Taming collective activity to crystallize an oscillator gas

Taming collective activity to crystallize an oscillator gas | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Taming collective activity to crystallize an oscillator gas Alexandre Morin, Marine Le Blay, Joshua Saldi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5004116/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 04 Aug, 2025 Read the published version in Nature Physics → Version 1 posted You are reading this latest preprint version Abstract In active matter, where constituents are intrinsically out-of-equilibrium, even the highest-symmetry phases come with surprises. When activity is coupled negatively to density, such as in assemblies of self-propelled units, phase separation can occur without attractive interaction, a well-studied phenomenon known as motility-induced phase separation. In stark contrast, the consequences of a positive coupling between density and activity on the collective behaviour of active matter remain uncharted. Here, we unveil the phenomenon of collective activity, which emerges from this positive coupling among non-motile active units. We demonstrate its genuine propensity for disorder and leverage its potential in guiding self-assembly. To do so, we experimentally study collectives of scalar active units undergoing self-sustained oscillations induced by contact-charge electrophoresis. We explain the spontaneous formation of an oscillator gas by collective activity resulting from super-elastic collisions. Unravelling the origin of binary collisions allows us to tame collective activity, giving us precise control on the structure of the oscillator gas and its eventual crystallization. Our work highlights and quantifies the importance of the coupling between activity and density in active phases. It is a launch pad for exploring lower-symmetry active systems with new eyes where activity may be coupled not only to density, but also to broken-symmetry variables. Physical sciences/Physics/Statistical physics, thermodynamics and nonlinear dynamics/Statistical physics Physical sciences/Physics/Statistical physics, thermodynamics and nonlinear dynamics/Phase transitions and critical phenomena Soft condensed matter Active matter Synchronization Phase transition Collective activity Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SuppVideo1CollectiveActivity.mp4 Supplementary Video 1: Collective activity SuppVideo2ActiveOscillatorGas.mp4 Supplementary Video 2: Active oscillator gas SuppVideo3ReversibleMeltingTransition.mp4 Supplementary Video 3: Reversible melting transition Cite Share Download PDF Status: Published Journal Publication published 04 Aug, 2025 Read the published version in Nature Physics → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5004116","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":362526293,"identity":"022e5f4e-2cbd-4512-940e-bbb2cf304062","order_by":0,"name":"Alexandre 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