Anisotropy and memory during cage breaking events close to a wall

TL;DR

This study investigates cage-breaking events near a wall in a glassy colloidal system, revealing anisotropic forces and memory effects crucial for understanding particle escape mechanisms in glassy dynamics.

Contribution

It introduces two one-particle models incorporating anisotropy and memory, linking microscopic dynamics near walls to structural and dynamical properties.

Findings

Memory effects influence cage escape dynamics.

Anisotropic two-particle density relates to cage-breaking trajectories.

Models with memory better describe particle escape behavior.

Abstract

The slow dynamics in a glassy hard-sphere system is dominated by cage breaking events, i.e., rearrangements where a particle escapes from the cage formed by its neighboring particles. We study such events for an overdamped colloidal system by the means of Brownian dynamics simulations. While it is difficult to relate cage breaking events to structural mean field results in bulk, we show that the microscopic dynamics of particles close to a wall can be related to the anisotropic two-particle density. In particular, we study cage-breaking trajectories, mean forces on a tracked particle, and the impact of the history of trajectories. Based on our simulation results, we further construct two different one-particle random-walk models - one without and one with memory incorporated - and find the local anisotropy and the history-dependence of particles as crucial ingredients to describe the escape from a cage. Finally, our detailed study of a rearrangement event close to a wall not only reveals the memory effect of cages, but leads to a deeper insight into the fundamental mechanisms of glassy dynamics.