Aging in a colloidal glass in creep flow: time-stress superposition.

We study the aging behavior of aqueous laponite suspension, a model soft glassy material, in creep. We observe that the viscoelastic behavior is time dependent and is strongly influenced by the deformation field; the effect is known to arise due to aging and rejuvenation. We show that irrespective of the strength of the deformation field (shear stress) and age, when the imposed time scale is normalized with a dominating relaxation mode of the system, universal aging behavior is obtained, demonstrating time-stress superposition, a phenomenon that may be generic in a variety of soft materials.