Chiral hedgehog textures in two-dimensionalXY-like ordered domains

Abstract

The textures associated with a point defect centered in a circular domain of a thin film with XY-like ordering have been analyzed. The family of equilibrium textures, both stable and metastable, can be classified by a new radial topological number in addition to the winding number of the defect. Chiral textures are supported in an achiral system as a result of spontaneously broken chiral symmetry. Among these chiral textures, our theoretical analysis accurately describes two categories of recently discovered "reversing spiral" textures, ones that are energetically stable and metastable.

Collective Molecular Precession Induced by Rotating Illumination in Photosensitive Langmuir Monolayers

“…We had reported before 17 that this model failed to faithfully reproduce the inverse spiral textures that characterize trans- 8Az3COOH droplets in the size range considered here. In the description of similar textures in chiral smectic-C* films, the system free energy may include extra terms that are, in principle, allowed only for chiral systems. , In particular, a term in the boundary condition of the form β 2 sin( φ − α) would break the symmetry between boundary orientations that depart from the radial direction either in the sense or against the sense of the droplet chirality. The use of this term can be made compatible with the achiral nature of our compound if β 2 is, in fact, proportional to the droplet chirality (so that its sign will differ for CW and CCW droplets), similar to what is suggested by Fischer et al in ref .…”

“…Brewster angle microscopy (BAM) , image analysis was used to reveal changes in the mesoscopic molecular ordering . At equilibrium, these textures adopt a spiral configuration: − a bend distortion around the point singularity in the droplet center, gradually turning to a radial orientation (splay) toward the droplet boundary (Figure ). Given the achiral nature of the compound, an equal number of droplets with a clockwise (CW) and a counterclockwise (CCW) bend distortion can be observed.…”

Effect of Molecular Chirality on the Morphology of Biomimetic Langmuir Monolayers

“…The authors used this free energy functional to predict various chiral features in the textural motif and in particular the l phase, where the chiral symmetry is broken. A Landau free energy functional is also used to explain the chiral hedgehog textures in thin films …”

Textural transformations in islands on free standing smectic-C*liquid crystal films

“…The theoretical analysis of the stability of textures around topological defects has been investigated for Langmuir monolayers with a tilted phase and for free standing Sm C films [5,6,7,8]. Especially important, K. K. Loh et al [9] pointed out that there can be more than one stable or metastable texture for a point defect centered in a circular domain, and described the reversing spiral texture of a circular domain in a chiral system, which can be energetically stable or metastable. The remarkable growth of islands to an equilibrium size, once they are nucleated, is a consequence of their chirality and their resulting polar (ferroelectric) symmetry.…”