Rémi Barbet-Massin
Thèse soutenue le 29 avril 1985
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Structure et propriétés optiques de la Phase Bleue I
des cristaux liquides cholestériques
P. Pieranski, P. Cladis, R. Barbet-Massin
„Experimental evidence for a hexagonal blue phase“
J. de Phys. Lettres 46 (1985) L973
R. Barbet-Massin, P. Pieranski
„Blue phase one - 1st optical measurements of the order parameter“
J. de Physique Lettres 45 (1984): L799
P. Pieranski, P. E. Cladis, T. Garel, and R. Barbet-Massin.
"Orientation of crystals of blue phases by electric fields."
Journal de Physique 47, no. 1 (1986) 139-143.
Crystal shapes of Blue Phases
Crystal shapes of Blue Phases
Faceting of BPI crystallites observed in a reflecting microscope under monochromatic illumination. (a) Scheme of the setup. (b) Step on the {110} facet connected to a dislocation piercing the crystal. Its spiral shape indicates that the crystal is growing. (c) Nucleation and growth of a new terrace on the {110} facet. (d–f) Facetted BPI crystal seen along [200, 110] and [211] axes.
Orientation of Blue Phases by an electric field
Orientation of Blue Phases by an electric field
Expression of the dielectric polarisation induced by an electric field in crystals. Due to the cubic symmetries of Blue Phases I and II their second order dielectric susceptibility is isotropic. For symmetry reason, the third order susceptibility vanishes and the anisotropic part of the fourth order susceptibility can be written as:
where n1 n2 and n3 are unit vectors parallel to the fourfold axes Blue Phase crystals. As a result the torque exerted by the electric field E on polarisation P vanishes when E is parallel to the twofold, threefold and fourfold symmetry axes.
Stereographic projection of the stability diagram of Blue Phases with A>0
Orientation of crystals of BPII with fourfold axes parallel to the electric field indicates that the coefficient A is positive.
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