Latest News

Here you find current and previous news from the PSI Center for Neutron and Muon Sciences. 

Shang et al

Simultaneous Nodal Superconductivity and Time-Reversal Symmetry Breaking in the Noncentrosymmetric Superconductor CaPtAs

By employing a series of experimental techniques, we provide clear evidence that CaPtAs represents a rare example of a noncentrosymmetric superconductor which simultaneously exhibits nodes in the superconducting gap and broken time-reversal symmetry (TRS) in its superconducting state (belowTc ≈ 1.5 K). Unlike in fully gapped superconductors, the magnetic penetration depth λ(T) does not saturate at low temperatures, but instead it shows a T2 dependence, characteristic of gap nodes.

Grinenko et al

Superconductivity with broken time-reversal symmetry inside a superconducting s-wave state

In general, magnetism and superconductivity are antagonistic to each other. However, there are several families of superconductors in which superconductivity coexists with magnetism, and a few examples are known where the superconductivity itself induces spontaneous magnetism. The best known of these compounds are Sr2RuO4 and some non-centrosymmetric superconductors. Here, we report the finding of ...

Pionic helium teaser

Laser focus on mesons

The first demonstration of laser spectroscopy of a meson, achieved at PSI's πE5 beamline, opens up new avenues for precision studies of ‘exotic atoms’.

Han purple

Understanding Quantum Critical Magnetism in Han Purple

The ancient purple pigment used to paint the terracotta warriors, BaCuSi2O6, is also a quantum magnetic material which consists of stacked Cu2+ bilayers hosting spin dimers. Magnetometry and NMR experiments have revealed puzzling critical phenomena at the quantum phase transition (QPT) caused by an applied magnetic field, which suggest that the universal behaviour of the system is not three- but only two-dimensional. By performing high-resolution neutron spectroscopy measurements .....

 

CMS 2020

Measurement of properties of Bs0 → μ+μ− decays and search for B0 → μ+μ− with the CMS experiment

Results are reported for the B0s → μ+μ branching fraction and effective lifetime and from a search for the decay B0 → μ+μ−. The analysis uses a data sample of proton-proton collisions accumulated by the CMS experiment in 2011, 2012, and 2016, with center-of-mass energies (integrated luminosities) of 7TeV (5fb−1), 8TeV (20fb−1),and 13TeV (36fb−1).

Teaser neutron stroboscopy

Batteries under the neutron stroboscope

The first application of stroboscopic neutron diffraction to studying lithium-ion batteries during operation establishes a new approach to unravelling the complex processes playing out in energy-storage materials.

Lawley et al

Examining the surface evolution of LaTiOxNy an oxynitride solar water splitting photocatalyst

LaTiOxNy oxynitride thin films are employed to study the surface modifications at the solid- liquid interface that occur during photoelectrocatalytic water splitting. Neutron reflectometry and grazing incidence x-ray absorption spectroscopy were utilised to distinguish between the surface and bulk signals, with a surface sensitivity of 3 nm.

Balsini PNAS

Electron–phonon-driven three-dimensional metallicity in an insulating cuprate

Elucidating the role of different degrees of freedom in a phase transition is crucial in the comprehension of complex materi- als. A phase transformation that attracts significant interest is the insulator-to-metal transition of Mott insulators, in which the electrons are thought to play the dominant role. Here, we use ultrafast laser spectroscopy and theoretical calculations ....

Octupole teaser

Spin ice expands to higher orders

With experimental work demonstrating that the correlated ground state of the pyrochlore system Ce2Sn2O7 is a quantum liquid of magnetic octupoles, an international team led by PSI researcher Romain Sibille establishes a fundamentally new state of matter: higher-rank multipole ice.

Octupole teaser

A quantum liquid of magnetic octupoles on the pyrochlore lattice

With experimental work demonstrating that the correlated ground state of the pyrochlore system Ce2Sn2O7 is a quantum liquid of magnetic octupoles, an international team led by PSI researcher Romain Sibille establishes a fundamentally new state of matter: higher-rank multipole ice.

moorsom_t.jpg

Reversible spin storage in metal oxide - fullerene heterojunctions

We show that hybrid MnOx/C60 heterojunctions can be used to design a storage device for spin-polarized charge: a spin capacitor. Hybridization at the carbon-metal oxide interface leads to spin-polarized charge trapping after an applied voltage or photocurrent. Strong electronic structure changes, including a 1-eV energy shift and spin polarization in the C60 lowest unoccupied molecular orbital, are then revealed by x-ray absorption spectroscopy, in agreement with density functional theory simulations.

Benedek et al

Quantifying Diffusion through Interfaces of Lithium-Ion Battery Active Materials

Detailed understanding of charge diffusion processes in a lithium-ion battery is crucial to enable its systematic improvement. Experimental investigation of diffusion at the interface between active particles and the electrolyte is challenging but warrants investigation as it can introduce resistances that, for example, limit the charge and discharge rates. Here, we show an approach to study diffusion at interfaces using muon spin spectroscopy.

 

bildschirmfoto_2020-03-16_t.jpg

Current-driven magnetic domain-wall logic

Spin-based logic architectures provide nonvolatile data retention, near-zero leakage, and scalability, extending the technology roadmap beyond complementary metal–oxide–semiconductor logic. Architectures based on magnetic domain walls take advantage of the fast motion, high density, non-volatility and flexible design of domain walls to process and store information. Such schemes, however, rely on domain-wall manipulation and clocking using an external magnetic field, which limits their implementation in dense, large-scale chips.

Avers at el

Broken time-reversal symmetry in the topological superconductor UPt3

Topological properties of materials are of fundamental as well as practical importance. Of particular interest are unconven- tional superconductors that break time-reversal symmetry, for which the superconducting state is protected topologically and vortices can host Majorana fermions with potential use in quantum computing. However, in striking contrast to the unconventional A phase of superfluid 3He where chiral symmetry was directly observed, .....

 

JP Blaser

Symposium in memory of Jean-Pierre Blaser

Jean-Pierre Blaser (1923-2019) was one of the founders of the Swiss Institute for Nuclear Research SIN - one of the two institutions, which merged to the Paul Scherrer Institut in 1988. From 1988-1990 he was the first Director of the Paul Scherrer Institut. On the occasion of his first obit ETH Zurich and PSI organised a symposium to honour the lifetime achievement of this outstanding Swiss physicist.

dehn_prx_t.jpg

Observation of a Charge-Neutral Muon-Polaron Complex in Antiferromagnetic Cr2O3

We report a comprehensive muon spin rotation (μSR) study of the prototypical magnetoelectric antiferromagnet Cr2O3. We find the positively charged muon (μ+) occupies several distinct interstitial sites and displays a rich dynamic behavior involving local hopping, thermally activated site transitions, and the formation of a charge-neutral complex composed of a muon and an electron polaron.

MuSR teaser

A link between quantum magnetism and electronic band topology

Muon spin rotation experiments establish a quantitative link between the magnetic and topological electronic properties of the kagome magnet Co3Sn2S2 — and demonstrate effective ways for tuning these properties.

guguchia_nc_t.jpg

Tunable anomalous Hall conductivity through volume-wise magnetic competition in a topological kagome magnet

Magnetic topological phases of quantum matter are an emerging frontier in physics and material science. Along these lines, several kagome magnets have appeared as the most promising platforms. Here, we explore magnetic correlations in the kagome magnet Co3Sn2S2. Using muon spin-rotation, we present evidence for competing magnetic orders in the kagome lattice of this compound.

eichenberger_prb_t.jpg

Possible room-temperature signatures of unconventional 4f-electron quantum criticality in YbMn6Ge6−xSnx

We investigate the Sn composition dependence of the Yb valence and local magnetization in YbMn6Ge6−xSnx (4.25 􏰁≤x≤ 5.80) using x-ray absorption spectroscopy (XANES) and x-ray magnetic circular dichroism at the Yb L3 edge. In these materials, where Mn is ferromagnetically ordered, we observe a decrease of the Yb valence upon reducing the chemical pressure by Sn doping and a suppression of the Yb magnetic moment for strongly hybridized  4f states (ν ∼ 2.77).

destraz_natqm_2020

Magnetism and anomalous transport in the Weyl semimetal PrAlGe: possible route to axial gauge fields

In magnetic Weyl semimetals, where magnetism breaks time-reversal symmetry, large magnetically sensitive anomalous transport responses are anticipated that could be useful for topological spintronics. The identification of new magnetic Weyl semimetals is therefore in high demand, particularly since in these systems Weyl node configurations may be easily modified using magnetic fields. Here we explore experimentally the magnetic semimetal PrAlGe, and unveil a direct correspondence between easy-axis Pr ferromagnetism and anomalous Hall and Nernst effects. 

Anna Soter

Anna Sótér starts Ambizione fellowship

Anna Sótér has started an Ambizione fellowship at ETH Zurich and PSI. Her project is dedicated to developing a novel source of cold muonium atoms, which will be used for a new interferometry experiment that enables testing the weak equivalence principle by directly probing gravitational interaction of antimatter.

puphal_prl_t.jpg

Topological Magnetic Phase in the Candidate Weyl Semimetal CeAlGe

We report the discovery of topological magnetism in the candidate magnetic Weyl semimetal CeAlGe. Using neutron scattering we find this system to host several incommensurate, square-coordinated multi-k⃗ magnetic phases below TN. The topological properties of a phase stable at intermediate magnetic fields parallel to the c axis are suggested by observation of a topological Hall effect. 

PSI2019

Workshop on the Physics of Fundamental Symmetries and Interactions

The 5th Workshop on the Physics of Fundamental Symmetries and Interactions (PSI2019) took place from 20 to 25 October 2019 at PSI, bringing together 200 scientists from all over the world working on some of today’s most precise particle-physics experiments at the low-energy frontier.

Luo et al

Determination and evaluation of the nonadditivity in wetting of molecularly heterogeneous surfaces

Every folded protein presents an interface with water that is composed of domains of varying hydrophilicity/-phobicity. Many simulation studies have highlighted the nonadditivity in the wetting of such nanostructured surfaces in contrast with the accepted theoretical formula that is additive. We present here an experimental study on surfaces of identical composition but different organization of hydrophobic and hydrophilic domains.