Macroscopic yielding in jammed solids is accompanied by a non-equilibrium first-order transition in particle trajectories

We use computer simulations to analyse the yielding transition during large-amplitude oscillatory shear of a simple model for soft jammed solids. Simultaneous analysis of global mechanical response and particle-scale motion demonstrates that macroscopic yielding, revealed by a smooth crossover in mechanical properties, is accompanied by a sudden change in the particle dynamics, which evolves from non-diffusive motion to irreversible diffusion as the amplitude of the shear is increased. We provide numerical evidence that this sharp change corresponds to a non-equilibrium first-order phase transition, thus establishing the existence of a well-defined microscopic signature of the yielding transition in amorphous materials in oscillatory shear.