Scientific Highlights

PSI scientists have developed tailored diffractive X-ray optics for a free electron laser that induces an optical vortex in extreme ultraviolet radiation. The experiment facilitates the first demonstration of orbital angular momentum in radiation created by a free electron laser in the extreme ultraviolet regime, with an extraordinary clean and defined wavefront. In a collaborative effort with researchers from the FERMI free electron laser in Trieste, Italy and from the University of Nova Gorica in Slovenia, the wavefront of the intense beams carrying an orbtial angular momentum was characterized. Furthermore, a method to characterize the footprint of a focused beam from a free electron laser was refined based on ablation imprints in polymers and subsequent treatment with organic solvents. In this way, the sensitivity of the imprint method could be enhanced to a dynamic range of three orders of magnitude in a single shot.

13 November 2017 – Brussels – 16 organisations representing 19 light sources facilities across Europe gathered to launch the LEAPS initiative and signed an agreement to strengthen their collaboration, in the presence of Robert-Jan Smits, Director General for Research and Innovation (RTD) at the European Commission, and Giorgio Rossi, Chair of the European Strategy Forum on Research Infrastructures (ESFRI).

The unexpected finding that in an ‘artificial spin ice’ magnetostatic energy can be transformed into directed rotation of magnetization provides fresh insights into such nano-patterned magnetic structures — and might enable novel applications in nanoscale devices.

Friday, October 20th, 2017, we brought the first light (wavelength 1.2 nm) into the experimental hutch of Bernina. The beam passed the Alvra endstation, went through the diagnostic devices and hit the diagnostic screen in front of the refocussing KB-system of Bernina. The upper picture shows the pink beam on the last diagnostic screen of the beamline. The lower left at the entrance of Bernina-hutch, 133 m downstream of the undulator. The lower right picture shows the beam centered in the alignment iris in front of the KB-system.

Fluid catalytic cracking catalysts, which are composite particles of hierarchical porosity, were examined using ptychographic X-ray tomography. These particles are essential to the conversion of crude oil into gasoline. Examination of catalysts at decreasing levels of catalytic conversion efficacy allowed the detection of possible deactivation causes.

Current-induced spin-orbit torques hold a great potential for manipulation of magnetization at ultrafast timescales. Researchers at ETH Zürich have demonstrated, using time-resolved STXM imaging at the Swiss Light Source, the influence of spin-orbit torques on the switching behaviour of Pt/Co/AlO_x nanostructured elements.

Highly crystalline thin films of organic semiconductors offer great potential for high-performance, low-cost flexible electronics. Researchers at IMEC Belgium have developed a new double-step thin film fabrication process that offers higher performance devices. Soft X-ray spectro-microscopy at the Swiss Light Source was used to prove that the increased performance comes from larger areas of material sharing the same molecular orientation.

The ATHOS Conceptual Design Report has recently been completed and describes the ATHOS project in detail. The CDR starts with a summary of the characteristics of the ATHOS undulator line. Especially the design parameters of the different ATHOS operation modes are explained and illustrated by simulation results. The core part of the report is a description of all key components, i.e. from the electron bunch extraction kicker down to the ATHOS experimental stations.

The SPS 2017 Prize in Condensed Matter Physics, sponsored by IBM, has been awarded to Dr. Nan Xu for his excellent work on topological quantum states. Dr. Nan Xu is a joint postdoc of Paul Scherrer Institute (PSI) and the École Polytechnique Fédérale de Lausanne (EPFL).

PSI scientists have developed a new type of X-ray optics that allows for analyzing the emission in resonant inelastic x-ray scattering (RIXS) experiments. The new approach combines the energy dispersion with imaging capabilities. In a collaborative effort with research groups from Göttingen and Hamburg, two new classes of RIXS experiments, energy mapping and RIXS imaging, have been demonstrated.

The advent of x-ray free electron lasers has extended the unique capabilities of resonant x-ray spectroscopy techniques to ultrafast time scales. Here, in collaboration between researchers from PSI, Sorbonne Universités, HASYLAB/DESY, Synchrotron SOLEIL, CNRS, and Uppsala University, we report on a novel experimental method that allows retrieving with a single x-ray pulse the time evolution of an ultrafast process, not only at a few discrete time delays, but continuously over an extended time window.

By combining a scalable cutting-edge synthesis method with time-resolved X-ray absorption spectroscopy measurements, it was possible to capture the dynamic local electronic and geometric structure during realistic operando conditions for highly active OER perovskite nanocatalysts.

Lignin is a major constituent of plants, and may be used as a precursor for fuels and fine chemicals. Catalytic fast pyrolysis of lignin is one of the most promising approaches. By using vacuum ultraviolet synchrotron radiation and threshold photoelectron spectroscopy we could identify elusive intermediates, which are responsible for the formation of phenol and benzene and could thus tackle this reaction mechanism. Mechanistic understanding could enable targeted improvement of production methods in the future, beyond the currently used "cook-and-look" approach.

Scientists at the SLAC National Accelerator Laboratory and Stanford University - one of the leading authors, Simon Gerber, has in the meantime relocated to PSI - have made the first direct measurements, and by far the most precise ones, of how electrons move in sync with atomic vibrations rippling through an quantum material, in the present study an unconventional superconductor, as if they were “dancing" to the same beat.

A very thin layer on this beetle’s wings exhibits a complicated structure on the nanoscale that gives them a bright white color. X-ray nanotomography acquired at the Swiss Light Source provides a faithful image of this structure in three dimensions with which scientists can confirm its evolutionary optimization: just enough material for an efficient reflection of white light.

Online combustion analysis relies heavily on spectral data to detect reactive intermediates isomer-selectively to establish e.g. kinetic flame models. Due to the difficulty to generate these species cleanly, spectral data are rather scarce. Here we report on the selective generation of three picolyl radical isomers (C₅H₄N-CH₂*) by deamination of aminomethylpyridines. Picolyl radicals are relevant in biofuel combustion, and could now be characterized by threshold photoelectron spectroscopy using synchrotron radiation. Vibrationally resolved bands and distinct ionization energies allow for isomer-specific detection of these elusive species in complex environments and permit us to explore new avenues in soot- and NOx formation kinetics.

Free electron lasers (FELs) like SwissFEL help scientists to understand the mechanisms that switch properties of materials which are the basis for functions in electronics, solar cells, chemistry and biology. By using ultrashort X-ray pulses it becomes possible to visualize the ultrafast rearrangements of electrons and atoms that enable the properties to switch in molecules or crystals.

Researchers from China and USA join forces with Swiss Light Source (SLS) macromolecular crystallography (MX) beamline scientists in a study, which aims at understanding an important step in the life cycle of the human betacoronavirus HKU1.

For the first time, researchers have produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Paul Scherrer Institute, in collaboration with their research partners, published the findings in the journal Nature Communications.

The electron beam energy of SwissFEL was recently increased to above 900 MeV by successfully bringing two new accelerating modules into operation. This allowed SwissFEL to produce laser radiation for the first time in the soft x-ray regime with a photon wavelength of 4.1 nm. During the next months, the electron beam energy will be progressively further increased with the goal of enabling first user experiments at a wavelength of around 0.5 nm towards the end of this year.

A novel type of diffractive lenses based on interlaced structures enable x-ray imaging at resolutions below 10 nm. The fabrication method and the test results of these novel x-ray lenses have been published in the journal Scientific Reports.

A nanofabricated low emittance field emitter array cathode was demonstrated for the first time, and successfully applied to observe the low-energy electron diffraction from suspended monolayer graphene. The work has an impact on the future development of compact X-ray free electron lasers, THz/RF vacuum electronic sources, and ultrafast electron imaging and diffraction experiments.

Single holmium atoms adsorbed on few monolayers of magnesium oxide are extraordinarily stable magnets. They retain a significant fraction of their magnetization when the external magnetic field is switched off. This has been shown recently in a study combining x-ray magnetic circular dichroism performed at the Swiss Light Source (SLS) and at the European Synchrotron Radiation Facility (ESRF) as well as scanning tunneling microscopy. The results open perspectives of storing and processing information at ultrahigh density.

The first example of an insulating phase which is close to the superconducting phase in an iron-pnictide system has been recently observed in heavy Cu-doped NaFe_1-xCuxAs (x > 0.3). A combined study by angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations revealed that on-site Coulomb repulsion and enhanced Hund’s rule coupling are responsible for the insulating behavior. The results show that the insulating phase in NaFe_0.5Cu_0.5As resembles the situation in the parent compounds of the high-T_c cuprate superconductors.

Researchers from PSI and EPFL have demonstrated that the magnetization hysteresis and remanence of TbPc₂ single-molecule magnets drastically depends on the substrate on which they are deposited. If a few atomic layers thick magnesium oxide film grown on a silver substrate is used, a record wide hysteresis and record large remanence can be obtained. Single-molecule magnets are attractive for molecular spintronics applications such as information processing or storage.

Researchers have overcome a number of challenges in order to employ an advanced probe in the study of an unusual material, barium bismuth oxide (BaBiO3) – an insulating parent compound of a family of high-temperature superconductors known since the late 80s. In order to finally realize the experiments, the researchers grew and studied thin films of the material completely in situ under ultrahigh vacuum conditions. The results show that superconductivity in bismuth oxides emerges out of a novel insulating phase, where hole pairs located on combinations of the oxygen orbitals are coupled with distortions of the crystal lattice.

A promising system for painless and minimally-invasive therapeutic drug monitoring has been demonstrated. The proposed device combines biofunctionalized hollow microneedles with an optofluidic system to measure drug concentrations in volumes as small as 0.6 nL.

A method to precisely alter the quantum mechanical states of electrons within an array of quantum boxes has been developped by an international consortium also including PSI. The method can be used to investigate the interactions between various types of atoms and electrons, which is essential for future quantum technologies.

The answer to this question could save food industry a lot of money and reduce food waste caused by faulty production. Researchers from the University of Copenhagen and the Paul Scherrer Institut have obtained a 3D image of food on the nanoscale using ptychographic X-ray computed tomography. This work paves the way towards a more detailed knowledge of the structure of complex food systems.

The Angle Resolved Photoemission Spectroscopy (ARPES) measurements performed on 2DEL at STO surface revealed that, at low carrier density, electrons are always accompanied by a quantized dynamic lattice deformation. Together with the electron, these phonon-cloud formed a new composite quasiparticle called Fröhlich polaron.