Orientational Order in Disordered Colloidal Suspensions

Exploring structural order in disordered systems including liquids and glasses is an intriguing but challenging issue in condensed matter physics. Here we construct a new parameter based on the angular distribution function of particles and show that this new orientational order has significantly higher correlation with dynamic heterogeneity compared to a translational parameter based on the radial distribution functions in colloidal glasses. The gradual development of orientational and translational order in supercooled liquids shows that the higher correlation between orientational order and dynamics comes from the onset of glass transition and the orientational order would dominate the glassy dynamics after a simple liquid is considerably supercooled. Our results suggest that orientational order reflects the formation of amorphous order during glass transition while translational order is mainly a result of density increase.