Local Excess Entropy, Microscopic Rearrangements, and Aging in Sheared Particle Film

A goal of many studies of disordered solids is to connect rheological properties to microscopic structure, or, put another way, to predict local microscopic rearrangements dynamics, which ultimately drive plastic flows, from local structure. In this study, we investigate the relationship between local structure and rearrangements in a non-thermal two-dimensional colloidal film subjected to oscillatory shear. This work builds on recent studies of excess entropy in this system [Galloway et al. PNAS 2020, Galloway et al. Nat. Phy. 2022] which showed that the temporal variation of the excess entropy (sample averaged) could be predictive of macroscopic rheology (i.e., the sample averaged ratio of viscous and elastic moduli). We developed a framework to continuously probe local excess entropy and local rearrangement dynamics in these same systems. Using this framework, we show that the excess entropy predictor is highly correlated with particle rearrangements on the microscopic scale. Surprisingly, this relation holds below and above yield. We further use this framework to study aging and find that reversible rearrangements are the most important to this correlation as the system evolves towards a steady state.