Dynamics below the depinning transition of interacting dislocations moving over fields of obstacles

The transition from the behavior of a single dislocation interacting with a field of fixed obstacles to the collective motion of multiple dislocations is studied below the depinning transition (thermally activated glide). In absence of interactions, a truncated power law distribution of jump amplitudes (avalanches) with a diverging cutoff toward the critical point, and intermittency are observed. Interactions lead to a modification of the correlation length exponent below the critical point and to more pronounced intermittency, a dynamics more compatible to acoustic emission experimental data.