Percolation transitions in the binary mixture of active Brownian particles with different softness

TL;DR

This study investigates how heterogeneity in particle softness within a binary mixture of active Brownian particles influences phase behavior, revealing complex structure formation and percolation transitions driven by composition and motility variations.

Contribution

It is the first to explore the effects of particle softness heterogeneity on phase transitions and structure formation in active Brownian particle systems.

Findings

Percolation transition occurs after motility-induced phase separation.

Complex structures form within the dense phase depending on softness ratios.

Non-linear scaling links composition to structural properties.

Abstract

Homogeneous active Brownian particle (ABP) systems with purely repulsive interactions are considered to have simple phase behavior, but various physical attributes of active entities can lead to variation in the collective dynamics. Recent studies have shown that even homogeneous ABPs exhibit complex behavior due to an interplay between particle softness and motility. However, the heterogeneity in composition of ABPs has not been explored yet. In this paper, we study the structural properties of a binary mixture of ABPs with different particle softness, by varying the relative softness and composition. We found that upon varying the motility parameter, the system underwent a motility-induced phase separation (MIPS) followed by a percolation transition similar to the homogeneous systems; however, there is complex structure formation within the dense phase of the MIPS which depends on the relative softness of the binary system. Furthermore, the presence of a non-linear scaling for different compositions of heterogeneous ABPs suggests that there is a complex relationship between the composition and the structural properties. Our study demonstrates that the composition heterogeneity of ABPs can also lead to complex phase behavior.