publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2006-10-23 | Theory of quasiparticle spectra for Fe, Co, and Ni: bulk and surface | The correlated electronic structure of iron, cobalt and nickel is
investigated within the dynamical mean-field theory formalism, using the newly
developed full-potential LMTO-based LDA+DMFT code. Detailed analysis of the
calculated electron self-energy, density of states and the spectral density are
presented for these... | 0610621v1 |
2006-10-25 | High quality Fe3-deltaO4/InAs hybrid structure for electrical spin injection | Single Crystalline Fe3-deltaO4 (0<=delta<=0.33) films have been epitaxially
grown on InAs (001) substrates by molecular beam epitaxy using O2 as source of
active oxygen. Under optimum growth conditions in-situ real time reflection
high-energy electron diffraction patterns along with ex-situ atomic force
microscopy indi... | 0610697v1 |
2004-02-14 | Effects of a cosmological constant on the X-ray fluorescence spectra of black hole accretion disks | We investigate the effects of cosmological constant on the characteristic
peaks in the iron line profile in the black hole accretion disk X-ray spectrum.
Our results show that for a fixed mass black hole, the peaks become less
pronounced and closer together with increasing cosmological constant. This
effect is mainly d... | 0402066v1 |
1997-06-26 | KARMEN: Present Neutrino-Oscillation Limits and Perspectives after the Upgrade | The neutrino experiment KARMEN is situated at the beam stop neutrino source
ISIS. It provides nu_mu's, nu_e's and nu_mu_bar's in equal intensities from the
pi+ mu+ decay at rest. The oscillation channels nu_mu->nu_e and
nu_mu_bar->nu_e_bar are investigated with a 56t liquid scintillation
calorimeter at a mean distance ... | 9706023v1 |
1999-10-14 | Search for nucleon decay into lepton + K0 final states using Soudan 2 | A search for nucleon decay into two-body final states containing K^0 mesons
has been conducted using the 963 metric ton Soudan 2 iron tracking calorimeter.
The topologies, ionizations, and kinematics of contained events recorded in a
5.52 kiloton-year total exposure (4.41 kton-year fiducial volume exposure) are
examine... | 9910026v2 |
2002-05-28 | Search for Neutron-Antineutron Oscillations Using Multiprong Events in Soudan 2 | We have searched for neutron-antineutron oscillations using the 5.56 fiducial
kiloton-year exposure of the Soudan 2 iron tracking calorimeter. We require
candidate n-nbar occurrences to have .GE. 4 prongs (tracks and showers) and to
have kinematics compatible with nbar-N annihilation within a nucleus. We
observe five c... | 0205093v1 |
1999-09-28 | Detection of Slow Magnetic Monopole | Numerous and all unsuccessful attempts of experimental search for monopole in
cosmic rays and on accelerators in high energy particle collisions have been
done since the possibility of existence of a magnetic monopole has been
surveyed in 1931. Also the searches have been carried out in mica for monopole
tracks as well... | 9909528v1 |
2005-05-03 | Exploration prospects of a long baseline Beta Beam neutrino experiment with an iron calorimeter detector | A high intensity source of a single neutrino flavour with known spectrum is
most desirable for precision measurements, the consensus direction for the
future. The beta beam is an especially suitable option for this. We discuss the
prospects of a very long baseline beta beam experiment with a magnetized iron
calorimeter... | 0505015v2 |
2002-12-17 | Destabilization of fronts in a class of bi-stable systems | In this article, we consider a class of bi-stable reaction-diffusion
equations in two components on the real line. We assume that the system is
singularly perturbed, i.e. that the ratio of the diffusion coefficients is
(asymptotically) small. This class admits front solutions that are
asymptotically close to the (stabl... | 0212231v1 |
1994-02-03 | Complete 0 hbar omega calculations of Gamow-Teller strengths for nuclei in the iron region | Gamow-Teller strengths for selected nuclei in the iron region (A~56) have
been investigated via shell-model Monte Carlo calculations with realistic
interactions in the complete fp basis. Results for all cases show significant
quenching relative to single-particle estimates, in quantitative agreement with
(n,p) data. Th... | 9402006v1 |
2000-03-27 | The role of $ν$-induced reactions on lead and iron in neutrino detectors | We have calculated cross sections and branching ratios for neutrino induced
reactions on ^{208}Pb and ^{56}Fe for various supernova and
accelerator-relevant neutrino spectra. This was motivated by the facts that
lead and iron will be used on one hand as target materials in future neutrino
detectors, on the other hand h... | 0003060v2 |
2005-03-17 | The Muon System of the Run II D0 Detector | We describe the design, construction and performance of the upgraded DO muon
system for Run II of the Fermilab Tevatron collider. Significant improvements
have been made to the major subsystems of the DO muon detector: trigger
scintillation counters, tracking detectors, and electronics. The Run II central
muon detector... | 0503151v1 |
2007-04-10 | Compton thick AGN in the Suzaku era | Suzaku observations of two hard X-ray (> 10 keV) selected nearby Seyfert 2
galaxies are presented. Both sources were clearly detected with the PIN Hard
X-ray Detector up to several tens of keV, allowing for a fairly good
characterization of the broad band X-ray continuum. Both sources are heavily
obscured, one of which... | 0704.1253v1 |
2007-05-30 | Two Modes of Magnetization Switching in a Simulated Iron Nanopillar in an Obliquely Oriented Field | Finite-temperature micromagnetics simulations are employed to study the
magnetization-switching dynamics driven by a field applied at an angle to the
long axis of an iron nanopillar. A bi-modal distribution in the switching times
is observed, and evidence for two competing modes of magnetization-switching
dynamics is p... | 0705.4454v1 |
2007-06-27 | Reconstructing WIMP properties with neutrino detectors | If the dark matter of the Universe is constituted by weakly interacting
massive particles (WIMP), they would accumulate in the core of astrophysical
objects as the Sun and annihilate into particles of the Standard Model.
High-energy neutrinos would be produced in the annihilations, both directly and
via the subsequent ... | 0706.3909v2 |
2007-07-06 | Muon Identification at ATLAS and CMS | Muonic final states will provide clean signatures formany physics processes
at the LHC. The two LHC experiments ATLAS and CMS will be able to identify
muons with a high reconstruction efficiency above 96% and a high transverse
momentum resolution better than 2% for transverse momenta below 400 GeV/c and
about 10% at 1 ... | 0707.0905v1 |
2007-07-16 | Zener double exchange from local valence fluctuations in magnetite | Magnetite (Fe$_{3}$O$_{4}$) is a mixed valent system where electronic
conductivity occurs on the B-site (octahedral) iron sublattice of the spinel
structure. Below $T_{V}=122$ K, a metal-insulator transition occurs which is
argued to arise from the charge ordering of 2+ and 3+ iron valences on the
B-sites (Verwey trans... | 0707.2253v1 |
2007-07-16 | Search for medium modification of the $ρ$ meson | The photoproduction of vector mesons on various nuclei has been studied using
the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory. The
vector mesons, $\rho$, $\omega$, and $\phi$, are observed via their decay to
$e^+e^-$, in order to reduce the effects of final state interactions in the
nucleus. Of p... | 0707.2324v3 |
2007-07-17 | New homogeneous iron abundances of double-mode Cepheids from high-resolution echelle spectroscopy | Aims: We define the relationship between the double-mode pulsation of
Cepheids and metallicity in a more accurate way, determine the empirical
metallicities of double-mode Cepheids from homogeneous, high-resolution
spectroscopic data, and study of the period-ratio -- metallicity dependence.
Methods: The high S/N echell... | 0707.2530v1 |
2007-07-19 | Nuclear Georeactor Generation of Earth's Geomagnetic Field | The purpose of this communication is to suggest that the mechanism for
generating the geomagnetic field and the energy source for powering it are one
and the same, a nuclear georeactor at the center of the Earth. Toward this end,
I: i) Present evidence that the nuclear georeactor fission-product sub-shell is
fluid; ii)... | 0707.2850v4 |
2007-08-07 | Near Optimal Broadcast with Network Coding in Large Sensor Networks | We study efficient broadcasting for wireless sensor networks, with network
coding. We address this issue for homogeneous sensor networks in the plane. Our
results are based on a simple principle (IREN/IRON), which sets the same rate
on most of the nodes (wireless links) of the network. With this rate selection,
we give... | 0708.0975v1 |
2007-08-08 | The Near-Infrared Broad Emission Line Region of Active Galactic Nuclei -- I. The Observations | We present high quality (high signal-to-noise ratio and moderate spectral
resolution) near-infrared (near-IR) spectroscopic observations of 23 well-known
broad-emission line active galactic nuclei (AGN). Additionally, we obtained
simultaneous (within two months) optical spectroscopy of similar quality. The
near-IR broa... | 0708.1083v1 |
2007-09-26 | High-resolution saturation spectroscopy of singly-ionized iron with a pulsed uv laser | We describe the design and realization of a scheme for uv laser spectroscopy
of singly-ionized iron (Fe II) with very high resolution. A buffer-gas cooled
laser ablation source is used to provide a plasma close to room temperature
with a high density of Fe II. We combine this with a scheme for pulsed-laser
saturation s... | 0709.4032v1 |
2007-10-01 | nu-Process Nucleosynthesis in Population III Core-Collapse Supernovae | We investigate the effects of neutrino-nucleus interactions (the nu-process)
on the production of iron-peak elements in Population III core-collapse
supernovae. The nu-process and the following proton and neutron capture
reactions produce odd-Z iron-peak elements in complete and incomplete Si
burning region. This react... | 0710.0251v1 |
2007-11-02 | Chandra Observations of Early-type Galaxies | We have performed uniform analysis of a sample of 54 nearby, early-type
galaxies observed with \emph{Chandra}. In this work we present the spectral
results for both the diffuse Interstellar Medium, ISM, and low-mass X-ray
binaries, LMXBs. We determine the metallicity of the hot ISM in the 22
brightest galaxies and find... | 0711.0395v1 |
2007-11-19 | A Time-Variable X-Ray Echo: Indications of a Past Flare of the Galactic-Center Black Hole | A time-variability study of the neutral iron line flux at 6.40keV in the Sgr
B2 region from data of Suzaku and Chandra is presented. The highly ionized iron
line at 6.68keV is due to Galactic Center Diffuse X-rays (GCDX), and is thus
time invariable. By comparing the 6.68keV and 6.40keV line fluxes, we found
that the 6... | 0711.2853v1 |
2007-11-26 | Cepheids as tracers of the metallicity gradient across the Galactic disk | We present iron abundance measurements, based on high resolution
spectroscopy, and accurate distance determinations, based on near infrared
photometry, for 34 Galactic Cepheids. The new data are used to constrain the
Galactic iron abundance gradient in the outer disk, namely from 10 to 14 kpc.
We confirm the flattening... | 0711.3988v1 |
2007-12-03 | Signatures of Granulation in the Spectra of K-Dwarfs | Very high resolution (R>150,000) spectra of a small sample of nearby K-dwarfs
have been acquired to measure the line asymmetries and central wavelength
shifts caused by convective motions present in stellar photospheres. This
phenomenon of granulation is modeled by 3D hydrodynamical simulations but they
need to be conf... | 0712.0387v1 |
2007-12-30 | Specific heat evidence for two-gap superconductivity in ternary-iron silicide Lu$_{2}$Fe$_{3}$Si$_{5}$ | We report low-temperature specific heat studies on single-crystalline
ternary-iron silicide superconductor Lu$_{2}$Fe$_{3}$Si$_{5}$ with$T_c$ = 6.1 K
down to $\sim T_c/20$. We confirm a reduced normalized jump in specific heat at
$T_c$, and find that the specific heat divided by temperature $C/T$ shows
sudden drop at $... | 0801.0111v1 |
2008-01-07 | DC transferred arc thermal plasma assisted growth of nanoparticles with different crystalline phases | The control of the crystalline phases of the nanoparticles grown in a
direct-current transferred-arc plasma-assisted reactor is reported. The
crystalline phases of the as synthesized nanoparticles are shown to critically
depend on the operating gas pressure. The paper reports about the change in the
crystalline phases ... | 0801.0945v1 |
2008-01-25 | Ab initio study of spin-dependent transport in carbon nanotubes with iron and vanadium adatoms | We present an ab initio study of spin dependent transport in armchair carbon
nanotubes with transition metal adsorbates, iron or vanadium. We neglect the
effect of tube curvature and model the nanotube by graphene with periodic
boundary conditions. A density functional theory based nonequilibrium Green's
function metho... | 0801.3997v1 |
2008-03-01 | Search For Iron, Nickel, and Fluorine in PG1159 Stars | A possible origin of the iron-deficiency in PG1159 stars could be neutron
captures on Fe nuclei. A nickel overabundance would corroborate this idea.
Consequently we are looking for nickel lines in PG1159 stars. Prime targets are
relatively cool objects, because Ni VI is the dominant ionisation stage and the
spectral li... | 0803.0066v1 |
2008-03-09 | Upper critical field, Hall effect and magnetoresistance in the iron-based layered superconductor LaFeAsO_{0.9}F_{0.1-δ} | By using a two-step method, we successfully synthesized the iron based new
superconductor LaFeAsO_{0.9}F_{0.1-\delta}$. The resistive transition curves
under different magnetic fields were measured, leading to the determination of
the upper critical field Hc2(T) of this new superconductor. The value of Hc2 at
zero temp... | 0803.1288v2 |
2008-03-24 | Tracing the [FeII]/[NeII] ratio within star forming dwarf galaxies: a Spitzer IRS archival study | Archival Spitzer observations of 41 starburst galaxies that span a wide range
in metallicity reveal for the first time a correlation between the
[FeII]/[NeII] 26.0/12.8 micron ratio and the electron gas density as traced by
the 18.7/33.4 micron [SIII] ratio, with the [FeII]/[NeII] ratio decreasing with
increasing gas d... | 0803.3403v1 |
2008-04-05 | Doubly degenerate orbital system in honeycomb lattice: implication of orbital state in layered iron oxide | We study a doubly-degenerate orbital model on a honeycomb attice. This is a
model for orbital states in multiferroic layered iron oxides. The classical and
quantum models are analyzed by spin-wave approximation, Monte-Carlo simulation
and Lanczos method. A macroscopic number of degeneracy exists in the classical
ground... | 0804.0843v1 |
2008-04-08 | Models of the iron K_alpha fluorescence line and the Compton shoulder in irradiated accretion disk spectra | We present a full set of model atmosphere equations for the accretion disk
around a supermassive black hole irradiated by hard X-ray lamp of power-law
spectral distribution. Model equations allow for multiple Compton scattering of
radiation on free electrons, and for large relative photon-electron energy
exchange at th... | 0804.1232v1 |
2008-04-08 | Nernst effect of the new iron-based superconductor LaO$_{1-x}$F$_{x}$FeAs | We report the first Nernst effect measurement on the new iron-based
superconductor LaO$_{1-x}$F$_{x}$FeAs $(x=0.1)$. In the normal state, the
Nernst signal is negative and very small. Below $T_{c}$ a large positive peak
caused by vortex motion is observed. The flux flowing regime is quite large
compared to conventional... | 0804.1324v2 |
2008-04-13 | Superconductivity at 55 K in iron-based F-doped layered quaternary compound Sm[O1-xFx]FeAs | Here we report the superconductivity in the iron-based oxyarsenide
Sm[O1-xFx]FeAs, with the onset resistivity transition temperature at 55.0 K and
Meissner transition at 54.6 K. This compound has the same crystal structure as
LaOFeAs with shrunk crystal lattices, and becomes the superconductor with the
highest critical... | 0804.2053v2 |
2008-04-16 | Strong Correlations and Magnetic Frustration in the High Tc Iron Pnictides | We consider the iron pnictides in terms of a proximity to a Mott insulator.
The superexchange interactions contain competing nearest-neighbor and
next-nearest-neighbor components. In the undoped parent compound, these
frustrated interactions lead to a two-sublattice collinear antiferromagnet
(each sublattice forming a ... | 0804.2480v2 |
2008-04-16 | Ab initio approach of the hydrogen insertion effects on the magnetic properties of $ {\bf ScFe_2} $ | The electronic and magnetic structures of $ {\rm ScFe_2} $ and of its
dihydride $ {\rm ScFe_2H_2} $ are self-consistently calculated within the
density functional theory (DFT) using the all electron augmented spherical wave
(ASW) method with the local spin density approximation (LSDA) for treating
effects of exchange a... | 0804.2537v1 |
2008-04-23 | Superconductivity of powder-in-tube LaO0.9F0.1FeAs wires | We demonstrate that Fe sheathed LaO0.9F0.1FeAs wires with Ti as a buffer
layer were successfully fabricated by the powder-in-tube (PIT) method.
Comparing to the common two-step vacuum quartz tube synthesis method, the PIT
method is more convenient and safe for synthesizing the novel iron-based
layered superconductors. ... | 0804.3738v2 |
2008-04-25 | Spin Fluctuations, Interband Coupling, and Unconventional Pairing in Iron-based Superconductors | Based on an effective two-band model and using the fluctuation-exchange
(FLEX) approach, we explore spin fluctuations and unconventional
superconducting pairing in Fe-based layer superconductors. It is elaborated
that one type of interband antiferromagnetic (AF) spin fluctuation stems from
the interband Coulomb repulsi... | 0804.4166v3 |
2008-04-28 | Ising and Spin orders in Iron-based Superconductors | Motivated by recent neutron scattering experiments, we study the ordering of
spins in the iron-based superconductors La(O_{1-x}F_x)FeAs, assuming them in
proximity to a Mott insulator in the phase diagram. The ground state of the
parent system with x = 0 is a spin density wave with ordering wave vector Q =
(0, \pi) or ... | 0804.4293v4 |
2008-05-07 | Pairing symmetry and properties of iron-based high temperature superconductors | Pairing symmetry is important to indentify the pairing mechanism. The
analysis becomes particularly timely and important for the newly discovered
iron-based multi-orbital superconductors. From group theory point of view we
classified all pairing matrices (in the orbital space) that carry irreducible
representations of ... | 0805.0923v3 |
2008-05-16 | Iron-60 evidence for early injection and efficient mixing of stellar debris in the protosolar nebula | Among extinct radioactivities present in meteorites, 60Fe (t1/2 = 1.49 Myr)
plays a key role as a high-resolution chronometer, a heat source in
planetesimals, and a fingerprint of the astrophysical setting of solar system
formation. A critical issue with 60Fe is that it could have been
heterogeneously distributed in th... | 0805.2607v1 |
2008-05-17 | Unusual Pseudogap-like Features Observed in Iron Oxypnictide Superconductors | We have performed a temperature-dependent angle-integrated laser
photoemission study of iron oxypnictide superconductors LaFeAsO:F and LaFePO:F
exhibiting critical transition temperatures (Tc's) of 26 K and 5 K,
respectively. We find that high-Tc LaFeAsO:F exhibits a temperature-dependent
pseudogap-like feature extendi... | 0805.2647v2 |
2008-05-20 | Superconducting Gap and Pseudogap in Iron-Based Layered Superconductor La(O$_{1-x}$F$_x$)FeAs | We report high-resolution photoemission spectroscopy of newly-discovered
iron-based layered superconductor La(O$_{0.93}$F$_{0.07}$)FeAs (Tc = 24 K). We
found that the superconducting gap shows a marked deviation from the isotropic
s-wave symmetry. The estimated gap size at 5 K is 3.6 meV in the s- or axial
p-wave case,... | 0805.3001v1 |
2008-05-23 | Discoveries of 3 K-shell Lines of Iron and a Coherent Pulsation of 593-sec from SAX J1748.2-2808 | SAX J1748.2$-$2808 is a unique X-ray object with a flat spectrum and strong
emission lines at 6.4--7.0 keV. The Suzaku satellite resolved the emission
lines into 3 K-shell lines from neutral and highly ionized irons. A clear
coherent pulsation with a period of 593-sec was found from the Suzaku and
XMM-Newton archives. ... | 0805.3608v2 |
2008-05-28 | Photonic Dipole Contours of Ferrofluid Hele-Shaw Cell | This investigation describes and demonstrates a novel technique for the
visualization of magnetic fields. Two ferrofluid Hele-Shaw cells have been
constructed to facilitate the imaging of magnetic field lines. We deduce that
magnetically induced photonic band gap arrays similar to electrostatic liquid
crystal operation... | 0805.4364v2 |
2008-05-30 | Multiband effects on the conductivity for a multiband Hubbard model | The newly discovered iron-based superconductors have attracted lots of
interests, and the corresponding theoretical studies suggest that the system
should have six bands. In this paper, we study the multiband effects on the
conductivity based on the exact solutions of one-dimensional two-band Hubbard
model. We find tha... | 0805.4669v1 |
2008-05-31 | Doping-insensitive density-of-states suppression in polycrystalline iron-based superconductor SmO$_{1-x}$F$_{x}$FeAs | We investigated the temperature dependence of the density-of-states in the
iron-based superconductor SmO_1-xF_xFeAs (x=0, 0.12, 0.15, 0.2) with high
resolution angle-integrated photoemission spectroscopy. The density-of-states
suppression is observed with decreasing temperature in all samples, revealing
two characteris... | 0806.0078v1 |
2008-06-20 | The Fermi surface of Ba(1-x)K(x)Fe2As2 and its evolution with doping | We use angle-resolved photoemission spectroscopy (ARPES) to investigate the
electronic properties of the newly discovered iron-arsenic superconductor,
Ba(1-x)K(x)Fe2As2 and non-supercondcuting BaFe2As2. Our study indicates that
the Fermi surface of the undoped, parent compound BaFe$_2$As$_2$ consists of
hole pocket(s) ... | 0806.3453v1 |
2008-06-22 | Electronic structures of ternary iron arsenides AFe$_2$As$_2$ (A=Ba, Ca, or Sr) | We have studied the electronic and magnetic structures of the ternary iron
arsenides AFe$_2$As$_2$ (A = Ba, Ca, or Sr) using the first-principles density
functional theory. The ground states of these compounds are in a collinear
antiferromagnetic order, resulting from the interplay between the nearest and
the next-near... | 0806.3526v3 |
2008-06-27 | 75As NMR study of the ternary iron arsenide BaFe2As2 | We report 75As-NMR measurements of the ternary iron arsenide BaFe2As2.
75As-NMR spectra clearly revealed that magnetic transition occurs at around 131
K in our samples, which corresponds to the emergence of spin density wave.
Temperature dependence of the internal magnetic field suggests that the
transition is likely o... | 0806.4514v3 |
2008-06-30 | Quantum oscillations in the parent magnetic phase of an iron arsenide high temperature superconductor | We report quantum oscillation measurements in SrFe2As2 - which is an
antiferromagnetic parent of the iron-arsenide family of superconductors - known
to become superconducting under doping and the application of pressure. The
magnetic field and temperature dependences of the oscillations between 20 and
55 T in the liqui... | 0806.4726v2 |
2008-06-29 | Structural and magnetic phase transitions in the ternary iron arsenides SrFe2As2 and EuFe2As2 | The structural and magnetic phase transitions of the ternary iron arsenides
SrFe2As2 and EuFe2As2 were studied by temperature-dependent x-ray powder
diffraction and 57-Fe Moessbauer spectroscopy. Both compounds crystallize in
the tetragonal ThCr2Si2-type structure at room temperature and exhibit
displacive structural t... | 0806.4782v2 |
2008-06-30 | LDA + Negative U Solves a Puzzle of too Large Calculated Magnetic Moment in Iron-based Superconductor LaFeAsO_{1-x}F_x | A puzzle in the iron-based superconductor LaFeAsO_{1-x}F_x is that the
magnetic moment obtained by first-principle electronic structure calculations
is unexpectedly much larger than the experimentally observed one. For example,
the calculated value is ~ 2.0 \mu_B in the mother compound, while it is ~ 0.3
\mu_B in exper... | 0806.4804v1 |
2008-07-21 | Superconductivity at 34.7 K in the iron arsenide Eu0.7Na0.3Fe2As2 | EuFe2As2 is a member of the ternary iron arsenide family. Similar to BaFe2As2
and SrFe2As2, EuFe2As2 exhibits a clear anomaly in resistivity near 200 K. It
suggests that EuFe2As2 is another promising parent compound in which
superconductivity may be realized by appropriate doping. Here we report the
discovery of superc... | 0807.3293v3 |
2008-08-05 | Local antiferromagnetic correlations in the iron pnictide superconductors LaFeAsO{1-x}F{x} and Ca(Fe,Co)2As2 as seen via normal-state susceptibility | We have studied the interplay of magnetism and superconductivity in
LaFeAsO$_{1-x}$F$_x$ and Ca(Fe$_{1-x}$Co$_x$)$_2$As$_2$. While
antiferromagnetic spin density wave formation is suppressed and
superconductivity evolves, all samples show a doping independent strong
increase of the normal state susceptibility upon heat... | 0808.0708v2 |
2008-08-07 | Sheet Dependence on Superconducting Gap in Oxygen-Deficient Iron-based Oxypnictide Superconductors NdFeAs0.85 | Photoemission spectroscopy with low-energy tunable photons on
oxygen-deficient iron-based oxypnictide superconductors NdFeAsO0.85 (Tc=52K)
reveals a distinct photon-energy dependence of the electronic structure near
the Fermi level (EF). A clear shift of the leading-edge can be observed in the
superconducting states wi... | 0808.1063v1 |
2008-08-08 | Electronic states and pairing symmetry in the two-dimensional 16 band d-p model for iron-based superconductor | The electronic states of the FeAs plane in iron-based superconductors are
investigated on the basis of the two-dimensional 16-band d-p model, where the
tight-binding parameters are determined so as to fit the band structure
obtained by the density functional calculation for LaFeAsO. The model includes
the Coulomb inter... | 0808.1192v3 |
2008-08-10 | Heavy anion solvation of polarity fluctuations in Pnictides | Once again the condensed matter world has been surprised by the discovery of
yet another class of high temperature superconductors. The discovery of
iron-pnictide (FeAs) and chalcogenide (FeSe) based superconductors with a $T_c$
of up to 55 K is again evidence of how complex the many body problem really is,
or in anoth... | 0808.1390v1 |
2008-09-01 | Competition between antiferromagnetic instability and frustrations in Fe-Se | Using linear-response density-functional theory, we obtain the magnetic
interactions in the several iron pnictides. The ground state has been found to
be non-collinear in FeSe, with a large continuum of nearly degenerate states
lying very close to the magnetic "striped" structure. The presence of
non-collinearity also ... | 0809.0283v2 |
2008-09-18 | Magnetism and Superconductivity in the Two-Dimensional 16 Band d-p Model for Iron-Based Superconductors | The electronic states of the Fe2As2 plane in iron-based superconductors are
investigated on the basis of the two-dimensional 16-band d-p model which
includes the Coulomb interaction on a Fe site: the intra- and inter-orbital
direct terms U and U', the Hund's coupling J and the pair-transfer J'. Using
the random phase a... | 0809.3189v5 |
2008-09-20 | Effect of magnetic state on the $γ-α$ transition in iron: First-principle calculations of the Bain transformation path | Energetics of the fcc ($\gamma$) - bcc ($\alpha$) lattice transformation by
the Bain tetragonal deformation is calculated for both magnetically ordered and
paramagnetic (disordered local moment) states of iron. The first-principle
computational results manifest a relevance of the magnetic order in a scenario
of the $\g... | 0809.3515v1 |
2008-09-23 | Universal linear-temperature dependence of static magnetic susceptibility in iron-pnictides | A universal linear-temperature dependence of the uniform magnetic
susceptibility has been observed in the nonmagnetic normal state of
iron-pnictides. This non-Pauli and non-Curie-Weiss-like paramagnetic behavior
cannot be understood within a pure itinerant picture. We argue that it results
from the existence of a wide ... | 0809.3874v3 |
2008-09-24 | A Unified Theory for the Cuprates, Iron-Based and Similar Superconducting Systems: Application for Spin and Charge Excitations in the Hole-Doped Cuprates | A unified theory for the cuprates and the iron-based superconductors is
derived on the basis of common features in their electronic structures
including quasi-two-dimensionality, and the large-U nature of the electron
orbitals close to E_F (smaller-U hybridized orbitals reside at bonding and
antibonding states away fro... | 0809.4237v3 |
2008-10-02 | Iron Emission Lines on the Galactic Ridge Observed with Suzaku | In order to elucidate origin of the Galactic Ridge X-ray Emission, we
analyzed Suzaku data taken at various regions along the Galactic plane and
studied their Fe-K emission line features. Suzaku resolved the Fe line complex
into three narrow lines at ~6.4 keV,~6.7 keV and ~6.97 keV, which are K-lines
from neutral (or l... | 0810.0317v1 |
2008-10-03 | Small anisotropy, weak thermal fluctuations, and high field superconductivity in Co-doped iron pnictide Ba(Fe1-xCox)2As2 | We performed high-field magnetotransport and magnetization measurements on a
single crystal of the 122-phase iron pnictide Ba(Fe1-xCox)2As2. Unlike the HTS
cuprates and 1111-phase oxypnictides, Ba(Fe1-xCox)2As2 showed practically no
broadening of the resistive transitions under magnetic fields up to 45 T. The
mass anis... | 0810.0699v2 |
2008-10-10 | Pseudogap and Superconductivity in Iron-Based Layered Superconductor studied by Fluctuation-Exchange Approximation | We investigate interplay between magnetic fluctuations and superconductivity
in the effective five-band Hubbard model for iron-oxypnictide superconductors
on the basis of the fluctuation-exchange approximation. As for the normal-state
properties, we find the pseudogap behavior in the NMR relaxation rate and the
spectra... | 0810.1828v2 |
2008-10-15 | Electronic Structure, Magnetism and Superconductivity of Layered Iron Compounds | The layered iron superconductors are discussed using electronic structure
calculations. The four families of compounds discovered so far, including
Fe(Se,Te) have closely related electronic structures. The Fermi surface
consists of disconnected hole and electron cylinders and additional hole
sections that depend on the... | 0810.2682v2 |
2008-10-15 | Temperature dependence and resonance effects in Raman scattering of phonons in NdFeAsO$_{x}$F$_{1-x}$ single crystals | We report plane-polarized Raman scattering spectra of iron oxypnictide
superconductor NdFeAsO$_{1-x}$F$_x$ single crystals with varying fluorine $x$
content. The spectra exhibit sharp and symmetrical phonon lines with a weak
dependence on fluorine doping $x$. The temperature dependence does not show any
phonon anomaly ... | 0810.2735v1 |
2008-10-18 | Elastic theory for the vortex-lattice melting in iron-based high-Tc superconductors | The vortex-lattice melting transitions in two typical iron-based high-Tc
superconductor $Ba(Fe_{1-x}Co_{x})_{2}As_{2}$ (122-type)
and$Nd(O_{1-x}F_{x})FeAs$ (1111-type) for magnetic fields both parallel and
perpendicular to the anisotropy axis are studied within the elastic theory.
Using the parameters from experiments,... | 0810.3292v2 |
2008-10-24 | Interplay between magnetic properties and Fermi surface nesting in iron pnictides | The wave-vector q and doping (x,y) dependences of the magnetic energy, iron
moment, and effective exchange interactions in LaFeAsO{1-x}F{x} and
Ba{1-2y}K{2y}Fe2As2 are studied by self-consistent LSDA calculations for
co-planar spin spirals. For the undoped compounds (x=0, y=0), the minimum of
the calculated total energ... | 0810.4469v2 |
2008-11-01 | Synthesis and Microstructural Studies of Iron Oxypnictide LaO1-xFxFeAs Superconductors | We report on the synthesis and structural/ microstructural studies of iron
based fluorine doped LaOFeAs superconductors. We have successfully synthesized
fluorine doped superconducting LaO1-xFxFeAs materials by choosing lower
temperature (1150^0C) and longer synthesis duration (60 hours) as compared to
the standard val... | 0811.0094v1 |
2008-11-11 | Unconventional superconductivity originating from disconnected Fermi surfaces in the iron-based compound | The iron-based LaFeAsO$_{1-x}$F$_x$ recently discovered by Hosono's group is
a fresh theoretical challenge as a new class of high-temperature
superconductors. Here we describe the electronic structure of the material and
the mechanism of superconductivity. We start with constructing a tight-binding
model in terms of th... | 0811.1656v1 |
2008-11-17 | Perturbation Theory of High-Tc Superconductivity in Iron Pnictides | The high-transition-temperature (high-Tc) superconductivity discovered
recently in iron pnictides is analyzed within a perturbation theory.
Specifically, the probable pairing symmetry, the doping dependence of the
transition temperature and the pairing mechanism are studied by solving the
Eliashberg equation for multi-... | 0811.2462v2 |
2008-11-25 | Spin-orbital frustrations and anomalous metallic state in iron-pnictide superconductors | We develop an understanding of the anomalous metal state of the parent
compounds of recently discovered iron based superconductors starting from a
strong coupling viewpoint, including orbital degrees of freedom. On the basis
of an intermediate-spin (S=1) state for the Fe^{2+} ions, we derive a
Kugel-Khomskii spin-orbit... | 0811.4104v1 |
2008-11-25 | Coexistence of Itinerant Electrons and Local Moments in Iron-Based Superconductors | In view of the recent experimental facts in the iron-pnictides, we make a
proposal that the itinerant electrons and local moments are simultaneously
present in such multiband materials. We study a minimal model composed of
coupled itinerant electrons and local moments to illustrate how a consistent
explanation of the e... | 0811.4111v4 |
2008-12-15 | Collective modes and emergent SO(6) symmetry in the iron pnictides | We show the existence of an emergent SO(6) symmetry in the low energy
description of the iron pnictides. This approximate symmetry provides a
unifying framework for the occurrence of spin density wave (SDW) and
superconductivity (SC) in these materials. We use this symmetry to make several
predictions for future experi... | 0812.2907v2 |
2008-12-16 | Hard (State) Problems | For microquasars, the one time when these systems exhibit steady and powerful
jets is when they are in the hard state. Thus, our understanding of this state
is key to learning about the disk/jet connection. Recent observational and
theoretical results have led to questions about whether we really understand
the physica... | 0812.2980v1 |
2008-12-19 | Evidence for nodal superconductivity in LaFePO | In several iron-arsenide superconductors there is strong evidence for a fully
gapped superconducting state consistent with either a conventional s-wave
symmetry or an unusual $s_\pm$ state where there the gap changes sign between
the electron and hole Fermi surface sheets. Here we report measurements of the
penetration... | 0812.3858v1 |
2008-12-22 | The role of striction at magnetic and structural transitions in iron-pnictides | We discuss the role of striction in the intertwined magnetic and structural
phase transitions in the underdoped iron-pnictides. The magneto-elastic
coupling to acoustic modes is then derived and estimated in framework of the
multiband spectrum for itinerant electrons with nesting features. We argue that
the 1-st order ... | 0812.4277v2 |
2008-12-30 | Structure and magnetism in ultrathin iron oxides characterized by low energy electron microscopy | We have grown epitaxial films a few atomic layers thick of iron oxides on
ruthenium. We characterize the growth by low energy electron microscopy. Using
selected area diffraction and intensity vs. voltage spectroscopy, we detect two
distinct phases which are assigned to wustite and magnetite. Spin polarized low
energy ... | 0812.5049v2 |
2009-01-01 | Multiple Bands - A Key to High - Temperature Superconductivity in Iron Arsenides? | In the framework of four-band model of superconductivity in iron arsenides
proposed by Barzykin and Gor'kov we analyze the gap ratios on hole - like and
electron - like Fermi - surface cylinders. It is shown that experimentally
observed (ARPES) gap ratios can be obtained only within rather strict limits on
the values o... | 0901.0164v1 |
2009-01-07 | Band renormalization and Fermi surface reconstruction in iron-based superconductors | Using the fluctuation exchange approximation and a three-orbital model, we
study the band renormalization, Fermi surface reconstruction and the
superconducting pairing symmetry in the newly-discovered iron-based
superconductors. We find that the inter-orbital spin fluctuations lead to the
strong anisotropic band renorm... | 0901.0821v1 |
2009-01-22 | Fermi surface in BaNi$_2$P$_2$ | We report measurements of the de Haas-van Alphen (dHvA) oscillation and a
band structure calculation for the pnictide superconductor BaNi$_2$P$_2$, which
is isostructural to BaFe$_2$As$_2$, the mother compound of the iron-pnictide
high-$T_c$ superconductor (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$. Six dHvA-frequency
branches with... | 0901.3394v3 |
2009-01-26 | Quantum Oscillation Studies of the Fermi Surface of LaFePO | We review recent experimental measurements of the Fermi surface of the
iron-pnictide superconductor LaFePO using quantum oscillation techniques. These
studies show that the Fermi surface topology is close to that predicted by
first principles density functional theory calculations, consisting of
quasi-two-dimensional e... | 0901.3976v2 |
2009-02-03 | Anharmonic softening of Raman active phonons in Iron-Pnictides; estimating the Fe isotope effect due to anharmonic expansion | We present Raman measurements on the iron-pnictide superconductors
CeFeAsO_{1-x}F_{x} and NdFeAsO{1-x}F_{x}. Modeling the Fe-As plane in terms of
harmonic and a cubic anharmonic Fe-As interaction we calculate the temperature
dependence of the energy and lifetime of the Raman active Fe B_{1g} mode and
fit to the observe... | 0902.0505v2 |
2009-02-13 | Dominant role of local-moment interactions in the magnetism in iron pnictides : comparative study of arsenides and antimonides from first-principles | The magnetic properties of various iron pnictides are investigated using
first-principles pseudopotential calculations. We consider three different
families, LaFePnO, BaFe$_2$Pn$_2$, and LiFePn with Pn=As and Sb, and find that
the Fe local spin moment and the stability of the stripe-type antiferromagnetic
phase increas... | 0902.2359v2 |
2009-02-16 | The f-spin physics of rare-earth iron pnictides: influence of d-electron antiferromagnetic order on the heavy fermion phase diagram | Some of the high Tc iron pnictides contain magnetic rare-earth elements,
raising the question of how the existence and tunability of a d-electron
antiferromagnetic order influences the heavy fermion behavior of the f-moments.
With CeOFeP and CeOFeAs in mind as prototypes, we derive an extended Anderson
lattice model ap... | 0902.2423v2 |
2009-02-16 | Point contact Andreev reflection spectroscopy of superconducting energy gaps in 122-type family of iron pnictides | A brief overview of the superconducting energy gap studies on 122-type family
of iron pnictides is given. It seems that the situation in the hole-doped
Ba1-xKxFe2As2 is well resolved. Most of the measurements including the
presented here point-contact Andreev reflection spectra agree on existence of
multiple nodeless g... | 0902.2667v1 |
2009-02-19 | Quantum Entanglement in Nitrosyl Iron Complexes | Recent magnetic susceptibility measurements for polycrystalline samples of
binuclear nitrosyl iron complexes [Fe_2(C_3H_3N_2S)_2(NO)_4] (I) and
[Fe_2(SC_3H_5N_2)_2(NO)_4] (II), suggest that quantum-mechanical entanglement
of the spin degrees of freedom exists in these compounds. Entanglement E exists
below the temperat... | 0902.3337v1 |
2009-02-19 | Theory of Multiband Superconductivity in Iron Pnictides | The precise nature of unconventional superconductivity in Iron Pnictides is
presently a hotly debated issue. Here, using insights from normal state
electronic structure and symmetry arguments, we show how an unconventional SC
emerges from the bad metal "normal" state. Short-ranged, multi-band spin- and
charge correlati... | 0902.3400v2 |
2009-02-27 | Probing the pairing symmetry of the iron pnictides with electronic Raman scattering | An important issue in the study of the iron-arsenic based superconductors is
the symmetry of the superconducting gap, a problem complicated by multiple gaps
on different Fermi surface sheets. Electronic Raman scattering is a flexible
bulk probe which allows one in principle to determine gap magnitudes and test
for gap ... | 0902.4745v1 |
2009-02-28 | Influence of Magnetism on Phonons in CaFe2As2 Via Inelastic X-ray Scattering | In the iron pnictides, the strong sensitivity of the iron magnetic moment to
the arsenic position suggests a significant relationship between phonons and
magnetism. We measured the phonon dispersion of several branches in the high
temperature tetragonal phase of CaFe2As2 using inelastic x-ray scattering on
single-cryst... | 0903.0017v2 |
2009-03-04 | Resistivity Anisotropy of $AE$Fe$_2$As$_2$ ($AE$ =Ca, Sr, Ba): direct versus Montgomery technique measurements | The anisotropy of electrical resistivity was measured in parent compounds of
the iron-arsenic high temperature superconductors, AEFe2As2 with Alkali Earth
elements AE=Ca,Sr, Ba. Measurements were performed using both the Montgomery
technique and direct resistivity measurements on samples cut along principal
crystallogr... | 0903.0820v1 |
2009-03-09 | Theory of Magnetic Fluctuations in Iron Pnictides | Magnetic fluctuations in an unconventional superconductor (U-SC) can
distinguish between distinct proposals for the symmetry of the order parameter.
Motivated thereby, we undertake a study magnetic fluctuations in Iron
pnictides, tracking their evolution from the incoherent normal, pseudogapped
metal, to the U-SC state... | 0903.1568v1 |
2009-03-10 | Quasiparticle Scattering Interference in Superconducting Iron-pnictides | Using both two orbital and five orbital models, we investigate the
quasiparticle interference (QPI) patterns in the superconducting (SC) state of
iron-based superconductors. We compare the results for nonmagnetic and magnetic
impurities in sign-changed s-wave $\cos(k_x)\cdot\cos(k_y)$ and sign-unchanged
$|\cos(k_x)\cdo... | 0903.1694v1 |
2009-03-11 | Magnetic Properties of the Superconducting State of Iron-Based Superconductors | We show that features of the dynamical spin susceptibility can unambiguously
distinguish between different pairing symmetries of the superconducting state
in iron-based superconductors. A magnetic resonance is a unique feature for the
extended $s_{x^2y^2}$-wave $\cos k_x\cos k_y$ pairing symmetry. It is present
in the ... | 0903.2025v1 |
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