Diagnosing hyperuniformity in two-dimensional disordered jammed-packings of soft spheres

Abstract

Hyperuniformity characterizes a state of matter for which density fluctuations diminish towards zero at the largest length scales. However, the task of determining whether or not an experimental system is hyperuniform is experimentally challenging due to finite-resolution, noise and sample-size effects that influence characterization measurements. Here we explore these issues, employing video optical microscopy to study hyperuniformity phenomena in disordered two-dimensional jammed packings of soft spheres. Using a combination of experiment and simulation we characterize the detrimental effects of particle polydispersity, image noise, and finite-size effects on the assignment of hyperuniformity, and we develop a methodology that permits improved diagnosis of hyperuniformity from real-space measurements. The key to this improvement is a simple packing reconstruction algorithm that incorporates particle polydispersity to minimize free volume. In addition, simulations show that hyperuniformity can be ascertained more accurately in direct space than in reciprocal space as a result of finite sample-size. Finally, experimental colloidal packings of soft polymeric spheres are shown to be hyperuniform.

12 pages, 9 figures

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• The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero
• Thermal fluctuations, mechanical response, and hyperuniformity in jammed solids
• Characterization of Maximally Random Jammed Sphere Packings: II. Correlation Functions and Density Fluctuations
• Effect of Window Shape on the Detection of Hyperuniformity via the Local Number Variance
• Structural characterization and statistical-mechanical model of epidermal patterns