Multiple modulations of coupling effects on directed transport of Brownian particles driven by nonequilibrium fluctuations.

Abstract

We investigate the overdamped directed transport of elastically coupled Brownian particles in asymmetric periodic potentials, driven by nonequilibrium fluctuations modeled as Poisson shot noise (PSN). Our findings reveal distinct modulations in the coupling effect, characterized by alternating regimes of transport enhancement, suppression, and even coupling-induced current reversal. This complex phenomenology arises from nonequilibrium fluctuations, whereas thermal equilibrium fluctuations are unable to induce net transport in the absence of external deterministic drives. Based on the discrete nature of PSN, we propose two underlying mechanisms responsible for these observed modulations: dual-mode motion and passive push-pull dynamics between coupled particles. By analyzing the velocity difference between coupled and single particles, we demonstrate that these modulations in coupling-induced transport are determined by the interplay between nonequilibrium fluctuations and the potential barrier height. Specifically, for low mean strengths of the nonequilibrium fluctuations, a characteristic three-stage pattern of coupling effects (suppression-enhancement-suppression) is observed with increasing potential barrier height. Furthermore, the interplay between the rate and average amplitude of the discrete pulses defining these nonequilibrium fluctuations also profoundly shapes the coupling effect, yielding diverse transport characteristics. Moreover, the potential's asymmetry coefficient, the noise skewness, and the interparticle coupling strength are shown to significantly modulate the coupling-induced transport. Our study establishes a theoretical framework for understanding the intricate collective transport dynamics of coupled particles driven by nonequilibrium fluctuations. These findings provide critical insights for the design and control of directed motion in artificial micro- and nanoscale systems operating under discrete energy pulses in nonequilibrium environments.