Aging and effective delays in colloidal glasses under shear

TL;DR

This study investigates how oscillatory shear affects the microscopic dynamics and aging behavior of colloidal glasses, revealing effects like overaging, rejuvenation, and altered relaxation times.

Contribution

It introduces a detailed analysis of aging and effective delays in colloidal glasses under shear, linking microscopic dynamics to relaxation time distribution broadening.

Findings

Low amplitude shear causes overaging.

High amplitude shear induces rejuvenation.

System exhibits weak long-term memory.

Abstract

In this paper we analyze the changes in the microscopic dynamics of a colloidal glass submitted to an oscillatory shear. We use Multispeckle diffusing Wave Spectroscopy to monitor the transient dynamical regimes following a shear application. We show that the system displays a spontaneous aging that is amplified by a low amplitude oscillation (overaging) but stopped by a high amplitude one (rejuvenation). Intermediate amplitudes drive the system into a dynamical state that cannot be reached through spontaneous evolution. We demonstrate that theses systems present a weak long term memory and that the all observed phenomenology can be explained by a broadening of the relaxation time distribution under oscillatory strain. We discussed the similarities of our results with the behavior of spin glasses upon temperature shifts. We eventually propose a scenario based on the existence of harder and softer regions in the material.