Rochette, Sophie; Ten Eyck, Gregory A.; Pluym, Tammy; Lilly, Michael P.; Carroll, Malcolm S.; Pioro-Ladrière, Michel
2015-03-01
Silicon quantum dots are promising candidates for quantum information processing as spin qubits with long coherence time. We present electrical transport measurements on a silicon metal-oxide-semiconductor (MOS) double quantum dot (DQD). First, Coulomb diamonds measurements demonstrate the one-electron regime at a relatively high temperature of 1.5 K. Then, the 8 mK stability diagram shows Pauli spin blockade with a large singlet-triplet separation of approximatively 0.40 meV, pointing towards a strong lifting of the valley degeneracy. Finally, numerical simulations indicate that by integrating a micro-magnet to those devices, we could achieve fast spin rotations of the order of 30 ns. Those results are part of the recent body of work demonstrating the potential of Si MOS DQD as reliable and long-lived spin qubits that could be ultimately integrated into modern electronic facilities. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Pauli Spin Blockade and the Ultrasmall Magnetic Field Effect
Danon, Jeroen
2013-08-06
Based on the spin-blockade model for organic magnetoresistance, we present an analytic expression for the polaron-bipolaron transition rate, taking into account the effective nuclear fields on the two sites. We reveal the physics behind the qualitatively different magnetoconductance line shapes observed in experiment, as well as the ultrasmall magnetic field effect (USFE). Since our findings agree in detail with recent experiments, they also indirectly provide support for the spin-blockade interpretation of organic magnetoresistance. In addition, we predict the existence of a similar USFE in semiconductor double quantum dots tuned to the spin-blockade regime.
Pauli Spin Blockade and the Ultrasmall Magnetic Field Effect
Danon, Jeroen; Wang, Xuhui; Manchon, Aurelien
2013-01-01
Based on the spin-blockade model for organic magnetoresistance, we present an analytic expression for the polaron-bipolaron transition rate, taking into account the effective nuclear fields on the two sites. We reveal the physics behind the qualitatively different magnetoconductance line shapes observed in experiment, as well as the ultrasmall magnetic field effect (USFE). Since our findings agree in detail with recent experiments, they also indirectly provide support for the spin-blockade interpretation of organic magnetoresistance. In addition, we predict the existence of a similar USFE in semiconductor double quantum dots tuned to the spin-blockade regime.
Energy Technology Data Exchange (ETDEWEB)
Wang, Jiyin; Huang, Shaoyun, E-mail: hqxu@pku.edu.cn, E-mail: syhuang@pku.edu.cn; Lei, Zijin [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Pan, Dong; Zhao, Jianhua [State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Xu, H. Q., E-mail: hqxu@pku.edu.cn, E-mail: syhuang@pku.edu.cn [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Division of Solid State Physics, Lund University, Box 118, S-22100 Lund (Sweden)
2016-08-01
We demonstrate direct measurements of the spin-orbit interaction and Landé g factors in a semiconductor nanowire double quantum dot. The device is made from a single-crystal pure-phase InAs nanowire on top of an array of finger gates on a Si/SiO{sub 2} substrate and the measurements are performed in the Pauli spin-blockade regime. It is found that the double quantum dot exhibits a large singlet-triplet energy splitting of Δ{sub ST} ∼ 2.3 meV, a strong spin-orbit interaction of Δ{sub SO} ∼ 140 μeV, and a large and strongly level-dependent Landé g factor of ∼12.5. These results imply that single-crystal pure-phase InAs nanowires are desired semiconductor nanostructures for applications in quantum information technologies.
Negative differential resistance in nanoscale transport in the Coulomb blockade regime
International Nuclear Information System (INIS)
Parida, Prakash; Lakshmi, S; Pati, Swapan K
2009-01-01
Motivated by recent experiments, we have studied the transport behavior of coupled quantum dot systems in the Coulomb blockade regime using the master (rate) equation approach. We explore how electron-electron interactions in a donor-acceptor system, resembling weakly coupled quantum dots with varying charging energy, can modify the system's response to an external bias, taking it from normal Coulomb blockade behavior to negative differential resistance (NDR) in the current-voltage characteristics.
On spinfoam models in large spin regime
International Nuclear Information System (INIS)
Han, Muxin
2014-01-01
We study the semiclassical behavior of Lorentzian Engle–Pereira–Rovelli–Livine (EPRL) spinfoam model, by taking into account the sum over spins in the large spin regime. We also employ the method of stationary phase analysis with parameters and the so-called, almost analytic machinery, in order to find the asymptotic behavior of the contributions from all possible large spin configurations in the spinfoam model. The spins contributing the sum are written as J f = λj f , where λ is a large parameter resulting in an asymptotic expansion via stationary phase approximation. The analysis shows that at least for the simplicial Lorentzian geometries (as spinfoam critical configurations), they contribute the leading order approximation of spinfoam amplitude only when their deficit angles satisfy γ Θ-ring f ≤λ −1/2 mod 4πZ. Our analysis results in a curvature expansion of the semiclassical low energy effective action from the spinfoam model, where the UV modifications of Einstein gravity appear as subleading high-curvature corrections. (paper)
Energy Technology Data Exchange (ETDEWEB)
Goettel, Stefan
2015-05-22
In this thesis, we study two recently developed methods to tackle low-dimensional correlated quantum systems. In the first part, we benchmark the extension of the functional renormalization group to spin-systems. We apply it to the two-dimensional XXZ model and reproduce the prediction for the phase transition from planar to axial ordering at the isotropic point. The interpretation of the critical scale (where the flow of the susceptibility diverges) as the critical temperature of the system can be questioned, since it yields only good results in the Ising limit. Especially near the isotropic point, this interpretation becomes unsatisfactory as the Mermin-Wagner theorem is violated. We discuss several problems of the method and conclude that it should only be used to explore phase diagrams. In the second part, we extend previous works to two-level quantum dots in the Coulomb blockade regime with special hopping matrices in nonequilibrium, e.g., the Kondo model, to the generic form, including ferromagnetic leads, spin-orbit interactions etc. The dot and the transport observables are determined completely by the hybridization matrix, leading to one of our major results that all these models can be mapped to the Anderson impurity model with ferromagnetic leads. We investigate this model with a well-controlled real-time renormalization group approach and justify the results of a poor man's scaling analysis. By using a singular value decomposition of the tunneling matrix we can rotate the model to the anisotropic Kondo model in the high-energy regime to solve the flow equations analytically. With this, we calculate the stationary dot magnetization and the current. The minimum of the magnetization is found to be an ellipsoid as function of the magnetic field, where the stretching factor determines the distance to the scaling limit. Afterwards, we consider the special case of two external reservoirs and the system being in the scaling limit and discuss the golden
Yu, Zhizhou; Chen, Jian; Zhang, Lei; Wang, Jian
2013-12-11
We report an investigation of Coulomb blockade transport through an endohedral N@C60 weakly coupled with aluminum leads, employing the first-principles method combined with the Keldysh non-equilibrium Green's function derived from the equation of motion beyond the Hartree-Fock approximation. The differential conductance characteristics of the molecular device are calculated within the Coulomb blockade regime, which shows the Coulomb diamond as observed experimentally. When the gate voltage is less than that of the degeneracy point, there are two peaks in the differential conductance with an excited state induced by the change of the exchange interaction between the spin of C60 and the encapsulated nitrogen atom due to the transition from N@C(1-)(60) to N@C(2-)(60), while for a gate voltage larger than that of the degeneracy point, no excited state is available due to the quenching of exchange energy. As a result, there is only one Coulomb blockade peak in the differential conductance from the electron tunneling through the highest energy level below the Fermi level. Our first-principles results are in good agreement with experimental data obtained by an endohedral N@C60 molecular device.
Energy Technology Data Exchange (ETDEWEB)
Amaha, S., E-mail: s-amaha@riken.jp [Quantum Spin Information Project, Japan Science and Technology Agency, ICORP, 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan); Quantum Functional System Research Group, RIKEN Center for Emergent Matter Science, RIKEN, 3-1 Wako-shi, Saitama 351-0198 (Japan); Hatano, T. [Quantum Spin Information Project, Japan Science and Technology Agency, ICORP, 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan); Department of Physics, Tohoku University, Sendai-shi, Miyagi 980-8578 (Japan); Tarucha, S. [Quantum Spin Information Project, Japan Science and Technology Agency, ICORP, 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan); Quantum Functional System Research Group, RIKEN Center for Emergent Matter Science, RIKEN, 3-1 Wako-shi, Saitama 351-0198 (Japan); Department of Applied Physics, School of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Gupta, J. A.; Austing, D. G. [National Research Council of Canada, M50, Montreal Road, Ottawa, Ontario K1A 0R6 (Canada)
2015-04-27
We investigate nuclear spin pumping with five-electron quadruplet spin states in a spin-blockaded weakly coupled vertical double quantum dot device. Two types of hysteretic steps in the leakage current are observed on sweeping the magnetic field and are associated with bidirectional polarization of nuclear spin. Properties of the steps are understood in terms of bias-voltage-dependent conditions for the mixing of quadruplet and doublet spin states by the hyperfine interaction. The hysteretic steps vanish when up- and down-nuclear spin pumping processes are in close competition.
Cooper pair splitters beyond the Coulomb blockade regime
Energy Technology Data Exchange (ETDEWEB)
Amitai, Ehud; Tiwari, Rakesh P.; Nigg, Simon E. [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Walter, Stefan [Institute for Theoretical Physics, University Erlangen Nuernberg, Staudtstrasse 7, 91058 Erlangen (Germany); Schmidt, Thomas L. [Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg (Luxembourg)
2016-07-01
We consider the setup of a conventional s-wave Cooper pair splitter. However, we consider the charging energies in the quantum dots to be finite and smaller than the superconducting gap. We find analytically that at low energies the superconductor mediates an inter-dot tunneling term, the spin symmetry of which is influenced by a finite Zeeman field. This effect, together with an electrical tuning scheme of the quantum dot levels, can be used to engineer a non local triplet state on the two quantum dots, thereby extending the non-local state engineering capabilities of the Cooper pair splitter system.
Thermal spin pumping mediated by magnons in the semiclassical regime
International Nuclear Information System (INIS)
Nakata, Kouki
2012-01-01
We microscopically analyze thermal spin pumping mediated by magnons, at the interface between a ferromagnetic insulator and a non-magnetic metal, in the semiclassical regime. The generation of a spin current is discussed by calculating the thermal spin transfer torque, which breaks the spin conservation law for conduction electrons and operates the coherent magnon state. Inhomogeneous thermal fluctuations between conduction electrons and magnons induce a net spin current, which is pumped into the adjacent non-magnetic metal. The pumped spin current is proportional to the temperature difference. When the effective temperature of magnons is lower than that of conduction electrons, localized spins lose spin angular momentum by emitting magnons and conduction electrons flip from down to up by absorbing all the emitted momentum, and vice versa. Magnons at the zero mode cannot contribute to thermal spin pumping because they are eliminated by the spin-flip condition. Consequently thermal spin pumping does not cost any kind of applied magnetic fields
Current hot spot in the spin-valley blockade in carbon nanotubes
Széchenyi, Gábor; Pályi, András
2013-12-01
We present a theoretical study of the spin-valley blockade transport effect in a double quantum dot defined in a straight carbon nanotube. We find that intervalley scattering due to short-range impurities completely lifts the spin-valley blockade and induces a large leakage current in a certain confined range of the external magnetic field vector. This current hot spot emerges due to different effective magnetic fields acting on the spin-valley qubit states of the two quantum dots. Our predictions are compared to a recent measurement [F. Pei , Nat. Nanotech.1748-338710.1038/nnano.2012.160 7, 630 (2012)]. We discuss the implications for blockade-based schemes for qubit initialization/readout and motion sensing of nanotube-based mechanical resonators.
Anisotropic Pauli Spin Blockade of Holes in a GaAs Double Quantum Dot
Wang, Qingwen; Klochan, Oleh; Hung, Jo-Tzu; Culcer, Dimitrie; Farrer, Ian; Ritchie, David; Hamilton, Alex
Electrically defined semiconductor quantum dots are appealing systems for spin manipulation and quantum information processing. Thanks to the weak hyperfine interaction and the strong spin-orbit interaction, heavy-holes in GaAs are promising candidates for all-electrical spin manipulation. However, making stable quantum dots in GaAs has only become possible recently, mainly because of difficulties in device fabrication and device stability. Here we present electrical transport measurements of heavy-holes in a lateral double quantum dot based on a GaAs /AlxGa1 - x As heterostructure. We observe clear Pauli spin blockade and show that the lifting of the spin blockade by an external magnetic field is extremely anisotropic. Numerical calculations of heavy-hole transport through a double quantum dot in the presence of strong spin-orbit interaction demonstrate quantitative agreement with experimental results, which indicates that the observed anisotropy can be explained by the anisotropic hole g-factor and the surface Dresselhaus spin-orbit coupling.
The superradiant instability regime of the spinning Kerr black hole
Hod, Shahar
2016-07-01
Spinning Kerr black holes are known to be superradiantly unstable to massive scalar perturbations. We here prove that the instability regime of the composed Kerr-black-hole-massive-scalar-field system is bounded from above by the dimensionless inequality Mμ r+ is the dimensionless ratio between the horizon radii of the black hole. It is further shown that this analytically derived upper bound on the superradiant instability regime of the spinning Kerr black hole agrees with recent numerical computations of the instability resonance spectrum.
Spin-wave damping in ferromagnets in the ordered regime
International Nuclear Information System (INIS)
Reinecke, T.L.; Stinchcombe, R.B.
1978-01-01
Theoretical results based on a high-density approach are compared with experimental measurements for the damping of long-wavelength spin waves in the nearly isotropic ferromagnet for temperatures up to the critical regime. The theory, which has no adjustable parameters, is shown to account well for the overall magnitude of the spin-wave widths measured in recent neutron scattering experiments on EuO, and it is also in satisfactory agreement with the measured wave vector and temperature dependence of these widths. An estimate is also given for the contribution of dipolar coupling to the spin-wave widths
Pauli-spin blockade in a vertical double quantum dot holding two to five electrons
International Nuclear Information System (INIS)
Kodera, T; Arakawa, Y; Tarucha, S; Ono, K; Amaha, S
2009-01-01
We use a vertical double quantum dot (QD) to study spin blockade (SB) for the two-to five-electron states. SB observed for the two- and four-electron states is both assigned to Pauli exclusion with formation of a spin triplet state, and lifted by singlet-triplet admixing due to fluctuating nuclear field. SB observed for the five-electron state is caused by combined Pauli effect and Hund's rule. We observe a hysteretic behavior of the SB leakage current for up and down sweep of magnetic field, and argue that SB and its lifting by hyperfine interaction are subtle with the spin configuration and modified depending on the inter-dot detuning and number of electrons.
Rostamzadeh Renani, Fatemeh; Kirczenow, George
2011-11-01
We investigate single-molecule-magnet transistors (SMMTs) with ligands that support transport resonances. We find the lowest unoccupied molecular orbitals of Mn12-benzoate SMMs (with and without thiol or methyl-sulfide termination) to be on ligands, the highest occupied molecular orbitals being on the Mn12 magnetic core. We predict gate-controlled switching between Coulomb blockade and coherent resonant tunneling in SMMTs based on such SMMs, strong spin filtering by the SMM in both transport regimes, and that if such switching is observed, then the magnetic easy axis of the SMM is parallel to the direction of the current through the SMM.
Spin transfer torque in antiferromagnetic spin valves: From clean to disordered regimes
Saidaoui, Hamed Ben Mohamed
2014-05-28
Current-driven spin torques in metallic spin valves composed of antiferromagnets are theoretically studied using the nonequilibrium Green\\'s function method implemented on a tight-binding model. We focus our attention on G-type and L-type antiferromagnets in both clean and disordered regimes. In such structures, spin torques can either rotate the magnetic order parameter coherently (coherent torque) or compete with the internal antiferromagnetic exchange (exchange torque). We show that, depending on the symmetry of the spin valve, the coherent and exchange torques can either be in the plane, ∝n×(q×n) or out of the plane ∝n×q, where q and n are the directions of the order parameter of the polarizer and the free antiferromagnetic layers, respectively. Although disorder conserves the symmetry of the torques, it strongly reduces the torque magnitude, pointing out the need for momentum conservation to ensure strong spin torque in antiferromagnetic spin valves.
Spin transfer torque in antiferromagnetic spin valves: From clean to disordered regimes
Saidaoui, Hamed Ben Mohamed; Manchon, Aurelien; Waintal, Xavier
2014-01-01
Current-driven spin torques in metallic spin valves composed of antiferromagnets are theoretically studied using the nonequilibrium Green's function method implemented on a tight-binding model. We focus our attention on G-type and L-type antiferromagnets in both clean and disordered regimes. In such structures, spin torques can either rotate the magnetic order parameter coherently (coherent torque) or compete with the internal antiferromagnetic exchange (exchange torque). We show that, depending on the symmetry of the spin valve, the coherent and exchange torques can either be in the plane, ∝n×(q×n) or out of the plane ∝n×q, where q and n are the directions of the order parameter of the polarizer and the free antiferromagnetic layers, respectively. Although disorder conserves the symmetry of the torques, it strongly reduces the torque magnitude, pointing out the need for momentum conservation to ensure strong spin torque in antiferromagnetic spin valves.
Charge Dynamics and Spin Blockade in a Hybrid Double Quantum Dot in Silicon
Directory of Open Access Journals (Sweden)
Matias Urdampilleta
2015-08-01
Full Text Available Electron spin qubits in silicon, whether in quantum dots or in donor atoms, have long been considered attractive qubits for the implementation of a quantum computer because of silicon’s “semiconductor vacuum” character and its compatibility with the microelectronics industry. While donor electron spins in silicon provide extremely long coherence times and access to the nuclear spin via the hyperfine interaction, quantum dots have the complementary advantages of fast electrical operations, tunability, and scalability. Here, we present an approach to a novel hybrid double quantum dot by coupling a donor to a lithographically patterned artificial atom. Using gate-based rf reflectometry, we probe the charge stability of this double quantum-dot system and the variation of quantum capacitance at the interdot charge transition. Using microwave spectroscopy, we find a tunnel coupling of 2.7 GHz and characterize the charge dynamics, which reveals a charge T_{2}^{*} of 200 ps and a relaxation time T_{1} of 100 ns. Additionally, we demonstrate a spin blockade at the inderdot transition, opening up the possibility to operate this coupled system as a singlet-triplet qubit or to transfer a coherent spin state between the quantum dot and the donor electron and nucleus.
Tornow, Sabine; Zwicknagl, Gertrud
2009-01-01
We investigate the transport characteristics of a redox system weakly coupled to leads in the Coulomb blockade regime. The redox system comprises a donor and acceptor separated by an insulating bridge in a solution. It is modeled by a two-site extended Hubbard model which includes on-site and inter-site Coulomb interactions and the coupling to a bosonic bath. The current voltage characteristics is calculated at high temperatures using a rate equation approach. For high voltages exceeding the ...
Semiclassical regime of Regge calculus and spin foams
International Nuclear Information System (INIS)
Bianchi, Eugenio; Satz, Alejandro
2009-01-01
Recent attempts to recover the graviton propagator from spin foam models involve the use of a boundary quantum state peaked on a classical geometry. The question arises whether beyond the case of a single simplex this suffices for peaking the interior geometry in a semiclassical configuration. In this paper we explore this issue in the context of quantum Regge calculus with a general triangulation. Via a stationary phase approximation, we show that the boundary state succeeds in peaking the interior in the appropriate configuration, and that boundary correlations can be computed order by order in an asymptotic expansion. Further, we show that if we replace at each simplex the exponential of the Regge action by its cosine-as expected from the semiclassical limit of spin foam models-then the contribution from the sign-reversed terms is suppressed in the semiclassical regime and the results match those of conventional Regge calculus
Datta-Das-type spin-field-effect transistor in the nonballistic regime
Ohno, Munekazu; Yoh, Kanji
2008-01-01
We analyzed the applicability of original Datta-Das proposal for spin-field-effect transistor (spin-FET) to nonballistic regime based on semiempirical Monte Carlo simulation for spin transport. It is demonstrated that the spin helix state in two-dimensional electron gas system is sufficiently robust against D'yakonov-Perel' spin relaxation to allow an operation of Datta-Das-type spin-FET in the nonballistic transport regime. It is also shown that the spin diffusion length of the spin helix st...
Energy Technology Data Exchange (ETDEWEB)
Bagraev, N. T., E-mail: Bagraev@mail.ioffe.ru [Ioffe Institute (Russian Federation); Chaikina, E. I. [Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Division de Fisica Aplicada (Mexico); Danilovskii, E. Yu.; Gets, D. S.; Klyachkin, L. E.; L’vova, T. V.; Malyarenko, A. M. [Ioffe Institute (Russian Federation)
2016-04-15
The sulfur passivation of the semi-insulating GaAs bulk (SI GaAs) grown in an excess phase of arsenic is used to observe the transition from the Coulomb blockade to the weak localization regime at room temperature. The I–V characteristics of the SI GaAs device reveal nonlinear behavior that appears to be evidence of the Coulomb blockade process as well as the Coulomb oscillations. The sulfur passivation of the SI GaAs device surface results in enormous transformation of the I–V characteristics that demonstrate the strong increase of the resistance and Coulomb blockade regime is replaced by the electron tunneling processes. The results obtained are analyzed within frameworks of disordering SI GaAs surface that is caused by inhomogeneous distribution of the donor and acceptor anti-site defects which affects the conditions of quantum- mechanical tunneling. Weak localization processes caused by the preservation of the Fermi level pinning are demonstrated by measuring the negative magnetoresistance in weak magnetic fields at room temperature. Finally, the studies of the magnetoresistance at higher magnetic fields reveal the h/2e Aharonov–Altshuler–Spivak oscillations with the complicated behavior due to possible statistical mismatch of the interference paths in the presence of different microdefects.
Berry-phase blockade in single-molecule magnets
Gonzalez, Gabriel; Leuenberger, Michael N.
2006-01-01
We formulate the problem of electron transport through a single-molecule magnet (SMM) in the Coulomb blockade regime taking into account topological interference effects for the tunneling of the large spin of a SMM. The interference originates from spin Berry phases associated with different tunneling paths. We show that in the case of incoherent spin states it is essential to place the SMM between oppositely spin-polarized source and drain leads in order to detect the spin tunneling in the s...
Pluchery, Olivier; Caillard, Louis; Dollfus, Philippe; Chabal, Yves J
2018-01-18
Single charge electronics offer a way for disruptive technology in nanoelectronics. Coulomb blockade is a realistic way for controlling the electric current through a device with the accuracy of one electron. In such devices the current exhibits a step-like increase upon bias which reflects the discrete nature of the fundamental charge. We have assembled a double tunnel junction on an oxide-free silicon substrate that exhibits Coulomb staircase characteristics using gold nanoparticles (AuNPs) as Coulomb islands. The first tunnel junction is an insulating layer made of a grafted organic monolayer (GOM) developed for this purpose. The GOM also serves for attaching AuNPs covalently. The second tunnel junction is made by the tip of an STM. We show that this device exhibits reproducible Coulomb blockade I-V curves at 40 K in vacuum. We also show that depending on the doping of the silicon substrate, the whole Coulomb staircase can be adjusted. We have developed a simulation approach based on the orthodox theory that was completed by calculating the bias dependent tunnel barriers and by including an accurate calculation of the band bending. This model accounts for the experimental data and the doping dependence of Coulomb oscillations. This study opens new perspectives toward designing new kind of single electron transistors (SET) based on this dependence of the Coulomb staircase with the charge carrier concentration.
Olsen, Stine T; Brøndsted Nielsen, Mogens; Hansen, Thorsten; Ratner, Mark A; Mikkelsen, Kurt V
2017-06-20
Molecular photoswitches incorporated in molecular junctions yield the possibility of light-controlled switching of conductance due to the electronic difference of the photoisomers. Another isomerization mechanism, dark photoswitching, promoted by a voltage stimulus rather than by light, can be operative in the Coulomb blockade regime for a specific charge state of the molecule. Here we elucidate theoretically the mechanistic and thermodynamic restrictions for this dark photoswitching for donor-acceptor substituted 4n and 4n+2 π-electron open-chain oligoenes (1,3-butadiene and 1,3,5-hexatriene) by considering the molecular energies and orbitals of the molecules placed in a junction. For an electrocyclic ring closure reaction to occur for these compounds, we put forward two requirements: a) the closed stereoisomer (cis or trans form) must be of lower energy than the open form, and b) the reaction pathway must be in accordance to the orbital symmetry rules expressed by the Woodward-Hoffmann rules (when the electrodes do not significantly alter the molecular orbital appearances). We find these two requirements to be valid for the dianion of (1E,3Z,5E)-hexa-1,3,5-triene-1,6-diamine, and the Coulomb blockade diamonds were therefore modeled for this compound to elucidate how a dark photoswitching event would manifest itself in the stability plot. From this modeling of conductance as a function of gate and bias potentials, we predict a collapse in Coulomb diamond size, that is, a decrease in the height of the island of zero conductance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Designing organic spin filters in the coherent tunneling regime.
Herrmann, Carmen; Solomon, Gemma C; Ratner, Mark A
2011-06-14
Spin filters, that is, systems which preferentially transport electrons of a certain spin orientation, are an important element for spintronic schemes and in chemical and biological instances of spin-selective electronic communication. We study the relation between molecular structure and spin filtering functionality employing a theoretical analysis of both model and stable organic radicals based on substituted benzene, which are bound to gold electrodes, with a combination of density functional theory and the Landauer-Imry-Büttiker approach. We compare the spatial distribution of the spin density and of the frontier central subsystem molecular orbitals, and local contributions to the transmission. Our results suggest that the delocalization of the singly occupied molecular orbital and of the spin density onto the benzene ring connected to the electrodes, is a good, although not the sole indicator of spin filtering functionality. The stable radicals under study do not effectively act as spin filters, while the model phenoxy-based radicals are effective due to their much larger spin delocalization. These conclusions may also be of interest for electron transfer experiments in electron donor-bridge-acceptor complexes.
Photon and spin dependence of the resonance line shape in the strong coupling regime
Miyashita, Seiji; Shirai, Tatsuhiko; Mori, Takashi; De Raedt, Hans; Bertaina, Sylvain; Chiorescu, Irinel
2012-01-01
We study the quantum dynamics of a spin ensemble coupled to cavity photons. Recently, related experimental results have been reported, showing the existence of the strong coupling regime in such systems. We study the eigenenergy distribution of the multi-spin system (following the Tavis-Cummings
Energy Technology Data Exchange (ETDEWEB)
Tornow, Sabine; Zwicknagl, Gertrud [Institut fuer Mathematische Physik, TU Braunschweig (Germany)
2010-02-15
We investigate the transport characteristics of a redox system weakly coupled to leads in the Coulomb blockade regime. The redox system comprises a donor and acceptor separated by an insulating bridge in a solution. It is modeled by a two-site extended Hubbard model which includes on-site and inter-site Coulomb interactions and the coupling to a bosonic bath. The current-voltage characteristics is calculated at high temperatures using a rate equation approach. For high voltages exceeding the Coulomb repulsion at the donor site the calculated transport characteristics exhibit pronounced deviations from the behavior expected from single-electron transport. Depending on the relative sizes of the effective on-site and inter-site Coulomb interactions on one side and the reorganization energy on the other side we find either negative differential resistance or current enhancement. Schematic view of the redox system with donor (D) and acceptor (A) coupled to the leads L and R. The electronic degrees of freedom of the DA system are coupled to the environment comprising internal vibrations and the solvent dynamics. The current is calculated as a function of the bias voltage V{sub b} and gate voltage V{sub g}. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Berry-Phase Blockade in Single-Molecule Magnets
González, Gabriel; Leuenberger, Michael N.
2007-06-01
We formulate the problem of electron transport through a single-molecule magnet (SMM) in the Coulomb blockade regime taking into account topological interference effects for the tunneling of the large spin of a SMM. The interference originates from spin Berry phases associated with different tunneling paths. We show that, in the case of incoherent spin states, it is essential to place the SMM between oppositely spin-polarized source and drain leads in order to detect the spin tunneling in the stationary current, which exhibits topological zeros as a function of the transverse magnetic field.
Spin-state blockade in Te6+-substituted electron-doped LaCoO3
Tomiyasu, Keisuke; Koyama, Shun-Ichi; Watahiki, Masanori; Sato, Mika; Nishihara, Kazuki; Onodera, Mitsugi; Iwasa, Kazuaki; Nojima, Tsutomu; Yamasaki, Yuuichi; Nakao, Hironori; Murakami, Youichi
2015-03-01
Perovskite-type LaCoO3 (Co3+: d6) is a rare inorganic material with sensitive and characteristic responses among low, intermediate, and high spin states. For example, in insulating nonmagnetic low-spin states below about 20 K, light hole doping (Ni substitution) induces much larger magnetization than expected; over net 10μB/hole (5μB/Ni) for 1μB/hole (1μB/Ni), in which the nearly isolated dopants locally change the surrounding Co low-spin states to magnetic ones and form spin molecules with larger total spin. Further, the former is isotropic, whereas the latter exhibits characteristic anisotropy probably because of Jahn-Teller distortion. In contrast, for electron doping, relatively insensitive spin-state responses were reported, as in LaCo(Ti4+) O3, but are not clarified, and are somewhat controversial. Here, we present macroscopic measurement data of another electron-doped system LaCo(Te6+) O3 and discuss the spin-state responses. This study was financially supported by Grants-in-Aid for Young Scientists (B) (No. 22740209 and 26800174) from the MEXT of Japan.
Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble
International Nuclear Information System (INIS)
Herzog, B. E.; Cadeddu, D.; Xue, F.; Peddibhotla, P.; Poggio, M.
2014-01-01
As the number of spins in an ensemble is reduced, the statistical fluctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer-scale ensembles of nuclear spins in a KPF 6 sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble.
Spin squeezing and Schrödinger cat generation in atomic samples with Rydberg blockade
DEFF Research Database (Denmark)
Opatrný, Tomáš; Mølmer, Klaus
2012-01-01
A scheme is proposed to prepare squeezed states and Schrödinger-cat-like states of the collective spin degrees of freedom associated with a pair of ground states in an atomic ensemble. The scheme uses an effective Jaynes-Cummings interaction which can be provided by excitation of the atoms...
Negativity as the Entanglement Measure to Probe the Kondo Regime in the Spin-Chain Kondo Model
Bayat, Abolfazl; Sodano, Pasquale; Bose, Sougato
2009-01-01
We study the entanglement of an impurity at one end of a spin chain with a block of spins using negativity as a true measure of entanglement to characterize the unique features of the gapless Kondo regime in the spin chain Kondo model. For this spin chain in the Kondo regime we determine- with a true entanglement measure- the spatial extent of the Kondo screening cloud, we propose an ansatz for its ground state and demonstrate that the impurity spin is indeed maximally entangled with the clou...
Heat transport in the XXZ spin chain: from ballistic to diffusive regimes and dephasing enhancement
International Nuclear Information System (INIS)
Mendoza-Arenas, J J; Al-Assam, S; Clark, S R; Jaksch, D
2013-01-01
In this work we study the heat transport in an XXZ spin-1/2 Heisenberg chain with homogeneous magnetic field, incoherently driven out of equilibrium by reservoirs at the boundaries. We focus on the effect of bulk dephasing (energy-dissipative) processes in different parameter regimes of the system. The non-equilibrium steady state of the chain is obtained by simulating its evolution under the corresponding Lindblad master equation, using the time evolving block decimation method. In the absence of dephasing, the heat transport is ballistic for weak interactions, while being diffusive in the strongly interacting regime, as evidenced by the heat current scaling with the system size. When bulk dephasing takes place in the system, diffusive transport is induced in the weakly interacting regime, with the heat current monotonically decreasing with the dephasing rate. In contrast, in the strongly interacting regime, the heat current can be significantly enhanced by dephasing for systems of small size. (paper)
Renani, Fatemeh Rostamzadeh; Kirczenow, George
2011-01-01
We investigate single molecule magnet transistors (SMMTs) with ligands that support transport resonances. We find the lowest unoccupied molecular orbitals of Mn12-benzoate SMMs (with and without thiol or methyl-sulfide termination) to be on ligands, the highest occupied molecular orbitals being on the Mn12 magnetic core. We predict gate controlled switching between Coulomb blockade and coherent resonant tunneling in SMMTs based on such SMMs, strong spin filtering by the SMM in both transport ...
Spinning Kerr black holes with stationary massive scalar clouds: the large-coupling regime
Energy Technology Data Exchange (ETDEWEB)
Hod, Shahar [Marine sciences, The Ruppin Academic Center,Ruppin, Emeq Hefer 40250 (Israel); Biotechnology, The Hadassah Academic College,37 Hanevi’im St., Jerusalem 9101001 (Israel)
2017-01-09
We study analytically the Klein-Gordon wave equation for stationary massive scalar fields linearly coupled to spinning Kerr black holes. In particular, using the WKB approximation, we derive a compact formula for the discrete spectrum of scalar field masses which characterize the stationary composed Kerr-black-hole-massive-scalar-field configurations in the large-coupling regime Mμ≫1 (here M and μ are respectively the mass of the central black hole and the proper mass of the scalar field). We confirm our analytically derived formula for the Kerr-scalar-field mass spectrum with numerical data that recently appeared in the literature.
Spin relaxation in quantum dots due to electron exchange with leads.
Vorontsov, A B; Vavilov, M G
2008-11-28
We calculate spin relaxation rates in lateral quantum dot systems due to electron exchange between dots and leads. Using rate equations, we develop a theoretical description of the experimentally observed electric current in the spin blockade regime of double quantum dots. A single expression fits the entire current profile and describes the structure of both the conduction peaks and the suppressed ("valley") region. Extrinsic rates calculated here have to be taken into account for accurate extraction of intrinsic relaxation rates due to the spin-orbit and hyperfine spin scattering mechanisms from spin blockade measurements.
Static and dynamic spin fluctuations in the spin glass doping regime in La2-xSrxCuO4+y
International Nuclear Information System (INIS)
Birgeneau, R.J.; Belk, N.; Kastner, M.A.; Keimer, B.; Shirane, G.
1991-01-01
We review the results of neutron scattering studies of the static and dynamic spin fluctuations crystals of La 2-x Sr x CuO 4+δ in the doping regime intermediate between the Neel and superconducting regions. In this regime the in-plane resistance is linear in temperature down to ∼80 K with a crossover due to logarithmic conductance effects at lower temperatures. The static spin correlations are well-described by a simple model in which the inverse correlation length κ(x,T) =κ(x,0) + κ(0,T). The most dramatic new result is the discovery by Keimer et al. that the dynamic spin fluctuations exhibit a temperature dependence which is a simple function of ω/T for temperatures 10 K≤T≤500 K for a wide range of energies. This scaling leads to a natural explanation of a variety of normal state properties of the copper oxides. 21 refs., 4 figs
Lin, Cheng-Ju; Motrunich, Olexei I.
2017-02-01
The eigenstate thermalization hypothesis provides one picture of thermalization in a quantum system by looking at individual eigenstates. However, it is also important to consider how local observables reach equilibrium values dynamically. Quench protocol is one of the settings to study such questions. A recent numerical study [Bañuls, Cirac, and Hastings, Phys. Rev. Lett. 106, 050405 (2007), 10.1103/PhysRevLett.106.050405] of a nonintegrable quantum Ising model with longitudinal field under such a quench setting found different behaviors for different initial quantum states. One particular case called the "weak-thermalization" regime showed apparently persistent oscillations of some observables. Here we provide an explanation of such oscillations. We note that the corresponding initial state has low energy density relative to the ground state of the model. We then use perturbation theory near the ground state and identify the oscillation frequency as essentially a quasiparticle gap. With this quasiparticle picture, we can then address the long-time behavior of the oscillations. Upon making additional approximations which intuitively should only make thermalization weaker, we argue that the oscillations nevertheless decay in the long-time limit. As part of our arguments, we also consider a quench from a BEC to a hard-core boson model in one dimension. We find that the expectation value of a single-boson creation operator oscillates but decays exponentially in time, while a pair-boson creation operator has oscillations with a t-3 /2 decay in time. We also study dependence of the decay time on the density of bosons in the low-density regime and use this to estimate decay time for oscillations in the original spin model.
Single excitation transfer in the quantum regime. A spin-based solid-state approach
Energy Technology Data Exchange (ETDEWEB)
Zollitsch, Christoph Wilhelm
2016-12-02
Realisation of strong coupling between a superconducting microwave resonator and an ensemble of phosphorus donor spins, contained in an isotopically purified silicon host crystal. Investigation of the dynamical properties of the coupled system at mK temperatures and ultra-low microwave powers. The relaxation and coherence times of the coupled system were extracted by pulsed microwave spectroscopy, with the result that the hybrid system's coherence time is enhanced compared to the uncoupled spin system.
Sire, Clément
2004-09-24
We study the autocorrelation function of a conserved spin system following a quench at the critical temperature. Defining the correlation length L(t) approximately t(1/z), we find that for times t' and t satisfying L(t')infinity limit, we show that lambda(')(c)=d+2 and phi=z/2. We give a heuristic argument suggesting that this result is, in fact, valid for any dimension d and spin vector dimension n. We present numerical simulations for the conserved Ising model in d=1 and d=2, which are fully consistent with the present theory.
Spin and charge transport in graphene devices in the classical and quantum regimes
Diniz Guimaraes, Marcos Henrique
2015-01-01
Grafeen, één atoom dik koolstofmateriaal, werd in het afgelopen decennium één van de meest veelbelovende materialen voor toekomstige elektronische apparaten. Grafeen heeft ook groot potentieel getoond voor spintronische toepassingen, waarbij het intrinsieke hoekmoment van het elektron (spin) wordt
Analysis of synchronized regimes for injection-locked spin-transfer nano-oscillators
Energy Technology Data Exchange (ETDEWEB)
D' Aquino, M., E-mail: daquino@uniparthenope.it [Department of Technology, University of Napoli ' Parthenope' , 80143 Napoli (Italy); Serpico, C. [Department of Engineering, University of Napoli Federico II, 80125 Napoli (Italy); Bonin, R. [Politecnico di Torino - Sede di Verres, 11029 Verres (Aosta) (Italy); Bertotti, G. [Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Mayergoyz, I.D. [ECE Dept. and UMIACS, University of Maryland, College Park, MD 20742 (United States)
2012-05-01
The large-angle magnetization dynamics of an injection-locked spin-transfer nano-oscillator (STNO) is studied. The magnetic system is subject to the action of time-varying spin-polarized currents and external magnetic fields. The uniform mode theory is developed and describes the hysteretic synchronization mechanism in terms of bifurcations of equilibria and limit cycles of appropriate dynamical systems. Analytical predictions of control parameters for the synchronization between the magnetization self-oscillation and the external microwave excitations (current, field) are provided. The effect of temperature on the locking band and the hysteretic character of the oscillation response is analyzed. An analytical approach is developed to determine the thermally induced sidebands in the power spectral density of phase-locked oscillations as a function of control parameters. The analytical predictions are in good agreement with the results of numerical simulations.
Heat transfer in the spin-boson model: a comparative study in the incoherent tunneling regime.
Segal, Dvira
2014-07-01
We study the transfer of heat in the nonequilibrium spin-boson model with an Ohmic dissipation. In the nonadiabatic limit we derive a formula for the thermal conductance based on a rate equation formalism at the level of the noninteracting blip approximation, valid for temperatures T>T(K), with T(K) as the Kondo temperature. We evaluate this expression analytically assuming either weak or strong couplings, and demonstrate that our results agree with exact relations. Far-from-equilibrium situations are further examined, showing a close correspondence to the linear response limit.
Ren, Y. J.; Deng, W. Y.; Geng, H.; Shen, R.; Shao, L. B.; Sheng, L.; Xing, D. Y.
2017-12-01
The spin-orbit torque provides an efficient method for switching the direction of a magnetization by using an electric field. Owing to the spin-orbit coupling, when an electric field is applied, a nonequilibrium spin density is generated, which exerts a torque on the local magnetization. Here, we investigate the spin-orbit torque in a thin film of topological insulator \\text{Bi}2\\text{Se}3 based upon a Boltzmann equation, with proper boundary conditions, which is applicable from the ballistic regime to the diffusive regime. It is shown that due to the spin-momentum interlocking of the electron surface states, the magnitude of the field-like torque is simply in linear proportion to the longitudinal electrical current. For a fixed electric field, the spin-orbit torque is proportional to the sample length in the ballistic limit, and saturates to a constant in the diffusive limit. The dependence of the torque on the magnetization direction and exchange coupling strength is also studied. Our theory may offer useful guidance for experimental investigations of the spin-orbit torque in finite-size systems.
Lin, Cheng-Ju; Motrunich, Olexei
Eigenstate Thermalization Hypothesis provides one picture of thermalization in a quantum system by looking at individual eigenstates. However, it is also important to consider how local observables reach equilibrium values dynamically. Quench protocol is one of the settings to study such questions. A recent numerical study [Banuls, Cirac, and Hastings, Phys. Rev. Lett. 106, 050405 (2011)] of a nonintegrable quantum Ising model with longitudinal field under such quench setting found different behaviors under different initial quantum states. One particular case termed ``weak thermalization'' regime showed apparently persistent oscillations of some observables. Here we provide an explanation of such oscillations. We use perturbation theory near the ground state of the model, and identify the oscillation frequency as the quasiparticle mass. With this quasiparticle picture, we can then address the long-time behavior of the oscillations.
X-ray detected magnetic resonance of YIG thin films in the nonlinear regime of spin waves
Energy Technology Data Exchange (ETDEWEB)
Goulon, J., E-mail: goulon@esrf.f [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France); Rogalev, A.; Wilhelm, F.; Goujon, G. [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France); Brouder, Ch. [Institut de Mineralogie et de Physique des Milieux Condenses, UMR-CNRS 7590, Universite Paris VI-VII, 4 place Jussieu, F-75252 Paris Cedex 05 (France); Yaresko, A. [Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Ben Youssef, J.; Indenbom, M.V. [Laboratoire de Magnetisme de Bretagne, CNRS FRE 2697, UFR Sciences et Techniques, F-29328 Brest Cedex (France)
2010-08-15
We discuss the information content of element/edge resolved X-ray detected magnetic resonance (XDMR) experiments carried out on yttrium iron garnet (YIG) thin films. Starting with a phenomenological approach, it is shown that the photoionisation of deep atomic core levels by circularly polarized X-rays can be used to probe the precession dynamics of spin or orbital magnetization components in empty final states of proper symmetry. Crude estimates of the opening angle of the uniform precession mode were tentatively deduced from the ratio of the XDMR and XMCD absorption cross-sections either at the iron or yttrium absorbing sites. The implications of the most recent experimental results collected at the ESRF are analyzed, keeping in mind that: (i) the Fe K-edge XDMR signal is largely dominated by the precession of orbital magnetization components at the tetrahedral iron sites; (ii) the Y L-edges XDMR signal essentially describes the precession of induced spin magnetization involving the 4d states of yttrium. In the magnetostatic regime, we produce clear experimental evidence of collective excitations of orbital magnetization waves, especially under high pumping power. Several coupling mechanisms could explain our observations, starting with pseudo-dipolar interactions in ferromagnetic systems. In ferrimagnetic systems in which orbital degeneracy and orbital ordering make the excitation of orbitons possible, one may envisage additional modes of excitation or relaxation of orbital magnetization waves. This interpretation looks fully consistent with the results of band structure calculations carried out recently on YIG with fully relativistic LMTO-LSDA methods.
Pohjola, Teemu; Schoeller, Herbert
2000-12-01
In this work, we study the spin dynamics of Mn12-acetate molecules in the regime of thermally assisted tunneling. In particular, we describe the system in the presence of a strong transverse magnetic field. Similar to recent experiments, the relaxation time/rate is found to display a series of resonances; their Lorentzian shape is found to stem from the tunneling. The dynamic susceptibility χ(ω) is calculated starting from the microscopic Hamiltonian and the resonant structure manifests itself also in χ(ω). Similar to recent results reported on another molecular magnet, Fe8, we find oscillations of the relaxation rate as a function of the transverse magnetic field when the field is directed along a hard axis of the molecules. This phenomenon is attributed to the interference of the geometrical or Berry phase. We propose susceptibility experiments to be carried out for strong transverse magnetic fields to study these oscillations and for a better resolution of the sharp satellite peaks in the relaxation rates.
Lateral spin-orbit coupling and the Kondo effect in quantum dots
Vernek, Edson; Ngo, Anh; Ulloa, Sergio
2010-03-01
We present studies of the Coulomb blockade and Kondo regimes of transport of a quantum dot connected to current leads through spin-polarizing quantum point contacts (QPCs) [1]. This configuration, arising from the effect of lateral spin-orbit fields, results in spin-polarized currents even in the absence of external magnetic fields and greatly affects the correlations in the dot. Using an equation-of-motion technique and numerical renormalization group calculations we obtain the conductance and spin polarization for this system under different parameter regimes. Our results show that both the Coulomb blockade and Kondo regimes exhibit non-zero spin-polarized conductance. We analyze the role that the spin-dependent tunneling amplitudes of the QPC play in determining the charge and net magnetic moment in the dot. We find that the Kondo regime exhibits a strongly dependent Kondo temperature on the QPC polarizability. These effects, controllable by lateral gate voltages, may provide a new approach for exploring Kondo correlations, as well as possible spin devices. Supported by NSF DMR-MWN and PIRE. [1] P. Debray et al., Nature Nanotech. 4, 759 (2009).
Electrical control of single hole spins in nanowire quantum dots.
Pribiag, V S; Nadj-Perge, S; Frolov, S M; van den Berg, J W G; van Weperen, I; Plissard, S R; Bakkers, E P A M; Kouwenhoven, L P
2013-03-01
The development of viable quantum computation devices will require the ability to preserve the coherence of quantum bits (qubits). Single electron spins in semiconductor quantum dots are a versatile platform for quantum information processing, but controlling decoherence remains a considerable challenge. Hole spins in III-V semiconductors have unique properties, such as a strong spin-orbit interaction and weak coupling to nuclear spins, and therefore, have the potential for enhanced spin control and longer coherence times. A weaker hyperfine interaction has previously been reported in self-assembled quantum dots using quantum optics techniques, but the development of hole-spin-based electronic devices in conventional III-V heterostructures has been limited by fabrication challenges. Here, we show that gate-tunable hole quantum dots can be formed in InSb nanowires and used to demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tunable between hole and electron quantum dots, which allows the hyperfine interaction strengths, g-factors and spin blockade anisotropies to be compared directly in the two regimes.
Antilocalization of Coulomb Blockade in a Ge-Si Nanowire
DEFF Research Database (Denmark)
Higginbotham, Andrew P.; Kuemmeth, Ferdinand; Larsen, Thorvald Wadum
2014-01-01
The distribution of Coulomb blockade peak heights as a function of magnetic field is investigated experimentally in a Ge-Si nanowire quantum dot. Strong spin-orbit coupling in this hole-gas system leads to antilocalization of Coulomb blockade peaks, consistent with theory. In particular, the peak...
Anisotropy and Suppression of Spin-Orbit Interaction in a GaAs Double Quantum Dot
Hofmann, A.; Maisi, V. F.; Krähenmann, T.; Reichl, C.; Wegscheider, W.; Ensslin, K.; Ihn, T.
2017-10-01
The spin-flip tunneling rates are measured in GaAs-based double quantum dots by time-resolved charge detection. Such processes occur in the Pauli spin blockade regime with two electrons occupying the double quantum dot. Ways are presented for tuning the spin-flip tunneling rate, which on the one hand gives access to measuring the Rashba and Dresselhaus spin-orbit coefficients. On the other hand, they make it possible to turn on and off the effect of spin-orbit interaction with a high on/off ratio. The tuning is accomplished by choosing the alignment of the tunneling direction with respect to the crystallographic axes, as well as by choosing the orientation of the external magnetic field with respect to the spin-orbit magnetic field. Spin lifetimes of 10 s are achieved at a tunneling rate close to 1 kHz.
Anisotropy and Suppression of Spin-Orbit Interaction in a GaAs Double Quantum Dot.
Hofmann, A; Maisi, V F; Krähenmann, T; Reichl, C; Wegscheider, W; Ensslin, K; Ihn, T
2017-10-27
The spin-flip tunneling rates are measured in GaAs-based double quantum dots by time-resolved charge detection. Such processes occur in the Pauli spin blockade regime with two electrons occupying the double quantum dot. Ways are presented for tuning the spin-flip tunneling rate, which on the one hand gives access to measuring the Rashba and Dresselhaus spin-orbit coefficients. On the other hand, they make it possible to turn on and off the effect of spin-orbit interaction with a high on/off ratio. The tuning is accomplished by choosing the alignment of the tunneling direction with respect to the crystallographic axes, as well as by choosing the orientation of the external magnetic field with respect to the spin-orbit magnetic field. Spin lifetimes of 10 s are achieved at a tunneling rate close to 1 kHz.
Roosen, David; Wegewijs, Maarten R.; Hofstetter, Walter
2008-02-01
We investigate the time-dependent Kondo effect in a single-molecule magnet (SMM) strongly coupled to metallic electrodes. Describing the SMM by a Kondo model with large spin S>1/2, we analyze the underscreening of the local moment and the effect of anisotropy terms on the relaxation dynamics of the magnetization. Underscreening by single-channel Kondo processes leads to a logarithmically slow relaxation, while finite uniaxial anisotropy causes a saturation of the SMM’s magnetization. Additional transverse anisotropy terms induce quantum spin tunneling and a pseudospin-1/2 Kondo effect sensitive to the spin parity.
Quantum ring with the Rashba spin-orbit interaction in the regime of strong light-matter coupling
Kozin, V. K.; Iorsh, I. V.; Kibis, O. V.; Shelykh, I. A.
2018-04-01
We developed the theory of electronic properties of semiconductor quantum rings with the Rashba spin-orbit interaction irradiated by an off-resonant high-frequency electromagnetic field (dressing field). Within the Floquet theory of periodically driven quantum systems, it is demonstrated that the dressing field drastically modifies all electronic characteristics of the rings, including spin-orbit coupling, effective electron mass, and optical response. In particular, the present effect paves the way to controlling the spin polarization of electrons with light in prospective ring-shaped spintronic devices.
Detecting phonon blockade with photons
International Nuclear Information System (INIS)
Didier, Nicolas; Pugnetti, Stefano; Fazio, Rosario; Blanter, Yaroslav M.
2011-01-01
Measuring the quantum dynamics of a mechanical system, when few phonons are involved, remains a challenge. We show that a superconducting microwave resonator linearly coupled to the mechanical mode constitutes a very powerful probe for this scope. This new coupling can be much stronger than the usual radiation pressure interaction by adjusting a gate voltage. We focus on the detection of phonon blockade, showing that it can be observed by measuring the statistics of the light in the cavity. The underlying reason is the formation of an entangled state between the two resonators. Our scheme realizes a phonotonic Josephson junction, giving rise to coherent oscillations between phonons and photons as well as a self-trapping regime for a coupling smaller than a critical value. The transition from the self-trapping to the oscillating regime is also induced dynamically by dissipation.
Spin-dependent transport through interacting graphene armchair nanoribbons
International Nuclear Information System (INIS)
Koller, Sonja; Mayrhofer, Leonhard; Grifoni, Milena
2010-01-01
We investigate spin effects in transport across fully interacting, finite-size graphene armchair nanoribbons (ACNs) contacted to collinearly spin-polarized leads. In such systems, the presence of short-range Coulomb interaction between bulk states and states localized at the ribbon ends leads to novel spin-dependent phenomena. Specifically, the total spin of the low-energy many-body states is conserved during tunneling but that of the bulk and end states is not. As a consequence, in the single-electron regime, dominated by Coulomb blockade phenomena, we find pronounced negative differential conductance features for ACNs contacted to parallel polarized leads. These features are, however, absent in an anti-parallel contact configuration, which in turn leads, within a certain gate and bias voltage region, to a negative tunneling magneto-resistance. Moreover, we analyze the changes in the transport characteristics under the influence of an external magnetic field.
Electric-field-controlled spin reversal in a quantum dot with ferromagnetic contacts
Hauptmann, J. R.; Paaske, J.; Lindelof, P. E.
2008-05-01
Manipulation of the spin states of a quantum dot by purely electrical means is a highly desirable property of fundamental importance for the development of spintronic devices such as spin filters, spin transistors and single spin memories as well as for solid-state qubits. An electrically gated quantum dot in the Coulomb blockade regime can be tuned to hold a single unpaired spin-1/2, which is routinely spin polarized by an applied magnetic field. Using ferromagnetic electrodes, however, the quantum dot becomes spin polarized by the local exchange field. Here, we report on the experimental realization of this tunnelling-induced spin splitting in a carbon-nanotube quantum dot coupled to ferromagnetic nickel electrodes with a strong tunnel coupling ensuring a sizeable exchange field. As charge transport in this regime is dominated by the Kondo effect, we can use this sharp many-body resonance to read off the local spin polarization from the measured bias spectroscopy. We demonstrate that the exchange field can be compensated by an external magnetic field, thus restoring a zero-bias Kondo resonance, and we demonstrate that the exchange field itself, and hence the local spin polarization, can be tuned and reversed merely by tuning the gate voltage.
Coulomb Blockade Plasmonic Switch.
Xiang, Dao; Wu, Jian; Gordon, Reuven
2017-04-12
Tunnel resistance can be modulated with bias via the Coulomb blockade effect, which gives a highly nonlinear response current. Here we investigate the optical response of a metal-insulator-nanoparticle-insulator-metal structure and show switching of a plasmonic gap from insulator to conductor via Coulomb blockade. By introducing a sufficiently large charging energy in the tunnelling gap, the Coulomb blockade allows for a conductor (tunneling) to insulator (capacitor) transition. The tunnelling electrons can be delocalized over the nanocapacitor again when a high energy penalty is added with bias. We demonstrate that this has a huge impact on the plasmonic resonance of a 0.51 nm tunneling gap with ∼70% change in normalized optical loss. Because this structure has a tiny capacitance, there is potential to harness the effect for high-speed switching.
Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve.
Ma, Jing-Min; Zhao, Jia; Zhang, Kai-Cheng; Peng, Ya-Jing; Chi, Feng
2011-03-28
Spin-dependent transport through a quantum-dot (QD) ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR) as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers:
Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve
Directory of Open Access Journals (Sweden)
Ma Jing-Min
2011-01-01
Full Text Available Abstract Spin-dependent transport through a quantum-dot (QD ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively. PACS numbers:
Dynamical nuclear spin polarization induced by electronic current through double quantum dots
International Nuclear Information System (INIS)
Lopez-Monis, Carlos; Platero, Gloria; Inarrea, Jesus
2011-01-01
We analyse electron-spin relaxation in electronic transport through coherently coupled double quantum dots (DQDs) in the spin blockade regime. In particular, we focus on hyperfine (HF) interaction as the spin-relaxation mechanism. We pay special attention to the effect of the dynamical nuclear spin polarization induced by the electronic current on the nuclear environment. We discuss the behaviour of the electronic current and the induced nuclear spin polarization versus an external magnetic field for different HF coupling intensities and interdot tunnelling strengths. We take into account, for each magnetic field, all HF-mediated spin-relaxation processes coming from different opposite spin level approaches. We find that the current as a function of the external magnetic field shows a peak or a dip and that the transition from a current dip to a current peak behaviour is obtained by decreasing the HF coupling or by increasing the interdot tunnelling strength. We give a physical picture in terms of the interplay between the electrons tunnelling out of the DQD and the spin-flip processes due to the nuclear environment.
1H NMR studies in the regime of the field-induced spin-density wave phases of (TMTSF)2PF6
International Nuclear Information System (INIS)
Brown, S.E.; Pieper, M.; Clark, W.G.; Chow, D.S.; Alavi, B.
1999-01-01
We report 1 H proton spin-lattice relaxation measurements T 1 -1 on pressurized (TMTSF) 2 PF 6 in high magnetic fields. Maxima in T 1 -1 identify the phase transition to the field-induced spin-density wave (FISDW) state. Fluctuation effects are evident at temperatures above the transition, and vanish continuously in strength as the field is lowered to the critical field B c for the onset of the FISDW cascade. (orig.)
Interplay between superconductivity and Coulomb blockade
Energy Technology Data Exchange (ETDEWEB)
Lorenz, Thomas; Sprenger, Susanne; Scheer, Elke [Universitaet Konstanz (Germany)
2016-07-01
Studying the interplay between superconductivity and Coulomb blockade (CB) can be achieved by investigating an all superconducting single electron transistor (SSET) consisting of an island coupled to the leads by two tunneling contacts. The majority of experiments performed so far were using superconducting tunnel contacts made from oxide layers, in which multiple Andreev reflections (MAR) can be excluded. Using a mechanically controlled break junction (MCBJ) made of aluminum enables tuning the contributions of MAR in one junction continuously and thereby addressing different transport regimes within the same sample. Our results offer the possibility to attribute particular features in the transport characteristics to the transmission probabilities of individual modes in the MCBJ contact. We discuss our findings in terms of dynamical CB, SSET behaviour and MAR when continuously opening the MCBJ from the fully closed state to a tunneling contact.
Spin drift and spin diffusion currents in semiconductors
Energy Technology Data Exchange (ETDEWEB)
Idrish Miah, M [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)], E-mail: m.miah@griffith.edu.au
2008-09-15
On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.
Spin drift and spin diffusion currents in semiconductors
Directory of Open Access Journals (Sweden)
M Idrish Miah
2008-01-01
Full Text Available On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.
Spin drift and spin diffusion currents in semiconductors
International Nuclear Information System (INIS)
Idrish Miah, M
2008-01-01
On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.
Fang, Tie-Feng; Guo, Ai-Min; Sun, Qing-Feng
2018-06-01
We investigate Kondo correlations in a quantum dot with normal and superconducting electrodes, where a spin bias voltage is applied across the device and the local interaction U is either attractive or repulsive. When the spin current is blockaded in the large-gap regime, this nonequilibrium strongly correlated problem maps into an equilibrium model solvable by the numerical renormalization group method. The Kondo spectra with characteristic splitting due to the nonequilibrium spin accumulation are thus obtained at high precision. It is shown that while the bias-induced decoherence of the spin Kondo effect is partially compensated by the superconductivity, the charge Kondo effect is enhanced out of equilibrium and undergoes an additional splitting by the superconducting proximity effect, yielding four Kondo peaks in the local spectral density. In the charge Kondo regime, we find a universal scaling of charge conductance in this hybrid device under different spin biases. The universal conductance as a function of the coupling to the superconducting lead is peaked at and hence directly measures the Kondo temperature. Our results are of direct relevance to recent experiments realizing a negative-U charge Kondo effect in hybrid oxide quantum dots [Nat. Commun. 8, 395 (2017), 10.1038/s41467-017-00495-7].
Photon blockade in optomechanical systems with a position-modulated Kerr-type nonlinear coupling
Zhang, X. Y.; Zhou, Y. H.; Guo, Y. Q.; Yi, X. X.
2018-03-01
We explore the photon blockade in optomechanical systems with a position-modulated Kerr-type nonlinear coupling, i.e. H_int˜\\hat{a}\\dagger2\\hat{a}^2(\\hat{b}_1^\\dagger+\\hat{b}_1) . We find that the Kerr-type nonlinear coupling can enhance the photon blockade greatly. We evaluate the equal-time second-order correlation function of the cavity photons and find that the optimal photon blockade does not happen at the single photon resonance. By working within the few-photon subspace, we get an approximate analytical expression for the correlation function and the condition for the optimal photon blockade. We also find that the photon blockade effect is not always enhanced as the Kerr-type nonlinear coupling strength g 2 increases. At some values of g 2, the photon blockade is even weakened. For the system we considered here, the second-order correlation function can be smaller than 1 even in the unresolved sideband regime. By numerically simulating the master equation of the system, we also find that the thermal noise of the mechanical environment can enhance the photon blockade. We give out an explanation for this counter-intuitive phenomenon qualitatively.
Michel, P.; Richardson, D. C.
2007-08-01
During their evolutions, the small bodies of our Solar System are affected by several mechanisms which can modify their properties. While dynamical mechanisms are at the origin of their orbital variations, there are other mechanisms which can change their shape, spin, and even their size when their strength threshold is reached, resulting in their disruption. Such mechanisms have been identified and studied, both by analytical and numerical tools. The main mechanisms that can result in the disruption of a small body are collisional events, tidal perturbations, and spin-ups. However, the efficiency of these mechanisms depends on the strength of the material constituing the small body, which also plays a role in its possible equilibrium shape. We will present several important aspects of material strength that are believed to be adapted to Solar System small bodies and briefly review the most recent studies of the different mechanisms that can be at the origin of the disruption of these bodies. In particular, we have recently made a major improvement in the simulations of asteroid disruption by computing explicitly the formation of aggregates during the gravitational reaccumulation of small fragments, allowing us to obtain information on their spin, the number of boulders composing them or lying on their surface, and their shape.We will present the first and preliminary results of this process taking as examples some asteroid families that we reproduced successfully with our previous simulations (Michel et al. 2001, 2002, 2003, 2004a,b), and their possible implications on the properties of asteroids generated by a disruption. Such information can for instance be compared with data provided by the Japanese space mission Hayabusa of the asteroid Itokawa, a body now understood to be a fragment of a larger parent body. It is also clear that future space missions to small bodies devoted to precise in-situ analysis and sample return will allow us to improve our
Coherent-feedback-induced controllable optical bistability and photon blockade
International Nuclear Information System (INIS)
Liu, Yu-Long; Liu, Zhong-Peng; Zhang, Jing
2015-01-01
It is well known that some nonlinear phenomena such as strong photon blockade are difficult to observe in optomechanical systems with current experimental technology. Here we present a coherent feedback control strategy in which a linear cavity is coherently controlled by an optomechanical controller in a feedback manner. The coherent feedback loop transfers quantum nonlinearity from the controller to the controlled cavity causing destructive quantum interference to occur, and making it possible to observe strong nonlinear effects. With the help of the coherent feedback loop, large and tunable bistability and strong photon blockade of the cavity modes can be achieved even in the optomechanical weak coupling regime. Additionally, the coherent feedback loop leads to two-photon and multiphoton tunnelings for the controlled linear cavity, which are also typical quantum nonlinear phenomena. We hope that our work can give new perspectives on engineering nonlinear interactions in quantum systems. (paper)
International Nuclear Information System (INIS)
Kh'yuitt, G.
1980-01-01
An introduction into the problem of two-phase flows is presented. Flow regimes arizing in two-phase flows are described, and classification of these regimes is given. Structures of vertical and horizontal two-phase flows and a method of their identification using regime maps are considered. The limits of this method application are discussed. The flooding phenomena and phenomena of direction change (flow reversal) of the flow and interrelation of these phenomena as well as transitions from slug regime to churn one and from churn one to annular one in vertical flows are described. Problems of phase transitions and equilibrium are discussed. Flow regimes in tubes where evaporating liquid is running, are described [ru
International Nuclear Information System (INIS)
Hakioglu, T
2009-01-01
Based on Khodas et al (2004 Phys. Rev. Lett. 92 086602), we propose a device acting like a controllable prism for an incident spin. The device is a large quantum well where Rashba and Dresselhaus spin-orbit interactions are present and controlled by the plunger gate potential, the electric field and the barrier height. A totally destructive interference can be manipulated externally between the Rashba and Dresselhaus couplings. The spin-dependent transmission/reflection amplitudes are calculated as the control parameters are changed. The device operates as a spin prism/converter/filter in different regimes and may stimulate research in promising directions in spintronics in analogy with linear optics.
International Nuclear Information System (INIS)
Liles, D.R.
1982-01-01
Internal boundaries in multiphase flow greatly complicate fluid-dynamic and heat-transfer descriptions. Different flow regimes or topological configurations can have radically dissimilar interfacial and wall mass, momentum, and energy exchanges. To model the flow dynamics properly requires estimates of these rates. In this paper the common flow regimes for gas-liquid systems are defined and the techniques used to estimate the extent of a particular regime are described. Also, the current computer-code procedures are delineated and introduce a potentially better method is introduced
Coulomb blockade induced by magnetic field
International Nuclear Information System (INIS)
Kusmartsev, F.V.
1992-01-01
In this paper, the authors found that a Coulomb blockade can be induced by magnetic field. The authors illustrated this effect on the example of a ring consisting of two and many Josephson junctions. For the ring with two junctions we present an exact solution. The transition into Coulomb blockade state on a ring transforms into a linear array of Josephson junctions, although in latter case the effect of magnetic field disappears. In the state of Coulomb blockade the magnetization may be both diamagnetic and paramagnetic. The Coulomb blockade may also be removed by external magnetic field
Single-photon blockade in a hybrid cavity-optomechanical system via third-order nonlinearity
Sarma, Bijita; Sarma, Amarendra K.
2018-04-01
Photon statistics in a weakly driven optomechanical cavity, with Kerr-type nonlinearity, are analyzed both analytically and numerically. The single-photon blockade effect is demonstrated via calculations of the zero-time-delay second-order correlation function g (2)(0). The analytical results obtained by solving the Schrödinger equation are in complete conformity with the results obtained through numerical solution of the quantum master equation. A systematic study on the parameter regime for observing photon blockade in the weak coupling regime is reported. The parameter regime where the photon blockade is not realizable due to the combined effect of nonlinearities owing to the optomechanical coupling and the Kerr-effect is demonstrated. The experimental feasibility with state-of-the-art device parameters is discussed and it is observed that photon blockade could be generated at the telecommunication wavelength. An elaborate analysis of the thermal effects on photon antibunching is presented. The system is found to be robust against pure dephasing-induced decoherences and thermal phonon number fluctuations.
Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.
2015-10-01
Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical
International Nuclear Information System (INIS)
Pilat, Joseph F.; Budlong-Sylvester, K.W.
2004-01-01
Following the 1998 nuclear tests in South Asia and later reinforced by revelations about North Korean and Iraqi nuclear activities, there has been growing concern about increasing proliferation dangers. At the same time, the prospects of radiological/nuclear terrorism are seen to be rising - since 9/11, concern over a proliferation/terrorism nexus has never been higher. In the face of this growing danger, there are urgent calls for stronger measures to strengthen the current international nuclear nonproliferation regime, including recommendations to place civilian processing of weapon-useable material under multinational control. As well, there are calls for entirely new tools, including military options. As proliferation and terrorism concerns grow, the regime is under pressure and there is a temptation to consider fundamental changes to the regime. In this context, this paper will address the following: Do we need to change the regime centered on the Treaty on the Nonproliferation of Nuclear Weapons (NPT) and the International Atomic Energy Agency (IAEA)? What improvements could ensure it will be the foundation for the proliferation resistance and physical protection needed if nuclear power grows? What will make it a viable centerpiece of future nonproliferation and counterterrorism approaches?
Directory of Open Access Journals (Sweden)
Danilo Icaza Ortiz
2013-01-01
Full Text Available This paper is a review of the competition regime works of various authors, published under the auspices of the University of the Hemispheres and the Corporation for Studies and Publications. Analyzes the structure, the general concepts, case law taken for development. Includes comments on the usefulness of this work for the study of competition law and the contribution to the lawyers who want to practice in this branch of economic law.
Nuclear spin dynamics in double quantum dots : Fixed points, transients, and intermittency
Rudner, M.S.; Koppens, F.H.L.; Folk, J.A.; Vandersypen, L.M.K.; Levitov, L.S.
2011-01-01
Transport through spin-blockaded quantum dots provides a means for electrical control and detection of nuclear spin dynamics in the host material. Although such experiments have become increasingly popular in recent years, interpretation of their results in terms of the underlying nuclear spin
Spin dynamics in the strong spin-orbit coupling regime
Czech Academy of Sciences Publication Activity Database
Liu, X.; Liu, X.-J.; Sinova, Jairo
2011-01-01
Roč. 84, č. 3 (2011), 035318/1-035318/9 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : semiconductor quntum- wells Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011 http://link.aps.org/doi/10.1103/PhysRevB.84.035318
Neurohumoral blockade in CHF management
Directory of Open Access Journals (Sweden)
Roland Willenbrock
2000-03-01
Full Text Available Is heart failure an endocrine disease? Historically, congestive heart failure (CHF has often been regarded as a mechanical and haemodynamic condition. However, there is now strong evidence that the activation of neuroendocrine systems, like the renin-angiotensin-aldosterone system (RAAS and sympathetic nervous system, as well as the activation of natriuretic peptides, endothelin and vasopressin, play key roles in the progression of CHF. In this context, agents targeting neurohormones offer a highly rational approach to CHF management, with ACE inhibitors, aldosterone antagonists and beta-adrenergic blockade improving the prognosis for many patients. Although relevant improvements in clinical status and survival can be achieved with these drug classes, mortality rates for patients with CHF are still very high. Moreover, most patients do not receive these proven life-prolonging drugs, partially due to fear of adverse events, such as hypotension (with ACE inhibitors, gynaecomastia (with spironolactone and fatigue (with beta-blockers.New agents that combine efficacy with better tolerability are therefore needed. The angiotensin II type 1 (AT1-receptor blockers have the potential to fulfil both these requirements, by blocking the deleterious cardiovascular and haemodynamic effects of angiotensin II while offering placebo-like tolerability. As shown with candesartan, AT1-receptor blockers also modulate the levels of other neurohormones, including aldosterone and atrial natriuretic peptide (ANP. Combined with its tight, long-lasting binding to AT1-receptors, this characteristic gives candesartan the potential for complete blockade of the RAAS-neurohormonal axis, along with the great potential to improve clinical outcomes.
Directory of Open Access Journals (Sweden)
Romain Maurand
2012-02-01
Full Text Available We study a carbon-nanotube quantum dot embedded in a superconducting-quantum-interference-device loop in order to investigate the competition of strong electron correlations with a proximity effect. Depending on whether local pairing or local magnetism prevails, a superconducting quantum dot will exhibit a positive or a negative supercurrent, referred to as a 0 or π Josephson junction, respectively. In the regime of a strong Coulomb blockade, the 0-to-π transition is typically controlled by a change in the discrete charge state of the dot, from even to odd. In contrast, at a larger tunneling amplitude, the Kondo effect develops for an odd-charge (magnetic dot in the normal state, and quenches magnetism. In this situation, we find that a first-order 0-to-π quantum phase transition can be triggered at a fixed valence when superconductivity is brought in, due to the competition of the superconducting gap and the Kondo temperature. The superconducting-quantum-interference-device geometry together with the tunability of our device allows the exploration of the associated phase diagram predicted by recent theories. We also report on the observation of anharmonic behavior of the current-phase relation in the transition regime, which we associate with the two accessible superconducting states. Our results finally demonstrate that the spin-singlet nature of the Kondo state helps to enhance the stability of the 0 phase far from the mixed-valence regime in odd-charge superconducting quantum dots.
Contemporary views on the lawfulness of naval blockades
Fink, M.D.
2011-01-01
The traditional law of blockade has several technical requirements that if not met renders a blockade unlawful. These traditional requirements balance the interests of the belligerent and neutrals. A more contemporary view on the law of blockade, however, emphasizes that blockades are also subject
Electron spin resonance and spin-valley physics in a silicon double quantum dot.
Hao, Xiaojie; Ruskov, Rusko; Xiao, Ming; Tahan, Charles; Jiang, HongWen
2014-05-14
Silicon quantum dots are a leading approach for solid-state quantum bits. However, developing this technology is complicated by the multi-valley nature of silicon. Here we observe transport of individual electrons in a silicon CMOS-based double quantum dot under electron spin resonance. An anticrossing of the driven dot energy levels is observed when the Zeeman and valley splittings coincide. A detected anticrossing splitting of 60 MHz is interpreted as a direct measure of spin and valley mixing, facilitated by spin-orbit interaction in the presence of non-ideal interfaces. A lower bound of spin dephasing time of 63 ns is extracted. We also describe a possible experimental evidence of an unconventional spin-valley blockade, despite the assumption of non-ideal interfaces. This understanding of silicon spin-valley physics should enable better control and read-out techniques for the spin qubits in an all CMOS silicon approach.
Inverse spin-valve effect in nanoscale Si-based spin-valve devices
Hiep, Duong Dinh; Tanaka, Masaaki; Hai, Pham Nam
2017-12-01
We investigated the spin-valve effect in nano-scale silicon (Si)-based spin-valve devices using a Fe/MgO/Ge spin injector/detector deposited on Si by molecular beam epitaxy. For a device with a 20 nm Si channel, we observed clear magnetoresistance up to 3% at low temperature when a magnetic field was applied in the film plane along the Si channel transport direction. A large spin-dependent output voltage of 20 mV was observed at a bias voltage of 0.9 V at 15 K, which is among the highest values in lateral spin-valve devices reported so far. Furthermore, we observed that the sign of the spin-valve effect is reversed at low temperatures, suggesting the possibility of a spin-blockade effect of defect states in the MgO/Ge tunneling barrier.
Spin transport in spin filtering magnetic tunneling junctions.
Li, Yun; Lee, Eok Kyun
2007-11-01
Taking into account spin-orbit coupling and s-d interaction, we investigate spin transport properties of the magnetic tunneling junctions with spin filtering barrier using Landauer-Büttiker formalism implemented with the recursive algorithm to calculate the real-space Green function. We predict completely different bias dependence of negative tunnel magnetoresistance (TMR) between the systems composed of nonmagnetic electrode (NM)/ferromagnetic barrier (FB)/ferromagnet (FM) and NM/FB/FM/NM spin filtering tunnel junctions (SFTJs). Analyses of the results provide us possible ways of designing the systems which modulate the TMR in the negative magnetoresistance regime.
Deep Neuromuscular Blockade Improves Laparoscopic Surgical Conditions
DEFF Research Database (Denmark)
Rosenberg, Jacob; Herring, W Joseph; Blobner, Manfred
2017-01-01
INTRODUCTION: Sustained deep neuromuscular blockade (NMB) during laparoscopic surgery may facilitate optimal surgical conditions. This exploratory study assessed whether deep NMB improves surgical conditions and, in doing so, allows use of lower insufflation pressures during laparoscopic cholecys...
Spin fluctuation and small polaron conduction dominated electrical ...
Indian Academy of Sciences (India)
Administrator
temperature regime (20 K < T < 53 K), shows a minima near 53 K and increases with T ... Manganite nanoparticles; resistivity; spin fluctuation; electron–phonon interaction; electron– ... the low-doped regime because of the series of structural,.
Spin current through quantum-dot spin valves
International Nuclear Information System (INIS)
Wang, J; Xing, D Y
2006-01-01
We report a theoretical study of the influence of the Coulomb interaction on the equilibrium spin current in a quantum-dot spin valve, in which the quantum dot described by the Anderson impurity model is coupled to two ferromagnetic leads with noncollinear magnetizations. In the Kondo regime, electrons transmit through the quantum dot via higher-order virtual processes, in which the spin of either lead electrons or a localized electron on the quantum dot may reverse. It is found that the magnitude of the spin current decreases with increasing Coulomb interactions due to spin flip effects on the dot. However, the spatial direction of the spin current remains unchanged; it is determined only by the exchange coupling between two noncollinear magnetizations
Dynamical spin accumulation in large-spin magnetic molecules
Płomińska, Anna; Weymann, Ireneusz; Misiorny, Maciej
2018-01-01
The frequency-dependent transport through a nanodevice containing a large-spin magnetic molecule is studied theoretically in the Kondo regime. Specifically, the effect of magnetic anisotropy on dynamical spin accumulation is of primary interest. Such accumulation arises due to finite components of frequency-dependent conductance that are off diagonal in spin. Here, employing the Kubo formalism and the numerical renormalization group method, we demonstrate that the dynamical transport properties strongly depend on the relative orientation of spin moments in electrodes of the device, as well as on intrinsic parameters of the molecule. In particular, the effect of dynamical spin accumulation is found to be greatly affected by the type of magnetic anisotropy exhibited by the molecule, and it develops for frequencies corresponding to the Kondo temperature. For the parallel magnetic configuration of the device, the presence of dynamical spin accumulation is conditioned by the interplay of ferromagnetic-lead-induced exchange field and the Kondo correlations.
Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi
2012-01-01
In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.
Sugammadex: A Review of Neuromuscular Blockade Reversal.
Keating, Gillian M
2016-07-01
Sugammadex (Bridion(®)) is a modified γ-cyclodextrin that reverses the effect of the steroidal nondepolarizing neuromuscular blocking agents rocuronium and vecuronium. Intravenous sugammadex resulted in rapid, predictable recovery from moderate and deep neuromuscular blockade in patients undergoing surgery who received rocuronium or vecuronium. Recovery from moderate neuromuscular blockade was significantly faster with sugammadex 2 mg/kg than with neostigmine, and recovery from deep neuromuscular blockade was significantly faster with sugammadex 4 mg/kg than with neostigmine or spontaneous recovery. In addition, recovery from neuromuscular blockade was significantly faster when sugammadex 16 mg/kg was administered 3 min after rocuronium than when patients spontaneously recovered from succinylcholine. Sugammadex also demonstrated efficacy in various special patient populations, including patients with pulmonary disease, cardiac disease, hepatic dysfunction or myasthenia gravis and morbidly obese patients. Intravenous sugammadex was generally well tolerated. In conclusion, sugammadex is an important option for the rapid reversal of rocuronium- or vecuronium-induced neuromuscular blockade.
Nonequilibrium electron transport through quantum dots in the Kondo regime
DEFF Research Database (Denmark)
Wölfle, Peter; Paaske, Jens; Rosch, Achim
2005-01-01
Electron transport at large bias voltage through quantum dots in the Kondo regime is described within the perturbative renormalization group extended to nonequilibrium. The conductance, local magnetization, dynamical spin susceptibility and local spectral function are calculated. We show how...
Quantum spin circulator in Y junctions of Heisenberg chains
Buccheri, Francesco; Egger, Reinhold; Pereira, Rodrigo G.; Ramos, Flávia B.
2018-06-01
We show that a quantum spin circulator, a nonreciprocal device that routes spin currents without any charge transport, can be achieved in Y junctions of identical spin-1 /2 Heisenberg chains coupled by a chiral three-spin interaction. Using bosonization, boundary conformal field theory, and density matrix renormalization group simulations, we find that a chiral fixed point with maximally asymmetric spin conductance arises at a critical point separating a regime of disconnected chains from a spin-only version of the three-channel Kondo effect. We argue that networks of spin-chain Y junctions provide a controllable approach to construct long-sought chiral spin-liquid phases.
Geometrical spin symmetry and spin
International Nuclear Information System (INIS)
Pestov, I. B.
2011-01-01
Unification of General Theory of Relativity and Quantum Mechanics leads to General Quantum Mechanics which includes into itself spindynamics as a theory of spin phenomena. The key concepts of spindynamics are geometrical spin symmetry and the spin field (space of defining representation of spin symmetry). The essence of spin is the bipolar structure of geometrical spin symmetry induced by the gravitational potential. The bipolar structure provides a natural derivation of the equations of spindynamics. Spindynamics involves all phenomena connected with spin and provides new understanding of the strong interaction.
Spin-Swapping Transport and Torques in Ultrathin Magnetic Bilayers
Saidaoui, Hamed Ben Mohamed; Manchon, Aurelien
2016-01-01
Planar spin transport in disordered ultrathin magnetic bilayers comprising a ferromagnet and a normal metal (typically used for spin pumping, spin Seebeck and spin-orbit torque experiments) is investigated theoretically. Using a tight-binding model that puts the extrinsic spin Hall effect and spin swapping on equal footing, we show that the nature of spin-orbit coupled transport dramatically depends on the ratio between the layer thickness d and the mean free path λ. While the spin Hall effect dominates in the diffusive limit (d≫λ), spin swapping dominates in the Knudsen regime (d≲λ). A remarkable consequence is that spin swapping induces a substantial fieldlike torque in the Knudsen regime.
Spin-Swapping Transport and Torques in Ultrathin Magnetic Bilayers
Saidaoui, Hamed Ben Mohamed
2016-07-12
Planar spin transport in disordered ultrathin magnetic bilayers comprising a ferromagnet and a normal metal (typically used for spin pumping, spin Seebeck and spin-orbit torque experiments) is investigated theoretically. Using a tight-binding model that puts the extrinsic spin Hall effect and spin swapping on equal footing, we show that the nature of spin-orbit coupled transport dramatically depends on the ratio between the layer thickness d and the mean free path λ. While the spin Hall effect dominates in the diffusive limit (d≫λ), spin swapping dominates in the Knudsen regime (d≲λ). A remarkable consequence is that spin swapping induces a substantial fieldlike torque in the Knudsen regime.
Coulomb Blockade of Tunnel-Coupled Quantum Dots
National Research Council Canada - National Science Library
Golden, John
1997-01-01
.... Though classical charging models can explain the Coulomb blockade of an isolated dot, they must be modified to explain the Coulomb blockade of dots coupled through the quantum mechanical tunneling of electrons...
Objective neuromuscular monitoring of neuromuscular blockade in Denmark
DEFF Research Database (Denmark)
Söderström, C M; Eskildsen, K Z; Gätke, M R
2017-01-01
BACKGROUND: Neuromuscular blocking agents are commonly used during general anaesthesia but can lead to postoperative residual neuromuscular blockade and associated morbidity. With appropriate objective neuromuscular monitoring (objNMM) residual blockade can be avoided. In this survey, we investig...
Neuromuscular blockade in the elderly patient
Directory of Open Access Journals (Sweden)
Lee LA
2016-06-01
Full Text Available Luis A Lee, Vassilis Athanassoglou, Jaideep J Pandit Nuffield Department of Anaesthetics, Oxford University Hospitals NHS Foundation Trust, Oxford, UK Abstract: Neuromuscular blockade is a desirable or even essential component of general anesthesia for major surgical operations. As the population continues to age, and more operations are conducted in the elderly, due consideration must be given to neuromuscular blockade in these patients to avoid possible complications. This review considers the pharmacokinetics and pharmacodynamics of neuromuscular blockade that may be altered in the elderly. Compartment distribution, metabolism, and excretion of drugs may vary due to age-related changes in physiology, altering the duration of action with a need for reduced dosage (eg, aminosteroids. Other drugs (atracurium, cisatracurium have more reliable duration of action and should perhaps be considered for use in the elderly. The range of interpatient variability that neuromuscular blocking drugs may exhibit is then considered and drugs with a narrower range, such as cisatracurium, may produce more predictable, and inherently safer, outcomes. Ultimately, appropriate neuromuscular monitoring should be used to guide the administration of muscle relaxants so that the risk of residual neuromuscular blockade postoperatively can be minimized. The reliability of various monitoring is considered. This paper concludes with a review of the various reversal agents, namely, anticholinesterase drugs and sugammadex, and the alterations in dosing of these that should be considered for the elderly patient. Keywords: anesthesia, elderly, drugs, pharmacokinetics, pharmacodynamics
IFR channel-guiding of spinning beams
International Nuclear Information System (INIS)
O'Brien, K.J.
1986-06-01
A simple model is adopted to study the Ion Focussed Regime (IFR) laser channel-guiding of a spinning relativistic electron beam. It is discovered that spinning beams precess about the IFR axis as they damp; whereas, nonspinning beams remain planarly polarized
Quantum dynamics of nuclear spins and spin relaxation in organic semiconductors
Mkhitaryan, V. V.; Dobrovitski, V. V.
2017-06-01
We investigate the role of the nuclear-spin quantum dynamics in hyperfine-induced spin relaxation of hopping carriers in organic semiconductors. The fast-hopping regime, when the carrier spin does not rotate much between subsequent hops, is typical for organic semiconductors possessing long spin coherence times. We consider this regime and focus on a carrier random-walk diffusion in one dimension, where the effect of the nuclear-spin dynamics is expected to be the strongest. Exact numerical simulations of spin systems with up to 25 nuclear spins are performed using the Suzuki-Trotter decomposition of the evolution operator. Larger nuclear-spin systems are modeled utilizing the spin-coherent state P -representation approach developed earlier. We find that the nuclear-spin dynamics strongly influences the carrier spin relaxation at long times. If the random walk is restricted to a small area, it leads to the quenching of carrier spin polarization at a nonzero value at long times. If the random walk is unrestricted, the carrier spin polarization acquires a long-time tail, decaying as 1 /√{t } . Based on the numerical results, we devise a simple formula describing the effect quantitatively.
Voltage switching technique for detecting nuclear spin polarization in a quantum dot
International Nuclear Information System (INIS)
Takahashi, Ryo; Kono, Kimitoshi; Tarucha, Seigo; Ono, Keiji
2010-01-01
We have introduced a source-drain voltage switching technique for studying nuclear spins in a vertical double quantum dot. Switching the source-drain voltage between the spin-blockade state and the zero-bias Coulomb blockade state can tune the energy difference between the spin singlet and triplet, and effectively turn on/off the hyperfine interaction. Since the change in the nuclear spin state affects the source-drain current, nuclear spin properties can only be detected by transport measurement. Using this technique, we have succeeded in measuring the timescale of nuclear spin depolarization. Furthermore, combining this technique and an RF ac magnetic field, we successfully detected continuous-wave NMR signals of 75 As, 69 Ga, and 71 Ga, which are contained in a quantum dot. (author)
Multi-Valued Spin Switch in a Semiconductor Microcavity
Paraïso, T. K.; Wouters, M.; Léger, Y.; Morier-Genoud, F.; Deveaudhyphen; Plédran, B.
2011-12-01
In this work, we report on the first realization of multi-valued spin switching in the solid-state. We investigate the physics of spinor bistability with microcavity polaritons in a trap. Spinor interactions lead to special bistability regimes with decoupled thresholds for spin-up and spin-down polaritons. This allows us to establish state-of-the-art spin switching operations. We evidence polarization hysteresis and determine appropriate conditions to achieve spin multistability. For a given excitation condition, three stable spin states coexist for the system. These results open new pathways for the development of innovative spin-based logic gates and memory devices.
Efficient Multiparticle Entanglement via Asymmetric Rydberg Blockade
DEFF Research Database (Denmark)
Saffman, Mark; Mølmer, Klaus
2009-01-01
We present an efficient method for producing N particle entangled states using Rydberg blockade interactions. Optical excitation of Rydberg states that interact weakly, yet have a strong coupling to a second control state is used to achieve state dependent qubit rotations in small ensembles. On t....... On the basis of quantitative calculations, we predict that an entangled quantum superposition state of eight atoms can be produced with a fidelity of 84% in cold Rb atoms.......We present an efficient method for producing N particle entangled states using Rydberg blockade interactions. Optical excitation of Rydberg states that interact weakly, yet have a strong coupling to a second control state is used to achieve state dependent qubit rotations in small ensembles...
Comparative Aspects of Spin-Dependent Interaction Potentials for Spin-1/2 and Spin-1 Matter Fields
Directory of Open Access Journals (Sweden)
P. C. Malta
2016-01-01
Full Text Available This paper sets out to establish a comparative study between classes of spin- and velocity-dependent potentials for spin-1/2 and spin-1 matter currents/sources in the nonrelativistic regime. Both (neutral massive scalar and vector particles are considered to mediate the interactions between (pseudo-scalar sources or (pseudo-vector currents. Though our discussion is more general, we contemplate specific cases in which our results may describe the electromagnetic interaction with a massive (Proca-type photon exchanged between two spin-1/2 or two spin-1 carriers. We highlight the similarities and peculiarities of the potentials for the two different types of charged matter and also focus our attention on the comparison between the particular aspects of two different field representations for spin-1 matter particles. We believe that our results may contribute to a further discussion of the relation between charge, spin, and extensibility of elementary particles.
International Nuclear Information System (INIS)
Lin, J.; Millis, A.J.
2011-01-01
We calculate the frequency-dependent longitudinal (σ xx ) and Hall (σ xy ) conductivities for two-dimensional metals with thermally disordered antiferromagnetism using a generalization of a theoretical model, involving a one-loop quasistatic fluctuation approximation, which was previously used to calculate the electron self-energy. The conductivities are calculated from the Kubo formula, with current vertex function treated in a conserving approximation satisfying the Ward identity. In order to obtain a finite dc limit, we introduce phenomenologically impurity scattering, characterized by a relaxation time τ. σ xx ((Omega)) satisfies the f-sum rule. For the infinitely peaked spin-correlation function, χ(q)∝(delta)(q-Q), we recover the expressions for the conductivities in the mean-field theory of the ordered state. When the spin-correlation length ζ is large but finite, both σ xx and σ xy show behaviors characteristic of the state with long-range order. The calculation runs into difficulty for (Omega) ∼ xx ((Omega)) and σ xy ((Omega)) are qualitatively consistent with data on electron-doped cuprates when (Omega) > 1/τ.
Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi
2017-01-01
Since the discovery of the giant magnetoresistance effect in magnetic multilayers in 1988, a new branch of physics and technology, called spin-electronics or spintronics, has emerged, where the flow of electrical charge as well as the flow of electron spin, the so-called “spin current,” are manipulated and controlled together. The physics of magnetism and the application of spin current have progressed in tandem with the nanofabrication technology of magnets and the engineering of interfaces and thin films. This book aims to provide an introduction and guide to the new physics and applications of spin current, with an emphasis on the interaction between spin and charge currents in magnetic nanostructures.
Vozková, Markéta
2011-01-01
1 ABSTRACT The aim of this text is to provide an analysis of the phenomenon of spin doctoring in the Euro-Atlantic area. Spin doctors are educated people in the fields of semiotics, cultural studies, public relations, political communication and especially familiar with the infrastructure and the functioning of the media industry. Critical reflection of manipulative communication techniques puts spin phenomenon in historical perspective and traces its practical use in today's social communica...
Charge and spin transport in mesoscopic superconductors
Directory of Open Access Journals (Sweden)
M. J. Wolf
2014-02-01
Full Text Available Background: Non-equilibrium charge transport in superconductors has been investigated intensely in the 1970s and 1980s, mostly in the vicinity of the critical temperature. Much less attention has been paid to low temperatures and the role of the quasiparticle spin.Results: We report here on nonlocal transport in superconductor hybrid structures at very low temperatures. By comparing the nonlocal conductance obtained by using ferromagnetic and normal-metal detectors, we discriminate charge and spin degrees of freedom. We observe spin injection and long-range transport of pure, chargeless spin currents in the regime of large Zeeman splitting. We elucidate charge and spin transport by comparison to theoretical models.Conclusion: The observed long-range chargeless spin transport opens a new path to manipulate and utilize the quasiparticle spin in superconductor nanostructures.
Spin and radiation in intense laser fields
International Nuclear Information System (INIS)
Walser, M.W.; Urbach, D.J.; Hatsagortsyan, K.Z.; Hu, S.X.; Keitel, C.H.
2002-01-01
The spin dynamics and its reaction on the particle motion are investigated for free and bound electrons in intense linearly polarized laser fields. Employing both classical and quantum treatments we analytically evaluate the spin oscillation of free electrons in intense laser fields and indicate the effect of spin-orbit coupling on the motion of the electron. In Mott scattering an estimation for the spin oscillation is derived. In intense laser ion dynamics spin signatures are studied in detail with emphasis on high-order harmonic generation in the tunneling regime. First- and second-order calculations in the ratio of electron velocity and the speed of light show spin signatures in the radiation spectrum and spin-orbit effects in the electron polarization
Bhagwat, Swetha; Kumar, Prayush; Barkett, Kevin; Afshari, Nousha; Brown, Duncan A.; Lovelace, Geoffrey; Scheel, Mark A.; Szilagyi, Bela; LIGO Collaboration
2016-03-01
Detection of gravitational wave involves extracting extremely weak signal from noisy data and their detection depends crucially on the accuracy of the signal models. The most accurate models of compact binary coalescence are known to come from solving the Einstein's equation numerically without any approximations. However, this is computationally formidable. As a more practical alternative, several analytic or semi analytic approximations are developed to model these waveforms. However, the work of Nitz et al. (2013) demonstrated that there is disagreement between these models. We present a careful follow up study on accuracies of different waveform families for spinning black-hole neutron star binaries, in context of both detection and parameter estimation and find that SEOBNRv2 to be the most faithful model. Post Newtonian models can be used for detection but we find that they could lead to large parameter bias. Supported by National Science Foundation (NSF) Awards No. PHY-1404395 and No. AST-1333142.
Pan, Bingying; Wang, Yang; Zhang, Lijuan; Li, Shiyan
2014-04-07
Single crystals of a metal organic complex (C5H12N)CuBr3 (C5H12N = piperidinium, pipH for short) have been synthesized, and the structure was determined by single-crystal X-ray diffraction. (pipH)CuBr3 crystallizes in the monoclinic group C2/c. Edging-sharing CuBr5 units link to form zigzag chains along the c axis, and the neighboring Cu(II) ions with spin-1/2 are bridged by bibromide ions. Magnetic susceptibility data down to 1.8 K can be well fitted by the Bonner-Fisher formula for the antiferromagnetic spin-1/2 chain, giving the intrachain magnetic coupling constant J ≈ -17 K. At zero field, (pipH)CuBr3 shows three-dimensional (3D) order below TN = 1.68 K. Calculated by the mean-field theory, the interchain coupling constant J' = -0.91 K is obtained and the ordered magnetic moment m0 is about 0.23 μB. This value of m0 makes (pipH)CuBr3 a rare compound suitable to study the 1D-3D dimensional cross-over problem in magnetism, since both 3D order and one-dimensional (1D) quantum fluctuations are prominent. In addition, specific heat measurements reveal two successive magnetic transitions with lowering temperature when external field μ0H ≥ 3 T is applied along the a' axis. The μ0H-T phase diagram of (pipH)CuBr3 is roughly constructed.
Hybrid spin-nanomechanics with single spins in diamond mechanical oscillators
Barfuss, Arne
2017-01-01
Hybrid spin-oscillator systems, formed by single spins coupled to mechanical oscillators, have attracted ever-increasing attention over the past few years, triggered largely by the prospect of employing such devices as high-performance nanoscale sensors or transducers in multi-qubit networks. Provided the spin-oscillator coupling is strong and robust, such systems can even serve as test-beds for studying macroscopic objects in the quantum regime. In this thesis we present a novel hybrid sp...
Tunneling spin injection into single layer graphene.
Han, Wei; Pi, K; McCreary, K M; Li, Yan; Wong, Jared J I; Swartz, A G; Kawakami, R K
2010-10-15
We achieve tunneling spin injection from Co into single layer graphene (SLG) using TiO₂ seeded MgO barriers. A nonlocal magnetoresistance (ΔR(NL)) of 130 Ω is observed at room temperature, which is the largest value observed in any material. Investigating ΔR(NL) vs SLG conductivity from the transparent to the tunneling contact regimes demonstrates the contrasting behaviors predicted by the drift-diffusion theory of spin transport. Furthermore, tunnel barriers reduce the contact-induced spin relaxation and are therefore important for future investigations of spin relaxation in graphene.
International Nuclear Information System (INIS)
Anton, Gisela
1990-01-01
The idea of the intrinsic angular momentum, or 'spin', of a particle has played an essential part in fundamental physics for more than 60 years, and its continuing importance was underlined at the 9th International Symposium on High Energy Spin Physics, held in September in Bonn.
Energy Technology Data Exchange (ETDEWEB)
Anton, Gisela
1990-12-15
The idea of the intrinsic angular momentum, or 'spin', of a particle has played an essential part in fundamental physics for more than 60 years, and its continuing importance was underlined at the 9th International Symposium on High Energy Spin Physics, held in September in Bonn.
Energy Technology Data Exchange (ETDEWEB)
D' Ariano, G M [Quantum Optics and Information Group, INFM Udr Pavia, Dipartimento di Fisica ' Alessandro Volta' and INFM, Via Bassi 6, 27100 Pavia (Italy); Maccone, L [Quantum Optics and Information Group, INFM Udr Pavia, Dipartimento di Fisica ' Alessandro Volta' and INFM, Via Bassi 6, 27100 Pavia (Italy); Paini, M [Quantum Optics and Information Group, INFM Udr Pavia, Dipartimento di Fisica ' Alessandro Volta' and INFM, Via Bassi 6, 27100 Pavia (Italy)
2003-02-01
We propose a tomographic reconstruction scheme for spin states. The experimental set-up, which is a modification of the Stern-Gerlach scheme, can be easily performed with currently available technology. The method is generalized to multiparticle states, analysing the spin-1/2 case for indistinguishable particles. Some Monte Carlo numerical simulations are given to illustrate the technique.
International Nuclear Information System (INIS)
D'Ariano, G M; Maccone, L; Paini, M
2003-01-01
We propose a tomographic reconstruction scheme for spin states. The experimental set-up, which is a modification of the Stern-Gerlach scheme, can be easily performed with currently available technology. The method is generalized to multiparticle states, analysing the spin-1/2 case for indistinguishable particles. Some Monte Carlo numerical simulations are given to illustrate the technique
Bovier, Anton
2007-01-01
Spin glass theory is going through a stunning period of progress while finding exciting new applications in areas beyond theoretical physics, in particular in combinatorics and computer science. This collection of state-of-the-art review papers written by leading experts in the field covers the topic from a wide variety of angles. The topics covered are mean field spin glasses, including a pedagogical account of Talagrand's proof of the Parisi solution, short range spin glasses, emphasizing the open problem of the relevance of the mean-field theory for lattice models, and the dynamics of spin glasses, in particular the problem of ageing in mean field models. The book will serve as a concise introduction to the state of the art of spin glass theory, usefull to both graduate students and young researchers, as well as to anyone curious to know what is going on in this exciting area of mathematical physics.
Energy Technology Data Exchange (ETDEWEB)
Anon.
1989-01-15
The recent 8th International Symposium on High Energy Spin Physics at the University of Minnesota in Minneapolis, Minnesota, opened with a bang when L. Pondrom (Wisconsin), donning a hard hat borrowed from construction workers, ventured that 'spin, the notorious inessential complication of hadronic physics, is finally telling us what real QCD (quantum chromodynamics, the field theory of quarks and gluons) looks like.' He was referring to an animated discussion on the meaning of the recent spin oriented (polarized) scattering results from the European Muon Collaboration (EMC) at CERN and reported at the Symposium by R. Garnet (Liverpool) and P. Schuler (Yale) which show that the proton spin is not simply a reflection of the spins of its constituent quarks.
Neuraxial blockade for external cephalic version: Cost analysis.
Yamasato, Kelly; Kaneshiro, Bliss; Salcedo, Jennifer
2015-07-01
Neuraxial blockade (epidural or spinal anesthesia/analgesia) with external cephalic version increases the external cephalic version success rate. Hospitals and insurers may affect access to neuraxial blockade for external cephalic version, but the costs to these institutions remain largely unstudied. The objective of this study was to perform a cost analysis of neuraxial blockade use during external cephalic version from hospital and insurance payer perspectives. Secondarily, we estimated the effect of neuraxial blockade on cesarean delivery rates. A decision-analysis model was developed using costs and probabilities occurring prenatally through the delivery hospital admission. Model inputs were derived from the literature, national databases, and local supply costs. Univariate and bivariate sensitivity analyses and Monte Carlo simulations were performed to assess model robustness. Neuraxial blockade was cost saving to both hospitals ($30 per delivery) and insurers ($539 per delivery) using baseline estimates. From both perspectives, however, the model was sensitive to multiple variables. Monte Carlo simulation indicated neuraxial blockade to be more costly in approximately 50% of scenarios. The model demonstrated that routine use of neuraxial blockade during external cephalic version, compared to no neuraxial blockade, prevented 17 cesarean deliveries for every 100 external cephalic versions attempted. Neuraxial blockade is associated with minimal hospital and insurer cost changes in the setting of external cephalic version, while reducing the cesarean delivery rate. © 2015 The Authors. Journal of Obstetrics and Gynaecology Research © 2015 Japan Society of Obstetrics and Gynecology.
Luengo-Kovac, M.; Moraes, F. C. D.; Ferreira, G. J.; Ribeiro, A. S. L.; Gusev, G. M.; Bakarov, A. K.; Sih, V.; Hernandez, F. G. G.
2017-06-01
Spin drag measurements were performed in a two-dimensional electron system set close to the crossed spin helix regime and coupled by strong intersubband scattering. In a sample with an uncommon combination of long spin lifetime and high charge mobility, the drift transport allows us to determine the spin-orbit field and the spin mobility anisotropies. We used a random walk model to describe the system dynamics and found excellent agreement for the Rashba and Dresselhaus couplings. The proposed two-subband system displays a large tuning lever arm for the Rashba constant with gate voltage, which provides a new path towards a spin transistor. Furthermore, the data show large spin mobility controlled by the spin-orbit constants setting the field along the direction perpendicular to the drift velocity. This work directly reveals the resistance experienced in the transport of a spin-polarized packet as a function of the strength of anisotropic spin-orbit fields.
Nonadiabatic holonomic quantum computation using Rydberg blockade
Kang, Yi-Hao; Chen, Ye-Hong; Shi, Zhi-Cheng; Huang, Bi-Hua; Song, Jie; Xia, Yan
2018-04-01
In this paper, we propose a scheme for realizing nonadiabatic holonomic computation assisted by two atoms and the shortcuts to adiabaticity (STA). The blockade effect induced by strong Rydberg-mediated interaction between two Rydberg atoms provides us the possibility to simplify the dynamics of the system, and the STA helps us design pulses for implementing the holonomic computation with high fidelity. Numerical simulations show the scheme is noise immune and decoherence resistant. Therefore, the current scheme may provide some useful perspectives for realizing nonadiabatic holonomic computation.
Caspers, W J
1989-01-01
This book is about spin systems as models for magnetic materials, especially antiferromagnetic lattices. Spin-systems are well-defined models, for which, in special cases, exact properties may be derived. These special cases are for the greater part, one- dimensional and restricted in their applicability, but they may give insight into general properties that also exist in higher dimension. This work pays special attention to qualitative differences between spin lattices of different dimensions. It also replaces the traditional picture of an (ordered) antiferromagnetic state of a Heisenberg sy
Rocuronium blockade reversal with sugammadex vs. neostigmine
DEFF Research Database (Denmark)
Wu, Xinmin; Oerding, Helle; Liu, Jin
2014-01-01
BACKGROUND: This study compared efficacy and safety of the selective relaxant binding agent sugammadex (2 mg/kg) with neostigmine (50 μg/kg) for neuromuscular blockade (NMB) reversal in Chinese and Caucasian subjects. METHODS: This was a randomized, active-controlled, multicenter, safety-assessor......BACKGROUND: This study compared efficacy and safety of the selective relaxant binding agent sugammadex (2 mg/kg) with neostigmine (50 μg/kg) for neuromuscular blockade (NMB) reversal in Chinese and Caucasian subjects. METHODS: This was a randomized, active-controlled, multicenter, safety...... twitch reappearance, after last rocuronium dose, subjects received sugammadex 2 mg/kg or neostigmine 50 μg/kg plus atropine 10-20 μg/kg, according to randomization. Primary efficacy variable was time from sugammadex/neostigmine to recovery of the train-of-four (TOF) ratio to 0.9. RESULTS: Overall, 230...... Chinese subjects (sugammadex, n = 119, neostigmine, n = 111); and 59 Caucasian subjects (sugammadex, n = 29, neostigmine, n = 30) had evaluable data. Geometric mean (95% CI) time to recovery to TOF ratio 0.9 was 1.6 (1.5-1.7) min with sugammadex vs 9.1 (8.0-10.3) min with neostigmine in Chinese subjects...
Spin relaxation through Kondo scattering in Cu/Py lateral spin valves
Batley, J. T.; Rosaond, M. C.; Ali, M.; Linfield, E. H.; Burnell, G.; Hickey, B. J.
Within non-magnetic metals it is reasonable to expect the Elliot-Yafet mechanism to govern spin-relaxation and thus the temperature dependence of the spin diffusion length might be inversely proportional to resistivity. However, in lateral spin valves, measurements have found that at low temperatures the spin diffusion length unexpectedly decreases. We have fabricated lateral spin valves from Cu with different concentrations of magnetic impurities. Through temperature dependent charge and spin transport measurements we present clear evidence linking the presence of the Kondo effect within Cu to the suppression of the spin diffusion length below 30 K. We have calculated the spin-relaxation rate and isolated the contribution from magnetic impurities. At very low temperatures electron-electron interactions play a more prominent role in the Kondo effect. Well below the Kondo temperature a strong-coupling regime exists, where the moments become screened and the magnetic dephasing rate is reduced. We also investigate the effect of this low temperature regime (>1 K) on a pure spin current. This work shows the dominant role of Kondo scattering, even in low concentrations of order 1 ppm, within pure spin transport.
Buhrman, Robert; Daughton, James; Molnár, Stephan; Roukes, Michael
2004-01-01
This report is a comparative review of spin electronics ("spintronics") research and development activities in the United States, Japan, and Western Europe conducted by a panel of leading U.S. experts in the field. It covers materials, fabrication and characterization of magnetic nanostructures, magnetism and spin control in magnetic nanostructures, magneto-optical properties of semiconductors, and magnetoelectronics and devices. The panel's conclusions are based on a literature review and a series of site visits to leading spin electronics research centers in Japan and Western Europe. The panel found that Japan is clearly the world leader in new material synthesis and characterization; it is also a leader in magneto-optical properties of semiconductor devices. Europe is strong in theory pertaining to spin electronics, including injection device structures such as tunneling devices, and band structure predictions of materials properties, and in development of magnetic semiconductors and semiconductor heterost...
International Nuclear Information System (INIS)
Anon.
1983-01-01
The 5th International Symposium on High Energy Spin Physics met in September at Brookhaven. The symposium has evolved to include a number of diverse specialities: theory, including parity violations and proposed quantum chromodynamics (QCD) tests with polarized beams; experiment, including the large spin effects discovered in high transverse momentum elastic scattering and hyperon production, dibaryons, and magnetic moments; acceleration and storage of polarized protons and electrons; and development of polarized sources and targets
The impact of acute preoperative beta-blockade on perioperative ...
African Journals Online (AJOL)
To determine the impact of acute preoperative β-blockade on the incidence of perioperative cardiovascular morbidity and all- ... Our findings suggest that acute preoperative β-blockade is associated with an increased risk of perioperative cardiac ..... Shammash JB, Trost JC, Gold JM, Berlin JA, Golden MA, Kimmel SE.
Scaling behavior of spin gap of the bond alternating anisotropic spin-1/2 Heisenberg chain
Energy Technology Data Exchange (ETDEWEB)
Paul, Susobhan, E-mail: suso.phy.paul@gmail.com [Department of Physics, Scottish Church College, 1 & 3 Urquhart Square, Kolkata-700006 (India); Ghosh, Asim Kumar, E-mail: asimkumar96@yahoo.com [Department of Physics, Jadavpur University, 188 Raja S C Mallik Road, Kolkata-700032 (India)
2016-05-06
Scaling behavior of spin gap of a bond alternating spin-1/2 anisotropic Heisenberg chain has been studied both in ferromagnetic (FM) and antiferromagnetic (AFM) cases. Spin gap has been estimated by using exact diagonalization technique. All those quantities have been obtained for a region of anisotropic parameter Δ defined by 0≤Δ≤1. Spin gap is found to develop as soon as the non-uniformity in the alternating bond strength is introduced in the AFM regime which furthermore sustains in the FM regime as well. Scaling behavior of the spin gap has been studied by introducing scaling exponent. The variation of scaling exponents with Δ is fitted with a regular function.
Bipolar spintronics: from spin injection to spin-controlled logic
International Nuclear Information System (INIS)
Zutic, Igor; Fabian, Jaroslav; Erwin, Steven C
2007-01-01
An impressive success of spintronic applications has been typically realized in metal-based structures which utilize magnetoresistive effects for substantial improvements in the performance of computer hard drives and magnetic random access memories. Correspondingly, the theoretical understanding of spin-polarized transport is usually limited to a metallic regime in a linear response, which, while providing a good description for data storage and magnetic memory devices, is not sufficient for signal processing and digital logic. In contrast, much less is known about possible applications of semiconductor-based spintronics and spin-polarized transport in related structures which could utilize strong intrinsic nonlinearities in current-voltage characteristics to implement spin-based logic. Here we discuss the challenges for realizing a particular class of structures in semiconductor spintronics: our proposal for bipolar spintronic devices in which carriers of both polarities (electrons and holes) contribute to spin-charge coupling. We formulate the theoretical framework for bipolar spin-polarized transport, and describe several novel effects in two- and three-terminal structures which arise from the interplay between nonequilibrium spin and equilibrium magnetization
Full counting statistics of a charge pump in the Coulomb blockade regime
Andreev, A. V.; Mishchenko, E. G.
2001-12-01
We study full charge counting statistics (FCCS) of a charge pump based on a nearly open single electron transistor. The problem is mapped onto an exactly soluble problem of a nonequilibrium g=1/2 Luttinger liquid with an impurity. We obtain an analytic expression for the generating function of the transmitted charge for an arbitrary pumping strength. Although this model contains fractionally charged excitations only integer transmitted charges can be observed. In the weak pumping limit FCCS correspond to a Poissonian transmission of particles with charge e*=e/2 from which all events with odd numbers of transferred particles are excluded.
Predicting transport regime and local electrostatic environment from Coulomb blockade diamond sizes
DEFF Research Database (Denmark)
Olsen, Stine Tetzschner; Hansen, Thorsten; Mikkelsen, Kurt Valentin
2017-01-01
by Bjørnholm and co-workers is performed. The experiments showed how two OPV3 derivatives performed very differently despite the strong similarity of the molecular structure, hence the experimental data showed two different transport mechanisms. The different transport mechanisms of the two OPV3 derivatives...
Sustainable urban regime adjustments
DEFF Research Database (Denmark)
Quitzau, Maj-Britt; Jensen, Jens Stissing; Elle, Morten
2013-01-01
The endogenous agency that urban governments increasingly portray by making conscious and planned efforts to adjust the regimes they operate within is currently not well captured in transition studies. There is a need to acknowledge the ambiguity of regime enactment at the urban scale. This direc...
Indian Academy of Sciences (India)
First page Back Continue Last page Overview Graphics. Flux scaling: Ultimate regime. With the Nusselt number and the mixing length scales, we get the Nusselt number and Reynolds number (w'd/ν) scalings: and or. and. scaling expected to occur at extremely high Ra Rayleigh-Benard convection. Get the ultimate regime ...
Robust spin transfer torque in antiferromagnetic tunnel junctions
Saidaoui, Hamed Ben Mohamed; Waintal, Xavier; Manchon, Aurelien
2017-01-01
We theoretically study the current-induced spin torque in antiferromagnetic tunnel junctions, composed of two semi-infinite antiferromagnetic layers separated by a tunnel barrier, in both clean and disordered regimes. We find that the torque
International Nuclear Information System (INIS)
Solontsov, A.
2015-01-01
The paper critically overviews the recent developments of the theory of spatially dispersive spin fluctuations (SF) in itinerant electron magnetism with particular emphasis on spin-fluctuation coupling or spin anharmonicity. It is argued that the conventional self-consistent renormalized (SCR) theory of spin fluctuations is usually used aside of the range of its applicability actually defined by the constraint of weak spin anharmonicity based on the random phase approximation (RPA) arguments. An essential step in understanding SF in itinerant magnets beyond RPA-like arguments was made recently within the soft-mode theory of SF accounting for strong spin anharmonicity caused by zero-point SF. In the present paper we generalize it to apply for a wider range of temperatures and regimes of SF and show it to lead to qualitatively new results caused by zero-point effects. - Highlights: • We review the spin-fluctuation theory of itinerant electron magnets with account of zero-point effects. • We generalize the existing theory to account for different regimes of spin fluctuations. • We show that zero-point spin fluctuations play a crucial role in both low- and high-temperature properties of metallic magnets. • We argue that a new scheme of calculation of ground state properties of magnets is needed including zero-point effects
Andreev, Pavel A.
2017-02-01
The dielectric permeability tensor for spin polarized plasmas is derived in terms of the spin-1/2 quantum kinetic model in six-dimensional phase space. Expressions for the distribution function and spin distribution function are derived in linear approximations on the path of dielectric permeability tensor derivation. The dielectric permeability tensor is derived for the spin-polarized degenerate electron gas. It is also discussed at the finite temperature regime, where the equilibrium distribution function is presented by the spin-polarized Fermi-Dirac distribution. Consideration of the spin-polarized equilibrium states opens possibilities for the kinetic modeling of the thermal spin current contribution in the plasma dynamics.
International Nuclear Information System (INIS)
Gaarde, C.
1985-01-01
An analysis of spectra of (p,n) reactions showed that they were very selective in exciting spin modes. Charge exchange reactions at intermediate energies give important new understanding of the M1-type of excitations and of the spin structure of continuum p spectra in general. In this paper, the author discusses three charge exchange reactions: (p,n); ( 3 H,t); and (d,2p) at several targets. Low-lying states and the Δ region are discussed separately. Finally, the charge exchange reaction with heavy ion beams is briefly discussed. (G.J.P./Auth.)
The spin-Peierls chain revisited
International Nuclear Information System (INIS)
Hager, Georg; Weisse, Alexander; Wellein, Gerhard; Jeckelmann, Eric; Fehske, Holger
2007-01-01
We extend previous analytical studies of the ground-state phase diagram of a one-dimensional Heisenberg spin chain coupled to optical phonons, which for increasing spin-lattice coupling undergoes a quantum phase transition from a gapless to a gaped phase with finite lattice dimerisation. We check the analytical results against established four-block and new two-block density matrix renormalisation group (DMRG) calculations. Different finite-size scaling behaviour of the spin excitation gaps is found in the adiabatic and anti-adiabatic regimes
Terletska, Hanna; Dobrovitski, Viatcheslav
2015-03-01
The electron spin of the NV center in diamond is a promising platform for spin sensing. Applying the dynamical decoupling, the NV electron spin can be used to detect the individual weakly coupled carbon-13 nuclear spins in diamond and employ them for small-scale quantum information processing. However, the nuclear spins within this approach remain unprotected from decoherence, which ultimately limits the detection and restricts the fidelity of the quantum operation. Here we investigate possible schemes for combining the resonant decoupling on the NV spin with the decoherence protection of the nuclear spins. Considering several schemes based on pulse and continuous-wave decoupling, we study how the joint electron-nuclear spin dynamics is affected. We identify regimes where the all-spin coherence protection improves the detection and manipulation. We also discuss potential applications of the all-spin decoupling for detecting spins outside diamond, with the purpose of implementing the nanoscale NMR. This work was supported by the US Department of Energy Basic Energy Sciences (Contract No. DE-AC02-07CH11358).
Directory of Open Access Journals (Sweden)
Casie Lindsly
Full Text Available Synaptic scaling represents a process whereby the distribution of a cell's synaptic strengths are altered by a multiplicative scaling factor. Scaling is thought to be a compensatory response that homeostatically controls spiking activity levels in the cell or network. Previously, we observed GABAergic synaptic scaling in embryonic spinal motoneurons following in vivo blockade of either spiking activity or GABAA receptors (GABAARs. We had determined that activity blockade triggered upward GABAergic scaling through chloride accumulation, thus increasing the driving force for these currents. To determine whether chloride accumulation also underlies GABAergic scaling following GABAAR blockade we have developed a new technique. We expressed a genetically encoded chloride-indicator, Clomeleon, in the embryonic chick spinal cord, which provides a non-invasive fast measure of intracellular chloride. Using this technique we now show that chloride accumulation underlies GABAergic scaling following blockade of either spiking activity or the GABAAR. The finding that GABAAR blockade and activity blockade trigger scaling via a common mechanism supports our hypothesis that activity blockade reduces GABAAR activation, which triggers synaptic scaling. In addition, Clomeleon imaging demonstrated the time course and widespread nature of GABAergic scaling through chloride accumulation, as it was also observed in spinal interneurons. This suggests that homeostatic scaling via chloride accumulation is a common feature in many neuronal classes within the embryonic spinal cord and opens the possibility that this process may occur throughout the nervous system at early stages of development.
Schwarz, H.
2017-01-01
The thesis "Spinning Worlds" is about the characterisation of two types of gas-giant exoplanets: Hot Jupiters, with orbital periods of fewer than five days, and young, wide-orbit gas giants, with orbital periods as long as thousands of years. The thesis is based on near-infrared observations of 1
Spin diffusion from an inhomogeneous quench in an integrable system.
Ljubotina, Marko; Žnidarič, Marko; Prosen, Tomaž
2017-07-13
Generalized hydrodynamics predicts universal ballistic transport in integrable lattice systems when prepared in generic inhomogeneous initial states. However, the ballistic contribution to transport can vanish in systems with additional discrete symmetries. Here we perform large scale numerical simulations of spin dynamics in the anisotropic Heisenberg XXZ spin 1/2 chain starting from an inhomogeneous mixed initial state which is symmetric with respect to a combination of spin reversal and spatial reflection. In the isotropic and easy-axis regimes we find non-ballistic spin transport which we analyse in detail in terms of scaling exponents of the transported magnetization and scaling profiles of the spin density. While in the easy-axis regime we find accurate evidence of normal diffusion, the spin transport in the isotropic case is clearly super-diffusive, with the scaling exponent very close to 2/3, but with universal scaling dynamics which obeys the diffusion equation in nonlinearly scaled time.
Computational assignment of redox states to Coulomb blockade diamonds.
Olsen, Stine T; Arcisauskaite, Vaida; Hansen, Thorsten; Kongsted, Jacob; Mikkelsen, Kurt V
2014-09-07
With the advent of molecular transistors, electrochemistry can now be studied at the single-molecule level. Experimentally, the redox chemistry of the molecule manifests itself as features in the observed Coulomb blockade diamonds. We present a simple theoretical method for explicit construction of the Coulomb blockade diamonds of a molecule. A combined quantum mechanical/molecular mechanical method is invoked to calculate redox energies and polarizabilities of the molecules, including the screening effect of the metal leads. This direct approach circumvents the need for explicit modelling of the gate electrode. From the calculated parameters the Coulomb blockade diamonds are constructed using simple theory. We offer a theoretical tool for assignment of Coulomb blockade diamonds to specific redox states in particular, and a study of chemical details in the diamonds in general. With the ongoing experimental developments in molecular transistor experiments, our tool could find use in molecular electronics, electrochemistry, and electrocatalysis.
Radiotherapy and immune checkpoint blockades: a snapshot in 2016
Energy Technology Data Exchange (ETDEWEB)
Koo, Tae Yool [Dept. of Radiation Oncology, Hallym University Chuncheon Sacred Heart Hospital, Chuncheon (Korea, Republic of); Kim, In Ah [Dept. of Radiation Oncology, Seoul National University College of Medicine, Seoul (Korea, Republic of)
2016-12-15
Immune checkpoint blockades including monoclonal antibodies (mAbs) of cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed death-1 (PD-1), and programmed death-ligand 1 (PD-L1) have been emerged as a promising anticancer therapy. Several immune checkpoint blockades have been approved by US Food and Drug Administration (FDA), and have shown notable success in clinical trials for patients with advanced melanoma and non-small cell lung cancer. Radiotherapy is a promising combination partner of immune checkpoint blockades due to its potent pro-immune effect. This review will cover the current issue and the future perspectives for combined with radiotherapy and immune checkpoint blockades based upon the available preclinical and clinical data.
Effects of sugammadex on incidence of postoperative residual neuromuscular blockade
DEFF Research Database (Denmark)
Brueckmann, B; Sasaki, N; Grobara, P
2015-01-01
BACKGROUND: This study aimed to investigate whether reversal of rocuronium-induced neuromuscular blockade with sugammadex reduced the incidence of residual blockade and facilitated operating room discharge readiness. METHODS: Adult patients undergoing abdominal surgery received rocuronium, followed...... by randomized allocation to sugammadex (2 or 4 mg kg(-1)) or usual care (neostigmine/glycopyrrolate, dosing per usual care practice) for reversal of neuromuscular blockade. Timing of reversal agent administration was based on the providers' clinical judgement. Primary endpoint was the presence of residual...... measured at PACU entry. Zero out of 74 sugammadex patients and 33 out of 76 (43.4%) usual care patients had TOF-Watch® SX-assessed residual neuromuscular blockade at PACU admission (odds ratio 0.0, 95% CI [0-0.06], P
International Nuclear Information System (INIS)
Chen, Kuo-Chin; Su, Yu-Hsin; Chang, Ching-Ray; Chen, Son-Hsien
2014-01-01
We study the electron spin transport in two dimensional electron gas (2DEG) system with both Rashba and Dresselhaus (001) spin-orbital coupling (SOC). We assume spatial behavior of spin precession in the non-equilibrium transport regime, and study also quantum interference induced by non-Abelian spin-orbit gauge field. The method we adopt in this article is the non-equilibrium Green's function within a tight binding framework. We consider one ferromagnetic lead which injects spin polarized electron to a system with equal strength of Rashba and Dresselhaus (001) SOC, and we observe the persistent spin helix property. We also consider two ferromagnetic leads injecting spin polarized electrons into a pure Dresselhaus SOC system, and we observe the resultant spin wave interference pattern
'CANDLE' burnup regime after LWR regime
International Nuclear Information System (INIS)
Sekimoto, Hiroshi; Nagata, Akito
2008-01-01
CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy producing reactor) burnup strategy can derive many merits. From safety point of view, the change of excess reactivity along burnup is theoretically zero, and the core characteristics, such as power feedback coefficients and power peaking factor, are not changed along burnup. Application of this burnup strategy to neutron rich fast reactors makes excellent performances. Only natural or depleted uranium is required for the replacing fuels. About 40% of natural or depleted uranium undergoes fission without the conventional reprocessing and enrichment. If the LWR produced energy of X Joules, the CANDLE reactor can produce about 50X Joules from the depleted uranium left at the enrichment facility for the LWR fuel. If we can say LWRs have produced energy sufficient for full 20 years, we can produce the energy for 1000 years by using the CANDLE reactors with depleted uranium. We need not mine any uranium ore, and do not need reprocessing facility. The burnup of spent fuel becomes 10 times. Therefore, the spent fuel amount per produced energy is also reduced to one-tenth. The details of the scenario of CANDLE burnup regime after LWR regime will be presented at the symposium. (author)
Directory of Open Access Journals (Sweden)
V.M. Loktev
2008-09-01
Full Text Available We analyze the spectral properties of a phenomenological model for a weakly doped two-dimensional antiferromagnet, in which the carriers move within one of the two sublattices where they were introduced. Such a constraint results in the free carrier spectra with the maxima at k=(± π/2 , ± π/2 observed in some cuprates. We consider the spectral properties of the model by taking into account fluctuations of the spins in the antiferromagnetic background. We show that such fluctuations lead to a non-pole-like structure of the single-hole Green's function and these fluctuations can be responsible for some anomalous "strange metal" properties of underdoped cuprates in the nonsuperconducting regime.
From Napoleon To Netanyahu: Blockading Through Two Centuries
2016-04-01
Hemisphere. With a range of only 2,500 miles per load of coal, steam powered ships could not reach Europe without refueling. Blockading actions at Vera ...BIBLIOGRAPHY Calore, Paul. Naval Campaigns of the Civil War. Jefferson, NC: McFarland and Co., 2003. Davis, Lance E . and Stanley L...Lance E . Davis and Stanley L. Engerman, Naval Blockades in Peace and War: An Economic History Since 1750
Dephasing due to Nuclear Spins in Large-Amplitude Electric Dipole Spin Resonance.
Chesi, Stefano; Yang, Li-Ping; Loss, Daniel
2016-02-12
We analyze effects of the hyperfine interaction on electric dipole spin resonance when the amplitude of the quantum-dot motion becomes comparable or larger than the quantum dot's size. Away from the well-known small-drive regime, the important role played by transverse nuclear fluctuations leads to a Gaussian decay with characteristic dependence on drive strength and detuning. A characterization of spin-flip gate fidelity, in the presence of such additional drive-dependent dephasing, shows that vanishingly small errors can still be achieved at sufficiently large amplitudes. Based on our theory, we analyze recent electric dipole spin resonance experiments relying on spin-orbit interactions or the slanting field of a micromagnet. We find that such experiments are already in a regime with significant effects of transverse nuclear fluctuations and the form of decay of the Rabi oscillations can be reproduced well by our theory.
Heat Coulomb blockade of one ballistic channel
Sivre, E.; Anthore, A.; Parmentier, F. D.; Cavanna, A.; Gennser, U.; Ouerghi, A.; Jin, Y.; Pierre, F.
2018-02-01
Quantum mechanics and Coulomb interaction dictate the behaviour of small circuits. The thermal implications cover fundamental topics from quantum control of heat to quantum thermodynamics, with prospects of novel thermal machines and an ineluctably growing influence on nanocircuit engineering. Experimentally, the rare observations thus far include the universal thermal conductance quantum and heat interferometry. However, evidence for many-body thermal effects paving the way to markedly different heat and electrical behaviours in quantum circuits remains wanting. Here we report on the observation of the Coulomb blockade of electronic heat flow from a small metallic circuit node, beyond the widespread Wiedemann-Franz law paradigm. We demonstrate this thermal many-body phenomenon for perfect (ballistic) conduction channels to the node, where it amounts to the universal suppression of precisely one quantum of conductance for the transport of heat, but none for electricity. The inter-channel correlations that give rise to such selective heat current reduction emerge from local charge conservation, in the floating node over the full thermal frequency range (laws for thermal transport in nanocircuits.
Checkpoint blockade in combination with cancer vaccines.
Morse, Michael A; Lyerly, H Kim
2015-12-16
Checkpoint blockade, prevention of inhibitory signaling that limits activation or function of tumor antigen-specific T cells responses, is revolutionizing the treatment of many poor prognosis malignancies. Indeed monoclonal antibodies that modulate signaling through the inhibitory molecules CTLA-4 and PD-1 are now clinically available; however, many tumors, demonstrate minimal response suggesting the need for combinations with other therapeutic strategies. Because an inadequate frequency of activated tumor antigen-specific T cells in the tumor environment, the so-called non-inflamed phenotype, is observed in some malignancies, other rationale partners are modalities that lead to enhanced T cell activation (vaccines, cytokines, toll-like receptor agonists, and other anticancer therapies such as chemo-, radio- or targeted therapies that lead to release of antigen from tumors). This review will focus on preclinical and clinical data supporting the use of cancer vaccines with anti-CTLA-4 and anti-PD-1/PD-L1 antibodies. Preliminary preclinical data demonstrate enhanced antitumor activity although the results in human studies are less clear. Broader combinations of multiple immune modulators are now under study. Copyright © 2015 Elsevier Ltd. All rights reserved.
Gaussian dominance on compact spin manifolds
International Nuclear Information System (INIS)
Patrascioiu, A.; Richard, J.L.
1984-07-01
The low temperature regime of continuous spin models is discussed. The relevance of the weak coupling expansion for the calculation of invariant Green's functions is analyzed. Notably it is found that in two dimensions Green's functions of invariant operators cannot be computed perturbatively
Topical review: spins and mechanics in diamond
Lee, Donghun; Lee, Kenneth W.; Cady, Jeffrey V.; Ovartchaiyapong, Preeti; Bleszynski Jayich, Ania C.
2017-03-01
There has been rapidly growing interest in hybrid quantum devices involving a solid-state spin and a macroscopic mechanical oscillator. Such hybrid devices create exciting opportunities to mediate interactions between disparate quantum bits (qubits) and to explore the quantum regime of macroscopic mechanical objects. In particular, a system consisting of the nitrogen-vacancy defect center (NV center) in diamond coupled to a high-quality-factor mechanical oscillator is an appealing candidate for such a hybrid quantum device, as it utilizes the highly coherent and versatile spin properties of the defect center. In this paper, we will review recent experimental progress on diamond-based hybrid quantum devices in which the spin and orbital dynamics of single defects are driven by the motion of a mechanical oscillator. In addition, we discuss prospective applications for this device, including long-range, phonon-mediated spin-spin interactions, and phonon cooling in the quantum regime. We conclude the review by evaluating the experimental limitations of current devices and identifying alternative device architectures that may reach the strong coupling regime.
Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L
2015-10-13
Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. © 2015 The Authors.
Directory of Open Access Journals (Sweden)
Gavril PANDI
2011-03-01
Full Text Available The influenced flow regimes. The presence and activities ofhumanity influences the uniform environmental system, and in this context, therivers water resources. In concordance with this, the natural runoff regime suffersbigger and deeper changes. The nature of these changes depending on the type anddegree of water uses. The multitude of the use cause different types of influence,whit different quantitative aspects. In the same time, the influences havequalitative connotations, too, regarding to the modifications of the yearly watervolume runoff. So the natural runoff regime is modified. After analyzing thedistribution laws of the monthly runoff, there have been differenced four types ofinfluenced runoff regimes. In the excess type the influenced runoff is bigger thanthe natural, continuously in the whole year. The deficient type is characterized byinverse rapports like the first type, in the whole year. In the sinusoidal type, theinfluenced runoff is smaller than the natural in the period when the water isretained in the lake reservoirs, and in the depletion period the situation inverts. Atthe irregular type the ratio between influenced and natural runoff is changeable ina random meaner monthly. The recognition of the influenced regime and the gradeof influence are necessary in the evaluation and analysis of the usable hydrologicalriver resources, in the flood defence activities, in the complex scheme of thehydrographic basins, in the environment design and so on.
Transport, atom blockade, and output coupling in a Tonks-Girardeau gas
International Nuclear Information System (INIS)
Rutherford, L.; McCann, J. F.; Goold, J.; Busch, Th.
2011-01-01
Recent experiments have demonstrated how quantum-mechanical impurities can be created within strongly correlated quantum gases and used to probe the coherence properties of these systems [S. Palzer, C. Zipkes, C. Sias, and M. Koehl, Phys. Rev. Lett. 103, 150601 (2009).]. Here we present a phenomenological model to simulate such an output coupler for a Tonks-Girardeau gas that shows qualitative agreement with the experimental results for atom transport and output coupling. Our model allows us to explore nonequilibrium transport phenomena in ultracold quantum gases and leads us to predict a regime of atom blockade, where the impurity component becomes localized in the parent cloud despite the presence of gravity. We show that this provides a stable mixed-species quantum gas in the strongly correlated limit.
DEFF Research Database (Denmark)
Nielsen, Max
2006-01-01
Supply in fisheries is traditionally known for its backward bending nature, owing to externalities in production. Such a supply regime, however, exist only for pure open access fisheries. Since most fisheries worldwide are neither pure open access, nor optimally managed, rather between the extremes......, the traditional understanding of supply regimes in fisheries needs modification. This paper identifies through a case study of the East Baltic cod fishery supply regimes in fisheries, taking alternative fisheries management schemes and mesh size limitations into account. An age-structured Beverton-Holt based bio......-economic supply model with mesh sizes is developed. It is found that in the presence of realistic management schemes, the supply curves are close to vertical in the relevant range. Also, the supply curve under open access with mesh size limitations is almost vertical in the relevant range, owing to constant...
Spin Coherence in Semiconductor Nanostructures
National Research Council Canada - National Science Library
Flatte, Michael E
2006-01-01
... dots, tuning of spin coherence times for electron spin, tuning of dipolar magnetic fields for nuclear spin, spontaneous spin polarization generation and new designs for spin-based teleportation and spin transistors...
Electron spin exchange of shallow donor muonium states
International Nuclear Information System (INIS)
Senba, Masayoshi
2005-01-01
Shallow donor muonium states with small hyperfine frequencies, recently observed in II-VI semiconductor compounds, have a number of unique features that present both opportunities and challenges in understanding muon spin dynamics in the presence of Heisenberg spin exchange. First, the shallow muonium state in CdSe with hyperfine frequency ω 0 /2π ∼ 0.1 MHz is already in the high field regime even in the earth's magnetic field, where only two precession frequencies are observable by the muon spin rotation (μSR) technique. Second, unlike in the case of more conventional muonium species with a larger hyperfine frequency, the μSR signal of shallow muonium states can be observed even in the transition region, between the slow spin-flip regime and the fast spin-flip regime, where the spin-flip rate and the hyperfine frequency are comparable. The muon spin dynamics in the transition region has not been theoretically explored previously, mainly because normal muonium in vacuum gives no observable signal in this region. Third, in the case of shallow muonium states, the incoherent process defined to be those spin-flip collisions that cause changes in muon spin precession frequencies, becomes crucially important in the transition region, where the incoherent process is entirely negligible in more conventional muonium species. By taking incoherent multiple collisions into account, an analytical expression for the time evolution of the muon spin polarization in Mu is derived, where Mu undergoes repeated spin-flip collisions. Comparisons with Monte Carlo calculations show that the analytical expression obtained in this work can reliably be used to analyse experimental data for shallow donor states not only in the slow spin-flip regime, but also in the transition region up to the onset of the fast regime. The present work confirms a recent experimental finding that, in the transition region, the initial phases of the two precession components of shallow donor states
2001-01-01
There are at present at least three international regimes of maritime cargo liability in force in different countries of the world - the original Hague rules (1924), the updated version known as the Hague-Visby rules (1968, further amended 1979), and...
Six, Frédérique; Verhoest, Koen
2017-01-01
Within political and administrative sciences generally, trust as a concept is contested, especially in the field of regulatory governance. This groundbreaking book is the first to systematically explore the role and dynamics of trust within regulatory regimes. Conceptualizing, mapping and analyzing
DEFF Research Database (Denmark)
Abrahamson, Peter
2017-01-01
The paper asks if East Asian welfare regimes are still productivist and Confucian? And, have they developed public care policies? The literature is split on the first question but (mostly) confirmative on the second. Care has to a large, but insufficient extent, been rolled out in the region...
Directory of Open Access Journals (Sweden)
A. V. Malov
2018-01-01
Full Text Available The review article reveals the content of the concept of Food Regime, which is little-known in the Russian academic reference. The author monitored and codified the semantic dynamic of the terminological unit from its original interpretations to modern formulations based on the retrospective analysis. The rehabilitation of the academic merits of D. Puchala and R. Hopkins — authors who used the concept Food Regime for a few years before its universally recognized origin and official scientific debut, was accomplished with help of historical and comparative methods. The author implemented the method of ascension from the abstract to the concrete to demonstrating the classification of Food Regimes compiled on the basis of geopolitical interests in the sphere of international production, consumption, and distribution of foodstuffs. The characteristic features of historically formed Food Regime were described in the chronological order, as well as modern tendencies possessing reformist potential were identified. In particular, it has been established that the idea of Food Sovereignty (which is an alternative to the modern Corporate Food Regime is the subject for acute academic disputes. The discussion between P. McMichael P. and H. Bernstein devoted to the “peasant question” — mobilization frame of the Food Sovereignty strategy was analyzed using the secondary data processing method. Due to the critical analysis, the author comes to the conclusion that it is necessary to follow the principles of the Food Sovereignty strategy to prevent the catastrophic prospects associated with ecosystem degradation, accelerated erosion of soils, the complete disappearance of biodiversity and corporate autoc racy successfully. The author is convinced that the idea of Food Sovereignty can ward off energetic liberalization of nature, intensive privatization of life and rapid monetization of unconditioned human reflexes.
Electrical manipulation of spin states in a single electrostatically gated transition-metal complex
DEFF Research Database (Denmark)
Osorio, Edgar A; Moth-Poulsen, Kasper; van der Zant, Herre S J
2010-01-01
-field on the Mn-atom. Adding a single electron thus stabilizes the low-spin configuration and the corresponding sequential tunnelling current is suppressed by spin-blockade. From low-temperature inelastic cotunneling spectroscopy, we infer the magnetic excitation spectrum of the molecule and uncover also...... a strongly gate-dependent singlet-triplet splitting on the low-spin side. The measured bias-spectroscopy is shown to be consistent with an exact diagonalization of the Mn-complex, and an interpretation of the data is given in terms of a simplified effective model....
International Nuclear Information System (INIS)
Mookerjee, Abhijit
1976-01-01
''Spin glasses'', are entire class of magnetic alloys of moderate dilution, in which the magnetic atoms are far enough apart to be unlike the pure metal, but close enough so that the indirect exchange energy between them (mediated by the s-d interaction between local moments and conduction electrons) dominates all other energies. Characteristic critical phenomena displayed such as freezing of spin orientation at 'Tsub(c)' and spreading of magnetic ordering, are pointed out. Anomalous behaviour, associated with these critical phenomena, as reflected in : (i) Moessbauer spectroscopy giving hyperfine splitting at Tsub(c), (ii) maxima in susceptibility and remanent magnetism, (iii) thermopower maxima and change in slope, (iv) Characteristic cusp in susceptibility and its removal by very small magnetic fields, and (v) conductivity-resistivity measurements, are discussed. Theoretical developments aimed at explaining these phenomena, in particular, the ideas from percolation and localisation theories, and the approach based on the gellations of polymers, are discussed. Finally, a new approach based on renormalisation group in disordered systems is also briefly mentioned. (K.B.)
The perturbative Regge-calculus regime of loop quantum gravity
International Nuclear Information System (INIS)
Bianchi, Eugenio; Modesto, Leonardo
2008-01-01
The relation between loop quantum gravity and Regge calculus has been pointed out many times in the literature. In particular the large spin asymptotics of the Barrett-Crane vertex amplitude is known to be related to the Regge action. In this paper we study a semiclassical regime of loop quantum gravity and show that it admits an effective description in terms of perturbative area-Regge-calculus. The regime of interest is identified by a class of states given by superpositions of four-valent spin networks, peaked on large spins. As a probe of the dynamics in this regime, we compute explicitly two- and three-area correlation functions at the vertex amplitude level. We find that they match with the ones computed perturbatively in area-Regge-calculus with a single 4-simplex, once a specific perturbative action and measure have been chosen in the Regge-calculus path integral. Correlations of other geometric operators and the existence of this regime for other models for the dynamics are briefly discussed
Nonlinear spin wave coupling in adjacent magnonic crystals
Energy Technology Data Exchange (ETDEWEB)
Sadovnikov, A. V., E-mail: sadovnikovav@gmail.com; Nikitov, S. A. [Laboratory “Metamaterials,” Saratov State University, Saratov 410012 (Russian Federation); Kotel' nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow 125009 (Russian Federation); Beginin, E. N.; Morozova, M. A.; Sharaevskii, Yu. P.; Grishin, S. V.; Sheshukova, S. E. [Laboratory “Metamaterials,” Saratov State University, Saratov 410012 (Russian Federation)
2016-07-25
We have experimentally studied the coupling of spin waves in the adjacent magnonic crystals. Space- and time-resolved Brillouin light-scattering spectroscopy is used to demonstrate the frequency and intensity dependent spin-wave energy exchange between the side-coupled magnonic crystals. The experiments and the numerical simulation of spin wave propagation in the coupled periodic structures show that the nonlinear phase shift of spin wave in the adjacent magnonic crystals leads to the nonlinear switching regime at the frequencies near the forbidden magnonic gap. The proposed side-coupled magnonic crystals represent a significant advance towards the all-magnonic signal processing in the integrated magnonic circuits.
Nonlinear spin wave coupling in adjacent magnonic crystals
International Nuclear Information System (INIS)
Sadovnikov, A. V.; Nikitov, S. A.; Beginin, E. N.; Morozova, M. A.; Sharaevskii, Yu. P.; Grishin, S. V.; Sheshukova, S. E.
2016-01-01
We have experimentally studied the coupling of spin waves in the adjacent magnonic crystals. Space- and time-resolved Brillouin light-scattering spectroscopy is used to demonstrate the frequency and intensity dependent spin-wave energy exchange between the side-coupled magnonic crystals. The experiments and the numerical simulation of spin wave propagation in the coupled periodic structures show that the nonlinear phase shift of spin wave in the adjacent magnonic crystals leads to the nonlinear switching regime at the frequencies near the forbidden magnonic gap. The proposed side-coupled magnonic crystals represent a significant advance towards the all-magnonic signal processing in the integrated magnonic circuits.
International Nuclear Information System (INIS)
Ohnuma, Yuichi; Matsuo, Mamoru; Maekawa, Sadamichi; Saitoh, Eeiji
2017-01-01
Spin Seebeck and spin Peltier effects, which are mutual conversion phenomena of heat and spin, are discussed on the basis of the microscopic theory. First, the spin Seebeck effect, which is the spin-current generation due to heat current, is discussed. The recent progress in research on the spin Seebeck effect are introduced. We explain the origin of the observed sign changes of the spin Seebeck effect in compensated ferromagnets. Next, the spin Peltier effect, which is the heat-current generation due to spin current, is discussed. Finally, we show that the spin Seebeck and spin Peltier effects are summarized by Onsager's reciprocal relation and derive Kelvin's relation for the spin and heat transports. (author)
Entangled spins and ghost-spins
Directory of Open Access Journals (Sweden)
Dileep P. Jatkar
2017-09-01
Full Text Available We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in [20] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves, the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.
Strain cupling of a nitrogen-vacancy center spin to a diamond mechanical oscillator
Teissier, J.; Barfuss, A.; Appel, P.; Neu, E.; Maletinsky, P.
2014-01-01
We report on single electronic spins coupled to the motion of mechanical resonators by a novel mechanism based on crystal strain. Our device consists of single-crystal diamond cantilevers with embedded nitrogen-vacancy center spins. Using optically detected electron spin resonance, we determine the unknown spin-strain coupling constants and demonstrate that our system resides well within the resolved sideband regime. We realize coupling strengths exceeding 10 MHz under mechanical driving and ...
Resolved sidebands in a strain-coupled hybrid spin-oscillator system
Teissier, Jean; Barfuss, Arne; Appel, Patrick; Neu, Elke; Maletinsky, P.
2014-01-01
We report on single electronic spins coupled to the motion of mechanical resonators by a novel mechanism based on crystal strain. Our device consists of single-crystalline diamond cantilevers with embedded Nitrogen-Vacancy center spins. Using optically detected electron spin resonance, we determine the unknown spin-strain coupling constants and demonstrate that our system resides well within the resolved sideband regime. We realize coupling strengths exceeding ten MHz under mechanical driving...
Large-amplitude superexchange of high-spin fermions in optical lattices
International Nuclear Information System (INIS)
Jürgensen, Ole; Heinze, Jannes; Lühmann, Dirk-Sören
2013-01-01
We show that fermionic high-spin systems with spin-changing collisions allow one to monitor superexchange processes in optical superlattices with large amplitudes and strong spin fluctuations. By investigating the non-equilibrium dynamics, we find a superexchange dominated regime at weak interactions. The underlying mechanism is driven by an emerging tunneling-energy gap in shallow few-well potentials. As a consequence, the interaction-energy gap that is expected to occur only for strong interactions in deep lattices is re-established. By tuning the optical lattice depth, a crossover between two regimes with negligible particle number fluctuations is found: firstly, the common regime with vanishing spin-fluctuations in deep lattices and, secondly, a novel regime with strong spin fluctuations in shallow lattices. We discuss the possible experimental realization with ultracold 40 K atoms and observable quantities in double wells and two-dimensional plaquettes. (paper)
Costimulatory signal blockade in murine relapsing experimental autoimmune encephalomyelitis
DEFF Research Database (Denmark)
Schaub, M; Issazadeh-Navikas, Shohreh; Stadlbauer, T H
1999-01-01
Blockade of the CD28-B7 or CD40L-CD40 T cell costimulatory signals prevents induction of experimental autoimmune encephalomyelitis (EAE). However, the effect of simultaneous blockade of these signals in EAE is unknown. We show that administration of either MR1 (to block CD40L) or CTLA4Ig (to block...... B7) after immunization or after the first attack protects from EAE. Treatment with a combination of CTLA4Ig and MR1 provides additive protection, and is associated with complete absence of mononuclear cell infiltrates in the central nervous system, and marked suppression of proliferation of primed T...... cells in the periphery. Selective B7-1 blockade did not protect from EAE. These observations have implications for therapy of autoimmune diseases....
Pramanik, S.; bandyopadhyay, S.; Cahay, M.
2003-01-01
We study high-field spin transport of electrons in a quasi one-dimensional channel of a $GaAs$ gate controlled spin interferometer (SPINFET) using a semiclassical formalism (spin density matrix evolution coupled with Boltzmann transport equation). Spin dephasing (or depolarization) is predominantly caused by D'yakonov-Perel' relaxation associated with momentum dependent spin orbit coupling effects that arise due to bulk inversion asymmetry (Dresselhaus spin orbit coupling) and structural inve...
Quader, Syed Manzur
2004-01-01
In recent years, many developing countries having a history of high inflation, unfavorable balance of payment situation and a high level of foreign currencies denominated debt, have switched or are in the process of switching to a more flexible exchange rate regime. Therefore, the stability of the exchange rate and the dynamics of its volatility are more crucial than before to prevent financial crises and macroeconomic disturbances. This paper is designed to find out the reasons behind Bangla...
Spin-orbit interaction in a dual gated InAs/GaSb quantum well
Beukman, Arjan J. A.; de Vries, Folkert K.; van Veen, Jasper; Skolasinski, Rafal; Wimmer, Michael; Qu, Fanming; de Vries, David T.; Nguyen, Binh-Minh; Yi, Wei; Kiselev, Andrey A.; Sokolich, Marko; Manfra, Michael J.; Nichele, Fabrizio; Marcus, Charles M.; Kouwenhoven, Leo P.
2017-12-01
The spin-orbit interaction is investigated in a dual gated InAs/GaSb quantum well. Using an electric field, the quantum well can be tuned between a single-carrier regime with exclusively electrons as carriers and a two-carrier regime where electrons and holes coexist. The spin-orbit interaction in both regimes manifests itself as a beating in the Shubnikov-de Haas oscillations. In the single-carrier regime the linear Dresselhaus strength is characterized by β =28.5 meV Å and the Rashba coefficient α is tuned from 75 to 53 meV Å by changing the electric field. In the two-carrier regime a quenching of the spin splitting is observed and attributed to a crossing of spin bands.
Circuit Simulation of All-Spin Logic
Alawein, Meshal
2016-05-01
With the aggressive scaling of complementary metal-oxide semiconductor (CMOS) nearing an inevitable physical limit and its well-known power crisis, the quest for an alternative/augmenting technology that surpasses the current semiconductor electronics is needed for further technological progress. Spintronic devices emerge as prime candidates for Beyond CMOS era by utilizing the electron spin as an extra degree of freedom to decrease the power consumption and overcome the velocity limit connected with the charge. By using the nonvolatility nature of magnetization along with its direction to represent a bit of information and then manipulating it by spin-polarized currents, routes are opened for combined memory and logic. This would not have been possible without the recent discoveries in the physics of nanomagnetism such as spin-transfer torque (STT) whereby a spin-polarized current can excite magnetization dynamics through the transfer of spin angular momentum. STT have expanded the available means of switching the magnetization of magnetic layers beyond old classical techniques, promising to fulfill the need for a new generation of dense, fast, and nonvolatile logic and storage devices. All-spin logic (ASL) is among the most promising spintronic logic switches due to its low power consumption, logic-in-memory structure, and operation on pure spin currents. The device is based on a lateral nonlocal spin valve and STT switching. It utilizes two nanomagnets (whereby information is stored) that communicate with pure spin currents through a spin-coherent nonmagnetic channel. By using the well-known spin physics and the recently proposed four-component spin circuit formalism, ASL can be thoroughly studied and simulated. Previous attempts to model ASL in the linear and diffusive regime either neglect the dynamic characteristics of transport or do not provide a scalable and robust platform for full micromagnetic simulations and inclusion of other effects like spin Hall
Stellate ganglion blockade for analgesia following upper limb surgery.
LENUS (Irish Health Repository)
McDonnell, J G
2012-01-31
We report the successful use of a stellate ganglion block as part of a multi-modal postoperative analgesic regimen. Four patients scheduled for orthopaedic surgery following upper limb trauma underwent blockade of the stellate ganglion pre-operatively under ultrasound guidance. Patients reported excellent postoperative analgesia, with postoperative VAS pain scores between 0 and 2, and consumption of morphine in the first 24 h ranging from 0 to 14 mg. While these are preliminary findings, and must be confirmed in a clinical trial, they highlight the potential for stellate ganglion blockade to provide analgesia following major upper limb surgery.
Neural Blockade for Persistent Pain After Breast Cancer Surgery
DEFF Research Database (Denmark)
Wijayasinghe, Nelun; Andersen, Kenneth Geving; Kehlet, Henrik
2014-01-01
involved in neuropathic pain syndromes or to be used as a treatment in its own right. The purpose of this review was to examine the evidence for neural blockade as a potential diagnostic tool or treatment for persistent pain after breast cancer surgery. In this systematic review, we found only 7 studies (n......Persistent pain after breast cancer surgery is predominantly a neuropathic pain syndrome affecting 25% to 60% of patients and related to injury of the intercostobrachial nerve, intercostal nerves, and other nerves in the region. Neural blockade can be useful for the identification of nerves...
Combination approaches with immune checkpoint blockade in cancer therapy
Directory of Open Access Journals (Sweden)
Maarten Swart
2016-11-01
Full Text Available In healthy individuals, immune checkpoint molecules prevent autoimmune responses and limit immune cell-mediated tissue damage. Tumors frequently exploit these molecules to evade eradication by the immune system. Over the past years, immune checkpoint blockade of cytotoxic T lymphocyte antigen-4 (CTLA-4 and programmed death-1 (PD-1 emerged as promising strategies to activate anti-tumor cytotoxic T cell responses. Although complete regression and long-term survival is achieved in some patients, not all patients respond. This review describes promising, novel combination approaches involving immune checkpoint blockade, aimed at increasing response-rates to the single treatments.
Busz, Piotr; Tomaszewski, Damian; Martinek, Jan
2017-08-01
We analyze a model of a double quantum dot Cooper pair splitter coupled to two ferromagnetic detectors and demonstrate the possibility of determination of spin correlation by current measurements. We use perturbation theory, taking account of the exchange interaction with the detectors, which leads to complex spin dynamics in the dots. This affects the measured spin and restricts the use of ferromagnetic detectors to the nonlinear current-voltage characteristic regime at the current plateau, where the relevant spin projection is conserved, in contrast to the linear current-voltage characteristic regime, in which the spin information is distorted. Moreover, we show that for separable states the spin correlation can only be determined in a limited parameter regime, much more restricted than in the case of entangled states. We propose an entanglement test based on the Bell inequality.
Efficient spin-current injection in single-molecule magnet junctions
Directory of Open Access Journals (Sweden)
Haiqing Xie
2018-01-01
Full Text Available We study theoretically spin transport through a single-molecule magnet (SMM in the sequential and cotunneling regimes, where the SMM is weakly coupled to one ferromagnetic and one normal-metallic leads. By a master-equation approach, it is found that the spin polarization injected from the ferromagnetic lead is amplified and highly polarized spin-current can be generated, due to the exchange coupling between the transport electron and the anisotropic spin of the SMM. Moreover, the spin-current polarization can be tuned by the gate or bias voltage, and thus an efficient spin injection device based on the SMM is proposed in molecular spintronics.
Efficient spin-current injection in single-molecule magnet junctions
Xie, Haiqing; Xu, Fuming; Jiao, Hujun; Wang, Qiang; Liang, J.-Q.
2018-01-01
We study theoretically spin transport through a single-molecule magnet (SMM) in the sequential and cotunneling regimes, where the SMM is weakly coupled to one ferromagnetic and one normal-metallic leads. By a master-equation approach, it is found that the spin polarization injected from the ferromagnetic lead is amplified and highly polarized spin-current can be generated, due to the exchange coupling between the transport electron and the anisotropic spin of the SMM. Moreover, the spin-current polarization can be tuned by the gate or bias voltage, and thus an efficient spin injection device based on the SMM is proposed in molecular spintronics.
Interaction between hopping and static spins in a discrete network
Energy Technology Data Exchange (ETDEWEB)
Ciccarello, Francesco, E-mail: francesco.ciccarello@sns.it [CNISM and Dipartimento di Fisica, Universita' degli Studi di Palermo, Viale delle Scienze, Edificio 18, I-90128 Palermo (Italy); NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza dei Cavalieri 7, I-56126 Pisa (Italy)
2011-06-27
We consider a process where a spin hops across a discrete network and at certain sites couples to static spins. While this setting is implementable in various scenarios (e.g. quantum dots or coupled cavities) the physics of such processes is still basically unknown. Here, we take a first step along this line by scrutinizing a two-site and a three-site lattices, each with two static spins. Despite a generally complex dynamics occurs, we show a regime such that the spin dynamics is described by an effective three-spin chain. Tasks such as entanglement generation and quantum state transfer can be achieved accordingly. -- Highlights: → We study mobile spins hopping in a discrete network and coupled to static spins. → This setting can be implemented in various scenarios. → We address a two-site and a three-site lattice, each with two static spins. → We show a regime where the setup can be described by an effective three-spin chain. → Accordingly, it is prone to be exploited for some QIP applications.
DEFF Research Database (Denmark)
Hellsten, Ylva; Krustrup, Peter; Iaia, F Marcello
2009-01-01
This study examined the role of acetylcholine for skeletal muscle blood flow during exercise by use of the competitive neuromuscular blocking agent cisatracurium in combination with the acetylcholine receptor blocker glycopyrrone. Nine healthy male subjects performed a 10-min bout of one-legged k......This study examined the role of acetylcholine for skeletal muscle blood flow during exercise by use of the competitive neuromuscular blocking agent cisatracurium in combination with the acetylcholine receptor blocker glycopyrrone. Nine healthy male subjects performed a 10-min bout of one...... conductance during exercise, events that are not associated with either acetylcholine or an increased oxygen demand. The results do not support an essential role for acetylcholine, released form the neuromuscular junction, in exercise hyperaemia or for the enhanced blood flow during neuromuscular blockade....... The enhanced exercise hyperemia during partial neuromuscular blockade may be related to a greater recruitment of fast-twitch muscle fibres. Key words: blood flow, neuromuscular blockade, exercise, skeletal muscle....
Reversal of profound rocuronium neuromuscular blockade by sugammadex in anesthetized rhesus monkeys.
Boer, H.D. de; Egmond, J. van; Pol, F. van de; Bom, A.; Booij, L.H.D.J.
2006-01-01
BACKGROUND: Reversal of neuromuscular blockade can be accomplished by chemical encapsulation of rocuronium by sugammadex, a synthetic gamma-cyclodextrin derivative. The current study determined the feasibility of reversal of rocuronium-induced profound neuromuscular blockade with sugammadex in the
Coulomb Blockade and Multiple Andreev Reflection in a Superconducting Single-Electron Transistor
Lorenz, Thomas; Sprenger, Susanne; Scheer, Elke
2018-06-01
In superconducting quantum point contacts, multiple Andreev reflection (MAR), which describes the coherent transport of m quasiparticles each carrying an electron charge with m≥3, sets in at voltage thresholds eV = 2Δ /m. In single-electron transistors, Coulomb blockade, however, suppresses the current at low voltage. The required voltage for charge transport increases with the square of the effective charge eV∝ ( me) ^2. Thus, studying the charge transport in all-superconducting single-electron transistors (SSETs) sets these two phenomena into competition. In this article, we present the fabrication as well as a measurement scheme and transport data for a SSET with one junction in which the transmission and thereby the MAR contributions can be continuously tuned. All regimes from weak to strong coupling are addressed. We extend the Orthodox theory by incorporating MAR processes to describe the observed data qualitatively. We detect a new transport process the nature of which is unclear at present. Furthermore, we observe a renormalization of the charging energy when approaching the strong coupling regime.
Magnetic Nanostructures Spin Dynamics and Spin Transport
Farle, Michael
2013-01-01
Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.
Frequency multiplexing for readout of spin qubits
Energy Technology Data Exchange (ETDEWEB)
Hornibrook, J. M.; Colless, J. I.; Mahoney, A. C.; Croot, X. G.; Blanvillain, S.; Reilly, D. J., E-mail: david.reilly@sydney.edu.au [ARC Centre of Excellence for Engineered Quantum Systems, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Lu, H.; Gossard, A. C. [Materials Department, University of California, Santa Barbara, California 93106 (United States)
2014-03-10
We demonstrate a low loss, chip-level frequency multiplexing scheme for readout of scaled-up spin qubit devices. By integrating separate bias tees and resonator circuits on-chip for each readout channel, we realise dispersive gate-sensing in combination with charge detection based on two radio frequency quantum point contacts. We apply this approach to perform multiplexed readout of a double quantum dot in the few-electron regime and further demonstrate operation of a 10-channel multiplexing device. Limitations for scaling spin qubit readout to large numbers of multiplexed channels are discussed.
DEFF Research Database (Denmark)
Skagen, K; Haxholdt, O; Henriksen, O
1982-01-01
local nervous blockade was induced by Lidocaine in 133Xe labelled subcutaneous tissue on one side. During epidural blockade and tilt blood flow increased by 12% whereas blood flow decreased by 30% on the control side. Thus epidural blockade had no influence on the vasoconstrictor response...
DEFF Research Database (Denmark)
Rosenberg, J; Pedersen, U; Erichsen, C J
1994-01-01
The effect of oxygen therapy (37% by face mask) and epidural local anesthetic blockade (9 ml 0.5% bupivacaine at Th9-11 level) on wound oxygenation was evaluated in eight otherwise healthy patients undergoing elective colorectal resection. The patients were monitored continuously for subcutaneous...... without epidural blockade and 15 (10-20) min with blockade (P surgery....
Spin-dependent tunneling transport in a lateral magnetic diode
International Nuclear Information System (INIS)
Wang, Yu; Shi, Ying
2012-01-01
Based on the gate-tunable two-dimensional electron gas, we have constructed laterally a double-barrier resonant tunneling structure by employing a peculiar triple-gate configuration, namely a ferromagnetic gate sandwiched closely by a pair of Schottky gates. Because of the in-plane stray field of ferromagnetic gate, the resulting bound spin state in well gives rise to the remarkable resonant spin polarization following the spin-dependent resonant tunneling regime. Importantly, by aligning the bound spin state through surface gate-voltage configuration, this resonant spin polarization can be externally manipulated, showing the desirable features for the spin-logic device applications. -- Highlights: ► A lateral spin-RTD was proposed by applying triple-gate modulated 2DEG. ► Spin-dependent resonant tunneling transport and large resonant spin polarization has been clarified from the systematic simulation. ► Both electric and/or magnetic strategies can be employed to modulate the system spin transport, providing the essential features for the spin-logic application.
Anti-Weak Localization Measurements in the Ballistic Regime
Jayathilaka, Dilhani; Dedigama, Aruna; Murphy, Sheena; Edirisooriya, Madhavie; Goel, Niti; Mishima, Tetsuya; Santos, Michael; Mullen, Kieran
2007-03-01
Anti-weak localization dominates at low fields in systems in which spin-orbit coupling is strong. The experimental results are well described by theory [1] in low mobility systems in which the magnetic length (lB) is greater than the mean free path; however high mobility systems with strong spin-orbit interactions, such the InSb based two dimensional systems (2DESs) examined here, are not in this diffusive regime. A recently developed theory [2] addresses both the diffusive and ballistic regimes taking into account both the backscattered and non-backscattered contributions to the conductivity. We will discuss the agreement of the new theory to measurements of InSb 2DESs prepared with both strong Dresselhaus and Rashba effects. [1] S.V. Iordanskii, Yu B. Lyanda-Geller, and G.E. Pikus, JETP Lett. 60, 206 (1994). [2] L.E. Golub, Phys. Rev. B. 71, 235310 (2005).
Lifetime-Enhanced Transport in Silicon due to Spin and Valley Blockade
Lansbergen, G.P.; Rahman, R.; Verduijn, J.; Tettamanzi, G.C.; Collaert, N.; Biesemans, S.; Klimeck, G.; Hollenberg, L.C.L.; Rogge, S.
2011-01-01
We report the observation of lifetime-enhanced transport (LET) based on perpendicular valleys in silicon by transport spectroscopy measurements of a two-electron system in a silicon transistor. The LET is manifested as a peculiar current step in the stability diagram due to a forbidden transition
Use of ropivacain and lidocaine for axillary plexus blockade ...
African Journals Online (AJOL)
Use of ropivacain and lidocaine for axillary plexus blockade. ... of the juvenile anatomy, psychological barriers, time constraints on block ... children in the age group of 2 to 10 years and undergoing short upper limb surgery. ... Browse By Category · Browse Alphabetically · Browse By Country · List All Titles · Free To Read ...
Sodium intake, RAAS-blockade and progressive renal disease
de Borst, Martin H; Navis, Gerjan
Pharmacological blockade of the renin-angiotensin-aldosterone system (RAAS) by angiotensin converting enzyme inhibitors or angiotensin receptor blockers is the current standard treatment to prevent progressive renal function loss in patients with chronic kidney disease. Yet in many patients the
Effective dermatomal blockade after subcostal transversus abdominis plane block
DEFF Research Database (Denmark)
Mitchell, Anja Ulrike; Torup, Henrik; Hansen, Egon G
2012-01-01
. Sensory assessment of a TAP block may guide the decision on the extent of the block. The purpose of this study was to investigate if the dermatomal extent of sensory blockade after injection of 20 ml 0.5% ropivacaine bilaterally into the TAP can be assessed using cold and pinprick sensation....
Neuromuscular blockade for improvement of surgical conditions during laparotomy
DEFF Research Database (Denmark)
Madsen, Matias Vested; Scheppan, Susanne; Kissmeyer, Peter
2015-01-01
neuromuscular blockade (NMB), defined as a post-tetanic-count (PTC) of 0-1, paralyses the abdominal wall muscles and the diaphragm. We hypothesised that deep NMB (PTC 0-1) would improve surgical conditions during upper laparotomy as compared to standard NMB with bolus administration. METHODS...
Why not treat human cancer with interleukin-1 blockade?
Dinarello, C.A.
2010-01-01
The clinical successes of targeting angiogenesis provide a basis for trials of interleukin-1 (IL-1) blockade and particularly anti-IL-1beta as an add-on therapy in human metastatic disease. In animal studies for over 20 years, IL-1 has been demonstrated to increase adherence of tumor cells to the
Topological matter with collective encoding and Rydberg blockade
DEFF Research Database (Denmark)
Nielsen, Anne E. B.; Mølmer, Klaus
2010-01-01
We propose to use a permutation symmetric sample of multilevel atoms to simulate the properties of topologically ordered states. The Rydberg blockade interaction is used to prepare states of the sample which are equivalent to resonating valence bond states, Laughlin states, and string-net condens......-net condensates and to create and study the properties of their quasi-particle-like fundamental excitations....
Entanglement of two ground state neutral atoms using Rydberg blockade
DEFF Research Database (Denmark)
Miroshnychenko, Yevhen; Browaeys, Antoine; Evellin, Charles
2011-01-01
We report on our recent progress in trapping and manipulation of internal states of single neutral rubidium atoms in optical tweezers. We demonstrate the creation of an entangled state between two ground state atoms trapped in separate tweezers using the effect of Rydberg blockade. The quality...... of the entanglement is measured using global rotations of the internal states of both atoms....
Effect of Dual Blockade of Renin-Angiotensin Aldosterone System ...
African Journals Online (AJOL)
Purpose: To investigate the dual effect of angiotensin blockade by irbesartan and enalapril on proteinuria in diabetic patients with azotemia. Methods: Patients with diabetes of > 5 years duration, proteinuria at a nephrotic level and serum creatinine > 1.5 mg/dL were enrolled in the study. Forty-five enrolled patients were ...
CARDIOVASCULAR ENDOCRINOLOGY Dual RAAS blockade has dual effects on outcome
Heerspink, Hiddo J. Lambers; de Zeeuw, Dick
Makani and colleagues report that dual blockade of the renin-angiotensin-aldosterone system is associated with harm despite previous studies showing that this approach decreases blood pressure and albuminuria. Do these results imply that we should abandon surrogate markers? Or should we become more
Benefits and harms of perioperative beta-blockade
DEFF Research Database (Denmark)
Wetterslev, Jørn; Juul, Anne Benedicte
2006-01-01
randomized trials. However, confidence intervals of the intervention effects in the meta-analyses are wide, leaving room for both benefits and harms. The largest observational study performed suggests that perioperative beta-blockade is associated with higher mortality in patients with low cardiac risk...
Pressure effect on hysteresis in spin-crossover solid materials
Energy Technology Data Exchange (ETDEWEB)
Gudyma, Iurii, E-mail: yugudyma@gmail.com [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Ivashko, Victor [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Dimian, Mihai [Department of Electrical and Computer Engineering, Howard University, Washington DC 20059 (United States); Faculty of Electrical Engineering and Computer Science & Integrated Center for Research, Development and Innovation in Advanced Materials, Nanotechnologies, and Distributed Systems for fabrication and control, Stefan cel Mare University, Suceava 720229 (Romania)
2016-04-01
A generalized microscopic Ising-like model is proposed to describe behavior of compressible spin-crossover solids with two states: low-spin and high-spin. The model was solved in mean-field approximation and shows hysteretic behavior at low energy difference between the states. We study the thermal transition between states under external hydrostatic pressure taking into account the changes in the volume of spin-crossover molecules in different states. Depending on the applied pressure, a spin-crossover system can have three types of behavior of molecular fraction in the high-spin state: hysteretic, second-order phase transition and no-phase transition. For the hysteretic regime, it is shown that the transition temperature under pressure is increased while the width of the hysteresis reduced.
Neuraxial blockade for external cephalic version: a systematic review.
Sultan, P; Carvalho, B
2011-10-01
The desire to decrease the number of cesarean deliveries has renewed interest in external cephalic version. The rationale for using neuraxial blockade to facilitate external cephalic version is to provide abdominal muscular relaxation and reduce patient discomfort during the procedure, so permitting successful repositioning of the fetus to a cephalic presentation. This review systematically examined the current evidence to determine the safety and efficacy of neuraxial anesthesia or analgesia when used for external cephalic version. A systematic literature review of studies that examined success rates of external cephalic version with neuraxial anesthesia was performed. Published articles written in English between 1945 and 2010 were identified using the Medline, Cochrane, EMBASE and Web of Sciences databases. Six, randomized controlled studies were identified. Neuraxial blockade significantly improved the success rate in four of these six studies. A further six non-randomized studies were identified, of which four studies with control groups found that neuraxial blockade increased the success rate of external cephalic version. Despite over 850 patients being included in the 12 studies reviewed, placental abruption was reported in only one patient with a neuraxial block, compared with two in the control groups. The incidence of non-reassuring fetal heart rate requiring cesarean delivery in the anesthesia groups was 0.44% (95% CI 0.15-1.32). Neuraxial blockade improved the likelihood of success during external cephalic version, although the dosing regimen that provides optimal conditions for successful version is unclear. Anesthetic rather than analgesic doses of local anesthetics may improve success. The findings suggest that neuraxial blockade does not compromise maternal or fetal safety during external cephalic version. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.
Nuclear spin bath effects in molecular nanomagnets: Direct quantum mechanical simulations
Sinitsyn, N. A.; Dobrovitski, V. V.
2004-11-01
We investigate the influence of nuclear spins on the electronic spin tunneling in magnetic molecules such as Fe8 , focusing on the role of the spin diffusion in the nuclear spin bath. We simulate the quantum spin dynamics by numerically solving the time-dependent Schrödinger equation for the compound system (the electronic spin plus the bath spins). Our results demonstrate that the effect of the spin bath cannot always be modeled as a randomly varying magnetic field acting on the electronic spin. We consider two dynamical regimes: the spin relaxation in a constant magnetic field, and the spin tunneling in the linearly varying magnetic field passing the avoided level crossing, so-called Landau-Zener-Stückelberg (LZS) transition. For the first regime, we confirmed that the hole in the magnetization distribution has the width of the hyperfine fields distribution. For the second regime, we found that the transition probability for moderately slow sweeps deviates from the standard LZS prediction, while for the fast sweeps the deviation is negligible.
Spin dynamics in relativistic ionization with highly charged ions in super-strong laser fields
International Nuclear Information System (INIS)
Klaiber, Michael; Yakaboylu, Enderalp; Bauke, Heiko; Hatsagortsyan, Karen Z; Müller, Carsten; Paulus, Gerhard G
2014-01-01
Spin dynamics and induced spin effects in above-threshold ionization of hydrogenlike highly charged ions in super-strong laser fields are investigated. Spin-resolved ionization rates in the tunnelling regime are calculated by employing two versions of a relativistic Coulomb-corrected strong-field approximation (SFA). An intuitive simpleman model is developed which explains the derived scaling laws for spin flip and spin asymmetry effects. The intuitive model as well as our ab initio numerical simulations support the analytical results for the spin effects obtained in the dressed SFA where the impact of the laser field on the electron spin evolution in the bound state is taken into account. In contrast, the standard SFA is shown to fail in reproducing spin effects in ionization even at a qualitative level. The anticipated spin-effects are expected to be measurable with modern laser techniques combined with an ion storage facility. (paper)
Spin-polarized spin excitation spectroscopy
International Nuclear Information System (INIS)
Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J
2010-01-01
We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu 2 N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.
Observation of Spin Superfluidity in a Bose Gas Mixture
Fava, Eleonora; Bienaimé, Tom; Mordini, Carmelo; Colzi, Giacomo; Qu, Chunlei; Stringari, Sandro; Lamporesi, Giacomo; Ferrari, Gabriele
2018-04-01
The spin dynamics of a harmonically trapped Bose-Einstein condensed binary mixture of sodium atoms is experimentally investigated at finite temperature. In the collisional regime the motion of the thermal component is shown to be damped because of spin drag, while the two condensates exhibit a counterflow oscillation without friction, thereby providing direct evidence for spin superfluidity. Results are also reported in the collisionless regime where the spin components of both the condensate and thermal part oscillate without damping, their relative motion being driven by a mean-field effect. We also measure the static polarizability of the condensed and thermal parts and we find a large increase of the condensate polarizability with respect to the T =0 value, in agreement with the predictions of theory.
Characteristics of regulatory regimes
Directory of Open Access Journals (Sweden)
Noralv Veggeland
2013-03-01
Full Text Available The overarching theme of this paper is institutional analysis of basic characteristics of regulatory regimes. The concepts of path dependence and administrative traditions are used throughout. Self-reinforcing or positive feedback processes in political systems represent a basic framework. The empirical point of departure is the EU public procurement directive linked to OECD data concerning use of outsourcing among member states. The question is asked: What has caused the Nordic countries, traditionally not belonging to the Anglo-Saxon market-centred administrative tradition, to be placed so high on the ranking as users of the Market-Type Mechanism (MTM of outsourcing in the public sector vs. in-house provision of services? A thesis is that the reason may be complex, but might be found in an innovative Scandinavian regulatory approach rooted in the Nordic model.
Spin nematics next to spin singlets
Yokoyama, Yuto; Hotta, Chisa
2018-05-01
We provide a route to generate nematic order in a spin-1/2 system. Unlike the well-known magnon-binding mechanism, our spin nematics requires neither the frustration effect nor spin polarization in a high field or in the vicinity of a ferromagnet, but instead appears next to the spin singlet phase. We start from a state consisting of a quantum spin-1/2 singlet dimer placed on each site of a triangular lattice, and show that interdimer ring exchange interactions efficiently dope the SU(2) triplets that itinerate and interact, easily driving a stable singlet state to either Bose-Einstein condensates or a triplet crystal, some hosting a spin nematic order. A variety of roles the ring exchange serves includes the generation of a bilinear-biquadratic interaction between nearby triplets, which is responsible for the emergent nematic order separated from the singlet phase by a first-order transition.
Thermally excited proton spin-flip laser emission in tokamaks
International Nuclear Information System (INIS)
Arunasalam, V.; Greene, G.J.
1993-07-01
Based on statistical thermodynamic fluctuation arguments, it is shown here for the first time that thermally excited spin-flip laser emission from the fusion product protons can occur in large tokamak devices that are entering the reactor regime of operation. Existing experimental data from TFTR supports this conjecture, in the sense that these measurements are in complete agreement with the predictions of the quasilinear theory of the spin-flip laser
Gate tunable spin transport in graphene with Rashba spin-orbit coupling
Tan, Xiao-Dong; Liao, Xiao-Ping; Sun, Litao
2016-10-01
Recently, it attracts much attention to study spin-resolved transport properties in graphene with Rashba spin-orbit coupling (RSOC). One remarkable finding is that Klein tunneling in single layer graphene (SLG) with RSOC (SLG + R for short below) behaves as in bi-layer graphene (BLG). Based on the effective Dirac theory, we reconsider this tunneling problem and derive the analytical solution for the transmission coefficients. Our result shows that Klein tunneling in SLG + R and BLG exhibits completely different behaviors. More importantly, we find two new transmission selection rules in SLG + R, i.e., the single band to single band (S → S) and the single band to multiple bands (S → M) transmission regimes, which strongly depend on the relative height among Fermi level, RSOC, and potential barrier. Interestingly, in the S → S transmission regime, only normally incident electrons have capacity to pass through the barrier, while in the S → M transmission regime the angle-dependent tunneling becomes very prominent. Using the transmission coefficients, we also derive spin-resolved conductance analytically, and conductance oscillation with the increasing barrier height and zero conductance gap are found in SLG + R. The present study offers new insights and opportunities for developing graphene-based spin devices.
Precessional Instability in Binary Black Holes with Aligned Spins.
Gerosa, Davide; Kesden, Michael; O'Shaughnessy, Richard; Klein, Antoine; Berti, Emanuele; Sperhake, Ulrich; Trifirò, Daniele
2015-10-02
Binary black holes on quasicircular orbits with spins aligned with their orbital angular momentum have been test beds for analytic and numerical relativity for decades, not least because symmetry ensures that such configurations are equilibrium solutions to the spin-precession equations. In this work, we show that these solutions can be unstable when the spin of the higher-mass black hole is aligned with the orbital angular momentum and the spin of the lower-mass black hole is antialigned. Spins in these configurations are unstable to precession to large misalignment when the binary separation r is between the values r(ud±)=(√(χ(1))±√(qχ(2)))(4)(1-q)(-2)M, where M is the total mass, q≡m(2)/m(1) is the mass ratio, and χ(1) (χ(2)) is the dimensionless spin of the more (less) massive black hole. This instability exists for a wide range of spin magnitudes and mass ratios and can occur in the strong-field regime near the merger. We describe the origin and nature of the instability using recently developed analytical techniques to characterize fully generic spin precession. This instability provides a channel to circumvent astrophysical spin alignment at large binary separations, allowing significant spin precession prior to merger affecting both gravitational-wave and electromagnetic signatures of stellar-mass and supermassive binary black holes.
Dispersive regime of the Jaynes–Cummings and Rabi lattice
International Nuclear Information System (INIS)
Zhu, Guanyu; Koch, Jens; Schmidt, Sebastian
2013-01-01
Photon-based strongly correlated lattice models like the Jaynes–Cummings and Rabi lattices differ from their more conventional relatives like the Bose–Hubbard model by the presence of an additional tunable parameter: the frequency detuning between the pseudo-spin degree of freedom and the harmonic mode frequency on each site. Whenever this detuning is large compared to relevant coupling strengths, the system is said to be in the dispersive regime. The physics of this regime is well-understood at the level of a single Jaynes–Cummings or Rabi site. Here, we extend the theoretical description of the dispersive regime to lattices with many sites, for both strong and ultra-strong coupling. We discuss the nature and spatial range of the resulting qubit–qubit and photon–photon coupling, demonstrate the emergence of photon-pairing and squeezing and illustrate our results by exact diagonalization of the Rabi dimer. (paper)
Semiclassical treatment of transport and spin relaxation in spin-orbit coupled systems
Energy Technology Data Exchange (ETDEWEB)
Lueffe, Matthias Clemens
2012-02-10
-state system in which effects of (pseudo)spin-orbit coupling come to light is monolayer graphene. The graphene Hamiltonian entirely consists of pseudospin-orbit coupling, yielding the peculiar Dirac-cone band structure. In the second part of this thesis, we have calculated corrections to the electrical conductivity of graphene in the Boltzmann regime, which are due to pseudospin coherences. We have found that several generally well-established formalisms for the derivation of kinetic equations yield different results for this problem. We cannot resolve this discrepancy, but we make propose an alternative ansatz for the nonequilibrium Green function, which would resolve some contradictions. The calculated corrections could possibly explain a part of the experimentally observed residual conductivity in graphene.
Controllable nonlinearity in a dual-coupling optomechanical system under a weak-coupling regime
Zhu, Gui-Lei; Lü, Xin-You; Wan, Liang-Liang; Yin, Tai-Shuang; Bin, Qian; Wu, Ying
2018-03-01
Strong quantum nonlinearity gives rise to many interesting quantum effects and has wide applications in quantum physics. Here we investigate the quantum nonlinear effect of an optomechanical system (OMS) consisting of both linear and quadratic coupling. Interestingly, a controllable optomechanical nonlinearity is obtained by applying a driving laser into the cavity. This controllable optomechanical nonlinearity can be enhanced into a strong coupling regime, even if the system is initially in the weak-coupling regime. Moreover, the system dissipation can be suppressed effectively, which allows the appearance of phonon sideband and photon blockade effects in the weak-coupling regime. This work may inspire the exploration of a dual-coupling optomechanical system as well as its applications in modern quantum science.
Coherent perfect absorption in a quantum nonlinear regime of cavity quantum electrodynamics
Wei, Yang-hua; Gu, Wen-ju; Yang, Guoqing; Zhu, Yifu; Li, Gao-xiang
2018-05-01
Coherent perfect absorption (CPA) is investigated in the quantum nonlinear regime of cavity quantum electrodynamics (CQED), in which a single two-level atom couples to a single-mode cavity weakly driven by two identical laser fields. In the strong-coupling regime and due to the photon blockade effect, the weakly driven CQED system can be described as a quantum system with three polariton states. CPA is achieved at a critical input field strength when the frequency of the input fields matches the polariton transition frequency. In the quantum nonlinear regime, the incoherent dissipation processes such as atomic and photon decays place a lower bound for the purity of the intracavity quantum field. Our results show that under the CPA condition, the intracavity field always exhibits the quadrature squeezing property manifested by the quantum nonlinearity, and the outgoing photon flux displays the super-Poissonian distribution.
Spin-3/2 Pentaquark Resonance Signature
International Nuclear Information System (INIS)
Ben Lasscock; John Hedditch; Derek Leinweber; Anthony Williams; Waseem Kamleh; Wolodymyr Melnitchouk; Anthony Thomas; Ross Young; James Zanotti
2005-01-01
We search for the standard lattice resonance signature of attraction between the resonance constituents which leads to a bound state at quark masses near the physical regime. We study a variety of spin-1/2 interpolators and for the first time, interpolators providing access to spin-3/2 pentaquark states. In looking for evidence of binding, a precise determination of the mass splitting between the pentaquark state and its lowest-lying decay channel is performed by constructing the effective mass splitting from the various two-point correlation functions. While the binding of the pentaquark state is not a requirement, the observation of such binding would provide compelling evidence for the existence of the theta+ pentaquark resonance. Evidence of binding is observed in the isoscalar spin-3/2 positive parity channel, making it an interesting state for further research
Self-interacting spin-2 dark matter
Chu, Xiaoyong; Garcia-Cely, Camilo
2017-11-01
Recent developments in bigravity allow one to construct consistent theories of interacting spin-2 particles that are free of ghosts. In this framework, we propose an elementary spin-2 dark matter candidate with a mass well below the TeV scale. We show that, in a certain regime where the interactions induced by the spin-2 fields do not lead to large departures from the predictions of general relativity, such a light dark matter particle typically self-interacts and undergoes self-annihilations via 3-to-2 processes. We discuss its production mechanisms and also identify the regions of the parameter space where self-interactions can alleviate the discrepancies at small scales between the predictions of the collisionless dark matter paradigm and cosmological N-body simulations.
Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi
2017-01-01
We investigate the interconversion phenomena between spin and mechanical angular momentum in moving objects. In particular, the recent results on spin manipulation and spin-current generation by mechanical motion are examined. In accelerating systems, spin-dependent gauge fields emerge, which enable the conversion from mechanical angular momentum into spins. Such a spin-mechanical effect is predicted by quantum theory in a non-inertial frame. Experiments which confirm the effect, i.e., the resonance frequency shift in nuclear magnetic resonance, the stray field measurement of rotating metals, and electric voltage generation in liquid metals, are discussed.
Interaction of antibiotics on pipecuronium-induced neuromuscular blockade.
de Gouw, N E; Crul, J F; Vandermeersch, E; Mulier, J P; van Egmond, J; Van Aken, H
1993-01-01
To measure the interaction of two antibiotics (clindamycin and colistin) on neuromuscular blockade induced by pipecuronium bromide (a new long-acting, steroidal, nondepolarizing neuromuscular blocking drug). Prospective, randomized, placebo-controlled study. Inpatient gynecologic and gastroenterologic service at a university medical center. Three groups of 20 ASA physical status I and II patients with normal kidney and liver function, taking no medication, and undergoing elective surgery under general anesthesia. Anesthesia was induced with propofol and alfentanil intravenously (IV) and maintained with a propofol infusion and 60% nitrous oxide in oxygen. Pipecuronium bromide 50 micrograms/kg was administered after reaching a stable baseline of single-twitch response. At 25% recovery of pipecuronium-induced neuromuscular blockade, patients received one of two antibiotics, clindamycin 300 mg or colistin 1 million IU, or a placebo. The recovery index (RI, defined as time from 25% to 75% recovery of neuromuscular blockade) was measured using the single-twitch response of the adductor pollicis muscle with supramaximal stimulation of the ulnar nerve at the wrist. RI after administration of an antibiotic (given at 25% recovery) was measured and compared with RI of the control group using Student's unpaired t-test. Statistical analyses of the results showed a significant prolongation of the recovery time (from 25% to 75% recovery) of 40 minutes for colistin. When this type of antibiotic is used during anesthesia with pipercuronium as a muscle relaxant, one must be aware of a significant prolongation of an already long-acting neuromuscular blockade and (although not observed in this study) possible problems in antagonism.
Intractable diarrhea in hyperthyroidism: management with beta-adrenergic blockade.
Bricker, L A; Such, F; Loehrke, M E; Kavanaugh, K
2001-01-01
To describe a patient with intractable diarrhea and thyrotoxic Graves' disease, for whom b-adrenergic blockade ultimately proved to be effective therapy for the diarrhea, and to review the types of hyperthyroidism-associated diarrhea. We present the clinical course of a young man with a prolonged siege of diarrhea that proved elusive to diagnostic inquiries and resistant to all means of management until its endocrine basis was discovered. Control of such cases with b-adrenergic blockade is discussed, as are the pathophysiologic bases of intestinal hypermotility in hyperthyroidism. A 26-year-old man with Down syndrome, and no prior gastrointestinal disorder, had insidious, chronic, constant diarrhea, which was associated with loss of 14 kg during a 5-month period. Numerous laboratory and imaging studies and endoscopic examinations failed to disclose the cause of the diarrhea. Furthermore, a broad range of antibiotics and other empiric remedies failed to control the problem. No other symptoms of hyperthyroidism were reported, but when the endocrinopathy was suspected and identified, the diarrhea was promptly controlled by treatment with propranolol. In patients with hyperthyroidism, two types of diarrheal disorders have been described-secretory diarrhea and steatorrhea; bile acid malabsorption may have a role in either of these settings. In addition to its capacity for blocking the peripheral effects of thyroid hormone on the heart and central nervous system, b-adrenergic blockade is effective in slowing intestinal transit time and ameliorating the uncommon diarrhea associated with hyperthyroidism. Thyroid hormone in excess, among its other possible effects on the gastrointestinal tract, may exert a stimulatory effect by means of intermediary sympathetic activation, as it does with the heart. Thus, sympathetic blockade can mimic the salutary effects on the gastrointestinal tract conventionally brought about by direct antithyroid therapy, and well before the
Transmutation of skyrmions to half-solitons driven by the nonlinear optical spin Hall effect.
Flayac, H; Solnyshkov, D D; Shelykh, I A; Malpuech, G
2013-01-04
We show that the spin domains, generated in the linear optical spin Hall effect by the analog of spin-orbit interaction for exciton polaritons, are associated with the formation of a Skyrmion lattice. In the nonlinear regime, the spin anisotropy of the polariton-polariton interactions results in a spatial compression of the domains and in a transmutation of the Skyrmions into oblique half-solitons. This phase transition is associated with both the focusing of the spin currents and the emergence of a strongly anisotropic emission pattern.
Spin-orbit-induced strong coupling of a single spin to a nanomechanical resonator
DEFF Research Database (Denmark)
Pályi, András; Struck, P R; Rudner, Mark
2012-01-01
as a realization of the Jaynes-Cummings model of quantum electrodynamics in the strong-coupling regime. A quantized flexural mode of the suspended tube plays the role of the optical mode and we identify two distinct two-level subspaces, at small and large magnetic field, which can be used as qubits in this setup......We theoretically investigate the deflection-induced coupling of an electron spin to vibrational motion due to spin-orbit coupling in suspended carbon nanotube quantum dots. Our estimates indicate that, with current capabilities, a quantum dot with an odd number of electrons can serve...
Blockade of Death Ligand TRAIL Inhibits Renal Ischemia Reperfusion Injury
International Nuclear Information System (INIS)
Adachi, Takaomi; Sugiyama, Noriyuki; Gondai, Tatsuro; Yagita, Hideo; Yokoyama, Takahiko
2013-01-01
Renal ischemia-reperfusion injury (IRI) is a leading cause of acute kidney injury (AKI). Many investigators have reported that cell death via apoptosis significantly contributed to the pathophysiology of renal IRI. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor superfamily, and induces apoptosis and inflammation. However, the role of TRAIL in renal IRI is unclear. Here, we investigated whether TRAIL contributes to renal IRI and whether TRAIL blockade could attenuate renal IRI. AKI was induced by unilateral clamping of the renal pedicle for 60 min in male FVB/N mice. We found that the expression of TRAIL and its receptors were highly upregulated in renal tubular cells in renal IRI. Neutralizing anti-TRAIL antibody or its control IgG was given 24 hr before ischemia and a half-dose booster injection was administered into the peritoneal cavity immediately after reperfusion. We found that TRAIL blockade inhibited tubular apoptosis and reduced the accumulation of neutrophils and macrophages. Furthermore, TRAIL blockade attenuated renal fibrosis and atrophy after IRI. In conclusion, our study suggests that TRAIL is a critical pathogenic factor in renal IRI, and that TRAIL could be a new therapeutic target for the prevention of renal IRI
Neuromuscular blockade in cardiac surgery: An update for clinicians
Directory of Open Access Journals (Sweden)
Hemmerling Thomas
2008-01-01
Full Text Available There have been great advancements in cardiac surgery over the last two decades; the widespread use of off-pump aortocoronary bypass surgery, minimally invasive cardiac surgery, and robotic surgery have also changed the face of cardiac anaesthesia. The concept of "Fast-track anaesthesia" demands the use of nondepolarising neuromuscular blocking drugs with short duration of action, combining the ability to provide (if necessary sufficiently profound neuromuscular blockade during surgery and immediate re-establishment of normal neuromuscular transmission at the end of surgery. Postoperative residual muscle paralysis is one of the major hurdles for immediate or early extubation after cardiac surgery. Nondepolarising neuromuscular blocking drugs for cardiac surgery should therefore be easy to titrate, of rapid onset and short duration of action with a pathway of elimination independent from hepatic or renal dysfunction, and should equally not affect haemodynamic stability. The difference between repetitive bolus application and continuous infusion is outlined in this review, with the pharmacodynamic and pharmacokinetic characteristics of vecuronium, pancuronium, rocuronium, and cisatracurium. Kinemyography and acceleromyography are the most important currently used neuromuscular monitoring methods. Whereas monitoring at the adductor pollicis muscle is appropriate at the end of surgery, monitoring of the corrugator supercilii muscle better reflects neuromuscular blockade at more central, profound muscles, such as the diaphragm, larynx, or thoraco-abdominal muscles. In conclusion, cisatracurium or rocuronium is recommended for neuromuscular blockade in modern cardiac surgery.
Energy Technology Data Exchange (ETDEWEB)
NONE
2006-07-01
The following topics were ealt with: Hadron physics with proton and deuteron probes, physics projects with Georgian participation, spin physics with antiprotons and leptons, spin filtering experiments, ISTC projects, technical issues for FAIR. (HSI)
Dynamic nuclear spin polarization
Energy Technology Data Exchange (ETDEWEB)
Stuhrmann, H B [GKSS-Forschungszentrum Geesthacht GmbH (Germany)
1996-11-01
Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.
Instantons and magnetization tunneling: Beyond the giant-spin approximation
International Nuclear Information System (INIS)
Florez, J.M.; Vargas, P.; Nunez, Alvaro S.
2009-01-01
In this work we show that commonly neglected fluctuations of the net total spin of a molecular nanomagnet strongly modified its tunneling properties and provide a scenario to explain some discrepancies between theory and experiment. Starting off from an effective spin Hamiltonian, we study the quantum tunneling of the magnetization of molecular nanomagnets in the regime where the giant-spin approximation is breaking down. This study is done using an instanton description of the tunneling path. The instanton is calculated considering its coupling to quantum fluctuations.
Ground states of a spin-boson model
International Nuclear Information System (INIS)
Amann, A.
1991-01-01
Phase transition with respect to ground states of a spin-boson Hamiltonian are investigated. The spin-boson model under discussion consists of one spin and infinitely many bosons with a dipole-type coupling. It is shown that the order parameter of the model vanishes with respect to arbitrary ground states if it vanishes with respect to ground states obtained as (biased) temperature to zero limits of thermic equilibrium states. The ground states of the latter special type have been investigated by H. Spohn. Spohn's respective phase diagrams are therefore valid for arbitrary ground states. Furthermore, disjointness of ground states in the broken symmetry regime is examined
Spin-Orbit Coupling for Photons and Polaritons in Microstructures
Directory of Open Access Journals (Sweden)
V. G. Sala
2015-03-01
Full Text Available We use coupled micropillars etched out of a semiconductor microcavity to engineer a spin-orbit Hamiltonian for photons and polaritons in a microstructure. The coupling between the spin and orbital momentum arises from the polarization-dependent confinement and tunneling of photons between adjacent micropillars arranged in the form of a hexagonal photonic molecule. It results in polariton eigenstates with distinct polarization patterns, which are revealed in photoluminescence experiments in the regime of polariton condensation. Thanks to the strong polariton nonlinearities, our system provides a photonic workbench for the quantum simulation of the interplay between interactions and spin-orbit effects, particularly when extended to two-dimensional lattices.
Long-Distance Entanglement of Spin Qubits via Ferromagnet
Directory of Open Access Journals (Sweden)
Luka Trifunovic
2013-12-01
Full Text Available We propose a mechanism of coherent coupling between distant spin qubits interacting dipolarly with a ferromagnet. We derive an effective two-spin interaction Hamiltonian and find a regime where the dynamics is coherent. Finally, we present a sequence for the implementation of the entangling controlled-not gate and estimate the corresponding operation time to be a few tens of nanoseconds. A particularly promising application of our proposal is to atomistic spin qubits such as silicon-based qubits and nitrogen-vacancy centers in diamond to which existing coupling schemes do not apply.
International Nuclear Information System (INIS)
Ji Xiangdong
2003-01-01
Spin is a beautiful concept that plays an ever important role in modern physics. In this talk, I start with a discussion of the origin of spin, and then turn to three themes in which spin has been crucial in subatomic physics: a lab to explore physics beyond the standard model, a tool to measure physical observables that are hard to obtain otherwise, a probe to unravel nonperturbative QCD. I conclude with some remarks on a world without spin
International Nuclear Information System (INIS)
Anon.
1980-01-01
From 25 September to 1 October, some 150 spin enthusiasts gathered in Lausanne for the 1980 International Symposium on High Energy Physics with Polarized Beams and Polarized Targets. The programme was densely packed, covering physics interests with spin as well as the accelerator and target techniques which make spin physics possible
DEFF Research Database (Denmark)
Yu, Xiao-Qin; Zhu, Zhen-Gang; Su, Gang
2017-01-01
The thermoelectric performance of a topological energy converter is analyzed. The H-shaped device is based on a combination of transverse topological effects involving the spin: the inverse spin Hall effect and the spin Nernst effect. The device can convert a temperature drop in one arm into an e...
Cross, Rod
2013-01-01
Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction…
Quantum Entanglement of a Tunneling Spin with Mechanical Modes of a Torsional Resonator
Directory of Open Access Journals (Sweden)
D. A. Garanin
2011-08-01
Full Text Available We solve the Schrödinger equation for various quantum regimes describing a tunneling macrospin coupled to a torsional oscillator. The energy spectrum and freezing of spin tunneling are studied. Magnetic susceptibility, noise spectrum, and decoherence due to entanglement of spin and mechanical modes are computed. We show that the presence of a tunneling spin can be detected via splitting of the mechanical mode at the resonance. Our results apply to experiments with magnetic molecules coupled to nanoresonators.
Higher-spin currents in the Gross-Neveu model at 1/n"2
International Nuclear Information System (INIS)
Manashov, A.N.
2016-10-01
We calculate the anomalous dimensions of higher-spin currents, both singlet and non-singlet, in the Gross - Neveu model at the 1/n"2 order. It was conjectured that in the critical regime this model is dual to a higher-spin gauge theory on AdS_4. The AdS/CFT correspondence predicts that the masses of higher-spin fields correspond to the scaling dimensions of the singlet currents in the Gross - Neveu model.
The spin structure of the nucleon
International Nuclear Information System (INIS)
Deur, A.
2008-02-01
This document describes the recent experimental results on the spin structure of the nucleon obtained with the electron accelerator Thomas Jefferson National Facility (Jefferson Lab), Virginia. We first discuss the goal of studying the nucleon spin structure and give the basis and phenomenology of high energy lepton scattering. Then, we discuss with some details a few sum rules concerning the spin structure of the nucleon. Those are important tools for studying the nucleon spin structure at Jefferson Lab. We then describe the present experimental situation and analyze the results. We have been able to determine an effective coupling constant for the strong interaction for any regime of quantum chromodynamics which proves that QCD is an approximately conformal theory. We conclude on the perspectives for this field of research, in particular with the 12 GeV energy upgrade of Jefferson Lab. The top priority will be the measurement of generalised parton distributions. The only issue that will stay misunderstood is the role of the very low x domain on the spin structure of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Evelt, M.; Demidov, V. E., E-mail: demidov@uni-muenster.de [Institute for Applied Physics and Center for Nanotechnology, University of Muenster, 48149 Muenster (Germany); Bessonov, V. [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Yekaterinburg 620041 (Russian Federation); Demokritov, S. O. [Institute for Applied Physics and Center for Nanotechnology, University of Muenster, 48149 Muenster (Germany); M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Yekaterinburg 620041 (Russian Federation); Prieto, J. L. [Instituto de Sistemas Optoelectrónicos y Microtecnologa (UPM), Ciudad Universitaria, Madrid 28040 (Spain); Muñoz, M. [IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), PTM, E-28760 Tres Cantos, Madrid (Spain); Ben Youssef, J. [Laboratoire de Magnétisme de Bretagne CNRS, Université de Bretagne Occidentale, 29285 Brest (France); Naletov, V. V. [Service de Physique de l' État Condensé, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette (France); Institute of Physics, Kazan Federal University, Kazan 420008 (Russian Federation); Loubens, G. de [Service de Physique de l' État Condensé, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette (France); Klein, O. [INAC-SPINTEC, CEA/CNRS and Univ. Grenoble Alpes, 38000 Grenoble (France); Collet, M.; Garcia-Hernandez, K.; Bortolotti, P.; Cros, V.; Anane, A. [Unité Mixte de Physique CNRS, Thales, Univ. Paris Sud, Université Paris-Saclay, 91767 Palaiseau (France)
2016-04-25
We study experimentally with submicrometer spatial resolution the propagation of spin waves in microscopic waveguides based on the nanometer-thick yttrium iron garnet and Pt layers. We demonstrate that by using the spin-orbit torque, the propagation length of the spin waves in such systems can be increased by nearly a factor of 10, which corresponds to the increase in the spin-wave intensity at the output of a 10 μm long transmission line by three orders of magnitude. We also show that, in the regime, where the magnetic damping is completely compensated by the spin-orbit torque, the spin-wave amplification is suppressed by the nonlinear scattering of the coherent spin waves from current-induced excitations.
International Nuclear Information System (INIS)
Evelt, M.; Demidov, V. E.; Bessonov, V.; Demokritov, S. O.; Prieto, J. L.; Muñoz, M.; Ben Youssef, J.; Naletov, V. V.; Loubens, G. de; Klein, O.; Collet, M.; Garcia-Hernandez, K.; Bortolotti, P.; Cros, V.; Anane, A.
2016-01-01
We study experimentally with submicrometer spatial resolution the propagation of spin waves in microscopic waveguides based on the nanometer-thick yttrium iron garnet and Pt layers. We demonstrate that by using the spin-orbit torque, the propagation length of the spin waves in such systems can be increased by nearly a factor of 10, which corresponds to the increase in the spin-wave intensity at the output of a 10 μm long transmission line by three orders of magnitude. We also show that, in the regime, where the magnetic damping is completely compensated by the spin-orbit torque, the spin-wave amplification is suppressed by the nonlinear scattering of the coherent spin waves from current-induced excitations.
Spin physics in semiconductors
2017-01-01
This book offers an extensive introduction to the extremely rich and intriguing field of spin-related phenomena in semiconductors. In this second edition, all chapters have been updated to include the latest experimental and theoretical research. Furthermore, it covers the entire field: bulk semiconductors, two-dimensional semiconductor structures, quantum dots, optical and electric effects, spin-related effects, electron-nuclei spin interactions, Spin Hall effect, spin torques, etc. Thanks to its self-contained style, the book is ideally suited for graduate students and researchers new to the field.
Stretchable Persistent Spin Helices in GaAs Quantum Wells
Dettwiler, Florian; Fu, Jiyong; Mack, Shawn; Weigele, Pirmin J.; Egues, J. Carlos; Awschalom, David D.; Zumbühl, Dominik M.
2017-07-01
The Rashba and Dresselhaus spin-orbit (SO) interactions in 2D electron gases act as effective magnetic fields with momentum-dependent directions, which cause spin decay as the spins undergo arbitrary precessions about these randomly oriented SO fields due to momentum scattering. Theoretically and experimentally, it has been established that by fine-tuning the Rashba α and renormalized Dresselhaus β couplings to equal fixed strengths α =β , the total SO field becomes unidirectional, thus rendering the electron spins immune to decay due to momentum scattering. A robust persistent spin helix (PSH), i.e., a helical spin-density wave excitation with constant pitch P =2 π /Q , Q =4 m α /ℏ2, has already been experimentally realized at this singular point α =β , enhancing the spin lifetime by up to 2 orders of magnitude. Here, we employ the suppression of weak antilocalization as a sensitive detector for matched SO fields together with independent electrical control over the SO couplings via top gate voltage VT and back gate voltage VB to extract all SO couplings when combined with detailed numerical simulations. We demonstrate for the first time the gate control of the renormalized β and the continuous locking of the SO fields at α =β ; i.e., we are able to vary both α and β controllably and continuously with VT and VB, while keeping them locked at equal strengths. This makes possible a new concept: "stretchable PSHs," i.e., helical spin patterns with continuously variable pitches P over a wide parameter range. Stretching the PSH, i.e., gate controlling P while staying locked in the PSH regime, provides protection from spin decay at the symmetry point α =β , thus offering an important advantage over other methods. This protection is limited mainly by the cubic Dresselhaus term, which breaks the unidirectionality of the total SO field and causes spin decay at higher electron densities. We quantify the cubic term, and find it to be sufficiently weak so that
Stretchable Persistent Spin Helices in GaAs Quantum Wells
Directory of Open Access Journals (Sweden)
Florian Dettwiler
2017-07-01
Full Text Available The Rashba and Dresselhaus spin-orbit (SO interactions in 2D electron gases act as effective magnetic fields with momentum-dependent directions, which cause spin decay as the spins undergo arbitrary precessions about these randomly oriented SO fields due to momentum scattering. Theoretically and experimentally, it has been established that by fine-tuning the Rashba α and renormalized Dresselhaus β couplings to equal fixed strengths α=β, the total SO field becomes unidirectional, thus rendering the electron spins immune to decay due to momentum scattering. A robust persistent spin helix (PSH, i.e., a helical spin-density wave excitation with constant pitch P=2π/Q, Q=4mα/ℏ^{2}, has already been experimentally realized at this singular point α=β, enhancing the spin lifetime by up to 2 orders of magnitude. Here, we employ the suppression of weak antilocalization as a sensitive detector for matched SO fields together with independent electrical control over the SO couplings via top gate voltage V_{T} and back gate voltage V_{B} to extract all SO couplings when combined with detailed numerical simulations. We demonstrate for the first time the gate control of the renormalized β and the continuous locking of the SO fields at α=β; i.e., we are able to vary both α and β controllably and continuously with V_{T} and V_{B}, while keeping them locked at equal strengths. This makes possible a new concept: “stretchable PSHs,” i.e., helical spin patterns with continuously variable pitches P over a wide parameter range. Stretching the PSH, i.e., gate controlling P while staying locked in the PSH regime, provides protection from spin decay at the symmetry point α=β, thus offering an important advantage over other methods. This protection is limited mainly by the cubic Dresselhaus term, which breaks the unidirectionality of the total SO field and causes spin decay at higher electron densities. We quantify the cubic term, and find it to be
Polarization of nuclear spins by a cold nanoscale resonator
International Nuclear Information System (INIS)
Butler, Mark C.; Weitekamp, Daniel P.
2011-01-01
A cold nanoscale resonator coupled to a system of nuclear spins can induce spin relaxation. In the low-temperature limit where spin-lattice interactions are ''frozen out,'' spontaneous emission by nuclear spins into a resonant mechanical mode can become the dominant mechanism for cooling the spins to thermal equilibrium with their environment. We provide a theoretical framework for the study of resonator-induced cooling of nuclear spins in this low-temperature regime. Relaxation equations are derived from first principles, in the limit where energy donated by the spins to the resonator is quickly dissipated into the cold bath that damps it. A physical interpretation of the processes contributing to spin polarization is given. For a system of spins that have identical couplings to the resonator, the interaction Hamiltonian conserves spin angular momentum, and the resonator cannot relax the spins to thermal equilibrium unless this symmetry is broken by the spin Hamiltonian. The mechanism by which such a spin system becomes ''trapped'' away from thermal equilibrium can be visualized using a semiclassical model, which shows how an indirect spin-spin interaction arises from the coupling of multiple spins to one resonator. The internal spin Hamiltonian can affect the polarization process in two ways: (1) By modifying the structure of the spin-spin correlations in the energy eigenstates, and (2) by splitting the degeneracy within a manifold of energy eigenstates, so that zero-frequency off-diagonal terms in the density matrix are converted to oscillating coherences. Shifting the frequencies of these coherences sufficiently far from zero suppresses the development of resonator-induced correlations within the manifold during polarization from a totally disordered state. Modification of the spin-spin correlations by means of either mechanism affects the strength of the fluctuating spin dipole that drives the resonator. In the case where product states can be chosen as energy
Inverse spin Hall effect by spin injection
Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.
2007-09-01
Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.
DEFF Research Database (Denmark)
Staehr-Rye, Anne K; Rasmussen, Lars S.; Rosenberg, Jacob
2014-01-01
: In this assessor-blinded study, 48 patients undergoing elective laparoscopic cholecystectomy were administered rocuronium for neuromuscular blockade and randomized to either deep neuromuscular blockade (rocuronium bolus plus infusion maintaining a posttetanic count 0-1) or moderate neuromuscular blockade...... (rocuronium repeat bolus only for inadequate surgical conditions with spontaneous recovery of neuromuscular function). Patients received anesthesia with propofol, remifentanil, and rocuronium. The primary outcome was the proportion of procedures with optimal surgical space conditions (assessed by the surgeon...
Transition from Spin Dewetting to continuous film in spin coating of Liquid Crystal 5CB.
Dhara, Palash; Bhandaru, Nandini; Das, Anuja; Mukherjee, Rabibrata
2018-05-08
Spin dewetting refers to spontaneous rupture of the dispensed solution layer during spin coating, resulting in isolated but periodic, regular sized domains of the solute and is pre-dominant when the solute concentration (C n ) is very low. In this article we report how the morphology of liquid crystal (LC) 5CB thin films coated on flat and patterned PMMA substrate transform from spin dewetted droplets to continuous films with increase in C n . We further show that within the spin dewetted regime, with gradual increase in the solute concentration, periodicity of the isotropic droplets (λ D ) as well as their mean diameter (d D ), gradually decreases, till the film becomes continuous at a critical concentration (C n *). Interestingly, the trend that λ D reduces with increase in C n is exact opposite to what is observed in thermal/solvent vapor induced dewetting of a thin film. The spin dewetted droplets exhibit transient Radial texture, in contrast to Schlieren texture observed in elongated threads and continuous films of 5CB, which remains in the Nematic phase at room temperature. Finally we show that by casting the film on a grating patterned substrate it becomes possible to align the spin dewetted droplets along the contours substrate patterns.
Electrically tunable spin polarization in silicene: A multi-terminal spin density matrix approach
International Nuclear Information System (INIS)
Chen, Son-Hsien
2016-01-01
Recent realized silicene field-effect transistor yields promising electronic applications. Using a multi-terminal spin density matrix approach, this paper presents an analysis of the spin polarizations in a silicene structure of the spin field-effect transistor by considering the intertwined intrinsic and Rashba spin–orbit couplings, gate voltage, Zeeman splitting, as well as disorder. Coexistence of the stagger potential and intrinsic spin–orbit coupling results in spin precession, making any in-plane polarization directions reachable by the gate voltage; specifically, the intrinsic coupling allows one to electrically adjust the in-plane components of the polarizations, while the Rashba coupling to adjust the out-of-plan polarizations. Larger electrically tunable ranges of in-plan polarizations are found in oppositely gated silicene than in the uniformly gated silicene. Polarizations in different phases behave distinguishably in weak disorder regime, while independent of the phases, stronger disorder leads to a saturation value. - Highlights: • Density matrix with spin rotations enables multi-terminal arbitrary spin injections. • Gate-voltage tunable in-plane polarizations require intrinsic SO coupling. • Gate-voltage tunable out-of-plane polarizations require Rashba SO coupling. • Oppositely gated silicene yields a large tunable range of in-plan polarizations. • Polarizations in different phases behave distinguishably only in weak disorder.
Transport through semiconductor nanowire quantum dots in the Kondo regime
Energy Technology Data Exchange (ETDEWEB)
Schmaus, Stefan; Koerting, Verena; Woelfle, Peter [Institut fuer Theorie der Kondensierten Materie, Universitaet Karlsruhe, Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe (Germany)
2008-07-01
Recent experiments on quantum dots made of semiconductor nanowires in the Coulomb blockade regime have shown the influence of several approximately equidistant levels on the conductance. We study a model with three levels occupied by three electrons. At finite bias voltage charge energy conserving excitations into several higher lying states occur leading to features in the differential conductance. We restrict our study to the six lowest lying states by performing a Schrieffer-Wolff type projection onto this subspace. The emerging effective Kondo Hamiltonian is treated in non-equilibrium perturbation theory in the coupling to the leads. For convenience we use a pseudoparticle representation and an exact projection method. The voltage-dependence of the occupation numbers is discussed. The density matrix on the dot turns out to be off-diagonal in the dot eigenstate Hilbert space in certain parameter regimes. The dependence of the differential conductance on magnetic field and temperature is calculated in lowest order in the dot-lead coupling and the results are compared with experiment.
Electronic Maxwell demon in the coherent strong-coupling regime
Schaller, Gernot; Cerrillo, Javier; Engelhardt, Georg; Strasberg, Philipp
2018-05-01
We consider an external feedback control loop implementing the action of a Maxwell demon. Applying control actions that are conditioned on measurement outcomes, the demon may transport electrons against a bias voltage and thereby effectively converts information into electric power. While the underlying model—a feedback-controlled quantum dot that is coupled to two electronic leads—is well explored in the limit of small tunnel couplings, we can address the strong-coupling regime with a fermionic reaction-coordinate mapping. This exact mapping transforms the setup into a serial triple quantum dot coupled to two leads. We find that a continuous projective measurement of the central dot occupation would lead to a complete suppression of electronic transport due to the quantum Zeno effect. In contrast, by using a microscopic detector model we can implement a weak measurement, which allows for closure of the control loop without transport blockade. Then, in the weak-coupling regime, the energy flows associated with the feedback loop are negligible, and dominantly the information gained in the measurement induces a bound for the generated electric power. In the strong coupling limit, the protocol may require more energy for operating the control loop than electric power produced, such that the whole device is no longer information dominated and can thus not be interpreted as a Maxwell demon.
Bulk electron spin polarization generated by the spin Hall current
Korenev, V. L.
2005-01-01
It is shown that the spin Hall current generates a non-equilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known equilibrium polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.
Bulk electron spin polarization generated by the spin Hall current
Korenev, V. L.
2006-07-01
It is shown that the spin Hall current generates a nonequilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known “equilibrium” polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.
Spin Sum Rules and Polarizabilities: Results from Jefferson Lab
International Nuclear Information System (INIS)
Jian-Ping Chen
2006-01-01
The nucleon spin structure has been an active, exciting and intriguing subject of interest for the last three decades. Recent experimental data on nucleon spin structure at low to intermediate momentum transfers provide new information in the confinement regime and the transition region from the confinement regime to the asymptotic freedom regime. New insight is gained by exploring moments of spin structure functions and their corresponding sum rules (i.e. the generalized Gerasimov-Drell-Hearn, Burkhardt-Cottingham and Bjorken). The Burkhardt-Cottingham sum rule is verified to good accuracy. The spin structure moments data are compared with Chiral Perturbation Theory calculations at low momentum transfers. It is found that chiral perturbation calculations agree reasonably well with the first moment of the spin structure function g 1 at momentum transfer of 0.05 to 0.1 GeV 2 but fail to reproduce the neutron data in the case of the generalized polarizability (delta) LT (the (delta) LT puzzle). New data have been taken on the neutron ( 3 He), the proton and the deuteron at very low Q 2 down to 0.02 GeV 2 . They will provide benchmark tests of Chiral dynamics in the kinematic region where the Chiral Perturbation theory is expected to work
Muon spin relaxation in random spin systems
International Nuclear Information System (INIS)
Toshimitsu Yamazaki
1981-01-01
The longitudinal relaxation function Gsub(z)(t) of the positive muon can reflect dynamical characters of local field in a unique way even when the correlation time is longer than the Larmor period of local field. This method has been applied to studies of spin dynamics in spin glass systems, revealing sharp but continuous temperature dependence of the correlation time. Its principle and applications are reviewed. (author)
Autonomic Blockade Reverses Endothelial Dysfunction in Obesity-Associated Hypertension.
Gamboa, Alfredo; Figueroa, Rocío; Paranjape, Sachin Y; Farley, Ginnie; Diedrich, Andre; Biaggioni, Italo
2016-10-01
Impaired nitric oxide (NO) vasodilation (endothelial dysfunction) is associated with obesity and thought to be a factor in the development of hypertension. We previously found that NO synthesis inhibition had similar pressor effects in obese hypertensives compared with healthy control during autonomic blockade, suggesting that impaired NO vasodilation is secondary to sympathetic activation. We tested this hypothesis by determining the effect of autonomic blockade (trimethaphan 4 mg/min IV) on NO-mediated vasodilation (increase in forearm blood flow to intrabrachial acetylcholine) compared with endothelial-independent vasodilation (intrabrachial sodium nitroprusside) in obese hypertensive subjects (30blood flow (from 3.9±0.7 to 5.2±1.2 mL/100 mL per minute, P=0.078). As expected, NO-mediated vasodilation was blunted on the intact day compared with NO-independent vasodilation; forearm blood flow increased from 3.6±0.6 to 10.1±1.1 with the highest dose of nitroprusside, but only from 3.7±0.4 to 7.2±0.8 mL/100 mL per minute with the highest dose of acetylcholine, Pblood flow responses to acetylcholine were restored by autonomic blockade and were no longer different to nitroprusside (from 6.2±1.1 to 11.4±1.6 mL/100 mL per minute and from 5.2±0.9 to 12.5±0.9, respectively, P=0.58). Our results support the concept that sympathetic activation contributes to the impairment in NO-mediated vasodilation seen in obesity-associated hypertension and provides further rationale to explore it as a therapeutic target. © 2016 American Heart Association, Inc.
Predictors of responses to immune checkpoint blockade in advanced melanoma
DEFF Research Database (Denmark)
Jacquelot, N; Roberti, M P; Enot, D P
2017-01-01
Immune checkpoint blockers (ICB) have become pivotal therapies in the clinical armamentarium against metastatic melanoma (MMel). Given the frequency of immune related adverse events and increasing use of ICB, predictors of response to CTLA-4 and/or PD-1 blockade represent unmet clinical needs....... Using a systems biology-based approach to an assessment of 779 paired blood and tumor markers in 37 stage III MMel patients, we analyzed association between blood immune parameters and the functional immune reactivity of tumor-infiltrating cells after ex vivo exposure to ICB. Based on this assay, we...
Current US nuclear liability regime
International Nuclear Information System (INIS)
Brown, O.F.
2000-01-01
The Price-Anderson Act Adopted by US Congress in 1957 as the world's first national nuclear liability regime. It is a comprehensive, complicated and unique system and stems from special features of US legal regime and federal system of government. It differs from other systems by providing for 'economic', not legal; channeling of liability to facility operator and not recommended as model for other states, but most features adopted by other states and international conventions
Merkel, Wolfgang
2004-01-01
"The development of the term and the analytical concept of totalitarianism have gone through several stages since the 1920s. However, even in its most sophisticated form, the version seen in Friedrich/ Brzezinski, the concept exhibits substantial systematic classification problems and analytical weaknesses. This article attempts to frame the type of totalitarian regime within a general typology of political regimes. Special attention is dedicated to the problem of distinguishing autocra...
Endogenous Monetary Policy Regime Change
Troy Davig; Eric M. Leeper
2006-01-01
This paper makes changes in monetary policy rules (or regimes) endogenous. Changes are triggered when certain endogenous variables cross specified thresholds. Rational expectations equilibria are examined in three models of threshold switching to illustrate that (i) expectations formation effects generated by the possibility of regime change can be quantitatively important; (ii) symmetric shocks can have asymmetric effects; (iii) endogenous switching is a natural way to formally model preempt...
Directory of Open Access Journals (Sweden)
Manuel Offidani
2018-05-01
Full Text Available We present a unified theoretical framework for the study of spin dynamics and relativistic transport phenomena in disordered two-dimensional Dirac systems with pseudospin-spin coupling. The formalism is applied to the paradigmatic case of graphene with uniform Bychkov-Rashba interaction and shown to capture spin relaxation processes and associated charge-to-spin interconversion phenomena in response to generic external perturbations, including spin density fluctuations and electric fields. A controlled diagrammatic evaluation of the generalized spin susceptibility in the diffusive regime of weak spin-orbit interaction allows us to show that the spin and momentum lifetimes satisfy the standard Dyakonov-Perel relation for both weak (Gaussian and resonant (unitary nonmagnetic disorder. Finally, we demonstrate that the spin relaxation rate can be derived in the zero-frequency limit by exploiting the SU(2 covariant conservation laws for the spin observables. Our results set the stage for a fully quantum-mechanical description of spin relaxation in both pristine graphene samples with weak spin-orbit fields and in graphene heterostructures with enhanced spin-orbital effects currently attracting much attention.
The susceptibilities in the spin-S Ising model
International Nuclear Information System (INIS)
Ainane, A.; Saber, M.
1995-08-01
The susceptibilities of the spin-S Ising model are evaluated using the effective field theory introduced by Tucker et al. for studying general spin-S Ising model. The susceptibilities are studied for all spin values from S = 1/2 to S = 5/2. (author). 12 refs, 4 figs
Neutron spin quantum precession using multilayer spin splitters and a phase-spin echo interferometer
International Nuclear Information System (INIS)
Ebisawa, Toru; Tasaki, Seiji; Kawai, Takeshi; Hino, Masahiro; Akiyoshi, Tsunekazu; Achiwa, Norio; Otake, Yoshie; Funahashi, Haruhiko.
1996-01-01
Neutron spin quantum precession by multilayer spin splitter has been demonstrated using a new spin interferometer. The multilayer spin splitter consists of a magnetic multilayer mirror on top, followed by a gap layer and a non magnetic multilayer mirror which are evaporated on a silicon substrate. Using the multilayer spin splitter, a polarized neutron wave in a magnetic field perpendicular to the polarization is split into two spin eigenstates with a phase shift in the direction of the magnetic field. The spin quantum precession is equal to the phase shift, which depends on the effective thickness of the gap layer. The demonstration experiments verify the multilayer spin splitter as a neutron spin precession device as well as the coherent superposition principle of the two spin eigenstates. We have developed a new phase-spin echo interferometer using the multilayer spin splitters. We present successful performance tests of the multilayer spin splitter and the phase-spin echo interferometer. (author)
Henneaux, Marc; Vasiliev, Mikhail A
2017-01-01
Symmetries play a fundamental role in physics. Non-Abelian gauge symmetries are the symmetries behind theories for massless spin-1 particles, while the reparametrization symmetry is behind Einstein's gravity theory for massless spin-2 particles. In supersymmetric theories these particles can be connected also to massless fermionic particles. Does Nature stop at spin-2 or can there also be massless higher spin theories. In the past strong indications have been given that such theories do not exist. However, in recent times ways to evade those constraints have been found and higher spin gauge theories have been constructed. With the advent of the AdS/CFT duality correspondence even stronger indications have been given that higher spin gauge theories play an important role in fundamental physics. All these issues were discussed at an international workshop in Singapore in November 2015 where the leading scientists in the field participated. This volume presents an up-to-date, detailed overview of the theories i...
Spin-orbit qubit in a semiconductor nanowire.
Nadj-Perge, S; Frolov, S M; Bakkers, E P A M; Kouwenhoven, L P
2010-12-23
Motion of electrons can influence their spins through a fundamental effect called spin-orbit interaction. This interaction provides a way to control spins electrically and thus lies at the foundation of spintronics. Even at the level of single electrons, the spin-orbit interaction has proven promising for coherent spin rotations. Here we implement a spin-orbit quantum bit (qubit) in an indium arsenide nanowire, where the spin-orbit interaction is so strong that spin and motion can no longer be separated. In this regime, we realize fast qubit rotations and universal single-qubit control using only electric fields; the qubits are hosted in single-electron quantum dots that are individually addressable. We enhance coherence by dynamically decoupling the qubits from the environment. Nanowires offer various advantages for quantum computing: they can serve as one-dimensional templates for scalable qubit registers, and it is possible to vary the material even during wire growth. Such flexibility can be used to design wires with suppressed decoherence and to push semiconductor qubit fidelities towards error correction levels. Furthermore, electrical dots can be integrated with optical dots in p-n junction nanowires. The coherence times achieved here are sufficient for the conversion of an electronic qubit into a photon, which can serve as a flying qubit for long-distance quantum communication.
Transition from weak wave turbulence regime to solitonic regime
Hassani, Roumaissa; Mordant, Nicolas
2017-11-01
The Weak Turbulence Theory (WTT) is a statistical theory describing the interaction of a large ensemble of random waves characterized by very different length scales. For both weak non-linearity and weak dispersion a different regime is predicted where solitons propagate while keeping their shape unchanged. The question under investigation here is which regime between weak turbulence or soliton gas does the system choose ? We report an experimental investigation of wave turbulence at the surface of finite depth water in the gravity-capillary range. We tune the wave dispersion and the level of nonlinearity by modifying the depth of water and the forcing respectively. We use space-time resolved profilometry to reconstruct the deformed surface of water. When decreasing the water depth, we observe a drastic transition between weak turbulence at the weakest forcing and a solitonic regime at stronger forcing. We characterize the transition between both states by studying their Fourier Spectra. We also study the efficiency of energy transfer in the weak turbulence regime. We report a loss of efficiency of angular transfer as the dispersion of the wave is reduced until the system bifurcates into the solitonic regime. This project has recieved funding from the European Research Council (ERC, Grant Agreement No. 647018-WATU).
Korenev, V. L.
2007-01-01
Linearly polarized light tuned slightly below the optical transition of the negatively charged exciton (trion) in a single quantum dot causes the spontaneous nuclear spin polarization (self-polarization) at a level close to 100%. The effective magnetic field of spin-polarized nuclei brings the optical transition energy into resonance with photon energy. The resonantly enhanced Overhauser effect sustains the stability of the nuclear self-polarization even in the absence of spin polarization of...
International Nuclear Information System (INIS)
Bahr, Benjamin; Hellmann, Frank; Kaminski, Wojciech; Kisielowski, Marcin; Lewandowski, Jerzy
2011-01-01
The goal of this paper is to introduce a systematic approach to spin foams. We define operator spin foams, that is foams labelled by group representations and operators, as our main tool. A set of moves we define in the set of the operator spin foams (among other operations) allows us to split the faces and the edges of the foams. We assign to each operator spin foam a contracted operator, by using the contractions at the vertices and suitably adjusted face amplitudes. The emergence of the face amplitudes is the consequence of assuming the invariance of the contracted operator with respect to the moves. Next, we define spin foam models and consider the class of models assumed to be symmetric with respect to the moves we have introduced, and assuming their partition functions (state sums) are defined by the contracted operators. Briefly speaking, those operator spin foam models are invariant with respect to the cellular decomposition, and are sensitive only to the topology and colouring of the foam. Imposing an extra symmetry leads to a family we call natural operator spin foam models. This symmetry, combined with assumed invariance with respect to the edge splitting move, determines a complete characterization of a general natural model. It can be obtained by applying arbitrary (quantum) constraints on an arbitrary BF spin foam model. In particular, imposing suitable constraints on a spin(4) BF spin foam model is exactly the way we tend to view 4D quantum gravity, starting with the BC model and continuing with the Engle-Pereira-Rovelli-Livine (EPRL) or Freidel-Krasnov (FK) models. That makes our framework directly applicable to those models. Specifically, our operator spin foam framework can be translated into the language of spin foams and partition functions. Among our natural spin foam models there are the BF spin foam model, the BC model, and a model corresponding to the EPRL intertwiners. Our operator spin foam framework can also be used for more general spin
Dieny, B.; Sousa, R.; Prejbeanu, L.
2007-04-01
Conventional electronics has in the past ignored the spin on the electron, however things began to change in 1988 with the discovery of giant magnetoresistance in metallic thin film stacks which led to the development of a new research area, so called spin-electronics. In the last 10 years, spin-electronics has achieved a number of breakthroughs from the point of view of both basic science and application. Materials research has led to several major discoveries: very large tunnel magnetoresistance effects in tunnel junctions with crystalline barriers due to a new spin-filtering mechanism associated with the spin-dependent symmetry of the electron wave functions new magnetic tunnelling barriers leading to spin-dependent tunnelling barrier heights and acting as spin-filters magnetic semiconductors with increasingly high ordering temperature. New phenomena have been predicted and observed: the possibility of acting on the magnetization of a magnetic nanostructure with a spin-polarized current. This effect, due to a transfer of angular momentum between the spin polarized conduction electrons and the local magnetization, can be viewed as the reciprocal of giant or tunnel magnetoresistance. It can be used to switch the magnetization of a magnetic nanostructure or to generate steady magnetic excitations in the system. the possibility of generating and manipulating spin current without charge current by creating non-equilibrium local accumulation of spin up or spin down electrons. The range of applications of spin electronics materials and phenomena is expanding: the first devices based on giant magnetoresistance were the magnetoresistive read-heads for computer disk drives. These heads, introduced in 1998 with current-in plane spin-valves, have evolved towards low resistance tunnel magnetoresistice heads in 2005. Besides magnetic recording technology, these very sensitive magnetoresistive sensors are finding applications in other areas, in particular in biology. magnetic
Detection of single electron spin resonance in a double quantum dota)
Koppens, F. H. L.; Buizert, C.; Vink, I. T.; Nowack, K. C.; Meunier, T.; Kouwenhoven, L. P.; Vandersypen, L. M. K.
2007-04-01
Spin-dependent transport measurements through a double quantum dot are a valuable tool for detecting both the coherent evolution of the spin state of a single electron, as well as the hybridization of two-electron spin states. In this article, we discuss a model that describes the transport cycle in this regime, including the effects of an oscillating magnetic field (causing electron spin resonance) and the effective nuclear fields on the spin states in the two dots. We numerically calculate the current flow due to the induced spin flips via electron spin resonance, and we study the detector efficiency for a range of parameters. The experimental data are compared with the model and we find a reasonable agreement.
VEGF blockade inhibits angiogenesis and reepithelialization of endometrium.
Fan, Xiujun; Krieg, Sacha; Kuo, Calvin J; Wiegand, Stanley J; Rabinovitch, Marlene; Druzin, Maurice L; Brenner, Robert M; Giudice, Linda C; Nayak, Nihar R
2008-10-01
Despite extensive literature on vascular endothelial growth factor (VEGF) expression and regulation by steroid hormones, the lack of clear understanding of the mechanisms of angiogenesis in the endometrium is a major limitation for use of antiangiogenic therapy targeting endometrial vessels. In the current work, we used the rhesus macaque as a primate model and the decidualized mouse uterus as a murine model to examine angiogenesis during endometrial breakdown and regeneration. We found that blockade of VEGF action with VEGF Trap, a potent VEGF blocker, completely inhibited neovascularization during endometrial regeneration in both models but had no marked effect on preexisting or newly formed vessels, suggesting that VEGF is essential for neoangiogenesis but not survival of mature vessels in this vascular bed. Blockade of VEGF also blocked reepithelialization in both the postmenstrual endometrium and the mouse uterus after decidual breakdown, evidence that VEGF has pleiotropic effects in the endometrium. In vitro studies with a scratch wound assay showed that the migration of luminal epithelial cells during repair involved signaling through VEGF receptor 2-neuropilin 1 (VEGFR2-NP1) receptors on endometrial stromal cells. The leading front of tissue growth during endometrial repair was strongly hypoxic, and this hypoxia was the local stimulus for VEGF expression and angiogenesis in this tissue. In summary, we provide novel experimental data indicating that VEGF is essential for endometrial neoangiogenesis during postmenstrual/postpartum repair.
Immunomodulation by gadolinium chloride-induced Kupffer cell phagocytosis blockade
International Nuclear Information System (INIS)
Lazar, G.; Husztik, E.; Kiss, I.; Szakacs, J.; Olah, J.
1998-01-01
Gadolinium chloride (GdCl 3 ), a rare earth metal salt, depresses macrophage activity, and is commonly used to study the physiology of the reticuloendothelial system. In the present work, the effect of GdCl 3 -induced Kupffer cell blockade on the humoral immune response in mice to sheep red blood cells (SRBC) was investigated. Kupffer cell phagocytosis blockade was found to increase both the primary and secondary immune responses to SRBC. The primary immune response was significantly augmented in animals injected intravenously with GdCl 3 2, 3 or 4 days before injection of the cellular antigen, but GdCl 3 injected 7 days before the antigen did not modify the immune response. Increased secondary humoral immune responses were also observed. When GdCl 3 was injected 2 days before the second dose of antigen, the numbers of both IgM and IgG-producing plaque forming cells were augmented. GdCl 3 injected 2 days before the first dose of SRBC did not modify the humoral immune response. Earlier studies with 51 Cr-labelled foreign red blood cells suggested that the augmentation of the humoral immune response in GdCl 3 -pretreated mice is a consequence of the spillover of the antigen from the liver into the spleen and other extrahepatic reticuloendothelial organs. (orig.)
Localized CD47 blockade enhances immunotherapy for murine melanoma.
Ingram, Jessica R; Blomberg, Olga S; Sockolosky, Jonathan T; Ali, Lestat; Schmidt, Florian I; Pishesha, Novalia; Espinosa, Camilo; Dougan, Stephanie K; Garcia, K Christopher; Ploegh, Hidde L; Dougan, Michael
2017-09-19
CD47 is an antiphagocytic ligand broadly expressed on normal and malignant tissues that delivers an inhibitory signal through the receptor signal regulatory protein alpha (SIRPα). Inhibitors of the CD47-SIRPα interaction improve antitumor antibody responses by enhancing antibody-dependent cellular phagocytosis (ADCP) in xenograft models. Endogenous expression of CD47 on a variety of cell types, including erythrocytes, creates a formidable antigen sink that may limit the efficacy of CD47-targeting therapies. We generated a nanobody, A4, that blocks the CD47-SIRPα interaction. A4 synergizes with anti-PD-L1, but not anti-CTLA4, therapy in the syngeneic B16F10 melanoma model. Neither increased dosing nor half-life extension by fusion of A4 to IgG2a Fc (A4Fc) overcame the issue of an antigen sink or, in the case of A4Fc, systemic toxicity. Generation of a B16F10 cell line that secretes the A4 nanobody showed that an enhanced response to several immune therapies requires near-complete blockade of CD47 in the tumor microenvironment. Thus, strategies to localize CD47 blockade to tumors may be particularly valuable for immune therapy.
The effect of adhesion molecule blockade on pulmonary reperfusion injury.
Levine, Adrian J; Parkes, Karen; Rooney, Stephen J; Bonser, Robert S
2002-04-01
Selectins are the molecules involved in the initial adhesion of the activated neutrophil on pulmonary endothelium. We investigated the efficacy of selectin blockade in a selective (monoclonal antibody RMP-1) and nonselective (Fucoidin) manner in pulmonary reperfusion injury. Groups of six rat lungs were flushed with University of Wisconsin solution then stored at 4 degrees C for 4 hours. They then underwent sanguinous reperfusion for 30 minutes during which functional measures (gas exchange, pulmonary artery pressure, and airway pressure) of lung performance were made. After reperfusion we estimated their capillary filtration coefficient (Kfc units g/cm water/minute/g wet lung tissue) using a gravimetric technique. Four groups were studied: group I had no reperfusion, group II had 30 minutes of reperfusion, group III had infusion of 20 mg/kg Fucoidin before reperfusion, and group IV had infusion of 20 microg/mL RMP-1 before reperfusion. Reperfusion injury was found between groups I and II by an increase in capillary filtration coefficient (1.048 +/- 0.316 to 3.063 +/- 0.466, p Kfc than group II (0.967 +/- 0.134 and 1.205 +/- 0.164, respectively, p < 0.01). There was no significant functional difference between groups II, III, and IV. Reperfusion-induced hyperpermeability was ameliorated by selective (RMP-1) and nonselective (Fucoidin) selectin blockade.
Philosophical Intelligence: Letters, Print, and Experiment during Napoleon's Continental Blockade.
Watts, Iain P
2015-12-01
This essay investigates scientific exchanges between Britain and France from 1806 to 1814, at the height of the Napoleonic Wars. It argues for a picture of scientific communication that sees letters and printed texts not as separate media worlds, but as interconnected bearers of time-critical information within a single system of intelligence gathering and experimental practice. During this period, Napoleon Bonaparte's Continental System blockade severed most links between Britain and continental Europe, yet scientific communications continued--particularly on electrochemistry, a subject of fierce rivalry between Britain and France. The essay traces these exchanges using the archive of a key go-between, the English man of science Sir Charles Blagden. The first two sections look at Blagden's letter-writing operation, reconstructing how he harnessed connections with neutral American diplomats, merchants, and the State to get scientific intelligence between London and Paris. The third section, following Blagden's words from Britain to France to America, looks at how information in letters cross-fertilized with information in print. The final section considers how letters and print were used together to solve the difficult practical problem of replicating experiments across the blockade.
International Nuclear Information System (INIS)
Alvarez, Gonzalo A.; Levstein, Patricia R.; Pastawski, Horacio M.
2007-01-01
We have observed an environmentally induced quantum dynamical phase transition in the dynamics of a two-spin experimental swapping gate [G.A. Alvarez, E.P. Danieli, P.R. Levstein, H.M. Pastawski, J. Chem. Phys. 124 (2006) 194507]. There, the exchange of the coupled states vertical bar ↑,↓> and vertical bar ↓,↑> gives an oscillation with a Rabi frequency b/ℎ (the spin-spin coupling). The interaction, ℎ/τ SE with a spin-bath degrades the oscillation with a characteristic decoherence time. We showed that the swapping regime is restricted only to bτ SE > or approx. ℎ. However, beyond a critical interaction with the environment the swapping freezes and the system enters to a Quantum Zeno dynamical phase where relaxation decreases as coupling with the environment increases. Here, we solve the quantum dynamics of a two-spin system coupled to a spin-bath within a Liouville-von Neumann quantum master equation and we compare the results with our previous work within the Keldysh formalism. Then, we extend the model to a three interacting spin system where only one is coupled to the environment. Beyond a critical interaction the two spins not coupled to the environment oscillate with the bare Rabi frequency and relax more slowly. This effect is more pronounced when the anisotropy of the system-environment (SE) interaction goes from a purely XY to an Ising interaction form
Topologically Massive Higher Spin Gravity
Bagchi, A.; Lal, S.; Saha, A.; Sahoo, B.
2011-01-01
We look at the generalisation of topologically massive gravity (TMG) to higher spins, specifically spin-3. We find a special "chiral" point for the spin-three, analogous to the spin-two example, which actually coincides with the usual spin-two chiral point. But in contrast to usual TMG, there is the
Spin-orbit and spin-lattice coupling
International Nuclear Information System (INIS)
Bauer, Gerrit E.W.; Ziman, Timothy; Mori, Michiyasu
2014-01-01
We pursued theoretical research on the coupling of electron spins in the condensed matter to the lattice as mediated by the spin-orbit interaction with special focus on the spin and anomalous Hall effects. (author)
Simon, Mischa J.G.
2006-01-01
Epidural neural blockade results from processes after the administration of a local anaesthetic in the epidural space until the uptake in neural tissue. The pharmacokinetics, neural blockade and haemodynamics after epidural anaesthesia may be influenced by several factors, with age as the most
Spin Relaxation in GaAs: Importance of Electron-Electron Interactions
Directory of Open Access Journals (Sweden)
Gionni Marchetti
2014-04-01
Full Text Available We study spin relaxation in n-type bulk GaAs, due to the Dyakonov–Perel mechanism, using ensemble Monte Carlo methods. Our results confirm that spin relaxation time increases with the electronic density in the regime of moderate electronic concentrations and high temperature. We show that the electron-electron scattering in the non-degenerate regime significantly slows down spin relaxation. This result supports predictions by Glazov and Ivchenko. Most importantly, our findings highlight the importance of many-body interactions for spin dynamics: we show that only by properly taking into account electron-electron interactions within the simulations, results for the spin relaxation time—with respect to both electron density and temperature—will reach good quantitative agreement with corresponding experimental data. Our calculations contain no fitting parameters.
Charge and spin current oscillations in a tunnel junction induced by magnetic field pulses
Energy Technology Data Exchange (ETDEWEB)
Dartora, C.A., E-mail: cadartora@eletrica.ufpr.br [Electrical Engineering Department, Federal University of Parana (UFPR), C.P. 19011 Curitiba, 81.531-970 PR (Brazil); Nobrega, K.Z., E-mail: bzuza1@yahoo.com.br [Federal Institute of Education, Science and Technolgy of Maranhão (IFMA), Av. Marechal Castelo Branco, 789, São Luís, 65.076-091 MA (Brazil); Cabrera, G.G., E-mail: cabrera@ifi.unicamp.br [Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas (UNICAMP), C.P. 6165, Campinas 13.083-970 SP (Brazil)
2016-08-15
Usually, charge and spin transport properties in tunnel junctions are studied in the DC bias regime and/or in the adiabatic regime of time-varying magnetic fields. In this letter, the temporal dynamics of charge and spin currents in a tunnel junction induced by pulsed magnetic fields is considered. At low bias voltages, energy and momentum of the conduction electrons are nearly conserved in the tunneling process, leading to the description of the junction as a spin-1/2 fermionic system coupled to time-varying magnetic fields. Under the influence of pulsed magnetic fields, charge and spin current can flow across the tunnel junction, displaying oscillatory behavior, even in the absence of DC bias voltage. A type of spin capacitance function, in close analogy to electric capacitance, is predicted.
Visser, W.A.; Eerd, M.J. van; Seventer, R. van; Gielen, M.J.M.; Giele, J.L.P.; Scheffer, G.J.
2007-01-01
BACKGROUND: Continuous positive airway pressure (CPAP) increases the caudad spread of sensory blockade after low-thoracic epidural injection of lidocaine. We hypothesized that CPAP would increase cephalad spread of blockade after cervicothoracic epidural injection. METHODS: Twenty patients with an
Spin Current Noise of the Spin Seebeck Effect and Spin Pumping
Matsuo, M.; Ohnuma, Y.; Kato, T.; Maekawa, S.
2018-01-01
We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal-metal-(NM-)ferromagnet(FM) bilayer system. Starting with a simple ferromagnet-insulator-(FI-)NM interface model with both spin-conserving and non-spin-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for a yttrium-iron-garnet-platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the non-spin-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.
Spin and wavelength multiplexed nonlinear metasurface holography
Ye, Weimin; Zeuner, Franziska; Li, Xin; Reineke, Bernhard; He, Shan; Qiu, Cheng-Wei; Liu, Juan; Wang, Yongtian; Zhang, Shuang; Zentgraf, Thomas
2016-06-01
Metasurfaces, as the ultrathin version of metamaterials, have caught growing attention due to their superior capability in controlling the phase, amplitude and polarization states of light. Among various types of metasurfaces, geometric metasurface that encodes a geometric or Pancharatnam-Berry phase into the orientation angle of the constituent meta-atoms has shown great potential in controlling light in both linear and nonlinear optical regimes. The robust and dispersionless nature of the geometric phase simplifies the wave manipulation tremendously. Benefitting from the continuous phase control, metasurface holography has exhibited advantages over conventional depth controlled holography with discretized phase levels. Here we report on spin and wavelength multiplexed nonlinear metasurface holography, which allows construction of multiple target holographic images carried independently by the fundamental and harmonic generation waves of different spins. The nonlinear holograms provide independent, nondispersive and crosstalk-free post-selective channels for holographic multiplexing and multidimensional optical data storages, anti-counterfeiting, and optical encryption.
Relativistic spin precession in the double pulsar.
Breton, Rene P; Kaspi, Victoria M; Kramer, Michael; McLaughlin, Maura A; Lyutikov, Maxim; Ransom, Scott M; Stairs, Ingrid H; Ferdman, Robert D; Camilo, Fernando; Possenti, Andrea
2008-07-04
The double pulsar PSR J0737-3039A/B consists of two neutron stars in a highly relativistic orbit that displays a roughly 30-second eclipse when pulsar A passes behind pulsar B. Describing this eclipse of pulsar A as due to absorption occurring in the magnetosphere of pulsar B, we successfully used a simple geometric model to characterize the observed changing eclipse morphology and to measure the relativistic precession of pulsar B's spin axis around the total orbital angular momentum. This provides a test of general relativity and alternative theories of gravity in the strong-field regime. Our measured relativistic spin precession rate of 4.77 degrees (-0 degrees .65)(+0 degrees .66) per year (68% confidence level) is consistent with that predicted by general relativity within an uncertainty of 13%.
Magnetic monopole dynamics in spin ice.
Jaubert, L D C; Holdsworth, P C W
2011-04-27
One of the most remarkable examples of emergent quasi-particles is that of the 'fractionalization' of magnetic dipoles in the low energy configurations of materials known as 'spin ice' into free and unconfined magnetic monopoles interacting via Coulomb's 1/r law (Castelnovo et al 2008 Nature 451 42-5). Recent experiments have shown that a Coulomb gas of magnetic charges really does exist at low temperature in these materials and this discovery provides a new perspective on otherwise largely inaccessible phenomenology. In this paper, after a review of the different spin ice models, we present detailed results describing the diffusive dynamics of monopole particles starting both from the dipolar spin ice model and directly from a Coulomb gas within the grand canonical ensemble. The diffusive quasi-particle dynamics of real spin ice materials within the 'quantum tunnelling' regime is modelled with Metropolis dynamics, with the particles constrained to move along an underlying network of oriented paths, which are classical analogues of the Dirac strings connecting pairs of Dirac monopoles.
Quantum criticality among entangled spin chains
Blanc, N.; Trinh, J.; Dong, L.; Bai, X.; Aczel, A. A.; Mourigal, M.; Balents, L.; Siegrist, T.; Ramirez, A. P.
2018-03-01
An important challenge in magnetism is the unambiguous identification of a quantum spin liquid1,2, of potential importance for quantum computing. In such a material, the magnetic spins should be fluctuating in the quantum regime, instead of frozen in a classical long-range-ordered state. While this requirement dictates systems3,4 wherein classical order is suppressed by a frustrating lattice5, an ideal system would allow tuning of quantum fluctuations by an external parameter. Conventional three-dimensional antiferromagnets can be tuned through a quantum critical point—a region of highly fluctuating spins—by an applied magnetic field. Such systems suffer from a weak specific-heat peak at the quantum critical point, with little entropy available for quantum fluctuations6. Here we study a different type of antiferromagnet, comprised of weakly coupled antiferromagnetic spin-1/2 chains as realized in the molecular salt K2PbCu(NO2)6. Across the temperature-magnetic field boundary between three-dimensional order and the paramagnetic phase, the specific heat exhibits a large peak whose magnitude approaches a value suggestive of the spinon Sommerfeld coefficient of isolated quantum spin chains. These results demonstrate an alternative approach for producing quantum matter via a magnetic-field-induced shift of entropy from one-dimensional short-range order to a three-dimensional quantum critical point.
Effects of adductor-canal-blockade on pain and ambulation after total knee arthroplasty
DEFF Research Database (Denmark)
Jenstrup, M T; Jæger, P; Lund, J
2012-01-01
Total knee arthroplasty (TKA) is associated with intense post-operative pain. Besides providing optimal analgesia, reduction in side effects and enhanced mobilization are important in this elderly population. The adductor-canal-blockade is theoretically an almost pure sensory blockade. We hypothe...... hypothesized that the adductor-canal-blockade may reduce morphine consumption (primary endpoint), improve pain relief, enhance early ambulation ability, and reduce side effects (secondary endpoints) after TKA compared with placebo.......Total knee arthroplasty (TKA) is associated with intense post-operative pain. Besides providing optimal analgesia, reduction in side effects and enhanced mobilization are important in this elderly population. The adductor-canal-blockade is theoretically an almost pure sensory blockade. We...
Spin-valley splitting of electron beam in graphene
Directory of Open Access Journals (Sweden)
Yu Song
2016-11-01
Full Text Available We study spatial separation of the four degenerate spin-valley components of an electron beam in a EuO-induced and top-gated ferromagnetic/pristine/strained graphene structure. We show that, in a full resonant tunneling regime for all beam components, the formation of standing waves can lead sudden phase jumps ∼−π and giant lateral Goos-Hänchen shifts as large as the transverse beam width, while the interplay of the spin and valley imaginary wave vectors in the modulated regions can lead differences of resonant angles for the four spin-valley flavors, manifesting a spin-valley beam splitting effect. The splitting effect is found to be controllable by the gating and strain.
Spin-flip induced magnetoresistance in positionally disordered organic solids.
Harmon, N J; Flatté, M E
2012-05-04
A model for magnetoresistance in positionally disordered organic materials is presented and solved using percolation theory. The model describes the effects of spin dynamics on hopping transport by considering changes in the effective density of hopping sites, a key quantity determining the properties of percolative transport. Faster spin-flip transitions open up "spin-blocked" pathways to become viable conduction channels and hence produce magnetoresistance. Features of this percolative magnetoresistance can be found analytically in several regimes, and agree with previous measurements, including the sensitive dependence of the magnetic-field dependence of the magnetoresistance on the ratio of the carrier hopping time to the hyperfine-induced carrier spin precession time. Studies of magnetoresistance in known systems with controllable positional disorder would provide an additional stringent test of this theory.
Robust spin transfer torque in antiferromagnetic tunnel junctions
Saidaoui, Hamed Ben Mohamed
2017-04-18
We theoretically study the current-induced spin torque in antiferromagnetic tunnel junctions, composed of two semi-infinite antiferromagnetic layers separated by a tunnel barrier, in both clean and disordered regimes. We find that the torque enabling electrical manipulation of the Néel antiferromagnetic order parameter is out of plane, ∼n×p, while the torque competing with the antiferromagnetic exchange is in plane, ∼n×(p×n). Here, p and n are the Néel order parameter direction of the reference and free layers, respectively. Their bias dependence shows behavior similar to that in ferromagnetic tunnel junctions, the in-plane torque being mostly linear in bias, while the out-of-plane torque is quadratic. Most importantly, we find that the spin transfer torque in antiferromagnetic tunnel junctions is much more robust against disorder than that in antiferromagnetic metallic spin valves due to the tunneling nature of spin transport.
Effect of spin rotation coupling on spin transport
International Nuclear Information System (INIS)
Chowdhury, Debashree; Basu, B.
2013-01-01
We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k → ⋅p → perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k → ⋅p → framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied
Effect of spin rotation coupling on spin transport
Energy Technology Data Exchange (ETDEWEB)
Chowdhury, Debashree, E-mail: debashreephys@gmail.com; Basu, B., E-mail: sribbasu@gmail.com
2013-12-15
We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k{sup →}⋅p{sup →} perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k{sup →}⋅p{sup →} framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied.
Spin temperature concept verified by optical magnetometry of nuclear spins
Vladimirova, M.; Cronenberger, S.; Scalbert, D.; Ryzhov, I. I.; Zapasskii, V. S.; Kozlov, G. G.; Lemaître, A.; Kavokin, K. V.
2018-01-01
We develop a method of nonperturbative optical control over adiabatic remagnetization of the nuclear spin system and apply it to verify the spin temperature concept in GaAs microcavities. The nuclear spin system is shown to exactly follow the predictions of the spin temperature theory, despite the quadrupole interaction that was earlier reported to disrupt nuclear spin thermalization. These findings open a way for the deep cooling of nuclear spins in semiconductor structures, with the prospect of realizing nuclear spin-ordered states for high-fidelity spin-photon interfaces.
International Nuclear Information System (INIS)
Lee, J. Y.; Guan, X. W.; Batchelor, M. T.; Lee, C.
2009-01-01
We investigate magnetism and quantum phase transitions in a one-dimensional system of integrable spin-1 bosons with strongly repulsive density-density interaction and antiferromagnetic spin-exchange interaction via the thermodynamic Bethe ansatz method. At zero temperature, the system exhibits three quantum phases: (i) a singlet phase of boson pairs when the external magnetic field H is less than the lower critical field H c1 ; (ii) a ferromagnetic phase of atoms in the hyperfine state |F=1, m F =1> when the external magnetic field exceeds the upper critical field H c2 ; and (iii) a mixed phase of singlet pairs and unpaired atoms in the intermediate region H c1 c2 . At finite temperatures, the spin fluctuations affect the thermodynamics of the model through coupling the spin bound states to the dressed energy for the unpaired m F =1 bosons. However, such spin dynamics is suppressed by a sufficiently strong external field at low temperatures. Thus the singlet pairs and unpaired bosons may form a two-component Luttinger liquid in the strong coupling regime.
Spin-orbit torque in two-dimensional antiferromagnetic topological insulators
Ghosh, Sumit; Manchon, Aurelien
2017-01-01
We investigate spin transport in two-dimensional ferromagnetic (FTI) and antiferromagnetic (AFTI) topological insulators. In the presence of an in-plane magnetization AFTI supports zero energy modes, which enables topologically protected edge conduction at low energy. We address the nature of current-driven spin torque in these structures and study the impact of spin-independent disorder. Interestingly, upon strong disorder the spin torque develops an antidamping component (i.e., even upon magnetization reversal) along the edges, which could enable current-driven manipulation of the antiferromagnetic order parameter. This antidamping torque decreases when increasing the system size and when the system enters the trivial insulator regime.
Exact ground and excited states of an antiferromagnetic quantum spin model
International Nuclear Information System (INIS)
Bose, I.
1989-08-01
A quasi-one-dimensional spin model which consists of a chain of octahedra of spins has been suggested for which a certain parameter regime of the Hamiltonian, the ground state, can be written down exactly. The ground state is highly degenerate and can be other than a singlet. Also, several excited states can be constructed exactly. The ground state is a local RVB state for which resonance is confined to rings of spins. Some exact numerical results for an octahedron of spins have also been reported. (author). 16 refs, 2 figs, 1 tab
Spin-orbit torque in two-dimensional antiferromagnetic topological insulators
Ghosh, Sumit
2017-01-24
We investigate spin transport in two-dimensional ferromagnetic (FTI) and antiferromagnetic (AFTI) topological insulators. In the presence of an in-plane magnetization AFTI supports zero energy modes, which enables topologically protected edge conduction at low energy. We address the nature of current-driven spin torque in these structures and study the impact of spin-independent disorder. Interestingly, upon strong disorder the spin torque develops an antidamping component (i.e., even upon magnetization reversal) along the edges, which could enable current-driven manipulation of the antiferromagnetic order parameter. This antidamping torque decreases when increasing the system size and when the system enters the trivial insulator regime.
Spin labels. Applications in biology
International Nuclear Information System (INIS)
Frangopol, T.P.; Frangopol, M.; Ionescu, S.M.; Pop, I.V.; Benga, G.
1980-11-01
The main applications of spin labels in the study of biomembranes, enzymes, nucleic acids, in pharmacology, spin immunoassay are reviewed along with the fundamentals of the spin label method. 137 references. (author)
Spin Switching via Quantum Dot Spin Valves
Gergs, N. M.; Bender, S. A.; Duine, R. A.; Schuricht, D.
2018-01-01
We develop a theory for spin transport and magnetization dynamics in a quantum dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot. Our theory is able to take into account effects of strong correlations. We demonstrate that, as a result of these strong correlations, the dot gate voltage enables control over the current-induced torques on the magnets and, in particular, enables voltage-controlled magnetic switching. The electrical resistance of the structure can be used to read out the magnetic state. Our model may be realized by a number of experimental systems, including magnetic scanning-tunneling microscope tips and artificial quantum dot systems.
Renin-angiotensin system blockade therapy after transcatheter aortic valve implantation.
Ochiai, Tomoki; Saito, Shigeru; Yamanaka, Futoshi; Shishido, Koki; Tanaka, Yutaka; Yamabe, Tsuyoshi; Shirai, Shinichi; Tada, Norio; Araki, Motoharu; Naganuma, Toru; Watanabe, Yusuke; Yamamoto, Masanori; Hayashida, Kentaro
2018-04-01
The persistence of left ventricular (LV) hypertrophy is associated with poor clinical outcomes after transcatheter aortic valve implantation (TAVI) for aortic stenosis. However, the optimal medical therapy after TAVI remains unknown. We investigated the effect of renin-angiotensin system (RAS) blockade therapy on LV hypertrophy and mortality in patients undergoing TAVI. Between October 2013 and April 2016, 1215 patients undergoing TAVI were prospectively enrolled in the Optimized CathEter vAlvular iNtervention (OCEAN)-TAVI registry. This cohort was stratified according to the postoperative usage of RAS blockade therapy with angiotensin-converting enzyme (ACE) inhibitors or angiotensin-receptor blockers (ARBs). Patients with at least two prescriptions dispensed 180 days apart after TAVI and at least a 6-month follow-up constituted the RAS blockade group (n=371), while those not prescribed any ACE inhibitors or ARBs after TAVI were included in the no RAS blockade group (n=189). At 6 months postoperatively, the RAS blockade group had significantly greater LV mass index regression than the no RAS blockade group (-9±24% vs -2±25%, p=0.024). Kaplan-Meier analysis revealed a significantly lower cumulative 2-year mortality in the RAS blockade than that in the no RAS blockade group (7.5% vs 12.5%; log-rank test, p=0.031). After adjusting for confounding factors, RAS blockade therapy was associated with significantly lower all-cause mortality (HR, 0.45; 95% CI 0.22 to 0.91; p=0.025). Postoperative RAS blockade therapy is associated with greater LV mass index regression and reduced all-cause mortality. These data need to be confirmed by a prospective randomised controlled outcome trial. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.
Hawkes, N
1999-01-01
RAL is fostering commerical exploitation of its research and facilities in two main ways : spin-out companies exploit work done at the lab, spin-in companies work on site taking advantage of the facilities and the expertise available (1/2 page).
International Nuclear Information System (INIS)
Haxton, W.C.
1988-01-01
I discuss a number of the themes of the Symmetries and Spin session of the 8th International Symposium on High Energy Spin Physics: parity nonconservation, CP/T nonconservation, and tests of charge symmetry and charge independence. 28 refs., 1 fig
International Nuclear Information System (INIS)
Peskin, M.E.
1994-01-01
When the strong interactions were a mystery, spin seemed to be just a complication on top of an already puzzling set of phenomena. But now that particle physicists have understood the strong, weak, and electromagnetic interactions, to be gauge theories, with matter built of quarks and leptons, it is recognized that the special properties of spin 1/2 and spin 1 particles have taken central role in the understanding of Nature. The lectures in this summer school will be devoted to the use of spin in unravelling detailed questions about the fundamental interactions. Thus, why not begin by posing a deeper question: Why is there spin? More precisely, why do the basic pointlike constituents of Nature carry intrinsic nonzero quanta of angular momentum? Though the authos has found no definite answer to this question, the pursuit of an answer has led through a wonderful tangle of speculations on the deep structure of Nature. Is spin constructed or is it fundamental? Is it the requirement of symmetry? In the furthest flights taken, it seems that space-time itself is too restrictive a notion, and that this must be generalized in order to gain a full appreciation of spin. In any case, there is no doubt that spin must play a central role in unlocking the mysteries of fundamental physics
Classical spins in superconductors
Energy Technology Data Exchange (ETDEWEB)
Shiba, H [Tokyo Univ.; Maki, K
1968-08-01
It is shown that there exists a localized excited state in the energy gap in a superconductor with a classical spin. At finite concentration localized excited states around classical spins form an impurity band. The process of growth of the impurity band and its effects on observable quantities are investigated.
Energy Technology Data Exchange (ETDEWEB)
Peskin, M.E. [Stanford Univ., CA (United States)
1994-12-01
When the strong interactions were a mystery, spin seemed to be just a complication on top of an already puzzling set of phenomena. But now that particle physicists have understood the strong, weak, and electromagnetic interactions, to be gauge theories, with matter built of quarks and leptons, it is recognized that the special properties of spin 1/2 and spin 1 particles have taken central role in the understanding of Nature. The lectures in this summer school will be devoted to the use of spin in unravelling detailed questions about the fundamental interactions. Thus, why not begin by posing a deeper question: Why is there spin? More precisely, why do the basic pointlike constituents of Nature carry intrinsic nonzero quanta of angular momentum? Though the authos has found no definite answer to this question, the pursuit of an answer has led through a wonderful tangle of speculations on the deep structure of Nature. Is spin constructed or is it fundamental? Is it the requirement of symmetry? In the furthest flights taken, it seems that space-time itself is too restrictive a notion, and that this must be generalized in order to gain a full appreciation of spin. In any case, there is no doubt that spin must play a central role in unlocking the mysteries of fundamental physics.
International Nuclear Information System (INIS)
Masaike, Akira
1993-01-01
Despite playing a major role in today's Standard Model, spin - the intrinsic angular momentum carried by particles - is sometimes dismissed as an inessential complication. However several major spin questions with important implications for the Standard Model remain unanswered, and recent results and new technological developments made the 10th International Symposium on High Energy Spin Physics, held in Nagoya, Japan, in November, highly topical. The symposium covered a wide range of physics, reflecting the diversity of spin effects, however four main themes were - the spin content of the nucleon, tests of symmetries and physics beyond standard models, intermediate energy physics, and spin technologies. Opening the meeting, T. Kinoshita reviewed the status of measurements of the anomalous magnetic moment (g-2) of the electron and the muon. The forthcoming experiment at Brookhaven (September 1991, page 23) will probe beyond the energy ranges open to existing electronpositron colliders. For example muon substructure will be opened up to 5 TeV and Ws to 2 TeV. R.L. Jaffe classified quark-parton distributions in terms of their spin dependence, pointing out their leftright attributes, and emphasized the importance of measuring transverse spin distributions through lepton pair production
Energy Technology Data Exchange (ETDEWEB)
Angelini, S.; Theofanous, T.G.; Yuen, W.W. [California Univ., Santa Barbara, CA (United States). Center for Risk Studies and Safety
1998-01-01
The conditions of the MAGICO-2000 experiment are extended to more broadly investigate the regimes of premixing, and the corresponding internal structures of mixing zones. With the help of the data and numerical simulations using the computer code PM-ALPHA, we can distinguish extremes of behavior dominated by inertia and thermal effects - we name these the inertia and thermal regimes, respectively. This is an important distinction that should guide future experiments aimed at code verification in this area. Interesting intermediate behaviors are also delineated and discussed. (author)
Directory of Open Access Journals (Sweden)
Jin Lan (兰金
2015-12-01
Full Text Available A diode, a device allowing unidirectional signal transmission, is a fundamental element of logic structures, and it lies at the heart of modern information systems. The spin wave or magnon, representing a collective quasiparticle excitation of the magnetic order in magnetic materials, is a promising candidate for an information carrier for the next-generation energy-saving technologies. Here, we propose a scalable and reprogrammable pure spin-wave logic hardware architecture using domain walls and surface anisotropy stripes as waveguides on a single magnetic wafer. We demonstrate theoretically the design principle of the simplest logic component, a spin-wave diode, utilizing the chiral bound states in a magnetic domain wall with a Dzyaloshinskii-Moriya interaction, and confirm its performance through micromagnetic simulations. Our findings open a new vista for realizing different types of pure spin-wave logic components and finally achieving an energy-efficient and hardware-reprogrammable spin-wave computer.
International Nuclear Information System (INIS)
Lowenstein, D.I.
1985-01-01
Spin Physics at the Alternating Gradient Synchrotron (AGS) of Brookhaven National Laboratory is the most recent of new capabilities being explored at this facility. During the summer of 1984 the AGS accelerated beams of polarized protons to 16.5 GeV/c at 40% polarization to two experiments (E782, E785). These experiments; single spin asymmetry in inclusive polarized pp interactions; and spin-spin effects in polarized pp elastic scattering, operated at the highest polarized proton energy ever achieved by any accelerator in the world. These experiments are reviewed after the complementary spin physics program with unpolarized protons, and the future possibilities with a booster injector for the AGS and the secondary benefits of a Relativisitic Heavy Ion Collider (RHIC), are placed within the context of the present physics program
Superconductivity and spin fluctuations
International Nuclear Information System (INIS)
Scalapino, D.J.
1999-01-01
The organizers of the Memorial Session for Herman Rietschel asked that the author review some of the history of the interplay of superconductivity and spin fluctuations. Initially, Berk and Schrieffer showed how paramagnon spin fluctuations could suppress superconductivity in nearly-ferromagnetic materials. Following this, Rietschel and various co-workers wrote a number of papers in which they investigated the role of spin fluctuations in reducing the Tc of various electron-phonon superconductors. Paramagnon spin fluctuations are also believed to provide the p-wave pairing mechanism responsible for the superfluid phases of 3 He. More recently, antiferromagnetic spin fluctuations have been proposed as the mechanism for d-wave pairing in the heavy-fermion superconductors and in some organic materials as well as possibly the high-Tc cuprates. Here the author will review some of this early history and discuss some of the things he has learned more recently from numerical simulations
Spin Hall and spin swapping torques in diffusive ferromagnets
Pauyac, C. O.
2017-12-08
A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precessional effects displays a complex spatial dependence that can be exploited to generate torques and nucleate/propagate domain walls in centrosymmetric geometries without use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.
Spin Hall and spin swapping torques in diffusive ferromagnets
Pauyac, C. O.; Chshiev, M.; Manchon, Aurelien; Nikolaev, S. A.
2017-01-01
A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precessional effects displays a complex spatial dependence that can be exploited to generate torques and nucleate/propagate domain walls in centrosymmetric geometries without use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.
Coulomb Blockade in a Two-Dimensional Conductive Polymer Monolayer.
Akai-Kasaya, M; Okuaki, Y; Nagano, S; Mitani, T; Kuwahara, Y
2015-11-06
Electronic transport was investigated in poly(3-hexylthiophene-2,5-diyl) monolayers. At low temperatures, nonlinear behavior was observed in the current-voltage characteristics, and a nonzero threshold voltage appeared that increased with decreasing temperature. The current-voltage characteristics could be best fitted using a power law. These results suggest that the nonlinear conductivity can be explained using a Coulomb blockade (CB) mechanism. A model is proposed in which an isotropic extended charge state exists, as predicted by quantum calculations, and percolative charge transport occurs within an array of small conductive islands. Using quantitatively evaluated capacitance values for the islands, this model was found to be capable of explaining the observed experimental data. It is, therefore, suggested that percolative charge transport based on the CB effect is a significant factor giving rise to nonlinear conductivity in organic materials.
Investigation of uncertainty components in Coulomb blockade thermometry
International Nuclear Information System (INIS)
Hahtela, O. M.; Heinonen, M.; Manninen, A.; Meschke, M.; Savin, A.; Pekola, J. P.; Gunnarsson, D.; Prunnila, M.; Penttilä, J. S.; Roschier, L.
2013-01-01
Coulomb blockade thermometry (CBT) has proven to be a feasible method for primary thermometry in every day laboratory use at cryogenic temperatures from ca. 10 mK to a few tens of kelvins. The operation of CBT is based on single electron charging effects in normal metal tunnel junctions. In this paper, we discuss the typical error sources and uncertainty components that limit the present absolute accuracy of the CBT measurements to the level of about 1 % in the optimum temperature range. Identifying the influence of different uncertainty sources is a good starting point for improving the measurement accuracy to the level that would allow the CBT to be more widely used in high-precision low temperature metrological applications and for realizing thermodynamic temperature in accordance to the upcoming new definition of kelvin
Effect of on-chip filter on Coulomb blockade thermometer
International Nuclear Information System (INIS)
Roschier, L; Penttilä, J S; Gunnarsson, D; Prunnila, M; Meschke, M; Savin, A
2012-01-01
Coulomb Blockade Thermometer (CBT) is a primary thermometer based on electric conductance of normal tunnel junction arrays. One limitation for CBT use at the lowest temperatures has been due to environmental noise heating. To improve on this limitation, we have done measurements on CBT sensors fabricated with different on-chip filtering structures in a dilution refrigerator with a base temperature of 10 mK. The CBT sensors were produced with a wafer scale tunnel junction process. We present how the different on-chip filtering schemes affect the limiting saturation temperatures and show that CBT sensors with proper on-chip filtering work at temperatures below 20 mK and are tolerant to noisy environment.
Investigation of uncertainty components in Coulomb blockade thermometry
Energy Technology Data Exchange (ETDEWEB)
Hahtela, O. M.; Heinonen, M.; Manninen, A. [MIKES Centre for Metrology and Accreditation, Tekniikantie 1, 02150 Espoo (Finland); Meschke, M.; Savin, A.; Pekola, J. P. [Low Temperature Laboratory, Aalto University, Tietotie 3, 02150 Espoo (Finland); Gunnarsson, D.; Prunnila, M. [VTT Technical Research Centre of Finland, Tietotie 3, 02150 Espoo (Finland); Penttilä, J. S.; Roschier, L. [Aivon Oy, Tietotie 3, 02150 Espoo (Finland)
2013-09-11
Coulomb blockade thermometry (CBT) has proven to be a feasible method for primary thermometry in every day laboratory use at cryogenic temperatures from ca. 10 mK to a few tens of kelvins. The operation of CBT is based on single electron charging effects in normal metal tunnel junctions. In this paper, we discuss the typical error sources and uncertainty components that limit the present absolute accuracy of the CBT measurements to the level of about 1 % in the optimum temperature range. Identifying the influence of different uncertainty sources is a good starting point for improving the measurement accuracy to the level that would allow the CBT to be more widely used in high-precision low temperature metrological applications and for realizing thermodynamic temperature in accordance to the upcoming new definition of kelvin.
Neuromuscular blockade for improvement of surgical conditions during laparotomy
DEFF Research Database (Denmark)
Madsen, Matias Vested; Scheppan, Susanne; Kissmeyer, Peter
2015-01-01
INTRODUCTION: During laparotomy, surgeons frequently experience difficult surgical conditions if the patient's abdominal wall or diaphragm is tense. This issue is particularly pertinent while closing the fascia and placing the intestines into the abdominal cavity. Establishment of a deep neuromus......INTRODUCTION: During laparotomy, surgeons frequently experience difficult surgical conditions if the patient's abdominal wall or diaphragm is tense. This issue is particularly pertinent while closing the fascia and placing the intestines into the abdominal cavity. Establishment of a deep...... neuromuscular blockade (NMB), defined as a post-tetanic-count (PTC) of 0-1, paralyses the abdominal wall muscles and the diaphragm. We hypothesised that deep NMB (PTC 0-1) would improve surgical conditions during upper laparotomy as compared to standard NMB with bolus administration. METHODS...
Ultra-high-ohmic microstripline resistors for Coulomb blockade devices
International Nuclear Information System (INIS)
Lotkhov, Sergey V
2013-01-01
In this paper, we report on the fabrication and low-temperature characterization of ultra-high-ohmic microstripline resistors made of a thin film of weakly oxidized titanium. Nearly linear voltage–current characteristics were measured at temperatures down to T ∼ 20 mK for films with sheet resistivities as high as ∼7 kΩ, i.e. about an order of magnitude higher than our previous findings for weakly oxidized Cr. Our analysis indicates that such an improvement can help to create an advantageous high-impedance environment for different Coulomb blockade devices. Further properties of the Ti film addressed in this work show the promise of low-noise behavior of the resistors when applied in different realizations of the quantum standard of current. (paper)
Femoral Nerve Injury Following a Lumbar Plexus Blockade
Directory of Open Access Journals (Sweden)
İrfan Güngör
2014-06-01
Full Text Available Background: Lumbar plexus blockade (LPB combined with sciatic nerve block (SNB is frequently used for lower extremity surgery. Perioperative nerve injury is a rarely encountered complication of peripheral nerve blocks (PNB. Case Report: Here we report a 44-year-old male patient who developed a partial femoral nerve injury (FNI following a LPB which was performed before the surgery of a patellar fracture. The clinical and electroneuromyographic findings of the patient were recovered almost completely within the following six months. Conclusion: The presented case demonstrated a FNI despite the absence of any pain or paresthesia sensation, with the disappearance of motor response under 0.3 mA of neurostimulation in the experienced hands.
PD-1 Blockade Expands Intratumoral Memory T Cells
DEFF Research Database (Denmark)
Ribas, Antoni; Shin, Daniel Sanghoon; Zaretsky, Jesse
2016-01-01
by multicolor flow cytometry using two computational approaches to resolve the leukocyte phenotypes at the single-cell level. There was a statistically significant increase in the frequency of T cells in patients who responded to therapy. The frequency of intratumoral B cells and monocytic myeloid......-derived suppressor cells significantly increased in patients' biopsies taken on treatment. The percentage of cells with a regulatory T-cell phenotype, monocytes, and natural killer cells did not change while on PD-1 blockade therapy. CD8+ memory T cells were the most prominent phenotype that expanded intratumorally...... on therapy. However, the frequency of CD4+ effector memory T cells significantly decreased on treatment, whereas CD4+ effector T cells significantly increased in nonresponding tumors on therapy. In peripheral blood, an unusual population of blood cells expressing CD56 was detected in two patients...
Treatment of resting tremor by beta-adrenergic blockade.
Foster, N L; Newman, R P; LeWitt, P A; Gillespie, M M; Chase, T N
1984-10-01
The effect of nadolol, a peripherally acting beta-adrenergic blocker, on resting tremor was examined in eight patients with idiopathic Parkinson's disease. With the use of a double-blind, placebo-controlled study of crossover design, patients received 80 to 320 mg of nadolol for 6 weeks while continuing their previous treatment regimen. Accelerometer readings showed a progressive reduction in tremor amplitude, but no change in tremor frequency, with increasing nadolol dosage. Maximum benefit was achieved at 240 mg, when resting tremor improved 50% (p less than 0.01). Physician ratings confirmed these findings. The results suggest that response to beta-adrenergic blockade may not be limited to postural or intention tremor and that such agents may not reliably differentiate between the tremor of Parkinson's disease and essential tremor.
Long Spin-Relaxation Times in a Transition-Metal Atom in Direct Contact to a Metal Substrate.
Hermenau, Jan; Ternes, Markus; Steinbrecher, Manuel; Wiesendanger, Roland; Wiebe, Jens
2018-03-14
Long spin-relaxation times are a prerequisite for the use of spins in data storage or nanospintronics technologies. An atomic-scale solid-state realization of such a system is the spin of a transition-metal atom adsorbed on a suitable substrate. For the case of a metallic substrate, which enables the direct addressing of the spin by conduction electrons, the experimentally measured lifetimes reported to date are on the order of only hundreds of femtoseconds. Here, we show that the spin states of iron atoms adsorbed directly on a conductive platinum substrate have a surprisingly long spin-relaxation time in the nanosecond regime, which is comparable to that of a transition metal atom decoupled from the substrate electrons by a thin decoupling layer. The combination of long spin-relaxation times and strong coupling to conduction electrons implies the possibility to use flexible coupling schemes to process the spin information.
Thermoelectric Phenomena in a Quantum Dot Attached to Ferromagnetic Leads in Kondo Regime
International Nuclear Information System (INIS)
Chen Qiao; Zhao Li-Li
2014-01-01
We have studied the thermoelectric properties through ferromagnetic leads-QD coupled system (F-QD-F) in the Kondo regime by nonequilibrium Green's functions method. The spin-flip effect induced by ferromagnetic leads and Kondo effect influence the thermoelectric properties significantly. The peak-valley structure emerges at the low temperature due to Kondo resonance, and the peak-valley structure also relies on the polarization angle θ, the spin-dependent linewidth function Γ γσ and the energy level of QD ∈ d . Novel resonant peak also emerges in the curve of ZT c versus polarization angle θ. The Kondo effect suppresses the figure of merit ZT c and the spin-dependent figure of merit ZT s . In addition, the spin-dependent figure of merit ZT s is relate with the gap between Γ γ↑ and Γ γ↓ . (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Tunable spin waves in diluted magnetic semiconductor nanoribbon
Lyu, Pin; Zhang, Jun-Yi
2018-01-01
The spin wave excitation spectrum in diluted magnetic semiconductor (DMS) nanoribbons was calculated by taking account of the quantum confinement effect of carriers and spin waves. By introducing the boundary condition for the spin waves, we derived the spin wave dispersion using the path-integral formulation and Green's function method. It was shown that the spin wave excitation spectrum is discrete due to the confinement effect and strongly dependent on the carrier density, the magnetic ion density, and the width of the nanoribbon. When the width of the nanoribbon is beyond the typical nanoscales, the size effect on the excitation energies of the spin waves disappears in our calculation, which is in qualitative agreement with no obvious size effect observed in the as-made nanodevices of (Ga,Mn)As in this size regime. Our results provide a potential way to control the spin waves in the DMS nanoribbon not only by the carrier density and the magnetic ion density but also by the nanostructure geometry.
Land degradation and property regimes
Paul M. Beaumont; Robert T. Walker
1996-01-01
This paper addresses the relationship between property regimes and land degradation outcomes, in the context of peasant agriculture. We consider explicitly whether private property provides for superior soil resource conservation, as compared to common property and open access. To assess this we implement optimization algorithms on a supercomputer to address resource...
Regime identification in ASDEX Upgrade
International Nuclear Information System (INIS)
Giannone, L; Sips, A C C; Kardaun, O; Spreitler, F; Suttrop, W
2004-01-01
The ability to recognize the transition from the L-mode to the H-mode or from the H-mode to the improved H-mode reliably from a conveniently small number of measurements in real time is of increasing importance for machine control. Discriminant analysis has been applied to regime identification of plasma discharges in the ASDEX Upgrade tokamak. An observation consists of a set of plasma parameters averaged over a time slice in a discharge. The data set consists of all observations over different discharges and time slices. Discriminant analysis yields coefficients allowing the classification of a new observation. The results of a frequentist and a formal Bayesian approach to discriminant analysis are compared. With five plasma variables, a failure rate of 1.3% for predicting the L-mode and the H-mode confinement regime was achieved. With five plasma variables, a failure rate of 5.3% for predicting the H-mode and the improved H-mode confinement regime was achieved. The coefficients derived by discriminant analysis have been applied subsequently to discharges to illustrate the operation of regime identification in a real time control system
Monetary regimes in open economies
Korpos, A.
2006-01-01
This thesis presents a two-country open economy framework for the analysis of strategic interactions among monetary authorities and wage bargaining institutions. From this perspective, the thesis investigates the economic consequences of replacing flexible and fixed exchange rate regimes with a
Electron spin relaxation in a transition-metal dichalcogenide quantum dot
Pearce, Alexander J.; Burkard, Guido
2017-06-01
We study the relaxation of a single electron spin in a circular quantum dot in a transition-metal dichalcogenide monolayer defined by electrostatic gating. Transition-metal dichalcogenides provide an interesting and promising arena for quantum dot nano-structures due to the combination of a band gap, spin-valley physics and strong spin-orbit coupling. First we will discuss which bound state solutions in different B-field regimes can be used as the basis for qubits states. We find that at low B-fields combined spin-valley Kramers qubits to be suitable, while at large magnetic fields pure spin or valley qubits can be envisioned. Then we present a discussion of the relaxation of a single electron spin mediated by electron-phonon interaction via various different relaxation channels. In the low B-field regime we consider the spin-valley Kramers qubits and include impurity mediated valley mixing which will arise in disordered quantum dots. Rashba spin-orbit admixture mechanisms allow for relaxation by in-plane phonons either via the deformation potential or by piezoelectric coupling, additionally direct spin-phonon mechanisms involving out-of-plane phonons give rise to relaxation. We find that the relaxation rates scale as \\propto B 6 for both in-plane phonons coupling via deformation potential and the piezoelectric effect, while relaxation due to the direct spin-phonon coupling scales independant to B-field to lowest order but depends strongly on device mechanical tension. We will also discuss the relaxation mechanisms for pure spin or valley qubits formed in the large B-field regime.
Heat Transport in Gapped Spin-Chain Systems
International Nuclear Information System (INIS)
Shimshoni, E.
2006-01-01
Full Text: We study the contribution of magnetic excitations to the heat transport in gapped spin-chain systems. These systems are characterized by a substantially enhanced heat conductivity, which can be traced back to the existence of weakly violated conservation laws. We focus particularly on the behavior of clean two-leg spin ladder compounds, where one-dimensional exotic spin excitations are coupled to three-dimensional phonons. We show that the contributions of the two types of heat carriers can not be easily disentangled. Depending on the ratios of spin gaps and the Debye energy, the heat conductivity can be either exponentially increasing or exponentially decreasing as a function of temperature (T). In addition, the magnetic contribution to the total heat conductivity may be either positive or negative. We discuss its T-dependence in various possible regimes, and note that in most regimes it is dominated by spin-phonon drag: the two types of heat carriers have almost the
Ting, David Z.
2007-01-01
The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.
Nuclear spins in nanostructures
International Nuclear Information System (INIS)
Coish, W.A.; Baugh, J.
2009-01-01
We review recent theoretical and experimental advances toward understanding the effects of nuclear spins in confined nanostructures. These systems, which include quantum dots, defect centers, and molecular magnets, are particularly interesting for their importance in quantum information processing devices, which aim to coherently manipulate single electron spins with high precision. On one hand, interactions between confined electron spins and a nuclear-spin environment provide a decoherence source for the electron, and on the other, a strong effective magnetic field that can be used to execute local coherent rotations. A great deal of effort has been directed toward understanding the details of the relevant decoherence processes and to find new methods to manipulate the coupled electron-nuclear system. A sequence of spectacular new results have provided understanding of spin-bath decoherence, nuclear spin diffusion, and preparation of the nuclear state through dynamic polarization and more general manipulation of the nuclear-spin density matrix through ''state narrowing.'' These results demonstrate the richness of this physical system and promise many new mysteries for the future. (Abstract Copyright [2009], Wiley Periodicals, Inc.)
Kar, Uddipta; Panda, J; Nath, T K
2018-06-01
The low temperature spin accumulation in p-Si using Co2CrAl/SiO2 tunnel junction has been investigated in detail. The heterojunction has been fabricated using electron beam evaporation (EBE) technique. The 3-terminal contacts in Hanle geometry has been made for spin transport measurements. The electrical transport properties have been investigated at different isothermal conditions in the temperature range of 10-300 K. The current-voltage characteristics of the junction shows excellent rectifying magnetic diode like behaviour in lower temperature range (below 200 K). At higher temperature, the junction shows nonlinear behaviour without rectifying characteristics. We have observed spin accumulation signal in p-Si semiconductor using SiO2/Co2CrAl tunnel junction in the low temperature regime (30-100 K). Hence the highly spin polarized Full Heusler alloys compounds, like Co2CrAl etc., are very attractive and can act as efficient tunnel device for spin injection in the area of spintronics devices in near future. The estimated spin life time is τ = 54 pS and spin diffusion length inside p-Si is LSD = 289 nm at 30 K for this heterostructure.
Current-induced damping of nanosized quantum moments in the presence of spin-orbit interaction
Mahfouzi, Farzad; Kioussis, Nicholas
2017-05-01
Motivated by the need to understand current-induced magnetization dynamics at the nanoscale, we have developed a formalism, within the framework of Keldysh Green function approach, to study the current-induced dynamics of a ferromagnetic (FM) nanoisland overlayer on a spin-orbit-coupling (SOC) Rashba plane. In contrast to the commonly employed classical micromagnetic LLG simulations the magnetic moments of the FM are treated quantum mechanically. We obtain the density matrix of the whole system consisting of conduction electrons entangled with the local magnetic moments and calculate the effective damping rate of the FM. We investigate two opposite limiting regimes of FM dynamics: (1) The precessional regime where the magnetic anisotropy energy (MAE) and precessional frequency are smaller than the exchange interactions and (2) the local spin-flip regime where the MAE and precessional frequency are comparable to the exchange interactions. In the former case, we show that due to the finite size of the FM domain, the "Gilbert damping" does not diverge in the ballistic electron transport regime, in sharp contrast to Kambersky's breathing Fermi surface theory for damping in metallic FMs. In the latter case, we show that above a critical bias the excited conduction electrons can switch the local spin moments resulting in demagnetization and reversal of the magnetization. Furthermore, our calculations show that the bias-induced antidamping efficiency in the local spin-flip regime is much higher than that in the rotational excitation regime.
Quantifying Spin Hall Angles from Spin Pumping : Experiments and Theory
Mosendz, O.; Pearson, J.E.; Fradin, F.Y.; Bauer, G.E.W.; Bader, S.D.; Hoffmann, A.
2010-01-01
Spin Hall effects intermix spin and charge currents even in nonmagnetic materials and, therefore, ultimately may allow the use of spin transport without the need for ferromagnets. We show how spin Hall effects can be quantified by integrating Ni80Fe20|normal metal (N) bilayers into a coplanar
Compound nucleus effects in spin-spin cross sections
International Nuclear Information System (INIS)
Thompson, W.J.
1976-01-01
By comparison with recent data, it is shown that spin-spin cross sections for low-energy neutrons may be dominated by a simple compound-elastic level-density effect, independent of spin-spin terms in the nucleon-nucleus optical-model potential. (Auth.)
2013-01-01
This book covers all principal aspects of currently investigated frustrated systems, from exactly solved frustrated models to real experimental frustrated systems, going through renormalization group treatment, Monte Carlo investigation of frustrated classical Ising and vector spin models, low-dimensional systems, spin ice and quantum spin glass. The reader can - within a single book - obtain a global view of the current research development in the field of frustrated systems.This new edition is updated with recent theoretical, numerical and experimental developments in the field of frustrated
SPINning parallel systems software
International Nuclear Information System (INIS)
Matlin, O.S.; Lusk, E.; McCune, W.
2002-01-01
We describe our experiences in using Spin to verify parts of the Multi Purpose Daemon (MPD) parallel process management system. MPD is a distributed collection of processes connected by Unix network sockets. MPD is dynamic processes and connections among them are created and destroyed as MPD is initialized, runs user processes, recovers from faults, and terminates. This dynamic nature is easily expressible in the Spin/Promela framework but poses performance and scalability challenges. We present here the results of expressing some of the parallel algorithms of MPD and executing both simulation and verification runs with Spin
McWeeny, Roy
2004-01-01
Originally delivered as a series of lectures, this volume systematically traces the evolution of the ""spin"" concept from its role in quantum mechanics to its assimilation into the field of chemistry. Author Roy McWeeny presents an in-depth illustration of the deductive methods of quantum theory and their application to spins in chemistry, following the path from the earliest concepts to the sophisticated physical methods employed in the investigation of molecular structure and properties. Starting with the origin and development of the spin concept, the text advances to an examination of sp
NUCLEON SPIN: Enigma confirmed
International Nuclear Information System (INIS)
Anon.
1994-01-01
In 1987 the European Muon Collaboration (EMC - June 1988, page 9) reported results from a polarized muon-proton scattering experiment at CERN which puzzled the particle and nuclear physics communities. Contrary to the prediction of the naive quark model, the EMC found that little of the proton spin seemed to be carried by the spins of the quarks. An extensive experimental programme was therefore immediately proposed at CERN, SLAC (Stanford) and DESY (Hamburg) to measure the spin structure function of the neutron and to repeat the proton measurement with improved accuracy
International Nuclear Information System (INIS)
Konoto, Makoto
2007-01-01
Development of highly effective evaluation technology of magnetic structures on a nanometric scale is a key to understanding spintronics and related phenomena. A high-resolution spin-polarized scanning electron microscope (spin SEM) developed recently is quite suitable for probing such nanostructures because of the capability of analyzing local magnetization vectors in three dimensions. Utilizing the spin SEM, a layered antiferromagnetic structure with the 1nm-alternation of bilayer-sheet magnetization has been successfully resolved. The real-space imaging with full analysis of the temperature-dependent magnetization vectors will be demonstrated. (author)
International Nuclear Information System (INIS)
Khan, H.
1990-01-01
This thesis explores deep inelastic scattering of a lepton beam from a polarized nuclear target with spin J=1. After reviewing the formation for spin-1/2, the structure functions for a spin-1 target are defined in terms of the helicity amplitudes for forward compton scattering. A version of the convolution model, which incorporates relativistic and binding energy corrections is used to calculate the structure functions of a neutron target. A simple parameterization of these structure functions is given in terms of a few neutron wave function parameters and the free nucleon structure functions. This allows for an easy comparison of structure functions calculated using different neutron models. (author)
Czech Academy of Sciences Publication Activity Database
Wunderlich, Joerg; Park, B.G.; Irvine, A.C.; Zarbo, Liviu; Rozkotová, E.; Němec, P.; Novák, Vít; Sinova, Jairo; Jungwirth, Tomáš
2010-01-01
Roč. 330, č. 6012 (2010), s. 1801-1804 ISSN 0036-8075 R&D Projects: GA AV ČR KAN400100652; GA MŠk LC510 EU Projects: European Commission(XE) 215368 - SemiSpinNet Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : spin Hall effect * spintronics * spin transistor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 31.364, year: 2010
International Nuclear Information System (INIS)
Chang Wenkua; Zheng Han
1989-01-01
The effects of spinning process parameters including max. pass percentage reduction, spinning temperature, feed rate, lubricant and annealing technology on the quality of shaped components are summarized and discussed in the present paper. The above mentioned parameters are adopted in the process of spinning of barrel-shaped and specially shaped components of refractory metals and their alloys W, Mo, Nb, Zr, TZM molybdenum alloy, C-103, C-752 niobium alloy etc. The cause of leading to usual defects of spun products of refractory metals such as lamellar as 'scaling', crack, swelling, wrinkle, etc. have been analysed and the ways to eliminate the defects have been put forward. 8 figs., 5 tabs. (Author)
Spin transfer torque with spin diffusion in magnetic tunnel junctions
Manchon, Aurelien
2012-08-09
Spin transport in magnetic tunnel junctions in the presence of spin diffusion is considered theoretically. Combining ballistic tunneling across the barrier and diffusive transport in the electrodes, we solve the spin dynamics equation in the metallic layers. We show that spin diffusion mixes the transverse spin current components and dramatically modifies the bias dependence of the effective spin transfer torque. This leads to a significant linear bias dependence of the out-of-plane torque, as well as a nonconventional thickness dependence of both spin torque components.
Electron spin and nuclear spin manipulation in semiconductor nanosystems
International Nuclear Information System (INIS)
Hirayama, Yoshiro; Yusa, Go; Sasaki, Satoshi
2006-01-01
Manipulations of electron spin and nuclear spin have been studied in AlGaAs/GaAs semiconductor nanosystems. Non-local manipulation of electron spins has been realized by using the correlation effect between localized and mobile electron spins in a quantum dot- quantum wire coupled system. Interaction between electron and nuclear spins was exploited to achieve a coherent control of nuclear spins in a semiconductor point contact device. Using this device, we have demonstrated a fully coherent manipulation of any two states among the four spin levels of Ga and As nuclei. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Spin effect on parametric interactions of waves in magnetoplasmas
International Nuclear Information System (INIS)
Shahid, M.; Melrose, D. B.; Jamil, M.; Murtaza, G.
2012-01-01
The parametric decay instability of upper hybrid wave into low-frequency electromagnetic Shear Alfvén wave and Ordinary mode radiation (O-mode) has been investigated in an electron-ion plasma immersed in the uniform external magnetic field. Incorporating quantum effect due to electron spin, the fluid model has been used to investigate the linear and nonlinear response of the plasma species for three-wave coupling in a magnetoplasma. It is shown that the spin of electrons has considerable effect on the parametric decay of upper hybrid wave into Ordinary mode radiation (O-mode) and Shear Alfvén wave even in classical regime.
Hamiltonian action of spinning particle with gravimagnetic moment
International Nuclear Information System (INIS)
Deriglazov, Alexei A; Ramírez, W Guzmán
2016-01-01
We develop Hamiltonian variational problem for spinning particle non-minimally interacting with gravity through the gravimagnetic moment κ. For κ = 0 our model yields Mathisson-Papapetrou-Tulczyjew-Dixon (MPTD) equations, the latter show unsatisfactory behavior of MPTD-particle in ultra-relativistic regime: its longitudinal acceleration increases with velocity. κ = 1 yields a modification of MPTD-equations with the reasonable behavior: in the homogeneous fields, both longitudinal acceleration and (covariant) precession of spin-tensor vanish as v→c. (paper)
Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains
Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.
2016-10-01
We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.
When measured spin polarization is not spin polarization
International Nuclear Information System (INIS)
Dowben, P A; Wu Ning; Binek, Christian
2011-01-01
Spin polarization is an unusually ambiguous scientific idiom and, as such, is rarely well defined. A given experimental methodology may allow one to quantify a spin polarization but only in its particular context. As one might expect, these ambiguities sometimes give rise to inappropriate interpretations when comparing the spin polarizations determined through different methods. The spin polarization of CrO 2 and Cr 2 O 3 illustrate some of the complications which hinders comparisons of spin polarization values. (viewpoint)
Spin-4 extended conformal algebras
International Nuclear Information System (INIS)
Kakas, A.C.
1988-01-01
We construct spin-4 extended conformal algebras using the second hamiltonian structure of the KdV hierarchy. In the presence of a U(1) current a family of spin-4 algebras exists but the additional requirement that the spin-1 and spin-4 currents commute fixes the algebra uniquely. (orig.)
Anisotropic spin relaxation in graphene
Tombros, N.; Tanabe, S.; Veligura, A.; Jozsa, C.; Popinciuc, M.; Jonkman, H. T.; van Wees, B. J.
2008-01-01
Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the nonlocal geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field B applied perpendicular
Spin squeezing and quantum correlations
Indian Academy of Sciences (India)
2 states. A coherent spin-s state. (CSS) θ φ can then be thought of as having no quantum correlations as the constituent. 2s elementary spins point in the same direction ˆn(θ φ) which is the mean spin direction. 2. State classification and squeezing. In order to discuss squeezing, we begin with the squeezing condition itself.
Geometry of spin coherent states
Chryssomalakos, C.; Guzmán-González, E.; Serrano-Ensástiga, E.
2018-04-01
Spin states of maximal projection along some direction in space are called (spin) coherent, and are, in many respects, the ‘most classical’ available. For any spin s, the spin coherent states form a 2-sphere in the projective Hilbert space \
Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures
Ortiz Pauyac, Christian; Wang, Xuhui; Chshiev, Mairbek; Manchon, Aurelien
2013-01-01
In a ferromagnetic heterostructure, the interplay between Rashba spin-orbit coupling and exchange splitting gives rise to a current-driven spin torque. In a realistic device setup, we investigate the Rashba spin torque in the diffusive regime and report two major findings: (i) a nonvanishing torque exists at the edges of the device even when the magnetization and effective Rashba field are aligned; (ii) anisotropic spin relaxation rates driven by the Rashba spin-orbit coupling assign the spin torque a general expression T = T y (θ) m × (y × m) + T y (θ) y × m + T z (θ) m × (z × m) + T z (θ) z × m, where the coefficients T, y, z depend on the magnetization direction. Our results agree with recent experiments. © 2013 AIP Publishing LLC.
Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures
Ortiz Pauyac, Christian
2013-06-26
In a ferromagnetic heterostructure, the interplay between Rashba spin-orbit coupling and exchange splitting gives rise to a current-driven spin torque. In a realistic device setup, we investigate the Rashba spin torque in the diffusive regime and report two major findings: (i) a nonvanishing torque exists at the edges of the device even when the magnetization and effective Rashba field are aligned; (ii) anisotropic spin relaxation rates driven by the Rashba spin-orbit coupling assign the spin torque a general expression T = T y (θ) m × (y × m) + T y (θ) y × m + T z (θ) m × (z × m) + T z (θ) z × m, where the coefficients T, y, z depend on the magnetization direction. Our results agree with recent experiments. © 2013 AIP Publishing LLC.
Exchange rate regimes and monetary arrangements
Directory of Open Access Journals (Sweden)
Ivan Ribnikar
2005-06-01
Full Text Available There is a close relationship between a country’s exchange rate regime and monetary arrangement and if we are to examine monetary arrangements then exchange rate regimes must first be analysed. Within the conventional and most widely used classification of exchange rate regimes into rigid and flexible or into polar regimes (hard peg and float on one side, and intermediate regimes on the other there, is a much greater variety among intermediate regimes. A more precise and, as will be seen, more useful classification of exchange rate regimes is the first topic of the paper. The second topic is how exchange rate regimes influence or determine monetary arrangements and monetary policy or monetary policy regimes: monetary autonomy versus monetary nonautonomy and discretion in monetary policy versus commitment in monetary policy. Both topics are important for countries on their path to the EU and the euro area
International Nuclear Information System (INIS)
O'FAllon, J.R.
1991-01-01
The history of spin physics experiments is presented, with emphasis of Kent Terwilliger's involvement. Development of polarized beams and targets at the ZGS and AGS is recalled. P-P elastic scattering experiments are reviewed
International Nuclear Information System (INIS)
Ratcliffe, P.G.
1993-01-01
A discussion is presented of the role that transverse spin physics can play in providing information on the bound state dynamics in hadronic physics. Care is taken to distinguish between single- and double-spin measurements, each being discussed separately. In the case of single-spin effects it is stressed that as yet no satisfactory explanation has been provided within the framework if perturbative QCD which in fact generally predicts negligible effects. In order to clarify the situation experimental data at yet higher p T are necessary and semi-leptonic data could shed some light on the underlying scattering mechanisms. As regards double-spin correlations, the theoretical picture (although clouded by some ill-informed, often erroneous statements and even recent papers) is rather well understood and what is dearly missing is the experimental study of, for example, g 2 in deep-inelastic scattering. (author). 31 refs
International Nuclear Information System (INIS)
Glyde, H.R.; Hernadi, S.I.
1986-01-01
Several ground state properties of (electron) spin-polarized deuterium (D) such as the energy, single quasiparticle energies and lifetimes, Landau parameters and sound velocities are evaluated. The calculations begin with the Kolos-Wolneiwicz potential and use the Galitskii-FeynmanHartree-Fock (GFHF) approximation. The deuteron nucleas has spin I = 1, and spin states I/sub z/ = 1,0,-1. We explore D 1 , D 2 and D 3 in which, respectively, one spin state only is populated, two states are equally populated, and three states are equally populated. We find the GFHF describes D 1 well, but D 2 and D 3 less well. The Landau parameters, F/sub L/, are small compared to liquid 3 He and very small for doubly polarized D 1 (i.e. the F/sub L/ decrease with nuclear polarization)
Microscopic studies of nonlocal spin dynamics and spin transport (invited)
Energy Technology Data Exchange (ETDEWEB)
Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris, E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)
2015-05-07
Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.
Microscopic studies of nonlocal spin dynamics and spin transport (invited)
Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris
2015-05-01
Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.
Microscopic studies of nonlocal spin dynamics and spin transport (invited)
International Nuclear Information System (INIS)
Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris
2015-01-01
Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems
Exertional Rhabdomyolysis after Spinning
Jeong, Youjin; Kweon, Hyuk-Jung; Oh, Eun-Jung; Ahn, Ah-Leum; Choi, Jae-Kyung; Cho, Dong-Yung
2016-01-01
Any strenuous muscular exercise may trigger rhabdomyolysis. We report an episode of clinically manifested exertional rhabdomyolysis due to stationary cycling, commonly known as spinning. Reports of spinning-related rhabdomyolysis are rare in the English literature, and the current case appears to be the first such case reported in South Korea. A previously healthy 21-year-old Asian woman presented with severe thigh pain and reddish-brown urinary discoloration 24?48 hours after attending a spi...
CERN. Geneva
2014-01-01
The conjectured relation between higher spin theories on anti de-Sitter (AdS) spaces and weakly coupled conformal field theories is reviewed. I shall then outline the evidence in favour of a concrete duality of this kind, relating a specific higher spin theory on AdS3 to a family of 2d minimal model CFTs. Finally, I shall explain how this relation fits into the framework of the familiar stringy AdS/CFT correspondence.
Salberger, Olof; Korepin, Vladimir
We introduce a new model of interacting spin 1/2. It describes interactions of three nearest neighbors. The Hamiltonian can be expressed in terms of Fredkin gates. The Fredkin gate (also known as the controlled swap gate) is a computational circuit suitable for reversible computing. Our construction generalizes the model presented by Peter Shor and Ramis Movassagh to half-integer spins. Our model can be solved by means of Catalan combinatorics in the form of random walks on the upper half plane of a square lattice (Dyck walks). Each Dyck path can be mapped on a wave function of spins. The ground state is an equally weighted superposition of Dyck walks (instead of Motzkin walks). We can also express it as a matrix product state. We further construct a model of interacting spins 3/2 and greater half-integer spins. The models with higher spins require coloring of Dyck walks. We construct a SU(k) symmetric model (where k is the number of colors). The leading term of the entanglement entropy is then proportional to the square root of the length of the lattice (like in the Shor-Movassagh model). The gap closes as a high power of the length of the lattice [5, 11].
Detecting spatial regimes in ecosystems
Sundstrom, Shana M.; Eason, Tarsha; Nelson, R. John; Angeler, David G.; Barichievy, Chris; Garmestani, Ahjond S.; Graham, Nicholas A.J.; Granholm, Dean; Gunderson, Lance; Knutson, Melinda; Nash, Kirsty L.; Spanbauer, Trisha; Stow, Craig A.; Allen, Craig R.
2017-01-01
Research on early warning indicators has generally focused on assessing temporal transitions with limited application of these methods to detecting spatial regimes. Traditional spatial boundary detection procedures that result in ecoregion maps are typically based on ecological potential (i.e. potential vegetation), and often fail to account for ongoing changes due to stressors such as land use change and climate change and their effects on plant and animal communities. We use Fisher information, an information theory-based method, on both terrestrial and aquatic animal data (U.S. Breeding Bird Survey and marine zooplankton) to identify ecological boundaries, and compare our results to traditional early warning indicators, conventional ecoregion maps and multivariate analyses such as nMDS and cluster analysis. We successfully detected spatial regimes and transitions in both terrestrial and aquatic systems using Fisher information. Furthermore, Fisher information provided explicit spatial information about community change that is absent from other multivariate approaches. Our results suggest that defining spatial regimes based on animal communities may better reflect ecological reality than do traditional ecoregion maps, especially in our current era of rapid and unpredictable ecological change.
Cloud regimes as phase transitions
Stechmann, Samuel; Hottovy, Scott
2017-11-01
Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes - open versus closed cells - fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells (POCs) as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. Similar viewpoints of deep convection and self-organized criticality will also be discussed. With these new conceptual viewpoints, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions. The research of S.N.S. is partially supported by a Sloan Research Fellowship, ONR Young Investigator Award N00014-12-1-0744, and ONR MURI Grant N00014-12-1-0912.
Spin storage in quantum dot ensembles and single quantum dots
International Nuclear Information System (INIS)
Heiss, Dominik
2009-01-01
electron spin lifetimes. The longest measured value is T 1 h =270 μs at B=1.5 T and T=8 K. Based on this spin detection technique in small ensembles, electron spin resonance experiments with the goal to study coherence properties were attempted. After optical charge generation and storage, a spin-conditional absorption of a circularly polarized light pulse tuned to the singly charged quantum dot s-shell absorption converts the spin information of the resident electron to charge information. Subsequently, time-gated photoluminescence directly reveals the charge state of the quantum dot (1e, 2e) and, therefore, the spin orientation of the resident electron. Schottky diode devices suitable for this single dot spin readout scheme were fabricated and characterized with time-gated photoluminescence. The electric field regimes applicable for reset, optical charging and reliable charge storage were identified. Furthermore, the fidelity of charge readout was investigated as a function of excitation wavelength, applied electric field and optical excitation power. Additional measurements using resonant excitation showed that a single quantum dot can be selectively charged with a single electron via optical excitation in its p-shell. The tunneling escape of this optically initialized electron has been determined, proving the feasibility of reliable charge detection in time-resolved measurements. Extrapolated to reasonable storage fields F=20 kV/cm the tunneling time of the electron exceeds seconds. The electron spin relaxation in a single quantum dot has been determined as a function of temperature at B=12 T. (orig.)
Spin storage in quantum dot ensembles and single quantum dots
Energy Technology Data Exchange (ETDEWEB)
Heiss, Dominik
2009-10-15
} in the microsecond range, therefore, comparable with electron spin lifetimes. The longest measured value is T{sub 1}{sup h} =270 {mu}s at B=1.5 T and T=8 K. Based on this spin detection technique in small ensembles, electron spin resonance experiments with the goal to study coherence properties were attempted. After optical charge generation and storage, a spin-conditional absorption of a circularly polarized light pulse tuned to the singly charged quantum dot s-shell absorption converts the spin information of the resident electron to charge information. Subsequently, time-gated photoluminescence directly reveals the charge state of the quantum dot (1e, 2e) and, therefore, the spin orientation of the resident electron. Schottky diode devices suitable for this single dot spin readout scheme were fabricated and characterized with time-gated photoluminescence. The electric field regimes applicable for reset, optical charging and reliable charge storage were identified. Furthermore, the fidelity of charge readout was investigated as a function of excitation wavelength, applied electric field and optical excitation power. Additional measurements using resonant excitation showed that a single quantum dot can be selectively charged with a single electron via optical excitation in its p-shell. The tunneling escape of this optically initialized electron has been determined, proving the feasibility of reliable charge detection in time-resolved measurements. Extrapolated to reasonable storage fields F=20 kV/cm the tunneling time of the electron exceeds seconds. The electron spin relaxation in a single quantum dot has been determined as a function of temperature at B=12 T. (orig.)
Chudnovsky, Eugene M.
2007-01-01
An extension of Drude model is proposed that accounts for spin and spin-orbit interaction of charge carriers. Spin currents appear due to combined action of the external electric field, crystal field and scattering of charge carriers. The expression for spin Hall conductivity is derived for metals and semiconductors that is independent of the scattering mechanism. In cubic metals, spin Hall conductivity $\\sigma_s$ and charge conductivity $\\sigma_c$ are related through $\\sigma_s = [2 \\pi \\hbar...
ABSTRACT BODY:Recent investigations have linked neurotrophins including NGF, NT-3, and BDNF to allergic airways diseases. Antibody blockade of NGF attenuates airway resistance associated with allergic airway responses in mice. Mice administered an antibody against the low aff...
Einstein, David J; McDermott, David F
2017-06-01
Targeted and immune-based therapies have improved outcomes in advanced kidney cancer, yet novel strategies are needed to extend the duration of these benefits and expand them to more patients. Combined inhibition of vascular endothelial growth factor (VEGF) and the programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) pathways with therapeutic agents already in clinical use may offer such a strategy. Here, we describe the development and clinical evaluation of VEGF inhibitors and, separately, PD-1/PD-L1 inhibitors. We present preclinical evidence of interaction between these pathways and the rationale for combined blockade. Beyond well-known effects on pathologic angiogenesis, VEGF blockade also may decrease immune tolerance and enhance PD-1/PD-L1 blockade. We conclude with the results of several early trials of combined VEGF and PD-1/PD-L1 blockade, which demonstrate encouraging antitumor activity, and we pose questions for future study.
Effects of dual renin-angiotensin system blockade on proteinuria in a ...
African Journals Online (AJOL)
Kidney diseases manifesting as proteinuria or elevated creatinine are increasingly prevalent complications of HIV infection. We report the effects of dual renin-angiotensin system blockade on proteinuria in a hypertensive black African HIV-infected patient.
Dynamics of the two-spin spin-boson model with a common bath
Energy Technology Data Exchange (ETDEWEB)
Deng, Tianrui [Division of Materials Science, Nanyang Technological University, Singapore 639798 (Singapore); Centre for Optical and Electromagnetic Research, Zhejiang Provincial Key Laboratory for Sensing Technologies, Zhejiang University, Hangzhou 310058 (China); Yan, Yiying; Chen, Lipeng; Zhao, Yang, E-mail: YZhao@ntu.edu.sg [Division of Materials Science, Nanyang Technological University, Singapore 639798 (Singapore)
2016-04-14
Dynamics of the two-spin spin-boson model in the presence of Ohmic and sub-Ohmic baths is investigated by employing a multitude of the Davydov D{sub 1} trial states, also known as the multi-D{sub 1} Ansatz. Its accuracy in dynamics simulations of the two-spin SBM is improved significantly over the single D{sub 1} Ansatz, especially in the weak to moderately strong coupling regime. Validity of the multi-D{sub 1} Ansatz for various coupling strengths is also systematically examined by making use of the deviation vector which quantifies how faithfully the trial state obeys the Schrödinger equation. The time evolution of population difference and entanglement has been studied for various initial conditions and coupling strengths. Careful comparisons are carried out between our approach and three other methods, i.e., the time-dependent numerical renormalization group (TD-NRG) approach, the Bloch-Redfield theory, and a method based on a variational master equation. For strong coupling, the multi-D{sub 1} trial state yields consistent results as the TD-NRG approach in the Ohmic regime while the two disagree in the sub-Ohmic regime, where the multi-D{sub 1} trial state is shown to be more accurate. For weak coupling, the multi-D{sub 1} trial state agrees with the two master-equation methods in the presence of both Ohmic and sub-Ohmic baths, but shows considerable differences with the TD-NRG approach in the presence of a sub-Ohmic bath, calling into question the validity of the TD-NRG results at long times in the literature.
Spin-current emission governed by nonlinear spin dynamics.
Tashiro, Takaharu; Matsuura, Saki; Nomura, Akiyo; Watanabe, Shun; Kang, Keehoon; Sirringhaus, Henning; Ando, Kazuya
2015-10-16
Coupling between conduction electrons and localized magnetization is responsible for a variety of phenomena in spintronic devices. This coupling enables to generate spin currents from dynamical magnetization. Due to the nonlinearity of magnetization dynamics, the spin-current emission through the dynamical spin-exchange coupling offers a route for nonlinear generation of spin currents. Here, we demonstrate spin-current emission governed by nonlinear magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current emission from the magnetic insulator is probed by the inverse spin Hall effect, which demonstrates nontrivial temperature and excitation power dependences of the voltage generation. The experimental results reveal that nonlinear magnetization dynamics and enhanced spin-current emission due to magnon scatterings are triggered by decreasing temperature. This result illustrates the crucial role of the nonlinear magnon interactions in the spin-current emission driven by dynamical magnetization, or nonequilibrium magnons, from magnetic insulators.
Spin Torques in Systems with Spin Filtering and Spin Orbit Interaction
Ortiz Pauyac, Christian
2016-06-19
In the present thesis we introduce the reader to the ﬁeld of spintronics and explore new phenomena, such as spin transfer torques, spin ﬁltering, and three types of spin-orbit torques, Rashba, spin Hall, and spin swapping, which have emerged very recently and are promising candidates for a new generation of memory devices in computer technology. A general overview of these phenomena is presented in Chap. 1. In Chap. 2 we study spin transfer torques in tunnel junctions in the presence of spin ﬁltering. In Chap. 3 we discuss the Rashba torque in ferromagnetic ﬁlms, and in Chap. 4 we study spin Hall eﬀect and spin swapping in ferromagnetic ﬁlms, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives are summarized in Chap. 5.
Lindesmith, Lisa C; Mallory, Michael L; Debbink, Kari; Donaldson, Eric F; Brewer-Jensen, Paul D; Swann, Excel W; Sheahan, Timothy P; Graham, Rachel L; Beltramello, Martina; Corti, Davide; Lanzavecchia, Antonio; Baric, Ralph S
2018-01-01
Extensive antigenic diversity within the GII.4 genotype of human norovirus is a major driver of pandemic emergence and a significant obstacle to development of cross-protective immunity after natural infection and vaccination. However, human and mouse monoclonal antibody studies indicate that, although rare, antibodies to conserved GII.4 blockade epitopes are generated. The mechanisms by which these epitopes evade immune surveillance are uncertain. Here, we developed a new approach for identifying conserved GII.4 norovirus epitopes. Utilizing a unique set of virus-like particles (VLPs) representing the in vivo -evolved sequence diversity within an immunocompromised person, we identify key residues within epitope F, a conserved GII.4 blockade antibody epitope. The residues critical for antibody binding are proximal to evolving blockade epitope E. Like epitope F, antibody blockade of epitope E was temperature sensitive, indicating that particle conformation regulates antibody access not only to the conserved GII.4 blockade epitope F but also to the evolving epitope E. These data highlight novel GII.4 mechanisms to protect blockade antibody epitopes, map essential residues of a GII.4 conserved epitope, and expand our understanding of how viral particle dynamics may drive antigenicity and antibody-mediated protection by effectively shielding blockade epitopes. Our data support the notion that GII.4 particle breathing may well represent a major mechanism of humoral immune evasion supporting cyclic pandemic virus persistence and spread in human populations. IMPORTANCE In this study, we use norovirus virus-like particles to identify key residues of a conserved GII.4 blockade antibody epitope. Further, we identify an additional GII.4 blockade antibody epitope to be occluded, with antibody access governed by temperature and particle dynamics. These findings provide additional support for particle conformation-based presentation of binding residues mediated by a particle
Emergent Chiral Spin State in the Mott Phase of a Bosonic Kane-Mele-Hubbard Model
Plekhanov, Kirill; Vasić, Ivana; Petrescu, Alexandru; Nirwan, Rajbir; Roux, Guillaume; Hofstetter, Walter; Le Hur, Karyn
2018-04-01
Recently, the frustrated X Y model for spins 1 /2 on the honeycomb lattice has attracted a lot of attention in relation with the possibility to realize a chiral spin liquid state. This model is relevant to the physics of some quantum magnets. Using the flexibility of ultracold atom setups, we propose an alternative way to realize this model through the Mott regime of the bosonic Kane-Mele-Hubbard model. The phase diagram of this model is derived using bosonic dynamical mean-field theory. Focusing on the Mott phase, we investigate its magnetic properties as a function of frustration. We do find an emergent chiral spin state in the intermediate frustration regime. Using exact diagonalization we study more closely the physics of the effective frustrated X Y model and the properties of the chiral spin state. This gapped phase displays a chiral order, breaking time-reversal and parity symmetry, but is not topologically ordered (the Chern number is zero).
Spin effects in nonlinear Compton scattering in a plane-wave laser pulse
International Nuclear Information System (INIS)
Boca, Madalina; Dinu, Victor; Florescu, Viorica
2012-01-01
We study theoretically the electron angular and energy distribution in the non-linear Compton effect in a finite plane-wave laser pulse. We first present analytical and numerical results for unpolarized electrons (described by a Volkov solution of the Dirac equation), in comparison with those corresponding to a spinless particle (obeying the Klein–Gordon equation). Then, in the spin 1/2 case, we include results for the spin flip probability. The regime in which the spin effects are negligible, i.e. the results for the unpolarized spin 1/2 particle coincide practically with those for the spinless particle, is the same as the regime in which the emitted radiation is well described by classical electrodynamics.
Glucagon and plasma catecholamines during beta-receptor blockade in exercising man
DEFF Research Database (Denmark)
Galbo, H; Holst, Janett; Christensen, N J
1976-01-01
Seven men ran at 60% of individual maximal oxygen uptake to exhaustion during beta-adrenergic blockade with propranolol (P), during lipolytic blockade with nicotinic acid (N), or without drugs (C). The total work times (83 +/- 9 (P), 122 +/- 8 (N), 166 +/- 10 (C) min, mean and SE) differed signif...... determinants for the exercise-induced glucagon secretion in man. It is suggested that decreased glucose availability enhances the secretion of glucagon and epinephrine during prolonged exercise....
Dual Blockade of the Renin-angiotensin-aldosterone System in Type 2 Diabetic Kidney Disease
Directory of Open Access Journals (Sweden)
Yan-Huan Feng
2016-01-01
Full Text Available Objective: To examine the efficacy and safety of dual blockade of the renin-angiotensin-aldosterone system (RAAS among patients with type 2 diabetic kidney disease. Data Sources: We searched the major literature repositories, including the Cochrane Central Register of Controlled Trials, MEDLINE and EMBASE, for randomized clinical trials published between January 1990 and October 2015 that compared the efficacy and safety of the use of dual blockade of the RAAS versus the use of monotherapy, without applying any language restrictions. Keywords for the searches included "diabetic nephropathy," "chronic kidney disease," "chronic renal insufficiency," "diabetes mellitus," "dual therapy," "combined therapy," "dual blockade," "renin-angiotensin system," "angiotensin-converting enzyme inhibitor," "angiotensin-receptor blocker," "aldosterone blockade," "selective aldosterone blockade," "renin inhibitor," "direct renin inhibitor," "mineralocorticoid receptor blocker," etc. Study Selection: The selected articles were carefully reviewed. We excluded randomized clinical trials in which the kidney damage of patients was related to diseases other than diabetes mellitus. Results: Combination treatment with an angiotensin-converting enzyme inhibitor supplemented by an angiotensin II receptor blocking agent is expected to provide a more complete blockade of the RAAS and a better control of hypertension. However, existing literature has presented mixed results, in particular, related to patient safety. In view of this, we conducted a comprehensive literature review in order to explain the rationale for dual blockade of the RAAS, and to discuss the pros and cons. Conclusions: Despite the negative results of some recent large-scale studies, it may be immature to declare that the dual blockade is a failure because of the complex nature of the RAAS surrounding its diversified functions and utility. Further trials are warranted to study the combination therapy as an
Hasanirokh, K.; Phirouznia, A.; Majidi, R.
2016-02-01
The influence of the electron coupling with non-polarized optical phonons on magnetoelectric effects of a two-dimensional electron gas system has been investigated in the presence of the Rashba and Dresselhaus spin-orbit couplings. Numerical calculations have been performed in the non-equilibrium regime. In the previous studies in this field, it has been shown that the Rashba and Dresselhaus couplings cannot generate non-equilibrium spin current and the spin current vanishes identically in the absence of other relaxation mechanisms such as lattice vibrations. However, in the current study, based on a semiclassical approach, it was demonstrated that in the presence of electron-phonon coupling, the spin current and other magnetoelectric quantities have been modulated by the strength of the spin-orbit interactions.
Lebre, M.C.; Vergunst, C.E.; Choi, I.Y.K.; Aarrass, S.; Oliveira, A.S.F.; Wyant, T.; Horuk, R.; Reedquist, K.A.; Tak, P.P.
2011-01-01
BACKGROUND: The aim of this study was to provide more insight into the question as to why blockade of CCR1, CCR2, and CCR5 may have failed in clinical trials in rheumatoid arthritis (RA) patients, using an in vitro monocyte migration system model. METHODOLOGY/PRINCIPAL FINDINGS: Monocytes from healthy donors (HD; n = 8) or from RA patients (for CCR2 and CCR5 antibody n = 8; for CCR1 blockade n = 13) were isolated from peripheral blood and pre-incubated with different concentrations of either ...
Simplified parent-child formalism for spin-0 and spin-1/2 parents
Butcher, J. B.; Jones, H. F.; Milani, P.
1980-06-01
We develop further the parent-child relation, that is the calculation of the cross-sections and correlations of observed particles, typically charged leptons, arising from the decay of long-lived primarily produced “parent” particles. In the high-momentum regime, when the momenta of parent and child are closely aligned, we show how, for spinless parents, the relation can be simplified by the introduction of “fragmentation” functions derived from the invariant inclusive decay distributions. We extend the formalism to the case of spin-1/2 parents and advocate its application to charm production and decay at the quark level.
International Nuclear Information System (INIS)
Furman, G.B.; Panich, A.M.; Goren, S.D.
1998-01-01
The phenomena of spin diffusion and spin lattice relaxation of nuclear dipolar order in solids containing paramagnetic impurities (PI) is considered. We show that at the beginning of the relaxation process the diffusion vanishing regime realizes with non-exponential time dependence, R(t) ∼ exp [- (t/T 1d ) α ], where T 1d ∼ C p -1/α , C p is PI's concentration. For a homogeneous distribution of Pis and nuclear spins, α=Q/6, where Q is the sample dimensionality; for an inhomogeneous distribution, the sample is divided into q-dimensional subsystems, each containing one PI, yield- ing α= (Q + q) /6. This result coincides with experimental data for CaF 2 doped with 0.8 - 10 -3 ωt % of Mn 2+ , where the non-exponential decay of the dipolar signal with α= 0.83 has been observed [3]. Fitting the experimental data yields a good agreement with T 1d = 66 ms . For another independent check of the obtained results we use dependence of the relaxation time on impurities concentration. In accordance that 1/α=1.2 , we have T 1d ∼ C p -1 '. 2 . Exactly this dependence on impurity concentration of the relaxation time has been found in the experiment. Then the relaxation regime starts as a non-exponential time dependent, proceed asymptotically to an to an exponential function of time, to so called diffusion limited relaxation regime with relaxation time T 1d D is inversely depends on impurities concentration. This kind of relaxation behavior of the dipolar order takes place in the experiment [2]. Using experimental results [2] from this two regime we can estimate the diffusion coefficient of the nuclear dipolar order in CaF 2 , which gives for typical values of impurity concentration C p ∼ 10 18 cm 3 the diffusion coefficient of dipolar order in the interval D ∼ 10 -11 -i- 10 -12 cm 2 /sec which is coincide to the case of Zeeman energy spin diffusion
Simplified parent-child formalism for spin-0 and spin- 1/2 parents
International Nuclear Information System (INIS)
Butcher, J.B.; Jones, H.F.; Milani, P.
1980-01-01
We develop further the parent-child relation, that is the calculation of the cross-sections and correlations of observed particles, typically charged leptons, arising from the decay of long-lived primarily produced 'parent' particles. In the high-momentum regime, when the momenta of parent and child are closely aligned we show how, for spinless parents, the relation can be simplified by the introduction of 'fragmentation' functions derived from the invariant inclusive decay distributions. We extend the formalism to the case of spin-1/2 parents and advocate its application to charm production and decay at the quark level. (orig.)
Vortices in spin-orbit-coupled Bose-Einstein condensates
International Nuclear Information System (INIS)
Radic, J.; Sedrakyan, T. A.; Galitski, V.; Spielman, I. B.
2011-01-01
Realistic methods to create vortices in spin-orbit-coupled Bose-Einstein condensates are discussed. It is shown that, contrary to common intuition, rotation of the trap containing a spin-orbit condensate does not lead to an equilibrium state with static vortex structures but gives rise instead to nonequilibrium behavior described by an intrinsically time-dependent Hamiltonian. We propose here the following alternative methods to induce thermodynamically stable static vortex configurations: (i) to rotate both the lasers and the anisotropic trap and (ii) to impose a synthetic Abelian field on top of synthetic spin-orbit interactions. Effective Hamiltonians for spin-orbit condensates under such perturbations are derived for most currently known realistic laser schemes that induce synthetic spin-orbit couplings. The Gross-Pitaevskii equation is solved for several experimentally relevant regimes. The new interesting effects include spatial separation of left- and right-moving spin-orbit condensates, the appearance of unusual vortex arrangements, and parity effects in vortex nucleation where the topological excitations are predicted to appear in pairs. All these phenomena are shown to be highly nonuniversal and depend strongly on a specific laser scheme and system parameters.
Spin-orbit-enhanced Wigner localization in quantum dots
DEFF Research Database (Denmark)
Cavalli, Andrea; Malet, F.; Cremon, J. C.
2011-01-01
We investigate quantum dots with Rashba spin-orbit coupling in the strongly-correlated regime. We show that the presence of the Rashba interaction enhances the Wigner localization in these systems, making it achievable for higher densities than those at which it is observed in Rashba-free quantum...... dots. Recurring shapes in the pair distribution functions of the yrast spectrum, which might be associated with rotational and vibrational modes, are also reported....
Injection of spin-polarized current into semiconductor
International Nuclear Information System (INIS)
Vedyayev, A.V.; Dieny, B.; Ryzhanova, N.V.; Zhukov, I.V.; Zhuravlev, M.Ye.; Lutz, H.O.
2003-01-01
A quantum-statistical theory of injection of spin-polarized current into a semiconductor in ferromagnet/tunnel barrier/semiconductor system is presented. The presence of Schottky barrier in the semiconductor is taken into account. The case of degenerated and non-degenerated semiconductors are considered. Both the diffusive and ballistic transport regime are investigated. The dependence of current polarization on barrier thickness and temperature is calculated
Optical spin generation/detection and spin transport lifetimes
International Nuclear Information System (INIS)
Miah, M. Idrish
2011-01-01
We generate electron spins in semiconductors by optical pumping. The detection of them is also performed by optical technique using time-resolved pump-probe photoluminescence polarization measurements in the presence of an external magnetic field perpendicular to the generated spin. The spin polarization in dependences of the pulse length, pump-probe delay and external magnetic field is studied. From the dependence of spin-polarization on the delay of the probe, the electronic spin transport lifetimes and the spin relaxation frequencies as a function of the strength of the magnetic field are estimated. The results are discussed based on hyperfine effects for interacting electrons.
Optical spin generation/detection and spin transport lifetimes
Energy Technology Data Exchange (ETDEWEB)
Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)
2011-02-25
We generate electron spins in semiconductors by optical pumping. The detection of them is also performed by optical technique using time-resolved pump-probe photoluminescence polarization measurements in the presence of an external magnetic field perpendicular to the generated spin. The spin polarization in dependences of the pulse length, pump-probe delay and external magnetic field is studied. From the dependence of spin-polarization on the delay of the probe, the electronic spin transport lifetimes and the spin relaxation frequencies as a function of the strength of the magnetic field are estimated. The results are discussed based on hyperfine effects for interacting electrons.
Magnetocaloric effect in quantum spin-s chains
Directory of Open Access Journals (Sweden)
A. Honecker
2009-01-01
Full Text Available We compute the entropy of antiferromagnetic quantum spin-s chains in an external magnetic field using exact diagonalization and Quantum Monte Carlo simulations. The magnetocaloric effect, i. e., temperature variations during adiabatic field changes, can be derived from the isentropes. First, we focus on the example of the spin-s=1 chain and show that one can cool by closing the Haldane gap with a magnetic field. We then move to quantum spin-s chains and demonstrate linear scaling with s close to the saturation field. In passing, we propose a new method to compute many low-lying excited states using the Lanczos recursion.
Rotational Invariance of the 2d Spin - Spin Correlation Function
Pinson, Haru
2012-09-01
At the critical temperature in the 2d Ising model on the square lattice, we establish the rotational invariance of the spin-spin correlation function using the asymptotics of the spin-spin correlation function along special directions (McCoy and Wu in the two dimensional Ising model. Harvard University Press, Cambridge, 1973) and the finite difference Hirota equation for which the spin-spin correlation function is shown to satisfy (Perk in Phys Lett A 79:3-5, 1980; Perk in Proceedings of III international symposium on selected topics in statistical mechanics, Dubna, August 22-26, 1984, JINR, vol II, pp 138-151, 1985).
Brueckmann, B; Sasaki, N; Grobara, P; Li, M K; Woo, T; de Bie, J; Maktabi, M; Lee, J; Kwo, J; Pino, R; Sabouri, A S; McGovern, F; Staehr-Rye, A K; Eikermann, M
2015-11-01
This study aimed to investigate whether reversal of rocuronium-induced neuromuscular blockade with sugammadex reduced the incidence of residual blockade and facilitated operating room discharge readiness. Adult patients undergoing abdominal surgery received rocuronium, followed by randomized allocation to sugammadex (2 or 4 mg kg(-1)) or usual care (neostigmine/glycopyrrolate, dosing per usual care practice) for reversal of neuromuscular blockade. Timing of reversal agent administration was based on the providers' clinical judgement. Primary endpoint was the presence of residual neuromuscular blockade at PACU admission, defined as a train-of-four (TOF) ratio sugammadex patients and 33 out of 76 (43.4%) usual care patients had TOF-Watch SX-assessed residual neuromuscular blockade at PACU admission (odds ratio 0.0, 95% CI [0-0.06], Psugammadex vs usual care (14.7 vs. 18.6 min respectively; P=0.02). After abdominal surgery, sugammadex reversal eliminated residual neuromuscular blockade in the PACU, and shortened the time from start of study medication administration to the time the patient was ready for discharge from the operating room. Clinicaltrials.gov:NCT01479764. © The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Resistance to checkpoint blockade therapy through inactivation of antigen presentation.
Sade-Feldman, Moshe; Jiao, Yunxin J; Chen, Jonathan H; Rooney, Michael S; Barzily-Rokni, Michal; Eliane, Jean-Pierre; Bjorgaard, Stacey L; Hammond, Marc R; Vitzthum, Hans; Blackmon, Shauna M; Frederick, Dennie T; Hazar-Rethinam, Mehlika; Nadres, Brandon A; Van Seventer, Emily E; Shukla, Sachet A; Yizhak, Keren; Ray, John P; Rosebrock, Daniel; Livitz, Dimitri; Adalsteinsson, Viktor; Getz, Gad; Duncan, Lyn M; Li, Bo; Corcoran, Ryan B; Lawrence, Donald P; Stemmer-Rachamimov, Anat; Boland, Genevieve M; Landau, Dan A; Flaherty, Keith T; Sullivan, Ryan J; Hacohen, Nir
2017-10-26
Treatment with immune checkpoint blockade (CPB) therapies often leads to prolonged responses in patients with metastatic melanoma, but the common mechanisms of primary and acquired resistance to these agents remain incompletely characterized and have yet to be validated in large cohorts. By analyzing longitudinal tumor biopsies from 17 metastatic melanoma patients treated with CPB therapies, we observed point mutations, deletions or loss of heterozygosity (LOH) in beta-2-microglobulin (B2M), an essential component of MHC class I antigen presentation, in 29.4% of patients with progressing disease. In two independent cohorts of melanoma patients treated with anti-CTLA4 and anti-PD1, respectively, we find that B2M LOH is enriched threefold in non-responders (~30%) compared to responders (~10%) and associated with poorer overall survival. Loss of both copies of B2M is found only in non-responders. B2M loss is likely a common mechanism of resistance to therapies targeting CTLA4 or PD1.
CTLA-4 blockade and the renaissance of cancer immunotherapy.
Mocellin, Simone; Nitti, Donato
2013-12-01
Cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) plays a key role in restraining the adaptive immune response of T-cells towards a variety of antigens including tumor associated antigens (TAAs). The blockade of this immune checkpoint elicits an effective anticancer immune response in a range of preclinical models, suggesting that naturally occurring (or therapeutically induced) TAA specific lymphocytes need to be "unleashed" in order to properly fight against malignant cells. Therefore, investigators have tested this therapeutic hypothesis also in humans: the favorable results obtained with this strategy in patients with advanced cutaneous melanoma are revolutionizing the management of this highly aggressive disease and are fueling new enthusiasm on cancer immunotherapy in general. Here we summarize the biology of CTLA-4, overview the experimental data supporting the rational for targeting CTLA-4 to treat cancer and review the main clinical findings on this novel anticancer approach. Moreover, we critically discuss the current challenges and potential developments of this promising field of cancer immunotherapy. Copyright © 2013 Elsevier B.V. All rights reserved.
Observation of the Photon-Blockade Breakdown Phase Transition
Directory of Open Access Journals (Sweden)
J. M. Fink
2017-01-01
Full Text Available Nonequilibrium phase transitions exist in damped-driven open quantum systems when the continuous tuning of an external parameter leads to a transition between two robust steady states. In second-order transitions this change is abrupt at a critical point, whereas in first-order transitions the two phases can coexist in a critical hysteresis domain. Here, we report the observation of a first-order dissipative quantum phase transition in a driven circuit quantum electrodynamics system. It takes place when the photon blockade of the driven cavity-atom system is broken by increasing the drive power. The observed experimental signature is a bimodal phase space distribution with varying weights controlled by the drive strength. Our measurements show an improved stabilization of the classical attractors up to the millisecond range when the size of the quantum system is increased from one to three artificial atoms. The formation of such robust pointer states could be used for new quantum measurement schemes or to investigate multiphoton phases of finite-size, nonlinear, open quantum systems.
Immune-Checkpoint Blockade and Active Immunotherapy for Glioma
Energy Technology Data Exchange (ETDEWEB)
Ahn, Brian J. [Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States); Brain Tumor Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213 (United States); Pollack, Ian F. [Brain Tumor Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213 (United States); Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States); Okada, Hideho, E-mail: okadah@upmc.edu [Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States); Brain Tumor Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213 (United States); Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States); Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States)
2013-11-01
Cancer immunotherapy has made tremendous progress, including promising results in patients with malignant gliomas. Nonetheless, the immunological microenvironment of the brain and tumors arising therein is still believed to be suboptimal for sufficient antitumor immune responses for a variety of reasons, including the operation of “immune-checkpoint” mechanisms. While these mechanisms prevent autoimmunity in physiological conditions, malignant tumors, including brain tumors, actively employ these mechanisms to evade from immunological attacks. Development of agents designed to unblock these checkpoint steps is currently one of the most active areas of cancer research. In this review, we summarize recent progresses in the field of brain tumor immunology with particular foci in the area of immune-checkpoint mechanisms and development of active immunotherapy strategies. In the last decade, a number of specific monoclonal antibodies designed to block immune-checkpoint mechanisms have been developed and show efficacy in other cancers, such as melanoma. On the other hand, active immunotherapy approaches, such as vaccines, have shown encouraging outcomes. We believe that development of effective immunotherapy approaches should ultimately integrate those checkpoint-blockade agents to enhance the efficacy of therapeutic approaches. With these agents available, it is going to be quite an exciting time in the field. The eventual success of immunotherapies for brain tumors will be dependent upon not only an in-depth understanding of immunology behind the brain and brain tumors, but also collaboration and teamwork for the development of novel trials that address multiple layers of immunological challenges in gliomas.
Immune-Checkpoint Blockade and Active Immunotherapy for Glioma
International Nuclear Information System (INIS)
Ahn, Brian J.; Pollack, Ian F.; Okada, Hideho
2013-01-01
Cancer immunotherapy has made tremendous progress, including promising results in patients with malignant gliomas. Nonetheless, the immunological microenvironment of the brain and tumors arising therein is still believed to be suboptimal for sufficient antitumor immune responses for a variety of reasons, including the operation of “immune-checkpoint” mechanisms. While these mechanisms prevent autoimmunity in physiological conditions, malignant tumors, including brain tumors, actively employ these mechanisms to evade from immunological attacks. Development of agents designed to unblock these checkpoint steps is currently one of the most active areas of cancer research. In this review, we summarize recent progresses in the field of brain tumor immunology with particular foci in the area of immune-checkpoint mechanisms and development of active immunotherapy strategies. In the last decade, a number of specific monoclonal antibodies designed to block immune-checkpoint mechanisms have been developed and show efficacy in other cancers, such as melanoma. On the other hand, active immunotherapy approaches, such as vaccines, have shown encouraging outcomes. We believe that development of effective immunotherapy approaches should ultimately integrate those checkpoint-blockade agents to enhance the efficacy of therapeutic approaches. With these agents available, it is going to be quite an exciting time in the field. The eventual success of immunotherapies for brain tumors will be dependent upon not only an in-depth understanding of immunology behind the brain and brain tumors, but also collaboration and teamwork for the development of novel trials that address multiple layers of immunological challenges in gliomas
Coulomb blockade and transfer of electrons one by one
International Nuclear Information System (INIS)
Pothier, Hugues
1991-01-01
Zero point fluctuations of the charge on the capacitance of a tunnel junction connected to a bias circuit are in almost all experimental situations larger than the electron charge. As a consequence, the effects of charge granularity are hidden, but in circuits with 'islands', which are electrodes connected to the rest of the circuit only through tunnel junctions and capacitors. The island charge being quantized, its fluctuations are blocked. If the island capacitance is sufficiently small, no electron can enter the island because of the increase of electrostatic energy that would occur. We have observed this effect, called 'Coulomb blockade', in the 'single electron box', where an island is formed between a tunnel junction and a capacitor. A bias voltage source coupled to the island through the capacitor allows to control the number of electrons. We have designed and operated two devices with nano-scale tunnel junctions based on this principle, the 'turnstile' and the 'pump', through which the current is controlled electron by electron. In our experiments, the precision of the transfer is of the order of one percent. It should be a million time better in versions of these devices with more junctions. One could then use them for a new measurement of the fine structure constant alpha. (author) [fr
Modeling spin magnetization transport in a spatially varying magnetic field
International Nuclear Information System (INIS)
Picone, Rico A.R.; Garbini, Joseph L.; Sidles, John A.
2015-01-01
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]). - Highlights: • A framework for modeling the transport of conserved magnetic and thermodynamic quantities in any spatial configuration. • A thermodynamically grounded model of spin magnetization transport valid in new regimes, including high-polarization. • Analysis of the separative quality of
Modeling spin magnetization transport in a spatially varying magnetic field
Energy Technology Data Exchange (ETDEWEB)
Picone, Rico A.R., E-mail: rpicone@stmartin.edu [Department of Mechanical Engineering, University of Washington, Seattle (United States); Garbini, Joseph L. [Department of Mechanical Engineering, University of Washington, Seattle (United States); Sidles, John A. [Department of Orthopædics, University of Washington, Seattle (United States)
2015-01-15
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]). - Highlights: • A framework for modeling the transport of conserved magnetic and thermodynamic quantities in any spatial configuration. • A thermodynamically grounded model of spin magnetization transport valid in new regimes, including high-polarization. • Analysis of the separative quality of
Stochastic dynamical models for ecological regime shifts
DEFF Research Database (Denmark)
Møller, Jan Kloppenborg; Carstensen, Jacob; Madsen, Henrik
the physical and biological knowledge of the system, and nonlinearities introduced here can generate regime shifts or enhance the probability of regime shifts in the case of stochastic models, typically characterized by a threshold value for the known driver. A simple model for light competition between...... definition and stability of regimes become less subtle. Ecological regime shifts and their modeling must be viewed in a probabilistic manner, particularly if such model results are to be used in ecosystem management....
Revisit the spin-FET: Multiple reflection, inelastic scattering, and lateral size effects
Xu, Luting; Li, Xin-Qi; Sun, Qing-feng
2014-01-01
We revisit the spin-injected field effect transistor (spin-FET) by simulating a lattice model based on recursive lattice Green's function approach. In the one-dimensional case and coherent regime, the simulated results reveal noticeable differences from the celebrated Datta-Das model, which motivate thus an improved treatment and lead to analytic and generalized result. The simulation also allows us to address inelastic scattering (using B\\"uttiker's fictitious reservoir approach) and lateral...
Efficient Spin Injection into Semiconductor
International Nuclear Information System (INIS)
Nahid, M.A.I.
2010-06-01
Spintronic research has made tremendous progress nowadays for making future devices obtain extra advantages of low power, and faster and higher scalability compared to present electronic devices. A spintronic device is based on the transport of an electron's spin instead of charge. Efficient spin injection is one of the very important requirements for future spintronic devices. However, the effective spin injection is an exceedingly difficult task. In this paper, the importance of spin injection, basics of spin current and the essential requirements of spin injection are illustrated. The experimental technique of electrical spin injection into semiconductor is also discussed based on the experimental experience. The electrical spin injection can easily be implemented for spin injection into any semiconductor. (author)
International Nuclear Information System (INIS)
Li, C; Lefkidis, G; Huebner, W
2010-01-01
A fully ab initio controlled ultrafast magnetooptical switching mechanism in small magnetic clusters is achieved through exploiting spin-orbit-coupling enabled Λ processes. The idea is that in the magnetic molecules a fast transition between two almost degenerate states with different spins can be triggered by a laser pulse, which leads to an electron excitation from one of the degenerate states to a highly spin-mixed state and a deexcitation to the state of opposite spin. In this paper a CO molecule is attached to one magnetic center of the clusters, which serves as an experimental marker to map the laser-induced spin manipulation to the IR spectrum of CO. The predicted spin-state-dependent CO frequencies can facilitate experimental monitoring of the processes. We show that spin flip in magnetic atoms can be achieved in structurally optimized magnetic clusters in a subpicosecond regime with linearly polarized light.
International Nuclear Information System (INIS)
Yokosawa, A.
1992-01-01
Spin physics activities at medium and high energies became significantly active when polarized targets and polarized beams became accessible for hadron-hadron scattering experiments. My overview of spin physics will be inclined to the study of strong interaction using facilities at Argonne ZGS, Brookhaven AGS (including RHIC), CERN, Fermilab, LAMPF, an SATURNE. In 1960 accelerator physicists had already been convinced that the ZGS could be unique in accelerating a polarized beam; polarized beams were being accelerated through linear accelerators elsewhere at that time. However, there was much concern about going ahead with the construction of a polarized beam because (i) the source intensity was not high enough to accelerate in the accelerator, (ii) the use of the accelerator would be limited to only polarized-beam physics, that is, proton-proton interaction, and (iii) p-p elastic scattering was not the most popular topic in high-energy physics. In fact, within spin physics, π-nucleon physics looked attractive, since the determination of spin and parity of possible πp resonances attracted much attention. To proceed we needed more data beside total cross sections and elastic differential cross sections; measurements of polarization and other parameters were urgently needed. Polarization measurements had traditionally been performed by analyzing the spin of recoil protons. The drawbacks of this technique are: (i) it involves double scattering, resulting in poor accuracy of the data, and (ii) a carbon analyzer can only be used for a limited region of energy
Electron spin resonance in YbRh2Si2: local-moment, unlike-spin and quasiparticle descriptions.
Huber, D L
2012-06-06
Electron spin resonance (ESR) in the Kondo lattice compound YbRh(2)Si(2) has stimulated discussion as to whether the low-field resonance outside the Fermi liquid regime in this material is more appropriately characterized as a local-moment phenomenon or one that requires a Landau quasiparticle interpretation. In earlier work, we outlined a collective mode approach to the ESR that involves only the local 4f moments. In this paper, we extend the collective mode approach to a situation where there are two subsystems of unlike spins: the pseudospins of the ground multiplet of the Yb ions and the spins of the itinerant conduction electrons. We assume a weakly anisotropic exchange interaction between the two subsystems. With suitable approximations our expression for the g-factor also reproduces that found in recent unlike-spin quasiparticle calculations. It is pointed out that the success of the local-moment approach in describing the resonance is due to the fact that the susceptibility of the Yb subsystem dominates that of the conduction electrons with the consequence that the relative shift in the resonance frequency predicted by the unlike-spin models (and absent in the local-moment models) is ≪ 1. The connection with theoretical studies of a two-component model with like spins is also discussed.
Noise in tunneling spin current across coupled quantum spin chains
Aftergood, Joshua; Takei, So
2018-01-01
We theoretically study the spin current and its dc noise generated between two spin-1 /2 spin chains weakly coupled at a single site in the presence of an over-population of spin excitations and a temperature elevation in one subsystem relative to the other, and we compare the corresponding transport quantities across two weakly coupled magnetic insulators hosting magnons. In the spin chain scenario, we find that applying a temperature bias exclusively leads to a vanishing spin current and a concomitant divergence in the spin Fano factor, defined as the spin current noise-to-signal ratio. This divergence is shown to have an exact analogy to the physics of electron scattering between fractional quantum Hall edge states and not to arise in the magnon scenario. We also reveal a suppression in the spin current noise that exclusively arises in the spin chain scenario due to the fermion nature of the spin-1/2 operators. We discuss how the spin Fano factor may be extracted experimentally via the inverse spin Hall effect used extensively in spintronics.
Alberta oil sands royalty regime
International Nuclear Information System (INIS)
Asgarpour, S.
2004-01-01
The long term objective of the Oil Sands Business Unit of Alberta Energy is to pave the way for Alberta's bitumen production to reach 3 million barrels per day by 2020. This presentation described the national government's role in resource development. It was emphasized that since the Crown is the owner of the oil sands resource, it would benefit by providing strategic leadership and by generating a larger royalty base. The oil sands fiscal regime was described with reference to generic royalty, risk sharing, investment, and project economics. Business rule principles were also outlined along with criteria for project expansions. Both upstream and downstream challenges and opportunities were listed. 4 figs
Coherent manipulation of dipolar coupled spins in an anisotropic environment
Baibekov, E. I.; Gafurov, M. R.; Zverev, D. G.; Kurkin, I. N.; Malkin, B. Z.; Barbara, B.
2014-11-01
We study coherent dynamics in a system of dipolar coupled spin qubits diluted in a solid and subjected to a driving microwave field. In the case of rare earth ions, an anisotropic crystal background results in anisotropic g tensor and thus modifies the dipolar coupling. We develop a microscopic theory of spin relaxation in a transient regime for the frequently encountered case of axially symmetric crystal field. The calculated decoherence rate is nonlinear in the Rabi frequency. We show that the direction of a static magnetic field that corresponds to the highest spin g factor is preferable in order to obtain a higher number of coherent qubit operations. The results of calculations are in excellent agreement with our experimental data on Rabi oscillations recorded for a series of CaW O4 crystals with different concentrations of N d3 + ions.
Propagation of nonclassical correlations across a quantum spin chain
Energy Technology Data Exchange (ETDEWEB)
Campbell, S. [Centre for Theoretical Atomic, Molecular and Optical Physics, School of Mathematics and Physics, Queen' s University, Belfast BT7 1NN, Northern Ireland (United Kingdom); Physics Department, University College Cork, Cork (Ireland); Quantum Systems Unit, Okinawa Institute of Science and Technology, Okinawa (Japan); Apollaro, T. J. G. [Dipartimento di Fisica e Astronomia, Universita di Firenze, Via G. Sansone 1, IT-50019 Sesto Fiorentino (Italy); Di Franco, C. [Physics Department, University College Cork, Cork, Republic of Ireland (Ireland); Banchi, L.; Cuccoli, A. [Dipartimento di Fisica e Astronomia, Universita di Firenze, Via G. Sansone 1, IT-50019 Sesto Fiorentino (Italy); INFN Sezione di Firenze, via G.Sansone 1, IT-50019 Sesto Fiorentino (Italy); Vaia, R. [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, IT-50019 Sesto Fiorentino (Italy); Plastina, F. [Dipartimento di Fisica, Universita della Calabria, IT-87036 Arcavacata di Rende (Italy); INFN Gruppo collegato di Cosenza, Universita della Calabria, IT-87036, Arcavacata di Rende (Italy); Paternostro, M. [Centre for Theoretical Atomic, Molecular and Optical Physics, School of Mathematics and Physics, Queen' s University, Belfast BT7 1NN, Northern Ireland (United Kingdom)
2011-11-15
We study the transport of quantum correlations across a chain of interacting spin-1/2 particles. As a quantitative figure of merit, we choose a symmetric version of quantum discord and compare it with the transported entanglement, addressing various operating regimes of the spin medium. Discord turns out to be better transported for a wide range of working points and initial conditions of the system. We relate this behavior to the efficiency of propagation of a single excitation across the spin chain. Moreover, we point out the role played by a magnetic field in the dynamics of discord in the effective channel embodied by the chain. Our analysis can be interestingly extended to transport processes in more complex networks and the study of nonclassical correlations under general quantum channels.
Spin Structures in Magnetic Nanoparticles
DEFF Research Database (Denmark)
Mørup, Steen; Brok, Erik; Frandsen, Cathrine
2013-01-01
Spin structures in nanoparticles of ferrimagnetic materials may deviate locally in a nontrivial way from ideal collinear spin structures. For instance, magnetic frustration due to the reduced numbers of magnetic neighbors at the particle surface or around defects in the interior can lead to spin...... canting and hence a reduced magnetization. Moreover, relaxation between almost degenerate canted spin states can lead to anomalous temperature dependences of the magnetization at low temperatures. In ensembles of nanoparticles, interparticle exchange interactions can also result in spin reorientation....... Here, we give a short review of anomalous spin structures in nanoparticles....
Controllable spin-charge transport in strained graphene nanoribbon devices
Energy Technology Data Exchange (ETDEWEB)
Diniz, Ginetom S., E-mail: ginetom@gmail.com; Guassi, Marcos R. [Institute of Physics, University of Brasília, 70919-970, Brasília-DF (Brazil); Qu, Fanyao [Institute of Physics, University of Brasília, 70919-970, Brasília-DF (Brazil); Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)
2014-09-21
We theoretically investigate the spin-charge transport in two-terminal device of graphene nanoribbons in the presence of a uniform uniaxial strain, spin-orbit coupling, exchange field, and smooth staggered potential. We show that the direction of applied strain can efficiently tune strain-strength induced oscillation of band-gap of armchair graphene nanoribbon (AGNR). It is also found that electronic conductance in both AGNR and zigzag graphene nanoribbon (ZGNR) oscillates with Rashba spin-orbit coupling akin to the Datta-Das field effect transistor. Two distinct strain response regimes of electronic conductance as function of spin-orbit couplings magnitude are found. In the regime of small strain, conductance of ZGNR presents stronger strain dependence along the longitudinal direction of strain. Whereas for high values of strain shows larger effect for the transversal direction. Furthermore, the local density of states shows that depending on the smoothness of the staggered potential, the edge states of AGNR can either emerge or be suppressed. These emerging states can be determined experimentally by either spatially scanning tunneling microscope or by scanning tunneling spectroscopy. Our findings open up new paradigms of manipulation and control of strained graphene based nanostructure for application on novel topological quantum devices.
Integer Quantum Magnon Hall Plateau-Plateau Transition in a Spin Ice Model
Xu, Baolong; Ohtsuki, Tomi; Shindou, Ryuichi
2016-01-01
Low-energy magnon bands in a two-dimensional spin ice model become integer quantum magnon Hall bands. By calculating the localization length and the two-terminal conductance of magnon transport, we show that the magnon bands with disorders undergo a quantum phase transition from an integer quantum magnon Hall regime to a conventional magnon localized regime. Finite size scaling analysis as well as a critical conductance distribution shows that the quantum critical point belongs to the same un...
Rackham, Neil
1995-01-01
True or false? In selling high-value products or services: "closing" increases your chance of success; it is essential to describe the benefits of your product or service to the customer; objection handling is an important skill; and open questions are more effective than closed questions. All false, says Neil Rackham. He and his team studied more than 35,000 sales calls made by 10,000 sales people in 23 countries over 12 years. Their findings revealed that many of the methods developed for selling low-value goods just don't work for major sales. Rackham went on to introduce his SPIN-selling method, where SPIN describes the whole selling process - Situation questions, Problem questions, Implication questions, Need-payoff questions. SPIN-selling provides you with a set of simple and practical techniques which have been tried in many of today's leading companies with dramatic improvements to their sales performance.
Contucci, Pierluigi
2013-01-01
Presenting and developing the theory of spin glasses as a prototype for complex systems, this book is a rigorous and up-to-date introduction to their properties. The book combines a mathematical description with a physical insight of spin glass models. Topics covered include the physical origins of those models and their treatment with replica theory; mathematical properties like correlation inequalities and their use in the thermodynamic limit theory; main exact solutions of the mean field models and their probabilistic structures; and the theory of the structural properties of the spin glass phase such as stochastic stability and the overlap identities. Finally, a detailed account is given of the recent numerical simulation results and properties, including overlap equivalence, ultrametricity and decay of correlations. The book is ideal for mathematical physicists and probabilists working in disordered systems.
Exertional Rhabdomyolysis after Spinning.
Jeong, Youjin; Kweon, Hyuk-Jung; Oh, Eun-Jung; Ahn, Ah-Leum; Choi, Jae-Kyung; Cho, Dong-Yung
2016-11-01
Any strenuous muscular exercise may trigger rhabdomyolysis. We report an episode of clinically manifested exertional rhabdomyolysis due to stationary cycling, commonly known as spinning. Reports of spinning-related rhabdomyolysis are rare in the English literature, and the current case appears to be the first such case reported in South Korea. A previously healthy 21-year-old Asian woman presented with severe thigh pain and reddish-brown urinary discoloration 24-48 hours after attending a spinning class at a local gymnasium. Paired with key laboratory findings, her symptoms were suggestive of rhabdomyolysis. She required hospital admission to sustain renal function through fluid resuscitation therapy and fluid balance monitoring. Because exertional rhabdomyolysis may occur in any unfit but otherwise healthy individual who indulges in stationary cycling, the potential health risks of this activity must be considered.
DEFF Research Database (Denmark)
Jensen, J.; Houmann, Jens Christian Gylden
1975-01-01
The selection rules for the linear couplings between magnons and phonons propagating in the c direction of a simple basal-plane hcp ferromagnet are determined by general symmetry considerations. The acoustic-optical magnon-phonon interactions observed in the heavy-rare-earth metals have been...... explained by Liu as originating from the mixing of the spin states of the conduction electrons due to the spin-orbit coupling. We find that this coupling mechanism introduces interactions which violate the selection rules for a simple ferromagnet. The interactions between the magnons and phonons propagating...... in the c direction of Tb have been studied experimentally by means of inelastic neutron scattering. The magnons are coupled to both the acoustic- and optical-transverse phonons. By studying the behavior of the acoustic-optical coupling, we conclude that it is a spin-mixed-induced coupling as proposed...
Adaptation in Collaborative Governance Regimes
Emerson, Kirk; Gerlak, Andrea K.
2014-10-01
Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.
International Nuclear Information System (INIS)
Schill, Christian
2012-01-01
The COMPASS experiment is a fixed target experiment at the CERN SPS using muon and hadron beams for the investigation of the spin structure of the nucleon and hadron spectroscopy. The main objective of the muon physics program is the study of the spin of the nucleon in terms of its constituents, quarks and gluons. COMPASS has accumulated data during 6 years scattering polarized muons off longitudinally or transversely polarized deuteron ( 6 LiD) or proton (NH 3 ) targets. Results for the gluon polarization are obtained from longitudinal double spin cross section asymmetries using two different channels, open charm production and high transverse momentum hadron pairs, both proceeding through the photon-gluon fusion process. Also, the longitudinal spin structure functions of the proton and the deuteron were measured in parallel as well as the helicity distributions for the three lightest quark flavours. With a transversely polarized target, results were obtained with proton and deuteron targets for the Collins and Sivers asymmetries for charged hadrons as well as for identified kaons and pions. The Collins asymmetry is sensitive to the transverse spin structure of the nucleon, while the Sivers asymmetry reflects correlations between the quark transverse momentum and the nucleon spin. Recently, a new proposal for the COMPASS II experiment was accepted by the CERN SPS which includes two new topics: Exclusive reactions like DVCS and DVMP using the muon beam and a hydrogen target to study generalized parton distributions and Drell-Yan measurements using a pion beam and a polarized NH 3 target to study transverse momentum dependent distributions.
Topologically induced fractional Hall steps in the integer quantum Hall regime of MoS 2
Firoz Islam, SK; Benjamin, Colin
2016-09-01
The quantum magnetotransport properties of a monolayer of molybdenum disulfide are derived using linear response theory. In particular, the effect of topological terms on longitudinal and Hall conductivity is analyzed. The Hall conductivity exhibits fractional steps in the integer quantum Hall regime. Further complete spin and valley polarization of the longitudinal conductivitity is seen in presence of these topological terms. Finally, the Shubnikov-de Hass oscillations are suppressed or enhanced contingent on the sign of these topological terms.
Control of electron spin decoherence in nuclear spin baths
Liu, Ren-Bao
2011-03-01
Nuclear spin baths are a main mechanism of decoherence of spin qubits in solid-state systems, such as quantum dots and nitrogen-vacancy (NV) centers of diamond. The decoherence results from entanglement between the electron and nuclear spins, established by quantum evolution of the bath conditioned on the electron spin state. When the electron spin is flipped, the conditional bath evolution is manipulated. Such manipulation of bath through control of the electron spin not only leads to preservation of the center spin coherence but also demonstrates quantum nature of the bath. In an NV center system, the electron spin effectively interacts with hundreds of 13 C nuclear spins. Under repeated flip control (dynamical decoupling), the electron spin coherence can be preserved for a long time (> 1 ms) . Thereforesomecharacteristicoscillations , duetocouplingtoabonded 13 C nuclear spin pair (a dimer), are imprinted on the electron spin coherence profile, which are very sensitive to the position and orientation of the dimer. With such finger-print oscillations, a dimer can be uniquely identified. Thus, we propose magnetometry with single-nucleus sensitivity and atomic resolution, using NV center spin coherence to identify single molecules. Through the center spin coherence, we could also explore the many-body physics in an interacting spin bath. The information of elementary excitations and many-body correlations can be extracted from the center spin coherence under many-pulse dynamical decoupling control. Another application of the preserved spin coherence is identifying quantumness of a spin bath through the back-action of the electron spin to the bath. We show that the multiple transition of an NV center in a nuclear spin bath can have longer coherence time than the single transition does, when the classical noises due to inhomogeneous broadening is removed by spin echo. This counter-intuitive result unambiguously demonstrates the quantumness of the nuclear spin bath
Measuring the effectiveness of international environmental regimes
Energy Technology Data Exchange (ETDEWEB)
Helm, C.; Sprinz, D.F.
1999-05-01
While past research has emphasized the importance of international regimes for international governance, systematic assessments of regime effects are missing. This article derives a standardized measurement concept for the effectiveness of international environmental regimes by developing an operational rational choice calculus to evaluate actual policy simultaneously against a non-regime counterfactual and a collective optimum. Subsequently, the empirical feasibility of the measurement instrument is demonstrated by way of two international treaties regulating transboundary air pollution in Europe. The results demonstrate that the regimes indeed show positive effects - but fall substantially short of the collective optima. (orig.)
International Nuclear Information System (INIS)
Ma, Minjie; Jalil, Mansoor Bin Abdul; Tan, Seng Gee
2013-01-01
The spin-dependent transport through a diluted magnetic semiconductor quantum dot (QD) which is coupled via magnetic tunnel junctions to two ferromagnetic leads is studied theoretically. A noncollinear system is considered, where the QD is magnetized at an arbitrary angle with respect to the leads’ magnetization. The tunneling current is calculated in the coherent regime via the Keldysh nonequilibrium Green’s function (NEGF) formalism, incorporating the electron–electron interaction in the QD. We provide the first analytical solution for the Green’s function of the noncollinear DMS quantum dot system, solved via the equation of motion method under Hartree–Fock approximation. The transport characteristics (charge and spin currents, and tunnel magnetoresistance (TMR)) are evaluated for different voltage regimes. The interplay between spin-dependent tunneling and single-charge effects results in three distinct voltage regimes in the spin and charge current characteristics. The voltage range in which the QD is singly occupied corresponds to the maximum spin current and greatest sensitivity of the spin current to the QD magnetization orientation. The QD device also shows transport features suitable for sensor applications, i.e., a large charge current coupled with a high TMR ratio. - Highlights: ► The spin polarized transport through a diluted magnetic quantum dot is studied. ► The model is based on the Green’s function and the equation of motion method.► The charge and spin currents and tunnel magnetoresistance (TMR) are investigated. ► The system is suitable for current-induced spin-transfer torque application. ► A large tunneling current and a high TMR are possible for sensor application.
International Nuclear Information System (INIS)
Bland, L.C.
2003-01-01
The physics goals that will be addressed by colliding polarized protons at the Relativistic Heavy Ion Collider (RHIC) are described. The RHIC spin program provides a new generation of experiments that will unfold the quark, anti-quark and gluon contributions to the proton's spin. In addition to these longer term goals, this paper describes what was learned from the first polarized proton collisions at √(s)=200 GeV. These collisions took place in a five-week run during the second year of RHIC operation
CONFERENCE: Muon spin rotation
Energy Technology Data Exchange (ETDEWEB)
Karlsson, Erik
1986-11-15
An international physics conference centred on muons without a word about leptons, weak interactions, EMC effects, exotic decay modes or any other standard high energy physics jargon. Could such a thing even have been imagined ten years ago? Yet about 120 physicists and chemists from 16 nations gathered at the end of June in Uppsala (Sweden) for their fourth meeting on Muon Spin Rotation, Relaxation and Resonance, without worrying about the muon as an elementary particle. This reflects how the experimental techniques based on the muon spin interactions have reached maturity and are widely recognized by condensed matter physicists and specialized chemists as useful tools.
DEFF Research Database (Denmark)
Jensen, J.; Houmann, Jens Christian Gylden; Bjerrum Møller, Hans
1975-01-01
with the symmetry, we deduce the dispersion relation for the spin waves in a basal-plane ferromagnet. This phenomenological spin-wave theory accounts for the observed behavior of the magnon energies in Tb. The two q⃗-dependent Bogoliubov components of the magnon energies are derived from the experimental results......, which are corrected for the effect of the direct coupling between the magnons and the phonons, and for the field dependence of the relative magnetization at finite temperatures. A large q⃗-dependent difference between the two energy components is observed, showing that the anisotropy of the two...
International Nuclear Information System (INIS)
Ramachandran, R.
1994-09-01
The object of this brief review is to reconcile different points of view on how the spin of proton is made up from its constituents. On the basis of naive quark model with flavour symmetry such as isospin or SU(3) one finds a static description. On the contrary the local SU(3) colour symmetry gives a dynamical view. Both these views are contrasted and the role of U(1) axial anomaly and the ambiguity for the measurable spin content is discussed. (author). 16 refs, 1 fig
Linda Tedrow; Wendel J. Hann
2015-01-01
The Fire Regime Condition Class (FRCC) is a composite departure measure that compares current vegetation structure and fire regime to historical reference conditions. FRCC is computed as the average of: 1) Vegetation departure (VDEP) and 2) Regime (frequency and severity) departure (RDEP). In addition to the FRCC rating, the Vegetation Condition Class (VCC) and Regime...
Spin magneto-transport in a Rashba-Dresselhaus quantum channel with single and double finger gates
Tang, Chi-Shung; Keng, Jia-An; Abdullah, Nzar Rauf; Gudmundsson, Vidar
2017-05-01
We address spin-resolved electronic transport properties in a Rashba-Dresselhaus quantum channel in the presence of an in-plane magnetic field. The strong Rashba-Dresselhaus effect induces an asymmetric spin-splitting energy spectrum with a spin-orbit-Zeeman gap. This asymmetric fact in energy spectrum may result in various quantum dynamic features in conductance due to the presence of finger gates. This asymmetric spin-splitting energy spectrum results in a bound state in continuum for electrons within ultralow energy regime with binding energies in order of 10-1 meV.
Spin transfer torque with spin diffusion in magnetic tunnel junctions
Manchon, Aurelien; Matsumoto, R.; Jaffres, H.; Grollier, J.
2012-01-01
in the metallic layers. We show that spin diffusion mixes the transverse spin current components and dramatically modifies the bias dependence of the effective spin transfer torque. This leads to a significant linear bias dependence of the out-of-plane torque
GHRH excess and blockade in X-LAG syndrome.
Daly, Adrian F; Lysy, Philippe A; Desfilles, Céline; Rostomyan, Liliya; Mohamed, Amira; Caberg, Jean-Hubert; Raverot, Veronique; Castermans, Emilie; Marbaix, Etienne; Maiter, Dominique; Brunelle, Chloe; Trivellin, Giampaolo; Stratakis, Constantine A; Bours, Vincent; Raftopoulos, Christian; Beauloye, Veronique; Barlier, Anne; Beckers, Albert
2016-03-01
X-linked acrogigantism (X-LAG) syndrome is a newly described form of inheritable pituitary gigantism that begins in early childhood and is usually associated with markedly elevated GH and prolactin secretion by mixed pituitary adenomas/hyperplasia. Microduplications on chromosome Xq26.3 including the GPR101 gene cause X-LAG syndrome. In individual cases random GHRH levels have been elevated. We performed a series of hormonal profiles in a young female sporadic X-LAG syndrome patient and subsequently undertook in vitro studies of primary pituitary tumor culture following neurosurgical resection. The patient demonstrated consistently elevated circulating GHRH levels throughout preoperative testing, which was accompanied by marked GH and prolactin hypersecretion; GH demonstrated a paradoxical increase following TRH administration. In vitro, the pituitary cells showed baseline GH and prolactin release that was further stimulated by GHRH administration. Co-incubation with GHRH and the GHRH receptor antagonist, acetyl-(d-Arg(2))-GHRH (1-29) amide, blocked the GHRH-induced GH stimulation; the GHRH receptor antagonist alone significantly reduced GH release. Pasireotide, but not octreotide, inhibited GH secretion. A ghrelin receptor agonist and an inverse agonist led to modest, statistically significant increases and decreases in GH secretion, respectively. GHRH hypersecretion can accompany the pituitary abnormalities seen in X-LAG syndrome. These data suggest that the pathology of X-LAG syndrome may include hypothalamic dysregulation of GHRH secretion, which is in keeping with localization of GPR101 in the hypothalamus. Therapeutic blockade of GHRH secretion could represent a way to target the marked hormonal hypersecretion and overgrowth that characterizes X-LAG syndrome. © 2016 Society for Endocrinology.
Blockade of mast cell activation reduces cutaneous scar formation.
Directory of Open Access Journals (Sweden)
Lin Chen
Full Text Available Damage to the skin initiates a cascade of well-orchestrated events that ultimately leads to repair of the wound. The inflammatory response is key to wound healing both through preventing infection and stimulating proliferation and remodeling of the skin. Mast cells within the tissue are one of the first immune cells to respond to trauma, and upon activation they release pro-inflammatory molecules to initiate recruitment of leukocytes and promote a vascular response in the tissue. Additionally, mast cells stimulate collagen synthesis by dermal fibroblasts, suggesting they may also influence scar formation. To examine the contribution of mast cells in tissue repair, we determined the effects the mast cell inhibitor, disodium cromoglycate (DSCG, on several parameters of dermal repair including, inflammation, re-epithelialization, collagen fiber organization, collagen ultrastructure, scar width and wound breaking strength. Mice treated with DSCG had significantly reduced levels of the inflammatory cytokines IL-1α, IL-1β, and CXCL1. Although DSCG treatment reduced the production of inflammatory mediators, the rate of re-epithelialization was not affected. Compared to control, inhibition of mast cell activity caused a significant decrease in scar width along with accelerated collagen re-organization. Despite the reduced scar width, DSCG treatment did not affect the breaking strength of the healed tissue. Tryptase β1 exclusively produced by mast cells was found to increase significantly in the course of wound healing. However, DSCG treatment did not change its level in the wounds. These results indicate that blockade of mast cell activation reduces scar formation and inflammation without further weakening the healed wound.
Beta-adrenergic blockade for the treatment of hyperthyroidism.
Geffner, D L; Hershman, J M
1992-07-01
To review the clinical and biochemical effects of beta-adrenergic blocking drugs on hyperthyroidism. Studies published since 1972 were identified through a computerized search of MEDLINE and extensive searching of the bibliographies of the articles identified. Based on an understanding of the differences in beta-blocker metabolism in euthyroid and hyperthyroid patients, we reviewed the differences in pharmacokinetics and metabolic and clinical outcomes during their use in hyperthyroidism, as reported in the articles reviewed. beta Blockers have been used to modify the severity of the hyperadrenergic symptoms of hyperthyroidism for the past 20 years. The clinical efficacy of these agents is affected by hyperthyroid-induced alterations in their gastrointestinal absorption, hepatic metabolism, and renal excretion. The mechanisms whereby these clinical changes are effected is unknown. The agents differ in their beta 1 cardioselectivity, membrane-stabilizing activity, intrinsic sympathomimetic activity, and lipid solubility. They do not appear to alter synthesis or secretion of thyroid hormone by the thyroid gland. Their effects on thyroxine metabolism are contradictory. Decreased thyroxine to triiodothyronine conversion is caused by some, but not all, beta blockers, and this appears to correlate with membrane-stabilizing activity. There does not appear to be any alteration in catecholamine sensitivity during beta-adrenergic blockade. The principal mechanism of action of beta blockers in hyperthyroidism is to antagonize beta-receptor-mediated effects of catecholamines. beta Blockers are effective in treating hypermetabolic symptoms in a variety of hyperthyroid states. Used alone, they offer significant symptomatic relief. They are also useful adjuvants to antithyroid medications, surgery, and radioactive iodide treatment in patients with Graves' disease and toxic nodular goiters.
Survey of external cephalic version for breech presentation and neuraxial blockade use.
Weiniger, Carolyn F; Sultan, Pervez; Dunn, Ashley; Carvalho, Brendan
2016-11-01
Neuraxial blockade may increase external cephalic version (ECV) success rates. This survey aimed to assess the frequency and characteristics of neuraxial blockade used to facilitate ECV. We surveyed Society for Obstetric Anesthesia and Perinatology members regarding ECV practice using a 15-item survey developed by 3 obstetric anesthesiologists and tested for face validity. The survey was e-mailed in January 2015 and again in February 2015 to the 1056 Society of Obstetric Anesthesiology and Perinatology members. We present descriptive statistics of responses. Our survey response rate was 322 of 1056 (30.5%). Neuraxial blockade was used for ECV always by 18 (5.6%), often by 52 (16.1%), sometimes by 98 (30.4%), rarely by 78 (24.2%), and never by 46 (14.3%) of respondents. An anesthetic sensory block target was selected by 141 (43.8%) respondents, and analgesic by 102 (31.7%) respondents. Epidural drug doses ranged widely, including sufentanil 5-25 μg; lidocaine 1% or 2% 10-20 mL, bupivacaine 0.0625% to 0.5% 6-15 mL, and ropivacaine 0.2% 20 mL. Intrathecal bupivacaine was used by 182 (56.5%) respondents; the most frequent doses were 2.5 mg used by 24 (7.5%), 7.5 mg used by 35 (10.9%), and 12 mg used by 30 (9.3%). Neuraxial blockade is not universally offered to facilitate ECV, and there is wide variability in neuraxial blockade techniques, in drugs and doses administered, and in the sensory blockade (anesthetic or analgesic) targeted. Future studies need to evaluate and remove barriers to allow for more widespread use of neuraxial blockade for pain relief and to optimize ECV success rates. Copyright © 2016 Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Souhami, R.L.; Patel, H.M.; Ryman, B.E.
1981-01-01
The blood clearance and tissue distribution of liposomes have been studied in mice subjected to reticuloendothelial blockade with dextran sulphate or carbon. The liposomes have been labelled in the lipid membranes with [ 3 H]-cholesterol, [ 14 C]phosphatidylcholine and/or 99 sup(m)Tc and the content with [ 14 C]inulin. Reticuloendothelial blockade has been shown to slow the rate of clearance of neutral, positively and negatively charged liposomes and of both small unilamellar vesicles and large multilamellar vesicles. In normal animals, the liver uptake accounted for only 20-55% of the total injected radioactivity, the amount varying with the charge and size of the liposomes. Following blockade, the liver uptake of charged and neutral multilamellar liposomes was depressed. This was also true for negatively charged small unilamellar vesicles. The degree of depression of hepatic uptake was between 25-50%, which contrasts with the 80-90% reduction in uptake of a wholly phagocytosed particle (sheep red cells). This difference suggets that mechanisms other than Kupffer cell phagocytosis are also responsible for the normal uptake of liposomes into the liver. In the case of neutral and positively charged small unilamellar vesicles, delayed clearance due to blockade was not associated with depressed hepatic uptake. The site of action of blockading agents for these preparations is not clear. With all preparations of liposomes, blockade produced a slight and variable increase in uptake in the lung and spleen. The alteration of distribution of liposomes by reticuloendothelial blockade is therefore not great and the value of the technique in modifying the tissue distribution of substances within liposomes may be limited. (orig.)
Transverse Spin Physics: Recent Developments
International Nuclear Information System (INIS)
Yuan, Feng
2008-01-01
Transverse-spin physics has been very active and rapidly developing in the last few years. In this talk, I will briefly summarize recent theoretical developments, focusing on the associated QCD dynamics in transverse spin physics
International Nuclear Information System (INIS)
Faris, W.G.
1981-01-01
Dankel has shown how to incorporate spin into stochastic mechanics. The resulting non-local hidden variable theory gives an appealing picture of spin correlation experiments in which Bell's inequality is violated. (orig.)
Higher-spin currents in the Gross-Neveu model at 1/n{sup 2}
Energy Technology Data Exchange (ETDEWEB)
Manashov, A.N. [Institut für Theoretische Physik, Universität Hamburg,Hamburg, D-22761 (Germany); Institut für Theoretische Physik, Universität Regensburg,Regensburg, D-93040 (Germany); Skvortsov, E.D. [Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians University Munich, Theresienstr. 37, Munich, D-80333 (Germany); Lebedev Institute of Physics,Leninsky ave. 53, Moscow, 119991 (Russian Federation)
2017-01-30
We calculate the anomalous dimensions of higher-spin currents, both singlet and non-singlet, in the Gross-Neveu model at the 1/n{sup 2} order. It was conjectured that in the critical regime this model is dual to a higher-spin gauge theory on AdS{sub 4}. The AdS/CFT correspondence predicts that the masses of higher-spin fields correspond to the scaling dimensions of the singlet currents in the Gross-Neveu model.
Fire regime in Mediterranean ecosystem
Biondi, Guido; Casula, Paolo; D'Andrea, Mirko; Fiorucci, Paolo
2010-05-01
The analysis of burnt areas time series in Mediterranean regions suggests that ecosystems characterising this area consist primarily of species highly vulnerable to the fire but highly resilient, as characterized by a significant regenerative capacity after the fire spreading. In a few years the area burnt may once again be covered by the same vegetation present before the fire. Similarly, Mediterranean conifer forests, which often refers to plantations made in order to reforest the areas most severely degraded with high erosion risk, regenerate from seed after the fire resulting in high resilience to the fire as well. Only rarely, and usually with negligible damages, fire affects the areas covered by climax species in relation with altitude and soil types (i.e, quercus, fagus, abies). On the basis of these results, this paper shows how the simple Drossel-Schwabl forest fire model is able to reproduce the forest fire regime in terms of number of fires and burned area, describing whit good accuracy the actual fire perimeters. The original Drossel-Schwabl model has been slightly modified in this work by introducing two parameters (probability of propagation and regrowth) specific for each different class of vegetation cover. Using model selection methods based on AIC, the model with the optimal number of classes with different fire behaviour was selected. Two different case studies are presented in this work: Regione Liguria and Regione Sardegna (Italy). Both regions are situated in the center of the Mediterranean and are characterized by a high number of fires and burned area. However, the two regions have very different fire regimes. Sardinia is affected by the fire phenomenon only in summer whilst Liguria is affected by fires also in winter, with higher number of fires and larger burned area. In addition, the two region are very different in vegetation cover. The presence of Mediterranean conifers, (Pinus Pinaster, Pinus Nigra, Pinus halepensis) is quite spread in
Large quantum rings in the ν > 1 quantum Hall regime
International Nuclear Information System (INIS)
Raesaenen, E; Aichinger, M
2009-01-01
We study computationally the ground-state properties of large quantum rings in the filling-factor ν>1 quantum Hall regime. We show that the arrangement of electrons into different Landau levels leads to clear signatures in the total energies as a function of the magnetic field. In this context, we discuss possible approximations for the filling factor ν in the system. We are able to characterize integer-ν states in quantum rings in an analogy with conventional quantum Hall droplets. We also find a partially spin-polarized state between ν = 2 and 3. Despite the specific topology of a quantum ring, this state is strikingly reminiscent of the recently found ν = 5/2 state in a quantum dot.
Large quantum rings in the ν > 1 quantum Hall regime.
Räsänen, E; Aichinger, M
2009-01-14
We study computationally the ground-state properties of large quantum rings in the filling-factor ν>1 quantum Hall regime. We show that the arrangement of electrons into different Landau levels leads to clear signatures in the total energies as a function of the magnetic field. In this context, we discuss possible approximations for the filling factor ν in the system. We are able to characterize integer-ν states in quantum rings in an analogy with conventional quantum Hall droplets. We also find a partially spin-polarized state between ν = 2 and 3. Despite the specific topology of a quantum ring, this state is strikingly reminiscent of the recently found ν = 5/2 state in a quantum dot.
Muonium spin exchange in spin-polarized media: Spin-flip and -nonflip collisions
International Nuclear Information System (INIS)
Senba, M.
1994-01-01
The transverse relaxation of the muon spin in muonium due to electron spin exchange with a polarized spin-1/2 medium is investigated. Stochastic calculations, which assume that spin exchange is a Poisson process, are carried out for the case where the electron spin polarization of the medium is on the same axis as the applied field. Two precession signals of muonium observed in intermediate fields (B>30 G) are shown to have different relaxation rates which depend on the polarization of the medium. Furthermore, the precession frequencies are shifted by an amount which depends on the spin-nonflip rate. From the two relaxation rates and the frequency shift in intermediate fields, one can determine (i) the encounter rate of muonium and the paramagnetic species, (ii) the polarization of the medium, and most importantly (iii) the quantum-mechanical phase shift (and its sign) associated with the potential energy difference between electron singlet and triplet encounters. Effects of spin-nonflip collisions on spin dynamics are discussed for non-Poisson as well as Poisson processes. In unpolarized media, the time evolution of the muon spin in muonium is not influenced by spin-nonflip collisions, if the collision process is Poissonian. This seemingly obvious statement is not true anymore in non-Poissonian processes, i.e., it is necessary to specify both spin-flip and spin-nonflip rates to fully characterize spin dynamics
Theory of spin-dependent tunnelling in magnetic junctions
International Nuclear Information System (INIS)
Mathon, J.
2002-01-01
Rigorous theory of the tunnelling magnetoresistance (TMR) based on the real-space Kubo formula and fully realistic tight-binding bands fitted to an ab initio band structure is described. It is first applied to calculate the TMR of two Co electrodes separated by a vacuum gap. The calculated TMR ratio reaches ∼65% in the tunnelling regime but can be as high as 280% in the metallic regime when the vacuum gap is of the order of the Co interatomic distance (abrupt domain wall). It is also shown that the spin polarization P of the tunnelling current is negative in the metallic regime but becomes positive P∼35% in the tunnelling regime. Calculation of the TMR of an epitaxial Fe/MgO/Fe(001) junction is also described. The calculated optimistic TMR ratio is in excess of 1000% for an MgO barrier of ∼20 atomic planes and the spin polarization of the tunnelling current is positive for all MgO thicknesses. It is also found that spin-dependent tunnelling in an Fe/MgO/Fe(001) junction is not entirely determined by states at the Γ point (k parallel = 0) even for MgO thicknesses as large as ∼20 atomic planes. Finally, it is demonstrated that the TMR ratio calculated from the Kubo formula remains non-zero when one of the Co electrodes is covered with a copper layer. It is shown that non-zero TMR is due to quantum well states in the Cu layer which do not participate in transport. Since these only occur in the down-spin channel, their loss from transport creates a spin asymmetry of electrons tunnelling from a Cu interlayer, i.e. non-zero TMR. Numerical modelling is used to show that diffuse scattering from a random distribution of impurities in the barrier may cause quantum well states to evolve into propagating states, in which case the spin asymmetry of the non-magnetic layer is lost and with it the TMR. (author)
Antiferromagnetic spin-orbitronics
Manchon, Aurelien; Saidaoui, Hamed Ben Mohamed; Ghosh, Sumit
2015-01-01
Antiferromagnets have long remained an intriguing and exotic state of matter, whose application has been restricted to enabling interfacial exchange bias in metallic and tunneling spin-valves [1]. Their role in the expanding field of applied spintronics has been mostly passive and the in-depth investigation of their basic properties mostly considered from a fundamental perspective.
Antiferromagnetic spin-orbitronics
Manchon, Aurelien
2015-05-01
Antiferromagnets have long remained an intriguing and exotic state of matter, whose application has been restricted to enabling interfacial exchange bias in metallic and tunneling spin-valves [1]. Their role in the expanding field of applied spintronics has been mostly passive and the in-depth investigation of their basic properties mostly considered from a fundamental perspective.
Brookhaven: Spin result underlined
Energy Technology Data Exchange (ETDEWEB)
Anon.
1990-09-15
A recent experiment looking at violent proton-proton elastic scattering confirms, with high precision, earlier data which puzzled many theorists. Most pictures of strong interactions based on perturbative quark-gluon field theory (Quantum Chromodynamics, QCD) suggested that spin effects should disappear with energy and as the collisions become more violent.
Indian Academy of Sciences (India)
IAS Admin
ments have shown that in some cases the nuclear spin systems may be held in special configurations called .... these methods have been commercialized, and used for clinical trials, in which hyperpolarized NMR is used to .... symmetric under exchange, meaning that exchanging the two nuclei leaves the state unchanged.
International Nuclear Information System (INIS)
1981-11-01
This booklet gives examples of 'nuclear spin off', from research programmes carried out for the UKAEA, under the following headings; non destructive testing; tribology; environmental protection; flow measurement; material sciences; mechanical engineering; marine services; biochemical technology; electronic instrumentation. (U.K.)
International Nuclear Information System (INIS)
Suzuki, T.; Sagawa, H.
2000-01-01
Complete text of publication follows. Spin and isospin modes in nuclei are investigated. We discuss some of the following topics. 1. Spin-dipole excitations in 12 C and 16 O are studied (1). Effects of tensor and spin-orbit interactions on the distribution of the strengths are investigated, and neutral current neutrino scattering cross sections in 16 O are obtained for heavy-flavor neutrinos from the supernovae. 2. Gamow-Teller (GT) and spin-dipole (SD) modes in 208 Bi are investigated. Quenching and fragmentation of the GT strength are discussed (2). SD excitations and electric dipole (E1) transitions between the GT and SD states are studied (3). Calculated E1 strengths are compared with the sum rule values obtained within the 1p-1h and 1p-1h + 2p-2h configuration spaces. 3. Coulomb displacement energy (CDE) of the IAS of 14 Be is calculated, and the effects of the halo on the CDE and the configuration of the halo state are investigated. 4. Spreading width of IAS and isospin dependence of the width are investigated (4). Our formula for the width explains very well the observed isospin dependence (5). (author)
International Nuclear Information System (INIS)
Johnson, Peter D.
1997-01-01
Spin-polarized photoemission has developed into a versatile tool for the study of surface and thin film magnetism. In this review, we examine the methodology of the technique and its application to a number of different problems, including both valence band and core level studies. After a detailed review of spin-polarization measurement techniques and the related experimental requirements we consider in detail studies of the bulk properties both above and below the Curie temperature. This section also includes a discussion of observations relating to unique metastable phases obtained via epitaxial growth. The application of the technique to the study of surfaces, both clean and adsorbate covered, is reviewed. The report then examines, in detail, studies of the spin-polarized electronic structure of thin films and the related interfacial magnetism. Finally, observations of spin-polarized quantum well states in non-magnetic thin films are discussed with particular reference to their mediation of the oscillatory exchange coupling in related magnetic multilayers. (author)
International Nuclear Information System (INIS)
Althoff, K.H.
1989-01-01
In 1987 the new Bonn stretcher accelerator ELSA came into operation. In this paper a short description of the accelerator and the three experimental facilities PHOENICS, ELAN and SAPHIR is given. The determination of spin observables is one of the main subjects of the experimental program. Some experiments are discussed in more detail
Spin physics in semiconductors
Dyakonov, Mikhail I
2008-01-01
This book describes beautiful optical and transport phenomena related to the electron and nuclear spins in semiconductors with emphasis on a clear presentation of the physics involved. Recent results on quantum wells and quantum dots are reviewed. The book is intended for students and researchers in the fields of semiconductor physics and nanoelectronics.
Brookhaven: Spin result underlined
International Nuclear Information System (INIS)
Anon.
1990-01-01
A recent experiment looking at violent proton-proton elastic scattering confirms, with high precision, earlier data which puzzled many theorists. Most pictures of strong interactions based on perturbative quark-gluon field theory (Quantum Chromodynamics, QCD) suggested that spin effects should disappear with energy and as the collisions become more violent
Spin polarizability of hyperons
Indian Academy of Sciences (India)
K B VIJAYA KUMAR. Department of Physics, Mangalore University, Mangalagangothri 574 199, India. E-mail: kbvijayakumar@yahoo.com. DOI: 10.1007/s12043-014-0869-4; ePublication: 4 November 2014. Abstract. We review the recent progress of the theoretical understanding of spin polarizabilities of the hyperon in the ...
International Nuclear Information System (INIS)
Bramson, B.D.
1978-01-01
An isolated system in general relativity makes a transition between stationary states. It is shown that the spin vectors of the system, long before and long after the emission of radiation, are supertranslation invariant and, hence, independent of the choice of Minkowski observation space. (author)
Neoclassical transport in ERS regime
International Nuclear Information System (INIS)
Lin, Z.; Tang, W.; Lee, W.W.
1996-01-01
The core ion thermal conductivity has been observed to fall below the standard neoclassical level in recent TFTR reversed magnetic shear discharges. Due to the combination of high central q and small local inverse aspect ratio, the ion poloidal gyroradius can be larger than the minor radius and comparable to the pressure gradient scale length in this ERS regime. It is then expected that finite orbit width effects play a key role in modifying the standard picture of neoclassical transport. Specifically, both the trapped particle fraction and the banana orbit width axe reduced by the finite minor radius and possibly by the pressure-gradient-driven radial electric field. In addition, the steep pressure gradient can generate neoclassical poloidal flows which, in turn, could reduce the particle and heat transports. Results from analytic estimates as well as those from full toroidal gyrokinetic neoclassical simulations will be presented
Unitary Housing Regimes in Transition
DEFF Research Database (Denmark)
Bengtsson, Bo; Jensen, Lotte
2013-01-01
Path dependence is strong in housing institutions and policy. In both Denmark and Sweden, today’s universal and ‘unitary’ (Kemeny) housing regimes can be traced back to institutions that were introduced fifty years back in history or more. Recently, universal and unitary housing systems...... in Scandinavia, and elsewhere, are under challenge from strong political and economic forces. These challenges can be summarized as economic cutbacks, privatization and Europeanization. Although both the Danish and the Swedish housing system are universal and unitary in character, they differ considerably...... in institutional detail. Both systems have corporatist features, however in Denmark public housing is based on local tenant democracy and control, and in Sweden on companies owned and controlled by the municipalities, combined with a centralized system of rent negotiations. In the paper the present challenges...
Reassessing the nuclear liability regime
International Nuclear Information System (INIS)
Havinh Phuong
1985-01-01
The nuclear liability regime was thoroughly reviewed by nuclear plant operators, officials of regulatory authorities, and legal and insurance experts at the Symposium on Nuclear Third Party Liability and Insurance, held in September 1984 in Munich, Federal Republic of Germany. The symposium highlighted specific areas where adjustments or improvements would be needed in order to cope with practical problems encountered or emerging issues. By focusing on questions of legitimate concern to the public, it also sought to promote confidence in a compensation system for public protection that is in many ways unique. Topics addressed included the following: greater harmonization of the compensation amounts for nuclear damage established in different countries and in territorial scope; the concept of unlimited liability; the time limitation for compensation claims; the problem of proving causation; the concept of nuclear damage; and insurance coverage
International Nuclear Information System (INIS)
Avdonin, A.; Skupiński, P.; Grasza, K.
2016-01-01
A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO. - Highlights: • Expressions for Hall coefficient and mobility for hopping conductivity are derived. • Theoretical result is compared with experimental curves measured on ZnO. • Simultaneous action of free and hopping conduction channels is considered. • Non-linearity of hopping Hall coefficient is predicted.
Energy Technology Data Exchange (ETDEWEB)
Avdonin, A., E-mail: avdonin@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Skupiński, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Grasza, K. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01-919 Warszawa (Poland)
2016-02-15
A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO. - Highlights: • Expressions for Hall coefficient and mobility for hopping conductivity are derived. • Theoretical result is compared with experimental curves measured on ZnO. • Simultaneous action of free and hopping conduction channels is considered. • Non-linearity of hopping Hall coefficient is predicted.
Influence of spin correlations in the transport properties of a double quantum dot system
Costa Ribeiro, Laercio; Hamad, Ignacio; Chiappe, Guillermo; Victoriano Anda, Enrique
2013-03-01
In this work we study the influence of spin correlations in the transport properties of a system consisting of two quantum dots (QDs) with high Coulomb interaction U which are interconnected through a chain of N non-interacting sites and individually coupled to two metallic leads. Using both the finite U slave boson mean field approach (FUSBMFA) and the Logarithmic-discretization-embedded-cluster approximation (LDECA) we studied the system in different regions of the parameter space for which we calculate many physical quantities, namely local density of states, conductance, total spin, spin correlations, in addition to the renormalization parameters associated with the FUSBMFA. The results reveled a very rich physical scenario which is manifested by at least two different Kondo regimes, the well-known spin s = 1/2 and some other type of Kondo effect which appears as a result of the coupling between the QDs and the non-interacting central sites. We also consider the possibility of accessing some kind of Kondo box effect due to the discrete nature of the central chain and study how this regime is affected by the magnetic interaction between the local spins of the QD's and by the interaction between these spins and the spins of the conduction electros in the leads.
One dimensionalization in the spin-1 Heisenberg model on the anisotropic triangular lattice
Gonzalez, M. G.; Ghioldi, E. A.; Gazza, C. J.; Manuel, L. O.; Trumper, A. E.
2017-11-01
We investigate the effect of dimensional crossover in the ground state of the antiferromagnetic spin-1 Heisenberg model on the anisotropic triangular lattice that interpolates between the regime of weakly coupled Haldane chains (J'≪J ) and the isotropic triangular lattice (J'=J ). We use the density-matrix renormalization group (DMRG) and Schwinger boson theory performed at the Gaussian correction level above the saddle-point solution. Our DMRG results show an abrupt transition between decoupled spin chains and the spirally ordered regime at (J'/J) c˜0.42 , signaled by the sudden closing of the spin gap. Coming from the magnetically ordered side, the computation of the spin stiffness within Schwinger boson theory predicts the instability of the spiral magnetic order toward a magnetically disordered phase with one-dimensional features at (J'/J) c˜0.43 . The agreement of these complementary methods, along with the strong difference found between the intra- and the interchain DMRG short spin-spin correlations for sufficiently large values of the interchain coupling, suggests that the interplay between the quantum fluctuations and the dimensional crossover effects gives rise to the one-dimensionalization phenomenon in this frustrated spin-1 Hamiltonian.
Unique spin-polarized transmission effects in a QD ring structure
Hedin, Eric; Joe, Yong
2010-10-01
Spintronics is an emerging field in which the spin of the electron is used for switching purposes and to communicate information. In order to obtain spin-polarized electron transmission, the Zeeman effect is employed to produce spin-split energy states in quantum dots which are embedded in the arms of a mesoscopic Aharonov-Bohm (AB) ring heterostructure. The Zeeman splitting of the QD energy levels can be induced by a parallel magnetic field, or by a perpendicular field which also produces AB-effects. The combination of these effects on the transmission resonances of the structure is studied analytically and several parameter regimes are identified which produce a high degree of spin-polarized output. Contour and line plots of the weighted spin polarization as a function of electron energy and magnetic field are presented to visualize the degree of spin-polarization. Taking advantage of these unique parameter regimes shows the potential promise of such devices for producing spin-polarized currents.
Optically tunable spin-exchange energy at donor:acceptor interfaces in organic solar cells
International Nuclear Information System (INIS)
Li, Mingxing; Wang, Hongfeng; He, Lei; Zang, Huidong; Xu, Hengxing; Hu, Bin
2014-01-01
Spin-exchange energy is a critical parameter in controlling spin-dependent optic, electronic, and magnetic properties in organic materials. This article reports optically tunable spin-exchange energy by studying the line-shape characteristics in magnetic field effect of photocurrent developed from intermolecular charge-transfer states based on donor:acceptor (P3HT:PCBM) system. Specifically, we divide magnetic field effect of photocurrent into hyperfine (at low field 10 mT) regimes. We observe that increasing photoexcitation intensity can lead to a significant line-shape narrowing in magnetic field effect of photocurrent occurring at the spin-exchange regime. We analyze that the line-shape characteristics is essentially determined by the changing rate of magnetic field-dependent singlet/triplet ratio when a magnetic field perturbs the singlet-triplet transition through spin mixing. Based on our analysis, the line-shape narrowing results indicate that the spin-exchange energy at D:A interfaces can be optically changed by changing photoexcitation intensity through the interactions between intermolecular charge-transfer states. Therefore, our experimental results demonstrate an optical approach to change the spin-exchange energy through the interactions between intermolecular charge-transfer states at donor:acceptor interface in organic materials.
Spin Injection in Indium Arsenide
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Mark eJohnson
2015-08-01
Full Text Available In a two dimensional electron system (2DES, coherent spin precession of a ballistic spin polarized current, controlled by the Rashba spin orbit interaction, is a remarkable phenomenon that’s been observed only recently. Datta and Das predicted this precession would manifest as an oscillation in the source-drain conductance of the channel in a spin-injected field effect transistor (Spin FET. The indium arsenide single quantum well materials system has proven to be ideal for experimental confirmation. The 2DES carriers have high mobility, low sheet resistance, and high spin orbit interaction. Techniques for electrical injection and detection of spin polarized carriers were developed over the last two decades. Adapting the proposed Spin FET to the Johnson-Silsbee nonlocal geometry was a key to the first experimental demonstration of gate voltage controlled coherent spin precession. More recently, a new technique measured the oscillation as a function of channel length. This article gives an overview of the experimental phenomenology of the spin injection technique. We then review details of the application of the technique to InAs single quantum well (SQW devices. The effective magnetic field associated with Rashba spin-orbit coupling is described, and a heuristic model of coherent spin precession is presented. The two successful empirical demonstrations of the Datta Das conductance oscillation are then described and discussed.
International Nuclear Information System (INIS)
Prescott, C.Y.
1991-07-01
Spin physics is playing an increasingly important role in high energy experiments and theory. This review looks at selected topics in high energy spin physics that were discussed at the 9th International Symposium on High Energy Spin Physics at Bonn in September 1990
Mechanical generation of spin current
Directory of Open Access Journals (Sweden)
Mamoru eMatsuo
2015-07-01
Full Text Available We focus the recent results on spin-current generation from mechanical motion such as rigid rotation and elastic deformations. Spin transport theory in accelerating frames is constructed by using the low energy expansion of the generally covariant Dirac equation. Related issues on spin-manipulation by mechanical rotation are also discussed.
Spin Transport in Semiconductor heterostructures
International Nuclear Information System (INIS)
Marinescu, Domnita Catalina
2011-01-01
The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.
Spin Seebeck effect in a metal-single-molecule-magnet-metal junction
Directory of Open Access Journals (Sweden)
Pengbin Niu
2018-01-01
Full Text Available We investigate the nonlinear regime of temperature-driven spin-related currents through a single molecular magnet (SMM, which is connected with two metal electrodes. Under a large spin approximation, the SMM is simplified to a natural two-channel model possessing spin-opposite configuration and Coulomb interaction. We find that in temperature-driven case the system can generate spin-polarized currents. More interestingly, at electron-hole symmetry point, the competition of the two channels induces a temperature-driven pure spin current. This device demonstrates that temperature-driven SMM junction shows some results different from the usual quantum dot model, which may be useful in the future design of thermal-based molecular spintronic devices.
Spin Seebeck effect in a metal-single-molecule-magnet-metal junction
Niu, Pengbin; Liu, Lixiang; Su, Xiaoqiang; Dong, Lijuan; Luo, Hong-Gang
2018-01-01
We investigate the nonlinear regime of temperature-driven spin-related currents through a single molecular magnet (SMM), which is connected with two metal electrodes. Under a large spin approximation, the SMM is simplified to a natural two-channel model possessing spin-opposite configuration and Coulomb interaction. We find that in temperature-driven case the system can generate spin-polarized currents. More interestingly, at electron-hole symmetry point, the competition of the two channels induces a temperature-driven pure spin current. This device demonstrates that temperature-driven SMM junction shows some results different from the usual quantum dot model, which may be useful in the future design of thermal-based molecular spintronic devices.
Thermal conductivity of magnetic insulators with strong spin-orbit coupling
Stamokostas, Georgios; Lapas, Panteleimon; Fiete, Gregory A.
We study the influence of spin-orbit coupling on the thermal conductivity of various types of magnetic insulators. In the absence of spin-orbit coupling and orbital-degeneracy, the strong-coupling limit of Hubbard interactions at half filling can often be adequately described in terms of a pure spin Hamiltonian of the Heisenberg form. However, in the presence of spin-orbit coupling the resulting exchange interaction can become highly anisotropic. The effect of the atomic spin-orbit coupling, taken into account through the effect of magnon-phonon interactions and the magnetic order and excitations, on the lattice thermal conductivity of various insulating magnetic systems is studied. We focus on the regime of low temperatures where the dominant source of scattering is two-magnon scattering to one-phonon processes. The thermal current is calculated within the Boltzmann transport theory. We are grateful for financial support from NSF Grant DMR-0955778.
Electron spin control and torsional optomechanics of an optically levitated nanodiamond in vacuum
Li, Tongcang; Hoang, Thai; Ahn, Jonghoon; Bang, Jaehoon
Electron spins of diamond nitrogen-vacancy (NV) centers are important quantum resources for nanoscale sensing and quantum information. Combining such NV spin systems with levitated optomechanical resonators will provide a hybrid quantum system for many novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centers in vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centers, indicating potential applications of NV centers in oxygen gas sensing. For spin-optomechanics, it is important to control the orientation of the nanodiamond and NV centers in a magnetic field. Recently, we have observed the angular trapping and torsional vibration of a levitated nanodiamond, which paves the way towards levitated torsional optomechanics in the quantum regime. NSF 1555035-PHY.
Response functions of cold neutron matter: density, spin and current fluctuations
Energy Technology Data Exchange (ETDEWEB)
Keller, Jochen; Sedrakian, Armen [Institut fuer Theoretische Physik, Goethe-Universitaet, Frankfurt am Main (Germany)
2014-07-01
We study the response of a single-component pair-correlated baryonic Fermi-liquid to density, spin, and their current perturbations. A complete set of response functions is calculated in the low-temperature regime. We derive the spectral functions of collective excitations associated with the density, density-current, spin, and spin-current perturbations. The dispersion relations of density and spin fluctuations are determined and it is shown that the density fluctuations lead to exciton-like undamped bound states, whereas the spin excitations correspond to diffusive modes above the pair-breaking threshold. The contribution of the collective pair-breaking modes to the specific heat of neutron matter at subnuclear densities is computed and is shown to be comparable to that of the degenerate electron gas at not too low temperatures.
Dynamical Negative Differential Resistance in Antiferromagnetically Coupled Few-Atom Spin Chains
Rolf-Pissarczyk, Steffen; Yan, Shichao; Malavolti, Luigi; Burgess, Jacob A. J.; McMurtrie, Gregory; Loth, Sebastian
2017-11-01
We present the appearance of negative differential resistance (NDR) in spin-dependent electron transport through a few-atom spin chain. A chain of three antiferromagnetically coupled Fe atoms (Fe trimer) was positioned on a Cu2 N /Cu (100 ) surface and contacted with the spin-polarized tip of a scanning tunneling microscope, thus coupling the Fe trimer to one nonmagnetic and one magnetic lead. Pronounced NDR appears at the low bias of 7 mV, where inelastic electron tunneling dynamically locks the atomic spin in a long-lived excited state. This causes a rapid increase of the magnetoresistance between the spin-polarized tip and Fe trimer and quenches elastic tunneling. By varying the coupling strength between the tip and Fe trimer, we find that in this transport regime the dynamic locking of the Fe trimer competes with magnetic exchange interaction, which statically forces the Fe trimer into its high-magnetoresistance state and removes the NDR.
An ALC study of spin exchange of a muoniated cosurfactant in lamellar phase surfactant dispersions
Energy Technology Data Exchange (ETDEWEB)
Dilger, H. [Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany)]. E-mail: h.dilger@ipc.uni-stuttgart.de; Martyniak, A. [Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany); Scheuermann, R. [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Vujosevic' , D. [Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany); Tucker, I.M. [Unilever Research and Development, Port Sunlight, Wirral, CH63 3JW (United Kingdom); McKenzie, I. [Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany); Roduner, E. [Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany)
2006-03-31
The Avoided Level Crossing muon spin resonance (ALC-{mu}SR) technique has been used to measure the Heisenberg spin exchange rate between the Mu adducts of 2-phenylethanol (PEA) and Ni{sup 2+} in a concentrated lamellar phase dispersion composed of the dichain cationic surfactant 2,3-diheptadecyl ester ethoxypropyl-1,1,1-trimethylammonium chloride (DHTAC) and water. Ni{sup 2+} is only dissolved in the aqueous phase, therefore information about the local environment of the PEA can be extracted from the spin exchange rate. In the high-temperature (L{sub {alpha}}) phase the spin exchange is very slow, revealing that PEA preferentially resides in the headgroup regime of the surfactant. In the low-temperature (L{sub {beta}}) phase the spin exchange is diffusion controlled, because the PEA is expelled into the water region between the bilayers.
An ALC study of spin exchange of a muoniated cosurfactant in lamellar phase surfactant dispersions
International Nuclear Information System (INIS)
Dilger, H.; Martyniak, A.; Scheuermann, R.; Vujosevic', D.; Tucker, I.M.; McKenzie, I.; Roduner, E.
2006-01-01
The Avoided Level Crossing muon spin resonance (ALC-μSR) technique has been used to measure the Heisenberg spin exchange rate between the Mu adducts of 2-phenylethanol (PEA) and Ni 2+ in a concentrated lamellar phase dispersion composed of the dichain cationic surfactant 2,3-diheptadecyl ester ethoxypropyl-1,1,1-trimethylammonium chloride (DHTAC) and water. Ni 2+ is only dissolved in the aqueous phase, therefore information about the local environment of the PEA can be extracted from the spin exchange rate. In the high-temperature (L α ) phase the spin exchange is very slow, revealing that PEA preferentially resides in the headgroup regime of the surfactant. In the low-temperature (L β ) phase the spin exchange is diffusion controlled, because the PEA is expelled into the water region between the bilayers
Spinning Them Off: Entrepreneuring Practices in Corporate Spin-Offs
Directory of Open Access Journals (Sweden)
Katja Maria Hydle
2016-01-01
Full Text Available This paper focuses on the practices between parent and child firms in corporate spinoffs. We uncover the enacted aspects of knowledge, called knowing, through theories from seven cases of incumbent-backed spin-offs and find that the management of the parent firms are highly involved in the spin-offs. The practices associated with spinning off are solving problems, involving multidisciplinary expertise and entrepreneuring management at the parent firm. We contribute to the spin-off literature by discussing the knowledge required for successfully spinning off child firms and to practice theory by empirically uncovering the practical understanding involved in the origin and perpetuation of an organization.
de Léséleuc, Sylvain; Weber, Sebastian; Lienhard, Vincent; Barredo, Daniel; Büchler, Hans Peter; Lahaye, Thierry; Browaeys, Antoine
2018-03-01
We study a system of atoms that are laser driven to n D3 /2 Rydberg states and assess how accurately they can be mapped onto spin-1 /2 particles for the quantum simulation of anisotropic Ising magnets. Using nonperturbative calculations of the pair potentials between two atoms in the presence of electric and magnetic fields, we emphasize the importance of a careful selection of experimental parameters in order to maintain the Rydberg blockade and avoid excitation of unwanted Rydberg states. We benchmark these theoretical observations against experiments using two atoms. Finally, we show that in these conditions, the experimental dynamics observed after a quench is in good agreement with numerical simulations of spin-1 /2 Ising models in systems with up to 49 spins, for which numerical simulations become intractable.
Spin-orbit induced electronic spin separation in semiconductor nanostructures.
Kohda, Makoto; Nakamura, Shuji; Nishihara, Yoshitaka; Kobayashi, Kensuke; Ono, Teruo; Ohe, Jun-ichiro; Tokura, Yasuhiro; Mineno, Taiki; Nitta, Junsaku
2012-01-01
The demonstration of quantized spin splitting by Stern and Gerlach is one of the most important experiments in modern physics. Their discovery was the precursor of recent developments in spin-based technologies. Although electrical spin separation of charged particles is fundamental in spintronics, in non-uniform magnetic fields it has been difficult to separate the spin states of charged particles due to the Lorentz force, as well as to the insufficient and uncontrollable field gradients. Here we demonstrate electronic spin separation in a semiconductor nanostructure. To avoid the Lorentz force, which is inevitably induced when an external magnetic field is applied, we utilized the effective non-uniform magnetic field which originates from the Rashba spin-orbit interaction in an InGaAs-based heterostructure. Using a Stern-Gerlach-inspired mechanism, together with a quantum point contact, we obtained field gradients of 10(8) T m(-1) resulting in a highly polarized spin current.
Spin Relaxation and Manipulation in Spin-orbit Qubits
Borhani, Massoud; Hu, Xuedong
2012-02-01
We derive a generalized form of the Electric Dipole Spin Resonance (EDSR) Hamiltonian in the presence of the spin-orbit interaction for single spins in an elliptic quantum dot (QD) subject to an arbitrary (in both direction and magnitude) applied magnetic field. We predict a nonlinear behavior of the Rabi frequency as a function of the magnetic field for sufficiently large Zeeman energies, and present a microscopic expression for the anisotropic electron g-tensor. Similarly, an EDSR Hamiltonian is devised for two spins confined in a double quantum dot (DQD). Finally, we calculate two-electron-spin relaxation rates due to phonon emission, for both in-plane and perpendicular magnetic fields. Our results have immediate applications to current EDSR experiments on nanowire QDs, g-factor optimization of confined carriers, and spin decay measurements in DQD spin-orbit qubits.
Excitation of coherent propagating spin waves by pure spin currents.
Demidov, Vladislav E; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O
2016-01-28
Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics.
Directory of Open Access Journals (Sweden)
Rogerio Carlos Sanfelice Nunes
2016-08-01
Full Text Available ABSTRACT OBJECTIVE: Sciatic pain secondary to lumbar disc herniation is a complex condition that is often highly limiting. The causes of pain in disc herniation are multifactorial. Two physiopathological mechanisms are involved in discogenic pain: mechanical deformation of nerve roots and a biochemical inflammatory component resulting from contact between the intervertebral disc and neural tissue, by way of the nucleus pulposus. The aim of this study was to evaluate the efficacy and safety of epidural blockade as therapy for bulging lumbar disc herniation. METHODS: A clinical study was conducted based on a retrospective and prospective survey. The blockade consisted of interlaminar puncture and bolus drug delivery. The number of procedures varied according to the clinical response, as determined through weekly evaluations and then 30, 90, and 180 days after the final session. A total of 124 patients who received one to five blockades were evaluated. RESULTS: The success rate (defining success as a reduction in sciatic pain of at least 80% was 75.8%. CONCLUSION: The results demonstrated the therapeutic action of epidural blockade over the short term, i.e. in cases of acute pain, thus showing that intense and excruciating sciatic pain can be relieved through this technique. Because of the multifactorial genesis of sciatica and the difficulties encountered by healthcare professionals in treating this condition, epidural blockade can become part of therapeutic arsenal available. This procedure is situated between conservative treatment with an eminently clinical focus and surgical approaches.
Profile of sugammadex for reversal of neuromuscular blockade in the elderly: current perspectives.
Carron, Michele; Bertoncello, Francesco; Ieppariello, Giovanna
2018-01-01
The number of elderly patients is increasing worldwide. This will have a significant impact on the practice of anesthesia in future decades. Anesthesiologists must provide care for an increasing number of elderly patients, who have an elevated risk of perioperative morbidity and mortality. Complications related to postoperative residual neuromuscular blockade, such as muscle weakness, airway obstruction, hypoxemia, atelectasis, pneumonia, and acute respiratory failure, are more frequent in older than in younger patients. Therefore, neuromuscular blockade in the elderly should be carefully monitored and completely reversed before awakening patients at the end of anesthesia. Acetylcholinesterase inhibitors are traditionally used for reversal of neuromuscular blockade. Although the risk of residual neuromuscular blockade is reduced by reversal with neostigmine, it continues to complicate the postoperative course. Sugammadex represents an innovative approach to reversal of neuromuscular blockade induced by aminosteroid neuromuscular-blocking agents, particularly rocuronium, with useful applications in clinical practice. However, aging is associated with certain changes in the pharmacokinetics of sugammadex, and to date there has been no thorough evaluation of the use of sugammadex in elderly patients. The aim of this review was to perform an analysis of the use of sugammadex in older adults based on the current literature. Major issues surrounding the physiologic and pharmacologic effects of aging in elderly patients and how these may impact the routine use of sugammadex in elderly patients are discussed.
McCaffrey, Gwen; Thompson, Michelle L; Majuta, Lisa; Fealk, Michelle N; Chartier, Stephane; Longo, Geraldine; Mantyh, Patrick W
2014-12-01
Studies in animals and humans show that blockade of nerve growth factor (NGF) attenuates both malignant and nonmalignant skeletal pain. While reduction of pain is important, a largely unanswered question is what other benefits NGF blockade might confer in patients with bone cancer. Using a mouse graft model of bone sarcoma, we demonstrate that early treatment with an NGF antibody reduced tumor-induced bone destruction, delayed time to bone fracture, and increased the use of the tumor-bearing limb. Consistent with animal studies in osteoarthritis and head and neck cancer, early blockade of NGF reduced weight loss in mice with bone sarcoma. In terms of the extent and time course of pain relief, NGF blockade also reduced pain 40% to 70%, depending on the metric assessed. Importantly, this analgesic effect was maintained even in animals with late-stage disease. Our results suggest that NGF blockade immediately upon detection of tumor metastasis to bone may help preserve the integrity and use, delay the time to tumor-induced bone fracture, and maintain body weight. ©2014 American Association for Cancer Research.
GOLLUM: a next-generation simulation tool for electron, thermal and spin transport
International Nuclear Information System (INIS)
Ferrer, J; García-Suárez, V M; Rodríguez-Ferradás, R; Lambert, C J; Manrique, D Zs; Visontai, D; Grace, I; Bailey, S W D; Gillemot, K; Sadeghi, Hatef; Algharagholy, L A; Oroszlany, L
2014-01-01
We have developed an efficient simulation tool ‘GOLLUM’ for the computation of electrical, spin and thermal transport characteristics of complex nanostructures. The new multi-scale, multi-terminal tool addresses a number of new challenges and functionalities that have emerged in nanoscale-scale transport over the past few years. To illustrate the flexibility and functionality of GOLLUM, we present a range of demonstrator calculations encompassing charge, spin and thermal transport, corrections to density functional theory such as local density approximation +U (LDA+U) and spectral adjustments, transport in the presence of non-collinear magnetism, the quantum Hall effect, Kondo and Coulomb blockade effects, finite-voltage transport, multi-terminal transport, quantum pumps, superconducting nanostructures, environmental effects, and pulling curves and conductance histograms for mechanically-controlled break-junction experiments. (paper)
Electron spin resonance for the detection of long-range spin nematic order
Furuya, Shunsuke C.; Momoi, Tsutomu
2018-03-01
Spin nematic phase is a quantum magnetic phase characterized by a quadrupolar order parameter. Since the quadrupole operators are directly coupled to neither the magnetic field nor the neutron, currently, it is an important issue to develop a method for detecting the long-range spin nematic order. In this paper, we propose that electron spin resonance (ESR) measurements enable us to detect the long-range spin nematic order. We show that the frequency of the paramagnetic resonance peak in the ESR spectrum is shifted by the ferroquadrupolar order parameter together with other quantities. The ferroquadrupolar order parameter is extractable from the angular dependence of the frequency shift. In contrast, the antiferroquadrupolar order parameter is usually invisible in the frequency shift. Instead, the long-range antiferroquadrupolar order yields a characteristic resonance peak in the ESR spectrum, which we call a magnon-pair resonance peak. This resonance corresponds to the excitation of the bound magnon pair at the wave vector k =0 . Reflecting the condensation of bound magnon pairs, the field dependence of the magnon-pair resonance frequency shows a singular upturn at the saturation field. Moreover, the intensity of the magnon-pair resonance peak shows a characteristic angular dependence and it vanishes when the magnetic field is parallel to one of the axes that diagonalize the weak anisotropic interactions. We confirm these general properties of the magnon-pair resonance peak in the spin nematic phase by studying an S =1 bilinear-biquadratic model on the square lattice in the linear flavor-wave approximation. In addition, we argue applications to the S =1/2 frustrated ferromagnets and also the S =1/2 orthogonal dimer spin system SrCu2(BO3)2, both of which are candidate materials of spin nematics. Our theory for the antiferroquadrupolar ordered phase is consistent with many features of the magnon-pair resonance peak experimentally observed in the low
Spin dynamics and Kondo physics in optical tweezers
Lin, Yiheng; Lester, Brian J.; Brown, Mark O.; Kaufman, Adam M.; Long, Junling; Ball, Randall J.; Isaev, Leonid; Wall, Michael L.; Rey, Ana Maria; Regal, Cindy A.
2016-05-01
We propose to use optical tweezers as a toolset for direct observation of the interplay between quantum statistics, kinetic energy and interactions, and thus implement minimum instances of the Kondo lattice model in systems with few bosonic rubidium atoms. By taking advantage of strong local exchange interactions, our ability to tune the spin-dependent potential shifts between the two wells and complete control over spin and motional degrees of freedom, we design an adiabatic tunneling scheme that efficiently creates a spin-singlet state in one well starting from two initially separated atoms (one atom per tweezer) in opposite spin state. For three atoms in a double-well, two localized in the lowest vibrational mode of each tweezer and one atom in an excited delocalized state, we plan to use similar techniques and observe resonant transfer of two-atom singlet-triplet states between the wells in the regime when the exchange coupling exceeds the mobile atom hopping. Moreover, we argue that such three-atom double-tweezers could potentially be used for quantum computation by encoding logical qubits in collective spin and motional degrees of freedom. Current address: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.