Sommaire:

Glasses and supercooled liquids are examples of frustrated systems: their characteristically slow dynamics and high viscosities are often thought as being linked to the impossibility for the constituents to satisfy local geometrical constraints at a global scale. Starting from experimental evidence in colloidal glasses, I will show that an analysis of local geometrical motifs in real space allows us to identify signatures of an emergent non-crystalline local order in an exceptionally deeply supercooled regime [1]. To understand how such emerging features affect the frustration of supercooled liquids, I will rationalise the experimental evidence with numerical models studied within the framework of large deviations of structural-dynamical observables [2]. First, I will show that an accurate measure of the fluctuations contains deep dynamical and thermodynamical information on very low temperature equilibrium states. Then, I will report the results for three distinct models of glass-formers analysed within this framework [2,3,4], for which slow dynamics corresponds to phase coexistence in an augmented dynamical space, with a non-trivial temperature dependence that allows us to reinterpret a variety of scenarios for the low-temperature behaviour of supercooled liquids in terms of amorphous-to-amorphous transitions.

[1] J. E. Hallett, F. Turci, C. P. Royall, Local structure in deeply supercooled liquids exhibits growing lengthscales and dynamical correlations. To appear in Nature Communications (2018).
[2] F. Turci, C. P. Royall, T. Speck, Non-equilibrium phase transition in an atomistic glassformer: The connection to thermodynamics, Phys. Rev. X 7, 031028 (2017)
[3] F. Turci and coworkers, Experimental evidence for a structural-dynamical transition in trajectory space, Phys. Rev. Lett. 119, 028004, (2017)
[4] F. Turci, T. Speck and C. P. Royall, Structural-dynamical transition in the Wahnström mixture. EPJ E 41: 54 (2018).

Pour plus d'informations, merci de contacter Coslovich D.