Silvestre N M, Patrício P, Telo da Gama M M, Pattanaporkratana A, Park C S, Maclennan J E, Clark N A
Departamento de Física da Faculdade de Ciências, Universidade de Lisboa, Avenida Professor Gama Pinto 2, P-1649-003 Lisboa Codex, Portugal.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Oct;80(4 Pt 1):041708. doi: 10.1103/PhysRevE.80.041708. Epub 2009 Oct 30.
We report a detailed theoretical analysis of quadrupolar interactions observed between islands, which are disklike inclusions of extra layers, floating in thin, freely suspended smectic- C liquid crystal films. Strong tangential anchoring at the island boundaries results in a strength +1 chiral defect in each island and a companion -1 defect in the film--these forming a topological dipole. While islands of the same handedness form linear chains with the topological dipoles pointing in the same direction, as reported in the literature, islands with different handedness form compact quadrupolar structures with the associated dipoles pointing in opposite directions. The interaction between such heterochiral-island-defect pairs is complex, with the defects moving to minimize the director field distortion as the distance between the islands changes. The details of the interisland potential and the trajectories of the -1 defects depend strongly on the elastic anisotropy of the liquid crystal, which can be modified in the experiments by varying the material chirality of the liquid crystal. A Landau model that describes the energetics of freely mobile defects is solved numerically to find equilibrium configurations for a wide range of parameters.
我们报告了对在薄的、自由悬浮的近晶C液晶薄膜中漂浮的、呈盘状额外层夹杂物的岛之间观察到的四极相互作用的详细理论分析。岛边界处的强切向锚定导致每个岛中出现强度为 +1 的手性缺陷以及薄膜中伴随的 -1 缺陷——这些形成了一个拓扑偶极子。正如文献中所报道的，相同手性的岛形成线性链，拓扑偶极子指向相同方向，而不同手性的岛形成紧凑的四极结构，相关偶极子指向相反方向。这种异手性岛 - 缺陷对之间的相互作用很复杂，随着岛之间距离的变化，缺陷会移动以最小化指向矢场的畸变。岛间势的细节以及 -1 缺陷的轨迹强烈依赖于液晶的弹性各向异性，在实验中可以通过改变液晶的材料手性来改变这种弹性各向异性。求解了一个描述自由移动缺陷能量学的朗道模型，以找到广泛参数范围内的平衡构型。
