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2013-01-16 | High-Pressure Evolution of the Specific Heat of a Strongly Underdoped Ba(Fe0.963Co0.037)As2 Iron-Based Superconductor | We report specific-heat experiments under the influence of high pressure on a
strongly underdoped Co-substituted BaFe2As2 single crystal. This allows us to
study the phase diagram of this iron pnictide superconductor with a bulk
thermodynamic method and pressure as a clean control parameter. The data show
large specifi... | 1301.3579v3 |
2013-01-31 | Electronic structure of vacancy-ordered iron-selenide K$_{0.5}$Fe$_{1.75}$Se$_2$ | The electronic structure of the vacancy-ordered K$_{0.5}$Fe$_{1.75}$Se$_2$
iron-selenide compound (278 phase) is studied using the first-principles
density functional method. The ground state of the 278 phase is stripe-like
antiferromagnetic, and its bare electron susceptibility shows a large peak
around $(\pi, \pi)$ i... | 1301.7655v3 |
2013-02-02 | Carrier density dependence of the magnetic properties in iron-doped Bi2Se3 topological insulator | The electronic and magnetic properties of iron-doped topological insulator
Bi1.84-xFe0.16CaxSe3 single crystals were studied. By co-doping Fe and Ca
atoms, ferromagnetic bulk states with different carrier density (from n-type to
p-type) were obtained. Effective magnetic moments for each Fe atom was
estimated as small a... | 1302.0371v1 |
2013-02-07 | Discovery of Fe K-alpha X-ray reverberation around the black holes in MCG-5-23-16 and NGC 7314 | Several X-ray observations have recently revealed the presence of
reverberation time delays between spectral components in AGN. Most of the
observed lags are between the power-law Comptonization component, seen
directly, and the soft excess produced by reflection in the vicinity of the
black hole. NGC 4151 was the firs... | 1302.1761v2 |
2013-02-10 | Nodal gap in iron-based superconductor CsFe$_2$As$_2$ probed by quasiparticle heat transport | The thermal conductivity of iron-based superconductor CsFe$_2$As$_2$ single
crystal ($T_c =$ 1.81 K) was measured down to 50 mK. A significant residual
linear term $\kappa_0/T$ = 1.27 mW K$^{-2}$ cm$^{-1}$ is observed in zero
magnetic field, which is about 1/10 of the normal-state value in upper critical
field $H_{c2}$... | 1302.2300v2 |
2013-02-12 | Anomalous Surface Segregation Profiles in Ferritic FeCr Stainless Steel | The iron-chromium alloy and its derivatives are widely used for their
remarkable resistance to corrosion, which only occurs in a narrow concentration
range around 9 to 13 atomic percent chromium. Although known to be due to
chromium enrichment of a few atoms thick layer at the surfaces, the
understanding of its complex... | 1302.2838v1 |
2013-02-19 | High critical current density and low anisotropy in textured Sr1-xKxFe2As2 tapes for high field applications | From the application point of view, large critical current densities Jc (H)
for superconducting wires are required, preferably for magnetic fields higher
than 5 T. Here we show that strong c-axis textured Sr1-xKxFe2As2 tapes with
nearly isotropic transport Jc were fabricated by an ex-situ powder-in-tube
(PIT) process. ... | 1302.4583v1 |
2013-02-19 | Orbital Resonance Mode in Superconducting Iron Pnictides | We show that the fluctuations associated with ferro orbital order in the
$d_{xz}$ and $d_{yz}$ orbitals can develop a sharp resonance mode in the
superconducting state with a nodeless gap on the Fermi surface. This orbital
resonance mode appears below the particle-hole continuum and is analogous to
the magnetic resonan... | 1302.4749v2 |
2013-02-28 | Superconducting Phases in Potassium-Intercalated Iron Selenides | The ubiquitous coexistence of majority insulating 245 phases and minority
superconducting (SC) phases in AxFe2-ySe2 (A = K, Cs, Rb, Tl/Rb, Tl/K) formed
by high-temperature routes makes pure SC phases highly desirable for studying
the intrinsic properties of this SC family. Here we report that there are at
least two pur... | 1302.7178v1 |
2013-03-11 | Magnetic glassy phase in FeSeTe single crystals | The evolution of the magnetic order in FeSeTe crystals as a function of Se
content was investigated by means of ac/dc magnetometry and muon-spin
spectroscopy. Experimental results and self-consistent DFT calculations both
indicate that muons are implanted in vacant iron-excess sites, where they probe
a local field main... | 1303.2585v1 |
2013-03-14 | Study of some steller iron group fusion materials for (n,p) reactions | The excitation functions for (n,p) reactions from reaction threshold to 24
MeV on some important iron (Fe) group target elements for astrophysical (n, p)
reactions such as Si, Ca, Sc, Ti, Cr, Fe, Co and Ni were calculated using
TALYS-1.0 nuclear model code. The new calculations on the excitation functions
Of 28Si(n,p)2... | 1303.3581v1 |
2013-03-15 | Superconductivity from orbital nematic fluctuations | Recent experiments suggest that besides of antiferromagnetic fluctuations
nematic fluctuations may contribute to the occurrence of superconductivity in
iron pnictides. Motivated by this observation we study superconductivity from
nematic fluctuations in a minimal two-band model. The employed band parameters
are appropr... | 1303.3806v2 |
2013-03-17 | Hidden $(π,0)$ instability as an itinerant origin of bicollinear antiferromagnetism in Fe$_{1+x}$Te | By calculating orbitally resolved Pauli susceptibilities within maximally
localized Wannier orbital basis transformed from first principles band
structures, we find that magnetism in Fe$_{1+x}$Te still has its itinerant
origin even without Fermi surface nesting, provided orbital modulation of
particle-hole excitations ... | 1303.4072v1 |
2013-03-18 | Superconductivity From Repulsive Electronic Correlations on Alternant Cuprate and Iron-based Lattices | A key question in the theory of high-temperature superconductivity is whether
Off-diagonal Long-Range Order (ODLRO) can be induced wholly or in large part by
repulsive electronic correlations. Electron pairs on Cuprate and the iron-based
pnictide and chalcogenide alternant lattices may interact with a strong
short-rang... | 1303.4235v1 |
2013-03-19 | In-plane optical spectroscopy study on FeSe epitaxial thin film grown on SrTiO$_3$ substrate | We perform in-plane optical spectroscopy measurement on (00l) FeSe thin-film
grown on SrTiO$_3$ substrate by pulsed laser deposition method. The study
indicates that the low frequency conductivity consists of two Drude components,
a broad one which takes up most of the spectral weight and a very narrow one
roughly belo... | 1303.4473v1 |
2013-03-19 | Electronic Structure and Resonant X-ray Emission Spectra of Carbon Shells of Iron Nanoparticles | The electronic structure of carbon shells of carbon encapsulated iron
nanoparticles carbon encapsulated Fe@C has been studied by X-ray resonant
emission and X-ray absorption spectroscopy. The recorded spectra have been
compared to the density functional calculations of the electronic structure of
graphene. It has been ... | 1303.4507v1 |
2013-03-20 | Optical Properties of Iron Silicates in the Infrared to Millimeter as a Function of Temperatures and Wavelength | The Optical Properties of Astronomical Silicates with Infrared Techniques
(OPASI-T) program utilizes multiple instruments to provide spectral data over a
wide range of temperature and wavelengths. Experimental methods include Vector
Network Analyzer (VNA) and Fourier Transform Spectroscopy (FTS) transmission,
and refle... | 1303.4950v1 |
2013-03-26 | Measurements of the fluctuation-induced in-plane magnetoconductivity at high reduced temperatures and magnetic fields in the iron arsenide BaFe(2-x)NixAs2 | The superconducting fluctuations well inside the normal state of Fe-based
superconductors were studied through measurements of the in-plane
paraconductivity and magnetoconductivity in high quality BaFe(2-x)NixAs2
crystals with doping levels from the optimal (x=0.10) up to the highly
overdoped (x=0.20). These measuremen... | 1303.6565v1 |
2013-04-02 | The effect of Hydrogen atom on the Screw Dislocation Mobility in BCC Iron: A First-Principles Study | We investigate the effect of hydrogen on the mobility of a screw dislocation
in body-centered cubic (bcc) iron using first-principles calculations, and show
that an increase of screw dislocation velocity is expected for a limited
temperature range. The interaction energy between a screw dislocation and
hydrogen atoms i... | 1304.0602v3 |
2013-04-04 | Surface parameters of ferritic iron-rich Fe-Cr alloy | Using first-principles density functional theory in the implementation of the
exact muffin-tin orbitals method and the coherent potential approximation, we
studied the surface energy and the surface stress of the thermodynamically most
stable surface facet (100) of the homogeneous disordered body-centred cubic
iron-chr... | 1304.1278v2 |
2013-04-13 | Intrinsic high-temperature superconductivity in ternary iron selenides | We examine superconductivity in the mesoscopically mixed
antiferromagnetic(AF) and superconducting (SC) phases of ternary iron selenides
K$_{y}$Fe$_{2-x}$Se$_{2}$. It is shown that the interlayer hopping and AF order
are key factors to determine $T_{c}$ of the SC phase. In general, the hopping
will produce deformed Fer... | 1304.3785v3 |
2013-04-16 | Possible Nematic Order Driven by Magnetic Fluctuations in Iron Pnictides | In this paper, instabilities of the isotropic metallic phase in iron
pnictides are investigated. The relevant quartic fermionic interaction terms in
the model are identified using phase space arguments. Using the functional
integral formalism, a Hubbard-Stratonovich transformation is used to decouple
these quartic term... | 1304.4617v1 |
2013-04-19 | Robust spin fluctuations and $s\pm$ pairing in the heavily electron doped iron-based superconductors | We theoretically study the spin fluctuation and superconductivity in La1111
and Sm1111 iron-based superconductors for a wide range of electron doping. When
we take into account the band structure variation by electron doping, the hole
Fermi surface originating from the $d_{X^2-Y^2}$ orbital turns out to be robust
again... | 1304.5303v2 |
2013-04-22 | Magnetic anisotropic energy gap and low energy spin wave excitation in antiferromagnetic block phase of K2Fe4Se5 | Neutron scattering experiments were performed to investigate magnetic order
and magnetic excitations in ternary iron chalcogenide K2Fe4Se5. The formation
of a superlattice structure below 580 K together with the decoupling between
the Fe-vacancy order-disorder transition and the antiferromagnetic order
transition appea... | 1304.5950v1 |
2013-05-13 | Normal state spin dynamics in the iron-pnictide superconductors BaFe2(As1-xPx)2 and Ba(Fe1-xCox)2As2 probed with NMR measurements | The NMR results in iron pnictides BaFe2(As1-xPx)2 and Ba(Fe1-xCox)2As2 are
analyzed based on the self-consistent renormalization (SCR) spin fluctuation
theory. The temperature dependence of the NMR relaxation rate (T_1)^{-1} as
well as the electrical resistivity is well reproduced by a SCR model where
two-dimensional a... | 1305.2656v1 |
2013-05-13 | Simultaneous optimization of spin fluctuations and superconductivity under pressure in an iron-based superconductor | We present a high-pressure NMR study of the overdoped iron pnictide
superconductor NaFe$_{0.94}$Co$_{0.06}$As. The low-energy antiferromagnetic
spin fluctuations in the normal state, manifest as the Curie-Weiss upturn in
the spin-lattice relaxation rate $1/^{75}T_1T$, first increase strongly with
pressure but fall agai... | 1305.2705v2 |
2013-05-14 | Effect of electron-phonon interactions on orbital fluctuations in iron-based superconductors | To investigate the possibility whether electron-phonon coupling can enhance
orbital fluctuations in iron-based superconductors, we develop an ab initio
method to construct the effective low-energy models including the
phonon-related terms. With the derived effective electron-phonon interactions
and phonon frequencies, ... | 1305.2995v2 |
2013-05-17 | Comparative Study of Electronic structure of New Superconductors (Sr,Ca)Pd2As2 and related compound BaPd2As2 | This paper presents the comparative study of LDA calculated electronic
structure of new isostructural to iron based systems superconductors
(Sr,Ca)Pd2As2 with Tc about 1K and similar but structurally different system
BaPd2As2. Despite chemical formula looks similar to iron superconductors and
even main structural motif... | 1305.3979v1 |
2013-05-20 | Effect of magnetic criticality and Fermi-surface topology on the magnetic penetration depth | We investigate the effect of anti-ferromagnetic (AF) quantum criticality on
the magnetic penetration depth $\lambda(T)$ in line-nodal superconductors,
including the cuprates, the iron pnictides, and the heavy-fermion
superconductors. The critical magnetic fluctuation renormalizes the current
vertex and drastically enha... | 1305.4427v1 |
2013-05-20 | How many quantum phase transitions exist inside the superconducting dome of the iron pnictides? | Recent experiments on two iron-pnictide families suggest the existence of a
single quantum phase transition (QPT) inside the superconducting dome despite
the fact that two separate transition lines - magnetic and nematic - cross the
superconducting dome at $T_{c}$. Here we argue that these two observations are
actually... | 1305.4670v2 |
2013-05-21 | Spin fluctuations away from (pi,0) in the superconducting phase of molecular-intercalated FeSe | Magnetic fluctuations in the molecular-intercalated FeSe superconductor
Li{x}(ND2){y}(ND3){1-y}Fe2Se2 (Tc = 43K) have been measured by inelastic
neutron scattering from a powder sample. The strongest magnetic scattering is
observed at a wave vector Q ~ 1.4 A^{-1}, which is not consistent with the
(pi,0) nesting wave ve... | 1305.4898v1 |
2013-06-03 | Scaling between magnetic and lattice fluctuations in iron-pnictide superconductors | The phase diagram of the iron arsenides is dominated by a magnetic and a
structural phase transition, which need to be suppressed in order for
superconductivity to appear. The proximity between the two transition
temperature lines indicates correlation between these two phases, whose nature
remains unsettled. Here, we ... | 1306.0521v2 |
2013-06-17 | Two-Fluid Description for Iron-Based Superconductors | We present a two-fluid description for iron-based superconductors, which
contains an itinerant electron Fermi-liquid and a local moment spin-liquid,
coupled together via an effective Hund's rule interaction. We examine the
low-energy collective behavior of such a system. We find that an
electron-spinon composite mode e... | 1306.3740v3 |
2013-06-18 | X-ray resonant photoexcitation: line widths and energies of Kα transitions in highly charged Fe ions | Photoabsorption by and fluorescence of the K{\alpha} transitions in highly
charged iron ions are essential mechanisms for X-ray radiation transfer in
astrophysical environments. We study photoabsorption due to the main K{\alpha}
transitions in highly charged iron ions from heliumlike to fluorinelike (Fe
24+...17+) usin... | 1306.4348v3 |
2013-06-20 | A new way to measure supermassive black hole spin in accretion disc dominated Active Galaxies | We show that disc continuum fitting can be used to constrain black hole spin
in a subclass of Narrow Line Seyfert 1 (NLS1) AGN as their low mass and high
mass accretion rate means that the disc peaks at energies just below the soft
X-ray bandpass. We apply the technique to the NLS1 PG1244+026, where the
optical/UV/X-ra... | 1306.4786v1 |
2013-06-28 | The role of orbital order in the stabilization of the $(π,0)$ ordered magnetic state in a minimal two-band model for iron pnictides | Spin wave excitations and stability of the ($\pi,0$) ordered magnetic state
are investigated in a minimal two-band itinerant-electron model for iron
pnictides. Presence of hopping anisotropy generates a strong ferro-orbital
order in the $d_{xz}$ and $d_{yz}$ Fe orbitals. The orbital order sign is as
observed in experim... | 1306.6727v2 |
2013-07-05 | Orbital-Selective Mottness in Layered Iron Oxychalcogenides: The Case of Na_{2}Fe_{2}OSe_{2} | Using a combination of th local-density approximtion (LDA) and dynamicla
mean-field theory (DMFT) calculations, we explore the correlated electronic
structure of a member of the layered Iron oxychalcogenide Na_{2}Fe_{2}OSe_{2}.
We find that the parent compund is a multi-orbital Mott insulator.
Surprisingly, and somewha... | 1307.1693v1 |
2013-07-08 | Weak magnetism and the Mott-state of vanadium in superconducting Sr2VO3FeAs | We report neutron scattering data and DFT calculations of the stoichiometric
iron-arsenide superconductor Sr2VO3FeAs. Rietveld refinements of neutron powder
patterns confirm the ideal composition without oxygen deficiencies. Experiments
with polarized neutrons prove weak magnetic ordering in the V-sublattice of
Sr2VO3F... | 1307.2138v1 |
2013-07-09 | Lattice Instability and Competing Spin Structures in the Double Perovskite Insulator Sr2FeOsO6 | The semiconductor Sr2FeOsO6, depending on temperature, adopts two types of
spin structures that differ in the spin sequence of ferrimagnetic iron - osmium
layers along the tetragonal c-axis. Neutron powder diffraction experiments,
57Fe M\"ossbauer spectra, and density-functional theory calculations suggest
that this be... | 1307.2587v2 |
2013-07-11 | Anomalous compressibility of ferropericlase throughout the iron spin crossover | The thermoelastic properties of ferropericlase Mg1-xFexO (x = 0.1875)
throughout the iron high-to-low spin crossover have been investigated by first
principles at Earth's lower mantle conditions. This crossover has important
consequences for elasticity such as an anomalous bulk modulus (KS) reduction.
At room temperatu... | 1307.3270v1 |
2013-07-12 | Swift and RXTE observations of the black hole transient GX 339-4 in the hard state between outbursts | We use simultaneous Swift and RXTE observations of the black hole binary GX
339-4 to measure the inner radius of its accretion disk in the hard state down
to 0.4% L_{Edd} via modeling of the thermal disk emission and the
relativistically broadened iron line. For the luminosity range covered in this
work, our results ru... | 1307.3503v1 |
2013-07-15 | The Roche limit for close-orbiting planets: Minimum density, composition constraints, and application to the 4.2-hour planet KOI 1843.03 | The requirement that a planet must orbit outside of its Roche limit gives a
lower limit on the planet's mean density. The minimum density depends almost
entirely on the orbital period and is immune to systematic errors in the
stellar properties. We consider the implications of this density constraint for
the newly-iden... | 1307.4080v1 |
2013-07-18 | Origin of electronic dimers in the spin-density wave phase of Fe-based superconductors | We investigate the emergent impurity-induced states arising from point-like
scatterers in the spin-density wave phase of iron-based superconductors within
a microscopic five-band model. Independent of the details of the band-structure
and disorder potential, it is shown how stable magnetic (pi,pi) unidirectional
nemato... | 1307.4913v2 |
2013-07-26 | Electron-phonon coupling in cuprate and iron-based superconductors revealed by Raman scattering | Electron-phonon coupling (EPC) is one of the most common and fundamental
interactions in solids. It not only dominates many basic dynamic processes like
resistivity, thermal conductivity etc, but also provides the pairing glue in
conventional superconductors. But in high-temperature superconductors (HTSC),
it is still ... | 1307.6972v1 |
2013-07-26 | Switching of intra-orbital spin excitations in electron-doped iron pnictide superconductors | We investigate the doping dependence of the magnetic excitations in
two-superconducting-dome-system LaFeAsO1-xDx. Using inelastic neutron
scattering, spin fluctuations at different wavenumbers were observed under both
superconducting domes around x = 0.1 and 0.4, but vanished at x = 0.2
corresponding to the Tc valley. ... | 1307.7016v2 |
2013-07-26 | Coupling of the A_{1g} As-phonon to magnetism in iron pnictides | Charge, spin and lattice degrees of freedom are strongly entangled in iron
superconductors. A neat consequence of this entanglement is the behavior of the
A_{1g} As-phonon resonance in the different polarization symmetries of Raman
spectroscopy when undergoing the magneto-structural transition. In this work we
show tha... | 1307.7065v1 |
2013-07-31 | A view from inside iron-based superconductors | Muon spin spectroscopy is one of the most powerful tools to investigate the
microscopic properties of superconductors. In this manuscript, an overview on
some of the main achievements obtained by this technique in the iron-based
superconductors (IBS) are presented. It is shown how the muons allow to probe
the whole pha... | 1307.8283v1 |
2013-08-12 | Constraining possible variations of the fine structure constant in strong gravitational fields with the K$α$ iron line | In extensions of general relativity and in theories aiming at unifying
gravity with the forces of the Standard Model, the value of the "fundamental
constants" is often determined by the vacuum expectation value of new fields,
which may thus change in different backgrounds. Variations of fundamental
constants with respe... | 1308.2470v2 |
2013-08-15 | Evidence of Increased UV FeII Emission in Quasars in Candidate Overdense Regions | We present evidence for a skewed distribution of UV FeII emission in quasars
within candidate overdense regions spanning spatial scales of ~ 50 Mpc at 1.11
< z < 1.67, compared to quasars in field environments at comparable redshifts.
The overdense regions have an excess of high equivalent width sources (W2400 >
42 \AA... | 1308.3514v1 |
2013-08-18 | Impurity-induced sub-gap bound gap states in alkali doped iron chalcogenide superconductors | Measurements of the local density of states near impurities can be useful for
identifying the superconducting gap structure in alkali doped iron chalcogenide
superconductors K_xFe_{2-y}Se_2. Here, we study the effects of nonmagnetic and
magnetic impurities within a nearest neighbor d-wave and next-nearest neighbor
s-wa... | 1308.3887v1 |
2013-09-03 | Producing a Set of Models for the Iron Homeostasis Network | This paper presents a method for modeling biological systems which combines
formal techniques on intervals, numerical simulations and satisfaction of
Signal Temporal Logic (STL) formulas. The main modeling challenge addressed by
this approach is the large uncertainty in the values of the parameters due to
the experimen... | 1309.0872v1 |
2013-09-05 | Influence of the spreading resistance on the conductance spectrum of planar hybrid thin film SNS' junctions based on iron pnictides | To investigate the superconducting properties of iron pnictides we prepared
planar hybrid SNS' junctions in thin film technology with a pnictide base
electrode, a gold barrier layer and a lead counter electrode. Our design allows
characterization of the electrodes and the junction independently in a 4-probe
method. We ... | 1309.1641v2 |
2013-09-10 | Microlensing of Quasar UV Iron Emission | We measure the differential microlensing of the UV Fe II and Fe III emission
line blends between 14 quasar image pairs in 13 gravitational lenses. We find
that the UV iron emission is strongly microlensed in 4 cases with amplitudes
comparable to that of the continuum. Statistically modeling the magnifications
we infer ... | 1309.2603v2 |
2013-09-13 | Adsorption geometry and electronic structure of iron phthalocyanine on Ag surfaces: A LEED and photoelectron momentum mapping study | We present a comprehensive study of the adsorption behavior of iron
phthalocyanine on the low-index crystal faces of silver. By combining
measurements of the reciprocal space by means of photoelectron momentum mapping
and low energy electron diffraction, the real space adsorption geometries are
reconstructed. At monola... | 1309.3476v1 |
2013-09-18 | Magnetocrystalline anisotropy energy of Fe$(001)$, Fe$(110)$ slabs and nanoclusters: a detailed local analysis within a tight-binding model | We report tight-binding (TB) calculations of magnetocrystalline anisotropy
energy (MAE) of Iron slabs and nanoclusters with a particuler focus on local
analysis. After clarifying various concepts and formulations for the
determination of MAE, we apply our realistic TB model to the analysis of the
magnetic anisotropy of... | 1309.4578v1 |
2013-09-20 | Evidence for Orbital Order and its Relation to Superconductivity in FeSe0.4Te0.6 | The emergence of nematic electronic states accompanied by a structural phase
transition is a recurring theme in many correlated electron materials,
including the high-temperature copper oxide- and iron-based superconductors. We
provide evidence for nematic electronic states in the iron-chalcogenide
superconductor FeSe0... | 1309.5210v3 |
2013-10-09 | Impurity states and cooperative magnetic order in Fe-based superconductors | We study impurity bound states and impurity-induced order in the
superconducting state of LiFeAs within a realistic five-band model based on the
band structure and impurity potentials obtained from density functional theory
(DFT). In agreement with recent experiments, we find that Co impurities are too
weak produce sub... | 1310.2455v1 |
2013-10-09 | Fe KαLine in Hard X-ray Emitting Symbiotic Stars | The 6.4 keV iron emission line is typically created by irradiation of the
neutral (or low ionized) iron by a hard X-ray source. Whereas the 6.7 and 7.0
keV emission lines are mainly produced by photoionization and collisional
excitation in hot plasma, the 6.4 keV fluorescence line is typically a
signature of either ref... | 1310.2461v2 |
2013-10-17 | Achievement of practical level critical current densities in PIT Ba1-xKxFe2As2/Ag tapes by conventional cold mechanical deformation | We found that transport critical current density (Jc) of the Ba1-xKxFe2As2/Ag
tapes is significantly enhanced by the combination process of cold flat rolling
and uniaxial pressing. At 4.2 K, the Jc reaches a high value of 9.1x104 A/cm2
in 4 T, which is almost the practical level of 105 A/cm2. The Jc-H curve shows
extre... | 1310.4623v1 |
2013-10-17 | Double neutron spin resonances and gap anisotropy in underdoped superconducting NaFe0.985Co0.015As | We use inelastic neutron scattering to show that superconductivity in
electron-underdoped NaFe0.985Co0.015As induces a dispersive sharp resonance
near Er1 = 3:25 meV and a broad dis- persionless mode at Er2 = 6 meV. However,
similar measurements on overdoped superconducting NaFe0:955Co0:045As find only
a single sharp r... | 1310.4817v1 |
2013-10-28 | Local correlation effects on the s+-- and s++-wave superconductivities mediated by magnetic and orbital fluctuations in the 5-orbital Hubbard model for iron pnictides | We investigate the electronic state and the superconductivity in the
5-orbital Hubbard model for iron pnictides by using the dynamical mean-field
theory in conjunction with the Eliashberg equation. The renormalization factor
exhibits significant orbital dependence resulting in the large change in the
band dispersion as... | 1310.7325v2 |
2013-11-06 | Discovery of New Layered Iron Arsenide Superconductor (Ca,Pr)FeAs2 | A new iron-based superconductor (Ca,Pr)FeAs2 was discovered. Plate-like
crystals of the new phase were obtained and crystal structure was investigated
by single-crystal X-ray diffraction analysis. The structure was identified as
the monoclinic system with space group P21/m, and is composed of two Ca(Pr)
planes, anti-fl... | 1311.1302v1 |
2013-11-06 | Superconductivity in Ca1-xLaxFeAs2: A Novel 112-Type Iron Pnictide with Arsenic Zigzag Bonds | We report superconductivity in the novel 112-type iron-based compound
Ca1-xLaxFeAs2. Single-crystal X-ray diffraction analysis revealed that the
compound crystallizes in a monoclinic structure (space group P21), in which
Fe2As2 layers alternate with Ca2As2 spacer layers such that monovalent arsenic
forms zigzag chains.... | 1311.1303v1 |
2013-11-06 | Non-conventional superconducting fluctuations in Ba(Fe1-xRhx)2As2 iron-based superconductors | We measured the static uniform spin susceptibility of
Ba(Fe$_{1-x}$Rh$_x$)$_2$As$_2$ iron-based superconductors, over a broad range
of doping ($0.041\leq x\leq 0.094$) and magnetic fields. At small fields ($H
\le$ 1 kOe) we observed, above the transition temperature $T_c$, the occurrence
of precursor diamagnetism, whic... | 1311.1336v2 |
2013-11-27 | Evolution of the Fermi surface topology in doped 122 iron pnictides | Based on the minimum two-orbital model and the phase diagram recently
proposed by Tai et al.\ (Europhys. Lett. \textbf{103}, 67001(2013)) for both
electron- and hole-doped 122 iron-based superconducting compounds, we use the
Bogoliubov-de Gennes equations to perform a comprehensive investigation of the
evolution of the... | 1311.7047v1 |
2013-12-09 | Memory function approach to in-plane anisotropic resistivity in the antiferromagnetic phase of iron arsenide superconductors | We theoretically examine anisotropy of in-plane resistivity in the striped
antiferromagnetic phase of an iron arsenide superconductor by applying a memory
function approach to the ordered phase with isotropic nonmagnetic impurity. We
find that the anisotropy of the scattering rate is independent of carrier
density when... | 1312.2322v3 |
2013-12-17 | Superconducting pairing in the spin-density-wave phase of iron pnictides | Some of the iron pnictides show coexisting superconductivity and
spin-density-wave order. We study the superconducting pairing instability in
the spin-density-wave phase. Assuming that the pairing interaction is due to
spin fluctuations, we calculate the effective pairing interactions in the
singlet and triplet channel... | 1312.4720v2 |
2013-12-20 | Impact of local-moment fluctuations on the magnetic degeneracy of iron arsenide superconductors | We investigate the fate of the orthorhombic stripe-type magnetic state
(ordering vectors $\left(\pi,0\right)$/$\left(0,\pi\right)$), observed in most
iron-pnictide superconductors, in the presence of localized magnetic moments
that tend to form a Neel state (ordering vector $\left(\pi,\pi\right)$). We
show that before ... | 1312.6176v2 |
2013-12-24 | Controlling Factors of Tc-Dome Structure in 1111-Type Iron Arsenide Superconductors | We investigated the effects of phosphorus substitution on the shape of the
Tc(x) dome in 1111-type SmFeAs1-yPyO1-xHx (0 < x < 0.5). Hydride ion
substitution of oxide sites (O2- -> H-) exerts a chemical pressure effect,
i.e., a structural reduction of the Pn-Fe-Pn angle {\alpha} (Pn = P, As) and
also dopes electrons int... | 1312.6747v1 |
2014-01-01 | Unfolding the electronic structure of Ca$_{10}$(Fe$_{1-x}$Pt$_x$As)$_{10}$(Pt$_n$As$_8$) | The platinum iron arsenides
Ca$_{10}$(Fe$_{1-x}$Pt$_x$As)$_{10}$(Pt$_n$As$_8$) are the first Fe based
superconductors with metallic spacer layers. Furthermore they display a large
variation in their critical temperatures depending on the amount of Pt in their
spacer layers: $(n=3,4)$. To gain more insight into the role... | 1401.0298v2 |
2014-01-01 | Analytic theory of Hund's metals: a renormalization group perspective | We study the emergence of quasiparticles in Hund's metals with an
SU($M$)$\times$SU($N$)-symmetric Kondo impurity model carrying both spin and
orbital degrees of freedom. We show that the coupling of the impurity spin to
the conduction electrons can be \emph{ferromagnetic}, notably for hole-doped
iron pnictides. We der... | 1401.0331v3 |
2014-01-03 | Effect of SDW fluctuations on the specific heat jump in iron pnictides at a superconducting transition | Measurements of the specific heat jump at the onset of superconducting
transition in the iron-pnictide compounds revealed strong variation of its
magnitude as a function of doping that is peaked near the optimal doping. We
show that this behavior is direct manifestation of the coexistence between
spin-density-wave and ... | 1401.1118v1 |
2014-01-13 | Simulation studies of hadron energy resolution as a function of iron plate thickness at INO-ICAL | We report on a detailed simulation study of the hadron energy resolution as a
function of the thickness of the absorber plates for the proposed Iron
Calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO). We
compare the hadron resolutions obtained with absorber thicknesses in the range
1.5--8 cm for ... | 1401.2779v2 |
2014-01-15 | Strong Coupling of the Iron-Quadrupole and Anion-Dipole Polarizations in Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ | We use a quantitative convergent beam electron diffraction (CBED) based
method to image the valence electron density distribution in
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. We show a remarkable increase in both the
charge quadrupole of the Fe cations and the charge dipole of the arsenic anions
upon Co doping from $x=0$ ($T_c=0... | 1401.3706v1 |
2014-01-18 | Quantum rate theory of the trapping of hydrogen and deuterium by a vacancy in iron | We apply quantum rate theory to calculate the transition rates as hydrogen or
deuterium atoms escape from a vacancy trap in iron into a neighbouring
metastable site. We determine transition rates and corresponding activation
energies over a wide range of temperatures covering both the quantum and
classically dominated ... | 1401.4530v1 |
2014-02-11 | Weak spin interactions in Mott insulating La2O2Fe2OSe2 | Identifying and characterizing the parent phases of iron-based
superconductors is an important step towards understanding the mechanism for
their high temperature superconductivity. We present an investigation into the
magnetic interactions in the Mott insulator La2O2Fe2OSe2. This iron oxyselenide
adopts a 2-k magnetic... | 1402.2684v1 |
2014-02-17 | A High-Tc Mechanism of Iron Pnictide Superconductivity due to Cooperation of Ferro-orbital and Antiferromagnetic Fluctuations | The electronic states and superconductivity in iron pnictides are studied on
the basis of the 16 band $d$-$p$ model which includes both the onsite Coulomb
interaction between Fe $d$ electrons and the intersite one between Fe $d$ and
pnictogen $p$ electrons. The model well accounts for experimentally observed
two fluctu... | 1402.3908v2 |
2014-02-19 | Coexistence of localized and itinerant magnetism in newly discovered iron-selenide superconductor LiFeO2Fe2Se2 | The electronic structure and magnetism of LiFeO$_{2}$Fe$_{2}$Se$_{2}$ are
investigated using the first-principle calculations. The ground state is
N$\acute{e}$el antiferromagnetic (AFM) Mott insulating state for Fe1 with
localized magnetism in LiFeO$_{2}$ layer and striped AFM metallic state for Fe2
with itinerant magn... | 1402.4711v1 |
2014-02-19 | The effect of As-Chain layers in CaFeAs$_2$ | The new discovered iron-based superconductors have chain-like As layers.
These layers generate an additional 3-dimensional hole pocket and cone-like
electron pockets. The former is attributed to the Ca $d$ and As1 $p_z$ orbitals
and the latter are attributed to the anisotropic Dirac cone, contributed by As1
$p_x$ and $... | 1402.4712v1 |
2014-02-19 | Electron-impact excitation of Fe$^{2+}$: a comparison of intermediate coupling frame transformation, Breit-Pauli and Dirac R-matrix calculations | Modeling the spectral emission of low-charge iron group ions enables the
diagnostic determination of the local physical conditions of many cool plasma
environments such as those found in H II regions, planetary nebulae, active
galactic nuclei etc. Electron-impact excitation drives the population of the
emitting levels ... | 1402.4743v1 |
2014-02-24 | Spectrally-resolved femtosecond reflectivity relaxation dynamics in undoped SDW 122-structure iron based pnictides | We systematically investigate temperature- and spectrally-dependent optical
reflectivity dynamics in AAs$_{2}$Fe$_{2}$, (A=Ba, Sr and Eu), iron-based
superconductors parent spin-density-wave (SDW) compounds. Two different
relaxation processes are identified. The behavior of the slower process, which
is strongly sensiti... | 1402.5811v1 |
2014-02-25 | Probing Lorentz and CPT Violation in a Magnetized Iron Detector using Atmospheric Neutrinos | We study the sensitivity of the Iron Calorimeter (ICAL) at the India-Based
Neutrino Observatory (INO) to Lorentz and CPT violation in the neutrino sector.
Its ability to identify the charge of muons in addition to their direction and
energy makes ICAL a useful tool in putting constraints on these fundamental
symmetries... | 1402.6265v1 |
2014-02-27 | Power Law Like Correlation between Condensation Energy and Superconducting Transition Temperatures in Iron Pnictide/Chalcogenide Superconductors: Beyond the BCS Understanding | Superconducting condensation energy $U_0^{int}$ has been determined by
integrating the electronic entropy in various iron pnictide/chalcogenide
superconducting systems. It is found that $U_0^{int}\propto T_c^n$ with $n$ = 3
to 4, which is in sharp contrast to the simple BCS prediction
$U_0^{BCS}=1/2N_F\Delta_s^2$ with ... | 1402.6762v1 |
2014-03-13 | Enhancing magnetic stripe order in iron pnictides by RKKY exchange interactions | Recent experimental studies have revealed several unexpected properties of
Mn-doped BaFe2As2. These include extension of the stripe-like magnetic (pi,0)
phase to high temperatures above a critical Mn concentration only, the presence
of diffusive and weakly temperature dependent magnetic (pi,pi) checkerboard
scattering,... | 1403.3324v1 |
2014-03-21 | Functional renormalization group study of an eight-band model for the iron arsenides | We investigate the superconducting pairing instabilities of eight-band models
for the iron arsenides. Using a functional renormalization group treatment, we
determine how the critical energy scale for superconductivity depends on the
electronic band structure. Most importantly, if we vary the parameters from
values cor... | 1403.5487v3 |
2014-03-24 | Effect of weak disorder on the phase competition in iron pnictides | We analyze the effect of weak disorder on the competition between
antiferromagnetic order and superconductivity in a model for iron-based
superconductors. Under the assumption of an approximate particle-hole symmetry
we show that conventional $s^{++}$ superconductivity cannot be realized in the
case of coexisting magne... | 1403.6103v2 |
2014-04-04 | Superconducting states of a J1-J2-K model for iron pnictides | We study the symmetry and strength of the superconducting pairing in a
two-orbital t-J1-J2-K model for iron pnictides using the salve boson mean-field
theory. We show that the nearest-neighbor biquadratic interaction -K (S_i *
S_j)^2 inflences the superconducting pairing phase diagram by promoting the
d_{x2-y2} B_{1g} ... | 1404.1307v1 |
2014-04-11 | A new library of theoretical stellar spectra with scaled-solar and alpha-enhanced mixtures | Theoretical stellar libraries have been increasingly used to overcome
limitations of empirical libraries, e.g. by exploring atmospheric parameter
spaces not well represented in the latter. This work presents a new theoretical
library which covers 3000 $\leq$ Teff $\leq$ 25000\,K, -0.5 $\leq$ log g $\leq$
5.5, and 12 ch... | 1404.3243v1 |
2014-04-14 | Magnetic correlations and pairing in the 1/5-depleted square lattice Hubbard model | We study the single-orbital Hubbard model on the 1/5-depleted square lattice
geometry, which arises in such diverse systems as the spin-gap magnetic
insulator CaV4O9 and ordered-vacancy iron selenides, presenting new issues
regarding the origin of both magnetic ordering and superconductivity in these
materials. We find... | 1404.3731v2 |
2014-04-25 | Role of vibrational entropy in the stabilization of the high-temperature phases of iron | The phonon dispersions of the bcc and fcc phases of pure iron ({\alpha}-Fe,
{\gamma}-Fe and {\delta}-Fe) at ambient pressure were investigated close to the
respective phase transition temperatures. In the open bcc structure the
transverse phonons along T1 [{\xi}{\xi}0] and T1 [{\xi}{\xi}2{\xi}] are of
particularly low ... | 1404.6459v1 |
2014-05-07 | Topological surface states and Andreev bound states in superconducting iron pnictides | The nontrivial topology of the electronic structure of iron pnictides can
lead to the appearance of surface states. We study such states in various strip
geometries with a focus on the superconducting phase. In the presence of
unconventional superconducting pairing with $s_\pm$-wave gap structure, the
topological state... | 1405.1632v2 |
2014-05-15 | High-pressure single-crystal neutron scattering study of magnetic and Fe vacancy orders in (Tl,Rb)2Fe4Se5 superconductor | The magnetic and iron vacancy orders in superconducting (Tl,Rb)2Fe4Se5
single-crystals are investigated by using a high-pressure neutron diffraction
technique. Similar to the temperature effect, the block antiferromagnetic order
gradually decreases upon increasing pressure while the Fe vacancy
superstructural order rem... | 1405.4020v2 |
2014-05-19 | Radiation from an emitter revolving around a magnetized non-rotating black hole | One of the methods of study of black holes in astrophysics is based on
broadening of the spectrum of radiation of ionized Iron atoms. The line
K$\alpha$ associated with Iron emission at 6.4 keV is very narrow. If such an
ion is revolving around a black hole, this line is effectively broadened as a
result of the Doppler... | 1405.4899v1 |
2014-05-20 | Resistive anisotropy due to spin-fluctuation scattering in the nematic phase of iron pnictides | The large in-plane anisotropy of the resistivity is a hallmark of the nematic
state of the iron pnictides. Solving the Boltzmann transport equation, we show
that the prominent doping dependence as well as the large values of the
anisotropy can be well explained by momentum-dependent spin-fluctuation
scattering without ... | 1405.5084v3 |
2014-05-21 | Theoretical approach to resonant inelastic x-ray scattering in iron-based superconductors at the energy scale of the superconducting gap | We develop a phenomenological theory to predict the characteristic features
of the momentum-dependent scattering amplitude in resonant inelastic x-ray
scattering (RIXS) at the energy scale of the superconducting gap in iron-based
superconductors. Taking into account all relevant orbital states as well as
their specific... | 1405.5556v2 |
2014-05-23 | Collective modes in multiband superconductors: Raman scattering in iron selenides | We study Raman scattering in the superconducting state of alkali-intercalated
iron selenide materials AxFe2-ySe2 (A=K,Rb,Cs) in which Fermi surface has only
electron pockets. Theory predicts that both s-wave and d-wave pairing channels
are attractive in this material, and the gap can have either s-wave or d-wave
symmet... | 1405.6246v1 |
2014-05-28 | A Simulations Study of the Muon Response of the Iron Calorimeter Detector at the India-based Neutrino Observatory | The magnetised Iron CALorimeter detector (ICAL), proposed to be built at the
India-based Neutrino Observatory (INO), is designed to study atmospheric
neutrino oscillations. The ICAL detector is optimized to measure the muon
momentum, its direction and charge. A GEANT4-based package has been developed
by the INO collabo... | 1405.7243v1 |
2014-06-19 | Magnetic form factor analysis on detwinned single crystal of BaFe$_2$As$_2$ | We have performed neutron diffraction measurement on a single crystal of
parent compound of iron-based superconductor, BaFe$_2$As$_2$ at 12~K. In order
to investigate in-plane anisotropy of magnetic form factor in the
antiferromagnetic phase, the detwinned single crystal is used in the
measurement. The magnetic structu... | 1406.4935v1 |
2014-06-20 | Coexistence of Antiferromagnetism and Superconductivity in Iron-Based Superconductors | We theoretically investigate the coexistence of antiferromagnetism and
superconductivity in the iron-based superconductors by using the mean-field
theory for two- and three-orbital models. We find that both the s_{+-}-wave and
s_{++}-wave superconductivity can coexist with antiferromagnetism in the two
models. On Dirac... | 1406.5339v2 |
2014-06-21 | Fermi-surface topology of the iron pnictide LaFe$_2$P$_2$ | We report on a comprehensive de Haas--van Alphen (dHvA) study of the iron
pnictide LaFe$_2$P$_2$. Our extensive density-functional band-structure
calculations can well explain the measured angular-dependent dHvA frequencies.
As salient feature, we observe only one quasi-two-dimensional Fermi-surface
sheet, i.e., a hole... | 1406.5642v1 |
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