Crystallization of Chiral Active Brownian Particles at Low Densities

TL;DR

This study demonstrates that two-dimensional chiral active Brownian particles can crystallize at low densities below equilibrium melting points, with phase behavior influenced by orbital radius and non-equilibrium conditions.

Contribution

It reveals the conditions under which chiral active particles crystallize and characterizes their phase diagram, highlighting non-equilibrium effects on melting transitions.

Findings

Crystallization occurs at low densities below equilibrium melting points.

Re-entrant melting transition depends on orbital radius.

Two-step melting scenario observed in the phase diagram.

Abstract

Chiral active matter is a variant of active matter systems in which the motion of the constituent particles violates mirror symmetry. In this letter, we simulate two-dimensional chiral Active Brownian Particles, the simplest chiral model in which each particle undergoes circular motion, and show that the system crystallizes at low densities well below the melting point of the equilibrium counterpart. Crystallization is only possible if the orbital radius is long enough to align the circulating particles, but short enough for neighboring particles to avoid collisions. Of course, the system must be driven sufficiently far from equilibrium, since chirality cannot affect thermodynamic properties in classical equilibrium systems. The fluid-crystal phase diagram shows a re-entrant melting transition as a function of the radius of the circles. We show that at least one of the two transitions follows the same two-step melting scenario as in equilibrium systems.