Caging dynamics in a granular fluid

TL;DR

This study experimentally examines particle motion in a heated granular fluid, revealing caging behavior and precursors to glassy dynamics at higher densities, despite the absence of a true glass transition.

Contribution

It provides the first detailed analysis of caging and glassy precursors in a granular fluid across various densities, highlighting structural arrest effects.

Findings

At low density, particles exhibit diffusive motion.

Increased density leads to cage formation and particle trapping.

Precursor features of glassy dynamics are observed despite no glass transition.

Abstract

We report an experimental investigation of the caging motion in a uniformly heated granular fluid, for a wide range of filling fractions, $\phi$. At low $\phi$ the classic diffusive behavior of a fluid is observed. However, as $\phi$ is increased, temporary cages develop and particles become increasingly trapped by their neighbors. We statistically analyze particle trajectories and observe a number of robust features typically associated with dense molecular liquids and colloids. Even though our monodisperse and quasi-2D system is known to not exhibit a glass transition, we still observe many of the precursors usually associated with glassy dynamics. We speculate that this is due to a process of structural arrest provided, in our case, by the presence of crystallization.