Interaction of Spin and Lattice Defects in Buckled Colloidal Monolayers

Defect and grain boundary motions critically impact properties of crystalline materials, and have been studied in colloidal monolayers where particle-scale mechanisms are directly observable. We study a buckled colloidal monolayer in which spherical particles confined between two flat surfaces spaced by ~1.5 particle diameters buckle up or down to act as "spins". The particles self organize into a triangular lattice in the plane and labyrinth-like patterns of alternating spins to maximize entropy. We have identified that the topological defects in the spin order create compression field dipoles analogous to those created by edge dislocations. This means that defects in the spin order bend lattice lines similarly to dislocations and therefore can contribute to grain boundaries. Preliminary results indicate that the compression field dipoles of defects in the spin order and dislocations interact nonlinearly or in a way that is dependent on the buckling strength. Understanding the rules of motion for interacting spin defects and dislocations enables us to understand the coarsening of grains in buckled colloidal monolayers and other similar systems.