Nematic-Cholesteric Droplets in an Electric Field: Dynamics of Defects, Structural Transformations

Abstract
he structural transformations and dynamics of defects in nematic-cholesteric droplets in an electric field have been studied experimentally. It was shown that the director configuration in droplets and the type of orientation-structural transformations depended on the ratio between the droplet radius and the equilibrium helical pitch R/P as well as the applied voltage magnitude. In particular, at the R/P<1 ratio only droplets with single destroyed boojum were observed. In a.c. electric field such droplets rotate slowly, but above some threshold voltage boojums are converted into defect strings ended with a «hedgehog». In the case of the R/P≈1 ratio the rotation dynamics of defect strings was changed to a periodical process of boojum transformation into two surface defects and back to initial boojum.

Keywords: nematic-cholesteric mixtures, liquid crystals, dynamics of defects, orientational structures