Active Particle Doping Suppresses Brittle Failure in Ultrastable Glasses

Ultrastable glasses are known for their exceptional mechanical stability but often fail in a brittle manner, typically marked by the formation of shear bands when subjected to shear deformation. An open question is how shear banding is affected by active particles. Here, we address this issue by investigating ultrastable glasses that are doped with self-propelled particles (SPPs) that perform run-and-tumble motions. In the presence of active particles, we find a crossover from heterogeneous to homogeneous yielding. Through extensive computer simulations of a polydisperse model, which is capable of producing ultrastable glasses using swap Monte Carlo Methods, we demonstrate the progressive emergence of multiple shear bands under activity, leading to continuous and delayed yielding. Interestingly, we uncover a compensatory relationship between active forces and global shear rates: a rise in one can offset a decline in the other, arising from the isomorphic-like behavior exhibited by different combinations of active forces and strain rates. We also identify a non-monotonic relationship between yielding and persistence time: while the yield stress increases at shorter persistence times with increasing active forces, it tends to decrease with longer persistence times. This observation highlights a tunable range of activity that can modify the yielding mode. Lastly, we show that the spacing between shear bands diminishes in a power law manner as the magnitude of the active force increases.