Measurement of Growing Dynamical Lengthscales and Prediction of the Jamming Transition in a Granular Material

TL;DR

This study investigates the growth of dynamical heterogeneities in granular materials approaching jamming, revealing universal behaviors similar to glass-forming liquids and supporting the jamming transition as a unifying concept.

Contribution

It provides experimental evidence of growing dynamical lengthscales in granular packings and links these to theoretical models like mode-coupling and VTF, advancing understanding of jamming universality.

Findings

Dynamical heterogeneities grow as jamming is approached.

Growth of time and length scales fits mode-coupling and VTF models.

Jamming point coincides with the VTF transition, indicating a zero-temperature glass transition.

Abstract

Supercooled liquids and dense colloids exhibit anomalous behaviour known as "spatially heterogeneous dynamics" (SHD), which becomes increasingly pronounced with approach to the glass transition. Recently, SHD has been observed in confined granular packings under slow shear near the onset of jamming, bolstering speculation that the two transitions are related. Here, we report measurements of SHD in a system of air-driven granular beads, as a function of both density and effective temperature. On approach to jamming, the dynamics become progressively slower and more spatially heterogeneous. The rapid growth of dynamical time and length scales characterizing the heterogeneities can be described both by mode-coupling theory and the Vogel-Tammann-Fulcher (VTF) equation, in analogy with glass-forming liquids. The value of the control variable at the VTF transition coincides with point-J, the random close-packed jamming density at which all motion ceases, indicating analogy with a zero temperature ideal glass transition. Our findings demonstrate further universality of the jamming concept and provide a significant step forward in the quest for a unified theory of jamming in disparate systems.