Eur. Phys. J. E (2006) 19: 119-128
https://doi.org/10.1140/epje/e2006-00016-5

Regular Articles

Substrate induced 1D tilt-modulated state in nematic monolayers

¹ 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

^* e-mail: ioannis.lelidis@u-picardie.fr

Received: 2 April 2004
Published online: 21 February 2006

Abstract

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.