Relaxation dynamics of stable glassesJavier Rodriguez-Viejo

The understanding of the glass transition remains incomplete after almost a century of intense investigation and debate. The conventional view is that the transition from glass to liquid appears as a dynamic process where atoms or molecules cooperatively relax into the equilibrium phase. In contrast to this picture, following fast temperature up-jumps above T_g, the emergence of liquid regions occurs in both liquid-cooled and vapor-deposited glasses provided the ratio between the relaxation time of the glass, τ_glass, and the alpha relaxation time, τ_α is sufficiently large [1,2]. At temperatures at which τ_glass/τ_α is large, high mobility regions directly transit into the liquid and subsequently grow by dynamic facilitation before – or while - cooperative glass relaxation sets into play. On the contrary, at temperatures associated with smaller τ_glass/τ_α the glass transition proceeds by cooperative relaxation dynamics all across the material. This behavior highly depends on the stability of the glass, since the time to transform the glass and the length scale between high mobility regions drastically changes with stability [3]. I will also discuss new evidences of the heterogeneous transformation of stable glasses by localized soft spots separated by giant length scales associated to dynamical heterogeneities in the glass and their growth by dynamic facilitation [4].