Screw dislocation interaction in smectic-A liquid crystals in an anharmonic approximation

位错与纤维化：扭结近晶缺陷的拓扑结构

Dislocations and Fibrations: The Topological Structure of Knotted Smectic Defects

本研究探究近晶液晶中扭结缺陷的拓扑性质，分析螺位错、刃型位错等缺陷与扭结纤维化的关联，给出点缺陷数量下界，深化了与焦锥畴的类比，为相关拓扑理论提供研究平台。

非手性液晶中近晶A层波纹表现为条纹织构

Undulations of smectic A layers in achiral liquid crystals manifested as stripe textures

本研究通过实验和光学方法，揭示了非手性液晶近晶A相中由热处理引起的微米尺度层波纹，表现为规则条纹，其形成关键在于高热膨胀系数的负值。

Smectic Liquid Crystals in Random Environments

We study smectic liquid crystals in random environments, e.g., aerogel. A low temperature analysis reveals that even arbitrarily weak quenched disorder (i.e., arbitrarily low aerogel density) destroys translational (smectic) order. A harmonic approximation to the elastic energy suggests that there is no ``smectic Bragg glass'' phase in this system: even at zero temperature, it is riddled with dislocation loops induced by the quenched disorder. This result implies the destruction of orientational (nematic) order as well, and that the thermodynamically sharp Nematic-Smectic-A transition is destr…

逃离二维：刃位错与螺位错之间的拓扑区分

Escape from the Second Dimension: A Topological Distinction Between Edge and Screw Dislocations

本文提出一种纯拓扑方法区分刃位错与螺位错，通过在层状相位错核心构造真实或虚拟向错线对实现统一分类，并可推广到三重周期序晶体。

Selection of defect structures in twist-grain-boundary-A phase of chiral liquid crystals

We study the structure of the twist grain boundary in chiral smectic liquid crystals using the Landau-de Gennes model. By considering spatial variation of the smectic order, we distinguish the Melted-Grain-Boundary-A (MGBA) structure with cholesteric-like domains and the Twist-Grain-Boundary-A (TGBA) structure consisting of screw dislocations. The MGBA structure becomes stable near the transition to the cholesteric phase. On approaching the transition, the cholesteric-like domain grows outside the grain boundary. Also, the dislocation spacings of the TGBA structure agree better with experiment…

The Topology of Dislocations in Smectic Liquid Crystals

The order parameter of the smectic liquid crystal phase is the same as that of a superfluid or superconductor, namely a complex scalar field. We show that the essential difference in boundary conditions between these systems leads to a markedly different topological structure of the defects. Screw and edge defects can be distinguished topologically. This implies an invariant on an edge dislocation loop so that smectic defects can be topologically linked not unlike defects in ordered systems with non-Abelian fundamental groups.

Dislocation Geometry in the TGB-A Phase: Linear Theory

We demonstrate that an arbitrary system of screw dislocations in a smectic-A liquid crystal may be consistently treated within harmonic elasticity theory, provided that the angles between dislocations are sufficiently small. Using this theory, we calculate the ground state configuration of the TGB-A phase. We obtain an estimate of the twist-grain-boundary spacing and screw dislocation spacing in a boundary in terms of the macroscopic parameters, in reasonable agreement with experimental results.

Numerical simulation of the twist-grain-boundary phase of chiral liquid crystals

We study the core structure of the twist-grain-boundary (TGB) phase of chiral liquid crystals by numerically minimizing the Landau-de Gennes free energy. We analyze the morphology of layers at the grain boundary, to better understand the mechanism of frustration between the smectic layer order and chirality. As the chirality increases, the effective bending rigidity of layers is reduced due to unlocking of the layer orientation and the director. This results in large deviation of the layer morphology from that of Scherk's first minimal surface and linear stack of screw dislocations (LSD).

侧向取代基增加的铁电液晶中镜像对称性破缺与平移对称性破缺之间的竞争

Competition between mirror symmetry breaking and translation symmetry breaking in ferroelectric liquid crystals with increasing lateral substitution

研究了侧向取代基长度对铁电液晶中NTBF相形成的影响，发现侧链增长抑制了近晶层形成并促使NTBF相取代SmAF相，揭示了层状与螺旋圆锥极性有序间的竞争，且该相具有极短螺距并可能存在螺位错阵列。