GLASSES INSENSITIVE TO IRRADIATION OBSERVED FOR THE FIRST TIME

New research on glasses sheds light on the interaction between amorphous materials and photons. A collaboration between the Disordered Systems group (http s://disorderedsystems.dfa.unipd.it/) of the Department of Physics and Astronomy and scientists from the German synchrotron facility PETRA III - Deutsches Elektronen-Synchrotron (DESY) has unveiled how glasses prepared using different methods respond to irradiation with hard X-rays. The simultaneous study of the structural, dynamic, and thermodynamic modifications induced by photons suggests that X-rays can generate an elasto-plastic transition in glasses. This research indicates a pathway to develop glasses that are insensitive to irradiation, a characteristic that could promote the use of glasses' unique features in various fields. Although glasses are ubiquitous in our everyday lives, describing the glass transition and their properties remains one of the most challenging problems in condensed matter physics. As out-of-equilibrium materials, their experimental and computational investigation is particularly difficult, since their characteristics also depend on the specific thermal history of the sample, which determines its energy (i.e., its position in the potential energy landscape). Using a novel experimental setup, researchers have demonstrated that all glasses, regardless of their thermal history and stability, reach a unique state when irradiated. Remarkably, this state is stationary: once attained, it remains unaffected by further irradiation. These results are consistent with how the glass responds to external stimuli. Pristine glasses behave as elastic media, while irradiated ones exhibit a plastic response. Although the yielding transition is typically studied by evaluating the material's response to mechanical stress, it has been shown that it can also be achieved through the accumulation of plastic defects induced by interaction with high-energy photons. The yielding state is related to the material’s failure and is of obvious general interest in all applications where materials are subjected to stress. This new research explores the properties of the yielded state, emphasizing its resilience to external stimuli. It has been demonstrated that its properties remain unchanged under further irradiation, suggesting a similar phenomenology under mechanical stresses. These findings may lead to a paradigm shift. Traditionally, the pursuit of the most stable glass—one with minimal energy—has been driven by its exceptional entropic properties. However, the recent findings indicate that the yielded state, with its inherent stability, may offer even greater potential for applications. For instance, a glass in its yielded state appears to be an optimal choice for all environments where materials must maintain their properties under external stimuli.

The article has been published in Reports on Progress in Physics and is available online (DOI: 10.1088/1361-6633/ad91df)