1. Curvature potential unveiled topological defect attractorsLuka Mesarec, Aleš Iglič, Veronika Kralj-Iglič, Wojciech Góźdź, Epifanio Giovanni Virga, Samo Kralj, 2021, original scientific article Abstract: We consider the theoretical and positional assembling of topological defects (TDs) in effectively two-dimensional nematic liquid crystal films. We use a phenomenological Helfrich–Landau–de Gennes-type mesoscopic model in which geometric shapes and nematic orientational order are expressed in terms of a curvature tensor field and a nematic tensor order parameter field. Extrinsic, intrinsic, and total curvature potentials are introduced using the parallel transport concept. These potentials reveal curvature seeded TD attractors. To test ground configurations, we used axially symmetric nematic films exhibiting spherical topology.
Keywords: topological defects, nematic liquid crystals, nematic shells, geometric potentials, curvature
Published in DKUM: 30.09.2024; Views: 0; Downloads: 7
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3. Fingered core structure of nematic boojumsSamo Kralj, Riccardo Rosso, Epifanio Giovanni Virga, 2008, original scientific article Abstract: Using the Landau-de Gennes phenomenological approach, we study the fine biaxial core structure of a boojum residing on the surface of a nematic liquid crystal phase. The core is formed by a negatively uniaxial finger, surrounded by a shell with maximal biaxiality. The characteristic finger's length and the shell's width are comparable to the biaxial correlation length. The finger tip is melted for topological reasons. Upon decreasing the surface anchoring strength below a critical value, the finger gradually leaves the bulk and it is expelled through the surface.
Keywords: physics, liquid crystals, nematic crystals, line defects, surface phenomena
Published in DKUM: 07.06.2012; Views: 2110; Downloads: 112
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4. Finite-size effects on order reconstruction around nematic defectsSamo Kralj, Riccardo Rosso, Epifanio Giovanni Virga, 2010, original scientific article Abstract: By use of the Landau-de Gennes phenomenological theory, we study the texture of a nematic liquid crystal confined within a hybrid cell. Precisely, we consider cylindrically symmetric solutions containing topological defects dictated by appropriate boundary conditions. We focus our attention on cells whose dimensions are comparable with the biaxial correlation length ▫$xi_b$▫. For such severe confinements the order reconstruction (OR) configuration could be stable. Its structural details reflect the balance among boundary-enforced frustration, elastic penalties, and finite-size effects. In particular, we analyze the interplay between finite-size effects and topological defects. We show that defects are always pinned to the negatively (planar) uniaxial sheet of the OR structure. The presence of a ring defect can dramatically increase the critical threshold below which the OR structure is stable.
Keywords: physics, liquid crystals, nematic crystals, nematic defects, structural transitions
Published in DKUM: 07.06.2012; Views: 2658; Downloads: 98
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