Prof. Agnes Buka: Patterns induced in nematics by asymmetrical (AC + DC) electric fields
Povzetek:
Patterns induced in nematics by asymmetrical (AC + DC) electric fields
Prof. Agnes Buka, Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P. O. Box 49,H-1525 Budapest, Hungary
Liquid crystals easily get unstable and readily form regular (or irregular) patterns under the action of an applied driving force, e.g. an electric field. The effect of superimposed AC and DC electric fields on the formation of electroconvection and flexoelectric domains in nematic liquid crystals has been studied. In contrast to the predictions of the standard theory of electroconvection (EC), our experiments showed that the action of superposed AC and DC voltages rather inhibits pattern formation than favors the emergence of instabilities; the patternless region may extend to much higher voltages than the individual AC or DC thresholds. The pattern formation induced by such asymmetrical voltage was explored in a nematic liquid crystal in a wide frequency range. The findings could be qualitatively explained for the conductive EC, but represent a challenging theoretical problem for the dielectric EC [1,2].
References:
1. Alexei Krekhov, Werner Decker, Werner Pesch, Nándor Éber, Péter Salamon, Balázs Fekete and Ágnes Buka: Patterns driven by combined ac and dc electric fields in nematic liquid crystals. Phys. Rev. E. 89, 052507 (2014).
2. Péter Salamon, Nándor Éber, Balázs Fekete and Ágnes Buka: Inhibited pattern formation by asymmetrical high-voltage excitation in nematic fluids. Phys.Rev. E 90, 022505 (2014).
