Short-ranged attractions in jammed liquids: How cooling can melt a glass
Phys. Rev. E , 71 (2004), p. 031206
We demonstrate that an extended picture of kinetic constraints in glass-forming liquids is sufficient to explain dynamic anomalies observed in dense suspensions of strongly attracting colloidal particles. We augment a simple model of heterogeneous relaxation with static attractions between facilitating excitations, mimicking the structural effect of short-ranged interparticle attractions. The resulting spatial correlations among facilitated and unfacilitated regions give rise to new relaxation mechanisms that account for non-monotonic dependence of relaxation times on attraction strength as well as logarithmic decay of density correlations in time. These unusual features are a simple consequence of spatial segregation of kinetic constraints, suggesting an alternative physical perspective on attractive colloids than that suggested by mode-coupling theory. Based on the behavior of our model, we predict a crossover from super-Arrhenius to Arrhenius temperature dependence as attractions become dominant at fixed packing fraction.
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