Dynamical Correlations near Dislocation Jamming

Dislocation assemblies exhibit a jamming or yielding transition at a critical external shear stress value σ=σc. Here we study the heterogeneous and collective nature of dislocation dynamics within a crystal plasticity model close to σc, by considering the first-passage properties of the dislocation dynamics. As the transition is approached in the moving phase, the first-passage time distribution exhibits scaling, and a related peak dynamical susceptibility χ₄* diverges as χ₄*~(σ-σc)^-α, with α≈1.1. We relate this scaling to an avalanche description of the dynamics. While the static structural correlations are found to be independent of the external stress, we identify a diverging dynamical correlation length ξy in the direction perpendicular to the dislocation glide motion.