiency of Brownian motors, revealing conditions for enhanced rectification and persistent unidirectional motion through tailored potentials and drive parameters.

Contribution

It introduces an analysis of current fluctuations in Brownian motors and identifies conditions that significantly improve rectification efficiency and persistent directional motion.

Findings

Broad velocity fluctuations lead to poor rectification performance.

Tailored potentials and drive parameters can drastically enhance efficiency.

Persistent, uni-directional motion with narrow velocity distribution is achievable.

Abstract

With this work we investigate an often neglected aspect of Brownian motor transport: The r\^{o}le of fluctuations of the noise-induced current and its consequences for the efficiency of rectifying noise. In doing so, we consider a Brownian inertial motor that is driven by an unbiased monochromatic, time-periodic force and thermal noise. Typically, we find that the asymptotic, time- and noise-averaged transport velocities are small, possessing rather broad velocity fluctuations. This implies a corresponding poor performance for the rectification power. However, for tailored profiles of the ratchet potential and appropriate drive parameters, we can identify a drastic enhancement of the rectification efficiency. This regime is marked by persistent, uni-directional motion of the Brownian motor with few back-turns, only. The corresponding asymmetric velocity distribution is then rather narrow, with a support that predominantly favors only one sign for the velocity.