Microscopic particle motions and topological defects in two dimensional hexatics and dense fluids*.

We have used time resolved digital imaging of uniform, charged polystyrene spheres in colloidal suspension confined between smooth glass plates to study in detail the nature of microscopic particle motions in equilibrium two dimensional dense fluid, hexatic, and crystalline phases near melting. Particle trajectories reveal the existence of dynamic ordered regions in the fluid and hexatic phases, with strongly correlated particle hopping near their borders associated with motions and rearrangements of overlapping elementary topological point defects.