1,538 research outputs found
Nonmetallic Low-Temperature Normal State of K0.70Fe1.46Se1.85Te0.15
The normal-state in-plane resistivity below the zero-field superconducting
transition temperature and the upper critical field Hc2 were measured by
suppressing superconductivity in pulsed magnetic fields for
K0.70Fe1.46Se1.85Te0.15. The normal-state resistivity is found to
increase logarithmically with decrasing temperature as
. Similar to granular metals, our results suggest
that a superconductor - insulator transition below zero-field T may be
induced in high magnetic fields. This is related to the intrinsic real-space
phase-separated states common to all inhomogeneous superconductors.Comment: 6 pages, 4 figure
Disparity of superconducting and pseudogap scales in low-Tc Bi-2201 cuprates
We experimentally study transport and intrinsic tunneling characteristics of
a single-layer cuprate Bi(2+x)Sr(2-y)CuO(6+delta) with a low superconducting
critical temperature Tc < 4 K. It is observed that the superconducting energy,
critical field and fluctuation temperature range are scaling down with Tc,
while the corresponding pseudogap characteristics have the same order of
magnitude as for high-Tc cuprates with 20 to 30 times higher Tc. The observed
disparity of the superconducting and pseudogap scales clearly reveals their
different origins.Comment: 5 page
Cosmic Ray Energy Spectra and Mass Composition at the Knee - Recent Results from KASCADE -
Recent results from the KASCADE experiment on measurements of cosmic rays in
the energy range of the knee are presented. Emphasis is placed on energy
spectra of individual mass groups as obtained from an two-dimensional unfolding
applied to the reconstructed electron and truncated muon numbers of each
individual EAS. The data show a knee-like structure in the energy spectra of
light primaries (p, He, C) and an increasing dominance of heavy ones (A > 20)
towards higher energies. This basic result is robust against uncertainties of
the applied interaction models QGSJET and SIBYLL which are used in the shower
simulations to analyse the data. Slight differences observed between
experimental data and EAS simulations provide important clues for further
improvements of the interaction models. The data are complemented by new limits
on global anisotropies in the arrival directions of CRs and by upper limits on
point sources. Astrophysical implications for discriminating models of maximum
acceleration energy vs galactic diffusion/drift models of the knee are
discussed based on this data.Comment: 8 pages, 7 figures, to appear in Nuclear Physics B, Proceedings
Supplements, as part of the volume for the CRIS 2004, Cosmic Ray
International Seminar: GZK and Surrounding
The Origin of Transverse Flow at the SPS
We study the transverse expansion in central Pb+Pb collisions at the CERN
SPS. Strong collective motion of hadrons can be created. This flow is mainly
due to meson baryon rescattering. It allows to study the angular distribution
of intermediate mass meson baryon interactions.Comment: submitted to Phys. Lett.
TeV gamma-UHECR anisotropy by decaying nuclei in flight: first neutrino traces?
Ultra High Cosmic Rays) made by He-like lightest nuclei might solve the AUGER
extragalactic clustering along Cen A. Moreover He like UHECR nuclei cannot
arrive from Virgo because the light nuclei fragility and opacity above a few
Mpc, explaining the Virgo UHECR absence. UHECR signals are spreading along
Cen-A as observed because horizontal galactic arms magnetic fields, bending
them on vertical angles. Cen A events by He-like nuclei are deflected as much
as the observed clustered ones; proton will be more collimated while heavy
(iron) nuclei are too much dispersed. Such a light nuclei UHECR component
coexist with the other Auger heavy nuclei and with the Hires nucleon
composition. Remaining UHECR spread group may hint for correlations with other
gamma (MeV-Al^{26} radioactive) maps, mainly due to galactic SNR sources as
Vela pulsar, the brightest, nearest GeV source. Other nearest galactic gamma
sources show links with UHECR via TeV correlated maps. We suggest that UHECR
are also heavy radioactive galactic nuclei as Ni^{56}, Ni^{57} and Co^{60}
widely bent by galactic fields. UHECR radioactivity (in and
channels) and decay in flight at hundreds keV is boosted (by huge Lorentz
factor (nearly a billion) leading to PeVs electrons and consequent synchrotron
TeVs gamma offering UHECR-TeV correlated sky anisotropy. Moreover also rarest
and non-atmospheric electron and tau neutrinos secondaries at PeVs, as the
first two rarest shower just discovered in ICECUBE, maybe the first signature
of such expected radioactive secondary tail.Comment: 7 pages,3 figures. arXiv admin note: substantial text overlap with
arXiv:1201.015
Correlation between Fermi surface transformations and superconductivity in the electron-doped high- superconductor NdCeCuO
Two critical points have been revealed in the normal-state phase diagram of
the electron-doped cuprate superconductor NdCeCuO by exploring
the Fermi surface properties of high quality single crystals by high-field
magnetotransport. First, the quantitative analysis of the Shubnikov-de Haas
effect shows that the weak superlattice potential responsible for the Fermi
surface reconstruction in the overdoped regime extrapolates to zero at the
doping level corresponding to the onset of superconductivity.
Second, the high-field Hall coefficient exhibits a sharp drop right below
optimal doping where the superconducting transition
temperature is maximum. This drop is most likely caused by the onset of
long-range antiferromagnetic ordering. Thus, the superconducting dome appears
to be pinned by two critical points to the normal state phase diagram.Comment: 9 pages; 7 figures; 1 tabl
Azimuthal Correlations in the Target Fragmentation Region of High Energy Nuclear Collisions
Results on the target mass dependence of proton and pion pseudorapidity
distributions and of their azimuthal correlations in the target rapidity range
are presented. The data have been taken with the
Plastic-Ball detector set-up for 4.9 GeV p + Au collisions at the Berkeley
BEVALAC and for 200 GeV/ p-, O-, and S-induced reactions on
different nuclei at the CERN-SPS. The yield of protons at backward rapidities
is found to be proportional to the target mass. Although protons show a typical
``back-to-back'' correlations, a ``side-by-side'' correlation is observed for
positive pions, which increases both with target mass and with impact parameter
of a collision. The data can consistently be described by assuming strong
rescattering phenomena including pion absorption effects in the entire excited
target nucleus.Comment: 7 pages, figures included, complete postscript available at
ftp://qgp.uni-muenster.de/pub/paper/azi-correlations.ps submitted to Phys.
Lett.
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