Scientific Highlights
Low-Temperature Micro-Solid Oxide Fuel Cells with Partially Amorphous La0.6Sr0.4CoO3-δ Cathodes
Partially amorphous La0.6Sr0.4CoO3-δ (LSC) thin-film cathodes are fabricated using pulsed laser deposition and are integrated in free-standing micro-solid oxide fuel cells (micro-SOFC) with a 3YSZ electrolyte and a Pt anode. A low degree of crystallinity of the LSC layers is achieved by taking advantage of the miniaturization of the cells, which permits low-temperature operation (300–450 °C).
Fast scanning coherent X-ray imaging using Eiger
The smaller pixel size, high frame rate, and high dynamic range of next-generation photon counting pixel detectors expedites measurements based on coherent diffractive imaging (CDI). The latter comprises methods that exploit the coherence of X-ray synchrotron sources to replace imaging optics by reconstruction algorithms. Researchers from the Paul Scherrer Institut have recently demonstrated fast CDI image acquisition above 25,000 resolution elements per second using an in-house developed Eiger detector. This rate is state of the art for diffractive imaging and even on a par with the fastest scanning X-ray transmission instruments. High image throughput is of crucial importance for both materials and biological sciences for studies with representative population sampling.
Correlated Decay of Triplet Excitations in the Shastry-Sutherland Compound SrCu2(BO3)2
The temperature dependence of the gapped triplet excitations (triplons) in the 2D Shastry-Sutherland quantum magnet SrCu2(BO3)2 is studied by means of inelastic neutron scattering. The excitation amplitude rapidly decreases as a function of temperature, while the integrated spectral weight can be explained by an isolated dimer model up to 10 K.
Square dance of the atoms: Shedding light on ultrafast phase transitions
The exploration of the interaction of structural and electronic degrees of freedom in strongly correlated electron systems on the femtosecond time scale is an emerging area of research. One goal of these studies is to advance our understanding of the underlying correlations, another to find ways to control the exciting properties of these materials on an ultrafast time scale.
Square dance of the atoms: Shedding light on ultrafast phase transitions
The exploration of the interaction of structural and electronic degrees of freedom in strongly correlated electron systems on the femtosecond time scale is an emerging area of research. One goal of these studies is to advance our understanding of the underlying correlations, another to find ways to control the exciting properties of these materials on an ultrafast time scale. So far a general model is lacking that provides a quantitiative description of the correlations between the structural and electronic degrees of freedom.
Negative Oxygen Isotope Effect on the Static Spin Stripe Order in Superconducting La2−xBaxCuO4(x=1/8) Observed by Muon-Spin Rot
Large negative oxygen-isotope (16O and 18O) effects (OIEs) on the static spin-stripe-ordering temperature Tso and the magnetic volume fraction Vm were observed in La2−xBaxCuO4(x=1/8) by means of muon-spin-rotation experiments. The corresponding OIE exponents were found to be αTso=-0.57(6) and αVm=-0.71(9), which are sign reversed to αTC=0.46(6) measured for the superconducting transition temperature Tc. This indicates that the electron-lattice interaction is involved in the stripe formation and plays an important role in the competition between bulk superconductivity and static stripe order in the cuprates.
Direct observation of the spin texture in SmB6 as evidence of the topological Kondo insulator
Topological Kondo insulators have been proposed as a new class of topological insulators in which non-trivial surface states reside in the bulk Kondo band gap at low temperature due to strong spin–orbit coupling. In contrast to other three-dimensional topological insulators, a topological Kondo insulator is truly bulk insulating. Furthermore, strong electron correlations are present in the system, which may interact with the novel topological phase. By applying spin- and angle-resolved photoemission spectroscopy, here we show that the surface states of SmB6 are spin polarized. The spin is locked to the crystal momentum, fulfilling time reversal and crystal symmetries.
Small-angle neutron scattering study of the mixed state of Yb3Rh4Sn13
Using the small angle neutron scattering (SANS) technique we investigated the vortex lattice (VL) in the mixed state of the stannide superconductor Yb3Rh4Sn13. We find a single domain VL of slightly distorted hexagonal geometry for field strengths between 350 and 18 500 G and temperatures between T=0.05 and 6.5 K. We observe a clear in-plane rotation of the VL for different magnetic field directions relative to the crystallographic axes.
Spin-Wave Spectrum of the Quantum Ferromagnet on the Pyrochlore Lattice Lu2V2O7
Neutron inelastic scattering has been used to probe the spin dynamics of the quantum (S=1/2) ferromagnet on the pyrochlore lattice Lu2V2O7. Well-defined spin waves are observed at all energies and wave vectors, allowing us to determine the parameters of the Hamiltonian of the system.
Polychlorinated biphenyls in glaciers
We present a highly time-resolved historical record of polychlorinated biphenyls (PCBs) from an Alpine ice core (Fiescherhorn glacier, Switzerland). Introduced in the 1940s, PCBs were widely used industrial chemicals. Because of their persistence they are still found in the environment, long after their production phase-out. The Fiescherhorn ice core record covers the entire time period of industrial use of PCBs, that is, 1940?2002. The total concentration of six PCBs varies from 0.5 to 5 ng/L and reveals a temporal trend, with an 8-fold increase from the early 1940s to the peak value in the 1970s.