title: Investigation of q-dependent dynamical heterogeneity in a colloidal gel by x-ray photon correlation spectroscopy.
abstract: We use time-resolved x-ray photon correlation spectroscopy to investigate the slow dynamics of colloidal gels made of moderately attractive carbon black particles. We show that the slow dynamics is temporally heterogeneous and quantify its fluctuations by measuring the variance chi of the instantaneous intensity correlation function. The amplitude of dynamical fluctuations has a nonmonotonic dependence on scattering vector q, in stark contrast with recent experiments on strongly attractive colloidal gels [Duri and Cipelletti, Europhys. Lett. 76, 972 (2006)]. We propose a simple scaling argument for the q-dependence of fluctuations in glassy systems that rationalizes these findings.
authors.affiliation: Departement de Physique, Université de Fribourg, Chemin du Musée 3, 1700 Fribourg, Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Trappe
authors.forename: E
authors.initials: E
authors.lastname: Pitard
authors.forename: L
authors.initials: L
authors.lastname: Ramos
authors.forename: A
authors.initials: A
authors.lastname: Robert
authors.forename: H
authors.initials: H
authors.lastname: Bissig
authors.forename: L
authors.initials: L
authors.lastname: Cipelletti