Electric field induced order reconstruction in a nematic cell
Dipartimento di Fisica, Istituto Nazionale di Fisica della Materia, Universitá di Calabria, 87036, Rende, Cosenza, Italy
2 Laboratoire de Physique des Solides associé au CNRS (LA2), Université Paris Sud, 91405, Orsay Cedex, France
3 Department of Mathematics, University of Strathclyde, 26 Richmond Street, G1 1XH, Glasgow, UK
4 Dipartimento di Matematica, Istituto Nazionale di Fisica della Materia, Universitá di Pavia, Via Ferrata 1, 27100, Pavia, Italy
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We have experimentally observed the biaxial switching between two topologically distinct textures of a nematic liquid crystal cell submitted to a strong electric field. The effect is deduced from optical and electrical measurements across the cell. Above a static threshold, a bulk order reconstruction is observed, where the final nematic orientation in the centre becomes perpendicular to its initial one, inducing a total change of orientation across the cell. Using short electric field pulses, a higher dynamical threshold is observed. These experiments are explained by a Landau-de Gennes-Khalatnikov model. The threshold implies the local exchange of two eigenvalues of the nematic order tensor through intermediate biaxial states. The onset of the effect in a thin splay-bend wall decreases the static threshold by almost an order of magnitude. The model explains reasonably well the static and dynamic measurements within the present description of nematic biaxiality.
© EDP Sciences, Società Italiana di Fisica, and Springer-Verlag, 2004