Attractive emulsion droplets probe the phase diagram of jammed granular matter

Ivane Jorjadze, Lea Laetitia Pontani, Katherine A. Newhall, Jasna Brujić

    Research output: Contribution to journalArticle

    Abstract

    It remains an open question whether statistical mechanics approaches apply to random packings of athermal particles. Although a jamming phase diagram has recently been proposed for hard spheres with varying friction, here we use a frictionless emulsion system in the presence of depletion forces to sample the available phase space of packing configurations. Using confocal microscopy, we access their packing microstructure and test the theoretical assumptions. As a function of attraction, our packing protocol under gravity leads to well-defined jammed structures in which global density initially increases above random close packing and subsequently decreases monotonically. Microscopically, the fluctuations in parameters describing each particle, such as the coordination number, number of neighbors, and local packing fraction, are for all attractions in excellent agreement with a local stochastic model, indicating that long-range correlations are not important. Furthermore, the distributions of local cell volumes can be collapsed onto a universal curve using the predicted k-gamma distribution, in which the shape parameter k is fixed by the polydispersity while the effect of attraction is captured by rescaling the average cell volume. Within the Edwards statistical mechanics framework, this result measures the decrease in compactivity with global density, which represents a direct experimental test of a jamming phase diagram in athermal systems. The success of these theoretical tools in describing yet another class of materials gives support to the much-debated statistical physics of jammed granular matter.

    Original languageEnglish (US)
    Pages (from-to)4286-4291
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume108
    Issue number11
    DOIs
    StatePublished - Mar 15 2011

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    Keywords

    • Depletion attraction
    • Granocentric model
    • Navigation map
    • Thermodynamics
    • Voronoi tessellation

    ASJC Scopus subject areas

    • General

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