Effects of a transverse electric field in nematics: Induced biaxiality and the bend Fréedericksz transition

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Abstract
We have studied the effects of a transverse electric field on director fluctuations in the nematic liquid crystal 5CB (4-n-pentyl-4′-cyanobiphenyl) in the bend Fréedericksz geometry. The sample was homeotropically aligned by surface treatment of the glass cell walls and an additional magnetic field was applied perpendicular to the walls. An electric field was then applied parallel to the walls; below the bend Fréedericksz transition, director fluctuations parallel to the electric field are enhanced. This field-induced biaxiality was observed and studied by monitoring the intensity of light transmitted by the sample placed between crossed polarizers. Landau theory for 5CB predicts the electric field induced bend transition to be first order. Our observations of the transmitted intensity are consistent with this prediction. We have also observed that this transition is to a modulated rather than to a uniform phase.