Do brittle-to-ductile transitions occur in dense active matter?

The nature of the yielding transition in sheared amorphous solids is highly dependent on material preparation. Well-annealed, highly stable packings yield in a brittle fashion accompanied by the formation of system-spanning shear bands, while poorly annealed system yield in a ductile manner. Recent works have shown that there is a direct link between the dynamics of sheared and dense active matter in the pre-yielding regime. Therefore, an interesting open question is whether this brittle-to-ductile paradigm for yielding still holds in dense active matter. Here we study the yielding transition for active matter in the limit of infinite persistence and quasi-static driving, and find that the magnitude of the observed stress drops, a measure of brittleness, decreases systematically with the spatial correlation length of the applied active field. We then study the spatial organization of the plasticity that occurs during yielding, and use extensions of the Radon transform to demonstrate that putative shear bands still form in active matter, but their lengthscale also decreases with decreasing input correlation length. This suggests that the brittle-to-ductile transition is governed not only by material preparation, but also by the symmetry and correlation length of the driving field