Giancarlo Jug

Abstract:

The vitreous state (bulk glasses and amorphous films) remains a challenging problem in physics owing to the lack of a regular crystalline background. Thus, most scientists approach this state from the liquid side, at high temperatures, where theoretical physics is quite well established. In this talk, I will present the embryo of an approach that looks at the glass transformation region from the low-temperature, solid-state side. I shall attempt, at the same time, to provide a reasonable description of the structure and ensuing physical properties of the glassy-state itself. This is mainly for silicates, but also for other classes of amorphous materials, including semiconductor films.
The surprising picture that is emerging is that the vitreous state appears to be a novel type of solid state, rather than a "dynamically arrested" liquid state, in that an amount of residual quasi-regular structure is still remaining in the highly-disordered medium. This is seen, however, only at the mesoscopic scale where the amorphous solid appears to be rather like a failed poly-crystalline medium. Important differences with true poly-crystalline solids is that, in-between the grains, there appear to be remnants of liquid-like regions and the grains themselves are only quasi-ordered.
This scenario is being investigated and developed by means of a phenomenological theory that takes its moves from the lowest temperatures phenomena, where bizarre magnetic effects have been reported which have been explained satisfactorily by means of this new theory. Presently, I have been able to conduct new experiments on glasses at temperatures up to 315 K and in a magnetic field. The analysis of the data corroborates the new approach and theory with surprising accuracy.
I will review this new theory and scenario, surveying the results obtained so far at the lower temperatures, and present the new results at higher temperatures. An embryo of the new approach's resulting description of the glass transformation will also be presented.

- G. Jug, M. Paliienko and S. Bonfanti, J. Non-Crystal. Solids 2014
- G. Jug, S. Bonfanti and W. Kob, Phil. Mag. 2016
- G. Jug, Ch. 13, Springer Book (A.V. Chalyi and L.A. Bulavin) 2018