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

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.

Failure of standard density functional theory to describe the phase behavior of a fluid of hard right isosceles triangles

“…These results suggested that entropic interactions are also important to determine the orientational ordering patterns observed in dissipative systems. Experiments conducted on vibrated granular rods [19] and equilibrated colloidal silica rods [20] under annular confinement showed the presence of topological defects and domains walls between regions of different orientational and spatial ordering. This in turn suggests similarities between dissipative and equilibrium systems in situations where entropic interactions play a dominant role, i.e., at high packing fractions.…”

Topological fine structure of smectic grain boundaries and tetratic disclination lines within three-dimensional smectic liquid crystals

“…As the go-to systems for investigating these ordering phenomena, liquid crystals have been enjoying continuous attention within the physical chemistry and chemical physics community over the decades and remain an active field of research relevant in a variety of different applications. The most prominent examples are colloidal systems [13][14][15], various forms of passive and active chemical molecules [16][17][18][19][20][21] and also living and artificial microscopic systems, such as swarms of bacteria [22][23][24][25], bacterial DNA [26,27] and viral colonies [28], that all exhibit liquid crystal mesophases and topological defects. Topological analysis even provides a tool for insight into the behavior of macroscopic systems, such as gracefully moving flocks of birds, often extending dozens of meters in the sky, as well as the collective behavior in shoals of fish, where local coherent swimming is a vital tool in the evasion of predators [29][30][31][32].…”

“…A convenient way to investigate these is therefore consideration in finite cavities. For 2d colloidal liquid crystals, in particular, we have previously shown that the consideration of those domain boundaries as coexisting nematic and tetratic charges yields insight into the orientational topology of smectics [14,83] (for a comprehensive summary see Sec. II C).…”

Defect Structures of Magnetic Nanoparticles in Smectic A Liquid Crystals

“…Generally, the interaction between particles and LC molecules depends on nanoparticle size, shape, and physical properties of both partners, NPs and organic molecules. Within the last two decades, the systems of LCs and nanoparticles have been intensively studied [ 2 ] and it has been confirmed that the orientational and positional ordering of mesogenic molecules can induce unexpected effects in the presence of nanoparticles [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ].…”