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2010-06-02 | Robust accidental nodes and zeroes and critical quasiparticle scaling in iron-based multiband superconductors | We study multigap superconductivity, with strong angular variations of one of
the gaps, as appropriate for certain iron-based high-temperature
superconductors. We solve the gap equations of this model and find that the
nodes or zeroes in the gap function present at Tc - although purely accidental
-- typically survive d... | 1006.0447v3 |
2010-06-18 | A New Iron Pnictide Oxide (Fe2As2)(Ca5(Mg,Ti)4Oy) and a New Phase in Fe-As-Ca-Mg-Ti-O system | A new layered iron arsenide oxide (Fe2As2)(Ca5(Mg,Ti)4Oy) and its structural
derivative were found in the Fe-As-Ca-Mg-Ti-O system. The crystal structure of
(Fe2As2)(Ca5(Mg,Ti)4Oy) is identical to that of (Fe2As2)(Ca5(Sc,Ti)4Oy), which
was reported in our previous study. The lattice constants of this compound are
a = 3.... | 1006.3769v4 |
2010-06-18 | Inelastic neutron scattering study on the resonance mode in an optimally doped superconductor LaFeAsO$_{0.92}$F$_{0.08}$ | An optimally doped iron-based superconductor LaFeAsO$_{0.92}$F$_{0.08}$ with
$T_c = 29$ K has been studied by inelastic powder neutron scattering. The
magnetic excitation at $Q=1.15$ \AA$^{-1}$ is enhanced below $T_c$, leading to
a peak at $E_{res}\sim13$ meV as the resonance mode, in addition to the
formation of a gap... | 1006.4640v1 |
2010-06-24 | Electronic correlations in iron-pnictide superconductors and beyond; what can we learn from optics | The Coulomb repulsion, impeding electrons' motion, has an important impact on
the charge dynamics. It mainly causes a reduction of the effective metallic
Drude weight (proportional to the so-called optical kinetic energy),
encountered in the optical conductivity, with respect to the expectation within
the nearly-free e... | 1006.4698v1 |
2010-06-27 | The effect of disorder on electronic Raman scattering in the superconducting state of iron pnictides | Electronic Raman scattering measures a polarization-dependent scattering
intensity which can provide information about the location of nodes in the
energy gap of an unconventional superconductor as well as its overall symmetry.
In this paper, we calculate the Raman intensity in the presence of disorder for
several mode... | 1006.5245v1 |
2010-07-06 | Spin waves in the (0,pi) and (0,pi,pi) ordered SDW states of the t-t' Hubbard model: Application to doped iron pnictides | Spin waves in (0,pi) and (0,pi,pi) ordered spin-density-wave (SDW) states of
the t-t' Hubbard model are investigated at finite doping. In the presence of
small t', these composite ferro-antiferromagnetic (F-AF) states are found to be
strongly stabilized at finite hole doping due to enhanced carrier-induced
ferromagneti... | 1007.0812v1 |
2010-07-08 | Optical properties of the iron-chalcogenide superconductor FeTe0.55Se0.45 | The complex optical properties of the iron-chalcogenide superconductor
FeTe0.55Se0.45 with Tc=14K have been examined over a wide frequency range for
light polarized in the Fe-Te(Se) planes above and below Tc. At room temperature
the optical response may be described by a weakly-interacting Fermi liquid;
however, just a... | 1007.1447v2 |
2010-07-15 | Absence of an appreciable iron isotope effect on the transition temperature of the optimally doped SmFeAsO_{1-y} superconductor | We report the iron (Fe) isotope effect on the transition temperature (Tc) in
the oxygen-deficient SmFeAsO_{1-y}, a 50 K-class Fe-based superconductor. For
the optimally-doped samples with Tc = 54 K, change of the Fe average atomic
mass (MFe) causes a negligibly small shift in Tc, with the Fe isotope
coefficient (alphaF... | 1007.2666v1 |
2010-07-16 | Fermi surfaces and quasi-particle band dispersions of the iron pnictides superconductor KFe2As2 observed by angle-resolved photoemission spectroscopy | We have performed an angle-resolved photoemission study of the iron pnictide
superconductor KFe2As2 with Tc 4 K. Most of the observed Fermi surfaces show
almost two-dimensional shapes, while one of the quasi-particle bands near the
Fermi level has a strong dispersion along the kz direction, consistent with the
result o... | 1007.2698v2 |
2010-07-20 | Conductivity anisotropy in the antiferromagnetic state of iron pnictides | Recent experiments on iron pnictides have uncovered a large in-plane
resistivity anisotropy with a surprising result: the system conducts better in
the antiferromagnetic x direction than in the ferromagnetic y direction. We
address this problem by calculating the ratio of the Drude weight along the x
and y directions, ... | 1007.3483v2 |
2010-07-22 | Stratification of the elements in the atmospheres of blue horizontal-branch stars | Blue horizontal-branch (BHB) stars with $T_{\rm eff}$ approximately larger
than 11500 K show several observational anomalies. In globular clusters, they
exhibit low rotational velocities, abundance anomalies (as compared to cluster
abundances), photometric jumps and gaps and spectroscopic gravities lower than
predicted... | 1007.4023v1 |
2010-08-08 | MHD Simulations of Core Collapse Supernovae with Cosmos++ | We performed 2D, axisymmetric, MHD simulations with Cosmos++ in order to
examine the growth of the magnetorotational instability (MRI) in core--collapse
supernovae. We have initialized a non--rotating 15 solar mass progenitor,
infused with differential rotation and poloidal magnetic fields. The collapse
of the iron cor... | 1008.1422v1 |
2010-08-29 | Quasiparticle interference in iron-based superconductors | We systematically calculate quasiparticle interference (QPI) signatures for
the whole phase diagram of iron-based superconductors. Impurities inherent in
the sample together with ordered phases lead to distinct features in the QPI
images that are believed to be measured in spectroscopic imaging-scanning
tunneling micro... | 1008.4930v2 |
2010-09-01 | Uniaxial "nematic-like" electronic structure and Fermi surface of untwinned CaFe2As2 | Obtaining the electronic structure of the newly discovered iron-based
superconductors is the key to understanding the mechanism of their
high-temperature superconductivity. We used angle-resolved photoemission
spectroscopy (ARPES) to make direct measurements of the electronic structure
and Fermi surface (FS) of the unt... | 1009.0271v1 |
2010-09-04 | Electronic dispersion anomalies in the iron pnictide superconductor Ba_{1-x}K_xFe_2As_2 | The pairing mechanism in the iron-pnictide superconductors is still unknown.
However, similarities to the cuprate high-temperature superconductors suggest
that a similar mechanism may be at work. Recently, careful experimental studies
of the spin excitation spectrum revealed, like in the cuprates, a strong
temperature ... | 1009.0849v1 |
2010-09-20 | Hydrogen in $α$ iron: modification of elastic properties and solubility in strain fields | The effect of interstitial hydrogen on the elastic properties of
$\alpha$-iron is investigated using \textit{ab initio} density functional
theory. We find that while the overall strength properties are reduced by H,
the effects are mainly due to the resulting local volume expansion. We use
these concentration-dependent... | 1009.3784v4 |
2010-09-30 | Effects of iron doping on the topological insulator surfaces | Topological insulators embody a newly discovered state of matter
characterized by conducting spin-momentum locked surface states that span the
bulk band gap. So far, most of the study on topological insulator surfaces has
been limited to understanding their properties without strong Coulomb
perturbation or breaking of ... | 1009.6216v2 |
2010-10-05 | Structural and magnetic characterization of self-assembled iron oxide nanoparticle arrays | We report about a combined structural and magnetometric characterization of
self-assembled magnetic nanoparticle arrays. Monodisperse iron oxide
nanoparticles with a diameter of 20 nm were synthesized by thermal
decomposition. The nanoparticle suspension was spin-coated on Si substrates to
achieve self-organized arrays... | 1010.0938v1 |
2010-10-12 | Turbulence and magnetic spots at the surface of hot massive stars | Hot luminous stars show a variety of phenomena in their photospheres and in
their winds which still lack clear physical explanations at this time. Among
these phenomena are non-thermal line broadening, line profile variability
(LPVs), discrete absorption components (DACs), wind clumping and stochastically
excited pulsa... | 1010.2498v1 |
2010-10-18 | Possible three dimensional nodes in the $s{\pm}$ superconducting gap of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ | We examine theoretically the superconducting state of
BaFe$_2$(As$_{1-x}$P$_x$)$_2$, an isovalent doping 122 iron pnictide
superconductor. We construct a three dimensional ten orbital model from first
principles band calculation, and investigate the superconducting gap within the
spin fluctuation mediated pairing mecha... | 1010.3542v2 |
2010-10-18 | Observation of anisotropic diamagnetism above the superconducting transition in iron-pnictide Ba_(1-x)K_xFe2As2 single crystals due to thermodynamic fluctuations | High resolution magnetization measurements performed in a high quality
Ba_(1-x)K_xFe2As2 single crystal allowed to determine the diamagnetism induced
above the superconducting transition by thermally activated Cooper pairs. These
data, obtained with magnetic fields applied along and transverse to the crystal
ab layers,... | 1010.3581v4 |
2010-10-22 | A single-sided linear synchronous motor with a high temperature superconducting coil as the excitation system | Thrust measurements were performed on a coil made of YBa2Cu3O7-d coated
conductor acting as the excitation system of a single-sided linear synchronous
motor. The superconducting coil was a single pancake in the shape of a
racetrack with 100 turns, the width and effective lengths were 42 mm and 84 mm,
respectively. The ... | 1010.4775v1 |
2010-10-25 | Discovery Prospects for a Supernova Signature of Biogenic Origin | Approximately 2.8 Myr before the present our planet was subjected to the
debris of a supernova explosion. The terrestrial proxy for this event was the
discovery of live atoms of 60Fe in a deep-sea ferromanganese crust. The
signature for this supernova event should also reside in magnetite Fe3O4
microfossils produced by... | 1010.5109v3 |
2010-10-28 | Magnetism and Disorder Effects on muSR Measurements of the Magnetic Penetration Depth in Iron-Based Superconductors | It is shown that attempts to accurately deduce the magnetic penetration depth
of overdoped BaFe_{1.82}Co_{0.18}As2 single crystals by transverse-field muon
spin rotation (TF-muSR) are thwarted by field-induced magnetic order and strong
vortex-lattice disorder. We explain how substantial deviations from the
magnetic fie... | 1010.6046v1 |
2010-11-03 | Electrostatic fluctuations promote the dynamical transition in proteins | Atomic displacements of hydrated proteins are dominated by phonon vibrations
at low temperatures and by dissipative large-amplitude motions at high
temperatures. A crossover between the two regimes is known as a dynamical
transition. Recent experiments indicate a connection between the dynamical
transition and the diel... | 1011.1023v1 |
2010-11-06 | Search for pressure induced superconductivity in CeFeAsO and CeFePO iron pnictides | The CeFeAsO and CeFePO iron pnictide compounds were studied via electrical
transport measurements under high-pressure. In CeFeAsO polycrystals, the
magnetic phases involving the Fe and Ce ions coexist up to 15 GPa, with no
signs of pressure-induced superconductivity up to 50 GPa. For the CeFePO single
crystals, pressur... | 1011.1593v2 |
2010-11-07 | Spectrophotometric variability of the magnetic CP star 56 Arietis in spectral region from 1950 to 3200 A | The spectrophotometric variability of the magnetic CP star 56 Arietis (56
Ari) in the ultraviolet spectral region from 1950 to 3200 A is investigated.
This study is based on the archival International Ultraviolet Explorer data
obtained at different phases of the rotational cycle. The brightness of 56 Ari
is not constan... | 1011.1659v1 |
2010-11-12 | Antiferromagnetic ordering in the absence of a structural distortion in Ba(Fe{1-x}Mn{x})2As2 | Neutron and x-ray diffraction studies of Ba(Fe{1-x}Mn{x})2As2 for low doping
concentrations (x <= 0.176) reveal that at a critical concentration, 0.102 < x
< 0.118, the tetragonal-to-orthorhombic transition abruptly disappears whereas
magnetic ordering with a propagation vector of (1/2 1/2 1) persists. Among all
of the... | 1011.2816v1 |
2010-11-14 | Strong spin resonance on BaFe2(As0.65P0.35)2 with Tc = 30 K | We performed inelastic neutron scattering on powder sample of the P-doped
iron-based superconductor BaFe2(As0.65P0.35)2 with Tc = 30K, whose
superconducting (SC) order parameter is expected to have line nodes. We have
observed spin resonance at Q $\sim$ 1.2{\AA}^{-1} and E=12 meV in the SC state.
The resonance enhancem... | 1011.3191v1 |
2010-11-26 | Advantageous grain boundaries in iron pnictide superconductors | High critical temperature superconductors have zero power consumption and
could be used to produce ideal electric power lines. The principal obstacle in
fabricating superconducting wires and tapes is grain boundaries-the
misalignment of crystalline orientations at grain boundaries, which is
unavoidable for polycrystals... | 1011.5721v2 |
2010-12-03 | Origin of In-Plane Anisotropy in Optical Conductivity for Antiferromagnetic Metallic Phase of Iron Pnictides | We examine the optical conductivity in antiferromagnetic (AFM) iron pnictides
by mean-field calculation in a five-band Hubbard model. The calculated spectra
are well consistent with the in-plane anisotropy observed in the measurements,
where the optical conductivity along the direction with the AFM alignment of
neighbo... | 1012.0670v2 |
2010-12-13 | Accretion and diffusion in the DAZ white dwarf GALEX J1931+0117 | We present an analysis of high-dispersion and high signal-to-noise ratio
spectra of the DAZ white dwarf GALEX J1931+0117. The spectra obtained with the
VLT-Kueyen/UV-Visual Echelle Spectrograph show several well-resolved Si II
spectral lines enabling a study of pressure effects on line profiles. We
observed large Stark... | 1012.2644v1 |
2010-12-14 | Electron and hole Dirac cone states in-pairs in Ba(FeAs)$_2$ confirmed by magnetoresistance | The quantum transport of Dirac cone states in the iron pnictide Ba(FeAs)$_2$
with a d-\,multiband system is studied by using single crystal samples. The
transverse magnetoresistance develops linearly against magnetic field at low
temperatures. The transport phenomena are interpreted in terms of the 0$^{th}$
Landau leve... | 1012.3029v4 |
2010-12-15 | Theory of two magnon Raman scattering in antiferromagnetic iron pnictides | Although the parent iron-based pnictides and chalcogenides are itinerant
antiferromagnets, the use of local moment picture to understand their magnetic
properties is still widespread. We study magnetic Raman scattering from a local
moment perspective for various quantum spin models proposed for this new class
of superc... | 1012.3254v2 |
2010-12-21 | Resistivity scaling in 1111 iron-pnictide superconductors | We show that the zero field normal-state resistivity above Tc for various
levels of electron doping - both for LaO1-xFxFeAs (La-1111) and SmO1-xFxFeAs
(Sm-1111) members of the 1111-iron-pnictide superconductor family - can be
scaled in a broad temperature range from 20 to 300 K onto single curves for
underdoped La-1111... | 1012.4682v1 |
2010-12-23 | Revised Phase Diagram for FeTe1-xSex system with less excess Fe atoms | We observed bulk superconductivity in the FeTe1-xSex crystals with a low Se
concentration after the excess Fe atoms existing unavoidably in crystals
as-grown are partially removed by means of annealing in the air. A revised
magnetism and superconductivity phase diagram is obtained via resistivity and
magnetic susceptib... | 1012.5188v1 |
2010-12-26 | Electronic and magnetic structures of ternary iron selenides AFe$_2$Se$_2$ (A=K, Cs, or Tl) | By the first-principles electronic structure calculations, we find that the
ground state of ternary iron selenides AFe$_2$Se$_2$ (A=K, Cs, or Tl) is in a
bi-collinear antiferromagnetic order, in which the Fe local moments
($\sim2.8\mu_B$) align ferromagnetically along a diagonal direction and
antiferromagnetically alon... | 1012.5536v1 |
2010-12-29 | Absence of holelike Fermi surface in superconducting K0.8Fe1.7Se2 revealed by ARPES | We have performed an angle-resolved photoemission spectroscopy study of the
new iron-based superconductor K0.8Fe1.7Se2 (Tc ~ 30 K). Clear band dispersion
is observed with the overall bandwidth renormalized by a factor of 2.5 compared
to our local density approximation calculations, indicating relatively strong
correlat... | 1012.6017v1 |
2010-12-30 | Possible Signs of Water and Differentiation in a Rocky Exoplanetary Body | Spitzer observations reveal the presence of warm debris from a tidally
destroyed rocky and possibly icy planetary body orbiting the white dwarf GD 61.
Ultraviolet and optical spectroscopy of the metal-contaminated stellar
photosphere reveal traces of hydrogen, oxygen, magnesium, silicon, iron, and
calcium. The nominal ... | 1101.0158v2 |
2011-01-03 | Observation of a first order phase transition in fluid iron at pressures of 3 to 5 GPa | Direct measurements of resistivity and caloric equation of state have been
performed for fluid iron at pressures of 2 to 12 GPa in a wide density range.
We found that the isochoric temperature coefficient of resistivity becomes
negative, and this is considered as an indication of the metal-to-nonmetal
transition, when ... | 1101.0487v2 |
2011-01-03 | Electronic Structure and Mott Localization in Iron Deficient TlFe$_{1.5}$Se$_2$ with Superstructures | Electronic structure and magnetic properties for iron deficient
TlFe$_{2-x}$Se$_2$ compounds are studied by first-principles calculations. We
find that for the case of $x=0.5$ with a Fe-vacancy ordered orthorhombic
superstructure, the ground state exhibits a stripe-like antiferromagnetic
ordering and opens a sizable ba... | 1101.0533v2 |
2011-01-03 | Infrared spectrum and its implications for the electronic structure of the semiconducting iron selenide K$_{0.83}$Fe$_{1.53}$Se$_2$ | We report an infrared spectroscopy study on K$_{0.83}$Fe$_{1.53}$Se$_2$, a
semiconducting parent compound of the new iron-selenide system. The major
spectral features are found to be distinctly different from all other Fe-based
superconducting systems. Our measurement revealed two peculiar spectral
structures: a double... | 1101.0572v3 |
2011-01-04 | Electronic structure and magnetic properties of the graphene/Fe/Ni(111) intercalation-like system | The electronic structure and magnetic properties of the graphene/Fe/Ni(111)
system were investigated via combination of the density functional theory
calculations and electron-spectroscopy methods. This system was prepared via
intercalation of thin Fe layer (1 ML) underneath graphene on Ni(111) and its
inert properties... | 1101.0771v1 |
2011-01-17 | The upper critical field and its anisotropy in LiFeAs | The upper critical field $\mu_0H_{c2}(T_c)$ of LiFeAs single crystals has
been determined by measuring the electrical resistivity using the facilities of
pulsed magnetic field at Los Alamos. We found that $\mu_0H_{c2}(T_c)$ of LiFeAs
shows a moderate anisotropy among the layered iron-based superconductors; its
anisotro... | 1101.3159v1 |
2011-01-19 | 77Se NMR Evidence of Strongly Coupled Superconductivity in K0.8Fe2-xSe2 | We report the 77Se NMR Knight shift and spin-lattice relaxation studies on
the superconducting state of the ternary iron selenide K0.8Fe2-xSe2 with Tc~30
K. Just below Tc, the Knight shift 77Kn shows an immediate drop, indicating a
singlet pairing. The spin-lattice relaxation rate 1/77T1 decreases rapidly in
the temper... | 1101.3687v1 |
2011-02-01 | Comprehensive study of the magnetic stars HD 5797 and HD 40711 with large chromium and iron overabundances | We present the results of a comprehensive study of the chemically peculiar
stars HD 5797 and HD 40711. The stars have the same effective temperature, Teff
= 8900 K, and a similar chemical composition with large iron (+1.5 dex) and
chromium (+3 dex) overabundances compared to the Sun. The overabundance of
rare-earth ele... | 1102.0150v1 |
2011-02-02 | Cation vacancy order in the K0.8+xFe1.6-ySe2 system: five-fold cell expansion accommodates 20% tetrahedral vacancies | Ordering of the tetrahedral site vacancies in two crystals of refined
compositions K0.93(1)Fe1.52(1)Se2 and K0.862(3)Fe1.563(4)Se2 produces a
fivefold expansion of the parent ThCr2Si2 unit cell in the ab plane which can
accommodate 20% vacancies on a single site within the square FeSe layer. The
iron charge state is ma... | 1102.0488v3 |
2011-02-10 | Impact of Valence States on Superconductivity of Oxygen Incorporated Iron Telluride and Iron Selenide Films | We report on the local electronic structure of oxygen incorporated FeTe and
FeSe films and how this relates to superconductivity observed in these films.
In the case of FeTe, intially grown films are measured to be
non-superconducting, but become superconducting following oxygen incorporation.
In FeSe the opposite happ... | 1102.2155v1 |
2011-02-15 | Magnetic and superconducting instabilities in a hybrid model of itinerant/localized electrons for iron pnictides | We study a unified mechanism for spin-density-wave (SDW) and
superconductivity in a minimal model, in which itinerant electrons and local
moments coexist as previously proposed for the iron pnictides [EPL, 88, 17010
(2009)]. The phase diagram obtained at the mean field level is in qualitative
agreement with the experim... | 1102.3200v2 |
2011-02-17 | Superconductivity tuned by the iron vacancy order in K$_{\bf x}$Fe$_{\bf 2-y}$Se$_2$ | Combining in-depth neutron diffraction and systematic bulk studies, we
discover that the $\sqrt{5}\times\sqrt{5}$ Fe vacancy order with its associated
block antiferromagnetic order is the ground state, with varying occupancy ratio
of the iron 16i and vacancy 4d sites, across the phase-diagram of K$_{\bf
x}$Fe$_{\bf 2-y... | 1102.3674v2 |
2011-02-21 | Structural, electronic properties and Fermi surface of ThCr2Si2-type tetragonal KFe2S2, KFe2Se2, and KFe2Te2 phases as parent systems of new ternary iron-chalcogenide superconductors | First principles FLAPW-GGA method was used for the comparative study of the
structural and electronic properties of three related tetragonal ThCr2Si2-type
phases KFe2Ch2, where Ch are S, Se, and Te. The main trends in electronic
bands, densities of states and Fermi surfaces for AFe2Ch2 are analyzed in
relation to their... | 1102.4173v2 |
2011-02-27 | Multiorbital Spin Susceptibility in a Magnetically Ordered State - Orbital versus Excitonic Spin Density Wave Scenario | We present a general theory of multiorbital spin waves in magnetically
ordered metallic systems. Motivated by the itinerant magnetism of iron-based
superconductors, we compare the magnetic excitations for two different
scenarios: when the magnetic order either sets in on the on-site orbital level;
or when it appears as... | 1102.5532v1 |
2011-03-01 | 57-Fe Mossbauer study of magnetic ordering in superconducting K_0.85Fe_1.83Se_2.09 single crystals | The magnetic ordering of superconducting single crystals of
K_0.85Fe_1.83Se_2.09 has been studied between 10K and 550K using 57-Fe
Mossbauer spectroscopy. Despite being superconducting below T_sc ~30K, the iron
sublattice in K_0.85Fe_1.83Se_2.09 clearly exhibits magnetic order from well
below T_sc to its N\'eel tempera... | 1103.0059v1 |
2011-03-01 | Spin excitations in K$_{0.84}$Fe$_{1.99}$Se$_2$ superconductor as studied by Mössbauer spectroscopy | M\"ossbauer spectroscopy was used to probe the site specific information of
the $K_{0.84}Fe_{1.99}Se_2$ superconductor. Possibility of coexistence of
superconductivity and magnetism is discussed. A spin excitation gap, $\Delta E
\approx$5\,meV, is observed by analyzing the temperature dependence of the
hyperfine magnet... | 1103.0098v5 |
2011-03-03 | Determination of the pairing state in iron-based superconductors through neutron scattering | We calculate the spin susceptibility in the s_{+-} and s_{++} superconducting
states of the iron pnictides using the effective five orbital model and
considering the quasiparticle damping. For the experimentally evaluated
magnitude of the quasiparticle damping and the superconducting gap, the results
at the wave vector... | 1103.0586v2 |
2011-03-06 | Hydrogen in layered iron arsenide: indirect electron doping to induce superconductivity | Utilizing the high stability of calcium and rare earth hydrides, CaFeAsF1-xHx
(x = 0.0-1.0) and SmFeAsO1-xHx (x = 0.0-0.47) have been first synthesized using
high pressure to form hydrogen-substituted 1111 type iron-arsenide
superconductors. Neutron diffraction and density functional calculations have
demonstrated that... | 1103.1177v3 |
2011-03-09 | Phase diagram and a possible unified description of intercalated iron selenide superconductors | We propose a theoretical description of the phase diagram and physical
properties in A2Fe4Se5-type (A=K, Tl) compounds based on a coexistent local
moment and itinerant electron picture. Using neutron scattering and ARPES
measurements to fix the general structure of the local moment and itinerant
Fermi pockets, we find ... | 1103.1902v3 |
2011-03-15 | Two-band model of Raman scattering on iron pnictide superconductors | Based on a two-band model, we study the electronic Raman scattering intensity
in both normal and superconducting states of iron-pnictide superconductors. For
the normal state, due to the match or mismatch of the symmetries between band
hybridization and Raman vertex, it is predicted that overall $B_{1g}$ Raman
intensit... | 1103.3191v1 |
2011-03-16 | Enhancement of the critical temperature in iron-pnictide superconductors by finite size effects | Recent experiments have shown that, in agreement with previous theoretical
predictions, superconductivity in metallic nanostructures can be enhanced with
respect to the bulk limit. Motivated by these results we study finite size
effects (FSE) in an iron-pnictide superconductor. For realistic values of the
bulk critical... | 1103.3290v1 |
2011-03-16 | High impact of spin-nematic order on the lattice domains in thin films of iron-based superconductors | The spin-nematic scenario proposed for the structural instability of
iron-based superconductors is studied theoretically within a Ginzburg-Landau
approach in epitaxial thin films. The transition temperature and the domains
that appear due the interface with the substrate are computed analytically by
following a variato... | 1103.3302v1 |
2011-04-12 | Synthesis, Structure and Magnetic Properties of New Layered Iron-Oxychalcogenide Na2Fe2OSe2 | A new layered iron-oxychalcogenide Na2Fe2OSe2 has been synthesized and
structurally characterized by powder X-ray diffraction. The structure is formed
by alternate stacking of the newly discovered [Fe2OSe2] blocks and double
layers of Na. Conductivity study shows that Na2Fe2OSe2 is a semiconductor with
activation energ... | 1104.2176v2 |
2011-04-21 | Importance of electronic correlations for structural and magnetic properties of the iron pnictide superconductor LaFeAsO | We present calculations of structural and magnetic properties of the
iron-pnictide superconductor LaFeAsO including electron-electron correlations.
For this purpose we apply a fully charge self-consistent combination of
Density-Functional Theory with the Dynamical Mean-Field theory, allowing for
the calculation of tota... | 1104.4361v2 |
2011-04-23 | Orbital density wave induced by electron-lattice coupling in orthorhombic iron pnictides | In this paper we explore the magnetic and orbital properties closely related
to a tetragonal-orthorhombic structural phase transition in iron pnictides
based on both two- and five-orbital Hubbard models. The electron-lattice
coupling, which interplays with electronic interaction, is self-consistently
treated. Our resul... | 1104.4575v1 |
2011-05-06 | Physical State of the Deep Interior of the CoRoT-7b Exoplanet | The present study takes the CoRoT-7b exoplanet as an analogue for massive
terrestrial planets to investigate conditions, under which intrinsic magnetic
fields could be sustained in liquid cores. We examine the effect of
depth-dependent transport parameters (e.g., activation volume of mantle rock)
on a planet's thermal ... | 1105.1271v1 |
2011-05-19 | Anisotropic in-plane resistivity in the nematic phase of the iron pnictides | We show that the interference between scattering by impurities and by
critical spin fluctuations gives rise to anisotropic transport in the
Ising-nematic state of the iron pnictides. The effect is closely related to the
non-Fermi liquid behavior of the resistivity near an antiferromagnetic quantum
critical point. Our t... | 1105.3906v2 |
2011-05-23 | Orbitally and Magnetically Induced Anisotropy in Iron-based Superconductors | Recent experimental developments in the iron pnictides have unambiguously
demonstrated the existence of in-plane electronic anisotropy in the absence of
the long-range magnetic order. Such anisotropy can arise from orbital ordering,
which is described by an energy splitting between the two otherwise degenerate
$d_{xz}$... | 1105.4630v3 |
2011-05-24 | Complete renormalization group calculation up to two-loop order of an effective two-band model for iron-based superconductors | We perform a renormalization group (RG) study up to two-loop order of an
effective low-energy two-band model to describe some of the recently discovered
iron-based superconductors. Our starting point is the itinerant electronic
model proposed by Chubukov \emph{et al.} [Phys. Rev. B \textbf{78}, 134512
(2008)], which di... | 1105.4897v2 |
2011-05-29 | Ab initio parametrised model of strain-dependent solubility of H in alpha-iron | The calculated effects of interstitial hydrogen on the elastic properties of
alpha-iron from our earlier work are used to describe the H interactions with
homogeneous strain fields using ab initio methods. In particular we calculate
the H solublility in Fe subject to hydrostatic, uniaxial, and shear strain. For
compari... | 1105.5758v3 |
2011-06-08 | Coexistence of Dirac-Cone States and Superconductivity in Iron Pnictide Ba(Fe$_{1-x}$Ru$_x$As)$_2$ | The Ru doping effect on the Dirac cone states is investigated in iron
pnictide superconductors Ba(Fe$_{1-x}$Ru$_x$As)$_2$ using the transverse
magnetoresistance (MR) measurements as a function of temperature. The linear
development of MR against magnetic field $B$ is observed for $x$ = 0 - 0.244 at
low temperatures bel... | 1106.1496v2 |
2011-06-08 | Superconductivity in Iron Compounds | Kamihara and coworkers' report of superconductivity at Tc = 26 K in
fluorine-doped LaFeAsO inspired a worldwide effort to understand the nature of
the superconductivity in this new class of compounds. These iron pnictide and
chalcogenide (FePn/Ch) superconductors have Fe electrons at the Fermi surface,
plus an unusual ... | 1106.1618v1 |
2011-06-13 | Comment on arXiv:1105.6233 entitled "Neutron-Inelastic-Scattering Peak by Dissipationless Mechanism in the s++-wave State in Iron-based Superconductors" by S. Onari and H. Kontani | Recently, Onari and Kontani submitted a paper [arXiv:1105.6233] which
criticizes our recent theoretical study [arXiv:1103.0586] on the neutron
scattering experiment as a probe for determining the superconducting gap in the
iron pnictides. In their paper, Onari and Kontani have developed a formalism in
which the imagina... | 1106.2376v1 |
2011-06-13 | Temperature dependent local structure of NdFeAsO1-xFx system using arsenic K-edge extended x-ray absorption fine structure | Local structure of NdFeAsO$_{1-x}$F$_{x}$ ($x$=0.0, 0.05, 0.15 and 0.18) high
temperature iron pnictide superconductor system is studied using arsenic
$K$-edge extended x-ray absorption fine structure measurements as a function of
temperature. Fe-As bondlength shows only a weak temperature and F-substitution
dependence... | 1106.2567v1 |
2011-06-14 | Crossover between two different magnetization reversal modes in arrays of iron oxide nanotubes | The magnetization reversal in ordered arrays of iron oxide nanotubes of 50 nm
outer diameter grown by atomic layer deposition is investigated theoretically
as a function of the tube wall thickness, $d_{w}$. In thin tubes ($d_{w}<13$
nm) the reversal of magnetization is achieved by the propagation of a vortex
domain bou... | 1106.2833v1 |
2011-06-17 | Influence of electronic correlations on orbital polarizations in the parent and doped iron pnictides | Orbital polarization and electronic correlation are two essential aspects in
understanding the normal state and superconducting properties of multiorbital
FeAs-based superconductors. In this Letter, we present a systematical study on
the orbital polarization of iron pnictides from weak to strong Coulomb
correlations wi... | 1106.3487v1 |
2011-06-22 | Extended Hubbard model of superconductivity driven by charge fluctuations in iron-pnictides | We present a scenario for iron-pnictide superconductivity mediated by charge
fluctuations that are strongly enhanced by Fe-As intersite electronic
interactions. Deriving an eight-band extended Hubbard model including Fe 3$d$
and As 4$p$ orbitals for the LaOFeAs family, we show that charge fluctuations
induced by $p$-$d... | 1106.4552v2 |
2011-07-01 | Spin Hall effect in iron-based superconductors: A Dirac-point effect | We have theoretically explored the intrinsic spin Hall effect (SHE) in the
iron-based superconductor family with a variety of materials. The study is
motivated by an observation that, in addition to an appreciable spin-orbit
coupling in the Fe 3d states, a character of the band structure in which Dirac
cones appear bel... | 1107.0122v2 |
2011-07-05 | Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in FeTe0.55Se0.45 | The momentum distribution of the energy gap opening at the Fermi level of
superconductors is a direct fingerprint of the pairing mechanism. While the
phase diagram of the iron-based superconductors promotes antiferromagnetic
fluctuations as a natural candidate for electron pairing, the precise origin of
the interaction... | 1107.0985v1 |
2011-07-08 | Magnetic Resonant Mode in the Low-Energy Spin-Excitation Spectrum of Superconducting Rb2Fe4Se5 Single Crystals | We have studied the low-energy spin-excitation spectrum of the
single-crystalline Rb2Fe4Se5 superconductor (Tc = 32 K) by means of inelastic
neutron scattering. In the superconducting state, we observe a magnetic
resonant mode centered at an energy of 14 meV and at the (0.5 0.25 0.5) wave
vector (unfolded Fe-sublattice... | 1107.1703v2 |
2011-07-12 | An aluminum/calcium-rich, iron-poor, white dwarf star: evidence for an extrasolar planetary lithosphere? | The presence of elements heavier than helium in white dwarf atmospheres is
often a signpost for the existence of rocky objects that currently or
previously orbited these stars. We have measured the abundances of various
elements in the hydrogen-atmosphere white dwarfs G149-28 and NLTT 43806. In
comparison with other wh... | 1107.2167v1 |
2011-07-12 | Magnetic interactions in iron superconductors studied with a five-orbital model within the Hartree-Fock and Heisenberg approximations | We have analyzed the magnetic interactions of a five orbital model for iron
superconductors treated both within Hartree-Fock and Heisenberg approximations.
We have found that the exchange constants depend non-trivially on the Fe-As-Fe
angle and on the charge and orbital filling. Within the localized picture,
columnar o... | 1107.2279v2 |
2011-07-22 | Nodeless vs nodal order parameters in LiFeAs and LiFeP superconductors | High-precision measurements of magnetic penetration depth $\lambda$ in clean
single crystals of LiFeAs and LiFeP superconductors reveal contrasting
low-energy quasiparticle excitations. In LiFeAs the low-temperature
$\lambda(T)$ shows a flat dependence indicative of a fully gapped state, which
is consistent with previo... | 1107.4505v1 |
2011-07-29 | Hyperfine Field and Hyperfine Anomalies of Copper Impurities in Iron | A new value for the hyperfine magnetic field of copper impurities in iron is
obtained by combining resonance frequencies from experiments involving
{\beta}-NMR on oriented nuclei on 59-Cu, 69-Cu, and 71-Cu with magnetic moment
values from collinear laser spectroscopy measurements on these isotopes. The
resulting value,... | 1107.5999v1 |
2011-07-29 | Superconductivity at 38 K in Iron-Based Compound with Platinum-Arsenide Layers Ca10(Pt4As8)(Fe2-xPtxAs2)5 | We report superconductivity in novel iron-based compounds
Ca10(PtnAs8)(Fe2-xPtxAs2)5 with n = 3 and 4. Both compounds crystallize in
triclinic structures (space group P-1), in which Fe2As2 layers alternate with
PtnAs8 spacer layers. Superconductivity with a transition temperature of 38 K
is observed in the n = 4 compou... | 1108.0029v2 |
2011-08-02 | Electronic structure and chemical bonding in novel tetragonal phase Ca10(Pt4As8)(Fe2As2)5 as a parent material for the new family of high-TC iron-pnictide superconductors | By means of first-principles calculations, the electronic structure and
chemical bonding for the recently discovered tetragonal (s.g. P4/n; # 85)
superconducting (Tc ~ 25K) phase Ca10(Pt4As8)(Fe2As2)5 have been examined in
details, and the optimized structural parameters, electronic bands, densities
of states, and inte... | 1108.0495v2 |
2011-08-02 | Fermi-Suface Evolution by Transition-metal Substitution in the Iron-based Superconductor LaFeAsO | We study how Co- and Ni-substitution affect the electronic structure of the
iron-based superconductor, LaFeAsO. We perform {\it ab initio} supercell
calculations and unfold the first Brillouin zone (BZ) to calculate the spectral
function in the BZ for the normal cell. The charge density distribution in real
space shows... | 1108.0585v2 |
2011-08-04 | The broad iron Kalpha line of Cygnus X-1 as seen by XMM-Newton in the EPIC-pn modified timing mode | We present the analysis of the broadened, flourescent iron Kalpha line in
simultaneous XMM-Newton and RXTE data from the black hole Cygnus X-1. The
XMM-Newton data were taken in a modified version of the timing mode of the
EPIC-pn camera. In this mode the lower energy threshold of the instrument is
increased to 2.8 keV... | 1108.1157v1 |
2011-08-11 | Effects of the vortices and impurities on the nuclear spin relaxation rate in iron-based superconductors | The effects of magnetic vortices and nonmagnetic impurities on the low energy
quasiparticle excitations and the spin-lattice relaxation rate are examined in
the iron-based superconductors for the $s_{\pm}$-, $s$- and d-wave pairing
symmetries, respectively. The main effect of the vortices is to enhance the
quasiparticl... | 1108.2312v1 |
2011-08-10 | The role of the coating and aggregation state in the interactions between iron oxide nanoparticles and 3T3 fibroblasts | Recent nanotoxicity studies revealed that the physico-chemical
characteristics of engineered nanomaterials play an important role in the
interactions with living cells. Here, we report on the toxicity and uptake of
the iron oxide sub-10 nm nanoparticles by NIH/3T3 mouse fibroblasts. Coating
strategies include low-molec... | 1108.2395v1 |
2011-08-25 | Fabrication of magnetic clusters and rods using electrostatic co-assembly | Using a novel protocol for mixing oppositely charged colloids and
macromolecules, magnetic clusters and rods are fabricated using 10 nm-iron
oxide nanoparticles and polymers. Here, we show that as the dispersions undergo
the so-called desalting transition, spherical clusters in the range 100 nm - 1
{\mu}m form spontane... | 1108.5023v1 |
2011-08-25 | Magnetic Reconnection in Non-Equilibrium Ionization Plasma | We have studied the effect of time-dependent ionization and recombination
processes on magnetic reconnection in the solar corona. Petschek-type steady
reconnection, in which model the magnetic energy is mainly converted at the
slow-mode shocks, was assumed. We carried out the time-dependent ionization
calculation in th... | 1108.5026v1 |
2011-08-25 | How the effects of resonant absorption on black hole reflection spectra can mimic high-velocity outflows | Narrow absorption lines seen in the 2-10 keV spectra of active galaxies and
Galactic black holes are normally attributed to iron in high velocity outflows
or inflows. We consider the possibility that such features could arise
naturally in the accretion disc. Resonant absorption by highly ionised iron
(e.g. Fe XXVI and ... | 1108.5060v1 |
2011-09-01 | Nodal superconducting gap structure in ferropnictide superconductor BaFe2(As0.7P0.3)2 | The superconducting gap is a pivotal character for a superconductor. While
the cuprates and conventional phonon-mediated superconductors are characterized
by distinct d-wave and s-wave pairing symmetry with nodal and nodeless gap
distribution respectively, the superconducting gap distributions in iron-based
superconduc... | 1109.0229v1 |
2011-09-02 | A gamma-ray signature of energetic sources of cosmic-ray nuclei | Astrophysical sources of nuclei are expected to produce a broad spectrum of
isotopes, many of which are unstable. An unstable nucleus can beta-decay
outside the source into a single-electron ion. Heavy one-electron ions, thus
formed, can be excited in their interactions with cosmic microwave background
photons, in whic... | 1109.0565v3 |
2011-09-14 | First-principles study of pressure-induced magnetic phase transitions in ternary iron selenide K$_{0.8}$Fe$_{1.6}$Se$_2$ | We have studied the pressure effect on electronic structures and magnetic
orders of ternary iron selenide K$_{0.8}$Fe$_{1.6}$Se$_2$ by the
first-principles electronic structure calculations. At low pressure, the
compound is in the blocked checkerboard antiferromagnetic (AFM) semiconducting
phase, as observed by the neu... | 1109.3049v1 |
2011-09-20 | Dynamical Ionic Clusters with Flowing Electron Bubbles from Warm to Hot Dense Iron along the Hugoniot Curve | The complex structures of warm and hot dense matter are essential to
understand the behaviors of materials in high energy density physics processes
and provide new features of matter constitutions. Here, along a new unified
first-principle determined Hugoniot curve of iron from normal condensed
condition up to 1 Gbar, ... | 1109.4252v3 |
2011-09-20 | Common origin of the two types of magnetic fluctuations in iron chalcogenides | We use inelastic neutron scattering to study the low energy spin excitations
in moderately doped non-superconducting Fe$_{1.01}$Te$_{0.72}$Se$_{0.28}$. The
spin excitations in this system contain components near (0.5,0,0) and
(0.5,0.5,0) in a-b plane reciprocal lattice units using tetragonal unit cell
notation (a=b=3.7... | 1109.4339v1 |
2011-09-22 | Self-Diffusion of Iron in L10 FePd film - as revealed by reflectometric methods | L10 (CuAu(I)-type) ordered FePd as well as FePt and CoPt, due to their high
magnetic anisotropy, are candidate materials for future ultra-high density
magnetic recording. Atomic diffusion governs the structural relaxation and
associated changes in the physical and magnetic properties in these alloys.
Such processes inv... | 1109.4751v1 |
2011-09-23 | Low-Energy Quasiparticles Probed by Heat Transport in the Iron Based Superconductor LaFePO | We have measured the thermal conductivity of the iron pnictide superconductor
LaFePO down to temperatures as low as T=60mK and in magnetic fields up to 5 T.
The data shows a large residual contribution that is linear in temperature,
consistent with the presence of low energy electronic quasiparticles. We
interpret the ... | 1109.5092v1 |
2011-09-26 | Vortex pinning : a probe for nanoscale disorder in iron-based superconductors | The pinning of quantized flux lines, or vortices, in the mixed state is used
to quantify the effect of impurities in iron-based superconductors (IBS).
Disorder at two length scales is relevant in these materials. Strong flux
pinning resulting from nm-scale heterogeneity of the superconducting properties
leads to the ve... | 1109.5479v1 |
2011-09-27 | Impurity-induced quasiparticle interference in the parent compounds of iron-pnictide superconductors | The impurity-induced quasiparticle interference(QPI) in the parent compounds
of iron-pnictide superconductors is investigated based on a phenomenological
two-orbital four-band model and T-matrix method. We find the QPI is sensitive
to the value of the magnetic order which may vary from one compound to another.
For smal... | 1109.5928v1 |
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