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DY: Fachverband Dynamik und Statistische Physik

DY 21: Soft Matter II

DY 21.5: Vortrag

Mittwoch, 24. März 2010, 17:30–17:45, H47

Electroconvection in a Liquid Crystal under a Symmetry Breaking Magnetic Field — •Andreas Walter, Wolfgang Schöpf, and Ingo Rehberg — Experimentalphysik V, Universität Bayreuth, 95440 Bayreuth

We investigate homeotropically aligned MBBA under the influence of electric and magnetic fields. MBBA has a negative dielectric anisotropy and a positive anisotropy of the magnetic susceptibility. Thus, when placed between two parallel electrodes, electroconvection takes place only after a symmetry breaking bend Fréedericksz transition.

A magnetic field is applied perpendicular to the driving electric field in order to establish a preferred direction within the system. We report on results for the primary instability, i.e. the Fréedericksz transition.

In contrast to the planar orientation, electroconvection occurs as a secondary bifurcation. Motivated by theoretical expectations, we search for a subcritical bifurcation leading to oscillating behaviour.