Localization effects in Co- and Ni-doped Bi2Sr2CaCu2O8+gamma

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The frustrated magnet Bi2Fe4O9 has been reported to exhibit complex spin dynamics coexisting with conventional spin wave excitations. The magnetic Fe3+ (S = 5/2) ions are arranged into a distorted two-dimensional Cairo pentagonal lattice with weak couplings between the layers, developing long-ranged noncollinear antiferromagnetic order below 245 K. In order to enable studies and modeling of the complex dynamics close to TN, we have reexamined the magnetic excitations across the complete energy scale (0 < h

The insulating chiral magnet Cu2OSeO3 exhibits a rich array of low-temperature magnetic phenomena, making it a prime candidate for the study of its spin dynamics. Using spin wave small-angle neutron scattering (SWSANS), we systematically investigated the temperature-dependent behavior of the helimagnon excitations in the field-polarized phase of Cu2OSeO3. Our measurements, spanning 5-55 K, reveal the temperature evolution of spin-wave stiffness and damping constant with unprecedented resolution, facilitated

Lithium thiophosphate (LPS) is a promising solid electrolyte for next-generation lithium-ion batteries due to its superior energy storage, high ionic conductivity, and low-flammability properties. Despite its potential, the high reactivity of LPS with common contaminants such as atmospheric water, preparation solvents, and electrode materials poses significant challenges for commercialization. The lack of understanding regarding the structure, morphology, and chemical behavior of the surface of LPS slows do

The electronic structure of the optimally hole-doped pnictide compound Ba0:6K0:4Fe2As2 was obtained and studied by angle resolved photoemission spectroscopy (ARPES). The light polarization dependence of the bands is explained by the selection rules contained in the photoemission transition matrix elements, and gives novel information on the possible orbital character of the bands. The Fermi surface geometry also shows important variations with light polarization. An attempt is made to analyze its more compl

We introduce a theoretical scheme to study defect energy levels and band alignments at semiconductor-oxide interfaces. The scheme relies on hybrid functionals to overcome the band gap underestimation typically achieved with semilocal density functionals. For atomically localized defects, the more accurate description achieved with, hybrid functionals does not lead to significant shifts of the charge transition levels, provided these levels are referred to a common reference potential. This result effectivel

The ac loss of superconducting composite depends strongly on coupling between superconducting filaments via the resistive matrix. The established technique for loss reduction using twisted filaments relies on the decoupling of the filaments below a critical coupling field Bc, which increases with the reduction of the twist pitch and the matrix conductivity. Although the concept of Bc may be clearly demonstrated using two infinite slabs of finite length, further details on its correlation with the filament/c

The index n of the voltage-current characteristic of large superconductors is a crucial parameter to assess the allowed range for coil operation. In the tests of the Insert coils at the CSMC as well as in the short sample test in the SULTAN facility, it is observed that the index n dramatically decreases from the Nb3Sn strands extracted from cable-in-conduit provide the evidence of a permanent performance drop in the strands, likely due to the transverse load accumulation at the strand crossovers in the cab

We analyze the electronic properties of quantum wires with a Z-like profile within four-band models for the valence band of a semiconductor of diamond and zinc blende type. Group-theoretical considerations show that the valence-band structure is doubly degenerate only when the linear k-terms (coming e.g. from the bulk crystal inversion asymmetry) are neglected. The considerations apply to the more general case of a profile containing a 2D center of inversion.

The Forschungszentrum Karlsruhe (FZK) and the Centre de Recherches en Physique des Plasmas (CRPP) are working on a joint development program to construct and test a 70 kA current lead using High Temperature Superconductors (HTS) for the Toroidal Field (TF) coil system of the International Thermonuclear Experimental Reactor, ITER-FEAT. This program follows the development program of an HTS current lead in the 20 kA range which was successfully completed in 2000. The HTS part of the current lead will be manuf

Disorder has a strong influence on the spectral properties of the Bi2Sr2CaCu2O8+x high-T-c superconductor, both in the normal and in the superconducting state. High-resolution photoemission reveals a progressive quasiparticle suppression with increasing disorder in electron-irradiated optimally doped single crystals. The spectral Line shapes of the disordered samples show striking analogies with those of underdoped samples specifically the widely discussed pseudogap at the chemical potential. Disorder provi

In YBa2Cu3O6+x the tetragonal to orthorhombic transition occurs around x equals 0.3, followed by a continuum variation of lattice parameters. Hence both, the structural and superconducting properties, depend upon the oxygen content in CuO chains. Conversely, the epitaxial stress, exerted by the substrate on YBCO films, modified the lattice parameters, influencing the oxygen stability in the chains. The understanding of this mechanism is essential when growing epitaxial films for in-situ photoemission studie

The effects of niobium doping on the hysteresis parameters of sol-gel Pb-1.1-x/2(Zr0.53Ti0.47)(1-x)NbxO3 (0 < x < 0.05) have been reported fbr two sets of films with analogous grain size and degree of (111) texture but with different surface microstructures. For both sets, a strong continuous decay of the remnant and maximum polarizations and slope of the hysteresis loop at the coercive field was observed with increasing niobium concentration. The held dependence of the remnant polarization for any given ni

Multilayered Co/Cu wires with a diameter of 80 nm and a length of 6 mu m were produced by electrodeposition in nanoporous polycarbonate membranes. Their magnetoresistance has been measured in a geometry where the current was perpendicular to the layer plane. The anisotropic part of the magnetoresistance was limited to 1.5%. The study, for layer thicknesses ranging from 3 to 100 nm interpreted in terms of the Valet and Fert model gave estimates of the spin dependent bulk and interface resistivities acid thei

A first-principles investigation of Si 2p core-level shifts at the Si(001)-SiO2 interface is presented. We introduce several relaxed interface models obtained by attaching different crystalline forms of SiO2 to Si(001). These model structures contain the minimal transition region required to accommodate the three intermediate oxidation states of silicon, in accord with photoemission experiments. The bond density mismatch is fixed by saturating all the bonds, as required by electrical measurements, Calculate

Photoemission has become a most powerful electronic probe of high-T-C superconductors. The main present emphasis is on the BCSCO-2212 gap symmetry. After much controversy a consensus emerges: (1) no symmetric s-waves; (2) the symmetry depends on temperature and doping; (3) the optimal doping data are consistent with d(x)2(y)2 waves; (4) for other dopings, the symmetry is consistent with mixed s and d-waves. The data, though, cannot rule out other hypotheses, specifically asymmetric s-waves. Photoemission al

We study the electrodynamics of a superlattice that consists of two kinds of layers: the layers of a type-II superconductor and the layers of a normal metal in a perpendicular magnetic field. The problem is treated in the framework of London electrodynamics taking into account simultaneously the nonlocality of the intervortex interaction and the Abrikosov vortex elasticity. The dependence of the surface impedance Z on the dc-magnetic-field induction B much less than H(c2) (H(c2) is the upper critical field)

Contact potential difference (CPD) measurements using a Kelvin probe coupled with synchrotron radiation are used to investigate the surface photovoltage (SPV) induced by synchrotron radiation at GaAs surfaces. A large and quasi-permanent SPV is found at surfaces of low-doped and low-temperature samples. SPV discharge mechanisms are investigated. The CPD technique is used to define conditions under which SPV is negligible, leading to reliable measurements of band bending at low temperature. Band bending meas

A Hall mobility as high as 176,200 cm2V-1s-1 at 77 K with N(d)-N(a) = 1.3 x 10(14) cm-3 has been obtained by adjusting the substrate and the phosphine cracker temperatures. The 2 K photoluminescence spectra show finely resolved excitonic transitions for layers grown above 535-degrees-C with linewidths of 0.07 meV. Excitonic transitions have been recorded between 2 and 250 K. The free exciton energy position leads to a highly accurate expression of the band gap energy, which extrapolates to E(g) = 1.347 eV a

Localization effects in Co- and Ni-doped Bi2Sr2CaCu2O8+gamma

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Refined Spin Hamiltonian on the Cairo Pentagonal Lattice of Bi2fe4o9

Helical spin dynamics in Cu2OSeO3 as measured with small-angle neutron scattering

Reconstructions and Dynamics of β -Lithium Thiophosphate Surfaces

Orbital characterization of iron-pnictide high-temperature superconductors by angle resolved photoemission spectroscopy

A hybrid functional scheme for defect levels and band alignments at semiconductor-oxide interfaces

3D Modeling of Coupling Between Superconducting Filaments via Resistive Matrix in AC Magnetic Field

The voltage/current characteristic (n index) of the cable-in-conduit conductors for fusion

The band structure of Z-like quantum wires

Development of high temperature superconductor current leads for 70 kA

Alternative pseudogap scenario: Spectroscopic analogies between underdoped and disordered Bi2Sr2CaCu2O8+x

Structural properties of strained YBa2Cu3O6+x superconducting films grown by pulsed laser deposition

Use of ferroelectric hysteresis parameters for evaluation of niobium effects in lead zirconate titanate thin films

Arrays of multilayered nanowires

Theory of Si 2p core-level shifts at the Si(001)-SiO2 interface

Photoemission studies of the normal and high-temperature superconducting states

Dc-Magnetic-Field Dependence of the Surface Impedance of a Multilayer Superconductor System in the Mixed-State

Kelvin Probe and Synchrotron Radiation Study of Surface Photovoltage and Band Bending at Metal GaAs (100) Interfaces

HIGH-PURITY INP GROWN BY CHEMICAL BEAM EPITAXY