Berlin 2012 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 12: Glasses II (joint session with DY)
CPP 12.3: Talk
Tuesday, March 27, 2012, 10:30–10:45, MA 004
Computer simulation of micro-rheology in glass-forming systems — David Winter1 and •Juergen Horbach2 — 1Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, 55099 Mainz, Germany — 2Institut für Theoretische Physik II, Heinrich Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
In the last ten years, micro-rheology has been established as a new tool to probe the non-linear response of soft-matter systems to external fields. In a micro-rheological experiment,single particles are pulled through a viscous medium by a constant or oscillatory force using, e.g., optical tweezers. In the work presented in this talk, the single-particle response to a constant external force of varying strength is investigated for a glass-forming Yukawa mixture using molecular dynamics computer simulation. Beyond linear response, a scaling regime is found where a force-temperature superposition principle of a Peclet number holds. In the latter regime, the diffusion dynamics perpendicular to the force can be mapped on the equilibrium dynamics in terms of an effective temperature whereas the diffusion coefficient parallel to the force does not exist. This behavior is associated with a hopping motion of the pulled particle from cage to cage and can be qualitatively understood by a simple trap model, as proposed by Bouchaud and coworkers.