Dynamic Analysis of Chevron Structures in Liquid Crystal Cells

TL;DR

This paper investigates the formation and evolution of chevron defects in liquid crystal cells during phase transitions, proposing a gradient flow model that accounts for layer melting and healing to understand switching behavior.

Contribution

It introduces a novel gradient flow model for liquid crystal energy that allows layer vanishing, enabling analysis of chevron defect dynamics during phase transitions.

Findings

Layer thinning leads to chevron defect formation.

The model predicts layer melting and healing near chevron tips.

Energy barriers influence switching dynamics.

Abstract

If a surface stabilized ferroelectric liquid crystal cell is cooled from the smectic-A to the smectic-C phase, its layers thin causing V-shaped (chevron like) defects to form. These create an energy barrier that can prevent switching between equilibrium patterns. We examine a gradient flow for a mesoscopic Chen-Lubensky energy $\mathcal{F}(\psi,\mathbf{n})$ that allows the order parameter to vanish, so that the energy barrier does not diverge if the layer thickness becomes small. The liquid crystal can evolve during switching in such a way that the layers are allowed to melt and heal near the chevron tip in the process.