Elettra Highlights 2024–2025
ELETTRA HIGHLIGHTS 2024 | 2025 Editorial committee Matteo Amati Valentina Bonanni Wibke Bronsch Marcello Coreno Maja de' Simoni Simone Di Mitri Paola Di Pietro Lara Gigli Luisa Napolitano Silvia Nappini Emiliano Principi Nadia Sambraello Browse the Elettra Highlights digital collection here
Introduction.............................................................................. 6 Functional materials Operando study reveals reaction pathways for direct methane activation on CuO/CeO2 green catalysts. . 10 Three-dimensional mapping of the altermagnetic spin splitting in CrSb . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Measuringelectron’squantumgeometry....................................................14 Designer graphene: High and uniform atomic-level transition metal substitution achieved. . . . . . . . . . . 16 Chemistry for microelectronics: how photoresists for extreme ultraviolet lithography work atthemolecularlevel................................................................... 18 Thermal response of graphene oxide and silver-functionalized graphene oxide loaded withperfluorinatedcompounds.......................................................... 20 Ligand conformation dictates function in 2D metal-organic frameworks. . . . . . . . . . . . . . . . . . . . . . . . . . 22 Spatial SAXS mapping of humidity-induced Pt3Co catalyst degradation inpolymerelectrolytefuelcells........................................................... 24 Reversible low-pressure CO₂ capture and release using flexible metal-organic framework films .. . . . . . 26 Revealing the Early-Stage Reduction Mechanism of ZnO Nanorods for Zinc-Ion Batteries.. . . . . . . . . . . 28 Design of sustainable plastics: a multi-technique characterization of tannin-furanic foams . . . . . . . . . . 30 Pressure induced electronic topological transitions in BiTe driven by metavalent bonding. . . . . . . . . . . 32 Magnetizing Silicon: doping dependent spin polarization at Ni/Si interfaces . . . . . . . . . . . . . . . . . . . . . . 34 Terahertz driven nanosecond dynamics of oxygen defect state in anatase TiO2−x................... 36 Tracking ultrafast charge transfer in thermite reactions with femtosecond EUV pulses. . . . . . . . . . . . . . 38 Low density and soft matter The Ion Chemistry of Methanol and Oxygen: A Path to HO₂ and protonated Formaldehyde. . . . . . . . . . . .42 Soft x-ray Hanle effect: A century old technique, rediscovered with x-rays.. . . . . . . . . . . . . . . . . . . . . . . 44 Lipid phase behaviour in plasma membranes: an overlooked determinant of membrane function.. . . . . 46 Crystals in resonance: how a low-frequency vibration triggers structural change.. . . . . . . . . . . . . . . . . . 48 Controlling quantum dynamics with shaped extreme ultraviolet pulses.. . . . . . . . . . . . . . . . . . . . . . . . . . 50 Life Science and cultural heritage How whey proteins aggregates: Uncovering amyloid formation in mixed systems. . . . . . . . . . . . . . . . . . .54 Multianalytical investigation reveals psychotropic substances in a Ptolemaic Egyptian vase . . . . . . . . . 56 Characterisation of covalent inhibition of 3CLpro from SARS-CoV-2 by halicin. . . . . . . . . . . . . . . . . . . . . 58 X-ray phase-contrast microtomography to monitor revascularization in ovarian tissue transplantation. 60 Micro-CT scanning sheds light on the cranial anatomy and unusual diet of theprehistoric crocodilian Acynodon adriaticus............................................ 62 A closer look at the toxicity mechanisms of erionite, one of the major natural carcinogens. . . . . . . . . . . 64 Nanoparticles in the lungs: a new study reveals the molecular mechanisms at play.. . . . . . . . . . . . . . . . 66 Bone mineral disruption in osteosarcoma revealed by micro-computed tomography andx-raydiffraction.................................................................... 68 Selective Structural Tuning Enables Mutagenic Base Deamination in Mycobacteria.. . . . . . . . . . . . . . . . 70 Targetingofourendocannabinoidsystemintherapy.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Table of contents
Structure and Dynamics Revealing working principles of perovskite nanowire devices: ion migration and redox reactions.. . . . . 76 Shedding light on carbon atomic wires growth with real-time in situ UV Raman spectroscopy. . . . . . . . .78 Turning noise into insight: Ultrafast pump-probe phase-randomized tomography . . . . . . . . . . . . . . . . . . 80 Giant band engineering in superlattices with rotation-symmetry-mismatched interfaces. . . . . . . . . . . . 82 Unraveling the secret of Ir-Ru catalysts for water electrolysis: Why are they so activeandyetsodurable?............................................................... 84 Tracking the magnetization dynamics of a magnetic vortex by magnetic helicoidal dichroism . . . . . . . . 86 Fundamental spatial limits of all-optical magnetization switching............................... 88 Control of nanoscale spin waves with spatially tailored extreme ultraviolet pulses.. . . . . . . . . . . . . . . . . 90 Self-inducednonlinearopticsintheXUVregime............................................. 92 Strain-enhanced charge order in a kagome metal unveiled by time-resolved optical spectroscopy. . . . 94 Full-solid-state electrolytes for aluminum batteries based on aluminated ammonium oxofluorotitanates...................................................................... 96 Structural evolution of manganese prussian blue analogue in aqueous ZnSO4 electrolyte.. . . . . . . . . . . 98 Surfaces and Interfaces Seeding the vertical growth of coordination polymers on rutile via pyridyl/M(II)-TTPs axial binding.. . 102 From localized states to dispersive bands in hierarchically grown 2D metal-organic frameworks..... 104 Reversible surface catalysis through ferroionic design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 Enhanced stability of Li ion batteries through surface modification and electron structure design.. . . 108 Probingnanoporouscoppercatalystlayersunderbias.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110 An innovative platform for NO2 detection for cleaner air and safer cities.. . . . . . . . . . . . . . . . . . . . . . . . . 112 Cracking the catalyst code: How tiny platinum clusters could power the hydrogen economy . . . . . . . . . 114 Caging molecular spins into 2D arrays: Protecting azafullerene radicals with nanohoop templates . . . . 116 Dual charge transfer process stabilizes the electronic properties of a 2D metal-organic framework.. . . 118 Challenging the oxidation state paradigm at the sub-nanometric scale.. . . . . . . . . . . . . . . . . . . . . . . . . 120 Oxygen adsorption limited to the uppermost atomic layer in in ultrasmall Pt clusters.. . . . . . . . . . . . . . 122 Friction without resistance: Directional superlubricity and Lévy flights in 2D nanostructures........ 124 ThepeculiarcaseofgraphenegrowthonCo(100).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Crystalline modification in AgI thin films loaded with Ag nanoparticles by laser beam irradiation . . . . . 128 The basal plane of graphene grown on nickel dissociates water molecules.. . . . . . . . . . . . . . . . . . . . . . 130 Europium’s effect: Unlocking spintronic potential in graphene.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Tuning surface enhanced Raman spectroscopy effect in porous ZIF-67/R6G systembyexternalpressure............................................................. 134
Photon sources and instrumentation Experimental photon e- yield from Rashid lunar rover at BABE-AHEAD: input for space chargemodeling...................................................................... 138 Coherent synchrotron radiation instability in low-emittance electron storage rings.. . . . . . . . . . . . . . . 140 Elettra 2.0, a technology driver for basic and applied science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 ElettraParameters..................................................................... 144 Elettra2.0........................................................................... 146 Multimodal Soft x-ray Microscopy: Integrating AFM, XRF, and STXM in a novel in-vacuum system . . . . 148 Transverse polarisation structure in extreme-ultraviolet light.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 Elliptically polarized free-electron laser pulses enable L-edge dichroism in magnetic metals. . . . . . . . 152 FERMI Status Report................................................................... 154 Shaping light to uncover hidden light–matter interactions at the nanoscale. . . . . . . . . . . . . . . . . . . . . . 156 Fact & Figures / Events Elettra and FERMI lightsources .......................................................... 160 Shareholders..........................................................................161 PartnershipsandAlliances...............................................................161 Organization......................................................................... 162 Staff................................................................................ 163 Budgetallocation2025................................................................. 163 ProjectsandInternationalInitiatives...................................................... 164 Ongoingresearchcontracts............................................................. 165 Ourbeamlines,laboratoriesandservices.................................................. 167 ProposalReviewPanels................................................................ 168 Users at Elettra and FERMI.............................................................. 169 ICTdevelopmentsforElettra2.0andbeyond................................................170 CERIC-ERIC...........................................................................172 IndustrialLiaisonOfficeNews............................................................174 Revolutionizing Insertion Device Design and Manufacturing at Kyma S.p.A.: ACutting-EdgeApproach................................................................175 InstitutionalVisitsandEvents............................................................176 Meetings,WorkshopsandSchools........................................................178 ScienceDiplomacyandCollaborativeNetworks............................................. 180 HeadingtoElettra2.0.................................................................. 182 PublicEngagementEvents.............................................................. 184 OtherNews.......................................................................... 186 Elettra Fellows.........................................................................187 Fonda Fasella Award....................................................................187
Alfonso Franciosi President and CEO Elettra-Sincrotrone Trieste S.C.p.A. This publication reporting our activities for 2024-2025 includes contributions from work performed at the Elettra third generation synchrotron radiation facility, at the FERMI free-electron laser (FEL) facility and at a number of support laboratories collected in the same thematic sections. Scientific articles published in the last year stemming from work performed at such facilities reached a total of 533, 34 of which were based on the use of FERMI. Due to the typical lag (1.5-2 years) with which publications follow experiments, a decline of approximately 10% compared to the annual scientific productivity of 2019-2022 only partially reflects the 40% reduction in the operation of Elettra and FERMI in 2023 and 2024 caused by rising energy costs. The energy situation will improve with the new Elettra 2.0 light source coming into operation, which will consume 20% less energy than the Elettra. source The Elettra 2.0 machine, belonging to the 4th generation diffraction-limited storage ring (DLSR) class, will be housed in the existing tunnel and utilize the existing injection system, in order to minimize the required infrastructural changes, cost and installation time. Its design adopts an enhanced symmetric 6-bend achromat lattice that will allow us to achieve an horizontal bare emittance of 212 pm.rad at 2.4 GeV, i.e., 50 times lower than the present Elettra value, with a 60fold increase in the coherence fraction at 1 keV. The brilliance will increase by more than 2 orders of magnitude at 10 keV. The Elettra source has operated throughout the first semester of 2025 offering to our users 2232 hours of beamtime (i.e., 45% of the normal yearly beamtime) on 24 beamlines and was turned off for the last time on July 3rd, 2025. Removal of the Elettra components has been completed, while installation of the Elettra 2.0 components and new beamlines will continue during the "dark period". The new Elettra 2.0 source will start commissioning at the beginning of September 2026. Commissioning of the beamlines will commence in mid-November. A fist call for proposal for user experiments will be published in September 2026, and the opening of the new facility to external users will take place in January 2027 with a first set of 15 operating beamlines. The number of operating beamlines will increase to 18 by the end of 2027, to 24 by the end of 2028 and to 30 by the end of 2029. During the "dark period" Elettra users can access several new or improved off-line facilities by submitting experimental proposals to specific peer-review subpanels. The new IUVS 2.0 Laboratory is allowing inelastic scattering experiments in the ultraviolet (UV) range previously performed at the IUVS beamline to continue with substantially improved signal-to-noise ratio and resolution using a number of tunable and fixed-energy laser sources. A finely tunable UV resonance Raman (UVRR) set-up operates in the 191-315 nm and 350-475 nm wavelength ranges and will be upgraded in order to reach wavelengths below 190 nm. A second, micro-UVRR station with excitation provided by 213 nm, 224 nm and 266 nm wavelength lasers allows users to perform spatially-resolved studies with μm lateral resolution. Finally, an integrated portable deep-UV (248 nm) Raman instrument is available to perform experiments in a Biological Safety Level 3 (BSL3) facility. The upgraded SISSI off-line infrared (IR) facility is enabling users to conduct Fourier-transform infrared (FTIR) imaging studies of large sample areas, also exploiting an IR tomographic setup, and sub-micrometer IR imaging of a large variety of both thin and thick samples by optical photothermal infrared (O-PTIR) correlated with Raman and fluorescence microscopy. The endstation for IR microscopy with nanometer lateral resolution continues to be operational with conventional laser source. In addition, a portable interferometer equipped with attenuated total reflection (ATR) and non-contact reflection modules is available to perform experiments on pathogens in a BSL3 facility. The number of proposals that is being received for the use of the IUVS 2.0 and SISSI off-line facilities compares well with the number of proposals that the two corresponding Elettra beamlies used to receive. The upgraded TomoLab X-ray micro computed tomography (micro-CT) facility is offering users two different micro-CT scanners and experimental set-ups. TOMO 1 is a conventional device operating in the 40-130 kVp range for 20 mmX30 mm samples, using an air-cooled sCMOS detector to yield micro-CT scans with 5-15 μm voxel size. TOMO 2 is a more complex and more flexible set-up that will reach 190 kVp, employ a variety of detectors (linear single-photon counting, large
area flat panel, high resolution sCMOS) and will enable the implementation of different scan modalities (helical and planar CT scans, as well as mosaic) for large samples with 15-100 μm voxel size. In collaboration with two Institutes of the Italian National Research Council (CNR), a new cryogenic electron microscopy (cryo-EM) facility will be available to external users in the second semester of 2026. The facility will include a Glacios 2 cryogenic transmission electron microscope (cryo-TEM) with energy filter and an Aquilos 2 cryogenic focused ion beam (cryo-FIB) facility. Interested users will be able to apply also for the support of our upgraded Structural Biology Laboratory for protein expression, purification, crystallization, and additional biophysical/biochemical protein characterization. In addition, a new high-speed, high-spatial-resolution atomic force microscope (AFM) is available in our NanoInnovatioLab for dynamic studies of hydrated biosystems, integrated with a high-throughput nanoindenter for mechanobiology of cells and tissues. The program to upgrade beamlines and experimental stations to fully exploit the capabilities of the new Elettra 2.0 source continued thoughout 20242025, giving priority to the activities of Phases 1 and 2 of the upgrade plan, namely those to be completed before the start of the "dark period" and those planned during the "dark period". The new experimental station of the Spectromicroscopy line has become operational for users. The new experimental station of the BaDElPh beamline has been installed on the VUV line managed by CNR-ISM, where the research groups of the two beamlines have started a joint user support program. The GasPhase line has been removed from its current location and placed in its final position where it will form the basis of the low-energy branch of the new MOST beamline for atomic and molecular physics. The new diffractometer of the MCX line for powder diffraction was received from the manufacturer. Construction of the new short undulators for the ALOISA and TwinMic beamlines has begun. The tender for the construction of the beam transport for the new beamlines fed by in-vacuum undulators (μXRD, μXRF, HB-SAXS) has been completed and the selected manufacturer will deliver the first beamline in 2026. An agreement has been signed between Elettra Sincrotrone Trieste, TU-Graz (Austria), and the Universities of Maribor and Primorska (Slovenia) for the construction of the new HB-SAXS beamline, designed for small-angle scattering experiments and other techniques with very bright and highly coherent beams even in the hard-ray energy range. The design of the new Coherent Diffraction Imaging (CDI) beamline was completed in collaboration with the NSLS-II optical team under an agreement between Elettra Sincrotrone Trieste and the U.S. Department of Energy (DOE) and all of the components of the new beamline have been ordered. The CDI beamline will be dedicated to the study of electronic phenomena in quantum solids and to the nanoscale visualization of the structure and internal composition of multifunctional and magnetic materials using scattering and coherent imaging techniques in the soft X-ray spectral range. Throughout 2025 and 2026 our users will be able to fully exploit the FERMI free-electron laser (FEL) facility, with a record-breaking number of hours of user beamtime (more than 6200 per year) expected and an ambitious target of 35 user experiments scheduled each year, all of them with a repetition rate of 50 Hz. FERMI currently is the only FEL source in the world that consistently exploits the external seeding method to offer unparalleled intensity, wavelength and linewidth stability. Last year FEL-1 in the new Echo Enabled Harmonic Generation (EEHG) mode was used in user experiments that were able to take advantage of the characteristics of particular spectral cleanliness and stability in a spectral range previously available only with FEL-2. FEL-1 in the new EEHG configuration allowed us to gain experience with this scheme, which is more complex to fine-tune than the one related to the original FERMI design. FEL-1 was also used in the first preparatory studies for the upgrade to FERMI 2.0. In 2024, a fourth harmonic input seed injection scheme was implemented. This allowed the spectral range of FERMI to be extended up to the nitrogen K-edge, although for the moment only on discrete seed harmonics. Among the outstanding results of the scientific program at FERMI, we mention the demonstration of the possibility of conducting quantum control experiments
using far-ultraviolet beams at the LDM beamline. At the TIMEX experimental station, thanks to the use of a pulsed electron beam, it was possible to measure the effect of FEL irradiation on a gold crystal, observing for the first time an ultrafast recrystallization of the system induced by vibrational modes generated by FERMI pulses. At the DiProI station, the evolution of surface acoustic waves generated by the interaction of infrared pulses was characterized as a function of the transferred momentum. The possibility of controlling these acoustic waves at the nanoscale is particularly significant for applications in electronic circuits such as filters, oscillators, and transformers based on acoustic wave transduction. At the TIMER beamline, experiments were performed with the transient grating set-up using two beams with orthogonal polarization. This allowed us to produce a helical response of the magnetic system under investigation, highlighting the fact that nonlinear optics experiments have a greater sensitivity than classical spectroscopies in the study of chiral systems. Finally, a Green Energy project with the objective of mitigating the impact of the high energy cost on the operation of the Elettra 2.0 and FERMI light sources was launched in 2025. The project envisages the construction of a solar farm with a power output of 8.8 MWp in a disused quarry. The photovoltaic system will consist of approximately 13,000 latest-generation bifacial photovoltaic modules, 27 inverters, and 3 transformer substations and will be connected to the Elettra Sincrotrone Trieste site by a 20 kV medium-voltage underground cable conduit approximately 4.2 km long, allowing for maximum photovoltaic production with a reliable connection and low environmental and landscape impact. The Green Energy Project is a strategic initiative capable of reducing energy dependence on fossil fuels, revitalizing a decommissioned site, and strengthening the scientific competitiveness of Elettra Sincrotrone Trieste, with environmental, economic, and social benefits at both the regional and national levels. Over the 25-30 years of operation, the facility will reduce CO2 emissions by approximately 120,000 tons. We take this opportunity to thank all of our employees and collaborators, our Partners and our users for their continuing support of our activities during the energy-related crisis and The "dark period", as well as for their enthusiasm and dedication over the years. Alfonso Franciosi President and CEO Elettra-Sincrotrone Trieste S.C.p.A.
Functional materials
Elettra | APE-HE The direct activation of methane at low temperatures remains a major challenge in catalysis due to the molecule’s high stability and strong C–H bond dissociation energy. Conventional processes require high temperatures and are often non-selective, leading to total oxidation of methane with consequent production of undesired products (carbon dioxide and water). In this context, the development of real catalysts that enable low-temperature methane activation, ideally through scalable and sustainable synthesis routes, is a critical research goal. In fact, at low temperature partial oxidation reaction pathways are possible, leading to the production of precious chemicals such as methanol or formaldehyde. In particular, methanol is considered nowadays fundamental in the context of the energy transition, due to its high potentialities to be employed as hydrogen liquid carrier and for industrial purposes. In this study, we report the synthesis, characterization, and mechanistic investigation of a copper-cerium mixed oxide catalyst (M-CuO/CeO2) prepared by ball milling method, a solvent-free, cheap and straightforward synthetic approach. Copper-Ceria formulations have indeed gained considerable attention through the years for their good catalytic activity in environmental reactions such as the oxidation of Volatile Organic Compounds (VOCs), water gas shift reaction and CO preferential Oxidation. The favorable characteristics of these systems, combined with the lower cost compared to noble metal-based catalysts, pushed scientific research toward identifying the specific catalytic active sites/interfaces responsible for the good catalytic performance. The catalyst synthesized in this work demonstrated activity for methane activation at temperatures as low as 250 °C, significantly lower than those typically required for such reactions, and shows stability over multiple redox cycles. A similar composite (I-CuO/CeO2) synthesized with a conventional impregnation method was also analyzed for comparison, in order to elucidate the origin of this peculiar catalytic activity. The success of this study was empowered by the use of a multi-technique approach comprising forefront spectroscopic techniques, possible thanks to the joint collaboration between different research institutes of Friuli Venezia Giulia (CNRIOM, Elettra Synchrotron, University of Udine, University of Trieste and Area Science Park). The standard ex situ characterization techniques used to investigate the main features of the materials revealed comparable morphological and structural/reduction properties between the ball milled and impregnated composites. However, the combined operando Near Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS) and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) investigation probed a considerably distinct surface reactivity for the two composites under actual operating conditions. At a temperature of 250 °C, the impregnated catalyst was indeed unable to activate methane, and resulted to be inactive for partial oxidation. Conversely, the ball-milled composite showed methane activation capabilities. The origin of this behavior was elucidated by NEXAFS spectroscopy (performed at APE-HE beamline) combined with DFT calculations, which indicated a net charge transfer occurring from CeO2 to CuO surfaces following the ball milling process and the thermal activation. The material exhibits specific reactive interfaces that are absent in the conventional impregnated catalyst and whose formation is likely to be favored by the mechanical energy supplied during milling (Fig. 1). The key factor was found to be the high concentration of Ce3+ ions (provided by the use of a high surface area CeO2 as a precursor for the milled composite), aided by the mechanical action provided by milling, effectively enhancing the Ce → Cu charge transfer, as also demonstrated by DFT calculations. The In situ DRIFT investigation showed that methane is adsorbed on the catalyst surface on reactive oxygen atoms, in the form of methane oxidation intermediates CxHyO2 (Fig. 2), leading to the formation of partial and total oxidation products, detected by the micro-GC directly connected to the operando NEXAFS reaction cell during the exposure of the sample to an oxidizing atmosphere. At the same time, during CH4 exposure NEXAFS spectra of Cu reveals the formation of Cu+ sites, a further validation of methane activation on the surface (Fig. 3). The desorption of products promoted by O2 restores the initial electronic configuration of the catalyst surface, allowing more cycles to be carried out without deactivation (Figs. 2,3). The in-depth spectroscopic investigation under real catalytic conditions coupled with DFT calculations has demonstrated to be fundamental in identifying the reaction active sites and in describing the reaction mechanism. These were oxygen atoms located close to the CeO2/CuO interface, able to activate the methane molecule (Fig. 1), which is consequently adsorbed on another O atom of the interface. The oxidizing agent (O2) acts as a promoter for the products desorption, refilling the created oxygen vacancies and thus recovering the initial catalyst surface. These results could help to pave the way to the design of more robust catalytic systems prepared by sustainable mechanical routes and highlight the role of mechanical activation of interfaces offering a valuable tool for catalyst engineering. Operando study reveals reaction pathways for direct methane activation on CuO/CeO2 green catalysts Elettra Highlights 2024–2025 10
Functional materials S. Mauri1, R. Calligaro2, C.F. Pauletti3, M.F. Camellone1, M. Boaro2, L. Braglia1,4, S. Fabris1, S. Piccinin1, P. Torelli1, A. Trovarelli2 1 CNR-IOM, Laboratorio TASC, Trieste, Italy 2 Università degli Studi di Udine, Dipartimento Politecnico, via del Cotonificio 108, 33100 Udine, and INSTM- University of Udine Research Unity, Udine, Italy 3 Università degli Studi di Trieste, Dipartimento di Fisica, via Alfonso Valerio 2, 34127 Trieste, Italy 4 AREA Science Park, Padriciano 99, I-34149 Trieste, Italy e-mail: mauri@iom.cnr.it; alessandro.trovarelli@uniud.it Acknowledgments This work was performed in the framework of the Nanoscience Foundry and Fine Analysis (NFFA-M UR Italy Progetti lnternazionali) facility (https:// www.trieste.nffa.eu/). L.B. acknowledges the (PNR) grant (J95F2100283000l) with the title "FAIR-by-Design". Original paper S. Mauri et al., Small 20, 2403028 (2024); DOI: 10.1002/smll.202403028. Figure 2. In-situ DRIFTS data acquired during two subsequent catalytic cycles. Step 1: He+CH4, Step 2: He, Step 3: He+O2. m = methoxy group; f = formate group. Figure 3. Operando NEXAFS data acquired during two subsequent catalytic cycles. Step 1: He+CH4, Step 2: He, Step 3: He+O2. Figure 1. Graphical representation of the CuO/CeO2 interface in the ball milled composites. Ce → Cu charge transfer occurring during the ball milling process takes to the formation of reactive O atoms able to activate the methane molecule. Fig. 3 Fig. 1 Fig. 2 Elettra Highlights 2024–2025 11
Elettra | APE-LE Three-dimensional mapping of the altermagnetic spin splitting in CrSb For decades, ferromagnetism and antiferromagnetism have been regarded as the two most fundamental types of magnetic orders. A novel type of collinear magnetism, dubbed altermagnetism, has recently attracted considerable interest in the field of condensed matter physics. In the absence of Spin-Orbit Coupling (SOC), altermagnets exhibit antiparallel collinear spin configuration with zero net magnetization. Unlike conventional antiferromagnets, the spin-opposite sublattices in altermagnets cannot be mapped onto each other by either realspace translation or inversion, lifting the Kramers spin degeneracy and resulting in momentum-dependent spin splitting in the band structure. The altermagnetic spin splitting originates from the interplay between crystal field and magnetic exchange interactions, which can have energy scales on the order of electron-volts (eV), enabling a wide range of exotic phenomena such as the anomalous Hall effect, spin current generation, spin caloritronics and etc.. Moreover, the absence of net magnetization makes altermagnets attractive for ultrafast spin manipulation and high-density, strayfield-free spintronic devices. The key physical manifestations of altermagnets originate from their anisotropic spin-polarized band structure. In this study, using synchrotron-based and spin-resolved Angle-Resolved Photoemission Spectroscopy (ARPES), we uncover a large altermagnetic splitting in CrSb with bulk-type g-wave character. CrSb crystallizes in the hexagonal NiAstype structure, as shown in Fig. 1 (a). The magnetic Cr (aligned along the [001] axis) are parallel within the hexagonal Cr layer and antiparallel between neighboring layers. As illustrated in Fig. 1 (b), the two Cr sublattices with opposite spins in CrSb are related by a spin group symmetry [C2 || Mz] or [C2 || C6z ]. Here C2 is the spin-flip operation, and Mz and C6z are the mirror operation and six-fold rotation along z axis combined with a translation t = (0,0, )c, both only acting in real space. Both the spin group symmetries [C2 || t] and [T || P] (space-time reversal) are broken in CrSb, resulting in momentumdependent altermagnetic spin splitting, unlike conventional antiferromagnets. The special spin group symmetry results in four spin-degenerate nodal planes labeled in Fig. 1 (c), referring to the bulk-type g-wave altermagnetism. The kz-dependent band splitting indicates the ”bulk-type” nature in CrSb, related to its [C2 || Mz] symmetry. We observed the largest altermagnetic spin splitting in CrSb near Fermi level, shown Fig. 1 (d). Its secondary derivative is shown in Fig. 1 (e): two sets of hole bands centered at Γ can be verified with an energy splitting up to 1.0 eV near EF, consistent with Density Functional Theory (DFT) calculations in Fig. 1 (f). The kx-kz map at E = -0.5 eV is shown in Fig. 1 (g): Along the P − Q path, the altermagnetic splitting, i.e., the separation between these two strings, is close to zero at kz = 0 and gradually increases to its maximal value at kz ~ 0.25c*, eventually decreasing to zero at kz = 0.5c*. The in-plane momentum dependence of the band splitting provides direct evidence for the g-wave altermagnetism in CrSb. Fig. 1 (h) shows the kx-ky map at E = -0.65 eV taken at kz ~ 0.28c* plane, where the flower-like pockets centered at Γ can be observed. The constant-energy contours from ab initio calculations are overlaid on top, consistent with the experimental data. To verify the spin polarization of the altermagnetically split bands, spinresolved ARPES measurements were conducted in BL9.2 APE-LE, Elettra. The spin-up/down distribution curves are shown in Fig. 1 (i), taken along the white dashed cut in Fig. 1 (e). Both curves exhibit a double-peak structure with large broadening. The obvious shifting of the peak center between these two curves reflects the spin splittings expected in CrSb. The corresponding spin polarization is extracted and shown in Fig. 1 (j). Our direct observation of appreciable spin polarization provides strong support for the altermagnetic spin splittings in CrSb. Moreover, our Tight-Binding (TB) model analysis indicates that the large altermagnetic splitting arises from strong Third-Nearest-Neighbor (3NN) hopping mediated by Sb ions. Both the Nearest Neighbor (NN) and the Next Nearest Neighbor (NNN) hopping terms preserve the translational spin-flip operation [C2 || t], thus incapable of lifting the Kramers spin degeneracy. By contrast, the second-order hopping process assisted by Sb 5p orbitals provides relatively large 3NN hopping parameters (q1,2,3,4), giving the large altermagnetic splitting. The spin polarized bands obtained from TB model and its dependence on 3NN parameters is shown in Figs. 1 (k-m). In summary, we present direct spectroscopic evidence of bulk-type g-wave altermagnetism in CrSb from high-resolution synchrotron-based and spin-resolved ARPES measurements. Our systematic kz and in-plane momentum dependent study confirms a large altermagnetic splitting up to 1.0 eV near EF, which is in good agreements with DFT. The spin polarization of split bands is further verified by spin-resolved ARPES measurements. Our TB model analysis reveals that the altermagnetic splitting arises mainly from the 3NN hopping of Cr 3d electrons mediated by Sb 5p orbitals, highlighting the important role of electronic coupling between magnetic and nonmagnetic ions. The insight can be important for finding/ tuning altermagnetic materials with enhanced properties. The large altermagnetic splitting near EF, together with the high ordering temperature up to 710 K in CrSb, paves the way for exploring emergent phenomena and practical applications based on altermagnets. Elettra Highlights 2024–2025 12
Functional materials G.W. Yang1, Z.H. Li2, S. Yang3, J.Y. Li3, H. Zheng1, W.F. Zhu1, Z. Pan1, Y.F. Xu1 S.Z. Cao1, W.X. Zhao4, A. Jana5,6, J.W. Zhang1, M. Ye7, Y. Song1, L.H. Hu1 L.X. Yang4, J. Fujii5, I. Vobornik5, M. Shi1, H.Q. Yuan1,8, Y.J. Zhang3, Y.F. Xu1, Y. Liu1,8 1 Center for Correlated Matter and School of Physics, Zhejiang University, Hangzhou, China 2 Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing, China 3 Hubei Key Laboratory of Photoelectric Materials and Devices, Hubei Normal University, Huangshi, China 4 State Key Laboratory of Low Dimensional Quantum Physics, Tsinghua University, Beijing, China 5 CNR-IOM, TASC Laboratory, Trieste, Italy 6 International Center for Theoretical Physics (ICTP), Trieste, Italy 7 Shanghai Synchrotron Radiation Facility, Chinese Academy of Sciences, Shanghai, China 8 Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China e-mail: yjzhang@hbnu.edu.cn; y.xu@zju.edu.cn; yangliuphys@zju.edu.cn Acknowledgments The spin-resolved ARPES measurement in this study was conducted in Beamline 9.2 APE-LE, Elettra. We acknowledge Elettra Sincrotrone Trieste for providing access to its synchrotron radiation facilities and for financial support. Original paper G.W. Yang et al., Nat. Commun. 16, 1442 (2025); DOI:10.1038/s41467-025-56647-7. Fig. 1 [C2||Mz] [C2||C6z] [C2|| t ] or [T||P] 60° s s s ~ → Γ K H L M A bulk-type g-wave AM Γ-K nodal planes k z= nc*2 BZ boundary (g) (f) hν=80eV -3 -2 -1 0 E (eV) Γ(kz=0.28) M M ARPES (d) Γ(kz=0.28) M M AM with SOC <sz>0.5 -0.5 0 (e) 4.6 3.8 E=-0.5eV 4.4 4.0 4.2 M Γ M kz (c*) Γ M M L A L 90eV 80eV 68eV -1 -1 0 1 ky (Å ) -1 0 kx (Å-1) θ hν=80eV, E=-0.65eV [C2||C6z] s spin up spin down (h) (i) Intensity (a.u.) Sz up/down / -4 +4 0 Polarization (%) Γ(kz=0.28) M M Second Derivative high low (j) MDC (k) 1 -1 -2 0 E (eV) Γ(kz=0.28) M M q1+q4=0.176, q2+q3=0.195 U ΔEU=0.99eV Best Fit spin up spin down Σqi=0 Σqi=0.52 Best Fit 1 Γ (kz=0.28c*) M ΔE (eV) 1.5 0 0.5 fixed q1:q2+q3:q4 U spin-ARPES 0.32 0 0 q2+q3 (eV) 0.35 q1+q4 (eV) ΔEU (eV) 1 0 Best fit uniform compression fixed q1:q4 (l) (m) (b) (c) Cr Sb NN NNN 3NN Q P (a) Figure 1. Large altermagnetic splitting in CrSb. (a) Spin and lattice structure of CrSb. The NN, NNN and 3NN Cr-Cr bonds are indicated by the black arrow lines. (b) Symmetry operations connecting the opposite-spin sublattices. (c) The three-dimensional Brillouin zone (BZ) with high symmetry points and nodal planes labeled. (d) ARPES spectra along the in-plane Γ − M direction, kz = 0.28c*. (e) The second derivatives of (d). (f) Spin-resolved band structure from DFT calculations corresponding to (d,e). (g) The kx-kz map at E = -0.5 eV. The green dashed rectangle marks half of the BZ from M − Γ −M (kz = 0) to L − A − L (kz = 0.5c*). (h) The constant-energy kx-ky map at -0.65 eV, taken with 80 eV photons(kz ~ 0.28c*). The corresponding constant-energy contours from DFT calculations are overlaid on top as dashed curves. (i) Spin-resolved MDCs along the white dashed cut in (e). (j) The spin polarization extracted from the spin-resolved MDCs in (i). (k) Band dispersion along the Γ − M direction at kz = 0.28c* obtained from the TB model fit to DFT calculations. (l) Altermagnetic splitting ΔEU defined in (k) as a function of q2 + q3 and q1 + q4. (m) Altermagnetic splitting ΔE along the Γ − M direction at kz = 0.28c* with different values of Σqi. Elettra Highlights 2024–2025 13
Elettra | APE-LE Measuring electron’s quantum geometry Following the seminar works of Lev Landau (1908-1968), conventional phase transitions in solids have long been understood within the framework of symmetry breaking. For instance, the transition from a paramagnetic to a ferromagnetic state is characterized by the breaking of spin-rotational symmetry, while the transition to superconducting state is marked by the gauge symmetry breaking. In the late 20th century, however, a paradigm shift emerged through the groundbreaking work of Michael Kosterlitz, David Thouless, and Duncan Haldane, who introduced a new class of phase transitions governed not by symmetry breaking, but by changes in electronic topology of solids. This new framework – often called topological phase transitions – earned them the Nobel Prize in Physics in 2016. Since then, understanding the topological properties of wavefunctions at the microscopic level and exploring their profound impact on macroscopic physical phenomena has become a central subject of modern condensed matter physics. Mathematically, topology is a global invariant property that is defined by the integration of local geometric quantities over a given parameter space. In condensed matter physics, the topology in solids is determined by the integrating the quantum geometry of electronic wavefunctions across momentum space. In this regard, a central quantity for describing topology and quantum geometry in solids is the so-called Quantum Geometric Tensor (QGT). The real and imaginary parts of the QGT are the quantum metric (Fig. 1 a) and the Berry curvature (Fig. 1 b), which describes the distance and phase information in the wavefunction space. Together, the quantum metric and Berry curvature encode the complete geometric information of electrons in solids, and underpin a wide range of exotic quantum phenomena, such as topologically-protected charge transport that can be harnessed for nextgeneration transistors, nonlinear Hall effects that have potential application in wireless energy transfer and rectification, and even unconventional superconductivity with critical temperature exceeding conventional limits. Despite its central importance, however, a direct experimental method to measure the quantum geometry of electrons in solids has long remained elusive. Roughly speaking, measuring the QGT of electrons is analogous to obtaining a complete understanding of electrons’ behavior in solids in wavefunctionlevel, which is an inherently challenging task. As a result, previous studies on quantum geometric properties in solids have almost always relied on theoretical calculation of the QGT, rather than its experimental measurements. To overcome this challenge, we have recently developed a novel strategy to measure the quantum geometry of electrons in solids using Angle-Resolved Photoemission Spectroscopy (ARPES) with both polarization- and spinresolution. While ARPES is best known as a direct tool for measuring the band structure of solids (a scalar property), the ARPES signal as a function of light polarization and electron spin also encodes wavefunction information (a vector property). This direct sensitivity to wavefunction properties suggests that carefully designed photoemission experiments and analysis can uncover the underlying quantum geometry of electronic wavefunctions in solids. We applied this idea to a model kagome lattice material, CoSn. Owing to its unique lattice symmetry, kagome lattice materials are known to host exotic electronic states, such as Dirac fermions (massless electrons that behave like light, m = 0) and flat band electrons (electrons with infinite mass, m = ∞) with intrinsic topology. By performing spin- and polarization-resolved ARPES measurements at the state-of-theart spin-ARPES facility at the APE-LE beamline of Elettra, we successfully reconstructed the quantum geometry and topology of these special electrons in the kagome lattice. Importantly, unlike previous approaches that were restricted to specific model systems, our methodology is completely general and broadly applicable to a wide class of quantum materials, including twodimensional semiconductors and topological metals. The range of exotic quantum matter phenomena governed by quantum geometry in solids is rapidly expanding. For example, while earlier studies primarily focused on the role of the imaginary part of the QGT (Berry curvature), more recent studies have demonstrated that the real part of the QGT (quantum metric) also gives rise to an equally important set of unconventional phenomena, such as anomalous Landau levels, flat band superfluidity, and exitonic Lamb shifts. Given this growing importance of quantum geometry in solids, we anticipate that our work – offering a general framework to quantify the QGT – will serve as an essential foundation for advanced understanding of quantumgeometric phenomena in solids and for guiding the discovery of new quantumgeometric materials. Elettra Highlights 2024–2025 14
Functional materials Band Drude weight (BDW) Orbital Angular Momentum (OAM) Quantum Metric (QM) Berry Curvature (BC) a b c d ψ(λ+dλ) ψ(λ) Quant. Dist. dΩ Y3 2 Mingu Kang1,2, Sunje Kim3,4,5, Yuting Qian3,4,5, Paul M. Neves1, Linda Ye1, Junseo Jung3,4,5, Denny Puntel6, Federico Mazzola7,8, Shiang Fang1, Chris Jozwiak9, Aaron Bostwick9, Eli Rotenberg9, Jun Fuji7, Ivana Vobornik7, Jae-Hoon Park2,10, Joseph G. Checkelsky1, Bohm-Jung Yang3,4,5, Riccardo Comin1 1 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA 2 Max Planck POSTECH/Korea Research Initiative, Center for Complex Phase of Materials Pohang, Republic of Korea 3 Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea 4 Center for Theoretical Physics (CTP), Seoul National University, Seoul, Republic of Korea 5 Institute of Applied Physics, Seoul National University, Seoul, Republic of Korea 6 Department of Physics, University of Trieste, Trieste, Italy 7 Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche, Trieste, Italy 8 Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Venice, Italy 9 Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, CA, USA 10 Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea e-mail: iordia@snu.ac.kr Acknowledgments M. Kang acknowledges a Kavli Postdoctoral Fellowship from the Kavli Nanoscience Institute at Cornell. Original paper M. Kang et al., Nat. Phys. 21, 110 (2025); DOI: 10.1038/s41567-024-02678-8. Fig. 1 Figure 1. Quantum geometry and experimentally measurable quantities in spin- and polarization-resolved ARPES at Elettra. (a) Real part of the quantum geometric tensor, the quantum metric, which describes the quantum distance between electronic wavefunctions in parameter space. (b) Imaginary part of the quantum geometric tensor, the Berry curvature, which describes the phase information of electronic wavefunctions in parameter space. (c),(d), Experimentally measurable quantities using spin- and polarization-resolved ARPES: the band Drude weight (c) and the orbital angular momentum (d). Band Drude weight and orbital angular momentum construct quasi-quantum geometric tensor, from which we could mathematically reconstruct quantum geometric tensor. Elettra Highlights 2024–2025 15
Elettra | BaDElPh, SuperESCA Designer graphene: High and uniform atomic-level transition metal substitution achieved Doping graphene with foreign substitutional atoms such as transition metals can help tailor its properties for applications ranging from magnetism and spintronics to single-atom catalysis. However, substitutional incorporation of transition metal atoms in graphene is generally not energetically favorable. Ion implantation makes this possible by introducing single atoms in bulk materials as the implantation process drives the material into a non-energetically favorable system. The same approach can be applied to graphene and other two-dimensional (2D) materials, but the ion energy must be of the order of tens of eV compared to keV and MeV for bulk materials. To this end, ultralow-energy (ULE) ion implantation has been successfully used to substitutionally dope graphene with manganese (Mn). Nonetheless, a low substitution efficiency of ~1% was observed indicating that the used ion energy (40 eV) may not have been optimal. Although the substitutional concentration can in principle be increased by increasing ion fluence, it may be accompanied by the appearance of unwanted radiation defects. Achieving higher substitution efficiencies would allow for a better compromise between a high concentration of dopants and low irradiation-induced disorder. Graphene on Cu(111) was implanted with Mn+ ions at an energy of 60 eV using ULE ion implantation. Scanning tunneling microscopy (STM) was used to estimate the average surface density of substitutional Mn atoms. Compared to the surface density of C atoms in graphene, it corresponds to a substitutional Mn concentration of 0.50 ± 0.14%; and considering the implanted fluence, this amounts to a substitution efficiency (fraction of implanted ions that are substitutionally incorporated) of 13 ± 4%. Compared to Mn implantation performed at 40 eV to the same fluence as here, the implantation at 60 eV results in a 10-fold increase in substitutional concentration and substitution efficiency. This increase can be understood as due to the fact that an increase in kinetic energy of the Mn ions is associated with more efficient displacement of the C atoms, as required for substitutional incorporation to occur. We used synchrotron x-ray photoelectron spectroscopy (XPS) to further characterize the Mn incorporation as a function of annealing temperature. Fig. 1 (a) shows Mn 2p core-level data fitted with multiple Voigt components from where we determine the total Mn concentration at the surface. Although it is not possible to identify a Mn 2p component that is clearly associated with the substitutional Mn fraction identified using STM, these XPS data still provide useful insights. At the lowest annealing temperatures, approximately half of the implanted Mn ions are detected at the surface (2.8% with respect to C in graphene), indicating that the other half experienced backscattering during implantation. From the fraction that is detected at the surface, approximately 10% of the implanted Mn ions are incorporated substitutionally, based on the STM data. The remaining fraction consists of intercalated Mn atoms. The decrease in Mn detected at the surface from the 200 °C to the 700 °C annealing step can be attributed to the diffusion of intercalated Mn into the Cu substrate. After 700 °C, our XPS measurements still detect about 0.9% Mn at the surface, significantly higher than the 0.5% substitutional concentration determined using STM. Although the difference may be within the experimental uncertainty (especially considering that we are comparing XPS to STM quantification), it supports the notion that some of the non substitutional Mn remains sufficiently close to the surface to still contribute to the XPS signal. The Dirac character of graphene is preserved upon substitutional Mn doping, even in this relatively high concentration regime (0.5%), as observed using angle-resolved photoemission spectroscopy (ARPES) in Fig. 1 (b). The ARPES measurements show only a subtle effect of Mn substitution in the band structure, compared to pristine (non implanted) graphene. When considering the values for the Dirac point position, the apparent band gap, and the Fermi velocities, obtained from the analysis of the momentum distribution curves extracted from the ARPES maps, only the Fermi velocities appear to show a measurable and relatively mild reduction. All other key features of the band structure are essentially unaffected: the discontinuity in the graphene π-band in Fig. 1 (d), resulting from the hybridization with the Cu 3d-band; the Cu surface state is also clearly visible in Fig. 1 (e), indicating that no significant oxidation of the interface has occurred. ULE (60 eV) ion implantation of Mn ions into graphene on Cu(111) followed by thermal annealing in UHV at 700 °C, resulted in a relatively high substitutional efficiency (13%) and high substitutional concentration (0.50%), while keeping the graphene layer virtually as clean and defect-free as in the as-grown state, except for the incorporated substitutional Mn atoms. In particular, the Dirac character of graphene is preserved, even in this relatively high concentration regime. ULE ion implantation is shown to be well suited for the functionalization of graphene with substitutional transition-metal atoms for a wide range of applications, from magnetism and spintronics to single-atom catalysis. In particular, our data show no indication of a limit on the achievable substitutional concentration; higher doping levels can in principle be achieved simply by increasing the implanted fluence. Moreover, one can expect that other transition elements can be substitutionally incorporated following a similar approach, allowing exploration of the functionalization effects over several orders of magnitude of concentration of different elements. Elettra Highlights 2024–2025 16
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