Universal nature of particle displacements close to glass and jamming transitions

TL;DR

This paper demonstrates that the distribution of particle displacements near glass and jamming transitions universally exhibits exponential tails, revealing dynamic heterogeneity and explaining diffusion-relaxation decoupling across various materials.

Contribution

It introduces a universal behavior of displacement distributions and a dynamical model that quantitatively describes data across different glassy and jammed systems.

Findings

Exponential tails are universal in particle displacement distributions.

The model accurately fits experimental and numerical data.

Distributions explain the decoupling of diffusion and relaxation.

Abstract

We examine the structure of the distribution of single particle displacements (van-Hove function) in a broad class of materials close to glass and jamming transitions. In a wide time window comprising structural relaxation, van-Hove functions reflect the coexistence of slow and fast particles (dynamic heterogeneity). The tails of the distributions exhibit exponential, rather than Gaussian, decay. We argue that this behavior is universal in glassy materials and should be considered the analog, in space, of the stretched exponential decay of time correlation functions. We introduce a dynamical model that describes quantitatively numerical and experimental data in supercooled liquids, colloidal hard spheres and granular materials. The tails of the distributions directly explain the decoupling between translational diffusion and structural relaxation observed in glassy materials.