Collisions enhance self-diffusion in odd-diffusive systems

TL;DR

In odd-diffusive systems characterized by antisymmetric diffusion tensors, particle collisions can unexpectedly increase self-diffusion due to a curving motion effect, as shown analytically and validated by simulations.

Contribution

This work reveals that collisions can enhance self-diffusion in odd-diffusive systems, a counterintuitive phenomenon not observed in normal diffusive systems.

Findings

Collisions can increase self-diffusion in odd-diffusive systems.

Analytical model predicts diffusion enhancement with density.

Simulations confirm the theoretical predictions.

Abstract

It is generally believed that collisions of particles reduce the self-diffusion coefficient. Here we show that in odd-diffusive systems, which are characterized by diffusion tensors with antisymmetric elements, collisions surprisingly can enhance the self-diffusion. In these systems, due to an inherent curving effect, the motion of particles is facilitated, instead of hindered by collisions leading to a mutual rolling effect. Using a geometric model, we analytically predict the enhancement of the self-diffusion coefficient with increasing density. This counterintuitive behaviour is demonstrated in the archetypal odd-diffusive system of Brownian particles under Lorentz force. We validate our findings by many body Brownian dynamics simulations in dilute systems.