Dynamic phase coexistence in glass-forming liquids

Abstract

One of the most controversial hypotheses for explaining the heterogeneous dynamics of glasses postulates the temporary coexistence of two phases characterized by a high and by a low diffusivity. In this scenario, two phases with different diffusivities coexist for a time of the order of the relaxation time and mix afterwards. Unfortunately, it is difficult to measure the single-particle diffusivities to test this hypothesis. Indeed, although the non-Gaussian shape of the van-Hove distribution suggests the transient existence of a diffusivity distribution, it is not possible to infer from this quantity whether two or more dynamical phases coexist. Here we provide the first direct observation of the dynamical coexistence of two phases with different diffusivities, by showing that in the deeply supercooled regime the distribution of the single-particle diffusivities acquires a transient bimodal shape. We relate this distribution to the heterogeneity of the dynamics and to the breakdown of the Stokes-Einstein relation, and we show that the coexistence of two dynamical phases occurs up to a timescale growing faster than the relaxation time on cooling, for some of the considered models. Our work offers a basis for rationalizing the dynamics of supercooled liquids and for relating their structural and dynamical properties.

12 pages, 7 figures

References in corpus (5)

• Universal nature of particle displacements close to glass and jamming transitions
• Excitation lines and the breakdown of Stokes-Einstein relations in supercooled liquids
• Tracking heterogeneous dynamics during the alpha-relaxation of a simple glass-former
• Connecting short and long time dynamics in hard-sphere-like colloidal glasses
• Energy-landscape network approach to the glass transition

Cited by in corpus (5)

• Length scale dependence of the Stokes-Einstein and Adam-Gibbs relations in model glass formers
• Cage Size and Jump Precursors in Glass-Forming Liquids: Experiment and Simulations
• Diffusion dynamics of supercooled water modeled with the cage-jump motion and hydrogen-bond rearrangement
• Hydrodynamics in kinetically-constrained lattice-gas models
• Dynamic heterogeneity in an orientational glass