301 research outputs found
Evidence of precursor superconductivity as high as 180 K from infrared spectroscopy
We show that a multilayer analysis of the infrared c-axis response of
RBa2Cu3O7-d (R=Y, Gd, Eu) provides important new information about the
anomalous normal state properties of underdoped cuprate high temperature
superconductors. Besides competing correlations which give rise to a pseudogap
that depletes the low-energy electronic states below T*>>Tc, it enables us to
identify the onset of a precursor superconducting state below Tons>Tc. We map
out the doping phase diagram of Tons which reaches a maximum of ~180 K at
strong underdoping and present magnetic field dependent data which confirm our
conclusions.Comment: 5 pages, 3 figure
Study of the reaction pbar p -> phi phi from 1.1 to 2.0 GeV/c
A study has been performed of the reaction pbar p -> 4K using in-flight
antiprotons from 1.1 to 2.0 GeV/c incident momentum interacting with a hydrogen
jet target. The reaction is dominated by the production of a pair of phi
mesons. The pbar p -> phi phi cross section rises sharply above threshold and
then falls continuously as a function of increasing antiproton momentum. The
overall magnitude of the cross section exceeds expectations from a simple
application of the OZI rule by two orders of magnitude. In a fine scan around
the xi/f_J(2230) resonance, no structure is observed. A limit is set for the
double branching ratio B(xi -> pbar p) * B(xi -> phi phi) < 6e-5 for a spin 2
resonance of M = 2.235 GeV and Width = 15 MeV.Comment: 13 pages, 13 figures, 2 tables, Latex. To be published in Phys. Rev.
Evidence of a Precursor Superconducting Phase at Temperatures as High as 180Â K in RBaâCuâO<sub>7-ÎŽ</sub>âââ(R=Y,Gd,Eu) Superconducting Crystals from Infrared Spectroscopy
We show that a multilayer analysis of the infrared c-axis response of RBaâCuâO7-ÎŽâââ(R=Y,Gd,Eu) provides important new information about the anomalous normal-state properties of underdoped cuprate high temperature superconductors. In addition to competing correlations which give rise to a pseudogap that depletes the low-energy electronic states below T*â«Tc, it enables us to identify the onset of a precursor superconducting state below Tons>Tc. We map out the doping phase diagram of Tons which reaches a maximum of 180Â K at strong underdoping and present magnetic field dependent data which confirm our conclusions
Muon spin rotation study of magnetism and superconductivity in BaFe2-xCoxAs2 and Pr1-xSrxFeAsO
We present a muon spin rotation (\muSR) study of the magnetic and
superconducting properties of single crystals of electron-doped BaFe2-xCoxAs2
with x=0.08, 0.20, and 0.25 (Tc=9, 25 and 20K) and of polycrystalline
hole-doped Pr1-xSrxFeAsO with x=0 and 0.2 (Tc=15 K). In the former series we
observe some interesting parallels with the electron doped SmFeAsO1-xFx
1111-type system [A.J. Drew et al., to appear in Nature Materials 2009 and
arXiv:0807.4876]. In particular, we obtain evidence that strongly disordered
static magnetism coexists with superconductivity on a microscopic scale in
underdoped samples and even at optimum doping there is a slowing down (or
enhancement) of dynamic magnetic correlations below Tc\approx25K. To the
contrary, for the hole-doped Pr1-xSrxFeAsO samples we obtain evidence for a
mesoscopic phase segregation into regions with nearly unperturbed AF order and
others that are non magnetic and most likely superconducting. The observed
trend resembles the one that was previously reported for hole-doped
Ba1-xKxFe2As2 [A.A. Aczel et al., Phys. Rev. B 78, 214503 (2008); J.T. Park et
al., arXiv:0811.2224] and thus seems to be fairly common in these hole doped
systems.Comment: 17 pages, 6 figure
Aszites, Pfortaderthrombose und hepatische Enzephalopathie bei Leberzirrhose: Aktuelle Therapieempfehlungen
Treatment of Ascites, Portal Vein Thrombosis and Hepatic Encephalopathy in Patients with Cirrhosis of the Liver Background: Ascites, portal vein thrombosis and hepatic encephalopathy are important complications of cirrhosis of the liver. Guidelines for the treatment of ascites have recently been published. Method: This manuscript summarizes up-to-date recommendations on the basis of the DGVS S3 guideline and of other guidelines as well as of the authors' experience. Results and Conclusions: TIPS (transjugular intrahepatic porto-systemic shunt) is the preferred treatment for refractory or recidivant ascites unless there are contraindications. The therapy of hepatorenal syndrome type 1 with albumin and the vasoconstrictor Terlipressin has been proven effective. Treatment of portal vein thrombosis comprises a strategy of anticoagulation, TIPS and liver transplantation. The most important therapeutic strategy for hepatic encephalopathy is the search for as well as the treatment of trigger events. Rifaximin is being increasingly used for the treatment and prophylaxis of hepatic encephalopathy
Coexistence of static magnetism and superconductivity in SmFeAsO1-xFx as revealed by muon spin rotation
The recent observation of superconductivity with critical temperatures up to
55 K in the FeAs based pnictide compounds marks the first discovery of a non
copper-oxide based layered high-Tc superconductor (HTSC) [1-3]. It has raised
the suspicion that these new materials share a similar pairing mechanism to the
cuprates, since both exhibit superconductivity following charge doping of a
magnetic parent material. Here we present a muon spin rotation study on
SmFeAsO1-xFx (x=0-0.30), which shows that static magnetism persists well into
the superconducting regime. The analogy with the cuprates is quite surprising
since the parent compounds appear to have different magnetic ground states:
itinerant spin density wave for the pnictides contrasted with the Mott-Hubbard
insulator in the cuprates. Our findings suggest that proximity to magnetic
order and associated soft magnetic fluctuations, rather than the strong
electronic correlations in the vicinity of a Mott-Hubbard-metal-to-insulator
transition, may be the key ingredients of HTSC.Comment: Accepted in Nature Material
Measurement of the pbar p -> Ks Ks Reaction from 0.6 to 1.9 GeV/c
The pbar p -> Ks Ks -> 4pi+/- cross section was measured at incident
antiproton momenta between 0.6 and 1.9 GeV/c using the CERN Low Energy
Antiproton Ring (LEAR). This investigation was part of a systematic study of
in-flight antiproton-proton annihilations into two-neutral-meson final states
in a search for hadronic resonances. A coarse scan of the pbar p -> Ks Ks cross
section as a function of center-of-mass energy between 1.964 and 2.395 GeV/c^2
and a fine scan of the region surrounding the Xi(2220) are presented. Upper
limits on the product branching ratio BR(Xi -> pbar p)BR(Xi -> Ks Ks) are
determined for a wide range of mass and width assumptions based on the
non-observation of the Xi(2220). A rise in the pbar p -> Ks Ks cross section is
observed near 2.15 GeV/c^2, which is consistent with the f2(2150) resonance.Comment: 11 pages, Latex, to be published in Phys Rev D (Oct 97
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