Roughness-induced diffusion enhancement in asymmetric potentials under nonequilibrium fluctuations.

Abstract

Roughness in a potential landscape is canonically understood as a kinetic impediment that invariably suppresses the diffusion of thermally driven particles, particularly in the absence of an external bias. Here we reveal a contrasting principle for systems driven by nonequilibrium fluctuations. Focusing on a paradigmatic model of such fluctuations, such as Poisson shot noise, we demonstrate that for driven particles, roughness on an asymmetric potential can act as an effective means to accelerate diffusion. In a specific regime, the effective diffusion coefficient exhibits a pronounced enhancement, culminating in a peak value that unambiguously surpasses the benchmark value set by free-particle diffusion. This phenomenon originates from a microscopic mechanism we term unidirectional slide inhibition: A synergy between the potential's global asymmetry and its local roughness selectively arrests the particle's backward slide on the gentler slope. This selective arrest acts as a ratchet, enhancing the efficiency of forward barrier crossings. This process simultaneously boosts net transport and magnifies displacement variance by promoting successful, long-range forward jumps over backward slides. Our findings establish a new principle for nonequilibrium control, demonstrating that potential roughness can be harnessed to dramatically enhance diffusion, opening avenues for novel particle separation technologies and offering a new framework for understanding transport in biological and soft-matter systems where such rugged energy landscapes are ubiquitous.