Substrate induced 1D tilt-modulated state in nematic monolayers
Dipartimento di Fisica del Politecnico and INFM corso Duca degli Abruzzi 24, 10129, Torino, Italy
2 Groupe des Cristaux Liquides, Université de Picardie, 33 rue Saint-Leu, 80039, Amiens Cedex, France
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Published online: 21 February 2006
Symmetry considerations yield the general form, up to second order terms, for the deformation elastic energy of a nematic monolayer, composed by symmetric achiral molecules, on a rigid planar substrate. The deformation energy contains an elastic contribution linear in the deformation tensor, whose elements are the spatial derivatives of the average molecular orientation. This linear Lifshitz-invariant-like term can be responsible for a ground state of the nematic monolayer periodically deformed if the relevant elastic constant is stiffer than a critical value. The wave-length of the modulation diverges at the transition threshold. We show that only large variations of the tilt angle form stable states. The effect of a destabilizing electric or magnetic field on the layer is to induce (i) the transition towards the tilt-modulated phase, while (ii) for higher enough values of the field the modulation is destroyed.
PACS: 61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order – / 68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces – / 83.10.Bb Kinematics of deformation and flow – / 83.60.Np Effects of electric and magnetic fields –
© EDP Sciences/Società Italiana di Fisica/Springer-Verlag, 2006