Active particles driven by competing spatially dependent self-propulsion and external force

Lorenzo Caprini; Umberto Marini Bettolo Marconi; René Wittmann; Hartmut Löwen

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arXiv · 2203.00603

Active particles driven by competing spatially dependent self-propulsion and external force

Lorenzo Caprini·Umberto Marini Bettolo Marconi·René Wittmann·Hartmut Löwen

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Abstract

We investigate how the competing presence of a nonuniform motility landscape and an external confining field affects the properties of active particles. We employ the active Ornstein-Uhlenbeck particle (AOUP) model with a periodic swim velocity profile to derive analytical approximations for the steady-state probability distribution of position and velocity, encompassing both the Unified Colored Noise Approximation and the theory of potential-free active particles with spatially dependent swim velocity recently developed. We test the theory by confining an active particle in a harmonic trap, which gives rise to interesting properties, such as a transition from a unimodal to a bimodal (and, eventually multimodal) spatial density, induced by decreasing the spatial period of the self propulsion. Correspondingly, the velocity distribution shows pronounced deviations from the Gaussian shape, even displaying a bimodal profile in the high-motility regions. Our results can be confirmed by real-space experiments on active colloidal Janus particles in external fields.

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Lorenzo Caprini, Umberto Marini Bettolo Marconi, René Wittmann, Hartmut Löwen. 2022-03-01. Active particles driven by competing spatially dependent self-propulsion and external force. https://arxiv.org/abs/2203.00603

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