WorldWideScience

Sample records for agents electron spin

  1. Spin electronics

    CERN Document Server

    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...

  2. Electronic structure of spin systems

    Energy Technology Data Exchange (ETDEWEB)

    Saha-Dasgupta, Tanusri

    2016-04-15

    Highlights: • We review the theoretical modeling of quantum spin systems. • We apply the Nth order muffin-tin orbital electronic structure method. • The method shows the importance of chemistry in the modeling. • CuTe{sub 2}O{sub 5} showed a 2-dimensional coupled spin dimer behavior. • Ti substituted Zn{sub 2}VO(PO{sub 4}){sub 2} showed spin gap behavior. - Abstract: Low-dimensional quantum spin systems, characterized by their unconventional magnetic properties, have attracted much attention. Synthesis of materials appropriate to various classes within these systems has made this field very attractive and a site of many activities. The experimental results like susceptibility data are fitted with the theoretical model to derive the underlying spin Hamiltonian. However, often such a fitting procedure which requires correct guess of the assumed spin Hamiltonian leads to ambiguity in deciding the representative model. In this review article, we will describe how electronic structure calculation within the framework of Nth order muffin-tin orbital (NMTO) based Wannier function technique can be utilized to identify the underlying spin model for a large number of such compounds. We will show examples from compounds belonging to vanadates and cuprates.

  3. Electron spin separation without magnetic field.

    Science.gov (United States)

    Pawłowski, J; Szumniak, P; Skubis, A; Bednarek, S

    2014-08-27

    A nanodevice capable of separating spins of two electrons confined in a quantum dot formed in a gated semiconductor nanowire is proposed. Two electrons confined initially in a single quantum dot in the singlet state are transformed into the system of two electrons confined in two spatially separated quantum dots with opposite spins. In order to separate the electrons' spins we exploit transitions between the singlet and the triplet state, which are induced by resonantly oscillating Rashba spin-orbit coupling strength. The proposed device is all electrically controlled and the electron spin separation can be realized within tens of picoseconds. The results are supported by solving numerically the quasi-one-dimensional time-dependent Schroedinger equation for two electrons, where the electron-electron correlations are taken into account in the exact manner.

  4. Theory of electron spin echoes in solids

    CERN Document Server

    Asadullina, N Y; Asadullin, Y Y

    2002-01-01

    We propose modified Bloch equations (MBEs) with specific power-dependent relaxation and dispersion parameters characteristic for two-pulse excitation and when the magnetic dipole-dipole interactions in the electron spin system control the dephasing. We discriminate between the 'active' (excited by both pulses) and 'passive' (excited by the second pulse only) spins: it is shown that the 'active' spins participate in a new effect, an active spin frequency modulation effect giving rise to the power-dependent dispersion and multiple electron spin echoes (ESEs); the 'passive' spins contribute to the power-dependent relaxation. The MBEs are solved and a general expression for the two-pulse ESEs is obtained. Detailed numerical analysis of this expression gives results in good quantitative agreement with the recent experiments on the two-pulse ESEs at conventional low applied fields. The developed theory is applied also to high field ESEs, which are promising for future investigations. On the basis of published resul...

  5. Quantum Computing with an Electron Spin Ensemble

    DEFF Research Database (Denmark)

    Wesenberg, Janus; Ardavan, A.; Briggs, G.A.D.;

    2009-01-01

    We propose to encode a register of quantum bits in different collective electron spin wave excitations in a solid medium. Coupling to spins is enabled by locating them in the vicinity of a superconducting transmission line cavity, and making use of their strong collective coupling to the quantized...

  6. Theoretical foundations of electron spin resonance

    CERN Document Server

    Harriman, John E

    2013-01-01

    Theoretical Foundations of Electron Spin Resonance deals with the theoretical approach to electron paramagnetic resonance. The book discusses electron spin resonance in applications related to polyatomic, probably organic, free radicals in condensed phases. The book also focuses on essentially static phenomena, that is, the description and determination of stationary-state energy levels. The author reviews the Dirac theory of the electron in which a four-component wave function is responsible for the behavior of the electron. The author then connects this theory with the nonrelativistic wave f

  7. Spin Decomposition of Electron in QED

    CERN Document Server

    Ji, Xiangdong; Yuan, Feng; Zhang, Jian-Hui; Zhao, Yong

    2015-01-01

    We perform a systematic study on the spin decomposition of an electron in QED at one-loop order. It is found that the electron orbital angular momentum defined in Jaffe-Manohar and Ji spin sum rules agrees with each other, and the so-called potential angular momentum vanishes at this order. The calculations are performed in both dimensional regularization and Pauli-Villars regularization for the ultraviolet divergences, and they lead to consistent results. We further investigate the calculations in terms of light-front wave functions, and find a missing contribution from the instantaneous interaction in light-front quantization. This clarifies the confusing issues raised recently in the literature on the spin decomposition of an electron, and will help to consolidate the spin physics program for nucleons in QCD.

  8. Suppression of electron spin-echo envelope modulation peaks in double quantum coherence electron spin resonance.

    Science.gov (United States)

    Bonora, Marco; Becker, James; Saxena, Sunil

    2004-10-01

    We show the use of the observer blind spots effect for the elimination of electron spin-echo envelope modulation (ESEEM) peaks in double quantum coherence (DQC) electron spin resonance (ESR). The suppression of ESEEM facilitates the routine and unambiguous extraction of distances from DQC-ESR spectra. This is also the first demonstration of this challenging methodology on commercial instrumentation.

  9. Quantum computing with an electron spin ensemble.

    Science.gov (United States)

    Wesenberg, J H; Ardavan, A; Briggs, G A D; Morton, J J L; Schoelkopf, R J; Schuster, D I; Mølmer, K

    2009-08-14

    We propose to encode a register of quantum bits in different collective electron spin wave excitations in a solid medium. Coupling to spins is enabled by locating them in the vicinity of a superconducting transmission line cavity, and making use of their strong collective coupling to the quantized radiation field. The transformation between different spin waves is achieved by applying gradient magnetic fields across the sample, while a Cooper pair box, resonant with the cavity field, may be used to carry out one- and two-qubit gate operations.

  10. Spin dependent electron transport in nanostructures

    Science.gov (United States)

    Yanik, Ahmet Ali

    2007-12-01

    Spin-electronic devices, exploiting the spin degree of freedom of the current carrying particles, are currently a topic of great interest. In parallel with experimental developments, theoretical studies in this field have been mainly focused on the coherent transport regime characteristics of these devices. However, spin dephasing processes are still a fundamental concern [1-6]. The Landauer transmission formalism has been the widely used method in the coherent transport regime [7]. Recently this formalism has been adapted to incorporate spin scattering processes by introducing random disorder directly into the conducting medium and subsequently solving the disordered transport problem over a large ensemble of disorder distributions [8-10]. Although proposed to be a way of incorporating spin scattering processes, what this approach basically offers is an averaged way of adding random coherent scatterings (similar to the scatterings from boundaries) into the transport problem. Certainly such a treatment of spin-dephasing processes misses the incoherent and inelastic nature of the scattering processes. As a result, a rigorous way of treating the spin scattering processes is still needed [10-12]. The objective of this thesis is to present a quantum transport model based on non-equilibrium Green's function (NEGF) formalism providing a unified approach to incorporate spin scattering processes using generalized interaction Hamiltonians. Here, the NEGF formalism is presented for both coherent and incoherent transport regimes without going into derivational details. Subsequently, spin scattering operators are derived for the specific case of electron-impurity exchange interactions and the model is applied to clarify the experimental measurements [5]. Device characteristics of magnetic tunnel junctions (MTJs) with embedded magnetic impurity layers are studied as a function of tunnel junction thicknesses and barrier heights for varying impurity concentrations in comparison

  11. Spin fluctuation theory of itinerant electron magnetism

    CERN Document Server

    Takahashi, Yoshinori

    2013-01-01

    This volume shows how collective magnetic excitations determine most of  the magnetic properties of itinerant electron magnets. Previous theories were mainly restricted to the Curie-Weiss law temperature dependence of magnetic susceptibilities. Based on the spin amplitude conservation idea including the zero-point fluctuation amplitude, this book shows that the entire temperature and magnetic field dependence of magnetization curves, even in the ground state, is determined by the effect of spin fluctuations. It also shows that the theoretical consequences are largely in agreement with many experimental observations. The readers will therefore gain a new comprehensive perspective of their unified understanding of itinerant electron magnetism.

  12. Theory of electron spin echoes in solids

    Energy Technology Data Exchange (ETDEWEB)

    Asadullina, N.Ya.; Asadullin, T.Ya.; Asadullin, Ya.Ya. [Kazan State Technical University, Department of General Physics, Karl Marx Street 10, Kazan (Russian Federation)

    2002-11-04

    We propose modified Bloch equations (MBEs) with specific power-dependent relaxation and dispersion parameters characteristic for two-pulse excitation and when the magnetic dipole-dipole interactions in the electron spin system control the dephasing. We discriminate between the 'active' (excited by both pulses) and 'passive' (excited by the second pulse only) spins: it is shown that the 'active' spins participate in a new effect, an active spin frequency modulation effect giving rise to the power-dependent dispersion and multiple electron spin echoes (ESEs); the 'passive' spins contribute to the power-dependent relaxation. The MBEs are solved and a general expression for the two-pulse ESEs is obtained. Detailed numerical analysis of this expression gives results in good quantitative agreement with the recent experiments on the two-pulse ESEs at conventional low applied fields. The developed theory is applied also to high field ESEs, which are promising for future investigations. On the basis of published results it is deduced that the instantaneous diffusion mechanism is ineffective.

  13. Undergraduate Electron-Spin-Resonance Experiment.

    Science.gov (United States)

    Willis, James S.

    1980-01-01

    Describes the basic procedures for use of an electron-spin resonance spectrometer and potassium azide (KN3) in an experiment which extends from the phase of sample preparation (crystal growth, sample mounting, and orientation) through data taking to the stages of calculation and theoretical explanation. (Author/DS)

  14. Quantum Computation and Spin Electronics

    OpenAIRE

    DiVincenzo, David P.; Burkard, Guido; Loss, Daniel; Sukhorukov, Eugene V.

    1999-01-01

    In this chapter we explore the connection between mesoscopic physics and quantum computing. After giving a bibliography providing a general introduction to the subject of quantum information processing, we review the various approaches that are being considered for the experimental implementation of quantum computing and quantum communication in atomic physics, quantum optics, nuclear magnetic resonance, superconductivity, and, especially, normal-electron solid state physics. We discuss five ...

  15. Electron-Spin Resonance in Boron Carbide

    Science.gov (United States)

    Wood, Charles; Venturini, Eugene L.; Azevedo, Larry J.; Emin, David

    1987-01-01

    Samples exhibit Curie-law behavior in temperature range of 2 to 100 K. Technical paper presents studies of electron-spin resonance of samples of hot pressed B9 C, B15 C2, B13 C2, and B4 C. Boron carbide ceramics are refractory solids with high melting temperatures, low thermal conductives, and extreme hardnesses. They show promise as semiconductors at high temperatures and have unusually large figures of merit for use in thermoelectric generators.

  16. Electron Doping a Kagome Spin Liquid

    Science.gov (United States)

    Kelly, Z. A.; Gallagher, M. J.; McQueen, T. M.

    2016-10-01

    Herbertsmithite, ZnCu3 (OH )6Cl2 , is a two-dimensional kagome lattice realization of a spin liquid, with evidence for fractionalized excitations and a gapped ground state. Such a quantum spin liquid has been proposed to underlie high-temperature superconductivity and is predicted to produce a wealth of new states, including a Dirac metal at 1 /3 electron doping. Here, we report the topochemical synthesis of electron-doped ZnLix Cu3 (OH )6Cl2 from x =0 to x =1.8 (3 /5 per Cu2 + ). Contrary to expectations, no metallicity or superconductivity is induced. Instead, we find a systematic suppression of magnetic behavior across the phase diagram. Our results demonstrate that significant theoretical work is needed to understand and predict the role of doping in magnetically frustrated narrow band insulators, particularly the interplay between local structural disorder and tendency toward electron localization, and pave the way for future studies of doped spin liquids.

  17. Observation of coherent oscillations in a single electron spin.

    Science.gov (United States)

    Jelezko, F; Gaebel, T; Popa, I; Gruber, A; Wrachtrup, J

    2004-02-20

    Rabi nutations and Hahn echo modulation of a single electron spin in a single defect center have been observed. The coherent evolution of the spin quantum state is followed via optical detection of the spin state. Coherence times up to several microseconds at room temperature have been measured. Optical excitation of the spin states leads to decoherence. Quantum beats between electron spin transitions in a single spin Hahn echo experiment are observed. A closer analysis reveals that beats also result from the hyperfine coupling of the electron spin to a single 14N nuclear spin. The results are analyzed in terms of a density matrix approach of an electron spin interacting with two oscillating fields.

  18. Spin current and polarization in impure two-dimensional electron systems with spin-orbit coupling.

    Science.gov (United States)

    Mishchenko, E G; Shytov, A V; Halperin, B I

    2004-11-26

    We derive the transport equations for two-dimensional electron systems with Rashba spin-orbit interaction and short-range spin-independent disorder. In the limit of slow spatial variations, we obtain coupled diffusion equations for the electron density and spin. Using these equations we calculate electric-field induced spin accumulation and spin current in a finite-size sample for an arbitrary ratio between spin-orbit energy splitting Delta and elastic scattering rate tau(-1). We demonstrate that the spin-Hall conductivity vanishes in an infinite system independent of this ratio.

  19. Electron spin coherence and effect of spin polarization on electron relaxation dynamics in GaAs

    Science.gov (United States)

    Teng, Lihua; Wang, Xia; Ge, Weikun; Lai, Tianshu

    2011-09-01

    Time-resolved circularly and linearly polarized pump-probe spectroscopy is used to study the evolution of the electron spin coherence and electron relaxation dynamics in bulk GaAs at 9.6 K. In particular, their dependence on photon energy (or electron excess energy) is carefully investigated. The absorption quantum beats which are observed in circularly polarized pump-probe spectroscopy are obtained, reflecting the dephasing of the electron spin coherence. A circularly dichromatic pump-probe model is developed with both the spin-polarization-dependent band-filling and band-gap renormalization effects being taken into account. The model is used to simulate the differential transmission spectra for the collinearly polarized, co-helicity circularly polarized and cross-helicity circularly polarized pump-probe configurations, respectively. It is found that the model simulates well the features of the absorption quantum beats for a spin-dependent thermalized distribution of the photocreated carriers by a circularly polarized pump pulse, such as the variation of the oscillatory amplitude and phase reversal of the absorption quantum beats with photon energy increase. The simulation is in good agreement with our experimental results and reveals the effect of spin polarization on electron relaxation dynamics.

  20. Evolution of electron spin polarization in semiconductor heterostructures

    Science.gov (United States)

    Pershin, Yuriy; Privman, Vladimir

    2004-03-01

    Last years theoretical and experimental investigations of electron spin-related effects in semiconductor heterostructures have received much consideration because of idea to create a semiconductor device based on the manipulation of electron spin. High degree of electron spin polarization is of crucial importance in operation of spintronic devices. We study possibilities to increase electron spin relaxation time by different means in systems where the D'yakonov-Perel' relaxation mechanism is dominant. Specifically, we show that the electron spin relaxation time in a two-dimensional electron gas with an antidote lattice increases exponentially with antidote radius for certain values of parameters. In another approach, we propose to use electron spin polarization having non-homogeneous direction of spin polarization vector in operation of a spintronic device. It is found that that the electron spin relaxation time essentially depends on the initial spin polarization distribution. This effect has its origin in the coherent spin precession of electrons diffusing in the same direction. We predict a long spin relaxation time of a novel structure: a spin coherence standing wave and discuss its experimental realization.

  1. Methodological considerations of electron spin resonance spin trapping techniques for measuring reactive oxygen species generated from metal oxide nanomaterials

    Science.gov (United States)

    Jeong, Min Sook; Yu, Kyeong-Nam; Chung, Hyun Hoon; Park, Soo Jin; Lee, Ah Young; Song, Mi Ryoung; Cho, Myung-Haing; Kim, Jun Sung

    2016-05-01

    Qualitative and quantitative analyses of reactive oxygen species (ROS) generated on the surfaces of nanomaterials are important for understanding their toxicity and toxic mechanisms, which are in turn beneficial for manufacturing more biocompatible nanomaterials in many industrial fields. Electron spin resonance (ESR) is a useful tool for detecting ROS formation. However, using this technique without first considering the physicochemical properties of nanomaterials and proper conditions of the spin trapping agent (such as incubation time) may lead to misinterpretation of the resulting data. In this report, we suggest methodological considerations for ESR as pertains to magnetism, sample preparation and proper incubation time with spin trapping agents. Based on our results, each spin trapping agent should be given the proper incubation time. For nanomaterials having magnetic properties, it is useful to remove these nanomaterials via centrifugation after reacting with spin trapping agents. Sonication for the purpose of sample dispersion and sample light exposure should be controlled during ESR in order to enhance the obtained ROS signal. This report will allow researchers to better design ESR spin trapping applications involving nanomaterials.

  2. Induction-detection electron spin resonance with spin sensitivity of a few tens of spins

    Energy Technology Data Exchange (ETDEWEB)

    Artzi, Yaron; Twig, Ygal; Blank, Aharon [Schulich Faculty of Chemistry Technion—Israel Institute of Technology, Haifa 32000 (Israel)

    2015-02-23

    Electron spin resonance (ESR) is a spectroscopic method that addresses electrons in paramagnetic materials directly through their spin properties. ESR has many applications, ranging from semiconductor characterization to structural biology and even quantum computing. Although it is very powerful and informative, ESR traditionally suffers from low sensitivity, requiring many millions of spins to get a measureable signal with commercial systems using the Faraday induction-detection principle. In view of this disadvantage, significant efforts were made recently to develop alternative detection schemes based, for example, on force, optical, or electrical detection of spins, all of which can reach single electron spin sensitivity. This sensitivity, however, comes at the price of limited applicability and usefulness with regard to real scientific and technological issues facing modern ESR which are currently dealt with conventional induction-detection ESR on a daily basis. Here, we present the most sensitive experimental induction-detection ESR setup and results ever recorded that can detect the signal from just a few tens of spins. They were achieved thanks to the development of an ultra-miniature micrometer-sized microwave resonator that was operated at ∼34 GHz at cryogenic temperatures in conjunction with a unique cryogenically cooled low noise amplifier. The test sample used was isotopically enriched phosphorus-doped silicon, which is of significant relevance to spin-based quantum computing. The sensitivity was experimentally verified with the aid of a unique high-resolution ESR imaging approach. These results represent a paradigm shift with respect to the capabilities and possible applications of induction-detection-based ESR spectroscopy and imaging.

  3. Spin Effects in Collisions of Electrons with Atoms and Molecules

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Some recent experimental and theoretical work on spin-dependent electron-atom and electron-molecule collisions is reviewed. The spin is involved in such collisions by explicit spin-dependent interactions such as the spin-orbit interaction of the continuum electron (Mott scattering) but also by exchange, which, in conjunction with the Pauli principle, gives rise to observable spin exchange effects. We present results for Mn and Na atoms and experiments in which electron dichroism with chiral molecules has been studied.

  4. Two-Dimensional Electron-Spin Resonance

    Science.gov (United States)

    Freed, Jack H.

    2000-03-01

    The extension of the concepts of 2D-NMR to ESR posed significant technological challenges, especially for liquids. ESR relaxation times are very short, as low as 10-15 ns. for T_2's. Spectral bandwidths are 100-250 MHz for nitroxide spin labels. Adequate coverage is obtained with 3-5 ns. π/2 (9-17 GHz) microwave pulses into a small low Q resonator. Dead-times are currently 25-30 ns. Additional requirements are rapid phase shifting for phase cycling, nsec. data acquisition, and fast repetition rates (10-100 kHz). 2D-ELDOR (electron-electron double resonance), which is a 3-pulse 2D-exchange experiment, takes about 30 minutes with just 0.5 nanomole spin-probe in solution (SNR 200). 2D-ELDOR is very useful in studies of molecular dynamics and local structure in complex fluids. For such media, the slow rotational dynamics requires a theory based upon the stochastic Liouville equation which enables quantitative interpretation of 2D-ELDOR experiments. In studies of spin-probes in a liquid crystal new insights could be obtained on the dynamic structure in different phases. One obtains, in addition to ordering and reorientation rates of the probes, details of the local dynamic cage: its orienting potential and (slow) relaxation rate. 2D-ELDOR overcomes the loss of resolution resulting from microscopically ordered but macroscopically disordered complex fluids. This is illustrated by studies of the dynamic structure of lipid membrane vesicles, and the effects of adding a peptide. The short dead times enable the observation of both the bulk lipids and the more immobilized lipids that coat (or are trapped) by the (aggregates of) peptides. Also, new developments of multi-quantum (2D) FT-ESR from nitroxide spin labels interacting by dipolar interactions show considerable promise in measuring distances of ca. 15-70A in macromolecules.

  5. Electron Spin Dephasing and Decoherence by Interaction with Nuclear Spins in Self-Assembled Quantum Dots

    Science.gov (United States)

    Lee, Seungwon; vonAllmen, Paul; Oyafuso, Fabiano; Klimeck, Gerhard; Whale, K. Birgitta

    2004-01-01

    Electron spin dephasing and decoherence by its interaction with nuclear spins in self-assembled quantum dots are investigated in the framework of the empirical tight-binding model. Electron spin dephasing in an ensemble of dots is induced by the inhomogeneous precession frequencies of the electron among dots, while electron spin decoherence in a single dot arises from the inhomogeneous precession frequencies of nuclear spins in the dot. For In(x)Ga(1-x) As self-assembled dots containing 30000 nuclei, the dephasing and decoherence times are predicted to be on the order of 100 ps and 1 (micro)s.

  6. A coherent beam splitter for electronic spin states.

    Science.gov (United States)

    Petta, J R; Lu, H; Gossard, A C

    2010-02-05

    Rapid coherent control of electron spin states is required for implementation of a spin-based quantum processor. We demonstrated coherent control of electronic spin states in a double quantum dot by sweeping an initially prepared spin-singlet state through a singlet-triplet anticrossing in the energy-level spectrum. The anticrossing serves as a beam splitter for the incoming spin-singlet state. When performed within the spin-dephasing time, consecutive crossings through the beam splitter result in coherent quantum oscillations between the singlet state and a triplet state. The all-electrical method for quantum control relies on electron-nuclear spin coupling and drives single-electron spin rotations on nanosecond time scales.

  7. Spin-to-Orbital Angular Momentum Conversion and Spin-Polarization Filtering in Electron Beams

    CERN Document Server

    Karimi, Ebrahim; Grillo, Vincenzo; Santamato, Enrico; 10.1103/PhysRevLett.108.044801

    2012-01-01

    We propose the design of a space-variant Wien filter for electron beams that induces a spin half-turn and converts the corresponding spin angular momentum variation into orbital angular momentum of the beam itself by exploiting a geometrical phase arising in the spin manipulation. When applied to a spatially coherent input spin-polarized electron beam, such a device can generate an electron vortex beam, carrying orbital angular momentum. When applied to an unpolarized input beam, the proposed device, in combination with a suitable diffraction element, can act as a very effective spin-polarization filter. The same approach can also be applied to neutron or atom beams.

  8. Kerr-Newman Electron as Spinning Soliton

    Science.gov (United States)

    Burinskii, Alexander

    2015-10-01

    Measurable parameters of the electron indicate that its background should be described by the Kerr-Newman (KN) solution. The spin/mass ratio of the electron is extreme large, and the black hole horizons disappear, opening a topological defect of space-time - the Kerr singular ring of Compton size, which may be interpreted as a closed fundamental string of low energy string theory. The singular and two-sheeted structure of the corresponding Kerr space has to be regularised, and we consider the old problem of regularising the source of the KN solution. As a development of the earlier Keres-Israel-Hamity-López model, we describe the model of smooth and regular source forming a gravitating and relativistically rotating soliton based on the chiral field model and the Higgs mechanism of broken symmetry. The model reveals some new remarkable properties: (1) the soliton forms a relativistically rotating bubble of Compton radius, which is filled by the oscillating Higgs field in a pseudo-vacuum state; (2) the boundary of the bubble forms a domain wall which interpolates between the internal flat background and the external exact Kerr-Newman (KN) solution; (3) the phase transition is provided by a system of chiral fields; (4) the vector potential of the external the KN solution forms a closed Wilson loop which is quantised, giving rise to a quantised spin of the soliton; (5) the soliton is bordered by a closed string, which is a part of the general complex stringy structure.

  9. Single-electron Spin Resonance in a Quadruple Quantum Dot

    Science.gov (United States)

    Otsuka, Tomohiro; Nakajima, Takashi; Delbecq, Matthieu R.; Amaha, Shinichi; Yoneda, Jun; Takeda, Kenta; Allison, Giles; Ito, Takumi; Sugawara, Retsu; Noiri, Akito; Ludwig, Arne; Wieck, Andreas D.; Tarucha, Seigo

    2016-08-01

    Electron spins in semiconductor quantum dots are good candidates of quantum bits for quantum information processing. Basic operations of the qubit have been realized in recent years: initialization, manipulation of single spins, two qubit entanglement operations, and readout. Now it becomes crucial to demonstrate scalability of this architecture by conducting spin operations on a scaled up system. Here, we demonstrate single-electron spin resonance in a quadruple quantum dot. A few-electron quadruple quantum dot is formed within a magnetic field gradient created by a micro-magnet. We oscillate the wave functions of the electrons in the quantum dots by applying microwave voltages and this induces electron spin resonance. The resonance energies of the four quantum dots are slightly different because of the stray field created by the micro-magnet and therefore frequency-resolved addressable control of each electron spin resonance is possible.

  10. Resonance fluorescence and electron spin in semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yong

    2009-11-18

    The work presented in this dissertation contains the first observation of spin-resolved resonance fluorescence from a single quantum dot and its application of direct measurement of electron spin dynamics. The Mollow triplet and the Mollow quintuplet, which are the hallmarks of resonance fluorescence, are presented as the non-spin-resolved and spin-resolved resonance fluorescence spectrum, respectively. The negligible laser background contribution, the near pure radiative broadened spectrum and the anti-bunching photon statistics imply the sideband photons are background-free and near transform-limited single photons. This demonstration is a promising step towards the heralded single photon generation and electron spin readout. Instead of resolving spectrum, an alternative spin-readout scheme by counting resonance fluorescence photons under moderate laser power is demonstrated. The measurements of n-shot time-resolved resonance fluorescence readout are carried out to reveal electron spin dynamics of the measurement induced back action and the spin relaxation. Hyperfine interaction and heavy-light hole mixing are identified as the relevant mechanisms for the back action and phonon-assistant spin-orbit interaction dominates the spin relaxation. After a detailed discussion on charge-spin configurations in coupled quantum dots system, the single-shot readout on electron spin are proposed. (orig.)

  11. Electron-spin dynamics in elliptically polarized light waves

    CERN Document Server

    Bauke, Heiko; Grobe, Rainer

    2014-01-01

    We investigate the coupling of the spin angular momentum of light beams with elliptical polarization to the spin degree of freedom of free electrons. It is shown that this coupling, which is of similar origin as the well-known spin-orbit coupling, can lead to spin precession. The spin-precession frequency is proportional to the product of the laser-field's intensity and its spin density. The electron-spin dynamics is analyzed by employing exact numerical methods as well as time-dependent perturbation theory based on the fully relativistic Dirac equation and on the nonrelativistic Pauli equation that is amended by a relativistic correction that accounts for the light's spin density.

  12. Electron spin resonance detected by a superconducting qubit

    CERN Document Server

    Kubo, Y; Grezes, C; Umeda, T; Isoya, J; Sumiya, H; Yamamoto, T; Abe, H; Onoda, S; Ohshima, T; Jacques, V; Dréau, A; Roch, J -F; Auffeves, A; Vion, D; Esteve, D; Bertet, P

    2012-01-01

    A new method for detecting the magnetic resonance of electronic spins at low temperature is demonstrated. It consists in measuring the signal emitted by the spins with a superconducting qubit that acts as a single-microwave-photon detector, resulting in an enhanced sensitivity. We implement this new type of electron-spin resonance spectroscopy using a hybrid quantum circuit in which a transmon qubit is coupled to a spin ensemble consisting of NV centers in diamond. With this setup we measure the NV center absorption spectrum at 30mK at an excitation level of \\thicksim15\\,\\mu_{B} out of an ensemble of 10^{11} spins.

  13. Spin Squeezing of Atomic Ensembles via Nuclear-Electronic Spin Entanglement

    DEFF Research Database (Denmark)

    Fernholz, Thomas; Krauter, Hanna; Jensen, K.;

    2008-01-01

    We demonstrate spin squeezing in a room temperature ensemble of ≈1012 cesium atoms using their internal structure, where the necessary entanglement is created between nuclear and electronic spins of each individual atom. This state provides improvement in measurement sensitivity beyond the standard...... quantum limit for quantum memory experiments and applications in quantum metrology and is thus a complementary alternative to spin squeezing obtained via interatom entanglement. Squeezing of the collective spin is verified by quantum state tomography....

  14. Spin polarization of electrons with Rashba double-refraction

    Energy Technology Data Exchange (ETDEWEB)

    Ramaglia, V Marigliano; Bercioux, D; Cataudella, V; De Filippis, G; Perroni, C A [Coherentia-INFM and Dipartimento di Scienze Fisiche Universita degli Studi Federico II, Naples, I-80126 (Italy)

    2004-12-22

    We demonstrate how the Rashba spin-orbit coupling in semiconductor heterostructures can produce and control a spin-polarized current without ferromagnetic leads. The key idea is to use spin-double refraction of an electronic beam with a nonzero incidence angle. A region where the spin-orbit coupling is present separates the source and the drain without spin-orbit coupling. We show how the transmission and the beam spin polarization critically depend on the incidence angle. The transmission halves when the incidence angle is greater than a limit angle and a significant spin polarization appears. On increasing the spin-orbit coupling one can obtain the modulation of the intensity and of the spin polarization of the output electronic current when the input current is unpolarized. Our analysis shows the possibility of realizing a spin-field-effect transistor based on the propagation of only one mode with the region with spin-orbit coupling, whereas the original Datta and Das device (1990 Appl. Phys. Lett. 56 665) uses the spin precession that originates from the interference between two modes with orthogonal spin.

  15. Trusted intermediating agents in electronic trade networks

    NARCIS (Netherlands)

    Klos, T.B.; Alkemade, F.

    2005-01-01

    Electronic commerce and trading of information goods significantly impact the role of intermediaries: consumers can bypass intermediating agents by forming direct links to producers. One reason that traditional intermediaries can still make a profit, is that they have more knowledge of the market, s

  16. Optically programmable electron spin memory using semiconductor quantum dots.

    Science.gov (United States)

    Kroutvar, Miro; Ducommun, Yann; Heiss, Dominik; Bichler, Max; Schuh, Dieter; Abstreiter, Gerhard; Finley, Jonathan J

    2004-11-04

    The spin of a single electron subject to a static magnetic field provides a natural two-level system that is suitable for use as a quantum bit, the fundamental logical unit in a quantum computer. Semiconductor quantum dots fabricated by strain driven self-assembly are particularly attractive for the realization of spin quantum bits, as they can be controllably positioned, electronically coupled and embedded into active devices. It has been predicted that the atomic-like electronic structure of such quantum dots suppresses coupling of the spin to the solid-state quantum dot environment, thus protecting the 'spin' quantum information against decoherence. Here we demonstrate a single electron spin memory device in which the electron spin can be programmed by frequency selective optical excitation. We use the device to prepare single electron spins in semiconductor quantum dots with a well defined orientation, and directly measure the intrinsic spin flip time and its dependence on magnetic field. A very long spin lifetime is obtained, with a lower limit of about 20 milliseconds at a magnetic field of 4 tesla and at 1 kelvin.

  17. Mechanism of spin diffusion in electron spin resonance spectra of trapped electrons in aqueous glasses. Electron--Electron double resonance studies. [. gamma. -rays

    Energy Technology Data Exchange (ETDEWEB)

    Lin, D.P.; Kevan, L.

    1977-05-19

    Electron--electron double resonance (ELDOR) has been used to test the validity of the noninteracting spin packet model for inhomogeneously broadened ESR lines. For trapped electrons in 10M NaOD/D/sub 2/O glassy ice the saturation of field-swept ELDOR spectra fits the above mentioned model in contrast to earlier work on trapped electrons in protiated matrices. In the protiated matrix spin diffusion produces significant interaction between the spin packets. The difference between the protiated and deuterated matrices suggests that nuclear relaxation is the mechanism for spin diffusion. The deuterated matrices show no structure in frequency-swept ELDOR spectra due to deuteron spin--flip transitions whereas structure due to proton spin--flips is seen in protiated matrices.

  18. Structure dependent spin selectivity in electron transport through oligopeptides

    Science.gov (United States)

    Kiran, Vankayala; Cohen, Sidney R.; Naaman, Ron

    2017-03-01

    The chiral-induced spin selectivity (CISS) effect entails spin-selective electron transmission through chiral molecules. In the present study, the spin filtering ability of chiral, helical oligopeptide monolayers of two different lengths is demonstrated using magnetic conductive probe atomic force microscopy. Spin-specific nanoscale electron transport studies elucidate that the spin polarization is higher for 14-mer oligopeptides than that of the 10-mer. We also show that the spin filtering ability can be tuned by changing the tip-loading force applied on the molecules. The spin selectivity decreases with increasing applied force, an effect attributed to the increased ratio of radius to pitch of the helix upon compression and increased tilt angles between the molecular axis and the surface normal. The method applied here provides new insights into the parameters controlling the CISS effect.

  19. Kerr-Newman electron as spinning soliton

    CERN Document Server

    Burinskii, Alexander

    2014-01-01

    Measurable parameters of the electron indicate that its background should be described by the Kerr-Newman (KN) solution. Spin/mass ratio of the electron is extreme large, and the black hole horizons disappear, opening a topological defect of spacetime -- the Kerr singular ring of the Compton size, which may be interpreted as a closed fundamental string to the low energy string theory. The singular and twosheeted structure of the corresponding Kerr space has to be regularized, and we consider the old problem of regular source of the KN solution. As a development of the earlier Keres-Israel-Hamity-L\\'opez model, we describe the model of smooth and regular source forming a gravitating and relativistically rotating soliton based on the chiral field model and the Higgs mechanism of broken symmetry. The model reveals some new remarkable properties: 1) the soliton forms a relativistically rotating bubble of the Compton radius, which is filled by the oscillating Higgs field in pseudo-vacuum state, 2) boundary of the ...

  20. Spin orbit torque based electronic neuron

    Energy Technology Data Exchange (ETDEWEB)

    Sengupta, Abhronil, E-mail: asengup@purdue.edu; Choday, Sri Harsha; Kim, Yusung; Roy, Kaushik [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2015-04-06

    A device based on current-induced spin-orbit torque (SOT) that functions as an electronic neuron is proposed in this work. The SOT device implements an artificial neuron's thresholding (transfer) function. In the first step of a two-step switching scheme, a charge current places the magnetization of a nano-magnet along the hard-axis, i.e., an unstable point for the magnet. In the second step, the SOT device (neuron) receives a current (from the synapses) which moves the magnetization from the unstable point to one of the two stable states. The polarity of the synaptic current encodes the excitatory and inhibitory nature of the neuron input and determines the final orientation of the magnetization. A resistive crossbar array, functioning as synapses, generates a bipolar current that is a weighted sum of the inputs. The simulation of a two layer feed-forward artificial neural network based on the SOT electronic neuron shows that it consumes ∼3× lower power than a 45 nm digital CMOS implementation, while reaching ∼80% accuracy in the classification of 100 images of handwritten digits from the MNIST dataset.

  1. Polarization Measurement of Spin-Polarized Electrons by Optical Electron Polarimeter

    Institute of Scientific and Technical Information of China (English)

    DING Hai-Bing; PANG Wen-Ning; LIU Yi-Bao; SHANG Ren-Cheng

    2005-01-01

    @@ The polarization of spin-polarized electrons, produced from a new GaAs spin-polarized electron source, is determined by an optical electron polarimeter. The He 3 3p → 23S1 (388.9nm) transition is used for the optical electron polarimetry. The structure and performance of the experimental setup of spin-polarized electron source and optical electron polarimeter are described. The result of polarization of 30.8% averaged spin-up and spindown polarized electrons is obtained and presented.

  2. Electron spin resonance and spin-valley physics in a silicon double quantum dot.

    Science.gov (United States)

    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.

  3. Universal Synchronous Spin Rotators for Electron-Ion Colliders

    CERN Document Server

    Chevtsov, Pavel; Krafft, Geoff; Zhang, Yuhong

    2016-01-01

    The paper provides mathematics and physics considerations concerning a special class of electron spin manipulating structures for future Electron-Ion Collider (EIC) projects. These structures, which we call Universal Synchronous Spin Rotators (USSR), consist of a sequence of standard basic spin manipulating elements or cells built with two solenoids and one bending magnet between them. When integrated into the ring arcs, USSR structures do not affect the central particle orbit, and their spin transformation functions can be described by a linear mathematical model. In spite of being relatively simple, the model allows one to design spin rotators, which are able to perform spin direction changes from vertical to longitudinal and vice versa in significant continuous intervals of the electron energy. This makes USSR especially valuable tools for EIC nuclear physics experiments.

  4. Frenkel electron and a spinning body in a curved background

    CERN Document Server

    Ramírez, Walberto Guzmán; Pupasov-Maksimov, Andrey M

    2014-01-01

    We develop variational formulation of a particle with spin in a curved space-time background. The model is based on a singular Lagrangian which provides equations of motion, fixed value of spin and Frenkel condition on spin-tensor. Comparing our equations with those of Papapetrou, we conclude that the Frenkel electron in gravitational field has the same behavior as a rotating body in pole-dipole and leading-spin approximation. Due to constraints presented in the formulation, position space is endowed with noncommutative structure induced by spin of the particle. Therefore the model provides physically interesting example of noncommutative particle in a curved background.

  5. Coherence and control of quantum registers based on electronic spin in a nuclear spin bath.

    Science.gov (United States)

    Cappellaro, P; Jiang, L; Hodges, J S; Lukin, M D

    2009-05-29

    We consider a protocol for the control of few-qubit registers comprising one electronic spin embedded in a nuclear spin bath. We show how to isolate a few proximal nuclear spins from the rest of the bath and use them as building blocks for a potentially scalable quantum information processor. We describe how coherent control techniques based on magnetic resonance methods can be adapted to these solid-state spin systems, to provide not only efficient, high fidelity manipulation but also decoupling from the spin bath. As an example, we analyze feasible performances and practical limitations in the realistic setting of nitrogen-vacancy centers in diamond.

  6. Electron-Nuclear Spin Transfer in Triple Quantum Dot Networks

    Science.gov (United States)

    Prada, Marta; Toonen, Ryan; Harrison, Paul

    2005-03-01

    We investigate the conductance spectra of coupled quantum dots to study systematically the nuclear spin relaxation of delta- and y-junction networks and observe spin blockade dependence on the electronic configurations. We derive the conductance using the Beenakker approach generalised to an array of quantum dots where we consider the nuclear spin transfer to electrons by hyperfine coupling. This allows us to predict the relevant memory effects on the different electronic states by studying the evolution of the single electron resonances in presence of nuclear spin relaxation. We find that the gradual depolarisation of the nuclear system is imprinted in the conductance spectra of the multidot system. Our calculations of the temporal evolution of the conductance resonance reveal that spin blockade can be lifted by hyperfine coupling.

  7. Electron nuclear spin transfer in quantum-dot networks

    Science.gov (United States)

    Prada, M.; Toonen, R. C.; Blick, R. H.; Harrison, P.

    2005-05-01

    We investigate the conductance spectra of coupled quantum dots to study systematically the nuclear spin relaxation of different geometries of a two-dimensional network of quantum dots and observe spin blockade dependence on the electronic configurations. We derive the conductance using the Beenakker approach generalized to an array of quantum dots where we consider the nuclear spin transfer to electrons by hyperfine coupling. This allows us to predict the relevant memory effects on the different electronic states by studying the evolution of the single electron resonances in the presence of nuclear spin relaxation. We find that the gradual depolarization of the nuclear system is imprinted in the conductance spectra of the multidot system. Our calculations of the temporal evolution of the conductance resonance reveal that spin blockade can be lifted by hyperfine coupling.

  8. Quantum many-body theory for electron spin decoherence in nanoscale nuclear spin baths

    Science.gov (United States)

    Yang, Wen; Ma, Wen-Long; Liu, Ren-Bao

    2017-01-01

    Decoherence of electron spins in nanoscale systems is important to quantum technologies such as quantum information processing and magnetometry. It is also an ideal model problem for studying the crossover between quantum and classical phenomena. At low temperatures or in light-element materials where the spin-orbit coupling is weak, the phonon scattering in nanostructures is less important and the fluctuations of nuclear spins become the dominant decoherence mechanism for electron spins. Since the 1950s, semi-classical noise theories have been developed for understanding electron spin decoherence. In spin-based solid-state quantum technologies, the relevant systems are in the nanometer scale and nuclear spin baths are quantum objects which require a quantum description. Recently, quantum pictures have been established to understand the decoherence and quantum many-body theories have been developed to quantitatively describe this phenomenon. Anomalous quantum effects have been predicted and some have been experimentally confirmed. A systematically truncated cluster-correlation expansion theory has been developed to account for the many-body correlations in nanoscale nuclear spin baths that are built up during electron spin decoherence. The theory has successfully predicted and explained a number of experimental results in a wide range of physical systems. In this review, we will cover this recent progress. The limitations of the present quantum many-body theories and possible directions for future development will also be discussed.

  9. Quantum many-body theory for electron spin decoherence in nanoscale nuclear spin baths.

    Science.gov (United States)

    Yang, Wen; Ma, Wen-Long; Liu, Ren-Bao

    2017-01-01

    Decoherence of electron spins in nanoscale systems is important to quantum technologies such as quantum information processing and magnetometry. It is also an ideal model problem for studying the crossover between quantum and classical phenomena. At low temperatures or in light-element materials where the spin-orbit coupling is weak, the phonon scattering in nanostructures is less important and the fluctuations of nuclear spins become the dominant decoherence mechanism for electron spins. Since the 1950s, semi-classical noise theories have been developed for understanding electron spin decoherence. In spin-based solid-state quantum technologies, the relevant systems are in the nanometer scale and nuclear spin baths are quantum objects which require a quantum description. Recently, quantum pictures have been established to understand the decoherence and quantum many-body theories have been developed to quantitatively describe this phenomenon. Anomalous quantum effects have been predicted and some have been experimentally confirmed. A systematically truncated cluster-correlation expansion theory has been developed to account for the many-body correlations in nanoscale nuclear spin baths that are built up during electron spin decoherence. The theory has successfully predicted and explained a number of experimental results in a wide range of physical systems. In this review, we will cover this recent progress. The limitations of the present quantum many-body theories and possible directions for future development will also be discussed.

  10. Controlling electron quantum dot qubits by spin-orbit interactions

    Energy Technology Data Exchange (ETDEWEB)

    Stano, P.

    2007-01-15

    Single electron confined in a quantum dot is studied. A special emphasis is laid on the spin properties and the influence of spin-orbit interactions on the system. The study is motivated by a perspective exploitation of the spin of the confined electron as a qubit, a basic building block of in a foreseen quantum computer. The electron is described using the single band effective mass approximation, with parameters typical for a lateral electrostatically defined quantum dot in a GaAs/AlGaAs heterostructure. The stemming data for the analysis are obtained by numerical methods of exact diagonalization, however, all important conclusions are explained analytically. The work focuses on three main areas -- electron spectrum, phonon induced relaxation and electrically and magnetically induced Rabi oscillations. It is shown, how spin-orbit interactions influence the energy spectrum, cause finite spin relaxation and allow for all-electrical manipulation of the spin qubit. Among the main results is the discovery of easy passages, where the spin relaxation is unusually slow and the qubit is protected against parasitic electrical fields connected with manipulation by resonant electromagnetic fields. The results provide direct guide for manufacturing quantum dots with much improved properties, suitable for realizing single electron spin qubits. (orig.)

  11. Entanglement manifestation in spin resolved electron–electron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Artamonov, O.M., E-mail: artaoleg@gmail.com [Institute of Physics, St Petersburg State University, St Petersburg (Russian Federation); Samarin, S.N., E-mail: sergey.samarin@uwa.edu.au [Institute of Physics, St Petersburg State University, St Petersburg (Russian Federation); School of Physics, the University of Western Australia, Crawley, Perth 6009, WA (Australia); Vetlugin, A.N.; Sokolov, I.V. [Institute of Physics, St Petersburg State University, St Petersburg (Russian Federation); Williams, J.F. [School of Physics, the University of Western Australia, Crawley, Perth 6009, WA (Australia)

    2015-11-15

    Highlights: • Spin entangled pairs is created by the Coulomb scattering of polarized electrons. • Polarization and separability of scattered electrons is investigated. • The model comparison with the experimental results shows qualitative agreement. • Analytical correlation between polarization and separability of pairs is found. - Abstract: The polarization vector P of scattered electrons interacting with a polarized target electrons is compared with the entanglement (or non-separability) of the electron states of the interacting electron pair. The separability S is defined as a linear function of the von Neumann entropy. The shapes of the functions P (θ,Ω,φ) and S (θ,Ω,φ) are similar and simultaneously achieve their maximum value at the scattering angle θ values close to 0 and π and simultaneously tend to zero in the case of symmetric scattering at θ ≈ π/2. In the latter case the scattered electrons are described by an asymmetric spin part of the wave function, which by definition corresponds to the spin entangled (S ≈ 0) electron states of the interacting electron pair. Comparison of the model calculation results with experimental results of the spin polarized electron spectroscopy of the ferromagnetic solid shows qualitative agreement. The analytical expression relating polarization and separability of the two interacting particles enables use the measured polarization of scattered electrons for estimation of the spin-entanglement or separability of the two particle systems.

  12. Electron spin control of optically levitated nanodiamonds in vacuum

    Science.gov (United States)

    Hoang, Thai M.; Ahn, Jonghoon; Bang, Jaehoon; Li, Tongcang

    2016-07-01

    Electron spins of diamond nitrogen-vacancy (NV) centres are important quantum resources for nanoscale sensing and quantum information. Combining NV spins with levitated optomechanical resonators will provide a hybrid quantum system for novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centres in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this system, we investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centres, indicating potential applications of NV centres in oxygen gas sensing. Our results pave the way towards a levitated spin-optomechanical system for studying macroscopic quantum mechanics.

  13. Electron spin control of optically levitated nanodiamonds in vacuum.

    Science.gov (United States)

    Hoang, Thai M; Ahn, Jonghoon; Bang, Jaehoon; Li, Tongcang

    2016-07-19

    Electron spins of diamond nitrogen-vacancy (NV) centres are important quantum resources for nanoscale sensing and quantum information. Combining NV spins with levitated optomechanical resonators will provide a hybrid quantum system for novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centres in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this system, we investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. We also observe that oxygen and helium gases have different effects on both the photoluminescence and the ESR contrast of nanodiamond NV centres, indicating potential applications of NV centres in oxygen gas sensing. Our results pave the way towards a levitated spin-optomechanical system for studying macroscopic quantum mechanics.

  14. Impurities and electron spin relaxations in nanodiamonds studied by multi-frequency electron spin resonance

    Science.gov (United States)

    Cho, Franklin; Takahashi, Susumu

    2014-03-01

    Nano-sized diamond or nanodiamond is a fascinating material for potential applications of fluorescence imaging and magnetic sensing of biological systems via nitrogen-vacancy defect centers in diamonds. Sensitivity of the magnetic sensing strongly depends on coupling to surrounding environmental noises, thus understanding of the environment is critical to realize the application. In the present study, we employ multi-frequency (X-band, 115 GHz and 230 GHz) continuous-wave (cw) and pulsed electron spin resonance (ESR) spectroscopy to investigate impurity contents and spin relaxation properties in various sizes of nanodiamonds. Spectra taken with our home-built 230/115 GHz cw/pulsed ESR spectrometer shows presence of two major impurity contents; single substitutional nitrogen impurities (P1) also common in bulk diamonds and paramagnetic impurities (denoted as X) unique to nanodiamonds. The ESR measurement also shows a strong dependence of the population ratio between P1 and X on particle size. Furthermore, we will discuss the nature of spin-lattice relaxation time T1 of nanodiamonds studied by pulsed ESR measurements at X-band, 115 GHz and 230 GHz.

  15. Spin Dynamics of Electrons Confined in Silicon Heterostructures

    Science.gov (United States)

    Jock, Ryan Michael

    The spin states of electrons confined in silicon heterostructures have shown promise as qubits for quantum information processing. Recently, a host of single and few electron silicon quantum dot device architectures have arisen as implementations for quantum computation. These devices often combine regions of low density two-dimensional (2D) electrons, localized electrons, and interfaces depleted of electrons. Electron spin resonance (ESR) is a unique tool for probing the spin dynamics of both mobile and localized electrons at silicon heterointerfaces and investigating the effects limiting the ability to control electrons and their spin states in these structures. We use a continuous wave ESR method to examine localized 2D electron band-tail states at Si/SiO 2 interfaces in large area metal-oxide-semiconductor transistors. We compare two devices, fabricated in different laboratories, which display similar low temperature (4.2 K) peak mobilities. We find that one of the devices displays a smaller band-tail density of confined states and a shallower characteristic confinement. Thus, ESR reveals a difference in device quality, which is not apparent from mobility measurements, and is a valuable tool for evaluating the interface quality in Si/SiO2 heterostructures. Additionally, we use pulsed ESR techniques to study the spin dynamics of electrons confined in Si/SiGe heterostructures. For mobile 2D electrons, the density-dependent Dyakonov-Perel mechanism dominates spin relaxation. At low 2D densities, stronger electron-electron interactions cause an increase in the electron effective mass, leading to an increase in spin susceptibility. For very low densities, natural disorder localizes electrons at the silicon heterointerface. Naturally localized electrons in these structures display short spin relaxation times (ensembles of around 108 quantum dots in Si/SiGe heterostructures. By tailoring the device structure, a long electron spin relaxation time (T1 = 1.4 ms) is

  16. Coupling of Photonic and Electronic Spin Catalyzed by Diatomic Molecules

    Science.gov (United States)

    Gay, Timothy

    2011-05-01

    Recent experiments involving the collisions of polarized photons or polarized electrons with simple diatomic molecules have shown novel ways in which the net spin of electrons can be converted into the net spin of photons following the collisions, or vice versa. I will discuss three recent experiments that illustrate such transformations: the production of nuclear rotational spin in nitrogen molecules excited by polarized electrons with the subsequent emission of polarized photons, the excitation by polarized electrons of rotational eigenstates of hydrogen molecules and the subsequent emission of circularly-polarized light, and the photolysis of hydrogen molecules by circularly-polarized light yielding photofragments that ``spin the wrong way.'' To our knowledge, these latter measurements represent the first observation of photofragment orientation by direct observation of the polarization of the photofragment fluoresence. Work supported by the NSF through grant PHY-0821385, the DOE through the use of the ALS at LBL, and ANSTO (Access to Major Research Facilities Programme).

  17. Electron with arbitrary pseudo-spins in multilayer graphene

    Institute of Scientific and Technical Information of China (English)

    Worasak Prarokijjak; Bumned Soodchomshom

    2015-01-01

    Using the low-energy effective Hamiltonian of the ABC-stacked multilayer graphene, the pseudo-spin coupling to real orbital angular momentum of electrons in multilayer graphene is investigated. We show that the electron wave function in N-layer graphene mimics the behavior of a particle with a spin of N × (}/2), where N={1, 2, 3, . . .}. It is said that for N>1 the low-energy effective Hamiltonian for ABC-stacked graphene cannot be used to describe pseudo-spin-1/2 particles. The wave function of electrons in multilayer graphene may behave like fermionic (or bosonic) particle for N being odd (or even). In this paper, we propose a theory of graphene serving as a host material of electrons with arbitrary pseudo-spins tunable by changing the number of graphene layers.

  18. Electronic spin transport and spin precession in single graphene layers at room temperature.

    Science.gov (United States)

    Tombros, Nikolaos; Jozsa, Csaba; Popinciuc, Mihaita; Jonkman, Harry T; van Wees, Bart J

    2007-08-02

    Electronic transport in single or a few layers of graphene is the subject of intense interest at present. The specific band structure of graphene, with its unique valley structure and Dirac neutrality point separating hole states from electron states, has led to the observation of new electronic transport phenomena such as anomalously quantized Hall effects, absence of weak localization and the existence of a minimum conductivity. In addition to dissipative transport, supercurrent transport has also been observed. Graphene might also be a promising material for spintronics and related applications, such as the realization of spin qubits, owing to the low intrinsic spin orbit interaction, as well as the low hyperfine interaction of the electron spins with the carbon nuclei. Here we report the observation of spin transport, as well as Larmor spin precession, over micrometre-scale distances in single graphene layers. The 'non-local' spin valve geometry was used in these experiments, employing four-terminal contact geometries with ferromagnetic cobalt electrodes making contact with the graphene sheet through a thin oxide layer. We observe clear bipolar (changing from positive to negative sign) spin signals that reflect the magnetization direction of all four electrodes, indicating that spin coherence extends underneath all of the contacts. No significant changes in the spin signals occur between 4.2 K, 77 K and room temperature. We extract a spin relaxation length between 1.5 and 2 mum at room temperature, only weakly dependent on charge density. The spin polarization of the ferromagnetic contacts is calculated from the measurements to be around ten per cent.

  19. Electron spin relaxation in cryptochrome-based magnetoreception

    DEFF Research Database (Denmark)

    Kattnig, Daniel R; Solov'yov, Ilia A; Hore, P J

    2016-01-01

    The magnetic compass sense of migratory birds is thought to rely on magnetically sensitive radical pairs formed photochemically in cryptochrome proteins in the retina. An important requirement of this hypothesis is that electron spin relaxation is slow enough for the Earth's magnetic field to have...... a significant effect on the coherent spin dynamics of the radicals. It is generally assumed that evolutionary pressure has led to protection of the electron spins from irreversible loss of coherence in order that the underlying quantum dynamics can survive in a noisy biological environment. Here, we address...... this question for a structurally characterized model cryptochrome expected to share many properties with the putative avian receptor protein. To this end we combine all-atom molecular dynamics simulations, Bloch-Redfield relaxation theory and spin dynamics calculations to assess the effects of spin relaxation...

  20. Foucault's pendulum, a classical analog for the electron spin state

    Science.gov (United States)

    Linck, Rebecca A.

    Spin has long been regarded as a fundamentally quantum phenomena that is incapable of being described classically. To bridge the gap and show that aspects of spin's quantum nature can be described classically, this work uses a classical Lagrangian based on the coupled oscillations of Foucault's pendulum as an analog for the electron spin state in an external magnetic field. With this analog it is possible to demonstrate that Foucault's pendulum not only serves as a basis for explaining geometric phase, but is also a basis for reproducing a broad range of behavior from Zeeman-like frequency splitting to precession of the spin state. By demonstrating that unmeasured electron spin states can be fully described in classical terms, this research opens the door to using the tools of classical physics to examine an inherently quantum phenomenon.

  1. Control and measurement of electron spins in semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Kouwenhoven, L.P.; Elzerman, J.M.; Hanson, R.; Willems van Beveren, L.H.; Vandersypen, L.M.K. [ERATO Mesoscopic Correlation Project, Delft University of Technology, Delft (Netherlands); Kavli Institute of Nanoscience Delft (Netherlands)

    2006-11-15

    We present an overview of experimental steps taken towards using the spin of a single electron trapped in a semiconductor quantum dot as a spin qubit [Loss and DiVincenzo, Phys. Rev. A 57, 120 (1998)]. Fabrication and characterization of a double quantum dot containing two coupled spins has been achieved, as well as initialization and single-shot read-out of the spin state. The relaxation time T {sub 1} of single-spin and two-spin states was found to be on the order of a millisecond, dominated by spin-orbit interactions. The time-averaged dephasing time T{sub 2}{sup *}, due to fluctuations in the ensemble of nuclear spins in the host semiconductor, was determined to be on the order of several tens of nanoseconds. Coherent manipulation of single-spin states can be performed using a microfabricated wire located close to the quantum dot, while two-spin interactions rely on controlling the tunnel barrier connecting the respective quantum dots [Petta et al., Science 309, 2180 (2005)]. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. 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.

  3. One-electron versus electron-electron interaction contributions to the spin-spin coupling mechanism in nuclear magnetic resonance spectroscopy: analysis of basic electronic effects.

    Science.gov (United States)

    Gräfenstein, Jürgen; Cremer, Dieter

    2004-12-22

    For the first time, the nuclear magnetic resonance (NMR) spin-spin coupling mechanism is decomposed into one-electron and electron-electron interaction contributions to demonstrate that spin-information transport between different orbitals is not exclusively an electron-exchange phenomenon. This is done using coupled perturbed density-functional theory in conjunction with the recently developed J-OC-PSP [=J-OC-OC-PSP: Decomposition of J into orbital contributions using orbital currents and partial spin polarization)] method. One-orbital contributions comprise Ramsey response and self-exchange effects and the two-orbital contributions describe first-order delocalization and steric exchange. The two-orbital effects can be characterized as external orbital, echo, and spin transport contributions. A relationship of these electronic effects to zeroth-order orbital theory is demonstrated and their sign and magnitude predicted using simple models and graphical representations of first order orbitals. In the case of methane the two NMR spin-spin coupling constants result from totally different Fermi contact coupling mechanisms. (1)J(C,H) is the result of the Ramsey response and the self-exchange of the bond orbital diminished by external first-order delocalization external one-orbital effects whereas (2)J(H,H) spin-spin coupling is almost exclusively mitigated by a two-orbital steric exchange effect. From this analysis, a series of prediction can be made how geometrical deformations, electron lone pairs, and substituent effects lead to a change in the values of (1)J(C,H) and (2)J(H,H), respectively, for hydrocarbons.

  4. Spin-polarizing interferometric beam splitter for free electrons

    CERN Document Server

    Dellweg, Matthias M

    2016-01-01

    A spin-polarizing electron beam splitter is described which relies on an arrangement of linearly polarized laser waves of nonrelativistic intensity. An incident electron beam is first coherently scattered off a bichromatic laser field, splitting the beam into two portions, with electron spin and momentum being entangled. Afterwards, the partial beams are coherently superposed in an interferometric setup formed by standing laser waves. As a result, the outgoing electron beam is separated into its spin components along the laser magnetic field, which is shown by both analytical and numerical solutions of Pauli's equation. The proposed laser field configuration thus exerts the same effect on free electrons like an ordinary Stern-Gerlach magnet does on atoms.

  5. Frenkel electron and a spinning body in a curved background

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez, Walberto Guzmán [Depto. de Matemática, ICE,Universidade Federal de Juiz de Fora, São Pedro, MG (Brazil); Deriglazov, Alexei A. [Depto. de Matemática, ICE,Universidade Federal de Juiz de Fora, São Pedro, MG (Brazil); Laboratory of Mathematical Physics, Tomsk Polytechnic University,634050 Tomsk, Lenin Ave. 30 (Russian Federation); Pupasov-Maksimov, Andrey M. [Depto. de Matemática, ICE,Universidade Federal de Juiz de Fora, São Pedro, MG (Brazil)

    2014-03-24

    We develop a variational formulation of a particle with spin in a curved space-time background. The model is based on a singular Lagrangian which provides equations of motion, a fixed value of spin and Frenkel condition on spin-tensor. Comparing our equations with those of Papapetrou we conclude that the Frenkel electron in a gravitational field has the same behavior as a rotating body in the pole-dipole and leading-spin approximation. Due to constraints presented in the formulation, position space is endowed with a noncommutative structure induced by the spin of the particle. Therefore, the model provides a physically interesting example of a noncommutative particle in a curved background.

  6. Optically oriented electron spin transmission across ferromagnet/semiconductor interfaces

    Science.gov (United States)

    Taniyama, T.; Suzuki, I.; Wada, E.; Shirahata, Y.; Naito, T.; Itoh, M.; Yamaguchi, M.

    2011-10-01

    Electron spin transmission across ferromagnetic metal/semiconductor interfaces with different ferromagnetic contacts, i.e., Fe and FeGa, is studied using optical spin orientation method. The bias dependence of spin dependent photocurrent, which is the difference between the photocurrents excited with left- and right- handed circularly polarized lights, is found to show a dip-like feature at -0.058 and 0.021 V for Fe and FeGa contacts, respectively. The origin of the bias dependence of the spin dependent photocurrent is discussed on the basis of the Breit-Wigner type resonant tunneling process via interface resonant states, comparing the results for the both contacts. The results also indicate that the control of interface states is crucial to achieve efficient spin filtering effect at the ferromagnet/semiconductor interfaces.

  7. Electron Spin Pairing in High-Tc Superconductors

    Institute of Scientific and Technical Information of China (English)

    郭卫; 韩汝珊

    2001-01-01

    An electron pairing theory based on effective electron spin coupling mediated by antiferromagnetically correlated local moments is presented to account for high-Tc phenomena. We show that Kondo scattering and the suppression of the antiferromagnetic superexchange between Cu2+ moments lead to local triplet pairing, the mechanism underlying high-Tc superconductivity.

  8. Electron Spin Resonance at the Level of 1 04 Spins Using Low Impedance Superconducting Resonators

    Science.gov (United States)

    Eichler, C.; Sigillito, A. J.; Lyon, S. A.; Petta, J. R.

    2017-01-01

    We report on electron spin resonance measurements of phosphorus donors localized in a 200 μ m2 area below the inductive wire of a lumped element superconducting resonator. By combining quantum limited parametric amplification with a low impedance microwave resonator design, we are able to detect around 2 ×1 04 spins with a signal-to-noise ratio of 1 in a single shot. The 150 Hz coupling strength between the resonator field and individual spins is significantly larger than the 1-10 Hz coupling rates obtained with typical coplanar waveguide resonator designs. Because of the larger coupling rate, we find that spin relaxation is dominated by radiative decay into the resonator and dependent upon the spin-resonator detuning, as predicted by Purcell.

  9. Electron-Spin Filters Based on the Rashba Effect

    Science.gov (United States)

    Ting, David Z.-Y.; Cartoixa, Xavier; McGill, Thomas C.; Moon, Jeong S.; Chow, David H.; Schulman, Joel N.; Smith, Darryl L.

    2004-01-01

    Semiconductor electron-spin filters of a proposed type would be based on the Rashba effect, which is described briefly below. Electron-spin filters more precisely, sources of spin-polarized electron currents have been sought for research on, and development of, the emerging technological discipline of spintronics (spin-based electronics). There have been a number of successful demonstrations of injection of spin-polarized electrons from diluted magnetic semiconductors and from ferromagnetic metals into nonmagnetic semiconductors. In contrast, a device according to the proposal would be made from nonmagnetic semiconductor materials and would function without an applied magnetic field. The Rashba effect, named after one of its discoverers, is an energy splitting, of 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. The present proposal evolved from recent theoretical studies that 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. Accordingly, a device according to the proposal would be denoted an asymmetric resonant interband tunneling diode [a-RITD]. An a-RITD could be implemented in a variety of forms, the form favored in the proposal being a double-barrier heterostructure containing an asymmetric quantum well. It is envisioned that a-RITDs would be designed and fabricated in the InAs/GaSb/AlSb material system for several reasons: Heterostructures in this material system are strong candidates for pronounced Rashba spin splitting because InAs and GaSb exhibit large spin-orbit interactions and because both InAs and GaSb would be available for the construction of highly asymmetric

  10. Foucault's Pendulum, Analog for an Electron Spin State

    Science.gov (United States)

    Linck, Rebecca

    2012-11-01

    The classical Lagrangian that describes the coupled oscillations of Foucault's pendulum presents an interesting analog to an electron's spin state in an external magnetic field. With a simple modification, this classical Lagrangian yields equations of motion that directly map onto the Schrodinger-Pauli Equation. This analog goes well beyond the geometric phase, reproducing a broad range of behavior from Zeeman-like frequency splitting to precession of the spin state. By demonstrating that unmeasured spin states can be fully described in classical terms, this research opens the door to using the tools of classical physics to examine an inherently quantum phenomenon.

  11. Tuning Electron Spin States in Quantum Dots by Spin-Orbit Interactions

    Institute of Scientific and Technical Information of China (English)

    LIU Yu; CHENG Fang

    2011-01-01

    @@ We theoretically investigate the influence of both Rashba spin-orbit interaction (RSOI) and Dresselhaus spin- orbit interaction (DSOI) on electron spin states, electron distribution and the optical absorption of a quantum dot.Our theoretical results show that the interplay between RSOI and DSOI results in an effective periodic potential, which consequently breaks the rotational symmetry and makes the quantum dot behave like two laterally coupled quantum dots.In the presence of RSOI and/or DSOI the spin is no longer a conserved quantity and its magnitude can be tuned by changing the strength of RSOI and/or DSOI.By reversing the direction of the perpendicular electric field, we can rotate the spatial distribution.This property provides us with a new way to control quantum states in a quantum dot by electrical means.

  12. Electron spin resonance studies on reduction process of nitroxyl spin radicals used in molecular imaging

    Energy Technology Data Exchange (ETDEWEB)

    Dhas, M. Kumara; Benial, A. Milton Franklin, E-mail: miltonfranklin@yahoo.com [Department of Physics, NMSSVN College, Nagamalai, Madurai-625019, Tamilnadu (India); Jawahar, A. [Department of Chemistry, NMSSVN College, Nagamalai, Madurai-625019, Tamilnadu (India)

    2014-04-24

    The Electron spin resonance studies on the reduction process of nitroxyl spin probes were carried out for 1mM {sup 14}N labeled nitroxyl radicals in pure water and 1 mM concentration of ascorbic acid as a function of time. The electron spin resonance parameters such as signal intensity ratio, line width, g-value, hyperfine coupling constant and rotational correlation time were determined. The half life time was estimated for 1mM {sup 14}N labeled nitroxyl radicals in 1 mM concentration of ascorbic acid. The ESR study reveals that the TEMPONE has narrowest line width and fast tumbling motion compared with TEMPO and TEMPOL. From the results, TEMPONE has long half life time and high stability compared with TEMPO and TEMPOL radical. Therefore, this study reveals that the TEMPONE radical can act as a good redox sensitive spin probe for molecular imaging.

  13. Electronic spin state of iron in lower mantle perovskite.

    Science.gov (United States)

    Li, Jie; Struzhkin, Viktor V; Mao, Ho-Kwang; Shu, Jinfu; Hemley, Russell J; Fei, Yingwei; Mysen, Bjorn; Dera, Przemek; Prakapenka, Vitali; Shen, Guoyin

    2004-09-28

    The electronic spin state of iron in lower mantle perovskite is one of the fundamental parameters that governs the physics and chemistry of the most voluminous and massive shell in the Earth. We present experimental evidence for spin-pairing transition in aluminum-bearing silicate perovskite (Mg,Fe)(Si,Al)O(3) under the lower mantle pressures. Our results demonstrate that as pressure increases, iron in perovskite transforms gradually from the initial high-spin state toward the final low-spin state. At 100 GPa, both aluminum-free and aluminum-bearing samples exhibit a mixed spin state. The residual magnetic moment in the aluminum-bearing perovskite is significantly higher than that in its aluminum-free counterpart. The observed spin evolution with pressure can be explained by the presence of multiple iron species and the occurrence of partial spin-paring transitions in the perovskite. Pressure-induced spin-pairing transitions in the perovskite would have important bearing on the magnetic, thermoelastic, and transport properties of the lower mantle, and on the distribution of iron in the Earth's interior.

  14. Metastable and spin-polarized states in electron systems with localized electron-electron interaction

    Science.gov (United States)

    Sablikov, Vladimir A.; Shchamkhalova, Bagun S.

    2014-05-01

    We study the formation of spontaneous spin polarization in inhomogeneous electron systems with pair interaction localized in a small region that is not separated by a barrier from surrounding gas of non-interacting electrons. Such a system is interesting as a minimal model of a quantum point contact in which the electron-electron interaction is strong in a small constriction coupled to electron reservoirs without barriers. Based on the analysis of the grand potential within the self-consistent field approximation, we find that the formation of the polarized state strongly differs from the Bloch or Stoner transition in homogeneous interacting systems. The main difference is that a metastable state appears in the critical point in addition to the globally stable state, so that when the interaction parameter exceeds a critical value, two states coexist. One state has spin polarization and the other is unpolarized. Another feature is that the spin polarization increases continuously with the interaction parameter and has a square-root singularity in the critical point. We study the critical conditions and the grand potentials of the polarized and unpolarized states for one-dimensional and two-dimensional models in the case of extremely small size of the interaction region.

  15. Influences of spin accumulation on the intrinsic spin Hall effect in two dimensional electron gases with Rashba spin-orbit coupling

    OpenAIRE

    Shen, SQ; Ma, X.; Hu, L.; R. Tao

    2004-01-01

    In a two-dimensional electron gas with Rashba spin-orbit coupling, the external electric field may cause a spin Hall current in the direction perpendicular to the electric field. This effect was called the intrinsic spin Hall effect. In this paper, we investigate the influences of spin accumulation on this intrinsic spin Hall effect. We show that due to the existence of boundaries in a real sample, the spin Hall current generated by the intrinsic spin Hall effect will cause spin accumulation ...

  16. Electrical Control, Read-out and Initialization of Single Electron Spins

    NARCIS (Netherlands)

    Shafiei, M.

    2013-01-01

    An electron, in addition to its electric charge, possesses a small magnetic moment, called spin. The spin of an electron can point parallel (spin-up) or antiparallel (spin-down) to the magnetic field. These two states are analogous to zero and one of the logical bit in current digital electronic dev

  17. Simulating electron spin entanglement in a double quantum dot

    Science.gov (United States)

    Rodriguez-Moreno, M. A.; Hernandez de La Luz, A. D.; Meza-Montes, Lilia

    2011-03-01

    One of the biggest advantages of having a working quantum-computing device when compared with a classical one, is the exponential speedup of calculations. This exponential increase is based on the ability of a quantum system to create and operate on entangled states. In order to study theoretically the entanglement between two electron spins, we simulate the dynamics of two electron spins in an electrostatically-defined double quantum dot with a finite barrier height between the dots. Electrons are initially confined to separated quantum dots. Barrier height is varied and the spin entanglement as a function of this variation is investigated. The evolution of the system is simulated by using a numerical approach for solving the time-dependent Schrödinger equation for two particles. Partially supported by VIEP-BUAP.

  18. Field theory of the spinning electron: I - Internal motions

    Energy Technology Data Exchange (ETDEWEB)

    Salesi, Giovanni [Universita Statale di Catania (Italy). Dipt. di Fisica; Recami, Erasmo [Universita Statale di Bergamo, Dalmine, BG (Italy). Facolta di Ingegneria]|[Universidade Estadual de Campinas, SP (Brazil). Dept. de Matematica Aplicada

    1994-05-01

    One of the most satisfactory picture of spinning particles is the Barut-Zanghi (BZ) classical theory for the relativistic electron, that relates the electron spin with the so-called Zitterbewegung (zbw). The BZ theory has been recently studied in the Lagrangian and Hamiltonian symplectic formulations, both in flat and in curved space-time. The BZ motion equations constituted the starting point for two recent works about spin and electron structure, co-authored by us, which adopted the Clifford algebra formalism. In this letter, by employing on the contrary the ordinary tensorial language, we first write down a meaningful (real) equation of motion, describing particle classical paths, quite different from the corresponding (complex) equation of the standard Dirac theory. As a consequence, we succeed in regarding the electron as an extended-type object with a classically intelligible structure (thus overcoming some long-standing, well-known problems). Second, we make explicit the kinematical properties of the 4-velocity field v{sup {mu}}, which also result to be quite different from the ordinary ones, valid for scalar particles. At last, we analyze the inner zbw motions, both time-like and light-like, as functions of the initial conditions (in particular, for the case of classical uniform motions, the z component of spin s is shown to be quantized). In so doing, we make explicit the strict correlation existing between electron polarization and zbw kinematics. (author). 9 refs.

  19. Electron spin resonance in a two-dimensional Fermi liquid with spin-orbit coupling

    Science.gov (United States)

    Maiti, Saurabh; Imran, Muhammad; Maslov, Dmitrii L.

    2016-01-01

    Electron spin resonance (ESR) is usually viewed as a single-particle phenomenon protected from the effect of many-body correlations. We show that this is not the case in a two-dimensional Fermi liquid (FL) with spin-orbit coupling (SOC). Depending on whether the in-plane magnetic field is below or above some critical value, ESR in such a system probes up to three chiral-spin collective modes, augmented by the spin mode in the presence of the field, or the Silin-Leggett mode. All the modes are affected by both SOC and FL renormalizations. We argue that ESR can be used as a probe not only for SOC but also for many-body physics.

  20. Sample heating system for spin-polarized scanning electron microscopy.

    Science.gov (United States)

    Kohashi, Teruo; Motai, Kumi

    2013-08-01

    A sample-heating system for spin-polarized scanning electron microscopy (spin SEM) has been developed and used for microscopic magnetization analysis at temperatures up to 500°C. In this system, a compact ceramic heater and a preheating operation keep the ultra-high vacuum conditions while the sample is heated during spin SEM measurement. Moreover, the secondary-electron collector, which is arranged close to the sample, was modified so that it is not damaged at high temperatures. The system was used to heat a Co(1000) single-crystal sample from room temperature up to 500°C, and the magnetic-domain structures were observed. Changes of the domain structures were observed around 220 and 400°C, and these changes are considered to be due to phase transitions of this sample.

  1. Coherence and control of a single electron spin in a quantum dot

    NARCIS (Netherlands)

    Koppens, F.H.L.

    2007-01-01

    An electron does not only have an electric charge, but also a small magnetic moment, called spin. In a magnetic field, the spin can point in the same direction as the field (spin-up) or in the opposite direction (spin-down). However, the laws of quantum mechanics also allow the spin to exist in both

  2. Electronic spin susceptibility of metallic superconductive nano-particles

    Institute of Scientific and Technical Information of China (English)

    Li Feng; Chen Zhi-Qian; Li Qing

    2006-01-01

    We have observed the thermodynamic properties of metallic superconductive nano-particles in the grand canonical ensemble; and the level distribution and the level correlation between the discrete electronic energy levels are considered in the calculation of the electronic spin susceptibility of the ensemble numerically. The quantum effect, even-odd effect and other special effects existing in the metallic nano-particles are also studied in this article.

  3. Quantum computing by optical control of electron spins

    CERN Document Server

    Liu, Ren-Bao; Sham, L J

    2010-01-01

    We review the progress and main challenges in implementing large-scale quantum computing by optical control of electron spins in quantum dots (QDs). Relevant systems include self-assembled QDs of III-V or II-VI compound semiconductors (such as InGaAs and CdSe), monolayer fluctuation QDs in compound semiconductor quantum wells, and impurity centers in solids such as P-donors in silicon and nitrogen-vacancy centers in diamond. The decoherence of the electron spin qubits is discussed and various schemes for countering the decoherence problem are reviewed. We put forward designs of local nodes consisting of a few qubits which can be individually addressed and controlled. Remotely separated local nodes are connected by photonic structures (microcavities and waveguides) to form a large-scale distributed quantum system or a quantum network. The operation of the quantum network consists of optical control of a single electron spin, coupling of two spins in a local nodes, optically controlled quantum interfacing betwe...

  4. Spin-Mediated Consciousness Theory Possible Roles of Oxygen Unpaired Electronic Spins and Neural Membrane Nuclear Spin Ensemble in Memory and Consciousness

    CERN Document Server

    Hu, H; Hu, Huping; Wu, Maoxin

    2002-01-01

    We postulate that consciousness is connected to quantum mechanical spin since said spin is embedded in the microscopic structure of spacetime and may be more fundamental than spacetime itself. Thus, we theorize that consciousness is connected with the fabric of spacetime through spin. That is, spin is the "pixel" and "antenna" of mind. The unity of mind is achieved by non-local means within the pre-spacetime domain interfaced with spacetime. Human mind is possible because of the particular structures and dynamics of our brain postulated working as follows: The unpaired electronic spins of highly lipid-soluble and rapidly diffusing oxygen molecules extract information from the dynamical neural membranes and communicate said information through strong spin-spin couplings to the nuclear spin ensemble in the membranes for consciousness-related quantum statistical processing which survives decoherence. In turn, the dynamics of the nuclear spin ensemble has effects through spin chemistry on the classical neural act...

  5. Investigations of ionomers by electron spin resonance

    CERN Document Server

    Sueleymanoglu, N

    1999-01-01

    through direct diffusion and ligand making manner. Cu''+ sup + and Mn''+''+ ion adsorption properties of Polyn (N-vinyl-2 pyrrolidone/Itaconic acid) P(VP/IA) hydrogels that were prepared to be used to remove some environmental agents from water were investigated and teh similarity of the structure which was formed by the adsorption of metal ions by hydrogels with so called ionomers was examined. For this purpose, the hydrogels that were formed with 2ml vinyl pyrrolidone (VP) aqueous solutions of 0.06, 0.09, 0.12, 0.18, 0.24g itaconic acid with 1 ml of distilled water and exposed to 6''0''Co gamma source were used. The adsorbed quantity of Cu''+''+ ions in hydrogels was determined with UV-Visible absorption spectroscopy and adsorption isotherms of hydrogels were formed. The shapes of the lines showed that the adsorption of metal ions by hydrogels was in accordance with the multilayer physical adsorption isoterms. Same isotherms were also obtained by the relative intensity values ESR spectra. DSC study was carr...

  6. Electronic transport through EuO spin filter tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Jutong, Nuttachai; Eckern, Ulrich [Institut fuer Physik, Universitaet Augsburg, 86135 Augsburg (Germany); Rungger, Ivan; Sanvito, Stefano [School of Physics and CRANN, Trinity College Dublin, Dublin (Ireland); Schwingenschloegl, Udo [KAUST, PSE Division, Thuwal 23955-6900, Kingdom of Saudi Arabia (Saudi Arabia)

    2012-07-01

    Spin filter tunnel junctions based on europium monoxide (EuO), a ferromagnetic semiconductor, are investigated by means of density functional theory. In particular, the spin transport of Cu/EuO/Cu junctions is investigated by using the self-consistent ab-initio electron transport code SMEAGOL. The dependence of the transmission coefficient on the interface spacing and on the EuO thickness is studied, and explained in terms of the density of states and the complex band structure of EuO. Our calculation indicates that EuO epitaxially grown on Cu can act as a perfect spin filter, with polarization close to 100%, which is related mainly to the Eu-4f states. The transmission coefficient is sensitive to the interface spacing, since this spacing determines the charge transfer between EuO and the Cu leads.

  7. Dynamical Decoupling of a single electron spin at room temperature

    CERN Document Server

    Naydenov, Boris; Hall, Liam T; Shin, Chang; Fedder, Helmut; Hollenberg, Lloyd C L; Jelezko, Fedor; Wrachtrup, Jörg

    2010-01-01

    Here we report the increase of the coherence time T$_2$ of a single electron spin at room temperature by using dynamical decoupling. We show that the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence can prolong the T$_2$ of a single Nitrogen-Vacancy center in diamond up to 2.44 ms compared to the Hahn echo measurement where T$_2 = 390~\\mu$s. Moreover, by performing spin locking experiments we demonstrate that with CPMG the maximum possible $T_2$ is reached. On the other hand, we do not observe strong increase of the coherence time in nanodiamonds, possibly due to the short spin lattice relaxation time $T_1=100~\\mu$s (compared to T$_1$ = 5.93 ms in bulk). An application for detecting low magnetic field is demonstrated, where we show that the sensitivity using the CPMG method is improved by about a factor of two compared to the Hahn echo method.

  8. Surface spin-electron acoustic waves in magnetically ordered metals

    CERN Document Server

    Andreev, Pavel A

    2015-01-01

    Degenerate plasmas with motionless ions show existence of three surface waves: the Langmuir wave, the electromagnetic wave, and the zeroth sound. Applying the separated spin evolution quantum hydrodynamics to half-space plasma we demonstrate the existence of the surface spin-electron acoustic wave (SSEAW). We study dispersion of the SSEAW. We show that there is hybridization between the surface Langmuir wave and the SSEAW at rather small spin polarization. In the hybridization area the dispersion branches are located close to each other. In this area there is a strong interaction between these waves leading to the energy exchange. Consequently, generating the Langmuir waves with the frequencies close to hybridization area we can generate the SSEAWs. Thus, we report a method of creation of the SEAWs.

  9. Reaching the quantum limit of sensitivity in electron spin resonance

    Science.gov (United States)

    Bienfait, A.; Pla, J. J.; Kubo, Y.; Stern, M.; Zhou, X.; Lo, C. C.; Weis, C. D.; Schenkel, T.; Thewalt, M. L. W.; Vion, D.; Esteve, D.; Julsgaard, B.; Mølmer, K.; Morton, J. J. L.; Bertet, P.

    2016-03-01

    The detection and characterization of paramagnetic species by electron spin resonance (ESR) spectroscopy is widely used throughout chemistry, biology and materials science, from in vivo imaging to distance measurements in spin-labelled proteins. ESR relies on the inductive detection of microwave signals emitted by the spins into a coupled microwave resonator during their Larmor precession. However, such signals can be very small, prohibiting the application of ESR at the nanoscale (for example, at the single-cell level or on individual nanoparticles). Here, using a Josephson parametric microwave amplifier combined with high-quality-factor superconducting microresonators cooled at millikelvin temperatures, we improve the state-of-the-art sensitivity of inductive ESR detection by nearly four orders of magnitude. We demonstrate the detection of 1,700 bismuth donor spins in silicon within a single Hahn echo with unit signal-to-noise ratio, reduced to 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance. The detection volume of our resonator is ˜0.02 nl, and our approach can be readily scaled down further to improve sensitivity, providing a new versatile toolbox for ESR at the nanoscale.

  10. Oxidative reactions during early stages of beer brewing studied by electron spin resonance and spin trapping.

    Science.gov (United States)

    Frederiksen, Anne M; Festersen, Rikke M; Andersen, Mogens L

    2008-09-24

    An electron spin resonance (ESR)-based method was used for evaluating the levels of radical formation during mashing and in sweet wort. The method included the addition of 5% (v/v) ethanol together with the spin trap alpha-4-pyridyl(1-oxide)- N- tert-butylnitrone (POBN) to wort, followed by monitoring the rate of formation of POBN spin adducts during aerobic heating of the wort. The presence of ethanol makes the spin trapping method more selective and sensitive for the detection of highly reactive radicals such as hydroxyl and alkoxyl radicals. Samples of wort that were collected during the early stages of the mashing process gave higher rates of spin adduct formation than wort samples collected during the later stages. The lower oxidative stability of the early wort samples was confirmed by measuring the rate of oxygen consumption during heating of the wort. The addition of Fe(II) to the wort samples increased the rate of spin adduct formation, whereas the addition of Fe(II) during the mashing had no effect on the oxidative stability of the wort samples. Analysis of the iron content in the sweet wort samples demonstrated that iron added during the mashing had no effect on the iron level in the wort. The moderate temperatures during the early steps of mashing allow the endogenous malt enzymes to be active. The potential antioxidative effects of different redox-active enzymes during mashing were tested by measuring the rate of spin adduct formation in samples of wort. Surprisingly, a high catalase dosage caused a significant, 20% reduction of the initial rate of radical formation, whereas superoxide dismutase had no effect on the oxidation rates. This suggests that hydrogen peroxide and superoxide are not the only intermediates that play a role in the oxidative reactions occurring during aerobic oxidation of sweet wort.

  11. MONTE CARLO SIMULATION OF SPIN-POLARIZED SECONDARY ELECTRONS FROM IRON

    Institute of Scientific and Technical Information of China (English)

    X. Sun; Z.J. Ding; H.M Li; K. Salma; Z.M. Zhang; W.S. Tan

    2005-01-01

    A Monte Carlo model considering the electron spin direction and spin asymmetry has been developed. The energy distribution of the secondary electron polarization and the primary energy dependence of the polarization from Fe are studied. The simulation results show that:(1) the intensity of the spin-up secondary electrons is larger thanvthat of thevspin-down secondary electrons, suggesting the secondary electrons are spin polarized; (2) the spin polarization of secondary electrons with nearly zero kinetic energy is higher than the average valance spin polarization, Pb=27% for Fe. With increasing kinetic energy, the spin polarization of the secondary electrons decreases to the value of Pb remaining constant at higher kinetic energies;(3) the spin polarization increases with an increase in the primary energy and reaches a saturation value at higher primary energy in both the Monte Carlo simulation and experimental results.

  12. Quantum Computing Using Pulse-Based Electron-Nuclear Double Resonance (endor):. Molecular Spin-Qubits

    Science.gov (United States)

    Sato, Kazuo; Nakazawa, Shigeki; Rahimi, Robabeh D.; Nishida, Shinsuke; Ise, Tomoaki; Shimoi, Daisuke; Toyota, Kazuo; Morita, Yasushi; Kitagawa, Masahiro; Carl, Parick; Höfner, Peter; Takui, Takeji

    2009-06-01

    Electrons with the spin quantum number 1/2, as physical qubits, have naturally been anticipated for implementing quantum computing and information processing (QC/QIP). Recently, electron spin-qubit systems in organic molecular frames have emerged as a hybrid spin-qubit system along with a nuclear spin-1/2 qubit. Among promising candidates for QC/QIP from the materials science side, the reasons for why electron spin-qubits such as molecular spin systems, i.e., unpaired electron spins in molecular frames, have potentialities for serving for QC/QIP will be given in the lecture (Chapter), emphasizing what their advantages or disadvantages are entertained and what technical and intrinsic issues should be dealt with for the implementation of molecular-spin quantum computers in terms of currently available spin manipulation technology such as pulse-based electron-nuclear double resonance (pulsed or pulse ENDOR) devoted to QC/QIP. Firstly, a general introduction and introductory remarks to pulsed ENDOR spectroscopy as electron-nuclear spin manipulation technology is given. Super dense coding (SDC) experiments by the use of pulsed ENDOR are also introduced to understand differentiating QC ENDOR from QC NMR based on modern nuclear spin technology. Direct observation of the spinor inherent in an electron spin, detected for the first time, will be shown in connection with the entanglement of an electron-nuclear hybrid system. Novel microwave spin manipulation technology enabling us to deal with genuine electron-electron spin-qubit systems in the molecular frame will be introduced, illustrating, from the synthetic strategy of matter spin-qubits, a key-role of the molecular design of g-tensor/hyperfine-(A-)tensor molecular engineering for QC/QIP. Finally, important technological achievements of recently-emerging CD ELDOR (Coherent-Dual ELectron-electron DOuble Resonance) spin technology enabling us to manipulate electron spin-qubits are described.

  13. Randomized benchmarking of quantum gates implemented by electron spin resonance

    Science.gov (United States)

    Park, Daniel K.; Feng, Guanru; Rahimi, Robabeh; Baugh, Jonathan; Laflamme, Raymond

    2016-06-01

    Spin systems controlled and probed by magnetic resonance have been valuable for testing the ideas of quantum control and quantum error correction. This paper introduces an X-band pulsed electron spin resonance spectrometer designed for high-fidelity coherent control of electron spins, including a loop-gap resonator for sub-millimeter sized samples with a control bandwidth ∼40 MHz. Universal control is achieved by a single-sideband upconversion technique with an I-Q modulator and a 1.2 GS/s arbitrary waveform generator. A single qubit randomized benchmarking protocol quantifies the average errors of Clifford gates implemented by simple Gaussian pulses, using a sample of gamma-irradiated quartz. Improvements in unitary gate fidelity are achieved through phase transient correction and hardware optimization. A preparation pulse sequence that selects spin packets in a narrowed distribution of static fields confirms that inhomogeneous dephasing (1 / T2∗) is the dominant source of gate error. The best average fidelity over the Clifford gates obtained here is 99.2 % , which serves as a benchmark to compare with other technologies.

  14. Inversion of electron spin resonance signal in coals

    Science.gov (United States)

    Poklonski, N. A.; Vyrko, S. A.; Poklonskaya, O. N.; Lapchuk, N. M.; Munkhtsetseg, S.

    2013-07-01

    Samples of coal from the Donetsk basin (carbon content ~90 mass%) in both lump and powder forms were studied by continuous-wave electron spin resonance (ESR) at room temperature in air. Inversion of the ESR signal (being in phase with modulation of the constant magnetic field) with an increase of lump size along the magnetic component of the microwave field was observed in the cavity of the radiospectrometer.

  15. Nanoscale microwave imaging with a single electron spin in diamond

    OpenAIRE

    Appel, Patrick; Ganzhorn, Marc; Neu, Elke; Maletinsky, Patrick

    2015-01-01

    We report on imaging of microwave (MW) magnetic fields using a magnetometer based on the electron spin of a nitrogen vacancy center in diamond. We quantitatively image the magnetic field generated by high frequency (GHz) MW current with nanoscale resolution using a scanning probe technique. We demonstrate a MW magnetic field sensitivity in the range of a few nT/$\\sqrt{\\text{Hz}}$, polarization selection and broadband capabilities under ambient conditions and thereby establish the nitrogen vac...

  16. RKKY interaction for the spin-polarized electron gas

    Science.gov (United States)

    Valizadeh, Mohammad M.; Satpathy, Sashi

    2015-11-01

    We extend the original work of Ruderman, Kittel, Kasuya and Yosida (RKKY) on the interaction between two magnetic moments embedded in an electron gas to the case where the electron gas is spin-polarized. The broken symmetry of a host material introduces the Dzyaloshinsky-Moriya (DM) vector and tensor interaction terms, in addition to the standard RKKY term, so that the net interaction energy has the form ℋ = JS1 ṡS2 + D ṡS1 ×S2 + S1 ṡΓ ↔ṡS2. We find that for the spin-polarized electron gas, a nonzero tensor interaction Γ ↔ is present in addition to the scalar RKKY interaction J, while D is zero due to the presence of inversion symmetry. Explicit expressions for these are derived for the electron gas both in 2D and 3D and we show that the net magnetic interaction can be expressed as a sum of Heisenberg and Ising like terms. The RKKY interaction exhibits a beating pattern, caused by the presence of the two Fermi momenta kF↑ and kF↓, while the R-3 distance dependence of the original RKKY result for the 3D electron gas is retained. This model serves as a simple example of the magnetic interaction in systems with broken symmetry, which goes beyond the RKKY interaction.

  17. Field-assisted spin-polarized electron transport through a single quantum well with spin-orbit coupling

    Institute of Scientific and Technical Information of China (English)

    Ding Xiu-Huan; Zhang Cun-Xi; Wang Rui; Zhou Yun-Qing; Kong Ling-Min

    2012-01-01

    We have investigated theoretically the field-driven electron transport through a single-quantum-well semiconductor heterostructure with spin-orbit coupling.The splitting of the asymmetric Fano-type resonance peaks due to the Dresselhaus spin-orbit coupling is found to be highly sensitive to the direction of the incident electron.The splitting of the Fano-type resonance induces the spin-polarization dependent electron current.The location and the line shape of the Fano-type resonance can be controlled by adjusting the energy and the direction of the incident electron,the oscillation frequency,and the amplitude of the external field.These interesting features may be used to devise tunable spin filters and realize pure spin transmission currents.

  18. Generation of a spin-polarized electron beam by multipole magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, Ebrahim, E-mail: ekarimi@uottawa.ca [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada); Grillo, Vincenzo [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Boyd, Robert W. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada); Institute of Optics, University of Rochester, Rochester, NY 14627 (United States); Santamato, Enrico [Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Compl. Univ. di Monte S. Angelo, 80126 Napoli (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Napoli (Italy)

    2014-03-01

    The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin–magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of this analysis could prove useful in the design of an improved electron microscope. - Highlights: • Theory of generating spin-polarized electron beams. • Interacting electron vortex beams with space-variant magnetic fields. • Bohr–Pauli impossibility of generating spin-polarized free electrons.

  19. Electron ionization and spin polarization control of Fe atom adsorbed graphene irradiated by a femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Dong [Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081 (China); Jiang, Lan, E-mail: jianglan@bit.edu.cn [Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081 (China); Wang, Feng; Li, Xin [Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081 (China); Qu, Liangti [Key Laboratory of Cluster Science, Ministry of Education, School of Chemistry, Beijing Institute of Technology, Beijing 100081 (China); Lu, Yongfeng [Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0511 (United States)

    2015-10-23

    We investigate the structural properties and ionized spin electrons of an Fe–graphene system, in which the time-dependent density functional theory (TDDFT) within the generalized gradient approximation is used. The electron dynamics, including electron ionization and ionized electron spin polarization, is described for Fe atom adsorbed graphene under femtosecond laser irradiation. The theoretical results show that the electron ionization and ionized electron spin polarization are sensitive to the laser parameters, such as the incident angle and the peak intensity. The spin polarization presents the maximum value under certain laser parameters, which may be used as a source of spin-polarized electrons. - Highlights: • The structural properties of Fe–graphene system are investigated. • The electron dynamics of Fe–graphene system under laser irradiation are described. • The Fe–graphene system may be used as a source of spin-polarized electrons.

  20. Spin-electron acoustic waves: The Landau damping and ion contribution in the spectrum

    CERN Document Server

    Andreev, Pavel A

    2014-01-01

    Separated spin-up and spin-down quantum kinetics is derived for more detailed research of the spin-electron acoustic waves. Kinetic theory allows to obtain spectrum of the spin-electron acoustic waves including effects of occupation of quantum states more accurately than quantum hydrodynamics. We apply quantum kinetic to calculate the Landau damping of the spin-electron acoustic waves. We have considered contribution of ions dynamics in the spin-electron acoustic wave spectrum. We obtain contribution of ions in the Landau damping in temperature regime of classic ions. Kinetic analysis for ion-acoustic, zero sound, and Langmuir waves at separated spin-up and spin-down electron dynamics is presented as well.

  1. Growth and Electronic Structure of Heusler Compounds for Use in Electron Spin Based Devices

    Science.gov (United States)

    Patel, Sahil Jaykumar

    Spintronic devices, where information is carried by the quantum spin state of the electron instead of purely its charge, have gained considerable interest for their use in future computing technologies. For optimal performance, a pure spin current, where all electrons have aligned spins, must be generated and transmitted across many interfaces and through many types of materials. While conventional spin sources have historically been elemental ferromagnets, like Fe or Co, these materials pro duce only partially spin polarized currents. To increase the spin polarization of the current, materials like half-metallic ferromagnets, where there is a gap in the minority spin density of states around the Fermi level, or topological insulators, where the current transport is dominated by spin-locked surface states, show promise. A class of materials called Heusler compounds, with electronic structures that range from normal metals, to half metallic ferromagnets, semiconductors, superconductors and even topological insulators, interfaces well with existing device technologies, and through the use of molecular beam epitaxy (MBE) high quality heterostructures and films can be grown. This dissertation examines the electronic structure of surfaces and interfaces of both topological insulator (PtLuSb-- and PtLuBi--) and half-metallic ferromagnet (Co2MnSi-- and Co2FeSi--) III-V semiconductor heterostructures. PtLuSb and PtLuBi growth by MBE was demonstrated on Alx In1--xSb (001) ternaries. PtLuSb (001) surfaces were observed to reconstruct with either (1x3) or c(2x2) unit cells depending on Sb overpressure and substrate temperature. viii The electronic structure of these films was studied by scanning tunneling microscopy/spectroscopy (STM/STS) and photoemission spectroscopy. STS measurements as well as angle resolved photoemission spectropscopy (ARPES) suggest that PtLuSb has a zero-gap or semimetallic band structure. Additionally, the observation of linearly dispersing surface

  2. Origin of the spin-asymmetry of hot-electron transmission in Fe

    NARCIS (Netherlands)

    Banerjee, T.; Lodder, J.C.; Jansen, R.

    2007-01-01

    Using the technique of ballistic electron magnetic microscopy, we have studied the spin-asymmetry of transmission of hot electrons in Fe, for which a recent ab initio calculation has shown that the inelastic lifetime is similar for majority and minority spin. Nevertheless, using a spin-valve structu

  3. Electron spin from Goudsmit and Uhlenbeck to Spintronics

    Science.gov (United States)

    Levy, Peter M.

    2010-03-01

    While the electron's spin was postulated by Goudsmit and Uhlenbeck to explain atomic spectra of gases, it was adopted in a very different setting a decade later to explain the unusual physical and electrical transport properties of ferromagnetic metals. A discovery in 1988 lead to control currents through the spin of the electron, i.e., spintronics. The initial idea of spin dependent transport dates back to Neville Mott's work in the mid- thirties in which he developed the s-d or two current model of conduction in the 3d transition-metal ferromagnetic metals. The methodology used for semiconductor heterostructures lead one to grow high quality metallic multilayers by the 1980's, and it was apparent to Albert Fert and Peter Gr"unberg [Nobel Laureates in Physics 2007] that one could alter the magnetic configuration in ferromagnetic metals with moderate magnetic fields, and thereby change their resistivities. I will review the principle ideas and developments that lead to this new field, called Spintronics, and focus on developments in three distinct time periods. The first from 1988-1995 which was dominated by metallic multilayers which displayed giant magnetoresistance (GMR), the second from 1995-2000 when reproducible magnetic tunnel junctions (MTJ's) were studied for their tunneling magnetoresistance (TMR), and the third period from 2000-2005 in which the ideas of Berger and Slonczewski were realized on the back action of currents on the magnetic background of the materials doing the conducting, i.e., current induced magnetization switching (CIMS). Current interest has focused on spin dependent transport in oxides and carbon based materials. These developments illustrate the broad range of activities in Spintronics; a field which is barely twenty years old.

  4. Spin blockade and coherent dynamics of high-spin states in a three-electron double quantum dot

    Science.gov (United States)

    Chen, Bao-Bao; Wang, Bao-Chuan; Cao, Gang; Li, Hai-Ou; Xiao, Ming; Guo, Guang-Can; Jiang, Hong-Wen; Hu, Xuedong; Guo, Guo-Ping

    2017-01-01

    Asymmetry in a three-electron double quantum dot (DQD) allows spin blockade, when spin-3/2 (quadruplet) states and spin-1/2 (doublet) states have different charge configurations. We have observed this DQD spin blockade near the (1,2)-(2,1) charge transition using a pulsed-gate technique and a charge sensor. We, then, use this spin blockade to detect Landau-Zener-Stückelberg interference and coherent oscillations between the spin quadruplet and doublet states. Such studies add to our understandings of coherence and control properties of three-spin states in a double dot, which, in turn, would benefit explorations into various qubit encoding schemes in semiconductor nanostructures.

  5. Electron spin resonance and transient photocurrent measurements on microcrystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Dylla, T.

    2004-09-01

    The electronic properties of microcrystalline silicon ({mu}c-Si:H) films have been studied using electron spin resonance (ESR), transient photocurrent time-of-flight (TOF) techniques, and electrical conductivity measurements. Structural properties were determined by Raman spectroscopy. A wide range of structure compositions, from highly crystalline films with no discernable amorphous content, to predominantly amorphous films with no crystalline phase contributions, was investigated. Models and possible explanations concerning the nature and energetic distribution of electronic defects as a function of film composition are discussed. It is shown that the spin density N{sub S} in {mu}c-Si:H films is linked strongly to the structure composition of the material. Both reversible and irreversible changes in the ESR signal and dark conductivity due to atmospheric effects are found in {mu}c-Si:H. The porous structure of highly crystalline material facilitates in-diffusion of atmospheric gases, which strongly affects the character and/or density of surface states. Two contributing processes have been identified, namely adsorption and oxidation. Both processes lead to an increase of N{sub S}. Measurements on n-type {mu}c-Si:H films were used as a probe of the density of gap states, confirming that the spin density NS is related to the density of defects. The results confirm that for a wide range of structural compositions, the doping induced Fermi level shift in {mu}c-Si:H is governed by compensation of defect states, for doping concentrations up to the dangling bond spin density. At higher concentrations a doping efficiency close to unity was found, confirming that in {mu}c-Si:H the measured spin densities represent the majority of gap states (N{sub S}=N{sub DB}). By applying the TOF technique to study pin solar cells based on {mu}c-Si:H, conclusive hole drift mobility data were obtained. Despite the predominant crystallinity of these samples, the temperature-dependence of

  6. Spin-polarized transport in a two-dimensional electron gas with interdigital-ferromagnetic contacts

    DEFF Research Database (Denmark)

    Hu, C.-M.; Nitta, Junsaku; Jensen, Ane

    2001-01-01

    Ferromagnetic contacts on a high-mobility, two-dimensional electron gas (2DEG) in a narrow gap semiconductor with strong spin-orbit interaction are used to investigate spin-polarized electron transport. We demonstrate the use of magnetized contacts to preferentially inject and detect specific spi...... orientations. Spin dephasing and spin precession effects are studied by temperature and 2DEG channel length dependent measurements. Interdigital-ferromagnetic contacts suppress unwanted effects due to ferromagnetic microstrip inhomogeneities by averaging....

  7. Single-shot read-out of an individual electron spin in a quantum dot.

    Science.gov (United States)

    Elzerman, J M; Hanson, R; Willems Van Beveren, L H; Witkamp, B; Vandersypen, L M K; Kouwenhoven, L P

    2004-07-22

    Spin is a fundamental property of all elementary particles. Classically it can be viewed as a tiny magnetic moment, but a measurement of an electron spin along the direction of an external magnetic field can have only two outcomes: parallel or anti-parallel to the field. This discreteness reflects the quantum mechanical nature of spin. Ensembles of many spins have found diverse applications ranging from magnetic resonance imaging to magneto-electronic devices, while individual spins are considered as carriers for quantum information. Read-out of single spin states has been achieved using optical techniques, and is within reach of magnetic resonance force microscopy. However, electrical read-out of single spins has so far remained elusive. Here we demonstrate electrical single-shot measurement of the state of an individual electron spin in a semiconductor quantum dot. We use spin-to-charge conversion of a single electron confined in the dot, and detect the single-electron charge using a quantum point contact; the spin measurement visibility is approximately 65%. Furthermore, we observe very long single-spin energy relaxation times (up to approximately 0.85 ms at a magnetic field of 8 T), which are encouraging for the use of electron spins as carriers of quantum information.

  8. Spin Relaxation of Electrons in Single InAs Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    MA Shan-Shan; DOU Xiu-Ming; CHANG Xiu-Ying; SUN Bao-Quan; XIONG Yong-Hua; NIU Zhi-Chuan; NI Hai-Qiao

    2009-01-01

    By using polarization-resolved photoluminescence spectra, we study the electron spin relaxation in single InAs quantum dots (QDs) with the configuration of positively charged excitons X~+ (one electron, two holes). The spin relaxation rate of the hot electrons increases with the increasing energy of exciting photons. For electrons localized in QDs the spin relaxation is induced by hyperfine interaction with the nuclei. A rapid decrease of polarization degree with increasing temperature suggests that the spin relaxation mechanisms are mainly changed from the hyperfine interaction with nuclei into an electron-hole exchange interaction.

  9. Interaction induced staggered spin-orbit order in two-dimensional electron gas

    Energy Technology Data Exchange (ETDEWEB)

    Das, Tanmoy [Los Alamos National Laboratory

    2012-06-05

    Decoupling spin and charge transports in solids is among the many prerequisites for realizing spin electronics, spin caloritronics, and spin-Hall effect. Beyond the conventional method of generating and manipulating spin current via magnetic knob, recent advances have expanded the possibility to optical and electrical method which are controllable both internally and externally. Yet, due to the inevitable presence of charge excitations and electrical polarizibility in these methods, the separation between spin and charge degrees of freedom of electrons remains a challenge. Here we propose and formulate an interaction induced staggered spin-orbit order as a new emergent phase of matter. We show that when some form of inherent spin-splitting via Rashba-type spin-orbit coupling renders two helical Fermi surfaces to become significantly nested, a Fermi surface instability arises. To lift this degeneracy, a spontaneous symmetry breaking spin-orbit density wave develops, causing a surprisingly large quasiparticle gapping with chiral electronic states, with no active charge excitations. Since the staggered spin-orbit order is associated with a condensation energy, quantified by the gap value, destroying such spin-orbit interaction costs sufficiently large perturbation field or temperature or de-phasing time. BiAg2 surface state is shown to be a representative system for realizing such novel spin-orbit interaction with tunable and large strength, and the spin-splitting is decoupled from charge excitations.

  10. Electron spin resonance in Eu-based iron pnictides

    Science.gov (United States)

    Krug von Nidda, H.-A.; Kraus, S.; Schaile, S.; Dengler, E.; Pascher, N.; Hemmida, M.; Eom, M. J.; Kim, J. S.; Jeevan, H. S.; Gegenwart, P.; Deisenhofer, J.; Loidl, A.

    2012-09-01

    The phase diagrams of EuFe2-xCoxAs2 (0≤x≤0.4) and EuFe2As2-yPy (0≤y≤0.43) are investigated by Eu2+ electron spin resonance (ESR) in single crystals. From the temperature dependence of the linewidth ΔH(T) of the exchange narrowed ESR line, the spin-density wave (SDW) (TTSDW) are clearly distinguished. At T>TSDW the isotropic linear increase of the linewidth is driven by the Korringa relaxation which measures the conduction-electron density of states at the Fermi level. For Trate from 8 Oe/K at x=y=0 down to 3 Oe/K at the onset of superconductivity. For x>0.2 and y>0.3 it remains nearly constant. Comparative ESR measurements on single crystals of the Eu diluted SDW compound Eu0.2Sr0.8Fe2As2 and superconducting (SC) Eu0.22Sr0.78Fe1.72Co0.28As2 corroborate the leading influence of the ligand field on the Eu2+ spin relaxation in the SDW regime as well as the Korringa relaxation in the normal metallic regime. A coherence peak is not detected in the latter compound below Tc=21 K, which is in agreement with the expected complex anisotropic SC gap structure. In contrast, indications for phase coexistence and BCS-type superconductivity are found in EuFe2As1.57P0.43.

  11. Electron spin polarization in strong-field ionization of xenon atoms

    Science.gov (United States)

    Hartung, Alexander; Morales, Felipe; Kunitski, Maksim; Henrichs, Kevin; Laucke, Alina; Richter, Martin; Jahnke, Till; Kalinin, Anton; Schöffler, Markus; Schmidt, Lothar Ph. H.; Ivanov, Misha; Smirnova, Olga; Dörner, Reinhard

    2016-08-01

    As a fundamental property of the electron, the spin plays a decisive role in the electronic structure of matter, from solids to molecules and atoms, for example, by causing magnetism. Yet, despite its importance, the spin dynamics of the electrons released during the interaction of atoms with strong ultrashort laser pulses has remained experimentally unexplored. Here, we report the experimental detection of electron spin polarization by the strong-field ionization of xenon atoms and support our results with theoretical analysis. We found up to 30% spin polarization changing its sign with electron energy. This work opens the new dimension of spin to strong-field physics. It paves the way to the production of sub-femtosecond spin-polarized electron pulses with applications ranging from probing the magnetic properties of matter at ultrafast timescales to testing chiral molecular systems with sub-femtosecond temporal and sub-ångström spatial resolutions.

  12. Doppler Velocimetry of Current Driven Spin Helices in a Two-Dimensional Electron Gas

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Luyi [Univ. of California, Berkeley, CA (United States)

    2013-05-17

    Spins in semiconductors provide a pathway towards the development of spin-based electronics. The appeal of spin logic devices lies in the fact that the spin current is even under time reversal symmetry, yielding non-dissipative coupling to the electric field. To exploit the energy-saving potential of spin current it is essential to be able to control it. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature remains elusive. Further progress requires a deeper understanding of the propagation of spin polarization, particularly in the high mobility semiconductors used for devices. This dissertation presents the demonstration and application of a powerful new optical technique, Doppler spin velocimetry, for probing the motion of spin polarization at the level of 1 nm on a picosecond time scale. We discuss experiments in which this technique is used to measure the motion of spin helices in high mobility n-GaAs quantum wells as a function of temperature, in-plane electric field, and photoinduced spin polarization amplitude. We find that the spin helix velocity changes sign as a function of wave vector and is zero at the wave vector that yields the largest spin lifetime. This observation is quite striking, but can be explained by the random walk model that we have developed. We discover that coherent spin precession within a propagating spin density wave is lost at temperatures near 150 K. This finding is critical to understanding why room temperature operation of devices based on electrical gate control of spin current has so far remained elusive. We report that, at all temperatures, electron spin polarization co-propagates with the high-mobility electron sea, even when this requires an unusual form of separation of spin density from photoinjected electron density. Furthermore, although the spin packet co-propagates with the two-dimensional electron gas, spin diffusion is strongly

  13. Spin-Hall effect in two-dimensional electron systems with Rashba spin-orbit coupling and disorder.

    Science.gov (United States)

    Sheng, L; Sheng, D N; Ting, C S

    2005-01-14

    Using the four-terminal Landauer-Bu ttiker formula and Green's function approach, we calculate numerically the spin-Hall conductance in a two-dimensional junction system with the Rashba spin-orbit (SO) coupling and disorder. We find that the spin-Hall conductance can be much greater or smaller than the universal value e/8pi, depending on the magnitude of the SO coupling, the electron Fermi energy, and the disorder strength. The spin-Hall conductance does not vanish with increasing sample size for a wide range of disorder strength. Our numerical calculation reveals that a nonzero SO coupling can induce electron delocalization for disorder strength smaller than a critical value, and the nonvanishing spin-Hall effect appears mainly in the metallic regime.

  14. Controllable spin-orbit couplings of trapped electrons for distant quantum manipulations

    CERN Document Server

    Zhang, Miao

    2012-01-01

    Spin-orbit interactions of carriers yield various many-body quantum effects in the semiconducting physics. Here, we propose an approach to coherently manipulate spin-orbit interactions of electrons trapped on the liquid Helium at a single quantum level. The configuration consists of single electrons, confined individually on the liquid Helium by the micro-electrodes, moving along the surface as the harmonic oscillators. The spin of an electron could be coupled to its orbit (i.e., the vibrational motion) by properly applying a magnetic field. Interestingly, a Jaynes-Cummings (JC) type interaction between the spin of an electron and the vibrational motion of another distant electron is induced by virtually exciting the vibrational motion of the electron. With the present JC model, the quantum information processing between the spin qubits of the distant electrons could be effectively realized without moving the electrons. The proposal could be generlizedly applied to the other Fermi-Bosonic systems.

  15. Characterization of hyperfine interaction between an NV electron spin and a first-shell 13C nuclear spin in diamond

    Science.gov (United States)

    Rao, K. Rama Koteswara; Suter, Dieter

    2016-08-01

    The nitrogen-vacancy (NV) center in diamond has attractive properties for a number of quantum technologies that rely on the spin angular momentum of the electron and the nuclei adjacent to the center. The nucleus with the strongest interaction is the 13C nuclear spin of the first shell. Using this degree of freedom effectively hinges on precise data on the hyperfine interaction between the electronic and the nuclear spin. Here, we present detailed experimental data on this interaction, together with an analysis that yields all parameters of the hyperfine tensor, as well as its orientation with respect to the atomic structure of the center.

  16. Dynamic electronic institutions in agent oriented cloud robotic systems.

    Science.gov (United States)

    Nagrath, Vineet; Morel, Olivier; Malik, Aamir; Saad, Naufal; Meriaudeau, Fabrice

    2015-01-01

    The dot-com bubble bursted in the year 2000 followed by a swift movement towards resource virtualization and cloud computing business model. Cloud computing emerged not as new form of computing or network technology but a mere remoulding of existing technologies to suit a new business model. Cloud robotics is understood as adaptation of cloud computing ideas for robotic applications. Current efforts in cloud robotics stress upon developing robots that utilize computing and service infrastructure of the cloud, without debating on the underlying business model. HTM5 is an OMG's MDA based Meta-model for agent oriented development of cloud robotic systems. The trade-view of HTM5 promotes peer-to-peer trade amongst software agents. HTM5 agents represent various cloud entities and implement their business logic on cloud interactions. Trade in a peer-to-peer cloud robotic system is based on relationships and contracts amongst several agent subsets. Electronic Institutions are associations of heterogeneous intelligent agents which interact with each other following predefined norms. In Dynamic Electronic Institutions, the process of formation, reformation and dissolution of institutions is automated leading to run time adaptations in groups of agents. DEIs in agent oriented cloud robotic ecosystems bring order and group intellect. This article presents DEI implementations through HTM5 methodology.

  17. Electron spin echo of Cu(2+) in the triglycine sulfate crystal family (TGS, TGSe, TGFB): electron spin-lattice relaxation, Debye temperature and spin-phonon coupling.

    Science.gov (United States)

    Lijewski, S; Goslar, J; Hoffmann, S K

    2006-07-05

    The electron spin-lattice relaxation of Cu(2+) has been studied by the electron spin echo technique in the temperature range 4.2-115 K in triglycine sulfate (TGS) family crystals. Assuming that the relaxation is due to Raman relaxation processes the Debye temperature Θ(D) was determined as 190 K for TGS, 168 K for triglycine selenate (TGSe) and 179 K for triglycine fluoroberyllate (TGFB). We also calculated the Θ(D) values from the sound velocities derived from available elastic constants. The elastic Debye temperatures were found as 348 K for TGS, 288 K for TGSe and 372 K for TGFB. The results shown good agreement with specific heat data for TGS. The elastic Θ(D) are considerably larger than those determined from the Raman spin-lattice relaxation. The possible reasons for this discrepancy are discussed. We propose to use a modified expression describing two-phonon Raman relaxation with a single variable only (Θ(D)) after elimination of the sound velocity. Moreover, we show that the relaxation data can be fitted using the elastic Debye temperature value as a constant with an additional relaxation process contributing at low temperatures. This mechanism can be related to a local mode of the Cu(2+) defect in the host lattice. Electron paramagnetic resonance g-factors and hyperfine splitting were analysed in terms of the molecular orbital theory and the d-orbital energies and covalency factors of the Cu(gly)(2) complexes were found. Using the structural data and calculated orbital energies the spin-phonon coupling matrix element of the second-order Raman process was calculated as 553 cm(-1) for TGS, 742 cm(-1) for TGSe and 569 cm(-1) for TGFB.

  18. Model for ballistic spin-transport in ferromagnet/two-dimensional electron gas/ferromagnet structures

    NARCIS (Netherlands)

    Schapers, T; Nitta, J; Heersche, HB; Takayanagi, H

    2002-01-01

    The spin dependent conductance of a ferromagnet/two-dimensional electron gas ferromagnet structure is theoretically examined in the ballistic transport regime. It is shown that the spin signal can be improved considerably by making use of the spin filtering effect of a barrier at the ferromagnet two

  19. Room-temperature electron spin amplifier based on Ga(In)NAs alloys.

    Science.gov (United States)

    Puttisong, Yuttapoom; Buyanova, Irina A; Ptak, Aaron J; Tu, Charles W; Geelhaar, Lutz; Riechert, Henning; Chen, Weimin M

    2013-02-06

    The first experimental demonstration of a spin amplifier at room temperature is presented. An efficient, defect-enabled spin amplifier based on a non-magnetic semiconductor, Ga(In)NAs, is proposed and demonstrated, with a large spin gain (up to 2700% at zero field) for conduction electrons and a high cut-off frequency of up to 1 GHz.

  20. Site directed spin labelling and pulsed dipolar electron paramagnetic resonance (double electron-electron resonance) of force activation in muscle

    Energy Technology Data Exchange (ETDEWEB)

    Fajer, Piotr G [Institute of Molecular Biophysics, Department of Biological Science, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States)

    2005-05-11

    The recent development of site specific spin labelling and advances in pulsed electron paramagnetic resonance(EPR) have established spin labelling as a viable structural biology technique. Specific protein sites or whole domains can be selectively targeted for spin labelling by cysteine mutagenesis. The secondary structure of the proteins is determined from the trends in EPR signals of labels attached to consecutive residues. Solvent accessibility or label mobility display periodicities along the labelled polypeptide chain that are characteristic of {beta}-strands (periodicity of 2 residues) or {alpha}-helices (3.6 residues). Low-resolution 3D structure of proteins is determined from the distance restraints. Two spin labels placed within 60-70 A of each other create a local dipolar field experienced by the other spin labels. The strength of this field is related to the interspin distance, {proportional_to} r{sup -3}. The dipolar field can be measured by the broadening of the EPR lines for the short distances (8-20 A) or for the longer distances (17-70 A) by the pulsed EPR methods, double electron-electron resonance(DEER) and double quantum coherence (DQC). A brief review of the methodology and its applications to the multisubunit muscle protein troponin is presented below.

  1. Doping-dependent magnetization plateaus of a coupled spin-electron chain: exact results

    Science.gov (United States)

    Strečka, Jozef; Čisárová, Jana

    2016-10-01

    A coupled spin-electron chain composed of localized Ising spins and mobile electrons is exactly solved in an external magnetic field within the transfer-matrix method. The ground-state phase diagram involves in total seven different ground states, which differ in the number of mobile electrons per unit cell and the respective spin arrangements. A rigorous analysis of the low-temperature magnetization process reveals doping-dependent magnetization plateaus, which may be tuned through the density of mobile electrons. It is demonstrated that the fractional value of the electron density is responsible for an enhanced magnetocaloric effect due to an annealed bond disorder of the mobile electrons.

  2. Agent-based services for B2B electronic commerce

    Science.gov (United States)

    Fong, Elizabeth; Ivezic, Nenad; Rhodes, Tom; Peng, Yun

    2000-12-01

    The potential of agent-based systems has not been realized yet, in part, because of the lack of understanding of how the agent technology supports industrial needs and emerging standards. The area of business-to-business electronic commerce (b2b e-commerce) is one of the most rapidly developing sectors of industry with huge impact on manufacturing practices. In this paper, we investigate the current state of agent technology and the feasibility of applying agent-based computing to b2b e-commerce in the circuit board manufacturing sector. We identify critical tasks and opportunities in the b2b e-commerce area where agent-based services can best be deployed. We describe an implemented agent-based prototype system to facilitate the bidding process for printed circuit board manufacturing and assembly. These activities are taking place within the Internet Commerce for Manufacturing (ICM) project, the NIST- sponsored project working with industry to create an environment where small manufacturers of mechanical and electronic components may participate competitively in virtual enterprises that manufacture printed circuit assemblies.

  3. Possible Roles of Neural Electron Spin Networks in Memory and Consciousness

    CERN Document Server

    Hu, H P

    2004-01-01

    Spin is the origin of quantum effects in both Bohm and Hestenes quantum formulism and a fundamental quantum process associated with the structure of space-time. Thus, we have recently theorized that spin is the mind-pixel and developed a qualitative model of consciousness based on nuclear spins inside neural membranes and proteins. In this paper, we explore the possibility of unpaired electron spins being the mind-pixels. Besides free O2 and NO, the main sources of unpaired electron spins in neural membranes and proteins are transition metal ions and O2 and NO bound/absorbed to large molecules, free radicals produced through biochemical reactions and excited molecular triplet states induced by fluctuating internal magnetic fields. We show that unpaired electron spin networks inside neural membranes and proteins are modulated by action potentials through exchange and dipolar coupling tensors and spin-orbital coupling and g-factor tensors and perturbed by microscopically strong and fluctuating internal magnetic...

  4. Electron spin relaxation of a boron-containing heterocyclic radical

    Science.gov (United States)

    Eaton, Sandra S.; Huber, Kirby; Elajaili, Hanan; McPeak, Joseph; Eaton, Gareth R.; Longobardi, Lauren E.; Stephan, Douglas W.

    2017-03-01

    Preparation of the stable boron-containing heterocyclic phenanthrenedione radical, (C6F5)2B(O2C14H8), by frustrated Lewis pair chemistry has been reported recently. Electron paramagnetic resonance measurements of this radical were made at X-band in toluene:dichloromethane (9:1) from 10 to 293 K, in toluene from 180 to 293 K and at Q-band at 80 K. In well-deoxygenated 0.1 mM toluene solution at room temperature hyperfine splittings from 11B, four pairs of 1H, and 5 pairs of 19F contribute to an EPR spectrum with many resolved lines. Observed hyperfine couplings were assigned based on DFT calculations and account for all of the fluorines and protons in the molecule. Rigid lattice g values are gx = 2.0053, gy = 2.0044, and gz = 2.0028. Near the melting point of the solvent 1/Tm is enhanced due to motional averaging of g and A anisotropy. Increasing motion above the melting point enhances 1/T1 due to contributions from tumbling-dependent processes. The overall temperature dependence of 1/T1 from 10 to 293 K was modeled with the sum of contributions of a process that is linear in T, a Raman process, spin rotation, and modulation of g anisotropy by molecular tumbling. The EPR measurements are consistent with the description of this compound as a substituted aromatic radical, with relatively small spin density on the boron.

  5. Coupling of spin and orbital motion of electrons in carbon nanotubes.

    Science.gov (United States)

    Kuemmeth, F; Ilani, S; Ralph, D C; McEuen, P L

    2008-03-27

    Electrons in atoms possess both spin and orbital degrees of freedom. In non-relativistic quantum mechanics, these are independent, resulting in large degeneracies in atomic spectra. However, relativistic effects couple the spin and orbital motion, leading to the well-known fine structure in their spectra. The electronic states in defect-free carbon nanotubes are widely believed to be four-fold degenerate, owing to independent spin and orbital symmetries, and also to possess electron-hole symmetry. Here we report measurements demonstrating that in clean nanotubes the spin and orbital motion of electrons are coupled, thereby breaking all of these symmetries. This spin-orbit coupling is directly observed as a splitting of the four-fold degeneracy of a single electron in ultra-clean quantum dots. The coupling favours parallel alignment of the orbital and spin magnetic moments for electrons and antiparallel alignment for holes. Our measurements are consistent with recent theories that predict the existence of spin-orbit coupling in curved graphene and describe it as a spin-dependent topological phase in nanotubes. Our findings have important implications for spin-based applications in carbon-based systems, entailing new design principles for the realization of quantum bits (qubits) in nanotubes and providing a mechanism for all-electrical control of spins in nanotubes.

  6. Suppression of Direct Spin Hall Currents in Two-Dimensional Electronic Systems with both Rashba and Dresselhaus Spin-Orbit Couplings

    Institute of Scientific and Technical Information of China (English)

    XIONG Jian-Wen; HU Liang-Bin; ZHANG Zhen-Xi

    2006-01-01

    @@ Based on the Heisenberg equations of motion for the electron orbital and spin degrees of freedom in two-dimensional electronic systems with both Rashba and Dresselhaus spin-orbit couplings, we show that an ac electric field can cause an ac spin Hall current in such a system. In contrast to some previous theoretical prediction, the spin Hall current will be suppressed completely in the dc limit. We argue that the suppression of dc spin Hall currents in such a system is actually a much natural result of the dynamic spin evolution due to the combined action of a dc external electric field and the intrinsic spin-orbit coupling.

  7. Bipolar tetraether lipids: chain flexibility and membrane polarity gradients from spin-label electron spin resonance.

    Science.gov (United States)

    Bartucci, R; Gambacorta, A; Gliozzi, A; Marsh, D; Sportelli, L

    2005-11-15

    Membranes of thermophilic Archaea are composed of unique tetraether lipids in which C40, saturated, methyl-branched biphytanyl chains are linked at both ends to polar groups. In this paper, membranes composed of bipolar lipids P2 extracted from the acidothermophile archaeon Sulfolobus solfataricus are studied. The biophysical basis for the membrane formation and thermal stability is investigated by using electron spin resonance (ESR) of spin-labeled lipids. Spectral anisotropy and isotropic hyperfine couplings are used to determine the chain flexibility and polarity gradients, respectively. For comparison, similar measurements have been carried out on aqueous dispersions of diacyl reference lipid dipalmitoyl phosphatidylcholine and also of diphytanoyl phosphatidylcholine, which has methyl-branched chains. At a given temperature, the bolaform lipid chains are more ordered and less flexible than in normal bilayer membranes. Only at elevated temperatures (80 degrees C) does the flexibility of the chain environment in tetraether lipid assemblies approach that of fluid bilayer membranes. The height of the hydrophobic barrier formed by a monolayer of archaebacterial lipids is similar to that in conventional fluid bilayer membranes, and the permeability barrier width is comparable to that formed by a bilayer of C16 lipid chains. At a mole ratio of 1:2, the tetraether P2 lipids mix well with dipalmitoyl phosphatidylcholine lipids and stabilize conventional bilayer membranes. The biological as well as the biotechnological relevance of the results is discussed.

  8. Electron Transfer Reactions: Generalized Spin-Boson Approach

    CERN Document Server

    Merkli, Marco

    2012-01-01

    We introduce a mathematically rigorous analysis of a generalized spin-boson system for the treatment of a donor-acceptor (reactant-product) quantum system coupled to a thermal quantum noise. The donor/acceptor probability dynamics describes transport reactions in chemical processes in presence of a noisy environment -- such as the electron transfer in a photosynthetic reaction center. Besides being rigorous, our analysis has the advantages over previous ones that (1) we include a general, non energy-conserving system-environment interaction, and that (2) we allow for the donor or acceptor to consist of multiple energy levels lying closely together. We establish explicit expressions for the rates and the efficiency (final donor-acceptor population difference) of the reaction. In particular, we show that the rate increases for a multi-level acceptor, but the efficiency does not.

  9. Effect of electronic reconstruction on cuprate-manganite spin switches.

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y.; Visani, C.; Nemes, N. M.; Fitzsimmons, M. R.; Zhu, L. Y.; Tornos, J.; Zhernenkov, M.; Hoffmann, A.; Leon, C.; Santamaria, J.; te Velthuis, S. G. E. (Materials Science Division); (Universidad Complutense de Madrid); (LANL)

    2012-01-01

    We examine the anomalous inverse spin switch behavior in La{sub 0.7}Ca{sub 0.3}MnO{sub 3}(LCMO)/YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO)/LCMO trilayers by combined transport studies and polarized neutron reflectometry. Measuring magnetization profiles and magnetoresistance in an in-plane rotating magnetic field, we prove that, contrary to many accepted theoretical scenarios, the relative orientation between the two LCMO's magnetizations is not sufficient to determine the magnetoresistance. Rather the field dependence of magnetoresistance is explained by the interplay between the applied magnetic field and the (exponential tail of the) induced exchange field in YBCO, the latter originating from the electronic reconstruction at the LCMO/YBCO interfaces.

  10. Nanoscale microwave imaging with a single electron spin in diamond

    Science.gov (United States)

    Appel, Patrick; Ganzhorn, Marc; Neu, Elke; Maletinsky, Patrick

    2015-11-01

    We report on imaging of microwave (MW) magnetic fields using a magnetometer based on the electron spin of a nitrogen vacancy (NV) center in diamond. We quantitatively image the magnetic field generated by high frequency (GHz) MW current with nanoscale resolution using a scanning probe technique. Together with a shot noise limited MW magnetic field sensitivity of 680 nT Hz-1/2 our room temperature experiments establish the NV center as a versatile and high performance tool for MW imaging, which furthermore offers polarization selectivity and broadband capabilities. As a first application of this scanning MW detector, we image the MW stray field around a stripline structure and thereby locally determine the MW current density with a MW current sensitivity of a few nA Hz-1/2.

  11. Thermal History of Archaeological Objects, Studied by Electron Spin Resonance

    Science.gov (United States)

    Bartoll, Jens; Tani, Atsushi

    Electron spin resonance (ESR) spectroscopy is a sensitive tool for distinguishing between "burned" and "unburned" states of archaeological objects. Prehistoric heating conditions, such as the temperature, atmosphere, time of exposure to heat, and when the heating took place, can be studied by this method with some success. ESR "reporters," such as (a) radiation defects, (b) pyrolytic defects, and (c) transition metal ions, can even reflect changes induced at relatively low temperatures (e.g., in the range of 200° C for objects containing organic compounds). Several ESR heating markers are so stable that samples dating back to the ages when fire first began to be used can be analyzed today. An overview is presented of the literature concerning objects, such as stone, soil, pottery, and plant and animal products.

  12. Generation of a spin-polarized electron beam by multipoles magnetic fields

    CERN Document Server

    Karimi, Ebrahim; Boyd, Robert W; Santamato, Enrico

    2013-01-01

    The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin--magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of these analysis could prove useful in the design of improved electron microscope.

  13. The effect of spin polarization on zero field splitting parameters in paramagnetic pi-electron molecules.

    Science.gov (United States)

    van Gastel, Maurice

    2009-09-28

    Spin polarization effects play an important role in the theory of isotropic hyperfine interactions for aromatic protons. The spin polarization gives rise to significant isotropic proton hyperfine interactions--spin-dependent one-electron properties--smaller than 0 MHz and the effect has been theoretically described [H. M. McConnell and D. B. J. Chesnut, Chem. Phys. 28, 107 (1958)]. The influence of spin polarization on the zero field splitting parameters, which are spin-dependent two-electron properties, has not been clearly identified yet. A phenomenological equation is proposed here for the contribution of spin polarization to the zero field splitting parameter D in analogy to McConnell's equation for hyperfine interactions. The presence of the effect is demonstrated in a series of calculations on polyacenes in the triplet state and turns out to be responsible for up to 50% of the D parameter in the case of naphthalene! It is found that spin-unrestricted single-determinant methods, including the widely used density functional theory methods, do not accurately reproduce the two-electron reduced electron density required for the evaluation of two-electron spin-dependent properties. For the accurate calculation of zero field splitting parameters by quantum chemical methods, it thus seems necessary to resort to correlated ab initio methods which do not give rise to spin contamination and which do provide an accurate description of the two-electron reduced electron density.

  14. Spin and Time-Reversal Symmetries of Superconducting Electron Pairs Probed by the Muon Spin Rotation and Relaxation Technique

    Science.gov (United States)

    Higemoto, Wataru; Aoki, Yuji; MacLaughlin, Douglas E.

    2016-09-01

    Unconventional superconductivity based on the strong correlation of electrons is one of the central issues of solid-state physics. Although many experimental techniques are appropriate for investigating unconventional superconductivity, a complete perspective has not been established yet. The symmetries of electron pairs are crucial properties for understanding the essential state of unconventional superconductivity. In this review, we discuss the investigation of the time-reversal and spin symmetries of superconducting electron pairs using the muon spin rotation and relaxation technique. By detecting a spontaneous magnetic field under zero field and/or the temperature dependence of the muon Knight shift in the superconducting phase, the time-reversal symmetry and spin parity of electron pairs have been determined for several unconventional superconductors.

  15. Extraordinary waves in two dimensional electron gas with separate spin evolution and Coulomb exchange interaction

    CERN Document Server

    Andreev, Pavel A

    2016-01-01

    Hydrodynamics analysis of waves in two-dimensional degenerate electron gas with the account of separate spin evolution is presented. The transverse electric field is included along with the longitudinal electric field. The Coulomb exchange interaction is included in the analysis. In contrast with the three-dimensional plasma-like mediums the contribution of the transverse electric field is small. We show the decrease of frequency of both the extraordinary (Langmuir) wave and the spin-electron acoustic wave due to the exchange interaction. Moreover, spin-electron acoustic wave has negative dispersion at the relatively large spin-polarization. Corresponding dispersion dependencies are presented and analyzed.

  16. Photon-assisted spin transport in a two-dimensional electron gas

    OpenAIRE

    Fistul, M. V.; Efetov, K. B.

    2007-01-01

    We study spin-dependent transport in a two-dimensional electron gas subject to an external step-like potential $V(x)$ and irradiated by an electromagnetic field (EF). In the absence of EF the electronic spectrum splits into spin sub-bands originating from the "Rashba" spin-orbit coupling. We show that the resonant interaction of propagating electrons with the component EF parallel to the barrier induces a \\textit{% non-equilibrium dynamic gap} $(2\\Delta_{R})$ between the spin sub-bands. Exist...

  17. Electrically detected electron spin resonance in a high-mobility silicon quantum well.

    Science.gov (United States)

    Matsunami, Junya; Ooya, Mitsuaki; Okamoto, Tohru

    2006-08-11

    The resistivity change due to electron spin resonance (ESR) absorption is investigated in a high-mobility two-dimensional electron system formed in a Si/SiGe heterostructure. Results for a specific Landau level configuration demonstrate that the primary cause of the ESR signal is a reduction of the spin polarization, not the effect of electron heating. The longitudinal spin relaxation time T1 is obtained to be of the order of 1 ms in an in-plane magnetic field of 3.55 T. The suppression of the effect of the Rashba fields due to high-frequency spin precession explains the very long T1.

  18. Measuring spin diffusion of electrons in bulk n-GaAs using circularly dichromatic absorption difference spectroscopy of spin gratings

    Science.gov (United States)

    Yu, Hua-Liang; Zhang, Xiu-Min; Wang, Peng-Fei; Ni, Hai-Qiao; Niu, Zhi-Chuan; Lai, Tianshu

    2009-05-01

    Circular dichromatic absorption difference spectroscopy is developed to measure the spin diffusion dynamics of electrons in bulk n-GaAs. This spectroscopy has higher detection sensitivity over homodyne detection of spin-grating-diffracted signal. A model to describe circular dichromatic absorption difference signal is derived and used to fit experimental signal to retrieve decaying rate of spin gratings. A spin diffusion constant of Ds=201±25 cm2/s for bulk n-GaAs has been measured at room temperature using this technique and is close to electron diffusion constant (Dc), which is much different from the case in GaAs quantum wells where Ds is markedly less than Dc.

  19. Spin-dependent electron transmission through ultra-thin magnetic layers: towards highly discriminative, compact spin detectors

    Energy Technology Data Exchange (ETDEWEB)

    Van der Sluijs, A.M.; Drouhin, H.J.; Lampel, G.; Lassailly, Y.; Marliere, C. [Ecole Polytechnique, 91 - Palaiseau (France)

    1994-10-01

    At low energy, a longitudinally spin-polarized electron beam impinges on an ultrathin, self-supported ferromagnetic target, consisting of a 1 nm-thick cobalt film sandwiched between 21 and 2 nm-thick gold layers, and which is magnetized perpendicularly to the surface. The current transmitted by the target depends on the spin of the electrons. Cesium deposition on both sides of the target increases the transmission ratio from about 1 x 10{sup -5} up to 3 x 10{sup -4} and also increases the transmission spin-asymmetry from 15 to about 40%. Such a structure is well suited to the construction of convenient and compact spin-detectors. (authors). 4 figs., 9 refs.

  20. Spatially confined electron spin diffusion in quasi-one-dimensional organic conductors

    CERN Document Server

    Wokrina, T

    2002-01-01

    After an introduction to the substances and some important properties of them the measurement principle, the time-resolved electron spin resonance is presented. Then the foundations and the technical realization of an image-shaping procedure on the base of electron spin tomography are described. The measurement of the spin dynamics for the three radical-ion salts form the main part and the conclusion of this thesis.

  1. Electron spin dynamics in GaAsN and InGaAsN structures

    Energy Technology Data Exchange (ETDEWEB)

    Lagarde, D.; Lombez, L.; Marie, X.; Balocchi, A.; Amand, T. [Laboratoire de Nanophysique, Magnetisme et Optoelectronique, INSA 135 avenue de Rangueil 31077 Toulouse Cedex 4 (France); Kalevich, V.K.; Shiryaev, A.; Ivchenko, E.; Egorov, A. [A.F. Ioffe Physico-Technical Institute, 194021 St-Petersburg (Russian Federation)

    2007-01-15

    We report on optical orientation experiments in undoped GaAsN epilayers and InGaAsN quantum wells (QW), showing that a strong electron spin polarisation can persist at room temperature. We demonstrate that the spin dynamics in these dilute nitride structures is governed by a spin-dependent recombination process of free conduction electrons on deep paramagnetic centres. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Pauli Spin Paramagnetism and Electronic Specific Heat in Generalised d-Dimensions

    Institute of Scientific and Technical Information of China (English)

    Muktish Acharyya

    2011-01-01

    The variations of pauli spin paramagnetic susceptibility and the electronic specific heat of solids, are calculated as functions of temperature following the free electron approximation, in generalised d-dimensions.The results are compared and become consistent with that obtained in three dimensions.Interestingly, the Pauli spin paramagnetic susceptibility becomes independent of temperature only in two dimensions.

  3. Relaxation of the electron spin in quantum dots via one- and two-phonon processes

    Energy Technology Data Exchange (ETDEWEB)

    Calero, C. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States)]. E-mail: carlos.calero-borrallo@lehman.cuny.edu; Chudnovsky, E.M. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States); Garanin, D.A. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States)

    2007-09-15

    We have studied direct and Raman processes of the decay of electron spin states in a quantum dot via radiation of phonons corresponding to elastic twists. Universal dependence of the spin relaxation rate on the strength and direction of the magnetic field has been obtained in terms of the electron gyromagnetic tensor and macroscopic elastic constants of the solid.

  4. 1H relaxation dispersion in solutions of nitroxide radicals: Influence of electron spin relaxation

    Science.gov (United States)

    Kruk, D.; Korpała, A.; Kubica, A.; Kowalewski, J.; Rössler, E. A.; Moscicki, J.

    2013-03-01

    The work presents a theory of nuclear (1H) spin-lattice relaxation dispersion for solutions of 15N and 14N radicals, including electron spin relaxation effects. The theory is a generalization of the approach presented by Kruk et al. [J. Chem. Phys. 137, 044512 (2012)], 10.1063/1.4736854. The electron spin relaxation is attributed to the anisotropic part of the electron spin-nitrogen spin hyperfine interaction modulated by rotational dynamics of the paramagnetic molecule, and described by means of Redfield relaxation theory. The 1H relaxation is caused by electron spin-proton spin dipole-dipole interactions which are modulated by relative translational motion of the solvent and solute molecules. The spectral density characterizing the translational dynamics is described by the force-free-hard-sphere model. The electronic relaxation influences the 1H relaxation by contributing to the fluctuations of the inter-molecular dipolar interactions. The developed theory is tested against 1H spin-lattice relaxation dispersion data for glycerol solutions of 4-oxo-TEMPO-d16-15N and 4-oxo-TEMPO-d16-14N covering the frequency range of 10 kHz-20 MHz. The studies are carried out as a function of temperature starting at 328 K and going down to 290 K. The theory gives a consistent overall interpretation of the experimental data for both 14N and 15N systems and explains the features of 1H relaxation dispersion resulting from the electron spin relaxation.

  5. Electronic spin transport in graphene field-effect transistors

    NARCIS (Netherlands)

    Popinciuc, M.; Jozsa, C.; Zomer, P. J.; Tombros, N.; Veligura, A.; Jonkman, H. T.; van Wees, B. J.

    2009-01-01

    Spin transport experiments in graphene, a single layer of carbon atoms ordered in a honeycomb lattice, indicate spin-relaxation times that are significantly shorter than the theoretical predictions. We investigate experimentally whether these short spin-relaxation times are due to extrinsic factors,

  6. High-frequency manipulation of few-electron double quantum dots-toward spin qubits

    Science.gov (United States)

    Kodera, T.; van der Wiel, W. G.; Ono, K.; Sasaki, S.; Fujisawa, T.; Tarucha, S.

    2004-04-01

    We use a photon-assisted tunneling (PAT) technique to study the high-frequency response of one- and two-electron states in a semiconductor vertically coupled double-dot system. In particular, PAT associated with two-electron spin states in the spin-blockade regime is observed up to the absorption of 10 photons, indicating the preservation of long relaxation times and hence the robustness of our electron spin device under strong microwave irradiation. An alternative double-dot structure with greater flexibility in tuning the inter-dot coupling is presented and its transport characteristics are discussed. This structure is proposed for high-frequency control of two-electron spin states, as required for quantum computation schemes using electron spins in quantum dots.

  7. Coupling of spin and orbital motion of electrons in carbon nanotubes

    DEFF Research Database (Denmark)

    Kuemmeth, Ferdinand; Ilani, S; Ralph, D C

    2008-01-01

    Electrons in atoms possess both spin and orbital degrees of freedom. In non-relativistic quantum mechanics, these are independent, resulting in large degeneracies in atomic spectra. However, relativistic effects couple the spin and orbital motion, leading to the well-known fine structure...... in their spectra. The electronic states in defect-free carbon nanotubes are widely believed to be four-fold degenerate, owing to independent spin and orbital symmetries, and also to possess electron–hole symmetry. Here we report measurements demonstrating that in clean nanotubes the spin and orbital motion...... of electrons are coupled, thereby breaking all of these symmetries. This spin–orbit coupling is directly observed as a splitting of the four-fold degeneracy of a single electron in ultra-clean quantum dots. The coupling favours parallel alignment of the orbital and spin magnetic moments for electrons...

  8. Generalized Elliott-Yafet theory of electron spin relaxation in metals: origin of the anomalous electron spin lifetime in MgB2.

    Science.gov (United States)

    Simon, F; Dóra, B; Murányi, F; Jánossy, A; Garaj, S; Forró, L; Bud'ko, S; Petrovic, C; Canfield, P C

    2008-10-24

    The temperature dependence of the electron-spin relaxation time in MgB2 is anomalous as it does not follow the resistivity above 150 K; it has a maximum around 400 K and decreases for higher temperatures. This violates the well established Elliot-Yafet theory of spin relaxation in metals. The anomaly occurs when the quasiparticle scattering rate (in energy units) is comparable to the energy difference between the conduction and a neighboring bands. The anomalous behavior is related to the unique band structure of MgB2 and the large electron-phonon coupling. The saturating spin relaxation is the spin transport analogue of the Ioffe-Regel criterion of electron transport.

  9. Spinning Carbon Nanotube Nanothread under a Scanning Electron Microscope

    Directory of Open Access Journals (Sweden)

    Mark Schulz

    2011-08-01

    Full Text Available Nanothread with a diameter as small as one hundred nanometers was manufactured under a scanning electron microscope. Made directly from carbon nanotubes, and inheriting their superior electrical and mechanical properties, nanothread may be the world’s smallest man-made fiber. The smallest thread that can be spun using a bench-top spinning machine is about 5 microns in diameter. Nanothread is a new material building block that can be used at the nanoscale or plied to form yarn for applications at the micro and macro scales. Preliminary electrical and mechanical properties of nanothread were measured. The resistivity of nanothread is less than 10−5 Ω∙m. The strength of nanothread is greater than 0.5 GPa. This strength was obtained from measurements using special glue that cures in an electron microscope. The glue weakened the thread, thus further work is needed to obtain more accurate measurements. Nanothread will have broad applications in enabling electrical components, circuits, sensors, and tiny machines. Yarn can be used for various macroscale applications including lightweight antennas, composites, and cables.

  10. Refined entanglement concentration for electron-spin entangled cluster states with quantum-dot spins in optical microcavities

    Science.gov (United States)

    Du, Fang-Fang; Long, Gui-Lu

    2017-01-01

    We present a refined entanglement concentration protocol (ECP) for an arbitrary unknown less-entangled four-electron-spin cluster state by exploring the optical selection rules derived from the quantum-dot spins in one-sided optical microcavities. In our ECP, the parties obtain not only the four-electron-spin systems in the partial entanglement with two unknown parameters, but also the less-entangled two-electron-spin systems in the first step. Utilizing the above preserved systems as the resource for the second step of our ECP, the parties can obtain a standard cluster state by keeping the robust odd-parity instances with two parity-check gates. Meanwhile, the systems in the rest three instances can be used as the resource in the next round of our ECP. The success probability of our ECP is largely increased by iteration of the ECP process. Moreover, all the coefficients of our ECP are unknown for the parties without assistance of extra single electron-spin, so our ECP maybe has good applications in quantum communication network in the future.

  11. Inelastic processes of electron interactions with halouracils - cancer therapy agents

    Science.gov (United States)

    Limbachiya, Chetan; Vinodkumar, Minaxi; Swadia, Mohit

    2014-10-01

    We report electron impact total inelastic cross sections for important cancer treatment agents, 5-fluorouracil (5FU), 5-chlorouracil (5ClU) and 5-bromouracil (5BrU) from ionization threshold through 5000 eV. We have employed Spherical Complex Optical Potential [1,2] method to compute total inelastic cross sections Qinel and Complex Scattering Potential - ionization contribution (CSP-ic) formalism, to calculate total ionization cross sections Qion. Electron driven ionization cross sections for these important compounds of therapeutic interest are reported for the first time in this work. In absence of any ionization study for these cancer therapy agents, we have compared the data with their parent molecule Uracil. Present cross sections may serve as a reference estimates for experimental work.

  12. Electron Spin-Lattice Relaxation of doped Yb3+ ions in YBa2Cu3Ox

    OpenAIRE

    2005-01-01

    The electron spin-lattice relaxation (SLR) times T1 of Yb3+‡ ions were measured from the temperature dependence of electron spin resonance linewidth in Y0.99Yb0.01Ba2Cu3Ox with different oxygen contents. Raman relaxation processes dominate the electron SLR. Derived from the temperature dependence of the SLR rate, the Debye temperature (Td) increases with the critical temperature Tc and oxygen content x. Keywords: EPR; ESR; Electron spin-lattice relaxation; Debye temperature; Critical tem...

  13. Electron spin interactions in chemistry and biology fundamentals, methods, reactions mechanisms, magnetic phenomena, structure investigation

    CERN Document Server

    Likhtenshtein, Gertz

    2016-01-01

    This book presents the versatile and pivotal role of electron spin interactions in nature. It provides the background, methodologies and tools for basic areas related to spin interactions, such as spin chemistry and biology, electron transfer, light energy conversion, photochemistry, radical reactions, magneto-chemistry and magneto-biology. The book also includes an overview of designing advanced magnetic materials, optical and spintronic devices and photo catalysts. This monograph appeals to scientists and graduate students working in the areas related to spin interactions physics, biophysics, chemistry and chemical engineering.

  14. Electron spin and the origin of Bio-homochirality I. Extant enzymatic reaction model

    CERN Document Server

    Wang, Wei

    2013-01-01

    In this paper, I tentatively put forward a new hypothesis that the emergence of a single chiral form of biomolecules in living organisms is specifically determined by the electron spin state during their enzyme-catalyzed synthesis processes. Specifically speaking, the electrons released from the coenzyme NAD(P)H of amino acid synthase are heterogeneous in spin states; however, when they pass through the chiral alpha-helix structure of the enzymes to the site of amino acid synthesis at the other end of the helix, their spin states are filtered and polarized, producing only spin up electrons; once the spin-polarized electrons participate in the reductive reaction between alpha-oxo acid and ammonia, only L-amino acids are formed according to the Pauli exclusion principle.

  15. Induction-Detection Electron Spin Resonance with Sensitivity of 1000 Spins: En Route to Scalable Quantum Computations

    CERN Document Server

    Blank, Aharon; Shklyar, Roman; Twig, Ygal

    2013-01-01

    Spin-based quantum computation (QC) in the solid state is considered to be one of the most promising approaches to scalable quantum computers. However, it faces problems such as initializing the spins, selectively addressing and manipulating single spins, and reading out the state of the individual spins. We have recently sketched a scheme that potentially solves all of these problems5. This is achieved by making use of a unique phosphorus-doped 28Si sample (28Si:P), and applying powerful new electron spin resonance (ESR) techniques for parallel excitation, detection, and imaging in order to implement QCs and efficiently obtain their results. The beauty of our proposed scheme is that, contrary to other approaches, single-spin detection sensitivity is not required and a capability to measure signals of ~100-1000 spins is sufficient to implement it. Here we take the first experimental step towards the actual implementation of such scheme. We show that, by making use of the smallest ESR resonator constructed to ...

  16. Concept of a multichannel spin-resolving electron analyzer based on Mott scattering

    Energy Technology Data Exchange (ETDEWEB)

    Strocov, Vladimir N., E-mail: vladimir.strocov@psi.ch [Paul Scherrer Institute, CH-5232 Villigen-PSI (Switzerland); Petrov, Vladimir N. [St Petersburg Polytechnical University, Polytechnicheskaya Str. 29, St Petersburg RU-195251 (Russian Federation); Dil, J. Hugo [Paul Scherrer Institute, CH-5232 Villigen-PSI (Switzerland); École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland)

    2015-04-10

    The concept of a two-dimensional multichannel electron spin detector based on Mott scattering and imaging-type electron optics is presented. The efficiency increase of about four orders of magnitude opens new scientific fields including buried magnetic interfaces. The concept of a multichannel electron spin detector based on optical imaging principles and Mott scattering (iMott) is presented. A multichannel electron image produced by a standard angle-resolving (photo) electron analyzer or microscope is re-imaged by an electrostatic lens at an accelerating voltage of 40 kV onto the Au target. Quasi-elastic electrons bearing spin asymmetry of the Mott scattering are imaged by magnetic lenses onto position-sensitive electron CCDs whose differential signals yield the multichannel spin asymmetry image. Fundamental advantages of this concept include acceptance of inherently divergent electron sources from the electron analyzer or microscope focal plane as well as small aberrations achieved by virtue of high accelerating voltages, as demonstrated by extensive ray-tracing analysis. The efficiency gain compared with the single-channel Mott detector can be a factor of more than 10{sup 4} which opens new prospects of spin-resolved spectroscopies in application not only to standard bulk and surface systems (Rashba effect, topological insulators, etc.) but also to buried heterostructures. The simultaneous spin detection combined with fast CCD readout enables efficient use of the iMott detectors at X-ray free-electron laser facilities.

  17. Organic electron donors as powerful single-electron reducing agents in organic synthesis.

    Science.gov (United States)

    Broggi, Julie; Terme, Thierry; Vanelle, Patrice

    2014-01-07

    One-electron reduction is commonly used in organic chemistry for the formation of radicals by the stepwise transfer of one or two electrons from a donor to an organic substrate. Besides metallic reagents, single-electron reducers based on neutral organic molecules have emerged as an attractive novel source of reducing electrons. The past 20 years have seen the blossoming of a particular class of organic reducing agents, the electron-rich olefins, and their application in organic synthesis. This Review gives an overview of the different types of organic donors and their specific characteristics in organic transformations.

  18. Spin-Orbit Coupling and Novel Electronic States at the Interfaces of Heavy Fermion Materials

    Science.gov (United States)

    2016-02-22

    spin-orbit coupling (SOC) may induce new electronic phases that are difficult to realize in bulk materials . With the support of this STIR grant, we have...Report: Spin-Orbit Coupling and Novel Electronic States at the Interfaces of Heavy Fermion Materials Report Title This report summarizes the progress...regime in the correlated- electron “global” phase diagram of heavy fermion materials and, in addition, paving the way for interactions between the

  19. Two dimensional electron spin resonance: Structure and dynamics of biomolecules

    Science.gov (United States)

    Saxena, Sunil; Freed, Jack H.

    1998-03-01

    The potential of two dimensional (2D) electron spin resonance (ESR) for measuring the structural properties and slow dynamics of labeled biomolecules will be presented. Specifically, it will be shown how the recently developed method of double quantum (DQ) 2D ESR (S. Saxena and J. H. Freed, J. Chem. Phys. 107), 1317, (1997) can be used to measure large interelectron distances in bilabeled peptides. The need for DQ ESR spectroscopy, as well as the challenges and advantages of this method will be discussed. The elucidation of the slow reorientational dynamics of this peptide (S. Saxena and J. H. Freed, J. Phys. Chem. A, 101) 7998 (1997) in a glassy medium using COSY and 2D ELDOR ESR spectroscopy will be demonstrated. The contributions to the homogeneous relaxation time, T_2, from the overall and/or internal rotations of the nitroxide can be distinguished from the COSY spectrum. The growth of spectral diffusion cross-peaks^2 with mixing time in the 2D ELDOR spectra can be used to directly determine a correlation time from the experiment which can be related to the rotational correlation time.

  20. Mechanical detection of electron spin resonance beyond 1 THz

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Hideyuki [Organization of Advanced Science and Technology, Kobe University, 1-1, Rokkodai, Nada, Kobe 657-8501 (Japan); Ohmichi, Eiji [Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan); Ohta, Hitoshi [Molecular Photoscience Research Center, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan)

    2015-11-02

    We report the cantilever detection of electron spin resonance (ESR) in the terahertz (THz) region. This technique mechanically detects ESR as a change in magnetic torque that acts on the cantilever. The ESR absorption of a tiny single crystal of Co Tutton salt, Co(NH{sub 4}){sub 2}(SO{sub 4}){sub 2}⋅6H{sub 2}O, was observed in frequencies of up to 1.1 THz using a backward travelling wave oscillator as a THz-wave source. This is the highest frequency of mechanical detection of ESR till date. The spectral resolution was evaluated with the ratio of the peak separation to the sum of the half-width at half maximum of two absorption peaks. The highest resolution value of 8.59 ± 0.53 was achieved at 685 GHz, while 2.47 ± 0.01 at 80 GHz. This technique will not only broaden the scope of ESR spectroscopy application but also lead to high-spectral-resolution ESR imaging.

  1. Coupling of spin and orbital motion of electrons in carbon nanotubes

    DEFF Research Database (Denmark)

    Kuemmeth, Ferdinand; Ilani, S; Ralph, D C;

    2008-01-01

    Electrons in atoms possess both spin and orbital degrees of freedom. In non-relativistic quantum mechanics, these are independent, resulting in large degeneracies in atomic spectra. However, relativistic effects couple the spin and orbital motion, leading to the well-known fine structure...... in their spectra. The electronic states in defect-free carbon nanotubes are widely believed to be four-fold degenerate, owing to independent spin and orbital symmetries, and also to possess electron–hole symmetry. Here we report measurements demonstrating that in clean nanotubes the spin and orbital motion...... and antiparallel alignment for holes. Our measurements are consistent with recent theories that predict the existence of spin–orbit coupling in curved graphene and describe it as a spin dependent topological phase in nanotubes. Our findings have important implications for spin-based applications in carbon- based...

  2. Heat transport and electron cooling in ballistic normal-metal/spin-filter/superconductor junctions

    Energy Technology Data Exchange (ETDEWEB)

    Kawabata, Shiro, E-mail: s-kawabata@aist.go.jp [Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Vasenko, Andrey S. [LPMMC, Université Joseph Fourier and CNRS, 25 Avenue des Martyrs, BP 166, 38042 Grenoble (France); Ozaeta, Asier [Centro de Física de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, Manuel de Lardizabal 5, E-20018 San Sebastián (Spain); Bergeret, Sebastian F. [Centro de Física de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, Manuel de Lardizabal 5, E-20018 San Sebastián (Spain); Donostia International Physics Center (DIPC), Manuel de Lardizabal 5, E-20018 San Sebastián (Spain); Hekking, Frank W.J. [LPMMC, Université Joseph Fourier and CNRS, 25 Avenue des Martyrs, BP 166, 38042 Grenoble (France)

    2015-06-01

    We investigate electron cooling based on a clean normal-metal/spin-filter/superconductor junction. Due to the suppression of the Andreev reflection by the spin-filter effect, the cooling power of the system is found to be extremely higher than that for conventional normal-metal/nonmagnetic-insulator/superconductor coolers. Therefore we can extract large amount of heat from normal metals. Our results strongly indicate the practical usefulness of the spin-filter effect for cooling detectors, sensors, and quantum bits.

  3. Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses.

    Science.gov (United States)

    Clark, Susan M; Fu, Kai-Mei C; Ladd, Thaddeus D; Yamamoto, Yoshihisa

    2007-07-27

    We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

  4. Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points

    KAUST Repository

    Bučinský, Lukáš

    2014-06-01

    The change of picture of the quasirelativistic Hartree-Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl5(Hpz)]- and [RuCl5(NO)]2- transition metal complexes are considered. Both, scalar relativistic and spin-orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.©2014 Elsevier B.V. All rights reserved.

  5. Quantum Monte Carlo study of the itinerant-localized model of strongly correlated electrons: Spin-spin correlation functions

    OpenAIRE

    Ivantsov, Ilya; Ferraz, Alvaro; Kochetov, Evgenii

    2016-01-01

    We perform quantum Monte Carlo simulations of the itinerant-localized periodic Kondo-Heisenberg model for the underdoped cuprates to calculate the associated spin correlation functions. The strong electron correlations are shown to play a key role in the abrupt destruction of the quasi long-range antiferromagnetic order in the lightly doped regime.

  6. Quantum Monte Carlo study of the itinerant-localized model of strongly correlated electrons: Spin-spin correlation functions

    Science.gov (United States)

    Ivantsov, Ilya; Ferraz, Alvaro; Kochetov, Evgenii

    2016-12-01

    We perform quantum Monte Carlo simulations of the itinerant-localized periodic Kondo-Heisenberg model for the underdoped cuprates to calculate the associated spin correlation functions. The strong electron correlations are shown to play a key role in the abrupt destruction of the quasi-long-range antiferromagnetic order in the lightly doped regime.

  7. Observation of vacuum-enhanced electron spin resonance of levitated nanodiamonds

    CERN Document Server

    Hoang, Thai M; Bang, Jaehoon; Li, Tongcang

    2015-01-01

    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 low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this novel system, we also investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. Our results show that optical levitation of nanodiamonds in vacuum not only can improve the mechanical quality of its oscillation, but also enhance the ESR contrast, which pave the way towards a novel levitated spin-optomechanical system for studying macroscopic quantum mechanics. The results also indicate potenti...

  8. Observation of vacuum-enhanced electron spin resonance of optically levitated nanodiamonds

    Science.gov (United States)

    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 low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this novel system, we also investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. Our results show that optical levitation of nanodiamonds in vacuum not only can improve the mechanical quality of its oscillation, but also enhance the ESR contrast, which pave the way towards a novel levitated spin-optomechanical system for studying macroscopic quantum mechanics. The results also indicate potential applications of NV centers in gas sensing.

  9. Direct Measurement of the Flip-Flop Rate of Electron Spins in the Solid State

    Science.gov (United States)

    Dikarov, Ekaterina; Zgadzai, Oleg; Artzi, Yaron; Blank, Aharon

    2016-10-01

    Electron spins in solids have a central role in many current and future spin-based devices, ranging from sensitive sensors to quantum computers. Many of these apparatuses rely on the formation of well-defined spin structures (e.g., a 2D array) with controlled and well-characterized spin-spin interactions. While being essential for device operation, these interactions can also result in undesirable effects, such as decoherence. Arguably, the most important pure quantum interaction that causes decoherence is known as the "flip-flop" process, where two interacting spins interchange their quantum state. Currently, for electron spins, the rate of this process can only be estimated theoretically, or measured indirectly, under limiting assumptions and approximations, via spin-relaxation data. This work experimentally demonstrates how the flip-flop rate can be directly and accurately measured by examining spin-diffusion processes in the solid state for physically fixed spins. Under such terms, diffusion can occur only through this flip-flop-mediated quantum-state exchange and not via actual spatial motion. Our approach is implemented on two types of samples, phosphorus-doped 28Si and nitrogen vacancies in diamond, both of which are significantly relevant to quantum sensors and information processing. However, while the results for the former sample are conclusive and reveal a flip-flop rate of approximately 12.3 Hz, for the latter sample only an upper limit of approximately 0.2 Hz for this rate can be estimated.

  10. Two-dimensional electron-electron double resonance and electron spin-echo study of solute dynamics in smectics

    Science.gov (United States)

    Gorcester, Jeff; Rananavare, Shankar B.; Freed, Jack H.

    1989-05-01

    Electron spin-echo (ESE) and two-dimensional electron-electron double resonance (2D ELDOR) experiments have been performed as a function of director orientation and temperature in the smectic A phase of the liquid crystal S2 for the spin-probe PD-tempone(2×10-3 M). Over the entire temperature range studied (288-323 K) we observe significant 2D ELDOR cross peaks only for ΔMI =±1 indicative of 14N spin-relaxation and negligible Heisenberg exchange. From the angular dependent 14N spin-relaxation rates we obtain the dipolar spectral densities at the hyperfine (hf) frequency, whereas from a combination of ESE and 2D ELDOR we obtain the dipolar and Zeeman-dipolar spectral densities at zero frequency. The angular dependent spectral densities were successfully decomposed into their basic components in accordance with theory. The angular dependent spectral densities at the hf frequency are not predicted by a model of anisotropic rotational diffusion in a nematic orienting potential, but are consistent with predictions of a model due to Moro and Nordio of solute rototranslational diffusion in a McMillan-type potential. The angular dependence also indicates that order director fluctuations in the smectic phase are suppressed at frequencies on the order of 10 MHz. An additional contribution to solute reorientation due to cooperative hydrocarbon chain fluctuations is suggested to account for the behavior of the observed spectral densities at zero frequency. An evaluation of the relevance of several other dynamical models to this experimental work is also presented.

  11. Electron spin relaxation can enhance the performance of a cryptochrome-based magnetic compass sensor

    DEFF Research Database (Denmark)

    Kattnig, Daniel R; Sowa, Jakub K; Solov'yov, Ilia A;

    2016-01-01

    The radical pair model of the avian magnetoreceptor relies on long-lived electron spin coherence. Dephasing, resulting from interactions of the spins with their fluctuating environment, is generally assumed to degrade the sensitivity of this compass to the direction of the Earth's magnetic field...

  12. Nuclear Tuning and Detuning of the Electron Spin Resonance in a Quantum Dot: Theoretical Consideration

    NARCIS (Netherlands)

    Danon, J.; Nazarov, Y.V.

    2008-01-01

    We study nuclear spin dynamics in a quantum dot close to the conditions of electron spin resonance. We show that at a small frequency mismatch, the nuclear field detunes the resonance. Remarkably, at larger frequency mismatch, its effect is opposite: The nuclear system is bistable, and in one of the

  13. Electron Spin Resonance and Related Phenomena in Low-Dimensional Structures

    CERN Document Server

    Fanciulli, Marco

    2009-01-01

    Deals with the discussion of the development of spin resonance in low dimensional structures, such as two-dimensional electron systems, quantum wires, and quantum dots. This title discusses opportunities for spin resonance techniques, with emphasis on fundamental physics, nanoelectronics, spintronics, and quantum information processing

  14. Proposed Coupling of an Electron Spin in a Semiconductor Quantum Dot to a Nanosize Optical Cavity

    DEFF Research Database (Denmark)

    Majumdar, Arka; Nielsen, Per Kær; Bajcsy, Michal

    2013-01-01

    We propose a scheme to efficiently couple a single quantum dot electron spin to an optical nano-cavity, which enables us to simultaneously benefit from a cavity as an efficient photonic interface, as well as to perform high fidelity (nearly 100%) spin initialization and manipulation achievable in...

  15. Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

    Energy Technology Data Exchange (ETDEWEB)

    Singamaneni, Srinivasa Rao, E-mail: ssingam@ncsu.edu [INPAC – Institute for Nanoscale Physics and Chemistry, Semiconductor Physics Laboratory, K.U. Leuven, Celestijnenlaan 200D, B–3001 Leuven (Belgium); Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Department of Material Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Stesmans, Andre [INPAC – Institute for Nanoscale Physics and Chemistry, Semiconductor Physics Laboratory, K.U. Leuven, Celestijnenlaan 200D, B–3001 Leuven (Belgium); Tol, Johan van [National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, Florida 32310 (United States); Kosynkin, D. V. [Department of Chemistry, Smalley Institute for Nanoscale Science and Technology, Rice University, MS-222, 6100 Main Street, Houston, Texas 77005 (United States); Tour, James M. [Department of Chemistry, Smalley Institute for Nanoscale Science and Technology, Rice University, MS-222, 6100 Main Street, Houston, Texas 77005 (United States); Department of Mechanical Engineering and Materials Science, Smalley Institute for Nanoscale Science and Technology, Rice University, MS-222, 6100 Main Street, Houston, Texas 77005 (United States); Smalley Institute for Nanoscale Science and Technology, Rice University, MS-222, 6100 Main Street, Houston, Texas 77005, USA. (United States)

    2014-04-15

    Electronic spin transport properties of graphene nanoribbons (GNRs) are influenced by the presence of adatoms, adsorbates and edge functionalization. To improve the understanding of the factors that influence the spin properties of GNRs, local (element) spin-sensitive techniques such as electron spin resonance (ESR) spectroscopy are important for spintronics applications. Here, we present results of multi-frequency continuous wave (CW), pulse and hyperfine sublevel correlation (HYSCORE) ESR spectroscopy measurements performed on oxidatively unzipped graphene nanoribbons (GNRs), which were subsequently chemically converted (CCGNRs) with hydrazine. ESR spectra at 336 GHz reveal an isotropic ESR signal from the CCGNRs, of which the temperature dependence of its line width indicates the presence of localized unpaired electronic states. Upon functionalization of CCGNRs with 4-nitrobenzene diazonium tetrafluoroborate, the ESR signal is found to be 2 times narrower than that of pristine ribbons. NH{sub 3} adsorption/desorption on CCGNRs is shown to narrow the signal, while retaining the signal intensity and g value. The electron spin-spin relaxation process at 10 K is found to be characterized by slow (163 ns) and fast (39 ns) components. HYSCORE ESR data demonstrate the explicit presence of protons and {sup 13}C atoms. With the provided identification of intrinsic point magnetic defects such as proton and {sup 13}C has been reported, which are roadblocks to spin travel in graphene-based materials, this work could help in advancing the present fundamental understanding on the edge-spin (or magnetic)-based transport properties of CCGNRs.

  16. Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

    Directory of Open Access Journals (Sweden)

    Srinivasa Rao Singamaneni

    2014-04-01

    Full Text Available Electronic spin transport properties of graphene nanoribbons (GNRs are influenced by the presence of adatoms, adsorbates and edge functionalization. To improve the understanding of the factors that influence the spin properties of GNRs, local (element spin-sensitive techniques such as electron spin resonance (ESR spectroscopy are important for spintronics applications. Here, we present results of multi-frequency continuous wave (CW, pulse and hyperfine sublevel correlation (HYSCORE ESR spectroscopy measurements performed on oxidatively unzipped graphene nanoribbons (GNRs, which were subsequently chemically converted (CCGNRs with hydrazine. ESR spectra at 336 GHz reveal an isotropic ESR signal from the CCGNRs, of which the temperature dependence of its line width indicates the presence of localized unpaired electronic states. Upon functionalization of CCGNRs with 4-nitrobenzene diazonium tetrafluoroborate, the ESR signal is found to be 2 times narrower than that of pristine ribbons. NH3 adsorption/desorption on CCGNRs is shown to narrow the signal, while retaining the signal intensity and g value. The electron spin-spin relaxation process at 10 K is found to be characterized by slow (163 ns and fast (39 ns components. HYSCORE ESR data demonstrate the explicit presence of protons and 13C atoms. With the provided identification of intrinsic point magnetic defects such as proton and 13C has been reported, which are roadblocks to spin travel in graphene-based materials, this work could help in advancing the present fundamental understanding on the edge-spin (or magnetic-based transport properties of CCGNRs.

  17. Spin labeling and Double Electron-Electron Resonance (DEER) to Deconstruct Conformational Ensembles of HIV Protease

    Science.gov (United States)

    Casey, Thomas M.; Fanucci, Gail E.

    2016-01-01

    An understanding of macromolecular conformational equilibrium in biological systems is oftentimes essential to understand function, dysfunction, and disease. For the past few years, our lab has been utilizing site-directed spin labeling (SDSL), coupled with electron paramagnetic resonance (EPR) spectroscopy, to characterize the conformational ensemble and ligand-induced conformational shifts of HIV-1 protease (HIV-1PR). The biomedical importance of characterizing the fractional occupancy of states within the conformational ensemble critically impacts our hypothesis of a conformational selection mechanism of drug-resistance evolution in HIV-1PR. The purpose of the following chapter is to give a timeline perspective of our SDSL EPR approach to characterizing conformational sampling of HIV-1PR. We provide detailed instructions for the procedure utilized in analyzing distance profiles for HIV-1PR obtained from pulsed electron–electron double resonance (PELDOR). Specifically, we employ a version of PELDOR known as double electron–electron resonance (DEER). Data are processed with the software package “DeerAnalysis” (http://www.epr.ethz.ch/software), which implements Tikhonov regularization (TKR), to generate a distance profile from electron spin-echo amplitude modulations. We assign meaning to resultant distance profiles based upon a conformational sampling model, which is described herein. The TKR distance profiles are reconstructed with a linear combination of Gaussian functions, which is then statistically analyzed. In general, DEER has proven powerful for observing structural ensembles in proteins and, more recently, nucleic acids. Our goal is to present our advances in order to aid readers in similar applications. PMID:26477251

  18. Density functional perturbational orbital theory of spin polarization in electronic systems. II. Transition metal dimer complexes.

    Science.gov (United States)

    Seo, Dong-Kyun

    2007-11-14

    We present a theoretical scheme for a semiquantitative analysis of electronic structures of magnetic transition metal dimer complexes within spin density functional theory (DFT). Based on the spin polarization perturbational orbital theory [D.-K. Seo, J. Chem. Phys. 125, 154105 (2006)], explicit spin-dependent expressions of the spin orbital energies and coefficients are derived, which allows to understand how spin orbitals form and change their energies and shapes when two magnetic sites are coupled either ferromagnetically or antiferromagnetically. Upon employment of the concept of magnetic orbitals in the active-electron approximation, a general mathematical formula is obtained for the magnetic coupling constant J from the analytical expression for the electronic energy difference between low-spin broken-symmetry and high-spin states. The origin of the potential exchange and kinetic exchange terms based on the one-electron picture is also elucidated. In addition, we provide a general account of the DFT analysis of the magnetic exchange interactions in compounds for which the active-electron approximation is not appropriate.

  19. Spin injection into a two-dimensional electron gas using inter-digital-ferromagnetic contacts

    DEFF Research Database (Denmark)

    Hu, C.M.; Nitta, J.; Jensen, Ane;

    2002-01-01

    We present a model that describes the spin injection across a single interface with two electrodes. The spin-injection rate across a typical hybrid junction made of ferromagnet (FM) and a two-dimensional electron gas (2DEG) is found at the percentage level. We perforin spin-injection-detection ex......-injection-detection experiment on devices with two ferromagnetic contacts on a 2DEG confined in an InAs quantum well. A spin-injection rate of 4.5% is estimated from the measured magnetoresistance....

  20. Electron Spin Resonance of Tetrahedral Transition Metal Oxyanions (MO4n-) in Solids.

    Science.gov (United States)

    Greenblatt, M.

    1980-01-01

    Outlines general principles in observing sharp electron spin resonance (ESR) lines in the solid state by incorporating the transition metal ion of interest into an isostructural diamagnetic host material in small concentration. Examples of some recent studies are described. (CS)

  1. Asymmetric recombination and electron spin relaxation in the semiclassical theory of radical pair reactions

    CERN Document Server

    Lewis, Alan M; Hore, P J

    2014-01-01

    We describe how the semiclassical theory of radical pair recombination reactions recently introduced by two of us [D. E. Manolopoulos and P. J. Hore, J. Chem. Phys. 139, 124106 (2013)] can be generalised to allow for different singlet and triplet recombination rates. This is a non-trivial generalisation because when the recombination rates are different the recombination process is dynamically coupled to the coherent electron spin dynamics of the radical pair. Furthermore, because the recombination operator is a two-electron operator, it is no longer sufficient simply to consider the two electrons as classical vectors: one has to consider the complete set of 16 two-electron spin operators as independent classical variables. The resulting semiclassical theory is first validated by comparison with exact quantum mechanical results for a model radical pair containing 12 nuclear spins. It is then used to shed light on the spin dynamics of a carotenoid-porphyrin-fullerene (CPF) triad containing considerably more nu...

  2. Spintronics and chirality: spin selectivity in electron transport through chiral molecules.

    Science.gov (United States)

    Naaman, Ron; Waldeck, David H

    2015-04-01

    Recent experiments have demonstrated that the electron transmission yield through chiral molecules depends on the electron spin orientation. This phenomenon has been termed the chiral-induced spin selectivity (CISS) effect, and it provides a challenge to theory and promise for organic molecule-based spintronic devices. This article reviews recent developments in our understanding of CISS. Different theoretical models have been used to describe the effect; however, they all presume an unusually large spin-orbit coupling in chiral molecules for the effect to display the magnitudes seen in experiments. A simplified model for an electron's transport through a chiral potential suggests that these large couplings can be manifested. Techniques for measuring spin-selective electron transport through molecules are overviewed, and some examples of recent experiments are described. Finally, we present results obtained by studying several systems, and we describe the possible application of the CISS effect for memory devices.

  3. Time-domain shape of electron spin echo signal of spin-correlated radical pairs in polymer/fullerene blends

    Science.gov (United States)

    Popov, Alexander A.; Lukina, Ekaterina A.; Rapatskiy, Leonid; Kulik, Leonid V.

    2017-03-01

    Temporal shape of electron spin echo (ESE) signal of photoinduced spin-correlated radical pairs (SCRP) in composite of conductive polymer P3HT and substituted fullerene PCBM is studied in details. ESE signals of radical pairs (RP) P3HT+/PCBM- are calculated in realistic model, taking into account finite microwave pulse length. Inhomogeneous broadening of resonant lines and interradical distance distribution are included. Experimentally observed ESE time-domain shape was found to contradict predictions of conventional SCRP theory, which would be valid in the case of very fast electron transfer. Thus, instantaneous formation of singlet SCRP is not the case for P3HT+/PCBM- pair, and spin system has enough time to evolve coherently during sequential electron transfer. While it is impossible to reproduce experimental data within simple singlet SCRP model, assumption of presence of additional - with respect to what is predicted by singlet SCRP theory - AE (absorption/emission) spin polarization gives convincing accordance with the experiment. Density matrix of RP P3HT+/PCBM- is a superposition of two contributions, namely the parts reflecting (i) antiphase polarization of original singlet-born SCRP and (ii) additional AE-polarization which is generated during initial stage of charge separation. AE-polarization affects experimental ESEEM (electron spin echo envelope modulation) traces, as well as ESE shape, making impossible their interpretation via simple singlet SCRP model. However, this effect can be eliminated by averaging of ESEEM traces over EPR spectral positions. Finally, choosing the optimal gate for ESE time-domain integration and proper microwave detection phase tuning are considered.

  4. Interplay between electron spin and orbital pseudospin in double quantum dots

    OpenAIRE

    Park, Sooa; Yang, S. -R. Eric

    2005-01-01

    We investigate theoretically spin and orbital pseudospin magnetic properties of a molecular orbital in parabolic and elliptic double quantum dots (DQDs). In our many body calculation we include intra- and inter-dot electron-electron interactions, in addition to the intradot exchange interaction of `p' orbitals. We find for parabolic DQDs that, except for the half or completely filled molecular orbital, spins in different dots are ferromagnetically coupled while orbital pseudospins are antifer...

  5. Alkali-metal electron spin density shift induced by a helium nanodroplet

    OpenAIRE

    Koch, Markus; Callegari, Carlo; Ernst, Wolfgang E.

    2010-01-01

    Abstract Helium (He) nanodroplets provide a cold and virtually unperturbing environment for the study of weakly bound molecules and van der Waals aggregates. High resolution microwave spectroscopy and the detection of electron spin transitions in doped He droplets have recently become possible. Measurements of hyperfine-resolved electron spin resonance in potassium (39K) and rubidium (85Rb) atoms on the surface of He droplets show small line shifts relative to the bare atoms. These...

  6. Electrical detection of the spin resonance of a single electron in a silicon field-effect transistor.

    Science.gov (United States)

    Xiao, M; Martin, I; Yablonovitch, E; Jiang, H W

    2004-07-22

    The ability to manipulate and monitor a single-electron spin using electron spin resonance is a long-sought goal. Such control would be invaluable for nanoscopic spin electronics, quantum information processing using individual electron spin qubits and magnetic resonance imaging of single molecules. There have been several examples of magnetic resonance detection of a single-electron spin in solids. Spin resonance of a nitrogen-vacancy defect centre in diamond has been detected optically, and spin precession of a localized electron spin on a surface was detected using scanning tunnelling microscopy. Spins in semiconductors are particularly attractive for study because of their very long decoherence times. Here we demonstrate electrical sensing of the magnetic resonance spin-flips of a single electron paramagnetic spin centre, formed by a defect in the gate oxide of a standard silicon transistor. The spin orientation is converted to electric charge, which we measure as a change in the source/drain channel current. Our set-up may facilitate the direct study of the physics of spin decoherence, and has the practical advantage of being composed of test transistors in a conventional, commercial, silicon integrated circuit. It is well known from the rich literature of magnetic resonance studies that there sometimes exist structural paramagnetic defects near the Si/SiO2 interface. For a small transistor, there might be only one isolated trap state that is within a tunnelling distance of the channel, and that has a charging energy close to the Fermi level.

  7. Conversion of electronic to magnonic spin current at a heavy-metal magnetic-insulator interface

    Science.gov (United States)

    Wang, Xi-guang; Li, Zhi-xiong; Zhou, Zhen-wei; Nie, Yao-zhuang; Xia, Qing-lin; Zeng, Zhong-ming; Chotorlishvili, L.; Berakdar, J.; Guo, Guang-hua

    2017-01-01

    Electronic spin current is convertible to magnonic spin current via the creation or annihilation of thermal magnons at the interface of a magnetic insulator and a metal with a strong spin-orbital coupling. So far this phenomenon was evidenced in the linear regime. Based on analytical and full-fledged numerical results for the nonlinear regime we demonstrate that the generated thermal magnons or magnonic spin current in the insulator is asymmetric with respect to the charge current direction in the metal and exhibits a nonlinear dependence on the charge current density, which is explained by the tuning effect of the spin Hall torque and the magnetization damping. The results are also discussed in light of, and are in line with, recent experiments pointing to a new way of nonlinear manipulation of spin with electrical means.

  8. Time-dependent tunneling of spin-polarized electrons in coupled quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, H; Luis, D [Departamento de Fisica Basica, Universidad de La Laguna, 38204 La Laguna, Tenerife (Spain)], E-mail: hcruz@ull.es

    2008-02-15

    We have solved the in-plane momentum-dependent effective-mass nonlinear Schroedinger equation for a spin-polarized electron wave packet in a InAs double quantum well system with an interlayer voltage. Considering a time-dependent Hartree potential, we have calculated the spin-polarized nonlinear electron dynamics between both quantum wells at different in-plane momentum values and applied bias. The spin-splitting caused by the Rashba effect is combined with the level matching between the spin dependent resonant tunneling levels making possible the observed local spin density oscillations which depend on the applied bias value. The filtering efficiency has been studied using time-dependent calculations.

  9. Spin-Selective Electron Quantum Transport in Nonmagnetic MgZnO/ZnO Heterostructures.

    Science.gov (United States)

    Maryenko, D; Falson, J; Bahramy, M S; Dmitriev, I A; Kozuka, Y; Tsukazaki, A; Kawasaki, M

    2015-11-06

    We report magnetotransport measurements on a high-mobility two-dimensional electron system at the nonmagnetic MgZnO/ZnO heterointerface showing distinct behavior for electrons with spin-up and spin-down orientations. The low-field Shubnikov-de Haas oscillations manifest alternating resistance peak heights which can be attributed to distinct scattering rates for different spin orientations. The tilt-field measurements at a half-integer filling factor reveal that the majority spins show usual diffusive behavior, i.e., peaks with the magnitude proportional to the index of the Landau level at the Fermi energy. By contrast, the minority spins develop "plateaus" with the magnitude of dissipative resistivity that is fairly independent of the Landau level index and is of the order of the zero-field resistivity.

  10. Temperature Dependence of Electron Spin Relaxation of 2,2-diphenyl-1-picrylhydrazyl in Polystyrene

    Science.gov (United States)

    Meyer, Virginia; Eaton, Sandra S.; Eaton, Gareth R.

    2012-01-01

    The electron spin relaxation rates for the stable radical DPPH (2,2-diphenyl-1-picrylhydrazyl) doped into polystyrene were studied by inversion recovery and electron spin echo at X-band and Q-band between 20 and 295 K. At low concentration (340 μM, 0.01%) spin-lattice relaxation was dominated by the Raman process and a local mode. At high concentration (140 mM, 5%) relaxation is orders of magnitude faster than at the lower concentration, and 1/T1 is approximately linearly dependent on temperature. Spin lattice relaxation rates are similar at X-band and Q-band. The temperature dependence of spin echo dephasing was faster at about 140 K than at higher or lower temperatures, which is attributed to a wagging motion of the phenyl groups. PMID:23565040

  11. Unified dynamics of electrons and photons via Zitterbewegung and spin-orbit interaction

    Science.gov (United States)

    Leary, C. C.; Smith, Karl H.

    2014-02-01

    We show that when an electron or photon propagates in a cylindrically symmetric waveguide, it experiences both a Zitterbewegung effect and a spin-orbit interaction leading to identical propagation dynamics for both particles. Applying a unified perturbative approach to both particles simultaneously, we find that to first order in perturbation theory, their Hamiltonians each contain identical Darwin (Zitterbewegung) and spin-orbit terms, resulting in the unification of their dynamics. The presence of the Zitterbewegung effect may be interpreted physically as the delocalization of the electron on the scale of its Compton wavelength, or the delocalization of the photon on the scale of its wavelength in the waveguide. The presence of the spin-orbit interaction leads to the prediction of several rotational effects: the spatial or time evolution of either particle's spin or polarization vector is controlled by the sign of its orbital angular momentum quantum number or, conversely, its spatial wave function is controlled by its spin angular momentum.

  12. Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

    Science.gov (United States)

    Wang, Zefang; Zhao, Liang; Mak, Kin Fai; Shan, Jie

    2017-02-01

    We study the electronic band structure in the K/K' valleys of the Brillouin zone of monolayer WSe2 and MoSe2 by optical reflection and photoluminescence spectroscopy on dual-gated field-effect devices. Our experiment reveals the distinct spin polarization in the conduction bands of these compounds by a systematic study of the doping dependence of the A and B excitonic resonances. Electrons in the highest-energy valence band and the lowest-energy conduction band have antiparallel spins in monolayer WSe2, and parallel spins in monolayer MoSe2. The spin splitting is determined to be hundreds of meV for the valence bands and tens of meV for the conduction bands, which are in good agreement with first principles calculations. These values also suggest that both n- and p-type WSe2 and MoSe2 can be relevant for spin- and valley-based applications

  13. Storage of Multiple Coherent Microwave Excitations in an Electron Spin Ensemble

    DEFF Research Database (Denmark)

    Wu, Hua; George, Richard E.; Wesenberg, Janus H.;

    2010-01-01

    stored and retrieved. Here we employ holographic techniques to realize a coherent memory using a pulsed magnetic field gradient and demonstrate the storage and retrieval of up to 100 weak 10 GHz coherent excitations in collective states of an electron spin ensemble. We further show that such collective......Strong coupling between a microwave photon and electron spins, which could enable a long-lived quantum memory element for superconducting qubits, is possible using a large ensemble of spins. This represents an inefficient use of resources unless multiple photons, or qubits, can be orthogonally...

  14. Evolution of Spin and Charge in a System with Interacting Impurity and Conducting Electrons

    Institute of Scientific and Technical Information of China (English)

    张永梅; 熊诗杰

    2003-01-01

    We investigate the dynamics of spin and charge in an interacting system consisting of impurity and conducting electrons.The time evolution of spin and charge in the impurity is given by solving the time-dependent Schrodinger equations for the many-body states of the interacting system.By switching on the interaction between impurity and conducting electrons,the spin and charge of the impurity begin oscillations with frequencies that reflect the elementary excitations of the interacting system.The dynamics reflects the basic picture of the Kondo effect.

  15. Direct observation of spin-resolved full and empty electron states in ferromagnetic surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Berti, G., E-mail: giulia.berti@polimi.it; Calloni, A.; Brambilla, A.; Bussetti, G.; Duò, L.; Ciccacci, F. [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133, Milano (Italy)

    2014-07-15

    We present a versatile apparatus for the study of ferromagnetic surfaces, which combines spin-polarized photoemission and inverse photoemission spectroscopies. Samples can be grown by molecular beam epitaxy and analyzed in situ. Spin-resolved photoemission spectroscopy analysis is done with a hemispherical electron analyzer coupled to a 25 kV-Mott detector. Inverse photoemission spectroscopy experiments are performed with GaAs crystals as spin-polarized electron sources and a UV bandpass photon detector. As an example, measurements on the oxygen passivated Fe(100)-p(1×1)O surface are presented.

  16. Gate-voltage control of spin interactions between electrons and nuclei in a semiconductor

    Science.gov (United States)

    Smet, J. H.; Deutschmann, R. A.; Ertl, F.; Wegscheider, W.; Abstreiter, G.; von Klitzing, K.

    2003-01-01

    Semiconductors are ubiquitous in device electronics, because their charge distributions can be conveniently manipulated with applied voltages to perform logic operations. Achieving a similar level of control over the spin degrees of freedom, either from electrons or nuclei, could provide intriguing prospects for information processing and fundamental solid-state physics issues. Here, we report procedures that carry out the controlled transfer of spin angular momentum between electrons-confined to two dimensions and subjected to a perpendicular magnetic field-and the nuclei of the host semiconductor, using gate voltages only. We show that the spin transfer rate can be enhanced near a ferromagnetic ground state of the electron system, and that the induced nuclear spin polarization can be subsequently stored and ‘read-out’. These techniques can also be combined into a spectroscopic tool to detect the low-energy collective excitations in the electron system that promote the spin transfer. The existence of such excitations is contingent on appropriate electron-electron correlations, and these can be tuned by changing, for example, the electron density via a gate voltage.

  17. Concept of a multichannel spin-resolving electron analyzer based on Mott scattering

    Science.gov (United States)

    Strocov, Vladimir N.; Petrov, Vladimir N.; Dil, J. Hugo

    2015-01-01

    The concept of a multichannel electron spin detector based on optical imaging principles and Mott scattering (iMott) is presented. A multichannel electron image produced by a standard angle-resolving (photo) electron analyzer or microscope is re-imaged by an electrostatic lens at an accelerating voltage of 40 kV onto the Au target. Quasi-elastic electrons bearing spin asymmetry of the Mott scattering are imaged by magnetic lenses onto position-sensitive electron CCDs whose differential signals yield the multichannel spin asymmetry image. Fundamental advantages of this concept include acceptance of inherently divergent electron sources from the electron analyzer or microscope focal plane as well as small aberrations achieved by virtue of high accelerating voltages, as demonstrated by extensive ray-tracing analysis. The efficiency gain compared with the single-channel Mott detector can be a factor of more than 104 which opens new prospects of spin-resolved spectroscopies in application not only to standard bulk and surface systems (Rashba effect, topological insulators, etc.) but also to buried heterostructures. The simultaneous spin detection combined with fast CCD readout enables efficient use of the iMott detectors at X-ray free-electron laser facilities. PMID:25931087

  18. Measurement of electron spin transport in graphene on 6H-silicon carbide(0001)

    Science.gov (United States)

    Abel, Joseph

    The focus of this thesis is to demonstrate the potential of wafer scale graphene spintronics. Graphene is a single atomic layer of sp 2-bonded carbon atoms that has high carrier mobilities, making it a desirable material for future nanoscale electronic devices. The vision of spintronics is to utilize the spin of the electron to produce novel high-speed low power consuming devices. Materials with long spin relaxation times and spin diffusion lengths are needed to realize these goals. Graphene is an ideal material as it meets these requirements and is amenable to planar device geometries. In this thesis, spin transport in wafer scale epitaxial graphene grown on the silicon face of silicon carbide is demonstrated. Non-local Hanle spin precession measurement devices were fabricated using graphene with and without a hafnium oxide interface layer between the ferromagnetic metal and graphene. The structural properties of the devices were investigated with Raman spectroscopy, x-ray photoelectric spectroscopy, Rutherford backscattering spectroscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The electrical properties of the graphene were measured utilizing Hall transport measurements. The magnetic properties of the contacts were investigated with vibrating sample magnetometery. The processes developed to fabricate the Hanle measurement devices are presented as well. A custom Hanle measurement setup was developed and utilized for the Hanle spin precession measurements. Spin precession is observed in the epitaxial graphene on silicon carbide, with improved spin transport properties with the utilization of a hafnium oxide barrier between the ferromagnetic contacts and graphene. The charge transport and spin transport properties are compared to determine the relevant spin relaxation mechanism in the devices. These results demonstrate that graphene has great potential for wafer scale production of future spintronic devices.

  19. Mobile agent application and integration in electronic anamnesis system.

    Science.gov (United States)

    Liu, Chia-Hui; Chung, Yu-Fang; Chen, Tzer-Shyong; Wang, Sheng-De

    2012-06-01

    Electronic anamnesis is to transform ordinary paper trails to digitally formatted health records, which include the patient's general information, health status, and follow-ups on chronic diseases. Its main purpose is to let the records could be stored for a longer period of time and could be shared easily across departments and hospitals. Which means hospital management could use less resource on maintaining ever-growing database and reduce redundancy, so less money would be spent for managing the health records. In the foreseeable future, building up a comprehensive and integrated medical information system is a must, because it is critical to hospital resource integration and quality improvement. If mobile agent technology is adopted in the electronic anamnesis system, it would help the hospitals to make the medical practices more efficiently and conveniently. Nonetheless, most of the hospitals today are still using paper-based health records to manage the medical information. The reason why the institutions continue using traditional practices to manage the records is because there is no well-trusted and reliable electronic anamnesis system existing and accepted by both institutions and patients. The threat of privacy invasion is one of the biggest concerns when the topic of electronic anamnesis is brought up, because the security threats drag us back from using such a system. So, the medical service quality is difficult to be improved substantially. In this case, we have come up a theory to remove such security threats and make electronic anamnesis more appealing for use. Our theory is to integrate the mobile agent technology with the backbone of electronic anamnesis to construct a hierarchical access control system to retrieve the corresponding information based upon the permission classes. The system would create a classification for permission among the users inside the medical institution. Under this framework, permission control center would distribute an

  20. Two Dimensional Spin-Polarized Electron Gas at the Oxide Interfaces

    OpenAIRE

    Nanda, B. R. K.; Satpathy, S.

    2008-01-01

    The formation of a novel spin-polarized 2D electron gas at the LaMnO$_3$ monolayer embedded in SrMnO$_3$ is predicted from the first-principles density-functional calculations. The La (d) electrons become confined in the direction normal to the interface in the potential well of the La layer, serving as a positively-charged layer of electron donors. These electrons mediate a ferromagnetic alignment of the Mn t$_{2g}$ spins near the interface via the Anderson-Hasegawa double exchange and becom...

  1. Quantum simulation of a spin polarization device in an electron microscope

    Science.gov (United States)

    Grillo, Vincenzo; Marrucci, Lorenzo; Karimi, Ebrahim; Zanella, Riccardo; Santamato, Enrico

    2013-09-01

    A proposal for an electron-beam device that can act as an efficient spin-polarization filter has been recently put forward (Karimi et al 2012 Phys. Rev. Lett. 108 044801). It is based on combining the recently developed diffraction technology for imposing orbital angular momentum to the beam with a multipolar Wien filter inducing a sort of artificial non-relativistic spin-orbit coupling. Here we reconsider the proposed device with a fully quantum-mechanical simulation of the electron-beam propagation, based on the well-established multi-slice method, supplemented with a Pauli term for taking into account the spin degree of freedom. Using this upgraded numerical tool, we study the feasibility and practical limitations of the proposed method for spin polarizing a free electron beam.

  2. Conversion from Single Photon to Single Electron Spin Using Electrically Controllable Quantum Dots

    Science.gov (United States)

    Oiwa, Akira; Fujita, Takafumi; Kiyama, Haruki; Allison, Giles; Ludwig, Arne; Wieck, Andreas D.; Tarucha, Seigo

    2017-01-01

    Polarization is a fundamental property of light and could provide various solutions to the development of secure optical communications with high capacity and high speed. In particular, the coherent quantum state conversion between single photons and single electron spins is a prerequisite for long-distance quantum communications and distributed quantum computation. Electrically defined quantum dots have already been proven to be suitable for scalable solid state qubits by demonstrations of single-spin coherent manipulations and two-qubit gate operations. Thus, their capacity for quantum information technologies would be considerably extended by the achievement of entanglement between an electron spin in the quantum dots and a photon. In this review paper, we show the basic technologies for trapping single electrons generated by single photons in quantum dots and for detecting their spins using the Pauli effect with sensitive charge sensors.

  3. Alkali-metal electron spin density shift induced by a helium nanodroplet

    Science.gov (United States)

    Koch, Markus; Callegari, Carlo; Ernst, Wolfgang E.

    2010-04-01

    Helium (He) nanodroplets provide a cold and virtually unperturbing environment for the study of weakly bound molecules and van der Waals aggregates. High resolution microwave spectroscopy and the detection of electron spin transitions in doped He droplets have recently become possible. Measurements of hyperfine-resolved electron spin resonance in potassium (39K) and rubidium (85Rb) atoms on the surface of He droplets show small line shifts relative to the bare atoms. These shifts were recorded for all 2I + 1 components (I is the nuclear spin) of a transition at high accuracy for He droplets ranging in size from 1000 to 15,000 He atoms. Evaluation of the spectra yields the influence of the He environment on the electron spin density at the alkali-metal nucleus. A semi-empirical model is presented that shows good qualitative agreement with the measured droplet size dependent increase of Fermi contact interaction at the nuclei of dopant K and Rb.

  4. Coherent manipulation of single electron spins with Landau-Zener sweeps

    Science.gov (United States)

    Rančić, Marko J.; Stepanenko, Dimitrije

    2016-12-01

    We propose a method to manipulate the state of a single electron spin in a semiconductor quantum dot (QD). The manipulation is achieved by tunnel coupling a QD, labeled L , and occupied with an electron to an adjacent QD, labeled R , which is not occupied by an electron but having an energy linearly varying in time. We identify a parameter regime in which a complete population transfer between the spin eigenstates |L ↑> and |L ↓> is achieved without occupying the adjacent QD. This method is convenient due to the fact that manipulation can be done electrically, without precise knowledge of the spin resonance condition, and is robust against Zeeman level broadening caused by nuclear spins.

  5. Momentum and Doping Dependence of Spin Excitations in Electron-Doped Cuprate Superconductors

    Science.gov (United States)

    Jing, Pengfei; Zhao, Huaisong; Kuang, Lülin; Lan, Yu; Feng, Shiping

    2017-01-01

    Superconductivity in copper oxides emerges on doping holes or electrons into their Mott-insulating parent compounds. The spin excitations are thought to be the mediating glue for the pairing in superconductivity. Here the momentum and doping dependence of the dynamical spin response in the electron-doped cuprate superconductors is studied based on the kinetic-energy-driven superconducting mechanism. It is shown that the dispersion of the low-energy spin excitations changes strongly upon electron doping; however, the hour-glass-shaped dispersion of the low-energy spin excitations appeared in the hole-doped case is absent on the electron-doped side due to the electron-hole asymmetry. In particular, the commensurate resonance appears in the superconducting state with the resonance energy that correlates with the dome-shaped doping dependence of the superconducting gap. Moreover, the spectral weight and dispersion of the high-energy spin excitations in the superconducting state are comparable with those in the corresponding normal state, indicating that the high-energy spin excitations do not play an important part in the pair formation.

  6. 3D optical manipulation of a single electron spin

    CERN Document Server

    Geiselmann, Michael; Renger, Jan; Say, Jana M; Brown, Louise J; de Abajo, F Javier García; Koppens, Frank; Quidant, Romain

    2013-01-01

    Nitrogen vacancy (NV) centers in diamond are promising elemental blocks for quantum optics [1, 2], spin-based quantum information processing [3, 4], and high-resolution sensing [5-13]. Yet, fully exploiting these capabilities of single NV centers requires strategies to accurately manipulate them. Here, we use optical tweezers as a tool to achieve deterministic trapping and 3D spatial manipulation of individual nano-diamonds hosting a single NV spin. Remarkably, we find the NV axis is nearly fixed inside the trap and can be controlled in-situ, by adjusting the polarization of the trapping light. By combining this unique spatial and angular control with coherent manipulation of the NV spin and fluorescent lifetime measurements near an integrated photonic system, we prove optically trapped NV center as a novel route for both 3D vectorial magnetometry and sensing of the local density of optical states.

  7. Long Spin Relaxation and Coherence Times of Electrons In Gated Si/SiGe Quantum Dots

    Science.gov (United States)

    He, Jianhua; Tyryshkin, A. M.; Lyon, S. A.; Lee, C.-H.; Huang, S.-H.; Liu, C. W.

    2012-02-01

    Single electron spin states in semiconductor quantum dots are promising candidate qubits. We report the measurement of 250 μs relaxation (T1) and coherence (T2) times of electron spins in gated Si/SiGe quantum dots at 350 mK. The experiments used conventional X-band (10 GHz) pulsed electron spin resonance (pESR), on a large area (3.5 x 20 mm^2) dual-gate undoped high mobility Si/SiGe heterostructure sample, which was patterned with 2 x 10^8 quantum dots using e-beam lithography. Dots having 150 nm radii with a 700 nm period are induced in a natural Si quantum well by the gates. The measured T1 and T2 at 350 mK are much longer than those of free 2D electrons, for which we measured T1 to be 10 μs and T2 to be 6.5 μs in this gated sample. The results provide direct proof that the effects of a fluctuating Rashba field have been greatly suppressed by confining the electrons in quantum dots. From 0.35 K to 0.8 K, T1 of the electron spins in the quantum dots shows little temperature dependence, while their T2 decreased to about 150 μs at 0.8 K. The measured 350 mK spin coherence time is 10 times longer than previously reported for any silicon 2D electron-based structures, including electron spins confined in ``natural quantum dots'' formed by potential disorder at the Si/SiO2ootnotetextS. Shankar et al., Phys. Rev. B 82, 195323 (2010) or Si/SiGe interface, where the decoherence appears to be controlled by spin exchange.

  8. Extended pump-probe Faraday rotation spectroscopy of the submicrosecond electron spin dynamics in n -type GaAs

    Science.gov (United States)

    Belykh, V. V.; Evers, E.; Yakovlev, D. R.; Fobbe, F.; Greilich, A.; Bayer, M.

    2016-12-01

    We develop an extended pump-probe Faraday rotation technique to study submicrosecond electron spin dynamics with picosecond time resolution in a wide range of magnetic fields. The electron spin dephasing time T2* and the longitudinal spin relaxation time T1, both approaching 250 ns in weak fields, are measured thereby in n -type bulk GaAs. By tailoring the pump pulse train through increasing the contained number of pulses, the buildup of resonant spin amplification is demonstrated for the electron spin polarization. The spin precession amplitude in high magnetic fields applied in the Voigt geometry shows a nonmonotonic dynamics deviating strongly from a monoexponential decay and revealing slow beatings. The beatings indicate a two spin component behavior with a g -factor difference of Δ g ˜4 ×10-4 , much smaller than the Δ g expected for free and donor-bound electrons. This g -factor variation indicates efficient, but incomplete spin exchange averaging.

  9. Analytical Determination of the Confinement Potential and Coupling Constant of Spin--Orbit Interactions of Electrons in Nanostructures

    CERN Document Server

    Dineykhan, M; Zhaugasheva, S A; Al Farabi Kazakh State National University. Almaty

    2005-01-01

    Multilayer nanocrystalline structure is represented by the electrostatic field inducted by total image charge, and the confinement potential for electrons is determined. Assuming that at a given distance the confinement potential is equal to the Coulomb repulsion and an interaction between electrons becomes spin-orbit, the constant of the spin-orbit interaction of electrons in nanostructures is determined. The dependence of the constant of the spin-orbit interaction on environment parameters and the distance between electrons is studied.

  10. Electron spin relaxation due to reorientation of a permanent zero field splitting tensor.

    Science.gov (United States)

    Schaefle, Nathaniel; Sharp, Robert

    2004-09-15

    Electron spin relaxation of transition metal ions with spin S> or =1 results primarily from thermal modulation of the zero field splitting (zfs) tensor. This occurs both by distortion of the zfs tensor due to intermolecular collisions and, for complexes with less than cubic symmetry, by reorientational modulation of the permanent zfs tensor. The reorientational mechanism is much less well characterized in previous work than the distortional mechanism although it is an important determinant of nuclear magnetic resonance (NMR) paramagnetic relaxation enhancement phenomena (i.e., the enhancement of NMR relaxation rates produced by paramagnetic ions in solution or NMR-PRE). The classical density matrix theory of spin relaxation does not provide an appropriate description of the reorientational mechanism at low Zeeman field strengths because the zero-order spin wave functions are stochastic functions of time. Using spin dynamics simulation techniques, the time correlation functions of the spin operators have been computed and used to determine decay times for the reorientational relaxation mechanism for S=1. In the zfs limit of laboratory field strengths (H(Zeem)spin decay is exponential, the spin relaxation time, tau(S) (composite function) approximately 0.53tau(R)((1)), where tau(R)((1)) is the reorientational correlation time of a molecule-fixed vector. The value of tau(S) (composite function) is independent of the magnitude of the cylindrical zfs parameter (D), but it depends strongly on low symmetry zfs terms (the E/D ratio). Other spin dynamics (SD) simulations examined spin decay in the intermediate regime of field strengths where H(Zeem) approximately H(zfs) (composite function), and in the vicinity of the Zeeman limit. The results demonstrate that the reorientational electron spin relaxation mechanism is often significant when H(zfs) (composite function)> or =H(Zeem), and that its neglect can lead to serious errors in the interpretation of NMR-PRE data.

  11. Lagrangian for Frenkel electron and position's non-commutativity due to spin

    Energy Technology Data Exchange (ETDEWEB)

    Deriglazov, Alexei A. [Universidade Federal de Juiz de Fora, Depto. de Matematica, ICE, Juiz de Fora, MG (Brazil); Tomsk Polytechnic University, Laboratory of Mathematical Physics, Tomsk (Russian Federation); Pupasov-Maksimov, Andrey M. [Universidade Federal de Juiz de Fora, Depto. de Matematica, ICE, Juiz de Fora, MG (Brazil)

    2014-10-15

    We construct a relativistic spinning-particle Lagrangian where spin is considered as a composite quantity constructed on the base of a non-Grassmann vector-like variable. The variational problem guarantees both a fixed value of the spin and the Frenkel condition on the spin-tensor. The Frenkel condition inevitably leads to relativistic corrections of the Poisson algebra of the position variables: their classical brackets became noncommutative. We construct the relativistic quantum mechanics in the canonical formalism (in the physical-time parametrization) and in the covariant formalism (in an arbitrary parametrization). We show how state vectors and operators of the covariant formulation can be used to compute the mean values of physical operators in the canonical formalism, thus proving its relativistic covariance. We establish relations between the Frenkel electron and positive-energy sector of the Dirac equation. Various candidates for the position and spin operators of an electron acquire clear meaning and interpretation in the Lagrangian model of the Frenkel electron. Our results argue in favor of Pryce's (d)-type operators as the spin and position operators of Dirac theory. This implies that the effects of non-commutativity could be expected already at the Compton wavelength. We also present the manifestly covariant form of the spin and position operators of the Dirac equation. (orig.)

  12. High-sensitivity Q-band electron spin resonance imaging system with submicron resolution

    Science.gov (United States)

    Shtirberg, Lazar; Twig, Ygal; Dikarov, Ekaterina; Halevy, Revital; Levit, Michael; Blank, Aharon

    2011-04-01

    A pulsed electron spin resonance (ESR) microimaging system operating at the Q-band frequency range is presented. The system includes a pulsed ESR spectrometer, gradient drivers, and a unique high-sensitivity imaging probe. The pulsed gradient drivers are capable of producing peak currents ranging from ˜9 A for short 150 ns pulses up to more than 94 A for long 1400 ns gradient pulses. Under optimal conditions, the imaging probe provides spin sensitivity of ˜1.6 × 108 spins/√Hz or ˜2.7 × 106 spins for 1 h of acquisition. This combination of high gradients and high spin sensitivity enables the acquisition of ESR images with a resolution down to ˜440 nm for a high spin concentration solid sample (˜108 spins/μm3) and ˜6.7 μm for a low spin concentration liquid sample (˜6 × 105 spins/μm3). Potential applications of this system range from the imaging of point defects in crystals and semiconductors to measurements of oxygen concentration in biological samples.

  13. Electrical detection of spin transport in Si two-dimensional electron gas systems

    Science.gov (United States)

    Chang, Li-Te; Fischer, Inga Anita; Tang, Jianshi; Wang, Chiu-Yen; Yu, Guoqiang; Fan, Yabin; Murata, Koichi; Nie, Tianxiao; Oehme, Michael; Schulze, Jörg; Wang, Kang L.

    2016-09-01

    Spin transport in a semiconductor-based two-dimensional electron gas (2DEG) system has been attractive in spintronics for more than ten years. The inherent advantages of high-mobility channel and enhanced spin-orbital interaction promise a long spin diffusion length and efficient spin manipulation, which are essential for the application of spintronics devices. However, the difficulty of making high-quality ferromagnetic (FM) contacts to the buried 2DEG channel in the heterostructure systems limits the potential developments in functional devices. In this paper, we experimentally demonstrate electrical detection of spin transport in a high-mobility 2DEG system using FM Mn-germanosilicide (Mn(Si0.7Ge0.3)x) end contacts, which is the first report of spin injection and detection in a 2DEG confined in a Si/SiGe modulation doped quantum well structure (MODQW). The extracted spin diffusion length and lifetime are l sf = 4.5 μm and {τ }{{s}}=16 {{ns}} at 1.9 K respectively. Our results provide a promising approach for spin injection into 2DEG system in the Si-based MODQW, which may lead to innovative spintronic applications such as spin-based transistor, logic, and memory devices.

  14. Subsecond spin relaxation times in quantum dots at zero applied magnetic field due to a strong electron-nuclear interaction.

    Science.gov (United States)

    Oulton, R; Greilich, A; Verbin, S Yu; Cherbunin, R V; Auer, T; Yakovlev, D R; Bayer, M; Merkulov, I A; Stavarache, V; Reuter, D; Wieck, A D

    2007-03-09

    A key to ultralong electron spin memory in quantum dots (QDs) at zero magnetic field is the polarization of the nuclei, such that the electron spin is stabilized along the average nuclear magnetic field. We demonstrate that spin-polarized electrons in n-doped (In,Ga)As/GaAs QDs align the nuclear field via the hyperfine interaction. A feedback onto the electrons occurs, leading to stabilization of their polarization due to formation of a nuclear spin polaron [I. A. Merkulov, Phys. Solid State 40, 930 (1998)]. Spin depolarization of both systems is consequently greatly reduced, and spin memory of the coupled electron-nuclear spin system is retained over 0.3 sec at temperature of 2 K.

  15. Note: High sensitivity pulsed electron spin resonance spectroscopy with induction detection.

    Science.gov (United States)

    Twig, Ygal; Dikarov, Ekaterina; Hutchison, Wayne D; Blank, Aharon

    2011-07-01

    Commercial electron spin resonance spectroscopy and imaging systems make use of the so-called "induction" or "Faraday" detection, which is based on a radio frequency coil or a microwave resonator. The sensitivity of induction detection does not exceed ~3 × 10(8) spins/√Hz. Here we show that through the use of a new type of surface loop-gap microresonators (inner size of 20 μm), operating at cryogenic temperatures at a field of 0.5 T, one can improve upon this sensitivity barrier by more than 2 orders of magnitude and reach spin sensitivities of ~1.5 × 10(6) spins/√Hz or ~2.5 × 10(4) spins for 1 h.

  16. Conduction electron spin resonance in Mg 1 - x Al x B2

    Science.gov (United States)

    Likodimos, V.; Koutandos, S.; Pissas, M.; Papavassiliou, G.; Prassides, K.

    2003-01-01

    Conduction electron spin resonance is employed to study the interplay of the electronic and structural properties in the normal state of Mg 1 - x Al x B2 alloys as a function of Al-doping for 0 <= x <= 1. The x-dependence of the spin susceptibility reveals considerable reduction of the total density of states N(EF) with increasing Al concentration, complying with theoretical predictions for a predominant filling effect of the hole σ bands by electron doping. The CESR linewidth exhibits significant broadening, especially prominent in the high-Al-content region, indicative of the presence of enhanced structural disorder, consistent with the presence of compositional fluctuations.

  17. Spin dynamics in Kapitza-Dirac scattering of electrons from bichromatic laser fields

    CERN Document Server

    Dellweg, Matthias M; Müller, Carsten

    2016-01-01

    Kapitza-Dirac scattering of nonrelativistic electrons from counterpropagating bichromatic laser waves of linear polarization i s studied. The focus lies on the electronic spin dynamics in the Bragg regime when the laser fields possess a frequency ratio of two. To this end, the time-dependent Pauli equation is solved numerically, both in coordinate space and momentum space. Our numerical results are corroborated by analytical derivations. We demonstrate that, for certain incident electron momenta, the scattering crucially relies on the electron spin which undergo es characteristic Rabi-like oscillations. A parameter regime is identified where the Rabi oscillations reach maximum amplitude. We also briefly discuss spin-dependent Kapitza-Dirac scattering of protons.

  18. A Spin-Light Polarimeter for Multi-GeV Longitudinally Polarized Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Mohanmurthy, Prajwal [Mississippi State University, Starkville, MS (United States); Dutta, Dipangkar [Mississippi State University, Starkville, MS (United States) and Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2014-02-01

    The physics program at the upgraded Jefferson Lab (JLab) and the physics program envisioned for the proposed electron-ion collider (EIC) include large efforts to search for interactions beyond the Standard Model (SM) using parity violation in electroweak interactions. These experiments require precision electron polarimetry with an uncertainty of < 0.5 %. The spin dependent Synchrotron radiation, called "spin-light," can be used to monitor the electron beam polarization. In this article we develop a conceptual design for a "spin-light" polarimeter that can be used at a high intensity, multi-GeV electron accelerator. We have also built a Geant4 based simulation for a prototype device and report some of the results from these simulations.

  19. Renormalization of spin polarized itinerant electron bands in the normal state of a model ferromagnetic superconductor

    Institute of Scientific and Technical Information of China (English)

    Ma Lei; Huang Ai-Qun; Li Jun

    2011-01-01

    This paper studies the normal state properties of itinerant electrons in a toy model, which is constructed according to the model for coexisting ferromagnetism and superconductivity proposed by Suhl [Suhl H 2001 Phys. Rev. Lett. 87 167007]. In this theory with ferromagnetic ordering based on localized spins, the exchange interaction J between conduction electrons and localized spin is taken as the pairing glue for s-wave superconductivity. It shows that this J term will first renormalize the normal state single conduction electron structures substantially. It finds dramatically enhanced or suppressed magnetization of itinerant electrons for positive or negative J. Singlet Cooper pairing can be ruled out due to strong spin polarisation in the J > 0 case while a narrow window for s-wave superconductivity is opened around some ferromagnetic J.

  20. Magnetotransport of hot electrons and holes in the spin-valve transistor

    NARCIS (Netherlands)

    Gökcan, Hüsey

    2006-01-01

    The conventional electronics uses the charge property of the electrons and holes. The building blocks are semiconductors which can be tuned to change the properties of the devices. In the field of spintronics, the spin property of the charge carriers is added to the functionality of the devices. The

  1. Towards quantum optics and entanglement with electron spin ensembles in semiconductors

    NARCIS (Netherlands)

    van der Wal, Caspar H.; Sladkov, Maksym

    2009-01-01

    We discuss a technique and a material system that enable the controlled realization of quantum entanglement between spin-wave modes of electron ensembles in two spatially separated pieces of semiconductor material. The approach uses electron ensembles in GaAs quantum wells that are located inside op

  2. Spin and charge transport in a gated two dimensional electron gas

    NARCIS (Netherlands)

    Lerescu, Alexandru Ionut

    2007-01-01

    The work presented in this thesis is centered around the idea of how one can inject, transport and detect the electron's spin in a two dimensional electron gas (a semiconductor heterostructure). Metal based spintronic devices have been established to be the easy way to implement spintronic concepts

  3. 2D Spin-Dependent Diffraction of Electrons From Periodical Chains of Nanomagnets

    Directory of Open Access Journals (Sweden)

    Teshome Senbeta

    2012-03-01

    Full Text Available The scattering of the unpolarized beams of electrons by nanomagnets in the vicinity of some scattering angles leads to complete spin polarized electrons. This result is obtained with the help of the perturbation theory. The dipole-dipole interaction between the magnetic moment of the nanomagnet and the magnetic moment of electron is treated as perturbation. This interaction is not spherically symmetric. Rather it depends on the electron spin variables. It in turn results in spinor character of the scattering amplitudes. Due to the smallness of the magnetic interactions, the scattering length of this process is very small to be proved experimentally. To enhance the relevant scattering lengths, we considered the diffraction of unpolarized beams of electrons by linear chains of nanomagnets. By tuning the distance between the scatterers it is possible to obtain the diffraction maximum of the scattered electrons at scattering angles which corresponds to complete spin polarization of electrons. It is shown that the total differential scattering length is proportional to N2 (N is a number of scatterers. Even small number of nanomagnets in the chain helps to obtain experimentally visible enhancement of spin polarization of the scattered electrons.

  4. Scalable quantum register based on coupled electron spins in a room temperature solid

    CERN Document Server

    Neumann, P; Naydenov, B; Beck, J; Rempp, F; Steiner, M; Jacques, V; Balasubramanian, G; Markham, M L; Twitchen, D J; Pezzagna, S; Meijer, J; Twamley, J; Jelezko, F; Wrachtrup, J; 10.1038/nphys1536

    2010-01-01

    Realization of devices based on quantum laws might lead to building processors that outperform their classical analogues and establishing unconditionally secure communication protocols. Solids do usually present a serious challenge to quantum coherence. However, owing to their spin-free lattice and low spin orbit coupling, carbon materials and particularly diamond are suitable for hosting robust solid state quantum registers. We show that scalable quantum logic elements can be realized by exploring long range magnetic dipolar coupling between individually addressable single electron spins associated with separate color centers in diamond. Strong distance dependence of coupling was used to characterize the separation of single qubits 98 A with unprecedented accuracy (3 A) close to a crystal lattice spacing. Our demonstration of coherent control over both electron spins, conditional dynamics, selective readout as well as switchable interaction, opens the way towards a room temperature solid state scalable quant...

  5. Spin-state blockade in Te6+-substituted electron-doped LaCoO3

    Science.gov (United States)

    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.

  6. New insights into electron spin dynamics in the presence of correlated noise.

    Science.gov (United States)

    Spezia, S; Adorno, D Persano; Pizzolato, N; Spagnolo, B

    2012-02-08

    The changes in the spin depolarization length in zinc-blende semiconductors when an external component of correlated noise is added to a static driving electric field are analyzed for different values of field strength, noise amplitude and correlation time. Electron dynamics is simulated by a Monte Carlo procedure which takes into account all the possible scattering phenomena of the hot electrons in the medium and includes the evolution of spin polarization. Spin depolarization is studied by examining the decay of the initial spin polarization of the conduction electrons through the D'yakonov-Perel process, the only relevant relaxation mechanism in III-V crystals. Our results show that, for electric field amplitudes lower than the Gunn field, the dephasing length shortens with increasing noise intensity. Moreover, a nonmonotonic behavior of spin depolarization length with the noise correlation time is found, characterized by a maximum variation for values of noise correlation time comparable with the dephasing time. Instead, in high field conditions, we find that, critically depending on the noise correlation time, external fluctuations can positively affect the relaxation length. The influence of the inclusion of the electron-electron scattering mechanism is also shown and discussed.

  7. Effect of Quantum Point Contact Measurement on Electron Spin State in Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    ZHU Fei-Yun; TU Tao; HAO Xiao-Jie; GUO Guang-Can; GUO Guo-Ping

    2009-01-01

    We study the time evolution of two electron spin states in a double quantum-dot system, which includes a nearby quantum point contact (QPC) as a measurement device. We find that the QPC measurement induced decoherence is in the microsecond timescale. We also find that the enhanced QPC measurement will trap the system in its initial spin states, which is consistent with the quantum Zeno effect.

  8. Electron spin relaxation can enhance the performance of a cryptochrome-based magnetic compass sensor

    DEFF Research Database (Denmark)

    Kattnig, Daniel R; Sowa, Jakub K; Solov'yov, Ilia A

    2016-01-01

    The radical pair model of the avian magnetoreceptor relies on long-lived electron spin coherence. Dephasing, resulting from interactions of the spins with their fluctuating environment, is generally assumed to degrade the sensitivity of this compass to the direction of the Earth's magnetic field...... to an Earth-strength magnetic field. Supported by calculations using toy radical pair models, we argue that these enhancements could be consistent with the molecular dynamics and magnetic interactions in avian cryptochromes....

  9. Detection of reactive oxygen species in isolated, perfused lungs by electron spin resonance spectroscopy

    OpenAIRE

    Schudt Christian; Schermuly Ralph T; Ghofrani Hossein A; Schütte Hartwig; Schäfer Rolf U; Tiyerili Vedat; Fuchs Beate; Kuzkaya Nermin; Weissmann Norbert; Sydykov Akylbek; Egemnazarow Bakytbek; Seeger Werner; Grimminger Friedrich

    2005-01-01

    Abstract Background The sources and measurement of reactive oxygen species (ROS) in intact organs are largely unresolved. This may be related to methodological problems associated with the techniques currently employed for ROS detection. Electron spin resonance (ESR) with spin trapping is a specific method for ROS detection, and may address some these technical problems. Methods We have established a protocol for the measurement of intravascular ROS release from isolated buffer-perfused and v...

  10. Imaging spin filter for electrons based on specular reflection from iridium (001)

    Energy Technology Data Exchange (ETDEWEB)

    Kutnyakhov, D.; Lushchyk, P. [Johannes Gutenberg-Universität, Institut für Physik, 55099 Mainz (Germany); Fognini, A.; Perriard, D. [Laboratorium für Festkörperphysik, ETH Zürich, 8093 Zürich (Switzerland); Kolbe, M.; Medjanik, K.; Fedchenko, E.; Nepijko, S.A.; Elmers, H.J. [Johannes Gutenberg-Universität, Institut für Physik, 55099 Mainz (Germany); Salvatella, G.; Stieger, C.; Gort, R.; Bähler, T.; Michlmayer, T.; Acremann, Y.; Vaterlaus, A. [Laboratorium für Festkörperphysik, ETH Zürich, 8093 Zürich (Switzerland); Giebels, F.; Gollisch, H.; Feder, R. [Universität Duisburg-Essen, Theoretische Festkörperphysik, 47057 Duisburg (Germany); Tusche, C. [Max Planck-Institut für Mikrostrukturphysik, 06120 Halle (Germany); and others

    2013-07-15

    As Stern–Gerlach type spin filters do not work with electrons, spin analysis of electron beams is accomplished by spin-dependent scattering processes based on spin–orbit or exchange interaction. Existing polarimeters are single-channel devices characterized by an inherently low figure of merit (FoM) of typically 10{sup −4}–10{sup −3}. This single-channel approach is not compatible with parallel imaging microscopes and also not with modern electron spectrometers that acquire a certain energy and angular interval simultaneously. We present a novel type of polarimeter that can transport a full image by making use of k-parallel conservation in low-energy electron diffraction. We studied specular reflection from Ir (001) because this spin-filter crystal provides a high analyzing power combined with a “lifetime” in UHV of a full day. One good working point is centered at 39 eV scattering energy with a broad maximum of 5 eV usable width. A second one at about 10 eV shows a narrower profile but much higher FoM. A relativistic layer-KKR SPLEED calculation shows good agreement with measurements. - Highlights: • Novel type of spin polarimeter can transport a full image by making use of k{sup →}{sub ||} conservation in LEED. • When combined with a hemispherical analyzer, it acquires a certain energy and angular interval simultaneously. • Ir (001) based spin-filter provides a high analyzing power combined with a “lifetime” in UHV of a full day. • Parallel spin detection improves spin polarimeter efficiency by orders of magnitude. • A relativistic layer-KKR SPLEED calculation shows good agreement with measurements.

  11. Electron spin-lattice and spin-spin relaxation study of a trinuclear iron(III) complex and its relevance in quantum computing.

    Science.gov (United States)

    Mitrikas, George; Sanakis, Yiannis; Raptopoulou, Catherine P; Kordas, George; Papavassiliou, Georgios

    2008-02-01

    Electron spins of molecular magnets are promising candidates for large scale quantum information processing because they exhibit a large number of low-lying excited states. In this paper X-band pulse electron paramagnetic resonance spectroscopy is used to determine the intrinsic relaxation times T1 and T2 of a molecular magnet with an S = 1/2 ground state, namely the neutral trinuclear oxo-centered iron (III) complex, [Fe3(micro3-O)(O2CPh)5(salox)(EtOH)(EtOH)(H2O)]. The temperature dependence of the spin-lattice relaxation time T1 between 4.5 and 11 K shows that the Orbach relaxation process is dominant with the first excited state lying 57 cm(-1) above the ground state, whereas the phase memory time T(M) is of the order of 2.6 micros and exhibits a modest temperature dependence. These results together with previous magnetic measurements give further insight into the magnetic properties of the complex. The coherent manipulation of the electron spins is also examined by means of transient nutation experiments.

  12. Quantum spin-glass transition in the two-dimensional electron gas

    Indian Academy of Sciences (India)

    Subir Sachdev

    2002-02-01

    We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment. We argue that a quantum transition involving the destruction of the spin-glass order in an applied in-plane magnetic field offers a natural explanation of some features of recent magnetoconductance measurements. We present a quantum field theory for such a transition and compute its mean field properties.

  13. Prediction of spin-dependent electronic structure in 3d-transition-metal doped antimonene

    Science.gov (United States)

    Yang, L. F.; Song, Y.; Mi, W. B.; Wang, X. C.

    2016-07-01

    We investigate the geometric structure and electronic and magnetic properties of 3d-transition-metal atom doped antimonene using spin-polarized first-principles calculations. Strong orbital hybridization exhibits between 3d-transition-metal and Sb atoms, where covalent bonds form in antimonene. A spin-polarized semiconducting state appears in Cr-doped antimonene, while half-metallic states appear by doping Ti, V, and Mn. These findings indicate that once combined with doping states, the bands of antimonene systems offer a variety of features. Specific dopants lead to half-metallic characters with high spin polarization that has potential application in spintronics.

  14. Spin-orbit-coupled two-electron Fermi gases of ytterbium atoms

    Science.gov (United States)

    Song, Bo; He, Chengdong; Zhang, Shanchao; Hajiyev, Elnur; Huang, Wei; Liu, Xiong-Jun; Jo, Gyu-Boong

    2016-12-01

    We demonstrate all-optical implementation of spin-orbit coupling (SOC) in a two-electron Fermi gas of 173Yb atoms by coupling two hyperfine ground states with a narrow optical transition. Due to the SU (N ) symmetry of the S10 ground-state manifold which is insensitive to external magnetic fields, an optical ac Stark effect is applied to split the ground spin states, which exhibits a high stability compared with experiments on alkali-metal and lanthanide atoms, and separate out an effective spin-1/2 subspace from other hyperfine levels for the realization of SOC. The dephasing spin dynamics when a momentum-dependent spin-orbit gap is suddenly opened and the asymmetric momentum distribution of the spin-orbit-coupled Fermi gas are observed as a hallmark of SOC. The realization of all-optical SOC for ytterbium fermions should offer a route to a long-lived spin-orbit-coupled Fermi gas and greatly expand our capability of studying spin-orbit physics with alkaline-earth-metal-like atoms.

  15. Electronic Spin Crossover of Iron in Ferroperclase in Earth?s Lower Mantle

    Energy Technology Data Exchange (ETDEWEB)

    Lin, J F; Vanko, G; Jacobsen, S D; Iota, V; Struzhkin, V V; Prakapenka, V B; Kuznetsov, A; Yoo, C S

    2007-01-25

    Pressure-induced electronic spin-pairing transitions of iron and associated effects on the physical properties have been reported to occur in the lower-mantle ferropericlase, silicate perosvkite, and perhaps in post silicate perovskite at high pressures and room temperature. These recent results are motivating geophysicists and geodynamicists to reevaluate the implications of spin transitions on the seismic heterogeneity, composition, as well as the stability of the thermal upwellings of the Earth's lower mantle. Here we have measured the spin states of iron in ferropericlase and its crystal structure up to 95 GPa and 2000 K using a newly constructed X-ray emission spectroscopy and diffraction with the laser-heated diamond cell. Our results show that an isosymmetric spin crossover occurs over a pressure-temperature range extending from the upper part to the lower part of the lower mantle, and low-spin ferropericlase likely exists in the lowermost mantle. Although continuous changes in physical and chemical properties are expected to occur across the spin crossover, the spin crossover results in peculiar behavior in the thermal compression and sound velocities. Therefore, knowledge of the fraction of the spin states in the lower-mantle phases is thus essential to correctly evaluate the composition, geophysics, and dynamics of the Earth's lower mantle.

  16. Spin-orbit coupled two-electron Fermi gases of ytterbium atoms

    CERN Document Server

    Song, Bo; Zhang, Shanchao; Zou, Yueyang; Haciyev, Elnur; Huang, Wei; Liu, Xiong-Jun; Jo, Gyu-Boong

    2016-01-01

    We demonstrate the spin-orbit coupling (SOC) in a two-electron Fermi gas of $^{173}$Yb atoms by coupling two hyperfine ground states via the two-photon Raman transition. Due to the SU($N$) symmetry of the $^1$S$_0$ ground-state manifold which is insensitive to external magnetic field, an optical AC Stark effect is applied to split the ground spin states and separate an effective spin-1/2 subspace out from other hyperfine levels for the realization of SOC. With a momentum-dependent spin-orbit gap being suddenly opened by switching on the Raman transition, the dephasing of spin dynamics is observed, as a consequence of the momentum-dependent Rabi oscillations. Moreover, the momentum asymmetry of the spin-orbit coupled Fermi gas is also examined after projection onto the bare spin state and the corresponding momentum distribution is measured for different two-photon detuning. The realization of SOC for Yb fermions may open a new avenue to the study of novel spin-orbit physics with alkaline-earth-like atoms.

  17. Towards a Methodology for Formal Design and Analysis of Agent Interaction Protocols --An Investigation in Electronic Commerce

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Various extensions of UML have been developed to meet thechallenges of designin g modern software systems, such as agent-based electronic commerce applications . Recent advances in model checking technology have led it to be introduced into the development of approaches and tools to check the correctness of electronic c ommerce protocols. This paper focuses on the research of a method that connects an extension of AUML to model checker-SPIN/Promela for the specification and v e rification of agent interaction protocols (AIP) in electronic commerce. The meth od presented here allows us to combine the benefits of visual specification with the power of some static analysis and model checking. Some algorithms and rules are developed to permit all visual modeling constructs translated mechanically into some Promela models of AIP, as supported by the model checker -SPIN. Moreo v er, a process is illustrated to guide the specification and verification of AIP. The method is demonstrated thoroughly using the e-commerce protocol -NetBill as an example.

  18. Concept of multichannel spin-resolving electron analyzer based on Mott scattering

    CERN Document Server

    Strocov, Vladimir N; Dil, J Hugo

    2014-01-01

    Concept of a multichannel electron spin detector based on optical imaging principles and Mott scattering (iMott) is presented. A multichannel electron image produced by standard angle-resolving (photo) electron analyzer or microscope is re-imaged by an electrostatic lens at an accelerating voltage of 40 keV onto the Au target. Quasi-elastic electrons bearing spin asymmetry of the Mott scattering are imaged by magnetic lenses onto position-sensitive electron CCDs whose differential signals yield the multichannel spin asymmetry image. Fundamental advantages of this concept include acceptance of inherently divergent electron sources from the electron analyzer or microscope focal plane as well as small aberrations achieved by virtue of high accelerating voltages, as demonstrated by extensive ray-tracing analysis. The efficiency gain compared to the single-channel Mott detector can be a factor of 1.5e4 and above, opening new prospects of spin-resolved spectroscopies in application not only to standard bulk and sur...

  19. Electronic spin transport and spin precession in single graphene layers at room temperature

    NARCIS (Netherlands)

    Tombros, Nikolaos; Jozsa, Csaba; Popinciuc, Mihaita; Jonkman, Harry T.; van Wees, Bart J.

    2007-01-01

    Electronic transport in single or a few layers of graphene is the subject of intense interest at present. The specific band structure of graphene, with its unique valley structure and Dirac neutrality point separating hole states from electron states, has led to the observation of new electronic tra

  20. Comparison of the electron-spin force and radiation reaction force

    Science.gov (United States)

    Mahajan, Swadesh M.; Asenjo, Felipe A.; Hazeltine, Richard D.

    2015-02-01

    It is shown that the forces that originate from the electron-spin interacting with the electromagnetic field can play, along with the Lorentz force, a fundamentally important role in determining the electron motion in a high energy density plasma embedded in strong high-frequency radiation, a situation that pertains to both laser-produced and astrophysical systems. These forces, for instance, dominate the standard radiation reaction force as long as there is a `sufficiently' strong ambient magnetic field for affecting spin alignment. The inclusion of spin forces in any advanced modelling of electron dynamics pertaining to high energy density systems (for instance in particle-in-cell codes), therefore, is a must.

  1. Size dependence of electron spin dephasing in InGaAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Y. Q.; Puttisong, Y.; Buyanova, I. A.; Chen, W. M. [Department of Physics, Chemistry and Biology, Linköping University, S-581 83 Linköping (Sweden); Yang, X. J.; Subagyo, A.; Sueoka, K.; Murayama, A. [Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814 (Japan)

    2015-03-02

    We investigate ensemble electron spin dephasing in self-assembled InGaAs/GaAs quantum dots (QDs) of different lateral sizes by employing optical Hanle measurements. Using low excitation power, we are able to obtain a spin dephasing time T{sub 2}{sup *} (in the order of ns) of the resident electron after recombination of negative trions in the QDs. We show that T{sub 2}{sup *} is determined by the hyperfine field arising from the frozen fluctuation of nuclear spins, which scales with the size of QDs following the Merkulov-Efros-Rosen model. This scaling no longer holds in large QDs, most likely due to a breakdown in the lateral electron confinement.

  2. Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells

    Science.gov (United States)

    Giorgioni, Anna; Paleari, Stefano; Cecchi, Stefano; Vitiello, Elisa; Grilli, Emanuele; Isella, Giovanni; Jantsch, Wolfgang; Fanciulli, Marco; Pezzoli, Fabio

    2016-12-01

    Control of electron spin coherence via external fields is fundamental in spintronics. Its implementation demands a host material that accommodates the desirable but contrasting requirements of spin robustness against relaxation mechanisms and sizeable coupling between spin and orbital motion of the carriers. Here, we focus on Ge, which is a prominent candidate for shuttling spin quantum bits into the mainstream Si electronics. So far, however, the intrinsic spin-dependent phenomena of free electrons in conventional Ge/Si heterojunctions have proved to be elusive because of epitaxy constraints and an unfavourable band alignment. We overcome these fundamental limitations by investigating a two-dimensional electron gas in quantum wells of pure Ge grown on Si. These epitaxial systems demonstrate exceptionally long spin lifetimes. In particular, by fine-tuning quantum confinement we demonstrate that the electron Landé g factor can be engineered in our CMOS-compatible architecture over a range previously inaccessible for Si spintronics.

  3. Spontaneous spin polarization of electrons in quantum wires

    CERN Document Server

    Shelykh, I A; Bagraev, N T; Klyachkin, L E

    2002-01-01

    The quantum ladder of the electric conductivity of an one-dimensional channel is analyzed at weak filling of low one-dimensional subbands when the exchange electron-electron interaction of current carrier dominate over their kinetic energy. The basic attention is given to the consideration of the behaviour of the feature 0.7 (2e sup 2 /h) which is identified as the result of the spontaneous polarization of the one-dimensional electron gas due to the exchange interaction in the zero magnetic field. The critical linear electron concentration is defined in the framework of the phenomenological theory

  4. Impact of electron-impurity scattering on the spin relaxation time in graphene: a first-principles study.

    Science.gov (United States)

    Fedorov, Dmitry V; Gradhand, Martin; Ostanin, Sergey; Maznichenko, Igor V; Ernst, Arthur; Fabian, Jaroslav; Mertig, Ingrid

    2013-04-12

    The effect of electron-impurity scattering on momentum and spin relaxation times in graphene is studied by means of relativistic ab initio calculations. Assuming carbon and silicon adatoms as natural impurities in graphene, we are able to simulate fast spin relaxation observed experimentally. We investigate the dependence of the relaxation times on the impurity position and demonstrate that C or Si adatoms act as real-space spin hot spots inducing spin-flip rates about 5 orders of magnitude larger than those of in-plane impurities. This fact confirms the hypothesis that the adatom-induced spin-orbit coupling leads to fast spin relaxation in graphene.

  5. Electron Spin Resonance Spectra of Photogenerated Polarons in Poly(Paraphenylene Vinylene)

    Science.gov (United States)

    Murata, Kazuhiro; Kuroda, Shin-ichi; Shimoi, Yukihiro; Abe, Shuji; Noguchi, Takanobu; Ohnishi, Toshihiro

    1996-12-01

    Light-induced ESR (LESR) measurements have been performed on undoped poly(parapheny- lene vinylene) (PPV) down to 4 K. The ESR signal increases significantly for the excitation energy above 3.1 3.2 eV, as in the case of the excitation spectra of photocarriers reported in PPV derivatives. The anisotropic light-induced ESR spectra in oriented samples are well reproduced by the spectra calculated using a theoretical polaron spin distribution in the case of finite electron-electron interaction. These spectral features indicate that the observed spins are photogenerated polarons.

  6. Spin excitations and the electronic specific heat of URu2Si2

    DEFF Research Database (Denmark)

    Mason, T.E.; Buyers, W.J.L.

    1991-01-01

    and conduction electrons yields m*/m(b) almost-equal-to 7.7 for T T(N) which is sufficient to account for the difference between band-structure calculations and the measured electronic specific heat. In addition, inclusion of the temperature dependence of the spin...... excitations as T(N) is approached from below reproduces, qualitatively, the peak observed in the specific heat at T(N). The peak arises from a gap in the spin, not charge spectrum below T(N)....

  7. Spin dependent transport of hot electrons through ultrathin epitaxial metallic films

    Energy Technology Data Exchange (ETDEWEB)

    Heindl, Emanuel

    2010-06-23

    In this work relaxation and transport of hot electrons in thin single crystalline metallic films is investigated by Ballistic Electron Emission Microscopy. The electron mean free paths are determined in an energy interval of 1 to 2 eV above the Fermi level. While fcc Au-films appear to be quite transmissive for hot electrons, the scattering lengths are much shorter for the ferromagnetic alloy FeCo revealing, furthermore, a strong spin asymmetry in hot electron transport. Additional information is gained from temperature dependent studies in combination with golden rule approaches in order to disentangle the impact of several relaxation and transport properties. It is found that bcc Fe-films are much less effective in spin filtering than films made of the FeCo-alloy. (orig.)

  8. Experimental study on the activation process of GaAs spin-polarized electron source

    Institute of Scientific and Technical Information of China (English)

    阮存军

    2003-01-01

    GaAs spin-polarized electron source is a new kind of electron source, where the GaAs semiconductor crystal is used as a photocathode under the irradiation of helicity light. In this paper the activation process of the GaAs spin-polarized electron source is investigated experimentally in detail, during which the negative electron affinity of the photo cathode should be achieved more carefully by absorbing the caesium and oxygen on the surface of the GaAs crystal under ultrahigh vacuum conditions. Besides the different activation processes, the important physical parameters are studied to achieve the optimum activation results. At the same time the stability and lifetime of the polarized electron beam are explored for future experiments. Some important experimental data have been acquired.

  9. Electric-field-induced interferometric resonance of a one-dimensional spin-orbit-coupled electron

    Science.gov (United States)

    Fan, Jingtao; Chen, Yuansen; Chen, Gang; Xiao, Liantuan; Jia, Suotang; Nori, Franco

    2016-01-01

    The efficient control of electron spins is of crucial importance for spintronics, quantum metrology, and quantum information processing. We theoretically formulate an electric mechanism to probe the electron spin dynamics, by focusing on a one-dimensional spin-orbit-coupled nanowire quantum dot. Owing to the existence of spin-orbit coupling and a pulsed electric field, different spin-orbit states are shown to interfere with each other, generating intriguing interference-resonant patterns. We also reveal that an in-plane magnetic field does not affect the interval of any neighboring resonant peaks, but contributes a weak shift of each peak, which is sensitive to the direction of the magnetic field. We find that this proposed external-field-controlled scheme should be regarded as a new type of quantum-dot-based interferometry. This interferometry has potential applications in precise measurements of relevant experimental parameters, such as the Rashba and Dresselhaus spin-orbit-coupling strengths, as well as the Landé factor. PMID:27966598

  10. The magnetism and spin-dependent electronic transport properties of boron nitride atomic chains.

    Science.gov (United States)

    An, Yipeng; Zhang, Mengjun; Wu, Dapeng; Fu, Zhaoming; Wang, Tianxing; Jiao, Zhaoyong; Wang, Kun

    2016-07-28

    Very recently, boron nitride atomic chains were successively prepared and observed in experiments [O. Cretu et al., ACS Nano 8, 11950 (2015)]. Herein, using a first-principles technique, we study the magnetism and spin-dependent electronic transport properties of three types of BN atomic chains whose magnetic moment is 1 μB for BnNn-1, 2 μB for BnNn, and 3 μB for BnNn+1 type atomic chains, respectively. The spin-dependent electronic transport results demonstrate that the short BnNn+1 chain presents an obvious spin-filtering effect with high spin polarization ratio (>90%) under low bias voltages. Yet, this spin-filtering effect does not occur for long BnNn+1 chains under high bias voltages and other types of BN atomic chains (BnNn-1 and BnNn). The proposed short BnNn+1 chain is predicted to be an effective low-bias spin filters. Moreover, the length-conductance relationships of these BN atomic chains were also studied.

  11. Spin dynamics in bilayer graphene: Role of electron-hole puddles and Dyakonov-Perel mechanism

    Science.gov (United States)

    Van Tuan, Dinh; Adam, Shaffique; Roche, Stephan

    2016-07-01

    We report on spin transport features which are unique to high quality bilayer graphene, in the absence of magnetic contaminants and strong intervalley mixing. The time-dependent spin polarization of a propagating wave packet is computed using an efficient quantum transport method. In the limit of vanishing effects of substrate and disorder, the energy dependence of the spin lifetime is similar to monolayer graphene with an M -shaped profile and minimum value at the charge neutrality point, but with an electron-hole asymmetry fingerprint. In sharp contrast, the incorporation of substrate-induced electron-hole puddles (characteristics of supported graphene either on SiO2 or hBN ) surprisingly results in a large enhancement of the low-energy spin lifetime and a lowering of its high-energy values. Such a feature, unique to the bilayer, is explained in terms of a reinforced Dyakonov-Perel mechanism at the Dirac point, whereas spin relaxation at higher energies is driven by pure dephasing effects. This suggests further electrostatic control of the spin transport length scales in graphene devices.

  12. Longitudinal spin relaxation of donor-bound electrons in direct band-gap semiconductors

    Science.gov (United States)

    Linpeng, Xiayu; Karin, Todd; Durnev, M. V.; Barbour, Russell; Glazov, M. M.; Sherman, E. Ya.; Watkins, S. P.; Seto, Satoru; Fu, Kai-Mei C.

    2016-09-01

    We measure the donor-bound electron longitudinal spin-relaxation time (T1) as a function of magnetic field (B ) in three high-purity direct band-gap semiconductors: GaAs, InP, and CdTe, observing a maximum T1 of 1.4, 0.4, and 1.2 ms, respectively. In GaAs and InP at low magnetic field, up to ˜2 T, the spin-relaxation mechanism is strongly density and temperature dependent and is attributed to the random precession of the electron spin in hyperfine fields caused by the lattice nuclear spins. In all three semiconductors at high magnetic field, we observe a power-law dependence T1∝B-ν with 3 ≲ν ≲4 . Our theory predicts that the direct spin-phonon interaction is important in all three materials in this regime in contrast to quantum dot structures. In addition, the "admixture" mechanism caused by Dresselhaus spin-orbit coupling combined with single-phonon processes has a comparable contribution in GaAs. We find excellent agreement between high-field theory and experiment for GaAs and CdTe with no free parameters, however a significant discrepancy exists for InP.

  13. Electric-field-induced interferometric resonance of a one-dimensional spin-orbit-coupled electron

    Science.gov (United States)

    Fan, Jingtao; Chen, Yuansen; Chen, Gang; Xiao, Liantuan; Jia, Suotang; Nori, Franco

    2016-12-01

    The efficient control of electron spins is of crucial importance for spintronics, quantum metrology, and quantum information processing. We theoretically formulate an electric mechanism to probe the electron spin dynamics, by focusing on a one-dimensional spin-orbit-coupled nanowire quantum dot. Owing to the existence of spin-orbit coupling and a pulsed electric field, different spin-orbit states are shown to interfere with each other, generating intriguing interference-resonant patterns. We also reveal that an in-plane magnetic field does not affect the interval of any neighboring resonant peaks, but contributes a weak shift of each peak, which is sensitive to the direction of the magnetic field. We find that this proposed external-field-controlled scheme should be regarded as a new type of quantum-dot-based interferometry. This interferometry has potential applications in precise measurements of relevant experimental parameters, such as the Rashba and Dresselhaus spin-orbit-coupling strengths, as well as the Landé factor.

  14. The magnetism and spin-dependent electronic transport properties of boron nitride atomic chains

    Science.gov (United States)

    An, Yipeng; Zhang, Mengjun; Wu, Dapeng; Fu, Zhaoming; Wang, Tianxing; Jiao, Zhaoyong; Wang, Kun

    2016-07-01

    Very recently, boron nitride atomic chains were successively prepared and observed in experiments [O. Cretu et al., ACS Nano 8, 11950 (2015)]. Herein, using a first-principles technique, we study the magnetism and spin-dependent electronic transport properties of three types of BN atomic chains whose magnetic moment is 1 μB for BnNn-1, 2 μB for BnNn, and 3 μB for BnNn+1 type atomic chains, respectively. The spin-dependent electronic transport results demonstrate that the short BnNn+1 chain presents an obvious spin-filtering effect with high spin polarization ratio (>90%) under low bias voltages. Yet, this spin-filtering effect does not occur for long BnNn+1 chains under high bias voltages and other types of BN atomic chains (BnNn-1 and BnNn). The proposed short BnNn+1 chain is predicted to be an effective low-bias spin filters. Moreover, the length-conductance relationships of these BN atomic chains were also studied.

  15. Electron spin relaxation in p-type GaAs quantum wells

    Science.gov (United States)

    Zhou, Y.; Jiang, J. H.; Wu, M. W.

    2009-11-01

    We investigate electron spin relaxation in p-type GaAs quantum wells from a fully microscopic kinetic spin Bloch equation approach, with all the relevant scatterings, such as electron-impurity, electron-phonon, electron-electron Coulomb, electron-hole Coulomb and electron-hole exchange (the Bir-Aronov-Pikus (BAP) mechanism) scatterings, explicitly included. Via this approach, we examine the relative importance of the D'yakonov-Perel' (DP) and BAP mechanisms in wide ranges of temperature, hole density, excitation density and impurity density, and present a phase-diagram-like picture showing the parameter regime where the DP or BAP mechanism is more important. It is discovered that in the impurity-free case the temperature regime where the BAP mechanism is more efficient than the DP one is around the hole Fermi temperature for high hole density, regardless of excitation density. However, in the high impurity density case with the impurity density identical to the hole density, this regime is roughly from the electron Fermi temperature to the hole Fermi temperature. Moreover, we predict that for the impurity-free case, in the regime where the DP mechanism dominates the spin relaxation at all temperatures, the temperature dependence of the spin relaxation time (SRT) presents a peak around the hole Fermi temperature, which originates from the electron-hole Coulomb scattering. We also predict that at low temperature, the hole-density dependence of the electron SRT exhibits a double-peak structure in the impurity-free case, whereas it shows first a peak and then a valley in the case of identical impurity and hole densities. These intriguing behaviors are due to the contribution from holes in high subbands.

  16. Excitation of bond-alternating spin-1/2 Heisenberg chains by tunnelling electrons.

    Science.gov (United States)

    Gauyacq, J-P; Lorente, N

    2014-10-01

    Inelastic electron tunneling spectra (IETS) are evaluated for spin-1/2 Heisenberg chains showing different phases of their spin ordering. The spin ordering is controlled by the value of the two different Heisenberg couplings on the two sides of each of the chain's atoms (bond-alternating chains). The perfect anti-ferromagnetic phase, i.e. a unique exchange coupling, marks a topological quantum phase transition (TQPT) of the bond-alternating chain. Our calculations show that the TQPT is recognizable in the excited states of the chain and hence that IETS is in principle capable of discriminating the phases. We show that perfectly symmetric chains, such as closed rings mimicking infinite chains, yield the same spectra on both sides of the TQPT and IETS cannot reveal the nature of the spin phase. However, for finite size open chains, both sides of the TQPT are associated with different IETS spectra, especially on the edge atoms, thus outlining the transition.

  17. Electron transport for a laser-irradiated quantum channel with Rashba spin-orbit coupling

    Institute of Scientific and Technical Information of China (English)

    Zhao Hua; Liao Wen-Hu; Zhou Guang-Hui

    2007-01-01

    We investigate theoretically the electron transport for a two-level quantum channel (wire) with Rashba spinorbit coupling under the irradiation of a longitudinally-polarized external laser field at low temperatures. Using the method of equation of motion for Keldysh nonequilibrium Green function, we examine the time-averaged spin polarized conductance for the system with photon polarization parallel to the wire direction. By analytical analysis and a few numerical examples, the interplay effects of the external laser field and the Rashba spin-orbit coupling on the spin-polarized conductance for the system are demonstrated and discussed. It is found that the longitudinally-polarized laser field can adjust the spin polarization rate and produce some photon sideband resonances of the conductance for the system.

  18. Excitation of plasmons in Ag/Fe/W structure by spin-polarized electrons

    Energy Technology Data Exchange (ETDEWEB)

    Samarin, Sergey N.; Kostylev, Mikhail; Williams, J. F. [School of Physics, The University of Western Australia, Perth WA 6009 (Australia); Artamonov, Oleg M.; Baraban, Alexander P. [St. Petersburg State University, Faculty of Physics, St. Petersburg 199034 (Russian Federation); Guagliardo, Paul [Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth WA 6009 (Australia)

    2015-09-07

    Using Spin-polarized Electron-Energy Loss Spectroscopy (SPEELS), the plasmon excitations were probed in a few atomic layers thick Ag film deposited on an Fe layer or on a single crystal of W(110). The measurements were performed at two specular geometries with either a 25° or 72° angle of incidence. On a clean Fe layer (10 atomic layers thick), Stoner excitation asymmetry was observed, as expected. Deposition of a silver film on top of the Fe layer dramatically changed the asymmetry of the SPEELS spectra. The spin-effect depends on the kinematics of the scattering: angles of incidence and detection. The spin-dependence of the plasmon excitations in the silver film on the W(110) surface and on the ferromagnetic Fe film is suggested to arise from the spin-active Ag/W or Ag/Fe interfaces.

  19. Is spin transport through molecules really occurring in organic spin valves? A combined magnetoresistance and inelastic electron tunnelling spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Galbiati, Marta; Tatay, Sergio; Delprat, Sophie; Khanh, Hung Le; Deranlot, Cyrile; Collin, Sophie; Seneor, Pierre, E-mail: pierre.seneor@thalesgroup.com; Mattana, Richard, E-mail: richard.mattana@thalesgroup.com; Petroff, Frédéric [Unité Mixte de Physique CNRS/Thales, 1 Av. A. Fresnel, 91767 Palaiseau, France and Université Paris-Sud, 91405 Orsay (France); Servet, Bernard [Thales Research and Technology, 1 Av. A. Fresnel, 91767 Palaiseau (France)

    2015-02-23

    Molecular and organic spintronics is an emerging research field which combines the versatility of chemistry with the non-volatility of spintronics. Organic materials have already proved their potential as tunnel barriers (TBs) or spacers in spintronics devices showing sizable spin valve like magnetoresistance effects. In the last years, a large effort has been focused on the optimization of these organic spintronics devices. Insertion of a thin inorganic tunnel barrier (Al{sub 2}O{sub 3} or MgO) at the bottom ferromagnetic metal (FM)/organic interface seems to improve the spin transport efficiency. However, during the top FM electrode deposition, metal atoms are prone to diffuse through the organic layer and potentially short-circuit it. This may lead to the formation of a working but undesired FM/TB/FM magnetic tunnel junction where the organic plays no role. Indeed, establishing a protocol to demonstrate the effective spin dependent transport through the organic layer remains a key issue. Here, we focus on Co/Al{sub 2}O{sub 3}/Alq{sub 3}/Co junctions and show that combining magnetoresistance and inelastic electron tunnelling spectroscopy measurements one can sort out working “organic” and short-circuited junctions fabricated on the same wafer.

  20. Asymmetric recombination and electron spin relaxation in the semiclassical theory of radical pair reactions

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Alan M.; Manolopoulos, David E.; Hore, P. J. [Department of Chemistry, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ (United Kingdom)

    2014-07-28

    We describe how the semiclassical theory of radical pair recombination reactions recently introduced by two of us [D. E. Manolopoulos and P. J. Hore, J. Chem. Phys. 139, 124106 (2013)] can be generalised to allow for different singlet and triplet recombination rates. This is a non-trivial generalisation because when the recombination rates are different the recombination process is dynamically coupled to the coherent electron spin dynamics of the radical pair. Furthermore, because the recombination operator is a two-electron operator, it is no longer sufficient simply to consider the two electrons as classical vectors: one has to consider the complete set of 16 two-electron spin operators as independent classical variables. The resulting semiclassical theory is first validated by comparison with exact quantum mechanical results for a model radical pair containing 12 nuclear spins. It is then used to shed light on the spin dynamics of a carotenoid-porphyrin-fullerene triad containing considerably more nuclear spins which has recently been used to establish a “proof of principle” for the operation of a chemical compass [K. Maeda, K. B. Henbest, F. Cintolesi, I. Kuprov, C. T. Rodgers, P. A. Liddell, D. Gust, C. R. Timmel, and P. J. Hore, Nature (London) 453, 387 (2008)]. We find in particular that the intriguing biphasic behaviour that has been observed in the effect of an Earth-strength magnetic field on the time-dependent survival probability of the photo-excited C{sup ·+}PF{sup ·−} radical pair arises from a delicate balance between its asymmetric recombination and the relaxation of the electron spin in the carotenoid radical.

  1. Solid effect in the electron spin dressed state: A new approach for dynamic nuclear polarization

    Science.gov (United States)

    Weis, V.; Bennati, M.; Rosay, M.; Griffin, R. G.

    2000-10-01

    We describe a new type of solid effect for dynamic nuclear polarization (DNP) that is based on simultaneous, near resonant microwave (mw) and radio frequency (rf) irradiation of a coupled electron nuclear spin system. The interaction of the electron spin with the mw field is treated as an electron spin dressed state. In contrast to the customary laboratory frame solid effect, it is possible to obtain nuclear polarization with the dressed state solid effect (DSSE) even in the absence of nonsecular hyperfine coupling. Efficient, selective excitation of dressed state transitions generates nuclear polarization in the nuclear laboratory frame on a time scale of tens of μs, depending on the strength of the electron-nuclear coupling, the mw and rf offset and field strength. The experiment employs both pulsed mw and rf irradiation at a repetition rate comparable to T1e-1, where T1e is the electronic spin lattice relaxation time. The DSSE is demonstrated on a perdeuterated BDPA radical in a protonated matrix of polystyrene.

  2. Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium

    Science.gov (United States)

    Sigillito, A. J.; Jock, R. M.; Tyryshkin, A. M.; Beeman, J. W.; Haller, E. E.; Itoh, K. M.; Lyon, S. A.

    2015-12-01

    Germanium is a widely used material for electronic and optoelectronic devices and recently it has become an important material for spintronics and quantum computing applications. Donor spins in silicon have been shown to support very long coherence times (T2 ) when the host material is isotopically enriched to remove any magnetic nuclei. Germanium also has nonmagnetic isotopes so it is expected to support long T2's while offering some new properties. Compared to Si, Ge has a strong spin-orbit coupling, large electron wave function, high mobility, and highly anisotropic conduction band valleys which will all give rise to new physics. In this Letter, the first pulsed electron spin resonance measurements of T2 and the spin-lattice relaxation (T1) times for 75As and 31P donors in natural and isotopically enriched germanium are presented. We compare samples with various levels of isotopic enrichment and find that spectral diffusion due to 73Ge nuclear spins limits the coherence in samples with significant amounts of 73Ge. For the most highly enriched samples, we find that T1 limits T2 to T2=2 T1. We report an anisotropy in T1 and the ensemble linewidths for magnetic fields oriented along different crystal axes but do not resolve any angular dependence to the spectral-diffusion-limited T2 in samples with 73Ge.

  3. Phospholipid bilayer relaxation dynamics as revealed by the pulsed electron-electron double resonance of spin labels

    Science.gov (United States)

    Syryamina, V. N.; Dzuba, S. A.

    2012-10-01

    Electron paramagnetic resonance (EPR) spectroscopy in the form of pulsed electron-electron double resonance (ELDOR) was applied to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipid bilayers containing lipids that were spin-labeled at different carbon positions along the lipid acyl chain. Pulsed ELDOR detects motionally induced spin flips of nitrogen nuclei in the nitroxide spin labels, which manifests itself as magnetization transfer (MT) in the nitroxide EPR spectrum. The MT effect was observed over a wide temperature range (100-225 K) on a microsecond time scale. In line with a previous study on molecular glasses [N. P. Isaev and S. A. Dzuba, J. Chem. Phys. 135, 094508 (2011), 10.1063/1.3633241], the motions that induce MT effect were suggested to have the same nature as those in dielectric secondary (β) Johari-Goldstein fast relaxation. The results were compared with literature dielectric relaxation data for POPC bilayers, revealing some common features. Molecular motions resulting in MT are faster for deeper spin labels in the membrane interior. The addition of cholesterol to the bilayer suppresses the lipid motions near the steroid nucleus and accelerates the lipid motions beyond the steroid nucleus, in the bilayer interior. This finding was attributed to the lipid acyl chains being more ordered near the steroid nucleus and less ordered in the bilayer interior. The motions are absent in dry lipids, indicating that the motions are determined by intermolecular interactions in the bilayer.

  4. Spin dynamics of photogenerated triradicals in fixed distance electron donor-chromophore-acceptor-TEMPO molecules.

    Science.gov (United States)

    Mi, Qixi; Chernick, Erin T; McCamant, David W; Weiss, Emily A; Ratner, Mark A; Wasielewski, Michael R

    2006-06-15

    The stable free radical 2,2,6,6-tetramethylpiperidinoxyl (TEMPO, T*) was covalently attached to the electron acceptor in a donor-chromophore-acceptor (D-C-A) system, MeOAn-6ANI-Phn-A-T*, having well-defined distances between each component, where MeOAn = p-methoxyaniline, 6ANI = 4-(N-piperidinyl)naphthalene-l,8-dicarboximide, Ph = 2,5-dimethylphenyl (n = 0,1), and A = naphthalene-1,8:4,5-bis(dicarboximide) (NI) or pyromellitimide (PI). Using both time-resolved optical and EPR spectroscopy, we show that T* influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+*-6ANI-Phn-A-*-T*), resulting in modulation of the charge recombination rate within the triradical compared with the corresponding biradical lacking T*. The observed spin-spin exchange interaction between the photogenerated radicals MeOAn+* and A-* is not altered by the presence of T*, which interacts most strongly with A-* and accelerates radical pair intersystem crossing. Charge recombination within the triradicals results in the formation of 2,4(MeOAn-6ANI-Phn-3*NI-T*) or 2,4(MeOAn-3*6ANI-Phn-PI-T*) in which T* is strongly spin polarized in emission. Normally, the spin dynamics of correlated radical pairs do not produce a net spin polarization; however, the rate at which the net spin polarization appears on T* closely follows the photogenerated radical ion pair decay rate. This effect is attributed to antiferromagnetic coupling between T* and the local triplet state 3NI, which is populated following charge recombination. These results are explained using a switch in the spin basis set between the triradical and the three-spin charge recombination product having both T* and 3*NI or 3*6ANI present.

  5. Electronic structure of EuO spin filter tunnel contacts directly on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Caspers, C.; Mueller, M. [Peter Gruenberg Institut (PGI-6), Forschungszentrum Juelich, 52425 Juelich (Germany); JARA Juelich-Aachen Research Alliance, Forschungszentrum Juelich, 52425 Juelich (Germany); Gray, A.X.; Fadley, C.S. [Department of Physics, University of California, Davis, California (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California (United States); Kaiser, A.M. [Peter Gruenberg Institut (PGI-6), Forschungszentrum Juelich, 52425 Juelich (Germany); Department of Physics, University of California, Davis, California (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California (United States); Gloskovskii, A. [Institut fuer Analytische und Anorganische Chemie, Johannes Gutenberg-Universitaet, 55128 Mainz (Germany); Drube, W. [DESY Photon Science, Deutsches Elektronen-Synchrotron, 22603 Hamburg (Germany); Schneider, C.M. [Peter Gruenberg Institut (PGI-6), Forschungszentrum Juelich, 52425 Juelich (Germany); JARA Juelich-Aachen Research Alliance, Forschungszentrum Juelich, 52425 Juelich (Germany); Fakultaet fuer Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), 47048 Duisburg (Germany)

    2011-12-15

    We present an electronic structure study of a magnetic oxide/ semiconductor model system, EuO on silicon, which is dedicated for efficient spin injection and spin detection in silicon-based spintronics devices. A combined electronic structure analysis of Eu core levels and valence bands using hard X-ray photoemission spectroscopy was performed to quantify the nearly ideal stoichiometry of EuO ''spin filter'' tunnel barriers directly on silicon, and the absence of silicon oxide at the EuO/Si interface. These results provide evidence for the successful integration of a magnetic oxide tunnel barrier with silicon, paving the way for the future integration of magnetic oxides into functional spintronics devices. Hard X-ray photoemission spectroscopy of an Al/EuO/Si heterostructure probing the buried EuO and EuO/Si interface. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); Vergara, Lucía [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); N' Diaye, Alpha T. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Quesada, Adrian [Instituto de Cerámica y Vidrio, CSIC, Calle Kelsen 5, 28049, Madrid (Spain); Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2013-07-15

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface <110> directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along <110> directions. ► Magnetic domain wall structures include wide Néel-caps.

  7. Resonant Transmission of Electron Spin States through Multiple Aharonov-Bohm Rings

    Science.gov (United States)

    Cutright, Jim; Hedin, Eric; Joe, Yong

    2011-10-01

    An Aharonov-Bohm (AB) ring with embedded quantum dots (QD) in each arm and one -dimensional nanowires attached as leads acts as a primitive cell in this analysis. When a tunable, external magnetic field is parallel to the surface area of the ring it causes Zeeman splitting in the energy levels of the QDs. An electron that traverses these energy levels has the potential to interfere with other electrons and to produce spin polarized output. It is already known that upon output the transmission of the electrons through this system will have a resonant peak at each Zeeman split energy level. A system where multiple AB rings are connected in series is studied, to see how having the electrons pass through multiple, identical rings effects the resonant peaks in the transmission and the degree of spin polarization.

  8. Slow-Motion Theory of Nuclear Spin Relaxation in Paramagnetic Low-Symmetry Complexes: A Generalization to High Electron Spin

    Science.gov (United States)

    Nilsson, T.; Kowalewski, J.

    2000-10-01

    The slow-motion theory of nuclear spin relaxation in paramagnetic low-symmetry complexes is generalized to comprise arbitrary values of S. We describe the effects of rhombic symmetry in the static zero-field splitting (ZFS) and allow the principal axis system of the static ZFS tensor to deviate from the molecule-fixed frame of the nuclear-electron dipole-dipole tensor. We show nuclear magnetic relaxation dispersion (NMRD) profiles for different illustrative cases, ranging from within the Redfield limit into the slow-motion regime with respect to the electron spin dynamics. We focus on S = 3/2 and compare the effects of symmetry-breaking properties on the paramagnetic relaxation enhancement (PRE) in this case with that of S = 1, which we have treated in a previous paper. We also discuss cases of S = 2, 5/2, 3, and 7/2. One of the main objectives of this investigation, together with the previous papers, is to provide a set of standard calculations using the general slow-motion theory, against which simplified models may be tested.

  9. Spin entanglement in elastic electron scattering from lithium atoms

    CERN Document Server

    Bartschat, K

    2016-01-01

    In two recent papers (Phys. Rev. Lett. {\\bf 116} (2016) 033201; Phys. Rev. A {\\bf 94} (2016) 032331), the possibility of continuously varying the degree of entanglement between an elastically scattered electron and the valence electron of an alkali target was discussed. In order to estimate how well such a scheme may work in practice, we present results for elastic electron scattering from lithium in the energy regime of 1$-$5~eV and the full range of scattering angles $0^\\circ - 180^\\circ$. The most promising regime for Bell-correlations in this particular collision system are energies between about 1.5 eV and 3.0 eV, in an angular range around $110^\\circ \\pm 10^\\circ$. In addition to the relative exchange asymmetry parameter, we present the differential cross section that is important when estimating the count rate and hence the feasibility of experiments using this system.

  10. Spin-polarized electron tunneling across a Si delta-doped GaMnAs/n-GaAs interface

    DEFF Research Database (Denmark)

    Andresen, S.E.; Sørensen, B.S.; Lindelof, P.E.;

    2003-01-01

    Spin-polarized electron coupling across a Si delta-doped GaMnAs/n-GaAs interface was investigated. The injection of spin-polarized electrons was detected as circular polarized emission from a GaInAs/GaAs quantum well light emitting diode. The angular momentum selection rules were simplified...

  11. On the Coupling of Photon Spin to Electron Orbital Angular Momentum

    CERN Document Server

    Fischer, Ulrich C; Fuchs, Harald; Salut, Roland; Lefier, Yannick; Grosjean, Thierry

    2016-01-01

    Partially gold coated 90 degree glass wedges and a semi - infinite slit in a thin film of gold ending in a conducting nano-junction serve as samples to investigate the transfer of photon spin to electron orbital angular momentum. These structures were specifically designed as samples where an incident beam of light is retroreflected. Since in the process of retroreflection the turning sense of a circularly polarized beam of light does not change and the direction of propagation is inverted, the photon spin is inverted. Due to conservation of angular momentum a transfer of photon spin to electron orbital angular momentum of conduction electrons occurs. In the structures a circular movement of electrons is blocked and therefore the transfered spin can be detected as a photovoltage due to an electromotive force which is induced by the transfer of angular momentum. Depending on the polarization of the incident beam, a maximum photovoltage of about 0,2 micro V was measured for both structures. The results are inte...

  12. Theoretical investigation of the hyperfine structure in spatially and spin degenerate electronic states

    Directory of Open Access Journals (Sweden)

    JELENA RADIC-PERIC

    2005-03-01

    Full Text Available The present paper reviews the results of ab initio studies on the magnetic hyperfine structure in spectra of spatially and spin degenerate electronic states of triatomic and tetra-atomic molecules. The main goal of the present paper is to show that such theoretical investigations can be used to reliably reproduce, explain and predict the results of the corresponding measurements.

  13. Temperature Regulating System for Use with an Electron Spin Resonance Spectrometer

    DEFF Research Database (Denmark)

    Fenger, J.

    1965-01-01

    A servosystem that controls the sample temperature in an electron spin resonance spectrometer is described. It is based upon the regulation of the combination of two nitrogen gas flows of different temperatures. The temperature can be preset with an accuracy to about 1 degC between -140 and 100°C...

  14. Electron spin relaxation governed by Raman processes both for Cu²⁺ ions and carbonate radicals in KHCO₃ crystals: EPR and electron spin echo studies.

    Science.gov (United States)

    Hoffmann, Stanislaw K; Goslar, Janina; Lijewski, Stefan

    2012-08-01

    EPR studies of Cu²⁺ and two free radicals formed by γ-radiation were performed for KHCO₃ single crystal at room temperature. From the rotational EPR results we concluded that Cu²⁺ is chelated by two carbonate molecules in a square planar configuration with spin-Hamiltonian parameters g(||)=2.2349 and A(||)=18.2 mT. Free radicals were identified as neutral HOCO· with unpaired electron localized on the carbon atom and a radical anion CO₃·⁻ with unpaired electron localized on two oxygen atoms. The hyperfine splitting of the EPR lines by an interaction with a single hydrogen atom of HOCO· was observed with isotropic coupling constants a₀=0.31 mT. Two differently oriented radical sites were identified in the crystal unit cell. Electron spin-lattice relaxation measured by electron spin echo methods shows that both Cu²⁺ and free radicals relax via two-phonon Raman processes with almost the same relaxation rate. The temperature dependence of the relaxation rate 1/T₁ is well described with the effective Debye temperature Θ(D)=175 K obtained from a fit to the Debye-type phonon spectrum. We calculated a more realistic Debye temperature value from available elastic constant values of the crystal as Θ(D)=246 K. This Θ(D)-value and the Debye phonon spectrum approximation give a much worse fit to the experimental results. Possible contributions from a local mode or an optical mode are considered and it is suggested that the real phonon spectrum should be used for the relaxation data interpretation. It is unusual that free radicals in KHCO₃ relax similarly to the well localized Cu²⁺ ions, which suggests a small destruction of the host crystal lattice by the ionizing irradiation allowing well coupling between radical and lattice dynamics.

  15. Electron spin relaxation governed by Raman processes both for Cu2+ ions and carbonate radicals in KHCO3 crystals: EPR and electron spin echo studies

    Science.gov (United States)

    Hoffmann, Stanislaw K.; Goslar, Janina; Lijewski, Stefan

    2012-08-01

    EPR studies of Cu2+ and two free radicals formed by γ-radiation were performed for KHCO3 single crystal at room temperature. From the rotational EPR results we concluded that Cu2+ is chelated by two carbonate molecules in a square planar configuration with spin-Hamiltonian parameters g|| = 2.2349 and A|| = 18.2 mT. Free radicals were identified as neutral HOCOrad with unpaired electron localized on the carbon atom and a radical anion CO3·- with unpaired electron localized on two oxygen atoms. The hyperfine splitting of the EPR lines by an interaction with a single hydrogen atom of HOCOrad was observed with isotropic coupling constants ao = 0.31 mT. Two differently oriented radical sites were identified in the crystal unit cell. Electron spin-lattice relaxation measured by electron spin echo methods shows that both Cu2+ and free radicals relax via two-phonon Raman processes with almost the same relaxation rate. The temperature dependence of the relaxation rate 1/T1 is well described with the effective Debye temperature ΘD = 175 K obtained from a fit to the Debye-type phonon spectrum. We calculated a more realistic Debye temperature value from available elastic constant values of the crystal as ΘD = 246 K. This ΘD-value and the Debye phonon spectrum approximation give a much worse fit to the experimental results. Possible contributions from a local mode or an optical mode are considered and it is suggested that the real phonon spectrum should be used for the relaxation data interpretation. It is unusual that free radicals in KHCO3 relax similarly to the well localized Cu2+ ions, which suggests a small destruction of the host crystal lattice by the ionizing irradiation allowing well coupling between radical and lattice dynamics.

  16. Spin-Droplet State of an Interacting 2D Electron System

    OpenAIRE

    Teneh, N.; Kuntsevich, A. Yu.; Pudalov, V. M.; Reznikov, M.

    2012-01-01

    We report thermodynamic magnetization measurements of two-dimensional electrons in several high mobility Si metal-oxide-semiconductor field-effect transistors. We provide evidence for an easily polarizable electron state in a wide density range from insulating to deep into the metallic phase. The temperature and magnetic field dependence of the magnetization is consistent with the formation of large-spin droplets in the insulating phase. These droplets melt in the metallic phase with increasi...

  17. Orthogonal Chip Based Electronic Sensors for Chemical Agents

    Science.gov (United States)

    2012-04-06

    have been spin coated and allowed to crystallize to make microwires on top contact FET devices. These materials show remarkably well-behaved...acute airway inflammation. Sterilization of medical /pharmaceutical equipment is commonly performed with VHP at concentrations 1000 times above the

  18. Electrons and Spin Waves in Heavy Rare Earth Metals

    DEFF Research Database (Denmark)

    Mackintosh, A. R.

    1972-01-01

    Although the main principles governing the magnetic interactions and magnetic ordering in rare earth metals have been qualitatively understood for some time, it is only relatively recently that a sufficiently detailed study has been made of their electronic and magnetic excitations to place...

  19. Introduction to Spin Label Electron Paramagnetic Resonance Spectroscopy of Proteins

    Science.gov (United States)

    Melanson, Michelle; Sood, Abha; Torok, Fanni; Torok, Marianna

    2013-01-01

    An undergraduate laboratory exercise is described to demonstrate the biochemical applications of electron paramagnetic resonance (EPR) spectroscopy. The beta93 cysteine residue of hemoglobin is labeled by the covalent binding of 3-maleimido-proxyl (5-MSL) and 2,2,5,5-tetramethyl-1-oxyl-3-methyl methanethiosulfonate (MTSL), respectively. The excess…

  20. Spin decoherence in electron storage rings --- more from a simple model

    CERN Document Server

    Barber, D P

    2015-01-01

    This is an addendum to the paper "Some models of spin coherence and decoherence in storage rings" by one of the authors [1] in which spin diffusion in simple electron storage rings is studied. In particular, we illustrate in a compact way, a key implication in the Epilogue of [1], namely that the exact formalism of [1] delivers a rate of depolarisation which can differ from that obtained by the conventional treatments of spin diffusion which rely on the use of the derivative $\\partial \\hat n/\\partial\\eta$ [2,3,4]. As a vehicle we consider a ring with a Siberian Snake and electron polarisation in the plane of the ring (Machine II in [1]). For this simple setup with its one-dimensional spin motion, we avoid having to deal directly with the Bloch equation [5,6] for the polarisation density. Our treatment, which is deliberately pedagogical, shows that the use of $\\partial \\hat n/\\partial\\eta$ provides a very good approximation to the rate of spin depolarisation in the model considered. But it then shows that the ...

  1. Spin decoherence in electron storage rings. More from a simple model

    Energy Technology Data Exchange (ETDEWEB)

    Barber, D.P. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Heinemann, K. [The Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Mathematics and Statistics

    2015-06-15

    This is an addendum to the paper ''Some models of spin coherence and decoherence in storage rings'' by one of the authors (K. Heinemann, DESY Report 97-166 (1997)), in which spin diffusion in simple electron storage rings is studied. In particular, we illustrate in a compact way, namely that the exact formalism of this article delivers a rate of depolarisation which can differ from that obtained by the conventional treatments of spin diffusion which rely on the use of the derivative ∂n/∂η. As a vehicle we consider a ring with a Siberian Snake and electron polarisation in the plane of the ring. For this simple setup with its one-dimensional spin motion, we avoid having to deal directly with the Bloch equation for the polarisation density. Our treatment, which is deliberately pedagogical, shows that the use of ∂n/∂η provides a very good approximation to the rate of spin depolarisation in the model considered. But it then shows that the exact rate of depolarisation can be obtained by replacing ∂n/∂η by another derivative, while giving a heuristic justification for the new derivative.

  2. Spin excitations in systems with hopping electron transport and strong position disorder in a large magnetic field

    Science.gov (United States)

    Shumilin, A. V.

    2016-10-01

    We discuss the spin excitations in systems with hopping electron conduction and strong position disorder. We focus on the problem in a strong magnetic field when the spin Hamiltonian can be reduced to the effective single-particle Hamiltonian and treated with conventional numerical technics. It is shown that in a 3D system with Heisenberg exchange interaction the spin excitations have a delocalized part of the spectrum even in the limit of strong disorder, thus leading to the possibility of the coherent spin transport. The spin transport provided by the delocalized excitations can be described by a diffusion coefficient. Non-homogenous magnetic fields lead to the Anderson localization of spin excitations while anisotropy of the exchange interaction results in the Lifshitz localization of excitations. We discuss the possible effect of the additional exchange-driven spin diffusion on the organic spin-valve devices.

  3. Electron Spin or "Classically Non-Describable Two-Valuedness"

    CERN Document Server

    Giulini, Domenico

    2007-01-01

    In December 1924 Wolfgang Pauli proposed the idea of an inner degree of freedom of the electron, which he insisted should be thought of as genuinely quantum mechanical in nature. Shortly thereafter Ralph Kronig and, independently, Samuel Goudsmit and George Uhlenbeck took up a less radical stance by suggesting that this degree of freedom somehow corresponded to an inner rotational motion, though it was unclear from the very beginning how literal one was actually supposed to take this picture, since it was immediately recognised (already by Goudsmit and Uhlenbeck) that it would very likely lead to serious problems with Special Relativity if the model were to reproduce the electron's values for mass, charge, angular momentum, and magnetic moment. However, probably due to the then overwhelming impression that classical concepts were generally insufficient for the proper description of microscopic phenomena, a more detailed reasoning was never given. In this contribution I shall investigate in some detail what th...

  4. Electron spin resonance (ESR) study of VO{sup 2+} doped germanium dioxide synthesized via the sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Mendez-Vivar, J.; Arroyo, R. [Univ. Autonoma Metropolitana-Iztapalapa (Mexico). Dept. de Quimica

    1994-12-31

    VOSO{sub 4}{center_dot}3H{sub 2}O was used as doping agent to prepare GeO{sub 2} xerogels, via the sol-gel process. Samples were analyzed by Thermal Gravimetric Analysis (TGA), Differential Thermal Analysis, (DTA), Diffuse reflectance (UV-Vis) spectroscopy and electron spin resonance (ESR). Study of thermally treated samples was performed. VO{sup 2+} were found in V{sub 2}O{sub 5} at 350 C. VO{sup 2+} ions were incorporated in the GeO{sub 2} network after thermal treatment at 700 C. From the results the authors propose that VO{sup 2+} acts as crystal former in these samples.

  5. An Electron-Nucleon Double Spin Solid-State Quantum Computer

    CERN Document Server

    Long, G L; Chen, H M; Long, Gui Lu; Ma, Ying-Jun; Chen, Hao-Ming

    2003-01-01

    An electron-nucleon double spin(ENDOS) solid-state quantum computer scheme is proposed. In this scheme, the qubits are the nuclear spins of phosphorus ion implanted on the (111) surface of $^{28}$Si substrate. An $^{13}$C atom on a scanning tunnelling probe tip is used both to complete single qubit and two-qubit control-not operation, and single qubit measurement. The scheme does not require interactions between qubits, and can accomplish two qubits without the use of SWAP gate. This scheme is scalable, and can be implemented with present-day or near-future technologies.

  6. Helium Droplets as Nano-Cryostats for Molecular Spectroscopy: Aggregation, State Selection and Electron Spin Resonance

    Science.gov (United States)

    Ernst, Wolfgang E.

    2009-06-01

    Droplets of about 10^{4} helium atoms generated in a supersonic expansion, represent a nanometer-sized superfluid medium of 0.4 K temperature and can be doped with one or several atoms or molecules that may form complexes in this cold environment. Using two-laser excitation schemes, we were able to identify the alkali trimers K_3, Rb_3, K_2Rb and KRb_2 in their lowest quartet states formed on helium droplets loaded with potassium and rubidium atoms and assign several excited states that underlie both Jahn-Teller and spin-orbit coupling. As helium provides a gentle and only weakly perturbing matrix, it appeared desirable to look for ways to measure fine and hyperfine structure directly in the microwave or radiofrequency regime. In preparation for experiments involving optical detection of electron spin transitions in cold molecules, we studied the electronic spin relaxation in alkali atoms and molecules that reside on the surface of a droplet. Measurements of the circular dichroism in the presence of a magnetic field showed that the populations of Zeeman sublevels in alkali atoms are not thermalized, while for dimers and trimers a temperature of 0.4 K was found, implicitly providing a first determination of the droplet's surface temperature. Optical detection of spin resonance is achieved in an optical pump-probe experiment with the electron spin transition induced in a microwave cavity in a magnetic field between the pump and probe regions. With the pump laser depleting a particular spin state by desorption of the species from the droplet beam or by optical pumping, the probe laser detects the successful spin flip induced by the microwave field. Examples will be presented showing up to 50 Rabi cycles of an electron spin transition on an alkali doped helium droplet during the flight time of 57 μs through the cavity. J. Nagl, G. Auböck, A. W. Hauser, O. Allard, C. Callegari, and W. E. Ernst, Phys. Rev. Lett. 100, 063001(2008)} G. Auböck, J. Nagl, C. Callegari, and

  7. Tunable photon transmission through a waveguide cavity coupled to an electron spin ensemble

    Science.gov (United States)

    Feng, Zhi-Bo; Yan, Run-Ying; Yan, Lei-Lei; Zhou, Yun-Qing

    2017-02-01

    We propose an effective scheme for implementing tunable photon transmission through a coplanar waveguide cavity. An electron spin ensemble of nitrogen-vacancy centers, behaving as a spin-boson mode, is coupled to the cavity mode. It is found that the transmittance of an incident photon depends on the coupling strength between the two modes, both with dissipative effects. In particular, the photon transmittance can be controlled at will by adjusting the external driving-induced detunings. This proposal could offer a promising avenue to coherently control photon propagation and is highly preferable for the experimental manipulations.

  8. Semiclassical Vlasov and fluid models for an electron gas with spin effects

    CERN Document Server

    Hurst, Jerome; Manfredi, Giovanni; Hervieux, Paul-Antoine

    2014-01-01

    We derive a four-component Vlasov equation for a system composed of spin-1/2 fermions (typically electrons). The orbital part of the motion is classical, whereas the spin degrees of freedom are treated in a completely quantum-mechanical way. The corresponding hydrodynamic equations are derived by taking velocity moments of the phase-space distribution function. This hydrodynamic model is closed using a maximum entropy principle in the case of three or four constraints on the fluid moments, both for Maxwell-Boltzmann and Fermi-Dirac statistics.

  9. Controllable Quantum State Transfer Between a Josephson Charge Qubit and an Electronic Spin Ensemble

    Science.gov (United States)

    Yan, Run-Ying; Wang, Hong-Ling; Feng, Zhi-Bo

    2016-01-01

    We propose a theoretical scheme to implement controllable quantum state transfer between a superconducting charge qubit and an electronic spin ensemble of nitrogen-vacancy centers. By an electro-mechanical resonator acting as a quantum data bus, an effective interaction between the charge qubit and the spin ensemble can be achieved in the dispersive regime, by which state transfers are switchable due to the adjustable electrical coupling. With the accessible experimental parameters, we further numerically analyze the feasibility and robustness. The present scheme could provide a potential approach for transferring quantum states controllably with the hybrid system.

  10. Electron density dependence of the spin Hall effect in GaAs probed by scanning Kerr rotation microscopy

    Science.gov (United States)

    Matsuzaka, S.; Ohno, Y.; Ohno, H.

    2009-12-01

    We studied electron density (n) dependence of the extrinsic spin Hall effect in n -doped GaAs with n raging from 1.8×1016 to 3.3×1017cm-3 . By scanning Kerr microscopy measurements, we observed spin accumulation near the channel edges in all the samples due to the extrinsic spin Hall effect. The spin Hall conductivity σSH is obtained for each sample by comparing the Kerr rotation induced by optically injected spins. σSH is found to increase with n , and it is shown that a theoretical model reported earlier agrees well with the experimental n dependence of σSH .

  11. Spin current

    CERN Document Server

    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.

  12. Electron spin resonance of YbRh{sub 2}Si{sub 2} under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Sichelschmidt, J.; Wykhoff, J.; Gruner, T.; Krellner, C.; Klingner, C.; Geibel, C.; Steglich, F. [MPI Chem. Physik fester Stoffe, Dresden (Germany); Krug von Nidda, H.A.; Zakharov, D.; Loidl, A. [EP V, EKM, Univ. Augsburg (Germany); Fazlishanov, I. [E.K. Zavoisky Physical Technical Inst., Kasan (Russian Federation)

    2010-07-01

    We investigated the electron spin resonance (ESR) in the heavy-fermion metal YbRh{sub 2}Si{sub 2} by applying hydrostatic pressure up to 3 GPa. We found that pressure increases the temperature dependence of the g factor and broadens the ESR line. These effects are similar to those observed in Yb(Rh{sub 1-x}Co{sub x}){sub 2}Si{sub 2} where Co substitution for Rh induces chemical pressure. However, the effect of chemical and external pressure on the ESR is not identical indicating the relevance of Co induced disorder on the spin dynamics. We compare our pressure ESR results with the behavior of the Gd ESR in CeAl{sub 3}. This reveals a similar behavior pointing on one hand to a local character Yb{sup 3+}-ESR, on the other hand on the properties of a heavy quasiparticle spin resonance upon changing the hybridization strength between 4f and conduction electrons. Both findings are consistent with the properties of a collective 4f-conduction electron spin mode which is supported by the Kondo effect.

  13. Spin Entangling Effects of Electron and Nucleus on Hopping Transfer in Organic Semiconductors

    Science.gov (United States)

    Zhao, Jun-Qing; Sun, Ling-Ling; Wang, Ting

    2016-05-01

    To study the spin entangling effects on organic magneto-resistance in organic semiconductors, we focused on the entanglement-related hopping transfer of electrons on the basis of the Miller-Abrahams hopping rate. Considering spin entanglement of localized electron with the nucleus in the hopping process, we deduced an attempt hopping rate of electrons as a function of the applied magnetic field and the localized hyperfine interaction, and thus established a model to calculate the organic magneto-resistance. The calculated results show that the magneto-resistance has a maximum in the lower magnetic field, and the corresponding magnetic field Bmax increases with the hyperfine interaction. In the higher magnetic field, the magneto-resistance tends to a negative saturation value. This analysis will be an valuable reference for deep understanding of the organic magneto-resistance.

  14. Strain-induced phase transition and electron spin-polarization in graphene spirals.

    Science.gov (United States)

    Zhang, Xiaoming; Zhao, Mingwen

    2014-07-16

    Spin-polarized triangular graphene nanoflakes (t-GNFs) serve as ideal building blocks for the long-desired ferromagnetic graphene superlattices, but they are always assembled to planar structures which reduce its mechanical properties. Here, by joining t-GNFs in a spiral way, we propose one-dimensional graphene spirals (GSs) with superior mechanical properties and tunable electronic structures. We demonstrate theoretically the unique features of electron motion in the spiral lattice by means of first-principles calculations combined with a simple Hubbard model. Within a linear elastic deformation range, the GSs are nonmagnetic metals. When the axial tensile strain exceeds an ultimate strain, however, they convert to magnetic semiconductors with stable ferromagnetic ordering along the edges. Such strain-induced phase transition and tunable electron spin-polarization revealed in the GSs open a new avenue for spintronics devices.

  15. Electron Spin Pairing and the Phase Diagram of High-Tc Superconductors

    Institute of Scientific and Technical Information of China (English)

    GUO Wei; HAN Ru-Shan

    2001-01-01

    The origin of the instability of the normal state of electrons in the superconducting copper oxides is shown by the K-J model, in which the superexchange (K) between local moments and the Kondo exchange ( J) between electron and local moment are considered. The suppression of superexchange via impurity doping may induce effective spin coupling between electrons and triplet pairing (S = 1, Sz = 0). The spin pairing theory explains the phase diagram of high-To superconductors, especially the superconducting transition temperature Tc, the pseudogap temperature T* and the magnetic crossover temperature Tn as a function of the doped hole concentration. The universal expression for the empirical law of the superconducting transition temperature is derived from the theory.

  16. Link between spin fluctuations and electron pairing in copper oxide superconductors.

    Science.gov (United States)

    Jin, K; Butch, N P; Kirshenbaum, K; Paglione, J; Greene, R L

    2011-08-03

    Although it is generally accepted that superconductivity is unconventional in the high-transition-temperature copper oxides, the relative importance of phenomena such as spin and charge (stripe) order, superconductivity fluctuations, proximity to a Mott insulator, a pseudogap phase and quantum criticality are still a matter of debate. In electron-doped copper oxides, the absence of an anomalous pseudogap phase in the underdoped region of the phase diagram and weaker electron correlations suggest that Mott physics and other unidentified competing orders are less relevant and that antiferromagnetic spin fluctuations are the dominant feature. Here we report a study of magnetotransport in thin films of the electron-doped copper oxide La(2 - x)Ce(x)CuO(4). We show that a scattering rate that is linearly dependent on temperature--a key feature of the anomalous normal state properties of the copper oxides--is correlated with the electron pairing. We also show that an envelope of such scattering surrounds the superconducting phase, surviving to zero temperature when superconductivity is suppressed by magnetic fields. Comparison with similar behaviour found in organic superconductors strongly suggests that the linear dependence on temperature of the resistivity in the electron-doped copper oxides is caused by spin-fluctuation scattering.

  17. Electron spin resonance and electron nuclear double resonance of photogenerated polarons in polyfluorene and its fullerene composite

    Science.gov (United States)

    Marumoto, K.; Kato, M.; Kondo, H.; Kuroda, S.; Greenham, N. C.; Friend, R. H.; Shimoi, Y.; Abe, S.

    2009-06-01

    Electron spin resonance (ESR) and electron-nuclear double resonance (ENDOR) of photogenerated polarons in poly(9,9-dioctylfluorene) (PFO) and its composite with fullerene (C60) using variable photoexcitation energy up to 4.1 eV are reported. For PFO, a light-induced ESR (LESR) signal (g=2.003) is observed below 60 K, and its transient response and excitation spectrum indicate that the observed spins are photogenerated polarons on PFO. For the PFO-C60 composite, two LESR signals of photogenerated positive polarons on PFO (g1=2.003) and radical anions on C60 (g2=1.999) , respectively, are observed below 120 K, which are caused by photoinduced electron transfer from PFO to C60 . A remarkable enhancement of the LESR signals in the excitation spectrum at ˜2.8eV is observed compared with the case of pure PFO. The bimolecular-recombination kinetics of photogenerated charge carriers in the composite are confirmed by the dependence of the LESR on excitation-light intensity and by the decay dynamics. Light-induced ENDOR (LENDOR) signals are clearly observed for excitation around 2.8 eV owing to the highly efficient photoinduced electron transfer in the composite. Broad LENDOR shifts directly reflect the spin-density distribution of the polarons in PFO. We have determined its maximum shift using LENDOR-induced ESR, and have evaluated the maximum spin density on the carbon site coupled to the proton as 0.032. This value is consistent with the theoretical result obtained by Pariser-Parr-Pople (PPP) model, where the spatial extent of the polarons is calculated as ˜3 monomer units of PFO. The calculated LESR spectra of PFO based on the PPP model are consistent with the experimental spectra, which confirm the above spatial extension of the polaron in PFO.

  18. EPR and DNP Properties of Certain Novel Single Electron Contrast Agents Intended for Oximetric Imaging

    DEFF Research Database (Denmark)

    Ardenkjær-Larsen, J. H.; Laursen, I; Leunbach, I.;

    1998-01-01

    Parameters of relevance to oximetry with Overhauser magnetic resonance imaging (OMRI) have been measured for three single electron contrast agents of the triphenylmethyl type. The single electron contrast agents are stable and water soluble. Magnetic resonance properties of the agents have been...... examined with electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and dynamic nuclear polarization (DNP) at 9.5 mT in water, isotonic saline, plasma, and blood at 23 and 37°C. The relaxivities of the agents are about 0.2–0.4 mM−1s−1and the DNP enhancements extrapolate close...... to the dipolar limit. The agents have a single, narrow EPR line, which is analyzed as a Voigt function. The linewidth is measured as a function of the agent concentration and the oxygen concentration. The concentration broadenings are about 1–3 μT/mM and the Lorentzian linewidths at infinite dilution are less...

  19. Emission of correlated electron pairs from Au(111) and Cu(111) surfaces under low-energy electron impact: Contribution of surface states, d-states and spin effects

    Energy Technology Data Exchange (ETDEWEB)

    Samarin, S., E-mail: samar@physics.uwa.edu.au [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia); Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Artamonov, O.M. [Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Guagliardo, P. [Centre for Microscopy, Characterisation and Analysis, UWA, Perth (Australia); Pravica, L. [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia); Baraban, A. [Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Schumann, F.O. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany); Williams, J.F. [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia)

    2015-01-15

    Highlights: • Spin-polarized two-electron spectroscopy (e,2e) was applied for studying surface states on Cu(111) and Au(111). • Relative (to d-states) contribution of surface states in the (e,2e) spectrum decreases exponentially when primary electron energy increases from 14 to 30 eV. • Spin asymmetry is readily observed in the spectra of Au(111) whereas in the spectra of Cu(111) the spin effect is negligible. - Abstract: The emission of correlated electron pairs excited from surfaces of Au(111) and Cu(111) by low-energy electrons is measured and analyzed. Energy and momentum conservation allows identification of electron pairs involving excitation of electrons from Shockley surface states and from valence d-states. The relative contributions of surface and d-states to the measured spectra of correlated electron pairs is shown to depend on the primary electron energy and is larger from surface states at relatively small primary energies. The use of a spin-polarized incident electron beam highlights the spin effects in producing an electron pair. Measurements show that spin effects are larger for the pair excitation from the valence d-states than for pairs excited from the surface states.

  20. Relaxation of a Classical Spin Coupled to a Strongly Correlated Electron System

    Science.gov (United States)

    Sayad, Mohammad; Rausch, Roman; Potthoff, Michael

    2016-09-01

    A classical spin which is antiferromagnetically coupled to a system of strongly correlated conduction electrons is shown to exhibit unconventional real-time dynamics which cannot be described by Gilbert damping. Depending on the strength of the local Coulomb interaction U , the two main electronic dissipation channels, namely transport of excitations via correlated hopping and via excitations of correlation-induced magnetic moments, become active on largely different time scales. We demonstrate that correlations can lead to a strongly suppressed relaxation which so far has been observed in purely electronic systems only and which is governed here by proximity to the divergent magnetic time scale in the infinite-U limit.

  1. Electron Scattering from Freely Moveable spin-$\\frac{1}{2}$ fermion in Strong Laser Field

    CERN Document Server

    Liu, Ai-Hua

    2014-01-01

    We study the electron scatter from the freely movable spin-$\\frac{1}{2}$ particle in the presence of a linearly polarized laser field in the first Born approximation. The dressed state of electrons is described by a time-dependent wave function derived from a perturbation treatment (of the laser field). With the aid of numerical results we explore the dependencies of the differential cross section on the laser field properties such as the strength, the frequency, as well as on the electron-impact energy, etc. Due to the targets are movable, the DCS of this process reduced comparing to the Mott scattering, especially in small scattering angles.

  2. Mapping spin distributions in electron acceptor molecules adsorbed on nanostructured graphene by the Kondo effect

    Science.gov (United States)

    Garnica, Manuela; Calleja, Fabián; Vázquez de Parga, Amadeo L.; Miranda, Rodolfo

    2014-12-01

    Electron acceptor molecules adsorbed on nanostructured graphene grown on Ru(0001) were investigated by low temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS). Our experiments reveal a considerable charge transfer from the substrate to the single molecules leading to the partial occupation of the LUMO of the neutral molecules. The nanostructured graphene modulates the hybridization between the transferred unpaired electron and the ruthenium conduction electrons leading to the appearance of a Kondo effect. Spatially resolved LT-STS allows the high resolution mapping of the spin distribution of the charge transferred and a characteristic inelastic Kondo features associated to specific vibrational modes.

  3. Electron spin resonance spectroscopy for the study of nanomaterial-mediated generation of reactive oxygen species

    Directory of Open Access Journals (Sweden)

    Weiwei He

    2014-03-01

    Full Text Available Many of the biological applications and effects of nanomaterials are attributed to their ability to facilitate the generation of reactive oxygen species (ROS. Electron spin resonance (ESR spectroscopy is a direct and reliable method to identify and quantify free radicals in both chemical and biological environments. In this review, we discuss the use of ESR spectroscopy to study ROS generation mediated by nanomaterials, which have various applications in biological, chemical, and materials science. In addition to introducing the theory of ESR, we present some modifications of the method such as spin trapping and spin labeling, which ultimately aid in the detection of short-lived free radicals. The capability of metal nanoparticles in mediating ROS generation and the related mechanisms are also presented.

  4. Electron interaction with the spin angular momentum of the electromagnetic field

    Science.gov (United States)

    O’Connell, R. F.

    2017-02-01

    We give a simple derivation and expansion of a recently proposed new relativistic interaction between the electron and the spin angular momentum of the electromagnetic field in quantum electrodynamics (QED). Our derivation is based on the work of Møller, who pointed out that, in special relativity, a particle with spin must always have a finite extension. After generalizing Møller’s classical result to include both rotation and quantum effects, we show that it leads to a new contribution to the energy, which is the special relativistic interaction term. In addition, we show that all relativistic terms involving spin terms arising from the Dirac equation may be obtained by this method.

  5. Studying lipid-protein interactions with electron paramagnetic resonance spectroscopy of spin-labeled lipids.

    Science.gov (United States)

    Páli, Tibor; Kóta, Zoltán

    2013-01-01

    Spin label electron paramagnetic resonance (EPR) of lipid-protein interactions reveals crucial features of the structure and assembly of integral membrane proteins. Spin label EPR spectroscopy is the technique of choice to characterize the protein-solvating lipid shell in its highly dynamic nature, because the EPR spectra of lipids that are spin labeled close to the terminal methyl end of their acyl chains display two spectral components, those corresponding to lipids directly contacting the protein and those corresponding to lipids in the bulk fluid bilayer regions of the membrane. In this chapter, typical spin label EPR procedures are presented that allow determination of the stoichiometry of interaction of spin-labeled lipids with the intra-membranous region of membrane proteins or polypeptides, as well as the association constant of the spin-labeled lipid with respect to the host lipid. The lipids giving rise to the so-called immobile spectral component in the EPR spectrum of such samples are identified as the motionally restricted first-shell lipids solvating membrane proteins in biomembranes. Stoichiometry and selectivity are directly related to the structure of the intra-membranous sections of membrane-associated proteins or polypeptides and can be used to study the state of assembly of such proteins in the membrane. Since these characteristics of lipid-protein interactions are discussed in detail in the literature [see Marsh (Eur Biophys J 39:513-525, 2010) for a most recent review], here we focus more on how to spin label model and biomembranes and how to measure and analyze the two-component EPR spectra of spin-labeled lipids in phospholipid bilayers that contain proteins or polypeptides. After a description of how to prepare spin-labeled model and native biological membranes, we present the reader with computational procedures for determining the molar fraction of motionally restricted lipids when both, one, or none of the pure isolated-mobile or

  6. Phonon spectrum, electron spin-lattice relaxation and spin-phonon coupling of Cu2+ ions in BaF2 crystal

    Science.gov (United States)

    Hoffmann, Stanislaw K.; Lijewski, Stefan

    2015-03-01

    Electron spin-lattice relaxation rate is determined by electron spin echo method in temperature range 4-60 K. The Raman relaxation processes dominate and its theory is outlined in a form suitable for calculations of relaxation rate using real phonon spectrum. A few approximations have been considered: when phonon spectrum and Debye temperature are not available; when Debye temperature is available but phonon spectrum is not; and when spin-phonon coupling is known. All these approximations use the Debye model of phonons and give a non-satisfactory description the temperature dependence of the relaxation rate. A perfect description of experimental results is obtained when real phonon spectrum is considered. The value of the spin-phonon coupling parameter was determined as G = = 1362cm-1 . This value is discussed by a comparison with G-values published for various ions and crystals.

  7. Zitterbewegung, internal momentum and spin of the circular travelling wave electromagnetic electron

    CERN Document Server

    Asif, Malik Mohammad

    2016-01-01

    The study of this paper demonstrates that electron has Dirac delta like internal momentum (u,p_{{\\theta}}), going round in a circle of radius equal to half the reduced Compton wavelength of electron with tangential velocity c. The circular momentum p_{{\\theta}} and energy u emanate from circular Dirac delta type rotating monochromatic electromagnetic (EM) wave that itself travels in another circle having radius equal to the reduced Compton wavelength of electron. The phenomenon of Zitterbewegung and the spin of electron are the natural consequences of the model. The spin is associated with the internal circulating momentum of electron in terms of four component spinor, which leads to the Dirac equation linking the EM electron model with quantum mechanical theory. Our model accurately explains the experimental results of electron channelling experiment, [P. Catillon et al., Found.Phys. 38, 659 (2008)], in which the momentum resonance is observed at 161.784MeV/c corresponding to Zitterbewegung frequency of 80.8...

  8. Heavy electrons and symplectic symmetry of a spin

    Science.gov (United States)

    Dzero, Maxim

    2009-03-01

    Motivated by the recent discovery of the heavy fermion materials NpPd5Al2 [1] and PuCoGa5 [2] which transform directly from Curie paramagnets into superconductors, we have developed a novel theory of these materials based on the idea of composite pairing between local moments and electron pairs. This talk will discuss a simple model of this kind of pairing that can be solved exactly in a large-N limit [3]. The talk will discuss how this concept enables us to understand the giant entropy of condensation, the symmetry of the order parameter as well as an enhancement of the Andreev reflection in tunneling measurements and an upturn in the NMR relaxation rate above Tc. [0pt] [1] D. Aoki et al., Jour. Phys. Soc. of Japan 76, 063701 (2007).[0pt] [2] J. Sarrao et al., Nature (London) 420, 297 (2002).[0pt] [3] R. Flint, M. Dzero and P. Coleman, Nature Physics 4, 643 (2008).

  9. Optical Transient-Grating Measurements of Spin Diffusion andRelaxation in a Two-Dimensional Electron Gas

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Christopher Phillip [Univ. of California, Berkeley, CA (United States)

    2005-01-01

    Spin diffusion in n-GaAs quantum wells, as measured by our optical transient-grating technique, is strongly suppressed relative to that of charge. Over a broad range of temperatures and dopings, the suppression of Ds relative to Dc agrees quantitatively with the prediction of ''spin Coulomb dra'' theory, which takes into account the exchange of spin in electron-electron collisions. Moreover, the spin-diffusion length, Ls, is a nearly constant 1 micrometer over the same range of T and n, despite Ds's varying by nearly two orders of magnitude. This constancy supports the D'yakonov-Perel'-Kachorovskii model of spin relaxation through interrupted precessional dephasing in the spin-orbit field.

  10. A novel method for measurement of the spin correlation function for relativistic electron pairs produced in Møller scattering

    Science.gov (United States)

    Bodek, K.; Kępka, D.; Rozpędzik, D.; Zejma, J.; Kozela, A.

    2017-04-01

    A self-calibrating double-Mott polarimeter is proposed for measurement of the spin correlation function of relativistic electron pairs produced in Møller scattering. The polarization of outgoing electrons (appearing when the beam is polarized) is utilized for calibration of effective analyzing powers in the secondary Mott scattering used for spin analysis. The experiment will measure the newly introduced relative spin correlation function. This new observable can be measured with a significantly better accuracy than the regular spin correlation function in a small scale experiment. It is shown that both the spin correlation function and the relative spin correlation function are theoretically equivalent. A specific experimental data analysis scenario is proposed, which effectively eliminates the systematic effects related to the imperfect geometry and detector efficiency.

  11. Optical Transient-Grating Measurements of Spin Diffusion andRelaxation in a Two-Dimensional Electron Gas

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Christopher P.

    2005-12-15

    Spin diffusion in n-GaAs quantum wells, as measured by our optical transient-grating technique, is strongly suppressed relative to that of charge. Over a broad range of temperatures and dopings, the suppression of Ds relative to Dc agrees quantitatively with the prediction of ''spin Coulomb dra'' theory, which takes into account the exchange of spin in electron-electron collisions. Moreover, the spin-diffusion length, Ls, is a nearly constant 1 micrometer over the same range of T and n, despite Ds's varying by nearly two orders of magnitude. This constancy supports the D'yakonov-Perel'-Kachorovskii model of spin relaxation through interrupted precessional dephasing in the spin-orbit field.

  12. Theory for magnetic linear dichroism of electronic transitions between twofold-degenerate molecular spin levels

    Science.gov (United States)

    Bominaar, Emile L.; Achim, Catalina; Peterson, Jim

    1998-07-01

    Magnetic linear dichroism (MLD) spectroscopy is a relatively new technique which previously has been almost exclusively applied to atoms. These investigations have revealed that the study of MLD, in conjunction with electronic absorption and magnetic circular dichroism (MCD) spectroscopies, provides significant additional information concerning the electronic structure of atoms. More recent measurements have indicated that MLD is also observable from transition ions in inorganic compounds and metalloproteins. While the theory for atomic MLD has been worked out in considerable detail during the last two decades, an MLD theory of practical utility for the analysis of the spectra derived from the majority of paramagnetic molecules is not available. In the present contribution, the MLD of an electric-dipole-allowed transition between twofold-degenerate molecular spin levels is analyzed, assuming nonsaturating conditions. As for atomic systems, it is found that the MLD of a single molecule is dominated by the term G0. However, this term vanishes in the powder average evaluated for a randomly oriented ensemble of molecules, leading to a drastic reduction of the MLD differential absorption for systems with spin S=1/2 compared to that observed for systems with higher ground-state spin. It is found that MLD and MCD spectroscopies on solution samples have complementary spin-state specific sensitivities which suggest that the two methods can be used to selectively probe the individual metal sites in multicenter metalloprotein assemblies.

  13. Universal quantum computation with electron spins in quantum dots based on superpositions of spacetime paths and Coulomb blockade

    CERN Document Server

    Lin, C C Y; Wu, Y Z; Zhang, W M; Lin, Cyrus C.Y.; Soo, Chopin; Wu, Yin-Zhong; Zhang, Wei-Min

    2004-01-01

    Using electrostatic gates to control the electron positions, we present a new controlled-NOT gate based on quantum dots. The qubit states are chosen to be the spin states of an excess conductor electron in the quantum dot; and the main ingredients of our scheme are the superpositions of space-time paths of electrons and the effect of Coulomb blockade. All operations are performed only on individual quantum dots and are based on fundamental interactions. Without resorting to spin-spin terms or other assumed interactions, the scheme can be realized with a dedicated circuit and a necessary number of quantum dots. Gate fidelity of the quantum computation is also presented.

  14. Electrical conductivity and electron-spin resonance in oxidatively stabilized polyacrylonitrile subjected to elevated temperature

    Science.gov (United States)

    Lerner, N. R.

    1981-01-01

    Electrical conductivity and electron spin resonance measurements are presented for oxidatively stabilized polyacrylonitrile (PAN) fibers subjected to heat treatment at temperatures ranging from 700 to 950 K. Conductivity measurements made at temperatures between 77 and 523 K reveal that PAN fibers heat treated in vacuum behave as semiconductors, with a room-temperature conductivity dominated by the contributions of impurity states, with an activation energy of 88 kcal/mole. A decrease in conductivity is observed upon air which is attributed to a decrease in the electron-phonon scattering time. ESR spectra indicate that conducting pathways having metallic properties are formed at temperatures as low as 715 K, although the contribution of these pathways to the room-temperature conductivity is extremely small next to the contribution of localized spin centers.

  15. Electron spin and the origin of Bio-homochirality II. Prebiotic inorganic-organic reaction model

    CERN Document Server

    Wang, Wei

    2014-01-01

    The emergence of biomolecular homochirality is a critically important question about life phenomenon and the origins of life. In a previous paper (arXiv:1309.1229), I tentatively put forward a new hypothesis that the emergence of a single chiral form of biomolecules in living organisms is specifically determined by the electron spin state during their enzyme-catalyzed synthesis processes. However, how a homochirality world of biomolecules could have formed in the absence of enzymatic networks before the origins of life remains unanswered. Here I discussed the electron spin properties in Fe3S4, ZnS, and transition metal doped dilute magnetic ZnS, and their possible roles in the prebiotic synthesis of chiral molecules. Since the existence of these minerals in hydrothermal vent systems is matter of fact, the suggested prebiotic inorganic-organic reaction model, if can be experimentally demonstrated, may help explain where and how life originated on early Earth.

  16. Strongly anisotropic spin-orbit splitting in a two-dimensional electron gas

    DEFF Research Database (Denmark)

    Michiardi, Matteo; Bianchi, Marco; Dendzik, Maciej

    2015-01-01

    Near-surface two-dimensional electron gases on the topological insulator Bi$_2$Te$_2$Se are induced by electron doping and studied by angle-resolved photoemission spectroscopy. A pronounced spin-orbit splitting is observed for these states. The $k$-dependent splitting is strongly anisotropic...... Rashba Hamiltonian. However, a $\\mathbf{k} \\cdot \\mathbf{p}$ model that includes the possibility of band structure anisotropy as well as both isotropic and anisotropic third order Rashba splitting can explain the results. The isotropic third order contribution to the Rashba Hamiltonian is found...... to be negative, reducing the energy splitting at high $k$. The interplay of band structure, higher order Rashba effect and tuneable doping offers the opportunity to engineer not only the size of the spin-orbit splitting but also its direction....

  17. Geometric quantum gates for an electron-spin qubit in a quantum dot

    Science.gov (United States)

    Malinovsky, Vladimir; Rudin, Sergey

    2012-06-01

    A scheme to perform arbitrary unitary operations on a single electron-spin qubit in a quantum dot is proposed. The design is based on the geometrical phase acquired after a cyclic evolution by the qubit state. The scheme is utilizing ultrafast linearly-chirped pulses providing adiabatic excitation of the qubit states and the geometric phase is fully controlled by the relative phase between pulses. The analytic expression of the evolution operator for the electron spin in a quantum dot, which provides a clear geometrical interpretation of the qubit dynamics, is obtained. Using parameters of InGAN/GaN, GaN/AlN quantum dots we provide an estimate for the time scale of the qubit rotations and parameters of the external fields. Robustness of the proposed scheme against external noise is also discussed.

  18. Ultrafast control of electron spin in a quantum dot using geometric phase

    Science.gov (United States)

    Malinovsky, V. S.; Rudin, S.

    2012-12-01

    We propose a scheme to perform arbitrary unitary operations on a single electron-spin qubit in a quantum dot. The design is solely based on the geometrical phase that the qubit state acquires after a cyclic evolution in the parameter space. The scheme is utilizing ultrafast linearly-chirped pulses providing adiabatic excitation of the qubit states and the geometric phase is fully controlled by the relative phase between pulses. The analytic expression of the evolution operator for the electron spin in a quantum dot, which provides a clear geometrical interpretation of the qubit dynamics is obtained. Using parameters of InGaN/GaN, GaN/AlN quantum dots we provide an estimate for the time scale of the qubit rotations and parameters of the external fields.

  19. Microscopic Examinations of Co Valences and Spin States in Electron-Doped LaCoO3

    Science.gov (United States)

    Tomiyasu, Keisuke; Koyama, Syun-Ichi; Watahiki, Masanori; Sato, Mika; Nishihara, Kazuki; Takahashi, Yuki; Onodera, Mitsugi; Iwasa, Kazuaki; Nojima, Tsutomu; Nojiri, Hiroyuki; Okamoto, Jun; Huang, Di-Jing; Yamasaki, Yuuichi; Nakao, Hironori; Murakami, Youichi

    2016-09-01

    We studied the Co valences and spin states in electron-doped LaCo1-yTeyO3 by measuring X-ray absorption spectra and electron spin resonance. The low-temperature insulating state involves the low-spin Co3+ state (S = 0) and the high-spin Co2+ state, where the latter is described by g = 3.8 and jeff = 1/2. The results, in concurrence with the electron-hole asymmetry confirmed in the electrical resistivity, coincide with the spin-blockade phenomenon in this system. Furthermore, we discuss the g factor in terms of the strong covalent-bonding nature and consider multiple origins of this phenomenon.

  20. Quantum field theory treatment of magnetic effects on the spin and orbital angular momentum of a free electron

    Energy Technology Data Exchange (ETDEWEB)

    Kurian, P., E-mail: pkurian@gmx.com [National Human Genome Center, Howard University, College of Medicine, Washington, DC (United States); Verzegnassi, C. [Department of Chemistry and Environmental Physics, University of Udine, Udine (Italy); Association for Medicine and Complexity (AMeC), Trieste (Italy)

    2016-01-28

    We consider in a quantum field theory framework the effects of a classical magnetic field on the spin and orbital angular momentum (OAM) of a free electron. We derive formulae for the changes in the spin and OAM due to the introduction of a general classical background field. We consider then a constant magnetic field, in which case the relevant expressions of the effects become much simpler and conversions between spin and OAM become readily apparent. An estimate of the expectation values for a realistic electron state is also given. Our findings may be of interest to researchers in spintronics and the field of quantum biology, where electron spin has been implicated on macroscopic time and energy scales. - Highlights: • We present the first field theory treatment of magnetic changes in electron spin. • Changes in spin and orbital angular momentum (OAM) are correlated and calculated. • Expectation values of spin–OAM changes for a realistic electron state are computed. • Earth's magnetic field produces non-negligible changes in spin of a few percent. • Results apply to spin–OAM conversion in electron vortex beams and quantum biology.

  1. Electronic properties of mesoscopic graphene structures: Charge confinement and control of spin and charge transport

    Energy Technology Data Exchange (ETDEWEB)

    Rozhkov, A.V., E-mail: arozhkov@gmail.co [Advanced Science Institute, RIKEN, Wako-shi, Saitama, 351-0198 (Japan); Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences, 125412, Moscow (Russian Federation); Giavaras, G. [Advanced Science Institute, RIKEN, Wako-shi, Saitama, 351-0198 (Japan); Bliokh, Yury P. [Advanced Science Institute, RIKEN, Wako-shi, Saitama, 351-0198 (Japan); Department of Physics, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Freilikher, Valentin [Advanced Science Institute, RIKEN, Wako-shi, Saitama, 351-0198 (Japan); Department of Physics, Bar-Ilan University, Ramat-Gan 52900 (Israel); Nori, Franco [Advanced Science Institute, RIKEN, Wako-shi, Saitama, 351-0198 (Japan); Department of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States)

    2011-06-15

    This brief review discusses electronic properties of mesoscopic graphene-based structures. These allow controlling the confinement and transport of charge and spin; thus, they are of interest not only for fundamental research, but also for applications. The graphene-related topics covered here are: edges, nanoribbons, quantum dots, pn-junctions, pnp-structures, and quantum barriers and waveguides. This review is partly intended as a short introduction to graphene mesoscopics.

  2. Electron spin resonance absorption spectrum of trivalent gadolinium in the oxide YAIG

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, S.A. (Argonne National Lab., IL); Marshall, T.; Serway, R.A.

    1978-01-01

    The electron spin resonance absorption spectrum of trivalent gadolinium in single crystals of yttrium-aluminium garnet is re-investigated at X-band and Q-band wavelengths. Fine structure spectral parameters deduced from Q-band wavelength measurements are found to predict satisfactorily spectral observations at both wavelengths. A list of spectral parameters deduced from data taken at 77/sup 0/K is given.

  3. Electron spin resonance study of the demagnetization fields of the ferromagnetic and paramagnetic films

    Directory of Open Access Journals (Sweden)

    I.I. Gimazov, Yu.I. Talanov

    2015-12-01

    Full Text Available The results of the electron spin resonance study of the La1-xCaxMnO3 manganite and the diphenyl-picrylhydrazyl thin films for the magnetic field parallel and perpendicular to plane of the films are presented. The temperature dependence of the demagnetizing field is obtained. The parameters of the Curie-Weiss law are estimated for the paramagnetic thin film.

  4. Efficient injection of spin-polarized electrons from manganese arsenide contacts into aluminum gallium arsenide/gallium arsenide spin LEDs

    Science.gov (United States)

    Schweidenback, Lars

    In this thesis we describe two spectroscopic projects project on semiconductor heterostructures, as well as putting together and testing a micro-photoluminescence/7 tesla magnet system for the study of micron size two-dimensional crystals. Below we discuss the three parts in more detail. i) MnAs-based spin light emitting diodes. We have studied the injection of spin-polarized electrons from a ferromagnetic MnAs contact into an AlGaAs(n)/GaAs(i)/AlGaAs(p) n-i-p light emitting diode. We have recorder the emitted electroluminescence as function of magnetic field applied at right angles to the device plane in the 7-300 K temperature range. It was found that at 7 Kelvin the emitted light is circularly polarized with a polarization that is proportional to the MnAs contact magnetization with a saturation value of 26% for B > 1.25 tesla. The polarization persists up to room temperature with a saturation value of 6%. ii) Optical Aharonov-Bohm effect in InGaAs quantum wells. The excitonic photoluminescence intensity from InGaAs quantum wells as function of magnetic field exhibits two local maxima superimposed on a decreasing background. The maxima are attributed to the optical Aharonov-Bohm effect of electrons orbiting around a hole localized at the center of an Indium rich InGaAs islands detected by cross sectional scanning tunneling microscopy. Analysis of the position of the maxima yields a value of the electron orbit radius. iii) Micro-Photoluminescence. We have put together a micro-photoluminescence /7 tesla system for the study of two dimensional crystals. The samples are placed inside a continuous flow cryostat whose tail is positioned in the bore of the 7 tesla magnet. A microscope objective is used to focus the exciting laser light and collect the emitted photoluminescence. The system was tested by recording the photoluminescence spectra of WS2 and WSe 2 monolayers at T = 77 K.

  5. Spin-liquid polymorphism in a correlated electron system on the threshold of superconductivity.

    Science.gov (United States)

    Zaliznyak, Igor; Savici, Andrei T; Lumsden, Mark; Tsvelik, Alexei; Hu, Rongwei; Petrovic, Cedomir

    2015-08-18

    We report neutron scattering measurements which reveal spin-liquid polymorphism in an "11" iron chalcogenide superconductor. It occurs when a poorly metallic magnetic state of FeTe is tuned toward superconductivity by substitution of a small amount of tellurium with isoelectronic sulfur. We observe a liquid-like magnetic response, which is described by the coexistence of two disordered magnetic phases with different local structures whose relative abundance depends on temperature. One is the ferromagnetic (FM) plaquette phase observed in undoped, nonsuperconducting FeTe, which preserves the C4 symmetry of the underlying square lattice and is favored at high temperatures, whereas the other is the antiferromagnetic plaquette phase with broken C4 symmetry, which emerges with doping and is predominant at low temperatures. These findings suggest the coexistence of and competition between two distinct liquid states, and a liquid-liquid phase transformation between these states, in the electronic spin system of FeTe(1-x)(S,Se)(x). We have thus discovered the remarkable physics of competing spin-liquid polymorphs in a correlated electron system approaching superconductivity. Our results facilitate an understanding of large swaths of recent experimental data in unconventional superconductors. In particular, the phase with lower C2 local symmetry, whose emergence precedes superconductivity, naturally accounts for a propensity for forming electronic nematic states which have been observed experimentally, in cuprate and iron-based superconductors alike.

  6. Photoinduced charge carriers in conjugated polymer-fullerene composites studied with light-induced electron-spin resonance

    NARCIS (Netherlands)

    Dyakonov, V.; Zoriniants, G.; Scharber, M.C.; Brabec, C.J.; Janssen, R.A.J.; Hummelen, J.C.

    1999-01-01

    Detailed studies on photoinduced spins in conjugated polymer/fullerene composites using (cw) light-induced electron-spin-resonance (LESR) technique are reported. Two overlapping LESR lines are observed, from positive polarons on the polymer chains and negative charges on the fullerene moieties. Micr

  7. Photoinduced charge carriers in conjugated polymer–fullerene composites studied with light-induced electron-spin resonance

    NARCIS (Netherlands)

    Dyakonov, V.; Zoriniants, G.; Scharber, M.; Brabec, C.J.; Janssen, R.A.J.; Hummelen, J.C.; Sariciftci, N.S.

    1999-01-01

    Detailed studies on photoinduced spins in conjugated polymer/fullerene composites using (cw) light-induced electron-spin-resonance (LESR) technique are reported. Two overlapping LESR lines are observed, from positive polarons on the polymer chains and negative charges on the fullerene moieties. Micr

  8. Mechanism of initiation of oxidation in mayonnaise enriched with fish oil as studied by electron spin resonance spectroscopy

    DEFF Research Database (Denmark)

    Thomsen, M.K.; Jacobsen, Charlotte; Skibsted, L.H.

    2000-01-01

    Electron spin resonance spectroscopy (spin trapping technique) has been used to identify the most important single factor for initiation of lipid oxidation in mayonnaise enriched with fish oil. Low pH increases the formation of radicals during incubation under mildly accelerated conditions at 37 ...

  9. Dynamic molecular structure of DPPC-DLPC-cholesterol ternary lipid system by spin-label electron spin resonance.

    Science.gov (United States)

    Chiang, Yun-Wei; Shimoyama, Yuhei; Feigenson, Gerald W; Freed, Jack H

    2004-10-01

    The hydrated ternary lamellar lipid mixture of dipalmitoyl-PC/dilauroyl-PC/cholesterol (DPPC/DLPC/Chol) has been studied by electron spin resonance (ESR) to reveal the dynamic structure on a molecular level of the different phases that exist and coexist over virtually the full range of composition. The spectra for more than 100 different compositions at room temperature were analyzed by nonlinear least-squares fitting to provide the rotational diffusion rates and order parameters of the end-chain labeled phospholipid 16-PC. The ESR spectra exhibit substantial variation as a function of composition, even though the respective phases generally differ rather modestly from each other. The Lalpha and Lbeta phases are clearly distinguished, with the former exhibiting substantially lower ordering and greater motional rates, whereas the well-defined Lo phase exhibits the greatest ordering and relatively fast motional rates. Typically, smaller variations occur within a given phase. The ESR spectral analysis also yields phase boundaries and coexistence regions which are found to be consistent with previous results from fluorescence methods, although new features are found. Phase coexistence regions were in some cases confirmed by observing the existence of isosbestic points in the absorption mode ESR spectra from the phases. The dynamic structural properties of the DPPC-rich Lbeta and DLPC-rich Lalpha phases, within their two-phase coexistence region do not change with composition along a tie-line, but the ratio of the two phases follows the lever rule in accordance with thermodynamic principles. The analysis shows that 16-PC spin-label partitions nearly equally between the Lalpha and Lbeta phases, making it a useful probe for studying such coexisting phases. Extensive study of two-phase coexistence regions requires the determination of tie-lines, which were approximated in this study. However, a method is suggested to accurately determine the tie-lines by ESR.

  10. Spin-orbit and electron correlation effects on the structure of EF3 (E = I, At, and element 117).

    Science.gov (United States)

    Kim, Hyoseok; Choi, Yoon Jeong; Lee, Yoon Sup

    2008-12-18

    Structures and vibrational frequencies of group 17 fluorides EF3 (E = I, At, and element 117) are calculated at the density functional theory (DFT) level of theory using relativistic effective core potentials (RECPs) with and without spin-orbit terms in order to investigate the effects of spin-orbit interactions and electron correlations on the structures and vibrational frequencies of EF3. Various tests imply that spin-orbit and electron correlation effects estimated presently from Hartree-Fock (HF) and DFT calculations with RECPs with and without spin-orbit terms are quite reasonable. Spin-orbit and electron correlation effects generally increase bond lengths and/or angles in both C2v and D3h structures. For IF3, the C2v structure is a global minimum, and the D3h structure is a second-order saddle point in both HF and DFT calculations with and without spin-orbit interactions. Spin-orbit effects for IF3 are negligible in comparison to electron correlation effects. The D3h global minimum is the only minimum structure for (117)F3 in all RECP calculations, and the C2v structure is neither a local minimum nor a saddle point. In the case of AtF3, the C2v structure is found to be a local minimum in all RECP calculations without spin-orbit terms, and the D3h structure becomes a local minimum at the DFT level of theory with and without spin-orbit interactions. In the HF calculation with spin-orbit terms, the D3h structure of AtF3 is a second-order saddle point. AtF3 is a borderline case between the valence-shell-electron-pair-repulsion (VSEPR) structure of IF3 and the non-VSEPR structure of (117)F3. Relativistic effects, including scalar relativistic and spin-orbit effects, and electron correlation effects together or separately stabilize the D3h structures more than the C2v structures. As a result, one may suggest that the VSEPR predictions agree very well with the structures optimized by the nonrelativistic HF level of theory even for heavy-atom molecules but not so

  11. Spin-droplet state of an interacting 2D electron system.

    Science.gov (United States)

    Teneh, N; Kuntsevich, A Yu; Pudalov, V M; Reznikov, M

    2012-11-30

    We report thermodynamic magnetization measurements of two-dimensional electrons in several high-mobility Si metal-oxide-semiconductor field-effect transistors. We provide evidence for an easily polarizable electron state in a wide density range from insulating to deep into the metallic phase. The temperature and magnetic field dependence of the magnetization is consistent with the formation of large-spin droplets in the insulating phase. These droplets melt in the metallic phase with increasing density and temperature, though they survive up to large densities.

  12. Spin-dependent electron scattering at graphene edges on Ni(111).

    Science.gov (United States)

    Garcia-Lekue, A; Balashov, T; Olle, M; Ceballos, G; Arnau, A; Gambardella, P; Sanchez-Portal, D; Mugarza, A

    2014-02-14

    We investigate the scattering of surface electrons by the edges of graphene islands grown on Ni(111). By combining local tunneling spectroscopy and ab initio electronic structure calculations we find that the hybridization between graphene and Ni states results in strongly reflecting graphene edges. Quantum interference patterns formed around the islands reveal a spin-dependent scattering of the Shockley bands of Ni, which we attribute to their distinct coupling to bulk states. Moreover, we find a strong dependence of the scattering amplitude on the atomic structure of the edges, depending on the orbital character and energy of the surface states.

  13. Quantum teleportation and entanglement swapping of electron spins in superconducting hybrid structures

    Energy Technology Data Exchange (ETDEWEB)

    Bubanja, Vladimir, E-mail: vladimir.bubanja@callaghaninnovation.govt.nz

    2015-06-15

    We present schemes for quantum teleportation and entanglement swapping of electronic spin states in hybrid superconductor–normal-metal systems. The proposed schemes employ subgap transport whereby the lowest order processes involve Cooper pair-electron and double Cooper-pair cotunneling in quantum teleportation and entanglement swapping protocols, respectively. The competition between elastic cotunneling and Cooper-pair splitting results in the success probability of 25% in both cases. Described implementations of these protocols are within reach of present-day experimental techniques.

  14. Coexistence of perfect spin filtering for entangled electron pairs and high magnetic storage efficiency in one setup.

    Science.gov (United States)

    Ji, T T; Bu, N; Chen, F J; Tao, Y C; Wang, J

    2016-04-14

    For Entangled electron pairs superconducting spintronics, there exist two drawbacks in existing proposals of generating entangled electron pairs. One is that the two kinds of different spin entangled electron pairs mix with each other. And the other is a low efficiency of entanglement production. Herein, we report the spin entanglement state of the ferromagnetic insulator (FI)/s-wave superconductor/FI structure on a narrow quantum spin Hall insulator strip. It is shown that not only the high production of entangled electron pairs in wider energy range, but also the perfect spin filtering of entangled electron pairs in the context of no highly spin-polarized electrons, can be obtained. Moreover, the currents for the left and right leads in the antiferromagnetic alignment both can be zero, indicating 100% tunnelling magnetoresistance with highly magnetic storage efficiency. Therefore, the spin filtering for entangled electron pairs and magnetic storage with high efficiencies coexist in one setup. The results may be experimentally demonstrated by measuring the tunnelling conductance and the noise power.

  15. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments

    Directory of Open Access Journals (Sweden)

    Maxime Deutsch

    2014-05-01

    Full Text Available Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  16. Spin-dependent electron-phonon interaction in SmFeAsO by low-temperature Raman spectroscopy.

    Science.gov (United States)

    Zhang, L; Guan, P F; Feng, D L; Chen, X H; Xie, S S; Chen, M W

    2010-11-03

    The interplay between spin dynamics and lattice vibration has been suggested as an important part of the puzzle of high-temperature superconductivity. Here, we report the strong interaction between spin fluctuation and phonon in SmFeAsO, a parent compound of the iron arsenide family of superconductors, revealed by low-temperature Raman spectroscopy. Anomalous zone-boundary-phonon Raman scattering from spin superstructure was observed at temperatures below the antiferromagnetic ordering point, which offers compelling evidence on spin-dependent electron-phonon coupling in pnictides.

  17. Spin-dependent asymmetry functions in the elastic and inelastic electron-cesium scattering at intermediate energies

    CERN Document Server

    Roth, B

    2001-01-01

    In this thesis the measurements of the relative differential cross section, the exchange asymmetry, the spin-orbit asymmetry, and the interference asymmetry for the electron scattering on cesium atoms from 4 to 18 eV is described. (HSI)

  18. Electron spin relaxation of copper(II) complexes in glassy solution between 10 and 120 K.

    Science.gov (United States)

    Fielding, Alistair J; Fox, Stephen; Millhauser, Glenn L; Chattopadhyay, Madhuri; Kroneck, Peter M H; Fritz, Günter; Eaton, Gareth R; Eaton, Sandra S

    2006-03-01

    The temperature dependence, between 10 and 120 K, of electron spin-lattice relaxation at X-band was analyzed for a series of eight pyrrolate-imine complexes and for ten other copper(II) complexes with varying ligands and geometry including copper-containing prion octarepeat domain and S100 type proteins. The geometry of the CuN4 coordination sphere for pyrrolate-imine complexes with R=H, methyl, n-butyl, diphenylmethyl, benzyl, 2-adamantyl, 1-adamantyl, and tert-butyl has been shown to range from planar to pseudo-tetrahedral. The fit to the recovery curves was better for a distribution of values of T1 than for a single time constant. Distributions of relaxation times may be characteristic of Cu(II) in glassy solution. Long-pulse saturation recovery and inversion recovery measurements were performed. The temperature dependence of spin-lattice relaxation rates was analyzed in terms of contributions from the direct process, the Raman process, and local modes. It was necessary to include more than one process to fit the experimental data. There was a small contribution from the direct process at low temperature. The Raman process was the dominant contribution to relaxation between about 20 and 60 K. Debye temperatures were between 80 and 120 K. For samples with similar Debye temperatures the coefficient of the Raman process tended to increase as gz increased, as expected if modulation of spin-orbit coupling is a major factor in relaxation rates. Above about 60 K local modes with energies in the range of 260-360 K (180-250 cm-1) dominated the relaxation. For molecules with similar geometry, relaxation rates were faster for more flexible molecules than for more rigid ones. Relaxation rates for the copper protein samples were similar to rates for small molecules with comparable coordination spheres. At each temperature studied the range of relaxation rates was less than an order of magnitude. The spread was smaller between 20 and 60 K where the Raman process dominates

  19. Simulation for a New Polarized Electron Injector (SPIN) for the S-DALINAC

    CERN Document Server

    Steiner, Bastian; Gräf, Hans Dieter; Richter, Achim; Roth, Markus; Weiland, Thomas

    2005-01-01

    The Superconducting DArmstädter LINear ACcelerator (S-DALINAC) is a 130 MeV recirculating electron accelerator serving several nuclear and radiation physics experiments. For future tasks, the 250 keV thermal electron source should be completed by a 100 keV polarized electron source. Therefore a new low energy injection concept for the S-DALINAC has to be designed. The main components of the injector are a polarized electron source, an alpha magnet, a Wien filter spin-rotator and a Mott polarimeter. In this paper we report over the first simulation and design results. For our simulations we used the TS2 and TS3 modules of the CST MAFIA (TM) programme which are PIC codes for two and three dimensions and the CST PARTICLE STUDIO (TM).

  20. Use of paramagnetic chelated metal derivatives of polysaccharides and spin-labeled polysaccharides as contrast agents in magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Bligh, S.W.; Harding, C.T.; Sadler, P.J.; Bulman, R.A.; Bydder, G.M.; Pennock, J.M.; Kelly, J.D.; Latham, I.A.; Marriott, J.A. (Department of Chemistry, Birkbeck College, London (England))

    1991-02-01

    Soluble and insoluble polysaccharides were derivatized with diethylenetriaminepentaacetic acid (DTPA) and/or spin-labeled with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). Polysaccharides derivatized with DTPA were prepared via cyanogen bromide activation, coupling to a diamine linker, and to DTPA anhydride. Spin-labeled polysaccharides were also prepared via cyanogen bromide activation. The extent of derivatization for dextran (18 kDa) was about 120 glucose units per DTPA, and for cellulose and starch about 15-30 units per DTPA. For spin-labeled polysaccharides, the average loading ranged from 1 nitroxide per 16 glucose units for starch to 181 for dextran (82 kDa). These derivatized paramagnetic polysaccharides were shown to be more effective relaxants than the small paramagnetic molecules alone. Both soluble and insoluble polysaccharide-linker-DTPA-Gd(3) complexes were effectively cleared from the body (rats) after oral administration. After intravenous administration, the biodistribution of dextran-linker-DTPA-Gd(3) complexes differed significantly from that of GdDTPA. Reduction of the nitroxide by ascorbic acid was retarded in the polysaccharide derivatives, particularly in starch derivatized with both nitroxide and linker-DTPA-Cu(2). These agents showed contrast enhancement in the gastrointestinal tract of rabbits.

  1. Electronic Publishing and Collection Development, a Subscription Agent's View.

    Science.gov (United States)

    Wallas, Philip

    Trends in publishing, advances in technology and pressures on library budgets have combined to put libraries and publishers at odds with each other. Research libraries expect broad, easy access to electronic information, greater convenience and faster delivery but at reduced cost. Publishers are exploring new channels for distributing their…

  2. Long spin lifetime and large barrier polarisation in single electron transport through a CoFe nanoparticle

    Science.gov (United States)

    Temple, R. C.; McLaren, M.; Brydson, R. M. D.; Hickey, B. J.; Marrows, C. H.

    2016-01-01

    We have investigated single electron spin transport in individual single crystal bcc Co30Fe70 nanoparticles using scanning tunnelling microscopy with a standard tungsten tip. Particles were deposited using a gas-aggregation nanoparticle source and individually addressed as asymmetric double tunnel junctions with both a vacuum and a MgO tunnel barrier. Spectroscopy measurements on the particles show a Coulomb staircase that is correlated with the measured particle size. Field emission tunnelling effects are incorporated into standard single electron theory to model the data. This formalism allows spin-dependent parameters to be determined even though the tip is not spin-polarised. The barrier spin polarisation is very high, in excess of 84%. By variation of the resistance, several orders of magnitude of the system timescale are probed, enabling us to determine the spin relaxation time on the island. It is found to be close to 10 μs, a value much longer than previously reported. PMID:27329575

  3. Random walk approach to spin dynamics in a two-dimensional electron gas with spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Luyi; Orenstein, J.; Lee, Dung-Hai

    2010-09-27

    We introduce and solve a semiclassical random walk (RW) model that describes the dynamics of spin polarization waves in zinc-blende semiconductor quantum wells. We derive the dispersion relations for these waves, including the Rashba, linear and cubic Dresselhaus spin-orbit interactions, as well as the effects of an electric field applied parallel to the spin polarization wave vector. In agreement with calculations based on quantum kinetic theory [P. Kleinert and V. V. Bryksin, Phys. Rev. B 76, 205326 (2007)], the RW approach predicts that spin waves acquire a phase velocity in the presence of the field that crosses zero at a nonzero wave vector, q{sub 0}. In addition, we show that the spin-wave decay rate is independent of field at q{sub 0} but increases as (q-q{sub 0}){sup 2} for q {ne} q{sub 0}. These predictions can be tested experimentally by suitable transient spin grating experiments.

  4. Magnetohydrodynamic waves with relativistic electrons and positrons in degenerate spin-1/2 astrophysical plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Maroof, R. [Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan); Department of Physics, University of Peshawar, Peshawar 25000 (Pakistan); National Center for Physics (NCP) at QAU Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Ali, S. [National Center for Physics (NCP) at QAU Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan); National Center for Physics (NCP) at QAU Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Qamar, A. [Department of Physics, University of Peshawar, Peshawar 25000 (Pakistan)

    2015-11-15

    Linear properties of high and low frequency waves are studied in an electron-positron-ion (e-p-i) dense plasma with spin and relativity effects. In a low frequency regime, the magnetohydrodynamic (MHD) waves, namely, the magnetoacoustic and Alfven waves are presented in a magnetized plasma, in which the inertial ions are taken as spinless and non-degenerate, whereas the electrons and positrons are treated quantum mechanically due to their smaller mass. Quantum corrections associated with the spin magnetization and density correlations for electrons and positrons are re-considered and a generalized dispersion relation for the low frequency MHD waves is derived to account for relativistic degeneracy effects. On the basis of angles of propagation, the dispersion relations of different modes are discussed analytically in a degenerate relativistic plasma. Numerical results reveal that electron and positron relativistic degeneracy effects significantly modify the dispersive properties of MHD waves. Our present analysis should be useful for understanding the collective interactions in dense astrophysical compact objects, like, the white dwarfs and in atmosphere of neutron stars.

  5. Field-assisted electron transport through a symmetric double-well structure with spin-orbit coupling and the Fano-resonance induced spin filtering

    Institute of Scientific and Technical Information of China (English)

    Zhang Cun-Xi; Nie Yi-Hang; Liang Jiu-Qing

    2008-01-01

    We have investigated theoretically the field-driven electron-transport through a double-quantum-well semiconductor-heterostructure with spin-orbit coupling. The numerical results demonstrate that the transmission spectra are divided into two sets due to the bound-state level-splitting and each set contains two asymmetric resonance peaks which may be selectively suppressed by changing the difference in phase between two driving fields. When the phase difference changes from O to π, the dip of asymmetric resonance shifts from one side of resonance peak to the other side and the asymmetric Fano resonance degenerates into the symmetric Breit-Wigner resonance at a critical value of phase difference. Within a given range of incident electron energy, the spin polarization of transmission current is completely governed by the phase difference which may be used to realize the tunable spin filtering.

  6. Anisotropy of superconducting MgB2 as seen in electron spin resonance and magnetization data.

    Science.gov (United States)

    Simon, F; Jánossy, A; Fehér, T; Murányi, F; Garaj, S; Forró, L; Petrovic, C; Bud'ko, S L; Lapertot, G; Kogan, V G; Canfield, P C

    2001-07-23

    We observed the conduction electron spin resonance (CESR) in fine powders of MgB2 both in the superconducting and normal states. The Pauli susceptibility is chi(s) = 2.0 x 10(-5) emu/mole in the temperature range of 450 to 600 K. The spin relaxation rate has an anomalous temperature dependence. The CESR measured below T(c) at several frequencies suggests that MgB2 is a strongly anisotropic superconductor with the upper critical field, H(c2), ranging between 2 and 16 T. The high-field reversible magnetization data of a randomly oriented powder sample are well described assuming that MgB2 is an anisotropic superconductor with H(ab)(c2)/H(c)(c2) approximately 6-9.

  7. Scaled Opposite Spin Second Order Moller-Plesset Correlation Energy: An Economical Electronic Structure Method

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Yousung; Lochan, Rohini C.; Dutoi, Anthony D.; Head-Gordon, Martin

    2004-08-02

    A simplified approach to treating the electron correlation energy is suggested in which only the alpha-beta component of the second order Moller-Plesset energy is evaluated, and then scaled by an empirical factor which is suggested to be 1.3. This scaled opposite spin second order energy (SOS-MP2) yields results for relative energies and derivative properties that are statistically improved over the conventional MP2 method. Furthermore, the SOS-MP2 energy can be evaluated without the 5th order computational steps associated with MP2 theory, even without exploiting any spatial locality. A 4th order algorithm is given for evaluating the opposite spin MP2 energy using auxiliary basis expansions, and a Laplace approach, and timing comparisons are given.

  8. Unveiling the Proton Spin Decomposition at a Future Electron-Ion Collider

    CERN Document Server

    Aschenauer, Elke C; Stratmann, M

    2015-01-01

    We present a detailed assessment of how well a future Electron-Ion Collider could constrain helicity parton distributions in the nucleon and, therefore, unveil the role of the intrinsic spin of quarks and gluons in the proton's spin budget. Any remaining deficit in this decomposition will provide the best indirect constraint on the contribution due to the total orbital angular momenta of quarks and gluons. Specifically, all our studies are performed in the context of global QCD analyses based on realistic pseudo-data and in the light of the most recent data obtained from polarized proton-proton collisions at BNL-RHIC that have provided evidence for a significant gluon polarization in the accessible, albeit limited range of momentum fractions. We also present projections on what can be achieved on the gluon's helicity distribution by the end of BNL-RHIC operations. All estimates of current and projected uncertainties are performed with the robust Lagrange multiplier technique.

  9. Entanglement dynamics of electron spins in quantum dots under a nonuniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Feng-Xue; Qi, Yi-Hong; Niu, Yue-Ping; Gong, Shang-Qing [East China University of Science and Technology, Shanghai (China); Qian, Jun [Chinese Academy of Sciences, Shanghai (China); Yu, Ting [Stevens Institute of Technology, Hoboken, NJ (United States)

    2012-04-15

    We investigate entanglement of two coupled electron spins in quantum dots (QDs) in the presence of an inhomogeneous magnetic field. The important effects of the inhomogeneous field are discussed for the dynamics of entanglement. Due to the system's symmetry, the inhomogeneity of the field is shown not to affect the evolution of entanglement for Φ-type Bell state while it plays a key role for Ψ-type Bell state. For the maximal entangled Bell states, the field is positive for the entanglement dynamics. The mean field can increase the entanglement revival for Φ-type Bell state while an inhomogeneous field can promote the entanglement revival for Ψ-type Bell state. For the unentangled initial states, the field is destructive for the entanglement generation induced by the coupling of the two spins.

  10. Heuristic model of chemically induced electron spin polarization in two dimensions

    Science.gov (United States)

    Adrian, Frank J.

    2010-11-01

    A heuristic model of chemically induced electron spin polarization (CIDEP) that breaks the polarization mechanism into its component steps, with each step governed by an appropriate solution of the diffusion equation, is extended from a three to a two-dimensional system. The required solution of the 2D diffusion equation is provided by a relatively simple analytic approximation to the usual infinite series solution. The model yields the polarization and its time development for weak to strong singlet-triplet mixing in the radical pairs, whereas previous models are limited to very weak or very strong mixing. Its results agree with a variational solution of an integral equation of Monchick and are encouraging for observation of CIDEP in dimensionally restricted systems. The method also may be applicable to other diffusion-controlled, spin-dependent chemistry in spatially restricted environments.

  11. On the structure of the energy-momentum and the spin currents in Dirac's electron theory

    CERN Document Server

    Hehl, F W; Mielke, E W; Obukhov, Yu N; Obukhov, Yu.N.

    1997-01-01

    We consider a classical Dirac field in flat Minkowski spacetime. We perform a Gordon decomposition of its canonical energy-momentum and spin currents, respectively. Thereby we find for each of these currents a convective and a polarization piece. The polarization pieces can be expressed as exterior covariant derivatives of the two-forms $\\check M_\\alpha$ and $M_{\\alpha\\beta}=-M_{\\beta\\alpha}$, respectively. In analogy to the magnetic moment in electrodynamics, we identify these two-forms as gravitational moments connected with the translation group and the Lorentz group, respectively. We point out the relation between the Gordon decomposition of the energy-momentum current and its Belinfante-Rosenfeld symmetrization. In the non-relativistic limit, the translational gravitational moment of the Dirac field is found to be proportional to the spin covector of the electron.

  12. Measurement of Integrated Stokes Parameters for He 3 3p State Excited by Spin-Polarized Electrons

    Institute of Scientific and Technical Information of China (English)

    DING Hai-Bing; PANG Wen-Ning; LIU Yi-Bao; SHANG Ren-Cheng

    2005-01-01

    @@ Integrated Stokes parameters Pi (i = 1, 2, 3) for the He 3 3p → 2 3S1 (388.9nm) transition after excitation from the ground state to the 3 3 P state by a transversely spin-polarized electron beam are measured in near threshold energy region. The experimental results are presented. The linear-polarization P2 are consistent with zero over the incident energy range, providing evidence for the LS coupling mechanism of the 3 3P state. The measured circular polarization P3 are non-zero, indicating strong electron-electron exchange effects in the spin-polarized electron-atom collision process.

  13. Spin contamination-free N-electron wave functions in the excitation-based configuration interaction treatment.

    Science.gov (United States)

    Alcoba, Diego R; Torre, Alicia; Lain, Luis; Massaccesi, Gustavo E; Oña, Ofelia B; Capuzzi, Pablo

    2016-07-07

    This work deals with the spin contamination in N-electron wave functions provided by the excitation-based configuration interaction methods. We propose a procedure to ensure a suitable selection of excited N-electron Slater determinants with respect to a given reference determinant, required in these schemes. The procedure guarantees the construction of N-electron wave functions which are eigenfunctions of the spin-squared operator Sˆ(2), avoiding any spin contamination. Our treatment is based on the evaluation of the excitation level of the determinants by means of the expectation value of an excitation operator formulated in terms of spin-free replacement operators. We report numerical determinations of energies and 〈Sˆ(2)〉 expectation values, arising from our proposal as well as from traditional configuration interaction methods, in selected open-shell systems, in order to compare the behavior of these procedures and their computational costs.

  14. Anisotropy of electron and hole g tensors of quantum dots: An intuitive picture based on spin-correlated orbital currents

    Science.gov (United States)

    van Bree, J.; Silov, A. Yu.; van Maasakkers, M. L.; Pryor, C. E.; Flatté, M. E.; Koenraad, P. M.

    2016-01-01

    Using single spins in semiconductor quantum dots as qubits requires full control over the spin state. As the g tensor provides the coupling in a Hamiltonian between a spin and an external magnetic field, a deeper understanding of the g tensor underlies magnetic-field control of the spin. The g tensor is affected by the presence of spin-correlated orbital currents, of which the spatial structure has been recently clarified. Here we extend that framework to investigate the influence of the shape of quantum dots on the anisotropy of the electron g tensor. We find that the spin-correlated orbital currents form a simple current loop perpendicular to the magnetic moment's orientation. The current loop is therefore directly sensitive to the shape of the nanostructure: for cylindrical quantum dots, the electron g -tensor anisotropy is mainly governed by the aspect ratio of the dots. Through a systematic experimental study of the size dependence of the separate electron and hole g tensors of InAs/InP quantum dots, we have validated this picture. Moreover, we find that through size engineering it is possible to independently change the sign of the in-plane and growth direction electron g factors. The hole g tensor is found to be strongly anisotropic and very sensitive to the radius and elongation. The comparable importance of itinerant and localized currents to the hole g tensor complicates the analysis relative to the electron g tensor.

  15. Spin-Resolved Electronic Structure of Ultrathin Epitaxial Fe Films on Vicinal and Singular GaAs(100) Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Morton, S A; Waddill, G D; Spangenberg, M; Seddon, E A; Neal, J; Shen, T; Tobin, J G

    2003-03-10

    Recently there has been considerable interest in the study of spin injection at ferromagnetic semiconductor heterojunctions and ferromagnetic metal--semiconductor contacts. Studies of ntype semiconductors have demonstrated spin-coherent transport over large distances5 and the persistence of spin coherence over a sizeable time scale. Clearly such investigations have been stimulated by the potential of the development of ''spintronics'', electronic devices utilizing the information of the electron spin states. To understand and improve the magnetic properties of ultrathin Fe films on GaAs has been the aim of many research groups over recent years. The interest in this system has both technological and fundamental scientific motivations. Technologically, Fe on GaAs may serve to realize spin electronic devices. From a fundamental science point of view, Fe on GaAs serves as a prototype for studies of the interplay between the crystalline structure and morphology of an ultrathin film, its electronic structure and the long range magnetic order it exhibits. Furthermore, it is well known that an oxidized Cs layer on GaAs substantially alters the work-function of the GaAs surface, which plays a very important role in the application of GaAs as a spin polarized electron source.

  16. Large Logarithms in the Beam Normal Spin Asymmetry of Elastic Electron--Proton Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Andrei Afanasev; Mykola Merenkov

    2004-06-01

    We study a parity-conserving single-spin beam asymmetry of elastic electron-proton scattering induced by an absorptive part of the two-photon exchange amplitude. It is demonstrated that excitation of inelastic hadronic intermediate states by the consecutive exchange of two photons leads to logarithmic and double-logarithmic enhancement due to contributions of hard collinear quasi-real photons. The asymmetry at small electron scattering angles is expressed in terms of the total photoproduction cross section on the proton, and is predicted to reach the magnitude of 20-30 parts per million. At these conditions and fixed 4-momentum transfers, the asymmetry is rising logarithmically with increasing electron beam energy, following the high-energy diffractive behavior of total photoproduction cross section on the proton.

  17. Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains

    Science.gov (United States)

    Tanveer, M.; Ruiz-Díaz, P.; Pastor, G. M.

    2016-09-01

    The electronic and magnetic properties of one-dimensional (1D) 3 d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation Δ E (q ⃗) as a function of the spin-density-wave vector q ⃗. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for Δ E (q ⃗) , the local magnetic moments μ⃗i at atom i , the magnetization-vector density m ⃗(r ⃗) , and the local electronic density of states ρi σ(ɛ ) . The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions Ji j between the local magnetic moments μ⃗i and μ⃗j are derived by fitting the ab initio Δ E (q ⃗) to a classical 1D Heisenberg model. The dominant competing interactions Ji j at the origin of the NC magnetic order are identified. The interplay between the various Ji j is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.

  18. Electron spin resonance of Er{sup 3+} in YBiPt

    Energy Technology Data Exchange (ETDEWEB)

    Martins, G.B. [Universidade Estadual de Campinas (Brazil). Inst. de Fisica; Rao, D. [Universidade Estadual de Campinas (Brazil). Inst. de Fisica; Barberis, G.E. [Universidade Estadual de Campinas (Brazil). Inst. de Fisica; Rettori, C. [Universidade Estadual de Campinas (Brazil). Inst. de Fisica; Duro, R.J. [La Coruna Univ., Ferrol (Spain). Dept. de Ingenieria Industrial; Sarrao, J. [Los Alamos National Lab., NM (United States); Fisk, Z. [Los Alamos National Lab., NM (United States)]|[Florida State Univ., Tallahassee, FL (United States). Nat. High Magnetic Field Lab.; Oseroff, S. [California State Univ., San Diego (United States). Dept. of Physics; Thompson, J.D. [Los Alamos National Lab., NM (United States)]|[Florida State Univ., Tallahassee, FL (United States). Nat. High Magnetic Field Lab.

    1996-07-01

    Electron spin resonance (ESR) experiments at 4.15 K of Er{sup 3+} in YBiPt show that Er{sup 3+} is in a site of cubic local symmetry, with a {Gamma}{sup (3)}{sub 8} ground state and an overall crystal field splitting of {proportional_to}85(10) K. We inferred from the spectra the existence of lattice distortions at the rare-earth (RE) site. These results may help in understanding the heavy-fermion system YbBiPt, which has the same structure as YBiPt. (orig.).

  19. Constraints on exotic spin-dependent interactions between electrons from helium fine-structure spectroscopy

    CERN Document Server

    Ficek, Filip; Kozlov, Mikhail; Leefer, Nathan; Pustelny, Szymon; Budker, Dmitry

    2016-01-01

    Agreement between theoretical calculations of atomic structure and spectroscopic measurements is used to constrain possible contribution of exotic spin-dependent interactions between electrons to the energy differences between states in helium-4. In particular, constraints on dipole-dipole interactions associated with the exchange of pseudoscalar bosons (such as axions or axion-like particles, ALPs) with masses $10^{-2}~{\\rm eV} \\lesssim m \\lesssim 10^{4}~{\\rm eV}$ are improved by a factor of $\\sim 100$. The first atomic-scale constraints on several exotic velocity-dependent dipole-dipole interactions are established as well.

  20. Optical control of electron spin qubit in InAs self-assembled quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Emary, Clive [TU Berlin, Sekr. PN 7-1, Institut fuer Theoretische Physik, Hardenbergstr. 36, D-10623 Berlin (Germany); Sham, Lu Jeu [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States)

    2008-07-01

    The spin of an electron trapped in a self-assembled quantum dot is viewed as a promising quantum bit. We present here a theory of the control of such qubits using short laser pulses to excite virtual trion states within the dots. We describe mechanisms for qubit initialisation and for performing universal one and two qubit operations. We show that, for InAs dots, initialisation can be achieved on the nanosecond time-scale, and that coherent operations can performed with laser pulses with durations of tens of picoseconds. These results are of direct relevance to current experiments.

  1. Solid-state pulsed microwave bridge for electron spin echo spectrometers of 8-mm wavelength range

    Directory of Open Access Journals (Sweden)

    Kalabukhova E. N.

    2012-12-01

    Full Text Available The article presents a construction of a coherent pulsed microwave bridge with an output power up to 10 Wt with a time resolution of 10–8 seconds at a pulse repetition rate of 1 kHz designed for electron spin echo spectrometers. The bridge is built on a homodyne scheme based on IMPATT diodes, which are used for modulation and amplification of microwave power coming from the reference Gunn diode oscillator. The advantages of the bridge are optimal power and minimum pulse width, simple operation, low cost.

  2. Spin-Polarized Electron Injection in Co/Cu/Fe Sandwich Structure

    Institute of Scientific and Technical Information of China (English)

    WANG Shou-Guo; CHEN Yan-Xue; WANG Zhi-He; CHEN Qiang; XIE Shi-Jie; MEI Liang-Mo

    2000-01-01

    A material asymmetry Co/Cu/Fe junction structure has been prepared for studying the spin-polarized electron injection at 77K. The sample performance was demonstrated to be analogous to that of a bipolar transistor. The maximal value of the output pulse voltage between Cu and Fe layers could reach the order of severalμV when the bias current between Co and Cu layers was 10μA. The interface roughness, photograph of material, magnetic loop and injection characteristic curves have been measured. Some important points on this topic have been discussed.

  3. Constraints on exotic spin-dependent interactions between electrons from helium fine-structure spectroscopy

    Science.gov (United States)

    Ficek, Filip; Kimball, Derek F. Jackson; Kozlov, Mikhail G.; Leefer, Nathan; Pustelny, Szymon; Budker, Dmitry

    2017-03-01

    Agreement between theoretical calculations of atomic structure and spectroscopic measurements is used to constrain possible contribution of exotic spin-dependent interactions between electrons to the energy differences between states in helium-4. In particular, constraints on dipole-dipole interactions associated with the exchange of pseudoscalar bosons (such as axions or axion-like particles) with masses 10-2≲m ≲104eV are improved by a factor of ˜100 . The first atomic-scale constraints on several exotic velocity-dependent dipole-dipole interactions are established as well.

  4. Electron-mediated nuclear-spin interactions between distant nitrogen-vacancy centers.

    Science.gov (United States)

    Bermudez, A; Jelezko, F; Plenio, M B; Retzker, A

    2011-10-07

    We propose a scheme enabling controlled quantum coherent interactions between separated nitrogen-vacancy centers in diamond in the presence of strong magnetic fluctuations. The proposed scheme couples nuclear qubits employing the magnetic dipole-dipole interaction between the electron spins and, crucially, benefits from the suppression of the effect of environmental magnetic field fluctuations thanks to a strong microwave driving. This scheme provides a basic building block for a full-scale quantum-information processor or quantum simulator based on solid-state technology.

  5. Electron-Mediated Nuclear-Spin Interactions Between Distant NV Centers

    CERN Document Server

    Bermudez, A; Plenio, M B; Retzker, A

    2011-01-01

    We propose a scheme enabling controlled quantum coherent interactions between separated nitrogen-vacancy centers in diamond in the presence of strong magnetic fluctuations. The proposed scheme couples nuclear qubits employing the magnetic dipole-dipole interaction between the electron spins and, crucially, benefits from the suppression of the effect of environmental magnetic field fluctuations thanks to a strong microwave driving. This scheme provides a basic building block for a full-scale quantum information processor or quantum simulator based on solid-state technology.

  6. Landau level spectroscopy of Dirac electrons in a polar semiconductor with giant Rashba spin splitting.

    Science.gov (United States)

    Bordács, Sándor; Checkelsky, Joseph G; Murakawa, Hiroshi; Hwang, Harold Y; Tokura, Yoshinori

    2013-10-18

    Optical excitations of BiTeI with large Rashba spin splitting have been studied in an external magnetic field (B) applied parallel to the polar axis. A sequence of transitions between the Landau levels (LLs), whose energies are in proportion to √B were observed, being characteristic of massless Dirac electrons. The large separation energy between the LLs makes it possible to detect the strongest cyclotron resonance even at room temperature in moderate fields. Unlike in 2D Dirac systems, the magnetic field induced rearrangement of the conductivity spectrum is directly observed.

  7. SPIN Effects, QCD, and Jefferson Laboratory with 12 GeV electrons

    Energy Technology Data Exchange (ETDEWEB)

    Prokudin, Alexey [JLAB

    2013-11-01

    QCD and Spin physics are playing important role in our understanding of hadron structure. I will give a short overview of origin of hadron structure in QCD and highlight modern understanding of the subject. Jefferson Laboratory is undergoing an upgrade that will increase the energy of electron beam up to 12 GeV. JLab is one of the leading facilities in nuclear physics studies and once operational in 2015 JLab 12 will be crucial for future of nuclear physics. I will briefly discuss future studies in four experimental halls of Jefferson Lab.

  8. Exchange Perturbation Theory for Multiatomic Electron System and Its Application to Spin Arrangement in Manganite Chains

    Directory of Open Access Journals (Sweden)

    E. V. Orlenko

    2011-01-01

    Full Text Available A new methodology of binding energy calculation with respect to different spin arrangements for a multiatomic electron system is developed from the first principle in the frame of the exchange perturbation theory (EPT. We developed EPT formalism in the general form of the Rayleigh-Srchödinger expansion with a symmetric Hamiltonian, taking into account an exchange and nonadditive contributions of a superexchange interaction. The expressions of all corrections to the energy and wave function were reduced to the nonsymmetric Hamiltonian form. The EPT method is extended for the case of degeneracy in the total spin of a system. As an example of the application of the developed EPT formalism for the degeneracy case, spin arrangements were considered for the key ⟨Mn⟩–O–⟨Mn⟩ (⟨Mn⟩: Mn3+ or Mn4+ fragments in manganites. In ⟨Mn⟩–O–⟨Mn⟩ for La1/3Ca2/3MnO3 are in good agreement the obtained estimations of Heisenberg parameter and binding energy with the available experimental data.

  9. Triggering of spin-flipping-modulated exchange bias in FeCo nanoparticles by electronic excitation

    Science.gov (United States)

    Sarker, Debalaya; Bhattacharya, Saswata; Srivastava, Pankaj; Ghosh, Santanu

    2016-12-01

    The exchange coupling between ferromagnetic (FM)-antiferromagnetic (AF) interfaces is a key element of modern spintronic devices. We here introduce a new way of triggering exchange bias (EB) in swift heavy ion (SHI) irradiated FeCo-SiO2 films, which is a manifestation of spin-flipping at high irradiation fluence. The elongation of FeCo nanoparticles (NPs) in SiO2 matrix gives rise to perpendicular magnetic anisotropy at intermediate fluence. However, a clear shift in hysteresis loop is evident at the highest fluence. This reveals the existence of an AF exchange pinning domain in the NPs, which is identified not to be oxide shell from XANES analysis. Thermal spike calculations along with first-principles based simulations under the framework of density functional theory (DFT) demonstrate that spin flipping of 3d valence electrons is responsible for formation of these AF domains inside the FM NPs. EXAFS experiments at Fe and Co K-edges further unravel that spin-flipping in highest fluence irradiated film results in reduced bond lengths. The results highlight the possibility of miniaturization of magnetic storage devices by using irradiated NPs instead of conventionally used FM-AF multilayers.

  10. Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres

    Science.gov (United States)

    Hensen, B.; Bernien, H.; Dréau, A. E.; Reiserer, A.; Kalb, N.; Blok, M. S.; Ruitenberg, J.; Vermeulen, R. F. L.; Schouten, R. N.; Abellán, C.; Amaya, W.; Pruneri, V.; Mitchell, M. W.; Markham, M.; Twitchen, D. J.; Elkouss, D.; Wehner, S.; Taminiau, T. H.; Hanson, R.

    2015-10-01

    More than 50 years ago, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory: in any local-realist theory, the correlations between outcomes of measurements on distant particles satisfy an inequality that can be violated if the particles are entangled. Numerous Bell inequality tests have been reported; however, all experiments reported so far required additional assumptions to obtain a contradiction with local realism, resulting in `loopholes'. Here we report a Bell experiment that is free of any such additional assumption and thus directly tests the principles underlying Bell's inequality. We use an event-ready scheme that enables the generation of robust entanglement between distant electron spins (estimated state fidelity of 0.92 +/- 0.03). Efficient spin read-out avoids the fair-sampling assumption (detection loophole), while the use of fast random-basis selection and spin read-out combined with a spatial separation of 1.3 kilometres ensure the required locality conditions. We performed 245 trials that tested the CHSH-Bell inequality S certification.

  11. Optimized quantum sensing with a single electron spin using real-time adaptive measurements

    Science.gov (United States)

    Bonato, C.; Blok, M. S.; Dinani, H. T.; Berry, D. W.; Markham, M. L.; Twitchen, D. J.; Hanson, R.

    2016-03-01

    Quantum sensors based on single solid-state spins promise a unique combination of sensitivity and spatial resolution. The key challenge in sensing is to achieve minimum estimation uncertainty within a given time and with high dynamic range. Adaptive strategies have been proposed to achieve optimal performance, but their implementation in solid-state systems has been hindered by the demanding experimental requirements. Here, we realize adaptive d.c. sensing by combining single-shot readout of an electron spin in diamond with fast feedback. By adapting the spin readout basis in real time based on previous outcomes, we demonstrate a sensitivity in Ramsey interferometry surpassing the standard measurement limit. Furthermore, we find by simulations and experiments that adaptive protocols offer a distinctive advantage over the best known non-adaptive protocols when overhead and limited estimation time are taken into account. Using an optimized adaptive protocol we achieve a magnetic field sensitivity of 6.1 ± 1.7 nT Hz-1/2 over a wide range of 1.78 mT. These results open up a new class of experiments for solid-state sensors in which real-time knowledge of the measurement history is exploited to obtain optimal performance.

  12. Beam-target double-spin asymmetry in quasielastic electron scattering off the deuteron with CLAS

    Science.gov (United States)

    Mayer, M.; Kuhn, S. E.; Adhikari, K. P.; Akbar, Z.; Anefalos Pereira, S.; Asryan, G.; Avakian, H.; Badui, R. A.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Boiarinov, S.; Bosted, P.; Briscoe, W. J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Charles, G.; Chetry, T.; Ciullo, G.; Clark, L.; Colaneri, L.; Cole, P. L.; Compton, N.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dupre, R.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fanchini, E.; Fedotov, G.; Fersch, R.; Filippi, A.; Fleming, J. A.; Forest, T. A.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Gleason, C.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Guo, L.; Hakobyan, H.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S. M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jiang, H.; Keith, C.; Keller, D.; Khachatryan, G.; Khachatryan, M.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Kubarovsky, V.; Lanza, L.; Lenisa, P.; Livingston, K.; MacGregor, I. J. D.; McKinnon, B.; Meekins, D.; Mirazita, M.; Mokeev, V.; Movsisyan, A.; Net, L. A.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A. I.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pogorelko, O.; Price, J. W.; Prok, Y.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Sabatié, F.; Schumacher, R. A.; Sharabian, Y. G.; Skorodumina, Iu.; Smith, G. D.; Sokhan, D.; Sparveris, N.; Stankovic, I.; Stepanyan, S.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Torayev, B.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zhang, J.; Zonta, I.; CLAS Collaboration

    2017-02-01

    Background: The deuteron plays a pivotal role in nuclear and hadronic physics, as both the simplest bound multinucleon system and as an effective neutron target. Quasielastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. Purpose: The experimental data presented here can be used to test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on spin-momentum correlations in the deuteron ground state (due to the D -state admixture) and on the limits of the impulse approximation (IA) picture as it applies to measurements of spin-dependent observables like spin structure functions for bound nucleons. Information on this reaction can also be used to reduce systematic uncertainties on the determination of neutron form factors or deuteron polarization through quasielastic polarized electron scattering. Method: We measured the beam-target double-spin asymmetry (A||) for quasielastic electron scattering off the deuteron at several beam energies (1.6 -1.7 , 2.5, 4.2, and 5.6 -5.8 GeV ), using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The deuterons were polarized along (or opposite to) the beam direction. The double-spin asymmetries were measured as a function of photon virtuality Q2(0.13 -3.17 (GeV/c ) 2) , missing momentum (pm=0.0 -0.5 GeV /c ), and the angle between the (inferred) spectator neutron and the momentum transfer direction (θn q). Results: The results are compared with a recent model that includes final-state interactions (FSI) using a complete parametrization of nucleon-nucleon scattering, as well as a simplified model using the plane wave impulse approximation (PWIA). We find overall good agreement with both the PWIA and FSI

  13. First principles study on the spin dependent electronic behavior of Co doped ZnO structures joining the Al electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Caliskan, S., E-mail: scaliskan@fatih.edu.tr; Guner, S.

    2015-01-15

    Highlights: • An atomic configuration joining the electrodes can govern spin resolved transport. • Co position and concentration in ZnO have a crucial effect on electronic behavior. • It is possible to obtain high spin polarization in Al–Co doped ZnO–Al systems. • Al–Co doped ZnO–Al device structures reveal Schottky-like contact at the interface. - Abstract: Employing first principles, Co doped ZnO systems between the Al electrodes were investigated through the Density Functional Theory combined with Non Equilibrium Green’s Function Formalism. Electronic transport properties of these systems, in the presence of spin property, were revealed using substitutional Co atoms in a supercell. Spin resolved electronic behavior was observed to be crucially governed by atomic configuration, defined by doping position and concentration, of the system joining the electrodes. Using this feature, one can manipulate both the electronic transport and magnetic properties of an Al–Co doped ZnO–Al device structure. A nonlinearity was exhibited in current–voltage characteristics for Co doped ZnO systems attached to the Al electrodes, which implies a Schottky-like contact at the interface. The induced magnetic moment and spin polarization in the system, yielding the spin dependent transport, were elucidated.

  14. Spin beam splitter based on Goos-Haenchen shifts in two-dimensional electron gas modulated by ferromagnetic and Schottky metal stripes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Mao-Wang; Huang, Xin-Hong; Zhang, Gui-Lin; Chen, Sai-Yan [College of Science, Guilin University of Technology, Guilin 541004 (China)

    2012-11-15

    We present a theoretical study on the spin-dependent Goos-Haenchen (GH) effect in a two-dimensional electron gas modulated by ferromagnetic and Schottky metal (SM) stripes. The GH shifts for spin electron beams across this device are calculated with the help of the stationary phase method. It is shown that the GH shift of spin-up beam is significantly different from that of spin-down beam, i.e., this device shows up a considerable spin polarization effect in GH shifts of electron beams. It also is shown that both magnitude and sign of spin polarization of GH shifts are closely related to the stripe width, the magnetic strength and the gated voltage under SM stripe. These interesting properties not only provide an effective method of spin injection for spintronics application, but also give rise to a tunable spin beam splitter. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Electron transport through a spin crossover junction. Perspectives from a wavefunction-based approach

    Science.gov (United States)

    Vela, Sergi; Verot, Martin; Fromager, Emmanuel; Robert, Vincent

    2017-02-01

    The present paper reports the application of a computational framework, based on the quantum master equation, the Fermi's golden Rule, and conventional wavefunction-based methods, to describe electron transport through a spin crossover molecular junction (Fe(bapbpy) (NCS)2, 1, bapbpy = N-(6-(6-(Pyridin-2-ylamino)pyridin-2-yl)pyridin-2-yl)-pyridin-2-amine). This scheme is an alternative to the standard approaches based on the relative position and nature of the frontier orbitals, as it evaluates the junction's Green's function by means of accurate state energies and wavefunctions. In the present work, those elements are calculated for the relevant states of the high- and low-spin species of 1, and they are used to evaluate the output conductance within a given range of bias- and gate-voltages. The contribution of the ground and low-lying excited states to the current is analyzed, and inspected in terms of their 2S + 1 Ms-states. In doing so, it is shown the relevance of treating not only the ground state in its maximum-Ms projection, as usually done in most computational-chemistry packages, but the whole spectrum of low-energy states of the molecule. Such improved representation of the junction has a notable impact on the total conductivity and, more importantly, it restores the equivalence between alpha and beta transport, which means that no spin polarization is observed in the absence of Zeeman splitting. Finally, this work inspects the strong- and weak-points of the suggested theoretical framework to understand electron transport through molecular switchable materials, identifies a pathway for future improvement, and offers a new insight into concepts that play a key role in spintronics.

  16. Spin-polarized electronic properties of NiHe0.25 under pressure

    Institute of Scientific and Technical Information of China (English)

    San Xiao-Jiao; Liu Zhi-Ming; Ma Yan-Ming; Cui Tian; Liu Bing-Bing; Zou Guang-Tian

    2009-01-01

    This paper studies the effects of He atom on the spin-polarized electronic properties of nickel under pressures using ab initio pseudopotential plan-wave method. Under high pressures, the compound of NiHeo.25 can exist and helium-bubble can not create in Ni. A pressure-induced ferromagnetic to paramagnetic phase transition has been predicted in NiHe0.25 at about 218 GPa. It is found that under pressures, the magnetic property of Ni atoms is more strongly affected by He atom than by H atom and that the behaviour of He atom in Ni are completely different from that of H atom, like the bonding characteristics and the electron transfer.

  17. On Photon Spin and the Electrodynamic Origin of the charge of the Electron

    CERN Document Server

    Fischer, Ulrich C

    2016-01-01

    We recently performed experiments on the transfer of photon spin to electron orbital angular momentum. For an interpretation of the experimental results we used a classical electrodynamic model of the photon as a propagating electromagnetic solitary wave which is developed in detail here. A linearly polarized monochromatic photon is considered as a propagating solitary electromagnetic wave of finite energy hf which carries an angular momentum h/2pi with the frequency f and Plancks constant h. This model has, apart from being a tool for an interpretation of our experimental results, far reaching consequences of fundamental relevance and guides us to an outline to a unified quantum theory of electromagnetism and gravitation including an explanation of the electrodynamic origin of the quantized charge of an electron.

  18. Anisotropic Heisenberg form of RKKY interaction in the one-dimensional spin-polarized electron gas

    Science.gov (United States)

    Valizadeh, M. M.

    2016-09-01

    We study the indirect exchange interaction between two localized magnetic moments, known as Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, in a one-dimensional (1D) spin-polarized electron gas. We find explicit expressions for each term of this interaction, study their oscillatory behaviors as a function of the distance between two magnetic moments, R, and compare them with the known results for RKKY interaction in the case of 1D standard electron gas. We show this interaction can be written in an anisotropic Heisenberg form, E(R) = λ2χ xx(S1xS2x + S1yS2y) + λ2χ zzS1zS2z, coming from broken time-reversal symmetry of the host material.

  19. Analysis of electron spin resonance spectra of irradiated gingers: Organic radical components derived from carbohydrates

    Energy Technology Data Exchange (ETDEWEB)

    Yamaoki, Rumi, E-mail: yamaoki@gly.oups.ac.j [Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094 (Japan); Kimura, Shojiro [Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094 (Japan); Ohta, Masatoshi [Faculty of Engineering, Niigata University, 8050 Igarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan)

    2010-04-15

    Electron spin resonance (ESR) spectral characterizations of gingers irradiated with electron beam were studied. Complex asymmetrical spectra (near g=2.005) with major spectral components (line width=2.4 mT) and minor signals (at 6 mT apart) were observed in irradiated gingers. The spectral intensity decreased considerably 30 days after irradiation, and continued to decrease steadily thereafter. The spectra simulated on the basis of characteristics of free radical components derived from carbohydrates in gingers are in good agreement with the observed spectra. Analysis showed that shortly after irradiation the major radical components of gingers were composed of radical species derived from amylose and cellulose, and the amylose radicals subsequently decreased considerably. At 30 days after irradiation, the major radical components of gingers were composed of radical species derived from cellulose, glucose, fructose or sucrose.

  20. Electron dynamics in the carbon atom induced by spin-orbit interaction

    CERN Document Server

    Rey, H F

    2014-01-01

    We use R-Matrix theory with Time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number $M_L$=0 and $M_L$=1 at a laser wavelength of 390 nm and peak intensity of 10$^{14}$ W cm$^{-2}$. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for $M_L$. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with $M_L=0$, the dynamics with respect to time delay of an ionizing probe pulse modelled using RMT theory is found to be in good agreement with available experimental data.

  1. Probing spin-orbit-interaction-induced electron dynamics in the carbon atom by multiphoton ionization

    Science.gov (United States)

    Rey, H. F.; van der Hart, H. W.

    2014-09-01

    We use R-matrix theory with time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number ML=0 and ML=1 at a laser wavelength of 390 nm and peak intensity of 1014W/cm2. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for ML. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with ML=0, the dynamics with respect to time delay of an ionizing probe pulse modeled by using RMT theory is found to be in good agreement with available experimental data.

  2. Spin-dependent electron transport through a magnetic resonant tunneling diode

    Science.gov (United States)

    Havu, P.; Tuomisto, N.; Väänänen, R.; Puska, M. J.; Nieminen, R. M.

    2005-06-01

    Electron-transport properties in nanostructures can be modeled, for example, by using the semiclassical Wigner formalism or the quantum-mechanical Green’s function formalism. We compare the performance and the results of these methods in the case of magnetic resonant-tunneling diodes. We have implemented the two methods within the self-consistent spin-density-functional theory. Our numerical implementation of the Wigner formalism is based on the finite-difference scheme whereas for the Green’s function formalism the finite-element method is used. As a specific application, we consider the device studied by Slobodskyy [Phys. Rev. Lett. 90, 246601 (2003)] and analyze their experimental results. The Wigner and Green’s function formalisms give similar electron densities and potentials but, surprisingly, the former method requires much more computer resources in order to obtain numerically accurate results for currents. Both of the formalisms can be used to model magnetic resonant tunneling diode structures.

  3. Sub-10 nm colloidal lithography for circuit-integrated spin-photo-electronic devices.

    Science.gov (United States)

    Iovan, Adrian; Fischer, Marco; Lo Conte, Roberto; Korenivski, Vladislav

    2012-01-01

    Patterning of materials at sub-10 nm dimensions is at the forefront of nanotechnology and employs techniques of various complexity, efficiency, areal scale, and cost. Colloid-based patterning is known to be capable of producing individual sub-10 nm objects. However, ordered, large-area nano-arrays, fully integrated into photonic or electronic devices have remained a challenging task. In this work, we extend the practice of colloidal lithography to producing large-area sub-10 nm point-contact arrays and demonstrate their circuit integration into spin-photo-electronic devices. The reported nanofabrication method should have broad application areas in nanotechnology as it allows ballistic-injection devices, even for metallic materials with relatively short characteristic relaxation lengths.

  4. Sub-10 nm colloidal lithography for circuit-integrated spin-photo-electronic devices

    Directory of Open Access Journals (Sweden)

    Adrian Iovan

    2012-12-01

    Full Text Available Patterning of materials at sub-10 nm dimensions is at the forefront of nanotechnology and employs techniques of various complexity, efficiency, areal scale, and cost. Colloid-based patterning is known to be capable of producing individual sub-10 nm objects. However, ordered, large-area nano-arrays, fully integrated into photonic or electronic devices have remained a challenging task. In this work, we extend the practice of colloidal lithography to producing large-area sub-10 nm point-contact arrays and demonstrate their circuit integration into spin-photo-electronic devices. The reported nanofabrication method should have broad application areas in nanotechnology as it allows ballistic-injection devices, even for metallic materials with relatively short characteristic relaxation lengths.

  5. Sub-10 nm colloidal lithography for circuit-integrated spin-photo-electronic devices

    Science.gov (United States)

    Iovan, Adrian; Fischer, Marco; Lo Conte, Roberto

    2012-01-01

    Summary Patterning of materials at sub-10 nm dimensions is at the forefront of nanotechnology and employs techniques of various complexity, efficiency, areal scale, and cost. Colloid-based patterning is known to be capable of producing individual sub-10 nm objects. However, ordered, large-area nano-arrays, fully integrated into photonic or electronic devices have remained a challenging task. In this work, we extend the practice of colloidal lithography to producing large-area sub-10 nm point-contact arrays and demonstrate their circuit integration into spin-photo-electronic devices. The reported nanofabrication method should have broad application areas in nanotechnology as it allows ballistic-injection devices, even for metallic materials with relatively short characteristic relaxation lengths. PMID:23365801

  6. Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering

    CERN Document Server

    Armstrong, D S; Asaturyan, R; Averett, T; Bailey, S L; Batigne, G; Beck, D H; Beise, E J; Benesch, J; Bimbot, L; Birchall, J; Biselli, A; Bosted, P; Boukobza, E; Breuer, H; Carlini, R; Carr, R; Chant, N; Chao, Y C; Chattopadhyay, S; Clark, R; Covrig, S; Cowley, A; Dale, D; Davis, C; Falk, W; Finn, J M; Forest, T; Franklin, G; Furget, C; Gaskell, D; Grames, J; Griffioen, K A; Grimm, K; Guillon, B; Guler, H; Hannelius, L; Hasty, R; Hawthorne Allen, A; Horn, T; Johnston, K; Jones, M; Kammel, P; Kazimi, R; King, P M; Kolarkar, A; Korkmaz, E; Korsch, W; Kox, S; Kühn, J; Lachniet, J; Lee, L; Lenoble, J; Liatard, E; Liu, J; Loupias, B; Lung, A; Marchand, D; Martin, J W; McFarlane, K W; McKee, D W; McKeown, R D; Merchez, F; Mkrtchyan, H; Moffit, B; Morlet, M; Nakagawa, I; Nakahara, K; Neveling, R; Niccolai, S; Ong, S; Page, S; Papavassiliou, V; Pate, S F; Phillips, S K; Pitt, M L; Poelker, M; Porcelli, T A; Quéméner, G; Quinn, B; Ramsay, W D; Rauf, A W; Real, J S; Roche, J; Roos, P; Rutledge, G A; Secrest, J; Simicevic, N; Smith, G R; Spayde, D T; Stepanyan, S; Stutzman, M; Sulkosky, V; Tadevosyan, V; Tieulent, R; Van de Wiele, J; Van Oers, W T H; Voutier, E; Vulcan, W; Warren, G; Wells, S P; Williamson, S E; Wood, S A; Yan, C; Yun, J; Zeps, V

    2007-01-01

    We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 values of 0.15 and 0.25 (GeV/c)^2 with results of A_n = -4.06 +- 0.99 (stat) +- 0.63 (syst) and A_n = -4.82 +- 1.87 (stat) +- 0.98 (syst) ppm. These results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the 2-gamma exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.

  7. Electron spin resonance study of chloroplast photosynthetic activity in the presence of amphiphilic amines.

    Science.gov (United States)

    Sersen, F; Balgavý, P; Devínsky, F

    1990-12-01

    Electron spin resonance spectroscopy (ESR) was used to study the effects of amphiphilic amines of the carbamate, amide, and ester type and amine oxide on the photosynthetic system of spinach chloroplasts. The ESR signal II connected to the photosynthetic center PS II donor side was observed to diminish in the presence of amines, whereas that of PS I remained unchanged. The inhibition of PS II increased with the increasing of amine concentration. In the presence of amines, the light: dark chloroplast ESR signals ratio as well as the intensity of the ESR signal of unbound Mn2+ increased. It is suggested that the amphiphilic amines affect the structure of PS II and the electron transfer to PS I. The effects of the amines tested on the photosynthetic system correlate with their potency to perturb the lipid membrane structure.

  8. Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering

    Energy Technology Data Exchange (ETDEWEB)

    David Armstrong; Francois Arvieux; Razmik Asaturyan; Todd Averett; Stephanie Bailey; Guillaume Batigne; Douglas Beck; Elizabeth Beise; Jay Benesch; Louis Bimbot; James Birchall; Angela Biselli; Peter Bosted; Elodie Boukobza; Herbert Breuer; Roger Carlini; Robert Carr; Nicholas Chant; Yu-Chiu Chao; Swapan Chattopadhyay; Russell Clark; Silviu Covrig; Anthony Cowley; Daniel Dale; Charles Davis; Willie Falk; John Finn; Tony Forest; Gregg Franklin; Christophe Furget; David Gaskell; Joseph Grames; Keith Griffioen; Klaus Grimm; Benoit Guillon; Hayko Guler; Lars Hannelius; Richard HASTY; Alice Hawthorne Allen; Tanja Horn; Kathleen Johnston; Mark Jones; Peter Kammel; Reza Kazimi; Paul King; Ameya Kolarkar; Elie Korkmaz; Wolfgang Korsch; Serge Kox; Joachim Kuhn; Jeff Lachniet; Lawrence Lee; Jason Lenoble; Eric Liatard; Jianglai Liu; Berenice Loupias; Allison Lung; Dominique Marchand; Jeffery Martin; Kenneth McFarlane; David McKee; Robert McKeown; Fernand Merchez; Hamlet Mkrtchyan; Bryan Moffit; M. Morlet; Itaru Nakagawa; Kazutaka Nakahara; Retief Neveling; Silvia Niccolai; S. Ong; Shelley Page; Vassilios Papavassiliou; Stephen Pate; Sarah Phillips; Mark Pitt; Benard Poelker; Tracy Porcelli; Gilles Quemener; Brian Quinn; William Ramsay; Aamer Rauf; Jean-Sebastien Real; Julie Roche; Philip Roos; Gary Rutledge; Jeffery Secrest; Neven Simicevic; Gregory Smith; Damon Spayde; Samuel Stepanyan; Marcy Stutzman; Vince Sulkosky; Vincent Sulkosky; Vince Sulkosky; Vincent Sulkosky; Vardan Tadevosyan; Raphael Tieulent; Jacques Van de Wiele; Willem van Oers; Eric Voutier; William Vulcan; Glen Warren; Steven Wells; Steven Williamson; Stephen Wood; Chen Yan; Junho Yun; Valdis Zeps

    2007-08-01

    We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 values of 0.15 and 0.25 (GeV/c)^2 with results of A_n = -4.06 +- 0.99(stat) +- 0.63(syst) and A_n = -4.82 +- 1.87(stat) +- 0.98(syst) ppm. These results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the two-photon exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.

  9. HNS+ and HSN+ cations: Electronic states, spin-rovibronic spectroscopy with planetary and biological implications

    Science.gov (United States)

    Trabelsi, Tarek; Ben Yaghlane, Saida; Al Mogren, Muneerah Mogren; Francisco, Joseph S.; Hochlaf, Majdi

    2016-08-01

    Ab initio methods in conjunction with a large basis set are used to compute the potential energy surfaces of the 12 lowest electronic states of the HNS+ and HSN+ isomeric forms. These potentials are used in discussions of the metastability of these cations and plausible mechanisms for the H+/H + SN+/SN, S/S+ + NH+/NH, N/N+ + SH+/SH ion-molecule reactions. Interestingly, the low rovibrational levels of HSN+(12A″) and HNS+(12A″) electronically excited ions are predicted to be long-lived. Both ions are suggested to be a suitable candidate for light-sensitive NOṡ donor in vivo and as a possible marker for the detection of intermediates in nitrites + H2S reactions at the cellular level. The full spin rovibronic levels of HNS+ are presented, which may assist in the experimental identification of HNS+ and HSN+ ions and in elucidating their roles in astrophysical and biological media.

  10. Influence of soliton distributions on the spin-dependent electronic transport through polyacetylene molecule

    Indian Academy of Sciences (India)

    Ketabi S A; Nakhaee M

    2016-03-01

    In this paper, a detailed numerical study of the role of selected soliton distributions on the spin-dependent transport through {\\it trans}-polyacetylene (PA) molecule is presented. The molecule is attached symmetrically to magnetic semi-infinite three-dimensional electrodes. Based on Su–Schrieffer–Heeger (SSH) Hamiltonian and using a generalized Green’s function formalism, wecalculate the spin-dependent currents, the electronic transmission and tunnelling magnetoresistance (TMR). We found that the presence of a uniform distribution of the soliton centres along the molecular chain reduced the size of the band gap of {\\it trans}-PA molecule. Moreover, a sublattice of the correlated solitons as binary clusters, which are randomly distributed along the chain, can induce extended electronic states in the band gap of the molecule. In this case, the band gap of the molecule is suppressed and at lower voltages, the TMR bandwidth is narrowed. The current–voltage characteristic then shows an ohmic-like behaviour.

  11. Investigation of defects in In–Ga–Zn oxide thin film using electron spin resonance signals

    Energy Technology Data Exchange (ETDEWEB)

    Nonaka, Yusuke; Kurosawa, Yoichi; Komatsu, Yoshihiro; Ishihara, Noritaka; Oota, Masashi; Nakashima, Motoki; Hirohashi, Takuya; Takahashi, Masahiro; Yamazaki, Shunpei [Semiconductor Energy Laboratory Co., Ltd., 398 Hase, Atsugi, Kanagawa 243-0036 (Japan); Obonai, Toshimitsu; Hosaka, Yasuharu; Koezuka, Junichi [Advanced Film Device, Inc., 161-2 Masuzuka, Tsuga-machi, Tochigi, Tochigi 328-0114 (Japan); Yamauchi, Jun [Semiconductor Energy Laboratory Co., Ltd., 398 Hase, Atsugi, Kanagawa 243-0036 (Japan); Emeritus Professor of Kyoto University, Oiwake-cho, Kitashirakawa, Kyoto 606-8502 (Japan)

    2014-04-28

    In–Ga–Zn oxide (IGZO) is a next-generation semiconductor material seen as an alternative to silicon. Despite the importance of the controllability of characteristics and the reliability of devices, defects in IGZO have not been fully understood. We investigated defects in IGZO thin films using electron spin resonance (ESR) spectroscopy. In as-sputtered IGZO thin films, we observed an ESR signal which had a g-value of g = 2.010, and the signal was found to disappear under thermal treatment. Annealing in a reductive atmosphere, such as N{sub 2} atmosphere, generated an ESR signal with g = 1.932 in IGZO thin films. The temperature dependence of the latter signal suggests that the signal is induced by delocalized unpaired electrons (i.e., conduction electrons). In fact, a comparison between the conductivity and ESR signal intensity revealed that the signal's intensity is related to the number of conduction electrons in the IGZO thin film. The signal's intensity did not increase with oxygen vacancy alone but also with increases in both oxygen vacancy and hydrogen concentration. In addition, first-principle calculation suggests that the conduction electrons in IGZO may be generated by defects that occur when hydrogen atoms are inserted into oxygen vacancies.

  12. Low-energy electron reflection from Au-passivated Ir(0 0 1) for application in imaging spin-filters

    Energy Technology Data Exchange (ETDEWEB)

    Vasilyev, D.; Tusche, C. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Giebels, F.; Gollisch, H. [Universität Duisburg-Essen, Fakultät für Physik, Campus Duisburg, Lotharstr. 1, 47048 Duisburg (Germany); Feder, R. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Universität Duisburg-Essen, Fakultät für Physik, Campus Duisburg, Lotharstr. 1, 47048 Duisburg (Germany); Kirschner, J., E-mail: sekrki@mpi-halle.mpg.de [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Martin-Luther-Universität Halle-Wittenberg, Institut für Physik, 06099 Halle (Germany)

    2015-02-15

    We describe the principle, the preparation, and the calibration of a spin-polarizing electron mirror in multichannel spin polarimetry. We show data obtained by two independent devices (a goniometer-type LEED set-up and a momentum-microscope set-up) and compare them to the results of a relativistic multiple scattering theory. We also discuss the effects of misalignment and mosaic structure of the crystal. For multi-channel detection we find a 5000-fold increase of efficiency over a single-channel spin-detector. The lifetime of the detector is more than 6 months in ultra-high vacuum.

  13. Effects of spin-orbit interaction and magnetic field on the electron transport in quasi-1D ferromagnetic/semiconductor/ferromagnetic system

    Institute of Scientific and Technical Information of China (English)

    Li Yu-Xian; Li Bo-Zang

    2005-01-01

    Based on the transfer matrix method, we investigate the effects of Rashba spin-orbit interaction and magnetic field on the electron transport in a quasi one-dimensional FM/S/FM system, where FM and S represent the ferromagnetic metal and semiconductor, respectively. The results show that the oscillating scope of the transmission increases with the magnetic field increasing. In the antiferromagnetic alignment, the spin-up and spin-down electrons make the same contribution to the transmission even if a magnetic field is applied. In the ferromagnetic alignment, however, at certain strengths of Rashba spin-orbit interaction and of magnetic field, the transmission coefficient for spin-up electrons is larger than that for spin-down electrons, and the sign of the spin polarization changes, which is opposite to that in the absence of the magnetic field.

  14. Spin of the ground quantum state of electrons from first principles in the representation of Feynman path integrals

    Science.gov (United States)

    Shevkunov, S. V.

    2016-08-01

    A method for calculating the spin of the ground quantum state of nonrelativistic electrons and distance between energy levels of quantum states differing in the spin magnitude from first principles is proposed. The approach developed is free from the one-electron approximation and applicable in multielectron systems with allowance for all spatial correlations. The possibilities of the method are demonstrated by the example of calculating the energy gap between spin states in model ellipsoidal quantum dots with a harmonic confining field. The results of computations by the Monte Carlo method point to high sensitivity of the energy gap to the break of spherical symmetry of the quantum dot. For three electrons, the phenomenon of inversion has been revealed for levels corresponding to high and low values of the spin. The calculations demonstrate the practical possibility to obtain spin states with arbitrarily close energies by varying the shape of the quantum dot, which is a key condition for development prospects in technologies of storage systems based on spin qubits.

  15. Native defect induced charge and ferromagnetic spin ordering and coexisting electronic phases in CoO epitaxial thin film

    Energy Technology Data Exchange (ETDEWEB)

    Negi, D. S., E-mail: devendranegi@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in; Loukya, B.; Datta, R., E-mail: devendranegi@jncasr.ac.in, E-mail: ranjan@jncasr.ac.in [International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India)

    2015-12-07

    We report on the observation of Co vacancy (V{sub Co}) induced charge ordering and ferromagnetism in CoO epitaxial thin film. The ordering is associated with the coexistence of commensurate, incommensurate, and discommensurate electronic phases. Density functional theory calculation indicates the origin of ordering in Co atoms undergoing high spin to low spin transition immediately surrounding the V{sub Co(16.6 at. %)}. Electron magnetic chiral dichroism experiment confirms the ferromagnetic signal at uncompensated Co spins. Such a native defects induced coexistence of different electronic phases at room temperature in a simple compound CoO is unique and adds to the richness of the field with the possibility of practical device application.

  16. The effects of gap parameter and spin polarization on electronic Hartree and correlation energies of doped graphene nanoribbon

    Science.gov (United States)

    Rezania, Hamed; Abdi, Ameneh

    2017-04-01

    We study the behaviors of both Hartree and correlation energies of undoped gapped armchair graphene nanoribbon using random phase approximation in the context of Hubbard model Hamiltonian. Specially, the effects of spin polarization and gap parameter on electron density dependence of Hartree and correlation energies of armchair graphene nanoribbon has been addressed. Our results show the variation of gap parameter leads to considerable effect on correlation and Hartree energy behavior of spin unpolarized gapped graphene in the middle electron density region. However local Hubbard interaction parameter affects the behaviors of Hartree and correlation energy on the whole range of electron density in zero magnetization case. We also show that a considerable reduction has been observed for density dependence of Hartree and correlation energies of spin polarized gapped graphene nanoribbon.

  17. Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

    Science.gov (United States)

    Santander-Syro, A. F.; Fortuna, F.; Bareille, C.; Rödel, T. C.; Landolt, G.; Plumb, N. C.; Dil, J. H.; Radović, M.

    2014-12-01

    Two-dimensional electron gases (2DEGs) forming at the interfaces of transition metal oxides exhibit a range of properties, including tunable insulator-superconductor-metal transitions, large magnetoresistance, coexisting ferromagnetism and superconductivity, and a spin splitting of a few meV (refs , ). Strontium titanate (SrTiO3), the cornerstone of such oxide-based electronics, is a transparent, non-magnetic, wide-bandgap insulator in the bulk, and has recently been found to host a surface 2DEG (refs , , , ). The most strongly confined carriers within this 2DEG comprise two subbands, separated by an energy gap of 90 meV and forming concentric circular Fermi surfaces. Using spin- and angle-resolved photoemission spectroscopy (SARPES), we show that the electron spins in these subbands have opposite chiralities. Although the Rashba effect might be expected to give rise to such spin textures, the giant splitting of almost 100 meV at the Fermi level is far larger than anticipated. Moreover, in contrast to a simple Rashba system, the spin-polarized subbands are non-degenerate at the Brillouin zone centre. This degeneracy can be lifted by time-reversal symmetry breaking, implying the possible existence of magnetic order. These results show that confined electronic states at oxide surfaces can be endowed with novel, non-trivial properties that are both theoretically challenging to anticipate and promising for technological applications.

  18. Extensive ab initio study of the electronic states of BSe radical including spin-orbit coupling

    Science.gov (United States)

    Liu, Siyuan; Zhai, Hongsheng; Liu, Yufang

    2016-06-01

    The internally contracted multi-reference configuration interaction method (MRCI) with Davidson modification and the Douglas-Kroll scalar relativistic correction has been used to calculate the BSe molecule at the level of aug-cc-pV5Z basis set. The calculated electronic states, including 9 doublet and 6 quartet Λ-S states, are correlated to the dissociation limit of B(2Pu) + Se(3Pg) and B(2Pu) + Se(1Dg). The Spin-orbit coupling (SOC) interaction is taken into account via the state interaction approach with the full Breit-Pauli Hamiltonian operator, which causes the entire 15 Λ-S states to split into 32 Ω states. This is the first time that the spin-orbit coupling calculation has been carried out on BSe. The potential energy curves of the Λ-S and Ω electronic states are depicted with the aid of the avoided crossing rule between electronic states of the same symmetry. The spectroscopic constants of the bound Λ-S and Ω states were determined, which are in good agreement with the experimental data. The transition dipole moments (TDMs) and the Franck-Condon factors (FCs) of the transitions from the low-lying bound Ω states A2Π(I)3/2, B2Π(I)1/2 and C2Δ(I)3/2 to the ground state X2Σ+1/2 have also been presented. Based on the previous calculations, the radiative lifetimes of the A2Π(I)3/2, B2Π(I)1/2 and C2Δ(I)3/2 were evaluated.

  19. High Efficiency and Light Mobile Electronic Business System Based on Mobile Agent Middleware

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yunyong; LIU Jinde

    2004-01-01

    Mobile Network technology has been being the research focus during the 1990's.The middleware technology is imported for the sake of running distributed transaction smoothly.In this paper,a mobile agent based middleware high efficiency mobile electronic business oriented middleware (HEMEBOM) is designed and implemented based on the requirement and background of collaborative electronic business.Its architecture,elements and excellent properties are mainly focused.Then high efficiency mobile electronic business systemμMcommerce is built using HEMEBOM.

  20. Electron transfer flavoprotein domain II orientation monitored using double electron-electron resonance between an enzymatically reduced, native FAD cofactor, and spin labels.

    Science.gov (United States)

    Swanson, Michael A; Kathirvelu, Velavan; Majtan, Tomas; Frerman, Frank E; Eaton, Gareth R; Eaton, Sandra S

    2011-03-01

    Human electron transfer flavoprotein (ETF) is a soluble mitochondrial heterodimeric flavoprotein that links fatty acid β-oxidation to the main respiratory chain. The crystal structure of human ETF bound to medium chain acyl-CoA dehydrogenase indicates that the flavin adenine dinucleotide (FAD) domain (αII) is mobile, which permits more rapid electron transfer with donors and acceptors by providing closer access to the flavin and allows ETF to accept electrons from at least 10 different flavoprotein dehydrogenases. Sequence homology is high and low-angle X-ray scattering is identical for Paracoccus denitrificans (P. denitrificans) and human ETF. To characterize the orientations of the αII domain of P. denitrificans ETF, distances between enzymatically reduced FAD and spin labels in the three structural domains were measured by double electron-electron resonance (DEER) at X- and Q-bands. An FAD to spin label distance of 2.8 ± 0.15 nm for the label in the FAD-containing αII domain (A210C) agreed with estimates from the crystal structure (3.0 nm), molecular dynamics simulations (2.7 nm), and rotamer library analysis (2.8 nm). Distances between the reduced FAD and labels in αI (A43C) were between 4.0 and 4.5 ± 0.35 nm and for βIII (A111C) the distance was 4.3 ± 0.15 nm. These values were intermediate between estimates from the crystal structure of P. denitrificans ETF and a homology model based on substrate-bound human ETF. These distances suggest that the αII domain adopts orientations in solution that are intermediate between those which are observed in the crystal structures of free ETF (closed) and ETF bound to a dehydrogenase (open).

  1. Spin-dependent Breit-Wigner and Fano resonances in photon-assisted electron transport through a semiconductor heterostructure

    Institute of Scientific and Technical Information of China (English)

    Hu Li-Yun; Zhou Bin

    2011-01-01

    We theoretically investigate the electron transmission through a seven-layer semiconductor heterostructure with the Dresselhaus spin-orbit coupling under two applied oscillating fields. Numerical results show that both of the spindependent symmetric Breit-Wigner and the asymmetric Fano resonances appear and that the properties of these two types of resonance peaks are dependent on the amplitude and the relative phases of the two applied oscillating fields.The modulation of the spin-polarization efficiency of transmitted electrons by the relative phase is also discussed.

  2. The importance of the on-site electron-electron interaction for the magnetic coupling in the zigzag spin-chain compound In2VO5

    KAUST Repository

    Wang, Hao

    2010-09-27

    We present first-principles electronic structure calculations for the zigzag spin-chain compound In2VO5 using the generalized gradient approximation both with and without inclusion of an on-site Coulomb interaction. It has been proposed that In2VO5 is characterized by itinerant V 3d electrons at high temperature and localized electrons at low temperature. Consequently, it is to be expected that electronic correlations play an important role for the magnetic transition from ferromagnetic to antiferromagnetic exchange around 120 K. In this context, we study the electronic and magnetic properties of a set of possible spin configurations. Our calculations show that inclusion of an on-site Coulomb interaction in fact changes the ground state from ferromagnetic to antiferromagnetic. © 2010 IOP Publishing Ltd.

  3. Electron spin resonance study of free radicals produced from ethanol and acetaldehyde after exposure to a Fenton system or to brain and liver microsomes

    Energy Technology Data Exchange (ETDEWEB)

    Gonthier, B.; Jeunet, A.; Barret, L. (Departement de Toxicologie, C.H.R.U. de Grenoble, (France))

    1991-09-01

    Free radical formation from ethanol and acetaldehyde was studied in the presence of a spin-trap and a NADPH generating system with a chemical model, Fenton's reagent, or by enzymatic oxidation of these solvents by rat liver and brain microsomes. The free radicals were detected by electron spin resonance spectroscopy (E.S.R.), using the spin-trapping agent, alpha-(4-pyridyl l-oxide)-N-tertbutyl-nitrone (POBN). Under such conditions, the hydroxyethyl radical derived from ethanol was obtained after both incubation in liver and brain microsomes as well as after exposure to the Fenton system. Enzymatic inhibition and activation showed that the mixed function oxidase system plays an important role in the generation of such a radical, even in the brain. Under all the experimental conditions acetaldehyde could also generate a free radical deriving directly from the parent molecule and modified by enzymatic activation or inhibition. A second, longer lasting radical was also observed in the presence of acetaldehyde. On the basis of a comparative study to a known process causing lipoperoxidation, its lipidic origin was suggested.

  4. Electronic equivalence of optical negative refraction and retroreflection in the two-dimensional systems with inhomogeneous spin-orbit couplings

    Science.gov (United States)

    Lv, Bo; Ma, Zhongshui

    2013-01-01

    The negative refracted transmission and retroreflection of electrons in low-electron-density semiconductors, in the presence of spin-orbit coupling, are theoretically predicted. It is shown that negative electronic transport may occur owing to the occurrence of additional states whose wave vectors are antiparallel to their group velocities. We conclude that the transport emerges as negative in nature in the scattering process if the sign of its ray equation is reversed with respect to that of the incidence's. We demonstrate this finding in the hybrid of two-dimensional electron gases with different Rashba spin-orbit couplings. We also show that the fundamental of negative electric transport is promising to focus a divergent electronic beam in a spintronic sandwich structure with flat surfaces.

  5. Effects of spin-orbit coupling on the electronic states and spectroscopic properties of diatomic SeS

    Science.gov (United States)

    Chattopadhyaya, Surya; Nath, Abhijit; Das, Kalyan Kumar

    2016-03-01

    The electronic states and spectroscopic properties of selenium monosulfide (78Se32S) have been studied using relativistic configuration interaction methodology that includes effective core potentials of the constituent atoms. Potential energy curves of several spin-excluded (Λ-S) electronic states have been constructed and spectroscopic constants of low-lying bound Λ-S states within 5.1 eV are reported in the first stage of the calculations. In the next stage, the spin-orbit interaction has been incorporated and its effects on the potential energy curves and spectroscopic properties of the species have been investigated in detail. After the inclusion of spin-orbit coupling, the {{{{X}}}{{1}}}{{3}}{Σ }{0+}- is identified as the spin-orbit (Ω) ground state of the species. The transition moments of several important dipole-allowed and spin-forbidden transitions are calculated and the radiative lifetimes of the excited states involved in the respective transitions are computed. Electric dipole moments (μ z) for some low-lying bound Λ-S states as well as a few low-lying spin-orbit states (Ω-states) are also calculated in the present study.

  6. Quasi 2D electronic states with high spin-polarization in centrosymmetric MoS2 bulk crystals.

    Science.gov (United States)

    Gehlmann, Mathias; Aguilera, Irene; Bihlmayer, Gustav; Młyńczak, Ewa; Eschbach, Markus; Döring, Sven; Gospodarič, Pika; Cramm, Stefan; Kardynał, Beata; Plucinski, Lukasz; Blügel, Stefan; Schneider, Claus M

    2016-06-01

    Time reversal dictates that nonmagnetic, centrosymmetric crystals cannot be spin-polarized as a whole. However, it has been recently shown that the electronic structure in these crystals can in fact show regions of high spin-polarization, as long as it is probed locally in real and in reciprocal space. In this article we present the first observation of this type of compensated polarization in MoS2 bulk crystals. Using spin- and angle-resolved photoemission spectroscopy (ARPES), we directly observed a spin-polarization of more than 65% for distinct valleys in the electronic band structure. By additionally evaluating the probing depth of our method, we find that these valence band states at the point in the Brillouin zone are close to fully polarized for the individual atomic trilayers of MoS2, which is confirmed by our density functional theory calculations. Furthermore, we show that this spin-layer locking leads to the observation of highly spin-polarized bands in ARPES since these states are almost completely confined within two dimensions. Our findings prove that these highly desired properties of MoS2 can be accessed without thinning it down to the monolayer limit.

  7. Quasi 2D electronic states with high spin-polarization in centrosymmetric MoS2 bulk crystals

    Science.gov (United States)

    Gehlmann, Mathias; Aguilera, Irene; Bihlmayer, Gustav; Młyńczak, Ewa; Eschbach, Markus; Döring, Sven; Gospodarič, Pika; Cramm, Stefan; Kardynał, Beata; Plucinski, Lukasz; Blügel, Stefan; Schneider, Claus M.

    2016-06-01

    Time reversal dictates that nonmagnetic, centrosymmetric crystals cannot be spin-polarized as a whole. However, it has been recently shown that the electronic structure in these crystals can in fact show regions of high spin-polarization, as long as it is probed locally in real and in reciprocal space. In this article we present the first observation of this type of compensated polarization in MoS2 bulk crystals. Using spin- and angle-resolved photoemission spectroscopy (ARPES), we directly observed a spin-polarization of more than 65% for distinct valleys in the electronic band structure. By additionally evaluating the probing depth of our method, we find that these valence band states at the point in the Brillouin zone are close to fully polarized for the individual atomic trilayers of MoS2, which is confirmed by our density functional theory calculations. Furthermore, we show that this spin-layer locking leads to the observation of highly spin-polarized bands in ARPES since these states are almost completely confined within two dimensions. Our findings prove that these highly desired properties of MoS2 can be accessed without thinning it down to the monolayer limit.

  8. Higher triplet state of fullerene C{sub 70} revealed by electron spin relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Uvarov, Mikhail N., E-mail: uvarov@kinetics.nsc.ru [Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian Academy of Sciences, Institutskaya St. 3, 630090 Novosibirsk (Russian Federation); Behrends, Jan [Berlin Joint EPR Lab, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany); Kulik, Leonid V. [Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian Academy of Sciences, Institutskaya St. 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova St. 2, Novosibirsk (Russian Federation)

    2015-12-28

    Spin-lattice relaxation times T{sub 1} of photoexcited triplets {sup 3}C{sub 70} in glassy decalin were obtained from electron spin echo inversion recovery dependences. In the range 30–100 K, the temperature dependence of T{sub 1} was fitted by the Arrhenius law with an activation energy of 172 cm{sup −1}. This indicates that the dominant relaxation process of {sup 3}C{sub 70} is described by an Orbach-Aminov mechanism involving the higher triplet state t{sub 2} which lies 172 cm{sup −1} above the lowest triplet state t{sub 1}. Chemical modification of C{sub 70} fullerene not only decreases the intrinsic triplet lifetime by about ten times but also increases T{sub 1} by several orders of magnitude. The reason for this is the presence of a low-lying excited triplet state in {sup 3}C{sub 70} and its absence in triplet C{sub 70} derivatives. The presence of the higher triplet state in C{sub 70} is in good agreement with the previous results from phosphorescence spectroscopy.

  9. Beta (β) tungsten thin films: Structure, electron transport, and giant spin Hall effect

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Qiang; Chen, Wenzhe; Xiao, Gang, E-mail: Gang-Xiao@Brown.edu [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States)

    2015-05-04

    We use a simple magnetron sputtering process to fabricate beta (β) tungsten thin films, which are capable of generating giant spin Hall effect. As-deposited thin films are always in the metastable β-W phase from 3.0 to 26.7 nm. The β-W phase remains intact below a critical thickness of 22.1 nm even after magnetic thermal annealing at 280 °C, which is required to induce perpendicular magnetic anisotropy (PMA) in a layered structure of β-W/Co{sub 40}Fe{sub 40}B{sub 20}/MgO. Intensive annealing transforms the thicker films (>22.1 nm) into the stable α-W phase. We analyze the structure and grain size of both β- and α-W thin films. Electron transport in terms of resistivity and normal Hall effect is studied over a broad temperature range of 10 K to at least 300 K on all samples. Very low switching current densities are achieved in β-W/Co{sub 40}Fe{sub 40}B{sub 20}/MgO with PMA. These basic properties reveal useful behaviors in β-W thin films, making them technologically promising for spintronic magnetic random access memories and spin-logic devices.

  10. Beta (β) tungsten thin films: Structure, electron transport, and giant spin Hall effect

    Science.gov (United States)

    Hao, Qiang; Chen, Wenzhe; Xiao, Gang

    2015-05-01

    We use a simple magnetron sputtering process to fabricate beta (β) tungsten thin films, which are capable of generating giant spin Hall effect. As-deposited thin films are always in the metastable β-W phase from 3.0 to 26.7 nm. The β-W phase remains intact below a critical thickness of 22.1 nm even after magnetic thermal annealing at 280 °C, which is required to induce perpendicular magnetic anisotropy (PMA) in a layered structure of β-W/Co40Fe40B20/MgO. Intensive annealing transforms the thicker films (>22.1 nm) into the stable α-W phase. We analyze the structure and grain size of both β- and α-W thin films. Electron transport in terms of resistivity and normal Hall effect is studied over a broad temperature range of 10 K to at least 300 K on all samples. Very low switching current densities are achieved in β-W/Co40Fe40B20/MgO with PMA. These basic properties reveal useful behaviors in β-W thin films, making them technologically promising for spintronic magnetic random access memories and spin-logic devices.

  11. Development of high-pressure, high-field and multifrequency electron spin resonance system.

    Science.gov (United States)

    Sakurai, T; Taketani, A; Tomita, T; Okubo, S; Ohta, H; Uwatoko, Y

    2007-06-01

    The electron spin resonance (ESR) system which covers the magnetic field region up to 16 T, the quasicontinuous frequency region from 60 to 700 GHz, the temperature region from 1.8 to 4.2 K, and the hydrostatic pressure region up to 1.1 GPa has been developed. This is the first pulsed high-field and multifrequency ESR system with the pressure region over 1 GPa as far as we know. Transmission ESR spectra under hydrostatic pressure can be obtained by combining a piston-cylinder-type pressure cell and the pulsed magnetic field ESR apparatus. The pressure cell consists of a NiCrAl cylinder and sapphire or zirconia inner parts. The use of sapphire or zirconia as inner parts enables us to observe ESR under pressure because these inner parts have high transmittance for the electromagnetic wave with millimeter and submillimeter wavelengths. We have successfully applied this system for the pressure dependence measurements of an isolated spin system NiSnCl(6)6H(2)O up to 1.1 GPa. It was found that the single ion anisotropy parameter D of this compound strongly depends on pressure. The parameter D is approximately proportional to the pressure up to 0.75 GPa, and the relation between D and the pressure can be used for the pressure calibration of this high-field and high-pressure ESR system.

  12. A Novel Spin-Light Polarimeter for the Electron Ion Collider

    CERN Document Server

    Mohanmurthy, Prajwal

    2013-01-01

    A novel precision polarimeter will go a long way in satisfying the requirements of the precision experiments being planned for a future facility such as the Electron Ion Collider. A polarimeter based on the asymmetry in the spacial distribution of the spin light component of synchrotron radiation will make for a fine addition to the existing-conventional M{\\o}ller and Compton polarimeters. The spin light polarimeter consists of a set of wriggler magnet along the beam that generate synchrotron radiation. The spacial distribution of synchrotron radiation will be measured by an ionization chamber after being collimated. The up-down spacial asymmetry in the transverse plane is used to quantify the polarization of the beam. As a part of the design process, firstly, a rough calculation was drawn out to establish the validity of such an idea. Secondly, the fringe fields of the wriggler magnet was simulated using a 2-D magnetic field simulation toolkit called Poisson Superfish, which is maintained by Los Alamos Natio...

  13. Air oxidation of the kerogen/asphaltene vanadyl porphyrins: an electron spin resonance study

    Directory of Open Access Journals (Sweden)

    MIRJANA S. PAVLOVIC

    2000-02-01

    Full Text Available The thermal behavior of vanadyl porphyrins was studied by electron spin resonance during heating of kerogens, isolated from the La Luna (Venezuela and Serpiano (Switzerland bituminous rocks, at 25°C for 1 to 20 days in the presence of air. During the thermal treatment of the kerogens, the vanadyl porphyrins resonance signals decrease monotonically and become quite small after 6 days of heating. Concomitantly, new vanadyl signals appear and, at longer heating times, dominate the spectrum. It is suggested that the secondary vanadyl species must have been formed from vanadyl porphyrins. Similar conversions of vanadyl porphyrins are observed under the same experimental conditions for asphaltenes extracted from the La Luna and Serpiano rocks, and floating asphalt from the Dead Sea (Israel. A comparison of the spin-Hamiltonian parameters for vanadyl porphyrins and the vanadyl compounds obtained during pyrolysis of the kerogens/asphaltenes suggests that the latter are of a non-porphyrin type. For comparison a study was conducted on Western Kentucky No. 9 coal enriched with vanadium (>>400 ppm from six mines. All the coal samples show only the presence of predominant by non-porphyrin vanadyl compounds, similar to those generated through laboratory heating of the kerogens/asphaltenes in air. In addition, some samples also contain a minor amount of vanadyl porphyrins.

  14. Assessment of fluidity of different invasomes by electron spin resonance and differential scanning calorimetry.

    Science.gov (United States)

    Dragicevic-Curic, Nina; Friedrich, Manfred; Petersen, Silvia; Scheglmann, Dietrich; Douroumis, Dennis; Plass, Winfried; Fahr, Alfred

    2011-06-30

    The aim of this study was to investigate the influence of membrane-softening components (terpenes/terpene mixtures, ethanol) on fluidity of phospholipid membranes in invasomes, which contain besides phosphatidylcholine and water, also ethanol and terpenes. Also mTHPC was incorporated into invasomes in order to study its molecular interaction with phospholipids in vesicular membranes. Fluidity of bilayers was investigated by electron spin resonance (ESR) using spin labels 5- and 16-doxyl stearic acid and by differential scanning calorimetry (DSC). Addition of 1% of a single terpene/terpene mixture led to significant fluidity increase around the C16 atom of phospholipid acyl chains comprising the vesicles. However, it was not possible to differentiate between the influences of single terpenes or terpene mixtures. Incorporation of mTHPC into the bilayer of vesicles decreased fluidity near the C16 atom of acyl chains, indicating its localization in the inner hydrophobic zone of bilayers. These results are in agreement with DSC measurements, which showed that terpenes increased fluidity of bilayers, while mTHPC decreased fluidity. Thus, invasomes represent vesicles with very high membrane fluidity. However, no direct correlation between fluidity of invasomes and their penetration enhancing ability was found, indicating that besides fluidity also other phenomena might be responsible for improved skin delivery of mTHPC.

  15. The Hanle effect and electron spin polarization in InAs/GaAs quantum dots up to room temperature

    Science.gov (United States)

    Beyer, J.; Buyanova, I. A.; Suraprapapich, S.; Tu, C. W.; Chen, W. M.

    2012-04-01

    The Hanle effect in InAs/GaAs quantum dots (QDs) is studied under optical orientation as a function of temperature over the range of 150-300 K, with the aim of understanding the physical mechanism responsible for the observed sharp increase of electron spin polarization with increasing temperature. The deduced spin lifetime Ts of positive trions in the QDs is found to be independent of temperature, and is also insensitive to excitation energy and density. It is argued that the measured Ts is mainly determined by the longitudinal spin-flip time (T1) and the spin dephasing time ({T}_{2}^{\\ast }) of the studied QD ensemble, of which both are temperature independent over the studied temperature range and the latter makes a larger contribution. The observed sharply rising QD spin polarization degree with increasing temperature, on the other hand, is shown to be induced by an increase in spin injection efficiency from the barrier/wetting layer and also by a moderate increase in spin detection efficiency of the QD.

  16. Insight into the spin state at the surface of LaCoO3 revealed by photoemission electron microscopy

    Science.gov (United States)

    Yaroslavtsev, A. A.; Izquierdo, M.; Carley, R.; Dávila, M. E.; Ünal, A. A.; Kronast, F.; Lichtenstein, A.; Scherz, A.; Molodtsov, S. L.

    2016-04-01

    The evolution of the spin transition in LaCoO3 has been investigated with photoemission electron microscopy (PEEM) as a function of temperature. The investigated temperature range spanned from a predominantly low spin configuration (125 K) to the proposed percolation limit for metallization (413 K). The data show that the spin configuration exhibits an inhomogeneous spatial distribution that is very sensitive to the surface preparation method. In the region of the semiconductor-to-metal transition (300 to 450 K), the spatial contrast is continuously reduced, indicating a smooth transition without domain percolation. These observations support a new interpretation of the temperature evolution of the system that is in agreement with current theoretical understanding of the spin transition.

  17. Spin-Dependent Scattering Effects and Dimensional Crossover in a Quasi-Two-Dimensional Disordered Electron System

    Institute of Scientific and Technical Information of China (English)

    YANG YongHong; WANG YongGang; LIU Mei; WANG Jin

    2002-01-01

    Two kinds of spin-depcndcnt scattering effects (magnetic-iinpurity and spin-orbit scatterings) axe investi-gated theoretically in a quasi-two-dimensional (quasi-2D) disordered electron system. By making use of the diagrammatictechniques in perturbation theory, we have calculated the dc conductivity and magnetoresistance due to weak-localizationeffects, the analytical expressions of them are obtained as functions of the interlayer hopping energy and the charac-teristic times: elastic, inelastic, magnetic and spin-orbit scattering times. The relevant dimensional crossover behaviorfrom 3D to 2D with decreasing the interlayer coupling is discussed, and the condition for the crossover is shown to bedependent on the aforementioned scattering times. At low temperature there exists a spin-dcpendent-scattering-induccddimensional crossover in this system.

  18. Giant photoinduced Faraday rotation due to the spin-polarized electron gas in an n-GaAs microcavity

    Science.gov (United States)

    Giri, R.; Cronenberger, S.; Vladimirova, M.; Scalbert, D.; Kavokin, K. V.; Glazov, M. M.; Nawrocki, M.; Lemaître, A.; Bloch, J.

    2012-05-01

    Faraday rotation up to 19∘ in the absence of an external magnetic field is demonstrated in an n-type bulk GaAs microcavity under circularly polarized optical excitation. This strong effect is achieved because (i) the spin-polarized electron gas is an efficient Faraday rotator and (ii) the light wave makes multiple round trips in the cavity. We introduce a concept of Faraday rotation cross section as a proportionality coefficient between the rotation angle, electron spin density and optical path and calculate this cross section for our system. From independent measurements of photoinduced Faraday rotation and electron spin polarization we obtain quantitatively the cross section of the Faraday rotation induced by free electron spin polarization σFexp=-(2.5±0.6)×10-15 rad×cm2 for photon energy 18 meV below the band gap of GaAs, and electron concentration 2×1016 cm-3. It appears to exceed the theoretical value σFth=-0.7×10-15 rad×cm2, calculated without fitting parameters. We also demonstrate the proof-of-principle of a fast optically controlled Faraday rotator.

  19. Spin Magnetohydrodynamics. Energy density and vorticity evolution in electron-ion quantum plasmas

    CERN Document Server

    Trukhanova, Mariya Iv

    2014-01-01

    In this paper, we explain a magneto quantum hydrodynamics (MQHD) method for the study of the quantum evolution of a system of spinning fermions in an external electromagnetic field. The fundamental equations of microscopic quantum hydrodynamics (the momentum balance equation, the energy evolution equation and the magnetic moment density equation) were derived from the many-particle microscopic Schredinger equation with a Spin-spin and Coulomb modified Hamiltonian. It has been showed that in the absence of external electromagnetic field the system of particles are subject to the usual quantum force (Bohm potential) and spin-dependent addition (Spin stress). Using the developed approach, an extended vorticity evolution equation for the quantum spinning plasma has been derived. The effects of the new spin forces and Spin-spin interaction contributions on the motion of fermions, the evolution of the magnetic moment density, the energy dynamics and vorticity generation have been predicted. The explicated MQHD appr...

  20. Electron spin resonance spectral study of PVC and XLPE insulation materials and their life time analysis

    Science.gov (United States)

    Morsy, M. A.; Shwehdi, M. H.

    2006-03-01

    Electron spin resonance (ESR) study is carried out to characterize thermal endurance of insulating materials used in power cable industry. The presented work provides ESR investigation and evaluation of widely used cable insulation materials, namely polyvinyl chloride (PVC) and cross-linked polyethylene (XLPE). The results confirm the fact that PVC is rapidly degrades than XLPE. The study also indicates that colorants and cable's manufacturing processes enhance the thermal resistance of the PVC. It also verifies the powerfulness and the importance of the ESR-testing of insulation materials compared to other tests assumed by International Electrotechnical Commission (IEC) Standard 216-procedure, e.g. weight loss (WL), electric strength (ES) or tensile strength (TS). The estimated thermal endurance parameters by ESR-method show that the other standard methods overestimate these parameters and produce less accurate thermal life time curves of cable insulation materials.

  1. Electron spin resonance dating of teeth from Western Brazilian megafauna - preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Kinoshita, Angela, E-mail: angela.kinoshita@usc.br [Departamento de Fisica, FFCLRP, Universidade de Sao Paulo, 14040-901 Ribeirao Preto-SP (Brazil); Universidade Sagrado Coracao, Rua Irma Arminda 10-50, 17011-160 Bauru - Sao Paulo (Brazil); Jose, Flavio A. [Departamento de Fisica, FFCLRP, Universidade de Sao Paulo, 14040-901 Ribeirao Preto-SP (Brazil); Sundaram, Dharani; Paixao, Jesus da S.; Soares, Isabella R.M. [Universidade Federal de Mato Grosso, Departamento de Geologia Geral, 78090-000 Cuiaba-MT (Brazil); Figueiredo, Ana Maria [Instituto de Pesquisas Energeticas e Nucleares (IPEN), 05422-970 Sao Paulo-SP (Brazil); Baffa, Oswaldo [Departamento de Fisica, FFCLRP, Universidade de Sao Paulo, 14040-901 Ribeirao Preto-SP (Brazil)

    2011-09-15

    Electron Spin Resonance (ESR) was applied to determine ages of Haplomastodon teeth from Western Brazilian Megafauna. The Equivalent Doses (D{sub e}) of (1.3 {+-} 0.2)kGy, (800 {+-} 100)Gy and (140 {+-} 20)Gy were found and the software ROSY ESR dating was employed to convert D{sub e} in age, using isotope concentrations determined by neutron activation analysis (NAA) and other information, resulting in (500 {+-} 100)ka, (320 {+-} 50) and (90 {+-} 10)ka considering the Combination Uptake (CU) model for Uranium uptake, set as an Early Uptake (EU) for dentine and Linear Uptake (LU) for enamel. There are scarce reports about Pleistocene Megafauna in this area. This paper presents the first dating of megafauna tooth and this study could contribute to improve the knowledge about the paleoclimate and paleoenvironment of this region and prompt more investigations in this area.

  2. Detection of irradiated fruits and vegetables by gas-chromatographic methods and electron spin-resonance

    Energy Technology Data Exchange (ETDEWEB)

    Farag, S.E.A. (National Centre for Radiation Research and Technology, Cairo (Egypt))

    1993-01-01

    Gas chromatographic methods detected some hydrocarbons esp. 17:1, 16:2, 15:0 and 14:1 in irradiated, Avocado, Papaya, Mangoes with 0.75, 1.5, 3.0 kGy and Apricot with 0.5 and 3.0 kGy. The detection of hydrocarbons was clearly at high doses but the low doses need more sensitive conditions using Liquid-Liquid-Gas chromatographic method as used here. Using Electron Spin-Resonance, produce a specific signal from irradiated onion (dried leaves) as well as apricot (hard coat of kernels) after some weeks of irradiation process but not clear with the other foodstuffs. (orig.)

  3. ESR (electron spin resonance)-determined osmotic behavior of bull spermatozoa

    Energy Technology Data Exchange (ETDEWEB)

    Du, J.; Kleinhans, F.W.; Spitzer, V.J.; Critser, J.K. (Methodist Hospital, Indianapolis, IN (USA). Dept. of Medical Research); Horstman, L. (Purdue Univ., Lafayette, IN (USA). School of Veterinary Medicine); Mazur, P. (Oak Ridge National Lab., TN (USA))

    1990-01-01

    Our laboratories are pursuing a fundamental approach to the problems of semen cryopreservation. For many cell types (human red cells, yeast, HeLa) it has been demonstrated that there is an optimum cooling rate for cryopreservation. Faster rates allow insufficient time for cell dehydration and result in intracellular ice formation and cell death. It is possible to predict this optimal rate provided that the cell acts as an ideal osmometer and several other cell parameters are known such as the membrane hydraulic conductivity. It is the purpose of this work to examine the osmotic response of bull sperm to sucrose and NaCl utilizing electron spin resonance (ESR) to measure cell volume. For calibration purposes we also measured the ESR response of human red cells (RBC), the osmotic response of which is well documented with other methods. 15 refs., 1 fig.

  4. Ultrafast Spin Density Wave Transition in Chromium Governed by Thermalized Electron Gas

    Science.gov (United States)

    Nicholson, C. W.; Monney, C.; Carley, R.; Frietsch, B.; Bowlan, J.; Weinelt, M.; Wolf, M.

    2016-09-01

    The energy and momentum selectivity of time- and angle-resolved photoemission spectroscopy is exploited to address the ultrafast dynamics of the antiferromagnetic spin density wave (SDW) transition photoexcited in epitaxial thin films of chromium. We are able to quantitatively extract the evolution of the SDW order parameter Δ through the ultrafast phase transition and show that Δ is governed by the transient temperature of the thermalized electron gas, in a mean field description. The complete destruction of SDW order on a sub-100 fs time scale is observed, much faster than for conventional charge density wave materials. Our results reveal that equilibrium concepts for phase transitions such as the order parameter may be utilized even in the strongly nonadiabatic regime of ultrafast photoexcitation.

  5. Electron spin resonance studies on PS, PP and PS/PP blends under gamma irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, Jacobo E-mail: reyesj@camelot.rect.ucv.ve; Albano, Carmen E-mail: calbano@ivic.vealbanoc@camelot.rect.ucv.ve; Claro, Marjorie; Moronta, Delfin

    2003-06-01

    Electron spin resonance studies on polystyrene (PS), polypropylene (PP) and on 80/20 PS/PP blends with and without compatibilizer (block SBS), at 7.5 wt%, irradiated with gamma rays from a {sup 60}Co source at a dose rate of 4.8 kGy/h and at integral irradiation doses of 10, 25, 50, 60, 70, 400, 800 and 1300 kGy in the presence of air and at room temperature are reported. Dependence of resonance line width, Hpp, resonance line shapes, K, and resonance line intensity, Ipp, on the integral dose of irradiation is investigated. Nature of free radicals after 10 days of air storage is discussed.

  6. Spin-polarized electronic structure of the Ni(001) surface and thin films

    DEFF Research Database (Denmark)

    Jepsen, O.; Madsen, J.; Andersen, O. K.

    1982-01-01

    of the five-layer film is used to calculate the electronic structure of a 13-layer film. The theoretical work function of 5.4 eV agrees well with the experimental value of 5.2 eV. The calculated spin moments are ordered ferromagnetically in all the films considered, and the moments of the atoms in the surface...... layer are 0.95, 0.69, and 0.65 Bohr magnetons for the one-, three-, and five-layer films, respectively. The moment of an atom in the central layer of the five-layer film is 0.61 Bohr magnetons as compared with the calculated (experimental) bulk value of 0.59±0.01 (0.56) Bohr magnetons. The increase...

  7. High-resolution electron microscopy in spin pumping NiFe/Pt interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ley Domínguez, D., E-mail: david.ley@cimav.edu.mx; Sáenz-Hernández, R. J.; Faudoa Arzate, A.; Arteaga Duran, A. I.; Ornelas Gutiérrez, C. E.; Solís Canto, O.; Botello-Zubiate, M. E.; Rivera-Gómez, F. J.; Matutes-Aquino, J. A. [Centro de Investigación en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31109 (Mexico); Azevedo, A.; Silva, G. L. da; Rezende, S. M. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil)

    2015-05-07

    In order to understand the effect of the interface on the spin pumping and magnetic proximity effects, high resolution transmission electron microscopy and ferromagnetic resonance (FMR) were used to analyze Py/Pt bilayer and Pt/Py/Pt trilayer systems. The samples were deposited by dc magnetron sputtering at room temperature on Si (001) substrates. The Py layer thickness was fixed at 12 nm in all the samples and the Pt thickness was varied in a range of 0–23 nm. A diffusion zone of approximately 8 nm was found in the Py/Pt interfaces and confirmed by energy dispersive X-ray microanalysis. The FMR measurements show an increase in the linewidth and a shift in the ferromagnetic resonance field, which reach saturation.

  8. Pre-Town Meeting on Spin Physics at an Electron-Ion Collider

    CERN Document Server

    Aschenauer, Elke-Caroline; Bland, Leslie; Brodsky, Stanley J; Burkardt, Matthias; Burkert, Volker; Chen, Jian-Ping; Deshpande, Abhay; Diehl, Markus; Gamberg, Leonard; Perdekamp, Matthias Grosse; Huang, Jin; Hyde, Charles; Ji, Xiangdong; Jiang, Xiaodong; Kang, Zhong-Bo; Kubarovsky, Valery; Lajoie, John; Liu, Keh-Fei; Liu, Ming; Liuti, Simonetta; Melnitchouk, Wally; Mulders, Piet; Prokudin, Alexei; Tarasov, Andrey; Qiu, Jian-Wei; Radyushkin, Anatoly; Richards, David; Sichtermann, Ernst; Stratmann, Marco; Vogelsang, Werner; Yuan, Feng

    2014-01-01

    A polarized $ep/eA$ collider (Electron--Ion Collider, or EIC), with polarized proton and light-ion beams and unpolarized heavy-ion beams with a variable center--of--mass energy $\\sqrt{s} \\sim 20$ to $\\sim100$~GeV (upgradable to $\\sim 150$ GeV) and a luminosity up to $\\sim 10^{34} \\, \\textrm{cm}^{-2} \\textrm{s}^{-1}$, would be uniquely suited to address several outstanding questions of Quantum Chromodynamics, and thereby lead to new qualitative and quantitative information on the microscopic structure of hadrons and nuclei. During this meeting at Jefferson Lab we addressed recent theoretical and experimental developments in the spin and the three--dimensional structure of the nucleon (sea quark and gluon spatial distributions, orbital motion, polarization, and their correlations). This mini--review contains a short update on progress in these areas since the EIC White paper~\\cite{Accardi:2012qut}.

  9. SPIN AND RELATIVITY: A SEMICLASSICAL MODEL FOR ELECTRON SPIN ESPÍN Y RELATIVIDAD: UN MODELO SEMICLASICO PARA EL ESPÍN DEL ELECTRÓN

    Directory of Open Access Journals (Sweden)

    Héctor Torres-Silva

    2008-11-01

    Full Text Available The quantum relationship may be regarded as the equivalence between two expressions for the rest energy of the particle, if is considered as the spin angular velocity of the particle in its rest frame. The invariance of the relativistic space-time interval to such a spin motion (space isotropy leads to the spin momentum for all structureless particles irrespective of their mass values. The inertia is an intrinsic property due to the spin motion of the particles. The signs of the mass values occurring in the solutions of the Dirac equation might be related to the orientation of the spin motion, as suggested by the fundamental relationship . Besides it deals with the electron, and more specifically with two key properties: its complex wavefunction, and its intrinsic spin. In the standard interpretation, there is no clear real-space picture of what is oscillating in the wave, or what is rotating in the spin. Indeed, it is generally believed that no simple model of rotation can account for the spin of the electron. On the contrary, the present paper shows that a crude mechanical model of coherently rotating vortices can account quantitatively not only for spin, but also for the wavefunction itself. The implications of this are discussed in this paper.La relación cuántica puede ser considerada como la equivalencia entre dos expresiones para la energía en reposo de la partícula, si se considera la velocidad angular de giro de partículas en su marco en reposo. La invariancia del intervalo relativista espacio- tiempo para tal movimiento de espín (isotropía espacial conduce al impulso de espín para todas las partículas sin estructura, independientemente de sus valores de masa. La inercia es una propiedad intrínseca debido al movimiento de spin de las partículas. Los signos de los valores de masa que se producen en las soluciones de la ecuación de Dirac podrían estar relacionados con la orientación del espín, según lo sugerido por la

  10. Electron Spin Resonance on Mobile and Confined States in Gated Modulation Doped Si/SiGe Heterostructures

    Science.gov (United States)

    He, Jianhua; Malissa, H.; Lu, Tzu-Ming; Shankar, S.; Tyryshkin, A. M.; Lyon, S. A.; Chen, Hung-Ming; Kuan, Chieh-Hsiung

    2010-03-01

    Electron spins in quantum dots in Si/SiGe heterostructures are promising qubits but controlling and measuring spins in gated dots is challenging. Fortunately, electrons confined into natural quantum dots by interface disorder can capture the spin physics with minimal processing, exhibiting long T1 and T2 at the Si/SiO2 interface^1. Natural quantum dots in the Si/SiGe system may be similarly useful. As a first step, we have fabricated a 2.2 x 13mm^2 Hall bar on a Si/SiGe substrate gated with an Al gate above an Al2O3 insulator, and performed electron spin resonance (ESR) at gate voltages above and below threshold. The ESR signal arising from the Si quantum well evolves with gate voltage, and its intensity (spin susceptibility) is measured as a function of temperature down to 0.4K. The susceptibility follows a Pauli dependence when the gate is biased above threshold, while it is Curie-like below threshold, indicating an evolution from a mobile 2D system towards localized states confined in natural dots by the intrinsic disorder in the quantum well. This work is supported by LPS and ARO. [1] S. Shankar, et al., Physica E, 40, 1659-1661 (2008).

  11. Resonant Spin-Flavor Conversion of Supernova Neutrinos: Dependence on Electron Mole Fraction

    CERN Document Server

    Yoshida, T; Kimura, K; Yokomakura, H; Kawagoe, S; Kajino, T

    2009-01-01

    Detailed dependence of resonant spin-flavor (RSF) conversion of supernova neutrinos on electron mole fraction Ye is investigated. Supernova explosion forms a hot-bubble and neutrino-driven wind region of which electron mole fraction exceeds 0.5 in several seconds after the core collapse. When a higher resonance of the RSF conversion is located in the innermost region, flavor change of the neutrinos strongly depends on the sign of 1-2Ye. At an adiabatic high RSF resonance the flavor conversion of bar{nu}_e -> nu_{mu,tau} occurs in Ye 0.5 and inverted mass hierarchy. In other cases of Ye values and mass hierarchies, the conversion of nu_e -> bar{nu}_{mu,tau} occurs. The final bar{nu}_e spectrum is evaluated in the cases of Ye 0.5 taking account of the RSF conversion. Based on the obtained result, time variation of the event number ratios of low bar{nu}_e energy to high bar{nu}_e energy is discussed. In normal mass hierarchy, an enhancement of the event ratio should be seen in the period when the electron frac...

  12. Making hybrid [n]-rotaxanes as supramolecular arrays of molecular electron spin qubits

    Science.gov (United States)

    Fernandez, Antonio; Ferrando-Soria, Jesus; Pineda, Eufemio Moreno; Tuna, Floriana; Vitorica-Yrezabal, Iñigo J.; Knappke, Christiane; Ujma, Jakub; Muryn, Christopher A.; Timco, Grigore A.; Barran, Perdita E.; Ardavan, Arzhang; Winpenny, Richard E. P.

    2016-01-01

    Quantum information processing (QIP) would require that the individual units involved--qubits--communicate to other qubits while retaining their identity. In many ways this resembles the way supramolecular chemistry brings together individual molecules into interlocked structures, where the assembly has one identity but where the individual components are still recognizable. Here a fully modular supramolecular strategy has been to link hybrid organic-inorganic [2]- and [3]-rotaxanes into still larger [4]-, [5]- and [7]-rotaxanes. The ring components are heterometallic octanuclear [Cr7NiF8(O2CtBu)16]- coordination cages and the thread components template the formation of the ring about the organic axle, and are further functionalized to act as a ligand, which leads to large supramolecular arrays of these heterometallic rings. As the rings have been proposed as qubits for QIP, the strategy provides a possible route towards scalable molecular electron spin devices for QIP. Double electron-electron resonance experiments demonstrate inter-qubit interactions suitable for mediating two-qubit quantum logic gates.

  13. Electron spin resonance study of chromium(V) formation and decomposition by basalt-inhabiting bacteria.

    Science.gov (United States)

    Kalabegishvili, Tamaz L; Tsibakhashvili, Nelly Y; Holman, Hoi-Ying N

    2003-10-15

    Bacterial reduction of Cr(VI) to Cr(III) compounds may produce reactive intermediates Cr(V) and Cr(IV), which can affect the mobility and toxicity of chromium in environments. To address this important subject, we conducted an electron spin resonance (ESR) study to understand the kinetics of the formation and decomposition of Cr(V) during Cr(VI) reduction by different gram-positive Cr(VI)-tolerant bacteria, which were isolated from polluted basalts from the United States of America and the Republic of Georgia. Results from our batch experiments show that during Cr(VI) reduction, the macromolecules at the cell wall of these bacteria could act as an electron donor to Cr(VI) to form a stable square-pyramidal Cr(V) complexes, which were reduced further probably via a one-electron transfer pathway to form Cr(IV) and Cr(III) compounds. The Cr(V) peak at the ESR spectrum possessed superhyperfine splitting characteristic of the Cr(V) complexes with diol-containing molecules. It appears that the kinetics of Cr(V) formation and decomposition depended on the bacterial growth phase and on the species. Both formation and decomposition of Cr(V) occurred more quickly when Cr(VI) was added at the exponential phase. In comparison with other gram-positive bacteria from the republic of Georgia, the formation and decomposition of Cr(V) in Arthrobacter species from the Unites States was significantly slower.

  14. Commensurate and incommensurate spin-density waves in heavy electron systems

    Directory of Open Access Journals (Sweden)

    P. Schlottmann

    2016-05-01

    Full Text Available The nesting of the Fermi surfaces of an electron and a hole pocket separated by a nesting vector Q and the interaction between electrons gives rise to itinerant antiferromagnetism. The order can gradually be suppressed by mismatching the nesting and a quantum critical point (QCP is obtained as the Néel temperature tends to zero. The transfer of pairs of electrons between the pockets can lead to a superconducting dome above the QCP (if Q is commensurate with the lattice, i.e. equal to G/2. If the vector Q is not commensurate with the lattice there are eight possible phases: commensurate and incommensurate spin and charge density waves and four superconductivity phases, two of them with modulated order parameter of the FFLO type. The renormalization group equations are studied and numerically integrated. A re-entrant SDW phase (either commensurate or incommensurate is obtained as a function of the mismatch of the Fermi surfaces and the magnitude of |Q − G/2|.

  15. Electronic Structure and Spin Configuration Trends of Single Transition Metal Impurity in Phase Change Material

    Science.gov (United States)

    Li, H.; Pei, J.; Shi, L. P.

    2016-10-01

    Fe doped phase change material GexSbyTez has shown experimentally the ability to alter its magnetic properties by phase change. This engineered spin degree of freedom into the phase change material offers the possibility of logic devices or spintronic devices where they may enable fast manipulation of ferromagnetism by a phase change mechanism. The electronic structures and spin configurations of isolated transition metal dopant in phase change material (iTM-PCM) is important to understand the interaction between localized metal d states and the unique delocalized host states of phase change material. Identifying an impurity center that has, in isolation, a nonvanishing magnetic moment is the first step to study the collective magnetic ordering, which originates from the interaction among close enough individual impurities. Theoretical description of iTM-PCM is challenging. In this work, we use a screened exchange hybrid functional to study the single 3d transition metal impurity in crystalline GeTe and GeSb2Te4. By curing the problem of local density functional (LDA) such as over-delocalization of the 3d states, we find that Fe on the Ge/Sb site has its majority d states fully occupied while its minority d states are empty, which is different from the previously predicted electronic configuration by LDA. From early transition metal Cr to heavier Ni, the majority 3d states are gradually populated until fully occupied and then the minority 3d states begin to be filled. Interpretive orbital interaction pictures are presented for understanding the local and total magnetic moments.

  16. Strongly correlated flat-band systems: The route from Heisenberg spins to Hubbard electrons

    Science.gov (United States)

    Derzhko, Oleg; Richter, Johannes; Maksymenko, Mykola

    2015-05-01

    On a large class of lattices (such as the sawtooth chain, the kagome and the pyrochlore lattices), the quantum Heisenberg and the repulsive Hubbard models may host a completely dispersionless (flat) energy band in the single-particle spectrum. The flat-band states can be viewed as completely localized within a finite volume (trap) of the lattice and allow for construction of many-particle states, roughly speaking, by occupying the traps with particles. If the flat-band happens to be the lowest-energy one, the manifold of such many-body states will often determine the ground-state and low-temperature physics of the models at hand even in the presence of strong interactions. The localized nature of these many-body states makes possible the mapping of this subset of eigenstates onto a corresponding classical hard-core system. As a result, the ground-state and low-temperature properties of the strongly correlated flat-band systems can be analyzed in detail using concepts and tools of classical statistical mechanics (e.g., classical lattice-gas approach or percolation approach), in contrast to more challenging quantum many-body techniques usually necessary to examine strongly correlated quantum systems. In this review, we recapitulate the basic features of the flat-band spin systems and briefly summarize earlier studies in the field. The main emphasis is made on recent developments which include results for both spin and electron flat-band models. In particular, for flat-band spin systems, we highlight field-driven phase transitions for frustrated quantum Heisenberg antiferromagnets at low temperatures, chiral flat-band states, as well as the effect of a slight dispersion of a previously strictly flat-band due to nonideal lattice geometry. For electronic systems, we discuss the universal low-temperature behavior of several flat-band Hubbard models, the emergence of ground-state ferromagnetism in the square-lattice Tasaki-Hubbard model and the related Pauli

  17. Spin decoherence in n-type GaAs: The effectiveness of the third-body rejection method for electron-electron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Marchetti, Gionni, E-mail: gionnimarchetti@gmail.com; Hodgson, Matthew, E-mail: matthew.hodgson@york.ac.uk; D' Amico, Irene, E-mail: irene.damico@york.ac.uk [Department of Physics, University of York, York, Heslington YO10 5DD (United Kingdom)

    2014-10-28

    We study the spin decoherence in n-type bulk GaAs for moderate electronic densities at room temperature using the Ensemble Monte Carlo method. We demonstrate that a technique called “third-body rejection method” devised by B. K. Ridley, J. Phys. C: Solid State Phys. 10, 1589 (1977) can be successfully adapted to Ensemble Monte Carlo method and used to tackle the problem of the electron-electron contribution to spin decoherence in the parameter region under study, where the electron-electron interaction can be reasonably described by a Yukawa potential. This scattering technique is employed in a doping region where one can expect that multiple collisions may play a role in carrier dynamics. By this technique, we are able to calculate spin relaxation times which are in very good agreement with the experimental results found by Oertel et al., Appl. Phys. Lett. 93, 13 (2008). Through this method, we show that the electron-electron scattering is overestimated in Born approximation, in agreement with previous results obtained by C. A. Kukkonen and H. Smith, Phys. Rev. B 8, 4601 (1973).

  18. Spin-Orbit induced semiconductor spin guides

    OpenAIRE

    Valin-Rodriguez, Manuel; Puente, Antonio; Serra, Llorens

    2002-01-01

    The tunability of the Rashba spin-orbit coupling allows to build semiconductor heterostructures with space modulated coupling intensities. We show that a wire-shaped spin-orbit modulation in a quantum well can support propagating electronic states inside the wire only for a certain spin orientation and, therefore, it acts as an effective spin transmission guide for this particular spin orientation.

  19. Application of High-Resolution Magic-Angle Spinning NMR Spectroscopy to Define the Cell Uptake of MRI Contrast Agents

    Science.gov (United States)

    Calabi, Luisella; Alfieri, Goffredo; Biondi, Luca; De Miranda, Mario; Paleari, Lino; Ghelli, Stefano

    2002-06-01

    A new method, based on proton high-resolution magic-angle spinning ( 1H HR-MAS) NMR spectroscopy, has been employed to study the cell uptake of magnetic resonance imaging contrast agents (MRI-CAs). The method was tested on human red blood cells (HRBC) and white blood cells (HWBC) by using three gadolinium complexes, widely used in diagnostics, Gd-BOPTA, Gd-DTPA, and Gd-DOTA, and the analogous complexes obtained by replacing Gd(III) with Dy(III), Nd(III), and Tb(III) (i.e., complexes isostructural to the ones of gadolinium but acting as shift agents). The method is based on the evaluation of the magnetic effects, line broadening, or induced lanthanide shift (LIS) caused by these complexes on NMR signals of intra- and extracellular water. Since magnetic effects are directly linked to permeability, this method is direct. In all the tests, these magnetic effects were detected for the extracellular water signal only, providing a direct proof that these complexes are not able to cross the cell membrane. Line broadening effects (i.e., the use of gadolinium complexes) only allow qualitative evaluations. On the contrary, LIS effects can be measured with high precision and they can be related to the concentration of the paramagnetic species in the cellular compartments. This is possible because the HR-MAS technique provides the complete elimination of bulk magnetic susceptibility (BMS) shift and the differentiation of extra- and intracellular water signals. Thus with this method, the rapid quantification of the MRI-CA amount inside and outside the cells is actually feasible.

  20. Spin-orbit interaction in quantum dots and quantum wires of correlated electrons - a way to spintronics?

    Energy Technology Data Exchange (ETDEWEB)

    Birkholz, Jens Eiko

    2008-10-06

    We study the influence of the spin-orbit interaction on the electronic transport through quantum dots and quantum wires of correlated electrons. Starting with a one-dimensional infinite continuum model without Coulomb interaction, we analyze the interplay of the spin-orbit interaction, an external magnetic field, and an external potential leading to currents with significant spin-polarization in appropriate parameter regimes. Since lattice models are known to often be superior to continuum models in describing the experimental situation of low-dimensional mesoscopic systems, we construct a lattice model which exhibits the same low-energy physics in terms of energy dispersion and spin expectation values. Confining the lattice to finite length and connecting it to two semi-infinite noninteracting Fermi liquid leads, we calculate the zero temperature linear conductance using the Landauer-Bttiker formalism and show that spin-polarization effects also evolve for the lattice model by adding an adequate potential structure and can be controlled by tuning the overall chemical potential of the system (quantum wire and leads). Next, we allow for a finite Coulomb interaction and use the functional renormalization group (fRG) method to capture correlation effects induced by the Coulomb interaction. The interacting system is thereby transformed into a noninteracting system with renormalized system parameters. For short wires ({proportional_to}100 lattice sites), we show that the energy regime in which spin polarization is found is strongly affected by the Coulomb interaction. For long wires (>1000 lattice sites), we find the power-law suppression of the total linear conductance on low energy scales typical for inhomogeneous Luttinger liquids while the degree of spin polarization stays constant. Considering quantum dots which consist of two lattice sites, we observe the well-known Kondo effect and analyze, how the Kondo temperature is affected by the spin-orbit interaction

  1. Magnetism of epitaxial Tb films on W(110) studied by spin-polarized low-energy electron microscopy

    Science.gov (United States)

    Prieto, J. E.; Chen, Gong; Schmid, A. K.; de la Figuera, J.

    2016-11-01

    Thin epitaxial films of Tb metal were grown on a clean W(110) substrate in ultrahigh vacuum and studied in situ by low-energy electron microscopy. Annealed films present magnetic contrast in spin-polarized low-energy electron microscopy. The energy dependence of the electron reflectivity was determined and a maximum value of its spin asymmetry of about 1% was measured. The magnetization direction of the Tb films is in-plane. Upon raising the temperature, no change in the domain distribution is observed, while the asymmetry in the electron reflectivity decreases when approaching the critical temperature, following a power law ˜(1-T /TC) β with a critical exponent β of 0.39.

  2. Magnetization and susceptibility of a parabolic InAs quantum dot with electron-electron and spin-orbit interactions in the presence of a magnetic field at finite temperature

    Science.gov (United States)

    Kumar, D. Sanjeev; Mukhopadhyay, Soma; Chatterjee, Ashok

    2016-11-01

    The magnetization and susceptibility of a two-electron parabolic quantum dot are studied in the presence of electron-electron and spin-orbit interactions as a function of magnetic field and temperature. The spin-orbit interactions are treated by a unitary transformation and an exactly soluble parabolic interaction model is considered to mimic the electron-electron interaction. The theory is finally applied to an InAs quantum dot. Magnetization and susceptibility are calculated using canonical ensemble approach. Our results show that Temperature has no effect on magnetization and susceptibility in the diamagnetic regime whereas electron-electron interaction reduces them. The temperature however reduces the height of the paramagnetic peak. The Rashba spin-orbit interaction is shown to shift the paramagnetic peak towards higher magnetic fields whereas the Dresselhaus spin-orbit interaction shifts it to the lower magnetic field side. Spin-orbit interaction has no effect on magnetization and susceptibility at larger temperatures.

  3. Vanishing electron g factor and long-lived nuclear spin polarization in weakly strained nanohole-filled GaAs/AlGaAs quantum dots

    OpenAIRE

    Ulhaq, A.; Duan, Q; Zallo, E.; Ding, F.; Schmidt, O. G.; Tartakovskii, A. I.; Skolnick, M. S.; Chekhovich, E. A.

    2016-01-01

    GaAs/AlGaAs quantum dots grown by in situ droplet etching and nanohole in-filling offer a combination of strong charge confinement, optical efficiency, and high spatial symmetry advantageous for polarization entanglement and spin-photon interface. Here, we study experimentally electron and nuclear spin properties of such dots. We find nearly vanishing electron g factors (ge

  4. Linear in-plane magnetoconductance and spin susceptibility of a 2D electron gas on a vicinal silicon surface

    OpenAIRE

    Proskuryakov, Y. Y.; Kvon, Z. D.; Savchenko, A. K.

    2003-01-01

    In this work we have studied the parallel magnetoresistance of a 2DEG near a vicinal silicon surface. An unusual, linear magnetoconductance is observed in the fields up to $B = 15$ T, which we explain by the effect of spin olarization on impurity scattering. This linear magnetoresistance shows strong anomalies near the boundaries of the minigap in the electron spectrum of the vicinal system.

  5. Characterization of Al2O3-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

    NARCIS (Netherlands)

    Kijlstra, W.S.; Poels, E.K.; Bliek, A.; Weckhuysen, B.M.; Schoonheydt, R.A.

    2001-01-01

    Alumina-supported manganese oxides, used as catalysts for the selective catalytic reduction of NO, were characterized by combined electron spin resonance and diffuse reflectance spectroscopies. Upon impregnation of the acetate precursor solution, the [Mn(H2O)6]^2+ complex interacts strongly with sur

  6. Identification of Copper(II) Complexes in Aqueous Solution by Electron Spin Resonance: An Undergraduate Coordination Chemistry Experiment.

    Science.gov (United States)

    Micera, G.; And Others

    1984-01-01

    Background, procedures, and results are provided for an experiment which examines, through electron spin resonance spectroscopy, complex species formed by cupric and 2,6-dihydroxybenzoate ions in aqueous solutions. The experiment is illustrative of several aspects of inorganic and coordination chemistry, including the identification of species…

  7. Spin dynamics in high-mobility two-dimensional electron systems embedded in GaAs/AlGaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Griesbeck, Michael

    2012-11-22

    Since many years there has been great effort to explore the spin dynamics in low-dimensional electron systems embedded in GaAs/AlGaAs based heterostructures for the purpose of quantum computation and spintronics applications. Advances in technology allow for the design of high quality and well-defined two-dimensional electron systems (2DES), which are perfectly suited for the study of the underlying physics that govern the dynamics of the electron spin system. In this work, spin dynamics in high-mobility 2DES is studied by means of the all-optical time-resolved Kerr/Faraday rotation technique. In (001)-grown 2DES, a strong in-plane spin dephasing anisotropy is studied, resulting from the interference of comparable Rashba and Dresselhaus contributions to the spin-orbit field (SOF). The dependence of this anisotropy on parameters like the confinement length of the 2DES, the sample temperature, as well as the electron density is demonstrated. Furthermore, coherent spin dynamics of an ensemble of ballistically moving electrons is studied without and within an applied weak magnetic field perpendicular to the sample plane, which forces the electrons to move on cyclotron orbits. Finally, strongly anisotropic spin dynamics is investigated in symmetric (110)-grown 2DES, using the resonant spin amplification method. Here, extremely long out-of-plane spin dephasing times can be achieved, in consequence of the special symmetry of the Dresselhaus SOF.

  8. Effect of temperature and glassy states on the molecular mobility of solutes in frozen tuna muscle as studied by electron spin resonance spectroscopy with spin probe detection.

    Science.gov (United States)

    Orlien, Vibeke; Andersen, Mogens L; Jouhtimäki, Saara; Risbo, Jens; Skibsted, Leif H

    2004-04-21

    The mobility of solutes in frozen food systems (tuna muscle, sarcoplasmic protein fraction of tuna muscle, and carbohydrate-water) has been studied using the temperature dependence of the shape of electron spin resonance (ESR) spectra of the spin probe 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL). The spin probe was incorporated into the tuna meat from an aqueous solution of TEMPOL or by contact with a layer of TEMPOL crystals. The melting/freezing of freeze-concentrated solutes in frozen tuna meat was observed to take place over a range of temperatures from -25 to -10 degrees C. Lower temperatures gave ESR powder spectra due to the decreased mobility of the spin probe, and the temperature dependence of the mobility of the spin probe did not show abrupt changes at the glass transition temperatures of the systems. The mobility of nonglass forming solutes is concluded to be decoupled from the glass forming components. Similar behavior was also observed for TEMPOL in frozen, aqueous carbohydrate systems. The temperature dependence of the mobility of TEMPOL in the frozen systems was analyzed using the Arrhenius equation, and the logarithm of the Arrhenius preexponential factor tau(a) was found to be linearly correlated with the activation energy for all of the tuna and carbohydrate samples, indicating a common molecular mechanism for the observed mobility of TEMPOL in all of the systems. The linear correlation also suggests that the observed mobility of TEMPOL in the frozen aqueous systems is dominated by enthalpy-entropy compensation effects, where the mobility of TEMPOL is thermodynamically strongly coupled to the closest surrounding molecules.

  9. Transient charging and discharging of spin-polarized electrons in a quantum dot

    DEFF Research Database (Denmark)

    De Souza, Fabricio; Leao, S.A.; Gester, R. M.;

    2007-01-01

    We study spin-polarized transient transport in a quantum dot coupled to two ferromagnetic leads subjected to a rectangular bias voltage pulse. Time-dependent spin-resolved currents, occupations, spin accumulation, and tunneling magnetoresistance TMR are calculated using both nonequilibrium Green ...

  10. Gate fidelity and coherence of an electron spin in an Si/SiGe quantum dot with micromagnet.

    Science.gov (United States)

    Kawakami, Erika; Jullien, Thibaut; Scarlino, Pasquale; Ward, Daniel R; Savage, Donald E; Lagally, Max G; Dobrovitski, Viatcheslav V; Friesen, Mark; Coppersmith, Susan N; Eriksson, Mark A; Vandersypen, Lieven M K

    2016-10-18

    The gate fidelity and the coherence time of a quantum bit (qubit) are important benchmarks for quantum computation. We construct a qubit using a single electron spin in an Si/SiGe quantum dot and control it electrically via an artificial spin-orbit field from a micromagnet. We measure an average single-qubit gate fidelity of ∼99% using randomized benchmarking, which is consistent with dephasing from the slowly evolving nuclear spins in the substrate. The coherence time measured using dynamical decoupling extends up to ∼400 μs for 128 decoupling pulses, with no sign of saturation. We find evidence that the coherence time is limited by noise in the 10-kHz to 1-MHz range, possibly because charge noise affects the spin via the micromagnet gradient. This work shows that an electron spin in an Si/SiGe quantum dot is a good candidate for quantum information processing as well as for a quantum memory, even without isotopic purification.

  11. Demonstration of quantum entanglement between a single electron spin confined to an InAs quantum dot and a photon.

    Science.gov (United States)

    Schaibley, J R; Burgers, A P; McCracken, G A; Duan, L-M; Berman, P R; Steel, D G; Bracker, A S; Gammon, D; Sham, L J

    2013-04-19

    The electron spin state of a singly charged semiconductor quantum dot has been shown to form a suitable single qubit for quantum computing architectures with fast gate times. A key challenge in realizing a useful quantum dot quantum computing architecture lies in demonstrating the ability to scale the system to many qubits. In this Letter, we report an all optical experimental demonstration of quantum entanglement between a single electron spin confined to a single charged semiconductor quantum dot and the polarization state of a photon spontaneously emitted from the quantum dot's excited state. We obtain a lower bound on the fidelity of entanglement of 0.59±0.04, which is 84% of the maximum achievable given the timing resolution of available single photon detectors. In future applications, such as measurement-based spin-spin entanglement which does not require sub-nanosecond timing resolution, we estimate that this system would enable near ideal performance. The inferred (usable) entanglement generation rate is 3×10(3) s(-1). This spin-photon entanglement is the first step to a scalable quantum dot quantum computing architecture relying on photon (flying) qubits to mediate entanglement between distant nodes of a quantum dot network.

  12. Non-equilibrium quantum transport of spin-polarized electrons and back action on molecular magnet tunnel-junction

    Science.gov (United States)

    Zhang, Chao; Yao, Hui; Nie, Yi-Hang; Liang, J.-Q.

    2016-11-01

    We investigate the non-equilibrium quantum transport through a single-molecule magnet embedded in a tunnel junction with ferromagnetic electrodes, which generate spin-polarized electrons. The lead magnetization direction is non-collinear with the uniaxial anisotropy easy-axis of molecule-magnet. Based on the Pauli rate-equation approach we demonstrate the magnetization reversion of molecule-magnet induced by the back action of spin-polarized current in the sequential tunnel regime. The asymptotic magnetization of molecular magnet and spin-polarization of transport current are obtained as functions of time by means of time-dependent solution of the rate equation. It is found that the antiparallel configuration of the ferromagnetic electrodes and molecular anisotropy easy-axis is an effective structure to reverse both the magnetization of molecule-magnet and spin-polarization of the transport current. Particularly the non-collinear angle dependence provides useful knowledge for the quantum manipulation of molecule-magnet and spin polarized electron-transport.

  13. Non-equilibrium quantum transport of spin-polarized electrons and back action on molecular magnet tunnel-junction

    Directory of Open Access Journals (Sweden)

    Chao Zhang

    2016-11-01

    Full Text Available We investigate the non-equilibrium quantum transport through a single-molecule magnet embedded in a tunnel junction with ferromagnetic electrodes, which generate spin-polarized electrons. The lead magnetization direction is non-collinear with the uniaxial anisotropy easy-axis of molecule-magnet. Based on the Pauli rate-equation approach we demonstrate the magnetization reversion of molecule-magnet induced by the back action of spin-polarized current in the sequential tunnel regime. The asymptotic magnetization of molecular magnet and spin-polarization of transport current are obtained as functions of time by means of time-dependent solution of the rate equation. It is found that the antiparallel configuration of the ferromagnetic electrodes and molecular anisotropy easy-axis is an effective structure to reverse both the magnetization of molecule-magnet and spin-polarization of the transport current. Particularly the non-collinear angle dependence provides useful knowledge for the quantum manipulation of molecule-magnet and spin polarized electron-transport.

  14. Magnetic and electron-transport properties of spin-gapless semiconducting CoFeCrAl films

    Science.gov (United States)

    Sellmyer, David; Jin, Yunlong; Kharel, Parashu; Valloppilly, Shah; George, Tom; Balasubramanian, Balamurugan; Skomski, Ralph

    Recently, spin-gapless semiconductors (SGS) with a semiconducting or insulating gap in one spin channel and zero gap in the other at the Fermi level have attracted much attention due to their new functionalities such as voltage-tunable spin polarization, the ability to switch between spin-polarized n-type and p-type conduction, high spin polarization and carrier mobility. For the development of spintronic devices utilizing SGS, it is necessary to have a better understanding of the magnetic and transport properties of the thin films of these materials. In this study, the structural, magnetic, and electron-transport properties of a SGS material CoFeCrAl in the thin film geometry have been investigated. CoFeCrAl films were grown on atomically flat SiO2 substrates using magnetron sputtering. The Curie temperature was measured to be 550 K very close to the value reported for bulk CoFeCrAl. Electron-transport measurements on the oriented films revealed a negative temperature coefficient of resistivity, small anomalous Hall conductivity and linear field dependence of magnetoresistance, which are transport signatures of SGS. The effect of elemental compositions and structural ordering on the SGS properties of the CoFeCrAl films will be discussed. Research supported by NSF (Y. J.), DoE (B. B., D. J. S), ARO (T. A. G., S. R. V.), SDSU (P. K.), and NRI (Facilities).

  15. An electronic nose for the detection of Sarin, Soman and Tabun mimics and interfering agents

    OpenAIRE

    2014-01-01

    An electronic nose system (E-nose) with metal oxide semiconductor sensors (MOS) has been designed to discriminate and quantify different chemical warfare agents (CWA) mimics. The E-nose consists of an array of commercial MOS for different gases, two sensors for temperature sensing, a sample handling system, a data acquisition system and a laptop with the data acquisition system control. With this device, discrimination studies have been carried out to detect specific CWA simulants...

  16. U(1) chiral symmetry in a one-dimensional interacting electron system with spin

    Science.gov (United States)

    Lee, Taejin

    2016-11-01

    We study a spin-dependent Tomonaga-Luttinger model in one dimension, which describes electron transport through a single barrier. Using the Fermi-Bose equivalence in one dimension, we map the model onto a massless Thirring model with a boundary interaction. A field theoretical perturbation theory for the model has been developed, and the chiral symmetry is found to play an important role. The classical bulk action possesses a global U A (1)4 chiral symmetry because the fermion fields are massless. This global chiral symmetry is broken by the boundary interaction, and the bosonic degrees of freedom, corresponding to a chiral phase transformation, become dynamical. They acquire an additional kinetic action from the fermion path-integral measure and govern the critical behaviors of the physical operators. On the critical line where the boundary interaction becomes marginal, they decouple from the fermi fields. Consequently, the action reduces to the free-field action, which contains only a fermion bilinear boundary mass term as an interaction term. By using a renormalization group analysis, we obtain a new critical line, which differs from the previously known critical lines in the literature. The result of this work implies that the phase diagram of the one-dimensional electron system may have a richer structure than previously thought.

  17. Quaternary dating by electron spin resonance (ESR applied to human tooth enamel

    Directory of Open Access Journals (Sweden)

    Carvajal Eduar

    2011-12-01

    Full Text Available This paper presents the results obtained from using electron paramagnetic resonance (EPR to analyse tooth enamel found at the Aguazuque archaeological site (Cundinamarca, Colombia, located on the savannah near Bogota at 4° 37' North and 74°17' West. It was presumed that the tooth enamel came from a collective burial consisting of 23 people, involving men, women and children. The tooth enamel was irradiated with gamma rays and the resulting free radicals were measured using an electron spin resonance (ESR X-band spectrometer to obtain a signal intensity compared to absorbed doses curve. Fitting this curve allowed the mean archaeological dose accumulated in the enamel during the period that it was buried to be estimated, giving a 2.10 ± 0.14 Gyvalue. ROSY software was used for estimating age, giving a mean 3,256 ± 190y before present (BP age. These results highlight EPR's potential when using the quaternary ancient ruins dating technique in Colombia and its use with other kinds of samples like stalagmites, calcite, mollusc shells and reefs.

  18. Detection of reactive oxygen species in isolated, perfused lungs by electron spin resonance spectroscopy

    Science.gov (United States)

    Weissmann, Norbert; Kuzkaya, Nermin; Fuchs, Beate; Tiyerili, Vedat; Schäfer, Rolf U; Schütte, Hartwig; Ghofrani, Hossein A; Schermuly, Ralph T; Schudt, Christian; Sydykov, Akylbek; Egemnazarow, Bakytbek; Seeger, Werner; Grimminger, Friedrich

    2005-01-01

    Background The sources and measurement of reactive oxygen species (ROS) in intact organs are largely unresolved. This may be related to methodological problems associated with the techniques currently employed for ROS detection. Electron spin resonance (ESR) with spin trapping is a specific method for ROS detection, and may address some these technical problems. Methods We have established a protocol for the measurement of intravascular ROS release from isolated buffer-perfused and ventilated rabbit and mouse lungs, combining lung perfusion with the spin probe l-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine (CPH) and ESR spectroscopy. We then employed this technique to characterize hypoxia-dependent ROS release, with specific attention paid to NADPH oxidase-dependent superoxide formation as a possible vasoconstrictor pathway. Results While perfusing lungs with CPH over a range of inspired oxygen concentrations (1–21 %), the rate of CP• formation exhibited an oxygen-dependence, with a minimum at 2.5 % O2. Addition of superoxide dismutase (SOD) to the buffer fluid illustrated that a minor proportion of this intravascular ROS leak was attributable to superoxide. Stimulation of the lungs by injection of phorbol-12-myristate-13-acetate (PMA) into the pulmonary artery caused a rapid increase in CP• formation, concomitant with pulmonary vasoconstriction. Both the PMA-induced CPH oxidation and the vasoconstrictor response were largely suppressed by SOD. When the PMA challenge was performed at different oxygen concentrations, maximum superoxide liberation and pulmonary vasoconstriction occurred at 5 % O2. Using a NADPH oxidase inhibitor and NADPH-oxidase deficient mice, we illustrated that the PMA-induced superoxide release was attributable to the stimulation of NADPH oxidases. Conclusion The perfusion of isolated lungs with CPH is suitable for detection of intravascular ROS release by ESR spectroscopy. We employed this technique to demonstrate that 1) PMA

  19. Detection of reactive oxygen species in isolated, perfused lungs by electron spin resonance spectroscopy

    Directory of Open Access Journals (Sweden)

    Schudt Christian

    2005-07-01

    Full Text Available Abstract Background The sources and measurement of reactive oxygen species (ROS in intact organs are largely unresolved. This may be related to methodological problems associated with the techniques currently employed for ROS detection. Electron spin resonance (ESR with spin trapping is a specific method for ROS detection, and may address some these technical problems. Methods We have established a protocol for the measurement of intravascular ROS release from isolated buffer-perfused and ventilated rabbit and mouse lungs, combining lung perfusion with the spin probe l-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine (CPH and ESR spectroscopy. We then employed this technique to characterize hypoxia-dependent ROS release, with specific attention paid to NADPH oxidase-dependent superoxide formation as a possible vasoconstrictor pathway. Results While perfusing lungs with CPH over a range of inspired oxygen concentrations (1–21 %, the rate of CP• formation exhibited an oxygen-dependence, with a minimum at 2.5 % O2. Addition of superoxide dismutase (SOD to the buffer fluid illustrated that a minor proportion of this intravascular ROS leak was attributable to superoxide. Stimulation of the lungs by injection of phorbol-12-myristate-13-acetate (PMA into the pulmonary artery caused a rapid increase in CP• formation, concomitant with pulmonary vasoconstriction. Both the PMA-induced CPH oxidation and the vasoconstrictor response were largely suppressed by SOD. When the PMA challenge was performed at different oxygen concentrations, maximum superoxide liberation and pulmonary vasoconstriction occurred at 5 % O2. Using a NADPH oxidase inhibitor and NADPH-oxidase deficient mice, we illustrated that the PMA-induced superoxide release was attributable to the stimulation of NADPH oxidases. Conclusion The perfusion of isolated lungs with CPH is suitable for detection of intravascular ROS release by ESR spectroscopy. We employed this technique to

  20. Carrier-Density-Dependent Electron Spin Relaxation in GaAs/AlGaAs Multi Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    SHOU Qian; WU Yu; LIU Lu-Ning; WEN Jin-Hui; LAI Tian-Shu; LIN Wei-Zhu

    2005-01-01

    @@ The carrier-density-dependent electron spin relaxation processes in GaAs/AlGaAs multi quantum wells are investigated by a femtosecond pump probe experiment. The spin relaxation time presents two distinguishable trends with the increasing excitation density. It increases from 60ps to 70ps with carrier densities from 1 × 1017 cm-3to 5 × 1017 cm-3 and gradually saturates up to ~80ps at 4 × 1018 cm-3. The experimental results are attributed to the combined competition between collision intensification and scattering potential screening and provide a good experimental confirmation for the theoretical D'yakonov-Perel' mechanism descriptions.

  1. Control of coherence among the spins of a single electron and the three nearest neighbor {sup 13}C nuclei of a nitrogen-vacancy center in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Shimo-Oka, T.; Miwa, S.; Suzuki, Y.; Mizuochi, N., E-mail: mizuochi@mp.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Kato, H.; Yamasaki, S. [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Jelezko, F. [Institut für Quantenoptik, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm (Germany)

    2015-04-13

    Individual nuclear spins in diamond can be optically detected through hyperfine couplings with the electron spin of a single nitrogen-vacancy (NV) center; such nuclear spins have outstandingly long coherence times. Among the hyperfine couplings in the NV center, the nearest neighbor {sup 13}C nuclear spins have the largest coupling strength. Nearest neighbor {sup 13}C nuclear spins have the potential to perform fastest gate operations, providing highest fidelity in quantum computing. Herein, we report on the control of coherences in the NV center where all three nearest neighbor carbons are of the {sup 13}C isotope. Coherence among the three and four qubits are generated and analyzed at room temperature.

  2. Theory of two-dimensional Fourier transform electron spin resonance for ordered and viscous fluids

    Science.gov (United States)

    Lee, Sanghyuk; Budil, David E.; Freed, Jack H.

    1994-10-01

    A comprehensive theory for interpreting two-dimensional Fourier transform (2D-FT) electron spin resonance (ESR) experiments that is based on the stochastic Liouville equation is presented. It encompasses the full range of motional rates from fast through very slow motions, and it also provides for microscopic as well as macroscopic molecular ordering. In these respects it is as sophisticated in its treatment of molecular dynamics as the theory currently employed for analyzing cw ESR spectra. The general properties of the pulse propagator superoperator, which describes the microwave pulses in Liouville space, are analyzed in terms of the coherence transfer pathways appropriate for COSY (correlation spectroscopy), SECSY (spin-echo correlation spectroscopy), and 2D-ELDOR (electron-electron double resonance) sequences wherein either the free-induction decay (FID) or echo decay is sampled. Important distinctions are made among the sources of inhomogeneous broadening, which include (a) incomplete spectral averaging in the slow-motional regime, (b) unresolved superhyperfine structure and related sources, and (c) microscopic molecular ordering but macroscopic disorder (MOMD). The differing effects these sources of inhomogeneous broadening have on the two mirror image coherence pathways observed in the dual quadrature 2D experiments, as well as on the auto vs crosspeaks of 2D-ELDOR, is described. The theory is applied to simulate experiments of nitroxide spin labels in complex fluids such as membrane vesicles, where the MOMD model applies and these distinctions are particularly relevant, in order to extract dynamic and ordering parameters. The recovery of homogeneous linewidths from FID-based COSY experiments on complex fluids with significant inhomogeneous broadening is also described. The theory is applied to the ultraslow motional regime, and a simple method is developed to determine rotational rates from the broadening of the autopeaks of the 2D-ELDOR spectra as a

  3. The degree of 5f electron localization in URu2Si2: electron energy-loss spectroscopy and spin-orbit sum rule analysis

    Energy Technology Data Exchange (ETDEWEB)

    Jeffries, J R; Moore, K T; Butch, N P; Maple, M B

    2010-05-19

    We examine the degree of 5f electron localization in URu{sub 2}Si{sub 2} using spin-orbit sum rule analysis of the U N{sub 4,5} (4d {yields} 5f) edge. When compared to {alpha}-U metal, US, USe, and UTe, which have increasing localization of the 5f states, we find that the 5f states of URu{sub 2}Si{sub 2} are more localized, although not entirely. Spin-orbit analysis shows that intermediate coupling is the correct angular momentum coupling mechanism for URu{sub 2}Si{sub 2} when the 5f electron count is between 2.6 and 2.8. These results have direct ramifications for theoretical assessment of the hidden order state of URu{sub 2}Si{sub 2}, where the degree of localization of the 5f electrons and their contribution to the Fermi surface are critical.

  4. Determination of the Potential Barrier at the Metal/Oxide Interface in a Specular Spin Valve Structure with Nano-oxide Layers Using Electron Holography

    Institute of Scientific and Technical Information of China (English)

    王岩国; 沈峰; 张泽; 蔡建旺; 赖武彦

    2002-01-01

    The local potential distribution in a specular spin valve structure with nano-oxide layers has been mapped byusing off-axis electron holography in a field emission gun transmission electron microscope. A potential jumpof 3-4 V across the metal/oxide interface was detected for the first time. The presence of the potential barrierconfirms the formation of the metal/insulator/metal structure, which contributes to the increasing mean free pathof spin-polarized electrons via the specular reflection of spin-polarized electrons at the metal/oxide interface. Itleads to nearly double enhancement of the magnetoresistance ratio from 8% to 15%.

  5. Proposal for manipulating and detecting spin and orbital States of trapped electrons on helium using cavity quantum electrodynamics.

    Science.gov (United States)

    Schuster, D I; Fragner, A; Dykman, M I; Lyon, S A; Schoelkopf, R J

    2010-07-23

    We propose a hybrid architecture in which an on-chip high finesse superconducting cavity is coupled to the lateral motion and spin state of a single electron trapped on the surface of superfluid helium. We estimate the motional coherence times to exceed 15  μs, while energy will be coherently exchanged with the cavity photons in less than 10 ns for charge states and faster than 1  μs for spin states, making the system attractive for quantum information processing and strong coupling cavity quantum electrodynamics experiments. The cavity is used for nondestructive readout and as a quantum bus mediating interactions between distant electrons or an electron and a superconducting qubit.

  6. First Measurements of the Unique Influence of Spin on the Energy Loss of Ultrarelativistic Electrons in Strong Electromagnetic Fields

    Science.gov (United States)

    Kirsebom, K.; Mikkelsen, U.; Uggerhøj, E.; Elsener, K.; Ballestrero, S.; Sona, P.; Vilakazi, Z. Z.

    2001-07-01

    Although some authors have claimed that the effect is not detectable, we show experimentally for the first time that as the quantum parameter χ grows beyond 1, an increasingly large part of the hard radiation emitted arises from the spin of the electron. Results for the energy loss of electrons in the energy range 35-243 GeV incident on a W single crystal are presented. Close to the axial direction the strong electromagnetic fields induce a radiative energy loss which is significantly enhanced compared to incidence on an amorphous target. In such continuously strong fields, the radiation process is highly nonperturbative for ultrarelativistic particles and a full quantum description is needed. The remarkable effect of spin flips and the energy loss is connected to the presence of a field comparable in magnitude to the Schwinger critical field, E0 = m2c3/eħ, in the rest frame of the emitting electron.

  7. Spin structure of Rashba-split electronic states of Bi overlayers on Cu(1 1 1)

    Energy Technology Data Exchange (ETDEWEB)

    Jakobs, S., E-mail: jakobs@physik.uni-kl.de [Department of Physics and Research Center OPTIMAS, TU Kaiserslautern, Kaiserslautern (Germany); Graduate School Materials Science in Mainz, Erwin Schrödinger Straße 46, 67663 Kaiserslautern (Germany); Ruffing, A.; Jungkenn, D.; Cinchetti, M.; Mathias, S.; Aeschlimann, M. [Department of Physics and Research Center OPTIMAS, TU Kaiserslautern, Kaiserslautern (Germany)

    2015-05-15

    Highlights: • The spin texture of the QW system 1 ML Bi/Cu(1 1 1) is investigated with SR-2PPE. • We confirm the Rashba-like behavior of the unoccupied spin-split states. • Large out-of-plane spin components are induced by in-plane potential gradients. - Abstract: We investigate the unoccupied Rashba-type spin-orbit split band structure of the commensurate and incommensurate Bi monolayer on Cu(1 1 1) with spin- and angle-resolved two-photon-photoemission spectroscopy. Because of the unique geometrical structure of these Bi monolayers on Cu(1 1 1), it can be expected that both in-plane and out-of-plane potential gradients play an important role for the Rashba-type spin-structure in these systems. Our spin-resolved data of spin-split states in Bi/Cu(1 1 1) confirm the expected Rashba behavior of the in-plane spin-components that is caused by the out-of-plane potential gradient. But in addition, we indeed find out-of-plane spin components with different magnitudes in both monolayer Bi/Cu(1 1 1) systems, which we therefore attribute to the structurally induced in-plane potential gradients.

  8. On the rich eight branch spectrum of the oblique propagating longitudinal waves in partially spin polarized electron-positron-ion plasmas

    CERN Document Server

    Andreev, Pavel A

    2016-01-01

    We consider the separate spin evolution of electrons and positrons in electron-positron and electron-positron-ion plasmas. We consider oblique propagating longitudinal waves in this systems. We report presence of the spin-electron acoustic waves and their dispersion dependencies. In electron-positron plasmas, similarly to the electron-ion plasmas, we find one spin-electron acoustic wave (SEAW) at propagation parallel or perpendicular to the external field and two spin-electron acoustic waves at the oblique propagation. At the parallel or perpendicular propagation of the longitudinal waves in electron-positron-ion plasmas we find four branches: the Langmuir wave, the positron-acoustic wave and pair of waves having spin nature, they are the SEAW and, as we called it, spin-electron-positron acoustic wave (SEPAW). At the oblique propagation we find eight longitudinal waves: the Langmuir wave, Trivelpiece-Gould wave, pair of positron-acoustic waves, pair of SEAWs, and pair of SEPAWs. Thus, for the first time, we r...

  9. High-Precision Calibration of Electron Beam Energy from the Hefei Light Source Using Spin Resonant Depolarization

    Science.gov (United States)

    Lan, Jie-Qin; Xu, Hong-Liang

    2014-12-01

    The electron beam energy at the Hefei Light Source (HLS) in the National Synchrotron Radiation Laboratory is highly precisely calibrated by using the method of spin resonant depolarization for the first time. The spin tune and the beam energy are determined by sweeping the frequency of a radial rf stripline oscillating magnetic field to artificially excite a spin resonance and depolarize the beam. The resonance signal is recognized by observing the sudden change of the Touschek loss counting rate of the beam. The possible systematic errors of the experiment are presented and the accuracy of the calibrated energy is shown to be about 10-4. A series of measurements show that the energy stability of the machine is of the order of 9 × 10-3.

  10. Superoxide Anion Radical Production in the Tardigrade Paramacrobiotus richtersi, the First Electron Paramagnetic Resonance Spin-Trapping Study.

    Science.gov (United States)

    Savic, Aleksandar G; Guidetti, Roberto; Turi, Ana; Pavicevic, Aleksandra; Giovannini, Ilaria; Rebecchi, Lorena; Mojovic, Milos

    2015-01-01

    Anhydrobiosis is an adaptive strategy that allows withstanding almost complete body water loss. It has been developed independently by many organisms belonging to different evolutionary lines, including tardigrades. The loss of water during anhydrobiotic processes leads to oxidative stress. To date, the metabolism of free radicals in tardigrades remained unclear. We present a method for in vivo monitoring of free radical production in tardigrades, based on electron paramagnetic resonance and spin-trap DEPMPO, which provides simultaneous identification of various spin adducts (i.e., different types of free radicals). The spin trap can be easily absorbed in animals, and tardigrades stay alive during the measurements and during 24-h monitoring after the treatment. The results show that hydrated specimens of the tardigrade Paramacrobiotus richtersi produce the pure superoxide anion radical ((•)O2(-)). This is an unexpected result, as all previously examined animals and plants produce both superoxide anion radical and hydroxyl radical ((•)OH) or exclusively hydroxyl radical.

  11. Lagrangian for Frenkel electron and position's non-commutativity due to spin

    CERN Document Server

    Deriglazov, Alexei A

    2014-01-01

    We construct relativistic-invariant spinning-particle Lagrangian without auxiliary variables. Spin is considered as a composed quantity constructed on the base of non-Grassmann vector-like variable. The variational problem guarantees both fixed value of spin and Frenkel condition on spin-tensor. Taking into account the Frenkel condition, we obtain, inevitably, relativistic corrections to the algebra of position variables: their classical brackets became noncommutative, with the "parameter of non-commutativity" proportional to the spin-tensor. This leads to a number of interesting consequences in quantum theory. We construct the relativistic quantum mechanics in canonical formalism (in physical-time parametrization) and in covariant formalism (in arbitrary parametrization). We show how state-vectors and operators of covariant formulation can be used to compute mean values of physical operators of position and spin. This proves relativistic covariance of canonical formalism. Various candidates for position and ...

  12. Gauge field theory approach to spin transport in a 2D electron gas

    Directory of Open Access Journals (Sweden)

    B. Berche

    2009-01-01

    Full Text Available We discuss the Pauli Hamiltonian including the spin-orbit interaction within an U(1×SU(2 gauge theory interpretation, where the gauge symmetry appears to be broken. This interpretation offers new insight into the problem of spin currents in the condensed matter environment, and can be extended to Rashba and Dresselhaus spin-orbit interactions. We present a few outcomes of the present formulation: i it automatically leads to zero spin conductivity, in contrast to predictions of Gauge symmetric treatments, ii a topological quantization condition leading to voltage quantization follows, and iii spin interferometers can be conceived in which, starting from an arbitrary incoming unpolarized spinor, it is always possible to construct a perfect spin filtering condition.

  13. Optical probing of spin dynamics of two-dimensional and bulk electrons in a GaAs/AlGaAs heterojunction system

    Energy Technology Data Exchange (ETDEWEB)

    Rizo, P J; Pugzlys, A; Slachter, A; Denega, S Z; Van Loosdrecht, P H M; Van der Wal, C H [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747AG Groningen (Netherlands); Reuter, D; Wieck, A D, E-mail: c.h.van.der.wal@rug.n [Angewandte Festkoerperphysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

    2010-11-15

    The electron spin dynamics in a GaAs/AlGaAs heterojunction system containing a high-mobility two-dimensional electron gas (2DEG) have been studied in this paper by using pump-probe time-resolved Kerr rotation experiments. Owing to the complex layer structure of this material, the transient Kerr response contains information about electron spins in the 2DEG, an epilayer and the substrate. We analyzed the physics that underlies this Kerr response, and established the conditions under which it is possible to unravel the signatures of the various photo-induced spin populations. This was used to explore how the electron spin dynamics of the various populations depend on the temperature, magnetic field and pump-photon density. The results show that the D'Yakonov-Perel' mechanism for spin dephasing (by spin-orbit fields) plays a prominent role in both the 2DEG and bulk populations over a wide range of temperatures and magnetic fields. Our results are of importance for future studies on the 2DEG in this type of heterojunction system, which offers interesting possibilities for spin manipulation and control of spin relaxation via tunable spin-orbit effects.

  14. The effect of spin magnetization in the damping of electron plasma oscillations

    CERN Document Server

    Moya, Pablo S

    2010-01-01

    The effect of spin of particles in the propagation of plasma waves is studied using a semi-classical kinetic theory for a magnetized plasma. We focus in the simple damping effects for the electrostatic wave modes besides Landau damping. Without taking into account more quantum effects than spin contribution to Vlasov's equation, we show that spin produces a new damping or instability which is proportional to the zeroth order magnetization of the system. This correction depends on the electromagnetic part of the wave which is coupled with the spin vector.

  15. Effects of line defects on spin-dependent electronic transport of zigzag MoS2 nanoribbons

    Directory of Open Access Journals (Sweden)

    Xin-Mei Li

    2016-01-01

    Full Text Available The nonlinear spin-dependent transport properties in zigzag molybdenum-disulfide nanoribbons (ZMNRs with line defects are investigated systematically using nonequilibrium Green’s function method combined with density functional theory. The results show that the line defects can enhance the electronic transfer ability of ZMNRs. The types and locations of the line defects are found critical in determining the spin polarization and the current-voltage (I-V characteristics of the line defected ZMNRs. For the same defect type, the total currents of the ribbons with the line defects in the centers are lager than those on the edges. And for the same location, the total currents of the systems with the sulfur (S line defect are larger than the according systems with the molybdenum (Mo line defect. All the considered systems present magnetism properties. And in the S line defected systems, the spin reversal behaviors can be observed. In both the spin-up and spin-down states of the Mo line defected systems, there are obvious negative differential resistance behaviors. The mechanisms are proposed for these phenomena.

  16. Strontium ruthenate-anatase titanium dioxide heterojunctions from first-principles: Electronic structure, spin, and interface dipoles

    Science.gov (United States)

    Ferdous, Naheed; Ertekin, Elif

    2016-07-01

    The epitaxial integration of functional oxides with wide band gap semiconductors offers the possibility of new material systems for electronics and energy conversion applications. We use first principles to consider an epitaxial interface between the correlated metal oxide SrRuO3 and the wide band gap semiconductor TiO2, and assess energy level alignment, interfacial chemistry, and interfacial dipole formation. Due to the ferromagnetic, half-metallic character of SrRuO3, according to which only one spin is present at the Fermi level, we demonstrate the existence of a spin dependent band alignment across the interface. For two different terminations of SrRuO3, the interface is found to be rectifying with a Schottky barrier of ≈1.3-1.6 eV, in good agreement with experiment. In the minority spin, SrRuO3 exhibits a Schottky barrier alignment with TiO2 and our calculated Schottky barrier height is in excellent agreement with previous experimental measurements. For majority spin carriers, we find that SrRuO3 recovers its exchange splitting gap and bulk-like properties within a few monolayers of the interface. These results demonstrate a possible approach to achieve spin-dependent transport across a heteroepitaxial interface between a functional oxide material and a conventional wide band gap semiconductor.

  17. Effects of line defects on spin-dependent electronic transport of zigzag MoS{sub 2} nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xin-Mei; Yang, Kai-Wei; Zhang, Dan; Ding, Jia-Feng; Xu, Hui, E-mail: xuhui@csu.edu.cn [Institute of Super-microstructure and Ultrafast Process in Advanced Materials & Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083 (China); Long, Meng-Qiu, E-mail: mqlong@csu.edu.cn [Institute of Super-microstructure and Ultrafast Process in Advanced Materials & Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083 (China); Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China); Cui, Li-Ling [Institute of Super-microstructure and Ultrafast Process in Advanced Materials & Hunan Key Laboratory for Super-microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083 (China); School of Science, Hunan University of Technology, Zhuzhou 412007 (China)

    2016-01-15

    The nonlinear spin-dependent transport properties in zigzag molybdenum-disulfide nanoribbons (ZMNRs) with line defects are investigated systematically using nonequilibrium Green’s function method combined with density functional theory. The results show that the line defects can enhance the electronic transfer ability of ZMNRs. The types and locations of the line defects are found critical in determining the spin polarization and the current-voltage (I-V) characteristics of the line defected ZMNRs. For the same defect type, the total currents of the ribbons with the line defects in the centers are lager than those on the edges. And for the same location, the total currents of the systems with the sulfur (S) line defect are larger than the according systems with the molybdenum (Mo) line defect. All the considered systems present magnetism properties. And in the S line defected systems, the spin reversal behaviors can be observed. In both the spin-up and spin-down states of the Mo line defected systems, there are obvious negative differential resistance behaviors. The mechanisms are proposed for these phenomena.

  18. Electron Spin Resonance and optical absorption spectroscopic studies of manganese centers in aluminium lead borate glasses

    Science.gov (United States)

    SivaRamaiah, G.; LakshmanaRao, J.

    2012-12-01

    Electron Spin Resonance (ESR) and optical absorption studies of 5Al2O3 + 75H3BO3 + (20-x)PbO + xMnSO4 (where x = 0.5, 1,1.5 and 2 mol% of MnSO4) glasses at room temperature have been studied. The ESR spectrum of all the glasses exhibits resonance signals with effective isotropic g values at ≈2.0, 3.3 and 4.3. The ESR resonance signal at isotropic g ≈ 2.0 has been attributed to Mn2+ centers in an octahedral symmetry. The ESR resonance signals at isotropic g ≈ 3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn2+ ions. The zero-field splitting parameter (zfs) has been calculated from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits an intense band in the visible region and it has been attributed to 5Eg → 5T2g transition of Mn3+centers in an octahedral environment. The optical band gap and the Urbach energies have been calculated from the ultraviolet absorption edges.

  19. Identification and dosimetric features of γ-irradiated cefadroxil by electron spin resonance

    Science.gov (United States)

    Aydaş, Canan; Polat, Mustafa; Korkmaz, Mustafa

    2008-01-01

    In the present work, electron spin resonance (ESR) identification of γ-irradiated cefadroxil monohydrate (CM), duricef capsule (DC) and duricef suspension (DS) and their potential use as normal and/or accidental dosimetric materials were investigated in the dose range of 1-25 kGy. Although unirradiated samples did not exhibit any ESR signals, irradiated samples were observed to present ESR spectra with many resonance lines originating from radiation induced radical or radicals. Dose-response curves associated with the resonance peak heights of CM ( I1, I2) and DS ( I3, I4, I5, I6) were found to follow linear and power functions of applied radiation dose, respectively. Simulation calculations were performed to determine the structure and spectral parameters of the radiation-induced radicalic species involved in the formation of experimental ESR spectrum of CM using, as input, the room temperature signal intensity data obtained for a sample irradiated at dose of 10 kGy. Kinetic behaviors and activation energies of the radicalic species were also calculated using the data obtained from annealing studies performed at five different temperatures. The presence of detectable signal intensities even after a storage period of 100 days was considered as providing an opportunity in the discrimination of irradiated CM and DS from unirradiated ones. Basing on room temperature signal intensity decay and dose-response data, it was concluded that CM and DS present the features of a good dosimetric material.

  20. Identification of irradiated wheat by germination test, DNA comet assay and electron spin resonance

    Science.gov (United States)

    Barros, Adilson C.; Freund, Maria Teresa L.; Villavicencio, Ana Lúcia C. H.; Delincée, Henry; Arthur, Valter

    2002-03-01

    In several countries, there has been an increase in the use of radiation for food processing thus improving the quality and sanitary conditions, inhibiting pathogenic microorganisms, delaying the natural aging process and so extending product lifetime. The need to develop analytical methods to detect these irradiated products is also increasing. The goal of this research was to identify wheat irradiated using different radiation doses. Seeds were irradiated with a gamma 60Co source (Gammacell 220 GC) in the Centro de Energia Nuclear na Agricultura and the Instituto de Pesquisas Energéticas e Nucleares. Dose rate used were 1.6 and 5.8kGy/h. Applied doses were 0.0, 0.10, 0.25, 0.50, 0.75, 1.0, and 2.0kGy. After irradiation, seeds were analysed over a 6 month period. Three different detection methods were employed to determine how irradiation had modified the samples. Screening methods consisted of a germination test measuring the inhibition of shooting and rooting and analysis of DNA fragmentation. The method of electron spin resonance spectroscopy allowed a better dosimetric evaluation. These techniques make the identification of irradiated wheat with different doses possible.

  1. Characterization of molecular mobility in seed tissues: an electron paramagnetic resonance spin probe study.

    Science.gov (United States)

    Buitink, J; Hemminga, M A; Hoekstra, F A

    1999-06-01

    The relationship between molecular mobility (tauR) of the polar spin probe 3-carboxy-proxyl and water content and temperature was established in pea axes by electron paramagnetic resonance (EPR) and saturation transfer EPR. At room temperature, tauR increased during drying from 10(-11) s at 2.0 g water/g dry weight to 10(-4) s in the dry state. At water contents below 0.07 g water/g dry weight, tauR remained constant upon further drying. At the glass transition temperature, tauR was constant at approximately 10(-4) s for all water contents studied. Above Tg, isomobility lines were found that were approximately parallel to the Tg curve. The temperature dependence of tauR at all water contents studied followed Arrhenius behavior, with a break at Tg. Above Tg the activation energy for rotational motion was approximately 25 kJ/mol compared to 10 kJ/mol below Tg. The temperature dependence of tauR could also be described by the WLF equation, using constants deviating considerably from the universal constants. The temperature effect on tauR above Tg was much smaller in pea axes, as found previously for sugar and polymer glasses. Thus, although glasses are present in seeds, the melting of the glass by raising the temperature will cause only a moderate increase in molecular mobility in the cytoplasm as compared to a huge increase in amorphous sugars.

  2. Protection of dehydrated chicken meat by natural antioxidants as evaluated by electron spin resonance spectrometry.

    Science.gov (United States)

    Nissen, L R; Månsson, L; Bertelsen, G; Huynh-Ba, T; Skibsted, L H

    2000-11-01

    Dehydrated chicken meat (a(w) = 0.20-0.35) made from mechanically deboned chicken necks can be protected against oxidative deterioration during storage by rosemary extract (at a sensory acceptable level of 1000 ppm, incorporated prior to drying). The efficiency of the rosemary extract was similar to that obtained by synthetic antioxidants in a reference product (70 ppm butylated hydroxyanisole and 70 ppm octyl gallate). Tea extract and coffee extract were less efficient than rosemary and synthetic antioxidants. Among the natural antioxidants tested, grape skin extract provided the least protection against oxidative changes in dehydrated chicken meat. Radicals in the product, quantified by direct measurement by electron spin resonance (ESR) spectrometry, developed similarly to headspace ethane, pentane, and hexanal, and to oxygen depletion both in unprotected and protected products. The ESR signal intensity and headspace hexanal both correlated with the sensory descriptor "rancidity" as evaluated by a trained sensory panel. Hexanal, as a secondary lipid oxidation product, showed an exponential dependence on the level of radicals in the product in agreement with a chain reaction mechanism for autoxidation, and direct ESR measurement may be used in quality control of dehydrated food products.

  3. Magnetic phase transitions in ferrite nanoparticles characterized by electron spin resonance

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Arias, Yesica, E-mail: yeika01@hotmail.com; Vázquez-Victorio, Gabriela; Ortega-Zempoalteca, Raul; Acevedo-Salas, Ulises; Valenzuela, Raul [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Ammar, Souad [Laboratoires ITODYS, Université de Paris-Diderot, PRES Sorbonne Paris Cité, CNRS-UMR 7086, 75205 Paris Cedex (France)

    2015-05-07

    Ferrite magnetic nanoparticles in the composition Zn{sub 0.7}Ni{sub 0.3}Fe{sub 2}O{sub 4} were synthesized by the polyol method, with an average size of 8 nm. Electron spin resonance (ESR) measurements were carried out at a frequency of 9.45 GHz in the 100–500 K temperature range. Obtained results exhibited a characteristic ESR signal in terms of resonance field, H{sub res}, linewidth, ΔH, and peak ratio, R, for each magnetic phase. At low temperatures, the ferrimagnetic phase showed low H{sub res}, broad ΔH, and asymmetric R. At high temperatures, these parameters exhibited opposite values: high H{sub res}, small ΔH, and R ∼ 1. For intermediate temperatures, a different phase was observed, which was identified as a superparamagnetic phase by means of zero-field cooling-field cooling and hysteresis loops measurements. The observed differences were explained in terms of the internal fields and especially due to the cubic anisotropy in the ordered phase.

  4. Comparison of defects in crystalline oxide semiconductor materials by electron spin resonance

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, Tokiyoshi, E-mail: toki@rins.ryukoku.ac.jp; Kimura, Mutsumi [Department of Electronics and Informatics, Faculty of Science and Technology, Ryukoku University, 1-438, 1-5 Yokotani, Seta Oe-Cho, Otsu, Shiga 520-2194, Japan and Joint Research Center for Science and Technology, Ryukoku University, 1-5 Yokotani, Seta Oe-Cho, Otsu, Shiga 520-2194 (Japan)

    2015-03-15

    Defects in crystalline InGaZnO{sub 4} (IGZO) induced by plasma were investigated using electron spin resonance (ESR). Thermal stabilities and g factors of two ESR signals (A and B observed at g = 1.939 and 2.003, respectively) in IGZO were different from those of the ESR signals observed in component materials such as Ga{sub 2}O{sub 3} (signal observed at g = 1.969), In{sub 2}O{sub 3} (no signal), and ZnO (signal observed at g = 1.957). Signal A in IGZO increased upon annealing at 300 °C for 1 h, but decreased when annealing was continued for more than 2 h. On the other hand, signal B decreased upon annealing at 300 °C for 1 h. The ESR signal in ZnO decayed in accordance with a second-order decay model with a rate constant of 2.1 × 10{sup −4} s{sup −1}; however, this phenomenon was not observed in other materials. This difference might have been due to randomly formed IGZO lattices such as asymmetrical (Ga, Zn)O and In-O layers. Defects in signals A and B in IGZO were formed in trap states (at the deep level) and tail states, respectively.

  5. Electron spin resonance and thermoluminescence in powder form of clear fused quartz: effects of grinding

    CERN Document Server

    Ranjbar, A H; Randle, K

    1999-01-01

    Clear fused quartz (CFQ) tubes were powdered either manually by using a mortar and pestle (for coarse production) or mechanically, using a micronising mill (for fine production). A high and multisignal electron spin resonance (ESR) background was found in the fine powder even after annealing it at 900 deg. C for 20 min. In the case of the coarse powder, the signal (ESR background) varied inversely with particle size and was quite high for particle sizes lower than 38 mu m. In a subsidiary experiment, using fine SiO sub 2 powder (99.8% pure, with the particle size of approx 0.007 mu m), manufactured by using flame hydrolysis, only a weak background signal was found. The sup 6 sup 0 Co gamma-ray irradiated powders (approx 22 Gy) were subjected to ESR analysis or thermoluminescence (TL) readout. The ESR intensity of the coarse powder varied directly with particle size. Thus, the intensity for a particle size of 20-38 mu m was very low and almost the same as the unirradiated intensity. In TL readout the results w...

  6. Identification of. gamma. -irradiated spices by electron spin resonance (ESR) spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Uchiyama, Sadao; Kawamura, Yoko; Saito, Yukio (National Inst. of Hygienic Sciences, Tokyo (Japan))

    1990-12-01

    The electron spin resonance (ESR) spectrometry spectra of white (WP), black (BP) and red (Capsicum annuum L. var. frutescerns L., RP) peppers each had a principal signal with a g-value of 2.0043, and the intensities of the principal signals were increased not only by {gamma}-irradiation but also by heating. Irradiated RP also showed a minor signal -30G from the principal one, and the intensity of the minor signal increased linearly with increasing dose from 10 to 50 kGy. Since the minor signal was observed in RP irradiated at 10 kGy and stored for one year, but did not appear either after heating or after exposure to this signal is unique to {gamma}-irradiated RP and should therefore be useful for the identification of {gamma}-irradiated spices of Capsicum genus, such as paprika and chili pepper. The computer simulation of the ESR spectra suggested that the minor signal should be assigned to methyl radical and the principal signal mainly to a combination of phenoxyl and peroxyl radicals. Such minor signals were found in {gamma}-irradiated allspice and cinnamon among 10 kinds of other spices. (author).

  7. Investigation of radiosterilization of Benzydamine Hydrochloride by electron spin resonance spectroscopy

    Science.gov (United States)

    Çolak, Şeyda

    2016-10-01

    The use of ionizing radiation for sterilization of pharmaceuticals is an attractive and growing technology. In the present work, the spectroscopic and kinetic features of the radicals induced in gamma irradiated solid Benzydamine Hydrochloride (BH) sample is investigated in the dose range of 3-34 kGy at different temperatures using Electron Spin Resonance (ESR) spectroscopy. Gamma irradiated BH indicated eight resonance peaks centered at g=2.0029 originating from two different radical species. Decay activation energy of the radical mostly responsible from central intense resonance line was calculated to be 25.6±1.5 kJ/mol by using the signal intensity decay data derived from annealing studies performed at high temperatures. A linear function of the applied dose was found to describe best the experimental dose-response data. However, the discrimination of irradiated BH from unirradiated one was possible even 3 months after storage at normal conditions. Basing on these findings it was concluded that BH and BH containing drugs could be safely sterilized by gamma radiation and that ESR spectroscopy could be successfully used as a potential technique for monitoring their radiosterilizations.

  8. Electron spin resonance. Part two: a diagnostic method in the environmental sciences.

    Science.gov (United States)

    Rhodes, Christopher J

    2011-01-01

    A review is presented of some of the ways in which electron spin resonance (ESR) spectroscopy may be useful to investigate systems of relevance to the environmental sciences. Specifically considered are: quantititave ESR, photocatalysis for pollution control; sorption and mobility of molecules in zeolites; free radicals produced by mechanical action and by shock waves from explosives; measurement of peroxyl radicals and nitrate radicals in air; determination of particulate matter polyaromatic hydrocarbons (PAH), soot and black carbon in air; estimation of nitrate and nitrite in vegetables and fruit; lipid-peroxidation by solid particles (silica, asbestos, coal dust); ESR of soils and other biogenic substances: formation of soil organic matter carbon capture and sequestration (CCS) and no-till farming; detection of reactive oxygen species in the photosynthetic apparatus of higher plants under light stress; molecular mobility and intracellular glasses in seeds and pollen; molecular mobility in dry cotton; characterisation of the surface of carbon black used for chromatography; ESR dating for archaeology and determining seawater levels; measurement of the quality of tea-leaves by ESR; green-catalysts and catalytic media; studies of petroleum (crude oil); fuels; methane hydrate; fuel cells; photovoltaics; source rocks; kerogen; carbonaceous chondrites to find an ESR-based marker for extraterrestrial origin; samples from the Moon taken on the Apollo 11 and Apollo 12 missions to understand space-weathering; ESR studies of organic matter in regard to oil and gas formation in the North Sea; solvation by ionic liquids as green solvents, ESR in food and nutraceutical research.

  9. Ternary complexes of albumin-Mn(II)-bilirubin and Electron Spin Resonance studies of gallstones

    CERN Document Server

    Chikvaidze, E N; Kirikashvili, I N; Mamniashvili, G I

    2009-01-01

    The stability of albumin-bilirubin complex was investigated depending on pH of solution. It was shown that the stability of complex increases in presence of Mn(II) ions. It was also investigated the paramagnetic composition of gallstones by the electron spin resonance (ESR) method. It turned out that all investigated gallstones contain a free bilirubin radical-the stable product of its radical oxidation. Accordingly the paramagnetic composition gallstones could be divided on three main types: cholesterol, brown pigment and black pigment stones. ESR spectra of cholesterol stones is singlet with g=2.003 and splitting between components 1.0 mT. At the same time the brown gallstones, besides aforementioned signal contain the ESR spectrum which is characteristics for Mn(II) ion complexes with inorganic compounds and, finally, in the black pigment stones it was found out Fe(III) and Cu(II) complexes with organic compounds and a singlet of bilirubin free radical. It is supposed that crystallization centers of gallst...

  10. Development of inhomogeneous conduction electron spin polarization in the antiferroquadrupolar phase of UPd{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Schenck, A.; Gygax, F.N. [Institute for Particle Physics of ETH Zuerich, Villigen (Switzerland); McEwen, K.A. [Department of Physics and Astronomy, University College London, London (United Kingdom)

    2002-05-06

    We have measured the Knight shift and inhomogeneous line broadening of positive muons implanted in monocrystalline UPd{sub 3} from 2 K up to 300 K. We find two components in the transverse-field (H{sub ext}=0.6 T) precession signal with amplitude ratio 2:1, which is independent of temperature up to 300 K. The two signals are associated with two different muon sites with axial symmetry. Both the Knight shifts and the relaxation rates show pronounced anomalies at the critical temperatures of T{sub 2}{approx_equal}4.4 K, believed to reflect, inter alia, a magnetic transition, T{sub 1}{approx_equal}6.8 K and T{sub 0}{approx_equal}7.6 K, originating from antiferroquadrupolar ordering. Details depend on sample orientation and signal component. It is argued that the particular temperature dependence of both the Knight shift and the inhomogeneous line broadening of the stronger component below 10 K is associated with the contact hyperfine contribution to the Knight shift and reflects an inhomogeneous conduction electron spin polarization caused by the antiferroquadrupolar order. Additional zero-field {mu}SR measurements yield a very small temperature-independent relaxation rate consistent with the field inhomogeneity arising from the Pd nuclear dipole fields. In particular, below 4.5 K there is no evidence for additional static fields due to a magnetically ordered state. (author)

  11. Optimization of a solid-state electron spin qubit using gate set tomography

    Science.gov (United States)

    Dehollain, Juan P.; Muhonen, Juha T.; Blume-Kohout, Robin; Rudinger, Kenneth M.; King Gamble, John; Nielsen, Erik; Laucht, Arne; Simmons, Stephanie; Kalra, Rachpon; Dzurak, Andrew S.; Morello, Andrea

    2016-10-01

    State of the art qubit systems are reaching the gate fidelities required for scalable quantum computation architectures. Further improvements in the fidelity of quantum gates demands characterization and benchmarking protocols that are efficient, reliable and extremely accurate. Ideally, a benchmarking protocol should also provide information on how to rectify residual errors. Gate set tomography (GST) is one such protocol designed to give detailed characterization of as-built qubits. We implemented GST on a high-fidelity electron-spin qubit confined by a single 31P atom in 28Si. The results reveal systematic errors that a randomized benchmarking analysis could measure but not identify, whereas GST indicated the need for improved calibration of the length of the control pulses. After introducing this modification, we measured a new benchmark average gate fidelity of 99.942(8) % , an improvement on the previous value of 99.90(2) % . Furthermore, GST revealed high levels of non-Markovian noise in the system, which will need to be understood and addressed when the qubit is used within a fault-tolerant quantum computation scheme.

  12. Beam-target double spin asymmetry in quasi-elastic electron scattering off the deuteron with CLAS

    CERN Document Server

    Mayer, Michael

    2016-01-01

    Quasi-elastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. The experimental data presented here can be used to test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on spin-momentum correlations in the deuteron ground state (due to the D-state admixture) and on the limits of the Impulse Approximation (IA) picture as it applies to measurements of spin-dependent observables like spin structure functions for bound nucleons. We measured the beam-target double spin asymmetry for quasi-elastic electron scattering off the deuteron at several beam energies using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The deuterons were polarized along (or opposite to) the beam direction. ...

  13. Raman electron spin-lattice relaxation with the Debye-type and with real phonon spectra in crystals.

    Science.gov (United States)

    Hoffmann, Stanislaw K; Lijewski, Stefan

    2013-02-01

    Electron spin-lattice relaxation temperature dependence was measured for Ti(2+) (S=1) and for Cu(2+) (S=1/2) ions in SrF(2) single crystal by electron spin echo method in temperature range 4-109K. The spin relaxation was governed by the two-phonon Raman processes. The relaxation theory is outlined and presented in a form suitable for applying with real phonon spectra. The experimental relaxation results were described using Debye-type phonon spectrum and the real phonon spectrum of SrF(2) crystal. The Debye approximation does not fit well the results for SrF(2) both at low and at high temperature. The relaxation rate is faster than that predicted by Debye-type phonon spectrum at low temperatures where excess of lattice vibrations over the Debye model exists but is slower at higher temperatures (above 50K) where density of phonon states continuously decreases when approaching to the maximal acoustic phonon frequency. The expected deviation from Debye approximation was analyzed also for Cu(2+) in NaCl and MgSiO(3) crystals for which phonon spectra are available. The fitting with the real phonon spectrum allowed us to calculate spin-phonon coupling parameter as 267 cm(-1) for Ti(2+) and 1285 cm(-1) for Cu(2+) in SrF(2).

  14. Experimental implementation of optimal phase-covariant quantum cloning machine with a single electron spin in diamond at room temperature

    CERN Document Server

    Pan, Xin-Yu; Yang, Li-Li; Fan, Heng

    2010-01-01

    Here we report an experimental realization of optimal phase-covariant quantum cloning machine with a single electron spin in solid state system at room temperature. The involved three states of two logic qubits are encoded physically in three levels of a single electron spin with two Zeeman sub-levels at a nitrogen-vacancy defect center in diamond. The preparation of input state and the phase-covariant quantum cloning transformation are controlled by two independent microwave fields. The center can be optically spin-polarized and the output state can be measured by combining confocal microscopy technique with spin-selective rates of fluorescence. The measured intensities of fluorescence of the output state are fitted in data of Rabi oscillations to find the exact form of the output. We provide the first solid-state proof-of-concept demonstration of the optimal phase-covariant quantum cloning. The combination of two microwave fields provides a technique to precisely control and measure a three-level superposed...

  15. A solid state paramagnetic maser device driven by electron spin injection

    NARCIS (Netherlands)

    Watts, S. M.; van Wees, B. J.

    2006-01-01

    In response to an external, microwave-frequency magnetic field, a paramagnetic medium will absorb energy from the field that drives the magnetization dynamics. Here we describe a new process by which an external spin-injection source, when combined with the microwave field spin pumping, can drive th

  16. Direct Microscopic Study of Doubly Polarized Atomic-Hydrogen by Electron-Spin Resonance

    NARCIS (Netherlands)

    van Yperen, G.H.; Silvera, I.F.; Walraven, J.T.M.; Berkhout, J.; Brisson, J.G.

    1983-01-01

    By means of ESR in a high magnetic field the hyperfine states of a gas of spin-polarized atomic hydrogen are directly probed. This allows a direct determination of the spin-state populations and nuclear polarization. The unusual ESR line shape is attributed to field inhomogeneities. The temperature

  17. Ultrafast electron, lattice and spin dynamics on rare earth metal surfaces. Investigated with linear and nonlinear optical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Radu, I.E.

    2006-03-15

    This thesis presents the femtosecond laser-induced electron, lattice and spin dynamics on two representative rare-earth systems: The ferromagnetic gadolinium Gd(0001) and the paramagnetic yttrium Y(0001) metals. The employed investigation tools are the time-resolved linear reflectivity and second-harmonic generation, which provide complementary information about the bulk and surface/interface dynamics, respectively. The femtosecond laser excitation of the exchange-split surface state of Gd(0001) triggers simultaneously the coherent vibrational dynamics of the lattice and spin subsystems in the surface region at a frequency of 3 THz. The coherent optical phonon corresponds to the vibration of the topmost atomic layer against the underlying bulk along the normal direction to the surface. The coupling mechanism between phonons and magnons is attributed to the modulation of the exchange interaction J between neighbour atoms due to the coherent lattice vibration. This leads to an oscillatory motion of the magnetic moments having the same frequency as the lattice vibration. Thus these results reveal a new type of phonon-magnon coupling mediated by the modulation of the exchange interaction and not by the conventional spin-orbit interaction. Moreover, we show that coherent spin dynamics in the THz frequency domain is achievable, which is at least one order of magnitude faster than previously reported. The laser-induced (de)magnetization dynamics of the ferromagnetic Gd(0001) thin films have been studied. Upon photo-excitation, the nonlinear magneto-optics measurements performed in this work show a sudden drop in the spin polarization of the surface state by more than 50% in a <100 fs time interval. Under comparable experimental conditions, the time-resolved photoemission studies reveal a constant exchange splitting of the surface state. The ultrafast decrease of spin polarization can be explained by the quasi-elastic spin-flip scattering of the hot electrons among spin

  18. THE ROTATION BARRIER OF ELECTRON SPIN PROBE IN THE STUDY OF POLYMER SYSTEM

    Institute of Scientific and Technical Information of China (English)

    YU Tongyin; GUO Shiqing; GE Mingtao

    1984-01-01

    In the study of molecular motion of polymer by means of ESR in combination with spin probe,owing to that the ESR spectrum depicts only the behavior of spin probe, the information obtained is of indirect nature. Hence the relationship between them must first be investigated before any conclusion could be drawn. In this paper, two parameters TR and CR are introduced to characterize the changing of tumbling rate of spin probe, and the concept of rotation barrier of spin probe is proposed. It is considered that the magnitude of the rotation barrier is determined by the internal cavity size and distribution in polymer. When the temperature is raised, the size and distribution of the cavities change accordingly, thus the tumbling of spin probe changes gradually from a slower to a higher rate.

  19. A Hückel source-sink-potential theory of Pauli spin blockade in molecular electronic devices

    Science.gov (United States)

    Pickup, Barry T.; Fowler, Patrick W.; Sciriha, Irene

    2016-11-01

    This paper shows how to include Pauli (exclusion principle) effects within a treatment of ballistic molecular conduction that uses the tight-binding Hückel Hamiltonian and the source-sink-potential (SSP) method. We take into account the many-electron ground-state of the molecule and show that we can discuss ballistic conduction for a specific molecular device in terms of four structural polynomials. In the standard one-electron picture, these are characteristic polynomials of vertex-deleted graphs, with spectral representations in terms of molecular-orbital eigenvectors and eigenvalues. In a more realistic many-electron picture, the spectral representation of each polynomial is retained but projected into the manifold of unoccupied spin-orbitals. Crucially, this projection preserves interlacing properties. With this simple reformulation, selection rules for device transmission, expressions for overall transmission, and partition of transmission into bond currents can all be mapped onto the formalism previously developed. Inclusion of Pauli spin blockade, in the absence of external perturbations, has a generic effect (suppression of transmission at energies below the Fermi level) and specific effects at anti-bonding energies, which can be understood using our previous classification of inert and active shells. The theory predicts the intriguing phenomenon of Pauli perfect reflection whereby, once a critical electron count is reached, some electronic states of devices can give total reflection of electrons at all energies.

  20. Electron spin resonance studies on intact cells and isolated lipid droplets from fatty acid-modified L1210 murine leukemia.

    Science.gov (United States)

    Simon, I; Burns, C P; Spector, A A

    1982-07-01

    It has been suggested that the formation of cytoplasmic lipid droplets may produce an artifact and be responsible for the differences in membrane physical properties detected in lipid-modified cells using fluorescence polarization or spin label probes. To investigate this, the electron spin resonance spectra of lipid droplets isolated from the cytoplasm of L1210 leukemia cells were compared with spectra obtained from the intact cell. Mice bearing the L1210 leukemia were fed diets containing either 16% sunflower oil or 16% coconut oil in order to modify the fatty acid composition of the tumor. A microsome-rich fraction prepared from L1210 cells grown in animals fed the sunflower oil-rich diet contained more polyenoic fatty acids (52 versus 29%), while microsomes from L1210 cells grown in animals fed the coconut oil-rich diets contained more monoenoic fatty acids (37 versus 12%). The order parameter calculated for lipid droplets labeled with the 5-nitroxystearic acid spin probe was only about one-half that of intact cells, whereas it was similar to that obtained for pure triolein droplets suspended in buffer. Order parameters of the inner hyperfine splittings calculated from the spectra of cells grown in the sunflower oil-fed animals [0.543 +/- 0.001 (S.E.)] were lower than those from the cells grown in animals fed the coconut oil diets (0.555 +/- 0.002) (p less than 0.005). In contrast, the order parameters of the lipid droplets isolated from the cells grown in animals fed sunflower oil (0.303 +/- 0.029) or coconut oil (0.295 +/- 0.021) were not significantly different, indicating that motion of a spin label probe in the highly fluid cytoplasmic lipid droplets is not affected by these types of modifications in cellular fatty acid composition. Therefore, the electron spin resonance changes that are observed in the intact cells cannot be due to localization of the probe in cytoplasmic lipid droplets. These results support the conclusion that the electron spin