AI 中文总结
该研究探究柔性核心苯甲酸苯酯二聚体向列相的自发及电场诱导图案态，通过模型解释准周期基态，明确不同电场下的不稳定性序列，测量阈值电压与惯性传导不稳定性理论预测吻合。
AI 中文摘要
本研究针对两种介电负性扭弯向列型液晶在向列相中观测到的自发形成结构与电场诱导结构展开研究。在平面盒中，向列层为非均匀结构，存在准周期基态，该基态本质上涉及方位角指向矢偏差。利用基于自由能中挠曲电贡献与弹性贡献相对关系的简单模型可解释该现象。在外电场作用下，会产生多种不稳定性：例如，在递增的静电场中，初始的周期性表面电对流不稳定性后会出现体周期性挠曲电不稳定性；不同寻常的是，后者的增长通过形核与前沿传播发生。由于弯曲弹性变形的能量成本较低，随电场递增，挠曲电带会在边缘位错介导下随宽度减小而逐渐变形，最终形成扇形结构。在兆赫区域，0V后的每个半周期内，电对流与挠曲电不稳定性会短暂出现，且后者在更高电压下触发；在几赫兹以上，挠曲电不稳定性消失，图案态序列变为斜卷→双峰网格→法向卷→人字形；在100kHz以上，在随频率升高而阈值电压降低的条件下，会获得垂直于摩擦轴的周期性宽带。本研究对该区域不同频率（或电导率、介电常数）对应的阈值电压测量结果，与早期关于惯性传导不稳定性的理论预测吻合良好。
英文摘要
This study deals with both spontaneously-formed and electrically-induced structures observed in the nematic phase of two dielectrically negative twist-bend nematogens. In planar cells, the nematic layers are inhomogeneous, existing in a quasiperiodic ground state that involves essentially azimuthal director deviations. This phenomenon is understood using a simple model based on the relative flexoelectric and elastic contributions to free-energy. In an external electric field, a variety of instabilities are obtained. In an increasing static field, for example, the initial periodic surface electroconvective instability is followed by the volume periodic flexoelectric instability. Uncommonly, the growth of the latter takes place via nucleation and front propagation. Due to the low bend elastic deformation cost, flexoelectric bands progressively distort as they narrow (mediated by edge dislocations) under an increasing field to eventually form fanlike objects. In the megahertz region, in each half cycle following 0 V, the electroconvective and flexoelectric instabilities appear transiently with the latter setting in at a higher voltage. Above a few hertz, flexoelectric instability ceases; the sequence of patterned states then is oblique roll to bimodal-grid to normal-roll to chevron. Above 100 kHz, periodic wide bands oriented normal to the rubbing axis are obtained at a threshold voltage that decreases with increasing frequency. Our measurement of threshold voltage corresponding to different frequencies (or electrical conductivity and permittivity values) in this regime agrees well with the earlier theoretical predictions relating to the inertial conduction instability.
Comments32 pages and 21 figures. Under review in Phys. Rev. E
