Here you find current and previous news from the PSI Center for Neutron and Muon Sciences.
Langlebiges pionisches Helium: exotische Materie erstmals experimentell nachgewiesen
Exotische Atome, in denen Elektronen durch andere Teilchen ersetzt werden, ermöglichen tiefe Einblicke in die Quantenwelt. Nach acht Jahren gelang einer internationalen Gruppe von Forschenden an der Pionenquelle des PSI ein schwieriges Experiment: Sie schufen ein künstliches Atom, sogenanntes «pionisches Helium».
Understanding Quantum Critical Magnetism in Han Purple
The ancient purple pigment used to paint the terracotta warriors, BaCuSi2O6, is also a quantum magnetic material which consists of stacked Cu2+ bilayers hosting spin dimers. Magnetometry and NMR experiments have revealed puzzling critical phenomena at the quantum phase transition (QPT) caused by an applied magnetic field, which suggest that the universal behaviour of the system is not three- but only two-dimensional. By performing high-resolution neutron spectroscopy measurements .....
Measurement of properties of Bs0 → μ+μ− decays and search for B0 → μ+μ− with the CMS experiment
Results are reported for the B0s → μ+μ− branching fraction and effective lifetime and from a search for the decay B0 → μ+μ−. The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7TeV (5fb−1), 8TeV (20fb−1),and 13TeV (36fb−1).
Batteries under the neutron stroboscope
The first application of stroboscopic neutron diffraction to studying lithium-ion batteries during operation establishes a new approach to unravelling the complex processes playing out in energy-storage materials.
Examining the surface evolution of LaTiOxNy an oxynitride solar water splitting photocatalyst
LaTiOxNy oxynitride thin films are employed to study the surface modifications at the solid- liquid interface that occur during photoelectrocatalytic water splitting. Neutron reflectometry and grazing incidence x-ray absorption spectroscopy were utilised to distinguish between the surface and bulk signals, with a surface sensitivity of 3 nm.
Professor Dr. Christian Rüegg neuer Direktor des Paul Scherrer Instituts
Der neue Direktor des Paul Scherrer Instituts tritt heute sein Amt an: Christian Rüegg will die Spitzenstellung der Grossforschungsanlagen des PSI weiter ausbauen und so den Forschungsstandort Schweiz stärken.
Electron–phonon-driven three-dimensional metallicity in an insulating cuprate
Elucidating the role of different degrees of freedom in a phase transition is crucial in the comprehension of complex materi- als. A phase transformation that attracts significant interest is the insulator-to-metal transition of Mott insulators, in which the electrons are thought to play the dominant role. Here, we use ultrafast laser spectroscopy and theoretical calculations ....
Spin ice expands to higher orders
With experimental work demonstrating that the correlated ground state of the pyrochlore system Ce2Sn2O7 is a quantum liquid of magnetic octupoles, an international team led by PSI researcher Romain Sibille establishes a fundamentally new state of matter: higher-rank multipole ice.
A quantum liquid of magnetic octupoles on the pyrochlore lattice
With experimental work demonstrating that the correlated ground state of the pyrochlore system Ce2Sn2O7 is a quantum liquid of magnetic octupoles, an international team led by PSI researcher Romain Sibille establishes a fundamentally new state of matter: higher-rank multipole ice.
Reversible spin storage in metal oxide - fullerene heterojunctions
We show that hybrid MnOx/C60 heterojunctions can be used to design a storage device for spin-polarized charge: a spin capacitor. Hybridization at the carbon-metal oxide interface leads to spin-polarized charge trapping after an applied voltage or photocurrent. Strong electronic structure changes, including a 1-eV energy shift and spin polarization in the C60 lowest unoccupied molecular orbital, are then revealed by x-ray absorption spectroscopy, in agreement with density functional theory simulations.
Quantifying Diffusion through Interfaces of Lithium-Ion Battery Active Materials
Detailed understanding of charge diffusion processes in a lithium-ion battery is crucial to enable its systematic improvement. Experimental investigation of diffusion at the interface between active particles and the electrolyte is challenging but warrants investigation as it can introduce resistances that, for example, limit the charge and discharge rates. Here, we show an approach to study diffusion at interfaces using muon spin spectroscopy.
Current-driven magnetic domain-wall logic
Spin-based logic architectures provide nonvolatile data retention, near-zero leakage, and scalability, extending the technology roadmap beyond complementary metal–oxide–semiconductor logic. Architectures based on magnetic domain walls take advantage of the fast motion, high density, non-volatility and flexible design of domain walls to process and store information. Such schemes, however, rely on domain-wall manipulation and clocking using an external magnetic field, which limits their implementation in dense, large-scale chips.
Broken time-reversal symmetry in the topological superconductor UPt3
Topological properties of materials are of fundamental as well as practical importance. Of particular interest are unconven- tional superconductors that break time-reversal symmetry, for which the superconducting state is protected topologically and vortices can host Majorana fermions with potential use in quantum computing. However, in striking contrast to the unconventional A phase of superfluid 3He where chiral symmetry was directly observed, .....
Symposium in memory of Jean-Pierre Blaser
Jean-Pierre Blaser (1923-2019) was one of the founders of the Swiss Institute for Nuclear Research SIN - one of the two institutions, which merged to the Paul Scherrer Institut in 1988. From 1988-1990 he was the first Director of the Paul Scherrer Institut. On the occasion of his first obit ETH Zurich and PSI organised a symposium to honour the lifetime achievement of this outstanding Swiss physicist.
Dem Rätsel der Materie auf der Spur
Forschende haben an der Quelle für ultrakalte Neutronen des PSI eine Eigenschaft des Neutrons so genau wie noch nie vermessen: sein elektrisches Dipolmoment. Denn bis heute wird nach einer Erklärung gesucht, weshalb es nach dem Urknall mehr Materie als Antimaterie gab.
Kurzfilm eines magnetischen Nanowirbels
Mit einer neu entwickelten Untersuchungsmethode konnten Forschende die magnetische Struktur im Inneren eines Materials mit Nanometer-Auflösung abbilden. Ihnen gelang ein kurzer «Film» aus sieben Bildern, der erstmalig in 3-D zeigt, wie sich winzige Wirbel der Magnetisierung tief im Inneren eines Materials verändern.
Observation of a Charge-Neutral Muon-Polaron Complex in Antiferromagnetic Cr2O3
We report a comprehensive muon spin rotation (μSR) study of the prototypical magnetoelectric antiferromagnet Cr2O3. We find the positively charged muon (μ+) occupies several distinct interstitial sites and displays a rich dynamic behavior involving local hopping, thermally activated site transitions, and the formation of a charge-neutral complex composed of a muon and an electron polaron.
A link between quantum magnetism and electronic band topology
Muon spin rotation experiments establish a quantitative link between the magnetic and topological electronic properties of the kagome magnet Co3Sn2S2 — and demonstrate effective ways for tuning these properties.
Tunable anomalous Hall conductivity through volume-wise magnetic competition in a topological kagome magnet
Magnetic topological phases of quantum matter are an emerging frontier in physics and material science. Along these lines, several kagome magnets have appeared as the most promising platforms. Here, we explore magnetic correlations in the kagome magnet Co3Sn2S2. Using muon spin-rotation, we present evidence for competing magnetic orders in the kagome lattice of this compound.
Possible room-temperature signatures of unconventional 4f-electron quantum criticality in YbMn6Ge6−xSnx
We investigate the Sn composition dependence of the Yb valence and local magnetization in YbMn6Ge6−xSnx (4.25 ≤x≤ 5.80) using x-ray absorption spectroscopy (XANES) and x-ray magnetic circular dichroism at the Yb L3 edge. In these materials, where Mn is ferromagnetically ordered, we observe a decrease of the Yb valence upon reducing the chemical pressure by Sn doping and a suppression of the Yb magnetic moment for strongly hybridized 4f states (ν ∼ 2.77).
Magnetism and anomalous transport in the Weyl semimetal PrAlGe: possible route to axial gauge fields
In magnetic Weyl semimetals, where magnetism breaks time-reversal symmetry, large magnetically sensitive anomalous transport responses are anticipated that could be useful for topological spintronics. The identification of new magnetic Weyl semimetals is therefore in high demand, particularly since in these systems Weyl node configurations may be easily modified using magnetic fields. Here we explore experimentally the magnetic semimetal PrAlGe, and unveil a direct correspondence between easy-axis Pr ferromagnetism and anomalous Hall and Nernst effects.
Anna Sótér starts Ambizione fellowship
Anna Sótér has started an Ambizione fellowship at ETH Zurich and PSI. Her project is dedicated to developing a novel source of cold muonium atoms, which will be used for a new interferometry experiment that enables testing the weak equivalence principle by directly probing gravitational interaction of antimatter.
Gut lackierte Geigen spielen länger
Traditionell werden Geigen lackiert, um sie vor Luftfeuchtigkeit und anderen Umwelteinflüssen zu schützen. Ein Wissenschaftler-Team hat am PSI untersucht, welchen Einfluss unterschiedliche Anstriche auf das Instrument haben. Tatsächlich sollte man auf den Lack keinesfalls komplett verzichten.
Topological Magnetic Phase in the Candidate Weyl Semimetal CeAlGe
We report the discovery of topological magnetism in the candidate magnetic Weyl semimetal CeAlGe. Using neutron scattering we find this system to host several incommensurate, square-coordinated multi-k⃗ magnetic phases below TN. The topological properties of a phase stable at intermediate magnetic fields parallel to the c axis are suggested by observation of a topological Hall effect.
Modellieren und Simulieren zahlt sich aus
Forschende des Labors für Simulation und Modellierung des PSI lösen durch die Kombination von Theorie, Modellierung und Hochleistungsrechnen komplexeste Probleme. Mit leistungsfähigen Computern simulieren sie kleinste Moleküle oder Grossforschungsanlagen.
Workshop on the Physics of Fundamental Symmetries and Interactions
The 5th Workshop on the Physics of Fundamental Symmetries and Interactions (PSI2019) took place from 20 to 25 October 2019 at PSI, bringing together 200 scientists from all over the world working on some of today’s most precise particle-physics experiments at the low-energy frontier.
Determination and evaluation of the nonadditivity in wetting of molecularly heterogeneous surfaces
Every folded protein presents an interface with water that is composed of domains of varying hydrophilicity/-phobicity. Many simulation studies have highlighted the nonadditivity in the wetting of such nanostructured surfaces in contrast with the accepted theoretical formula that is additive. We present here an experimental study on surfaces of identical composition but different organization of hydrophobic and hydrophilic domains.
TecDay: LMX meets Hohe Promenade
TecDay is an SATW initiative that was developed at the Kantonsschule Limmattal in 2007 and has since been rolled out to more than 60 secondary schools across Switzerland. By the end of 2017 it had reached around 45,000 students and 5,000 teachers. In December 2019 the LMX contributed in one module, that received a total of 16 students over the course of a morning. The module was organized in three different “stations”, each one focusing on one topic or area that the group is working on.
Field-induced double spin spiral in a frustrated chiral magnet
Magnetic ground states with peculiar spin textures, such as magnetic skyrmions and multifunctional domains are of enormous interest for the fundamental physics governing their origin as well as potential applications in emerging technologies. Of particular interest are multiferroics, where sophisticated interactions between electric and magnetic phenomena can be used to tailor several functionalities.
The multi-layered physics of layered superconductors
Muon spin rotation experiments provide unique microscopic insight into the superconductivity and magnetism of transition metal dichalcogenides — and reveal complex and unconventional patterns, hinting towards a common mechanism for and electronic origin of ‘unconventional’ superconductivity.