Percolation transition in phase separating active fluid

TL;DR

This paper investigates how the softness of interactions and motility in active particles lead to a percolation transition and porous cluster formation, revealing a richer phase diagram for active matter.

Contribution

It demonstrates that interaction softness and increased motility induce a percolation transition in active particles, expanding understanding of phase behavior in active matter.

Findings

Soft interaction destabilizes dense phases, forming porous clusters.

A critical motility induces a percolation transition.

Active particles exhibit similar transitions at low motility in the athermal limit.

Abstract

The motility-induced phase separation exhibited by active particles with repulsive interactions is well known. We show that the interaction softness of active particles destabilizes the highly ordered dense phase, leading to the formation of a porous cluster which spans the system. This \emph{soft limit} can also be achieved if the particle motility is increased beyond a critical value, at which the system clearly exhibits all the characteristics of a standard percolation transition. We also show that in the athermal limit, active particles exhibit similar transitions even at low motility. With these additional new phases, the phase diagram of repulsive active particles is revealed to be richer than what was previously conceived.