Drifting abnormal rolls in electroconvection of hybrid aligned nematic

We report experimental and theoretical results on the conductive regime of electroconvection in hybrid aligned nematics. The drifting oblique/normal r olls below/above the Lifshitz frequency are observed at the onset of electr oconvection under a.c. voltage. The experimental data on the threshold volt age, wavelength, oblique angle and drift period of the rolls as function of a.c. frequency are in good agreement with the results of linear stability analysis. The transition from drifting oblique rolls to abnormal rolls is f ound below the Lifshitz frequency with increasing applied voltage.