X-Ray Study of Fluctuations near the Nematic-Smectic-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>A</mml:mi></mml:math>-Smectic-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi></mml:math>Multicritical Point

Abstract

We present the results of a high-resolution x-ray-scattering study of the pretransitional fluctuations above the nematic-to-smectic-$C$ phase boundary in the \ifmmode\bar\else\textasciimacron\fi{}7S5/8OCB system. The fluctuations are well described by the Lifshitz-point model of Chen and Lubensky with minimal adjustable parameters. We have located the line along which the x-ray cross section $\ensuremath{\sigma}(\mathrm{q})$ exhibits pure ${q}_{\ensuremath{\perp}}^{\ensuremath{-}4}$ fluctuations. Close to the nematic-smectic-$A$-smectic-$C$ point this line is simply related to the smectic-$A$-smectic-$C$ transition boundary.