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arXiv · 1604.02837

Field-induced superdiffusion and dynamical heterogeneity

Giacomo Gradenigo·Eric Bertin·Giulio Biroli
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Abstract

By analyzing two Kinetically Constrained Models of supercooled liquids we show that the anomalous transport of a driven tracer observed in supercooled liquids is another facet of the phenomenon of dynamical heterogeneity. We focus on the Fredrickson-Andersen and the Bertin-Bouchaud-Lequeux models. By numerical simulations and analytical arguments we demonstrate that the violation of the Stokes-Einstein relation and the observed field-induced superdiffusion have the same physical origin: while a fraction of probes do not move, others jump repeatedly because they are close to local mobile regions. The anomalous fluctuations observed out of equilibrium in presence of a pulling force $ε$, $σ_x^2(t) = \langle x_ε^2(t) \rangle - \langle x_ε(t) \rangle^2 \sim t^{3/2}$, which are accompanied by the asymptotic decay $α_ε(t)\sim t^{-1/2}$ of the non-Gaussian parameter from non-trivial values to zero, are due to the splitting of the probes population in the two (mobile and immobile) groups and to dynamical correlations, a mechanism expected to happen generically in supercooled liquids.

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Giacomo Gradenigo, Eric Bertin, Giulio Biroli. 2016-04-11. Field-induced superdiffusion and dynamical heterogeneity. https://doi.org/10.1103/physreve.93.060105

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