Polar Smectic Films

TL;DR

This paper introduces a new experimental method for creating and analyzing polar smectic liquid crystal films, revealing novel textures influenced by elastic energy considerations.

Contribution

It presents a novel experimental setup for polar smectic films and uncovers new textures, including a spiral texture with reversed winding direction.

Findings

Observation of boojum and spiral textures in polar smectic films

Identification of a Ksb elastic term influencing textures

Reversal of spiral winding direction at finite radius

Abstract

We report on a new experimental procedure for forming and studying polar smectic liquid crystal films. A free standing smectic film is put in contact with a liquid drop, so that the film has one liquid crystal/liquid interface and one liquid crystal/air interface. This polar environment results in changes in the textures observed in the film, including a boojum texture and a previously unobserved spiral texture in which the winding direction of the spiral reverses at a finite radius from its center. Some aspects of these textures are explained by the presence of a Ksb term in the bulk elastic free energy density that favors a combination of splay and bend deformations.