Flashing flexodomains and electroconvection rolls in a nematic liquid crystal

Salamon, Péter and Éber, Nándor and Krekhov, A. and Buka, Ágnes (2013) Flashing flexodomains and electroconvection rolls in a nematic liquid crystal. PHYSICAL REVIEW E - STATISTICAL, NONLINEAR AND SOFT MATTER PHYSICS (2001-2015), 87 (3). ISSN 1539-3755

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Abstract

Pattern forming instabilities induced by ultralow frequency sinusoidal voltages were studied in a rod-like nematic liquid crystal by microscopic observations and simultaneous electric current mea- surements. Two pattern morphologies, electroconvection (EC) and flexodomains (FD), were distin- guished; both appearing as time separated flashes within each half period of driving. A correlation was found between the time instants of the EC flashes and that of the nonlinear current response. The voltage dependence of the pattern contrast C(U ) for EC has a different character than that for the FD. The flattening of C(U ) at reducing the frequency was described in terms of an imperfect bifurcation model. Analysing the threshold characteristics of FD the temperature dependence of the difference |e1 − e3| of the flexoelectric coefficients were also determined by considering elastic anisotropy.

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