Microscopic origin of internal stresses in jammed soft particle suspensions.

The long time persistence of mechanical stresses is a generic property of glassy materials. Here we identify the microscopic mechanisms that control internal stresses in highly concentrated suspensions of soft particles brought to rest from steady flow. The persistence of the asymmetric angular distortions which characterize the pair distribution function during flow is at the origin of the internal stresses. Their long time evolution is driven by in-cage rearrangements of the elastic contacts between particles. The trapped macroscopic stress is related to the solvent viscosity, particle elasticity and volume fraction through a universal scaling derived from simulations and experiments.