Coupling of polarization and dislocation in ferroelectric smectic liquid-crystal films

The polarization vector in ferroelectric smectic-C* films preferably aligns along a dislocation line due to the Coulomb interaction between polarization charges. The electric field locally perpendicular to the dislocation line distorts it, and in the case of a dislocation loop an n-finger structure is formed, with n depending on the applied voltage. This phenomenon has been observed in an experiment in which the screening effect of ion impurities has been partially lifted in a low-frequency (3 Hz) electric field. A characteristic length scale related to this phenomenon is of the order of 10(4) Angstrom.