Smectics: Symmetry Breaking, Singularities, and Surfaces

Computing with non-orientable defects: nematics, smectics and natural patterns

Defects are a ubiquitous feature of ordered media. They have certain universal features, independent of the underlying physical system, reflecting their topological origins. While the topological properties of defects are robust, they appear as `unphysical' singularities, with non-integrable energy densities in coarse-grained macroscopic models. We develop a principled approach for enriching coarse-grained theories with enough of the `micro-physics' to obtain thermodynamically consistent, well-set models, that allow for the investigations of dynamics and interactions of defects in extended sys…

Phase Behavior of Bent-Core Molecules

Recently, a new class of smectic liquid crystal phases (SmCP phases) characterized by the spontaneous formation of macroscopic chiral domains from achiral bent-core molecules has been discovered. We have carried out Monte Carlo simulations of a minimal hard spherocylinder dimer model to investigate the role of excluded volume interations in determining the phase behavior of bent-core materials and to probe the molecular origins of polar and chiral symmetry breaking. We present the phase diagram as a function of pressure or density and dimer opening angle $ψ$. With decreasing $ψ$, a transition …

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。

Point Defects, Chirality and Singularity Theory in Cholesteric Liquid Crystal Droplets

We develop a theory of point defects in cholesterics and textures in spherical droplets with normal anchoring. The local structure of chiral defects is described by singularity theory and a smectic-like gradient field establishing a nexus between cholesterics and smectics mediated by their defects. We identify the defects of degree $-2$ and $-3$ observed experimentally with the singularities $D_4^{-}$ and $T_{4,4,4}$, respectively. Radial point defects typical of nematics cannot be perturbed into chiral structures with a single handedness by general topological considerations. For the same rea…

倾斜或扭曲——弯曲核心介晶SmC相中的同倾与反倾竞争相互作用

Tilt or twist-competing synclinic and anticlinic interactions in SmC phases of bent-core mesogens

本研究通过共振软X射线散射技术，探究了结合刚性弯曲核心与极性基团的混合介晶结构，揭示了同系物长度对倾斜近晶相、螺旋近晶相及调制近晶相形成的偏好，阐明了同倾与反倾竞争相互作用下高层级结构形成的先决条件。

自发手性极性液晶中的亚铁电与铁电开关

Ferri- and Ferro-Electric Switching in Spontaneously Chiral Polar Liquid Crystals

本研究发现首个自发手性铁电向列相分子的极性近晶中间相为螺旋形且织构形态因热历史变化，两种手性相均有场诱导相变，近晶相首次呈现伪亚铁电开关，螺旋形成含一级和二级相变。

共轭聚合物中表面诱导的有序化与平移对称性的连续破缺

Surface-induced ordering and continuous breaking of translational symmetry in conjugated polymers

本研究利用表面敏感掠入射X射线散射，揭示自由表面可诱导两类共轭聚合物形成有序中间相，其平移对称性破缺呈连续特性，为理解表面诱导有序化机制提供了实验与理论依据。

Electronic polymers and soft-matter-like broken symmetries in underdoped cuprates

Empirical evidence in heavy fermion, pnictide, and other systems suggests that unconventional superconductivity appears associated to some form of real-space electronic order. For the cuprates, despite several proposals, the emergence of order in the phase diagram between the commensurate antiferromagnetic state and the superconducting state is not well understood. Here we show that in this regime doped holes assemble in "electronic polymers." Within a Monte Carlo study we find, that in clean systems by lowering the temperature the polymer melt condenses first in a smectic state and then in a …

近似高形式对称性、拓扑缺陷与动力学相变

Approximate higher-form symmetries, topological defects, and dynamical phase transitions

本文提出近似高形式对称性的有效理论与流体动力学框架，刻画显式、自发及伪自发破缺、对偶网络和涡旋缺陷增殖，并统一解释多种凝聚态与等离子体相变。

弯曲棒状分子向列相中的熵稳定形态手性：结构与对称性

Entropy stabilized form chirality in curved rod nematics: structure and symmetries

本文通过蒙特卡洛模拟揭示弯曲棒状分子可形成极性扭曲向列相，其纳米尺度螺旋极性结构由熵稳定，并阐明了形态手性与扭曲-弯曲向列相的本质区别。