Nonstandard electroconvection with Hopf bifurcation in a nematic liquid crystal with negative electric anisotropies.
Electric-field-driven pattern formation has been investigated in a nematic liquid crystal with negative dielectric and conductivity anisotropies. Despite the fact that the standard Carr-Helfrich theory predicts no hydrodynamic instability for such compound, experiments reveal convection patterns which we call nonstandard electroconvection (ns-EC). In this work, we characterize the ns-EC patterns by measuring the frequency, thickness, and temperature dependence of the threshold voltage, wave number, roll orientation, etc., and compare them with the standard-EC (s-EC) characteristics. For the first time, we report traveling rolls in ns-EC, and we give the dependence of the Hopf frequency on the driving frequency, temperature, and sample thickness. Finally, we discuss possible sources for the existence of these patterns.
Tóth-Katona
Tibor
T
Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O.Box 49, H-1525 Budapest, Hungary.
Cauquil-Vergnes
Aude
A
Eber
Nándor
N
Buka
Agnes
A