Activity induced delocalization and freezing in self-propelled systems
Abstract
We study a system of interacting active particles, propelled by colored noises, characterized by an activity time {\tau}, and confined by a single-well anharmonic potential. We assume pair-wise repulsive forces among particles, modelling the steric interactions among microswimmers. This system has been experimentally studied in the case of a dilute suspension of Janus particles confined through acoustic traps. We observe that already in the dilute regime - when inter-particle interactions are negligible - increasing the persistent time pushes the particles away from the potential minimum, until a saturation distance is reached. We compute the phase diagram (activity versus interaction length), showing that the interaction does not suppress this delocalization phenomenon but induces a liquid- or solid-like structure in the densest regions. Interestingly a reentrant behavior is observed: a first increase of {\tau} from small values acts as an effective warming, favouring fluidization; at higher values, when the delocalization occurs, a further increase of {\tau} induces freezing inside the densest regions. An approximate analytical scheme gives fair predictions for the density profiles in the weakly interacting case. The analysis of non-equilibrium heat fluxes reveals that in the region of largest particle concentration equilibrium is restored in several aspects.
Cite
@article{arxiv.1810.12652,
title = {Activity induced delocalization and freezing in self-propelled systems},
author = {Lorenzo Caprini and Umberto Marini Bettolo Marconi and Andrea Puglisi},
journal= {arXiv preprint arXiv:1810.12652},
year = {2018}
}