Many facets of intermittent dynamics in colloidal and molecular glasses

A popular picture of the intermittent dynamics of glassy materials depicts each particle as localized in a temporary cage formed by its neighbors, and seldom jumping to another cage. Drawing on experiments on hard sphere colloidal glasses and molecular dynamic simulations of supercooled liquids, here we show how this simplified scenario leads to quantitative relations between single particle motion and macroscopic properties, within a Continuous Time Random Walk (CTRW) framework. For example, the diffusivity and the relaxation time at different length scales can be directly predicted from the jump properties. In the accessible range of temperatures and volume fractions, these predictions work well, although the CTRW formalism neglects the spatially heterogeneous dynamics of glassy systems. In this respect, we show how these dynamic heterogeneities can be highlighted from a study of the correlations between jumps. Finally, the intermittent motion is exploited to infer correlations between local structure and dynamics.