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2016-01-14
Coupled multiple-mode theory for $s_{\pm}$ pairing mechanism in iron based superconductors
We investigate the interplay between the magnetic and the superconducting degrees of freedom in unconventional multi-band superconductors such as iron pnictides. For this purpose a dynamical mode-mode coupling theory is developed based on the coupled Bethe-Salpeter equations. In order to investigate the region of the p...
1601.03552v2
2016-01-21
Effect of nonsymmorphic space group on correlation functions in iron-based superconductors
The orbital basis is natural when one needs to calculate the effect of local interactions or to unravel the role of orbital physics in the response to external probes. In systems with nonsymmorphic point groups, such as the iron-based superconductors, we show that symmetries that emerge in observable response functions...
1601.05813v3
2016-02-02
Fast synthesis of Fe1.1Se1-xTex superconductors in a self-heating and furnace-free way
A fast and furnace-free method of combustion synthesis is employed for the first time to synthesize iron-based superconductors. Using this method, Fe1.1Se1-xTex (0<=x<=1) samples can be prepared from self-sustained reactions of element powders in only tens of seconds. The obtained Fe1.1Se1-xTex samples show clear zero ...
1602.00880v1
2016-02-04
A quantum protective mechanism in photosynthesis
Since the emergence of oxygenic photosynthesis, living systems have developed protective mechanisms against reactive oxygen species. During charge separation in photosynthetic reaction centres, triplet states can react with molecular oxygen generating destructive singlet oxygen. The triplet product yield in bacteria is...
1602.01689v1
2016-02-12
Nucleosynthesis in the first massive stars
The nucleosynthesis in the first massive stars may be constrained by observing the surface composition of long-lived very iron-poor stars born around 10 billion years ago from material enriched by their ejecta. Many interesting clues on physical processes having occurred in the first stars can be obtained just based on...
1602.04122v1
2016-02-15
Electrical Switching of Magnetization in Films of alpha-Iron with Naturally Hydroxidized Surface
Control of the magnetization vector in ferromagnetic films and heterostructures by using electric tools instead of external magnetic fields can lead to low-power memory devices. We observe the robust changes in magnetization states of a thin (about 30 nm) film of alpha-Fe covered by the naturally formed layer ( about 6...
1602.04590v1
2016-03-01
Nuclear medium effects in $F_{2A}^{EM}(x,Q^2)$ and $F_{2A}^{Weak}(x,Q^2)$ structure functions
Recent phenomenological analysis of experimental data on DIS processes induced by charged leptons and neutrinos/antineutrinos beams on nuclear targets by CTEQ collaboration has confirmed the observation of CCFR and NuTeV collaborations, that weak structure function $F_{2A}^{Weak} (x,Q^2)$ is different from electromagne...
1603.00164v2
2016-03-07
A new insight into neutrino energy loss by electron capture of iron group nuclei in magnetars surface
Based on the relativistic mean-field effective interactions theory, and Lai dong model \citep{b37, b38, b39}, we discuss the influences of superstrong magnetic fields (SMFs) on electron Fermi energy, nuclear blinding energy, and single-particle level structure in magnetars surface. By using the method of Shell-Model Mo...
1603.01898v2
2016-03-08
Quasiparticle scattering interference in iron pnictides: A probe of the origin of nematicity
In this paper, we investigate the quasiparticle scattering interference(QPI) in the nematic phase of iron pnictides, based on the magnetic and orbital scenarios of nematicity, respectively. In the spin density wave(SDW) state, the QPI pattern exhibits a dimer structure in the energy region of the SDW gap, with its orie...
1603.02517v2
2016-03-09
Antiferroquadrupolar order and rotational symmetry breaking in a generalized bilinear-biquadratic model on a square lattice
The magnetic and nematic properties of the iron chalcogenides have recently been the subject of intense interest. Motivated by the proposed antiferroquadrupolar and Ising-nematic orders for the bulk FeSe, we study the phase diagram of an $S=1$ generalized bilinear-biquadratic model with multi-neighbor interactions. We ...
1603.03027v5
2016-03-14
Strong cooperative coupling of pressure-induced magnetic order and nematicity in FeSe
A hallmark of the iron-based superconductors is the strong coupling between magnetic, structural and electronic degrees of freedom. However, a universal picture of the normal state properties of these compounds has been confounded by recent investigations of FeSe where the nematic (structural) and magnetic transitions ...
1603.04135v1
2016-03-22
Thermal Conductivity of the Iron-Based Superconductor FeSe : Nodeless Gap with Strong Two-Band Character
The thermal conductivity of the iron-based superconductor FeSe was measured at temperatures down to 50 mK in magnetic fields up to 17 T. In zero magnetic field, the electronic residual linear term in the T = 0 limit, \kappa_0/T, is vanishingly small. Application of a magnetic field H causes no increase in \kappa_0/T in...
1603.06917v1
2016-04-01
Nematic quantum critical point without magnetism in FeSe1-xSx superconductors
The importance of antiferromagnetic fluctuations are widely acknowledged in most unconventional superconductors. In addition, cuprates and iron pnictides often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing....
1604.00184v2
2016-04-05
Effects of single- and multi-substituted Zn ions in doped-122 type iron-based superconductors
Recent experiments on Zn-substituted 122-type iron-based superconductors (FeSCs) at electron- and hole- doped region provide us with a testing ground for understanding the effect of Zn impurities in these systems. Our first-principle calculations of the electronic structure reveal that the Zn 3d orbitals are far below ...
1604.01323v1
2016-04-06
Effect of strain and temperature on the threshold displacement energy in body-centered cubic iron
The threshold displacement energy (TDE) is the minimum amount of kinetic energy required to displace an atom from its lattice site. The magnitude of the TDE displays significant variance as a function of the crystallographic direction, system temperature and applied strain, among a variety of other factors. It is criti...
1604.01791v1
2016-04-08
Tribochemistry of graphene on iron and its possible role in lubrication of steel
Recent tribological experiments revealed that graphene is able to lubricate macroscale steel-on-steel sliding contacts very effectively both in dry and humid conditions. This effect has been attributed to a mechanical action of graphene related to its load-carrying capacity. Here we provide further insight into the fun...
1604.02306v2
2016-04-10
Quasi-periodic oscillations as a tool for testing the Kerr metric: A comparison with gravitational waves and iron line
QPOs are a common feature in the X-ray power density spectrum of black hole binaries and a potentially powerful tool to probe the spacetime geometry around these objects. Here we discuss their constraining power to test the Kerr black hole hypothesis within the relativistic precession model. We compare our results with...
1604.02643v2
2016-04-11
Interatomic Fe-H potential for irradiation and embrittlement simulations
The behavior of hydrogen in iron and iron alloys is of interest in many fields of physics and materials science. To enable large-scale molecular dynamics simulations of systems with Fe-H interactions, we develop, based on density-functional theory calculations, an interatomic Fe-H potential in the Tersoff-Brenner forma...
1604.02829v1
2016-04-11
Anomalous carrier density independent superconductivity in iron pnictides
Dome-shape superconductivity phase diagram can commonly be observed in cuprate and iron-based systems via tuning parameters such as charge carrier doping, pressure, bond angle, and etc. We report doping electrons from transition-metal elements (TM = Co, Ni) substitution can induce high-Tc superconductivity around 35 K ...
1604.02839v1
2016-04-18
Observation of two distinct superconducting domes under pressure in tetragonal FeS
As the simplest iron-based superconductor, FeSe forms a tetragonal structure with transition temperature Tc ~ 8 K. With assistance of pressure, or other techniques, Tc can be greatly enhanced, even to above liquid nitrogen temperature. The newly discovered superconducting tetragonal FeS (Tc ~ 4.5 K), a sulfide counterp...
1604.05254v2
2016-04-22
Temperature-induced band selective localization and coherent-incoherent crossover in single-layer FeSe/Nb:BaTiO3 /KTaO3
Iron chalcogenide superconductors are multi-band systems with strong electron correlations. Here we use angle-resolved photoemission spectroscopy to study band dependent correlation effects in single-layer FeSe/Nb:BaTiO3/KTaO3, a new iron chalcogenide superconductor with non-degenerate electron pockets and interface-en...
1604.06526v1
2016-05-12
The production of proton-rich isotopes beyond iron: The $γ$ process in stars
Beyond iron, a small fraction of the total abundances in the Solar System is made of proton-rich isotopes, the p nuclei. The clear understanding of their production is a fundamental challenge for nuclear astrophysics. The p nuclei constrain the nucleosynthesis in core-collapse and thermonuclear supernovae. The $\gamma$...
1605.03690v1
2016-06-08
Large enhancement in high-energy photoionization of Fe XVII and missing continuum plasma opacity
Aimed at solving the outstanding problem of solar opacity, and radiation transport plasma models in general, we report substantial photoabsorption in the high-energy regime due to atomic core photo-excitations not heretofore considered. In extensive R-Matrix calculations of unprecedented complexity for an important iro...
1606.02731v1
2016-06-09
Effect of nematic ordering on electronic structure of FeSe
Electronically driven nematic order is often considered as an essential ingredient of high-temperature superconductivity. Its elusive nature in iron-based supercon- ductors resulted in a controversy not only as regards its origin but also as to the degree of its influence on the electronic structure even in the simples...
1606.03022v1
2016-06-15
Signature of the Leggett mode in the A1g Raman response: from MgB2 to iron-based superconductors
The Raman response in a superconductor is a powerful probe to investigate the symmetry of the superconducting gap. Here we show that in a multiband superconductor it also offers the unique opportunity to establish if the driving pairing interaction has an intraband or interband character. In the model with one hole and...
1606.04784v2
2016-06-20
Nodeless multiband superconductivity in stoichiometric single crystalline CaKFe$_4$As$_4$
Measurements of the London penetration depth and tunneling conductance in single crystals of the recently discovered stoicheometric, iron - based superconductor, CaKFe$_4$As$_4$ (CaK1144) show nodeless, two effective gap superconductivity with a larger gap of about 6-9 meV and a smaller gap of about 1-4 meV. Having a c...
1606.06245v1
2016-06-28
Resonant inelastic x-ray scattering study of entangled spin-orbital excitations in superconducting PrFeAsO0.7
Low-energy electron excitation spectra were measured on a single crystal of a typical iron-based superconductor PrFeAsO$_{0.7}$ using resonant inelastic X-ray scattering (RIXS) at the Fe-$L_3$ edge. Characteristic RIXS features are clearly observed around 0.5, 1-1.5 and 2-3 eV energy losses. These excitations are analy...
1606.08917v2
2016-07-01
Oxygen, $α$-element and iron abundance distributions in the inner part of the Galactic thin disc. II
We have derived the abundances of 36 chemical elements in one Cepheid star, ASAS 181024--2049.6, located R$_{\rm G}= 2.53$ kpc from the Galactic center. This star falls within a region of the inner thin disc poorly sampled in Cepheids. Our spectral analysis shows that iron, magnesium, silicon, calcium and titanium LTE ...
1607.00129v1
2016-07-01
Evolution of superconducting gap anisotropy in hole-doped 122 iron pnictides
Motivated by recent experimental findings, we investigate the evolution of the superconducting gap anisotropy in 122 iron pnictides as a function of hole doping. Employing both a functional and a weak coupling renormalization group approach (FRG and WRG), we analyse the Fermi surface instabilities of an effective 122 m...
1607.00412v1
2016-07-03
First-Principles Momentum Dependent Local Ansatz Approach to the Ground-State Properties of Iron-Group Transition Metals
The ground-state properties of iron-group transition metals from Sc to Cu have been investigated on the basis of the first-principles momentum dependent local ansatz (MLA) theory. Correlation energy gain is found to show large values for Mn and Fe: 0.090 Ry (Mn) and 0.094 Ry (Fe). The Hund-rule coupling energies are fo...
1607.00632v1
2016-07-07
Orbital-selective Mott phase of Cu-substituted iron-based Superconductors
We study the phase transition in Cu-substituted iron-based superconductors with a new developed real-space Green's function method. We find that Cu substitution has strong effect on the orbital-selective Mott transition introduced by the Hund's rule coupling. The redistribution of the orbital occupancy which is caused ...
1607.01900v1
2016-07-11
Impact of Iron-site defects on Superconductivity in LiFeAs
In conventional s-wave superconductors, only magnetic impurities exhibit impurity bound states, whereas for an s+- order parameter they can occur for both magnetic and non-magnetic impurities. Impurity bound states in superconductors can thus provide important insight into the order parameter. Here, we present a combin...
1607.03192v1
2016-07-14
Room temperature polarization in the ferrimagnetic Ga2-xFexO3 ceramics
The effect of the Fe-Ga ratio on the magnetic and electric properties of the multiferroic Ga2-xFexO3 compound has been studied in order to determine the composition range exhibiting magnetic and electric orders coexistence and their critical temperatures. A magnetoelectric phase diagram, showing the evolution of both t...
1607.04312v1
2016-07-18
Unified Spin Model for Magnetic Excitations in Iron Chalcogenides
Recent inelastic neutron scattering (INS) measurements on FeSe and Fe(Te$_{1-x}$Se$_x$), have sparked intense debate over the nature of the ground state in these materials. Here we propose an effective bilinear-biquadratic spin model which is shown to consistently describe the evolution of low-energy spin excitations i...
1607.05295v3
2016-07-28
Modeling many-body physics with Slave-Spin Mean-Field: Mott and Hund's physics in Fe-superconductors
Slave-spin mean-field theory, a light and accurate technique to model electronic correlations in Fermi-liquid phases of multi-orbital materials, is pedagogically exposed in this chapter, with a focus on its recent successful application to the physics of Iron-based superconductors. Beside introducing electronic correla...
1607.08468v1
2016-07-31
Spin resonance peak in Fe-based superconductors with unequal gaps
We study the spin resonance in superconducting state of iron-based materials within multiband models with two unequal gaps, $\Delta_L$ and $\Delta_S$, on different Fermi surface pockets. We show that due to the indirect nature of the gap entering the spin susceptibility at the nesting wave vector $\mathbf{Q}$ the total...
1608.00245v2
2016-08-22
Nano-scale Inhomogeneous Superconductivity in Fe(Te1-xSex) Probed by Nanostructure-transport
Among iron based superconductors, the layered iron chalcogenide Fe(Te1-xSex) is structurally the simplest and has attracted considerable attentions. It has been speculated from bulk studies that nanoscale inhomogeneous superconductivity may inherently exist in this system. However, this has not been directly observed f...
1608.06332v1
2016-08-29
Impurity effects on spin dynamics in magnetic and superconducting iron pnictides and chalcogenides
In this paper we summarize the effects of magnetic and nonmagnetic impurities on the spin dynamics in Febased superconductors and their parent compounds. The effects of chemical substitution, vacancies, and disorder on the suppression or stabilization of superconductivity and spin-density-wave phases are reviewed in th...
1608.08123v4
2016-09-05
Cationic Effect on Pressure driven Spin-State Transition and cooperativity in Hybrid Perosvkites
Hybrid or metal organic framework (MOF) perovskites of general composition, ABX$_3$, are known to show interesting properties which can lead to variety of technological applications. Our first principles study shows they are also potential candidates for exhibiting cooperative spin-state transitions upon application of...
1609.01020v1
2016-09-08
Block antiferromagnetism and possible ferroelectricity in KFe$_2$Se$_2$
Superconductors and multiferroics are two of the hottest branches in condensed matter physics. The connections between those two fields are fundamentally meaningful to unify the physical rules of correlated electrons. Recently, BaFe$_2$Se$_3$, was predicted to be multiferroic [Phys. Rev. Lett. 113, 187204 (2014)] due t...
1609.02614v2
2016-09-15
Highly siderophile elements were stripped from Earth's mantle by iron sulfide segregation
Highly siderophile elements (HSEs) are strongly depleted in the bulk silicate Earth (BSE) but are present in near-chondritic relative abundances. The conventional explanation is that the HSEs were stripped from the mantle by the segregation of metal during core formation but were added back in near-chondritic proportio...
1609.04751v1
2016-09-16
A new Measurement of Thermal Conductivity of Iron at high pressures and temperatures
Thermal conductivity of the most abundant element in the planetary core, Iron (Fe) is measured up to Earth's outer core pressure $\sim 120$ GPa. The measurements are carried out using the laser heated diamond anvil cell facility, where the absorbed power by Fe metal foil is calculated using thermodynamical equation. Th...
1609.05088v2
2016-09-26
Topology optimized permanent magnet systems
Topology optimization of permanent magnet systems consisting of permanent magnets, high permeability iron and air is presented. An implementation of topology optimization for magnetostatics is discussed and three examples are considered. First, the Halbach cylinder is topology optimized with iron and an increase of 15%...
1609.08113v2
2016-09-29
Prediction of superconducting iron-bismuth intermetallic compounds at high pressure
The synthesis of materials in high-pressure experiments has recently attracted increasing attention, especially since the discovery of record breaking superconducting temperatures in the sulfur-hydrogen and other hydrogen-rich systems. Commonly, the initial precursor in a high pressure experiment contains constituent e...
1609.09536v1
2016-10-26
Influence of the iron spin crossover in ferropericlase on the lower mantle geotherm
The iron spin crossover in ferropericlase introduces anomalies in its thermodynamics and thermoelastic properties. Here we investigate how these anomalies can affect the lower mantle geotherm. The effect is examined in mantle aggregates consisting of mixtures of bridgmanite, ferropericlase, and CaSiO$_3$ perovskite, wi...
1610.08412v2
2016-10-27
Constraining the Kerr parameters via X-ray reflection spectroscopy
In a recent paper [Ghasemi-Nodehi & Bambi, EPJC 76 (2016) 290], we have proposed a new parametrization for testing the Kerr nature of astrophysical black hole candidates. In the present work, we study the possibility of constraining the "Kerr parameters" of our proposal using X-ray reflection spectroscopy, the so-calle...
1610.08791v2
2016-10-29
Searching for New Spin-Dependent Interactions with SmCo$_5$ Spin Sources and a SERF Comagnetometer
We propose a novel method to search for possible new macro-scale spin- and/or velocity-dependent forces (SVDFs) based on specially designed SmCo$_5$ spin sources and a spin exchange relaxation-free (SERF) comagnetometer. A simulation shows that, by covering a SmCo$_5$ permanent magnet with a layer of pure iron, a high ...
1610.09483v1
2016-10-29
Strong correlations and the search for high-Tc superconductivity in chromium pnictides and chalcogenides
Undoped iron superconductors accommodate $n=6$ electrons in five d-orbitals. Experimental and theoretical evidence shows that the strength of correlations increases with hole-doping, as the electronic filling approaches half-filling with $n=5$ electrons. This evidence delineates a scenario in which the parent compound ...
1610.09560v1
2016-11-01
Shear softening of Earth's inner core indicated by its high Poisson's ratio and elastic anisotropy
Earth's inner core exhibits an unusually high Poisson's ratio and noticeable elastic anisotropy. The mechanisms responsible for these features are critical for understanding the evolution of the Earth but remain unclear. This study indicates that once the correct formula for the shear modulus is used, shear softening c...
1611.00244v1
2016-11-02
Surface effects on ferromagnetic resonance in magnetic nanocubes
We study the effect of surface anisotropy on the spectrum of spin-wave excitations in a magnetic nanocluster and compute the corresponding absorbed power. For this, we develop a general numerical method based on the (undamped) Landau-Lifshitz equation, either linearized around the equilibrium state leading to an eigenv...
1611.00614v1
2016-11-08
Orbital selective pairing and gap structures of iron-based superconductors
We discuss the influence on spin-fluctuation pairing theory of orbital selective strong correlation effects in Fe-based superconductors, particularly Fe chalcogenide systems. We propose that a key ingredient for an improved itinerant pairing theory is orbital selectivity, i.e., incorporating the reduced coherence of qu...
1611.02643v2
2016-11-09
A possible new family of unconventional high temperature superconductors
We suggest a new family of Co/Ni-based materials that may host unconventional high temperature superconductivity (high-T$_c$). These materials carry layered square lattices with each layer being formed by vertex-shared transition metal tetrahedra cation-anion complexes. The electronic physics in these materials is dete...
1611.02835v1
2016-11-21
Discovery of a novel 112-type iron-pnictide and La-doping induced superconductivity in Eu1-xLaxFeAs2 (x = 0 ~ 0.15)
We report the discovery and characterization of a novel 112-type iron pnictide EuFeAs2, with La-doping induced superconductivity in a series of Eu1-xLaxFeAs2. The polycrystalline samples were synthesized through solid state reaction method only within a very narrow temperature window around 1073 K. Small single crystal...
1611.06821v1
2016-12-15
Magnetic excitations in the normal and nematic phases of iron pnictides
In this paper, we study theoretically the behaviors of the magnetic excitations(MEs) in the normal and nematic phases of iron pnictides. The normal state MEs exhibit commensurability to diamond and to square-like structure transition with the increase of energy. This structure transition persists in the spin and orbita...
1612.04961v1
2016-12-19
Ultra metal-poor stars: Spectroscopic determination of stellar atmospheric parameters using iron Non-LTE line abundances
We present new ultra-metal-poor (UMP) stars parameters with [Fe/H]<-4.0 based on line-by-line non-local thermodynamic equilibrium (NLTE) abundances using an up-to-date iron model atom with a new recipe for non-elastic hydrogen collision rates. We study the departures from LTE in their atmospheric parameter and show tha...
1612.06309v2
2016-12-22
Tunable Finite-Sized Chains to Control Magnetic Relaxation
The magnetic dynamics of low-dimensional iron ion chains have been studied with regards to the tunable finite-sized chain length using iron phthalocyanine thin films. The deposition temperature varies the diffusion length during thin film growth by limiting the average crystal size in the range from 40 to 110 nm. Using...
1612.07397v1
2017-01-03
Magnetite nano-islands on silicon-carbide with graphene
X-ray magnetic circular dichroism (XMCD) measurements of iron nano-islands grown on graphene and covered with a Au film for passivation reveal that the oxidation through defects in the Au film spontaneously leads to the formation of magnetite nano-particles (i.e, $Fe_3$$O_4$). The Fe nano-islands (20 and 75 monolayers;...
1701.00861v1
2017-01-10
Ru-doping on iron based pnictides: the "unfolded" dominant role of structural effects for superconductivity
We present an ab-initio study of Ru substitution in two different compounds, BaFe2As2 and LaFeAsO, pure and F-doped. Despite the many similarities among them, Ru substitution has very different effects on these compounds. By means of an unfolding technique, which allows us to trace back the electronic states into the p...
1701.02498v1
2017-01-18
Ion beam test results of the Plastic Scintillator Detector of DAMPE
The DArk Matter Particle Explorer (DAMPE) is one of the four satellites within Strategic Pioneer Research Program in Space Science of the Chinese Academy of Science (CAS). DAMPE can detect electrons, photons and ions in a wide energy range (5 GeV to 10 TeV) and ions up to iron (100GeV to 100 TeV). Plastic Scintillator ...
1701.04947v2
2017-01-20
Plasma Effects On Atomic Data For The K-Vacancy States Of Highly Charged Iron Ions
The main goal of the present work is to estimate the effects of plasma environment on the atomic parameters associated with the K-vacancy states in highly charged iron ions within the astrophysical context of accretion disks around black holes. In order to do this, multiconfiguration Dirac-Fock computations have been c...
1701.05757v1
2017-02-01
Nanoscratching of iron: a novel approach to characterize dislocation microstructures
A new approach for characterizing the dislocation microstructure obtained from atomistic simulations is introduced, which relies on converting properties of discrete lines to continuous data. This data is represented by a number of density and density-like field variables containing detailed information about propertie...
1702.00457v3
2017-02-02
Two-temperature equations of state for d-band metals irradiated by femtosecond laser pulses
The cold curves for energy and pressure of Copper, Iron, and Tantalum were obtained using methods of the density functional theory. We consider hydrostatic and uniaxial deformations in the range from double compression of the initial volume per atom to double stretching. The presence of allotropic transformation from $...
1702.00825v3
2017-02-05
First-Principles Momentum Dependent Local Ansatz Approach to the Momentum Distribution Function in Iron-Group Transition Metals
The momentum distribution function (MDF) bands of iron-group transition metals from Sc to Cu have been investigated on the basis of the first-principles momentum dependent local ansatz wavefunction method. It is found that the MDF for $d$ electrons show a strong momentum dependence and a large deviation from the Fermi-...
1702.01370v1
2017-02-07
Pure iron grains are rare in the universe
The abundant forms in which the major elements in the universe exist have been determined from numerous astronomical observations and meteoritic analyses. Iron (Fe) is an exception, in that only depletion of gaseous Fe has been detected in the interstellar medium, suggesting that Fe is condensed into a solid, possibly ...
1702.01921v1
2017-02-07
Anomalous temperature evolution of the electronic structure of FeSe
We present ARPES data taken from the structurally simplest representative of iron-based superconductors, FeSe, in a wide temperature range. Apart from the variations related to the nematic transition, we detect very pronounced shifts of the dispersions on the scale of hundreds of kelvins. Remarkably, upon warming the s...
1702.02088v1
2017-02-13
Coexistence of localized and itinerant magnetism in intercalated iron-selenide (Li,Fe)OHFeSe
The electronic structure and magnetism of a new magnetic intercalation compound (Li0.8Fe0.2)OHFeSe are investigated theoretically. The electronic structure calculations predict that the Fe in the (Li,Fe)OH intercalated layer is in +2 valence state, i.e. there is electron doping to the FeSe layer, resulting in the shrin...
1702.03845v1
2017-02-16
Thermal and structural properties of iron at high pressure by molecular dynamics
We investigate the basic thermal, mechanical and structural properties of body centred cubic iron ($\alpha$-Fe) at several temperatures and positive loading by means of Molecular Dynamics simulations in conjunction with the embedded-atom method potential and its modified counterpart one. Computations of its thermal pro...
1702.04909v1
2017-02-20
Evolution of magnetism in cerium doped LaCo2P2 crystals: a magnetic phase diagram
ThCr2Si2-type phosphide ACo2P2 (A=Rare earth elements) has the same structure as iron arsenides, but their magnetic behaviors are quite distinct. In this paper, we for the first time grew a series of La1-xCexCo2P2 single crystals (x=0.0 to1.0), and made structural and magnetic characterizations. This allows us to carry...
1702.05965v1
2017-03-20
Spin-wave excitations in the SDW state of doped iron pnictides
We investigate the spin-wave excitations in the spin-density wave state of doped iron pnictides within a five-orbital model. We find that the excitations along ($\pi, 0$)$\rightarrow$($\pi, \pi$) are very sensitive to the doping whereas they do not exhibit a similar sensitivity along ($0, 0$) $\rightarrow$ ($\pi, 0$). ...
1703.06601v1
2017-03-20
Iron K$α$ line of Kerr black holes with Proca hair
We continue our study on the capabilities of present and future X-ray missions to test the nature of astrophysical black hole candidates via X-ray reflection spectroscopy and distinguish Kerr black holes from other solutions of 4-dimensional Einstein's gravity in the presence of a matter field. Here we investigate the ...
1703.06836v2
2017-03-20
Imaging the Real Space Structure of the Spin Fluctuations in an Iron-based superconductor
Spin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by the common appearance of a distinct resonance in the spin susceptibility across the cuprates, iron-based superconductors and many heavy fermion materials. The information we have about the spin resonanc...
1703.07002v2
2017-04-05
Coexistence of magnetism and superconductivity in separate layers of the iron-based superconductor Li_{1-x}Fe_{x}(OH)Fe_{1-y}Se
The magnetic properties attributed to the hydroxide layer of Li1-xFex(OH)Fe1-ySe have been elucidated by the study of superconducting and nonsuperconducting members of this family. Both ac magnetometry and muon spin relaxation measurements of nonsuperconductors find a magnetic state existing below approximately 10 K wh...
1704.01492v1
2017-04-16
Highly anisotropic quasiparticle interference patterns in the spin-density wave state of the iron pnictides
We investigate the impurity scattering induced quasiparticle interference in the ($\pi, 0$) spin-density wave phase of the iron pnictides. We use a five orbital tight binding model and our mean field theory in the clean limit captures key features of the Fermi surface observed in angle-resolved photoemission. We use a ...
1704.04783v1
2017-04-26
Magnetic Force Microscopy Characterization of Superparamagnetic Iron Oxide Nanoparticles (SPIONs)
Superparamagnetic iron oxide nanoparticles (SPIONs), due to their controllable sizes, relatively long in vivo half-life and limited agglomeration, are ideal for biomedical applications such as magnetic labeling, hyperthermia cancer treatment, targeted drug delivery and for magnetic resonance imaging (MRI) as contrast e...
1704.08316v1
2017-04-27
The utility of a Bayesian analysis of complex models and the study of archeological ${}^{14}$C data
The paper presents a critical introduction to the complex statistical models used in ${}^{14}$C dating. The emphasis is on the estimation of the transit time between a sequence of archeological layers. Although a frequentist estimation of the parameters is relatively simple, confidence intervals constructions are not s...
1704.08479v1
2017-05-15
Momentum-dependent susceptibilities and magnetic exchange in bcc iron from supercell DMFT calculations
We analyze the momentum- and temperature dependences of the magnetic susceptibilities and magnetic exchange interaction in paramagnetic bcc iron by a combination of density functional theory and dynamical mean-field theory (DFT+DMFT). By considering a general derivation of the orbital-resolved effective model for spin ...
1705.05296v2
2017-05-15
Orbital superconductivity, defects and pinned nematic fluctuations in the doped iron chalcogenide FeSe$_{0.45}$Te$_{0.55}$
We demonstrate that the differential conductance, $dI/dV$, measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe$_{0.45}$Te$_{0.55}$, possesses a series of characteristic features that allow one to extract the orbital structure of the superconducting gaps. This yields near...
1705.05384v1
2017-05-16
A large moment antiferromagnetic order in overdoped high-Tc superconductor 154SmFeAsO1-xDx
In iron-based superconductors, high critical temperature (Tc) superconductivity over 50 K has only been accomplished in electron-doped hREFeAsO (hRE = heavy rare earth (RE) element). While hREFeAsO has the highest bulk Tc (58 K), progress in understanding its physical properties has been relatively slow due to difficul...
1705.05504v1
2017-05-02
Nesting-induced Local Electronic Patterns around a Single As (Te, Se) Vacancy in Iron-based Superconductors
The local electronic states around a single As (Te, Se) vacancy are investigated in order to shed light on the role of ligands in a series of iron-based superconductors. Such a vacancy can produce a local hopping correction ranging from $-0.22$ eV to 0.12 eV and always induce two in-gap resonance peaks in the local den...
1705.06570v1
2017-06-06
A uniform metallicity in the outskirts of massive, nearby galaxy clusters
Suzaku measurements of a homogeneous metal distribution of $Z\sim0.3$ Solar in the outskirts of the nearby Perseus cluster suggest that chemical elements were deposited and mixed into the intergalactic medium before clusters formed, likely over 10 billion years ago. A key prediction of this early enrichment scenario is...
1706.01567v2
2017-06-06
Comparison of the Structure Function F2 as Measured by Charged Lepton and Neutrino Scattering from Iron Targets
A comparison study of world data for the structure function F2 for Iron, as measured by both charged lepton and neutrino scattering experiments, is presented. Consistency of results for both charged lepton and neutrino scattering is observed for the full global data set in the valence regime. Consistency is also observ...
1706.02002v1
2017-06-08
Characterization of physicochemical and colloidal properties of hydrogel chitosan-coated iron-oxide nanoparticles for cancer therapy
Superparamagnetic iron oxide nanoparticles have recently been investigated for their potential to kill cancer cells with promising results, owing to their ability to be targeted and heated by magnetic fields. In this study, novel hydrogel, chitosan Fe3O4 magnetic nanoparticles were synthesized to induce magnetic hypert...
1706.02590v1
2017-06-19
Competing Ferromagnetic and Anti-Ferromagnetic interactions in Iron Nitride $ζ$-Fe$_2$N
The paper discusses the magnetic state of zeta phase of iron nitride viz. $\zeta$-Fe$_2$N on the basis of spin polarized first principles electronic structure calculations together with a review of already published data. Results of our first principles study suggest that the ground state of $\zeta$-Fe$_2$N is ferromag...
1706.05879v1
2017-06-20
Spatially resolved Fe K spectroscopy of NGC 4945
We present the imaging and spectroscopic analysis of the combined Chandra ACIS-S observations of the Compton-thick Seyfert 2 galaxy NGC 4945. We performed a spatially-resolved spectroscopy of the circumnuclear environment of the source, picturing the innermost 200 parsecs around the highly absorbed nucleus. The additio...
1706.06362v1
2017-06-25
Local stability and global instability in iron-opaque disks
The thermal stability of accretion disk and the possibility to see a limit-cycle behaviour strongly depends on the ability of the disk plasma to cool down. Various processes connected with radiation-matter interaction appearing in hot accretion disk plasma contribute to opacity. For the case of geometrically thin and o...
1706.08180v1
2017-06-30
Achieving DFT accuracy with a machine-learning interatomic potential: thermomechanics and defects in bcc ferromagnetic iron
We show that the Gaussian Approximation Potential machine learning framework can describe complex magnetic potential energy surfaces, taking ferromagnetic iron as a paradigmatic challenging case. The training database includes total energies, forces, and stresses obtained from density-functional theory in the generaliz...
1706.10229v1
2017-07-13
Towards the ab initio based theory of the phase transformations in iron and steel
Despite of the appearance of numerous new materials, the iron based alloys and steels continue to play an essential role in modern technology. The properties of a steel are determined by its structural state (ferrite, cementite, pearlite, bainite, martensite, and their combination) that is formed under thermal treatmen...
1707.04287v1
2017-07-26
Evidence of Spontaneous Vortex Ground State in An Iron-Based Ferromagnetic Superconductor
Spontaneous vortex phase (SVP) is an exotic quantum matter in which quantized superconducting vortices form in the absence of external magnetic field. Although being predicted theoretically nearly 40 years ago, its rigorous experimental verification still appears to be lacking. Here we present low-field magnetic measur...
1707.08420v1
2017-07-27
Impact of Disorder on the Superconducting Phase Diagram in BaFe$_2$(As$_{1-x}$P$_x$)$_2$
In many classes of unconventional superconductors, the question of whether the superconductivity is enhanced by the quantum-critical fluctuations on the verge of an ordered phase remains elusive. One of the most direct ways of addressing this issue is to investigate how the superconducting dome traces a shift of the or...
1707.08670v1
2017-08-03
Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4
The dynamical spin susceptibility in the new-structure-type iron-based superconductor CaKFe$_4$As$_4$ was investigated by using a combination of inelastic neutron scattering (INS) measurements and random phase approximation (RPA) calculations. Powder INS measurements show that the spin resonance at $Q_\text{res}=1.17(1...
1708.01006v2
2017-08-09
Bubble Magnetometry of Nanoparticle Heterogeneity and Interaction
Bubbles have a rich history as transducers in particle-physics experiments. In a solid-state analogue, we use bubble domains in nanomagnetic films to measure magnetic nanoparticles. This technique can determine the magnetic orientation of a single nanoparticle in a fraction of a second, and generate a full hysteresis l...
1708.02706v2
2017-08-11
Critical divergence of the symmetric ($A_{1g}$) nonlinear elastoresistance near the nematic transition in an iron-based superconductor
We report the observation of a nonlinear elastoresistivity response for the prototypical underdoped iron pnictide Ba(Fe$_{0.975}$Co$_{0.025}$)$_2$As$_2$. Our measurements reveal a large quadratic term in the isotropic ($A_{1g}$) electronic response that was produced by a purely shear ($B_{2g}$) strain. The divergence o...
1708.03682v1
2017-08-21
Solar Line Asymmetries: Modelling the Effect of Granulation on the Solar Spectrum
A parametric model of granulation employing a small number of parameters was developed. Synthetic spectra calculated using this model closely match observed spectra and, in particular, reproduce the asymmetries observed in spectral lines. Both the microturbulent motions and the large-scale flow velocity decrease expone...
1708.06408v1
2017-08-27
Electronic and spin dynamics in the insulating iron pnictide NaFe$_{0.5}$Cu$_{0.5}$As
NaFe$_{0.5}$Cu$_{0.5}$As represents a rare exception in the metallic iron pnictide family, in which a small insulating gap is opened. Based on first-principles study, we provide a comprehensive theoretical characterization of this insulating compound. The Fe$^{3+} $spin degree of freedom is quantified as a quasi-1D $S=...
1708.08065v1
2017-09-09
Nature of the electromagnetic force between classical magnetic dipoles
The Lorentz force law of classical electrodynamics states that the force F exerted by the magnetic induction B on a particle of charge q moving with velocity V is given by F=qVxB. Since this force is orthogonal to the direction of motion, the magnetic field is said to be incapable of performing mechanical work. Yet the...
1709.02921v1
2017-09-10
High pressure growth and electron transport properties of superconducting SmFeAsO1-xHx single crystals
We report the single crystal growth and characterization of the highest Tc iron-based superconductor SmFeAsO1-xHx. Some sub-millimeter-sized crystals were grown using the mixture flux of Na3As + 3NaH + As at 3.0 GPa and 1473 K. The chemical composition analyses confirmed 10% substitution of hydrogen for the oxygen site...
1709.03049v1
2017-09-08
Ultrafast carbon monoxide photolysis and heme spin-crossover in myoglobin via nonadiabatic quantum dynamics
Light absorption of myoglobin triggers diatomic ligand photolysis and spin crossover transition of iron(II) that initiate protein conformational change. The photolysis and spin crossover reactions happen concurrently on a femtosecond timescale. The microscopic origin of these reactions remains controversial. Here, we a...
1709.03402v4
2017-09-26
Frustrated spin order and stripe fluctuations in FeSe
The charge and spin dynamics of the structurally simplest iron-based superconductor, FeSe, may hold the key to understanding the physics of high temperature superconductors in general. Unlike the iron pnictides, FeSe lacks long range magnetic order in spite of a similar structural transition around 90\,K. Here, we repo...
1709.08998v3
2017-10-18
Quantum Phase transition under pressure in a heavily hydrogen-doped iron-based superconductor LaFeAsO
Hydrogen (H)-doped LaFeAsO is a prototypical iron-based superconductor. However, its phase diagram extends beyond the standard framework, where a superconducting (SC) phase follows an antiferromagnetic (AF) phase upon carrier doping; instead, the SC phase is sandwiched between two AF phases appearing in lightly and hea...
1710.06640v1
2017-10-25
Determination of the Superconducting Order Parameter from Defect Bound State Quasiparticle Interference
The superconducting order parameter is directly related to the pairing interaction, with the amplitude determined by the interaction strength, while the phase reflects the spatial structure of the interaction. However, given the large variety of materials and their rich physical properties within the iron-based high-Tc...
1710.09089v1