IN15 High Resolution Spin-echo spectrometer

Surface fluctuations

Low-dimensional ordering and the associated fluctuation behavior are of considerable general interest and have been studied for a wide variety of systems such as smectic liquid-crystal membranes.

We show here the study of surface fluctuations of smectic-A membranes of the compound 4-octyl-40-cyanobiphenyl (8CB). Combined x-ray photon correlation spectroscopy (XPCS) and neutron spin echo (NSE) measurements lead to the observation in smectic membranes of both surface-dominated (long-wavelength) and bulk-elasticity-dominated (short-wavelength) fluctuations in the range from 10 ns to 10 µs.
NSE reveals a new regime, determined by bulk elasticity, in which relaxation times decrease with the wave vector of the fluctuations.

Ref.: I. Sikharulidze, B. Farago, I. P. Dolbnya, A. Madsen, W. H. de Jeu, Phys. Rev. Lett 91. 165504 (2003).