The glass transition in molecules, colloids and grains: universality and specificity

TL;DR

This paper reviews experimental findings on molecular, colloidal, and granular glassformers, focusing on universality and differences in phenomena like dynamical heterogeneity, lengthscales, and structural changes across these systems.

Contribution

It provides a comparative analysis of experimental results across three classes of glassformers, highlighting both universal behaviors and class-specific phenomena.

Findings

Dynamical heterogeneity is well established in all three classes.

Growing lengthscales are observed near the glass transition.

Evidence for class-specific phenomena like the Gardner transition is discussed.

Abstract

We highlight certain key achievements in experimental work on molecular, colloidal and granular glassformers. This short review considers these three classes of experimental systems and focusses largely on the work of the authors and their coworkers and thus is far from exhaustive. Our goal is rather to discuss particular experimental results from these classes and to explore universality and specificity across the broad range of length- and time-scales they span. We emphasize that a variety of phenomena, not least dynamical heterogeneity, growing lengthscales and a change in structure, albeit subtle, are now well established in these three classes of glassformer. We then review some experimental measurements which depend more specifically on the class of glassformer, such as the Gardner transition and some which have been investigated more in one or two classes than in all, such as configurational entropy and evidence for a dynamical phase transition. We finally put forward some open questions and consider what could be done to fill some of the gaps between theoretical approaches and experiments.