EXPMFSG · Search for an experimental test of the mean-field theory of simple glasses

Search for an experimental test of the mean-field theory of simple glasses

The goal of my project was to provide a precise test for the recent mean field theory for simple glasses, first numerical, and at a second stage, experimental. Among the predictions of the theory, the most unexpected and relevant for the field was the prediction of a new phase transition inside the glass phase, separating two kinds of glasses: a standard glass, akin to a crystal, and a marginal one, akin to a spin glass, where vibrations would be strongly correlated both in time and space. This transition is known as the Gardner transition due to the analogy to the transition predicted by Gardner in certain models of spin glasses more than 30 years ago. While the existence of this transition in magnetic system was nothing more than a curiosity, it has attracted great attention in the field of glasses. The reason is simple, the mere existence of the new glass phase would provide a first-principles and universal explanation for the anomalies of amorphous solids with respect to the Debye theory of solids (i.e. the abundance of low energy modes, the ‘boson peak’, anomalous scalings with of the heat capacity or conductivity with the temperature, drastic and irreversible response to tiny perturbations, etc.), thus paving the way for the development of a theory for amorphous solids. This project has focused the attention in determining the existence of the Gardner transition in realistic systems, both in simulations and experiments. This task represented a great challenge three years ago, mainly because such a transition had never been observed, even though decades of intense investigation of these materials (even in the relevant parameter space).

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