Particle-resolved topological defects of smectic colloidal liquid crystals in extreme confinement

TL;DR

This study investigates the complex topological defect structures in smectic colloidal liquid crystals confined in extreme geometries, revealing diverse defect states and their theoretical understanding through experiments and density functional theory.

Contribution

It introduces a detailed analysis of defect structures in confined smectic colloids, combining microscopy and density functional theory for the first time.

Findings

Identification of various defect states including laminar and multi-domain configurations

Quantitative agreement between experimental microscopy and theoretical models

Discovery of Shubnikov states analogous to type-II superconductors

Abstract

Confined samples of liquid crystals are characterized by a variety of topological defects and can be exposed to external constraints such as extreme confinements with nontrivial topology. Here we explore the intrinsic structure of smectic colloidal layers dictated by the interplay between entropy and an imposed external topology. Considering an annular confinement as a basic example, a plethora of competing states is found with nontrivial defect structures ranging from laminar states to multiple smectic domains and arrays of edge dislocations which we refer to as Shubnikov states in formal analogy to the characteristic of type-II superconductors. Our particle-resolved results, gained by a combination of real-space microscopy of thermal colloidal rods and fundamental-measure-based density functional theory of hard anisotropic bodies, agree on a quantitative level.