Partial rejuvenation of a colloidal glass

We study the effect of shear on the aging dynamics of a colloidal suspension of synthetic clay particles. We find that a shear of amplitude $gamma$ reduces the relaxation time measured just after the cessation of shear by a factor $exp(-gamma/gamma_c)$, with $gamma_c sim 5%$, and is independent of the duration and the frequency of the shear. This simple law for the rejuvenation effect shows that the energy involved in colloidal rearrangements is proportional to the shear amplitude, $gamma$, rather than $gamma^2$, leading to an Eyring-like description of the dynamics of our system.