publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2009-05-26 | Analysis of transport properties of iron pnictides: spin-fluctuation scenario | We present a phenomenological theory of quasiparticle scattering and
transport relaxation in the normal state of iron pnictides based on the
simplified two-band model coupled via spin fluctuations. In analogy with
anomalous properties of cuprates it is shown that a large and anomalous
normal-state resistivity and therm... | 0905.4153v2 |
2009-05-29 | Tight-binding models for the new iron based superconductor materials | The rich novel materials class of iron based superconductors turned out to
exhibit a very complex electronic structure, despite of the simplicity of their
crystal structures. For various approaches to study the instability against
magnetic order or superconductivity, a real space description of the electronic
structure... | 0905.4844v2 |
2009-07-01 | The Stoichiometry of FeSe | Tetragonal iron selenide, FeSe, 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 near 8 K. There has,
however, been a lack of consensus as to whether selenium vacancies present due
to larg... | 0907.0174v1 |
2009-09-07 | Modeling Antiferromagnetic Phase in Iron Pnictides: Weakly Ordered State | We examine electronic states of antiferromagnetic phase in iron pnictides by
mean-field calculations of the optical conductivity. We find that a five-band
model exhibiting a small magnetic moment, inconsistent with the
first-principles calculations, reproduces well the excitation spectra
characterized by a multi-peak s... | 0909.1081v2 |
2009-09-07 | First-principles-based $\pm s$-wave modelling for iron-based superconductors:Studies for specific heat and nuclear magnetic relaxation rate | In order to consistently explain controversial experimental results on
superconducting states observed by different probes in typical iron-based
superconductors, we construct a realistic multi-band $\pm s$-wave pairing model
by combining the quasiclassical formalism with the first-principles
calculation. The model succ... | 0909.1195v1 |
2009-09-15 | Bulk Superconductivity at 2.6 K in Undoped RbFe_2As_2 | The iron arsenide RbFe_2As_2 with the ThCr_2Si_2-type structure is found to
be a bulk superconductor with T_c=2.6 K. The onset of diamagnetism was used to
estimate the upper critical field H_c2(T), resulting in dH_c2/dT=-1.4 T/K and
an extrapolated H_c2(0)=2.5 T. As a new representative of iron pnictide
superconductors... | 0909.2740v1 |
2009-11-16 | Simple Real-Space Picture of Nodeless and Nodal s-wave Gap Functions in Iron Pnictide Superconductors | We propose a simple way to parameterize the gap function in iron pnictides.
The key idea is to use orbital representation, not band representation, and to
assume real-space short-range pairing. Our parameterization reproduces fairly
well the structure of gap function obtained in microscopic calculation. At the
same tim... | 0911.2959v2 |
2009-11-16 | Nuclear Magnetic Relaxation Rate in Iron-Pnictide Superconductors | Nuclear magnetic relaxation rate 1/T_1 in iron-pnictide superconductors is
calculated using the gap function obtained in a microscopic calculation. Based
on the obtained results, we discuss the issues such as the rapid decrease of
1/T_1 just below the transition temperature and the difference between nodeless
and nodal... | 0911.2963v1 |
2009-12-09 | FERO (Finding Extreme Relativistic Objects): relativistic Iron K alpha lines in type 1 AGN | The observational evidence for AGN relativistic Iron lines is very much
debated. To address this topic, the FERO project makes use of the largest
sample of X-ray spectra of radio quiet Type 1 AGN available in the XMM-Newton
archive. We perform a systematic fit of the individual sources using a full
relativistic code. R... | 0912.1889v1 |
2009-12-16 | Anomalous normal-state properties of iron pnictides: phenomenological theory | We employ the phenomenological theory of the quasiparticle relaxation based
on the simplified two-band description and the spin-fluctuation induced
interband coupling to analyze recent normal-state transport data in
electron-doped iron pnictides, in particular the Ba(Fe_1-x Co_x)_2As_2 family.
Temperature dependence of... | 0912.3122v2 |
2010-01-26 | On spatial non-homogeneity in iron pnictides: formation of stripes | The heterogeneous coexistence of antiferromagnetism (SDW) and
superconductivity on a mesoscopic scale was observed in iron-pnictides in many
recent experiments. We suggest and discuss the scenario in which the
heterogeneity is caused by formation of domain walls inherent to the SDW state
of pnictides at a proper doping... | 1001.4641v2 |
2010-02-13 | Spin and Charge Dynamics Ruled by Antiferromagnetic Order in Iron Pnictides | We examine the spin and charge excitations in antiferromagnetic iron
pnictides by mean-field calculations with a random phase approximation in a
five-band itinerant model. The calculated excitation spectra reproduce well
spin-wave dispersions observed in inelastic neutron scattering, with a
realistic magnetic moment fo... | 1002.2701v2 |
2010-02-17 | Evidence for an electron nematic phase transition in underdoped iron pnictide superconductors | Electrical resistivity measurements of detwinned single crystals of the
representative iron arsenide Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ reveal a dramatic
in-plane anisotropy associated with the tetragonal-to-orthorhombic structural
transition that precedes the onset of long-range antiferromagnetic order. These
results indi... | 1002.3364v2 |
2010-03-03 | Relationship between Colours of Ochre from Roussillon and Content of Iron-Bearing Minerals | Nine samples of ochre originating from the Sentier des Ocres near Roussillon,
France, were studied with Mossbauer spectroscopy and Spectro-photo-colorimetry.
The former yielded a quantitative phase analysis of iron containing minerals
(goethite, hematite and kaolin), and the latter enabled determination of the
CIE-L*a*... | 1003.0760v1 |
2010-03-10 | Dichotomy between large local and small ordered magnetic moment in Iron-based superconductors | We study a four band model for iron-based superconductors within local
density approximation + dynamical mean field theory (LDA+DMFT). This
successfully reproduces the results of models which take As p degrees of
freedom explicitly into account and has several physical advantages over the
standard five d-band model. Ou... | 1003.2162v1 |
2010-03-19 | Gamma ray production in inelastic scattering of neutrons produced by cosmic muons in $^{56}$Fe | We report on the study of the intensities of several gamma lines emitted
after the inelastic scattering of neutrons in $^{56}$Fe. Neutrons were produced
by cosmic muons passing the 20t massive iron cube placed at the Earth's surface
and used as a passive shield for the HPGe detector. Relative intensities of
detected ga... | 1003.3890v1 |
2010-05-06 | Self consistent GW determination of the interaction strength: application to the iron arsenide superconductors | We introduce a first principles approach to determine the strength of the
electronic correlations based on the fully self consistent GW approximation.
The approach provides a seamless interface with dynamical mean field theory,
and gives good results for well studied correlated materials such as NiO.
Applied to the rec... | 1005.0885v1 |
2010-06-11 | Structural Features of Layered Iron Pnictide Oxides (Fe2As2)(Sr4M2O6) | Structural features of newly found perovskite-based iron pnictide oxide
system have been systematically studied. Compared to REFePnO system,
perovskite-based system tend to have lower Pn-Fe-Pn angle and higher pnictogen
height owing to low electronegativity of alkaline earth metal and small
repulsive force between pnic... | 1006.2351v1 |
2010-06-21 | Phase Field Crystal Study of Symmetric Tilt Grain Boundaries of Iron | We apply the phase field crystal model to study the structure and energy of
symmetric tilt grain boundaries of bcc iron in 3D. The parameters for the model
are obtained by using a recently developed eight-order fitting scheme [A.
Jaatinen et al., Phys. Rev. B 80, 031602 (2009)]. The grain boundary free
energies we obta... | 1006.5405v1 |
2010-06-28 | Eliashberg Analysis of Optical Spectra Reveals Strong Coupling of Charge Carriers to Spin Fluctuations in Superconducting Iron Pnictides | The temperature and frequency dependences of the optical conductivity of Co
and Ni-doped BaFe2As2 are analyzed and the electron-boson spectral density
a2F(w) extracted using Eliashberg's formalism. The characteristic energy of a
large peak in the spectrum around 10 meV coincide with the resonance peak in
the spin excit... | 1006.5468v1 |
2010-07-15 | The electronic instabilities of the Iron-based superconductors: a variational Monte-Carlo study | We report the first variational Monte Carlo (VMC) study of the iron-based
superconductors. We use realistic band structures, and the ordering
instabilities/variational ansatzs are suggested by previous functional
renormalization group calculations. We examine antiferromagnetism,
superconducting pairing, normal state fe... | 1007.2643v4 |
2010-08-03 | Rescaled potential for transition metal solutes in a-iron | We present empirical potentials for dilute transition metal solutes in
a-iron. It is in the Finnis-Sinclair form and is therefore suitable for billion
atom molecular dynamics simulations. First principles calculation shows that
there are clear trends across the transition metal series which enable us to
relate the resc... | 1008.0508v1 |
2010-08-17 | Domain Walls in Normal and Superconducting States of Iron Pnictides | The electronic and magnetic structures in the normal and superconducting
states of iron pnictides are investigated by solving self-consistently the
Bogoliubov-de Gennes equation. It is shown that strong electron correlations
can induce domain walls, which separate regions with different spin density
wave orders. At zer... | 1008.2981v1 |
2010-09-02 | Toroidal Carbon Nanotubes with Encapsulated Atomic Metal Loops | Toroidal carbon nanotubes can serve as hosts for encapsulated loops of atomic
metal wires. Such composite structures have been analyzed using density
functional theory for a semiconducting C$_{120}$ torus encapsulating chains of
Fe, Au and Cu atoms. The sheathed metal necklaces form a zigzag structure and
drops the HOM... | 1009.0442v1 |
2010-09-20 | Non-Fermi-Liquid-Like Behaviors and Superconductivity Driven by Orbital Fluctuations in Iron Pnictides: Analysis by Fluctuation-Exchange Approximation | We study the five-orbital Hubbard-Holstein model for iron pnictides with
small electron-phonon interaction due to Fe-ion Einstein oscillators. Using the
fluctuation-exchange (FLEX) approximation, orbital fluctuations evolve
inversely proportional to the temperature, and therefore the resistivity shows
linear or convex ... | 1009.3882v1 |
2010-09-29 | Phase Separation and Chemical Inhomogeneity in the Iron Chalcogenide Superconductor Fe1+yTexSe1-x | We report investigation on Fe1+yTexSe1-x single crystals by using scanning
transmission electron microscopy (STEM) and electron energy loss spectroscopy
(EELS). Both nonsuperconducting samples with excess iron and superconducting
samples demonstrate nanoscale phase separation and chemical inhomogeneity of
Te/Se content... | 1009.6010v1 |
2010-12-02 | Comment on "Violation of Anderson's Theorem for the sign-reversing s-wave state of Iron-Pnictide Superconductors" by Onari et al., Phys. Rev. Lett. 103, 177001(2009)[1] | We pointed out that the main claim of Ref.[1] that the presence of the
orbital degree of freedom is essential to describe the correct impurity effects
for Iron-based superconductors is incorrect and demonstrated the equivalent
results of Tc suppression due to impurities by both the band basis model and
the orbital basi... | 1012.0414v1 |
2011-01-05 | 77Se NMR study of pairing symmetry and spin dynamics in KyFe2-xSe2 | We present a 77Se NMR study of the newly discovered iron selenide
superconductor KyFe2-xSe2, in which Tc = 32 K. Below Tc, the Knight shift 77K
drops sharply with temperature, providing strong evidence for singlet pairing.
Above Tc, Korringa-type relaxation indicates Fermi-liquid behavior. Our
experimental results set ... | 1101.1017v2 |
2011-01-06 | Comment on "Orbital Order, Structural Transition and Superconductivity in Iron Pnictides" [arXiv:1010.0129] by Yanagi et al | In contrast to the claim by Yanagi et al. in Ref. [1], the development of
orbital fluctuations at $q ~ 0$ due to the "orthorhombic phonon" is unable to
explain the high-Tc superconductivity in iron pnictides. The reason is that the
orthorhombic-phonon is acoustic with the energy $\omega_q \propto q$, although
the autho... | 1101.1157v3 |
2011-01-18 | Temperature-dependent spin resonance energy in iron pnictides and multiband s\pm Eliashberg theory | The phenomenology of iron-pnictides superconductors can be explained in the
framework of a three bands s\pm wave Eliashberg theory with only two free
parameters plus a feedback effect i.e. the effect of the condensate on the
antiferromagnetic spin fluctuactions responsible of the superconductivity in
these compounds. I... | 1101.3473v2 |
2011-02-18 | Maximizing Fermi surface multiplicity optimizes superconductivity in iron pnictides | We study the condition for optimizing superconductivity in the iron pnictides
from the lattice structure point of view. Studying the band structure of the
hypothetical lattice structure of LaFeAsO, the hole Fermi surface multiplicity
is found to be maximized around the Fe-As-Fe bond angle regime where the
arsenic atoms... | 1102.3765v1 |
2011-03-10 | From density functional theory to the functional renormalization group: superconductivity in the iron pnictide LiFeAs | A combined density functional theory and functional renormalization group
method is introduced which takes into account orbital-dependent interaction
parameters to derive the effective low-energy theory of weakly to
intermediately correlated Fermi systems. As an application, the competing
fluctuations in LiFeAs are inv... | 1103.2101v1 |
2011-04-07 | Detection of melting by in-situ observation of spherical-drop formation in laser-heated diamond-anvil cells | A simple method for detection of melting event in laser-heated diamond anvil
cells (DACs) is introduced. The melting is registered optically by the
formation of spherical drops of the investigated material as heated in an inert
pressure transmitting medium. Feasibility of the method is demonstrated on the
examples of m... | 1104.1304v1 |
2011-04-26 | Specific heat jump at superconducting transition in the presence of Spin-Density-Wave in iron-pnictides | We analyze the magnitude of the specific heat jump \Delta C at the
superconducting transition temperature T_c in the situation when
superconductivity develops in the pre-existing antiferromagnetic phase. We show
that \Delta C/T_c differs from the BCS value and is peaked at the tri-critical
point where this coexistence ... | 1104.5037v1 |
2011-04-28 | Spin and Orbital Characters of Excitations in Iron Arsenide Superconductors Revealed by Simulated Fe L-Edge RIXS | We theoretically examine the orbital excitations coupled to the spin degree
of freedom in the parent state of the iron-arsenide superconductor, based on
the calculation in a five-band itinerant model. The calculated Fe $L_3$-edge
resonant inelastic x-ray scattering (RIXS) spectra disclose the presence of
spin-flip exci... | 1104.5424v2 |
2011-05-10 | Consistent picture for the electronic structure around a vortex core in iron-based superconductors | Based on a two-orbital model and taking into account the presence of the
impurity, we studied theoretically the electronic structure in the vortex core
of the iron-Pnictide superconducting materials. The vortex is pinned when the
impurity is close to the vortex core. The bound states shows up for the
unpinned vortex an... | 1105.1851v1 |
2011-05-19 | Differential conductance of point contacts between an iron-based superconductor and a normal metal | We present a theoretical description of the differential conductance of point
contacts between a normal metal and a multi-band superconductor with extended
s\pm pairing symmetry. We demonstrate that the interband impurity scattering
broadens the coherent peak near the superconducting gap and significantly
reduces its h... | 1105.3926v2 |
2011-05-26 | Orbital-spin ordering in the striped antiferromagnetic state of iron-based superconductors | The magnetic properties of iron-arsenides are investigated using the LSDA+U
approach. In addition to one high moment state, we find that a positive U also
produces two low moment states with m~0.4 $\mu_{B}$ and m~1.0 $\mu_{B}$. The
electronic structures indicate that the low moment states originate in the
strong orbita... | 1105.5412v1 |
2011-06-12 | Anomalies in the Multicritical Behavior of Staggered Magnetic and Direct Magnetic Susceptibilities of Iron Group Dihalides | In this study, the temperature dependencies of magnetic response functions of
the anhydrous dihalides of iron-group elements are examined in the neighborhood
of multi-critical points (tricritical, critical end point, double critical end
point) and first order transition temperatures within molecular field
approximation... | 1106.2308v1 |
2011-06-22 | Magnetic excitations in iron pnictides | Spin wave dispersion and damping are investigated in the metallic SDW state
of different itinerant electron models including a small interlayer hopping.
Magnetic excitations in iron pnictides are shown to be well understood in terms
of physical mechanisms characteristic of metallic magnets, such as
carrier-induced ferr... | 1106.4421v1 |
2011-07-04 | Reply to Comment on "Neutron-Inelastic-Scattering Peak by Dissipationless Mechanism in the $s_{++}$-wave State in Iron-based Superconductors" [arXiv:1106.2376] by Y. Nagai and K. Kuroki | This article is a reply to the comment by Nagai and Kuroki [arXiv:1106.2376]
for our unpublished paper in arXiv [arXiv:1105.6233]. Contrary to their claim,
we certainly obtain a large hump structure at $q=(\pi,0)$ in the $s_{++}$-wave
state in iron pnictides due to the ``dissipationless mechanism'', even when
similar p... | 1107.0748v1 |
2011-11-15 | First principles study of iron-based molecule grafted on graphene | Motivated by recent experimental studies on single molecular magnets grafted
on graphene and single walled carbon nanotubes, we investigate the structural,
electronic, and magnetic properties of an iron based magnetic molecule grafted
on a graphene sheet using \textit{ab initio} calculations.
In particular, the induc... | 1111.3516v1 |
2011-11-30 | Electronic and Magnetic Structure of Possible Iron Based Superconductor BaFe2Se3 | We present results of LDA calculations (band structure, densities of states,
Fermi surfaces) for possible iron based superconductor BaFe2Se3 (Ba123) in
normal (paramagnetic) phase. Results are briefly compared with similar data on
prototype BaFe2As2 and (K,Cs)Fe2Se2 superconductors. Without doping this system
is antife... | 1111.7046v1 |
2011-12-20 | Ab initio Evidence for Strong Correlation Associated with Mott Proximity in Iron-based Superconductors | We predict that iron-based superconductors discovered near d6 configuration
(5 Fe 3d orbitals filled by 6 electrons) is located on the foot of an
unexpectedly large dome of correlated electron matter centered at the Mott
insulator at d5 (namely, half filling). This is based on the many-variable
variational Monte-Carlo ... | 1112.4682v1 |
2011-12-21 | Dislocation core field. II. Screw dislocation in iron | The dislocation core field, which comes in addition to the Volterra elastic
field, is studied for the <111> screw dislocation in alpha-iron. This core
field, evidenced and characterized using ab initio calculations, corresponds to
a biaxial dilatation, which we modeled within the anisotropic linear
elasticity. We show ... | 1112.4936v1 |
2011-12-31 | Brief review on iron-based superconductors: are there clues for unconventional superconductivity? | Study of superconductivity in layered iron-based materials was initiated in
2006 by Hosono's group, and boosted in 2008 by the superconducting transition
temperature, Tc, of 26 K in LaFeAsO1-xFx. Since then, enormous researches have
been done on the materials, with Tc reaching as high as 55 K. Here, we review
briefly e... | 1201.0237v1 |
2012-01-26 | Effect of uniaxial pressure on the magneto-structural transitions of iron arsenide superconductors | We study theoretically the variation of the magnetic and the structural
transition temperatures of the iron arsenide superconductors with external
uniaxial stress. We show that the increase of the transition temperatures
reported in recent experiments is compatible with a simple magneto-elastic
model in which the physi... | 1201.5594v2 |
2012-03-05 | Iron-platinum-arsenide superconductors Ca10(PtnAs8)(Fe2-xPtxAs2)5 | An overview of the crystal structures and physical properties of the recently
discovered iron-platinum-arsenide superconductors, Ca10(PtnAs8)(Fe2-xPtxAs2)5
(n = 3 and 4), which have a superconducting transition temperature up to 38 K,
is provided. The crystal structure consists of superconducting Fe2As2 layers
alternat... | 1203.0821v1 |
2012-03-15 | Divergent nematic susceptibility in an iron arsenide superconductor | Within the Landau paradigm of continuous phase transitions, ordered states of
matter are characterized by a broken symmetry. Although the broken symmetry is
usually evident, determining the driving force behind the phase transition is
often a more subtle matter due to coupling between otherwise distinct order
parameter... | 1203.3239v1 |
2012-04-07 | Rotationally-Invariant Exchange Interaction: The Case of Paramagnetic Iron | We present a generalization of the spin-fluctuation theory of magnetism which
allows us to treat the full rotational invariance of the exchange interaction.
The approach is formulated in terms of the local density approximation plus
dynamical mean-field theory (LDA+DMFT), providing a systematic many-body
treatment of t... | 1204.1636v1 |
2012-05-29 | Ab initio study of helium and hydrogen interactions in $α$-Fe | Density Functional Theory (DFT) calculations show a weak interaction between
hydrogen and helium in iron, in contrast to previous reports of a strong
trapping of hydrogen at helium. The strong preference of He and H to occupy
regions with low electronic density (such as vacancies) explains this
discrepancy, with vacanc... | 1205.6374v2 |
2012-05-30 | Multiple Superconducting Gaps, Anisotropic Spin Fluctuations and Spin-Orbit Coupling in Iron-Pnictides | This article reviews the NMR and NQR studies on iron-based high-temperature
superconductors by the IOP/Okayama group. It was found that the electron pairs
in the superconducting state are in the spin-singlet state with multiple
fully-opened energy gaps. The antiferromagnetic spin fluctuations in the normal
state are fo... | 1205.6589v1 |
2012-06-11 | Chemical Bonds and Spin State Splittings in Spin Crossover Complexes. A DFT and QTAIM Analysis | Density functional theory (DFT) calculations have been performed for the
high-spin (HS) and low-spin (LS) isomers of a series of iron(II) spin crossover
complexes with nitrogen ligands. The calculated charge densities have been
analyzed in the framework of the quantum theory of atoms in molecules (QTAIM).
For a number ... | 1206.2136v1 |
2012-06-13 | Nuclear Resonance Vibrational Spectroscopy of Iron Sulfur Proteins | Nuclear inelastic scattering in conjunction with density functional theory
(DFT) calculations has been applied for the identification of vibrational modes
of the high-spin ferric and the high-spin ferrous iron-sulfur center of a
rubredoxin-type protein from the thermophylic bacterium Pyrococcus abysii. | 1206.2788v1 |
2012-10-26 | Finite-size effect of antiferromagnetic transition and electronic structure in LiFePO4 | The finite-size effect on the antiferromagnetic (AF) transition and
electronic configuration of iron has been observed in LiFePO4. Determination of
the scaling behavior of the AF transition temperature (TN) versus the
particle-size dimension (L) in the critical regime 1-TN(L)/TN(XTL)\simL^-1
reveals that the activation... | 1210.7167v1 |
2012-12-07 | Molecular Dynamics and OKMC Study of Radiation Induced Motion of Voids and He Bubbles in BCC Iron | We show that voids adjacent to radiation damage cascades can be moved in
their entirety by several lattice spacings. This is done using molecular
dynamics cascade simulations in iron at energies of 1-5 keV. The effect of this
mechanism is studied further using an OKMC code and shows enhancement of void
diffusion by 2 o... | 1212.1652v2 |
2012-12-13 | Consequence of total lepton number violation in strongly magnetized iron white dwarfs | The influence of neutrinoless electron to positron conversion on cooling of
strongly magnetized iron white dwarfs is studied. It is shown that they can be
good candidates for soft gamma-ray repeaters and anomalous X-ray pulsars. | 1212.3155v4 |
2013-01-08 | Mechanism for the α -> ε phase transition in iron | The mechanism of the {\alpha}-{\epsilon} transition in iron is reconsidered.
A path in the Burgers description of the bcc/hcp transition different from
those previously considered is proposed. It relies on the assumption that shear
and shuffle are decoupled and requires some peculiar magnetic order, different
from that... | 1301.1623v1 |
2013-03-06 | Mixed-State Effect on the Low-Energy Spin Dynamics in Optimally-doped Iron Pnictide Superconductors | Based on a phenomenological model with $s_{\pm}$ or s-wave pairing symmetry,
the mixed-state effect on the low-energy spin dynamics in optimally-doped iron
pnictide superconductors is studied by solving Bogoliubov-de Gennes equations.
Our results of the spin susceptibility at $\mathbf{q}=\mathbf{Q}$ in the
normal, supe... | 1303.1557v1 |
2013-03-15 | van der Waals interaction in iron-chalcogenide superconductors | We demonstrate that the inclusion of van der Waals dispersive interaction
sensibly improves the prediction of lattice constants by density functional
theory in iron-chalcogenides (FeCh) superconductor compounds, namely FeSe and
FeTe. We show how generalized gradient approximation (GGA) for the exchange
correlation pote... | 1303.3747v2 |
2013-03-25 | To the interpretation of the upturn observed by ATIC in heavy nuclei to iron ratios | It is argued that the upturn observed in heavy nuclei to iron ratios as
measured in the ATIC experiment could be understood within the model of closed
galaxy with embedded local regions containing the sources of CR (Peters,
Westergaard, 1977). The universal upturn near the energies of 200-300 GeV/n in
the spectra of ab... | 1303.6102v1 |
2013-04-29 | Bulk Synthesis of Iron-based Superconductors | Exploratory synthesis efforts for iron-based superconductors (FeSC) have been
driven by hopes of improving superconducting critical temperatures (TCs),
providing high-quality samples for in-depth studies of intrinsic properties,
and exploring potential superconductivity in similar families of materials.
This manuscript... | 1304.7708v1 |
2013-05-03 | Fermiology, Orbital Order, Orbital Fluctuation and Cooper Pairing in Iron-based Superconductors | We address two important issues that arise in recent studies of iron-based
superconductivity. (1) Why are the T_c of A_xFe_{2-y}Se_2 and the single unit
cell FeSe on SrTiO$_3$ so high despite both only have electron pockets? (2)
What (if any) are the effects of orbital order and orbital fluctuation on the
Cooper pairin... | 1305.0605v3 |
2013-05-08 | Topological Surface States in Paramagnetic and Antiferromagnetic Iron Pnictides | The electronic structure of iron pnictides is topologically nontrivial,
leading to the appearance of Dirac cones in the band structure for the
antiferromagnetic phase. Motivated by the analogy with Dirac cones in graphene,
we explore the possible existence of topologically protected surface states.
Surprisingly, bands ... | 1305.1770v2 |
2013-05-15 | Nematic susceptibility of hole- and electron-doped BaFe2As2 iron-based superconductors from shear modulus measurements | The nematic susceptibility of hole-doped Ba1-xKxFe2As2 and electron-doped
Ba(Fe1-xCox)2As2 iron-based superconductors is obtained from measurements of
the elastic shear modulus using a three-point bending setup in a capacitance
dilatometer. Nematic fluctuations, although weakened by doping, extend over the
whole superc... | 1305.3515v2 |
2013-07-04 | Unusual band renormalization in the simplest iron based superconductor | The electronic structure of the iron chalcogenide superconductor FeSe_{1-x}
was investigated by high- resolution angle-resolved photoemission spectroscopy
(ARPES). The results were compared to DFT calculations showing some significant
differences between the experimental electronic structure of FeSe_{1-x}, DFT
calculat... | 1307.1280v1 |
2013-09-25 | Superconductivity in 1111-type CaFeAsF1-xHx induced by selective hydrogen elimination | The difference in thermal stability of F- and H- in 1111-type iron based
superconductors, allows selective hydrogen elimination from non-superconductive
CaFeAsF0.8H0.2 by thermal annealing. The analyzed chemical composition of the
resulting samples indicates that incorporated hydrogen was selectively
eliminated by ther... | 1309.6398v2 |
2013-10-03 | Raman scattering as a probe of charge nematic fluctuations in iron based superconductors | We report Raman scattering measurement of charge nematic fluctuations in the
tetragonal phase of BaFe$_2$As$_2$ and Sr(Fe$_{1-x}$Co$_x$)$_2$As$_2$ (x=0.04)
single crystals. In both systems, the observed nematic fluctuations are found
to exhibit divergent Curie-Weiss like behavior with very similar characteristic
temper... | 1310.0934v2 |
2013-12-17 | Nesting Induced Large Magnetoelasticity in the Iron Arsenide Systems | A novel feature of the iron arsenides is the magnetoelastic coupling between
the long wavelength in-plane strains of the lattice and the collective spin
fluctuations of the electrons near the magnetic ordering wavevectors. Here, we
study its microscopic origin from an electronic model with nested Fermi pockets
and a no... | 1312.4968v3 |
2014-01-15 | X-ray absorption spectroscopy characterization of iron-oxide nanoparticles synthesized by high temperature plasma processing | Iron-oxide nanoparticles have been synthesized by high temperature arc plasma
route with different plasma currents and characterized for their structure,
morphology and local atomic order. Fe K-edge x-ray absorption spectra reveal
distinct local structure of the samples grown with different plasma currents.
We have sho... | 1401.3655v1 |
2014-01-17 | Globular clusters: a chemical roadmap between anomalies and homogeneity | For several decades, globular clusters have been considered the best example
of simple stellar populations, hosting coeval and chemical homogeneous stars.
The last decade of spectroscopic and photometric studies has revealed a more
complex view of their chemical composition, with a high level of homogeneity in
their ir... | 1401.4323v1 |
2014-03-25 | Functional Renormalization Group Analysis of $η$-Pairing in Iron-based Superconductors | Using functional renormalization group (FRG) approach, we analyze the $\eta$
pairing in a five d-orbital model for iron-pncitides. We find that the $\eta$
pairing between two hole pockets is a leading instability at low energy when
the two hole pockets are close to a nesting condition. The result suggests that
the syst... | 1403.6240v1 |
2014-03-31 | Evaluation of the Debye temperature for iron cores in human liver ferritin and its pharmaceutical analogue Ferrum Lek using Mossbauer spectroscopy | An iron polymaltose complex Ferrum Lek used as antianemic drug and considered
as a ferritin analogue and human liver ferritin were investigated in the
temperature range from 295K to 90K by means of 57Fe Mossbauer spectroscopy with
a high velocity resolution i.e. in 4096 channels. The Debye temperatures equal
to 502K fo... | 1403.7900v1 |
2014-09-17 | Electronic structure, spin excitations, and orbital ordering in a three-orbital model for iron pnictides | A three-orbital itinerant-electron model involving d_{xz}, d_{yz} and d_{xy}
Fe 3d orbitals is proposed for iron pnictides towards understanding the (\pi,0)
ordered magnetism and magnetic excitations in these materials. It is shown that
this model at half filling yields a gapped (\pi,0) magnetic state with high
degree ... | 1409.4984v2 |
2014-10-18 | Structural and magnetic characterisation of iron oxyselenides Ce2O2Fe2OSe2 and Nd2O2Fe2OSe2 | We present here an investigation of the magnetic ordering in the Mott
insulating oxyselenide materials Ln2O2Fe2OSe2 (Ln = Ce, Nd). Neutron powder
diffraction data are consistent with a non-collinear multi-k ordering on the
iron sublattice structure and analysis indicates a reduced magnetic correlation
length perpendicu... | 1410.4990v1 |
2014-11-21 | Spontaneous appearance of nonzero momentum Cooper pairing: Possible application to the iron-pnictides | We suggest that an inhomogeneous (non-zero momentum) paired phase can appear
in the absence of an external magnetic field in the system with a predominant
interband pairing and with separate Fermi-surface sheets. The Fermi wave vector
mismatch which appears in such situation can be compensated by nonzero
center-of-mass... | 1411.5882v1 |
2015-01-28 | Synthesis of endohedral iron-fullerenes by ion implantation | In this paper, we discuss the results of our study of the synthesis of
endohedral iron-fullerenes. A low energy Fe+ ion beam was irradiated to C60
thin film by using a deceleration system. Fe+-irradiated C60 thin film was
analyzed by high performance liquid chromatography and laser
desorption/ionization time-of-flight ... | 1501.07022v1 |
2015-06-30 | Orbital-selective electronic excitations in iron arsenides revealed by simulated nonresonant inelastic x-ray scattering | Nonresonant inelastic x-ray scattering (NIXS) is a possible tool to detect
charge excitations in electron systems. In addition, multipole transitions at
high-momentum-transfer region open a new possibility to determine
orbital-selective electronic excitations in multi-orbital itinerant 3d electron
systems. As a theoret... | 1506.08972v1 |
2015-07-05 | Magneto-orbital coupling in iron pnictides | A magneto-orbital coupling mechanism is proposed to account for the weak
energy gap at the Fermi energy in the $(\pi,0)$ ordered SDW state of a
realistic three band model for iron pnictides involving $d_{xz}$, $d_{yz}$, and
$d_{xy}$ Fe orbitals. The orbital mixing terms between the $d_{xy}$ and
$d_{xz}/d_{yz}$ orbitals... | 1507.01189v1 |
2015-08-11 | Multiple phase transitions in Pauli limited iron-based superconductors | Specific heat measurements have been successfully used to probe
unconventional superconducting phases in one-band heavy-fermion and organic
superconductors. We extend the method to study successive phase transitions in
multi-band materials such as iron based superconductors. The signatures are
multiple peaks in the spe... | 1508.02740v2 |
2015-09-16 | Structural transition and superconductivity in hydrothermally synthesized FeX (X = S, Se) | Tetragonal beta-FeSe obtained by hydrothermal reaction is not superconducting
and transforms to a triclinic structure at 60 K unlike superconducting FeSe
from solid state synthesis, which becomes orthorhombic at 90 K. In contrast,
tetragonal iron sulphide FeS from hydrothermal synthesis is superconducting at
4.8 K but ... | 1509.04851v1 |
2015-11-21 | Ironing in the Dark | This paper presents the first polynomial-time algorithm for position and
matroid auction environments that learns, from samples from an unknown bounded
valuation distribution, an auction with expected revenue arbitrarily close to
the maximum possible. In contrast to most previous work, our results apply to
arbitrary (n... | 1511.06918v1 |
2015-11-24 | Testing the no-hair theorem with the continuum-fitting and the iron line methods: a short review | The continuum-fitting and the iron line methods are leading techniques
capable of probing the spacetime geometry around astrophysical black hole
candidates and testing the no-hair theorem. In the present paper, we review the
two approaches, from the astrophysical models and their assumptions, to the
constraining power ... | 1511.07587v2 |
2016-05-06 | Investigation of magnetic phases in parent compounds of Iron-chalcogenides via quasiparticle scattering interference | We employ a five-orbital tight-binding model to develop the mean field
solution for various possible spin density wave states in the
iron-chalcogenides. The quasiparticle interference (QPI) technique is applied
to detect signatures of these states due to scatterings arising from
non-magnetic impurities. Apart from the ... | 1605.01798v1 |
2016-05-11 | Vibrational and thermoelastic properties of bcc iron from selected EAM potentials | A comprehensive, critical study of the vibrational, thermodynamic and
thermoelastic properties of bcc iron is presented, using well established
semi-empirical embedded-atom method potentials available in the literature.
Classical molecular dynamics simulations are used to address temperature
effects, where dynamical ma... | 1605.03334v2 |
2016-07-25 | Evidences of Mott physics in iron pnictides from x-ray spectroscopy | X-ray emission and absorption spectroscopies are jointly used as fast probes
to determine the evolution as a function of doping of the fluctuating local
magnetic moments in K- and Cr- hole-doped BaFe2As2. An increase in the local
moment with hole-doping is found, supporting the theoretical scenario in which
a Mott insu... | 1607.07417v1 |
2016-12-21 | Unconventional superconductors: Iron-based diversity | Nine years ago, superconductors based on the magnetic element iron were
discovered. A flurry of research activity has revealed an unprecedented
diversity of chemical structures and physical properties. Similarly to other
unconventional superconductors, stripe-type antiferromagnetism seems to play an
important role. Par... | 1612.07356v1 |
2017-03-09 | Spin-wave excitations in the SDW state of iron pnictides: a comparison between the roles of interaction parameters | We investigate the role of Hund's coupling in the spin-wave excitations of
the ($\pi, 0$) ordered magnetic state within a five-orbital tight-binding model
for iron pnictides. To differentiate between the roles of intraorbital Coulomb
interaction and Hund's coupling, we focus on the self-consistently obtained
mean-field... | 1703.03228v2 |
2017-04-13 | Roles of anisotropic and unequal gaps in the quasiparticle interference of superconducting iron pnictides | We investigate the role of gap characteristics such as anisotropy and
inequality of the gaps in the quasiparticle interferences of iron pnictides
using a five-orbital tight-binding model. We examine how the difference in the
sensitivities exhibited by the sign-changing and -preserving $s$-wave
superconductivity in an a... | 1704.04069v1 |
2017-04-18 | Tilting the balance towards d-wave in iron-based superconductors | The intricate interplay of interactions and Fermiology can give rise to a
close competition between nodeless (e.g. s-wave) and nodal (e.g. d-wave) order
in electronically driven unconventional superconductors. We analyze how such a
scenario is affected by a Zeeman magnetic field $H_{\text{Z}}$ and temperature
$T$. In t... | 1704.05525v1 |
2017-06-27 | Orbital mismatch boosting nematic instability in iron-based superconductors | We derive the effective action for the collective spin modes in iron-based
superconductors. We show that, due to the orbital-selective nature of spin
fluctuations, the magnetic and nematic instabilities are controlled by the
degrees of orbital nesting between electron and hole pockets. Within a
prototypical three-pocke... | 1706.08953v2 |
2017-07-08 | Quasi-2D behavior of 112-type iron-based superconductors | Fluctuation magnetoconductivity and magnetization above the superconducting
transition temperature (Tc) are measured on the recently discovered 112 family
of iron-based superconductors (IBS), Ca$_{1-x}$La$_x$Fe$_{1-y}$Ni$_y$As$_2$,
which presents an extra As-As chain spacer-layer. The analysis in terms of a
generalizat... | 1707.02470v1 |
2017-08-29 | A compact cosmic muon veto detector and possible use with the Iron Calorimeter detector for neutrinos | The motivation for a cosmic muon veto (CMV) detector is to explore the
possibility of locating the proposed large Iron Calorimeter (ICAL) detector at
the India based Neutrino Observatory (INO) at a shallow depth. An initial
effort in that direction, through the assembly and testing of a $\sim$ 1 m
$\times$ 1 m $\times$... | 1708.08597v2 |
2017-11-13 | A possible explanation of the void discovered in the pyramid of Khufu on the basis of the pyramid texts | A recent exploration has shown the presence of a significant void in the
pyramid of Khufu at Giza. A possible explanation of this space, interpreted as
a chamber connected to the lower north channel and aimed to contain a specific
funerary equipment is tentatively proposed. According to the Pyramid Texts,
this equipmen... | 1711.04617v2 |
2018-01-16 | Iron single crystal growth from a lithium-rich melt | \alpha-Fe single crystals of rhombic dodecahedral habit were grown from a
melt of Li$_{84}$N$_{12}$Fe$_{\sim 3}$. Crystals of several millimeter along a
side form at temperatures around $T \approx 800^\circ$C. Upon further cooling
the growth competes with the formation of Fe-doped Li$_3$N. The b.c.c.
structure and good... | 1801.05287v1 |
2018-03-21 | Self-assembly of magnetic iron oxide nanoparticles into cuboidal superstructures | This chapter describes the synthesis and some characteristics of magnetic
iron oxide nanoparticles, mainly nanocubes, and focus on their self-assembly
into crystalline cuboids in dispersion. The influence of external magnetic
fields, the concentration of particles, and the temperature on the assembly
process is experim... | 1803.07922v1 |
2018-04-14 | "With 1 follower I must be AWESOME :P". Exploring the role of irony markers in irony recognition | Conversations in social media often contain the use of irony or sarcasm, when
the users say the opposite of what they really mean. Irony markers are the
meta-communicative clues that inform the reader that an utterance is ironic. We
propose a thorough analysis of theoretically grounded irony markers in two
social media... | 1804.05253v1 |
2018-12-02 | Novel Magnetic Block States in Low-Dimensional Iron-Based Superconductors | Inelastic neutron scattering recently confirmed the theoretical prediction of
a $\uparrow\uparrow\downarrow\downarrow$-magnetic state along the legs of
quasi-one-dimensional (quasi-1D) iron-based ladders in the orbital-selective
Mott phase (OSMP). We show here that electron-doping of the OSMP induces a
whole class of n... | 1812.00325v2 |
2019-01-25 | Polarized neutron reflectometry study from iron oxide nanoparticles monolayer | We report on the polarized neutron reflectometry investigation of monolayer
of magnetic iron oxide nanoparticles assembled by the Langmuir-Schaefer method.
After deposition onto a solid substrate the polarized neutron reflectometry
measurements in the external magnetic field were carried out. Thickness,
density, roughn... | 1901.08819v1 |
2019-10-09 | Electric-field control of magnetism in iron oxide nanoparticle / BaTiO3 film composites | We study composites of monodisperse ferrimagnetic nanoparticles (NPs)
embedded into ferroelectric barium titanate (BTO) films. The BTO films were
prepared by pulsed laser deposition. The composite consists of a stack of two
BTO films sandwiching one monolayer of iron oxide NPs. We observe a
magnetoelectric coupling due... | 1910.04127v1 |
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