Coexisting nematic and smectic A phases in a twisted liquid crystal cell

Ruan, L.Z. and Sambles, J.R. and Osipov, M.A. (2001) Coexisting nematic and smectic A phases in a twisted liquid crystal cell. Physical Review Letters, 86 (20). pp. 4548-4551. ISSN 1079-7114 (http://dx.doi.org/10.1103/PhysRevLett.86.4548)

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Abstract

Twisted homogeneously planar-aligned nematic liquid-crystal cells are cooled into the smectic- A phase. The expected defective structure does not form. Instead the cells still show good optical-guiding characteristics. Exploration of the cells using a half-leaky guided-mode arrangement reveals that the liquid-crystal phase separates into three or more regions. Adjacent to both the upper and lower boundaries is a region of highly twisted nematic liquid crystal. In the center of the cell is one or more homogeneous smectic- A regions with smectic layers normal to the cell surfaces, separated by twisted nematic. As the cell is cooled so the smectic- A regions grow in thickness with the nematic regions progressively thinning but with increased twist gradient. A theoretical model of these novel results is presented.