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2012-06-30
Anticollinear magnetic order induced by impurities in the frustrated Heisenberg model of pnictides
We present Monte Carlo simulations for a classical antiferromagnetic Heisenberg model with both nearest ($J_1$) and next-nearest ($J_2$) exchange couplings on the square lattice in the presence of non-magnetic impurities. We show that the order-by-disorder entropy selection, associated with the Ising-like phase transit...
1207.0095v1
2012-07-13
Theoretical study of the hyperfine field at Cu impurities diluted in an iron host
Magnetic hyperfine field at Cu isotopes as impurities in Fe were recently measured at low temperature. A model to explain these experimental results is proposed. The diluted Cu impurities in the ferromagnetic Fe host are described by an extension of the Daniel-Friedel model, including the next neighbor perturbation. In...
1207.3327v1
2012-08-09
E906/SeaQuest MARS15 Simulation
A series of MARS15 simulations were done to verify and guide the design of steel and concrete shielding, around the first E906-SeaQuest spectrometer magnet, and the target area immediately upstream of it. The result of the last round of simulations is summarized here. This magnet is a solid iron dipole magnet and serve...
1208.1998v1
2012-08-17
Majorana Zero Modes in Semiconductor Nanowires in Contact with Higher-$T_c$ Superconductors
We analyze the prospects for stabilizing Majorana zero modes in semiconductor nanowires that are proximity-coupled to higher-temperature superconductors. We begin with the case of iron pnictides which, though they are s-wave superconductors, are believed to have superconducting gaps that change sign. We then consider t...
1208.3701v2
2012-09-16
Stabilization of STEP electrolyses in lithium-free molten carbonates
This communication reports on effective electrolyses in lithium-free molten carbonates. Processes that utilize solar thermal energy to drive efficient electrolyses are termed Solar Thermal Electrochemical Processes (STEP). Lithium-free molten carbonates, such as a sodium-potassium carbonate eutectic using an iridium an...
1209.3512v1
2012-09-17
Size and polydispersity effect on the magnetization of densely packed magnetic nanoparticles
The magnetic properties of densely packed magnetic nanoparticles (MNP) assemblies are investigated from Monte Carlo simulations. The case of iron oxide nanoparticles is considered as a typical example of MNP. The main focus is put on particle size and size polydispersity influences on the magnetization curve. The parti...
1209.3566v1
2012-10-01
Disc atmospheres and winds in X-ray binaries
We review the current status of studies of disc atmospheres and winds in low mass X-ray binaries. We discuss the possible wind launching mechanisms and compare the predictions of the models with the existent observations. We conclude that a combination of thermal and radiative pressure (the latter being relevant at hig...
1210.0318v1
2012-10-09
Thermopower as sensitive probe of electronic nematicity in iron pnictides
We study the in-plane anisotropy of the thermoelectric power and electrical resistivity on detwinned single crystals of isovalent substituted EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_2$. Compared to the resistivity anisotropy the thermopower anisotropy is more pronounced and clearly visible already at temperatures much above the...
1210.2634v2
2012-10-22
Holographic model of the S^{+/-} multiband superconductor
We construct the holographic model of an $S^\pm$ multiband superconductor. This system is a candidate to explain the anomalous features of the iron-based superconductors (e.g. LaFeAsO, BFe2As2, and other pnictides and arsenides). We study the framework, which allows formation of the sign-interchanging order parameter. ...
1210.6074v3
2012-12-13
On the existence of solutions for a drift-diffusion system arising in corrosion modelling
In this paper, we consider a drift-diffusion system describing the corrosion of an iron based alloy in a nuclear waste repository. In comparison with the classical drift-diffusion system arising in the modeling of semiconductor devices, the originality of the corrosion model lies in the boundary conditions which are of...
1212.3279v1
2012-12-23
Excited nuclei in neutron star crusts
The paper considers the chains of successive electron capture reactions by nuclei of the iron group which take place in the crystal structures of neutron star envelopes. It is shown that as a result of such reactions the daughter nuclei in excited states accumulate within certain layers of neutron star crusts. The phon...
1212.5767v1
2012-12-23
Acausality of Massive Gravity
We show, by analyzing its characteristics, that the ghost-free, 5 degree of freedom, Wess--Zumino massive gravity model admits superluminal shock wave solutions and thus is acausal. Ironically, this pathology arises from the very constraint that removes the (sixth) Boulware-Deser ghost mode.
1212.5835v3
2013-01-08
Normal and superconducting properties of LiFeAs explained in the framework of four-band Eliashberg Theory
In this paper we propose a model to reproduce superconductive and normal properties of the iron pnictide LiFeAs in the framework of the four-band spm wave Eliashberg theory. A confirmation of the multiband nature of the system rises from the experimental measurements of the superconductive gaps and resistivity as funct...
1301.1542v1
2013-01-24
Pressure effects in hollow and solid iron oxide nanoparticles
We report a study on the pressure response of the anisotropy energy of hollow and solid maghemite nanoparticles. The differences between the maghemite samples are understood in terms of size, magnetic anisotropy and shape of the particles. In particular, the differences between hollow and solid samples are due to the d...
1301.5708v1
2013-04-10
Normal state bottleneck and nematic fluctuations from femtosecond quasi-particle relaxation dynamics in Sm(Fe,Co)AsO
We investigate temperature and fluence dependent dynamics of the photoexcited quasi-particle relaxation and low-energy electronic structure in electron-doped 1111-structure Sm(Fe_{0.93}Co_{0.07})AsO single crystal. We find that the behavior is qualitatively identical to the 122-structure Ba(Fe,Co)_{2}As_{2} including t...
1304.2866v1
2013-04-26
Ferroelectricity from iron valence ordering in rare earth ferrites?
The possibility of multiferroicity arising from charge ordering in LuFe2O4 and structurally related rare earth ferrites is reviewed. Recent experimental work on macroscopic indications of ferroelectricity and microscopic determination of coupled spin and charge order indicates that this scenario does not hold. Understa...
1304.7255v1
2013-07-04
Molten Air -- A new, highest energy class of rechargeable batteries
This study introduces the principles of a new class of batteries, rechargeable molten air batteries, and several battery chemistry examples are demonstrated. The new battery class uses a molten electrolyte, are quasi reversible, and have amongst the highest intrinsic battery electric energy storage capacities. Three ex...
1307.1305v1
2013-07-16
On the He burning phases of the Carina dSph
We performed a detailed comparison between predicted He burning phases and multiband photometry of the Carina dwarf spheroidal galaxy. We found a good agreement with the predictions computed assuming an {\alpha}-enhanced chemical mixture, indicating a mean metallicity [Fe/H] ~ -1.8 with a raw observed peak-to-peak spre...
1307.4324v1
2013-08-05
Sub-Piconewton Force Detection using Micron-Size Wire Deflections
The mechanical properties of nanostructured wires obtained by co-assembly of iron oxide particles are studied. The intrinsic magnetic properties of the wires are used to induce and quantify the bending of the one-dimensional objects. From the relationship between the deflection and the magnitude of the magnetic field, ...
1308.0893v1
2013-08-13
Strain effects on electronic structure of the iron selenide superconductor
The influence of various strains on crystal and electronic structures of superconducting FeSe has been studied ab initio. We consider changes in the Fermi surface nesting with a vector Q=(0.5,0.5)*(2\pi /a) as crucial for rising superconductivity (SC) mediated by spin-fluctuations (SF). Our results indicate that the c-...
1308.2933v1
2013-08-26
Modélisation micromagnétique du comportement magnéto-mécanique
A magneto-mechanical static modeling of ferromagnetic particle based on minimization of an energy function is presented. This modeling is made of a conjugate gradient method coupled with finite element method for the mechanical problem resolution. Some illustrations on iron single crystal are given in 2D framework.
1308.5494v1
2013-08-26
Sulfur annealing effect for superconductivity in iron chalcogenide compounds
We discovered a novel annealing method for Fe-chalcogenide superconductors. It was found that sulfur annealing deintercalated excess Fe via formation of FeS2. Due to its specifics, sulfur annealing is applicable when preparing Fe-chalcogenide-based wires or cables.
1308.5642v1
2013-08-28
26Al in the Early Solar System: Not so Unusual After All
Recently acquired evidence shows that extrasolar asteroids exhibit over a factor of 100 variation in the iron to aluminum abundance ratio. This large range likely is a consequence of igneous differentiation that resulted from heating produced by radioactive decay of 26Al with an abundance comparable to that in the sola...
1308.6325v2
2013-09-11
Investigating of longitudinal development parameters through air shower simulation by different hadronic models
In this work the simulation of the Extensive Air Showers was performed by investigating the longitudinal development parameters (N and Xmax) by using a system for air shower simulation which is called AIRES version 2.6.0 at the energy range (10^14-10^19 eV) for different primary particles like (gamma, electron, positro...
1309.2934v1
2013-10-11
Impurity bound states and disorder-induced orbital and magnetic order in the s+- state of Fe-based superconductors
We study the presence of impurity bound states within a five-band Hubbard model relevant to iron-based superconductors. In agreement with earlier studies, we find that in the absence of Coulomb correlations there exists a range of repulsive impurity potentials where in-gap states are generated. In the presence of weak ...
1310.3022v1
2013-10-14
From quantum mechanics to the physical metallurgy of steels
In the last decade there has been a breakthrough in the construction of theories leading to models for the simulation of atomic scale processes in steel. In this paper the theory is described and developed and used to demonstrate calculations of the diffusivity and trapping of hydrogen in iron and the structures of car...
1310.3778v3
2013-11-13
A DFT+Nonhomogeneous DMFT approach for Finite Systems
For reliable and efficient inclusion of electron-electron correlation effects in nanosystems we propose a combined density-functional-theory/nonhomogeneous dynamical-mean-field-theory (DFT + DMFT) approach which employs an approximate Iterative Perturbative Theory (IPT) impurity solver. The validity of the method is de...
1311.3147v1
2014-01-10
A density functional theory study of FeAs comparing LDA+U, GGA+U and hybrid functionals
We use density functional theory within the local density approximation (LDA), LDA+U, generalized gradient approximation (GGA), GGA+U, and hybrid-functional methods to calculate the properties of iron monoarsenide. FeAs, which forms in the MnP structure, is of current interest for potential spintronic applications as w...
1401.2277v1
2014-03-19
Spin-orbit coupling effects on spin-dependent inelastic electronic lifetimes in ferromagnets
For the 3d ferromagnets iron, cobalt and nickel we compute the spin-dependent inelastic electronic lifetimes due to carrier-carrier Coulomb interaction including spin-orbit coupling. We find that the spin-dependent density-of-states at the Fermi energy does not, in general, determine the spin dependence of the lifetime...
1403.4728v1
2014-03-19
Topological Phases in the Single-Layer FeSe
A distinct electronic structure was observed in the single-layer FeSe which shows surprising high temperature superconductivity over 65k. Here we demonstrate that the electronic structure can be explained by the strain effect due to substrates. More importantly, we find that this electronic structure can be tuned into ...
1403.4740v1
2014-05-23
New observations of chemically peculiar stars with ESPaDOnS
We present the first results of the estimation of gravity and effective temperature for some poorly studied chemically peculiar stars that were recently observed with the spectropolarimeter ESPaDOnS at CFHT. We have analyzed the spectra of HD71030, HD95608 and HD116235 to determine their radial velocity, Vsin(i) and th...
1405.6203v1
2014-06-12
A Simple Apparatus for the Direct Measurement of Magnetic Forces and Magnetic Properties of Materials
In this paper, we describe a simple apparatus consisting of a scale, capable of a one milligram resolution, and a commonly obtainable magnet to measure magnetic forces. This simple apparatus is capable of measuring magnetic properties of materials in either a research or an instructional laboratory. We illustrate the c...
1406.3341v3
2014-06-15
Magnetotransport studies of FeSe under hydrostatic pressure
The discoveries of iron-based superconductors with relatively high transition temperature are under intense experimental and theoretical investigation. Here we present magnetotransport measurements on FeSe superconductor under hydrostatic pressure. We show that in Fe-deficient tetragonal FeSe binary compound, the onset...
1406.3795v2
2014-06-29
Specific Heat of Ca0.33Na0.67Fe2As2
The specific heat of single crystal hole-doped Ca0.33Na0.67Fe2As2, Tc(onset)=33.7 K, was measured from 0.4 to 40 K. The discontinuity in the specific heat at Tc, deltaC, divided by Tc is 105 +- 5 mJ/molK2, consistent with values found previously for hole-doped Ba0.6K0.4Fe2As2 and somewhat above the general trend for de...
1406.7519v1
2014-06-30
Primary Beam Steering Due to Field Leakage from Superconducting SHMS Magnets
Simulations of the magnetic fields from the Super High Momentum Spectrometer in Hall C at Thomas Jefferson National Accelerator Facility show significant field leakage into the region of the primary beam line between the target and the beam dump. Without mitigation, these remnant fields will steer the unscattered beam ...
1406.7856v2
2014-07-13
Investigation on mass composition of UHE cosmic rays using CRPropa 2.0
In this paper, we used the Monte Carlo code CRPropa version 2.0 to simulate the propagation of UHE cosmic rays. In the simulation, uniform cosmic ray sources with spectral indices of {\alpha} = 1.4, {\alpha} = 2 and Emax = 1021 eV for pure iron composition at the source position are assumed. We obtained the logarithmic...
1407.3468v1
2014-07-18
Superconductivity in FeTe{1-x}S_x induced by electrochemical reaction using ionic liquid solution
Superconductivity in FeTe0.8S0.2 is successfully induced by an electrochemical reaction using an ionic liquid solution. A clear correlation between the Fe concentration in the solution and the manifestation of superconductivity was confirmed, suggesting that superconductivity was induced by the deintercalation of exces...
1407.4932v1
2014-07-22
Femtosecond intrapulse evolution of the magneto-optic Kerr effect in magnetoplasmonic crystals
In magnetoplasmonics, it is possible to tailor the magneto-optical properties of nanostructures by exciting surface plasmon polaritons (SPPs). Thus far, magnetoplasmonic effects have been considered static. Here, we describe ultrafast manifestations of magnetoplasmonics by observing the non-trivial evolution of the tra...
1407.5845v1
2014-07-28
Minimal model of point contact Andreev reflection spectroscopy of multiband superconductors
We formulate a minimal model of point contact Andreev reflection spectroscopy of a normal- metal/multiband superconductor interface. The theory generalizes the Blonder-Tinkham-Klapwijk (BTK) formulation to a multiband superconductor and it is based on the quantum waveguides theory. The proposed approach allows an analy...
1407.7397v1
2014-06-18
Artificial_Micrometeorites
An iron ball, a beryllium sphere and a tungsten tube segment with diameter twenty microns, are electrically charged while proton beam irradiating. These bodies are accelerated by the running pulse field in a spiral waveguide up to velocity: thirty kilometers per second. The accelerator, generating micrometeorites is pl...
1407.8542v1
2014-08-10
Growth of (NaxKy)FezSe2 crystals by chlorides flux at low temperatures
(NaxKy)FezSe2 crystals are prepared by Na, Fe, and Se as starting materials in NaCl/KCl flux at low temperatures~720 {\deg}C. It is found that K is more preferred than Na to enter in between FeSe layers and forms the phase. Thus-obtained crystals contain more superconducting phase in volume fraction and exhibit new fea...
1408.2181v1
2014-09-16
X-ray Filament with a Strong 6.7 keV Line in the Galactic Center Region
An elongated X-ray source with a strong K-shell line from He-like iron (Fe XXVI) is found at (RA, Dec)_{J2000.0}=(17h44m00s.0, -29D13'40''.9) in the Galactic center region. The position coincides with the X-ray thread, G359.55+0.16, which is aligned with the radio non-thermal filament. The X-ray spectrum is well fitted...
1409.4520v1
2014-09-22
Local magnetization nucleated by non-magnetic impurities in Fe-based superconductors
We study impurity-induced magnetic order within a five-band Hubbard model relevant to the normal paramagnetic phase of iron-based superconductors. The existence of the local magnetic order is explained in terms of an impurity-enhancement of states near the Fermi level, and we map out the resulting phase diagram of the ...
1409.6068v1
2014-10-06
Analysis of point contact spectra of kfe2as2 in the thermal regime
The point-contact spectra of the iron-based compound KFe2As2 were analyzed according to the thermal regime theory. We have obtained the values of the residual resistivity, the Lorentz number, and the electron mean free path in the contacts. It was shown that the most point-contact spectra can be described by this theor...
1410.1322v1
2014-10-21
Concentrator of elastic waves
This article is dedicated to an opportunity of concentrating elastic waves in the iron and water cones on the square of the cone vertex of the order of one square centimeter. The square of the base of the cone is equal to one square meter, its height one meter. The calculations assume that the cone hexogen network lyin...
1410.5537v1
2014-11-08
Ab-initio theory of Iron based superconductors
We report the first-principles study of superconducting critical temperature and superconducting properties of Fe-based superconductors taking into account on the same footing phonon, charge and spin-fluctuation mediated Cooper pairing. We show that in FeSe this leads to a modulated s$\pm$ gap symmetry, and that the an...
1411.2121v1
2014-11-16
Replica-exchange Wang-Landau sampling: Pushing the limits of Monte Carlo simulations in materials sciences
We describe the study of thermodynamics of materials using replica-exchange Wang-Landau (REWL) sampling, a generic framework for massively parallel implementations of the Wang-Landau Monte Carlo method. To evaluate the performance and scalability of the method, we investigate the magnetic phase transition in body-cente...
1411.4212v1
2015-01-28
Magnetic Design of Superconducting Magnets
In this paper we discuss the main principles of magnetic design for superconducting magnets (dipoles and quadrupoles) for particle accelerators. We give approximated equations that govern the relation between the field/gradient, the current density, the type of superconductor (Nb-Ti or Nb3Sn), the thickness of the coil...
1501.07149v1
2015-01-31
Calculation of the specific heat of optimally K-doped BaFe$_2$As$_2$
The calculated specific heat of optimally K-doped BaFe$_2$As$_2$ in density functional theory is about five times smaller than that found in the experiment. We report that by adjusting the potential on the iron atom to be slightly more repulsive for electrons improves the calculated heat capacity as well as the structu...
1502.00055v2
2015-04-20
Orbital-lattice coupling and orbital ordering instability in iron pnictides
Orbital-ordering instability arising due to the intrapocket nesting is investigated for the tight-binding models of pnictides in the presence of orbital-lattice coupling. The incommensurate instabilities with small momentum, which may play an important role in the nematic-ordering transition, vary from model to model b...
1504.04915v1
2015-05-12
Unified picture for the colossal thermopower compound FeSb$_2$
We identify the driving mechanism of the gigantic Seebeck coefficient in FeSb$_2$ as the phonon-drag effect associated with an in-gap density of states that we demonstrate to derive from excess iron. We accurately model electronic and thermoelectric transport coefficients and explain the so far ill-understood correlati...
1505.02946v1
2015-05-26
Violation of the Wiedemann-Franz law as an evidence of the pseudogap in the iron-based superconductor Ba(Fe1-xCox)2As2
Longitudinal and transverse transport coefficients of the Ba(Fe1-xCox)2As2 single crystals with x = 0, 0.045, 0.06 and 0.244 were measured in the temperature range 1.4 - 300 K and in magnetic fields up to 12.5 T. The resulting data were used to determine the temperature dependence of the Hall Lorenz number (Lxy) and it...
1505.06993v1
2015-06-09
Convergence of a Finite Volume Scheme for a Corrosion Model
In this paper, we study the numerical approximation of a system of partial dif-ferential equations describing the corrosion of an iron based alloy in a nuclear waste repository. In particular, we are interested in the convergence of a numerical scheme consisting in an implicit Euler scheme in time and a Scharfetter-Gum...
1506.02996v1
2015-06-12
Predicting Unconventional High Temperature Superconductors in Trigonal Bipyramidal Coordinations
Cuprates and iron-based superconductors are two classes of unconventional high Tc superconductors based on 3d transition elements. Recently, two principles, correspondence principle and magnetic selective pairing rule, have been emerged to unify their high Tc superconducting mechanisms. These principles strongly regula...
1506.03904v2
2015-08-06
Time-reversal symmetry breaking state in dirty three-band superconductor
I study the effects of disorder on the superconductivity of a three-band model with repulsive interband pairing. Such a model can support several possible superconducting order parameters, including a complex time-reversal symmetry breaking (TRSB) state. Impurity scattering suppresses the critical temperature of all th...
1508.01517v1
2015-09-14
A Practioner's Guide to Evaluating Entity Resolution Results
Entity resolution (ER) is the task of identifying records belonging to the same entity (e.g. individual, group) across one or multiple databases. Ironically, it has multiple names: deduplication and record linkage, among others. In this paper we survey metrics used to evaluate ER results in order to iteratively improve...
1509.04238v1
2015-09-15
Lambda Boo Abundance Patterns: Accretion from Orbiting Sources
The abundance anomalies in lambda Boo stars are popularly explained by element-specific mass inflows at rates that are much greater than empirically-inferred bounds for interstellar accretion. Therefore, a lambda Boo star's thin outer envelope must derive from a companion star, planet, analogs to Kuiper Belt Objects or...
1509.04672v2
2015-09-20
Antimatter in the Direct-Action Theory of Fields
One of Feynman's greatest contributions to physics was the interpretation of negative energies as antimatter in quantum field theory. A key component of this interpretation is the Feynman propagator, which seeks to describe the behavior of antimatter at the virtual particle level. Ironically, it turns out that one can ...
1509.06040v1
2015-10-07
Electromagnetically controlled multiferroic thermal diode
We propose an electromagnetically tunable thermal diode based on a two phase multiferroics composite. Analytical and full numerical calculations for prototypical heterojunction composed of Iron on Barium titanate in the tetragonal phase demonstrate a strong heat rectification effect that can be controlled externally by...
1510.02058v1
2015-10-29
New intercalation superconductor Lix(C6H16N2)yFe2-zSe2 with a very large interlayer-spacing and Tc = 38 K
A new iron-based superconductor, Lix(C6H16N2)yFe2-zSe2, with Tc = 38 K has successfully been synthesized via the intercalation of lithium and hexamethylenediamine into FeSe. The superconducting transition has been confirmed not only by magnetic susceptibility measurements but also by electrical resistivity ones. The in...
1510.08625v1
2015-10-29
First-principles study of FeSe epitaxial films on SrTiO3
The discovery of high temperature superconductivity in FeSe films on SrTiO3 substrate has inspired great experimental and theoretical interests. First-principles density functional theory calculations, which have played an important role in the study of bulk iron-based superconductors, also participate in the investiga...
1510.08630v1
2015-11-10
Slow in-plane magnetoresistance oscillations in multiband quasi-two-dimensional metals
Slow oscillations (SlO) of magnetoresistance is a convenient tool to measure electronic structure parameters in quasi-two-dimensional metals. We study the possibility to apply this method to multi-band conductors, e.g. to iron-based high-temperature superconducting materials. We show that SlO can be used to measure the...
1511.03178v1
2015-11-16
Mixture model of pottery distributions from Lake Chad Basin archaeological sites reveals ancient segregation patterns
We present a new statistical approach to analyzing an extremely common archaeological data type -- potsherds -- that infers the structure of cultural relationships across a set of excavations. This method, applied to data from a set of complex, culturally heterogeneous sites around the Mandara mountains in the Lake Cha...
1511.05185v1
2015-12-17
Point defect absorption by grain boundaries in $α$-iron by atomic density function modeling
Using the atomic density function theory (ADFT), we examine the point defect absorption at [110] symmetrical tilt grain boundaries in body-centered cubic iron. It is found that the sink strength strongly depends on misorientation angle. We also show that the ADFT is able to reproduce reasonably well the elastic propert...
1512.05492v1
2016-01-14
Giant domain wall response of highly twinned ferroelastic materials
Many ferroelastic crystals display at sufficiently low measurement frequencies a huge elastic softening below Tc which is caused by domain wall motion. Materials range from perovskites to iron based superconductors and shape memory materials. We present a model - based on Landau-Ginzburg theory including long range ela...
1601.03590v1
2016-01-25
Influence of Lifshitz transitions and correlation effects on the scattering rates of the charge carriers in iron-based superconductors
Minimum model calculations on the co-action of hole vanishing Lifshitz transitions and correlation effects in ferropnictides are presented. The calculations predict non-Fermi-liquid behaviour and huge mass enhancements of the charge carriers at the Fermi level. The findings are compared with recent ARPES experiments an...
1601.06516v1
2016-02-01
A Short Note on Improved Logic Circuits in a Hexagonal Minesweeper
This paper aims to present an advanced version of PP-hardness proof of Minesweeper by Bondt. The advancement includes improved Minesweeper configurations for 'logic circuits' in a hexagonal Minesweeper. To do so, I demonstrate logical uncertainty in Minesweeper, which ironically allows a possibility to make some Boolea...
1602.00398v1
2016-03-10
First-Principles Momentum-Dependent Local Ansatz Wavefunction and Momentum Distribution Function Bands of Iron
We have developed a first-principles local ansatz wavefunction approach with momentum-dependent variational parameters on the basis of the tight-binding LDA+U Hamiltonian. The theory goes beyond the first-principles Gutzwiller approach and quantitatively describes correlated electron systems. Using the theory, we find ...
1603.03118v1
2016-03-19
Magnetic behaviour of dirty multiband superconductors near the upper critical field
Magnetic properties of dirty multiband superconductors near the upper critical field are studied. The parameter $\kappa_2$ characterizing magnetization slope is shown to have a significant temperature variation which is quite sensitive to the pairing interactions and relative strengths of intraband impurity scattering....
1603.06054v1
2016-03-23
Large Magnetoresistance at Room Temperature in Ferromagnet/Topological Insulator Contacts
We report magnetoresistance for current flow through iron/topological insulator (Fe/TI) and Fe/evaporated-oxide/TI contacts when a magnetic field is used to initially orient the magnetic alignment of the incorporated ferromagnetic Fe bar, at temperatures ranging from 100 K to room temperature. This magnetoresistance is...
1603.07283v1
2016-04-11
Doubling of the critical temperature of FeSe observed in point contacts
Rise in superconducting critical temperature Tc more than two times (exceeding 20 K) is discov- ered in point-contacts created between iron-chalcogenide FeSe single crystal and Cu. The possible reasons of such Tc increase in point-contacts are discussed. The most probable cause for this may be the interfacial carriers ...
1604.02921v2
2016-04-04
The Fine Structure Constant and Habitable Planets
We use the existence of habitable planets to impose anthropic requirements on the fine structure constant, $\alpha$. To this effect, we present two considerations that restrict its value to be very near the one observed. The first, that the end product of stellar fusion is iron and not one of its neighboring elements, ...
1604.03151v1
2016-04-15
Electron magnetic resonance in magnetic nanoparticles: dependence on the particle size and applicability of the modified giant spin model
Superparamagnetic nanoparticles containing hundreds and thousands of coupled electron spins are on the boundary between classical and quantum behavior, and demonstrate features which are typical for paramagnetic spins and absent in macroscopic ferromagnetic systems. In order to better understand the evolution of magnet...
1604.04594v2
2016-04-21
Non-equilibrium magnetic fields in ab initio spin dynamics
Starting from the continuity equation for the magnetization in time-dependent spin-density functional theory, we derive an expression for the effective time-dependent magnetic fields driving the out-of-equilibrium spin dynamics in magnetic systems. We evaluate these, so called, kinetic magnetic fields in the ultrafast ...
1604.06262v2
2016-05-02
Study of glass properties as electrode for RPC
Operation and performance of the Resistive Plate Chambers (RPCs) mostly depend on the quality and characteristics of the electrode materials. The India-based Neutrino Observatory collaboration has chosen glass RPCs as the active detector elements for its Iron Calorimeter detector and is going to deploy RPCs in an unpre...
1605.01044v1
2016-05-07
Effect of glass thickness variations on the performance of RPC detectors
The India-based Neutrino Observatory (INO) is planning to build a magnetized iron calorimeter detector (ICAL) in which Resistive Plate Chambers (RPCs) will be the active detector elements. A study of the performance of RPCs, made using electrodes of various thicknesses, is pivotal in optimizing the design parameters of...
1605.02189v2
2016-06-11
Hydrodynamics of Domain Walls in Multiferroics: Impact on Memory Devices
We show that switching in ferroelectric lead germanate and lead iron tantalate zirconate titanate (PZTFT) does not resemble the equilibrium domain structure evolution of the Landau-Lifshitz-Kittel model but is instead highly nonequilibrium and similar, respectively, to the Richtmyer-Meshkov instability in liquids and t...
1606.03586v1
2016-06-12
Validity of the Local Approximation in Iron- Pnictides and Chalcogenides
We introduce a cluster DMFT (Dynamical Mean Field Theory) approach to study the normal state of the iron pnictides and chalcogenides. In the regime of moderate mass renormalizations, the self-energy is very local, justifying the success of single site DMFT for these materials and for other Hunds metals. We solve the co...
1606.03660v1
2016-06-16
Three-dimensional Critical Dirac semimetal in KMgBi
We predicted that AMgBi (A=K,Rb Cs), which have the same lattice structures as the 111 family of iron-based superconductors (Na/LiFeAs), are symmetry-protected Dirac semimetals located near the boundary of type-I and type-II Dirac semimetal phases. Doping Rb or Cs into KMgBi can drive the transition between the two pha...
1606.05042v2
2016-06-23
Understanding doping, vacancy, lattice stability and superconductivity in KxFe2-ySe2
Metal-intercalated iron selenides are a class of superconductors that have received much attention but are less understood in comparison with their FeAs-based counterparts. Here, the controversial issues such as Fe vacancy, the real phase responsible for superconductivity, and lattice stability have been addressed base...
1606.07217v1
2016-08-03
Compressive deformation of Fe nanopillar : Modalities of dislocation dynamics
Unlike the tensile mode, compressive deformation of a bcc metallic nanostructure is mediated by the glide of screw dislocation. Although the bcc screw dislocations are well known to possess unusual attributes, it is still unclear how these unique effects manifest in a nanoscale solid. In the present study, atomistic si...
1608.01166v1
2016-08-07
Spin-orbit coupling in Fe-based superconductors
We study the spin resonance peak in recently discovered iron-based superconductors. The resonance peak observed in inelastic neutron scattering experiments agrees well with predicted results for the extended $s$-wave ($s_\pm$) gap symmetry. Recent neutron scattering measurements show that there is a disparity between l...
1608.02230v1
2016-08-09
Theory Perspective: SCES 2016
New discoveries and developments in almost every area of correlated electron physics were presented at SCES 2016. Here, I provide a personal perspective on some of these developments, highlighting some new ideas in computational physics, discussing the "hidden order" challenges of cuprate and heavy electron superconduc...
1608.02925v3
2016-08-15
Design and Measurement of Dipole Magnets for CSNS 1.6GeV RCS
The Rapid Cycling Synchrotron (RCS) in Chinese Spallation Neutron Source (CSNS) accelerates proton beam from 80Mev to 1.6GeV at a repetition rate of 25Hz. All dipole magnets of RCS are operated at AC with biased DC. Aiming at the properties of these dipole magnets, we take some methods to improve magnetic field quality...
1608.04199v1
2016-08-25
Two-dimensional Superconductors with Atomic-scale Thicknesses
Recent progress in two-dimensional superconductors with atomic-scale thicknesses is reviewed mainly from the experimental point of view. The superconducting systems treated here involve a variety of materials and forms: elemental-metal ultrathin films and atomic layers on semiconductor surfaces; interfaces and superlat...
1608.06997v1
2016-09-18
Lattice dynamics of KNi2Se2
We report the first principle calculations of the lattice dynamics of KNi$_{2}$Se$_2$ together with the Raman scattering study.\ We have observed three out of four Raman active modes predicted by the factor group analysis. Calculated phonon frequencies are in good agreement with experimental findings.\ Contrary to its ...
1609.05547v1
2016-10-08
Causal-order superposition as an enabler of free will
It is often argued that bottom-up causation under a physicalist, reductionist worldview precludes free will in the libertarian sense. On the one hand, the paradigm of classical mechanics makes determinism inescapable, while on the other, the leading models that allow a role for quantum effects are noncommittal regardin...
1610.02395v1
2016-12-12
Classification of exoplanets according to density
Considering probability distribution as a function of the average density $\bar{\rho}$ computed for 424 extrasolar planets we identify three log-normal Gaussian population components. The two most populous components at $\bar{\rho}\simeq0.7$ g/cc and $\bar{\rho}\simeq7$ g/cc are the ice/gas giants and iron/rock super-E...
1612.03556v1
2016-12-21
MPS and ACS with an atomic magnetometer
We show that a single atomic magnetometer in a magnetically unshielded environment can be used to perform magnetic particle spectroscopy (MPS) and AC susceptometry (ACS) on liquid-suspended magnetic nanoparticles. We demonstrate methods allowing a simultaneous recording of M(H) and dM/dH(H) dependences of samples conta...
1612.07094v1
2016-12-21
Grain boundary relaxation and reconstruction: effect on local magnetic moment
We present a detailed numerical study on structure and local magnetic properties of $\langle 100 \rangle$ symmetric tilt grain boundaries in bcc-iron. Particular attention is paid to connection between type of grain boundary relaxation and local magnetic properties. Results from first principles calculation showed that...
1612.07181v1
2017-01-10
The giant effect of magnetic ordering on a sound velocity in a sigma-Fe55Cr45 alloy
We studied atomic dynamics of sigma-Fe(100-x)Cr(x) (x=45 and 49.5) alloys using nuclear inelastic scattering of synchrotron radiation. For the sigma-Fe55Cr45 alloy, the derived reduced iron-partial density of phonon states reveal a huge difference in the low-energy region between magnetic and paramagnetic states. The l...
1701.02467v1
2017-02-01
Structural characterization of magnetoferritin
The physicochemical characterization of the magnetoferritin biomacromolecule in terms of morphology, structural and magnetic properties shows that iron oxides can be efficiently loaded into apoferritin molecules, preserving their native biocompatible structure and affecting the morphology of the protein shell.
1702.00138v1
2017-02-09
Site-Selective Antimony Doping in Arsenic Zigzag Chains of 112-type Ca1-xLaxFeAs2
Single crystal X-ray diffraction studies were performed for the Sb-doped 112-type iron-based superconductor Ca1-xLaxFeAs2 with the superconducting transition temperature Tc of 47 K. Doped Sb preferably substituted not for As(1) in the FeAs layers but for As(2) in the layers of As zigzag chains. Structural reasons for T...
1702.02672v1
2017-02-14
Hidden radical reactivity of the [FeO]2+ group of the (hydro)oxide species in the H-abstraction from methane: a DFT and CASPT2 study
Reactivity of the [FeO]2+ group in the abstraction of hydrogen from methane is determined by metastable oxyl state FeIII-O* causing the negative spin polarization of the methyl moiety as was shown by quantum-chemical means with the use of model iron hydroxide species FeO(OH)2, Fe2O(OH)5, and Fe4O5(OH)3 as an example.
1702.04092v1
2017-04-19
Remote Document Encryption - encrypting data for e-passport holders
We show how any party can encrypt data for an e-passport holder such that only with physical possession of the e-passport decryption is possible. The same is possible for electronic identity cards and driver licenses. We also indicate possible applications. Dutch passports allow for 160 bit security, theoretically givi...
1704.05647v3
2017-05-02
Computation of the unifying thread in high temperature superconductors from first principles quantum Monte Carlo
It has long been a challenge to describe the origin of unconventional superconductivity. The two known examples with high Tc, based on iron and copper, have very different electronic structures, while other materials with similar electronic structure may not show superconductivity at all. In this paper, the authors sho...
1705.01008v1
2017-06-09
Ultrasound attenuation in $s^\pm$-wave two-band superconductors
The two-band $s^{\pm}$-wave state is currently considered to be the most promising candidate for newly discovered iron-based high-$T_c$ superconductors. In this work we study theoretically the ultrasound attenuation in $s^{\pm}$-wave two-band superconductors. The impurity effect is calculated within the $\mathcal{T}$-m...
1706.02963v1
2017-07-29
Thermodynamics of the SmCo5 compound doped with Fe and Ni: an ab initio study
SmCo5 permanent magnets exhibit enormous uniaxial magnetocrystalline anisotropy energy and have a high Curie temperature. However, a low energy product presents a significant drawback in the performance of SmCo5 permanent magnets. In order to increase the energy product in SmCo5, we propose substituting fixed amount of...
1707.09447v1
2017-08-29
Prediction of a new efficient permanent magnet SmCoNiFe3
We propose a new efficient permanent magnet, SmCoNiFe3, that is a breakthrough development of the well-known SmCo5 prototype. More modern neodymium magnets of the Nd-Fe-B type have an advantage over SmCo5 because of their greater maximum energy products due to their iron-rich stoichiometry. Our new magnet, however, rem...
1708.08957v1
2017-09-08
Enhanced superconducting-fluctuation effects on thermodynamic properties in BCS-BEC-crossover regime
Effects of superconducting fluctuation (SCF) on thermodynamic properties of electron systems in the so-called BCS-BEC-crossover regime are studied. As the attractive interaction between electrons becomes stronger upon approaching the BCS-BEC-crossover regime, importance of the mode coupling between SCF drastically incr...
1709.02553v1