Twist disclinations mediated transformations in confined nematic liquid crystals

Svetec, Milan (author), Harkai, Saša (author), Pal, Kaushik (author), Kralj, Samo (author)

We studied numerically structural transformations in different confined nematic liquid crystals (LC) mediated by chargeless (twist) disclinations. Firstly, we focus on the role of twist disclinations in Moiré-type geometrical setup where LC is confined in a plane-parallel cell. We impose an azimuthal rotation to initially parallel wedge disclinations where the total topological charge of the system equals to zero. Two qualitatively different scenarii are observed depending on the cell thickness. In thin enough cells the disclinations touch in the mid-plane which enables continuous transformation into a final structure consisting of two twist disclinations confined to the limiting substrates. On the other hand, in thinner cells an additional chargeless loop is formed in the mid-plane. In this case, on rotating the initially parallel disclinations periodic structural reentrant behavior is observed. In cylindrical geometry we considered transformations between the initial metastable escaped radial structure with point defects (ERPD) into escaped radial (ER) or planar polar structure with line defects (PPLD). In both cases two nearby ring-like point defects within the ERPD structure collide and temporarily form a chargeless twist disclination loop. The latter in the ERPD-ER transformation shrinks and enables continuous transformation into the final thermodynamically stable structure. On the contrary, in the ERPD-PPLD transformation the twist loop, whose local structure matches PPLD configuration, increases and converts the system continuously into the global PPLD configuration. Detailed understanding of chargeless defect mediated transformations is beneficial for development of future switching devices based on continuous nematic structural transformations between LC structures exhibiting significantly different optical features.

• Language: English
• Keywords: nematic liquid crystals, structural transitions, twist disclinations, nucleation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: 10 str.
• Numbering: Vol. 414, pt. B, art. 126138
• PID: 20.500.12556/RUL-164768
• UDC: 544.252.22
• ISSN on article: 1873-3166
• DOI: 10.1016/j.molliq.2024.126138
• COBISS.SI-ID: 214061315
• Publication date in RUL: 11.11.2024

Record is a part of a journal

• Title: Journal of molecular liquids
• Publisher: Elsevier
• ISSN: 1873-3166
• COBISS.SI-ID: 23074821

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: nematski tekoči kristali, fazni prehodi, disklinacije, nukleacija

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P1-0099
• Name: Fizika mehkih snovi, površin in nanostruktur

• Funder: ARRS - Slovenian Research Agency
• Project number: J2-4447
• Name: Vpliv mehanike in topologije membrane na celično ujetje bakterij, virionov in anorganskih delcev