ELFT HÍRADÓ

[Szeminárium koordinátor <szfi-seminar AT wigner.mta.hu>]

WIGNER SZFI Seminar

Multistability in confined nematic systems: analytical and numerical approaches

Apala Majumdar
Multistability in confined nematic systems: analytical and numerical approaches (host: Buka Ágnes)

Tuesday, 12 June 2018 10:00, KFKI Campus, Bldg. 1, 2nd floor, Conference Room

Nematic liquid crystals are classical examples of mesogenic materials that combine the fluidity of liquids with a degree of long range orientational order or "special directions". Nematics in confinement offer exciting possibilities for pattern formation, topological singularities and multistability or multiple stable states without any external fields. These multiple stable states typically arise from geometrical, boundary and topological constraints.

As an example, we mathematically model nematic equilibria or stable states in square or rectangular wells with tangent/planar boundary conditions, motivated by recent experiments, within the powerful Landau-de Gennes theory which can account for uniaxiality, biaxiality and variable order. We numerically reproduce the experimentally observed diagonal and rotated states and find a new "Well Order Reconstruction Solution" not previously reported in the literature. This Well Order Reconstruction Solution (WORS) is featured by an uniaxial cross with negative order parameter connecting the four square vertices, which can be regarded as a pair of intersecting defect lines. The WORS exists for all square sizes, is globally stable for nano-scale wells and loses stability with respect to the diagonal and rotated states for larger micron-scale wells. We numerically find 21 different critical points, some of which are unstable but may be stabilised by appropriate control variables. We also study the effect of isotropic inclusions on the solution landscape and classify solutions into three different families according to the number of degrees of freedom. In other words, the simple square geometry is an ideal playground to study multistability analytically, numerically and experimentally. This is joint work with a number of collaborators - Samo Kralj, Giacomo Canevari, Amy Spicer, Yiwei Wang, Chong Luo, Martin Robinson, Patrick Farrell and Radek Erban.
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Everyone is welcome to attend.

János Asbóth
szfi-seminar AT wigner.mta.hu