Solitons in a discrete model of chiral liquid crystals with competing interactions

TL;DR

This paper investigates the formation and stability of domain-wall solitons in smectic chiral liquid crystals, highlighting how chiral interactions and electric fields influence soliton properties and stability.

Contribution

It introduces a discrete model analyzing the effects of chiral and symmetric interactions, as well as electric fields, on soliton formation and stability in liquid crystals.

Findings

Chiral interactions increase kink width at moderate electric fields.

Electric fields can destabilize solitons, especially along the x-axis.

Chirality reduces the Peierls-Nabarro barrier, enhancing soliton lifetime.

Abstract

Chiral liquid crystals exhibit in-plane spontaneous polarizations, however in their smectic phase the primary order parameter is a tilt vector associated with molecular rotations around the long molecular axis parallel to the director. The molecular rotations lead to several distinct phases among which a domain-wall texture with a periodic-kink soliton profile. In this study the formation of domain walls in smectic chiral liquid crystals is analyzed, with emphasis on the competition between ising-type symmetric and antisymmetric nearest-neighbor interactions, and an in-plane electric field. It is found that antisymmetric intermolecular interactions, which are of chiral origin, increase the width of kink structures in the domain wall at moderate intensity of the $y$ component of the electric field. Increasing the $x$ component of the electric field creates unstable condition for soliton formation irrespective of magnitudes of the symmetric and chiral intermolecular interactions. Stability condition for single-kink domain-wall structures in the discrete molecular chain, is discussed by estimating the Peierls stress experienced by the single-kink soliton. Results suggest that chirality lowers the Peierls-Nabarro barrier, hence increasing the lifetime of single-kink structures in the discrete medium.