Imperfections in Focal Conic Domains: the Role of Dislocations

Maurice Kleman (1) , Claire Meyer (2) , Yuriy A. Nastyshyn (3)

1 IMPMC - Institut de minéralogie et de physique des milieux condensés
2 LPMC - Laboratoire de Physique de la Matière Condensée - UR UPJV 2081
3 Institute of Physical Optics

It is usual to think of Focal Conic Domains (FCD) as perfect geometric constructions in which the layers are folded into Dupin cyclides, about an ellipse and a hyperbola that are conjugate. This ideal picture is often far from reality. We have investigated in detail the FCDs in several materials that have a transition from a smectic A (SmA) to a nematic phase (N). The ellipse and the hyperbola are seldom perfect, and the FCD textures also suffer large transformations (in shape or/and in nature) when approaching the transition to the nematic phase, or appear imperfect on cooling from the nematic phase. We interpret these imperfections as due to the interaction of FCDs with dislocations. We analyze theoretically the general principles subtending the interaction mechanisms between FCDs and finite Burgers vector dislocations, namely the formation of \textit{kinks} on disclinations, to which dislocations are attached, and we present models relating to some experimental results. Whereas the principles of the interactions are very general, their realizations can differ widely in function of the boundary conditions.

Keywords: Physical Sciences

Maurice Kleman, Claire Meyer, Yuriy A. Nastyshyn. Imperfections in Focal Conic Domains: the Role of Dislocations. Philosophical Magazine, 2006, 86 (28), pp.4439-4458. ⟨10.1080/14786430600724496⟩. ⟨hal-00513699⟩