Latest News

Here you find current and previous news from the NUM division. For scientific highlights, please have a look here.

Origami_Nature

Nanomagnetic encoding of shape-morphing micromachines

Shape-morphing systems, which can perform complex tasks through morphological transformations, are of great interest for future applications in minimally invasive medicine, soft robotics, active metamaterials and smart surfaces. With current fabrication methods, shape-morphing configurations have been embedded into structural design by, for example, spatial distribution of heterogeneous materials, which cannot be altered once fabricated. 

Wang PRL -Normand

One Proximate Kitaev Spin Liquid in the K-J-Γ Model on the Honeycomb Lattice

In addition to the Kitaev (K) interaction, candidate Kitaev materials also possess Heisenberg (J) and off- diagonal symmetric (Γ) couplings. We investigate the quantum (S=1/2) K-J-Γ model on the honeycomb lattice by a variational Monte Carlo method. In addition to the “generic” Kitaev spin liquid (KSL), we find that there is just one proximate KSL (PKSL) phase, while the rest of the phase diagram contains different magnetically ordered states.

LENS

European neutron facilities come together for LENS General Assembly

The League of advanced European Neutron Sources (LENS) with the participation of PSI held its second General Assembly at Institut Laue-Langevin (ILL) together with meetings of its five working groups and the LENS Executive Board. The meetings brought the consortium’s operational working groups together with the leaders of the LENS member facilities to advance priority actions for the organisation in the months to come.

ESTIA Teaser

Take a flight through ESTIA

PSI is entirely responsible to build the polarised neutron reflectometer ESTIA at the European Spallation Source ESS in Lund, Sweden. The lead ESTIA scientist Artur Glavic (LNS/NUM) has now simulated a virtual tour of the neutrons travelling through the instrument from the focusing neutron guide to the detector.

LENS WG3 Teaser

PSI hosting meeting of the LENS working group on technology development and operation

On October 1 and 2, the Laboratory of Neutron and Muon Instrumentation (LIN) hosted the first meeting of the working group on “Synergies in Technology Development and Operation” of the League of Advanced European Neutron Sources, LENS, to kick off developments aimed at creating a new generation of neutron technology.

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Extended Magnetic Dome Induced by Low Pressures in Superconducting FeSe(1 − x)Sx

We report muon spin rotation and magnetization measurements under pressure on Fe1+δSe1−xSx with x ≈ 0.11. Above p ≈ 0.6 GPa we find a microscopic coexistence of superconductivity with an extended dome of long range magnetic order that spans a pressure range between previously reported separated magnetic phases. 

ESS Teaser

Visit of ESS Council to Switzerland

On 24 September the Paul Scherrer Institut was the venue of a meeting between the top supervisory board of the European Spallation Source ESS to be built in Lund, Sweden, and representatives of the Swiss government from SERI. The chair and the vice chair of the ESS Council, Beatrix Vierkorn-Rudolph and Kurt Clausen, respectively came to Switzerland to discuss the Swiss In-Kind Contributions to the largest spallation neutron source under construction in Sweden.

Yazdani et al

Nanocrystal superlattices as phonon-engineered solids and acoustic metamaterials

Phonon engineering of solids enables the creation of materials with tailored heat-transfer properties, controlled elastic and acoustic vibration propagation, and custom phonon-electron and phonon-photon interactions. These can be leveraged for energy transport, harvesting, or isolation applications and in the creation of novel phonon-based devices, including photoacoustic systems and phonon-communication networks.

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Nodeless superconductivity and its evolution with pressure in the layered dirac semimetal 2M-WS2

Recently, the transition metal dichalcogenide (TMD) system 2M-WS2 has been identified as a Dirac semimetal exhibiting both superconductivity with the highest Tc ~ 8.5 K among all the TMD materials and topological surface states. Here we report on muon spin rotation (μSR) and density functional theory studies of microscopic SC properties and the electronic structure in 2M-WS2 at ambient and under hydrostatic pressures (pmax = 1.9 GPa).

Michał Rawlik awarded CHIPP Prize 2019

Michał Rawlik awarded the CHIPP Prize 2019

PSI researcher Dr. Michał Rawlik has been awarded the CHIPP Prize 2019 "for his outstanding contribution to the improvement of experimental techniques aimed at detecting the Electric Dipole Moment of the neutron, and exploiting the consequences of such measurements in setting bounds on possible Axion fields".

Mazzone_PRL

Evolution of Magnetic Order from the Localized to the Itinerant Limit

Quantum materials that feature magnetic long-range order often reveal complex phase diagrams when localized electrons become mobile. In many materials magnetism is rapidly suppressed as electronic charges dissolve into the conduction band. In materials where magnetism persists, it is unclear how the magnetic properties are affected. 

Valsecchi Nat. Comm

Visualization and quantification of inhomogeneous and anisotropic magnetic fields by polarized neutron grating interferometry

The intrinsic magnetic moment of a neutron, combined with its charge neutrality, is a unique property which allows the investigation of magnetic phenomena in matter. Here we present how the utilization of a cold polarized neutron beam in neutron grating interferometry enables the visualization and characterization of magnetic properties on a microscopic scale in macroscopic samples.

matviykiv-Langmuir-2019

Small-Angle Neutron Scattering Study of Temperature-Induced Structural Changes in Liposomes

Liposomes of specific artificial phospholipids, such as Pad-PC-Pad and Rad-PC-Rad, are mechanically responsive. They can release encapsulated therapeutics via physical stimuli, as naturally present in blood flow of constricted vessel segments. The question is how these synthetic liposomes change their structure in the medically relevant temperature range from 22 to 42 °C.

DMC Detector teaser

LIN builds pressure vessels for joint detector project with FRM-II in Munich

Highly efficient two-dimensional detectors are essential for the performance of modern neutron diffractometers. The NUM Division of PSI and the Technical University Munich TUM jointly develop two identical new 3He gas detectors, one for the diffractometer DMC at SINQ and the other for operation at FRM-II in Munich. 

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Experimental signatures of a three-dimensional quantum spin liquid in effective spin-1/2 Ce2Zr2O7 pyrochlore

A quantum spin liquid is a state of matter where unpaired electrons’ spins, although entangled, do not show magnetic order even at the zero temperature. The realization of a quantum spin liquid is a long-sought goal in condensed-matter physics.

LENS-teaser

PSI participates in ECNS in St Petersburg

The European Conference on Neutron Scattering (ECNS) with its recent 2019 edition in St. Petersburg is a spree of lectures, poster sessions, and expert talks on the current trends and future possibilities in neutron science. PSI with its neutron source SINQ was represented by members of the three NUM laboratories LNS, LMX and LIN. In addition, PSI was silver sponsor of ECNS 2019 and is also a member of the LENS consortium (League of Advanced European Neutron Sources).

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Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd2As2

Weyl fermions as emergent quasiparticles can arise in Weyl semimetals (WSMs) in which the energy bands are nondegenerate, resulting from inversion or time-reversal symmetry breaking. Nevertheless, experimental evidence for magnetically induced WSMs is scarce. Here, using photoemission spectroscopy, we observe that the degeneracy of Bloch bands is already lifted in the paramagnetic phase of EuCd2As2. We attribute this effect to the itinerant electrons experiencing quasi-static and quasi–long-range ferromagnetic fluctuations.

manni_naturenanotechnology

Soft biomimetic nanoconfinement promotes amorphous water over ice

Water is a ubiquitous liquid with unique physicochemical properties, whose nature has shaped our planet and life as we know it. Water in restricted geometries has different properties than in bulk. Confinement can prevent low-temperature crystalliza- tion of the molecules into a hexagonal structure and thus create a state of amorphous water. To understand the survival of life at subzero temperatures, it is essential to elucidate this behaviour in the presence of nanoconfining lipidic membranes.

Faure PRL

Tomonaga-Luttinger Liquid Spin Dynamics in the Quasi-One-Dimensional Ising-Like Antiferromagnet BaCo2V2O8

Combining inelastic neutron scattering and numerical simulations, we study the quasi-one-dimensional Ising anisotropic quantum antiferromagnet BaCo2V2O8 in a longitudinal magnetic field. This material shows a quantum phase transition from a Néel ordered phase at zero field to a longitudinal incommensurate spin density wave at a critical magnetic field of 3.8 T. 

Metamagnetic texture in a polar antiferromagnet

Metamagnetic texture in a polar antiferromagnet

The notion of a simple ordered state implies homogeneity. If the order is established by a broken symmetry, the elementary Landau theory of phase transitions shows that only one symmetry mode describes this state. At the exact points of phase coexistence, domain states composed of large regions of different phases can be stabilized by long-range interactions.

Mogi_PRL

Large Anomalous Hall Effect in Topological Insulators with Proximitized Ferromagnetic Insulators

We report a proximity-driven large anomalous Hall effect in all-telluride heterostructures consisting of the ferromagnetic insulator Cr2Ge2Te6 and topological insulator (Bi,Sb)2Te3. Despite small magnetization in the (Bi,Sb)2Te3 layer, the anomalous Hall conductivity reaches a large value of 0.2e2/h in accord with a ferromagnetic response of the Cr2Ge2Te6.

LIN people

New NUM Laboratory for Neutron and Muon Instrumentation (LIN)

In the division Research with Neutrons and Muons (NUM) all technical knowledge and expertise concerned with the development and operation of the scientific instrumentation for neutron and muon experiments at our user facilities have been united in the new Laboratory for Neutron and Muon Instrumentation (LIN). 

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Critical fields of Nb3Sn prepared for superconducting cavities

Nb3Sn is currently the most promising material other than niobium for future superconducting radiofrequency cavities. Critical fields above 120 mT in pulsed operation and about 80 mT in CW have been achieved in cavity tests. This is large compared to the lower critical field as derived from the London penetration depth, extracted from low field surface impedance measurements. 

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Phase transition in the cuprates from a magnetic-field-free stiffness meter viewpoint

A method to measure the superconducting (SC) stiffness tensor ρs, without subjecting the sample to external magnetic field, is applied to La1.875Sr0.125CuO4. The method is based on the London equation J=-ρsA, where J is the current density and A is the vector potential which is applied in the SC state.

 

shape memory 2019

Magnetically Addressable Shape-Memory and Stiffening in a Composite Elastomer

With a specific stimulus, shape‐memory materials can assume a temporary shape and subsequently recover their original shape, a functionality that renders them relevant for applications in fields such as biomedicine, aerospace, and wearable electronics. Shape‐memory in polymers and composites is usually achieved by exploiting a thermal transition to program a temporary shape and subsequently recover the original shape.

Leo et al

Multidimensional Characterization of Mixed Ligand Nanoparticles Using Small Angle Neutron Scattering

The properties of ligand protected gold nanoparticles are determined by the synergistic interplay of their structural components, including the metal core, the ligand shell, and the solvation layer. However, the simultaneous characterization of all these components remains a major challenge given their disparate chemical nature.

Gomilsek et al

Kondo screening in a charge-insulating spinon metal

The Kondo effect, an eminent manifestation of many-body physics in condensed matter, is traditionally explained as exchange scattering of conduction electrons on a spinful impurity in a metal. The resulting screening of the impurity's local moment by the electron Fermi sea is characterized by a Kondo temperature TK, below which the system enters a strongly coupled regime.

Pregelj et al

Elementary excitation in the spin-stripe phase in quantum chains

Elementary excitations in condensed matter capture the complex many-body dynamics of interacting basic entities in a simple quasiparticle picture. In magnetic systems the most established quasiparticles are magnons, collective excitations that reside in ordered spin structures, and spinons, their fractional counterparts that emerge in disordered, yet correlated spin states.

Choi PRL

Exotic Low-Energy Excitations Emergent in the Random Kitaev Magnet Cu2IrO3

We report on magnetization M(H), dc and ac magnetic susceptibility Χ(T), specific heat Cm(T) and muon spin relaxation (μSR) measurements of the Kitaev honeycomb iridate Cu2IrO3 with quenched disorder. In spite of the chemical disorders, we find no indication of spin glass down to 260 mK from the Cm(T) and μSR data.