Scientific Highlights: Research Division "Research with Neutrons and Muons"
Tuning Nanoparticle–Micelle Interactions and Resultant Phase Behavior
The evolution of the interaction between an anionic nanoparticle and a nonionic surfactant and their resultant phase behavior in aqueous solution in the presence of electrolyte and ionic surfactants have been studied. The mixed system of anionic silica nanoparticles (Ludox LS30) with nonionic surfactant decaethylene glycol monododecylether (C12E10) forms a highly stable clear phase over a wide concentration range of surfactant.
Gapless Spin Excitations in the Field-Induced Quantum Spin Liquid Phase of α-RuCl3
α-RuCl3 is a leading candidate material for the observation of physics related to the Kitaev quantum spin liquid (QSL). By combined susceptibility, specific-heat, and nuclear-magnetic-resonance measurements, we demonstrate that α-RuCl3 undergoes a quantum phase transition to a QSL in a magnetic field of 7.5 T applied in the ab plane. We show further that this high-field QSL phase has gapless spin excitations over a field range up to 16 T.
Search for Axionlike Dark Matter through Nuclear Spin Precession in Electric and Magnetic Fields
We report on a search for ultralow-mass axionlike dark matter by analyzing the ratio of the spin-precession frequencies of stored ultracold neutrons and 199Hg atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range 10-24 ≤ ma ≤ 10-17eV.
A null result full of insights
A laboratory-based search for axion dark matter ended, not unexpectedly, without a discovery. It provides, however, valuable constraints for the properties that these hypothetical particles can have — and thus a guide to where to look next.
Spin Resonance and Magnetic Order in an Unconventional Superconductor
Unconventional superconductivity in many materials is believed to be mediated by magnetic fluctuations. It is an open question how magnetic order can emerge from a superconducting condensate and how it competes with the magnetic spin resonance in unconventional superconductors. Here we study a model d-wave superconductor that develops spin-density wave order, and find that the spin resonance is unaffected by the onset of static magnetic order.
Magnetic structures take a new turn
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.
Emergent dynamic chirality in a thermally driven artificial spin ratchet
Modern nanofabrication techniques have opened the possibility to create novel functional materials, whose properties transcend those of their constituent elements. In particular, tuning the magnetostatic interactions in geometrically frustrated arrangements of nanoelements called artificial spin ice can lead to specific collective behaviour, including emergent magnetic monopoles, charge screening and transport, as well as magnonic response.
The importance of knowing your stripes
A collaboration between three NUM laboratories has found that magnetic ‘stripe order’ in high-temperature superconductors not only co-exists with superconducting order, but might very well be intimately connected with it.
MultiFLEXX - The new multi-analyzer at the cold triple-axis spectrometer FLEXX
The first experimental characterization of a multiple energy analysis wide angle backend for a cold triple-axis spectrometer is reported. The multi-analyzer module MultiFLEXX employs 155 detection channels which simultaneously probe an extensive range in wavevector and energy transfer. Successful mapping of magnetic excitations in MnF2 and Ho demonstrate order of magnitude gains in data collection efficiency using this novel type backend.
Signatures of the topological s+- superconducting order parameter in the type-II Weyl semimetal Td-MoTe2
In its orthorhombic Td polymorph, MoTe2 is a type-II Weyl semimetal, where the Weyl fermions emerge at the boundary between electron and hole pockets. Non-saturating magnetoresistance and superconductivity were also observed in Td-MoTe2. Understanding the superconductivity in Td-MoTe2, which was proposed to be topologically non-trivial, is of eminent interest.
Frustratingly disordered
A study of how disorder affects a ‘frustrated’ magnet reveals a surprising robustness of the underlying quantum many-body state, and provides evidence for emerging quantum phenomena induced by disorder.
Coulomb spin liquid in anion-disordered pyrochlore Tb2Hf2O7
The charge ordered structure of ions and vacancies characterizing rare-earth pyrochlore oxides serves as a model for the study of geometrically frustrated magnetism. The organization of magnetic ions into networks of corner-sharing tetrahedra gives rise to highly correlated magnetic phases with strong fluctuations, including spin liquids and spin ices. It is an open question how these ground states governed by local rules are affected by disorder.
From golden emperor to filled Buddha
Ancient metal objects are illuminated by neutrons at the Paul Scherrer Institute PSI. This enables researchers to discover what is hidden inside them, how they were made and how they can be preserved.
Commissioning and first performance studies of the new CMS pixel detector
In the previous months the new CMS pixel detector was brought into operation. The detector was moved from PSI to CERN and installed in February, followed by an intensive period of commissioning and calibration. This process mostly involved the adjustment of many operational parameters which influence the detector performance, e.g.
The hard worker from Val Mesolcina
For Aldo Antognini, physics and conviviality are in the bloodPSI researcher Aldo Antognini has received more than 2.2 million Swiss francs from the EU for his latest experiment. He wants to find out how magnetism is distributed in the proton. The particle physicist will be able to apply not only his scientific and technical talents, but his social flair as well.
Complementary Response of Static Spin-Stripe Order and Superconductivity to Nonmagnetic Impurities in Cuprates
We report muon-spin rotation and neutron-scattering experiments on nonmagnetic Zn impurity effects on the static spin-stripe order and superconductivity of the La214 cuprates. Remarkably, it was found that, for samples with hole doping x ≈ 1/8, the spin-stripe ordering temperature Tso decreases linearly with Zn doping y and disappears at y ≈ 4%, demonstrating a high sensitivity of static spin-stripe order to impurities within a CuO2 plane.
Equilibrium Skyrmion Lattice Ground State in a Polar Easy-plane Magnet
The skyrmion lattice state (SkL), a crystal built of mesoscopic spin vortices, gains its stability via thermal fluctuations in all bulk skyrmion host materials known to date. Therefore, its existence is limited to a narrow temperature region below the paramagnetic state. This stability range can drastically increase in systems with restricted geometries, such as thin films, interfaces and nanowires.
Understanding the Enhanced Magnetic Response of Aminocholesterol Doped Lanthanide-Ion-Chelating Phospholipid Bicelles
Cholesterol (Chol-OH) and its conjugates are powerful molecules for engineering the physicochemical and magnetic properties of phospholipid bilayers in bicelles.
High-Tc superconductivity in undoped ThFeAsN
Unlike the widely studied ReFeAsO series, the newly discovered iron-based superconductor ThFeAsN exhibits a remarkably high critical temperature of 30 K, without chemical doping or external pressure. Here we investigate in detail its magnetic and superconducting properties via muon-spin rotation/relaxation and nuclear magnetic resonance techniques and show that ThFeAsN exhibits strong magnetic fluctuations, suppressed below ≈35 K, but no magnetic order.
Diving into magnets
For the first time, scientists have made visible the directions of the magnetisation inside a 3D magnetic object. The smallest details in their visualisation were ten thousand times smaller than a millimetre. Among others, the magnetic structure contained one outstanding kind of pattern: magnetic singularities called Bloch points, which up to now were only known in theory.