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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.