Switching dynamics of surface stabilized ferroelectric liquid crystal cells: effects of anchoring energy asymmetry

TL;DR

This study combines theoretical modeling and experimental measurements to analyze how asymmetric boundary conditions influence the switching dynamics and hysteresis behavior in surface stabilized ferroelectric liquid crystal cells, emphasizing the role of polar anchoring.

Contribution

It introduces a dynamical model incorporating asymmetric anchoring energy and demonstrates the impact of polar contributions on switching behavior, supported by experimental validation.

Findings

Polar anchoring dominates asymmetry effects.

Unstable cycles exist only below a critical frequency.

Model predictions align with experimental hysteresis shifts.

Abstract

We study both theoretically and experimentally switching dynamics in surface stabilized ferroelectric liquid crystal cells with asymmetric boundary conditions. In these cells the bounding surfaces are treated differently to produce asymmetry in their anchoring properties. Our electro-optic measurements of the switching voltage thresholds that are determined by the peaks of the reversal polarization current reveal the frequency dependent shift of the hysteresis loop. We examine the predictions of the uniform dynamical model with the anchoring energy taken into account. It is found that the asymmetry effects are dominated by the polar contribution to the anchoring energy. Frequency dependence of the voltage thresholds is studied by analyzing the properties of time-periodic solutions to the dynamical equation (cycles). For this purpose, we apply the method that uses the parameterized half-period mappings for the approximate model and relate the cycles to the fixed points of the composition of two half-period mappings. The cycles are found to be unstable and can only be formed when the driving frequency is lower than its critical value. The polar anchoring parameter is estimated by making a comparison between the results of modelling and the experimental data for the shift vs frequency curve. For a double-well potential considered as a deformation of the Rapini-Papoular potential, the branch of stable cycles emerges in the low frequency region separated by the gap from the high frequency interval for unstable cycles.