Optimal diffusion of chiral active particles with strategic reorientations

TL;DR

This paper explores how strategic reorientations, such as optimal tumbling and directional reversals, can enhance the diffusion of chiral active particles, providing exact analytical expressions and identifying optimal strategies for increased transport efficiency.

Contribution

It introduces a comprehensive analysis of how different reorientation strategies can optimize diffusion in chiral active particles, including exact solutions and universal diffusion limits.

Findings

Symmetric tumbles universally enhance diffusion with a fixed effective coefficient.

Asymmetric tumbles can surpass symmetric strategies in diffusion enhancement.

Dynamic reorientations in finite time can further improve particle transport.

Abstract

We investigate the competing effects of simultaneous presence of chirality and generalised tumbles in the dynamics of an active Brownian particle. Chiral active particles perform circular motions that give rise to slow transport at late times. By interrupting these circular trajectories at the right time or by performing a tumble at the correct angle, we show that particles can enhance their diffusion. After deriving exact expressions for the orientational propagator and correlations, we use this to calculate the first two moments of displacement. For the effective diffusion coefficient, we study various optimal tumbling strategies. We show that under optimisation of the tumbling rate, the case of symmetrically distributed tumbles always give rise to enhanced diffusion, with an effective diffusion coefficient taking a universal value. Next, two cases are considered in detail, namely directional reversal and tumbles at an arbitrary but fixed angle. We discuss how asymmetric tumbles can enhance diffusion beyond that of symmetric tumbles. Finally, we discuss a situation where the reorientations are realized dynamically in finite time.