Recherche sur le Covid-19

Novel topological phases of matter are fruitful platforms for the discovery of unconventional electromagnetic phenomena. Higher-fold topology is one example, where the low-energy description goes beyond standard model analogs. Despite intensive experimental studies, conclusive evidence remains elusive for the multigap topological nature of higher-fold chiral fermions. In this Letter, we leverage a combination of fine-tuned chemical engineering and photoemission spectroscopy with photon energy contrast to discover the higher-fold topology of a chiral crystal.

Operando/in situ spectro-electrochemical studies often require high loadings and thick catalyst layers (CLs) leading to large ion- and mass-transport limitations. In this study we investigate PdH-formation in two Pd-catalysts with similar surface areas but drastically different morphologies. Our results unveil that the CL-thickness largely determines the PdH formation trends calling for the minimization of the CL-thickness in such experiments.

For contributions to the development of detectors for XFELs and specifically for their verification, characterization, and calibration

We report on the commissioning results of the cold neutron multiplexing secondary spectrometer CAMEA (Continuous Angle Multi-Energy Analysis) at the Swiss Spallation Neutron Source at the Paul Scherrer Institut, Switzerland. CAMEA is optimized for ...

Zeolites are a class of shapely, colourful minerals with very special properties, making them omnipresent in our surroundings. They accelerate chemical reactions, absorb hazardous contaminants and water to a high degree, for example. Their only limitation is that they usually lose their peculiar crystalline structure at high temperatures. Now researchers at the University of Bern have found an unexpected exception.

3d transition metals often exhibit a quenched orbital moment when in a solid state system. Therefore, the proposition of a large unquenched orbital moment for V in VI₃ caused some surprise and discussion in the scientific community. Experimental and theoretical works diverge on the fact of whether the orbital moment is quenched or not. In our work we have been able to give an answer this open issue, proposing also a model for the ground state of VI₃.

As one of the first CHART projects, the MagDev activity at PSI designed and built a canted-cosine theta (CCT) demonstrator magnet, wound from Nb3Sn conductor.

The thermal conditions during laser-based additive manufacturing are inferred from high-speed X-ray diffraction data and can be linked to a model for rapid solidification.

We report on the properties of laser-induced plasma plumes generated by ns pulsed excimer lasers as used for pulsed laser deposition to prepare thin oxide films. A focus is on the time and spatial evolution of chemical species in the plasma plume as well as the mechanisms related to the plume expansion. The overall dynamics of such a plume is governed by the species composition in particular if three or more elements are involved. We studied the temporal evolution of the plume, the composition of the chemical species in the plasma, as well as their electric charge. In particular, ionized species can have an important influence on film growth. Likewise, the different oxygen sources contributing to the overall oxygen content of an oxide film are presented and discussed. Important for the growth of oxide thin films is the compositional transfer of light element such as oxygen or Li. We will show and discuss how to monitor these light elements using plasma spectroscopy and plasma imaging and outline some consequences of our experimental results.

In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. How this stripe order evolves across optimal doping remains a controversial question. Here we present a systematic resonant inelastic x-ray scattering study of weak charge correlations in La_2−xSr_xCuO₄ and La_1.8−xEu_0.2Sr_xCuO₄. Ultra high energy resolution experiments demonstrate the importance of the separation of inelastic and elastic scattering processes. Long-range temperature-dependent stripe order is only found below optimal doping. At higher doping, short-range temperature-independent correlations are present up to the highest doping measured. This transformation is distinct from and preempts the pseudogap critical doping. We argue that the doping and temperature-independent short-range correlations originate from unresolved electron–phonon coupling that broadly peaks at the stripe ordering vector. In La_2−xSr_xCuO₄, long-range static stripe order vanishes around optimal doping and we discuss both quantum critical and crossover scenarios.

In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. How this stripe order evolves across optimal doping remains a controversial question. Here we present a systematic resonant inelastic x-ray scattering study of weak charge correlations in La_2−xSr_xCuO₄ and La_1.8−xEu_0.2Sr_xCuO₄. Ultra high energy resolution experiments demonstrate the importance of the separation of inelastic and elastic scattering processes.

Rare ferrimagnet states in a phase competing antiferromagnet.