Polarization and tilt-angle measurements near the smectic-A chiral smectic-C transition of p-(n-decyloxybenzylidene)-p-amino-(2-methyl-butyl) cinnamate (DOBAMBC)

For a given temperature below the smectic-A (SmA)chiralsmectic-C (SmC*) transition of DOBAMBC, polarization (P) and tilt-angle (theta) have been measured almost simultaneously with high resolution. The ratio P/theta stays fairly constant for Tc-T>2 K and shows a precipitous drop near the transition temperature (Tc). A calculation based on a generalized mean-field model, similar to the one proposed by Zeks, is in good agreement with our result. This generalized mean-field model also gives the prominent feature of the helical pitch anomaly just below the SmA-SmC* transition.