Single file diffusion of macroscopic charged particles

TL;DR

This study investigates single file diffusion in a macroscopic system of charged metallic beads, revealing non-Fickian behavior and comparing experimental results with extended theoretical models, highlighting the importance of dynamics assumptions.

Contribution

The paper demonstrates that realistic potentials and non-overdamped dynamics are crucial for accurately modeling single file diffusion in macroscopic charged particles.

Findings

Observed non-Fickian single file diffusion at large times.

Quantitative agreement achieved with extended theoretical models.

Identified the role of non-overdamped dynamics in discrepancies.

Abstract

In this paper, we study a macroscopic system of electrically interacting metallic beads organized as a sequence along an annulus. A random mechanical shaking mimics the thermal excitation. We exhibit non Fickian diffusion (Single File Diffusion) at large time. We measure the mobility of the particles, and compare it to theoretical expectations. We show that our system cannot be accurately described by theories assuming only hard sphere interactions. Its behavior is qualitatively described by a theory extended to more realistic potentials [Kollmann, PRL {\bf 90} 180602, (2003)]. A correct quantitative agreement is shown, and we interpret the discrepancies by the violation of a key assumption of the theory, that of overdamped dynamics. We recast previous results on colloids with known interaction potentials, and compare them quantitatively to the theory. Focusing on the transition between ordinary and single file diffusion, we exhibit a dimensionless crossover time that is of order one both for colloids and our system, although the time and length scales differ by several orders of magnitude.