Publications

2026

• EPR investigation of the radiation response of different types of germanosilicate optical fibers
  
  • Travailleur Allan
  • Fanetti Mattia
  • Ollier Nadège
  • de Noirfontaine Marie-Noëlle
  • Cavani Olivier
  • Girard Sylvain
  • Alessi Antonino
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2026, 581, pp.166342. In this study, we investigate through Electron Paramagnetic Resonance (EPR) measurements the radiation response of a set of multimode Telecom-grade optical fibers (OF) responding to the standards of ISO/IEC. The doping levels of these germanium-doped OFs have been adjusted to optimize their bandwidth and loss levels through controlling their refractive index profiles. The purpose of this paper is to understand if the modification of the manufacturing process changed their radiation response, through the radiation induced point defects. We irradiated those fiber samples with different types of particles (X, ɣ and e-) reaching different doses and dose rates. EPR spectroscopy was exploited to track the evolution of paramagnetic Ge-related point defects such as Ge(1), Ge(2), E´Ge and E´Si. Our results show that the concentrations of these defects do not depend drastically on the fiber type, suggesting that the applied changes in the manufacturing process have minor impact on their generation efficiencies under irradiation. However, we note a detectable difference of E´Ge induced concentration in one of the fibers up to a 45 %. This can be explained by the fact that there is a greater concentration of strain bonds in the silica network. (10.1016/j.nimb.2026.166342)
  DOI : 10.1016/j.nimb.2026.166342
• Competing regimes of charge-carrier and impurity scattering limiting phonon heat conduction in heavily-doped silicon
  
  • Sen Raja
  • Acosta Abanto Juan Carlos
  • Brouillard Mélanie
  • Gomès Séverine
  • Robillard Jean-François
  • Ciavatta Alessandro
  • Paulatto Lorenzo
  • Vast Nathalie
  • Saint-Martin Jérôme
  • Sjakste Jelena
  • Chapuis Pierre-Olivier
  , 2026. With respect to undoped semiconductors, thermal transport by phonons is limited by two additional mechanisms when doping increases: charge-carrier and impurity scattering. Previous works provided contradicting conclusions on the dominant doping-induced scattering mechanism in silicon. In this work, we clarify the competing roles of impurity and charge-carrier scatterings of phonons in the reduction of the lattice thermal conductivity in n-and p-doped silicon, by comparing experimental results obtained with the 3ω method and predictive DFT-based calculations for a large set of doping concentrations and a wide temperature range. The analysis allows delimiting the doping and temperature ranges where (i) extrinsic scattering surpasses intrinsic (phonon-phonon and phonon-isotope) one and (ii) one of the two doping-induced mechanisms plays the dominant role. We observe that the experimental setup impacts both the thermal conductivity value and the critical doping concentration at which the thermal conductivity is reduced by half.
• Spin-Hall devices: spin relaxation spatially separates current injection from Joule dissipation
  
  • Qiao Yanbo
  • Saati Sariah Al
  • Wegrowe Jean-Eric
  , 2026. The stationary state of a spin Hall bar connected to an external load circuit is investigated through a variational approach based on the principle of minimum power dissipation generalized to the two-spin-channel model. The self-consistent distributions of longitudinal and transverse current densities, alongside the corresponding spin and charge accumulations and dissipation power in the resistance, are derived. Surprisingly, it is shown that the Joule dissipation vanishes when the load resistance is placed at a sufficiently large distance compared with the spin-relaxation length. Such a highly non-trivial global stationary state appears as the most striking characteristic of the injection of pure spin current compared with more usual current injection.
• Wood and paper biomass fly ash physicochemical properties: focus on the amorphous fraction
  
  • Mériot Alexis
  • de Noirfontaine Marie-Noëlle
  • Courtial Mireille
  • Saoût Gwenn Le
  • Poussardin Victor
  • Brielles Nelly
  • Plassais Arnaud
  Advances in Cement Research, Thomas Telford, 2026, pp.1-13. To achieve zero net carbon dioxide (CO2) emissions by 2050, the search for new alternative materials to replace Portland clinker is urgent. Biomass fly ash (BFA) is one of the possible materials. Given the extremely high variability in the mineralogical, chemical and microstructural properties of these ashes, a large number of samples must be explored. This study presents a physicochemical characterisation of wood and paper BFA, offering guidelines for sample preparation and data analysis. Four BFAs were characterised using particle size analysis, specific gravity, Brunauer–Emmett–Teller (BET)-surface area analysis, total carbon analysis, scanning electron microscopy, X-ray fluorescence, thermogravimetric analysis and X-ray diffraction (XRD). The studied biomass ashes were found to contain more than 15 phases, with 30 wt.% of potentially reactive phases, including both crystalline and amorphous components. The chemical composition of the amorphous phase is estimated to lie between that of calcareous fly ash and blast-furnace slag. The correlation between the XRD amorphous hump position and the calcium oxide/(silicon dioxide + aluminium oxide) (CaO/(SiO2+Al2O3)) ratio of the amorphous phase is further refined within the calcareous fly ash domain. (10.1680/jadcr.26.00037)
  DOI : 10.1680/jadcr.26.00037
• Fingerprints of Excitonic Collective Modes in the Two-Dimensional Electron Gas
  
  • Wolff Jakob
  • Botti Silvana
  • Reining Lucia
  • Gatti Matteo
  Physical Review B, American Physical Society, 2026, 114 (23), pp.L231302. The two-dimensional homogeneous electron gas (2D HEG) is a prototype system of fundamental interest that can be realized experimentally over a wide range of densities. Here, we investigate its collective charge excitations at low densities, using time-dependent density functional theory. We demonstrate that, beyond traditional plasmons, new collective excitonic modes emerge for a Wigner-Seitz radius larger than rs ≈ 1. These excitonic modes leave characteristic fingerprints in experimentally accessible quantities, namely, asymmetric peak structures in the loss function and very strong Friedel-like oscillations in the static linear density response that increase when the system approaches a regime of instability. Indeed, at low enough densities the collective modes cross the zero energy axis, indicating an instability of the paramagnetic 2D HEG towards the formation of a charge-density-wave phase with excitonic origin. These findings provide valuable insights for the experimental detection of excitonic collective modes in tunable 2D electron systems and contribute to the fundamental understanding of many-body effects in low-density electron gases. (10.1103/2vyb-gzg9)
  DOI : 10.1103/2vyb-gzg9
• Unbiased Diffusion Monte Carlo for non local operators
  
  • Perez Carlos Rodriguez
  • Olevano Valerio
  • Sottile Francesco
  • Gorelov Vitaly
  , 2026. We propose a new mathematically exact method for computing unbiased Diffusion Monte Carlo (DMC) estimates of non-local operators. We demonstrate that the current state-of- the-art technique, Forward Walking, is only exact for local quantities and fails to yield unbiased results for the non-local components of reduced density matrices (RDMs). Our method significantly outperforms Forward Walking, as shown in two systems: in the symmetric Hubbard dimer it yields a pure 1RDM; while in the Helium atom it will give an unbiased 1RDM in the limits of zero time step and infinite walkers.
• Structural characterization of iodate and carbonate substituted calcium hydroxyapatites: insights from XRD, SEM, and TEM
  
  • Audouard Lisa
  • de Noirfontaine Marie‐noëlle
  • Courtial Mireille
  • Tusseau-Nenez Sandrine
  • Aubrit Florian
  • Dautain Olivier
  • Combes Christèle
  • Coumes Céline Cau Dit
  • Campayo Lionel
  Journal of the American Ceramic Society, Wiley, 2026, 109 (9), pp.e71164. This study investigates the structure and microstructure of hydroxyapatite substituted with iodate (IO$_3^−$) and/or carbonate (CO$_3^{2−}$) ions, within the context of long‐lived radionuclide waste conditioning. The role of the synthesis protocol, “reverse” or “direct” precipitation from aqueous solution, as well as the nature and amount of substituted anions on the structure and microstructure of hydroxyapatite samples, was evaluated using XRD, SEM, and HRTEM. The anisotropic crystallite shape assessed by HRTEM analyses was taken into account for the Rietveld refinements of the XRD patterns. Considering the reverse synthesis protocol, these refinements revealed the formation of a single hydroxyapatite phase. Despite the use of long counting times, no crystalline secondary phases were detected by XRD, regardless of the nature and amount of the substituting anions. Iodate ions substituting for A sites tend to expand the lattice, while carbonate ions located in B sites induce lattice contraction. Clearly, the influence of iodate substitution on the structural modifications is lower than that of carbonate substitution. Moreover, co‐substitution seems to modify the incorporation mode of iodate ions within the structure. The intended application of this work requires studying high substitution rates, thereby addressing gaps in the literature regarding the structural evolution of hydroxyapatite with increasing substitution rates. In this study, substitution levels reached up to 15.4 wt.% for iodate mono‐substitutions, 11.9 wt.% for carbonate mono‐substitutions, and approximately 20 wt.% for combined iodate and carbonate ions co‐substitutions. (10.1111/jace.71164)
  DOI : 10.1111/jace.71164
• Plasmonic metamaterial time crystal
  
  • Guo Tingwen
  • Sueiro Jules
  • Andolina Gian Marcello
  • Levchuk Artem
  • Ponzoni Stefano
  • Grasset Romain
  • Monthe Donald
  • Aupiais Ian
  • Daineka Dmitri
  • Briatico Javier
  • de Oliveira Thales Vag
  • Ponomaryov Alexey
  • Arshad Atiqa
  • Karimbana-Kandy Arjun
  • Prajapati Gulloo Lal
  • Ilyakov Igor
  • Deinert Jan-Christoph
  • Maehrlein Sebastian F
  • Perfetti Luca
  • Schirò Marco
  • Laplace Yannis
  Nature, Nature Publishing Group, 2026, 656 (8127), pp.343-348. (10.1038/s41586-026-10825-9)
  DOI : 10.1038/s41586-026-10825-9
• In Situ Growth of Vertically Aligned Gold Nanoparticles within Functionalized Polyvinylidene Fluoride Nanochannels for Optical Property Tuning
  
  • Aubrit Florian
  • Sigallon Marie
  • Oral Ozlem
  • Medjoubi Kadda
  • Clochard Marie-Claude
  ACS Omega, ACS Publications, 2026, 11 (28), pp.42297-42311. A solid synthetic pathway for the localized formation of vertically aligned and well-distributed individual gold nanoparticles (AuNPs) in transparent ion-track-etched polyvinylidene fluoride membranes is herein reported. After a successful preconcentration of the Au(III) precursor within the functionalized cylindrical nanochannels of these membranes, i.e., ion-track-etched radiografted with poly(4-vinylpyridine) (P4VP), a Au(IIII)-to-Au(0) chemical reduction was performed to in situ grow AuNPs inside the nanopores. Four classical reducing agents [ascorbic acid, hydroquinone, sodium citrate, and sodium borohydride (NaBH 4 )] were studied, which led, at first glance, to similar composites. The reducing power of each reducing agent has been shown to affect the AuNP nucleation and growth processes. At room temperature, the reduction led to the synthesis of well-dispersed AuNPs along the whole pore length, with the exception of sodium citrate, which was found to be too weak to reduce efficiently the gold precursor. When energy was provided to the system by operating the reaction at 70 °C, the reduction was boosted and the synthesis with sodium citrate gave similar results to those obtained with the other reducing agents at 20 °C, i.e., well-distributed AuNPs of around 30 nm of mean size. Increasing the number of reduction cycles resulted in an increase in AuNP size and, in the case of hydroquinone, in the elongation of the gold nanocrystals. This phenomenon was attributed to template-assisted AuNP growth in the nanopores. Despite the low amount of gold in the material (less than 0.2 %), the alignment of individual AuNPs all along the high aspect ratio nanopores (50:10,000) had a significant effect on the optical properties of the whole material, with the appearance of plasmonic properties for the nanocomposite membranes (λ plasmon around 530 nm) and a further decrease of the effective refractive index of the nanoporous membranes. (10.1021/acsomega.6c02970)
  DOI : 10.1021/acsomega.6c02970
• Rapport du projet EquipEnigme (IDF-DIM-MAP-2018-5-001)
  
  • Sottile Francesco
  , 2026. Le projet EquipEnigme a été conçu pour fournir le support technique et matériel nécessaire au projet scientifique "Enigme" (IDF-DIM-MAP-2017-1-009). Ce dernier porte sur l'étude et la description des propriétés optiques des halogénures d'argent, des composants fondamentaux ayant permis les premières photographies couleur réalisées par Edmond Becquerel. L'objectif principal était de pallier le manque de ressources de calcul spécifiques pour la génération de spectres optiques
• FD‐7 Dosimeters Irradiated in Different Radiation Environments: A Comparison Between Monte Carlo Simulations and Experiments
  
  • Avesani Matilde
  • Ferrari Matteo
  • Raj Mandal Aditya
  • Q. Aguiar Ygor
  • Garcia Alia Rubén
  • Gaillardin Marc
  • Poujols David
  • Alessi Antonino
  • Cavani Olivier
  • Girard Sylvain
  Physica Status Solidi A (applications and materials science), Wiley, 2026, 223 (8). This work presents a comparison between experimental data and Monte Carlo simulations realized with particle and heavy ion transport code system to evaluate radiation transport in commercial FD‐7 radiophotoluminescent (RPL) glass dosimeters exposed to different radiation environments. The analysis is performed for photon and electron, representative of experimental irradiation conditions encountered in research and industrial facilities where RPL dosimeters are employed. Photon sources include Co‐60 gamma rays, X‐ray tubes with tungsten targets operating at 100, 160, and 225 kV, and high‐energy photons produced by 6 MeV electrons impinging on a tungsten target. Monoenergetic electron beams of 2.5 and 6 MeV are also studied. For each configuration, the depth‐dose distributions within the RPL dosimeter are analyzed to evaluate dose homogeneity across the detector volume. Conversion factors between absorbed dose in RPL and reference materials commonly used in dosimetry, such as water, air, and silica, are calculated. Experimental data from various irradiation campaigns realized using the mentioned sources are presented and used to validate the simulation methodology. Agreement between simulated and measured doses is found, supporting the validity of the modeling approach. The results provide a tool to better design irradiation test campaigns and for the interpretation of RPL readouts in a variety of irradiation conditions. (10.1002/pssa.202500782)
  DOI : 10.1002/pssa.202500782
• Static and dynamic Monte Carlo simulations of phonon drag effects on thermoelectric properties in silicon nanostructures
  
  • Ghanem Mohammad
  • Dollfus Philippe
  • Sen Raja
  • Sjakste Jelena
  • Saint-Martin Jérôme
  Computational Materials Science, Elsevier, 2026, 268, pp.114630. Thermoelectric transport in silicon nanofilms is investigated using a self-consistent electro-thermal Monte Carlo simulator that couples electron dynamics to a phonon bath with spatially varying temperature. A key novelty of this work is the explicit inclusion of the phonon-drag contribution, implemented by modifying the electron-phonon momentum exchange based on the local deviation of the phonon distribution from equilibrium. The method is validated against bulk silicon data and extended to incorporate rough boundary scattering for both electrons and phonons, yielding excellent agreement with experimental measurements on nanofilms. We also analyze the transient regime and show that a temperature bias produces a slower current response than a voltage bias, although the phonon-drag effect itself tends to accelerate the response. These results demonstrate that the proposed framework provides a powerful tool for predicting both steady-state and time-dependent thermoelectric behavior in semiconductor nanostructures. (10.1016/j.commatsci.2026.114630)
  DOI : 10.1016/j.commatsci.2026.114630
• Potential of wollastonite-based brushite cement for the conditioning of radioactive waste contaminated by 90Sr
  
  • Jdaini Jihane
  • Cau Dit Coumes Céline
  • Barré Yves
  • de Noirfontaine Marie-Noëlle
  • Courtial Mireille
  Materials, MDPI, 2026, 19 (6), pp.1136. This work investigates the potential of wollastonite-based brushite cement (WBC) for the stabilization and solidification of radioactive waste contaminated by 90 Sr. This phosphate binder was formed by the reaction of wollastonite (CaSiO 3 ) with a phosphoric acid solution containing borax and metallic cations (Al 3+ , Zn 2+ ). Two cement pastes were investigated: a commercial binder (WBC-C) and an optimized formulation (WBC-O), produced using a zinc-free mixing solution with a higher aluminum content than that of WBC-C. Mineralogical characterizations using XRD, TGA, XRF, SEM-EDX, and Raman spectroscopy showed that both materials mainly contained amorphous hydrated silica and calcium aluminophosphate, along with crystalline brushite, residual wollastonite, and quartz. The stability of WBC-C under γ-irradiation was evaluated up to a dose of 1 MGy. The only observable effect was water radiolysis, leading to dihydrogen production at yields comparable to Portland cement matrices and geopolymers. Strontium leaching, assessed using the ANSI/ANS-16.1-2003 (R2008) procedure, followed a two-stage release mechanism combining surface wash-off and diffusion. The apparent diffusion coefficient D a of Sr in WBC-C was markedly lower than typical values reported for Portland cement matrices. WBC-O exhibited enhanced Sr retention, possibly due to its higher aluminum content, which refines mesopores and reduces diffusion pathways accessible to Sr. WBC binders therefore appear to be promising candidates for strontium immobilization. (10.3390/ma19061136)
  DOI : 10.3390/ma19061136
• Irradiation-resistant heterostructures based on monolayer MoS 2
  
  • Sangiorgi Emanuele
  • Migliore Francesca
  • Madonia Antonino
  • Alessi Antonino
  • Grasset Romain
  • Cavani Olivier
  • Panasci Salvatore Ethan
  • Schilirò Emanuela
  • Giannazzo Filippo
  • Seravalli Luca
  • Cannas Marco
  • Agnello Simonpietro
  Physica Status Solidi A (applications and materials science), Wiley, 2026. Monolayer molybdenum disulfide is a semiconducting 2D material presenting very appealing characteristics for its incorporation into electronic flexible devices. At present, atomic vacancies in its structure are known to significantly affect its properties. Nonetheless, the effects of electron irradiation on it are still under investigation. In this work, the structural, electronic, and optical properties of monolayer molybdenum disulfide are studied before and after electron irradiation. By analyzing samples either obtained via a mechanical exfoliation process or grown via chemical vapor deposition, we show that following irradiation no significant change is present. This result indicates a strong resistance to the effect of electron irradiation at energies able to induce the formation of sulfur vacancies. By comparing our results to the current literature, we hypothesize that previously reported effects of electron irradiation are either due to the formation of molybdenum vacancies or to ionization of the electronic shell of this material. The presented results help to shed light on the role of atomic vacancies on the properties of this 2D material from a fundamental point of view and on its usage in extreme environment applications. (10.1002/pssa.202500759)
  DOI : 10.1002/pssa.202500759
• 4D‐Printed Magneto‐Plasmonic Microrobots for Programmable Spatiotemporal De‐Icing
  
  • Pérot Amélie
  • Cosola Andrea
  • Aïdonidis Eléonore
  • Fresnais Jérôme
  • Sanchez Clément
  • Belleville Philippe
  • Rizza Giancarlo
  • Faustini Marco
  Advanced Functional Materials, Wiley, 2026, 36 (42), pp.e30657. <div><p>Icing poses a significant challenge in energy, transportation, and (soft) robotic applications, leading to disfunctions and efficiency losses. Traditional de‐icing methods are often energy‐intensive, non‐selective, or difficult to integrate with robotic and autonomous systems. Here, we introduce a 4D‐printing strategy that enables programmable spatio‐temporal de‐icing, providing an energy‐efficient pathway to precisely control when and where ice is removed at the millimeter scale. By integrating raspberry‐like gold–magnetite nanofillers into a photosensitive resin and employing a magnetic‐assisted Digital Light Processing (DLP), we align the fillers into oriented nanoparticle chains, producing anisotropic architectures with dual functionality: magnetic‐driven mobility actuation and plasmonic heating for localized thermal release. Hyperspectral analysis shows that the photothermal response can be finely tuned through plasmonic grafting density, while geometric programming governs the amplitude and spatial distribution of heating. As a demonstration of this multifunctional platform, we develop an autonomous icebreaking microrobot capable of navigating frozen landscapes while melting ice with pinpoint accuracy. This work introduces a new class of 4D‐printed magneto‐plasmonic materials enabling on‐demand phase‐transition control, opening opportunities for energy‐efficient de‐icing, adaptive soft robotics for extreme environments and time‐programmable devices.</p></div> (10.1002/adfm.202530657)
  DOI : 10.1002/adfm.202530657
• Interfacial thermal transport analysis using machine learning potential at AlN/Cu van der Waals interface
  
  • Wang Weitao
  • Wu Xin
  • Wu Yunhui
  • Volz Sebastian
  • Takagi Takeshi
  • Nomura Masahiro
  Materials Today Physics, Elsevier, 2026, 62, pp.102057. Three-dimensional integration is critical for next-generation integrated circuits, yet thermal management remains challenging due to complex interface environment. Owing to its high thermal conductivity, aluminum nitride (AlN) is a promising insulating layer for through-silicon via structures, yet its interfacial thermal behavior with copper (Cu) electrodes remains insufficiently understood. Here, we investigate phonon transport across non-bonded AlN-Cu interfaces governed by van der Waals (vdW) interactions using a machine learning potential (MLP) trained by density functional theory (DFT) data. The MLP accurately reproduces DFT-level phonon dispersion, energy-volume relationships, and interfacial binding energies. Non-equilibrium molecular dynamics simulations reveal total thermal resistance values of 10-14 m 2 K/GW at room temperature, approximately five times smaller than values obtained with empirical potentials and in excellent agreement with experimental data for similar semiconductormetal interfaces. Unlike empirical potentials, the MLP predicts increasing thermal resistance with temperature, attributed to phonon softening and vibrational mismatch. Spectral decomposition analyses confirm reduced phonon thermal conductance at elevated temperatures. This work provides fundamental insights into weakly bonded semiconductor-metal interfaces and guidance for thermal management in 3D integrated systems. (10.1016/j.mtphys.2026.102057)
  DOI : 10.1016/j.mtphys.2026.102057
• Combined Temperature and Photobleaching Effects on P‐Doped Optical Fibers
  
  • Travailleur Allan
  • Roche Martin
  • Alessi Antonino
  • Ollier Nadège
  • de Noirfontaine Marie‐noëlle
  • Girard Sylvain
  Physica Status Solidi A (applications and materials science), Wiley, 2026, 223 (5). In this paper, we investigate the combined effects of temperature and photobleaching (PB) on multimode phosphorus‐doped (P‐doped) optical fibers (OFs) response under irradiation. To achieve this purpose, we investigate the kinetics of the radiation‐induced attenuation (RIA) in the visible spectral range (450–800 nm) under X‐ray irradiation up to 5Gy(SiO 2 ) with a dose rate of 10 mGy(SiO 2 )/s, varying the temperature of irradiation from −80°C to +80°C. This study is part of a recent series of investigations on the regeneration of these radiation‐sensitive optical fibers after they have served as dosimeters. The spectral range investigated allows us to study absorbing defects such as the metastable and stable phosphorus oxygen hole centers (POHC) and the P2 point defects. Our data suggests that thermally‐assisted bleaching has an impact during and after irradiation on the RIA. It is clear that thermal bleaching is relevant, especially for wavelengths below 580 nm; its contribution remains minor compared to that of the PB by 408 nm laser. Furthermore, thermal bleaching appears to be negligible for wavelengths above 580 nm. This work provides further understanding of the combined temperature and photobleaching effects on the regeneration of transmission capability of P‐doped fiber dosimeters in the visible range. (10.1002/pssa.202500774)
  DOI : 10.1002/pssa.202500774
• Near-field thermal radiation between deep subwavelength membranes driven by corner and edge modes
  
  • Ordonez-Miranda Jose
  • Anufriev Roman
  • Liñán-Abanto Rafael
  • Coral Maelie
  • Nomura Masahiro
  • Volz Sebastian
  Journal of Applied Physics, American Institute of Physics, 2026, 139 (8), pp.085108. We demonstrate that the thermal radiation between deep subwavelength membranes of silicon carbide (SiC) exhibits a maximum enhancement over that of infinite SiC surfaces separated by the same vacuum gap. Based on fluctuational electrodynamics, we show that this enhancement occurs at a separation distance of 200nm and increases for thinner and colder membranes. This peak arises from the dominant contribution of electromagnetic modes localized at the corner and vertical edges of sufficiently thin membranes, which enable a strong coupling of surface phonon-polaritons appearing along their top and bottom surfaces. These resonant corner and edge modes effectively extend the emission cross-sectional area of the membranes over their geometrical one and, therefore, amplify their thermal radiation. For 10-nm-thick membranes of SiC at 300 K, the thermal conductance reaches 54 pWK−1, which yields a maximum enhancement of 4.5 over the value for infinite SiC surfaces. Our findings, thus, reveal that the regime of near-field thermal radiation driven by corner and edge modes emerges and is optimized in deep subwavelength membranes separated by intermediate distances. (10.1063/5.0311645)
  DOI : 10.1063/5.0311645
• Experimental study of spin pumping and spin-to-charge conversion in superconductor/ferromagnet heterostructures
  
  • Hassan Hadi H.
  , 2026. Superconducting spintronics" aims to merge dissipationless superconducting correlations with the spin degree of freedom of spintronics. Superconductor/Ferromagnet (S/F) bilayers constitute a simple superconducting spintronic device, and have been under study for years. The main focus so far has been on s-wave superconductors, meanwhile, high-Tc d-wave superconductors are more easily accessible thanks to critical temperatures (Tc) exceeding the boiling point of liquid nitrogen (77K). In this thesis, we leverage two experimental techniques to study multiple S/F heterostructures: ferromagnetic resonance (FMR) -driven spin pumping and spintronic terahertz emission. The first technique relies on exciting the magnetization of the ferromagnet, producing a spin current that diffuses into the adjacent materials, and probing its effect through optical and electrical responses. The second technique is based on an ultrafast demagnetization which drives a current of superdiffusive spin polarized hot electrons; when these hot electrons propagate in a material with high spin Hall angle, a transverse charge current is produced, emitting a THz electromagnetic pulse. We use an s-wave superconductor (MoSi) and a d-wave cuprate (YBCO), with either an insulating ferrimagnet (YIG) or metallic ferromagnets (Py, LSMO, CoFeB). We started by comparing YIG/MoSi bilayers with a YBCO/Py: both systems show a drop of the Gilbert damping at the superconducting transition, consistent with the conventional picture stating that the opening of superconducting gap suppresses the quasiparticle spin sink in the superconductor. YBCO/Py shows nevertheless an upturn in the damping at low temperatures, as reported by S. J. Carreira et al. (2021), linked to the emergence of Andreev bound states at faceted interfaces. When we probe the electrical response of lithographically patterned bilayers of YIG/MoSi and YBCO/Py, both systems share a behavior that appears to be universal: transverse voltages, odd in magnetic field reversal, exhibit a large increase across the superconducting transition, with varying intensity as a function of the superconductor's thickness, reaching up to two orders of magnitude higher than the normal-state voltages. The evidenced decrease of spin pumping across the superconducting transition exclude spin Hall conversion as the mechanism behind the simultaneous voltage increase. We propose a theoretical explanation of the anomalous voltage peak based on the superconducting diode effect, in collaboration with A. Buzdin et al.. We pushed our FMR study into half-metallic ferromagnets in YBCO/LSMO bilayers, which exhibit an upturn in the damping below Tc instead of a drop. Thanks to the atomically abrupt interface of these bilayers, we interpret the damping increase as a successful access to unconventional superconducting spin sinking channels, notably interface-bound quasiparticles and spin triplet correlations. Finally, we demonstrated the feasibility of d-wave-superconductor/spintronic-terahertz-emitter (YBCO/Pt/CoFeB) heterostructures through a thin film structure optimization. Exploratory THz emission and transmission measurements show promising preliminary results of the superconducting proximity effect on the THz emission of superconducting terahertz emitters. Overall, this manuscript argues for a shift from bulk-material selection toward interface engineering as the primary lever in superconducting spintronic devices. (10.70675/bf2c3f04z8a99z403dz9430z2386565c6065)
  DOI : 10.70675/bf2c3f04z8a99z403dz9430z2386565c6065
• A short derivation of Boltzmann distribution and Gibbs entropy formula from the fundamental postulate
  
  • Lairez Didier
  , 2022. Introducing the Boltzmann distribution very early in a statistical thermodynamics course (in the spirit of Feynmann) has many didactic advantages, in particular that of easily deriving the Gibbs entropy formula. In this note, a short derivation is proposed from the fundamental postulate of statistical mechanics and basics calculations accessible to undergraduate students. (10.48550/arXiv.2211.02455)
  DOI : 10.48550/arXiv.2211.02455
• Energy and Information:a Chronicle of Hesitations on the Role of the Observer in Physics
  
  • Lairez Didier
  , 2025. Energy has no definition, except that given by a conservation principle which essentially amounts to defining it as the elements of an open list of unknown cardinality. Entropy, identified by Shannon as information we lack, has too many definitions. This results in an unstable and hesitant interpretation of their link. Thermodynamics, the science of changes in form of energy, is phenomenological, all its laws are induced from observation. From the origin, the concept of energy is linked to the observer's knowledge, to the information he has: what and where to look and with what instruments. Thermodynamics only addresses the sensible world. It is Aristotelian. But this is disturbing if we consider that reason can give us access to Plato's intelligible world, the one that is beyond the sensible world and independent of us. This is disturbing if we consider that science can access to the intrinsic properties of things, those which are independent of us. This is disturbing if we have a purely Platonic conception of science. Hence the statistical mechanics approach ("The rational foundation of thermodynamics", J.W. Gibbs). This is the first pendulum movement of ideas, whose oscillations continue to this day, because unfortunately statistical mechanics introduces many inconsistencies, mainly due to the ergodic hypothesis. Luckily, these inconsistencies are all solved by Shannon's information theory. Sadly, information theory is too Aristotelian and too conceptual. Fortunately, Landauer principle makes it more \textquote{physical}. This is currently the latest attempt to bringing the notions of energy and information back to what is considered the right side of science, that of Plato. Landauer principle is now commonly regarded as a fundamental law of physics. Unpleasantly, it can be shown that this principle is not one. (10.20944/preprints202505.2245.v1)
  DOI : 10.20944/preprints202505.2245.v1
• Electron charge dynamics and charge separation: A response theory approach
  
  • Lacombe Lionel
  • Reining Lucia
  • Gorelov Vitaly
  SciPost Physics, SciPost Foundation, 2026, 20 (2), pp.035. This study applies response theory to investigate electron charge dynamics, with a particular focus on charge separation. We analytically assess the strengths and limitations of linear and quadratic response theories in describing charge density and current, illustrated by a model that simulates charge transfer systems. While linear response accurately captures optical properties, the quadratic response contains the minimal ingredients required to describe charge dynamics and separation. Notably, it closely matches exact time propagation results in some regime that we identify. We propose and test several approximations to the quadratic response and explore the influence of higher-order terms and the effect of on-site and nearest-neighbour interactions U U and V V . (10.21468/SciPostPhys.20.2.035)
  DOI : 10.21468/SciPostPhys.20.2.035
• Unraveling energy flow mechanisms in semiconductors by ultrafast spectroscopy: Germanium as a case study
  
  • Raciti Grazia
  • Abad Begoña
  • Dettori Riccardo
  • Sen Raja
  • K. Sivan Aswathi
  • Sojo-Gordillo Jose M
  • Vast Nathalie
  • Rurali Riccardo
  • Melis Claudio
  • Sjakste Jelena
  • Zardo Ilaria
  Advanced Science, Wiley Open Access, 2026, pp.e15470. Semiconductor materials are the foundation of modern electronics, and their functionality is dictated by the interactions between fundamental excitations occurring on (sub-)picosecond timescales. Using time-resolved Raman spectroscopy and transient reflectivity measurements, we shed light on the ultrafast dynamics in germanium. We observe an increase in the optical phonon temperature in the first few picoseconds, driven by the energy transfer from photoexcited holes, and the subsequent decay into acoustic phonons through anharmonic coupling. Moreover, the temperature, Raman frequency, and linewidth of this phonon mode show strikingly different decay dynamics. This difference was ascribed to the local thermal strain generated by the ultrafast excitation. We also observe Brillouin oscillations, given by a strain pulse traveling through germanium, whose damping is correlated to the optical phonon mode. These findings, supported by density functional theory and molecular dynamics simulations, provide a better understanding of the energy dissipation mechanisms in semiconductors. (10.1002/advs.202515470)
  DOI : 10.1002/advs.202515470
• Effective residual interaction kernel approach for optical spectra
  
  • Aichner Marc
  • Gatti Matteo
  • Reining Lucia
  Physical Review Letters, American Physical Society, 2026, 137 (12), pp.126901. Excitonic effects dominate absorption and loss spectra in many materials. However, they are hard to access computationally, because of the cost of first-principles calculations and because of the scarce reliability of simple approximations. We overcome both limitations by combining a part of the electron-hole Bethe-Salpeter equation with an effective scalar interaction. The partitioning is motivated by the general form of the electron-hole interaction and it can be applied to all materials. First-principles calculations for prototypical semiconductors and insulators demonstrate a speedup of 1 to 2 orders of magnitude for results close to those where the full interaction matrix is used. The method is systematic and can be converged to the benchmark (10.1103/nk3g-crbw)
  DOI : 10.1103/nk3g-crbw
• About Carrier's Self‐Trapping and Dynamical Rashba Splitting in the 2D Hybrid Perovskite (BA)₂(MA)₂Pb₃l₁₀
  
  • Qi Weiyan
  • Ponzoni Stefano
  • Huitric Guénolé
  • Gorelov Vitaly
  • Pramanik Ashim
  • Laplace Yannis
  • Marsi Marino
  • Papalazarou Evangelos
  • Maehrlein Sebastian
  • Deleporte Emmanuelle
  • Mallik Nitin
  • Taleb-Ibrahimi Amina
  • Bendounan Azzedine
  • Zheng Kaibo
  • Pullerits Tönu
  • Perfetti Luca
  Small, Wiley-VCH Verlag, 2026, 22 (17). Time‐ and Angle‐Resolved Photoelectron Spectroscopy (tr‐ARPES) is employed to monitor photoexcited electrons in the 2D hybrid perovskite (BA)₂(MA)₂Pb₃l₁₀. Photoelectron intensity maps are in good agreement with ab‐initio calculations of the band structure. The effective mass is −0.18±0.02<i>m_e</i> and 0.12±0.02<i>m_e</i> for holes and electrons, respectively. In the photoexcited state, spin‐orbit splitting of the conduction band cannot be resolved. This sets the upper bound of photoinduced Rashba coupling to eVÅ. The correlated electron‐hole plasma evolves in Wannier excitons with Bohr radius of 2.8 nm, while no sign of self‐trapping in small polarons is found within the investigated time window of up to 120 ps following photoexcitation. (10.1002/smll.202511410)
  DOI : 10.1002/smll.202511410