Surface anchoring as a control parameter for stabilizing torons, skyrmions, twisted walls, fingers, and their hybrids in chiral nematics

Abstract

Chiral condensed matter systems, such as liquid crystals and magnets, exhibit a host of spatially localized topological structures that emerge from the medium's tendency to twist and its competition with confinement and field coupling effects. We show that the strength of perpendicular surface boundary conditions can be used to control the structure and topology of solitonic and other localized field configurations. By combining numerical modeling and threedimensional imaging of the director field, we reveal structural stability diagrams and intertransformation of twisted walls and fingers, torons and skyrmions and their crystalline organizations upon changing boundary conditions. Our findings provide a recipe for controllably realizing skyrmions, torons and hybrid solitonic structures possessing features of both of them, which will aid in fundamental explorations and technological uses of such topological solitons.Moreover, with limited examples, we discuss how similar principles can be systematically used to tune stability of twisted walls versus cholesteric fingers and hopfions versus skyrmions, torons and twistions.

Engineered liquid crystal nano droplets: insights from multi-scale simulations

“…Moreover, the approach could be extended to investigate twisted structures within LC droplets, in the presence of either chiral and achiral molecules, which is an area of intense interest. 49,50 While additional calculations will provide more robust relationships than that shown in eqn (5), having established a quantitative meso-scale correspondence across scales and models will hopefully lead to improved understanding of the behaviour of LC assemblies, which is needed to further advanced applications.…”

Nematic Order, Plasmonic Switching and Self‐Patterning of Colloidal Gold Bipyramids

“…Topological structures in chiral LC‐GNPB were modeled by numerically minimizing the Frank–Oseen free energy functional [ 1 , 25 , 38 ] where K 11 = 6.4 pN, K 22 = 3 pN, K 33 = 10 pN are the splay, twist and bend elastic constants of 5CB (average elastic constant K = 6.47 pN), [ 38 ] and p is the equilibrium cholesteric pitch. The saddle‐splay deformation and surface energy are not included by assuming strong boundary conditions on the surfaces, consistent with experiments.…”

Surface Stabilized Topological Solitons in Nematic Liquid Crystals

“…A local disturbance in a director field that is homogeneous in the far-field can be considered as a soliton. These particle-like topological structures have been studied extensively in LCs since they are an ideal material system to obtain controlled, sometimes reconfigurable, topological patterning of condensed matter [15,26,27,[31][32][33][34][35][36][37][38]. Different from previous work, we use achiral LC in combination with two patterned planar alignment surfaces to stabilize soliton-like structures.…”

“…This in contrast to previous works where one patterned substrate was combined with a uniformly aligned substrate [15,26,27]. Solitons, or so-called particle-like topological states, are usually studied in chiral LC samples with strong confinement [31][32][33][34][35][36][37], but photo-alignment techniques allow studying soliton structures in less confined configurations [38] and non-chiral cells [15,26,27]. We investigate new soliton-like NLC structures induced by well-designed ring-shaped alignment patterns at the confining substrates.…”