%0 Journal Article
%T Length scale dependence of dynamical heterogeneity in a colloidal fractal gel
%+ Laboratoire des colloïdes, verres et nanomatériaux (LCVN)
%A Duri, Agnes
%A Cipelletti, Luca
%Z Revised and improved, to appear in Europhys. Lett.
%< avec comité de lecture
%@ 0295-5075
%J EPL - Europhysics Letters
%I European Physical Society/EDP Sciences/Società Italiana di Fisica/IOP Publishing
%V 76
%N 5
%P 972
%8 2006-12-01
%D 2006
%Z cond-mat/0606051
%R 10.1209/epl/i2006-10357-4
%K glassy dynamics
%K dynamical heterogeneity
%K gel
%K colloids
%K light scattering
%Z 82.70.Dd, 64.70.Pf, 82.70.Gg, 61.43.Hv
%Z Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft]Journal articles
%X We use time-resolved dynamic light scattering to investigate the slow dynamics of a colloidal gel. The final decay of the average intensity autocorrelation function is well described by $g_2(q,\tau)-1 \sim \exp[-(\tau/\tau_\mathrm{f})^p]$, with $\tau_\mathrm{f} \sim q^{-1}$ and $p$ decreasing from 1.5 to 1 with increasing $q$. We show that the dynamics is not due to a continuous ballistic process, as proposed in previous works, but rather to rare, intermittent rearrangements. We quantify the dynamical fluctuations resulting from intermittency by means of the variance $\chi(\tau,q)$ of the instantaneous autocorrelation function, the analogous of the dynamical susceptibility $\chi_4$ studied in glass formers. The amplitude of $\chi$ is found to grow linearly with $q$. We propose a simple --yet general-- model of intermittent dynamics that accounts for the $q$ dependence of both the average correlation functions and $\chi$.
%G English
%2 https://hal.science/hal-00078005v2/document
%2 https://hal.science/hal-00078005v2/file/Duri_revised.pdf
%L hal-00078005
%U https://hal.science/hal-00078005
%~ CNRS
%~ UNIV-MONTP2
%~ LCVN
%~ UNIV-MONTPELLIER
%~ INRAE
%~ UM1-UM2