615 research outputs found
Signatures of modulated pair interaction in cuprate superconductors
Recent low-temperature scanning tunnelling spectroscopy experiments on the
surface of BSCCO-2212 have revealed a strong positive correlation between the
position of localized resonances at -960 meV identified with interstitial
oxygen dopants and the size of the local spectral gap. We review efforts to
understand these correlations within a model where the dopants modulate the
pair interaction on an atomic scale. We provide further evidence for this model
by comparing the correlations between the dopants and the local density of
states with experimental results.Comment: 4 pages, 2 figures, submitted to M2S-HTSC VIII, Dresden 200
Quasilinear spin voltage profiles in spin thermoelectrics
Recent experiments show that spin thermoelectrics is a promising approach to
generate spin voltages. While spin chemical potentials are often limited to a
surface layer of the order of the spin diffusion length, we show that
thermoelectrically induced spin chemical potentials can extend much further in
itinerant ferromagnets with paramagnetic impurities. In some cases,
conservation laws, e.g., for a combination of spin and heat currents, give rise
to a linear spin voltage profile. More generally, we find quasilinear profiles
involving a spin thermoelectric length scale which far exceeds the spin
diffusion length.Comment: 4+ page
Imperfect nesting and Peierls instability for a two-dimensional tight-binding model
Based on a half-filled two-dimensional tight-binding model with
nearest-neighbour and next nearest-neighbour hopping the effect of imperfect
Fermi surface nesting on the Peierls instability is studied at zero
temperature. Two dimerization patterns corresponding to a phonon vector are considered. It is found that the Peierls instability will be
suppressed with an increase of next nearest-neighbour hopping which
characterizes the nesting deviation. First and second order transitions to a
homogeneous state are possible. The competition between the two dimerized
states is discussed.Comment: 17 pages, 10 eps figure
Anomalous Hall effect in a two dimensional electron gas with magnetic impurities
Magnetic impurities play an important role in many spintronics-related
materials. Motivated by this fact, we study the anomalous Hall effect in the
presence of magnetic impurities, focusing on two-dimensional electron systems
with Rashba spin-orbit coupling. We find a highly nonlinear dependence on the
impurity polarization, including possible sign changes. At small impurity
magnetizations, this is a consequence of the remarkable result that the linear
term is independent of the spin-orbit coupling strength. Near saturation of the
impurity spins, the anomalous Hall conductivity can be resonantly enhanced, due
to interference between potential and magnetic scattering.Comment: 5 pages, 3 figure
Microwave conductivity of d-wave superconductors with extended impurities
We investigate the influence of extended scatterers on the finite temperature
and finite frequency microwave conductivity of d-wave superconductors. For this
purpose we generalize a previous treatment by Durst and Lee, which is based on
a nodal approximation of the quasiparticle excitations and scattering
processes, and apply it to the analysis of experimental spectra of YBCO-123 and
BSCCO-2212. For YBCO, we find that accounting for a slight spatial extension of
the strong scattering in-plane defects improves the fit of the low temperature
microwave conductivity to experiment. With respect to BSCCO we conclude that it
is necessary to include a large concentration of weak-to-intermediate strength
extended scatterers, which we attribute to the out-of plane disorder introduced
by doping. These findings for BSCCO are consistent with similar analyses of the
normal state ARPES spectra and of STM spectra in the superconducting state,
where an enhanced forward scattering has been inferred as well.Comment: 10 pages, 11 figure
Dopant-modulated pair interaction in cuprate superconductors
Comparison of recent experimental STM data with single-impurity and
many-impurity Bogoliubov-de Gennes calculations strongly suggests that random
out-of-plane dopant atoms in cuprates modulate the pair interaction locally.
This type of disorder is crucial to understanding the nanoscale electronic
structure inhomogeneity observed in BSCCO-2212, and can reproduce observed
correlations between the positions of impurity atoms and various aspects of the
local density of states such as the gap magnitude and the height of the
coherence peaks. Our results imply that each dopant atom modulates the pair
interaction on a length scale of order one lattice constant.Comment: 5 pages, 4 figure
Andreev states near short-ranged pairing potential impurities
We study Andreev states near atomic scale modulations in the pairing
potential in both - and d-wave superconductors with short coherence lengths.
For a moderate reduction of the local gap, the states exist only close to the
gap edge. If one allows for local sign changes of the order parameter, however,
resonances can occur at energies close to the Fermi level. The local density of
states (LDOS) around such pairing potential defects strongly resembles the
patterns observed by tunneling measurements around Zn impurities in
BiSrCaCuO (BSCCO). We discuss how this phase impurity model
of the Zn LDOS pattern can be distinguished from other proposals
experimentally.Comment: 4 pages, 4 figure
From debt to discharge: Consumer insolvency proceedings in Austria
In jüngster Zeit haben zwei Gesetzgebungsakte das österreichische Insolvenzrecht erheblich verändert: Zum einen hat die "Gesamtreform des Exekutionsrechts" (GREx) die Schnittstelle zwischen Einzel- und Gesamtvollstreckung entscheidend umgestaltet. Zum anderen hat die Umsetzung der europäischen Restrukturierungs- und Insolvenzrichtlinie die Rahmenbedingungen für die Restschuldbefreiung nicht nur für Unternehmer, sondern auch für Verbraucher verbessert. Dieser Artikel gibt einen detaillierten Überblick über das Verbraucherinsolvenzverfahren in Österreich und geht hierbei auch auf die Tätigkeiten der anerkannten Schuldenberatungsstellen ein.Recently, two legislative acts have significantly changed Austrian insolvency law: Firstly, the overall reform of enforcement law (“Gesamtreform des Exekutionsrechts – GREx”) has drastically altered the interface between individual and general enforcement. And secondly, the implementation of the European Restructuring and Insolvency Directive has improved the framework for debt discharge not only for entrepreneurs but also for consumers. This article provides a detailed overview of the consumer insolvency proceedings in Austria and also addresses the activities of the recognised debt counselling agencies
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