Scientific Highlights: Research Division "Research with Neutrons and Muons"
4-spin plaquette singlet state in the Shastry–Sutherland compound SrCu2(BO3)2
The study of interacting spin systems is of fundamental importance for modern condensed-matter physics. On frustrated lattices, magnetic exchange interactions cannot be simultaneously satisfied, and often give rise to competing exotic ground states. The frustrated two-dimensional Shastry–Sutherland lattice realized by SrCu2(BO3)2 is an important test to our understanding of quantum magnetism.
Three-Dimensional Electronic Structure of the Type-II Weyl Semimetal WTe2
By combining bulk sensitive soft-x-ray angular-resolved photoemission spectroscopy and first- principles calculations we explored the bulk electron states of WTe2, a candidate type-II Weyl semimetal featuring a large nonsaturating magnetoresistance. Despite the layered geometry suggesting a two-dimensional electronic structure, we directly observe a three-dimensional electronic dispersion.
Quantum Griffiths Phase Inside the Ferromagnetic Phase of Ni1-xVx
We study by means of bulk and local probes the d-metal alloy Ni1-xVx close to the quantum critical concentration, xc ≈ 11.6%, where the ferromagnetic transition temperature vanishes. The magnetization-field curve in the ferromagnetic phase takes an anomalous power-law form with a nonuniversal exponent that is strongly x dependent and mirrors the behavior in the paramagnetic phase.
Comparison of ultracold neutron sources for fundamental physics measurements
Ultracold neutrons (UCNs) are key for precision studies of fundamental parameters of the neutron and in searches for new charge-parity-violating processes or exotic interactions beyond the Standard Model of particle physics. The most prominent example is the search for a permanent electric-dipole moment of the neutron (nEDM). We have performed an experimental comparison of the leading UCN sources currently operating.
Methods for Generating Highly Magnetically Responsive Lanthanide-Chelating Phospholipid Polymolecular Assemblies
Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln3+) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive polymolecular assemblies such as DMPC/DMPE-DTPA/Ln3+ (molar ratio 4:1:1) bicelles.
Superlattice growth and rearrangement during evaporation-induced nanoparticle self-assembly
Understanding the assembly of nanoparticles into superlattices with well-defined morphology and structure is technologically important but challenging as it requires novel combinations of in-situ methods with suitable spatial and temporal resolution.
Coupled multiferroic domain switching in the canted conical spin spiral system Mn2GeO4
Despite remarkable progress in developing multifunctional materials, spin-driven ferro-electrics featuring both spontaneous magnetization and electric polarization are still rare. Among such ferromagnetic ferroelectrics are conical spin spiral magnets with a simultaneous reversal of magnetization and electric polarization that is still little understood. Such materials can feature various multiferroic domains that complicates their study.
Distinct, but not so different
Among superconducting materials, CeCoIn5 stands out as a rare case where superconductivity gives rise to magnetic order. An international team led by PSI physicist Michel Kenzelmann now reports that when small amounts of impurities are implanted into CeCoIn5, then two distinct magnetic phases appear — and these are surprisingly similar to one another.
Pressure-induced magnetic order in FeSe: A muon spin rotation study
The magnetic order induced by the pressure was studied in FeSe by means of muon spin rotation (μSR) technique.
Emergent magnetism at transition-metal-nanocarbon interfaces
Interfaces are critical in quantum physics, and therefore we must explore the potential for designer hybrid materials that profit from promising combinatory effects. In particular, the fine-tuning of spin polarization at metallo–organic interfaces opens a realm of possibilities, from the direct applications in molecular spintronics and thin-film magnetism to biomedical imaging or quantum computing.
Determination of Conduction and Valence Band Electronic Structure of LaTiOxNy Thin Films
The nitrogen substitution into the oxygen sites of several oxide materials leads to a reduction of the band gap to the visible-light energy range, which makes these oxynitride semiconductors potential photocatalysts for efficient solar water splitting. Oxynitrides typically show a different crystal structure compared to the pristine oxide material.
Unconventional magnetic order in the conical state of MnSi
In the temperature-magnetic field phase diagram, the binary metallic compound MnSi exhibits three magnetic phases below Tc ≈ 29K.An unconventional helicoidal phase is observed in zero field. At moderate field intensity a conical phase sets in. Near Tc, in an intermediate field range, a skyrmion lattice phase appears.
Anomalous Thermal Conductivity and Magnetic Torque Response in the Honeycomb Magnet α-RuCl3
We report on the unusual behavior of the in-plane thermal conductivity κ and torque τ response in the Kitaev-Heisenberg material α-RuCl3. κ shows a striking enhancement with linear growth beyond H = 7T, where magnetic order disappears, while τ for both of the in-plane symmetry directions shows an anomaly at the same field.
Climbing the ladder
Quantum phenomena can lead to intriguing effects in materials, but are famously difficult to predict and understand. A combined experimental and theoretical study of a model quantum system provides insight into excitations that involve multiple particles at once.
Bound States and Field-Polarized Haldane Modes in a Quantum Spin Ladder
The challenge of one-dimensional systems is to understand their physics beyond the level of known elementary excitations. By high-resolution neutron spectroscopy in a quantum spin-ladder material, we probe the leading multiparticle excitation by characterizing the two-magnon bound state at zero field.
Amyloid fibril systems reduce, stabilize and deliver bioavailable nanosized iron
Iron-deficiency anaemia (IDA) is a major global public health problem. A sustainable and cost-effective strategy to reduce IDA is iron fortification of foods, but the most bioavailable fortificants cause adverse organoleptic changes in foods. Iron nanoparticles are a promising solution in food matrices, although their tendency to oxidize and rapidly aggregate in solution severely limits their use in fortification.
Doping Dependence of Collective Spin and Orbital Excitations in the Spin-1 Quantum Antiferromagnet La2-xSrxNiO4 Observed by X-Rays
We report the first empirical demonstration that resonant inelastic x-ray scattering (RIXS) is sensitive to collective magnetic excitations in S=1 systems by probing the Ni L3 edge of La2-xSrxNiO4 (x=0, 0.33, 0.45). The magnetic excitation peak is asymmetric, indicating the presence of single and multi-spin-flip excitations.
High hydrostatic pressure specifically affects molecular dynamics and shape of low-density lipoprotein particles
Lipid composition of human low-density lipoprotein (LDL) and its physicochemical characteristics are relevant for proper functioning of lipid transport in the blood circulation. To explore dynamical and structural features of LDL particles with either a normal or a triglyceride-rich lipid composition we combined coherent and incoherent neutron scattering methods.
Amplitude Mode in Three-Dimensional Dimerized Antiferromagnets
The amplitude ("Higgs") mode is a ubiquitous collective excitation related to spontaneous breaking of a continuous symmetry. We combine quantum Monte Carlo (QMC) simulations with stochastic analytic continuation to investigate the dynamics of the amplitude mode in a three-dimensional dimerized quantum spin system.
LaTiOxNy thin film model systems for photocatalytic water splitting: physicochemical evolution of the solid-liquid interface and the role of the crystallographic orientation
The size of the band gap and the energy position of the band edges make several oxynitride semiconductors promising candidates for efficient hydrogen and oxygen production under solar light illumination. The intense research efforts dedicated to oxynitride materials have unveiled the majority of their most important properties. However, two crucial aspects have received much less attention.