Dichotomic Aging Behaviour in a Colloidal Glass

TL;DR

This study reveals a dichotomic aging behavior in colloidal glasses, showing different relaxation dynamics depending on whether the system is spontaneously aged or rejuvenated by shear, advancing understanding of anomalous glassy dynamics.

Contribution

It uncovers a novel dichotomic aging behavior in colloidal glasses, linking shear rejuvenation to compressed exponential relaxation.

Findings

Spontaneously aged samples exhibit stretched exponential relaxation.

Shear rejuvenation induces compressed exponential relaxation.

Relaxation times scale as Q^{-1} in both cases.

Abstract

An unexpected dichotomic long time aging behaviour is observed in a glassy colloidal clay suspension investigated by X-Ray Photon Correlation Spectroscopy and Dynamic Light Scattering. In the long time aging regime the intensity autocorrelations are non-exponential, following the Kohlrausch-Williams-Watts functional form with exponent bQ. We show that for spontaneously aged samples a stretched behaviour (\beta_Q < 1) is always found. Surprisingly a compressed exponent (\beta_Q > 1) appears only when the system is rejuvenated by application of a shear field. In both cases the relaxation times scale as Q^{-1}. These observations shed light on the origin of compressed exponential behaviour and helps in classifying previous results in the literature on anomalous dynamics.