title: Longitudinal and normal electroconvection rolls in a nematic liquid crystal with positive dielectric and negative conductivity anisotropy.
abstract: We study electroconvection patterns that appear above the splay Fréedericksz transition in a bent-core nematic liquid crystal with positive dielectric and negative conductivity anisotropy. In contrast to most of the previously observed convection rolls in nematics, they are not shadowgraph patterns at onset. Unusual effects are observed like a transition between longitudinal and normal rolls, controlled by the excitation frequency, as well as a voltage dependent reorientation of the convection rolls in a metastable domain. We present experimentally determined pattern state diagrams for planar alignment and characterize the patterns optically.
authors.affiliation: Otto-von-Guericke-University, Institute of Experimental Physics, Universitätsplatz 2, 39106 Magdeburg, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Heuer
authors.forename: Ralf
authors.initials: R
authors.lastname: Stannarius
authors.forename: Maria-Gabriela
authors.initials: MG
authors.lastname: Tamba
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Weissflog