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(326) Production(s) de BERTHIER L.
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Spatial correlations in the dynamics of glassforming liquids: Experimental determination of their temperature dependence 
Auteur(s): Dalle-Ferrier C., Thibierge C., Alba-Simionesco C., Berthier L., Biroli G., Bouchaud J.-P., Ladieu F., L’hôte D., Tarjus G.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 76 p.041510 (2007)
Texte intégral en Openaccess : 
Ref HAL: cea-01395180_v1
DOI: 10.1103/PhysRevE.76.041510
WoS: 000250621900078
Exporter : BibTex | endNote
192 Citations
Résumé: We use recently introduced three-point dynamic susceptibilities to obtain an experimental determination of the temperature evolution of the number of molecules N corr that are dynamically correlated during the structural relaxation of supercooled liquids. We first discuss in detail the physical content of three-point functions that relate the sensitivity of the averaged two-time dynamics to external control parameters such as temperature or density, as well as their connection to the more standard four-point dynamic susceptibility associated with dynamical heterogeneities. We then demonstrate that these functions can be experimentally determined with good precision. We gather available data to obtain the temperature dependence of N corr for a large number of supercooled liquids over a wide range of relaxation time scales from the glass transition up to the onset of slow dynamics. We find that N corr systematically grows when approaching the glass transition. It does so in a modest manner close to the glass transition, which is consistent with an activation-based picture of the dynamics in glassforming materials. For higher temperatures, there appears to be a regime where N corr behaves as a power-law of the relaxation time. Finally, we find that the dynamic response to density, while being smaller than the dynamic response to temperature, behaves similarly, in agreement with theoretical expectations.
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Activated aging dynamics and negative fluctuation-dissipation ratios
Auteur(s): Mayer Peter, Leonard Sébastien, Berthier L., Garrahan Juan P., Sollich Peter
(Article) Publié:
Physical Review Letters, vol. 96 p.030602 (2006)
Texte intégral en Openaccess : 
Ref HAL: hal-00115937_v1
PMID 16486676
Ref Arxiv: cond-mat/0508686
DOI: 10.1103/PhysRevLett.96.030602
WoS: 000234969300010
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
26 Citations
Résumé: In glassy materials aging proceeds at large times via thermal activation. We show that this can lead to negative dynamical response functions and novel and well-defined violations of the fluctuation-dissipation theorem, in particular, negative fluctuation-dissipation ratios. Our analysis is based on detailed theoretical and numerical results for the activated aging regime of simple kinetically constrained models. The results are relevant to a variety of physical situations such as aging in glass-formers, thermally activated domain growth and granular compaction.
Commentaires: 4 pages, 4 figs; v2 final version (minor modifs) published in Phys. Rev. Lett
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Fluctuation-dissipation relations in plaquette spin systems with multi-stage relaxation
Auteur(s): Jack R. L., Berthier L., Garrahan J.P.
(Article) Publié:
Journal Of Statistical Mechanics: Theory And Experiment, vol. P12005 p. (2006)
Résumé: We study ageing dynamics in two non-disordered spin models with multi-spin interactions, following a sudden quench to low temperature. The models are relevant to the physics of supercooled liquids. Their low temperature dynamics resemble those of kinetically constrained models, and obey dynamical scaling, controlled by zero-temperature critical points. Dynamics in both models are thermally activated, resulting in multi-stage relaxation towards equilibrium. We study several two-time correlation and response functions. We find that equilibrium fluctuation-dissipation relations are generically not satisfied during the ageing regime, but deviations from them are well described by fluctuationdissipation ratios, as found numerically in supercooled liquids. These ratios are purely dynamic objects, containing information about the nature of relaxation in the models. They are non-universal, and can even be negative as a result of activated dynamics. Thus, effective temperatures are not well defined in these models.
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Slow dynamics in glassy materials : insights from computer simulations
Auteur(s): Berthier L.
Conference: Summer school on complex systems (Les Houches, FR, 2006-08-03)
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Experimental evidence of growing lengthscales escorting the glass transition
Auteur(s): Berthier L.
Conference: The 2006 Berkeley mini stat mech meeting (, FR, 2006)
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Experimental evidence of growing lenghts cales escorting the glass transition
Auteur(s): Berthier L.
Conference: Relaxation dynamics of macroscopic systems (, FR, 2006)
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Structure, Dynamics and Gelation in a Transient Network Fluid
Auteur(s): Berthier L.
Conference: Workshop Cecam "Patchy Colloids Proteins and Network Froming Liquids (Lyon, France, FR, 2006-06-26)
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