Latest News Here you find current and previous news from the NUM division. For scientific highlights, please have a look here. Titel - Select -20242023202220212020201920182017201620152014201320122011201020092008 Year - Select -JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember Month 20.09.2017 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. 14.09.2017 •Fundamentals of Nature •7 min The hard worker from Val Mesolcina Further information aboutParticle physics Further information aboutCHRISP 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. 22.08.2017 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. 08.08.2017 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. 31.07.2017 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. 31.07.2017 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. 20.07.2017 •Future Technologies •9 min Diving into magnets Further information aboutMaterials research Further information aboutSLS 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. 20.07.2017 Three-dimensional magnetization structures revealed with X-ray vector nanotomography In soft ferromagnetic materials, the smoothly varying magnetization leads to the formation of fundamental patterns such as domains, vortices and domain walls. These have been studied extensively in thin films of thicknesses up to around 200 nanometres, in which the magnetization is accessible with current transmission imaging methods that make use of electrons or soft X-rays. 17.07.2017 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. 17.07.2017 New quantum state observed in a Shastry–Sutherland compound Scientists from PSI and the École polytechnique fédérale de Lausanne (EPFL) have shown experimentally, for the first time, a quantum phase transition in strontium copper borate, the only material to date that realizes the famous Shastry–Sutherland quantum many-body model. 14.07.2017 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. 28.06.2017 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. 19.06.2017 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. 08.06.2017 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. 05.06.2017 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. 05.06.2017 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. 19.05.2017 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. 18.05.2017 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. 15.05.2017 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. 12.05.2017 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. 10.05.2017 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. 05.05.2017 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. 28.04.2017 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. 28.04.2017 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. 24.04.2017 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. 12.04.2017 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. 06.04.2017 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. 06.04.2017 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. 03.04.2017 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. 29.03.2017 Gapless Spin-Liquid Ground State in the S=1/2 Kagome Antiferromagnet The defining problem in frustrated quantum magnetism, the ground state of the nearest-neighbor S=1/2 antiferromagnetic Heisenberg model on the kagome lattice, has defied all theoretical and numerical methods employed to date. We apply the formalism of tensor-network states, specifically the method of projected entangled simplex states, which combines infinite system size with a correct accounting for multipartite entanglement. First page « First Previous page ‹‹ … 10 11 12 13 14 15 16 17 18 … Next page ›› Last page Last »
20.09.2017 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.
14.09.2017 •Fundamentals of Nature •7 min The hard worker from Val Mesolcina Further information aboutParticle physics Further information aboutCHRISP 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.
22.08.2017 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.
08.08.2017 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.
31.07.2017 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.
31.07.2017 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.
20.07.2017 •Future Technologies •9 min Diving into magnets Further information aboutMaterials research Further information aboutSLS 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.
20.07.2017 Three-dimensional magnetization structures revealed with X-ray vector nanotomography In soft ferromagnetic materials, the smoothly varying magnetization leads to the formation of fundamental patterns such as domains, vortices and domain walls. These have been studied extensively in thin films of thicknesses up to around 200 nanometres, in which the magnetization is accessible with current transmission imaging methods that make use of electrons or soft X-rays.
17.07.2017 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.
17.07.2017 New quantum state observed in a Shastry–Sutherland compound Scientists from PSI and the École polytechnique fédérale de Lausanne (EPFL) have shown experimentally, for the first time, a quantum phase transition in strontium copper borate, the only material to date that realizes the famous Shastry–Sutherland quantum many-body model.
14.07.2017 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.
28.06.2017 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.
19.06.2017 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.
08.06.2017 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.
05.06.2017 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.
05.06.2017 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.
19.05.2017 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.
18.05.2017 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.
15.05.2017 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.
12.05.2017 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.
10.05.2017 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.
05.05.2017 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.
28.04.2017 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.
28.04.2017 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.
24.04.2017 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.
12.04.2017 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.
06.04.2017 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.
06.04.2017 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.
03.04.2017 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.
29.03.2017 Gapless Spin-Liquid Ground State in the S=1/2 Kagome Antiferromagnet The defining problem in frustrated quantum magnetism, the ground state of the nearest-neighbor S=1/2 antiferromagnetic Heisenberg model on the kagome lattice, has defied all theoretical and numerical methods employed to date. We apply the formalism of tensor-network states, specifically the method of projected entangled simplex states, which combines infinite system size with a correct accounting for multipartite entanglement.