Sommaire:

Understanding physical aging in glasses is essential for building a detailed picture of the glass transition and discriminating among different theoretical models. Notwithstanding, due to experimental and numerical limitations, no data directly probing the dynamics of realistic molecular glasses at a microscopic level are available so far. Here, we provide the first experimental study of the evolution of the structural relaxation process in a metallic glass on the atomic length scale: using different cooling rates we observe a complex hierarchy of dynamic processes characterized by distinct aging regimes. We furthermore report evidence for a dynamical crossover between the metastable glassy state and the equilibrium liquid phase. Strong analogies with the aging dynamics of soft glassy materials, such as gels and concentrated colloidal suspensions, point at stress relaxation as a universal mechanism driving the relaxation dynamics of out-of-equilibrium systems.

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