title: Theory for the evolution of ferroelectric, antiferroelectric, and ferrielectric smectic phases in the electric field.
abstract: An evolution of Sm-C(A)∗, biaxial intermediate phases, and Sm-C∗ in the electric field is investigated in a framework of molecular-statistical approach [A. V. Emelyanenko et al., Phys. Rev. E 74, 011705 (2006); A. V. Emelyanenko, Eur. Phys. J. E 28, 441 (2009)]. The "electric field-temperature" phase diagrams including the possibility of existence of various tilted smectic phases are plotted and compared with the experimental ones. Permanent transverse molecular dipole moments (without electric field participating only in the spontaneous polarization) were also found to generate the induced polarization in the presence of electric field and to produce very strong dielectriclike effect. This effect is positive in Sm-C∗ (tilt planes have a tendency of orienting along or against the electric field) and is negative in Sm-C(A)∗ and in biaxial intermediate phases (tilt planes have a tendency of orienting perpendicular to the electric field). In the ferrielectric intermediate phases both spontaneous and induced polarizations favor similar tendencies and provide the helix unwinding at very low electric field. At the same time, the tendencies provided by spontaneous and induced polarizations are opposite in Sm-C∗, and therefore the unwinding threshold is larger. It was shown that interplay between spontaneous and induced polarizations can lead to the formation of complex bidomain smectic structures. A single parameter regulating an evolution of structure of Sm-C∗, Sm-C(A)∗, and biaxial intermediate phases in the electric field was found. We suppose that bidomain helical structure is the same as additional ferrielectric phase FiLC existing in some materials just below Sm-C∗. The numerical calculations are done with help of AFLC phase diagram plotter software developed by the author and available at his webpage.
authors.affiliation: Department of Physics, Moscow State University, Moscow 119991, Russia.
authors.forename: A V
authors.initials: AV
authors.lastname: Emelyanenko