Topological defects in buckled colloidal monolayers

TL;DR

This study investigates topological defects in buckled colloidal monolayers, revealing how defects influence grain boundaries and spin domain evolution, which is crucial for predicting material properties in frustrated self-assembled systems.

Contribution

It provides a detailed classification of spin and translational defects, rules for their motion, and insights into defect interactions and phase space in buckled colloidal monolayers.

Findings

Both translational and spin defects influence grain boundary structure.

Interactions between dislocations and spin defects are observed.

Defect dynamics are mapped to understand coarsening behavior.

Abstract

When colloidal particles are vertically confined to a gap of between 1.3-1.6 particle diameters, they pack into buckled crystals of particles in either "up" or "down" states. Neighboring particles tend to occupy opposite states, analogous to the behavior of antiferromagnetic spins. The particles sit on a nearly-triangular lattice, and the spins of trios of adjacent particles are geometrically frustrated. Two levels of translational order exist in this system: that of the underlying triangular lattice in the horizontal plane, and that of the emergent frustrated spin lattice in the vertical dimension. We study the topological defects of both levels of translational order, and we find that both types of defects play a role in crystal grain boundary structure and spin domain coarsening. We classify the spin defects and outline the basic rules for their motion, and we observe interactions between dislocations and spin defects. Finally, we map the phase space of spin coarsening in the buckled monolayer, characterizing which types of defects drive the dynamics. Understanding defect formation, motion, and interaction in the buckled monolayer is the first step in predicting the material properties and aging of this geometrically frustrated, self-assembled system.