Probing the "cage effect" in grain boundary dynamics using impurity particles in a 2D colloidal crystal

Grain boundaries are ubiquitous defects in crystalline solids, yet they are poorly understood. Recently it was reported that grain boundaries in a colloidal crystal exhibit caging effect which was often found in glassy materials. Here, we study the dynamics of grain boundaries in a 2D colloidal crystal of monodispersed microspheres doped with impurities of ellipsoidal particles. As the impurities increase, the long range orientational order of the system is broken and the glassy dynamics of the impurities appears. The cage effect is revealed by the plateau effect in the mean square displacement vs. time curve. We will discuss the possible underlying physics of this “cage effect”.