Understanding Slow and Heterogeneous Dynamics in Model Supercooled Glass-Forming Liquids.

Glasses are ubiquitous in nature. Many common items such as ketchups, cosmetic products, toothpaste, etc. and metallic glasses are examples of such glassy materials whose dynamical and rheological properties matter in our daily life. The dynamics of these glass-forming systems are known to be very sluggish and heterogeneous, but a detailed understanding of the origin of such slowing down is still lacking. Slow heterogeneous dynamics occur in a wide variety of systems at scales ranging from microscopic to macroscopic. Polymeric liquids, granular material, such as powder and sand, gels, and foams and also metallic alloys show such complex glassy dynamics at appropriate conditions. Recently, the existence of dynamical heterogeneity has also been found in biological systems starting from collective cell migration in a monolayer of cells to embryonic morphogenesis, cancer invasion, and wound healing. Extensive research in the past decade or so lead to the understanding that there are growing dynamic and static correlation lengths associated with the observed dynamical heterogeneity and rapid rise in viscosity. In this review, we have highlighted the recent developments on measuring these correlation lengths in glass-forming liquids and their possible implications in the physics of the glass transition.