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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 30: Glasses and Glass Transition I (jointly with DY, DF)
CPP 30.6: Talk
Wednesday, March 16, 2011, 11:30–11:45, KÖN Farb
Lorentz-like power-law decay of velocity anti-correlations in a supercooled liquid — •Felix Höfling1 and Peter Colberg2,3 — 1Max-Planck-Institut für Metallforschung, Stuttgart, and Institut für Theoretische und Angewandte Physik, Universität Stuttgart — 2Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Canada — 3Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Köln
Harnessing the compute power of recent graphics processors, we have measured the velocity-autocorrelation function (VACF) in the supercooled Kob-Andersen mixture for large systems of 50,000 particles, providing data with an excellent signal-to-noise ratio. The emergence of glassy dynamics upon supercooling is systematically accompanied by a power-law decay of the VACF at intermediate times with exponent 5/2 and negative prefactor, similarly as observed recently for the hard sphere liquid (Williams et al., PRL 2006). Such anti-correlations are reminiscent of the well-known, universal long-time tail in the Lorentz model with the same exponent and sign. The role of dynamic heterogeneities for the power-law decay is addressed by considering correlation functions that are restricted to the most mobile or immobile particles. We find that the Lorentz-like decay is absent in the VACF of the most mobile particles and conclude that the power law is not a manifestation of dynamic heterogeneities. For the most immobile particles, however, the power-law decay is well pronounced and we propose that the relevant mechanism is given by repeated encounters with the quasi-arrested, microscopic particle cages.