17 research outputs found
Full orbital decomposition of Yu-Shiba-Rusinov states based on first principles
We have implemented the Bogoliubov-de Gennes (BdG) equation in a screened
Korringa-Kohn- Rostoker (KKR) method for solving, self-consistently, the
superconducting state for 3d crystals including substitutional impurities. In
this report we extend this theoretical framework to allow for collinear
magnetism and apply it to fcc Pb with 3d magnetic impurities. In the presence
of magnetic impurities, there is a pair-breaking effect that results in sup-gap
Yu-Shiba-Rusinov (YSR) states which we decompose into contributions from the
individual orbital character. We determine the spatial extent of these impurity
states, showing how the different orbital character affects the details of the
YSR states within the superconducting gap. Our work highlights the importance
of the first principles based description which captures the quantitative
details making direct comparisons possible with experimental findings
Gap Anisotropy in Multiband Superconductors Based on Multiple Scattering Theory
We implement the Bogoliubov-de Gennes equation in a screened Korringa-Kohn-Rostoker method for solving, self-consistently, the superconducting state for three-dimensional crystals. This method combines the full complexity of the underlying electronic structure and Fermi surface geometry with a simple phenomenological parametrization for the superconductivity. We apply this theoretical framework to the known s-wave superconductors Nb, Pb, and MgB2. In these materials multiple distinct peaks at the gap in the density of states were observed, showing significant gap anisotropy which is in good agreement with experiment. Qualitatively, the results can be explained in terms of the k-dependent Fermi velocities on the Fermi surface sheets exploiting concepts from BCS theory
Real-space multiple scattering theory for superconductors with impurities
We implement the Bogoliubov-de Gennes (BdG) equation in real-space using the
screened Korringa-Kohn-Rostoker (KKR) method. This allows us to solve,
self-consistently, the superconducting state for 3d crystals including
substitutional impurities with a full normal-state DFT band structure. We apply
the theoretical framework to bulk Nb with impurities. Without impurities, Nb
has an anisotropic gap structure with two distinct peaks around the Fermi
level. In the presence of non-magnetic impurities those peaks are broadened due
to the scattering between the two bulk superconducting gaps, however the peaks
remain separated. As a second example of self-consistent real-space solutions
of the BdG equations we examine superconducting clusters embedded within a
non-superconducting bulk metallic host. This allows us to estimate the
coherence length of the superconductor and we show that, within our framework,
the coherence length of the superconductor is related to the inverse of the gap
size, just as in bulk BCS theory.Comment: 9pages, 15 figure
Gap anisotropy in multiband superconductors based on multiple scattering theory
We implement the Bogoliubov-de Gennes equation in a screened Korringa-Kohn-Rostoker method for solving, self-consistently, the superconducting state for three-dimensional crystals. This method combines the full complexity of the underlying electronic structure and Fermi surface geometry with a simple phenomenological parametrization for the superconductivity. We apply this theoretical framework to the known s-wave superconductors Nb, Pb, and MgB2. In these materials multiple distinct peaks at the gap in the density of states were observed, showing significant gap anisotropy which is in good agreement with experiment. Qualitatively, the results can be explained in terms of the k-dependent Fermi velocities on the Fermi surface sheets exploiting concepts from BCS theory
First principles based proximity effect of superconductor–normal metal heterostructures
In this paper we study the proximity effect in superconductor-normal metal heterostructures based on first principles calculations with treating the pairing potential as an adjustable parameter. The superconducting order parameter (anomalous density) is obtained from the Green-function by solving the Kohn-Sham-Bogoliubov-de Gennes equations with the Screened Korringa-Kohn-Rostoker method. The results are interpreted for an Au/Nb(0 0 1) system. The layer resolved anomalous spectral function is also obtained which is closely related to the superconducting order parameter. We find that the anomalous spectral function has the fingerprint of the Andreev scattering process and it is connected to the electron-hole ratio of the quasiparticle states. We also show that the proximity effect can be understood via the anomalous spectral function.</p
Prediction of superconducting transition temperatures of heterostructures based on the quasiparticle spectrum
Endotoxins do not influence transplacental transmission of lymphotropic human herpesviruses and human papillomaviruses into amniotic fluid taken from healthy mothers before parturition in Hungary
Pregnant women were examined following healthy pregnancies at term. Amniotic fluids were sampled before arteficial rupture of membranes using closed vacutainer system. Blood samples were also taken from the pregnants simultaneously. Endotoxin concentrations of amniotic fluids were tested by the semiquantitative Limulus amebocyte lysate. Both amniotic fluids and blood samples were tested for the presence of DNA of lymphotropic human herpesviruses. The DNA of human papillomaviruses were tested only in the amniotic fluid samples. One-third of the amniotic fluids tested were found to contain measurable amounts of endotoxin. Lymphotropic herpesvirus DNA was deteced in every fourth amniotic fluid sample and in every 8th blood sample. The prevalence of papillomaviruses was 7 of 96 samples. No significant correlation was found between the presence of endotoxin and viruses in the amniotic fluids. Epstein-Barr virus, human cytomegalovirus and human herpesvirus type 7 were found more frequently in the amniotic fluids than in blood samples (7 to 1). The prevalence of human herpesvirus 6 and 8 was higher in the blood samples than that in the amniotic fluids. The mean weight of the neonates were not impaired significantly by the presence of either viruses or endotoxin. Possible post partum consequences, i.e. partial immunotolerance to viruses is discussed