Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 16: Poster: Colloids and Complex Liquids

CPP 16.1: Poster

Tuesday, March 27, 2012, 18:15–20:45, Poster A

Directional locking of colloidal monolayers driven across quasiperiodic substrate potentials — •Thomas Bohlein and Clemens Bechinger — 2. Physikalisches Institut, Universität Stuttgart, Germany

Particles driven across an ordered potential energy surface may either follow the direction of the driving force or become entrained along any of the commensurate directions of the substrate. Such directional locking effects are of great technological relevance since they allow sorting of particles according to their size or refractive index. In recent numerical simulations it was predicted that kinetically locked-in states also occur on quasiperiodic potential landscapes which raises the question whether periodicity or long range order of the substrate is the essential ingredient for directional locking. Here we experimentally study the sliding behavior of a two dimensional colloidal monolayer interacting with quasiperiodic light induced substrate potentials. When the direction of the driving is varied with respect to the substrate, we find directional locking at angles corresponding to the symmetry axes of the underlying potential. On the locking steps the colloids exhibit a cooperative, kink-driven particle motion and assemble into dynamically ordered structures.