Chiral Active Hexatics: Giant Number Fluctuations, Waves, and Destruction of Order

Ananyo Maitra, Martin Lenz, and Raphael Voituriez
Phys. Rev. Lett. 125, 238005 – Published 2 December 2020
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Abstract

Active materials, composed of internally driven particles, have properties that are qualitatively distinct from matter at thermal equilibrium. However, the most spectacular departures from equilibrium phase behavior are thought to be confined to systems with polar or nematic asymmetry. In this Letter, we show that such departures are also displayed by more symmetric phases such as hexatics if, in addition, the constituent particles have chiral asymmetry. We show that chiral active hexatics whose rotation rate does not depend on density have giant number fluctuations. If the rotation rate depends on density, the giant number fluctuations are suppressed due to a novel orientation-density sound mode with a linear dispersion which propagates even in the overdamped limit. However, we demonstrate that beyond a finite but large length scale, a chirality and activity-induced relevant nonlinearity invalidates the predictions of the linear theory and destroys the hexatic order. In addition, we show that activity modifies the interactions between defects in the active chiral hexatic phase, making them nonmutual. Finally, to demonstrate the generality of a chiral active hexatic phase we show that it results from the melting of chiral active crystals in finite systems.

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  • Received 11 May 2020
  • Accepted 6 November 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.238005

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ananyo Maitra1,*, Martin Lenz2,3, and Raphael Voituriez1,4

  • 1Sorbonne Université and CNRS, Laboratoire Jean Perrin, F-75005, Paris, France
  • 2LPTMS, CNRS, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France
  • 3PMMH, CNRS, ESPCI Paris, PSL University, Sorbonne Université, Université de Paris, F-75005, Paris, France
  • 4Sorbonne Université and CNRS, Laboratoire de Physique Théorique de la Matière Condensée, F-75005, Paris, France

  • *nyomaitra07@gmail.com

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Issue

Vol. 125, Iss. 23 — 4 December 2020

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