title: Patterns driven by combined ac and dc electric fields in nematic liquid crystals.
abstract: The effect of superimposed ac and dc electric fields on the formation of electroconvection and flexoelectric patterns in nematic liquid crystals was studied. For selected ac frequencies, an extended standard 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 electric field components. Numerical as well as approximate analytical calculations demonstrate 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 patterns. The theoretical predictions are qualitatively confirmed by experiments in most cases. Some discrepancies, however, seem to indicate the need to extend the theoretical description.
authors.affiliation: Max Planck Institute for Dynamics and Self-Organization, D-37077 Göttingen, Germany.
authors.forename: Alexei
authors.initials: A
authors.lastname: Krekhov
authors.affiliation: Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Decker
authors.affiliation: Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Pesch
authors.affiliation: Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P. O. Box 49, H-1525 Budapest, Hungary.
authors.forename: Nándor
authors.initials: N
authors.lastname: Eber
authors.affiliation: Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P. O. Box 49, H-1525 Budapest, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Salamon
authors.affiliation: Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P. O. Box 49, H-1525 Budapest, Hungary.
authors.forename: Balázs
authors.initials: B
authors.lastname: Fekete
authors.affiliation: Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P. O. Box 49, H-1525 Budapest, Hungary.
authors.forename: Agnes
authors.initials: A
authors.lastname: Buka