NBIA Colloquium – Niels Bohr Institute - University of Copenhagen

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NBIA Colloquium

Speaker: David Nelson (Harvard University)

Title: Theory of Topological Emulsions

Abstract:  Although rarely studied, two-dimensional XY models with extended orientational correlations can exhibit a strong first order phase transition to the disordered state. Motivated by the statistical physics of lipid rafts in lipid-bilayer vesicles and in the walls of living cells, we construct such a model and describe the associated phenomenon of defect-mediated emulsification at low temperatures. We consider two-dimensional dispersions of droplets of isotropic phase in a liquid with an XY-like order parameter, tilt, nematic, and hexatic symmetries being included. With strong anchoring boundary conditions, we find a continuous family of order parameter textures that mediate a universal droplet-droplet pair potential. Defect-mediated interactions between droplets lead to a preferred droplet separation and stabilize the emulsion.