Creep dynamics of structural defects in ferroelectric liquid crystals with chevron geometry

Abstract

Electric-field induced motions of zigzag walls forming defects in the chevron structure of surface stabilized ferroelectric liquid crystals are investigated. An explicit experimental evidence, including direct microscopic observation, is reported that the walls display viscous creep motions at small length scales, being dependent on the amplitude $U$ and frequency $f$ of an applied voltage. The relaxation-to-creep transition is analyzed using both the electro-optical response and dynamic hysteresis data recorded at different values of $U$ and $f$. It is shown that, at any fixed temperature below the chevron-to-bookshelf transition point, there exists a critical line in the $U\text{\ensuremath{-}}f$ plane, separating the relaxation and creep dynamic regions. In contrast to field-activated nonlocal excitations discovered in various disordered media, the creep motions of zigzag walls are found to occur not only at low or very low field frequencies.