publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2008-08-12 | Magnetism Driven by Anion Vacancies in Superconducting $α$--FeSe$_{1-x}$ | To study the microscopic electronic and magnetic interactions in the
substoichiometric iron chalcogenide FeSe$_{1-x}$ which is observed to
superconduct at x~1/8 up to $T_c$=27 K, we use first principles methods to
study the Se vacancy in this nearly magnetic FeSe system. The vacancy forms a
ferrimagnetic cluster of eig... | 0808.1733v2 |
2008-08-13 | Jet modification in 200 AGeV Au-Au collisions | The computation of hard processes in hadronic collisions is a major success
of perturbative Quantum Chromodynamics. The environment of heavy-ion collisions
offers the opportunity to embed such hard processes into a soft medium which is
created simultaneously and study the medium-induced modifications. On the level
of s... | 0808.1803v1 |
2008-08-13 | Ranges of Atmospheric Mass and Composition of Super Earth Exoplanets | Terrestrial-like exoplanets may obtain atmospheres from three primary
sources: Capture of nebular gases, degassing during accretion, and degassing
from subsequent tectonic activity. Here we model degassing during accretion to
estimate the range of atmospheric mass and composition on exoplanets ranging
from 1 to 30 Eart... | 0808.1909v1 |
2008-08-17 | Spin Dynamics in Iron-based Layered Superconductor (La_{0.87}Ca_{0.13})FePO Revealed by ^{31}P and ^{139}La NMR Studies | We report ^{31}P and ^{139}La NMR studies of (La_{0.87}Ca_{0.13})FePO, which
is a family member of the recently discovered superconductor
LaFeAs(O_{1-x}F_x). In the normal state, Knight shift and $1/T_1T$ show that a
Fermi-liquid state with moderate ferromagnetic fluctuations emerges below 30K.
From 1/T_1T of ^{31}P ... | 0808.2293v1 |
2008-08-20 | Correlation effects of exchange splitting and coexistence of spin-density-wave and superconductivity in single crystalline Sr1-xKxFe2As2 | The nature of spin-density wave and its relation with superconductivity are
crucial issues in the newly discovered Fe-based high temperature
superconductors. Particularly it is unclear whether the superconducting phase
and spin density wave (SDW) are truly exclusive from each other as suggested by
certain experiments. ... | 0808.2738v1 |
2008-08-20 | Superconducting Properties of Two-Orbital t-t'-J-J' Models | Motivated by the recent contradiction of the superconducting pairing symmetry
in the angle-resolved photoemission spectra (ARPES) and the nuclear magnetic
resonance (NMR) data in the FeAs superconductors, we present the theoretical
results on the phase diagram, the temperature dependent Fermi surfaces in
normal state, ... | 0808.2763v2 |
2008-08-21 | High energy spin excitations in BaFe2As2 | We report neutron scattering measurements of cooperative spin excitations in
antiferromagnetically ordered BaFe2As2, the parent phase of an iron pnictide
superconductor. The data extend up to ~100meV and show that the spin excitation
spectrum is sharp and highly dispersive. By fitting the spectrum to a linear
spin-wave... | 0808.2836v2 |
2008-08-26 | Impurity suppression of the critical temperature in the iron-based superconductors | We study the impurity suppression of the critical temperature $T_c$ of the
FeAs superconductors theoretically based on the the $\pm$s-wave pairing state
of a two band model. The effects of non-magnetic and magnetic impurities are
studied with the $\mathcal{T}$-matrix approximation, which can continuously
treat impurity... | 0808.3473v2 |
2008-08-28 | Orbital Selective Superconductivity in Two-Orbital Asymmetric t-J Models | We present the zero-temperature superconducting (SC) ground states of the
two-orbital asymmetric $t-J$ model on a square lattice by means of the
auxiliary-boson approach. Besides the two-gap SC phase, we find an orbital
selective SC (OSSC) phase, which is simultaneously SC in one orbit and normal
in another orbit. The ... | 0808.3809v1 |
2008-09-02 | Near-Infrared Photometry of Four Stellar Clusters in the Small Magellanic Cloud | We present high-quality J, H and K photometry of four Small Magellanic Cloud
stellar clusters with intermediate ages in the 1-7 Gyr range (namely NGC 339,
361, 416 and 419) . We obtained deep Color-Magnitude Diagrams to study the
evolved sequences and providing a detailed census of the Red Giant Branch
(RGB), Asymptoti... | 0809.0495v1 |
2008-09-10 | Kramers degeneracy in a magnetic field and Zeeman spin-orbit coupling in antiferromagnets | In this article, I analyze the symmetries and degeneracies of electron
eigenstates in a commensurate collinear antiferromagnet. In a magnetic field
transverse to the staggered magnetization, a hidden anti-unitary symmetry
protects double degeneracy of the Bloch eigenstates at a special set of
momenta. In addition to th... | 0809.1893v3 |
2008-09-13 | Chemical Abundances from the Continuum | The calculation of solar absolute fluxes in the near-UV is revisited,
discussing in some detail recent updates in theoretical calculations of
bound-free opacity from metals. Modest changes in the abundances of elements
such as Mg and the iron-peak elements have a significant impact on the
atmospheric structure, and the... | 0809.2364v1 |
2008-09-15 | Role of covalent Fe-As bonding in the magnetic moment formation and exchange mechanisms in iron-pnictide superconductors | The electronic origin of the huge magnetostructural effect in layered Fe-As
compounds is elucidated using LiFeAs as a prototype. The crucial feature of
these materials is the strong covalent bonding between Fe and As, which tends
to suppress the exchange splitting. The bonding-antibonding splitting is very
sensitive to... | 0809.2586v3 |
2008-09-19 | An ab-initio calculation of the core-level x-ray photoemission spectra -Fe 3s- and 1s-core levels- | We develop a method of the ab-initio calculation for the core-level x-ray
photoemission spectroscopy (XPS). By calculating one-electron states in the
presence of core-hole potential, excited states are constructed by distributing
electrons on these one-electron states. The overlap integrals between the
excited states a... | 0809.3296v1 |
2008-09-23 | Ab initio exchange interactions and magnetic properties of Gd2Fe17 iron sublattice: rhombohedral vs. hexagonal phases | In the framework of the LSDA+U method electronic structure and magnetic
properties of the intermetallic compound Gd2Fe17 for both rhombohedral and
hexagonal phases have been calculated. On top of that, ab initio exchange
interaction parameters within the Fe sublattice for all present nearest and
some next nearest Fe io... | 0809.3905v2 |
2008-10-01 | Anomalous behavior of the Debye temperature in Fe-rich Fe-Cr alloys | Debye temperature, $\Theta_D$, of Fe-rich Fe$_{100-x}$Cr$_x$ disordered
alloys with $0\le x \le 22.3$ was determined from the temperature dependence of
the central shift of M\"ossbauer spectra recorded in the temperature range of
60 -- 300 K. Its compositional dependence shows a maximum at $x \approx 5$ with
a relative... | 0810.0123v1 |
2008-10-01 | Pressure effects on the electron-doped high Tc superconductor BaFe(2-x)Co(x)As(2) | Application of pressures or electron-doping through Co substitution into Fe
sites transforms the itinerant antiferromagnet BaFe(2)As(2) into a
superconductor with the Tc exceeding 20K. We carried out systematic transport
measurements of BaFe(2-x)Co(x)As(2) superconductors in pressures up to 2.5GPa,
and elucidate the in... | 0810.0287v1 |
2008-10-01 | NMR measurements of intrinsic spin susceptibility in LaFeAsO(0.9)F(0.1) | We will probe the intrinsic behavior of spin susceptibility chi_(spin) in the
LaFeAsO(1-x)F(x) superconductor (x ~ 0.1, Tc ~ 27K) using 19-F and 75-As NMR
techniques. Our new results firmly establish the pseudo-gap behavior with
Delta_(PG)/kB ~ 140K. The estimated magnitude of chi_(spin) at 290K,
~1.8x10^(-4) [emu/mol-... | 0810.0305v1 |
2008-10-06 | Pairing State with a time-reversal symmetry breaking in FeAs based superconductors | We investigate the competition between the extended $s_{\pm}$-wave and
$d_{x^2-y^2}$-wave pairing order parameters in the iron-based superconductors.
Because of the frustrating pairing interactions among the electron and the hole
fermi pockets, a time reversal symmetry breaking $s+id$ pairing state could be
favored. We... | 0810.0887v3 |
2008-10-06 | Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe$_{1.8}$Co$_{0.2}$As$_2$ | We present an atomic resolution scanning tunneling spectroscopy study of
superconducting BaFe$_{1.8}$Co$_{0.2}$As$_2$ single crystals in magnetic fields
up to $9 \text{Tesla}$. At zero field, a single gap with coherence peaks at
$\overline{\Delta}=6.25 \text{meV}$ is observed in the density of states. At $9
\text{T}$ a... | 0810.1048v2 |
2008-10-08 | Dielectric anomalies induced by different mechanisms in Pb(Fe1/2Nb1/2)1-xTixO3 single crystals | We investigated the dielectric properties of Pb(Fe1/2Nb1/2)1-xTixO3 single
crystals below room temperature. Two dielectric anomalies were detected in
sample A while only one was detected in sample B in the temperature range
90~300 K. A Debye-like relaxation with strong frequency dispersion was detected
in both samples.... | 0810.1346v3 |
2008-10-08 | Interband superconductivity: contrasts between BCS and Eliashberg theory | The newly discovered iron pnictide superconductors apparently present an
unusual case of interband-channel pairing superconductivity. Here we show that,
in the limit where the pairing occurs within the interband channel, several
surprising effects occur quite naturally and generally: different
density-of-states on the ... | 0810.1476v1 |
2008-10-09 | Muon-spin rotation study of the in-plane magnetic penetration depth of FeSe_0.85: evidence for nodeless superconductivity | The in-plane magnetic penetration depth \lambda_{ab} of the iron selenide
superconductor with the nominal composition FeSe_0.85 was studied by means of
muon-spin rotation. The measurements of \lambda_{ab}^{-2}(T) are inconsistent
with the presence of nodes in the gap as well as with a simple isotropic s-wave
type of th... | 0810.1716v1 |
2008-10-09 | Kondo decoherence: finding the right spin model for iron impurities in gold and silver | We exploit the decoherence of electrons due to magnetic impurities, studied
via weak localization, to resolve a longstanding question concerning the
classic Kondo systems of Fe impurities in the noble metals gold and silver:
which Kondo-type model yields a realistic description of the relevant multiple
bands, spin and ... | 0810.1771v2 |
2008-10-10 | Inverse Raman Scattering in Silicon | Stimulated Raman scattering is a well-known nonlinear process that can be
harnessed to produce optical gain in a wide variety of media. This effect has
been used to produce the first silicon-based lasers and high-gain amplifiers.
Interestingly, the Raman effect can also produce intensity-dependent nonlinear
loss throug... | 0810.1939v1 |
2008-10-14 | SrFeAsF as a parent compound for iron pnictide superconductors | We have successfully synthesized the fluo-arsenide SrFeAsF, a new parent
phase with the ZrCuAsSi structure. The temperature dependence of resistivity
and dc magnetization both reveal an anomaly at about T_{an} = 173 K, which may
correspond to the structural and/or Spin-Density-Wave (SDW) transition. Strong
Hall effect ... | 0810.2475v2 |
2008-10-15 | On the origin of microturbulence in hot stars | We present results from the first extensive study of convection zones in the
envelopes of hot massive stars, which are caused by opacity peaks associated
with iron and helium ionization. These convective regions can be located very
close to the stellar surface. Recent observations of microturbulence in massive
stars fr... | 0810.2546v1 |
2008-10-17 | Band Structure and Fermi Surface of an Extremely Overdoped Iron-Based Superconductor KFe2As2 | We have performed high-resolution angle-resolved photoemission spectroscopy
on heavily overdoped KFe_2As_2 (transition temperature (Tc = 3 K). We observed
several renormalized bands near the Fermi level with a renormalization factor
of 2-4. While the Fermi surface (FS) around the Brillouin-zone center is
qualitatively ... | 0810.3047v1 |
2008-10-19 | Cosmic Ray Results from the IceTop Air Shower Array | We report on the first results obtained with the IceTop air shower array on
the cosmic ray energy spectrum and mass composition in the range of 1 PeV to 80
PeV. IceTop is the surface detector of the IceCube neutrino telescope currently
under construction at the South Pole. A high sensitivity to the primary mass
composi... | 0810.3409v1 |
2008-10-20 | Systematic ^{75}As NMR study of the dependence of low-lying excitations on F doping in the iron oxypnictide LaFeAs(O_{1-x}F_{x}) | We report systematic $^{75}$As NMR studies on LaFeAs(O$_{1-x}$F$_{x}$) ($0\le
x\le0.14$). At $x=0.04$ near the phase boundary, from resistivity, spin-lattice
relaxation rate $1/T_1$, and NMR spectrum measurements, we found weak magnetic
order at $T_N\simeq 30$ K. Antiferromagnetic (AFM) fluctuations proved through
$1/T... | 0810.3569v2 |
2008-10-23 | The Age and Metallicity of the Bootes I System | We present Washington photometry of a field central to the Bootes I dwarf
spheroidal galaxy, which was discovered as a stellar overdensity in the Sloan
Digital Sky Survey (DR5). We show that the Washington filters are much more
effective than the Sloan filters in separating the metal-poor turn-off stars in
the dwarf ga... | 0810.4353v1 |
2008-10-25 | Detection of Hard X-Rays from the Compton-Thick Seyfert 2 Galaxy NGC 2273 with Suzaku | We have obtained a broad-band spectrum of the Compton-thick Seyfert 2 galaxy
NGC 2273 with Suzaku. The spectrum reveals the first detection of hard X-rays
above ~10 keV from NGC 2273. The broad-band spectrum is well represented by a
three-component model, accompanied by both a strong iron Ka line with an
equivalent wid... | 0810.4570v1 |
2008-10-26 | Development of Glass Resistive Plate Chambers for INO | The India-based Neutrino Observatory (INO) collaboration is planning to build
a massive 50kton magnetised Iron Calorimeter (ICAL) detector, to study
atmospheric neutrinos and to make precision measurements of the parameters
related to neutrino oscillations. Glass Resistive Plate Chambers (RPCs) of
about 2m X 2m in size... | 0810.4693v1 |
2008-10-27 | Anisotropic itinerant magnetism and spin fluctuations in BaFe2As2: A neutron scattering study | Neutron scattering measurements were performed to investigate magnetic
excitations in a single-crystal sample of the ternary iron arsenide BaFe2As2, a
parent compound of a recently discovered family of Fe-based superconductors. In
the ordered state, we observe low energy spin-wave excitations with a gap
energy of 9.8(4... | 0810.4790v2 |
2008-10-31 | The minimum stellar metallicity observable in the Galaxy | The first stars fundamentally transformed the early Universe through their
production of energetic radiation and the first heavy chemical elements. The
impact on cosmic evolution sensitively depends on their initial mass function
(IMF), which can be empirically constrained through detailed studies of
ancient, metal-poo... | 0811.0020v1 |
2008-10-31 | Anisotropy, Itineracy, and Magnetic Frustration in High-Tc Iron Pnictides | Using first-principle density functional theory calculations combined with
insight from a tight-binding representation, dynamical mean field theory, and
linear response theory, we have extensively investigated the electronic
structures and magnetic interactions of nine ferropnictides representing three
different struct... | 0811.0034v3 |
2008-11-05 | Superconductivity at 56 K in Samarium-doped SrFeAsF | We synthesized the samples Sr$_{1-x}$Sm$_x$FFeAs with ZrCuSiAs-type
structure. These samples were characterized by resistivity and susceptibility.
It is found that substitution of rare earth metal for alkaline earth metal in
this system suppresses the anomaly in resistivity and induces
superconductivity. Superconductiv... | 0811.0761v3 |
2008-11-06 | Resolution-dependent mechanisms for bimodal switching-time distributions in simulated Fe nanopillars | We study the magnetization-switching statistics following reversal of the
applied field for three separate computational models representing the same
physical system, an iron nanopillar. The primary difference between the models
is the resolution of the computational lattice and, consequently, the intrinsic
parameters ... | 0811.1028v1 |
2008-11-07 | Substitution Effects on FeSe Superconductor | We have investigated the effect of atomic substitutions in the FeSe system,
which exhibits the simplest crystal structure among the iron-based
superconductors. An enhancement of the superconducting transition temperature
Tc was observed with the substitution of S or Te for Se; the Tc increased with
S substitution by up... | 0811.1123v3 |
2008-11-10 | Strong short-range magnetic order in a frustrated FCC lattice and its possible role in the iron structural transformation | We investigate magnetic properties of a frustrated Heisenberg antiferromagnet
with a face-centered cubic (FCC) lattice and exchange interactions between the
nearest- and next-nearest neighbours, J1 and J2. In a collinear phase with the
wave vector Q = (pi,pi,pi) the equations of the self-consistent spin-wave
theory for... | 0811.1472v1 |
2008-11-10 | The XMM-Newton long look of NGC 1365: uncovering of the obscured X-ray source | We present an analysis of the extreme obscuration variability observed during
an XMM-Newton 5-days continuous monitoring of the AGN in NGC 1365. The source
was in a reflection-dominated state in the first ~1.5 days, then a strong
increase of the 7-10 keV emission was observed in ~10 hours, followed by a
symmetric decre... | 0811.1594v2 |
2008-11-12 | CERN-INO magical Beta-beam experiment: A high precision probe for neutrino parameters | This talk is an attempt to underscore in detail the physics reach of an
experimental set-up where neutrinos produced in a beta-beam facility at CERN
would be observed in the proposed large magnetized iron calorimeter detector
(ICAL) at the India-based Neutrino Observatory (INO). The "magical" CERN-INO
beta-beam set-up ... | 0811.1822v1 |
2008-11-12 | X-Ray Reflection Nebulae with Large Equivalent Widths of Neutral Iron Ka Line in the Sgr C Region | This paper reports on the first results of the Suzaku observation in the Sgr
C region. We detected four diffuse clumps with strong line emission at 6.4keV,
Ka from neutral or low-ionized Fe. One of them, M359.38-0.00, is newly
discovered with Suzaku. The X-ray spectra of the two bright clumps,
M359.43-0.07 and M359.47-... | 0811.1830v1 |
2008-11-12 | Bond analysis of cobalt and iron based skutterudites: elongated lanthanum bonds in LaFe4P12 | Motivated by the possibility of further improving the thermoelectric
properties of skutterudites we investigate charge transfer and bonding in this
class of materials using density functional calculations. Results for the CoP3,
CoSb3, LaFe4P12 and the hypothetical FeP3 compounds are presented using the
procrystal as th... | 0811.1889v1 |
2008-11-14 | Metallicities for 13 nearby open clusters from high-resolution spectroscopy of dwarf and giant stars. Stellar metallicity, stellar mass, and giant planets | We present a study of accurate stellar parameters and iron abundances for 39
giants and 16 dwarfs in the 13 open clusters IC2714, IC4651, IC4756, NGC2360,
NGC2423, NGC2447 (M93), NGC2539, NGC2682 (M67), NGC3114, NGC3680, NGC4349,
NGC5822, NGC6633. The analysis was done using a set of high-resolution and
high-S/N spectr... | 0811.2392v1 |
2008-11-16 | Solar neutrinos and the solar composition problem | Standard solar models (SSM) are facing nowadays a new puzzle: the solar
composition problem. New determinations of solar metal abundances lead SSM
calculations to conflict with helioseismological measurements, showing
discrepancies that extend from the convection zone to the solar core and can
not be easily assigned to... | 0811.2424v1 |
2008-11-16 | The Absence of Superconductivity in Single Phase CaFe2As2 under Hydrostatic Pressure | Recent high-pressure studies found that superconductivity can be achieved
under very low pressure in the parent iron arsenide compound CaFe2As2, although
details of the sharpness and temperature of transitions vary between liquid
medium and gas medium measurements. To better understand this issue, we
performed high-pre... | 0811.2554v2 |
2008-11-19 | The location and kinematics of the coronal-line emitting regions in AGN | We use the photoionisation code Cloudy to determine both the location and the
kinematics of the optical forbidden, high ionisation line (hereafter, FHIL)
emitting gas in the narrow line Seyfert 1 galaxy Ark 564. The results of our
models are compared with the observed properties of these emission lines to
produce a phy... | 0811.3204v1 |
2008-11-20 | A critical re-examination of resonant soft x-ray Bragg forbidden reflections in magnetite | Magnetite, Fe$_3$O$_4$, displays a highly complex low temperature crystal
structure that may be charge and orbitally ordered. Many of the recent
experimental claims of such ordering rely on resonant soft x-ray diffraction at
the oxygen K and iron L edges. We have re-examined this system and undertaken
soft x-ray diffra... | 0811.3350v2 |
2008-11-22 | 75As-NMR studies on La FeAsO1-xFx (x=0.14) under a pressure of 3GPa | 75As-nuclear magnetic resonance (NMR) on an iron-based superconductor
LaFeAsO1-xFx (x=0.14) was performed under a pressure of 3GPa. Enhancement of
superconducting transition temperature Tc was confirmed from the relaxation
rate 1/T1; Tc goes up to 40K by applying pressure up to 3GPa. 1/T1T, which is
temperature indepen... | 0811.3672v3 |
2008-11-26 | Ironing out primordial temperature fluctuations with polarisation: optimal detection of cosmic structure imprints | Secondary anisotropies of the cosmic microwave background (CMB) can be
detected by using the cross-correlation between the large-scale structure (LSS)
and the CMB temperature fluctuations. In such studies, chance correlations of
primordial CMB fluctuations with the LSS are the main source of uncertainty. We
present a m... | 0811.4433v2 |
2008-11-27 | A unified theory for the cuprates, iron-based and similar superconducting systems: non-Fermi-liquid to Fermi-liquid crossover, low-energy and waterfall anomalies | A unified theory is outlined for the cuprates, Fe-based, and related
superconductors. Their low-energy excitations are approached in terms of
auxiliary particles representing combinations of atomic-like electron
configurations, and the introduction of a Lagrange Bose field enables their
treatment as bosons or fermions.... | 0811.4561v1 |
2008-11-27 | Two-dimensional magnetism in the pnictide superconductor parent material SrFeAsF probed by muon-spin relaxation | We report muon-spin relaxation measurements on SrFeAsF, which is the parent
compound of a newly discovered iron-arsenic-fluoride based series of
superconducting materials. We find that this material has very similar magnetic
properties to LaFeAsO, such as separated magnetic and structural transitions
(TN = 120 K, Ts = ... | 0811.4598v1 |
2008-11-30 | Andreev Bound states as a phase sensitive probe of the pairing symmetry of the iron pnictide superconductors | A leading contender for the pairing symmetry in the Fe-pnictide high
temperature superconductors is extended s-wave $s_\pm$, a nodeless state in
which the pairing changes sign between Fermi surfaces. Verifying such a pairing
symmetry requires a special phase sensitive probe that is also momentum
selective. We show that... | 0812.0015v1 |
2008-11-28 | Small RNAs Establish Delays and Temporal Thresholds in Gene Expression | Non-coding RNAs are crucial regulators of gene expression in prokaryotes and
eukaryotes, but it remains poorly understood how they affect the dynamics of
transcriptional networks. We analyzed the temporal characteristics of the
cyanobacterial iron stress response by mathematical modeling and quantitative
experimental a... | 0812.0025v1 |
2008-12-01 | Near-degeneracy of several pairing channels in multiorbital models for the Fe-pnictides | Weak-coupling approaches to the pairing problem in the iron pnictide
superconductors have predicted a wide variety of superconducting ground states.
We argue here that this is due both to the inadequacy of certain approximations
to the effective low-energy band structure, and to the natural near-degeneracy
of different... | 0812.0343v2 |
2008-12-04 | Medium Effects in rho-Meson Photoproduction | We compute dilepton invariant mass spectra from the decays of rho mesons
produced by photon reactions off nuclei. Our calculations employ a realistic
model for the rho photoproduction amplitude on the nucleon which provides fair
agreement with measured cross sections. Medium effects are implemented via an
earlier const... | 0812.0987v3 |
2008-12-09 | Insular superconductivity in Co-doped iron pnictide CaFe$_{1-x}$Co$_x$AsF | The presence of macroscopic phase separation between the superconducting and
magnetic phases in \cfcaf is demonstrated by muon spin rotation (muSR)
measurements conducted across their phase boundaries (x=0.05-0.15). The
magnetic phase tends to retain the high transition temperature (T_m > T_c),
while Co-doping induces ... | 0812.1670v3 |
2008-12-10 | Disk reflection signatures in the spectrum of the bright Z-source GX 340+0 | We present the preliminary results of a 50 ks long XMM-Newton observation of
the bright Z-source GX 340+0. In this Letter we focus on the study of a broad
asymmetric emission line in the Fe K alpha energy band, whose shape is clearly
resolved and compatible with a relativistically smeared profile arising from
reflectio... | 0812.1974v1 |
2008-12-11 | Full Gap Superconductivity in Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ Probed by Muon Spin Rotation | Superfluid density ($n_s$) in the mixed state of an iron pnictide
superconductor Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ is determined by muon spin
rotation for a sample with optimal doping ($x=0.4$). The temperature dependence
of $n_s$ is perfectly reproduced by the conventional BCS model for s-wave
paring, where the order pa... | 0812.2069v2 |
2008-12-11 | Impurity-induced in-gap state and Tc in sign-reversing s-wave superconductors: analysis of iron oxypnictide superconductors | The sign-reversing fully gapped superconducting state, which is expected to
be realized in oxypnictide superconductors, can be prominently affected by
nonmagnetic impurities due to the interband scattering of Cooper pairs. We
study this problem based on the isotropic two-band BCS model: In oxypnictide
superconductors, ... | 0812.2100v2 |
2008-12-11 | Quantum and classical structures in nondeterminstic computation | In categorical quantum mechanics, classical structures characterize the
classical interfaces of quantum resources on one hand, while on the other hand
giving rise to some quantum phenomena. In the standard Hilbert space model of
quantum theories, classical structures over a space correspond to its
orthonormal bases. In... | 0812.2266v3 |
2008-12-15 | Microscopic origin of pressure-induced phase transitions in iron-pnictide $AFe_2As_2$ superconductors: an {ab initio} molecular-dynamics study | Using {\it ab initio} molecular dynamics we investigate the electronic and
lattice structure of $A$Fe$_2$As$_2$ ($A$=Ca, Sr, Ba) under pressure. We find
that the structural phase transition (orthorhombic to tetragonal symmetry) is
always accompanied by a magnetic phase transition in all the compounds, while
the nature ... | 0812.2920v3 |
2008-12-16 | Anomalous Hall effect in granular ferromagnetic metals and effects of weak localization | We theoretically investigate the anomalous Hall effect in a system of
dense-packed ferromagnetic grains in the metallic regime. Using the formalism
recently developed for the conventional Hall effect in granular metals, we
calculate the residual anomalous Hall conductivity $\sigma_{xy}$ and
resistivity $\rho_{xy}$ and ... | 0812.3085v2 |
2008-12-18 | Observation of the Josephson effect in Pb/(Ba,K)Fe2As2 single crystal junctions | We have fabricated c-axis Josephson junctions on single crystals of
(Ba,K)Fe2As2 by using Pb as the counter electrode in two geometries, planar and
point contact. Junctions in both geometries show resistively shunted junction
I-V curves below the Tc of the counter electrode. Microwave induced steps were
observed in the... | 0812.3605v2 |
2008-12-21 | Suppression of antiferromagnetic spin fluctuations in the collapsed tetragonal phase of CaFe2As2 | Inelastic neutron scattering measurements of CaFe2As2 under applied
hydrostatic pressure show that the antiferromagnetic spin fluctuations observed
in the ambient pressure, paramagnetic, tetragonal (T) phase are strongly
suppressed, if not absent, in the collapsed tetragonal (cT) phase. These
results are consistent wit... | 0812.4056v1 |
2008-12-22 | Electronic structure of heavily electron-doped BaFe$_{1.7}$Co$_{0.3}$As$_2$ studied by angle-resolved photoemission | We have performed high-resolution angle-resolved photoemission spectroscopy
on heavily electron-doped non-superconducting (SC)
BaFe$_{1.7}$Co$_{0.3}$As$_2$. We find that the two hole Fermi surface pockets
at the zone center observed in the hole-doped superconducting
Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ are absent or very sm... | 0812.4111v3 |
2008-12-29 | Superconducting properties of the oxygen-vacant iron oxyarsenide TbFeAsO1-x from underdoped to overdoped compositions | A wide-range doping was achieved by a high-pressure method for TbFeAsO1-x
from "under doped" to "over doped" superconducting compositions throughout the
optimized superconductivity (Tc of 44 K). Tc vs. lattice constant shows a
dome-shaped feature, while Tc vs. the lattice constant likely follows a unique
empirical curv... | 0812.4907v2 |
2009-01-01 | 75As NMR Study of Hole-Doped Superconductor Ba1-xKxFe2As2 (Tc = 38K) | We report the 75As nuclear magnetic resonance (NMR) measurement of the
hole-doped superconductor Ba1-xKxFe2As2 with different lattice parameters and
different superconducting volume fractions (Tc = 38K). 75As-NMR spectra
revealed that the magnetically ordered and superconducting phases are
microscopically separated. Th... | 0901.0177v2 |
2009-01-02 | Electronic structure and Magnetism in BaMn$_2$As$_2$ and BaMn$_2$Sb$_2$ | We study the properties of ThCr$_2$Si$_2$ structure BaMn$_2$As$_2$ and
BaMn$_2$Sb$_2$ using density functional calculations of the electronic and
magnetic as well experimental measurements on single crystal samples of
BaMn$_2$As$_2$. These materials are local moment magnets with moderate band gap
antiferromagnetic semi... | 0901.0272v2 |
2009-01-09 | Fermi surface topology and low-lying quasiparticle structure of magnetically ordered Fe1+xTe | We report the first photoemission study of Fe1+xTe - the host compound of the
newly discovered iron-chalcogenide superconductors. Our results reveal a pair
of nearly electron- hole compensated Fermi pockets, strong Fermi velocity
renormalization and an absence of a spin-density-wave gap. A shadow hole pocket
is observe... | 0901.1299v1 |
2009-01-11 | Theory of tunnelling into a multi-band superconductor: decoherence and interference | By an exact formulation of tunnelling into a multi-band superconductor in
terms of Green's functions, we demonstrate that the multi-band feature of the
iron-based superconductors can lead to novel interference between Andreev
reflections and decoherence effect of quasi-particles to Andreev reflections in
a tunnelling j... | 0901.1419v2 |
2009-01-14 | Plasma focus based repetitive source of fusion neutrons and hard x-rays | A plasma focus device capable of operating at 0.2 pulses per second during
several minutes is used as a source of hard x-rays and fast neutrons. An
experimental demonstration of the use of the neutrons emissions for radiation
probing of hydrogenated substances is presented, showing a particular
application in detecting... | 0901.2007v1 |
2009-01-16 | Star Formation in HII Galaxies. Properties of the ionized gas | We propose a methodology to perform a self-consistent analysis of the
physical properties of the emitting gas of HII galaxies adequate to the data
that can be obtained with the XXI century technology. This methodology requires
the production and calibration of empirical relations between the different
line temperatures... | 0901.2465v1 |
2009-01-19 | NMR Studies on the Superconducting Symmetry of Iron Pnictide Systems | NMR longitudinal relaxation rates 1/T1 and Knight shifts K have been measured
for superconducting samples of LaFe1-yCoyAsO1-xFx with y=0.0 and 0.0075 and for
a nonsuperconducting metallic sample with y=0.1, where the x values are always
fixed at 0.11. The temperature (T) dependence the relaxation rates 1/T1 of the
supe... | 0901.2830v1 |
2009-01-20 | Broad relativistic iron emission line observed in SAX J1808.4-3658 | During the September-October 2008 outburst of the accreting millisecond
pulsar SAX J1808.4-3658, the source was observed by both Suzaku and XMM-Newton
approximately 1 day apart. Spectral analysis reveals a broad relativistic Fe
K-alpha emission line which is present in both data-sets, as has recently been
reported for ... | 0901.3142v2 |
2009-01-21 | Superconductivity up to 30 K in the vicinity of quantum critical point in BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ | We report bulk superconductivity induced by an isovalent doping of phosphorus
in BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$. The P-for-As substitution results in
shrinkage of lattice, especially for the FeAs block layers. The resistivity
anomaly associated with the spin-density-wave (SDW) transition in the undoped
compound is... | 0901.3227v2 |
2009-01-26 | RXTE confirmation of the intermediate polar status of IGR J15094-6649 | Aims. To establish the X-ray properties of the intermediate polar candidate
IGR J15094-6649 and therefore confirm its inclusion into the class.
Methods. 42 856 s of X-ray data from RXTE was analysed. Frequency analysis
was used to constrain temporal variations and spectral analysis used to
characterise the emission a... | 0901.3983v1 |
2009-01-28 | Chemical evolution of the galactic bulge: single and double infall models | Recent work has produced a wealth of data concerning the chemical evolution
of the galactic bulge, both for stars and nebulae. Present theoretical models
generally adopt a limited range of such constraints, frequently using a single
chemical element (usually iron), which is not enough to describe it
unambiguously. In t... | 0901.4382v1 |
2009-02-06 | Superconductivity, magnetism and crystal chemistry of Ba1-xKxFe2As2 | BaFe2As2 is the parent compound of the '122' iron arsenide superconductors
and crystallizes with the tetragonal ThCr2Si2 type structure, space group
I4/mmm. A spin density wave transition at 140 K is accompanied by a symmetry
reduction to space group Fmmm and simultaneously by antiferromagnetic ordering.
Hole-doping in... | 0902.1085v1 |
2009-02-07 | Superconducting fluctuations in the reversible magnetization of the iron-pnictide $Ba_{1-x}K_xFe_2As_2$ | We report on isofield magnetization curves obtained as a function of
temperature in two single crystals of $Ba_{1-x}K_xFe_2As_2$ with
superconducting transition temperature $T_c$=28K and 32.7 K. Results obtained
for fields above 20 kOe show a well defined rounding effect on the reversible
region extending 1-3 K above $... | 0902.1252v2 |
2009-02-10 | Enhancement of electronic anomalies in iron-substituted La_2-x_Sr_x_Cu_1-y_Fe_y_O_4_ around x=0.22 | We have measured the temperature dependences of Rho and Chi for
Fe-substituted La_2-x_Sr_x_Cu_1-y_Fe_y_O_4_ in the overdoped regime, in order
to investigate Fe-substitution effects on electronic properties around x=0.22.
From the Rho measurements, it has been found around x=0.22 that the values of
Rho are large at ro... | 0902.1618v1 |
2009-02-10 | The Role of Dust Clouds in the Atmospheres of Brown Dwarfs | The new spectroscopic classes, L and T, are defined by the role of dust
clouds in their atmospheres, the former by their presence and the latter by
their removal and near absence. Moreover, the M to L and L to T transitions are
intimately tied to the condensation and character of silicate and iron grains,
and the assoc... | 0902.1777v1 |
2009-02-13 | Growth and Superconductivity of FeSex Crystals | Iron selenide (FeSex) crystals with lateral dimensions up to millimeters were
grown via a vapor self-transport method. The crystals consist of the dominant
alpha - phase with trace amounts of beta- phase as identified by powder x-ray
diffraction. With four-probe resistance measurements we obtained a
zero-resistance cri... | 0902.2240v1 |
2009-02-14 | ARPES studies of the electronic structure of LaOFe(P,As) | We report a comparison study of LaOFeP and LaOFeAs, two parent compounds of
recently discovered iron-pnictide superconductors, using angle-resolved
photoemission spectroscopy. Both systems exhibit some common features that are
very different from well-studied cuprates. In addition, important differences
have also been ... | 0902.2503v1 |
2009-02-18 | Ultra High Energy Cosmic Ray, Neutrino, and Photon Propagation and the Multi-Messenger Approach | The propagation of UHECR nuclei for A=1 (protons) to A=56 (iron) from
cosmological sources through extragalactic space is discussed in the first
lecture. This is followed in the second and third lectures by a consideration
of the generation and propagation of secondary particles produced via the UHECR
loss interactions... | 0902.3012v1 |
2009-02-18 | Doppler-Broadened Iron X-ray Lines from Tycho's Supernova Remnant | We use \suzaku observations to measure the spatial variation of the Fe
K$\alpha$ line with radius in the \tycho supernova remnant. The Fe line widths
show a significant decrease from a FWHM value of 210 eV at the center to 130 eV
at the rim. Over the same radial range the line center energy remains nearly
constant. The... | 0902.3049v1 |
2009-02-23 | Why Does Undoped FeSe Become A High Tc Superconductor Under Pressure? | Unlike the parent phases of the iron-arsenide high Tc superconductors,
undoped FeSe is not magnetically ordered and exhibits superconductivity with
Tc~9K. Equally surprising is the fact that applied pressure dramatically
enhances the modest Tc to ~37K. We investigate the electronic properties of
FeSe using 77Se NMR to ... | 0902.3832v2 |
2009-02-23 | Superconductivity at 22.3 K in SrFe2-xIrxAs2 | By substituting the Fe with the 5d-transition metal Ir in SrFe2As2, we have
successfully synthesized the superconductor SrFe2-xIrxAs2 with Tc = 22.3 K at x
= 0.5. X-ray diffraction indicates that the material has formed the
ThCr2Si2-type structure with a space group I4/mmm. The temperature dependence
of resistivity and... | 0902.3957v2 |
2009-02-24 | Thermal instability in X-ray photoionized media in Active Galactic Nuclei: II. Role of the thermal conduction in warm absorber | A photoionized gas under constant pressure can display a thermal instability,
with three or more solutions for possible thermal equilibrium. A unique
solution of the structure of the irradiated medium is obtained only if electron
conduction is considered. The subject of our study is to estimate how the
effect of therma... | 0902.4083v1 |
2009-02-24 | Frontiers of the physics of dense plasmas and planetary interiors: experiments, theory, applications | Recent developments of dynamic x-ray characterization experiments of dense
matter are reviewed, with particular emphasis on conditions relevant to
interiors of terrestrial and gas giant planets. These studies include
characterization of compressed states of matter in light elements by x-ray
scattering and imaging of sh... | 0902.4115v1 |
2009-02-24 | Heating and cooling of magnetars with accreted envelopes | We study the thermal structure and evolution of magnetars as cooling neutron
stars with a phenomenological heat source in an internal layer. We focus on the
effect of magnetized (B > 10^{14} G) non-accreted and accreted outermost
envelopes composed of different elements, from iron to hydrogen or helium. We
discuss a co... | 0902.4213v1 |
2009-02-26 | Tricritical Points and Liquid-Solid Critical Lines | Tricritical points separate continuous and discontinuous symmetry breaking
transitions. They occur in a variety of physical systems and their mathematical
models. A tricritical point is used to determine a liquid-solid phase
transition line in the pressure-temperature plane [Aitta, J. Stat. Mech.,
2006]. Excellent expe... | 0902.4578v1 |
2009-02-27 | Looking outside the Galaxy: the discovery of chemical anomalies in 3 old Large Magellanic Cloud clusters | By using the multifiber spectrograph FLAMES mounted at the ESO-VLT, we have
obtained high-resolution spectra for 18 giant stars, belonging to 3 old
globular clusters of the Large Magellanic Cloud (namely NGC 1786, 2210 and
2257). While stars in each cluster showed quite homogeneous iron content,
within a few cents of d... | 0902.4778v1 |
2009-02-27 | The superconductor KxSr(1-x)Fe2As2: Normal state and superconducting properties | The normal state and superconducting properties are investigated in the phase
diagram of K_xSr_{1-x}Fe_2As_2 for 0<x<1. The ground state upper critical
field, H_{c2}(0), is extrapolated from magnetic field dependent resistivity
measurements. H_{c2}(0) scales with the critical temperature, T_c, of the
superconducting tr... | 0903.0013v1 |
2009-03-09 | Cohesive and magnetic properties of grain boundaries in bcc Fe with Cr additions | Structural, cohesive, and magnetic properties of two symmetric $\Sigma3(111)$
and $\Sigma5(210)$ tilt grain boundaries (GBs) in pure bcc Fe and in dilute
FeCr alloys are studied from first principles. Different concentration and
position of Cr solute atoms are considered. We found that Cr atoms placed in
the GB interst... | 0903.1618v2 |
2009-03-12 | Pressure evolution of low-temperature crystal structure and bonding of 37 K $T_c$ FeSe superconductor | FeSe with the PbO structure is a key member of the family of new high-$T_c$
iron pnictide and chalcogenide superconductors, as while it possesses the basic
layered structural motif of edge-sharing distorted FeSe$_4$ tetrahedra, it
lacks interleaved ion spacers or charge-reservoir layers. We find that
application of hyd... | 0903.2204v1 |
2009-03-12 | Universal relation between magnetic resonance and superconducting gap in unconventional superconductors | Unconventional superconductors such as the high-transition temperature
cuprates, heavy-fermion systems and iron arsenide-based compounds exhibit
antiferromagnetic fluctuations that are dominated by a resonance, a collective
spin-one excitation mode in the superconducting state. Here we demonstrate the
existence of a un... | 0903.2291v1 |
2009-03-13 | The nature of the magnetic and structural phase transitions in BaFe$_{2}$As$_{2}$ | We present the results of an investigation of both the magnetic and
structural phase transitions in a high quality single crystalline sample of the
undoped, iron pnictide compound BaFe$_2$As$_2$. Both phase transitions are
characterized via neutron diffraction measurements which reveal simultaneous,
continuous magnetic... | 0903.2430v2 |
2009-03-23 | On Estimating the Flux of the Brightest Cosmic Ray Source above 57x10^18 eV | The sources of ultra-high energy cosmic rays are not yet known. However, the
discovery of anisotropic cosmic rays above 57x10^18 eV by the Pierre Auger
Observatory suggests that a direct source detection may soon be possible. The
near-future prospects for such a measurement are heavily dependent on the flux
of the brig... | 0903.3981v1 |
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