Entropy production of active Brownian particles going from liquid to hexatic and solid phases

TL;DR

This study investigates entropy production in active Brownian particles across liquid, hexatic, and solid phases, revealing continuous average trends with notable derivative changes at phase transitions and complex tail behaviors linked to microscopic configurations.

Contribution

It provides a detailed numerical analysis of entropy production in active particles across phase transitions, highlighting microscopic mechanisms behind observed statistical features.

Findings

No singularity in average entropy production trends at phase transitions.

Distinct tail structures in entropy production distributions linked to local particle arrangements.

A simple single-particle model reproduces the observed tail behaviors.

Abstract

Due to its inherent intertwinement with irreversibility, entropy production is a prime observable to monitor in systems of active particles. In this numerical study, entropy production in the liquid, hexatic and solid phases of a two-dimensional system of active Brownian particles is examined at both average and fluctuation level. The trends of averages as functions of density show no singularity and marked changes in their derivatives at the hexatic-solid transition. Distributions show instead peculiar tail structures interpreted by looking at microscopic configurations. Particles in regions of low local order generate tail values according to different dynamical mechanisms: they move towards empty regions or bounce back and forth into close neighbours. The tail structures are reproduced by a simple single-particle model including an intermittent harmonic potential.