Electroconvection in nematics above the splay Fréedericksz transition
Electroconvection in nematics above the splay Fréedericksz transition
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DOI：
10.1140/epje/i2007-10207-3
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发表时间：
2007-09
期刊：
影响因子：
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通讯作者：
R. Stannarius;J. Heuer
中科院分区：
文献类型：
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作者：
R. Stannarius;J. Heuer
我们提出了一个不稳定性的基本模型，该不稳定性导致了在向列相中Splay Fréedericksz相变上方观察到的一种新型的电对流图案。这种波矢垂直于指向矢易轴的图案在平面夹层小室中是在交叉偏振器下发现的，它们在开始时不会产生阴影图像。介绍了经典Carr Helfrich机制的一种改进。基态是在晶胞平面上均匀分布的倾斜的指向矢场。所提出的机制破坏了这种指向矢场的稳定性，并导致了具有调制的面外(扭曲)变形的结构。偏光显微镜提供了实验上的证实。用该模型定性地解释了所有的实验观测结果。
We present a basic model for an instability leading to a novel type of electroconvection patterns observed above the splay Fréedericksz transition in nematics. Such patterns, with wave vector perpendicular to the director easy axis, are found in planar sandwich cells under crossed polarizers, they do not produce shadowgraph images at onset. An adaptation of the classical Carr Helfrich mechanism is introduced. The ground state is a tilted director field uniform in the cell plane. The proposed mechanism destabilizes this director field and leads to a structure with modulated out-of-plane (twist) deformations. Experimental confirmation is provided by polarizing microscopy. All experimental observations are qualitatively explained with the proposed model.