Self-propelled rods exhibit a phase-separated state characterized by the presence of active stresses and the ejection of polar clusters

Sebastian Weitz, Andreas Deutsch, and Fernando Peruani
Phys. Rev. E 92, 012322 – Published 27 July 2015
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Abstract

We study collections of self-propelled rods (SPR) moving in two dimensions for packing fractions less than or equal to 0.3. We find that in the thermodynamical limit the SPR undergo a phase transition between a disordered gas and a novel phase-separated system state. Interestingly, (global) orientational order patterns—contrary to what has been suggested—vanish in this limit. In the found novel state, the SPR self-organize into a highly dynamical, high-density, compact region—which we call aggregate—which is surrounded by a disordered gas. Active stresses build inside aggregates as a result of the combined effect of local orientational order and active forces. This leads to the most distinctive feature of these aggregates: constant ejection of polar clusters of SPR. This novel phase-separated state represents a novel state of matter characterized by large fluctuations in volume and shape, related to mass ejection, and exhibits positional as well as orientational local order. SPR systems display new physics unseen in other active matter systems.

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  • Received 15 November 2014
  • Revised 10 May 2015

DOI:https://doi.org/10.1103/PhysRevE.92.012322

©2015 American Physical Society

Authors & Affiliations

Sebastian Weitz1,2, Andreas Deutsch1, and Fernando Peruani3

  • 1Zentrum für Informationsdienste und Hochleistungsrechnen, Technische Universität Dresden, Zellescher Weg 12, 01069 Dresden, Germany
  • 2Clermont Université, ENSCCF, Institut Pascal - UMR CNRS 6602, BP 10448, F-63000 Clermont-Ferrand, France
  • 3Université Nice Sophia Antipolis, Laboratoire J.A. Dieudonné, UMR 7351 CNRS, Parc Valrose, F-06108 Nice Cedex 02, France

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Issue

Vol. 92, Iss. 1 — July 2015

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