Here you find current and previous news from the NUM division. For scientific highlights, please have a look here.
Strong Superexchange in a d^(9−δ) Nickelate Revealed by Resonant Inelastic X-Ray Scattering
The discovery of superconductivity in a d9−δ nickelate has inspired disparate theoretical perspectives regarding the essential physics of this class of materials. A key issue is the magnitude of the magnetic superexchange, which relates to whether cuprate-like high-temperature nickelate superconductivity could be realized. We address this question using Ni L-edge and O K-edge spectroscopy of the reduced d9−1/3 trilayer nickelates R4Ni3O8 (where R = La, Pr) and associated theoretical modeling.
The Swiss research infrastructure for particle physics CHRISP
Researchers are looking for deviations in the current standard model of physics and want to find out how our universe is constructed.
Unconventional Transverse Transport above and below the Magnetic Transition Temperature in Weyl Semimetal EuCd2As2
As exemplified by the growing interest in the quantum anomalous Hall effect, the research on topology as an organizing principle of quantum matter is greatly enriched from the interplay with magnetism. In this vein, we present a combined electrical and thermoelectrical transport study on the magnetic Weyl semimetal EuCd2As2. Unconventional contribution to the anomalous Hall and anomalous Nernst effects were observed both above and below the magnetic transition temperature of EuCd2As2, indicating the existence of significant Berry curvature.
Decomposing Magnetic Dark-Field Contrast in Spin Analyzed Talbot-Lau Interferometry: A Stern-Gerlach Experiment without Spatial Beam Splitting
We have recently shown how a polarized beam in Talbot-Lau interferometric imaging can be used to analyze strong magnetic fields through the spin dependent differential phase effect at field gradients. While in that case an adiabatic spin coupling with the sample field is required, here we investigate a nonadiabatic coupling causing a spatial splitting of the neutron spin states with respect to the external magnetic field. This subsequently leads to no phase contrast signal but a loss of interferometer visibility referred to as dark-field contrast.
Size of helium nucleus measured more precisely than ever before
In experiments at the Paul Scherrer Institute PSI, an international research collaboration has measured the radius of the atomic nucleus of helium five times more precisely than ever before. The researchers are publishing their results today in the journal Nature.
Size of helium nucleus measured more precisely than ever before
In experiments at the Paul Scherrer Institute PSI, an international research collaboration has measured the radius of the atomic nucleus of helium five times more precisely than ever before. The new value can be used to test fundamental physical theories.
Magnetically shielded from the rest of the world
At the Paul Scherrer Institute PSI, researchers together with a company have constructed a room that is one of the best magnetically shielded places on the earth. With its help, they want to solve the last mysteries of matter and answer a fundamental question: Why does matter - and thus why do we - exist at all?
Interdependent scaling of long-range oxygen and magnetic ordering in nonstoichiometric Nd2NiO4.10
The interplay between oxygen and spin ordering for the low oxygen doped Nd2NiO4.10 has been investigated by single-crystal neutron diffraction. We find a coexistence of the magnetic order below TN with the 3D ordering of excess oxygen atoms, which has not been previously observed for the homologous nickelates. Moreover, the magnetic ordering modulation vectors are no longer independent and exactly follow the modulation vectors of the oxygen ordering.
A new small angle neutron scattering instrument arrives at SINQ from LLB
In 2018 an agreement between the Laboratoire Léon Brillouin (LLB) and Paul Scherrer Institut has been signed with the aim to jointly operate a new small angle neutron scattering (SANS) instrument at the Swiss spallation neutron source SINQ.
Marc Janoschek appointed Associate Professor ad personam at University of Zurich
Marc Janoschek, the head of the Laboratory for Neutron and Muon Instrumentation (LIN), was appointed as Associate Professor ad personam for experimental physics – correlated quantum materials at the University of Zurich starting February 1, 2021.
Quantum spin-liquid states in an organic magnetic layer and molecular rotor hybrid
A better understanding of quantum spin liquids (QSLs), where spin dimer configurations are fluctuating even at the low- est temperatures, could be of use in quantum information, in superconducting or other technologies. This macroscopic collective state typically arises from geometrical frustration or low dimensionality. In the layered EDT-BCO, we report a QSL state, which is generated, on different bases, with the intrinsic disorder.
FALCON - a new instrument project at SINQ
Early 2020, an agreement between the Helmholtz-Zentrum Berlin and Paul Scherrer Institut has been signed, according to which the recently commissioned Laue Diffractometer Falcon (E11) would be transferred from HZB to PSI. The purpose of this agreement was to make state-of-the-art equipment from the recently closed research reactor BER-II at HZB work for scientific community at SINQ.
Observation of plaquette fluctuations in the spin-1/2 honeycomb lattice
Quantum spin liquids are materials that feature quantum entangled spin correlations and avoid magnetic long-range order at T =0 K. Particularly interesting are two-dimensional honeycomb spin lattices where a plethora of exotic quantum spin liquids have been predicted. Here, we experimentally study an effective S = 1/2 Heisenberg honeycomb lattice with competing nearest and next-nearest-neighbour interactions.
Revealing Creep Motion of a Skyrmion Lattice at Ultra-Low Current Densities
Magnetic skyrmions are well-suited for encoding information because they are nano-sized, topologically stable, and only require ultra-low critical current densities jc to depin from the underlying atomic lattice. Above jc, skyrmions exhibit well-controlled motion, making them prime candidates for race-track memories. In thin films thermally-activated creep motion of isolated skyrmions was observed below jc as predicted by theory.
Particle-size dependent structural transformation of skyrmion lattice
Magnetic skyrmion is a topologically protected particle-like object in magnetic materials, appearing as a nanometric swirling spin texture. The size and shape of skyrmion particles can be flexibly controlled by external stimuli, which suggests unique features of their crystallization and lattice transformation process. Here, we investigated the detailed mechanism of structural transition of skyrmion lattice (SkL) in a prototype chiral cubic magnet Cu2OSeO3, by combining resonant soft X-ray scattering (RSXS) experiment and micromagnetic simulation...
Multiphase magnetism in Yb2Ti2O7
Quantum materials have properties that defy conventional theories of solids. Explaining these unusual properties is a frontier in physics, which promises both technological applications and fundamentally new states of matter. Yb2Ti2O7 is a center of attention in this work. While it becomes ferromagnetic at very low temperature, its excitation spectrum resembles that of a quantum spin liquid. We show using neutron scattering ...
Prestigious IEEE award for Stefan Ritt
Stefan Ritt, leader of the Muon Physics group at the Laboratory for Particle Physics, has received today the prestigious IEEE Emilio Gatti Radiation Instrumentation Technical Achievement Award, for "contributions to the development and democratization of ultra-high-speed digitizers”.
On the winners’ podium at the SwissSkills professional championships
With Mario Liechti (gold) and Melvin Deubelbeiss (bronze) two of our electronics apprentices achieved a place on the winners’ podium at the SwissSkills 2020. The SwissSkills are the Swiss professional championships organized by the leading industry associations. The final competition took place October 27 - 30, 2020 at Schindler Elevators in Ebikon.
Re(1−x)Mox as an ideal test case of time-reversal symmetry breaking in unconventional superconductors
Non-centrosymmetric superconductors (NCSCs) are promising candidates in the search for unconventional and topological superconductivity. The α-Mn-type rhenium-based alloys represent excellent examples of NCSCs, where spontaneous magneticfields, peculiar to time-reversal symmetry (TRS) breaking, have been shown to develop in the superconducting phase. By converse, TRS is preserved in many other isostructural NCSCs, thus leaving the key question about its origin fully open. Here, we consider ...
From magnetic order to quantum disorder in the Zn-barlowite series of S = 1/2 kagomé antiferromagnets
We report a comprehensive muon spectroscopy study of the Zn-barlowite series of S=1/2 kagomé antiferromagnets, ZnxCu4−x(OH)6FBr, for x = 0.00 to 0.99(1). By combining muon spin relaxation and rotation measurements with state-of-the-art density-functional theory muon-site calculations, we observe the formation of both μ–F and μ–OH complexes in Zn-barlowite. From these stopping sites, implanted muon spins reveal the suppression of long-range magnetic order into a possible quantum spin liquid state upon the increasing concentration of Zn-substitution.
Front passivation of Cu(In,Ga)Se2 solar cells using Al2O3: Culprits and benefits
In the past years, the strategies used to break the Cu(In,Ga)Se2 (CIGS) light to power conversion effi- ciency world record value were based on improvements of the absorber optoelectronic and crystalline properties, mainly using complex post-deposition treatments. To reach even higher efficiency values, fur- ther advances in the solar cell architecture are needed, in particular, with respect to the CIGS interfaces. In this study, we evaluate the structural, morphological and optoelectronic impact of an Al2O3 layer as a potential front passivation layer on the CIGS properties, as well as an Al2O3 tunneling layer between CIGS and CdS.
Demonstration of Muon-Beam Transverse Phase-Space Compression
We demonstrate efficient transverse compression of a 12.5 MeV=c muon beam stopped in a helium gas target featuring a vertical density gradient and crossed electric and magnetic fields. The muon stop distribution extending vertically over 14 mm was reduced to a 0.25 mm size (rms) within 3.5 μs. The simulation including cross sections ...
Electroless Deposition of Ni–Fe Alloys on Scaffolds for 3D Nanomagnetism
3D magnetic nanostructures are of great interest due to the possibility to design novel properties and the benefits for both technological applications such as high-density data storage, as well as more fundamental studies.
One of the main challenges facing the realization of these three-dimensional systems is their fabrication, which includes the deposition of magnetic materials on 3D surfaces. In this work, the electroless deposition of Ni–Fe
on a 3D-printed, non-conductive microstructure is presented.
Swiss National Science Foundation Ambizione grant for Franziska Hagelstein
Franziska Hagelstein has been awarded a Swiss National Science Foundation Ambizione grant with PSI as host institution. She joined the particle theory group (NUM, Laboratory of Particle Physics LTP) in October 2020. In the near future she will be accompanied by a PhD student.
Direct Observation of the Statics and Dynamics of Emergent Magnetic Monopoles in a Chiral Magnet
In the three-dimensional (3D) Heisenberg model, topological point defects known as spin hedgehogs behave as emergent magnetic monopoles, i.e., quantized sources and sinks of gauge fields that couple strongly to conduction electrons, and cause unconventional transport responses such as the gigantic Hall effect. We observe a dramatic change in the Hall effect upon the transformation of a spin hedgehog crystal in a chiral magnet MnGe through combined measurements of magnetotransport and small-angle neutron scattering (SANS).
Nanostructures with a unique property
Researchers at the Paul Scherrer Institute PSI have for the first time identified special nano-vortices in a material: antiferromagnetic skyrmions.
Fractional antiferromagnetic skyrmion lattice induced by anisotropic couplings
Magnetic skyrmions are topological solitons with a nanoscale winding spin texture that hold promise for spintronics applications. Skyrmions have so far been observed in a variety of magnets that exhibit nearly parallel alignment for neighbouring spins, but theoretically skyrmions with anti-parallel neighbouring spins are also possible. Such antiferromagnetic skyrmions may allow more flexible control than conventional ferromagnetic skyrmions. Here, by combining neutron scattering measurements and Monte Carlo simulations, we show that a fractional antiferromagnetic skyrmion lattice is stabilized in MnSc2S4 through anisotropic couplings.
Strain engineering of the charge and spin-orbital interactions in Sr2IrO4
Understanding the relationship between entangled degrees of freedom (DOF) is a central problem in correlated materials and the possibility to influence their balance is promising toward realizing novel functionalities. In Sr2IrO4, the interaction between spin–orbit coupling and electron correlations induces an exotic ground state with magnetotransport properties promising for antiferromagnetic spintronics applications.
One-pot neutron imaging of surface phenomena, swelling and diffusion during methane absorption in ethanol and n-decane under high pressure
We study the gas diffusion in still liquids under gas high pressures. We demonstrate that the pressure-induced gas diffusion, liquid swelling and the liquid surface tension can be measured simultaneously in a one-pot experiment. The measurements are performed using the high-resolution neutron imaging in a non-tactile way. A major advantage of this new method is that the determination of surface tension necessitate no assumptions imposed on the properties of the liquid.
Signatures of a Spin-1/2 Cooperative Paramagnet in the Diluted Triangular Lattice of Y2CuTiO6
We present a combination of thermodynamic and dynamic experimental signatures of a disorder driven dynamic cooperative paramagnet in a 50% site diluted triangular lattice spin-1/2 system: Y2CuTiO6. Magnetic ordering and spin freezing are absent down to 50 mK, far below the Curie-Weiss scale (-θCW) of ∼134 K.