Ring-Pattern Dynamics in Smectic-C* and Smectic-C_A* Freely Suspended Liquid Crystal Films

TL;DR

This paper investigates the formation and dynamics of ring patterns in chiral smectic liquid crystal films under electric fields, revealing layer-dependent relaxation behaviors linked to spontaneous polarization differences.

Contribution

It introduces a simple model for ring pattern dynamics and uncovers an odd-even layer effect related to spontaneous polarization in smectic C* films.

Findings

Ring patterns form in response to in-plane rotating electric fields.

Odd layer films relax much slower than even layer films.

Spontaneous polarization differences explain the layer-dependent relaxation rates.

Abstract

Ring patterns of concentric 2pi-solitons in molecular orientation, form in freely suspended chiral smectic-C films in response to an in-plane rotating electric field. We present measurements of the zero-field relaxation of ring patterns and of the driven dynamics of ring formation under conditions of synchronous winding, and a simple model which enables their quantitative description in low polarization DOBAMBC. In smectic C_A* TFMHPOBC we observe an odd-even layer number effect, with odd number layer films exhibiting order of magnitude slower relaxation rates than even layer films. We show that this rate difference is due to much larger spontaneous polarization in odd number layer films.