One-step electro-spinning/netting technique for controllably preparing polyurethane nano-fiber/net.
Hu, Juanping; Wang, Xianfeng; Ding, Bin; Lin, Jinyou; Yu, Jianyong; Sun, Gang
2011-11-01
Electro-spinning/netting (ESN) as a cutting-edge technique evokes much interest because of its ability in the one-step preparation of versatile nano-fiber/net (NFN) membranes. Here, a controllable fabrication of polyurethane (PU) NFN membranes with attractive structures, consisting of common electrospun nanofibers and two-dimensional (2D) soap bubble-like structured nano-nets via an ESN process is reported. The unique nanoscaled NFN architecture can be finely controlled by regulating the solution properties and several ESN process parameters. The versatile PU nano-nets comprising interlinked nanowires with ultrathin diameters (5-40 nm) mean that the NFN structured membranes possess several excellent characteristics, such as an extremely large specific surface area, high porosity and large stacking density, which would be particularly useful for applications in ultrafiltration, special protective clothing, ultrasensitive sensors, catalyst support and so on. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Spin- and Pair-Density-Wave Glasses
Mross, David F.; Senthil, T.
2015-07-01
Spontaneous breaking of translational symmetry, known as density-wave order, is common in nature. However, such states are strongly sensitive to impurities or other forms of frozen disorder leading to fascinating glassy phenomena. We analyze impurity effects on a particularly ubiquitous form of broken translation symmetry in solids: a spin-density wave (SDW) with spatially modulated magnetic order. Related phenomena occur in pair-density-wave (PDW) superconductors where the superconducting order is spatially modulated. For weak disorder, we find that the SDW or PDW order can generically give way to a SDW or PDW glass—new phases of matter with a number of striking properties, which we introduce and characterize here. In particular, they exhibit an interesting combination of conventional (symmetry-breaking) and spin-glass (Edwards-Anderson) order. This is reflected in the dynamic response of such a system, which—as expected for a glass—is extremely slow in certain variables, but, surprisingly, is fast in others. Our results apply to all uniaxial metallic SDW systems where the ordering vector is incommensurate with the crystalline lattice. In addition, the possibility of a PDW glass has important consequences for some recent theoretical and experimental work on La2 -xBaxCu2O4 .
Electro-gravity spin density waves
Syromyatnikov, A. G.
dimension N) under the Conformal Gauge Theory of Gravity (CGTG), here is considered an exact cosmological solution with Friedman’s asymptotic in the form of conformal flat Fock’s metrics at large times, describing the stage of decay on a cold dust-like medium of do-not-interacting-among-themselves particles and a light-like isotropic radiation. It is shown that at high times, indeed, the process of enlarging the space-time in the model metrics Friedman conformal is equivalent to Minkowski space with a gradient torsion trace in the CGTG Newtonian limit, accompanied by a polarization effect separation of electric charges induced by an electric field E⇀F is manifested in the formation of plasma-like medium with a zero complete electric charge, that in the later stages of evolution is identical to the Fock’s model of a cold dust-like medium of do-not-interacting-among-themselves particles moving here with the same speed. The trace of torsion on the CGTG formula is freezing into an electromagnetic field spin tensor trace density and E⇀F defined inside a spherical surface, moving at the speed of light, on which experiencing a gap. Therefore, this decision takes the form of an electro-gravity spin density wave, as performed in kinematic and dynamic close connection conditions for theorems on spin shock waves with spin flip at the front of the wave, moving at the speed of light in a vacuum. The theoretical dependence of electro-gravity wave energy output from the size of the emitting object is received. When applied to GRBs, this can give a new mechanism of nonthermal gamma rays production.
DEFF Research Database (Denmark)
Sharma, S.; Pittalis, S.; Kurth, S.
2007-01-01
The relative merits of current-spin-density- and spin-density-functional theory are investigated for solids treated within the exact-exchange-only approximation. Spin-orbit splittings and orbital magnetic moments are determined at zero external magnetic field. We find that for magnetic (Fe, Co...
Spin Densities and Currents in the Routhian Approximation
Bartel, Johann; Bencheikh, Kamel; Quentin, Philippe
The structure of spin densities and the associated spin-current densities, induced by the coupling of external vector fields to the orbital and spin degrees of freedom, is studied within the framework of the Extended Thomas-Fermi method, a semiclassical version of the density-functional theory. A special emphasis is put on the rotational case where our approach amounts to perform a semiclassical approximation of the so-called generalized Routhian approach.
Spin orbit coupling in the spin-current-density-functional theory
Bencheikh, K.
2003-12-01
Starting from the spin-current-density-functional theory for electronic systems, we extend the formulation to include spin-orbit coupling. Particular attention is devoted to the symmetry of the problem. Here we show that the exchange-correlation energy functional is invariant by the U(1)em × SU(2)spin gauge transformations. We give the transformation laws of the paramagnetic current and also the paramagnetic spin current density by the U(1)em × SU(2)spin gauge transformations. For the case where the spin-orbit coupling is taken into account, we generalize the equations of continuity satisfied by the current density and the spin current density, derived by Vignale and Rasolt.
Spin mixing conductance enhancement by increasing magnetic density
Directory of Open Access Journals (Sweden)
Hiromi Yuasa
2017-05-01
Full Text Available We obtained the spin Seebeck effect enhancement in Y3Fe5O12 (YIG/Pt system by inserting a very thin Ni80Fe20 at the interface of YIG/Pt. One of important parameters determining the spin Seebeck coefficient is the spin mixing conductance at the interface between magnetic oxide and nonmagnetic metal, and it was theoretically reported that the spin mixing conductance depends on the magnetic density at the interface. However, a ferrimagnetic oxide such as YIG has a small magnetic moment density. In this report, we fabricated YIG (1 mm/Ni80Fe20 (t nm/Pt (5 nm and the spin Seebeck coefficient of t=0.6 nm becomes 2.1 times larger than that of t=0. It is considered owing to improvement of the magnetic moment density and the spin mixing conductance.
Serra, Ll.; Barranco, M.; Emperador, A.; Pi, M.; Lipparini, E.
1999-06-01
The longitudinal dipole response of a quantum dot has been calculated in the far-infrared regime using local-spin-density-functional theory. We have studied the coupling between the collective spin and density modes as a function of the magnetic field. We have found that the spin dipole mode and single-particle excitations have a sizable overlap, and that the magnetoplasmon modes can be excited by the dipole spin operator if the dot is spin polarized. The frequency of the dipole spin edge mode presents an oscillation which is clearly filling factor (ν) related. We have found that the spin dipole mode is especially soft for even-ν values. Results for selected numbers of electrons and confining potentials are discussed.
Spin Propensities of Octahedral Complexes From Density Functional Theory
DEFF Research Database (Denmark)
Mortensen, Sara R.; Kepp, Kasper Planeta
2015-01-01
The fundamental balance between high- and low-spin states of transition metal systems depends on both the metal ion and the ligands surrounding it, as often visualized by the spectrochemical series. Most density functionals do not reproduce this balance, and real spin state propensities depend...... on orbital pairing and vibrational entropies absent in the spectrochemical series. Thus, we systematically computed the tendency toward high or low spin of "text-book" octahedral metal complexes versus ligand and metal type, using eight density functionals. Dispersion effects were generally
Spin gaps and spin-flip energies in density-functional theory
Capelle, K.; Vignale, G.; Ullrich, C. A.
2010-03-01
Energy gaps are crucial aspects of the electronic structure of finite and extended systems. Whereas much is known about how to define and calculate charge gaps in density-functional theory (DFT), and about the relation between these gaps and derivative discontinuities of the exchange-correlation functional, much less is known about spin gaps. In this paper we give density-functional definitions of spin-conserving gaps, spin-flip gaps and the spin stiffness in terms of many-body energies and in terms of single-particle (Kohn-Sham) energies. Our definitions are as analogous as possible to those commonly made in the charge case, but important differences between spin and charge gaps emerge already on the single-particle level because unlike the fundamental charge gap spin gaps involve excited-state energies. Kohn-Sham and many-body spin gaps are predicted to differ, and the difference is related to derivative discontinuities that are similar to, but distinct from, those usually considered in the case of charge gaps. Both ensemble DFT and time-dependent DFT (TDDFT) can be used to calculate these spin discontinuities from a suitable functional. We illustrate our findings by evaluating our definitions for the Lithium atom, for which we calculate spin gaps and spin discontinuities by making use of near-exact Kohn-Sham eigenvalues and, independently, from the single-pole approximation to TDDFT. The many-body corrections to the Kohn-Sham spin gaps are found to be negative, i.e., single-particle calculations tend to overestimate spin gaps while they underestimate charge gaps.
Spin-density functional for exchange anisotropic Heisenberg model
Energy Technology Data Exchange (ETDEWEB)
Prata, G.N.; Penteado, P.H.; Souza, F.C. [Departamento de Fisica e Informatica, Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, CP 369, Sao Carlos - SP (Brazil); Libero, Valter L., E-mail: valter@if.sc.usp.b [Departamento de Fisica e Informatica, Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, CP 369, Sao Carlos - SP (Brazil)
2009-10-15
Ground-state energies for antiferromagnetic Heisenberg models with exchange anisotropy are estimated by means of a local-spin approximation made in the context of the density functional theory. Correlation energy is obtained using the non-linear spin-wave theory for homogeneous systems from which the spin functional is built. Although applicable to chains of any size, the results are shown for small number of sites, to exhibit finite-size effects and allow comparison with exact-numerical data from direct diagonalization of small chains.
Spin polarization in high density quark matter
DEFF Research Database (Denmark)
Bohr, Henrik; Panda, Prafulla K.; Providênci, Constanca
2013-01-01
We investigate the occurrence of a ferromagnetic phase transition in high density hadronic matter (e.g., in the interior of a neutron star). This could be induced by a four-fermion interaction analogous to the one which is responsible for chiral symmetry breaking in the Nambu-Jona-Lasinio model, ...
Thermal Reduced Density Matrices in Fermion and Spin Ladder Systems
Chen, Xiao; Fradkin, Eduardo
2013-03-01
A recent numerical study found that the reduced density matrix of a spin 1/2 system on a two-leg ladder is the same as the spectrum of a spin 1/2 chain at a finite temperature determined by the spin gap of the ladder. We investigate this interesting result by considering two-leg ladders of free fermions and spin systems with a gapped ground state using several controlled approximations. We calculate the entanglement entropy for the cut made between the chains. In the fermionic system we find the explicit form of the reduced density matrix for one of the chains and determine the entanglement spectrum explicitly. In the case of the spin system, we consider both the strong coupling limit by using perturbation theory and weak coupling limit by using replica trick method. The calculation shows that, 1) the Von Neumann entropy equals to the thermal entropy of one chain, 2) the R'enyi entropy is equivalent to the free energy of one chain, and 3) the coupling constant (gap) plays the role of effective temperature. This result can be generalized to other coupled critical systems with a bulk gap. This work was supported in part by the NSF grant DMR-1064319 at the University of Illinois
Density dependence of spin relaxation in GaAs quantum well at room temperature
Teng, L. H.; Zhang, P.; Lai, T. S.; Wu, M. W.
2008-10-01
Carrier density dependence of electron spin relaxation in an intrinsic GaAs quantum well is investigated at room temperature using time-resolved circularly polarized pump-probe spectroscopy. It is revealed that the spin relaxation time first increases with density in the relatively low-density regime where the linear D'yakonov-Perel' spin-orbit coupling terms are dominant, and then tends to decrease when the density is large and the cubic D'yakonov-Perel' spin-orbit coupling terms become important. These features are in good agreement with theoretical predictions on density dependence of spin relaxation by Lüet al. (Phys. Rev. B, 73 (2006) 125314). A fully microscopic calculation based on numerically solving the kinetic spin Bloch equations with both the D'yakonov-Perel' and the Bir-Aronov-Pikus mechanisms included, reproduces the density dependence of spin relaxation very well.
Energy Technology Data Exchange (ETDEWEB)
Melnikov, N.B., E-mail: melnikov@cs.msu.su [Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Reser, B.I., E-mail: reser@imp.uran.ru [Miheev Institute of Metal Physics, Ural Branch of Russian Academy of Sciences, Ekaterinburg 620990 (Russian Federation); Paradezhenko, G.V., E-mail: gparadezhenko@cs.msu.su [Lomonosov Moscow State University, Moscow 119991 (Russian Federation)
2016-08-01
To study the spin-density correlations in the ferromagnetic metals above the Curie temperature, we relate the spin correlator and neutron scattering cross-section. In the dynamic spin-fluctuation theory, we obtain explicit expressions for the effective and local magnetic moments and spatial spin-density correlator. Our theoretical results are demonstrated by the example of bcc Fe. The effective and local moments are found in good agreement with results of polarized neutron scattering experiment over a wide temperature range. The calculated short-range order is small (up to 4 Å) and slowly decreases with temperature.
Spin glass-like behavior in spin-density-wave CrCoMn alloys
Energy Technology Data Exchange (ETDEWEB)
Galkin, Vladimir Yu. E-mail: galkin@magn.ru; Ortiz, Wilson A.; Ali, Naushad
2003-03-01
Magnetic susceptibility and magnetization of spin-density-wave (SDW) alloy systems (Cr+3.2%Co){sub 1-x}Mn{sub x} and (Cr+6.5%Co){sub 1-x}Mn{sub x} have been measured with a SQUID magnetometer. Magnetic properties of the studied alloys are compared with those exhibited by binary Cr{sub 1-x}Mn{sub x} and ternary (CrFe){sub 1-x}Mn{sub x} and (CrSi){sub 1-x}Mn{sub x} alloys. All these alloys show spin glass (SG)-like behavior; however, some of their magnetic properties are quite different from those exhibited by conventional metallic spin glasses. Though both Fe and Co produce a local moment in Cr and CrMn, addition of Co to CrMn does not result in suppression of SG-like phase like that in (CrFe){sub 1-x}Mn{sub x}. This seems to be a result of essentially different strengths of Fe-Cr and Co-Cr couplings. All alloys studied show a low-temperature SG-like magnetic hysteresis. Such hysteresis is shifted to negative fields by cooling the alloys in a strong magnetic field through the Neel temperature. This effect is caused by unidirectional anisotropy of Co atoms frozen in the SDW matrix.
Influence of throat configuration and fish density on escapement of channel catfish from hoop nets
Porath, Mark T.; Pape, Larry D.; Richters, Lindsey K.
2011-01-01
In recent years, several state agencies have adopted the use of baited, tandemset hoop nets to assess lentic channel catfish Ictalurus punctatus populations. Some level of escapement from the net is expected because an opening exists in each throat of the net, although factors influencing rates of escapement from hoop nets have not been quantified. We conducted experiments to quantify rates of escapement and to determine the influence of throat configuration and fish density within the net on escapement rates. An initial experiment to determine the rate of escapement from each net compartment utilized individually tagged channel catfish placed within the entrance (between the two throats) and cod (within the second throat) compartments of a single hoop net for overnight sets. From this experiment, the mean rate (±SE) of channel catfish escaping was 4.2% (±1.5) from the cod (cod throat was additionally restricted from the traditionally manufactured product), and 74% (±4.2) from the entrance compartments. In a subsequent experiment, channel catfish were placed only in the cod compartment with different throat configurations (restricted or unrestricted) and at two densities (low [6 fish per net] and high [60 fish per net]) for overnight sets to determine the influence of fish density and throat configuration on escapement rates. Escapement rates between throat configurations were doubled at low fish density (13.3 ± 5.4% restricted versus 26.7 ± 5.6% unrestricted) and tripled at high fish density (14.3 ± 4.9% restricted versus 51.9 ± 5.0% unrestricted). These results suggest that retention efficiency is high from cod compartments with restricted throat entrances. However, managers and researchers need to be aware that modification to the cod throats (restrictions) is needed for hoop nets ordered from manufacturers. Managers need to be consistent in their use and reporting of cod end throat configurations when using this gear.
Bencheikh, K.; Vignale, G.
2008-04-01
We present a simple analytical method, based on the canonical density matrix, for the calculation of the equilibrium spin current as a function of temperature in a two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit coupling terms. We find that the persistent spin current is extremely robust against thermal disorder: its variation with temperature is exponentially small (∝e-TF/T) at temperatures much smaller than the Fermi temperature TF and changes to a power law TF/T for T≫TF .
Solovyeva, Alisa; Pavanello, Michele; Neugebauer, Johannes
2012-05-01
Subsystem density-functional theory (DFT) is a powerful and efficient alternative to Kohn-Sham DFT for large systems composed of several weakly interacting subunits. Here, we provide a systematic investigation of the spin-density distributions obtained in subsystem DFT calculations for radicals in explicit environments. This includes a small radical in a solvent shell, a π-stacked guanine-thymine radical cation, and a benchmark application to a model for the special pair radical cation, which is a dimer of bacteriochlorophyll pigments, from the photosynthetic reaction center of purple bacteria. We investigate the differences in the spin densities resulting from subsystem DFT and Kohn-Sham DFT calculations. In these comparisons, we focus on the problem of overdelocalization of spin densities due to the self-interaction error in DFT. It is demonstrated that subsystem DFT can reduce this problem, while it still allows to describe spin-polarization effects crossing the boundaries of the subsystems. In practical calculations of spin densities for radicals in a given environment, it may thus be a pragmatic alternative to Kohn-Sham DFT calculations. In our calculation on the special pair radical cation, we show that the coordinating histidine residues reduce the spin-density asymmetry between the two halves of this system, while inclusion of a larger binding pocket model increases this asymmetry. The unidirectional energy transfer in photosynthetic reaction centers is related to the asymmetry introduced by the protein environment.
Energy Technology Data Exchange (ETDEWEB)
Solovyeva, Alisa [Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Technical University Braunschweig, Institute for Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig (Germany); Pavanello, Michele [Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Neugebauer, Johannes [Technical University Braunschweig, Institute for Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig (Germany)
2012-05-21
Subsystem density-functional theory (DFT) is a powerful and efficient alternative to Kohn-Sham DFT for large systems composed of several weakly interacting subunits. Here, we provide a systematic investigation of the spin-density distributions obtained in subsystem DFT calculations for radicals in explicit environments. This includes a small radical in a solvent shell, a {pi}-stacked guanine-thymine radical cation, and a benchmark application to a model for the special pair radical cation, which is a dimer of bacteriochlorophyll pigments, from the photosynthetic reaction center of purple bacteria. We investigate the differences in the spin densities resulting from subsystem DFT and Kohn-Sham DFT calculations. In these comparisons, we focus on the problem of overdelocalization of spin densities due to the self-interaction error in DFT. It is demonstrated that subsystem DFT can reduce this problem, while it still allows to describe spin-polarization effects crossing the boundaries of the subsystems. In practical calculations of spin densities for radicals in a given environment, it may thus be a pragmatic alternative to Kohn-Sham DFT calculations. In our calculation on the special pair radical cation, we show that the coordinating histidine residues reduce the spin-density asymmetry between the two halves of this system, while inclusion of a larger binding pocket model increases this asymmetry. The unidirectional energy transfer in photosynthetic reaction centers is related to the asymmetry introduced by the protein environment.
Interplay between spin polarization and color superconductivity in high density quark matter
DEFF Research Database (Denmark)
Tsue, Yasuhiko; da Providência, João; Providência, Constança
2013-01-01
Here, it is suggested that a four-point interaction of the tensor type may lead to spin polarization in quark matter at high density. It is found that the two-flavor superconducting phase and the spin polarized phase correspond to distinct local minima of a certain generalized thermodynamical...... potential. It follows that a transition from one to the other phase occurs, passing through true minima with both a spin polarization and a color superconducting gap. It is shown that the quark spin polarized phase is realized at rather high density, while the two-flavor color superconducting phase...
Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points
Bučinský, Lukáš
2014-06-01
The change of picture of the quasirelativistic Hartree-Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl5(Hpz)]- and [RuCl5(NO)]2- transition metal complexes are considered. Both, scalar relativistic and spin-orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.©2014 Elsevier B.V. All rights reserved.
Leading twist generalized parton distributions and spin densities in a proton
Maji, Tanmay; Mondal, Chandan; Chakrabarti, Dipankar
2017-07-01
We evaluate both chirally even and odd generalized parton distributions (GPDs) in the leading twist in a recently proposed quark-diquark model for the proton where the light front wave functions are constructed from the soft-wall AdS/QCD prediction. The GPDs in transverse impact parameter space give the spin densities for different quark and proton polarizations. For longitudinally polarized proton only chiral even GPDs contribute but for transversely polarized proton both chiral even and chiral odd GPDs contribute to the spin densities. We present a detail study of the spin densities in this model.
Spin density measurement of water-bridged Co-dimer using polarized neutrons
DEFF Research Database (Denmark)
Damgaard-Møller, Emil; Overgaard, Jacob; Chilton, Nick
present an experimentally determined spin density using polarized neutron diffraction in a simple water-bridged cobalt dimer [Co2(H2O)(piv)4(Hpiv)2(py)2] which is known to have a small ferromagnetic coupling between the spin centers. Visualizing the SDD could get us one step further in understanding...
Spin Measurements of n +87Sr for Level Density Studies
Gunsing, F.; Fraval, K.; Mathelie, M.; Valenta, S.; Bečvář, F.; Rusev, G.; Tonchev, A. P.; Mitchell, G.; Baramsai, B.; Altstadt, S.; Andrzejewski, J.; Audouin, L.; Barbagallo, M.; Bécares, V.; Belloni, F.; Berthoumieux, E.; Billowes, J.; Boccone, V.; Bosnar, D.; Brugger, M.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Carrapiço, C.; Cerutti, F.; Chiaveri, E.; Chin, M.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Diakaki, M.; Domingo-Pardo, C.; Duran, I.; Dressler, R.; Eleftheriadis, C.; Ferrari, A.; Ganesan, S.; García, A. R.; Giubrone, G.; Gonçalves, I. F.; González-Romero, E.; Griesmayer, E.; Guerrero, C.; Hernández-Prieto, A.; Jenkins, D. G.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karadimos, D.; Koehler, P.; Kokkoris, M.; Krtička, M.; Kroll, J.; Lampoudis, C.; Langer, C.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Leong, L. S.; Losito, R.; Manousos, A.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Mondalaers, W.; Paradela, C.; Pavlik, A.; Perkowski, J.; Plompen, A.; Praena, J.; Quesada, J. M.; Rauscher, T.; Reifarth, R.; Riego, A.; Robles, M. S.; Rubbia, C.; Sabaté-Gilarte, M.; Sarmento, R.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Tagliente, G.; Tain, J. L.; Tarrío, D.; Tassan-Got, L.; Tsinganis, A.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vermeulen, M. J.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Ware, T.; Weigand, M.; Weiß, C.; Wright, T.; Žugec, P.
2014-05-01
We have used the 4π BaF2 gamma-ray detector array at the n_TOF neutron time-of-flight facility at CERN for an experiment in order to determine the spins of resonances of n +87Sr by measuring the gamma-ray spectra and multiplicity distributions. The first results are presented here. We have assigned the orbital momentum ℓ to all evaluated resonances on the basis of their neutron widths. Further we have assigned the spin J to 16 s-wave resonances on based the population of low-lying levels.
Constrained spin-density dynamics of an iron-sulfur complex: ferredoxin cofactor.
Ali, Md Ehesan; Nair, Nisanth N; Staemmler, Volker; Marx, Dominik
2012-06-14
The computation of antiferromagnetic exchange coupling constants J by means of efficient density-based approaches requires in practice to take care of both spin projection to approximate the low spin ground state and proper localization of the magnetic orbitals at the transition metal centers. This is demonstrated here by a combined approach where the extended broken-symmetry (EBS) technique is employed to include the former aspect, while spin density constraints are applied to ensure the latter. This constrained EBS (CEBS) approach allows us to carry out ab initio molecular dynamics on a spin-projected low spin potential energy surface that is generated on-the-fly by propagating two coupled determinants and thereby accessing the antiferromagnetic coupling along the trajectory. When applied to the prototypical model of the oxidized [2Fe-2S] cofactor in Ferredoxins, [Fe(2)S(2)(SH)(4)](2-), at room temperature, CEBS leads to remarkably good results for geometrical structures and coupling constants J.
The Spin Density Matrix II: Application to a system of two quantum dots
Kunikeev, Sharif D
2007-01-01
This work is a sequel to our work "The Spin Density Matrix I: General Theory and Exact Master Equations" (eprint cond-mat/0708.0644). Here we compare pure- and pseudo-spin dynamics using as an example a system of two quantum dots, a pair of localized conduction-band electrons in an n-doped GaAs semiconductor. Pure-spin dynamics is obtained by tracing out the orbital degrees of freedom, whereas pseudo-spin dynamics retains (as is conventional) an implicit coordinate dependence. We show that magnetic field inhomogeneity and spin-orbit interaction result in a non-unitary evolution in pure-spin dynamics, whereas these interactions contribute to the effective pseudo-spin Hamiltonian via terms that are asymmetric in spin permutations, in particular, the Dzyaloshinskii-Moriya (DM) spin-orbit interaction. We numerically investigate the non-unitary effects in the dynamics of the triplet states population, purity, and Lamb energy shift, as a function of interdot distance and magnetic field difference. The spin-orbit in...
Investigation of the spin density wave in Na{sub x}CoO{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Wooldridge, J; Paul, D McK; Balakrishnan, G; Lees, M R [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom)
2005-02-02
Magnetic susceptibility, transport and heat capacity measurements for single-crystal Na{sub x}CoO{sub 2} (x = 0.71) are reported. A transition to a spin density wave (SDW) state at T{sub mag} = 22 K is observable in all measurements, except {chi}{sub ac} data in which a cusp is observed at 4 K and attributed to a low temperature glassy phase. M(H) loops are hysteretic below 15 K. Both the SDW transition and low temperature hysteresis are only visible along the c-axis. The system also exhibits a substantial ({approx}40%) positive magnetoresistance below this temperature. Calculations of the electronic heat capacity {gamma} above and below T{sub mag} and the size of the jump in C indicate that the onset of the SDW brings about the opening of a gap and the removal of part of the Fermi surface. Reduced in-plane electron-electron scattering counteracts the loss of carriers below the transition and as a result we see a net reduction in resistivity below T{sub mag}. Sodium ordering transitions at higher temperatures are observable as peaks in the heat capacity with a corresponding increase in resistivity.
Fukui and dual-descriptor matrices within the framework of spin-polarized density functional theory.
Alcoba, Diego R; Lain, Luis; Torre, Alicia; Oña, Ofelia B; Chamorro, Eduardo
2013-06-28
This work deals with the Fukui and dual reactivity descriptors within the framework of the spin-polarized density functional theory. The first and second derivatives of the electron density and the spin density with respect to the total number of electrons N = Nα + Nβ and with respect to the spin number NS = Nα-Nβ have been formulated by means of reduced density matrices in the representation of the spin-orbitals of a given basis set, providing the matrix extension of those descriptors. The analysis of the eigenvalues and eigenvectors of the Fukui and dual-descriptor matrices yields information on the role played by the molecular orbitals in charge-transfer and spin-polarization processes. This matrix formulation enables determining similarity indices which allows one to evaluate quantitatively the quality of the simple frontier molecular orbital model in conceptual density functional theory. Selected closed- and open-shell systems in different spin symmetries have been studied with this matrix formalism at several levels of electronic correlation. The results confirm the suitability of this approach.
Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points
Energy Technology Data Exchange (ETDEWEB)
Bučinský, Lukáš, E-mail: lukas.bucinsky@stuba.sk [Slovak University of Technology, FCHPT, Institute of Physical Chemistry and Chemical Physics, Radlinskeho 9, Bratislava SK-812 37 (Slovakia); Kucková, Lenka; Malček, Michal; Kožíšek, Jozef; Biskupič, Stanislav [Slovak University of Technology, FCHPT, Institute of Physical Chemistry and Chemical Physics, Radlinskeho 9, Bratislava SK-812 37 (Slovakia); Jayatilaka, Dylan [University of Western Australia, Department of Chemistry, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Büchel, Gabriel E. [University of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna (Austria); King Abdullah University of Science and Technology, Division for Physical Sciences and Engineering and KAUST Catalysis Center, Thuwal (Saudi Arabia); Arion, Vladimir B. [University of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna (Austria)
2014-06-25
Highlights: • Quasirelativistic study of electron density topology of Os and Ru complexes. • Electron/spin densities and negative Laplacian of electron density presented. • Analytic correction of picture change error at IOTC level. • Relativistic and spin–orbit effects are considered, IOTC vs. DKH2 compared. - Abstract: The change of picture of the quasirelativistic Hartree–Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl{sub 5}(Hpz)]{sup −} and [RuCl{sub 5}(NO)]{sup 2−} transition metal complexes are considered. Both, scalar relativistic and spin–orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.
Spin-polarized versus chiral condensate in quark matter at finite temperature and density
DEFF Research Database (Denmark)
Matsuoka, Hiroaki; Tsue, Yasuhiko; da Providencia, Joao
2016-01-01
It is shown that the spin-polarized condensate appears in quark matter at high baryon density and low temperature due to the tensor-type four-point interaction in the Nambu-Jona-Lasiniotype model as a low-energy effective theory of quantum chromodynamics. It is indicated within this low-energy ef......It is shown that the spin-polarized condensate appears in quark matter at high baryon density and low temperature due to the tensor-type four-point interaction in the Nambu-Jona-Lasiniotype model as a low-energy effective theory of quantum chromodynamics. It is indicated within this low......-energy effective model that the chiral symmetry is broken again by the spin-polarized condensate on increasing the quark number density, while chiral symmetry restoration occurs, in which the chiral condensate disappears at a certain density....
It's like night and day: Diel net-effects on Cercopagidae densities in the Laurentian Great Lakes
Armenio, Patricia M.; Bunnell, David B.; Adams, Jean V.; Watson, Nicole M.; Woelmer, Whitney
2017-01-01
In the Laurentian Great Lakes, zooplankters are often sampled using standard ≤153 μm mesh nets without regard to the time of day they are collected. We sampled Cercopagidae during 2013–2014 in northern Lake Huron during day, dusk, and night using two different nets (a 0.5 m wide 153 μm mesh “standard” net and a 0.75 m wide 285 μm mesh “Bythotrephes” net) to determine if there were any differences in their sampled densities. Bythotrephes densities with the standard net were approximately 2.07-fold greater when captured at night than during the day. No time of day bias occurred with the Bythotrephes net. Nighttime Bythotrephes densities did not differ between the two net types. Cercopagis densities did not vary with net type or the time of day in this study, but future work should revisit this result given our low sample size and the low occurrence of Cercopagis in Lake Huron. To reduce bias and calculate accurate density estimates, Cercopagidae should be sampled at night if using a standard net or any time of day with the Bythotrephes net. Given the large impact of invasive predatory cladocerans Bythotrephes longimanus and Cercopagis pengoi on food webs since their invasion in the Laurentian Great Lakes in the 1980s, proper estimation of their densities is essential.
Currents, Spin Densities and Mean-Field Form Factors in Rotating Nuclei:
Bartel, J.; Bencheikh, K.; Quentin, P.
We present self-consistent semi-classical local densities characterising the structure of rotating nuclei. A particular emphasis is put on those densities which are generated by the breaking of time-reversal symmetry through the cranking piece of the Routhian, namely the current density and the spin vector density. Our approach which is based on the Extended-Thomas-Fermi method goes beyond the Inglis cranking approach and contains naturally the Thouless-Valatin self-consistency terms expressing the response of the mean field to the time-odd part of the density matrix.
Glass transition in the spin-density wave phase of (TMTSF)2PF6
DEFF Research Database (Denmark)
Lasjaunias, J.C.; Biljakovic, K.; Nad, F.
1994-01-01
We present the results of low frequency dielectric measurements and a detailed kinetic investigation of the specific heat anomaly in the spin-density wave phase of (TMTSF)(2)PF6 in the temperature range between 2 and 4 K. The dielectric relaxation shows a critical slowing down towards a ''static......'' glass transition around 2 K. The jump in the specific heat in different controlled kinetic conditions shows all the characteristics of freezing in supercooled liquids. Both effects give direct evidence of a glass transition in the spin-density wave ground state....
Waveform measurement of charge- and spin-density wavepackets in a chiral Tomonaga-Luttinger liquid
Hashisaka, M.; Hiyama, N.; Akiho, T.; Muraki, K.; Fujisawa, T.
2017-06-01
In contrast to a free-electron system, a Tomonaga-Luttinger (TL) liquid in a one-dimensional (1D) electron system hosts charge and spin excitations as independent entities. When an electron is injected into a TL liquid, it transforms into charge- and spin-density wavepackets that propagate at different group velocities and move away from each other. This process, known as spin-charge separation, is the hallmark of TL physics. While spin-charge separation has been probed in momentum- or frequency-domain measurements in various 1D systems, waveforms of separated excitations, which are a direct manifestation of the TL behaviour, have been long awaited to be measured. Here, we present a waveform measurement for the pseudospin-charge separation process in a chiral TL liquid comprising quantum Hall edge channels. The charge- and pseudospin-density waveforms are captured by utilizing a spin-resolved sampling scope that records the spin-up or -down component of the excitations. This experimental technique provides full information for time evolution of the 1D electron system, including not only propagation of TL eigenmodes but also their decay in a practical device.
Quantum entanglement and thermal reduced density matrices in fermion and spin systems on ladders
Chen, Xiao; Fradkin, Eduardo
2013-08-01
Numerical studies of the reduced density matrix of a gapped spin-1/2 Heisenberg antiferromagnet on a two-leg ladder find that it has the same form as the Gibbs density matrix of a gapless spin-1/2 Heisenberg antiferromagnetic chain at a finite temperature determined by the spin gap of the ladder. We investigate this interesting result by considering a model of free fermions on a two-leg ladder (gapped by the inter-chain tunneling operator) and in spin systems on a ladder with a gapped ground state using exact solutions and several controlled approximations. We calculate the reduced density matrix and the entanglement entropy for a leg of the ladder (i.e. a cut made between the chains). In the fermionic system we find the exact form of the reduced density matrix for one of the chains and determine the entanglement spectrum explicitly. Here we find that in the weak tunneling limit of the ladder the entanglement entropy of one chain of the gapped ladder has a simple and universal form dictated by conformal invariance. In the case of the spin system, we consider the strong coupling limit by using perturbation theory and get the reduced density matrix by the Schmidt decomposition. The entanglement entropies of a general gapped system of two coupled conformal field theories (in 1 + 1 dimensions) are discussed using the replica trick and scaling arguments. We show that (1) for a system with a bulk gap the reduced density matrix has the form of a thermal density matrix, (2) the long-wavelength modes of one subsystem (a chain) of a gapped coupled system are always thermal, (3) the von Neumann entropy equals the thermodynamic entropy of one chain, and (4) the bulk gap plays the role of effective temperature.
Directory of Open Access Journals (Sweden)
Lars Kreutzburg
2017-02-01
Full Text Available The total enthalpies of the 16 different spin conﬁgurations that can be realized in the unit cell of the archetype spin crossover complex [Fe(phen2(NCS2] (phen = 1,2-phenanthroline were calculated, applying periodic density functional theory combined with the Hubbard model and the Grimme-D2 dispersion correction (DFT+U+D2. The obtained enthalpy differences between the individual spin conﬁgurations were used to determine spin couplings of an Ising-like model, and subsequent Monte Carlo simulations for this model allowed the estimation of the phenomenological interaction parameter Γ of the Slichter–Drickamer model, which is commonly used to describe the cooperativity of the spin transition. The calculation procedure described here-which led to an estimate of about 3 kJ·mol-1 for Γ, in good agreement with experiment—may be used to predict from ﬁrst principles how modiﬁcations of spin crossover complexes can change the character of the spin transition from gradual to abrupt and vice versa.
The increase of the spin-transfer torque threshold current density in coupled vortex domain walls
Lepadatu, S.; Mihai, A. P.; Claydon, J. S.; Maccherozzi, F.; Dhesi, S. S.; Kinane, C. J.; Langridge, S.; Marrows, C. H.
2012-01-01
We have studied the dependence on the domain wall structure of the spin-transfer torque current density threshold for the onset of wall motion in curved, Gd-doped Ni80Fe20 nanowires with no artificial pinning potentials. For single vortex domain walls, for both 10% and 1% Gd-doping concentrations, the threshold current density is inversely proportional to the wire width and significantly lower compared to the threshold current density measured for transverse domain walls. On the other hand for high Gd concentrations and large wire widths, double vortex domain walls are formed which require an increase in the threshold current density compared to single vortex domain walls at the same wire width. We suggest that this is due to the coupling of the vortex cores, which are of opposite chirality, and hence will be acted on by opposing forces arising through the spin-transfer torque effect.
DEFF Research Database (Denmark)
Bast, Radovan; Jensen, Hans Jørgen Aagaard; Saue, Trond
2009-01-01
We report an implementation of adiabatic time-dependent density functional theory based on the 4-component relativistic Dirac-Coulomb Hamiltonian and a closed-shell reference. The implementation includes noncollinear spin magnetization and full derivatives of functionals, including hybrid general...
Spin polarization versus color–flavor locking in high-density quark matter
DEFF Research Database (Denmark)
Tsue, Yasuhiko; da Providência, João; Providência, Constança
2015-01-01
It is shown that spin polarization with respect to each flavor in three-flavor quark matter occurs instead of color–flavor locking at high baryon density by using the Nambu–Jona-Lasinio model with four-point tensor-type interaction. Also, it is indicated that the order of phase transition between...
Strain-spin density wave coupling in heavy fermion compounds. [U-Pd-Al; U-Ru-Si
Energy Technology Data Exchange (ETDEWEB)
Luethi, B. (Physikalisches Inst., Univ. Frankfurt (Germany)); Wolf, B. (Physikalisches Inst., Univ. Frankfurt (Germany)); Thalmeier, P. (Physikalisches Inst., Univ. Frankfurt (Germany)); Guenther, M. (Physikalisches Inst., Univ. Frankfurt (Germany)); Sixl, W. (Physikalisches Inst., Univ. Frankfurt (Germany)); Bruls, G. (Physikalisches Inst., Univ. Frankfurt (Germany))
1993-04-12
The strain-spin density wave coupling in heavy fermion systems in the vicinity of the magnetic transition temperature is discussed. Through a comparison of the effects in UPd[sub 2]Al[sub 3] and URu[sub 2]Si[sub 2] it is shown that in the latter substance the magnetic ordering cannot be a conventional spin density wave state. The influence of a spin nematic ordering on elastic constants is discussed. (orig.)
State sum constructions of spin-TFTs and string net constructions of fermionic phases of matter
Bhardwaj, Lakshya; Gaiotto, Davide; Kapustin, Anton
2017-04-01
It is possible to describe fermionic phases of matter and spin-topological field theories in 2+1 d in terms of bosonic "shadow" theories, which are obtained from the original theory by "gauging fermionic parity". The fermionic/spin theories are recovered from their shadow by a process of fermionic anyon condensation: gauging a one-form symmetry generated by quasi-particles with fermionic statistics. We apply the formalism to theories which admit gapped boundary conditions. We obtain Turaev-Viro-like and Levin-Wen-like constructions of fermionic phases of matter. We describe the group structure of fermionic SPT phases protected by ℤ 2 f × G. The quaternion group makes a surprise appearance.
Effect of deformation and orientation on spin orbit density dependent nuclear potential
Mittal, Rajni; Kumar, Raj; Sharma, Manoj K.
2017-11-01
Role of deformation and orientation is investigated on spin-orbit density dependent part VJ of nuclear potential (VN=VP+VJ) obtained within semi-classical Thomas Fermi approach of Skyrme energy density formalism. Calculations are performed for 24-54Si+30Si reactions, with spherical target 30Si and projectiles 24-54Si having prolate and oblate shapes. The quadrupole deformation β2 is varying within range of 0.023 ≤ β2 ≤0.531 for prolate and -0.242 ≤ β2 ≤ -0.592 for oblate projectiles. The spin-orbit dependent potential gets influenced significantly with inclusion of deformation and orientation effect. The spin-orbit barrier and position gets significantly influenced by both the sign and magnitude of β2-deformation. Si-nuclei with β220. The possible role of spin-orbit potential on barrier characteristics such as barrier height, barrier curvature and on the fusion pocket is also probed. In reference to prolate and oblate systems, the angular dependence of spin-orbit potential is further studied on fusion cross-sections.
Time-dependent local spin density approximation study of Luttinger liquids
Lipparini, E.; Zobele, G.
2011-08-01
We perform a time-dependent local spin density approximation (TDLSDA) study of one-dimensional Fermions with a contact interaction. We show that the simple TDLSDA approximation provides an exact description for density and spin density modes and conductance G in one-dimensional quantum wires, by establishing a general equivalence between TDSLDA and Tomonaga-Luttinger model for the elementary excitation spectra in one-dimensional Fermi systems. The role of interaction effects is carefully analyzed especially in relation to the problem of the universality of the result G=2e2/h for the conductance of one-dimensional systems. Finally our results are in good agreement with the available experimental data on the one-dimensional plasmon dispersion, and conductance in GaAs quantum wires.
Open Systems with Error Bounds: Spin-Boson Model with Spectral Density Variations.
Mascherpa, F; Smirne, A; Huelga, S F; Plenio, M B
2017-03-10
In the study of open quantum systems, one of the most common ways to describe environmental effects on the reduced dynamics is through the spectral density. However, in many models this object cannot be computed from first principles and needs to be inferred on phenomenological grounds or fitted to experimental data. Consequently, some uncertainty regarding its form and parameters is unavoidable; this in turn calls into question the accuracy of any theoretical predictions based on a given spectral density. Here, we focus on the spin-boson model as a prototypical open quantum system, find two error bounds on predicted expectation values in terms of the spectral density variation considered, and state a sufficient condition for the strongest one to apply. We further demonstrate an application of our result, by bounding the error brought about by the approximations involved in the hierarchical equations of motion resolution method for spin-boson dynamics.
Critical current density of domain wall oscillation due to spin-transfer torque
Taniguchi, T.; Imamura, H.
2011-04-01
The domain wall oscillation due to spin-transfer torque was studied by numerically solving the Landau-Lifshitz-Gilbert (LLG) equation. For a domain wall whose rotation angle θmax is less than 180°, we found the existence of the critical current density above which the magnetization dynamics are induced. We studied the dependence of the critical current density on the rotation angle θmax and found that the critical current density is proportional to 180° - θmax.
Critical current density of domain wall oscillation due to spin-transfer torque
Energy Technology Data Exchange (ETDEWEB)
Taniguchi, T; Imamura, H, E-mail: tomohiro-taniguchi@aist.go.jp, E-mail: h-imamura@aist.go.jp [Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)
2011-04-01
The domain wall oscillation due to spin-transfer torque was studied by numerically solving the Landau-Lifshitz-Gilbert (LLG) equation. For a domain wall whose rotation angle {theta}{sub max} is less than 180{sup 0}, we found the existence of the critical current density above which the magnetization dynamics are induced. We studied the dependence of the critical current density on the rotation angle {theta}{sub max} and found that the critical current density is proportional to 180{sup 0} - {theta}{sub max}.
Impact of spin-orbit density dependent potential in heavy ion reactions forming Se nuclei
Energy Technology Data Exchange (ETDEWEB)
Rajni; Sharma, Ishita; Sharma, Manoj K. [Thapar University, School of Physics and Materials Science, Patiala (India); Jain, Deepika [Mata Gujri College, Department of Physics, Fatehgarh Sahib (India)
2017-10-15
The Skyrme energy density formalism is employed to explore the effect of spin-orbit interaction potential by considering a two nucleon transfer process via various entrance channels such as {sup 23}Na + {sup 49}V, {sup 25}Mg + {sup 47}Ti, {sup 27}Al + {sup 45}Sc, {sup 29}Si + {sup 43}Ca and {sup 31}P + {sup 41}K, all forming the same compound system {sup 72}Se*, using both spherical as well as quadrupole deformed (β{sub 2}) nuclei. For spherical nuclei, the spin-orbit density part V{sub J} of nuclear potential remains unaffected with the transfer of two nucleons from the target to the projectile, however, show notable variation in magnitude after inclusion of deformation effects. Likewise, deformations play an important role in the spin-orbit density independent part V{sub P}, as the fusion pocket start appears, which otherwise diminish for the spherical nuclei. Further, the effect of an increase in the N/Z ratio of Se is explored on V{sub J} as well as V{sub P} and results are compared with transfer channels. In addition to this, the role of double spin-orbit parameters (W{sub 0} and W{sub 0}{sup '}) with relative contribution of the isoscalar and isovector parts of spin-orbit strength is explored in view of SkI2, SkI3 and SkI4 Skyrme forces. Beside this, the decay path of {sup 72}Se* nucleus formed in {sup 27}Al + {sup 45}Sc reaction is investigated within the framework of dynamical cluster decay model (DCM), where the nuclear proximity potential is obtained by both Skyrme energy density formalism (SEDF) and proximity pocket formula. The fusion hindrance in the {sup 27}Al + {sup 45}Sc reaction is also addressed via the barrier lowering parameter ΔV{sub B}. Finally, the contribution of spin-orbit density dependent interaction potential is estimated for the {sup 27}Al + {sup 45}Sc reaction using single (W{sub 0} or W{sub 0}{sup '}) and double spin-orbit parameters (W{sub 0} and W{sub 0}{sup '}). (orig.)
Efficient calculation of nuclear spin-rotation constants from auxiliary density functional theory
Energy Technology Data Exchange (ETDEWEB)
Zuniga-Gutierrez, Bernardo, E-mail: bzuniga.51@gmail.com [Departamento de Ciencias Computacionales, Universidad de Guadalajara, Blvd. Marcelino García Barragán 1421, C.P. 44430 Guadalajara, Jalisco (Mexico); Camacho-Gonzalez, Monica [Universidad Tecnológica de Tecámac, División A2, Procesos Industriales, Carretera Federal México Pachuca Km 37.5, Col. Sierra Hermosa, C.P. 55740 Tecámac, Estado de México (Mexico); Bendana-Castillo, Alfonso [Universidad Tecnológica de Tecámac, División A3, Tecnologías de la Información y Comunicaciones, Carretera Federal México Pachuca Km 37.5, Col. Sierra Hermosa, C.P. 55740 Tecámac, Estado de México (Mexico); Simon-Bastida, Patricia [Universidad Tecnlógica de Tulancingo, División Electromecánica, Camino a Ahuehuetitla No. 301, Col. Las Presas, C.P. 43642 Tulancingo, Hidalgo (Mexico); Calaminici, Patrizia; Köster, Andreas M. [Departamento de Química, CINVESTAV, Avenida Instituto Politécnico Nacional 2508, A.P. 14-740, México D.F. 07000 (Mexico)
2015-09-14
The computation of the spin-rotation tensor within the framework of auxiliary density functional theory (ADFT) in combination with the gauge including atomic orbital (GIAO) scheme, to treat the gauge origin problem, is presented. For the spin-rotation tensor, the calculation of the magnetic shielding tensor represents the most demanding computational task. Employing the ADFT-GIAO methodology, the central processing unit time for the magnetic shielding tensor calculation can be dramatically reduced. In this work, the quality of spin-rotation constants obtained with the ADFT-GIAO methodology is compared with available experimental data as well as with other theoretical results at the Hartree-Fock and coupled-cluster level of theory. It is found that the agreement between the ADFT-GIAO results and the experiment is good and very similar to the ones obtained by the coupled-cluster single-doubles-perturbative triples-GIAO methodology. With the improved computational performance achieved, the computation of the spin-rotation tensors of large systems or along Born-Oppenheimer molecular dynamics trajectories becomes feasible in reasonable times. Three models of carbon fullerenes containing hundreds of atoms and thousands of basis functions are used for benchmarking the performance. Furthermore, a theoretical study of temperature effects on the structure and spin-rotation tensor of the H{sup 12}C–{sup 12}CH–DF complex is presented. Here, the temperature dependency of the spin-rotation tensor of the fluorine nucleus can be used to identify experimentally the so far unknown bent isomer of this complex. To the best of our knowledge this is the first time that temperature effects on the spin-rotation tensor are investigated.
Wave-vector dependence of spin and density multipole excitations in quantum dots
Barranco, Manuel; Colletti, Leonardo; Lipparini, Enrico; Emperador, Agustí; Pi, Martí; Serra, Llorenç
2000-03-01
We have employed time-dependent local-spin density-functional theory to analyze the multipole spin and charge density excitations in GaAs-AlxGa1-xAs quantum dots. The on-plane transferred momentum degree of freedom has been taken into account, and the wave-vector dependence of the excitations is discussed. In agreement with previous experiments, we have found that the energies of these modes do not depend on the transferred wave vector, although their intensities do. Comparison with a recent resonant Raman scattering experiment [C. Schüller et al., Phys. Rev. Lett. 80, 2673 (1998)] is made. This allows us to identify the angular momentum of several of the observed modes as well as to reproduce their energies.
To which densities is spin-polarized neutron matter a weakly interacting Fermi gas?
Directory of Open Access Journals (Sweden)
T. Krüger
2015-05-01
Full Text Available We study the properties of spin-polarized neutron matter at next-to-next-to-next-to-leading order in chiral effective field theory, including two-, three-, and four-neutron interactions. The energy of spin-polarized neutrons is remarkably close to a non-interacting system at least up to saturation density, where interaction effects provide less than 10% corrections. This shows that the physics of neutron matter is similar to a unitary gas well beyond the scattering-length regime. Implications for energy-density functionals and for a possible ferromagnetic transition in neutron stars are discussed. Our predictions can be tested with lattice QCD, and we present results for varying pion mass.
Directory of Open Access Journals (Sweden)
Gábor Milisits
2010-01-01
Full Text Available The frequency of some behaviours of growing rabbits was studied in pens keeping the animals either on wire net or combined (half of the floor wire net, half of the floor straw litter floor at different stocking densities. The combined floor could be favourable by increasing the frequency of the social behaviour and decreasing the frequency of the stereotypes, but it decreases the comfort behaviours and the resting time. The decrease of stocking density from 16 to 12 or 8 rabbits/m² significantly increased the stereotypes.
Spin-density-wave antiferromagnetism of Cr in Fe/Cr(001) superlattices
Energy Technology Data Exchange (ETDEWEB)
Fullerton, E.E.; Bader, S.D. [Argonne National Lab., IL (United States); Robertson, J.L. [Oak Ridge National Lab., TN (United States)
1996-10-01
The antiferromagnetic spin-density-wave (SDW) order of Cr layers in Fe/Cr(001) superlattices was investigated by neutron scattering. For Cr thickness 51-190 {Angstrom}, a transverse SDW is formed for all temperatures below Neel temperature with a single wavevector Q normal to the layers. A coherent magnetic structure forms with the nodes of the SDW near the Fe-Cr interfaces. For thinner Cr layers, the magnetic scattering can be described by commensurate antiferromagnetic order.
Energy Technology Data Exchange (ETDEWEB)
Teng, L H; Chen, K; Wen, J H; Lin, W Z; Lai, T S, E-mail: stslts@mail.sysu.edu.c [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Zhongshan (Sen Yat-Sen) University, Guangzhou, Guangdong 510275 (China)
2009-07-07
Time-resolved circularly polarized pump-probe spectroscopy is used to study the carrier-density dependence of the electron-spin polarization and spin relaxation dynamics in bulk intrinsic GaAs near the bottom of the conduction band. The experimental result shows that the initial degree of the electron-spin polarization is less than 0.5, and both the initial degree of spin polarization and the spin relaxation time decrease with increasing carrier densities. The simulation calculation shows that the band-gap renormalization effect has a significant influence on the initial degree of spin polarization, but it is not the physical origin of the decrease in the electron-spin polarization. Contrarily, the initial degree of spin polarization can be greatly enhanced by the band-gap renormalization effect for carrier densities above 3.5 x 10{sup 17} cm{sup -3}. In intrinsic GaAs, both the D'yakonov-Perel' and the Bir-Aronov-Pikus mechanisms play an important role. The Bir-Aronov-Pikus mechanism becomes stronger with the increase in the carrier density, and becomes dominant at high carrier density.
Teng, L. H.; Chen, K.; Wen, J. H.; Lin, W. Z.; Lai, T. S.
2009-07-01
Time-resolved circularly polarized pump-probe spectroscopy is used to study the carrier-density dependence of the electron-spin polarization and spin relaxation dynamics in bulk intrinsic GaAs near the bottom of the conduction band. The experimental result shows that the initial degree of the electron-spin polarization is less than 0.5, and both the initial degree of spin polarization and the spin relaxation time decrease with increasing carrier densities. The simulation calculation shows that the band-gap renormalization effect has a significant influence on the initial degree of spin polarization, but it is not the physical origin of the decrease in the electron-spin polarization. Contrarily, the initial degree of spin polarization can be greatly enhanced by the band-gap renormalization effect for carrier densities above 3.5 × 1017 cm-3. In intrinsic GaAs, both the D'yakonov-Perel' and the Bir-Aronov-Pikus mechanisms play an important role. The Bir-Aronov-Pikus mechanism becomes stronger with the increase in the carrier density, and becomes dominant at high carrier density.
Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains
Tanveer, M.; Ruiz-Díaz, P.; Pastor, G. M.
2016-09-01
The electronic and magnetic properties of one-dimensional (1D) 3 d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation Δ E (q ⃗) as a function of the spin-density-wave vector q ⃗. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for Δ E (q ⃗) , the local magnetic moments μ⃗i at atom i , the magnetization-vector density m ⃗(r ⃗) , and the local electronic density of states ρi σ(ɛ ) . The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions Ji j between the local magnetic moments μ⃗i and μ⃗j are derived by fitting the ab initio Δ E (q ⃗) to a classical 1D Heisenberg model. The dominant competing interactions Ji j at the origin of the NC magnetic order are identified. The interplay between the various Ji j is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.
Influence of the Kondo effect on spin density waves in the Kondo lattice model
Energy Technology Data Exchange (ETDEWEB)
Peters, Robert, E-mail: robert.peters@riken.jp [Computational Condensed Matter Physics Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan); Kawakami, Norio [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)
2016-02-15
We analyze the influence of the Kondo effect on the spin density wave (SDW) phase in the Kondo lattice model (KLM) for a two-dimensional square lattice. We demonstrate that in the isotropic KLM the SDW phase is divided into a small Fermi-surface region and a large Fermi-surface region and vanishes for strong interaction. On the other hand, in the Ising-spin KLM, where the Kondo effect is absent, we only find a small Fermi-surface SDW phase, which does not vanish at strong coupling. This demonstrates the importance of the Kondo effect for the large Fermi surface SDW phase as well as for the existence of the quantum critical transition between the SDW phase and the paramagnetic phase. - Highlights: • We compare the isotropic and Ising spin Kondo lattice model. • We show the importance of the Kondo effect in the isotropic model for the large Fermi surface SDW, paramagnetic phase, and the quantum phase transition. • In the Ising spin Kondo lattice model the small Fermi surface SDW phase exists for any interaction strength.
Spin polarization in high density quark matter under a strong external magnetic field
DEFF Research Database (Denmark)
Tsue, Yasuhiko; Da Providência, João; Providência, Constança
2016-01-01
In high density quark matter under a strong external magnetic field, possible phases are investigated by using the two-flavor Nambu-Jona-Lasinio (NJL) model with tensor-type four-point interaction between quarks, as well as the axial-vector-type four-point interaction. In the tensor......-type interaction under the strong external magnetic field, it is shown that a quark spin polarized phase is realized in all regions of the quark chemical potential under consideration within the lowest Landau level approximation. In the axial-vector-type interaction, it is also shown that the quark spin polarized...... phase appears in the wide range of the quark chemical potential. In both the interactions, the quark mass in zero and small chemical potential regions increases which indicates that the chiral symmetry breaking is enhanced, namely the magnetic catalysis occurs....
Zhang, Yachao
2014-12-01
A first-principles study of critical temperatures (Tc) of spin crossover (SCO) materials requires accurate description of the strongly correlated 3d electrons as well as much computational effort. This task is still a challenge for the widely used local density or generalized gradient approximations (LDA/GGA) and hybrid functionals. One remedy, termed density functional theory plus U (DFT+U) approach, introduces a Hubbard U term to deal with the localized electrons at marginal computational cost, while treats the delocalized electrons with LDA/GGA. Here, we employ the DFT+U approach to investigate the Tc of a pair of iron(II) SCO molecular crystals (α and β phase), where identical constituent molecules are packed in different ways. We first calculate the adiabatic high spin-low spin energy splitting ΔEHL and molecular vibrational frequencies in both spin states, then obtain the temperature dependent enthalpy and entropy changes (ΔH and ΔS), and finally extract Tc by exploiting the ΔH/T - T and ΔS - T relationships. The results are in agreement with experiment. Analysis of geometries and electronic structures shows that the local ligand field in the α phase is slightly weakened by the H-bondings involving the ligand atoms and the specific crystal packing style. We find that this effect is largely responsible for the difference in Tc of the two phases. This study shows the applicability of the DFT+U approach for predicting Tc of SCO materials, and provides a clear insight into the subtle influence of the crystal packing effects on SCO behavior.
Bučinský, Lukáš
2015-05-11
"Kramers pairs symmetry breaking" is evaluated at the 2-component (2c) Kramers unrestricted and/or general complex Hartree-Fock (GCHF) level of theory, and its analogy with "spin contamination" at the 1-component (1c) unrestricted Hartree-Fock (UHF) level of theory is emphasized. The GCHF "Kramers pairs symmetry breaking" evaluation is using the square of overlaps between the set of occupied spinorbitals with the projected set of Kramers pairs. In the same fashion, overlaps between α and β orbitals are used in the evaluation of "spin contamination" at the UHF level of theory. In this manner, UHF Š2 expectation value is made formally extended to the GCHF case. The directly evaluated GCHF expectation value of the Š2 operator is considered for completeness. It is found that the 2c GCHF Kramers pairs symmetry breaking has a very similar extent in comparison to the 1c UHF spin contamination. Thus higher excited states contributions to the 1c and 2c unrestricted wave functions of open shell systems have almost the same extent and physical consequences. Moreover, it is formally shown that a single determinant wave function in the restricted open shell Kramers case has the expectation value of K2 operator equal to the negative number of open shell electrons, while the eigenvalue of K2 for the series of simple systems (H, He, He*-triplet, Li and Li*-quartet) are found to be equal to minus the square of the number of open shell electrons. The concept of unpaired electron density is extended to the GCHF regime and compared to UHF and restricted open shell Hartree-Fock spin density. The "collinear" and "noncollinear" analogs of spin density at the GCHF level of theory are considered as well. Spin contamination and/or Kramers pairs symmetry breaking, spin populations and spin densities are considered for H2O+, Cl, HCl+, phenoxyl radical (C6H5O) as well as for Cu, Cu2+, Fe and the [OsCl5(1H-pyrazole)]- anion. The 1c and 2c unpaired electron density representation is found
Raichle, M.; Reehuis, M.; André, G.; Capogna, L.; Sofin, M.; Jansen, M.; Keimer, B.
2008-07-01
Neutron diffraction has been used to determine the magnetic structure of Na8Cu5O10, a stoichiometric compound containing chains based on edge-sharing CuO4 plaquettes. The chains are doped with 2/5 hole per Cu site and exhibit long-range commensurate charge order with an onset well above room temperature. Below TN=23K, the neutron data indicate long-range collinear magnetic order with a spin-density modulation whose propagation vector is commensurate along, and incommensurate perpendicular to, the chains. Competing interchain exchange interactions are discussed as a possible origin of the incommensurate magnetic order.
A new Skyrme energy density functional for a better description of spin-isospin resonances
Energy Technology Data Exchange (ETDEWEB)
Roca-Maza, X., E-mail: xavier.roca.maza@mi.infn.it [Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sez. di Milano, via Celoria 16, 20133 Milano (Italy); Colò, G. [Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Sez. di Milano, via Celoria 16, 20133 Milano (Italy); Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China); Cao, Li-Gang [Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China); School of Mathematics and Physics, North China Electric Power University, Beijing 102206 (China); State Key Laboratory of Theoretical Physics, ITP, Chinese Academy of Sciences, Beijing 100190 (China); National Laboratory of Heavy Ion Accelerator of Lanzhou, Lanzhou 730000 (China); Sagawa, H. [Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China); Center for Mathematics and Physics, University of Aizu, Aizu-Wakamatsu, Fukushima 965-8580 (Japan); RIKEN, Nishina Center, Wako, 351-0198 (Japan)
2015-10-15
A correct determination of the isospin and spin-isospin properties of the nuclear effective interaction should lead to an accurate description of the Gamow-Teller resonance (GT), the Spin Dipole Resonance (SDR), the Giant Dipole Resonance (GDR) or the Antianalog Giant Dipole Resonance (AGDR), among others. A new Skyrme energy density functional named SAMi is introduced with the aim of going a step forward in setting the bases for a more precise description of spin-isospin resonances [1, 2]. In addition, we will discuss some new features of our analysis on the AGDR in {sup 208}Pb [3] as compared with available experimental data on this resonance [4, 5, 6], and on the GDR [7]. Such study, guided by a simple yet physical pocket formula, has been developed by employing the so called SAMi-J family of systematically varied interactions. This set of interactions is compatible with experimental data for values of the symmetry energy at saturation J and slope parameter L falling in the ranges 31−33 MeV and 75−95 MeV, respectively.
Spin-flip reactions of Zr + C2H6 researched by relativistic density functional theory.
Xiao, Yi; Chen, Xian-Yang; Qiu, Yi-Xiang; Wang, Shu-Guang
2013-09-01
Density functional theory (DFT) with relativistic corrections of zero-order regular approximation (ZORA) has been applied to explore the reaction mechanisms of ethane dehydrogenation by Zr atom with triplet and singlet spin-states. Among the complicated minimum energy reaction path, the available states involves three transition states (TS), and four stationary states (1) to (4) and one intersystem crossing with spin-flip (marked by -->): (3) Zr + C 2 H 6 → (3) Zr-CH 3 -CH 3 ((3)1) → (3)TS 1/2 → (3) ZrH-CH 2 -CH 3 ((3)2) → (3) TS 2/3 --> (1) ZrH2-CH2 = CH2 ((1) 3) → (1) TS 3/4 → (1) ZrH 3 -CH = CH 2 ((1)4). The minimum energy crossing point is determined with the help of the DFT fractional-occupation-number (FON) approach. The spin inversion leads the reaction pathway transferring from the triplet potential energy surface (PES) to the singlet's accompanying with the activation of the second C-H bond. The overall reaction is calculated to be exothermic by about 231 kJ mol(-1). Frequency and NBO analysis are also applied to confirm with the experimental observed data.
Tao, Jianmin; Perdew, John P.; Almeida, Luís Miguel; Fiolhais, Carlos; Kümmel, Stephan
2008-06-01
Jellium, a simple model of metals, is a standard testing ground for density functionals both for bulk and for surface properties. Earlier tests show that the Tao-Perdew-Staroverov-Scuseria (TPSS) nonempirical metageneralized gradient approximation (meta-GGA) for the exchange-correlation energy yields more accurate surface energies than the local spin density (LSD) approximation for spin-unpolarized jellium. In this study, work functions and surface energies of a jellium metal in the presence of “internal” and external magnetic fields are calculated with LSD, Perdew-Burke-Ernzerhof (PBE) GGA, and TPSS meta-GGA and its predecessor, the nearly nonempirical Perdew-Kurth-Zupan-Blaha meta-GGA, using self-consistent LSD orbitals and densities. The results show that (i) For normal bulk densities, the surface correlation energy is the same in TPSS as in PBE, as it should be since TPSS strives to represent a self-correlation correction to PBE; (ii) Normal surface density profiles can be scaled uniformly to the low-density or strong-interaction limit, and TPSS provides an estimate for that limit that is consistent with (but probably more accurate than) other estimates; (iii) For both normal and low densities, TPSS provides the same description of surface magnetism as PBE, suggesting that these approximations may be generally equivalent for magnetism. The energies of jellium spheres with up to 106 electrons are calculated using density functionals and compared to those obtained with diffusion quantum Monte Carlo data, including our estimate for the fixed-node correction. Typically, while PBE energies are too low for spheres with more than about two electrons, LSD and TPSS are accurate there. We confirm that curvature energies are lower in PBE and TPSS than in LSD. Finally, we calculate the linear response of bulk jellium using these density functionals and find that not only LSD but also PBE GGA and TPSS meta-GGA yield a linear response in good agreement with that of the
Kumar, Jitendra; Nemade, Harshal B; Giri, P K
2017-11-08
Using density functional theory calculations in combination with a non-equilibrium Green's function method, we explore the transport properties of a niobium-doped (∼3.57%) armchair graphene nanoribbon of dimer length 7 in a two-terminal device configuration. The band structure of the supercell with niobium atoms showed spin splitting near the Fermi level. The spin-dependent transport properties and spin-resolved band structure of electrodes with applied bias values were calculated to understand the spin filter and the negative differential resistance (NDR) effect. The spin filter efficiency of the device was found to be more than 95% in the applied voltage range of 0.15 V to 0.5 V for the antiparallel configuration, and the device is suitable as an efficient spin filter at room temperature. The parallel configuration has a higher range, 0 V to 0.5 V, with an efficiency more than 70%. The peak-to-valley ratios in the parallel configuration for spin-up and spin-down currents were 4.5 and 17.8, respectively, while in the antiparallel configuration, the values were 4.57 and 37.5, respectively. The combined NDR characteristic showed figure of merit with a peak current density of ∼6 mA μm(-1) and a PVR of ∼4.6, useful for logical application. Our findings open a new way to produce multifunctional spintronic devices based on niobium-doped armchair graphene nanoribbons.
Du, Li-Bo; Wang, Lan-Fen; Liu, Yang-Ping; Jia, Hong-Ying; Liu, Yang; Liu, Ke Jian; Tian, Qiu
2011-01-01
To design efficient spin traps for superoxide radicals, interest in the elucidation of substituent effects on the stability of superoxide spin adducts has become a necessary priority. In the present study, five cyclic nitrone superoxide spin adducts, i.e. DMPO-OOH, M3PO-OOH, EMPO-OOH, DEPMPO-OOH, and DEPDMPO-OOH, were chosen as model compounds to investigate the effect of 2,5-subsitituents on their stability, through structural analysis and decay thermodynamics using density functional theory (DFT) calculations. Analysis of the optimized geometries reveals that none of the previously proposed stabilizing factors, including intramolecular H-bonds, intramolecular nonbonding interactions, bulky steric protection, nor the C(2)–N(1) bond distance can be used to clearly explain the effect of 2,5-substituents on the stability of the spin adducts. Additionally the effect of the 2,5-substituents on the stability of the superoxide spin adducts cannot be simply clarified by Milliken charges on both atoms (nitroxyl nitrogen and nitroxyl oxygen). Subsequent study found that spin densities on the nitroxyl nitrogen and oxygen are well correlated with the half-life times of the spin adducts, and consequently are the proper parameters to characterize the effect of 2,5-substituents on their stability. Examination of the decomposition thermodynamics further supports the effect of the substituents on the persistence of cyclic nitrone superoxide spin adducts. PMID:20370568
Körner, Michael; Smith, Dominik; Buividovich, Pavel; Ulybyshev, Maksim; von Smekal, Lorenz
2017-11-01
We report on Hybrid Monte Carlo simulations at finite spin density of the π -band electrons in monolayer graphene with realistic interelectron interactions. Unlike simulations at finite charge-carrier density, these are not affected by a fermion-sign problem. Our results are in qualitative agreement with an interaction-induced warping of the Fermi contours and a reduction of the bandwidth as observed in angle-resolved photoemission spectroscopy experiments on charge-doped graphene systems. Furthermore, we find evidence that the neck-disrupting Lifshitz transition, which occurs when the Fermi level traverses the van Hove singularity (VHS), becomes a true quantum phase transition due to interactions. This is in line with an instability of the VHS toward the formation of ordered electronic phases, which has been predicted by a variety of different theoretical approaches.
Quantum Monte Carlo studies of a metallic spin-density wave transition
Energy Technology Data Exchange (ETDEWEB)
Gerlach, Max Henner
2017-01-20
Plenty experimental evidence indicates that quantum critical phenomena give rise to much of the rich physics observed in strongly correlated itinerant electron systems such as the high temperature superconductors. A quantum critical point of particular interest is found at the zero-temperature onset of spin-density wave order in two-dimensional metals. The appropriate low-energy theory poses an exceptionally hard problem to analytic theory, therefore the unbiased and controlled numerical approach pursued in this thesis provides important contributions on the road to comprehensive understanding. After discussing the phenomenology of quantum criticality, a sign-problem-free determinantal quantum Monte Carlo approach is introduced and an extensive toolbox of numerical methods is described in a self-contained way. By the means of large-scale computer simulations we have solved a lattice realization of the universal effective theory of interest. The finite-temperature phase diagram, showing both a quasi-long-range spin-density wave ordered phase and a d-wave superconducting dome, is discussed in its entirety. Close to the quantum phase transition we find evidence for unusual scaling of the order parameter correlations and for non-Fermi liquid behavior at isolated hot spots on the Fermi surface.
Filatov, M; Cremer, D
2005-01-01
It is demonstrated that the LYP correlation functional is not suited to be used for the calculation of electron spin resonance hyperfine structure (HFS) constants, nuclear magnetic resonance spin-spin coupling constants, magnetic, shieldings and other properties that require a balanced account of
Reduced-Density-Matrix Description of Decoherence and Relaxation Processes for Electron-Spin Systems
Jacobs, Verne
2017-04-01
Electron-spin systems are investigated using a reduced-density-matrix description. Applications of interest include trapped atomic systems in optical lattices, semiconductor quantum dots, and vacancy defect centers in solids. Complimentary time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations are self-consistently developed. The general non-perturbative and non-Markovian formulations provide a fundamental framework for systematic evaluations of corrections to the standard Born (lowest-order-perturbation) and Markov (short-memory-time) approximations. Particular attention is given to decoherence and relaxation processes, as well as spectral-line broadening phenomena, that are induced by interactions with photons, phonons, nuclear spins, and external electric and magnetic fields. These processes are treated either as coherent interactions or as environmental interactions. The environmental interactions are incorporated by means of the general expressions derived for the time-domain and frequency-domain Liouville-space self-energy operators, for which the tetradic-matrix elements are explicitly evaluated in the diagonal-resolvent, lowest-order, and Markov (short-memory time) approximations. Work supported by the Office of Naval Research through the Basic Research Program at The Naval Research Laboratory.
Finite-connectivity spin-glass phase diagrams and low-density parity check codes.
Migliorini, Gabriele; Saad, David
2006-02-01
We obtain phase diagrams of regular and irregular finite-connectivity spin glasses. Contact is first established between properties of the phase diagram and the performance of low-density parity check (LDPC) codes within the replica symmetric (RS) ansatz. We then study the location of the dynamical and critical transition points of these systems within the one step replica symmetry breaking theory (RSB), extending similar calculations that have been performed in the past for the Bethe spin-glass problem. We observe that the location of the dynamical transition line does change within the RSB theory, in comparison with the results obtained in the RS case. For LDPC decoding of messages transmitted over the binary erasure channel we find, at zero temperature and rate , an RS critical transition point at while the critical RSB transition point is located at , to be compared with the corresponding Shannon bound . For the binary symmetric channel we show that the low temperature reentrant behavior of the dynamical transition line, observed within the RS ansatz, changes its location when the RSB ansatz is employed; the dynamical transition point occurs at higher values of the channel noise. Possible practical implications to improve the performance of the state-of-the-art error correcting codes are discussed.
Lin, Tzu-Jen; O'Malley, Patrick J
2011-04-14
ONIOM (QM/MM) calculations are used to calculate the spin density distribution for the plastosemiquinone anion radical in the Q(A) binding site of photosystem II. A number of models are examined that explore the effect of iron depletion on the Q(A) site semiquinone spin density distribution and resultant hyperfine couplings. For a model system with a divalent metal ion in the nonheme site the calculated spin density in the Q(A) site model suggests that differential hydrogen-bonding strength to the O1 and O4 oxygen atoms of the radical results in an asymmetric spin density distribution in the semiquinone anion free radical form. The hydrogen bond to the proximal O1 atom is significantly stronger. This is similar to the situation shown to exist previously in the bacterial reaction center of Rba sphaeroides. Various models of depleted nonheme site metal show the profound effect that the presence of a divalent ion in this site has on the spin density distribution of the Q(A) site semiquinone. The variation in calculated spin density distribution of the Q(A) site plastosemiquinone as a function of the occupancy of the nonheme site needs to be taken into account in the interpretation of experimental paramagnetic resonance data. For Type II reaction centers a major role for Fe(2+) in the nonheme site may be the raising of the redox potential of the Q(A)/Q(A)(-) couple to ensure that electron transfer from the (bacterio)pheophytin anion free radical occurs at a sufficient rate to compete with wasteful back-reactions.
Spin density waves predicted in zigzag puckered phosphorene, arsenene and antimonene nanoribbons
Directory of Open Access Journals (Sweden)
Xiaohua Wu
2016-04-01
Full Text Available The pursuit of controlled magnetism in semiconductors has been a persisting goal in condensed matter physics. Recently, Vene (phosphorene, arsenene and antimonene has been predicted as a new class of 2D-semiconductor with suitable band gap and high carrier mobility. In this work, we investigate the edge magnetism in zigzag puckered Vene nanoribbons (ZVNRs based on the density functional theory. The band structures of ZVNRs show half-filled bands crossing the Fermi level at the midpoint of reciprocal lattice vectors, indicating a strong Peierls instability. To remove this instability, we consider two different mechanisms, namely, spin density wave (SDW caused by electron-electron interaction and charge density wave (CDW caused by electron-phonon coupling. We have found that an antiferromagnetic Mott-insulating state defined by SDW is the ground state of ZVNRs. In particular, SDW in ZVNRs displays several surprising characteristics:1 comparing with other nanoribbon systems, their magnetic moments are antiparallelly arranged at each zigzag edge and almost independent on the width of nanoribbons; 2 comparing with other SDW systems, its magnetic moments and band gap of SDW are unexpectedly large, indicating a higher SDW transition temperature in ZVNRs; 3 SDW can be effectively modified by strains and charge doping, which indicates that ZVNRs have bright prospects in nanoelectronic device.
Spin density waves predicted in zigzag puckered phosphorene, arsenene and antimonene nanoribbons
Energy Technology Data Exchange (ETDEWEB)
Wu, Xiaohua; Zhang, Xiaoli; Wang, Xianlong [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zeng, Zhi, E-mail: zzeng@theory.issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China)
2016-04-15
The pursuit of controlled magnetism in semiconductors has been a persisting goal in condensed matter physics. Recently, Vene (phosphorene, arsenene and antimonene) has been predicted as a new class of 2D-semiconductor with suitable band gap and high carrier mobility. In this work, we investigate the edge magnetism in zigzag puckered Vene nanoribbons (ZVNRs) based on the density functional theory. The band structures of ZVNRs show half-filled bands crossing the Fermi level at the midpoint of reciprocal lattice vectors, indicating a strong Peierls instability. To remove this instability, we consider two different mechanisms, namely, spin density wave (SDW) caused by electron-electron interaction and charge density wave (CDW) caused by electron-phonon coupling. We have found that an antiferromagnetic Mott-insulating state defined by SDW is the ground state of ZVNRs. In particular, SDW in ZVNRs displays several surprising characteristics:1) comparing with other nanoribbon systems, their magnetic moments are antiparallelly arranged at each zigzag edge and almost independent on the width of nanoribbons; 2) comparing with other SDW systems, its magnetic moments and band gap of SDW are unexpectedly large, indicating a higher SDW transition temperature in ZVNRs; 3) SDW can be effectively modified by strains and charge doping, which indicates that ZVNRs have bright prospects in nanoelectronic device.
Time-dependent spin-density-functional-theory description of He+-He collisions
Baxter, Matthew; Kirchner, Tom; Engel, Eberhard
2017-09-01
Theoretical total cross-section results for all ionization and capture processes in the He+-He collision system are presented in the approximate impact energy range of 10-1000 keV/amu. Calculations were performed within the framework of time-dependent spin-density functional theory. The Krieger-Li-Iafrate approximation was used to determine an accurate exchange-correlation potential in the exchange-only limit. The results of two models, one where electron translation factors in the orbitals used to calculate the potential are ignored and another where partial electron translation factors are included, are compared with available experimental data as well as a selection of previous theoretical calculations.
Kumar, Manoranjan
2016-02-03
An efficient density matrix renormalization group (DMRG) algorithm is presented and applied to Y junctions, systems with three arms of n sites that meet at a central site. The accuracy is comparable to DMRG of chains. As in chains, new sites are always bonded to the most recently added sites and the superblock Hamiltonian contains only new or once renormalized operators. Junctions of up to N=3n+1≈500 sites are studied with antiferromagnetic (AF) Heisenberg exchange J between nearest-neighbor spins S or electron transfer t between nearest neighbors in half-filled Hubbard models. Exchange or electron transfer is exclusively between sites in two sublattices with NA≠NB. The ground state (GS) and spin densities ρr=⟨Szr⟩ at site r are quite different for junctions with S=1/2, 1, 3/2, and 2. The GS has finite total spin SG=2S(S) for even (odd) N and for MG=SG in the SG spin manifold, ρr>0(<0) at sites of the larger (smaller) sublattice. S=1/2 junctions have delocalized states and decreasing spin densities with increasing N. S=1 junctions have four localized Sz=1/2 states at the end of each arm and centered on the junction, consistent with localized states in S=1 chains with finite Haldane gap. The GS of S=3/2 or 2 junctions of up to 500 spins is a spin density wave with increased amplitude at the ends of arms or near the junction. Quantum fluctuations completely suppress AF order in S=1/2 or 1 junctions, as well as in half-filled Hubbard junctions, but reduce rather than suppress AF order in S=3/2 or 2 junctions.
Energy Technology Data Exchange (ETDEWEB)
Soderlind, P; Wolfer, W
2007-07-27
Spin and orbital and electron correlations are known to be important when treating the high-temperature {delta} phase of plutonium within the framework of density-functional theory (DFT). One of the more successful attempts to model {delta}-Pu within this approach has included condensed-matter generalizations of Hund's three rules for atoms, i.e., spin polarization, orbital polarization, and spin-orbit coupling. Here they perform a quantitative analysis of these interactions relative rank for the bonding and electronic structure in {delta}-Pu within the DFT model. The result is somewhat surprising in that spin-orbit coupling and orbital polarization are far more important than spin polarization for a realistic description of {delta}-Pu. They show that these orbital correlations on their own, without any formation of magnetic spin moments, can account for the low atomic density of the {delta} phase with a reasonable equation-of-state. In addition, this unambiguously non-magnetic (NM) treatment produces a one-electron spectra with resonances close to the Fermi level consistent with experimental valence band photoemission spectra.
Self-Calibrating Wave-Encoded Variable-Density Single-Shot Fast Spin Echo Imaging.
Chen, Feiyu; Taviani, Valentina; Tamir, Jonathan I; Cheng, Joseph Y; Zhang, Tao; Song, Qiong; Hargreaves, Brian A; Pauly, John M; Vasanawala, Shreyas S
2017-09-14
It is highly desirable in clinical abdominal MR scans to accelerate single-shot fast spin echo (SSFSE) imaging and reduce blurring due to T2 decay and partial-Fourier acquisition. To develop and investigate the clinical feasibility of wave-encoded variable-density SSFSE imaging for improved image quality and scan time reduction. Prospective controlled clinical trial. With Institutional Review Board approval and informed consent, the proposed method was assessed on 20 consecutive adult patients (10 male, 10 female, range, 24-84 years). A wave-encoded variable-density SSFSE sequence was developed for clinical 3.0T abdominal scans to enable high acceleration (3.5×) with full-Fourier acquisitions by: 1) introducing wave encoding with self-refocusing gradient waveforms to improve acquisition efficiency; 2) developing self-calibrated estimation of wave-encoding point-spread function and coil sensitivity to improve motion robustness; and 3) incorporating a parallel imaging and compressed sensing reconstruction to reconstruct highly accelerated datasets. Image quality was compared pairwise with standard Cartesian acquisition independently and blindly by two radiologists on a scale from -2 to 2 for noise, contrast, confidence, sharpness, and artifacts. The average ratio of scan time between these two approaches was also compared. A Wilcoxon signed-rank tests with a P value under 0.05 considered statistically significant. Wave-encoded variable-density SSFSE significantly reduced the perceived noise level and improved the sharpness of the abdominal wall and the kidneys compared with standard acquisition (mean scores 0.8, 1.2, and 0.8, respectively, P variable-density sampling SSFSE achieves improved image quality with clinically relevant echo time and reduced scan time, thus providing a fast and robust approach for clinical SSFSE imaging. 1 TECHNICAL EFFICACY: Stage 6 J. Magn. Reson. Imaging 2017. © 2017 International Society for Magnetic Resonance in Medicine.
Thompson, Lee M; Hratchian, Hrant P
2015-08-13
Spin contamination in density functional studies has been identified as a cause of discrepancies between theoretical and experimental spectra of metal oxide clusters such as MoNbO2. We perform calculations to simulate the photoelectron spectra of the MoNbO2 anion using broken-symmetry density functional theory incorporating recently developed approximate projection methods. These calculations are able to account for the presence of contaminating spin states at single-reference computational cost. Results using these new tools demonstrate the significant effect of spin-contamination on geometries and force constants and show that the related errors in simulated spectra may be largely overcome by using an approximate projection model.
Acoustic noise reduction in T 1- and proton-density-weighted turbo spin-echo imaging.
Ott, Martin; Blaimer, Martin; Breuer, Felix; Grodzki, David; Heismann, Björn; Jakob, Peter
2016-02-01
To reduce acoustic noise levels in T 1-weighted and proton-density-weighted turbo spin-echo (TSE) sequences, which typically reach acoustic noise levels up to 100 dB(A) in clinical practice. Five acoustic noise reduction strategies were combined: (1) gradient ramps and shapes were changed from trapezoidal to triangular, (2) variable-encoding-time imaging was implemented to relax the phase-encoding gradient timing, (3) RF pulses were adapted to avoid the need for reversing the polarity of the slice-rewinding gradient, (4) readout bandwidth was increased to provide more time for gradient activity on other axes, (5) the number of slices per TR was reduced to limit the total gradient activity per unit time. We evaluated the influence of each measure on the acoustic noise level, and conducted in vivo measurements on a healthy volunteer. Sound recordings were taken for comparison. An overall acoustic noise reduction of up to 16.8 dB(A) was obtained by the proposed strategies (1-4) and the acquisition of half the number of slices per TR only. Image quality in terms of SNR and CNR was found to be preserved. The proposed measures in this study allowed a threefold reduction in the acoustic perception of T 1-weighted and proton-density-weighted TSE sequences compared to a standard TSE-acquisition. This could be achieved without visible degradation of image quality, showing the potential to improve patient comfort and scan acceptability.
On the definition of the spin-free cumulant of the second-order reduced density matrix
Lain, Luis; Torre, Alicia; Bochicchio, Roberto
2002-09-01
This note deals with the appropriate definition for the spin-free cumulant of the second-order reduced density matrix. Our approach leads to a direct derivation of one of the proposals reported by Kutzelnigg and Mukherjee [J. Chem. Phys. 116, 4787 (2002)] and it points out its suitability.
DEFF Research Database (Denmark)
Lodahl, Peter; Johansen, Jeppe; Julsgaard, Brian
2009-01-01
on time-resolved detection of spontaneous emission. Using the modified local density of optical states of a GaAs-air interface and its known dependence on distance (z), it was recently shown that the bright exciton radiative and non-radiative processes could be fully unravelled. Hence, the spin-flip rate...
Jiang, J. H.; Wu, M. W.
2009-12-01
We comment on the conclusion by Teng et al (2009 J. Phys. D: Appl. Phys. 42 135111) that the Bir-Aronov-Pikus mechanism is more important than the D'yakonov-Perel' mechanism at a high carrier density in intrinsic bulk GaAs. We point out that the spin relaxation is solely from the D'yakonov-Perel' mechanism.
Datta, Dipayan; Gauss, Jürgen
2015-07-07
We report analytical calculations of isotropic hyperfine-coupling constants in radicals using a spin-adapted open-shell coupled-cluster theory, namely, the unitary group based combinatoric open-shell coupled-cluster (COSCC) approach within the singles and doubles approximation. A scheme for the evaluation of the one-particle spin-density matrix required in these calculations is outlined within the spin-free formulation of the COSCC approach. In this scheme, the one-particle spin-density matrix for an open-shell state with spin S and MS = + S is expressed in terms of the one- and two-particle spin-free (charge) density matrices obtained from the Lagrangian formulation that is used for calculating the analytic first derivatives of the energy. Benchmark calculations are presented for NO, NCO, CH2CN, and two conjugated π-radicals, viz., allyl and 1-pyrrolyl in order to demonstrate the performance of the proposed scheme.
Directory of Open Access Journals (Sweden)
Shenghan Jiang
2014-09-01
Full Text Available Recently, two interesting candidate quantum phases—the chiral spin-density wave state featuring anomalous quantum Hall effect and the d+id superconductor—were proposed for the Hubbard model on the honeycomb lattice at 1/4 doping. Using a combination of exact diagonalization, density matrix renormalization group, the variational Monte Carlo method, and quantum field theories, we study the quantum phase diagrams of both the Hubbard model and the t-J model on the honeycomb lattice at 1/4 doping. The main advantage of our approach is the use of symmetry quantum numbers of ground-state wave functions on finite-size systems (up to 32 sites to sharply distinguish different quantum phases. Our results show that for 1≲U/t<40 in the Hubbard model and for 0.1
Evolution of the phonon density of states of LaCoO3 over the spin state transition
Energy Technology Data Exchange (ETDEWEB)
Golosova, N. O. [Joint Institute for Nuclear Research, Dubna, Russia; Kozlenko, D. P. [Joint Institute for Nuclear Research, Dubna, Russia; Kolesnikov, Alexander I [ORNL; Kazimirov, V. Yu. [Joint Institute for Nuclear Research, Dubna, Russia; Smirnov, M. B. [St. Petersburg State University, St. Petersburg, Russia; Jirak, Z. [Institute of Physics, Czech Republic; Savenko, B. N. [Joint Institute for Nuclear Research, Dubna, Russia
2011-01-01
The phonon spectra of LaCoO3 were studied by inelastic neutron scattering in the temperature range of 4 120 K. The DFT calculations of the lattice dynamics have been made for interpretation of the experimental data. The observed and calculated phonon frequencies were found to be in a reasonable agreement. The evolution of the phonon density of states over the spin state transition was analyzed. In the low-temperature range (T < 50 K), an increase in the energy of resolved breathing, stretching, and bending phonon modes was found, followed by their softening and broadening at higher temperatures due to the spin state transition and relevant orbital-phonon coupling.
Density of states, specific heat and nuclear spin-lattice relaxation rate in PrOs4Sb12
Abu Alrub, Tayseer; Curnoe, Stephanie
2007-03-01
We present a theoretical study of the density of states, specific heat and nuclear spin-relaxation rate in the unconventional superconductor PrOs4Sb12. In this material, superconductivity is best described by a three component order parameter in the triplet channel. Instead of nodes, deep dips appear in the gap function producing power law temperature dependencies at higher temperatures and exponential suppression at low temperatures of the specific heat and the nuclear spin lattice relaxation rate. Various experimental observations will be discussed in this context.
Li, Zhendong; Liu, Wenjian
2010-08-14
The spin-adaptation of single-reference quantum chemical methods for excited states of open-shell systems has been nontrivial. The primary reason is that the configuration space, generated by a truncated rank of excitations from only one component of a reference multiplet, is spin-incomplete. Those "missing" configurations are of higher ranks and can, in principle, be recaptured by a particular class of excitation operators. However, the resulting formalisms are then quite involved and there are situations [e.g., time-dependent density functional theory (TD-DFT) under the adiabatic approximation] that prevent one from doing so. To solve this issue, we propose here a tensor-coupling scheme that invokes all the components of a reference multiplet (i.e., a tensor reference) rather than increases the excitation ranks. A minimal spin-adapted n-tuply excited configuration space can readily be constructed by tensor products between the n-tuple tensor excitation operators and the chosen tensor reference. Further combined with the tensor equation-of-motion formalism, very compact expressions for excitation energies can be obtained. As a first application of this general idea, a spin-adapted open-shell random phase approximation is first developed. The so-called "translation rule" is then adopted to formulate a spin-adapted, restricted open-shell Kohn-Sham (ROKS)-based TD-DFT (ROKS-TD-DFT). Here, a particular symmetry structure has to be imposed on the exchange-correlation kernel. While the standard ROKS-TD-DFT can access only excited states due to singlet-coupled single excitations, i.e., only some of the singly excited states of the same spin (S(i)) as the reference, the new scheme can capture all the excited states of spin S(i)-1, S(i), or S(i)+1 due to both singlet- and triplet-coupled single excitations. The actual implementation and computation are very much like the (spin-contaminated) unrestricted Kohn-Sham-based TD-DFT. It is also shown that spin-contaminated spin
Competition between itinerant ferromagnetism and spin-density wave antiferromagnetism in FeGa
Wu, Yan; Cao, Huibo; McCandles, Gregory; Chan, Julia; Karki, Amar; Jin, Rongying; Ditusa, John
2015-03-01
The metallic magnetFeGadisplays a rich magnetic behavior that includes transitions between a FM ground state to a AFM intermediate state at 68 K and back to a FM state at 360 K. The phase transition at 360 K is accompanied by a discontinuous hysteretic change in the electrical resistivity. In addition, the application of moderate magnetic fields cause a sharp transformation from the AFM to FM state with a critical Hthat grows dramatically with T.To explore the cause of this unusual competition of magnetic states, we investigated the magnetic structure of FeGavia extensive single crystal neutron diffraction measurements. These measurements revealed a FM ordering with magnetic moments lying along the crystallographic c-axis both below 68 K and above 360 K as well as incommensurate spin density wave order between these temperatures. Our refinement of the diffraction data has uncovered the existence of a small non-coplanar moment which may be the origin of our previously discovered topological Hall Effect.
Quantum critical properties of a metallic spin-density-wave transition
Gerlach, Max H.; Schattner, Yoni; Berg, Erez; Trebst, Simon
2017-01-01
We report on numerically exact determinantal quantum Monte Carlo simulations of the onset of spin-density-wave (SDW) order in itinerant electron systems captured by a sign-problem-free two-dimensional lattice model. Extensive measurements of the SDW correlations in the vicinity of the phase transition reveal that the critical dynamics of the bosonic order parameter are well described by a dynamical critical exponent z =2 , consistent with Hertz-Millis theory, but are found to follow a finite-temperature dependence that does not fit the predicted behavior of the same theory. The presence of critical SDW fluctuations is found to have a strong impact on the fermionic quasiparticles, giving rise to a dome-shaped superconducting phase near the quantum critical point. In the superconducting state we find a gap function that has an opposite sign between the two bands of the model and is nearly constant along the Fermi surface of each band. Above the superconducting Tc, our numerical simulations reveal a nearly temperature and frequency independent self-energy causing a strong suppression of the low-energy quasiparticle weight in the vicinity of the hot spots on the Fermi surface. This indicates a clear breakdown of Fermi liquid theory around these points.
Commensurate and incommensurate spin-density waves in heavy electron systems
Directory of Open Access Journals (Sweden)
P. Schlottmann
2016-05-01
Full Text Available The nesting of the Fermi surfaces of an electron and a hole pocket separated by a nesting vector Q and the interaction between electrons gives rise to itinerant antiferromagnetism. The order can gradually be suppressed by mismatching the nesting and a quantum critical point (QCP is obtained as the Néel temperature tends to zero. The transfer of pairs of electrons between the pockets can lead to a superconducting dome above the QCP (if Q is commensurate with the lattice, i.e. equal to G/2. If the vector Q is not commensurate with the lattice there are eight possible phases: commensurate and incommensurate spin and charge density waves and four superconductivity phases, two of them with modulated order parameter of the FFLO type. The renormalization group equations are studied and numerically integrated. A re-entrant SDW phase (either commensurate or incommensurate is obtained as a function of the mismatch of the Fermi surfaces and the magnitude of |Q − G/2|.
Pi, Martí; Ancilotto, Francesco; Lipparini, Enrico; Mayol, Ricardo
2004-09-01
We perform adiabatic time-dependent local spin-density approximation (TDLSDA) calculations in real time of the excitation spectrum of three-dimensional quantum dots (QD's) in magnetic fields of arbitrary direction. In the case of parabolic confinement and electric dipole modes, the calculations reproduce exactly the generalized Kohn theorem, which is a stringent test of the numerical accuracy achieved by our practical implementation of TDLSDA. We apply the method to the study of spin dipole modes in a QD. Real time TDLSDA can be more efficient than Green's function methods to compute the dynamical properties of confined electrons, especially when the finite thickness of the system has to be taken into account. As an illustration, we obtain the dipole spin modes and the acoustic modes of vertical diatomic artificial quantum molecules at zero magnetic field.
Nawa, Kazuhiro; Yoshida, Makoto; Takigawa, Masashi; Okamoto, Yoshihiko; Hiroi, Zenji
2017-11-01
The phase diagram of the quasi-one-dimensional magnet NaCuMoO4(OH ) is established through single-crystal NMR and heat-capacity measurements. The 23Na and 1H NMR experiments indicate a spiral and a collinear spin density wave (SDW) order below and above Bc = 1.5-1.8 T, respectively. Moreover, in the paramagnetic state above the SDW transition temperature, the nuclear spin-lattice relaxation rate 1 /T1 indicates anisotropic spin fluctuations that have gapped excitations in the transverse spectrum but gapless ones in the longitudinal spectrum. These static and dynamic properties are well described by a theoretical model assuming quasi-one-dimensional chains with competing ferromagnetic nearest-neighbor interactions J1 and antiferromagnetic next-nearest-neighbor interactions J2 (J1-J2 chains). Because of the excellent crystal quality and good one-dimensionality, NaCuMoO4(OH ) is a promising compound to elucidate the unique physics of the frustrated J1-J2 chain.
Spin polarization driven by a charge-density wave in monolayer 1T−TaS2
Zhang, Qingyun
2014-08-06
Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer T-phase TaS2. We demonstrate that a charge-density wave is energetically favorable at low temperature, similar to bulk 1T-TaS2. Electron-phonon coupling is found to be essential for the lattice reconstruction. The charge-density wave results in a strong localization of the electronic states near the Fermi level and consequently in spin polarization, transforming the material into a magnetic semiconductor with enhanced electronic correlations. The combination of inherent spin polarization with a semiconducting nature distinguishes the monolayer fundamentally from the bulk compound as well as from other two-dimensional transition metal dichalcogenides. Monolayer T-phase TaS2 therefore has the potential to enable two-dimensional spintronics. © 2014 American Physical Society.
Wu, Ya-Jie; Li, Ning; He, Jing; Kou, Su-Peng
2016-03-23
In this paper, based on mean-field approach and random-phase-approximation, we study the magnetic properties of the repulsive Haldane-Hubbard model on a square lattice. We find antiferromagnetic order driven topological spin density waves beyond Landau's symmetry-breaking paradigm, for which the effective low energy physics is determined by Chern-Simons-Hopf gauge field theories with different K matrices.
Solid-liquid density and spin crossovers in (Mg, Fe)O system at deep mantle conditions.
Ghosh, Dipta B; Karki, Bijaya B
2016-11-22
The low/ultralow-velocity zones in the Earth's mantle can be explained by the presence of partial melting, critically depending on density contrast between the melt and surrounding solid mantle. Here, first-principles molecular dynamics simulations of (Mg, Fe) O ferropericlase in the solid and liquid states show that their densities increasingly approach each other as pressure increases. The isochemical density difference between them diminishes from 0.78 (±0.7) g/cm3 at zero pressure (3000 K) to 0.16 (±0.04) g/cm3 at 135 GPa (4000 K) for pure and alloyed compositions containing up to 25% iron. The simulations also predict a high-spin to low-spin transition of iron in the liquid ferropericlase gradually occurring over a pressure interval centered at 55 GPa (4000 K) accompanied by a density increase of 0.14 (±0.02) g/cm3. Temperature tends to widen the transition to higher pressure. The estimated iron partition coefficient between the solid and liquid ferropericlase varies from 0.3 to 0.6 over the pressure range of 23 to 135 GPa. Based on these results, an excess of as low as 5% iron dissolved in the liquid could cause the solid-liquid density crossover at conditions of the lowermost mantle.
Heida, J.P.; Wees, B.J. van; Kuipers, J.J.; Klapwijk, T.M.; Borghs, G.
1998-01-01
We present experiments on the tuning of the spin-orbit interaction in a two-dimensional electron gas in an asymmetric InAs/AlSb quantum well using a gate. The observed dependence of the spin splitting energy on the electron density can be attributed solely to the change in the Fermi wave vector. The
Karakatsanis, Konstantinos; Lalazissis, G. A.; Ring, Peter; Litvinova, Elena
2017-03-01
Spin-orbit splitting is an essential ingredient for our understanding of the shell structure in nuclei. One of the most important advantages of relativistic mean-field (RMF) models in nuclear physics is the fact that the large spin-orbit (SO) potential emerges automatically from the inclusion of Lorentz-scalar and -vector potentials in the Dirac equation. It is therefore of great importance to compare the results of such models with experimental data. We investigate the size of 2 p and 1 f splittings for the isotone chain 40Ca, 38Ar, 36S, and 34Si in the framework of various relativistic and nonrelativistic density functionals. They are compared with the results of nonrelativistic models and with recent experimental data.
Zarycz, M Natalia C; Provasi, Patricio F; Sauer, Stephan P A
2015-12-28
It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH4, NH3, H2O, SiH4, PH3, SH2, C2H2, C2H4, and C2H6. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.
Energy Technology Data Exchange (ETDEWEB)
Zarycz, M. Natalia C., E-mail: mnzarycz@gmail.com; Provasi, Patricio F., E-mail: patricio@unne.edu.ar [Department of Physics, University of Northeastern - CONICET, Av. Libertad 5500, Corrientes W3404AAS (Argentina); Sauer, Stephan P. A., E-mail: sauer@kiku.dk [Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø (Denmark)
2015-12-28
It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH{sub 4}, NH{sub 3}, H{sub 2}O, SiH{sub 4}, PH{sub 3}, SH{sub 2}, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, and C{sub 2}H{sub 6}. The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states.
Redmond, Matthew; Mastropietro, A. J.; Pauken, Michael; Mobley, Brandon
2014-01-01
Future missions to Mars will require improved entry, descent, and landing (EDL) technology over the Viking-heritage systems which recently landed the largest payload to date, the 900 kg Mars Science Laboratory. As a result, NASA's Low Density Supersonic Decelerator (LDSD) project is working to advance the state of the art in Mars EDL systems by developing and testing three key technologies which will enable heavier payloads and higher altitude landing sites on the red planet. These technologies consist of a large 33.5 m diameter Supersonic Disk Sail (SSDS) parachute and two different Supersonic Inflatable Aerodynamic Decelerator (SIAD) devices - a robotic class that inflates to a 6 m diameter torus (SIAD-R), and an exploration class that inflates to an 8 m diameter isotensoid (SIADE). All three technologies will be demonstrated on test vehicles at high earth altitudes in order to simulate the Mars EDL environment. Each vehicle will be carried to altitude by a large helium balloon, released, spun up using spin motors to stabilize the vehicle's trajectory, and accelerated to supersonic speeds using a large solid rocket motor. The vehicle will then be spun down using another set of spin motors, and will deploy either the SIAD-R or SIAD-E, followed by the SSDS parachute until the vehicle lands in the ocean. Component level testing and bounding analysis are used to ensure the survival of system components in extreme thermal environments and predict temperatures throughout the flight. This paper presents a general description of the thermal testing, model correlation, and analysis of the spin motor passive thermal control sub-system to maintain spin motor performance, prescribed vehicle trajectory, and structural integrity of the test vehicle. The spin motor subsystem is predicted to meet its requirements with margin.
Spin Measurements of n+Sr-87 for Level Density Studies
Gunsing, F; Mathelie, M; Valenta, S; Bečvář, F; Rusev, G; Tonchev, A P; Mitchell, G; Baramsai, B; Altstadt, S; Andrzejewski, J; Audouin, L; Barbagallo, M; Bécares, V; Belloni, F; Berthoumieux, E; Billowes, J; Boccone, V; Bosnar, D; Brugger, M; Calviani, M; Calviño, F; Cano-Ott, D; Carrapiço, C; Cerutti, F; Chiaveri, E; Chin, M; Colonna, N; Cortés, G; Cortés-Giraldo, M A; Diakaki, M; Domingo-Pardo, C; Duran, I; Dressler, R; Eleftheriadis, C; Ferrari, A; Ganesan, S; García, A R; Giubrone, G; Gonçalves, I.F.; González-Romero, E; Griesmayer, E; Guerrero, C; Hernández-Prieto, A; Jenkins, D G; Jericha, E; Kadi, Y; Käppeler, F; Karadimos, D; Koehler, P; Kokkoris, M; Krtička, M; Kroll, J; Lampoudis, C; Langer, C; Leal-Cidoncha, E; Lederer, C; Leeb, H; Leong, L S; Losito, R; Manousos, A; Marganiec, J; Martínez, T; Massimi, C; Mastinu, P F; Mastromarco, M; Mendoza, E; Mengoni, A; Milazzo, P M; Mingrone, F; Mirea, M; Mondalaers, W; Paradela, C; Pavlik, A; Perkowski, J; Plompen, A; Praena, J; Quesada, J M; Rauscher, T; Reifarth, R; Riego, A; Robles, M S; Rubbia, C; Sabaté-Gilarte, M; Sarmento, R; Saxena, A; Schillebeeckx, P; Schmidt, S; Schumann, D; Tagliente, G; Tain, J L; Tarrío, D; Tassan-Got, L; Tsinganis, A; Vannini, G; Variale, V; Vaz, P; Ventura, A; Vermeulen, M J; Vlachoudis, V; Vlastou, R; Wallner, A; Ware, T; Weigand, M; Weiß, C; Wright, T; Žugec, P
2014-01-01
We have used the 4 pi BaF2 gamma-ray detector array at the n\\_TOF neutron time-of-flight facility at CERN for an experiment in order to determine the spins of resonances of n+Sr-87 by measuring the gamma-ray spectra and multiplicity distributions. The first results are presented here. We have assigned the orbital momentum l to all evaluated resonances on the basis of their neutron widths. Further we have assigned the spin J to 16 s-wave resonances on based the population of low-lying levels.
Prakash Nepal; Peter J. Ince; Kenneth E. Skog; Sun J. Chang
2012-01-01
This paper describes a set of empirical net forest growth models based on forest growing-stock density relationships for three U.S. regions (North, South, and West) and two species groups (softwoods and hardwoods) at the regional aggregate level. The growth models accurately predict historical U.S. timber inventory trends when we incorporate historical timber harvests...
In this study, we used data from an OPC, and LOPC, and vertical net tows to estimate densities and describe the day/night vertical distribution of Mysis at a series of stations distributed throughout Lake Superior, and to evaluate the efficacy of using (L)OPC for examining DVM of...
O, Sungmin; Foelsche, U.; Kirchengast, G.; Fuchsberger, J.
2018-01-01
Eight years of daily rainfall data from WegenerNet were analyzed by comparison with data from Austrian national weather stations. WegenerNet includes 153 ground level weather stations in an area of about 15 km × 20 km in the Feldbach region in southeast Austria. Rainfall has been measured by tipping bucket gauges at 150 stations of the network since the beginning of 2007. Since rain gauge measurements are considered close to true rainfall, there are increasing needs for WegenerNet data for the validation of rainfall data products such as remote sensing based estimates or model outputs. Serving these needs, this paper aims at providing a clearer interpretation on WegenerNet rainfall data for users in hydro-meteorological communities. Five clusters - a cluster consists of one national weather station and its four closest WegenerNet stations - allowed us close comparison of datasets between the stations. Linear regression analysis and error estimation with statistical indices were conducted to quantitatively evaluate the WegenerNet daily rainfall data. It was found that rainfall data between the stations show good linear relationships with an average correlation coefficient (r) of 0.97 , while WegenerNet sensors tend to underestimate rainfall according to the regression slope (0.87). For the five clusters investigated, the bias and relative bias were - 0.97 mm d-1 and - 11.5 % on average (except data from new sensors). The average of bias and relative bias, however, could be reduced by about 80 % through a simple linear regression-slope correction, with the assumption that the underestimation in WegenerNet data was caused by systematic errors. The results from the study have been employed to improve WegenerNet data for user applications so that a new version of the data (v5) is now available at the WegenerNet data portal (www.wegenernet.org).
Polarization dependence of the spin-density-wave excitations in single-domain chromium
Energy Technology Data Exchange (ETDEWEB)
Boeni, P. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Roessli, B. [Institut Max von Laue - Paul Langevin, 75 - Paris (France); Sternlieb, B.J. [Brookhaven (United States); Lorenzo, E. [Centre National de la Recherche Scientifique (CNRS), 38 - Grenoble (France); Werner, S.A. [Missouri (United States)
1997-09-01
A polarized neutron scattering experiment has been performed with a single-Q, single domain sample of chromium in a magnetic field of 4 T. It is confirmed that the longitudinal fluctuations are enhanced for small energy transfers and that the spin wave modes with {delta}S parallel to Q and {delta}S perpendicular to Q are similar. (author) 2 figs., 1 tab., 2 refs.
Low-frequency permittivity of spin-density wave in (TMTSF)2PF6 at low temperatures
DEFF Research Database (Denmark)
Nad, F.; Monceau, P.; Bechgaard, K.
1995-01-01
Conductivity and permittivity epsilon of(TMTSF)(2)PF6 have been measured at low frequencies of (10(2)-10(7) Hz) at low temperatures below the spin-density wave (SDW) transition temperature T-p. The temperature dependence of the conductivity shows a deviation from thermally activated behavior at T...... less than or equal to 2 K and a transition to hopping type conductivity. The frequency dependences of Re epsilon = epsilon' and Im epsilon = epsilon '' show log f scaling as it is typical for various disordered systems. The temperature dependence of epsilon' exhibits a maximum which shifts to lower...... evidence for a transition of the SDW conductor into a glassy-like state at low temperatures similarly to the case of charge density waves....
Energy Technology Data Exchange (ETDEWEB)
Wolff, Andrew B.; Pesce, Lorenzo L.; Wu, Jim S.; Smart, L.R.; Medvecky, Michael J.; Haims, Andrew H. [Yale University School of Medicine, Department of Diagnostic Radiology, P.O. Box 208042, New Haven, CT (United States)
2009-01-15
At our institution, fast spin-echo (FSE) proton density (PD) imaging is used to evaluate articular cartilage, while conventional spin-echo (CSE) T1-weighted sequences have been traditionally used to characterize meniscal pathology. We sought to determine if FSE PD-weighted sequences are equivalent to CSE T1-weighted sequences in the detection of meniscal tears, obviating the need to perform both sequences. We retrospectively reviewed the records of knee arthroscopies performed by two arthroscopy-focused surgeons from an academic medical center over a 2-year period. The preoperative MRI images were interpreted independently by two fellowship-trained musculoskeletal radiologists who graded the sagittal CSE T1 and FSE PD sequences at different sittings with grades 1-5, where 1 = normal meniscus, 2 = probable normal meniscus, 3 = indeterminate, 4 = probable torn meniscus, and 5 = torn meniscus. Each meniscus was divided into an anterior and posterior half, and these halves were graded separately. Operative findings provided the gold standard. Receiver operating characteristic (ROC) analysis was performed to compare the two sequences. There were 131 tears in 504 meniscal halves. Using ROC analysis, the reader 1 area under curve for FSE PD was significantly better than CSE T1 (0.939 vs. 0.902, >95% confidence). For reader 2, the difference met good criteria for statistical non-inferiority but not superiority (0.913 for FSE PD and 0.908 for CSE T1; >95% non-inferiority for difference at most of -0.027). FSE PD-weighted sequences, using our institutional protocol, are not inferior to CSE T1-weighted sequences for the detection of meniscal tears and may be superior. (orig.)
Xu, Xuefei; Yang, Ke R; Truhlar, Donald G
2014-05-13
Conventional time-dependent density functional theory (TDDFT) is based on a closed-shell Kohn-Sham (KS) singlet ground state with the adiabatic approximation, using either linear response (KS-LR) or the Tamm-Dancoff approximation (KS-TDA); these methods can only directly predict singly excited states. This deficiency can be overcome by using a triplet state as the reference in the KS-TDA approximation and "exciting" the singlet by a spin flip (SF) from the triplet; this is the method suggested by Krylov and co-workers, and we abbreviate this procedure as SF-KS-TDA. SF-KS-TDA can be applied either with the original collinear kernel of Krylov and co-workers or with a noncollinear kernel, as suggested by Wang and Ziegler. The SF-KS-TDA method does bring some new practical difficulties into play, but it can at least formally model doubly excited states and states with double-excitation character, so it might be more useful than conventional TDDFT (both KS-LR and KS-TDA) for photochemistry if these additional difficulties can be surmounted and if it is accurate with existing approximate exchange-correlation functionals. In the present work, we carried out calculations specifically designed to understand better the accuracy and limitations of the conventional TDDFT and SF-KS-TDA methods; we did this by studying closed-shell atoms and closed-shell monatomic cations because they provide a simple but challenging testing ground for what we might expect in studying the photochemistry of molecules with closed-shell ground states. To test their accuracy, we applied conventional KS-LR and KS-TDA and 18 versions of SF-KS-TDA (nine collinear and nine noncollinear) to the same set of vertical excitation energies (including both Rydberg and valence excitations) of Be, B(+), Ne, Na(+), Mg, and Al(+). We did this for 10 exchange-correlation functionals of various types, both local and nonlocal. We found that the GVWN5 and M06 functionals with nonlocal kernels in spin-flip calculations
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-03-01
Development of high performance spin valves formed by amorphous magnetic layer and head-medium interface with nano-thickness molecular film for realizing an ultra-high density of 20 Gbit/in{sup 2} using contact recording. The giant magnetoresistance effect was investigated for spin valves using very thin amorphous magnetic layer. In amorphous-CoFeB/Cu/ Co spin valves, the maximum MR ratio of 6% was achieved at the thickness of the amorphous layer of 2 nm. The spin valves with the amorphous layer exhibit very good thermal stability. Design guideline for molecularly thin lubricant was established using newly derived lubrication equation considering lubricant porosity. Novel method for accurately measuring surface force due to molecularly thin lubricant was developed by using Michelson interferometry to detect cantilever displacement, which enabled two-dimensional transient force measurement. (NEDO)
Xu, Jie; Chang, Chia-Chen; Walter, Eric J; Zhang, Shiwei
2011-12-21
The ground states of the two-dimensional repulsive Hubbard model are studied within the unrestricted Hartree-Fock (UHF) theory. Magnetic and charge properties are determined by systematic, large-scale, exact numerical calculations, and quantified as a function of electron doping, h. In the solution of the self-consistent UHF equations, multiple initial configurations and simulated annealing are used to facilitate convergence to the global minimum. New approaches are employed to minimize finite-size effects in order to reach the thermodynamic limit. At low to moderate interacting strengths and low doping, the UHF ground state is a linear spin-density wave (l-SDW), with antiferromagnetic order and a modulating wave. The wavelength of the modulating wave is 2/h. Corresponding charge order exists but is substantially weaker than the spin order, hence holes are mobile. As the interaction is increased, the l-SDW states evolve into several different phases, with the holes eventually becoming localized. A simple pairing model is presented with analytic calculations for low interaction strength and small doping, to help understand the numerical results and provide a physical picture for the properties of the SDW ground state. By comparison with recent many-body calculations, it is shown that, for intermediate interactions, the UHF solution provides a good description of the magnetic correlations in the true ground state of the Hubbard model. © 2011 IOP Publishing Ltd Printed in the UK & the USA
Kaushal, Nitin; Herbrych, Jacek; Nocera, Alberto; Alvarez, Gonzalo; Moreo, Adriana; Reboredo, F. A.; Dagotto, Elbio
2017-10-01
Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ , at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase to an excitonic insulator with increasing λ at intermediate U . In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum 〈(Jeff)2〉≠0 near the excitonic phase, smoothly connected to the 〈(Jeff)2〉=0 regime. We also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.
Energy Technology Data Exchange (ETDEWEB)
Afzali, R., E-mail: afzali@kntu.ac.ir [Department of Physics, K. N. Toosi University of Technology, Tehran, 15418 (Iran, Islamic Republic of); Ebrahimian, N., E-mail: n.ebrahimian@shahed.ac.ir [Department of Physics, Faculty of Basic Sciences, Shahed University, Tehran, 18155-159 (Iran, Islamic Republic of); Eghbalifar, B., E-mail: b.eghbali2011@yahoo.com [Department of Agricultural Management, Marvdasht Branch, Azad University, Marvdasht (Iran, Islamic Republic of)
2016-10-07
Highlights: • In contrast to a s-wave superconductor, the quantum correlation of the d-wave superconductor is sensitive to the change of the gap magnitude. • Quantum discord of the d-wave superconductor oscillates. • Quantum discord becomes zero at a characteristic length of the d-wave superconductor. • Quantum correlation strongly depends on the length of grain. Length of the superconductor lower, the quantum correlation length higher. • Quantum tripartite entanglement for a nano-scale d-wave superconductor is better than for a bulk d-wave superconductor. - Abstract: By approximating the energy gap, entering nano-size effect via gap fluctuation and calculating the Green's functions and the space-spin density matrix, the dependence of quantum correlation (entanglement, discord and tripartite entanglement) on the relative distance of two electron spins forming Cooper pairs, the energy gap and the length of bulk and nano interacting Fermi system (a nodal d-wave superconductor) is determined. In contrast to a s-wave superconductor, quantum correlation of the system is sensitive to the change of the gap magnitude and strongly depends on the length of the grain. Also, quantum discord oscillates. Furthermore, the entanglement length and the correlation length are investigated. Discord becomes zero at a characteristic length of the d-wave superconductor.
Energy Technology Data Exchange (ETDEWEB)
Fawcett, E. [Toronto Univ., ON (Canada). Dept. of Physics
1997-08-01
Decreasing the volume by applying pressure in many Cr alloy systems Cr{sub 1-x}A{sub x} produces a similar magnetic phase diagram to that obtained at ambient pressure by changing the concentration x of the dopant A. In several cases a decrease in electron concentration, in a rigid-band model, parallels a decrease in volume (and conversely). The experimental data are reviewed in terms of a universal magnetic phase diagram. It is proposed, in view of the failure of the canonical model of nesting electron and hole Fermi surfaces, which is commonly used to account for variation with composition of the magnetic properties of spin-density-wave Cr alloys, to explain the close parallelism between the effects of pressure and alloy composition, that their strong volume dependence has a quite different origin. The use of the magnetic anomalies around the ordering temperature in the thermal expansion and the bulk modulus is critically reviewed. (orig.). 25 refs.
Directory of Open Access Journals (Sweden)
Mahdi Afshar
2013-11-01
Full Text Available We have demonstrated electronic structure and magnetic properties of Cu3, Ag3 and Au3 trimers using a full potential local orbital method in the framework of relativistic density functional theory. We have also shown that the non-relativistic generalized gradient approximation for the exchange-correlation energy functional gives reliable magnetic properties in coinage metal trimers compared to experiment. In addition we have indicated that the spin-orbit coupling changes the structure and magnetic properties of gold trimer while the structure and magnetic properties of copper and silver trimers are marginally affected. A significant orbital moment of 0.21μB was found for most stable geometry of the gold trimer whereas orbital magnetism is almost quenched in the copper and silver trimers.
Polarized proton spin density images the tyrosyl radical locations in bovine liver catalase
Directory of Open Access Journals (Sweden)
Oliver Zimmer
2016-09-01
Full Text Available A tyrosyl radical, as part of the amino acid chain of bovine liver catalase, supports dynamic proton spin polarization (DNP. Finding the position of the tyrosyl radical within the macromolecule relies on the accumulation of proton polarization close to it, which is readily observed by polarized neutron scattering. The nuclear scattering amplitude due to the polarization of protons less than 10 Å distant from the tyrosyl radical is ten times larger than the amplitude of magnetic neutron scattering from an unpaired polarized electron of the same radical. The direction of DNP was inverted every 5 s, and the initial evolution of the intensity of polarized neutron scattering after each inversion was used to identify those tyrosines which have assumed a radical state. Three radical sites, all of them close to the molecular centre and the haem, appear to be equally possible. Among these is tyr-369, the radical state of which had previously been proven by electron paramagnetic resonance.
Spin density waves predicted in zigzag puckered phosphorene, arsenene and antimonene nanoribbons
Xiaohua Wu; Xiaoli Zhang; Xianlong Wang; Zhi Zeng
2016-01-01
The pursuit of controlled magnetism in semiconductors has been a persisting goal in condensed matter physics. Recently, Vene (phosphorene, arsenene and antimonene) has been predicted as a new class of 2D-semiconductor with suitable band gap and high carrier mobility. In this work, we investigate the edge magnetism in zigzag puckered Vene nanoribbons (ZVNRs) based on the density functional theory. The band structures of ZVNRs show half-filled bands crossing the Fermi level at the midpoint of r...
Pletyukhov, Mikhail; Shnirman, Alexander
2009-01-01
We consider the magnetic response of a two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit coupling to a microwave excitation. We generalize the results of Shnirman and Martin [Europhys. Lett. 78, 27001 (2007)], where pure Rashba coupling was studied. We observe that the microwave with the in-plane electric field and the out-of-plane magnetic field creates an out-of-plane spin polarization. The effect is more prominent in clean systems with resolved spin-orbit-split subbands. Considered as response to the microwave magnetic field, the spin-orbit contribution to the magnetization far exceeds the usual Zeeman contribution in the clean limit. The effect vanishes when the Rashba and the Dresselhaus couplings have equal strength.
Wittkop, C
2000-01-01
In the framework of this thesis it was successfully shown that a spin- selective measurement of the unoccupied density od states by means of resonant inelastic X-ray scattering is possible. Especially for this studies were performed on the unoccupied 5d conduction band of EuO. As essential results it can be stated that a temperature- dependent shift of the 5d arrow up to the 5d arrow down density of states is present.
A density functional theory investigation of the electronic structure and spin moments of magnetite
Noh, Junghyun
2014-08-01
We present the results of density functional theory (DFT) calculations on magnetite, Fe3O4, which has been recently considered as electrode in the emerging field of organic spintronics. Given the nature of the potential applications, we evaluated the magnetite room-temperature cubic phase in terms of structural, electronic, and magnetic properties. We considered GGA (PBE), GGA + U (PBE + U), and range-separated hybrid (HSE06 and HSE(15%)) functionals. Calculations using HSE06 and HSE(15%) functionals underline the impact that inclusion of exact exchange has on the electronic structure. While the modulation of the band gap with exact exchange has been seen in numerous situations, the dramatic change in the valence band nature and states near the Fermi level has major implications for even a qualitative interpretation of the DFT results. We find that HSE06 leads to highly localized states below the Fermi level while HSE(15%) and PBE + U result in delocalized states around the Fermi level. The significant differences in local magnetic moments and atomic charges indicate that describing room-temperature bulk materials, surfaces and interfaces may require different functionals than their low-temperature counterparts.
Jiang, Kun; Zhang, Yi; Zhou, Sen; Wang, Ziqiang
2015-05-29
We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping t_{1} and second nearest-neighbor hopping t_{2}, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction U induces antiferromagnetic (AF) chiral spin density wave (χSDW) order in a wide range of κ=t_{2}/t_{1} where both the two-sublattice AF order at small κ and the decoupled three-sublattice 120° order at large κ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a χSDW semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a χSDW insulator with a zero total Chern number but an anomalous ac Hall effect. The χSDW is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.
Energy Technology Data Exchange (ETDEWEB)
Di, Ningning; Pang, Haopeng; Ren, Yan; Yao, Zhenwei; Feng, Xiaoyuan [Huashan Hospital Fudan University, Department of Radiology, Shanghai (China); Dang, Xuefei [Shang Hai Gamma Knife Hospital, Shanghai (China); Cheng, Wenna [Binzhou Medical University Affiliated Hospital, Department of Pharmacy, Binzhou (China); Wu, Jingsong; Yao, Chengjun [Huashan Hospital Fudan University, Department of Neurosurgery, Shanghai (China)
2017-01-15
This study was designed to determine if cerebral blood flow (CBF) derived from arterial spin labeling (ASL) perfusion imaging could be used to quantitatively evaluate the microvascular density (MVD) of brain gliomas on a ''point-to-point'' basis by matching CBF areas and surgical biopsy sites as accurate as possible. The study enrolled 47 patients with treatment-naive brain gliomas who underwent preoperative ASL, 3D T1-weighted imaging with gadolinium contrast enhancement (3D T1C+), and T2 fluid acquisition of inversion recovery (T2FLAIR) sequences before stereotactic surgery. We histologically quantified MVD from CD34-stained sections of stereotactic biopsies and co-registered biopsy locations with localized CBF measurements. The correlation between CBF and MVD was determined using Spearman's correlation coefficient. P ≤.05 was considered statistically significant. Of the 47 patients enrolled in the study, 6 were excluded from the analysis because of brain shift or poor co-registration and localization of the biopsy site during surgery. Finally, 84 biopsies from 41 subjects were included in the analysis. CBF showed a statistically significant positive correlation with MVD (ρ = 0.567; P =.029). ASL can be a useful noninvasive perfusion MR method for quantitative evaluation of the MVD of brain gliomas. (orig.)
Lecomte, Xavier; Fedriani, José M; Caldeira, Maria C; Clemente, Adelaide S; Olmi, Alessandro; Bugalho, Miguel N
2016-01-01
Plant-animal interactions imply costs and benefits with net balance depending on interacting species and ecological context. Ungulates, in particular, confer costs (e.g., plant leaf consumption, flower bud predation) and benefits (e.g., plant overcompensation, seed dispersal) to plants. Magnitude of costs and benefits may be altered by habitat management or ecological conditions favoring high density ungulate populations. Little is known however on whether plant costs or benefits predominate over the years, or the long-term outcomes of plant-animal interactions in habitat types sustaining high density ungulate populations. We investigated how high density ungulate populations alter plant costs and benefits by quantifying ungulate long-term effects on the shrub Cistus ladanifer (Cistaceae) individual size, seed weight and number, seed bank, and population density, through a 12-year ungulate exclusion experiment in a Mediterranean scrubland. We monitored plant size and flower buds in plants exposed or protected from ungulates and number of developed capsules and seeds consumed (potential seed dispersal) by ungulates during three reproductive seasons. We found that ungulates negatively affected shrub size and led to a dramatically decline of shrub reproductive structures and seed production, affecting the plant reproductive cycle. Number of buds was 27 times higher and number of developed seed 5 times higher in ungulate-excluded as compared to ungulate-exposed plots. After 9 years of ungulate exclusion, the C. ladanifer seed bank was 2.6 times higher in ungulate-excluded plots. The population density of C. ladanifer was 4 times higher in ungulate-excluded plots. Our long-term experiment showed that high density ungulate populations can alter plant-animal interactions by reducing plant benefits and increasing plant costs.
Directory of Open Access Journals (Sweden)
Xavier Lecomte
Full Text Available Plant-animal interactions imply costs and benefits with net balance depending on interacting species and ecological context. Ungulates, in particular, confer costs (e.g., plant leaf consumption, flower bud predation and benefits (e.g., plant overcompensation, seed dispersal to plants. Magnitude of costs and benefits may be altered by habitat management or ecological conditions favoring high density ungulate populations. Little is known however on whether plant costs or benefits predominate over the years, or the long-term outcomes of plant-animal interactions in habitat types sustaining high density ungulate populations. We investigated how high density ungulate populations alter plant costs and benefits by quantifying ungulate long-term effects on the shrub Cistus ladanifer (Cistaceae individual size, seed weight and number, seed bank, and population density, through a 12-year ungulate exclusion experiment in a Mediterranean scrubland. We monitored plant size and flower buds in plants exposed or protected from ungulates and number of developed capsules and seeds consumed (potential seed dispersal by ungulates during three reproductive seasons. We found that ungulates negatively affected shrub size and led to a dramatically decline of shrub reproductive structures and seed production, affecting the plant reproductive cycle. Number of buds was 27 times higher and number of developed seed 5 times higher in ungulate-excluded as compared to ungulate-exposed plots. After 9 years of ungulate exclusion, the C. ladanifer seed bank was 2.6 times higher in ungulate-excluded plots. The population density of C. ladanifer was 4 times higher in ungulate-excluded plots. Our long-term experiment showed that high density ungulate populations can alter plant-animal interactions by reducing plant benefits and increasing plant costs.
Abreu, P; Adye, T; Alekseev, G D; Alemany, R; Allport, P P; Almehed, S; Amaldi, Ugo; Amato, S; Andersson, P; Andreazza, A; Antilogus, P; Apel, W D; Arnoud, Y; Åsman, B; Augustin, J E; Augustinus, A; Baillon, Paul; Bambade, P; Barão, F; Barbi, M S; Barbiellini, Guido; Bardin, Dimitri Yuri; Barker, G; Baroncelli, A; Bärring, O; Bates, M J; Battaglia, Marco; Baubillier, M; Baudot, J; Becks, K H; Begalli, M; Beillière, P; Belokopytov, Yu A; Benvenuti, Alberto C; Bérat, C; Berggren, M; Bertini, D; Bertrand, D; Besançon, M; Bianchi, F; Bigi, M; Bilenky, S M; Billoir, P; Bizouard, M A; Bloch, D; Blume, M; Bonesini, M; Bonivento, W; Booth, P S L; Borgland, A W; Borisov, G; Bosio, C; Botner, O; Boudinov, E; Bouquet, B; Bourdarios, C; Bowcock, T J V; Bozzo, M; Branchini, P; Brand, K D; Brenke, T; Brenner, R A; Bricman, C; Brown, R C A; Brückman, P; Brunet, J M; Bugge, L; Buran, T; Burgsmüller, T; Buschmann, P; Cabrera, S; Caccia, M; Calvi, M; Camacho-Rozas, A J; Camporesi, T; Canale, V; Canepa, M; Cao, F; Carena, F; Carroll, L; Caso, Carlo; Castillo-Gimenez, M V; Cattai, A; Cavallo, F R; Chabaud, V; Chapkin, M M; Charpentier, P; Chaussard, L; Checchia, P; Chelkov, G A; Chen, M; Chierici, R; Chliapnikov, P V; Chochula, P; Chorowicz, V; Chudoba, J; Cindro, V; Collins, P; Contri, R; Cortina, E; Cosme, G; Cossutti, F; Cowell, J H; Crawley, H B; Crennell, D J; Crosetti, G; Cuevas-Maestro, J; Czellar, S; Dahm, J; D'Almagne, B; Dam, M; Damgaard, G; Dauncey, P D; Davenport, Martyn; Da Silva, W; Deghorain, A; Della Ricca, G; Delpierre, P A; Demaria, N; De Angelis, A; de Boer, Wim; De Brabandere, S; De Clercq, C; La Vaissière, C de; De Lotto, B; De Min, A; De Paula, L S; Dijkstra, H; Di Ciaccio, Lucia; Di Diodato, A; Djannati, A; Dolbeau, J; Doroba, K; Dracos, M; Drees, J; Drees, K A; Dris, M; Durand, J D; Edsall, D M; Ehret, R; Eigen, G; Ekelöf, T J C; Ekspong, Gösta; Elsing, M; Engel, J P; Erzen, B; Espirito-Santo, M C; Falk, E; Fanourakis, G K; Fassouliotis, D; Feindt, Michael; Fenyuk, A; Ferrari, P; Ferrer, A; Fichet, S; Filippas-Tassos, A; Firestone, A; Fischer, P A; Föth, H; Fokitis, E; Fontanelli, F; Formenti, F; Franek, B J; Frodesen, A G; Frühwirth, R; Fulda-Quenzer, F; Fuster, J A; Galloni, A; Gamba, D; Gandelman, M; García, C; García, J; Gaspar, C; Gasparini, U; Gavillet, P; Gazis, E N; Gelé, D; Gerber, J P; Gerdyukov, L N; Gokieli, R; Golob, B; Gonçalves, P; Gopal, Gian P; Gorn, L; Górski, M; Guz, Yu; Gracco, Valerio; Graziani, E; Green, C; Grefrath, A; Gris, P; Grosdidier, G; Grzelak, K; Günther, M; Guy, J; Hahn, F; Hahn, S; Hajduk, Z; Hallgren, A; Hamacher, K; Harris, F J; Hedberg, V; Henriques, R P; Hernández, J J; Herquet, P; Herr, H; Hessing, T L; Heuser, J M; Higón, E; Holmgren, S O; Holt, P J; Holthuizen, D J; Hoorelbeke, S; Houlden, M A; Hrubec, Josef; Huet, K; Hultqvist, K; Jackson, J N; Jacobsson, R; Jalocha, P; Janik, R; Jarlskog, C; Jarlskog, G; Jarry, P; Jean-Marie, B; Johansson, E K; Jönsson, L B; Jönsson, P E; Joram, Christian; Juillot, P; Kaiser, M; Kapusta, F; Karafasoulis, K; Katsanevas, S; Katsoufis, E C; Keränen, R; Khokhlov, Yu A; Khomenko, B A; Khovanskii, N N; King, B J; Kjaer, N J; Klapp, O; Klein, H; Kluit, P M; Knoblauch, D; Kokkinias, P; Koratzinos, M; Korcyl, K; Kostyukhin, V; Kourkoumelis, C; Kuznetsov, O; Krammer, Manfred; Kreuter, C; Kronkvist, I J; Krstic, J; Krumshtein, Z; Krupinski, W; Kubinec, P; Kucewicz, W; Kurvinen, K L; Lacasta, C; Laktineh, I; Lamsa, J; Lanceri, L; Lane, D W; Langefeld, P; Laugier, J P; Lauhakangas, R; Leder, Gerhard; Ledroit, F; Lefébure, V; Legan, C K; Leisos, A; Leitner, R; Lemonne, J; Lenzen, Georg; Lepeltier, V; Lesiak, T; Libby, J; Liko, D; Lipniacka, A; Lippi, I; Lörstad, B; Loken, J G; López, J M; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J N; Maehlum, G; Mahon, J R; Maio, A; Malmgren, T G M; Malychev, V; Mandl, F; Marco, J; Marco, R P; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Martínez-Rivero, C; Martínez-Vidal, F; Martí i García, S; Masik, J; Matorras, F; Matteuzzi, C; Matthiae, Giorgio; Mazzucato, M; McCubbin, M L; McKay, R; McNulty, R; McPherson, G; Medbo, J; Meroni, C; Meyer, S; Meyer, W T; Myagkov, A; Michelotto, M; Migliore, E; Mirabito, L; Mitaroff, Winfried A; Mjörnmark, U; Moa, T; Møller, R; Mönig, K; Monge, M R; Morettini, P; Müller, H; Münich, K; Mulders, M; Mundim, L M; Murray, W J; Muryn, B; Myatt, Gerald; Myklebust, T; Naraghi, F; Navarria, Francesco Luigi; Navas, S; Nawrocki, K; Negri, P; Némécek, S; Neumann, W; Neumeister, N; Nicolaidou, R; Nielsen, B S; Nieuwenhuizen, M; Nikolaenko, V; Nikolenko, M; Niss, P; Nomerotski, A; Normand, Ainsley; Nygren, A; Oberschulte-Beckmann, W; Obraztsov, V F; Olshevskii, A G; Onofre, A; Orava, Risto; Orazi, G; Österberg, K; Ouraou, A; Paganini, P; Paganoni, M; Pain, R; Palka, H; Papadopoulou, T D; Papageorgiou, K; Pape, L; Parkes, C; Parodi, F; Parzefall, U; Passeri, A; Pegoraro, M; Peralta, L; Pernegger, H; Pernicka, Manfred; Perrotta, A; Petridou, C; Petrolini, A; Phillips, H T; Piana, G; Pierre, F; Pimenta, M; Podobnik, T; Podobrin, O; Pol, M E; Polok, G; Poropat, P; Pozdnyakov, V; Privitera, P; Pukhaeva, N; Pullia, Antonio; Radojicic, D; Ragazzi, S; Rahmani, H; Ratoff, P N; Read, A L; Reale, M; Rebecchi, P; Redaelli, N G; Regler, Meinhard; Reid, D; Reinhardt, R; Renton, P B; Resvanis, L K; Richard, F; Rídky, J; Rinaudo, G; Røhne, O M; Romero, A; Ronchese, P; Roos, L; Rosenberg, E I; Rosinsky, P; Roudeau, Patrick; Rovelli, T; Ruhlmann-Kleider, V; Ruiz, A; Rybicki, K; Saarikko, H; Sacquin, Yu; Sadovskii, A; Sajot, G; Salt, J; Sannino, M; Schneider, H; Schwickerath, U; Schyns, M A E; Sciolla, G; Scuri, F; Seager, P; Sedykh, Yu; Segar, A M; Seitz, A; Sekulin, R L; Serbelloni, L; Shellard, R C; Sheridan, A; Siegrist, P; Silvestre, R; Simonetto, F; Sissakian, A N; Skaali, T B; Smadja, G; Smirnov, N; Smirnova, O G; Smith, G R; Sokolov, A; Solovyanov, O; Sosnowski, R; Souza-Santos, D; Spassoff, Tz; Spiriti, E; Sponholz, P; Squarcia, S; Stampfer, D; Stanescu, C; Stanic, S; Stapnes, Steinar; Stavitski, I; Stevenson, K; Stocchi, A; Strauss, J; Strub, R; Stugu, B; Szczekowski, M; Szeptycka, M; Tabarelli de Fatis, T; Tavernet, J P; Tegenfeldt, F; Terranova, F; Thomas, J; Tilquin, A; Timmermans, J; Tkatchev, L G; Todorov, T; Todorova, S; Toet, D Z; Tomaradze, A G; Tonazzo, A; Tortora, L; Tranströmer, G; Treille, D; Tristram, G; Trombini, A; Troncon, C; Tsirou, A L; Turluer, M L; Tyapkin, I A; Tyndel, M; Tzamarias, S; Überschär, B; Ullaland, O; Uvarov, V; Valenti, G; Vallazza, E; van Apeldoorn, G W; van Dam, P; Van Eldik, J; Van Lysebetten, A; Vassilopoulos, N; Vegni, G; Ventura, L; Venus, W A; Verbeure, F; Verlato, M; Vertogradov, L S; Vilanova, D; Vincent, P; Vitale, L; Vlasov, E; Vodopyanov, A S; Vrba, V; Wahlen, H; Walck, C; Weiser, C; Wetherell, Alan M; Wicke, D; Wickens, J H; Wielers, M; Wilkinson, G R; Williams, W S C; Winter, M; Witek, M; Wlodek, T; Yi, J; Yip, K; Yushchenko, O P; Zach, F; Zaitsev, A; Zalewska-Bak, A; Zalewski, Piotr; Zavrtanik, D; Zevgolatakos, E; Zimin, N I; Zucchelli, G C; Zumerle, G
1997-01-01
The spin density matrix elements for the $\\rho^0$, K$^{*0}(892)$ and $\\phi$ produced in hadronic Z$^0$ decays are measured in the DELPHI detector. There is no evidence for spin alignment of the K$^{*0}(892)$ and $\\phi$ in the region $x_p \\leq 0.3$ ($x_p = p/p_{beam}$), where $\\rho_{00} = 0.33 \\pm 0.05$ and $\\rho_{00} = 0.30 \\pm 0.04$, respectively. In the fragmentation region, $x_p \\geq 0.4$, there is some indication for spin alignment of the $\\rho^0$ and K$^{*0}(892)$, since $\\rho_{00} = 0.43 \\pm 0.05$ and $\\rho_{00} = 0.46 \\pm 0.08$, respectively. These values are compared with those found in meson-induced hadronic reactions. For the $\\phi$, $\\rho_{00} = 0.30 \\pm 0.04$ for $x_p \\geq 0.4$ and $0.55 \\pm 0.10$ for $x_p \\geq 0.7$. The off-diagonal spin density matrix element $\\rho_{1-1}$ is consistent with zero in all cases.
DEFF Research Database (Denmark)
Zarycz, M. Natalia C.; Provasi, Patricio F.; Sauer, Stephan P. A.
2015-01-01
It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCC), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections......-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated...... to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states....
Malet, F.; Pi, M.; Barranco, M.; Lipparini, E.; Serra, Ll.
2006-11-01
We have investigated the dipole charge- and spin-density response of few-electron two-dimensional concentric nanorings as a function of the intensity of a perpendicularly applied magnetic field. We show that the dipole response displays signatures associated with the localization of electron states in the inner and outer ring favored by the perpendicularly applied magnetic field. Electron localization produces a more fragmented spectrum due to the appearance of additional edge excitations in the inner and outer ring.
Level Density in 51V at spin 9/2-15/2 Measured with the 50V(n,γ) Reaction
Michaelsen, S.; Lieb, K. P.; Robinson, S. J.
1991-10-01
Neutron capture in 50V(IT = 6+) was studied at the ILL high flux reactor and nearly 60 states in the spin range [9/2,15/2] were identified leading to a ``complete'' level scheme up to 5.5 MeV. Fermi gas model level density parameters were deduced. The energy scaling of the primary dipole spectrum and its correlation with the p-wave neutron-transfer strength are discussed.
Energy Technology Data Exchange (ETDEWEB)
Jiang, J H; Wu, M W, E-mail: mwwu@ustc.edu.c [Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026 (China)
2009-12-07
We comment on the conclusion by Teng et al (2009 J. Phys. D: Appl. Phys. 42 135111) that the Bir-Aronov-Pikus mechanism is more important than the D'yakonov-Perel' mechanism at a high carrier density in intrinsic bulk GaAs. We point out that the spin relaxation is solely from the D'yakonov-Perel' mechanism. (comment)
Energy Technology Data Exchange (ETDEWEB)
Embaid, B.P., E-mail: pembaid@fisica.ciens.ucv.ve [Laboratorio de Magnetismo, Escuela de Fisica, Universidad Central de Venezuela, Apartado 47586, Los Chaguaramos, Caracas 1041-A (Venezuela, Bolivarian Republic of); Gonzalez-Jimenez, F. [Laboratorio de Magnetismo, Escuela de Fisica, Universidad Central de Venezuela, Apartado 47586, Los Chaguaramos, Caracas 1041-A (Venezuela, Bolivarian Republic of)
2013-03-15
Iron-vanadium sulfides of the monoclinic system Fe{sub x}V{sub 3-x}S{sub 4} (1.0{<=}x{<=}2.0) have been investigated by {sup 57}Fe Moessbauer Spectroscopy in the temperature range 30-300 K. Incommensurate spin density waves (SDW) have been found in this system. An alternative treatment of the spectra allows a direct measurement of the temperature evolution of condensate density of the SDW state which follows the Maki-Virosztek formula. For composition (x=1.0) the SDW condensate is unpinned while for compositions (x>1.0) the SDW condensate is pinned. Possible causes of the pinning-unpinning SDW will be discussed. - Highlights: Black-Right-Pointing-Pointer Fe{sub x}V{sub 3-x}S{sub 4}(1.0{<=}x{<=}2.0) system was investigated by {sup 57}Fe Moessbauer Spectroscopy. Black-Right-Pointing-Pointer Incommensurate spin density wave (SDW) has been found in this system. Black-Right-Pointing-Pointer We report the temperature evolution of the condensate density of SDW state. Black-Right-Pointing-Pointer For composition (x=1.0) the SDW is unpinned while for (x>1.0) is pinned.
Devolder, Thibaut
2017-09-01
We study how the shape of the spin-wave resonance lines in rf voltage induced FMR can be used to extract the spin-wave density of states and the Gilbert damping within the precessing layer in nanoscale magnetic tunnel junctions that possess perpendicular magnetic anisotropy. We work with a field applied along the easy axis to preserve the cylindrical symmetry of the uniaxial perpendicularly magnetized systems. We first describe the experimental setup to study the susceptibility contributions of the spin waves in the field-frequency space. We then identify experimentally the maximum device size above which the spin waves confined in the free layer can no longer be studied in isolation as the linewidths of their discrete responses make them overlap into a continuous density of states. The rf voltage induced signal is the sum of two voltages that have comparable magnitudes: a first voltage that originates from the linear transverse susceptibility and rectification by magnetoresistance and a second voltage that arises from the nonlinear longitudinal susceptibility and the resultant time-averaged change of the exact micromagnetic configuration of the precessing layer. The transverse and longitudinal susceptibility signals have different dc bias dependencies such that they can be separated by measuring how the device rectifies the rf voltage at different dc bias voltages. The transverse and longitudinal susceptibility signals have different line shapes; their joint studies in both fixed field-variable frequency, or fixed frequency-variable field configurations can yield the Gilbert damping of the free layer of the device with a degree of confidence that compares well with standard ferromagnetic resonance. Our method is illustrated on FeCoB-based free layers in which the individual spin waves can be sufficiently resolved only for disk diameters below 200 nm. The resonance line shapes on devices with 90-nm diameters are consistent with a Gilbert damping of 0.011 . A single
Huhn, William P.; Blum, Volker
2017-08-01
We quantify the accuracy of different non-self-consistent and self-consistent spin-orbit coupling (SOC) treatments in Kohn-Sham and hybrid density functional theory by providing a band-structure benchmark set for the valence and low-lying conduction energy bands of 103 inorganic compounds, covering chemical elements up to polonium. Reference energy band structures for the PBE density functional are obtained using the full-potential (linearized) augmented plane wave code wien2k, employing its self-consistent treatment of SOC including Dirac-type p1 /2 orbitals in the basis set. We use this benchmark set to benchmark a computationally simpler, non-self-consistent all-electron treatment of SOC based on scalar-relativistic orbitals and numeric atom-centered orbital basis functions. For elements up to Z ≈50 , both treatments agree virtually exactly. For the heaviest elements considered (Tl, Pb, Bi, Po), the band-structure changes due to SOC are captured with a relative deviation of 11% or less. For different density functionals (PBE versus the hybrid HSE06), we show that the effect of spin-orbit coupling is usually similar but can be dissimilar if the qualitative features of the predicted underlying scalar-relativistic band structures do not agree. All band structures considered in this work are available online via the NOMAD repository to aid in future benchmark studies and methods development.
Márquez Cruz, Antonio Marcial; Pacheco, Laura C.; Fernández Sanz, Javier
2017-01-01
We present in this work density functional theory calculations of the structural and electronic properties of (PbS)n nanoparticles with n=4-32. Particular care has been taken on the correct description of their electronic structure by using a hybrid functional including the spin-orbit coupling effects. We demonstrate that the bonding in PbS nanoparticles is quite different from bulk PbS as the six Pb-S bonds around a single Pb atom are found to have a different character while in bulk PbS all...
Caffarel, Michel; Scemama, Anthony; Ramírez-Solís, Alejandro
2014-01-01
We present a comparative study of the spatial distribution of the spin density (SD) of the ground state of CuCl2 using Density Functional Theory (DFT), quantum Monte Carlo (QMC), and post-Hartree-Fock wavefunction theory (WFT). A number of studies have shown that an accurate description of the electronic structure of the lowest-lying states of this molecule is particularly challenging due to the interplay between the strong dynamical correlation effects in the 3d shell of the copper atom and the delocalization of the 3d hole over the chlorine atoms. It is shown here that qualitatively different results for SD are obtained from these various quantum-chemical approaches. At the DFT level, the spin density distribution is directly related to the amount of Hartree-Fock exchange introduced in hybrid functionals. At the QMC level, Fixed-node Diffusion Monte Carlo (FN-DMC) results for SD are strongly dependent on the nodal structure of the trial wavefunction employed (here, Hartree-Fock or Kohn-Sham with a particula...
Williams, Mike
This work presents measurements of differential cross sections, dsigma/dcos qwCM , and spin density matrix elements, r0MM' , for the reaction gammap → po in the energy range 1.72 GeVjob of describing our data. In particular, u-channel models fail to reproduce our highest energy backwards r0MM' measurements. A mass-independent partial wave analysis has also been performed. Near threshold, the dominant resonance contributions extracted are the **** F15 (1680) and *** D 13(1700). Together with the t-channel pi0 exchange, these three waves provide a remarkably good description of our differential cross section and spin density matrix element measurements for s < 2 GeV. Strong, but not conclusive, evidence for the **** G17(2190) has also been extracted. Improved non-resonant models may be necessary to irrefutably show whether this state contributes to o photoproduction. Evidence for missing resonances is suggestive, but inconclusive without theoretical input.
Rojas-Sanchez, J.-Carlos; Pham, T.-H.; Vallobra, P.; Lacour, D.; Malinowski, G.; Hehn, M.; Mangin, S.; Cyrille, M.-C.; Je, S.-G.; Gaudin, G.; Boulle, O.
We show the SOT-switching of perpendicularly magnetized //W(3nm)/CoxTb1-x(3.5nm)/AlOx(3nm) structure. Ferrimagnetic alloys allow us to tune the net magnetic moment by varying the Co concentration. Samples were grown by sputtering on Si-SiO2 substrates and characterized by MOKE and SQUID measurements which allow us to estimate the critical compensation where the net moment reaches zero at room temperature. Then we studied the magnetization reversal in Hall crosses by analyzing the anomalous Hall Effect (AHE) when applying in-plane current pulses and an in-plane field Hx parallel to the current direction. A minimum Hx of the order of 1 mT is needed for fully reverse the magnetization. The full reversal of magnetization has been observed in all our samples. More importantly, critical current densities for switching were found to decrease systematic when decreasing the Co concentration even in the Tb rich compositions samples. Our results bring out the role of different concentration of Co in CoxTb1-x alloys on SOT-switching providing a method to reduce the current density using ferrimagnetic alloys.
Freire, Hermann
2017-06-01
We compute the Hall angle and the magnetoresistance of the spin-fermion model, which is a successful phenomenological theory to describe the physics of the cuprates and iron-based superconductors within a wide range of doping regimes. We investigate both the role of the spin-fermion interaction that couples the large-momentum antiferromagnetic fluctuations to the so-called “hot-spots” at the Fermi surface and also of an effective higher-order composite operator in the theory. The latter operator provides a scattering mechanism such that the momentum transfer for the fermions close to the Fermi surface can be small. We also include weak disorder that couples to both the bosonic order-parameter field and the fermionic degrees of freedom. Since the quasiparticle excitations were shown in recent works to be destroyed at the “hot-spots” in the low-energy limit of the model, we employ the Mori-Zwanzig memory matrix approach that permits the evaluation of all transport coefficients without assuming well-defined Landau quasiparticles in the system. We then apply this transport theory to discuss universal metallic-state properties as a function of temperature and magnetic field of the cuprates from the perspective of their fermiology, which turn out to be in qualitative agreement with key experiments in those materials.
DEFF Research Database (Denmark)
de Souza e Silva, Adriana Araujo; Gordon, Eric
Provides an introduction to the new theory of Net Locality and the profound effect on individuals and societies when everything is located or locatable. Describes net locality as an emerging form of location awareness central to all aspects of digital media, from mobile phones, to Google Maps...... of emerging technologies, from GeoCities to GPS, Wi-Fi, Wiki Me, and Google Android....
DEFF Research Database (Denmark)
Savin, Andrej
2017-01-01
Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else.......Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else....
Energy Technology Data Exchange (ETDEWEB)
Pasquier, C.R., E-mail: pasquier@lps.u-psud.fr [Laboratoire de Physique des Solides, UMR8502-CNRS, Universite Paris-Sud, Orsay F-91405 (France); Kang, N.; Salameh, B.; Auban-Senzier, P.; Jerome, D. [Laboratoire de Physique des Solides, UMR8502-CNRS, Universite Paris-Sud, Orsay F-91405 (France); Brazovskii, S. [LPTMS-CNRS, UMR8626, Universite Paris-Sud Bat 100, Orsay F-91405 (France)
2012-06-01
We report an investigation at the endpoint region of the spin density wave state in (TMTSF){sub 2}PF{sub 6} where metal and superconductivity emerge. Thanks to resistivity measurements along the three main crystallographic directions, we are able to follow the texture in this phase coexistence regime. In this respect, superconductivity is used as a decoration technique of the metallic pattern. We show that metal (superconductivity) emerges first along the c{sup Low-Asterisk} direction in a counterintuitive manner. Then metal (superconductivity) domains evolves from filaments along the c{sup Low-Asterisk} axis towards slabs perpendicular to the a-axis which melt together in the homogeneous phase at high pressure. This evolution is compatible with the proposition of the formation of a soliton phase in the vicinity of the critical pressure of the (TMTSF){sub 2}PF{sub 6} phase diagram.
Evidence of spin-density-wave order in RFeAsO1-xFx from measurements of thermoelectric power
Matusiak, M.; Plackowski, T.; Bukowski, Z.; Zhigadlo, N. D.; Karpinski, J.
2009-06-01
Data on the magnetothermopower and specific heat of three compounds belonging to “1111” oxypnictides family are reported. One specimen (SmAsFeO0.8F0.2) is a superconductor with Tc=53K , while two others (SmAsFeO and NdAsFeO) are nonsuperconducting parent compounds. Our results confirm that spin-density-wave (SDW) order is present in SmAsFeO and NdAsFeO. In these two samples a strict connection between the thermoelectric power and electronic specific heat is found in the vicinity of SDW transition, which indicates that the chemical potential of charge carriers strongly depends on temperature in this region. Low-temperature data suggest presence of significant contribution magnon drag to the thermoelectric power.
Directory of Open Access Journals (Sweden)
Q. Q. Ge (葛青亲
2013-03-01
Full Text Available The coexisting regime of spin-density wave (SDW and superconductivity in iron pnictides represents a novel ground state. We have performed high-resolution angle-resolved photoemission measurements on NaFe_{1-x}Co_{x}As (x=0.0175 in this regime and revealed its distinctive electronic structure, which provides some microscopic understandings of its behavior. The SDW signature and the superconducting gap are observed on the same bands, illustrating the intrinsic nature of the coexistence. However, because the SDW and superconductivity are manifested in different parts of the band structure, their competition is nonexclusive. Particularly, we find that the gap distribution is anisotropic and nodeless, in contrast to the isotropic superconducting gap observed in a SDW-free NaFe_{1-x}Co_{x}As (x=0.045, which puts strong constraints on theory.
Roch, Loïc M; Baldridge, Kim K
2017-10-04
A general optimization procedure towards the development and implementation of a new family of minimal parameter spin-component-scaled double-hybrid (mSD) density functional theory (DFT) is presented. The nature of the proposed exchange-correlation functional establishes a methodology with minimal empiricism. This new family of double-hybrid (DH) density functionals is demonstrated using the PBEPBE functional, illustrating the optimization procedure to the mSD-PBEPBE method, and the performance characteristics shown for a set of non-covalent complexes covering a broad regime of weak interactions. With only two parameters, mSD-PBEPBE and its cost-effective counterpart, RI-mSD-PBEPBE, show a mean absolute error of ca. 0.4 kcal mol -1 averaged over 66 weak interacting systems. Following a successive 2D-grid refinement for a CBS extrapolation of the coefficients, the optimization procedure can be recommended for the design and implementation of a variety of additional DH methods using any of the plethora of currently available functionals.
Jamshidi, Zahra; Kaveei, Elham; Mohammadpour, Mozhdeh
2015-08-13
The effects of the weak interactions of rare gas atoms on the UV-visible absorption spectra of gold dimer and tetramer clusters are investigated. The time-dependent density functional theory based on the two-component relativistic zeroth-order regular approximation that considered spin-orbit coupling is performed to estimate the absorption spectra of Au2,4-Rgn (Rg = Ne-Xe, and n = 1-6) complexes. Using spin-orbit, including the appropriate functional, shows a close correlation between experiment and our calculations. It is also demonstrated that the weak interactions between rare gas atoms and gold clusters affect the UV-vis spectra of Au2,4 clusters by shifting the electronic transition toward the blue. Moreover, we find that the order of change in peak position, Δν̃, is proportional to the strength of interactions: Δν̃Au2,4-Xe > Δν̃Au2,4-Kr > Δν̃Au2,4-Ar > Δν̃Au2,4-Ne. In addition, comparing the UV-visible spectra of Au2,4-Rgn complexes with those of isolated Au2 and Au4 clusters shows that for Au2,4-Rg2,4,6 complexes in which Rg atoms interacted symmetrically with gold clusters no additional peaks are observed compared to isolated clusters; however, for Au2,4-Rg1,3,5 complexes, extra peaks appear because of the decrease in symmetry.
Flanders, Jon
2008-01-01
RESTful .NET is the first book that teaches Windows developers to build RESTful web services using the latest Microsoft tools. Written by Windows Communication Foundation (WFC) expert Jon Flanders, this hands-on tutorial demonstrates how you can use WCF and other components of the .NET 3.5 Framework to build, deploy and use REST-based web services in a variety of application scenarios. RESTful architecture offers a simpler approach to building web services than SOAP, SOA, and the cumbersome WS- stack. And WCF has proven to be a flexible technology for building distributed systems not necessa
Indian Academy of Sciences (India)
Associate Professor of. Computer Science and. Automation at the Indian. Institute of Science,. Bangalore. His research interests are broadly in the areas of stochastic modeling and scheduling methodologies for future factories; and object oriented modeling. GENERAL I ARTICLE. Petri Nets. 1. Overview and Foundations.
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 8. Petri Nets - Overview and Foundations. Y Narahari. General Article Volume 4 Issue 8 August 1999 pp ... Author Affiliations. Y Narahari1. Department ot Computer Science and Automation, Indian Institute of Science, Bangalore 560 012, India.
Energy Technology Data Exchange (ETDEWEB)
Wang, Qiang, E-mail: wangqiang@njtech.edu.cn; Wang, Xinyan; Liu, Jianlan; Yang, Yanhui [Nanjing Tech University, School of Chemistry and Molecular Engineering, Institute of Advanced Synthesis (IAS) (China)
2017-02-15
Bimetallic core–shell nanoparticles (CSNPs) have attracted great interest not only because of their superior stability, selectivity, and catalytic activity but also due to their tunable properties achieved by changing the morphology, sequence, and sizes of both core and shell. In this study, the structure, stability, charge transfer, electronic, and magnetic properties of 13-atom and 55-atom Cu and Cu–Ni CSNPs were investigated using the density functional theory (DFT) calculations. The results show that Ni@Cu CSNPs with a Cu surface shell are more energetically favorable than Cu@Ni CSNPs with a Ni surface shell. Interestingly, three-shell Ni@Cu{sub 12}@Ni{sub 42} is more stable than two-shell Cu{sub 13}@Ni{sub 42}, while two-shell Ni{sub 13}@Cu{sub 42} is more stable than three-shell Cu@Ni{sub 12}@Cu{sub 42}. Analysis of Bader charge illustrates that the charge transfer increases from Cu core to Ni shell in Cu@Ni NPs, while it decreases from Ni core to Cu shell in Ni@Cu NPs. Furthermore, the charge transfer results that d-band states have larger shift toward the Fermi level for the Ni@Cu CSNPs with Cu surface shell, while the Cu@Ni CSNPs with Ni surface shell have similar d-band state curves and d-band centers with the monometallic Ni NPs. In addition, the Cu–Ni CSNPs possess higher magnetic moment when the Ni atoms aggregated at core region of CSNPs, while having lower magnetic moment when the Ni atoms segregate on surface region. The change of the Cu atom location in CSNPs has a weak effect on the total magnetic moment. Our findings provide useful insights for the design of bimetallic core–shell catalysts.
Energy Technology Data Exchange (ETDEWEB)
Minezawa, Noriyuki, E-mail: minezawa@fukui.kyoto-u.ac.jp [Fukui Institute for Fundamental Chemistry, Kyoto University, Sakyo-ku, Kyoto 606-8103 (Japan)
2014-10-28
Examining photochemical processes in solution requires understanding the solvent effects on the potential energy profiles near conical intersections (CIs). For that purpose, the CI point in solution is determined as the crossing between nonequilibrium free energy surfaces. In this work, the nonequilibrium free energy is described using the combined method of linear-response free energy and collinear spin-flip time-dependent density functional theory. The proposed approach reveals the solvent effects on the CI geometries of stilbene in an acetonitrile solution and those of thymine in water. Polar acetonitrile decreases the energy difference between the twisted minimum and twisted-pyramidalized CI of stilbene. For thymine in water, the hydrogen bond formation stabilizes significantly the CI puckered at the carbonyl carbon atom. The result is consistent with the recent simulation showing that the reaction path via this geometry is open in water. Therefore, the present method is a promising way of identifying the free-energy crossing points that play an essential role in photochemistry of solvated molecules.
Spin response of unpolarized quantum dots
Serra, L.; Lipparini, E.
1997-12-01
The spin response function for electrons confined in a quantum dot is studied within the time-dependent local spin density approximation (TDLSDA) of density functional theory. In the long-wavelength regime we predict the existence of a low-energy collective dipole (ell = 1) spin mode. The evolution with electron number of the spin response is studied and compared with that of the density response. Predictions for the static dipole polarizability are given.
Bradas, James C.; Fennelly, Alphonsus J.; Smalley, Larry L.
1987-01-01
It is shown that a generalized (or 'power law') inflationary phase arises naturally and inevitably in a simple (Bianchi type-I) anisotropic cosmological model in the self-consistent Einstein-Cartan gravitation theory with the improved stress-energy-momentum tensor with the spin density of Ray and Smalley (1982, 1983). This is made explicit by an analytical solution of the field equations of motion of the fluid variables. The inflation is caused by the angular kinetic energy density due to spin. The model further elucidates the relationship between fluid vorticity, the angular velocity of the inertially dragged tetrads, and the precession of the principal axes of the shear ellipsoid. Shear is not effective in damping the inflation.
Local Noncollinear Spin Analysis.
Abate, Bayileyegn A; Joshi, Rajendra P; Peralta, Juan E
2017-12-12
In this work, we generalize the local spin analysis of Clark and Davidson [J. Chem. Phys. 2001 115 (16), 7382] for the partitioning of the expectation value of the molecular spin square operator, ⟨Ŝ 2 ⟩, into atomic contributions, ⟨Ŝ A ·Ŝ B ⟩, to the noncollinear spin case in the framework of density functional theory (DFT). We derive the working equations, and we show applications to the analysis of the noncollinear spin solutions of typical spin-frustrated systems and to the calculation of magnetic exchange couplings. In the former case, we employ the triangular H 3 He 3 test molecule and a Mn 3 complex to show that the local spin analysis provides additional information that complements the standard one-particle spin population analysis. For the calculation of magnetic exchange couplings, J AB , we employ the local spin partitioning to extract ⟨Ŝ A ·Ŝ B ⟩ as a function of the interatomic spin orientation given by the angle θ. This, combined with the dependence of the electronic energy with θ, provides a methodology to extract J AB from DFT calculations that, in contrast to conventional energy differences based methods, does not require the use of ad hoc S A and S B values.
Isegawa, Miho; Truhlar, Donald G.
2013-04-01
Time-dependent density functional theory (TDDFT) holds great promise for studying photochemistry because of its affordable cost for large systems and for repeated calculations as required for direct dynamics. The chief obstacle is uncertain accuracy. There have been many validation studies, but there are also many formulations, and there have been few studies where several formulations were applied systematically to the same problems. Another issue, when TDDFT is applied with only a single exchange-correlation functional, is that errors in the functional may mask successes or failures of the formulation. Here, to try to sort out some of the issues, we apply eight formulations of adiabatic TDDFT to the first valence excitations of ten molecules with 18 density functionals of diverse types. The formulations examined are linear response from the ground state (LR-TDDFT), linear response from the ground state with the Tamm-Dancoff approximation (TDDFT-TDA), the original collinear spin-flip approximation with the Tamm-Dancoff (TD) approximation (SF1-TDDFT-TDA), the original noncollinear spin-flip approximation with the TDA approximation (SF1-NC-TDDFT-TDA), combined self-consistent-field (SCF) and collinear spin-flip calculations in the original spin-projected form (SF2-TDDFT-TDA) or non-spin-projected (NSF2-TDDFT-TDA), and combined SCF and noncollinear spin-flip calculations (SF2-NC-TDDFT-TDA and NSF2-NC-TDDFT-TDA). Comparing LR-TDDFT to TDDFT-TDA, we observed that the excitation energy is raised by the TDA; this brings the excitation energies underestimated by full linear response closer to experiment, but sometimes it makes the results worse. For ethylene and butadiene, the excitation energies are underestimated by LR-TDDFT, and the error becomes smaller making the TDA. Neither SF1-TDDFT-TDA nor SF2-TDDFT-TDA provides a lower mean unsigned error than LR-TDDFT or TDDFT-TDA. The comparison between collinear and noncollinear kernels shows that the noncollinear kernel
Energy Technology Data Exchange (ETDEWEB)
Barnes, Alexander E. [Carnegie Mellon Univ., Pittsburgh, PA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2017-05-31
The quark model has been successful in classifying the spectrum of mesons observed since the 1960s, however, it fails to explain some of the measured bound states. Lattice QCD predictions have shown that an excited gluonic field may contribute to the quantum numbers of the bound state and form hybrid mesons, qq-bar-g, where g is a constituent gluon. It is possible for some hybrids to possess quantum numbers forbidden by the quark model and are known as \\smoking gun" hybrids due to their lack of mixing with conventional qq-bar states. The GlueX photoproduction experiment at Jefferson Lab in Newport News, VA is designed to study hybrid mesons and to map their spectrum. A 12 GeV electron beam produces 9 GeV linearly polarized photons via coherent bremsstrahlung in a diamond radiator which are incident on a liquid H2 target. In order to determine the photon energy, the use of a tagging spectrometer which measures the energy of the post-bremsstrahlung electron is required. The tagger microscope is a scintillating fiber detector designed to measure the energy of electrons corresponding to the polarized photons. The main focus of this work is the design and construction of the tagger microscope electronics as well as the calibration of the microscope within the experiment. Additionally, the analysis of the reaction gamma-p -> phi-p, where phi (1020) -> K+K-, is discussed. This analysis provides a high-level calibration for GlueX in regards to understanding the acceptance and sensitivity of the detectors to mesons with strange quark content. By studying the phi with linearly polarized photons, information on the production mechanism can be extracted. The measurement of the phi spin-density matrix elements are shown and compared with past data which are found to be in agreement.
Teale, Andrew M; Lutnæs, Ola B; Helgaker, Trygve; Tozer, David J; Gauss, Jürgen
2013-01-14
Accurate sets of benchmark nuclear-magnetic-resonance shielding constants and spin-rotation constants are calculated using coupled-cluster singles-doubles (CCSD) theory and coupled-cluster singles-doubles-perturbative-triples [CCSD(T)] theory, in a variety of basis sets consisting of (rotational) London atomic orbitals. The accuracy of the calculated coupled-cluster constants is established by a careful comparison with experimental data, taking into account zero-point vibrational corrections. Coupled-cluster basis-set convergence is analyzed and extrapolation techniques are employed to estimate basis-set-limit quantities, thereby establishing an accurate benchmark data set. Together with the set provided for rotational g-tensors and magnetizabilities in our previous work [O. B. Lutnæs, A. M. Teale, T. Helgaker, D. J. Tozer, K. Ruud, and J. Gauss, J. Chem. Phys. 131, 144104 (2009)], it provides a substantial source of consistently calculated high-accuracy data on second-order magnetic response properties. The utility of this benchmark data set is demonstrated by examining a wide variety of Kohn-Sham exchange-correlation functionals for the calculation of these properties. None of the existing approximate functionals provide an accuracy competitive with that provided by CCSD or CCSD(T) theory. The need for a careful consideration of vibrational effects is clearly illustrated. Finally, the pure coupled-cluster results are compared with the results of Kohn-Sham calculations constrained to give the same electronic density. Routes to future improvements are discussed in light of this comparison.
Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi
2012-01-01
In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.
Giant Spin Accumulation in Silicon Nonlocal Spin-Transport Devices
Spiesser, A.; Saito, H.; Fujita, Y.; Yamada, S.; Hamaya, K.; Yuasa, S.; Jansen, R.
2017-12-01
Although the electrical injection, transport, and detection of spins in silicon have been achieved, the induced spin accumulation is much smaller than expected and desired, limiting the potential impact of Si-based spintronic devices. Here, using nonlocal spin-transport devices with an n -type Si channel and Fe /MgO magnetic tunnel contacts, we demonstrate that it is possible to create a giant spin accumulation in Si, with the spin splitting reaching 13 meV at 10 K and 3.5 meV at room temperature. The nonlocal spin signals are in good agreement with a numerical evaluation of spin injection and diffusion that explicitly takes the size of the injector contact into account. The giant spin accumulation originates from the large tunnel spin polarization of the Fe /MgO contacts (53% at 10 K and 18% at 300 K) and from the spin-density enhancement that is achieved by using a spin injector with a size comparable to the spin-diffusion length of the Si. The ability to induce a giant spin accumulation enables the development of Si spintronic devices with a large magnetic response.
Generalized boundary conditions for spin transfer
Tserkovnyak, Yaroslav; Ochoa, Hector
2017-09-01
We develop a comprehensive description of static and dynamic spin-transfer torque at interfaces between a normal metal and a magnetic material. Specific examples of the latter include ferromagnets, collinear and noncollinear antiferromagnets, general ferrimagnets, and spin glasses. We study the limit of the exchange-dominated interactions, so that the full system is isotropic in spin space, apart from a possible symmetry-breaking order. A general such interface yields three coefficients (corresponding to three independent generators of rotations) generalizing the well-established notion of the spin-mixing conductance, which pertains to the collinear case. We develop a nonequilibrium thermodynamic description of the emerging interfacial spin transfer and its effect on the collective spin dynamics, while circumventing the usual discussion of spin currents and net spin dynamics. Instead, our focus is on the dissipation and work effectuated by the interface. Microscopic scattering-matrix based expressions are derived for the generalized spin-transfer coefficients.
Factors associated with mosquito net use by individuals in households owning nets in Ethiopia
Directory of Open Access Journals (Sweden)
Graves Patricia M
2011-12-01
Full Text Available Abstract Background Ownership of insecticidal mosquito nets has dramatically increased in Ethiopia since 2006, but the proportion of persons with access to such nets who use them has declined. It is important to understand individual level net use factors in the context of the home to modify programmes so as to maximize net use. Methods Generalized linear latent and mixed models (GLLAMM were used to investigate net use using individual level data from people living in net-owning households from two surveys in Ethiopia: baseline 2006 included 12,678 individuals from 2,468 households and a sub-sample of the Malaria Indicator Survey (MIS in 2007 included 14,663 individuals from 3,353 households. Individual factors (age, sex, pregnancy; net factors (condition, age, net density; household factors (number of rooms [2006] or sleeping spaces [2007], IRS, women's knowledge and school attendance [2007 only], wealth, altitude; and cluster level factors (rural or urban were investigated in univariate and multi-variable models for each survey. Results In 2006, increased net use was associated with: age 25-49 years (adjusted (a OR = 1.4, 95% confidence interval (CI 1.2-1.7 compared to children U5; female gender (aOR = 1.4; 95% CI 1.2-1.5; fewer nets with holes (Ptrend = 0.002; and increasing net density (Ptrend [all nets in HH good] = 1.6; 95% CI 1.2-2.1; increasing net density (Ptrend [per additional space] = 0.6, 95% CI 0.5-0.7; more old nets (aOR [all nets in HH older than 12 months] = 0.5; 95% CI 0.3-0.7; and increasing household altitude (Ptrend Conclusion In both surveys, net use was more likely by women, if nets had fewer holes and were at higher net per person density within households. School-age children and young adults were much less likely to use a net. Increasing availability of nets within households (i.e. increasing net density, and improving net condition while focusing on education and promotion of net use, especially in school-age children
Li, Xiaojuan; Shet, Keerthi; Xu, Kaipin; Rodríguez, Juan Pablo; Pino, Ana María; Kurhanewicz, John; Schwartz, Ann; Rosen, Clifford J
2017-12-01
There are increasing evidences suggesting bone marrow adiposity tissue (MAT) plays a critical role in affecting both bone quantity and quality. However, very limited studies that have investigated the association between the composition of MAT and bone mineral density (BMD). The goal of this study was to quantify MAT unsaturation profile of marrow samples from post-menopausal women using ex vivo high-resolution magic angle spinning (HRMAS) proton nuclear magnetic resonance (1H NMR) spectroscopy, and to investigate the relationship between MAT composition and BMD. Bone marrow samples were obtained by iliac crest aspiration during surgical procedures from 24 postmenopausal women (65-89years) who had hip surgery due to bone fracture or arthroplasty. Marrow fat composition parameters, in particular, unsaturation level (UL), mono-unsaturation level (MUL) and saturation level (SL), were quantified using HRMAS 1H NMR spectroscopy. The patients were classified into three groups based on the DXA BMD T-scores: controls, osteopenia and osteoporosis. Marrow fat composition was compared between these three groups as well as between subjects with and without factures using ANOCOVA, adjusted for age. Subjects with lower BMD (n=17) had significantly lower MUL (P=0.003) and UL (P=0.039), and significantly higher SL (P=0.039) compared to controls (n=7). When separating lower BMD into osteopenia (n=9) and osteoporosis (n=8) groups, subjects with osteopenia had significantly lower MUL (P=0.002) and UL (P=0.010), and significantly higher SL (P=0.010) compared to healthy controls. No significant difference was observed between subjects with osteopenia and osteoporosis. Using HRMAS 1H NMR, significantly lower unsaturation and significantly higher saturation levels were observed in the marrow fat of subjects with lower BMD. HRMAS 1H NMR was shown to be a powerful tool for identifying novel MR markers of marrow fat composition that are associated with bone quality and potentially fracture
Diffusion equation and spin drag in spin-polarized transport
DEFF Research Database (Denmark)
Flensberg, Karsten; Jensen, Thomas Stibius; Mortensen, Asger
2001-01-01
We study the role of electron-electron interactions for spin-polarized transport using the Boltzmann equation, and derive a set of coupled transport equations. For spin-polarized transport the electron-electron interactions are important, because they tend to equilibrate the momentum of the two......: it equilibrates the spin density imbalance and, provided it has a non-s-wave component, also a current imbalance....
Directory of Open Access Journals (Sweden)
D. H. Berman
2014-03-01
Full Text Available Resonant behavior involving spin-orbit entangled states occurs for spin transport along a narrow channel defined in a two-dimensional electron gas, including an apparent rapid relaxation of the spin polarization for special values of the channel width and applied magnetic field (so-called ballistic spin resonance. A fully quantum-mechanical theory for transport using multiple subbands of the one-dimensional system provides the dependence of the spin density on the applied magnetic field and channel width and position along the channel. We show how the spatially nonoscillating part of the spin density vanishes when the Zeeman energy matches the subband energy splittings. The resonance phenomenon persists in the presence of disorder.
Hermes, Matthew R.; Hirata, So
2015-09-01
One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree-Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree-Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard-Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga-Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.
Energy Technology Data Exchange (ETDEWEB)
Hermes, Matthew R. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)
2015-09-14
One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree–Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree–Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard–Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga–Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.
A high-temperature quantum spin liquid with polaron spins
Klanjšek, Martin; Zorko, Andrej; Žitko, Rok; Mravlje, Jernej; Jagličić, Zvonko; Biswas, Pabitra Kumar; Prelovšek, Peter; Mihailovic, Dragan; Arčon, Denis
2017-11-01
The existence of a quantum spin liquid (QSL) in which quantum fluctuations of spins are sufficiently strong to preclude spin ordering down to zero temperature was originally proposed theoretically more than 40 years ago, but its experimental realization turned out to be very elusive. Here we report on an almost ideal spin liquid state that appears to be realized by atomic-cluster spins on the triangular lattice of a charge-density wave state of 1T-TaS2. In this system, the charge excitations have a well-defined gap of ~0.3 eV, while nuclear quadrupole resonance and muon-spin-relaxation experiments reveal that the spins show gapless QSL dynamics and no long-range magnetic order at least down to 70 mK. Canonical T2 power-law temperature dependence of the spin relaxation dynamics characteristic of a QSL is observed from 200 K to Tf = 55 K. Below this temperature, we observe a new gapless state with reduced density of spin excitations and high degree of local disorder signifying new quantum spin order emerging from the QSL.
Spin Funneling for Enhanced Spin Injection into Ferromagnets
Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo
2016-07-01
It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory.
Energy Technology Data Exchange (ETDEWEB)
Vuletic, T.; Herman, D.; Biskup, N.; Omerzu, A.; Tomic, S. [Zagreb Univ. (Croatia). Inst. za Fiziku; Pinteric, M. [Zagreb Univ. (Croatia). Inst. za Fiziku; Faculty of Civil Engineering, Univ. of Maribor (Slovenia); Nagasawa, M. [Hokkaido Univ., Sapporo (Japan). Dept. of Physics
1999-12-01
We present the results of DC and AC (100 mHz-1 MHz) electrical transport measurements in low and high electric fields performed in the spin-density wave (SDW) state of the Bechgaard salts (TMTSF){sub 2}PF{sub 6} and (TMTSF){sub 2}AsF{sub 6}. We argue that a degree of complex structure of the SDW ground state which is unfolded in a particular experiment depends strongly on the chosen experimental probe and the crystal measured. (orig.)
Spin currents in metallic nanostructures
Energy Technology Data Exchange (ETDEWEB)
Czeschka, Franz Dominik
2011-09-05
A pure spin current, i.e., a flow of angular momentum without accompanying net charge current, is a key ingredient in the field of spintronics. In this thesis, we experimentally investigated two different concepts for pure spin current sources suggested by theory. The first is based on a time-dependent magnetization precession which ''pumps'' a pure spin current into an adjacent non-magnetic conductor. Our experiments quantitatively corroborated important predictions expected theoretically for this approach, including the dependence of the spin current on the sample geometry and the microwave power. Even more important, we could show for the first time that the spin pumping concept is viable in a large variety of ferromagnetic materials and that it only depends on the magnetization damping. Therefore, our experiments established spin pumping as generic phenomenon and demonstrated that it is a powerful way to generate pure spin currents. The second theoretical concept is based on the conversion of charge currents into spin currents in non-magnetic nanostructures via the spin Hall effect. We experimentally investigated this approach in H-shaped, metallic nanodevices, and found that the predictions are linked to requirements not realizable with the present experimental techniques, neither in sample fabrication nor in measurement technique. Indeed, our experimental data could be consistently understood by a spin-independent transport model describing the transition from diffusive to ballistic transport. In addition, the implementation of advanced fabrication and measurement techniques allowed to discover a new non-local phenomenon, the non-local anisotropic magnetoresistance. Finally, we also studied spin-polarized supercurrents carried by spin-triplet Cooper pairs. We found that low resistance interfaces are a key requirement for further experiments in this direction. (orig.)
Spin superconductor in ferromagnetic graphene
Sun, Qing-feng; Jiang, Zhao-tan; Yu, Yue; Xie, X. C.
2010-01-01
We show a spin superconductor (SSC) in ferromagnetic graphene as the counterpart to the charge superconductor, in which a spin-polarized electron-hole pair plays the role of the spin $2 (\\hbar/2)$ `Cooper pair' with a neutral charge. We present a BCS-type theory for the SSC. With the `London-type equations' of the super-spin-current density, we show the existence of an electric `Meissner effect' against a spatial varying electric field. We further study a SSC/normal conductor/SSC junction and...
Near Net Manufacturing Using Thin Gage Friction Stir Welding
Takeshita, Jennifer; Potter, David; Holquin, Michael
2006-01-01
Friction Stir Welding (FSW) and near net spin forming of FSW aluminumn blanks were investigated for large-scale pressure vessel applications. With a specific focus on very thin gage 2xxx and 7xxx aluminum alloys, the program concentrated on the following: the criteria used for material selection, a potential manufacturing flow, and the effectiveness and associated risks of near net spin forming. Discussion will include the mechanical properties of the friction stir welds and the parent material from before and after the spin forming process. This effort was performed under a NASA Space Exploration initiative focused on increasing the affordability, reliability and performance of pressure vessels larger than 10 ft. diameter.
Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi
2017-01-01
Since the discovery of the giant magnetoresistance effect in magnetic multilayers in 1988, a new branch of physics and technology, called spin-electronics or spintronics, has emerged, where the flow of electrical charge as well as the flow of electron spin, the so-called “spin current,” are manipulated and controlled together. The physics of magnetism and the application of spin current have progressed in tandem with the nanofabrication technology of magnets and the engineering of interfaces and thin films. This book aims to provide an introduction and guide to the new physics and applications of spin current, with an emphasis on the interaction between spin and charge currents in magnetic nanostructures.
Energy Technology Data Exchange (ETDEWEB)
Curtright, T.L., E-mail: curtright@miami.edu [Department of Physics, University of Miami, Coral Gables, FL 33124-8046 (United States); Van Kortryk, T.S., E-mail: vankortryk@gmail.com [Department of Physics, University of Miami, Coral Gables, FL 33124-8046 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439-4815 (United States); Zachos, C.K., E-mail: zachos@anl.gov [Department of Physics, University of Miami, Coral Gables, FL 33124-8046 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439-4815 (United States)
2017-02-05
The number of times spin s appears in the Kronecker product of n spin j representations is computed, and the large n asymptotic behavior of the result is obtained. Applications are briefly sketched. - Highlights: • We give a self-contained derivation of the spin multiplicities that occur in n-fold tensor products of spin-j representations. • We make use of group characters, properties of special functions, and asymptotic analysis of integrals. • We emphasize patterns that arise when comparing different values of j, and asymptotic behavior for large n. • Our methods and results should be useful for various statistical and quantum information theory calculations.
Spin states of multielectron systems and the action of multi-spin bans
Arifullin, M. R.; Berdinskii, V. L.
2013-07-01
Magnetic and spin effects in chemical reactions are caused by the effect of spin bans, which control the elementary acts of radical and ion-radical reactions involving, as a rule, two paramagnetic particles. Any description of spin bans acting in chemical and enzymatic reactions, which is accompanied by transfer of several electrons, as well as in the reactions of high spin molecules, requires knowledge of spin states. It is shown that spin states of multi-electron states should be described by a spin density matrix; rules for their construction are given and their properties are described. As a first step, the construction of four-density matrix is described in detail. The application of four- and three-spin density matrixes is shown for analyzing the formation of superoxide anion in respiratory chains of mitochondria.
Transverse dipole spin modes in quantum dots
Lipparini, E.; Barranco, M.; Emperador, A.; Pi, M.; Serra, Ll.
1999-09-01
We have carried out a systematic analysis of the transverse dipole spin response of a large-size quantum dot within time-dependent current density functional theory. Results for magnetic fields corresponding to integer filling factors are reported, as well as a comparison with the longitudinal dipole spin response. As in the two-dimensional electron gas, the spin response at high-spin magnetization is dominated by a low-energy transverse mode.
Constraints on vector meson photoproduction spin observables
Kloet, W. M.; Tabakin, Frank
2000-01-01
Extraction of spin observables from vector meson photoproduction on a nucleon target is described. Starting from density matrix elements in the vector meson's rest frame, we transform to spin observables in the photon-nucleon c.m. frame. Several constraints on the transformed density matrix and on the spin observables follow from requiring that the angular distribution and the density matrix be positive definite. A set of constraints that are required in order to extract meaningful spin observables from forthcoming data are enunciated.
Possible evidence for spin-transfer torque induced by spin-triplet supercurrent
Li, Lailai
2017-10-04
Cooper pairs in superconductors are normally spin singlet. Nevertheless, recent studies suggest that spin-triplet Cooper pairs can be created at carefully engineered superconductor-ferromagnet interfaces. If Cooper pairs are spin-polarized they would transport not only charge but also a net spin component, but without dissipation, and therefore minimize the heating effects associated with spintronic devices. Although it is now established that triplet supercurrents exist, their most interesting property - spin - is only inferred indirectly from transport measurements. In conventional spintronics, it is well known that spin currents generate spin-transfer torques that alter magnetization dynamics and switch magnetic moments. The observation of similar effects due to spin-triplet supercurrents would not only confirm the net spin of triplet pairs but also pave the way for applications of superconducting spintronics. Here, we present a possible evidence for spin-transfer torques induced by triplet supercurrents in superconductor/ferromagnet/superconductor (S/F/S) Josephson junctions. Below the superconducting transition temperature T_c, the ferromagnetic resonance (FMR) field at X-band (~ 9.0 GHz) shifts rapidly to a lower field with decreasing temperature due to the spin-transfer torques induced by triplet supercurrents. In contrast, this phenomenon is absent in ferromagnet/superconductor (F/S) bilayers and superconductor/insulator/ferromagnet/superconductor (S/I/F/S) multilayers where no supercurrents pass through the ferromagnetic layer. These experimental observations are discussed with theoretical predictions for ferromagnetic Josephson junctions with precessing magnetization.
Optimization of spin injection and spin detection in lateral nanostructures by geometrical means
Energy Technology Data Exchange (ETDEWEB)
Stejskal, Ondřej [Nanotechnology Centre and IT4Innovations, VSB – Technical University of Ostrava, 708 33 Ostrava (Czech Republic); Hamrle, Jaroslav [Nanotechnology Centre and IT4Innovations, VSB – Technical University of Ostrava, 708 33 Ostrava (Czech Republic); Institute of Physics, VSB – Technical University of Ostrava, 708 33 Ostrava (Czech Republic); Pištora, Jaromír [Nanotechnology Centre and IT4Innovations, VSB – Technical University of Ostrava, 708 33 Ostrava (Czech Republic); Otani, Yoshichika [Center of Emergent Matter Science, The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Institute for Solid State Physics, University of Tokyo, Kashiwa-shi, Chiba 277-8581 (Japan)
2016-09-15
Lateral spin devices are an important concept in nowadays all-metallic spintronic devices. One of the key problems is to obtain large spin injection and detection efficiency. Several concepts has been envisaged, such as to use half-metallic ferromagnetic electrodes or spin-polarized interface barriers. Within this work, we address the optimization of spin devices (namely optimization of spin current density, spin current and spin accumulation) based on adjustment of the geometry (dimensions) of the lateral device, material selection of spin conductors, jointly with optimization of the interface resistance. - Highlights: • Maximization of spin injection and spin detection in lateral nanostructures. • Calculations based on one-dimensional Valet–Fert model. • Maximization by adjusting dimensions and interface resistances of the lateral devices.
2003-08-01
spin resonance of rare earth and transition metal impurities in chalcopyrite semiconductors. They also have worked in diluted magnetic...past, the ferromagnetic injector had been a ferromagnetic metal or alloy containing 3d transition elements with fractional spin polarization of the...polarized carriers. There have been numerous attempts to inject transition metals or their alloys into semiconductors, either directly (Johnson and
Bovier, Anton
2007-01-01
Spin glass theory is going through a stunning period of progress while finding exciting new applications in areas beyond theoretical physics, in particular in combinatorics and computer science. This collection of state-of-the-art review papers written by leading experts in the field covers the topic from a wide variety of angles. The topics covered are mean field spin glasses, including a pedagogical account of Talagrand's proof of the Parisi solution, short range spin glasses, emphasizing the open problem of the relevance of the mean-field theory for lattice models, and the dynamics of spin glasses, in particular the problem of ageing in mean field models. The book will serve as a concise introduction to the state of the art of spin glass theory, usefull to both graduate students and young researchers, as well as to anyone curious to know what is going on in this exciting area of mathematical physics.
Unconventional spin texture of a topologically nontrivial semimetal Sb(110)
DEFF Research Database (Denmark)
Strózecka, A.; Eiguren, A.; Bianchi, Marco
2012-01-01
The surfaces of antimony are characterized by the presence of spin-split states within the projected bulk band gap and the Fermi contour is thus expected to exhibit a spin texture. Using spin-resolved density functional theory calculations, we determine the spin polarization of the surface bands...
Energy Technology Data Exchange (ETDEWEB)
Dongarra, J. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science]|[Oak Ridge National Lab., TN (United States); Rosener, B. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science
1991-12-01
This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host ``na-net.ornl.gov`` at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message ``send index`` to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user`s perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.
Energy Technology Data Exchange (ETDEWEB)
Dongarra, J. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science Oak Ridge National Lab., TN (United States)); Rosener, B. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science)
1991-12-01
This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host na-net.ornl.gov'' at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message send index'' to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user's perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.
Spin wave amplification using the spin Hall effect in permalloy/platinum bilayers
Energy Technology Data Exchange (ETDEWEB)
Gladii, O.; Henry, Y.; Bailleul, M. [Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 CNRS, Université de Strasbourg, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2 (France); Collet, M.; Garcia-Hernandez, K.; Cheng, C.; Bortolotti, P.; Cros, V.; Anane, A. [Unité Mixte de Physique CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767 Palaiseau (France); Xavier, S. [Thales Research and Technology, 1 Av. A. Fresnel, Campus de l' Ecole Polytechnique, 91767 Palaiseau (France); Kim, J.-V. [Institut d' Electronique Fondamentale, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France)
2016-05-16
We investigate the effect of an electrical current on the attenuation length of a 900 nm wavelength spin-wave in a permalloy/Pt bilayer using propagating spin-wave spectroscopy. The modification of the spin-wave relaxation rate is linear in current density, reaching up to 14% for a current density of 2.3 × 10{sup 11} A/m{sup 2} in Pt. This change is attributed to the spin transfer torque induced by the spin Hall effect and corresponds to an effective spin Hall angle of 0.13, which is among the highest values reported so far. The spin Hall effect thus appears as an efficient way of amplifying/attenuating propagating spin waves.
TOPICAL REVIEW: Spin current, spin accumulation and spin Hall effect
Directory of Open Access Journals (Sweden)
Saburo Takahashi and Sadamichi Maekawa
2008-01-01
Full Text Available Nonlocal spin transport in nanostructured devices with ferromagnetic injector (F1 and detector (F2 electrodes connected to a normal conductor (N is studied. We reveal how the spin transport depends on interface resistance, electrode resistance, spin polarization and spin diffusion length, and obtain the conditions for efficient spin injection, spin accumulation and spin current in the device. It is demonstrated that the spin Hall effect is caused by spin–orbit scattering in nonmagnetic conductors and gives rise to the conversion between spin and charge currents in a nonlocal device. A method of evaluating spin–orbit coupling in nonmagnetic metals is proposed.
Universal Spin-Momentum Locked Optical Forces
Kalhor, Farid; Jacob, Zubin
2015-01-01
Evanescent electromagnetic waves possess spin-momentum locking, where the direction of propagation (momentum) is locked to the inherent polarization of the wave (transverse spin). We study the optical forces arising from this universal phenomenon and show that the fundamental origin of recently reported non-trivial optical chiral forces is spin-momentum locking. For evanescent waves, we show that the direction of energy flow, direction of decay, and direction of spin follow a right hand rule for three different cases of total internal reflection, surface plasmon polaritons, and $HE_{11}$ mode of an optical fiber. Furthermore, we explain how the recently reported phenomena of lateral optical force on chiral and achiral particles is caused by the transverse spin of the evanescent field and the spin-momentum locking phenomenon. Finally, we propose an experiment to identify the unique lateral forces arising from the transverse spin in the optical fiber and point to fundamental differences of the spin density from...
U.S. Geological Survey, Department of the Interior — Net Ecosystem Carbon Flux is defined as the year-over-year change in Total Ecosystem Carbon Stock, or the net rate of carbon exchange between an ecosystem and the...
Buhrman, Robert; Daughton, James; Molnár, Stephan; Roukes, Michael
2004-01-01
This report is a comparative review of spin electronics ("spintronics") research and development activities in the United States, Japan, and Western Europe conducted by a panel of leading U.S. experts in the field. It covers materials, fabrication and characterization of magnetic nanostructures, magnetism and spin control in magnetic nanostructures, magneto-optical properties of semiconductors, and magnetoelectronics and devices. The panel's conclusions are based on a literature review and a series of site visits to leading spin electronics research centers in Japan and Western Europe. The panel found that Japan is clearly the world leader in new material synthesis and characterization; it is also a leader in magneto-optical properties of semiconductor devices. Europe is strong in theory pertaining to spin electronics, including injection device structures such as tunneling devices, and band structure predictions of materials properties, and in development of magnetic semiconductors and semiconductor heterost...
Singh, Simranjeet; Katoch, Jyoti; Zhu, Tiancong; Wu, Ryan J; Ahmed, Adam S; Amamou, Walid; Wang, Dongying; Mkhoyan, K Andre; Kawakami, Roland K
2017-11-16
The quality of the tunnel barrier at the ferromagnet/graphene interface plays a pivotal role in graphene spin valves by circumventing the impedance mismatch problem, decreasing interfacial spin dephasing mechanisms and decreasing spin absorption back into the ferromagnet. It is thus crucial to integrate superior tunnel barriers to enhance spin transport and spin accumulation in graphene. Here, we employ a novel tunnel barrier, strontium oxide (SrO), onto graphene to realize high quality spin transport as evidenced by room-temperature spin relaxation times exceeding a nanosecond in graphene on silicon dioxide substrates. Furthermore, the smooth and pinhole-free SrO tunnel barrier grown by molecular beam epitaxy (MBE), which can withstand large charge injection current densities, allows us to experimentally realize large spin accumulation in graphene at room temperature. This work puts graphene on the path to achieve efficient manipulation of nanomagnet magnetization using spin currents in graphene for logic and memory applications.
Bias-dependent spin relaxation in a Spin-LED
Energy Technology Data Exchange (ETDEWEB)
Bosco, C.A. C. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands)]. E-mail: c.a.c.bosco@tue.nl; Snouck, D. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Van Dorpe, P. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Van Roy, W. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Koopmans, B. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands)
2006-01-25
We have investigated the bias-dependent spin relaxation in Cu-CoFe-AlO{sub x}-GaAs/AlGaAs-type of Spin-LEDs using microscopic time-resolved magnetization modulation spectroscopy (TIMMS). We observed a significant dependence of the electron spin relaxation time (effects as large as 40%) as a function of applied bias. The additional spin relaxation at non-zero bias is found to scale almost linearly with the injection current, and thereby with the current-induced hole density in the active region. This observation is indicative for a dominant contribution by Bir-Aronov-Pikus (BAP) electron-hole spin-flip scattering. In agreement with this observation, a similar BAP-enhanced spin relaxation shows up at increased laser fluence. From spatio-temporal imaging of spin relaxation, scanning pump and probe beams across the {approx}50{mu} m outside of optical window, we found a significant position dependence (lateral effects) of the spin dynamics.
Arking, Jon
2010-01-01
Comprehensive coverage to help experienced .NET developers create flexible, extensible enterprise application code If you're an experienced Microsoft .NET developer, you'll find in this book a road map to the latest enterprise development methodologies. It covers the tools you will use in addition to Visual Studio, including Spring.NET and nUnit, and applies to development with ASP.NET, C#, VB, Office (VBA), and database. You will find comprehensive coverage of the tools and practices that professional .NET developers need to master in order to build enterprise more flexible, testable, and ext
Black Hole Spin Measurement Uncertainty
Salvesen, Greg; Begelman, Mitchell C.
2018-01-01
Angular momentum, or spin, is one of only two fundamental properties of astrophysical black holes, and measuring its value has numerous applications. For instance, obtaining reliable spin measurements could constrain the growth history of supermassive black holes and reveal whether relativistic jets are powered by tapping into the black hole spin reservoir. The two well-established techniques for measuring black hole spin can both be applied to X-ray binaries, but are in disagreement for cases of non-maximal spin. This discrepancy must be resolved if either technique is to be deemed robust. We show that the technique based on disc continuum fitting is sensitive to uncertainties regarding the disc atmosphere, which are observationally unconstrained. By incorporating reasonable uncertainties into black hole spin probability density functions, we demonstrate that the spin measured by disc continuum fitting can become highly uncertain. Future work toward understanding how the observed disc continuum is altered by atmospheric physics, particularly magnetic fields, will further strengthen black hole spin measurement techniques.
On the spin-liquid phase of one-dimensional spin-1 bosons
Essler, F.H.L.; Shlyapnikov, G.V.; Tsvelik, A.M.
2009-01-01
We consider a model of one-dimensional spin-1 bosons with repulsive density-density interactions and antiferromagnetic exchange. We show that the low energy effective field theory is given by a spin-charge separated theory of a Tomonaga-Luttinger Hamiltonian and the O(3) non-linear sigma model
High spin injection polarization at an elevated dc bias in tunnel-junction-based lateral spin valves
Wang, X. J.; Zou, H.; Ocola, L. E.; Ji, Y.
2009-07-01
Submicron metallic lateral spin valves are fabricated with AlOx tunnel junctions as spin injection and detection barriers. The spin polarization is estimated to be ˜20%, determined by both Hanle effect and variations of device dimensions. The polarization is maintained at a large dc injection current density >2×106 A/cm2. Both the spin polarization and spin diffusion length are weakly temperature dependent.
Zhu, Jian-Xin; Ting, C. S.
2001-01-01
The local density of states (LDOS) at one of the vortex lattice cores in a high Tc superconductor is studied by using a self-consistent mean field theory including interactions for both antiferromagnetism (AF) and d-wave superconductivity (DSC). The parameters are chosen in such a way that in an optimally doped sample the AF order is completely suppressed while DSC prevails. In the mixed state, we show that the local AF-like SDW order appears near the vortex core and acts as an effective loca...
Inhomogeneous Spin Diffusion in Traps with Cold Atoms
DEFF Research Database (Denmark)
Heiselberg, Henning
2012-01-01
The spin diusion and damped oscillations are studied in the collision of two spin polarized clouds of cold atoms with resonant interactions. The strong density dependence of the diusion coecient leads to inhomogeneous spin diusion that changes from central to surface spin ow as the temperature...... increases. The inhomogeneity and the smaller nite trap size signicantly reduce the spin diusion rate at low temperatures. The resulting spin diusion rates and spin drag at longer time scales are compatible with measurements at low to high temperatures for resonant attractive interactions...
Andersen, John A.; Flanigan, John J.; Kindley, Robert J.
1978-01-01
The disclosure relates to an apparatus for spin ejecting a body having a flat plate base containing bosses. The apparatus has a base plate and a main ejection shaft extending perpendicularly from the base plate. A compressible cylindrical spring is disposed about the shaft. Bearings are located between the shaft and the spring. A housing containing a helical aperture releasably engages the base plate and surrounds the shaft bearings and the spring. A piston having an aperture follower disposed in the housing aperture is seated on the spring and is guided by the shaft and the aperture. The spring is compressed and when released causes the piston to spin eject the body.
Observation of the spin Seebeck effect.
Uchida, K; Takahashi, S; Harii, K; Ieda, J; Koshibae, W; Ando, K; Maekawa, S; Saitoh, E
2008-10-09
The generation of electric voltage by placing a conductor in a temperature gradient is called the Seebeck effect. Its efficiency is represented by the Seebeck coefficient, S, which is defined as the ratio of the generated electric voltage to the temperature difference, and is determined by the scattering rate and the density of the conduction electrons. The effect can be exploited, for example, in thermal electric-power generators and for temperature sensing, by connecting two conductors with different Seebeck coefficients, a device called a thermocouple. Here we report the observation of the thermal generation of driving power, or voltage, for electron spin: the spin Seebeck effect. Using a recently developed spin-detection technique that involves the spin Hall effect, we measure the spin voltage generated from a temperature gradient in a metallic magnet. This thermally induced spin voltage persists even at distances far from the sample ends, and spins can be extracted from every position on the magnet simply by attaching a metal. The spin Seebeck effect observed here is directly applicable to the production of spin-voltage generators, which are crucial for driving spintronic devices. The spin Seebeck effect allows us to pass a pure spin current, a flow of electron spins without electric currents, over a long distance. These innovative capabilities will invigorate spintronics research.
2015-10-30
Coastal Inlets Research Program WaveNet WaveNet is a web-based, Graphical-User-Interface ( GUI ) data management tool developed for Corps coastal...generates tabular and graphical information for project planning and design documents. The WaveNet is a web-based GUI designed to provide users with a...data from different sources, and employs a combination of Fortran, Python and Matlab codes to process and analyze data for USACE applications
Polarization puts a New Spin on Physics
Ellis, Jonathan Richard
2007-01-01
Polarization and spin effects are useful for probing the Standard Model, in both the electroweak sector and the strong sector, where the spin decomposition of the nucleon is still a hot topic, with important new data on the net polarizations of the gluon and the strange quarks. Spin phenomena are also useful in searches for new physics, for example via measurements of the anomalous magnetic moment of the muon and searches for electric dipole moments. The cross sections for the direct detection of dark matter may also have an important spin-dependent component, related to the spin decomposition of the nucleon, that could be an important diagnostic tool. Polarization effects are also important diagnostic aids for high-energy experiments at electron-proton, proton-proton and electron-positron colliders.
DEFF Research Database (Denmark)
Jensen, Kurt
1991-01-01
This paper describes how Coloured Petri Nets (CP-nets) have been developed — from being a promising theoretical model to being a full-fledged language for the design, specification, simulation, validation and implementation of large software systems (and other systems in which human beings and...... use of CP-nets — because it means that the function representation and the translations (which are a bit mathematically complex) no longer are parts of the basic definition of CP-nets. Instead they are parts of the invariant method (which anyway demands considerable mathematical skills...
DEFF Research Database (Denmark)
Westergaard, Michael
2006-01-01
This paper introduces the notion of game coloured Petri nets. This allows the modeler to explicitly model what parts of the model comprise the modeled system and what parts are the environment of the modeled system. We give the formal definition of game coloured Petri nets, a means of reachability...... analysis of this net class, and an application of game coloured Petri nets to automatically generate easy-to-understand visualizations of the model by exploiting the knowledge that some parts of the model are not interesting from a visualization perspective (i.e. they are part of the environment...
Ferrara, Alex
2007-01-01
Web services are poised to become a key technology for a wide range of Internet-enabled applications, spanning everything from straight B2B systems to mobile devices and proprietary in-house software. While there are several tools and platforms that can be used for building web services, developers are finding a powerful tool in Microsoft's .NET Framework and Visual Studio .NET. Designed from scratch to support the development of web services, the .NET Framework simplifies the process--programmers find that tasks that took an hour using the SOAP Toolkit take just minutes. Programming .NET
Annotating Coloured Petri Nets
DEFF Research Database (Denmark)
Lindstrøm, Bo; Wells, Lisa Marie
2002-01-01
-net. An example of such auxiliary information is a counter which is associated with a token to be able to do performance analysis. Modifying colour sets and arc inscriptions in a CP-net to support a specific use may lead to creation of several slightly different CP-nets – only to support the different uses...... a method which makes it possible to associate auxiliary information, called annotations, with tokens without modifying the colour sets of the CP-net. Annotations are pieces of information that are not essential for determining the behaviour of the system being modelled, but are rather added to support...
Strong Linear Dichroism in Spin-Polarized Photoemission from Spin-Orbit-Coupled Surface States
Bentmann, H.; Maaß, H.; Krasovskii, E. E.; Peixoto, T. R. F.; Seibel, C.; Leandersson, M.; Balasubramanian, T.; Reinert, F.
2017-09-01
A comprehensive understanding of spin-polarized photoemission is crucial for accessing the electronic structure of spin-orbit coupled materials. Yet, the impact of the final state in the photoemission process on the photoelectron spin has been difficult to assess in these systems. We present experiments for the spin-orbit split states in a Bi-Ag surface alloy showing that the alteration of the final state with energy may cause a complete reversal of the photoelectron spin polarization. We explain the effect on the basis of ab initio one-step photoemission theory and describe how it originates from linear dichroism in the angular distribution of photoelectrons. Our analysis shows that the modulated photoelectron spin polarization reflects the intrinsic spin density of the surface state being sampled differently depending on the final state, and it indicates linear dichroism as a natural probe of spin-orbit coupling at surfaces.
Schwarz, H.
2017-01-01
The thesis "Spinning Worlds" is about the characterisation of two types of gas-giant exoplanets: Hot Jupiters, with orbital periods of fewer than five days, and young, wide-orbit gas giants, with orbital periods as long as thousands of years. The thesis is based on near-infrared observations of 1
Reactivity of Graphene Investigated by Density-Functional Theory
Soni, Himadri; Gebhardt, Julian; Görling, Andreas; Chair of Theoretical Chemistry Team
Using spin-polarized density-functional theory, we study the adsorption and reaction of hydrogen and fluorine with graphene. Graphene has a bipartite lattice with two different sublattices and hence, due to Lieb's theorem, the inequality between two sublattices should lead to a net magnetic moment upon adsorption of hydrogen or fluorine. Our calculations using density-functional theory with the generalized gradient approximation predict a magnetic moment of 1 µB for a single hydrogen adsorbed on graphene but not for a single fluorine atom adsorbed on graphene. Switching to hybrid density-functional theory with the HSE functional, we obtain a magnetic moment of 1 µB for of a single fluorine atom adsorption on graphene. This is in line with work of Kim et al., who also found in density-functional theory calculations with the HSE exchange-correlation functional spin-polarization for a fluorine adatom on graphene. Here, we present a systematic study of the reactivity and relevant adsorption mechanism for single-sided graphene, i.e., a graphene sheet which is accessible by an adsorbate from only one side with hydrogen and fluorine using hybrid density-functional theory. German Research Council (DFG) by the Collaborative Research Center 953.
The realization of half-metal and spin-semiconductor for metal adatoms on arsenene
Li, Geng; Zhao, Yinchang; Zeng, Shuming; Ni, Jun
2016-12-01
First-principles calculations have been performed to study the adsorption of 15 different metal adatoms on silicenelike arsenene. The adsorption energies, geometries, density of states, dipole moments, work functions, net magnetic moments and Bader charges transferred from adatoms to arsenene sheet are calculated. All of the 15 metal adatoms on arsenene have binding energies larger than cohesive energies of the bulk metal, implying that stable adsorbates can be formed. As a result of the localized states originating from adatoms, the adsorption systems show a rich variety of electronic properties, such as metal, half-metal, semiconducting, and spin-semiconducting behaviors. The Co doped arsenene displays a half-metal property. The adsorption of Cu, Ag, and Au turns semiconducting arsenene into a narrow gap spin-semiconductor. These results indicate potential applications of functionalizations of silicenelike arsenene with metal adatoms, in particular for spintronics and dilute magnetic semiconductor materials.
Spin currents, spin torques, and the concept of spin superfluidity
Rückriegel, Andreas; Kopietz, Peter
2017-01-01
In magnets with non-collinear spin configuration the expectation value of the conventionally defined spin current operator contains a contribution which renormalizes an external magnetic field and hence affects only the precessional motion of the spin polarization. This term, which has been named angular spin current by Sun and Xie [Phys. Rev B 72, 245305 (2005)], does not describe the translational motion of magnetic moments. We give a prescription how to separate these two types of spin tra...
Effective spin-spin interaction in neutron matter
Energy Technology Data Exchange (ETDEWEB)
Zverev, M.V. [Moscow Engineering Physics Institute, Moscow (Russian Federation); Khafizov, R.U.; Khodel, V.A. [Kurchatov Institute Russian Research Centre, Moscow (Russian Federation); Shaginyan, V.R. [Petersburg Institute of Nuclear Physics, Gatchina (Russian Federation)
1995-09-01
A set of equations for calculating the effective-interaction matrix R{sup ik}(q, {omega}) and the response function X{sup ik}(q, {omega}) is derived. These equations take into account the spin degrees of freedom of infinite neutron matter. For isotropic neutron matter with the Bethe interaction, the effective spin-spin interaction g(k) is calculated in the local approximation of the functional approach in the density range from {rho} = 0.17 to 25 fm{sup -3}. It is shown that this interaction weakly depends on the density within the range under consideration and that neither ferromagnetic nor antiferromagnetic phase transitions occur in the system. 7 refs., 2 figs.
CSIR Research Space (South Africa)
Lindeque, M
2013-01-01
Full Text Available Is it possible to develop a building that uses a net zero amount of water? In recent years it has become evident that it is possible to have buildings that use a net zero amount of electricity. This is possible when the building is taken off...
DEFF Research Database (Denmark)
Jordan, Ulrike; Vajen, Klaus; Bales, Chris
2014-01-01
SolNet, founded in 2006, is the first coordinated International PhD education program on Solar Thermal Engineering. The SolNet network is coordinated by the Institute of Thermal Engineering at Kassel University, Germany. The network offers PhD courses on solar heating and cooling, conference...
DEFF Research Database (Denmark)
Hørning, Annette
1994-01-01
Artiklen beskæftiger sig med muligheden for at anvende kunstige neurale net i forbindelse med datamatisk procession af naturligt sprog, specielt automatisk talegenkendelse.......Artiklen beskæftiger sig med muligheden for at anvende kunstige neurale net i forbindelse med datamatisk procession af naturligt sprog, specielt automatisk talegenkendelse....
Ma, Yitao; Miura, Sadahiko; Honjo, Hiroaki; Ikeda, Shoji; Hanyu, Takahiro; Ohno, Hideo; Endoh, Tetsuo
2017-04-01
A high-density nonvolatile associative memory (NV-AM) based on spin transfer torque magnetoresistive random access memory (STT-MRAM), which achieves highly concurrent and ultralow-power nearest neighbor search with full adaptivity of the template data format, has been proposed and fabricated using the 90 nm CMOS/70 nm perpendicular-magnetic-tunnel-junction hybrid process. A truly compact current-mode circuitry is developed to realize flexibly controllable and high-parallel similarity evaluation, which makes the NV-AM adaptable to any dimensionality and component-bit of template data. A compact dual-stage time-domain minimum searching circuit is also developed, which can freely extend the system for more template data by connecting multiple NM-AM cores without additional circuits for integrated processing. Both the embedded STT-MRAM module and the computing circuit modules in this NV-AM chip are synchronously power-gated to completely eliminate standby power and maximally reduce operation power by only activating the currently accessed circuit blocks. The operations of a prototype chip at 40 MHz are demonstrated by measurement. The average operation power is only 130 µW, and the circuit density is less than 11 µm2/bit. Compared with the latest conventional works in both volatile and nonvolatile approaches, more than 31.3% circuit area reductions and 99.2% power improvements are achieved, respectively. Further power performance analyses are discussed, which verify the special superiority of the proposed NV-AM in low-power and large-memory-based VLSIs.
Horner, Olivier; Oddou, Jean-Louis; Jeandey, Claudine; Nivière, Vincent; Mattioli, Tony A; Mathé, Christelle; Fontecave, Marc; Maldivi, Pascale; Bonville, Pierre; Halfen, Jason A; Latour, Jean-Marc
2014-01-01
Superoxide reductase (SOR) is an Fe protein that catalyzes the reduction of superoxide to give H(2)O(2). Recently, the mutation of the Glu47 residue into alanine (E47A) in the active site of SOR from Desulfoarculus baarsii has allowed the stabilization of an iron-peroxo species when quickly reacted with H(2)O(2) [Math{\\'e} et al. (2002) J. Am. Chem. Soc. 124, 4966-4967]. To further investigate this non-heme peroxo-iron species, we have carried out a M{\\"o}ssbauer study of the (57)Fe-enriched E47A SOR from D. baarsii reacted quickly with H(2)O(2). Considering the M{\\"o}ssbauer data, we conclude, in conjunction with the other spectroscopic data available and with the results of density functional calculations on related models, that this species corresponds to a high-spin side-on peroxo-Fe(3+) complex. This is one of the first examples of such a species in a biological system for which M{\\"o}ssbauer parameters are now available: delta(/Fe) = 0.54 (1) mm/s, DeltaE(Q) = -0.80 (5) mm/s, and the asymmetry parameter...
African Journals Online (AJOL)
PROJET SOJA
Intense UV photoluminescence is observed for intrinsic ZnO film. Keywords : thin films, oxidize zinc doped aluminium (ZnO:Al), sol-gel, spin coating, structural analysis, electric and optical properties. 1. Introduction. Depuis ces vingt dernières années les couches minces d'oxyde de zinc ont connu un intérêt croissant dans ...
Bias-independent spin signals in a tunnel-junction-based non-local spin valve
Wang, Xiaojun; Zou, Han; Ocola, L. E.; Divan, R.; Ji, Yi
2009-03-01
A pure spin current can be generated in the non-magnetic component of a non-local spin valve (NLSV). It has been demonstrated recently that the pure spin current can be used for spin transfer torque and spin-Hall effects. A high spin current density is desirable for realizing these effects, and therefore a large d.c. bias current will be applied. It is essential to maintain high degree of spin polarization at a high bias current. It has been previously reported that the spin polarization decreases drastically in a tunnel-junction-based CoFe/Al/NiFe NLSV. The goal of this study is to investigate the dependence of spin signals upon a d.c. bias current in tunnel-junction-based Co/Cu/Co NLSV's. Submicron Co/Cu/Co NLSV's are fabricated by e-beam lithography combined with angle deposition. A layer of 2 nm Al2O3 is deposited at the Co/Cu interface to form a tunnel barrier. A spin signal > 1mφ is observed at room temperature (RT). A d.c. current up to 1.0mA is applied at both 4.2 K and RT. No change of spin signal is observed for an injection current density > 10^6 A/cm^2.
Spin-Circuit Representation of Spin Pumping
Roy, Kuntal
2017-07-01
Circuit theory has been tremendously successful in translating physical equations into circuit elements in an organized form for further analysis and proposing creative designs for applications. With the advent of new materials and phenomena in the field of spintronics and nanomagnetics, it is imperative to construct the spin-circuit representations for different materials and phenomena. Spin pumping is a phenomenon by which a pure spin current can be injected into the adjacent layers. If the adjacent layer is a material with a high spin-orbit coupling, a considerable amount of charge voltage can be generated via the inverse spin Hall effect allowing spin detection. Here we develop the spin-circuit representation of spin pumping. We then combine it with the spin-circuit representation for the materials having spin Hall effect to show that it reproduces the standard results as in the literature. We further show how complex multilayers can be analyzed by simply writing a netlist.
Nonequilibrium thermal entanglement for simple spin chains
Sinayskiy, I.; Pumulo, N.; Petruccione, F.
2012-09-01
The dynamics of a chain of two and three spins coupled at both ends to separate bosonic baths at different temperatures is studied. An exact analytical solution of the quantum master equation in the Born-Markov approximation for the reduced density matrix of the chain is constructed. It is shown that for long times the reduced density matrix converges to the nonequilibrium steady-state. Dynamical and steady state properties of the concurrence between the first and the last spin are studied.
Energy Technology Data Exchange (ETDEWEB)
Wang, C.M., E-mail: cmwangsjtu@gmail.co [School of Physics and Electrical Engineering, Anyang Normal University, Anyang 455000 (China); Pang, M.Q. [School of Physics and Electrical Engineering, Anyang Normal University, Anyang 455000 (China); Liu, S.Y.; Lei, X.L. [Department of Physics, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China)
2010-02-22
The current-induced spin polarization (CISP) is investigated in a combined Rashba-Dresselhaus spin-orbit-coupled two-dimensional electron gas, subjected to a homogeneous out-of-plane magnetization. It is found that, in addition to the usual collision-related in-plane parts of CISP, there are two impurity-density-free contributions, arising from intrinsic and disorder-mediated mechanisms. The intrinsic parts of spin polarization are related to the Berry curvature, analogous with the anomalous and spin Hall effects. For short-range collision, the disorder-mediated spin polarizations completely cancel the intrinsic ones and the total in-plane components of CISP equal those for systems without magnetization. However, for remote disorders, this cancellation does not occur and the total in-plane components of CISP strongly depend on the spin-orbit interaction coefficients and magnetization for both pure Rashba and combined Rashba-Dresselhaus models.
Ritchie, Stephen D
2011-01-01
Pro .NET Best Practices is a practical reference to the best practices that you can apply to your .NET projects today. You will learn standards, techniques, and conventions that are sharply focused, realistic and helpful for achieving results, steering clear of unproven, idealistic, and impractical recommendations. Pro .NET Best Practices covers a broad range of practices and principles that development experts agree are the right ways to develop software, which includes continuous integration, automated testing, automated deployment, and code analysis. Whether the solution is from a free and
Energy Technology Data Exchange (ETDEWEB)
2016-09-01
The technology necessary to build net zero energy buildings (NZEBs) is ready and available today, however, building to net zero energy performance levels can be challenging. Energy efficiency measures, onsite energy generation resources, load matching and grid interaction, climatic factors, and local policies vary from location to location and require unique methods of constructing NZEBs. It is recommended that Components start looking into how to construct and operate NZEBs now as there is a learning curve to net zero construction and FY 2020 is just around the corner.
Heydt, Michael
2013-01-01
Filled with practical, step-by-step instructions and clear explanations for the most important and useful tasks. A step-by-step guide that helps you to index, search, and retrieve unstructured data with the help of Lucene.NET.Instant Lucene.NET How-to is essential for developers new to Lucene and Lucene.NET who are looking to get an immediate foundational understanding of how to use the library in their application. It's assumed you have programming experience in C# already, but not that you have experience with search techniques such as information retrieval theory (although there will be a l
Competition between Bose-Einstein Condensation and Spin Dynamics.
Naylor, B; Brewczyk, M; Gajda, M; Gorceix, O; Maréchal, E; Vernac, L; Laburthe-Tolra, B
2016-10-28
We study the impact of spin-exchange collisions on the dynamics of Bose-Einstein condensation by rapidly cooling a chromium multicomponent Bose gas. Despite relatively strong spin-dependent interactions, the critical temperature for Bose-Einstein condensation is reached before the spin degrees of freedom fully thermalize. The increase in density due to Bose-Einstein condensation then triggers spin dynamics, hampering the formation of condensates in spin-excited states. Small metastable spinor condensates are, nevertheless, produced, and they manifest in strong spin fluctuations.
Spin currents, spin torques, and the concept of spin superfluidity
Rückriegel, Andreas; Kopietz, Peter
2017-03-01
In magnets with noncollinear spin configuration the expectation value of the conventionally defined spin current operator contains a contribution which renormalizes an external magnetic field and hence affects only the precessional motion of the spin polarization. This term, which has been named angular spin current by Sun and Xie [Phys. Rev. B 72, 245305 (2005)], 10.1103/PhysRevB.72.245305, does not describe the translational motion of magnetic moments. We give a prescription for how to separate these two types of spin transport and show that the translational movement of the spin is always polarized along the direction of the local magnetization. We also show that at vanishing temperature the classical magnetic order parameter in magnetic insulators cannot carry a translational spin current and elucidate how this affects the interpretation of spin supercurrents.
Zhu, Zhiyong
2011-10-14
Fully relativistic first-principles calculations based on density functional theory are performed to study the spin-orbit-induced spin splitting in monolayer systems of the transition-metal dichalcogenides MoS2, MoSe2, WS2, and WSe2. All these systems are identified as direct-band-gap semiconductors. Giant spin splittings of 148–456 meV result from missing inversion symmetry. Full out-of-plane spin polarization is due to the two-dimensional nature of the electron motion and the potential gradient asymmetry. By suppression of the Dyakonov-Perel spin relaxation, spin lifetimes are expected to be very long. Because of the giant spin splittings, the studied materials have great potential in spintronics applications.
High spin-filter efficiency and Seebeck effect through spin-crossover iron-benzene complex.
Yan, Qiang; Zhou, Liping; Cheng, Jue-Fei; Wen, Zhongqian; Han, Qin; Wang, Xue-Feng
2016-04-21
Electronic structures and coherent quantum transport properties are explored for spin-crossover molecule iron-benzene Fe(Bz)2 using density functional theory combined with non-equilibrium Green's function. High- and low-spin states are investigated for two different lead-molecule junctions. It is found that the asymmetrical T-shaped contact junction in the high-spin state behaves as an efficient spin filter while it has a smaller conductivity than that in the low-spin state. Large spin Seebeck effect is also observed in asymmetrical T-shaped junction. Spin-polarized properties are absent in the symmetrical H-shaped junction. These findings strongly suggest that both the electronic and contact configurations play significant roles in molecular devices and metal-benzene complexes are promising materials for spintronics and thermo-spintronics.
DEFF Research Database (Denmark)
Marszal, Anna Joanna; Bourrelle, Julien S.; Musall, Eike
2010-01-01
and identify possible renewable energy supply options which may be considered in calculations. Finally, the gap between the methodology proposed by each organisation and their respective national building code is assessed; providing an overview of the possible changes building codes will need to undergo......The international cooperation project IEA SHC Task 40 / ECBCS Annex 52 “Towards Net Zero Energy Solar Buildings”, attempts to develop a common understanding and to set up the basis for an international definition framework of Net Zero Energy Buildings (Net ZEBs). The understanding of such buildings...... parameters used in the calculations are discussed and the various renewable supply options considered in the methodologies are summarised graphically. Thus, the paper helps to understand different existing approaches to calculate energy balance in Net ZEBs, highlights the importance of variables selection...
U.S. Department of Health & Human Services — The PhysioNet Resource is intended to stimulate current research and new investigations in the study of complex biomedical and physiologic signals. It offers free...
DEFF Research Database (Denmark)
Horn, Heiko; Lawrence, Michael S; Chouinard, Candace R
2018-01-01
Methods that integrate molecular network information and tumor genome data could complement gene-based statistical tests to identify likely new cancer genes; but such approaches are challenging to validate at scale, and their predictive value remains unclear. We developed a robust statistic (Net......Sig) that integrates protein interaction networks with data from 4,742 tumor exomes. NetSig can accurately classify known driver genes in 60% of tested tumor types and predicts 62 new driver candidates. Using a quantitative experimental framework to determine in vivo tumorigenic potential in mice, we found that Net......Sig candidates induce tumors at rates that are comparable to those of known oncogenes and are ten-fold higher than those of random genes. By reanalyzing nine tumor-inducing NetSig candidates in 242 patients with oncogene-negative lung adenocarcinomas, we find that two (AKT2 and TFDP2) are significantly amplified...
2015-10-30
query tide data sources in a desired geographic region of USA and its territories (Figure 1). Users can select a tide data source through the Google Map ...select data sources according to the desired geographic region. It uses the Google Map interface to display data from different sources. Recent...Coastal Inlets Research Program TideNet The TideNet is a web-based Graphical User Interface (GUI) that provides users with GIS mapping tools to
Neto, João Pedro; Costa, José Félix
1999-01-01
In a recent paper [Neto et al. 97] we showed that programming languages can be translated on recurrent (analog, rational weighted) neural nets. The goal was not efficiency but simplicity. Indeed we used a number-theoretic approach to machine programming, where (integer) numbers were coded in a unary fashion, introducing a exponential slow down in the computations, with respect to a two-symbol tape Turing machine. Implementation of programming languages in neural nets turns to be not only theo...
Salikhmetov, Anton
2013-01-01
Draft translation to Russian of Chapter 7, Interaction-Based Models of Computation, from Models of Computation: An Introduction to Computability Theory by Maribel Fernandez. "In this chapter, we study interaction nets, a model of computation that can be seen as a representative of a class of models based on the notion of 'computation as interaction'. Interaction nets are a graphical model of computation devised by Yves Lafont in 1990 as a generalisation of the proof structures of linear logic...
Liberty, Jesse
2009-01-01
Bestselling author Jesse Liberty and industry expert Alex Horovitz uncover the common threads that unite the .NET 3.5 technologies, so you can benefit from the best practices and architectural patterns baked into the new Microsoft frameworks. The book offers a Grand Tour" of .NET 3.5 that describes how the principal technologies can be used together, with Ajax, to build modern n-tier and service-oriented applications. "
Shi, Shuyuan; Wang, Aizhu; Wang, Yi; Ramaswamy, Rajagopalan; Shen, Lei; Moon, Jisoo; Zhu, Dapeng; Yu, Jiawei; Oh, Seongshik; Feng, Yuanping; Yang, Hyunsoo
2018-01-01
We report the observation of efficient charge-to-spin conversion in the three-dimensional topological insulator (TI) B i2S e3 and Ag bilayer by the spin-torque ferromagnetic resonance technique. The spin-orbit-torque ratio in the B i2S e3/Ag /CoFeB heterostructure shows a significant enhancement as the Ag thickness increases to ˜2 nm and reaches a value of 0.5 for 5 nm Ag, which is ˜3 times higher than that of B i2S e3/CoFeB at room temperature. The observation reveals the interfacial effect of B i2S e3/Ag exceeds that of the topological surface states (TSSs) in the B i2S e3 layer and plays a dominant role in the charge-to-spin conversion in the B i2S e3/Ag /CoFeB system. Based on first-principles calculations, we attribute our observation to the large Rashba splitting bands which wrap the TSS band and have the same net spin polarization direction as the TSS of B i2S e3 . Subsequently, we demonstrate Rashba-induced magnetization switching in B i2S e3/Ag /Py with a low current density of 5.8 ×105A /c m2 .
African Journals Online (AJOL)
PROJET SOJA
Dans ce travail nous avons préparé des couches minces de l'oxyde de zinc ZnO dopées à l'aluminium et non dopées par la technique Sol-Gel associée au « spin coating » sur des substrats en verre « pyrex » à partir de l'acétate de zinc dissous dans une solution de l'éthanol. Nous avons ensuite effectué des analyses ...
Magnetic cellular nonlinear network with spin wave bus for image processing
Khitun, Alexander; Bao, Mingqiang; Wang, Kang L.
2010-03-01
We describe and analyze a cellular nonlinear network based on magnetic nanostructures for image processing. The network consists of magneto-electric cells integrated onto a common ferromagnetic film-spin wave bus. The magneto-electric cell is an artificial two-phase multiferroic structure comprising piezoelectric and ferromagnetic materials. A bit of information is assigned to the cell's magnetic polarization, which can be controlled by the applied voltage. The information exchange among the cells is via the spin waves propagating in the spin wave bus. Each cell changes its state as a combined effect: magneto-electric coupling and the interaction with the spin waves. The distinct feature of a network with a spin wave bus is the ability to control the inter-cell communication by an external global parameter — magnetic field. The latter makes it possible to realize different image processing functions on the same template without rewiring or reconfiguration. We present the results of numerical simulations illustrating image filtering, erosion, dilation, horizontal and vertical line detection, inversion and edge detection accomplished on one template by the proper choice of the strength and direction of the external magnetic field. We also present numerical assets on the major network parameters such as cell density, power dissipation and functional throughput, and compare them with the parameters projected for other nano-architectures such as CMOL-CrossNet, Quantum-Dot Cellular Automata, and Quantum Dot-Image Processor. Potentially, the utilization of spin wave phenomena at the nanometer scale may provide a route to low-power consumption and functional logic circuits for special task data processing.
Semiclassical backreaction around a nearly spinning cosmic string
De Lorenci, Vitorio A
2009-01-01
This paper investigates semiclassical backreaction of a conformally coupled massless scalar field on the geometrical background of a nearly spinning cosmic string - the spin density is smaller than, but arbitrarily close to, the dislocation parameter. As the spin density approaches the dislocation parameter, it is shown that an "ergoregion" spreads around the cosmic string, boosting along the string axis the once static observers. Considering that the geometrical background contains closed timelike curves when the spin density exceeds the dislocation parameter, it is argued that the appearance of the "ergoregion" may be part of a chronology protection mechanism that takes place in related non stationary geometries.
Klengel, Alexis; Stumpp, Patrick; Klengel, Steffen; Böttger, Ina; Rönisch, Nadja; Kahn, Thomas
2017-05-01
Purpose To compare single-shot echo-planar diffusion-weighted imaging-derived apparent diffusion coefficient (ADC) maps with fat-saturated (FS) proton density (PD)-weighted turbo spin-echo (TSE) imaging in the detection of bone marrow lesions (BMLs) after knee trauma. Materials and Methods Institutional review board approval was obtained from Leipzig University. Written informed consent was waived. Three radiologists retrospectively re-examined 97 consecutive patients with reported knee trauma who underwent 1.5-T magnetic resonance (MR) imaging within 90 days of knee trauma. The following sequences were used: (a) sagittal T1-weighted TSE and FS PD-weighted TSE and (b) sagittal T1-weighted TSE and single-shot echo-planar diffusion-weighted imaging-derived ADC mapping. BMLs on the lateral and medial femoral condyle, lateral and medial aspect of the tibial plateau, and patella were documented. Volumetry was performed on BMLs with a thickness of at least 15 mm (major BMLs). ADC values were measured in intact bone marrow and major BMLs. A McNemar test and t tests were used as appropriate to test for significant differences between BML number and volume at an α level of .05. Results Significantly more patients showed at least one BML on ADC maps (98%, 95 of 97 patients) than on FS PD-weighted TSE images (86%, 84 of 97 patients) (P maps. Only 58% of the affected regions detected on ADC maps (170 of 293 regions) were identified on FS PD-weighted TSE images (P maps (81 cm3) than on FS PD-weighted TSE images (39 cm3) (P maps are more sensitive than corresponding FS PD-weighted TSE images for detection of BML after knee trauma and allow detection of significantly more and larger BMLs. ADC map evaluation improves diagnostic performance in regions with insufficient spectral fat saturation, such as the patella. © RSNA, 2016 Online supplemental material is available for this article.
Kyômen, Tôru; Asaka, Yoshinori; Itoh, Mitsuru
2005-01-01
Magnetic susceptibility and heat capacity due to the spin-state transition in LaCoO3 were calculated by a molecular-field model in which the energy-level diagram of high-spin state reported by Ropka and Radwanski [Phys. Rev. B 67, 172401 (2003)] is assumed for the excited state, and the energy and entropy of mixing of high-spin Co ions and low-spin Co ions are introduced phenomenologically. The experimental data below 300K were well reproduced by this model, which proposes that the high-spin excited state can be populated even if the energy of high-spin state is much larger than that of low-spin state, because the negatively large energy of mixing reduces the net excitation energy. The stability of each spin state including the intermediate-spin state is discussed based on the present results and other reports.
Spin Transport and Dynamics in Antiferromagnetic Metals and Magnetic Insulators
Swaving, A.C.|info:eu-repo/dai/nl/313938083
2012-01-01
It is demonstrated that in an antiferromagnetic metal a steady-state transport current generates a current-induced out-of-plane spin density, resulting in torques on the magnetization. This spin density is parameterized by a velocity that is proportional to the current. The generalization of the
Manz, Thomas A; Sholl, David S
2011-12-13
The partitioning of electron spin density among atoms in a material gives atomic spin moments (ASMs), which are important for understanding magnetic properties. We compare ASMs computed using different population analysis methods and introduce a method for computing density derived electrostatic and chemical (DDEC) ASMs. Bader and DDEC ASMs can be computed for periodic and nonperiodic materials with either collinear or noncollinear magnetism, while natural population analysis (NPA) ASMs can be computed for nonperiodic materials with collinear magnetism. Our results show Bader, DDEC, and (where applicable) NPA methods give similar ASMs, but different net atomic charges. Because they are optimized to reproduce both the magnetic field and the chemical states of atoms in a material, DDEC ASMs are especially suitable for constructing interaction potentials for atomistic simulations. We describe the computation of accurate ASMs for (a) a variety of systems using collinear and noncollinear spin DFT, (b) highly correlated materials (e.g., magnetite) using DFT+U, and (c) various spin states of ozone using coupled cluster expansions. The computed ASMs are in good agreement with available experimental results for a variety of periodic and nonperiodic materials. Examples considered include the antiferromagnetic metal organic framework Cu3(BTC)2, several ozone spin states, mono- and binuclear transition metal complexes, ferri- and ferro-magnetic solids (e.g., Fe3O4, Fe3Si), and simple molecular systems. We briefly discuss the theory of exchange-correlation functionals for studying noncollinear magnetism. A method for finding the ground state of systems with highly noncollinear magnetism is introduced. We use these methods to study the spin-orbit coupling potential energy surface of the single molecule magnet Fe4C40H52N4O12, which has highly noncollinear magnetism, and find that it contains unusual features that give a new interpretation to experimental data.
Rise of Racetrack Memory! Domain Wall Spin-Orbitronics
Parkin, Stuart
Memory-storage devices based on the current controlled motion of a series of domain walls (DWs) in magnetic racetracks promise performance and reliability beyond that of conventional magnetic disk drives and solid state storage devices (1). Racetracks that are formed from atomically thin, perpendicularly magnetized nano-wires, interfaced with adjacent metal layers with high spin-orbit coupling, give rise to domain walls that exhibit a chiral Néel structure (2). These DWs can be moved very efficiently with current via chiral spin-orbit torques (2,3). Record-breaking current-induced DW speeds exceeding 1,000 m/sec are found in synthetic antiferromagnetic structures (3) in which the net magnetization of the DWs is tuned to almost zero, making them ``invisible''. Based on these recent discoveries, Racetrack Memory devices have the potential to operate on picosecond timescales and at densities more than 100 times greater than other memory technologies. (1) S.S.P. Parkin et al., Science 320, 5873 (2008); S.S.P. Parkin and S.-H. Yang, Nat. Nano. 10, 195 (2015). (2) K.-S. Ryu metal. Nat. Nano. 8, 527 (2013). (3) S.-H. Yang, K.-S. Ryu and S.S.P. Parkin, Nat. Nano. 10, 221 (2015). (4). S.S.P. Parkin, Phys. Rev. Lett. 67, 3598 (1991).
Spin echo magnetic resonance imaging.
Jung, Bernd André; Weigel, Matthias
2013-04-01
The spin echo sequence is a fundamental pulse sequence in MRI. Many of today's applications in routine clinical use are based on this elementary sequence. In this review article, the principles of the spin echo formation are demonstrated on which the generation of the fundamental image contrasts T1, T2, and proton density is based. The basic imaging parameters repetition time (TR) and echo time (TE) and their influence on the image contrast are explained. Important properties such as the behavior in multi-slice imaging or in the presence of flow are depicted and the basic differences with gradient echo imaging are illustrated. The characteristics of the spin echo sequence for different magnetic field strengths with respect to clinical applications are discussed. Copyright © 2013 Wiley Periodicals, Inc.
Fornas Estrada, Miquel
2008-01-01
L'aparició de la plataforma .NET Framework ha suposat un canvi molt important en la forma de crear i distribuir aplicacions, degut a que incorpora una sèrie d'innovacions tècniques i productives que simplifiquen molt les tasques necessàries per desenvolupar un projecte. La aparición de la plataforma. NET Framework ha supuesto un cambio muy importante en la forma de crear y distribuir aplicaciones, debido a que incorpora una serie de innovaciones técnicas y productivas que simplifican mucho...
Wingender, E
2011-01-01
It was suggested some years ago that Petri nets might be well suited to modeling metabolic networks, overcoming some of the limitations encountered by the use of systems employing ODEs (ordinary differential equations). Much work has been done since then which confirms this and demonstrates the usefulness of this concept for systems biology. Petri net technology is not only intuitively understood by scientists trained in the life sciences, it also has a robust mathematical foundation and provides the required degree of flexibility. As a result it appears to be a very promising approach to mode
Magnetic Nanostructures Spin Dynamics and Spin Transport
Farle, Michael
2013-01-01
Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.
Spin-drift transport in semiconductors
Idrish Miah, M.
2008-02-01
We present a study on spin transport in semiconductors under applied electric fields. Our experiments detect photoinjected electron spins and their relaxation during drift transport in intrinsic and moderately n-doped GaAs, based on the extraordinary Hall (eH) effect. For relatively low electric field (E), the optically spin-induced eH effect in n-doped GaAs is found to be enhanced with increasing doping density and not to depend much on E, indicating that a substantial amount of optical spin polarization is preserved during the drift transport in these extrinsic semiconductors. However, when the spin-oriented electrons are injected with a high E, a very significant decrease is observed in the eH voltage (VeH) due to an increase in the spin precession frequency of the hot electrons. Spin relaxation by the D'yakonov-Perel' mechanism is calculated, and is suggested to be the reason for such a rapid spin relaxation for hot electrons under a high E. However, in an intrinsic GaAs (i-GaAs), a much weaker VeH is observed and, as the electron spins scattered by holes due to the Coulomb interaction in i-GaAs, the spin relaxation by the Bir-Aronov-Pikus mechanism is considered. Skew scattering and side jump as possible mechanisms of the optically spin-induced transverse Hall currents are discussed. Based on a spin drift-diffusion model, drift and diffusion contributions to the VeH are examined. The results are also discussed in comparison with theoretical investigations.
Spin-drift transport in semiconductors
Energy Technology Data Exchange (ETDEWEB)
Miah, M Idrish [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong, Chittagong-4331 (Bangladesh)
2008-02-07
We present a study on spin transport in semiconductors under applied electric fields. Our experiments detect photoinjected electron spins and their relaxation during drift transport in intrinsic and moderately n-doped GaAs, based on the extraordinary Hall (eH) effect. For relatively low electric field (E), the optically spin-induced eH effect in n-doped GaAs is found to be enhanced with increasing doping density and not to depend much on E, indicating that a substantial amount of optical spin polarization is preserved during the drift transport in these extrinsic semiconductors. However, when the spin-oriented electrons are injected with a high E, a very significant decrease is observed in the eH voltage (V{sub eH}) due to an increase in the spin precession frequency of the hot electrons. Spin relaxation by the D'yakonov-Perel' mechanism is calculated, and is suggested to be the reason for such a rapid spin relaxation for hot electrons under a high E. However, in an intrinsic GaAs (i-GaAs), a much weaker V{sub eH} is observed and, as the electron spins scattered by holes due to the Coulomb interaction in i-GaAs, the spin relaxation by the Bir-Aronov-Pikus mechanism is considered. Skew scattering and side jump as possible mechanisms of the optically spin-induced transverse Hall currents are discussed. Based on a spin drift-diffusion model, drift and diffusion contributions to the V{sub eH} are examined. The results are also discussed in comparison with theoretical investigations.
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 9. Petri Nets - Applications. Y Narahari. General Article Volume 4 Issue 9 September 1999 pp 44-52. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/09/0044-0052. Author Affiliations. Y Narahari ...
DEFF Research Database (Denmark)
Ilsøe, Anna
2012-01-01
Does regulation of working hours at national and sector level impose straitjackets, or offer safety nets to employees seeking working time flexibility? This article compares legislation and collective agreements in the metal industries of Denmark, Germany and the USA. The industry has historically...
Jensen, Kurt
2009-01-01
Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. This book introduces the constructs of the CPN modelling language and presents the related analysis methods. It provides a comprehensive road map for the practical use of CPN.
DEFF Research Database (Denmark)
Grimshaw, Mark Nicholas; Yong, Louisa; Dobie, Ian
1999-01-01
of an existing Internet radio station; Boom Booom Net Radio. Whilst necessity dictates some use of technology-related terminology, wherever possible we have endeavoured to keep such jargon to a minimum and to either explain it in the text or to provide further explanation in the appended glossary....
Shor, Mikhael
2003-01-01
States making game theory relevant and accessible to students is challenging. Describes the primary goal of GameTheory.net is to provide interactive teaching tools. Indicates the site strives to unite educators from economics, political and computer science, and ecology by providing a repository of lecture notes and tests for courses using…
DEFF Research Database (Denmark)
Jensen, Kurt; Kristensen, Lars Michael
Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism...
Control phase shift of spin-wave by spin-polarized current and its application in logic gates
Energy Technology Data Exchange (ETDEWEB)
Chen, Xiangxu; Wang, Qi; Liao, Yulong; Tang, Xiaoli; Zhang, Huaiwu; Zhong, Zhiyong, E-mail: zzy@uestc.edu.cn
2015-11-15
We proposed a new ways to control the phase shift of propagating spin waves by applying a local spin-polarized current on ferromagnetic stripe. Micromagnetic simulation showed that a phase shift of about π can be obtained by designing appropriate width and number of pinned magnetic layers. The ways can be adopted in a Mach-Zehnder-type interferometer structure to fulfill logic NOT gates based on spin waves. - Highlights: • Spin-wave phase shift can be controlled by a local spin-polarized current. • Spin-wave phase shift increased with the increasing of current density. • Spin-wave phase shift can reach about 0.3π at a particular current density. • The ways can be used in a Mach-Zehnder-type interferometer to fulfill logic gates.
Spin diffusion in bulk GaN measured with MnAs spin injector
Jahangir, Shafat
2012-07-16
Spin injection and precession in bulk wurtzite n-GaN with different doping densities are demonstrated with a ferromagnetic MnAs contact using the three-terminal Hanle measurement technique. Theoretical analysis using minimum fitting parameters indicates that the spin accumulation is primarily in the n-GaN channel rather than at the ferromagnet (FM)/semiconductor (SC) interface states. Spin relaxation in GaN is interpreted in terms of the D’yakonov-Perel mechanism, yielding a maximum spin lifetime of 44 ps and a spin diffusion length of 175 nm at room temperature. Our results indicate that epitaxial ferromagnetic MnAs is a suitable high-temperature spin injector for GaN.
Energy Technology Data Exchange (ETDEWEB)
BAI,M.; ROSER, T.
2007-06-25
This paper proposes a new design of spin flipper for RHIC to obtain full spin flip with the spin tune staying at half integer. The traditional technique of using an rf dipole or solenoid as spin flipper to achieve full spin flip in the presence of full Siberian snake requires one to change the snake configuration to move the spin tune away from half integer. This is not practical for an operational high energy polarized proton collider like RHIC where beam lifetime is sensitive to small betatron tune change. The design of the new spin flipper as well as numerical simulations are presented.
Disambiguating bilingual nominal entries against WordNet
Rigau, G; Rigau, German; Agirre, Eneko
1995-01-01
This paper explores the acquisition of conceptual knowledge from bilingual dictionaries (French/English, Spanish/English and English/Spanish) using a pre-existing broad coverage Lexical Knowledge Base (LKB) WordNet. Bilingual nominal entries are disambiguated agains WordNet, therefore linking the bilingual dictionaries to WordNet yielding a multilingual LKB (MLKB). The resulting MLKB has the same structure as WordNet, but some nodes are attached additionally to disambiguated vocabulary of other languages. Two different, complementary approaches are explored. In one of the approaches each entry of the dictionary is taken in turn, exploiting the information in the entry itself. The inferential capability for disambiguating the translation is given by Semantic Density over WordNet. In the other approach, the bilingual dictionary was merged with WordNet, exploiting mainly synonymy relations. Each of the approaches was used in a different dictionary. Both approaches attain high levels of precision on their own, sh...
SPINS OF LARGE ASTEROIDS: A HINT OF A PRIMORDIAL DISTRIBUTION IN THEIR SPIN RATES
Energy Technology Data Exchange (ETDEWEB)
Steinberg, Elad; Sari, Re’em [The Hebrew University of Jerusalem, Jerusalem (Israel)
2015-04-15
The Asteroid Belt and the Kuiper Belt are relics from the formation of our solar system. Understanding the size and spin distribution of the two belts is crucial for a deeper understanding of the formation of our solar system and the dynamical processes that govern it. In this paper, we investigate the effect of collisions on the evolution of the spin distribution of asteroids and KBOs. We find that the power law nature of the impactors’ size distribution leads to a Lévy distribution of the spin rates. This results in a power law tail in the spin distribution, in stark contrast to the usually quoted Maxwellian distribution. We show that for bodies larger than 10 km, collisions alone lead to spin rates peaking at 0.15–0.5 revolutions per day. Comparing that to the observed spin rates of large asteroids (R > 50 km), we find that the spins of large asteroids, peaking at ∼1–2 revolutions per day, are dominated by a primordial component that reflects the formation mechanism of the asteroids. Similarly, the Kuiper Belt has undergone virtually no collisional spin evolution, assuming current densities. Collisions contribute a spin rate of ∼0.01 revolutions per day, thus the observed fast spin rates of KBOs are also primordial in nature.
Decoherence dynamics of a single spin versus spin ensemble
Dobrovitski, V.V.; Feiguin, A.E.; Awschalom, D.D.; Hanson, R.
2008-01-01
We study decoherence of central spins by a spin bath, focusing on the difference between measurement of a single central spin and measurement of a large number of central spins (as found in typical spin-resonance experiments). For a dilute spin bath, the single spin demonstrates Gaussian
The net charge at interfaces between insulators
Bristowe, N. C.; Littlewood, P. B.; Artacho, Emilio
2011-03-01
The issue of the net charge at insulating oxide interfaces is briefly reviewed with the ambition of dispelling myths of such charges being affected by covalency and related charge density effects. For electrostatic analysis purposes, the net charge at such interfaces is defined by the counting of discrete electrons and core ion charges, and by the definition of the reference polarization of the separate, unperturbed bulk materials. The arguments are illustrated for the case of a thin film of LaAlO3 over SrTiO3 in the absence of free carriers, for which the net charge is exactly 0.5e per interface formula unit, if the polarization response in both materials is referred to zero bulk values. Further consequences of the argument are extracted for structural and chemical alterations of such interfaces, in which internal rearrangements are distinguished from extrinsic alterations (changes of stoichiometry, redox processes), only the latter affecting the interfacial net charge. The arguments are reviewed alongside the proposal of Stengel and Vanderbilt (2009 Phys. Rev. B 80 241103) of using formal polarization values instead of net interfacial charges, based on the interface theorem of Vanderbilt and King-Smith (1993 Phys. Rev. B 48 4442-55). Implications for non-centrosymmetric materials are discussed, as well as for interfaces for which the charge mismatch is an integer number of polarization quanta.
The net charge at interfaces between insulators
Energy Technology Data Exchange (ETDEWEB)
Bristowe, N C; Littlewood, P B [Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Artacho, Emilio, E-mail: ncb30@cam.ac.uk [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom)
2011-03-02
The issue of the net charge at insulating oxide interfaces is briefly reviewed with the ambition of dispelling myths of such charges being affected by covalency and related charge density effects. For electrostatic analysis purposes, the net charge at such interfaces is defined by the counting of discrete electrons and core ion charges, and by the definition of the reference polarization of the separate, unperturbed bulk materials. The arguments are illustrated for the case of a thin film of LaAlO{sub 3} over SrTiO{sub 3} in the absence of free carriers, for which the net charge is exactly 0.5e per interface formula unit, if the polarization response in both materials is referred to zero bulk values. Further consequences of the argument are extracted for structural and chemical alterations of such interfaces, in which internal rearrangements are distinguished from extrinsic alterations (changes of stoichiometry, redox processes), only the latter affecting the interfacial net charge. The arguments are reviewed alongside the proposal of Stengel and Vanderbilt (2009 Phys. Rev. B 80 241103) of using formal polarization values instead of net interfacial charges, based on the interface theorem of Vanderbilt and King-Smith (1993 Phys. Rev. B 48 4442-55). Implications for non-centrosymmetric materials are discussed, as well as for interfaces for which the charge mismatch is an integer number of polarization quanta. (viewpoint)
Current-induced Rashba spin orbit torque in silicene
Chen, Ji; Peng, Yingzi; Zhou, Jie
2017-06-01
We study theoretically the spin torque of a ferromagnetic layer coupled to a silicene in the presence of the intrinsic Rashba spin orbit coupling (RSOC) effect. By using gauge field method, we find that under the applied current, the RSOC can induce an effective field which will result in the spin precession of conduction electron without applying any magnetic field. We also derive the spin torques due to the RSOC, which generalize the Landau-Lifshitz-Gilbert (LLG) equation. The spin torques are related to the applied current, the carrier density and Rashba strength of the system.
Arian Zad, Hamid; Ananikian, Nerses
2017-11-15
We consider a symmetric spin-1/2 Ising-XXZ double sawtooth spin ladder obtained from distorting a spin chain, with the XXZ interaction between the interstitial Heisenberg dimers (which are connected to the spins based on the legs via an Ising-type interaction), the Ising coupling between nearest-neighbor spins of the legs and rungs spins, respectively, and additional cyclic four-spin exchange (ring exchange) in the square plaquette of each block. The presented analysis supplemented by results of the exact solution of the model with infinite periodic boundary implies a rich ground state phase diagram. As well as the quantum phase transitions, the characteristics of some of the thermodynamic parameters such as heat capacity, magnetization and magnetic susceptibility are investigated. We prove here that among the considered thermodynamic and thermal parameters, solely heat capacity is sensitive versus the changes of the cyclic four-spin exchange interaction. By using the heat capacity function, we obtain a singularity relation between the cyclic four-spin exchange interaction and the exchange coupling between pair spins on each rung of the spin ladder. All thermal and thermodynamic quantities under consideration should be investigated by regarding those points which satisfy the singularity relation. The thermal entanglement within the Heisenberg spin dimers is investigated by using the concurrence, which is calculated from a relevant reduced density operator in the thermodynamic limit.
Arian Zad, Hamid; Ananikian, Nerses
2017-11-01
We consider a symmetric spin-1/2 Ising-XXZ double sawtooth spin ladder obtained from distorting a spin chain, with the XXZ interaction between the interstitial Heisenberg dimers (which are connected to the spins based on the legs via an Ising-type interaction), the Ising coupling between nearest-neighbor spins of the legs and rungs spins, respectively, and additional cyclic four-spin exchange (ring exchange) in the square plaquette of each block. The presented analysis supplemented by results of the exact solution of the model with infinite periodic boundary implies a rich ground state phase diagram. As well as the quantum phase transitions, the characteristics of some of the thermodynamic parameters such as heat capacity, magnetization and magnetic susceptibility are investigated. We prove here that among the considered thermodynamic and thermal parameters, solely heat capacity is sensitive versus the changes of the cyclic four-spin exchange interaction. By using the heat capacity function, we obtain a singularity relation between the cyclic four-spin exchange interaction and the exchange coupling between pair spins on each rung of the spin ladder. All thermal and thermodynamic quantities under consideration should be investigated by regarding those points which satisfy the singularity relation. The thermal entanglement within the Heisenberg spin dimers is investigated by using the concurrence, which is calculated from a relevant reduced density operator in the thermodynamic limit.
Gate-Driven Pure Spin Current in Graphene
Lin, Xiaoyang; Su, Li; Si, Zhizhong; Zhang, Youguang; Bournel, Arnaud; Zhang, Yue; Klein, Jacques-Olivier; Fert, Albert; Zhao, Weisheng
2017-09-01
The manipulation of spin current is a promising solution for low-power devices beyond CMOS. However, conventional methods, such as spin-transfer torque or spin-orbit torque for magnetic tunnel junctions, suffer from large power consumption due to frequent spin-charge conversions. An important challenge is, thus, to realize long-distance transport of pure spin current, together with efficient manipulation. Here, the mechanism of gate-driven pure spin current in graphene is presented. Such a mechanism relies on the electrical gating of carrier-density-dependent conductivity and spin-diffusion length in graphene. The gate-driven feature is adopted to realize the pure spin-current demultiplexing operation, which enables gate-controllable distribution of the pure spin current into graphene branches. Compared with the Elliott-Yafet spin-relaxation mechanism, the D'yakonov-Perel spin-relaxation mechanism results in more appreciable demultiplexing performance. The feature of the pure spin-current demultiplexing operation will allow a number of logic functions to be cascaded without spin-charge conversions and open a route for future ultra-low-power devices.
Spin Dependent Collision of Ultracold Metastable Atoms
Uetake, Satoshi; Doyle, John M; Takahashi, Yoshiro
2015-01-01
Spin-polarized metastable atoms of ultracold ytterbium are trapped at high density and their inelastic collisional properties are measured. We reveal that in collisions of Yb(3P2) with Yb(1S0) there is relatively weak inelastic loss, but with a significant spin-dependence consistent with Zeeman sublevel changes as being the dominant decay process. This is in strong contrast to our observations of Yb(3P2)-Yb(3P2) collisional loss, which are, at low field, much more rapid and have essentially no spin dependence. Our results give a guideline to use the 3P2 states in many possible applications.
On the free vibrations of spinning paraboloids
Shoemaker, W. L.; Utku, S.
1986-01-01
The dynamic behavior of a spinning linear-elastic paraboloid subject to nonaxisymmetric deformation is investigated analytically, applying the Rayleigh-Ritz procedure described by Utku et al. (1983). Energy-density, strain-displacement, and velocity-displacement expressions are generated; expressions for the generalized strain and position vector are derived; and the discretized dynamic equations are obtained. Numerical results obtained with a computer-program implementation of the method are presented in extensive tables and graphs. The effects of spin rate and bending rigidity and results for the special case of a spinning disk are included.
Further Problems with Integral Spin Charged Particles
Directory of Open Access Journals (Sweden)
Comay E.
2013-07-01
Full Text Available The structure of the Lagrangian density of quantum theories of electrically charged particles is analyzed. It is pointed out that a well known and self-consistent expression exists for the electromagnetic interactions of a spin-1/2 Dirac particle. On the other hand, using the Noether theorem, it is shown that no such expression exists for the spin-0 Klein-Gordon charged particle as well as for the W spin-1 particle. It is also explained why effective expressions used in practical analysis of collider data cannot be a part of a self-consistent theory. The results cast doubt on the validity of the electroweak theory.
Haggblade, Steven; Diallo, Boubacar; Staatz, John; Theriault, Veronique; Traoré, Abdramane
2013-01-01
Food and social safety nets have a history as long as human civilization. In hunter gatherer societies, food sharing is pervasive. Group members who prove unlucky in the short run, hunting or foraging, receive food from other households in anticipation of reciprocal consideration at a later time (Smith 1988). With the emergence of the first large sedentary civilizations in the Middle East, administrative systems developed specifically around food storage and distribution. The ancient Egyptian...
Wegmann, David G.
1989-01-01
Approved for public release; distribution is unlimited. The present and near term military balance of power between the U.S. and the Soviet Union can be expressed in a variety of net assessments. One can examine the strategic nuclear balance, the conventional balance in Europe, the maritime balance, and many others. Such assessments are essential not only for policy making but for arms control purposes and future force structure planning. However, to project the future military balance, on...
Using WordNet for Building WordNets
Farreres, X; Farreres, Xavier; Rodriguez, Horacio; Rigau, German
1998-01-01
This paper summarises a set of methodologies and techniques for the fast construction of multilingual WordNets. The English WordNet is used in this approach as a backbone for Catalan and Spanish WordNets and as a lexical knowledge resource for several subtasks.
Coarse graining flow of spin foam intertwiners
Dittrich, Bianca; Seth, Cameron J; Steinhaus, Sebastian
2016-01-01
Simplicity constraints play a crucial role in the construction of spin foam models, yet their effective behaviour on larger scales is scarcely explored. In this article we introduce intertwiner and spin net models for the quantum group $\\text{SU}(2)_k \\times \\text{SU}(2)_k$, which implement the simplicity constraints analogous to 4D Euclidean spin foam models, namely the Barrett-Crane (BC) and the Engle-Pereira-Rovelli-Livine/Freidel-Krasnov (EPRL/FK) model. These models are numerically coarse grained via tensor network renormalization, allowing us to trace the flow of simplicity constraints to larger scales. In order to perform these simulations we have substantially adapted tensor network algorithms, which we discuss in detail. The BC and the EPRL/FK model behave very differently under coarse graining: While the unique BC intertwiner model is a fixed point and therefore constitutes a 2D topological phase, BC spin net models flow away from the initial simplicity constraints and converge to several different ...
Effect of spinning workouts on affect.
Szabo, Attila; Gáspár, Zoltán; Kiss, Nikolett; Radványi, Alexandra
2015-06-01
Numerous physical exercises trigger positive changes in affect after relatively short workouts. Spinning, also known as indoor-cycling, is a very popular form of exercise, especially among women, but its impact on affect have not been examined to date. The purpose of the current work was to investigate the possible benefits of spinning on affect in self-controlled and in instructor-led exercise sessions. Using baseline measures and pre- to post-exercise design with a psychometrically validated questionnaire, the net effects of spinning (without music) on positive- and negative-affect were measured in two exercise conditions: (1) self-controlled workout (i.e. without an instructor) and (2) instructor-led workout. After both conditions, 18 women rated the extent which they enjoyed the exercise session on a 10-point Likert scale. The findings revealed that positive affect increased while negative affect decreased after both workouts. Exerted effort, measured through the heart rate, did not differ between the two conditions. However, participants enjoyed more the instructor-led exercise session than the self-regulated workout (effect size, Cohen's d = 0.93). This research reveals that spinning improves post-exercise affect, even without music and regardless of instructor's presence. Therefore, it demonstrates the net benefits of this popular exercise on affect.
Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi
2017-01-01
We investigate the interconversion phenomena between spin and mechanical angular momentum in moving objects. In particular, the recent results on spin manipulation and spin-current generation by mechanical motion are examined. In accelerating systems, spin-dependent gauge fields emerge, which enable the conversion from mechanical angular momentum into spins. Such a spin-mechanical effect is predicted by quantum theory in a non-inertial frame. Experiments which confirm the effect, i.e., the resonance frequency shift in nuclear magnetic resonance, the stray field measurement of rotating metals, and electric voltage generation in liquid metals, are discussed.
Proof nets for lingusitic analysis
Moot, R.C.A.
2002-01-01
This book investigates the possible linguistic applications of proof nets, redundancy free representations of proofs, which were introduced by Girard for linear logic. We will adapt the notion of proof net to allow the formulation of a proof net calculus which is soundand complete for the
Teaching Tennis for Net Success.
Young, Bryce
1989-01-01
A program for teaching tennis to beginners, NET (Net Easy Teaching) is described. The program addresses three common needs shared by tennis students: active involvement in hitting the ball, clearing the net, and positive reinforcement. A sample lesson plan is included. (IAH)
DEFF Research Database (Denmark)
Christensen, Henrik Bærbak; Hansen, Klaus Marius; Rasmussen, Morten
2012-01-01
is a tele-monitoring scenario in which Net4Care clients are deployed in a gateway in private homes. Medical devices then connect to these gateways and transmit their observations to a Net4Care server. In turn the Net4Care server creates valid clinical HL7 documents, stores them in a national XDS repository...
Shimizu, Kaoru; Tokura, Yasuhiro
2015-12-01
This paper presents a theoretical framework for analyzing the quantum fluctuation properties of a quantum spin chain subject to a quantum phase transition. We can quantify the fluctuation properties by examining the correlation between the fluctuations of two neighboring spins subject to the quantum uncertainty. To do this, we first compute the reduced density matrix ρ of the spin pair from the ground state |Ψ⟩ of a spin chain, and then identify the quantum correlation part ρ(q) embedded in ρ. If the spin chain is translationally symmetric and characterized by a nearest-neighbor two-body spin interaction, we can determine uniquely the form of ρ(q) as W|Φ〉〈Φ| with the weight W ≤1, and quantify the fluctuation properties using the two-spin entangled state |Φ〉. We demonstrate the framework for a transverse-field quantum Ising spin chain and indicate its validity for more general spin chain models.
Directory of Open Access Journals (Sweden)
Vladimir Lipunov
2010-01-01
Full Text Available The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19-20. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovae (including SNIa, search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System, and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.
DEFF Research Database (Denmark)
Andersen, Christian Ulrik; Lindstrøm, Hanne
2006-01-01
The seminar Art|Net|Work deals with two important changes in our culture. On one side, the network has become essential in the latest technological development. The Internet has entered a new phase, Web 2.0, including the occurrence of as ‘Wiki’s’, ‘Peer-2-Peer’ distribution, user controlled...... the praxis of the artist. We see different kinds of interventions and activism (including ‘hacktivism’) using the network as a way of questioning the invisible rules that govern public and semi-public spaces. Who ‘owns’ them? What kind of social relationships do they generate? On what principle...
Spin dynamics in a two-dimensional quantum gas
DEFF Research Database (Denmark)
Pedersen, Poul Lindholm; Gajdacz, Miroslav; Deuretzbacher, Frank
2014-01-01
We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions...... with superimposed angular density modulations. The density distributions depend on the applied magnetic field and are well explained by a simple Bogoliubov model. We show that the two clouds are anticorrelated in momentum space. The observed momentum correlations pave the way towards the creation of an atom source...
National Research Council Canada - National Science Library
Gutperle, Michael; Kraus, Per
2011-01-01
.... We find solutions that generalize the BTZ black hole and carry spin-3 charge. The black hole entropy formula yields a result for the asymptotic growth of the partition function at finite spin-3 chemical potential...
Energy Technology Data Exchange (ETDEWEB)
Haxton, W.C. (Institute for Nuclear Theory, Department of Physcis, FM-15, University of Washington, Seattle, Washington 98195 (US))
1989-05-01
I discuss a number of the themes of the Symmetries and Spin session of the 8th International Symposium on High Energy Spin Physics: parity non-conservation, CP/T nonconservation, and tests of charge symmetry and charge independence.
Dynamic nuclear spin polarization
Energy Technology Data Exchange (ETDEWEB)
Stuhrmann, H.B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany)
1996-11-01
Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.
Spin injection from a normal metal into a mesoscopic superconductor
Energy Technology Data Exchange (ETDEWEB)
Wolf, Michael J.; Kolenda, Stefan [Institut fuer Nanotechnologie, KIT, 76021 Karlsruhe (Germany); Huebler, Florian [Institut fuer Nanotechnologie, KIT, 76021 Karlsruhe (Germany); Center for Functional Nanostructures, KIT, 76131 Karlsruhe (Germany); Institut fuer Festkoerperphysik, KIT, 76021 Karlsruhe (Germany); Loehneysen, Hilbert v. [Center for Functional Nanostructures, KIT, 76131 Karlsruhe (Germany); Institut fuer Festkoerperphysik, KIT, 76021 Karlsruhe (Germany); Physikalisches Institut, KIT, 76128 Karlsruhe (Germany); Beckmann, Detlef [Institut fuer Nanotechnologie, KIT, 76021 Karlsruhe (Germany); Center for Functional Nanostructures, KIT, 76131 Karlsruhe (Germany)
2013-07-01
We report on nonlocal transport in superconductor hybrid structures, with ferromagnetic as well as normal-metal tunnel junctions attached to the superconductor. In the presence of a strong Zeeman splitting of the density of states, both charge and spin imbalance is injected into the superconductor. While previous experiments demonstrated spin injection from ferromagnetic electrodes, we show that spin imbalance is also created for normal-metal injector contacts. Using the combination of ferromagnetic and normal-metal detectors allows us to directly discriminate between charge and spin injection, and demonstrate a complete separation of charge and spin imbalance. The relaxation length of the spin imbalance is of the order of several μm and is found to increase with a magnetic field, but is independent of temperature. We further discuss possible relaxation mechanisms for the explanation of the spin relaxation length.
Spin-Tensor-Momentum-Coupled Bose-Einstein Condensates
Luo, Xi-Wang; Sun, Kuei; Zhang, Chuanwei
2017-11-01
The recent experimental realization of spin-orbit coupling for ultracold atomic gases provides a powerful platform for exploring many interesting quantum phenomena. In these studies, spin represents the spin vector (spin 1 /2 or spin 1) and orbit represents the linear momentum. Here we propose a scheme to realize a new type of spin-tensor-momentum coupling (STMC) in spin-1 ultracold atomic gases. We study the ground state properties of interacting Bose-Einstein condensates with STMC and find interesting new types of stripe superfluid phases and multicritical points for phase transitions. Furthermore, STMC makes it possible to study quantum states with dynamical stripe orders that display density modulation with a long tunable period and high visibility, paving the way for the direct experimental observation of a new dynamical supersolidlike state. Our scheme for generating STMC can be generalized to other systems and may open the door for exploring novel quantum physics and device applications.
Helminth.net: expansions to Nematode.net and an introduction to Trematode.net
Martin, John; Rosa, Bruce A.; Ozersky, Philip; Hallsworth-Pepin, Kymberlie; Zhang, Xu; Bhonagiri-Palsikar, Veena; Tyagi, Rahul; Wang, Qi; Choi, Young-Jun; Gao, Xin; McNulty, Samantha N.; Brindley, Paul J.; Mitreva, Makedonka
2015-01-01
Helminth.net (http://www.helminth.net) is the new moniker for a collection of databases: Nematode.net and Trematode.net. Within this collection we provide services and resources for parasitic roundworms (nematodes) and flatworms (trematodes), collectively known as helminths. For over a decade we have provided resources for studying nematodes via our veteran site Nematode.net (http://nematode.net). In this article, (i) we provide an update on the expansions of Nematode.net that hosts omics data from 84 species and provides advanced search tools to the broad scientific community so that data can be mined in a useful and user-friendly manner and (ii) we introduce Trematode.net, a site dedicated to the dissemination of data from flukes, flatworm parasites of the class Trematoda, phylum Platyhelminthes. Trematode.net is an independent component of Helminth.net and currently hosts data from 16 species, with information ranging from genomic, functional genomic data, enzymatic pathway utilization to microbiome changes associated with helminth infections. The databases’ interface, with a sophisticated query engine as a backbone, is intended to allow users to search for multi-factorial combinations of species’ omics properties. This report describes updates to Nematode.net since its last description in NAR, 2012, and also introduces and presents its new sibling site, Trematode.net. PMID:25392426
Directory of Open Access Journals (Sweden)
Mosher Aryc W
2011-04-01
Full Text Available Abstract Background There has been recent large scale-up of malaria control interventions in Ethiopia where transmission is unstable. While household ownership of long-lasting insecticidal nets (LLIN has increased greatly, there are concerns about inadequate net use. This study aimed to investigate factors associated with net use at two time points, before and after mass distribution of nets. Methods Two cross sectional surveys were carried out in 2006 and 2007 in Amhara, Oromia and SNNP regions. The latter was a sub-sample of the national Malaria Indicator Survey (MIS 3R. Each survey wave used multi-stage cluster random sampling with 25 households per cluster (224 clusters with 5,730 households in Baseline 2006 and 245 clusters with 5,910 households in MIS 3R 2007. Net ownership was assessed by visual inspection while net utilization was reported as use of the net the previous night. This net level analysis was restricted to households owning at least one net of any type. Logistic regression models of association between net use and explanatory variables including net type, age, condition, cost and other household characteristics were undertaken using generalized linear latent and mixed models (GLLAMM. Results A total of 3,784 nets in 2,430 households were included in the baseline 2006 analysis while the MIS 3R 2007 analysis comprised 5,413 nets in 3,328 households. The proportion of nets used the previous night decreased from 85.1% to 56.0% between baseline 2006 and MIS 3R 2007, respectively. Factors independently associated with increased proportion of nets used were: LLIN net type (at baseline 2006; indoor residual spraying (at MIS 3R 2007; and increasing wealth index at both surveys. At both baseline 2006 and MIS 3R 2007, reduced proportion of nets used was independently associated with increasing net age, increasing damage of nets, increasing household net density, and increasing altitude (>2,000 m. Conclusion This study identified
Intrinsic spin Seebeck effect in Au/YIG.
Qu, D; Huang, S Y; Hu, Jun; Wu, Ruqian; Chien, C L
2013-02-08
The acute magnetic proximity effects in Pt/YIG compromise the suitability of Pt as a spin current detector. We show that Au/YIG, with no anomalous Hall effect and a negligible magnetoresistance, allows the measurements of the intrinsic spin Seebeck effect with a magnitude much smaller than that in Pt/YIG. The experiment results are consistent with the spin polarized density functional calculations for Pt with a sizable and Au with a negligible magnetic moment near the interface with YIG.
NETS FOR PEACH PROTECTED CULTIVATION
Directory of Open Access Journals (Sweden)
Evelia Schettini
2012-06-01
Full Text Available The aim of this paper was to investigate the radiometric properties of coloured nets used to protect a peach cultivation. The modifications of the solar spectral distribution, mainly in the R and FR wavelength band, influence plant photomorphogenesis by means of the phytochrome and cryptochrome. The phytochrome response is characterized in terms of radiation rate in the red wavelengths (R, 600-700 nm to that in the farred radiation (FR, 700-800 nm, i.e. the R/FR ratio. The effects of the blue radiation (B, 400-500 nm is investigated by the ratio between the blue radiation and the far-red radiation, i.e. the B/FR ratio. A BLUE net, a RED net, a YELLOW net, a PEARL net, a GREY net and a NEUTRAL net were tested in Bari (Italy, latitude 41° 05’ N. Peach trees were located in pots inside the greenhouses and in open field. The growth of the trees cultivated in open field was lower in comparison to the growth of the trees grown under the nets. The RED, PEARL, YELLOW and GREY nets increased the growth of the trees more than the other nets. The nets positively influenced the fruit characteristics, such as fruit weight and flesh firmness.
Brächer, T; Fabre, M; Meyer, T; Fischer, T; Auffret, S; Boulle, O; Ebels, U; Pirro, P; Gaudin, G
2017-12-13
The miniaturization of complementary metal-oxide-semiconductor (CMOS) devices becomes increasingly difficult due to fundamental limitations and the increase of leakage currents. Large research efforts are devoted to find alternative concepts that allow for a larger data-density and lower power consumption than conventional semiconductor approaches. Spin waves have been identified as a potential technology that can complement and outperform CMOS in complex logic applications, profiting from the fact that these waves enable wave computing on the nanoscale. The practical application of spin waves, however, requires the demonstration of scalable, CMOS compatible spin-wave detection schemes in material systems compatible with standard spintronics as well as semiconductor circuitry. Here, we report on the wave-vector independent detection of short-waved spin waves with wavelengths down to 150 nm by the inverse spin Hall effect in spin-wave waveguides made from ultrathin Ta/Co 8 Fe 72 B 20 /MgO. These findings open up the path for miniaturized scalable interconnects between spin waves and CMOS and the use of ultrathin films made from standard spintronic materials in magnonics.
Savary, Lucile; Balents, Leon
2016-01-01
Quantum spin liquids may be considered "quantum disordered" ground states of spin systems, in which zero point fluctuations are so strong that they prevent conventional magnetic long range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects, such as non-local e...
Cross, Rod
2013-01-01
Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction between the egg and the surface on which it spins.
Semiclassical treatment of transport and spin relaxation in spin-orbit coupled systems
Energy Technology Data Exchange (ETDEWEB)
Lueffe, Matthias Clemens
2012-02-10
The coupling of orbital motion and spin, as derived from the relativistic Dirac equation, plays an important role not only in the atomic spectra but as well in solid state physics. Spin-orbit interactions are fundamental for the young research field of semiconductor spintronics, which is inspired by the idea to use the electron's spin instead of its charge for fast and power saving information processing in the future. However, on the route towards a functional spin transistor there is still some groundwork to be done, e.g., concerning the detailed understanding of spin relaxation in semiconductors. The first part of the present thesis can be placed in this context. We have investigated the processes contributing to the relaxation of a particularly long-lived spin-density wave, which can exist in semiconductor heterostructures with Dresselhaus and Rashba spin-orbit coupling of precisely the same magnitude. We have used a semiclassical spindiffusion equation to study the influence of the Coulomb interaction on the lifetime of this persistent spin helix. We have thus established that, in the presence of perturbations that violate the special symmetry of the problem, electron-electron scattering can have an impact on the relaxation of the spin helix. The resulting temperature-dependent lifetime reproduces the experimentally observed one in a satisfactory manner. It turns out that cubic Dresselhaus spin-orbit coupling is the most important symmetry-breaking element. The Coulomb interaction affects the dynamics of the persistent spin helix also via an Hartree-Fock exchange field. As a consequence, the individual spins precess about the vector of the surrounding local spin density, thus causing a nonlinear dynamics. We have shown that, for an experimentally accessible degree of initial spin polarization, characteristic non-linear effects such as a dramatic increase of lifetime and the appearance of higher harmonics can be expected. Another fascinating solid
Gauge invariant gluon spin operator for spinless nonlinear wave solutions
Lee, Bum-Hoon; Kim, Youngman; Pak, D. G.; Tsukioka, Takuya; Zhang, P. M.
2017-04-01
We consider nonlinear wave type solutions with intrinsic mass scale parameter and zero spin in a pure SU(2) quantum chromodynamics (QCD). A new stationary solution which can be treated as a system of static Wu-Yang monopole dressed in off-diagonal gluon field is proposed. A remarkable feature of such a solution is that it possesses a finite energy density everywhere. All considered nonlinear wave type solutions have common features: presence of the mass scale parameter, nonvanishing projection of the color fields along the propagation direction and zero spin. The last property requires revision of the gauge invariant definition of the spin density operator which is supposed to produce spin one states for the massless vector gluon field. We construct a gauge invariant definition of the classical gluon spin density operator which is unique and Lorentz frame independent.
Carrier spin relaxation in diluted magnetic quantum wells: Effect of Mn spin correlations
Krainov, I. V.; Vladimirova, M.; Scalbert, D.; Lähderanta, E.; Dmitriev, A. P.; Averkiev, N. S.
2017-10-01
We demonstrate theoretically that the presence of holes, either resident or photocreated, in diluted magnetic quantum wells accelerates the spin relaxation of electrons via a mechanism which has been previously overlooked. This effect is due to the spin correlations, which establish between magnetic ions coupled via hole-mediated Ruderman-Kittel-Kasuya-Yoshida interactions in the paramagnetic phase. As a consequence, the electron spin relaxation becomes temperature and hole density dependent, in contrast to existing theories. Our theory qualitatively reproduces the increase of the electron spin relaxation rate with pump power observed in n -doped CdMnTe magnetic quantum wells [Ben Cheikh et al., Phys. Rev. B 88, 201306 (2013), 10.1103/PhysRevB.88.201306]. It also predicts a decrease of the spin relaxation rate with temperature, as observed, although not in the same temperature range.
DEFF Research Database (Denmark)
Yu, Xiao-Qin; Zhu, Zhen-Gang; Su, Gang
2017-01-01
The thermoelectric performance of a topological energy converter is analyzed. The H-shaped device is based on a combination of transverse topological effects involving the spin: the inverse spin Hall effect and the spin Nernst effect. The device can convert a temperature drop in one arm into an e...
Parsons, A S L
1976-01-01
Describes six projects which use the frozen-spin principle: Helium-3 R.M.S. and longitudinally polarized frozen spin targets at Rutherford Laboratory, and the frozen spin targets at KEK, Saclay and the one used by the CERN-Helsinki collaboration. (7 refs).
2006-01-01
A new branch of physics and nanotechnology called spin electronics has emerged, which aims at simultaneously exploiting the charge and spin of electrons in the same device. The aim of this book is to present new directions in the development of spin electronics in both the basic physics and the future electronics.
Cross, Rod
2013-01-01
Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction…
Optical conversion of pure spin currents in hybrid molecular devices.
Wheeler, May C; Ma'Mari, Fatma Al; Rogers, Matthew; Gonçalves, Francisco J; Moorsom, Timothy; Brataas, Arne; Stamps, Robert; Ali, Mannan; Burnell, Gavin; Hickey, B J; Cespedes, Oscar
2017-10-13
Carbon-based molecules offer unparalleled potential for THz and optical devices controlled by pure spin currents: a low-dissipation flow of electronic spins with no net charge displacement. However, the research so far has been focused on the electrical conversion of the spin imbalance, where molecular materials are used to mimic their crystalline counterparts. Here, we use spin currents to access the molecular dynamics and optical properties of a fullerene layer. The spin mixing conductance across Py/C60 interfaces is increased by 10% (5 × 1018 m-2) under optical irradiation. Measurements show up to a 30% higher light absorbance and a factor of 2 larger photoemission during spin pumping. We also observe a 0.15 THz slowdown and a narrowing of the vibrational peaks. The effects are attributed to changes in the non-radiative damping and energy transfer. This opens new research paths in hybrid magneto-molecular optoelectronics, and the optical detection of spin physics in these materials.Carbon-based molecules could prove useful in terahertz and optical devices controlled by pure spin currents. Here, conversely, the authors use spin currents to probe molecular dynamics and enhance the optical response of a fullerene layer, enabling hybrid magneto-molecular optoelectronic devices.
Quantum Spin Hall phase in multilayer graphene
Garcia, Noel; Lado, Jose Luis; Fernandez-Rossier, Joaquin; Theory of Nanostructures Team
2015-03-01
We address the question of whether multilayer graphene systems are Quantum Spin Hall (QSH) insulators. Since interlayer coupling coples pz orbitals to s orbitals of different layers and Spin-Orbit (SO) couples pz orbitals with px and py of opposite spins, new spins mixing channels appear in the multilayer scenario that were not present in the monolayer. These new spin-mixing channels cast a doubt on the validity of the spin-conserving Kane-Mele model for multilayers and motivates our choice of a four orbital tight-binding model in the Slater-Koster approximation with intrinsic Spin-Orbit interaction. To completely determine if the QSH phase is present we calculate for different number of layers both the Z2 invariant for different stackings (only for inversion symmetric systems), and the density of states at the edge of semi-infinite graphene ribbon with armchair termination. We find that systems with even number of layers are normal insulators while systems with odd number of layers are QSH insulators, regardless of the stacking. We acknowledge financial support by Marie-Curie-ITN 607904-SPINOGRAPH.
The equivalency between logic Petri workflow nets and workflow nets.
Wang, Jing; Yu, ShuXia; Du, YuYue
2015-01-01
Logic Petri nets (LPNs) can describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. Logic Petri workflow nets (LPWNs) are proposed based on LPNs in this paper. Process mining is regarded as an important bridge between modeling and analysis of data mining and business process. Workflow nets (WF-nets) are the extension to Petri nets (PNs), and have successfully been used to process mining. Some shortcomings cannot be avoided in process mining, such as duplicate tasks, invisible tasks, and the noise of logs. The online shop in electronic commerce in this paper is modeled to prove the equivalence between LPWNs and WF-nets, and advantages of LPWNs are presented.
Quantum spin chains with multiple dynamics
Chen, Xiao; Fradkin, Eduardo; Witczak-Krempa, William
2017-11-01
Many-body systems with multiple emergent time scales arise in various contexts, including classical critical systems, correlated quantum materials, and ultracold atoms. We investigate such nontrivial quantum dynamics in a different setting: a spin-1 bilinear-biquadratic chain. It has a solvable entangled ground state, but a gapless excitation spectrum that is poorly understood. By using large-scale density matrix renormalization group simulations, we find that the lowest excitations have a dynamical exponent z that varies from 2 to 3.2 as we vary a coupling in the Hamiltonian. We find an additional gapless mode with a continuously varying exponent 2 ≤z capture the excitations of the chain. By using an exact mapping to the nonequilibrium dynamics of a classical spin chain, we find that the large dynamical exponent is due to subdiffusive spin motion. Finally, we discuss the connections to other spin chains and to a family of quantum critical models in two dimensions.
Spin-adapted matrix product states and operators
Keller, Sebastian; Reiher, Markus
2016-04-01
Matrix product states (MPSs) and matrix product operators (MPOs) allow an alternative formulation of the density matrix renormalization group algorithm introduced by White. Here, we describe how non-abelian spin symmetry can be exploited in MPSs and MPOs by virtue of the Wigner-Eckart theorem at the example of the spin-adapted quantum chemical Hamiltonian operator.
Crystalline Kitaev spin liquids
Yamada, Masahiko G.; Dwivedi, Vatsal; Hermanns, Maria
2017-10-01
Frustrated magnetic systems exhibit many fascinating phases. Prime among them are quantum spin liquids, where the magnetic moments do not order even at zero temperature. A subclass of quantum spin liquids called Kitaev spin liquids are particularly interesting, because they are exactly solvable, can be realized in certain materials, and show a large variety of gapless and gapped phases. Here we show that nonsymmorphic symmetries can enrich spin liquid phases, such that the low-energy spinon degrees of freedom form three-dimensional Dirac cones or nodal chains. In addition, we suggest a realization of such Kitaev spin liquids in metal-organic frameworks.
Spin physics in semiconductors
2017-01-01
This book offers an extensive introduction to the extremely rich and intriguing field of spin-related phenomena in semiconductors. In this second edition, all chapters have been updated to include the latest experimental and theoretical research. Furthermore, it covers the entire field: bulk semiconductors, two-dimensional semiconductor structures, quantum dots, optical and electric effects, spin-related effects, electron-nuclei spin interactions, Spin Hall effect, spin torques, etc. Thanks to its self-contained style, the book is ideally suited for graduate students and researchers new to the field.
Observation of nuclear spin waves in spin-polarized atomic hydrogen gas
Energy Technology Data Exchange (ETDEWEB)
Johson, B.R.; Denker, J.S.; Bigelow, N.; Levy, L.P.; Freed, J.H.; Lee, D.M.
1984-04-23
We have observed narrow, distinct resonances in the NMR spectrum of dilute spin-polarized atomic hydrogen gas (nroughly-equal10/sup 16/ atoms/cm/sup 3/). The dependence of the observed spectra on temperature, density, polarization, and magnetic field gradient is consistent with theoretical predictions for spin-wave excitations damped by diffusion. We have measured the parameter ..mu.., which is a measure of the importance of exchange effects in spin transport processes, and the diffusion coefficient D/sub 0/, both of which are in reasonable agreement with theory.
Charge and Spin Transport in Spin-orbit Coupled and Topological Systems
Ndiaye, Papa Birame
2017-10-31
thermally driven. Chapters 5 and 6 carry throughout tight-binding studies on the topological charge-spin transport in two-dimensional lattices with ferromagnetic skyrmions and 3Q magnetic structure. We use the Landauer-Buttiker formalism and evaluate the robustness of the topological signals. For the 3Q state, a spin-polarized quantum anomalous Hall state with chiral edge modes, unaffected by deformation and disorder, is reachable in zero net magnetization. We finish with concluding remarks and perspectives.
DEFF Research Database (Denmark)
Jensen, Kurt; Kristensen, Lars Michael
studies that illustrate the practical use of CPN modelling and validation for design, specification, simulation, verification and implementation in various application domains. Their presentation primarily aims at readers interested in the practical use of CPN. Thus all concepts and constructs are first......Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism...... and the immense number of possible execution sequences. In this textbook, Jensen and Kristensen introduce the constructs of the CPN modelling language and present the related analysis methods in detail. They also provide a comprehensive road map for the practical use of CPN by showcasing selected industrial case...
Spin-torque generation in topological insulator based heterostructures
Fischer, Mark H.
2016-03-11
Heterostructures utilizing topological insulators exhibit a remarkable spin-torque efficiency. However, the exact origin of the strong torque, in particular whether it stems from the spin-momentum locking of the topological surface states or rather from spin-Hall physics of the topological-insulator bulk, remains unclear. Here, we explore a mechanism of spin-torque generation purely based on the topological surface states. We consider topological-insulator-based bilayers involving ferromagnetic metal (TI/FM) and magnetically doped topological insulators (TI/mdTI), respectively. By ascribing the key theoretical differences between the two setups to location and number of active surface states, we describe both setups within the same framework of spin diffusion of the nonequilibrium spin density of the topological surface states. For the TI/FM bilayer, we find large spin-torque efficiencies of roughly equal magnitude for both in-plane and out-of-plane spin torques. For the TI/mdTI bilayer, we elucidate the dominance of the spin-transfer-like torque. However, we cannot explain the orders of magnitude enhancement reported. Nevertheless, our model gives an intuitive picture of spin-torque generation in topological-insulator-based bilayers and provides theoretical constraints on spin-torque generation due to topological surface states.
SD-CAS: Spin Dynamics by Computer Algebra System.
Filip, Xenia; Filip, Claudiu
2010-11-01
A computer algebra tool for describing the Liouville-space quantum evolution of nuclear 1/2-spins is introduced and implemented within a computational framework named Spin Dynamics by Computer Algebra System (SD-CAS). A distinctive feature compared with numerical and previous computer algebra approaches to solving spin dynamics problems results from the fact that no matrix representation for spin operators is used in SD-CAS, which determines a full symbolic character to the performed computations. Spin correlations are stored in SD-CAS as four-entry nested lists of which size increases linearly with the number of spins into the system and are easily mapped into analytical expressions in terms of spin operator products. For the so defined SD-CAS spin correlations a set of specialized functions and procedures is introduced that are essential for implementing basic spin algebra operations, such as the spin operator products, commutators, and scalar products. They provide results in an abstract algebraic form: specific procedures to quantitatively evaluate such symbolic expressions with respect to the involved spin interaction parameters and experimental conditions are also discussed. Although the main focus in the present work is on laying the foundation for spin dynamics symbolic computation in NMR based on a non-matrix formalism, practical aspects are also considered throughout the theoretical development process. In particular, specific SD-CAS routines have been implemented using the YACAS computer algebra package (http://yacas.sourceforge.net), and their functionality was demonstrated on a few illustrative examples. Copyright © 2010 Elsevier Inc. All rights reserved.
The spin content of the proton in full QCD
Energy Technology Data Exchange (ETDEWEB)
Alles, B. [Milan Univ. (Italy). Dipt. di Fisica; Boyd, G. [Center for Computational Physics, University of Tsukuba, Tsukuba, Ibaraki 305 (Japan); D`Elia, M.; Di Giacomo, A. [Dipartimento di Fisica, Universita di Pisa and INFN, Piazza Torricelli 2, 56126 Pisa (Italy)
1998-04-01
We present preliminary results on the proton spin structure function in full QCD. The measurement has been done using 4 flavours of staggered fermions and an improved definition of the lattice topological charge density. (orig.). 17 refs.
Spin-wave excitations in quantum dots
Lipparini, Enrico; Serra, Llorenç
1998-03-01
The transverse response function for a quantum dot in a uniform magnetic field B is calculated using current-density-functional theory. The poles corresponding to the ΔLz=+/-1 and ΔSz=+/-1 spin waves are investigated as a function of B.
Pressure and Temperature Sensors Using Two Spin Crossover Materials
Directory of Open Access Journals (Sweden)
Catalin-Maricel Jureschi
2016-02-01
Full Text Available The possibility of a new design concept for dual spin crossover based sensors for concomitant detection of both temperature and pressure is presented. It is conjectured from numerical results obtained by mean field approximation applied to a Ising-like model that using two different spin crossover compounds containing switching molecules with weak elastic interactions it is possible to simultaneously measure P and T. When the interaction parameters are optimized, the spin transition is gradual and for each spin crossover compounds, both temperature and pressure values being identified from their optical densities. This concept offers great perspectives for smart sensing devices.
Über die Bestimmung des Spin-Absehneidekoeffizienten σ
DEFF Research Database (Denmark)
Schult, O. W. B.; Maier, B.P.K.; Gruber, U.
1965-01-01
A value σ=3, 5±1 is obtained for the spin cut off coefficient in the Fermi gas level density formula from a comparison of calculated and experimental (n, gamma)-intensities feeding the observed levels of deformed nuclei in the rare earths region. The model used for the computations is tested at two...... nuclei with compound states of low spin (I c =1/2) and high spin (I c =13/2 or 15/2). The calculations can help to determine spins of nuclear levels in some cases....
Non-equilibrium thermal entanglement for a three spin chain
Pumulo, N.; Sinayskiy, I.; Petruccione, F.
2011-08-01
The dynamics of a chain of three spins coupled at both ends to separate bosonic baths at different temperatures is studied. An exact analytical solution of the master equation in the Born-Markov approximation for the reduced density matrix of the chain is constructed. It is shown that for long times the reduced density matrix converges to the non-equilibrium steady state. Dynamical and steady state properties of the concurrence between the first and the last spin are studied.
Intermediate-spin state and properties of LaCoO3
Korotin, MA; Ezhov, SY; Solovyev, [No Value; Anisimov, [No Value; Khomskii, DI; Sawatzky, GA
1996-01-01
The electronic structure of the perovskite LaCoO3 for different spin states of Co ions was calculated in the local-density approximation LDA+U approach. The ground state is found to be a nonmagnetic insulator with Co ions in a low-spin state. Somewhat higher in energy, we find two intermediate-spin
MOKE measurements of spin polarization in topological insulators
Jonker, Berend; van't Erve, Olaf; Rajput, S.; Li, Lian; Li, Connie
The Dirac surface states of a topological insulator (TI) exhibit spin-momentum locking, where an unpolarized charge current creates a net spin polarization whose amplitude and orientation are controlled by the charge current. This polarization has been detected electrically using a magnetic contact. Here we use the magneto optic Kerr effect (MOKE) to detect this spin polarization optically. We deposit a 10nm layer of Al on a Bi2Se3 TI film and measure the Kerr rotation produced by an unpolarized bias current. Aluminum was chosen because it is a good spin diffusion layer and is optically opaque, making the MOKE measurement more sensitive to the spins generated near the top surface of the TI film. Modulating the charge current through the TI produces a corresponding response in the MOKE signal. We also show that spin diffusion from the TI into an Fe surface contact can rotate the Fe magnetization by spin transfer torque. We apply a constant bias field of 32 Oe and modulate the in-plane bias current while measuring the Kerr rotation of the Fe contact. A clear correlation between charge current and Kerr rotation is observed that cannot be explained by simple Oersted fields arising from the charge current, indicating that the spin transfer torque from Bi2Se3 into Fe is responsible. Supported by core programs at the NRL, and by NSF (DMR-1105839) at the University of Wisconsin, Milwaukee.
Influence of dc bias currents on Co/Cu/Co nonlocal spin valves
Wang, X. J.; Zou, H.; Ocola, L. E.; Divan, R.; Ji, Y.
2009-05-01
The spin signals of three Co/Cu/Co nonlocal spin valves have been measured as a function of a dc bias current. Both increases and decreases of spin signals have been observed. The increase in spin signal is attributed to the redistribution of the injection current at a high current density. A shift in effective injection point up to ˜100 nm is estimated. The decrease in spin signals is attributed to structural change of the materials and interfaces due to the prolonged exposure to a high-density current.
Directory of Open Access Journals (Sweden)
Mauricio Valenzuela
2017-10-01
Full Text Available We propose a hybrid class of theories for higher spin gravity and matrix models, i.e., which handle simultaneously higher spin gravity fields and matrix models. The construction is similar to Vasiliev’s higher spin gravity, but part of the equations of motion are provided by the action principle of a matrix model. In particular, we construct a higher spin (gravity matrix model related to type IIB matrix models/string theory that have a well defined classical limit, and which is compatible with higher spin gravity in A d S space. As it has been suggested that higher spin gravity should be related to string theory in a high energy (tensionless regime, and, therefore to M-Theory, we expect that our construction will be useful to explore concrete connections.
Spin caloritronics in graphene
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Angsula; Frota, H. O. [Department of Physics, Federal University of Amazonas, Av. Rodrigo Octavio 3000-Japiim, 69077-000 Manaus, AM (Brazil)
2015-06-14
Spin caloritronics, the combination of spintronics with thermoelectrics, exploiting both the intrinsic spin of the electron and its associated magnetic moment in addition to its fundamental electronic charge and temperature, is an emerging technology mainly in the development of low-power-consumption technology. In this work, we study the thermoelectric properties of a Rashba dot attached to two single layer/bilayer graphene sheets as leads. The temperature difference on the two graphene leads induces a spin current, which depends on the temperature and chemical potential. We demonstrate that the Rashba dot behaves as a spin filter for selected values of the chemical potential and is able to filter electrons by their spin orientation. The spin thermopower has also been studied where the effects of the chemical potential, temperature, and also the Rashba term have been observed.
Henneaux, Marc; Vasiliev, Mikhail A
2017-01-01
Symmetries play a fundamental role in physics. Non-Abelian gauge symmetries are the symmetries behind theories for massless spin-1 particles, while the reparametrization symmetry is behind Einstein's gravity theory for massless spin-2 particles. In supersymmetric theories these particles can be connected also to massless fermionic particles. Does Nature stop at spin-2 or can there also be massless higher spin theories. In the past strong indications have been given that such theories do not exist. However, in recent times ways to evade those constraints have been found and higher spin gauge theories have been constructed. With the advent of the AdS/CFT duality correspondence even stronger indications have been given that higher spin gauge theories play an important role in fundamental physics. All these issues were discussed at an international workshop in Singapore in November 2015 where the leading scientists in the field participated. This volume presents an up-to-date, detailed overview of the theories i...
DEFF Research Database (Denmark)
Engberg, Uffe Henrik; Winskel, Glynn
This article shows how individual Petri nets form models of Girard's intuitionistic linear logic. It explores questions of expressiveness and completeness of linear logic with respect to this interpretation. An aim is to use Petri nets to give an understanding of linear logic and give some apprai...
Zee M van der; Verspaij GJ; Rosbergen S; IMP; NMD
2003-01-01
Developers, administrators and managers can get more understanding of the .NET technology with this report. They can also make better choices how to use this technology. The report describes the results and conclusions of a study of the usability for the RIVM of this new generation .NET development
Net neutrality and audiovisual services
van Eijk, N.; Nikoltchev, S.
2011-01-01
Net neutrality is high on the European agenda. New regulations for the communication sector provide a legal framework for net neutrality and need to be implemented on both a European and a national level. The key element is not just about blocking or slowing down traffic across communication
Union Density and Hospital Outcomes.
Koys, Daniel J; Martin, Wm Marty; LaVan, Helen; Katz, Marsha
2015-01-01
The authors address the hospital outcomes of patient satisfaction, healthcare quality, and net income per bed. They define union density as the percentage of a hospital's employees who are in unions, healthcare quality as its 30-day acute myocardial infraction (AMI; heart attack) mortality rate, and patient satisfaction as its overall Hospital Consumer Assessment of Healthcare Providers and Systems score. Using a random sample of 84 union and 84 nonunion hospitals from across the United States, multiple regression analyses show that union density is negatively related to patient satisfaction. Union density is not related to healthcare quality as measured by the AMI mortality rate or to net income per bed. This implies that unions per se are not good or bad for hospitals. The authors suggest that it is better for hospital administrators to take a Balanced Scorecard approach and be concerned about employee satisfaction, patient satisfaction, healthcare quality, and net income.
Dynamics of nonequilibrium thermal entanglement for simple spin chains
Sinayskiy, I.; Pumulo, N.; Petruccione, F.
2011-10-01
The dynamics of simple spin chains of two and three spins coupled at both ends to separate bosonic baths at different temperatures is studied. An exact analytical solution of the master equation in the Born-Markov approximation for the reduced density matrix of the chain is constructed. It is shown that for long times the reduced density matrix converges to the non-equilibrium steady-state. Dynamical and steady state properties of the concurrence between the first and the last spin are studied.
Creating and manipulating nonequilibrium spins in nanoscale superconductors
Energy Technology Data Exchange (ETDEWEB)
Wolf, Michael J.; Kolenda, Stefan; Beckmann, Detlef [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (Germany); Huebler, Florian [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (Germany); Institut fuer Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany); Suergers, Christoph; Fischer, Gerda [Physikalisches Institut, Karlsruher Institut fuer Technologie (Germany); Loehneysen, Hilbert von [Institut fuer Festkoerperphysik, Karlsruher Institut fuer Technologie (Germany); Physikalisches Institut, Karlsruher Institut fuer Technologie (Germany)
2015-07-01
We report on nonlocal transport in superconductor hybrid structures, with ferromagnetic as well as normal-metal tunnel junctions attached to the superconductor. In the presence of a strong Zeeman splitting of the density of states, we find signatures of spin transport over distances of several μm, exceeding other length scales such as the coherence length, the normal-state spin-diffusion length, and the charge-imbalance length. Using a combination of ferromagnetic and normal-metal contacts, we demonstrate spin injection from a normal metal, and show a complete separation of charge and spin imbalance. An exchange splitting induced by the ferromagnetic insulator europium sulfide enables spin transport at very small applied magnetic fields, and therefore paves the way to manipulating spin currents by local exchange fields.
Perfect spin filtering effect in ultrasmall helical zigzag graphene nanoribbons
Energy Technology Data Exchange (ETDEWEB)
Zhang, Zi-Yue, E-mail: zzy8423@jiangnan.edu.cn
2017-02-05
The spin-polarized transport properties of helical zigzag graphene nanoribbons (ZGNRs) are investigated by first-principles calculations. It is found that although all helical ZGNRs have similar density of states and edge states, they show obviously different transport characteristics depending on the curling manners. ZGNRs curled along zigzag orientation exhibit perfect spin filtering effect with a large spin-split gap near the Fermi level, while ZGNRs curled along armchair orientation behave as conventional conductors for both two spin channels. The spin filtering effect will be weakened with the increase of either ribbon width or curling diameter. The results suggest that ultrasmall helical ZGNRs have important potential applications in spintronics and flexible electronics. - Highlights: • Perfect spin filtering effect has been found in helical ZGNRs. • The effect strongly depends on the curling manners of ZGNRs. • Different transport properties do not induced by distinct electronic properties. • The effect may be weakened with increasing either ribbon width or curling diameter.
Spin diffusion from an inhomogeneous quench in an integrable system
Ljubotina, Marko; Žnidarič, Marko; Prosen, Tomaž
2017-07-01
Generalized hydrodynamics predicts universal ballistic transport in integrable lattice systems when prepared in generic inhomogeneous initial states. However, the ballistic contribution to transport can vanish in systems with additional discrete symmetries. Here we perform large scale numerical simulations of spin dynamics in the anisotropic Heisenberg XXZ spin 1/2 chain starting from an inhomogeneous mixed initial state which is symmetric with respect to a combination of spin reversal and spatial reflection. In the isotropic and easy-axis regimes we find non-ballistic spin transport which we analyse in detail in terms of scaling exponents of the transported magnetization and scaling profiles of the spin density. While in the easy-axis regime we find accurate evidence of normal diffusion, the spin transport in the isotropic case is clearly super-diffusive, with the scaling exponent very close to 2/3, but with universal scaling dynamics which obeys the diffusion equation in nonlinearly scaled time.
Ballistic spin filtering across the ferromagnetic-semiconductor interface
Directory of Open Access Journals (Sweden)
Y.H. Li
2012-03-01
Full Text Available The ballistic spin-filter effect from a ferromagnetic metal into a semiconductor has theoretically been studied with an intention of detecting the spin polarizability of density of states in FM layer at a higher energy level. The physical model for the ballistic spin filtering across the interface between ferromagnetic metals and semiconductor superlattice is developed by exciting the spin polarized electrons into n-type AlAs/GaAs superlattice layer at a much higher energy level and then ballistically tunneling through the barrier into the ferromagnetic film. Since both the helicity-modulated and static photocurrent responses are experimentally measurable quantities, the physical quantity of interest, the relative asymmetry of spin-polarized tunneling conductance, could be extracted experimentally in a more straightforward way, as compared with previous models. The present physical model serves guidance for studying spin detection with advanced performance in the future.
Dery, Hanan; Song, Yang; Li, Pengke; Zutic, Igor
2011-01-01
Recent experimental breakthroughs have demonstrated that the electron spin in silicon can be reliably injected and detected as well as transferred over distances exceeding 1 mm. We propose an on-chip communication paradigm which is based on modulating spin polarization of a constant current in silicon wires. We provide figures of merit for this scheme by studying spin relaxation and drift-diffusion models in silicon.
Torczynski, John R.
2000-01-01
A spin coating apparatus requires less cleanroom air flow than prior spin coating apparatus to minimize cleanroom contamination. A shaped exhaust duct from the spin coater maintains process quality while requiring reduced cleanroom air flow. The exhaust duct can decrease in cross section as it extends from the wafer, minimizing eddy formation. The exhaust duct can conform to entrainment streamlines to minimize eddy formation and reduce interprocess contamination at minimal cleanroom air flow rates.
Directory of Open Access Journals (Sweden)
Dmitry A. Zaitsev
2013-09-01
Full Text Available A universal deterministic inhibitor Petri net with 14 places, 29 transitions and 138 arcs was constructed via simulation of Neary and Woods' weakly universal Turing machine with 2 states and 4 symbols; the total time complexity is exponential in the running time of their weak machine. To simulate the blank words of the weakly universal Turing machine, a couple of dedicated transitions insert their codes when reaching edges of the working zone. To complete a chain of a given Petri net encoding to be executed by the universal Petri net, a translation of a bi-tag system into a Turing machine was constructed. The constructed Petri net is universal in the standard sense; a weaker form of universality for Petri nets was not introduced in this work.
StreamNet Query System: Smolt Density Model
Pacific States Marine Fisheries Commission — In response to a need for Columbia Basin wide evaluation of anadromous production potential during the Northwest Power Planning Council's Subbasin Planning Process,...
DEFF Research Database (Denmark)
Jensen, J.; Houmann, Jens Christian Gylden; Bjerrum Møller, Hans
1975-01-01
The energies of spin waves propagating in the c direction of Tb have been studied by inelastic neutron scattering, as a function of a magnetic field applied along the easy and hard directions in the basal plane, and as a function of temperature. From a general spin Hamiltonian, consistent...... with the symmetry, we deduce the dispersion relation for the spin waves in a basal-plane ferromagnet. This phenomenological spin-wave theory accounts for the observed behavior of the magnon energies in Tb. The two q⃗-dependent Bogoliubov components of the magnon energies are derived from the experimental results...
Dieny, B.; Sousa, R.; Prejbeanu, L.
2007-04-01
Conventional electronics has in the past ignored the spin on the electron, however things began to change in 1988 with the discovery of giant magnetoresistance in metallic thin film stacks which led to the development of a new research area, so called spin-electronics. In the last 10 years, spin-electronics has achieved a number of breakthroughs from the point of view of both basic science and application. Materials research has led to several major discoveries: very large tunnel magnetoresistance effects in tunnel junctions with crystalline barriers due to a new spin-filtering mechanism associated with the spin-dependent symmetry of the electron wave functions new magnetic tunnelling barriers leading to spin-dependent tunnelling barrier heights and acting as spin-filters magnetic semiconductors with increasingly high ordering temperature. New phenomena have been predicted and observed: the possibility of acting on the magnetization of a magnetic nanostructure with a spin-polarized current. This effect, due to a transfer of angular momentum between the spin polarized conduction electrons and the local magnetization, can be viewed as the reciprocal of giant or tunnel magnetoresistance. It can be used to switch the magnetization of a magnetic nanostructure or to generate steady magnetic excitations in the system. the possibility of generating and manipulating spin current without charge current by creating non-equilibrium local accumulation of spin up or spin down electrons. The range of applications of spin electronics materials and phenomena is expanding: the first devices based on giant magnetoresistance were the magnetoresistive read-heads for computer disk drives. These heads, introduced in 1998 with current-in plane spin-valves, have evolved towards low resistance tunnel magnetoresistice heads in 2005. Besides magnetic recording technology, these very sensitive magnetoresistive sensors are finding applications in other areas, in particular in biology. magnetic
Lepadatu, S.; Claydon, J. S.; Kinane, C. J.; Charlton, T. R.; Langridge, S.; Potenza, A.; Dhesi, S. S.; Keatley, P. S.; Hicken, R. J.; Hickey, B. J.; Marrows, C. H.
2010-01-01
Using pulsed-current measurements we investigate the domain-wall depinning via spin-transfer torque from pinning potentials in V-doped Ni80Fe20 wires. The domain-wall depinning boundary, showing the variation of threshold current density with longitudinal magnetic field is measured and reproduced using micromagnetic simulations. This method allows us to determine the spin-current polarization and nonadiabaticity parameter in these materials. By increasing the V concentration we show that the nonadiabaticity parameter is increased while the Gilbert damping is unaffected. On the other hand the spin-current polarization is decreased, resulting in larger threshold current densities.
Spin-orbit effects on the Larmor dispersion relation in GaAs quantum wells
Malet, Francesc; Lipparini, Enrico; Barranco, Manuel; Pi, Martí
2006-03-01
We have studied the relevance of spin-orbit coupling to the dispersion relation of the Larmor resonance observed in inelastic light scattering and electron-spin resonance experiments on GaAs quantum wells. We show that the spin-orbit interaction, here described by a sum of Dresselhaus and Bychkov-Rashba terms, couples Zeeman and spin-density excitations. We have evaluated its contribution to the spin splitting as a function of the magnetic field B , and have found that in the small B limit, the spin-orbit interaction does not contribute to the spin splitting, whereas at high magnetic fields it yields a B independent contribution to the spin splitting given by 2(λR2-λD2) , with λR,D being the intensity of the Bychkov-Rashba and Dresselhaus spin-orbit terms.
Spin Current Noise of the Spin Seebeck Effect and Spin Pumping.
Matsuo, M; Ohnuma, Y; Kato, T; Maekawa, S
2018-01-19
We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal-metal-(NM-)ferromagnet(FM) bilayer system. Starting with a simple ferromagnet-insulator-(FI-)NM interface model with both spin-conserving and non-spin-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for a yttrium-iron-garnet-platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the non-spin-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.
Dissociative dynamics of spin-triplet and spin-singlet O2 on Ag(100).
Alducin, M; Busnengo, H F; Díez Muiño, R
2008-12-14
We study the dissociative dynamics of O(2) molecules on the Ag(100) surface. Initially, the impinging molecules are either in the spin-triplet ground state or in the spin-singlet excited state. The molecule-surface interaction is obtained in each case by constructing the six-dimensional potential energy surface (PES) from the interpolation of the energies calculated with spin-polarized and non-spin-polarized density functional theories, respectively. Classical trajectory calculations performed in both PESs show that O(2) molecules initially in the spin-triplet ground state only dissociate for incidence energies above 1.05 eV. This result is consistent with molecular beam experiments performed in this system. Interestingly, our results also suggest that for the spin-singlet O(2) dissociation occurs even for incidence energies as low as 50 meV. We propose the use of spin-singlet excited O(2) molecules to improve the otherwise low dissociative reactivity of O(2) at clean Ag(100).
Spin transition in arrays of gold nanoparticles and spin crossover molecules.
Devid, Edwin J; Martinho, Paulo N; Kamalakar, M Venkata; Šalitroš, Ivan; Prendergast, Úna; Dayen, Jean-François; Meded, Velimir; Lemma, Tibebe; González-Prieto, Rodrigo; Evers, Ferdinand; Keyes, Tia E; Ruben, Mario; Doudin, Bernard; van der Molen, Sense Jan
2015-04-28
We investigate if the functionality of spin crossover molecules is preserved when they are assembled into an interfacial device structure. Specifically, we prepare and investigate gold nanoparticle arrays, into which room-temperature spin crossover molecules are introduced, more precisely, [Fe(AcS-BPP)2](ClO4)2, where AcS-BPP = (S)-(4-{[2,6-(dipyrazol-1-yl)pyrid-4-yl]ethynyl}phenyl)ethanethioate (in short, Fe(S-BPP)2). We combine three complementary experiments to characterize the molecule-nanoparticle structure in detail. Temperature-dependent Raman measurements provide direct evidence for a (partial) spin transition in the Fe(S-BPP)2-based arrays. This transition is qualitatively confirmed by magnetization measurements. Finally, charge transport measurements on the Fe(S-BPP)2-gold nanoparticle devices reveal a minimum in device resistance versus temperature, R(T), curves around 260-290 K. This is in contrast to similar networks containing passive molecules only that show monotonically decreasing R(T) characteristics. Backed by density functional theory calculations on single molecular conductance values for both spin states, we propose to relate the resistance minimum in R(T) to a spin transition under the hypothesis that (1) the molecular resistance of the high spin state is larger than that of the low spin state and (2) transport in the array is governed by a percolation model.
Global phase diagram and quantum spin liquids in a spin-1/2 triangular antiferromagnet
Gong, Shou-Shu; Zhu, W.; Zhu, J.-X.; Sheng, D. N.; Yang, Kun
2017-08-01
We study the spin-1 /2 Heisenberg model on the triangular lattice with the nearest-neighbor J1>0 , the next-nearest-neighobr J2>0 Heisenberg interactions, and the additional scalar chiral interaction Jχ(S⃗i×S⃗j) .S⃗k for the three spins in all the triangles using large-scale density matrix renormalization group calculation on cylinder geometry. With increasing J2 (J2/J1≤0.3 ) and Jχ (Jχ/J1≤1.0 ) interactions, we establish a quantum phase diagram with the magnetically ordered 120∘, stripe, and noncoplanar tetrahedral phase. In between these magnetic order phases, we find a chiral spin liquid (CSL) phase, which is identified as a ν =1 /2 bosonic fractional quantum Hall state with possible spontaneous rotational symmetry breaking. By switching on the chiral interaction, we find that the previously identified spin liquid in the J1-J2 triangular model (0.08 ≲J2/J1≲0.15 ) shows a phase transition to the CSL phase at very small Jχ. We also compute the spin triplet gap in both spin liquid phases, and our finite-size results suggest a large gap in the odd topological sector but a small or vanishing gap in the even sector. We discuss the implications of our results on the nature of the spin liquid phases.
Zhou, Yi; Kanoda, Kazushi; Ng, Tai-Kai
2017-04-01
This is an introductory review of the physics of quantum spin liquid states. Quantum magnetism is a rapidly evolving field, and recent developments reveal that the ground states and low-energy physics of frustrated spin systems may develop many exotic behaviors once we leave the regime of semiclassical approaches. The purpose of this article is to introduce these developments. The article begins by explaining how semiclassical approaches fail once quantum mechanics become important and then describe the alternative approaches for addressing the problem. Mainly spin-1 /2 systems are discussed, and most of the time is spent in this article on one particular set of plausible spin liquid states in which spins are represented by fermions. These states are spin-singlet states and may be viewed as an extension of Fermi liquid states to Mott insulators, and they are usually classified in the category of so-called S U (2 ), U (1 ), or Z2 spin liquid states. A review is given of the basic theory regarding these states and the extensions of these states to include the effect of spin-orbit coupling and to higher spin (S >1 /2 ) systems. Two other important approaches with strong influences on the understanding of spin liquid states are also introduced: (i) matrix product states and projected entangled pair states and (ii) the Kitaev honeycomb model. Experimental progress concerning spin liquid states in realistic materials, including anisotropic triangular-lattice systems [κ -(ET )2Cu2(CN )3 and EtMe3Sb [Pd (dmit )2]2 ], kagome-lattice system [ZnCu3(OH )6Cl2 ], and hyperkagome lattice system (Na4 Ir3 O8 ), is reviewed and compared against the corresponding theories.
Joint Evolution of Spinning Supermassive Black Holes and Rotating Nuclei
Merritt, David; Vasiliev, Eugene
2015-01-01
A rotating supermassive black hole (SBH) interacts with stars in a galactic nucleus via torques due to dragging of inertial frames. If the stars orbit preferentially about an axis that is misaligned with the SBH's spin, the SBH will experience a net torque and its spin vector will precess; individual stellar orbits also precess about the instantaneous SBH spin vector, although at different rates depending on their orbital elements. Solution of the coupled, post-Newtonian equations describing this interaction reveals two evolutionary modes: sustained precession of the SBH; and damped precession, leading to alignment of the SBH spin with the nuclear angular momentum. Beyond a certain radius, stars interact gravitationally with each other in a time shorter than the Lense-Thirring time. Long-term evolution in this case is well described as uniform precession of the SBH about the cluster's rotational axis, with a stochastic contribution due to star-star interactions.
DEFF Research Database (Denmark)
High-level Petri nets are now widely used in both theoretical analysis and practical modelling of concurrent systems. The main reason for the success of this class of net models is that they make it possible to obtain much more succinct and manageable descriptions than can be obtained by means...... of low-level Petri nets - while, on the other hand, they still offer a wide range of analysis methods and tools. The step from low-level nets to high-level nets can be compared to the step from assembly languages to modern programming languages with an elaborated type concept. In low-level nets...... there is only one kind of token and this means that the state of a place is described by an integer (and in many cases even by a boolean). In high-level nets each token can carry a complex information/data - which, e.g., may describe the entire state of a process or a data base. Today most practical...
Zhang, X.; Wan, C. H.; Yuan, Z. H.; Fang, C.; Kong, W. J.; Wu, H.; Zhang, Q. T.; Tao, B. S.; Han, X. F.
2017-04-01
Confronting with the gigantic volume of data produced every day, raising integration density by reducing the size of devices becomes harder and harder to meet the ever-increasing demand for high-performance computers. One feasible path is to actualize more logic functions in one cell. In this respect, we experimentally demonstrate a prototype spin-orbit torque based spin logic cell integrated with five frequently used logic functions (AND, OR, NOT, NAND and NOR). The cell can be easily programmed and reprogrammed to perform desired function. Furthermore, the information stored in cells is symmetry-protected, making it possible to expand into logic gate array where the cell can be manipulated one by one without changing the information of other undesired cells. This work provides a prospective example of multi-functional spin logic cell with reprogrammability and nonvolatility, which will advance the application of spin logic devices.
Spin-spin correlations in ferromagnetic nanosystems
Vedmedenko, E. Y.; Mikuszeit, N.; Stapelfeldt, T.; Wieser, R.; Potthoff, M.; Lichtenstein, A. I.; Wiesendanger, R.
2011-04-01
Using exact diagonalization, Monte-Carlo, and mean-field techniques, characteristic temperature scales for ferromagnetic order are discussed for the Ising and the classical anisotropic Heisenberg model on finite lattices in one and two dimensions. The interplay between nearest-neighbor exchange, anisotropy and the presence of surfaces leads, as a function of temperature, to a complex behavior of the distance-dependent spin-spin correlation function, which is very different from what is commonly expected. A finite experimental observation time is considered in addition, which is simulated within the Monte-Carlo approach by an incomplete statistical average. We find strong surface effects for small nanoparticles, which cannot be explained within a simple Landau or mean-field concept and which give rise to characteristic trends of the spin-correlation function in different temperature regimes. Unambiguous definitions of crossover temperatures for finite systems and an effective method to estimate the critical temperature of corresponding infinite systems are given.
Pro asynchronous programming with .NET
Blewett, Richard; Ltd, Rock Solid Knowledge
2014-01-01
Pro Asynchronous Programming with .NET teaches the essential skill of asynchronous programming in .NET. It answers critical questions in .NET application development, such as: how do I keep my program responding at all times to keep my users happy how do I make the most of the available hardware how can I improve performanceIn the modern world, users expect more and more from their applications and devices, and multi-core hardware has the potential to provide it. But it takes carefully crafted code to turn that potential into responsive, scalable applications.With Pro Asynchronous Programming
Conformal Nets II: Conformal Blocks
Bartels, Arthur; Douglas, Christopher L.; Henriques, André
2017-08-01
Conformal nets provide a mathematical formalism for conformal field theory. Associated to a conformal net with finite index, we give a construction of the `bundle of conformal blocks', a representation of the mapping class groupoid of closed topological surfaces into the category of finite-dimensional projective Hilbert spaces. We also construct infinite-dimensional spaces of conformal blocks for topological surfaces with smooth boundary. We prove that the conformal blocks satisfy a factorization formula for gluing surfaces along circles, and an analogous formula for gluing surfaces along intervals. We use this interval factorization property to give a new proof of the modularity of the category of representations of a conformal net.
Spin Switching via Quantum Dot Spin Valves
Gergs, N. M.; Bender, S. A.; Duine, R. A.; Schuricht, D.
2018-01-01
We develop a theory for spin transport and magnetization dynamics in a quantum dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot. Our theory is able to take into account effects of strong correlations. We demonstrate that, as a result of these strong correlations, the dot gate voltage enables control over the current-induced torques on the magnets and, in particular, enables voltage-controlled magnetic switching. The electrical resistance of the structure can be used to read out the magnetic state. Our model may be realized by a number of experimental systems, including magnetic scanning-tunneling microscope tips and artificial quantum dot systems.
Antiferromagnetic spin Seebeck effect.
Energy Technology Data Exchange (ETDEWEB)
Wu, Stephen M.; Zhang, Wei; KC, Amit; Borisov, Pavel; Pearson, John E.; Jiang, J. Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand
2016-03-03
We report on the observation of the spin Seebeck effect in antiferromagnetic MnF2. A device scale on-chip heater is deposited on a bilayer of MnF2 (110) (30nm)/Pt (4 nm) grown by molecular beam epitaxy on a MgF2(110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF2 through the inverse spin Hall effect. The low temperature (2–80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9T) are applied parallel to the easy axis of the MnF2 thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.
Energy Technology Data Exchange (ETDEWEB)
Peskin, M.E. [Stanford Univ., CA (United States)
1994-12-01
When the strong interactions were a mystery, spin seemed to be just a complication on top of an already puzzling set of phenomena. But now that particle physicists have understood the strong, weak, and electromagnetic interactions, to be gauge theories, with matter built of quarks and leptons, it is recognized that the special properties of spin 1/2 and spin 1 particles have taken central role in the understanding of Nature. The lectures in this summer school will be devoted to the use of spin in unravelling detailed questions about the fundamental interactions. Thus, why not begin by posing a deeper question: Why is there spin? More precisely, why do the basic pointlike constituents of Nature carry intrinsic nonzero quanta of angular momentum? Though the authos has found no definite answer to this question, the pursuit of an answer has led through a wonderful tangle of speculations on the deep structure of Nature. Is spin constructed or is it fundamental? Is it the requirement of symmetry? In the furthest flights taken, it seems that space-time itself is too restrictive a notion, and that this must be generalized in order to gain a full appreciation of spin. In any case, there is no doubt that spin must play a central role in unlocking the mysteries of fundamental physics.
Stetter, Joseph R.; Maclay, G. Jordan
1989-01-01
Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.
Antiferromagnetic Spin Seebeck Effect.
Wu, Stephen M; Zhang, Wei; Kc, Amit; Borisov, Pavel; Pearson, John E; Jiang, J Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand
2016-03-04
We report on the observation of the spin Seebeck effect in antiferromagnetic MnF_{2}. A device scale on-chip heater is deposited on a bilayer of MnF_{2} (110) (30 nm)/Pt (4 nm) grown by molecular beam epitaxy on a MgF_{2} (110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF_{2} through the inverse spin Hall effect. The low temperature (2-80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9 T) are applied parallel to the easy axis of the MnF_{2} thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.
Hawkes, N
1999-01-01
RAL is fostering commerical exploitation of its research and facilities in two main ways : spin-out companies exploit work done at the lab, spin-in companies work on site taking advantage of the facilities and the expertise available (1/2 page).
Spin-orbit splitting of the cyclotron resonance in GaAs
Tonello, P.; Lipparini, E.
2004-08-01
We have studied the relevance of spin-orbit coupling to the splitting of the cyclotron resonance of electron space-charge layers in GaAs recently observed by Manger [Phys. Rev. B 63, 121203R (2001)]. We show that the spin-orbit interaction couples density and spin-density excitations in the long-wavelength limit and is able to explain all the features observed in the experiment.
Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins
Norris, Leigh Morgan
Large atomic ensembles interacting with light are one of the most promising platforms for quantum information processing. In the past decade, novel applications for these systems have emerged in quantum communication, quantum computing, and metrology. Essential to all of these applications is the controllability of the atomic ensemble, which is facilitated by a strong coupling between the atoms and light. Non-classical spin squeezed states are a crucial step in attaining greater ensemble control. The degree of entanglement present in these states, furthermore, serves as a benchmark for the strength of the atom-light interaction. Outside the broader context of quantum information processing with atomic ensembles, spin squeezed states have applications in metrology, where their quantum correlations can be harnessed to improve the precision of magnetometers and atomic clocks. This dissertation focuses upon the production of spin squeezed states in large ensembles of cold trapped alkali atoms interacting with optical fields. While most treatments of spin squeezing consider only the case in which the ensemble is composed of two level systems or qubits, we utilize the entire ground manifold of an alkali atom with hyperfine spin f greater than or equal to 1/2, a qudit. Spin squeezing requires non-classical correlations between the constituent atomic spins, which are generated through the atoms' collective coupling to the light. Either through measurement or multiple interactions with the atoms, the light mediates an entangling interaction that produces quantum correlations. Because the spin squeezing treated in this dissertation ultimately originates from the coupling between the light and atoms, conventional approaches of improving this squeezing have focused on increasing the optical density of the ensemble. The greater number of internal degrees of freedom and the controllability of the spin-f ground hyperfine manifold enable novel methods of enhancing squeezing. In
Spin Hall and spin swapping torques in diffusive ferromagnets
Pauyac, C. O.
2017-12-08
A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precessional effects displays a complex spatial dependence that can be exploited to generate torques and nucleate/propagate domain walls in centrosymmetric geometries without use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.
DEFF Research Database (Denmark)
Jensen, Kurt; Feldbrugge, Frits
1987-01-01
This paper provides an overview of the characteristics of all currently available net based tools. It is a compilation of information provided by tool authors or contact persons. A concise one page overview is provided as well....
Understanding Net Zero Energy Buildings
DEFF Research Database (Denmark)
Salom, Jaume; Widén, Joakim; Candanedo, José
2011-01-01
Although several alternative definitions exist, a Net-Zero Energy Building (Net ZEB) can be succinctly described as a grid-connected building that generates as much energy as it uses over a year. The “net-zero” balance is attained by applying energy conservation and efficiency measures...... and by incorporating renewable energy systems. While based on annual balances, a complete description of a Net ZEB requires examining the system at smaller time-scales. This assessment should address: (a) the relationship between power generation and building loads and (b) the resulting interaction with the power grid....... This paper presents and categorizes quantitative indicators suitable to describe both aspects of the building’s performance. These indicators, named LMGI - Load Matching and Grid Interaction indicators, are easily quantifiable and could complement the output variables of existing building simulation tools...
Social Security Administration — The PolicyNet Publication System project will merge the Oracle-based Policy Repository (POMS) and the SQL-Server CAMP system (MSOM) into a new system with an Oracle...
KM3NeT is a large scale next-generation neutrino telescope located in the deep waters of the Mediterranean Sea, optimized for the discovery of galactic neutrino sources emitting in the TeV energy region.
Net Neutrality: Background and Issues
National Research Council Canada - National Science Library
Gilroy, Angele A
2006-01-01
.... The move to place restrictions on the owners of the networks that compose and provide access to the Internet, to ensure equal access and nondiscriminatory treatment, is referred to as "net neutrality...
Petri Nets in Cryptographic Protocols
DEFF Research Database (Denmark)
Crazzolara, Federico; Winskel, Glynn
2001-01-01
A process language for security protocols is presented together with a semantics in terms of sets of events. The denotation of process is a set of events, and as each event specifies a set of pre and postconditions, this denotation can be viewed as a Petri net. By means of an example we illustrate...... how the Petri-net semantics can be used to prove security properties....
The Economics of Net Neutrality
Hahn, Robert W.; Wallsten, Scott
2006-01-01
This essay examines the economics of "net neutrality" and broadband Internet access. We argue that mandating net neutrality would be likely to reduce economic welfare. Instead, the government should focus on creating competition in the broadband market by liberalizing more spectrum and reducing entry barriers created by certain local regulations. In cases where a broadband provider can exercise market power the government should use its antitrust enforcement authority to police anticompetitiv...
Atomistic spin dynamics and surface magnons
Etz, Corina; Bergqvist, Lars; Bergman, Anders; Taroni, Andrea; Eriksson, Olle
2015-06-01
Atomistic spin dynamics simulations have evolved to become a powerful and versatile tool for simulating dynamic properties of magnetic materials. It has a wide range of applications, for instance switching of magnetic states in bulk and nano-magnets, dynamics of topological magnets, such as skyrmions and vortices and domain wall motion. In this review, after a brief summary of the existing investigation tools for the study of magnons, we focus on calculations of spin-wave excitations in low-dimensional magnets and the effect of relativistic and temperature effects in such structures. In general, we find a good agreement between our results and the experimental values. For material specific studies, the atomistic spin dynamics is combined with electronic structure calculations within the density functional theory from which the required parameters are calculated, such as magnetic exchange interactions, magnetocrystalline anisotropy, and Dzyaloshinskii-Moriya vectors.
26 CFR 1.904(f)-3 - Allocation of net operating losses and net capital losses.
2010-04-01
... 26 Internal Revenue 9 2010-04-01 2010-04-01 false Allocation of net operating losses and net....904(f)-3 Allocation of net operating losses and net capital losses. For rules relating to the allocation of net operating losses and net capital losses, see § 1.904(g)-3T. ...
29 CFR 4204.13 - Net income and net tangible assets tests.
2010-07-01
... 29 Labor 9 2010-07-01 2010-07-01 false Net income and net tangible assets tests. 4204.13 Section....13 Net income and net tangible assets tests. (a) General. The criteria under this section are that either— (1) Net income test. The purchaser's average net income after taxes for its three most recent...
Kraus, Per; Ross, Simon F.
2013-05-01
The principles of quantum mechanics and relativity impose rigid constraints on theories of massless particles with nonzero spin. Indeed, Yang-Mills theory and General Relativity are the unique solution in the case of spin-1 and spin-2. In asymptotically flat spacetime, there are fundamental obstacles to formulating fully consistent interacting theories of particles of spin greater than 2. However, indications are that such theories are just barely possible in asymptotically anti-de Sitter or de Sitter spacetimes, where the non-existence of an S-matrix provides an escape from the theorems restricting theories in Minkowski spacetime. These higher spin gravity theories are therefore of great intrinsic interest, since they, along with supergravity, provide the only known field theories generalizing the local invariance principles of Yang-Mills theory and General Relativity. While work on higher spin gravity goes back several decades, the subject has gained broader appeal in recent years due to its appearance in the AdS/CFT correspondence. In three and four spacetime dimensions, there exist duality proposals linking higher spin gravity theories to specific conformal field theories living in two and three dimensions respectively. The enlarged symmetry algebra of the conformal field theories renders them exactly soluble, which makes them excellent laboratories for understanding in detail the holographic mechanism behind AdS/CFT duality. Steady progress is also being made on better understanding the space of possible higher spin gravity theories and their physical content. This work includes classifying the possible field multiplets and their interactions, constructing exact solutions of the nonlinear field equations, and relating higher spin theories to string theory. A full understanding of these theories will involve coming to grips with the novel symmetry principles that enlarge those of General Relativity and Yang-Mills theory, and one can hope that this will provide
Establishing a relation between the mass and the spin of stellar-mass black holes.
Banerjee, Indrani; Mukhopadhyay, Banibrata
2013-08-09
Stellar mass black holes (SMBHs), forming by the core collapse of very massive, rapidly rotating stars, are expected to exhibit a high density accretion disk around them developed from the spinning mantle of the collapsing star. A wide class of such disks, due to their high density and temperature, are effective emitters of neutrinos and hence called neutrino cooled disks. Tracking the physics relating the observed (neutrino) luminosity to the mass, spin of black holes (BHs) and the accretion rate (M) of such disks, here we establish a correlation between the spin and mass of SMBHs at their formation stage. Our work shows that spinning BHs are more massive than nonspinning BHs for a given M. However, slowly spinning BHs can turn out to be more massive than spinning BHs if M at their formation stage was higher compared to faster spinning BHs.
Radu, I; Vahaplar, K; Stamm, C; Kachel, T; Pontius, N; Dürr, H A; Ostler, T A; Barker, J; Evans, R F L; Chantrell, R W; Tsukamoto, A; Itoh, A; Kirilyuk, A; Rasing, Th; Kimel, A V
2011-04-14
Ferromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism. Understanding spin dynamics in magnetic materials is an issue of crucial importance for progress in information processing and recording technology. Usually the dynamics are studied by observing the collective response of exchange-coupled spins, that is, spin resonances, after an external perturbation by a pulse of magnetic field, current or light. The periods of the corresponding resonances range from one nanosecond for ferromagnets down to one picosecond for antiferromagnets. However, virtually nothing is known about the behaviour of spins in a magnetic material after being excited on a timescale faster than that corresponding to the exchange interaction (10-100 fs), that is, in a non-adiabatic way. Here we use the element-specific technique X-ray magnetic circular dichroism to study spin reversal in GdFeCo that is optically excited on a timescale pertinent to the characteristic time of the exchange interaction between Gd and Fe spins. We unexpectedly find that the ultrafast spin reversal in this material, where spins are coupled antiferromagnetically, occurs by way of a transient ferromagnetic-like state. Following the optical excitation, the net magnetizations of the Gd and Fe sublattices rapidly collapse, switch their direction and rebuild their net magnetic moments at substantially different timescales; the net magnetic moment of the Gd sublattice is found to reverse within 1.5 picoseconds, which is substantially slower than the Fe reversal time of 300 femtoseconds. Consequently, a transient state characterized by a temporary parallel alignment of the net Gd and Fe moments emerges, despite their ground-state antiferromagnetic coupling. These surprising observations, supported by atomistic simulations, provide a concept for the possibility of manipulating magnetic order on the timescale of the exchange interaction.
Spin features in the Raman spectrum of nanoscopic rings
Emperador, A.; Pi, M.; Barranco, M.; Lipparini, E.
2002-01-01
We have studied physical aspects of the charge and spin density responses of nanoscopic rings that might be detected by Raman spectroscopy. We have taken an InAs-GaAs ring as a case of study with N=10 electrons and several values of the on-plane transferred momentum q. Distinct monopole to quadrupole modes appear in the spin density, and especially in the charge density channel. We have found that both channels are coupled if the ground-state is ferromagnetic.
Scaling effect of spin-torque nano-oscillators
Directory of Open Access Journals (Sweden)
Xiaohui Chao
2017-05-01
Full Text Available We have investigated the impact of device size on the characteristics of spin-torque nano-oscillators by studying the frequency and linewidth of the oscillator as a function of current density utilizing micromagnetic simulations at room temperature. Upon reduction of the device size from 40 down to 10 nm, thermal noise flattens the frequency and linewidth trends with current density and lowers the threshold current density of the oscillation. The magnetization vector trajectories reveal that irregular oscillations exist in smaller devices. Our findings suggest that a 20 × 20 nm2 spin-torque oscillator could be a viable candidate for a magnetic read sensor.
Spin transfer torque with spin diffusion in magnetic tunnel junctions
Manchon, Aurelien
2012-08-09
Spin transport in magnetic tunnel junctions in the presence of spin diffusion is considered theoretically. Combining ballistic tunneling across the barrier and diffusive transport in the electrodes, we solve the spin dynamics equation in the metallic layers. We show that spin diffusion mixes the transverse spin current components and dramatically modifies the bias dependence of the effective spin transfer torque. This leads to a significant linear bias dependence of the out-of-plane torque, as well as a nonconventional thickness dependence of both spin torque components.
Spin transverse force on spin current in an electric field.
Shen, Shun-Qing
2005-10-28
As a relativistic quantum mechanical effect, it is shown that the electron field exerts a transverse force on an electron spin 1/2 only if the electron is moving. The spin force, analogue to the Lorentz for an electron charge in a magnetic field, is perpendicular to the electric field and the spin current whose spin polarization is projected along the electric field. This spin-dependent force can be used to understand the Zitterbewegung of the electron wave packet with spin-orbit coupling and is relevant to the generation of the charge Hall effect driven by the spin current in semiconductors.
McWeeny, Roy
2004-01-01
Originally delivered as a series of lectures, this volume systematically traces the evolution of the ""spin"" concept from its role in quantum mechanics to its assimilation into the field of chemistry. Author Roy McWeeny presents an in-depth illustration of the deductive methods of quantum theory and their application to spins in chemistry, following the path from the earliest concepts to the sophisticated physical methods employed in the investigation of molecular structure and properties. Starting with the origin and development of the spin concept, the text advances to an examination of sp
Energy Technology Data Exchange (ETDEWEB)
Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-01-15
The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.
Energy Technology Data Exchange (ETDEWEB)
Mila, Frederic [Institut de Physique Theorique, Universite de Lausanne, BSP, Lausanne (Switzerland)
2000-11-01
This paper presents an overview of the properties of magnetic insulators, with emphasis on quantum effects. In particular, the consequences of strong quantum fluctuations on the low-energy properties of a number of systems are reviewed: the occurrence of a spin gap in spin-1 chains and other low-dimensional magnets; the presence of low-lying singlet excitations in several frustrated magnets; the interplay of orbital and spin fluctuations in orbitally degenerate Mott insulators. This review is intended as a pedagogical introduction to the field, and the formalism has been kept at a minimal level. (author)
2013-01-01
This book covers all principal aspects of currently investigated frustrated systems, from exactly solved frustrated models to real experimental frustrated systems, going through renormalization group treatment, Monte Carlo investigation of frustrated classical Ising and vector spin models, low-dimensional systems, spin ice and quantum spin glass. The reader can - within a single book - obtain a global view of the current research development in the field of frustrated systems.This new edition is updated with recent theoretical, numerical and experimental developments in the field of frustrated
Spin versus charge noise from Kondo traps
da Silva, Luis G. G. V. Dias; de Sousa, Rogério
2015-08-01
Magnetic and charge noise have a common microscopic origin in solid-state devices, as described by a universal electron trap model. In spite of this common origin, magnetic (spin) and charge noise spectral densities display remarkably different behaviors when many-particle correlations are taken into account, leading to the emergence of the Kondo effect. We derive exact frequency sum rules for trap noise and perform numerical renormalization-group calculations to show that while spin noise is a universal function of the Kondo temperature, charge noise remains well described by single-particle theory even when the trap is deep in the Kondo regime. We obtain simple analytical expressions for charge and spin noise that account for Kondo screening in all frequency and temperature regimes, enabling the study of the impact of disorder and the emergence of magnetic 1 /f noise from Kondo traps. We conclude that the difference between charge and spin noise survives even in the presence of disorder, showing that noise can be more manageable in devices that are sensitive to magnetic (rather than charge) fluctuations and that the signature of the Kondo effect can be observed in spin noise spectroscopy experiments.
Method for estimating spin-spin interactions from magnetization curves
Tamura, Ryo; Hukushima, Koji
2017-02-01
We develop a method to estimate the spin-spin interactions in the Hamiltonian from the observed magnetization curve by machine learning based on Bayesian inference. In our method, plausible spin-spin interactions are determined by maximizing the posterior distribution, which is the conditional probability of the spin-spin interactions in the Hamiltonian for a given magnetization curve with observation noise. The conditional probability is obtained with the Markov chain Monte Carlo simulations combined with an exchange Monte Carlo method. The efficiency of our method is tested using synthetic magnetization curve data, and the results show that spin-spin interactions are estimated with a high accuracy. In particular, the relevant terms of the spin-spin interactions are successfully selected from the redundant interaction candidates by the l1 regularization in the prior distribution.
Finkelstein, Ran; Cohen, Kobi; Jouault, Benoit; West, Ken; Pfeiffer, Loren N.; Vladimirova, Masha; Rapaport, Ronen
2017-08-01
We measure the spin-resolved transport of dipolar excitons in a biased GaAs double quantum well structure. From these measurements we extract both spin lifetime and mobility of the excitons. We find that below a temperature of 4.8 K there is a sharp increase in the spin lifetime of the excitons, together with a sharp reduction in their mobility. Below a critical power the spin lifetime increases with increasing mobility and density, while above the critical power the opposite trend is observed. We interpret this transition as evidence of the interplay between two different spin dephasing mechanisms: at low mobility the dephasing is dominated by the hyperfine interaction with the lattice nuclei spins, while at higher mobility the spin-orbit interaction dominates and a Dyakonov-Perel spin relaxation takes over. The excitation power and temperature regime where the hyperfine interaction induced spin dephasing is observed correlates with the regime where a dark dipolar quantum liquid was reported recently on a similar sample.
Radiation reaction for spinning bodies in effective field theory. II. Spin-spin effects
Maia, Natália T.; Galley, Chad R.; Leibovich, Adam K.; Porto, Rafael A.
2017-10-01
We compute the leading post-Newtonian (PN) contributions at quadratic order in the spins to the radiation-reaction acceleration and spin evolution for binary systems, entering at four-and-a-half PN order. Our calculation includes the backreaction from finite-size spin effects, which is presented for the first time. The computation is carried out, from first principles, using the effective field theory framework for spinning extended objects. At this order, nonconservative effects in the spin-spin sector are independent of the spin supplementary conditions. A nontrivial consistency check is performed by showing that the energy loss induced by the resulting radiation-reaction force is equivalent to the total emitted power in the far zone. We find that, in contrast to the spin-orbit contributions (reported in a companion paper), the radiation reaction affects the evolution of the spin vectors once spin-spin effects are incorporated.
Supplying Spin-Offs: Collaboration Practices in the Perpetuation of an Organizaton
Directory of Open Access Journals (Sweden)
Katja Maria Hydle
2016-01-01
Full Text Available This paper focuses on the collaboration practices between spin-offs and their customers and suppliers. With empirical material from seven cases of incumbentbacked spin-offs, we find that suppliers are highly involved in the development of the innovation that spin-offs are based upon and specifically, the practices of understanding customers, identifying a market gap and collaborating with suppliers. We contribute to the spin-off literature by revealing which activities are at play for successful spin-offs, and we contribute to practice theory by empirically uncovering the general understandings in the perpetuation of an organization and the nets between the spin-offs and their suppliers.
Hsieh, Chang-Yu; Cao, Jianshu
2018-01-07
We use the "generalized hierarchical equation of motion" proposed in Paper I [C.-Y. Hsieh and J. Cao, J. Chem. Phys. 148, 014103 (2018)] to study decoherence in a system coupled to a spin bath. The present methodology allows a systematic incorporation of higher-order anharmonic effects of the bath in dynamical calculations. We investigate the leading order corrections to the linear response approximations for spin bath models. Two kinds of spin-based environments are considered: (1) a bath of spins discretized from a continuous spectral density and (2) a bath of localized nuclear or electron spins. The main difference resides with how the bath frequency and the system-bath coupling parameters are distributed in an environment. When discretized from a continuous spectral density, the system-bath coupling typically scales as ∼1/NB where NB is the number of bath spins. This scaling suppresses the non-Gaussian characteristics of the spin bath and justifies the linear response approximations in the thermodynamic limit. For the nuclear/electron spin bath models, system-bath couplings are directly deduced from spin-spin interactions and do not necessarily obey the 1/NB scaling. It is not always possible to justify the linear response approximations in this case. Furthermore, if the spin-spin Hamiltonian is highly symmetrical, there exist additional constraints that generate highly non-Markovian and persistent dynamics that is beyond the linear response treatments.
Bradley, Jonathan P; Tripon, Carmen; Filip, Claudiu; Brown, Steven P
2009-08-28
ratio of the squares of the corresponding dipolar coupling constants. While the simulated (1)H DQ build-up curves reproduce most of the features of the experimental curves, maximum intensity is often observed at a longer recoupling time in simulations. In this respect, simulations for two to eight spins show a trend towards a faster decay for an increasing number of considered spins. Finally, simulations show that increasing either the Larmor frequency (to 1 GHz) or the MAS frequency (to 125 kHz) does not lead to changes in the marked differences between the (1)H DQ build-up curves at the CH(Asp) SQ frequency for DQCs to the CH(2)(a) and OH protons that correspond to similar H-H distances (2.39 A and 2.49 A, respectively).
Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas
Energy Technology Data Exchange (ETDEWEB)
Yang, Luyi [Univ. of California, Berkeley, CA (United States)
2013-05-17
Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This dissertation presents the demonstration and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly
Roy, Kuntal
2017-11-01
There exists considerable confusion in estimating the spin diffusion length of materials with high spin-orbit coupling from spin pumping experiments. For designing functional devices, it is important to determine the spin diffusion length with sufficient accuracy from experimental results. An inaccurate estimation of spin diffusion length also affects the estimation of other parameters (e.g., spin mixing conductance, spin Hall angle) concomitantly. The spin diffusion length for platinum (Pt) has been reported in the literature in a wide range of 0.5-14 nm, and in particular it is a constant value independent of Pt's thickness. Here, the key reasonings behind such a wide range of reported values of spin diffusion length have been identified comprehensively. In particular, it is shown here that a thickness-dependent conductivity and spin diffusion length is necessary to simultaneously match the experimental results of effective spin mixing conductance and inverse spin Hall voltage due to spin pumping. Such a thickness-dependent spin diffusion length is tantamount to the Elliott-Yafet spin relaxation mechanism, which bodes well for transitional metals. This conclusion is not altered even when there is significant interfacial spin memory loss. Furthermore, the variations in the estimated parameters are also studied, which is important for technological applications.
Stretchable Persistent Spin Helices in GaAs Quantum Wells
Dettwiler, Florian; Fu, Jiyong; Mack, Shawn; Weigele, Pirmin J.; Egues, J. Carlos; Awschalom, David D.; Zumbühl, Dominik M.
2017-07-01
The Rashba and Dresselhaus spin-orbit (SO) interactions in 2D electron gases act as effective magnetic fields with momentum-dependent directions, which cause spin decay as the spins undergo arbitrary precessions about these randomly oriented SO fields due to momentum scattering. Theoretically and experimentally, it has been established that by fine-tuning the Rashba α and renormalized Dresselhaus β couplings to equal fixed strengths α =β , the total SO field becomes unidirectional, thus rendering the electron spins immune to decay due to momentum scattering. A robust persistent spin helix (PSH), i.e., a helical spin-density wave excitation with constant pitch P =2 π /Q , Q =4 m α /ℏ2, has already been experimentally realized at this singular point α =β , enhancing the spin lifetime by up to 2 orders of magnitude. Here, we employ the suppression of weak antilocalization as a sensitive detector for matched SO fields together with independent electrical control over the SO couplings via top gate voltage VT and back gate voltage VB to extract all SO couplings when combined with detailed numerical simulations. We demonstrate for the first time the gate control of the renormalized β and the continuous locking of the SO fields at α =β ; i.e., we are able to vary both α and β controllably and continuously with VT and VB, while keeping them locked at equal strengths. This makes possible a new concept: "stretchable PSHs," i.e., helical spin patterns with continuously variable pitches P over a wide parameter range. Stretching the PSH, i.e., gate controlling P while staying locked in the PSH regime, provides protection from spin decay at the symmetry point α =β , thus offering an important advantage over other methods. This protection is limited mainly by the cubic Dresselhaus term, which breaks the unidirectionality of the total SO field and causes spin decay at higher electron densities. We quantify the cubic term, and find it to be sufficiently weak so that
Stretchable Persistent Spin Helices in GaAs Quantum Wells
Directory of Open Access Journals (Sweden)
Florian Dettwiler
2017-07-01
Full Text Available The Rashba and Dresselhaus spin-orbit (SO interactions in 2D electron gases act as effective magnetic fields with momentum-dependent directions, which cause spin decay as the spins undergo arbitrary precessions about these randomly oriented SO fields due to momentum scattering. Theoretically and experimentally, it has been established that by fine-tuning the Rashba α and renormalized Dresselhaus β couplings to equal fixed strengths α=β, the total SO field becomes unidirectional, thus rendering the electron spins immune to decay due to momentum scattering. A robust persistent spin helix (PSH, i.e., a helical spin-density wave excitation with constant pitch P=2π/Q, Q=4mα/ℏ^{2}, has already been experimentally realized at this singular point α=β, enhancing the spin lifetime by up to 2 orders of magnitude. Here, we employ the suppression of weak antilocalization as a sensitive detector for matched SO fields together with independent electrical control over the SO couplings via top gate voltage V_{T} and back gate voltage V_{B} to extract all SO couplings when combined with detailed numerical simulations. We demonstrate for the first time the gate control of the renormalized β and the continuous locking of the SO fields at α=β; i.e., we are able to vary both α and β controllably and continuously with V_{T} and V_{B}, while keeping them locked at equal strengths. This makes possible a new concept: “stretchable PSHs,” i.e., helical spin patterns with continuously variable pitches P over a wide parameter range. Stretching the PSH, i.e., gate controlling P while staying locked in the PSH regime, provides protection from spin decay at the symmetry point α=β, thus offering an important advantage over other methods. This protection is limited mainly by the cubic Dresselhaus term, which breaks the unidirectionality of the total SO field and causes spin decay at higher electron densities. We quantify the cubic term, and find it to be
Jiang, J. H.; Wu, M. W.
2009-03-01
Electron spin relaxation in bulk III-V semiconductors is investigated from a fully microscopic kinetic spin Bloch equation approach where all relevant scatterings, such as, the electron-nonmagnetic-impurity, electron-phonon, electron-electron, electron-hole, and electron-hole exchange (the Bir-Aronov-Pikus mechanism) scatterings are explicitly included. The Elliott-Yafet mechanism is also fully incorporated. This approach offers a way toward thorough understanding of electron spin relaxation both near and far away from the equilibrium in the metallic regime. The dependences of the spin relaxation time on electron density, temperature, initial spin polarization, photo-excitation density, and hole density are studied thoroughly with the underlying physics analyzed. We find that these dependences are usually qualitatively different in the nondegenerate and degenerate regimes. In contrast to the previous investigations in the literature, we find that: (i) In n -type materials, the Elliott-Yafet mechanism is less important than the D’yakonov-Perel’ mechanism, even for the narrow band-gap semiconductors such as InSb and InAs. (ii) The density dependence of the spin relaxation time is nonmonotonic and we predict a peak in the metallic regime in both n -type and intrinsic materials. (iii) In intrinsic materials, the Bir-Aronov-Pikus mechanism is found to be negligible compared with the D’yakonov-Perel’ mechanism. We also predict a peak in the temperature dependence of spin relaxation time which is due to the nonmonotonic temperature dependence of the electron-electron Coulomb scattering in intrinsic materials with small initial spin polarization. (iv) In p -type III-V semiconductors, the Bir-Aronov-Pikus mechanism dominates spin relaxation in the low-temperature regime only when the photoexcitation density is low. When the photoexcitation density is high, the Bir-Aronov-Pikus mechanism can be comparable with the D’yakonov-Perel’ mechanism only in the moderate
Optimal Charge-to-Spin Conversion in Graphene on Transition-Metal Dichalcogenides
Offidani, Manuel; Milletarı, Mirco; Raimondi, Roberto; Ferreira, Aires
2017-11-01
When graphene is placed on a monolayer of semiconducting transition metal dichalcogenide (TMD) its band structure develops rich spin textures due to proximity spin-orbital effects with interfacial breaking of inversion symmetry. In this work, we show that the characteristic spin winding of low-energy states in graphene on a TMD monolayer enables current-driven spin polarization, a phenomenon known as the inverse spin galvanic effect (ISGE). By introducing a proper figure of merit, we quantify the efficiency of charge-to-spin conversion and show it is close to unity when the Fermi level approaches the spin minority band. Remarkably, at high electronic density, even though subbands with opposite spin helicities are occupied, the efficiency decays only algebraically. The giant ISGE predicted for graphene on TMD monolayers is robust against disorder and remains large at room temperature.
Spontaneous Breaking of Spatial and Spin Symmetry in Spinor Condensates
DEFF Research Database (Denmark)
Scherer, M.; Lücke, B.; Gebreyesus, G.
2010-01-01
Parametric amplification of quantum fluctuations constitutes a fundamental mechanism for spontaneous symmetry breaking. In our experiments, a spinor condensate acts as a parametric amplifier of spin modes, resulting in a twofold spontaneous breaking of spatial and spin symmetry in the amplified...... broken, but phase squeezing prevents spin-symmetry breaking. If, however, nondegenerate spin modes contribute to the amplification, quantum interferences lead to spin-dependent density profiles and hence spontaneously formed patterns in the longitudinal magnetization....... clouds. Our experiments permit a precise analysis of the amplification in specific spatial Bessel-like modes, allowing for the detailed understanding of the double symmetry breaking. On resonances that create vortex-antivortex superpositions, we show that the cylindrical spatial symmetry is spontaneously...
Electron spin dynamics in cubic GaN
Buß, J. H.; Schupp, T.; As, D. J.; Brandt, O.; Hägele, D.; Rudolph, J.
2016-12-01
The electron spin dynamics in cubic GaN is comprehensively investigated by time-resolved magneto-optical Kerr-rotation spectroscopy over a wide range of temperatures, magnetic fields, and doping densities. The spin dynamics is found to be governed by the interplay of spin relaxation of localized electrons and Dyakonov-Perel relaxation of delocalized electrons. Localized electrons significantly contribute to spin relaxation up to room temperature at moderate doping levels, while Dyakonov-Perel relaxation dominates for high temperatures or degenerate doping levels. Quantitative agreement to Dyakonov-Perel theory requires a larger value of the spin-splitting constant than theoretically predicted. Possible reasons for this discrepancy are discussed, including the role of charged dislocations.
Hu, Jiazhong; Chen, Wenlan; Vendeiro, Zachary; Urvoy, Alban; Braverman, Boris; Vuletić, Vladan
2017-11-01
We investigate the generation of entanglement (spin squeezing) in an optical-transition atomic clock through the coupling to an optical cavity in its vacuum state. We show that if each atom is prepared in a superposition of the ground state and a long-lived electronic excited state, and viewed as a spin-1/2 system, then the collective vacuum light shift entangles the atoms, resulting in a squeezed distribution of the ensemble collective spin, without any light applied. This scheme reveals that even an electromagnetic vacuum can constitute a useful resource for entanglement and quantum manipulation. By rotating the spin direction while coupling to the vacuum, the scheme can be extended to implement two-axis twisting resulting in stronger squeezing.
Jansen, R.
An efficient way to transport electron spins from a ferromagnet into silicon essentially makes silicon magnetic, and provides an exciting step towards integration of magnetism and mainstream semiconductor electronics.
Ke, Yougang; Liu, Zhenxing; Liu, Yachao; Zhou, Junxiao; Shu, Weixing; Luo, Hailu; Wen, Shuangchun
2016-10-01
In this letter, we propose and experimentally demonstrate a compact photonic spin filter formed by integrating a Pancharatnam-Berry phase lens (focal length of ±f ) into a conventional plano-concave lens (focal length of -f). By choosing the input port of the filter, photons with a desired spin state, such as the right-handed component or the left-handed one, propagate alone its original propagation direction, while the unwanted spin component is quickly diverged after passing through the filter. One application of the filter, sorting the spin-dependent components of vector vortex beams on higher-order Poincaré sphere, is also demonstrated. Our scheme provides a simple method to manipulate light, and thereby enables potential applications for photonic devices.
Schill, C
2012-01-01
The COMPASS experiment is a fixed target experiment at the CERN SPS using muon and hadron beams for the investigation of the spin structure of the nucleon and hadron spectroscopy. The main objective of the muon physics program is the study of the spin of the nucleon in terms of its constituents, quarks and gluons. COMPASS has accumulated data during 6 years scattering polarized muons off a longitudinally or a transversely polarized deuteron (6LiD) or proton (NH3) target. Results for the gluon polarization are obtained from longitudinal double spin cross section asymmetries using two different channels, open charm production and high transverse momentum hadron pairs, both proceeding through the photon-gluon fusion process. Also, the longitudinal spin structure functions of the proton and the deuteron were measured in parallel as well as the helicity distributions for the three lightest quark flavors. With a transversely polarized target, results were obtained with proton and deuteron targets for the Collins an...
Picosecond Spin Seebeck Effect.
Kimling, Johannes; Choi, Gyung-Min; Brangham, Jack T; Matalla-Wagner, Tristan; Huebner, Torsten; Kuschel, Timo; Yang, Fengyuan; Cahill, David G
2017-02-03
We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect in normal metal/Y_{3}Fe_{5}O_{12} bilayers driven by an interfacial temperature difference between electrons and magnons. The measured time evolution of spin accumulation induced by laser excitation indicates transfer of angular momentum across normal metal/Y_{3}Fe_{5}O_{12} interfaces on a picosecond time scale, too short for contributions from a bulk temperature gradient in an yttrium iron garnet. The product of spin-mixing conductance and the interfacial spin Seebeck coefficient determined is of the order of 10^{8} A m^{-2} K^{-1}.
Udagawa, Masafumi
2014-03-01
Spin ice is a prototypical frustrated magnet defined on a pyrochlore lattice. The ground state of spin ice is described by a simple rule called ``ice rule'': out of four spins on a tetrahedron, two spins point inward, while the other two outward. This simple rule is not sufficient to determine the spin configuration uniquely, but it leaves macroscopic degeneracy in the ground state. Despite the macroscopic degeneracy, however, the ground state is not completely disordered, but it exhibits algebraic spatial correlation, which characterizes this state as ``Coulomb phase'' where various exotic properties, such as monopole excitations and unusual magnetic responses are observed. Given the peculiar spatial correlation, it is interesting to ask what happens if itinerant electrons coexist and interact with spin ice. Indeed, this setting is relevant to several metallic Ir pyrochlore oxides, such as Ln2Ir2O7 (Ln=Pr, Nd), where Ir 5d itinerant electrons interact with Ln 4f localized moments. In these compounds, anomalous transport phenomena have been reported, such as non-monotonic magnetic field dependence of Hall conductivity and low-temperature resistivity upturn. To address these issues, we adopt a spin-ice-type Ising Kondo lattice model on a pyrochlore lattice, and solve this model by applying the cluster dynamical mean-field theory and the perturbation expansion in terms of the spin-electron coupling. As a result, we found that (i) the resistivity shows a minimum at a characteristic temperature below which spin ice correlation sets in. Moreover, (ii) the Hall conductivity shows anisotropic and non-monotonic magnetic field dependence due to the scattering from the spatially extended spin scalar chirality incorporated in spin ice manifold. These results give unified understanding to the thermodynamic and transport properties of Ln2Ir2O7 (Ln=Pr, Nd), and give new insights into the role of geometrical frustration in itinerant systems. This work has been done in
Squaroglitter: A 3,4-Connected Carbon Net
Prasad, Dasari L. V. K.
2013-08-13
Theoretical calculations are presented on a new hypothetical 3,4-connected carbon net (called squaroglitter) incorporating 1,4 cyclohexadiene units. The structure has tetragonal space group P4/mmm (No. 123) symmetry. The optimized geometry shows normal distances, except for some elongated bonds in the cyclobutane ring substructures in the network. Squaroglitter has an indirect bandgap of about 1.0 eV. The hypothetical lattice, whose density is close to graphite, is more stable than other 3,4-connected carbon nets. A relationship to a (4,4)nanotube is explored, as is a potential threading of the lattice with metal needles. © 2013 American Chemical Society.
CERN. Geneva
2014-01-01
The conjectured relation between higher spin theories on anti de-Sitter (AdS) spaces and weakly coupled conformal field theories is reviewed. I shall then outline the evidence in favour of a concrete duality of this kind, relating a specific higher spin theory on AdS3 to a family of 2d minimal model CFTs. Finally, I shall explain how this relation fits into the framework of the familiar stringy AdS/CFT correspondence.
2015-07-15
Progress Report (ONR Award No. N00014-14-1-0804) Quantum Spin Gyroscope August 2014-July 2015 Report Type: Annual Report Primary Contact E-mail...Quantum Spin Gyroscope Grant/Contract Number: N00014-14-1-0804 Principal Investigator Name: Paola Cappellaro Program Manager: Richard Tommy Willis...Abstract Gyroscopes find wide application in everyday life, from navigation to rotation sensors in hand-held devices and automobiles. In addition, they can
Folkerts, Sarah; Wintergerst, Nico
2014-01-01
We give an introduction to massive spin-2 theories (including massive gravity) and the problem of their non-linear completion. We review the Boulware-Deser ghost problem and two ways to circumvent classic no-go theorems. In turn, massive spin-2 theories are not uniquely defined. In the case of truncated theories, we show that the Boulware-Deser ghost may only be avoided if the derivative structure of the theory is not tuned to be Einsteinian.
Spinning Induced Compression Strength of Precast Hollow Concrete Piles
Directory of Open Access Journals (Sweden)
Gogot Setyo Budi
2017-09-01
Full Text Available Prefabricated precast-hollow concrete pile is widely used as deep foundations due to its several benefits such as the uniformity in concrete quality and its durability. It is also called spun pile since the spinning method is utilized to compact the fresh concrete. During spinning, the fresh concrete is propelled outward due to centrifugal force, which generates a compaction process and develops a hollow in the center of the pile. Several factors, such as the rate of spinning, frequency, and duration of spinning, are affecting the quality of the pile. This paper presents the study of density and compressive strength of spun piles. The specimens were cored from the spun piles with diameter of 800 mm. The results show that the density and the compressive strength of the concrete at outer region of the spun pile are bigger than those at the inner side.
Energy Technology Data Exchange (ETDEWEB)
Goll, Erich [Institut fuer Theoretische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart (Germany)], E-mail: goll@theochem.uni-stuttgart.de; Werner, Hans-Joachim [Institut fuer Theoretische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart (Germany); Stoll, Hermann [Institut fuer Theoretische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart (Germany); Leininger, Thierry [Laboratoire de Physique Quantique, UMR 5626 du CNRS, Universite Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse Cedex 04 (France); Gori-Giorgi, Paola [Laboratoire de Chimie Theorique, CNRS UMR7616, Universite Pierre et Marie Curie, 4 Place Jussieu, F-75252 Paris (France); Savin, Andreas [Laboratoire de Chimie Theorique, CNRS UMR7616, Universite Pierre et Marie Curie, 4 Place Jussieu, F-75252 Paris (France)
2006-10-26
We extend our recently published short-range gradient-corrected density functional from the closed-shell to Open-shell case, combine it with long-range coupled-cluster methods (CCSD, CCSD(T)), and apply it to the weakly bound alkali-metal rare-gas dimers AmRg (Am = Li-Cs; Rg = Ne-Xe). The results are shown to be superior, with medium-size basis sets, to pure DFT and pure coupled-cluster calculations.
TimeNET Optimization Environment
Directory of Open Access Journals (Sweden)
Christoph Bodenstein
2015-12-01
Full Text Available In this paper a novel tool for simulation-based optimization and design-space exploration of Stochastic Colored Petri nets (SCPN is introduced. The working title of this tool is TimeNET Optimization Environment (TOE. Targeted users of this tool are people modeling complex systems with SCPNs in TimeNET who want to find parameter sets that are optimal for a certain performance measure (fitness function. It allows users to create and simulate sets of SCPNs and to run different optimization algorithms based on parameter variation. The development of this tool was motivated by the need to automate and speed up tests of heuristic optimization algorithms to be applied for SCPN optimization. A result caching mechanism is used to avoid recalculations.
Neutron resonance spin echo with longitudinal DC fields
Krautloher, Maximilian; Kindervater, Jonas; Keller, Thomas; Häußler, Wolfgang
2016-12-01
We report on the design, construction, and performance of a neutron resonance spin echo (NRSE) instrument employing radio frequency (RF) spin flippers combining RF fields with DC fields, the latter oriented parallel (longitudinal) to the neutron propagation direction (longitudinal NRSE (LNRSE)). The advantage of the longitudinal configuration is the inherent homogeneity of the effective magnetic path integrals. In the center of the RF coils, the sign of the spin precession phase is inverted by a π flip of the neutron spins, such that non-uniform spin precession at the boundaries of the RF flippers is canceled. The residual inhomogeneity can be reduced by Fresnel- or Pythagoras-coils as in the case of conventional spin echo instruments (neutron spin echo (NSE)). Due to the good intrinsic homogeneity of the B0 coils, the current densities required for the correction coils are at least a factor of three less than in conventional NSE. As the precision and the current density of the correction coils are the limiting factors for the resolution of both NSE and LNRSE, the latter has the intrinsic potential to surpass the energy resolution of present NSE instruments. Our prototype LNRSE spectrometer described here was implemented at the resonance spin echo for diverse applications (RESEDA) beamline at the MLZ in Garching, Germany. The DC fields are generated by B0 coils, based on resistive split-pair solenoids with an active shielding for low stray fields along the beam path. One pair of RF flippers at a distance of 2 m generates a field integral of ˜0.5 Tm. The LNRSE technique is a future alternative for high-resolution spectroscopy of quasi-elastic excitations. In addition, it also incorporates the MIEZE technique, which allows to achieve spin echo resolution for spin depolarizing samples and sample environments. Here we present the results of numerical optimization of the coil geometry and first data from the prototype instrument.
Observation of Spin Relaxation in InGaAs/AlAsSb Quantum Wells
Sotaro Izumi,; Shin-Ichiro Gozu,; Teruo Mozume,; Yu Saeki,; Takao Nukui,; Atsushi Tackeuchi,
2010-04-01
We have investigated the exciton spin relaxation in InGaAs/AlAsSb quantum wells using time-resolved spin-dependent pump and probe reflectance measurements. The spin relaxation time of 1.46 μm electron-heavy hole excitons at room temperature is obtained to be 27-54 ps for an excitation power of 20-100 mW. The carrier density dependence of the exciton spin relaxation time was clearly observed, suggesting that the spin relaxation mechanism is strongly related to the Bir-Aronov-Pikus process at room temperature.
Carrier spin relaxation in InGaAs/AlAsSb quantum wells
Nukui, T.; Gozu, S.; Mozume, T.; Izumi, S.; Saeki, Y.; Tackeuchi, A.
2011-12-01
We have investigated the exciton spin relaxation in InGaAs/AlAsSb quantum wells by time-resolved spin-dependent pump and probe reflectance measurements. The spin relaxation time of 1.38 μm-electron-heavy-hole excitons at 150 K is obtained to be 34-43 ps at an excitation power of 50-80 mW. The observed carrier density dependence and temperature independence of the spin relaxation time indicate that the spin relaxation mechanism is dominated by the Bir-Aronov-Pikus process.
Spin-Charge Separation in Finite Length Metallic Carbon Nanotubes
Zhang, Yongyou
2017-10-17
Using time-dependent density functional theory, we study the optical excitations in finite length carbon nanotubes. Evidence of spin-charge separation is given in the spacetime domain. We demonstrate that the charge density wave is due to collective excitations of electron singlets, while the accompanying spin density wave is due to those of electron triplets. The Tomonaga–Luttinger liquid parameter and density–density interaction are extrapolated from the first-principles excitation energies. We show that the density–density interaction increases with the length of the nanotube. The singlet and triplet excitation energies, on the other hand, decrease for increasing length of the nanotube. Their ratio is used to establish a first-principles approach for deriving the Tomonaga–Luttinger parameter (in excellent agreement with experimental data). Time evolution analysis of the charge and spin line densities evidences that the charge and spin density waves are elementary excitations of metallic carbon nanotubes. Their dynamics show no dependence on each other.
Quantum entanglement and spin control in silicon nanocrystal.
Directory of Open Access Journals (Sweden)
Vesna Berec
Full Text Available Selective coherence control and electrically mediated exchange coupling of single electron spin between triplet and singlet states using numerically derived optimal control of proton pulses is demonstrated. We obtained spatial confinement below size of the Bohr radius for proton spin chain FWHM. Precise manipulation of individual spins and polarization of electron spin states are analyzed via proton induced emission and controlled population of energy shells in pure (29Si nanocrystal. Entangled quantum states of channeled proton trajectories are mapped in transverse and angular phase space of (29Si axial channel alignment in order to avoid transversal excitations. Proton density and proton energy as impact parameter functions are characterized in single particle density matrix via discretization of diagonal and nearest off-diagonal elements. We combined high field and low densities (1 MeV/92 nm to create inseparable quantum state by superimposing the hyperpolarizationed proton spin chain with electron spin of (29Si. Quantum discretization of density of states (DOS was performed by the Monte Carlo simulation method using numerical solutions of proton equations of motion. Distribution of gaussian coherent states is obtained by continuous modulation of individual spin phase and amplitude. Obtained results allow precise engineering and faithful mapping of spin states. This would provide the effective quantum key distribution (QKD and transmission of quantum information over remote distances between quantum memory centers for scalable quantum communication network. Furthermore, obtained results give insights in application of channeled protons subatomic microscopy as a complete versatile scanning-probe system capable of both quantum engineering of charged particle states and characterization of quantum states below diffraction limit linear and in-depth resolution.PACS NUMBERS: 03.65.Ud, 03.67.Bg, 61.85.+p, 67.30.hj.
Sandbu, Marius
2014-01-01
An easy-to-follow guide with detailed step-by step-instructions on how to implement the different key components in NetScaler, with real-world examples and sample scenarios.If you are a Citrix or network administrator who needs to implement NetScaler in your virtual environment to gain an insight on its functionality, this book is ideal for you. A basic understanding of networking and familiarity with some of the different Citrix products such as XenApp or XenDesktop is a prerequisite.
DEFF Research Database (Denmark)
2014-01-01
The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the SimpleClinicalDocument......The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the Simple...
Wu, Chaur
2011-01-01
Microsoft's Dynamic Language Runtime (DLR) is a platform for running dynamic languages such as Ruby and Python on an equal footing with compiled languages such as C#. Furthermore, the runtime is the foundation for many useful software design and architecture techniques you can apply as you develop your .NET applications. Pro DLR in .NET 4 introduces you to the DLR, showing how you can use it to write software that combines dynamic and static languages, letting you choose the right tool for the job. You will learn the core DLR components such as LINQ expressions, call sites, binders, and dynami
Hierarchies in Coloured Petri Nets
DEFF Research Database (Denmark)
Huber, Peter; Jensen, Kurt; Shapiro, Robert M.
1991-01-01
The paper shows how to extend Coloured Petri Nets with a hierarchy concept. The paper proposes five different hierarchy constructs, which allow the analyst to structure large CP-nets as a set of interrelated subnets (called pages). The paper discusses the properties of the proposed hierarchy...... constructs, and it illustrates them by means of two examples. The hierarchy constructs can be used for theoretical considerations, but their main use is to describe and analyse large real-world systems. All of the hierarchy constructs are supported by the editing and analysis facilities in the CPN Palette...
Lepadatu, S.; Hickey, M. C.; Potenza, A.; Marchetto, H.; Charlton, T. R.; Langridge, S.; Dhesi, S. S.; Marrows, C. H.
2009-03-01
The domain-wall depinning boundary, showing the variation in critical current density with magnetic field, is measured for notched permalloy wires using pulsed-current measurements. The structure of domain walls trapped at the pinning potential provided by the notch is imaged using photoemission electron microscopy. The experimental depinning boundary is compared with those obtained by micromagnetic simulations including the adiabatic and nonadiabatic spin-torque terms. This method allows for the determination of both the nonadiabaticity parameter β and spin current polarization P , which we obtain as β=0.040±0.005 and P=0.40±0.02 at room temperature.
Farberovich, Oleg V.; Mazalova, Victoria L.; Soldatov, Alexander V.
2015-11-01
We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals Jij of the nanosystem Ni7-Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni7-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy pattern with the
Non-Abelian hydrodynamics and the flow of spin in spin orbit coupled substances
Leurs, B. W. A.; Nazario, Z.; Santiago, D. I.; Zaanen, J.
2008-04-01
-conservation of the incoherent spin currents of the high temperature limit. We analyze the quantum-mechanical single particle currents of relevance to mesoscopic transport with as highlight the Ahronov-Casher effect, where we demonstrate that the intricacies of the non-Abelian transport render this effect to be much more fragile than its abelian analog, the Ahronov-Bohm effect. We subsequently focus on spin flows protected by order parameters. At present there is much interest in multiferroics where non-collinear magnetic order triggers macroscopic electric polarization via the spin-orbit coupling. We identify this to be a peculiarity of coherent non-Abelian hydrodynamics: although there is no net particle transport, the spin entanglement is transported in these magnets and the coherent spin 'super' current in turn translates into electric fields with the bonus that due to the requirement of single valuedness of the magnetic order parameter a true hydrodynamics is restored. Finally, 'fixed-frame' coherent non-Abelian transport comes to its full glory in spin-orbit coupled 'spin superfluids', and we demonstrate a new effect: the trapping of electrical line charge being a fixed frame, non-Abelian analog of the familiar magnetic flux trapping by normal superconductors. The only known physical examples of such spin superfluids are the 3He A- and B-phase where unfortunately the spin-orbit coupling is so weak that it appears impossible to observe these effects.
Spin Resonance and Magnetic Order in an Unconventional Superconductor
Mazzone, D. G.; Raymond, S.; Gavilano, J. L.; Steffens, P.; Schneidewind, A.; Lapertot, G.; Kenzelmann, M.
2017-11-01
Unconventional superconductivity in many materials is believed to be mediated by magnetic fluctuations. It is an open question how magnetic order can emerge from a superconducting condensate and how it competes with the magnetic spin resonance in unconventional superconductors. Here we study a model d -wave superconductor that develops spin-density wave order, and find that the spin resonance is unaffected by the onset of static magnetic order. This result suggests a scenario, in which the resonance in Nd0.05Ce0.95CoIn5 is a longitudinal mode with fluctuating moments along the ordered magnetic moments.
Spin Resonance and Magnetic Order in an Unconventional Superconductor.
Mazzone, D G; Raymond, S; Gavilano, J L; Steffens, P; Schneidewind, A; Lapertot, G; Kenzelmann, M
2017-11-03
Unconventional superconductivity in many materials is believed to be mediated by magnetic fluctuations. It is an open question how magnetic order can emerge from a superconducting condensate and how it competes with the magnetic spin resonance in unconventional superconductors. Here we study a model d-wave superconductor that develops spin-density wave order, and find that the spin resonance is unaffected by the onset of static magnetic order. This result suggests a scenario, in which the resonance in Nd_{0.05}Ce_{0.95}CoIn_{5} is a longitudinal mode with fluctuating moments along the ordered magnetic moments.
Spin-Current and Spin-Splitting in Helicoidal Molecules Due to Spin-Orbit Coupling
Caetano, R. A.
2016-03-01
The use of organic materials in spintronic devices has been seriously considered after recent experimental works have shown unexpected spin-dependent electrical properties. The basis for the confection of any spintronic device is ability of selecting the appropriated spin polarization. In this direction, DNA has been pointed out as a potential candidate for spin selection due to the spin-orbit coupling originating from the electric field generated by accumulated electrical charges along the helix. Here, we demonstrate that spin-orbit coupling is the minimum ingredient necessary to promote a spatial spin separation and the generation of spin-current. We show that the up and down spin components have different velocities that give rise to a spin-current. By using a simple situation where spin-orbit coupling is present, we provide qualitative justifications to our results that clearly point to helicoidal molecules as serious candidates to integrate spintronic devices.
Spin Torques in Systems with Spin Filtering and Spin Orbit Interaction
Ortiz Pauyac, Christian
2016-06-19
In the present thesis we introduce the reader to the ﬁeld of spintronics and explore new phenomena, such as spin transfer torques, spin ﬁltering, and three types of spin-orbit torques, Rashba, spin Hall, and spin swapping, which have emerged very recently and are promising candidates for a new generation of memory devices in computer technology. A general overview of these phenomena is presented in Chap. 1. In Chap. 2 we study spin transfer torques in tunnel junctions in the presence of spin ﬁltering. In Chap. 3 we discuss the Rashba torque in ferromagnetic ﬁlms, and in Chap. 4 we study spin Hall eﬀect and spin swapping in ferromagnetic ﬁlms, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives are summarized in Chap. 5.
Net-Zero Energy Technical Shelter
DEFF Research Database (Denmark)
Zhang, Chen; Heiselberg, Per; Jensen, Rasmus Lund
2014-01-01
Technical shelters are the basic structures for storing electronic and technical equipment, and commonly used for telecommunication base station, windmill, gas station, etc. Due to their high internal heat load density and special operation schedule, they consume more energy than normal residential...... or commercial buildings. On the other hand, it is a big challenge to power the technical shelter in remote area where the grids are either not available or the expansion of grid is expensive. In order to minimize the energy consumption and obtain a reliable and cost-efficient power solution for technical...... shelter, this study will apply the net-zero energy concept into the technical shelter design. The energy conservation can be achieved by proper design of building envelop and optimization of the cooling strategies. Both experiments and numerical simulations are carried out to investigate the indoor...
de Graaf, S E; Adamyan, A A; Lindström, T; Erts, D; Kubatkin, S E; Tzalenchuk, A Ya; Danilov, A V
2017-02-03
An on-chip electron spin resonance technique is applied to reveal the nature and origin of surface spins on Al_{2}O_{3}. We measure a spin density of 2.2×10^{17} spins/m^{2}, attributed to physisorbed atomic hydrogen and S=1/2 electron spin states on the surface. This is direct evidence for the nature of spins responsible for flux noise in quantum circuits, which has been an issue of interest for several decades. Our findings open up a new approach to the identification and controlled reduction of paramagnetic sources of noise and decoherence in superconducting quantum devices.
Universal spin transport in a strongly interacting Fermi gas.
Sommer, Ariel; Ku, Mark; Roati, Giacomo; Zwierlein, Martin W
2011-04-14
Transport of fermions, particles with half-integer spin, is central to many fields of physics. Electron transport runs modern technology, defining states of matter such as superconductors and insulators, and electron spin is being explored as a new carrier of information. Neutrino transport energizes supernova explosions following the collapse of a dying star, and hydrodynamic transport of the quark-gluon plasma governed the expansion of the early Universe. However, our understanding of non-equilibrium dynamics in such strongly interacting fermionic matter is still limited. Ultracold gases of fermionic atoms realize a pristine model for such systems and can be studied in real time with the precision of atomic physics. Even above the superfluid transition, such gases flow as an almost perfect fluid with very low viscosity when interactions are tuned to a scattering resonance. In this hydrodynamic regime, collective density excitations are weakly damped. Here we experimentally investigate spin excitations in a Fermi gas of (6)Li atoms, finding that, in contrast, they are maximally damped. A spin current is induced by spatially separating two spin components and observing their evolution in an external trapping potential. We demonstrate that interactions can be strong enough to reverse spin currents, with components of opposite spin reflecting off each other. Near equilibrium, we obtain the spin drag coefficient, the spin diffusivity and the spin susceptibility as a function of temperature on resonance and show that they obey universal laws at high temperatures. In the degenerate regime, the spin diffusivity approaches a value set by [planck]/m, the quantum limit of diffusion, where [planck]/m is Planck's constant divided by 2π and m the atomic mass. For repulsive interactions, our measurements seem to exclude a metastable ferromagnetic state.
Measurements of nuclear spin dynamics by spin-noise spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); Kavokin, K. V.; Glazov, M. M. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); Ioffe Institute, Russian Academy of Sciences, 26 Polytechnicheskaya, St.-Petersburg 194021 (Russian Federation); Vladimirova, M.; Scalbert, D.; Cronenberger, S. [Laboratoire Charles Coulomb UMR 5221 CNRS/Université de Montpellier, Place Eugene Bataillon, 34095 Montpellier Cedex 05 (France); Kavokin, A. V. [Spin Optics Laboratory, St. Petersburg State University, 1 Ul' anovskaya, Peterhof, St. Petersburg 198504 (Russian Federation); School of Physics and Astronomy, University of Southampton, SO17 1NJ Southampton (United Kingdom); Lemaître, A.; Bloch, J. [Laboratoire de Photonique et de Nanostructures, UPR CNRS, Route de Nozay, 91460 Marcoussis (France)
2015-06-15
We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamics in n-GaAs. The SNS experiments were performed on bulk n-type GaAs layers embedded into a high-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation initially prepared by optical pumping is monitored in real time via a shift of the peak position in the electron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauser field acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependent on the electron concentration.
A first-principles DFT+GW study of spin-filter and spin-gapless semiconducting Heusler compounds
Tas, M.; Şaşıoğlu, E.; Friedrich, C.; Galanakis, I.
2017-11-01
Among Heusler compounds, the ones being magnetic semiconductors (also known as spin-filter materials) are widely studied as they offer novel functionalities in spintronic and magnetoelectronic devices. The spin-gapless semiconductors are a special case. They possess a zero or almost-zero energy gap in one of the two spin channels. We employ the GW approximation to simulate the electronic band structure of these materials. Our results suggest that in most cases the use of GW self energy instead of the usual density functionals is important to accurately determine the electronic properties of magnetic semiconductors.
Celi, Alessio; Grass, Tobias; Ferris, Andrew J.; Padhi, Bikash; Raventós, David; Simonet, Juliette; Sengstock, Klaus; Lewenstein, Maciej
2016-08-01
Ultracold bosons in a triangular lattice are a promising candidate for observing quantum spin liquid behavior. Here we investigate, for such system, the role of a harmonic trap giving rise to an inhomogeneous density. We construct a modified spin-wave theory for arbitrary filling and predict the breakdown of order for certain values of the lattice anisotropy. These regimes, identified with the spin liquid phases, are found to be quite robust upon changes in the filling factor. This result is backed by an exact diagonalization study on a small lattice.
Spin selection at organic spinterface by anchoring group
Energy Technology Data Exchange (ETDEWEB)
Zhang, Zhao; Qiu, Shuai; Miao, Yuan-yuan; Ren, Jun-feng; Wang, Chuan-kui [School of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Hu, Gui-chao, E-mail: hgc@sdnu.edu.cn [School of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Institute of Theoretical Physics, Technische Universität Dresden, 01062 Dresden (Germany)
2017-07-01
Highlights: • The sign of interfacial spin polarization can be selected by using different anchoring groups. • A sp{sup 3}-d or sp-d hybridization may occur and induce spin polarization when the anchoring group changes. • Interfacial spin polarization depends on both the type of the outer orbital of the anchoring atom as well as its energy. - Abstract: Control of organic interfacial spin polarization is crucial in organic spintronics. Based on ab initio theory, here we proposed a spin selection at organic interface via anchoring group by adsorbing an organic molecule onto Ni(111) surface. The results demonstrate that either a positive or negative interfacial spin polarization may be obtained by choosing different anchoring groups. The orbital analysis via the projected density of states shows that the interfacial spin polarization is sensitive to the hybridization of the outer orbital of the anchoring atom as well as its energy relative to the d orbital of the ferromagnetic atom. The work indicates a feasible way to realize spin selection at the organic spinterface by anchoring group.
Competition between spin and charge order in a one-dimensional lattice
Talebi, Amir Hossein; Davoudi, Bahman; Rahimitabar, M. Reza
2017-10-01
In this paper, we study the presence of competing instabilities in one-dimensional (1D) extended Hubbard model (EHM). Using the extended two-particle self-consistent approximation (ETPSC), we derive the density and interaction dependent crossover diagram for spin and charge density wave fluctuations at arbitrary wave number. We determine the phase transitions of the system by means of spin and charge susceptibilities. We draw the phase diagram which separates different phases of the model for several effective particle densities.
International Development Research Centre (IDRC) Digital Library (Canada)
lremy
developing products, marketing tools and building capacity of the grass root telecentre workers. D.Net recognized that it had several ideas worth developing into small interventions that would make big differences, but resource constraints were a barrier for scaling-up these initiatives. More demands, limited resources.
DEFF Research Database (Denmark)
Knigge, Ulrich; Hansen, Carsten Palnæs
2012-01-01
Surgery is the only treatment that may cure the patient with gastroentero-pancreatic (GEP) neuroendocrine tumours (NET) and neuroendocrine carcinomas (NEC) and should always be considered as first line treatment if R0/R1 resection can be achieved. The surgical and interventional procedures for GEP...
Net Neutrality in the Netherlands
van Eijk, N.
2014-01-01
The Netherlands is among the first countries that have put specific net neutrality standards in place. The decision to implement specific regulation was influenced by at least three factors. The first was the prevailing social and academic debate, partly due to developments in the United States. The
Complexity Metrics for Workflow Nets
DEFF Research Database (Denmark)
Lassen, Kristian Bisgaard; van der Aalst, Wil M.P.
2009-01-01
Process modeling languages such as EPCs, BPMN, flow charts, UML activity diagrams, Petri nets, etc.\\ are used to model business processes and to configure process-aware information systems. It is known that users have problems understanding these diagrams. In fact, even process engineers and system...
TU-EF-BRA-02: Longitudinal Proton Spin Relaxation and T1-Imaging
Energy Technology Data Exchange (ETDEWEB)
Lemen, L. [Univ Cincinnati (United States)
2015-06-15
NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm. MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common
TU-EF-BRA-03: Free Induction Decay (without the Decay) and Spin-Echo Imaging
Energy Technology Data Exchange (ETDEWEB)
Price, R. [Vanderbilt Medical Center (United States)
2015-06-15
NMR, and Proton Density MRI of the 1D Patient - Anthony Wolbarst Net Voxel Magnetization, m(x,t). T1-MRI; The MRI Device - Lisa Lemen ‘Classical’ NMR; FID Imaging in 1D via k-Space - Nathan Yanasak Spin-Echo; S-E/Spin Warp in a 2D Slice - Ronald Price Magnetic resonance imaging not only reveals the structural, anatomic details of the body, as does CT, but also it can provide information on the physiological status and pathologies of its tissues, like nuclear medicine. It can display high-quality slice and 3D images of organs and vessels viewed from any perspective, with resolution better than 1 mm. MRI is perhaps most extraordinary and notable for the plethora of ways in which it can create unique forms of image contrast, reflective of fundamentally different biophysical phenomena. As with ultrasound, there is no risk from ionizing radiation to the patient or staff, since no X-rays or radioactive nuclei are involved. Instead, MRI harnesses magnetic fields and radio waves to probe the stable nuclei of the ordinary hydrogen atoms (isolated protons) occurring in water and lipid molecules within and around cells. MRI consists, in essence, of creating spatial maps of the electromagnetic environments around these hydrogen nuclei. Spatial variations in the proton milieus can be related to clinical differences in the biochemical and physiological properties and conditions of the associated tissues. Imaging of proton density (PD), and of the tissue proton spin relaxation times known as T1 and T2, all can reveal important clinical information, but they do so with approaches so dissimilar from one another that each is chosen for only certain clinical situations. T1 and T2 in a voxel are determined by different aspects of the rotations and other motions of the water and lipid molecules involved, as constrained by the local biophysical surroundings within and between its cells – and they, in turn, depend on the type of tissue and its state of health. Three other common
U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...
Lee, Na Young; Mandal, Debasish; Bae, Seong Hee; Seo, Mi Sook; Lee, Yong-Min; Shaik, Sason
2017-01-01
The spin states (S = 1 and S = 2) of nonheme FeIVO intermediates are believed to play an important role in determining their chemical properties in enzymatic and biomimetic reactions. However, it is almost impossible to investigate the spin state effect of nonheme FeIVO species experimentally, since FeIVO models having the S = 1 and S = 2 spin states at the same time neither exist nor can be synthesized. However, recent synthesis of an FeIVO complex with an S = 1 spin state (triplet), [(Me3NTB)FeIVO]2+ (1), and a structurally similar FeIVO complex but with an S = 2 spin state (quintet), [(TQA)FeIVO]2+ (2), has allowed us to compare their reactivities at 233 K. In the present study, we show that structural variants control the spin-state selectivity and reactivity of nonheme FeIVO complexes. While 1 and 2 were proposed to be in an octahedral geometry based on DFT calculations and spectroscopic characterization done at 4 K, further DFT calculations show that these species may well assume a trigonal bipyramidal structure by losing one coordinated solvent ligand at 233 K. Thus, the present study demonstrates that the structure and spin state of nonheme FeIVO complexes can be different at different temperatures; therefore, the structural and/or spin state information obtained at 4 K should be carefully used at a higher temperature (e.g., 233 K). In addition to 1 and 2, [(TPA)FeIVO]2+ (3) with an S = 1 spin state, whose spin state was determined spectroscopically and theoretically at 233 K, is included in this study to compare the chemical properties of S = 1 and S = 2 FeIVO complexes. The present results add another dimension to the discussion of the reactivites of nonheme FeIVO species, in which the structural preference and spin state of nonheme FeIVO species can vary depending on temperature. PMID:28970926
Effects of impurities and vortices on the low-energy spin excitations in high-T_{c} materials
DEFF Research Database (Denmark)
Andersen, Brian Møller; Graser, S.; Schmid, M.
2011-01-01
a quasi-long range ordered state. When correlations are sufficiently strong, disorder is unimportant for the generation of static magnetism but plays an additional role of pinning disordered stripe configurations. We calculate the spin excitations in a disordered spin-density wave phase, and show how...... disorder and/or applied magnetic fields lead to a slowing down of the dynamical spin fluctuations in agreement with neutron scattering and muon spin rotation (mSR) experiments....
Giant spin-phonon bottleneck effects in evaporable vanadyl-based molecules with long spin coherence.
Tesi, L; Lunghi, A; Atzori, M; Lucaccini, E; Sorace, L; Totti, F; Sessoli, R
2016-11-14
Vanadium(iv) complexes have recently shown record quantum spin coherence times that in several circumstances are limited by spin-lattice relaxation. The role of the environment and vibronic properties in the low temperature dynamics is here investigated by a comparative study of the magnetization dynamics as a function of crystallite size and the steric hindrance of the β-diketonate ligands in VO(acac)2 (1), VO(dpm)2 (2) and VO(dbm)2 (3) evaporable complexes (acac(-) = acetylacetonate, dpm(-) = dipivaloylmethanate, and dbm(-) = dibenzoylmethanate). A pronounced crystallite size dependence of the relaxation time is observed at unusually high temperatures (up to 40 K), which is associated with a giant spin-phonon bottleneck effect. We model this behaviour by an ad hoc force field approach derived from density functional theory calculations, which evidences a correlation of the intensity of the phenomenon with ligand dimensions and the unit cell size.
Spin Structures in Magnetic Nanoparticles
DEFF Research Database (Denmark)
Mørup, Steen; Brok, Erik; Frandsen, Cathrine
2013-01-01
Spin structures in nanoparticles of ferrimagnetic materials may deviate locally in a nontrivial way from ideal collinear spin structures. For instance, magnetic frustration due to the reduced numbers of magnetic neighbors at the particle surface or around defects in the interior can lead to spin...... canting and hence a reduced magnetization. Moreover, relaxation between almost degenerate canted spin states can lead to anomalous temperature dependences of the magnetization at low temperatures. In ensembles of nanoparticles, interparticle exchange interactions can also result in spin reorientation....... Here, we give a short review of anomalous spin structures in nanoparticles....
Caught in the Net: Perineuronal Nets and Addiction
Directory of Open Access Journals (Sweden)
Megan Slaker
2016-01-01
Full Text Available Exposure to drugs of abuse induces plasticity in the brain and creates persistent drug-related memories. These changes in plasticity and persistent drug memories are believed to produce aberrant motivation and reinforcement contributing to addiction. Most studies have explored the effect drugs of abuse have on pre- and postsynaptic cells and astrocytes; however, more recently, attention has shifted to explore the effect these drugs have on the extracellular matrix (ECM. Within the ECM are unique structures arranged in a net-like manner, surrounding a subset of neurons called perineuronal nets (PNNs. This review focuses on drug-induced changes in PNNs, the molecules that regulate PNNs, and the expression of PNNs within brain circuitry mediating motivation, reward, and reinforcement as it pertains to addiction.
Army Net Zero Prove Out. Army Net Zero Training Report
2014-11-20
sensors were strategically placed throughout the installation by magnetically attaching them to water main valve stems. The sensors check sound...Recycle Wrap Substitutes for Packaging Materials Re-Use of Textiles and Linens Setting Printers to Double-Sided Printing Net Zero Waste...can effectively achieve source reduction. Clean and Re-Use Shop Rags - Shop rags represent a large textile waste stream at many installations. As a
Army Net Zero Prove Out. Net Zero Waste Best Practices
2014-11-20
Anaerobic Digesters – Although anaerobic digestion is not a new technology and has been used on a large-scale basis in wastewater treatment , the...technology and has been used on a large-scale basis in wastewater treatment , the use of the technology should be demonstrated with other...approaches can be used for cardboard and cellulose -based packaging materials. This approach is in line with the Net Zero Waste hierarchy in terms of
Spinning Them Off: Entrepreneuring practices in Corporate Spin-Offs
National Research Council Canada - National Science Library
Hydle, Katja Maria; Meland, Kjersti Vikse; Haus-Reve, Silje
2016-01-01
.... We uncover the enacted aspects of knowledge, called knowing, through theories from seven cases of incumbent-backed spin-offs and find that the management of the parent firms are highly involved in the spin-offs...
Quantum spin transistor with a Heisenberg spin chain
Marchukov, O. V.; Volosniev, A. G.; Valiente, M.; Petrosyan, D.; Zinner, N. T.
2016-01-01
Spin chains are paradigmatic systems for the studies of quantum phases and phase transitions, and for quantum information applications, including quantum computation and short-distance quantum communication. Here we propose and analyse a scheme for conditional state transfer in a Heisenberg XXZ spin chain which realizes a quantum spin transistor. In our scheme, the absence or presence of a control spin excitation in the central gate part of the spin chain results in either perfect transfer of an arbitrary state of a target spin between the weakly coupled input and output ports, or its complete blockade at the input port. We also discuss a possible proof-of-concept realization of the corresponding spin chain with a one-dimensional ensemble of cold atoms with strong contact interactions. Our scheme is generally applicable to various implementations of tunable spin chains, and it paves the way for the realization of integrated quantum logic elements. PMID:27721438
Mechanisms of Spin-Dependent Heat Generation in Spin Valves
Zhang, Xiao-Xue; Zhu, Yao-Hui; He, Pei-Song; Li, Bao-He
2017-06-01
The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. By reformulating the heat generation rate, we found alternative current-force pairs without cross effects, which enable us to interpret the product of each pair as a distinct mechanism of heat generation. The results show that the spin-dependent part of the heat generation includes two terms. One of them is proportional to the square of the spin accumulation and arises from the spin relaxation. However, the other is proportional to the square of the spin-accumulation gradient and should be attributed to another mechanism, the spin diffusion. We illustrated the characteristics of the two mechanisms in a typical spin valve with a finite nonmagnetic spacer layer.
Demonstration of the spin solar cell and spin photodiode effect
Endres, B.; Ciorga, M.; Schmid, M.; Utz, M.; Bougeard, D.; Weiss, D.; Bayreuther, G.; Back, C.H.
2013-01-01
Spin injection and extraction are at the core of semiconductor spintronics. Electrical injection is one method of choice for the creation of a sizeable spin polarization in a semiconductor, requiring especially tailored tunnel or Schottky barriers. Alternatively, optical orientation can be used to generate spins in semiconductors with significant spin-orbit interaction, if optical selection rules are obeyed, typically by using circularly polarized light at a well-defined wavelength. Here we introduce a novel concept for spin injection/extraction that combines the principle of a solar cell with the creation of spin accumulation. We demonstrate that efficient optical spin injection can be achieved with unpolarized light by illuminating a p-n junction where the p-type region consists of a ferromagnet. The discovered mechanism opens the window for the optical generation of a sizeable spin accumulation also in semiconductors without direct band gap such as Si or Ge. PMID:23820766
Krishnan, Chethan; Raju, Avinash
2017-06-01
We construct a candidate for the most general chiral higher spin theory with AdS3 boundary conditions. In the Chern-Simons language, on the left it has the Drinfeld-Sokolov reduced form, but on the right all charges and chemical potentials are turned on. Altogether (for the spin-3 case) these are 19 functions. Despite this, we show that the resulting metric has the form of the "most general" AdS3 boundary conditions discussed by Grumiller and Riegler. The asymptotic symmetry algebra is a product of a W3 algebra on the left and an affine s l (3 )k current algebra on the right, as desired. The metric and higher spin fields depend on all the 19 functions. We compare our work with previous results in the literature.
Miller, Jan D; Hupka, Jan; Aranowski, Robert
2012-11-20
A spinning fluids reactor, includes a reactor body (24) having a circular cross-section and a fluid contactor screen (26) within the reactor body (24). The fluid contactor screen (26) having a plurality of apertures and a circular cross-section concentric with the reactor body (24) for a length thus forming an inner volume (28) bound by the fluid contactor screen (26) and an outer volume (30) bound by the reactor body (24) and the fluid contactor screen (26). A primary inlet (20) can be operatively connected to the reactor body (24) and can be configured to produce flow-through first spinning flow of a first fluid within the inner volume (28). A secondary inlet (22) can similarly be operatively connected to the reactor body (24) and can be configured to produce a second flow of a second fluid within the outer volume (30) which is optionally spinning.
Rackham, Neil
1995-01-01
True or false? In selling high-value products or services: "closing" increases your chance of success; it is essential to describe the benefits of your product or service to the customer; objection handling is an important skill; and open questions are more effective than closed questions. All false, says Neil Rackham. He and his team studied more than 35,000 sales calls made by 10,000 sales people in 23 countries over 12 years. Their findings revealed that many of the methods developed for selling low-value goods just don't work for major sales. Rackham went on to introduce his SPIN-selling method, where SPIN describes the whole selling process - Situation questions, Problem questions, Implication questions, Need-payoff questions. SPIN-selling provides you with a set of simple and practical techniques which have been tried in many of today's leading companies with dramatic improvements to their sales performance.
Contucci, Pierluigi
2013-01-01
Presenting and developing the theory of spin glasses as a prototype for complex systems, this book is a rigorous and up-to-date introduction to their properties. The book combines a mathematical description with a physical insight of spin glass models. Topics covered include the physical origins of those models and their treatment with replica theory; mathematical properties like correlation inequalities and their use in the thermodynamic limit theory; main exact solutions of the mean field models and their probabilistic structures; and the theory of the structural properties of the spin glass phase such as stochastic stability and the overlap identities. Finally, a detailed account is given of the recent numerical simulation results and properties, including overlap equivalence, ultrametricity and decay of correlations. The book is ideal for mathematical physicists and probabilists working in disordered systems.
Yang, Xi-Feng; Zhou, Wen-Qian; Hong, Xue-Kun; Liu, Yu-Shen; Wang, Xue-Feng; Feng, Jin-Fu
2015-01-14
Ab initio calculations combining density-functional theory and nonequilibrium Green's function are performed to investigate the effects of either single B atom or single N atom dopant in zigzag-edged graphene nanoribbons (ZGNRs) with the ferromagnetic state on the spin-dependent transport properties and thermospin performances. A spin-up (spin-down) localized state near the Fermi level can be induced by these dopants, resulting in a half-metallic property with 100% negative (positive) spin polarization at the Fermi level due to the destructive quantum interference effects. In addition, the highly spin-polarized electric current in the low bias-voltage regime and single-spin negative differential resistance in the high bias-voltage regime are also observed in these doped ZGNRs. Moreover, the large spin-up (spin-down) Seebeck coefficient and the very weak spin-down (spin-up) Seebeck effect of the B(N)-doped ZGNRs near the Fermi level are simultaneously achieved, indicating that the spin Seebeck effect is comparable to the corresponding charge Seebeck effect.
Longitudinal spin physics results from COMPASS
Peshekhonov, D
2011-01-01
The COMPASS experiment at the CERN SPS has a broad physics program focused on the nucleon spin structure and hadron spectroscopy, using muon and hadron beams, respectively. Results from the COMPASS on the inclusive longitudinal double spin asymmetries $A^{d,p}_{1}$ measured in deep-inelastic polarized muon scattering off the polarized $^{6}LiD$ and $NH_{3}$ targets are presented. The new proton data cover the range $Q^{2}$ > 1( GeV$^{2}/c$), 0.004 < $x$ < 0.7 and improve the statistical precision of $g^{p}_{1} (x)$ by factor of two at $x$ < 0.02 compared to previous measurements. The spin-dependent non-singlet function $g^{NS}_{1} (x, Q^{2})$ extracted from the data allows to evaluate the isovector quark density $Δq_{3}(x, Q^{2})$ and check the Bjorken sum rule prediction. The helicity distributions for the three lightest quark and antiquark flavours extracted from the measured double spin asymmetries for production of charged pions and kaons in semi-inclusive deep-inelastic scattering are also pres...
Fermi Liquid Instabilities in the Spin Channel
Energy Technology Data Exchange (ETDEWEB)
Wu, Congjun; /Santa Barbara, KITP; Sun, Kai; Fradkin, Eduardo; /Illinois U., Urbana; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-03-16
We study the Fermi surface instabilities of the Pomeranchuk type in the spin triplet channel with high orbital partial waves (F{sub l}{sup a} (l > 0)). The ordered phases are classified into two classes, dubbed the {alpha} and {beta}-phases by analogy to the superfluid {sup 3}He-A and B-phases. The Fermi surfaces in the {alpha}-phases exhibit spontaneous anisotropic distortions, while those in the {beta}-phases remain circular or spherical with topologically non-trivial spin configurations in momentum space. In the {alpha}-phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone modes in the spin channel have nearly isotropic underdamped dispersion relation at small propagating wavevectors. Due to the coupling to the Goldstone modes, the spin wave spectrum develops resonance peaks in both the {alpha} and {beta}-phases, which can be detected in inelastic neutron scattering experiments. In the p-wave channel {beta}-phase, a chiral ground state inhomogeneity is spontaneously generated due to a Lifshitz-like instability in the originally nonchiral systems. Possible experiments to detect these phases are discussed.
Paramagnetic spin seebeck effect.
Wu, Stephen M; Pearson, John E; Bhattacharya, Anand
2015-05-08
We report the observation of the longitudinal spin Seebeck effect in paramagnetic insulators. By using a microscale on-chip local heater, we generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. Using this technique at low temperatures (Seebeck effect in the insulating paramagnets Gd3Ga5O12 (gadolinium gallium garnet) and DyScO3 (DSO), using either W or Pt as the spin detector layer. By taking advantage of the strong magnetocrystalline anisotropy of DSO, we eliminate contributions from the Nernst effect in W or Pt, which produces a phenomenologically similar signal.
Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid
Jiang, Hong-Chen; Devereaux, T.; Kivelson, S. A.
2017-08-01
We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the t -J model on a kagome lattice with a small but nonzero concentration δ of doped holes. It is now widely accepted that the undoped (δ =0 ) spin-1 /2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole per unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. Our results may be relevant to kagome lattice herbertsmithite upon doping.
Exciton spin relaxation dynamics in InGaAs /InP quantum wells
Akasaka, Shunsuke; Miyata, Shogo; Kuroda, Takamasa; Tackeuchi, Atsushi
2004-09-01
We have investigated the exciton spin relaxation mechanism between 13 and 300K in InGaAs /InP quantum wells using time-resolved spin-dependent pump and probe absorption measurements. The exciton spin relaxation time, τs above 40K was found to depend on temperature, T, according to τs∝T-1.1, although the spin relaxation time is constant below 40K. The clear carrier density dependence of the exciton spin relaxation time was observed below 40K, although the carrier density dependence is weak above 40K. These results imply that the main spin relaxation mechanism above and below 40K are the D'yakonov-Perel' process and the Bir-Aronov-Pikus process, respectively.
National Aeronautics and Space Administration — The Human Appropriation of Net Primary Productivity (HANPP) as a Percentage of Net Primary Productivity (NPP) portion of the Human Appropriation of Net Primary...
Hydrodynamic characteristics of plane netting used for aquaculture net cages in uniform current
National Research Council Canada - National Science Library
DONG, SHUCHUANG; HU, FUXIANG; KUMAZAWA, TAISEI; SIODE, DAISUKE; TOKAI, TADASHI
2016-01-01
The hydrodynamic characteristics of polyethylene (PE) netting and chain link wire netting with different types of twine diameter and mesh size for aquaculture net cages were examined by experiments in a flume tank...
Spin injection and perpendicular spin transport in graphite nanostructures
Banerjee, T.; van der Wiel, Wilfred Gerard; Jansen, R.
2010-01-01
Organic- and carbon-based materials are attractive for spintronics because their small spin-orbit coupling and low hyperfine interaction is expected to give rise to large spin-relaxation times. However, the corresponding spin-relaxation length is not necessarily large when transport is via weakly
Aspects of spin polarised transport
Allen, W D
1999-01-01
Spin electronics is the emerging discipline which seeks to exploit the spin of the electron in the pursuit of new areas of physics and of novel devices and applications. It can be broadly defined as the technology which differentially manipulates the two families of electronic carriers, the up and down spins. The technical basis for Spin Electronics resides in the transport properties of metallic ferromagnets which are central to the discipline and are used as sources and analysers of spin-polarised currents. We have developed a totally new model for domain wall resistance in the framework of the two spin channel model which invokes spin mixing which derives from the deviation of spin direction from the local magnetisation direction in passage through the wall
Spin-flipping polarized electrons
Directory of Open Access Journals (Sweden)
V. S. Morozov
2001-10-01
Full Text Available We recently used a prototype rf dipole magnet to study the spin flipping of a 669 MeV horizontally polarized electron beam stored in the presence of a nearly full Siberian snake in the new MIT-Bates storage ring. We flipped the spin by ramping the rf dipole's frequency through an rf-induced depolarizing resonance. After optimizing the frequency ramp parameters, we used multiple spin flipping to measure a spin-flip efficiency of 94.5±2.5%. The spin-flip efficiency was apparently limited by the field strength in the air-core prototype rf dipole magnet. This unexpectedly high efficiency indicates that very efficient spin flipping of the ring's stored polarized electron beam should be possible using the much stronger ferrite spin flipper, which is now being built by the University of Michigan's Spin Physics Center.
Haukilehto, Tero
2013-01-01
In this thesis isolation in unit testing is studied to get a precise picture of the isolation frameworks available for .Net environment. At the beginning testing is discussed in theory with the benefits and the problems it may have been linked with. The theory includes software development in general in connection with testing. Theory of isolation is also described before the actual isolation frameworks are represented. Common frameworks are described in more detail and comparable informa...
Effect of Twisting and Stretching on Magneto Resistance and Spin Filtration in CNTs
Directory of Open Access Journals (Sweden)
Anil Kumar Singh
2017-08-01
Full Text Available Spin-dependent quantum transport properties in twisted carbon nanotube and stretched carbon nanotube are calculated using density functional theory (DFT and non-equilibrium green’s function (NEGF formulation. Twisting and stretching have no effect on spin transport in CNTs at low bias voltages. However, at high bias voltages the effects are significant. Stretching restricts any spin-up current in antiparallel configuration (APC, which results in higher magneto resistance (MR. Twisting allows spin-up current almost equivalent to the pristine CNT case, resulting in lower MR. High spin filtration is observed in PC and APC for pristine, stretched and twisted structures at all applied voltages. In APC, at low voltages spin filtration in stretched CNT is higher than in pristine and twisted ones, with pristine giving a higher spin filtration than twisted CNT.
Anomalously large spin susceptibility enhancement in n-doped CdMnTe quantum wells
Energy Technology Data Exchange (ETDEWEB)
Ben Cheikh, Z. [Laboratoire Charles Coulomb, UMR 5221, Département Semi-conducteurs, Matériaux et Capteurs, Université Montpellier 2, France and Laboratoire de Physique des Matériaux: Structures et Propriétés, Faculté (Tunisia); Cronenberger, S.; Vladimirova, M.; Scalbert, D. [Laboratoire Charles Coulomb, UMR 5221, Departement Semi-conducteurs, Materiaux et Capteurs, Universite Montpellier 2 (France); Boujdaria, K. [Laboratoire de Physique des Matériaux: Structures et Propriétés, Faculté des Sciences de Bizerte, Université de Carthage, 7021 Zarzouna (Tunisia); Baboux, F.; Perez, F. [Institut des NanoSciences de Paris, CNRS/Université Paris 6, 4 place Jussieu, F-75005 Paris (France); Wojtowicz, T.; Karczewski, G. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland)
2013-12-04
We report on time-resolved Kerr rotation (TRKR) experiments done on n-doped CdMnTe quantum wells (QWs), in the regime where strong coupling between the electron and the Mn spin-flip excitations shows up. It has been proposed previously to deduce the 2D electron gas spin susceptibility from the coupling energy between these spin excitations. Here we measure the coupling energy on a high mobility sample down to very low excitation density, and compare the results with spin-flip Raman scattering (SFRS) on the same sample. The electron spin polarizations measured by TRKR and SFRS are found in relatively good agreement. However the spin susceptibility measured by TRKR exceeds systematically the values predicted by many-body theory. This could be an indication that the two-oscillator model used to describe mixed electron-Mn spin excitations needs to be improved.
Lattice dynamics in spin-crossover nanoparticles through nuclear inelastic scattering
Félix, Gautier; Mikolasek, Mirko; Peng, Haonan; Nicolazzi, William; Molnár, Gábor; Chumakov, Aleksandr I.; Salmon, Lionel; Bousseksou, Azzedine
2015-01-01
We used nuclear inelastic scattering (NIS) to investigate the lattice dynamics in [Fe(pyrazine)(Ni(CN)4)] spin crossover nanoparticles. The vibrational density of states of iron was extracted from the NIS data, which allowed to determine characteristic thermodynamical and lattice dynamical parameters as well as their spin-state dependence. The optical part of the NIS spectra compares well with the Raman scattering data reflecting the expansion/contraction of the coordination octahedron during the spin transition. From the acoustic part, we extracted the sound velocity in the low-spin (vLS=2073 ±31 m s-1) and high-spin (vHS=1942 ±23 m s-1) states of the particles. The spin-state dependence of this parameter is of primary interest to rationalize the spin-transition behavior in solids as well as its dynamics and finite size effects.
Observations of exciton and carrier spin relaxation in Be doped p-type GaAs
Asaka, Naohiro; Harasawa, Ryo; Lu, Shulong; Dai, Pan; Tackeuchi, Atsushi
2014-03-01
We have investigated the exciton and carrier spin relaxation in Be-doped p-type GaAs. Time-resolved spin-dependent photoluminescence (PL) measurements revealed spin relaxation behaviors between 10 and 100 K. Two PL peaks were observed at 1.511 eV (peak 1) and 1.497 eV (peak 2) at 10 K, and are attributed to the recombination of excitons bound to neutral Be acceptors (peak 1) and the band-to-acceptor transition (peak 2). The spin relaxation times of both PL peaks were measured to be 1.3-3.1 ns at 10-100 K, and found to originate from common electron spin relaxation. The observed existence of a carrier density dependence of the spin relaxation time at 10-77 K indicates that the Bir-Aronov-Pikus process is the dominant spin relaxation mechanism.
Nanda, B. R. K.; Sherafati, M.; Popović, Z. S.; Satpathy, S.
2012-08-01
We study the electronic structure of graphene with a single substitutional vacancy using a combination of the density-functional, tight-binding and impurity Green's function approaches. Density-functional studies are performed with the all-electron spin-polarized linear augmented plane wave (LAPW) method. The three sp2σ dangling bonds adjacent to the vacancy introduce localized states (Vσ) in the mid-gap region, which split due to the crystal field and a Jahn-Teller distortion, while the pzπ states introduce a sharp resonance state (Vπ) in the band structure. For a planar structure, symmetry strictly forbids hybridization between the σ and the π states, so that these bands are clearly identifiable in the calculated band structure. As to the magnetic moment of the vacancy, the Hund's rule coupling aligns the spins of the four localized Vσ1↑↓, Vσ2↑ and Vπ↑ electrons, resulting in an S = 1 state, with a magnetic moment of 2μB, which is reduced by about 0.3μB due to the anti-ferromagnetic spin polarization of the π band itinerant states in the vicinity of the vacancy. This results in the net magnetic moment of 1.7μB. Using the Lippmann-Schwinger equation, we reproduce the well-known ˜1/r decay of the localized Vπ wave function with distance, and in addition, find an interference term coming from the two Dirac points, previously unnoticed in the literature. The long-range nature of the Vπ wave function is a unique feature of the graphene vacancy and we suggest that this may be one of the reasons for the widely varying relaxed structures and magnetic moments reported from the supercell band calculations in the literature.
Photoluminescence of p-doped quantum wells with strong spin splitting
Kossacki, P.; Boukari, H.; Bertolini, M; Ferrand, D.; Cibert, J.; Tatarenko, S.; Gaj, J. A.; Deveaud, B.; Ciulin, V.; Potemski, M.
2004-01-01
The spectroscopic properties of a spin polarized two-dimensional hole gas are studied in modulation doped (Cd,Mn)Te quantum wells. The giant Zeeman effect induces a significant spin splitting even at very small values of the applied field. Several methods of measuring the carrier density (Hall effect, filling factors of the Landau levels at high field, various manifestations of Moss-Burstein shifts) are described and calibrated. The value of the spin splitting needed to fully polarize the hol...
Spin-dependent thermoelectric effects in superconductor-ferromagnet tunnel junctions
Energy Technology Data Exchange (ETDEWEB)
Kolenda, Stefan; Beckmann, Detlef [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (Germany); Suergers, Christoph [Physikalisches Institut, Karlsruher Institut fuer Technologie (Germany)
2016-07-01
Recently, large thermoelectric effects were predicted to occur in superconductor-ferromagnet tunnel junctions with a spin-splitting of the density of states. We have reported on the observation of these effects in samples where the spin splitting was induced by an applied magnetic field. Here, we show results on samples where the spin splitting is enhanced by exchange coupling to the ferromagnetic insulator europium sulfide.
Sosenko, Evan Boyd
Recent focus on two dimensional materials and spin-coupled phenomena holds future potential for fast, efficient, flexible, and transparent devices. The fundamental operation of a spintronic device depends on the injection, transmission, and detection of spins in a conducting channel. Long spin lifetimes during transit are critical for realizing this technology. An attractive platform for this purpose is graphene, which has high mobilities and low spin-orbit coupling. Unfortunately, measured spin lifetimes are orders of magnitude smaller than theoretically expected. A source of spin loss is the resistance mismatch between the ferromagnetic electrodes and graphene. While this has been studied numerically, here we provide a closed form expression for Hanle spin precession which is the standard method of measuring spin lifetimes. This allows for a detailed characterization of the nonlocal spin valve device. Strong spin-orbit interaction has the potential to engender unconventional superconducting states. A cousin to graphene, two dimensional transition metal dichalcogenides entwine interaction, spin-orbit coupling, and topology. The noninteracting electronic states have multiple valleys in the energy dispersion and are topologically nontrivial. We report on the possible superconducting states of hole-doped systems, and analyze to what extent the correlated phase inherits the topological aspects of the parent crystal. We find that local attractive interactions or proximal coupling to s-wave superconductors lead to a pairing which is an equal mixture of a spin singlet and the m = 0 spin triplet. Its topology allows quasiparticle excitations of net nonzero Berry curvature via pair-breaking by circularly polarized light. The valley contrasting optical response, where oppositely circularly polarized light couples to different valleys, is present even in the superconducting state, though with smaller magnitude.
Bidirectional resonant tunneling spin pump
Ting, David Z. -Y.; Cartoixà Soler, Xavier
2003-01-01
We propose a mechanism for achieving bidirectional spin pumping in conventional nonmagnetic semiconductorresonant tunnelingheterostructures under zero magnetic field. The device is designed specifically to take advantage of the special spin configuration described by the Rashba effect in asymmetric quantum wells. It induces the simultaneous flow of oppositely spin-polarized current components in opposite directions through spin-dependent resonant tunneling, and can thus generate significant l...
Directory of Open Access Journals (Sweden)
Akihiko Sekine
2017-05-01
Full Text Available We study theoretically spin dynamics in three-dimensional antiferromagnetic insulators with spin-orbit coupling. We focus on the antiferromagnetic insulators whose low-energy effective model possesses a topological term called the θ term. By solving the Landau-Lifshitz-Gilbert equation in the presence of the θ term, we show that the antiferromagnetic resonance can be realized by ac electric fields along with static magnetic fields. The antiferromagnetic resonance can be detected via the spin pumping from the Néel field and net magnetization. We calculate both contributions to the pumped spin current, and find that the magnitude of the ac electric field to cause the resonance state is very small (∼ 1 V/m. This indicates that spin currents can be generated efficiently. The mechanism of the antiferromagnetic resonance in this study is understood as the inverse process of the dynamical chiral magnetic effect.
DEFF Research Database (Denmark)
Garnett, E S; Webber, C E; Coates, G
1977-01-01
The density of a defined volume of the human lung can be measured in vivo by a new noninvasive technique. A beam of gamma-rays is directed at the lung and, by measuring the scattered gamma-rays, lung density is calculated. The density in the lower lobe of the right lung in normal man during quiet...... breathing in the sitting position ranged from 0.25 to 0.37 g.cm-3. Subnormal values were found in patients with emphsema. In patients with pulmonary congestion and edema, lung density values ranged from 0.33 to 0.93 g.cm-3. The lung density measurement correlated well with the findings in chest radiographs...... but the lung density values were more sensitive indices. This was particularly evident in serial observations of individual patients....
TRANSVERSITY SINGLE SPIN ASYMMETRIES.
Energy Technology Data Exchange (ETDEWEB)
BOER,D.
2001-04-27
The theoretical aspects of two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions, are reviewed. Issues of factorization, evolution and Sudakov factors for the relevant observables are discussed. These theoretical considerations pinpoint the most realistic scenarios towards measurements of transversity.
Spin physics in semiconductors
Dyakonov, Mikhail I
2008-01-01
This book describes beautiful optical and transport phenomena related to the electron and nuclear spins in semiconductors with emphasis on a clear presentation of the physics involved. Recent results on quantum wells and quantum dots are reviewed. The book is intended for students and researchers in the fields of semiconductor physics and nanoelectronics.
Antiferromagnetic spin-orbitronics
Manchon, Aurelien
2015-05-01
Antiferromagnets have long remained an intriguing and exotic state of matter, whose application has been restricted to enabling interfacial exchange bias in metallic and tunneling spin-valves [1]. Their role in the expanding field of applied spintronics has been mostly passive and the in-depth investigation of their basic properties mostly considered from a fundamental perspective.
Quantum coherent switch utilizing commensurate nanoelectrode and charge density periodicities
Harrison, Neil [Santa Fe, NM; Singleton, John [Los Alamos, NM; Migliori, Albert [Santa Fe, NM
2008-08-05
A quantum coherent switch having a substrate formed from a density wave (DW) material capable of having a periodic electron density modulation or spin density modulation, a dielectric layer formed onto a surface of the substrate that is orthogonal to an intrinsic wave vector of the DW material; and structure for applying an external spatially periodic electrostatic potential over the dielectric layer.
Indian Academy of Sciences (India)
up of high-spin configurations outlined above, a detailed and careful study of the medium spin, near yrast states in this nucleus is important for reliable assignments of spins and parities to states in superdeformed bands [1,6] in mass region 60. Also, the observation of direct proton decay from excited states in Cu nuclei [14] ...
Spin Injection in Indium Arsenide
Directory of Open Access Journals (Sweden)
Mark eJohnson
2015-08-01
Full Text Available In a two dimensional electron system (2DES, coherent spin precession of a ballistic spin polarized current, controlled by the Rashba spin orbit interaction, is a remarkable phenomenon that’s been observed only recently. Datta and Das predicted this precession would manifest as an oscillation in the source-drain conductance of the channel in a spin-injected field effect transistor (Spin FET. The indium arsenide single quantum well materials system has proven to be ideal for experimental confirmation. The 2DES carriers have high mobility, low sheet resistance, and high spin orbit interaction. Techniques for electrical injection and detection of spin polarized carriers were developed over the last two decades. Adapting the proposed Spin FET to the Johnson-Silsbee nonlocal geometry was a key to the first experimental demonstration of gate voltage controlled coherent spin precession. More recently, a new technique measured the oscillation as a function of channel length. This article gives an overview of the experimental phenomenology of the spin injection technique. We then review details of the application of the technique to InAs single quantum well (SQW devices. The effective magnetic field associated with Rashba spin-orbit coupling is described, and a heuristic model of coherent spin precession is presented. The two successful empirical demonstrations of the Datta Das conductance oscillation are then described and discussed.
DEFF Research Database (Denmark)
Bruun, Georg
2011-01-01
We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of temperature and interaction strength. For low temperatures...
Mechanical generation of spin current
Directory of Open Access Journals (Sweden)
Mamoru eMatsuo
2015-07-01
Full Text Available We focus the recent results on spin-current generation from mechanical motion such as rigid rotation and elastic deformations. Spin transport theory in accelerating frames is constructed by using the low energy expansion of the generally covariant Dirac equation. Related issues on spin-manipulation by mechanical rotation are also discussed.
Spin dynamics in general relativity
Saravanan, S.
2016-01-01
Since all astrophysical objects spin, it is important to study the dynamics of spinning objects in curved space-time. The dynamics of spinning particles are described with a covariant Hamiltonian formalism. In this formalism, the closed set of equations of motion are obtained from Poisson-Dirac
Spinning Them Off: Entrepreneuring Practices in Corporate Spin-Offs
Directory of Open Access Journals (Sweden)
Katja Maria Hydle
2016-01-01
Full Text Available This paper focuses on the practices between parent and child firms in corporate spinoffs. We uncover the enacted aspects of knowledge, called knowing, through theories from seven cases of incumbent-backed spin-offs and find that the management of the parent firms are highly involved in the spin-offs. The practices associated with spinning off are solving problems, involving multidisciplinary expertise and entrepreneuring management at the parent firm. We contribute to the spin-off literature by discussing the knowledge required for successfully spinning off child firms and to practice theory by empirically uncovering the practical understanding involved in the origin and perpetuation of an organization.
Microwave generation by spin Hall nanooscillators with nanopatterned spin injector
Energy Technology Data Exchange (ETDEWEB)
Zholud, A., E-mail: azholud@emory.edu; Urazhdin, S. [Department of Physics, Emory University, Atlanta, Georgia 30322 (United States)
2014-09-15
We experimentally study spin Hall nano-oscillators based on Pt/ferromagnet bilayers with nanopatterned Pt spin injection layer. We demonstrate that both the spectral characteristics and the electrical current requirements can be simultaneously improved by reducing the spin injection area. Moreover, devices with nanopatterned Pt spin injector exhibit microwave generation over a wide temperature range that extends to room temperature. Studies of devices with additional Pt spacers under the device electrodes show that the oscillation characteristics are affected not only by the spin injection geometry but also by the effects of Pt/ferromagnet interface on the dynamical properties of the ferromagnet.
DEFF Research Database (Denmark)
Pedersen, Bolette Sandford; Nimb, Sanni
2008-01-01
Artiklen omhandler udarbejdelsen af et verbumshierarki i det leksikalsk-semantiske ordnet, DanNet.......Artiklen omhandler udarbejdelsen af et verbumshierarki i det leksikalsk-semantiske ordnet, DanNet....
The Uniframe .Net Web Service Discovery Service
National Research Council Canada - National Science Library
Berbeco, Robert W
2003-01-01
Microsoft .NET allows the creation of distributed systems in a seamless manner Within NET small, discrete applications, referred to as Web services, are utilized to connect to each other or larger applications...
U.S. Environmental Protection Agency — This RadNet Quality Data Asset includes all data since initiation and when ERAMS was expanded to become RadNet, name changed to reflect new mission. This includes...
Simulations of defect spin qubits in piezoelectric semiconductors
Seo, Hosung
In recent years, remarkable advances have been reported in the development of defect spin qubits in semiconductors for solid-state quantum information science and quantum metrology. Promising spin qubits include the nitrogen-vacancy center in diamond, dopants in silicon, and the silicon vacancy and divacancy spins in silicon carbide. In this talk, I will highlight some of our recent efforts devoted to defect spin qubits in piezoelectric wide-gap semiconductors for potential applications in mechanical hybrid quantum systems. In particular, I will describe our recent combined theoretical and experimental study on remarkably robust quantum coherence found in the divancancy qubits in silicon carbide. We used a quantum bath model combined with a cluster expansion method to identify the microscopic mechanisms behind the unusually long coherence times of the divacancy spins in SiC. Our study indicates that developing spin qubits in complex crystals with multiple types of atom is a promising route to realize strongly coherent hybrid quantum systems. I will also discuss progress and challenges in computational design of new spin defects for use as qubits in piezoelectric crystals such as AlN and SiC, including a new defect design concept using large metal ion - vacancy complexes. Our first principles calculations include DFT computations using recently developed self-consistent hybrid density functional theory and large-scale many-body GW theory. This work was supported by the National Science Foundation (NSF) through the University of Chicago MRSEC under Award Number DMR-1420709.
Spin-optical metamaterial route to spin-controlled photonics.
Shitrit, Nir; Yulevich, Igor; Maguid, Elhanan; Ozeri, Dror; Veksler, Dekel; Kleiner, Vladimir; Hasman, Erez
2013-05-10
Spin optics provides a route to control light, whereby the photon helicity (spin angular momentum) degeneracy is removed due to a geometric gradient onto a metasurface. The alliance of spin optics and metamaterials offers the dispersion engineering of a structured matter in a polarization helicity-dependent manner. We show that polarization-controlled optical modes of metamaterials arise where the spatial inversion symmetry is violated. The emerged spin-split dispersion of spontaneous emission originates from the spin-orbit interaction of light, generating a selection rule based on symmetry restrictions in a spin-optical metamaterial. The inversion asymmetric metasurface is obtained via anisotropic optical antenna patterns. This type of metamaterial provides a route for spin-controlled nanophotonic applications based on the design of the metasurface symmetry properties.
Spin-wave-induced spin torque in Rashba ferromagnets
Umetsu, Nobuyuki; Miura, Daisuke; Sakuma, Akimasa
2015-05-01
We study the effects of Rashba spin-orbit coupling on the spin torque induced by spin waves, which are the plane-wave dynamics of magnetization. The spin torque is derived from linear-response theory, and we calculate the dynamic spin torque by considering the impurity-ladder-sum vertex corrections. This dynamic spin torque is divided into three terms: a damping term, a distortion term, and a correction term for the equation of motion. The distorting torque describes a phenomenon unique to the Rashba spin-orbit coupling system, where the distorted motion of magnetization precession is subjected to the anisotropic force from the Rashba coupling. The oscillation mode of the precession exhibits an elliptical trajectory, and the ellipticity depends on the strength of the nesting effects, which could be reduced by decreasing the electron lifetime.
Artificial neural nets application in the cotton yarn industry
Directory of Open Access Journals (Sweden)
Gilberto Clóvis Antoneli
2016-06-01
Full Text Available The competitiveness in the yarn production sector has led companies to search for solutions to attain quality yarn at a low cost. Today, the difference between them, and thus the sector, is in the raw material, meaning processed cotton and its characteristics. There are many types of cotton with different characteristics due to its production region, harvest, storage and transportation. Yarn industries work with cotton mixtures, which makes it difficult to determine the quality of the yarn produced from the characteristics of the processed fibers. This study uses data from a conventional spinning, from a raw material made of 100% cotton, and presents a solution with artificial neural nets that determine the thread quality information, using the fibers’ characteristics values and settings of some process adjustments. In this solution a neural net of the type MultiLayer Perceptron with 11 entry neurons (8 characteristics of the fiber and 3 process adjustments, 7 output neurons (yarn quality and two types of training, Back propagation and Conjugate gradient descent. The selection and organization of the production data of the yarn industry of the cocamar® indústria de fios company are described, to apply the artificial neural nets developed. In the application of neural nets to determine yarn quality, one concludes that, although the ideal precision of absolute values is lacking, the presented solution represents an excellent tool to define yarn quality variations when modifying the raw material composition. The developed system enables a simulation to define the raw material percentage mixture to be processed in the plant using the information from the stocked cotton packs, thus obtaining a mixture that maintains the stability of the entire productive process.
PsychoNet: a psycholinguistc commonsense ontology
Mohtasseb, Haytham; Ahmed, Amr
2010-01-01
Ontologies have been widely accepted as the most advanced knowledge representation model. This paper introduces PsychoNet, a new knowledgebase that forms the link between psycholinguistic taxonomy, existing in LIWC, and its semantic textual representation in the form of commonsense semantic ontology, represented by ConceptNet. The integration of LIWC and ConceptNet and the added functionalities facilitate employing ConceptNet in psycholinguistic studies. Furthermore, it simplifies utilization...
Strain-induced large spin splitting and persistent spin helix at LaAlO3/SrTiO3 interface
Yamaguchi, Naoya; Ishii, Fumiyuki
2017-12-01
We investigate the effect of tensile strain on spin splitting at the n-type interface of LaAlO3/SrTiO3 in terms of spin–orbit coupling coefficient α and spin texture in the momentum space using first-principles density-functional calculations. Our results show that α could be controlled by the tensile strain, and can be enhanced by up to 5 times for a tensile strain of 7%, and the effect of the tensile strain leads to a persistent spin helix, which has a long spin lifetime. The strain effect on the LaAlO3/SrTiO3 interface is important for various applications such as spin field-effect transistors and spin-to-charge conversion.
Spin formalism and applications to new physics searches
Energy Technology Data Exchange (ETDEWEB)
Haber, H.E. [Univ. of California, Santa Cruz, CA (United States)
1994-12-01
An introduction to spin techniques in particle physics is given. Among the topics covered are: helicity formalism and its applications to the decay and scattering of spin-1/2 and spin-1 particles, techniques for evaluating helicity amplitudes (including projection operator methods and the spinor helicity method), and density matrix techniques. The utility of polarization and spin correlations for untangling new physics beyond the Standard Model at future colliders such as the LHC and a high energy e{sup +}e{sup {minus}} linear collider is then considered. A number of detailed examples are explored including the search for low-energy supersymmetry, a non-minimal Higgs boson sector, and new gauge bosons beyond the W{sup {+-}} and Z.