Rejuvenation and memory effects in active glasses induced by thermal and active cycling

TL;DR

This study demonstrates that active glasses exhibit rejuvenation and memory effects under thermal and activity cycling, unlike passive glasses, due to the enhanced motility of active particles enabling cage escape and re-aging.

Contribution

It reveals that active matter can show rejuvenation and memory effects through thermal and activity cycling, a phenomenon not observed in passive glasses, highlighting the role of activity in non-equilibrium aging.

Findings

Active glasses show rejuvenation and memory effects under thermal cycling.

Passive glasses lack rejuvenation under the same thermal cycle.

Activity cycling between active and passive states induces rejuvenation.

Abstract

It has recently been shown that thermal active glasses can display physical aging behavior comparable to that of passive glasses, although there are some notable distinctions due to the intrinsic non-equilibrium nature of active matter. The question whether active disordered materials can also exhibit rejuvenation and memory effects, akin to the phenomenology of e.g.\ spin glasses, has thus far remained unexplored. Here we address this question by numerical simulations of active glasses composed of active Brownian particles that are subjected to a thermal or active cycling protocol. We find that an active system undergoing thermal cycling indeed shows rejuvenation and memory effects, with the strength of rejuvenation depending on the persistence time. In contrast, however, a passive Brownian system subjected to the same thermal cycle lacks the rejuvenation effect. We attribute this to the enhanced motility of active particles, which enables them to escape from their cages and restart aging at the new temperature, thus rejuvenating the material. Finally, we also demonstrate that both rejuvenation and memory effects can be induced by an activity cycle which quenches the material from an active to passive glass and back, providing a unique means to rejuvenate active matter.