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Crystallization of chiral active Brownian particles at low densities

Kangeun Jeong1,*, Yuta Kuroda1, Yuki Asatani1, Takeshi Kawasaki2,3, and Kunimasa Miyazaki1,†

  • *Contact author: jeong@r.phys.nagoya-u.ac.jp
  • †Contact author: miyazaki@r.phys.nagoya-u.ac.jp
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Phys. Rev. Research 7, 043212 – Published 24 November, 2025

DOI: https://doi.org/10.1103/yntx-ss9r

Abstract

Chiral active matter is a variant of active matter systems in which the motion of the constituent particles violates mirror symmetry. In this article, 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.

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Phys. Rev. Research 7, 043212– Published 24 November, 2025
  • Received 14 July 2025
  • Accepted 12 October 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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