Competing relaxation channels in continuously polydisperse fluids: A mode-coupling study

We perform a systematic analysis of continuously polydisperse hard-sphere fluids as a function of the degree of polydispersity within the framework of the mode-coupling theory of the glass transition (MCT). Our results show that a high degree of polydispersity tends to stabilize the liquid phase against vitrification, the magnitude of which depends on the shape of the polydispersity distribution. Furthermore, we report on a separation between the localization lengths of the smallest and largest particles. A diameter-resolved analysis of the intermediate scattering functions reveals that this separation significantly stretches the relaxation patterns, which we quantitatively study by an analysis of the dynamical exponents predicted by the theory. Our observations have strong implications for our understanding of the nature of dynamical heterogeneities and localization lengths in continuously polydisperse systems with hard-core interactions. These results suggest that the dynamics of the smallest particles is of central importance to understand structural relaxation of such systems, already in the mildly supercooled regime where MCT is usually applicable.