Giulio Monaco

---

Illuminating an insulating or semiconducting glass using X-rays changes the properties of the glass, no matter what dose and dose-rates are used. The reason behind this is the complexity of the energy landscape of glasses, characterized by a huge number of different minima: during x-ray illumination the glass becomes an active system, powered by the absorbed energy, and explores this landscape. An x-ray illuminated glass becomes then the playground to study, under controlled conditions, phenomena which also appear in other contexts.
On the basis of x-ray scattering combined with nano-calorimetry experiments, I will discuss how x-ray irradiation can be used to prepare rejuvenated, high-enthalpy glasses [1,2]. In particular, while enthalpy increases with irradiation in a first stage, a sufficiently long irradiation results in a stationary state, independent of the initial state of the glass. The transition to this stationary state corresponds to the yielding transition, usually encountered in glasses under active dynamics as well as in stress-strain experiments [3]. In that context, a solid loaded beyond the yield stress loses its elastic properties and becomes plastic. Here, the yield point is reached by increasing the density of plastic regions by generation of point defects during x-ray irradiation. As the density of defects increases, the mechanical response of the glass changes from elastic to more and more plastic, until reaching the limit where it becomes the one characteristic of a flowing system, which signals that the yield point is reached.

References
[1] J. Baglioni et al., Rep. Prog. Phys. 87, 120503 (2024).
[2] J. Baglioni et al., Newton 2, 100338 (2026).
[3] A. Martinelli et al., Phys. Rev. X 13, 041031 (2023).

---

Universita' degli studi di Padova
PH2
Contact: Markus Grüninger / Matteo Cacco