publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2009-11-19 | Comparison of Ab initio Low-Energy Models for LaFePO, LaFeAsO, BaFe2As2, LiFeAs, FeSe and FeTe: Electron Correlation and Covalency | Effective low-energy Hamiltonians for several different families of
iron-based superconductors are compared after deriving them from the
downfolding scheme based on first-principles calculations. Systematic
dependences of the derived model parameters on the families are elucidated,
many of which are understood from the... | 0911.3705v2 |
2009-11-19 | Metallicity gradients in the Milky Way | Radial metallicity gradients are observed in the disks of the Milky Way and
in several other spiral galaxies. In the case of the Milky Way, many objects
can be used to determine the gradients, such as HII regions, B stars, Cepheids,
open clusters and planetary nebulae. Several elements can be studied, such as
oxygen, s... | 0911.3763v1 |
2009-11-19 | Magnetic Anistropy due to the Casimir Effect | We consider the Casimir interaction between a ferromagnetic and a
non-magnetic mirror, and show how the Casimir effect gives rise to a magnetic
anisotropy in the ferromagnetic layer. The anisotropy is out-of-plane if the
non-magnetic plate is optically isotropic. If the non-magnetic plate shows a
uniaxial optical aniso... | 0911.3854v1 |
2009-11-19 | In-plane electronic anisotropy in underdoped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ revealed by detwinning in a magnetic field | We present results of angle-dependent magnetoresistance measurements and
direct optical images of underdoped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ which reveal
partial detwinning by action of a 14T magnetic field. Driven by a substantial
magneto-elastic coupling, this result provides evidence for an electronic
origin of the l... | 0911.3878v1 |
2009-11-21 | Spectroscopic Study of $^{75}$As and $^{139}$La NMR on Layered Structure Ferromagnet LaCoAsO | $^{75}$As and $^{139}$La field-swept NMR spectra were obtained for the novel
weakly itinerant ferromagnet LaCoAsO with 2D layered structure above the Curie
temperature of 55 K. By analyzing NMR spectra, temperature dependences of
Knight shift $K$ and nuclear quadrupole resonance frequency $\nu_Q$ were
obtained successf... | 0911.4166v2 |
2009-11-24 | Incommensurate itinerant antiferromagnetic excitations and spin resonance in the FeTe$_{0.6}$Se$_{0.4}$ superconductor | We report on inelastic neutron scattering measurements that find
incommensurate itinerant like magnetic excitations in the normal state of
superconducting FeTe$_{0.6}$Se$_{0.4}$ (\Tc=14K) at wave-vector
$\mathbf{Q}_{inc}=(1/2\pm\epsilon,1/2\mp\epsilon)$ with $\epsilon$=0.09(1). In
the superconducting state only the low... | 0911.4713v1 |
2009-11-24 | Stellar Parameters for a Sample of Stars with Planets | The study of chemical abundances in stars with planets is an important
ingredient for the models of formation and evolution of planetary systems. In
order to determine accurate abundances, it is crucial to have a reliable set of
atmospheric parameters. In this work, we describe the homogeneous determination
of effectiv... | 0911.4723v1 |
2009-11-30 | Disorder Induced Effects on the Critical Current Density of Iron Pnictide BaFe_1.8 Co_0.2 As_2 single crystals | Investigating the role of disorder in superconductors is an essential part of
characterizing the fundamental superconducting properties as well as assessing
potential applications of the material. In most cases, the information
available on the defect matrix is poor, making such studies difficult, but the
situation can... | 0911.5582v1 |
2009-12-07 | Direct observation of a nodeless superconducting energy gap in the optical conductivity of iron-pnictides | The temperature-dependent optical reflectivity and complex transmissivity of
an epitaxially grown Ba(Fe$_{0.9}$Co$_{0.1}$)$_2$As$_2$ thin film were measured
and the optical conductivity and permittivity evaluated over a wide frequency
range. The opening of the superconducting gap $2\Delta_0 = 3.7$ meV below
$T_c\approx... | 0912.1256v1 |
2009-12-08 | The possible feature of the energy spectrum of the primary cosmic rays at ultra-high energies | The energies of the most energetic extensive air showers observed at the
Yakutsk array have been estimated with help of the all detectors readings
instead of using of the standard procedure with a parameter s(600). The energy
of the most energetic extensive air shower observed at the Yakutsk array
happened to be 200, 2... | 0912.1473v1 |
2009-12-10 | Interplay between charge-order, ferroelectricity and ferroelasticity: tungsten bronze structures as a playground for multiferroicity | Large electron-electron Coulomb-interactions in correlated systems can lead
to a periodic arrangement of localized electrons, the so called "charge-order".
The latter is here proposed as a driving force behind ferroelectricity in iron
fluoride K0.6FeF3. By means of density functional theory, we propose different
non-ce... | 0912.1960v1 |
2009-12-10 | Superconductivity at 31 K in 111 type iron arsenide superconductor NaxFeAs induced by pressure | The effect of pressure on superconductivity of 111 type NaxFeAs is
investigated through temperature dependent electrical resistance measurement in
a diamond anvil cell. The superconducting transition temperature (Tc) increases
from 26 K to a maximum 31 K as the pressure increases from ambient to 3 GPa.
Further increasi... | 0912.2025v1 |
2009-12-10 | Towards a consistent picture for quasi-1D organic superconductors | The electrical resistivity of the quasi-1D organic superconductor (TMTSF)2PF6
was recently measured at low temperature from the critical pressure needed to
suppress the spin-density-wave state up to a pressure where superconductivity
has almost disappeared. This data revealed a direct correlation between the
onset of s... | 0912.2049v1 |
2009-12-12 | Two types of s-wave pairing due to magnetic and orbital fluctuations in the two-dimensional 16-band d-p model for iron-based superconductors | We study superconductivity in the two-dimensional 16-band d-p model extracted
from a tight-binding fit to the band structure of LaFeAsO, using the random
phase approximation. When the intraorbital repulsion U is larger than the
interorbital one U', an extended s-wave (s+--wave) pairing with sign reversal
of order param... | 0912.2392v4 |
2009-12-15 | Superconductivity at 23 K in Pt doped BaFe2As2 single crystals | We report superconductivity in single crystals of the new iron-pnictide
system BaFe1.9Pt0.1As2 grown by a self-flux solution method and characterized
via x-ray, transport, magnetic and thermodynamic measurements. The magnetic
ordering associated with a structural transition at 140 K present in BaFe2As2
is completely su... | 0912.2752v2 |
2009-12-15 | Quadratic X-ray magneto-optical effect in reflection at the M-edges of 3d transition metals | We have observed a quadratic x-ray magneto-optical effect in near-normal
incidence reflection at the M-edges of iron. The effect appears as the
magnetically induced rotation of ca. 0.1$ degrees of the polarization plane of
linearly polarized x-ray radiation upon reflection. A comparison of the
measured rotation spectru... | 0912.2867v1 |
2009-12-16 | Coupling of spin and orbital excitations in the iron-based superconductor FeSe(0.5)Te(0.5) | We present a combined analysis of neutron scattering and photoemission
measurements on superconducting FeSe(0.5)Te(0.5). The low-energy magnetic
excitations disperse only in the direction transverse to the characteristic
wave vector (1/2,0,0), whereas the electronic Fermi surface near (1/2,0,0)
appears to consist of fo... | 0912.3205v2 |
2009-12-17 | Droplet-like Fermi surfaces in the anti-ferromagnetic phase of EuFe$_2$As$_2$, an Fe-pnictide superconductor parent compound | Using angle resolved photoemission it is shown that the low lying electronic
states of the iron pnictide parent compound EuFe$_2$As$_2$ are strongly
modified in the magnetically ordered, low temperature, orthorhombic state
compared to the tetragonal, paramagnetic case above the spin density wave
transition temperature.... | 0912.3434v1 |
2009-12-18 | Elastic isotropy of hcp-Fe under Earth core conditions | Our first-principles calculations show that both the compressional and shear
waves of hcp-Fe become elastically isotropic under the high temperatures of
Earth inner core conditions, with the variation in sound velocities along
different angles from the c axis within 1%. We computed the thermoelasticity at
high pressure... | 0912.3587v1 |
2009-12-18 | The crystal structure of FeSe0.44Te0.56 | The crystal structure of the superconductor FeSe0.44Te0.56 was redetermined
by high-resolution X-ray single crystal diffraction at 173 K (anti-PbO-type,
P4/nmm, a=3.7996(2), c=5.9895(6) A, R1=0.022, wR2=0.041, 173 F^2).
Significantly different z-coordinates of tellurium and selenium at the 2c site
are clearly discernib... | 0912.3706v2 |
2009-12-21 | Electronic Ferroelectricity and Frustration | Beyond a conventional classification of ferroelectricity, there is a class of
materials where electronic degrees of freedom and electronic interactions are
directly responsible for electric polarization and ferroelectric transition.
This is termed electronic ferroelectricity. In this article, we review
electronic ferro... | 0912.4083v1 |
2009-12-28 | Volovik effect in the $\pm$s-wave state for the iron-based superconductors | We studied the field dependencies of specific heat coefficient $\gamma(H) =
\lim_{T \rightarrow 0} C(T,H)/T $ and thermal conductivity coefficient $\lim_{T
\rightarrow 0} \kappa(T ,H)/T$ of the $\pm$s-wave state in the mixed state. We
found that it is a generic feature of the two band s-wave state with the
unequal size... | 0912.5049v2 |
2009-12-27 | Observation of intertwined Fermi surface topology, orbital parity symmetries and electronic interactions in iron arsenide superconductors | We present a polarization and topology resolved study of the low energy band
structure in optimally doped superconducting Ba0.6K0.4Fe2As2 using angle
resolved photoemission spectroscopy. Polarization-contrasted measurements allow
us to identify and trace all low energy bands expected in models, revealing
unexpected sym... | 0912.5089v1 |
2009-12-29 | The quite complex "Simple Stellar Populations" of Globular Clusters | There is compelling observational evidence that globular clusters (GCs) are
quite complex objects. A growing body of photometric results indicate that the
evolutionary sequences are not simply isochrones in the observational plane -as
believed until a few years ago- from the main sequence, to the subgiant, giant,
and h... | 0912.5280v1 |
2010-01-05 | Magnetic frustration in an iron based Cairo pentagonal lattice | The Fe3+ lattice in the Bi2Fe4O9 compound is found to materialize the first
analogue of a magnetic pentagonal lattice. Due to its odd number of bonds per
elemental brick, this lattice, subject to first neighbor antiferromagnetic
interactions, is prone to geometric frustration. The Bi2Fe4O9 magnetic
properties have been... | 1001.0710v1 |
2010-01-10 | Chemical composition of stellar populations in Omega Centauri | We derive abundances of Fe, Na, O, and s-elements from GIRAFFE@VLT spectra
for more than 200 red giant stars in the Milky Way satellite Omega Centauri.
Our preliminary results are that: (i) we confirm that Omega Centauri exibiths
large star-to-star metallicity variations ($\sim$ 1.4 dex); (ii) the
metallicity distribut... | 1001.1500v1 |
2010-01-11 | Measurement of neutron star parameters: a review of methods for low-mass X-ray binaries | Measurement of at least three independent parameters, for example, mass,
radius and spin frequency, of a neutron star is probably the only way to
understand the nature of its supranuclear core matter. Such a measurement is
extremely difficult because of various systematic uncertainties. The lack of
knowledge of several... | 1001.1642v1 |
2010-01-17 | The Interior Dynamics of Water Planets | The ever-expanding catalog of detected super-Earths calls for theoretical
studies of their properties in the case of a substantial water layer. This work
considers such water planets with a range of masses and water mass fractions (2
to 5 M_Earth, 0.02% to 50% H2 O). First, we model the thermal and dynamical
structure ... | 1001.2890v1 |
2010-01-18 | The metal-insulator transition and lattice distortion in semiconductors | A relation between the energy of an elementary `insulating' excitation
corresponding to the metal-insulator transition and the bandgap width in a
semiconductor is obtained. An effect of atomic relaxation on the temperature
and pressure dependence of the bandgap width is considered. It is shown that
the metal-insulator ... | 1001.3061v3 |
2010-01-19 | Theory of Normal State Pseudogap Behavior in FeSe(1-x)$Te(x) | The normal state of the recently discovered Iron Selenide (FeSe)-based
superconductors shows a range of inexplicable features. Along with bad-metallic
resistivity, characteristic pseudogap features and proximity to insulating
states, reminiscent of the underdoped high-Tc cuprates, mark these systems as
strongly correla... | 1001.3273v1 |
2010-01-20 | Fermi surface and mass enhancement in KFe$_2$As$_2$ from de Haas-van Alphen effect measurements | We report on a band structure calculation and de Haas-van Alphen measurements
of KFe$_2$As$_2$. Three cylindrical Fermi surfaces are found. Effective masses
of electrons range from 6 to 18$m_e$, $m_e$ being the free electron mass.
Remarkable discrepancies between the calculated and observed Fermi surface
areas and the ... | 1001.3441v2 |
2010-01-26 | Gap structure in the electron-doped Iron-Arsenide Superconductor Ba(Fe0.92Co0.08)2As2: low-temperature specific heat study | We report the field and temperature dependence of the low-temperature
specific heat down to 400 mK and in magnetic fields up to 9 T of the
electron-doped Ba(Fe0.92Co0.08)2As2 superconductor. Using the phonon specific
heat obtained from pure BaFe2As2 we find the normal state Sommerfeld
coefficient to be 18 mJ/mol.K^2 an... | 1001.4564v1 |
2010-01-27 | Coupled structural and magnetic properties of ferric fluoride nanostructures: part II, a Monte-Carlo Heisenberg study | We present a numerical study of the magnetic structure of nanostructured iron
fluoride, using the Monte-Carlo-Metropolis simulated annealing technique and a
classical Heisenberg Hamiltonian with a superexchange angle dependence. The
parameters are adjusted on experimental results, and the atomic structure and
topology ... | 1001.4959v1 |
2010-01-27 | Coupled structural and magnetic properties of ferric fluoride nanostructures part I: a Metropolis atomistic study | A modified Metropolis atomistic simulation is proposed to model the structure
of grain boundaries (GBs) and interfaces in ionic nanostructured systems and is
applied to the magnetically interesting case of iron trifluoride (FeF3). We
chose long-range interatomic potentials adjusted on experimental results, and
adapted ... | 1001.4971v2 |
2010-01-27 | A real-space effective c-axis lattice constant theory of superconductivity | Based on the recent developed real-space picture of superconductivity, we
study the stability of the superconducting vortex lattices in layered
superconductors. It is shown that the effective c-axis lattice constant play a
significant role in promoting the superconducting transition temperature in
these materials. An u... | 1001.5067v1 |
2010-01-28 | EC 11481-2303 - A Peculiar Subdwarf OB Star Revisited | EC 11481-2303 is a peculiar, hot, high-gravity pre-white dwarf. Previous
optical spectroscopy revealed that it is a sdOB star with an effective
temperature (Teff) of 41790 K, a surface gravity log(g)= 5.84, and He/H = 0.014
by number. We present an on-going spectral analysis by means of non-LTE
model-atmosphere techniq... | 1001.5115v1 |
2010-01-29 | Strong correlation and massive spectral-weight redistribution induced spin density wave in a-Fe1.06Te | The electronic structure of a-Fe1.06Te is studied with angle-resolved
photoemission spectroscopy. We show that there is substantial spectral weight
around Gamma and X, and lineshapes are intrinsically incoherent in the
paramagnetic state. The magnetic transition is characterized by a massive
spectral-weight transfer ov... | 1001.5327v1 |
2010-02-01 | Statistics of subgap states in $s_\pm$ superconductors | There is strong support in favor of an unusual $s_{\pm}$ superconducting
state in the new iron-based superconductors, in which the gap parameter has
opposite signs in different bands. In this case scattering between different
bands by impurities has a pair-breaking effect and introduces states inside the
gap. We studie... | 1002.0363v1 |
2010-02-02 | Structural and Magnetic Properties of Co1-xFexSr2YCu2O7 compounds | Here we study the structural and magnetic properties of the CoFeSr2YCu2O7
compound with x = 0.0 to 1.0. X-ray diffraction patterns and simulated data
obtained from Rietveld refinement of the same indicate that the iron ion
replacement in CoFeSr2YCu2O7 induces a change in crystal structure. The
orthorhombic Ima2 space g... | 1002.0402v2 |
2010-02-02 | Comparative study on the thermoelectric effect of parent oxypnictides La$T$AsO ($T$ = Fe, Ni) | The thermopower and Nernst effect were investigated for undoped parent
compounds LaFeAsO and LaNiAsO. Both thermopower and Nernst signal in iron-based
LaFeAsO are significantly larger than those in nickel-based LaNiAsO.
Furthermore, abrupt changes in both thermopower and Nernst effect are observed
below the structural ... | 1002.0417v1 |
2010-02-03 | Orbital Symmetry of Ba(Fe1-xCox)2As2 Superconductors Probed with X-ray Absorption Spectroscopy | The orbital symmetries of electron doped iron-arsenide superconductors
Ba(Fe1-xCox)2As2 have been measured with x-ray absorption spectroscopy. The
data reveal signatures of Fe d electron itinerancy, weak electronic
correlations, and a high degree of Fe-As hybridization related to the bonding
topology of the Fe dxz+yz s... | 1002.0769v2 |
2010-02-04 | Magnetic excitations in ferro-pnictide materials controlled by a quantum critical point into hidden order | The two-orbital J1-J2 model that describes a square lattice of frustrated
spin-1 iron atoms is analyzed within the linear spin-wave approximation and by
exact diagonalization over a 4x4 cluster. A quantum critical point (QCP) is
identified that separates hidden magnetic order at weak Hund's rule coupling
from a commens... | 1002.0891v3 |
2010-02-05 | Incommensurate spin-density wave and magnetic lock-in transition in CaFe4As3 | The magnetic structure for the newly discovered iron-arsenide compound
\CaFeAs has been studied by neutron powder diffraction. Long-range magnetic
order is detected below 85K, with an incommensurate modulation described by the
propagation vector k=(0,$\delta$,0), $\delta\sim$ 0.39. Below $\sim$ 25K, our
measurements de... | 1002.1336v1 |
2010-02-07 | Proposal to determine the Fermi-surface topology of a doped iron-based superconductor using bulk-sensitive Fourier-transform Compton scattering | We have carried out first-principles calculations of the Compton scattering
spectra to demonstrate that the filling of the hole Fermi surface in
LaO$_{1-x}$F$_{x}$FeAs produces a distinct signature in the Fourier transformed
Compton spectrum when the momentum transfer vector lies along the [100]
direction. We thus show... | 1002.1483v1 |
2010-02-08 | A Triplet Resonance in Superconducting FeSe0.4Te0.6 | From heavy fermions to cuprates and iron pnictides, a spin resonance is a
staple of nearly magnetic superconductors. Possible explanations include a
two-particle bound state or loss of magnon damping in the superconductor. While
both scenarios suggest a central role for magnetic fluctuations, distinguishing
them is imp... | 1002.1617v2 |
2010-02-08 | Determination of the Nature of the Tetragonal to Orthorhombic Phase Transition in SrFe_2As_2 by Measurement of the Local Order Parameter | SrFe2As2 is the end-member for a series of iron-pnictide superconductors and
has a tetragonal-to-orthorhombic phase transition near 200 K. Previous
macroscopic measurements to determine the nature of the transition gave
seemingly inconsistent results so we use electron microscopy to monitor the
local order parameter sh... | 1002.1639v2 |
2010-02-09 | High Resolution X-Ray Spectroscopy of SN 1987A: Monitoring with XMM-Newton | We report the results of our XMM-Newton monitoring of SN 1987A. The ongoing
propagation of the supernova blast wave through the inner circumstellar ring
caused a drastic increase in X-ray luminosity during the last years, enabling
detailed high resolution X-ray spectroscopy with the Reflection Grating
Spectrometer. The... | 1002.1865v1 |
2010-02-11 | Numerical Forecast of the Melting and Thermal Histories of Particles Injected in a Plasma Jet | This work presents the numerical simulation of the melting process of a
particle injected in a plasma jet. The plasma process is nowadays applied to
produce thin coatings on metal mechanical components with the aim of improving
the surface resistance to different phenomena such as corrosion, temperature or
wear. In thi... | 1002.2370v1 |
2010-02-12 | Electron-phonon coupling and charge gap in spin-density-wave iron-pnictides from quasiparticle relaxation dynamics | We investigate the quasiparticle relaxation and low-energy electronic
structure in undoped SrFe_2As_2 exhibiting spin-density wave (SDW) ordering
using optical pump-probe femtosecond spectroscopy. A remarkable critical
slowing down of the quasiparticle relaxation dynamics at the SDW transition
temperature T_SDW = 200K ... | 1002.2582v1 |
2010-02-17 | Scaling relations in anisotropic superconductors with strong pair-breaking | Following the work of Abrikosov and Gor'kov on the pair-breaking effects, one
can derive the temperature dependencies of the electronic specific heat
$C_s/T=\gamma^\prime+\mu T^2$ (with the jump at the superconducting transition
$\Delta C \propto T_c^3$) for materials with zero Fermi surface average of the
order parame... | 1002.3390v1 |
2010-02-19 | Dielectronic recombination data for astrophysical applications: Plasma rate-coefficients for Fe^q+ (q=7-10, 13-22) and Ni^25+ ions from storage-ring experiments | This review summarizes the present status of an ongoing experimental effort
to provide reliable rate coefficients for dielectronic recombination of highly
charged iron ions for the modeling of astrophysical and other plasmas. The
experimental work has been carried out over more than a decade at the heavy-ion
storage-ri... | 1002.3678v1 |
2010-02-25 | Signatures of pressure induced superconductivity in insulating Bi2212 | We have performed several high pressure electrical resistance experiments on
Bi1.98Sr2.06Y0.68Cu2O8, an insulating parent compound of the high-Tc Bi2212
family of copper oxide superconductors. We find a resistive anomaly, a downturn
at low temperature, that onsets with applied pressure in the 20-40 kbar range.
Through ... | 1002.4672v1 |
2010-02-26 | Significant reduction of electronic correlations upon isovalent Ru substitution of BaFe2As2 | We present a detailed investigation of Ba(Fe0.65Ru0.35)2As2 by transport
measurements and Angle Resolved photoemission spectroscopy. We observe that Fe
and Ru orbitals hybridize to form a coherent electronic structure and that Ru
does not induce doping. The number of holes and electrons, deduced from the
area of the Fe... | 1002.4952v2 |
2010-02-28 | Low-temperature synthesis of SmFeAsO0.7F0.3 wires with high transport critical current density | Ag-sheathed SmFeAsO0.7F0.3 (Sm-1111) superconducting wires were prepared by a
one-step solid state reaction at temperatures as low as 850~900C, instead of
commonly used temperatures of 1150~1250C. The X-ray diffraction pattern of the
as-sintered samples is well indexed on the basis of tetragonal ZrCuSiAs-type
structure... | 1003.0153v1 |
2010-03-04 | Medium Modifications of the Rho Meson in Nuclear Photoproduction | We extend our recent study of dilepton invariant-mass spectra from the decays
of rho mesons produced by photon reactions off nuclei. We specifically focus on
experimental spectra as recently measured by the CLAS Collaboration at the
Thomas Jefferson National Accelerator Facility using carbon and iron nuclei.
Building o... | 1003.0910v2 |
2010-03-04 | Comparative study of transport and magnetic Jc in the polycrystalline iron-based superconductor NdFeAsO{0.88}F{0.12} | Polycrystalline NdFeAsO0.88F0.12 superconductors prepared by high pressure
(HP) and ambient pressure (AP) method were comparatively studied by
magnetization and transport measurements. Upper critical field (Hc2),
irreversibility field (Hirr) and the anisotropy parameter were estimated from
resistance transition curves.... | 1003.0946v2 |
2010-03-11 | Superconductivity and spin-density-waves in multi-band metals | We present a detailed description of two-band quasi-2D metals with s-wave
superconducting (SC) and antiferromagnetic spin-density wave (SDW)
correlations. We present a general approach and use it to investigate the
influence of the difference between the shapes and the areas of the two Fermi
surfaces on the phase diagr... | 1003.2389v2 |
2010-03-14 | Site-dependent NMR Spin-lattice Relaxation in the Superconducting State of an Iron Pnictide Superconductor | In a conventional superconductor, the spin-lattice relaxation rate on all
nuclei should have the same temperature dependence below Tc. We performed
$^{23}$Na, $^{75}$As, and $^{59}$Co NMR studies on single crystals of
NaFe0.95Co0.05As, and found that spin-lattice relaxation rates show very
different temperature depende... | 1003.2775v1 |
2010-03-19 | Leaving the ISCO: the inner edge of a black-hole accretion disk at various luminosities | The "radiation inner edge" of an accretion disk is defined as the inner
boundary of the region from which most of the luminosity emerges. Similarly,
the "reflection edge" is the smallest radius capable of producing a significant
X-ray reflection of the fluorescent iron line. For black hole accretion disks
with very sub... | 1003.3887v1 |
2010-03-24 | Broad Balmer-line Absorption in SDSS J172341.10+555340.5 | I present the discovery of Balmer-line absorption from H alpha to H9 in iron
low-ionizaton broad absorption line (FeLoBAL) quasar, SDSS~J172341.10+555340.5
by near-infrared spectroscopy with the Cooled Infrared Spectrograph and Camera
for OHS (CISCO) attached to the Subaru telescope. The redshift of the
Balmer-line abs... | 1003.4622v2 |
2010-03-26 | Evolution of the optical spectrum with doping in iron pnictides Ba(Fe1-xCox)2As2 | We investigated the optical spectrum of Ba(Fe1-xCox)2As2 single crystals with
various doping levels. It is found that the low-energy optical conductivity
spectrum of this system can be decomposed into two components: a sharp Drude
term and a broad "incoherent" term. For the compounds showing magnetic order, a
gap appea... | 1003.5038v1 |
2010-03-27 | Weak-Coupling Theory for Multiband Superconductivity Induced by Jahn-Teller Phonons | Emergence of superconductivity in a two-band system coupled with breathing
and Jahn-Teller phonons is discussed in a weak-coupling limit. With the use of
a standard quantum mechanical procedure, the phonon-mediated attraction is
derived. From the analysis of the model including such attraction, a BCS-like
formula for a... | 1003.5274v1 |
2010-03-30 | Influence of magnetism on the superconducting properties of iron-based superconductor NdFeAsO0.88F0.12 | Both DC and AC magnetization measurements were performed on the
NdFeAsO0.88F0.12 superconductor to investigate the influence of magnetism on
the superconducting properties of this system. The crossover of the ZFC and FC
magnetic susceptibility curves under 7.5KOe was observed. The imaginary
component of the first harmo... | 1003.5807v2 |
2010-03-31 | Evidence for superconducting gap nodes in the zone-centered hole bands of KFe2As2 from magnetic penetration-depth measurements | Among the iron-based pnictide superconductors the material KFe$_2$As$_2$ is
unusual in that its Fermi surface does not consist of quasi-nested electron and
hole pockets. Here we report measurements of the temperature dependent London
penetration depth of very clean crystals of this compound with residual
resistivity ra... | 1003.6022v2 |
2010-04-02 | Performance of the MIND detector at a Neutrino Factory using realistic muon reconstruction | A Neutrino Factory producing an intense beam composed of nu_e(nubar_e) and
nubar_mu(nu_mu) from muon decays has been shown to have the greatest
sensitivity to the two currently unmeasured neutrino mixing parameters,
theta_13 and delta_CP . Using the `wrong-sign muon' signal to measure nu_e to
nu_mu(nubar_e to nubar_mu)... | 1004.0358v1 |
2010-04-09 | No anomalous spin fluctuation in optimally doped and overdoped iron-based oxypnictide superconductors LaFeAsO$_{1-x}$F$_x$ probed by muon spin relaxation | Zero field and longitudinal field muon spin relaxation measurements have been
performed in optimally doped and overdoped superconductors LaFeAsO$_{1-x}$F$_x$
in order to investigate the magnetic fluctuation over a wide range of
temperature and longitudinal field. We have observed no sign of magnetic
fluctuation against... | 1004.1589v1 |
2010-04-12 | Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure | The temperature and pressure dependence of the partial density of phonon
states of iron atoms in superconducting Fe1.01Se was studied by 57Fe nuclear
inelastic scattering (NIS). The high energy resolution allows for a detailed
observation of spectral properties. A sharpening of the optical phonon modes
and shift of all... | 1004.2007v1 |
2010-04-13 | Dissipationless Anomalous Hall Current in $Fe_{100-x}(SiO_2)_x$ Films | The observation of dissipationless anomalous Hall current is one of the
experimental evidences to confirm the intrinsic origin of anomalous Hall
effect. To study the origin of anomalous Hall effect in iron,
Fe$_{100-x}$(SiO$_{2}$)$_{x}$ granular films with volume fraction of SiO$_{2}$
0\le x \le 40.51 were fabricated u... | 1004.2105v1 |
2010-04-13 | Heat treatment effects on the superconducting properties of Ag-doped SrKFeAs compound | The superconducting properties of polycrystalline Sr0.6K0.4Fe2As2 were
strongly influenced by Ag doping (Supercond. Sci. Technol. 23 (2010) 025027).
Ag addition is mainly dominated by silver diffusing, so the annealing process
is one of the essential factors to achieve high quality Ag doped
Sr0.6K0.4Fe2As2. In this pap... | 1004.2137v2 |
2010-04-17 | Structural and superconducting properties in LaFeAs1-xSbxO1-yFy | We report the antimony (Sb) doping effect in a prototype system of iron-based
supercon-ductors LaFeAsO1-yFy (y=0, 0.1, 0.15). X-ray powder diffraction
indicates that the lattice pa-rameters increase with Sb content within the
doping limit. Rietveld structural refinements show that, with the partial
substitution of Sb f... | 1004.2940v1 |
2010-04-21 | Precise determination of muon and electromagnetic shower contents from shower universality property | We consider two new aspects of Extensive Air Shower development universality
allowing to make accurate estimation of muon and electromagnetic (EM) shower
contents in two independent ways. In the first case, to get muon (or EM) signal
in water Cherenkov tanks or in scintillator detectors it is enough to know the
vertica... | 1004.3673v1 |
2010-04-21 | A minimal Beta Beam with high-Q ions to address CP violation in the leptonic sector | In this paper we consider a Beta Beam setup that tries to leverage at most
existing European facilities: i.e. a setup that takes advantage of facilities
at CERN to boost high-Q ions (8Li and 8B) aiming at a far detector located at L
= 732 Km in the Gran Sasso Underground Laboratory. The average neutrino energy
for 8Li ... | 1004.3773v2 |
2010-04-27 | Orbital-weight redistribution triggered by spin order in the pnictides | The one-particle spectral function and its orbital composition are
investigated in a three-orbital model for the undoped parent compounds of the
iron-based superconductors. In the realistic parameter regime, where results
best fit experimental data, it is observed that the magnetization in the xz and
yz orbitals are ma... | 1004.4803v2 |
2010-05-03 | Collective spin mode in a multi-component system of coupled itinerant and localized electrons | We study collective spin excitations of a magnetically ordered state in a
multi-component system composed of both itinerant electrons and local moments.
Here the induced spin-density-wave (SDW) ordering of itinerant electrons and
the collinear antiferromangetic (AF) ordering of local moments are locked
together via a H... | 1005.0421v1 |
2010-05-04 | Competition between Ferrimagnetism and Magnetic Frustration in Zinc Substituted YBaFe4O7 | The substitution of zinc for iron in YBaFe4O7 has allowed the oxide series
YBaFe4-xZnxO7, with 0.40 < x < 1.50, belonging to the "114" structural family
to be synthesized. These oxides crystallize in the hexagonal symmetry (P63mc),
as opposed to the cubic symmetry (F-43m) of YBaFe4O7. Importantly, the d.c.
magnetizatio... | 1005.0480v1 |
2010-05-04 | Magnetic ordering and dense Kondo behaviour in EuFe$_{2}$P$_{2}$ | Ternary iron phosphide EuFe$_2$P$_2$ with ThCr$_2$Si$_2$-type structure has
been systematically studied by the measurements of crystal structure,
magnetization, M\"{o}ssbauer effect, transport properties and specific heat.
The structural refinement result confirms no direct P-P covalent bonding. The
M\"{o}ssbauer spect... | 1005.0516v2 |
2010-05-06 | Chemical composition of the old globular clusters NGC 1786, NGC 2210 and NGC 2257 in the Large Magellanic Cloud | This paper presents the chemical abundance analysis of a sample of 18 giant
stars in 3 old globular clusters in the Large Magellanic Cloud, namely NGC
1786, NGC 2210 and NGC 2257. The derived iron content is [Fe/H]= --1.75+-0.01
dex (sigma= 0.02 dex), --1.65+-0.02 dex (sigma= 0.04 dex) and --1.95+-0.02 dex
(sigma= 0.04... | 1005.0964v1 |
2010-05-10 | 23Na and 75As NMR Studies on NaFeAs0.8P0.2 Single Crystals | We report our $^{23}$Na and $^{75}$As NMR studies on isovalent
phosphorus-doped NaFeAs$_{0.8}$P$_{0.2}$ ($T_c=$ 33 K) single crystals. Our
data suggest a dramatic enhancement of the electron density of states on the
Fermi surface, and a large residual electron density of state below $T_c$.
However, evidence of antiferr... | 1005.1448v2 |
2010-05-12 | Transfer of optical spectral weight in magnetically ordered superconductors | We show that, in antiferromagnetic superconductors, the optical spectral
weight transferred to low frequencies below the superconducting transition
temperature originates from energies that can be much larger than twice the
superconducting gap $\Delta$. This contrasts to non-magnetic superconductors,
where the optical ... | 1005.2174v3 |
2010-05-17 | Cooperative effects of Coulomb and electron-phonon interactions in the two-dimensional 16-band d-p model for iron-based superconductors | We study the electronic states and the superconductivity in the
two-dimensional 16-band d-p model coupled with A1g, B1g and Eg local phonons
and obtain the rich phase diagram including the magnetic, charge and orbital
ordered phases on the parameter plane of the Coulomb and electron-phonon
interactions. When the electr... | 1005.2814v2 |
2010-05-17 | Electron-Hole Asymmetry in Superconductivity of Pnictides Originated from the Observed Rigid Chemical Potential Shift | We have performed a systematic photoemission study of the chemical potential
shift as a function of carrier doping in a pnictide system based on
BaFe$_2$As$_2$. The experimentally determined chemical potential shift is
consistent with the prediction of a rigid band shift picture by the
renormalized first-principle band... | 1005.2966v1 |
2010-05-18 | Superconductivity induced by doping Rh in CaFe2-xRhxAs2 | In this paper we report the synthesis of iron-based superconductors
CaFe2-xRhxAs2 using one-step solid state reaction method, which crystallizes in
the ThCr2Si2-type structure with a space group I4/mmm. The systematic evolution
of the lattice constants demonstrates that the Fe ions are successfully
replaced by the Rh. ... | 1005.3172v2 |
2010-05-20 | Distinct high-T transitions in underdoped Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ | In contrast to the simultaneous structural and magnetic first order phase
transition $T_{0}$ previously reported, our detailed investigation on an
underdoped Ba$_{0.84}$K$_{0.16}$Fe$_{2}$As$_{2}$ single crystal unambiguously
revealed that the transitions are not concomitant. The tetragonal ($\tau$:
I4/mmm) - orthorhomb... | 1005.3718v1 |
2010-05-21 | Microscopic Study of the Superconducting State of the Iron Pnictide RbFe_2As_2 | A study of the temperature and field dependence of the penetration depth
\lambda of the superconductor RbFe_2As_2 (T_c=2.52 K) was carried out by means
of muon-spin rotation measurements. In addition to the zero temperature value
of the penetration depth \lambda(0)=267(5) nm, a determination of the upper
critical field... | 1005.3989v3 |
2010-05-23 | Inelastic x-ray scattering investigations of lattice dynamics in SmFeAsO$_{1-x}$F$_y$ superconductors | We report measurements of the phonon density of states as measured with
inelastic x-ray scattering in SmFeAsO$_{1-x}$F$_y$ powders. An unexpected
strong renormalization of phonon branches around 23 meV is observed as fluorine
is substituted for oxygen. Phonon dispersion measurements on
SmFeAsO$_{1-x}$F$_y$ single cryst... | 1005.4165v1 |
2010-05-24 | The Puzzle of High Temperature Superconductivity in Layered Iron Pnictides and Chalcogenides | The response of the worldwide scientific community to the discovery in 2008
of superconductivity at Tc = 26 K in the Fe-based compound LaFeAsO_{1-x}F_x has
been very enthusiastic. In short order, other Fe-based superconductors with the
same or related crystal structures were discovered with Tc up to 56 K. Many
experime... | 1005.4392v2 |
2010-05-26 | RXTE observations of the 1A 1118-61 in an outburst, and the discovery of a cyclotron line | We present the analysis of RXTE monitoring data obtained during the January
2009 outburst of the hard X-ray transient 1A 1118-61. Using these observations
the broadband (3.5-120 keV) spectrum of the source was measured for the first
time ever. We have found that the broadband continuum spectrum of the source is
similar... | 1005.4782v1 |
2010-05-26 | Probing CPT violation in neutrino oscillation: A three flavor analysis | We have studied $CPT$ violation in neutrino oscillation considering three
flavor framework with matter effect. We have constructed a new way to find the
oscillation probability incorporating $CPT$ violating terms without any
approximation. Then $CPT$ violation with atmospheric neutrinos for a magnetized
iron calorimete... | 1005.4851v3 |
2010-05-27 | Milne-Eddington inversion of the Fe I line pair at 630~nm | The iron lines at 630.15 and 630.25 nm are often used to determine the
physical conditions of the solar photosphere. A common approach is to invert
them simultaneously under the Milne-Eddington approximation. The same
thermodynamic parameters are employed for the two lines, except for their
opacities, which are assumed... | 1005.5013v2 |
2010-05-29 | {\it Ab initio} calculations of magnetic structure and lattice dynamics of Fe/Pt multilayers | The magnetization distribution, its energetic characterization by the
interlayer coupling constants and lattice dynamics of (001)-oriented Fe/Pt
multilayers are investigated using density functional theory combined with the
direct method to determine phonon frequencies. It is found that ferromagnetic
order between cons... | 1005.5454v1 |
2010-06-02 | X-ray reflected spectra from accretion disk models. I. Constant density atmospheres | We present new models for illuminated accretion disks, their structure and
reprocessed emission. We consider the effects of incident X-rays on the surface
of an accretion disk by solving simultaneously the equations of radiative
transfer, energy balance and ionization equilibrium over a large range of
column densities.... | 1006.0485v1 |
2010-06-03 | Unusual Nernst effect and spin density wave precursors in superconducting $\rm\bf LaFeAsO_{1-x}F_x$ | The Nernst effect has recently proven as a sensitive probe for detecting
unusual normal state properties of unconventional superconductors. Here we
present a systematic study of the Nernst effect of the iron pnictide
superconductor \laf with a particular focus on its evolution upon doping. For
the parent compound we ob... | 1006.0715v1 |
2010-06-04 | Surface-driven electronic structure in LaFeAsO studied by angle resolved photoemission spectroscopy | We measured the electronic structure of an iron arsenic parent compound
LaFeAsO using angle resolved photoemission spectroscopy (ARPES). By comparing
with a full-potential Linear Augmented PlaneWave calculation we show that the
extra large Gamma hole pocket measured via ARPES comes from electronic
structure at the samp... | 1006.0929v1 |
2010-06-09 | Comment on "Symmetries and Interaction Coefficients of Kelvin waves" [arXiv:1005.4575] by Lebedev and L'vov | We comment on the claim by Lebedev and L'vov [arXiv:1005.4575] that the
symmetry with respect to a tilt of a quantized vortex line does not yet
prohibit coupling between Kelvin waves and the large-scale slope of the line.
Ironically, the counterexample of an effective scattering vertex in the local
induction approximat... | 1006.1789v2 |
2010-06-11 | Thermal nuclear pairing within the self-consistent quasiparticle RPA | The self-consistent quasiparticle RPA (SCQRPA) is constructed to study the
effects of fluctuations on pairing properties in nuclei at finite temperature
and z-projection M of angular momentum. Particle-number projection (PNP) is
taken into account within the Lipkin-Nogami method. Several issues such as the
smoothing of... | 1006.2201v1 |
2010-06-15 | Angular resolved specific heat in iron-based superconductors: the case for nodeless extended $s$-wave gap | We consider the variation of the field-induced component of the specific heat
$C({\bf H})$ with the direction of the applied field in $Fe-$pnictides within
quasi-classical Doppler-shift approximation, with special emphasis to recent
experiments on FeSe$_{0.4}$Te$_{0.6}$ [Zheng et al., arXiv:1004.2236]. We show
that for... | 1006.3091v1 |
2010-06-17 | Homogeneous Cu-Fe super saturated solid solutions prepared by severe plastic deformation | A Cu-Fe nanocomposite containing 50 nm thick iron filaments dispersed in a
copper matrix was processed by torsion under high pressure at various strain
rates and temperatures. The resulting nanostructures were characterized by
transmission electron microscopy, atom probe tomography and M\"ossbauer
spectrometry. It is s... | 1006.3433v1 |
2010-06-17 | Competition of local-moment ferromagnetism and superconductivity in Co-substituted EuFe2As2 | In contrast to SrFe2As2, where only the iron possesses a magnetic moment, in
EuFe2As2 an additional large, local magnetic moment is carried by Eu2+. Like
SrFe2As2, EuFe2As2 exhibits a spin-density wave transition at high
temperatures, but in addition the magnetic moments of the Eu2+ order at around
20 K. The interplay ... | 1006.3471v1 |
2010-06-17 | Ultrafast transient response and electron-phonon coupling in the iron-pnictide superconductor Ba(Fe(1-x)Co(x))2As2 | The transient response of Ba(Fe(1-x)Co(x))2As2, x=0.08 was studied by
pump-probe optical reflectivity. After ultrafast photoexcitation, hot electrons
were found to relax with two different characteristic times, indicating the
presence of two distinct decay channels: a faster one, of less than 1 ps in the
considered pum... | 1006.3490v2 |
2010-06-20 | Out-of-plane momentum and symmetry dependent superconducting gap in Ba0.6K0.4Fe2As2 | The three-dimensional band structure and superconducting gap of
Ba0.6K0.4Fe2As2 are studied with high-resolution angle-resolved photoemission
spectroscopy. In contrast to previous results, we have identified three
hole-like Fermi surfaces near the zone center with sizable out-of-plane or kz
dispersion. The superconduct... | 1006.3936v1 |
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