Hyperuniform states generated by a critical friction field

TL;DR

This paper demonstrates that a vibrated granular layer at the liquid-to-solid transition exhibits dynamic hyperuniformity, with a simple model explaining how coupling to a fluctuating friction field causes this phenomenon.

Contribution

It reveals the emergence of dynamic hyperuniformity at a critical phase transition in granular materials and introduces a model linking friction fluctuations to hyperuniform states.

Findings

Hyperuniformity appears at the critical point of the transition.

Density fluctuations are blocked by diverging patches near the transition.

Structure factor better detects hyperuniformity than particle number variance.

Abstract

Hyperuniform states are an efficient way to fill up space for disordered systems. In these states the particle distribution is disordered at the short scale but becomes increasingly uniform when looked at large scales. Hyperuniformity appears in several systems, in static or quasistatic regimes as well as close to transitions to absorbing states. Here, we show that a vibrated granular layer, at the critical point of the liquid-to-solid transition, displays dynamic hyperuniformity. Prior to the transition, patches of the solid phase form, with length scales and mean lifetimes that diverge critically at the transition point. When reducing the wavenumber, density fluctuations encounter increasingly more patches that block their propagation, resulting in a static structure factor that tends to zero for small wavenumbers at the critical point, which is a signature of hyperuniformity. A simple model demonstrates that this coupling of a density field to a highly fluctuating scalar friction field gives rise to dynamic hyperuniform states. Finally, we show that the structure factor detects better the emergence of hyperuniformity, compared to the particle number variance.