Scientific Highlights: Research Division "Research with Neutrons and Muons"
Spin-triplet superconductivity in Weyl nodal-line semimetals
Topological semimetals are three dimensional materials with symmetry-protected massless bulk excitations. As a special case, Weyl nodal-line semimetals are realized in materials having either no inversion or broken time-reversal symmetry and feature bulk nodal lines. The 111-family, including LaNiSi, LaPtSi and LaPtGe materials (all lacking inversion symmetry), belongs to this class. Here, by combining muon-spin rotation and relaxation with thermodynamic measurements, we find that these materials exhibit a fully- gapped superconducting ground state, while spontaneously breaking time-reversal symmetry at the superconducting transition.
First demonstration of tuning between the Kitaev and Ising limits in a honeycomb lattice
Recent observations of novel spin-orbit coupled states have generated interest in 4d/5d transition metal systems. A prime example is the Jeff = 1/2 state in iridate materials and α-RuCl that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction (λSOC) and trigonal crystal field (ΔT), we restructure the spin-orbital wave functions into a previously unobserved μ=1/2 state that drives Ising interactions.
The Running Bottom Quark Mass and the Higgs Boson
We present a new measurement of the bottom quark mass in the MS scheme at the renormalization scale of the Higgs boson mass from measurements of Higgs boson decay rates at the LHC: mb (mH) = 2.6 +0.36-0.31 GeV. The measurement has a negligible theory uncertainty and excellent prospects to improve at the HL-LHC and a future Higgs factory.
Antiprotons in superfluid helium: a new way for sensitive measurements of antimatter
Scientists, publishing in Nature, have found that a hybrid antimatter-matter atom behaves in an unexpected way when submerged in superfluid helium.
Two million Swiss francs granted to search for new physics
Philipp Schmidt-Wellenburg will set up a novel experiment at a muon beamline at PSI.
Direct observation of a dynamical glass transition in a nanomagnetic artificial Hopfield network
Spin glasses, generally defined as disordered systems with randomized competing interactions, are a widely investigated complex system. Theoretical models describing spin glasses are broadly used in other complex systems, such as those describing brain function, error-correcting codes or stock-market dynamics. This wide interest in spin glasses provides strong motivation to generate an artificial spin glass within the framework of artificial spin ice systems. Here we present the experimental realization of an artificial spin glass consisting of dipolar coupled single-domain Ising-type nanomagnets arranged onto an interaction network that replicates the aspects of a Hopfield neural network.
Waves on circular paths
Just as electrons flow through an electrical conductor, magnetic excitations can travel through certain materials. Such excitations, known in physics as "magnons" in analogy to the electron, could transport information much more easily than electrical conductors. An international research team has now made an important discovery on the way towards such components, which could be highly energy-efficient and considerably smaller.
Optical Setup for a Piston-Cylinder Pressure Cell: A Two-Volume Approach
Measurement of the absolute value of the applied pressure in high-pressure muon and neutron experiments is a complicated task. It often requires the presence of a calibration material inside the sample volume, and could also cause additional time to obtain the response of the calibrant. Here we describe the use of optical calibrants for precise determination of the pressure value inside the piston-cylinder clamp cells.
Antiferromagnetic excitonic insulator state in Sr3Ir2O7
Excitonic insulators are usually considered to form via the condensation of a soft charge mode of bound electron-hole pairs. This, however, presumes that the soft exciton is of spin-singlet character. Early theoretical considerations have also predicted a very distinct scenario, in which the condensation of magnetic excitons results in an antiferromagnetic excitonic insulator state. Here we report resonant inelastic x-ray scattering (RIXS) measurements of Sr3Ir2O7.
New insight into unconventional superconductivity
Signatures for a novel electronic phase that enables charge to flow spontaneously in loops have been observed in a kagome superconductor. The findings are published today in Nature.
Muon spin spectroscopy
Muons are particles with a spin of 1⁄2 that can be implanted into a wide range of condensed matter materials to act as a local probe of the surrounding atomic environment. Measurement of the muon’s precession and relaxation provides an insight into how it interacts with its local environment. From this, unique information is obtained about the static and dynamic properties of the material of interest ...
Celebrating 25 years of SINQ
On January 17th, 2022, we celebrated the 25th anniversary of the inauguration of the Swiss Spallation Neutron Source SINQ. Today, SINQ is firmly embedded in the European research landscape and has established itself as an important center for neutron research.
Confirming the trilinear form of the optical magnetoelectric effect in the polar honeycomb antiferromagnet Co2Mo3O8
Magnetoelectric phenomena are intimately linked to relativistic effects and also require the material to break spatial inversion symmetry and time-reversal invariance. Magnetoelectric coupling can substantially affect light–matter interaction and lead to non-reciprocal light propagation. Here, we confirm on a fully experimental basis, without invoking either symmetry-based or material-specific assumptions, that the optical magnetoelectric effect in materials with non-parallel magnetization (M) and electric polarization (P) generates a trilinear term in the refractive index...
Precision Measurement of the Lamb Shift in Muonium
We report a new measurement of the n=2 Lamb shift in Muonium. Our result of 1047.2(2.3)stat(1.1)syst MHz comprises an order of magnitude improvement upon the previous best measurement. This value matches ...
Signatures of Weyl Fermion Annihilation in a Correlated Kagome Magnet
The manipulation of topological states in quantum matter is an essential pursuit of fundamental physics and next-generation quantum technology. Here we report the magnetic manipulation of Weyl fermions in the kagome spin-orbit semimetal Co3Sn2S2, observed by high-resolution photoemission spectroscopy. We demonstrate the exchange collapse of spin-orbit-gapped ferromagnetic Weyl loops into paramagnetic Dirac loops under suppression of the magnetic order.
The world’s most powerful neutron microscope
PSI scientists help construct the new European Spallation Source ESS
Amyloid β 42 fibril structure based on small-angle scattering
Alzheimers disease is one of the major global health challenges. Neuronal cell dysfunction and death are connected to the self-assembly of the amyloid β peptide (Aβ42) into oligomeric and fibrillar aggregates. The fibril surface can catalyze the formation of toxic oligomers via secondary nucleation.
Unconventional Pressure Dependence of the Superfluid Density in the Nodeless Topological Superconductor α-PdBi2
We investigated the superconducting properties of the topological superconductor α-PdBi2 at ambient and external pressures up to 1.77 GPa using muon spin rotation experiments. The ambient pressure measurements evince a fully gapped s-wave superconducting state in the bulk of the specimen. Alternating current magnetic susceptibility and muon spin rotation measurements manifest a continuous suppression of Tc with increasing pressure.
What you see is what you get: Automated particle detection without the false positives
A new algorithm by PSI researchers enables fast and reliable detection of spherical objects in images with a complex background.
Coexistence of structural and magnetic phases in van der Waals magnet CrI3
CrI3 has raised as an important system to the emergent field of two-dimensional van der Waals magnetic materials. However, it is still unclear why CrI3 which has a ferromagnetic rhombohedral structure in bulk, changed to anti-ferromagnetic monoclinic at thin layers. Here we show that this behaviour is due to the coexistence of both monoclinic and rhombohedral crystal phases followed by three magnetic transitions at TC1 = 61 K, TC2 = 50 K and TC3 = 25 K.