Chiral active gyrator: Memory induced direction reversal of rotational motion

TL;DR

This paper investigates how memory effects in viscoelastic environments can induce a reversal in the rotational direction of a chiral active particle, revealing a novel memory-driven control mechanism.

Contribution

It introduces a theoretical framework showing that memory effects can cause direction reversal in active particles, a phenomenon absent in purely viscous environments.

Findings

Memory induces direction reversal of rotational motion.

Temperature gradients influence the magnitude and direction of angular momentum.

Reversal phenomena are unique to viscoelastic media.

Abstract

We theoretically explore the dynamics of a chiral active Ornstein Uhlenbeck particle confined in a two-dimensional anisotropic harmonic trap. The particle is driven by chirality and is coupled to two orthogonal heat baths, potentially at two different temperatures. Using both analytical approach and numerical simulation, we explore the rotational dynamics of the particle in both viscous and viscoelastic environments. While the particle is suspended in a viscoelastic bath, characterized by a finite memory time scale, we interestingly observe that even in the absence of a temperature gradient, the angular momentum changes its sign as a function of the memory timescale, reflecting the direction reversal of rotational motion of the particle, and it is solely due to the interplay between memory and chirality. This direction reversal is a distinct memory-induced phenomenon and does not occur in the viscous limit. Moreover, increasing (or decreasing) the temperature gradient shifts the magnitude of the angular momentum further into the negative (or positive) direction, selecting a unique direction of rotation for the particle throughout the activity-memory parameter space. However, in the viscous limit, the direction reversal of the rotational motion is still possible but occurs only across a neutral line in parameter space, along which the contributions from both chirality and thermal anisotropy to the net angular momentum exactly cancel. These results highlight a distinct mechanism for directional control in active systems, with memory enabling reversal phenomena unique to viscoelastic media.