Scientific Highlights: Research Division "Research with Neutrons and Muons"
A plan for the world’s biggest machine
Interview with Lea Caminada, head of the High Energy Particle Physics Group at PSI, about the next potential large project at CERN.
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 ...
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 ...
Electron Glass Phase with Resilient Zhang-Rice Singlets in LiCu3O3
LiCu3O3 is an antiferromagnetic mixed valence cuprate where trilayers of edge-sharing Cu(II)O (3d9) are sandwiched in between planes of Cu(I) (3d10) ions, with Li stochastically substituting Cu(II). Angle-resolved photoemission spectroscopy (ARPES) and density functional theory reveal two insulating electronic subsystems that are segregated in spite of sharing common oxygen atoms: a Cu dz2/O pz derived valence band (VB) dispersing on the Cu(I) plane, and a Cu 3dx2−y2/O 2px,y derived Zhang-Rice singlet (ZRS) band dispersing on the Cu(II)O planes.
Making powerful lithium-air batteries suitable for everyday use
Chemical processes in lithium-air batteries revealed using neutron beams and synchrotron light.
Flat-band hybridization between f and d states near the Fermi energy of SmCoIn5
We present high-quality angle-resolved photoemission (ARPES) and density functional theory calculations (DFT+U) of SmCoIn5. We find broad agreement with previously published studies of LaCoIn5 and CeCoIn5, confirming that the Sm 4f electrons are mostly localized. Nevertheless, our model is consistent with an additional delocalized Sm component, stemming from hybridization between the 4f electrons and the metallic bands at “hot spot” positions in the Brillouin zone.
Introduction to Muon Spin Spectroscopy
Alex Amato and Elvezio Morenzoni (both NUM) have published a new textbook entitled 'Introduction to Muon Spin Spectroscopy: Applications to Solid State and Material Sciences'. The book is ideal for a first course in muon spin spectroscopy (µSR), comes enriched with exercises and solutions to master the subject and includes practical examples to quantify key experimental parameters.
Observation by SANS and PNR of pure Néel-type domain wall profiles and skyrmion suppression below room temperature in magnetic [Pt/CoFeB/Ru]10 multilayers
The study presents a unique investigation of [Pt/CoFeB/Ru]10 multilayers, revealing suppressed skyrmion phases, intricate magnetic domain structures, and Néel-type domain walls, providing crucial insights for spintronic applications.
Cause of clogged hypodermic needles discovered
Researchers at PSI and the ANAXAM technology transfer center have found the cause of clogging in prefilled syringes.
Protons and other particles: The HIPA facility turns 50
Since 1974 HIPA has been accelerating protons for research.
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 ...
Tuning of the flat band and its impact on superconductivity in Mo5Si3−xPx
The superconductivity in systems containing dispersionless (flat) bands is seemingly paradoxical, as traditional Bardeen-Cooper-Schrieffer theory requires an infinite enhancement of the carrier masses. However, the combination of flat and steep (dispersive) bands within the multiple band scenario might boost superconducting responses, potentially explaining high-temperature superconductivity in cuprates and metal hydrides. Here, we report ...
Interface-induced superconductivity in magnetic topological insulators
One of the recipes for realizing topological superconductivity calls for interfacing a topological insulator with a superconductor. In a variant of that approach, Yi et al. grew a heterostructure consisting of layers of a magnetic topological insulator, (Bi,Sb)2Te3 doped with chromium, and antiferromagnetic iron telluride. Neither of these materials is superconducting, but iron telluride is a parent compound for a family of iron-based superconductors. Interfacing the layers led to the appearance of superconductivity in the presence of ferromagnetism and topological band structure. This combination of properties makes the heterostructure a promising, although not yet proven, platform for observing chiral topological superconductivity.
Magnetostriction-Driven Muon Localization in an Antiferromagnetic Oxide
Magnetostriction results from the coupling between magnetic and elastic degrees of freedom. Though it is associated with a relatively small energy, we show that it plays an important role in determining the site of an implanted muon, so that the energetically favorable site can switch on crossing a magnetic phase transition. This surprising effect is demonstrated in the cubic rocksalt antiferromagnet MnO which undergoes a magnetostriction-driven rhombohedral distortion at the Néel temperature TN = 118 K. Above TN ...
A precision mechanical masterpiece in miniature
With the discovery of a golden miniature box lock, an extraordinary and unique archaeological find was made in north-western Germany by a licensed detectorist.
The object represents an extremely reduced and valuable version of the provincial Roman box locks. These everyday objects were in general significantly larger and normally made either of iron, iron with silver or bronze bands or bronze.
Field-induced bound-state condensation and spin-nematic phase in SrCu2(BO3)2 revealed by neutron scattering up to 25.9 T
In quantum magnetic materials, ordered phases induced by an applied mag- netic field can be described as the Bose-Einstein condensation (BEC) of mag- non excitations. In the strongly frustrated system SrCu2(BO3)2, no clear magnon BEC could be observed, pointing to an alternative mechanism, but the high fields required to probe this physics have remained a barrier to detailed investigation.Here we exploit the first purpose-built high-field neutron scattering facility to measure ...
Designing the stripe-ordered cuprate phase diagram through uniaxial-stress
Understanding the degree to which charge-stripe, spin-stripe, and superconducting orders compete/coexist is paramount for elucidating the microscopic pairing mechanism in the cuprate high-temperature superconductors. We explore the tunability of magnetism, superconductivity, and crystal structure in the stripe phase of the cuprate La2−xBaxCuO4, by employing complementary techniques under compressive uniaxial stress in the CuO2 plane. Our results show a sixfold increase ...
Dichotomous Electrons: Travelling without Moving
Neutron scattering experiments give new understanding of how localized and free-flowing electrons collaborate to create material functionality.