Ferrielectric smectic with layer-by-layer change of the two-component order parameter
P. V. Dolganov, V. M. Zhilin, V. K. Dolganov, E. I. Kats+
Institute of Solid State Physics RAS, 142432 Moscow Region, Chernogolovka, Russia
+Laue-Langevin Institute, F-38042, Grenoble, France and
L.D. Landau Institute for Theoretical Physics RAS, 117940 GSP-1, Moscow, Russia
PACS: 61.30.Eb, 64.70.Md, 68.10.Cr
Abstract
One of the most remarkable properties of smectics is the wide
variety of possible equilibrium structures. In this paper, based
on Landau theory of the phase transitions, the transitions between
ferroelectric and antiferroelectric phases and structure formed by
smectic layers with different azimuthal and polar orientation of
molecules were calculated. This unique structure has been
predicted (P.V. Dolganov et al., Pis'ma v ZhETF
76, 579 (2002)) using the minimization of the free energy
with respect to the phase and modulus of the two-component order
parameter, but never detected before. Recently non-resonant Bragg
reflection, consistent with the predictions of the model, was
found (P. Fernandes et al., Eur. Phys. J. E 20,
81 (2006)) in ferrielectric smectic CFI1* (SmCFI1*)
phase. In the 3-layer ferrielectric structure with a macroscopic
helical pitch the modulus of the order parameter is larger in
anticlinic-like layers and smaller in layers with mixed ordering.
The values of the interlayer interactions were determined for
smectic liquid crystalline materials forming different polar
structures.