Regensburg 2013 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Poster: Colloids and Complex Liquids

CPP 20.20: Poster

Tuesday, March 12, 2013, 18:15–20:15, Poster C

Friction of colloidal monolayers on a periodic substrate — •Christoph July, Thomas Bohlein, and Clemens Bechinger — 2. physikalisches Institut, Universität Stuttgart

Friction is an ubiquitous and fundamental phenomenon in our every day life. While its precise control is highly desirable for technical applications, a comprehensive understanding of friction is still lacking. On the macroscopic level asperities mediate a partial contact between two surfaces leading to the well known static and dynamic friction. However, many interesting friction effects only happen on an atomic scale. Friction phenomena of sliding atomic monolayers in this regime are theoretically described by the Frenkel-Kontrova model. One particular effect, that is predicted by this theory, is the so called Aubry-Transition. This transition gives rise to a jump from static friction to a superlubric state (frictionless) between two incommensurate monolayers as the interaction between the atoms of a single monolayer grows in strength and exceeds a critical value. Yet systems of nano meter size are very hard to observe experimentally. To overcome this difficulty we devised a colloidal model system to emulate the nanoscopic world, enabling us to measure nano tribologic effects with microscopic particles. For this purpose we employ para-magnetic particles, which allow us to tune the particle-particle interaction by applying an external magnetic field. Monolayers of these particles are situated on a potential landscape generated by a light field and pulled across this periodic substrate. In doing so, we are able to directly observe the Aubry transition for the first time.