Diffusion dynamics of an overdamped active ellipsoidal particle in two dimensions

TL;DR

This paper analyzes the diffusion behavior of active ellipsoidal particles in two dimensions, revealing three distinct regimes and examining effects of external forces and rotational dynamics through analytical and simulation methods.

Contribution

It introduces a comprehensive analysis of active ellipsoidal particle diffusion, including transient, super-diffusive, and long-term regimes, extending understanding beyond passive particles.

Findings

Identification of three diffusion regimes: transient, super-diffusive, and diffusive.

Analysis of diffusion under external forces and harmonic traps.

Insights into rotational diffusion and torque production in active particles.

Abstract

Shape asymmetry is the most abundant in nature and attracted great interest in recent research. The phenomenon is widely recognized: a free ellipsoidal Brownian particle displays anisotropic diffusion during short time intervals, which subsequently transitions to an isotropic diffusion pattern over longer time scales. We have further expanded this concept to incorporate active ellipsoidal particles characterized by an initial self-propelled velocity. This paper provides analytical and simulation results of diffusion dynamics of an active ellipsoidal particle. The active ellipsoidal particle manifests three distinct regimes in its diffusion dynamics over time. In the transient regime, it displays diffusive behavior followed by a super-diffusive phase, and in the longer time duration, it transitions to purely diffusive dynamics. We investigated diffusion dynamics for the free particle as well as the particle in a harmonic trap, and the particle subject to a constant field force. Moreover, we have studied the rotational diffusion dynamics and torque production resulting from an external constant force field. Furthermore, our investigation extends to the examination of the scaled average velocity of an ellipsoidal active particle, considering both a constant force field and a one-dimensional ratchet.