Co-doped Bi2Sr2CaCu2Ox: Anderson localization and superconductivity

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SrCu2(BO3)2 is a frustrated quantum magnet which realizes the Shastry–Sutherland model. The system exhibits a sequence of pressure-induced phases, including a long-range antiferromagnetically ordered state. We have performed inelastic neutron scattering experiments on a single crystal at 4.2 (2) GPa, in the antiferromagnetic phase. The observed dispersive spin excitations were modeled using linear-spin-wave theory to extract exchange parameters. Our results are consistent with previously reported parameters

We report the multiferroic properties of 12R-type hexagonal Ba(Ti1/3Mn2/3)O3-delta found in Mn-doped BaTiO3 series samples. Hysteresis measurements reveal the coexistence of weak ferromagnetism and ferroelectricity at room temperature. Furthermore, frequen ...

High-temperature superconductivity emerges from an un-conventional metallic state. This has stimulated strong efforts to understand exactly how Fermi liquids breakdown and evolve into an un-conventional metal. A fundamental question is how Fermi liquid quasiparticle excitations break down in momentum space. Here we show, using angle-resolved photoemission spectroscopy, that the Fermi liquid quasiparticle excitations of the overdoped superconducting cuprate La1.77Sr0.23CuO4 is highly anisotropic in momentum

In order to determine the orbital characters on the various Fermi surface pockets of the Fe-based superconductors Ba0.6K0.4Fe2As2 and FeSe0.45Te0.55, we introduce a method to calculate photoemission matrix elements. We compare our simulations to experiment ...

From small-angle neutron scattering studies of the flux line lattice (FLL) in CeCoIn5, with magnetic field applied parallel to the crystal c-axis, we obtain the field and temperature dependence of the FLL form factor (FF), which is a measure of the spatial ...

Experiments directly probing the electronic states using angle-resolved photoemission (ARPES) were carried out on La2/3Sr1/3MnO3 in order to elucidate its electronic properties. ARPES is a surface sensitive technique where bulk and surface states are usually both present. We present high-resolution ARPES studies in the (1 0 0) and (1 1 0) mirror planes and compare them with simulated ARPES based on GGA + U band structure calculations. In the (1 1 0) mirror plane we identify surface umklapps accounted by (ro

Surface-state-mediated interactions influence the spatial distribution of adatoms at surfaces. These indirect interactions are the driving force for the creation of superlattices of individual adsorbed atoms when the adatom concentration, the sample temperature, and the adatom diffusion barrier are in a subtle balance, as it has been first reported for Ce adatoms on Ag(1 1 1). The conditions for the formation of such superlattices are discussed. Specifically, the adatom concentration is shown to modify cons

Reduction of the specific fuel consumption of gas turbines can be achieved by maximizing the turbine inlet temperature. However, this requires a detailed understanding of the cooling performance in order to ensure safe and economical operation of the engin ...

Structural stability issues in planar solid oxide fuel cells (SOFC) arise from the mismatch between the coefficients of thermal expansion (CTE) of the components. The stress state at operating temperature is the superposition of several contributions, which differ depending on the component. First, the cells undergo residual stresses due to the sintering phase during the manufacturing process. Furthermore, the load applied during the assembly of the stack to ensure the electric contact and flatten the cells

Thin films are very promising for the design of novel and efficient Fault Current Limiter (FCL) made of high-temperature superconductors (HTS). However, their thermal and highly non-linear electromagnetic behavior in the presence of over-critical currents is crucial to their use in future electrical grid. In this paper, we propose a numerical approach to solve magneto-thermal models for geometries of high aspect ratio. The used electromagnetic formulation, inspired in good part from the work of Brambilla et

In the frame of the European Fusion Technology Programme, the Forschungszentrum Karlsruhe and the Centre de Recherches en Physique des Plasmas, CRPP, Villigen, develop a 70 kA current lead to demonstrate the feasibility of the usage of High Temperature Superconductors (HTS) for the current leads of the ITER TF coils. Design and fabrication of the conventional heat exchanger that covers the temperature range from 65 K to room temperature is done at the Forschungszentrum Karlsruhe. The HTS module connects the

We study the effect of a magnetic field (applied along the c axis) on the low-energy, incommensurate magnetic fluctuations in superconducting La1.82Sr0.18CuO4. The incommensurate peaks at 9 meV, which in zero field were previously shown to sharpen in q on cooling below T-c [T. E. Mason , Phys. Rev. Lett. 77, 1604 (1996)], are found to broaden in q when a field of 10 T is applied. The applied field also causes scattered intensity to shift into the spin gap. We point out that the response at 9 meV, though occ

The electrical conductivity of Ce0.992Nb0.008O2−δ was measured as a function of oxygen partial pressure between 10−28 and 1 bar in the temperature range of 873–1173 K. The activation energy for the conductivity at an oxygen partial pressure of 10−4 bar was 0.29 eV. This value was too small to be assigned for oxide ion conduction, indicating that, in oxidizing atmospheres, electronic conduction is dominant due to Nb doping. On the other hand, the oxygen partial pressure dependence of conductivity was complic

The experimentally observed temperature dependence of the quartic coefficients in the Landau-Devonshire expansion for BaTiO3 is naturally accounted for within a proper fluctuation model. It is explained, in particular, why one of the quartic coefficients varies with temperature above T-c, while the second is constant. It is argued that the tetragonal phase in BaTiO3 exists essentially due to thermal fluctuations, while the true Landau-Devonshire expansion with temperature-independent coefficients favors the

Measurements of critical temperature T-c in superconducting YBa2Cu3O6.9 films with reduced long-range structural order show the validity of the empirical scaling relation Delta T-c proportional to r(c)(-2) between disorder-induced reduction of T-c and structural coherence length r(c) in the ab-plane. This result is quantitatively explained by the disorder-induced confinement of the charge carriers within each ordered domain of size r(c). Our analysis of the data based on this picture enables us to precisely

We have exploited angle-resolved photoelectron spectroscopy to study changes in the quasiparticle excitations of CuO2 planes as a function of the carrier density, in optimally doped and underdoped Bi2Sr2CaCuO8+x and in Sr2CuO2Cl2. We have observed large changes in the E versus k dispersion of the quasiparticle bands, and in the topology of the Fermi surface away from optimal doping. We have also found that the carrier density has a nontrivial effect on the symmetry properties of these states.

A comprehensive micro-macroscopic model of the continuous hardening of 3d-axisymmetric steel components by induction heating has been developed. At the macroscopic scale, the Maxwell and heat flow equations are solved using a mixed numerical formulation : the inductor and the workpiece are enmeshed with finite elements (FE) but boundary elements (BE) are used for the solution of the electromagnetic equations in the ambient air. This method allows the inductor to be moved with respect to the workpiece withou

Co-doped Bi2Sr2CaCu2Ox: Anderson localization and superconductivity

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Spin excitations near the pressure-induced antiferromagnetic transition in SrCu2(BO3)2

Polaron response dominated multiferroic property in 12R-type hexagonal Ba(Ti1/3Mn2/3)O3-delta ceramics

Anisotropic breakdown of Fermi liquid quasiparticle excitations in overdoped La2−xSrxCuO4

Orbital characters determined from Fermi surface intensity patterns using angle-resolved photoemission spectroscopy

Observations of Pauli paramagnetic effects on the flux line lattice in CeCoIn5

Bulk vs. surface effects in ARPES experiment from La2/3Sr1/3MnO3 thin films

Creation, electronic properties, disorder, and melting of two-dimensional surface-state-mediated adatom superlattices

Application of Photoluminescent Measurement Techniques for Quantitative Assessment of Turbine Film Cooling

Simulation of Thermal stresses in anode-supported solid oxide fuel cell stacks

2D Magneto-Thermal Modeling of Coated High-Temperature Superconductors

Design and fabrication of a 70 kA current lead using Ag/Au stabilized Bi-2223 tapes as a demonstrator for the ITER TF-coil system

Evidence for an incommensurate magnetic resonance in La2-xSrxCuO4

Electrical properties and defect structure of niobia-doped ceria

Fluctuations and Landau-Devonshire expansion for barium titanate

Scaling between superconducting critical temperature and structural coherence length in TBa2Cu3O6.9 films

Doping effects on the electronic structure of CuO2 planes

Modelling of electromagnetic heating, cooling and phase transformations during surface hardening of steels