Glassy Dislocation Dynamics in 2-D Colloidal Dimer Crystals

TL;DR

This study uncovers a new type of glassy relaxation behavior in 2-D colloidal dimer crystals caused by dislocation dynamics, characterized by initial glide and slow hopping between caged states, supported by experiments and simulations.

Contribution

It demonstrates that dislocation motion in colloidal dimer crystals exhibits glassy dynamics, a phenomenon previously associated mainly with disordered systems.

Findings

Dislocations initially glide freely before becoming caged by particles.

Dislocation relaxation occurs logarithmically slowly after initial glide.

Dislocation mean squared displacement shows a caging plateau similar to glassy systems.

Abstract

Although glassy relaxation is typically associated with disorder, here we report on a new type of glassy dynamics relating to dislocations within 2-D crystals of colloidal dimers. Previous studies have demonstrated that dislocation motion in dimer crystals is restricted by certain particle orientations. Here, we drag an optically trapped particle through such dimer crystals, creating dislocations. We find a two-stage relaxation response where initially dislocations glide until encountering particles that cage their motion. Subsequent relaxation occurs logarithmically slowly through a second process where dislocations hop between caged configurations. Finally, in simulations of sheared dimer crystals, the dislocation mean squared displacement displays a caging plateau typical of glassy dynamics. Together, these results reveal a novel glassy system within a colloidal crystal.