publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2010-01-12 | London penetration depth and superfluid density in single crystals of Fe(Te,Se) and Fe(Te,S) superconductors | The in-plane London penetration depth, $\lambda(T)$, was measured in single
crystals of the iron-chalcogenide superconductors
Fe$_{1.03}$(Te$_{0.63}$Se$_{0.37}$) and Fe$_{1.06}$(Te$_{0.88}$S$_{0.14}$) by
using a radio-frequency tunnel diode resonator. As is also the case for the
iron-pnictides, these iron-chalcogenides... | 1001.2042v1 |
2010-01-20 | The magnetic form factor of iron in SrFe2As2 | The iron magnetic form factor in SrFe2As2 has been determined by neutron
diffraction and by density functional theory (DFT). As noted previously, the
magnitude of the calculated moment using DFT is sensitive to the Fe-As
distance. However, the shape of the calculated form factor is practically
insensitive to the Fe-As ... | 1001.3658v1 |
2010-02-18 | Why some Iron-based superconductors are nodal while others are nodeless | The symmetry of the order parameter in iron-based superconductors, especially
the presence or absence of nodes, is still a question of debate. While
contradictory experiments can be explained by appropriately tuned theories of
nodeless superconductivity in the iron-arsenide compounds, for LaOFeP all
experiments clearly... | 1002.3599v1 |
2010-03-02 | Unified Picture for Magnetic Correlations in Iron-Based Superconductors | The varying metallic antiferromagnetic correlations observed in iron-based
superconductors are unified in a model consisting of both itinerant electrons
and localized spins. The decisive factor is found to be the sensitive
competition between the superexchange antiferromagnetism and the
orbital-degenerate double-exchan... | 1003.0512v2 |
2010-03-26 | Strong carrier-scattering in iron-pnictide superconductors with highest Tc obtained from charge transport experiments | Characteristic normal-state charge transport is found in the oxygen-deficient
iron-arsenides LnFeAsO1-y (Ln: La and Nd) with the highest Tc's among known
Fe-based superconductors. The effect of "doping" in this system is mainly on
the carrier scattering, quite distinct from that in high-Tc cuprates. In the
superconduct... | 1003.5039v1 |
2010-04-10 | $^{75}$As NQR and NMR studies of superconductivity and electron correlations in iron arsenide Li$_{x}$FeAs | We report the $^{75}$As-NQR and NMR studies on the iron arsenide
superconductor Li$_{x}$FeAs with $T_{\rm c} \sim 17$ K. The spin lattice
relaxation rate, $1/T_{1}$, decreases below $T_{\rm c}$ without a coherence
peak, and can be fitted by gaps with s$^{\pm}$-wave symmetry in the presence of
impurity scattering. In th... | 1004.1688v5 |
2010-04-28 | Single Impurity Problem in Iron-Pnictide Superconductors | Single impurity problem in iron-pnictide superconductors is investigated by
solving Bogoliubov-de Gennes (BdG) equation in the five-orbital model, which
enables us to distinguish s$_{+-}$ and s$_{++}$ superconducting states. We
construct a five-orbital model suitable to BdG analysis. This model reproduces
the results o... | 1004.5093v1 |
2010-05-07 | Importance of Itinerancy and Quantum Fluctuations for the Magnetism in Iron Pnictides | By applying density functional theory, we find strong evidence for an
itinerant nature of magnetism in two families of iron pnictides. Furthermore,
by employing dynamical mean field theory with continuous time quantum Monte
Carlo as an impurity solver, we observe that the antiferromagnetic metal with
small magnetic mom... | 1005.1170v2 |
2010-06-03 | Nodes vs. minima in the energy gap of iron-pnictides from field-induced anisotropy | We develop the formalism for computing the oscillations of the specific heat
and thermal transport under rotated magnetic field in multiband superconductors
with anisotropic gap and apply it to iron-pnictides. We show that these
oscillations change sign at low temperatures and fields, which strongly
influences the conc... | 1006.0738v2 |
2010-06-11 | Superconductivity Above 40 K Observed in a New Iron Arsenide Oxide (Fe2As2)(Ca4(Mg,Ti)3Oy) | A new layered iron arsenide oxide (Fe2As2)(Ca4(Mg,Ti)3Oy) was discovered. Its
crystal structure is tetragonal with a space group of I4/mmm consisted of the
anti-fluorite type FeAs layer and blocking layer of triple perovskite cells and
is identical with (Fe2As2)(Sr4(Sc,Ti)3O8) discovered in our previous study. The
latt... | 1006.2367v2 |
2010-06-15 | Quantum Dielectric Fluctuation in an Electronic Ferroelectricity studied by Variational Monte-Carlo Method | Electronic structure and dielectric property in an electronic
ferroelectricty, where electric polarization is driven by an electronic charge
order without inversion symmetry, are studied. Motivated from layered iron
oxides, roles of quantum fluctuation on ferroelectricity in a paired-triangular
lattice are focused on. ... | 1006.2889v1 |
2010-06-16 | Sub-monolayers of carbon on alpha-iron facets: an ab-initio study | Motivated by recent in situ studies of carbon nanotube growth from large
transition-metal nanoparticles, we study various alpha-iron (ferrite) facets at
different carbon concentrations using ab initio methods. The studied (110),
(100) and (111) facets show qualitatively different behaviour when carbon
concentration cha... | 1006.3187v1 |
2010-06-23 | High-temperature superconductivity in iron-based materials | The surprising discovery of superconductivity in layered iron-based
materials, with transition temperatures climbing as high as 55 K, has lead to
thousands of publications on this subject over the past two years. While there
is general consensus on the unconventional nature of the Cooper pairing state
of these systems,... | 1006.4618v2 |
2010-07-09 | Contrasted role of disorder for magnetic properties in an original mixed valency iron Phosphate | We have measured the magnetic properties of a mixed valency iron phosphate.
It presents an original structure with crossed chains containing Fe II and
orthogonal to the longest direction of the crystallites. Microstructural
investigations using electron microscopy show the presence of random
nano-twinning. The ac susce... | 1007.1607v1 |
2010-08-13 | Anion height as a controlling parameter for the superconductivity in iron pnictides and cuprates | Both families of high $T_c$ superconductors, iron pnictides and cuprates,
exhibit material dependence of superconductivity. Here, we study its origin
within the spin fluctuation pairing theory based on multiorbital models that
take into account realistic band structures. For pnictides, we show that the
presence and abs... | 1008.2286v1 |
2010-08-25 | Detailed abundances of Red Giants in the Globular Cluster NGC~1851: C+N+O and the Origin of Multiple Populations | We present chemical abundance analysis of a sample of 15 red giant branch
(RGB) stars of the Globular Cluster NGC~1851 distributed along the two RGBs of
the (v, v-y) CMD. We determined abundances for C+N+O, Na, $\alpha$, iron-peak,
and s-elements. We found that the two RGB populations significantly differ in
their ligh... | 1008.4372v1 |
2010-09-03 | Pnicogen-bridged antiferromagnetic superexchange interactions in iron pnictides | The first-principles electronic structure calculations made substantial
contribution to study of high $T_c$ iron-pnictide superconductors. By the
calculations, LaFeAsO was first predicted to be an antiferromagnetic semimetal,
and the novel bi-collinear antiferromagnetic order was predicted for
$\alpha$-FeTe. Moreover, ... | 1009.0726v1 |
2010-09-06 | Spin Dynamics of a $J_1-J_2$ Antiferromagnet and its Implications for Iron Pnictides | Motivated by the recent observation of antiferromagnetic correlations in the
paramagnetic phase of iron pnictides, we study the finite-temperature spin
dynamics of a two-dimensional $J_1-J_2$ antiferromagnet. We consider the
paramagnetic phase in the $J_2>J_1$ regime of a $(\pi,0)$ collinear ground
state, using the mod... | 1009.1111v3 |
2010-09-29 | Superconductivity-induced optical anomaly in an iron arsenide | One of the central tenets of conventional theories of superconductivity,
including most models proposed for the recently discovered iron-pnictide
superconductors, is the notion that only electronic excitations with energies
comparable to the superconducting energy gap are affected by the transition.
Here we report the ... | 1009.5915v1 |
2010-10-01 | Orbital Order, Structural Transition and Superconductivity in Iron Pnictides | We investigate the 16-band d-p model for iron pnictide superconductors in the
presence of the electron-phonon coupling g with the orthorhombic mode which is
crucial for reproducing the recently observed ultrasonic softening. Within the
RPA, we obtain the ferro-orbital order below TQ which induces the
tetragonal-orthorh... | 1010.0129v3 |
2010-10-02 | The layered compound CaClFeP is an Arsenic-free high $T_c$ iron-pnictide | We first analyze why the iron pnictides with high $T_c$ superconductivity so
far are As-based, by the Hund's rule correlation picture, then examine the
P-based and Sb-based cases, respectively. Consequently, we propose that CaClFeP
with ZrCuSiAs-type structure is an As-free high $T_c$ iron-pnictide. The
subsequent dens... | 1010.0342v1 |
2010-10-18 | Quasiparticle interference in an iron-based superconductor | We develop a model for the effect of a magnetic field on quasiparticle
interference in an iron-based superconductor. Recently, scanning tunneling
experiments have been performed on Fe(Se,Te) to determine the relative sign of
the superconducting gap from the magnetic-field dependence of quasiparticle
scattering amplitud... | 1010.3545v3 |
2010-11-10 | Theory of Valley-Density Wave and Hidden Order in Iron-Pnictides | In the limit of perfect nesting, the physics of iron-pnictides is governed by
the density wave formation at the zone-edge vector M. At high energies, various
spin- (SDW), charge- (CDW), orbital/pocket- (PDW) density waves, and their
linear combinations, all appear equally likely, unified within the unitary
order parame... | 1011.2499v3 |
2010-12-04 | Epitaxial Growth of Superconducting Ba(Fe1-xCox)2As2 Thin Films on Technical IBAD-MgO Substrates | The biaxially textured growth of superconducting Co-doped BaFe2As2 (Ba-122)
thin films has been realized on ion beam assisted deposition (IBAD) MgO coated
conductor templates by employing an iron buffer architecture. The iron pnictide
coated conductor showed a superconducting transition temperature of 21.5 K,
which is ... | 1012.0894v1 |
2010-12-12 | S-wave superconductivity with orbital dependent sign change in the checkerboard models of iron-based superconductors | We study three different multi-orbital models for iron-based superconductors
(iron-SCs) in the solvable limit of weakly coupled square plaquettes. The
strongest superconducting (SC) pairing is in the $A_{1g}$ $s$-wave channel and
its development is correlated with the emergence of the next-nearest-neighbour
antiferroma... | 1012.2566v1 |
2010-12-19 | Bistability of Free Cobalt and Iron Clusters | The cobalt and iron clusters CoN, FeN (20 < N < 150) measured in a cryogenic
molecular beam are found to be bistable with magnetic moments per atom both
{\mu}N/N 2{\mu}B in the ground states and {\mu}N */N {\mu}B in the metastable
excited states (for iron clusters, {\mu}N ~3N{\mu}B and {\mu}N* N{\mu}B). This
energy gap... | 1012.4133v1 |
2010-12-23 | Electronic structure and Fermi surface of new K intercalated iron selenide superconductor KxFe2Se2 | Using the ab initio FLAPW-GGA method we examine the electronic band
structure, densities of states, and the Fermi surface topology for a very
recently synthesized ThCr2Si2-type potassium intercalated iron selenide
superconductor KxFe2Se2. We found that the electronic state of the
stoichiometric KFe2Se2 is far from that... | 1012.5164v1 |
2010-12-23 | Discovery of Iron in PG1159 Stars | The lack of FeVII lines in PG1159 stars had led to the conclusion that in
some objects iron must be strongly depleted. We have now detected FeX lines in
FUSE spectra of the very hottest PG1159 stars Teff=150,000 - 200,000 K;
RXJ2117.1+3412, K1-16, NGC 246, Longmore 4). Surprisingly, we derive a solar
iron abundance. It... | 1012.5228v1 |
2010-12-29 | Heavily electron-doped electronic structure and isotropic superconducting gap in AxFe2Se2 (A=K,Cs) | The low energy band structure and Fermi surface of the newly discovered
superconductor, AxFe2Se2 (A=K,Cs), have been studied by angle-resolved
photoemission spectroscopy. Compared with iron pnictide superconductors,
AxFe2Se2 (A=K,Cs) is the most heavily electron-doped with Tc~30 K. Only
electron pockets are observed wi... | 1012.5980v1 |
2011-01-17 | Mott transition in Modulated Lattices and Parent Insulator of (K,Tl)yFexSe2 Superconductors | The degree of electron correlations remains a central issue in the iron-based
superconductors. The parent iron pnictides are antiferromagnetic, and their
bad-metal behavior has been interpreted in terms of proximity to a Mott
transition. We study such a transition in multi-orbital models on modulated
lattices containin... | 1101.3307v2 |
2011-02-13 | Orbital magnetic moment and extrinsic spin Hall effect for iron impurity in gold | We report electronic structure calculations of an iron impurity in gold host.
The spin, orbital and dipole magnetic moments were investigated using the
LDA+$U$ correlated band theory. We show that the {\em
around-mean-field}-LDA+$U$ reproduces the XMCD experimental data well and does
not lead to formation of a large or... | 1102.2614v1 |
2011-02-16 | Ionization structure and Fe K$α$ energy for irradiated accretion disks | We study the radial ionization structure at the surface of an X-ray
illuminated accretion disk. We plot the expected iron K$\alpha$ line energy as
a function of the Eddington ratio and of the distance of the emitting matter
from the central source, for a non-rotating and a maximally-rotating black
hole. We compare the ... | 1102.3327v1 |
2011-02-22 | Superconductivity mediated by the antiferromagnetic spin-wave in chalcogenide iron-base superconductors | The ground state of K$_{0.8+x}$Fe$_{1.6+y}$Se$_2$ and other iron-based
selenide superconductors are doped antiferromagnetic semiconductors. There are
well defined iron local moments whose energies are separated from those of
conduction electrons by a large band gap in these materials. We propose that
the low energy phy... | 1102.4575v1 |
2011-03-03 | Electron correlation induced small anisotropy in iron-based superconductors | We have investigated the electron correlation effect on the electronic
structures and transport properties of the iron-based superconductors using the
density functional theory (DFT) and dynamical mean field theory (DMFT). By
considering the Fe 3d electron correlation using the DMFT, the bandwidth near
the Fermi level ... | 1103.0678v2 |
2011-03-10 | Iron Depletion in ionized Nebulae of the Large Magellanic Cloud | We present here preliminary results of an analysis of the iron abundance in
the ionized gas of three planetary nebulae and one H II region of the Large
Magellanic Cloud (LMC). These results are compared with the ones we obtain for
a sample of Galactic and extragalactic nebulae. We find that the amounts of
iron depletio... | 1103.2158v1 |
2011-03-13 | Topological insulators with perfect vacancy superstructure and possible implications for iron chalcogenide superconductors | Motivated by the newly-discovered intercalated iron chalcogenide
superconductors, we construct a single orbital tight-binding model for
topological insulators on the square lattice with a perfect vacancy
superstructure. We find that such lattice structure naturally accommodates a
non-vanishing geometry phase associated... | 1103.2538v2 |
2011-03-25 | Local spin fluctuations in iron-based superconductors: 77Se and 87Rb NMR measurements of Tl0.47Rb0.34Fe1.63Se2 | We report nuclear magnetic resonance (NMR) studies of the intercalated iron
selenide superconductor (Tl, Rb)$_{y}$Fe$_{2-x}$Se$_2$ ($T_c = 32$ K).
Single-crystal measurements up to 480 K on both $^{77}$Se and $^{87}$Rb nuclei
show a superconducting phase with no magnetic order. The Knight shifts $K$ and
relaxation rate... | 1103.4960v5 |
2011-04-10 | Interplay of orbital and spin ordering in the iron pnictides | A number of recent experiments exhibit electronic anisotropy in the iron
pnictides, and there is a growing body of experimental evidence that its origin
is related to orbital ordering in Fe d_{xz} and d_{yz} orbitals. We examine
this problem in the parent compounds of the iron pnictides by a combination of
ab initio ba... | 1104.1747v1 |
2011-04-18 | New ternary ThCr2Si2-type iron-selenide superconducting materials: synthesis, properties and simulations | Very recently (November, 2010, PRB, 82, 180520R), the first ThCr2Si2-type
ternary superconductor K0.8Fe2Se2 with enhanced TC ~ 31 K has been discovered.
This finding has stimulated much activity in search for related materials and
triggered intense studies of their properties. Indeed, very soon
superconductivity (TC ~ ... | 1104.3400v1 |
2011-05-04 | Structural Phase Transformations in Iron-Chalcogen under High Pressures | We report high pressure structural phase transformation sequence in a layered
Iron-based superconducting compound FeSe0.3Te0.7 to 31 GPa at room temperature.
The ambient pressure PbO type tetragonal phase (Space Group - P4/nmm)
transforms to a monoclinic phase (Space group - P21/m) at a pressure of 7.3 \pm
0.9 GPa. Thi... | 1105.0908v1 |
2011-05-05 | Robustness of s-wave Pairing in Electron-Overdoped $\text{A}_{1-y}\text{Fe}_{2-x}\text{Se}_2$ | Using self consistent mean field and functional renormalization group
approaches we show that s-wave pairing symmetry is robust in the heavily
electron-doped iron chalcogenides $(\text{K, Cs}) \text{Fe}_{2-x}\text{Se}_2 $.
This is because in these materials the leading antiferromagnetic (AFM) exchange
coupling is betwe... | 1105.1135v1 |
2011-05-09 | Anomalous Tail Effect on Resistivity Transition and Weak-link Behavior of Iron Based Superconductor | Temperature dependent resistivity of the iron-based superconductor
NdFeAsO0.88F0.12 was measured under different applied fields and excitation
currents. Arrhenius plot shows an anomalous tail effect, which contains obvious
two resistivity dropping stages. The first is caused by the normal
superconducting transition, an... | 1105.1648v1 |
2011-05-24 | Unidirectional Electronic Structure in the Parent State of Iron-Chalcogenide Superconductor Fe$_{1+δ}$Te | We use scanning tunnelling microscopy and spectroscopy to explore the
electronic structure of Fe$_{1.07}$Te which is the parent compound of the
iron-chalcogenide superconductors. A unidirectional electronic structure with a
period of $a_{0}$ (where $a_{0}$ is the lattice constant) along the a-axis is
observed. The unid... | 1105.4754v2 |
2011-05-31 | Role of Hund's coupling in stabilization of the (0,pi) ordered SDW state within the minimal two-band model for iron pnictides | Spin wave excitations and stability of the (0,pi) ordered SDW state are
investigated within the minimal two-band model for iron pnictides including a
Hund's coupling term. The SDW state is shown to be stable in two distinct
doping regimes --- finite hole doping in the lower SDW band for small second
neighbour hoppings,... | 1105.6191v1 |
2011-05-31 | Neutron-Inelastic-Scattering Peak by Dissipationless Mechanism in the s++ -wave State in Iron-based Superconductors | We investigate the neutron scattering spectrum in iron pnictides based on the
random-phase approximation in the five-orbital model with a realistic
superconducting (SC) gap, Delta=5meV. In the normal state, the neutron spectrum
is suppressed by large inelastic quasi-particle (QP) scattering rate gamma* ~
Delta. In the ... | 1105.6233v3 |
2011-06-13 | Iron-chalcogenide FeSe$_{0.5}$Te$_{0.5}$ coated superconducting tapes for high field applications | The high upper critical field characteristic of the recently discovered
iron-based superconducting chalcogenides opens the possibility of developing a
new type of non-oxide high-field superconducting wires. In this work, we
utilize a buffered metal template on which we grow a textured
FeSe$_{0.5}$Te$_{0.5}$ layer, an a... | 1106.2466v1 |
2011-06-14 | Fermi surfaces of iron-pnictide high-Tc superconductors from the limit of local magnetic moments | A 2-orbital t-J model over the square lattice that describes low-energy
electronic excitations in iron-pnictide high-Tc superconductors is analyzed
with Schwinger-boson-slave-fermion meanfield theory and by exact numerical
diagonalization on a finite system. A quantum critical point (QCP) is
identified that separates a... | 1106.2600v3 |
2011-06-25 | An unified minimum effective model of magnetism in iron-based superconductors | Since 2008, many new families of iron-based high temperature (high-$T_c$)
superconductors have been discovered \cite{Hosono,ChenXH,FeTe,ChenXL}. Unlike
all parent compounds of cuprates that share a common antiferromagnetically (AF)
ordered ground state, those of iron-based superconductors exhibit many
different AF orde... | 1106.5169v1 |
2011-06-27 | Lattice expansion from isotope substitution in the Iron based superconductors | We estimate the changes in lattice parameters due to iron isotope
substitution in the iron-based high temperature superconductors using a
variational calculation based on the anharmonicity of the Fe-As(Se) bond. For
BaFe2As2 and 57Fe to 54$Fe substitution we find a c-axis expansion of 1
10^{-3}{\AA} and in-plane a-axis... | 1106.5332v1 |
2011-06-29 | Mechanism for a Pairing State with Time-Reversal Symmetry Breaking in Iron-Based Superconductors | The multipocket Fermi surfaces of iron-based superconductors promote pairing
states with both s_{+-}-wave and d_{x^2-y^2}-wave symmetry. We argue that the
competition between these two order parameters could lead to a
time-reversal-symmetry breaking state with s+id-pairing symmetry in the
iron-based superconductors, an... | 1106.5964v1 |
2011-07-11 | Magnetotransport properties of iron microwires fabricated by focused electron beam induced autocatalytic growth | We have prepared iron microwires in a combination of focused electron beam
induced deposition (FEBID) and autocatalytic growth from the iron
pentacarbonyl, Fe(CO)5, precursor gas under UHV conditions. The electrical
transport properties of the microwires were investigated and it was found that
the temperature dependenc... | 1107.2014v1 |
2011-08-11 | Excitation functions and isotopic effects in (n,p) reactions for stable iron isotopes from reaction threshold to 20 MeV | The excitation functions for (n,p) reactions from reaction threshold to 20
MeV on four stable Iron isotopes viz; 54Fe,56Fe,57Fe and 58Fe were calculated
using Talys-1.2 nuclear model code, this essentially involves fitting a set of
global parameters. An excellent agreement between the calculated and
experimental data i... | 1108.2661v1 |
2011-08-15 | Iron Displacements and Magnetoelastic Coupling in the Spin-Ladder Compound BaFe2Se3 | We report long-range ordered antiferromagnetism concomitant with local iron
displacements in the spin-ladder compound BaFe$_2$Se$_3$. Short-range magnetic
correlations, present at room temperature, develop into long-range
antiferromagnetic order below T$_N$ = 256 K, with no superconductivity down to
1.8 K. Built of fer... | 1108.2928v2 |
2011-08-24 | Effective tight-binding model for the iron vacancy ordered A$_{y}$Fe$%_{1.6}$Se$_{2}$ | We investigate the electronic structure of the ternary iron selenide K$_{y}$%
Fe$_{1.6}$Se$_{2}$ by considering the spatial symmetry of the $\sqrt{5}% \times
\sqrt{5}$ vacancy ordered structure. Based on three orbitals of $% t_{2g}$,
which are believed to play major physics in iron-based superconductors, an
effective t... | 1108.4787v3 |
2011-09-09 | C/O Abundance Ratios and Dust Features in Galactic Planetary Nebulae | The iron depletion factors found in Galactic planetary nebulae (PNe) span
over two orders of magnitude, suggesting that there are differences in the
grain formation and destruction processes from object to object. We explore
here the relation between the iron depletions, the infrared dust features, and
the C/O abundanc... | 1109.1867v1 |
2011-09-13 | Formation of iron nitride thin films with Al and Ti additives | In this work we investigate the process of iron nitride (Fe-N) phase
formation using 2 at.% Al or 2 at.% Ti as additives. The samples were prepared
with a magnetron sputtering technique using different amount of nitrogen during
the deposition process. The nitrogen partial pressure (\pn) was varied between
0-50% (rest A... | 1109.2725v1 |
2011-10-03 | Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors | We present the first study of codoped iron-arsenide superconductors of the
122 family (Sr/Ba)_(1-x)K_xFe_(2-y)Co_yAs_2 with the purpose to increase the
upper critical field H_c2 compared to single doped (Sr/Ba)Fe_2As_2 materials.
H_c2 was investigated by measuring the magnetoresistance in high pulsed
magnetic fields up... | 1110.0478v1 |
2011-10-04 | Inter-layer Superconducting Pairing Induced c-axis Nodal Lines in Iron-based Superconductors | A layered superconductor with a full pairing energy gap can be driven into a
nodal superconducting (SC) state by inter-layer pairing when the SC state
becomes more quasi-3D. We propose that this mechanism is responsible for the
observed nodal behavior in a class of iron-based SCs. We show that the intra-
and inter-laye... | 1110.0695v1 |
2011-10-05 | Phase diagram of iron-pnictides if doping acts as a disorder | We obtain and analyze the phase diagram of doped iron-pnictides under the
assumption that doping adds non-magnetic impurities to the system but does not
change the densities of carriers. We show that the phase diagram is quite
similar to the one obtained under the opposite rigid band assumption. In both
cases, there is... | 1110.0972v2 |
2011-10-06 | Quantum oscillation studies of the Fermi surface of iron-pnictide superconductors | This paper reviews quantum oscillation studies of iron-pnictide
superconductors and related materials. These measurements give unique
information regarding the full three dimensional topology of the Fermi surfaces
and the renormalisation of the quasi-particle masses. The review will cover
measurements of the 122 arseni... | 1110.1326v1 |
2011-10-11 | Impurity-Induced Electronic Nematic State in Iron-Pnictide Superconductors | We propose that impurity-induced electronic nematic state is realized above
the orthorhombic structure transition temperature $T_S$ in iron-pnictide
superconductors. In the presence of strong orbital fluctuations near $T_S$, it
is theoretically revealed that a single impurity induces non-local orbital
order with $C_2$-... | 1110.2401v2 |
2011-10-20 | First-Principles Study on the Mobility of Screw Dislocations in BCC Iron | The fully two-dimensional Peierls barrier map of screw dislocations in BCC
iron has been calculated using the first principles method to identify the
migration path of a dislocation core. An efficient method to correct the effect
of the finite size cell used in the first principles method on the energy of a
lattice def... | 1110.4487v4 |
2011-10-21 | Fermi surface topology and low-lying electronic structure of a new iron-based superconductor Ca10(Pt3As8)(Fe2As2)5 | We report a first study of low energy electronic structure and Fermi surface
topology for the recently discovered iron-based superconductor
Ca10(Pt3As8)(Fe2As2)5 (the 10-3-8 phase, with Tc = 8K), via angle-resolved
photoemission spectroscopy (ARPES). Despite its triclinic crystal structure,
ARPES results reveal a fourf... | 1110.4687v1 |
2011-10-20 | Hydrogen Geysers: Explanation for Observed Evidence of Geologically Recent Volatile-Related Activity on Mercury's Surface | High resolution images of Mercury's surface, from the MESSENGER spacecraft,
reveal many bright deposits associated with irregular, shallow, rimless
depressions whose origins were attributed to volatile-related activity, but
absent information on the nature and origin of that volatile matter. Here I
describe planetary f... | 1110.5796v2 |
2011-12-01 | Simulation of Proton and Iron Induced Extensive Air Showers | The reliable simulation of extensive air showers induced by different primary
particles (e. g. proton, iron, gamma etc.) is of great importance in high
energy cosmic ray research. The CORSIKA is a standard Monte-Carlo simulation
package to simulate the four dimensional evolution of Extensive Air Shower
(EAS) in the atm... | 1112.0356v1 |
2012-01-12 | Universal behavior of the upper critical field in iron based superconductors | The newly discovered iron-based high temperature superconductors have
demonstrated rich physical properties. Here we give a brief review on the
recent studies of the upper critical field and its anisotropy in a few typical
series of the iron-based superconductors (FeSCs). In spite of their characters
of a layered cryst... | 1201.2548v1 |
2012-01-13 | The Solar Flare Iron Abundance | The abundance of iron is measured from emission line complexes at 6.65 keV
(Fe line) and 8 keV (Fe/Ni line) in {\em RHESSI} X-ray spectra during solar
flares. Spectra during long-duration flares with steady declines were selected,
with an isothermal assumption and improved data analysis methods over previous
work. Two ... | 1201.2875v1 |
2012-03-12 | Pairing Symmetry in Iron-Pnictide Superconductor KFe$_2$As$_2$ | The pairing symmetry is one of the major issues in the study of iron-based
superconductors. We adopt a low-energy effective kinetic model based on the
first-principles band structure calculations combined with the $J_1$-$J_2$
model for KFe$_2$As$_2$, the phase diagram of pairing symmetries is
constructed. Putting the v... | 1203.2581v4 |
2012-03-14 | Enhancement of $T_{c}$ by disorder in underdoped iron pnictides | We analyze how disorder affects the transition temperature $T_{c}$ of the
$s^{+-}$superconducting state in the iron pnictides. The conventional wisdom is
that $T_{c}$ should rapidly decrease with increasing inter-band non-magnetic
impurity scattering, but we show that this behavior holds only in the overdoped
region of... | 1203.3012v2 |
2012-04-02 | Red Supergiant Stars as Cosmic Abundance Probes: NLTE Effects in J-band Iron and Titanium Lines | Detailed non-LTE calculations for red supergiant stars are presented to
investigate the influence of NLTE on the formation of atomic iron and titanium
lines in the J-band. With their enormous brightness at J-band red supergiant
stars are ideal probes of cosmic abundances. Recent LTE studies have found that
metallicitie... | 1204.0511v1 |
2012-04-08 | Least momentum space frustration as a condition for "high $T_c$ sweet spot" in the iron-based superconductors | In the present paper, we describe how the band structure and the Fermi
surface of the iron-based superconductors vary as the Fe-As-Fe bond angle
changes. We discuss how these Fermi surface configurations affect the
superconductivity mediated by spin fluctuations, and show that in several
situations, frustration in the ... | 1204.1717v1 |
2012-05-02 | Evidence of a spin resonance mode in the iron-based superconductor Ba$_{0.6}$K$_{0.4}$Fe$_{2}$As$_{2}$ from scanning tunneling spectroscopy | We used high-resolution scanning tunneling spectroscopy to study the
hole-doped iron pnictide superconductor Ba$_{0.6}$K$_{0.4}$Fe$_{2}$As$_{2}$
($T_c=38$ K). Features of a bosonic excitation (mode) are observed in the
measured quasiparticle density of states. The bosonic features are intimately
associated with the sup... | 1205.0352v1 |
2012-05-08 | Anisotropy of strong pinning in multi-band superconductors | The field-angular dependence and anisotropy of the critical current density
in iron-based superconductors is evaluated using a phenomenological approach
featuring distinct anisotropy factors for the penetration depth and the
coherence length. Both the weak collective pinning limit, and the strong
pinning limit relevant... | 1205.1741v3 |
2012-05-11 | Anisotropic Energy Gaps of Iron-based Superconductivity from Intra-band Quasiparticle Interference in LiFeAs | If strong electron-electron interactions between neighboring Fe atoms mediate
the Cooper pairing in iron-pnictide superconductors, then specific and distinct
anisotropic superconducting energy gaps \Delta_i(k) should appear on the
different electronic bands i. Here we introduce intra-band Bogoliubov
quasiparticle scatt... | 1205.2673v1 |
2012-05-15 | A relativistic iron emission line from the neutron star low-mass X-ray binary GX 3+1 | We present the results of a spectroscopic study of the Fe K{\alpha} emission
of the persistent neutron-star atoll low-mass X-ray binary and type I X-ray
burster GX 3+1 with the EPIC-PN on board XMM-Newton. The source shows a flux
modulation over several years and we observed it during its fainter phase,
which correspon... | 1205.3348v1 |
2012-05-23 | Superfluid density in the $s_{\pm}$-wave state of clean iron-based superconductors | Based on a phenomenological model and the Kubo formula, we investigate the
superfluid density $\rho_s(T)$ and then the penetration depth $\lambda(T)$ of
the iron-based superconductors in the coexistence region of the
spin-density-wave(SDW) and superconductivity, and also in the over-doped
region. Our calculations show ... | 1205.5086v2 |
2012-05-23 | Dimer Impurity Scattering, "Reconstructed" Nesting and Density-Wave Diagnostics in Iron Pnictides | While the impurity-induced nanoscale electronic disorder has been extensively
reported in the underdoped iron pnictides, its microscopic origins remain
elusive. Recent scanning tunneling microscopy (STM) measurements reveal a
dimer-type resonant structure induced by cobalt doping. These dimers are
randomly distributed ... | 1205.5280v3 |
2012-06-05 | The effect of spin fluctuations on the electronic structure in iron based superconductors | Magnetic inelastic neutron scattering (INS) studies of iron-based
superconductors reveal a strongly temperature-dependent spin-fluctuation
spectrum in the normal conducting state, which develops a prominent low-energy
resonance feature when entering the superconducting state. Angle-resolved
photoemission spectroscopy (... | 1206.0904v2 |
2012-07-02 | Consequences of extended $s_\pm$-wave pairing in iron-based superconductors | Motivated by a recent experiment of Song \emph{et al.} [Science {\bf 332},
1410 (2011)], we theoretically study the spin dynamics, charge dynamics, and
point-contact Andreev-reflection spectroscopy (PCARS) of two-band iron-based
superconductors of a possible extended $s_\pm$-wave pairing symmetry. We
consider the case ... | 1207.0270v1 |
2012-07-10 | Deviating band symmetries and many-body interactions in a model hole doped iron pnictide superconductor | We present a polarization resolved study of the low energy band structure in
the optimally doped iron pnictide superconductor
Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ (T$_c$=37K) using angle resolved photoemission
spectroscopy. Polarization-contrasted measurements are used to identify and
trace all three low energy hole-like ba... | 1207.2221v2 |
2012-09-11 | Many-body effects in iron pnictides and chalcogenides -- non-local vs dynamic origin of effective masses | We apply the quasi-particle self-consistent GW (QSGW) approximation to some
of the iron pnictide and chalcogenide superconductors. We compute Fermi
surfaces and density of states, and find excellent agreement with experiment,
substantially improving over standard band-structure methods. Analyzing the
QSGW self-energy w... | 1209.2213v1 |
2012-10-17 | Superconductivity in a single layer alkali-doped FeSe: a weakly coupled two-leg ladder system | We prepare single layer potassium-doped iron selenide (110) film by molecular
beam expitaxy. Such a single layer film can be viewed as a two-dimensional
system composed of weakly coupled two-leg iron ladders. Scanning tunneling
spectroscopy reveals that superconductivity is developed in this two-leg ladder
system. The ... | 1210.4619v1 |
2012-11-15 | LDA'+DMFT Investigation of Electronic Structure of K{1-x}Fe{2-y}Se2 Superconductor | We investigate electronic structure of the new iron chalcogenide high
temperature superconductor K{1-x}Fe{2-y}Se2 (hole doped case with x=0.24,
y=0.28) in the normal phase using the novel LDA'+DMFT computational approach.
We show that this iron chalcogenide is more correlated in a sense of bandwidth
renormalization (en... | 1211.3499v1 |
2012-11-20 | $a-b$ Plane Point Contact Spectroscopy measurements of optimally Cobalt doped Ba-122 iron-pnictide superconductors | Point contact spectroscopy (PCS) is a technique which can reveal the size and
symmetry of a superconducting gap ($\Delta$) and is especially useful for new
materials such as the iron-based superconductors. PCS is usually employed in
conjunction with the extended Blonder-Tinkham-Klapwijk (BTK) model which is
used to ext... | 1211.4659v1 |
2012-12-05 | Investigation of variability of iron emission lines in Centaurus X-3 | We present the results obtained from a study of the variability of iron
emission lines in the high mass X-ray binary pulsar Cen X-3 during the eclipse,
eclipse-egress and out-of-eclipse phases using XMM-Newton observations. Three
iron emission lines at 6.4 keV, 6.7 keV, and 6.97 keV are clearly detected in
the spectrum... | 1212.0949v1 |
2012-12-20 | Pairing insights in iron-based superconductors from scanning tunneling microscopy | Scanning tunneling microscopy (STM) has made tremendous progress in the study
and understanding of both classical and unconventional superconductors. This
has motivated a rapidly growing effort to apply the same techniques to the
iron-based high-Tc superconductors since their discovery in 2008. Five years
have brought ... | 1212.5164v2 |
2013-01-18 | Unusual persistence of superconductivity against high magnetic fields in the strongly-correlated iron-chalcogenide film FeTe:O$_{x}$ | We report an unusual persistence of superconductivity against high magnetic
fields in the iron chalcogenide film FeTe:O$_{x}$ below ~ 2.5 K. Instead of
saturating like a mean-field behavior with a single order parameter, the
measured low-temperature upper critical field increases progressively,
suggesting a large suppl... | 1301.4487v3 |
2013-01-27 | Iron-Based Superconductors as Parity Odd Superconductors | Parity is a fundamental quantum number to classify a state of matter.
Materials rarely possess ground states with odd parity. We show that the
superconducting state in iron-based superconductors is classified as an odd
parity s-wave spin-singlet pairing state in a single trilayer FeAs/Se, the
building block of the mate... | 1301.6342v5 |
2013-01-28 | Evolution of the multiband RKKY interaction: Application to iron pnictides and chalcogenides | The indirect RKKY interaction in iron pnictide and chalcogenide metals is
calculated for a simplified four bands Fermi surface (FS) model. We investigate
the specific multi-band features and show that distinct length scales of the
RKKY oscillations appear. For the regular lattice of the local moments, the
generalized R... | 1301.6497v1 |
2013-02-22 | Surface Atom Motion to Move Iron Nanocrystals through Constrictions in Carbon Nanotubes under the Action of an Electric Current | Under the application of electrical currents, metal nanocrystals inside
carbon nanotubes can be bodily transported. We examine experimentally and
theoretically how an iron nanocrystal can pass through a constriction in the
carbon nanotube with a smaller cross-sectional area than the nanocrystal
itself. Remarkably, thro... | 1302.5709v2 |
2013-03-25 | Elementary Excitations due to Orbital Degrees of Freedom in Iron Based Superconductors | One central issue under intense debate in the study of the iron based
superconductors is the origin of the structural phase transition that changes
the crystal lattice symmetry from tetragonal to orthorhombic. This structural
phase transition, occurring universally in almost every family of the
iron-based superconducto... | 1303.6295v1 |
2013-04-04 | Study of the itinerant electron magnetism of Fe-based superconductors by the proximity effect | We used the proximity effect as a tool to achieve an ideal (barrier - free)
NS boundary for quantitative evaluation of transport phenomena that accompany
converting dissipative current into supercurrent in NS systems with
unconventional superconductors, single - crystal chalcogenide FeSe and
granulated pnictide LaO(F)F... | 1304.1418v1 |
2013-04-08 | Electronic phase separation in iron pnictides | A mechanism for electronic phase separation in iron pnictides is proposed. It
is based on the competition between commensurate and incommensurate
spin-density-wave phases in a system with an imperfect doping-dependent nesting
of a multi-sheeted Fermi surface. We model the Fermi surface by two elliptical
electron pocket... | 1304.2175v2 |
2013-04-18 | Discovery of a superhard iron tetraboride superconductor | Single crystals of novel orthorhombic (space group Pnnm) iron tetraboride
FeB4 were synthesised at pressures above 8 GPa and high temperatures. Magnetic
susceptibility measurements demonstrated bulk superconductivity below 2.9 K.
The putative isotope effect on the superconducting critical temperature
indicates that FeB... | 1304.5106v1 |
2013-04-23 | Quantum critical point lying beneath the superconducting dome in iron-pnictides | Whether a quantum critical point (QCP) lies beneath the superconducting dome
has been a long-standing issue that remains unresolved in many classes of
unconventional superconductors, notably cuprates, heavy fermion compounds and
most recently iron-pnictides. The existence of a QCP may offer a route to
understand: the o... | 1304.6387v1 |
2013-05-08 | Functional renormalization group study of the pairing symmetry and pairing mechanism in iron-selenide superconductors | In iron selenide superconductors only electron-like Fermi pockets survive,
challenging the $S^{\pm}$ pairing based on the quasi-nesting between the
electron and hole Fermi pockets (as in iron arsenides). By functional
renormalization group study we show that an in-phase $S$-wave pairing on the
electron pockets ($S^{++}... | 1305.1806v2 |
2013-05-22 | Odd parity pairing and nodeless anti-phase $s^\pm$ in Iron-Based Superconductors | We discuss the sign change of superconducting order parameters in both real
and reciprocal spaces when the odd parity spin singlet pairing proposed
recently in\cite{huoddparity} is allowed. We show that in this case an nodeless
anti-phase $s^\pm$ can be generated. In a 2-Fe Brilliouin zone (BZ), sign
change exists betw... | 1305.5034v2 |
2013-05-30 | Observation of isosceles triangular electronic structure around excess iron atoms in Fe$_{1+δ}$Te | We present scanning tunneling microscopy and spectroscopy studies around an
individual excess Fe atom, working as a local perturbation, in the parent
material of the iron-chalcogenide superconductor Fe$_{1+\delta}$Te.
Spectroscopic imaging reveals a novel isosceles triangular electronic structure
around the excess Fe a... | 1305.7206v1 |
2013-06-05 | Nematicity as a probe of superconducting pairing in iron-based superconductors | In several families of iron-based superconducting materials, a d-wave pairing
instability may compete with the leading s-wave instability. Here we show that
when both states have comparable free energies, superconducting and nematic
degrees of freedom are strongly coupled. While nematic order causes a sharp
non-analyti... | 1306.1125v2 |
2013-06-18 | Orbital-selective superconductivity, gap anisotropy and spin resonance excitations in a multiorbital t-J1-J2 model for iron pnictides | We study the orbital-dependent superconducting pairing in a five-orbital
t-J1-J2 model for iron pnictides. Depending on the orbital selectivity of
electron correlations and the orbital characters along the Fermi surface, the
superconducting gap in an A_{1g} pairing state may exhibit anisotropy. This
anisotropy varies w... | 1306.4184v1 |
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