Recherche sur le Covid-19

An international group of researchers led by the Paul Scherrer Institute has carried out in-depth analyses of the climate impact of blue hydrogen. This is produced from natural gas, with the CO₂ resulting from the process captured and permanently stored. The study concludes that blue hydrogen can play a positive role in the energy transition – under certain conditions.

The development of next-generation perovskite-based optoelectronic devices relies critically on the understanding of the interaction between charge carriers and the polar lattice in out-of-equilibrium conditions. While it has become increasingly evident for CsPbBr₃ perovskites that the Pb–Br framework flexibility plays a key role in their light-activated functionality, the corresponding local structural rearrangement has not yet been unambiguously identified. In this work the photoinduced lattice changes were investigated using combination of time-resolved and temperature-dependent studies at Br K and Pb L₃ X-ray absorption edges and ab initio simulations.

The recently discovered kagome superconductor CsV₃Sb₅ (T_c ≃ 2.5 K) has been found to host charge order as well as a non-trivial band topology, encompassing multiple Dirac points and probable surface states. Such a complex and phenomenologically rich system is, therefore, an ideal playground for observing unusual electronic phases. Here, we report anisotropic superconducting properties of CsV₃Sb₅ by means of transverse-field muon spin rotation (μSR) experiments.

Aerosols in the atmosphere react to incident sunlight. This light is amplified in the interior of the aerosol droplets and particles, accelerating reactions. ETH and PSI researchers have now been able to demonstrate and quantify this effect and recommend factoring it into future climate models.

Many in-memory computing frameworks demand electronic devices with specific switching characteristics to achieve the desired level of computational complexity. Existing memristive devices cannot be reconfigured to meet the diverse volatile and non-volatile switching requirements, and hence rely on tailored material designs specific to the targeted application, limiting their universality. “Reconfigurable memristors” that combine both ionic diffusive and drift mechanisms could address these limitations, but they remain elusive. Here we present a reconfigurable halide perovskite nanocrystal memristor that achieves on-demand switching between diffusive/volatile and drift/non-volatile modes by controllable electrochemical reactions.

This highlight presents a successful, in-house developed integration of an Electron Beam Ion Source (EBIS) able to ionize gases to high charge states with a customized commercial MC-ICP-MS. The successful joining of the two ion flight paths is a milestone towards comprehensive routine analyses of solids, liquids, and gases using THE SAME MASS SPECTROMETER, the latter analyses free from atmospheric contamination. After implementation of an introduction system for gas mass spectrometry, routine analyses will comprise isotope ratio and relative abundance determinations of fission gases in used nuclear fuel. In addition to the unique versatility of the MC-EBIS-ICP-MS, inclusion of the EBIS furthers opens the little-studied field of mass spectrometry of highly charged ions.

The reaction of elemental scandium and zirconium powders with liquid aluminum is observed directly via operando X-ray diffraction during laser 3D printing. This work demonstrates that elemental blends can be used to create fine-grained crack-free Al-alloys and highlights the importance of feature size.

The layered perovskite YBaCuFeO₅ is a rare example of a cycloidal spiral magnet whose ordering temperature Tspiral can be tuned far beyond room temperature by adjusting the degree of Cu²⁺/ Fe³⁺ chemical disorder in the structure. This unusual property qualifies this material as one of the most promising spin-driven multiferroic candidates. However, very little is known about the response of the spiral to magnetic fields, crucial for magnetoelectric cross-control applications. Using bulk magnetization and neutron powder diffraction measurements under magnetic fields up to 9 T, we report here a temperature-magnetic field phase diagram of this material. Besides revealing a strong stability of the spiral state, our data uncover the presence of weak ferromagnetism coexisting with the spiral modulation. Since ferromagnets can be easily manipulated with magnetic fields, this observation opens new perspectives for the control of the spiral orientation, directly linked to the polarization direction, as well as for a possible future use of this material in technological applications.

Combining time-resolved soft X-ray STXM imaging with magnetic laminography, researchers were able to investigate magnetization dynamics in a ferromagnetic microstructure resolved in all three spatial dimensions and in time. Thanks to the possibility of freely selecting the frequency of the excitation applied to the magnetic element, this technique opens the possibility to investigate resonant magneto-dynamical processes, such as e.g. magnetic vortex core gyration and switching, and spinwave emission.

Water boiling control evolution of natural geothermal systems is widely exploited in industrial processes due to the unique non-linear thermophysical behavior. Even though the properties of water both in the liquid and gas state have been extensively studied experimentally and by numerical simulations, there is still a fundamental knowledge gap in understanding the mechanism of the heterogeneous nucleate boiling controlling evaporation and condensation. In this study, the molecular mechanism of bubble nucleation at the hydrophilic and hydrophobic solid–water interface was determined by performing unbiased molecular dynamics simulations using the transition path sampling scheme. Analyzing the liquid to vapor transition path, the initiation of small void cavities (vapor bubbles nuclei) and their subsequent merging mechanism, leading to successively growing vacuum domains (vapor phase), has been elucidated. The simulations reveal the impact of the surface functionality on the adsorbed thin water molecules film structuring and the location of high probability nucleation sites.

Static stripe order is detrimental to superconductivity. Yet, it has been proposed that transverse stripe fluctuations may enhance the inter-stripe Josephson coupling and thus promote superconductivity. Direct experimental studies of stripe dynamics, however, remain difficult. From a strong-coupling perspective, transverse stripe fluctuations are realized in the form of dynamic “kinks”—sideways shifting stripe sections. Here, we show how modest uniaxial pressure tuning reorganizes directional kink alignment.

Magnetic skyrmions are topologically stable swirling spin textures with particle-like char- acter, and have been intensively studied as a candidate of high-density information bit. While magnetic skyrmions were originally discovered in noncentrosymmetric systems with Dzyaloshinskii-Moriya interaction, recently a nanometric skyrmion lattice has also been reported for centrosymmetric rare-earth compounds, such as Gd₂PdSi₃ and GdRu₂Si₂. For the latter systems, a distinct skyrmion formation mechanism mediated by itinerant electrons has been proposed, and the search of a simpler model system allowing for a better understanding of their intricate magnetic phase diagram is highly demanded. Here, we report the discovery of square and rhombic lattices of nanometric skyrmions in a centrosymmetric binary compound EuAl₄, by performing small-angle neutron and resonant elastic X-ray scattering experiments.

PSI hosted again the Hercules School in March 2022. We had the pleasure to welcome 20 international PhD students, PostDocs and scientists to demonstrate our state-of-the-art techniques and methodologies at our large scale facilities, the Swiss Light Source (SLS), the Swiss Spallation Neutron Source (SINQ) and our free electron laser SwissFEL.