Measurement of growing dynamical length scales and prediction of the jamming transition in a granular material

Abstract

Supercooled liquids and dense colloidal suspensions exhibit anomalous behaviour known as spatially heterogeneous dynamics (SHD), which becomes increasingly pronounced as the system approaches the glass transition. Recently, the observation of SHD in confined granular packings under slow shear near the onset of jamming has bolstered 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 becomes progressively slower and more spatially heterogeneous. The rapid growth of timescales and dynamical length scales characterizing the heterogeneities can be described both by mode-coupling theory and the Vogel-Tammann-Fulcher (VTF) equation, such as in glass-forming liquids. The value of the control variable at the VTF transition coincides with point J (refs9, 10), the random close-packed jamming density at which all motion ceases, in analogy to 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. ©2007 Nature Publishing Group.