Crossover from normal to anomalous diffusion in field-aligned dipolar systems

TL;DR

This study uses molecular dynamics simulations to explore how particles with dipolar interactions transition from normal to anomalous diffusion under strong external fields, revealing complex cooperative behaviors and cage effects.

Contribution

It uncovers the crossover from normal to anomalous diffusion in dipolar systems under external fields, highlighting the role of chain formation and cooperative motion.

Findings

Anisotropic diffusion becomes anomalous at high dipolar coupling and field strength.

Chain formation leads to cage-like and superdiffusive behaviors.

Enhanced dynamics vanish near crystallization densities.

Abstract

Using molecular dynamics simulations we investigate the translational dynamics of particles with dipolar interactions in homogenous external fields. For a broad range of concentrations, we find that the anisotropic, yet normal diffusive behavior characterizing weakly coupled systems becomes anomalous both parallel and perpendicular to the field at sufficiently high dipolar coupling and field strength. After the ballistic regime, chain formation first yields cage-like motion in all directions, followed by transient, mixed diffusive-superdiffusive behavior resulting from cooperative motion of the chains. The enhanced dynamics disappears only at higher densities close to crystallization.