Structure of smectic defect cores: an X-ray study of 8CB liquid crystal ultra-thin films

TL;DR

This study uses X-ray diffraction to analyze the detailed structure of defect cores in ultra-thin smectic liquid crystal films, revealing split tube-shaped cores with larger-than-expected dimensions and energies.

Contribution

It provides the first detailed X-ray structural analysis of defect cores in ultra-thin smectic liquid crystal films, highlighting novel core geometries and energy evaluations.

Findings

Defect cores are split in half tube-shaped RGB.

RGB spatial extension is larger than previously proposed.

Energy per unit line of RGB is significantly larger.

Abstract

We study the structure of very thin liquid crystal films frustrated by antagonistic anchorings in the smectic phase. In a cylindrical geometry, the structure is dominated by the defects for film thicknesses smaller than 150 nm and the detailed topology of the defects cores can be revealed by x-ray diffraction. They appear to be split in half tube-shaped Rotating Grain Boundaries (RGB). We determine the RGB spatial extension and evaluate its energy per unit line. Both are significantly larger than the ones usually proposed in the literature