Investigation of $q$-dependent dynamical heterogeneity in a colloidal gel by x-ray photon correlation spectroscopy

Veronique Trappe (1) , Estelle Pitard (2) , Laurence Ramos (2) , Aymeric Robert (3) , Hugo Bissig (1) , Luca Cipelletti (2)

1 FRIBPHYS - Physics Department
2 LCVN - Laboratoire des colloïdes, verres et nanomatériaux
3 ESRF - European Synchrotron Radiation Facility

We use time-resolved X-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 non-monotonic dependence on scattering vector $q$, in stark contrast with recent experiments on strongly attractive colloidal gels [Duri and Cipelletti, \textit{Europhys. Lett.} \textbf{76}, 972 (2006)]. We propose a simple scaling argument for the $q$-dependence of fluctuations in glassy systems that rationalizes these findings.

Mots clés: glasses; gels; X-photon correlation spectroscopy; dynamical heterogeneity

Domaines: Matière Molle [cond-mat.soft]

Veronique Trappe, Estelle Pitard, Laurence Ramos, Aymeric Robert, Hugo Bissig, et al.. Investigation of $q$-dependent dynamical heterogeneity in a colloidal gel by x-ray photon correlation spectroscopy. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2007, 76 (5), pp.051404. ⟨10.1103/PhysRevE.76.051404⟩. ⟨hal-00133792v3⟩