Annihilation of Point Defect Pairs in Freely Suspended Liquid-Crystal Films

TL;DR

This study investigates the dynamics of topological defect pair annihilation in freely suspended liquid-crystal films, confirming theoretical predictions and highlighting the role of defect orientations in their interactions.

Contribution

It provides experimental validation of defect interaction models in 2D liquid crystals, emphasizing the influence of orientations and trajectories on annihilation processes.

Findings

Square-root dependence of separation on time to annihilation

Asymmetry in defect propagation velocities confirmed

Defect orientations significantly affect trajectories

Abstract

We study the annihilation of topological defect pairs in the quasi-twodimensional (2D) geometry of freely suspended smectic films. This elementary process is at the basis of all models describing the statistics of complex defect patterns. We prepare pairs with opposite topological charges and retrieve the interaction mechanisms from their trajectories. The square-root dependence of the defect separation on the time until annihilation and the asymmetry in propagation velocities of the opponents predicted by theory are confirmed. The importance of defect orientations is demonstrated. Trajectories are in general curved, depending on the mutual orientations (phase mismatch) of the defects and on the orientation of the pair respective to the far, undisturbed director. The experiments provide the basis for an adaption of the theoretical models to the real complexity of the annihilation.