title: Field-induced superdiffusion and dynamical heterogeneity.
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 field-induced superdiffusion observed during a long preasymptotic regime 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 the presence of a pulling force ε,σ_{x}^{2}(t)=〈x_{ε}^{2}(t)〉-〈x_{ε}(t)〉^{2}∼t^{3/2}, which are accompanied by the asymptotic decay α_{ε}(t)∼t^{-1/2} of the non-Gaussian parameter from nontrivial 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.
authors.affiliation: Université Grenoble Alpes, LIPHY, F-38000 Grenoble, France.|CNRS, LIPHY, F-38000 Grenoble, France.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Gradenigo
authors.affiliation: Université Grenoble Alpes, LIPHY, F-38000 Grenoble, France.|CNRS, LIPHY, F-38000 Grenoble, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Bertin
authors.affiliation: IPhT, Université Paris Saclay, CEA, CNRS, F-91191 Gif-sur-Yvette Cedex, France.|Laboratoire de Physique Statistique, Ecole Normale Supérieure, PSL Research University, Université Paris Diderot Sorbonne Paris-Cité, Sorbonne Universités UPMC Université Paris 06, CNRS, 24 rue Lhomond, 75005 Paris, France.
authors.forename: Giulio
authors.initials: G
authors.lastname: Biroli