Critical Fluctuations in Free-Standing Smectic Films: An X-Ray Reflectivity Study
We report on the x-ray reflectivity of free-standing smectic films of 8CB. At temperatures well below the second-order nematic-to-smectic transition temperature TNA we find that the fluctuations of the smectic layers in the middle and at the surfaces have the same amplitude. However, on approaching TNA the fluctuations of the middle layers of the film are found to diverge while those at the surfaces are still quenched. The results can be understood qualitatively by including an additional surface term in the well-known Landau-De Gennes free energy for the smectic-A phase.
KeywordsMiddle Layer Bragg Peak Smectic Layer Critical Fluctuation Smectic Liquid Crystal
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