We report combined x-ray photon correlation spectroscopy (XPCS) and neutron spin echo (NSE) measurements of the layer-displacement fluctuations in smectic liquid-crystal membranes 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. XPCS probes slower surface-tension-dominated relaxation times, independent of the wave vector. XPCS gives a difference in correlation times at specular and off-specular positions that can be related to different detection schemes.

Phys. Rev. Lett.

Sikharulidze, I., Farago, B., Dolbnya, I. P., Madsen, A., & de Jeu, W. H. (2003). Surface and bulk-elasticity determined fluctuation regimes in smectic membranes. Phys.Rev.Lett., 91(Article number: 165504), 1–4.