Geometric view on colloidal interactions above the nematic-isotropic phase transition.

Particles dispersed in a liquid crystal above the nematic-isotropic phase transition are surrounded by a surface-induced nematic wetting layer. When the nematic coronas of two particles overlap, they experience a strong attraction since the volume of nematic ordering and therefore the free energy is reduced. For normal anchoring of the liquid-crystal molecules on the particles' surfaces, we demonstrate that the implementation of this geometric view reproduces the Yukawa interaction derived by Galatola and Fournier in a recent paper [Phys. Rev. Lett. 86, 3915 (2001)], however with half the strength. To understand the factor 2, we rederive the Yukawa potential with the approximation of linear superposition of two one-particle profiles. At the end, we comment on the similarities of our approach to the screened electrostatic interaction of charged colloids.