LNS - Scientific Highlights

Zhu et al

Continuum Excitations in a Spin Supersolid on a Triangular Lattice

Magnetic, thermodynamic, neutron diffraction and inelastic neutron scattering are used to study spin correlations in the easy-axis XXZ triangular lattice magnet K2Co(SeO3)2. Despite the presence of quasi-2D “supersolid” magnetic order, the low-energy excitation spectrum contains no sharp modes and is instead a broad and structured multiparticle continuum. Applying a weak magnetic field ...

Andriushin et al

Reentrant multiple-q magnetic order and a “spin meta-cholesteric” phase in Sr3Fe2O7

Topologically nontrivial magnetic structures such as skyrmion lattices are well known in materials lacking lattice inversion symmetry, where antisymmetric exchange interactions are allowed. Only recently, topological multi-q magnetic textures that spontaneously break the chiral symmetry, for example, three-dimensional hedgehog lattices, were discovered in centrosymmetric compounds, where they are instead driven by frustrated interactions. Here we show that ...

Shin et al

Ferromagnetic quantum critical point protected by nonsymmorphic symmetry in a Kondo metal

Quantum critical points (QCPs), zero-temperature phase transitions, are win- dows to fundamental quantum-mechanical phenomena associated with universal behaviour. Magnetic QCPs have been extensively investigated in the vicinity of antiferromagnetic order. However, QCPs are rare in metallic ferromagnets due to the coupling of the order parameter to electronic soft modes. Recently, antisymmetric spin-orbit coupling in noncentrosymmetric systems was suggested to protect ferromagnetic QCPs. Nonetheless, multiple centrosymmetric materials ...

Xie et al

Quantum Spin Dynamics Due to Strong Kitaev Interactions in the Triangular-Lattice Antiferromagnet CsCeSe2

The extraordinary properties of the Kitaev model have motivated an intense search for new physics in materials that combine geometrical and bond frustration. In this Letter, we employ inelastic neutron scattering, spin wave theory, and exact diagonalization to study the spin dynamics in the perfect triangular-lattice antiferromagnet (TLAF) CsCeSe2. This material orders into a stripe phase, which is demonstrated to arise as a consequence of the off-diagonal bond-dependent terms in the spin Hamiltonian ...

Gawryluk et al

Magnetostructural Coupling at the Néel Point in YNiO3 Single Crystals

The recent discovery of superconductivity in infinite layer thin films and bulk Ruddlesden–Popper nickelates has stimulated the investigation of other predicted properties of these materials. Among them, the existence of magnetism-driven ferroelectricity in the parent compounds RNiO3 (R = 4f lanthanide and Y) at the onset of the Néel order, TN, has remained particularly elusive. Using diffraction techniques, we reveal here the existence of magnetostriction at TN in bulk YNiO3 single crystals. Interestingly, the associated lattice anomalies ...

Teaser

Move the soft mode by electric fields in quantum paraelectric SrTiO3

PSI Researcher used inelastic neutron scattering to show how collective lattice vibrations can be controlled by electric fields. These results indicate that different eigenmodes can couple in field in this incipient ferroelectric.

Xie et al

Conventional superconductivity in the doped kagome superconductor Cs(V0.86Ta0.14)3Sb5 from vortex lattice studies

A hallmark of unconventional superconductors is a complex electronic phase diagram where intertwined orders of charge-spin-lattice degrees of freedom compete and coexist. While the kagome metals such as CsV3Sb5 also exhibit complex behavior, involving coexisting charge density wave order and superconductivity, much is unclear about the microscopic origin of the superconducting pairing. We study the vortex lattice in the superconducting state of Cs(V0.86Ta0.14)3Sb5, where the Ta-doping suppresses charge order and enhances superconductivity. Using small-angle neutron scattering ...

Akatsuka et al (2)

Non-coplanar helimagnetism in the layered van-der-Waals metal DyTe3

Van-der-Waals magnetic materials can be exfoliated to realize ultrathin sheets or interfaces with highly controllable optical or spintronics responses. In majority, these are collinear ferro-, ferri-, or antiferromagnets, with a particular scarcity of lattice-incommensurate helimagnets of defined left- or right-handed rotation sense, or helicity. Here, we report polarized neutron scattering experiments on DyTe3, whose layered structure has highly metallic tellurium layers separated by double-slabs of dysprosium square nets...

Zeng et al

Spectral evidence for Dirac spinons in a kagome lattice antiferromagnet

Emergent quasiparticles with a Dirac dispersion in condensed matter systems can be described by the Dirac equation for relativistic electrons, in analogy with Dirac particles in high-energy physics. For example, electrons with a Dirac dispersion have been intensively studied in electronic systems such as graphene and topological insulators. However, charge is not a prerequisite for Dirac fermions, and the emergence of Dirac fermions without a charge degree of freedom has been theoretically predicted to be realized in Dirac quantum spin liquids. These quasiparticles ...

Consiglio et al

Electron Glass Phase with Resilient Zhang-Rice Singlets in LiCu3O3

LiCu3O3 is an antiferromagnetic mixed valence cuprate where trilayers of edge-sharing Cu(II)O (3d9) are sandwiched in between planes of Cu(I) (3d10) ions, with Li stochastically substituting Cu(II). Angle-resolved photoemission spectroscopy (ARPES) and density functional theory reveal two insulating electronic subsystems that are segregated in spite of sharing common oxygen atoms: a Cu dz2/O pz derived valence band (VB) dispersing on the Cu(I) plane, and a Cu 3dx2−y2/O 2px,y derived Zhang-Rice singlet (ZRS) band dispersing on the Cu(II)O planes.

Tam et al

Flat-band hybridization between f and d states near the Fermi energy of SmCoIn5

We present high-quality angle-resolved photoemission (ARPES) and density functional theory calculations (DFT+U) of SmCoIn5. We find broad agreement with previously published studies of LaCoIn5 and CeCoIn5, confirming that the Sm 4f electrons are mostly localized. Nevertheless, our model is consistent with an additional delocalized Sm component, stemming from hybridization between the 4f electrons and the metallic bands at “hot spot” positions in the Brillouin zone. 

Ukleev et al

Observation by SANS and PNR of pure Néel-type domain wall profiles and skyrmion suppression below room temperature in magnetic [Pt/CoFeB/Ru]10 multilayers

The study presents a unique investigation of [Pt/CoFeB/Ru]10 multilayers, revealing suppressed skyrmion phases, intricate magnetic domain structures, and Néel-type domain walls, providing crucial insights for spintronic applications.

Dosenschloss

A precision mechanical masterpiece in miniature

With the discovery of a golden miniature box lock, an extraordinary and unique archaeological find was made in north-western Germany by a licensed detectorist.

The object represents an extremely reduced and valuable version of the provincial Roman box locks. These everyday objects were in general significantly larger and normally made either of iron, iron with silver or bronze bands or bronze.

 

Fogh et al

Field-induced bound-state condensation and spin-nematic phase in SrCu2(BO3)2 revealed by neutron scattering up to 25.9 T

In quantum magnetic materials, ordered phases induced by an applied mag- netic field can be described as the Bose-Einstein condensation (BEC) of mag- non excitations. In the strongly frustrated system SrCu2(BO3)2, no clear magnon BEC could be observed, pointing to an alternative mechanism, but the high fields required to probe this physics have remained a barrier to detailed investigation.Here we exploit the first purpose-built high-field neutron scattering facility to measure ...

Park et al

Tetrahedral triple-Q magnetic ordering and large spontaneous Hall conductivity in the metallic triangular AFM Co1/3TaS2

The triangular lattice antiferromagnet (TLAF) has been the standard paradigm of frustrated magnetism for several decades. The most common magnetic ordering in insulating TLAFs is the 120° structure. However, a new triple-Q chiral ordering can emerge in metallic TLAFs, representing the short wave- length limit of magnetic skyrmion crystals. We report the metallic TLAF Co1/3TaS2 as the first example of tetrahedral triple-Q magnetic ordering with the associated topological Hall effect (non-zero σxy(H = 0)). We also ...

Andriushin et al

Phonon Topology and Winding of Spectral Weight in Graphite

The topology of electronic and phonon band structures of graphene is well studied and known to exhibit a Dirac cone at the K point of the Brillouin zone. Here, we applied inelastic x-ray scattering (IXS) along with ab initio calculations to investigate phonon topology in graphite, the 3D analog of graphene. We identified a pair of modes that form a very weakly gapped linear anticrossing at the K point that can be essentially viewed as a Dirac cone approximant. The IXS intensity ...

Singh et al

Skyrmion metamorphosis: Lattice transitions of hybrid skyrmions in a polar magnet

Magnetic skyrmions, with their distinctive vortex-like magnetic spin configurations, continue to intrigue researchers due to their potential applications in nanoscience and technology. Traditionally skyrmions form two-dimensional hexagonal close-packed lattices, with the skyrmions themselves displaying one of just two types of internal magnetization texture known as Bloch- or Néel-type. Recent theories hinted at the prospect of reconfigurable transitions between skyrmion phases of different lattice types and internal textures. Until now, experimental evidence supporting such theories has been scarce.

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Cobalt-free layered perovskites RBaCuFeO5+d (R = 4f lanthanide) as electrocatalysts for the oxygen evolution reaction

Co oxides with perovskite-related structure are particularly promising, cost-effective OER catalysts. However, the increasing Co demand by the battery industry is pushing the search for Co-free alternatives. Here we investigate the potential of the Co-free layered perovskite family RBaCuFeO5+δ (R = 4f lanthanide), where we identify the critical structural and electronic variables leading to high OER catalytical performance. The employed methodology, based in the use of advanced neutron and X-ray synchrotron techniques combined with ab initio DFT calculations allowed to reveal LaBaCuFeO5+δ as new, promising Co-free electroctalyst. Moreover, we could show that this material can be industrially produced in nanocrystalline form. We believe that the reported results and methodology may contribute to the implementation of new technologies aimed to generate energy with lower carbon emissions, and can also inspire the scientific community in their search of other Co-free materials with good OER electrocatalytical properties.

Dorn et al

Integrative solution structure of PTBP1-IRES complex reveals strong compaction and ordering with residual conformational flexibility

RNA-binding proteins (RBPs) are crucial regulators of gene expression, often composed of defined domains interspersed with flexible, intrinsically disordered regions. Determining the structure of ribonucleoprotein (RNP) complexes involving such RBPs necessitates integrative structural modeling due to their lack of a single stable state. In this study, we integrate magnetic resonance, mass spectrometry, and small-angle scattering data to determine the solution structure of ...

Bao et al

Direct observation of topological magnon polarons in a multiferroic material

Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic Fe2Mo3O8 possessing strong magnon-phonon coupling.

Xie et al

Complete field-induced spectral response of the spin-1/2 triangular-lattice antiferromagnet CsYbSe2

Fifty years after Anderson’s resonating valence-bond proposal, the spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLHAF) remains the ultimate platform to explore highly entangled quantum spin states in proximity to magnetic order. Yb-based delafossites are ideal candidate TLHAF materials, which allow experimental access to the full range of applied in-plane magnetic fields. We perform a systematic neutron scattering study of CsYbSe2, first proving the Heisenberg character of the interactions and quantifying the second-neighbor coupling.

Sala et al

Field-tuned quantum renormalization of spin dynamics in the honeycomb lattice Heisenberg antiferromagnet YbCl3

The basis for our understanding of quantum magnetism has been the study of elegantly simple model systems. However, even for the antiferromagnetic honeycomb lattice with isotropic spin interactions – one of the simplest model systems – a detailed understanding of quantum effects is still lacking. Here, using inelastic neutron scattering measurements of the honeycomb lattice material YbCl3, we elucidate how quantum effects renormalize ...

Han et al

Strong phonon softening and avoided crossing in aliovalence-doped heavy-band thermoelectrics

Aliovalent doping is a way to optimize the electrical properties of semiconductors, but its impact on the phonon structure and propagation is seldom considered properly. Here we show that aliovalent doping can be much more effective in reducing the lattice thermal conductivity of thermoelectric semiconductors than the commonly employed isoelectronic alloying strategy. We demonstrate ...

grab_prr_ca

Direct observation of exchange anisotropy in the helimagnetic insulator Cu2OSeO3

The helical magnetic structures of cubic chiral systems are well explained by the competition among Heisen- berg exchange, Dzyaloshinskii-Moriya interaction, cubic anisotropy, and anisotropic exchange interaction (AEI). Recently, the role of the latter has been argued theoretically to be crucial for the low-temperature phase diagram of the cubic chiral magnet Cu2OSeO3, which features tilted conical and disordered skyrmion states for a specific orientation of the applied magnetic field (μ0H⃗ ∥ [001]). In this study ...

Fogh et al

Tuning magnetoelectricity in a mixed-anisotropy antiferromagnet

Control of magnetization and electric polarization is attractive in relation to tailoring materials for data storage and devices such as sensors or antennae. In magnetoelectric materials, these degrees of freedom are closely coupled, allowing polarization to be controlled by a magnetic field, and magnetization by an electric field, but the magnitude of the effect remains a challenge in the case of single-phase magnetoelectrics for applications. 

Cement hydration on the micro- and nanoscale

A deep look into hydration of cement

Researchers led by the University of Málaga show the Portland cement early age hydration with microscopic detail and high contrast between the components. This knowledge may contribute to more environmentally friendly manufacturing processes.

Teixeira et al

Active learning-assisted neutron spectroscopy with log-Gaussian processes

Neutron scattering experiments at three-axes spectrometers (TAS) investigate magnetic and lattice excitations by measuring intensity distributions to understand the origins of materials properties. The high demand and limited availability of beam time for TAS experiments however raise the natural question whether we can improve their efficiency and make better use of the experimenter’s time. 

Peydayesh et al

Amyloid-polysaccharide interfacial coacervates as therapeutic materials

Coacervation via liquid-liquid phase separation provides an excellent oppor- tunity to address the challenges of designing nanostructured biomaterials with multiple functionalities. Protein-polysaccharide coacervates, in particular, offer an appealing strategy to target biomaterial scaffolds, but these systems suffer from the low mechanical and chemical stabilities of protein-based condensates. Here we overcome these limitations by transforming native proteins into amyloid fibrils and demonstrate ...