Controlling competition between crystallization and glass formation in binary colloids with an external field

Abstract

The mechanism by which a liquid may become arrested, forming a glass, is a long-standing problem. So far no clear structural mechanism has been found. One promising approach is to use real space analysis of colloidal dispersions at the single-particle level to reveal local structural details which are inaccessible to many experimental techniques. Here we report a simple method to control glass formation which enables us to tackle the competition between crystallization and vitrification. While monodisperse colloidal hard spheres may readily crystallize, polydisperse suspensions tend to form glassy structures. We exploit the difference in sedimentation velocities of colloidal particles of different sizes, leading to a sediment which changes continuously in composition as a function of height, revealing glassy and crystalline states.