Electric-field-induced twist and bend Freedericksz transitions in nematic liquid crystals

Abstract

By considering the Frank free energy, we show that the electric-field-induced twist and bend Freedericksz transitions can be first order. This agrees with the prediction of Arakelyan, Karayan, and Chilingaryan [Sov. Phys.--Dokl. 29, 202 (1984)] from Landau theory for the bend geometry. We have carried out dielectric measurements on the liquid-crystal 5CB (4-cyano-4'-n-pentylbiphenyl) that provide the first experimental evidence that these transitions are first order. The effects of a competing magnetic field on the threshold voltage and on the width of the transition region are compared with theory. In the presence of a competing magnetic field, the bend transition in 5CB is to a modulated rather than a uniform phase.