Preparing the Future of PSI Large Facilities in Atmospheric Research
The Multiphase Chemistry Group in the Laboratory of Atmospheric Chemistry (LAC) looks back to a nearly 20 years record of activities with in situ X-ray photoelectron spectroscopy (XPS) and in situ scanning transmission X-ray spectromicroscopy (STXM) to address key fundamental questions in atmospheric chemistry. This is the time to consider new horizons, align with current and future needs in atmospheric sciences, and to identify novel opportunities driven by upcoming trends in methods, technologies and facilities. This has been the topic of the Workshop ‘X-ray and Neutron Spectroscopy, Scattering and Imaging in Atmospheric Chemistry’, held at PSI 13 – 15 November 2024.
Anionic Disorder and Its Impact on the Surface Electronic Structure of Oxynitride Photoactive Semiconductors
The conversion of solar energy into chemical energy, stored in the form of hydrogen, bears enormous potential as a sustainable fuel for powering emerging technologies. Photoactive oxynitrides are promising materials for splitting water into molecular oxygen and hydrogen. However, one of the issues limiting widespread commercial use of oxynitrides is degradation during operation. While recent studies have shown the loss of nitrogen, its relation to reduced efficiency has not been directly and systematically addressed with experiments. In this study, we demonstrate the impact of the anionic stoichiometry of BaTaOxNy on its electronic structure and functional properties. Through experimental ion scattering, electron microscopy, and photoelectron spectroscopy investigations, we determine the anionic composition ranging from the bulk toward the surface of BaTaOxNy thin films. This further serves as input for band structure computations modeling the substitutional disorder of the anion sites. Combining our experimental and computational approaches, we reveal the depth-dependent elemental composition of oxynitride films, resulting in downward band bending and the loss of semiconducting character toward the surface. Extending beyond idealized systems, we demonstrate the relation between the electronic properties of real oxynitride photoanodes and their performance, providing guidelines for engineering highly efficient photoelectrodes and photocatalysts for clean hydrogen production.
Acoustic emission signature of a martensitic transformation
Acoustic emission monitoring in 3D printing: real-time insights into martensitic phase transformations and crack formation.
Exact solution of the classical and quantum Heisenberg mean field spin glasses
We solve and elucidate the physics of quantum Heisenberg spins glasses, which governs the local moments in randomly doped, strongly correlated materials.
Continuum Excitations in a Spin Supersolid on a Triangular Lattice
Magnetic, thermodynamic, neutron diffraction and inelastic neutron scattering are used to study spin correlations in the easy-axis XXZ triangular lattice magnet K2Co(SeO3)2. Despite the presence of quasi-2D “supersolid” magnetic order, the low-energy excitation spectrum contains no sharp modes and is instead a broad and structured multiparticle continuum. Applying a weak magnetic field ...
Reentrant multiple-q magnetic order and a “spin meta-cholesteric” phase in Sr3Fe2O7
Topologically nontrivial magnetic structures such as skyrmion lattices are well known in materials lacking lattice inversion symmetry, where antisymmetric exchange interactions are allowed. Only recently, topological multi-q magnetic textures that spontaneously break the chiral symmetry, for example, three-dimensional hedgehog lattices, were discovered in centrosymmetric compounds, where they are instead driven by frustrated interactions. Here we show that ...
Skyrmion topology quantified in 3D
Researchers from an international collaboration between the United States of America and Switzerland have performed three-dimensional magnetic imaging of a magnetic skyrmion using soft X-ray laminography. This allowed for the investigation, in three dimensions, of the topological profile of the magnetic skyrmions.
Dual-site reaction mechanism for the simultaneous reduction of nitrous and nitric oxides
We have applied three spectroscopic techniques (XAS, EPR and DRIFTS) in combination withe modulated excitation and catalytic data to decipher and propose the complete reaction mechanism of the simultaneous reduction of N2O and NO
Discovery of charge order above roomtemperature in the prototypical kagome superconductor La(Ru1−xFex)3Si2
The kagome lattice is an intriguing and rich platform for discovering, tuning and understanding the diverse phases of quantum matter, crucial for advancing modern and future electronics. Despite considerable efforts, accessing correlated phases at room temperature has been challenging.
Recognition at MNE 2024 Micrograph Contest
The MNE conference is the flagship event of the International Society for Micro- and Nanotechnology (iMNEs). The research fields covered by the MNE conferences have consistently driven advancements in the development of smaller and smaller structures. To emphasize the significance of micrographs in this field, the conference features a micrograph contest, sponsored and hosted by Zyvex Labs. Entries are judged based on both their technological relevance and artistic merit.
This year, Peng Qi from the X-ray Nano Optics group, LXN, CPS, earned third place and an honorable mention for his two submitted images.
Ferromagnetic quantum critical point protected by nonsymmorphic symmetry in a Kondo metal
Quantum critical points (QCPs), zero-temperature phase transitions, are win- dows to fundamental quantum-mechanical phenomena associated with universal behaviour. Magnetic QCPs have been extensively investigated in the vicinity of antiferromagnetic order. However, QCPs are rare in metallic ferromagnets due to the coupling of the order parameter to electronic soft modes. Recently, antisymmetric spin-orbit coupling in noncentrosymmetric systems was suggested to protect ferromagnetic QCPs. Nonetheless, multiple centrosymmetric materials ...
Uncovering the secrets of rapid and green metal-organic framework synthesis
Using ATR-IR spectroscopy and high-energy XRD, we have studied the mechanism of ambient temperature aqueous synthesis of Zn-MOF-74. Starting from the need to change Zn precursor to disentangle signals in ATR-IR spectroscopy, we also developed a rapid synthesis of Zn-MOF-74 with Zn perchlorate.
Carbenium ions in the methanol-to-olefins process
The methanol-to-olefins process converts methanol into hydrocarbons over zeolite-based catalysts following a dual-cycle reaction mechanism within the paradigm of an hydrocarbon pool chemistry. In this work, we use operando DRIFTS/GC to correlate the nature of species residing within the porosity of zeolites (DRIFTS) and the products distribution (GC).
Quantum Spin Dynamics Due to Strong Kitaev Interactions in the Triangular-Lattice Antiferromagnet CsCeSe2
The extraordinary properties of the Kitaev model have motivated an intense search for new physics in materials that combine geometrical and bond frustration. In this Letter, we employ inelastic neutron scattering, spin wave theory, and exact diagonalization to study the spin dynamics in the perfect triangular-lattice antiferromagnet (TLAF) CsCeSe2. This material orders into a stripe phase, which is demonstrated to arise as a consequence of the off-diagonal bond-dependent terms in the spin Hamiltonian ...
Evidence for time-reversal symmetry-breaking kagome superconductivity
Superconductivity and magnetism are often antagonistic in quantum matter, although their intertwining has long been considered in frustrated-lattice systems. Here we utilize scanning tunnelling microscopy and muon spin resonance to demonstrate time-reversal symmetry-breaking superconductivity in kagome metal Cs(V, Ta)3Sb5, where the Cooper pairing exhibits magnetism and is modulated by it. In the magnetic channel, we observe spontaneous internal magnetism ...
Hydrogen Electrode for Membrane Water Electrolyzers with Low Gas Crossover
Proton exchange membrane (PEM) water electrolyzer are considered a for the Energy Transition to produce green hydrogen for fuel cell-based mobility, industrial processes, and seasonal storage. Platinum group metals (PGMs) are conventionally used as catalysts for electrode reactions due to their outstanding catalytic activity and chemical stability in the harsh acidic environment of the cell. Commercial carbon-supported platinum (Pt/C) electrocatalysts remains a state-of-the-art choice for the hydrogen evolution reaction (HER) on the cathode side of the cell. While a high Pt loading between 0.5 and 1.0 mgPt/cm2 is commonly used today, a reduction of the Pt loading to below 0.05 mgPt/cm2 is desired to reduce the cost of PGM usage in megawatt-scale PEM water electrolysis systems. In addition, in connection with the trend towards the use of thinner membranes (<0.1 mm), gas crossover through the membrane from the cathode to the anode side can lead to the formation of an explosive gas mixture in the anode product stream. In this study, we varied the design parameters for the cathode catalyst layer to reduce the Pt loading to 0.025 mg/cm2 while at the same time minimizing the rate of hydrogen crossover to the anode.
Controlling magnetic waves in a spin liquid
Scientists at the Paul Scherrer Institute PSI have shown that excitation of a spin liquid with intense THz pulses causes spins to appear and align within less than a picosecond. This induced coherent state causes a magnetic field to form inside the material, which is detected using ultrashort X-ray pulses at the X-ray Free Electron Laser SwissFEL.
Novel Photoresist Chemistry Enables Lithography Approaching Angstrom-Scale Resolution
Photoresist materials are crucial in the manufacturing of computer chips, where the circuits are initially printed in the photoresist using photolithography. As the demand for smaller and more precise circuitry in computer chips grows, photoresists must resolve features with smaller sizes and higher density. One of the factors determining the ultimate resolution in lithography is the molecular size/mass of the photoresists.
Chiral kagome superconductivity modulations with residual Fermi arcs
Superconductivity involving finite-momentum pairing can lead to spatial-gap and pair-density modulations, as well as Bogoliubov Fermi states within the superconducting gap. However, the experimental realization of their intertwined relations has been challenging. Here we detect chiral kagome superconductivity modulations with residual Fermi arcs in KV3Sb5 and CsV3Sb5 using normal and Josephson scanning tunnelling microscopy down to 30 millikelvin with a resolved electronic energy difference at the microelectronvolt level. We observe a U-shaped ...
Room temperature magnetoelectric magnetic spirals by design
Frustrated magnets with ordered magnetic spiral phases that spontaneously break inversion symmetry have received significant attention from both fundamental and applied sciences communities due to the experimental demonstration that some of these materials can couple to the lattice and induce electric polarization. In these materials, the common origin of the electric and magnetic orders guarantees substantial coupling between them, which is highly desirable for applications ...
Magnetostructural Coupling at the Néel Point in YNiO3 Single Crystals
The recent discovery of superconductivity in infinite layer thin films and bulk Ruddlesden–Popper nickelates has stimulated the investigation of other predicted properties of these materials. Among them, the existence of magnetism-driven ferroelectricity in the parent compounds RNiO3 (R = 4f lanthanide and Y) at the onset of the Néel order, TN, has remained particularly elusive. Using diffraction techniques, we reveal here the existence of magnetostriction at TN in bulk YNiO3 single crystals. Interestingly, the associated lattice anomalies ...
Elusive multiferroicity in RNiO3 perovskites
In our recent paper we examined YNiO3 and proved that the RNiO3 type material known for its metal-insulator transition is in fact a type II multiferroic. We provide direct evidence of an electric-field-driven switch of the noncolliear magnetic state finally confirming the proposed type II multiferroic nature of YNiO3.
Move the soft mode by electric fields in quantum paraelectric SrTiO3
PSI Researcher used inelastic neutron scattering to show how collective lattice vibrations can be controlled by electric fields. These results indicate that different eigenmodes can couple in field in this incipient ferroelectric.
Move the soft mode by electric fields in quantum paraelectric SrTiO3
PSI Researcher used inelastic neutron scattering to show how collective lattice vibrations can be controlled by electric fields. These results indicate that different eigenmodes can couple in field in this incipient ferroelectric.
Conventional superconductivity in the doped kagome superconductor Cs(V0.86Ta0.14)3Sb5 from vortex lattice studies
A hallmark of unconventional superconductors is a complex electronic phase diagram where intertwined orders of charge-spin-lattice degrees of freedom compete and coexist. While the kagome metals such as CsV3Sb5 also exhibit complex behavior, involving coexisting charge density wave order and superconductivity, much is unclear about the microscopic origin of the superconducting pairing. We study the vortex lattice in the superconducting state of Cs(V0.86Ta0.14)3Sb5, where the Ta-doping suppresses charge order and enhances superconductivity. Using small-angle neutron scattering ...
Nanoimaging Reveals Topological Textures in Nanoscale Crystalline Networks
X-ray nano-tomography reveals collective behavior in synthetic self-assembled nanostructures. The new method opens opportunities for the synthesis of photonic and plasmonic materials with improved long-range ordering.
Installation of the first two front ends for the SLS2.0 completed
At the Swiss Light Source SLS of the Paul Scherrer Institute, another important step has been taken towards the completion of the SLS 2.0 upgrade project.
Insights into the superior oxygen evolution reaction activity of CoOx/CeO2 composite electrocatalyst
CeO2 significantly enhances the oxygen evolution reaction (OER) activity of CoOx, although the mechanism behind this synergy is still unclear. Here, operando hard X-ray absorption spectroscopy (hXAS) is applied to monitor the Co-K edge and Ce L3 edge in CoOx/CeO2 to shed light on the evolution of Co and Ce oxidation states during OER. In addition, ex situ soft XAS (sXAS) characterizations provide information on the irreversible surface-specific transformations of the Co L3 edge as well as the O K edge.
Real-Time Insights into Sodium-Ion Battery Chemistry
Identification of gaseous decomposition products from irreversible side-reactions enables understanding of inner working of rechargeable batteries. Unlike for Li-ion batteries, the knowledge of the gas-evolution processes in Na-ion batteries is limited. Our study revealed that Na-ion cells develop a less stable solid-electrolyte interphase (SEI) compared to Li-ion cells due to higher solubility of SEI constituents in Na-electrolytes.
Anomalous spin precession systematic effects in the search for a muon EDM using the frozen-spin technique
In the paper, the international muEDM collaboration at PSI discusses systematic effects of the most sensitive measurement of the muon's electric dipole moment (EDM). Scientists from Europe are developing a prototype experiment using the frozen-spin technique (FST) to achieve unprecedented sensitivity. The FST meticulously aligns a magnetic field with a perpendicular electric field so that the muon's spin orientation always follows its momentum. This enhances the sensitivity to the muon EDM by about 3 orders of magnitude compared to the best result from the muon g-2 experiment at Brookhaven National Lab.
The paper addresses systematic effects that could mimic an EDM signal when E- and B-fields are not perfectly aligned, adjusted, or stable over time. While most effects cancel out when reversing the magnetic field, some residual effects the specifications for the fields' uniformity, stability, and orientation,
which are challenging but achievable.
Removal of ionic and colloidal 110 mAg from radioactive wastewater using radiografted chelating adsorbents
Nuclear power plays a crucial role in a sustainable future due to its ability to generate large amounts of low-carbon electricity, which is essential for mitigating climate change. Unlike fossil fuels, nuclear energy produces minimal greenhouse gas emissions, helping to reduce the overall carbon footprint of power generation. However, the main concern is the inevitable accumulation of nuclear waste, and this needs to be properly addressed. With the anticipated increase in the number of operating nuclear power plants around the world it is essential to develop new materials and technologies for nuclear waste management. In our latest study we have developed and tested new radiografted materials as potential 110mAg adsorbents. This silver radionuclide is a very elusive contaminant in the pressurized water reactors (PWR) and represents a major problem for normal operation. Additionally, 110mAg possess a significant danger to the environment, if not removed completely from the PWR wastewater.
Towards fast ptychography image reconstruction of EUV masks by deep neural networks
In this study, we explore and demonstrate a rapid method for actinic patterned EUV mask inspection based on a deep neural network (DNN) architecture which exploits a-priori information of the photomask sample. We aim to achieve fast, high-quality image reconstruction of an EUV mask by using comparatively few diffraction patterns in a formalism consistent with the ptychography approach.
We tested our prior-primed DNN method on both synthetic and experimental data, demonstrating that the sample can be reconstructed fast and with high fidelity, allowing us to map out the mask defects down to a size of about 40 nm.
Design and Preclinical Evaluation of a Novel Prostate-Specific Membrane Antigen Radioligand Modified with a Transthyretin Binder
Radioligands targeting the prostate-specific membrane antigen (PSMA) are currently used in the clinics to treat patients with metastatic castration-resistant prostate cancer. Continuous investigations are, nevertheless, conducted to design new small molecule-based radioligands and improve their respective pharmacokinetic properties. Various strategies have been devised to reasonably prolong the blood circulation, which would result into enhanced tumor accumulation and radiation dose delivered to eliminate the cancer cells. The goal of this study was to investigate the influence of the incorporation of a transthyretin binder (TB-01) in the tumor uptake of the resultant PSMA-targeted radioligand.
International collaboration lays the foundation for future AI for materials via the OPTIMADE standard
Artificial intelligence (AI) is accelerating the development of new materials. A prerequisite for AI in materials research is large-scale use and exchange of data on materials, which is facilitated by a broad international standard. A major international collaboration including researchers from the LMS laboratory now presents an extended version of the OPTIMADE standard.
Observation of Mermin-Wagner behavior in LaFeO3/SrTiO3 superlattices
Two-dimensional magnetic materials can exhibit new magnetic properties due to the enhanced spin fluctuations that arise in reduced dimension. However, the suppression of the long-range magnetic order in two dimensions due to long-wavelength spin fluctuations, as suggested by the Mermin-Wagner theorem, has been questioned for finite-size laboratory samples. Here we study ...
Coexistence of Superconductivity and Antiferromagnetism in Topological Magnet MnBi2Te4 Films
The interface of two materials can harbor unexpected emergent phenomena. One example is interface-induced superconductivity. In this work, we employ molecular beam epitaxy to grow a series of heterostructures formed by stacking together two nonsuperconducting antiferromagnetic materials, an intrinsic antiferromagnetic topological insulator MnBi2Te4 and an antiferromagnetic iron chalcogenide FeTe.
Phonon promoted charge density wave in topological kagome metal ScV6Sn6
Charge density wave (CDW) orders in vanadium-based kagome metals have recently received tremendous attention, yet their origin remains a topic of debate. The discovery of ScV6Sn6, a bilayer kagome metal featuring an intriguing √3 × √3 × √3 CDW order, offers a novel platform to explore the underlying mechanism behind the unconventional CDW. Here we combine ...
Promotion versus Poisoning in Copper–Gallium-Based CO2-to-Methanol Hydrogenation Catalysts
Cu–Ga-based CO2-to-methanol hydrogenation catalysts display a range of catalytic performance, depending on their preparation. Here, we investigated how the Ga/Cu ratio and Ga speciation affect the catalytic activity. Using surface organometallic chemistry, we prepared a series of silica-supported 3–6 nm Cu1–xGaxOy nanoparticles with a range of xGa. The materials display a volcano-type activity behavior, where methanol formation is promoted when xGa < 0.13–0.18 and is suppressed at higher values, indicating a poisoning of the catalysts. In situ X-ray absorption spectroscopy and in situ infrared spectroscopy helped to understand the structure-activity relationship.
Optimizing a radiochemical separation of 26Al from an acidic V-rich matrix
At the Paul Scherrer Institute (PSI), within the Isotope and Target Chemistry (ITC) group, various radiochemical methods are developed to fully separate and purify individual radionuclides. These separation methods are devised for both new experiments and for reprocessing radioactive waste from previous experiments.
Non-coplanar helimagnetism in the layered van-der-Waals metal DyTe3
Van-der-Waals magnetic materials can be exfoliated to realize ultrathin sheets or interfaces with highly controllable optical or spintronics responses. In majority, these are collinear ferro-, ferri-, or antiferromagnets, with a particular scarcity of lattice-incommensurate helimagnets of defined left- or right-handed rotation sense, or helicity. Here, we report polarized neutron scattering experiments on DyTe3, whose layered structure has highly metallic tellurium layers separated by double-slabs of dysprosium square nets...
How the orientation of molecular single-ion magnets affects their magnetic hysteresis
Molecular single-ion magnets act as ultra-small magnets that can retain their magnetization. When organized on a well defined surface, they could allow storing information at 100 and more times higher storage densities than nowadays available.
In the present study performed at the Swiss Light Source an international research team investigated monolayers of two very similar types of organometallic single-ion magnets, that, however, behave very differently on a flat silver surface. They link the vastly different magnetic behavior with the different orientation and adsorption configurations on the surface.
Spectral evidence for Dirac spinons in a kagome lattice antiferromagnet
Emergent quasiparticles with a Dirac dispersion in condensed matter systems can be described by the Dirac equation for relativistic electrons, in analogy with Dirac particles in high-energy physics. For example, electrons with a Dirac dispersion have been intensively studied in electronic systems such as graphene and topological insulators. However, charge is not a prerequisite for Dirac fermions, and the emergence of Dirac fermions without a charge degree of freedom has been theoretically predicted to be realized in Dirac quantum spin liquids. These quasiparticles ...
Weyl spin-momentum locking in a chiral topological semimetal
Spin–orbit coupling in noncentrosymmetric crystals leads to spin–momentum locking – a directional relationship between an electron’s spin angular momentum and its linear momentum. Isotropic orthogonal Rashba spin–momentum locking has been studied for decades, while its counterpart, isotropic parallel Weyl spin–momentum locking has remained elusive in experiments. Theory predicts ...
Breaking the Drops
For water-cooled nuclear reactors, a loss of coolant accident constitutes one of the key scenarios to be evaluated for the design of the plant and associated safety systems. Even if these accidents are not expected to occur at all during reactor lifetime, their potential consequences include the heat up of the fuel in the reactor core. For the recovery of the plant to safe conditions, safety systems are in place to inject water in order to reflood the core and to quench the high temperature fuel. The two-phase flow behaviour during this reflooding phase is extremely complex. In particular, the prediction of the behaviour of small liquid droplets generated as the quench front propagates upwards has a significant effect on the fuel temperatures in the upper regions of the reactor core. In collaboration with the US Nuclear Regulatory Commission (NRC), we have been working to improve our modelling of the droplet behaviour and their impact on key safety parameters.
Dr. Chiara Favaretto has been honored with the Alavi-Mandell Award 2024
We congratulate Dr. Chiara Favaretto for the excellent research work she did during her time at the Center for Radiopharmaceutical Sciences.
Three-dimensional magnonics
Researchers from an international collaboration between Switzerland, Italy, and Germany have performed the first time-resolved imaging at sub-ns timescales of the three-dimensional propagation dynamics of a spinwave in a synthetic antiferromagnetic nanostructured device, opening up the possibility to investigate magnon dynamics in complex three-dimensional geometries.
Surface oxidation/spin state determines oxygen evolution reaction activity of cobalt-based catalysts in acidic environment
Co-based catalysts are promising candidates to replace Ir/Ru-based oxides for oxygen evolution reaction (OER) catalysis in an acidic environment. However, both the reaction mechanism and the active species under acidic conditions remain unclear. In this study, by combining surface-sensitive soft X-ray absorption spectroscopy characterization with electrochemical analysis, we discover that the acidic OER activity of Co-based catalysts are determined by their surface oxidation/spin state.
All Two-Loop Feynman Integrals for Five-Point One-Mass Scattering
We compute the complete set of two-loop master integrals for the scattering of four massless particles and a massive one. Our results are ready for phenomenological applications, removing a major obstacle to the computation of complete next-to-next-to-leading order QCD corrections to processes such as the production of a H/Z/W boson in association with two jets at the LHC. Furthermore ...