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Sample records for pulse electron spin

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  3. Gradient ascent pulse engineering approach to CNOT gates in donor electron spin quantum computing

    SciTech Connect

    Tsai, D.-B.; Goan, H.-S.

    2008-11-07

    In this paper, we demonstrate how gradient ascent pulse engineering (GRAPE) optimal control methods can be implemented on donor electron spin qubits in semiconductors with an architecture complementary to the original Kane's proposal. We focus on the high fidelity controlled-NOT (CNOT) gate and we explicitly find the digitized control sequences for a controlled-NOT gate by optimizing its fidelity using the effective, reduced donor electron spin Hamiltonian with external controls over the hyperfine A and exchange J interactions. We then simulate the CNOT-gate sequence with the full spin Hamiltonian and find that it has an error of 10{sup -6} that is below the error threshold of 10{sup -4} required for fault-tolerant quantum computation. Also the CNOT gate operation time of 100 ns is 3 times faster than 297 ns of the proposed global control scheme.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Membrane-Sugar Interactions Probed by Pulsed Electron Paramagnetic Resonance of Spin Labels.

    PubMed

    Konov, Konstantin B; Leonov, Dmitry V; Isaev, Nikolay P; Fedotov, Kirill Yu; Voronkova, Violeta K; Dzuba, Sergei A

    2015-08-13

    Sugars can stabilize biological systems under extreme desiccation and freezing conditions. Hypothetical molecular mechanisms suggest that the stabilization effect may be determined either by specific interactions of sugars with biological molecules or by the influence of sugars on the solvating shell of the biomolecule. To explore membrane-sugar interactions, we applied electron spin echo envelope modulation (ESEEM) spectroscopy, a pulsed version of electron paramagnetic resonance (EPR), to phospholipid bilayers with spin-labeled lipids added and solvated by aqueous deuterated sucrose and trehalose solutions. The phospholipids were 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The spin-labeled lipids were 1,2-dipalmitoyl-sn-glycero-3-phospho(TEMPO)choline (T-PCSL), with spin-label TEMPO at the lipid polar headgroup. The deuterium ESEEM amplitude was calibrated using known concentrations of glassy deuterated sugar solvents. The data obtained indicated that the sugar concentration near the membrane surface obeyed a simple Langmuir model of monolayer adsorption, which assumes direct sugar-molecule bonding to the bilayer surface.

  6. Optical Pulse Control of Electron and Nuclear Spins in Quantum Dots

    DTIC Science & Technology

    2009-01-01

    2 T. Kennedy,1 A. Bracker,1 and T. Reinecke1 1Electronics Science and Technology Division 2George Mason University Introduction: Quantum information...decryption of codes with long encryption keys. Electron spins in quantum dots (QDs) are being widely investigated as qubits for storage and processing...field quantum dot la se r pu ls es z x y nuclear spins electron spin + nuclear spin field Sx El lip tic ity ( ra d) Delay time (ps) tim e Sy

  7. Reaction between ortho-semiquinones and oxygen: pulse radiolysis, electron spin resonance, and oxygen uptake studies.

    PubMed

    Kalyanaraman, B; Korytowski, W; Pilas, B; Sarna, T; Land, E J; Truscott, T G

    1988-10-01

    The cytotoxicity to tumor cells or cardiotoxic side effects of certain para-quinone antitumor drugs have been attributed to the corresponding semiquinones and derived superoxide and hydroxyl radicals. It has also been suggested that ortho-semiquinones, including those that arise during melanogenesis, produced via either the one-electron oxidation of catechol(amine)s or the one-electron reduction of the corresponding quinones, react with molecular oxygen to give superoxide and hydrogen peroxide. Furthermore it has been shown that catechol(amine)s which form noncyclizable quinones are more cytotoxic toward melanogenic cells than those forming cyclizable quinones. In order to provide further kinetic information on the interaction of oxygen with ortho-semiquinones, using pulse radiolysis we directly measured the rates of reaction of various ortho-semiquinones with molecular oxygen. The semiquinones of the corresponding catechol(amine)s were also produced by the horseradish peroxidase/hydrogen peroxide system, and detected by electron spin resonance spectroscopy using the spin stabilization method. Oxygen consumption was monitored using a standard Clark oxygen electrode. Our data indicate that while ortho-semiquinones from catechol(amine)s and catechol estrogens do not react with molecular oxygen at a rate equal to or greater than k less than or equal to 10(5) M-1 s-1, semiquinones from hydroxy-substituted catechol(amine)s react with dioxygen with rates in the range k = 10(6)-10(7) M-1 s-1.

  8. Spin Electronics

    DTIC Science & Technology

    2003-08-01

    spectroscopy laboratory including high pulse power capabilities (regenerative amplifiers and optical parametric amplifiers ) and broad spectral range ...The data identify narrow ranges of doping concentrations where spin lifetimes in semiconductors are enhanced by orders of magnitude, culminating in... dynamic measurements in the 10 to 100 picoseconds (ps) range . • A second program, which will come to fruition within one to two years, has the name

  9. Fourier-transform electron spin resonance with bandwidth-compensated chirp pulses

    NASA Astrophysics Data System (ADS)

    Doll, Andrin; Jeschke, Gunnar

    2014-09-01

    Electron spin echo experiments using chirp pulses at X-band around 9 GHz have been performed with a home-built spectrometer based on an arbitrary waveform generator. Primary echoes without phase dispersion were obtained by employing the Böhlen-Bodenhausen scheme with the refocusing pulse being half as long as the coherence-generating pulse. To account for physical bandwidth limitation by the resonator, the instantaneous sweep rate of the chirps was adapted to the spectrometer’s frequency response function, which can be recorded from the sample under study within a few minutes. Such bandwidth-compensated chirp pulses are experimentally shown to achieve an almost uniform excitation bandwidth that exceeds the resonator bandwidth. This uniform excitation allows for computing frequency-domain spectra by Fourier-transformation (FT) of the echo signal. For a nitroxide in dilute solid solution with a spectral width of 200 MHz, the FT EPR spectrum agrees remarkably well with a field-swept echo-detected EPR spectrum. The overall spectral perturbation for operation far beyond the resonator bandwidth was characterized by acquiring a 700 MHz wide spectral range of a copper (II) EPR spectrum with nearly uniform amplitude with excitation and refocusing pulses of 200 and 100 ns, respectively. Furthermore, peculiarities were observed in solid-state FT EPR spectra of disordered systems. To understand these peculiarities two-dimensional data sets were acquired that correlate the FT EPR spectrum to inversion recovery or nuclear modulation. The echo envelope modulation experiments reveal echo decay rates increased by enhanced instantaneous diffusion and passage-specific effects in the nuclear modulations. The latter effect can be suppressed by nuclear modulation averaging. Apparent longitudinal relaxation times for a given subset of orientations are influenced by nuclear modulation effects. Proper extraction of orientation-dependent relaxation times thus requires an experimental

  10. Fourier-transform electron spin resonance with bandwidth-compensated chirp pulses.

    PubMed

    Doll, Andrin; Jeschke, Gunnar

    2014-09-01

    Electron spin echo experiments using chirp pulses at X-band around 9GHz have been performed with a home-built spectrometer based on an arbitrary waveform generator. Primary echoes without phase dispersion were obtained by employing the Böhlen-Bodenhausen scheme with the refocusing pulse being half as long as the coherence-generating pulse. To account for physical bandwidth limitation by the resonator, the instantaneous sweep rate of the chirps was adapted to the spectrometer's frequency response function, which can be recorded from the sample under study within a few minutes. Such bandwidth-compensated chirp pulses are experimentally shown to achieve an almost uniform excitation bandwidth that exceeds the resonator bandwidth. This uniform excitation allows for computing frequency-domain spectra by Fourier-transformation (FT) of the echo signal. For a nitroxide in dilute solid solution with a spectral width of 200MHz, the FT EPR spectrum agrees remarkably well with a field-swept echo-detected EPR spectrum. The overall spectral perturbation for operation far beyond the resonator bandwidth was characterized by acquiring a 700MHz wide spectral range of a copper (II) EPR spectrum with nearly uniform amplitude with excitation and refocusing pulses of 200 and 100ns, respectively. Furthermore, peculiarities were observed in solid-state FT EPR spectra of disordered systems. To understand these peculiarities two-dimensional data sets were acquired that correlate the FT EPR spectrum to inversion recovery or nuclear modulation. The echo envelope modulation experiments reveal echo decay rates increased by enhanced instantaneous diffusion and passage-specific effects in the nuclear modulations. The latter effect can be suppressed by nuclear modulation averaging. Apparent longitudinal relaxation times for a given subset of orientations are influenced by nuclear modulation effects. Proper extraction of orientation-dependent relaxation times thus requires an experimental setup

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

    PubMed

    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.

  12. Effects of finite pulse width on two-dimensional Fourier transform electron spin resonance

    NASA Astrophysics Data System (ADS)

    Liang, Zhichun; Crepeau, Richard H.; Freed, Jack H.

    2005-12-01

    Two-dimensional (2D) Fourier transform ESR techniques, such as 2D-ELDOR, have considerably improved the resolution of ESR in studies of molecular dynamics in complex fluids such as liquid crystals and membrane vesicles and in spin labeled polymers and peptides. A well-developed theory based on the stochastic Liouville equation (SLE) has been successfully employed to analyze these experiments. However, one fundamental assumption has been utilized to simplify the complex analysis, viz. the pulses have been treated as ideal non-selective ones, which therefore provide uniform irradiation of the whole spectrum. In actual experiments, the pulses are of finite width causing deviations from the theoretical predictions, a problem that is exacerbated by experiments performed at higher frequencies. In the present paper we provide a method to deal with the full SLE including the explicit role of the molecular dynamics, the spin Hamiltonian and the radiation field during the pulse. The computations are rendered more manageable by utilizing the Trotter formula, which is adapted to handle this SLE in what we call a "Split Super-Operator" method. Examples are given for different motional regimes, which show how 2D-ELDOR spectra are affected by the finite pulse widths. The theory shows good agreement with 2D-ELDOR experiments performed as a function of pulse width.

  13. Spatial arrangement of rhodopsin in retinal rod outer segment membranes studied by spin-labeling and pulsed electron double resonance.

    PubMed

    Yasuda, Satoshi; Hara, Hideyuki; Tokunaga, Fumio; Arata, Toshiaki

    2012-08-24

    We have determined the spatial arrangement of rhodopsin in the retinal rod outer segment (ROS) membrane by measuring the distances between rhodopsin molecules in which native cysteines were spin-labeled at ~1.0 mol/mol rhodopsin. The echo modulation decay of pulsed electron double resonance (PELDOR) from spin-labeled ROS curved slightly with strong background decay. This indicated that the rhodopsin was densely packed in the retina and that the rhodopsin molecules were not aligned well. The curve was simulated by a model in which rhodopsin is distributed randomly as monomers in a planar membrane.

  14. Photoexcitation of electron wave packets in quantum spin Hall edge states: Effects of chiral anomaly from a localized electric pulse

    NASA Astrophysics Data System (ADS)

    Dolcini, Fabrizio; Iotti, Rita Claudia; Montorsi, Arianna; Rossi, Fausto

    2016-10-01

    We show that, when a spatially localized electric pulse is applied at the edge of a quantum spin Hall system, electron wave packets of the helical states can be photoexcited by purely intrabranch electrical transitions, without invoking the bulk states or the magnetic Zeeman coupling. In particular, as long as the electric pulse remains applied, the photoexcited densities lose their character of right and left movers, whereas after the ending of the pulse they propagate in opposite directions without dispersion, i.e., maintaining their space profile unaltered. Notably we find that, while the momentum distribution of the photoexcited wave packets depends on the temperature T and the chemical potential μ of the initial equilibrium state and displays a nonlinear behavior on the amplitude of the applied pulse, in the mesoscopic regime the space profile of the wave packets is independent of T and μ . Instead, it depends purely on the applied electric pulse, in a linear manner, as a signature of the chiral anomaly characterizing massless Dirac electrons. We also discuss how the photoexcited wave packets can be tailored with the electric pulse parameters, for both low and finite frequencies.

  15. Quantum control of electron spins in the two-dimensional electron gas of a CdTe quantum well with a pair of Raman-resonant phase-locked laser pulses

    NASA Astrophysics Data System (ADS)

    Sweeney, Timothy M.; Phelps, Carey; Wang, Hailin

    2011-08-01

    We demonstrated optical spin control of a two-dimensional electron gas in a modulation-doped CdTe quantum well by driving a spin-flip Raman transition with a pair of phase-locked laser pulses. In contrast to single-pulse optical spin control, which features a fixed spin-rotation axis, manipulation of the initial relative phase of the pulse pair enables us to control the axis of the optical spin rotation. We show that the Raman pulse pair acts like an effective microwave field, mapping the relative optical phase onto the phase of the electron spin polarization and making possible ultrafast, all-optical, and full quantum control of the electron spins.

  16. Optically pulsed electron accelerator

    DOEpatents

    Fraser, J.S.; Sheffield, R.L.

    1985-05-20

    An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radiofrequency-powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  17. Optically pulsed electron accelerator

    DOEpatents

    Fraser, John S.; Sheffield, Richard L.

    1987-01-01

    An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radio frequency powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  18. Broadband excitation by chirped pulses: application to single electron spins in diamond

    NASA Astrophysics Data System (ADS)

    Niemeyer, I.; Shim, J. H.; Zhang, J.; Suter, D.; Taniguchi, T.; Teraji, T.; Abe, H.; Onoda, S.; Yamamoto, T.; Ohshima, T.; Isoya, J.; Jelezko, F.

    2013-03-01

    Pulsed excitation of broad spectra requires very high field strengths if monochromatic pulses are used. If the corresponding high power is not available or not desirable, the pulses can be replaced by suitable low-power pulses that distribute the power over a wider bandwidth. As a simple case, we use microwave pulses with a linear frequency chirp. We use these pulses to excite spectra of single nitrogen-vacancy centres in a Ramsey experiment. Compared to the conventional Ramsey experiment, our approach increases the bandwidth by at least an order of magnitude. Compared to the conventional continuous wave-ODMR experiment, the chirped Ramsey experiment does not suffer from power broadening and increases the resolution by at least an order of magnitude. As an additional benefit, the chirped Ramsey spectrum contains not only ‘allowed’ single quantum transitions, but also ‘forbidden’ zero- and double quantum transitions, which can be distinguished from the single quantum transitions by phase-shifting the readout pulse with respect to the excitation pulse or by variation of the external magnetic field strength.

  19. Pulsed electron spin nutation spectroscopy for weakly exchange-coupled multi-spin molecular systems with nuclear hyperfine couplings: a general approach to bi- and triradicals and determination of their spin dipolar and exchange interactions

    NASA Astrophysics Data System (ADS)

    Ayabe, Kazuki; Sato, Kazunobu; Nakazawa, Shigeaki; Nishida, Shinsuke; Sugisaki, Kenji; Ise, Tomoaki; Morita, Yasushi; Toyota, Kazuo; Shiomi, Daisuke; Kitagawa, Masahiro; Suzuki, Shuichi; Okada, Keiji; Takui, Takeji

    2013-10-01

    Weakly exchange-coupled biradicals have attracted much attention in terms of their dynamic nuclear polarisation application in NMR spectroscopy for biological systems or the use of synthetic electron-spin qubits in quantum information processing/quantum-computing technology. Analogues multi-partite molecular systems are important in entering a new phase of the relevant fields. Many stable organic biradicals known so far have nitrogen nuclei at their electron spin sites, where singly occupied molecular orbitals are dominating and large hyperfine couplings occur. A salient feature of such weakly exchange-coupled molecular systems in terms of electronic spin structures is underlain by small zero-field splitting (ZFS) parameters comparable with nuclear hyperfine and/or exchange interactions. Pulse-based electron spin nutation (ESN) spectroscopy of weakly exchange-coupled biradicals, applicable to oriented or non-oriented media, has proven to be a useful and facile approach to the determination of ZFS parameters, which reflect relatively short distances between unpaired electron spins. In the present study, we first treat two-dimensional single-crystal ESN spectroscopy (Q-band) of a 15N-labelled weakly exchange-coupled biradical, showing the nuclear hyperfine effects on the ESN phenomena from both the experimental and theoretical side. ESN spectroscopy is transition moment spectroscopy, in which the nutation frequency as a function of the microwave irradiation strength ω1 (angular frequency) for any cases of weakly exchange-coupled systems can be treated. The results provide a testing ground for the simplified but general approach to the ESN analysis. In this study, we have invoked single-crystal electron-electron double resonance measurements on a typical biradical well incorporated in a diamagnetic host lattice and checked the accuracy of our ESN analysis for the spin dipolar tensor and exchange interaction. Next, we extend the general approach to analogues multi

  20. PREFACE: Spin Electronics

    NASA Astrophysics Data System (ADS)

    Dieny, B.; Sousa, R.; Prejbeanu, L.

    2007-04-01

    Conventional electronics has in the past ignored the spin on the electron, however things began to change in 1988 with the discovery of giant magnetoresistance in metallic thin film stacks which led to the development of a new research area, so called spin-electronics. In the last 10 years, spin-electronics has achieved a number of breakthroughs from the point of view of both basic science and application. Materials research has led to several major discoveries: very large tunnel magnetoresistance effects in tunnel junctions with crystalline barriers due to a new spin-filtering mechanism associated with the spin-dependent symmetry of the electron wave functions new magnetic tunnelling barriers leading to spin-dependent tunnelling barrier heights and acting as spin-filters magnetic semiconductors with increasingly high ordering temperature. New phenomena have been predicted and observed: the possibility of acting on the magnetization of a magnetic nanostructure with a spin-polarized current. This effect, due to a transfer of angular momentum between the spin polarized conduction electrons and the local magnetization, can be viewed as the reciprocal of giant or tunnel magnetoresistance. It can be used to switch the magnetization of a magnetic nanostructure or to generate steady magnetic excitations in the system. the possibility of generating and manipulating spin current without charge current by creating non-equilibrium local accumulation of spin up or spin down electrons. The range of applications of spin electronics materials and phenomena is expanding: the first devices based on giant magnetoresistance were the magnetoresistive read-heads for computer disk drives. These heads, introduced in 1998 with current-in plane spin-valves, have evolved towards low resistance tunnel magnetoresistice heads in 2005. Besides magnetic recording technology, these very sensitive magnetoresistive sensors are finding applications in other areas, in particular in biology. magnetic

  1. Spin diffusion induced by pulsed-laser heating and the role of spin heat accumulation

    NASA Astrophysics Data System (ADS)

    Kimling, Johannes; Cahill, David G.

    2017-01-01

    We present a model for describing spin diffusion in normal-metal/ferromagnetic-metal heterostructures induced by pulsed-laser heating. The model is based on the assumptions that electronic heat currents give rise to the spin-dependent Seebeck effect and that ultrafast demagnetization generates spin accumulation with a rate proportional to the demagnetization rate measured. Spin-diffusion currents are then driven by gradients in spin accumulation and electron temperature. The model considers spin-dependent thermal conductivity and electron-phonon coupling, which can give rise to different effective temperatures for majority and minority spins, known as spin heat accumulation. We find that spin heat accumulation can significantly enhance the spin-dependent Seebeck effect.

  2. Pulsed electron beam precharger

    SciTech Connect

    Finney, W.C.; Shelton, W.N.

    1990-01-01

    Florida State University is investigating the concept of pulsed electron beams for fly ash precipitation. This report describes the results and data on three of the subtasks of this project and preliminary work only on the remaining five subtasks. Described are the modification of precharger for pulsed and DC energization of anode; installation of the Q/A measurement system; and modification and installation of pulsed power supply to provide both pulsed and DC energization of the anode. The other tasks include: measurement of the removal efficiency for monodisperse simulated fly ash particles; measurement of particle charge; optimization of pulse energization schedule for maximum removal efficiency; practical assessment of results; and measurement of the removal efficiency for polydisperse test particles. 15 figs., 1 tab. (CK)

  3. Ultrafast Manipulation of Electron Spin Coherence

    NASA Astrophysics Data System (ADS)

    Gupta, J. A.; Awschalom, D. D.; Knobel, R.; Samarth, N.

    2002-03-01

    A technique is developed with the potential for coherent all-optical control over electron spins in semiconductors on femtosecond time scales.footnote J.A. Gupta et al., Science 292, 2458 (2001) The experiments show that optical “tipping” pulses can enact significant rotations of electron spins through an effective magnetic field generated when the tipping pulse energy is tuned below the semiconductor bandgap (the optical Stark effect). Measurements of Stark shifts in ZnCdSe quantum wells suggest that field strengths of order 20T are achieved. Rotations due to this effective field approaching 90 degrees were measured as changes in the amplitude of spin precession following optical excitation in a transverse magnetic field. A prototype sequence of two tipping pulses indicates that the rotation is reversible, a result that establishes the coherent nature of the tipping process.

  4. Pulsed eldor measurement of nitrogen T1 in spin labels

    NASA Astrophysics Data System (ADS)

    Hyde, James S.; Froncisz, W.; Mottley, C.

    1984-10-01

    A 180° pulse is delivered to one hyperfine line of a nitroxide spin label, and the arrival and disappearance of saturation at another hyperfine line is monitored with a second microwave field. Electron and nitrogen nuclear relaxation times are found to be in poor agreement ,vith the electron-nuclear dipolar (END) mechanism.

  5. Fast electron spin resonance controlled manipulation of spin injection into quantum dots

    SciTech Connect

    Merz, Andreas Siller, Jan; Schittny, Robert; Krämmer, Christoph; Kalt, Heinz; Hetterich, Michael

    2014-06-23

    In our spin-injection light-emitting diodes, electrons are spin-polarized in a semimagnetic ZnMnSe spin aligner and then injected into InGaAs quantum dots. The resulting electron spin state can be read out by measuring the circular polarization state of the emitted light. Here, we resonantly excite the Mn 3d electron spin system with microwave pulses and perform time-resolved measurements of the spin dynamics. We find that we are able to control the spin polarization of the injected electrons on a microsecond timescale. This electron spin resonance induced spin control could be one of the ingredients required to utilize the quantum dot electrons or the Mn spins as qubits.

  6. Electron Spin and Its History

    NASA Astrophysics Data System (ADS)

    Commins, Eugene D.

    2012-11-01

    The history of electron spin is summarized. Topics include the discovery of electron spin, the birth of quantum electrodynamics, the invention of magnetic resonance, the invention of renormalization, the anomalous magnetic moment of the electron in experiment and theory, and searches for the electron electric dipole moment.

  7. Pulsed Electron Spin Resonance Resolves the Coordination Site of Cu2+ Ions in α1-Glycine Receptor

    PubMed Central

    Ruthstein, Sharon; Stone, Katherine M.; Cunningham, Timothy F.; Ji, Ming; Cascio, Michael; Saxena, Sunil

    2010-01-01

    Herein, we identify the coordination environment of Cu2+ in the human α1-glycine receptor (GlyR). GlyRs are members of the pentameric ligand-gated ion channel superfamily (pLGIC) that mediate fast signaling at synapses. Metal ions like Zn2+ and Cu2+ significantly modulate the activity of pLGICs, and metal ion coordination is essential for proper physiological postsynaptic inhibition by GlyR in vivo. Zn2+ can either potentiate or inhibit GlyR activity depending on its concentration, while Cu2+ is inhibitory. To better understand the molecular basis of the inhibitory effect we have used electron spin resonance to directly examine Cu2+ coordination and stoichiometry. We show that Cu2+ has one binding site per α1 subunit, and that five Cu2+ can be coordinated per GlyR. Cu2+ binds to E192 and H215 in each subunit of GlyR with a 40 μM apparent dissociation constant, consistent with earlier functional measurements. However, the coordination site does not include several residues of the agonist/antagonist binding site that were previously suggested to have roles in Cu2+ coordination by functional measurements. Intriguingly, the E192/H215 site has been proposed as the potentiating Zn2+ site. The opposing modulatory actions of these cations at a shared binding site highlight the sensitive allosteric nature of GlyR. PMID:20959090

  8. Generation and coherent control of pure spin currents via terahertz pulses

    NASA Astrophysics Data System (ADS)

    Schüler, Michael; Berakdar, Jamal

    2014-04-01

    We inspect the time and spin-dependent, inelastic tunneling in engineered semiconductor-based double quantum well driven by time-structured terahertz pulses. An essential ingredient is an embedded spin-active structure with vibrational modes that scatter the pulse driven carriers. Due to the different time scales of the charge and spin dynamics, the spin-dependent electron-vibron coupling may result in pure net spin current (with negligible charge current). Heating the vibrational site may affect the resulting spin current. Furthermore, by controlling the charge dynamics, the spin dynamics and the generated spin current can be manipulated and switched on and off coherently.

  9. Electron Spin Density on the N-Donor Atoms of Cu(II)-(Bis)oxamidato Complexes As Probed by a Pulse ELDOR Detected NMR.

    PubMed

    Aliabadi, Azar; Zaripov, Ruslan; Salikhov, Kev; Voronkova, Violeta; Vavilova, Evgeniya; Abdulmalic, Mohammad A; Rüffer, Tobias; Büchner, Bernd; Kataev, Vladislav

    2015-10-29

    We have applied the pulse ELDOR detected NMR (EDNMR) technique to determine the tensors of the transferred Cu (S = 1/2) - (14)N (I = 1) hyperfine (HF) interaction in single crystals of diamagnetically diluted mononuclear o-phenylenebis(N(R)-oxamide) complexes of [(n)Bu4N]2[Cu(opboR2)] (R = Et 1, (n)Pr 2) (1%) in a host lattice of [(n)Bu4N]2[Ni(opboR2)] (R = Et 3, (n)Pr 4) (99%) (1@3 and 2@4)). To facilitate the analysis of our EDNMR data and to analyze possible manifestations of the nuclear quadrupole interaction in the EDNMR spectra, we have treated a model electron-nuclear system of the coupled S = 1/2 and I = 1 spins using the spin density matrix formalism. It appears that this interaction yields a peculiar asymmetry of the EDMR spectra that manifests not only in the shift of the positions of the EDNMR lines that correspond to the forbidden EPR transitions, as expected, but also in the intensities of the EDNMR lines. The symmetric shape of the experimental spectra suggests the conclusion that, in the studied complexes, the quadrupole interaction is negligible. This has simplified the analysis of the spectra. The HF tensors of all four N donor atoms could be accurately determined. On the basis of the HF tensors, an estimate of the spin density transferred from the central paramagnetic Cu(II) ion to the N donor atoms reveals its unequal distribution. We discuss possible implications of our estimates for the magnetic exchange paths and interaction strengths in respective trinuclear complexes [Cu3(opboR2) (pmdta)2](NO3)2 (R = Et 6, (n)Pr 7).

  10. ELECTRONIC PULSE SCALING CIRCUITS

    DOEpatents

    Cooke-Yarborough, E.H.

    1958-11-18

    Electronic pulse scaling circults of the klnd comprlsing a serles of bi- stable elements connected ln sequence, usually in the form of a rlng so as to be cycllcally repetitive at the highest scallng factor, are described. The scaling circuit comprises a ring system of bi-stable elements each arranged on turn-off to cause, a succeeding element of the ring to be turned-on, and one being arranged on turn-off to cause a further element of the ring to be turned-on. In addition, separate means are provided for applying a turn-off pulse to all the elements simultaneously, and for resetting the elements to a starting condition at the end of each cycle.

  11. Pulsed electron beam precharger

    SciTech Connect

    Finney, W.C.; Shelton, W.N.

    1990-01-01

    In this report, a short review of electron beam particle precharging using a pulsed electric field is presented in Section B-1. Section B-2 details the design and installation of a remote focusing gear train which will allow much greater control over the particle charge measurement capability of the charge vs. radius apparatus. Under Section B-3, progress on the electrical shielding of the rotating spark gap power supply using a large Faraday cage is described. Efforts to prevent RFI interference from adversely affecting the Climet particle counter and the MicroMac current measurement device using a variety of techniques are also presented in this section. The basic effort is to optimize the removal efficiency for fly ash particles. 13 figs.

  12. Measuring central-spin interaction with a spin-bath by pulsed ENDOR: Towards suppression of spin diffusion decoherence

    PubMed Central

    Balian, S. J.; Kunze, M. B. A.; Mohammady, M. H.; Morley, G. W.; Witzel, W. M.; Kay, C. W. M.; Monteiro, T. S.

    2012-01-01

    We present pulsed electron-nuclear double resonance (ENDOR) experiments which enable us to characterize the coupling between bismuth donor spin-qubits in Si and the surrounding spin-bath of 29Si impurities which provides the dominant decoherence mechanism (nuclear spin diffusion) at low temperatures (< 16 K). Decoupling from the spin-bath is predicted and cluster correlation expansion simulations show near-complete suppression of spin diffusion, at optimal working points. The suppression takes the form of sharply peaked divergences of the spin diffusion coherence time, in contrast with previously identified broader regions of insensitivity to classical fluctuations. ENDOR data shows anisotropic contributions are comparatively weak, so the form of the divergences is independent of crystal orientation. PMID:23082071

  13. Spin-polarized Auger electrons

    NASA Astrophysics Data System (ADS)

    Merz, H.; Semke, J.

    1990-12-01

    The spin polarization of Auger electrons will be discussed within the standard two-step model of the Auger emission process for different situations: target polarized, projectile polarized, targe and projectile unpolarized. In these three cases different interaction mechanisms are responsible for the polarization of the emitted Auger electrons. The present theoretical and experimental situation will be reviewed.

  14. Stark Tuning of Donor Electron Spins of Silicon

    SciTech Connect

    Bradbury, Forrest R.; Tyryshkin, Alexei M.; Sabouret, Guillaume; Bokor, Jeff; Schenkel, Thomas; Lyon, Stephen A.

    2006-03-23

    We report Stark shift measurements for {sup 121}Sb donor electron spins in silicon using pulsed electron spin resonance. Interdigitated metal gates on top of a Sb-implanted {sup 28}Si epi-layer are used to apply electric fields. Two Stark effects are resolved: a decrease of the hyperfine coupling between electron and nuclear spins of the donor and a decrease in electron Zeeman g-factor. The hyperfine term prevails at X-band magnetic fields of 0.35T, while the g-factor term is expected to dominate at higher magnetic fields. A significant linear Stark effect is also resolved presumably arising from strain.

  15. Imaging Electronic Motion with Attosecond Electron Pulses

    NASA Astrophysics Data System (ADS)

    Shao, Hua-Chieh; Starace, Anthony F.

    2010-03-01

    Ultrashort electron pulses have been proposed to observe time-dependent phenomena in atoms and molecules [1]. Owing to the temporal and spatial resolutions of short keV electron pulses, studying electronic motion in attosecond and sub-Angstrom regimes is feasible. We report benchmark calculations for oscillating electronic charge distributions in the H atom and in the H2^+ molecule to determine the effect of such charge oscillations on the elastic scattering cross section for a sub-fs electron pulse. In the pump/probe calculations, a femtosecond laser pulse is used to excite a coherent superposition of states, whose charge distribution oscillates with the beat frequency. The electron pulse scattering cross sections are calculated in the Born approximation. For the H atom, the cross section exhibits an oscillating effective radius. For the H2^+ molecules, the superposed state is chosen such that the electronic charge distribution oscillates from one nucleus to the other; hence, the differential cross section shows the localization of the electron.[4pt] [1] P. Baum and A.H. Zewail, PNAS 104, 18409 (2007).

  16. Specific features of optical orientation and relaxation of electron spins in quantum wells with a large spin splitting

    SciTech Connect

    Averkiev, N. S.; Glazov, M. M.

    2008-08-15

    The processes of optical spin orientation and spin relaxation of electrons are treated theoretically for semiconductor quantum wells, in which the spin splitting of the energy spectrum is comparable with the characteristic energy of charge carriers. The density matrix of photoexcited electrons at the instant of optical excitation is obtained in explicit form. A system of kinetic equations describing the behavior of the spin density matrix at an arbitrary relation between the average energy of charge carriers and the spin splitting is derived. It is demonstrated that, upon photoexcitation, a noticeable degree of orientation can be attained only in the pulse mode of operation, when the photoexcitation pulse duration is comparable with the period of spin precession in the field of spin splitting. It is shown that the total spin of the ensemble of electrons exhibits oscillations damping with time; the shape and damping time of the oscillations are sensitive to the parameters of photoexcitation and the spin splitting.

  17. (Pulsed electron beam precharger)

    SciTech Connect

    Finney, W.C.; Shelton, W.N.

    1990-01-01

    This report discusses the following topics on electron beam guns: Precharger Modification; Installation of Charge vs. Radius Apparatus; High Concentration Aerosol Generation; and Data Acquisition and Analysis System.

  18. Two-Dimensional Electron-Spin Resonance

    NASA Astrophysics Data System (ADS)

    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.

  19. Pulsed ELDOR in spin-labeled polypeptides

    NASA Astrophysics Data System (ADS)

    Milov, Alexander D.; Maryasov, Alexander G.; Tsvetkov, Yuri D.; Raap, Jan

    1999-04-01

    The pulsed electron-electron double-resonance (PELDOR) technique was applied to obtain information about the structure of the synthetic polypeptide-biradical in a frozen glassy solution. From the concentration dependence of the PELDOR signal, the effects of intermolecular and intramolecular interactions were separated. It was found that the intramolecular dipole-dipole interactions in the biradical peptide led to the modulation effects in the PELDOR signal decay. This may be attributed to the existence of a conformational population having a distance between the two unpaired electrons of ˜20 Å with a distribution of (˜2 Å). Its fraction is estimated as about 25%.

  20. Electron spin from self interaction

    SciTech Connect

    Spavieri, G. |

    1992-06-01

    The author explores the possibility that the electron self-interaction is the origin of the spin and of the radiative effects of QED. The electron is conceived as a charged, massless, point particle with a quantum or stochastic, internal motion about its center of mass and bound by a self-interaction potential. The hydrodynamic equations of motion describing the electron in its center of mass frame are related to non-Markovian stochastic equations recently used to derive the Schroedinger equation. By averaging over this stochastic internal motion and identifying the energy with the rest mass energy, the angular momentum exhibits properties characteristic of spin. The electromagnetic self-interactions added to the Hamiltonian of the particle correct the g factor to yield the anomalous value (g{minus}2)/2 {approx} 1159.7(2.3) X 10{sup {minus}6} in agreement with experiment. Calculations of other {open_quotes}radiative{close_quotes} effects including the Lamb shift are presented. The results obtained are finite and suggest that the QED corrections attributed to radiative effects could be obtained classically, i.e., without second quantization and renormalization, by complementing the Dirac theory with this self-interaction mechanism. The g factor dependence on the external magnetic field of this and other spin models is compared with that of QED, showing that these theories can be tested by the present precision measurements of the g factor. 33 refs., 2 tabs.

  1. Locking electron spins into resonance by electron-nuclear feedback

    NASA Astrophysics Data System (ADS)

    Nowack, Katja

    2009-03-01

    All basic building blocks for spin-based quantum information processing using electron spins in GaAs quantum dots have recently been realized. Recent experiments have shown single-shot read-out of an individual spin [1], the implementation of the SWAP gate [2] and (magnetically induced) coherent single electron spin rotations [3]. However, the main drawback of using electron spins in a GaAs environment is the short spin coherence time, which is measured to be in the nanosecond range [2,4]. The source of this fast decoherence is the hyperfine interaction of the localized electron spin with the randomly fluctuating nuclear spins of the host lattice. The fluctuations of the nuclear spins have to be reduced to extend the electron spin coherence time. We therefore study the electron-nuclear spin interaction and use magnetically driven spin resonance to control the electron spin and indirectly manipulate the nuclear spins. We apply continuous microwave excitation to the electron spin and observe strong electron-nuclear feedback. One experimental signature of this feedback is the locking of the electron spin system into resonance with the microwaves. Once the electron spin is locked into resonance, this resonance condition remains fullfilled even when the external magnetic field or the microwave frequency is changed. This is due to dynamically build up nuclear polarizations (up to 500 mT) which generally counteract the external magnetic field. Locking of the electron spin system into resonance might indicate that the nuclear polarization exhibits stable configurations where fluctuations of the nuclear distribution are reduced [5]. [4pt] References [0pt] [1] J. M. Elzerman et al. , Nature 430, 431 (2004) [0pt] [2]. J. R. Petta et al., Science 309, 2180 (2005). [0pt] [3] F. H. L. Koppens et al., Nature 442, 766 (2006). [0pt] [4] F. H. L. Koppens et al., Phys. Rev. Lett. 100, 236802 (2008). [0pt] [5] J. Danon and Yu. V. Nazarov, private communication.

  2. Short pulse free electron laser amplifier

    DOEpatents

    Schlitt, Leland G.; Szoke, Abraham

    1985-01-01

    Method and apparatus for amplification of a laser pulse in a free electron laser amplifier where the laser pulse duration may be a small fraction of the electron beam pulse duration used for amplification. An electron beam pulse is passed through a first wiggler magnet and a short laser pulse to be amplified is passed through the same wiggler so that only the energy of the last fraction, f, (f<1) of the electron beam pulse is consumed in amplifying the laser pulse. After suitable delay of the electron beam, the process is repeated in a second wiggler magnet, a third, . . . , where substantially the same fraction f of the remainder of the electron beam pulse is consumed in amplification of the given short laser pulse in each wiggler magnet region until the useful electron beam energy is substantially completely consumed by amplification of the laser pulse.

  3. Effective Spin Squeezing Through Optimized Pulse Sequences

    NASA Astrophysics Data System (ADS)

    Shen, Chao; Duan, Luming

    2013-05-01

    Spin squeezed states have attracted a lot of interest due to both its role in the fundamental study of many-particle entanglement and its practical application to precision measurement with a Ramsey interferometer. In recent years, spin squeezing with one-axis twisting (OAT) has been demonstrated experimentally with spinor BECs with more than 103 atoms. Although the noise is below the standard quantum limit, OAT scheme cannot achieve the ultimate Heisenberg limit of noise. There have been different theoretical proposals to enhance OAT which suffer different problems. Here we propose an experimentally very simple scheme based on optimized quantum control to greatly enhance the performance of OAT, requiring only an OAT Hamiltonian and the use of several single-qubit coherent pulses. This new scheme offers an opportunity to trade preparation speed for squeezing quality continuously, including OAT as a special case. We believe our scheme can be readily implemented experimentally. This work was supported by the NBRPC(973 Program), the IARPA MUSIQC program, the DARPA OLE program, the ARO and the AFOSR MURI program.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Stark tuning of donor electron spins in silicon

    SciTech Connect

    Bradbury, F.R.; Tyryshkin, A.M.; Sabouret, G.; Bokor, J.; Schenkel, T.; Lyon, S.A.

    2006-03-12

    We report Stark shift measurements for 121Sb donor electronspins in silicon using pulsed electron spin resonance. Interdigitatedmetal gates on top of a Sb-implanted 28Si epi-layer are used to applyelectric fields. Two Stark effects are resolved: a decrease of thehyperfine coupling between electron and nuclear spins of the donor and adecrease in electron Zeeman g-factor. The hyperfine term prevails atX-band magnetic fields of 0.35T, while the g-factor term is expected todominate at higher magnetic fields. A significant linear Stark effect isalso resolved presumably arising from strain.

  6. Spin Dynamics of Electrons Confined in Silicon Heterostructures

    NASA Astrophysics Data System (ADS)

    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 (< 0.1 ms). By electrostatically confining electrons to quantum dots, the spin relaxation time may be extended. We fabricate large-area dual-gated devices which

  7. Electron Spin Precession at CEBAF

    SciTech Connect

    Douglas Higinbotham

    2009-08-01

    The nuclear physics experiments at the Thomas Jefferson National Accelerator Facility often require longitudinally polarized electrons to be simultaneously delivered to three experimental halls. The degree of longitudinal polarization to each hall varies as function of the accelerator settings, making it challenging in certain situations to deliver a high degree of longitudinal polarization to all the halls simultaneously. Normally, the degree of longitudinal polarization the halls receive is optimized by changing the initial spin direction at the beginning of the machine with a Wien filter. Herein, it is shown that it is possible to further improve the degree of longitudinal polarization for multiple experimental halls by redistributing the energy gain of the CEBAF linacs while keeping the total energy gain fixed.

  8. Versatile spin-polarized electron source

    DOEpatents

    Jozwiak, Chris; Park, Cheol -Hwan; Gotlieb, Kenneth; Louie, Steven G.; Hussain, Zahid; Lanzara, Alessandra

    2015-09-22

    One or more embodiments relate generally to the field of photoelectron spin and, more specifically, to a method and system for creating a controllable spin-polarized electron source. One preferred embodiment of the invention generally comprises: method for creating a controllable spin-polarized electron source comprising the following steps: providing one or more materials, the one or more materials having at least one surface and a material layer adjacent to said surface, wherein said surface comprises highly spin-polarized surface electrons, wherein the direction and spin of the surface electrons are locked together; providing at least one incident light capable of stimulating photoemission of said surface electrons; wherein the photon polarization of said incident light is tunable; and inducing photoemission of the surface electron states.

  9. Ultrafast control of nuclear spins using only microwave pulses: Towards switchable solid-state quantum gates

    SciTech Connect

    Mitrikas, George; Sanakis, Yiannis; Papavassiliou, Georgios

    2010-02-15

    We demonstrate the control of the {alpha}-proton nuclear spin, I =1/2, coupled to the stable radical {center_dot}CH(COOH){sub 2}, S =1/2, in a {gamma}-irradiated malonic acid single crystal using only microwave pulses. We show that, depending on the state of the electron spin (m{sub S}={+-}1/2), the nuclear spin can be locked in a desired state or oscillate between m{sub I}=+1/2 and m{sub I}=-1/2 on the nanosecond time scale. This approach provides a fast way of controlling nuclear spin qubits and also enables the design of switchable spin-based quantum gates by addressing only the electron spin.

  10. Ultrafast spintronics roadmap: from femtosecond spin current pulses to terahertz non-uniform spin dynamics via nano-confined spin transfer torques (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Melnikov, Alexey; Razdolski, Ilya; Alekhin, Alexandr; Ilin, Nikita; Meyburg, Jan; Diesing, Detlef; Roddatis, Vladimir; Rungger, Ivan; Stamenova, Maria; Sanvito, Stefano; Bovensiepen, Uwe

    2016-10-01

    Further development of spintronics requires miniaturization and reduction of characteristic timescales of spin dynamics combining the nanometer spatial and femtosecond temporal ranges. These demands shift the focus of interest towards the fundamental open question of the interaction of femtosecond spin current (SC) pulses with a ferromagnet (FM). The spatio-temporal properties of the spin transfer torque (STT) exerted by ultrashort SC pulses on the FM open the time domain for studying STT fingerprint on spatially non-uniform magnetization dynamics. Using the sensitivity of magneto-induced second harmonic generation to SC, we develop technique for SC monitoring. With 20 fs resolution, we demonstrate the generation of 250 fs-long SC pulses in Fe/Au/Fe/MgO(001) structures. Their temporal profile indicates (i) nearly-ballistic hot electron transport in Au and (ii) that the pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Together with strongly spin-dependent Fe/Au interface transmission calculated for these carriers, this suggests the non-thermal spin-dependent Seebeck effect dominating the generation of ultrashort SC pulses. The analysis of SC transmission/reflection at the Au/Fe interface shows that hot electron spins orthogonal to the Fe magnetization rotate gaining huge parallel (anti-parallel) projection in transmitted (reflected) SC. This is accompanied by a STT-induced perturbation of the magnetization localized at the interface, which excites the inhomogeneous high-frequency spin dynamics in the FM. Time-resolved magneto-optical studies reveal the excitation of several standing spin wave modes in the Fe film with their spectrum extending up to 0.6 THz and indicating the STT spatial confinement to 2 nm.

  11. Charge and spin current oscillations in a tunnel junction induced by magnetic field pulses

    NASA Astrophysics Data System (ADS)

    Dartora, C. A.; Nobrega, K. Z.; Cabrera, G. G.

    2016-08-01

    Usually, charge and spin transport properties in tunnel junctions are studied in the DC bias regime and/or in the adiabatic regime of time-varying magnetic fields. In this letter, the temporal dynamics of charge and spin currents in a tunnel junction induced by pulsed magnetic fields is considered. At low bias voltages, energy and momentum of the conduction electrons are nearly conserved in the tunneling process, leading to the description of the junction as a spin-1/2 fermionic system coupled to time-varying magnetic fields. Under the influence of pulsed magnetic fields, charge and spin current can flow across the tunnel junction, displaying oscillatory behavior, even in the absence of DC bias voltage. A type of spin capacitance function, in close analogy to electric capacitance, is predicted.

  12. Synthetic Approach To Determine the Effect of Nuclear Spin Distance on Electronic Spin Decoherence.

    PubMed

    Graham, Michael J; Yu, Chung-Jui; Krzyaniak, Matthew D; Wasielewski, Michael R; Freedman, Danna E

    2017-03-01

    Nuclear-electronic interactions are a fundamental phenomenon which impacts fields from magnetic resonance imaging to quantum information processing (QIP). The realization of QIP would transform diverse areas of research including accurate simulation of quantum dynamics and cryptography. One promising candidate for the smallest unit of QIP, a qubit, is electronic spin. Electronic spins in molecules offer significant advantages with regard to QIP, and for the emerging field of quantum sensing. Yet relative to other qubit candidates, they possess shorter superposition lifetimes, known as coherence times or T2, due to interactions with nuclear spins in the local environment. Designing complexes with sufficiently long values of T2 requires an understanding of precisely how the position of nuclear spins relative to the electronic spin center affects decoherence. Herein, we report the first synthetic study of the relationship between nuclear spin-electron spin distance and decoherence. Through the synthesis of four vanadyl complexes, (Ph4P)2[VO(C3H6S2)2] (1), (Ph4P)2[VO(C5H6S4)2] (2), (Ph4P)2[VO(C7H6S6)2] (3), and (Ph4P)2[VO(C9H6S8)2] (4), we are able to synthetically place a spin-laden propyl moiety at well-defined distances from an electronic spin center by employing a spin-free carbon-sulfur scaffold. We interrogate this series of molecules with pulsed electron paramagnetic resonance (EPR) spectroscopy to determine their coherence times. Our studies demonstrate a sharp jump in T2 when the average V-H distance is decreased from 6.6(6) to 4.0(4) Å, indicating that spin-active nuclei sufficiently close to the electronic spin center do not contribute to decoherence. These results illustrate the power of synthetic chemistry in elucidating the fundamental mechanisms underlying electronic polarization transfer and provide vital principles for the rational design of long-coherence electronic qubits.

  13. Pulse Control Assisted Dynamical Decoupling in a Central Spin Model

    NASA Astrophysics Data System (ADS)

    Li, Zhao-Yan; Wei, Yong-Bo; Wang, Zhao-Ming; Gu, Yong-Jian; Li, Wen-Dong; Ma, Xiao-Ping

    2017-02-01

    We study pulse control assisted dynamical decoupling through a central spin model in a total Hilbert space. We find that the effective decoupling can be realized by applying a sequence of external pulses. Compared with the bang-bang control which needs infinite strength and infinitesimal short pulses, we show that there is a large parameter space that allows an effective nonperturbative dynamical control. Furthermore, our numerical calculation shows that the reliability can be held for random pulses, such as random pulse time interval or random strength.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Electron spin polarization transfer from photogenerated spin-correlated radical pairs to a stable radical observer spin.

    PubMed

    Colvin, Michael T; Carmieli, Raanan; Miura, Tomoaki; Richert, Sabine; Gardner, Daniel M; Smeigh, Amanda L; Dyar, Scott M; Conron, Sarah M; Ratner, Mark A; Wasielewski, Michael R

    2013-06-27

    A series of donor-chromophore-acceptor-stable radical (D-C-A-R(•)) molecules having well-defined molecular structures were synthesized to study the factors affecting electron spin polarization transfer from the photogenerated D(+•)-C-A(-•) spin-correlated radical pair (RP) to the stable radical R(•). Theory suggests that the magnitude of this transfer depends on the spin-spin exchange interaction (2JDA) of D(+•)-C-A(-•). Yet, the generality of this prediction has never been demonstrated. In the D-C-A-R(•) molecules described herein, D is 4-methoxyaniline (MeOAn), 2,3-dihydro-1,4-benzodioxin-6-amine (DioxAn), or benzobisdioxole aniline (BDXAn), C is 4-aminonaphthalene-1,8-dicarboximide, and A is naphthalene-1,8:4,5-bis(dicarboximide) (1A,B-3A,B) or pyromellitimide (4A,B-6A,B). The terminal imide of the acceptors is functionalized with either a hydrocarbon (1A-6A) or a 2,2,6,6-tetramethyl-1-piperidinyloxyl radical (R(•)) (1B-6B). Photoexcitation of C with 416-nm laser pulses results in two-step charge separation to yield D(+•)-C-A(-•)-(R(•)). Time-resolved electron paramagnetic resonance (TREPR) spectroscopy using continuous-wave (CW) microwaves at both 295 and 85 K and pulsed microwaves at 85 K (electron spin-echo detection) was used to probe the initial formation of the spin-polarized RP and the subsequent polarization of the attached R(•) radical. The TREPR spectra show that |2JDA| for D(+•)-C-A(-•) decreases in the order MeOAn(+•) > DioxAn(+•) > BDXAn(+•) as a result of their spin density distributions, whereas the spin-spin dipolar interaction (dDA) remains nearly constant. Given this systematic variation in |2JDA|, electron spin-echo-detected EPR spectra of 1B-6B at 85 K show that the magnitude of the spin polarization transferred from the RP to R(•) depends on |2JDA|.

  16. Miniature Magnet for Electron Spin Resonance Experiments

    ERIC Educational Resources Information Center

    Rupp, L. W.; And Others

    1976-01-01

    Describes commercially available permanent magnets that have been incorporated in a compact and inexpensive structure providing both field sweep and modulation suitable for electron spin resonance at microwave frequencies. (MLH)

  17. Spin-electron acoustic soliton and exchange interaction in separate spin evolution quantum plasmas

    SciTech Connect

    Andreev, Pavel A.

    2016-01-15

    Separate spin evolution quantum hydrodynamics is generalized to include the Coulomb exchange interaction, which is considered as interaction between the spin-down electrons being in quantum states occupied by one electron. The generalized model is applied to study the non-linear spin-electron acoustic waves. Existence of the spin-electron acoustic soliton is demonstrated. Contributions of concentration, spin polarization, and exchange interaction to the properties of the spin electron acoustic soliton are studied.

  18. Separated spin-up and spin-down quantum hydrodynamics of degenerated electrons: Spin-electron acoustic wave appearance.

    PubMed

    Andreev, Pavel A

    2015-03-01

    The quantum hydrodynamic (QHD) model of charged spin-1/2 particles contains physical quantities defined for all particles of a species including particles with spin-up and with spin-down. Different populations of states with different spin directions are included in the spin density (the magnetization). In this paper I derive a QHD model, which separately describes spin-up electrons and spin-down electrons. Hence electrons with different projections of spins on the preferable direction are considered as two different species of particles. It is shown that the numbers of particles with different spin directions do not conserve. Hence the continuity equations contain sources of particles. These sources are caused by the interactions of the spins with the magnetic field. Terms of similar nature arise in the Euler equation. The z projection of the spin density is no longer an independent variable. It is proportional to the difference between the concentrations of the electrons with spin-up and the electrons with spin-down. The propagation of waves in the magnetized plasmas of degenerate electrons is considered. Two regimes for the ion dynamics, the motionless ions and the motion of the degenerate ions as the single species with no account of the spin dynamics, are considered. It is shown that this form of the QHD equations gives all solutions obtained from the traditional form of QHD equations with no distinction of spin-up and spin-down states. But it also reveals a soundlike solution called the spin-electron acoustic wave. Coincidence of most solutions is expected since this derivation was started with the same basic equation: the Pauli equation. Solutions arise due to the different Fermi pressures for the spin-up electrons and the spin-down electrons in the magnetic field. The results are applied to degenerate electron gas of paramagnetic and ferromagnetic metals in the external magnetic field. The dispersion of the spin-electron acoustic waves in the partially spin

  19. Electrically and mechanically tunable electron spins in silicon carbide color centers.

    PubMed

    Falk, Abram L; Klimov, Paul V; Buckley, Bob B; Ivády, Viktor; Abrikosov, Igor A; Calusine, Greg; Koehl, William F; Gali, Adám; Awschalom, David D

    2014-05-09

    The electron spins of semiconductor defects can have complex interactions with their host, particularly in polar materials like SiC where electrical and mechanical variables are intertwined. By combining pulsed spin resonance with ab initio simulations, we show that spin-spin interactions in 4H-SiC neutral divacancies give rise to spin states with a strong Stark effect, sub-10(-6) strain sensitivity, and highly spin-dependent photoluminescence with intensity contrasts of 15%-36%. These results establish SiC color centers as compelling systems for sensing nanoscale electric and strain fields.

  20. All-optical tomography of electron spins in (In,Ga)As quantum dots

    NASA Astrophysics Data System (ADS)

    Varwig, S.; René, A.; Economou, Sophia E.; Greilich, A.; Yakovlev, D. R.; Reuter, D.; Wieck, A. D.; Reinecke, T. L.; Bayer, M.

    2014-02-01

    We demonstrate the basic features of an all-optical spin tomography on picosecond time scale. The magnetization vector associated with a mode-locked electron spin ensemble in singly charged quantum dots is traced by ellipticity measurements using picosecond laser pulses. After optical orientation the spins precess about a perpendicular magnetic field. By comparing the dynamics of two interacting ensembles with the dynamics of a single ensemble we find buildup of a spin component along the magnetic field in the two-ensemble case. This component arises from a Heisenberg-like spin-spin interaction.

  1. Direct observation of the electron spin relaxation induced by nuclei in quantum dots

    NASA Astrophysics Data System (ADS)

    Braun, P.-F.; Lombez, L.; Marie, X.; Urbaszek, B.; Amand, T.; Renucci, P.; Lagarde, D.; Kalevich, V. K.; Kavokin, K. V.; Krebs, O.; Voisin, P.

    2006-02-01

    We have investigated the electron and hole spin dynamics in p-doped semiconductor InAs/GaAs quantum dots by time resolved photoluminescence. We observe a decay of the average electron spin polarisation down to 1/3 of its initial value with a characteristic time of T Δ ~ 500ps. We attribute this decay to the hyperfine interaction of the electron spin with randomly orientated nuclear spins. Magnetic field dependent studies reveal that this efficient spin relaxation mechanism can be suppressed by a field in the order of 100mT. In pump-probe like experiments we demonstrate that the resident hole spin, "written" with a first pulse, remains stable long enough to be "read" 15ns later with a second pulse.

  2. Spin system trajectory analysis under optimal control pulses

    NASA Astrophysics Data System (ADS)

    Kuprov, Ilya

    2013-08-01

    Several methods are proposed for the analysis, visualization and interpretation of high-dimensional spin system trajectories produced by quantum mechanical simulations. It is noted that expectation values of specific observables in large spin systems often feature fast, complicated and hard-to-interpret time dynamics and suggested that populations of carefully selected subspaces of states are much easier to analyze and interpret. As an illustration of the utility of the proposed methods, it is demonstrated that the apparent "noisy" appearance of many optimal control pulses in NMR and EPR spectroscopy is an illusion - the underlying spin dynamics is shown to be smooth, orderly and very tightly controlled.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Spin readout of trapped electron qubits

    NASA Astrophysics Data System (ADS)

    Peng, Pai; Matthiesen, Clemens; Häffner, Hartmut

    2017-01-01

    We propose a scheme to read out the spin of a single electron quantum bit in a surface Paul trap using oscillating magnetic-field gradients. The readout sequence is composed of cooling, driving, amplification, and detection of the electron's motion. We study the scheme in the presence of noise and trap anharmonicities at liquid-helium temperatures. An analysis of the four procedures shows short measurement times (25 μ s ) and high fidelities (99.7 % ) are achievable with realistic experimental parameters. Our scheme performs the function of fluorescence detection in ion trapping schemes, highlighting the potential to build all-electric quantum computers based on trapped electron-spin qubits.

  5. Spin-orbit-based device for electron spin polarization

    NASA Astrophysics Data System (ADS)

    Avishai, Y.; Band, Y. B.

    2017-03-01

    We propose quantum devices having spin-orbit coupling (but no magnetic fields or magnetic materials) that, when attached to leads, yield a high degree of transmitted electron polarization. An example of such a simple device is treated within a tight binding model composed of two one-dimensional chains coupled by several consecutive rungs (i.e., a ladder) and subject to a gate voltage. The ensuing scattering problem (with Rashba spin-orbit coupling) is solved, and a sizable polarization is predicted. When the ladder is twisted into a helix (as in DNA), the curvature energy augments the polarization. For a system with random spin-orbit coupling, the distribution of polarization is broad; hence a high degree of polarization can be obtained in a measurement of a given disorder realization. When disorder occurs in a double helix structure then, depending on scattering energy, the variance of the polarization distribution can increase even further due to helix curvature.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Timekeeping with electron spin states in diamond

    NASA Astrophysics Data System (ADS)

    Hodges, J. S.; Yao, N. Y.; Maclaurin, D.; Rastogi, C.; Lukin, M. D.; Englund, D.

    2013-03-01

    Frequency standards based on atomic states, such as Rb or Cs vapors, or single-trapped ions, are the most precise measures of time. Here we propose and analyze a precision oscillator approach based upon spins in a solid-state system, in particular, the nitrogen-vacancy defect in single-crystal diamond. We show that this system can have stability approaching portable atomic standards and is readily incorporable as a chip-scale device. Using a pulsed spin-echo technique, we anticipate an Allan deviation of σy=10-7τ-1/2 limited by thermally-induced strain variations; in the absence of such thermal fluctuations, the system is limited by spin dephasing and harbors an Allan deviation nearing ˜10-12τ-1/2. Potential improvements based upon advanced diamond material processing, temperature stabilization, and nanophotonic engineering are discussed.

  8. Spin Polarized Electron Probes and Magnetic Nanostructures

    SciTech Connect

    D.L. Mills

    2003-10-15

    OAK B188 This report summarizes progress to date in our theoretical research program, for the period from July 1, 2002 to November 1, 2003. In addition, our research priorities for the coming year are set forth. The reporting period has been a most exciting and significant one. For the past several years, one of our principal thrust areas has been development of the theory of spin dynamics in magnetic nanostructures with emphasis on the use of spin polarized electrons as probes of short wavelength spin dynamics in such entities. Our program stimulated the first experiment which detected large wave vector spin waves in ultrathin films in 1999 through spin polarized electron loss spectroscopy (SPEELS); the publication which announced this discovery was a joint publication between a group in Halle (Germany) with our theory effort. The continued collaboration has led to the design and implementation of the new SPEELS spectrometer and we now have in hand the first detailed measurements of spin wave dispersion in an ultrathin film. A second such spectrometer is now operational in the laboratory of Prof. H. Hopster, at UC Irvine. We are thus entering a most exciting new era in the spectroscopy of spin excitations in magnetic nanostructures. During the reporting period, we have completed very important new analyses which predict key aspects of the spectra which will be uncovered by these new instruments, and the calculations continue to be developed and to expand our understanding. In addition, we have initiated a new series of theoretical studies directed toward spin dynamics of single magnetic adatoms on metal surfaces, with STM based studies of this area n mind. In the near future, these studies will continue, and we will expand our effort into new areas of spin dynamics in magnetic nanostructures.

  9. Reconstitution and electron spin resonance spin labeling studies of nucleosomes

    SciTech Connect

    Chan, D.C.F.; Grover, T.A.; Piette, L.H.

    1980-10-01

    The spin label, N-(2,2,5,5-tetramethyl-3-carbonylpyrrolidine-1-oxyl)-imidazole, was used to study the mode of reconstitution of nucleosome core particles. The histone cores in 2 M NaCl were first reacted with the imidazole spin label. After the removal of unreacted label, the histone cores were mixed with purified core DNA (145 base pairs) in 2 M NaCl. The mixture was then reconstituted by salt step-gradient dialysis according to Tatchell and Van Holde. At each step of the dialysis, an electron spin resonance (ESR) spectrum of the labeled tyrosyls was recorded and the correlation time of the label determined. As the ionic strength was gradually decreased, the correlation time of the spin label increased. This is in contrast to what we observed previously for the histone core alone, in which a decrease in the ionic strength caused the histone core (in the absence of DNA) to dissociate, freeing up the label and decreasing its correlation tie. Judging from the change in rotational correlation times for the spin label, we concluded that the histone core binds progressively to the DNA in the range of 2 M-0.3 M NaCl. When the ionic strength is <0.3 M, full association between the histone core and DNA takes place. These reconstituted spin labelled nucleosome core complexes, purified by isokinetic sucrose gradient, were found to have identical physical properties (histone content, sedimentation coefficient, thermal melting profile, and ciruclar dichroism) as the native particle.

  10. Ultra-low power microwave manipulation of electron spin ensembles

    NASA Astrophysics Data System (ADS)

    Sigillito, A. J.; Malissa, H.; Tyryshkin, A. M.; Lyon, S. A.

    2014-03-01

    Superconducting coplanar waveguide (CPW) resonators are a promising alternative to standard dielectric resonators for many electron spin resonance experiments. Their high sensitivity and low power requirements make them particularly well suited to applications where the sample volume is small and when microwave heating is a concern. Experiments utilizing rectangular pulses are possible with a peak microwave power of less than 1uW for 400ns pi-rotations, and under 100 uW of peak power for 40ns pi-rotations. However, CPW resonators have an inherently inhomogeneous microwave magnetic field (B1) . Therefore, to uniformly rotate all spins in a sample, adiabatic microwave pulses must be used. Here we report on the use of such pulses to correct B1 inhomogeneities spanning an order of magnitude. We also present data indicating single shot sensitivity to 1x107 phosphorus donors in isotopically enriched 28Si at 1.7K. These show that superconducting CPW resonators are fully compatible with experiments requiring rapid manipulation of spins in dilution refrigerators. This work was supported in part by NSF through the Materials World Network program (DMR-1107606) and the Princeton MRSEC (DMR-0819860), and in part by the U.S. Army Research Office (W911NF-13-1-0179).

  11. Coherent control with optical pulses for deterministic spin-photon entanglement

    NASA Astrophysics Data System (ADS)

    Truex, Katherine; Webster, L. A.; Duan, L.-M.; Sham, L. J.; Steel, D. G.

    2013-11-01

    We present a procedure for the optical coherent control of quantum bits within a quantum dot spin-exciton system, as a preliminary step to implementing a proposal by Yao, Liu, and Sham [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.95.030504 95, 030504 (2005)] for deterministic spin-photon entanglement. The experiment proposed here utilizes a series of picosecond optical pulses from a single laser to coherently control a single self-assembled quantum dot in a magnetic field, creating the precursor state in 25 ps with a predicted fidelity of 0.991. If allowed to decay in an appropriate cavity, the ideal precursor superposition state would create maximum spin-photon entanglement. Numerical simulations using values typical of InAs quantum dots give a predicted entropy of entanglement of 0.929, largely limited by radiative decay and electron spin flips.

  12. Electron trajectories in pulsed radiation fields

    SciTech Connect

    Einwohner, T.; Lippmann, B.A.

    1987-05-01

    The work reported here analyzes the dynamical behavior of an electron, initially at rest, when subjected to a radiation pulse of arbitrary, but integrable, shape. This is done by a general integration procedure that has been programmed in VAXIMA. Upon choosing a specific shape for the pulse, VAXIMA finds both the space-time trajectory and the four-momentum of the electron. These are obtained in analytic or numerical form - or both - at the choice of the user. Several examples of analytical and numerical solutions, for different pulse shapes, are given.

  13. Ultrafast spin-transfer torque driven by femtosecond pulsed-laser excitation

    NASA Astrophysics Data System (ADS)

    Koopmans, Bert

    A hot topic in the field of ultrafast laser-induced manipulation of the magnetic state is that of the role and exploitation of laser-induced spin currents. Intense debate has been triggered by claims that such a spin-transfer, e.g. in the form of super-diffusive spin currents over tens of nanometers, might be a main contributor to the demagnetization process in ferromagnetic thin films after femtosecond laser excitation. In this presentation the underlying concepts will be introduced and recent developments reviewed. Particularly we demonstrate the possibility to apply a laser-induced spin transfer torque on a free magnetic layer, using a non-collinear multilayer configuration consisting of a free in-plane layer on top of a perpendicularly magnetized injection layer, as separated by a nonmagnetic spacer. Interestingly, this approach allows for a quantitative measurement of the amount of spin transfer. Moreover, it might provide access to novel device architectures in which the magnetic state is controlled by fs laser pulses. Careful analysis of the resulting precession of the free layer allows us to quantify the applied torque, and distinguish between driving mechanisms based on laser-induced transfer of hot electrons versus a spin Seebeck effect due to the large thermal gradients. Further engineering of the layered structures in order to gain fundamental understanding and optimize efficiencies will be reported. A simple model that treats local non-equilibrium magnetization dynamics to spin transport effects via a spin-dependent chemical potential will be introduced.

  14. Undergraduate Electron-Spin-Resonance Experiment.

    ERIC Educational Resources Information Center

    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)

  15. Electron beam stimulated spin reorientation

    NASA Astrophysics Data System (ADS)

    Monchesky, T. L.; Unguris, J.; Celotta, R. J.

    2003-05-01

    Using scanning electron microscopy with polarization analysis, we observed the electron beam induced switching of the magnetic state of epitaxial single-crystal Fe(110) films grown on atomically flat cleaved GaAs(110). For low film thickness the magnetization lies along the [-110] in-plane direction, while above a thickness of 19 monolayers, the ground state magnetization configuration switches to the [001] in-plane direction. If Fe films are grown to a thickness greater than the critical thickness of the reorientation, the magnetization is caught in a metastable state, oriented along [-110]. We discovered that we can locally switch the metastable state to the stable [001] direction by irradiating the metastable magnetic state with a suitable electron current density. The reversal proceeds by the nucleation and growth of lancet-shaped domains that move in discrete jumps between pinning sites. Our results show that there is a permanent reduction of the strength of defect sites without a permanent change in the overall anisotropy. We demonstrate how an electron beam can be used to locally control domain structure.

  16. Pulse-noise approach for classical spin systems

    NASA Astrophysics Data System (ADS)

    Garanin, D. A.

    2017-01-01

    For systems of classical spins interacting with the bath via damping and thermal noise, an approach is suggested to replace the white noise by a pulse noise acting at regular time intervals Δ t , within which the system evolves conservatively. The method is working well in the typical case of a small dimensionless damping constant λ and allows a considerable speedup of computations by using high-order numerical integrators with a large time step δ t (up to a fraction of the precession period), while keeping δ t ≪Δ t to reduce the relative contribution of noise-related operations. In cases when precession can be discarded, δ t can be increased up to a fraction of the relaxation time ∝1 /λ that leads to a further speedup. This makes equilibration speed comparable with that of the Metropolis Monte Carlo method. The pulse-noise approach is tested on single-spin and multispin models.

  17. Pulse-noise approach for classical spin systems.

    PubMed

    Garanin, D A

    2017-01-01

    For systems of classical spins interacting with the bath via damping and thermal noise, an approach is suggested to replace the white noise by a pulse noise acting at regular time intervals Δt, within which the system evolves conservatively. The method is working well in the typical case of a small dimensionless damping constant λ and allows a considerable speedup of computations by using high-order numerical integrators with a large time step δt (up to a fraction of the precession period), while keeping δt≪Δt to reduce the relative contribution of noise-related operations. In cases when precession can be discarded, δt can be increased up to a fraction of the relaxation time ∝1/λ that leads to a further speedup. This makes equilibration speed comparable with that of the Metropolis Monte Carlo method. The pulse-noise approach is tested on single-spin and multispin models.

  18. High field electron spin resonance experiments on spin - Peierls compounds

    NASA Astrophysics Data System (ADS)

    Palme, W.; Schmidt, S.; Lüthi, B.; Boucher, J. P.; Weiden, M.; Hauptmann, R.; Geibel, C.; Revcolevschi, A.; Dhalenne, G.

    1998-05-01

    The spin-Peierls (SP) transition is still one of the most challenging effects in quasi-one-dimensional magnetism. A few years ago the first inorganic spin-Peierls compound CuGeO 3 with TSP=14.3 K was discovered, and recently α‧-NaV 2O 5 was found to be another inorganic SP system with the highest transition temperature so far observed: TSP=35 K. Electron spin resonance (ESR) is the only direct way to probe electron spin dynamics in magnetic fields higher than 12 T, where a transition to an incommensurate magnetic phase can occur. We present ESR results on single crystals of pure and Si-doped CuGeO 3 and pure α‧-NaV 2O 5. Our experiments were done in a wide frequency range 35-440 GHz in magnetic fields up to 16 T, covering a large temperature range 1.5-100 K. The temperature dependence of the ESR absorption in the D-phase in α‧-NaV 2O 5 points to transitions among triplet states, which are separated from the singlet ground state by an energy gap Δ≈85 K for T →0 . In contrast to χ( T) the ESR absorption does not stay finite for T →0 . In the incommensurate phase of slightly Si-doped CuGeO 3 (0.2% Si) ESR signals were observed, but their behaviour is much different from the ones in the pure compound.

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

    SciTech Connect

    Yang, Luyi

    2013-05-17

    suppressed by electron-electron interactions, leading to remarkable resistance to diffusive spreading of the drifting pulse of spin polarization. Finally, we show that spin helices continue propagate at the same speed as the Fermi sea even when the electron drift velocity exceeds the Fermi velocity of 107 cm s-1.

  20. Electron Ion Collider transverse spin physics

    SciTech Connect

    Prokudin, Alexei

    2011-07-01

    Electron Ion Collider is a future high energy facility for studies of the structure of the nucleon. Three-dimensional parton structure is one of the main goals of EIC. In momentum space Transverse Momentum Dependent Distributions (TMDs) are the key ingredients to map such a structure. At leading twist spin structure of spin-1/2 hadron can be described by 8 TMDs. Experimentally these functions can be studied in polarised SIDIS experiments. We discuss Sivers distribution function that describes distribution of unpolarised quarks in a transversely polarised nucleon and transversity that measures distribution of transversely polarised quarks in a transversely polarised nucleon

  1. Electron Ion Collider transverse spin physics

    SciTech Connect

    Prokudin, Alexei

    2011-07-15

    Electron Ion Collider is a future high energy facility for studies of the structure of the nucleon. Three-dimensional parton structure is one of the main goals of EIC. In momentum space Transverse Momentum Dependent Distributions (TMDs) are the key ingredients to map such a structure. At leading twist spin structure of spin-1/2 hadron can be described by 8 TMDs. Experimentally these functions can be studied in polarised SIDIS experiments. We discuss Sivers distribution function that describes distribution of unpolarised quarks in a transversely polarised nucleon and transversity that measures distribution of transversely polarised quarks in a transversely polarised nucleon.

  2. Optical control and coherence of electron or hole spins in coupled quantum dots

    NASA Astrophysics Data System (ADS)

    Carter, Samuel

    2013-03-01

    The spin of an electron or hole in an InAs quantum dot is an attractive qubit because it combines the advantages of a semiconductor platform with the power of ultrafast optical coherent control techniques. In the last few years, basic quantum operations such as initialization, rotation, and readout have become possible using single spins, but now improvements in spin coherence and demonstrations of multi-qubit systems are needed. In this work, we combine advances in the design and growth of coupled quantum dots with optical coherent control techniques to demonstrate ultrafast manipulation and coherence improvements for one or two interacting electron or hole spins in a coupled pair of InAs dots. For each of these spin systems, we use a sequence of picosecond and nanosecond pulses to initialize, manipulate, and measure the coherent spin dynamics. These dynamics include precession about a magnetic field and also entangling dynamics from the exchange interaction for coupled spins. For a single electron spin, precession dephases after only a few nanoseconds due to the hyperfine interaction with nuclear spins. For hole spins, we measure a dephasing time an order of magnitude longer due to a weaker hyperfine interaction. Coupled electron and hole spins are essential for multi-qubit systems, and they can also be used to decrease sensitivity to the environment. In these systems, we typically measure the coherent dynamics of the singlet-triplet states (ms = 0), which are much less sensitive to the nuclear environment. At present, dephasing is due to fluctuations in the electrical environment. With careful sample design, we can make these systems much less sensitive to electrical fluctuations, giving a powerful combination of long coherence times and ultrafast gates. Finally, we demonstrate that these spin qubits can be incorporated into a photonic crystal cavity and manipulated with optical pulses, a major step toward a quantum interface between photons and these spin

  3. Pulsed EPR Determination of Water Accessibility to Spin-Labeled Amino Acid Residues in LHCIIb

    PubMed Central

    Volkov, A.; Dockter, C.; Bund, T.; Paulsen, H.; Jeschke, G.

    2009-01-01

    Membrane proteins reside in a structured environment in which some of their residues are accessible to water, some are in contact with alkyl chains of lipid molecules, and some are buried in the protein. Water accessibility of residues may change during folding or function-related structural dynamics. Several techniques based on the combination of pulsed electron paramagnetic resonance (EPR) with site-directed spin labeling can be used to quantify such water accessibility. Accessibility parameters for different residues in major plant light-harvesting complex IIb are determined by electron spin echo envelope modulation spectroscopy in the presence of deuterated water, deuterium contrast in transversal relaxation rates, analysis of longitudinal relaxation rates, and line shape analysis of electron-spin-echo-detected EPR spectra as well as by the conventional techniques of measuring the maximum hyperfine splitting and progressive saturation in continuous-wave EPR. Systematic comparison of these parameters allows for a more detailed characterization of the environment of the spin-labeled residues. These techniques are applicable independently of protein size and require ∼10–20 nmol of singly spin-labeled protein per sample. For a residue close to the N-terminus, in a domain unresolved in the existing x-ray structures of light-harvesting complex IIb, all methods indicate high water accessibility. PMID:19186148

  4. Pulsed electron paramagnetic resonance spectroscopy powered by a free-electron laser.

    PubMed

    Takahashi, S; Brunel, L-C; Edwards, D T; van Tol, J; Ramian, G; Han, S; Sherwin, M S

    2012-09-20

    Electron paramagnetic resonance (EPR) spectroscopy interrogates unpaired electron spins in solids and liquids to reveal local structure and dynamics; for example, EPR has elucidated parts of the structure of protein complexes that other techniques in structural biology have not been able to reveal. EPR can also probe the interplay of light and electricity in organic solar cells and light-emitting diodes, and the origin of decoherence in condensed matter, which is of fundamental importance to the development of quantum information processors. Like nuclear magnetic resonance, EPR spectroscopy becomes more powerful at high magnetic fields and frequencies, and with excitation by coherent pulses rather than continuous waves. However, the difficulty of generating sequences of powerful pulses at frequencies above 100 gigahertz has, until now, confined high-power pulsed EPR to magnetic fields of 3.5 teslas and below. Here we demonstrate that one-kilowatt pulses from a free-electron laser can power a pulsed EPR spectrometer at 240 gigahertz (8.5 teslas), providing transformative enhancements over the alternative, a state-of-the-art ∼30-milliwatt solid-state source. Our spectrometer can rotate spin-1/2 electrons through π/2 in only 6 nanoseconds (compared to 300 nanoseconds with the solid-state source). Fourier-transform EPR on nitrogen impurities in diamond demonstrates excitation and detection of EPR lines separated by about 200 megahertz. We measured decoherence times as short as 63 nanoseconds, in a frozen solution of nitroxide free-radicals at temperatures as high as 190 kelvin. Both free-electron lasers and the quasi-optical technology developed for the spectrometer are scalable to frequencies well in excess of one terahertz, opening the way to high-power pulsed EPR spectroscopy up to the highest static magnetic fields currently available.

  5. Kondo spin screening cloud in two-dimensional electron gas with spin-orbit couplings.

    PubMed

    Feng, Xiao-Yong; Zhang, Fu-Chun

    2011-03-16

    A spin-1/2 Anderson impurity in a semiconductor quantum well with Rashba and Dresselhaus spin-orbit couplings is studied by using a variational wavefunction method. The local magnetic moment is found to be quenched at low temperatures. The spin-spin correlations of the impurity and the conduction electron density show anisotropy in both spatial and spin spaces, which interpolates the Kondo spin screenings of a conventional metal and of a surface of three-dimensional topological insulators.

  6. Exactly solvable spin dynamics of an electron coupled to a large number of nuclei; the electron-nuclear spin echo in a quantum dot

    SciTech Connect

    Kozlov, G. G.

    2007-10-15

    The model used to describe the spin dynamics in quantum dots after optical excitation is considered. Problems of the electron-spin polarization decay and the dependence of the steady-state polarization on magnetic field are solved on the basis of exact diagonalization of the model Hamiltonian. An important role of the nuclear state is shown and methods of its calculation for different regimes of optical excitation are proposed. The effect of spin echo generation after application of a {pi} pulse of a magnetic field is predicted for the system under consideration.

  7. Electron-Spin Filters Would Offer Spin Polarization Greater than 1

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2009-01-01

    A proposal has been made to develop devices that would generate spin-polarized electron currents characterized by polarization ratios having magnitudes in excess of 1. Heretofore, such devices (denoted, variously, as spin injectors, spin polarizers, and spin filters) have typically offered polarization ratios having magnitudes in the approximate range of 0.01 to 0.1. The proposed devices could be useful as efficient sources of spin-polarized electron currents for research on spintronics and development of practical spintronic devices.

  8. Electron spin resonance identification of irradiated fruits

    NASA Astrophysics Data System (ADS)

    Raffi, Jacques J.; Agnel, Jean-Pierre L.

    The electron spin resonance spectrum of achenes, pips, stalks and stones from irradiated fruits (strawberry, raspberry, red currant, bilberry, apple, pear, fig, french prune, kiwi, water-melon and cherry) always displays, just after γ-treatment, a weak triplet ( aH≈30 G) due to a cellulose radical; its left line (lower field) can be used as an identification test of irradiation, at least for strawberries, rapsberries, red currants or bilberries irradiated in order to improve their storage time.

  9. Electron-Spin Resonance in Boron Carbide

    NASA Technical Reports Server (NTRS)

    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.

  10. Electron Doping a Kagome Spin Liquid

    NASA Astrophysics Data System (ADS)

    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.

  11. A compact high current pulsed electron gun with subnanosecond electron pulse widths

    NASA Technical Reports Server (NTRS)

    Khakoo, M. A.; Srivastava, S. K.

    1984-01-01

    A magnetically-collimated, double-pulsed electron gun capable of generating electron pulses with a peak instantaneous current of approximately 70 microamps and a temporal width of 0.35 ns (FWHM) has been developed. Calibration is accomplished by measuring the lifetime of the well known 2(1P)-to-1(1S) transition in helium (58.4nm) at a near-threshold electron-impact energy by use of the delayed-coincidence technique.

  12. Inverse spin Hall effect from pulsed spin current in organic semiconductors with tunable spin-orbit coupling.

    PubMed

    Sun, Dali; van Schooten, Kipp J; Kavand, Marzieh; Malissa, Hans; Zhang, Chuang; Groesbeck, Matthew; Boehme, Christoph; Valy Vardeny, Z

    2016-08-01

    Exploration of spin currents in organic semiconductors (OSECs) induced by resonant microwave absorption in ferromagnetic substrates is appealing for potential spintronics applications. Owing to the inherently weak spin-orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE) response is very subtle; limited by the microwave power applicable under continuous-wave (cw) excitation. Here we introduce a novel approach for generating significant ISHE signals in OSECs using pulsed ferromagnetic resonance, where the ISHE is two to three orders of magnitude larger compared to cw excitation. This strong ISHE enables us to investigate a variety of OSECs ranging from π-conjugated polymers with strong SOC that contain intrachain platinum atoms, to weak SOC polymers, to C60 films, where the SOC is predominantly caused by the curvature of the molecule's surface. The pulsed-ISHE technique offers a robust route for efficient injection and detection schemes of spin currents at room temperature, and paves the way for spin orbitronics in plastic materials.

  13. Process integration and electron spin coherence of donor atom implants in silicon

    NASA Astrophysics Data System (ADS)

    Schenkel, T.; Persaud, A.; Tyryshkin, A. M.; Lyon, S. A.; Bokor, J.; Lo, C. C.; Desousa, R.; Chakarov, I.

    2007-03-01

    We implanted low doses (2 to 4 x 10^11cm-2) of P, Sb, and Bi ions into isotopically enriched silicon (28-Si) and characterized diffusion, electrical activation and electron spin coherence after rapid thermal annealing. Phosphorus and bismuth both exhibit enhanced segregation to an imperfect Si/SiO2 interface, while dopant movement is suppressed for antimony ions. Pulsed electron spin resonance shows that spin echo decay is sensitive to the dopant depths, and the interface quality. At 5.2 K, a spin de-coherence time, T2, of 0.3 ms is found for Sb profiles peaking 50 nm below a Si/SiO2 interface, increasing to 0.75 ms when the surface is passivated with hydrogen. These measurements provide benchmark data for the development of devices in which quantum information is encoded in donor electron spins [1]. [1] T. Schenkel, et al., Appl. Phys. Lett. 88, 112101 (2006).

  14. Charge and spin dynamics driven by ultrashort extreme broadband pulses: A theory perspective

    NASA Astrophysics Data System (ADS)

    Moskalenko, Andrey S.; Zhu, Zhen-Gang; Berakdar, Jamal

    2017-02-01

    This article gives an overview on recent theoretical progress in controlling the charge and spin dynamics in low-dimensional electronic systems by means of ultrashort and ultrabroadband electromagnetic pulses. A particular focus is put on sub-cycle and single-cycle pulses and their utilization for coherent control. The discussion is mostly limited to cases where the pulse duration is shorter than the characteristic time scales associated with the involved spectral features of the excitations. The relevant current theoretical knowledge is presented in a coherent, pedagogic manner. We work out that the pulse action amounts in essence to a quantum map between the quantum states of the system at an appropriately chosen time moment during the pulse. The influence of a particular pulse shape on the post-pulse dynamics is reduced to several integral parameters entering the expression for the quantum map. The validity range of this reduction scheme for different strengths of the driving fields is established and discussed for particular nanostructures. Acting with a periodic pulse sequence, it is shown how the system can be steered to and largely maintained in predefined states. The conditions for this nonequilibrium sustainability are worked out by means of geometric phases, which are identified as the appropriate quantities to indicate quasistationarity of periodically driven quantum systems. Demonstrations are presented for the control of the charge, spin, and valley degrees of freedom in nanostructures on picosecond and subpicosecond time scales. The theory is illustrated with several applications to one-dimensional semiconductor quantum wires and superlattices, double quantum dots, semiconductor and graphene quantum rings. In the case of a periodic pulsed driving the influence of the relaxation and decoherence processes is included by utilizing the density matrix approach. The integrated and time-dependent spectra of the light emitted from the driven system deliver

  15. Evolution of electron spin polarization in semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Artzi, Yaron; Twig, Ygal; Blank, Aharon

    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.

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

    NASA Astrophysics Data System (ADS)

    Artzi, Yaron; Twig, Ygal; Blank, Aharon

    2015-02-01

    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.

  18. Implanted bismuth donors in 28-Si: Process development and electron spin resonance measurements

    NASA Astrophysics Data System (ADS)

    Weis, C. D.; Lo, C. C.; Lang, V.; George, R. E.; Tyryshkin, A. M.; Bokor, J.; Lyon, S. A.; Morton, J. J. L.; Schenkel, T.

    2012-02-01

    Spins of donor atoms in silicon are excellent qubit candidates. Isotope engineered substrates provide a nuclear spin free host environment, resulting in long spin coherence times [1,2]. The capability of swapping quantum information between electron and nuclear spins can enable quantum communication and gate operation via the electron spin and quantum memory via the nuclear spin [2]. Spin properties of donor qubit candidates in silicon have been studied mostly for phosphorous and antimony [1-3]. Bismuth donors in silicon exhibit a zero field splitting of 7.4 GHz and have attracted attention as potential nuclear spin memory and spin qubit candidates [4,5] that could be coupled to superconducting resonators [4,6]. We report on progress in the formation of bismuth doped 28-Si epi layers by ion implantation, electrical dopant activation and their study via pulsed electron spin resonance measurements showing narrow linewidths and good coherence times. [4pt] [1] A. M. Tyryshkin, et al. arXiv: 1105.3772 [2] J. J. L. Morton, et al. Nature (2008) [3] T. Schenkel, et al APL 2006; F. R. Bradbury, et al. PRL (2006) [4] R. E. George, et al. PRL (2010) [5] G. W. Morley, et al. Nat Mat (2010) [6] M. Hatridge, et al. PRB (2011), R. Vijay, et al. APL (2010) This work was supported by NSA (100000080295) and DOE (DE-AC02-05CH11231).

  19. Optimization of spin-torque switching using AC and DC pulses

    SciTech Connect

    Dunn, Tom; Kamenev, Alex

    2014-06-21

    We explore spin-torque induced magnetic reversal in magnetic tunnel junctions using combined AC and DC spin-current pulses. We calculate the optimal pulse times and current strengths for both AC and DC pulses as well as the optimal AC signal frequency, needed to minimize the Joule heat lost during the switching process. The results of this optimization are compared against numeric simulations. Finally, we show how this optimization leads to different dynamic regimes, where switching is optimized by either a purely AC or DC spin-current, or a combination AC/DC spin-current, depending on the anisotropy energies and the spin-current polarization.

  20. Spintronics: a spin-based electronics vision for the future.

    PubMed

    Wolf, S A; Awschalom, D D; Buhrman, R A; Daughton, J M; von Molnár, S; Roukes, M L; Chtchelkanova, A Y; Treger, D M

    2001-11-16

    This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

  1. Pulsed electron-nuclear-electron triple resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Thomann, Hans; Bernardo, Marcelino

    1990-05-01

    A new experimental technique, pulsed electron-nuclear-electron triple resonance spectroscopy, is demonstrated. It is based on a modification of the pulse sequence for electron-nuclear double resonance (ENDOR) in which two EPR and one NMR transition are irradiated. The irradiation of one EPR transition is detected via a second EPR transition. The nuclear hyperfine coupling, which separates these EPR transition frequencies, is the irradiated NMR transition. The major advantages of triple resonance spectroscopy include the ability to resolve overlapping nuclear resonances in the ENDOR spectrum and a more direct quantitative assignment of nuclear hyperfine and quadrupole couplings. The triple resonance experiment is an alternative to the recently proposed method of employing rapid magnetic field jumps between microwave pulses for generating hyperfine selective ENDOR spectra.

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

    NASA Technical Reports Server (NTRS)

    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.

  3. Zeeman energy and spin relaxation in a one-electron quantum dot.

    PubMed

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

    2003-11-07

    We have measured the relaxation time, T1, of the spin of a single electron confined in a semiconductor quantum dot (a proposed quantum bit). In a magnetic field, applied parallel to the two-dimensional electron gas in which the quantum dot is defined, Zeeman splitting of the orbital states is directly observed by measurements of electron transport through the dot. By applying short voltage pulses, we can populate the excited spin state with one electron and monitor relaxation of the spin. We find a lower bound on T1 of 50 micros at 7.5 T, only limited by our signal-to-noise ratio. A continuous measurement of the charge on the dot has no observable effect on the spin relaxation.

  4. Generating Coherent Phonons and Spin Excitations with Ultrafast Light Pulses

    NASA Astrophysics Data System (ADS)

    Merlin, Roberto

    2006-03-01

    Recent work on the generation of coherent low-lying excitations by ultrafast laser pulses will be reviewed, emphasizing the microscopic mechanisms of light-matter interaction. The topics covered include long-lived phonons in ZnO [C. Aku-Leh, J. Zhao, R. Merlin, J. Men'endez and M. Cardona, Phys. Rev.B 71, 205211 (2005)], squeezed magnons [J. Zhao, A. V. Bragas, D. J. Lockwood and R. Merlin, Phys. Rev. Lett. 93, 107203 (2004)], spin- and charge-density fluctuations [J. M. Bao et al., Phys. Rev. Lett. 92, 236601 (2004)] and cyclotron resonance [J. K. Wahlstrand, D. M. Wang, P. Jacobs, J. M. Bao, R. Merlin, K. W. West and L. N. Pfeiffer, AIP Conference Proceedings 772 (2005), p. 1313] in GaAs quantum wells. In addition, unpublished results on surface -avoiding phonons in GaAs-AlAs superlattices [M. Trigo et al., unpublished] and magnons in ferromagnetic Ga1-xMnxAs [D. M. Wang et al., unpublished] will be discussed. It will also be shown that frequencies can be measured using pump-probe techniques with a precision comparable to that of Brillouin scattering. It is now widely accepted that stimulated Raman scattering (SRS) is (often but not always) the mechanism responsible for the coherent coupling. Results will be presented showing that SRS is described by two separate tensors, one of which accounts for the excitation-induced modulation of the susceptibility, and the other one for the dependence of the amplitude of the oscillation on the light intensity [T. E. Stevens, J. Kuhl and R. Merlin, Phys. Rev. B 65, 144304 (2002)]. These tensors have the same real component, associated with impulsive coherent generation, but different imaginary parts. If the imaginary term dominates, that is, for strongly absorbing substances, the mechanism for two-band processes becomes displacive in nature, as in the DECP (displacive excitation of coherent phonons) model. It will be argued that DECP is not a separate mechanism, but a particular case of SRS. In the final part of the talk, an

  5. Design and implementation of an FPGA-based timing pulse programmer for pulsed-electron paramagnetic resonance applications.

    PubMed

    Sun, Li; Savory, Joshua J; Warncke, Kurt

    2013-08-01

    The design, construction and implementation of a field-programmable gate array (FPGA) -based pulse programmer for pulsed-electron paramagnetic resonance (EPR) experiments is described. The FPGA pulse programmer offers advantages in design flexibility and cost over previous pulse programmers, that are based on commercial digital delay generators, logic pattern generators, and application-specific integrated circuit (ASIC) designs. The FPGA pulse progammer features a novel transition-based algorithm and command protocol, that is optimized for the timing structure required for most pulsed magnetic resonance experiments. The algorithm was implemented by using a Spartan-6 FPGA (Xilinx), which provides an easily accessible and cost effective solution for FPGA interfacing. An auxiliary board was designed for the FPGA-instrument interface, which buffers the FPGA outputs for increased power consumption and capacitive load requirements. Device specifications include: Nanosecond pulse formation (transition edge rise/fall times, ≤3 ns), low jitter (≤150 ps), large number of channels (16 implemented; 48 available), and long pulse duration (no limit). The hardware and software for the device were designed for facile reconfiguration to match user experimental requirements and constraints. Operation of the device is demonstrated and benchmarked by applications to 1-D electron spin echo envelope modulation (ESEEM) and 2-D hyperfine sublevel correlation (HYSCORE) experiments. The FPGA approach is transferrable to applications in nuclear magnetic resonance (NMR; magnetic resonance imaging, MRI), and to pulse perturbation and detection bandwidths in spectroscopies up through the optical range.

  6. Design and implementation of an FPGA-based timing pulse programmer for pulsed-electron paramagnetic resonance applications

    PubMed Central

    Sun, Li; Savory, Joshua J.; Warncke, Kurt

    2014-01-01

    The design, construction and implementation of a field-programmable gate array (FPGA) -based pulse programmer for pulsed-electron paramagnetic resonance (EPR) experiments is described. The FPGA pulse programmer offers advantages in design flexibility and cost over previous pulse programmers, that are based on commercial digital delay generators, logic pattern generators, and application-specific integrated circuit (ASIC) designs. The FPGA pulse progammer features a novel transition-based algorithm and command protocol, that is optimized for the timing structure required for most pulsed magnetic resonance experiments. The algorithm was implemented by using a Spartan-6 FPGA (Xilinx), which provides an easily accessible and cost effective solution for FPGA interfacing. An auxiliary board was designed for the FPGA-instrument interface, which buffers the FPGA outputs for increased power consumption and capacitive load requirements. Device specifications include: Nanosecond pulse formation (transition edge rise/fall times, ≤3 ns), low jitter (≤150 ps), large number of channels (16 implemented; 48 available), and long pulse duration (no limit). The hardware and software for the device were designed for facile reconfiguration to match user experimental requirements and constraints. Operation of the device is demonstrated and benchmarked by applications to 1-D electron spin echo envelope modulation (ESEEM) and 2-D hyperfine sublevel correlation (HYSCORE) experiments. The FPGA approach is transferrable to applications in nuclear magnetic resonance (NMR; magnetic resonance imaging, MRI), and to pulse perturbation and detection bandwidths in spectroscopies up through the optical range. PMID:25076864

  7. Spin relaxation of electrons in bulk CdTe

    NASA Astrophysics Data System (ADS)

    Sprinzl, Daniel; Nahalkova, Petra; Kunc, Jan; Maly, Petr; Horodysky, Petr; Grill, Roman; Belas, Eduard; Franc, Jan; Nemec, Petr

    2007-03-01

    We report on the measurements of the spin relaxation time T1 of photo-excited electrons in bulk CdTe. The carrier dynamics were investigated by transient absorption experiments using 80 fs circularly polarized laser pulses at sample temperatures from 20 to 300 K. We studied both p and n type doped CdTe samples, which were prepared in the form of thin platelets from the crystals grown by the modified Bridgman method. The obtained results are compared with the spin relaxation times reported for other semiconductors with the same crystal structure (e.g., GaAs [1]). Finally, the relative contributions of the D'yakonov-Perel, Elliott-Yafet, Bir-Aronov-Pikus, and other mechanisms to the measured spin relaxation times in CdTe are discussed. This work was supported by the Grant Agency of the Czech Republic (grant 202/03/H003), by the Ministry of Education of the Czech Republic in the framework of the research centre LC510 and the research plan MSM 0021620834. [1] J. M. Kikkawa and D. D. Awschalom, Phys. Rev. Lett. 80, 4313 (1998).

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    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

    2016-01-01

    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. PMID:27550534

  10. Transient effects on electron spin observation

    NASA Astrophysics Data System (ADS)

    Larson, J.; Garraway, B. M.; Stenholm, S.

    2004-03-01

    In an earlier publication we addressed the problem of splitting an electron beam in the Stern-Gerlach experiment. In contrast to arguments put forward in the early days of quantum theory, we concluded that there are no issues of principle preventing the observation of electron spin during free flight. In that paper, however, we considered only a sudden switch off of the separating magnetic field. In this work we consider the possible effects of finite switching times at the beginning and the end of the interaction period. We consider a model where the coupling between the electron and the field is time dependent. As a result of the time dependence, the field also acquires an electric component, but this seems to cause no significant change of our conclusions. On the other hand, the smooth change of the interaction enforces the same longitudinal velocity on the electron both at the beginning and end of the interaction period because of conservation laws; this effect was missing in our earlier calculations. As the electrons are supposed to travel as a beam, this feature helps by restoring the beam quality after the interaction.

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

    SciTech Connect

    Singamaneni, Srinivasa Rao; Stesmans, Andre; Tol, Johan van; Kosynkin, D. V.; Tour, James M.

    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.

  12. Ultrafast Electron Pulse (e,2e) Processes

    NASA Astrophysics Data System (ADS)

    Shao, Hua-Chieh; Starace, Anthony; Madsen, Lars

    2012-06-01

    Techniques for producing ultrafast electron pulses have been proposedootnotetextP. Baum and A.H. Zewail, Proc. Natl. Acad. Sci. U.S.A. 104, 18409 (2007); S.A. Hilbert, C. Ulterwaal, B. Barwick, H. Betalaan, and A.H. Zewail, ibid. 106, 10558 (2009). and prospects for using such pulses to image electron dynamics in the H atom and the hydrogen molecular ion have been theoretically demonstrated.ootnotetextH.-C. Shao and A.F. Starace, Phys. Rev. Lett. 105, 263201 (2010). The (e,2e) process provides a means to directly image the momentum distribution of the target.ootnotetextM.A. Coplan, J.H. Moore, and J.P. Doering, Rev. Mod. Phys. 66, 985 (1994). We explore here the possibility of observing the time dependence of a coherent superposition of target orbitals by means of the (e,2e) process with ultrafast incident electron pulses. Using scattering theory for a longitudinally coherent beam,ootnotetextF. Robicheaux, Phys. Rev. A 62, 062706 (2000). we find that the momentum distribution of a coherent state of the H atom can be retrieved.

  13. Shaped electric fields for fast optimal manipulation of electron spin and position in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Budagosky, J. A.; Khomitsky, D. V.; Sherman, E. Ya.; Castro, Alberto

    2016-01-01

    We use quantum optimal control theory algorithms to design external electric fields that drive the coupled spin and orbital dynamics of an electron in a double quantum dot, subject to the spin-orbit coupling and Zeeman magnetic fields. We obtain time profiles of multifrequency electric field pulses which increase the rate of spin-flip transitions by several orders of magnitude in comparison with monochromatic fields, where the spin Rabi oscillations were predicted to be very slow. This precise (with fidelity higher than 1 ×10-4 ) and fast (at the time scale of the order of 0.1 ns, comparable with the Zeeman spin rotation and the interdot tunneling time) simultaneous control of the spin and position is achieved while keeping the electron in the four lowest tunneling- and Zeeman-split levels through the duration of the pulse. The proposed algorithms suggest effective applications in spintronics and quantum information devices.

  14. Bulk Quantum Computation with Pulsed Electron Paramagnetic Resonance: Simulations of Single-Qubit Error Correction Schemes

    NASA Astrophysics Data System (ADS)

    Ishmuratov, I. K.; Baibekov, E. I.

    2016-12-01

    We investigate the possibility to restore transient nutations of electron spin centers embedded in the solid using specific composite pulse sequences developed previously for the application in nuclear magnetic resonance spectroscopy. We treat two types of systematic errors simultaneously: (i) rotation angle errors related to the spatial distribution of microwave field amplitude in the sample volume, and (ii) off-resonance errors related to the spectral distribution of Larmor precession frequencies of the electron spin centers. Our direct simulations of the transient signal in erbium- and chromium-doped CaWO4 crystal samples with and without error corrections show that the application of the selected composite pulse sequences can substantially increase the lifetime of Rabi oscillations. Finally, we discuss the applicability limitations of the studied pulse sequences for the use in solid-state electron paramagnetic resonance spectroscopy.

  15. Clarification of the measurement of surface spin relaxation via conduction electron spin resonance

    NASA Astrophysics Data System (ADS)

    Eigler, D. M.; Schultz, S.

    1982-12-01

    We clarify the parameterization of the probability of transverse conduction electron spin relaxation. ɛ, at the surface of a metal. Using Walker's boundary condition on the transverse spin magnetization, we have calculated the ɛ and thickness dependence of the spin resonance linewidth. The results are discussed in simple physical terms. The recent work of Allam and Vigouroux is shown to contain errors.

  16. Double quantum coherence electron spin resonance on coupled Cu(II)-Cu(II) electron spins

    NASA Astrophysics Data System (ADS)

    Becker, James S.; Saxena, Sunil

    2005-10-01

    We demonstrate for the first time the ability to generate double quantum coherences (DQCs) for the case of Cu(II). We show that small splittings (˜7 MHz) from the Cu(II)-Cu(II) electron-electron magnetic dipolar interaction can be reliably resolved even though the inhomogeneously broadened Cu(II) linewidth is ˜2 GHz. A Cu(II)-Cu(II) distance of 2.0 nm was measured on a model peptide system, thus, demonstrating that distances on the nanometer scale may be measured using DQC electron spin resonance (ESR).

  17. Ultrafast optical coherent control of individual electron and hole spins in a semiconductor quantum dot

    NASA Astrophysics Data System (ADS)

    de Greve, Kristiaan

    2012-02-01

    We report on the complete optical coherent control of individual electron and hole spin qubits in InAs quantum dots. With a magnetic field in Voigt geometry, broadband, detuned optical pulses couple the spin-split ground states, resulting in Rabi flopping. In combination with the Larmor precession around the external magnetic field, this allows an arbitrary single-qubit operation to be realized in less than 20 picoseconds [1,2]. Slow fluctuations in the spin's environment lead to shot-to-shot variations in the Larmor precession frequency. In a time-ensemble measurement, these would prevent a measurement of the true decoherence of the qubit, and instead give rise to ensemble dephasing. This effect was overcome by implementing a spin echo measurement scheme for both electron and hole spins, where an optical π-pulse refocuses the spin coherence and filters out the slow variations in Larmor precession frequency. We measured coherence times up to 3 microseconds [2,3]. Finally, our optical pulse manipulation scheme allows us to probe the hyperfine interaction between the single spin and the nuclei in the quantum dot. Interesting non-Markovian dynamics could be observed in the free-induction decay of a single electron spin, whereas the complete absence of such effects illustrates the reduction of the hyperfine interaction for hole spin qubits. We measured and modeled these effects, and explain the non-Markovian electron spin dynamics as involving a feedback effect resulting from both the strong Overhauser shift of the electron spin and spin dependent nuclear relaxation [2,4]. [4pt] [1] D. Press, T. D. Ladd, B. Zhang and Y. Yamamoto, Nature 456, 218 (2008)[0pt] [2] K. De Greve, P. McMahon, D. Press et al., Nat. Phys. 7, 872 (2011)[0pt] [3] D. Press, K. De Greve, P. McMahon et al., Nat. Phot. 4, 367 (2010)[0pt] [4] T. D. Ladd, D. Press, K. De Greve et al., Phys. Rev. Lett. 105, 107401 (2010)

  18. A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures

    NASA Astrophysics Data System (ADS)

    Yap, Yung Szen; Tabuchi, Yutaka; Negoro, Makoto; Kagawa, Akinori; Kitagawa, Masahiro

    2015-06-01

    We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using γ-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, we observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously—a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK.

  19. A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures

    SciTech Connect

    Yap, Yung Szen; Tabuchi, Yutaka; Negoro, Makoto; Kagawa, Akinori; Kitagawa, Masahiro

    2015-06-15

    We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using γ-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, we observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously—a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK.

  20. Study of electronic structure and spin polarization of dysprosium

    SciTech Connect

    Mund, H. S.

    2015-06-24

    In this paper, I have presented the spin-dependent momentum density of ferromagnetic dysprosium using spin polarized relativistic Korringa-Kohn-Rostoker method. A fully relativistic approach has been used to determine the magnetic Compton profile. The density of state in term of majority-spin and minority-spin of Dy also calculated using SPR-KKR. The magnetic Compton profile discussed in term of 4f and diffused electrons.

  1. Spin relaxation in bilayer graphene: the role of electron-electron scattering

    NASA Astrophysics Data System (ADS)

    Katiyar, Saurabh; Ghosh, Bahniman; Salimath, Akshay Kumar

    2016-02-01

    This paper investigates the influence of electron-electron scattering on spin relaxation length in bilayer graphene using semiclassical Monte Carlo simulation. Both D'yakonov-P'erel and Elliot-Yafet mechanisms are considered for spin relaxation. It is shown that spin relaxation length decreases by 17 % at 300 K on including electron-electron scattering. The reason of this variation in spin relaxation length is that the ensemble spin is modified upon an e-e collision, and also e-e scattering rate is greater than phonon scattering rate which causes change in spin transport profile.

  2. Millisecond Coherence Time in a Tunable Molecular Electronic Spin Qubit.

    PubMed

    Zadrozny, Joseph M; Niklas, Jens; Poluektov, Oleg G; Freedman, Danna E

    2015-12-23

    Quantum information processing (QIP) could revolutionize areas ranging from chemical modeling to cryptography. One key figure of merit for the smallest unit for QIP, the qubit, is the coherence time (T 2), which establishes the lifetime for the qubit. Transition metal complexes offer tremendous potential as tunable qubits, yet their development is hampered by the absence of synthetic design principles to achieve a long T 2. We harnessed molecular design to create a series of qubits, (Ph4P)2[V(C8S8)3] (1), (Ph4P)2[V(β-C3S5)3] (2), (Ph4P)2[V(α-C3S5)3] (3), and (Ph4P)2[V(C3S4O)3] (4), with T 2s of 1-4 μs at 80 K in protiated and deuterated environments. Crucially, through chemical tuning of nuclear spin content in the vanadium(IV) environment we realized a T 2 of ∼1 ms for the species (d 20-Ph4P)2[V(C8S8)3] (1') in CS2, a value that surpasses the coordination complex record by an order of magnitude. This value even eclipses some prominent solid-state qubits. Electrochemical and continuous wave electron paramagnetic resonance (EPR) data reveal variation in the electronic influence of the ligands on the metal ion across 1-4. However, pulsed measurements indicate that the most important influence on decoherence is nuclear spins in the protiated and deuterated solvents utilized herein. Our results illuminate a path forward in synthetic design principles, which should unite CS2 solubility with nuclear spin free ligand fields to develop a new generation of molecular qubits.

  3. Millisecond Coherence Time in a Tunable Molecular Electronic Spin Qubit

    PubMed Central

    2015-01-01

    Quantum information processing (QIP) could revolutionize areas ranging from chemical modeling to cryptography. One key figure of merit for the smallest unit for QIP, the qubit, is the coherence time (T2), which establishes the lifetime for the qubit. Transition metal complexes offer tremendous potential as tunable qubits, yet their development is hampered by the absence of synthetic design principles to achieve a long T2. We harnessed molecular design to create a series of qubits, (Ph4P)2[V(C8S8)3] (1), (Ph4P)2[V(β-C3S5)3] (2), (Ph4P)2[V(α-C3S5)3] (3), and (Ph4P)2[V(C3S4O)3] (4), with T2s of 1–4 μs at 80 K in protiated and deuterated environments. Crucially, through chemical tuning of nuclear spin content in the vanadium(IV) environment we realized a T2 of ∼1 ms for the species (d20-Ph4P)2[V(C8S8)3] (1′) in CS2, a value that surpasses the coordination complex record by an order of magnitude. This value even eclipses some prominent solid-state qubits. Electrochemical and continuous wave electron paramagnetic resonance (EPR) data reveal variation in the electronic influence of the ligands on the metal ion across 1–4. However, pulsed measurements indicate that the most important influence on decoherence is nuclear spins in the protiated and deuterated solvents utilized herein. Our results illuminate a path forward in synthetic design principles, which should unite CS2 solubility with nuclear spin free ligand fields to develop a new generation of molecular qubits. PMID:27163013

  4. Torque for electron spin induced by electron permanent electric dipole moment

    SciTech Connect

    Senami, Masato E-mail: akitomo@scl.kyoto-u.ac.jp; Fukuda, Masahiro E-mail: akitomo@scl.kyoto-u.ac.jp; Ogiso, Yoji E-mail: akitomo@scl.kyoto-u.ac.jp; Tachibana, Akitomo E-mail: akitomo@scl.kyoto-u.ac.jp

    2014-10-06

    The spin torque of the electron is studied in relation to the electric dipole moment (EDM) of the electron. The spin dynamics is known to be given by the spin torque and the zeta force in quantum field theory. The effect of the EDM on the torque of the spin brings a new term in the equation of motion of the spin. We study this effect for a solution of the Dirac equation with electromagnetic field.

  5. Spin decoherence and electron spin bath noise of a nitrogen-vacancy center in diamond

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Hui; Takahashi, Susumu

    2013-03-01

    We theoretically investigate spin decoherence of a single nitrogen-vacancy (NV) center in diamond. Using the spin coherent-state P-representation method, we simulate coherence evolution of the NV center coupled to surrounding nitrogen electron (N) spins. In the system, the strength of N-N coupling is the same order as that of NV-N coupling (the strong intrabath coupling regime). We find that spin decoherence time as well as free-induction decay of the NV center depend on the spatial configuration of N spins. Both the spin decoherence rate (1/T2) and dephasing rate (1/T2*) of the NV center increase linearly with the concentration of the N spins. Using the P-representation method, we also demonstrate extracting the noise spectrum of the N spin bath. The capability to calculate the noise spectrum will provide promising pathways to suppress decoherence of spin systems in the strong intrabath coupling regime.

  6. Strong-field Breit-Wheeler pair production in short laser pulses: Relevance of spin effects

    NASA Astrophysics Data System (ADS)

    Jansen, M. J. A.; Kamiński, J. Z.; Krajewska, K.; Müller, C.

    2016-07-01

    Production of electron-positron pairs in the collision of a high-energy photon with a high-intensity few-cycle laser pulse is studied. By utilizing the frameworks of laser-dressed spinor and scalar quantum electrodynamics, a comparison between the production of pairs of Dirac and Klein-Gordon particles is drawn. Positron energy spectra and angular distributions are presented for various laser parameters. We identify conditions under which predictions from Klein-Gordon theory either closely resemble or largely differ from those of the proper Dirac theory. In particular, we address the question to which extent the relevance of spin effects is influenced by the short duration of the laser pulse.

  7. Electron spin control of optically levitated nanodiamonds in vacuum

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  8. Spin Interactions and Spin Dynamics in Electronic Nanostructures

    DTIC Science & Technology

    2007-11-02

    of technological importance, and the spectroscopic study of the spin transport properties of nanoscale systems, the demonstration of terahertz spin...dynamics at near- terahertz frequencies in magnetically doped quantum wells,” R. C. Myers. K. C. Ku, X. Li, N. Samarth, and D. D. Awschalom, Phys. Rev. B 72...dynamics at near- terahertz frequencies in magnetically doped quantum wells,” R. C. Myers. K. C. Ku, X. Li, N. Samarth, and D. D. Awschalom, Phys. Rev

  9. Theory of ultrafast optical manipulation of electron spins in quantum wells

    NASA Astrophysics Data System (ADS)

    Jin, Jinshuang; Li, Xin-Qi

    2005-12-01

    Based on a multiparticle-state stimulated Raman adiabatic passage approach, a comprehensive theoretical study of the ultrafast optical manipulation of electron spins in quantum wells is presented. In addition to corroborating experimental findings [Gupta et al., Science 292, 2458 (2001)], we improve the expression for the optical-pulse-induced effective magnetic field, in comparison with the one obtained via the conventional single-particle ac Stark shift. Further study of the effect of hole-spin relaxation reveals that, while the coherent optical manipulation of electron spin in undoped quantum wells would deteriorate in the presence of relatively fast hole-spin relaxation, the coherent control in doped systems can be quite robust against decoherence. The implications of the present results on quantum dots will also be discussed.

  10. Understanding and controlling spin-systems using electron spin resonance techniques

    NASA Astrophysics Data System (ADS)

    Martens, Mathew

    Single molecule magnets (SMMs) posses multi-level energy structures with properties that make them attractive candidates for implementation into quantum information technologies. However there are some major hurdles that need to be overcome if these systems are to be used as the fundamental components of an eventual quantum computer. One such hurdle is the relatively short coherence times these systems display which severely limits the amount of time quantum information can remain encoded within them. In this dissertation, recent experiments conducted with the intent of bringing this technology closer to realization are presented. The detailed knowledge of the spin Hamiltonian and mechanisms of decoherence in SMMs are absolutely essential if these systems are to be used in technologies. To that effect, experiments were done on a particularly promising SMM, the complex K6[VIV15AsIII 6O42(H2O)] · 8H2O, known as V15. High-field electron spin resonance (ESR) measurements were performed on this system at the National High Magnetic Field Laboratory. The resulting spectra allowed for detailed analysis of the V15 spin Hamiltonian which will be presented as well as the most precise values yet reported for the g-factors of this system. Additionally, the line widths of the ESR spectra are studied in depth and found to reveal that fluctuations within the spin-orbit interaction are a mechanism for decoherence in V15. A new model for decoherence is presented that describes very well both the temperature and field orientation dependences of the measured ESR line widths. Also essential is the ability to control spin-states of SMMs. Presented in this dissertation as well is the demonstration of the coherent manipulation of the multi-state spin system Mn2+ diluted in MgO by means of a two-tone pulse drive. Through the detuning between the excitation and readout radio frequency pulses it is possible to select the number of photons involved in a Rabi oscillation as well as increase

  11. Electron acceleration by a propagating laser pulse in vacuum

    SciTech Connect

    Wang Fengchao; Shen Baifei; Zhang Xiaomei; Li Xuemei; Jin Zhangying

    2007-08-15

    Electrons accelerated by a propagating laser pulse of linear or circular polarization in vacuum have been investigated by one-dimensional particle-in-cell simulations and analytical modeling. A stopping target is used to stop the laser pulse and extract the energetic electrons from the laser field. The effect of the reflected light is taken into account. The maximum electron energy depends on the laser intensity and initial electron energy. There is an optimal acceleration length for electrons to gain maximum energy where electrons meet the peak of the laser pulse. The optimal acceleration length depends strongly on the laser pulse duration and amplitude.

  12. Dynamic field-frequency lock for tracking magnetic field fluctuations in electron spin resonance experiments

    NASA Astrophysics Data System (ADS)

    Asfaw, Abraham; Tyryshkin, Alexei; Lyon, Stephen

    Global magnetic field fluctuations present significant challenges to pulsed electron spin resonance experiments on systems with long spin coherence times. We will discuss results from experiments in which we follow instantaneous changes in magnetic field by locking to the free induction decay of a proton NMR signal using a phase-locked loop. We extend conventional field-frequency locking techniques used in NMR to follow slow magnetic field drifts by using a modified Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence in which the phase of the pi-pulses follows the phase of the proton spins at all times. Hence, we retain the ability of the CPMG pulse sequence to refocus local magnetic field inhomogeneities without refocusing global magnetic field fluctuations. In contrast with conventional field-frequency locking techniques, our experiments demonstrate the potential of this method to dynamically track global magnetic field fluctuations on timescales of about 2 seconds and with rates faster than a kHz. This frequency range covers the dominant noise frequencies in our electron spin resonance experiments as previously reported.

  13. Structure dependent spin selectivity in electron transport through oligopeptides

    NASA Astrophysics Data System (ADS)

    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.

  14. Sensitive surface loop-gap microresonators for electron spin resonance.

    PubMed

    Twig, Ygal; Suhovoy, Ekaterina; Blank, Aharon

    2010-10-01

    This work presents the design, construction, and experimental testing of unique sensitive surface loop-gap microresonators for electron spin resonance (ESR) measurements. These resonators are made of "U"-shaped gold structures with typical sizes of 50 and 150 μm that are deposited on a thin (220 μm) rutile substrate and fed from the rear by a microstrip line. This allows accommodating a large flat sample above the resonator in addition to having variable coupling properties. Such resonators have a very small volume which, compared to previous designs, improves their absolute spin sensitivity by a factor of more than 2 (based on experimental results). They also have a very high microwave field-power conversion ratio of up to 86 gauss/√Hz. This could facilitate the use of very short excitation pulses with relatively low microwave power. Following the presentation and the discussion of the experimental results, ways to further increase sensitivity significantly are outlined.

  15. Spin orbit torque based electronic neuron

    SciTech Connect

    Sengupta, Abhronil Choday, Sri Harsha; Kim, Yusung; Roy, Kaushik

    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.

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

    PubMed

    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.

  17. Dependence of Distance Distributions Derived from Double Electron-Electron Resonance Pulsed EPR on Pulse Sequence Time**

    PubMed Central

    Louis, John M.

    2015-01-01

    Pulsed double electron-electron resonance (DEER) provides pairwise P(r) distance distributions in doubly spin-labeled proteins. We report that in protonated proteins P(r) is dependent on the length of the second echo period T owing to local environmental effects on spin-label phase memory relaxation time Tm. For the protein ABD, this effect results in a 1.4 Å increase in the P(r) maximum from T = 6 to 20 μs. Protein A has a bimodal P(r) distribution and the relative height of the shorter distance peak at T = 10 μs, the shortest value required to obtain a reliable P(r), is reduced by 40% relative to that obtained by extrapolation to T = 0. Our results indicate that data at a series of T values are essential for quantitative interpretation of DEER to determine the extent of the T dependence and to extrapolate the results to T= 0. Complete deuteration (99%) of the protein is accompanied by a significant increase in Tm and effectively abolishes the P(r) dependence on T. PMID:25757985

  18. Electron spin transport through an Aharonov Bohm ring—a spin switch

    NASA Astrophysics Data System (ADS)

    Jia, Cheng-Long; Wang, Shun-Jin; Luo, Hong-Gang; An, Jun-Hong

    2004-03-01

    Electron spin transport through an Aharonov-Bohm ring driven by time-dependent inhomogeneous magnetic fields is treated. The system possesses an su(2)l × su(2)s dynamical symmetry in both orbital angular momentum space and spin space, and is thus proved to be integrable according to algebraic dynamics. Based on the analytical solutions, the relevant physical quantities such as electric current, spin current, magnetization and conductance are calculated. It is found that for a magnetic field with pgr/2 twist angle, the direction of spin-polarization will be reversed at zero magnetic flux. In the resonant rotating magnetic field, the spin transmission is oscillating with time t, and can reach unity, so that a complete spin flip can also be induced. The results obtained may be of practical significance for the design of nano-electromagnetic spin devices, such as a spin switch, in a controllable way.

  19. Kinetics of ultrashort relativistic electron pulses emitted from solid targets.

    PubMed

    Fill, Ernst E

    2004-09-01

    Interaction of ultrashort high-intensity laser pulses with solid targets generates relativistic electrons which escape from the target. The kinetics of these ultrashort electron pulses is governed by self-fields generated by the charge of the electron cloud. In this paper an analytical theory is developed which allows calculation of electron trajectories, electron fluxes, and electron spectra at any distance from the target. The theory is exact for two limiting cases: (a) a monoenergetic electron pulse with an arbitrary temporal shape; (b) an infinitely short electron pulse with an arbitrary energy spectrum. These results have applications in high-intensity irradiation experiments, e.g., in experiments irradiating samples with ultrashort electron or x-ray pulses, in developing optics for fourth-generation light sources, and in work relating to x-ray lasers.

  20. Direct excitation of propagating spin waves by focused ultrashort optical pulses.

    PubMed

    Au, Y; Dvornik, M; Davison, T; Ahmad, E; Keatley, P S; Vansteenkiste, A; Van Waeyenberge, B; Kruglyak, V V

    2013-03-01

    An all-optical experiment long utilized to image phonons excited by ultrashort optical pulses has been applied to a magnetic sample. In addition to circular ripples due to surface acoustic waves, we observe an X-shaped pattern formed by propagating spin waves. The emission of spin waves from the optical pulse epicenter in the form of collimated beams is qualitatively reproduced by micromagnetic simulations. We explain the observed pattern in terms of the group velocity distribution of Damon-Eshbach magnetostatic spin waves in the reciprocal space and the wave vector spectrum of the focused ultrafast laser pulse.

  1. Direct Excitation of Propagating Spin Waves by Focused Ultrashort Optical Pulses

    NASA Astrophysics Data System (ADS)

    Au, Y.; Dvornik, M.; Davison, T.; Ahmad, E.; Keatley, P. S.; Vansteenkiste, A.; Van Waeyenberge, B.; Kruglyak, V. V.

    2013-03-01

    An all-optical experiment long utilized to image phonons excited by ultrashort optical pulses has been applied to a magnetic sample. In addition to circular ripples due to surface acoustic waves, we observe an X-shaped pattern formed by propagating spin waves. The emission of spin waves from the optical pulse epicenter in the form of collimated beams is qualitatively reproduced by micromagnetic simulations. We explain the observed pattern in terms of the group velocity distribution of Damon-Eshbach magnetostatic spin waves in the reciprocal space and the wave vector spectrum of the focused ultrafast laser pulse.

  2. Electron spin dynamics in cubic GaN

    NASA Astrophysics Data System (ADS)

    Buß, J. H.; Schupp, T.; As, D. J.; Brandt, O.; Hägele, D.; Rudolph, J.

    2016-12-01

    The electron spin dynamics in cubic GaN is comprehensively investigated by time-resolved magneto-optical Kerr-rotation spectroscopy over a wide range of temperatures, magnetic fields, and doping densities. The spin dynamics is found to be governed by the interplay of spin relaxation of localized electrons and Dyakonov-Perel relaxation of delocalized electrons. Localized electrons significantly contribute to spin relaxation up to room temperature at moderate doping levels, while Dyakonov-Perel relaxation dominates for high temperatures or degenerate doping levels. Quantitative agreement to Dyakonov-Perel theory requires a larger value of the spin-splitting constant than theoretically predicted. Possible reasons for this discrepancy are discussed, including the role of charged dislocations.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Electron nuclear spin transfer in quantum-dot networks

    NASA Astrophysics Data System (ADS)

    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.

  5. Spin-dependent Electron Correlations of a System with Broken Spin Symmetry

    NASA Astrophysics Data System (ADS)

    Yi, K. S.; Kim, J. I.; Kim, J. S.

    2001-04-01

    The spin-dependent local field corrections Gσ, σ'/ (q, ω) of a spin-polarized electron gas(SPEG) are examined within a genralized RPA. Numerical results of Gσ, σ/ (q, 0) for both the majority and minority spin electrons of SPEG show a complicated but interesting behavior as one varies the spin polarization ζ of the SPEG. A pronounced maximum in Gσ, σ/ (q, 0) is observed and the location of the peaks are found to depend strongly on the values of ζ. We also show some numerical results of the mixed susceptibilities χem and χme, which are finite and not identical in SPEG.

  6. Electron Spin Relaxation and Coherence Times in Si/SiGe Quantum Dots

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    Single electron spin states in Si/SiGe quantum dots have shown promise as qubits for quantum information processing. Recently, electron spins in gated Si/SiGe quantum dots have displayed relaxation (T1) and coherence (T2) times of 250 μs at 350mK. The experiments used conventional X-band (10 GHz) pulsed Electron Spin Resonance (pESR) on a large area (3.5 x 20 mm2) , double gated, undoped Si/SiGe heterostructure, which was patterned with 2 x 108 quantum dots using e-beam lithography. Dots with 150 nm radii and 700 nm period are induced in a natural Si quantum well by the gates. Smaller dots are expected to reduce the effects of nearly degenerate valley states and spin-orbit coupling on the electron spin coherence. However, the small number of spins makes signal recovery extremely challenging. We have implemented a broadband cryogenic HEMT low-noise-amplifier and a high-speed single-pole double-throw switch operating at liquid helium temperatures. The switch and preamp have improved our signal to noise by an order of magnitude, allowing for smaller samples and shorter measurement times. We will describe these improvements and the data they have enabled. supported by the ARO

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

    NASA Astrophysics Data System (ADS)

    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. Maximal charge injection of consecutive electron pulses with uniform temporal pulse separation

    SciTech Connect

    Liu, Y. L.; Zhang, P.; Chen, S. H.; Ang, L. K.

    2015-08-15

    A charge sheet model is proposed for the study of the space-charge limited density of consecutive electron pulses injected to in a diode with uniform temporal pulse separation. Based on the model, an analytical formula is derived for expressing the dependency of the charge density limit on the gap spacing, gap voltage, and pulse separation. The theoretical results are verified by numerical solutions up to electron energy of a few MeV, including relativistic effects. The model can be applied to the design of multiple-pulse electron beams for time resolved electron microscopy and free electron lasers.

  9. Anomalous organic magnetoresistance from competing carrier-spin-dependent interactions with localized electronic and nuclear spins

    NASA Astrophysics Data System (ADS)

    Flatté, Michael E.

    Transport of carriers through disordered electronic energy landscapes occurs via hopping or tunneling through various sites, and can enhance the effects of carrier spin dynamics on the transport. When incoherent hopping preserves the spin orientation of carriers, the magnetic-field-dependent correlations between pairs of spins influence the charge conductivity of the material. Examples of these phenomena have been identified in hopping transport in organic semiconductors and colloidal quantum dots, as well as tunneling through oxide barriers in complex oxide devices, among other materials. The resulting room-temperature magnetic field effects on the conductivity or electroluminescence require external fields of only a few milliTesla. These magnetic field effects can be dramatically modified by changes in the local spin environment. Recent theoretical and experimental work has identified a regime for low-field magnetoresistance in organic semiconductors in which the spin-relaxing effects of localized nuclear spins and electronic spins interfere1. The regime is studied experimentally by the controlled addition of localized electronic spins, through the addition of a stable free radical (galvinoxyl) to a material (MEH-PPV) that exhibits substantial room-temperature magnetoresistance (20 initially suppressed by the doping, as the localized electronic spin mixes one of the two spins whose correlation controls the transport. At intermediate doping, when one spin is fully decohered but the other is not, there is a regime where the magnetoresistance is insensitive to the doping level. For much greater doping concentrations the magnetoresistance is fully suppressed as both spins that control the charge conductivity of the material are mixed. The behavior is described within a theoretical model describing the effect of carrier spin dynamics on the current. Generalizations to amorphous and other disordered crystalline semiconductors will also be described. This work was

  10. Optical detection of spin-filter effect for electron spin polarimetry

    SciTech Connect

    Li, X.; Majee, S.; Lampel, G.; Lassailly, Y.; Paget, D.; Peretti, J.; Tereshchenko, O. E.

    2014-08-04

    We have monitored the cathodoluminescence (CL) emitted upon injection of free electrons into a hybrid structure consisting of a thin magnetic Fe layer deposited on a p-GaAs substrate, in which InGaAs quantum wells are embedded. Electrons transmitted through the unbiased metal/semiconductor junction recombine radiatively in the quantum wells. Because of the electron spin-filtering across the Fe/GaAs structure, the CL intensity, collected from the backside, is found to depend on the relative orientation between the injected electronic spin polarization and the Fe layer magnetization. The spin asymmetry of the CL intensity in such junction provides a compact optical method for measuring spin polarization of free electrons beams or of hot electrons in solid-state devices.

  11. Diagnostic Potential of Pulsed Arterial Spin Labeling in Alzheimer's Disease

    PubMed Central

    Trebeschi, Stefano; Riederer, Isabelle; Preibisch, Christine; Bohn, Karl P.; Förster, Stefan; Alexopoulos, Panagiotis; Zimmer, Claus; Kirschke, Jan S.; Valentinitsch, Alexander

    2016-01-01

    Alzheimers disease (AD) is the most common cause of dementia. Although the underlying pathology is still not completely understood, several diagnostic methods are available. Frequently, the most accurate methods are also the most invasive. The present work investigates the diagnostic potential of Pulsed Arterial Spin Labeling (PASL) for AD: a non-invasive, MRI-based technique for the quantification of regional cerebral blood flow (rCBF). In particular, we propose a pilot computer aided diagnostic (CAD) procedure able to discriminate between healthy and diseased subjects, and at the same time, providing visual informative results. This method encompasses the creation of a healthy model, the computation of a voxel-wise likelihood function as comparison between the healthy model and the subject under examination, and the correction of the likelihood function via prior distributions. The discriminant analysis is carried out to maximize the accuracy of the classification. The algorithm has been trained on a dataset of 81 subjects and achieved a sensitivity of 0.750 and a specificity of 0.875. Moreover, in accordance with the current pathological knowledge, the parietal lobe, and limbic system are shown to be the main discriminant factors. PMID:27147946

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Studies of electron spin in GaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Craft, Daniel; Colton, John; Park, Tyler; White, Phil

    2013-03-01

    We have studied electron spins in GaAs quantum dots with a pump-probe technique that normally yields the T1 spin lifetime, the time required for initially polarized electrons to relax and randomize. Using a circularly polarized laser tuned to the wavelength response of the quantum dot we can ``pump'' the spins into alignment. After aligning the spins we can detect them using a second, linearly polarized ``probe'' laser. By changing the delay between the two lasers we can trace out the spin response over time. In contrast with other samples (bulk GaAs and a GaAs quantum well), where the spin response decayed exponentially with time, initial data on the quantum dots has shown an unexpected, oscillating behavior which dies out on the order of 700 ns, independent of both temperature and magnetic field.

  15. Pulse saturation recovery, pulse ELDOR, and free induction decay electron paramagnetic resonance detection using time-locked subsampling

    NASA Astrophysics Data System (ADS)

    Froncisz, W.; Camenisch, Theodore G.; Ratke, Joseph J.; Hyde, James S.

    2001-03-01

    Time locked subsampling (TLSS) in electron paramagnetic resonance (EPR) involves the steps of (i) translation of the signal from a microwave carrier to an intermediate frequency (IF) carrier where the (IF) offset between the signal oscillator and local oscillator frequencies is synthesized, (ii) sampling the IF carrier four times in an odd number of cycles, say 4 in 3, where the analog-to-digital (A/D) converter is driven by a frequency synthesizer that has the same clock input as the IF synthesizer, (iii) signal averaging as required for adequate signal to noise, (iv) separating the even and odd digitized words into two separate signal channels, which correspond to signals in phase and in quadrature with respect to the IF carrier, i.e., I and Q, and (v) detecting the envelope of I and also of Q by changing the signs of alternate words in each of the two channels. TLSS detection has been demonstrated in three forms of pulse EPR spectroscopy at X band: saturation recovery, pulse electron-electron double resonance, and free induction decay. The IF was 187.5 MHz, the A/D converter frequency was 250 MHz, the overall bandwidth was 125 MHz, and the bandwidths for the separate I and Q channels were each 62.5 MHz. Experiments were conducted on nitroxide radical spin labels. The work was directed towards development of methodology to monitor bimolecular collisions of oxygen with spin labels in a context of site-directed spin labeling.

  16. Pulse requirements for electron diffraction imaging of single biological molecules

    SciTech Connect

    Hau-Riege, S; London, R; Chapman, H

    2004-10-20

    The pulse requirements for electron diffraction imaging of single biological molecules are calculated. We find that the electron fluence and pulse length requirements imposed by the damage limit and by the need to classify the diffraction patterns according to their angular orientation cannot be achieved with today's electron beam technology. A simple analytical model shows that the pulse requirements cannot be achieved due to beam broadening due to spacecharge effects.

  17. Electron spin changes during general anesthesia in Drosophila

    PubMed Central

    Turin, Luca; Skoulakis, Efthimios M. C.; Horsfield, Andrew P.

    2014-01-01

    We show that the general anesthetics xenon, sulfur hexafluoride, nitrous oxide, and chloroform cause rapid increases of different magnitude and time course in the electron spin content of Drosophila. With the exception of CHCl3, these changes are reversible. Anesthetic-resistant mutant strains of Drosophila exhibit a different pattern of spin responses to anesthetic. In two such mutants, the spin response to CHCl3 is absent. We propose that these spin changes are caused by perturbation of the electronic structure of proteins by general anesthetics. Using density functional theory, we show that general anesthetics perturb and extend the highest occupied molecular orbital of a nine-residue α-helix. The calculated perturbations are qualitatively in accord with the Meyer–Overton relationship and some of its exceptions. We conclude that there may be a connection between spin, electron currents in cells, and the functioning of the nervous system. PMID:25114249

  18. Electron spin control of optically levitated nanodiamonds in vacuum

    NASA Astrophysics Data System (ADS)

    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.

  19. Spin fluctuations of nonequilibrium electrons and excitons in semiconductors

    NASA Astrophysics Data System (ADS)

    Glazov, M. M.

    2016-03-01

    Effects that are related to deviations from thermodynamic equilibrium have a special place in modern physics. Among these, nonequilibrium phenomena in quantum systems attract the highest interest. The experimental technique of spin-noise spectroscopy has became quite widespread, which makes it possible to observe spin fluctuations of charge carriers in semiconductors under both equilibrium and nonequilibrium conditions. This calls for the development of a theory of spin fluctuations of electrons and electron-hole complexes for nonequilibrium conditions. In this paper, we consider a range of physical situations where a deviation from equilibrium becomes pronounced in the spin noise. A general method for the calculation of electron and exciton spin fluctuations in a nonequilibrium state is proposed. A short review of the theoretical and experimental results in this area is given.

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

    PubMed

    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.

  1. Flux noise in SQUIDs: Electron versus nuclear spins

    NASA Astrophysics Data System (ADS)

    de Sousa, Rogerio; Laforest, Stephanie

    2015-03-01

    Superconducting Quantum Interference Devices (SQUIDs) are limited by intrinsic flux noise whose origin is unknown. We develop a method to accurately calculate the flux produced by spin impurities in realistic superconducting thin film wires, and show that the flux produced by each spin is much larger than anticipated by former calculations. Remarkably, the total flux noise power due to electron spins at the thin side surface of the wires is found to be of similar magnitude as the one due to electrons at the wide top surface of the wires. In addition, flux noise due to lattice nuclear spins in the bulk of the wires is found to be a sizable fraction of the total noise for some SQUID geometries. We discuss the relative importance of electron and nuclear spin species in determining the total noise power, and propose strategies to design SQUIDs with lower flux noise. We acknowledge support from the Canadian agency NSERC through its Discovery and Engage programs.

  2. Resolving the role of femtosecond heated electrons in ultrafast spin dynamics

    PubMed Central

    Mendil, J.; Nieves, P.; Chubykalo-Fesenko, O.; Walowski, J.; Santos, T.; Pisana, S.; Münzenberg, M.

    2014-01-01

    Magnetization manipulation is essential for basic research and applications. A fundamental question is, how fast can the magnetization be reversed in nanoscale magnetic storage media. When subject to an ultrafast laser pulse, the speed of the magnetization dynamics depends on the nature of the energy transfer pathway. The order of the spin system can be effectively influenced through spin-flip processes mediated by hot electrons. It has been predicted that as electrons drive spins into the regime close to almost total demagnetization, characterized by a loss of ferromagnetic correlations near criticality, a second slower demagnetization process takes place after the initial fast drop of magnetization. By studying FePt, we unravel the fundamental role of the electronic structure. As the ferromagnet Fe becomes more noble in the FePt compound, the electronic structure is changed and the density of states around the Fermi level is reduced, thereby driving the spin correlations into the limit of critical fluctuations. We demonstrate the impact of the electrons and the ferromagnetic interactions, which allows a general insight into the mechanisms of spin dynamics when the ferromagnetic state is highly excited, and identifies possible recording speed limits in heat-assisted magnetization reversal. PMID:24496221

  3. Spin dynamics simulation of electron spin relaxation in Ni{sup 2+}(aq)

    SciTech Connect

    Rantaharju, Jyrki Mareš, Jiří Vaara, Juha

    2014-07-07

    The ability to quantitatively predict and analyze the rate of electron spin relaxation of open-shell systems is important for electron paramagnetic resonance and paramagnetic nuclear magnetic resonance spectroscopies. We present a combined molecular dynamics (MD), quantum chemistry (QC), and spin dynamics simulation method for calculating such spin relaxation rates. The method is based on the sampling of a MD trajectory by QC calculations, to produce instantaneous parameters of the spin Hamiltonian used, in turn, to numerically solve the Liouville-von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by simulating the relaxation of electron spin in an aqueous solution of Ni{sup 2+} ion. The spin-lattice (T{sub 1}) and spin-spin (T{sub 2}) relaxation rates are extracted directly from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available, indirectly obtained experimental data is obtained by our method.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Casey, Thomas M; Fanucci, Gail E

    2015-01-01

    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.

  9. Ponderomotive acceleration of electrons by a self focused laser pulse

    SciTech Connect

    Singh, Rohtash; Sharma, A. K.

    2010-12-15

    Ponderomotive acceleration of electrons by a short laser pulse undergoing relativistic self-focusing in a plasma is investigated. The saturation in nonlinear plasma permittivity causes periodic self-focusing of the laser. The periodicity lengths are different for different axial segments of the pulse. As a result, pulse shape is distorted. An electron initially on the laser axis and at the front of the self-focusing pulse gains energy from the pulse until it is run over by the pulse peak. By the time electron reaches the tail, if pulse begins diverging, the deceleration of the electron is slower and the electron is left with net energy gain. The electrons slightly off the laser axis see a radial ponderomotive force too. Initially, when they are accelerated by the pulse front the acceleration is strong as they are closer to the axis. When they see the tail of the pulse (after being run by the pulse), they are farther from the axis and the retardation ponderomotive force is weaker. Thus, there is net energy gain.

  10. Suppressing the spin relaxation of electrons in silicon

    NASA Astrophysics Data System (ADS)

    Chalaev, Oleg; Song, Yang; Dery, Hanan

    2017-01-01

    Uniaxial compressive strain along the [001] direction strongly suppresses the spin relaxation in silicon. When the strain level is large enough so that electrons are redistributed only in the two valleys along the strain axis, the dominant scattering mechanisms are quenched and electrons mainly experience intra-axis scattering processes (intravalley or intervalley scattering within valleys on the same crystal axis). We first derive the spin-flip matrix elements due to intra-axis electron scattering off impurities, and then provide a comprehensive model of the spin relaxation time due to all possible interactions of conduction-band electrons with impurities and phonons. We predict a nearly three orders of magnitude improvement in the spin relaxation time of ˜1019cm-3 antimony-doped silicon (Si:Sb) at low temperatures.

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

    NASA Astrophysics Data System (ADS)

    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).

  12. Electron Spin Relaxation in Irradiated Solids.

    DTIC Science & Technology

    1996-03-01

    the development and use of ELDOR techniques to study the spectral diffusion in irradiated L-alanine and other irradiated organic solids. Pulsed STELDOR...and pulsed two-frequency ELDOR methods were developed and the details of the implementation is reported. The assignment of relaxation times that gave

  13. Dissipative long-range entanglement generation between electronic spins

    NASA Astrophysics Data System (ADS)

    Benito, M.; Schuetz, M. J. A.; Cirac, J. I.; Platero, G.; Giedke, G.

    2016-09-01

    We propose a scheme for deterministic generation and long-term stabilization of entanglement between two electronic spin qubits confined in spatially separated quantum dots. Our approach relies on an electronic quantum bus, consisting either of quantum Hall edge channels or surface acoustic waves, that can mediate long-range coupling between localized spins over distances of tens of micrometers. Since the entanglement is actively stabilized by dissipative dynamics, our scheme is inherently robust against noise and imperfections.

  14. Spatially resolved two-dimensional Fourier transform electron spin resonance

    NASA Astrophysics Data System (ADS)

    Ewert, Uwe; Crepeau, Richard H.; Lee, Sanghyuk; Dunnam, Curt R.; Xu, Dajiang; Freed, Jack H.

    1991-09-01

    Fourier transform ESR methods have been extended to permit spatially resolved two-dimensional (2D)-ESR experiments. This is illustrated for the case of 2D-electron-electron double resonance (2D-ELDOR) spectra of nitroxides in a liquid that exhibits appreciable cross-peaks due to Heisenberg spin exchange. The use of spin-echo decays in spatially resolved FT-ESR is also demonstrated.

  15. Dephasing of optically generated electron spins in semiconductors

    NASA Astrophysics Data System (ADS)

    Idrish Miah, M.

    2010-09-01

    Dephasing of optically generated electron spins in the presence of the external magnetic field and electric bias in semiconductor nano-structures has been studied by time- and polarization-resolved spectrometry. The obtained experimental data are presented in dependence of the strength of the magnetic field. The optically generated electron-spin precession frequency and dephasing time and rate are estimated. It is found that both the spin precession frequency and dephasing rate increase linearly with the external magnetic field up to about 9 T. However, the spin dephasing time is within sub- μs and is found to decrease exponentially with the strength of the external magnetic field. The results are discussed by exploring possible mechanisms of spin dephasing in low-dimensional semiconductor structures, where the quantum-confinement persists within the nano-range.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Pulsed magnetic field-electron cyclotron resonance ion source operation

    SciTech Connect

    Muehle, C.; Ratzinger, U.; Joest, G.; Leible, K.; Schennach, S.; Wolf, B.H.

    1996-03-01

    The pulsed magnetic field (PuMa)-electron cyclotron resonance (ECR) ion source uses a pulsed coil to improve the peak current by opening the magnetic bottle along the beam axis. After demonstration of the principle of the pulsed magnetic extraction, the ion source was tested with different gases. We received promising results from helium to krypton. The influence of the current in the pulsed coil on the analyzed ion current was measured. With increased current levels within the pulsed coil not only the pulse height of the PuMa pulse, but the pulse length can also be controlled. By using the pulsed coil the maximum of the charge state distribution can be shifted to higher charge states. {copyright} {ital 1996 American Institute of Physics.}

  18. Nanometer-scale probing of spin waves using single electron spins

    NASA Astrophysics Data System (ADS)

    van der Sar, Toeno; Casola, Francesco; Walsworth, Ronald; Yacoby, Amir

    2015-05-01

    We have developed a new approach to exploring magnetic excitations in correlated-electron systems, based on single electronic spins in atom-like defects diamond known as nitrogen-vacancy (NV) color centers. We demonstrate the power of this approach by detecting spin-wave excitations in a ferromagnetic microdisc with nanoscale spatial sensitivity over a broad range of frequencies and magnetic fields. We show how spin-wave resonances can be exploited for on-chip amplification of microwave magnetic fields, allowing strongly increased spin manipulation rates and single-spin magnetometry with enhanced sensitivity. Finally, we show the possibility to detect the magnetic spin noise produced by a thin (~ 30 nm) layer of a patterned ferromagnet. For the interpretation of our results, we develop a general framework describing single-spin stray field detection in terms of a filter function sensitive mostly to spin fluctuations with wavevector ~ 1 / d , where d is the NV-ferromagnet distance. Our results pave the way towards quantitative and non-perturbative detection of spectral properties in nanomagnets, establishing NV center magnetometry as an emergent probe of collective spin dynamics in condensed matter.

  19. Optimizing chirped laser pulse parameters for electron acceleration in vacuum

    SciTech Connect

    Akhyani, Mina; Jahangiri, Fazel; Niknam, Ali Reza; Massudi, Reza

    2015-11-14

    Electron dynamics in the field of a chirped linearly polarized laser pulse is investigated. Variations of electron energy gain versus chirp parameter, time duration, and initial phase of laser pulse are studied. Based on maximizing laser pulse asymmetry, a numerical optimization procedure is presented, which leads to the elimination of rapid fluctuations of gain versus the chirp parameter. Instead, a smooth variation is observed that considerably reduces the accuracy required for experimentally adjusting the chirp parameter.

  20. Visualization of Distance Distribution from Pulsed Double Electron-Electron Resonance Data

    SciTech Connect

    Bowman, Michael K.; Maryasov, Alexander G.; Kim, Nak-Kyoon; DeRose, Victoria J.

    2004-01-01

    Double electron-electron resonance (DEER), also known as pulsed electron-electron double resonance (PELDOR), is a time-domain electron paramagnetic resonance method that can measure the weak dipole-dipole interactions between unpaired electrons. DEER has been applied to discrete pairs of free radicals in biological macromolecules and to clusters containing small numbers of free radicals in polymers and irradiated materials. The goal of such work is to determine the distance or distribution of distances between radicals, which is an underdetermined problem. That is, the spectrum of dipolar interactions can be readily calculated for any distribution of free radicals, but there are many, quite different distributions of radicals that could produce the same experimental dipolar spectrum. This paper describes two methods that are useful for approximating the distance distributions for the large subset of cases in which the mutual orientations of the free radicals are uncorrelated and the width of the distribution is more than a few percent of its mean. The first method relies on a coordinate transformation and is parameter free, while the second is based on iterative least-squares with Tikhonov regularization. Both methods are useful in DEER studies of spin labeled biomolecules containing more than two labels.

  1. Spin dynamics of a confined electron interacting with magnetic or nuclear spins: A semiclassical approach

    NASA Astrophysics Data System (ADS)

    Dietl, Tomasz

    2015-03-01

    A physically transparent and mathematically simple semiclassical model is employed to examine dynamics in the central-spin problem. The results reproduce previous findings obtained by various quantum approaches and, at the same time, provide information on the electron spin dynamics and Berry's phase effects over a wider range of experimentally relevant parameters than available previously. This development is relevant to dynamics of bound magnetic polarons and spin dephasing of an electron trapped by an impurity or a quantum dot, and coupled by a contact interaction to neighboring localized magnetic impurities or nuclear spins. Furthermore, it substantiates the applicability of semiclassical models to simulate dynamic properties of spintronic nanostructures with a mesoscopic number of spins.

  2. Determining the exchange parameters of spin-1 metal-organic molecular magnets in pulsed magnetic fields

    SciTech Connect

    Mcdonald, Ross D; Singleton, John; Lancaster, Tom; Goddard, Paul; Manson, Jamie

    2011-01-14

    the Cu-pyz-Cu directions. The structure of the two compounds is similar, but in the case of the Cu-compound the Cu-Cu pathways are linear, whereas in the Ni-compound they are kinked. The pulsed-field data combined with information from temperature-dependent susceptibility, muon-spin rotation, electron-spin resonance and ligand-field calculations suggest that, far from being magnetically Q2D, the Ni-compound is fairly one-dimensional with the dominant exchange (J{sub 1D} = 3.1 K and J{sub {perpendicular}}/J{sub 1D} = 0.63) directed along the Ni-FHF-Ni direction. Ni(NCS){sub 2}(pyzdo){sub 2} was also investigated. Previous ultra-high field measurements using the 100 T magnet have shown that this compound has a saturation field close to 80 T. The purpose of the present studies is to map out the phase diagram of this material at mid-range fields. The data are shown in the inset to the figure. This continuing project probes the ability of organic ligands to mediate magnetic exchange, the link between structure, dimensionality and bulk magnetic properties, as well as the role of spin number in quantum magnets. Ultimately the investigations aim to determine to what extent it is possible to produce self-assembly molecular materials with tailor-made magnetic characteristics.

  3. Generation of ultrashort electron bunches by colliding laser pulses.

    PubMed

    Schroeder, C B; Lee, P B; Wurtele, J S; Esarey, E; Leemans, W P

    1999-05-01

    A proposed laser-plasma-based relativistic electron source [E. Esarey et al., Phys. Rev. Lett. 79, 2682 (1997)] using laser-triggered injection of electrons is investigated. The source generates ultrashort electron bunches by dephasing and trapping background plasma electrons undergoing fluid oscillations in an excited plasma wake. The plasma electrons are dephased by colliding two counterpropagating laser pulses which generate a slow phase velocity beat wave. Laser pulse intensity thresholds for trapping and the optimal wake phase for injection are calculated. Numerical simulations of test particles, with prescribed plasma and laser fields, are used to verify analytic predictions and to study the longitudinal and transverse dynamics of the trapped plasma electrons. Simulations indicate that the colliding laser pulse injection scheme has the capability to produce relativistic femtosecond electron bunches with fractional energy spread of order a few percent and normalized transverse emittance less than 1 mm mrad using 1 TW injection laser pulses.

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

    PubMed

    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.

  5. Electron spin control of optically levitated nanodiamonds in vacuum

    PubMed Central

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

    2016-01-01

    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. PMID:27432560

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

    PubMed

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

    2016-12-14

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    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

  9. Spin-Polarizing Interferometric Beam Splitter for Free Electrons.

    PubMed

    Dellweg, Matthias M; Müller, Carsten

    2017-02-17

    A spin-polarizing electron beam splitter is described that 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 as an ordinary Stern-Gerlach magnet does on atoms.

  10. Spin-Polarizing Interferometric Beam Splitter for Free Electrons

    NASA Astrophysics Data System (ADS)

    Dellweg, Matthias M.; Müller, Carsten

    2017-02-01

    A spin-polarizing electron beam splitter is described that 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 as an ordinary Stern-Gerlach magnet does on atoms.

  11. The Boersch effect in a picosecond pulsed electron beam emitted from a semiconductor photocathode

    NASA Astrophysics Data System (ADS)

    Kuwahara, Makoto; Nambo, Yoshito; Aoki, Kota; Sameshima, Kensuke; Jin, Xiuguang; Ujihara, Toru; Asano, Hidefumi; Saitoh, Koh; Takeda, Yoshikazu; Tanaka, Nobuo

    2016-07-01

    The space charge effect has been clearly observed in the energy distributions of picosecond pulse beams from a spin-polarized electron microscope, and was found to depend upon the quantity of charge per pulse. The non-linear phenomena associated with this effect have also been replicated in beam simulations that take into account of a three-dimensional space charge. The results show that a charge of 500 aC/pulse provides the highest brightness with a 16-ps pulse duration, a 30-keV beam energy, and an emission spot of 1.8 μm. Furthermore, the degeneracy of the wave packet of the pulsed electron beam has been evaluated to be 1.6 × 10-5 with a charge of 100 aC/pulse, which is higher than that for a continuously emitted electron beam despite the low beam energy of 30 keV. The high degeneracy and high brightness contribute to the realization of high temporal and energy resolutions in low-voltage electron microscopy, which will serve to reduce radiolysis damage and enhance scattering contrast.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Spin Measurements of an Electron Bound to a Single Phosphorous Donor in Silicon

    NASA Astrophysics Data System (ADS)

    Luhman, D. R.; Nguyen, K.; Tracy, L. A.; Carr, S. M.; Borchardt, J.; Bishop, N. C.; Ten Eyck, G. A.; Pluym, T.; Wendt, J.; Carroll, M. S.; Lilly, M. P.

    2014-03-01

    The spin of an electron bound to a single donor implanted in silicon is potentially useful for quantum information processing. We report on our efforts to measure and manipulate the spin of an electron bound to a single P donor in silicon. A low number of P donors are implanted using a self-aligned process into a silicon substrate in close proximity to a single-electron-transistor (SET) defined by lithographically patterned polysilicon gates. The SET is used to sense the occupancy of the electron on the donor and for spin read-out. An adjacent transmission line allows the application of microwave pulses to rotate the spin of the electron. We will present data from various experiments designed to exploit these capabilities. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. The work was supported by Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

  14. Proposal for a High-Brightness Pulsed Electron Source

    SciTech Connect

    Zolotorev, M.; Commins, E.D.; Heifets, S.; Sannibale, F.; /LBL, Berkeley /UC, Berkeley /SLAC

    2006-10-16

    We propose a novel scheme for a high-brightness pulsed electron source, which has the potential for many useful applications in electron microscopy, inverse photo-emission, low energy electron scattering experiments, and electron holography. A description of the proposed scheme is presented.

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

    PubMed Central

    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

  16. Pulse Splitting in Short Wavelength Seeded Free Electron Lasers

    SciTech Connect

    Labat, M.; Couprie, M. E.; Joly, N.; Bruni, C.

    2009-12-31

    We investigate a fundamental limitation occurring in vacuum ultraviolet and extreme ultraviolet seeded free electron lasers (FELs). For a given electron beam and undulator configuration, an increase of the FEL output energy at saturation can be obtained via an increase of the seed pulse duration. We put in evidence a complex spatiotemporal deformation of the amplified pulse, leading ultimately to a pulse splitting effect. Numerical studies of the Colson-Bonifacio FEL equations reveal that slippage length and seed laser pulse wings are core ingredients of the dynamics.

  17. Entanglement purification and concentration of electron-spin entangled states using quantum-dot spins in optical microcavities

    SciTech Connect

    Wang Chuan; Zhang Yong; Jin Guangsheng

    2011-09-15

    We present an entanglement purification protocol and an entanglement concentration protocol for electron-spin entangled states, resorting to quantum-dot spin and optical-microcavity-coupled systems. The parity-check gates (PCGs) constructed by the cavity-spin-coupling system provide a different method for the entanglement purification of electron-spin entangled states. This protocol can efficiently purify an electron ensemble in a mixed entangled state. The PCGs can also concentrate electron-spin pairs in less-entangled pure states efficiently. The proposed methods are more flexible as only single-photon detection and single-electron detection are needed.

  18. Quantum and classical correlations in electron-nuclear spin echo

    SciTech Connect

    Zobov, V. E.

    2014-11-15

    The quantum properties of dynamic correlations in a system of an electron spin surrounded by nuclear spins under the conditions of free induction decay and electron spin echo have been studied. Analytical results for the time evolution of mutual information, classical part of correlations, and quantum part characterized by quantum discord have been obtained within the central-spin model in the high-temperature approximation. The same formulas describe discord in both free induction decay and spin echo although the time and magnetic field dependences are different because of difference in the parameters entering into the formulas. Changes in discord in the presence of the nuclear polarization β{sub I} in addition to the electron polarization β{sub S} have been calculated. It has been shown that the method of reduction of the density matrix to a two-spin electron-nuclear system provides a qualitatively correct description of pair correlations playing the main role at β{sub S} ≈ β{sub I} and small times. At large times, such correlations decay and multispin correlations ensuring nonzero mutual information and zero quantum discord become dominant.

  19. Ultra-bright pulsed electron beam with low longitudinal emittance

    DOEpatents

    Zolotorev, Max

    2010-07-13

    A high-brightness pulsed electron source, which has the potential for many useful applications in electron microscopy, inverse photo-emission, low energy electron scattering experiments, and electron holography has been described. The source makes use of Cs atoms in an atomic beam. The source is cycled beginning with a laser pulse that excites a single Cs atom on average to a band of high-lying Rydberg nP states. The resulting valence electron Rydberg wave packet evolves in a nearly classical Kepler orbit. When the electron reaches apogee, an electric field pulse is applied that ionizes the atom and accelerates the electron away from its parent ion. The collection of electron wave packets thus generated in a series of cycles can occupy a phase volume near the quantum limit and it can possess very high brightness. Each wave packet can exhibit a considerable degree of coherence.

  20. Gate-controlled electron spins in quantum dots

    SciTech Connect

    Prabhakar, Sanjay; Melnik, Roderick; Bonilla, Luis L.

    2013-12-16

    In this paper we study the properties of anisotropic semiconductor quantum dots (QDs) formed in the conduction band in the presence of the magnetic field. The Kane-type model is formulated and is analyzed by using both analytical and finite element techniques. Among other things, we demonstrate that in such quantum dots, the electron spin states in the phonon-induced spin-flip rate can be manipulated with the application of externally applied anisotropic gate potentials. More precisely, such potentials enhance the spin flip rates and reduce the level crossing points to lower quantum dot radii. This happens due to the suppression of the g-factor towards bulk crystal. We conclude that the phonon induced spin-flip rate can be controlled through the application of spin-orbit coupling. Numerical examples are shown to demonstrate these findings.

  1. Optically-pumped spin-exchange polarized electron source

    NASA Astrophysics Data System (ADS)

    Pirbhai, Munir Hussein

    Polarized electron beams are an indispensable probe of spin-dependent phenomena in fields of atomic and molecular physics, magnetism and biophysics. While their uses have become widespread, the standard source based on negative electron affinity gallium arsenide (GaAs) remains technically complicated. This has hindered progress on many experiments involving spin-polarized electrons, especially those using target gas loads, which tend to adversely affect the performance of GaAs sources. A robust system based on an alternative way to make polarized electron beams has been devised in this study, which builds on previous work done in our lab. It involves spin-exchange collisions between free, unpolarized electrons and oriented rubidium atoms in the presence of a quenching gas. This system has less stringent vacuum requirements than those of GaAs sources, and is capable of operating in background pressures of ~1mTorr. Beams with ~24% polarization and 4μA of current have been recorded, which is comparable to the performance obtained with the earlier version built in our lab. The present system is however not as unstable as in the previous work, and has the potential to be developed into a "turn-key" source of polarized electron beams. It has also allowed us to undertake a study to find factors which affect the beam polarization in this scheme of producing polarized electrons. Such knowledge will help us to design better optically-pumped spin-exchange polarized electron sources.

  2. Access to long-term optical memories using photon echoes retrieved from electron spins in semiconductor quantum wells

    NASA Astrophysics Data System (ADS)

    Poltavtsev, S. V.; Langer, L.; Yugova, I. A.; Salewski, M.; Kapitonov, Y. V.; Yakovlev, D. R.; Karczewski, G.; Wojtowicz, T.; Akimov, I. A.; Bayer, M.

    2016-10-01

    We use spontaneous (two-pulse) and stimulated (three-pulse) photon echoes for studying the coherent evolution of optically excited ensemble of trions which are localized in semiconductor CdTe/CdMgTe quantum well. Application of transverse magnetic field leads to the Larmor precession of the resident electron spins, which shuffles optically induced polarization between optically accessible and inaccessible states. This results in several spectacular phenomena. First, magnetic field induces oscillations of spontaneous photon echo amplitude. Second, in three-pulse excitation scheme, the photon echo decay is extended by several orders of magnitude. In this study, short-lived optical excitation which is created by the first pulse is coherently transferred into a long-lived electron spin state using the second optical pulse. This coherent spin state of electron ensemble persists much longer than any optical excitation in the system, preserving information on initial optical field, which can be retrieved as a photon echo by means of third optical pulse.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Highly selective detection of individual nuclear spins with rotary echo on an electron spin probe

    DOE PAGES

    Mkhitaryan, V. V.; Jelezko, F.; Dobrovitski, V. V.

    2015-10-26

    We consider an electronic spin, such as a nitrogen-vacancy center in diamond, weakly coupled to a large number of nuclear spins, and subjected to the Rabi driving with a periodically alternating phase. We show that by switching the driving phase synchronously with the precession of a given nuclear spin, the interaction to this spin is selectively enhanced, while the rest of the bath remains decoupled. The enhancement is of resonant character. The key feature of the suggested scheme is that the width of the resonance is adjustable, and can be greatly decreased by increasing the driving strength. Thus, the resonancemore » can be significantly narrowed, by a factor of 10–100 in comparison with the existing detection methods. Significant improvement in selectivity is explained analytically and confirmed by direct numerical many-spin simulations. As a result, the method can be applied to a wide range of solid-state systems.« less

  5. Highly selective detection of individual nuclear spins with rotary echo on an electron spin probe

    SciTech Connect

    Mkhitaryan, V. V.; Jelezko, F.; Dobrovitski, V. V.

    2015-10-26

    We consider an electronic spin, such as a nitrogen-vacancy center in diamond, weakly coupled to a large number of nuclear spins, and subjected to the Rabi driving with a periodically alternating phase. We show that by switching the driving phase synchronously with the precession of a given nuclear spin, the interaction to this spin is selectively enhanced, while the rest of the bath remains decoupled. The enhancement is of resonant character. The key feature of the suggested scheme is that the width of the resonance is adjustable, and can be greatly decreased by increasing the driving strength. Thus, the resonance can be significantly narrowed, by a factor of 10–100 in comparison with the existing detection methods. Significant improvement in selectivity is explained analytically and confirmed by direct numerical many-spin simulations. As a result, the method can be applied to a wide range of solid-state systems.

  6. Ultrafast spin-transfer torque driven by femtosecond pulsed-laser excitation.

    PubMed

    Schellekens, A J; Kuiper, K C; de Wit, R R J C; Koopmans, B

    2014-07-10

    Spin currents have an important role in many proposed spintronic devices, as they govern the switching process of magnetic bits in random access memories or drive domain wall motion in magnetic shift registers. The generation of these spin currents has to be fast and energy efficient for realization of these envisioned devices. Recently it has been shown that femtosecond pulsed-laser excitation of thin magnetic films creates intense and ultrafast spin currents. Here we utilize this method to change the orientation of the magnetization in a magnetic bilayer by spin-transfer torque on sub-picosecond timescales. By analysing the dynamics of the magnetic bilayer after laser excitation, the rich physics governing ultrafast spin-transfer torque are elucidated opening up new pathways to ultrafast magnetization reversal, but also providing a new method to quantify optically induced spin currents generated on femtosecond timescales.

  7. Electron-Spin Filters Based on the Rashba Effect

    NASA Technical Reports Server (NTRS)

    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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Dhas, M. Kumara; Benial, A. Milton Franklin; Jawahar, A.

    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.

  10. Spin-polarized electron transport through helicene molecular junctions

    NASA Astrophysics Data System (ADS)

    Pan, Ting-Rui; Guo, Ai-Min; Sun, Qing-Feng

    2016-12-01

    Recently, the spin-selectivity effect of chiral molecules has been attracting extensive and growing interest among the scientific communities. Here, we propose a model Hamiltonian to study spin-dependent electron transport through helicene molecules which are connected by two semi-infinite graphene nanoribbons and try to elucidate a recent experiment of the spin-selectivity effect observed in the helicene molecules. The results indicate that the helicene molecules can present a significant spin-filtering effect in the case of extremely weak spin-orbit coupling, which is three orders of magnitude smaller than the hopping integral. The underlying physics is attributed to intrinsic chiral symmetry of the helicene molecules. When the chirality is switched from the right-handed species to the left-handed species, the spin polarization is reversed exactly. These results are consistent with a recent experiment [V. Kiran et al., Adv. Mater. 28, 1957 (2016), 10.1002/adma.201504725]. In addition, the spin-filtering effect of the helicene molecules is robust against molecular lengths, dephasing strengths, and space position disorder. This theoretical work may motivate further studies on chiral-induced spin selectivity in molecular systems.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Temporal lenses for attosecond and femtosecond electron pulses.

    PubMed

    Hilbert, Shawn A; Uiterwaal, Cornelis; Barwick, Brett; Batelaan, Herman; Zewail, Ahmed H

    2009-06-30

    Here, we describe the "temporal lens" concept that can be used for the focus and magnification of ultrashort electron packets in the time domain. The temporal lenses are created by appropriately synthesizing optical pulses that interact with electrons through the ponderomotive force. With such an arrangement, a temporal lens equation with a form identical to that of conventional light optics is derived. The analog of ray diagrams, but for electrons, are constructed to help the visualization of the process of compressing electron packets. It is shown that such temporal lenses not only compensate for electron pulse broadening due to velocity dispersion but also allow compression of the packets to durations much shorter than their initial widths. With these capabilities, ultrafast electron diffraction and microscopy can be extended to new domains,and, just as importantly, electron pulses can be delivered directly on an ultrafast techniques target specimen.

  13. Comparison of electron paramagnetic resonance methods to determine distances between spin labels on human carbonic anhydrase II.

    PubMed Central

    Persson, M; Harbridge, J R; Hammarström, P; Mitri, R; Mårtensson, L G; Carlsson, U; Eaton, G R; Eaton, S S

    2001-01-01

    Four doubly spin-labeled variants of human carbonic anhydrase II and corresponding singly labeled variants were prepared by site-directed spin labeling. The distances between the spin labels were obtained from continuous-wave electron paramagnetic resonance spectra by analysis of the relative intensity of the half-field transition, Fourier deconvolution of line-shape broadening, and computer simulation of line-shape changes. Distances also were determined by four-pulse double electron-electron resonance. For each variant, at least two methods were applicable and reasonable agreement between methods was obtained. Distances ranged from 7 to 24 A. The doubly spin-labeled samples contained some singly labeled protein due to incomplete labeling. The sensitivity of each of the distance determination methods to the non-interacting component was compared. PMID:11371461

  14. Probing Electron Dynamics in Simple Molecules with Attosecond Pulses

    NASA Astrophysics Data System (ADS)

    Rivière, Paula; Palacios, Alicia; Pérez-Torres, Jhon Fredy; Martín, Fernando

    Attosecond pulses are an ideal tool to explore electron and nuclear dynamics in atoms and molecules. Either as single attosecond pulses (SAP), in attosecond pulse trains (APT), or in combination with infrared (IR) pulses, these pulses, with frequencies in the VUV-XUV regime, have been widely used to probe ionization, electron tunneling, or autoionization in atoms. More recently, similar processes have been studied in molecules. A correct theoretical description of such processes in molecules often requires a fully dimensional treatment due to the important role of nuclear motion and electron correlation. This restricts ab initio calculations to the simplest molecules. In this chapter, we discuss single ionization of hydrogen molecules (H2 and D2) induced by time-delayed SAP+IR and APT+IR schemes. Ab initio time-dependent theoretical calculations are compared with existing experiments.

  15. A two-dimensional Fourier transform electron-spin resonance (ESR) study of nuclear modulation and spin relaxation in irradiated malonic acid

    NASA Astrophysics Data System (ADS)

    Lee, Sanghyuk; Patyal, Baldev R.; Freed, Jack H.

    1993-03-01

    Nuclear modulation in electron-spin-echo spectroscopy is conventionally studied by one-dimensional electron-spin-echo envelope modulation (1D-ESEEM). Two-dimensional Fourier transform electron-spin resonance (2D-FTESR) studies of nuclear modulation have the promise of enhancing the spectral resolution and clarifying the key details of the relaxation processes. We present a 2D-FTESR study on single proton nuclear modulation from γ-irradiated malonic acid single crystals to test the validity of the Gamliel-Freed theory and to assess the value of the new methods. The two pulse spin-echo correlation spectroscopy (SECSY) spectra as a function of orientation of the single crystal show very good agreement with the Gamliel-Freed theory extended to the general case of nonaxially symmetric hyperfine interaction. It is very simply affected by spin relaxation, such that relative intensities are essentially unaffected. Thus SECSY-ESR can most reliably be utilized for studying nuclear modulation. Stimulated SECSY provides the simplest nuclear modulation patterns, which, however, do exhibit the suppression effect well known in three-pulse ESEEM studies. Two-dimensional electron-electron double resonance (2D-ELDOR) provides nuclear modulation patterns similar to that of SECSY-ESR, so the suppression effect is absent. Both three-pulse methods exhibit complex relaxation behavior which can affect relative intensities. This is a feature characteristic of three-pulse ESEEM, but is not well understood. It is shown how the 2D-FTESR methods enable one to obtain the details of the complex spin relaxation, and in the process, obtain very good agreement between experiment and theory. 2D-ELDOR exhibits exchange cross peaks as well as coherence peaks from the nuclear modulation. It is shown how experiments, as a function of mixing time, enable one to separate the effects of the two. It is pointed out that such experiments are in the spirit of 3D spectroscopy. A new observation of the

  16. Solid-State Electronic Spin Coherence Time Approaching One Second

    DTIC Science & Technology

    2013-04-23

    Methods) allows for common-mode rejection of noise, but does not remove the effect of pulse errors. We noticed a modest reduction in signal contrast and...for natural abundance diamond (1.1% 13C), as the dynamical decoupling sequences we employ are also effective in suppressing dephasing caused by the...since for ensembles of NVs in the presence of 13C nuclear spins, additional decoherence is caused by variations in the effective Larmor frequency of

  17. Electron beam switched discharge for rapidly pulsed lasers

    DOEpatents

    Pleasance, Lyn D.; Murray, John R.; Goldhar, Julius; Bradley, Laird P.

    1981-01-01

    Method and apparatus for electrical excitation of a laser gas by application of a pulsed voltage across the gas, followed by passage of a pulsed, high energy electron beam through the gas to initiate a discharge suitable for laser excitation. This method improves upon current power conditioning techniques and is especially useful for driving rare gas halide lasers at high repetition rates.

  18. Electronic spin state of iron in lower mantle perovskite

    SciTech Connect

    Li, J.; Struzhkin, V.; Mao, H.-k.; Shu, J.; Hemley, R.; Fei, Y.; Mysen, B.; Dera, P.; Parapenka, V.; Shen, G.

    2010-11-16

    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{sub 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. The lower mantle constitutes more than half of the Earth's interior by volume (1), and it is believed to consist predominantly (80-100%) of (Mg,Fe)(Si,Al)O{sub 3} perovskite (hereafter called perovskite), with up to 20% (Mg,Fe)O ferropericlase (2). The electronic spin state of iron has direct influence on the physical properties and chemical behavior of its host phase. Hence, knowledge on the spin state of iron is important for the interpretation of seismic observations, geochemical modeling, and geodynamic simulation of the Earth's deep interior (3, 4). Crystal field theory (4, 5) and band theory (6) predicted that a high-spin to low-spin transition would occur as a result of compression. To date, no experimental data exist on the spin sate of iron in Al-bearing perovskite. To detect possible spinpairing transition of iron in perovskite under the lower mantle

  19. All-optical three-dimensional electron pulse compression

    NASA Astrophysics Data System (ADS)

    Jie Wong, Liang; Freelon, Byron; Rohwer, Timm; Gedik, Nuh; Johnson, Steven G.

    2015-01-01

    We propose an all-optical, three-dimensional electron pulse compression scheme in which Hermite-Gaussian optical modes are used to fashion a three-dimensional optical trap in the electron pulse’s rest frame. We show that the correct choices of optical incidence angles are necessary for optimal compression. We obtain analytical expressions for the net impulse imparted by Hermite-Gaussian free-space modes of arbitrary order. Although we focus on electrons, our theory applies to any charged particle and any particle with non-zero polarizability in the Rayleigh regime. We verify our theory numerically using exact solutions to Maxwell’s equations for first-order Hermite-Gaussian beams, demonstrating single-electron pulse compression factors of \\gt {{10}2} in both longitudinal and transverse dimensions with experimentally realizable optical pulses. The proposed scheme is useful in ultrafast electron imaging for both single- and multi-electron pulse compression, and as a means of circumventing temporal distortions in magnetic lenses when focusing ultrashort electron pulses. Other applications include the creation of flat electron beams and ultrashort electron bunches for coherent terahertz emission.

  20. Pulsed Orotron - A new microwave source for submillimeter pulse high-field electron paramagnetic resonance spectroscopy

    SciTech Connect

    Grishin, Yu.A.; Fuchs, M.R.; Schnegg, A.; Dubinskii, A.A.; Dumesh, B.S.; Rusin, F.S.; Bratman, V.L.; Moebius, K.

    2004-09-01

    A vacuum-tube device for the generation of pulsed microwave radiation in the submillimeter range (up to 380 GHz) is presented, designed for use as a source in a 360 GHz high-field/high-frequency electron paramagnetic resonance (EPR) spectrometer - the pulsed Orotron. Analogous to the known continuous wave (cw) version, in the pulsed Orotron microwave radiation is generated by the interaction of a nonrelativistic electron beam with a diffraction grating (stimulated Smith-Purcell radiation) in feedback with an open Fabry-Perot resonator construction. The presented design extends the cw Orotron by a gate electrode and a high-voltage pulsing unit to control the electron beam current. The generated pulses at 360 GHz have pulse lengths from 100 ns-10 {mu}s and a pulse power of (22{+-}5) mW. The output in a broader frequency band between 320 and 380 GHz ranges from 20 up to 60 mW. Within a 10 {mu}s time slot, incoherent pulse trains of arbitrary duration can be generated. The pulsed Orotron has been incorporated in the quasioptical microwave bridge of a heterodyne induction mode EPR spectrometer. The first free induction decay measurements at a microwave frequency of 360 GHz and a magnetic field of 12.8 T on a polycrystalline perylenyl-ion sample are presented and future applications and extensions of Orotron-EPR spectroscopy are discussed.

  1. NMR spin locking of proton magnetization under a frequency-switched Lee-Goldburg pulse sequence.

    PubMed

    Fu, Riqiang; Tian, Changlin; Cross, Timothy A

    2002-01-01

    The spin dynamics of NMR spin locking of proton magnetization under a frequency-switched Lee-Goldburg (FSLG) pulse sequence is investigated for a better understanding of the line-narrowing mechanism in PISEMA experiments. For the sample of oriented 15N(1,3,5,7)-labeled gramicidin A in hydrated DMPC bilayers, it is found that the spin-lattice relaxation time T(1rho)(H) in the tilted rotating frame is about five times shorter when the 1H magnetization is spin locked at the magic angle by the FSLG sequence compared to the simple Lee-Goldburg sequence. It is believed that the rapid phase alternation of the effective fields during the FSLG cycles results in averaging of the spin lock field so that the spin lock becomes less efficient. A FSLG supercycle has been suggested here to slow the phase alternation. It has been demonstrated experimentally that a modified PISEMA pulse sequence with such supercycles gives rise to about 30% line narrowing in the dipolar dimension in the PISEMA spectra compared to a standard PISEMA pulse sequence.

  2. Pulse-Width Dependent Radiation Effects on Electronic Components

    DTIC Science & Technology

    1989-11-01

    d’un accelerateur lineaire ( LINAC ) a et6 realisee par le CRDO et d’autres groupes. Par contre, l’emploi du LINAC donne normalement des impulsions plus... LINAC ) has been performed by DREO and other groups. However, the use of a LINAC normally entails wider pulses than those expected on the battlefield...nuclear weapon on electronics, an electron linear accelerator ( LINAC ) is often used. The pulse widths available from most LINACs are longer than the

  3. Pulse-Width Dependent Radiation Effects on Electronic Components

    DTIC Science & Technology

    1989-11-01

    lineaire ( LINAC ) a ete realisee par le CRDO et d’autres groupes. Par contre, l’emploi du LINAC donne normalement des impulsions plus larges que celles...xtyibudon UnUSIId~ Z -!_ ABSTRACT The simulation of the prompt gamma-ray pulse effects on electronics with an electron linear accelerator ( LINAC ) has been...performed by DREO and other groups. However, the use of a LINAC normally entails wider pulses than those expected on the battlefield. This rcport

  4. Use of high observing power in electron spin resonance saturation-recovery experiments in spin-labeled membranes

    NASA Astrophysics Data System (ADS)

    Yin, Jun-Jie; Hyde, James S.

    1989-11-01

    Biomolecular collision rates of 14N-containing nitroxide radical labeled stearic acid with similar 15N-containing species in dimyristoylphosphatidylcholine (DMPC) liposomes have been determined using the saturation-recovery electron spin resonance (ESR) method. It is shown that high microwave observing powers can be used to obtain these rates, thereby increasing the signal-to-noise ratio by about ten times relative to methods previously used. The data are analyzed using the rate-equation approach with inclusion of the observing transition probability. A number of solutions to these equations for other experimental situations and for pulse and continuous wave electron-electron double resonance (ELDOR) are also presented. The bimolecular collision rate of labels at the C16 position was found to be 20% greater than for labels at the C12 position, suggesting that the interaction distance differs at these two positions. Even though the high observing power does not affect the ability to extract bimolecular collision rates, the effective spin-lattice relaxation rates are altered. Plots of these latter rates versus power are linear and the slope can be used to determine the absolute microwave field at the sample for a given input power.

  5. Spin-valley splitting of electron beam in graphene

    NASA Astrophysics Data System (ADS)

    Song, Yu; Xie, Lei; Shi, Zhi-Gui; Li, Shun; Zhang, Jian

    2016-11-01

    We study spatial separation of the four degenerate spin-valley components of an electron beam in a EuO-induced and top-gated ferromagnetic/pristine/strained graphene structure. We show that, in a full resonant tunneling regime for all beam components, the formation of standing waves can lead sudden phase jumps ˜-π and giant lateral Goos-Hänchen shifts as large as the transverse beam width, while the interplay of the spin and valley imaginary wave vectors in the modulated regions can lead differences of resonant angles for the four spin-valley flavors, manifesting a spin-valley beam splitting effect. The splitting effect is found to be controllable by the gating and strain.

  6. Electronic measurement of strain effects on spin transport in silicon

    NASA Astrophysics Data System (ADS)

    Qing, Lan; Tinkey, Holly; Appelbaum, Ian

    Spin transport in silicon is limited by the Elliott-Yafet spin relaxation mechanism, which is driven by scattering between degenerate conduction band valleys. Mechanical strain along a valley axis partially breaks this degeneracy, and will ultimately quench intervalley spin relaxation for transitions between states on orthogonal axes. Using a custom-designed and constructed strain probe, we study the effects of uniaxial compressive strain along the < 100 > direction on ballistic tunnel junction devices used to inject spin-polarized electrons into silicon. The effects of strain-induced valley splitting will be presented and compared to our theoretical model. This work is supported by the Office of Naval Research under Contract No. N000141410317, the National Science Foundation under Contract No. ECCS-1231855, the Defense Threat Reduction Agency under Contract No. HDTRA1-13-1-0013, and the Maryland NanoCenter.

  7. Synchronization of sub-picosecond electron and laser pulses

    SciTech Connect

    Rosenzweig, J.B.; Le Sage, G.P.

    1999-07-01

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is sub-picosecond, with tens of femtosecond synchronization implied for next generation experiments. The design of a microwave timing modulator system is now being investigated in more detail. (AIP) {copyright} {ital 1999 American Institute of Physics.}

  8. Synchronization of sub-picosecond electron and laser pulses

    SciTech Connect

    Rosenzweig, J. B.; Le Sage, G. P.

    1999-07-12

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is sub-picosecond, with tens of femtosecond synchronization implied for next generation experiments. The design of a microwave timing modulator system is now being investigated in more detail.

  9. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, D.L.; Reginato, L.L.

    1984-03-22

    An electron beam accelerator is described comprising an electron beam generator-injector to produce a focused beam of greater than or equal to .1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electron by about .1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially .1-1 MeV maximum energy over a time duration of less than or equal to 1 ..mu..sec.

  10. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, Daniel L.; Reginato, Louis L.

    1987-01-01

    An electron beam accelerator comprising an electron beam generator-injector to produce a focused beam of .gtoreq.0.1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electrons by about 0.1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially 0.1-1 MeV maximum energy over a time duration of .ltoreq.1 .mu.sec.

  11. Electron beam accelerator with magnetic pulse compression and accelerator switching

    DOEpatents

    Birx, Daniel L.; Reginato, Louis L.

    1988-01-01

    An electron beam accelerator comprising an electron beam generator-injector to produce a focused beam of .gtoreq.0.1 MeV energy electrons; a plurality of substantially identical, aligned accelerator modules to sequentially receive and increase the kinetic energies of the beam electrons by about 0.1-1 MeV per module. Each accelerator module includes a pulse-forming network that delivers a voltage pulse to the module of substantially .gtoreq.0.1-1 MeV maximum energy over a time duration of .ltoreq.1 .mu.sec.

  12. Directly probing spin dynamics in insulating antiferromagnets using ultrashort terahertz pulses

    SciTech Connect

    Bowlan, Pamela Renee; Trugman, Stuart Alan; Wang, X.; Dai, Yaomin; Cheong, S.-W.; Bauer, Eric Dietzgen; Taylor, Antoinette Jane; Yarotski, Dmitry Anatolievitch; Prasankumar, Rohit Prativadi

    2016-11-22

    We investigate spin dynamics in the antiferromagnetic (AFM) multiferroic TbMnO3 using opticalpump, terahertz (THz)-probe spectroscopy. Photoexcitation results in a broadband THz transmission change, with an onset time of 25 ps at 6 K that becomes faster at higher temperatures. We attribute this time constant to spin-lattice thermalization. The excellent agreement between our measurements and previous ultrafast resonant x-ray diffraction measurements on the same material confirms that our THz pulse directly probes spin order. We suggest that this could be the case in general for insulating AFM materials, if the origin of the static absorption in the THz spectral range is magnetic.

  13. Electron Spin Resonance as a route to Spin-Gap detection in Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ngai, Darryl H.; Leclair, Andre'; Kim, Eun-Ah

    2012-02-01

    The recent observation of a charge-neutral excitation gap in ultraclean carbon nanotubesootnotetext[1]V. V. Deshpande et al., Science 323, 106 (2009) raises the intriguing possibility of a phase with gapless charge spectrum and gapped spin spectrum: the Luther-Emery liquid. We note that ESR would be an ideal probe to directly test whether the observed gap is a spin-gap, as it probes the non-local correlations of conduction electron spins. We focus on the Luther-Emery point (Ks=1/2, also known as free fermion point) where an explicit calculation of relevant spin-spin correlation function is possible, to calculate the ESR signal in a Luther-Emery liquid. At high frequencies of φ>2 δs where δs is the spin-gap, the ESR signal of the Luther-Emery liquid will exhibits a second peak at magnetic fields away from the resonance condition of B=φ/μBg Ks. We discuss how to measure the spin-gap from the location of this additional peak as a function of applied field strength.

  14. Zitterbewegung of electrons in carbon nanotubes created by laser pulses.

    PubMed

    Rusin, T M; Zawadzki, W

    2014-05-28

    We describe a possibility of creating non-stationary electron wave packets in zigzag carbon nanotubes (CNT) illuminated by short laser pulses. After the disappearance of the pulse the packet experiences a trembling motion (Zitterbewegung, ZB). The band structure of CNT is calculated using the tight-binding approximation generalized for the presence of radiation. By employing realistic pulse and CNT parameters we obtain the ZB oscillations with interband frequencies corresponding to specific pairs of energy bands. A choice of optimal parameters is presented in order to observe the phenomenon of ZB experimentally. The use of Gaussian wave packets to trigger the electron Zitterbewegung, as used in the literature, is critically reexamined.

  15. Phase-controllable spin wave generation in iron garnet by linearly polarized light pulses

    SciTech Connect

    Yoshimine, Isao; Iida, Ryugo; Shimura, Tsutomu; Satoh, Takuya; Stupakiewicz, Andrzej; Maziewski, Andrzej

    2014-07-28

    A phase-controlled spin wave was non-thermally generated in bismuth-doped rare-earth iron garnet by linearly polarized light pulses. We controlled the initial phase of the spin wave continuously within a range of 180° by changing the polarization azimuth of the excitation light. The azimuth dependences of the initial phase and amplitude of the spin wave were attributed to a combination of the inverse Cotton-Mouton effect and photoinduced magnetic anisotropy. Temporally and spatially resolved spin wave propagation was observed with a CCD camera, and the waveform was in good agreement with calculations. A nonlinear effect of the spin excitation was observed for excitation fluences higher than 100 mJ/cm{sup 2}.

  16. Oblique propagation of longitudinal waves in magnetized spin-1/2 plasmas: Independent evolution of spin-up and spin-down electrons

    SciTech Connect

    Andreev, Pavel A. Kuz’menkov, L.S.

    2015-10-15

    We consider quantum plasmas of electrons and motionless ions. We describe separate evolution of spin-up and spin-down electrons. We present corresponding set of quantum hydrodynamic equations. We assume that plasmas are placed in an uniform external magnetic field. We account different occupation of spin-up and spin-down quantum states in equilibrium degenerate plasmas. This effect is included via equations of state for pressure of each species of electrons. We study oblique propagation of longitudinal waves. We show that instead of two well-known waves (the Langmuir wave and the Trivelpiece–Gould wave), plasmas reveal four wave solutions. New solutions exist due to both the separate consideration of spin-up and spin-down electrons and different occupation of spin-up and spin-down quantum states in equilibrium state of degenerate plasmas.

  17. Spin Relaxation in III-V Semiconductors in various systems: Contribution of Electron-Electron Interaction

    NASA Astrophysics Data System (ADS)

    Dogan, Fatih; Kesserwan, Hasan; Manchon, Aurelien

    2015-03-01

    In spintronics, most of the phenomena that we are interested happen at very fast time scales and are rich in structure in time domain. Our understanding, on the other hand, is mostly based on energy domain calculations. Many of the theoretical tools use approximations and simplifications that can be perceived as oversimplifications. We compare the structure, material, carrier density and temperature dependence of spin relaxation time in n-doped III-V semiconductors using Elliot-Yafet (EY) and D'yakanov-Perel'(DP) with real time analysis using kinetic spin Bloch equations (KSBE). The EY and DP theories fail to capture details as the system investigated is varied. KSBE, on the other hand, incorporates all relaxation sources as well as electron-electron interaction which modifies the spin relaxation time in a non-linear way. Since el-el interaction is very fast (~ fs) and spin-conserving, it is usually ignored in the analysis of spin relaxation. Our results indicate that electron-electron interaction cannot be neglected and its interplay with the other (spin and momentum) relaxation mechanisms (electron-impurity and electron-phonon scattering) dramatically alters the resulting spin dynamics. We use each interaction explicitly to investigate how, in the presence of others, each relaxation source behaves. We use GaAs and GaN for zinc-blend structure, and GaN and AlN for the wurtzite structure.

  18. Quantum information processing with electronic and nuclear spins in semiconductors

    NASA Astrophysics Data System (ADS)

    Klimov, Paul Victor

    Traditional electronic and communication devices operate by processing binary information encoded as bits. Such digital devices have led to the most advanced technologies that we encounter in our everyday lives and they influence virtually every aspect of our society. Nonetheless, there exists a much richer way to encode and process information. By encoding information in quantum mechanical states as qubits, phenomena such as coherence and entanglement can be harnessed to execute tasks that are intractable to digital devices. Under this paradigm, it should be possible to realize quantum computers, quantum communication networks and quantum sensors that outperform their classical counterparts. The electronic spin states of color-center defects in the semiconductor silicon carbide have recently emerged as promising qubit candidates. They have long-lived quantum coherence up to room temperature, they can be controlled with mature magnetic resonance techniques, and they have a built-in optical interface operating near the telecommunication bands. In this thesis I will present two of our contributions to this field. The first is the electric-field control of electron spin qubits. This development lays foundation for quantum electronics that operate via electrical gating, much like traditional electronics. The second is the universal control and entanglement of electron and nuclear spin qubits in an ensemble under ambient conditions. This development lays foundation for quantum devices that have a built-in redundancy and can operate in real-world conditions. Both developments represent important steps towards practical quantum devices in an electronic grade material.

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

    PubMed

    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.

  20. Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources.

    PubMed

    Pincelli, T; Petrov, V N; Brajnik, G; Ciprian, R; Lollobrigida, V; Torelli, P; Krizmancic, D; Salvador, F; De Luisa, A; Sergo, R; Gubertini, A; Cautero, G; Carrato, S; Rossi, G; Panaccione, G

    2016-03-01

    ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

  1. Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources

    NASA Astrophysics Data System (ADS)

    Pincelli, T.; Petrov, V. N.; Brajnik, G.; Ciprian, R.; Lollobrigida, V.; Torelli, P.; Krizmancic, D.; Salvador, F.; De Luisa, A.; Sergo, R.; Gubertini, A.; Cautero, G.; Carrato, S.; Rossi, G.; Panaccione, G.

    2016-03-01

    ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

  2. Spatially-distributed pulsed gradient spin echo NMR using single-wire proximity

    NASA Astrophysics Data System (ADS)

    Callaghan, Paul T.; Stepisnik, Janez

    1995-12-01

    NMR microimaging may be used to observe the effect of molecular diffusion in the vicinity of a thin wire subjected to current pulses. By this means the pulsed gradient spin echo technique can utilize very large pulsed magnetic field gradients, on the order of 100 T m-1. The quadratic dependence of gradient amplitude on distance from the wire leads to large dynamic range while the distribution of local gradient vectors makes it possible to image anisotropic diffusion. We demonstrate these properties in measurements on polymer solutions and liquid crystals.

  3. Sensitivity enhancement of MQMAS NMR spectra of spin 3/2 nuclei using hyperbolic secant pulses

    NASA Astrophysics Data System (ADS)

    Siegel, Renée; Nakashima, Thomas T.; Wasylishen, Roderick E.

    2005-02-01

    The use of hyperbolic secant (HS) pulses to enhance the intensity of the central transition in MQMAS experiments for spin 3/2 quadrupolar nuclei is investigated by examining 87Rb NMR spectra of a powder sample of RbNO 3. The application of HS pulses prior to the triple-quantum (3Q) excitation provides sensitivity enhancements in MQMAS spectra that are superior to those previously reported. For the conversion of 3Q to single-quantum (1Q) observables, the HS pulses have an efficiency similar to that reported for double frequency sweeps (DFS) but greater than that of the fast amplitude modulation (FAM) technique.

  4. Slice-selective broadband refocusing pulses for the robust generation of crushed spin-echoes.

    PubMed

    Janich, Martin A; McLean, Mary A; Noeske, Ralph; Glaser, Steffen J; Schulte, Rolf F

    2012-10-01

    A major challenge for in vivo magnetic resonance spectroscopy with point-resolved spectroscopy (PRESS) is the low signal intensity for the measurement of weakly scalar coupled spins, for example lactate. The chemical-shift displacement error between the two coupling partners of the lactate molecule leads to a signal decrease. The chemical-shift displacement error is decreased and therefore the lactate signal is increased by using refocusing pulses with a broad bandwidth. Previously, slice-selective broadband universal rotation pulses (S-BURBOP) were designed and applied as refocusing pulses in the PRESS pulse sequence (Janich MA, et al., Journal of Magnetic Resonance, 2011, 213, 126-135). However, S-BURBOP pulses leave a phase error across the slice which is superimposed on the spectra when spatially resolving the PRESS voxel. In the present novel design of slice-selective broadband refocusing pulses (S-BREBOP) this phase error is avoided. S-BREBOP pulses obtain 2.5 times the bandwidth of conventional Shinnar-Le Roux pulses and are robust against ±20% miscalibration of the B(1) amplitude. S-BREBOP pulses were validated in phantoms and in a low-grade brain tumor of a patient. Compared to conventional Shinnar-Le Roux pulses they lead to a decrease of the chemical-shift displacement error and consequently a lactate signal increase.

  5. Spin coherence and 14N ESEEM effects of nitrogen-vacancy centers in diamond with X-band pulsed ESR

    NASA Astrophysics Data System (ADS)

    Rose, B. C.; Weis, C. D.; Tyryshkin, A. M.; Schenkel, T.; Lyon, S. A.

    2017-02-01

    Pulsed ESR experiments are reported for ensembles of negatively-charged nitrogen-vacancy centers (NV$^-$) in diamonds at X-band magnetic fields (280-400 mT) and low temperatures (2-70 K). The NV$^-$ centers in synthetic type IIb diamonds (nitrogen impurity concentration $<1$~ppm) are prepared with bulk concentrations of $2\\cdot 10^{13}$ cm$^{-3}$ to $4\\cdot 10^{14}$ cm$^{-3}$ by high-energy electron irradiation and subsequent annealing. We find that a proper post-radiation anneal (1000$^\\circ$C for 60 mins) is critically important to repair the radiation damage and to recover long electron spin coherence times for NV$^-$s. After the annealing, spin coherence times of T$_2 = 0.74$~ms at 5~K are achieved, being only limited by $^{13}$C nuclear spectral diffusion in natural abundance diamonds. At X-band magnetic fields, strong electron spin echo envelope modulation (ESEEM) is observed originating from the central $^{14}$N nucleus. The ESEEM spectral analysis allows for accurate determination of the $^{14}$N nuclear hypefine and quadrupole tensors. In addition, the ESEEM effects from two proximal $^{13}$C sites (second-nearest neighbor and fourth-nearest neighbor) are resolved and the respective $^{13}$C hyperfine coupling constants are extracted.

  6. Measurements of spin life time of an antimony-bound electron in silicon

    NASA Astrophysics Data System (ADS)

    Lu, T. M.; Bishop, N. C.; Tracy, L. A.; Blume-Kohout, R.; Pluym, T.; Wendt, J. R.; Dominguez, J.; Lilly, M. P.; Carroll, M. S.

    2013-03-01

    We report our measurements of spin life time of an antimony-bound electron in silicon. The device is a double-top-gated silicon quantum dot with antimony atoms implanted near the quantum dot region. A donor charge transition is identified by observing a charge offset in the transport characteristics of the quantum dot. The tunnel rates on/off the donor are first characterized and a three-level pulse sequence is then used to measure the spin populations at different load-and-wait times in the presence of a fixed magnetic field. The spin life time is extracted from the exponential time dependence of the spin populations. A spin life time of 1.27 seconds is observed at B = 3.25 T. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. The work was supported by the Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  7. Collective Dynamics in Spin-Textured Electronic Systems

    NASA Astrophysics Data System (ADS)

    Wong, Clement H.

    2010-06-01

    In chapter I and II, we develop the hydrodynamic theory of collinear spin currents coupled to magnetization dynamics in metallic ferromagnets. The collective spin density couples to the spin current through a U(1) Berry-phase gauge field determined by the local texture and dynamics of the magnetization. We determine phenomenologically the dissipative corrections to the equation of motion for the electronic current, which consist of a dissipative spin-motive force generated by magnetization dynamics and a magnetic texture-dependent resistivity tensor. The reciprocal dissipative, adiabatic spin torque on the magnetic texture follows from the Onsager principle. By applying general thermodynamic relations, we determine a lower bound on the magnetic-texture resistivity. We investigate the effects of thermal fluctuations and find that electronic dynamics contribute to a nonlocal Gilbert damping tensor in the Landau-Lifshitz-Gilbert equation for the magnetization. In chapter III, we apply our general theory to soliton dynamics in spin-textured metals. We find it necessary to modify the Landau-Lifshitz-Gilbert equation and the corresponding solitonic equations of motion to include higher-order texture effects stemming hydrodynamic backaction. As an example, we consider the gyration of a vortex in a point-contact spin valve, and discuss modifications of orbit radius, frequency, and dissipation power. In chapter IV, we generalize our hydrodynamic theory to a kinetic equation, which we derive in a semiclassical expansion of the density-matrix equation of motion up to the first order in quantum mechanical corrections for a general two-band Hamiltonian. We find, in addition to corrections to the single-particle equation of motion due to Berry curvatures, a modification to the phase-space density of states, and interband terms associated with transport through a general curved phase space. We apply our kinetic equation to the case of inhomogeneities stemming from gauge

  8. Electron acceleration by a chirped Gaussian laser pulse in vacuum

    SciTech Connect

    Sohbatzadeh, F.; Mirzanejhad, S.; Ghasemi, M.

    2006-12-15

    Electron acceleration by a chirped Gaussian laser pulse is investigated numerically. A linear and negative chirp is employed in this study. At first, a simple analytical description for the chirp effect on the electron acceleration in vacuum is provided in one-dimensional model. The chirp mechanism is then extended to the interaction of a femtosecond laser pulse and electron. The electron final energy is obtained as a function of laser beam waist, laser intensity, chirp parameter, and initial phase of the laser pulse. It is shown that the electron final energy depends strongly on the chirp parameter and the initial phase of the laser pulse. There is an optimal value for the chirp parameter in which the electron acceleration takes place effectively. The energy gain increases with laser beam waist and intensity. It is also shown that the electron is accelerated within a few degrees to the axial direction. Emphasis is on the important aspect of the chirp effect on the energy gained by an electron from the electromagnetic wave.

  9. Pulsed electron accelerator for radiation technologies in the enviromental applications

    NASA Astrophysics Data System (ADS)

    Korenev, Sergey

    1997-05-01

    The project of pulsed electron accelerator for radiation technologies in the environmental applications is considered. An accelerator consists of high voltage generator with vacuum insulation and vacuum diode with plasma cathode on the basis discharge on the surface of dielectric of large dimensions. The main parameters of electron accelerators are following: kinetic energy 0.2 - 2.0 MeV, electron beam current 1 - 30 kA and pulse duration 1- 5 microseconds. The main applications of accelerator for decomposition of wastewaters are considered.

  10. Self-diffusion in nanopores studied by the NMR pulse gradient spin echo

    NASA Astrophysics Data System (ADS)

    Stepišnik, Janez; Fritzinger, Bernd; Scheler, Ulrich; Mohorič, Aleš

    2012-06-01

    NMR pulse gradient spin echo is the most efficient method for non-invasive elucidation of molecular transport in heterogeneous media. With a proper interpretation of experimental data, the method can also be applied to investigate molecular self-diffusion in pores small enough that the characteristic diffusion times are much shorter than time, needed to build up the spin phase structure by the pulse of magnetic field gradient. This is demonstrated by the analysis of restricted self-diffusion measurement of water molecules trapped in a polyamide membrane. The results are presented as a distribution of spin-relaxation rates and pore sizes in this nanoporous system that also present the method in its true colors as a useful tool in the bio-nanotechology.

  11. Nanometre-scale probing of spin waves using single-electron spins

    PubMed Central

    van der Sar, Toeno; Casola, Francesco; Walsworth, Ronald; Yacoby, Amir

    2015-01-01

    Pushing the frontiers of condensed-matter magnetism requires the development of tools that provide real-space, few-nanometre-scale probing of correlated-electron magnetic excitations under ambient conditions. Here we present a practical approach to meet this challenge, using magnetometry based on single nitrogen-vacancy centres in diamond. We focus on spin-wave excitations in a ferromagnetic microdisc, and demonstrate local, quantitative and phase-sensitive detection of the spin-wave magnetic field at ∼50 nm from the disc. We map the magnetic-field dependence of spin-wave excitations by detecting the associated local reduction in the disc's longitudinal magnetization. In addition, we characterize the spin–noise spectrum by nitrogen-vacancy spin relaxometry, finding excellent agreement with a general analytical description of the stray fields produced by spin–spin correlations in a 2D magnetic system. These complementary measurement modalities pave the way towards imaging the local excitations of systems such as ferromagnets and antiferromagnets, skyrmions, atomically assembled quantum magnets, and spin ice. PMID:26249673

  12. Electronic measurement of microchannel plate pulse height distributions

    SciTech Connect

    Gamboa, E. J.; Huntington, C. M.; Harding, E. C.; Drake, R. P.

    2010-10-15

    Microchannel plates are a central component of the x-ray framing cameras used as analog imagers in many plasma experiment diagnostic systems. The microchannel plate serves as an amplifying element, increasing the electronic signal from incident radiation by factors of 10{sup 3}-10{sup 5}, with a broad pulse-height distribution. Seeking to optimize the photon-to-electron conversion efficiency and noise distribution of x-ray cameras, we will characterize the pulse-height distribution of the electron output from a single microchannel plate. Replacing the framing camera's phosphor-coated fiber optic screen with a charge-collection plate and coupling to a low-noise multichannel analyzer, we quantified the distribution in the total charge generated per photon event. The electronically measured pulse height distribution is used to estimate the signal-to-noise ratio of radiographic images from framing cameras.

  13. Electron spin resonance and muon spin relaxation studies of single molecule magnets

    NASA Astrophysics Data System (ADS)

    Blundell, Stephen

    2005-03-01

    We use a combination of electron spin resonance, muon-spin relaxation and SQUID magnetometry to study polycrystalline and single crystal samples of various novel single molecule magnets (SMMs). We also describe a theoretical framework which can be used to analyse the results from each technique. Electron spin resonance measurements are performed using a millimetre vector network analyser and data are presented on several SMM systems using microwave frequencies from 40-300 GHz. Muon-spin relaxation measurements have been performed on several SMM systems in applied longitudinal magnetic field and in temperatures down to 20 mK. The results suggest that dynamic local magnetic field fluctuations are responsible for the relaxation of the muon spin ensemble. We discuss what can be learned from these experiments concerning SMMs and suggest experiments which can probe the quantum nature of SMMs. (Work in collaboration with S Sharmin, T Lancaster, A Ardavan, F L Pratt, E J L McInnes and R E P Winpenny) References: S. J. Blundell and F. L. Pratt, J. Phys.: Condens. Matter 16, R771 (2004); T. Lancaster et al., J. Phys.: Condens. Matter 16, S4563 (2004); S. Sharmin et al., Appl. Phys. Lett. in press.

  14. Dose rate effect on micronuclei induction in human blood lymphocytes exposed to single pulse and multiple pulses of electrons.

    PubMed

    Acharya, Santhosh; Bhat, N N; Joseph, Praveen; Sanjeev, Ganesh; Sreedevi, B; Narayana, Y

    2011-05-01

    The effects of single pulses and multiple pulses of 7 MV electrons on micronuclei (MN) induction in cytokinesis-blocked human peripheral blood lymphocytes (PBLs) were investigated over a wide range of dose rates per pulse (instantaneous dose rate). PBLs were exposed to graded doses of 2, 3, 4, 6, and 8 Gy of single electron pulses of varying pulse widths at different dose rates per pulse, ranging from 1 × 10(6) Gy s(-1) to 3.2 × 10(8) Gy s(-1). Different dose rates per pulse were achieved by changing the dose per electron pulse by adjusting the beam current and pulse width. MN yields per unit absorbed dose after irradiation with single electron pulses were compared with those of multiple pulses of electrons. A significant decrease in the MN yield with increasing dose rates per pulse was observed, when dose was delivered by a single electron pulse. However, no reduction in the MN yield was observed when dose was delivered by multiple pulses of electrons. The decrease in the yield at high dose rates per pulse suggests possible radical recombination, which leads to decreased biological damage. Cellular response to the presence of very large numbers of chromosomal breaks may also alter the damage.

  15. Separating the Spin States of a Free Electron Beam

    NASA Astrophysics Data System (ADS)

    Rifkin, Neil

    2008-10-01

    In 1922 Otto Stern and Walther Gerlach set out to test the spacial quantization of the electron by passing a beam of neutral silver atoms through a transverse magnetic field. The interaction of the two projections of the electron's magnetic moment with the magnetic field resulted in a splitting of the beam. However, for some sixty years it was generally accepted that the spin of free electrons, and thus their magnetic moment, could not be measured with an experiment similar to that of Stern and Gerlach. The reason being that the lorentz force on charged particles is far greater than the force due to the magnetic moment of the electron, thus blurring any desired results. To reduce the lorentz force, the electrons could be passed through a magnetic field whose gradient is in the direction of the electrons' momentum. This longitudinal Stern-Gerlach device, with a superconducting magnet, could polarize the tails of a low energy electron beam.

  16. On Cu(II) Cu(II) distance measurements using pulsed electron electron double resonance

    NASA Astrophysics Data System (ADS)

    Yang, Zhongyu; Becker, James; Saxena, Sunil

    2007-10-01

    The effects of orientational selectivity on the 4-pulse electron electron double resonance (PELDOR) ESR spectra of coupled Cu(II)-Cu(II) spins are presented. The data were collected at four magnetic fields on a poly-proline peptide containing two Cu(II) centers. The Cu(II)-PELDOR spectra of this peptide do not change appreciably with magnetic field at X-band. The data were analyzed by adapting the theory of Maryasov, Tsvetkov, and Raap [A.G. Maryasov, Y.D. Tsvetkov, J. Raap, Weakly coupled radical pairs in solids:ELDOR in ESE structure studies, Appl. Magn. Reson. 14 (1998) 101-113]. Simulations indicate that orientational effects are important for Cu(II)-PELDOR. Based on simulations, the field-independence of the PELDOR data for this peptide is likely due to two effects. First, for this peptide, the Cu(II) g-tensor(s) are in a very specific orientation with respect to the interspin vector. Second, the flexibility of the peptide washes out the orientation effects. These effects reduce the suitability of the poly-proline based peptide as a good model system to experimentally probe orientational effects in such experiments. An average Cu(II)-Cu(II) distance of 2.1-2.2 nm was determined, which is consistent with earlier double quantum coherence ESR results.

  17. Role of the Electron Spin Polarization in Water Splitting

    PubMed Central

    2015-01-01

    We show that in an electrochemical cell, in which the photoanode is coated with chiral molecules, the overpotential required for hydrogen production drops remarkably, as compared with cells containing achiral molecules. The hydrogen evolution efficiency is studied comparing seven different organic molecules, three chiral and four achiral. We propose that the spin specificity of electrons transferred through chiral molecules is the origin of a more efficient oxidation process in which oxygen is formed in its triplet ground state. The new observations are consistent with recent theoretical works pointing to the importance of spin alignment in the water-splitting process. PMID:26615833

  18. Shutterless ion mobility spectrometer with fast pulsed electron source

    NASA Astrophysics Data System (ADS)

    Bunert, E.; Heptner, A.; Reinecke, T.; Kirk, A. T.; Zimmermann, S.

    2017-02-01

    Ion mobility spectrometers (IMS) are devices for fast and very sensitive trace gas analysis. The measuring principle is based on an initial ionization process of the target analyte. Most IMS employ radioactive electron sources, such as 63Ni or 3H. These radioactive materials have the disadvantage of legal restrictions and the electron emission has a predetermined intensity and cannot be controlled or disabled. In this work, we replaced the 3H source of our IMS with 100 mm drift tube length with our nonradioactive electron source, which generates comparable spectra to the 3H source. An advantage of our emission current controlled nonradioactive electron source is that it can operate in a fast pulsed mode with high electron intensities. By optimizing the geometric parameters and developing fast control electronics, we can achieve very short electron emission pulses for ionization with high intensities and an adjustable pulse width of down to a few nanoseconds. This results in small ion packets at simultaneously high ion densities, which are subsequently separated in the drift tube. Normally, the required small ion packet is generated by a complex ion shutter mechanism. By omitting the additional reaction chamber, the ion packet can be generated directly at the beginning of the drift tube by our pulsed nonradioactive electron source with only slight reduction in resolving power. Thus, the complex and costly shutter mechanism and its electronics can also be omitted, which leads to a simple low-cost IMS-system with a pulsed nonradioactive electron source and a resolving power of 90.

  19. Controlling Electron Dynamics of Oriented Molecules Using Attosecond Pulses

    NASA Astrophysics Data System (ADS)

    Miyabe, S.; Lucchese, R.; Rescigno, T.; Midorikawa, K.; McCurdy, C. W.

    2016-05-01

    Attosecond pulses offer routes to study and potentially manipulate ultrafast electron dynamics of atoms and molecules on their intrinsic time scale, and therefore attracted attention from various disciplines. In this report we show that for a molecule, oriented in space and excited by an attosecond pulse, the amount of electronic coherence left in the ion depends not only on the orientation of the electric field polarization vector in the molecular-frame, but also on the angular distribution in molecular-frame of electrons ejected in different ionization channels. In our numerical simulation we use one-photon single ionization amplitudes calculated using the complex-Kohn variational method, and we express the amount of coherence in the ion in terms of the (N+1)-electron reduced density matrix of the full N-electron system of the ion plus ionized electron.

  20. Pulsed Power for a Dynamic Transmission Electron Microscope

    SciTech Connect

    dehope, w j; browning, n; campbell, g; cook, e; king, w; lagrange, t; reed, b; stuart, b; Shuttlesworth, R; Pyke, B

    2009-06-25

    Lawrence Livermore National Laboratory (LLNL) has converted a commercial 200kV transmission electron microscope (TEM) into an ultrafast, nanoscale diagnostic tool for material science studies. The resulting Dynamic Transmission Electron Microscope (DTEM) has provided a unique tool for the study of material phase transitions, reaction front analyses, and other studies in the fields of chemistry, materials science, and biology. The TEM's thermionic electron emission source was replaced with a fast photocathode and a laser beam path was provided for ultraviolet surface illumination. The resulting photoelectron beam gives downstream images of 2 and 20 ns exposure times at 100 and 10 nm spatial resolution. A separate laser, used as a pump pulse, is used to heat, ignite, or shock samples while the photocathode electron pulses, carefully time-synchronized with the pump, function as probe in fast transient studies. The device functions in both imaging and diffraction modes. A laser upgrade is underway to make arbitrary cathode pulse trains of variable pulse width of 10-1000 ns. Along with a fast e-beam deflection scheme, a 'movie mode' capability will be added to this unique diagnostic tool. This talk will review conventional electron microscopy and its limitations, discuss the development and capabilities of DTEM, in particularly addressing the prime and pulsed power considerations in the design and fabrication of the DTEM, and conclude with the presentation of a deflector and solid-state pulser design for Movie-Mode DTEM.

  1. Pulsed-Electron-Beam Processing of Materials for Medical Applications

    NASA Astrophysics Data System (ADS)

    Koval, N. N.; Ivanov, Yu. F.; Teresov, A. D.; Denisova, Yu. A.; Petrikova, E. A.

    2014-02-01

    The data on investigation of sample materials used for fabrication of medical implants (stainless steel 316L, and VT1-0 and CoCrMo (Wironit) alloys) are reported, which were subjected to surface treatment with the pulsed electron beam having the following parameters: pulse duration - 20-200 μs, energy density per pulse - 8-20 J/cm2, number of pulses - 1-5, and pulse repetition frequency - 0.3-1 Hz. A significant structure rearrangement is revealed, which is followed by changes in the modified surface layer properties of these materials. The surface roughness is found to decrease, while the corrosion resistance is improved; slight changes are also observed in the modified layer microhardness compared to the initial state.

  2. BANSHEE: High-voltage repetitively pulsed electron-beam driver

    SciTech Connect

    VanHaaften, F.

    1992-01-01

    BANSHEE (Beam Accelerator for a New Source of High-Energy Electrons) this is a high-voltage modulator is used to produce a high-current relativistic electron beam for high-power microwave tube development. The goal of the BANSHEE research is first to achieve a voltage pulse of 700--750 kV with a 1-{mu}s pulse width driving a load of {approximately}100 {Omega}, the pulse repetition frequency (PRF) of a few hertz. The ensuing goal is to increase the pulse amplitude to a level approaching 1 MV. We conducted tests using half the modulator with an output load of 200 {Omega}, up to a level of {approximately}650 kV at a PRF of 1 Hz and 525 kV at a PRF of 5 Hz. We then conducted additional testing using the complete system driving a load of {approximately}100 {Omega}.

  3. BANSHEE: High-voltage repetitively pulsed electron-beam driver

    SciTech Connect

    VanHaaften, F.

    1992-08-01

    BANSHEE (Beam Accelerator for a New Source of High-Energy Electrons) this is a high-voltage modulator is used to produce a high-current relativistic electron beam for high-power microwave tube development. The goal of the BANSHEE research is first to achieve a voltage pulse of 700--750 kV with a 1-{mu}s pulse width driving a load of {approximately}100 {Omega}, the pulse repetition frequency (PRF) of a few hertz. The ensuing goal is to increase the pulse amplitude to a level approaching 1 MV. We conducted tests using half the modulator with an output load of 200 {Omega}, up to a level of {approximately}650 kV at a PRF of 1 Hz and 525 kV at a PRF of 5 Hz. We then conducted additional testing using the complete system driving a load of {approximately}100 {Omega}.

  4. Vacuum electron acceleration by using two variable frequency laser pulses

    SciTech Connect

    Saberi, H.; Maraghechi, B.

    2013-12-15

    A method is proposed for producing a relativistic electron bunch in vacuum via direct acceleration by using two frequency-chirped laser pulses. We consider the linearly polarized frequency-chiped Hermit-Gaussian 0, 0 mode lasers with linear chirp in which the local frequency varies linearly in time and space. Electron motion is investigated through a numerical simulation using a three-dimensional particle trajectory code in which the relativistic Newton's equations of motion with corresponding Lorentz force are solved. Two oblique laser pulses with proper chirp parameters and propagation angles are used for the electron acceleration along the z-axis. In this way, an electron initially at rest located at the origin could achieve high energy, γ=319 with the scattering angle of 1.02{sup ∘} with respect to the z-axis. Moreover, the acceleration of an electron in different initial positions on each coordinate axis is investigated. It was found that this mechanism has the capability of producing high energy electron microbunches with low scattering angles. The energy gain of an electron initially located at some regions on each axis could be greatly enhanced compared to the single pulse acceleration. Furthermore, the scattering angle will be lowered compared to the acceleration by using laser pulses propagating along the z-axis.

  5. Hot-electron effect in spin relaxation of electrically injected electrons in intrinsic Germanium.

    PubMed

    Yu, T; Wu, M W

    2015-07-01

    The hot-electron effect in the spin relaxation of electrically injected electrons in intrinsic germanium is investigated by the kinetic spin Bloch equations both analytically and numerically. It is shown that in the weak-electric-field regime with E ≲ 0.5 kV cm(-1), our calculations have reasonable agreement with the recent transport experiment in the hot-electron spin-injection configuration (2013 Phys. Rev. Lett. 111 257204). We reveal that the spin relaxation is significantly enhanced at low temperature in the presence of weak electric field E ≲ 50 V cm(-1), which originates from the obvious center-of-mass drift effect due to the weak electron-phonon interaction, whereas the hot-electron effect is demonstrated to be less important. This can explain the discrepancy between the experimental observation and the previous theoretical calculation (2012 Phys. Rev. B 86 085202), which deviates from the experimental results by about two orders of magnitude at low temperature. It is further shown that in the strong-electric-field regime with 0.5 ≲ E ≲ 2 kV cm(-1), the spin relaxation is enhanced due to the hot-electron effect, whereas the drift effect is demonstrated to be marginal. Finally, we find that when 1.4 ≲ E ≲ 2 kV cm(-1) which lies in the strong-electric-field regime, a small fraction of electrons (≲5%) can be driven from the L to Γ valley, and the spin relaxation rates are the same for the Γ and L valleys in the intrinsic sample without impurity. With the negligible influence of the spin dynamics in the Γ valley to the whole system, the spin dynamics in the L valley can be measured from the Γ valley by the standard direct optical transition method.

  6. Electron beam-switched discharge for rapidly pulsed lasers

    DOEpatents

    Pleasance, L.D.; Murray, J.R.; Goldhar, J.; Bradley, L.P.

    1979-12-11

    A method and apparatus are designed for electrical excitation of a laser gas by application of a pulsed voltage across the gas, followed by passage of a pulsed, high energy electron beam through the gas to initiate a discharge suitable for laser excitation. This method improves upon current power conditioning techniques and is especially useful for driving rare gas halide lasers at high repetition rates.

  7. Effects of the electron-electron interaction in the spin resonance in 2D systems with Dresselhaus spin-orbit coupling

    SciTech Connect

    Krishtopenko, S. S.

    2015-02-15

    The effect of the electron-electron interaction on the spin-resonance frequency in two-dimensional electron systems with Dresselhaus spin-orbit coupling is investigated. The oscillatory dependence of many-body corrections on the magnetic field is demonstrated. It is shown that the consideration of many-body interaction leads to a decrease or an increase in the spin-resonance frequency, depending on the sign of the g factor. It is found that the term cubic in quasimomentum in Dresselhaus spin-orbit coupling partially decreases exchange corrections to the spin resonance energy in a two-dimensional system.

  8. Dynamics Of Electronic Excitation Of Solids With Ultrashort Laser Pulse

    SciTech Connect

    Medvedev, Nikita; Rethfeld, Baerbel

    2010-10-08

    When ultrashort laser pulses irradiate a solid, photoabsorption by electrons in conduction band produces nonequilibrium highly energetic free electrons gas. We study the ionization and excitation of the electronic subsystem in a semiconductor and a metal (solid silicon and aluminum, respectively). The irradiating femtosecond laser pulse has a duration of 10 fs and a photon energy of h-bar {omega} = 38 eV. The classical Monte Carlo method is extended to take into account the electronic band structure and Pauli's principle for electrons excited to the conduction band. In the case of semiconductors this applies to the holes as well. Conduction band electrons and valence band holes induce secondary excitation and ionization processes which we simulate event by event. We discuss the transient electron dynamics with respect to the differences between semiconductors and metals. For metals the electronic distribution is split up into two branches: a low energy distribution as a slightly distorted Fermi-distribution and a long high energy tail. For the case of semiconductors it is split into two parts by the band gap. To thermalize, these excited electronic subsystems need longer times than the characteristic pulse duration. Therefore, the analysis of experimental data with femtosecond lasers must be based on non-equilibrium concepts.

  9. Electron spin relaxation in x-lithium phthalocyanine.

    PubMed

    Sato, Hideo; Dalton, Lauraine A; Ha, Duc; Quine, Richard W; Eaton, Sandra S; Eaton, Gareth R

    2007-07-19

    Continuous-wave linewidths and spin susceptibilities, spin-spin relaxation rates (1/T2), and spin-lattice relaxation rates (1/T1) for two sources of x-LiPc were measured at 9.5 GHz between 15 and 298 K. Relaxation rates at 34 GHz were measured between 80 and 298 K. Room-temperature relaxation rates also were measured at 250 MHz, 1.9 GHz, and 2.76 GHz. The temperature dependences of linewidths and spin susceptibilities are characteristic of 1-D organic conductors. The ratio of populations of localized and delocalized electrons varies with sample preparation. For a single needle between 15 and about 200 K, 1/T2 is higher for the parallel orientation, but 1/T1 is higher for the perpendicular orientation, consistent with predictions based on dipolar interactions. Between about 60 and 150 K, which is the temperature regime in which spin susceptibility is changing rapidly with temperature, 1/T1 exhibits a non-monotonic dependence on temperature and is lower at 34 GHz than at 9.5 GHz. In other organic conductors, this dependence has been attributed to a bottleneck mechanism of relaxation. At higher temperatures, 1/T1 becomes less orientation-dependent. At room temperature, T1 increases rapidly between 250 MHz (3.0 micros) and 2.76 GHz (6.3 micros) and then shows less frequency dependence up to 34 GHz (9.8 micros). The relaxation rate near room temperature might have a substantial contribution from spin hopping perpendicular to the stacking axis of the molecules.

  10. Pulse-assisted homonuclear dipolar recoupling of half-integer quadrupolar spins in magic-angle spinning NMR

    NASA Astrophysics Data System (ADS)

    Edén, Mattias; Annersten, Hans; Zazzi, Åsa

    2005-07-01

    We demonstrate numerically and experimentally that zero-quantum homonuclear dipolar recoupling techniques employing rotor-synchronized 180° pulses, previously introduced for spin-1/2 applications, are useful also for magnetization transfers between half-integer quadrupolar nuclei in rotating solids. The recoupling sequences are incorporated as mixing periods in two-dimensional experimental protocols, that correlate either single-quantum coherences of coupled spins, or triple-quantum with single-quantum coherences for improving spectral resolution. We present 23Na and 27Al NMR experiments on powders of sodium sulphite [Na 2SO 3], YAG [Y 3Al 5O 12] and a synthetic chlorite mineral [Mg 4.5Al 3Si 2.5O 10(OH) 8].

  11. Spatially modulated laser pulses for printing electronics.

    PubMed

    Auyeung, Raymond C Y; Kim, Heungsoo; Mathews, Scott; Piqué, Alberto

    2015-11-01

    The use of a digital micromirror device (DMD) in laser-induced forward transfer (LIFT) is reviewed. Combining this technique with high-viscosity donor ink (silver nanopaste) results in laser-printed features that are highly congruent in shape and size to the incident laser beam spatial profile. The DMD empowers LIFT to become a highly parallel, rapidly reconfigurable direct-write technology. By adapting half-toning techniques to the DMD bitmap image, the laser transfer threshold fluence for 10 μm features can be reduced using an edge-enhanced beam profile. The integration of LIFT with this beam-shaping technique allows the printing of complex large-area patterns with a single laser pulse.

  12. Half-metallic alloys: electronic structure, magnetism and spin polarization.

    PubMed

    Dederichs, P H; Galanakis, I; Mavropoulos, Ph

    2005-01-01

    Using the state-of-the-art screened Korringa-Kohn-Rostoker Green function method we study the electronic and magnetic properties of NiMnSb and similar Heusler alloys. We show that all these compounds are half-metals, e.g. the minority-spin band is semiconducting and the Fermi level falls within this gap resulting in 100% spin polarization at the Fermi level. The total spin moment M(t) shows the so-called Slater-Pauling behaviour and scales with the total valence charge Z(t) following the rule M(t) = Z(t) - 18 for half and M(t) = Z(t) - 24 for full Heusler alloys. These rules are connected to the origin of the gap. Finally we show that the inclusion of the spin-orbit interaction in our calculations kills the half-metallic gap but the spin-polarization at the Fermi level can be still very high, approximately 99% for NiMnSb, but much lower for a half-metallic compound like zinc-blende MnBi (77%).

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

    PubMed

    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.

  14. Spin-resolved inelastic mean free path of slow electrons in Fe.

    PubMed

    Zdyb, R; Bauer, E

    2013-07-10

    The spin-dependent reflectivity of slow electrons from ultrathin Fe films on W(110) has been measured with spin polarized low energy electron microscopy. From the amplitude of the quantum size oscillations observed in the reflectivity curves the spin-dependent inelastic mean free path (IMFP) of electrons in Fe has been determined in the energy range from 5 to 16 eV above the vacuum level. The resulting IMFP values for the spin-up electrons are clearly larger than those for the spin-down electrons and the difference between the two values decreases with increasing electron energy in agreement with theoretical predictions.

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

    PubMed

    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.

  16. Synchronization of Sub-Picosecond Electron and Laser Pulses

    SciTech Connect

    Rosenzweig, J.B.; Le Sage G.P.

    2000-08-15

    Sub-picosecond laser-electron synchronization is required to take full advantage of the experimental possibilities arising from the marriage of modern high intensity lasers and high brightness electron beams in the same laboratory. Two particular scenarios stand out in this regard, injection of ultra-short electron pulses in short wavelength laser-driven plasma accelerators, and Compton scattering of laser photons from short electron pulses. Both of these applications demand synchronization, which is subpicosecond, with tens of femtosecond synchronization implied for next-generation experiments. Typically, an RF electron accelerator is synchronized to a short pulse laser system by detecting the repetition signal of a laser oscillator, adjusted to an exact subharmonic of the linac RF frequency, and multiplying or phase locking this signal to produce the master RF clock. Pulse-to-pulse jitter characteristic of self-mode-locked laser oscillators represents a direct contribution to the ultimate timing jitter between a high intensity laser focus and electron beam at the interaction point, or a photocathode drive laser in an RF photoinjector. This timing jitter problem has been addressed most seriously in the context of the RF photoinjector, where the electron beam properties are sensitive functions of relative timing jitter. The timing jitter achieved in synchronized photocathode drive laser systems is near, or slightly below one picosecond. The ultimate time of arrival jitter of the beam at the photoinjector exit is typically a bit smaller than the photocathode drive-laser jitter due to velocity compression effects in the first RF cell of the gun. This tendency of the timing of the electron beam arrival at a given spatial point to lock to the RF lock is strongly reinforced by use of magnetic compression.

  17. Electron-spin-reversal phenomenon in optically pumped rubidium

    SciTech Connect

    Norrgard, E. B.; Dreiling, J. M.; Gay, T. J.; Tupa, D.

    2010-09-15

    We have studied the optical pumping of mixtures of Rb vapor and N{sub 2} buffer gas by laser light tuned to the D{sub 1} transition having a spectral width of {approx}500 MHz. The Rb densities are of the order of 10{sup 13} cm{sup -3}, while the buffer-gas pressures range from 0.1 to 10 torr. As the frequency of the right-hand circularly polarized laser is varied across the D{sub 1} absorption profile, the electron spin polarization of the Rb is found to take on negative values for small negative values of pump detuning from the absorption profile center. This occurs for N{sub 2} pressures below {approx}1 torr; at 10 torr the electron spins consistently point in the same direction as the angular momentum of the pump light. The spin-reversal effect can be understood in terms of populations of the F=2 ({sup 85}Rb) and F=1 ({sup 87}Rb) states caused by small unpolarized fractions in the pump beam and its elimination in terms of pressure broadening caused by the N{sub 2} buffer gas. We speculate that this effect could be used for fast Rb spin modulation.

  18. Cantilever detection of electron spin resonance in the terahertz region

    NASA Astrophysics Data System (ADS)

    Takahashi, Hideyuki; Ohmichi, Eiji; Ohta, Hitoshi

    Electron spin resonance (ESR) is used in a wide range of research areas. Most commercially available spectrometers operate at the X- band (~10 GHz). However, high-frequency ESR (>100 GHz) has many advantages, such as the high spectral resolution, the ESR detection beyond the zero-field splitting etc. We report the cantilever detection of electron spin resonance in the terahertz region. This technique mechanically detects ESR as a change in magnetic torque that acts on the cantilever, while the conventional method, such as the cavity perturbation and the transmission method, directly measures the absorption of electromagnetic wave power. Backward wave oscillators (BWO) were used as THz-wave sources. Despite the small sample mass (m = 4 μg) and low power output of the BWO (P < 4 mW above 1 THz), we observed ESR absorption of Co Tutton salt, Co(NH4)2(SO4)2 .6H2O, in frequencies of up to 1.1 THz. Spin sensitivity was estimated to be the order of 1011-1012 spins/gauss above 1 THz. This technique will not only broaden the scope of ESR spectroscopy application but also lead to high-spectral-resolution ESR imaging.[1] H. Takahashi, E. Ohmichi and H. Ohta, Appl. Phys. Lett. 107, 182405 (2015).

  19. Theory of coupled spin-charge transport due to spin-orbit interaction in inhomogeneous two-dimensional electron liquids

    NASA Astrophysics Data System (ADS)

    Shen, Ka; Raimondi, R.; Vignale, G.

    2014-12-01

    Spin-orbit interactions in two-dimensional electron liquids are responsible for many interesting transport phenomena in which particle currents are converted to spin polarizations and spin currents and vice versa. Prime examples are the spin Hall effect, the Edelstein effect, and their inverses. By similar mechanisms, it is also possible to partially convert an optically induced electron-hole density wave to a spin density wave and vice versa. In this paper, we present a unified theoretical treatment of these effects based on quantum kinetic equations that include not only the intrinsic spin-orbit coupling from the band structure of the host material, but also the spin-orbit coupling due to an external electric field and a random impurity potential. The drift-diffusion equations we derive in the diffusive regime are applicable to a broad variety of experimental situations, both homogeneous and nonhomogeneous, and include on equal footing "skew scattering" and "side jump" from electron-impurity collisions. As a demonstration of the strength and usefulness of the theory we apply it to the study of several effects of current experimental interest: the inverse Edelstein effect, the spin-current swapping effect, and the partial conversion of an electron-hole density wave to a spin density wave in a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit couplings, subject to an electric field.

  20. Pulsed-electron-beam annealing of ion-implantation damage

    NASA Technical Reports Server (NTRS)

    Greenwald, A. C.; Kirkpatrick, A. R.; Little, R. G.; Minnucci, J. A.

    1979-01-01

    Short-duration high-intensity pulsed electron beams have been used to anneal ion-implantation damage in silicon and to electrically activate the dopant species. Lattice regrowth and dopant activation were determined using He(+)-4 backscattering, SEM, TEM, and device performance characteristics as diagnostic techniques. The annealing mechanism is believed to be liquid-phase epitaxial regrowth initiating from the substrate. The high-temperature transient pulse produced by the electron beam causes the dopant to diffuse rapidly in the region where the liquid state is achieved.

  1. Actin-binding cleft closure in myosin II probed by site-directed spin labeling and pulsed EPR.

    PubMed

    Klein, Jennifer C; Burr, Adam R; Svensson, Bengt; Kennedy, Daniel J; Allingham, John; Titus, Margaret A; Rayment, Ivan; Thomas, David D

    2008-09-02

    We present a structurally dynamic model for nucleotide- and actin-induced closure of the actin-binding cleft of myosin, based on site-directed spin labeling and electron paramagnetic resonance (EPR) in Dictyostelium myosin II. The actin-binding cleft is a solvent-filled cavity that extends to the nucleotide-binding pocket and has been predicted to close upon strong actin binding. Single-cysteine labeling sites were engineered to probe mobility and accessibility within the cleft. Addition of ADP and vanadate, which traps the posthydrolysis biochemical state, influenced probe mobility and accessibility slightly, whereas actin binding caused more dramatic changes in accessibility, consistent with cleft closure. We engineered five pairs of cysteine labeling sites to straddle the cleft, each pair having one label on the upper 50-kDa domain and one on the lower 50-kDa domain. Distances between spin-labeled sites were determined from the resulting spin-spin interactions, as measured by continuous wave EPR for distances of 0.7-2 nm or pulsed EPR (double electron-electron resonance) for distances of 1.7-6 nm. Because of the high distance resolution of EPR, at least two distinct structural states of the cleft were resolved. Each of the biochemical states tested (prehydrolysis, posthydrolysis, and rigor), reflects a mixture of these structural states, indicating that the coupling between biochemical and structural states is not rigid. The resulting model is much more dynamic than previously envisioned, with both open and closed conformations of the cleft interconverting, even in the rigor actomyosin complex.

  2. Graphene-diamond interface: Gap opening and electronic spin injection

    NASA Astrophysics Data System (ADS)

    Ma, Yandong; Dai, Ying; Guo, Meng; Huang, Baibiao

    2012-06-01

    Creating a finite band gap, injecting electronic spin, and finding a suitable substrate are the three important challenges for building graphene-based devices. Here, first-principles calculations are performed to investigate the electronic and magnetic properties of graphene adsorbed on the (111) surface of diamond, which is synthesized experimentally [Nature10.1038/nature09979 472, 74 (2011); J. Appl. Phys.10.1063/1.3627370 110, 044324 (2011); Nano Lett.10.1021/nl204545q 12, 1603 (2012); ACS Nano10.1021/nn204362p 6, 1018 (2012)]. Our results reveal that the graphene adsorbed on the diamond surface is a semiconductor with a finite gap depending on the adsorption arrangements due to the variation of on-site energy induced by the diamond surface, with the extra advantage of maintaining main characters of the linear band dispersion of graphene. More interestingly, different from typical graphene/semiconductor hybrid systems, we find that electronic spin can arise ``intrinsically'' in graphene owing to the exchange proximity interaction between electrons in graphene and localized electrons in the diamond surface rather than the characteristic graphene states. These predications strongly revive this new synthesized system as a viable candidate to overcome all the aforementioned challenges, providing an ideal platform for future graphene-based electronics.

  3. Synthesis Properties and Electron Spin Resonance Properties of Titanic Materials

    SciTech Connect

    Cho, Jung Min; Lee, Jun; Kim, Tak Hee; Sun, Min Ho; Jang, Young Bae; Cho, Sung June

    2009-04-19

    Titanic materials were synthesized by hydrothermal method of TiO{sub 2} anatase in 10M LiOH, 10M NaOH, and 14M KOH at 130 deg. C for 30 hours. Alkaline media were removed from the synthesized products using 0.1N HCl aqueous solution. The as-prepared samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, Brunauer-Emmett-Teller isotherm, and electron spin resonance. Different shapes of synthesized products were observed through the typical electron microscope and indicated that the formation of the different morphologies depends on the treatment conditions of highly alkaline media. Many micropores were observed in the cubic or octahedral type of TiO{sub 2} samples through the typical electron microscope and Langmuir adsorption-desorption isotherm of liquid nitrogen at 77 deg. K. Electron spin resonance studies have also been carried out to verify the existence of paramagnetic sites such as oxygen vacancies on the titania samples. The effect of alkali metal ions on the morphologies and physicochemical properties of nanoscale titania are discussed.

  4. A Lagrangian theory of the classical spinning electron

    NASA Technical Reports Server (NTRS)

    Nash, P. L.

    1984-01-01

    A Lagrangian is defined that governs the dynamics of a classical electron with spin, moving under the influence of electromagnetic forces. The Euler-Lagrange equations associated with this Lagrangian for space-time position x exp-alpha provide a generalization of the Lorentz force law. The remaining Euler-Lagrange equations lead directly to the (generalized) Frenkel (1926)-Thomas (1927)-BMT (1959) equations.

  5. The role of spinning electrons in paramagnetic phenomena

    NASA Technical Reports Server (NTRS)

    Bose, D. M.

    1986-01-01

    An attempt is made to explain paramagnetic phenomena without assuming the orientation of a molecule or ion in a magnetic field. Only the spin angular momentum is assumed to be responsible. A derivative of the Gurie-Langevin law and the magnetic moments of ions are given as a function of the number of electrons in an inner, incomplete shell. An explanation of Gerlach's experiments with iron and nickel vapors is attempted. An explanation of magnetomechanical experiments with ferromagne elements is given.

  6. Fundamental Study of Three-dimensional Fast Spin-echo Imaging with Spoiled Equilibrium Pulse.

    PubMed

    Ogawa, Masashi; Kaji, Naoto; Tsuchihashi, Toshio

    2017-01-01

    Three-dimensional fast spin-echo (3D FSE) imaging with variable refocusing flip angle has been recently applied to pre- or post-enhanced T1-weighted imaging. To reduce the acquisition time, this sequence requires higher echo train length (ETL), which potentially causes decreased T1 contrast. Spoiled equilibrium (SpE) pulse consists of a resonant +90° radiofrequency (RF) pulse and is applied at the end of the echo train. This +90° RF pulse brings residual transverse magnetization to the negative longitudinal axis, which makes it possible to increase T1 contrast. The purpose of our present study was to examine factors that influence the effect of spoiled equilibrium pulse and the relationship between T1 contrast improvement and imaging parameters and to understand the characteristics of spoiled equilibrium pulse. Phantom studies were conducted using an magnetic resonance imaging (MRI) phantom made of polyvinyl alcohol gel. To evaluate the effect of spoiled equilibrium pulse with changes in repetition time (TR), ETL, and refocusing flip angle, we measured the signal-to-noise ratio and contrast-to-noise ratio (CNR). The effect of spoiled equilibrium pulse was evaluated by calculating the enhancement rate of CNR. The factors that influence the effect of spoiled equilibrium pulse are TR, ETL, and relaxation time of tissues. Spoiled equilibrium pulse is effective with increasing TR and decreasing ETL. The shorter the T1 value, the better the spoiled equilibrium pulse functions. However, for tissues in which the T1 value is long (>600 ms), at a TR of 600 ms, improvement in T1 contrast by applying spoiled equilibrium pulse cannot be expected.

  7. Magnus expansion paradoxes in the study of equilibrium magnetization and entanglement in multi-pulse spin locking

    NASA Astrophysics Data System (ADS)

    Kuznetsova, E. I.; Fel'dman, E. B.; Feldman, D. E.

    2016-06-01

    Divergence of the Magnus expansion leads to paradoxes in the spin dynamics of solid-state NMR and in quantum informatics. This review presents results on quasi-equilibrium magnetization in a system of dipole-dipole (DD) coupled spins at times T_2\\ll t \\ll T1ρ in multiple-pulse spin locking ( T_2 is the transverse spin relaxation time and T1ρ is the rotating-frame spin-lattice relaxation time). It is shown how contradictions between the results obtained with the Magnus expansion and experimental data can be removed. Systems of two and three DD coupled spins in multi-pulse spin locking are considered, and the entanglement evolution is investigated using both the Magnus expansion and the exact solution. The critical temperature for an entangled state is also found.

  8. Electron spin resonance spectroscopy of small ensemble paramagnetic spins using a single nitrogen-vacancy center in diamond

    NASA Astrophysics Data System (ADS)

    Abeywardana, Chathuranga; Stepanov, Viktor; Cho, Franklin H.; Takahashi, Susumu

    2016-09-01

    A nitrogen-vacancy (NV) center in diamond is a promising sensor for nanoscale magnetic sensing. Here, we report on electron spin resonance (ESR) spectroscopy using a single NV center in diamond. First, using a 230 GHz ESR spectrometer, we performed ensemble ESR of a type-Ib sample crystal and identified a substitutional single nitrogen impurity as a major paramagnetic center in the sample crystal. Then, we carried out free-induction decay and spin echo measurements of the single NV center to study static and dynamic properties of nanoscale bath spins surrounding the NV center. We also measured ESR spectrum of the bath spins using double electron-electron resonance spectroscopy with the single NV center. The spectrum analysis of the NV-based ESR measurement identified that the detected spins are the nitrogen impurity spins. The experiment was also performed with several other single NV centers in the diamond sample and demonstrated that the properties of the bath spins are unique to the NV centers indicating the probe of spins in the microscopic volume using NV-based ESR. Finally, we discussed the number of spins detected by the NV-based ESR spectroscopy. By comparing the experimental result with simulation, we estimated the number of the detected spins to be ≤50 spins.

  9. Magic-angle sample spinning electron paramagnetic resonance--instrumentation, performance, and limitations.

    PubMed

    Hessinger, D; Bauer, C; Hubrich, M; Jeschke, G; Spiess, H W

    2000-12-01

    An electron paramagnetic resonance (EPR) setup for line narrowing experiments with fast sample spinning at variable angles between the rotation axis and the static magnetic field is described and applied in the magic-angle sample spinning (MAS) EPR experiment at X-band frequencies (9.5 GHz). Sample spinning speeds up to 17 kHz at temperatures down to 200 K can be achieved with rotors of 4-mm outer and 2.5-mm inner diameter without severe losses in microwave amplitude compared to standard pulse EPR probeheads. A phase cycle is introduced that provides pure absorption MAS EPR spectra and allows one to distinguish between positive and negative frequency offsets (pseudo-quadrature detection). Possible broadening mechanisms in MAS EPR spectra are discussed. It is demonstrated both by theory and by experiment that the MAS EPR experiment requires excitation bandwidths that are comparable to the total spectral width, since otherwise destructive interference between contributions of spins with similar resonance offsets suppresses the signal. Experimental observations on the E(1) center in gamma-irradiated silica glass and on the SO(-)(3) radical in gamma-irradiated sulfamic acid are reported.

  10. Detection of pulsed neutrons with solid-state electronics

    NASA Astrophysics Data System (ADS)

    Chatzakis, J.; Rigakis, I.; Hassan, S. M.; Clark, E. L.; Lee, P.

    2016-09-01

    Measurements of the spatial and time-resolved characteristics of pulsed neutron sources require large area detection materials and fast circuitry that can process the electronic pulses readout from the active region of the detector. In this paper, we present a solid-state detector based on the nuclear activation of materials by neutrons, and the detection of the secondary particle emission of the generated radionuclides’ decay. The detector utilizes a microcontroller that communicates using a modified SPI protocol. A solid-state, pulse shaping filter follows a charge amplifier, and it is designed as an inexpensive, low-noise solution for measuring pulses measured by a digital counter. An imaging detector can also be made by using an array of these detectors. The system can communicate with an interface unit and pass an image to a personal computer.

  11. Development of an (e,2e) electron momentum spectroscopy apparatus using an ultrashort pulsed electron gun

    SciTech Connect

    Yamazaki, M.; Kasai, Y.; Oishi, K.; Nakazawa, H.; Takahashi, M.

    2013-06-15

    An (e,2e) apparatus for electron momentum spectroscopy (EMS) has been developed, which employs an ultrashort-pulsed incident electron beam with a repetition rate of 5 kHz and a pulse duration in the order of a picosecond. Its instrumental design and technical details are reported, involving demonstration of a new method for finding time-zero. Furthermore, EMS data for the neutral Ne atom in the ground state measured by using the pulsed electron beam are presented to illustrate the potential abilities of the apparatus for ultrafast molecular dynamics, such as by combining EMS with the pump-and-probe technique.

  12. Room-temperature electron spin relaxation of nitroxides immobilized in trehalose: Effect of substituents adjacent to NO-group.

    PubMed

    Kuzhelev, Andrey A; Strizhakov, Rodion K; Krumkacheva, Olesya A; Polienko, Yuliya F; Morozov, Denis A; Shevelev, Georgiy Yu; Pyshnyi, Dmitrii V; Kirilyuk, Igor A; Fedin, Matvey V; Bagryanskaya, Elena G

    2016-05-01

    Trehalose has been recently promoted as efficient immobilizer of biomolecules for room-temperature EPR studies, including distance measurements between attached nitroxide spin labels. Generally, the structure of nitroxide influences the electron spin relaxation times, being crucial parameters for room-temperature pulse EPR measurements. Therefore, in this work we investigated a series of nitroxides with different substituents adjacent to NO-moiety including spirocyclohexane, spirocyclopentane, tetraethyl and tetramethyl groups. Electron spin relaxation times (T1, Tm) of these radicals immobilized in trehalose were measured at room temperature at X- and Q-bands (9/34GHz). In addition, a comparison was made with the corresponding relaxation times in nitroxide-labeled DNA immobilized in trehalose. In all cases phase memory times Tm were close to 700ns and did not essentially depend on structure of substituents. Comparison of temperature dependences of Tm at T=80-300K shows that the benefit of spirocyclohexane substituents well-known at medium temperatures (∼100-180K) becomes negligible at 300K. Therefore, unless there are specific interactions between spin labels and biomolecules, the room-temperature value of Tm in trehalose is weakly dependent on the structure of substituents adjacent to NO-moiety of nitroxide. The issues of specific interactions and stability of nitroxide labels in biological media might be more important for room temperature pulsed dipolar EPR than differences in intrinsic spin relaxation of radicals.

  13. Pulsed field gradient multiple-quantum MAS NMR spectroscopy of half-integer spin quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Fyfe, C. A.; Skibsted, J.; Grondey, H.; Meyer zu Altenschildesche, H.

    1997-12-01

    Pulsed field gradients (PFGs) have been applied to select coherence transfer pathways in multiple-quantum (MQ) MAS NMR spectra of half-integer spin quadrupolar nuclei in rigid solids. 27Al triple-quantum (3Q) MAS NMR spectra of the aluminophosphate molecular sieves VPI-5 and AlPO 4-18 have been used to demonstrate the selection of the (0)→(3)→(-1) coherence transfer pathway using PFGs and no phase cycling. Compared to MQMAS experiments that employ phase cycling schemes, the main advantage of the PFG-MQMAS technique is its simplicity, which should facilitate the combination of MQMAS with other pulse sequences.

  14. Pulsed electron beam propagation in argon and nitrogen gas mixture

    SciTech Connect

    Kholodnaya, G. E.; Sazonov, R. V.; Ponomarev, D. V.; Remnev, G. E.; Zhirkov, I. S.

    2015-10-15

    The paper presents the results of current measurements for the electron beam, propagating inside a drift tube filled in with a gas mixture (Ar and N{sub 2}). The experiments were performed using the TEA-500 pulsed electron accelerator. The main characteristics of electron beam were as follows: 60 ns pulse duration, up to 200 J energy, and 5 cm diameter. The electron beam propagated inside the drift tube assembled of three sections. Gas pressures inside the drift tube were 760 ± 3, 300 ± 3, and 50 ± 1 Torr. The studies were performed in argon, nitrogen, and their mixtures of 33%, 50%, and 66% volume concentrations, respectively.

  15. The envelope Hamiltonian for electron interaction with ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Toyota, Koudai; Saalmann, Ulf; Rost, Jan M.

    2015-07-01

    For ultrashort VUV pulses with a pulse length comparable to the orbital time of the bound electrons they couple to, we propose a simplified envelope Hamiltonian. It is based on the Kramers-Henneberger representation in connection with a Floquet expansion of the strong-field dynamics but keeps the time dependence of the pulse envelope explicit. Thereby, the envelope Hamiltonian captures the essence of the physics—light-induced shifts of bound states, single-photon absorption, and non-adiabatic electronic transitions. It delivers quantitatively accurate ionization dynamics and allows for a physical insight into the processes occurring. Its minimal requirements for construction in terms of laser parameters make it ideally suited for a large class of atomic and molecular problems.

  16. Electron rescattering at metal nanotips induced by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Wachter, G.; Lemell, C.; Burgdörfer, J.

    2014-04-01

    We theoretically investigate the interaction of moderate intensity near-infrared few cycle laser pulses with nano-scale metal tips. Local field enhancement in a nanometric region around the tip apex triggers coherent electron emission on the nanometer length and femtosecond time scale. The quantum dynamics at the surface are simulated with time-dependent density functional theory (TDDFT) and interpreted based on the simple man's model. We investigate the dependence of the emitted electron spectra on the laser wavelength.

  17. Spin precession by pulsed inductive magnetometry in thin amorphous plates

    SciTech Connect

    Magni, Alessandro; Bottauscio, Oriano; Caprile, Ambra Celegato, Federica; Ferrara, Enzo; Fiorillo, Fausto

    2014-05-07

    Broadband magnetic loss and damping behavior of Co-based amorphous ribbons and thin films have been investigated. The permeability and loss response of the transverse anisotropy ribbon samples in the frequency range DC to 1 GHz is interpreted in terms of combined and distinguishable contributions to the magnetization process by domain wall displacements and magnetization rotations. The latter alone are shown to survive at the highest frequencies, where the losses are calculated via coupled Maxwell and Landau–Lifshitz–Gilbert (LLG) equations. Remarkably high values of the LLG damping coefficient α = 0.1–0.2 are invoked in this theoretical prediction. Direct measurements of α by pulsed inductive microwave magnetometry are thus performed, both in these laminae and in amorphous films of identical composition, obtaining about one order of magnitude increase of the α value upon the 100 nm÷10 μm thickness range. This confirms that dissipation by eddy currents enters the LLG equation via large increase of the damping coefficient.

  18. Electron spin-lattice relaxation in radicals containing two methyl groups, generated by /γ-irradiation of polycrystalline solids

    NASA Astrophysics Data System (ADS)

    Harbridge, James R.; Eaton, Sandra S.; Eaton, Gareth R.

    2002-12-01

    The effects of methyl rotation on electron spin-lattice relaxation times were examined by pulsed electron paramagnetic resonance for the major radicals in γ-irradiated polycrystalline α-amino isobutyric acid, dimethyl-malonic acid, and L-valine. The dominant radical is the same in irradiated dimethyl-malonic acid and α-amino isobutyric acid. Continuous wave saturation recovery was measured between 10 and 295 K at S-band and X-band. Inversion recovery, echo-detected saturation recovery, and pulsed electron-electron double resonance (ELDOR) data were obtained between 77 and 295 K. For the radicals in the three solids, recovery time constants measured by the various techniques were not the same, because spectral diffusion processes contribute differently for each measurement. Hyperfine splitting due to the protons of two methyl groups is resolved in the EPR spectra for each of the samples. Pulsed ELDOR data were obtained to characterize the spectral diffusion processes that transfer magnetization between hyperfine lines. Time constants were obtained for electron spin-lattice relaxation ( T1e), nuclear spin relaxation ( T1n), cross-relaxation ( Tx1), and spin diffusion ( Ts). Between 77 and 295 K rapid cross-relaxation (Δ Ms=±1, Δ MI=∓1) was observed for each sample, which is attributed to methyl rotation at a rate that is approximately equal to the electron Larmor frequency. The large temperature range over which cross-relaxation was observed suggests that methyl groups in the radical and in the lattice, with different activation energies for rotation, contribute to the rapid cross-relaxation. Activation energies for methyl and amino group rotation between 160 and 1900 K (1.3-16 kJ/mol) were obtained by analysis of the temperature dependence of 1/ T1e at S-band and X-band in the temperature intervals where the dynamic process dominates T1e.

  19. Directly probing spin dynamics in insulating antiferromagnets using ultrashort terahertz pulses

    DOE PAGES

    Bowlan, Pamela Renee; Trugman, Stuart Alan; Wang, X.; ...

    2016-11-22

    We investigate spin dynamics in the antiferromagnetic (AFM) multiferroic TbMnO3 using opticalpump, terahertz (THz)-probe spectroscopy. Photoexcitation results in a broadband THz transmission change, with an onset time of 25 ps at 6 K that becomes faster at higher temperatures. We attribute this time constant to spin-lattice thermalization. The excellent agreement between our measurements and previous ultrafast resonant x-ray diffraction measurements on the same material confirms that our THz pulse directly probes spin order. We suggest that this could be the case in general for insulating AFM materials, if the origin of the static absorption in the THz spectral range ismore » magnetic.« less

  20. Possibility of introducing spin into attoscience with spin-polarized electrons produced by a bichromatic circularly polarized laser field

    NASA Astrophysics Data System (ADS)

    Milošević, D. B.

    2016-05-01

    We show that the electrons, produced in strong-bicircular-field-induced above-threshold ionization of inert-gas atoms, have a large spin asymmetry if the ions exhibit fine-structure splitting. For a bicircular field, which consists of two coplanar counterrotating circularly polarized fields of frequencies ω and 2 ω , the spin-asymmetry parameter changes rapidly with the electron energy. Since the electron-parent-ion rescattering in a counterrotating bicircular field is characterized on the attosecond time scale, this spin asymmetry may introduce the spin degree of freedom into attoscience. We show that the high-energy backward and low-energy forward scattered electrons, which are produced on the scale of a fraction of the laser cycle, exhibit spin asymmetry.

  1. Compact femtosecond electron diffractometer with 100 keV electron bunches approaching the single-electron pulse duration limit

    SciTech Connect

    Waldecker, Lutz Bertoni, Roman; Ernstorfer, Ralph

    2015-01-28

    We present the design and implementation of a highly compact femtosecond electron diffractometer working at electron energies up to 100 keV. We use a multi-body particle tracing code to simulate electron bunch propagation through the setup and to calculate pulse durations at the sample position. Our simulations show that electron bunches containing few thousands of electrons per bunch are only weakly broadened by space-charge effects and their pulse duration is thus close to the one of a single-electron wavepacket. With our compact setup, we can create electron bunches containing up to 5000 electrons with a pulse duration below 100 fs on the sample. We use the diffractometer to track the energy transfer from photoexcited electrons to the lattice in a thin film of titanium. This process takes place on the timescale of few-hundred femtoseconds and a fully equilibrated state is reached within 1 ps.

  2. Evidence of Spin-Injection-Induced Cooper Pair Breaking in Perovskite Ferromagnet-Insulator-Superconductor Heterostructures via Pulsed Current Measurements

    NASA Technical Reports Server (NTRS)

    Yeh, N. C.; Samoilov, A. V.; Veasquez, R. P.; Li, Y.

    1998-01-01

    The effect of spin-polarized currents on the critical current densities of cuprate superconductors is investigated in perovskite ferromagnet-insulator-superconductor heterostructures with a pulsed current technique.

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

    NASA Astrophysics Data System (ADS)

    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

  4. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Spin Relaxation of Electrons in Single InAs Quantum Dots

    NASA Astrophysics Data System (ADS)

    Ma, Shan-Shan; Dou, Xiu-Ming; Chang, Xiu-Ying; Sun, Bao-Quan; Xiong, Yong-Hua; Niu, Zhi-Chuan; Ni, Hai-Qiao

    2009-11-01

    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.

  5. Electron density and electron temperature measurements in nanosecond pulse discharges over liquid water surface

    NASA Astrophysics Data System (ADS)

    Simeni Simeni, M.; Roettgen, A.; Petrishchev, V.; Frederickson, K.; Adamovich, I. V.

    2016-12-01

    Time-resolved electron density, electron temperature, and gas temperature in nanosecond pulse discharges in helium and O2-He mixtures near liquid water surface are measured using Thomson/pure rotational Raman scattering, in two different geometries, (a) ‘diffuse filament’ discharge between a spherical high-voltage electrode and a grounded pin electrode placed in a reservoir filled with distilled water, with the tip exposed, and (b) dielectric barrier discharge between the high-voltage electrode and the liquid water surface. A diffuse plasma filament generated between the electrodes in helium during the primary discharge pulse exhibits noticeable constriction during the secondary discharge pulse several hundred ns later. Adding oxygen to the mixture reduces the plasma filament diameter and enhances constriction during the secondary pulse. In the dielectric barrier discharge, diffuse volumetric plasma occupies nearly the entire space between the high voltage electrode and the liquid surface, and extends radially along the surface. In the filament discharge in helium, adding water to the container results in considerable reduction of plasma lifetime compared to the discharge in dry helium, by about an order of magnitude, indicating rapid electron recombination with water cluster ions. Peak electron density during the pulse is also reduced, by about a factor of two, likely due to dissociative attachment to water vapor during the discharge pulse. These trends become more pronounced as oxygen is added to the mixture, which increases net rate of dissociative attachment. Gas temperature during the primary discharge pulse remains near room temperature, after which it increases up to T ~ 500 K over 5 µs and decays back to near room temperature before the next discharge pulse several tens of ms later. As expected, electron density and electron temperature in diffuse DBD plasmas are considerably lower compared to peak values in the filament discharge. Use of Thomson

  6. Broadband geodesic pulses for three spin systems: time-optimal realization of effective trilinear coupling terms and indirect SWAP gates.

    PubMed

    Reiss, Timo O; Khaneja, Navin; Glaser, Steffen J

    2003-11-01

    Broadband implementations of time-optimal geodesic pulse elements are introduced for the efficient creation of effective trilinear coupling terms for spin systems consisting of three weakly coupled spins 1/2. Based on these pulse elements, the time-optimal implementation of indirect SWAP operations is demonstrated experimentally. The duration of indirect SWAP gates based on broadband geodesic sequence is reduced by 42.3% compared to conventional approaches.

  7. Fatty Acid Desaturase Mutants of Yeast: Growth Requirements and Electron Spin Resonance Spin-Label Distribution

    PubMed Central

    Wisnieski, Bernadine J.; Kiyomoto, Richard K.

    1972-01-01

    Two respiratory-sufficient and one respiratory-deficient (nuclear petite) strains of yeast Δ9-desaturase mutants were analyzed to determine which fatty acids would serve as replacements for the naturally occurring fatty acids, 16:1 Δ9cis and 18:1 Δ9cis. The requirement can be satisfied by several fatty acids differing in double-bond position, steric configuration, chain length, and degree of unsaturation. The features common to growth-supporting fatty acids are presented and the effects of varying the carbon source and temperature are considered. In addition, we illustrate several pitfalls encountered in membrane studies which exploit lipid-requiring organisms. Since the membrane fatty acid composition of these mutants can be modified readily, electron spin resonance spectroscopy is used to compare membranes of mutant strains enriched for different fatty acids. The lipid distribution pattern of the most commonly employed electron spin resonance spin-label, 12-nitroxide stearate, was ascertained and compared to that of 18:1 Δ9cis. PMID:4333377

  8. Superradiance of short electron pulses in regular and corrugated waveguides

    SciTech Connect

    Ginzburg, N.S.; Konoplev, I.V.; Sergeev, A.S.

    1995-12-31

    The report is devoted to theoretical and experimental study of superradiance of short electron pulses moving through waveguide systems. It is suggested that electrons oscillate or in undulator field (undulator SR) or in homogeneous magnetic field (cyclotron SR). We studied specific regimes of SR which may occur due to peculiarities of waveguide dispersion. Among them there are regimes of radiation near cut-off frequency as well as regimes of group synchronism. At the last operating regimes an electron bunch longitudinal velocity coincide with group velocity of e.m. wave. It is found the increasing of the SR instability grows rate and energy extraction efficiency in such regimes. It is also possible to observe the same enhancement using external feedback in periodically corrugated waveguide when Bragg resonance condition with forward propagated e.m. wave is fulfill. For experimental observation of cyclotron SR we intend to use compact subnanosecond accelerator RADAN 303B on the base of the high voltage generator with special subnansecond transformer. Accelerator generates short 0.3ns electron pulses with current about 1kA and particles energy 200keV. Design of magnetic confound system provide possibility to install an active locker to impose to electrons cyclotron rotation with pitch-factor about 1-1.5. According to numerical simulation at the mm and submm wavebands it is possible to achieve radiation pick power about 5-10MW with pulse duration less than 1ns.

  9. Ab initio calculations of correlated electron dynamics in ultrashort pulses

    NASA Astrophysics Data System (ADS)

    Feist, Johannes

    2010-03-01

    The availability of ultrashort and intense light pulses on the femtosecond and attosecond timescale promises to allow to directly probe and control electron dynamics on their natural timescale. A crucial ingredient to understanding the dynamics in many-electron systems is the influence of electron correlation, induced by the interelectronic repulsion. In order to study electron correlation in ultrafast processes, we have implemented an ab initio simulation of the two-electron dynamics in helium atoms. We solve the time-dependent Schr"odinger equation in its full dimensionality, with one temporal and five spatial degrees of freedom in linearly polarized laser fields. In our computational approach, the wave function is represented through a combination of time-dependent close coupling with the finite element discrete variable representation, while time propagation is performed using an Arnoldi-Lanczos approximation with adaptive step size. This approach is optimized to allow for efficient parallelization of the program and has been shown to scale linearly using up to 1800 processor cores for typical problem sizes. This has allowed us to perform highly accurate and well- converged computations for the interaction of ultrashort laser pulses with He. I will present some recent results on using attosecond and femtosecond pulses to probe and control the temporal structure of the ionization process. This work was performed in collaboration with Stefan Nagele, Renate Pazourek, Andreas Kaltenb"ack, Emil Persson, Barry I. Schneider, Lee A. Collins, and Joachim Burgd"orfer.

  10. Spin noise of localized electrons: Interplay of hopping and hyperfine interaction

    NASA Astrophysics Data System (ADS)

    Glazov, M. M.

    2015-05-01

    The theory of spin fluctuations is developed for an ensemble of localized electrons, taking into account both the hyperfine interaction of electron and nuclear spins and electron hopping between the sites. The analytical expression for the spin noise spectrum is derived for an arbitrary relation between the electron spin precession frequency in a field of nuclear fluctuations and the hopping rate. An increase in the hopping rate results in a drastic change in the spin noise spectrum. The effect of an external magnetic field is briefly addressed.

  11. Measuring multimegavolt pulsed voltages using Compton-generated electrons

    NASA Astrophysics Data System (ADS)

    Swanekamp, S. B.; Weber, B. V.; Pereira, N. R.; Hinshelwood, D. D.; Stephanakis, S. J.; Young, F. C.

    2004-01-01

    The "Compton-Hall" voltmeter is a radiation-based voltage diagnostic that has been developed to measure voltages on high-power (TW) pulsed generators. The instrument collimates photons generated from bremsstrahlung produced in the diode onto an aluminum target to generate Compton-generated electrons. Permanent magnets bend the Compton electron orbits that escape the target toward a silicon pin diode detector. A GaAs photoconductive detector (PCD) detects photons that pass through the Compton target. The diode voltage is determined from the ratio of the electron dose in the pin detector to the x-ray dose in the PCD. The Integrated Tiger Series of electron-photon transport codes is used to determine the relationship between the measured dose ratio and the diode voltage. Variations in the electron beam's angle of incidence on the bremsstrahlung target produce changes in the shape of the photon spectrum that lead to large variations in the voltage inferred from the voltmeter. The voltage uncertainty is minimized when the voltmeter is fielded at an angle of 45° with respect to the bremsstrahlung target. In this position, the photon spectra for different angles of incidence all converge onto a single spectrum reducing the uncertainty in the voltage to less than 10% for voltages below 4 MV. Higher and lower voltages than the range considered in this article can be measured by adjusting the strength of the applied magnetic field or the position of the electron detector relative to the Compton target. The instrument was fielded on the Gamble II pulsed-power generator configured with a plasma opening switch. Measurements produced a time-dependent voltage with a peak (3.7 MV) that agrees with nuclear activation measurements and a pulse shape that is consistent with the measured radiation pulse shape.

  12. Probing spin-orbit-interaction-induced electron dynamics in the carbon atom by multiphoton ionization

    NASA Astrophysics Data System (ADS)

    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.

  13. Restricted active space spin-flip configuration interaction: theory and examples for multiple spin flips with odd numbers of electrons.

    PubMed

    Zimmerman, Paul M; Bell, Franziska; Goldey, Matthew; Bell, Alexis T; Head-Gordon, Martin

    2012-10-28

    The restricted active space spin flip (RAS-SF) method is extended to allow ground and excited states of molecular radicals to be described at low cost (for small numbers of spin flips). RAS-SF allows for any number of spin flips and a flexible active space while maintaining pure spin eigenfunctions for all states by maintaining a spin complete set of determinants and using spin-restricted orbitals. The implementation supports both even and odd numbers of electrons, while use of resolution of the identity integrals and a shared memory parallel implementation allow for fast computation. Examples of multiple-bond dissociation, excited states in triradicals, spin conversions in organic multi-radicals, and mixed-valence metal coordination complexes demonstrate the broad usefulness of RAS-SF.

  14. Phase relaxed localized excitation pulses for inner volume fast spin echo imaging

    PubMed Central

    Hajnal, Joseph V.

    2015-01-01

    Purpose To design multidimensional spatially selective radiofrequency (RF) pulses for inner volume imaging (IVI) with three‐dimensional (3D) fast spin echo (FSE) sequences. Enhanced background suppression is achieved by exploiting particular signal properties of FSE sequences. Theory and Methods The CPMG condition dictates that echo amplitudes will rapidly decrease if a 90° phase difference between excitation and refocusing pulses is not present, and refocusing flip angles are not precisely 180°. This mechanism is proposed as a means for generating additional background suppression for spatially selective excitation, by biasing residual excitation errors toward violating the CPMG condition. 3D RF pulses were designed using this method with a 3D spherical spiral trajectory, under‐sampled by factor 5.6 for an eight‐channel PTx system, at 3 Tesla. Results 3D‐FSE IVI with pulse durations of approximately 12 ms was demonstrated in phantoms and for T2‐weighted brain imaging in vivo. Good image quality was obtained, with mean background suppression factors of 103 and 82 ± 6 in phantoms and in vivo, respectively. Conclusion Inner Volume Imaging with 3D‐FSE has been demonstrated in vivo with tailored 3D‐RF pulses. The proposed design methods are also applicable to 2D pulses. Magn Reson Med 76:848–861, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine PMID:26451691

  15. Spin-photo-currents generated by femtosecond laser pulses in a ferrimagnetic GdFeCo/Pt bilayer

    NASA Astrophysics Data System (ADS)

    Huisman, T. J.; Ciccarelli, C.; Tsukamoto, A.; Mikhaylovskiy, R. V.; Rasing, Th.; Kimel, A. V.

    2017-02-01

    Using THz emission spectroscopy, we detect spin-photo-currents from a ferrimagnetic amorphous alloy GdFeCo to an adjacent Pt capping layer. The currents are generated upon excitation of a GdFeCo/Pt heterostructure with femtosecond laser pulses. It is found that the polarization of the spin-polarized current is determined by magnetic sublattice sensitivity rather than the total magnetization, allowing for spin-polarized current generation when the net magnetization is zero.

  16. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Spin-dependent electron transport of a waveguide with Rashba spin-orbit coupling in an electromagnetic field

    NASA Astrophysics Data System (ADS)

    Xiao, Xian-Bo; Li, Xiao-Mao; Chen, Yu-Guang

    2009-12-01

    We investigate theoretically the spin-dependent electron transport in a straight waveguide with Rashba spin-orbit coupling (SOC) under the irradiation of a transversely polarized electromagnetic (EM) field. Spin-dependent electron conductance and spin polarization are calculated as functions of the emitting energy of electrons or the strength of the EM field by adopting the mode matching approach. It is shown that the spin polarization can be manipulated by external parameters when the strength of Rashba SOC is strong. Furthermore, a sharp step structure is found to exist in the total electron conductance. These results can be understood by the nontrivial Rashba subbands intermixing and the electron intersubband transition when a finite-range transversely polarized EM field irradiates a straight waveguide.

  17. Tunable surface electron spin splitting with electric double-layer transistors based on InN.

    PubMed

    Yin, Chunming; Yuan, Hongtao; Wang, Xinqiang; Liu, Shitao; Zhang, Shan; Tang, Ning; Xu, Fujun; Chen, Zhuoyu; Shimotani, Hidekazu; Iwasa, Yoshihiro; Chen, Yonghai; Ge, Weikun; Shen, Bo

    2013-05-08

    Electrically manipulating electron spins based on Rashba spin-orbit coupling (SOC) is a key pathway for applications of spintronics and spin-based quantum computation. Two-dimensional electron systems (2DESs) offer a particularly important SOC platform, where spin polarization can be tuned with an electric field perpendicular to the 2DES. Here, by measuring the tunable circular photogalvanic effect (CPGE), we present a room-temperature electric-field-modulated spin splitting of surface electrons on InN epitaxial thin films that is a good candidate to realize spin injection. The surface band bending and resulting CPGE current are successfully modulated by ionic liquid gating within an electric double-layer transistor configuration. The clear gate voltage dependence of CPGE current indicates that the spin splitting of the surface electron accumulation layer is effectively tuned, providing a way to modulate the injected spin polarization in potential spintronic devices.

  18. Force detected electron spin resonance at 94 GHz.

    PubMed

    Cruickshank, Paul A S; Smith, Graham M

    2007-01-01

    Force detected electron spin resonance (FDESR) detects the presence of unpaired electrons in a sample by measuring the change in force on a mechanical resonator as the magnetization of the sample is modulated under magnetic resonance conditions. The magnetization is coupled to the resonator via a magnetic field gradient. It has been used to both detect and image distributions of electron spins, and it offers both extremely high absolute sensitivity and high spatial imaging resolution. However, compared to conventional induction mode ESR the technique also has a comparatively poor concentration sensitivity and it introduces complications in interpreting and combining both spectroscopy and imaging. One method to improve both sensitivity and spectral resolution is to operate in high magnetic fields in order to increase the sample magnetization and g-factor resolution. In this article we present FDESR measurements on the organic conductor (fluoranthene)(2)PF(6) at 3.2 T, with a corresponding millimeter-wave frequency of 93.5 GHz, which we believe are the highest field results for FDESR reported in the literature to date. A magnet-on-cantilever approach was used, with a high-anisotropy microwave ferrite as the gradient source and employing cyclic saturation to modulate the magnetization at the cantilever fundamental frequency.

  19. Electron spin resonance in Eu-based iron pnictides

    NASA Astrophysics Data System (ADS)

    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 Telectrons is strongly weakened. With increasing substitution of x or y the transition temperature TSDW decreases linearly accompanied by a linear decrease of the Korringa-relaxation rate 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.

  20. Lesion-induced DNA weak structural changes detected by pulsed EPR spectroscopy combined with site-directed spin labelling

    PubMed Central

    Sicoli, Giuseppe; Mathis, Gérald; Aci-Sèche, Samia; Saint-Pierre, Christine; Boulard, Yves; Gasparutto, Didier; Gambarelli, Serge

    2009-01-01

    Double electron-electron resonance (DEER) was applied to determine nanometre spin–spin distances on DNA duplexes that contain selected structural alterations. The present approach to evaluate the structural features of DNA damages is thus related to the interspin distance changes, as well as to the flexibility of the overall structure deduced from the distance distribution. A set of site-directed nitroxide-labelled double-stranded DNA fragments containing defined lesions, namely an 8-oxoguanine, an abasic site or abasic site analogues, a nick, a gap and a bulge structure were prepared and then analysed by the DEER spectroscopic technique. New insights into the application of 4-pulse DEER sequence are also provided, in particular with respect to the spin probes’ positions and the rigidity of selected systems. The lesion-induced conformational changes observed, which were supported by molecular dynamics studies, confirm the results obtained by other, more conventional, spectroscopic techniques. Thus, the experimental approaches described herein provide an efficient method for probing lesion-induced structural changes of nucleic acids. PMID:19304747

  1. Electronic Quasiparticle Renormalization on the Spin Wave Energy Scale

    NASA Astrophysics Data System (ADS)

    Schäfer, J.; Schrupp, D.; Rotenberg, Eli; Rossnagel, K.; Koh, H.; Blaha, P.; Claessen, R.

    2004-03-01

    High-resolution photoemission data of the (110) iron surface reveal the existence of well-defined metallic surface resonances in good correspondence to band calculations. Close to the Fermi level, their dispersion and momentum broadening display anomalies characteristic of quasiparticle renormalization due to coupling to bosonic excitations. Its energy scale exceeds that of phonons by far, and is in striking coincidence with that of the spin wave spectrum in iron. The self-energy behavior thus gives spectroscopic evidence of a quasiparticle mass enhancement due to electron-magnon coupling.

  2. Broadband electron spin resonance at low frequency without resonant cavity

    SciTech Connect

    Jang, Z.; Suh, B.; Corti, M.; Cattaneo, L.; Hajny, D.; Borsa, F.; Luban, M.

    2008-04-09

    We have developed a nonconventional broadband electron spin resonance (ESR) spectrometer operating continuously in the frequency range from 0.5 to 9 GHz. Dual antenna structure and the microwave absorbing environment differentiate the setup from the conventional one and enable broadband operation with any combination of frequency or magnetic field modulation and frequency or magnetic field sweeping. Its performance has been tested with the measurements on a 1,1-diphenyl-2-picrylhydrazyl (DPPH) sample and with the measurements on the single molecular magnet, V6, in solid state at low temperature.

  3. Magnetism of gold nanorods probed using electron spin resonance

    NASA Astrophysics Data System (ADS)

    Inagaki, Y.; Yonemura, H.; Sakai, N.; Makihara, Y.; Kawae, T.; Yamada, S.

    2016-08-01

    Electron spin resonance (ESR) spectroscopy has been performed for gold nanorods (AuNRs) of four different sizes covered with a diamagnetic stabilizing component, cetyltrimethylammonium bromide. ESR signals were detected in AuNRs except the largest one. Two smallest AuNRs showed an abrupt change in the temperature dependence of resonance field and line width at around 60 K, indicating ferromagnetic phase transition. In medium-size AuNRs, the resonance with a large shift was observed below 100 K. The resonance field shifts at the lowest temperature exhibit systematic variation with the system size, which is explained by considering magnetic anisotropy for the ferromagnetic resonance.

  4. Local electron-electron interaction strength in ferromagnetic nickel determined by spin-polarized positron annihilation.

    PubMed

    Ceeh, Hubert; Weber, Josef Andreas; Weber, Josef Andreass; Böni, Peter; Leitner, Michael; Benea, Diana; Chioncel, Liviu; Ebert, Hubert; Minár, Jan; Vollhardt, Dieter; Hugenschmidt, Christoph

    2016-02-16

    We employ a positron annihilation technique, the spin-polarized two-dimensional angular correlation of annihilation radiation (2D-ACAR), to measure the spin-difference spectra of ferromagnetic nickel. The experimental data are compared with the theoretical results obtained within a combination of the local spin density approximation (LSDA) and the many-body dynamical mean-field theory (DMFT). We find that the self-energy defining the electronic correlations in Ni leads to anisotropic contributions to the momentum distribution. By direct comparison of the theoretical and experimental results we determine the strength of the local electronic interaction U in ferromagnetic Ni as 2.0 ± 0.1 eV.

  5. Local electron-electron interaction strength in ferromagnetic nickel determined by spin-polarized positron annihilation

    PubMed Central

    Ceeh, Hubert; Weber, Josef Andreass; Böni, Peter; Leitner, Michael; Benea, Diana; Chioncel, Liviu; Ebert, Hubert; Minár, Jan; Vollhardt, Dieter; Hugenschmidt, Christoph

    2016-01-01

    We employ a positron annihilation technique, the spin-polarized two-dimensional angular correlation of annihilation radiation (2D-ACAR), to measure the spin-difference spectra of ferromagnetic nickel. The experimental data are compared with the theoretical results obtained within a combination of the local spin density approximation (LSDA) and the many-body dynamical mean-field theory (DMFT). We find that the self-energy defining the electronic correlations in Ni leads to anisotropic contributions to the momentum distribution. By direct comparison of the theoretical and experimental results we determine the strength of the local electronic interaction U in ferromagnetic Ni as 2.0 ± 0.1 eV. PMID:26879249

  6. Pulse-fluence-specified optimal control simulation with applications to molecular orientation and spin-isomer-selective molecular alignment

    SciTech Connect

    Yoshida, Masataka; Nakashima, Kaoru; Ohtsuki, Yukiyoshi

    2015-12-31

    We propose an optimal control simulation with specified pulse fluence and amplitude. The simulation is applied to the orientation control of CO molecules to examine the optimal combination of THz and laser pulses, and to discriminate nuclear-spin isomers of {sup 14}N{sub 2} as spatially anisotropic distributions.

  7. Electron spin resonance shifts in S=1 antiferromagnetic chains

    NASA Astrophysics Data System (ADS)

    Furuya, Shunsuke C.; Maeda, Yoshitaka; Oshikawa, Masaki

    2013-03-01

    We discuss electron spin resonance (ESR) shifts in spin-1 Heisenberg antiferromagnetic chains with a weak single-ion anisotropy, based on several effective field theories: the O(3) nonlinear sigma model (NLSM) in the Haldane phase, free-fermion theories around the lower and the upper critical fields. In the O(3) NLSM, the single-ion anisotropy corresponds to a composite operator which creates two magnons at the same time and position. Therefore, even inside a parameter range where free magnon approximation is valid for thermodynamics, we have to take interactions among magnons into account in order to include the single-ion anisotropy as a perturbation. Although the O(3) NLSM is only valid in the Haldane phase, an appropriate translation of Faddeev-Zamolodchikov operators of the O(3) NLSM to fermion operators enables one to treat ESR shifts near the lower critical field in a similar manner to discussions in the Haldane phase. Our theory gives quantitative agreements with a numerical evaluation using quantum Monte Carlo simulation, and also with recent ESR experimental results on a spin-1 chain compound Ni(C5H14N2)2N3(PF6).

  8. Electron detachment from negative ions in a short laser pulse

    SciTech Connect

    Shearer, S. F. C.; Smyth, M. C.; Gribakin, G. F.

    2011-09-15

    We present an efficient and accurate method to study electron detachment from negative ions by a few-cycle linearly polarized laser pulse. The adiabatic saddle-point method of Gribakin and Kuchiev [Phys. Rev. A 55, 3760 (1997)] is adapted to calculate the transition amplitude for a short laser pulse. Its application to a pulse with N optical cycles produces 2(N+1) saddle points in complex time, which form a characteristic 'smile.' Numerical calculations are performed for H{sup -} in a 5-cycle pulse with frequency 0.0043 a.u. and intensities of 10{sup 10}, 5x10{sup 10}, and 10{sup 11} W/cm{sup 2}, and for various carrier-envelope phases. We determine the spectrum of the photoelectrons as a function of both energy and emission angle, as well as the angle-integrated energy spectra and total detachment probabilities. Our calculations show that the dominant contribution to the transition amplitude is given by 5-6 central saddle points, which correspond to the strongest part of the pulse. We examine the dependence of the photoelectron angular distributions on the carrier-envelope phase and show that measuring such distributions can provide a way of determining this phase.

  9. Pulsed power requirements for the Sandia recirculating electron beam linac

    SciTech Connect

    Tucker, W.K.; Shope, S.L.; Hasti, D.E.

    1987-01-01

    Compact, high gradient, linear induction accelerators may be achieved by recirculating the electron beam in phase with a repeating accelerating voltage. A two-cavity recirculating accelerator has been designed and operated in a single-pass mode. The prototype accelerator uses a 2.5-MV, 20-kA, 25-ns duration injector and an accelerating cavity that will produce a total accelerating voltage of 5.3 MV for four passes. The design of this machine involved key areas of development in pulsed power, specifically, low-jitter spark gaps and vacuum-liquid interfaces for bipolar electric fields. The extension of this technology to multiple-pulse machines will require advances in liquid dielectric breakdown strength and switch surface flashover, as well as additional improvements in lower inductance switching and vacuum-liquid interface flashover. This paper will discuss the recirculation concept, pulsed-power design parameters, machine scaling relationships that are valid for state-of-the-art and near-term pulsed-power parameters, and summarize the pulsed-power and beam transport experiments.

  10. Local spin torque induced by electron electric dipole moment in the YbF molecule

    SciTech Connect

    Fukuda, Masahiro; Senami, Masato; Ogiso, Yoji; Tachibana, Akitomo

    2014-10-06

    In this study, we show the modification of the equation of motion of the electronic spin, which is derived by the quantum electron spin vorticity principle, by the effect of the electron electric dipole moment (EDM). To investigate the new contribution to spin torque by EDM, using first principle calculations, we visualize distributions of the local spin angular momentum density and local spin torque density of the YbF molecule on which the static electric field and magnetic field are applied at t = 0.

  11. Pulsed Electric Discharge Laser Technology. Electron Beam Window Foil Material.

    DTIC Science & Technology

    1984-01-01

    6.0 INTERFEROMETRIC MEASUREMENT OF FOIL MOVEMENT A simple Michelson interferometer was used to measure foil movement on the test rig. Because the...TURNING BEAM MIRRORS BEAM DISPLAYFOCUEED IRIS AT FOOS. OPTICAL FIBRE * BUNDLE Figure 49. Schematic of interferometer . -98-7 reflected speckle. The...As a check on the pulse simulation, the actual movement of an electron-beam foil window was measured by interferometry. A speckle interferometer which

  12. Nonlocal Nuclear Spin Quieting in Quantum Dot Molecules: Optically Induced Extended Two-Electron Spin Coherence Time

    NASA Astrophysics Data System (ADS)

    Chow, Colin M.; Ross, Aaron M.; Kim, Danny; Gammon, Daniel; Bracker, Allan S.; Sham, L. J.; Steel, Duncan G.

    2016-08-01

    We demonstrate the extension of coherence between all four two-electron spin ground states of an InAs quantum dot molecule (QDM) via nonlocal suppression of nuclear spin fluctuations in two vertically stacked quantum dots (QDs), while optically addressing only the top QD transitions. Long coherence times are revealed through dark-state spectroscopy as resulting from nuclear spin locking mediated by the exchange interaction between the QDs. Line shape analysis provides the first measurement of the quieting of the Overhauser field distribution correlating with reduced nuclear spin fluctuations.

  13. Spin Excitation Under Electron Delocalization of Side Radicals in Quasi-One-Dimensional Organic Ferromagnet

    NASA Astrophysics Data System (ADS)

    Jiang, Hong; Hu, Xue-Ning; Zhao, Yin-chang; Zhang, Chao

    2017-02-01

    Spin excitation in poly(1,4-bis(2,2,6,6-tetramethyl-4-oxy-piperidyl-1-oxyl)-butadiin) (poly-BIPO), a quasi-one-dimensional organic ferromagnet, was investigated based on the extended Su-Schriffer-Heeger model by considering electron hopping and the spin correlation between the main chain and side radicals. The lattice, charge density, and spin density configurations of the single spin as well as spin domain excited states of the organic ferromagnet poly-BIPO were systematically studied. The side radical spin excitation gives rise to lattice distortion, charge density localization, and a spin density defect on the main chain. A peak induced by spin excitation is predicted to appear in the density of states of the organic ferromagnet poly-BIPO based on calculations for different spin electron states. These results expand knowledge on elementary excitation in organic materials and have significant implications for the design of spintronic devices.

  14. Propagation of pulsed surface spin-wave signals at millikelvin temperatures

    NASA Astrophysics Data System (ADS)

    van Loo, Arjan; Morris, Richard; Karenowska, Alexy

    Propagating microwave-frequency magnons in magnetic films attract increasing attention on account of their potential interface with superconducting quantum circuit and qubit systems. Their rich dynamics and slow speeds make magnons an interesting addition to the circuit quantum electrodynamics toolbox and, at the same time, superconducting circuit technology promises to be a powerful tool in the investigation of their quantum properties. We have studied the propagation of pulsed surface spin-wave signals over millimeter distances in yttrium iron garnet waveguides at ~ 10 mK . Input microwave pulses and pulse trains with various envelope shapes were applied to an inductive input antenna, and the resulting magnons were detected by an output antenna of identical design. The shape of the output signal was observed to depend on the frequency content (carrier and pulse shape) of the input pulse. By performing measurements at varying frequencies and magnetic fields we have been able to map out the dispersion relation for surface magnon modes. These experiments were undertaken as a first step towards coupling propagating magnons in thin films to other quantum systems with microwave-frequency transition energies, and superconducting qubits in particular. The authors acknowledge support from the EPSRC (EP/K032690/1).

  15. Photoemission studies using femtosecond pulses for high brightness electron beams

    NASA Astrophysics Data System (ADS)

    Srinivasan-Rao, T.; Tsang, T.; Fischer, J.

    1990-06-01

    We present the results of a series of experiments where various metal photocathodes are irradiated with ultrashort laser pulses, whose characteristics are: (lambda) = 625 nm, (tau) = 100 fs, PRR = 89.5 MHz, H(nu) = 2 eV and average power 25 mW in each of the two beams. The quantum efficiency of the metals range from approximately 10(exp -12) to 10(exp -8) at a power density of 100 MW/sq cm at normal incidence. Since all the electrons are emitted due to multiphoton processes, these efficiencies are expected to increase substantially at large intensities. The efficiency at 100 MW/sq cm was increased by using p-polarized light at oblique incidence by approximately 20 x and by mediating the electron emission through surface plasmon excitation by approximately 10(exp 3) x. For the low intensities used in these experiments, the electron pulse duration is almost the same as the laser pulse duration for both the bulk and the surface plasmon mediated photoemission.

  16. Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses

    NASA Astrophysics Data System (ADS)

    Calegari, F.; Ayuso, D.; Trabattoni, A.; Belshaw, L.; De Camillis, S.; Anumula, S.; Frassetto, F.; Poletto, L.; Palacios, A.; Decleva, P.; Greenwood, J. B.; Martín, F.; Nisoli, M.

    2014-10-01

    In the past decade, attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules, and solids. Here, we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine and the subsequent detection of ultrafast dynamics on a sub-4.5-femtosecond temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving toward the investigation of more and more complex systems.

  17. Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses.

    PubMed

    Calegari, F; Ayuso, D; Trabattoni, A; Belshaw, L; De Camillis, S; Anumula, S; Frassetto, F; Poletto, L; Palacios, A; Decleva, P; Greenwood, J B; Martín, F; Nisoli, M

    2014-10-17

    In the past decade, attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules, and solids. Here, we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine and the subsequent detection of ultrafast dynamics on a sub-4.5-femtosecond temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving toward the investigation of more and more complex systems.

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

    SciTech Connect

    Das, Tanmoy

    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.

  19. Single-Shot Ternary Readout of Two-Electron Spin States in a Quantum Dot Using Spin Filtering by Quantum Hall Edge States.

    PubMed

    Kiyama, H; Nakajima, T; Teraoka, S; Oiwa, A; Tarucha, S

    2016-12-02

    We report on the single-shot readout of three two-electron spin states-a singlet and two triplet substates-whose z components of spin angular momentum are 0 and +1, in a gate-defined GaAs single quantum dot. The three spin states are distinguished by detecting spin-dependent tunnel rates that arise from two mechanisms: spin filtering by spin-resolved edge states and spin-orbital correlation with orbital-dependent tunneling. The three states form one ground state and two excited states, and we observe the spin relaxation dynamics among the three spin states.

  20. Electronic spin polarization and the spin-dependent bandstructure in GaAs probed by optically pumped NMR

    SciTech Connect

    Crooker, Scott A; Ramaswamy, Kannan; Mui, Stacy; Hayes, Sophia E; Pan, Xingyuan; Sanders, Gary D; Stanton, Christopher J

    2008-01-01

    High resolution optically pumped NMR (OPNMR) experiments are used to resolve fine features in the spin-dependent electronic structure of the valence bands in semi-insulating GaAs. By theoretically calculating oscillations in the OPNMR signal intensity with respect to the excitation energy, we have mapped out the conduction band electronic spin polarization under optical pumping. Comparison with a theoretical analysis of the oscillatory experimental features allows the extraction of semiconductor energy band parameters.

  1. Electron-electron double resonance in electron spin echo: Model biradical systems and the sensitized photolysis of decalin

    NASA Astrophysics Data System (ADS)

    Milov, A. D.; Ponomarev, A. B.; Tsvetkov, Yu. D.

    1984-09-01

    Model systems, comprising frozen glassy solutions of stabilized radicals and biradicals of the nitroxyl type, have been used to test the applicability of electron-electron double resonance in electron spin echo (ELDOR ESE) in studies of the spatial distributions of free radicals arranged in groups in solids. The method was used to investigate the spatial distribution of alkyl radicals generated by the sensitized photolysis of glassy naphthalene solutions in decalin at 77 K. and detected radical pairs.

  2. Electron spin resonance study of ion-implanted polymers

    NASA Astrophysics Data System (ADS)

    Wasserman, B.; Dresselhaus, M. S.; Braunstein, G.; Wnek, G. E.; Roth, G.

    1985-03-01

    The effect of ion implantation on the polymers PAN (polyacrylonitrile), PPO (poly 2,6-dimethylphenylene oxide) and PPS (p-polyphenylene sulfide) is studied using electron spin resonance. ESR measurements on these polymers were performed as a function of ion species and fluence in the temperature range 10 spin diffusion is determined to be larger than 1000. The temperature dependence of the unpaired carrier concentration shows a strong deviation from a Curie law behavior, which can be explained by assuming that a defect band is formed with a bandgap due to strong Coulomb interaction between electrons on the defect sites.

  3. Using attosecond pulses to probe ultrafast electronic motions inside atoms

    NASA Astrophysics Data System (ADS)

    Collins, L. A.; Hu, S. X.

    2006-05-01

    With using an efficient and accurate parallel solver for the time-dependent Schr"odinger equation, we have performed full-dimensional numerical simulations of the proposed attosecond pump-probe for exploring the extremely fast motion of an electronic wave packet inside atoms. Pumped by a broadband femtosecond UV pulse, one electron of ground-state Helium can be launched into a superposition of low-lying excited states, thus forming a bound wavepacket oscillating relative to the atomic core. A time-delayed attosecond EUV (probe) pulse then ionizes the atom causing three-body breakup. Measuring either the energy sharing of the ionized electrons or the total ionization probability as a function of the time delay traces out the internal motion of the excited electron. Our simulations have shown that an ultrashort oscillating period of 2 fs can be followed for several cylces. This opens the prospect of a wealth of similar pump-probe experiments to examine ultrafast electronic motions.

  4. Elucidation of the electronic structure of molecules with the help of NMR spin-spin coupling constants: the FH molecule.

    PubMed

    Gräfenstein, Jürgen; Tuttle, Tell; Cremer, Dieter

    2005-03-17

    It is demonstrated how the one-bond NMR spin-spin coupling constant (SSCC) (1)J(FH) can be used as a source of information on the electronic structure of the FH molecule. For this purpose, the best possible agreement between measured and calculated SSCC is achieved by large basis set coupled perturbed density functional theory calculations. Then, the calculated value is dissected into its four Ramsey terms: Fermi contact, the paramagnetic spin-orbit term, the diamagnetic spin-orbit term, and the spin dipole term, which in turn are decomposed into orbital contributions and then described by their spin densities and orbital current densities. In this way, the SSCC gives detailed information about the electronegativity of F, the bond polarity, the bond polarizability, the volume and the polarizability of sigma and pi lone pair orbitals, the s- or p-character of the bond orbital, the nature of the LUMO, and the density distribution around F.

  5. Inactivation kinetics of Escherichia coli by pulsed electron beam.

    PubMed

    Chalise, P R; Hotta, E; Matak, K E; Jaczynski, J

    2007-09-01

    A novel and compact low-energy (keV) high-power pulsed electron beam (e-beam) that utilizes a secondary emission electron gun (SEEG) was designed and constructed. Escherichia coli JM 109 at a concentration of 10(6) CFU/mL was spread-plated on Luria-Bertani (LB) medium and subjected to the SEEG e-beam. The e-beam was administered as 1 or 5 pulses. The duration of a single pulse was constant at 5 micros, e-beam current density was constant at 25 mA/cm2, and e-beam energy varied between 60 and 82.5 keV. Following treatment with the SEEG e-beam, survivors of the irradiated E. coli samples were enumerated by a standard 10-fold dilution and spread-plated. The survivor curves were plotted on logarithmic scale as a function of e-beam dose. The D10-values were calculated as a negative reciprocal of the slope of the survivor curves. The D10-values for E. coli inactivated with 1- and 5-pulse SEEG e-beam were 0.0026 and 0.0217 Gy, respectively. These D10-values were considerably lower than published D10-values for E. coli inactivated with conventional high-energy continuous e-beam, likely due to shorter exposure time (t), greater current density (J), and a pulse mode of the SEEG e-beam. The SEEG e-beam showed promising results for microbial inactivation in a nonthermal manner; however, due to low energy of the SEEG e-beam, current applications are limited to surface decontamination. The SEEG e-beam may be an efficient processing step for surface inactivation of food-borne pathogens on ready-to-eat products, including fresh and leafy vegetables.

  6. Observation of electron spin resonance of negative ions in liquid helium

    NASA Technical Reports Server (NTRS)

    Reichert, J. F.; Dahm, A. J.

    1973-01-01

    Electron spin resonance signals of negative ions in liquid helium were observed. The line width and g-value were measured. Electrons injected into helium by field emission from ferromagnetic tips are shown to be polarized. A new technique for the measurement of electron spin polarization is presented.

  7. Quadrupolar and anisotropy effects on dephasing in two-electron spin qubits in GaAs

    PubMed Central

    Botzem, Tim; McNeil, Robert P. G.; Mol, Jan-Michael; Schuh, Dieter; Bougeard, Dominique; Bluhm, Hendrik

    2016-01-01

    Understanding the decoherence of electron spins in semiconductors due to their interaction with nuclear spins is of fundamental interest as they realize the central spin model and of practical importance for using them as qubits. Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence. Here we show experimentally that for gate-defined GaAs quantum dots, quadrupolar broadening of the nuclear Larmor precession reduces electron spin coherence by causing faster decorrelation of transverse nuclear fields. However, this effect disappears for appropriate field directions. Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor. These results complete our understanding of dephasing in gated quantum dots and point to mitigation strategies. They may also help to unravel unexplained behaviour in self-assembled quantum dots and III–V nanowires. PMID:27079269

  8. Pulse profiles from spinning neutron stars in the Hartle-Thorne approximation

    SciTech Connect

    Psaltis, Dimitrios; Özel, Feryal E-mail: fozel@email.arizone.edu

    2014-09-10

    We present a new numerical algorithm for the calculation of pulse profiles from spinning neutron stars in the Hartle-Thorne approximation. Our approach allows us to formally take into account the effects of Doppler shifts and aberration, of frame dragging, as well as of the oblateness of the stellar surface and of its quadrupole moment. We confirm an earlier result that neglecting the oblateness of the neutron-star surface leads to ≅ 5%-30% errors in the calculated profiles and further show that neglecting the quadrupole moment of its spacetime leads to ≅ 1%-5% errors at a spin frequency of ≅ 600 Hz. We discuss the implications of our results for the measurements of neutron-star masses and radii with upcoming X-ray missions, such as NASA's NICER and ESA's LOFT.

  9. Electron-electron interaction, weak localization and spin valve effect in vertical-transport graphene devices

    SciTech Connect

    Long, Mingsheng; Gong, Youpin; Wei, Xiangfei; Zhu, Chao; Xu, Jianbao; Liu, Ping; Guo, Yufen; Li, Weiwei; Liu, Liwei; Liu, Guangtong

    2014-04-14

    We fabricated a vertical structure device, in which graphene is sandwiched between two asymmetric ferromagnetic electrodes. The measurements of electron and spin transport were performed across the combined channels containing the vertical and horizontal components. The presence of electron-electron interaction (EEI) was found not only at low temperatures but also at moderate temperatures up to ∼120 K, and EEI dominates over weak localization (WL) with and without applying magnetic fields perpendicular to the sample plane. Moreover, spin valve effect was observed when magnetic filed is swept at the direction parallel to the sample surface. We attribute the EEI and WL surviving at a relatively high temperature to the effective suppress of phonon scattering in the vertical device structure. The findings open a way for studying quantum correlation at relatively high temperature.

  10. Electron-spin-dependent terahertz light transport in spintronic-plasmonic media.

    PubMed

    Chau, K J; Johnson, Mark; Elezzabi, A Y

    2007-03-30

    In this Letter, we demonstrate that electron spin can influence near-field mediated light propagation through a dense ensemble of subwavelength bimetallic ferromagnetic/nonmagnetic microparticles. In particular, we show that ferromagnetic particles coated with nonmagnetic metal nanolayers exhibit an enhanced magnetic field controlled attenuation of the electromagnetic field propagated through the sample. The mechanism is related to dynamic, electromagnetically induced electron spin accumulation in the nonmagnet. The discovery of an electron spin phenomenon in the light interaction with metallic particles opens the door to the marriage of spintronic and plasmonic technologies and could pave the way for the development of light-based devices that exploit the electron spin state.

  11. Gate fidelity and coherence of an electron spin in an Si/SiGe quantum dot with micromagnet

    PubMed Central

    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.

    2016-01-01

    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. PMID:27698123

  12. Gate fidelity and coherence of an electron spin in an Si/SiGe quantum dot with micromagnet

    SciTech Connect

    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.

    2016-10-03

    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. Furthermore, 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.

  13. Gate fidelity and coherence of an electron spin in an Si/SiGe quantum dot with micromagnet

    DOE PAGES

    Kawakami, Erika; Jullien, Thibaut; Scarlino, Pasquale; ...

    2016-10-03

    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 limitedmore » by noise in the 10-kHz to 1-MHz range, possibly because charge noise affects the spin via the micromagnet gradient. Furthermore, 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.« less

  14. Electron heating enhancement by frequency-chirped laser pulses

    SciTech Connect

    Yazdani, E.; Afarideh, H.; Sadighi-Bonabi, R.; Riazi, Z.; Hora, H.

    2014-09-14

    Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic field is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a₀=5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about n{sub e}≈6n{sub c}, where n{sub c} is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.

  15. Magnetically insulated electron flows in pulsed power systems

    NASA Astrophysics Data System (ADS)

    Lawconnell, Robert I.

    1989-08-01

    Magnetic insulation is crucial in the operation of large pulsed power systems. Particular attention will be paid to describing magnetic insulation in realistic pulsed power systems. A theoretical model is developed that allows the production of self consistent magnetically insulated laminar flows in perturbed cylindrical systems given only the electron density profile. The theory is checked and justified by detailed comparisons with results from a 2-dimensional electromagnetic code, MASK. The procedure followed in the theoretical development is to use the relativistic Vlasov equation, Ampere's law and Gauss' law, to obtain a relation between the density profile and the velocity profile for insulated flows. Given the density profile and the corresponding derived velocity profile, a self consistent flow solution is obtained by means of Maxwell's equations. It is checked by taking a special case (corresponding to no perturbations) which results in the well known Brillouin flow theory. Emphasis is placed on determining the magnetic insulation threshold of a pulsed power system employing a plasma erosion opening switch. The procedure employed in the computational study is to vary critical aspects of the pulsed power system and then note whether magnetic insulation breaks down. The point at which magnetic insulation breaks down (as a function of geometry, load impedance, and applied voltage) is the magnetic insulation threshold for the system.

  16. Infrared imaging diagnostics for intense pulsed electron beam

    SciTech Connect

    Yu, Xiao; Shen, Jie; Liu, Wenbin; Zhong, Haowen; Zhang, Jie; Zhang, Gaolong; Le, Xiaoyun; Qu, Miao; Yan, Sha

    2015-08-15

    Infrared imaging diagnostic method for two-dimensional calorimetric diagnostics has been developed for intense pulsed electron beam (IPEB). By using a 100-μm-thick tungsten film as the infrared heat sink for IPEB, the emitting uniformity of the electron source can be analyzed to evaluate the efficiency and stability of the diode system. Two-dimensional axisymmetric finite element method heat transfer simulation, combined with Monte Carlo calculation, was performed for error estimation and optimization of the method. The test of the method was finished with IPEB generated by explosive emission electron diode with pulse duration (FWHM) of 80 ns, electron energy up to 450 keV, and a total beam current of over 1 kA. The results showed that it is possible to measure the cross-sectional energy density distribution of IPEB with energy sensitivity of 0.1 J/cm{sup 2} and spatial resolution of 1 mm. The technical details, such as irradiation protection of bremsstrahlung γ photons and the functional extensibility of the method were discussed in this work.

  17. Infrared imaging diagnostics for intense pulsed electron beam.

    PubMed

    Yu, Xiao; Shen, Jie; Qu, Miao; Liu, Wenbin; Zhong, Haowen; Zhang, Jie; Yan, Sha; Zhang, Gaolong; Le, Xiaoyun

    2015-08-01

    Infrared imaging diagnostic method for two-dimensional calorimetric diagnostics has been developed for intense pulsed electron beam (IPEB). By using a 100-μm-thick tungsten film as the infrared heat sink for IPEB, the emitting uniformity of the electron source can be analyzed to evaluate the efficiency and stability of the diode system. Two-dimensional axisymmetric finite element method heat transfer simulation, combined with Monte Carlo calculation, was performed for error estimation and optimization of the method. The test of the method was finished with IPEB generated by explosive emission electron diode with pulse duration (FWHM) of 80 ns, electron energy up to 450 keV, and a total beam current of over 1 kA. The results showed that it is possible to measure the cross-sectional energy density distribution of IPEB with energy sensitivity of 0.1 J/cm(2) and spatial resolution of 1 mm. The technical details, such as irradiation protection of bremsstrahlung γ photons and the functional extensibility of the method were discussed in this work.

  18. Tools for Studying Electron and Spin Transport in Single Molecules

    NASA Astrophysics Data System (ADS)

    Ralph, Daniel C.

    2005-03-01

    Experiments in the field of single-molecule electronics are challenging in part because it can be very difficult to control and characterize the device structure. Molecules contacted by metal electrodes cannot easily be imaged by microscopy techniques. Moreover, if one attempts to characterize the device structure simply by measuring a current-voltage curve, it is easy to mistake nonlinear transport across a bare tunnel junction or a metallic short for a molecular signal. I will discuss the development of a set of experimental test structures that enable the properties of a molecular device to be tuned controllably in-situ, so that the transport mechanisms can be studied more systematically and compared with theoretical predictions. My collaborators and I are developing the means to use several different types of such experimental "knobs" in coordination: electrostatic gating to shift the energy levels in a molecule, mechanical motion to adjust the molecular configuration or the molecule-electrode coupling strength, illumination with light to promote electrons to excited states or to make and break chemical bonds, and the use of ferromagnetic electrodes to study spin-polarized transport. Our work so far has provided new insights into Kondo physics, the coupling between a molecule's electronic and mechanical degrees of freedom, and spin transport through a molecule between magnetic electrodes. Collaborators: Radek Bialczak, Alex Champagne, Luke Donev, Jonas Goldsmith, Jacob Grose, Janice Guikema, Jiwoong Park, Josh Parks, Abhay Pasupathy, Jason Petta, Sara Slater, Burak Ulgut, Alexander Soldatov, H'ector Abruña, and Paul McEuen.

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

    PubMed

    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. Enantiospecific spin polarization of electrons photoemitted through layers of homochiral organic molecules.

    PubMed

    Niño, Miguel Ángel; Kowalik, Iwona Agnieszka; Luque, Francisco Jesús; Arvanitis, Dimitri; Miranda, Rodolfo; de Miguel, Juan José

    2014-11-26

    Electrons photoemitted through layers of purely organic chiral molecules become strongly spin-polarized even at room temperature and for double-monolayer thicknesses. The substitution of one enantiomer for its mirror image does not revert the sign of the spin polarization, rather its direction in space. These findings might lead to the obtention of highly efficient spin filters for spintronic applications.

  1. Electron spin resonance studies on deuterated nitroxyl spin probes used in Overhauser-enhanced magnetic resonance imaging.

    PubMed

    David Jebaraj, D; Utsumi, Hideo; Milton Franklin Benial, A

    2017-01-04

    The electron spin resonance studies were carried out for 2 mm concentration of (14) N-labeled and (15) N-labeled 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl and their deuterated nitroxyl radicals using X-band electron spin resonance spectrometer. The electron spin resonance line shape analysis was carried out. The electron spin resonance parameters such as linewidth, Lorentzian component, signal intensity ratio, rotational correlation time, hyperfine coupling constant and g-factor were estimated. The deuterated nitroxyl radicals have narrow linewidth and an increase in Lorentzian component, compared with undeuterated nitroxyl radicals. The dynamic nuclear polarization factor was observed for all nitroxyl radicals. Upon (2) H labeling, about 70% and 40% increase in dynamic nuclear polarization factor were observed for (14) N-labeled and (15) N-labeled nitroxyl radicals, respectively. The signal intensity ratio and g-value indicate the isotropic nature of the nitroxyl radicals in pure water. Therefore, the deuterated nitroxyl radicals are suitable spin probes for in vivo/in vitro electron spin resonance and Overhauser-enhanced magnetic resonance imaging modalities. Copyright © 2017 John Wiley & Sons, Ltd.

  2. Spin-entanglement between two freely propagating electrons: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Vasilyev, D.; Schumann, F. O.; Giebels, F.; Gollisch, H.; Kirschner, J.; Feder, R.

    2017-03-01

    Theory predicts that electron pairs, which are emitted from a crystalline surface upon impact of spin-polarized low-energy electrons, can be spin-entangled. We quantify this entanglement by the von Neumann entropy, which we show to be closely related to the spin polarization of the emitted electrons. Measurement of the spin polarization therefore facilitates an experimental study of the entanglement. As target we used a Cu(111) surface, which exhibits an electronic surface state giving rise to a high pair emission intensity. Experimental spin polarization spectra for several orientations of the reaction plane broadly agree with their theoretical counterparts. They are consistent with spin entanglement of the electron pair at a macroscopic distance.

  3. Room Temperature Single-Spin Tunneling Force Microscopy for Characterization of Paramagnetic Defects in Electronic Materials

    DTIC Science & Technology

    2014-04-08

    atomic   scale  spatial  resolution,  using  tunneling   force   microscopy .  To achieve this goal, an electron must spontaneously shuttle back and...trap states imaged by Dynamic  Tunneling   Force   Microscopy  line  scans .  Previous evidence for trap states created by AFM probe tip voltage pulses involved...Payne, K. Ambal, C. Boehme and C.C. Williams, “A concept for room temperature single‐ spin  tunneling   force   microscopy  with  atomic  resolution,” to be

  4. Spin-dependent electron emission from metals in the neutralization of He{sup +} ions

    SciTech Connect

    Alducin, M.; Roesler, M.; Juaristi, J.I.

    2005-08-15

    We calculate the spin-polarization of electrons emitted in the neutralization of He{sup +} ions interacting with metals. All stages of the emission process are included: the spin-dependent perturbation induced by the projectile, the excitation of electrons in Auger neutralization processes, the creation of a cascade of secondaries, and the escape of the electrons through the surface potential barrier. The model allows us to explain in quantitative terms the measured spin-polarization of the yield in the interaction of spin-polarized He{sup +} ions with paramagnetic surfaces, and to disentangle the role played by each of the involved mechanisms. We show that electron-electron scattering processes at the surface determine the spin-polarization of the total yield. High energy emitted electrons are the ones providing direct information on the He{sup +} ion neutralization process and on the electronic properties of the surface.

  5. Spin Filtering in a Rashba Electron Waveguide Induced by Edge Disorder

    NASA Astrophysics Data System (ADS)

    Xiao, Xian-Bo; Li, Fei; Liu, Nian-Hua

    2012-08-01

    We theoretically study the spin-dependent electron transport in a Rashba electron waveguide with rough edges, attached to ideal leads without spin-orbit interaction. The influence of the edge disorder on the charge and spin conductances is clarified by using the spin-resolved lattice Green function method. It is found that a spin-polarized current can be generated in the output lead and its spin polarization can be manipulated by varying the waveguide length. The underlying physics is attributed to the broken longitudinal symmetry and the spin-dependent quantum interference induced by the rough boundaries. Our results may provide a new method to design a spin filter without using magnetic materials or applying a magnetic field.

  6. Thermal creation of electron spin polarization in n-type silicon

    SciTech Connect

    Dankert, André Dash, Saroj P.

    2013-12-09

    Conversion of heat into a spin-current in electron doped silicon can offer a promising path for spin-caloritronics. Here, we create an electron spin polarization in the conduction band of n-type silicon by producing a temperature gradient across a ferromagnetic tunnel contact. The substrate heating experiments induce a large spin signal of 95 μV, corresponding to 0.54 meV spin-splitting in the conduction band of n-type silicon by Seebeck spin tunneling mechanism. The thermal origin of the spin injection has been confirmed by the quadratic scaling of the spin signal with the Joule heating current and linear dependence with the heating power.

  7. Chirped pulse inverse free-electron laser vacuum accelerator

    DOEpatents

    Hartemann, Frederic V.; Baldis, Hector A.; Landahl, Eric C.

    2002-01-01

    A chirped pulse inverse free-electron laser (IFEL) vacuum accelerator for high gradient laser acceleration in vacuum. By the use of an ultrashort (femtosecond), ultrahigh intensity chirped laser pulse both the IFEL interaction bandwidth and accelerating gradient are increased, thus yielding large gains in a compact system. In addition, the IFEL resonance condition can be maintained throughout the interaction region by using a chirped drive laser wave. In addition, diffraction can be alleviated by taking advantage of the laser optical bandwidth with negative dispersion focusing optics to produce a chromatic line focus. The combination of these features results in a compact, efficient vacuum laser accelerator which finds many applications including high energy physics, compact table-top laser accelerator for medical imaging and therapy, material science, and basic physics.

  8. Strong electron spin-Hall effect by a coherent optical potential

    NASA Astrophysics Data System (ADS)

    Sherman, E. Ya; Muga, J. G.; Dugaev, V. K.; Ruschhaupt, A.

    2010-09-01

    We demonstrate theoretically that a coherent manipulation of electron spins in low-dimensional semiconductor structures with a spin-orbit coupling by infrared radiation is possible. The proposed approach is based on using a dipole force acting on a two-level system in a nonuniform optical field, similar to that employed in the design of the cold atoms diode. For ballistic electrons the spin-dependent force, proportional to the intensity of external radiation, leads to a spin-Hall effect and the resulting spin separation even if the spin-orbit coupling itself does not allow for these effects. Achievable spatial separation of electrons with opposite spins can be of the order of several tenths of a micron; an order of magnitude larger than that can be produced by the charged impurity scattering in the diffusive regime.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Electron spin resonance and electron-spin-echo study of oriented multilayers of L alpha-dipalmitoylphosphatidylcholine water systems.

    PubMed Central

    Kar, L; Ney-Igner, E; Freed, J H

    1985-01-01

    A detailed electron spin resonance (ESR) study of spin-labeled-oriented multilayers of L alpha-dipalmitoylphosphatidylcholine (DPPC) water systems for low water content (2-10% by weight) is reported with the purpose of characterizing the dynamical and structural properties of model membrane systems. Emphasis is placed on the value of combining such experiments with detailed simulations based on current slow-motional theories. Information is obtained regarding ordering and anisotropic rotational diffusion rates via ESR lineshape analysis over the entire motional range, from the fast motional region through the moderately slow and slow to the rigid limit. This includes the low-temperature gel phase, the liquid crystalline L alpha (1) phase and what appears to be a third high-temperature phase above the L alpha phase. Cholestane (CSL) and spin-labeled DPPC (5-PC, 8-PC, and 16-PC) have been used to probe different depths of the bilayer. While CSL and 5-PC both reflect the high ordering of the bilayer close to the lipid-water interface, CSL appears to be located close enough to the water for the nitroxide to be involved in hydrogen bonding with water molecules. 16-PC reflects the relatively low ordering near the tail of the hydrocarbon chain in the bilayer. Quantitative estimates of ordering and motion are obtained for these cases. The results from CSL indicate that close to the lipid-water interface the DPPC molecule is oriented approximately perpendicular to the bilayer in these low water-content systems. However, all three labeled lipid probes indicate that the hydrocarbon chain of DPPC may be bent away from the bilayer normal by as much as 30 degrees and this evidence is stronger at low temperatures. When cholesterol is added to the DPPC-water system at a concentration greater than or equal to 2.5 mol %, the ordering is greatly increased although the rotational diffusion rate remains almost unaffected in the gel phase. Electron spin echoes (ESE) are observed for the

  11. Strain dependent electron spin dynamics in bulk cubic GaN

    SciTech Connect

    Schaefer, A.; Buß, J. H.; Hägele, D.; Rudolph, J.; Schupp, T.; Zado, A.; As, D. J.

    2015-03-07

    The electron spin dynamics under variable uniaxial strain is investigated in bulk cubic GaN by time-resolved magneto-optical Kerr-rotation spectroscopy. Spin relaxation is found to be approximately independent of the applied strain, in complete agreement with estimates for Dyakonov-Perel spin relaxation. Our findings clearly exclude strain-induced relaxation as an effective mechanism for spin relaxation in cubic GaN.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Scanning SQUID microscopy with single electron spin sensitivity

    NASA Astrophysics Data System (ADS)

    Vasyukov, Denis

    2014-03-01

    Superconducting interference devices (SQUIDs) have been traditionally used for studying fundamental properties of magnetic materials and superconductors. Although widely used in scanning magnetic microscopy, their progress towards detection of small magnetic moments was stagnating of late due to limitations imposed by conventional designs of planar SQUIDs and contemporary lithography techniques, restricting sample-to-sensor distance smaller than ~ 0.5 micron and SQUIDs diameters smaller than ~ 200 nm. These limitations were overcome by the invention of a SQUID-on-tip device, subsequent realization of a SQUID-on-tip microscope, and by creation of an ultra-small sensor with spatial resolution of 20 nm and sensitivity to a single electron spin per 1 Hz bandwidth. In this talk I will describe the principles of scanning SQUID magnetometry, its applications to study superconductors and its potential for magnetic nano-scale imaging of novel materials.

  14. Clinical applications of alanine/electron spin resonance dosimetry.

    PubMed

    Baffa, Oswaldo; Kinoshita, Angela

    2014-05-01

    This paper discusses the clinical applications of electron spin resonance (ESR) dosimetry focusing on the ESR/alanine system. A review of few past studies in this area is presented offering a critical overview of the challenges and opportunities for extending this system into clinical applications. Alanine/ESR dosimetry fulfills many of the required properties for several clinical applications such as water-equivalent composition, independence of the sensitivity for the energy range used in therapy and high precision. Improvements in sensitivity and the development of minidosimeters coupled with the use of a spectrometer of higher microwave frequency expanded the possibilities for clinical applications to the new modalities of radiotherapy (intensity-modulated radiation therapy and radiosurgery) and to the detection of low doses such as those present in some radiological image procedures.

  15. Electronics for the pulsed rubidium clock: design and characterization.

    PubMed

    Calosso, Claudio E; Micalizio, Salvatore; Godone, Aldo; Bertacco, Elio K; Levi, Filippo

    2007-09-01

    Pulsing the different operation phases of a vapor-cell clock (optical pumping, interrogation, and detection) has been recognized as one of the most effective techniques to reduce light shift and then to improve the stability perspectives of vapor cell clocks. However, in order to take full advantage of the pulsed scheme, a fast-gated electronics is required, the times involved being of the order of milliseconds. In this paper we describe the design and the implementation of the electronics that synchronizes the different phases of the clock operation, as well as of the electronics that is mainly devoted to the thermal stabilization of the clock physics package. We also report some characterization measurements, including a measurement of the clock frequency stability. In particular, in terms of Allan deviation, we measured a frequency stability of 1.2 x 10(-12) tao(-1/2) for averaging times up to tao = 10(5) s, a very interesting result by itself and also for a possible space application of such a clock.

  16. Electronic Transitions and Spin-Orbit Splitting of Lanthanum Dimer

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wu, Lu; Zhang, Changhua; Yang, Dong-Sheng

    2011-06-01

    Lanthanum dimer (La_2) was studied by mass-analyzed threshold ionization (MATI) spectroscopy and a series of high-level multi-configuration ab initio calculations (CASSCF, CASPT2, and MRCI). The MATI spectrum exhibits three band systems originating at 39044, 40312, and 40862 Cm-1, respectively. Above the band origin, the first band system displays a vibrational progression of ˜232 Cm-1, and the other two show vibrational progression with the same interval of ˜240 Cm-1. Below the band origin, the three systems exhibit the same vibrational interval of ˜207 Cm-1. These band systems are assigned to three electronic transitions from the ground state of La_2 to the low-lying electronic states of La_2^+: ^2Σ^+_g ← ^1Σ^+_g, ^2Πu,1/2 ← ^1Σ^+_g, and ^2Πu,3/2 ← ^1Σ^+_g. The spin-orbit splitting in the ^2ΠU ion state is 550 Cm-1. In addition, the electronic states and bonding of La_2 will be compared with those of Sc_2 and Y_2.

  17. Optimal pulse spacing for dynamical decoupling in the presence of a purely dephasing spin bath

    SciTech Connect

    Ajoy, Ashok; Alvarez, Gonzalo A.; Suter, Dieter

    2011-03-15

    Maintaining quantum coherence is a crucial requirement for quantum computation; hence protecting quantum systems against their irreversible corruption due to environmental noise is an important open problem. Dynamical decoupling (DD) is an effective method for reducing decoherence with a low control overhead. It also plays an important role in quantum metrology, where, for instance, it is employed in multiparameter estimation. While a sequence of equidistant control pulses [the Carr-Purcell-Meiboom-Gill (CPMG) sequence] has been ubiquitously used for decoupling, Uhrig recently proposed that a nonequidistant pulse sequence [the Uhrig dynamic decoupling (UDD) sequence] may enhance DD performance, especially for systems where the spectral density of the environment has a sharp frequency cutoff. On the other hand, equidistant sequences outperform UDD for soft cutoffs. The relative advantage provided by UDD for intermediate regimes is not clear. In this paper, we analyze the relative DD performance in this regime experimentally, using solid-state nuclear magnetic resonance. Our system qubits are {sup 13}C nuclear spins and the environment consists of a {sup 1}H nuclear spin bath whose spectral density is close to a normal (Gaussian) distribution. We find that in the presence of such a bath, the CPMG sequence outperforms the UDD sequence. An analogy between dynamical decoupling and interference effects in optics provides an intuitive explanation as to why the CPMG sequence performs better than any nonequidistant DD sequence in the presence of this kind of environmental noise.

  18. Optimal pulse spacing for dynamical decoupling in the presence of a purely dephasing spin bath

    NASA Astrophysics Data System (ADS)

    Ajoy, Ashok; Álvarez, Gonzalo A.; Suter, Dieter

    2011-03-01

    Maintaining quantum coherence is a crucial requirement for quantum computation; hence protecting quantum systems against their irreversible corruption due to environmental noise is an important open problem. Dynamical decoupling (DD) is an effective method for reducing decoherence with a low control overhead. It also plays an important role in quantum metrology, where, for instance, it is employed in multiparameter estimation. While a sequence of equidistant control pulses [the Carr-Purcell-Meiboom-Gill (CPMG) sequence] has been ubiquitously used for decoupling, Uhrig recently proposed that a nonequidistant pulse sequence [the Uhrig dynamic decoupling (UDD) sequence] may enhance DD performance, especially for systems where the spectral density of the environment has a sharp frequency cutoff. On the other hand, equidistant sequences outperform UDD for soft cutoffs. The relative advantage provided by UDD for intermediate regimes is not clear. In this paper, we analyze the relative DD performance in this regime experimentally, using solid-state nuclear magnetic resonance. Our system qubits are C13 nuclear spins and the environment consists of a H1 nuclear spin bath whose spectral density is close to a normal (Gaussian) distribution. We find that in the presence of such a bath, the CPMG sequence outperforms the UDD sequence. An analogy between dynamical decoupling and interference effects in optics provides an intuitive explanation as to why the CPMG sequence performs better than any nonequidistant DD sequence in the presence of this kind of environmental noise.

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

    PubMed

    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.

  20. Synthesis, electronic, photoacoustic and electron spin resonance investigations on some tetrathiocyanate binuclear mixed-metal complexes

    NASA Astrophysics Data System (ADS)

    Singh, Raghuvir

    Complexes of the type M 1M 2(SCN) 4xL[M 1 = Ni(II); M 2 = Cd(II) and Hg(II) and L = pyridine, morpholine, dioxan, benzo(f)quinoline, 2,2'-bipyridine, 2,2'-bipyridine N, N'-dioxide, isonicotinic acid hydrazide and 1,10-phenanthroline: x = 2 or 4] have been synthesized and characterized by chemical analysis, magnetic susceptibility, infrared, electronic and photoacoustic (PAS) spectra as well as electron spin resonance (ESR) spectral studies in the solid and solution state. The different coordination sites have been investigated in these ligands towards metal coordination and the behaviour of thiocyanate anions studied. Electron spin resonance spectral data for copper complexes show the distorted octahedral stereochemistry around copper(II) in these complexes. The parameters such as g∥, g⊥, A∥, A⊥, < g>, < A> and α 2 calculated for the copper complexes from their ESR spectra indicate the presence of unpaired electron in d x2- y2 or d z2 orbitals. The photoacoustic and electronic spectra of these complexes were studied in the solid state to see the nature of thiocyanate and overall symmetry of the complexes. The results on electronic and photoacoustic spectral studies are in good agreement with ESR data.

  1. Manipulation of a single electron spin in a quantum dot without magnetic field

    NASA Astrophysics Data System (ADS)

    Bednarek, S.; Pawłowski, J.; Skubis, A.

    2012-05-01

    In this paper, we propose the construction of a nanodevice performing the spin rotations of an electron confined in an electrostatic quantum dot without the use of a magnetic field. Sinusoidally varying voltage applied in different phases to four gates causes the electron to move along a two-dimensional closed path. The spin-orbit interaction that is present in the structure induces spin rotations. For a properly adjusted AC signal duration, the logical NOT operation or the Hadamard quantum gate can be performed on the electron spin. We perform a simulation of the nanodevice's time evolution.

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

    PubMed

    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.

  3. Behavior Genetics and the Within-Person Variability of Daily Interpersonal Styles: The Heritability of Flux, Spin and Pulse.

    PubMed

    Markey, Patrick M; Racine, Sarah E; Markey, Charlotte N; Hopwood, Christopher J; Keel, Pamela K; Burt, S Alexandra; Neale, Michael C; Sisk, Cheryl L; Boker, Steven M; Klump, Kelly L

    2014-04-01

    A classical twin study was used to estimate the magnitude of genetic and environmental influences on four measurements of within-person variability: dominance flux, warmth flux, spin and pulse. Flux refers to the variability of an individual's interpersonal dominance and warmth. Spin measures changes in the tone of interpersonal styles and pulse measures changes in the intensity of interpersonal styles. Daily reports of interpersonal styles were collected from 494 same-sex female twins (142 monozygotic pairs and 105 dizygotic pairs) over 45 days. For dominance flux, warmth flux, and spin, genetic effects accounted for a larger proportion of variance (37%, 24%, and 30%, respectively) than shared environmental effects (14%, 13%, 0%, respectively), with the remaining variance due to the non-shared environment (62%, 50%, 70% respectively). Pulse appeared to be primarily influenced by the non-shared environment, although conclusions about the contribution of familial influences were difficult to draw from this study.

  4. Teleportation of electronic many-qubit states encoded in the electron spin of quantum dots via single photons.

    PubMed

    Leuenberger, Michael N; Flatté, Michael E; Awschalom, D D

    2005-03-18

    We propose a teleportation scheme that relies only on single-photon measurements and Faraday rotation, for teleportation of many-qubit entangled states stored in the electron spins of a quantum dot system. The interaction between a photon and the two electron spins, via Faraday rotation in microcavities, establishes Greenberger-Horne-Zeilinger entanglement in the spin-photon-spin system. The appropriate single-qubit measurements, and the communication of two classical bits, produce teleportation. This scheme provides the essential link between spintronic and photonic quantum information devices by permitting quantum information to be exchanged between them.

  5. Universal set of single-qubit gates based on geometric phase of electron spin in a quantum dot

    NASA Astrophysics Data System (ADS)

    Malinovsky, Vladimir; Rudin, Sergey

    2012-02-01

    The electron spin in a single quantum dot is one of the perspective realizations of a qubit for the implementation of a quantum computer. During last decade several control schemes to perform single gate operations on a single quantum dot spin have been reported. We propose a scheme that allows performing ultrafast arbitrary unitary operations on a single qubit. We demonstrate how to use the geometric phase, which the Bloch vector gains along the cyclic path, to prepare an arbitrary state of a single qubit. It is shown that, the geometrical phase is fully controllable by the relative phase between the external fields. Using the analytic expression of the evolution operator for the electron spin in a quantum dot, we propose a scheme to design a universal set of single-qubit gates based solely 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.

  6. Electron spin polarization by isospin ordering in correlated two-layer quantum Hall systems.

    PubMed

    Tiemann, L; Wegscheider, W; Hauser, M

    2015-05-01

    Enhancement of the electron spin polarization in a correlated two-layer, two-dimensional electron system at a total Landau level filling factor of 1 is reported. Using resistively detected nuclear magnetic resonance, we demonstrate that the electron spin polarization of two closely spaced two-dimensional electron systems becomes maximized when interlayer Coulomb correlations establish spontaneous isospin ferromagnetic order. This correlation-driven polarization dominates over the spin polarizations of competing single-layer fractional quantum Hall states under electron density imbalances.

  7. Determination of nitrogen spin concentration in diamond using double electron-electron resonance

    NASA Astrophysics Data System (ADS)

    Stepanov, Viktor; Takahashi, Susumu

    2016-07-01

    Diamond has been extensively investigated recently due to a wide range of potential applications of nitrogen-vacancy (NV) defect centers existing in a diamond lattice. The applications include magnetometry and quantum information technologies, and long decoherence time (T2) of NV centers is critical for those applications. Although it has been known that T2 highly depends on the concentration of paramagnetic impurities in diamond, precise measurement of the impurity concentration remains challenging. In the present work we show a method to determine a wide range of the nitrogen concentration (n ) in diamond using a wide-band high-frequency electron spin resonance and double electron-electron resonance spectrometer. Moreover, we investigate T2 of the nitrogen impurities and show the relationship between T2 and n . The method developed here is applicable for various spin systems in solid and implementable in nanoscale magnetic resonance spectroscopy with NV centers to characterize the concentration of the paramagnetic spins within a microscopic volume.

  8. Reflection of attosecond x-ray free electron laser pulses

    SciTech Connect

    Hau-Riege, S; Chapman, H

    2006-10-30

    In order to utilize hard x-ray free electron lasers (XFEL's) when they are extended to attosecond pulse lengths, it is necessary to choose optical elements with minimal response time. Specular grazing incidence optics made of low-Z materials are popular candidates for reflectors since they are likely to withstand x-ray damage and provide sufficiently large reflectivities. Using linear-optics reflection theory, we calculated the transient reflectivity of a delta-function electric pulse from a homogeneous semi-infinite medium as a function of angle of incidence for s- and p-polarized light. We specifically considered the pulse response of Be, diamond, silicon carbide, and silicon, all of which are of relevance to the XFEL's that are currently being built. We found that the media emit energy in a damped oscillatory way, and that the impulse-response times are shorter than 0.3 fs for normal incidence. For grazing incidence, the impulse-response time is substantially shorter, making grazing-incidence mirrors a good choice for deep-sub-femtosecond reflective optics.

  9. Reflection of attosecond x-ray free electron laser pulses

    SciTech Connect

    Hau-Riege, Stefan P.; Chapman, Henry N.

    2007-01-15

    In order to utilize hard x-ray free electron lasers (XFEL's) when they are extended to attosecond pulse lengths, it is necessary to choose optical elements with minimal response time. Specular grazing-incidence optics made of low-Z materials are popular candidates for reflectors since they are likely to withstand x-ray damage and provide sufficiently large reflectivities. Using linear-optics reflection theory, we calculated the transient reflectivity of a delta-function electric pulse from a homogenous semi-infinite medium as a function of angle of incidence for s- and p-polarized light. We specifically considered the pulse response of beryllium, diamond, silicon carbide, and silicon, all of which are of relevance to the XFEL's that are currently being built. We found that the media emit energy in a damped oscillatory way, and that the impulse-response times are shorter than 0.3 fs for normal incidence. For grazing incidence, the impulse-response time is substantially shorter, making grazing-incidence mirrors a good choice for deep subfemtosecond reflective optics.

  10. Design and commissioning of an aberration-corrected ultrafast spin-polarized low energy electron microscope with multiple electron sources.

    PubMed

    Wan, Weishi; Yu, Lei; Zhu, Lin; Yang, Xiaodong; Wei, Zheng; Liu, Jefferson Zhe; Feng, Jun; Kunze, Kai; Schaff, Oliver; Tromp, Ruud; Tang, Wen-Xin

    2016-12-27

    We describe the design and commissioning of a novel aberration-corrected low energy electron microscope (AC-LEEM). A third magnetic prism array (MPA) is added to the standard AC-LEEM with two prism arrays, allowing the incorporation of an ultrafast spin-polarized electron source alongside the standard cold field emission electron source, without degrading spatial resolution. The high degree of symmetries of the AC-LEEM are utilized while we design the electron optics of the ultrafast spin-polarized electron source, so as to minimize the deleterious effect of time broadening, while maintaining full control of electron spin. A spatial resolution of 2nm and temporal resolution of 10ps (ps) are expected in the future time resolved aberration-corrected spin-polarized LEEM (TR-AC-SPLEEM). The commissioning of the three-prism AC-LEEM has been successfully finished with the cold field emission source, with a spatial resolution below 2nm.

  11. Time-resolved electron density and electron temperature measurements in nanosecond pulse discharges in helium

    NASA Astrophysics Data System (ADS)

    Roettgen, A.; Shkurenkov, I.; Simeni Simeni, M.; Petrishchev, V.; Adamovich, I. V.; Lempert, W. R.

    2016-10-01

    Thomson scattering is used to study temporal evolution of electron density and electron temperature in nanosecond pulse discharges in helium sustained in two different configurations, (i) diffuse filament discharge between two spherical electrodes, and (ii) surface discharge over plane quartz surface. In the diffuse filament discharge, the experimental results are compared with the predictions of a 2D plasma fluid model. Electron densities are put on an absolute scale using pure rotational Raman spectra in nitrogen, taken without the plasma, for calibration. In the diffuse filament discharge, electron density and electron temperature increase rapidly after breakdown, peaking at n e  ≈  3.5 · 1015 cm-3 and T e  ≈  4.0 eV. After the primary discharge pulse, both electron density and electron temperature decrease (to n e ~ 1014 cm-3 over ~1 µs and to T e ~ 0.5 eV over ~200 ns), with a brief transient rise produced by the secondary discharge pulse. At the present conditions, the dominant recombination mechanism is dissociative recombination of electrons with molecular ions, \\text{He}2+ . In the afterglow, the electron temperature does not relax to gas temperature, due to superelastic collisions. Electron energy distribution functions (EEDFs) inferred from the Thomson scattering spectra are nearly Maxwellian, which is expected at high ionization fractions, when the shape of EEDF is controlled primarily by electron-electron collisions. The kinetic model predictions agree well with the temporal trends detected in the experiment, although peak electron temperature and electron density are overpredicted. Heavy species temperature predicted during the discharge and the early afterglow remains low and does not exceed T  =  400 K, due to relatively slow quenching of metastable He* atoms in two-body and three-body processes. In the surface discharge, peak electron density and electron temperature are n e  ≈  3 · 1014 cm3 and T e

  12. 1H relaxation dispersion in solutions of nitroxide radicals: influence of electron spin relaxation.

    PubMed

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

    2013-03-28

    The work presents a theory of nuclear ((1)H) spin-lattice relaxation dispersion for solutions of (15)N and (14)N 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)]. 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 (1)H 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 (1)H relaxation by contributing to the fluctuations of the inter-molecular dipolar interactions. The developed theory is tested against (1)H spin-lattice relaxation dispersion data for glycerol solutions of 4-oxo-TEMPO-d16-(15)N and 4-oxo-TEMPO-d16-(14)N 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 (14)N and (15)N systems and explains the features of (1)H relaxation dispersion resulting from the electron spin relaxation.

  13. 1H relaxation dispersion in solutions of nitroxide radicals: Influence of electron spin relaxation

    NASA Astrophysics Data System (ADS)

    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.

  14. Quasimonoenergic collimated electrons from the ionization of nitrogen by a chirped intense laser pulse

    SciTech Connect

    Singh, Kunwar Pal; Sajal, Vivek

    2009-04-15

    A scheme is proposed for quasimonoenergic collimated GeV electrons generated during ionization of nitrogen by a chirped intense laser pulse. The electrons accelerated by a laser pulse without a frequency chirp are known for poor-quality beams. If a suitable frequency chirp is introduced, then the energy of the electrons increases significantly. It is shown that quasimonoenergic collimated GeV electrons can be produced using a right choice of laser spot size, frequency chirp, and pulse duration.

  15. Effects of spin diffusion on electron spin relaxation time measured with a time-resolved microscopic photoluminescence technique

    SciTech Connect

    Ikeda, Kazuhiro Kawaguchi, Hitoshi

    2015-02-07

    We performed measurements at room temperature for a GaAs/AlGaAs multiple quantum well grown on GaAs(110) using a time-resolved microscopic photoluminescence (micro-PL) technique to find what effects spin diffusion had on the measured electron spin relaxation time, τ{sub s}, and developed a method of estimating the spin diffusion coefficient, D{sub s}, using the measured data and the coupled drift-diffusion equations for spin polarized electrons. The spatial nonuniformities of τ{sub s} and the initial degree of electron spin polarization caused by the pump intensity distribution inside the focal spot were taken into account to explain the dependence of τ{sub s} on the measured spot size, i.e., a longer τ{sub s} for a smaller spot size. We estimated D{sub s} as ∼100 cm{sup 2}/s, which is similar to a value reported in the literature. We also provided a qualitative understanding on how spin diffusion lengthens τ{sub s} in micro-PL measurements.

  16. Measurement of vascular water transport in human subjects using time-resolved pulsed arterial spin labelling.

    PubMed

    Bibic, Adnan; Knutsson, Linda; Schmidt, Anders; Henningsson, Erik; Månsson, Sven; Abul-Kasim, Kasim; Åkeson, Jonas; Gunther, Matthias; Ståhlberg, Freddy; Wirestam, Ronnie

    2015-08-01

    Most approaches to arterial spin labelling (ASL) data analysis aim to provide a quantitative measure of the cerebral blood flow (CBF). This study, however, focuses on the measurement of the transfer time of blood water through the capillaries to the parenchyma (referred to as the capillary transfer time, CTT) as an alternative parameter to characterise the haemodynamics of the system. The method employed is based on a non-compartmental model, and no measurements need to be added to a common time-resolved ASL experiment. Brownian motion of labelled spins in a potential was described by a one-dimensional general Langevin equation as the starting point, and as a Fokker-Planck differential equation for the averaged distribution of labelled spins at the end point, which takes into account the effects of flow and dispersion of labelled water by the pseudorandom nature of the microvasculature and the transcapillary permeability. Multi-inversion time (multi-TI) ASL data were acquired in 14 healthy subjects on two occasions in a test-retest design, using a pulsed ASL sequence and three-dimensional gradient and spin echo (3D-GRASE) readout. Based on an error analysis to predict the size of a region of interest (ROI) required to obtain reasonably precise parameter estimates, data were analysed in two relatively large ROIs, i.e. the occipital lobe (OC) and the insular cortex (IC). The average values of CTT in OC were 260 ± 60 ms in the first experiment and 270 ± 60 ms in the second experiment. The corresponding IC values were 460 ± 130 ms and 420 ± 139 ms, respectively. Information related to the water transfer time may be important for diagnostics and follow-up of cerebral conditions or diseases characterised by a disrupted blood-brain barrier or disturbed capillary blood flow.

  17. Detection of spin-resolved electronic structures from a buried ferromagnetic layer utilizing forward Mott scattering

    SciTech Connect

    Ueda, S.; Mizuguchi, M.; Kojima, T.; Takanashi, K.; Ishimaru, S.; Tsujikawa, M.; Shirai, M.

    2014-03-31

    We report ultrahigh-resolution spin-resolved hard X-ray photoemission (HAXPES) for a buried FeNi alloy film. By utilizing the forward Mott scattering in a Au layer on FeNi, our spin-resolved HAXPES method does not require a standard spin detector and allows us to use the multi-channel electron detection system for the high-efficient electron detection as used in conventional photoemission spectroscopy. A combination of the forward Mott scattering and multi-channel detection leads us to measure a clear spin polarization as well as spin-resolved majority and minority states in the Fe 2p core-level spectra without using the standard spin detector. This method enables us to measure spin-resolved core-level spectra for buried ferromagnetic materials.

  18. Effect of Rashba and Dresselhaus Spin-Orbit Couplings on Electron Spin Polarization in a Hybrid Magnetic-Electric Barrier Nanostructure

    NASA Astrophysics Data System (ADS)

    Yang, Shi-Peng; Lu, Mao-Wang; Huang, Xin-Hong; Tang, Qiang; Zhou, Yong-Long

    2017-04-01

    A theoretical study has been carried out on the spin-dependent electron transport in a hybrid magnetic-electric barrier nanostructure with both Rashba and Dresselhaus spin-orbit couplings, which can be experimentally realized by depositing a ferromagnetic strip and a Schottky metal strip on top of a semiconductor heterostructure. The spin-orbit coupling-dependent transmission coefficient, conductance, and spin polarization are calculated by solving the Schrödinger equation exactly with the help of the transfer-matrix method. We find that both the magnitude and sign of the electron spin polarization vary strongly with the spin-orbit coupling strength. Thus, the degree of electron spin polarization can be manipulated by properly adjusting the spin-orbit coupling strength, and such a nanosystem can be employed as a controllable spin filter for spintronics applications.

  19. Electron spin resonance spectral analysis of irradiated royal jelly.

    PubMed

    Yamaoki, Rumi; Kimura, Shojiro; Ohta, Masatoshi

    2014-01-15

    The analysis of unpaired electron components in royal jelly was carried out using electron spin resonance (ESR) with the aim to develop a detection method for irradiated royal jelly. The ESR spectrum of royal jelly had natural signals derived from transition metals, including Fe(3+) and Cu(2+), and a signal line near g=2.00. After irradiation, a new splitting asymmetric spectrum with overall spectrum width ca. 10mT at g=2.004 was observed. The intensities of the signals at g=2.004 increased in proportion to the absorbed dose in samples under different storage conditions: fresh frozen royal jelly and dried royal jelly powder at room temperature. The signal intensity of the fresh frozen sample was stable after irradiation. One year after 10kGy irradiation of dried powder, the signal intensity was sevenfold greater than before irradiation, although the intensity continued to steadily decrease with time. This stable radiation-induced radical component was derived from the poorly soluble constituent of royal jelly.

  20. Pulse radiolysis of alkanes: A time-resolved electron paramagnetic resonance study

    SciTech Connect

    Shkrob, I.A.; Trifunac, A.D.

    1994-02-14

    Time-resolved spin-echo-detected electron paramagnetic resonance (EPR) was applied to examine short-lived alkyl radicals formed in pulse radiolysis of liquid alkanes. It was found that the ratio of yields of penultimate and interior radicals in n-alkanes at the instant of their generation is temperature-independent and is ca. 1.25 times greater than the statistical quantity. This higher-than-statistical production of penultimate radicals indicates that the fast ion molecule reactions involving radical cations are a significant route of radical generation. The analysis of spin-echo kinetics in n-alkanes suggests that the alkyl radicals are emissively polarized in spur reactions. this initial polarization rapidly increases with shortening of the aliphatic chain. Another finding is that a long-chain structure of these radicals results in much higher rate of Heisenberg spin exchange relative to the recombination rate. The relative yields of hydrogen abstraction and fragmentation for various branched alkanes are estimated. It is concluded that the fragmentation occurs prior to the formation of radicals in an excited precursor species. Effects of phenolic and alkene additives in radiolysis of n-alkanes are examined. It is demonstrated that phenoxy radicals are produced in dissociative capture of electrons and alkane holes. Another route is a reaction of phenols with free hydrogen atoms. A rapid transfer of singlet correlation from the geminate radical ion pairs is responsible for unusual polarization patterns in the phenoxy and cyclohexadienyl radicals. The significance of these results in the context of cross-linking in polyethylene and higher paraffins is discussed. 56 refs.

  1. Room-Temperature Electron Spin Relaxation of Triarylmethyl Radicals at X- and Q-bands

    PubMed Central

    Krumkacheva, Olesya A.; Strizhakov, Rodion K.; Rogozhnikova, Olga Yu.; Troitskaya, Tatiana I.

    2016-01-01

    Triarylmethyl radicals (trityls, TAMs) represent a relatively new class of spin labels. The long relaxation of trityls at room temperature in liquid solutions makes them a promising alternative for traditional nitroxides. In this work we have synthesized a series of TAMs including perdeuterated Finland trityl (D36 form) , mono-, di-, and tri-ester derivatives of Finland-D36 trityl, deuterated form of OX63, dodeca-n-butyl homologue of Finland trityl, and triamide derivatives of Finland trityl with primary and secondary amines attached. We have studied room-temperature relaxation properties of these TAMs in liquids using pulsed Electron Paramagnetic Resonance (EPR) at two microwave frequency bands. We have found the clear dependence of phase memory time (Tm~T2) on magnetic field: room-temperature Tm values are ~1.5-2.5 times smaller at Q-band (34 GHz, 1.2 T) compared to X-band (9 GHz, 0.3 T). This trend is ascribed to the contribution from g-anisotropy that is negligible at lower magnetic fields but comes into play at Q-band. In agreement with this, while T1~Tm at X-band, we observe T1>Tm at Q-band due to increased contributions from incomplete motional averaging of g-anisotropy. In addition, the viscosity dependence shows that (1/Tm-1/T1) is proportional to the tumbling correlation time of trityls. Based on the analysis of previous data and results of the present work, we conclude that in general situation where spin label is at least partly mobile, X-band is most suitable for application of trityls for room-temperature pulsed EPR distance measurements. PMID:26001103

  2. University of Utah four-channel pulse-to-pulse commutated SUPER-LOKI rocket meteorological parachutesonde (electronics)

    NASA Technical Reports Server (NTRS)

    Atwood, K. W.; Soss, D. A.

    1976-01-01

    The electronics and temperature sensing units of the pulse-to-pulse rocketsonde are described. The sonde is designed for the 2 1/8-inch dart of the SUPER-LOKI meteorological rocket. In flight, the sonde descends by parachute from rocket apogees of about 75 kilometers. As the sonde descends, it transmits air temperature data back to ground radio receiving stations.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Ab-initio calculation of electron-phonon coupling for spin relaxation in metals.

    NASA Astrophysics Data System (ADS)

    Pruneda, Miguel; Souza, Ivo

    2007-03-01

    Spin-electronic devices have motivated an important effort in understanding the mechanisms for spin-relaxation, because the operation of such devices requires long spin-diffusion lenghts. Two main factors contribute to spin relaxation: (i) spin-orbit interaction, which mixes the spin-up and spin-down components of the electronic wavefunction, and (ii) electron scattering from defects or phonons. In metals, the phonon-mediated Elliot-Yafet mechanism is believed to be dominant. Realistic calculations are computationally demanding, requiring an accurate description of the electronic states near the Fermi surface and their coupling to the lattice (phonons). Here we use a Density Functional Perturbation Theory implementation to calculate from first-principles the electron-phonon interaction in systems with spin-orbit coupling. Combined with recently-developed Wannier-interpolation methods for sampling efficiently the Brillouin zone, this will allow for a fully ab-initio calculation of the spin relaxation in metals. J. Fabian and S. Das Sarma, Phys. Rev. Lett. 83, 1211 (1999).

  5. Scattering of spin-polarized electron in an Aharonov-Bohm potential

    SciTech Connect

    Khalilov, V.R.; Ho, C.-L.

    2008-05-15

    The scattering of spin-polarized electrons in an Aharonov-Bohm vector potential is considered. We solve the Pauli equation in 3 + 1 dimensions taking into account explicitly the interaction between the three-dimensional spin magnetic moment of electron and magnetic field. Expressions for the scattering amplitude and the cross section are obtained for spin-polarized electron scattered off a flux tube of small radius. It is also shown that bound electron states cannot occur in this quantum system. The scattering problem for the model of a flux tube of zero radius in the Born approximation is briefly discussed.

  6. Electron spin resonance from NV centers in diamonds levitating in an ion trap

    NASA Astrophysics Data System (ADS)

    Delord, T.; Nicolas, L.; Schwab, L.; Hétet, G.

    2017-03-01

    We report observations of the electron spin resonance (ESR) of nitrogen vacancy centers in diamonds that are levitating in an ion trap. Using a needle Paul trap operating under ambient conditions, we demonstrate efficient microwave driving of the electronic spin and show that the spin properties of deposited diamond particles measured by the ESR are retained in the Paul trap. We also exploit the ESR signal to show angle stability of single trapped mono-crystals, a necessary step towards spin-controlled levitating macroscopic objects.

  7. Electronic and spin structures of solids investigated by means of synchrotron radiation photoemission

    NASA Astrophysics Data System (ADS)

    Taniguchi, M.; Iwasawa, H.; Miyamoto, K.; Okuda, T.

    2013-12-01

    Recent progress in research on electronic and spin structures of solids and instrumentation on spin-resolved photoemission at Hiroshima Synchrotron Radiation Center are reported. The fine details of electron dynamics of a typical multiband superconductor Sr2RuO4 were uncovered by high-resolution angle-resolved photoemission spectroscopy (ARPES) with tunable polarizations, and the surface of W(1 1 0) was found to have a Dirac-corn-like state of d character with nearly massless energy dispersion by high-resolution ARPES and spin-resolved ARPES (SARPES). The SARPES system with very low energy electron diffraction spin detector and modified VG-SCIENTA R4000 electron analyzer brought a breakthrough in spin detection efficiency as well as energy and angular resolution, and enables precise SARPES measurements for materials that require high energy and angular resolution.

  8. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Controllable Spin Polarization of Charge Current by Rashba Spin Orbital Coupling

    NASA Astrophysics Data System (ADS)

    Cui, Juan; Yang, Yong-Hong; Wang, Jun

    2009-11-01

    We report a theoretic study on modulating the spin polarization of charge current in a mesoscopic four-terminal device of cross structure by using the inverse spin hall effect. The scattering region of device is a two-dimensional electron gas (2DEG) with Rashba spin orbital interaction (RSOI), one of lead is ferromagnetic metal and other three leads are spin-degenerate normal metals. By using Landauer-Büttiker formalism, we found that when a longitudinal charge current flows through 2DEG scattering region from FM lead by external bias, the transverse current can be either a pure spin current or full-polarized charge current due to the combined effect of spin hall effect and its inverse process, and the polarization of this transverse current can be easily controlled by several device parameters such as the Fermi energy, ferromagnetic magnetization, and the RSOI constant. Our method may pave a new way to control the spin polarization of a charge current.

  9. Multifrequency resonances in multiple-pulse NMR on a spin-1/2 system

    SciTech Connect

    Furman, G.B.; Goren, S.D.; Meerovich, V.M.; Sokolovsky, V.L.; Kibrik, G.E.; Polyakov, A.Yu.

    2003-12-01

    We have observed multifrequency resonances in a system with a spin 1/2 located in dc magnetic field and irradiated simultaneously by a multiple-pulse radio frequency sequence and a low-frequency field swept in the range 0-80 kHz. The used excitation scheme allowed us to measure the effective field of the radio frequency sequence. A peculiarity of this scheme is that the intensity of the resonance lines decreases slowly with the mode number. The theoretical description of the effect is presented using both the rotating frame approximation and the Floquet theory. Both approaches give identical results at the calculation of the resonance frequencies, transition probabilities, and shifts of resonance frequency. The calculated magnetization vs the frequency of the low-frequency field agrees well with the obtained experimental data. The multifrequency spectra give a way for studying slow atomic motion in solids.

  10. DrSPINE - New approach to data reduction and analysis for neutron spin echo experiments from pulsed and reactor sources

    SciTech Connect

    Monkenbusch, Michael; Holderer, Olaf; Ohl, Michael

    2015-01-01

    Neutron spin echo (NSE) method at a pulsed neutron source presents new challenges to the data reduction and analysis as compared to the instruments installed at reactor sources. The main advantage of the pulsed source NSE is the ability to resolve the neutron wavelength and collect neutrons over a wider bandwidth. This allows us to more precisely determine the symmetry phase and measure the data for several Q-values at the same time. Based on the experience gained at the SNS NSE - the first, and to date the only one, NSE instrument installed at a pulsed spallation source, we propose a novel and unified approach to the NSE data processing.

  11. Measurement of electron spin-lattice relaxation times in radical doped butanol samples at 1 K using the NEDOR method

    NASA Astrophysics Data System (ADS)

    Hess, C.; Herick, J.; Berlin, A.; Meyer, W.; Reicherz, G.

    2012-12-01

    The electron spin-lattice relaxation time (T1e) of TEMPO- and trityl-doped butanol samples at 2.5 T and temperatures between 0.95 K and 2.17 K was studied by pulsed nuclear magnetic resonance (NMR) using the nuclear-electron double resonance (NEDOR) method. This method is based on the idea to measure the NMR lineshift produced by the local field of paramagnetic impurities, whose polarization can be manipulated. This is of technical advantage as measurements can be performed under conditions typically used for the dynamic nuclear polarization (DNP) process - in our case 2.5 T and temperatures around 1 K - where a direct measurement on the electronic spins would be far more complicated to perform. As T1e is a crucial parameter determining the overall efficiency of DNP, the effect of the radical type, its spin concentration, the temperature and the oxygen content on T1e has been investigated. For radical concentrations as used in DNP (several 1019 spins/cm3) the relaxation rate (T1e-1) has shown a linear dependence on the paramagnetic electron concentration for both radicals investigated. Experiments with perdeuterated and ordinary butanol have given no indication for any influence of the host materials isotopes. The measured temperature dependence has shown an exponential characteristic. It is further observed that the oxygen content in the butanol samples has a considerable effect on the electron relaxation time and thus influences the nuclear relaxation time and polarization rate during the DNP. The experiments also show a variation in the NMR linewidth, leading to comparable time constants as determined by the lineshift. NEDOR measurements were also performed on irradiated, crystal grains of 6LiD. These samples exhibited a linewidth behavior similar to that of the cylindrically shaped butanol samples.

  12. Precession dynamics of the relativistic electron spin in laser-plasma acceleration

    SciTech Connect

    Pugacheva, D V; Andreev, N E

    2016-01-31

    A model is developed to study the precession dynamics of the relativistic electron spin in a laser-plasma accelerator versus the initial energy of the electron and its injection phase. Optimal parameters providing minimum depolarisation of the electron in the acceleration process are determined. (laser -plasma acceleration of electrons)

  13. Optically induced spin gates in coupled quantum dots using the electron-hole exchange interaction

    NASA Astrophysics Data System (ADS)

    Economou, Sophia E.; Reinecke, T. L.

    2008-09-01

    We propose a fast optically induced two-qubit C-PHASE gate between two resident spins in a pair of coupled quantum dots. An excited bound state which extends over the two dots provides an effective electron-electron exchange interaction. The gate is made possible by the electron-hole exchange interaction, which isolates a single transition in the system. When combined with appropriate single-qubit rotations, this gate generates an entangled state of the two spins.

  14. Pyroelectric materials as electronic pulse detectors of ultraheavy nuclei

    NASA Technical Reports Server (NTRS)

    Simpson, J. A.; Tuzzolino, A. J.

    1984-01-01

    The design and testing of ultraheavy-nucleus pulse detectors based on pyroelectric materials are reported, extending the preliminary findings of Tuzzolino (1983) and Simpson and Tuzzolino (1983). Uranium-ion beams of about 240 MeV/u are detected by a 39.5-micron-thick Si detector, degraded to about 175 MeV/u by Al absorbers, and then strike 700-micron-thick polyvinylidene fluoride or 1000-micron-thick LiTaO3 pyroelectric samples. Both detector systems are connected to a coincidence circuit via charge-sensitive preamplifiers, shaping amplifiers with 30-microsec effective time constants, and electronic discriminators. Sample spectra are shown, and the pulse heights measured are found to agree with theoretical calculations to within a factor of about 2. The response of the pyroelectric materials is found to be unaffected by exposure to about 10 Mrad of 2-7-MeV/u heavy ion radiation. With further study and improvement of the detection sensitivity, devices of this type could be applied to large-area space measurements of low ultraheavy-ion fluxes.

  15. Circulating blood volume determination using electronic spin resonance spectroscopy.

    PubMed

    Facorro, Graciela; Bianchin, Ana; Boccio, José; Hager, Alfredo

    2006-09-01

    There have been numerous methods proposed to measure the circulating blood volume (CBV). Nevertheless, none of them have been massively and routinely accepted in clinical diagnosis. This study describes a simple and rapid method, on a rabbit model, using the dilution of autologous red cells labeled with a nitroxide radical (Iodoacetamide-TEMPO), which can be detected by electronic spin resonance (ESR) spectroscopy. Blood samples were withdrawn and re-injected using the ears' marginal veins. The average CBV measured by the new method/body weight (CBV(IAT)/BW) was 59 +/- 7 mL/kg (n = 33). Simultaneously, blood volume determinations using the nitroxide radical and (51)Cr (CBV(Cr)) were performed. In the plot of the difference between the methods (CBV(IAT) - CBV(Cr)) against the average (CBV(IAT) + CBV(Cr))/2, the mean of the bias was -1.1 +/- 6.9 mL and the limits of agreement (mean difference +/-2 SD) were -14.9 and 12.7 mL. Lin's concordance correlation coefficient p(c) = 0.988. Thus, both methods are in close agreement. The development of a new method that allows a correct estimation of the CBV without using radioactivity, avoiding blood manipulation, and decreasing the possibility of blood contamination with similar accuracy and precision of that of the "gold standard method" is an innovative proposal.

  16. Mechanical detection of electron spin resonance beyond 1 THz

    SciTech Connect

    Takahashi, Hideyuki; Ohmichi, Eiji; Ohta, Hitoshi

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Fast pulsed operation of a small non-radioactive electron source with continuous emission current control

    SciTech Connect

    Cochems, P.; Kirk, A. T.; Bunert, E.; Runge, M.; Goncalves, P.; Zimmermann, S.

    2015-06-15

    Non-radioactive electron sources are of great interest in any application requiring the emission of electrons at atmospheric pressure, as they offer better control over emission parameters than radioactive electron sources and are not subject to legal restrictions. Recently, we published a simple electron source consisting only of a vacuum housing, a filament, and a single control grid. In this paper, we present improved control electronics that utilize this control grid in order to focus and defocus the electron beam, thus pulsing the electron emission at atmospheric pressure. This allows short emission pulses and excellent stability of the emitted electron current due to continuous control, both during pulsed and continuous operations. As an application example, this electron source is coupled to an ion mobility spectrometer. Here, the pulsed electron source allows experiments on gas phase ion chemistry (e.g., ion generation and recombination kinetics) and can even remove the need for a traditional ion shutter.

  19. Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond

    NASA Astrophysics Data System (ADS)

    Farfurnik, D.; Jarmola, A.; Pham, L. M.; Wang, Z. H.; Dobrovitski, V. V.; Walsworth, R. L.; Budker, D.; Bar-Gill, N.

    2015-08-01

    We demonstrate significant improvements of the spin coherence time of a dense ensemble of nitrogen-vacancy (NV) centers in diamond through optimized dynamical decoupling (DD). Cooling the sample down to 77 K suppresses longitudinal spin relaxation T1 effects and DD microwave pulses are used to increase the transverse coherence time T2 from ˜0.7 ms up to ˜30 ms . We extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. Following a theoretical and experimental characterization of pulse and detuning errors, we compare the performance of various DD protocols. We identify that the optimal control scheme for preserving an arbitrary spin state is a recursive protocol, the concatenated version of the XY8 pulse sequence. The improved spin coherence might have an immediate impact on improvements of the sensitivities of ac magnetometry. Moreover, the protocol can be used on denser diamond samples to increase coherence times up to NV-NV interaction time scales, a major step towards the creation of quantum collective NV spin states.

  20. Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond

    SciTech Connect

    Farfurnik, D.; Jarmola, A.; Pham, L. M.; Wang, Z. H.; Dobrovitski, V. V.; Walsworth, R. L.; Budker, D.; Bar-Gill, N.

    2015-08-24

    In this study, we demonstrate significant improvements of the spin coherence time of a dense ensemble of nitrogen-vacancy (NV) centers in diamond through optimized dynamical decoupling (DD). Cooling the sample down to 77 K suppresses longitudinal spin relaxation T1 effects and DD microwave pulses are used to increase the transverse coherence time T2 from ~0.7ms up to ~30ms. Furthermore, we extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. Following a theoretical and experimental characterization of pulse and detuning errors, we compare the performance of various DD protocols. We also identify that the optimal control scheme for preserving an arbitrary spin state is a recursive protocol, the concatenated version of the XY8 pulse sequence. The improved spin coherence might have an immediate impact on improvements of the sensitivities of ac magnetometry. Moreover, the protocol can be used on denser diamond samples to increase coherence times up to NV-NV interaction time scales, a major step towards the creation of quantum collective NV spin states.

  1. Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond

    DOE PAGES

    Farfurnik, D.; Jarmola, A.; Pham, L. M.; ...

    2015-08-24

    In this study, we demonstrate significant improvements of the spin coherence time of a dense ensemble of nitrogen-vacancy (NV) centers in diamond through optimized dynamical decoupling (DD). Cooling the sample down to 77 K suppresses longitudinal spin relaxation T1 effects and DD microwave pulses are used to increase the transverse coherence time T2 from ~0.7ms up to ~30ms. Furthermore, we extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. Following a theoretical and experimental characterization of pulse and detuning errors, we compare the performance of various DD protocols. We also identify that the optimal controlmore » scheme for preserving an arbitrary spin state is a recursive protocol, the concatenated version of the XY8 pulse sequence. The improved spin coherence might have an immediate impact on improvements of the sensitivities of ac magnetometry. Moreover, the protocol can be used on denser diamond samples to increase coherence times up to NV-NV interaction time scales, a major step towards the creation of quantum collective NV spin states.« less

  2. Spin Dynamics Simulations of Multiple Echo Spacing Pulse Sequences in Grossly Inhomogeneous Fields

    NASA Astrophysics Data System (ADS)

    Heidler, R.; Bachman, H. N.; Johansen, Y.

    2008-12-01

    Pulse sequences with multiple lengths of echo spacings are used in oilfield NMR logging for diffusion-based NMR applications such as rock and fluid characterization. One specific implementation is the so-called diffusion editing sequence comprising two long echo spacings followed by a standard CPMG at a shorter echo spacing. The echoes in the CPMG portion contain signal from both the direct and stimulated echoes. Modern oilfield NMR logging tools are designed for continuous depth logging of earth formations by projecting both the static (B0) and dynamic (B1) fields into the formation. Both B0 and B1 profiles are grossly inhomogeneous which results in non-steady-state behavior in the early echoes. The spin dynamics effects present a challenge for processing the echo amplitudes to measure porosity (amplitude extrapolated to zero time) and attenuations for fluid or pore size characterization. In this work we describe a calculation of the spin dynamics of the diffusion editing sequence with two long echo spacings. The calculation takes into account full B1 and B0 field maps, and comparisons will be made for sensors and parameters typical of oilfield logging tools and environments.

  3. Spin-dependent electron transport in zinc- and manganese-doped adenine molecules

    SciTech Connect

    Simchi, Hamidreza; Esmaeilzadeh, Mahdi Mazidabadi, Hossein

    2014-01-28

    The spin-dependent electron transport properties of zinc- and manganese-doped adenine molecules connected to zigzag graphene leads are studied in the zero bias regime using the non-equilibrium Green's function method. The conductance of the adenine molecule increased and became spin-dependent when a zinc or manganese atom was doped into the molecules. The effects of a transverse electric field on the spin-polarization of the transmitted electrons were investigated and the spin-polarization was controlled by changing the transverse electric field. Under the presence of a transverse electric field, both the zinc- and manganese-doped adenine molecules acted as spin-filters. The maximum spin-polarization of the manganese-doped adenine molecule was greater than the molecule doped with zinc.

  4. Optical investigation of electrical spin injection into an inverted two-dimensional electron gas structure

    NASA Astrophysics Data System (ADS)

    Buchner, M.; Kuczmik, T.; Oltscher, M.; Ciorga, M.; Korn, T.; Loher, J.; Schuh, D.; Schüller, C.; Bougeard, D.; Weiss, D.; Back, C. H.

    2017-01-01

    We report on electrical spin injection from (Ga,Mn)As into a high-mobility two-dimensional electron gas confined at an (Al,Ga)As/GaAs interface. Besides standard nonlocal electrical detection, we use a magneto-optical approach which provides cross-sectional images of the spin accumulation at the cleaved edge of the sample, yielding spin decay lengths on the order of 2 μ m . In some cases we find a nonmonotonic bias voltage dependence of the spin signal, which may be linked to ballistic tunneling effects during spin injection. We observe a clear Hanle depolarization using a technique which is free of dynamic nuclear polarization effects. Fitting the data with the standard drift-diffusion model of spin injection suggests averaged in-plane spin lifetimes on the order of 1 ns.

  5. Extended coherence length of spatially oscillating electron-spin polarization in dilute-magnetic-semiconductor quantum wells

    SciTech Connect

    Tsuchiya, Takuma

    2013-12-04

    We have investigated the possibility that the coherence length of spatially oscillating electron-spin polarization is improved in dilute magnetic semiconductors. In usual nonmagnetic quantum wells, the spin polarization of the electrons injected from a ferromagnetic source electrode oscillates spatially because of the spin precession due to spin-orbit effective magnetic fields, i.e., the Rashba and Dresselhaus fields. However, the polarization is damped within an oscillation period by the D’yakonov-Perel’ spin relaxation. In paramagnetic dilute magnetic semiconductors, impurity spin polarization is induced under the electron-spin polarization, and this impurity polarization influences the electron-spin precession and possibly improves the spatial electron-spin coherence. The validity of this effect is demonstrated by a numerical simulation for a CdMnTe quantum well.

  6. Electron-Nuclear Spin Dynamics in a Mesoscopic Solid-State Quantum Computer

    SciTech Connect

    Berman, G.P.; Campbell, D.K.; Doolen, G.D.; Nagaev, K.E.

    1998-12-07

    We numerically simulate the process of nuclear spin measurement in Kane's quantum computer. For this purpose, we model the quantum dynamics of two coupled nuclear spins located on {sup 31}P donors implanted in Si. We estimate the minimum time of measurement necessary for the reliable transfer of quantum information from the nuclear spin subsystem to the electronic one and the probability of error for typical values of external noise.

  7. Spin relaxations in 2D electron gas determined by the memory in the carrier dynamics.

    NASA Astrophysics Data System (ADS)

    Sherman, Eugene; Glazov, Mikhail

    2007-03-01

    The effects of long memory, in carrier dynamics in a magnetic field, on spin polarization evolution in 2D electron gas are investigated qualitatively and quantitatively. As examples we consider (i) systems with random Rashba-type SO coupling and (ii) quantum wells with rigid short-range scatterers (antidotes) and regular Dresselhaus SO coupling. In both cases the spin dynamics is strongly non-Markovian. In the system with the random SO coupling the time dependence of the spin polarization shows Gaussian rather than exponential behavior with the cusps corresponding to the electron revolutions. The relaxation speeds up with the increase of the magnetic field. In the system with antidotes scattering, the spin polarization shows a long-tail behavior with the relaxation rate determined by inelastic electron-phonon and electron-electron collisions and demonstrates unusual field dependence.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Plasma chemical conversion of sulphur hexafluoride initiated by a pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Kholodnaya, Galina; Sazonov, Roman; Ponomarev, Denis; Guzeeva, Tatiana

    2017-01-01

    This paper presents the results of the experimental investigation of plasma chemical conversion of sulphur hexafluoride initiated by a pulsed electron beam (TEA-500 pulsed electron accelerator) with the following characteristics: 400-450 keV electron energy, 60 ns pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. Experiments were conducted on the effect of the pulsed electron beam on SF6 and on mixtures of SF6 with O2, Ar, or N2. For the mixture of SF6 and oxygen, the results indicated chemical reactions involving the formation of a number of products of which one is sulphur, confirming the Wray - Fluorescence Analysis. The plasma chemical conversion of SF6 initiated by the pulsed electron beam was not detected when SF6 was mixed with Ar or N2, suggesting a possible mechanism for the reaction of SF6 in the presence of O2.

  10. Few-cycle attosecond pulse chirp effects on asymmetries in ionized electron momentum distributions

    SciTech Connect

    Peng Liangyou; Tan Fang; Gong Qihuang; Pronin, Evgeny A.; Starace, Anthony F.

    2009-07-15

    The momentum distributions of electrons ionized from H atoms by chirped few-cycle attosecond pulses are investigated by numerically solving the time-dependent Schroedinger equation. The central carrier frequency of the pulse is chosen to be 25 eV, which is well above the ionization threshold. The asymmetry (or difference) in the yield of electrons ionized along and opposite to the direction of linear laser polarization is found to be very sensitive to the pulse chirp (for pulses with fixed carrier-envelope phase), both for a fixed electron energy and for the energy-integrated yield. In particular, the larger the pulse chirp, the larger the number of times the asymmetry changes sign as a function of ionized electron energy. For a fixed chirp, the ionized electron asymmetry is found to be sensitive also to the carrier-envelope phase of the few-cycle pulse.

  11. Electron paramagnetic resonance study of the nuclear spin dynamics in an AlAs quantum well

    NASA Astrophysics Data System (ADS)

    Shchepetilnikov, A. V.; Frolov, D. D.; Nefyodov, Yu. A.; Kukushkin, I. V.; Tiemann, L.; Reichl, C.; Dietsche, W.; Wegscheider, W.

    2016-12-01

    The nuclear spin dynamics in an asymmetrically doped 16-nm AlAs quantum well grown along the [001] direction has been studied experimentally using the time decay of the Overhauser shift of paramagnetic resonance of conduction electrons. The nonzero spin polarization of nuclei causing the initial observed Overhauser shift is due the relaxation of the nonequilibrium spin polarization of electrons into the nuclear subsystem near electron paramagnetic resonance owing to the hyperfine interaction. The measured relaxation time of nuclear spins near the unity filling factor is (530 ± 30) min at the temperature T = 0.5 K. This value exceeds the characteristic spin relaxation times of nuclei in GaAs/AlGaAs heterostructures by more than an order of magnitude. This fact indicates the decrease in the strength of the hyperfine interaction in the AlAs quantum well in comparison with GaAs/AlGaAs heterostructures.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Detection of nanoscale electron spin resonance spectra demonstrated using nitrogen-vacancy centre probes in diamond

    PubMed Central

    Hall, L. T.; Kehayias, P.; Simpson, D. A.; Jarmola, A.; Stacey, A.; Budker, D.; Hollenberg, L. C. L.

    2016-01-01

    Electron spin resonance (ESR) describes a suite of techniques for characterizing electronic systems with applications in physics, chemistry, and biology. However, the requirement for large electron spin ensembles in conventional ESR techniques limits their spatial resolution. Here we present a method for measuring ESR spectra of nanoscale electronic environments by measuring the longitudinal relaxation time of a single-spin probe as it is systematically tuned into resonance with the target electronic system. As a proof of concept, we extracted the spectral distribution for the P1 electronic spin bath in diamond by using an ensemble of nitrogen-vacancy centres, and demonstrated excellent agreement with theoretical expectations. As the response of each nitrogen-vacancy spin in this experiment is dominated by a single P1 spin at a mean distance of 2.7 nm, the application of this technique to the single nitrogen-vacancy case will enable nanoscale ESR spectroscopy of atomic and molecular spin systems. PMID:26728001

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Spin polarized electronic states and spin textures at the surface of oxygen-deficient SrTiO3

    NASA Astrophysics Data System (ADS)

    Jeschke, Harald O.; Altmeyer, Michaela; Rozenberg, Marcelo; Gabay, Marc; Valenti, Roser

    We investigate the electronic structure and spin texture at the (001) surface of SrTiO3 in the presence of oxygen vacancies by means of ab initio density functional theory (DFT) calculations of slabs. Relativistic non-magnetic DFT calculations exhibit Rashba-like spin winding with a characteristic energy scale ~ 10 meV. However, when surface magnetism on the Ti ions is included, bands become spin-split with an energy difference ~ 100 meV at the Γ point. This energy scale is comparable to the observations in SARPES experiments performed on the two-dimensional electronic states confined near the (001) surface of SrTiO3. We find the spin polarized state to be the ground state of the system, and while magnetism tends to suppress the effects of the relativistic Rashba interaction, signatures of it are still clearly visible in terms of complex spin textures. We gratefully acknowledge financial support from the Deutsche Forschungsgemeinschaft through grants SFB/TR 49 and FOR 1346.

  18. Measurement of Spatial and Temporal Profiles of Electron Plasma Oscillation Excited by Ultrashort Laser Pulse

    NASA Astrophysics Data System (ADS)

    Takahashi, Eiji; Katsura, Keisuke; Miura, Eisuke; Yugami, Noboru; Nishida, Yasushi; Honda, Hiroshi; Kondo, Kiminori

    1999-11-01

    Large amplitude electron plasma waves (EPW), which are produced by ultrashort laser pulses, are of great interest for particle acceleration or photon acceleration. In this study, we present the temporally and spatially resolved measurements of the electron density perturbation produced by the laser wakefield (LWF) process. 0.6 TW Ti:sapphire laser pulse ionized the helium gas of ~ 1 Torr near the focus and excited the electron density perturbation. We observed this electron density perturbation by the frequency-domain interferometry technique. The probe pulse was the second harmonic of the partially separated pulse from the main pump pulse. The probe pulse was sent into the Michelson interferometer and make two colinear pulses. These two probe pulses go through the EPW, and are affected by EPW of which phase velocity is almost equal to the light velocity. Each pulse obtains a phase shift depending on the phase of EPW. These two pulses interfer each other in the spectometer. Spatialy resolved relative phase shift can be obtained from the interferogram. With varying the relative delay between the two probe pulses, 2 THz periodic change of the relative phase shift was observed. It was caused by 2THz electron density oscillation in LWF.

  19. Concentration dependence of nitroxyl spin probes in liposomal solution: electron spin resonance and overhauser-enhanced magnetic resonance studies.

    PubMed

    Meenakumari, V; Utsumi, Hideo; Jawahar, A; Franklin Benial, A Milton

    2016-12-21

    In this work, the detailed studies of electron spin resonance (ESR) and overhauser-enhanced magnetic resonance imaging (OMRI) were carried out for permeable nitroxyl spin probe, MC-PROXYL as a function of agent concentration in liposomal solution. In order to compare the impermeable nature of nitroxyl radical, the study was also carried out only at 2 mM concentration of carboxy-PROXYL. The ESR parameters were estimated using L-band and 300 MHz ESR spectrometers. The line width broadening was measured as a function of agent concentration in liposomal solution. The estimated rotational correlation time is proportional to the agent concentration, which indicates that less mobile nature of nitroxyl spin probe in liposomal solution. The partition parameter and permeability values indicate that the diffusion of nitroxyl spin probe distribution into the lipid phase is maximum at 2 mM concentration of MC-PROXYL. The dynamic nuclear polarization (DNP) parameters such as DNP factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for 2 mM MC-PROXYL in 400 mM liposomal dispersion. The spin lattice relaxation time was shortened in liposomal solution, which leads to the high relaxivity. Reduction in coupling factor is due to less interaction between the electron and nuclear spins, which causes the reduction in enhancement. The leakage factor increases with increasing agent concentration. The increase in DNP enhancement was significant up to 2 mM in liposomal solution. These results paves the way for choosing optimum agent concentration and OMRI scan parameters used in intra and extra membrane water by loading the liposome vesicles with a lipid permeable nitroxyl spin probes in OMRI experiments.

  20. Adiabatic quantum computing with spin qubits hosted by molecules.

    PubMed

    Yamamoto, Satoru; Nakazawa, Shigeaki; Sugisaki, Kenji; Sato, Kazunobu; Toyota, Kazuo; Shiomi, Daisuke; Takui, Takeji

    2015-01-28

    A molecular spin quantum computer (MSQC) requires electron spin qubits, which pulse-based electron spin/magnetic resonance (ESR/MR) techniques can afford to manipulate for implementing quantum gate operations in open shell molecular entities. Importantly, nuclear spins, which are topologically connected, particularly in organic molecular spin systems, are client qubits, while electron spins play a role of bus qubits. Here, we introduce the implementation for an adiabatic quantum algorithm, suggesting the possible utilization of molecular spins with optimized spin structures for MSQCs. We exemplify the utilization of an adiabatic factorization problem of 21, compared with the corresponding nuclear magnetic resonance (NMR) case. Two molecular spins are selected: one is a molecular spin composed of three exchange-coupled electrons as electron-only qubits and the other an electron-bus qubit with two client nuclear spin qubits. Their electronic spin structures are well characterized in terms of the quantum mechanical behaviour in the spin Hamiltonian. The implementation of adiabatic quantum computing/computation (AQC) has, for the first time, been achieved by establishing ESR/MR pulse sequences for effective spin Hamiltonians in a fully controlled manner of spin manipulation. The conquered pulse sequences have been compared with the NMR experiments and shown much faster CPU times corresponding to the interaction strength between the spins. Significant differences are shown in rotational operations and pulse intervals for ESR/MR operations. As a result, we suggest the advantages and possible utilization of the time-evolution based AQC approach for molecular spin quantum computers and molecular spin quantum simulators underlain by sophisticated ESR/MR pulsed spin technology.

  1. Electronic states and spin-orbit splitting of lanthanum dimer

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wu, Lu; Zhang, Chang-Hua; Krasnokutski, Serge A.; Yang, Dong-Sheng

    2011-07-01

    Lanthanum dimer (La2) was studied by mass-analyzed threshold ionization (MATI) spectroscopy and a series of multi-configuration ab initio calculations. The MATI spectrum exhibits three band systems originating from ionization of the neutral ground electronic state, and each system shows vibrational frequencies of the neutral molecule and singly charged cation. The three ionization processes are La2+ (a2∑g+) ← La2 (X1∑g+), La2+ (b2Π3/2, u) ← La2 (X1∑g+), and La2+ (b2Π1/2, u) ← La2 (X1∑g+), with the ionization energies of 39 046, 40 314, and 40 864 cm-1, respectively. The vibrational frequency of the X1Σg+ state is 207 cm-1, and those of the a2Σg+, b2Π3/2, u and b2Π1/2, u are 235.7, 242.2, and 240 cm-1. While X1Σg+ is the ground state of the neutral molecule, a2Σg+ and b2Πu are calculated to be the excited states of the cation. The spin-orbit splitting in the b2Πu ion is 550 cm-1. An X4Σg- state of La2+ was predicted by theory, but not observed by the experiment. The determination of a singlet ground state of La2 shows that lanthanum behaves differently from scandium and yttrium.

  2. Spin-dependent electron transmission through bacteriorhodopsin embedded in purple membrane

    PubMed Central

    Mishra, Debabrata; Markus, Tal Z.; Naaman, Ron; Kettner, Matthias; Göhler, Benjamin; Zacharias, Helmut; Friedman, Noga; Sheves, Mordechai; Fontanesi, Claudio

    2013-01-01

    Spin-dependent photoelectron transmission and spin-dependent electrochemical studies were conducted on purple membrane containing bacteriorhodopsin (bR) deposited on gold, aluminum/aluminum-oxide, and nickel substrates. The result indicates spin selectivity in electron transmission through the membrane. Although the chiral bR occupies only about 10% of the volume of the membrane, the spin polarization found is on the order of 15%. The electrochemical studies indicate a strong dependence of the conduction on the protein’s structure. Denaturation of the protein causes a sharp drop in the conduction through the membrane. PMID:23980184

  3. Novel effects of spin-orbit interaction in interacting electronic systems

    NASA Astrophysics Data System (ADS)

    Sun, Jianmin

    Over the last several years there has been a remarkable growth in research activity in the physical properties of mesoscopic systems. Significant results, which were obtained by both theoretical and experimental studies, together with the enormous promise of nano-technology applications, contribute to this interest. In mesoscopic systems, there are 1023 or so electrons with strong Coulomb interaction. The length scale governing the electrons motion is small enough to cause quantization of the energy levels. In this work we study such quantum systems: quantum wires, quantum dots. During the last decade several experimental techniques have been developed for manufacturing both kinds of devices, which are currently an important tool for understanding low dimensions physics. The finite spin-orbit coupling is very natural, and, strictly speaking, unavoidable, in semiconducting quantum wires due to pronounced structural asymmetry inherent in the fabrication process. Thus the interplay between Coulomb interaction and spin-orbit coupling is important to investigate. The magnetic field also plays an important role which breaks the time-reversal symmetry of the Hamiltonian and splits the band of free electrons into two, corresponding to up-spin and down-spin electrons, reducing spin-rotational symmetry of the system from SU(2) to U(1). The dissertation takes account of the effect of the spin-orbit coupling interactions in the properties of mesoscopic systems. The manuscript is divided in four Chapters. In Chapter 1, the field theory in mesoscopic system is introduced. I present the relations between bosonic and fermionic operators in one dimension. These relations are used to bosonize spin 1/2 interaction fermion system. I show how to derive the RG equations around a fixed-point from the Operator Product Expansion (OPE). In Chapter 2, I present analysis of the interacting quantum wire problem in the presence of magnetic field and spin-orbital interaction. I show that an

  4. Spintronics and Chirality: Spin Selectivity in Electron Transport Through Chiral Molecules

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

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

    ERIC Educational Resources Information Center

    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)

  7. Multifrequency electron spin resonance study of the dynamics of spin labeled T4 lysozyme.

    PubMed

    Zhang, Ziwei; Fleissner, Mark R; Tipikin, Dmitriy S; Liang, Zhichun; Moscicki, Jozef K; Earle, Keith A; Hubbell, Wayne L; Freed, Jack H

    2010-04-29

    An extensive set of electron spin resonance spectra was obtained over a wide range of frequencies (9, 95, 170, and 240 GHz) and temperatures (2 to 32 degrees C) to explore the dynamic modes of nitroxide-labeled T4 lysozyme in solution. A commonly used nitroxide side chain (R1), or a methylated analogue with hindered internal motion (R2), was substituted for the native side chain at solvent-exposed helical sites, 72 or 131. The spectra at all four frequencies were simultaneously fit with the slowly relaxing local structure (SRLS) model. Good fits were achieved at all the temperatures. Two principle dynamic modes are included in the SRLS model, the global tumbling of the protein and the internal motion consisting of backbone fluctuations and side chain isomerizations. Three distinct spectral components were required for R1 and two for R2 to account for the spectra at all temperatures. One is a highly ordered and slow motional component, which is observed in the spectra of both R1 and R2; it may correspond to conformers stabilized by interaction with the protein surface. The fraction of this component decreases with increasing temperature and is more populated in the R2 spectra, possibly arising from stronger interaction of the nitroxide ring with the protein surface due to the additional methyl group. The other two components of R1 and the second component of R2 are characterized by fast anisotropic diffusion and relatively low ordering, most likely corresponding to conformers having little or no interactions with nearby residues. Ficoll of different concentrations was added to increase the solution viscosity, thereby slowing down the global tumbling of the protein. A significant effect of Ficoll on the internal motion of an immobilized component was apparent in R2 but not in R1. The ability of such multifrequency studies to separate the effects of faster internal modes of motion from slower overall motions is clearly demonstrated, and its utility in future studies

  8. Optically Imaged Striped Domains of Nonequilibrium Electronic and Nuclear Spins in a Fractional Quantum Hall Liquid.

    PubMed

    Moore, John N; Hayakawa, Junichiro; Mano, Takaaki; Noda, Takeshi; Yusa, Go

    2017-02-17

    Using photoluminescence microscopy enhanced by magnetic resonance, we visualize in real space both electron and nuclear polarization occurring in nonequilibrium fraction quantum Hall (FQH) liquids. We observe stripelike domain regions comprising FQH excited states which discretely form when the FQH liquid is excited by a source-drain current. These regions are deformable and give rise to bidirectionally polarized nuclear spins as spin-resolved electrons flow across their boundaries.

  9. Optically Imaged Striped Domains of Nonequilibrium Electronic and Nuclear Spins in a Fractional Quantum Hall Liquid

    NASA Astrophysics Data System (ADS)

    Moore, John N.; Hayakawa, Junichiro; Mano, Takaaki; Noda, Takeshi; Yusa, Go

    2017-02-01

    Using photoluminescence microscopy enhanced by magnetic resonance, we visualize in real space both electron and nuclear polarization occurring in nonequilibrium fraction quantum Hall (FQH) liquids. We observe stripelike domain regions comprising FQH excited states which discretely form when the FQH liquid is excited by a source-drain current. These regions are deformable and give rise to bidirectionally polarized nuclear spins as spin-resolved electrons flow across their boundaries.

  10. Spin dynamics and relaxation in graphene dictated by electron-hole puddles

    NASA Astrophysics Data System (ADS)

    van Tuan, Dinh; Ortmann, Frank; Cummings, Aron W.; Soriano, David; Roche, Stephan

    2016-02-01

    The understanding of spin dynamics and relaxation mechanisms in clean graphene, and the upper time and length scales on which spin devices can operate, are prerequisites to realizing graphene-based spintronic technologies. Here we theoretically reveal the nature of fundamental spin relaxation mechanisms in clean graphene on different substrates with Rashba spin-orbit fields as low as a few tens of μeV. Spin lifetimes ranging from 50 picoseconds up to several nanoseconds are found to be dictated by substrate-induced electron-hole characteristics. A crossover in the spin relaxation mechanism from a Dyakonov-Perel type for SiO2 substrates to a broadening-induced dephasing for hBN substrates is described. The energy dependence of spin lifetimes, their ratio for spins pointing out-of-plane and in-plane, and the scaling with disorder provide a global picture about spin dynamics and relaxation in ultraclean graphene in the presence of electron-hole puddles.

  11. Spin dynamics and relaxation in graphene dictated by electron-hole puddles

    PubMed Central

    Van Tuan, Dinh; Ortmann, Frank; Cummings, Aron W.; Soriano, David; Roche, Stephan

    2016-01-01

    The understanding of spin dynamics and relaxation mechanisms in clean graphene, and the upper time and length scales on which spin devices can operate, are prerequisites to realizing graphene-based spintronic technologies. Here we theoretically reveal the nature of fundamental spin relaxation mechanisms in clean graphene on different substrates with Rashba spin-orbit fields as low as a few tens of μeV. Spin lifetimes ranging from 50 picoseconds up to several nanoseconds are found to be dictated by substrate-induced electron-hole characteristics. A crossover in the spin relaxation mechanism from a Dyakonov-Perel type for SiO2 substrates to a broadening-induced dephasing for hBN substrates is described. The energy dependence of spin lifetimes, their ratio for spins pointing out-of-plane and in-plane, and the scaling with disorder provide a global picture about spin dynamics and relaxation in ultraclean graphene in the presence of electron-hole puddles. PMID:26876333

  12. Effect of electron spin dynamics on solid-state dynamic nuclear polarization performance.

    PubMed

    Siaw, Ting Ann; Fehr, Matthias; Lund, Alicia; Latimer, Allegra; Walker, Shamon A; Edwards, Devin T; Han, Song-I

    2014-09-21

    For the broadest dissemination of solid-state dynamic nuclear polarization (ssDNP) enhanced NMR as a material characterization tool, the ability to employ generic mono-nitroxide radicals as spin probes is critical. A better understanding of the factors contributing to ssDNP efficiency is needed to rationally optimize the experimental condition for the practically accessible spin probes at hand. This study seeks to advance the mechanistic understanding of ssDNP by examining the effect of electron spin dynamics on ssDNP performance at liquid helium temperatures (4-40 K). The key observation is that bi-radicals and mono-radicals can generate comparable nuclear spin polarization at 4 K and 7 T, which is in contrast to the observation for ssDNP at liquid nitrogen temperatures (80-150 K) that finds bi-radicals to clearly outperform mono-radicals. To rationalize this observation, we analyze the change in the DNP-induced nuclear spin polarization (Pn) and the characteristic ssDNP signal buildup time as a function of electron spin relaxation rates that are modulated by the mono- and bi-radical spin concentration. Changes in Pn are consistent with a systematic variation in the product of the electron spin-lattice relaxation time and the electron spin flip-flop rate that constitutes an integral saturation factor of an inhomogeneously broadened EPR spectrum. We show that the comparable Pn achieved with both radical species can be reconciled with a comparable integral EPR saturation factor. Surprisingly, the largest Pn is observed at an intermediate spin concentration for both mono- and bi-radicals. At the highest radical concentration, the stronger inter-electron spin dipolar coupling favors ssDNP, while oversaturation diminishes Pn, as experimentally verified by the observation of a maximum Pn at an intermediate, not the maximum, microwave (μw) power. At the maximum μw power, oversaturation reduces the electron spin population differential that must be upheld between

  13. Persistent Skyrmion Lattice of Noninteracting Electrons with Spin-Orbit Coupling

    NASA Astrophysics Data System (ADS)

    Fu, Jiyong; Penteado, Poliana H.; Hachiya, Marco O.; Loss, Daniel; Egues, J. Carlos

    2016-11-01

    A persistent spin helix (PSH) is a robust helical spin-density pattern arising in disordered 2D electron gases with Rashba α and Dresselhaus β spin-orbit (SO) tuned couplings, i.e., α =±β . Here, we investigate the emergence of a persistent Skyrmion lattice (PSL) resulting from the coherent superposition of PSHs along orthogonal directions—crossed PSHs—in wells with two occupied subbands ν =1 , 2. For realistic GaAs wells, we show that the Rashba αν and Dresselhaus βν couplings can be simultaneously tuned to equal strengths but opposite signs, e.g., α1=β1 and α2=-β2. In this regime, and away from band anticrossings, our noninteracting electron gas sustains a topologically nontrivial Skyrmion-lattice spin-density excitation, which inherits the robustness against spin-independent disorder and interactions from its underlying crossed PSHs. We find that the spin relaxation rate due to the interband SO coupling is comparable to that of the cubic Dresselhaus term as a mechanism of the PSL decay. Near anticrossings, the interband-induced spin mixing leads to unusual spin textures along the energy contours beyond those of the Rahsba-Dresselhaus bands. Our PSL opens up the unique possibility of observing topological phenomena, e.g., topological and Skyrmion Hall effects, in ordinary GaAs wells with noninteracting electrons.

  14. Persistent Skyrmion Lattice of Noninteracting Electrons with Spin-Orbit Coupling.

    PubMed

    Fu, Jiyong; Penteado, Poliana H; Hachiya, Marco O; Loss, Daniel; Egues, J Carlos

    2016-11-25

    A persistent spin helix (PSH) is a robust helical spin-density pattern arising in disordered 2D electron gases with Rashba α and Dresselhaus β spin-orbit (SO) tuned couplings, i.e., α=±β. Here, we investigate the emergence of a persistent Skyrmion lattice (PSL) resulting from the coherent superposition of PSHs along orthogonal directions-crossed PSHs-in wells with two occupied subbands ν=1, 2. For realistic GaAs wells, we show that the Rashba α_{ν} and Dresselhaus β_{ν} couplings can be simultaneously tuned to equal strengths but opposite signs, e.g., α_{1}=β_{1} and α_{2}=-β_{2}. In this regime, and away from band anticrossings, our noninteracting electron gas sustains a topologically nontrivial Skyrmion-lattice spin-density excitation, which inherits the robustness against spin-independent disorder and interactions from its underlying crossed PSHs. We find that the spin relaxation rate due to the interband SO coupling is comparable to that of the cubic Dresselhaus term as a mechanism of the PSL decay. Near anticrossings, the interband-induced spin mixing leads to unusual spin textures along the energy contours beyond those of the Rahsba-Dresselhaus bands. Our PSL opens up the unique possibility of observing topological phenomena, e.g., topological and Skyrmion Hall effects, in ordinary GaAs wells with noninteracting electrons.

  15. Electron retroreflection and spin beam splitting in a twisted graphene bilayer

    NASA Astrophysics Data System (ADS)

    Xu, Yafang; Jin, Guojun

    2016-12-01

    We theoretically investigate the various reflection processes in a twisted graphene bilayer-based normal conductor/superconductor junction. It is found that the special spinor wave functions in strongly doped superconductor region lead the Andreev reflection to be suppressed completely. For the 100% electronelectron reflection, except the traditional specular reflection, electrons can undergo retroreflection, which is sensitive to the band contour and can be used to confirm the van Hove singularities in the twisted graphene bilayer. By depositing a ferromagnetic insulator on the N region, we further find that electrons can be spatially separated with spin-down electrons specular reflected and spin-up electrons retroreflected, or vice versa. It provides a new mechanism to realize a spin beam splitter.

  16. Control of spin dynamics in a two-dimensional electron gas by electromagnetic dressing

    NASA Astrophysics Data System (ADS)

    Pervishko, A. A.; Kibis, O. V.; Morina, S.; Shelykh, I. A.

    2015-11-01

    We solved the Schrödinger problem for a two-dimensional electron gas (2DEG) with the Rashba spin-orbit interaction in the presence of a strong high-frequency electromagnetic field (dressing field). The found eigenfunctions and eigenenergies of the problem are used to describe the spin dynamics of the dressed 2DEG within the formalism of the density matrix response function. Solving the equations of spin dynamics, we show that the dressing field can switch the spin relaxation in the 2DEG between the cases corresponding to the known Elliott-Yafet and D'yakonov-Perel' regimes. As a result, the spin properties of the 2DEG can be tuned by a high-frequency electromagnetic field. The present effect opens an unexplored way for controlling the spin with light and, therefore, forms the physical prerequisites for creating light-tuned spintronics devices.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. SINGLE-SHOT TURBO SPIN ECHO PULSE SEQUENCE FINDINGS IN DOGS WITH AND WITHOUT PROGRESSIVE MYELOMALACIA.

    PubMed

    Gilmour, Lindsey J; Jeffery, Nick D; Miles, Kristina; Riedesel, Elizabeth

    2017-03-01

    Progressive myelomalacia is an uncommon type of ischemic, hemorrhagic spinal cord infarction. Diagnosis can be difficult, but prompt recognition is important. We hypothesized that cerebrospinal fluid signal attenuation on magnetic resonance (MR) images would be more extensive in dogs that developed progressive myelomalacia vs. control dogs. A retrospective analytic cohort study was designed. Dogs were included if they presented for acute paraplegia and loss of deep pain perception and had undergone MR imaging using both sagittal single-shot turbo spin echo (SSTSE) and standard sagittal T2-weighted fast spin echo (T2W) pulse sequences. Dogs were divided into progressive myelomalacia and control groups for comparisons. All MR examinations were evaluated by three reviewers blinded to patient outcome. Length of cerebrospinal fluid attenuation was recorded as a ratio to the length of the L2 vertebral body in SSTSE and T2W sequences (CSF:L2SSTSE and CSF:L2T2 , respectively). Length of intramedullary spinal cord hyperintensity was recorded as a ratio to the length of the L2 vertebral body in T2W sequences. A total of 21 dogs were included (five in the progressive myelomalacia group and 16 in the control group). The mean CSF:L2SSTSE attenuation value was significantly higher in dogs that developed progressive myelomalacia (CSF:L2SSTSE = 10.7) compared to controls (CSF:L2SSTSE = 5.4; P = 0.015). A cut off ratio of attenuation >7.4 provided optimal differentiation between groups in this study. Findings supported the conclusion that dogs with CSF:L2SSTSE ≤ 7.4 are unlikely to develop progressive myelomalacia while dogs with CSF:L2SSTSE > 7.4 are indeterminate for progressive myelomalacia.

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

    PubMed

    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.

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

    PubMed

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

    2017-02-08

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  3. Growth direction dependence of the electron spin dynamics in {111} GaAs quantum wells

    NASA Astrophysics Data System (ADS)

    Ye, H. Q.; Wang, G.; Liu, B. L.; Shi, Z. W.; Wang, W. X.; Fontaine, C.; Balocchi, A.; Amand, T.; Lagarde, D.; Renucci, P.; Marie, X.

    2012-07-01

    The electron spin dynamics is studied by time-resolved Kerr rotation in GaAs/AlGaAs quantum wells embedded in NIP structures grown on (111)A or (111)B-oriented substrates. In both cases the spin lifetimes are significantly increased by applying an external electric field, but this field has to point along the growth direction for structures grown on (111)A and opposite to it for the ones grown on (111)B. This extended electron spin lifetime is the result of the suppression of the D'yakonov-Perel spin relaxation mechanism [Sov. Phys. Solid State 13, 3023 (1972)] due to the cancellation effect of the internal Dresselhaus term [Phys. Rev. 100, 580 (1955)] with the external electric field induced Rashba one [J. Phys. C 17, 6039 (1984)], both governing the conduction band spin-orbit splitting. These results demonstrate the key role played by the growth direction in the design of spintronic devices.

  4. Spin-orbit coupling and electron correlation in relativistic configuration interaction and coupled-cluster methods

    NASA Astrophysics Data System (ADS)

    Kim, Inkoo; Park, Young Choon; Kim, Hyungjun; Lee, Yoon Sup

    2012-02-01

    We studied convergence characteristics of relativistic effective core potential (RECP) based configuration interaction (CI) and coupled-cluster (CC) schemes in terms of spin-orbit coupling and electron correlation. The relativistic correlated methods can be divided into Kramers restricted (KR) and spin-orbit (SO) methods which differ by the stage of spin-orbit treatment: the KR method employs two-component Kramers restricted Hartree-Fock (HF) spinors as the one-electron basis in which spin-orbit coupling is included, whereas the SO method is based on one-component molecular orbitals generated from scalar relativistic HF and the spin-orbit interaction is then entered in post-HF step. The KR method is usually superior to the SO method for molecules containing heavy elements since spin-orbit coupling is included from the HF step. A performance calibration of the SO method against the KR method is performed by computations of the ground state energies and equilibrium bond lengths of MH (M = Tl, Pb, Bi, Po, and At). Spin-orbit coupling of each molecule was systematically increased by adjusting the spin-orbit operator of RECP to investigate its impact on the SO method. Although KRCI and SOCI converged to the same full-CI limit, for the strong spin-orbit coupling SOCI required higher levels of correlation compared to KRCI to account for the orbital relaxation effect. SOCC, in contrast, was able to recover both spin-orbit interaction and electron correlation in CC steps regardless of the spin-orbit strength, implying that SOCC could be the reliable and efficient relativistic ab initio method for moderate sized molecules containing heavy elements.

  5. Influence of Radical Bridges on Electron Spin Coupling.

    PubMed

    Steenbock, Torben; Shultz, David A; Kirk, Martin L; Herrmann, Carmen

    2017-01-12

    Increasing interactions between spin centers in molecules and molecular materials is a desirable goal for applications such as single-molecule magnets for information storage or magnetic metal-organic frameworks for adsorptive separation and targeted drug delivery and release. To maximize these interactions, introducing unpaired spins on bridging ligands is a concept used in several areas where such interactions are otherwise quite weak, in particular, lanthanide-based molecular magnets and magnetic metal-organic frameworks. Here, we use Kohn-Sham density functional theory to study how much the ground spin state is stabilized relative to other low-lying spin states by creating an additional spin center on the bridge for a series of simple model compounds. The di- and triradical structures consist of nitronyl nitroxide (NNO) and semiquinone (SQ) radicals attached to a meta-phenylene(R) bridge (where R = -NH(•)/-NH2, -O(•)/OH, -CH2(•)/CH2). These model compounds are based on a fully characterized SQ-meta-phenylene-NNO diradical with moderately strong antiferromagnetic coupling. Replacing closed-shell substituents CH3 and NH2 with their radical counterparts CH2(•) and NH(•) leads to an increase in stabilization of the ground state with respect to other low-lying spin states by a factor of 3-6, depending on the exchange-correlation functional. For OH compared with O(•) substituents, no conclusions can be drawn as the spin state energetics depend strongly on the functional. This could provide a basis for constructing sensitive test systems for benchmarking theoretical methods for spin state energy splittings. Reassuringly, the stabilization found for a potentially synthesizable complex (up to a factor of 3.5) is in line with the simple model systems (where a stabilization of up to a factor of 6.2 was found). Absolute spin state energy splittings are considerably smaller for the potentially stable system than those for the model complexes, which points to a

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

    SciTech Connect

    Berti, G. Calloni, A.; Brambilla, A.; Bussetti, G.; Duò, L.; Ciccacci, F.

    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.

  7. Effect of spin-flip scattering on the electron transport through double quantum dots

    NASA Astrophysics Data System (ADS)

    Yang, Fu-Bin; Huang, Rui; Cheng, Yan

    2015-05-01

    We systematically investigate the electron transport through double quantum dots (DQD) with particular emphasis on the spin-flip scattering of an electron in the DQD. By means of the slave-boson mean-field approximation, we calculate the linear conductance and the transmission in the Kondo regime at zero temperature. The obtained results show that both the linear conductance and transmission probability are quite sensitive to the spin-flip strength when the DQD structure is changed among the serial, parallel and T-shaped. It is suggested that such a theoretical model can be used to study the physical phenomenon related to the spin manipulation transport.

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

    PubMed Central

    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

  9. Rotatable spin-polarized electron source for inverse-photoemission experiments

    SciTech Connect

    Stolwijk, S. D. Wortelen, H.; Schmidt, A. B.; Donath, M.

    2014-01-15

    We present a ROtatable Spin-polarized Electron source (ROSE) for the use in spin- and angle-resolved inverse-photoemission (SR-IPE) experiments. A key feature of the ROSE is a variable direction of the transversal electron beam polarization. As a result, the inverse-photoemission experiment becomes sensitive to two orthogonal in-plane polarization directions, and, for nonnormal electron incidence, to the out-of-plane polarization component. We characterize the ROSE and test its performance on the basis of SR-IPE experiments. Measurements on magnetized Ni films on W(110) serve as a reference to demonstrate the variable spin sensitivity. Moreover, investigations of the unoccupied spin-dependent surface electronic structure of Tl/Si(111) highlight the capability to analyze complex phenomena like spin rotations in momentum space. Essentially, the ROSE opens the way to further studies on complex spin-dependent effects in the field of surface magnetism and spin-orbit interaction at surfaces.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Spin response to localized pumps: Exciton polaritons versus electrons and holes

    NASA Astrophysics Data System (ADS)

    Sacksteder, Vincent; Pervishko, A. A.; Shelykh, I. A.

    2016-02-01

    Polariton polarization can be described in terms of a pseudospin which can be oriented along the x ,y , or z axis, similarly to electron and hole spin. Unlike electrons and holes where time-reversal symmetry requires that the spin-orbit interaction be odd in the momentum, the analog of the spin-orbit interaction for polaritons, the so-called TE-TM splitting, is even in the momentum. We calculate and compare spin transport of polariton, electron, and hole systems, in the diffusive regime of many scatterings. After dimensional rescaling diffusive systems with spatially uniform particle densities have identical dynamics, regardless of the particle type. Differences between the three particles appear in spatially nonuniform systems, with pumps at a specific localized point. We consider both oscillating pumps and transient (delta function) pumps. In such systems each particle type produces distinctive spin patterns. The particles can be distinguished by their differing spatial multipole character, their response and resonances in a perpendicular magnetic field, and their relative magnitude which is largest for electrons and weakest for holes. These patterns are manifested both in response to unpolarized pumps which produce in-plane and perpendicular spin signals, and to polarized pumps where the spin precesses from in-plane to out-of-plane and vice versa. These results will be useful for designing systems with large spin polarization signals, for identifying the dominant spin-orbit interaction and measuring subdominant terms in experimental devices, and for measuring the scattering time and the spin-orbit coupling's magnitude.

  12. A spin rotator for producing a longitudinally polarized electron beam with MAMI

    NASA Astrophysics Data System (ADS)

    Steffens, K.-H.; Andresen, H. G.; Blume-Werry, J.; Klein, F.; Aulenbacher, K.; Reichert, E.

    1993-02-01

    The design and performance characteristics of a full 4 π-space spin rotator for 100 keV electrons are described. The spin rotator was developed as part of the acceleration scheme for polarized electrons in the MAINZ race track microtron cascade MAMI [1]. It allows to orientate the polarization vector in any direction before injection. Thus it is possible to optimize the longitudinal polarization component, required for experiments with polarized high energy electrons, at target position. With this scheme various experimental halls can be supplied with longitudinally polarized electrons in the full energy range of MAMI between 180 and 855 MeV.

  13. A high current, short pulse electron source for wakefield accelerators

    SciTech Connect

    Ho, Ching-Hung.

    1992-01-01

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  14. A high current, short pulse electron source for wakefield accelerators

    SciTech Connect

    Ho, Ching-Hung

    1992-12-31

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  15. Theory of two-dimensional Fourier transform electron spin resonance for ordered and viscous fluids

    NASA Astrophysics Data System (ADS)

    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

  16. Generation and measurement of ultrashort pulses from the Stanford Superconducting Accelerator free-electron laser

    SciTech Connect

    Richman, B.A.; DeLong, K.W.; Trebino, R.

    1995-11-01

    The authors present results of frequency resolved optical gating (FROG) measurements on the Superconducting Accelerator (SCA) mid-IR free-electron laser (FEL) at Stanford. FROG retrieves complete amplitude and phase content of an optical pulse. First, they review the properties of FELs including the ability to tune wavelength and pulse length. In addition, the electron beam driving the FEL often affects the optical pulse shape. The SCA mid-IR FEL currently operates at wavelengths between 4 {micro}m and 10 {micro}m and its pulse length can be varied from 700 fs to 2 ps. They then describe details of the experimental layout and procedures particular to FELs and to the mid-IR. Finally, they show FROG measurements on the FEL including examples of nearly transform limited pulses, frequency chirped pulses, and pulses distorted by atmospheric water vapor absorption.

  17. Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source.

    PubMed

    Lord, J S; McKenzie, I; Baker, P J; Blundell, S J; Cottrell, S P; Giblin, S R; Good, J; Hillier, A D; Holsman, B H; King, P J C; Lancaster, T; Mitchell, R; Nightingale, J B; Owczarkowski, M; Poli, S; Pratt, F L; Rhodes, N J; Scheuermann, R; Salman, Z

    2011-07-01

    The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.

  18. Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source

    SciTech Connect

    Lord, J. S.; McKenzie, I.; Baker, P. J.; Cottrell, S. P.; Giblin, S. R.; Hillier, A. D.; Holsman, B. H.; King, P. J. C.; Nightingale, J. B.; Pratt, F. L.; Rhodes, N. J.; Blundell, S. J.; Lancaster, T.; Good, J.; Mitchell, R.; Owczarkowski, M.; Poli, S.; Scheuermann, R.; Salman, Z.

    2011-07-15

    The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.

  19. Spin-orbit coupling and electronic charge effects in Mott insulators

    DOE PAGES

    Zhu, Shan; Li, You -Quan; Batista, Cristian D.

    2014-11-04

    We derive the effective charge- and current-density operators for the strong-coupling limit of a single-band Mott insulator in the presence of spin-orbit coupling and show that the spin-orbit contribution to the effective charge density leads to novel mechanisms for multiferroic behavior. In some sense, these mechanisms are the electronic counterpart of the ionic-based mechanisms, which have been proposed for explaining the electric polarization induced by spiral spin orderings. In addition, the new electronic mechanisms are illustrated by considering cycloidal and proper-screw magnetic orderings on sawtooth and kagome lattices. As for the isotropic case, geometric frustration is crucial for achieving thismore » purely electronic coupling between spin and charge degrees of freedom.« less

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

    NASA Astrophysics Data System (ADS)

    Andreev, Pavel A.

    2017-02-01

    The hydrodynamics analysis of waves in a two-dimensional degenerate electron gas with a 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 media, the contribution of the transverse electric field is rather small, but it decreases the frequency of the extraordinary wave at small wave vectors. We show the decrease in the frequency of both the extraordinary (Langmuir) wave and the spin-electron acoustic wave due to the exchange interaction. Moreover, spin-electron acoustic waves have negative dispersion at the relatively large spin-polarization. The corresponding dispersion dependencies are presented and analyzed.

  1. Spin-orbit coupling and electronic charge effects in Mott insulators

    SciTech Connect

    Zhu, Shan; Li, You -Quan; Batista, Cristian D.

    2014-11-04

    We derive the effective charge- and current-density operators for the strong-coupling limit of a single-band Mott insulator in the presence of spin-orbit coupling and show that the spin-orbit contribution to the effective charge density leads to novel mechanisms for multiferroic behavior. In some sense, these mechanisms are the electronic counterpart of the ionic-based mechanisms, which have been proposed for explaining the electric polarization induced by spiral spin orderings. In addition, the new electronic mechanisms are illustrated by considering cycloidal and proper-screw magnetic orderings on sawtooth and kagome lattices. As for the isotropic case, geometric frustration is crucial for achieving this purely electronic coupling between spin and charge degrees of freedom.

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

    NASA Astrophysics Data System (ADS)

    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. Graphene single-electron transistor as a spin sensor for magnetic adsorbates

    NASA Astrophysics Data System (ADS)

    González, J. W.; Delgado, F.; Fernández-Rossier, J.

    2013-02-01

    We study single-electron transport through a graphene quantum dot with magnetic adsorbates. We focus on the relation between the spin order of the adsorbates and the linear conductance of the device. The electronic structure of the graphene dot with magnetic adsorbates is modeled through numerical diagonalization of a tight-binding model with an exchange potential. We consider several mechanisms by which the adsorbate magnetic state can influence transport in a single-electron transistor: tuning the addition energy, changing the tunneling rate, and in the case of spin-polarized electrodes, through magnetoresistive effects. Whereas the first mechanism is always present, the others require that the electrode has to have either an energy- or spin-dependent density of states. We find that graphene dots are optimal systems to detect the spin state of a few magnetic centers.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Evidence of secondary electron emission during PIII pulses as measured by calorimetric probe

    NASA Astrophysics Data System (ADS)

    Haase, Fabian; Manova, Darina; Mändl, Stephan; Kersten, Holger

    2016-09-01

    Secondary electrons are an ubiquitous nuisance during plasma immersion ion implantation (PIII) necessitating excessive current supplies and shielding for X-rays generated by them. However, additional effects - especially at low pulse voltages - can include interactions with the plasma and transient increases in the plasma density. Here, it is shown that the transient thermal flux associated with secondary electrons emitted from the pulsed substrate can be directly measured using a passive calorimetric probe mounted near the chamber wall away from the pulsed substrate holder. A small increase of a directed energy flux from the substrate towards the probe is consistently observed on top of the isotropic flux from the plasma surrounding the probe, scaling with pulse frequency, pulse voltage, pulse length - as well as depending on gas and substrate material. A strong correlation between voltage and substrate-probe distance is observed, which should allow further investigation of low energy electrons with the plasma itself.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Optimization of a solid-state electron spin qubit using gate set tomography

    NASA Astrophysics Data System (ADS)

    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.

  10. Creating intense polarized electron beam via laser stripping and spin-orbit interaction

    SciTech Connect

    Danilov, V.; Ptitsyn, V.; Gorlov, T.

    2010-12-01

    The recent advance in laser field make it possible to excite and strip electrons with definite spin from hydrogen atoms. The sources of hydrogen atoms with orders of magnitude higher currents (than that of the conventional polarized electron cathods) can be obtained from H{sup -} sources with good monochromatization. With one electron of H{sup -} stripped by a laser, the remained electron is excited to upper state (2P{sup 3/2} and 2P{sup 1/2}) by a circular polarization laser light from FEL. Then, it is excited to a high quantum number (n=7) with mostly one spin direction due to energy level split of the states with a definite direction of spin and angular momentum in an applied magnetic field and then it is stripped by a strong electric field of an RF cavity. This paper presents combination of lasers and fields to get high polarization and high current electron source.

  11. Quantitative analysis of polymer mixtures in solution by pulsed field-gradient spin echo NMR spectroscopy.

    PubMed

    Van Lokeren, Luk; Ben Sassi, Hanen; Van Assche, Guy; Ribot, François

    2013-06-01

    Pulsed Field-Gradient Spin Echo (PGSE) NMR, which associates to a spectral dimension the measure of diffusion coefficients, is a convenient technique for mixture analysis. Unfortunately, because of relaxation, the quantification of mixtures by PGSE NMR is far from straightforward for mixtures with strong spectral overlap. Antalek (J. Am. Chem. Soc. 128 (2006) 8402-8403) proposed a quantification strategy based on DECRA analysis and extrapolation to zero of the diffusion delay. More recently, Barrère et al. (J. Magn. Reson. 216 (2012) 201-208) presented a new strategy based also on DECRA and on the renormalization of the intensities using estimates of the T1 and T2 relaxation times. Here we report an alternative quantification approach in which the fractions are obtained by analyzing the PGSE attenuation profile with a general Stejskal-Tanner equation that explicitly includes the relaxation effects. The required values of T1 and T2 relaxation times are either independently measured with conventional sequences or determined, along with the fractions and the diffusion coefficients, from the simultaneous analysis of up to 6 PGSE data sets recorded with different diffusion delays. This method yields errors lower than 3% for the fractions, even for complete spectral overlap, as demonstrated on model binary and ternary mixtures of polystyrene in the case of a convection compensating double stimulated echo (DSTE) sequence.

  12. Molecular weight determination of block copolymers by pulsed gradient spin echo NMR.

    PubMed

    Barrère, Caroline; Mazarin, Michaël; Giordanengo, Rémi; Phan, Trang N T; Thévand, André; Viel, Stéphane; Charles, Laurence

    2009-10-01

    Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) is the technique of choice to achieve molecular weight data for synthetic polymers. Because the success of a MALDI-MS analysis critically depends on a proper matrix and cation selection, which in turn relates closely to the polymer chemical nature and size, prior estimation of the polymer size range strongly helps in rationalizing MALDI sample preparation. We recently showed how pulsed gradient spin echo (PGSE) nuclear magnetic resonance could be used as an advantageous alternative to size exclusion chromatography, to rationalize MALDI sample preparation and confidently interpret MALDI mass spectra for homopolymers. Our aim here is to extend this methodology to the demanding case of amphiphilic block copolymers, for which obtaining prior estimates on the Mw values appears as an even more stringent prerequisite. Specifically, by studying poly(ethylene oxide) polystyrene block copolymers of distinct molecular weights and relative block weight fractions, we show how PGSE data can be used to derive the block Mw values. In contrast to homopolymers, such determination requires not only properly recorded calibration curves for each of the polymers constituting the block copolymers but also an appropriate hydrodynamic model to correctly interpret the diffusion data.

  13. Experimental study of resolution of proton chemical shifts in solids: Combined multiple pulse NMR and magic-angle spinning

    SciTech Connect

    Ryan, L.M.; Taylor, R.E.; Paff, A.J.; Gerstein, B.C.

    1980-01-01

    High-resolution nuclear magnetic resonance spectra of protons in rigid, randomly oriented solids have been measured using combined homonuclear dipolar decoupling (via multiple pulse techniques) and attenuation of chemical shift anisotropies (via magic-angle sample spinning). Under those conditions, isotropic proton chemical shifts were recorded for a variety of chemical species, with individual linewidths varying from about 55 to 110 Hz (1--2 ppm). Residual line broadening was due predominately to (i) magnetic-field instability and inhomogeneity, (ii) unresolved proton--proton spin couplings, (iii) chemical shift dispersion, (iv) residual dipolar broadening, and (v) lifetime broadening under the multiple pulse sequences used. The magnitudes of those effects and the current limits of resolution for this experiment in our spectrometer have been investigated. The compounds studied included organic solids (4, 4'-dimethylbenzophenone, 2, 6-dimethylbenzoic acid, and aspirin), polymers (polystyrene and polymethylmethacrylate), and the vitrain portion of a bituminous coal.

  14. Energy- and momentum-resolved exchange and spin-orbit interaction in cobalt film by spin-polarized two-electron spectroscopy.

    PubMed

    Samarin, S; Artamonov, O M; Sergeant, A D; Stamps, R; Williams, J F

    2006-09-01

    Spontaneous ordering of electronic spins in ferromagnetic materials is one of the best known and most studied examples of quantum correlations. Exchange correlations are responsible for long range spin order and the spin-orbit interaction (SOI) can create preferred crystalline directions for the spins, i.e., magnetic anisotropy. Presented experimental data illustrate how novel spin-polarized two-electron spectroscopy in-reflection mode allows observation of the localization of spin-dependent interactions in energy-momentum space. Comparison of spin-orbit asymmetries in spectra of Co film and clean W(110) may indicate the presence of interface specific proximity effects providing important clues to the formation of preferred orientations for the magnetic moment of the Co film. These results may help to understand the microscopic origin of interface magnetic anisotropy.

  15. Electron spin echo modulation studies of doxylstearic acid spin probes in frozen vesicles: Interaction of the spin probe with D sub 2 O and effects of cholesterol addition

    SciTech Connect

    Hiff, T.; Kevan, L. )

    1989-02-23

    Electron spin echo studies have been carried out for a series of x-doxylstearic acid (x = 5, 7, 10, 12 and 16) spin probes in frozen deuteriated aqueous solutions of phospholipid vesicles and cationic dioctadecyldimethylammonium chloride (DODAC) vesicles. Modulation effects due to interactions of the nitroxide group of the spin probes with D{sub 2}O give information about the conformations of the probes and the degree of hydration of the surfactant headgroups as well as about the degree of packing of the alkyl chain. We show that DODAC headgroups are more hydrated than choline headgroups and that the doxylstearic acid probes show a larger tendency for bending in DODAC vesicles than in phospholipid vesicles. Upon addition of cholesterol into phospholipid vesicles, the headgroups are separated and their degree of hydration increases.

  16. Status of the pulsed magnetic field electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Mühle, C.; Ratzinger, U.; Bleuel, W.; Jöst, G.; Leible, K.; Schennach, S.; Wolf, B. H.

    1994-04-01

    Synchrotrons like the heavy-ion synchrotron SIS at GSI need an efficient low duty cycle injector (typical 1-pulse/s and 200-μs pulse length). To improve the peak current, an electron cyclotron resonance (ECR) ion source has been designed using a pulsed magnetic field (PuMa) to force ion extraction. We replaced the hexapole of a 10-GHz Minimafios ECR ion source by a vacuum chamber containing a water-cooled bilayered solenoid coil and a decapole permanent magnetic structure. A pulse line feeds the solenoid with a 250-μs pulse which increases the magnetic field in the minimum B region by 0.3 T. This process opens the magnetic bottle along the beam axis resulting in an extracted ion pulse. First tests of the PuMa ECR configuration in cw and pulsed operation are presented and analyzed.

  17. Discovery of Pulsed Gamma Rays and a New Spin-Down State of the LMC Pulsar B0540-69

    NASA Astrophysics Data System (ADS)

    Marshall, Francis E.; Guillemot, Lucas; Kust Harding, Alice; Martin, Pierrick; Smith, David A.

    2016-01-01

    The young pulsar B0540-69 in the nearby Large Magellanic Cloud has the third largest spin-down luminosity of the ~2500 known pulsars. Multi-year observations with Fermi/LAT using the ephemerides from RXTE reveal that B0540-69 is the most luminous gamma-ray pulsar ever detected. Its pulsed luminosity above 100 MeV is 5.7x1036 erg/s, about 20 times brighter than the Crab Pulsar, the next brightest. The pulse profile in gamma rays is similar to that seen in X-rays and optical light; the giant radio pulses align with the shoulders of the high-energy profiles. The detection of B0540-69 in gamma rays offers a new look at particle acceleration and emission in the magnetospheres of very young pulsars. Unpulsed gamma-ray emission has also been detected from PSR J0537-6910, another young pulsar in the LMC. The two pulsars contribute most of the gamma-ray emission from the 30 Doradus nebula, indicating that cosmic rays contribute only a small part. Recent monitoring of B0540-69 with the Swift/XRT shows a large, sudden, and persistent increase in the spin-down rate of B0540-69. The relative increase in the spin-down rate of 36% is unprecedented for B0540-69. No accompanying change in the spin rate was seen, and no change was seen in the pulsed X-ray emission from B0540-69 following the change in the spin-down rate. Such large relative changes in the spin-down rate are seen in the recently discovered class of ``intermittent pulsars'', and we compare the properties of B0540-69 to such pulsars. We consider possible changes in the magnetosphere of the pulsar that could cause such a large change in the spin-down rate. These changes are likely to result in a new braking index for the pulsar. We report on continued monitoring with Swift/XRT to determine the new braking index and to detect a new state change, should it occur.

  18. 3D Electron Spin Relaxation Control by Electric Field in Quantum Wells

    NASA Astrophysics Data System (ADS)

    Marie, Xavier

    2012-02-01

    We have measured the electron spin relaxation time in (111)-oriented GaAs quantum wells by time-resolved photoluminescence. By embedding the QWs in a PIN or NIP structure we demonstrate the tuning of the conduction band spin splitting and hence the spin relaxation time with an applied external electric field applied along the growth z direction . The application of an external electric field of 50 kV/cm yields a two-order of magnitude increase of the spin relaxation time which can reach values larger than 30 ns; this is a consequence of the electric field tuning of the spin-orbit conduction band splitting which can almost vanish when the Rashba term compensates exactly the Dresselhaus one [1]. The spin quantum beats measurements under transverse magnetic field prove that the D'Yakonov-Perel (DP) spin relaxation time is not only increased for the Sz electron spin component but also for both Sx and Sy. These results contrast drastically with the (001) and (110) quantum wells.The role of the cubic Dresselhaus terms on the spin relaxation anisotropy will finally be discussed. The tuning or suppression of the DP electron spin relaxation demonstrated here for GaAs/AlGaAs quantum wells grown on (111) substrates is also possible in many other III-V and II-VI zinc-blende nanostructures since the principle relies only on symmetry considerations. [4pt] [1] A. Balocchi, Q. H. Duong, P. Renucci, B. L. Liu, C. Fontaine, T. Amand, D. Lagarde, and X. Marie, Phys. Rev. Lett 107, 136604(2011)

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

    PubMed

    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

  20. Controlled laser plasma wakefield acceleration of electrons via colliding pulse injection in non-collinear geometry

    NASA Astrophysics Data System (ADS)

    Toth, Csaba; Nakamura, Kei; Geddes, Cameron; Panasenko, Dmitriy; Plateau, Guillaume; Matlis, Nicholas; Schroeder, Carl; Esarey, Eric; Leemans, Wim

    2007-11-01

    Colliding laser pulses [1] have been proposed as a method for controlling injection of electrons into a laser wakefield accelerator (LWFA) and hence producing high quality electron beams with energy spread below 1% and normalized emittances < 1 micron. The. One pulse excites a plasma wake, and a collinear pulse following behind it collides with a counterpropagating pulse forming a beat pattern that boosts background electrons into accelerating phase. A variation of the original method uses only two laser pulses [2] which may be non-collinear. The first pulse drives the wake, and beating of the trailing edge of this pulse with the colliding pulse injects electrons. Non-collinear injection avoids optical elements on the electron beam path (avoiding emittance growth). We report on progress of non-collinear experiments at LBNL, using the Ti:Sapphire laser at the LOASIS facility of LBNL. New results indicate that the electron beam properties are affected by the presence of the second beam. [1] E. Esarey, et al, Phys. Rev. Lett 79, 2682 (1997) [2] G. Fubiani, Phys. Rev. E 70, 016402 (2004)