The Influence of Particle Softness on Active Glassy Dynamics

• Main Authors: Debets, Vincent E, Janssen, Liesbeth M. C
• Format: Journal Article
• Language: English
• Published: 06-09-2022
• Subjects: Physics - Soft Condensed Matter
• DOI: 10.48550/arxiv.2209.02301

Phys. Rev. Research 4, L042033 (2022) Active matter studies are increasingly geared towards the high-density or
glassy limit. This is mainly inspired by the remarkable resemblance between
active glassy materials and conventional passive glassy matter. Interestingly,
within this limit it has recently been shown that the relaxation dynamics of
active quasi-hard spheres is non-monotonic and most enhanced by activity when
the intrinsic active length scale (e.g., the persistence length) is equal to
the cage length, i.e. the length scale of local particle caging. This optimal
enhancement effect is claimed to result from the most efficient scanning of
local particle cages. Here we demonstrate that this effect and its physical
explanation are fully retained for softer active spheres. We perform extensive
simulations of athermal active Brownian particles (ABPs) and show that the
non-monotonic change of the relaxation dynamics remains qualitatively similar
for varying softness. We explain quantitative differences by relating them to
the longer range of the softer interaction potential, which decreases the cage
length and obscures the intrinsic active motion. Moreover, we observe that only
when the persistence length surpasses the cage length, distinct qualitative
changes with respect to an equivalent passive Brownian particle system start to
manifest themselves. Overall, our results further strengthen the importance of
the cage length and its relation to the relevant active length scale in the
context of active glassy materials.