Origin of the slow dynamics and the aging of a soft glass

TL;DR

This study reveals that slow, aging dynamics in a soft glass are driven by temperature fluctuations causing local shear, leading to reversible and irreversible rearrangements that slow down over time.

Contribution

It demonstrates that thermal fluctuations induce intermittent shear in soft glasses, explaining their aging and slow dynamics, a novel insight into soft glass behavior.

Findings

Temperature fluctuations cause local shear in soft glasses.

Rearrangements decrease with sample age, leading to slowed dynamics.

Aging is driven by thermal effects causing mechanical responses.

Abstract

We study by light microscopy a soft glass consisting of a compact arrangement of polydisperse elastic spheres. We show that its slow and non-stationary dynamics results from the unavoidable small fluctuations of temperature, which induce intermittent local mechanical shear in the sample, because of thermal expansion and contraction. Temperature-induced shear provokes both reversible and irreversible rearrangements whose amplitude decreases with time, leading to an exponential slowing down of the dynamics with sample age.