Anomalous x-ray scattering: Relativistic effects in x-ray dispersion analysis
Rayleigh scattering by bound electrons is reduced from the free-electron Thomson value at x-ray wavelengths by relativistic effects. To first order this arises from the relativistic increase in mass of the core electrons. The reduction is overestimated by more than a factor of 2 by the commonly used dipole approximation. Inclusion of higher multipole and retardation terms in dispersion analysis resolves reported conflicts between values of the anomalous scattering factor as measured interferometrically and as calculated from attenuation measurements. These considerations further imply that several scattering-factor tabulations in current use for diffraction studies require revision to take relativity fully into account. This correction is particularly significant in regions of anomalous dispersion and at low energies, where the scattering factor is small relative to the atomic number
Soejima, Y; Sugiyama, M; Annaka, M; Nakamura, A; Hiramatsu, N; Hara, K
2003-01-01
The structure of copper ion clusters in dehydrated N-isopropylacrylamide/sodium acrylate (NIPA/SA) gel has been studied by means of small angle X-ray scattering (SAXS) method. In order to distinguish the intensity scattered by Cu ions, the X-ray anomalous dispersion effect around the Cu K absorption edge has been coupled with SAXS. It is found that the dispersion effect dependent on the incident X-ray energy is remarkable only at the momentum transfer q = 0.031 A sup - sup 1 , where a SAXS peak is observed. The results indicate that copper ions form clusters in the dehydrated gel, and that the mean size of clusters is the same as that of SA clusters produced by microphase separation. It is therefore naturally presumed that copper ions are adsorbed into the SA molecules. On the basis of the presumption, a mechanism is proposed for microphase-separation and clustering of Cu ions.
Mizuki, J; Tanaka, H
2003-01-01
The employment of the X-ray anomalous dispersion effect allows us to detect the change in structure of catalytic converters with the environment exposed. Here we show that palladium atoms in a perovskite crystal move into and out of the crystal by anomalous X-ray diffraction and absorption techniques. This movement of the precious metal plays an important role to keep the catalytic activity long-lived. (author)
Anomalous dispersion enhanced Cerenkov phase-matching
Kowalczyk, T.C.; Singer, K.D. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Physics; Cahill, P.A. [Sandia National Labs., Albuquerque, NM (United States)
1993-11-01
The authors report on a scheme for phase-matching second harmonic generation in polymer waveguides based on the use of anomalous dispersion to optimize Cerenkov phase matching. They have used the theoretical results of Hashizume et al. and Onda and Ito to design an optimum structure for phase-matched conversion. They have found that the use of anomalous dispersion in the design results in a 100-fold enhancement in the calculated conversion efficiency. This technique also overcomes the limitation of anomalous dispersion phase-matching which results from absorption at the second harmonic. Experiments are in progress to demonstrate these results.
Anomalous hydrodynamical dispersion and the Coats-Smith equation: the finite size effects
We investigate a family of probability distributions that shows anomalous hydrodynamics dispersion, by solving a particular class of coupled generalized master equations. The Fourier-Laplace solution is obtained analytically in terms of the matrix Green function method; then the Coats-Smith concentration profile is revisited in a particular case. Two models of disorder are worked out explicitly, and the mean current is asymptotically calculated. We present an approximation method to calculate the first passage time distribution for this stochastic transport process, and as an example an exact Markovian result is worked out; scaling results are also shown. We discuss the comparison with other different methods to work out complex diffusion phenomena in the presence of disordered multiple transport paths. Extensions when the models are non diffusive can also be solved in the Fourier-Laplace representation. (author)
Anomalous dispersions of `hedgehog' particles
Bahng, Joong Hwan; Yeom, Bongjun; Wang, Yichun; Tung, Siu On; Hoff, J. Damon; Kotov, Nicholas
2015-01-01
Hydrophobic particles in water and hydrophilic particles in oil aggregate, but can form colloidal dispersions if their surfaces are chemically camouflaged with surfactants, organic tethers, adsorbed polymers or other particles that impart affinity for the solvent and increase interparticle repulsion. A different strategy for modulating the interaction between a solid and a liquid uses surface corrugation, which gives rise to unique wetting behaviour. Here we show that this topographical effect can also be used to disperse particles in a wide range of solvents without recourse to chemicals to camouflage the particles' surfaces: we produce micrometre-sized particles that are coated with stiff, nanoscale spikes and exhibit long-term colloidal stability in both hydrophilic and hydrophobic media. We find that these `hedgehog' particles do not interpenetrate each other with their spikes, which markedly decreases the contact area between the particles and, therefore, the attractive forces between them. The trapping of air in aqueous dispersions, solvent autoionization at highly developed interfaces, and long-range electrostatic repulsion in organic media also contribute to the colloidal stability of our particles. The unusual dispersion behaviour of our hedgehog particles, overturning the notion that like dissolves like, might help to mitigate adverse environmental effects of the use of surfactants and volatile organic solvents, and deepens our understanding of interparticle interactions and nanoscale colloidal chemistry.
Analytical solutions for anomalous dispersion transport
O'Malley, D.; Vesselinov, V. V.
2014-06-01
Groundwater flow and transport often occur in a highly heterogeneous environment (potentially heterogeneous at multiple spatial scales) and is impacted by geochemical reactions, advection, diffusion, and other pore scale processes. All these factors can give rise to large-scale anomalous dispersive behavior that can make complex model representation and prediction of plume concentrations challenging due to difficulties unraveling all the complexities associated with the governing processes, flow medium, and their parameters. An alternative is to use upscaled stochastic models of anomalous dispersion, and this is the approach used here. Within a probabilistic framework, we derive a number of analytical solutions for several anomalous dispersion models. The anomalous dispersion models are allowed to be either non-Gaussian (α-stable Lévy), correlated, or nonstationary from the Lagrangian perspective. A global sensitivity analysis is performed to gain a greater understanding of the extent to which uncertainty in the parameters associated with the anomalous behavior can be narrowed by examining concentration measurements from a network of monitoring wells and to demonstrate the computational speed of the solutions. The developed analytical solutions are encoded and available for use in the open source computational framework MADS (http://mads.lanl.gov).
Comparative study of anomalous dispersive transparent media
We present a comparative theoretical analysis of five different atomic schemes with respect to their performance as negative (anomalous) dispersive transparent media. The schemes discussed are the strongly driven and the degenerate two-level system, two closely spaced gain lines, and two slightly different double-Λ schemes with incoherent pumping. The analysis shows that the degenerate two-level scheme is best suited for applications for which only modest negative dispersion but strongly reduced absorption is required, and dissipation and loss of the optical fields have to be avoided. Two closely spaced gain lines and one of the double-Λ schemes are the best choice for applications which rely on large negative dispersion, but are not too sensitive to residual absorption and dissipation
Nagaosa, N.; Sinova, Jairo; Onoda, S.; MacDonald, A. H.; Ong, N. P.
2010-01-01
Roč. 82, č. 2 (2010), s. 1539-1592. ISSN 0034-6861 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 51.695, year: 2010
Nonlocal Anomalous Hall Effect
Zhang, Steven S.-L.; Vignale, Giovanni
2016-04-01
The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect—the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt /YIG structures.
Normal and Anomalous Dispersion in Fluvial Sediment Transport
Bradley, D. N.; Tucker, G. E.
2005-12-01
Understanding the rate of motion and pattern of dispersion in fluvial sediment transport is essential for a variety of applications, including predicting the fate and transport of solid-phase contaminants and modeling the cosmogenic-nuclide inheritance of water-borne sediment. In order to create a probabilistic model of sediment particle motion, it is necessary to characterize the statistical properties of fluvial sediment dispersion. In general, two modes of behavior have been observed in advective-diffusive transport systems: normal and anomalous dispersion. Normal dispersion is characterized by a well-defined mean position and spatial variance and the time evolution of particle concentration is described by a simple advection-diffusion equation. In contrast, a transport system that exhibits anomalous dispersion will tend to have a heavy-tailed spatial distribution, a mean position that is different from the peak concentration, and a large variance. The fundamental difference lies in the probability distribution of individual particle velocities. When the distribution is sufficiently heavy-tailed, the resulting dispersion pattern will be anomalous. Anomalous dispersion has been observed in geophysical systems ranging from turbulent flow to transport in heterogeneous porous media. Several lines of evidence from the sediment transport literature suggest that fluvial sediment may undergo anomalous dispersion. Tracer experiments show a preference for right-skewed travel distance distributions, a characteristic of anomalous diffusion. Studies suggest that large inputs of sediment to rivers (such as a landslide) tend to disperse in place rather than translate downstream. In addition, the fact that sediment grains can become trapped in flood plains and bars for long periods of time and then move long distances in rare, short duration events such as floods suggests a potential for anomalous dispersion due to a broad distribution of particle residence times. We develop a
Huang, S.; Ma, Y. Q.; Xu, S. T.
2015-12-01
Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point, and characterized by XRD, TEM and detailed magnetic measurements. The moments of CoFe2O4 nanoparticles consist of the core and canted surface moments below 200 K, and the exchange-coupling between the surface and core spins enhanced the remanence (Mr) to saturation (Ms) magnetization ratio (Mr/Ms) at the temperature of 10 K. Interestingly, the anomalous memory effect was observed in a broad temperature range which can be attributed to the relaxation of surface spins below 200 K and the one from the moments of magnetically ordered entity larger than one particle above 200 K.
The quantum anomalous Hall effect
LIU, CHAO-XING; Zhang, Shou-Cheng; Qi, Xiao-Liang
2015-01-01
The quantum anomalous Hall effect is defined as a quantized Hall effect realized in a system without external magnetic field. Quantum anomalous Hall effect is a novel manifestation of topological structure in many-electron systems, and may have potential applications in future electronic devices. In recent years, quantum anomalous Hall effect has been proposed theoretically and realized experimentally. In this review article, we provide a systematic overview of the theoretical and experimenta...
What Matters When and Where for Anomalous Dispersion/Diffusion
O'Malley, D.; Vesselinov, V. V.
2013-12-01
The classical Lagrangian model of Fickian dispersion/diffusion is given by Brownian motion of fluid particles representing contaminant migration. Brownian motion is defined via three conceptual assumptions about the distribution of (spatial) displacements: 1. The displacements are independent. 2. The displacements are stationary. 3. The displacements are normally distributed. Anomalous dispersion/diffusion occurs when one or more of these assumptions fails. Two of the hallmarks of anomalous dispersion/diffusion are nonlinear mean square displacement (often modeled as a power-law) and heavy tails. While these calling cards are important indicators of anomalous behavior, its origin is in the violation of any of the three assumptions. Anomalous behavior associated with such as violation has been observed in a variety of application areas including surface and subsurface hydrology. Anomalous dispersion/diffusion can create significant problems in efforts to characterize contaminant transport and design remediation strategies that protect groundwater resources. The impact at varied spatial and temporal scales of relaxing these assumptions in concert is not well understood. In order to gain a better understanding, a global sensitivity analysis (based on Sobol's method) of predicted contaminant concentrations at a number of spatial and temporal scales is performed with respect to the relaxation of these three assumptions. That is, the sensitivity of contaminant concentration (particle density) to variations in the degree to which the displacements are correlated, nonstationary, and non-normal is computed. The analyses are performed using the code MADS (Model Analyses for Decision Support; http://mads.lanl.gov).
Transfer of information in an anomalous dispersion medium
黄超光; 张元仲
2003-01-01
The transfer of information and signal velocity in an anomalous dispersion medium are studied. We propose that the discontinuous points in the envelop and its derivatives of any order are the information carried by a pulse different from others. The signal velocity will not exceed the speed of the shift of these discontinuous points. We study the propagation of pulses with a triangle envelop and with the envelop made up by three pieces of quadratic curve in dilute, anomalous dispersion gas with double gain lines. The discontinuous points of the envelop, its first derivative, and its second derivative are shown to propagate with vacuum speed of light c in the medium. A criterion has been suggested to determine theoretically whether the distortion of a pulse can be ignored.
Effective actions for anomalous hydrodynamics
We argue that an effective field theory of local fluid elements captures the constraints on hydrodynamic transport stemming from the presence of quantum anomalies in the underlying microscopic theory. Focussing on global current anomalies for an arbitrary flavour group, we derive the anomalous constitutive relations in arbitrary even dimensions. We demonstrate that our results agree with the constraints on anomaly governed transport derived hitherto using a local version of the second law of thermodynamics. The construction crucially uses the anomaly inflow mechanism and involves a novel thermofield double construction. In particular, we show that the anomalous Ward identities necessitate non-trivial interaction between the two parts of the Schwinger-Keldysh contour
Hollow cathode lamp based Faraday anomalous dispersion optical filter.
Pan, Duo; Xue, Xiaobo; Shang, Haosen; Luo, Bin; Chen, Jingbiao; Guo, Hong
2016-01-01
The Faraday anomalous dispersion optical filter (FADOF), which has acquired wide applications, is mainly limited to some gaseous elements and low melting-point metals before, for the restriction of the attainable atomic density. In conventional FADOF systems a high atomic density is usually achieved by thermal equilibrium at the saturated vapor pressure, hence for elements with high melting-points a high temperature is required. To avoid this restriction, we propose a scheme of FADOF based on the hollow cathode lamp (HCL), instead of atomic vapor cells. Experimental results in strontium atoms verified this scheme, where a transmission peak corresponding to the (88)Sr (5s(2))(1)S0 - (5s5p)(1)P1 transition (461 nm) is obtained, with a maximum transmittance of 62.5% and a bandwith of 1.19 GHz. The dependence of transmission on magnetic field and HCL discharge current is also studied. Since the state-of-art commercial HCLs cover about 70 elements, this scheme can greatly expand the applications of FADOFs, and the abundant atomic transitions they provide bring the HCL based FADOFs potential applications for frequency stabilization. PMID:27418112
Capilla, J. E.; Sanchez Fuster, I.; Sanchez Barrero, L.
2012-12-01
The limitations of the classical Advection-Dispersion Equation (ADE) approach to model mass transport remain a subject of research. The term anomalous transport is usually applied when the ADE fails to reproduce real field or lab experiments tracer tests data. Some authors address this limitation using high-resolution heterogeneous hydraulic conductivity (K) fields. Besides, the non-Fickian behavior of transport is another issue addressed. However, the effects of the spatial variability of dispersivity, and the influence of the model support scale on this property, have been rarely studied. The lack of experimental knowledge on the dispersivity behavior leads to model this basic parameter as an averaged calibrated parameter highly dependent on the model discretization size. In order to study the local behavior of the dispersivity a porous medium tank was designed and built at the Technical University of Valencia (Spain). This paper presents new results and conclusions obtained from the experiments conducted in this lab prototype. The steady flow through the porous medium tank lab is quasi-2D, and the K field imitates the patterns of spatial variability found in a real and highly heterogeneous formation (MADE2 site). The tracer tests are run using a conservative dye tracer and the tank is monitored by a grid of pressure transducers and taking digital images that are processed to map the evolution of solute concentrations in the tank. The set of exhaustive head and concentration data is used to compute detail local information of the effective dispersivity field at different time steps, and at different support scales. The analysis of results shows that the dispersivity field displays patterns of spatial variability related with the physical nature of the local material and also with the local evolution of concentrations at every grid block. We have found that the anomalous transport behavior observed in the lab tank can be accurately modeled using the classical ADE
Anomalous Hall effect in polycrystalline Ni films
Guo, Zaibing
2012-02-01
We systematically studied the anomalous Hall effect in a series of polycrystalline Ni films with thickness ranging from 4 to 200 nm. It is found that both the longitudinal and anomalous Hall resistivity increased greatly as film thickness decreased. This enhancement should be related to the surface scattering. In the ultrathin films (46 nm thick), weak localization corrections to anomalous Hall conductivity were studied. The granular model, taking into account the dominated intergranular tunneling, has been employed to explain this phenomenon, which can explain the weak dependence of anomalous Hall resistivity on longitudinal resistivity as well. © 2011 Elsevier Ltd. All rights reserved.
Bache, Morten; Zhou, Binbin
A new high-energy pulse compressor uses self-defocusing spectral broadening in anomalously dispersive quadratic nonlinear crystals, followed by positive group-delay-dispersion compensation. Compression to sub-50 fs is possible from Joule-class 1.03 µm femtosecond amplifiers in large-aperture KDP....
Dispersion properties of transverse magnetic (TM) waves in a subwavelength metallic waveguide loaded by uniaxial metamaterials are investigated, based on two kinds of uniaxial metamaterials with different orientations of optical axis. The numerical results show that the existence of fundamental TM0 mode and high-order TM modes in the waveguide system is dependent on the orientation of optical axis. In addition, their anomalous dispersion properties are clarified. When the orientation of optical axis is selected properly, there are two branches of dispersion curves for each high-order mode—one is normal dispersion and another belongs to anomalous dispersion, showing a transition from a backward wave to a forward one with the increase of working frequency. Moreover, the group velocity and energy flow distribution for TM1 mode are also demonstrated. These properties may have potential applications in optical information storage, integrated optics and nanophotonic devices. - Highlights: • Two kinds of subwavelength uniaxial metamaterial waveguides are constructed. • We demonstrate anomalous dispersion properties of transverse magnetic (TM) guided modes. • There are two branches of dispersion curves for high-order TM modes, showing a transition from a backward wave to a forward one. • Group velocity can approach to zero, having potential application in optical information storage. • Negative group velocity and energy flow distribution for TM modes are shown
Cs 728 nm excited state Faraday anomalous dispersion optical filter with indirect pump
Tao, Zhiming; Zhang, Xiaogang; Chen, Mo; Liu, Zhongzheng; Zhu, Chuanwen; Liu, Zhiwen; Chen, Jingbiao
2016-06-01
We demonstrate a Cs excited state Faraday anomalous dispersion optical filter (ESFADOF) operating at 728 nm using a novel pump method, by which the pump beam and the probe beam in the ESFADOF realized here have no a common energy level. Using this method, the ESFADOF achieves a transmission of 2.39% with a bandwidth of 22.52 MHz, which can be applied to both laser frequency stabilization and future four-level active optical clocks. Under the 455 nm laser pump, in addition to 52D5/2, other states such as 72S1/2, 72P3/2, 62P3/2, 62P1/2 and 52D3/2 have also been populated effectively. Meanwhile, multiple wavelength filters exploiting atomic transitions to these states can be realized.
Poynting vector, energy density, and energy velocity in an anomalous dispersion medium
The Poynting vector, energy density, and energy velocity of light pulses propagating in an anomalous dispersion medium with two closely spaced gain lines are calculated. The results show that a negative energy density in the medium propagates along the opposite direction of incidence with a velocity similar to the negative group velocity vg while Poynting vector is in the same direction of incidence. In other words, one might say that a positive energy density in the medium would propagate along the positive direction with a speed |vg|. We further point out that neither energy velocity nor group velocity is a good concept to describe the propagation process of light pulse inside the medium in the Wang, Kuzmich, and Dogaiu [Nature (London) 406, 277 (2000)] experiment owing to the strong accumulation and dissipation effects
Multisplitting and collapse of self-focusing anisotropic beams in normal/anomalous dispersive media
Bergé, L.; Juul Rasmussen, J.
1996-01-01
Three-dimensional self-focusing light pulses in normal and anomalous dispersive media are investigated by means of a waveguide instability analysis, a Lagrangian approach, and a quasi-self-similar analysis. In the case of normal dispersion for which no localized ground state exists, it is shown...... that a high-intensity elongated beam cannot self-similarly collapse. Even when the incident beam power widely exceeds the critical power for a two-dimensional self-focusing, the beam is shown to split into multiple cells that ultimately disperse when their individual mass lies below the critical power...... pulses also play an important role in an anomalous dispersive medium. In this case, unlike the former one, the beam self-contracts along its propagation axis and reconcentrates its shape back toward the center where it ultimately collapses in a finite time. (C) 1996 American Institute of Physics....
X-ray diffraction has been developed since the beginning of the century for the determination of crystallographic structures. Most complex structures (proteins, incommensurate crystals...) require the use of anomalous diffraction, i.e. the measurement of diffracted intensities at several wavelengths around the absorption edge of one element of the crystal. This technique allows the determination of the phase of the structure factor, as well as the positions of the anomalous atoms. In this thesis, we present the Dispersive Anomalous Diffraction (DAD) method, which allows the simultaneous measure of diffracted intensities at a number of wavelengths for many reflections. Two collection modes can be used, either continuous (DDAFS-Dispersive Diffraction Anomalous Fine Structure) or discrete (SMAD-Simultaneous Multiwavelength Anomalous Diffraction. A specific procedure and a program (DAD) have been developed for the quantitative analysis of dispersive diffraction images. This program also allows the analysis of monochromatic diffraction images, with satellite reflections near main diffraction peaks. We present the first two quantitative experiments in dispersive diffraction for biological compounds. Our results show that the use of SMAD for structure determination is possible, although several improvements are still necessary for both data collection and analysis. An important point in this thesis is the study of quasi-1D compound (TaSe4)2I: this crystal exhibits a Peierls transition, for which no condensation of the metallic atoms was shown for the last 15 years. Our study has characterized the domain structure of this material, and anomalous diffraction has shown in a specific way the tetramerisation of tantalum atoms, which exists along the already-known acoustic modulation. (author)
Anomalous Hall effect for semiclassical chiral fermions
Zhang, Pengming, E-mail: zhpm@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Horváthy, P.A., E-mail: horvathy@lmpt.univ-tours.fr [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China); Laboratoire de Mathématiques et de Physique Théorique, Université de Tours (France)
2015-03-06
Semiclassical chiral fermions manifest the anomalous spin-Hall effect: when put into a pure electric field they suffer a side jump, analogous to what happens to their massive counterparts in non-commutative mechanics. The transverse shift is consistent with the conservation of the angular momentum. In a pure magnetic field, instead, spiraling motion is found. Motion in Hall-type perpendicular electric and magnetic fields is also studied. - Highlights: • Chiral fermions exhibit an anomalous spin-Hall effect. • Transverse shift appears in a pure electric field. • In a pure magnetic field spiraling motion is found.
Two-dimensional solitons and vortices in normal and anomalous dispersive media
We study solitons and vortices described by the (2+1)-dimensional fourth-order generalized nonlinear Schroedinger equation with cubic-quintic nonlinearity. Necessary conditions for the existence of such structures are investigated analytically using conservation laws and asymptotic behavior of localized solutions. We derive the generalized virial relation, which describes the combined influence of linear and nonlinear effects on the evolution of the wave packet envelope. By means of refined variational analysis, we predict the main features of steady soliton solutions, which have been shown to be in good agreement with our numerical results. Soliton and vortex stability is investigated by linear analysis and direct numerical simulations. We show that stable bright solitons exist in nonlinear Kerr media both in anomalous and normal dispersive regimes, even if only the fourth-order dispersive effect is taken into account. Vortices occur robust with respect to symmetry-breaking azimuthal instability only in the presence of additional defocusing quintic nonlinearity in the strongly nonlinear regime. We apply our results to the theoretical explanation of whistler self-induced waveguide propagation in plasmas, and discuss possible applications to light beam propagation in cubic-quintic optical materials and to solitons in two-dimensional molecular systems
Inosov, D. S.; Fink, J.; Kordyuk, A. A.; Borisenko, S. V.; Zabolotnyy, V. B.; Schuster, R.; Knupfer, M.; Büchner, B.; Follath, R.; Dürr, H. A.; Eberhardt, W.; Hinkov, V.; Keimer, B.; Berger, H.
2007-12-01
Using high-resolution angle-resolved photoemission spectroscopy we have studied the momentum and photon energy dependence of the anomalous high-energy dispersion, termed waterfalls, between the Fermi level and 1 eV binding energy in several high-Tc superconductors. We observe strong changes of the dispersion between different Brillouin zones and a strong dependence on the photon energy around 75 eV, which we associate with the resonant photoemission at the Cu3p→3dx2-y2 edge. We conclude that the high-energy “waterfall” dispersion results from a strong suppression of the photoemission intensity at the center of the Brillouin zone due to matrix element effects and is, therefore, not an intrinsic feature of the spectral function. This indicates that the new high-energy scale in the electronic structure of cuprates derived from the waterfall-like dispersion may be incorrect.
Anomalous Hall Effect for chiral fermions
Zhang, P -M
2014-01-01
Semiclassical chiral fermions manifest the anomalous spin-Hall effect: when put into a pure electric field, they suffer a side jump, analogous to what happens to their massive counterparts in non-commutative mechanics. The transverse shift is consistent with the conservation of the angular momentum. In a pure magnetic field a cork-screw-like, spiraling motion is found.
Anomalous Hall effect in disordered multiband metals
Kovalev, A.A.; Sinova, Jairo; Tserkovnyak, Y.
2010-01-01
Roč. 105, č. 3 (2010), 036601/1-036601/4. ISSN 0031-9007 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.621, year: 2010
无
2002-01-01
The selenomethionyl derivative of the thermostable catechol 2,3-dioxygenase (SeMet-TC23O) is expressed,purified and crystallized. By using multiwave length anomalous dispersion (MAD) phasing techniques, the crystal structure of TC23O at 0.3 nm resolutions is determined.TC23O is a homotetramer. Each monomer is composed of N-terminal and C-terminal domains (residues 1～153 and 153～319, respectively). The two domains are proximately symmetric by a non-crystallographic axis. Each domain contains two characteristic motifs which are found in almost all of extradial dioxygenases.Kevwords: multiwavelength anomalous dispersion (MAD), X-ray diffraction, thermostable catechol 2,3-dioxygenase, crystal structure,synchrotron light source.
Anomalous dispersion analysis of inhibitor flexibility: a case study of the kinase inhibitor H-89
The anomalous dispersion signal of the bromine-containing kinase inhibitor H-89 was used to characterize discrete binding modes of the compound when complexed with the catalytic subunit of protein kinase A. With its ability to show the interactions between drug-target proteins and small-molecule ligands, X-ray crystallography is an essential tool in drug-discovery programmes. However, its usefulness can be limited by crystallization artifacts or by the data resolution, and in particular when assumptions of unimodal binding (and isotropic motion) do not apply. Discrepancies between the modelled crystal structure and the physiological range of structures generally prevent quantitative estimation of binding energies. Improved crystal structure resolution will often not aid energy estimation because the conditions which provide the highest rigidity and resolution are not likely to reflect physiological conditions. Instead, strategies must be employed to measure and model flexibility and multiple binding modes to supplement crystallographic information. One useful tool is the use of anomalous dispersion for small molecules that contain suitable atoms. Here, an analysis of the binding of the kinase inhibitor H-89 to protein kinase A (PKA) is presented. H-89 contains a bromobenzene moiety that apparently binds with multiple conformations in the kinase ATP pocket. Using anomalous dispersion methods, it was possible to resolve these conformations into two distinct binding geometries
A Non-Invasive Phase Sensor for Permittivity and Moisture Estimation Based on Anomalous Dispersion
Siddiqui, Omar; Ramzan, Rashad; Amin, Muhammad; Ramahi, Omar M.
2016-06-01
The traditional microwave resonance sensors are based on the measurement of the frequency shift and bandwidth of a resonator’s amplitude spectrum. Here we propose a novel sensing scheme in which the material properties are estimated by determining the changes in the phase spectrum of an anomalous-phase resonator. In the proposed phase sensing, we exploit the unique double phase reversal which takes place on the edges of the anomalous dispersion region as a signature to detect the resonance. We show that with the phase sensing, a significant reduction in detection errors compared to the traditional sensing can be obtained because of the noise immunity offered by the phase detection and also due to the strong dispersive phase response that reduces the sensor’s dependence on the external environment. We also show that the bandwidth determination procedure of the resonance which is needed to characterize the sample losses is significantly simplified. The concept of phase sensing is shown by devising an experimental microstrip open stub resonator whose frequency response lies in the anomalous dispersion region. The dielectric characteristics of the samples placed on the stub are extracted from the resonant frequency and the slope of the phase response. We also demonstrate that the changes in moisture levels can also be detected by utilizing the phase sensing method.
A Non-Invasive Phase Sensor for Permittivity and Moisture Estimation Based on Anomalous Dispersion
Siddiqui, Omar; Ramzan, Rashad; Amin, Muhammad; Ramahi, Omar M.
2016-01-01
The traditional microwave resonance sensors are based on the measurement of the frequency shift and bandwidth of a resonator’s amplitude spectrum. Here we propose a novel sensing scheme in which the material properties are estimated by determining the changes in the phase spectrum of an anomalous-phase resonator. In the proposed phase sensing, we exploit the unique double phase reversal which takes place on the edges of the anomalous dispersion region as a signature to detect the resonance. We show that with the phase sensing, a significant reduction in detection errors compared to the traditional sensing can be obtained because of the noise immunity offered by the phase detection and also due to the strong dispersive phase response that reduces the sensor’s dependence on the external environment. We also show that the bandwidth determination procedure of the resonance which is needed to characterize the sample losses is significantly simplified. The concept of phase sensing is shown by devising an experimental microstrip open stub resonator whose frequency response lies in the anomalous dispersion region. The dielectric characteristics of the samples placed on the stub are extracted from the resonant frequency and the slope of the phase response. We also demonstrate that the changes in moisture levels can also be detected by utilizing the phase sensing method. PMID:27346337
Pratt, J; Mueller, W -C; Chapman, S C; Watkins, N W
2014-01-01
Local regions of anomalous particle dispersion, and intermittent events that occur in turbulent flows can greatly influence the global statistical description of the flow. These local behaviors can be identified and analyzed by comparing the growth of neighboring convex hulls of Lagrangian tracer particles. Although in our simulations of homogeneous turbulence the convex hulls generally grow in size, after the Lagrangian particles that define the convex hulls begin to disperse, our analysis reveals short periods when the convex hulls of the Lagrangian particles shrink, evidence that particles are not dispersing simply. Shrinkage can be associated with anisotropic flows, since it occurs most frequently in the presence of a mean magnetic field or thermal convection. We compare dispersion between a wide range of statistically homogeneous and stationary turbulent flows ranging from homogeneous isotropic Navier-Stokes turbulence over different configurations of magnetohydrodynamic turbulence and Boussinesq convect...
Anomalous Hall effect in Weyl superconductors
Bednik, G.; Zyuzin, A. A.; Burkov, A. A.
2016-08-01
We present a theory of the anomalous Hall effect in a topological Weyl superconductor with broken time reversal symmetry. Specifically, we consider a ferromagnetic Weyl metal with two Weyl nodes of opposite chirality near the Fermi energy. In the presence of inversion symmetry, such a metal experiences a weak-coupling Bardeen–Cooper–Schrieffer instability, with pairing of parity-related eigenstates. Due to the nonzero topological charge, carried by the Weyl nodes, such a superconductor is necessarily topologically nontrivial, with Majorana surface states coexisting with the Fermi arcs of the normal Weyl metal. We demonstrate that, surprisingly, the anomalous Hall conductivity of such a superconducting Weyl metal coincides with that of a nonsuperconducting one, under certain conditions, in spite of the nonconservation of charge in a superconductor. We relate this to the existence of an extra (nearly) conserved quantity in a Weyl metal, the chiral charge.
Matin, Rastin; Misztal, Marek K.; Hernandez-Garcia, Anier; Mathiesen, Joachim
2015-11-01
Many hydrodynamic phenomena such as flows at micron scale in porous media, large Reynolds numbers flows, non-Newtonian and multiphase flows have been simulated numerically using the lattice Boltzmann method. By solving the Lattice Boltzmann Equation on three-dimensional unstructured meshes, we efficiently model single-phase fluid flow in real rock samples. We use the flow field to estimate the permeability and further investigate the anomalous dispersion of passive tracers in porous media. By extending our single-phase model with a free-energy based method, we are able to simulate binary systems with moderate density ratios in a thermodynamically consistent way. In this presentation we will present our recent results on both anomalous transport and multiphase segregation.
Excited state Faraday anomalous dispersion optical filters based on indirect laser pumping.
Yin, Longfei; Luo, Bin; Chen, Zhongjie; Zhong, Lei; Guo, Hong
2014-02-15
The direct pump method now used in excited state Faraday anomalous dispersion optical filters (ES-FADOFs) requires that the transition between the target and the ground state is an electric dipole allowed transition and that a laser that operates at the exact pump wavelength is available. This is not always satisfied in practice. An indirect laser pump method for ES-FADOF is proposed and experimentally realized. Compared with the commonly used direct pump method, this indirect pump method can reach the same performance using lasers at very different wavelengths. This method can greatly extend the wavelength range of FADOF and provide a novel scheme for ES-FADOF design. PMID:24562221
Smetanina, E O; Kompanets, V O; Chekalin, Sergei V; Kandidov, V P
2012-10-31
We report the results of investigation of femtosecond laser pulse filamentation in fused silica by varying the wavelength in the range from 800 to 2300 nm. It is shown that in the case of the anomalous group-velocity dispersion, a sequence of 'light bullets' with a high spatial and temporal localisation of the light field is formed along the filament. The relation of the formation and propagation of light bullets with the formation of an isolated anti-Stokes wing of the supercontinuum spectrum is established. (nonlinear optical phenomena)
Xin, Xu; Xiaohong, Hu; Ye, Feng; Yuanshan, Liu; Wei, Zhang; Zhi, Yang; Wei, Zhao; Yishan, Wang
2016-03-01
We study the spatiotemporal evolution of the electromagnetic field inside a microresonator showing an anomalous dispersion at the pump wavelength by using the normalized Lugiato-Lefever equation. Unlike the traditional single continuous wave (CW) pumping, an additional pump source consisting of periodical pulse train with variable repetition rate is adopted. The influences of the microresonator properties and the pump parameters on the field evolution and the electromagnetic field profile are analyzed. The simulation results indicate that, in the anomalous dispersion regime, both increases of the input pulse amplitude and the repetition frequency can result in the field profiles consisting of multiple peaks. A series of equidistant pulses can also be obtained by increasing the CW pump power. In addition, we find that a large physical detuning between the pump laser carrier and the cavity resonance frequency also causes the splitting of the inside field. Project supported by the National Major Scientific Instrumentation Development Program of China (Grant No. 2011YQ120022), CAS/SAFEA International Partnership Program for Creative Research Teams, China, and the National Natural Science Foundation of China (Grant No. 61275164).
Anomalous Josephson Hall effect in magnet/triplet superconductor junctions
Yokoyama, Takehito
2015-01-01
We investigate anomalous Hall effect in a magnet coupled to a triplet superconductor under phase gradient. It is found that the anomalous Hall supercurrent arises from non-trivial structure of the magnetization. The magnetic structure manifested in the Hall supercurrent is characterized by even order terms of the exchange coupling, essentially different from that discussed in the context of anomalous Hall effect, reflecting the disspationless nature of supercurrent. We also discuss a possible...
Anomalous Hall effect in YIG$|$Pt bilayers
Meyer, Sibylle; Schlitz, Richard; Geprägs, Stephan; Opel, Matthias; Huebl, Hans; Gross, Rudolf; Goennenwein, Sebastian T. B.
2015-01-01
We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet$|$platinum (YIG$|$Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall like signature in Pt, sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing ...
Cushman, J. H.; Moroni, M.
2002-12-01
Velocity fluctuations over evolving scales of motion, on the scale of observation, often lead to anomalous dispersion of conservative tracers in fluid mechanics studies of turbulence and heterogeneous porous media. Recent theories of anomalous dispersion lead to space-time non-local constitutive models for the flux of concentration, which can adequately model this problem. We review one such model, which has its foundations in non-equilibrium statistical mechanics. The basic premise is that knowledge of the evolution of the self-part of the intermediate scattering function is all that is required to model the phenomena of interest. We derive the basic integro-partial-differential equation this function satisfies and solve the inverse problem to obtain the kernels and use these to describe the wave-vector and frequency dependent dispersion tensor. Subsequently we use this information to study the transition from anomalous to Fickian dispersion. We also make use of the finite size Lyapunov exponent in the description of the dispersive process. Three-camera, three-dimensional, particle -tracking velocimetry experiments are undertaken to study dispersion within a matched-index heterogeneous porous medium. Particle trajectories, mean square displacements, velocity covariance's, intermediate scattering functions, classical dispersion tensors, wave-vector and frequency dependent generalized dispersion tensors and the finite-size Lyapunov exponents are obtained. Comparisons are made in the small frequency and small wave vector limits to obtain the transition from preasymptotic to asymptotic dispersion.
Dynamic polarization of the LiH molecule in strong light field in anomalous-dispersion domain
Shtoff, A V; Gusarov, S I; Dmitriev, Yu
1995-01-01
A new method is proposed to calculate the polarization vector of a molecule in a monochromatic external field in the anomalous-despersion domain. The method takes into account the instantaneous switching of the field. A simple modification of the method allows one to consider a more general switching procedure. As an illustration of the method Fourier components of the polarization vector of the LiH molecule in the anomalous -dispersion domain is calculated.
Photoinduced Anomalous Hall Effects in Weyl Semimetals
Chan, Ching-Kit; Lee, Patrick A.; Burch, Kenneth S.; Han, Jung Hoon; Ran, Ying
We examine theoretically the interplay between chiral photons and chiral electrons in Weyl semimetals. Owing to its monopole nature, a three-dimensional Weyl node is topologically-robust against a circularly polarized light. A driven Weyl system exhibits node shifts in the momentum space, in sharp contrast to the gap opening in a driven two-dimensional Dirac system. We show that the node shift leads to a change of the Chern vector which gives arise to a net photoinduced anomalous Hall conductivity, in the plane perpendicular to the light propagation. We shall describe the basic idea behind this generic photoinduced Hall effect, illustrate it with a concrete microscope model, and estimate its feasibility based on current optical experimental techniques.
Localization corrections to the anomalous Hall effect in a ferromagnet
Dugaev, V. K.; Crepieux, A.; Bruno, P
2001-01-01
We calculate the localization corrections to the anomalous Hall conductivity related to the contribution of spin-orbit scattering into the current vertex (side-jump mechanism). We show that in contrast to the ordinary Hall effect, there exists a nonvanishing localization correction to the anomalous Hall resistivity. The correction to the anomalous Hall conductivity vanishes in the case of side-jump mechanism, but is nonzero for the skew scattering. The total correction to the nondiagonal cond...
Anomalous supercurrent switching in graphene under proximity effect
Levchenko, Alex; Coskun, U. C.; Brenner, M.; Hymel, T.; Vakaryuk, V.; Bezryadin, A.
2012-02-01
We report a study of hysteretic current-voltage characteristics in superconductor-graphene-superconductor (SGS) junctions. The stochastic nature of the phase slips is characterized by measuring the distribution of the switching currents. We find that in SGS junctions the dispersion of the switching current scales with temperature as σIT^αG with αG 1/3. This observation is in sharp contrast with the known Josephson junction behavior where σIT^αJ with αJ=2/3. We propose an explanation using a modified version of Kurkijarvi's theory for the flux stability in rf-SQUID and attribute this anomalous effect to the temperature dependence of the critical current which persists down to low temperatures.
High-power Kerr-lens mode-locked thin-disk oscillator in the anomalous and normal dispersion regimes
Pronin, Oleg; Brons, Jonathan; Seidel, Marcus; Lücking, Fabian; Grasse, Christian; Boehm, Gerhard; Amann, Marcus C.; Pervak, Vladimir; Apolonski, Alexander; Kalashnikov, Vladimir L.; Krausz, Ferenc
2013-03-01
A femtosecond thin-disk Yb:YAG oscillator in both the anomalous and the normal dispersion regime is demonstrated. Both regimes are realized with practically the same resonator configuration. The power scaling potential of the anomalous and normal dispersion regimes is analyzed both theoretically and experimentally. The recipe to obtain Kerr-lens mode-locking (KLM) in the thin-disk configuration is presented here and oscillator characteristics as well as start-up difficulties are described. The oscillator stability in terms of output power, beam pointing and sensitivity to back reflections is measured and corresponds to the level of commercial systems.
Chen, Yu; Chen, Shuqing; Liu, Jun; Gao, Yanxia; Zhang, Wenjing
2016-06-13
By using evanescent field optical deposition method, we had successfully fabricated an effective optoelectronic device based on multi-layer black phosphorus (BP), which is been heavily investigating 2 dimensional (2D) semiconducting material with similar structure as graphene and thickness dependent direct band-gap. By placing this BP-based optoelectronic device inside a highly compact all-anomalous dispersion fiber laser cavity, stable passive mode-locking operation could be ensured and eventually a record 280 fs transmission limited soliton pulse with tunable central wavelength had been obtained through finely tailoring the cavity length. Other operation states, like bound soliton and noise-like state, had also been observed as well. This work demonstrates the enormous potential of BP for ultra-short pulse generation as an effective optoelectronic device. PMID:27410348
Anomalous Hall Effect in non-commutative mechanics
Horvathy, P. A.
2006-01-01
The anomalous velocity term in the semiclassical model of a Bloch electron deviates the trajectory from the conventional one. When the Berry curvature (alias noncommutative parameter) is a monopole in momentum space as found recently in some ferromagnetic semiconductors while observing the anomalous Hall effect, we get a transverse shift, similar to that in the optical Hall effect.
Anomalous Wien Effects in Supercooled Ionic Liquids
Patro, L. N.; Burghaus, O.; Roling, B.
2016-05-01
We have measured conductivity spectra of several supercooled monocationic and dicationic ionic liquids in the nonlinear regime by applying ac electric fields with large amplitudes up to about 180 kV /cm . Thereby, higher harmonic ac currents up to the 7th order were detected. Our results point to the existence of anomalous Wien effects in supercooled ionic liquids. Most ionic liquids studied here exhibit a conductivity-viscosity relation, which is close to the predictions of the Nernst-Einstein and Stokes-Einstein equations, as observed for classical strong electrolytes like KCl. These "strong" ionic liquids show a much stronger nonlinearity of the conductivity than classical strong electrolytes. On the other hand, the conductivity-viscosity relation of the ionic liquid [P6 ,6 ,6 ,14][Cl ] points to ion association effects. This "weak" ionic liquid shows a strength of the nonlinear effect, which is comparable to classical weak electrolytes. However, the nonlinearity increases quadratically with the field. We suggest that a theory for explaining these anomalies will have to go beyond the level of Coulomb lattice gas models.
Anomalous Wien Effects in Supercooled Ionic Liquids.
Patro, L N; Burghaus, O; Roling, B
2016-05-01
We have measured conductivity spectra of several supercooled monocationic and dicationic ionic liquids in the nonlinear regime by applying ac electric fields with large amplitudes up to about 180 kV/cm. Thereby, higher harmonic ac currents up to the 7th order were detected. Our results point to the existence of anomalous Wien effects in supercooled ionic liquids. Most ionic liquids studied here exhibit a conductivity-viscosity relation, which is close to the predictions of the Nernst-Einstein and Stokes-Einstein equations, as observed for classical strong electrolytes like KCl. These "strong" ionic liquids show a much stronger nonlinearity of the conductivity than classical strong electrolytes. On the other hand, the conductivity-viscosity relation of the ionic liquid [P_{6,6,6,14}][Cl] points to ion association effects. This "weak" ionic liquid shows a strength of the nonlinear effect, which is comparable to classical weak electrolytes. However, the nonlinearity increases quadratically with the field. We suggest that a theory for explaining these anomalies will have to go beyond the level of Coulomb lattice gas models. PMID:27203333
Apetrei, Alin Marian; Minot, Christophe; Moison, Jean-Marie; Belabas, Nadia; Tascu, Sorin
2016-01-01
Knowing the dispersion regime (normal vs anomalous) is important for both an isolated waveguide and a waveguide array. We investigate by the Finite Element Method the dispersion properties of a LiNbO3 waveguides array using two techniques. The first one assumes the Coupled Mode Theory in a 2-waveguide system. The other one uses the actual diffraction curve determined in a 7-waveguide system. In both approaches we find that by decreasing the array period, one passes from normal dispersion by achromatic point to anomalous array dispersion. We then illustrate the wavelength separation by doing Runge-Kutta light propagation simulations in waveguide array. As all the parameters values are technologically feasible, this opens new possibilities for optical data processing.
Anomalous Nernst Effect with Magnetocrystalline Anisotropy (110)
Chesman, Carlos; Costa Neto, Jose; Department of Physics-UFRN Team
2014-03-01
When a ferromagnetic material is submitted to a temperature gradient and the magnetic field generates voltage on the edges of the samples, this is called the Anomalous Nernst Effect (ANE). The Heusler alloys that currently exhibit this effect are the most promising for spintronics and spin caloritronics. In this study we perform a theoretical investigation of voltage curves associated to the ANE, when the material displays magnetocrystalline anisotropy for experimental results in two configurations, ANE versus applied magnetic field and planar angle variations of ANE. We analyzed three types of magnetocrystalline anisotropy: cubic anisotropy (100) with C4 symmetry, uniaxial anisotropy with C2 symmetry and cubic anisotropy (110). The aim was to prove that cubic anisotropy (110) is equivalent to anisotropy (100) combined with uniaxial anisotropy. Theoretical fitting of experimental ANE data demonstrates this total equivalence and that a new interpretation with the use of cubic anisotropy (110) may be due to the atomic arrangement of the so-called full-Heusler. Comparative analyses of Co2FeAl and Co2MnGe alloys will be presented. CNPq, CAPES, FAPERN.
Smetanina, E O; Kompanets, V O; Chekalin, Sergei V; Kandidov, V P
2012-10-31
We have studied experimentally and analytically the formation of the supercontinuum (SC) spectrum during femtosecond laser pulse filamentation in fused silica under conditions of zero and anomalous group velocity dispersions. It is found that with increasing centre wavelength from 1300 to 2300 nm, the SC spectrum of the anti-Stokes wing narrows, shifting to the blue. It is shown that the anti-Stokes (blue) shift of the SC spectrum increases with the multiphoton order of the medium ionisation by the light field in the filament. It is found that a broad minimum in the SC spectrum, separating the anti-Stokes wing from the centre wavelength, is a result of the interference of radiation from a moving broadband source, stemming from self-phase modulation of the high-intensity light field. The interference factors of the SC spectra obtained for this source, which moves along the emitting region of the filament in a dispersive medium, are in agreement with experimental and numerical results. (nonlinear optical phenomena)
Spurious dispersion effects at FLASH
The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)
It is shown that a ''nanofluid'' consisting of copper nanometer-sized particles dispersed in ethylene glycol has a much higher effective thermal conductivity than either pure ethylene glycol or ethylene glycol containing the same volume fraction of dispersed oxide nanoparticles. The effective thermal conductivity of ethylene glycol is shown to be increased by up to 40% for a nanofluid consisting of ethylene glycol containing approximately 0.3 vol% Cu nanoparticles of mean diameter <10 nm. The results are anomalous based on previous theoretical calculations that had predicted a strong effect of particle shape on effective nanofluid thermal conductivity, but no effect of either particle size or particle thermal conductivity
Klimczak, Mariusz; Soboń, Grzegorz; Kasztelanic, Rafał; Abramski, Krzysztof M.; Buczyński, Ryszard
2016-01-01
Coherence of supercontinuum sources is critical for applications involving characterization of ultrafast or rarely occurring phenomena. With the demonstrated spectral coverage of supercontinuum extending from near-infrared to over 10 μm in a single nonlinear fiber, there has been a clear push for the bandwidth rather than for attempting to optimize the dynamic properties of the generated spectrum. In this work we provide an experimental assessment of the shot-to-shot noise performance of supercontinuum generation in two types of soft glass photonic crystal fibers. Phase coherence and intensity fluctuations are compared for the cases of an anomalous dispersion-pumped fiber and an all-normal dispersion fiber. With the use of the dispersive Fourier transformation method, we demonstrate that a factor of 100 improvement in signal-to-noise ratio is achieved in the normal-dispersion over anomalous dispersion-pumped fiber for 390 fs long pump pulses. A double-clad design of the photonic lattice of the fiber is further postulated to enable a pump-related seeding mechanism of normal-dispersion supercontinuum broadening under sub-picosecond pumping, which is otherwise known for similar noise characteristics as modulation instability driven, soliton-based spectra.
Klimczak, Mariusz; Soboń, Grzegorz; Kasztelanic, Rafał; Abramski, Krzysztof M; Buczyński, Ryszard
2016-01-01
Coherence of supercontinuum sources is critical for applications involving characterization of ultrafast or rarely occurring phenomena. With the demonstrated spectral coverage of supercontinuum extending from near-infrared to over 10 μm in a single nonlinear fiber, there has been a clear push for the bandwidth rather than for attempting to optimize the dynamic properties of the generated spectrum. In this work we provide an experimental assessment of the shot-to-shot noise performance of supercontinuum generation in two types of soft glass photonic crystal fibers. Phase coherence and intensity fluctuations are compared for the cases of an anomalous dispersion-pumped fiber and an all-normal dispersion fiber. With the use of the dispersive Fourier transformation method, we demonstrate that a factor of 100 improvement in signal-to-noise ratio is achieved in the normal-dispersion over anomalous dispersion-pumped fiber for 390 fs long pump pulses. A double-clad design of the photonic lattice of the fiber is further postulated to enable a pump-related seeding mechanism of normal-dispersion supercontinuum broadening under sub-picosecond pumping, which is otherwise known for similar noise characteristics as modulation instability driven, soliton-based spectra. PMID:26759188
Understanding the anomalous dispersion of doubly-ionized carbon plasmas near 47 nm
Nilsen, J; Castor, J I; Iglesias, C A; Cheng, K T; Dunn, J; Johnson, W R; Filevich, J; Purvis, M A; Grava, J; Rocca, J J
2008-04-15
Over the last several years we have predicted and observed plasmas with an index of refraction greater than one in the soft X-ray regime. These plasmas are usually a few times ionized and have ranged from low-Z carbon plasmas to mid-Z tin plasmas. Our main calculational tool has been the average atom code. We have recently observed C{sup 2+} plasmas with an index of refraction greater than one at a wavelength of 46.9 nm (26.44 eV). In this paper we compare the average atom method, AVATOMKG, against two more detailed methods, OPAL and CAK, for calculating the index of refraction for the carbon plasmas and discuss the different approximations used. We present experimental measurements of carbon plasmas that display this anomalous dispersion phenomenon. It is shown that the average atom calculation is a good approximation when the strongest lines dominate the dispersion. However, when weaker lines make a significant contribution, the more detailed calculations such as OPAL and CAK are essential. During the next decade X-ray free electron lasers and other X-ray sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential. With the advent of tunable X-ray lasers the frequency dependent interferometer measurements of the index of refraction may enable us to determine the absorption coefficients and line-shapes and make detailed comparisons against our atomic physics codes.
780nm Rubdium Faraday Anomalous Dispersion Optical Filter with Buffer Gas Xe
Xiong, Junyu; Yin, Longfei; Luo, Bin; Guo, Hong; Cream Team
2016-05-01
Faraday anomalous dispersion optical filter (FADOF) is the most commonly used atomic filter, which is usually realized using alkali metal vapor cells. The filter has wide applications fields such as free-space optical communication, lidar and ghost imaging due to its high transmittance and ultra-narrow bandwidth. However, because FADOF is based on the resonant transitions of atoms, and due to the hyperfine structure of alkali elements, the transmittance spectrum of FADOF usually exhibit multi-peak form, which is not appropriate for applications requiring for single peak and will also reduce the signal to noise ratio(SNR). In this work, a 4cm long rubidium cell filled with 1torr Xenon as buffer gas has been used to realize a 780nm FADOF. Under the influence of the buffer gas Xenon, the sidebands of the transmittance spectrum has been removed, and a 780nm FADOF with single peak transmittance spectrum is achieved, which still keeps the high transmittance and ultra-narrow bandwidth. The peak transmittance of the filter is 82.7% if the power loss caused by the optical instruments (38%) is not included, and the bandwidth equals 1.2GHz. This work is supported by the National Science Fund for Distinguished Young Scholars of China (61225003), the National Natural Science Foundation of China (61401036, 61531003, 61571018), the China Postdoctoral Science Foundation (2015M580008).
A classical picture of anomalous effects in a Tokamak
Hirano, K.
1984-01-01
Atomic collisions between plasma ions and a very small amount of neutral particles remaining in a hot plasma plays a very important role for plasma transports and may be an origin of anomalous effects observed in a Tokamak such as the diffusion coefficient independent of the field strength, a rapid plasma density increase during gas puffing and current penetration with anomalously high speed in the start-up phase. The Ohm's law derived by Cowling is used for the analysis.
Large anomalous Nernst effect in a skyrmion crystal
Mizuta, Yo Pierre; Ishii, Fumiyuki
2016-06-01
Thermoelectric properties of a model skyrmion crystal were theoretically investigated, and it was found that its large anomalous Hall conductivity, corresponding to large Chern numbers induced by its peculiar spin structure leads to a large transverse thermoelectric voltage through the anomalous Nernst effect. This implies the possibility of finding good thermoelectric materials among skyrmion systems, and thus motivates our quests for them by means of the first-principles calculations as were employed in this study.
Chekalin, Sergei V; Kompanets, V O; Smetanina, E O; Kandidov, V P
2013-04-30
We report the results of theoretical and experimental research on spectrum transformation and spatiotemporal distribution of the femtosecond laser radiation intensity during filamentation in fused silica. The formation of light bullets with a high power density is first observed in a femtosecond laser pulse in the anomalous group velocity dispersion regime at a wavelength of 1800 nm. The minimum duration of the light bullet is about two oscillation cycles of the light field. (extreme light fields and their applications)
Anomalous magnetic field effects on graphene
Full text: Graphene exhibits anomalous properties in externally applied magnetic field. The orbital susceptibility of graphene has a singularity expressed as a delta function in Fermi energy EF, which diverges at Dirac point (EF =0) and vanishes otherwise. The singular diamagnetism is modified by various external factors such as the disorder potential [1], and the band gap opening [2,3], the finite-size effect [4] and the multilayer stacking [5], and studying those effects give deeper insights into the origin of the diamagnetic singularity of Dirac electron. The delta-function singularity is generally weakened by the electronic coupling between different graphene layers. In usual AB-stacked multilayer graphite, the interlayer coupling changes monlayer's linear band to quadratic, and then the susceptibility peak is broadened into a less singular logarithmic curve [5]. In a turbostratic (randomly-stacked) graphene multilayer, on the other hand, the diamagnetism generally becomes much stronger than in AB-stacked graphite, because the interlayer coupling is significantly reduced in misoriented lattice structure. There the external magnetic field is significantly screened inside the sample in low temperatures, and even a perfect screening is achieved at zero temperature in an ideal sample [4]. When the stacking angle between two graphene layers becomes as small as a few degree, the electronic structure is strongly modified by the long-period lattice structure with a Moire pattern. In increasing magnetic field, the spectrum gradually evolves into a fractal band structure called Hofstadter's butterfly, where the Hall conductivity exhibits a nonmonotonic behavior as a function of Fermi energy [6]. In finite-sized graphene system such as graphene ribbon and graphene nano-islands, the finite-size effect also changes the singular diamagnetism.[4] At T=0, the susceptibility χ(EF) oscillates between diamagnetism and paramagnetism in accordance with the subband structure formed
Anomalous radiation effects on oxide material surface
Various different kind of radiation influence on surface properties, in particular, adsorptive, was revealed and at some cases the general observation regularity of the radiation adsorption is upset. So, the hydrogen photo-adsorption is not observed on silicon dioxide and on some other oxides. At the same time hydrogen adsorption takes place at the same oxides irradiation by more power nuclear particles, such as gamma-rays, protons of high energies, alpha-particles, neutrons, high-velocity electrons, and also at a X-ray irradiation. At the same time oxygen adsorption takes place on the majority of the studied oxides. So it is possible to conclude that at the irradiated adsorbents the formation of electronic centers is general regularity. The radiation adsorption of oxygen is well studied on many systems and its regularities are established on numerous experiments. On an example of such oxide systems, as silicon dioxide, oxides of rare-earth elements, beryllium oxide, aluminum oxide, the zeolites we have studied a general regularity of the oxygen and hydrogen radiation adsorption, i.e. their electron-hole properties at irradiation by protons with energy 30 MeV, alpha-particles and ions of helium-3 with energy 40 and 50 MeV, gamma-rays and ultra-violet-radiation, and also neutrons from the nuclear reactor. Parallel with adsorptive properties of oxides their paramagnetic properties and thermal desorption characteristics in a wide range of temperatures were studied. The received data have allowed to find the dependence of paramagnetic centers from adsorptive centers. It was established that the adsorptive centers do not always coincide with paramagnetic ones and vise versa. It was established that the anomalous effects in a radiation adsorption at irradiation of the oxide rare-earth elements on of scandium, lanthanum, erbium and dysprosium oxides are observed. It was found out that radiation adsorption of hydrogen is absent on oxides of a lanthanum, erbium and
Phenomenological Spin Transport Theory Driven by Anomalous Nernst Effect
Taniguchi, Tomohiro
2016-07-01
Several experimental efforts such as material investigation and structure improvement have been made recently to find a large anomalous Nernst effect in ferromagnetic metals. Here, we develop a theory of spin transport driven by the anomalous Nernst effect in a diffusive ferromagnetic/nonmagnetic multilayer. Starting from a phenomenological formula of a spin-dependent electric current, the theoretical formulas of electric voltage and spin torque generated by the anomalous Nernst effect are derived. The magnitude of the electric voltage generated from the spin current via the inverse spin Hall effect is on the order of 0.1 µV for currently available experimental parameter values. The temperature gradient necessary to switch the magnetization is quite larger than the typical experimental value. The separation of the contributions of the Seebeck and transverse spin Seebeck effects is also discussed.
Anomalous Hall effect in YIG|Pt bilayers
We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet|platinum (YIG|Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall effect like voltage in Pt, which is sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing conductance Gi plays a crucial role in YIG|Pt bilayers. In particular, our data suggest a sign change in Gi between 10 K and 300 K. Additionally, we report a higher order Hall effect contribution, which appears in thin Pt films on YIG at low temperatures
Anomalous Hall effect in YIG|Pt bilayers
Meyer, Sibylle, E-mail: sibylle.meyer@wmi.badw.de; Schlitz, Richard [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany); Geprägs, Stephan; Opel, Matthias [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Huebl, Hans; Goennenwein, Sebastian T. B. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Nanosystems Initiative Munich, 80799 München (Germany); Gross, Rudolf [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Physik-Department, Technische Universität München, 85748 Garching (Germany); Nanosystems Initiative Munich, 80799 München (Germany)
2015-03-30
We measure the ordinary and the anomalous Hall effect in a set of yttrium iron garnet|platinum (YIG|Pt) bilayers via magnetization orientation dependent magnetoresistance experiments. Our data show that the presence of the ferrimagnetic insulator YIG leads to an anomalous Hall effect like voltage in Pt, which is sensitive to both Pt thickness and temperature. Interpretation of the experimental findings in terms of the spin Hall anomalous Hall effect indicates that the imaginary part of the spin mixing conductance G{sub i} plays a crucial role in YIG|Pt bilayers. In particular, our data suggest a sign change in G{sub i} between 10 K and 300 K. Additionally, we report a higher order Hall effect contribution, which appears in thin Pt films on YIG at low temperatures.
Conradson, Steven D.; Andersson, David A.; Bagus, Paul S.; Boland, Kevin S.; Bradley, Joseph A.; Byler, Darrin D.; Clark, David L.; Conradson, Dylan R.; Espinosa-Faller, Francisco J.; Lezama Pacheco, Juan S.; Martucci, Mary B.; Nordlund, Dennis; Seidler, Gerald T.; Valdez, James A.
2016-05-01
Hypervalent UO2, UO2(+x) formed by both addition of excess O and photoexcitation, exhibits a number of unusual or often unique properties that point to it hosting a polaronic Bose-Einstein(-Mott) condensate. A more thorough analysis of the O X-ray absorption spectra of UO2, U4O9, and U3O7 shows that the anomalous increase in the width of the spectral features assigned to predominantly U 5f and 6d final states that points to increased dispersion of these bands occurs on the low energy side corresponding to the upper edge of the gap bordered by the conduction or upper Hubbard band. The closing of the gap by 1.5 eV is more than twice as much as predicted by calculations, consistent with the dynamical polaron found by structural measurements. In addition to fostering the excitation that is the proposed mechanism for the coherence, the likely mirroring of this effect on the occupied, valence side of the gap below the Fermi level points to increased complexity of the electronic structure that could be associated with the Fermi topology of BEC-BCS crossover and two band superconductivity.
Non-Fermi-liquid scattering rates and anomalous band dispersion in ferropnictides
Fink, J.; Charnukha, A.; Rienks, E. D. L.; Liu, Z. H.; Thirupathaiah, S.; Avigo, I.; Roth, F.; Jeevan, H. S.; Gegenwart, P.; Roslova, M.; Morozov, I.; Wurmehl, S.; Bovensiepen, U.; Borisenko, S.; Vojta, M.; Büchner, B.
2015-11-01
Angle-resolved photoemission spectroscopy is used to study the band dispersion and the quasiparticle scattering rates in two ferropnictide systems. We find the scattering rate for any given band to depend linearly on energy but to be independent of the control parameter. We demonstrate that the linear energy dependence gives rise to a weakly dispersing band with a strong mass enhancement when the band maximum crosses the chemical potential. The resulting small effective Fermi energy favors a BCS [J. Bardeen et al., Phys. Rev. 108, 1175 (1957), 10.1103/PhysRev.108.1175] -Bose-Einstein [S. N. Bose, Z. Phys. 26, 178 (1924), 10.1007/BF01327326] crossover state in the superconducting phase.
Effects of chemical dispersants on oil physical properties and dispersion
Khelifa, A.; Fingas, M.; Hollebone, B.P.; Brown, C.E. [Environment Canada, Ottawa, ON (Canada). ; Pjontek, D. [Ottawa Univ., ON (Canada). Dept. of Chemical Engineering
2007-07-01
Laboratory and field testing have shown that the dispersion of oil spilled in water is influenced by chemical dispersants via the modification of the interfacial properties of the oil, such as oil-brine interfacial tension (IFT). This study focused on new laboratory experiments that measured the effects on the physical properties and dispersion of oil, with particular reference to the effects of chemical dispersants on IFT and oil viscosity and the subsequent effects on oil droplet formation. Experiments were conducted at 15 degrees C using Arabian Medium, Alaska North Slope and South Louisiana crude and Corexit 9500 and Corexit 9527 chemical dispersants. The dispersants were denser than the 3 oils. The effect of IFT reduction on oil dispersion was measured and showed substantial reduction in the size and enhancement of the concentration of oil droplets in the water column. It was shown that the brine-oil IFT associated with the 3 crudes reduced to less than 3.6 mN/m with the application of the chemical dispersants, even at a low dispersant-to-oil ratio (DOR) value of 1:200. The use of chemical dispersants increased the viscosity of the dispersant-oil mixture up to 40 per cent over the neat crude oil. It was shown that for each mixing condition, an optimum value of DOR exists that provides for maximal dispersant effectiveness. The IFT reaches maximum reduction at optimum DOR. It was suggested that oil spill modelling can be improved with further study of IFT reduction with DOR and variations of critical micelle concentration with the type and solubility of chemical dispersant, oil type and oil to water ratio. 13 refs., 3 tabs., 7 figs.
Quantum Anomalous Hall Effect in Magnetic Insulator Heterostructure
Xu, Gang; Jing WANG; FELSER, CLAUDIA; Qi, Xiao-Liang; Zhang, Shou-Cheng
2014-01-01
Based on ab initio calculations, we predict that a monolayer of Cr-doped (Bi,Sb)2Te3 and GdI2 heterostructure is a quantum anomalous Hall insulator with a non-trivial band gap up to 38 meV. The principle behind our prediction is that the band inversion between two topologically trivial ferromagnetic insulators can result in a non-zero Chern number, which offers a better way to realize the quantum anomalous Hall state without random magnetic doping. In addition, a simple effective model is pre...
Anomalous Hall Effect in a 2D Rashba Ferromagnet.
Ado, I A; Dmitriev, I A; Ostrovsky, P M; Titov, M
2016-07-22
Skew scattering on rare impurity configurations is shown to dominate the anomalous Hall effect in a 2D Rashba ferromagnet. The mechanism originates in scattering on rare impurity pairs separated by distances of the order of the Fermi wavelength. The corresponding theoretical description goes beyond the conventional noncrossing approximation. The mechanism provides the only contribution to the anomalous Hall conductivity in the most relevant metallic regime and strongly modifies previously obtained results for lower energies in the leading order with respect to impurity strength. PMID:27494487
Kordts, Arne; Guo, Hairun; Brasch, Victor; Kippenberg, Tobias J
2015-01-01
High-Q silicon nitride (SiN) microresonators enable optical Kerr frequency comb generation on a photonic chip and have recently been shown to support fully coherent combs based on temporal dissipative Kerr soliton formation. For bright soliton formation it is necessary to operate SiN waveguides in the multimode regime so as to produce anomalous group velocity dispersion. This can lead to local disturbances of the dispersion due to avoided crossings caused by coupling between different mode families, and therefore prevent the soliton formation. Here we demonstrate that a single mode "filtering" section inside high-Q resonators enables to efficiently suppress avoided crossings, while preserving high quality factors (Q~10^6). We demonstrate the approach by single soliton formation in SiN resonators with filtering section.
Kordts, A; Pfeiffer, M H P; Guo, H; Brasch, V; Kippenberg, T J
2016-02-01
High-Q silicon nitride (SiN) microresonators enable optical Kerr frequency comb generation on a photonic chip and have recently been shown to support fully coherent combs based on temporal dissipative Kerr soliton formation. For bright soliton formation, it is necessary to operate SiN waveguides in the multimode regime in order to produce waveguide induced anomalous group velocity dispersion. However, this regime can lead to local disturbances of the dispersion due to avoided crossings caused by coupling between different mode families and, therefore, prevent the soliton formation. Here, we demonstrate that a single-mode "filtering" section inside high-Q resonators enables efficiently suppression of avoided crossings, while preserving high quality factors (Q∼10(6)). We verify the approach by demonstrating single soliton formation in SiN resonators with a filtering section. PMID:26907395
2015-01-01
A method and a pulse compressor (1) for compressing an optical pulse, wherein the pulse compressor comprising a bulk quadratic nonlinear medium (2) adapted for generating a negative nonlinear phase variation on the optical pulse and having a negative group-velocity dispersion, and a dispersive unit...... subsequently be compressed by providing normal dispersion. As KDP crystals can be glued together, large apertures of the pulse compressor are possible making this method suitable for pulse compression in Joule-class lasers....
Anomalous screening in two-dimensional materials with an extremum ring in the dispersion law
Kolomeisky, Eugene B.; Straley, Joseph P.
2016-01-01
A variety of two-dimensional materials possess a band structure with an energy extremal ridge along a ring in momentum space. Examples are biased bilayer graphene, and surfaces and interfaces with a Rashba spin-orbit interaction where at low doping the carriers fill an annulus. This topological feature causes an anomalous screening behavior, which we study using the Thomas-Fermi theory. Specifically, reducing the doping is predicted to enhance the linear screening response, while at zero dopi...
Anomalous Doppler effects in bulk phononic crystal
Doppler effects in simple cubic phononic crystal are studied theoretically and numerically. In addition to observing Doppler shifts from a moving source's frequencies inside the gap, we find that Doppler shifts can be multi-order, anisotropic, and the dominant order of shift depends on the band index that the source's frequency is in.
Effects of Anomalous Propagation Conditions on Weather Radar Observations
Bech, Joan; Magaldi, Adolfo; Codina, Bernat; Lorente, Jeroni
2012-01-01
In this chapter our objective is to provide an overview of the effects of anomalous propagation conditions on weather radar observations, based mostly on studies performed by the authors during the last decade, summarizing results from recent publications, presentations, or unpublished material. We believe this chapter may be useful as an introductory text for graduate students, or researchers and practitioners dealing with this topic. Throughout the text a spherical symmetric atmosphere is a...
Anomalous Hall Effect in Geometrically Frustrated Magnets
D. Boldrin
2012-01-01
space mechanism based on spin chirality that was originally applied to the pyrochlore Nd2Mo2O7 appears unsatisfactory. Recently, an orbital description based on the Aharonov-Bohm effect has been proposed and applied to both the ferromagnetic pyrochlores Nd2Mo2O7 and Pr2Ir2O7; the first of which features long-ranged magnetic order while the latter is a chiral spin liquid. Two further examples of geometrically frustrated conducting magnets are presented in this paper—the kagome-like Fe3Sn2 and the triangular PdCrO2. These possess very different electronic structures to the 3-dimensional heavy-metal pyrochlores and provide new opportunities to explore the different origins of the AHE. This paper summarises the experimental findings in these materials in an attempt to unite the conflicting theoretical arguments.
Effects of surface and interface scattering on anomalous Hall effect in Co/Pd multilayers
Guo, Z. B.
2012-09-27
In this paper, we report the results of surface and interface scattering on anomalous Hall effect in Co/Pd multilayers with perpendicular magnetic anisotropy. The surface scattering effect has been extracted from the total anomalous Hall effect. By scaling surface scattering contribution with ρAHs∼ργss, the exponent γ has been found to decrease with the increase of surface scattering resistivity, which could account for the thickness-dependent anomalous Hall effect. Interface diffusion induced by rapid thermal annealing modifies not only the magnetization and longitudinal resistivity but also the anomalous Hall effect; a large exponent γ ∼ 5.7 has been attributed to interface scattering-dominated anomalous Hall effect.
Quantum anomalous Hall effect in magnetic topological insulators
Jing WANG; Lian, Biao; Zhang, Shou-Cheng
2014-01-01
The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimension (2D) and three-dimension (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magn...
Quantized Anomalous Hall Effect in Magnetic Topological Insulators
YU Rui
2011-01-01
The Hall effect, the anomalous Hall effect （AHE） and the spin Hall effect are thndamental transport processes in solids arising from the Lorentz force and the spin-orbit coupling respectively. The AHE, in which a voltage transverse to the electric current appears even in the absence of an external magnetic field, was first detected in ferromagnetic （FM） metals in 1881 and later found to arise from the spin-orbit coupling （SOC） between the current and magnetic moments.
Chekalin, S V; Kompanets, V O [Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow (Russian Federation); Smetanina, E O; Spirkov, A I; Kandidov, V P [Department of Physics, M.V. Lomonosov Moscow State University (Russian Federation)
2014-06-30
We have investigated experimentally and numerically the influence of the initial temporal phase modulation of a pulse on the spatiotemporal intensity distribution and the frequency-angular spectrum of femtosecond laser pulses with self-channelling in a condensed medium. We have detected a decrease in the intensity of divergent anti-Stokes frequency components during filamentation of radiation under conditions of normal group-velocity dispersion (GVD) and strong phase modulation. In the zero-GVD regime under conditions of the phase modulation of radiation, the spatiotemporal transformation of the pulse is similar to that in the normal-GVD regime, which leads to a qualitative change in the supercontinuum spectrum. In the anomalous-GVD regime, a sequence of 'light bullets' is formed in the filament for both a phase-modulated and a transform-limited pulse. (extreme light fields and their applications)
SHU Wei-Xing; LUO Hai-Lu; LI Fei; REN Zhong-Zhou
2006-01-01
@@ We investigate the propagation of electromagnetic waves at the interface between an isotropic material and the anisotropic medium with a unique dispersion relation. We show that the refraction behaviour of E-polarized waves is opposite to that of H-polarized waves, though the dispersion relations for E- and H-polarized waves are the same. It is found that waves exhibit different propagation properties in anisotropic media with different sign combinations of the permittivity and permeability tensors. Some interesting properties of propagation are also found in the special anisotropic media, leading to potential applications.
Anomalous Hall Effect in a Feromagnetic Rare-Earth Cobalite
Samoilov, A. V.; Yeh, N. C.; Vasquez, R. P.
1996-01-01
Rare-Earth manganites and cobalites with the perovskite structure have been a subject of great recent interest because their electrical resistance changes significantly when a magnetic field is applied...we have studied the Hall effect in thin film La(sub 0.5)Ca(sub 0.5)CoO(sub 3) material and have obtained convincing evidence fo the so called anomalous Hall effect, typical for magnetic metals...Our results suggest that near the ferromagnetic ordering temperature, the dominant electron scattering mechanism is the spin fluctuation.
Structure determination by multiple-wavelength anomalous dispersion (MAD) at the Pr LIII edge
A successful MAD experiment has been conducted at the Pr LIII edge on HZB beamline BL14.2. The use of longer X-ray wavelengths in macromolecular crystallography has grown significantly over the past few years. The main reason for this increased use of longer wavelengths has been to utilize the anomalous signal from sulfur, providing a means for the experimental phasing of native proteins. Here, another possible application of longer X-ray wavelengths is presented: MAD at the LIII edges of various lanthanide compounds. A first experiment at the LIII edge of Pr was conducted on HZB MX beamline BL14.2 and resulted in the successful structure determination of the C-terminal domain of a spliceosomal protein. This experiment demonstrates that LIII edges of lanthanides constitute potentially attractive targets for long-wavelength MAD experiments
Elastic scattering cross-sections for Pd, Ag, Cd, In, Sn, Sb, Pt, Au and Pb are measured at an angle of 90 circle in the X-ray region 5.41≤E≤8.04 keV. These energies fall between the high-energy side of the L- and M-shell absorption edges of the atoms considered. The present atomic region is significant for solid X-rays to assess the contribution of resonance and solid-state environmental effects. Also it is the anomalous scattering region for many of the atoms of the periodic table. Experimental results are compared with theoretical calculations based on form factor formalisms including the anomalous corrections and available recent S-matrix values. Based on the experimental evidence, the present results indicate the influence of solid-state environmental effects, the importance of anomalous corrections nearer to absorption edges, the correctness of revised high-energy limit values, the superiority of S-matrix predictions over form factor values on measured elastic scattering cross-sections in the X-ray regime and also show the resonance behavior around K,L and M absorption edges. (orig.)
Quantized Anomalous Hall Effect in Magnetic Topological Insulators
YU Rui
2011-01-01
@@ The Hall effect, the anomalous Hall effect (AHE) and the spin Hall effect are fundamental transport processes in solids arising from the Lorentz force and the spin-orbit coupling respectively.The AHE, in which a voltage transverse to the electric current appears even in the absence of an external magnetic field, was first detected in ferromagnetic (FM) metals in 1881 and later found to arise from the spin-orbit coupling (SOC) between the current and magnetic moments.Recent progress on the mechanism of AHE has established a link between the AHE and the topological nature of the Hall current by adopting the Berry-phase concepts in close analogy to the intrinsic spin Hall effect.Given the experimental discovery of the quantum Hall and the quantum spin Hall effects, it is natural to ask whether the AHE can also be quantized.In a quantized anomalous Hall (QAH) insulator, spontaneous magnetic moments and spin-orbit coupling combine to give rise to a topologically non-trivial electronic structure, leading to the quantized Hall effect without any external magnetic field.
Urbanization effects on natural radiation in anomalous areas
The urbanization effects and their possible causes on the environmental gamma radiation levels, in an anomalous area, were studied. The field work was accomplished in Guarapari, located in the seacoast of the Brazilian state of Espirito Santo, which is rich in monazite sands, with thorium and uranium contents. The results show clearly that there was a reduction in the levels of external exposition in the streets and squares of Guarapari. It was ascertained that the reduction was due to the materials used in the urbanization. (L.C.J.A.)
Quantum anomalous Hall effect in topological insulator memory
Jalil, Mansoor B. A., E-mail: elembaj@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); Tan, S. G. [Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117576 (Singapore); Siu, Z. B. [Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore (Singapore)
2015-05-07
We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σ{sup xy} of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σ{sup xy} and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σ{sup xy} as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs.
Quantum anomalous Hall effect in topological insulator memory
We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σxy of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σxy and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σxy as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs
Pawlus, Sebastian; Paluch, Marian; Ziolo, Jerzy [Institute of Physics, University of Silesia, Uniwersytecka 4, Katowice 40-007 (Poland); Kolel-Veetil, Manoj K [Chemistry Division, Code 6127, Naval Research Laboratory, Washington, DC 20375-5342 (United States)
2010-10-20
Broadband dielectric spectroscopic investigations of a vinyl-terminated carboranylenesiloxane, VCS, were performed at ambient and elevated pressures. At a constant structural relaxation time, results show that the structural relaxation dispersion function of VCS narrows with both increasing pressure and temperature. This narrowing is substantial in the case of pressurization and, consequently, the breakdown of the temperature-pressure superposition rule is observed. The interpretation of this breakdown is presented.
Anomalous Hall effect in Fe/Au multilayers
Zhang, Q.
2016-07-22
To understand the interfacial scattering effect on the anomalous Hall effect (AHE), we prepared multilayers of (Fe(36/n)nm/Au(12/n)nm)n using an e-beam evaporator. This structure design allowed us to investigate the effect of interfacial scattering on the AHE, while keeping the samples\\' thickness and composition unchanged. We measured the (magneto)transport properties of the samples in a wide temperature range (10–310 K) with magnetic fields up to 50 kOe. We found that the scaling between the anomalous Hall resistivity (ρAHE) and longitudinal resistivity (ρxx) can be roughly described by ρAHE∼ργxx with γ=2.65±0.10 and 1.90 ± 0.04 for samples from n=1 to n=4 and samples from n=4 to n=12, respectively. Our quantitative analysis results showed that the interfacial scattering suppresses the contribution of the intrinsic mechanism and gives rise to a side-jump contribution.
Nonlinear dynamics induced anomalous Hall effect in topological insulators
Wang, Guanglei; Xu, Hongya; Lai, Ying-Cheng
2016-01-01
We uncover an alternative mechanism for anomalous Hall effect. In particular, we investigate the magnetisation dynamics of an insulating ferromagnet (FM) deposited on the surface of a three-dimensional topological insulator (TI), subject to an external voltage. The spin-polarised current on the TI surface induces a spin-transfer torque on the magnetisation of the top FM while its dynamics can change the transmission probability of the surface electrons through the exchange coupling and hence the current. We find a host of nonlinear dynamical behaviors including multistability, chaos, and phase synchronisation. Strikingly, a dynamics mediated Hall-like current can arise, which exhibits a nontrivial dependence on the channel conductance. We develop a physical understanding of the mechanism that leads to the anomalous Hall effect. The nonlinear dynamical origin of the effect stipulates that a rich variety of final states exist, implying that the associated Hall current can be controlled to yield desirable behaviors. The phenomenon can find applications in Dirac-material based spintronics.
Correlations and anomalous transport effects related to stochastic instability
In this paper, we analyse turbulent transport in the framework of the correlation approach to obtain the effective diffusion coefficient and characteristic increment in the scaling form. Such factors as anisotropy, seed diffusion mechanisms and reconstruction of flow topology significantly have an impact on the effective diffusivity. We consider the different aspects of stochastic instability such as the decorrelation mechanism to estimate characteristic correlation times and correlation scales in the framework of the scaling approach. The topics to be discussed include the Rechester-Rosenbluth correlation scalings, percolation transport in time dependent flows, anisotropic MHD spectra and a multi-scale approach to the analysis of anomalous transport. To treat long-range correlation effects, the percolation renormalization is analysed in time-dependent regimes. In the framework of the multiscale approach, a scaling for an increment of the stochastic instability in two-dimensional random flow is suggested
Correlations and anomalous transport effects related to stochastic instability
Bakunin, O G [Department of Physics and Astronomy, University of Kansas, Malott Hall, 1251 Wescoe Hall Drive, Lawrence, KS 66044 (United States); Nuclear Fusion Institute, RRC ' Kurchatov Institute' , pl. Kurchatova 1, Moscow, 123182 (Russian Federation); FOM Instituut voor Plasmafysica ' Rijnhuizen' , Associate Euroatom-FOM, 3430 BE Nieuwegein (Netherlands)
2005-11-15
In this paper, we analyse turbulent transport in the framework of the correlation approach to obtain the effective diffusion coefficient and characteristic increment in the scaling form. Such factors as anisotropy, seed diffusion mechanisms and reconstruction of flow topology significantly have an impact on the effective diffusivity. We consider the different aspects of stochastic instability such as the decorrelation mechanism to estimate characteristic correlation times and correlation scales in the framework of the scaling approach. The topics to be discussed include the Rechester-Rosenbluth correlation scalings, percolation transport in time dependent flows, anisotropic MHD spectra and a multi-scale approach to the analysis of anomalous transport. To treat long-range correlation effects, the percolation renormalization is analysed in time-dependent regimes. In the framework of the multiscale approach, a scaling for an increment of the stochastic instability in two-dimensional random flow is suggested.
Anomalous Skin Effect for Anisotropic Electron Velocity Distribution Function
Igor Kaganovich; Edward Startsev; Gennady Shvets
2004-02-19
The anomalous skin effect in a plasma with a highly anisotropic electron velocity distribution function (EVDF) is very different from skin effect in a plasma with the isotropic EVDF. An analytical solution was derived for the electric field penetrated into plasma with the EVDF described as a Maxwellian with two temperatures Tx >> Tz, where x is the direction along the plasma boundary and z is the direction perpendicular to the plasma boundary. The skin layer was found to consist of two distinctive regions of width of order nTx/w and nTz/w, where nTx,z/w = (Tx,z/m)1/2 is the thermal electron velocity and w is the incident wave frequency.
Precise quantization of anomalous Hall effect near zero magnetic field
Bestwick, A. J. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Fox, E. J. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Kou, Xufeng [Univ. of California, Los Angeles, CA (United States); Pan, Lei [Univ. of California, Los Angeles, CA (United States); Wang, Kang L. [Univ. of California, Los Angeles, CA (United States); Goldhaber-Gordon, D. [Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
2015-05-04
In this study, we report a nearly ideal quantum anomalous Hall effect in a three-dimensional topological insulator thin film with ferromagnetic doping. Near zero applied magnetic field we measure exact quantization in the Hall resistance to within a part per 10,000 and a longitudinal resistivity under 1 Ω per square, with chiral edge transport explicitly confirmed by nonlocal measurements. Deviations from this behavior are found to be caused by thermally activated carriers, as indicated by an Arrhenius law temperature dependence. Using the deviations as a thermometer, we demonstrate an unexpected magnetocaloric effect and use it to reach near-perfect quantization by cooling the sample below the dilution refrigerator base temperature in a process approximating adiabatic demagnetization refrigeration.
Anomalous transport effects in magnetically-confined plasma columns
The evolution of density structure in a magnetized plasma column is analyzed accounting for anomalous diffusion due to the lower hybrid drift instability. The plasma column is found to be divided into regions of classical, anomalous, and intermediate diffusivity. The bulk behavior, described in terms of radial confinement time, depends most sensitively upon the particle line density (ion/cm). For broad plasmas (large line density), the transport is characteristic of classical diffusion, and for slender plasmas (small line density) the transport is characteristic of anomalous diffusion. For intermediate line densities, the transport undertakes a rapid transition from classical to anomalous. Correlations between the theoretical results and past experiments are described
Dispersant effectiveness in a simulated shallow embayment
Page, C.; Bonner, J.; Fuller, C. [Texas A and M Univ., Corpus Christi, TX (United States); Sterling, M. [Texas A and M Univ., College Station, TX (United States)
2002-07-01
An experiment was conducted in a wave tank at Corpus Christi, Texas to test the effectiveness of a dispersant in treating an oil spill. Dispersants can be used as a chemical countermeasure to disperse accidentally spilled oil into the water column. In the United States, however, dispersants are not pre-approved for near-shore applications. Therefore, if an oil spill occurs in shallow marine waters response teams cannot use dispersants right away and the chances for the oil to move onto shore is increased. The use of dispersants in coastal marine ecosystems is approached with caution because the first generation of dispersants were highly toxic. New formulations, however, are considered to be more effective and substantially less toxic. The tank in this study simulated a shallow embayment with wave conditions similar to those in Corpus Christi Bay. A known volume of weathered Arabian medium crude oil was intentionally spilled onto the water surface and the dispersant Corexit 9500 manufactured by Nalco/Exxon was applied in aerosol form at a dispersion to oil ratio of 1:10. A mass balance on the oil was performed to quantify the effectiveness of the dispersant. The compartments for oil accumulation were the water column, the water surface and the tank walls. Gas chromatography-mass spectrometry was used to analyze the samples. After 4 hours, more than two-thirds of the oil was found in the water column, suggesting the dispersant was effective in dispersing the crude oil under wave energy conditions. After 24 hours, much of the oil had resurfaced. A lab scale version of the same experiment showed similar results. 15 refs., 6 figs.
Dispersant effectiveness in a simulated shallow embayment
An experiment was conducted in a wave tank at Corpus Christi, Texas to test the effectiveness of a dispersant in treating an oil spill. Dispersants can be used as a chemical countermeasure to disperse accidentally spilled oil into the water column. In the United States, however, dispersants are not pre-approved for near-shore applications. Therefore, if an oil spill occurs in shallow marine waters response teams cannot use dispersants right away and the chances for the oil to move onto shore is increased. The use of dispersants in coastal marine ecosystems is approached with caution because the first generation of dispersants were highly toxic. New formulations, however, are considered to be more effective and substantially less toxic. The tank in this study simulated a shallow embayment with wave conditions similar to those in Corpus Christi Bay. A known volume of weathered Arabian medium crude oil was intentionally spilled onto the water surface and the dispersant Corexit 9500 manufactured by Nalco/Exxon was applied in aerosol form at a dispersion to oil ratio of 1:10. A mass balance on the oil was performed to quantify the effectiveness of the dispersant. The compartments for oil accumulation were the water column, the water surface and the tank walls. Gas chromatography-mass spectrometry was used to analyze the samples. After 4 hours, more than two-thirds of the oil was found in the water column, suggesting the dispersant was effective in dispersing the crude oil under wave energy conditions. After 24 hours, much of the oil had resurfaced. A lab scale version of the same experiment showed similar results. 15 refs., 6 figs
Dispersant effectiveness: Studies into the causes of effectiveness variations
Effectiveness, a key issue of using dispersants, is affected by many interrelated factors. The principal factors involved are the oil composition, dispersant formulation, sea surface turbulence and dispersant quantity. Oil composition is a very strong determinant. Current dispersant formulation effectiveness correlates strongly with the amount of saturate component in the oil. The other components of the oil, the asphaltenes, resins or polars and aromatic fractions show a negative correlation with the dispersant effectiveness. Viscosity is also a predictor of dispersant effectiveness and may have an effect because it is in turn determined by oil composition. Dispersant composition is significant and interacts with oil composition. Dispersants show high effectiveness at HLB values near 10. Sea turbulence strongly affects dispersant effectiveness.Effectiveness rises with increasing turbulence to a maximum value. Effectiveness for current commercial dispersants is gaussian around a peak salinity value. Peak effectiveness is achieved at very high dispersant quantities--at a ratio of 1:5, dispersant-to-oil volume. Dispersant effectiveness for those oils tested and under the conditions measured, is approximately logarithmic with dispersant quantity and will reach about 50% of its peak value at a dispersant to oil ratio of about 1:20 and near zero at a ratio of about 1:50
Anomalous Nernst Effect of Perpendicularly Magnetic Anisotropy TbFeCo Thin Films
Ando, Ryo; Komine, Takashi; Hasegawa, Yasuhiro
2016-07-01
In this study, we investigated anomalous Nernst effect (ANE) of perpendicularly magnetized TbFeCo thin films with various Tb content, and especially studied the relation between ANE and anomalous Hall effect. As a result, the hysteresis of anomalous Nernst coefficient showed the same behavior as that of anomalous Hall resistivity, and the sign of anomalous Nernst coefficient was consistent with that of anomalous Hall voltage in any Tb content, whereas the Seebeck coefficient and the resistivity were almost constant even if the applied magnetic field was varied. Taking into account of thermoelectric coefficient tensor, it was revealed that the off-diagonal thermopower corresponding to the ANE in TbFeCo thin films is the product of Hall angle and Seebeck coefficient.
Effectiveness of dispersants on thick oil slicks
Experiments were conducted to determine the relationship between dispersant effectiveness and oil slick thickness, and thereby determine the optimum time for applying dispersant onto spilled oil at sea. Tests were completed at a lab-scale level by varying the three parameters of oil type, dispersant application, and oil thickness. The tests were intended to be comparative only. The primary oils used were Alberta sweet mix blend and Hibernia B-27 crude. The dispersant, Corexit 9527, was applied either premixed with the oil, dropwise in one application, or dropwise in multiple applications to simulate a multi-hit aircraft operation. The apparatus used in the experiment was an oscillating hoop tank, with oil-containing rings used to obtain and maintain uniform slick thickness. The results indicate that the effectiveness potential of a chemical dispersant does not decrease as slick thickness increases. In fact, results of the tests involving Hibernia oil suggest that oils that tend to herd easily would be treated more effectively if dispersant were applied when the oil was relatively thick (1 mm or greater) to avoid herding problems. The oil slicks premixed with dispersant did not disperse well in the thick oil tests, not because of dispersant-oil interaction problems but because of reduced mixing energy. 6 refs., 4 figs., 1 tab
Quantum anomalous Hall effect in atomic crystal layers from in-plane magnetization
Ren, Yafei; Zeng, Junjie; Deng, Xinzhou; Yang, Fei; Pan, Hui; Qiao, Zhenhua
2016-08-01
We theoretically demonstrate that with in-plane magnetization, the quantum anomalous Hall effect (QAHE) can be realized in two-dimensional atomic crystal layers with preserved inversion symmetry but broken out-of-plane mirror reflection symmetry. By taking the honeycomb lattice system as an example, we find that the low-buckled structure satisfying the symmetry criteria is crucial to induce QAHE. The topologically nontrivial bulk gap carrying a Chern number of C =±1 opens in the vicinity of the saddle points M , where the band dispersion exhibits strong anisotropy. We further show that the QAHE with electrically tunable Chern number can be achieved in Bernal-stacked multilayer systems, and the applied interlayer potential differences can dramatically decrease the critical magnetization to make the QAHE experimentally feasible.
Employment Effects of Spatial Dispersal of Refugees
Damm, Anna Piil; Rosholm, Michael
We argue that spatial dispersal influences labour market assimilation of refugees through two mechanisms: first, the local job offer arrival rate and, second, place utility. Our partial search model with simultaneous job and residential location search predicts that the reservation wage for local...... evaluating the employment effects of the Danish spatial dispersal policy carried out 1986-1998....
Quantum anomalous Hall effect in magnetic topological insulators
Wang, Jing; Lian, Biao; Zhang, Shou-Cheng
2015-12-01
The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimensions (2D) and three-dimensions (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magnetic order opens up a gap for the topological surface states, and chiral edge state has been predicted to exist on the magnetic domain walls. We present the phase diagram in thin films of a magnetic topological insulator and review the basic mechanism of ferromagnetic order in magnetically doped topological insulators. We also review the recent experimental observation of the QAH effect. We discuss more recent theoretical work on the coexistence of the helical and chiral edge states, multi-channel chiral edge states, the theory of the plateau transition, and the thickness dependence in the QAH effect.
Origin of anomalous inverse notch effect in bulk metallic glasses
Pan, J.; Zhou, H. F.; Wang, Z. T.; Li, Y.; Gao, H. J.
2015-11-01
Understanding notch-related failure is crucial for the design of reliable engineering structures. However, substantial controversies exist in the literature on the notch effect in bulk metallic glasses (BMGs), and the underlying physical mechanism responsible for the apparent confusion is still poorly understood. Here we investigate the physical origin of an inverse notch effect in a Zr-based metallic glass, where the tensile strength of the material is dramatically enhanced, rather than decreased (as expected from the stress concentration point of view), by introduction of a notch. Our experiments and molecular dynamics simulations show that the seemingly anomalous inverse notch effect is in fact caused by a transition in failure mechanism from shear banding at the notch tip to cavitation and void coalescence. Based on our theoretical analysis, the transition occurs as the stress triaxiality in the notched sample exceeds a material-dependent threshold value. Our results fill the gap in the current understanding of BMG strength and failure mechanism by resolving the conflicts on notch effects and may inspire re-interpretation of previous reports on BMG fracture toughness where pre-existing notches were routinely adopted.
Effect of anomalous resistivity on the dynamics of plasma switching
Some of the conditions for electron MHD are recollected, and it is shown how this leads to anomalous resistivity which may play an important role in the dynamics of POS. It has been shown that not only the order of value of the resistance of the plasma-filled diode but rather basic scalings have to be changed in the regime of essential anomalous resistivity. (author). 11 refs
Transverse Fresnel-Fizeau drag effects in strongly dispersive media
A light beam normally incident upon an uniformly moving dielectric medium is, in general, subject to bendings due to a transverse Fresnel-Fizeau light drag effect. In most familiar dielectrics, the magnitude of this bending effect is very small and hard to detect. Yet, the effect can be dramatically enhanced in strongly dispersive media where slow group velocities in the m/s range have been recently observed taking advantage of the electromagnetically induced transparency effect. In addition to the usual downstream drag that takes place for positive group velocities, we discuss a significant anomalous upstream drag which is expected to occur for negative group velocities. Furthermore, for sufficiently fast speeds of the medium, higher-order dispersion terms are found to play an important role and to be responsible for light propagation along curved paths or the restoration of the time and space coherence of an incident noisy beam. The physics underlying this class of slow-light effects is thoroughly discussed
Review of monitoring protocols for dispersant effectiveness
Dispersant applications to an oil spill were monitored to determine their effectiveness. Current protocols consist of some visual criteria or a surface monitoring program using in-situ fluorometers to gauge the relative effectiveness of dispersant application. However, this study shows that there are many false positives and false negatives with these monitoring techniques. The problem can be addressed to some degree, by paying attention to the science and technology. The current published methods such as SMART and the SERVS protocols do not necessarily assure that effectiveness is accurately gauged. It was also argued that current protocols are very limited by basic physical and chemical problems, and therefore can only supply estimates as to the effectiveness of dispersant application. It was recommended that a screening test of the dispersant effectiveness be conducted before any test application of dispersants. The test should indicate a dispersion of approximately one-half of the oil. It was also suggested that since visual methods are the the main monitoring method, more work is needed to produce visual monitoring guidelines and visual aids. It was also suggested that monitoring of oil concentrations in the water column would provide valuable scientific information. 52 refs., 2 tabs., 5 figs
文双春; 范滇元
2002-01-01
Spatiotemporal instability in nonlinear dispersive media is investigated on the basis of the nonlinear envelope equation. A general expression for instability gain which includes the effects of space-time focusing, arbitrarily higher-order dispersions and self-steepening is obtained. It is found that, for both normal and anomalous group-velocity dispersions, space-time focusing may lead to the appearance of new instability regions and influence the original instability gain spectra mainly by shrinking their regions. The region of the original instability gain spectrum shrinks much more in normal dispersion case than in anomalous one. In the former case, space-time focusing completely suppresses the growing of higher frequency components. In addition, we find that all the oddth-order dispersions contribute none to instability, while all the eventh-order dispersions influence instability region and do not influence the maximum instability gain, therein the fourth-order dispersion plays the same role as space-time focusing in spatiotemporal instability. The main role played by self-steepening in spatiotemporal instability is that it reduces the instability gain and exerts much more significant influence on the new instability regions resulting from space-time focusing.
Chang, CuiZu; Liu, MinHao; Zhang, ZuoCheng; Wang, YaYu; He, Ke; Xue, QiKun
2016-03-01
High quality chromium (Cr) doped three-dimensional topological insulator (TI) Sb2Te3 films are grown via molecular beam epitaxy on heat-treated insulating SrTiO3 (111) substrates. We report that the Dirac surface states are insensitive to Cr doping, and a perfect robust long-range ferromagnetic order is unveiled in epitaxial Sb2- x Cr x Te3 films. The anomalous Hall effect is modulated by applying a bottom gate, contrary to the ferromagnetism in conventional diluted magnetic semiconductors (DMSs), here the coercivity field is not significantly changed with decreasing carrier density. Carrier-independent ferromagnetism heralds Sb2- x Cr x Te3 films as the base candidate TI material to realize the quantum anomalous Hall (QAH) effect. These results also indicate the potential of controlling anomalous Hall voltage in future TI-based magneto-electronics and spintronics.
Semaan, Georges; Ben Braham, Fatma; Salhi, Mohamed; Meng, Yichang; Bahloul, Faouzi; Sanchez, François
2016-04-18
We have experimentally demonstrated square pulses emission from a co-doped Er:Yb double-clad fiber laser operating in anomalous dispersion DSR regime using the nonlinear polarization evolution technique. Stable mode-locked pulses have a repetition rate of 373 kHz with 2.27 µJ energy per pulse under a pumping power of 30 W in cavity. With the increase of pump power, both the duration and the energy of the output square pulses broaden. The experimental results demonstrate that the passively mode-locked fiber laser operating in the anomalous regime can also realize a high-energy pulse, which is different from the conventional low-energy soliton pulse. PMID:27137277
Carrier-independent ferromagnetism and giant anomalous Hall effect in magnetic topological insulator
Chang, Cui-Zu; Zhang, Jin-song; Liu, Min-Hao; Zhang, Zuo-Cheng; Feng, Xiao; Li, Kang; Wang, Li-Li; Chen, Xi; Dai, Xi; Fang, Zhong; Qi, Xiao-Liang; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Ma, Xu-Cun
2011-01-01
Breaking the time-reversal symmetry of a topological insulator (TI) by ferromagnetism can induce exotic magnetoelectric phenomena such as quantized anomalous Hall (QAH) effect. Experimental observation of QAH effect in a magnetically doped TI requires ferromagnetism not relying on the charge carriers. We have realized the ferromagnetism independent of both polarity and density of carriers in Cr-doped BixSb2-xTe3 thin films grown by molecular beam epitaxy. Meanwhile, the anomalous Hall effect ...
Localization correction to the anomalous Hall effect in amorphous CoFeB thin films
丁进军; 吴少兵; 杨晓非; 朱涛
2015-01-01
An obvious weak localization correction to anomalous Hall conductance (AHC) in very thin CoFeB film is reported. We find that both the weak localization to AHC and the mechanism of anomalous Hall effect are related to the CoFeB thickness. When the film is thicker than 3 nm, the side jump mechanism dominates and the weak localization to AHC vanishes. For very thin CoFeB films, both the side jump and skew scattering mechanisms contribute to the anomalous Hall effect, and the weak localization correction to AHC is observed.
Magnetic Topological Insulators and Quantum Anomalous Hall Effect
Kou, Xufeng
The engineering of topological surface states is a key to realize applicable devices based on topological insulators (TIs). Among various proposals, introducing magnetic impurities into TIs has been proven to be an effective way to open a surface gap and integrate additional ferromagnetism with the original topological order. In this Dissertation, we study both the intrinsic electrical and magnetic properties of the magnetic TI thin films grown by molecular beam epitaxy. By doping transition element Cr into the host tetradymite-type V-VI semiconductors, we achieve robust ferromagnetic order with a strong perpendicular magnetic anisotropy. With additional top-gating capability, we realize the electric-field-controlled ferromagnetism in the magnetic TI systems, and demonstrate such magneto-electric effects can be effectively manipulated, depending on the interplays between the band topology, magnetic exchange coupling, and structural engineering. Most significantly, we report the observation of quantum anomalous Hall effect (QAHE) in the Cr-doped (BiSb)2Te3 samples where dissipationless chiral edge conduction is realized in the macroscopic millimeter-size devices without the presence of any external magnetic field, and the stability of the quantized Hall conductance of e2/h is well-maintained as the film thickness varies across the 2D hybridization limit. With additional quantum confinement, we discover the metal-to-insulator switching between two opposite QAHE states, and reveal the universal QAHE phase diagram in the thin magnetic TI samples. In addition to the uniform magnetic TIs, we further investigate the TI/Cr-doped TI bilayer structures prepared by the modulation-doped growth method. By controlling the magnetic interaction profile, we observe the Dirac hole-mediated ferromagnetism and develop an effective way to manipulate its strength. Besides, the giant spin-orbit torque in such magnetic TI-based heterostructures enables us to demonstrate the current
Thickness Dependence of the Quantum Anomalous Hall Effect in Magnetic Topological Insulator Films.
Feng, Xiao; Feng, Yang; Wang, Jing; Ou, Yunbo; Hao, Zhenqi; Liu, Chang; Zhang, Zuocheng; Zhang, Liguo; Lin, Chaojing; Liao, Jian; Li, Yongqing; Wang, Li-Li; Ji, Shuai-Hua; Chen, Xi; Ma, Xucun; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Xue, Qi-Kun
2016-08-01
The evolution of the quantum anomalous Hall effect with the thickness of Cr-doped (Bi,Sb)2 Te3 magnetic topological insulator films is studied, revealing how the effect is caused by the interplay of the surface states, band-bending, and ferromagnetic exchange energy. Homogeneity in ferromagnetism is found to be the key to high-temperature quantum anomalous Hall material. PMID:27166762
Anomalous effects due to the inertial anti-gravitational potential of the sun
Khokhlov, D. L.
2007-01-01
It is introduced inertial anti-gravitational potential into the theory of gravity to stop gravitational collapse at the nuclear density and thus prevent singularities. It is considered effective gravity which includes Newtonian potential and inertial anti-gravitational potential. It is investigated footprints of the effective gravity in the solar system. The inertial anti-gravitational potential of the sun allows to explain the anomalous acceleration of Pioneer 10 and 11, the anomalous increa...
Effect of entropy on anomalous transport in electron-temperature-gradient-modes
Yaqub Khan, M., E-mail: myaqubsultani@gmail.com [Department of Basic Sciences, Riphah International University, Islamabad 44000 (Pakistan); National Centre for Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Iqbal, J. [Department of Mathematics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Ul Haq, A. [Faculty of Engineering and Applied Physics, Riphah International University, Islamabad 44000 (Pakistan)
2014-05-15
Due to the interconnection of entropy with temperature and density of plasma, it would be interesting to investigate plasma related phenomena with respect to entropy. By employing Braginskii transport equations, it is proved that entropy is proportional to a function of potential and distribution function of entropy is re-defined, ∇S–drift in obtained. New dispersion relation is derived; it is found that the anomalous transport depends on the gradient of the entropy.
Anomalous Hall effect on the surface of topological Kondo insulators
König, E. J.; Ostrovsky, P. M.; Dzero, M.; Levchenko, A.
2016-07-01
We calculate the anomalous Hall conductivity σx y of the surface states in cubic topological Kondo insulators. We consider a generic model for the surface states with three Dirac cones on the (001) surface. The Fermi velocity, the Fermi momentum, and the Zeeman energy in different Dirac pockets may be unequal. The microscopic impurity potential mediates mixed intra- and interband extrinsic scattering processes. Our calculation of σx y is based on the Kubo-Streda diagrammatic approach. It includes diffractive skew scattering contributions originating from the rare two-impurity complexes. Remarkably, these contributions yield anomalous Hall conductivity that is independent of impurity concentration, and thus is of the same order as other known extrinsic side jump and skew scattering terms. We discuss various special cases of our results and the experimental relevance of our study in the context of the recent hysteretic magnetotransport data in SmB6 samples.
Anomalous $tqZ$ coupling effects in rare B- and K-meson decays
Li, Xin-Qiang; Yuan, Xing-Bo
2011-01-01
As a top-factory, the LHC is performing a direct study of top-quark anomalous FCNC couplings, which are, however, correlated closely with the rare B- and K-meson decays. In this paper, we study the effects of anomalous $tqZ$ (with $q=u,c$) couplings in the rare decays $B_{s,d}\\to \\mu^+\\mu^-$, $B\\to X_s \
Theory of the anomalous Hall effect from the Kubo formula and the Dirac equation
Crépieux, A.; Bruno, P
2001-01-01
A model to treat the anomalous Hall effect is developed. Based on the Kubo formalism and on the Dirac equation, this model allows the simultaneous calculation of the skew-scattering and side-jump contributions to the anomalous Hall conductivity. The continuity and the consistency with the weak-relativistic limit described by the Pauli Hamiltonian is shown. For both approaches, Dirac and Pauli, the Feynman diagrams, which lead to the skew-scattering and the side-jump contributions, are underli...
Guo, Zaibing
2015-05-01
The effect of interfacial intermixing on magnetization and anomalous Hall effect (AHE) in Co/Pd multilayers is studied by using rapid thermal annealing to enhance the interfacial diffusion. The dependence of saturation magnetization and coercivity on the temperature of rapid thermal annealing at 5 K is discussed. It is found that AHE is closely related to the relative thickness of the Co and Pd layers. Localized paramagnetism has been observed which destroys AHE, while AHE can be enhanced by annealing.
Lu, Y. M.
2013-03-05
Scaling of the anomalous Hall conductivity to longitudinal conductivity σAH∝σ2xx has been observed in the dirty regime of two-dimensional weak and strong localization regions in ultrathin, polycrystalline, chemically disordered, ferromagnetic FePt films. The relationship between electron transport and temperature reveals a quantitatively insignificant Coulomb interaction in these films, while the temperature dependent anomalous Hall conductivity experiences quantum correction from electron localization. At the onset of this correction, the low-temperature anomalous Hall resistivity begins to be saturated when the thickness of the FePt film is reduced, and the corresponding Hall conductivity scaling exponent becomes 2, which is above the recent unified theory of 1.6 (σAH∝σ1.6xx). Our results strongly suggest that the correction of the electron localization modulates the scaling exponent of the anomalous Hall effect.
Large anomalous Hall effect in a non-collinear antiferromagnet at room temperature.
Nakatsuji, Satoru; Kiyohara, Naoki; Higo, Tomoya
2015-11-12
In ferromagnetic conductors, an electric current may induce a transverse voltage drop in zero applied magnetic field: this anomalous Hall effect is observed to be proportional to magnetization, and thus is not usually seen in antiferromagnets in zero field. Recent developments in theory and experiment have provided a framework for understanding the anomalous Hall effect using Berry-phase concepts, and this perspective has led to predictions that, under certain conditions, a large anomalous Hall effect may appear in spin liquids and antiferromagnets without net spin magnetization. Although such a spontaneous Hall effect has now been observed in a spin liquid state, a zero-field anomalous Hall effect has hitherto not been reported for antiferromagnets. Here we report empirical evidence for a large anomalous Hall effect in an antiferromagnet that has vanishingly small magnetization. In particular, we find that Mn3Sn, an antiferromagnet that has a non-collinear 120-degree spin order, exhibits a large anomalous Hall conductivity of around 20 per ohm per centimetre at room temperature and more than 100 per ohm per centimetre at low temperatures, reaching the same order of magnitude as in ferromagnetic metals. Notably, the chiral antiferromagnetic state has a very weak and soft ferromagnetic moment of about 0.002 Bohr magnetons per Mn atom (refs 10, 12), allowing us to switch the sign of the Hall effect with a small magnetic field of around a few hundred oersted. This soft response of the large anomalous Hall effect could be useful for various applications including spintronics--for example, to develop a memory device that produces almost no perturbing stray fields. PMID:26524519
A laboratory dispersant effectiveness test which reflects dispersant efficiency in the field
Oil dispersion efficiencies of surfactants, from laboratory dispersion tests and field data were compared and calibrated. Data from an oil spill, where dispersants were used as a major part of the response, was analysed. The data was accumulated through the monitoring of the dispersant operation of the Sea Empress spill incident, in which Forties Blend oil was spilled at sea. This detailed data set was used to calibrate existing laboratory dispersant tests, and to devise a new International Dispersant Effectiveness Test. The objective was to create a comprehensive guide to decision making on whether and when to start a dispersant spraying operation. The dispersion efficiencies obtained from the laboratory dispersant tests were compared with field data. Flume tests produced the highest percentage of dispersed oil for all the dispersal tests. However, it was emphasised that the total percentage of oil dispersed should not be the only measure of dispersant effectiveness, since it does not distinguish between the contribution of natural and chemically enhanced dispersion. 9 refs., 1 tab., 9 figs
Anomalous Hall effect in Fe/Gd bilayers
Xu, W. J.
2010-04-01
Non-monotonic dependence of anomalous Hall resistivity on temperature and magnetization, including a sign change, was observed in Fe/Gd bilayers. To understand the intriguing observations, we fabricated the Fe/Gd bilayers and single layers of Fe and Gd simultaneously. The temperature and field dependences of longitudinal resistivity, Hall resistivity and magnetization in these films have also been carefully measured. The analysis of these data reveals that these intriguing features are due to the opposite signs of Hall resistivity/or spin polarization and different Curie temperatures of Fe and Gd single-layer films. Copyright (C) EPLA, 2010
The availability of tunable synchrotron radiation has made it possible systematically to perform x-ray diffraction studies in regions of anomalous scattering near absorption edges, e.g. in order to derive phase information for crystal structure determination. An overview is given of recent experimental and theoretical work and discuss the properties of the anomalous atomic scattering factor, with emphasis on threshold resonances and damping effects. The results are applied to a discussion of the very strong anomalous dispersion recently observed near the L3 edge in a cesium complex. Also given is an overview of elements and levels where similar behavior can be expected. Finally, the influence of solid state and chemical effects on the absorption edge structure is discussed. 64 references
Anomalous transport effects and possible environmental symmetry 'violation' in heavy-ion collisions
Jinfeng Liao
2015-05-01
The heavy-ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur and in a sense allow environmental symmetry 'violation' phenomena. For example, certain anomalous transport processes, forbidden in usual medium, become possible in such domains. We briefly review recent progress in both the theoretical understanding and experimental search of various anomalous transport effects (such as the chiral magnetic effect, chiral separation effect, chiral electric separation effect, chiral electric/magnetic waves, etc.) in the hot QCD fluid formed by such collisions.
Anomalous transport effects and possible environmental symmetry violation in heavy-ion collisions
The heavy-ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur and in a sense allow environmental symmetry 'violation' phenomena. For example, certain anomalous transport processes, forbidden in usual medium, become possible in such domains. We briefly review recent progress in both the theoretical understanding and experimental search of various anomalous transport effects (such as the chiral magnetic effect, chiral separation effect, chiral electric separation effect, chiral electric/magnetic waves, etc.) in the hot QCD fluid formed by such collisions. (author)
Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG
The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE
Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG
Miao, B. F., E-mail: bfmiao@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Huang, S. Y. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Qu, D.; Chien, C. L., E-mail: clchien@jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)
2016-01-15
The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.
Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG
Miao, B. F.; Huang, S. Y.; Qu, D.; Chien, C. L.
2016-01-01
The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE), inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE) may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.
Absence of anomalous Nernst effect in spin Seebeck effect of Pt/YIG
B. F. Miao
2016-01-01
Full Text Available The Pt/YIG structure has been widely used to study spin Seebeck effect (SSE, inverse spin Hall effect, and other pure spin current phenomena. However, the magnetic proximity effect in Pt when in contact with YIG, and the potential anomalous Nernst effect (ANE may compromise the spin current phenomena in Pt/YIG. By inserting a Cu layer of various thicknesses between Pt and YIG, we have separated the signals from the SSE and that of the ANE. It is demonstrated that the thermal voltage in Pt/YIG mainly comes from spin current due to the longitudinal SSE with negligible contribution from the ANE.
Anomalous Hall effect from vortex motion in high-Tc superconductors
In this work, the unusual Seebeck effect is taken into consideration in explaining the possible origin of the anomalous Hall effect for high-Tc superconductors. Combining Maki's theory of transport entropy and Tinkham's theory of resistive transition, we explain why the anomalous Hall effect can be observed in high-Tc superconductors, but is absent in most conventional superconductors. The behavior of ρxy(H,T) in our theory is qualitatively consistent with experiments. In addition, our theory not only predicts that ρxy will become positive from ρxyxy|∝ρxx2 in the region of ρxyxy will diminish with increasing defect concentration
Anomalous effects of moderation in transportation and storage arrays - revisited
A number of anomalies have been observed for fissile material arrays. This paper will review anomalous behavior associated with interstitial array moderation and correct one previously-mis-identified anomaly. Most arrays show a maximum keff with low-density water moderation. An earlier study, however, did not show this maximum for unreflected 5x5x5 and 10x10x10 arrays of 15-kg 235U spheres. Our present calculations with MCNP and KENO V.a, however, show low-density maximums for both unreflected and reflected arrays of these units. We conclude that the earlier calculations for unreflected arrays were in error -- perhaps due to problem setup or code errors. The reactivity enhancement due to fissile material density reductions, however, still exits and is now seen to occur for both unreflected and water-reflected arrays
Inverse Spin Hall Effect and Anomalous Hall Effect in a Two-Dimensional Electron Gas
Schwab, Peter; Raimondi, Roberto; Gorini, Cosimo
2010-01-01
We study the coupled dynamics of spin and charge currents in a two-dimensional electron gas in the transport diffusive regime. For systems with inversion symmetry there are established relations between the spin Hall effect, the anomalous Hall effect and the inverse spin Hall effect. However, in two-dimensional electron gases of semiconductors like GaAs, inversion symmetry is broken so that the standard arguments do not apply. We demonstrate that in the presence of a Rashba type of spin-orbit...
Effects of surface charge on the anomalous light extinction from metallic nanoparticles
Sijercic, Edin; Leung, P. T.
2016-07-01
The effects of extraneous surface charges on the anomalous extinction from metallic nanoparticles are studied via an application of the extended Mie theory by Bohren and Hunt. Due to the sensitivity of the higher multipolar resonance on the surface charges, it is found that quenching of the anomalous resonance can be observed with presence of only a modest amount of charges on these particles. The observed effects thus provide a rather sensitive mechanism for the monitoring of the neutrality of these nanoparticles using far field scattering approaches.
Spontaneous magnetization and anomalous Hall effect in an emergent Dice lattice
Dutta, Omjyoti; Przysiężna, Anna; Zakrzewski, Jakub
2015-06-01
Ultracold atoms in optical lattices serve as a tool to model different physical phenomena appearing originally in condensed matter. To study magnetic phenomena one needs to engineer synthetic fields as atoms are neutral. Appropriately shaped optical potentials force atoms to mimic charged particles moving in a given field. We present the realization of artificial gauge fields for the observation of anomalous Hall effect. Two species of attractively interacting ultracold fermions are considered to be trapped in a shaken two dimensional triangular lattice. A combination of interaction induced tunneling and shaking can result in an emergent Dice lattice. In such a lattice the staggered synthetic magnetic flux appears and it can be controlled with external parameters. The obtained synthetic fields are non-Abelian. Depending on the tuning of the staggered flux we can obtain either anomalous Hall effect or its quantized version. Our results are reminiscent of Anomalous Hall conductivity in spin-orbit coupled ferromagnets.
Liu, Shuo; Yan, Feng-Ping; Zhang, Lu-Na; Han, Wen-Guo; Bai, Zhuo-Ya; Zhou, Hong
2016-01-01
A passively mode-locked thulium-doped fiber laser (TDFL) based on a nonlinear amplifying loop mirror (NALM) is presented. By adjusting the polarization controllers, stable noise-like (NL) mode-locked femtosecond pulse operation is obtained at the 2 μm band. In the experimental period of 200 min, the output power fluctuation is less than 0.06 dB and the 3 dB spectral bandwidth variation is less than 0.02 nm, indicating that the pulsed TDFL possesses good long-term stability. To the best of our knowledge, this is the first 2 μm band NALM-based TDFL with small net anomalous dispersion for a NL femtosecond pulse. At the maximum pump power of 3.52 W, the emitting laser has a NL pulse width of 460 fs, the repetition rate of 9.1 MHz, and the NL pulse energy of 32.72 nJ.
Vattuone, L; Smerieri, M; Langer, T; Tegenkamp, C; Pfnür, H; Silkin, V M; Chulkov, E V; Echenique, P M; Rocca, M
2013-03-22
The linear dispersion of the low-dimensional acoustic surface plasmon (ASP) opens perspectives in energy conversion, transport, and confinement far below optical frequencies. Although the ASP exists in a wide class of materials, ranging from metal surfaces and ultrathin films to graphene and topological insulators, its properties are still largely unexplored. Taking Au(111) as a model system, our combined experimental and theoretical study revealed an intriguing interplay between collective and single particle excitations, causing the ASP associated with the Shockley surface state to be embedded within the intraband transitions without losing its sharp character and linear dispersion. PMID:25166849
Effects of chemical dispersants on oil physical properties and dispersion. Volume 1
Khelifa, A.; Fingas, M.; Hollebone, B.P.; Brown, C.E. [Environment Canada, Ottawa, ON (Canada). ; Pjontek, D. [Ottawa Univ., ON (Canada). Dept. of Chemical Engineering
2007-07-01
Laboratory and field testing have shown that the dispersion of oil spilled in water is influenced by chemical dispersants via the modification of the interfacial properties of the oil, such as oil-brine interfacial tension (IFT). This study focused on new laboratory experiments that measured the effects on the physical properties and dispersion of oil, with particular reference to the effects of chemical dispersants on IFT and oil viscosity and the subsequent effects on oil droplet formation. Experiments were conducted at 15 degrees C using Arabian Medium, Alaska North Slope and South Louisiana crude and Corexit 9500 and Corexit 9527 chemical dispersants. The dispersants were denser than the 3 oils. The effect of IFT reduction on oil dispersion was measured and showed substantial reduction in the size and enhancement of the concentration of oil droplets in the water column. It was shown that the brine-oil IFT associated with the 3 crudes reduced to less than 3.6 mN/m with the application of the chemical dispersants, even at a low dispersant-to-oil ratio (DOR) value of 1:200. The use of chemical dispersants increased the viscosity of the dispersant-oil mixture up to 40 per cent over the neat crude oil. It was shown that for each mixing condition, an optimum value of DOR exists that provides for maximal dispersant effectiveness. The IFT reaches maximum reduction at optimum DOR. It was suggested that oil spill modelling can be improved with further study of IFT reduction with DOR and variations of critical micelle concentration with the type and solubility of chemical dispersant, oil type and oil to water ratio. 13 refs., 3 tabs., 7 figs.
Scaling of anomalous hall effect in amorphous CoFeB Films with accompanying quantum correction
Zhang, Yan
2015-05-08
Scaling of anomalous Hall effect in amorphous CoFeB films with thickness ranging from 2 to 160 nm have been investigated. We have found that the scaling relationship between longitudinal (ρxx) and anomalous Hall (ρAH) resistivity is distinctly different in the Bloch and localization regions. For ultrathin CoFeB films, the sheet resistance (Rxx) and anomalous Hall conductance (GAH) received quantum correction from electron localization showing two different scaling relationships at different temperature regions. In contrast, the thicker films show a metallic conductance, which have only one scaling relationship in the entire temperature range. Furthermore, in the dirty regime of localization regions, an unconventional scaling relationship View the MathML sourceσAH∝σxxα with α=1.99 is found, rather than α=1.60 predicted by the unified theory.
Møller, Uffe Visbech; Bang, Ole
2013-01-01
The relative intensity noise (RIN) properties at different wavelengths and power levels for picosecond supercontinuum (SC) generated by pumping a PCF in its normal dispersion regime is investigated. For low power levels the all-normal SC is generated while the generated SC extends beyond the zero...
Zhang, Han; Zhao, Luming; Bao, Qiaoliang; Loh, Kian Ping; Lin, Bo; Tjin, Swee Chuan
2010-01-01
Soliton operation and soliton wavelength tuning of erbium-doped fiber lasers mode locked with atomic layer graphene was experimentally investigated under various cavity dispersion conditions. It was shown that not only wide range soliton wavelength tuning but also soltion pulse width variation could be obtained in the fiber lasers. Our results show that the graphene mode locked erbium-doped fiber lasers provide a compact, user friendly and low cost wavelength tunable ultrahsort pulse source.
Delalande, M.; Engelen, J.B.C.; Febre, le A.J.; Abelmann, L.; Lodder, J.C.
2008-01-01
Anomalous Hall Effect (AHE) measurements have previously been used to measure the magnetization of L10-FePt [1] and Co/Pt multilayer nanodots [2]. The high sensitivity allows us to measure the magnetization reversal behaviour of sub-100-nm dots. In this work, we investigate the magnetization reversa
Anomalous Hall effects in pseudo-single-crystal γ'-Fe4N thin films
Kabara, Kazuki; Tsunoda, Masakiyo; Kokado, Satoshi
2016-05-01
The anomalous Hall effects (AHE) were investigated at various temperatures for the pseudo-single-crystal Fe4N films, deposited on MgO substrates with changing the degree of order (S) of the nitrogen site. Both the anomalous Hall resistivity and the longitudinal resistivity simply decrease with lowering temperature for all the specimens. The AHE of the Fe4N films is presumed to arise from an intrinsic mechanism because of the relationship between the anomalous Hall resistivity and longitudinal resistivity. The anomalous Hall conductivity, σAH, exhibits a specific behavior at low temperature. In the case of the film with S = 0.93, the σAH drastically drops below 50 K, while it simply increases with lowering temperature in the range of 50-300 K. This low-temperature anomaly decays with decreasing S of the film and nearly vanishes in the films with low S. The threshold temperature and the dependence on S of the low-temperature anomaly of the σAH well correspond to those of the anisotropic magnetoresistance effects in the Fe4N films, reported in the literatures. From these results, it is suggested that the low-temperature anomaly of the σAH originates from the crystal field effect which reflects the structural transformation from a cubic to a tetragonal symmetry below 50 K and provides a modulation of the orbital angular momentum of the 3d orbitals at the Fermi level.
Quantized topological magnetoelectric effect of the zero-plateau quantum anomalous Hall state
Jing WANG; Lian, Biao; Qi, Xiao-Liang; Zhang, Shou-Cheng
2015-01-01
Topological magnetoelectric effect in a three-dimensional topological insulator is a novel phenomenon, where an electric field induces a magnetic field in the same direction, with a universal coefficient of proportionality quantized in units of $e^2/2h$. Here we propose that the topological magnetoelectric effect can be realized in the zero-plateau quantum anomalous Hall state of magnetic topological insulators or ferromagnet-topological insulator heterostructure. The finite-size effect is al...
Daniel Guterding; Jeschke, Harald O.; Roser Valentí
2015-01-01
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice M...
Artificial ferroelectricity due to anomalous Hall effect in magnetic tunnel junctions
Vedyayev, A.; Ryzhanova, N.; Strelkov, N.; Dieny, B
2012-01-01
We theoretically investigated Anomalous Hall Effect (AHE) and Spin Hall Effect (SHE) transversally to the insulating spacer O, in magnetic tunnel junctions of the form F/O/F where F are ferromagnetic layers and O represents a tunnel barrier. We considered the case of purely ballistic (quantum mechanical) transport, taking into account the assymetric scattering due to spin-orbit interaction in the tunnel barrier. AHE and SHE in the considered case have a surface nature due to proximity effect....
The neutron diffraction anomalous dispersion technique and its application to vitreous Sm2O3.4P2O5
The first successful complete neutron diffraction anomalous dispersion experiment has been performed to investigate the role of the Sm3+ ions in the structure of vitreous Sm2O3.4P2O5. The ideal form of this technique, which employs the wavelength dependence of the real and imaginary parts of the neutron scattering length close to an absorption resonance, is used and involves measurements at two pairs of wavelengths: the real part of the scattering length is varied, keeping the imaginary part constant, and then the imaginary part is varied, keeping the real part constant. If A denotes the element with the isotope (149Sm) having the absorption resonance and X any other element present in the sample, the first measurement can be used to extract the A-A+A-X or A-A+X-X contribution to the real space correlation function, T(r), and the second yields the A-A component correlation function. For the present glass, the Sm-Sm+Sm-X contribution (X=P or O) reveals that the Sm3+ ions have an average co-ordination number, n Sm(O), of 7, with a mean Sm-O bond length of 2.375±0.005 A, while the anomalous difference correlation function indicates that the Sm3+ ions are ∼4.6 A apart. The paper concludes with a discussion of the relative merits of the various neutron diffraction techniques for isolating individual or subsets of real-space component correlation functions
佛克脱反常色散原子滤光器工作机理研究%Mechanism of Voigt Anomalous Dispersion Optical Filter
王江波; 汤俊雄; 段明浩; 李吉红
2001-01-01
对佛克脱(Voigt)型反常色散原子滤光器的工作机理和各种性能进行讨论，该种滤光器的实验研究表明理论与实验结果符合得很好。滤光器在外加磁场为0.02T、汽室温度为110℃的单峰带宽为0.8GHz，比相同条件下的法拉第型反常色散原子滤光器小0.5GHz，并且工程化实现比法拉第型反常色散原子滤光器容易。佛克脱型反常色散原子滤光器在卫星光通信领域有潜在的极大应用前景。%The mechanism and performances of Voigt anomalous dispersionatomic optical filter (VADOF) are studied. The experimental results agree well with the theoretical calculation. When the magnetic field is 0.02 T and the cell temperature is 110 ℃, this kind of filter exhibited a FWHM of 0.8 GHz which is 0.5 GHz smaller than that of Faraday anomalous dispersion optical filter (FADOF), and the VADOF is easy to be integrated than FADOF. VADOF has a potential application in the field of optical communication inter-satellite.
Allen, Thomas S.; Prchlik, Jakub J.; Megeath, S. Thomas [University of Toledo, Ritter Astrophysical Observatory, Department of Physics and Astronomy, Toledo, OH 43606 (United States); Gutermuth, Robert A. [Five College Astronomy Department, Smith College, Northampton, MA 01063 (United States); Pipher, Judith L. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Naylor, Tim [School of Physics, University of Exeter, Exeter, UK EX4 4QL (United Kingdom); Jeffries, R. D. [Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire, UK ST5 5BG (United Kingdom)
2014-05-10
We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and K{sub s} photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is intermediate between the R{sub V} = 3.1 and R{sub V} = 5 laws commonly used for the diffuse atomic interstellar medium and dense molecular clouds, respectively. The dependence of the extinction law on line-of-sight A{sub V} is investigated and we find the extinction law becomes shallower for regions with A{sub V} > 2.5 mag. We speculate that the intermediate dust law results from dust processing during the dispersal of the molecular cloud by the cluster.
Effect of anomalous plasma transport on radial electric field in torsatron/heliotron
Anomalous cross field plasma fluxes induced by the electric field fluctuations has been evaluated in a rotating plasma with shear flow in a helical system. The plasma rotation frequency due to the radial electric field makes the Doppler frequency shift which does not explicitly affect the cross field flux. The anomalous ion flux is evaluated by the ion curvature drift resonance continuum in the test particle model. The curvature drift resonance induces a new force term '/ which did not make large influence in the ion flux. The shear flow term in the anomalous flux combined with the electric field in neoclassical flux reduces to a first order differential equation which governs the radial profile of the electric field. A general exact analytical solution for the differential equation is derived and a simple approximate solution for the radial electric field is also given. Numerical results indicate that the shear flow effect is important for the anomalous cross field flux and for determination of the radial electric field particularly in the peripheral region. (author)
Guterding, Daniel; Jeschke, Harald O; Valentí, Roser
2016-01-01
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. PMID:27185665
Weak localization and Anomalous Hall Effect in Chemically Disordered L10-Mn1.5Ga
Zhu, L. J.; Pan, D.; J. H. Zhao
2013-01-01
The anomalous Hall effect (AHE) in perpendicularly magnetized L10-Mn1.5Ga single-crystalline films is investigated as a function of degree of long-range chemical ordering and temperature. Our results provide firm evidence that weak localization, phonons and magnons have negligibly smaller effect on skew scattering contributions to AHE resistivity than defects, the overlook of which in conventional scaling laws results in significant discrepancies and exponent n beyond 2 when fitting the data....
In this work, we made use of the technique of X-ray fluorescence for dispersion in energy, to study a phytopathology denominated 'sooty mould' on leaves of Olive trees of Mediterranean area. The Olive trees are quite common and of great economical value in that area,especially in the island of Sardegna in Italy, where this work was developed, for treating one of the income main sources of the local economy. We observed a correlation between the elements Fe and Ca among infected leaves of Olive trees and not infected that is: leaves infected by the sooty mould present a large concentration of Fe and a low concentration of Ca when compared to the leaves not infected by the sooty mould. The oxidation state of Fe was determined by Moessbauer spectroscopy that revealed that this was Fe3+. (author)
Dispersant effectiveness testing : laboratory studies of fresh and weathered oils
Fingas, M.F.; Fieldhouse, B.; Sigouin, L.; Wang, Z. [Environment Canada, Ottawa, ON (Canada). Emergencies Science Div
2001-07-01
A dispersant called Corexit 9500 was tested to determine its effectiveness on various oils including several new and weathered oils. Dispersant effectiveness is defined as the amount of oil that the dispersant puts into the water column versus that which remains on the surface. Many factors influence dispersant effectiveness, including sea energy, oil composition, state of oil weathering, rate of dispersant application, dispersant type, temperature, and salinity of the water. In this study, a series of 6 oil-in-solvent standards were prepared for evaluating the efficiency of the dispersant for each dispersant/oil combination. The effectiveness of these oils was measured using the swirling flask test. Tests of crude oil as well as weathered crude oil were presented. The effectiveness for the weathered crude oils was found to drop off significantly. The weathering effect was analyzed using mathematical regressions. It was concluded that the dispersabilities of crude oils vary and the effectiveness of dispersion decreases as the oils are weathered or evaporated. The typical trend that emerged is oil specific and does not correlate with simple oil properties such as density, viscosity or maximum weathering percentage. 4 refs., 2 tabs., 4 figs.
Charge transport in manganites: Hopping conduction, the anomalous Hall effect, and universal scaling
The low-temperature Hall resistivity ρxy of La2/3A1/3MnO3 single crystals (where A stands for Ca, Pb, and Ca, or Sr) can be separated into ordinary and anomalous contributions, giving rise to ordinary and anomalous Hall effects, respectively. However, no such decomposition is possible near the Curie temperature which, in these systems, is close to metal-to-insulator transition. Rather, for all of these compounds and to a good approximation, the ρxy data at various temperatures and magnetic fields collapse (up to an overall scale), on to a single function of the reduced magnetization m(equivalent to)M/Msat, the extremum of this function lying at m∼0.4. A mechanism for the anomalous Hall effect in the inelastic hopping regime, which reproduces these scaling curves, is identified. This mechanism, which is an extension of Holstein's model for the ordinary Hall effect in the hopping regime, arises from the combined effects of the double-exchange-induced quantal phase in triads of Mn ions and spin-orbit interactions. We identify processes that lead to the anomalous Hall effect for localized carriers and, along the way, analyze issues of quantum interference in the presence of phonon-assisted hopping. Our results suggest that, near the ferromagnet-to-paramagnet transition, it is appropriate to describe transport in manganites in terms of carrier hopping between states that are localized due to the combined effect of magnetic and nonmagnetic disorder. We attribute the qualitative variations in resistivity characteristics across manganite compounds to the differing strengths of their carrier self-trapping, and conclude that both disorder-induced localization and self-trapping effects are important for transport
Temperature correction to the Casimir force in cryogenic range and anomalous skin effect
The temperature correction to the Casimir force is considered for real metals at low temperatures. With the temperature decrease, the mean free path for electrons becomes larger than the field penetration depth. In this condition, description of metals with the impedance of anomalous skin effect is shown to be more appropriate than with the permittivity. The effect is crucial for the temperature correction. It is demonstrated that in the zero-frequency limit, the reflection coefficients should coincide with those of ideal metal if we demand the entropy to be zero at T=0. All the other prescriptions discussed in the literature for the n=0 term in the Lifshitz formula give negative entropy. It is shown that the temperature correction in the region of anomalous skin effect is not suppressed as it happens in the plasma model. This correction will be important in the future cryogenic measurements of the Casimir force
Numerical study of effective optical nonlinear properties in composites with anomalous distribution
We investigate the nonlinear optical response of random composites consisting of nonlinear conductors and linear conductors with an anomalous distribution. Random resistor-capacitor networks are used to simulate our model, in which the nonlinear component with the fraction p is taken as i=g1ν+χ1 vertical ν vertical bar2v and the linear component with the fraction 1-p obeys an anomalous distribution h(g2)∼g2-α, where 02<1. We find that the distribution exponent α plays an important role in the effective linear and nonlinear optical response. As α decreases, the enhancement of optical nonlinear χe can be achieved. Moreover, the effective nonlinear optical response exhibits a sharp peak at a moderate volume fraction, dependent on α. The effective medium approximation is found to be in good agreement with linear response of numerical simulation, and describes nonlinear response of our numerical results qualitatively
Finite-volume effects in the muon anomalous magnetic moment on the lattice
Aubin, Christopher; Blum, Thomas; Chau, Peter; Golterman, Maarten; Peris, Santiago; Tu, Cheng
2016-03-01
We investigate finite-volume effects in the hadronic vacuum polarization, with an eye toward the corresponding systematic error in the muon anomalous magnetic moment. We consider both recent lattice data as well as lowest-order, finite-volume chiral perturbation theory, in order to get a quantitative understanding. Even though leading-order chiral perturbation theory does not provide a good description of the hadronic vacuum polarization, it turns out that it gives a good representation of finite-volume effects. We find that finite-volume effects cannot be ignored when the aim is a few percent level accuracy for the leading-order hadronic contribution to the muon anomalous magnetic moment, even when using ensembles with mπL ≳4 and mπ˜200 MeV .
Finite-volume effects in the muon anomalous magnetic moment on the lattice
Aubin, Christopher; Chau, Peter; Golterman, Maarten; Peris, Santiago; Tu, Cheng
2015-01-01
We investigate finite-volume effects in the hadronic vacuum polarization, with an eye toward the corresponding systematic error in the muon anomalous magnetic moment. We consider both recent lattice data as well as lowest-order, finite-volume chiral perturbation theory, in order to get a quantitative understanding. Even though leading-order chiral perturbation theory does not provide a good description of the hadronic vacuum polarization, it turns out that it gives a reasonably good representation of finite-volume effects. We find that finite-volume effects cannot be ignored when the aim is a few percent level accuracy for the leading-order hadronic contribution to the muon anomalous magnetic moment, even when using ensembles with $m_\\pi L> 4$ and $m_\\pi \\sim 200$ MeV.
Employment Effects of Dispersal Policies on Refugee Immigrants
Damm, Anna Piil; Rosholm, Michael
Do spatial dispersal policies on refugees promote their labour market outcomes? To investigate this we estimate the effects of location characteristics and the average effect of geographical mobility on the hazard rate into first job of refugees subjected to the Danish spatial dispersal policy 1986...... findings support dispersal policies. Second, on average geographical mobility had large, positive effects on the hazard rate into first job, suggesting that restrictions on placed refugees' subsequent out-migration would hamper labour market integration of refugees....
Monolayer dispersion thresholds and threshold effect displayed by supported catalysts
Cun DENG
2008-01-01
The principle of spontaneous monolayer dis-persion holds that active components of many supported catalysts will disperse spontaneously onto the surface of the carrier. The monolayer dispersion threshold of the active component on the surface of the carrier can be measured by X-ray diffraction phase-quantitative extra-polation method, etc. By measuring the monolayer disper-sion threshold, beneficial information on the surface structure and dispersion of supported catalysts can be obtained, and the optimal preparative processing condi-tions of the catalysts can be chosen. The proportion of the active component of many supported catalysts can be optimized while its monolayer dispersion threshold is observed. Mutation values of many physicochemical properties of supported catalysts are related to monolayer dispersion thresholds; the threshold effect on catalysts is apparent, and the proposal regarding the threshold effect provides instruction for the research on catalysts.
Anomalous effective charges and far-IR optical absorption of Al2Ru from first principles
For the orthorhombic intermetallic semiconductor Al2Ru, the band structure, valence charge density, zone-center optical-phonon frequencies, and Born effective-charge and electronic dielectric tensors are calculated using variational density-functional perturbation theory with ab initio pseudopotentials and a plane-wave basis set. Good agreement is obtained with recent measurements on polycrystalline samples, which showed anomalously strong far-IR absorption by optical phonons, while analysis of the valence charge density shows that the static ionic charges of Al and Ru are negligible. Hybridization is proposed as the single origin both of the semiconducting gap and the anomalous Born effective charges. Analogous behavior is expected in related compounds such as NiSnZr, PbTe, skutterudites, and Al-transition-metal quasicrystals. copyright 1996 The American Physical Society
Surface impedance in the anomalous skin effect regime
Chrzanowski, Janusz; Kirkiewicz, Józef
2008-12-01
An analytical solution of the surface impedance is obtained using the kinetic equation with the collision integral that takes into account the Fermi liquid effects. It is assumed that the reflection of electrons is purely diffusive. Particular attention is paid to the influence of external magnetic field and polarization of the incident wave on the real and imagine part of the surface impedance.
Highlights: ► Cu2ZnSnS4 thin films as a solar cell material were synthesized. ► The wavelength dependences of the diffraction intensity were measured. ► The crystal structures were clearly identified as kesterite structure for all samples. ► Crystal structure analysis revealed that the atomic compositions were Cu/(Zn + Sn) = 0.97 and Zn/Sn = 1.42 for the sample synthesized using stoichiometric amount of starting materials. - Abstract: The crystal structure of Cu2ZnSnS4 (CZTS) thin films fabricated by vapor-phase sulfurization was determined using X-ray anomalous dispersion. High statistic synchrotron radiation X-ray diffraction data were collected from very small amounts of powder. By analyzing the wavelength dependencies of the diffraction peak intensities, the crystal structure was clearly identified as kesterite. Rietveld analysis revealed that the atomic composition deviated from stoichiometric composition, and the compositions were Cu/(Zn + Sn) = 0.97, and Zn/Sn = 1.42.
Critical Review of Theoretical Models for Anomalous Effects (Cold Fusion) in Deuterated Metals
Chechin, V. A.; Tsarev, V. A.; Rabinowitz, M; Kim, Y. E.
2003-01-01
We briefly summarize the reported anomalous effects in deuterated metals at ambient temperature, commonly known as "Cold Fusion" (CF), with an emphasis on important experiments as well as the theoretical basis for the opposition to interpreting them as cold fusion. Then we critically examine more than 25 theoretical models for CF, including unusual nuclear and exotic chemical hypotheses. We conclude that they do not explain the data.
Critical Review of Theoretical Models for Anomalous Effects (Cold Fusion) in Deuterated Metals
Chechin, V A; Rabinowitz, M; Kim, Y E
1994-01-01
We briefly summarize the reported anomalous effects in deuterated metals at ambient temperature, commonly known as "Cold Fusion" (CF), with an emphasis on important experiments as well as the theoretical basis for the opposition to interpreting them as cold fusion. Then we critically examine more than 25 theoretical models for CF, including unusual nuclear and exotic chemical hypotheses. We conclude that they do not explain the data.
Arita, Ken-ichiro
2014-01-01
Shell structures in single-particle energy spectra are investigated against regular tetrahedral type deformation using radial power-law potential model. Employing a natural way of shape parametrization which interpolate sphere and regular tetrahedron, we find prominent shell effects at rather large tetrahedral deformations, which bring about shell energies much larger than the cases of spherical and quadrupole type shapes. We discuss the semiclassical origin of these anomalous shell structures using periodic orbit theory.
3d Transition Metal Adsorption Induced Vally-polarized Anomalous Hall Effect in Germanene
Zhou, P; Sun, L. Z.
2015-01-01
Based on DFT+U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atom on its surface. A finite valley hall voltage can be easily detected in its nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and ...
Nonadiabatic Effects in Ultracold Molecules via Anomalous Linear and Quadratic Zeeman Shifts
McGuyer, B. H.; Osborn, C. B.; McDonald, M.; Reinaudi, G.; Skomorowski, W.; Moszynski, R.; Zelevinsky, T.
2013-01-01
Anomalously large linear and quadratic Zeeman shifts are measured for weakly bound ultracold $^{88}$Sr$_2$ molecules near the intercombination-line asymptote. Nonadiabatic Coriolis coupling and the nature of long-range molecular potentials explain how this effect arises and scales roughly cubically with the size of the molecule. The linear shifts yield nonadiabatic mixing angles of the molecular states. The quadratic shifts are sensitive to nearby opposite $f$-parity states and exhibit fourth...
Anomalous effective action, Noether current, Virasoro algebra and Horizon entropy
Several investigations show that in a very small length scale there exist corrections to the entropy of black hole horizon. Due to fluctuations of the background metric and the external fields the action incorporates corrections. In the low energy regime, the one-loop effective action in four dimensions leads to trace anomaly. We start from the Noether current corresponding to the Einstein-Hilbert plus the one-loop effective action to calculate the charge for the diffeomorphisms which preserve the Killing horizon structure. Then a bracket for the charges is calculated. We show that the Fourier modes of the bracket are exactly similar to the Virasoro algebra. Then using the Cardy formula the entropy is evaluated. Finally, the explicit terms of the entropy expression is calculated for a classical background. It turns out that the usual expression for the entropy; i.e. the Bekenstein-Hawking form, is not modified. (orig.)
Evidence for Anomalous Effects on the Current Evolution in Tokamak Operating Scenarios
Casper, T; Jayakumar, R; Allen, S; Holcomb, C; Makowski, M; Pearlstein, L; Berk, H; Greenfield, C; Luce, T; Petty, C; Politzer, P; Wade, M; Murakami, M; Kessel, C
2006-10-03
Alternatives to the usual picture of advanced tokamak (AT) discharges are those that form when anomalous effects alter the plasma current and pressure profiles and those that achieve stationary characteristics through mechanisms so that a measure of desired AT features is maintained without external current-profile control. Regimes exhibiting these characteristics are those where the safety factor (q) evolves to a stationary profile with the on-axis and minimum q {approx} 1 and those with a deeply hollow current channel and high values of q. Operating scenarios with high fusion performance at low current and where the inductively driven current density achieves a stationary configuration with either small or non-existing sawteeth may enhance the neutron fluence per pulse on ITER and future burning plasmas. Hollow current profile discharges exhibit high confinement and a strong ''box-like'' internal transport barrier (ITB). We present results providing evidence for current profile formation and evolution exhibiting features consistent with anomalous effects or with self-organizing mechanisms. Determination of the underlying physical processes leading to these anomalous effects is important for scaling of current experiments for application in future burning plasmas.
Giant Anomalous Hall Effect in the Chiral Antiferromagnet Mn3Ge
Kiyohara, Naoki; Tomita, Takahiro; Nakatsuji, Satoru
2016-06-01
The external field control of antiferromagnetism is a significant subject both for basic science and technological applications. As a useful macroscopic response to detect magnetic states, the anomalous Hall effect (AHE) is known for ferromagnets, but it has never been observed in antiferromagnets until the recent discovery in Mn3Sn . Here we report another example of the AHE in a related antiferromagnet, namely, in the hexagonal chiral antiferromagnet Mn3Ge . Our single-crystal study reveals that Mn3Ge exhibits a giant anomalous Hall conductivity |σx z|˜60 Ω-1 cm-1 at room temperature and approximately 380 Ω-1 cm-1 at 5 K in zero field, reaching nearly half of the value expected for the quantum Hall effect per atomic layer with Chern number of unity. Our detailed analyses on the anisotropic Hall conductivity indicate that in comparison with the in-plane-field components |σx z| and |σz y|, which are very large and nearly comparable in size, we find |σy x| obtained in the field along the c axis to be much smaller. The anomalous Hall effect shows a sign reversal with the rotation of a small magnetic field less than 0.1 T. The soft response of the AHE to magnetic field should be useful for applications, for example, to develop switching and memory devices based on antiferromagnets.
Anomalous piezoelectric effects, found in the laboratory and reconstructed by numerical simulation
K. P. Teisseyre
2002-06-01
Full Text Available Various rocks and minerals, which are not piezoelectric in the common sense, exhibit transient electric polarization in response to sudden changes in stress load. This anomalous piezoelectric effect differs from the regular, static piezoelectric response, in which electric charges appear as a result of crystal lattice deformation. The anomalous piezoelectricity is dynamic decaying in a few seconds or a few tens of seconds. However, in some materials different polarization properties are discovered. To explain certain aspects of the polarization signal increase and decay, some complicated mechanisms of electric charge generation and relaxation need to be assumed in their number ? concurrence of two or three relaxation processes. The hypothetical mechanisms are only mentioned, as the purpose of this work is to construct numerical models, behaving like the rocks investigated. Examples of experimental plots are shown together with the results of the numerical simulation of these experiments.
Kushagra, Arindam
2016-02-01
Anomalous subdiffusion governs the processes which are not energetically driven, on a molecular scale. This paper proposes a model to predict the response of electrochemical impedance due to such diffusion process. Previous works considered the use of fractional calculus to predict the impedance behaviour in response to the anomalous diffusion. Here, we have developed an expression which predicts the skin-effect, marked by an increase in the impedance with increasing frequency, in this regime. Negative inductances have also been predicted as a consequence of the inertial response of adsorbed species upon application of frequency-mediated perturbations. It might help the researchers in the fields of impedimetric sensors to choose the working frequency and those working in the field of batteries to choose the parameters, likewise. This work would shed some light into the molecular mechanisms governing the impedance when exposed to frequency-based perturbations like electromagnetic waves (microwaves to ionizing radiations) and in charge storage devices like batteries etc.
Origin of enhanced anomalous Hall effect in ultrathin Pt/permalloy bilayers
Y. Q. Zhang
2016-02-01
Full Text Available There are two mechanisms which could enhance spin-dependent scattering in a low dimensional Pt/Ferromagnetic metal structure. One is magnetic proximity effect. The other is spin orbit coupling proximity effect which was suggested recently. This work demonstrates that, through a series of experiments on anomalous Hall effect, the spin orbit coupling proximity effect dominates the enhancement in very thin Pt/Permalloy bilayers. It may help to find a way to optimize magnetic transport property of spintronics devices in which the spin orbit coupling is deeply involved.
Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells
Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Dai, Xi; Fang, Zhong; /Beijing, Inst. Phys.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-03-19
The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.
Anomalous diffraction in hyperbolic materials
Alberucci, Alessandro; Boardman, Allan D; Assanto, Gaetano
2016-01-01
We demonstrate that light is subject to anomalous (i.e., negative) diffraction when propagating in the presence of hyperbolic dispersion. We show that light propagation in hyperbolic media resembles the dynamics of a quantum particle of negative mass moving in a two-dimensional potential. The negative effective mass implies time reversal if the medium is homogeneous. Such property paves the way to diffraction compensation, spatial analogue of dispersion compensating fibers in the temporal domain. At variance with materials exhibiting standard elliptic dispersion, in inhomogeneous hyperbolic materials light waves are pulled towards regions with a lower refractive index. In the presence of a Kerr-like optical response, bright (dark) solitons are supported by a negative (positive) nonlinearity.
Nayak, Ajaya K; Fischer, Julia Erika; Sun, Yan; Yan, Binghai; Karel, Julie; Komarek, Alexander C; Shekhar, Chandra; Kumar, Nitesh; Schnelle, Walter; Kübler, Jürgen; Felser, Claudia; Parkin, Stuart S P
2016-04-01
It is well established that the anomalous Hall effect displayed by a ferromagnet scales with its magnetization. Therefore, an antiferromagnet that has no net magnetization should exhibit no anomalous Hall effect. We show that the noncolinear triangular antiferromagnet Mn3Ge exhibits a large anomalous Hall effect comparable to that of ferromagnetic metals; the magnitude of the anomalous conductivity is ~500 (ohm·cm)(-1) at 2 K and ~50 (ohm·cm)(-1) at room temperature. The angular dependence of the anomalous Hall effect measurements confirms that the small residual in-plane magnetic moment has no role in the observed effect except to control the chirality of the spin triangular structure. Our theoretical calculations demonstrate that the large anomalous Hall effect in Mn3Ge originates from a nonvanishing Berry curvature that arises from the chiral spin structure, and that also results in a large spin Hall effect of 1100 (ħ/e) (ohm·cm)(-1), comparable to that of platinum. The present results pave the way toward the realization of room temperature antiferromagnetic spintronics and spin Hall effect-based data storage devices. PMID:27152355
Added mass and effective density of dispersed media
The review of dependences of added mass (AM) coefficients of liquid on concentration of inclusions in dispersion medium available in literature are given. It is shown that in the processes taking place under the action of surface forces effecting dispersion medium (pressure wave propagation, equipment vibrations), AM of liquid grows with the increase of concentration of inclusions. When dispersion medium moves under the action of body forces AM of liquid decreases with the increase of concentration of inclusions. The examples of calculations of effective density of dispersion media with the use of considered concentration dependences of AM coefficient are given. The comparison with experimental results is conducted
Dispersion engineering for integrated nanophotonics
Vanbésien, Olivier
2014-01-01
This book shows how dispersion engineering in two dimensional dielectric photonic crystals can provide new effects for the precise control of light propagation for integrated nanophotonics.Dispersion engineering in regular and graded photonic crystals to promote anomalous refraction effects is studied from the concepts to experimental demonstration via nanofabrication considerations. Self collimation, ultra and negative refraction, second harmonic generation, mirage and invisibility effects which lead to an unprecedented control of light propagation at the (sub-)wavelength scale for the
Employment Effects of Spatial Dispersal of Refugees
Damm, Anna Piil; Rosholm, Michael
Spatial dispersal policies may influence labour market integration of refugees through two mechanisms. First, it may affect the local job offer arrival rate, and second, it may affect place utility. We investigate the second mechanism theoretically by formulating a partial search model in which an...... individual searches simultaneously for a job and for a new residential location. The model predicts that the reservation wage for local jobs is decreasing in place utility. We argue that spatial dispersal policies decrease average place utility of refugees which decrease the transition rate into first job...
Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru
2016-05-01
Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large
Akdogan, E. K.; Savkl Latin-Small-Letter-Dotless-I y Latin-Small-Letter-Dotless-I ld Latin-Small-Letter-Dotless-I z, I.; Bicer, H.; Paxton, W.; Toksoy, F.; Tsakalakos, T. [Department of Materials Science and Engineering, Rutgers University, Piscataway, New Jersey 08854-8065 (United States); Zhong, Z. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States)
2013-06-21
Nonisothermal densification in 8% yttria doped zirconia (8YSZ) particulate matter of 250 nm median particle size was studied under 215 V/cm dc electric field and 9 Degree-Sign C/min heating rate, using time-resolved in-situ high temperature energy dispersive x-ray diffractometry with a polychromatic 200 keV synchrotron probe. Densification occurred in the 876-905 Degree-Sign C range, which resulted in 97% of the theoretical density. No local melting at particle-particle contacts was observed in scanning electron micrographs, implying densification was due to solid state mass transport processes. The maximum current draw at 905 Degree-Sign C was 3 A, corresponding to instantaneous absorbed power density of 570 W/cm{sup 3}. Densification of 8YSZ was accompanied by anomalous elastic volume expansions of the unit cell by 0.45% and 2.80% at 847 Degree-Sign C and 905 Degree-Sign C, respectively. The anomalous expansion at 905 Degree-Sign C at which maximum densification was observed is characterized by three stages: (I) linear stage, (II) anomalous stage, and (III) anelastic recovery stage. The densification in stage I (184 s) and II (15 s) was completed in 199 s, while anelastic relaxation in stage III lasted 130 s. The residual strains ({epsilon}) at room temperature, as computed from tetragonal (112) and (211) reflections, are {epsilon}{sub (112)} = 0.05% and {epsilon}{sub (211)} = 0.13%, respectively. Time dependence of (211) and (112) peak widths ({beta}) show a decrease with both exhibiting a singularity at 905 Degree-Sign C. An anisotropy in (112) and (211) peak widths of {l_brace} {beta}{sub (112)}/{beta}{sub (211)}{r_brace} = (3:1) magnitude was observed. No phase transformation occurred at 905 Degree-Sign C as verified from diffraction spectra on both sides of the singularity, i.e., the unit cell symmetry remains tetragonal. We attribute the reduction in densification temperature and time to ultrafast ambipolar diffusion of species arising from the
Quantum Anomalous Hall Effect in Hg$_{1-y}$Mn$_{y}$Te Quantum Wells
Liu, Chao-Xing; Qi, Xiao-Liang; Dai, Xi; Fang, Zhong; Zhang, Shou-Cheng
2008-01-01
The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg$_{1-y}$Mn$_{y}$Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the $Mn$ atoms, and the quantized Hall conductance is predi...
When effective theories predict: the inevitability of Mercury's anomalous perihelion precession
Wells, James D
2012-01-01
If the concepts underlying Effective Theory were appreciated from the earliest days of Newtonian gravity, Le Verrier's announcement in 1845 of the anomalous perihelion precession of Mercury would have been no surprise. Furthermore, the size of the effect could have been anticipated through "naturalness" arguments well before the definitive computation in General Relativity. Thus, we have an illustration of how Effective Theory concepts can guide us in extending our knowledge to "new physics", and not just in how to reduce larger theories to restricted (e.g., lower energy) domains.
Anomalous coupling, top-mass and parton-shower effects in W + W - production
Bellm, J.; Gieseke, S.; Greiner, N.; Heinrich, G.; Plätzer, S.; Reuschle, C.; von Soden-Fraunhofen, J. F.
2016-05-01
We calculate the process ppto {W}+{W}-to {e}+{ν}_e{μ}-{overline{ν}}_{μ } at NLO QCD, including also effective field theory (EFT) operators mediating the ggW + W - interaction, which first occur at dimension eight. We further combine the NLO and EFT matrix elements produced by G oS am with the H erwig7/M atchbox framework, which offers the possibility to study the impact of a parton shower. We assess the effects of the anomalous couplings by comparing them to top-mass effects as well as uncertainties related to variations of the renormalisation, factorisation and hard shower scales.
The method of electron polarization by pumping the electron spin resonance (ESR), using a running wave with a phase velocity close to the electron beam velocity,is proposed. Repeatedly alternating pumping by the following wave and by the counter wave, it is possible to realize nearly full electron polarization. Similar,and even more effective, this method can make electron polarization using alternation of a normal Doppler effect on the following wave (thus the wave phase velocity exceeds the velocity of the beam) and an anomalous Doppler effect on the following wave too (when, on the contrary, the velocity of the beam exceeds the phase velocity of the wave)
Sex-biased dispersal promotes adaptive parental effects
Franc Alain; Revardel Emmanuelle; Petit Rémy J
2010-01-01
Abstract Background In heterogeneous environments, sex-biased dispersal could lead to environmental adaptive parental effects, with offspring selected to perform in the same way as the parent dispersing least, because this parent is more likely to be locally adapted. We investigate this hypothesis by simulating varying levels of sex-biased dispersal in a patchy environment. The relative advantage of a strategy involving pure maternal (or paternal) inheritance is then compared with a strategy ...
The effect of dispersion mechanisms on aroma delivery
Pearson, Kris S.K.
2005-01-01
Dispersion of aroma compounds in food matrices is a common process in the production of many food products. However, the degrees of dispersion on the distribution and subsequent release of these compounds during consumption may have considerable consequences for perception of these flavours. This thesis investigates the effects of a range of dispersion techniques on the delivery and release of aroma compounds from several solid and semi-solid matrices which commonly contain added flavouri...
Spectrum of anomalous magnetohydrodynamics
Giovannini, Massimo
2016-05-01
The equations of anomalous magnetohydrodynamics describe an Abelian plasma where conduction and chiral currents are simultaneously present and constrained by the second law of thermodynamics. At high frequencies the magnetic currents play the leading role, and the spectrum is dominated by two-fluid effects. The system behaves instead as a single fluid in the low-frequency regime where the vortical currents induce potentially large hypermagnetic fields. After deriving the physical solutions of the generalized Appleton-Hartree equation, the corresponding dispersion relations are scrutinized and compared with the results valid for cold plasmas. Hypermagnetic knots and fluid vortices can be concurrently present at very low frequencies and suggest a qualitatively different dynamics of the hydromagnetic nonlinearities.
Employment effects of spatial dispersal of refugees
Damm, Anna Piil; Rosholm, Michael
2010-01-01
Refugees subjected to a spatial dispersal tend to be assigned to a location outside the immigrant-dense cities. We argue that such locations are associated with low place utility. Our partial equilibrium search model with simultaneous job and residential location search predicts that the reservat...
Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So
2016-05-01
Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of
Spin Seebeck Effect vs. Anomalous Nernst Effect in Ta/CoFeB /Ta Structures
Yang, Bowen; Xu, Yadong; Schneider, Mike; Shi, Jing; Univ of California-Riverside Team; Everspin Technologies Inc. Team
2014-03-01
We have studied the spin Seebeck effect (SSE) and anomalous Nernst effect (ANE) in a vertical trilayer structure under a vertical temperature gradient. The structure consists of a 3nm CoFeB layer sandwiched by β-phase tantalum (Ta) layers. The samples are deposited by magnetron sputtering. The existence of Ta β-phase is verified by the resistivity and its negative temperature coefficient of resistance(TCR). Under a fixed vertical temperature gradient, the measured transverse thermoelectric voltage is linearly proportional to the total sample resistance when the Ta thickness exceeds 2 nm, which can be explained by a shunting resistor model. When the Ta thickness is below 2 nm, the voltage deviates from the linear resistance dependence and merges to the ANE voltage of the CoFeB single layer, due to a weakened inverse spin Hall effect (ISHE) in Ta thinner than the spin diffusion length. In the linear regime, the slope contains both a varying SSE and a fixed ANE responses, thus the SSE contribution could be quantitatively separated out from the ANE of CoFeB. Our results indicate a large SSE from the β-phase Ta due to its large Spin Hall Angle. This work was supported by CNN/DMEA and DOE.
Effect of third-order dispersion on dark solitons
Afanasjev, Vsevolod V.; Kivshar, Yuri S.; Menyuk, Curtis R.
1996-12-01
Third-order dispersion has a detrimental effect on dark solitons, leading to resonant generation of growing soliton tails and soliton decay. This effect is shown to be much stronger than that for bright solitons.
Effect of Center High Explosive in Dispersion of Fuel
张奇; 林大超; 白春华; 郭彦懿
2004-01-01
The dispersion of the fuel due to the center high explosive, including several different physical stages, is analyzed by means of experimental results observed with a high speed motion analysis system, and the effect of center high explosive charge is suggested. The process of the fuel dispersion process can be divided into three main stages, acceleration, deceleration and turbulence. Within a certain scope, the radius of the final fuel cloud dispersed is independent of the center explosive charge mass in an FAE (fuel air explosive) device, while only dependent both on the duration of acceleration stage and on that of the deceleration. In these two stages, the dispersion of the fuel dust mainly occurs along the radial direction. There is a close relation between the fuel dispersion process and the center explosive charge mass. To describe the motion of fuel for different stages of dispersion, different mechanical models should be applied.
The anomalous Hall effect of two-dimensional holes in a GaAs/AlGaAs heterostructure was measured under a slightly tilted-from-parallel magnetic field (B). In addition to the dominant ordinary Hall resistivity, which is linear in B, there is a small anomalous Hall resistivity correlated with the perpendicular spin magnetization of the holes due to the subband depopulation. When the anomalous Hall conductivity (σAxy) is extracted from the experimental data, it exhibits a nonmonotonic dependence on B, a behavior expected for the intrinsic anomalous Hall effect in the 2D Rashba model. If σAxy is plotted as a function of the longitudinal conductivity (σxx), an intrinsic region in which σAxy is almost constant and is several tenths of e2/h for σxx of several tens of e2/h is identified.
Anomalous Josephson Effect in Junctions with Rashba Spin-Orbit Coupling
Nesterov, Konstantin; Houzet, Manuel; Meyer, Julia
2015-03-01
We study two-dimensional double-barrier SINIS Josephson junctions in which the inversion symmetry in the normal part is broken by Rashba spin-orbit coupling. In the presence of a suitably oriented Zeeman field in the normal part, the system displays the anomalous Josephson effect: the current is nonzero even at zero phase difference between two superconductors. We investigate this effect by means of the Ginzburg-Landau formalism and microscopic Green's functions approach in the clean limit. This work was supported in part by the Grants No. ANR-12-BS04-0016-03 and an EU-FP7 Marie Curie IRG.
Anomalous acoustic effect during martensitic transformations in titanium nickelide base alloys
One carried out experiments to determine effect of external static stress on martensitic transformations and acoustic emission, Martensitic transformations in titanium nickelide base alloys under mechanical stress were determined to change nature of acoustic emission to anomalous one - cycling of transformations under gradual increase of mechanical stress during direct martensitic transformation was followed by increase of acoustic emission energy instead of reduction. The mentioned nature of acoustic emission is indicative of essential effect of external stress on martensitic transformations and energy dissipation during transformations
Inverted effective SUSY with combined Z' and gravity mediation, and muon anomalous magnetic moment
Kim, Jihn E.
2012-01-01
Effective supersymmetry(SUSY) where stop is the lightest squark may run into a two-loop tachyonic problem in some Z' mediation models. In addition, a large A term or/and a large stop mass are needed to have about a 126 GeV Higgs boson with three families of quarks and leptons. Thus, we suggest an inverted effective SUSY(IeffSUSY) where stop mass is larger compared to those of the first two families. In this case, it is possible to have a significant correction to the anomalous magnetic moment...
Kim, Sang-Il; Seo, Min-Su; Park, Seung-Young, E-mail: parksy@kbsi.re.kr [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-806 (Korea, Republic of); Kim, Dong-Jun; Park, Byong-Guk [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of)
2015-05-07
The dependence of the measured DC voltage on the non-magnetic material (NM) in NM/CoFeB and CoFeB/NM bilayers is studied under ferromagnetic resonance conditions in a TE{sub 011} resonant cavity. The directional change of the inverse spin Hall effect (ISHE) voltage V{sub ISHE} for the stacking order of the bilayer can separate the pure V{sub ISHE} and the anomalous Hall effect (AHE) voltage V{sub AHE} utilizing the method of addition and subtraction. The Ta and Ti NMs show a broad deviation of the spin Hall angle θ{sub ISH}, which originates from the AHE in accordance with the high resistivity of NMs. However, the Pt and Pd NMs show that the kinds of NMs with low resistivity are consistent with the previously reported θ{sub ISH} values. Therefore, the characteristics that NM should simultaneously satisfy to obtain a reasonable V{sub ISHE} value in bilayer systems are large θ{sub ISH} and low resistivity.
The role of the Sm3+ ions in the structure of vitreous Sm2O3·4P2O5 has been investigated using the neutron diffraction anomalous dispersion technique, which employs the wavelength dependence of the real and imaginary parts of the neutron scattering length close to an absorption resonance. The data described here represent the first successful complete neutron anomalous dispersion study on an amorphous material. This experimental methodology permits one to determine exclusively the closest Sm-Sm separation. Knowledge of the R - R (R = rare-earth) pairwise correlation is key to understanding the optical and magnetic properties of rare-earth phosphate glasses. The anomalous difference correlation function, ΔT''(r), shows a dominant feature pertaining to a Sm - Sm separation, centred at 4.8 A. The substantial width and marked asymmetry of this peak indicates that the minimum approach of Sm3+ ions could be as close as 4 A. Information on other pairwise correlations is also revealed via analysis of T(r) and ΔT(r) correlation functions: Sm3+ ions display an average co-ordination number, nSm(O), of 7, with a mean Sm-O bond length of 2.375(5) A whilst the PO4 tetrahedra have a mean P-O bond length of 1.538(2) A. Second- and third-neighbour correlations are also identified. These results corroborate previous findings. Such consistency lends support to the application of the anomalous dispersion technique to determine Sm - Sm separations
Saurabh D Rindani
2000-06-01
We obtain analytic expressions for the energy and polar-angle double differential distributions of a secondary lepton +(-) arising from the decay of ($\\overline{t}$) in + - → $t\\overline{t}$ with an anomalous decay vertex. We also obtain analytic expressions for the various differential cross-sections with the lepton energy integrat ed over. In this case, we ﬁnd that the angular distributions of the secondary lepton do not depend on the anomalous coupling in the decay, regardless of possible anomalous couplings occurring in the production amplitude for + - → $t\\overline{t}$. Our study includes the effect of longitudinal - and + beam polarization. We also study the lepton energy and beam polarization dependence of certain CP-violating lepton angular asymmetries arising from an anomalous decay vertex and compare them with the asymmetries arising due to CP-violation in the production process due to the top electric or weak dipole moment.
Evaluation of three oil spill laboratory dispersant effectiveness tests
Sullivan, D.; Farlow, J.; Sahatjian, K.A.
1993-01-01
EPA evaluated three laboratory methods: the Revised Standard Dispersant Effectiveness Test currently used (and currently required by regulation) in the United States, the Swirling Flask Test (developed by Environment Canada), and the IFP-Dilution Test (used in France and other European countries). Six test oils and three dispersants were evaluated; dispersants were applied to the oil at an average 1:10 ratio (dispersant to oil) for each of the three laboratory methods. A screening criterion was established that required a combination that gave at least 20 percent effectiveness results. The selected combination turned out to be Prudhoe Bay crude oil (an EPA-American Petroleum Institute Standard Reference Oil) and the dispersant Corexit 9527. EPA's evaluation concluded that the three tests give similar precision results, but that the Swirling Flask Test was fastest, cheapest, simplest, and required least operator skill.
From magnetically doped topological insulator to the quantum anomalous Hall effect
He Ke; Ma Xu-Cun; Chen Xi; Lü Li; Wang Ya-Yu; Xue Qi-Kun
2013-01-01
Quantum Hall effect (QHE),as a class of quantum phenomena that occur in macroscopic scale,is one of the most important topics in condensed matter physics.It has long been expected that QHE may occur without Landau levels so that neither extemal magnetic field nor high sample mobility is required for its study and application.Such a QHE free of Landau levels,can appear in topological insulators (TIs) with ferromagnetism as the quantized version of the anomalous Hall effect,i.e.,quantum anomalous Hall (QAH) effect.Here we review our recent work on experimental realization of the QAH effect in magnetically doped TIs.With molecular beam epitaxy,we prepare thin films of Cr-doped (Bi,Sb)2Te3 TIs with wellcontrolled chemical potential and long-range ferromagnetic order that can survive the insulating phase.In such thin films,we eventually observed the quantization of the Hall resistance at h/e2 at zero field,accompanied by a considerable drop in the longitudinal resistance.Under a strong magnetic field,the longitudinal resistance vanishes,whereas the Hall resistance remains at the quantized value.The realization of the QAH effect provides a foundation for many other novel quantum phenomena predicted in TIs,and opens a route to practical applications of quantum Hall physics in low-power-consumption electronics.
Effectiveness of chemical dispersants under breaking wave conditions
Mackay, D. [Univ. of Toronto, Ontario (Canada). Chemical Engineering Dept.
1995-06-01
A study is described in which the effectiveness of Corexit 9527 on Alaskan North Slope crude oil was assessed by conducting laboratory and wave basin tests. Three laboratory dispersant test systems were used: the MNS, Labofina and EXDET procedures. It was concluded that for the present purposes the EXDET system was most suitable, and it was used for subsequent tests. The dependence of effectiveness on dispersant to oil ratio, extent of weathering, temperature, water salinity, energy level and the presence of emulsified water (mousse) were determined. The results were used to guide a subsequent program of tests at the Esso Resources Canada Ltd. Wave Basin in Calgary in which the effectiveness was determined under breaking wave conditions. From the results a correlating equation was developed to express effectiveness as a function of dispersant to oil ratio and delay time between dispersant application and the onset of breaking waves. Significant quantities of oil were dispersed under breaking wave conditions, even at what are conventionally regarded as low dispersant to oil ratios. The implications of the results for assessing the actual and potential extent of chemical dispersion following the Exxon Valdez spill in March 1989 are discussed. Assuming that the dispersion efficiencies from the wave basin could have been achieved at the incident, it is believed that because of the onset of the storm with breaking wave conditions some 60 hours after the grounding, approximately 38% of the spilled oil could have been dispersed had available dispersants been applied to the spilled oil in the days following the grounding.
Experimental research of electron beam instability on the Doppler anomalous effect
Beam instability caused by the Doppler anomalous effect (DAE) at electron beam interaction with the decelerating electrodynamic system (a resonator with a single-thread spiral and a resonator with a space-periodic structure) placed in the external homogeneous field are studied experimentally to investigate main mechanisms of instability of charged particle beams. Such general properties of DAE as resonance conditions for instability excitation, increase of the internal energy of oscillators (Larmor and Langmuir) during radiation, energy ratios for slow cyclotron and plasma waves of an electron beam are studied. Good agreement between experimental and theoretical results is obtained
3d Transition Metal Adsorption Induced the valley-polarized Anomalous Hall Effect in Germanene
Zhou, P.; Sun, L. Z.
2016-06-01
Based on DFT + U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous Hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atoms on its surface. A finite valley Hall voltage can be easily detected in their nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and even reversible valley Hall voltage can be archived by shifting the Fermi energy of the systems. Such versatile features of the systems show potential in next generation electronics devices.
Di Gennaro, Emiliano; Savo, Salvatore; Andreone, Antonello; Morello, Davide; Galdi, Vincenzo; Castaldi, Giuseppe; Pierro, Vincenzo
2008-01-01
We present the key results from a comprehensive study of the refraction and focusing properties of a two-dimensional dodecagonal photonic ``quasicrystal'' (PQC), carried out via both full-wave numerical simulations and microwave measurements on a slab made of alumina rods inserted in a parallel-plate waveguide. We observe anomalous refraction and focusing in several frequency regions, confirming some recently published results. However, our interpretation, based on numerical and experimental evidence, differs substantially from the one in terms of ``effective negative refractive-index'' that was originally proposed. Instead, our study highlights the critical role played by short-range interactions associated with local order and symmetry.
Hysteretic magnetoresistance and unconventional anomalous Hall effect in the frustrated magnet TmB4
Sunku, Sai Swaroop; Kong, Tai; Ito, Toshimitsu; Canfield, Paul C.; Shastry, B. Sriram; Sengupta, Pinaki; Panagopoulos, Christos
2016-05-01
We study TmB4, a frustrated magnet on the Archimedean Shastry-Sutherland lattice, through magnetization and transport experiments. The lack of anisotropy in resistivity shows that TmB4 is an electronically three-dimensional system. The magnetoresistance (MR) is hysteretic at low temperature even though a corresponding hysteresis in magnetization is absent. The Hall resistivity shows unconventional anomalous Hall effect (AHE) and is linear above saturation despite a large MR. We propose that complex structures at magnetic domain walls may be responsible for the hysteretic MR and may also lead to the AHE.
Global Constraints on Anomalous Triple Gauge Couplings in the Effective Field Theory Approach
Falkowski, Adam; González-Alonso, Martín; Greljo, Admir; Marzocca, David
2016-01-01
We present a combined analysis of LHC Higgs data (signal strengths) together with LEP-2 W W production measurements. To characterize possible deviations from the standard model (SM) predictions, we employ the framework of an effective field theory (EFT) where the SM is extended by higher-dimensional operators suppressed by the mass scale of new physics Λ . The analysis is performed consistently at the order Λ-2 in the EFT expansion keeping all the relevant operators. While the two data sets suffer from flat directions, together they impose stringent model-independent constraints on the anomalous triple gauge couplings.
Anomalous transport model study of chiral magnetic effects in heavy ion collisions
Sun, Yifeng; Li, Feng
2016-01-01
Using an anomalous transport model for massless quarks, we study the effect of magnetic field on the elliptic flows of quarks and antiquarks in relativistic heavy ion collisions. With initial conditions from a blast wave model and assuming that the strong magnetic field produced in non-central heavy ion collisions can last for a sufficiently long time, we obtain an appreciable electric quadrupole moment in the transverse plane of a heavy ion collision, which subsequently leads to a splitting between the elliptic flows of quarks and antiquarks as expected from the chiral magnetic wave formed in the produced QGP and observed in experiments at the Relativistic Heavy Ion Collider (RHIC).
Anomalous Hall effect of heavy holes in Ⅲ-Ⅴ semiconductor quantum wells
Wang Zhi-Gang; Zhang Ping
2007-01-01
The anomalous Hall effect of heavy holes in semiconductor quantum wells is studied in the intrinsic transport regime, where the Berry curvature governs the Hall current properties. Based on the first-order perturbation of wave function the expression of the Hall conductivity the same as that from the semiclassical equation of motion of the Bloch particles is derived. The dependence of Hall conductivity on the system parameters is shown. The amplitude of Hall conductivity is found to be balanced by a competition between the Zeeman splitting and the spin-orbit splitting.
Nonadiabatic effects in ultracold molecules via anomalous linear and quadratic Zeeman shifts.
McGuyer, B H; Osborn, C B; McDonald, M; Reinaudi, G; Skomorowski, W; Moszynski, R; Zelevinsky, T
2013-12-13
Anomalously large linear and quadratic Zeeman shifts are measured for weakly bound ultracold 88Sr2 molecules near the intercombination-line asymptote. Nonadiabatic Coriolis coupling and the nature of long-range molecular potentials explain how this effect arises and scales roughly cubically with the size of the molecule. The linear shifts yield nonadiabatic mixing angles of the molecular states. The quadratic shifts are sensitive to nearby opposite f-parity states and exhibit fourth-order corrections, providing a stringent test of a state-of-the-art ab initio model. PMID:24483652
McGuyer, B H; McDonald, M; Reinaudi, G; Skomorowski, W; Moszynski, R; Zelevinsky, T
2013-01-01
Anomalously large linear and quadratic Zeeman shifts are measured for weakly bound ultracold $^{88}$Sr$_2$ molecules near the intercombination line asymptote. Nonadiabatic Coriolis coupling and the nature of long-range molecular potentials explain how this effect arises and scales roughly cubically with the size of the molecule. The linear shifts yield nonadiabatic mixing angles of the molecular states. The quadratic shifts are sensitive to fourth-order contributions and to nearby opposite $f$-parity states, and provide a stringent test of a state-of-the-art ab initio model.
Numerous laboratory test systems have been developed for the comparison of efficacy between various chemical oil dispersant formulations. However, for the assessment of chemical dispersant effectiveness under realistic sea state, test protocols are required to produce hydrodynam...
Dispersant effectiveness testing in cold water and brash ice
Owens, C.K. [ExxonMobil Upstream Research Co., Houston, TX (United States); Belore, R.S. [S.L. Ross Environmental Research Ltd., Ottawa, ON (Canada)
2004-07-01
This paper presents the results of a wave tank test conducted at OHMSETT to determine the effectiveness of chemical dispersants on oil spilled in brash ice. In particular, Alaska North Slope, Hibernia and Chayvo crude oils were tested and the factors affecting the dispersion process were examined. The dispersant, Corexit 9527 was tested on both fresh and weathered oils under cold water and icy conditions. Dispersion was observed for waves with 17 cm average height and a 5.5 second period, as well as with waves of 33 cm average height and 4 second period. The energy level in the tank was much lower than typically found in open waters. The presence of ice enhanced the dispersion processes compared to what would occur in similar open water conditions. Higher wave energy levels were needed to disperse oil in rings containing a 4/10 ice cover than in rings containing a 8/10 ice cover. This result is likely due to the the higher surface activity observed in the 8/10 covered rings. More than 90 per cent dispersion was achieved in all tests with fresh crude oil in ice. For weathered crudes, the dispersion was less effective but still significant. 11 refs., 4 tabs., 12 figs.
The effectiveness of dispersants under various temperature and salinity regimes
Fingas, M.; Fieldhouse, B.; Wang, Z. [Environment Canada, Ottawa, ON (Canada). Emergencies Science and Technology Div; Environment Canada, Ottawa, ON (Canada). Environmental Technology Centre
2005-07-01
A series of tests were conducted to determine the effectiveness of dispersants in Arctic waters where salinity and temperature interactions play a critical role. In particular, Corexit 9500 was tested on Alaska North Slope oil at different temperatures and salinity using the ASTM standard test and variations of this test. Results were compared to the only historically reported test in which both temperature and salinity were changed over a range of values. This series of tests demonstrated that there is an interaction between salinity, temperature and dispersant effectiveness. It was shown that conventional and currently available dispersants are nearly ineffective at 0 salinity. Dispersant effectiveness peaks at 20 to 40 units of salinity, depending on the type of dispersant. Corexit is less sensitive to salinity, while Corexit 9527 is more sensitive to salinity. There is a smooth gradient of effectiveness with salinity both as the salinity rises to a peak point of effectiveness and as it exceeds this value. Results from the 2 field trials in fresh water suggest that laboratory tests correctly conclude that the effectiveness of dispersants is very low in freshwater. The study also examined several analytical factors such as the total petroleum hydrocarbon (TPH) versus relative petroleum hydrocarbon (RPH) methods, specific versus general calibration curves, and automatic versus manual baseline placement. The analytical variations of effectiveness by RPH or TPH methods do not affect the fundamental relationship between salinity and temperature. 6 refs., 6 tabs., 8 figs.
Identification of Dispersion Effects in 2k Factorial Design
Viviane Leite Mattos; Pedro Alberto Barbetta; Dalton Francisco de Andrade
2010-01-01
The identification of dispersion effects is a very important stage in developing robust products and processes. Several methods to identify dispersion effects are present in statistical and quality engineering literature, especially methods which use 2K or 2K-p
unreplicated factorial designs, such as Box-Meyer, Harvey, Brenemann-Nair and Bergman- Hynén methods. In this paper we considered generalizations of these methods for replicated
experiments, and compare...
Shade Effects on the Dispersal of Airborne Hemileia vastatrix Uredospores.
Boudrot, Audrey; Pico, Jimmy; Merle, Isabelle; Granados, Eduardo; Vílchez, Sergio; Tixier, Philippe; Filho, Elías de Melo Virginio; Casanoves, Fernando; Tapia, Ana; Allinne, Clémentine; Rice, Robert A; Avelino, Jacques
2016-06-01
Hemileia vastatrix caused a severe epidemic in Central America in 2012-13. The gradual development of that epidemic on nearly a continental scale suggests that dispersal at different scales played a significant role. Shade has been proposed as a way of reducing uredospore dispersal. The effect of shade (two strata: Erythrina poeppigiana below and Chloroleucon eurycyclum above) and full sun on H. vastatrix dispersal was studied with Burkard traps in relation to meteorological records. Annual and daily patterns of dispersal were observed, with peaks of uredospore capture obtained during wet seasons and in the early afternoon. A maximum of 464 uredospores in 1 day (in 14.4 m(3) of air) was recorded in October 2014. Interactions between shade/full sun and meteorological conditions were found. Rainfall, possibly intercepted by tree cover and redistributed by raindrops of higher kinetic energy, was the main driver of uredospore dispersal under shade. Wind gusts reversed this effect, probably by inhibiting water accumulation on leaves. Wind gusts also promoted dispersal under dry conditions in full sun, whereas they had no effect under shaded conditions, probably because the canopy blocked the wind. Our results indicate the importance of managing shade cover differentially in rainy versus dry periods to control the dispersal of airborne H. vastatrix uredospores. PMID:26828230
Dispersive force between dissimilar materials: Geometrical effects
We calculate the Casimir force or dispersive van der Waals force between a spherical nanoparticle and a planar substrate, both with arbitrary dielectric properties. We show that the force between the sphere and half-space can be calculated through the interacting surface plasmons of the bodies. Using a Spectral Representation formalism, we show that the force of a sphere made of a material A and a half-space made of a material B differs from the case when the sphere is made of B, and the half-space is made of A. We find that the difference depends on the plasma frequency of the materials, the geometry, and the distance of separation between the sphere and half-space. The differences show the importance of the geometry, and make evident the necessity of realistic descriptions of the system beyond the Derjaguin Approximation or Proximity Theorem Approximation
Large anomalous Hall effect in Pt interfaced with perpendicular anisotropy ferrimagnetic insulator
Tang, Chi; Sellappan, Pathikumar; Liu, Yawen; Garay, Javier; Shi, Jing; Shines Team
We demonstrate the strain induced perpendicular magnetic anisotropy (PMA) in a ferrimagnetic insulator (FMI), Tm3Fe5O12 (TIG) and the first observation of large anomalous Hall effect (AHE) in TIG/Pt bilayers. Atomically flat TIG films were deposited by a laser molecular beam epitaxy system on (111)-orientated substituted gadolinium gallium garnet substrates. The strength of PMA could be effectively tuned by controlling the oxygen pressure during deposition. Sharp squared anomalous Hall hysteresis loops were observed in bilayers of TIG/Pt over a range of thicknesses of Pt, with the maximum AHE conductivity reaching 1 S/cm at room temperature. The AHE vanishes when a 5 nm Cu layer was inserted between Pt and TIG, strongly indicating the proximity-induced ferromagnetism in Pt. The large AHE in the bilayer structures demonstrates a potential use of PMA-FMI related heterostructures in spintronics. This work was supported as part of the SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # SC0012670.
Effect of Solvation Film on the Viscosity of Colloidal Dispersions
PENG Chang-Sheng; GU Qing-Bao; SONG Shao-Xian
2005-01-01
Viscosity is one of the most important properties of colloids in mixing, transportation, stabilization, energy consumption, and so on. According to Einstein's viscosity equation, the viscosity of a colloidal dispersion increases with the increase of particle concentration. And the equation can be applicable to all micro-particle dispersions, because the effect of solvation films coated on particles can be neglectable in that case. But with the decrease of particle size to nano-scale, the formation of solvation films on nano-particles can greatly affect the viscosity of a dispersion, and Einstein's equation may not be applicable to this case. In this work, one kind of micro-size silica particle and two kinds of nano-size silica particles were used to investigate the effect of solvation films on dispersion viscosity, dispersed in water and ethyl alcohol solvents, respectively. The results of theoretical calculation and experimental investigation show that the increase of viscosity is contributed from solvation films by more than 95 percent for nano-particle dispersions, while less than 10 percent for micro-particle dispersions.
The interaction of chemical dispersants and suspended sediments with crude oil influences the fate and transport of oil spills in coastal waters. A wave tank study was conducted to investigate the effects of chemical dispersants and mineral fines on the dispersion of oil and the ...
Anomalous Hall effect in the prospective spintronic material Eu1‑x Gd x O integrated with Si
Parfenov, Oleg E.; Averyanov, Dmitry V.; Tokmachev, Andrey M.; Taldenkov, Alexander N.; Storchak, Vyacheslav G.
2016-06-01
Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm‑1 in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies.
Anomalous Hall effect in the prospective spintronic material Eu1-x Gd x O integrated with Si.
Parfenov, Oleg E; Averyanov, Dmitry V; Tokmachev, Andrey M; Taldenkov, Alexander N; Storchak, Vyacheslav G
2016-06-01
Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm(-1) in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies. PMID:27165844
Anomalous skin effects in relativistic parallel propagating weakly magnetized electron plasma waves
Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized electron plasma is presented and general expressions for longitudinal and transverse permittivites are derived. It is found that the penetration depth for R- and L-waves increases as we move from non-relativistic to highly relativistic regime. The ambient magnetic field reduces/enhances the skin effects for R-wave/L-wave as the strength of the field is increased. In general, the weak magnetic field effects are pronounced for the weakly relativistic regime as compared with other relativistic cases. The results are also graphically illustrated. On switching off the magnetic field, previous results for field free case are retrieved [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Priniples of Plasma Electrodynamics (Springer-Verlag, Berlin, Heidelberg, 1984), Vol. 9, p. 106].
Nanoparticles modulate autophagic effect in a dispersity-dependent manner
Huang, Dengtong; Zhou, Hualu; Gao, Jinhao
2015-09-01
Autophagy plays a key role in human health and disease, especially in cancer and neurodegeneration. Many autophagy regulators are developed for therapy. Diverse nanomaterials have been reported to induce autophagy. However, the underlying mechanisms and universal rules remain unclear. Here, for the first time, we show a reliable and general mechanism by which nanoparticles induce autophagy and then successfully modulate autophagy via tuning their dispersity. Various well-designed univariate experiments demonstrate that nanomaterials induce autophagy in a dispersity-dependent manner. Aggregated nanoparticles induce significant autophagic effect in comparison with well-dispersed nanoparticles. As the highly stable nanoparticles may block autophagic degradation in autolysosomes, endocytosis and intracellular accumulation of nanoparticles can be responsible for this interesting phenomenon. Our results suggest dispersity-dependent autophagic effect as a common cellular response to nanoparticles, reveal the relationship between properties of nanoparticles and autophagy, and offer a new alternative way to modulate autophagy.
Antonov, N. V.; Kostenko, M. M.
2015-11-01
The field-theoretic renormalization group and the operator product expansion are applied to the model of passive vector (magnetic) field advected by a random turbulent velocity field. The latter is governed by the Navier-Stokes equation for compressible fluid, subject to external random force with the covariance ∝δ (t -t') k4 -d -y , where d is the dimension of space and y is an arbitrary exponent. From physics viewpoints, the model describes magnetohydrodynamic turbulence in the so-called kinematic approximation, where the effects of the magnetic field on the dynamics of the fluid are neglected. The original stochastic problem is reformulated as a multiplicatively renormalizable field-theoretic model; the corresponding renormalization group equations possess an infrared attractive fixed point. It is shown that various correlation functions of the magnetic field and its powers demonstrate anomalous scaling behavior in the inertial-convective range already for small values of y . The corresponding anomalous exponents, identified with scaling (critical) dimensions of certain composite fields ("operators" in the quantum-field terminology), can be systematically calculated as series in y . The practical calculation is performed in the leading one-loop approximation, including exponents in anisotropic contributions. It should be emphasized that, in contrast to Gaussian ensembles with finite correlation time, the model and the perturbation theory presented here are manifestly Galilean covariant.
Antonov, N V; Kostenko, M M
2015-11-01
The field-theoretic renormalization group and the operator product expansion are applied to the model of passive vector (magnetic) field advected by a random turbulent velocity field. The latter is governed by the Navier-Stokes equation for compressible fluid, subject to external random force with the covariance ∝ δ(t-t')k(4-d-y), where d is the dimension of space and y is an arbitrary exponent. From physics viewpoints, the model describes magnetohydrodynamic turbulence in the so-called kinematic approximation, where the effects of the magnetic field on the dynamics of the fluid are neglected. The original stochastic problem is reformulated as a multiplicatively renormalizable field-theoretic model; the corresponding renormalization group equations possess an infrared attractive fixed point. It is shown that various correlation functions of the magnetic field and its powers demonstrate anomalous scaling behavior in the inertial-convective range already for small values of y. The corresponding anomalous exponents, identified with scaling (critical) dimensions of certain composite fields ("operators" in the quantum-field terminology), can be systematically calculated as series in y. The practical calculation is performed in the leading one-loop approximation, including exponents in anisotropic contributions. It should be emphasized that, in contrast to Gaussian ensembles with finite correlation time, the model and the perturbation theory presented here are manifestly Galilean covariant. PMID:26651785
Anomalous memory effect in the breakdown of low-pressure argon in a long discharge tube
The characteristics of breakdown of argon in a long tube (with a gap length of 75 cm and diameter of 2.8 cm) at pressures of 1 and 5 Torr and stationary discharge currents of 5–40 mA were studied experimentally. The breakdown was initiated by paired positive voltage pulses with a rise rate of ∼108–109 V/s and duration of ∼1–10 ms. The time interval between pairs was varied in the range of Τ ∼ 0.1–1 s, and that between pulses in a pair was varied from τ = 0.4 ms to ≈Τ/2. The aim of this work was to detect and study the so-called “anomalous memory effect” earlier observed in breakdown in nitrogen. The effect consists in the dynamic breakdown voltage in the second pulse in a pair being higher than in the first pulse (in contrast to the “normal” memory effect, in which the relation between the breakdown voltages is opposite). It is found that this effect is observed when the time interval between pairs of pulses is such that the first pulse in a pair is in the range of the normal memory effect of the preceding pair (under the given conditions, Τ ≈ 0.1–0.4 s). In this case, at τ ∼ 10 ms, the breakdown voltage of the second pulse is higher than the reduced breakdown voltage of the first pulse. Optical observations of the ionization wave preceding breakdown in a long tube show that, in the range of the anomalous memory effect and at smaller values of τ, no ionization wave is detected before breakdown in the second pulse. A qualitative interpretation of the experimental results is given
Boglaienko, Daria; Tansel, Berrin
2016-06-15
When three or more high and low energy substrates are mixed, wetting order can significantly affect the behavior of the mixture. We analyzed the phase distribution of fresh floating Louisiana crude oil into dispersed, settled and floating phases depending on the exposure sequence to Corexit 9500A (dispersant) and granular materials. In the experiments artificial sea water at salinity 34‰ was used. Limestone (2.00-0.300 mm) and quartz sand (0.300-0.075 mm) were used as the natural granular materials. Dispersant Corexit 9500A increased the amount of dispersed oil up to 33.76 ± 7.04%. Addition of granular materials after the dispersant increased dispersion of oil to 47.96 ± 1.96%. When solid particles were applied on the floating oil before the dispersant, oil was captured as oil-particle aggregates and removed from the floating layer. However, dispersant addition led to partial release of the captured oil, removing it from the aggregated form to the dispersed and floating phases. There was no visible oil aggregation with the granular materials when quartz or limestone was at the bottom of the flask before the addition of oil and dispersant. The results show that granular materials can be effective when applied from the surface for aggregating or dispersing oil. However, the granular materials in the sediments are not effective neither for aggregating nor dispersing floating oil. PMID:27019358
Resonant cavity mode dependence of anomalous and inverse spin Hall effect
The direct current electric voltage induced by the Inverse Spin Hall Effect (ISHE) and Anomalous Hall Effect (AHE) was investigated in the TE011 and TE102 cavities. The ISHE and AHE components were distinguishable through the fitting of the voltage spectrum. The unwanted AHE was minimized by placing the DUT (Device Under Test) at the center of both the TE011 and TE102 cavities. The voltage of ISHE in the TE011 cavity was larger than that in the TE102 cavity due to the higher quality factor of the former. Despite optimized centering, AHE voltage from TE011 cavity was also higher. The reason was attributed to the E-field distribution inside the cavity. In the case of the TE011 cavity, the DUT was easily exposed to the E-field in all directions. Therefore, the parasitic AHE voltage in the TE102 cavity was less sensitive than that in the TE011 cavity to decentering problem
Anomalous finite-size effects for the mean-squared gyration radius of Gaussian random knots
Anomalously strong finite-size effects have been observed for the mean square radius of gyration R2K of Gaussian random polygons with a fixed knot K as a function of the number N of polygonal nodes. Through computer simulations with N2K can be approximated by a power law, R2K∼N2νKeff, for several knots, where the effective exponents νKeff are larger than 0.5 and less than 0.6. Furthermore, a crossover occurs for the gyration radius of the trivial knot, when N is roughly equal to the characteristic length Nc of random knotting. Assuming an asymptotic fitting formula, we also discuss possible asymptotic behaviours for RK2 of Gaussian random polygons. (author). Letter-to-the-editor
Scaling of Anomalous Hall Effects in Facing-Target Reactively Sputtered Fe4N Films
Zhang, Yan
2015-05-13
Anomalous Hall effect (AHE) in the reactively sputtered epitaxial and polycrystalline γ′-Fe4N films is investigated systematically. The Hall resistivity is positive in the entire temperature range. The magnetization, carrier density and grain boundaries scattering have a major impact on the AHE scaling law. The scaling exponent γ in the conventional scaling of is larger than 2 in both the epitaxial and polycrystalline γ′-Fe4N films. Although γ>2 has been found in heterogeneous systems due to the effects of the surface and interface scattering on AHE, γ>2 is not expected in homogenous epitaxial systems. We demonstrated that γ>2 results from residual resistivity (ρxx0) in γ′-Fe4N films. Furthermore, the side-jump and intrinsic mechanisms are dominant in both epitaxial and polycrystalline samples according to the proper scaling relation.
Effect of polysaccharides on the gelatinization properties of cornstarch dispersions.
Xu, Zhiting; Zhong, Fang; Li, Yue; Shoemaker, Charles F; Yokoyama, Wallace H; Xia, Wenshui
2012-01-18
Konjac glucomannan (KG, neutral), carboxymethylcellulose (CMC, negatively charged), and chitosan (positively charged) were added to cornstarch dispersions to study the effect of polysaccharide-starch interactions on starch gelatinization properties. Pasting and retrogradation properties were measured with a rheometer and DSC. Swelling properties of the starch granules were determined by solubility index, swelling power, and particle size distribution. Depending on the nature of the different polysaccharides, viscosities of cornstarch dispersions were affected differently. The particle size distributions were not influenced by the addition of any of the polysaccharides. Swelling results showed that the KG and CMC molecules interacted with the released or partly released amylose in the cornstarch dispersions. This was correlated with the short-term retrogradation of the starch pastes being retarded by the additions of KG and CMC. However, the chitosan molecules appeared not to associate with the amylose, so the retrogradation of the chitosan-cornstarch dispersions was not retarded. PMID:22224479
Toxic effects of oil and dispersant on marine microalgae.
Garr, Amber L; Laramore, Susan; Krebs, William
2014-12-01
To better understand the potential impacts of the deepwater horizon oil spill on lower trophic level food sources, a series of toxicological laboratory experiments were conducted with two microalgae species. The acute toxicity of oil (tar mat and MC252 crude oil), dispersant (Corexit 9500A), and dispersed oil on growth inhibition (IC50) and motility of Isochrysis galbana and Chaetoceros sp. were determined. There was no impact on cell division (growth) for microalgae exposed to both oil types and mean motility of I. galbana never dropped below 79 %. However, the addition of dispersant inhibited cell division and motility within 24 h, with Chaetoceros sp. being more susceptible to sublethal effects than I. galbana. These results highlight microalgae sensitivity to the use of dispersants in bioremediation processes, which may be a concern for long-term impacts on fisheries recruitment. PMID:25283369
Reducing losses and dispersion effects in multilayer metamaterial tunnelling devices
This paper focuses on reduction of losses and dispersion effects on tunnelling through waveguides filled with metamaterial. It will be shown that these unwanted effects could be reduced by dividing the metamaterial into several regions separated by air slabs. In the first part, these effects will be studied for isotropic left-handed media (LHM). Later this will be substituted by an anisotropic magnetic medium which will lead to a practical realization with broadside coupled split ring resonators (BC-SRRs). Finally, it is shown that quasi-perfect tunnelling is possible, even in the presence of unavoidable losses and dispersion in the metamaterial
Verhoef, A. J.; Zhu, L.; Israelsen, Stine Møller; Grüner-Nielsen, Lars Erik; Unterhuber, A.; Kautek, W.; Rottwitt, Karsten; Baltuška, A.; Fernandez, Alicia Jimenez
2015-01-01
We present an Yb-fiber oscillator with an all-polarizationmaintaining cavity with a higher-order-mode fiber for dispersion compensation. The polarization maintaining higher order mode fiber introduces not only negative second order dispersion but also negative third order dispersion in the cavity...
Anomalous Hall effect and magnetoresistance behavior in Co/Pd1−xAgx multilayers
Guo, Z. B.
2013-02-13
In this paper, we report anomalous Hall effect (AHE) correlated with the magnetoresistance behavior in [Co/Pd1-xAg x]n multilayers. For the multilayers with n = 6, the increase in Ag content from x = 0 to 0.52 induces the change in AHE sign from negative surface scattering-dominated AHE to positive interface scattering-dominated AHE, which is accompanied with the transition from anisotropy magnetoresistance (AMR) dominated transport to giant magnetoresistance (GMR) dominated transport. For n = 80, scaling analysis with Rs ∝ρ xx γ yields γ ∼ 3.44 for x = 0.52 which presents GMR-type transport, in contrast to γ ∼ 5.7 for x = 0 which presents AMR-type transport. © 2013 American Institute of Physics.
Theory for the anomalous electron transport in Hall effect thrusters. II. Kinetic model
Lafleur, T.; Baalrud, S. D.; Chabert, P.
2016-05-01
In Paper I [T. Lafleur et al., Phys. Plasmas 23, 053502 (2016)], we demonstrated (using particle-in-cell simulations) the definite correlation between an anomalously high cross-field electron transport in Hall effect thrusters (HETs), and the presence of azimuthal electrostatic instabilities leading to enhanced electron scattering. Here, we present a kinetic theory that predicts the enhanced scattering rate and provides an electron cross-field mobility that is in good agreement with experiment. The large azimuthal electron drift velocity in HETs drives a strong instability that quickly saturates due to a combination of ion-wave trapping and wave-convection, leading to an enhanced mobility many orders of magnitude larger than that expected from classical diffusion theory. In addition to the magnetic field strength, B0, this enhanced mobility is a strong function of the plasma properties (such as the plasma density) and therefore does not, in general, follow simple 1 /B02 or 1 /B0 scaling laws.
Global constraints on anomalous triple gauge couplings in effective field theory approach
Falkowski, Adam; Greljo, Admir; Marzocca, David
2016-01-01
We present a combined analysis of LHC Higgs data (signal strengths) together with LEP-2 WW production measurements. To characterize possible deviations from the Standard Model (SM) predictions, we employ the framework of an Effective Field Theory (EFT) where the SM is extended by higher-dimensional operators suppressed by the mass scale of new physics $\\Lambda$. The analysis is performed consistently at the order $\\Lambda^{-2}$ in the EFT expansion keeping all the relevant operators. While the two data sets suffer from flat directions, together they impose stringent model-independent constraints on the anomalous triple gauge couplings. As a side product, we provide the results of the combined fit in different EFT bases.
Hwang, Kyusung; Kim, Yong Baek
2016-01-01
We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293
Hwang, Kyusung; Kim, Yong Baek
2016-01-01
We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293