Shape of Dynamical Heterogeneities and the Stokes-Einstein and Stokes-Einstein-Debye Relations in Suspensions of Colloidal Ellipsoids

摘要

We examine the role of shape of dynamical heterogeneities on the validity ofthe Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) relations inquasi-two-dimensional suspensions of colloidal ellipsoids. For ellipsoids withrepulsive interactions, although the orientational relaxation time remainscoupled to the structural one, the SED relation by the Einstein formalism showsa breakdown. Strikingly, we find that it is the change in the shape of thedynamical heterogeneities from string-like to compact and not just theirpresence that results in the breakdown of both the SE and SED relations. Onintroducing a short-range depletion attraction between the ellipsoids,associated with the lack of morphological evolution of dynamicalheterogeneities, the SE and SED relations remain valid even for deepsupercooling. Our observations are consistent with numerical predictions.