publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2009-03-19 | Superconductivity at 17 K in (Fe2P2)(Sr4Sc2O6): a new superconducting layered pnictide oxide with a thick perovskite oxide layer | A new layered oxypnictide (Fe2P2)(Sr4Sc2O6) have been synthesized by
solid-state reaction. This material has an alternating layer stacking structure
of anti-fluorite Fe2P2 and perovskite-based Sr4Sc2O6 oxide layers. Space group
of the material is P4/nmm and lattice constants a and c are 4.016 A and 15.543
A, respective... | 0903.3314v3 |
2009-03-20 | Inverse Iron Isotope Effect on the transition temperature of the (Ba,K)Fe2As2 superconductor | We report that (Ba,K)Fe2As2 superconductor (a transition temperature, Tc = 38
K) shows inverse Iron isotope effect (-0.18) (the sample including the larger
atomic weight of Fe depicts higher Tc). Measurements of both temperature
dependent magnetization and resistivity reveal a clear inverse shift by
systematic studies ... | 0903.3515v3 |
2009-03-25 | Orbital coupling and superconductivity in the iron pnictides | We demonstrate that strong inter-orbital interaction is very efficient to
achieve superconductivity due to magnetic fluctuations in the iron pnictides.
Fermi surface states that are coupled by the antiferromagnetic wave vector are
often of different orbital nature, causing pair-hopping interactions between
distinct Fe-... | 0903.4473v2 |
2009-03-30 | New iron-based arsenide oxides (Fe2As2)(Sr4M2O6)(M = Sc, Cr) | We have discovered new layered oxyarsenides (Fe2As2)(Sr4M2O6) (M = Sc, Cr:
M-22426). These materials are isostructural with (Fe2P2)(Sr4Sc2O6), which was
found in our previous study. The new compounds are tetragonal with a space
group of P4/nmm and consist of the anti-fluorite type FeAs layer and
perovskite-type blockin... | 0903.5124v3 |
2009-03-31 | Structure and Physical properties of New layered oxypnictides $Sr_4Sc_2O_6M_2As_2$ (M=Fe and Co) | We have successfully prepared the new layered oxypnictides
$Sr_4Sc_2O_6M_2As_2$ (M=Fe and Co). They adopt the tetragonal structure, being
the same as that of $Sr_4Sc_2O_6Fe_2P_2$. The lattice constants are a=0.4045 nm
and c= 0.5802 nm for M=Fe, and a=0.4045 nm and c=1.5695 nm for M=Co,
respectively. Their transport and... | 0903.5484v1 |
2009-03-31 | Momentum dependence and nodes of the superconducting gap in iron-pnictides | We discuss the structure of the superconducting gap in iron pnictides. In the
itinerant electron picture, gaps with or without nodes have the extended s-wave
(s+) symmetry and emerge within the same pairing mechanism, determined by the
interplay between intra-pocket repulsion and inter-band pair hopping. If the
pair ho... | 0903.5547v1 |
2009-04-05 | Superconductivity in Ir-doped LaFe1-xIrxAsO | We report the realization of superconductivity by 5d element Ir doping in
LaFeAsO, a prototype parent compound of high-temperature iron based
superconductors. X-ray diffraction patterns indicate that the material has
formed the ZrCuSiAs-type structure with a space group P4/nmm. The systematic
evolution of the lattice c... | 0904.0772v4 |
2009-04-06 | Superconductivity in Ti-doped Iron-Arsenide Compound Sr4Cr0.8Ti1.2O6Fe2As2 | Superconductivity was achieved in Ti-doped iron-arsenide compound
Sr4Cr0.8Ti1.2O6Fe2As2 (abbreviated as Cr-FeAs-42622). The x-ray diffraction
measurement shows that this material has a layered structure with the space
group of \emph{P4/nmm}, and with the lattice constants a = b = 3.9003 A and c =
15.8376 A. Clear diama... | 0904.0972v3 |
2009-04-20 | Constraints on the absorption-dominated model for the X-ray spectrum of MCG-6-30-15 | Complexities in the X-ray spectrum of the nearby Seyfert 1.2 galaxy
MCG-6-30-15 are commonly interpreted in terms of a broad iron line and the
associated Compton reflection hump from the innermost relativistic regions of
an accretion disk around a rapidly spinning black hole. However, an alternative
model has recently ... | 0904.3099v1 |
2009-04-24 | Synthesis, characterization and low temperature studies of iron chalcogenide superconductors | We have synthesized tetragonal iron selenide and telluride superconductors
through solid state reaction at 450deg.C and 550deg.C respectively. These
synthesis temperatures have been established by optimization. Electrical
resistivity and magnetic susceptibility measurements (4.2-300 K) confirm
superconductivity with Tc... | 0904.3851v1 |
2009-04-26 | Computational Physics and Reality: Looking for Some Overlap at the Blacksmith Shop | The paper describes two general problems encountered in computational
assignments at the introductory level. First, novice students often treat
computer code as almost magic incantations, and like novices in many fields,
have trouble creating new algorithms or procedures to solve novel problems.
Second, the nature of c... | 0904.3960v3 |
2009-04-28 | Impurity effect as a probe for order parameter symmetry in iron-based superconductors | The pointlike impurity scattering is studied for a superconductor with
different pairing symmetries based on a minimal two band model proposed by S.
Raghu $et$ $al.$ [Phys. Rev. B {\bf 77}, R220503 (2008)], and the
self-consistent Bogoliubov-de Gennes equations. Two intra-gap resonance peaks
are found at or near the no... | 0904.4273v8 |
2009-04-28 | Low-temperature thermal conductivity of BaFe2As2: Parent compound of iron-arsenide superconductors | We report low-temperature thermal conductivity down to 40 mK of the
antiferromagnet BaFe$_2$As$_{2}$, which is the parent compound of recently
discovered iron-based superconductors. In the investigated temperature range
below 4 K, the thermal conductivity $\kappa$ is well described by the
expression $\kappa$ = $aT$ + $... | 0904.4470v3 |
2009-05-04 | Unusual Fermi surface nesting in parent compounds of iron arsenic high temperature superconductors revealed by Angle Resolved Photoemission Spectroscopy | We use angle resolved photoemission spectroscopy (ARPES) to study the band
structure of BaFe2As2 and CaFe2As2, two of the parent compounds of the iron
arsenic high temperature superconductors. We find clear evidence for band back
folding and hybridization demonstrating that conduction electrons are strongly
affected by... | 0905.0271v1 |
2009-05-12 | Metal - Insulator transition in Fe1.01-xCuxSe | Iron Selenide, Fe1.01Se, the layered parent compound of the recently
discovered superconducting arsenide family, has previously been shown to be non
magnetic and superconducting with a critical temperature of 8 K. Here we show
that copper can be substituted at the iron site in Fe1.01Se up to a solubility
limit of 20-30... | 0905.1875v1 |
2009-05-22 | Intergrain Josephson Currents in Multigap Superconductors: Microscopic Origin of Low Intergrain Critical Current and Its Recovery Potential in Iron-Pnictide Materials | We microscopically examine the intergrain Josephson current in iron-pnictide
superconductors in order to solve the puzzle of why the intergrain current is
much lower than the intragrain one. The theory predicts that the intergrain
Josephson current is significantly reduced by the $\pm$s-wave symmetry when the
incoheren... | 0905.3592v3 |
2009-05-29 | Bragg diffraction and the Iron crust of cold Neutron Stars | If cooled-down neutron stars have a thin atomic crystalline-iron crust, they
must diffract X-rays of appropriate wavelength. If the diffracted beam is to be
visible from Earth, the illuminating source must be very intense and near the
reflecting star. An example is a binary system composed of two neutron stars in
close... | 0905.4837v3 |
2009-06-10 | Three-dimensional electronic structure of superconducting iron pnictides observed by angle-resolved photoemission spectroscopy | We have performed an angle-resolved photoemission spectroscopy (ARPES) study
of the undoped and electron-doped iron pnictides BaFe2\_{-x}CoxAs2 (Ba122)
(x=0, 0.14) and studied the Fermi surfaces (FSs) and band dispersions near the
Fermi level. The FS sheets we observed are consistent with the shrinkage of the
hole-like... | 0906.1846v1 |
2009-06-19 | High Resolution Optical Spectroscopy of a Newly Discovered Post-AGB Star with a Surprising Metallicity in the Globular Cluster M79 | An abundance analysis based on a high-resolution spectrum is presented for a
newly discovered post-AGB star in the globular cluster M79. The surprising
result is that the iron abundance of the star is apparently about 0.6 dex less
than that of the cluster's red giants as reported by published studies
including a recent... | 0906.3706v2 |
2009-06-21 | Multi-gap nodeless superconductivity in iron selenide FeSe$_x$: evident from quasiparticle heat transport | The in-plane thermal conductivity $\kappa$ of the iron selenide
superconductor FeSe$_x$ ($T_c$ = 8.8 K) were measured down to 120 mK and up to
14.5 T ($\simeq 3/4 H_{c2}$). In zero field, the residual linear term
$\kappa_0/T$ at $ T \to 0$ is only about 16 $\mu$W K$^{-2}$ cm$^{-1}$, less
than 4% of its normal state val... | 0906.3852v1 |
2009-06-24 | Doping-dependent pairing symmetry in the Iron-Pnictides | We use the functional renormalization group method to analyze the phase
diagram of a 4-band model for the iron-pnictides subject to band interactions
with certain A_{1g} momentum dependence. We determine the parameter regimes
where an extended s-wave pairing instability with and without nodes emerges. On
the electron-d... | 0906.4475v1 |
2009-06-25 | Doping dependence of the lattice dynamics in Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ studied by Raman spectroscopy | We report Raman scattering spectra of iron-pnictide superconductor
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals with varying cobalt $x$ content.
Upon cooling through the tetragonal-to-orthorhombic transition, we observe a
large splitting of the E$_g$ in-plane phonon modes involving Fe and As
displacements. The splitt... | 0906.4569v1 |
2009-06-26 | A consistent description of the iron dimer spectrum with a correlated single-determinant wave function | We study the iron dimer by using an accurate ansatz for quantum chemical
calculations based on a simple variational wave function, defined by a single
geminal expanded in molecular orbitals and combined with a real space
correlation factor. By means of this approach we predict that, contrary to
previous expectations, t... | 0906.4824v1 |
2009-07-01 | The CTOF measurements and Monte Carlo analyses of neutron spectra for backward direction from iron target irradiated by protons with energies from 400 to 1200 MeV | A calorimetric-time-of-flight (CTOF) technique was used for real-time,
high-precision measurement of neutron spectrum at the angle of 175 degrees from
the initial proton beam direction, which hits a face plane of a cylindrical
iron target of 20 cm in diameter and 25 cm thick. A comparison was performed
between the neut... | 0907.0181v1 |
2009-07-06 | Electrosteric enhanced stability of functional sub-10 nm cerium and iron oxide particles in cell culture medium | Applications of nanoparticles in biology require that the nanoparticles
remain stable in solutions containing high concentrations of proteins and
salts, as well as in cell culture media. In this work, we developed simple
protocols for the coating of sub-10 nm nanoparticles and evaluated the
colloidal stability of dispe... | 0907.1008v1 |
2009-07-07 | Tight binding model for iron pnictides | We propose a five-band tight-binding model for the Fe-As layers of iron
pnictides with the hopping amplitudes calculated within the Slater-Koster
framework. The band structure found in DFT, including the orbital content of
the bands, is well reproduced using only four fitting parameters to determine
all the hopping amp... | 0907.1259v2 |
2009-07-16 | Spin-Phonon Coupling and Superconductivity in Fe Pnictides | We propose a theory of strong spin-lattice and spin-phonon coupling in iron
pnictides and discuss its implications on superconductivity. Strong
magneto-volume effect in iron compounds has long been known as the Invar
effect. Fe pnictides also exhibit this effect, reflected in particular to the
atomic volume of Fe defin... | 0907.2734v1 |
2009-07-22 | Relativistic Broadening of Iron Emission Lines in a Sample of AGN | We present a uniform X-ray spectral analysis of eight type-1 active galactic
nuclei (AGN) that have been previously observed with relativistically broadened
iron emission lines. Utilizing data from the XMM-Newton European Photon Imaging
Camera (EPIC-pn) we carefully model the spectral continuum, taking complex
intrinsi... | 0907.3850v1 |
2009-07-23 | Large specific absorption rates in the magnetic hyperthermia properties of metallic iron nanocubes | We report on the magnetic hyperthermia properties of chemically synthesized
ferromagnetic 11 and 16 nm Fe(0) nanoparticles of cubic shape displaying the
saturation magnetization of bulk iron. The specific absorption rate measured on
16 nm nanocubes is 1690+-160 W/g at 300 kHz and 66 mT. This corresponds to
specific los... | 0907.4063v3 |
2009-07-23 | Superconductivity in the Iron-Pnictide Parent Compound SrFe2As2 | The appearance of superconductivity at ambient pressures in the undoped iron
pnictide parent compound SrFe2As2 is studied experimentally using several
techniques and approaches to aid in understanding the nature of this phase. Low
temperature magnetization measurements of single crystals of SrFe2As2 reveal
diamagnetic ... | 0907.4141v1 |
2009-08-21 | Magnetooptic enhancement and magnetic properties in Fe antidot films with hexagonal symmetry | The magnetooptic and magnetic properties of hexagonal arrays of holes in
optically thin iron films are presented. We analyze their dependence on the
hole radius and compare the results to a continuous iron film of same
thickness. We observe a large enhancement of the magnetooptic Kerr rotation
with respect to that of t... | 0908.3129v2 |
2009-09-02 | Origin of critical-temperature enhancement of an iron-based high-T_c superconductor, LaFeAsO_{1-x}F_{x} : NMR study under high pressure | Nuclear magnetic resonance (NMR) measurements of an iron (Fe)-based
superconductor LaFeAsO_{1-x}F_x (x = 0.08 and 0.14) were performed at ambient
pressure and under pressure. The relaxation rate 1/T_1 for the overdoped
samples (x = 0.14) shows T-linear behavior just above T_c, and pressure
application enhances 1/T_1T s... | 0909.0318v2 |
2009-09-02 | Computational study of boron nitride nanotube synthesis: how catalyst morphology stabilizes the boron nitride bond | In an attempt to understand why catalytic methods for the growth of boron
nitride nanotubes work much worse than for their carbon counterparts, we use
first-principles calculations to study the energetics of elemental reactions
forming N2, B2 and BN molecules on an iron catalyst. We observe that in the
case of these sm... | 0909.0545v1 |
2009-09-07 | On the Crustal Matter of Magnetars | We have investigated some of the properties of dense sub-nuclear matter at
the crustal region (both the outer crust and the inner crust region) of a
magnetar. The relativistic version of Thomas-Fermi (TF) model is used in
presence of strong quantizing magnetic field for the outer crust matter. The
compressed matter in ... | 0909.1173v1 |
2009-09-08 | Molecular dynamics study of hcp/fcc nucleation and growth in bcc iron driven by uniaxial strain | Molecular dynamics simulations are performed to investigate the structural
phase transition in body-centered cubic (bcc) single crystal iron under high
strain rate loading. We study the nucleation and growth of the
hexagonal-close-packed (hcp) and face-centered-cubic (fcc) phases, and their
crystal orientation dependen... | 0909.1407v1 |
2009-09-16 | Chalcogen-height dependent magnetic interactions and magnetic order switching in FeSe$_x$Te$_{1-x}$ | Magnetic properties of iron chalcogenide superconducting materials are
investigated using density functional calculations. We find the stability of
magnetic phases is very sensitive to the height of chalcogen species from the
Fe plane: while FeTe with optimized Te height has the double-stripe-type
$(\pi,0)$ magnetic or... | 0909.2916v1 |
2009-09-16 | Superconductivity at 39 K in New Iron Pnictide Oxide (Fe2As2)(Sr4(Mg,Ti)2O6) | We have discovered a new iron pnictide oxide superconductor
(Fe2As2)(Sr4(Mg,Ti)2O6). This material is isostructual with (Fe2As2)(Sr4M2O6)
(M = Sc, Cr), which was found in our previous study. The structure of this
compound is tetragonal with a space group of P4/nmm and consists of the
anti-fluorite type FeAs and perovsk... | 0909.2945v3 |
2009-09-21 | Study of sdO models. Pulsation Analysis | We have explored the possibility of driving pulsation modes in models of sdO
stars in which the effects of element diffusion, gravitational settling and
radiative levitation have been neglected so that the distribution of iron-peak
elements remains uniform throughout the evolution. The stability of these
models was det... | 0909.3778v1 |
2009-10-01 | First-Principles Study for the Anisotropy of Iron-based Superconductors toward Power and Device Applications | Performing the first-principles calculations, we investigate the anisotropy
in the superconducting state of iron-based superconductors to gain an insight
into their potential applications. The anisotropy ratio $\gamma_\lambda$ of the
c-axis penetration depth to the ab-plane one is relatively small in BaFe2As2
and LiFeA... | 0910.0107v1 |
2009-10-12 | Neutrino and Antineutrino Inclusive Charged-current Cross Section Measurements with the MINOS Near Detector | The energy dependence of the neutrino-iron and antineutrino-iron inclusive
charged-current cross sections and their ratio have been measured using a
high-statistics sample with the MINOS Near Detector exposed to the NuMI beam
from the Main Injector at Fermilab. Neutrino and antineutrino fluxes were
determined using a l... | 0910.2201v2 |
2009-10-30 | Antiphase magnetic boundaries in iron-based superconductors: A first-principle density-functional theory study | Superconductivity arises in the layered iron-pnictide compounds when magnetic
long range order disappears. We use first principles density functional methods
to study magnetic arrangements that may compete with long range order near the
phase boundary. Specifically, we study the energetics and charge density
distributi... | 0911.0036v1 |
2009-11-01 | Andreev bound states in iron pnictide superconductors | Recently, Andreev bound states in iron pnictide have been proposed as an
experimental probe to detect the relative minus sign in the $s_\pm$-wave
pairing. While previous theoretical investigations demonstrated the feasibility
of the approach, the local density of states in the midgap regime is small,
making the detecti... | 0911.0175v1 |
2009-11-02 | Spin-Density-Wave and Asymmetry of Coherence Peaks in iron-Pnictide Superconductors from a two-orbital model | We study theoretically the coexistence of the spin-density-wave (SDW) and
superconductivity in electron-doped iron-pnictide superconductors based on the
two orbital model and Bogoliubov-de Gennes equations. The phase diagram is
mapped out and the evolution of the Fermi surface as the doping varies is
presented. The loc... | 0911.0385v3 |
2009-11-02 | Non-stoichiometry and the magnetic structure of Sr2CrO3FeAs | The iron arsenide Sr2CrO3FeAs with the tetragonal Sr2GaO3CuS-type structure
was synthesized and its crystal structure re-determined by neutron powder
diffraction. In contrast to previous X-ray crystallographic studies, a mixed
occupancy of chromium and iron was found within the FeAs4/4 layer (93+/-1% Fe :
7+/-1% Cr). W... | 0911.0450v2 |
2009-11-09 | Small-q Phonon Mediated Unconventional Superconductivity in the Iron Pnictides | We report self-consistent calculations of the gap symmetry for the iron-based
high-temperature superconductors using realistic small-q phonon mediated
pairing potentials and four-band energy dispersions. When both electron and
hole Fermi surface pockets are present, we obtain the nodeless $s_\pm$ state
that was first e... | 0911.1461v3 |
2009-11-10 | Fermi-liquid, non-Fermi-liquid, and Mott phases in iron pnictides and cuprates | The role of Coulomb correlations in the iron pnictide LaFeAsO is studied by
generalizing exact diagonalization dynamical mean field theory to five
orbitals. For rotationally invariant Hund's rule coupling a continuous
transition from a paramagnetic Fermi-liquid phase to a non-Fermi-liquid
metallic phase exhibiting froz... | 0911.1940v2 |
2009-11-17 | A re--analysis of the iron line in the XMM-Newton data from the low/hard state in GX339--4 | The detection of an extremely broad iron line in XMM-Newton MOS data from the
low/hard state of the black hole binary GX339-4 is the only piece of evidence
which unambiguously conflicts with the otherwise extremely successful truncated
disc interpretation of this state. However, it also conflicts with some aspect
of ob... | 0911.3243v2 |
2009-11-19 | Magnetic impurity resonance states and symmetry of the superconducting order parameter in iron-based superconductors | We investigate the effect of magnetic impurities on the local quasiparticle
density of states (LDOS) in iron-based superconductors. Employing the
two-orbital model where 3$d$ electron and hole conduction bands are hybridizing
with the localized $f$-orbital of the impurity spin, we investigate how various
symmetries of ... | 0911.3738v2 |
2009-11-20 | HTSC-glue in doped copper oxides and iron pnictides: mobile CT-excitons within in-plane Ginzburg HTSC-sandwich | It is demonstrated that high critical temperature of superconducting
transition in cuprates and new iron-based superconductors is reached because of
the Little-Ginzburg exciton mechanism of HTSC when Cooper pairing of mobile
charge carriers is mediated by excitons which characteristic energy is
essentially higher than ... | 0911.4089v1 |
2009-11-27 | Superconductivity in iron telluride thin films under tensile stress | By realizing in thin films a tensile stress state, superconductivity of 13 K
was introduced into FeTe, an non-superconducting parent compound of the iron
pnictides and chalcogenides, with transition temperature higher than that of
its superconducting isostructural counterpart FeSe. For these tensile stressed
films, the... | 0911.5282v1 |
2009-11-30 | Stochastic statistical theory of nucleation and evolution of nano-sized precipitates in alloys with application to precipitation of copper in iron | The consistent and computationally efficient stochastic statistical approach
(SSA) is suggested to study kinetics of nucleation and evolution of nano-sized
precipitates in alloys. An important parameter of the theory is the size of
locally equilibrated regions at the nucleation stage which is estimated using
the "maxim... | 0911.5558v2 |
2009-12-02 | Vortex as a probe - suggested measurement of the order parameter structure in iron-based superconductors | Impurities, inevitably present in all samples, induce elastic transitions
between quasiparticle states on the contours of constant energy. These
transitions may be seen in Fourier transformed scanning tunneling spectroscopy
experiments, sorted by their momentum transfer. In a superconductor, anomalous
scattering in the... | 0912.0527v2 |
2009-12-08 | About chemical composition of the primary cosmic radiation at ultra-high energies | The fluxes of electrons, positrons, gammas, Cherenkov photons and muons in
individual extensive air showers induced by the primary protons and helium,
oxygen and iron nuclei at the level of observation have been estimated with
help of the code CORSICA 6.616. The comparison show that the values of the
function Xi**2 per... | 0912.1478v1 |
2009-12-08 | Neutron diffraction study on phase transition and thermal expansion of SrFeAsF | The magnetic ordering and crystal structure of iron pnictide SrFeAsF was
investigated by using neutron powder diffraction method. With decreasing
temperature, the tetragonal to orthorhombic phase transition is found at 180 K,
while the paramagnetic to antiferromagnetic phase transition set in at 133 K.
Similar to the p... | 0912.1530v1 |
2009-12-09 | Superconductivity in New Iron Pnictide Oxide (Fe2As2)(Sr4(Mg,Ti)2O6) | We have discovered a new iron pnictide oxide superconductor
(Fe2As2)(Sr4(Mg,Ti)2O6). This material is isostructual with (Fe2As2)(Sr4M2O6)
(M = Sc, Cr, V), which were found in previous studies. The structure of this
compound is tetragonal with a space group of P4/nmm and consists of the
anti-fluorite type FeAs layer and... | 0912.1840v1 |
2009-12-10 | Phase diagram and Gap anisotropy in Iron-Pnictide Superconductors | Using the fluctuation-exchange (FLEX) approximation we study an effective
five-band Hubbard model for iron-pnictide superconductors obtained from the
first-principles band structure. We preclude deformations of the Fermi surface
due to electronic correlations by introducing a static potential, which mimics
the effect o... | 0912.1893v2 |
2009-12-10 | Orbital Fluctuation Mediated Superconductivity in Iron Pnictides: Analysis of Five Orbital Hubbard-Holstein Model | In iron pnictides, we find that the moderate electron-phonon interaction due
to the Fe-ion oscillation can induce the critical d-orbital fluctuations,
without being prohibited by the Coulomb interaction. These fluctuations give
rise to the strong pairing interaction for the s-wave superconducting (SC)
state without sig... | 0912.1975v2 |
2009-12-11 | Superconductivity in a Two-Orbital Hubbard Model with Electron and Hole Fermi Pockets: Application in Iron Oxypnictide Superconductors | We investigate the electronic states of a one-dimensional two-orbital Hubbard
model with band splitting by the exact diagonalization method. The Luttinger
liquid parameter $K_{\rho}$ is calculated to obtain superconducting (SC) phase
diagram as a function of on-site interactions: the intra- and inter-orbital
Coulomb $U... | 0912.2173v1 |
2009-12-16 | Strong electron correlations in the normal state of FeSe0.42Te0.58 | We investigate the normal state of the '11' iron-based superconductor
FeSe0.42Te0.58 by angle resolved photoemission. Our data reveal a highly
renormalized quasiparticle dispersion characteristic of a strongly correlated
metal. We find sheet dependent effective carrier masses between ~ 3 - 16 m_e
corresponding to a mas... | 0912.3152v2 |
2009-12-17 | Universal Decomposition of the Low-Frequency Conductivity Spectra of Iron-Pnictides Uncovering Fermi-Liquid Behavior | Infrared reflectivity measurements on 122 iron-pnictides reveal the existence
of two electronic subsystems. The one gapped due to the spin-density-wave
transition in the parent materials, such as EuFe$_2$As$_{2}$, is responsible
for superconductivity in the doped compounds, like
Ba(Fe$_{0.92}$Co$_{0.08})_2$As$_{2}$ and... | 0912.3334v2 |
2009-12-18 | Coexistence between superconducting and spin density wave states in iron-based superconductors: Ginzburg-Landau analysis | We consider the interplay between superconducting (SC) and commensurate
spin-density-wave (SDW) orders in iron-pnictides by analyzing a multiple order
Ginzburg-Landau free energy. We are particularly interested in whether the
doping-induced transition between the two states is first order, or the two
pure phases are se... | 0912.3556v1 |
2009-12-21 | Possible origin of the reduced magnetic moment in iron pnictides: A dynamical mean field theory study | We investigate the phase diagram of a two-band frustrated Hubbard model in
the framework of dynamical mean field theory. While a first-order phase
transition occurs from a paramagnetic (PM) metal to an antiferromagnetic (AF)
insulator when both bands are equally frustrated, an intermediate AF metallic
phase appears in ... | 0912.4024v2 |
2010-01-07 | Superconductivity without magnetism in LiFeAs | The particular shape of the Fermi surface can give rise to a number of
collective quantum phenomena in solids, such as density wave orderings or even
superconductivity. In many new iron superconductors this shape, the 'nested'
Fermi surface, is indeed observed, but its role in the formation of
spin-density waves or sup... | 1001.1147v1 |
2010-01-12 | Magnetic form factor of SrFe$_2$As$_2$ | Neutron diffraction measurements have been carried out to investigate the
magnetic form factor of the parent SrFe2As2 system of the iron-based
superconductors. The general feature is that the form factor is approximately
isotropic in wave vector, indicating that multiple d-orbitals of the iron atoms
are occupied as exp... | 1001.1941v1 |
2010-01-22 | X-ray spectroscopy of the hot has in the M31 bulge | We present an X-ray spectroscopic study of the nuclear region of the M31
bulge, based on observations of the Xmm-Newton Reflection Grating
Spectrometers. The obtained high-resolution grating spectra clearly show
individual emission lines of highly-ionized iron and oxygen, which
unambiguously confirm the presence of dif... | 1001.4058v1 |
2010-01-30 | Magnetic properties of iron pnictides from spin-spiral calculations | The wave-vector (q) and doping dependences of the magnetic energy, iron
moment, and effective exchange interactions in LaFeAsO, BaFe2As2, and SrFe2As2\
are studied by self-consistent LSDA calculations for co-planar spin spirals.
For the undoped compounds, the calculated total energy, E(q), reaches its
minimum at q corr... | 1002.0061v1 |
2010-02-08 | Theory of itinerant magnetic excitations in the SDW phase of iron-based superconductors | We argue that salient experimental features of the magnetic excitations in
the SDW phase of iron-based superconductors can be understood within an
itinerant model. We identify a minimal itinerant model and use a multi-band RPA
treatment of the dynamical spin susceptibility. Weakly-damped spin-waves are
found near the o... | 1002.1668v2 |
2010-02-09 | Pressure-induced high-Tc superconducting phase in FeSe: correlation between anion height and Tc | In this study, we performed high-pressure electrical resistivity measurements
of polycrystalline FeSe in the pressure range of 1-16.0 GPa at temperatures of
4-300 K. A precise evaluation of Tc from zero-resistivity temperatures revealed
that Tc shows a slightly distorted dome-shaped curve, with maximum Tc (30 K) at
6 G... | 1002.1832v2 |
2010-02-09 | Normal state charge dynamics of Fe1.06Te0.88S0.14 superconductor probed with infrared spectroscopy | We have used optical spectroscopy to probe the normal state electrodynamic
response of Fe$_{1.06}$Te$_{0.88}$S$_{0.14}$, a member of the 11 family of
iron-based superconductors with T$_c$= 8 K. Measurements have been conducted
over a wide frequency range (50 - 50000 cm$^{-1}$) at selected temperatures
between 10 and 30... | 1002.1948v1 |
2010-02-10 | Half-metallic Antiferromagnet BaCrFeAs2 | First-principles calculations and a tight-binding analysis predict that the
iron-pnictide BaCrFeAs2 is a promising candidate for half-metallic material
with fully-compensated magnetization. The transition-metal ions Cr and Fe
prefer the three-dimensional intervening lattice, which yields the
antiferromagnetic order of ... | 1002.2018v2 |
2010-02-16 | Orbital Ordering and Unfrustrated $(π,0)$ Magnetism from Degenerate Double Exchange in the Iron Pnictides | The magnetic excitations of the iron pnictides are explained within a
degenerate double-exchange model. The local-moment spins are coupled by
superexchanges $J_1$ and $J_2$ between nearest and next-nearest neighbors,
respectively, and interact with the itinerant electrons of the degenerate
$d_{xz}$ and $d_{yz}$ orbital... | 1002.3165v3 |
2010-02-17 | Nodes in the Gap Function of LaFePO, the Gap Function of the Fe(Se,Te) Systems, and the STM Signature of the s$_{\pm}$ Pairing | We reiterate, in more details, our previous proposal of using quasi-particle
interference to determine the pairing form factor in iron-based
superconductors. We also present our functional renormalization group(FRG)
results on LaFePO and Fe(Se,Te) superconductors. In particular we found that
the leading pairing channel... | 1002.3358v2 |
2010-02-18 | Nanocrystal Growth on Graphene with Various Degrees of Oxidation | We show a general two-step method to grow hydroxide and oxide nanocrystals of
the iron family elements (Ni, Co, Fe) on graphene with two degrees of
oxidation. Drastically different nanocrystal growth behaviors were observed on
low-oxidation graphene sheets (GS) and highly oxidized graphite oxide (GO) in
hydrothermal re... | 1002.3435v1 |
2010-02-24 | Doping dependence of spin fluctuations and electron correlations in iron pnictides | Doping dependence of the spin fluctuations and the electron correlations in
the effective five-band Hubbard model for iron pnictides is investigated using
the fluctuation-exchange approximation. For a moderate hole doping, we find a
dominant low-energy spin excitation at Q=(\pi,0), which becomes critical at low
tempera... | 1002.4471v2 |
2010-02-25 | Electronic correlations and unusual superconducting response in the optical properties of the iron-chalcogenide FeTe0.55Se0.45 | The in-plane complex optical properties of the iron-chalcogenide
superconductor FeTe0.55Se0.45 have been determined above and below the critical
temperature Tc = 14 K. At room temperature the conductivity is described by a
weakly-interacting Fermi liquid; however, below 100 K the scattering rate
develops a frequency de... | 1002.4846v2 |
2010-02-28 | Iron Rings, Doctor Honoris Causa Raoul Bott, Carl Herz, and a Hidden Hand | The degree of Doctor of Sciences, honoris causa, was conferred on Raoul Bott
by McGill University in 1987. Much of the work to make this happen was done by
Carl Herz. Some of the author's personal recollections of both professors are
included, along with some context for the awarding of this degree and ample
historical... | 1003.0152v1 |
2010-03-01 | Minimum Radii of Super-Earths: Constraints from Giant Impacts | The detailed interior structure models of super-Earth planets show that there
is degeneracy in the possible bulk compositions of a super-Earth at a given
mass and radius, determined via radial velocity and transit measurements,
respectively. In addition, the upper and lower envelopes in the mass--radius
relationship, c... | 1003.0451v1 |
2010-03-03 | Atomic data activities by the OP and IP consortia: past, present and new perspectives within the VAMDC | The Opacity Project (OP) and Iron Project (IP) are pioneering international
collaborations which have been computing, for more than 25 years, massive
atomic data sets for astrophysical applications. We review the data activities
that have been carried out, namely curation, analysis and preservation, and the
development... | 1003.0843v1 |
2010-03-04 | Zeeman Relaxation of Cold Atomic Iron and Nickel in Collisions with 3He | We have measured the ratio of the diffusion cross-section to the angular
momentum reorientation cross-section in the colliding Fe-3He and Ni-3He
systems. Nickel (Ni) and iron (Fe) atoms are introduced via laser ablation into
a cryogenically cooled experimental cell containing cold (< 1 K) 3He buffer
gas. Elastic collis... | 1003.1106v1 |
2010-03-08 | Design and construction of a novel tribometer with on-line topography and wear measurement | We present a novel experimental platform that links topographical and
material changes with the friction and wear behavior of oil-lubricated metal
surfaces. This concept combines state-of-the-art methods for the analysis of
the surface topography on the micro- and nano-scale with the online measurement
of wear. At the ... | 1003.1638v1 |
2010-03-08 | Orbital-transverse density-wave instabilities in iron-based superconductors | Besides the conventional spin-density-wave (SDW) state, a new kind of
orbital-transverse density-wave (OTDW) state is shown to exist generally in
multi-orbital systems. We demonstrate that the orbital character of Fermi
surface nesting plays an important role in density responses. The relationship
between antiferromagn... | 1003.1660v2 |
2010-03-29 | Topological and Transport Properties of Dirac Fermions in Antiferromagnetic Metallic Phase of Iron-Based Superconductors | We investigate Dirac fermions in the antifferomagnetic metallic state of
iron-based superconduc- tors. Deriving an effective Hamiltonian for Dirac
fermions, we reveal that there exist two Dirac cones carrying the same
chirality, contrary to graphene, compensated by a Fermi surface with a
quadratic energy dispersion as ... | 1003.5469v3 |
2010-04-01 | Ambegaokar-Baratoff relations of Josephson critical current in heterojunctions with multi-gap superconductors | An extension of the Ambegaokar-Baratoff relation to a
superconductor-insulator-superconductor (SIS) Josephson junction with multiple
tunneling channels is derived. Appling the resultant relation to a SIS
Josephson junction formed by an iron-based (five-band) and a single-band
Bardeen-Cooper-Schrieffer (BCS) type superc... | 1004.0044v2 |
2010-04-09 | Electrodynamics of electron doped iron-pnictide superconductors: Normal state properties | The electrodynamic properties of Ba(Fe$_{0.92}$Co$_{0.08})_2$As$_{2}$ and
Ba(Fe$_{0.95}$Ni$_{0.05})_As$_{2}$ single crystals have been investigated by
reflectivity measurements in a wide frequency range. In the metallic state, the
optical conductivity consists of a broad incoherent background and a narrow
Drude-like co... | 1004.1658v1 |
2010-04-19 | Magnetic and Quasiparticle Excitation Spectra of an Itinerant $J_1-J_2$ Model for Iron Pnictide Superconductors | We calculate the magnetic and quasiparticle excitation spectra of an
itinerant $J_1-J_2$ model for iron pnictides. In addition to an acoustic
spin-wave branch, the magnetic spectrum has a second, optical branch, resulting
from the coupled four-sublattice magnetic structure. The spin-wave velocity has
also a planar dire... | 1004.3187v2 |
2010-04-20 | Leggett mode in a strong-coupling model of iron arsenide superconductors | Using a two-orbital model of the superconducting phase of the pnictides, we
compute the spectrum of the Leggett mode -- a collective excitation of the
phase of the superconducting gap known to exist in multi-gap superconductors --
for different possible symmetries of the superconducting order parameter.
Specifically, w... | 1004.3576v1 |
2010-04-22 | Discovery of K-Shell Emission Lines of Neutral Atoms in the Galactic Center Region | The K-shell emission line of neutral irons from the Galactic center (GC)
region is one of the key for the structure and activity of the GC. The origin
is still open question, but possibly due either to X-ray radiation or to
electron bombarding to neutral atoms. To address this issue, we analyzed the
Suzaku X-ray spectr... | 1004.3891v1 |
2010-04-26 | Orbital Order and Spontaneous Orthorhombicity in Iron Pnictides | A growing list of experiments show orthorhombic electronic anisotropy in the
iron pnictides, in some cases at temperatures well above the spin density wave
transition. These experiments include neutron scattering, resistivity and
magnetoresistance measurements, and a variety of spectroscopies. We explore the
idea that ... | 1004.4611v2 |
2010-04-29 | Large $D-2$ Theory of Superconducting Fluctuations in a Magnetic Field and its Application to Iron-Pnictides | A Ginzburg-Landau approach to fluctuations of a layered superconductor in a
magnetic field is used to show that the interlayer coupling can be incorporated
within an interacting self-consistent theory of a single layer, in the limit of
a large number of neighboring layers. The theory exhibits two phase transitions
-- a... | 1004.5277v3 |
2010-04-30 | Quasiparticle interference in the spin-density wave phase of iron-based superconductors | We propose an explanation for the electronic nematic state observed recently
in parent iron-based superconductors [T.-M. Chuang et al., Science 327, 181
(2010)]. We argue that the quasi-one-dimensional nanostructure identified in
the quasiparticle interference (QPI) is a consequence of the interplay of the
magnetic ($\... | 1004.5460v1 |
2010-04-30 | Coherent interfacial bonding on the FeAs tetrahedron in Fe/Ba(Fe(1-x)Co(x))2As2 bilayers | We demonstrate the growth of epitaxial Fe/Ba(Fe(1-x)Co(x))2As2 (Fe/Ba-122)
bilayers on MgO(001) and LSAT(001) single crystal substrates using Pulsed Laser
Deposition (PLD). By exploiting the metallic nature of the FeAs tetrahedron in
the Ba-122 crystal structure, we achieve a coherent interfacial bond between
bcc iron ... | 1004.5557v1 |
2010-05-03 | Strong Coupling Superconductivity in Iron-Chalcogenide FeTe$_{0.55}$Se$_{0.45}$ | The superconducting order parameter in the iron-chalcogenide superconductor
FeTe$_{0.55}$Se$_{0.45}$ ($T_\textrm{c}$ = 14.2 K) is investigated by
point-contact Andreev reflection spectroscopy. The energy gap magnitude (3.8
meV at 1.70 K) and temperature dependence as extracted from the Andreev
conductance spectra revea... | 1005.0190v1 |
2010-05-04 | High Pressure Synthesis of Indirectly electron-doped 122 Iron Superconductor Sr1-xLaxFe2As2 with a maximum Tc = 22 K | Compounds of Sr1-xLaxFe2As2 were synthesized by solid state reaction at 1273
K, under pressures of 2 or 3 GPa. The Sr1-xLaxFe2As2 phase was dominant up to x
= 0.5, and superconductivity was observed at $x \ge 0.2$. A maximum critical
temperature Tc of 22 K, and a maximum shielding volume fraction of ~70 % were
obtained... | 1005.0528v2 |
2010-05-06 | Electronic structure and possible pseudogap behavior in iron based superconductors | Starting from the simplified analytic model of electronic spectrum of iron -
pnictogen (chalcogen) high - temperature superconductors close to the Fermi
level, we discuss the influence of antiferromagneting (AFM)scattering both for
stoichiometric case and the region of possible short - range order AFM
fluctuations in d... | 1005.0884v4 |
2010-05-12 | Stripe antiferromagnetic correlations in LaFeAsO1-xFx probed by 75As NMR | The anisotropy of the nuclear spin-lattice relaxation rate $1/T_{1}$ of
$^{75}$As was investigated in the iron-based superconductor
LaFeAs(O$_{1-x}$F$_{x}$) ($x = 0.07, 0.11$ and 0.14) as well as LaFeAsO. While
the temperature dependence of the normal-state $1/T_1T$ in the superconducting
(SC) $x = 0.07$ is different f... | 1005.2013v2 |
2010-05-12 | Striped-magnetic-order suppresses giant optical anisotropy and drives structural distortion in iron arsenide superconductors | To examine the role of magnetism in superconductivity of iron-based
superconductors, we first present first-principles optical calculations on
three representative parent compounds: LaFeAsO, BaFe2As2 and LiFeAs. Both
nonmagnetic (NM) and spin-density wave (SDW) with striped antiferromagnetic
order are considered. Due t... | 1005.2121v2 |
2010-05-12 | Charge doping-induced quasiparticle scattering in iron-pnictide superconductors as probed by vortex pinning | Charge doping of iron-pnictide superconductors leads to collective pinning of
flux vortices, whereas isovalent doping does not. Moreover, flux pinning in the
charge-doped compounds is consistently described by the mean-free path
fluctuations introduced by the dopant atoms, allowing for the extraction of the
elastic qua... | 1005.2129v2 |
2010-05-15 | A Theoretical Study of the Equation of States for Crustal Matter of Strongly Magnetized Neutron Stars | We have investigated some of the properties of dense sub-nuclear matter at
the crustal region (both the outer crust and the inner crust region) of a
magnetar. The relativistic version of Thomas-Fermi (TF) model is used in
presence of strong quantizing magnetic field for the outer crust matter. The
compressed matter in ... | 1005.2658v1 |
2010-05-24 | Reduction in iron losses in Indirect Vector-Controlled IM Drive using FLC | This paper describes the use of fuzzy logic controller for efficiency
optimization control of a drive while keeping good dynamic response. At
steady-state light-load condition, the fuzzy controller adaptively adjusts the
excitation current with respect to the torque current to give the minimum total
copper and iron los... | 1005.4265v1 |
2010-06-02 | Local moments and symmetry breaking in metallic PrMnSbO | We report a combined experimental and theoretical investigation of the
layered antimonide PrMnSbO which is isostructural to the parent phase of the
iron pnictide superconductors. We find linear resistivity near room temperature
and Fermi liquid-like T^{2} behaviour below 150 K. Neutron powder diffraction
shows that unf... | 1006.0341v1 |
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