Spatial correlations in the dynamics of glassforming liquids: Experimental determination of their temperature dependence

C. Dalle-Ferrier (1) , C. Thibierge (2) , C. Alba-Simionesco (1) , L. Berthier (3) , G. Biroli (4) , J.-P. Bouchaud (5, 6) , F. Ladieu (2, 6) , D. L’hôte (2) , G. Tarjus (7)

1 LCPO - Laboratoire de Chimie Physique D'Orsay
2 SPHYNX - Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes
3 L2C - Laboratoire Charles Coulomb
4 IPHT - Institut de Physique Théorique - UMR CNRS 3681
5 CFM - Capital Fund Management
6 SPEC - UMR3680 - Service de physique de l'état condensé
7 LPTMC - Laboratoire de Physique Théorique de la Matière Condensée

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.

Domaines: Physique [physics]

C. Dalle-Ferrier, C. Thibierge, C. Alba-Simionesco, L. Berthier, G. Biroli, et al.. Spatial correlations in the dynamics of glassforming liquids: Experimental determination of their temperature dependence. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2007, 76, pp.041510. ⟨10.1103/PhysRevE.76.041510⟩. ⟨cea-01395180⟩