Straight Round the Twist: Frustration and Chirality in Smectics-A

TL;DR

This paper investigates how frustration between chirality and layer spacing in smectic liquid crystals leads to complex textures and different stable phases, including the twist grain boundary and hierarchical helical nanofilament phases.

Contribution

It compares the stability of TGB and HN phases in chiral smectics using Landau-de Gennes free energy analysis, revealing conditions favoring each phase.

Findings

TGB phase is the ground state for typical chiral smectics.

Highly chiral systems favor the hierarchical helical nanofilament phase.

Frustration induces defect-rich textures in smectic liquid crystals.

Abstract

Frustration is a powerful mechanism in condensed matter systems, driving both order and co plexity. In smectics, the frustration between macroscopic chirality and equally spaced layers generates textures characterised by a proliferation of defects. In this article, we study several different ground states of the chiral Landau-de Gennes free energy for a smectic liquid crystal. The standard theory finds the twist grain boundary (TGB) phase to be the ground state for chiral type II smectics. However, for very highly chiral systems, the hierarchical helical nanofilament (HN) phase can form and is stable over the TGB.