Berlin 2015 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 44: Pattern Formation
DY 44.2: Vortrag
Donnerstag, 19. März 2015, 09:45–10:00, BH-N 333
Patterns driven by combined ac and dc electric fields in nematic liquid crystals — •Alexei Krekhov1, Werner Pesch2, Nandor Eber3, and Agnes Buka3 — 1Max Planck Institute for Dynamics and Self-Organization, 37077 Göttingen, Germany — 2Institute of Physics, University of Bayreuth, 95440 Bayreuth, Germany — 3Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, H-1525 Budapest, Hungary
Electroconvection and flexoelectric patterns in a nematic liquid crystal layer driven by two superimposed ac and dc voltages, where each of them would separately trigger patterns of different spato-temporal symmetry, are investigated. An extended model of the electrohydrodynamic instabilities was used to characterize the onset of pattern formation in the two-dimensional parameter space of the magnitudes of the ac and dc voltages. It is demonstrated that depending on the type of patterns and on the ac frequency, the combined action of ac and dc fields may either enhance or suppress the formation of spatially periodic patterns. The theoretical predictions are compared with representative experiments.