Residual stresses and plasticity are well-known companions of all glassy materials. In the years, it was understood that macroscopic stress fields can be tuned to severely affect some physical properties of the material, like for example the strength in tempered glasses. Despite this, their nature at the microscopic length scale is still unclear: their behaviour is tightly linked to plasticity, i.e. local non-affine deformations that in glasses behave as stress sources coupled to the elasticity of the material. In this talk I will discuss recent X-Ray Photon Correlation Spectroscopy (XPCS) results exploring the interplay between plasticity, stress fields and the microscopic dynamics in very different systems i.e., colloidal and atomic glasses. In the colloidal system, I will show how the dynamics is dominated by residual stresses trapped-in during the preparation procedure, which give rise to a very rich phenomenology in the observed dynamical properties, as the presence of compressed relaxation functions, ballistic dynamics and dynamical heterogeneities [1]. In the second part of the talk, I will focus on oxide glasses illuminated with hard X-rays. I will show that the absorbed photons create point defects which behave as plastic regions, and their number is directly controlled by the delivered dose [2]. Following the atomic dynamics on different length-scales, I will show how the glass can behave both elastically and plastically, eventually reaching a state where the microscopic dynamical properties resemble that of a flowing system [2]. Finally, I will present a CNRS project aiming at pushing our understanding of plasticity at the microscopic length-scale. I will propose to leverage the properties of new thermo-sensitive colloidal glasses to investigate plastic activity for different level of glass equilibration (i.e., residual stresses) and external applied perturbations, combining cutting-edge experiments involving rheology, time- and space- resolved visible scattering and synchrotron-based X-ray photon correlation. [1] F. Dallari, A. Martinelli, et al., Sci. Adv. 6(12), eaaz2982 (2020). [2] A. Martinelli et al., Phys. Rev. X CR, 04LF31 (2023).

Carbon nanostructures as functional and sustainable device components

Controlling and detecting individual spins in solids is interesting for high-resolution magnetic resonance spectroscopy and quantum computing. I will present a new set of methods that we have recently developed to do so, at millikelvin temperatures. The key idea is to count the microwave photons that an electron spin emits after excitation, in complete analogy with optical fluorescence [1]. The spin radiative rate is enhanced via the spin Purcell effect, by coupling the spins to an on-chip planar superconducting microwave resonator [2]. Microwave photon counting is performed using a detector that we have developed and which is based on a superconducting transmon qubit [3]. We detect individual Er3+ spins in a CaWO4 crystal [4]. Using an electron spin, we sense individual 183W nuclear spins. We achieve nuclear spin readout, polarization, and coherent control [5]. The nuclear spins have seconds-long coherence times. We also develop new control methods based on stimulated Raman microwave drives. Using an Er3+ spin strongly coupled to two 183W spins, we demonstrate a two-nuclear-spin-qubit gate, and generate an entangled state with second-long lifetime [6]. [1] Albertinale et al., Nature 600, 434 (2021) [2] Bienfait et al., Nature 531, 74 (2016) [3] Balembois et al., PRApplied 21, 014043 (2024) [4] Wang et al., Nature 619, 276 (2023) [5] Travesedo et al., arXiv:2408.14282 [6] O'Sullivan et al., arxiv:24LF.LF432