publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2011-11-16 | Metamagnetic Behavior and Kondo Breakdown in Heavy-Fermion CeFePO | We report that nonmagnetic heavy-fermion (HF) iron oxypnictide CeFePO with
two-dimensional XY-type anisotropy shows a metamagnetic behavior at the
metamagnetic field H_M \simeq 4 T perpendicular to the c-axis and that a
critical behavior is observed around H_M. Although the magnetic character is
entirely different from... | 1111.3749v3 |
2011-11-18 | Magnetoelastic coupling in iron | Exchange interactions in {\alpha}- and {\gamma}-Fe are investigated within an
ab-initio spin spiral approach. We have performed total energy calculations for
different magnetic structures as a function of lattice distortions, related
with various cell volumes and the Bain tetragonal deformations. The effective
exchange... | 1111.4432v1 |
2011-11-21 | Dissipative electro-elastic network model of protein electrostatics | We propose a dissipative electro-elastic network model (DENM) to describe the
dynamics and statistics of electrostatic fluctuations at active sites of
proteins. The model combines the harmonic network of residue beads with
overdamped dynamics of the normal modes of the network characterized by two
friction coefficients... | 1111.4726v1 |
2011-11-21 | Pairing Glue Activation in Cuprates within the Quantum Critical Regime | A grand challenge in many-body quantum physics is to explain the apparent
connection between quantum criticality and high-temperature superconductivity
in the cuprates and similar systems, such as the iron pnictides and
chalcogenides. Here we argue that the quantum-critical regime plays an
essential role in activating ... | 1111.5033v3 |
2011-11-17 | About a possible path towards the reverse engineering of quantum mechanics | An out of the box intellectual path exploring the foundations of quantum
mechanics is discussed in some detail, in order to clarify why a possibly
different way to look at the relevant fundamental questions can be identified
and can support further research. Two key concepts arise. (1) Einstein critics
to quantum mecha... | 1111.5215v1 |
2011-11-24 | Interplay between superconductivity and antiferromagnetism in some iron-pnictide single crystals studied by $^{57}$Fe Mössbauer spectroscopy | We have performed detailed $^{57}$Fe M\"ossbauer spectroscopy measurements on
Ba$_{0.78}$K$_{0.22}$Fe$_2$As$_2$ and BaFe$_{2-x}$Ni$_x$As$_2$ single crystal
mosaics showing antiferromagnetic ordering below $T_N$ with superconductivity
below $T_C$. Analysis of the M\"ossbauer spectra shows a decrease in the
magnetic hype... | 1111.5853v1 |
2011-11-28 | Phase diagram and oxygen annealing effect of FeTe1-xSex iron-based superconductor | Phase diagrams of as-grown and O2-annealed FeTe1-xSex determined from
magnetic susceptibility measurement were obtained. For as-grown samples, the
antiferromagnetic order was fully suppressed in the range region x \geq 0.15,
and weak superconductivity appeared when x \geq 0.1. Beginning at x = 0.5, weak
superconductivi... | 1111.6472v3 |
2011-12-01 | Detailed abundances for M giants in two inner bulge fields from Infrared Spectroscopy | We report abundance analysis for 30 M giant stars in two inner Galactic bulge
fields at (l,b)=(0,-1.75) deg and at (l,b)=(1,-2.65) deg, based on R=25,000
infrared spectroscopy from 1.5-1.8um using NIRSPEC at the Keck II telescope. We
find iron abundances of <[Fe/H]>=-0.16 +/- 0.03 dex with a 1-sigma dispersion
of 0.12 ... | 1112.0306v1 |
2011-12-08 | Photovoltaic Effect on Molecule Coupled Ferromagnetic Films of a Magnetic Tunnel Junction | Economical solar energy conversion to electricity can be boosted by the
discovery of fundamentally new photovoltaic mechanism, and a suitable system to
realize it with commonly available materials like iron (Fe) and nickel (Ni).
This paper reports the observation of photovoltaic effect on a molecular
spintronics device... | 1112.1879v2 |
2011-12-10 | Existence of Orbital Order and its Fluctuation in Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ Revealed by X-ray Absorption Spectroscopy | We performed temperature dependent X-ray linear dichroism (XLD) experiments
on an iron pnictide system, Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ with $x$=0.00 and
0.05, to experimentally verify existence of orbital ordering (OO). We observed
clear XLD in polarization dependent X-ray absorption spectra of Fe $L$ edges.
By exploit... | 1112.2243v1 |
2011-12-20 | A Constructive Approach to Reduced-Form Auctions with Applications to Multi-Item Mechanism Design | We provide a constructive proof of Border's theorem [Bor91, HR15a] and its
generalization to reduced-form auctions with asymmetric bidders [Bor07, MV10,
CKM13]. Given a reduced form, we identify a subset of Border constraints that
are necessary and sufficient to determine its feasibility. Importantly, the
number of the... | 1112.4572v2 |
2011-12-20 | Observation of Multiple Superconducting Gaps in the Infrared Reflectivity Spectra of Ba(Fe0.9Co0.1)2As2 | The results of infrared reflectivity measurements for the iron-based
high-temperature superconductor Ba(Fe0.9Co0.1)2As2 are reported. The
reflectivity is found to be close to unity at frequencies w lower than 2Delta/h
(2Delta is the superconducting gap and h is Planck's constant). This is
evidence for the s+/- or s+/+ ... | 1112.4636v2 |
2011-12-21 | Optical properties and electronic structure of multiferroic hexagonal orthoferrites RFeO3 (R=Ho, Er, Lu) | We report on optical studies of the thin films of multiferroic hexagonal
(P.G. 6mm) rare-earth orthoferrites RFeO3 (R=Ho, Er, Lu) grown epitaxially on a
(111)-surface of ZrO2(Y2O3) substrate. The optical absorption study in the
range of 0.6-5.6 eV shows that the films are transparent below 1.9 eV; above
this energy fou... | 1112.5102v3 |
2011-12-26 | Surface properties of the clean and Au/Pd covered Fe$_3$O$_4$(111): a DFT and DFT+$U$ study | The spin-density functional theory (DFT) and DFT+$U$ with Hubbard $U$ term
accounting for on-site Coulomb interactions were applied to investigate
structure, stability, and electronic properties of different terminations of
the Fe$_3$O$_4$(111) surface. All terminations of the ferrimagnetic
Fe$_3$O$_4$(111) surface exh... | 1112.5827v1 |
2011-12-28 | Possibility of Horizontal Line Node in KFe$_2$As$_2$ Probed by Muon Spin Rotation | The anisotropy and temperature dependence of the magnetic field penetration
depth in the iron-based superconductor KFe$_2$As$_2$ have been measured down to
20 mK by means of muon spin rotation. We have observed that the flux-line
lattice forms triangular symmetry when we applied the field parallel to c-axis,
suggesting... | 1112.6078v1 |
2011-12-29 | Phenomenology of Neutrino Oscillations at the Neutrino Factory | We consider the prospects for a neutrino factory to measure mixing angles,
the CP violating phase and mass-squared differences by detecting wrong-charged
muons arising from the chain \mu^+ to \nu_e to \nu_\mu\ to \mu^- and the
right-charged muons coming from the chain \mu^+ to \bar{\nu}_\mu\ to
\bar{\nu}_\mu\ to \mu^+ ... | 1112.6259v1 |
2012-01-04 | KxFe2-ySe2 single crystals: Floating-zone growth, Transport and Structural properties | Single crystals of superconducting KxFe2-ySe2 have been grown with the
optical floating-zone technique under application of 8 bar of argon pressure.
We found that large and high quality single crystals with dimensions of
~\varnothing6 \times 10 mm could be obtained at the termination of the grown
ingot through quenchin... | 1201.0902v1 |
2012-01-04 | A new candidate for probing Population III nucleosynthesis with carbon-enhanced damped Lyman-alpha systems | We report the identification of a very metal-poor damped Lyman-alpha system
(DLA) at z_abs = 3.067295 that is modestly carbon-enhanced, with an iron
abundance of ~1/700 solar ([Fe/H] = -2.84) and [C,O/Fe] ~ +0.6. Such an
abundance pattern is likely to be the result of nucleosynthesis by massive
stars. On the basis of 1... | 1201.1004v2 |
2012-01-05 | Metallicities for 6 nearby open clusters from high-resolution spectra of giant stars. [Fe/H] values for a planet search sample | We present a study of the stellar parameters and iron abundances of 18 giant
stars in 6 open clusters. The analysis was based on high-resolution and
high-S/N spectra obtained with the UVES spectrograph (VLT-UT2). The results
complement our previous study where 13 clusters were already analyzed. The
total sample of 18 c... | 1201.1108v1 |
2012-01-09 | A General Mechanism for Orbital Selective Phase Transitions | Based on the analysis of a two-orbital Hubbard model within a mean-field
approach, we propose a mechanism for an orbital selective phase transition
(OSPT) where coexistence of localized and itinerant electrons can be realized.
We show that this OSPT exists both at and near half filling even in the absence
of crystal fi... | 1201.1689v2 |
2012-01-19 | Impact of microstructure, temperature and strain ratio on energy-based low- cycle fatigue life prediction models for TiAl alloys | In this paper, two fatigue lifetime prediction models are tested on TiAl
intermetallic using results from uniaxial low-cycle fatigue tests. Both
assessments are based on dissipated energy but one of them considers a
hydrostatic pressure correction. This work allows to confirm, on this kind of
material, the linear natur... | 1201.4084v1 |
2012-01-20 | Magnetic origin of chemical balance in alloyed Fe-Cr stainless steels: first-principles and Ising model study | Iron-chromium forms the basis of most of the stainless steel grades in the
markets. Recently new insights into the physical and chemical properties of
Fe-Cr based alloys have been obtained. Some of the new results are quite
unexpected and call for further investigations. The present study addresses the
magnetic contrib... | 1201.4336v1 |
2012-01-23 | Influence of the magnetoelectric coupling on the electric field induced magnetization reversal in a composite non-strained multiferroic chain | We study theoretically the multiferroic dynamics in a composite
one-dimensional system consisting of BaTiO3 multiferroically coupled to an iron
chain. The method treats the magnetization and the polarization as
thermodynamic quantities describable via a combination of the Landau-Lifshits-
Gilbert and the Ginzburg-Landa... | 1201.4740v1 |
2012-01-24 | Electronic Orders in the Verwey Structure of Magnetite | Electronic structure calculations of the Verwey ground state of magnetite,
Fe3O4, using density functional theory with treatment of on-site Coulomb
interactions (DFT+U scheme) are reported. These calculations use the
recently-published experimental crystal structure coordinates for magnetite in
the monoclinic space gro... | 1201.5106v2 |
2012-01-25 | Effect of impurities on growth and morphology of cementite nanowires | Effects of doping on morphology of iron carbide (cementite) nanowires have
been explored by first principle electronic structure calculations. We examined
the role of several realistic impurities (Si, Mn, V, P and S) in the formation
energies of the cementite nanowires with different sizes and morphologies. It
is shown... | 1201.5327v2 |
2012-01-26 | Infrared emissivity spectroscopy of a soda-lime silicate glass up to the melt | The short-range structure of an iron doped soda-lime glass was investigated
by infrared emissivity spectroscopy from room temperature up to the melt.
Quantitative information on the distribution of the Q^n tetrahedral units was
obtained by fitting the emissivity spectra using a dielectric function model
(DFM). The DFM ... | 1201.5676v1 |
2012-01-27 | The effects of Vanadium on the strength of a bcc Fe Σ3(111)[1-10] grain boundary | The effects of micro-alloying element, vanadium, on a bcc Fe \Sigma
3(111)[1-10] symmetric tilt grain boundary strength are studied using density
functional theory calculations. The lowest energy configuration of the grain
boundary structure are obtained from the first-principles calculations. The
substitutional and in... | 1201.5915v1 |
2012-02-01 | Theory of High-Tc Superconductivity: Transition Temperature | It is demonstrated that the transition temperature (Tc) of high-Tc
superconductors is determined by their layered crystal structure, bond lengths,
valency properties of the ions, and Coulomb coupling between electronic bands
in adjacent, spatially separated layers. Analysis of 31 high-Tc materials
(cuprates, ruthenates... | 1202.0306v1 |
2012-02-03 | Experimental and theoretical electronic structure of EuRh2As2 | The Fermi surfaces (FS's) and band dispersions of EuRh2As2 have been
investigated using angle-resolved photoemission spectroscopy. The results in
the high-temperature paramagnetic state are in good agreement with the full
potential linearized augmented plane wave calculations, especially in the
context of the shape of ... | 1202.0744v1 |
2012-02-12 | Theory of High-Tc Superconductivity: Accurate Predictions of Tc | The superconducting transition temperatures of high-Tc compounds based on
copper, iron, ruthenium and certain organic molecules are discovered to be
dependent on bond lengths, ionic valences, and Coulomb coupling between
electronic bands in adjacent, spatially separated layers [1]. Optimal
transition temperature, denot... | 1202.2480v2 |
2012-02-16 | Orbital Selective Magnetism in the Spin-Ladder Iron Selenides Ba$_{1-x}$K$_{x}$Fe$_2$Se$_3$ | Here we show that the 2.80(8) {\mu}B/Fe block antiferromagnetic order of
BaFe2Se3 transforms into stripe antiferromagnetic order in KFe2Se3 with a
decrease in moment to 2.1(1) {\mu}B/Fe. This reduction is larger than expected
from the change in electron count from Ba$^{2+}$ to K$^{+}$, and occurs with
the loss of the d... | 1202.3676v2 |
2012-02-19 | High $T_c$ superconductivity at the FeSe/SrTiO$_3$ Interface | In a recent experiment the superconducting gap of a single unit cell thick
FeSe film on SrTiO$_3$ substrate is observed by scanning tunneling spectroscopy
and angle-resolved photoemission spectroscopy. The value of the superconducting
gap is much larger than that of the bulk FeSe under ambient pressure. In this
paper w... | 1202.4141v2 |
2012-02-20 | Observation of superconductivity at 30 K~46 K in AxFe2Se2 (A = Li, Na, Ba, Sr, Ca, Yb, and Eu) | New iron selenide superconductors by intercalating smaller-sized alkali
metals (Li, Na) and alkaline earths using high-temperature routes have been
pursued ever since the discovery of superconductivity at about 30 K in KFe2Se2,
but all have failed so far. Here we demonstrate that a series of
superconductors with enhanc... | 1202.4340v2 |
2012-02-20 | Antiferromagnetic Domain Wall Engineering in Chromium Films | We have engineered an antiferromagnetic domain wall by utilizing a magnetic
frustration effect of a thin iron cap layer deposited on a chromium film.
Through lithography and wet etching we selectively remove areas of the Fe cap
layer to form a patterned ferromagnetic mask over the Cr film. Removing the Fe
locally remov... | 1202.4401v1 |
2012-02-21 | A first-principles investigation on the effects of magnetism on the Bain transformation of $α$-phase FeNi systems | The effects of magnetism on the Bain transformation of $\alpha$-phase FeNi
systems are investigated by using the full potential linearized augmented plane
wave (FLAPW) method based on the generalized gradient approximation (GGA). We
found that Ni impurity in bcc Fe increases the lattice constant in
ferromagnetic (FM) s... | 1202.4726v1 |
2012-02-23 | Tuning magnetism in FeAs-based materials via tetrahedral structure | Resistivity, magnetic susceptibility, neutron scattering and x-ray
crystallography measurements were used to study the evolution of magnetic order
and crystallographic structure in single-crystal samples of the Ba1-xSrxFe2As2
and Sr1-yCayFe2As2 series. A non-monotonic dependence of the magnetic ordering
temperature T0 ... | 1202.5324v2 |
2012-02-24 | Block magnetism coupled with local distortion in the iron-based spin-ladder compound BaFe2Se3 | Magnetism in the insulating BaFe$_2$Se$_3$ was examined through
susceptibility, specific heat, resistivity and neutron diffraction
measurements. After formation of a short-range magnetic correlation, a
long-range ordering was observed below $T_{\rm N}\sim 255$ K. The transition is
obscured by bulk properties. Magnetic ... | 1202.5371v1 |
2012-02-24 | Nanoscale layering of antiferromagnetic and superconducting phases in Rb2Fe4Se5 | We studied phase separation in a single-crystalline antiferromagnetic
superconductor Rb2Fe4Se5 (RFS) using a combination of scattering-type scanning
near-field optical microscopy (s-SNOM) and low-energy muon spin rotation
(LE-\mu SR). We demonstrate that the antiferromagnetic and superconducting
phases segregate into n... | 1202.5446v2 |
2012-02-28 | Conductance of non-ballistic point contacts in hybrid systems "normal metal/superconductor" Cu/Mo-C and Cu/LaOFFeAs | We consider the shape of the curves of "Andreev" conductance of non-ballistic
point contact NS heterosystems depending on the bias voltage at the contact.
The obtained shape of those curves is caused by the contribution from the
mechanism of coherent scattering by impurities which doubles the scattering
cross section. ... | 1202.6173v1 |
2012-03-01 | Macroscopic phase segregation in superconducting K0.73Fe1.67Se2 as seen by muon spin rotation and infrared spectroscopy | Using muon spin rotation (\muSR) and infrared spectroscopy we investigated
the recently discovered superconductor K0.73Fe1.67Se2 with Tc = 32 K. We show
that the combined data can be consistently described in terms of a
macroscopically phase segregated state with a matrix of ~88% volume fraction
that is insulating and ... | 1203.0286v2 |
2012-03-03 | Extension of the Wu-Jing equation of state (EOS) for highly porous materials: calculations to validate and compare the thermoelectron model | In order to verify and validate the newly developed thermoelectron equation
of state (EOS) model that is based on the Wu-Jing (W-J) EOS, calculations of
shock compression behavior have been made on five different porous metals-iron,
copper, lead, tungsten, and aluminum-which are commonly used as standards. The
model wa... | 1203.0619v1 |
2012-03-07 | The interplay of electron doping and chemical pressure in Ba(Fe(1-y)Coy)2(As(1-x)Px)2 | The effects of internal chemical pressure on electron doped iron arsenide
superconductors are studied in the series Ba(Fe(1-y)Coy)2(As(1-x)Px)2.
Combinations of both dopants induce superconductivity also in such areas where
only one would not suffice, and can likewise move the system into an overdoped
state, while no h... | 1203.1459v1 |
2012-03-12 | Suppression of Superconductivity by Twin Boundaries in FeSe | Low-temperature scanning tunneling microscopy and spectroscopy are employed
to investigate twin boundaries in stoichiometric FeSe films grown by molecular
beam epitaxy. Twin boundaries can be unambiguously identified by imaging the
90{\deg} change in the orientation of local electronic dimers from Fe site
impurities on... | 1203.2629v2 |
2012-03-13 | Coexistence and competition of the short-range incommensurate antiferromagnetic order with superconductivity in BaFe2-xNixAs2 | Superconductivity in the iron pnictides develops near antiferromagnetism, and
the antiferromagnetic (AF) phase appears to overlap with the superconducting
phase in some materials such as BaFe2-xTxAs2 (where T = Co or Ni). Here we use
neutron scattering to demonstrate that genuine long-range AF order and
superconductivi... | 1203.2759v2 |
2012-03-17 | Magnetic Phase Transition and Relaxation Effects in LiFePO4 | We report the observation of para - antiferromagnetic transition at ~ 50 K in
lithium iron phosphate, LiFePO4 through DC magnetization and M\"ossbauer
spectroscopy. The Ferrous ion Fe2+ (3d6, 5D) in LiFePO4 exhibits relaxation
effects with a relaxation frequency ~1.076 \times 10(rise to 7) s-1 at 300 K.
The temperature... | 1203.3863v2 |
2012-03-19 | Antiferromagnetic Order and Superconductivity in Sr4(Mg0.5-xTi0.5+x)2O6Fe2As2 with Electron Doping: 75As-NMR Study | We report an 75As-NMR study on iron (Fe)-based superconductors with thick
perovskitetype blocking layers Sr4(Mg0.5-xTi0.5+x)2O6Fe2As2 with x=0 and 0.2.
We have found that antiferromagnetic (AFM) order takes place when x=0, and
superconductivity (SC) emerges below Tc=36 K when x=0.2. These results reveal
that the Fe-pni... | 1203.4190v1 |
2012-03-20 | Phase soliton and pairing symmetry of a two-band superconductor: Role of the proximity effect | We suggest a mechanism which promotes the existence of a phase soliton --
topological defect formed in the relative phase of superconducting gaps of a
two-band superconductor with s+- type of pairing. This mechanism exploits the
proximity effect with a conventional s-wave superconductor which favors the
alignment of th... | 1203.4554v3 |
2012-03-25 | First Principles Calculation of Helical Spin Order in Iron Perovskite SrFeO3 and BaFeO3 | Motivated by recent discovery of ferromagnetism in cubic perovskite BaFeO3
under small magnetic field, we investigate spin order in BaFeO3 and
isostructual SrFeO3 by the first principles calculation. The on-site Coulomb
and exchange interactions are necessary for the helical spin order consistent
with experiments. SrFe... | 1203.5470v1 |
2012-03-26 | Probing the role of Co substitution in the electronic structure of iron-pnictides | The role of Co substitution in the low-energy electronic structure of
Ca(Fe$_{0.944}$Co$_{0.056}$)$_2$As$_2$ is investigated by resonant
photoemission spectroscopy and density functional theory. The Co 3d-state
center-of-mass is observed at 250 meV higher binding energy than Fe's,
indicating that Co posses one extra va... | 1203.5814v1 |
2012-03-28 | Opening of the superconducting gap in the hole pockets of Ba(Fe(1-x)Co(x))2As2 as seen via Angle-Resolved PhotoElectron Spectroscopy | We present an Angle-Resolved PhotoElectron Spectroscopy study of the changes
in the electronic structure of electron doped Ba(Fe(1-x)Co(x))2As2 across the
superconducting phase transition. By changing the polarization of the incoming
light, we were able to observe the opening of the gap for the inner hole pocket
alpha,... | 1203.6194v2 |
2012-04-02 | Abrupt change in the energy gap of superconducting Ba1-xKxFe2As2 single crystals with hole doping | We performed a Laser angle-resolved photoemission spectroscopy (ARPES) study
on a wide doping range of Ba1-xKxFe2As2 (BaK) and precisely determined the
doping evolution of the superconducting (SC) gaps in this compound. The gap
size of the outer hole Fermi surface (FS) sheet around the Brillioun zone (BZ)
center shows ... | 1204.0326v1 |
2012-04-02 | Quantum critical point for stripe order: An organizing principle of cuprate superconductivity | A spin density-wave quantum critical point (QCP) is the central organizing
principle of organic, iron-pnictide, heavy-fermion and electron-doped cuprate
superconductors. It accounts for the superconducting Tc dome, the
non-Fermi-liquid resistivity, and the Fermi-surface reconstruction. Outside the
magnetically ordered ... | 1204.0490v1 |
2012-04-03 | A photonic crystal cavity-optical fiber tip nanoparticle sensor for biomedical applications | We present a sensor capable of detecting solution-based nanoparticles using
an optical fiber tip functionalized with a photonic crystal cavity. When sensor
tips are retracted from a nanoparticle solution after being submerged, we find
that a combination of convective fluid forces and optically-induced trapping
cause an... | 1204.0818v1 |
2012-04-05 | Gaseous Material Orbiting the Polluted, Dusty White Dwarf HE1349-2305 | We present new spectroscopic observations of the polluted, dusty,
helium-dominated atmosphere white dwarf star HE1349-2305. Optical spectroscopy
reveals weak CaII infrared triplet emission indicating that metallic gas debris
orbits and is accreted by the white dwarf. Atmospheric abundances are measured
for magnesium an... | 1204.1132v1 |
2012-04-04 | Rare earth substitution in lattice-tuned Sr0.3Ca0.7Fe2As2 solid solutions | The effects of aliovalent rare earth substitution on the physical properties
of Sr0.3Ca0.7Fe2As2 solid solutions are explored. Electrical transport,
magnetic susceptibility and structural characterization data as a function of
La substitution into (Sr_1-y_Ca_y)_1-x_La_x_Fe2As2 single crystals confirm the
ability to sup... | 1204.1335v2 |
2012-04-08 | Two successive field-induced spin-flop transitions in single-crystalline CaCo$_{2}$As$_{2}$ | CaCo$_{2}$As$_{2}$, a ThCr$_{2}$Si$_{2}$-structure compound, undergoes an
antiferromagnetic transition at \emph{T$_{N}$}=76K with the magnetic moments
being aligned parallel to the \emph{c} axis. Electronic transport measurement
reveals that the coupling between conducting carriers and magnetic order in
CaCo$_{2}$As$_{... | 1204.1736v1 |
2012-04-09 | Measurement of The Broad Line Region Size in a Luminous MACHO Quasar | We measure the broad emission line region (BLR) size of a luminous, L~1E47
erg/s, high-z quasar using broadband photometric reverberation mapping. To this
end, we analyze ~7.5 years of photometric data for MACHO 13.6805.324 (z~1.72)
in the B and R MACHO bands and find a time delay of 180+/-40 days in the rest
frame of ... | 1204.1862v1 |
2012-04-19 | Plasma Pressure Driven Asymmetric Supernovae and Highly Collimated Gamma-Ray Bursts | During the process of collapse of a massive star, a cavity is generated
between the central iron core and an outer stellar envelope. The dynamics of
this cavity, filled with plasma and magnetic field of the rapidly rotating
proto-magnetar's magnetosphere, is believed to be very relevant in
understanding supernovae and ... | 1204.4360v2 |
2012-04-23 | Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition | We discover that hcp phases of Fe and Fe0.9Ni0.1 undergo an electronic
topological transition at pressures of about 40 GPa. This topological change of
the Fermi surface manifests itself through anomalous behavior of the Debye
sound velocity, c/a lattice parameter ratio and M\"ossbauer center shift
observed in our exper... | 1204.5130v1 |
2012-05-03 | Generalized joint density of states and its application to exploring the pairing symmetry of superconductors | We introduce a generalized joint density of states (GJDOS), which
incorporates the coherent factor into the JDOS, to study quasiparticle
interference (QPI) in superconductors. The intimate relation between the
Fourier-transformed local density of states and GJDOS is revealed: they corre-
spond respectively to the real ... | 1205.0598v1 |
2012-05-03 | Quenched Fe Moment in the Collapsed Tetragonal Phase of Ca$_{1-x}$Pr$_{x}$Fe$_2$As$_2$ | We report $^{75}$As NMR studies on single crystals of rare-earth doped iron
pnictides superconductor Ca$_{1-x}$Pr$_{x}$Fe$_{2}$As$_{2}$ ($x$=0.075 and
0.15). The $^{75}$As spectra show a chemical pressure effect with doping and a
first order structure transition to the collapsed tetragonal phase upon
cooling. A sharp d... | 1205.0604v1 |
2012-05-09 | Pseudo-potentials based first-principles approach to the magneto-optical Kerr effect: from metals to the inclusion of local fields and excitonic effects | We propose a first-principles scheme for the description of the
magneto-optical kerr effect within density functional theory (DFT). Though the
computation of Kerr parameters is often done within DFT, starting from the
conductivity or the dielectric tensor, there is no formal justification to this
choice.
As a first s... | 1205.1994v3 |
2012-05-14 | Isotope shifts and hyperfine structure of the Fe I 373.7 nm resonance line | We report measurements of the isotope shifts of the 3d6 4s2 a 5D3 - 3d6 4s4p
z 5F4o FeI resonance line at 373.7 nm between all four stable isotopes 54Fe,
56Fe, 57Fe and 58Fe, as well as the complete hyperfine structure of that line
for 57Fe, the only stable isotope having a non-zero nuclear spin. The field and
specific... | 1205.3146v1 |
2012-05-17 | Interstellar Dust Close to the Sun | The low density interstellar medium (ISM) close to the Sun and inside of the
heliosphere provides a unique laboratory for studying interstellar dust grains.
Grain characteristics in the nearby ISM are obtained from observations of
interstellar gas and dust inside of the heliosphere and the interstellar gas
towards near... | 1205.4017v1 |
2012-05-19 | Iron spin-reorientation transition in NdFeAsO | The low-temperature magnetic structure of NdFeAsO has been revisited using
neutron powder diffraction and symmetry analysis using the Sarah
representational analysis program. Four magnetic models with one magnetic
variable for each of the Nd and Fe sublattices were tested. The best fit was
obtained using a model with F... | 1205.4312v1 |
2012-05-22 | Theory of nonequilibrium dynamics of multiband superconductors | We study the nonequilibrium dynamics of multiband BCS superconductors
subjected to ultrashort pump pulses. Using density-matrix theory, the time
evolution of the Bogoliubov quasiparticle densities and the superconducting
order parameters are computed as a function of pump pulse frequency, duration,
and intensity. Focus... | 1205.4861v2 |
2012-05-23 | Bulk electronic structure of superconducting LaRu2P2 single crystals measured by soft x-ray angle-resolved photoemission spectroscopy | We present a soft X-ray angle-resolved photoemission spectroscopy (SX-ARPES)
study of the stoichiometric pnictide superconductor LaRu2P2. The observed
electronic structure is in good agreement with density functional theory (DFT)
calculations. However, it is significantly different from its counterpart in
high-temperat... | 1205.5216v1 |
2012-05-23 | Electronic phase diagram of disordered Co doped BaFe2As2 | Superconducting and normal state transport properties in iron pnictides are
sensitive to disorder and impurity scattering. By investigation of
Ba(Fe1-xCox)2As2 thin films with varying Co concentration, we demonstrate that
in the dirty limit the superconducting dome in the electronic phase diagram of
Ba(Fe1-xCox)2As2 sh... | 1205.5219v3 |
2012-05-25 | Superconductivity at Tc = 44 K in LixFe2Se2(NH3)y | Following a recent proposal by Burrard-Lucas et al. [unpublished, arXiv:
1203.5046] we intercalated FeSe by Li in liquid ammonia. We report on the
synthesis of new LixFe2Se2(NH3)y phases as well as on their magnetic and
superconducting properties. We suggest that the superconducting properties of
these new hybride mate... | 1205.5731v1 |
2012-05-31 | Superconducting Fluctuations and Anomalous Phonon Renormalization much above superconducting transition temperature in Ca4Al2O5.7Fe2As2 | Raman studies on Ca4Al2O5.7Fe2As2 superconductor in the temperature range of
5 K to 300 K, covering the superconducting transition temperature Tc ~ 28.3 K,
reveal that the Raman mode at ~ 230 cm-1 shows a sharp jump in frequency by ~ 2
% and linewidth increases by ~ 175 % at To ~ 60 K. Below To, anomalous
softening of ... | 1205.7033v1 |
2012-06-03 | Importance of many body effects in the kernel of hemoglobin for ligand binding | We propose a mechanism for binding of diatomic ligands to heme based on a
dynamical orbital selection process. This scenario may be described as bonding
determined by local valence fluctuations. We support this model using
linear-scaling first-principles calculations, in combination with dynamical
mean-field theory, ap... | 1206.0412v2 |
2012-06-08 | Substituent Effects on the Spin-Transition Temperature in Complexes with Tris(pyrazolyl) Ligands | Iron (II) complexes with substituted tris(pyrazolyl) ligands, which exhibit a
thermally driven transition from a low-spin state at low temperatures to a
high-spin state at elevated temperatures, have been studied by M\"ossbauer
spectroscopy and magnetic susceptibility measurements. From the observed
spectra the molar h... | 1206.1883v1 |
2012-06-10 | Anomalous impurity effects in the iron-based superconductor KFe$_2$As$_2$ | High-quality K(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals have been grown by
using KAs flux method. Instead of increasing the superconducting transition
temperature $T_{\rm c}$ through electron doping, we find that Co impurities
rapidly suppress $T_{\rm c}$ down to zero at only $x \approx$ 0.04. Such an
effective supp... | 1206.2030v3 |
2012-06-11 | Diffusion of hydrogen within idealised grains of bcc-Fe: A kinetic Monte Carlo study | Structural defects in materials such as vacancies, grain boundaries, and
dislocations may trap hydrogen and a local accumulation of hydrogen at these
defects can lead to the degradation of the materials properties. An important
aspect in obtaining insight into hydrogen induced embrittlement on the
atomistic level is to... | 1206.2314v1 |
2012-06-12 | Electric field control of magnetic exchange coupling | Electric control of magnetism is a vision which drives intense research on
magnetic semiconductors and multiferroics. Recently, also ultrathin metallic
films were reported to show magnetoelectric effects at room temperature. Here
we demonstrate much stronger effects by exploiting reduction/oxidation
reactions in a natu... | 1206.2467v3 |
2012-06-13 | Mn local moments prevent superconductivity in iron-pnictides Ba(Fe 1-x Mn x)2As2 | 75As nuclear magnetic resonance (NMR) experiments were performed on
Ba(Fe1-xMnx)2As2 (xMn = 2.5%, 5% and 12%) single crystals. The Fe layer
magnetic susceptibility far from Mn atoms is probed by the75As NMR line shift
and is found similar to that of BaFe2As2, implying that Mn does not induce
charge doping. A satellite ... | 1206.2741v2 |
2012-06-15 | Pressure-induced changes of the vibrational modes of spin-crossover complexes studied by nuclear resonance scattering of synchrotron radiation | Nuclear inelastic scattering (NIS) spectra were recorded for the
spin-crossover complexes STP and ETP (STP =
[Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg- ethane)](ClO4)2 and
ETP =
[Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg-butane)](ClO4)2) at
30 K and at room temperature and also at ambient... | 1206.3451v1 |
2012-06-20 | Evolution of band structure from optimally doped to heavily overdoped Co-substituted NaFeAs | Using angle-resolved photoemission spectroscopy, we studied the electronic
structure of NaFe$_{1-x}$Co$_x$As from an optimally doped superconducting
compound ($x=0.028$) to a heavily overdoped non-superconducting one
($x=0.109$). Similar to the case of "122" type iron pnictides, our data suggest
that Co dopant in NaFe$... | 1206.4402v1 |
2012-06-27 | BaFe2Se2O as an Iron-Based Mott Insulator with Antiferromagnetic Order | A new compound with a quasi-two-dimensional array of FeSe3O tetrahedra and an
orthorombic structure, namely BaFe2Se2O, has been successfully fabricated.
Experimental results show that this compound is an insulator and has an
antiferromagnetic (AF) transition at 240 K. Band structure calculation reveals
the narrowing of... | 1206.6154v3 |
2012-06-27 | Effect of Ru susbstitution on atomic displacements in the layered SmFe_{1-x}Ru_xAsO_{0.85}F_{0.15} superconductor | The effect of Ru substitution on the local structure of layered
SmFe$_{1-x}$Ru$_x$AsO$_{0.85}$F$_{0.15}$ superconductor has been studied by As
$K$- and Sm $L_3$ - edges x-ray-absorption spectroscopy. The extended
x-ray-absorption fine-structure measurements reveal distinct Fe-As and Ru-As
bondlengths in the Ru substitu... | 1206.6526v1 |
2012-06-29 | Ferromagnetism and superconductivity in P-doped CeFeAsO | We report on superconductivity in CeFeAs1-xPxO and the possible coexistence
with Ce- ferromagnetism (FM) in a small homogeneity range around x = 30% with
ordering temperatures of T_SC = T_C = 4K. The antiferromagnetic (AFM) ordering
temperature of Fe at this critical concentration is suppressed to T^N_Fe ~ 40K
and does... | 1206.7088v2 |
2012-07-02 | Germanium, Arsenic, and Selenium Abundances in Metal-Poor Stars | The elements germanium (Ge, Z=32), arsenic (As, Z=33), and selenium (Se,
Z=34) span the transition from charged-particle or explosive synthesis of the
iron-group elements to neutron-capture synthesis of heavier elements. Among
these three elements, only the chemical evolution of germanium has been studied
previously. H... | 1207.0518v1 |
2012-07-03 | Updated Atomic Data and Calculations for X-ray Spectroscopy | We describe the latest release of AtomDB, version 2.0.2, a database of atomic
data and a plasma modeling code with a focus on X-ray astronomy. This release
includes several major updates to the fundamental atomic structure and process
data held within AtomDB, incorporating new ionization balance data,
state-selective r... | 1207.0576v1 |
2012-07-05 | Spin reorientation in TlFe1.6Se2 with complete vacancy ordering | The relationship between vacancy ordering and magnetism in TlFe1.6Se2 has
been investigated via single crystal neutron diffraction, nuclear forward
scattering, and transmission electron microscopy. The examination of chemically
and structurally homogenous crystals allows the true ground state to be
revealed, which is c... | 1207.1318v2 |
2012-07-06 | Two-band superconductivity featuring different anisotropies in the ternary iron silicide Lu$_{2}$Fe$_{3}$Si$_{5}$ | We report detailed studies of the upper critical field and low-temperature
specific heat in the two-gap superconductor Lu$_{2}$Fe$_{3}$Si$_{5}$. The
anisotropy of the upper critical field suggests that the active band is
quasi-one-dimensional. Low-temperature specific heat in magnetic fields reveals
that the virtual $H... | 1207.1502v1 |
2012-07-08 | Emergent Phases of Nodeless and Nodal Superconductivity Separated by Antiferromagnetic Order in Iron-based Superconductor (Ca4Al2O6)Fe2(As1-xPx)2: 75As- and 31P-NMR Studies | We report $^{31}$P- and $^{75}$As-NMR studies on
(Ca$_4$Al$_2$O$_{6}$)Fe$_2$(As$_{1-x}$P$_x$)$_2$ with an isovalent substitution
of P for As. We present the novel evolution of emergent phases that the
nodeless superconductivity (SC) in 0$\le x \le$0.4 and the nodal one around
$x$=1 are intimately separated by the onset... | 1207.1920v2 |
2012-07-09 | Time-Dependent Density Diagnostics of Solar Flare Plasmas Using SDO/EVE | Temporally-resolved electron density measurements of solar flare plasmas are
presented using data from the EUV Variability Experiment (EVE) onboard the
Solar Dynamics Observatory (SDO). The EVE spectral range contains emission
lines formed between 10^4-10^7 K, including transitions from highly ionized
iron (>10 MK). Us... | 1207.1990v1 |
2012-07-10 | Magnetism in parent Fe-chalcogenides: quantum fluctuations select a plaquette order | We analyze magnetic order in iron-chalcogenide Fe$_{1+y}$Te -- the parent
compound of high-temperature superconductor Fe$_{1+y}$Te$_{1-x}$Se$_x$. Neutron
scattering experiments show that magnetic order in this material contains
components with momentum $Q_1=(\pi/2, \pi/2)$ and $Q_2 =(\pi/2, -\pi/2)$ in
Fe-only Brilloui... | 1207.2201v2 |
2012-07-16 | CVD Synthesis of Small-Diameter Single Walled Carbon Nanotubes on Silicon | A simple process for chemical vapor deposition of ultra SD single wall carbon
nanotubes has been developed. In this process, an iron nitrate nonahydrate
solution in isopropyl alcohol with a concentration of 400 ug/mlit was used to
catalyze nanoparticles formation on an oxidized silicon wafer. The oxide on the
substrate... | 1207.3555v1 |
2012-07-16 | Infrared Measurement of the Pseudogap in P-Doped and Co-Doped BaFe2As2 High-Temperature Superconductors | We report on infrared studies of charge dynamics in a prototypical pnictide
system: the BaFe2As2 family. Our experiments have identified hallmarks of the
pseudogap state in the BaFe2As2 system that mirror the spectroscopic
manifestations of the pseudogap in the cuprates. The magnitude of the infrared
pseudogap is in ac... | 1207.3567v1 |
2012-07-17 | Magneto-elastically coupled structural, magnetic and superconducting order parameters in BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ | We measure the transport properties of mechanically strained single crystals
of BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ over a wide range of $x$. The N\'eel
transition is extremely sensitive to stress and this sensitivity increases as
optimal doping is approached, even though the transition itself is strongly
suppressed. F... | 1207.3858v1 |
2012-07-17 | Non-Fermi Liquid behavior at the Orbital Ordering Quantum Critical Point in the Two-Orbital Model | The critical behavior of a two-orbital model with degenerate $d_{xz}$ and
$d_{yz}$ orbitals is investigated by multidimensional bosonization. We find
that the corresponding bosonic theory has an overdamped collective mode with
dynamical exponent $z=3$, which appears to be a general feature of a
two-orbital model and be... | 1207.4206v2 |
2012-07-18 | Bound States of Defects in Superconducting LiFeAs Studied by Scanning Tunneling Spectroscopy | Defects in LiFeAs are studied by scanning tunneling microscopy (STM) and
spectroscopy (STS). Topographic images of the five predominant defects allow
the identification of their position within the lattice. The most commonly
observed defect is associated with an Fe site and does not break the local
lattice symmetry, ex... | 1207.4249v2 |
2012-07-18 | Detection of Iron Kα Emission from a Complete Sample of Submillimeter Galaxies | We present an X-ray stacking analysis of a sample of 38 submillimeter
galaxies with <z>=2.6 discovered at >4{\sigma} significance in the Lockman Hole
North with the MAMBO array. We find a 5{\sigma} detection in the stacked soft
band (0.5-2.0 keV) image, and no significant detection in the hard band (2.0-8
keV). We also... | 1207.4486v1 |
2012-07-27 | Evidence for a cos(4\varphi) Modulation of the Superconducting Energy Gap of Optimally Doped FeTe_{0.6}Se_{0.4} Single Crystals Using Laser Angle-Resolved Photoemission Spectroscopy | We study the superconducting(SC)-gap anisotropy of the \Gamma-centered hole
Fermi surface in optimally doped FeTe_{0.6}Se_{0.4} (T_c = 14.5 K), using
laser-excited angle-resolved photoemission spectroscopy (ARPES). We observe
sharp superconducting coherence peaks at T = 2.5 K. In contrast to earlier
ARPES studies but c... | 1207.6571v3 |
2012-07-28 | Self-doping effect and possible antiferromagnetism at titanium-layers in the iron-based superconductor Ba$_2$Ti$_2$Fe$_2$As$_4$O | The electronic structure of Ba$_2$Ti$_2$Fe$_2$As$_4$O, a newly discovered
superconductor, is investigated using first-principles calculations based on
local density approximations. Multiple Fermi surface sheets originating from
Ti-3$d$ and Fe-3$d$ states are present corresponding to the conducting
Ti$_2$As$_2$O and Fe$... | 1207.6705v1 |
2012-07-29 | Dynamic approach to finite-temperature magnetic phase transitions in the extended J1- J2 model with vacancy order | The recently discovered iron-based superconductors A$_{y}$Fe$_{2-x}$Se$_{2}$
($A$=K, Rb, Cs, Tl) show a long-range antiferromagnetic order with an
unexpected high transition temperature $T_N \sim 550$ K and a unique $\sqrt{5}
\times \sqrt{5}$ vacancy order. Taking the extended $J_1$-$J_2$ model as a
minimal model, we i... | 1207.6740v3 |
2012-07-29 | Quantum Criticality Stabilizes High T_c Superconductivity Against Competing Symmetry-Breaking Instabilities | The occurrence of high-T_c superconductivity in systems including the
cuprates and the iron-based superconductors, is known to coincide with the
existence of anomalous normal-state properties which have been associated with
quantum criticality. We argue here that this observation results from the fact
that quantum crit... | 1207.6789v1 |
2012-08-06 | Spin-state Crossover Model for the Magnetism of Iron Pnictides | We propose a minimal model describing magnetic behavior of Fe-based
superconductors. The key ingredient of the model is a dynamical mixing of
quasi-degenerate spin states of Fe2+ ion by intersite electron hoppings,
resulting in an effective local spin Seff. The moments Seff tend to form
singlet pairs, and may condense ... | 1208.1197v3 |
2012-08-07 | Anisotropic electrical resistivity of LaFeAsO: evidence for electronic nematicity | Single crystals of LaFeAsO were successfully grown out of KI flux.
Temperature dependent electrical resistivity was measured with current flow
along the basal plane, \rho_perpend(T), as well as with current flow along the
crystallographic c-axis, \rho_parallel(T), the latter one utilizing electron
beam lithography and ... | 1208.1480v3 |
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