Connecting Shear Thinning and Dynamic Heterogeneity in Supercooled Liquids by Localized Elasticity

Abstract

Supercooled liquids exhibit complicated dynamical behaviors: At the microscopic level, the dynamics is heterogeneous spatially, known as dynamic heterogeneity. At the macroscopic level, the shear viscosity $\eta$ decreases as shear rate $\dot{\gamma}$ increases with a power law $\eta\sim\dot{\gamma}^{-\lambda}$, known as shear thinning. The relation between these two universal dynamical phenomena remains elusive. With simulations of several model liquids in two and three dimensions, we show that they are quantitatively bridged by localized elasticity embodied as transient clusters that elastically respond to shear. Prominent dynamic heterogeneity emerges right after the massive yielding of these clusters, which is initiated by shear transformation zones and facilitated by elasticity-mediated interaction. With this picture, a scaling law relating shear thinning to the characteristic length of dynamic heterogeneity is found.