DCMPMS Seminars


by Prof. Surajit Dhara (Department of Physics, University of Hyderabad, Hyderabad)

Monday, August 14, 2017 from to (Asia/Kolkata)
at AG69
Topological defects have been objects of intense studies in various disciplines starting from cosmology to condensed matter, optics and more recently in active matter. In liquid crystals (LCs) they are created during the isotropic to nematic phase transition. The defects can also be induced by dispersing foreign nano- and micro-particles in LCs. The embedded particles create elastic distortions in the LC medium inducing topological defects, and they interact via long-range anisotropic elastic forces so generated. These forces obviously have no analogues in regular colloidal systems in an isotropic dispersive medium. An interesting manifestation of such novel forces is the ability of the colloidal system to self-assemble. In an experiment, such a process can be conveniently guided to create 2d and 3d colloidal crystals, with complex architectures. In this talk we will briefly present some of our recent results on transformations of such topological defects associated with the colloidal particles, such as hyperbolic hedgehogs, Saturn-rings and boojums, across the nematic to mectic-A and smectic-C phase transitions. We show that the divergence of bend elastic constant and the emergence of smectic layering have profound effects on these defects, in terms of the colloidal pair-interactions and their resulting two-dimensional assemblies. Finally we will discuss driven active-colloids in which the motion of the colloidal particles is powered by externally applied electric fields.