Local excess Entropy and Microscopic Rearrangements in Sheared Particle Films

A central goal in the study of disordered solids is to connect rheological properties to microscopic structure—in particular, to predict local rearrangement dynamics that underlie plastic flow from local structural measures. Here, we examine this connection in a non-thermal two-dimensional colloidal film subjected to oscillatory shear. Building on recent studies of excess entropy in this system [Galloway et al., PNAS 2020; Nat. Phys. 2022], which demonstrated that temporal variations in sample-averaged excess entropy can predict macroscopic rheology, we extend the analysis to the local scale. We develop a framework to quantify rearrangements and local structure within each shear cycle. To connect microscopic and macroscopic behavior, we coarse-grain these quantities over local neighborhoods of variable size. Remarkably, strong correlations between excess entropy and rearrangements emerge even with minimal coarse-graining, and persist across a wide range of strain amplitudes, both below and above yield. Our results demonstrate that temporal fluctuations of structural order within shear cycles encode the microscopic dynamics that govern plasticity in driven disordered materials.