Critical Fluctuations near a Nematic-Smectic-<span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>A</mi></math></span>-Smectic-<span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi></math></span> Multicritical Point

C. R. Safinya; R. J. Birgeneau; J. D. Litster; M. E. Neubert

doi:10.1103/PhysRevLett.47.668

Critical Fluctuations near a Nematic-Smectic- $A$ -Smectic- $C$ Multicritical Point

C. R. Safinya, R. J. Birgeneau, J. D. Litster, and M. E. Neubert

Phys. Rev. Lett. 47, 668 – Published 31 August 1981

Abstract

We report a high-resolution x-ray study of the fluctuations in a system exhibiting nematic, smectic- $A$ , and smectic- $C$ phases, with emphasis on the NAC multicritical region. We find that the transverse mass density fluctuations are always Lorentzian in character in explicit disagreement with the Lifshitz model for this system. Unexpectedly, both the mass density fluctuations and the tilt order parameter exhibit isotropic heliumlike critical exponents near the NAC point.