Thursday,
August 14, 2008 - 4:00 P.M., NSH 202
Colloidal structures in confined nematic liquid crystals are described. Theoretical predictions based on phenomenological approaches are contrasted with the latest experimental studies. Effective inter-colloidal couplings in a nematic solvent lead to numerous colloidal structures not present in simple liquids. First we describe 2D lattices of colloidal particles coupled by localized defects [1]. Their strong dependences on the confinement and external fields are illustrated. Particularly interesting are colloidal structures where particles are coupled by an entangled network of singular or nonsingular disclination loops. Sharing of disclination loops leads to string-like and allows formation of colloidal dimers, chains, and braids [2]. The resulting robust colloidal structures open new ways to the assembling of photonic materials and metamaterials.
[1] Two-dimensional Nematic Colloidal Crystals Self-assembled by Topological Defects, I. Musevic, M. Skarabot, M. Ravnik, U. Tkalec, S. Zumer, Science 313, 954 (2006).
[2] Entangled Nematic Colloidal Dimers and Wires, M. Ravnik, M. Skarabot, S. Zumer, U. Tkalec, I. Poberaj, D. Babic, N. Osterman, and I. Musevic, Phys. Rev. Lett. 99, 247801 (2007).
Slobodan Zumer received his B.Sc. and Ph.D. from the University of Ljubljana where he also continued his career. For several years he was adjunct professor at Kent State University. He is presently the Professor of Physics at the University of Ljubljana and the Head of the research program Physics of soft matter, surfaces, and nanostructures at Josef Stefan Institute, Ljubljana, Slovenia. His research interests are modeling, simulations, and theory of soft matter systems that include liquid crystals, polymers, nematic elastomers, colloids, etc. In 2008 he also started a 4-year term as a President of the International Liquid Crystal Society.