Physics (Internal)

Study Hard Condensed Matter Physics in Soft Colloidal Crystals

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract: The beautiful colors of opal are due to the Bragg diffraction of visible light from the ordered array of tiny rock particles. One can make such synthetic opals using colloidal particles from polystyrene microspheres. These colloidal crystals are soft, easily deformable (e.g. using optical tweezers). They provide convenient model system for studying hard condensed matter physics. In this talk, I’ll discuss our ongoing research in 2D colloidal physics. As a highlight of this effort, we can make a point defect by hand (not literally) and observe in real time how a point defect of vacancy can be thermally excited into a pair of topological defects (edge dislocations). We also demonstrated the first realization of the random pinning problem in a 2D colloidal system. It is found that the “collective pinning” concept of Larkin-Imry-Ma provides an excellent description of the statics: a 2D colloidal crystal is indeed balkanized by random pinning. However, the driven dynamcs cannot be described by the “collective creep” model. A co-existence model is proposed to explain the observed phenomena.