WorldWideScience

Sample records for electron spin networks

  1. Spin electronics

    CERN Document Server

    Buhrman, Robert; Daughton, James; Molnár, Stephan; Roukes, Michael

    2004-01-01

    This report is a comparative review of spin electronics ("spintronics") research and development activities in the United States, Japan, and Western Europe conducted by a panel of leading U.S. experts in the field. It covers materials, fabrication and characterization of magnetic nanostructures, magnetism and spin control in magnetic nanostructures, magneto-optical properties of semiconductors, and magnetoelectronics and devices. The panel's conclusions are based on a literature review and a series of site visits to leading spin electronics research centers in Japan and Western Europe. The panel found that Japan is clearly the world leader in new material synthesis and characterization; it is also a leader in magneto-optical properties of semiconductor devices. Europe is strong in theory pertaining to spin electronics, including injection device structures such as tunneling devices, and band structure predictions of materials properties, and in development of magnetic semiconductors and semiconductor heterost...

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

    CERN Document Server

    Hu, H P

    2004-01-01

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

  3. Spin Electronics

    Science.gov (United States)

    2003-08-01

    spin resonance of rare earth and transition metal impurities in chalcopyrite semiconductors. They also have worked in diluted magnetic...past, the ferromagnetic injector had been a ferromagnetic metal or alloy containing 3d transition elements with fractional spin polarization of the...polarized carriers. There have been numerous attempts to inject transition metals or their alloys into semiconductors, either directly (Johnson and

  4. Concepts in spin electronics

    CERN Document Server

    2006-01-01

    A new branch of physics and nanotechnology called spin electronics has emerged, which aims at simultaneously exploiting the charge and spin of electrons in the same device. The aim of this book is to present new directions in the development of spin electronics in both the basic physics and the future electronics.

  5. PREFACE: Spin Electronics

    Science.gov (United States)

    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

  6. Spin-flipping polarized electrons

    Directory of Open Access Journals (Sweden)

    V. S. Morozov

    2001-10-01

    Full Text Available We recently used a prototype rf dipole magnet to study the spin flipping of a 669 MeV horizontally polarized electron beam stored in the presence of a nearly full Siberian snake in the new MIT-Bates storage ring. We flipped the spin by ramping the rf dipole's frequency through an rf-induced depolarizing resonance. After optimizing the frequency ramp parameters, we used multiple spin flipping to measure a spin-flip efficiency of 94.5±2.5%. The spin-flip efficiency was apparently limited by the field strength in the air-core prototype rf dipole magnet. This unexpectedly high efficiency indicates that very efficient spin flipping of the ring's stored polarized electron beam should be possible using the much stronger ferrite spin flipper, which is now being built by the University of Michigan's Spin Physics Center.

  7. Spin transport in tilted electron vortex beams

    OpenAIRE

    Basu, Banasri; Chowdhury, Debashree

    2016-01-01

    In this paper we have enlightened the spin related issues of tilted Electron vortex beams. We have shown that in the skyrmionic model of electron we can have the spin Hall current considering the tilted type of electron vortex beam. We have considered the monopole charge of the tilted vortex as time dependent and through the time variation of the monopole charge we can explain the spin Hall effect of electron vortex beams. Besides, with an external magnetic field we can have a spin filter con...

  8. Designing Electron Spin Textures and Spin Interferometers by Shape Deformations

    NARCIS (Netherlands)

    Ying, Zu-Jian; Gentile, Paola; Ortix, Carmine; Cuoco, Mario

    2016-01-01

    We demonstrate that the spin orientation of an electron propagating in a one-dimensional nanostructure with Rashba spin-orbit (SO) coupling can be manipulated on demand by changing the geometry of the nanosystem. Shape deformations that result in a non-uniform curvature give rise to complex

  9. Three-electron spin qubits

    Science.gov (United States)

    Russ, Maximilian; Burkard, Guido

    2017-10-01

    The goal of this article is to review the progress of three-electron spin qubits from their inception to the state of the art. We direct the main focus towards the exchange-only qubit (Bacon et al 2000 Phys. Rev. Lett. 85 1758-61, DiVincenzo et al 2000 Nature 408 339) and its derived versions, e.g. the resonant exchange (RX) qubit, but we also discuss other qubit implementations using three electron spins. For each three-spin qubit we describe the qubit model, the envisioned physical realization, the implementations of single-qubit operations, as well as the read-out and initialization schemes. Two-qubit gates and decoherence properties are discussed for the RX qubit and the exchange-only qubit, thereby completing the list of requirements for quantum computation for a viable candidate qubit implementation. We start by describing the full system of three electrons in a triple quantum dot, then discuss the charge-stability diagram, restricting ourselves to the relevant subsystem, introduce the qubit states, and discuss important transitions to other charge states (Russ et al 2016 Phys. Rev. B 94 165411). Introducing the various qubit implementations, we begin with the exchange-only qubit (DiVincenzo et al 2000 Nature 408 339, Laird et al 2010 Phys. Rev. B 82 075403), followed by the RX qubit (Medford et al 2013 Phys. Rev. Lett. 111 050501, Taylor et al 2013 Phys. Rev. Lett. 111 050502), the spin-charge qubit (Kyriakidis and Burkard 2007 Phys. Rev. B 75 115324), and the hybrid qubit (Shi et al 2012 Phys. Rev. Lett. 108 140503, Koh et al 2012 Phys. Rev. Lett. 109 250503, Cao et al 2016 Phys. Rev. Lett. 116 086801, Thorgrimsson et al 2016 arXiv:1611.04945). The main focus will be on the exchange-only qubit and its modification, the RX qubit, whose single-qubit operations are realized by driving the qubit at its resonant frequency in the microwave range similar to electron spin resonance. Two different types of two-qubit operations are presented for the exchange

  10. Versatile spin-polarized electron source

    Science.gov (United States)

    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.

  11. Holographic spin networks from tensor network states

    Science.gov (United States)

    Singh, Sukhwinder; McMahon, Nathan A.; Brennen, Gavin K.

    2018-01-01

    In the holographic correspondence of quantum gravity, a global on-site symmetry at the boundary generally translates to a local gauge symmetry in the bulk. We describe one way how the global boundary on-site symmetries can be gauged within the formalism of the multiscale renormalization ansatz (MERA), in light of the ongoing discussion between tensor networks and holography. We describe how to "lift" the MERA representation of the ground state of a generic one dimensional (1D) local Hamiltonian, which has a global on-site symmetry, to a dual quantum state of a 2D "bulk" lattice on which the symmetry appears gauged. The 2D bulk state decomposes in terms of spin network states, which label a basis in the gauge-invariant sector of the bulk lattice. This decomposition is instrumental to obtain expectation values of gauge-invariant observables in the bulk, and also reveals that the bulk state is generally entangled between the gauge and the remaining ("gravitational") bulk degrees of freedom that are not fixed by the symmetry. We present numerical results for ground states of several 1D critical spin chains to illustrate that the bulk entanglement potentially depends on the central charge of the underlying conformal field theory. We also discuss the possibility of emergent topological order in the bulk using a simple example, and also of emergent symmetries in the nongauge (gravitational) sector in the bulk. More broadly, our holographic model translates the MERA, a tensor network state, to a superposition of spin network states, as they appear in lattice gauge theories in one higher dimension.

  12. Electron Spins in Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Hanson, R.

    2005-01-01

    This thesis describes a series of experiments aimed at understanding and controlling the behavior of the spin degree of freedom of single electrons, confined in semiconductor quantum dots. This research work is motivated by the prospects of using the electron spin as a quantum bit (qubit), the basic

  13. Theory of electron spin echoes in solids

    CERN Document Server

    Asadullina, N Y; Asadullin, Y Y

    2002-01-01

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

  14. Theoretical foundations of electron spin resonance

    CERN Document Server

    Harriman, John E

    2013-01-01

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

  15. Spin current swapping and Hanle spin Hall effect in a two-dimensional electron gas

    NARCIS (Netherlands)

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

    2015-01-01

    We analyze the effect known as “spin current swapping” (SCS) due to electron-impurity scattering in a uniform spin-polarized two-dimensional electron gas. In this effect a primary spin current Jai (lower index for spatial direction, upper index for spin direction) generates a secondary spin current

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

    Science.gov (United States)

    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.

  17. Spin orbit torque based electronic neuron

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-06

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

  18. Quantum Computing with an Electron Spin Ensemble

    DEFF Research Database (Denmark)

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

    2009-01-01

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

  19. Spin dependent electron transport in nanostructures

    Science.gov (United States)

    Yanik, Ahmet Ali

    2007-12-01

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

  20. Spin Polarized Electron Probes and Magnetic Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Electron-spin resonance, nuclear polarization, and spin relaxation of spin-polarized atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Statt, B.W.; Berlinsky, A.J.; Hardy, W.N.

    1985-03-01

    Electron-spin-resonance measurements of spin-polarized hydrogen are presented. Excellent signal-to-noise ratio, previously obtainable only in pressure studies, allows quantitative fits to the separate a and b (proton up and down) decays of the nuclear-spin-polarized samples, yielding separate temperature dependences of the recombination rate constants K/sub a/a and K/sub a/b. Spin relaxation due to magnetic particles in the substrate is studied for different thicknesses of solid H/sub 2/ wall coating, and the results are compared with a new theoretical model.

  2. Logical spin-filtering in a triangular network of quantum nanorings with a Rashba spin-orbit interaction

    Science.gov (United States)

    Dehghan, E.; Sanavi Khoshnoud, D.; Naeimi, A. S.

    2018-01-01

    The spin-resolved electron transport through a triangular network of quantum nanorings is studied in the presence of Rashba spin-orbit interaction (RSOI) and a magnetic flux using quantum waveguide theory. This study illustrates that, by tuning Rashba constant, magnetic flux and incoming electron energy, the triangular network of quantum rings can act as a perfect logical spin-filtering with high efficiency. By changing in the energy of incoming electron, at a proper value of the Rashba constant and magnetic flux, a reverse in the direction of spin can take place in the triangular network of quantum nanorings. Furthermore, the triangular network of quantum nanorings can be designed as a device and shows several simultaneous spintronic properties such as spin-splitter and spin-inverter. This spin-splitting is dependent on the energy of the incoming electron. Additionally, different polarizations can be achieved in the two outgoing leads from an originally incoming spin state that simulates a Stern-Gerlach apparatus.

  3. Spin-polarized free electron beam interaction with radiation and superradiant spin-flip radiative emission

    Directory of Open Access Journals (Sweden)

    A. Gover

    2006-06-01

    Full Text Available The problems of spin-polarized free-electron beam interaction with electromagnetic wave at electron-spin resonance conditions in a magnetic field and of superradiant spin-flip radiative emission are analyzed in the framework of a comprehensive classical model. The spontaneous emission of spin-flip radiation from electron beams is very weak. We show that the detectivity of electron spin resonant spin-flip and combined spin-flip/cyclotron-resonance-emission radiation can be substantially enhanced by operating with ultrashort spin-polarized electron beam bunches under conditions of superradiant (coherent emission. The proposed radiative spin-state modulation and the spin-flip radiative emission schemes can be used for control and noninvasive diagnostics of polarized electron/positron beams. Such schemes are of relevance in important scattering experiments off nucleons in nuclear physics and off magnetic targets in condensed matter physics.

  4. Electronic spin precession in semiconductor quantum dots with spin-orbit coupling

    Science.gov (United States)

    Valín-Rodríguez, Manuel; Puente, Antonio; Serra, Llorenç; Lipparini, Enrico

    2002-12-01

    The electronic spin precession in semiconductor dots is strongly affected by the spin-orbit coupling. We present a theory of the electronic spin resonance at low magnetic fields that predicts a strong dependence on the dot occupation, the magnetic field and the spin-orbit coupling strength. Coulomb interaction effects are also taken into account in a numerical approach.

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

    Science.gov (United States)

    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.

  6. Robust quantum-network memory using decoherence-protected subspaces of nuclear spins

    NARCIS (Netherlands)

    Reiserer, A.A.; Kalb, N.; Blok, M.S.; van Bemmelen, Koen J M; Taminiau, T.H.; Hanson, R.; Twitchen, Daniel J.; Markham, Matthew

    2016-01-01

    The realization of a network of quantum registers is an outstanding challenge in quantum science and technology. We experimentally investigate a network node that consists of a single nitrogen-vacancy center electronic spin hyperfine coupled to nearby nuclear spins. We demonstrate individual

  7. Spin filtration of unpolarized electrons by impurity centers in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bobin, E. G.; Berdinskiy, V. L., E-mail: bvl@unpk.osu.ru [Orenburg State University (Russian Federation)

    2011-11-15

    It is shown that unpolarized paramagnetic centers can implement the spin filtration of unpolarized conduction electrons in semiconductors. This ability of paramagnetic centers is caused by the difference in the spin evolution of the states of electron-paramagnetic-center pairs and by the spin selectivity of electron capture exclusively from singlet pairs. The electron spin polarization should be opposite to the paramagneticcenter polarization. To implement spin filtration, an external magnetic field is necessary. The polarization can attain the largest values ({approx}10%) if the probability of spin-selective electron capture from singlet pairs exceeds the pair-decay rate by a factor of 5-7.

  8. Structurally Dynamic Spin Market Networks

    Science.gov (United States)

    Horváth, Denis; Kuscsik, Zoltán

    The agent-based model of stock price dynamics on a directed evolving complex network is suggested and studied by direct simulation. The stationary regime is maintained as a result of the balance between the extremal dynamics, adaptivity of strategic variables and reconnection rules. The inherent structure of node agent "brain" is modeled by a recursive neural network with local and global inputs and feedback connections. For specific parametric combination the complex network displays small-world phenomenon combined with scale-free behavior. The identification of a local leader (network hub, agent whose strategies are frequently adapted by its neighbors) is carried out by repeated random walk process through network. The simulations show empirically relevant dynamics of price returns and volatility clustering. The additional emerging aspects of stylized market statistics are Zipfian distributions of fitness.

  9. Modelling Electron Spin Accumulation in a Metallic Nanoparticle

    OpenAIRE

    Wei, Y.G.; Malec, C. E.; Davidović, D.

    2008-01-01

    A model describing spin-polarized current via discrete energy levels of a metallic nanoparticle, which has strongly asymmetric tunnel contacts to two ferromagnetic leads, is presented. In absence of spin-relaxation, the model leads to a spin-accumulation in the nanoparticle, a difference ($\\Delta\\mu$) between the chemical potentials of spin-up and spin-down electrons, proportional to the current and the Julliere's tunnel magnetoresistance. Taking into account an energy dependent spin-relaxati...

  10. Electron Doping a Kagome Spin Liquid

    Directory of Open Access Journals (Sweden)

    Z. A. Kelly

    2016-10-01

    Full Text Available Herbertsmithite, ZnCu_{3}(OH_{6}Cl_{2}, 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 ZnLi_{x}Cu_{3}(OH_{6}Cl_{2} from x=0 to x=1.8 (3/5 per Cu^{2+}. 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. Spin Echo of a Single Electron Spin in a Quantum Dot

    NARCIS (Netherlands)

    Koppens, F.H.L.; Nowack, K.C.; Vandersypen, L.M.K.

    2008-01-01

    We report a measurement of the spin-echo decay of a single electron spin confined in a semiconductor quantum dot. When we tip the spin in the transverse plane via a magnetic field burst, it dephases in 37 ns due to the Larmor precession around a random effective field from the nuclear spins in the

  12. Electronic spin storage in an electrically readable nuclear spin memory with a lifetime >100 seconds.

    Science.gov (United States)

    McCamey, D R; Van Tol, J; Morley, G W; Boehme, C

    2010-12-17

    Electron spins are strong candidates with which to implement spintronics because they are both mobile and able to be manipulated. The relatively short lifetimes of electron spins, however, present a problem for the long-term storage of spin information. We demonstrated an ensemble nuclear spin memory in phosphorous-doped silicon, which can be read out electrically and has a lifetime exceeding 100 seconds. The electronic spin information can be mapped onto and stored in the nuclear spin of the phosphorus donors, and the nuclear spins can then be repetitively read out electrically for time periods that exceed the electron spin lifetime. We discuss how this memory can be used in conjunction with other silicon spintronic devices.

  13. Spin current swapping and Hanle spin Hall effect in a two-dimensional electron gas

    Science.gov (United States)

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

    2015-07-01

    We analyze the effect known as "spin current swapping" (SCS) due to electron-impurity scattering in a uniform spin-polarized two-dimensional electron gas. In this effect a primary spin current Jia (lower index for spatial direction, upper index for spin direction) generates a secondary spin current Jai if i ≠a , or Jjj, with j ≠i , if i =a . Contrary to naive expectation, the homogeneous spin current associated with the uniform drift of the spin polarization in the electron gas does not generate a swapped spin current by the SCS mechanism. Nevertheless, a swapped spin current will be generated, if a magnetic field is present, by a completely different mechanism, namely, the precession of the spin Hall spin current in the magnetic field. We refer to this second mechanism as Hanle spin Hall effect, and we notice that it can be observed in an experiment in which a homogeneous drift current is passed through a uniformly magnetized electron gas. In contrast to this, we show that an unambiguous observation of SCS requires inhomogeneous spin currents, such as those that are associated with spin diffusion in a metal, and no magnetic field. An experimental setup for the observation of the SCS is therefore proposed.

  14. A molecular quantum spin network controlled by a single qubit.

    Science.gov (United States)

    Schlipf, Lukas; Oeckinghaus, Thomas; Xu, Kebiao; Dasari, Durga Bhaktavatsala Rao; Zappe, Andrea; de Oliveira, Felipe Fávaro; Kern, Bastian; Azarkh, Mykhailo; Drescher, Malte; Ternes, Markus; Kern, Klaus; Wrachtrup, Jörg; Finkler, Amit

    2017-08-01

    Scalable quantum technologies require an unprecedented combination of precision and complexity for designing stable structures of well-controllable quantum systems on the nanoscale. It is a challenging task to find a suitable elementary building block, of which a quantum network can be comprised in a scalable way. We present the working principle of such a basic unit, engineered using molecular chemistry, whose collective control and readout are executed using a nitrogen vacancy (NV) center in diamond. The basic unit we investigate is a synthetic polyproline with electron spins localized on attached molecular side groups separated by a few nanometers. We demonstrate the collective readout and coherent manipulation of very few (≤ 6) of these S = 1/2 electronic spin systems and access their direct dipolar coupling tensor. Our results show that it is feasible to use spin-labeled peptides as a resource for a molecular qubit-based network, while at the same time providing simple optical readout of single quantum states through NV magnetometry. This work lays the foundation for building arbitrary quantum networks using well-established chemistry methods, which has many applications ranging from mapping distances in single molecules to quantum information processing.

  15. Spin-to-orbital angular momentum conversion and spin-polarization filtering in electron beams.

    Science.gov (United States)

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

    2012-01-27

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

  16. Few electron quantum dot coupling to donor implanted electron spins

    Science.gov (United States)

    Rudolph, Martin; Harvey-Collard, Patrick; Neilson, Erik; Gamble, John; Muller, Richard; Jacobson, Toby; Ten-Eyck, Greg; Wendt, Joel; Pluym, Tammy; Lilly, Michael; Carroll, Malcolm

    2015-03-01

    Donor-based Si qubits are receiving increased interest because of recent demonstrations of high fidelity electron or nuclear spin qubits and their coupling. Quantum dot (QD) mediated interactions between donors are of interest for future coupling of two donors. We present experiment and modeling of a polysilicon/Si MOS QD, charge-sensed by a neighboring many electron QD, capable of coupling to one or two donor implanted electron spins (D) while tuned to the few electron regime. The unique design employs two neighboring gated wire FETs and self-aligned implants, which supports many configurations of implanted donors. We can access the (0,1) ⇔(1,0) transition between the D and QD, as well as the resonance condition between the few electron QD and two donors ((0,N,1) ⇔(0,N +1,0) ⇔(1,N,0)). We characterize capacitances and tunnel rate behavior combined with semi-classical and full configuration interaction simulations to study the energy landscape and kinetics of D-QD transitions. 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 operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

  17. Resonance fluorescence and electron spin in semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yong

    2009-11-18

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

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

    DEFF Research Database (Denmark)

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

    2008-01-01

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

  19. Spin-resolved inelastic electron scattering by spin waves in noncollinear magnets

    Science.gov (United States)

    dos Santos, Flaviano José; dos Santos Dias, Manuel; Guimarães, Filipe Souza Mendes; Bouaziz, Juba; Lounis, Samir

    2018-01-01

    Topological noncollinear magnetic phases of matter are at the heart of many proposals for future information nanotechnology, with novel device concepts based on ultrathin films and nanowires. Their operation requires understanding and control of the underlying dynamics, including excitations such as spin waves. So far, no experimental technique has attempted to probe large wave-vector spin waves in noncollinear low-dimensional systems. In this paper, we explain how inelastic electron scattering, being suitable for investigations of surfaces and thin films, can detect the collective spin-excitation spectra of noncollinear magnets. To reveal the particularities of spin waves in such noncollinear samples, we propose the usage of spin-polarized electron-energy-loss spectroscopy augmented with a spin analyzer. With the spin analyzer detecting the polarization of the scattered electrons, four spin-dependent scattering channels are defined, which allow us to filter and select specific spin-wave modes. We take as examples a topological nontrivial skyrmion lattice, a spin-spiral phase, and the conventional ferromagnet. Then we demonstrate that, counterintuitively and in contrast to the ferromagnetic case, even non-spin-flip processes can generate spin waves in noncollinear substrates. The measured dispersion and lifetime of the excitation modes permit us to fingerprint the magnetic nature of the substrate.

  20. Spin relaxation via exchange with donor impurity-bound electrons

    Science.gov (United States)

    Appelbaum, Ian

    In the Bir-Aronov-Pikus depolarization process affecting conduction electrons in p-type cubic semiconductors, spin relaxation is driven by exchange with short-lived valence band hole states. We have identified an analogous spin relaxation mechanism in nominally undoped silicon at low temperatures, when many electrons are bound to dilute dopant ion potentials. Inelastic scattering with externally injected conduction electrons accelerated by electric fields can excite transitions into highly spin-orbit-mixed bound excited states, driving strong spin relaxation of the conduction electrons via exchange interaction. We reveal the consequences of this spin depolarization mechanism both below and above the impact ionization threshold, where conventional charge and spin transport are restored. Based upon: Lan Qing, Jing Li, Ian Appelbaum, and Hanan Dery, Phys Rev. B 91, 241405(R) (2015). We acknowledge support from NSF, DTRA, and ONR.

  1. Spin dynamics in electron synchrotrons; Spindynamik in Elektronensynchrotronen

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Jan Felix

    2017-07-14

    Providing spin polarized particle beams with circular accelerators requires the consideration of depolarizing resonances which may significantly reduce the desired degree of polarization at specific beam energies. The corresponding spin dynamical effects are typically analyzed with numerical methods. In case of electron beams the influence of the emission of synchrotron radiation has to be taken into account. On short timescales, as in synchrotrons with a fast energy ramp or in damping rings, spin dynamics are investigated with spin tracking algorithms. This thesis presents the spin tracking code Polematrix as a versatile tool to study the impact of synchrotron radiation on spin dynamics. Spin tracking simulations have been performed based on the well established particle tracking code Elegant. The numerical studies demonstrate effects which are responsible for beam depolarization: Synchrotron side bands of depolarizing resonances and decoherence of spin precession. Polematrix can be utilized for any electron accelerator with minimal effort as it imports lattice files from the tracking programs MAD-X or Elegant. Polematrix has been published as open source software. Currently, the Electron Stretcher Accelerator ELSA at Bonn University is the only electron synchrotron worldwide providing a polarized beam. Integer and intrinsic depolarizing resonances are compensated with dedicated countermeasures during the fast energy ramp. Polarization measurements from ELSA demonstrate the particular spin dynamics of electrons and confirm the results of the spin tracking code Polematrix.

  2. Spin dynamics of equilibrium electrons in gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Georg Martin

    2010-12-08

    In this dissertation, spin noise spectroscopy is applied to study spin dynamics in GaAs based semiconductor structures close to thermal equilibrium. Semiconductor spin noise spectroscopy measures the stochastic spin polarization of the electron ensemble via off-resonant Faraday rotation. Correspondingly, no energy has to be deposited in the sample system contrary to other experimental techniques, in which the dephasing or the depolarization of an artificially injected spin polarization is measured. Since the spin fluctuations are measured in real-time, spin noise spectroscopy had been hitherto limited to frequencies below 1 GHz. This thesis introduces the experimental advancement of ultrafast spin noise spectroscopy, in which the fluctuations are probed by pulsed light, and detection of spin noise at frequencies up to 16 GHz is demonstrated. These frequencies exceed the bandwidth of the photoreceiver by a factor of around 200. To further explore the limitations of the finite bandwidth of the detection system, electrical frequency mixing is applied for down-conversion of the electrical spin noise signal. Furthermore, spin noise measurements are simulated revealing that also ultrafast digitizers with low resolution can be utilized for spectral analysis in spin noise spectroscopy without any significant loss of sensitivity. The spin dynamics in a symmetrically grown, modulation-doped, (110)-oriented GaAs/AlGaAs multiple quantum well structure are investigated in this work. This experiment represents the first spin noise measurements on a semiconductor system of reduced effective dimensionality. The Dyakonov-Perel mechanism that usually dominates spin dephasing of free electrons in GaAs is ineffective in (110)-oriented structures for spins along the growth direction. Nevertheless, the correspondingly anticipated long spin dephasing times in (110) GaAs/AlGaAs quantum wells at low temperatures are not accessible with conventional experiments that rely on optical spin

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

    Science.gov (United States)

    Hao, Xiaojie; Ruskov, Rusko; Xiao, Ming; Tahan, Charles; Jiang, HongWen

    2014-05-14

    Silicon quantum dots are a leading approach for solid-state quantum bits. However, developing this technology is complicated by the multi-valley nature of silicon. Here we observe transport of individual electrons in a silicon CMOS-based double quantum dot under electron spin resonance. An anticrossing of the driven dot energy levels is observed when the Zeeman and valley splittings coincide. A detected anticrossing splitting of 60 MHz is interpreted as a direct measure of spin and valley mixing, facilitated by spin-orbit interaction in the presence of non-ideal interfaces. A lower bound of spin dephasing time of 63 ns is extracted. We also describe a possible experimental evidence of an unconventional spin-valley blockade, despite the assumption of non-ideal interfaces. This understanding of silicon spin-valley physics should enable better control and read-out techniques for the spin qubits in an all CMOS silicon approach.

  4. Coherent electron-spin-resonance manipulation of three individual spins in a triple quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Noiri, A. [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Yoneda, J.; Nakajima, T.; Otsuka, T.; Delbecq, M. R.; Takeda, K.; Tarucha, S. [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); RIKEN, Center for Emergent Matter Science (CEMS), Wako-shi, Saitama 351-0198 (Japan); Amaha, S.; Allison, G. [RIKEN, Center for Emergent Matter Science (CEMS), Wako-shi, Saitama 351-0198 (Japan); Ludwig, A.; Wieck, A. D. [Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

    2016-04-11

    Quantum dot arrays provide a promising platform for quantum information processing. For universal quantum simulation and computation, one central issue is to demonstrate the exhaustive controllability of quantum states. Here, we report the addressable manipulation of three single electron spins in a triple quantum dot using a technique combining electron-spin-resonance and a micro-magnet. The micro-magnet makes the local Zeeman field difference between neighboring spins much larger than the nuclear field fluctuation, which ensures the addressable driving of electron-spin-resonance by shifting the resonance condition for each spin. We observe distinct coherent Rabi oscillations for three spins in a semiconductor triple quantum dot with up to 25 MHz spin rotation frequencies. This individual manipulation over three spins enables us to arbitrarily change the magnetic spin quantum number of the three spin system, and thus to operate a triple-dot device as a three-qubit system in combination with the existing technique of exchange operations among three spins.

  5. Electron vortex beams in a magnetic field and spin filter

    OpenAIRE

    Chowdhury, Debashree; Basu, Banasri; Bandyopadhyay, Pratul

    2015-01-01

    We investigate the propagation of electron vortex beams in a magnetic field. It is pointed out that when electron vortex beams carrying orbital angular momentum propagate in a magnetic field, the Berry curvature associated with the scalar electron moving in a cyclic path around the vortex line is modified from that in free space. This alters the spin-orbit interaction, which affects the propagation of nonparaxial beams. The electron vortex beams with tilted vortex lead to spin Hall effect in ...

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

    Science.gov (United States)

    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).

  7. The Electron Spin in Silicon, a Promising Qubit

    Science.gov (United States)

    Yablonovitch, Eli

    2003-03-01

    The electron spin in Silicon has emerged as a leading qubit candidate. The T2 lifetime of electron spins in Silicon has now been measured to be >7msec at 8K. It is also clear that more patient experiments, that allow for extremely slow relaxation, will permit observations at 4K where lifetimes of T2 1sec should be observable. Electron spins can be rapidly rotated in 1nsec leading to a very favorable figure of merit for quantum information processing. There are problems however. While single spins have been detected in condensed matter, single spin states have not yet been measured in a semiconductor. I will describe transistor-like devices that should make it possible to routinely measure single spin states as part of conventional silicon circuitry. Among other important issues are: 1. The non-exponential decay of electron spin coherence, that makes it necessary to understand the initial 0.1coherence rather than the 1/e time. 2. The imminent availability of g-tensor modulation to create rapid gate induced spin rotations in a field effect transistor structure. 3. The possibility of transferring photon polarization directly to photo-electron spin polarization in an entanglement preserving photo-detector.

  8. Electron spin dynamics in cubic GaN

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2017-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Stano, P.

    2007-01-15

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

  11. Inductive-detection electron-spin resonance spectroscopy with 65 spins/ √{Hz } sensitivity

    Science.gov (United States)

    Probst, S.; Bienfait, A.; Campagne-Ibarcq, P.; Pla, J. J.; Albanese, B.; Da Silva Barbosa, J. F.; Schenkel, T.; Vion, D.; Esteve, D.; Mølmer, K.; Morton, J. J. L.; Heeres, R.; Bertet, P.

    2017-11-01

    We report electron spin resonance spectroscopy measurements performed at millikelvin temperatures in a custom-built spectrometer comprising a superconducting micro-resonator at 7 GHz and a Josephson parametric amplifier. Owing to the small ( ˜10-12λ3 ) magnetic resonator mode volume and to the low noise of the parametric amplifier, the spectrometer's single shot sensitivity reaches 260 ± 40 spins/echo translating into 65 ±10 spins/√{Hz } for repeated acquisition.

  12. Modeling electron-spin accumulation in a metallic nanoparticle

    Science.gov (United States)

    Wei, Y. G.; Malec, C. E.; Davidović, D.

    2008-07-01

    A model describing spin-polarized current via discrete energy levels of a metallic nanoparticle, which has strongly asymmetric tunnel contacts to two ferromagnetic leads, is presented. In absence of spin relaxation, the model leads to a spin accumulation in the nanoparticle, a difference (Δμ) between the chemical potentials of spin-up and spin-down electrons, proportional to the current and the Julliere tunnel magnetoresistance. Taking into account an energy dependent spin-relaxation rate Ω(ω) , Δμ as a function of bias voltage (V) exhibits a crossover from linear to a much weaker dependence, when |e|Ω(Δμ) equals the spin-polarized current through the nanoparticle. Assuming that the spin relaxation takes place via electron-phonon emission and Elliot-Yafet mechanism, the model leads to a crossover from linear to V1/5 dependence. The crossover explains recent measurements of the saturation of the spin-polarized current with V in aluminum nanoparticles, and leads to the spin-relaxation rate of ≈1.6MHz in an aluminum nanoparticle of diameter 6 nm, for a transition with an energy difference of one level spacing.

  13. Engineering the spin polarization of one-dimensional electrons

    Science.gov (United States)

    Yan, C.; Kumar, S.; Thomas, K.; See, P.; Farrer, I.; Ritchie, D.; Griffiths, J.; Jones, G.; Pepper, M.

    2018-02-01

    We present results of magneto-focusing on the controlled monitoring of spin polarization within a one-dimensional (1D) channel, and its subsequent effect on modulating the spin–orbit interaction (SOI) in a 2D GaAs electron gas. We demonstrate that electrons within a 1D channel can be partially spin polarized as the effective length of the 1D channel is varied in agreement with the theoretical prediction. Such polarized 1D electrons when injected into a 2D region result in a split in the odd-focusing peaks, whereas the even peaks remain unaffected (single peak). On the other hand, the unpolarized electrons do not affect the focusing spectrum and the odd and even peaks remain as single peaks, respectively. The split in odd-focusing peaks is evidence of direct measurement of spin polarization within a 1D channel, where each sub-peak represents the population of a particular spin state. Confirmation of the spin splitting is determined by a selective modulation of the focusing peaks due to the Zeeman energy in the presence of an in-plane magnetic field. We suggest that the SOI in the 2D regime is enhanced by a stream of polarized 1D electrons. The spatial control of spin states of injected 1D electrons and the possibility of tuning the SOI may open up a new regime of spin-engineering with application in future quantum information schemes.

  14. Current-induced spin polarization in a spin-polarized two-dimensional electron gas with spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.M., E-mail: cmwangsjtu@gmail.co [School of Physics and Electrical Engineering, Anyang Normal University, Anyang 455000 (China); Pang, M.Q. [School of Physics and Electrical Engineering, Anyang Normal University, Anyang 455000 (China); Liu, S.Y.; Lei, X.L. [Department of Physics, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030 (China)

    2010-02-22

    The current-induced spin polarization (CISP) is investigated in a combined Rashba-Dresselhaus spin-orbit-coupled two-dimensional electron gas, subjected to a homogeneous out-of-plane magnetization. It is found that, in addition to the usual collision-related in-plane parts of CISP, there are two impurity-density-free contributions, arising from intrinsic and disorder-mediated mechanisms. The intrinsic parts of spin polarization are related to the Berry curvature, analogous with the anomalous and spin Hall effects. For short-range collision, the disorder-mediated spin polarizations completely cancel the intrinsic ones and the total in-plane components of CISP equal those for systems without magnetization. However, for remote disorders, this cancellation does not occur and the total in-plane components of CISP strongly depend on the spin-orbit interaction coefficients and magnetization for both pure Rashba and combined Rashba-Dresselhaus models.

  15. Precession mechanism of spin relaxation at frequent electron-electron collisions

    CERN Document Server

    Glazov, M M

    2002-01-01

    It is shown that the spin relaxation mechanism in the two-dimensional electron gas, is controlled not only through the electron pulse relaxation processes, determining the mobility, but through the electron-electron collisions as well. It is decided to use the kinetic equation, describing the electron spin mixing in the k-space, for determining the spin relaxation time tau sub s at frequent electron-electron collisions. The tau sub s time is calculated for the nondegenerated electron gas both with an account and with no account of the exchange interaction

  16. Electronic spin drift in graphene field-effect transistors

    NARCIS (Netherlands)

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

    2008-01-01

    We studied the drift of electron spins under an applied dc electric field in single layer graphene spin valves in a field-effect transport geometry at room temperature. In the metallic conduction regime (n similar or equal to 3.5x10(16) m(-2)), for dc fields of about +/- 70 kV/m applied between the

  17. Electron refrigeration in hybrid structures with spin-split superconductors

    Science.gov (United States)

    Rouco, M.; Heikkilä, T. T.; Bergeret, F. S.

    2018-01-01

    Electron tunneling between superconductors and normal metals has been used for an efficient refrigeration of electrons in the latter. Such cooling is a nonlinear effect and usually requires a large voltage. Here we study the electron cooling in heterostructures based on superconductors with a spin-splitting field coupled to normal metals via spin-filtering barriers. The cooling power shows a linear term in the applied voltage. This improves the coefficient of performance of electron refrigeration in the normal metal by shifting its optimum cooling to lower voltage, and also allows for cooling the spin-split superconductor by reverting the sign of the voltage. We also show how tunnel coupling spin-split superconductors with regular ones allows for a highly efficient refrigeration of the latter.

  18. Resistive Detection of Single Electron Motion and Spin Resonance

    Science.gov (United States)

    Jiang, Hongwen; Yablonovitch, Eli; Wang, Kang; Roychowdhury, Vwani; Divincenzo, David

    2000-03-01

    For any of the quantum computing proposals involving spin states in solids, the spin orientations of individual qubit has to be measured at the end of the operations. In the design of the spin-resonance-transistors, a conventional field-effect-transistor (FET) channel is used to accomplish this seemingly almost impossible task. Toward this end, we have performed a sequence of exploratory experiments in Si and GaAs based FET devices. Current noise spectrum in a short channel Si FET, known as the random telegraph signal, is measured for different temperatures and gate voltages. Using a GaAs/AlGaAs heterostructure, we have detected electron spin resonance of a spin-split Landau level by a transport measurement in microwave fields. The extension of our results to the actual implementation of the spin-resonance-transistors will be discussed.

  19. Electron spin dynamics due to hyperfine coupling in quantum dots

    Science.gov (United States)

    Woods, L. M.; Reinecke, T. L.; Rajagopal, A. K.

    2008-02-01

    The dynamics of spins in semiconductor quantum dots often is controlled by their hyperfine coupling to nuclear spins. We develop a straightforward and efficient approach to describe the dynamics and the effective decoherence of the electron spins due to hyperfine coupling in realistic quantum dots. Systems with a large number of nuclei and an arbitrary initial nuclear polarization for which the number of nuclei initially flipped over is much less than the total number of nuclei are treated. This treatment employs a pole approximation within a Schrödinger equation of motion for the state of the coupled electron and nuclear spin system, and it allows us to treat systems with arbitrary initial conditions. We find that typical time scales for the effective spin decoherence are on the order of tens of microseconds.

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

    Science.gov (United States)

    Linck, Rebecca A.

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

  1. Electron spin relaxation in cryptochrome-based magnetoreception

    DEFF Research Database (Denmark)

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

    2016-01-01

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

  2. Spin noise spectroscopy in GaAs (110) quantum wells: access to intrinsic spin lifetimes and equilibrium electron dynamics.

    Science.gov (United States)

    Müller, Georg M; Römer, Michael; Schuh, Dieter; Wegscheider, Werner; Hübner, Jens; Oestreich, Michael

    2008-11-14

    In this Letter, the first spin noise spectroscopy measurements in semiconductor systems of reduced effective dimensionality are reported. The nondemolition measurement technique gives access to the otherwise concealed intrinsic, low temperature electron spin relaxation time of n-doped GaAs (110) quantum wells and to the corresponding low temperature anisotropic spin relaxation. The Brownian motion of the electrons within the spin noise probe laser spot becomes manifest in a modification of the spin noise line width. Thereby, the spatially resolved observation of the stochastic spin polarization uniquely allows to study electron dynamics at equilibrium conditions with a vanishing total momentum of the electron system.

  3. An elementary quantum network using robust nuclear spin qubits in diamond

    Science.gov (United States)

    Kalb, Norbert; Reiserer, Andreas; Humphreys, Peter; Blok, Machiel; van Bemmelen, Koen; Twitchen, Daniel; Markham, Matthew; Taminiau, Tim; Hanson, Ronald

    Quantum registers containing multiple robust qubits can form the nodes of future quantum networks for computation and communication. Information storage within such nodes must be resilient to any type of local operation. Here we demonstrate multiple robust memories by employing five nuclear spins adjacent to a nitrogen-vacancy defect centre in diamond. We characterize the storage of quantum superpositions and their resilience to entangling attempts with the electron spin of the defect centre. The storage fidelity is found to be limited by the probabilistic electron spin reset after failed entangling attempts. Control over multiple memories is then utilized to encode states in decoherence protected subspaces with increased robustness. Furthermore we demonstrate memory control in two optically linked network nodes and characterize the storage capabilities of both memories in terms of the process fidelity with the identity. These results pave the way towards multi-qubit quantum algorithms in a remote network setting.

  4. Spin frustration and fermionic entanglement in an exactly solved hybrid diamond chain with the localized Ising spins and mobile electrons

    OpenAIRE

    Torrico, J.; Rojas, M.; Pereira, M. S. S.; Strecka, J.; Lyra, M. L.

    2015-01-01

    The strongly correlated spin-electron system on a diamond chain containing localized Ising spins on its nodal lattice sites and mobile electrons on its interstitial sites is exactly solved in a magnetic field using the transfer-matrix method. We have investigated in detail all available ground states, the magnetization processes, the spin-spin correlation functions around an elementary plaquette, fermionic quantum concurrence and spin frustration. It is shown that the fermionic entanglement b...

  5. Spin Relaxation in GaAs: Importance of Electron-Electron Interactions

    Directory of Open Access Journals (Sweden)

    Gionni Marchetti

    2014-04-01

    Full Text Available We study spin relaxation in n-type bulk GaAs, due to the Dyakonov–Perel mechanism, using ensemble Monte Carlo methods. Our results confirm that spin relaxation time increases with the electronic density in the regime of moderate electronic concentrations and high temperature. We show that the electron-electron scattering in the non-degenerate regime significantly slows down spin relaxation. This result supports predictions by Glazov and Ivchenko. Most importantly, our findings highlight the importance of many-body interactions for spin dynamics: we show that only by properly taking into account electron-electron interactions within the simulations, results for the spin relaxation time—with respect to both electron density and temperature—will reach good quantitative agreement with corresponding experimental data. Our calculations contain no fitting parameters.

  6. Engineering the spin polarization of one-dimensional electrons.

    Science.gov (United States)

    Yan, Chengyu; Kumar, Sanjeev; Thomas, Kalarikad; See, Patrick; Farrer, Ian; Ritchie, David A; Griffiths, John; Jones, G A C; Pepper, Michael

    2018-01-15

    We present results of magneto-focusing on the controlled monitoring of spin polarization within a one-dimensional (1D) channel, and its subsequent effect on modulating the spin-orbit interaction (SOI) in a 2D GaAs electron gas. We demonstrate that electrons within a 1D channel can be partially spin polarized as the effective length of the 1D channel is varied in agreement with the theoretical prediction. Such polarized 1D electrons when injected into a 2D region result in a split in the odd-focusing peaks, whereas the even peaks remain unaffected (single peak). On the other hand, the unpolarized electrons, achieved by reducing the effective length of the 1D channel, do not affect the focusing spectrum and the odd and even peaks remain as single peaks, respectively. The split in odd-focusing peaks is evidence of direct measurement of spin polarization within a 1D channel, where each sub-peak represents the population of a particular spin state. Confirmation of the spin splitting is determined by a selective modulation of the focusing peaks due to the Zeeman energy in the presence of an in-plane magnetic field. We suggest that the SOI in the 2D regime is enhanced by a stream of polarized 1D electrons. The spatial control of spin states of injected 1D electrons and the possibility of tuning the SOI may open up a new regime of spin-engineering with application in future quantum information schemes. Creative Commons Attribution license.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zobov, V. E., E-mail: rsa@iph.krasn.ru [Russian Academy of Sciences, Kirensky Institute of Physics, Siberian Branch (Russian Federation)

    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.

  8. Magnetohydrodynamic spin waves in degenerate electron-positron-ion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Mushtaq, A. [TPPD, PINSTECH Nilore, 44000 Islamabad (Pakistan); National Center for Physics, Shahdrah Valley Road, 44000 Islamabad (Pakistan); Maroof, R.; Ahmad, Zulfiaqr [Institute of Physics and Electronics, University of Peshawar, 25000 Peshawar (Pakistan); Qamar, A. [National Center for Physics, Shahdrah Valley Road, 44000 Islamabad (Pakistan); Institute of Physics and Electronics, University of Peshawar, 25000 Peshawar (Pakistan)

    2012-05-15

    Low frequency magnetosonic waves are studied in magnetized degenerate electron-positron-ion plasmas with spin effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, and spin magnetization energy, a generalized dispersion relation for oblique magnetosonic waves is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. For three different values of angle {theta}, the generalized dispersion relation is reduced to three different relations under the low frequency magnetohydrodynamic assumptions. It is found that the effect of quantum corrections in the presence of positron concentration significantly modifies the dispersive properties of these modes. The importance of the work relevant to compact astrophysical bodies is pointed out.

  9. Electron spin control and spin-libration coupling of a levitated nanodiamond

    Science.gov (United States)

    Hoang, Thai; Ma, Yue; Ahn, Jonghoon; Bang, Jaehoon; Robicheaux, Francis; Gong, Ming; Yin, Zhang-Qi; Li, Tongcang

    2017-04-01

    Hybrid spin-mechanical systems have great potentials in sensing, macroscopic quantum mechanics, and quantum information science. Recently, we optically levitated a nanodiamond and demonstrated electron spin control of its built-in nitrogen-vacancy (NV) centers in vacuum. We also observed the libration (torsional vibration) of a nanodiamond trapped by a linearly polarized laser beam in vacuum. We propose to achieve strong coupling between the electron spin of a NV center and the libration of a levitated nanodiamond with a uniform magnetic field. With a uniform magnetic field, multiple spins can couple to the torsional vibration at the same time. We propose to use this strong coupling to realize the Lipkin-Meshkov-Glick (LMG) model and generate rotational superposition states. This work is supported by the National Science Foundation under Grant No. 1555035-PHY.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-04-24

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

  11. Coherent single electron spin control in a slanting Zeeman field

    NARCIS (Netherlands)

    Tokura, Yasuhiro; van der Wiel, Wilfred Gerard; Obata, Toshiaki; Tarucha, Seigo

    2006-01-01

    We consider a single electron in a 1D quantum dot with a static slanting Zeeman field. By combining the spin and orbital degrees of freedom of the electron, an effective quantum two-level (qubit) system is defined. This pseudospin can be coherently manipulated by the voltage applied to the gate

  12. Electron spin and charge in semiconductor quantum dots

    NARCIS (Netherlands)

    Elzerman, J.M.

    2004-01-01

    In this thesis, the spin and charge degree of freedom of electrons in semiconductor lateral and vertical quantum dots are experimentally investigated. The lateral quantum dot devices are defined in a two-dimensional electron gas (2DEG) below the surface of a GaAs/AlGaAs heterostructure, by metallic

  13. Theoretical evaluation of the electron paramagnetic resonance spin ...

    Indian Academy of Sciences (India)

    Theoretical evaluation of the electron paramagnetic resonance spin Hamiltonian parameters for the impurity displacements for Fe3+ and Ru3+ in corundum. Q FU1,SYWU1,2∗, J Z LIN1 and J S YAO1. 1Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, People's ...

  14. Manipulating single electron spins and coherence in quantum dots

    Science.gov (United States)

    Awschalom, David

    2008-05-01

    The non-destructive detection of a single electron spin in a quantum dot (QD) is demonstrated using a time- averaged magneto-optical Kerr rotation measurementootnotetextJ. Berezovsky, M. H. Mikkelsen, O. Gywat, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 314, 1916 (2006).. This technique provides a means to directly probe the spin off- resonance, thus minimally disturbing the system. Furthermore, the ability to sequentially initialize, manipulate, and read out the state of a qubit, such as an electron spin in a quantum dot, is necessary for virtually any scheme for quantum information processing. In addition to the time-averaged measurements, we have extended the single dot KR technique into the time domain with pulsed pump and probe lasers, allowing the observation of the coherent evolution of an electron spin stateootnotetextM. H. Mikkelsen, J. Berezovsky, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Nature Physics 3, 770 (2007).. The dot is formed by interface fluctuations of a GaAs quantum well and embedded in a diode structure to allow controllable gating/charging of the QD. To enhance the small single spin signal, the QD is positioned within a vertical optical cavity. Observations of coherent single spin precession in an applied magnetic field allow a direct measurement of the electron g-factor and transverse spin lifetime. These measurements reveal information about the relevant spin decoherence mechanisms, while also providing a sensitive probe of the local nuclear spin environment. Finally, we have recently eveloped a scheme for high speed all-optical manipulation of the spin state that enables multiple operations within the coherence timeootnotetextJ. Berezovsky, M. H. Mikkelsen, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, accepted for publication (2008).. The results represent progress toward the control and coupling of single spins and photons for quantum information processingootnotetextS. Ghosh, W.H. Wang, F. M. Mendoza, R. C

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

    Science.gov (United States)

    Linck, Rebecca

    2012-11-01

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

  16. Spin effects on the semiclassical trajectories of Dirac electrons

    Science.gov (United States)

    Gutiérrez-Jáuregui, R.; Pérez-Pascual, R.; Jáuregui, R.

    2017-11-01

    The relativistic semiclassical evolution of the position of an electron in the presence of an external electromagnetic field is studied in terms of a Newton equation that incorporates spin effects directly. This equation emerges from the Dirac equation and allows the identification of scenarios where spin effects are necessary to understand the main characteristics of the electron trajectories. It involves the eigenvalues of the non-Hermitian operator Σμ νFμ ν , with Σμ ν and Fμ ν as the spin and electromagnetic tensors. The formalism allows a deeper understanding on the physics behind known analytical solutions of the Dirac equation when translational dynamics seem to decouple from spin evolution. As an illustrative example, it is applied to an electron immersed in an electromagnetic field which exhibits chiral symmetry and optical vortices. It is shown that the polarization of intense structured light beams can be used to suppress or enhance spin effects on the electron semiclassical trajectory; the latter configuration yields a realization of a Stern-Gerlach apparatus for an electron.

  17. Action Potential Modulation of Neural Spin Networks Suggests Possible Role of Spin

    CERN Document Server

    Hu, H P

    2004-01-01

    In this paper we show that nuclear spin networks in neural membranes are modulated by action potentials through J-coupling, dipolar coupling and chemical shielding tensors and perturbed by microscopically strong and fluctuating internal magnetic fields produced largely by paramagnetic oxygen. We suggest that these spin networks could be involved in brain functions since said modulation inputs information carried by the neural spike trains into them, said perturbation activates various dynamics within them and the combination of the two likely produce stochastic resonance thus synchronizing said dynamics to the neural firings. Although quantum coherence is desirable and may indeed exist, it is not required for these spin networks to serve as the subatomic components for the conventional neural networks.

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

    NARCIS (Netherlands)

    Shafiei, M.

    2013-01-01

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

  19. Coupling of Electron Spin Ensembles to Superconducting Transmission Line Resonators

    Science.gov (United States)

    Sears, Adam; Schuster, David; Dicarlo, Leo; Bishop, Lev; Ginossar, Eran; Frunzio, Luigi; Wesenberg, Janus; Ardavan, Arzhang; Briggs, Andrew; Moelmer, Klauss; Morton, John; Schoelkopf, Robert

    2010-03-01

    Recent proposals have suggested using a mesoscopic ensemble of electron spins to create a quantum memory for superconducting qubits in solid state systems[1]. Such ensembles can have large cavity couplings (˜MHz) and should have long coherence times. Here we show the measurement and coupling of electron spins in ruby and diamond to multiplexed superconducting coplanar waveguide (CPW) cavities, as well as broadband spectroscopy of ruby using a CPW transmission line. We discuss the application of these techniques to electron spin resonance at low power, millikelvin temperatures, and over many gigahertz and evaluate the suitability of our materials for quantum computing. [4pt] [1] Wesenberg J et al 2009 Phys. Rev. Lett. 103 070502

  20. Simulating electron spin entanglement in a double quantum dot

    Science.gov (United States)

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

    2011-03-01

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

  1. Spin-valley splitting of electron beam in graphene

    Directory of Open Access Journals (Sweden)

    Yu Song

    2016-11-01

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

  2. All-electric spin control in interference single electron transistors.

    Science.gov (United States)

    Donarini, Andrea; Begemann, Georg; Grifoni, Milena

    2009-08-01

    Single particle interference lies at the heart of quantum mechanics. The archetypal double-slit experiment(1) has been repeated with electrons in vacuum(2,3) up to the more massive C(60) molecules.(4) Mesoscopic rings threaded by a magnetic flux provide the solid-state analogues.(5,6) Intramolecular interference has been recently discussed in molecular junctions.(7-11) Here we propose to exploit interference to achieve all-electrical control of a single electron spin in quantum dots, a highly desirable property for spintronics(12-14) and spin-qubit applications.(15-19) The device consists of an interference single electron transistor,(10,11) where destructive interference between orbitally degenerate electronic states produces current blocking at specific bias voltages. We show that in the presence of parallel polarized ferromagnetic leads the interplay between interference and the exchange interaction on the system generates an effective energy renormalization yielding different blocking biases for majority and minority spins. Hence, by tuning the bias voltage full control over the spin of the trapped electron is achieved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1994-05-01

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

  4. Electron spin relaxation in graphene nanoribbon quantum dots

    Science.gov (United States)

    Droth, Matthias; Burkard, Guido

    2013-05-01

    Graphene is promising as a host material for electron spin qubits because of its predicted potential for long coherence times. In armchair graphene nanoribbons (aGNRs) a small band gap is opened, allowing for electrically gated quantum dots, and furthermore the valley degeneracy is lifted. The spin lifetime T1 is limited by spin relaxation, where the Zeeman energy is absorbed by lattice vibrations, mediated by spin-orbit and electron-phonon coupling. We have calculated T1 by treating all couplings analytically and find that T1 can be in the range of seconds for several reasons: (i) low phonon density of states away from Van Hove singularities; (ii) destructive interference between two relaxation mechanisms; (iii) Van Vleck cancellation at low magnetic fields; (iv) vanishing coupling to out-of-plane modes in lowest order due to the electronic structure of aGNRs. Owing to the vanishing nuclear spin of 12C, T1 may be a good measure for overall coherence. These results and recent advances in the controlled production of graphene nanoribbons make this system interesting for spintronics applications.

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

    NARCIS (Netherlands)

    Koppens, F.H.L.

    2007-01-01

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

  6. Measuring Electron Tunneling Times as a Means of Single Shot/Single Electron Spin Readout

    Science.gov (United States)

    Robinson, Hans D.; Szkopek, Thomas; Rao, Deepak S.; Yablonovitch, Eli

    2004-03-01

    In this talk, we present our strategy for measuring the spin of a single electron trapped in an gate-defined quantum dot in a single shot measurement. The electron is allowed to tunnel out of the electron into a spin dependent final state, or conversely, an external electron with a definite spin is allowed to tunnel onto the dot. The measurement of spin is thereby turned into a measurement of time. A necessary prerequisite is the ability to reliably and accurately measure the dwell time for single electrons on the quantum dot with microsecond accuracy. We report on our experimental progress in this area, where rather than using a relatively hard to fabricate SET for charge detection, we employ a quantum point contact FET that is cofabricated with the quantum dot.

  7. Optical absorption and electron spin resonance studies of Cu in ...

    Indian Academy of Sciences (India)

    Unknown

    Oxide glasses formed with heavy metal ions have received significant attention owing to their interesting optical applications. These glasses are better competitors for opti- cal transmission studies due to their long infrared cut-off. (Fu and Yatsuda 1995; Pan and Ghosh 2000). Electron spin resonance (ESR) spectroscopy is ...

  8. ELECTRON SPIN RESONANCE SPECTRA OF NITRIC OXIDE ADSORBED ON ZEOLITES,

    Science.gov (United States)

    Electron spin resonance (e.s.r.) spectra of NO adsorbed on the 4 zeolites Linde 4A, 5A, 13X , and hydrogen mordenite were measured at 77K. No e.s.r...the quadrupole moment with the corresponding electric field gradients, the non-axial component of the latter is estimated for the surface fields of the zeolites . (Author)

  9. Electron spin resonance dating of fault gouge from Desamangalam ...

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    The preliminary results from the electron spin resonance (ESR) dating on the quartz grains from the fault gouge indicate that the last major faulting in this site occurred 430 ± 43ka ago. The experiments on different grain sizes of quartz from the gouge showed consistent decrease in age to a plateau of low values, indicating ...

  10. Electron spin resonance dating of fault gouge from Desamangalam ...

    Indian Academy of Sciences (India)

    The preliminary results from the electron spin resonance (ESR) dating on the quartz grains from the fault gouge indicate that the last major faulting in this site occurred 430 ± 43 ka ago. The experiments on different grain sizes of quartz from the gouge showed consistent decrease in age to a plateau of low values, indicating ...

  11. Detection and Imaging of Superoxide in Roots by an Electron Spin Resonance Spin-Probe Method

    Science.gov (United States)

    Warwar, Nasim; Mor, Avishai; Fluhr, Robert; Pandian, Ramasamy P.; Kuppusamy, Periannan; Blank, Aharon

    2011-01-01

    The detection, quantification, and imaging of short-lived reactive oxygen species, such as superoxide, in live biological specimens have always been challenging and controversial. Fluorescence-based methods are nonspecific, and electron spin resonance (ESR) spin-trapping methods require high probe concentrations and lack the capability for sufficient image resolution. In this work, a novel (to our knowledge), sensitive, small ESR imaging resonator was used together with a stable spin probe that specifically reacts with superoxide with a high reaction rate constant. This ESR spin-probe-based methodology was used to examine superoxide generated in a plant root as a result of an apical leaf injury. The results show that the spin probe rapidly permeated the plant's extracellular space. Upon injury of the plant tissue, superoxide was produced and the ESR signal decreased rapidly in the injured parts as well as in the distal part of the root. This is attributed to superoxide production and thus provides a means of quantifying the level of superoxide in the plant. The spin probe's narrow single-line ESR spectrum, together with the sensitive imaging resonator, facilitates the quantitative measurement of superoxide in small biological samples, such as the plant's root, as well as one-dimensional imaging along the length of the root. This type of methodology can be used to resolve many questions involving the production of apoplastic superoxide in plant biology. PMID:21943435

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

    OpenAIRE

    Wang, Wei

    2014-01-01

    The emergence of biomolecular homochirality is a critically important question about life phenomenon and the origins of life. In a previous paper (arXiv:1309.1229), I tentatively put forward a new hypothesis that the emergence of a single chiral form of biomolecules in living organisms is specifically determined by the electron spin state during their enzyme-catalyzed synthesis processes. However, how a homochirality world of biomolecules could have formed in the absence of enzymatic networks...

  13. The electronic spin state of iron in Earth's mantle

    Science.gov (United States)

    Catalli, K.; Grocholski, B.; Shim, S.

    2011-12-01

    Mg-silicate perovskite and ferropericlase are thought to be the dominant minerals existing in the Earth's lower mantle, making understanding their properties integral for interpretations of seismic and geodynamic models of the mantle. Of specific interest over the past decade is the electronic spin state of iron in these minerals and the effect of spin crossovers on elasticity and transport properties (Badro et al., 2003, 2004, Science). Ferropericlase, the structurally simpler of the two minerals with only one valence state of iron (Fe2+) entering only one crystallographic site, has been shown to undergo a high-spin to low-spin crossover over an extended pressure-temperature range in the mantle. This spin crossover has been found to have a substantial effect on the elasticity of the mineral during the spin transition (e.g., Fei et al., 2007, GRL; Crowhurst et al., 2008, Science; Marquardt et al., 2009, Science). The spin behavior of Mg-silicate, on the other hand, is complicated by the existence of two potential crystallographic sites and two valence states for iron and affected by other chemical variability such as the presence of aluminum. Although controversial, recent studies found Fe2+ remains high-spin in perovskite (e.g., Grocholski et al., 2009, GRL; Bengtson, 2009, GRL), and the presence of Fe2+ has not been found to have any effect on the compressibility of perovskite (Lundin et al., 2008, PEPI). However, Fe3+ in the B site of perovskite has been found to become low spin at mid-lower mantle pressures (Catalli et al., 2010, EPSL), though the nature of the spin transition is likely affected by the presence of aluminum, and at least when in large concentrations, has been found to have a strong effect on compressibility. Here we summarize some of the findings of the last decade on the spin state of iron in Mg-silicate perovskite and ferropericlase under lower mantle conditions and their effects on the mineral properties that are of likely interest to mantle

  14. Spin frustration and fermionic entanglement in an exactly solved hybrid diamond chain with localized Ising spins and mobile electrons

    Science.gov (United States)

    Torrico, J.; Rojas, M.; Pereira, M. S. S.; Strečka, J.; Lyra, M. L.

    2016-01-01

    The strongly correlated spin-electron system on a diamond chain containing localized Ising spins on its nodal lattice sites and mobile electrons on its interstitial sites is exactly solved in a magnetic field using the transfer-matrix method. We have investigated in detail all available ground states, the magnetization processes, the spin-spin correlation functions around an elementary plaquette, fermionic quantum concurrence, and spin frustration. It is shown that the fermionic entanglement between mobile electrons hopping on interstitial sites and the kinetically induced spin frustration are closely related yet independent phenomena. In the ground state, quantum entanglement only appears within a frustrated unsaturated paramagnetic phase, while thermal fluctuations can promote some degree of quantum entanglement above the nonfrustrated ground states with saturated paramagnetic or classical ferrimagnetic spin arrangements.

  15. High-power 95 GHz pulsed electron spin resonance spectrometer

    Science.gov (United States)

    Hofbauer, W.; Earle, K. A.; Dunnam, C. R.; Moscicki, J. K.; Freed, J. H.

    2004-05-01

    High-field/high-frequency electron spin resonance (ESR) offers improved sensitivity and resolution compared to ESR at conventional fields and frequencies. However, most high-field/high-frequency ESR spectrometers suffer from limited mm-wave power, thereby requiring long mm-wave pulses. This precludes their use when relaxation times are short, e.g., in fluid samples. Low mm-wave power is also a major factor limiting the achievable spectral coverage and thereby the multiplex advantage of Fourier transform ESR (FTESR) experiments. High-power pulses are needed to perform two-dimensional (2D) FTESR experiments, which can unravel the dynamics of a spin system in great detail, making it an excellent tool for studying spin and molecular dynamics. We report on the design and implementation of a high-power, high-bandwidth, pulsed ESR spectrometer operating at 95 GHz. One of the principal design goals was the ability to investigate dynamic processes in aqueous samples at physiological temperatures with the intent to study biological systems. In initial experiments on aqueous samples at room temperature, we achieved 200 MHz spectral coverage at a sensitivity of 1.1×1010√s spins and a dead time of less than 50 ns. 2D-electron-electron double resonance experiments on aqueous samples are discussed to demonstrate the practical application of such a spectrometer.

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

    CERN Document Server

    Andreev, Pavel A

    2015-01-01

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

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

    Science.gov (United States)

    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.

  18. Electric-Field-Induced Nuclear Spin Resonance Mediated by Oscillating Electron Spin Domains in GaAs-Based Semiconductors

    OpenAIRE

    Kumada, N.; Kamada, T.; Miyashita, S.; Hirayama, Y.; Fujisawa, T.

    2008-01-01

    We demonstrate an alternative nuclear spin resonance using radio frequency (RF) electric field (nuclear electric resonance: NER) instead of magnetic field. The NER is based on the electronic control of electron spins forming a domain structure. The RF electric field applied to a gate excites spatial oscillations of the domain walls and thus temporal oscillations of the hyperfine field to nuclear spins. The RF power and burst duration dependence of the NER spectrum provides insight into the in...

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

    Science.gov (United States)

    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.

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

    OpenAIRE

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

    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 ...

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

    DEFF Research Database (Denmark)

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

    2001-01-01

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

  2. A quantum spin-liquid in correlated relativistic electrons

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Z.Y. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA (United States); Institut fuer Theoretische Physik III, Universitaet Stuttgart (Germany); Lang, T.C.; Wessel, S. [Institute for Theoretical Solid State Physics, RWTH Aachen University, Aachen (Germany); Assaad, F.F. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Muramatsu, A. [Institut fuer Theoretische Physik III, Universitaet Stuttgart (Germany)

    2012-04-02

    In recent years, an increasing number of systems displaying exotic quantum states like unconventional superconductivity, quantum spin-liquids, or topological states were experimentally found. Here we summarize findings in quantum Monte Carlo simulations of correlated electrons on a honeycomb lattice, the structure of graphene, that revealed an unexpected spin-liquid emerging between a state described by massless Dirac fermions and an antiferromagnetically ordered Mott insulator. Moreover, we found that this quantum-disordered state is a resonating valence-bond (RVB) liquid, akin to the one proposed for high temperature superconductors. This was the first unbiased determination of a RVB-liquid in an electronic system. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Spin correlation tensor for measurement of quantum entanglement in electron-electron scattering

    Science.gov (United States)

    Tsurikov, D. E.; Samarin, S. N.; Williams, J. F.; Artamonov, O. M.

    2017-04-01

    We consider the problem of correct measurement of a quantum entanglement in the two-body electron-electron scattering. An expression is derived for a spin correlation tensor of a pure two-electron state. A geometric measure of a quantum entanglement as the distance between two forms of this tensor in entangled and separable cases is presented. Due to such definition, one does not need to look for the closest separable state to the analyzed state. We prove that introduced measure satisfies properties of a valid entanglement measure: nonnegativity, discriminance, normalization, non-growth under local operations and classical communication. This measure is calculated for a problem of electron-electron scattering. We prove that it does not depend on the azimuthal rotation angle of the second electron spin relative to the first electron spin before scattering. We specify how to find a spin correlation tensor and the related measure of a quantum entanglement in an experiment with electron-electron scattering. Finally, the introduced measure is extended to the mixed states.

  4. Magnetic dipole transitions and spin currents in inelastic electron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Lipas, P.O.; Koskinen, M. (Jyvaeskylae Univ. (Finland). Dept. of Physics); Harter, H.; Nojarov, R.; Faessler, A. (Tuebingen Univ. (Germany, F.R.). Inst. fuer Theoretische Physik)

    1989-10-26

    We use the microscopic interacting-boson approximation (IBA-2) to calculate the nuclear M1 transition current density for excitation by inelastic electron scattering. Although the strong 1{sup +} excitations are commonly regarded as due to proton convection, we find, with {sup 164}Dy as a test case, that proton and neutron spins cause strong oscillations in the current and are responsible for high-q-scattering. (orig.).

  5. Measuring exchange interactions between atomic spins using electron spin resonance STM

    Science.gov (United States)

    Yang, Kai; Paul, William; Natterer, Fabian; Choi, Taeyoung; Heinrich, Andreas; Lutz, Christopher

    Exchange interactions between neighboring atoms give rise to magnetic order in magnetic materials. As the size of the electronic device is miniaturized toward the limit of single atoms, magnetic nanostructures such as coupled atomic dimers and clusters are explored more as prototypes for possible data storage, spintronics as well as quantum computing applications. Characterizing inter-atom exchange interactions calls for increasing spatial resolution and higher energy sensitivity to better understand this fundamental interaction. Here, using spin-polarized scanning tunneling microscopy (STM), we studied a magnetically coupled atomic dimer consisting of two 3d transition metal atoms, with one adsorbed on an insulating layer (MgO) and the other attached to the STM tip. We demonstrate the ability to measure the short-range exchange interaction between the two atomic spins with orders-of-magnitude variation ranging from milli-eV all the way to micro-eV. This is realized by the successful combination of inelastic electron tunneling spectroscopy (IETS) and electron spin resonance (ESR) techniques in STM implemented at different energy scales. We unambiguously confirm the exponential decay behavior of the direct exchange interaction.

  6. Position, spin, and orbital angular momentum of a relativistic electron

    Science.gov (United States)

    Bliokh, Konstantin Y.; Dennis, Mark R.; Nori, Franco

    2017-08-01

    Motivated by recent interest in relativistic electron vortex states, we revisit the spin and orbital angular momentum properties of Dirac electrons. These are uniquely determined by the choice of the position operator for a relativistic electron. We consider two main approaches discussed in the literature: (i) the projection of operators onto the positive-energy subspace, which removes the Zitterbewegung effects and correctly describes spin-orbit interaction effects, and (ii) the use of Newton-Wigner-Foldy-Wouthuysen operators based on the inverse Foldy-Wouthuysen transformation. We argue that the first approach [previously described in application to Dirac vortex beams in K. Y. Bliokh et al., Phys. Rev. Lett. 107, 174802 (2011), 10.1103/PhysRevLett.107.174802] has a more natural physical interpretation, including spin-orbit interactions and a nonsingular zero-mass limit, than the second one [S. M. Barnett, Phys. Rev. Lett. 118, 114802 (2017), 10.1103/PhysRevLett.118.114802].

  7. Electron Tunneling in Lithium Ammonia Solutions Probed by Frequency-Dependent Electron-Spin Relaxation Studies

    Science.gov (United States)

    Maeda, Kiminori; Lodge, Matthew T.J.; Harmer, Jeffrey; Freed, Jack H.; Edwards, Peter P.

    2012-01-01

    Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T1) and spin-spin (T2) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multi-exponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1–10)×10−12 s over a temperature range 230–290K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a timescale of ca. 10−13 s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great potential

  8. Electron tunneling in lithium-ammonia solutions probed by frequency-dependent electron spin relaxation studies.

    Science.gov (United States)

    Maeda, Kiminori; Lodge, Matthew T J; Harmer, Jeffrey; Freed, Jack H; Edwards, Peter P

    2012-06-06

    Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T(1)) and spin-spin (T(2)) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multiexponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1-10) × 10(-12) s over a temperature range 230-290 K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a time scale of ∼10(-13) s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great

  9. Monte Carlo method for studies of spin relaxation in degenerate electron gas: Application to monolayer graphene

    Science.gov (United States)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2017-07-01

    Monte Carlo method allowing to account for the effect of Pauli Exclusion Principle in the case of spin polarized electron gas is demonstrated. Modeling requires calculation of electron states occupancy accounting for the direction of the spin of the scattered electron. As an example of application, calculations for the case of spin and energy relaxation of initially polarized electrons in monolayer graphene have been performed. Model includes D'yakonov-Perel' and Elliot-Yafet relaxation mechanisms. It is demonstrated that electron distribution function and energy relaxation follow the spin polarization relaxation and they are mainly governed by spin related scattering processes.

  10. Electric field induced nuclear spin resonance mediated by oscillating electron spin domains in GaAs-based semiconductors.

    Science.gov (United States)

    Kumada, N; Kamada, T; Miyashita, S; Hirayama, Y; Fujisawa, T

    2008-09-26

    We demonstrate an alternative nuclear spin resonance using a radio frequency (rf) electric field [nuclear electric resonance (NER)] instead of a magnetic field. The NER is based on the electronic control of electron spins forming a domain structure. The rf electric field applied to a gate excites spatial oscillations of the domain walls and thus temporal oscillations of the hyperfine field to nuclear spins. The rf power and burst duration dependence of the NER spectrum provides insight into the interplay between nuclear spins and the oscillating domain walls.

  11. Introduction to spin-polarized ballistic hot electron injection and detection in silicon.

    Science.gov (United States)

    Appelbaum, Ian

    2011-09-28

    Ballistic hot electron transport overcomes the well-known problems of conductivity and spin lifetime mismatch that plague spin injection attempts in semiconductors using ferromagnetic ohmic contacts. Through the spin dependence of the mean free path in ferromagnetic thin films, it also provides a means for spin detection after transport. Experimental results using these techniques (consisting of spin precession and spin-valve measurements) with silicon-based devices reveals the exceptionally long spin lifetime and high spin coherence induced by drift-dominated transport in the semiconductor. An appropriate quantitative model that accurately simulates the device characteristics for both undoped and doped spin transport channels is described; it can be used to recover the transit-time distribution from precession measurements and determine the spin current velocity, diffusion constant and spin lifetime, constituting a spin 'Haynes-Shockley' experiment without time-of-flight techniques. A perspective on the future of these methods is offered as a summary.

  12. Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin.

    Science.gov (United States)

    He, Yu; He, Yu-Ming; Wei, Yu-Jia; Jiang, Xiao; Chen, Kai; Lu, Chao-Yang; Pan, Jian-Wei; Schneider, Christian; Kamp, Martin; Höfling, Sven

    2017-08-11

    Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of 0.796±0.020. Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path, and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 m. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axes on the Bloch sphere, with an average fidelity of 78.5%.

  13. Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin

    Science.gov (United States)

    He, Yu; He, Yu-Ming; Wei, Yu-Jia; Jiang, Xiao; Chen, Kai; Lu, Chao-Yang; Pan, Jian-Wei; Schneider, Christian; Kamp, Martin; Höfling, Sven

    2017-08-01

    Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of 0.796 ±0.020 . Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path, and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 m. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axes on the Bloch sphere, with an average fidelity of 78.5%.

  14. Rabi oscillation and electron-spin-echo envelope modulation of the photoexcited triplet spin system in silicon

    Science.gov (United States)

    Akhtar, Waseem; Sekiguchi, Takeharu; Itahashi, Tatsumasa; Filidou, Vasileia; Morton, John J. L.; Vlasenko, Leonid; Itoh, Kohei M.

    2012-09-01

    We report on a pulsed electron paramagnetic resonance (EPR) study of the photoexcited triplet state (S=1) of oxygen-vacancy centers in silicon. Rabi oscillations between the triplet sublevels are observed using coherent manipulation with a resonant microwave pulse. The Hahn echo and stimulated echo decay profiles are superimposed with strong modulations known as electron-spin-echo envelope modulation (ESEEM). The ESEEM spectra reveal a weak but anisotropic hyperfine coupling between the triplet electron spin and a 29Si nuclear spin (I=1/2) residing at a nearby lattice site, that cannot be resolved in conventional field-swept EPR spectra.

  15. Dissipationless transport of spin-polarized electrons and Cooper pairs in an electron waveguide

    Science.gov (United States)

    Levy, J.; Annadi, A.; Lu, S.; Cheng, G.; Tylan-Tyler, A.; Briggeman, M.; Tomczyk, M.; Huang, M.; Pekker, D.; Irvin, P.; Lee, H.; Lee, J.-W.; Eom, C.-B.

    Electron systems undergo profound changes in their behavior when constrained to move along a single axis. To date, clean one-dimensional (1D) electron transport has only been observed in carbon-based nanotubes and nanoribbons, and compound semiconductor nanowires. Complex-oxide heterostructures can possess conductive two-dimensional (2D) interfaces with much richer chemistries and properties, e.g., superconductivity, but with mobilities that appear to preclude ballistic transport in 1D. Here we show that nearly ideal 1D electron waveguides exhibiting ballistic transport of electrons and non-superconducting Cooper pairs can be formed at the interface between the two band insulators LaAlO3 and SrTiO3. The electron waveguides possess gate and magnetic-field selectable spin and charge degrees of freedom, and can be tuned to the one-dimensional limit of a single spin-polarized quantum channel. The strong attractive electron-electron interactions enable a new mode of dissipationless transport of electron pairs that is not superconducting. The selectable spin and subband quantum numbers of these electron waveguides may be useful for quantum simulation, quantum informatio We gratefully acknowledge financial support from ONR N00014-15-1-2847 (JL), AFOSR (FA9550-15-1-0334 (CBE) and FA9550-12-1-0057 (JL, CBE)), AOARD FA2386-15-1-4046 (CBE) and NSF (DMR-1104191 (JL), DMR-1124131 (CBE, JL) and DMR-1234096 (CBE)).

  16. Non linear analysis of obliquely propagating spin electron acoustic wave in a partially spin polarized degenerate plasma

    Science.gov (United States)

    Iqbal, Z.; Murtaza, G.

    2018-01-01

    By employing the separated spin evolution quantum hydrodynamic model, non-linear evolution of obliquely propagating spin electron acoustic wave (SEAW) is presented. The solitary structures of SEAW is investigated through the Korteweg-de Vries (KdV) equation derived using reductive perturbation method. From the first order perturbations we derive the dispersion relation of SEAW and find that both the spin polarization and the propagation angle reduce the phase velocity while the electron streaming enhances it. Using small amplitude approximation, the solitary structure of SEAW is analyzed and the effects of spin polarization, propagation angle and electron streaming on the SEA soliton are studied. Our numerical results demonstrate that the spin polarization and the propagation angle play a balancing act on the soliton structures. The possible applications of our investigation to the astrophysical environments like white dwarfs is also discussed.

  17. Spin relaxation of electrons in bulk CdTe

    Science.gov (United States)

    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).

  18. Lateral shifts of spin electron beams in antiparallel double {delta}-magnetic-barrier nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Kong Yonghong [Department of Electronic Engineering, Hunan University Science and Engineering, Hunan 425100 (China); Lu Maowang, E-mail: m_w_lu@126.com [Department of Electronic Engineering, Hunan University Science and Engineering, Hunan 425100 (China); Chen Saiyan; Zhang Guilian [Department of Electronic Engineering, Hunan University Science and Engineering, Hunan 425100 (China)

    2012-08-15

    We investigate the Goos-Haenchen (GH) effect of spin electron beams in a magnetic-barrier (MB) nanostructure consisting of antiparallel double {delta}-MBs, which can be experimentally realized by depositing two ferromagnetic (FM) stripes on top and bottom of the semiconductor heterostructure. GH shifts for spin electron beams across this type of MB nanostructures, is derived exactly, with the help of the stationary phase method. It is shown that GH shifts depend strongly on the spin directions for double {delta}-MBs with unidentical magnetic strengths, giving rise to a considerable spin polarization effect. It also is shown that spin polarization of GH shifts is closely relative to the separation and magnetic-strength difference of two {delta}-MBs. These interesting properties may provide an alternative scheme to spin-polarize electrons into the semiconductor, and the devices can serve as tunable spin beam splitters. - Highlights: Black-Right-Pointing-Pointer Spin Goos-Haenchen effect of electron beams through a kind of MB nanostructures. Black-Right-Pointing-Pointer GH shift depends greatly on electron-spins, which is used to spin polarize electrons in semiconductor. Black-Right-Pointing-Pointer Spin polarization in GH shift is tunable. Black-Right-Pointing-Pointer A tunable spin beam splitter is achieved.

  19. Monte Carlo study of electron relaxation in graphene with spin polarized, degenerate electron gas in presence of electron-electron scattering

    Science.gov (United States)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2017-12-01

    The Monte Carlo simulation method is applied to study the relaxation of excited electrons in monolayer graphene. The presence of spin polarized background electrons population, with density corresponding to highly degenerate conditions is assumed. Formulas of electron-electron scattering rates, which properly account for electrons presence in two energetically degenerate, inequivalent valleys in this material are presented. The electron relaxation process can be divided into two phases: thermalization and cooling, which can be clearly distinguished when examining the standard deviation of electron energy distribution. The influence of the exchange effect in interactions between electrons with parallel spins is shown to be important only in transient conditions, especially during the thermalization phase.

  20. Spin g -factor due to electronic interactions in graphene

    Science.gov (United States)

    Menezes, Natália; Alves, Van Sérgio; Marino, E. C.; Nascimento, Leonardo; Nascimento, Leandro O.; Morais Smith, C.

    2017-06-01

    The gyromagnetic factor is an important physical quantity relating the magnetic-dipole moment of a particle to its spin. The electron spin g -factor in vacuo is one of the best model-based theoretical predictions ever made, showing agreement with the measured value up to ten parts per trillion [J. Schwinger, Phys. Rev. 73, 416 (1948), 10.1103/PhysRev.73.416; R. S. Van Dyck, Jr. et al., Phys. Rev. Lett. 59, 26 (1987), 10.1103/PhysRevLett.59.26; D. Hanneke et al., Phys. Rev. Lett. 100, 120801 (2008), 10.1103/PhysRevLett.100.120801; T. Aoyama et al., Phys. Rev. Lett. 109, 111807 (2012), 10.1103/PhysRevLett.109.111807]. However, for electrons in a material the g -factor is modified with respect to its value in vacuo because of environment interactions. Here, we show how interaction effects lead to the spin g -factor correction in graphene by considering the full electromagnetic interaction in the framework of pseudo-QED [A. Kovner et al., Phys. Rev. B 42, 4748 (1990), 10.1103/PhysRevB.42.4748; N. Dorey et al., Nucl. Phys. B 386, 614 (1992), 10.1016/0550-3213(92)90632-L; S. Teber, Phys. Rev. D 86, 025005 (2012), 10.1103/PhysRevD.86.025005; S. Teber, Phys. Rev. D 89, 067702 (2014), 10.1103/PhysRevD.89.067702; E. C. Marino, Nucl. Phys. B 408, 551 (1993), 10.1016/0550-3213(93)90379-4]. We compare our theoretical prediction with experiments performed on graphene deposited on SiO2 and SiC, and we find a very good agreement between them.

  1. Electron-spin relaxation in bulk III-V semiconductors from a fully microscopic kinetic spin Bloch equation approach

    Science.gov (United States)

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

    2009-03-01

    Electron spin relaxation in bulk III-V semiconductors is investigated from a fully microscopic kinetic spin Bloch equation approach where all relevant scatterings, such as, the electron-nonmagnetic-impurity, electron-phonon, electron-electron, electron-hole, and electron-hole exchange (the Bir-Aronov-Pikus mechanism) scatterings are explicitly included. The Elliott-Yafet mechanism is also fully incorporated. This approach offers a way toward thorough understanding of electron spin relaxation both near and far away from the equilibrium in the metallic regime. The dependences of the spin relaxation time on electron density, temperature, initial spin polarization, photo-excitation density, and hole density are studied thoroughly with the underlying physics analyzed. We find that these dependences are usually qualitatively different in the nondegenerate and degenerate regimes. In contrast to the previous investigations in the literature, we find that: (i) In n -type materials, the Elliott-Yafet mechanism is less important than the D’yakonov-Perel’ mechanism, even for the narrow band-gap semiconductors such as InSb and InAs. (ii) The density dependence of the spin relaxation time is nonmonotonic and we predict a peak in the metallic regime in both n -type and intrinsic materials. (iii) In intrinsic materials, the Bir-Aronov-Pikus mechanism is found to be negligible compared with the D’yakonov-Perel’ mechanism. We also predict a peak in the temperature dependence of spin relaxation time which is due to the nonmonotonic temperature dependence of the electron-electron Coulomb scattering in intrinsic materials with small initial spin polarization. (iv) In p -type III-V semiconductors, the Bir-Aronov-Pikus mechanism dominates spin relaxation in the low-temperature regime only when the photoexcitation density is low. When the photoexcitation density is high, the Bir-Aronov-Pikus mechanism can be comparable with the D’yakonov-Perel’ mechanism only in the moderate

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-05-17

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

  3. Phase Transitions in Electron Spin Resonance Under Continuous Microwave Driving

    Science.gov (United States)

    Karabanov, A.; Rose, D. C.; Köckenberger, W.; Garrahan, J. P.; Lesanovsky, I.

    2017-10-01

    We study an ensemble of strongly coupled electrons under continuous microwave irradiation interacting with a dissipative environment, a problem of relevance to the creation of highly polarized nonequilibrium states in nuclear magnetic resonance. We analyze the stationary states of the dynamics, described within a Lindblad master equation framework, at the mean-field approximation level. This approach allows us to identify steady-state phase transitions between phases of high and low polarization controlled by the distribution of disordered electronic interactions. We compare the mean-field predictions to numerically exact simulations of small systems and find good agreement. Our study highlights the possibility of observing collective phenomena, such as metastable states, phase transitions, and critical behavior, in appropriately designed paramagnetic systems. These phenomena occur in a low-temperature regime which is not theoretically tractable by conventional methods, e.g., the spin-temperature approach.

  4. New electron spin resonance and mass spectrometric studies of metallofullerenes

    Science.gov (United States)

    Bartl, A.; Dunsch, L.; Froehner, J.; Kirbach, U.

    1994-10-01

    The preparation by arc vaporization of graphite rods of metal-containing fullerene samples with metals inside the fullerene molecules is described. The metals lanthanum, scandium, holmium and yttrium were used for this study. Results in mass spectrometry confirm the existence and stability of several Me at C82 species. Electron spin resonance (ESR) spectroscopic measurements of metallofullerene samples in the solid state and in tetrachloroethane solution favor the existence of endohedral systems. The splitting of the ESR spectra is interpreted by isotropic hyperfine coupling of an unpaired electron with the nuclear magnetic moment of a metal ion inside a fullerene molecule. It is concluded that the metal atoms exist in ionic form in endohedral fullerenes both in solid and liquid state of the fullerene. Furthermore it is shown that there is more than one stable position of the metal ion inside the fullerene molecule.

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

    Science.gov (United States)

    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

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

    NARCIS (Netherlands)

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

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

  7. Systematic investigations of transient response of nuclear spins in the presence of polarized electrons

    Science.gov (United States)

    Rasly, Mohmoud; Lin, Zhichao; Uemura, Tetsuya

    2017-11-01

    We electrically probed the transient response of nuclear spins in an n -GaAs channel by performing Hanle signal and spin-valve signal measurements on an all-electrical spin-injection device having a half-metallic spin source of C o2MnSi . Furthermore, we simulated the Hanle and spin-valve signals by using the time evolution of nuclear-spin polarization under the presence of polarized electron spins by taking both T1 e and T1 into consideration, where T1e -1 is the polarization rate of nuclear spins through the transfer of angular momentum from polarized electron spins and T1-1 is the depolarization rate of nuclear spins through the interaction with the lattice. The simulation results reproduced our experimental results on all the nuclear-spin-related phenomena appearing in the Hanle and spin-valve signals at different measurement conditions, providing quantitative explanation for the transient response of nuclear spins in GaAs to a change in magnetic fields and an estimate of the time scales of T1 e and T1. These experimental and simulated results will deepen the understanding of nuclear-spin dynamics in semiconductors.

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

    Energy Technology Data Exchange (ETDEWEB)

    Long, Mingsheng; Gong, Youpin; Wei, Xiangfei; Zhu, Chao; Xu, Jianbao; Liu, Ping; Guo, Yufen; Li, Weiwei; Liu, Liwei, E-mail: lwliu2007@sinano.ac.cn [Key Laboratory of Nanodevices and Applications-CAS and Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Liu, Guangtong [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    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.

  9. Electronic, Spin and Valley Transport in Two Dimensional Dirac Systems

    Science.gov (United States)

    Xu, Hongya

    This dissertation aims to study and understand relevant issues related to the electronic, spin and valley transport in two-dimensional Dirac systems for different given physical settings. In summary, four key findings are achieved. First, studying persistent currents in confined chaotic Dirac fermion systems with a ring geometry and an applied Aharonov-Bohm flux, unusual whispering-gallery modes with edge-dependent currents and spin polarization are identified. They can survive for highly asymmetric rings that host fully developed classical chaos. By sustaining robust persistent currents, these modes can be utilized to form a robust relativistic quantum two-level system. Second, the quantized topological edge states in confined massive Dirac fermion systems exhibiting a remarkable reverse Stark effect in response to an applied electric field, and an electrically or optically controllable spin switching behavior are uncovered. Third, novel wave scattering and transport in Dirac-like pseudospin-1 systems are reported. (a), for small scatterer size, a surprising revival resonant scattering with a peculiar boundary trapping by forming unusual vortices is uncovered. Intriguingly, it can persist in arbitrarily weak scatterer strength regime, which underlies a superscattering behavior beyond the conventional scenario. (b), for larger size, a perfect caustic phenomenon arises as a manifestation of the super-Klein tunneling effect. (c), in the far-field, an unexpected isotropic transport emerges at low energies. Fourth, a geometric valley Hall effect (gVHE) originated from fractional singular Berry flux is revealed. It is shown that gVHE possesses a nonlinear dependence on the Berry flux with asymmetrical resonance features and can be considerably enhanced by electrically controllable resonant valley skew scattering. With the gVHE, efficient valley filtering can arise and these phenomena are robust against thermal fluctuations and disorder averaging.

  10. Modeling Spin Creation and Mass Generation in the Electron Motivated by an Angle Doubler Mechanism

    Science.gov (United States)

    2017-11-01

    particle duality, (4) the apparent instantaneous connection between particles that are in entanglement, (5) the apparent collapse of the wave function...the field (spin down). We can prepare spin states using what are known as spin filters. The spin filter takes in a beam of particles , say electrons...continent on the surface of the sphere will then project that continent’s shape onto the planes, P1 and P2. The South Pole and its surroundings would

  11. Electron spin relaxation in GaAs1-xBix: Effects of spin-orbit tuning by Bi incorporation

    Science.gov (United States)

    Tong, H.; Marie, X.; Wu, M. W.

    2012-09-01

    The electron spin relaxation in n-type and intrinsic GaAs1-xBix with Bi composition 0≤x≤0.1 is investigated from the microscopic kinetic spin Bloch equation approach. The incorporation of Bi is shown to markedly decrease the spin relaxation time as a consequence of the modification of the spin-orbit interaction, which shows the feasibility of GaAs1-xBix in the applications of spintronic devices. We demonstrate that the density and temperature dependences of spin relaxation time in GaAs1-xBix resemble the ones in GaAs. Meanwhile, the Bir-Aronov-Pikus mechanism is found to be negligible compared to the D'yakonov-Perel' mechanism in intrinsic sample. Due to the absence of direct measurement of the electron effective mass in the whole compositional range under investigation, we further explore the effect of a possible variation of electron effective mass on the electron spin relaxation.

  12. Superconducting coplanar waveguide resonators for electron spin resonance applications

    Science.gov (United States)

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

    2013-03-01

    Superconducting coplanar waveguide (CPW) resonators are a promising alternative to conventional volume resonators for electron spin resonance (ESR) experiments where the sample volume and thus the number of spins is small. However, the magnetic fields required for ESR could present a problem for Nb superconducting resonators, which can be driven normal. Very thin Nb films (50 nm) and careful alignment of the resonators parallel to the magnetic field avoid driving the Nb normal, but flux trapping can still be an issue. Trapped flux reduces the resonator Q-factor, can lead to resonant frequency instability, and can lead to magnetic field inhomogeneities. At temperatures of 1.9 K and in a magnetic field 0.32 T, we have tested X-band resonators fabricated directly on the surface of a silicon sample. Q-factors in excess of 15,000 have been obtained. A thin layer of GE varnish applied directly to the resonator has been used to glue a sapphire wafer to its surface, and we still find Q-factors of 16,000 or more in the 0.32 T field. ESR applications of these resonators will be discussed. Supported in part by the ARO.

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

    Science.gov (United States)

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

    2017-03-01

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

  14. Single-chip electron spin resonance detectors operating at 50GHz, 92GHz, and 146GHz.

    Science.gov (United States)

    Matheoud, Alessandro V; Gualco, Gabriele; Jeong, Minki; Zivkovic, Ivica; Brugger, Jürgen; Rønnow, Henrik M; Anders, Jens; Boero, Giovanni

    2017-05-01

    We report on the design and characterization of single-chip electron spin resonance (ESR) detectors operating at 50GHz, 92GHz, and 146GHz. The core of the single-chip ESR detectors is an integrated LC-oscillator, formed by a single turn aluminum planar coil, a metal-oxide-metal capacitor, and two metal-oxide semiconductor field effect transistors used as negative resistance network. On the same chip, a second, nominally identical, LC-oscillator together with a mixer and an output buffer are also integrated. Thanks to the slightly asymmetric capacitance of the mixer inputs, a signal at a few hundreds of MHz is obtained at the output of the mixer. The mixer is used for frequency down-conversion, with the aim to obtain an output signal at a frequency easily manageable off-chip. The coil diameters are 120μm, 70μm, and 45μm for the U-band, W-band, and the D-band oscillators, respectively. The experimental frequency noises at 100kHz offset from the carrier are 90Hz/Hz 1/2 , 300Hz/Hz 1/2 , and 700Hz/Hz 1/2 at 300K, respectively. The ESR spectra are obtained by measuring the frequency variations of the single-chip oscillators as a function of the applied magnetic field. The experimental spin sensitivities, as measured with a sample of α,γ-bisdiphenylene-β-phenylallyl (BDPA)/benzene complex, are 1×10 8 spins/Hz 1/2 , 4×10 7 spins/Hz 1/2 , 2×10 7 spins/Hz 1/2 at 300K, respectively. We also show the possibility to perform experiments up to 360GHz by means of the higher harmonics in the microwave field produced by the integrated single-chip LC-oscillators. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Intrinsic and Extrinsic Spin Hall Effects of Dirac Electrons

    Science.gov (United States)

    Fukazawa, Takaaki; Kohno, Hiroshi; Fujimoto, Junji

    2017-09-01

    We investigate the spin Hall effect (SHE) of electrons described by the Dirac equation, which is used as an effective model near the L-points in bismuth. By considering short-range nonmagnetic impurities, we calculate the extrinsic as well as intrinsic contributions on an equal footing. The vertex corrections are taken into account within the ladder type and the so-called skew-scattering type. The intrinsic SHE which we obtain is consistent with that of Fuseya et al. [https://doi.org/10.1143/JPSJ.81.093704" xlink:type="simple">J. Phys. Soc. Jpn. 81, 093704 (2012)]. It is found that the extrinsic contribution dominates the intrinsic one when the system is metallic. The extrinsic SHE due to the skew scattering is proportional to Δ/niu, where 2Δ is the band gap, ni is the impurity concentration, and u is the strength of the impurity potential.

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

    Science.gov (United States)

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

    2014-03-01

    The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin-magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of this analysis could prove useful in the design of an improved electron microscope. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Temperature dependence of persistent spin currents in a spin-orbit-coupled electron gas: A density-matrix approach

    Science.gov (United States)

    Bencheikh, K.; Vignale, G.

    2008-04-01

    We present a simple analytical method, based on the canonical density matrix, for the calculation of the equilibrium spin current as a function of temperature in a two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit coupling terms. We find that the persistent spin current is extremely robust against thermal disorder: its variation with temperature is exponentially small (∝e-TF/T) at temperatures much smaller than the Fermi temperature TF and changes to a power law TF/T for T≫TF .

  18. Electron spin dynamics in GaAsN and InGaAsN structures

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-01-15

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

  19. Effect of Rashba and Dresselhaus Spin-Orbit Couplings on Electron Spin Polarization in a Hybrid Magnetic-Electric Barrier Nanostructure

    Science.gov (United States)

    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.

  20. Electron correlations and the minority-spin band gap in half-metallic Heusler alloys

    NARCIS (Netherlands)

    Chioncel, L.; Arrigoni, E.; Katsnelson, M.I.; Lichtenstein, A.I.

    2006-01-01

    Electron-electron correlations affect the band gap of half-metallic ferromagnets by introducing nonquasiparticle states just above the Fermi level. In contrast with the spin-orbit coupling, a large asymmetric nonquasiparticle spectral weight is present in the minority-spin channel, leading to a

  1. Electron transport and spin phenomena in hybrid organic/inorganic systems

    NARCIS (Netherlands)

    Naber, W.J.M.

    2010-01-01

    This thesis describes several experiments in hybrid organic/inorganic systems, in which electron transport and/or spin behavior is studied. The basic concepts of organic electronics and spintronics are given, to understand the described spin-valve experiments. The problems and obstacles for

  2. Electronic spin transport in graphene field-effect transistors

    NARCIS (Netherlands)

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

    2009-01-01

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

  3. Theoretical evaluation of the electron paramagnetic resonance spin ...

    Indian Academy of Sciences (India)

    The impurity displacements for Fe3+ and Ru3+ in corundum (Al2O3) are theoretically studied using the perturbation formulas of the spin Hamiltonian parameters (zero-field splitting and anisotropic factors) for a 3d5 (with high spin = 5/2) and a 4d5 (with low spin = 1/2) ion in trigonal symmetry, respectively. According ...

  4. Spin-orbit coupling, electron transport and pairing instabilities in two-dimensional square structures

    Energy Technology Data Exchange (ETDEWEB)

    Kocharian, Armen N. [Department of Physics, California State University, Los Angeles, CA 90032 (United States); Fernando, Gayanath W.; Fang, Kun [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Palandage, Kalum [Department of Physics, Trinity College, Hartford, Connecticut 06106 (United States); Balatsky, Alexander V. [AlbaNova University Center Nordita, SE-106 91 Stockholm (Sweden)

    2016-05-15

    Rashba spin-orbit effects and electron correlations in the two-dimensional cylindrical lattices of square geometries are assessed using mesoscopic two-, three- and four-leg ladder structures. Here the electron transport properties are systematically calculated by including the spin-orbit coupling in tight binding and Hubbard models threaded by a magnetic flux. These results highlight important aspects of possible symmetry breaking mechanisms in square ladder geometries driven by the combined effect of a magnetic gauge field spin-orbit interaction and temperature. The observed persistent current, spin and charge polarizations in the presence of spin-orbit coupling are driven by separation of electron and hole charges and opposite spins in real-space. The modeled spin-flip processes on the pairing mechanism induced by the spin-orbit coupling in assembled nanostructures (as arrays of clusters) engineered in various two-dimensional multi-leg structures provide an ideal playground for understanding spatial charge and spin density inhomogeneities leading to electron pairing and spontaneous phase separation instabilities in unconventional superconductors. Such studies also fall under the scope of current challenging problems in superconductivity and magnetism, topological insulators and spin dependent transport associated with numerous interfaces and heterostructures.

  5. Spin-orbit coupling, electron transport and pairing instabilities in two-dimensional square structures

    Directory of Open Access Journals (Sweden)

    Armen N. Kocharian

    2016-05-01

    Full Text Available Rashba spin-orbit effects and electron correlations in the two-dimensional cylindrical lattices of square geometries are assessed using mesoscopic two-, three- and four-leg ladder structures. Here the electron transport properties are systematically calculated by including the spin-orbit coupling in tight binding and Hubbard models threaded by a magnetic flux. These results highlight important aspects of possible symmetry breaking mechanisms in square ladder geometries driven by the combined effect of a magnetic gauge field spin-orbit interaction and temperature. The observed persistent current, spin and charge polarizations in the presence of spin-orbit coupling are driven by separation of electron and hole charges and opposite spins in real-space. The modeled spin-flip processes on the pairing mechanism induced by the spin-orbit coupling in assembled nanostructures (as arrays of clusters engineered in various two-dimensional multi-leg structures provide an ideal playground for understanding spatial charge and spin density inhomogeneities leading to electron pairing and spontaneous phase separation instabilities in unconventional superconductors. Such studies also fall under the scope of current challenging problems in superconductivity and magnetism, topological insulators and spin dependent transport associated with numerous interfaces and heterostructures.

  6. Electron-Positron Cascade in Magnetospheres of Spinning Black Holes

    Science.gov (United States)

    Ford, Alex L.; Keenan, Brett D.; Medvedev, Mikhail V.

    2017-10-01

    We quantitatively study the stationary, axisymmetric, force-free magnetospheres of spinning (Kerr) black holes (BHs) and the conditions needed for relativistic jets to be powered by the Blandford-Znajek mechanism. These jets could be from active galactic nuclei, blazars, quasars, micro-quasars, radio active galaxies, and other systems that host Kerr BHs. The structure of the magnetosphere determines how the BH energy is extracted, e.g., via Blandford-Znajek mechanism, which converts the BH rotational energy into Poynting flux. The key assumption is the force-free condition, which requires the presence of plasma with the density being above the Goldreich-Julian density. Unlike neutron stars, which in principle can supply electrons from the surface, BH cannot supply plasma at all. The plasma must be generated in situ via an electron-positron cascade, presumably in the gap region. Here we study varying conditions that provide a sufficient amount of plasma for the Blandford-Znajek mechanism to work effectively. The authors acknowledge DOE partial support via Grant DE-SC0016368.

  7. Spin lifetimes of electrons injected into GaAs and GaN

    Science.gov (United States)

    Krishnamurthy, Srinivasan; van Schilfgaarde, Mark; Newman, Nathan

    2003-09-01

    The spin relaxation times of electrons in GaAs and GaN are determined with a model that includes momentum scattering by phonons and ionized impurities, and spin scattering by the Elliot-Yafet, D'yakonov-Perel, and Bir-Aronov-Pikus mechanisms. Accurate bands generated using a long-range tight-binding Hamiltonian obtained from empirical pseudopotentials are used. The inferred temperature dependence of the spin relaxation lifetime agrees well with measured values in GaAs. We further show that the spin lifetimes decrease rapidly with injected electron energy and reach a local maximum at the longitudinal optical phonon energy. Our calculation predicts that electron spin lifetime in pure GaN is about three orders of magnitude longer than in GaAs at all temperatures, primarily as a result of the lower spin-orbit interaction and higher conduction band density of states.

  8. Fast spin information transfer between distant quantum dots using individual electrons.

    Science.gov (United States)

    Bertrand, B; Hermelin, S; Takada, S; Yamamoto, M; Tarucha, S; Ludwig, A; Wieck, A D; Bäuerle, C; Meunier, T

    2016-08-01

    Transporting ensembles of electrons over long distances without losing their spin polarization is an important benchmark for spintronic devices. It usually requires injecting and probing spin-polarized electrons in conduction channels using ferromagnetic contacts or optical excitation. In parallel with this development, important efforts have been dedicated to achieving control of nanocircuits at the single-electron level. The detection and coherent manipulation of the spin of a single electron trapped in a quantum dot are now well established. Combined with the recently demonstrated control of the displacement of individual electrons between two distant quantum dots, these achievements allow the possibility of realizing spintronic protocols at the single-electron level. Here, we demonstrate that spin information carried by one or two electrons can be transferred between two quantum dots separated by a distance of 4 μm with a classical fidelity of 65%. We show that at present it is limited by spin flips occurring during the transfer procedure before and after electron displacement. Being able to encode and control information in the spin degree of freedom of a single electron while it is being transferred over distances of a few micrometres on nanosecond timescales will pave the way towards 'quantum spintronics' devices, which could be used to implement large-scale spin-based quantum information processing.

  9. Spin splitting of electron states in lattice-mismatched (110)-oriented quantum wells

    Science.gov (United States)

    Nestoklon, M. O.; Tarasenko, S. A.; Benchamekh, R.; Voisin, P.

    2016-09-01

    We show that for lattice-mismatched zinc-blende-type (110)-grown quantum wells a significant contribution to the zero-magnetic-field spin splitting of electron subbands comes from strain-induced spin-orbit coupling. Combining the envelope function theory and atomistic tight-binding approach, we calculate spin-orbit splitting constants for realistic quantum wells. It is found that the strain due to lattice mismatch in conventional GaAs/AlGaAs structures may noticeably modify the spin splitting while in InGaAs/GaAs structures it plays a major role and may even change the sign of the spin splitting constant.

  10. Increase of spin dephasing times in a 2D electron system with degree of initial spin polarization

    Science.gov (United States)

    Stich, D.; Korn, T.; Schulz, R.; Schuh, D.; Wegscheider, W.; Schüller, C.

    2008-03-01

    We report on time-resolved Faraday/Kerr rotation measurements on a high-mobility 2D electron system. A variable initial spin polarization is created in the sample by a circularly polarized pump pulse, and the spin polarization is tracked by measuring the Faraday/Kerr rotation of a time-delayed probe pulse. By varying the pump intensity, the initial spin polarization is changed from the low-polarization limit to a polarization degree of several percent. The observed spin dephasing time increases from less than 20 ps to more than 200 ps as the initial spin polarization is increased. To exclude sample heating effects, additional measurements with constant pump intensity and variable degree of circular polarization are performed. The results confirm the theoretical prediction by Weng and Wu [Phys. Rev. B 68 (2003) 075312] that the spin dephasing strongly depends on the initial spin polarization degree. The microscopic origin for this is the Hartree-Fock term in the Coulomb interaction, which acts as an effective out-of plane magnetic field.

  11. Time-bin state transfer to electron spin coherence in solids

    Science.gov (United States)

    Kosaka, Hideo; Inagaki, Takahiro; Hitomi, Ryuta; Izawa, Fumishige; Rikitake, Yoshiaki; Imamura, Hiroshi; Mitsumori, Yasuyoshi; Edamatsu, Keiichi

    2014-12-01

    We demonstrate that a coherent superposition state of two temporally separated optical pulses, called a time-bin state, can be transferred to that of up/down electron spins in a semiconductor by synchronizing the time separation to the precession period of either electrons or holes. The time-bin transfer scheme does not require polarization mode degeneracy and can map the time-bin state to the electron spin state that is not accessible directly using only polarization. The scheme offers a new approach for quantum interfaces between photons and electron spins.

  12. Time-bin state transfer to electron spin coherence in solids

    Energy Technology Data Exchange (ETDEWEB)

    Kosaka, Hideo; Inagaki, Takahiro; Hitomi, Ryuta; Izawa, Fumishige; Mitsumori, Yasuyoshi; Edamatsu, Keiichi [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Rikitake, Yoshiaki [Sendai National College of Technology, Sendai 989-3128 (Japan); Imamura, Hiroshi [Nanosystem Research Institute, AIST, Tsukuba 305-8568 (Japan)

    2014-12-04

    We demonstrate that a coherent superposition state of two temporally separated optical pulses, called a time-bin state, can be transferred to that of up/down electron spins in a semiconductor by synchronizing the time separation to the precession period of either electrons or holes. The time-bin transfer scheme does not require polarization mode degeneracy and can map the time-bin state to the electron spin state that is not accessible directly using only polarization. The scheme offers a new approach for quantum interfaces between photons and electron spins.

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

    CERN Document Server

    Likhtenshtein, Gertz

    2016-01-01

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

  14. Electron spin dynamics in heavily Mn-doped (Ga,Mn)As

    Science.gov (United States)

    Zhu, Yonggang; Han, Lifen; Chen, Lin; Zhang, Xinhui; Zhao, Jianhua

    2010-12-01

    Electron spin relaxation and related mechanisms in heavily Mn-doped (Ga,Mn)As are studied by performing time-resolved magneto-optical Kerr effect measurements. At low temperature, s-d exchange scattering dominates electron spin relaxation, whereas the Bir-Aronov-Pikus mechanism and Mn impurity scattering play important roles at high temperature. The temperature-dependent spin relaxation time exhibits an anomaly around the Curie temperature (Tc) that implies that thermal fluctuation is suppressed by short-range correlated spin fluctuation above Tc.

  15. Coherence transfer and electron T1-, T2-relaxation in nitroxide spin labels

    Science.gov (United States)

    Marsh, Derek

    2017-04-01

    Abragam's double-commutator spin operator method is used to analyse: 1) electron coherence transfer by intermolecular dipolar interaction between spin-label radicals, and 2) longitudinal and transverse electron spin relaxation by rotational modulation of the Zeeman and nitrogen-hyperfine anisotropies of isolated nitroxide spin labels. Results compatible with earlier treatments by Redfield theory are obtained without specifically evaluating matrix elements. Extension to single-transition operators for isolated nitroxides predicts electron coherence transfer by pseudosecular electron-nuclear dipolar interaction, in the absence of intermolecular dipolar coupling. This explains earlier experimental findings that coherence transfer (specifically dispersion-like distortion of the EPR absorption line shape) does not extrapolate to zero at low concentrations of nitroxide spin labels.

  16. Coherence transfer and electron T1-, T2-relaxation in nitroxide spin labels

    DEFF Research Database (Denmark)

    Marsh, Derek

    2017-01-01

    Abragam's double-commutator spin operator method is used to analyse: 1) electron coherence transfer by intermolecular dipolar interaction between spin-label radicals, and 2) longitudinal and transverse electron spin relaxation by rotational modulation of the Zeeman and nitrogen......-hyperfine anisotropies of isolated nitroxide spin labels. Results compatible with earlier treatments by Redfield theory are obtained without specifically evaluating matrix elements. Extension to single-transition operators for isolated nitroxides predicts electron coherence transfer by pseudosecular electron......-nuclear dipolar interaction, in the absence of intermolecular dipolar coupling. This explains earlier experimental findings that coherence transfer (specifically dispersion-like distortion of the EPR absorption line shape) does not extrapolate to zero at low concentrations of nitroxide spin labels....

  17. Quantum Information Processing by Electron Spin Resonance in a Transistor Structure

    Science.gov (United States)

    Yablonovitch, Eli

    2001-03-01

    Isolated electron spins in low temperature semiconductors are now recognized to have considerable potential for storing and manipulating quantum information. One of the great advantages of a spin in a semiconductor is that it can be embedded into a transistor structure, and it can thereby lend itself to large-scale integration of a quantum information processor. One essential element for spin-based quantum information processing is to be able to individually address the spins, or qubits, rotations. The electron spin resonance (ESR) electrons in a GaAs/AlGaAs heterostructure can be tuned by means of a gate voltage. The front and back gates of the heterostructure produce opposite g-factor shift, suggesting that electron g-factor is being electrostatically controlled by shifting the electron wave function from one epitaxial layer to another with different g-factors. We report our observations of gate-voltage tuned ESR in a two-dimensional electron system. We demonstrate that the electrostatic field of a gate can effectively adjust the weighting of the electron wave function between heterostructure layers of different composition producing a large g-factor change. We have monitored the ESR spin flips by means of the source/drain channel current, and conversely we have tuned the spin resonance frequency by means of the gate voltage. These are two of the elementary operations required in a quantum information processor.

  18. Electron spin resonance in silicon substituted apatite and tricalcium phosphate.

    Science.gov (United States)

    Pietak, Alexis M; Reid, Joel W; Sayer, Michael

    2005-06-01

    Impurity centers associated with silicon have been observed in the phase mixture of silicon substituted apatite (Si-Ap) and silicon stabilized tricalcium phosphate (Si-TCP) using electron spin resonance (ESR). Two unique centers occur upon addition of SiO2 to the calcium phosphate system: an orthorhombic center with g-values 2.0072+/-0.0001, 2.0024+/-0.0001 and 2.0003+/-0.0001 (Si-h1) and a center with tetrahedral symmetry having g-values components 2.0054+/-0.0001 and 1.9992+/-0.0003 (Si-h2). Both centers are hypothesized to be characteristic of defects associated with silicon in the Si-Ap phase. Through comparison of the intensity of F-OH centers in undoped calcium hydroxyapatite (HA) prepared with various levels of OH occupancy, a relationship is demonstrated between the ESR intensity of an F-center signal with g = 2.0019+0.0004 (F-OH) and the OH occupation of HA. Relative changes in the intensity of ESR signals Si-h1 and F-OH are consistent with a chemical model describing the substitution of SiO4(4-) for PO4(3-) in HA with the creation of OH- vacancies as charge compensation, resulting in a mixed phase composition of Si-Ap and Si-TCP that results when a hydroxyapatite precipitate (HA) is heated in the presence of added SiO2.

  19. Mechanical detection of electron spin resonance beyond 1 THz

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-02

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

  20. Optically driven Rabi oscillations and adiabatic passage of single electron spins in diamond.

    Science.gov (United States)

    Golter, D Andrew; Wang, Hailin

    2014-03-21

    Rabi oscillations and adiabatic passage of single electron spins in a diamond nitrogen vacancy center are demonstrated with two Raman-resonant optical pulses that are detuned from the respective dipole optical transitions. We show that the optical spin control is nuclear-spin selective and can be robust against rapid decoherence, including radiative decay and spectral diffusion, of the underlying optical transitions. A direct comparison between the Rabi oscillation and the adiabatic passage, along with a detailed theoretical analysis, provides significant physical insights into the connections and differences between these coherent spin processes and also elucidates the role of spectral diffusion in these processes. The optically driven coherent spin processes enable the use of nitrogen vacancy excited states to mediate coherent spin-phonon coupling, opening the door to combining optical control of both spin and mechanical degrees of freedom.

  1. Duality in spin fluctuation in correlated electron systems

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Takashi, E-mail: t-yanagisawa@aist.go.jp; Hase, Izumi

    2016-11-15

    Highlights: • We propose improved wave functions, based on the well-known Gutzwiller wave function, for the two-dimensional Hubbard model. • Our wave function gives the best variational energy compared to several wave functions previously proposed for the Hubbard model. It is now a best wave function for the Hubbard model. • We found that the antiferromagnetic state becomes instable due to charge fluctuation of carriers when the on-site repulsive interaction U is greater than the bandwidth. • The superconducting-condensation energy becomes large due to large spin fluctuation indicating a possibility of high-temperature superconductivity. - Abstract: An origin of high-temperature superconductivity for cuprate superconductors is investigated on the basis of the two-dimensional Hubbard model. The Coulomb interaction is a candidate that can bring about high-temperature superconductivity because its characteristic energy is of the order of eV. It is not trivial whether the on-site Coulomb interaction U leads to a pairing interaction between two electrons. We argue that the antiferromagnetic fluctuation and the kinetic charge fluctuation are responsible for high-temperature superconductivity. The kinetic charge fluctuation is induced by large U to get the kinetic energy gain in the strongly correlated region. We consider electron correlation beyond the Gutzwiller ansatz, by taking account of inter-site correlation such as doublon–holon correlation and kinetic correlation. We show that high-temperature superconductivity is possible in the strongly correlated region, where U is greater than the bandwidth, by using the variational Monte Carlo method.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-06-01

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

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

    DEFF Research Database (Denmark)

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

    2013-01-01

    We propose a scheme to efficiently couple a single quantum dot electron spin to an optical nano-cavity, which enables us to simultaneously benefit from a cavity as an efficient photonic interface, as well as to perform high fidelity (nearly 100%) spin initialization and manipulation achievable...... in bulk semiconductors. Moreover, the presence of the cavity speeds up the spin initialization process beyond the GHz range....

  4. Optical neural network system for pose determination of spinning satellites

    Science.gov (United States)

    Lee, Andrew; Casasent, David

    1990-01-01

    An optical neural network architecture and algorithm based on a Hopfield optimization network are presented for multitarget tracking. This tracker utilizes a neuron for every possible target track, and a quadratic energy function of neural activities which is minimized using gradient descent neural evolution. The neural net tracker is demonstrated as part of a system for determining position and orientation (pose) of spinning satellites with respect to a robotic spacecraft. The input to the system is time sequence video from a single camera. Novelty detection and filtering are utilized to locate and segment novel regions from the input images. The neural net multitarget tracker determines the correspondences (or tracks) of the novel regions as a function of time, and hence the paths of object (satellite) parts. The path traced out by a given part or region is approximately elliptical in image space, and the position, shape and orientation of the ellipse are functions of the satellite geometry and its pose. Having a geometric model of the satellite, and the elliptical path of a part in image space, the three-dimensional pose of the satellite is determined. Digital simulation results using this algorithm are presented for various satellite poses and lighting conditions.

  5. Interaction between air plasma-produced aqueous 1O2 and the spin trap DMPO in electron spin resonance

    Science.gov (United States)

    Chen, Chen; Li, Fanying; Chen, Hai-Lan; Kong, Michael G.

    2017-10-01

    A series of electron spin resonance (ESR) experiments is done to quantitatively measure the concentrations of aqueous 1O2 and ˙OH produced by a surface micro-discharge air plasma device. 1O2 is tested to be existed in the plasma treated solution by using the spin trap of TEMP. However, the unexpected DMPOX spectrum is observed in measuring ˙OH by the spin trap of 5,5-Dimethyl-1-Pyrroline-N-Oxide (DMPO). With more chemical scavenger experiments, it is found that removal of aqueous 1O2 leads to the disappearance of DMPOX in ESR. Therefore, the generation of DMPOX is directly related to the oxidation of DMPO by plasma-produced aqueous 1O2. This oxidation process and interactions between DMPO and chemical scavengers used in experiments can all be well explained by a proposed reaction mechanism. The revelation of interactions between aqueous 1O2 and the spin trap DMPO shows that the observation of spectra of DMPOX in the ESR measurement can be regarded as a marker of high concentrations of plasma-produced 1O2 in liquid. These results also prove the existence of interactions between spin traps and non-targeted plasma-produced reactive species in ESR experiments. Also, these results have offered a better understanding of the use of spin traps such as DMPO in the plasma-induced highly oxidative aqueous environment.

  6. Spin polarization of electrons in a magnetic impurity doped ...

    Indian Academy of Sciences (India)

    Abstract. A theoretical model is presented in this paper for degree of spin polarization in a light emitting diode (LED) whose epitaxial region contains quantum dots doped with magnetic impurity. The model is then used to investigate the effect of electron–phonon interaction on degree of spin polarization at different ...

  7. Spin polarization of electrons in a magnetic impurity doped ...

    Indian Academy of Sciences (India)

    A theoretical model is presented in this paper for degree of spin polarization in alight emitting diode (LED) whose epitaxial region contains quantum dots doped with magnetic impurity. The model is then used to investigate the effect of electron–phonon interaction on degree of spin polarization at different temperatures and ...

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

    Science.gov (United States)

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

    2007-07-27

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

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

    KAUST Repository

    Bučinský, Lukáš

    2014-06-01

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

  10. Nanosecond-timescale spin transfer using individual electrons in a quadruple-quantum-dot device

    Energy Technology Data Exchange (ETDEWEB)

    Baart, T. A.; Jovanovic, N.; Vandersypen, L. M. K. [QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Reichl, C.; Wegscheider, W. [Solid State Physics Laboratory, ETH Zürich, 8093 Zürich (Switzerland)

    2016-07-25

    The ability to coherently transport electron-spin states between different sites of gate-defined semiconductor quantum dots is an essential ingredient for a quantum-dot-based quantum computer. Previous shuttles using electrostatic gating were too slow to move an electron within the spin dephasing time across an array. Here, we report a nanosecond-timescale spin transfer of individual electrons across a quadruple-quantum-dot device. Utilizing enhanced relaxation rates at a so-called hot spot, we can upper bound the shuttle time to at most 150 ns. While actual shuttle times are likely shorter, 150 ns is already fast enough to preserve spin coherence in, e.g., silicon based quantum dots. This work therefore realizes an important prerequisite for coherent spin transfer in quantum dot arrays.

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

    DEFF Research Database (Denmark)

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

    2010-01-01

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

  12. Electronic Social Networks, Teaching, and Learning

    Science.gov (United States)

    Pidduck, Anne Banks

    2010-01-01

    This paper explores the relationship between electronic social networks, teaching, and learning. Previous studies have shown a strong positive correlation between student engagement and learning. By extending this work to engage instructors and add an electronic component, our study shows possible teaching improvement as well. In particular,…

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

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 2 ... Spin glasses; quantum phase transition; ferromagnetism; electron gas. ... We argue that a quantum transition involving the destruction of the spin-glass order in an applied in-plane magnetic field offers a natural explanation of some features of recent ...

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

    Indian Academy of Sciences (India)

    Abstract. We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment.

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

    Directory of Open Access Journals (Sweden)

    Srinivasa Rao Singamaneni

    2014-04-01

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

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

    CERN Document Server

    Fanciulli, Marco

    2009-01-01

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

  17. Electron-spin-resonance studies of spin-polarized hydrogen on the surface of liquid /sup 4/He

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, M.W.; Shinkoda, I.; Hardy, W.N.; Berlinsky, A.J.; Bridges, F.; Statt, B.W.

    1985-06-01

    Electron-spin resonance at 114 GHz is used to measure the three-body recombination rate (L/sub 3/) and the two-body surface relaxation rate (G/sub 2s/) for doubly-spin-polarized H between 100 and 200 mK. Our results for L/sub 3/ confirm and extend those of Cline, Greytak, and Kleppner. We find that G/sub 2s/ is much smaller than previously reported and in reasonable agreement with theory. Around 100 mK, we also observe sidebands due to surface atoms whose frequency is shifted by dipole-dipole interactions.

  18. Statistical reconstruction algorithms for continuous wave electron spin resonance imaging

    Science.gov (United States)

    Kissos, Imry; Levit, Michael; Feuer, Arie; Blank, Aharon

    2013-06-01

    Electron spin resonance imaging (ESRI) is an important branch of ESR that deals with heterogeneous samples ranging from semiconductor materials to small live animals and even humans. ESRI can produce either spatial images (providing information about the spatially dependent radical concentration) or spectral-spatial images, where an extra dimension is added to describe the absorption spectrum of the sample (which can also be spatially dependent). The mapping of oxygen in biological samples, often referred to as oximetry, is a prime example of an ESRI application. ESRI suffers frequently from a low signal-to-noise ratio (SNR), which results in long acquisition times and poor image quality. A broader use of ESRI is hampered by this slow acquisition, which can also be an obstacle for many biological applications where conditions may change relatively quickly over time. The objective of this work is to develop an image reconstruction scheme for continuous wave (CW) ESRI that would make it possible to reduce the data acquisition time without degrading the reconstruction quality. This is achieved by adapting the so-called "statistical reconstruction" method, recently developed for other medical imaging modalities, to the specific case of CW ESRI. Our new algorithm accounts for unique ESRI aspects such as field modulation, spectral-spatial imaging, and possible limitation on the gradient magnitude (the so-called "limited angle" problem). The reconstruction method shows improved SNR and contrast recovery vs. commonly used back-projection-based methods, for a variety of simulated synthetic samples as well as in actual CW ESRI experiments.

  19. New-type spin polarized electron source and its applications; Atarashii spin henkyoku denshi sengen to sono oyo

    Energy Technology Data Exchange (ETDEWEB)

    Saka, T.; Kato, T. [Daido Steel Co. Ltd., Nagoya (Japan); Nakanishi, T.; Okumi, S. [Nagoya University, Nagoya (Japan); Horinaka, H. [Osaka Prefectural University, Osaka (Japan). College of Engineering

    1998-08-20

    This paper reveals that using distorted thin GaAs film can realize high polarization in spin polarized electron ray, and introduces properties of the developed ray source. The paper also touches on the application thereof to property physics. Realization of the high spin polarization is based on use of the `optical polarization method`. With this method, electrons in specific spin state are excited into a conduction band by utilizing the selection law used when valency electrons of zincblende type crystal such as GaAs absorb circular polarization. These electrons are taken out into vacuum and used as polarized electron beams. In order to realize uniformly distorted GaAs film, a method was discussed, with which the thin GaAs films are grown on substrates with different lattice constants, and the films are distorted by means of lattice mismatch. GaAs(1-x)Px was used for the substrates. GaAs(1-x)Px has the lattice constant decrease as the P`s mixed crystal ratio `x` increases. If a thin GaAs film is grown on this substrate, it is possible to obtain GaAs which is subjected to compression stress in the direction parallel with the growing surface, and tensile stress in the vertical direction. 13 refs., 5 figs., 1 tab.

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

    DEFF Research Database (Denmark)

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

    2002-01-01

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

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

    DEFF Research Database (Denmark)

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

    2008-01-01

    of electrons are coupled, thereby breaking all of these symmetries. This spin–orbit coupling is directly observed as a splitting of the four-fold degeneracy of a single electron in ultra-clean quantum dots. The coupling favours parallel alignment of the orbital and spin magnetic moments for electrons......Electrons in atoms possess both spin and orbital degrees of freedom. In non-relativistic quantum mechanics, these are independent, resulting in large degeneracies in atomic spectra. However, relativistic effects couple the spin and orbital motion, leading to the well-known fine structure...... systems, entailing new design principles for the realization of quantum bits (qubits) in nanotubes and providing a mechanism for all-electrical control of spins in nanotubes....

  2. Synthesizing complex spin networks with spin-motion coupled neutral atoms in photonic crystals

    Science.gov (United States)

    Dong, Ying

    2017-04-01

    We develop a toolbox for realizing ``fully programmable'' d-dimensional pairwise interacting lattice spin systems with spin-motion coupled neutral atoms in the vicinity of 1D photonic crystal waveguides. The enabling platform thereby allows to synthesize a wide range of strongly interacting quantum materials by way of vacuum-engineered interatomic kinetic interactions. We demonstrate the versatility of our assembly language approach towards arbitrary SU(2)-lattice spin models with explicit constructions of familiar Hamiltonians for perfect state transfer in 1D spin chains, lattice gauge theories, and topologicallyquantum spin liquids. We further construct Dzyaloshinski-Moriya interaction for the realization ofspin liquids and long-range random quantum magnets with spin-glass phase.

  3. Spin switching in electronic devices based on 2D assemblies of spin-crossover nanoparticles.

    Science.gov (United States)

    Dugay, Julien; Giménez-Marqués, Mónica; Kozlova, Tatiana; Zandbergen, Henny W; Coronado, Eugenio; van der Zant, Herre S J

    2015-02-18

    Two-dimensional assemblies of triazole-based spin-crossover nanoparticles (SCO NPs) presenting different morphologies are prepared and electrically characterized. The thermal hysteresis loop in the electrical conductance near room temperature correlates with the NP morphologies and their 2D organization. The unprecedentedly large difference - up to two orders of magnitude - in the electrical conductance of the two spin states is of interest for applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Optically Imaged Striped Domains of Nonequilibrium Electronic and Nuclear Spins in a Fractional Quantum Hall Liquid.

    Science.gov (United States)

    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.

  5. Detection and characterisation of radicals using electron paramagnetic resonance (EPR) spin trapping and related methods

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan

    2016-01-01

    Electron paramagnetic resonance (EPR) spectroscopy (also known as electron spin resonance, ESR, or electron magnetic resonance, EMR, spectroscopy) is often described as the “gold standard” for the detection and characterisation of radicals in chemical, biological and medical systems. The article...

  6. Persistent Skyrmion Lattice of Noninteracting Electrons with Spin-Orbit Coupling.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2004-07-01

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

  8. Study of f electron correlations in nonmagnetic Ce by means of spin resolved resonant photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Yu, S; Komesu, T; Chung, B W; Waddill, G D; Morton, S A; Tobin, J G

    2005-11-28

    We have studied the spin-spin coupling between two f electrons of nonmagnetic Ce by means of spin resolved resonant photoemission using circularly polarized synchrotron radiation. The two f electrons participating in the 3d{sub 5/2} {yields} 4f resonance process are coupled in a singlet while the coupling is veiled in the 3d{sub 3/2} {yields} 4f process due to an additional Coster-Kronig decay channel. The identical singlet coupling is observed in the 4d {yields} 4f resonance process. Based on the Ce measurements, it is argued that spin resolved resonant photoemission is a unique approach to study the correlation effects, particularly in the form of spin, in the rare-earths and the actinides.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-02-15

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

  10. Theoretical study of hysteresis in electron transport through spin-crossover molecules

    Science.gov (United States)

    Brown, Kristen; Park, Kyungwha

    2012-02-01

    Recent advances in nanoscale molecular systems stimulate experimental studies of electron transport across molecular junctions formed by single molecules or nanoparticles bridged between electrodes, or molecular monolayers adsorbed onto surfaces, using three-terminal set-ups or scanning tunneling microscope. Among them, spin-crossover molecular systems draw attention due to their unusual coupling between spin degrees of freedom and external stimuli. Spin magnetic moments of these molecular systems increase with increasing temperature or pressure, or shining light, and their magnetization shows hysteresis behavior with temperature, pressure, or light. Recent transport measurements across nanoparticles made of such spin-crossover molecules reveal hysteresis behavior in current-voltage characteristics, driven by voltage at a given temperature. In this talk, we present our work on understanding of hysteresis in electron transport through a nanoparticle consisting of Fe-based spin-crossover molecules, using a model-Hamiltonian approach and insight obtained from density functional theory.

  11. Spin- and Energy Relaxation of Hot Electrons at GaAs Surfaces

    Science.gov (United States)

    Ohms, Torsten; Hiebbner, Kevin; Schneider, Hans Christian; Aeschlimann, Martin

    The mechanisms for spin relaxation in semiconductors are reviewed, and the mechanism prevalent in p-doped semiconductors, namely spin relaxation due to the electron-hole exchange interaction, or Bir-Aronov-Pikus mechanism, is presented in some depth. It is shown that the solution of Boltzmann-type kinetic equations allows one to obtain quantitative results for spin relaxation in semiconductors that go beyond the original Bir-Aronov-Pikus relaxation-rate approximation. Experimental results using surface-sensitive two-photon photoemission techniques show that the relaxation time of the electron spin polarization in p-doped GaAs at a semiconductor/metal surface is several times longer than the corresponding bulk spin-relaxation times. A theoretical explanation of these results in terms of the reduced density of holes in the band-bending region at the surface is presented.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-15

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

  13. Non-abelian Gauge Fields from Defects in Spin-Networks

    CERN Document Server

    Vaid, Deepak

    2013-01-01

    \\emph{Effective} gauge fields arise in the description of the dynamics of defects in lattices of graphene in condensed matter. The interactions between neighboring nodes of a lattice/spin-network are described by the Hubbard model whose effective field theory at long distances is given by the Dirac equation for an \\emph{emergent} gauge field. The spin-networks in question can be used to describe the geometry experienced by a non-inertial observer in flat spacetime moving at a constant acceleration in a given direction. We expect such spin-networks to describe the structure of quantum horizons of black holes in loop quantum gravity. We argue that the abelian and non-abelian gauge fields of the Standard Model can be identified with the emergent degrees of freedom required to describe the dynamics of defects in symmetry reduced spin-networks.

  14. Electron spin relaxation in paramagnetic Ga(Mn)As quantum wells

    Science.gov (United States)

    Jiang, J. H.; Zhou, Y.; Korn, T.; Schüller, C.; Wu, M. W.

    2009-04-01

    Electron spin relaxation in paramagnetic Ga(Mn)As quantum wells is studied via the fully microscopic kinetic spin Bloch equation approach where all the scatterings, such as the electron-impurity, electron-phonon, electron-electron Coulomb, electron-hole Coulomb, electron-hole exchange (the Bir-Aronov-Pikus mechanism) and the s-d exchange scatterings, are explicitly included. The Elliott-Yafet mechanism is also incorporated. From this approach, we study the spin relaxation in both n -type and p -type Ga(Mn)As quantum wells. For n -type Ga(Mn)As quantum wells, where most Mn ions take the interstitial positions, we find that the spin relaxation is always dominated by the D’yakonov-Perel’ (DP) mechanism in the metallic region. Interestingly, the Mn concentration dependence of the spin relaxation time is nonmonotonic and exhibits a peak. This is due to the fact that the momentum scattering and the inhomogeneous broadening have different density dependences in the nondegenerate and degenerate regimes. For p -type Ga(Mn)As quantum wells, we find that the Mn concentration dependence of the spin relaxation time is also nonmonotonic and shows a peak. The cause of this behavior is that the s-d exchange scattering (or the Bir-Aronov-Pikus) mechanism dominates the spin relaxation in the high Mn concentration regime at low (or high) temperature, whereas the DP mechanism determines the spin relaxation in the low Mn concentration regime. The Elliott-Yafet mechanism also contributes to the spin relaxation at intermediate temperatures. The spin relaxation time due to the DP mechanism increases with increasing Mn concentration due to motional narrowing, whereas those due to the spin-flip mechanisms decrease with it, which thus leads to the formation of the peak. The temperature, photoexcitation density, and magnetic field dependences of the spin relaxation time in p -type Ga(Mn)As quantum wells are investigated systematically with the underlying physics revealed. Our results are

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

    Science.gov (United States)

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

    2017-01-01

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

  16. Coupling a Surface Acoustic Wave to an Electron Spin in Diamond via a Dark State

    Directory of Open Access Journals (Sweden)

    D. Andrew Golter

    2016-12-01

    Full Text Available The emerging field of quantum acoustics explores interactions between acoustic waves and artificial atoms and their applications in quantum information processing. In this experimental study, we demonstrate the coupling between a surface acoustic wave (SAW and an electron spin in diamond by taking advantage of the strong strain coupling of the excited states of a nitrogen vacancy center while avoiding the short lifetime of these states. The SAW-spin coupling takes place through a Λ-type three-level system where two ground spin states couple to a common excited state through a phonon-assisted as well as a direct dipole optical transition. Both coherent population trapping and optically driven spin transitions have been realized. The coherent population trapping demonstrates the coupling between a SAW and an electron spin coherence through a dark state. The optically driven spin transitions, which resemble the sideband transitions in a trapped-ion system, can enable the quantum control of both spin and mechanical degrees of freedom and potentially a trapped-ion-like solid-state system for applications in quantum computing. These results establish an experimental platform for spin-based quantum acoustics, bridging the gap between spintronics and quantum acoustics.

  17. Coupling a Surface Acoustic Wave to an Electron Spin in Diamond via a Dark State

    Science.gov (United States)

    Golter, D. Andrew; Oo, Thein; Amezcua, Mayra; Lekavicius, Ignas; Stewart, Kevin A.; Wang, Hailin

    2016-10-01

    The emerging field of quantum acoustics explores interactions between acoustic waves and artificial atoms and their applications in quantum information processing. In this experimental study, we demonstrate the coupling between a surface acoustic wave (SAW) and an electron spin in diamond by taking advantage of the strong strain coupling of the excited states of a nitrogen vacancy center while avoiding the short lifetime of these states. The SAW-spin coupling takes place through a Λ -type three-level system where two ground spin states couple to a common excited state through a phonon-assisted as well as a direct dipole optical transition. Both coherent population trapping and optically driven spin transitions have been realized. The coherent population trapping demonstrates the coupling between a SAW and an electron spin coherence through a dark state. The optically driven spin transitions, which resemble the sideband transitions in a trapped-ion system, can enable the quantum control of both spin and mechanical degrees of freedom and potentially a trapped-ion-like solid-state system for applications in quantum computing. These results establish an experimental platform for spin-based quantum acoustics, bridging the gap between spintronics and quantum acoustics.

  18. Spin- and valley-dependent electronic band structure and electronic heat capacity of ferromagnetic silicene in the presence of strain, exchange field and Rashba spin-orbit coupling

    Science.gov (United States)

    Hoi, Bui Dinh; Yarmohammadi, Mohsen; Kazzaz, Houshang Araghi

    2017-10-01

    We studied how the strain, induced exchange field and extrinsic Rashba spin-orbit coupling (RSOC) enhance the electronic band structure (EBS) and electronic heat capacity (EHC) of ferromagnetic silicene in presence of external electric field (EF) by using the Kane-Mele Hamiltonian, Dirac cone approximation and the Green's function approach. Particular attention is paid to investigate the EHC of spin-up and spin-down bands at Dirac K and K‧ points. We have varied the EF, strain, exchange field and RSOC to tune the energy of inter-band transitions and consequently EHC, leading to very promising features for future applications. Evaluation of EF exhibits three phases: Topological insulator (TI), valley-spin polarized metal (VSPM) and band insulator (BI) at given aforementioned parameters. As a new finding, we have found a quantum anomalous Hall phase in BI regime at strong RSOCs. Interestingly, the effective mass of carriers changes with strain, resulting in EHC behaviors. Here, exchange field has the same behavior with EF. Finally, we have confirmed the reported and expected symmetry results for both Dirac points and spins with the study of valley-dependent EHC.

  19. Electronic device aspects of neural network memories

    Science.gov (United States)

    Lambe, J.; Moopenn, A.; Thakoor, A. P.

    1985-01-01

    The basic issues related to the electronic implementation of the neural network model (NNM) for content addressable memories are examined. A brief introduction to the principles of the NNM is followed by an analysis of the information storage of the neural network in the form of a binary connection matrix and the recall capability of such matrix memories based on a hardware simulation study. In addition, materials and device architecture issues involved in the future realization of such networks in VLSI-compatible ultrahigh-density memories are considered. A possible space application of such devices would be in the area of large-scale information storage without mechanical devices.

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

    CERN Document Server

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

    2005-01-01

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

  1. Layered Chalcogenides beyond Graphene: from Electronic Structure Evolution to the Spin Transport

    Science.gov (United States)

    Yuan, Hongtao

    2014-03-01

    Recent efforts on graphene-like atomic layer materials, aiming at novel electronic properties and quantum phenomena beyond graphene, have attracted much attention for potential electronics/spintronics applications. Compared to the weak spin-orbit-interaction (SOI) in graphene, metal chalcogenides MX2 have heavy 4d/5d elements with strong atomic SOI, providing a unique way for generating spin polarization based on valleytronics physics. Indeed, such a spin-polarized band structure has been demonstrated theoretically and supported by optical investigations. However, despite these exciting progresses, following two important issues in MX2 community remain elusive: 1. the quantitative band structure of MX2 compounds (where are the valleys -band maxima/minima- locating in the BZ) have not been experimentally confirmed. Especially for those cleaved ultrathin mono- and bi-layer flakes hosting most of recently-reported exotic phenomena at the 2D limit, the direct detection for band dispersion becomes of great importance for valleytronics. 2. Spin transports have seldom been reported even though such a strong SOI system can serve as an ideal platform for the spin polarization and spin transport. In this work, we started from the basic electronic structures of representative MX2, obtained by ARPES, and investigated both the band variation between these compounds and their band evolution from bulk to the monolayer limit. After having a systematic understanding on band structures, we reported a giant Zeeman-type spin-polarization generated and modulated by an external electric field in WSe2 electric-double-layer transistors. The non-magnetic approach for realizing such an intriguing spin splitting not only keeps the system time-reversally invariant but also suggests a new paradigm for manipulating the spin-degrees of freedom of electrons. Acknowledge the support from DoE, BES, Division of MSE under contract DE-AC02-76SF00515.

  2. Gate-Controlled Electron Spin Resonance in a GaAs/AlGaAs Heterostructure

    OpenAIRE

    Jiang, H. W.; Yablonovitch, E.

    2001-01-01

    The electron spin resonance (ESR) of two-dimensional electrons is investigated in a gated GaAs/AlGaAs heterostructure. We found that the ESR resonance frequency can be turned by means of a gate voltage. The front and back gates of the heterostructure produce opposite g-factor shift, suggesting that electron g-factor is being electrostatically controlled by shifting the equilibrium position of the electron wave function from one epitaxial layer to another with different g-factors.

  3. Ising Spin Network States for Loop Quantum Gravity: a Toy Model for Phase Transitions

    CERN Document Server

    Feller, Alexandre

    2015-01-01

    Non-perturbative approaches to quantum gravity call for a deep understanding of the emergence of geometry and locality from the quantum state of the gravitational field. Without background geometry, the notion of distance should entirely emerge from the correlations between the gravity fluctuations. In the context of loop quantum gravity, quantum states of geometry are defined as spin networks. These are graphs decorated with spin and intertwiners, which represent quantized excitations of areas and volumes of the space geometry. Here, we develop the condensed matter point of view on extracting the physical and geometrical information out of spin network states: we introduce new Ising spin network states, both in 2d on a square lattice and in 3d on a hexagonal lattice, whose correlations map onto the usual Ising model in statistical physics. We construct these states from the basic holonomy operators of loop gravity and derive a set of local Hamiltonian constraints which entirely characterize our states. We di...

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

    DEFF Research Database (Denmark)

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

    2016-01-01

    The radical pair model of the avian magnetoreceptor relies on long-lived electron spin coherence. Dephasing, resulting from interactions of the spins with their fluctuating environment, is generally assumed to degrade the sensitivity of this compass to the direction of the Earth's magnetic field....... Here we argue that certain spin relaxation mechanisms can enhance its performance. We focus on the flavin-tryptophan radical pair in cryptochrome, currently the only candidate magnetoreceptor molecule. Correlation functions for fluctuations in the distance between the two radicals in Arabidopsis...... thaliana cryptochrome 1 were obtained from molecular dynamics (MD) simulations and used to calculate the spin relaxation caused by modulation of the exchange and dipolar interactions. We find that intermediate spin relaxation rates afford substantial enhancements in the sensitivity of the reaction yields...

  5. Architecture for networked electronic patient record systems.

    Science.gov (United States)

    Takeda, H; Matsumura, Y; Kuwata, S; Nakano, H; Sakamoto, N; Yamamoto, R

    2000-11-01

    There have been two major approaches to the development of networked electronic patient record (EPR) architecture. One uses object-oriented methodologies for constructing the model, which include the GEHR project, Synapses, HL7 RIM and so on. The second approach uses document-oriented methodologies, as applied in examples of HL7 PRA. It is practically beneficial to take the advantages of both approaches and to add solution technologies for network security such as PKI. In recognition of the similarity with electronic commerce, a certificate authority as a trusted third party will be organised for establishing networked EPR system. This paper describes a Japanese functional model that has been developed, and proposes a document-object-oriented architecture, which is-compared with other existing models.

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

    Science.gov (United States)

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

    2003-01-01

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

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

    CERN Document Server

    Dellweg, Matthias M; Müller, Carsten

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-02-01

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

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

    NARCIS (Netherlands)

    Lerescu, Alexandru Ionut

    2007-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Bučinský, Lukáš, E-mail: lukas.bucinsky@stuba.sk [Slovak University of Technology, FCHPT, Institute of Physical Chemistry and Chemical Physics, Radlinskeho 9, Bratislava SK-812 37 (Slovakia); Kucková, Lenka; Malček, Michal; Kožíšek, Jozef; Biskupič, Stanislav [Slovak University of Technology, FCHPT, Institute of Physical Chemistry and Chemical Physics, Radlinskeho 9, Bratislava SK-812 37 (Slovakia); Jayatilaka, Dylan [University of Western Australia, Department of Chemistry, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Büchel, Gabriel E. [University of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna (Austria); King Abdullah University of Science and Technology, Division for Physical Sciences and Engineering and KAUST Catalysis Center, Thuwal (Saudi Arabia); Arion, Vladimir B. [University of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna (Austria)

    2014-06-25

    Highlights: • Quasirelativistic study of electron density topology of Os and Ru complexes. • Electron/spin densities and negative Laplacian of electron density presented. • Analytic correction of picture change error at IOTC level. • Relativistic and spin–orbit effects are considered, IOTC vs. DKH2 compared. - Abstract: The change of picture of the quasirelativistic Hartree–Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl{sub 5}(Hpz)]{sup −} and [RuCl{sub 5}(NO)]{sup 2−} transition metal complexes are considered. Both, scalar relativistic and spin–orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.

  11. Spin-charge separation and electron pairing instabilities in Hubbard nanoclusters.

    Science.gov (United States)

    Kocharian, A N; Fernando, G W; Palandage, K; Davenport, J W

    2009-07-01

    Electron charge and spin pairing instabilities in various cluster geometries for attractive and repulsive electrons are studied exactly under variation of interaction strength, electron doping and temperature. The exact diagonalization, level crossing degeneracies, spin-charge separation and separate condensation of paired electron charge and opposite spins yield intriguing insights into the origin of magnetism, ferroelectricity and superconductivity seen in inhomogeneous bulk nanomaterials and various phenomena in cold fermionic atoms in optical lattices. Phase diagrams resemble a number of inhomogeneous, coherent and incoherent nanoscale phases found recently in high-T(c) cuprates, manganites and multiferroic nanomaterials probed by scanning tunneling microscopy. Separate condensation of electron charge and spin degrees at various crossover temperatures offers a new route for superconductivity, different from the BCS scenario. The calculated phase diagrams resemble a number of inhomogeneous paired phases, superconductivity, ferromagnetism and ferroelectricity found in Nb and Co nanoparticles. The phase separation and electron pairing, monitored by electron doping and magnetic field surprisingly resemble incoherent electron pairing in the family of doped high-T(c) cuprates, ruthenocuprates, iron pnictides and spontaneous ferroelectricity in multiferroic materials.

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

    NARCIS (Netherlands)

    Gökcan, H.

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

  13. 2D Spin-Dependent Diffraction of Electrons From Periodical Chains of Nanomagnets

    Directory of Open Access Journals (Sweden)

    Teshome Senbeta

    2012-03-01

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

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

    NARCIS (Netherlands)

    van der Wal, Caspar H.; Sladkov, Maksym

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

  15. Application of electron spin resonance for evaluation of the level of ...

    Indian Academy of Sciences (India)

    Unknown

    logic processes, ranging from intermediates in enzyme reaction to effectors. Electron spin resonance (ESR) or electron paramagnetic resonance (EPR) can be used to provide insight into the free radical state of cells, bio- chemical reactions and measure free radical levels in human tissues (Zyrianov and Sumovskaya 2001).

  16. Geometric structure, electronic structure, and spin transition of several Fe{sup II} spin-crossover molecules

    Energy Technology Data Exchange (ETDEWEB)

    Tuan, Nguyen Anh [Faculty of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam)

    2012-04-01

    We present a density functional study on the geometric structure, electronic structure, and spin transition of a series of Fe{sup II} spin-crossover (SCO) molecules, i.e., [Fe(abpt){sub 2}(NCS){sub 2}] (1), [Fe(abpt){sub 2}(NCSe){sub 2}] (2), and [Fe(dpbo)(HIm){sub 2}] (3) with dpbo diethyl(E,E)-2,2'-[1,2-phenylbis(iminomethylidyne)]bis[3-oxobutanoate](2-), N',O{sup 3},O{sup 3}', and abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole in order to explore more about the way to control SCO behavior of transition metal complexes. Our calculated results show that the spin transition of these Fe{sup II} molecules is accompanied with charge transfer between the Fe atom and ligands. This causes change in the electrostatic energy ({Delta}U) as well as the total electronic energy of SCO molecules. Moreover, our calculated results demonstrate an important contribution of the interionic interactions to {Delta}U, and there is the relation between {Delta}U and the thermal hysteresis behavior of SCO molecules. These results should be helpful for developing new SCO molecules.

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

    Science.gov (United States)

    Tomiyasu, Keisuke; Koyama, Shun-Ichi; Watahiki, Masanori; Sato, Mika; Nishihara, Kazuki; Onodera, Mitsugi; Iwasa, Kazuaki; Nojima, Tsutomu; Yamasaki, Yuuichi; Nakao, Hironori; Murakami, Youichi

    2015-03-01

    Perovskite-type LaCoO3 (Co3+: d6) is a rare inorganic material with sensitive and characteristic responses among low, intermediate, and high spin states. For example, in insulating nonmagnetic low-spin states below about 20 K, light hole doping (Ni substitution) induces much larger magnetization than expected; over net 10μB/hole (5μB/Ni) for 1μB/hole (1μB/Ni), in which the nearly isolated dopants locally change the surrounding Co low-spin states to magnetic ones and form spin molecules with larger total spin. Further, the former is isotropic, whereas the latter exhibits characteristic anisotropy probably because of Jahn-Teller distortion. In contrast, for electron doping, relatively insensitive spin-state responses were reported, as in LaCo(Ti4+) O3, but are not clarified, and are somewhat controversial. Here, we present macroscopic measurement data of another electron-doped system LaCo(Te6+) O3 and discuss the spin-state responses. This study was financially supported by Grants-in-Aid for Young Scientists (B) (No. 22740209 and 26800174) from the MEXT of Japan.

  18. Collective spin states in the electron gas in different dimensions and geometries

    Science.gov (United States)

    Lipparini, Enrico; Colletti, Leonardo; Orlandini, Giusi; Serra, Liorenç

    1998-06-01

    We study spin longitudinal and transverse linear response of the 3-dimensional electron gas, metal clusters and quantum dots. When the systems are spin unpolarized in the ground state, a low energy collective state emerges in finite size systems due to the discrete shell structure, whereas it is absent in the bulk due to the Landau damping. In the case of spin polarization of the ground state a collective state is present also in the bulk and a family of new collective states appears in finite size systems.

  19. Influence of soliton distributions on the spin-dependent electronic ...

    Indian Academy of Sciences (India)

    distribution of the paired solitons the band gap closed (figure 4c) such that the current– voltage characteristic of the junction shows an ohmic-like behaviour. Figure 5 shows the. TMR ratio using the results of the P and AP spin currents in the absence (figure 5a) and in the presence of solitons (figures 5b and 5c) as a function ...

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

    Science.gov (United States)

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

    2012-02-08

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

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

    CERN Document Server

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

    2016-01-01

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

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

    NARCIS (Netherlands)

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

    2007-01-01

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

  3. Optical, magnetic, and electronic control of free carrier spin in semiconductors

    Science.gov (United States)

    Johnston-Halperin, Ezekiel

    Semiconductor physics has traditionally been dominated by consideration of electronic charge. However, recent discoveries concerning the manipulation and detection of the spin degree of freedom have led to rapid advances in the fields of magneto-electronics/spintronics, quantum information, and quantum computation. Here I present a series of experiments that utilize both coherent optical techniques and sophisticated materials synthesis to examine and control electron spin in semiconducting materials. First, we use femtosecond-resolved pump-probe spectroscopy to optically generate and detect non-equilibrium electron spin populations in GaN. We observe robust spin dynamics with nanosecond lifetimes and which persist to room temperature despite a defect density eight orders of magnitude higher than is found in typical semiconductors. Additionally systematic low-temperature measurements as a function of electronic doping and magnetic field reveal an anomalous spin scattering mechanism, distinct from traditional mechanisms found in semiconductors (D'yakonv-Perel, Bir-Aronov-Pikus, Elliot-Yafet) and consistent with similar studies in GaAs. In a parallel effort with the aim of exerting magnetic control over electronic spin, we exploit advanced molecular beam eptixay (MBE) growth techniques to atomically engineer the distribution of magnetic impurities within a GaAs matrix. These materials exhibit tunable ferromagnetism while allowing us to simultaneously and independently control the electronic and band structure of the host semiconductor lattice. This allows for the synthesis of ferromagnetic materials which are ˜3--5 monolayers thick and maintain their magnetic order in the presence of both p- and n-type doping. Finally, we further exploit the flexibility of semiconductor materials in the design and fabrication of a spin-polarized Zener tunneling diode. This device overcomes the limitation that (Ga,Mn)As is inherently p-type by generating a spin-polarized electron

  4. Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide

    DEFF Research Database (Denmark)

    Javadi, Alisa; Ding, Dapeng; Appel, Martin Hayhurst

    2017-01-01

    Access to the electron spin is at the heart of many protocols for integrated and distributed quantum-information processing [1-4]. For instance, interfacing the spin-state of an electron and a photon can be utilized to perform quantum gates between photons [2,5] or to entangle remote spin states [6......-9]. Ultimately, a quantum network of entangled spins constitutes a new paradigm in quantum optics [1]. Towards this goal, an integrated spin-photon interface would be a major leap forward. Here we demonstrate an efficient and optically programmable interface between the spin of an electron in a quantum dot...... and photons in a nanophotonic waveguide. The spin can be deterministically prepared with a fidelity of 96\\%. Subsequently the system is used to implement a "single-spin photonic switch", where the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may...

  5. Electrons in strong electromagnetic fields: spin effects and radiation reaction (Conference Presentation)

    Science.gov (United States)

    Bauke, Heiko; Wen, Meng; Keitel, Christoph H.

    2017-05-01

    Various different classical models of electrons including their spin degree of freedom are commonly applied to describe the coupled dynamics of relativistic electron motion and spin precession in strong electromagnetic fields. The spin dynamics is usually governed by the Thomas-Bargmann-Michel-Telegdi equation [1, 2] in these models, while the electron's orbital motion follows the (modified) Lorentz force and a spin-dependent Stern-Gerlach force. Various classical models can lead to different or even contradicting predictions how the spin degree of freedom modifies the electron's orbital motion when the electron moves in strong electromagnetic fields. This discrepancy is rooted in the model-specific energy dependency of the spin induced relativistic Stern-Gerlach force acting on the electron. The Frenkel model [3, 4] and the classical Foldy-Wouthuysen model 5 are compared exemplarily against each other and against the quantum mechanical Dirac equation in order to identify parameter regimes where these classical models make different predictions [6, 7]. Our theoretical results allow for experimental tests of these models. In the setup of the longitudinal Stern-Gerlach effect, the Frenkel model and classical Foldy-Wouthuysen model lead in the relativistic limit to qualitatively different spin effects on the electron trajectory. Furthermore, it is demonstrated that in tightly focused beams in the near infrared the effect of the Stern-Gerlach force of the Frenkel model becomes sufficiently large to be potentially detectable in an experiment. Among the classical spin models, the Frenkel model is certainly prominent for its long history and its wide application. Our results, however, suggest that the classical Foldy-Wouthuysen model is superior as it is qualitatively in better agreement with the quantum mechanical Dirac equation. In ultra strong laser setups at parameter regimes where effects of the Stern-Gerlach force become relevant also radiation reaction effects are

  6. Effect of the anisotropy of the electron g-factor in spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong, Chittagong 4331 (Bangladesh); Gray, E. MacA. [Queensland Micro- and Nanotechnology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)

    2010-02-15

    Spin polarization in the presence of an external magnetic field and electric bias in quantum confined semiconductor structures has been studied by time- and polarization-resolved spectrometry. From measurements with angular variations of the magnetic field from the Voigt configuration (VC) it was found that both the frequency ({Omega}) and decay rate ({beta}) of the oscillatory component of the polarization increase with variation of the angle from the VC. Their dependences are discussed based on the electron spin dephasing related to the spread of the electron g-factor (g{sub e}) (i.e. unequal values of the longitudinal (g{sub e||}) and transverse (g{sub e}-perpendicular) components of g{sub e}) and the exchange interaction between the electron and hole spins. It is demonstrated that the increase in {Omega} upon deviation of the magnetic field from the VC relates to the anisotropy of g{sub e} (g{sub e||} and g{sub e}-perpendicular) resulting from the quantum confinement effect. However, the angular dependence on {beta} is related to the residual exchange interaction between the electron spin and rapidly relaxing hole spin.

  7. Annealing effect on the electron spin dynamics in heavily Mn-doped (Ga,Mn)As

    Energy Technology Data Exchange (ETDEWEB)

    Yue, Han; Chen, Lin; Gao, Haixia; Zhao, Jianhua; Zhang, Xinhui [Institute of Semiconductors, Chinese Academy of Sciences, Beijing (China)

    2014-05-15

    A temperature- and photo-excitation-density-dependent electron spin dephasing process has been studied by time-resolved magneto-optical Kerr effect (TR-MOKE) measurements for heavily-doped (Ga,Mn)As after appropriate annealing treatment. Unlike the as-grown (Ga,Mn)As in which s-d scattering is dominant for spin dephasing at low temperature, the exchange scattering induced by Mn ions is efficiently suppressed after annealing. For annealed (Ga,Mn)As, the p-d exchange coupling proves to be important for the electron spin dephasing process. Moreover, the Coulomb scattering arising from the weakly-localized holes and Mn impurities is revealed to play an important role in the electron spin dephasing after annealing. Our results demonstrate that the impurity induced disorder plays a significant role in the electron spin-dephasing process in (Ga,Mn)As when Mn is over doped by as much as 15%, which is a critical issue that needs to be considered to achieve high-quality (Ga,Mn)As thin films with a higher Curie temperature T{sub C} and better functionality.

  8. ν =2 /3 fractional quantum Hall state in an AlAs quantum well probed by electron spin resonance

    Science.gov (United States)

    Shchepetilnikov, A. V.; Frolov, D. D.; Nefyodov, Yu. A.; Kukushkin, I. V.; Tiemann, L.; Reichl, C.; Dietsche, W.; Wegscheider, W.

    2017-10-01

    The electron spin resonance (ESR) of two-dimensional electrons confined in a high-quality, 16-nm AlAs quantum well was investigated near the filling factor ν =2 /3 of the fractional quantum Hall effect (FQHE). The spin resonance was robust in the vicinity of the fractional filling ν =2 /3 , indicating that the ν =2 /3 state is at least partially spin polarized. The formation of the 2 /3 FQHE state did not result in any modifications of the ESR linewidth and, hence, of the electron spin relaxation rate. Yet the nuclear spin-lattice relaxation rate extracted from the time decay of the ESR Overhauser shift demonstrated a strong nonmonotonic dependence on the electron filling factor with a minimum near ν =2 /3 . This observation suggests the enhancement of the energy gap in the spin excitation spectrum of two-dimensional electrons at the ν =2 /3 state.

  9. Electron spin relaxation enhancement measurements of interspin distances in human, porcine, and Rhodobacter electron transfer flavoprotein ubiquinone oxidoreductase (ETF QO)

    Science.gov (United States)

    Fielding, Alistair J.; Usselman, Robert J.; Watmough, Nicholas; Simkovic, Martin; Frerman, Frank E.; Eaton, Gareth R.; Eaton, Sandra S.

    2008-02-01

    Electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) is a membrane-bound electron transfer protein that links primary flavoprotein dehydrogenases with the main respiratory chain. Human, porcine, and Rhodobacter sphaeroides ETF-QO each contain a single [4Fe-4S] 2+,1+ cluster and one equivalent of FAD, which are diamagnetic in the isolated enzyme and become paramagnetic on reduction with the enzymatic electron donor or with dithionite. The anionic flavin semiquinone can be reduced further to diamagnetic hydroquinone. The redox potentials for the three redox couples are so similar that it is not possible to poise the proteins in a state where both the [4Fe-4S] + cluster and the flavoquinone are fully in the paramagnetic form. Inversion recovery was used to measure the electron spin-lattice relaxation rates for the [4Fe-4S] + between 8 and 18 K and for semiquinone between 25 and 65 K. At higher temperatures the spin-lattice relaxation rates for the [4Fe-4S] + were calculated from the temperature-dependent contributions to the continuous wave linewidths. Although mixtures of the redox states are present, it was possible to analyze the enhancement of the electron spin relaxation of the FAD semiquinone signal due to dipolar interaction with the more rapidly relaxing [4Fe-4S] + and obtain point-dipole interspin distances of 18.6 ± 1 Å for the three proteins. The point-dipole distances are within experimental uncertainty of the value calculated based on the crystal structure of porcine ETF-QO when spin delocalization is taken into account. The results demonstrate that electron spin relaxation enhancement can be used to measure distances in redox poised proteins even when several redox states are present.

  10. Spin-electronic devices with half-metallic Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Huetten, A. [Institute of Nanotechnology, Forschungszentrum Karlsruhe GmbH, P.O. Box 3640, D-76021 Karlsruhe (Germany)]. E-mail: Andreas.Huetten@fzk.de; Schmalhorst, J. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Thomas, A. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Kaemmerer, S. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Sacher, M. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Ebke, D. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Liu, N.-N. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Kou, X. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Reiss, G. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany)

    2006-10-26

    We have integrated Co{sub 2}MnSi as a representative of the full-Heusler compound family as one magnetic electrode into technological relevant magnetic tunnel junctions. The resulting tunnel magnetoresistance at 20 K currently achieved is 108% associated with a Co{sub 2}MnSi spin polarization of 70% clearly proving that Co{sub 2}MnSi is already superior to 3d-based magnetic elements or their alloys. The corresponding room temperature value of the tunnel magnetoresistance is 42%. The presence of a step like tunnel barrier which is already created during plasma oxidation, while preparing the AlO {sub x} tunnel barrier, has been identified as the current limitation to achieve larger tunnel magnetoresistance and hence larger spin polarization and is a direct consequence of the oxygen affinity of the Co{sub 2}MnSi-Heusler element Mn. In addition preliminarily results on Co{sub 2}FeSi as a new full-Heusler compound integrated as magnetic electrode into technological relevant magnetic tunnel junctions are shown and discussed.

  11. Spin polarized electron-positron pair production via elliptical polarized laser fields

    CERN Document Server

    Wöllert, Anton; Keitel, Christoph H

    2015-01-01

    We study nonperturbative multiphoton electron-positron pair creation in ultra-strong electromagnetic fields formed by two counterpropagating pulses with elliptic polarization. Our numerical approach allows us to take into account the temporal as well as the spatial variation of the standing electromagnetic field. The spin and momentum resolved pair creation probabilities feature characteristic Rabi oscillations and resonance spectra. Therefore, each laser frequency features a specific momentum distribution of the created particles. We find that depending on the relative polarization of both pulses the created electrons may be spin polarized along the direction of field propagation.

  12. Spin excitations and the electronic specific heat of URu2Si2

    DEFF Research Database (Denmark)

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

    1991-01-01

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

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

    DEFF Research Database (Denmark)

    Michiardi, Matteo; Bianchi, Marco; Dendzik, Maciej

    2015-01-01

    Near-surface two-dimensional electron gases on the topological insulator Bi$_2$Te$_2$Se are induced by electron doping and studied by angle-resolved photoemission spectroscopy. A pronounced spin-orbit splitting is observed for these states. The $k$-dependent splitting is strongly anisotropic...... to be negative, reducing the energy splitting at high $k$. The interplay of band structure, higher order Rashba effect and tuneable doping offers the opportunity to engineer not only the size of the spin-orbit splitting but also its direction....

  14. Using spin trapping electron spin resonance for determining the degradation mechanism of membranes used in fuel cells

    Science.gov (United States)

    Schlick, Shulamith; Danilczuk, Marek; Spulber, Mariana

    2013-10-01

    Fuel cells (FCs) convert the chemical energy from the reaction of H2 with O2 to electrical energy, and have become an alternative clean energy source for automotive, portable and stationary applications. FC operation is possible when the membrane located between the electrodes maintains its integrity in the oxidising FC environment. Spin trapping electron spin resonance (ESR) has been used for determining the degradation mechanism of the perfluorinated membranes used in FCs. The study of low molecular weight model compounds confirmed two possible degradation mechanisms in membranes: initiated at the backbone and at the side chain. In situ experiments in a FC inserted in the resonator of an ESR spectrometer offered the ability to monitor radical processes in a FC. The presence of the radicals was determined by addition of 5,5-dimethy-l-pyrroline N-oxide (DMPO) as a spin trap. Taken together, the in situ results pointed to crossover processes, reactions at the catalyst surface, and the involvement of H• atoms in attack on the membrane; these processes cannot be visualised in ex situ studies. Therefore different membrane degradation mechanisms in the two types of experiments can be expected. The stability of the DMPO/OH adduct was increased by complexation with cavitands such as β-cyclodextrins and cucurbiturils.

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

    Science.gov (United States)

    Galbiati, Marta; Tatay, Sergio; Delprat, Sophie; Khanh, Hung Le; Servet, Bernard; Deranlot, Cyrile; Collin, Sophie; Seneor, Pierre; Mattana, Richard; Petroff, Frédéric

    2015-02-01

    Molecular and organic spintronics is an emerging research field which combines the versatility of chemistry with the non-volatility of spintronics. Organic materials have already proved their potential as tunnel barriers (TBs) or spacers in spintronics devices showing sizable spin valve like magnetoresistance effects. In the last years, a large effort has been focused on the optimization of these organic spintronics devices. Insertion of a thin inorganic tunnel barrier (Al2O3 or MgO) at the bottom ferromagnetic metal (FM)/organic interface seems to improve the spin transport efficiency. However, during the top FM electrode deposition, metal atoms are prone to diffuse through the organic layer and potentially short-circuit it. This may lead to the formation of a working but undesired FM/TB/FM magnetic tunnel junction where the organic plays no role. Indeed, establishing a protocol to demonstrate the effective spin dependent transport through the organic layer remains a key issue. Here, we focus on Co/Al2O3/Alq3/Co junctions and show that combining magnetoresistance and inelastic electron tunnelling spectroscopy measurements one can sort out working "organic" and short-circuited junctions fabricated on the same wafer.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-02-23

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

  17. Von Neumann entropy in a Rashba-Dresselhaus nanodot; dynamical electronic spin-orbit entanglement

    Science.gov (United States)

    Safaiee, Rosa; Golshan, Mohammad Mehdi

    2017-06-01

    The main purpose of the present article is to report the characteristics of von Neumann entropy, thereby, the electronic hybrid entanglement, in the heterojunction of two semiconductors, with due attention to the Rashba and Dresselhaus spin-orbit interactions. To this end, we cast the von Neumann entropy in terms of spin polarization and compute its time evolution; with a vast span of applications. It is assumed that gate potentials are applied to the heterojunction, providing a two dimensional parabolic confining potential (forming an isotropic nanodot at the junction), as well as means of controlling the spin-orbit couplings. The spin degeneracy is also removed, even at electronic zero momentum, by the presence of an external magnetic field which, in turn, leads to the appearance of Landau states. We then proceed by computing the time evolution of the corresponding von Neumann entropy from a separable (spin-polarized) initial state. The von Neumann entropy, as we show, indicates that electronic hybrid entanglement does occur between spin and two-dimensional Landau levels. Our results also show that von Neumann entropy, as well as the degree of spin-orbit entanglement, periodically collapses and revives. The characteristics of such behavior; period, amplitude, etc., are shown to be determined from the controllable external agents. Moreover, it is demonstrated that the phenomenon of collapse-revivals' in the behavior of von Neumann entropy, equivalently, electronic hybrid entanglement, is accompanied by plateaus (of great importance in quantum computation schemes) whose durations are, again, controlled by the external elements. Along these lines, we also make a comparison between effects of the two spin-orbit couplings on the entanglement (von Neumann entropy) characteristics. The finer details of the electronic hybrid entanglement, which may be easily verified through spin polarization measurements, are also accreted and discussed. The novel results of the present

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

    Science.gov (United States)

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

    2016-09-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Heindl, Emanuel

    2010-06-23

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

  20. Spin-Momentum Correlations in Quasi-Elastic Electron Scattering from Deuterium

    CERN Document Server

    Passchier, I; Szczerba, D; Alarcon, R; Bauer, T S; Boersma, D J; Van den Brand, J F J; Bulten, H J; Ent, R; Ferro-Luzzi, M; Harvey, M; Heimberg, P; Higinbotham, D W; Klous, S; Kolster, H; Lang, J; Militsyn, B L; Nikolenko, D M; Nooren, G J L; Norum, B E; Poolman, H R; Rachek, Igor A; Simani, M C; Six, E; De Vries, H; Wang, K; Zhou, Z L; Bauer, Th.S.

    2002-01-01

    We report on a measurement of spin-momentum correlations in quasi-elastic scattering of longitudinally polarized electrons with an energy of 720 MeV from vector-polarized deuterium. The spin correlation parameter $A^V_{ed}$ was measured for the $^2 \\vec{\\rm H}(\\vec e,e^\\prime p)n$ reaction for missing momenta up to 350 MeV/$c$ at a four-momentum transfer squared of 0.21 (GeV/c)$^2$. The data give detailed information about the spin structure of the deuteron, and are in good agreement with the predictions of microscopic calculations based on realistic nucleon-nucleon potentials and including various spin-dependent reaction mechanism effects. The experiment demonstrates in a most direct manner the effects of the D-state in the deuteron ground-state wave function and shows the importance of isobar configurations for this reaction.

  1. Correlation Effects and Hidden Spin-Orbit Entangled Electronic Order in Parent and Electron-Doped Iridates Sr2 IrO4

    Science.gov (United States)

    Zhou, Sen; Jiang, Kun; Chen, Hua; Wang, Ziqiang

    2017-10-01

    Analogs of the high-Tc cuprates have been long sought after in transition metal oxides. Because of the strong spin-orbit coupling, the 5 d perovskite iridates Sr2 IrO4 exhibit a low-energy electronic structure remarkably similar to the cuprates. Whether a superconducting state exists as in the cuprates requires understanding the correlated spin-orbit entangled electronic states. Recent experiments discovered hidden order in the parent and electron-doped iridates, some with striking analogies to the cuprates, including Fermi surface pockets, Fermi arcs, and pseudogap. Here, we study the correlation and disorder effects in a five-orbital model derived from the band theory. We find that the experimental observations are consistent with a d -wave spin-orbit density wave order that breaks the symmetry of a joint twofold spin-orbital rotation followed by a lattice translation. There is a Berry phase and a plaquette spin flux due to spin procession as electrons hop between Ir atoms, akin to the intersite spin-orbit coupling in quantum spin Hall insulators. The associated staggered circulating Jeff=1 /2 spin current can be probed by advanced techniques of spin-current detection in spintronics. This electronic order can emerge spontaneously from the intersite Coulomb interactions between the spatially extended iridium 5 d orbitals, turning the metallic state into an electron-doped quasi-2D Dirac semimetal with important implications on the possible superconducting state suggested by recent experiments.

  2. Correlation Effects and Hidden Spin-Orbit Entangled Electronic Order in Parent and Electron-Doped Iridates Sr_{2}IrO_{4}

    Directory of Open Access Journals (Sweden)

    Sen Zhou

    2017-10-01

    Full Text Available Analogs of the high-T_{c} cuprates have been long sought after in transition metal oxides. Because of the strong spin-orbit coupling, the 5d perovskite iridates Sr_{2}IrO_{4} exhibit a low-energy electronic structure remarkably similar to the cuprates. Whether a superconducting state exists as in the cuprates requires understanding the correlated spin-orbit entangled electronic states. Recent experiments discovered hidden order in the parent and electron-doped iridates, some with striking analogies to the cuprates, including Fermi surface pockets, Fermi arcs, and pseudogap. Here, we study the correlation and disorder effects in a five-orbital model derived from the band theory. We find that the experimental observations are consistent with a d-wave spin-orbit density wave order that breaks the symmetry of a joint twofold spin-orbital rotation followed by a lattice translation. There is a Berry phase and a plaquette spin flux due to spin procession as electrons hop between Ir atoms, akin to the intersite spin-orbit coupling in quantum spin Hall insulators. The associated staggered circulating J_{eff}=1/2 spin current can be probed by advanced techniques of spin-current detection in spintronics. This electronic order can emerge spontaneously from the intersite Coulomb interactions between the spatially extended iridium 5d orbitals, turning the metallic state into an electron-doped quasi-2D Dirac semimetal with important implications on the possible superconducting state suggested by recent experiments.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-28

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

  4. Gd3+ spin-lattice relaxation via multi-band conduction electrons in Y(1-x)Gd(x)In3: an electron spin resonance study.

    Science.gov (United States)

    Cabrera-Baez, M; Iwamoto, W; Magnavita, E T; Osorio-Guillén, J M; Ribeiro, R A; Avila, M A; Rettori, C

    2014-04-30

    Interest in the electronic structure of the intermetallic compound YIn3 has been renewed with the recent discovery of superconductivity at T ∼ 1 K, which may be filamentary in nature. In this work we perform electron spin resonance (ESR) experiments on Gd(3+) doped YIn3 (Y1-xGdxIn3; 0.001 ⪅ x ⩽̸ 0.08), showing that the spin-lattice relaxation of the Gd(3+) ions, due to the exchange interaction between the Gd(3+) localized magnetic moment and the conduction electrons (ce), is processed via the presence of s-, p- and d-type ce at the YIn3 Fermi level. These findings are revealed by the Gd(3+) concentration dependence of the Korringa-like relaxation rate d(ΔH)/dT and g-shift (Δg = g - 1.993), that display bottleneck relaxation behavior for the s-electrons and unbottleneck behavior for the p- and d-electrons. The Korringa-like relaxation rates vary from 22(2) Oe/K for x ⪅ 0.001 to 8(2) Oe/K for x = 0.08 and the g-shift values change, respectively, from a positive Δg = +0.047(10) to a negative Δg = -0.008(4). Analysis in terms of a three-band ce model allows the extraction of the corresponding exchange interaction parameters Jfs, Jfp and Jfd.

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

    Science.gov (United States)

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

    2009-11-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Y; Wu, M W [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Jiang, J H [Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)], E-mail: mwwu@ustc.edu.cn

    2009-11-15

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

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

    Science.gov (United States)

    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.

  8. Electron-spin dynamics in Mn-doped GaAs using time-resolved magneto-optical techniques

    Science.gov (United States)

    Akimov, I. A.; Dzhioev, R. I.; Korenev, V. L.; Kusrayev, Yu. G.; Zhukov, E. A.; Yakovlev, D. R.; Bayer, M.

    2009-08-01

    We study the electron-spin dynamics in p -type GaAs doped with magnetic Mn acceptors by means of time-resolved pump-probe and photoluminescence techniques. Measurements in transverse magnetic fields show a long spin-relaxation time of 20 ns that can be uniquely related to electrons. Application of weak longitudinal magnetic fields above 100 mT extends the spin-relaxation times up to microseconds which is explained by suppression of the Bir-Aronov-Pikus spin relaxation for the electron on the Mn acceptor.

  9. Spin dynamics of FeGa3‑x Ge x studied by electron spin resonance

    Science.gov (United States)

    Koo, Bonho; Bader, Kristian; Burkhardt, Ulrich; Baenitz, Michael; Gille, Peter; Sichelschmidt, Jörg

    2018-01-01

    The intermetallic semiconductor FeGa3 acquires itinerant ferromagnetism upon electron doping by a partial replacement of Ga with Ge. We studied the electron spin resonance (ESR) of high-quality single crystals of FeGa3‑x Ge x for x from 0 up to 0.162 where ferromagnetic order is observed. For x  =  0 we observed a well-defined ESR signal, indicating the presence of pre-formed magnetic moments in the semiconducting phase. Upon Ge doping the occurrence of itinerant magnetism clearly affects the ESR properties below  ≈40 K, whereas at higher temperatures an ESR signal as seen in FeGa3 prevails independent on the Ge content. The present results show that the ESR of FeGa3‑x Ge x is an appropriate and direct tool to investigate the evolution of 3d-based itinerant magnetism.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-15

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

  11. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2012-01-01

    In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.

  12. Enhancement of spin injection from ferromagnetic metal into a two-dimensional electron gas using a tunnel barrier

    NARCIS (Netherlands)

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

    2001-01-01

    Using free electron approximation, we calculated the spin dependent tunnel conductance of ballistic ferromagnet/tunnel barrier/two-dimensional electron gas (FM/I/2DEG) junctions and FM/I/2DEG/I/FM double junctions for different barrier strengths. We find that a tunnel barrier improves spin injection

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

    DEFF Research Database (Denmark)

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

    2003-01-01

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

  14. Stabilizing nuclear spins around semiconductor electrons via the interplay of optical coherent population trapping and dynamic nuclear polarization

    NARCIS (Netherlands)

    Onur, A. R.; de Jong, J.P.; O'Shea, D.; Reuter, D.; Wieck, A. D.; Wal, van der C.H.

    2016-01-01

    We experimentally demonstrate how coherent population trapping (CPT) for donor-bound electron spins in GaAs results in autonomous feedback that prepares stabilized states for the spin polarization of nuclei around the electrons. CPT was realized by excitation with two lasers to a bound-exciton

  15. Networking Carbon Nanotubes for Integrated Electronics.

    Science.gov (United States)

    Romo-Herrera, J. M.; Terrones, M.; Terrones, H.; Meunier, V.

    2006-03-01

    The unique electronic and mechanical properties of individual Carbon Nanotubes (CNTs) have attracted much interest as candidates for molecular electronic devices and reinforced materials. However, their integration in organized architectures remains a major challenge. Recent breakthroughs reported on the Self-Assembly of 1D Nanostructures[1], and on the coalescence mechanism for interconnecting CNTs[2], point to the possibility of designing and obtaining Ordered Networks based on CNTs (ON- CNTs). We propose a set with different complex architectures of ON- CNTs based on --but not limited to-- armchair and zigzag nanotubes. In addition to the study of the energetics of the structures, we have systematically investigated their electronic transport properties in the framework of the Landauer-Buttiker formalism and equilibrium Green functions. To take curvature into account, we employed a semi-empirical Hamiltonian based on 4 orbitals (s,px,py,pz) per carbon atom. Further insight is obtained analyzing the electron pathways from a scattering point of view, which allows a real-space analysis of the wave function from the transmitted electrons across the structure. [1]Whang D etal. Nanoletters,3 (2003). Tao A etal. Nanoletters,3 (2003). [2]Terrones M etal. PRL,89 (2002). Endo M etal. Nanoletters,5 (2005).

  16. The HERA polarimeter and the first observation of electron spin polarization at HERA

    Energy Technology Data Exchange (ETDEWEB)

    Barber, D.P.; Bremer, H.D.; Boege, M.; Brinkmann, R.; Gianfelice-Wendt, E.; Kaiser, H.; Klanner, R.; Lewin, H.C.; Meyners, N.; Vogel, W. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Brueckner, W.; Buescher, C.; Dueren, M.; Gaul, H.G.; Muecklich, A.; Neunreither, F.; Rith, K.; Scholz, C.; Steffens, E.; Veltri, M.; Wander, W.; Zapfe, K.; Zetsche, F. [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Chapman, M.; Milner, R. [Massachusetts Inst. of Tech., Boston, MA (United States); Coulter, K. [Argonne National Lab., IL (United States); Delheij, P.P.J.; Haeusser, O.; Henderson, R.; Levy, P.; Vetterli, M. [British Columbia Univ., Vancouver (Canada). TRIUMF Facility; Green, P.E.W.; Kitching, P. [Alberta Univ., Edmonton (Canada)]|[Simon Fraser Univ., Burnaby, British Columbia (Canada); Gressmann, H.; Janke, T.; Micheel, B.; Westphal, D. [Hamburg Univ. (Germany); Kaiser, R. [Muenster Univ. (Germany). Inst. fuer Kernphysik; Lomperski, M. [Wisconsin Univ., Madison, WI (United States). Dept. of Physics; Lorenson, W.; McKeown, R.D. [California Inst. of Tech., Pasadena, CA (United States); Losev, L. [Lebedev Physical Inst., Moscow (Russia); Nowak, W.D. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). Inst. fuer Hochenergiephysik; Patel, P.M. [McGill Univ., Montreal, Quebec (Canada)

    1992-10-01

    Electron spin polarizations of about 8% were observed at HERA in November 1991. In runs during 1992 utilizing special orbit corrections, polarization values close to 60% have been achieved. In this paper the polarimeter, the machine conditions, the data analysis, the first results and plans for future measurements are described. (orig.).

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

    CERN Document Server

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

    2016-01-01

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

  18. Electron Spin Resonance Spectroscopy for Studying the Generation and Scavenging of Reactive Oxygen Species by Nanomaterials

    Science.gov (United States)

    Yin, Jun-Jie; Zhao, Baozhong; Xia, Qingsu; Fu, Peter P.

    2013-09-01

    One fundamental mechanism widely described for nanotoxicity involves oxidative damage due to generation of free radicals and other reactive oxygen species. Indeed, the ability of nanoscale materials to facilitate the transfer of electrons, and thereby promote oxidative damage or in some instances provide antioxidant protection, may be a fundamental property of these materials. Any assessment of a nanoscale material's safety must therefore consider the potential for toxicity arising from oxidative damage. Therefore, rapid and predictive methods are needed to assess oxidative damage elicited by nanoscale materials. The use of electron spin resonance (ESR) to study free radical related bioactivity of nanomaterials has several advantages for free radical determination and identification. Specifically it can directly assess antioxidant quenching or prooxidant generation of relevant free radicals and reactive oxygen species. In this chapter, we have reported some nonclassical behaviors of the electron spin relaxation properties of unpaired electrons in different fullerenes and the investigation of anti/prooxidant activity by various types of nanomaterials using ESR. In addition, we have reviewed the mechanisms of free radical formation photosensitized by different nanomaterials. This chapter also included the use of spin labels, spin traps and ESR oximetry to systematically examine the enzymatic mimetic activities of nanomaterials.

  19. Scanning electron microscopy with polarization analysis for multilayered chiral spin textures

    NARCIS (Netherlands)

    Lucassen, Juriaan; Kloodt-Twesten, Fabian; Frömter, Robert; Oepen, Hans Peter; Duine, Rembert A.|info:eu-repo/dai/nl/304830127; Swagten, Henk J. M.; Koopmans, Bert; Lavrijsen, Reinoud

    We show that scanning electron microscopy with polarization analysis (SEMPA) that is sensitive to both in-plane magnetization components can be used to image the out-of-plane magnetized multi-domain state in multilayered chiral spin textures. By depositing a thin layer of Fe on top of the multilayer

  20. Loophole-free Bell test using electron spins in diamond : Second experiment and additional analysis

    NARCIS (Netherlands)

    Hensen, B.J.; Kalb, N.; Blok, M.S.; Dréau, A.E.; Reiserer, A.A.; Vermeulen, R.F.L.; Schouten, R.N.; Markham, M.; Twitchen, D.J.; Goodenough, K.D.; Elkouss Coronas, D.; Wehner, S.D.C.; Taminiau, T.H.; Hanson, R.

    2016-01-01

    The recently reported violation of a Bell inequality using entangled electronic spins in diamonds (Hensen et al., Nature 526, 682–686) provided the first loophole-free evidence against local-realist theories of nature. Here we report on data from a second Bell experiment using the same

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

    DEFF Research Database (Denmark)

    Fenger, J.

    1965-01-01

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

  2. Electrons and Spin Waves in Heavy Rare Earth Metals

    DEFF Research Database (Denmark)

    Mackintosh, A. R.

    1972-01-01

    Although the main principles governing the magnetic interactions and magnetic ordering in rare earth metals have been qualitatively understood for some time, it is only relatively recently that a sufficiently detailed study has been made of their electronic and magnetic excitations to place...... this understanding on a more quantitative basis. The experimental evidence on the electronic structure of the rare earths is still rather meager but, so far as it goes, is in accord with the detailed description provided by band structure calculations. On the other hand, the experimental study of the magnon...... dispersion relations by inelastic neutron scattering has provided a wealth of information about the interactions between the local moments, associated with the incompletely filled 4f subshell, and the rest of the crystal. The main emphasis in these notes will be on the interrelation between the electronic...

  3. Spin-orbit interaction in a two-dimensional electron gas in a InAs/AlSb quantum well with gate-controlled electron density

    NARCIS (Netherlands)

    Heida, J.P.; Wees, B.J. van; Kuipers, J.J.; Klapwijk, T.M.; Borghs, G.

    1998-01-01

    We present experiments on the tuning of the spin-orbit interaction in a two-dimensional electron gas in an asymmetric InAs/AlSb quantum well using a gate. The observed dependence of the spin splitting energy on the electron density can be attributed solely to the change in the Fermi wave vector. The

  4. Bell-state preparation for fullerene based electron spins in distant peapod nanotubes

    OpenAIRE

    Yang, W. L.; Wei, H; Zhang, X. L.; Feng, M.

    2008-01-01

    We propose a potentially practical scheme, in combination with the Bell-state analyzer [Zhang et al., Phys. Rev. A 73, 014301 (2006)], to generate Bell states for two electron spins confined, respectively, in two distant fullerenes. To this end, we consider the endohedral fullerenes staying in single walled carbon nanotubes (SWCNTs) and employ auxiliary mobile electrons and selective microwave pulses. The application and the experimental feasibility of our scheme are discussed.

  5. Programmable synaptic chip for electronic neural networks

    Science.gov (United States)

    Moopenn, A.; Langenbacher, H.; Thakoor, A. P.; Khanna, S. K.

    1988-01-01

    A binary synaptic matrix chip has been developed for electronic neural networks. The matrix chip contains a programmable 32X32 array of 'long channel' NMOSFET binary connection elements implemented in a 3-micron bulk CMOS process. Since the neurons are kept off-chip, the synaptic chip serves as a 'cascadable' building block for a multi-chip synaptic network as large as 512X512 in size. As an alternative to the programmable NMOSFET (long channel) connection elements, tailored thin film resistors are deposited, in series with FET switches, on some CMOS test chips, to obtain the weak synaptic connections. Although deposition and patterning of the resistors require additional processing steps, they promise substantial savings in silicon area. The performance of synaptic chip in a 32-neuron breadboard system in an associative memory test application is discussed.

  6. Influence of soliton distributions on the spin-dependent electronic ...

    Indian Academy of Sciences (India)

    We found that the presence of a uniform distribution of the soliton centres along the molecular chain reduced the size of the band gap of {\\it trans}-PA molecule. Moreover, a sublattice of the correlated solitons as binary clusters, which are randomly distributed along the chain, can induce extended electronic states in the ...

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

    Science.gov (United States)

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

    2013-01-01

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

  8. Electronic Power Transformer for Power Distribution Networks

    Directory of Open Access Journals (Sweden)

    Ermuraсhi Iu.V.

    2017-12-01

    Full Text Available Reducing losses in electricity distribution networks is a current technical problem. This issue also has social and environmental aspects. As a promising solution one can examine the direct distribution from the medium voltage power network using new equipment based on the use of power electronics. The aim of the paper is to propose and argue an innovative technical solution for the realization of the Solid State Transformer (SST in order to decrease the number of energy transformation stages compared to the known solutions, simplifying the topology of the functional scheme with the reduction of production costs and the loss of energy in transformers used in electrical distribution networks. It is proposed the solution of simplifying the topology of the AC/AC electronic transformer by reducing the number of passive electronic components (resistors, inductors, capacitors and active (transistors. The inverter of the SST transformer ensures the switching mode of the transistors, using for this purpose the inductance of the magnetic leakage flux of the high frequency transformer. The robustness of the laboratory sample of the SST 10 / 0.22 kV transformer with the power of 20 kW was manufactured and tested. Testing of the laboratory sample confirmed the functionality of the proposed scheme and the possibility of switching of the transistors to at zero current (ZCS mode with the reduction of the energy losses. In the proposed converter a single high-frequency transformer with a simplified construction with two windings is used, which reduces its mass and the cost of making the transformer. The reduction in the manufacturing cost of the converter is also due to the decrease in the number of links between the functional elements.

  9. Recent progress on correlated electron systems with strong spin-orbit coupling

    Science.gov (United States)

    Schaffer, Robert; Kin-Ho Lee, Eric; Yang, Bohm-Jung; Kim, Yong Baek

    2016-09-01

    The emergence of novel quantum ground states in correlated electron systems with strong spin-orbit coupling has been a recent subject of intensive studies. While it has been realized that spin-orbit coupling can provide non-trivial band topology in weakly interacting electron systems, as in topological insulators and semi-metals, the role of electron-electron interaction in strongly spin-orbit coupled systems has not been fully understood. The availability of new materials with significant electron correlation and strong spin-orbit coupling now makes such investigations possible. Many of these materials contain 5d or 4d transition metal elements; the prominent examples are iridium oxides or iridates. In this review, we succinctly discuss recent theoretical and experimental progress on this subject. After providing a brief overview, we focus on pyrochlore iridates and three-dimensional honeycomb iridates. In pyrochlore iridates, we discuss the quantum criticality of the bulk and surface states, and the relevance of the surface/boundary states in a number of topological and magnetic ground states, both in the bulk and thin film configurations. Experimental signatures of these boundary and bulk states are discussed. Domain wall formation and strongly-direction-dependent magneto-transport are also discussed. In regard to the three-dimensional honeycomb iridates, we consider possible quantum spin liquid phases and unusual magnetic orders in theoretical models with strongly bond-dependent interactions. These theoretical ideas and results are discussed in light of recent resonant x-ray scattering experiments on three-dimensional honeycomb iridates. We also contrast these results with the situation in two-dimensional honeycomb iridates. We conclude with the outlook on other related systems.

  10. Insights on the Structural Details of Endonuclease EcoRI-DNA Complexes by Electron Spin Resonance

    Science.gov (United States)

    Sarver, Jessica

    2009-03-01

    Pulsed electron spin resonance (ESR) was used to probe the binding specificity of EcoRI, a restriction endonuclease. Using site-directed spin labeling, a nitroxide side chain was incorporated into the protein, enabling the use of ESR to study structural details of EcoRI. Distance measurements were performed on EcoRI mutants when bound to varying sequences of DNA using the Double Electron-Electron Resonance experiment. These distances demonstrated that the average structure in the arm regions of EcoRI, thought to play a major role in binding specificity, is the same when the protein binds to different sequences of DNA. Also, it was determined that the arms exhibit higher flexibility when bound to sequences other than the specific sequence due to the larger distance distributions acquired from these spin labeled complexes. Molecular dynamics (MD) simulations were performed on the spin-label-modified specific EcoRI-DNA crystal structure to model the average nitroxide orientation. The distance distributions from MD were found to be narrower than experiment, indicating the need for a more rigorous sampling of the nitroxide conformers in silico.

  11. Magnetic cellular nonlinear network with spin wave bus for image processing

    Science.gov (United States)

    Khitun, Alexander; Bao, Mingqiang; Wang, Kang L.

    2010-03-01

    We describe and analyze a cellular nonlinear network based on magnetic nanostructures for image processing. The network consists of magneto-electric cells integrated onto a common ferromagnetic film-spin wave bus. The magneto-electric cell is an artificial two-phase multiferroic structure comprising piezoelectric and ferromagnetic materials. A bit of information is assigned to the cell's magnetic polarization, which can be controlled by the applied voltage. The information exchange among the cells is via the spin waves propagating in the spin wave bus. Each cell changes its state as a combined effect: magneto-electric coupling and the interaction with the spin waves. The distinct feature of a network with a spin wave bus is the ability to control the inter-cell communication by an external global parameter — magnetic field. The latter makes it possible to realize different image processing functions on the same template without rewiring or reconfiguration. We present the results of numerical simulations illustrating image filtering, erosion, dilation, horizontal and vertical line detection, inversion and edge detection accomplished on one template by the proper choice of the strength and direction of the external magnetic field. We also present numerical assets on the major network parameters such as cell density, power dissipation and functional throughput, and compare them with the parameters projected for other nano-architectures such as CMOL-CrossNet, Quantum-Dot Cellular Automata, and Quantum Dot-Image Processor. Potentially, the utilization of spin wave phenomena at the nanometer scale may provide a route to low-power consumption and functional logic circuits for special task data processing.

  12. Hidden mediator roles of university spin-offs in Triple Helix networks

    NARCIS (Netherlands)

    van Geenhuizen, M.S.; Ye, Q; Taheri, M.

    2016-01-01

    University spin-off firms contribute to bringing knowledge created at university to market. The networks these firms employ with other Triple Helix actors serve as not only getting access to resources but also shaping processes of collective learning in transforming the knowledge most adequately. In

  13. Resonance estimates for single spin asymmetries in elastic electron-nucleon scattering

    Energy Technology Data Exchange (ETDEWEB)

    Barbara Pasquini; Marc Vanderhaeghen

    2004-07-01

    We discuss the target and beam normal spin asymmetries in elastic electron-nucleon scattering which depend on the imaginary part of two-photon exchange processes between electron and nucleon. We express this imaginary part as a phase space integral over the doubly virtual Compton scattering tensor on the nucleon. We use unitarity to model the doubly virtual Compton scattering tensor in the resonance region in terms of {gamma}* N {yields} {pi} N electroabsorption amplitudes. Taking those amplitudes from a phenomenological analysis of pion electroproduction observables, we present results for beam and target normal single spin asymmetries for elastic electron-nucleon scattering for beam energies below 1 GeV and in the 1-3 GeV region, where several experiments are performed or are in progress.

  14. Optical power-driven electron spin relaxation regime crossover in Mn-doped bulk GaAs

    Science.gov (United States)

    Münzhuber, F.; Kiessling, T.; Ossau, W.; Molenkamp, L. W.; Astakhov, G. V.

    2015-09-01

    We demonstrate tunability of the electron spin lifetime in Mn-doped GaAs by purely optical means. The observed behavior stems from a crossover of the electron spin relaxation rate with increasing excitation density, first decreasing due to the exchange interaction of Mn bound holes with Mn ions, and then increasing again as the valence band is populated and Bir-Aranov-Pikus relaxation sets in. On this account, we explain the complex spatial spin polarization profiles emerging from inhomogeneous optical excitation, which are the result of the combined action of this nonmonotonic spin relaxation characteristics and the intricate photocarrier decay dynamics.

  15. Control of the electron spin relaxation by the built-in piezoelectric field in InGaAs quantum wells

    Science.gov (United States)

    Azaizia, S.; Balocchi, A.; Carrère, H.; Renucci, P.; Amand, T.; Arnoult, A.; Fontaine, C.; Marie, X.

    2016-02-01

    The electron spin dynamics is studied by time-resolved optical orientation experiments in strained InGaAs/GaAs quantum wells (QWs) grown on (111) or (001) substrates. For a given well width, the electron spin relaxation time in (111) InGaAs QWs decreases by an order of magnitude when the indium fraction in the well varies only from 4% to 12%. In contrast, the electron spin relaxation time depends weakly on the indium fraction in similar InGaAs quantum wells grown on (001) substrates. The strong variation of the electron spin relaxation time in (111) strained quantum well can be well interpreted by the Dyakonov-Perel spin relaxation mechanism where the conduction band spin-orbit splitting is dominated by the structural inversion asymmetry (Rashba term) induced by the piezoelectric field. In (001) QWs, due to the absence of piezoelectric field, the electron spin relaxation time is solely controlled by the Dresselhaus term. These results demonstrate the possibility to engineer the electron spin relaxation time in (111)-oriented quantum wells by the piezoelectric field induced by the built-in strain.

  16. ESPINTRÓNICA, LA ELECTRONICA DEL ESPÍN SPINTRONICS, SPIN ELECTRONICS

    KAUST Repository

    Monteblanco, Elmer

    2017-03-14

    Current technology seeks to develop nanoscale devices capable of storing and processing information. These devices would be difficult to make in the area of electronics, which is based on the manipulation of electric charge. However, thanks to advances in experimental and theoretical physics in the field of condensed matter, these devices are already a reality, belonging to the field of what we now call spintronics, which bases its functionality on the control of the electron’s spin, a property that can only be conceived at the quantum level. In this article we review this new perspective, describing giant- and tunneling- magnetoresistance, the spin transfer torque, and their applications such as MRAM memories, nano-oscillators and lateral spin valves.

  17. The Verwey transition observed by spin-resolved photoemission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química Física “Rocasolano”, CSIC, Madrid E-28006 (Spain); Tusche, Christian [Max Planck Institute of Microstructure Physics, Halle D-06120 (Germany); Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-6), D-52425 Jülich (Germany)

    2017-01-01

    Highlights: • First observations of magnetic domains on magnetite (001) by spin-resolved PEEM. • Spin-polarization through the Verwey transitions does not change appreciably. • Shape and distribution of domains has been observed through the Verwey transition. - Abstract: We have imaged the magnetic domains on magnetite (001) through the Verwey transition by means of spin-resolved photoemission electron microscopy. A He laboratory source is used for illumination. The magnetic domains walls above the Verwey transition are aligned with 〈110〉 in-plane directions. Below the Verwey transition, the domain structure is interpreted as arising from a distribution of areas with different monoclinic c-axis, with linear 180° domain walls within each area and ragged edges when the magnetic domain boundaries coincide with structural domain walls. The domains evolve above the Verwey transition, while they are static below.

  18. Coherence of a spin-polarized electron beam emitted from a semiconductor photocathode in a transmission electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Kuwahara, Makoto, E-mail: kuwahara@esi.nagoya-u.ac.jp; Saitoh, Koh; Tanaka, Nobuo [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); EcoTopia Science Institute, Nagoya University, Nagoya 464-8603 (Japan); Kusunoki, Soichiro; Nambo, Yoshito; Ujihara, Toru; Asano, Hidefumi [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Jin, Xiuguang [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Takeda, Yoshikazu [Aichi Synchrotron Radiation Center, Seto 489-0965 (Japan); Nagoya Science Industry Institute, Nagoya 460-0008 (Japan)

    2014-11-10

    The brightness and interference fringes of a spin-polarized electron beam extracted from a semiconductor photocathode excited by laser irradiation are directly measured via its use in a transmission electron microscope. The brightness was 3.8 × 10{sup 7 }A cm{sup −2 }sr{sup −1} for a 30-keV beam energy with the polarization of 82%, which corresponds to 3.1 × 10{sup 8 }A cm{sup −2 }sr{sup −1} for a 200-keV beam energy. The resulting electron beam exhibited a long coherence length at the specimen position due to the high parallelism of (1.7 ± 0.3) × 10{sup −5 }rad, which generated interference fringes representative of a first-order correlation using an electron biprism. The beam also had a high degeneracy of electron wavepacket of 4 × 10{sup −6}. Due to the high polarization, the high degeneracy and the long coherence length, the spin-polarized electron beam can enhance the antibunching effect.

  19. Spin-resolved correlations in the warm-dense homogeneous electron gas

    Science.gov (United States)

    Arora, Priya; Kumar, Krishan; Moudgil, R. K.

    2017-04-01

    We have studied spin-resolved correlations in the warm-dense homogeneous electron gas by determining the linear density and spin-density response functions, within the dynamical self-consistent mean-field theory of Singwi et al. The calculated spin-resolved pair-correlation function gσσ'(r) is compared with the recent restricted path-integral Monte Carlo (RPIMC) simulations due to Brown et al. [Phys. Rev. Lett. 110, 146405 (2013)], while interaction energy Eint and exchange-correlation free energy Fxc with the RPIMC and very recent ab initio quantum Monte Carlo (QMC) simulations by Dornheim et al. [Phys. Rev. Lett. 117, 156403 (2016)]. g↑↓(r) is found to be in good agreement with the RPIMC data, while a mismatch is seen in g↑↑(r) at small r where it becomes somewhat negative. As an interesting result, it is deduced that a non-monotonic T-dependence of g(0) is driven primarily by g↑↓(0). Our results of Eint and Fxc exhibit an excellent agreement with the QMC study due to Dornheim et al., which deals with the finite-size correction quite accurately. We observe, however, a visible deviation of Eint from the RPIMC data for high densities ( 8% at rs = 1). Further, we have extended our study to the fully spin-polarized phase. Again, with the exception of high density region, we find a good agreement of Eint with the RPIMC data. This points to the need of settling the problem of finite-size correction in the spin-polarized phase also. Interestingly, we also find that the thermal effects tend to oppose spatial localization as well as spin polarization of electrons. Supplementary material in the form of one zip file available from the Journal web page at http://https://doi.org/10.1140/epjb/e2017-70532-y

  20. Spin–spin correlations and entanglement in elastic electron scattering from hydrogen atoms

    Science.gov (United States)

    Bartschat, Klaus

    2017-11-01

    In two recent papers, Blum and Lohmann (2016 Phys. Rev. Lett. 116 033201) and Lohmann et al (2016 Phys. Rev. A 94 032331), the possibility of continuously varying the degree of entanglement between an elastically scattered electron and the valence electron of quasi-one electron targets was discussed. Here we present results for elastic electron scattering from atomic hydrogen in the energy regime of 1‑10 eV and the full range of scattering angles 0^\\circ -180^\\circ . We confirm previous calculations at very low energies, which predicted that the hydrogen target is not a promising candidate for Bell correlations through electron collisions. This finding remains unchanged in the near-resonance regime of incident electron energies just below 10 eV. In addition to the spin-correlation parameter P, we present the angle-integrated total cross section, as well as the angle-differential cross section at a few representative collision energies.

  1. Spin polarization and exchange-correlation effects in transport properties of two-dimensional electron systems in silicon

    Science.gov (United States)

    Dolgopolov, V. T.; Shashkin, A. A.; Kravchenko, S. V.

    2017-08-01

    We show that the parallel magnetic field-induced increase in the critical electron density for the Anderson transition in a strongly interacting two-dimensional electron system is caused by the effects of exchange and correlations. If the transition occurs when electron spins are only partially polarized, additional increase in the magnetic field is necessary to achieve the full spin polarization in the insulating state due to the exchange effects.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-01-01

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

  3. Electron-spin-resonance transistors for quantum computing in silicon-germanium heterostructures

    Science.gov (United States)

    Vrijen, Rutger; Yablonovitch, Eli; Wang, Kang; Jiang, Hong Wen; Balandin, Alex; Roychowdhury, Vwani; Mor, Tal; Divincenzo, David

    2000-07-01

    We apply the full power of modern electronic band-structure engineering and epitaxial heterostructures to design a transistor that can sense and control a single-donor electron spin. Spin-resonance transistors may form the technological basis for quantum information processing. One- and two-qubit operations are performed by applying a gate bias. The bias electric field pulls the electron wave function away from the dopant ion into layers of different alloy composition. Owing to the variation of the g factor (Si:g=1.998,Ge:g=1.563), this displacement changes the spin Zeeman energy, allowing single-qubit operations. By displacing the electron even further, the overlap with neighboring qubits is affected, which allows two-qubit operations. Certain silicon-germanium alloys allow a qubit spacing as large as 200 nm, which is well within the capabilities of current lithographic techniques. We discuss manufacturing limitations and issues regarding scaling up to a large size computer.

  4. Formation of charge and spin ordering in strongly correlated electron systems

    Directory of Open Access Journals (Sweden)

    P. Farkašovsky

    2011-12-01

    Full Text Available In this review we present results of our theoretical study of charge and spin ordering in strongly correlated electron systems obtained within various generalizations of the Falicov-Kimball model. The primary goal of this study was to identify crucial interactions that lead to the stabilization of various types of charge ordering in these systems, like the axial striped ordering, diagonal striped ordering, phase-separated ordering, phase-segregated ordering, etc. Among the major interactions that come into account, we have examined the effect of local Coulomb interaction between localized and itinerant electrons, long-range and correlated hopping of itinerant electrons, long-range Coulomb interaction between localized and itinerant electrons, local Coulomb interaction between itinerant electrons, local Coulomb interaction between localized electrons, spin-dependent interaction between localized and itinerant electrons, both for zero and nonzero temperatures, as well as for doped and undoped systems. Finally, the relevance of resultant solutions for a description of rare-earth and transition-metal compounds is discussed.

  5. Untangling complex networks: risk minimization in financial markets through accessible spin glass ground states.

    Science.gov (United States)

    Lisewski, Andreas Martin; Lichtarge, Olivier

    2010-08-15

    Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the relative margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network's Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.

  6. Electron spin-echo techniques for the study of protein motion

    Science.gov (United States)

    Kar, Leela; Johnson, Michael E.; Bowman, Michael K.

    Electron spin-echo (ESE) spectroscopy has been used to make the first direct measurements of spin-spin relaxation times of a spin-labeled protein at physiological temperatures. Results from experiments using maleimide-labeled deoxygenated hemoglobin (dHb) from individuals homozygous for sickle cell anemia (dHbS) have been compared with those from control experiments using dHb from normal adults (dHbA). Hb "immobilized" by ammonium sulfate precipitation and by siloxane polymer entrapment have been studied for a suitable "rigid" reference. Two-dimensional ESE (2D-ESE) experiments have been performed using all of these systems. The 2D contour plots show that 2D-ESE is sensitive to the slow motion of dHbS polymers and can differentiate it from both that of immobilized Hb and of HbA molecules in solution at the same temperature and concentration. More importantly, the 2D-ESE technique enables one to select for slower motion and thereby extract the dHbS polymer signal from the total signal generated by the heterogeneous system containing dHbS molecules in solution as well as in the polymer. Computer simulations using current slow motional theories show that detailed motional and structural information may be obtained by such studies. The considerable potential of 2D-ESE spectroscopy in the study of macromolecular motion is illustrated by comparing 2D-ESE with the nonlinear technique of saturation transfer electron paramagnetic resonance.

  7. Spin-polarized electronic structure of the Ni(001) surface and thin films

    DEFF Research Database (Denmark)

    Jepsen, O.; Madsen, J.; Andersen, O. K.

    1982-01-01

    of the five-layer film is used to calculate the electronic structure of a 13-layer film. The theoretical work function of 5.4 eV agrees well with the experimental value of 5.2 eV. The calculated spin moments are ordered ferromagnetically in all the films considered, and the moments of the atoms in the surface...... of the magnetic moment at the surface is mainly of d(x2-y2) character. The calculated 4s contribution to the hyperfine field changes sign and becomes positive in the outermost layer. Near k=0, between the Fermi level and the d-band edge (which lies 0.3 eV below the Fermi level), we find no majority-spin surface...... states that can explain the sign reversal of the electron spin polarization near threshold. This supports the suggestion by Liebsch that, in photoemission experiments on Ni, correlation effects make the majority-spin bands appear higher in energy. With such an adjustment of our energy bands we are able...

  8. Validation of Bosch' Mobile Communication NetworkArchitecture with SPIN

    NARCIS (Netherlands)

    Ruys, T.C.; Langerak, Romanus

    This paper discusses validation projects carried out for the Mobile Communication Division of Robert Bosch GmbH. We verified parts of their Mobile Communication Network (MCNet), a communication system which is to be used in infotainment systems of future cars. The protocols of the MCNet have been

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

    Science.gov (United States)

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

    2016-09-01

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

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

    Science.gov (United States)

    Schweidenback, Lars

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

  11. Entrepreneurial Networks of University Spin-offs : How Social Networks Affect the Growth of Firms

    NARCIS (Netherlands)

    Soetanto, D.P.

    2009-01-01

    Knowledge can be valorized in many different ways. University spin-offs have proven to be very effective as the knowledge generated in a university or research institute is directly translated into commercial activities. In addition, university spin-offs have played an important role in the economic

  12. Electron Spin Resonance investigation of undoped and Li-doped CdWO_4 scintillator crystals

    OpenAIRE

    Laguta, V. V.; Nikl, M.; Buryi, M.

    2009-01-01

    Electron spin resonance (ESR) spectra of Fe3+ and Mn2+ ions have been studied in the nominally pure and 0.05% Li-doped single crystals of CdWO4. The zero-field splitting parameters are determined with a high precision for both of the impurities. The result suggest that the Li-doping leads to the increase of the ionic charge of iron from 3+ to 4+ and of manganese, from 1+ to 2+.

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

    Directory of Open Access Journals (Sweden)

    I.I. Gimazov, Yu.I. Talanov

    2015-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1978-01-01

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

  15. Synthesis Properties and Electron Spin Resonance Properties of Titanic Materials (abstract)

    Science.gov (United States)

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

    2009-04-01

    Titanic materials were synthesized by hydrothermal method of TiO2 anatase in 10M LiOH, 10M NaOH, and 14M KOH at 130° 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 TiO2 samples through the typical electron microscope and Langmuir adsorption-desorption isotherm of liquid nitrogen at 77° 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.

  16. Electron spin resonance probed competing states in NiMnInSi Heusler alloy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.S. [Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan (China); Lin, J.G., E-mail: jglin@ntu.edu.tw [Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan (China); Titov, I.S.; Granovsky, A.B. [Faculty of Physics, Lomonosov Moscow State University, Vorob' evy Gory, 11999l Moscow (Russian Federation)

    2016-06-01

    Shape memory Heusler alloy Ni{sub 50}Mn{sub 35}In{sub 12}Si{sub 3} is investigated with electron spin resonance (ESR) technique in a temperature range of 200–300 K. ESR is a dynamic probe allowing us to separate the responses from various magnetic phases, thus to study the complex phase transitions. The sample shows three transition temperatures: T{sub c}{sup A} (271 K), T{sub M} (247 K) and T{sub c}{sup M} (212 K), where T{sub c}{sup A} is the Curie temperature of austenitic phase, T{sub M} and T{sub c}{sup M} are the temperatures of magnetostructural martensitic transition and the Curie temperature of martensitic phase, respectively. Furthermore, ESR data reveals the coexistence of two magnetic modes in whole temperature range of 200–300 K. Particularly in martensitic phase, two magnetic modes are attributed to two different kinds of lattice deformation, the slip and twinning deformations. - Highlights: • Electron spin resonance study on magnetocaloric Heusler alloy within 200–300 K. • Magnetic phase separation below and above the structural transition temperature. • Phase competing is in association with different types of lattice distortions. • Electron spin resonance results are complementary to the magnetization data.

  17. Chiral Selective Chemistry Induced by Natural Selection of Spin-Polarized Electrons.

    Science.gov (United States)

    Rosenberg, Richard A; Mishra, Debabrata; Naaman, Ron

    2015-06-15

    The search to understand the origin of homochirality in nature has been ongoing since the time of Pasteur. Previous work has shown that DNA can act as a spin filter for low-energy electrons and that spin-polarized secondary electrons produced by X-ray irradiation of a magnetic substrate can induce chiral selective chemistry. In the present work it is demonstrated that secondary electrons from a substrate that are transmitted through a chiral overlayer cause enantiomeric selective chemistry in an adsorbed adlayer. We determine the quantum yields (QYs) for dissociation of (R)- or (S)-epichlorohydrin adsorbed on a chiral self-assembled layer of DNA on gold and on bare gold (for control). The results show that there is a significant difference in the QYs between the two enantiomers when adsorbed on DNA, but none when they are adsorbed on bare Au. We propose that the effect results from natural spin filtering effects cause by the chiral monolayer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Transverse Beam Spin Asymmetries at Backward Angles in Elastic Electron-Proton and Quasi-elastic Electron-Deuteron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Androic, D; Armstrong, D S; Bailey, S L; Beck, D H; Beise, E J; Benesch, J; Benmokhtar, F; Bimbot, L; Birchall, J; Bosted, P; Breuer, K; Capuano, C L; Chao, Y -C; Coppens, A; Davis, C A; Ellis, C; Flores, G; Franklin, G; Furget, C; Gaskell, D; Gericke, M.T.W.; Grames, J; Guillard, G; Hansknecht, J; Horn, T; Jones, M K; King, P M; Korsch, W; Kox, S; Lee, L; Liu, J; Lung, A; Mammei, J; Martin, J W; McKeown, R D; Micherdzinska, A; Mihovilovic, M; Mkrtchyan, H; Muether, M; Page, S A; Papavassiliou, V; Pate, S F; Phillips, S K; Pillot, P; Pitt, M L; Poelker, M; Quinn, B; Ramsay, W D; Real, J -S; Roche, J; Roos, P; Schaub, J; Seva, T; Simicevic, N; Smith, G R; Spayde, D T; Stutzman, M; Suleiman, R; Tadevosyan, V; van Oers, W.T.H.; Versteegen, M; Voutier, E; Vulcan, W; Wells, S P; Williamson, S E; Wood, S A; Pasquini, B

    2011-07-01

    We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasi-elastic scattering on the deuteron, at backward angles (lab scattering angle of 108 degrees) for Q2 = 0.22 GeV^2/c^2 and 0.63 GeV^2/c^2 at beam energies of 362 MeV and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (piN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasi-static deuterium approximation, and is also in agreement with theory.

  19. First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments

    Directory of Open Access Journals (Sweden)

    Maxime Deutsch

    2014-05-01

    Full Text Available Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

  20. Spin density induced by electromagnetic waves in a two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit coupling

    Science.gov (United States)

    Pletyukhov, Mikhail; Shnirman, Alexander

    2009-01-01

    We consider the magnetic response of a two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit coupling to a microwave excitation. We generalize the results of Shnirman and Martin [Europhys. Lett. 78, 27001 (2007)], where pure Rashba coupling was studied. We observe that the microwave with the in-plane electric field and the out-of-plane magnetic field creates an out-of-plane spin polarization. The effect is more prominent in clean systems with resolved spin-orbit-split subbands. Considered as response to the microwave magnetic field, the spin-orbit contribution to the magnetization far exceeds the usual Zeeman contribution in the clean limit. The effect vanishes when the Rashba and the Dresselhaus couplings have equal strength.

  1. Spin-resolved state-selective electron capture in C5+-H collisions

    Science.gov (United States)

    Liu, C. H.; Wang, J. G.; Janev, R. K.

    2016-09-01

    The electron capture processes in the C5+(1s)+H(1s) collision system are investigated by the quantum-mechanical molecular orbital close-coupling (QMOCC) method in the energy range of 10-5-10 keV u-1. Accurate molecular structure calculations are performed by the ab initio multireference single- and double-excitation configuration interaction method. The electron translational effects are included in the calculations. The total and spin-resolved state-selective cross sections are presented and compared with the available experimental and theoretical data. The present results have a good agreement with the experimental measurements. Our calculations show that the electron translation factors play a very important role for energies above 0.1 keV u-1 leading to significant differences between the present and the previous QMOOC cross section results of Nolte et al 2012 (J. Phys. B: At. Mol. Opt. Phys. 45 245202). The effects of the core electron also cannot be ignored below 2 keV u-1. Model potential calculations, in which the core electron is treated as frozen, cannot give accurate spin-resolved cross sections.

  2. Untangling complex networks: Risk minimization in financial markets through accessible spin glass ground states

    Science.gov (United States)

    Lisewski, Andreas Martin; Lichtarge, Olivier

    2010-08-01

    Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network’s Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.

  3. Random walk approach to spin dynamics in a two-dimensional electron gas with spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Luyi; Orenstein, J.; Lee, Dung-Hai

    2010-09-27

    We introduce and solve a semiclassical random walk (RW) model that describes the dynamics of spin polarization waves in zinc-blende semiconductor quantum wells. We derive the dispersion relations for these waves, including the Rashba, linear and cubic Dresselhaus spin-orbit interactions, as well as the effects of an electric field applied parallel to the spin polarization wave vector. In agreement with calculations based on quantum kinetic theory [P. Kleinert and V. V. Bryksin, Phys. Rev. B 76, 205326 (2007)], the RW approach predicts that spin waves acquire a phase velocity in the presence of the field that crosses zero at a nonzero wave vector, q{sub 0}. In addition, we show that the spin-wave decay rate is independent of field at q{sub 0} but increases as (q-q{sub 0}){sup 2} for q {ne} q{sub 0}. These predictions can be tested experimentally by suitable transient spin grating experiments.

  4. Simulation for a New Polarized Electron Injector (SPIN) for the S-DALINAC

    CERN Document Server

    Steiner, Bastian; Gräf, Hans Dieter; Richter, Achim; Roth, Markus; Weiland, Thomas

    2005-01-01

    The Superconducting DArmstädter LINear ACcelerator (S-DALINAC) is a 130 MeV recirculating electron accelerator serving several nuclear and radiation physics experiments. For future tasks, the 250 keV thermal electron source should be completed by a 100 keV polarized electron source. Therefore a new low energy injection concept for the S-DALINAC has to be designed. The main components of the injector are a polarized electron source, an alpha magnet, a Wien filter spin-rotator and a Mott polarimeter. In this paper we report over the first simulation and design results. For our simulations we used the TS2 and TS3 modules of the CST MAFIA (TM) programme which are PIC codes for two and three dimensions and the CST PARTICLE STUDIO (TM).

  5. Electron magnetic resonance data on high-spin Mn(III; S=2) ions in porphyrinic and salen complexes modeled by microscopic spin Hamiltonian approach.

    Science.gov (United States)

    Tadyszak, Krzysztof; Rudowicz, Czesław; Ohta, Hitoshi; Sakurai, Takahiro

    2017-10-01

    The spin Hamiltonian (SH) parameters experimentally determined by EMR (EPR) may be corroborated or otherwise using various theoretical modeling approaches. To this end semiempirical modeling is carried out for high-spin (S=2) manganese (III) 3d 4 ions in complex of tetraphenylporphyrinato manganese (III) chloride (MnTPPCl). This modeling utilizes the microscopic spin Hamiltonians (MSH) approach developed for the 3d 4 and 3d 6 ions with spin S=2 at orthorhombic and tetragonal symmetry sites in crystals, which exhibit an orbital singlet ground state. Calculations of the zero-field splitting (ZFS) parameters and the Zeeman electronic (Ze) factors (g || =g z , g ⊥ =g x =g y ) are carried out for wide ranges of values of the microscopic parameters using the MSH/VBA package. This enables to examine the dependence of the theoretically determined ZFS parameters b k q (in the Stevens notation) and the Zeeman factors g i on the spin-orbit (λ), spin-spin (ρ) coupling constant, and the ligand-field energy levels (Δ i ) within the 5 D multiplet. The results are presented in suitable tables and graphs. The values of λ, ρ, and Δ i best describing Mn(III) ions in MnTPPCl are determined by matching the theoretical second-rank ZFSP b 2 0 (D) parameter and the experimental one. The fourth-rank ZFS parameters (b 4 0 , b 4 4 ) and the ρ (spin-spin)-related contributions, which have been omitted in previous studies, are considered for the first time here and are found important. Semiempirical modeling results are compared with those obtained recently by the density functional theory (DFT) and/or ab initio methods. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Density dependence of electron-spin polarization and relaxation in intrinsic GaAs at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Teng, L H; Chen, K; Wen, J H; Lin, W Z; Lai, T S, E-mail: stslts@mail.sysu.edu.c [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Zhongshan (Sen Yat-Sen) University, Guangzhou, Guangdong 510275 (China)

    2009-07-07

    Time-resolved circularly polarized pump-probe spectroscopy is used to study the carrier-density dependence of the electron-spin polarization and spin relaxation dynamics in bulk intrinsic GaAs near the bottom of the conduction band. The experimental result shows that the initial degree of the electron-spin polarization is less than 0.5, and both the initial degree of spin polarization and the spin relaxation time decrease with increasing carrier densities. The simulation calculation shows that the band-gap renormalization effect has a significant influence on the initial degree of spin polarization, but it is not the physical origin of the decrease in the electron-spin polarization. Contrarily, the initial degree of spin polarization can be greatly enhanced by the band-gap renormalization effect for carrier densities above 3.5 x 10{sup 17} cm{sup -3}. In intrinsic GaAs, both the D'yakonov-Perel' and the Bir-Aronov-Pikus mechanisms play an important role. The Bir-Aronov-Pikus mechanism becomes stronger with the increase in the carrier density, and becomes dominant at high carrier density.

  7. Density dependence of electron-spin polarization and relaxation in intrinsic GaAs at room temperature

    Science.gov (United States)

    Teng, L. H.; Chen, K.; Wen, J. H.; Lin, W. Z.; Lai, T. S.

    2009-07-01

    Time-resolved circularly polarized pump-probe spectroscopy is used to study the carrier-density dependence of the electron-spin polarization and spin relaxation dynamics in bulk intrinsic GaAs near the bottom of the conduction band. The experimental result shows that the initial degree of the electron-spin polarization is less than 0.5, and both the initial degree of spin polarization and the spin relaxation time decrease with increasing carrier densities. The simulation calculation shows that the band-gap renormalization effect has a significant influence on the initial degree of spin polarization, but it is not the physical origin of the decrease in the electron-spin polarization. Contrarily, the initial degree of spin polarization can be greatly enhanced by the band-gap renormalization effect for carrier densities above 3.5 × 1017 cm-3. In intrinsic GaAs, both the D'yakonov-Perel' and the Bir-Aronov-Pikus mechanisms play an important role. The Bir-Aronov-Pikus mechanism becomes stronger with the increase in the carrier density, and becomes dominant at high carrier density.

  8. Electron spin resonance and nuclear magnetic resonance of sodium macrostructures in strongly irradiated NaCl-K crystals: Manifestation of quasi-one-dimensional behavior of electrons

    NARCIS (Netherlands)

    Cherkasov, FG; Mustafin, RG; L'vov, SG; Denisenko, GA; den Hartog, HW; Vainshtein, D. I.

    1998-01-01

    Data from an investigation of electron spin resonance and nuclear magnetic resonance of NaCl-K (similar to 1 mole%) crystals strongly irradiated with electrons imply the observation of a metal-insulator transition with decreasing temperature and the manifestation of quasi-one-dimensional electron

  9. Use of spin labels and electron spin resonance spectroscopy to characterize membranes of bovine sperm: effect of butylated hydroxytoluene and cold shock

    Energy Technology Data Exchange (ETDEWEB)

    Hammerstedt, R.H.; Amann, R.P.; Rucinsky, T.; Morse, P.D. II; Lepock, J.; Snipes, W.; Keith, A.D.

    1976-05-01

    Spin label probes were used in conjunction with measurements of metabolic rate and electron microscopy to characterize bovine sperm membranes. Aqueous compartments, membrane hydrocarbon zones and lipid : water interfaces were studied separately using appropriate spin labels. For sperm suspended in aqueous medium, the cold shock associated with rapid cooling from room temperature to 0/sup 0/ increased membrane permeability. This membrane damage was readily detected using spin labels but was not detected using thin section electron microscopy. This change was prevented by the addition of butylated hydroxy toluene (BHT). BHT provided partial protection against further damage caused by freezing sperm on solid CO/sub 2/. ESR techniques provide a rapid means to quantify the changes in sperm membranes occurring during the epididymal maturation of sperm and subsequent events within the female tract leading to fertilization. The technique also could be used to assess damage to sperm, ova or embryos during preparation for storage in cryoprotective diluents.

  10. Topological phase transition of a fractal spin system: The relevance of the network complexity

    Directory of Open Access Journals (Sweden)

    Felipe Torres

    2016-05-01

    Full Text Available A new type of collective excitations, due to the topology of a complex random network that can be characterized by a fractal dimension DF, is investigated. We show analytically that these excitations generate phase transitions due to the non-periodic topology of the DF > 1 complex network. An Ising system, with long range interactions, is studied in detail to support the claim. The analytic treatment is possible because the evaluation of the partition function can be decomposed into closed factor loops, in spite of the architectural complexity. The removal of the infrared divergences leads to an unconventional phase transition, with spin correlations that are robust against thermal fluctuations.

  11. Spin dephasing and photoinduced spin diffusion in a high-mobility two-dimensional electron system embedded in a GaAs-(Al,Ga)As quantum well grown in the [110] direction

    Science.gov (United States)

    Völkl, R.; Griesbeck, M.; Tarasenko, S. A.; Schuh, D.; Wegscheider, W.; Schüller, C.; Korn, T.

    2011-06-01

    We have studied spin dephasing and spin diffusion in a high-mobility two-dimensional electron system, embedded in a GaAs/AlGaAs quantum well grown in the [110] direction, by a two-beam Hanle experiment. For very low excitation density, we observe spin lifetimes of more than 16 ns, which rapidly decrease as the pump intensity is increased. Two mechanisms contribute to this decrease: The optical excitation produces holes, which lead to a decay of electron spin via the Bir-Aronov-Pikus mechanism and recombination with spin-polarized electrons. By scanning the distance between the pump and probe beams, we observe the diffusion of spin-polarized electrons over more than 20 μm. For high pump intensity, the spin polarization in a distance of several micrometers from the pump beam is larger than at the pump spot, due to the reduced influence of photogenerated holes.

  12. Magnetohydrodynamic waves with relativistic electrons and positrons in degenerate spin-1/2 astrophysical plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Maroof, R. [Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan); Department of Physics, University of Peshawar, Peshawar 25000 (Pakistan); National Center for Physics (NCP) at QAU Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Ali, S. [National Center for Physics (NCP) at QAU Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan); National Center for Physics (NCP) at QAU Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Qamar, A. [Department of Physics, University of Peshawar, Peshawar 25000 (Pakistan)

    2015-11-15

    Linear properties of high and low frequency waves are studied in an electron-positron-ion (e-p-i) dense plasma with spin and relativity effects. In a low frequency regime, the magnetohydrodynamic (MHD) waves, namely, the magnetoacoustic and Alfven waves are presented in a magnetized plasma, in which the inertial ions are taken as spinless and non-degenerate, whereas the electrons and positrons are treated quantum mechanically due to their smaller mass. Quantum corrections associated with the spin magnetization and density correlations for electrons and positrons are re-considered and a generalized dispersion relation for the low frequency MHD waves is derived to account for relativistic degeneracy effects. On the basis of angles of propagation, the dispersion relations of different modes are discussed analytically in a degenerate relativistic plasma. Numerical results reveal that electron and positron relativistic degeneracy effects significantly modify the dispersive properties of MHD waves. Our present analysis should be useful for understanding the collective interactions in dense astrophysical compact objects, like, the white dwarfs and in atmosphere of neutron stars.

  13. Geometrical contributions to the exchange constants: Free electrons with spin-orbit interaction

    Science.gov (United States)

    Freimuth, Frank; Blügel, Stefan; Mokrousov, Yuriy

    2017-05-01

    Using thermal quantum field theory, we derive an expression for the exchange constant that resembles Fukuyama's formula for orbital magnetic susceptibility (OMS). Guided by this formal analogy between the exchange constant and OMS, we identify a contribution to the exchange constant that arises from the geometrical properties of the band structure in mixed phase space. We compute the exchange constants for free electrons and show that the geometrical contribution is generally important. Our formalism allows us to study the exchange constants in the presence of spin-orbit interaction. Thereby, we find sizable differences between the exchange constants of helical and cycloidal spin spirals. Furthermore, we discuss how to calculate the exchange constants based on a gauge-field approach in the case of the Rashba model with an additional exchange splitting, and we show that the exchange constants obtained from this gauge-field approach are in perfect agreement with those obtained from the quantum field theoretical method.

  14. 14 GHz longitudinally detected electron spin resonance using microHall sensors

    Science.gov (United States)

    Bouterfas, M.; Mouaziz, S.; Popovic, R. S.

    2017-09-01

    In this work we developed a home-made LOngitudinally Detected Electron Spin Resonance (LODESR) spectrometer based on a microsize Hall sensor. A coplanar waveguide (CPW)-resonator is used to induce microwave-excitation on the sample at 14 GHz. We used InSb cross-shaped Hall devices with active areas of (10 μm × 10 μm) and (5 μm × 5 μm) . Signal intensities of the longitudinal magnetization component of DPPH and YIG samples of volumes about (10 μm) 3 and (5 μm) 3 , are measured under amplitude and frequency modulated microwave magnetic field generated by the CPW-resonator. At room temperature, 109spins /G √Hz sensitivity is achieved for 0.2mT linewidth, a result which is still better than most of inductive detected LODESR sensitivities.

  15. Equation-of-motion coupled cluster method for high spin double electron attachment calculations

    Energy Technology Data Exchange (ETDEWEB)

    Musiał, Monika, E-mail: musial@ich.us.edu.pl; Lupa, Łukasz; Kucharski, Stanisław A. [Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice (Poland)

    2014-03-21

    The new formulation of the equation-of-motion (EOM) coupled cluster (CC) approach applicable to the calculations of the double electron attachment (DEA) states for the high spin components is proposed. The new EOM equations are derived for the high spin triplet and quintet states. In both cases the new equations are easier to solve but the substantial simplification is observed in the case of quintets. Out of 21 diagrammatic terms contributing to the standard DEA-EOM-CCSDT equations for the R{sub 2} and R{sub 3} amplitudes only four terms survive contributing to the R{sub 3} part. The implemented method has been applied to the calculations of the excited states (singlets, triplets, and quintets) energies of the carbon and silicon atoms and potential energy curves for selected states of the Na{sub 2} (triplets) and B{sub 2} (quintets) molecules.

  16. Ferromagnetic Resonance Characterization of Nano-FePt by Electron Spin Resonance

    Directory of Open Access Journals (Sweden)

    S. S. Nkosi

    2013-01-01

    Full Text Available Electron spin resonance (ESR measurements at room temperature and X-band microwave frequency were performed on highly crystalline FePt system thin films. Fairly high DC static magnetic field absorption of about 300 mT was observed in these films. We attribute the high field absorption to ferromagnetic resonance (FMR. Upon increasing iron content in FePt system, no detectable spin waves modes were identified already at room temperature. This signifies a homogeneous distribution of the magnetization across the films. We qualitatively attributed such homogeneity distribution in the films to self-assembly of these Fe–Pt system nanoparticles. The results revealed that the FePt system contains hyperfine coupling with sextet I=5/2 exhibiting a phase reversal behaviour compared to FMR line. Both iron content and crystallite size increased the FMR intensity making the films good candidates for large data storage mediums and spintronics.

  17. Relevance of ferromagnetic correlations for the electron spin resonance in Kondo lattice systems.

    Science.gov (United States)

    Krellner, C; Förster, T; Jeevan, H; Geibel, C; Sichelschmidt, J

    2008-02-15

    Electron spin resonance (ESR) measurements of the ferromagnetic (FM) Kondo lattice system CeRuPO show a well defined ESR signal which is related to the Ce3+ magnetism. In contrast, no ESR could be observed in the antiferromagnetic (AFM) homologue CeOsPO. Additionally, we detect an ESR signal in ferromagnetic YbRh while it was absent in a number of Ce or Yb intermetallic compounds with dominant AFM exchange. Thus, the observation of an ESR signal in a Kondo lattice is neither specific to Yb nor to the proximity to a quantum critical point, but seems to be connected to the presence of FM fluctuations. These conclusions not only provide a basic concept to understand the ESR in Kondo lattice systems even well below the Kondo temperature (as observed in YbRh2Si2) but point out ESR as a prime method to investigate directly the spin dynamics of the Kondo ion.

  18. Tracking the charge and spin dynamics of electronic excited states in inorganic complexes

    Science.gov (United States)

    Gaffney, Kelly

    2015-03-01

    Inorganic complexes have many advantageous properties for solar energy applications, including strong visible absorption and photocatalytic activity. Whether used as a photocatalyst or a photosensitizer, the lifetime of electronic excited states and the earth abundance of the molecular components represent a key property for solar energy applications. These dual needs have undermined the usefulness of many coordination compounds. Isoelectronic iron and ruthenium based complexes represent a clear example. Ru-polypyridal based molecules have been the workhorse of solar energy related research and dye sensitized solar cells for decades, but the replacement of low abundance Ru with Fe leads to million-fold reductions in metal to ligand charge transfer (MLCT) excited state lifetimes. Understanding the origin of this million-fold reduction in lifetime and how to control excited state relaxation in 3d-metal complexes motivates the work I will discuss. We have used the spin sensitivity of hard x-ray fluorescence spectroscopy and the intense femtosecond duration pulses generated by the LCLS x-ray laser to probe the spin dynamics in a series of electronically excited [Fe(CN)6-2N(2,2'-bipyridine)N]2 N - 4 complexes, with N = 1-3. These femtosecond resolution measurements demonstrate that modification of the solvent and ligand environment can lengthen the MLCT excited state lifetime by more than two orders of magnitude. They also verify the role of triplet ligand field excited states in the spin crossover dynamics from singlet to quintet spin configurations. Work supported by the AMOS program within the Chemical Sciences, Geosciences, and Biosciences Division of the Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

  19. Electron spin resonance studies of Bi1-xScxFeO3 nanoparticulates: Observation of an enhanced spin canting over a large temperature range

    Science.gov (United States)

    Titus, S.; Balakumar, S.; Sakar, M.; Das, J.; Srinivasu, V. V.

    2017-12-01

    Bi1-xScxFeO3 (x = 0.0, 0.1, 0.15, 0.25) nano particles were synthesized by sol gel method. We then probed the spin system in these nano particles using electron spin resonance technique. Our ESR results strongly suggest the scenario of modified spin canted structures. Spin canting parameter Δg/g as a function of temperature for Scandium doped BFO is qualitatively different from undoped BFO. A broad peak is observed for all the Scandium doped BFO samples and an enhanced spin canting over a large temperature range (75-210 K) in the case of x = 0.15 doping. We also showed that the asymmetry parameter and thereby the magneto-crystalline anisotropy in these BSFO nanoparticles show peaks around 230 K for (x = 0.10 and 0.15) and beyond 300 K for x = 0.25 system. Thus, we established that the Sc doping significantly modifies the spin canting and magneto crystalline anisotropy in the BFO system.

  20. Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains

    Science.gov (United States)

    Tanveer, M.; Ruiz-Díaz, P.; Pastor, G. M.

    2016-09-01

    The electronic and magnetic properties of one-dimensional (1D) 3 d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation Δ E (q ⃗) as a function of the spin-density-wave vector q ⃗. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for Δ E (q ⃗) , the local magnetic moments μ⃗i at atom i , the magnetization-vector density m ⃗(r ⃗) , and the local electronic density of states ρi σ(ɛ ) . The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions Ji j between the local magnetic moments μ⃗i and μ⃗j are derived by fitting the ab initio Δ E (q ⃗) to a classical 1D Heisenberg model. The dominant competing interactions Ji j at the origin of the NC magnetic order are identified. The interplay between the various Ji j is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.

  1. Optical control of electron spin qubit in InAs self-assembled quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Emary, Clive [TU Berlin, Sekr. PN 7-1, Institut fuer Theoretische Physik, Hardenbergstr. 36, D-10623 Berlin (Germany); Sham, Lu Jeu [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States)

    2008-07-01

    The spin of an electron trapped in a self-assembled quantum dot is viewed as a promising quantum bit. We present here a theory of the control of such qubits using short laser pulses to excite virtual trion states within the dots. We describe mechanisms for qubit initialisation and for performing universal one and two qubit operations. We show that, for InAs dots, initialisation can be achieved on the nanosecond time-scale, and that coherent operations can performed with laser pulses with durations of tens of picoseconds. These results are of direct relevance to current experiments.

  2. Solid-state pulsed microwave bridge for electron spin echo spectrometers of 8-mm wavelength range

    Directory of Open Access Journals (Sweden)

    Kalabukhova E. N.

    2012-12-01

    Full Text Available The article presents a construction of a coherent pulsed microwave bridge with an output power up to 10 Wt with a time resolution of 10–8 seconds at a pulse repetition rate of 1 kHz designed for electron spin echo spectrometers. The bridge is built on a homodyne scheme based on IMPATT diodes, which are used for modulation and amplification of microwave power coming from the reference Gunn diode oscillator. The advantages of the bridge are optimal power and minimum pulse width, simple operation, low cost.

  3. Triggering of spin-flipping-modulated exchange bias in FeCo nanoparticles by electronic excitation

    Science.gov (United States)

    Sarker, Debalaya; Bhattacharya, Saswata; Srivastava, Pankaj; Ghosh, Santanu

    2016-12-01

    The exchange coupling between ferromagnetic (FM)-antiferromagnetic (AF) interfaces is a key element of modern spintronic devices. We here introduce a new way of triggering exchange bias (EB) in swift heavy ion (SHI) irradiated FeCo-SiO2 films, which is a manifestation of spin-flipping at high irradiation fluence. The elongation of FeCo nanoparticles (NPs) in SiO2 matrix gives rise to perpendicular magnetic anisotropy at intermediate fluence. However, a clear shift in hysteresis loop is evident at the highest fluence. This reveals the existence of an AF exchange pinning domain in the NPs, which is identified not to be oxide shell from XANES analysis. Thermal spike calculations along with first-principles based simulations under the framework of density functional theory (DFT) demonstrate that spin flipping of 3d valence electrons is responsible for formation of these AF domains inside the FM NPs. EXAFS experiments at Fe and Co K-edges further unravel that spin-flipping in highest fluence irradiated film results in reduced bond lengths. The results highlight the possibility of miniaturization of magnetic storage devices by using irradiated NPs instead of conventionally used FM-AF multilayers.

  4. Exchange Perturbation Theory for Multiatomic Electron System and Its Application to Spin Arrangement in Manganite Chains

    Directory of Open Access Journals (Sweden)

    E. V. Orlenko

    2011-01-01

    Full Text Available A new methodology of binding energy calculation with respect to different spin arrangements for a multiatomic electron system is developed from the first principle in the frame of the exchange perturbation theory (EPT. We developed EPT formalism in the general form of the Rayleigh-Srchödinger expansion with a symmetric Hamiltonian, taking into account an exchange and nonadditive contributions of a superexchange interaction. The expressions of all corrections to the energy and wave function were reduced to the nonsymmetric Hamiltonian form. The EPT method is extended for the case of degeneracy in the total spin of a system. As an example of the application of the developed EPT formalism for the degeneracy case, spin arrangements were considered for the key ⟨Mn⟩–O–⟨Mn⟩ (⟨Mn⟩: Mn3+ or Mn4+ fragments in manganites. In ⟨Mn⟩–O–⟨Mn⟩ for La1/3Ca2/3MnO3 are in good agreement the obtained estimations of Heisenberg parameter and binding energy with the available experimental data.

  5. Electron spin relaxation time in (110) InGaAs/InAlAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Yokota, Nobuhide; Yasuda, Yusuke; Ikeda, Kazuhiro; Kawaguchi, Hitoshi, E-mail: khitoshi@ms.naist.jp [Graduate School of Materials Science, Nara Institute of Science and Technology 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan)

    2014-07-14

    Electron spin relaxation time τ{sub s} in InGaAs/InAlAs quantum wells (QWs) grown on (110) and (100) InP substrates was investigated by pump-probe transmission measurements. Similar τ{sub s} of 0.83–1.0 ns were measured at room temperature for all the measured (110) and (100) QWs, indicating suppression of the D'yakonov-Perel' spin relaxation mechanism in (110) QWs is not effective in InGaAs/InAlAs QWs as opposed to GaAs/AlGaAs QWs. Contribution of the Bir-Aronov-Pikus mechanism dominant in (110) GaAs/AlGaAs QWs was found to be small in both the (110) and (100) InGaAs/InAlAs QWs from the weak dependences of τ{sub s} on pump intensity at room temperature. These results suggest that the spin relaxation mechanism dominant in InGaAs/InAlAs QWs at a temperature higher than 200 K is the Elliott-Yafet mechanism independent of the crystal orientation among the above three major mechanisms.

  6. Electron spin relaxation time in (110) InGaAs/InAlAs quantum wells

    Science.gov (United States)

    Yokota, Nobuhide; Yasuda, Yusuke; Ikeda, Kazuhiro; Kawaguchi, Hitoshi

    2014-07-01

    Electron spin relaxation time τs in InGaAs/InAlAs quantum wells (QWs) grown on (110) and (100) InP substrates was investigated by pump-probe transmission measurements. Similar τs of 0.83-1.0 ns were measured at room temperature for all the measured (110) and (100) QWs, indicating suppression of the D'yakonov-Perel' spin relaxation mechanism in (110) QWs is not effective in InGaAs/InAlAs QWs as opposed to GaAs/AlGaAs QWs. Contribution of the Bir-Aronov-Pikus mechanism dominant in (110) GaAs/AlGaAs QWs was found to be small in both the (110) and (100) InGaAs/InAlAs QWs from the weak dependences of τs on pump intensity at room temperature. These results suggest that the spin relaxation mechanism dominant in InGaAs/InAlAs QWs at a temperature higher than 200 K is the Elliott-Yafet mechanism independent of the crystal orientation among the above three major mechanisms.

  7. Gate-controlled electron spin resonance in GaAs/AlxGa1-xAs heterostructures

    Science.gov (United States)

    Jiang, H. W.; Yablonovitch, Eli

    2001-07-01

    The electron spin resonance (ESR) of two-dimensional electrons is investigated in a gated GaAs/AlGaAs heterostructure. We found that the ESR resonance frequency can be tuned by means of a gate voltage. The front and back gates of the heterostructure produce opposite g-factor shift, suggesting that electron g factor is being electrostatically controlled by shifting the equilibrium position of the electron wave function from one epitaxial layer to another with different g factors.

  8. Beam-target double-spin asymmetry in quasielastic electron scattering off the deuteron with CLAS

    Science.gov (United States)

    Mayer, M.; Kuhn, S. E.; Adhikari, K. P.; Akbar, Z.; Anefalos Pereira, S.; Asryan, G.; Avakian, H.; Badui, R. A.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Boiarinov, S.; Bosted, P.; Briscoe, W. J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Charles, G.; Chetry, T.; Ciullo, G.; Clark, L.; Colaneri, L.; Cole, P. L.; Compton, N.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dupre, R.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fanchini, E.; Fedotov, G.; Fersch, R.; Filippi, A.; Fleming, J. A.; Forest, T. A.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Gleason, C.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Guo, L.; Hakobyan, H.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S. M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jiang, H.; Keith, C.; Keller, D.; Khachatryan, G.; Khachatryan, M.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Kubarovsky, V.; Lanza, L.; Lenisa, P.; Livingston, K.; MacGregor, I. J. D.; McKinnon, B.; Meekins, D.; Mirazita, M.; Mokeev, V.; Movsisyan, A.; Net, L. A.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A. I.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pogorelko, O.; Price, J. W.; Prok, Y.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Sabatié, F.; Schumacher, R. A.; Sharabian, Y. G.; Skorodumina, Iu.; Smith, G. D.; Sokhan, D.; Sparveris, N.; Stankovic, I.; Stepanyan, S.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Torayev, B.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zhang, J.; Zonta, I.; CLAS Collaboration

    2017-02-01

    Background: The deuteron plays a pivotal role in nuclear and hadronic physics, as both the simplest bound multinucleon system and as an effective neutron target. Quasielastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. Purpose: The experimental data presented here can be used to test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on spin-momentum correlations in the deuteron ground state (due to the D -state admixture) and on the limits of the impulse approximation (IA) picture as it applies to measurements of spin-dependent observables like spin structure functions for bound nucleons. Information on this reaction can also be used to reduce systematic uncertainties on the determination of neutron form factors or deuteron polarization through quasielastic polarized electron scattering. Method: We measured the beam-target double-spin asymmetry (A||) for quasielastic electron scattering off the deuteron at several beam energies (1.6 -1.7 , 2.5, 4.2, and 5.6 -5.8 GeV ), using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The deuterons were polarized along (or opposite to) the beam direction. The double-spin asymmetries were measured as a function of photon virtuality Q2(0.13 -3.17 (GeV/c ) 2) , missing momentum (pm=0.0 -0.5 GeV /c ), and the angle between the (inferred) spectator neutron and the momentum transfer direction (θn q). Results: The results are compared with a recent model that includes final-state interactions (FSI) using a complete parametrization of nucleon-nucleon scattering, as well as a simplified model using the plane wave impulse approximation (PWIA). We find overall good agreement with both the PWIA and FSI

  9. Socio-Psychological Factors in Electronic Networking.

    Science.gov (United States)

    Boshier, Roger

    1990-01-01

    This paper analyzes electronic mail and its role in adult education, identifies research on the educational implications of electronic mail, and discusses theoretical issues from an economic, psychological, and sociological perspective. (SK)

  10. Electron-phonon coupling of light-actinides. Effect of spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Castelazo, Paola; Pena-Seaman, Omar de la [Benemerita Universidad Autonoma de Puebla (BUAP), Institute of Physics (IFUAP) (Mexico); Heid, Rolf; Bohnen, Klaus-Peter [Karlsruher Institut fuer Technologie (KIT), Institut fuer Festkoerperphysik (IFP) (Germany)

    2014-07-01

    The physics of actinide metals is quite complex and rich due to the behavior of 5f electrons in the valence region: it goes from itinerant on the early stages of the actinide series to highly localized for the elements with a higher number of 5f electrons involved. In addition, in this systems should be mandatory the inclusion of spin-orbit coupling (SOC). However, only in few cases on electronic and lattice dynamical properties the SOC has been taking into account, while for the electron-phonon (e-ph) coupling such analysis has not been performed so far. Thus, as a first approach we have systematically studied the SOC influence on the full-phonon dispersion and the e-ph coupling for the simplest light-actinide metals: Ac and Th. These elements have been studied within the framework of density functional perturbation theory, using a mixed-basis pseudopotential method. The full-phonon dispersion as well as the Eliashberg spectral function and the electron-phonon coupling parameter have been calculated with and without SOC. The observed effects of SOC in the full-phonon dispersion and Eliashberg function are discussed in detail, together with an analysis of the differences on the electronic properties due to the SOC inclusion in the calculations.

  11. Probing new spin-independent interactions through precision spectroscopy in atoms with few electrons

    Science.gov (United States)

    Delaunay, Cédric; Frugiuele, Claudia; Fuchs, Elina; Soreq, Yotam

    2017-12-01

    The very high precision of current measurements and theory predictions of spectral lines in few-electron atoms allows us to efficiently probe the existence of exotic forces between electrons, neutrons and protons. We investigate the sensitivity to new spin-independent interactions in transition frequencies (and their isotopic shifts) of hydrogen, helium and some heliumlike ions. We find that present data probe new regions of the force-carrier couplings to electrons and neutrons around the MeV mass range. We also find that, below few keV, the sensitivity to the electron coupling in precision spectroscopy of helium and positronium is comparable to that of the anomalous magnetic moment of the electron. Finally, we interpret our results in the dark-photon model where a new gauge boson is kinetically mixed with the photon. There, we show that helium transitions, combined with the anomalous magnetic moment of the electron, provide the strongest indirect bound from laboratory experiments above 100 keV.

  12. Distance Dependence of Electron Spin Polarization during Photophysical Quenching of Excited Naphthalene by TEMPO Radical.

    Science.gov (United States)

    Rane, Vinayak; Das, Ranjan

    2015-06-04

    Quenching of excited states by a free radical is generally studied in systems where these two are separate entities freely moving in a liquid solution. Random diffusive encounters bring them together to cause the quenching and leave the spins of the radical polarized. In the dynamics of the radical-triplet pair mechanism of the generation of electron spin polarization (ESP), the distance-dependent exchange interaction plays a crucial role. To investigate how the distance between the excited molecule and the radical influences the ESP, we have covalently linked a naphthalene moiety to a TEMPO free radical through a spacer group of three different lengths. We compared the ESP process of these linked compounds with that of the usual "unlinked system" of naphthalene and TEMPO through time-resolved EPR experiments at low temperature in n-hexane solution. The time evolution of both the linked and the "unlinked system" was treated on a similar footing. The time-dependent EPR signal was analyzed by combining photophysical kinetics and time-dependent Bloch equations incorporating spin dynamics. Sequential quenching of the singlet state and the triplet state of naphthalene was seen in all the systems, as revealed through the spin-polarized TREPR spectra of opposite phase. The magnitudes of the ESP in the linked molecules were higher than those of the "unlinked system," showing that when the two moieties are held together greater mixing of quartet-doublet states takes place. The magnitudes of ESP steadily decrease with increasing the length of the spacer group. The polarization magnitudes due to triplet quenching and singlet quenching are very similar, differing by a factor of only ∼2. These characteristics show that for all the linked molecules the quenching takes place in the "weak exchange" regime and at almost the same distance of separation between the two moieties. Our results also showed that observation of small absorptive TREPR signals does not necessarily imply

  13. Synthesis of Lead Sulfide Nanocrystals and Their Two-Dimensional Electronic Spectra in a Spinning Cell

    Science.gov (United States)

    Baranov, Dmitry

    This thesis describes new aspects of the synthesis and ultrafast spectroscopy of PbS nanocrystals. The first part of the thesis investigates two aspects of PbS nanocrystal synthesis: the identity and composition of oleylamine reagent and the nature of sulfur species in sulfur solutions in long-chain amines. Oleylamine, formally cis-9-octadecyl-1-amine, is a solvent, a reactant, and a ligand in the synthesis of high-quality PbS nanocrystals and other nanomaterials. It is shown that commercial oleylamine samples contain elaidylamine, trans-9-octadecen-1-amine. Sulfur solutions in long-chain amines (n-octylamine and oleylamine) are common precursors in metal sulfide nanomaterial synthesis. Resonance Raman experiments on sulfur-amine solutions established the presence of various polysulfide anions, which slowly equilibrate on the timescale of days, causing a change in reactivity of the sulfur precursor. This aging of sulfur-amine solutions is shown to be strongly correlated with irreproducibility in PbS nanocrystal syntheses. The second part of the thesis deals with non-linear optical experiments on sensitive samples, where vibrational stability, repetitive excitation, and sensitivity to air and moisture constitute a set of challenges often preventing an experiment without photoproduct contamination. As a solution to this problem, we designed, constructed and characterized a compact spinning sample cell suitable for liquid and thin film samples. The spinning sample cell, enclosed in a copper gasket sealed enclosure, enables complete sample exchange in optical experiments with up to 100 kHz repetition rates while maintaining an oxygen and water free environment at the 1 ppm level for over a month. The spinning sample cell was successfully used in a two-dimensional electronic spectroscopy experiment on PbS nanocrystals in solution, eliminating the buildup of the long-lived photoproducts and reducing trap emission in the spinning sample.

  14. Spin beam splitter based on Goos-Haenchen shifts in two-dimensional electron gas modulated by ferromagnetic and Schottky metal stripes

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Mao-Wang; Huang, Xin-Hong; Zhang, Gui-Lin; Chen, Sai-Yan [College of Science, Guilin University of Technology, Guilin 541004 (China)

    2012-11-15

    We present a theoretical study on the spin-dependent Goos-Haenchen (GH) effect in a two-dimensional electron gas modulated by ferromagnetic and Schottky metal (SM) stripes. The GH shifts for spin electron beams across this device are calculated with the help of the stationary phase method. It is shown that the GH shift of spin-up beam is significantly different from that of spin-down beam, i.e., this device shows up a considerable spin polarization effect in GH shifts of electron beams. It also is shown that both magnitude and sign of spin polarization of GH shifts are closely related to the stripe width, the magnetic strength and the gated voltage under SM stripe. These interesting properties not only provide an effective method of spin injection for spintronics application, but also give rise to a tunable spin beam splitter. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Origin of the decoherence of the extended electron spin state in Ti-doped β-Ga2O3

    Science.gov (United States)

    Mentink-Vigier, F.; Binet, L.; Gourier, D.; Vezin, H.

    2013-08-01

    The mechanism of decoherence of the electron spin of Ti3+ in β-Ga2O3 was investigated by pulsed electron paramagnetic resonance. At 4.2 K, both instantaneous and spectral diffusion contribute to the decoherence. For electron spin concentrations ≈1025 m-3 in the studied samples, calculations indicate that electron-electron couplings and electron couplings with 69Ga and 71Ga nuclei yield similar contributions to the spectral diffusion, but that electron-nuclei interactions could become the dominant cause of spectral diffusion for only slightly lower spin concentrations. Above 20 K, an additional contribution to the decoherence as well as to the spin-lattice relaxation arises from a two-optical-phonon Raman process, which becomes the leading decoherence mechanism for T > 39 K. Rabi oscillations with a damping time of about 79 ns at 4.2 K could also be observed. The damping of the Rabi oscillations, independent of the oscillation frequency, is suspected to arise from electron-nuclei interactions.

  16. Origin of the decoherence of the extended electron spin state in Ti-doped β-Ga2O3.

    Science.gov (United States)

    Mentink-Vigier, F; Binet, L; Gourier, D; Vezin, H

    2013-08-07

    The mechanism of decoherence of the electron spin of Ti(3+) in β-Ga2O3 was investigated by pulsed electron paramagnetic resonance. At 4.2 K, both instantaneous and spectral diffusion contribute to the decoherence. For electron spin concentrations ≈10(25) m(-3) in the studied samples, calculations indicate that electron-electron couplings and electron couplings with (69)Ga and (71)Ga nuclei yield similar contributions to the spectral diffusion, but that electron-nuclei interactions could become the dominant cause of spectral diffusion for only slightly lower spin concentrations. Above 20 K, an additional contribution to the decoherence as well as to the spin-lattice relaxation arises from a two-optical-phonon Raman process, which becomes the leading decoherence mechanism for T > 39 K. Rabi oscillations with a damping time of about 79 ns at 4.2 K could also be observed. The damping of the Rabi oscillations, independent of the oscillation frequency, is suspected to arise from electron-nuclei interactions.

  17. Spin-dependent electron-phonon coupling in the valence band of single-layer WS2

    DEFF Research Database (Denmark)

    Hinsche, Nicki Frank; Ngankeu, Arlette S.; Guilloy, Kevin

    2017-01-01

    The absence of inversion symmetry leads to a strong spin-orbit splitting of the upper valence band of semiconducting single-layer transition-metal dichalchogenides such as MoS2 or WS2. This permits a direct comparison of the electron-phonon coupling strength in states that only differ by their spin....... Here, the electron-phonon coupling in the valence band maximum of single-layer WS2 is studied by first-principles calculations and angle-resolved photoemission. The coupling strength is found to be drastically different for the two spin-split branches, with calculated values of λK=0.0021 and 0.......40 for the upper and lower spin-split valence band of the freestanding layer, respectively. This difference is somewhat reduced when including scattering processes involving the Au(111) substrate present in the experiment but it remains significant, in good agreement with the experimental results....

  18. Electronic document delivery: directing interlibrary loan traffic through multiple electronic networks.

    Science.gov (United States)

    Weaver, C G

    1984-04-01

    The University of Nebraska Medical Center (UNMC) uses five different electronic networks for interlibrary loan (ILL) request transmission. The advantages and problems of using electronic networks for ILL request transmission are discussed. Advantages include speed of request transmission, improved capabilities for locating documents, lower labor costs, improved turnaround time, and production of user reports and statistics. Disadvantages include increased work load, additional staff training, coordination of non-standard networks, determining access protocols, and establishing priorities for handling requests.

  19. Low-energy electron reflection from Au-passivated Ir(0 0 1) for application in imaging spin-filters

    Energy Technology Data Exchange (ETDEWEB)

    Vasilyev, D.; Tusche, C. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Giebels, F.; Gollisch, H. [Universität Duisburg-Essen, Fakultät für Physik, Campus Duisburg, Lotharstr. 1, 47048 Duisburg (Germany); Feder, R. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Universität Duisburg-Essen, Fakultät für Physik, Campus Duisburg, Lotharstr. 1, 47048 Duisburg (Germany); Kirschner, J., E-mail: sekrki@mpi-halle.mpg.de [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Martin-Luther-Universität Halle-Wittenberg, Institut für Physik, 06099 Halle (Germany)

    2015-02-15

    We describe the principle, the preparation, and the calibration of a spin-polarizing electron mirror in multichannel spin polarimetry. We show data obtained by two independent devices (a goniometer-type LEED set-up and a momentum-microscope set-up) and compare them to the results of a relativistic multiple scattering theory. We also discuss the effects of misalignment and mosaic structure of the crystal. For multi-channel detection we find a 5000-fold increase of efficiency over a single-channel spin-detector. The lifetime of the detector is more than 6 months in ultra-high vacuum.

  20. On Photon Spin and the Electrodynamic Origin of the charge of the Electron

    CERN Document Server

    Fischer, Ulrich C

    2016-01-01

    We recently performed experiments on the transfer of photon spin to electron orbital angular momentum. For an interpretation of the experimental results we used a classical electrodynamic model of the photon as a propagating electromagnetic solitary wave which is developed in detail here. A linearly polarized monochromatic photon is considered as a propagating solitary electromagnetic wave of finite energy hf which carries an angular momentum h/2pi with the frequency f and Plancks constant h. This model has, apart from being a tool for an interpretation of our experimental results, far reaching consequences of fundamental relevance and guides us to an outline to a unified quantum theory of electromagnetism and gravitation including an explanation of the electrodynamic origin of the quantized charge of an electron.

  1. Analysis of electron spin resonance spectra of irradiated gingers: Organic radical components derived from carbohydrates

    Science.gov (United States)

    Yamaoki, Rumi; Kimura, Shojiro; Ohta, Masatoshi

    2010-04-01

    Electron spin resonance (ESR) spectral characterizations of gingers irradiated with electron beam were studied. Complex asymmetrical spectra (near g=2.005) with major spectral components (line width=2.4 mT) and minor signals (at 6 mT apart) were observed in irradiated gingers. The spectral intensity decreased considerably 30 days after irradiation, and continued to decrease steadily thereafter. The spectra simulated on the basis of characteristics of free radical components derived from carbohydrates in gingers are in good agreement with the observed spectra. Analysis showed that shortly after irradiation the major radical components of gingers were composed of radical species derived from amylose and cellulose, and the amylose radicals subsequently decreased considerably. At 30 days after irradiation, the major radical components of gingers were composed of radical species derived from cellulose, glucose, fructose or sucrose.

  2. Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering

    CERN Document Server

    Armstrong, D S; Asaturyan, R; Averett, T; Bailey, S L; Batigne, G; Beck, D H; Beise, E J; Benesch, J; Bimbot, L; Birchall, J; Biselli, A; Bosted, P; Boukobza, E; Breuer, H; Carlini, R; Carr, R; Chant, N; Chao, Y C; Chattopadhyay, S; Clark, R; Covrig, S; Cowley, A; Dale, D; Davis, C; Falk, W; Finn, J M; Forest, T; Franklin, G; Furget, C; Gaskell, D; Grames, J; Griffioen, K A; Grimm, K; Guillon, B; Guler, H; Hannelius, L; Hasty, R; Hawthorne Allen, A; Horn, T; Johnston, K; Jones, M; Kammel, P; Kazimi, R; King, P M; Kolarkar, A; Korkmaz, E; Korsch, W; Kox, S; Kühn, J; Lachniet, J; Lee, L; Lenoble, J; Liatard, E; Liu, J; Loupias, B; Lung, A; Marchand, D; Martin, J W; McFarlane, K W; McKee, D W; McKeown, R D; Merchez, F; Mkrtchyan, H; Moffit, B; Morlet, M; Nakagawa, I; Nakahara, K; Neveling, R; Niccolai, S; Ong, S; Page, S; Papavassiliou, V; Pate, S F; Phillips, S K; Pitt, M L; Poelker, M; Porcelli, T A; Quéméner, G; Quinn, B; Ramsay, W D; Rauf, A W; Real, J S; Roche, J; Roos, P; Rutledge, G A; Secrest, J; Simicevic, N; Smith, G R; Spayde, D T; Stepanyan, S; Stutzman, M; Sulkosky, V; Tadevosyan, V; Tieulent, R; Van de Wiele, J; Van Oers, W T H; Voutier, E; Vulcan, W; Warren, G; Wells, S P; Williamson, S E; Wood, S A; Yan, C; Yun, J; Zeps, V

    2007-01-01

    We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 values of 0.15 and 0.25 (GeV/c)^2 with results of A_n = -4.06 +- 0.99 (stat) +- 0.63 (syst) and A_n = -4.82 +- 1.87 (stat) +- 0.98 (syst) ppm. These results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the 2-gamma exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.

  3. Coherent coupling of a superconducting flux qubit to an electron spin ensemble in diamond

    Science.gov (United States)

    Zhu, Xiaobo; Saito, Shiro; Kemp, Alexander; Kakuyanagi, Kosuke; Karimoto, Shin-Ichi; Nakano, Hayato; Munro, William J.; Tokura, Yasuhiro; Everitt, Mark S.; Nemoto, Kae; Kasu, Makoto; Mizuochi, Norikazu; Semba, Kouichi

    2012-02-01

    We have experimentally demonstrated coherent strong coupling between a single macroscopic superconducting artificial atom (a gap tunable flux qubit [1]) and an ensemble of electron spins in the form of nitrogen--vacancy color centres in diamond. We have observed coherent exchange of a single quantum of energy between a flux qubit and a macroscopic ensemble consisting of about 3.0*10^7 NV- centers [2]. This is the first step towards the realization of a long-lived quantum memory and hybrid devices coupling microwave and optical systems. [1] Coherent operation of a gap-tunable flux qubit X. B. Zhu, A. Kemp, S. Saito, K. Semba, APPLIED PHYSICS LETTERS, Volume: 97, Issue: 10 pp. 102503 (2010) [2] Coherent coupling of a superconducting flux qubit to an electron spin ensemble in diamond Xiaobo Zhu, Shiro Saito, Alexander Kemp, Kosuke Kakuyanagi, Shin-ichi Karimoto, Hayato Nakano, William J. Munro, Yasuhiro Tokura, Mark S. Everitt, Kae Nemoto, Makoto Kasu, Norikazu Mizuochi, and Kouichi Semba, Nature, Volume: 478, 221-224 (2011)

  4. Modelling Infectious Disease Spreading Dynamic via Magnetic Spin Distribution: The Stochastic Monte Carlo and Neural Network Analysis

    Science.gov (United States)

    Laosiritaworn, Yongjua; Laosiritaworn, Yongyut; Laosiritaworn, Wimalin S.

    2017-09-01

    In this work, the disease spreading under SIR framework (susceptible-infected-recovered) agent-based model was investigated via magnetic spin model, stochastic Monte Carlo simulation, and Neural Network analysis. The defined systems were two-dimensional lattice-like, where the spins (representing susceptible, infected, and recovered agents) were allocated on lattice cells. The lattice size, spin density, and infectious period were varied to observe its influence on disease spreading period. In the simulation, each spin was randomly allocated on the lattice and interacted with its first neighbouring spins for disease spreading. The subgroup magnetization profiles were recorded. From the results, numbers of agents in each subgroup as a function of time was found to depend on all considered parameters. Specifically, the disease spreading period slightly increases with increasing system size, decreases with increasing spin density, and exponentially decays with increasing infectious period. Due to many degrees of freedom associated, Neural Network was used to establish complex relationship among parameters. Multi-layer perceptron was considered, where optimized network architecture of 3-19-15-1 was found. Good agreement between predicted and actual outputs was evident. This confirms the validity of using Neural Network as supplements in modelling SIR disease spreading and provides profound database for future deployment.

  5. The co-evolutionary dynamics of directed network of spin market agents

    Science.gov (United States)

    Horváth, Denis; Kuscsik, Zoltán; Gmitra, Martin

    2006-09-01

    The spin market model [S. Bornholdt, Int. J. Mod. Phys. C 12 (2001) 667] is generalized by employing co-evolutionary principles, where strategies of the interacting and competitive traders are represented by local and global couplings between the nodes of dynamic directed stochastic network. The co-evolutionary principles are applied in the frame of Bak-Sneppen self-organized dynamics [P. Bak, K. Sneppen, Phys. Rev. Lett. 71 (1993) 4083] that includes the processes of selection and extinction actuated by the local (node) fitness. The local fitness is related to orientation of spin agent with respect to the instant magnetization. The stationary regime is formed due to the interplay of self-organization and adaptivity effects. The fat tailed distributions of log-price returns are identified numerically. The non-trivial model consequence is the evidence of the long time market memory indicated by the power-law range of the autocorrelation function of volatility with exponent smaller than one. The simulations yield network topology with broad-scale node degree distribution characterized by the range of exponents 1.3<γin<3 coinciding with social networks.

  6. Two-band electronic metal and neighboring spin liquid (spin Bose-metal) on a zigzag strip with longer-ranged repulsion

    Science.gov (United States)

    Lai, Hsin-Hua; Motrunich, Olexei I.

    2010-03-01

    We consider an electronic model for realizing the Spin Bose-metal (SBM) phase on a 2-leg triangular strip -- a spin liquid phase found by D. N. Sheng et al. [Phys. Rev. B 79, 205112 (2009)] in a spin-1/2 model with ring exchanges. Starting from a two-band ``C2S2'' metal, the SBM can be viewed as a ``C1S2'' Mott insulator with gapped overall conducting charge mode. We consider extended repulsive interactions motivated by the ab initio derivation of an electronic model for κ-ET spin liquid material [K. Nakamura et al., J. Phys. Soc. Jpn. 78, 083710(2009)]. Using weak coupling renormalization group analysis, we find that such interactions allow much wider C2S2 metallic phase than in the Hubbard model with on-site repulsion only. We identify a valid eight-fermion Umklapp term that is crucial for producing a Mott insulator and use Bosonization to study phases obtained out of the C2S2 metal upon increasing overall repulsion strength, finding that the SBM phase is a natural outcome for extended interactions.

  7. Spin entanglement in elastic electron scattering from quasi-one electron atoms

    Science.gov (United States)

    Fonseca Dos Santos, Samantha; Bartschat, Klaus

    2017-04-01

    We have extended our work on e-Li collisions to investigate low-energy elastic electron collisions with atomic hydrogen and other alkali targets (Na,K,Rb). These systems have been suggested for the possibility of continuously varying the degree of entanglement between the elastically scattered projectile and the valence electron. In order to estimate how well such a scheme may work in practice, we carried out overview calculations for energies between 0 and 10 eV and the full range of scattering angles 0° -180° . In addition to the relative exchange asymmetry parameter that characterizes the entanglement, we present the differential cross section in order to estimate whether the count rates in the most interesting energy-angle regimes are sufficient to make such experiments feasible in practice. Work supported by the NSF under PHY-1403245.

  8. Forecasting the Acquisition of University Spin-Outs: An RBF Neural Network Approach

    Directory of Open Access Journals (Sweden)

    Weiwei Liu

    2017-01-01

    Full Text Available University spin-outs (USOs, creating businesses from university intellectual property, are a relatively common phenomena. As a knowledge transfer channel, the spin-out business model is attracting extensive attention. In this paper, the impacts of six equities on the acquisition of USOs, including founders, university, banks, business angels, venture capitals, and other equity, are comprehensively analyzed based on theoretical and empirical studies. Firstly, the average distribution of spin-out equity at formation is calculated based on the sample data of 350 UK USOs. According to this distribution, a radial basis function (RBF neural network (NN model is employed to forecast the effects of each equity on the acquisition. To improve the classification accuracy, the novel set-membership method is adopted in the training process of the RBF NN. Furthermore, a simulation test is carried out to measure the effects of six equities on the acquisition of USOs. The simulation results show that the increase of university’s equity has a negative effect on the acquisition of USOs, whereas the increase of remaining five equities has positive effects. Finally, three suggestions are provided to promote the development and growth of USOs.

  9. Electric Field Generation and Control of Bipartite Quantum Entanglement between Electronic Spins in Mixed Valence Polyoxovanadate [GeV14O40](8).

    Science.gov (United States)

    Palii, Andrew; Aldoshin, Sergey; Tsukerblat, Boris; Borràs-Almenar, Juan José; Clemente-Juan, Juan Modesto; Cardona-Serra, Salvador; Coronado, Eugenio

    2017-08-21

    As part of the search for systems in which control of quantum entanglement can be achieved, here we consider the paramagnetic mixed valence polyoxometalate K2Na6[GeV14O40]·10H2O in which two electrons are delocalized over the 14 vanadium ions. Applying a homogeneous electric field can induce an antiferromagnetic coupling between the two delocalized electronic spins that behave independently in the absence of the field. On the basis of the proposed theoretical model, we show that the external field can be used to generate controllable quantum entanglement between the two electronic spins traveling over a vanadium network of mixed valence polyoxoanion [GeV14O40](8-). Within a simplified two-level picture of the energy pattern of the electronic pair based on the previous ab initio analysis, we evaluate the temperature and field dependencies of concurrence and thus indicate that the entanglement can be controlled via the temperature, magnitude, and orientation of the electric field with respect to molecular axes of [GeV14O40](8-).

  10. Exact computation and large angular momentum asymptotics of 3nj symbols: Semiclassical disentangling of spin networks.

    Science.gov (United States)

    Anderson, Roger W; Aquilanti, Vincenzo; da Silva Ferreira, Cristiane

    2008-10-28

    Spin networks, namely, the 3nj symbols of quantum angular momentum theory and their generalizations to groups other than SU(2) and to quantum groups, permeate many areas of pure and applied science. The issues of their computation and characterization for large values of their entries are a challenge for diverse fields, such as spectroscopy and quantum chemistry, molecular and condensed matter physics, quantum computing, and the geometry of space time. Here we record progress both in their efficient calculation and in the study of the large j asymptotics. For the 9j symbol, a prototypical entangled network, we present and extensively check numerically formulas that illustrate the passage to the semiclassical limit, manifesting both the occurrence of disentangling and the discrete-continuum transition.

  11. Optical control of electron spin dynamics in self-assembled (In,Ga)As/GaAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Greilich, A.; Oulton, R.; Zhukov, E.A.; Yugova, I.A.; Yakovlev, D.R.; Bayer, M. [Experimentelle Physik II, Universitaet Dortmund, 44221 Dortmund (Germany); Shabaev, A.; Efros, Al.L. [Naval Research Laboratory, Washington, DC 20375 (United States); Stavarache, V.; Reuter, D.; Wieck, A. [Angewandte Festkoerperphysik, Ruhr-Universitaet Bochum, 44780 Bochum (Germany)

    2006-11-15

    Spin coherence has been studied in self-assembled (In,Ga)As/GaAs quantum dots which contain on average a single electron per dot due to n-type modulation doping. A magnetic field was applied in the Voigt geometry, in order to study the precession of the electron spins which are oriented normal to the field. Here we address the mechanism by which such a normal orientation can be achieved by resonant excitation with circularly polarized laser pulses. Further, we discuss, how long this coherence is maintained within an ensemble of quantum dots. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. 5th International Conference on Electronics, Communications and Networks

    CERN Document Server

    2016-01-01

    This book comprises peer-reviewed contributions presented at the 5th International Conference on Electronics, Communications and Networks (CECNet 2015), held in Shanghai, China, 12-15 December, 2015. It includes new multi-disciplinary topics spanning a unique depth and breadth of cutting-edge research areas in Electronic Engineering, Communications and Networks, and Computer Technology. More generally, it is of interest to academics, students and professionals involved in Consumer Electronics Technology, Communication Engineering and Technology, Wireless Communication Systems and Technology, and Computer Engineering and Technology.

  13. SPIN AND RELATIVITY: A SEMICLASSICAL MODEL FOR ELECTRON SPIN ESPÍN Y RELATIVIDAD: UN MODELO SEMICLASICO PARA EL ESPÍN DEL ELECTRÓN

    Directory of Open Access Journals (Sweden)

    Héctor Torres-Silva

    2008-11-01

    Full Text Available The quantum relationship may be regarded as the equivalence between two expressions for the rest energy of the particle, if is considered as the spin angular velocity of the particle in its rest frame. The invariance of the relativistic space-time interval to such a spin motion (space isotropy leads to the spin momentum for all structureless particles irrespective of their mass values. The inertia is an intrinsic property due to the spin motion of the particles. The signs of the mass values occurring in the solutions of the Dirac equation might be related to the orientation of the spin motion, as suggested by the fundamental relationship . Besides it deals with the electron, and more specifically with two key properties: its complex wavefunction, and its intrinsic spin. In the standard interpretation, there is no clear real-space picture of what is oscillating in the wave, or what is rotating in the spin. Indeed, it is generally believed that no simple model of rotation can account for the spin of the electron. On the contrary, the present paper shows that a crude mechanical model of coherently rotating vortices can account quantitatively not only for spin, but also for the wavefunction itself. The implications of this are discussed in this paper.La relación cuántica puede ser considerada como la equivalencia entre dos expresiones para la energía en reposo de la partícula, si se considera la velocidad angular de giro de partículas en su marco en reposo. La invariancia del intervalo relativista espacio- tiempo para tal movimiento de espín (isotropía espacial conduce al impulso de espín para todas las partículas sin estructura, independientemente de sus valores de masa. La inercia es una propiedad intrínseca debido al movimiento de spin de las partículas. Los signos de los valores de masa que se producen en las soluciones de la ecuación de Dirac podrían estar relacionados con la orientación del espín, según lo sugerido por la

  14. Reduced-Density-Matrix Description of Decoherence and Relaxation Processes for Electron-Spin Systems

    Science.gov (United States)

    Jacobs, Verne

    2017-04-01

    Electron-spin systems are investigated using a reduced-density-matrix description. Applications of interest include trapped atomic systems in optical lattices, semiconductor quantum dots, and vacancy defect centers in solids. Complimentary time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations are self-consistently developed. The general non-perturbative and non-Markovian formulations provide a fundamental framework for systematic evaluations of corrections to the standard Born (lowest-order-perturbation) and Markov (short-memory-time) approximations. Particular attention is given to decoherence and relaxation processes, as well as spectral-line broadening phenomena, that are induced by interactions with photons, phonons, nuclear spins, and external electric and magnetic fields. These processes are treated either as coherent interactions or as environmental interactions. The environmental interactions are incorporated by means of the general expressions derived for the time-domain and frequency-domain Liouville-space self-energy operators, for which the tetradic-matrix elements are explicitly evaluated in the diagonal-resolvent, lowest-order, and Markov (short-memory time) approximations. Work supported by the Office of Naval Research through the Basic Research Program at The Naval Research Laboratory.

  15. Electron spin resonance study of the kerogen/asphaltene vanadyl porphyrins: air oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Premovic, P.I.; Tonsa, I.R.; Pajovic, M.T.; Lopez, L.; Monaco, S.L.; Dordevic, D.M.; Pavlovic, M.S. [University of Nis, Nis (Yugosalvia). Lab. for Geochemistry and Cosmochemistry, Dept. of Chemistry

    2001-04-01

    Thermal behavior of vanadyl porphyrins was studied by electron spin resonance during heating of the kerogens isolated from the La Luna (Venezuela), Maganik (Montenegro) and Serpiano (Switzerland) bituminous rocks at 150 and 250{degree}C for 1 to 20 days in the presence of air. During the thermal treatment of the kerogens the vanadyl porphyrins' resonance signals decrease monotonically and become quite small after six days of heating. Concomitantly, new vanadyl signals appear, and, at longer heating times, dominate the spectrum. It is suggested that the secondary vanadyl species must have been formed from vanadyl porphyrins. Similar conversion of vanadyl porphyrins are observed under the same experimental conditions for the asphaltenes extracted from the La Luna and Serpiano rocks, and the floating asphalt from the Dead Sea (Israel). A comparison of the spin-Hamiltonian parameters for vandyl porphyrisn and vanadyl compounds obtained during pyrolysis of the kerogens/asphaltenes suggests that these are of non-porphyrin type. For comparison, a study was conducted on the Western Kentucky No. 9 coal enriched with vanadium (up to 800 ppm) from six mines. All coal samples show only the presence of predominant vanadyl-non-porphyrin compounds similar to those generated through laboratory heating of the kerogens/asphaltenes in air. In addition, some samples also contain a minor amount of vanadyl porphyrins. 21 refs., 2 figs.

  16. Air oxidation of the kerogen/asphaltene vanadyl porphyrins: an electron spin resonance study

    Directory of Open Access Journals (Sweden)

    MIRJANA S. PAVLOVIC

    2000-02-01

    Full Text Available The thermal behavior of vanadyl porphyrins was studied by electron spin resonance during heating of kerogens, isolated from the La Luna (Venezuela and Serpiano (Switzerland bituminous rocks, at 25°C for 1 to 20 days in the presence of air. During the thermal treatment of the kerogens, the vanadyl porphyrins resonance signals decrease monotonically and become quite small after 6 days of heating. Concomitantly, new vanadyl signals appear and, at longer heating times, dominate the spectrum. It is suggested that the secondary vanadyl species must have been formed from vanadyl porphyrins. Similar conversions of vanadyl porphyrins are observed under the same experimental conditions for asphaltenes extracted from the La Luna and Serpiano rocks, and floating asphalt from the Dead Sea (Israel. A comparison of the spin-Hamiltonian parameters for vanadyl porphyrins and the vanadyl compounds obtained during pyrolysis of the kerogens/asphaltenes suggests that the latter are of a non-porphyrin type. For comparison a study was conducted on Western Kentucky No. 9 coal enriched with vanadium (>>400 ppm from six mines. All the coal samples show only the presence of predominant by non-porphyrin vanadyl compounds, similar to those generated through laboratory heating of the kerogens/asphaltenes in air. In addition, some samples also contain a minor amount of vanadyl porphyrins.

  17. Insight into the spin state at the surface of LaCoO3 revealed by photoemission electron microscopy

    Science.gov (United States)

    Yaroslavtsev, A. A.; Izquierdo, M.; Carley, R.; Dávila, M. E.; Ünal, A. A.; Kronast, F.; Lichtenstein, A.; Scherz, A.; Molodtsov, S. L.

    2016-04-01

    The evolution of the spin transition in LaCoO3 has been investigated with photoemission electron microscopy (PEEM) as a function of temperature. The investigated temperature range spanned from a predominantly low spin configuration (125 K) to the proposed percolation limit for metallization (413 K). The data show that the spin configuration exhibits an inhomogeneous spatial distribution that is very sensitive to the surface preparation method. In the region of the semiconductor-to-metal transition (300 to 450 K), the spatial contrast is continuously reduced, indicating a smooth transition without domain percolation. These observations support a new interpretation of the temperature evolution of the system that is in agreement with current theoretical understanding of the spin transition.

  18. Effect of on-site Coulomb interaction on electronic and transport properties of 100% spin polarized CoMnVAs

    Science.gov (United States)

    Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

    2017-08-01

    The structural, electronic, magnetic and transport properties of a new quaternary Heusler alloy CoMnVAs have been investigated by employing generalized gradient approximation (GGA), modified Becke-Johnson (mBJ) and GGA with Hubbard U correction (GGA + U). The alloy is energetically more stable in ferromagnetic Y1 type structure. Elastic parameters reveal high anisotropy and ductile nature of the material. CoMnVAs shows half-metallic ferromagnet character with 100% spin polarization at Fermi level with band gap of 0.55 eV in the minority spin state. The alloy also possesses high electrical conductivity and Seebeck coefficients with 15 μVK-1 at room temperature, achieving a figure of merit of 0.65 at high temperatures. The high degree of ductility, 100% spin polarization and large Seebeck coefficient, makes it an attractive candidate to be used in spin voltage generators and thermoelectric materials.

  19. The importance of the on-site electron-electron interaction for the magnetic coupling in the zigzag spin-chain compound In2VO5

    KAUST Repository

    Wang, Hao

    2010-09-27

    We present first-principles electronic structure calculations for the zigzag spin-chain compound In2VO5 using the generalized gradient approximation both with and without inclusion of an on-site Coulomb interaction. It has been proposed that In2VO5 is characterized by itinerant V 3d electrons at high temperature and localized electrons at low temperature. Consequently, it is to be expected that electronic correlations play an important role for the magnetic transition from ferromagnetic to antiferromagnetic exchange around 120 K. In this context, we study the electronic and magnetic properties of a set of possible spin configurations. Our calculations show that inclusion of an on-site Coulomb interaction in fact changes the ground state from ferromagnetic to antiferromagnetic. © 2010 IOP Publishing Ltd.

  20. Electrical properties comparison of TiO2/PS/Si devices fabricated by spin coating and electron beam gun

    Science.gov (United States)

    Dariani, R. S.; Faraji, F.

    2016-04-01

    Three porous silicon (PS) samples with different porosities by electrochemical anodization are fabricated. Then, TiO2 nanoparticles are deposited on PS by two methods, spin coating and electron beam gun. I- V characteristics of all samples show diode behavior. Our result showed that transient current decreases with increasing porosity for PS/Si samples while increases for TiO2/PS/Si samples in both deposition methods. The reason could be due to filling pores by TiO2 nanoparticles and reduction of resistivity on PS surface. Also, our result showed that transient current increases highly for samples which were deposited by electron beam gun with respect to spin coating. The reason could be that in spin coating method TiO2 sol with high viscosity was used and causes that TiO2 nanoparticles cannot easily penetrate into PS pores. But in electron beam gun method TiO2 nanoparticles reaches to PS surface as a few atoms and can easily penetrate into PS pores. Ideality factor of our samples reduces after TiO2 deposition. Also, ideality factor of samples which were deposited by electron beam gun decreases with respect to spin coating, since transient current and I- V curve slop increase in electron beam gun.

  1. Electron spin resonance dating of teeth from Western Brazilian megafauna - preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Kinoshita, Angela, E-mail: angela.kinoshita@usc.br [Departamento de Fisica, FFCLRP, Universidade de Sao Paulo, 14040-901 Ribeirao Preto-SP (Brazil); Universidade Sagrado Coracao, Rua Irma Arminda 10-50, 17011-160 Bauru - Sao Paulo (Brazil); Jose, Flavio A. [Departamento de Fisica, FFCLRP, Universidade de Sao Paulo, 14040-901 Ribeirao Preto-SP (Brazil); Sundaram, Dharani; Paixao, Jesus da S.; Soares, Isabella R.M. [Universidade Federal de Mato Grosso, Departamento de Geologia Geral, 78090-000 Cuiaba-MT (Brazil); Figueiredo, Ana Maria [Instituto de Pesquisas Energeticas e Nucleares (IPEN), 05422-970 Sao Paulo-SP (Brazil); Baffa, Oswaldo [Departamento de Fisica, FFCLRP, Universidade de Sao Paulo, 14040-901 Ribeirao Preto-SP (Brazil)

    2011-09-15

    Electron Spin Resonance (ESR) was applied to determine ages of Haplomastodon teeth from Western Brazilian Megafauna. The Equivalent Doses (D{sub e}) of (1.3 {+-} 0.2)kGy, (800 {+-} 100)Gy and (140 {+-} 20)Gy were found and the software ROSY ESR dating was employed to convert D{sub e} in age, using isotope concentrations determined by neutron activation analysis (NAA) and other information, resulting in (500 {+-} 100)ka, (320 {+-} 50) and (90 {+-} 10)ka considering the Combination Uptake (CU) model for Uranium uptake, set as an Early Uptake (EU) for dentine and Linear Uptake (LU) for enamel. There are scarce reports about Pleistocene Megafauna in this area. This paper presents the first dating of megafauna tooth and this study could contribute to improve the knowledge about the paleoclimate and paleoenvironment of this region and prompt more investigations in this area.

  2. High-resolution electron microscopy in spin pumping NiFe/Pt interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ley Domínguez, D., E-mail: david.ley@cimav.edu.mx; Sáenz-Hernández, R. J.; Faudoa Arzate, A.; Arteaga Duran, A. I.; Ornelas Gutiérrez, C. E.; Solís Canto, O.; Botello-Zubiate, M. E.; Rivera-Gómez, F. J.; Matutes-Aquino, J. A. [Centro de Investigación en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, Chihuahua 31109 (Mexico); Azevedo, A.; Silva, G. L. da; Rezende, S. M. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil)

    2015-05-07

    In order to understand the effect of the interface on the spin pumping and magnetic proximity effects, high resolution transmission electron microscopy and ferromagnetic resonance (FMR) were used to analyze Py/Pt bilayer and Pt/Py/Pt trilayer systems. The samples were deposited by dc magnetron sputtering at room temperature on Si (001) substrates. The Py layer thickness was fixed at 12 nm in all the samples and the Pt thickness was varied in a range of 0–23 nm. A diffusion zone of approximately 8 nm was found in the Py/Pt interfaces and confirmed by energy dispersive X-ray microanalysis. The FMR measurements show an increase in the linewidth and a shift in the ferromagnetic resonance field, which reach saturation.

  3. Conditioned spin and charge dynamics of a single-electron quantum dot

    Science.gov (United States)

    Greplova, Eliska; Laird, Edward A.; Briggs, G. Andrew D.; Mølmer, Klaus

    2017-11-01

    In this article we describe the incoherent and coherent spin and charge dynamics of a single-electron quantum dot. We use a stochastic master equation to model the state of the system, as inferred by an observer with access to only the current signal through a quantum point contact, acting as a charge sensor. Measurements obtained during an interval of time contribute, by a past quantum state analysis, to our knowledge about the system at any time t within that interval. Such analysis permits precise estimation of physical parameters and we propose and test a modification of the classical Baum-Welch parameter reestimation method to systems driven by both coherent and incoherent processes.

  4. Electron spin resonance characterization of radical components in irradiated black pepper skin and core

    Science.gov (United States)

    Yamaoki, Rumi; Kimura, Shojiro; Ohta, Masatoshi

    2011-11-01

    Characteristics of free radical components of irradiated black pepper fruit (skin) and the pepper seed (core) were analyzed using electron spin resonance. A weak signal near g=2.005 was observed in black pepper before irradiation. Complex spectra near g=2.005 with three lines (the skin) or seven lines (the core) were observed in irradiated black pepper (both end line width; ca. 6.8 mT). The spectral intensities decreased considerably at 30 days after irradiation, and continued to decrease steadily thereafter. The spectra simulated on the basis of the content and the stability of radical components derived from plant constituents, including fiber, starch, polyphenol, mono- and disaccharide, were in good agreement with the observed spectra. Analysis showed that the signal intensities derived from fiber in the skin for an absorbed dose were higher, and the rates of decrease were lower, than that in the core. In particular, the cellulose radical component in the skin was highly stable.

  5. Detection of irradiated fruits and vegetables by gas-chromatographic methods and electron spin-resonance

    Energy Technology Data Exchange (ETDEWEB)

    Farag, S.E.A. (National Centre for Radiation Research and Technology, Cairo (Egypt))

    1993-01-01

    Gas chromatographic methods detected some hydrocarbons esp. 17:1, 16:2, 15:0 and 14:1 in irradiated, Avocado, Papaya, Mangoes with 0.75, 1.5, 3.0 kGy and Apricot with 0.5 and 3.0 kGy. The detection of hydrocarbons was clearly at high doses but the low doses need more sensitive conditions using Liquid-Liquid-Gas chromatographic method as used here. Using Electron Spin-Resonance, produce a specific signal from irradiated onion (dried leaves) as well as apricot (hard coat of kernels) after some weeks of irradiation process but not clear with the other foodstuffs. (orig.)

  6. Spin electronic manipulation based on zigzag-edgegraphene nanojunction with a line defect

    Science.gov (United States)

    Li, Haidong; Zheng, Lili; Li, Ruixue

    2017-01-01

    We investigate the transport of spin electron through the zigzag-edge graphene nanojunction with a line defect. When the magnetization is zero, the conductance spectra exhibits a well-defined insulating band around the point far away from Dirac point. And the width of the insulating band is exactly equal to the energy splitting between the lowest conduction band of the left lead and the new state of the device region. For the parallel configuration, with the enhancement of the magnetization, the conductance value will be reduced by half around the Dirac point. For the antiparallel configuration, the width of the well-defined insulating band becomes larger with the rising of the magnetization.

  7. Relation between molecular electronic structure and nuclear spin-induced circular dichroism

    DEFF Research Database (Denmark)

    Štěpánek, Petr; Coriani, Sonia; Sundholm, Dage

    2017-01-01

    The recently theoretically described nuclear spin-induced circular dichroism (NSCD) is a promising method for the optical detection of nuclear magnetization. NSCD involves both optical excitations of the molecule and hyperfine interactions and, thus, it offers a means to realize a spectroscopy...... with the spatial distribution of the excited states and couplings between them, reflecting changes in molecular structure and conformation. This constitutes a marked difference to the nuclear magnetic resonance (NMR) chemical shift, which only reflects the local molecular structure in the ground electronic state...... are discussed. The results underline NSCD spectroscopy as a plausible tool with a power for the identification of not only different molecules, but their specific structures as well....

  8. Castanea sativa Mill. leaves as new sources of natural antioxidant: an electronic spin resonance study.

    Science.gov (United States)

    Calliste, Claude-Alain; Trouillas, Patrick; Allais, Daovy-Paulette; Duroux, Jean-Luc

    2005-01-26

    The antioxidant potential of Castanea sativa Mill. leaf (sweet chestnut) was explored as a new source of active extracts. The capacity of the different fractions issued from aqueous, methanol, and ethyl acetate extracts to inhibit the stable free radical 2,2-diphenyl-1-pycryl-hydrazyl, superoxide anion, and hydroxyl radical was measured by electronic spin resonance. Their scavenging potential was analyzed versus their amount of phenolic compounds. Among the active fractions, the most effective one was A6, an ethyl acetate fraction, which contained a high level of total phenolic compounds (29.1 g/100 g). Thus, a different extraction procedure was performed to concentrate the active compounds of A6 in the new C. sativa leaf extract (CSLE). Compared to reference antioxidants (quercetin and vitamin E) and standard extracts (Pycnogenol, from French Pinus maritima bark, and grape marc extract), it was observed that A6 and CSLE have high antioxidant potentials, equivalent to at least those of reference compounds.

  9. ESR (electron spin resonance)-determined osmotic behavior of bull spermatozoa

    Energy Technology Data Exchange (ETDEWEB)

    Du, J.; Kleinhans, F.W.; Spitzer, V.J.; Critser, J.K. (Methodist Hospital, Indianapolis, IN (USA). Dept. of Medical Research); Horstman, L. (Purdue Univ., Lafayette, IN (USA). School of Veterinary Medicine); Mazur, P. (Oak Ridge National Lab., TN (USA))

    1990-01-01

    Our laboratories are pursuing a fundamental approach to the problems of semen cryopreservation. For many cell types (human red cells, yeast, HeLa) it has been demonstrated that there is an optimum cooling rate for cryopreservation. Faster rates allow insufficient time for cell dehydration and result in intracellular ice formation and cell death. It is possible to predict this optimal rate provided that the cell acts as an ideal osmometer and several other cell parameters are known such as the membrane hydraulic conductivity. It is the purpose of this work to examine the osmotic response of bull sperm to sucrose and NaCl utilizing electron spin resonance (ESR) to measure cell volume. For calibration purposes we also measured the ESR response of human red cells (RBC), the osmotic response of which is well documented with other methods. 15 refs., 1 fig.

  10. Reactions of 1-Hydroxy-1-methylethyl Radicals with NO2-: Time-Resolved Electron Spin Resonance

    Energy Technology Data Exchange (ETDEWEB)

    Filipiak, Piotr; Camaioni, Donald M.; Fessenden, Richard W.; Carmichael, Ian; Hug, Gordon L.

    2006-09-11

    The reaction of the ?-hydroxyalkyl radical of 2-propanol (1-hydroxy-1-methylethyl radical) with nitrite ions was characterized. A product of the reaction was assigned as the adduct nitro radical anion, [HO-C(CH3)2NO2]??. This radical was identified using time-resolved electron spin resonance (TRESR). The radical?s magnetic parameters, the nitrogen hyperfine coupling constant aN of 26.39 G and its g-factor of 2.0052, are the same as those of the nitro radical anion previously discovered in ?OH spin-trapping experiments with the aci-anion of (CH3)2CHNO2. The rate constant for the decay of the ESR kinetic trace of (CH3)2C?-OH is of the same order of magnitude as the rate constant for the growth of the ESR kinetic trace of [HO-C(CH3)2NO2]??, further confirming the nature of the reaction. The bimolecular rate constant for the reaction at pH 7 is {approx}1.7 ? 106 M?1 s?1 measured by following ESR kinetic traces of (CH3)2C?-OH and 2.4 ? 106 M?1 s?1 following the growth of [HO-C(CH3)2NO2]??. The lack of better match in these two measurements is discussed. The yield of [HO-C(CH3)2NO2]?? was measured to be {approx}27% of the reaction of (CH3)2C?-OH with nitrite. Pulse radiolysis-conductivity experiments at lower pH (4.7) also show that electron transfer or the equivalent formation of [HO-C(CH3)2ONO]?? followed by rapid loss of ?NO represent only part of the reaction. These reactions are discussed with guidance by computations using density functional theory.

  11. Electronic Structure and Spin Configuration Trends of Single Transition Metal Impurity in Phase Change Material

    Science.gov (United States)

    Li, H.; Pei, J.; Shi, L. P.

    2016-10-01

    Fe doped phase change material GexSbyTez has shown experimentally the ability to alter its magnetic properties by phase change. This engineered spin degree of freedom into the phase change material offers the possibility of logic devices or spintronic devices where they may enable fast manipulation of ferromagnetism by a phase change mechanism. The electronic structures and spin configurations of isolated transition metal dopant in phase change material (iTM-PCM) is important to understand the interaction between localized metal d states and the unique delocalized host states of phase change material. Identifying an impurity center that has, in isolation, a nonvanishing magnetic moment is the first step to study the collective magnetic ordering, which originates from the interaction among close enough individual impurities. Theoretical description of iTM-PCM is challenging. In this work, we use a screened exchange hybrid functional to study the single 3d transition metal impurity in crystalline GeTe and GeSb2Te4. By curing the problem of local density functional (LDA) such as over-delocalization of the 3d states, we find that Fe on the Ge/Sb site has its majority d states fully occupied while its minority d states are empty, which is different from the previously predicted electronic configuration by LDA. From early transition metal Cr to heavier Ni, the majority 3d states are gradually populated until fully occupied and then the minority 3d states begin to be filled. Interpretive orbital interaction pictures are presented for understanding the local and total magnetic moments.

  12. Delta(X)-L intervalley mixing in SiGe heterostructures for electron spin manipulation

    Science.gov (United States)

    Kiselev, A. A.; Kim, K. W.; Yablonovitch, E.

    2004-03-01

    The technical ability to manipulate quantum information can result from the intervalley mixing in heterostructures. A SiGe structure with two active layers, Si-rich and Ge-rich can serve as an example. g factors for Delta and L electrons are way different, so shifting electron across the interface can be used for the practical spin manipulation, with the degree of modulation governed by the strength of intervalley mixing. We propose a general approach to the problem of intervalley mixing of electron states in heterostructures in the framework of transparent effective mass method. Calculation of the mixing potentials can be done, considering changes in the constituent concentrations of individual heterolayers from some "virtual crystal level" as a bunch of microscopic single-ion perturbations. For the Delta and L states at the (001) interface, the magnitude of mixing is random and residually small. For the (111) interface, large mixing does take place, but only for one of the higher confinement-shifted L valleys. The (311) interface presents a solution, allowing, simultaneously, to (i) lift degeneracy of the Delta states; (ii) lift degeneracy of the L states, and (iii) allow strong mixing between lowest L and Delta states.

  13. Variability of electron spin resonance (ESR) signal of γ -irradiated starches

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Gilberto D.; Rodrigues Junior, Orlando; Mastro, Nelida L. del, E-mail: nlmastro@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-11-01

    Food preservation is one of the practical applications of radiation processing of materials. Starch is an abundant and cheap nutritious biopolymer and also is the material for appropriate food systems and for technical industries. Starch granules are partially crystalline structures composed mainly of two types of starch: amylose, an essentially linear polymer, and amylopectin, with 3-44% of branch points. Electron spin resonance (ESR) spectroscopy is a very powerful and sensitive method for the characterization of the electronic structures of materials with unpaired electrons. The aim of the present work was to monitor the disappearance of the short life and long-life free radicals formed during γ-irradiation of 3 different starches. Corn, potato and fermented cassava starches were irradiated in a {sup 60}Co source Gammacell 220 with 20 kGy, dose rate around 1 kGy h{sup -1}. EPR spectra were obtained at room temperature using a Bruker EMX plus model, X band equipment. The main type of ESR signal from irradiated starch is a singlet with a g-value of about 2.0. The fading of ESR signals was followed for 350 hours, and presents differences among the different starch type reflecting differences in molecular arrangements of starch crystalline and amorphous fractions, although ESR spectra seemed to be common for all starches. (author)

  14. Commensurate and incommensurate spin-density waves in heavy electron systems

    Directory of Open Access Journals (Sweden)

    P. Schlottmann

    2016-05-01

    Full Text Available The nesting of the Fermi surfaces of an electron and a hole pocket separated by a nesting vector Q and the interaction between electrons gives rise to itinerant antiferromagnetism. The order can gradually be suppressed by mismatching the nesting and a quantum critical point (QCP is obtained as the Néel temperature tends to zero. The transfer of pairs of electrons between the pockets can lead to a superconducting dome above the QCP (if Q is commensurate with the lattice, i.e. equal to G/2. If the vector Q is not commensurate with the lattice there are eight possible phases: commensurate and incommensurate spin and charge density waves and four superconductivity phases, two of them with modulated order parameter of the FFLO type. The renormalization group equations are studied and numerically integrated. A re-entrant SDW phase (either commensurate or incommensurate is obtained as a function of the mismatch of the Fermi surfaces and the magnitude of |Q − G/2|.

  15. Electronic Properties of Quantum Wire Networks

    OpenAIRE

    Kuzmenko, Igor

    2005-01-01

    Quantum wire networks (``quantum crossbars'', QCB) represent a 2D grid formed by superimposed crossing arrays of parallel conducting quantum wires, molecular chains or metallic single-wall carbon nanotubes. QCB coupled only by capacitive interaction in the crosses have similar low-energy, long-wave properties characterized as a crossed sliding Luttinger liquid (CSLL) phase. In this Thesis we develop a theory of interacting Bose excitations (plasmons) in QCB. We analyze spectrum of boson field...

  16. Trusted intermediating agents in electronic trade networks

    NARCIS (Netherlands)

    T.B. Klos (Tomas); F. Alkemade (Floortje)

    2005-01-01

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

  17. High-Resolution Two-Dimensional Optical Spectroscopy of Electron Spins

    Directory of Open Access Journals (Sweden)

    M. Salewski

    2017-08-01

    Full Text Available Multidimensional coherent optical spectroscopy is one of the most powerful tools for investigating complex quantum mechanical systems. While it was conceived decades ago in magnetic resonance spectroscopy using microwaves and radio waves, it has recently been extended into the visible and UV spectral range. However, resolving MHz energy splittings with ultrashort laser pulses still remains a challenge. Here, we analyze two-dimensional Fourier spectra for resonant optical excitation of resident electrons to localized trions or donor-bound excitons in semiconductor nanostructures subject to a transverse magnetic field. Particular attention is devoted to Raman coherence spectra, which allow one to accurately evaluate tiny splittings of the electron ground state and to determine the relaxation times in the electron spin ensemble. A stimulated steplike Raman process induced by a sequence of two laser pulses creates a coherent superposition of the ground-state doublet which can be retrieved only optically because of selective excitation of the same subensemble with a third pulse. This provides the unique opportunity to distinguish between different complexes that are closely spaced in energy in an ensemble. The related experimental demonstration is based on photon-echo measurements in an n-type CdTe/(Cd,MgTe quantum-well structure detected by a heterodyne technique. The difference in the sub-μeV range between the Zeeman splittings of donor-bound electrons and electrons localized at potential fluctuations can be resolved even though the homogeneous linewidth of the optical transitions is larger by 2 orders of magnitude.

  18. Electron spin resonance and optical resonance studies on copper(II) complexes with vanadate, molybdate and tungstate anions

    Science.gov (United States)

    Singh, Raghuvir

    1983-09-01

    A series of complexes of the form Cu(An) nL x · yH 2O, where An = vanadate, molybdate or tungstate anion, L = pyridine, α-, β- or γ-picoline, n = 1 or 2; x = 1-4 and y = 0-3, have been synthesized and characterized by electron spin resonance, photoacoustic and electronic spectral studies as well as infrared spectroscopy in the solid and solution state. The different coordination sites of the ligands and anions have been interpreted from infrared and electronic spectral data. Electron spin resonance spectral data show the square planar or distorted octahedral (in a few cases five-coordinate geometry) stereochemistry around copper(II) in these complexes. Parameters such as g∥, g⊥, A∥, A⊥, , , α 2 and β 21 calculated from electron spin resonance data indicate the presence of unpaired electrons in dx2- y2 or dz2 orbitals. The results of electronic and photoacoustic spectral studies are in good accord with ESR data.

  19. Spin-orbit interaction in quantum dots and quantum wires of correlated electrons - a way to spintronics?

    Energy Technology Data Exchange (ETDEWEB)

    Birkholz, Jens Eiko

    2008-10-06

    We study the influence of the spin-orbit interaction on the electronic transport through quantum dots and quantum wires of correlated electrons. Starting with a one-dimensional infinite continuum model without Coulomb interaction, we analyze the interplay of the spin-orbit interaction, an external magnetic field, and an external potential leading to currents with significant spin-polarization in appropriate parameter regimes. Since lattice models are known to often be superior to continuum models in describing the experimental situation of low-dimensional mesoscopic systems, we construct a lattice model which exhibits the same low-energy physics in terms of energy dispersion and spin expectation values. Confining the lattice to finite length and connecting it to two semi-infinite noninteracting Fermi liquid leads, we calculate the zero temperature linear conductance using the Landauer-Bttiker formalism and show that spin-polarization effects also evolve for the lattice model by adding an adequate potential structure and can be controlled by tuning the overall chemical potential of the system (quantum wire and leads). Next, we allow for a finite Coulomb interaction and use the functional renormalization group (fRG) method to capture correlation effects induced by the Coulomb interaction. The interacting system is thereby transformed into a noninteracting system with renormalized system parameters. For short wires ({proportional_to}100 lattice sites), we show that the energy regime in which spin polarization is found is strongly affected by the Coulomb interaction. For long wires (>1000 lattice sites), we find the power-law suppression of the total linear conductance on low energy scales typical for inhomogeneous Luttinger liquids while the degree of spin polarization stays constant. Considering quantum dots which consist of two lattice sites, we observe the well-known Kondo effect and analyze, how the Kondo temperature is affected by the spin-orbit interaction

  20. Electron spin relaxation enhancement measurements of interspin distances in human, porcine, and Rhodobacter electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO).

    Science.gov (United States)

    Fielding, Alistair J; Usselman, Robert J; Watmough, Nicholas; Simkovic, Martin; Frerman, Frank E; Eaton, Gareth R; Eaton, Sandra S

    2008-02-01

    Electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) is a membrane-bound electron transfer protein that links primary flavoprotein dehydrogenases with the main respiratory chain. Human, porcine, and Rhodobacter sphaeroides ETF-QO each contain a single [4Fe-4S](2+,1+) cluster and one equivalent of FAD, which are diamagnetic in the isolated enzyme and become paramagnetic on reduction with the enzymatic electron donor or with dithionite. The anionic flavin semiquinone can be reduced further to diamagnetic hydroquinone. The redox potentials for the three redox couples are so similar that it is not possible to poise the proteins in a state where both the [4Fe-4S](+) cluster and the flavoquinone are fully in the paramagnetic form. Inversion recovery was used to measure the electron spin-lattice relaxation rates for the [4Fe-4S](+) between 8 and 18K and for semiquinone between 25 and 65K. At higher temperatures the spin-lattice relaxation rates for the [4Fe-4S](+) were calculated from the temperature-dependent contributions to the continuous wave linewidths. Although mixtures of the redox states are present, it was possible to analyze the enhancement of the electron spin relaxation of the FAD semiquinone signal due to dipolar interaction with the more rapidly relaxing [4Fe-4S](+) and obtain point-dipole interspin distances of 18.6+/-1A for the three proteins. The point-dipole distances are within experimental uncertainty of the value calculated based on the crystal structure of porcine ETF-QO when spin delocalization is taken into account. The results demonstrate that electron spin relaxation enhancement can be used to measure distances in redox poised proteins even when several redox states are present.

  1. Use of spin labels to study membrane proteins by high-frequency electron nuclear double resonance spectroscopy

    NARCIS (Netherlands)

    Orlinkskii, S.B.; Borovykh, I.V.; Zielke, V.; Steinhoff, H.J.

    2007-01-01

    The applicability of spin labels to study membrane proteins by high-frequency electron nuclear double resonance spectroscopy is demonstrated. With the use of bacteriorhodopsin embedded in a lipid membrane as an example, the spectra of protons of neighboring amino acids are recorded, electric field

  2. Identification of Copper(II) Complexes in Aqueous Solution by Electron Spin Resonance: An Undergraduate Coordination Chemistry Experiment.

    Science.gov (United States)

    Micera, G.; And Others

    1984-01-01

    Background, procedures, and results are provided for an experiment which examines, through electron spin resonance spectroscopy, complex species formed by cupric and 2,6-dihydroxybenzoate ions in aqueous solutions. The experiment is illustrative of several aspects of inorganic and coordination chemistry, including the identification of species…

  3. Characterization of Al2O3-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

    NARCIS (Netherlands)

    Kijlstra, W.S.; Poels, E.K.; Bliek, A.; Weckhuysen, B.M.; Schoonheydt, R.A.

    1996-01-01

    Alumina-supported manganese oxides, used as catalysts for the selective catalytic reduction of NO, were characterized by combined electron spin resonance and diffuse reflectance spectroscopies. Upon impregnation of the acetate precursor solution, the [Mn(H2O)6]^2+ complex interacts strongly with

  4. Spin dynamics in high-mobility two-dimensional electron systems embedded in GaAs/AlGaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Griesbeck, Michael

    2012-11-22

    Since many years there has been great effort to explore the spin dynamics in low-dimensional electron systems embedded in GaAs/AlGaAs based heterostructures for the purpose of quantum computation and spintronics applications. Advances in technology allow for the design of high quality and well-defined two-dimensional electron systems (2DES), which are perfectly suited for the study of the underlying physics that govern the dynamics of the electron spin system. In this work, spin dynamics in high-mobility 2DES is studied by means of the all-optical time-resolved Kerr/Faraday rotation technique. In (001)-grown 2DES, a strong in-plane spin dephasing anisotropy is studied, resulting from the interference of comparable Rashba and Dresselhaus contributions to the spin-orbit field (SOF). The dependence of this anisotropy on parameters like the confinement length of the 2DES, the sample temperature, as well as the electron density is demonstrated. Furthermore, coherent spin dynamics of an ensemble of ballistically moving electrons is studied without and within an applied weak magnetic field perpendicular to the sample plane, which forces the electrons to move on cyclotron orbits. Finally, strongly anisotropic spin dynamics is investigated in symmetric (110)-grown 2DES, using the resonant spin amplification method. Here, extremely long out-of-plane spin dephasing times can be achieved, in consequence of the special symmetry of the Dresselhaus SOF.

  5. Electronic Circuit Analog of Synthetic Genetic Networks: Revisited

    CERN Document Server

    Hellen, Edward H

    2016-01-01

    Electronic circuits are useful tools for studying potential dynamical behaviors of synthetic genetic networks. The circuit models are complementary to numerical simulations of the networks, especially providing a framework for verification of dynamical behaviors in the presence of intrinsic and extrinsic noise of the electrical systems. Here we present an improved version of our previous design of an electronic analog of genetic networks that includes the 3-gene Repressilator and we show conversions between model parameters and real circuit component values to mimic the numerical results in experiments. Important features of the circuit design include the incorporation of chemical kinetics representing Hill function inhibition, quorum sensing coupling, and additive noise. Especially, we make a circuit design for a systematic change of initial conditions in experiment, which is critically important for studies of dynamical systems' behavior, particularly, when it shows multistability. This improved electronic ...

  6. Transient charging and discharging of spin-polarized electrons in a quantum dot

    DEFF Research Database (Denmark)

    De Souza, Fabricio; Leao, S.A.; Gester, R. M.

    2007-01-01

    We study spin-polarized transient transport in a quantum dot coupled to two ferromagnetic leads subjected to a rectangular bias voltage pulse. Time-dependent spin-resolved currents, occupations, spin accumulation, and tunneling magnetoresistance TMR are calculated using both nonequilibrium Green ...

  7. Electron spin resonance study of oriented allyl-type free radicals of butene and butadienecarboxylic acids and derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Muszkat, L.

    1981-10-01

    Single-crystal electron spin resonance studies of free radicals formed by ..gamma.. irradiation were performed on a series of unsaturated carboxylic acids and their derivatives. As a rule, allyl-type extended ..pi..-electron free radicals are the most persistent species observed in the butene series molecules (2- and 3-hexenedioic acids) and in the butadiene series molecules (sorbic acid, sorbamide, and dimethyl muconate).

  8. Effect of on-site Coulomb interaction on electronic and transport properties of 100% spin polarized CoMnVAs

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, Tahir Mohiuddin; Gupta, Dinesh C., E-mail: sosfizix@gmail.com

    2017-08-01

    Highlights: • 100% spin-polarized material important for the application in spintronics. • Ferromagnetic nature. • Ductile in nature for mechanical applications. • Semiconducting behavior with a band gap of 0.55 eV in minority spin channel. • Possibly efficient thermoelectric material. - Abstract: The structural, electronic, magnetic and transport properties of a new quaternary Heusler alloy CoMnVAs have been investigated by employing generalized gradient approximation (GGA), modified Becke-Johnson (mBJ) and GGA with Hubbard U correction (GGA + U). The alloy is energetically more stable in ferromagnetic Y{sub 1} type structure. Elastic parameters reveal high anisotropy and ductile nature of the material. CoMnVAs shows half-metallic ferromagnet character with 100% spin polarization at Fermi level with band gap of 0.55 eV in the minority spin state. The alloy also possesses high electrical conductivity and Seebeck coefficients with 15 μVK{sup −1} at room temperature, achieving a figure of merit of 0.65 at high temperatures. The high degree of ductility, 100% spin polarization and large Seebeck coefficient, makes it an attractive candidate to be used in spin voltage generators and thermoelectric materials.

  9. Non-equilibrium quantum transport of spin-polarized electrons and back action on molecular magnet tunnel-junction

    Directory of Open Access Journals (Sweden)

    Chao Zhang

    2016-11-01

    Full Text Available We investigate the non-equilibrium quantum transport through a single-molecule magnet embedded in a tunnel junction with ferromagnetic electrodes, which generate spin-polarized electrons. The lead magnetization direction is non-collinear with the uniaxial anisotropy easy-axis of molecule-magnet. Based on the Pauli rate-equation approach we demonstrate the magnetization reversion of molecule-magnet induced by the back action of spin-polarized current in the sequential tunnel regime. The asymptotic magnetization of molecular magnet and spin-polarization of transport current are obtained as functions of time by means of time-dependent solution of the rate equation. It is found that the antiparallel configuration of the ferromagnetic electrodes and molecular anisotropy easy-axis is an effective structure to reverse both the magnetization of molecule-magnet and spin-polarization of the transport current. Particularly the non-collinear angle dependence provides useful knowledge for the quantum manipulation of molecule-magnet and spin polarized electron-transport.

  10. Non-equilibrium quantum transport of spin-polarized electrons and back action on molecular magnet tunnel-junction

    Science.gov (United States)

    Zhang, Chao; Yao, Hui; Nie, Yi-Hang; Liang, J.-Q.

    2016-11-01

    We investigate the non-equilibrium quantum transport through a single-molecule magnet embedded in a tunnel junction with ferromagnetic electrodes, which generate spin-polarized electrons. The lead magnetization direction is non-collinear with the uniaxial anisotropy easy-axis of molecule-magnet. Based on the Pauli rate-equation approach we demonstrate the magnetization reversion of molecule-magnet induced by the back action of spin-polarized current in the sequential tunnel regime. The asymptotic magnetization of molecular magnet and spin-polarization of transport current are obtained as functions of time by means of time-dependent solution of the rate equation. It is found that the antiparallel configuration of the ferromagnetic electrodes and molecular anisotropy easy-axis is an effective structure to reverse both the magnetization of molecule-magnet and spin-polarization of the transport current. Particularly the non-collinear angle dependence provides useful knowledge for the quantum manipulation of molecule-magnet and spin polarized electron-transport.

  11. Magnetic and electron-transport properties of spin-gapless semiconducting CoFeCrAl films

    Science.gov (United States)

    Sellmyer, David; Jin, Yunlong; Kharel, Parashu; Valloppilly, Shah; George, Tom; Balasubramanian, Balamurugan; Skomski, Ralph

    Recently, spin-gapless semiconductors (SGS) with a semiconducting or insulating gap in one spin channel and zero gap in the other at the Fermi level have attracted much attention due to their new functionalities such as voltage-tunable spin polarization, the ability to switch between spin-polarized n-type and p-type conduction, high spin polarization and carrier mobility. For the development of spintronic devices utilizing SGS, it is necessary to have a better understanding of the magnetic and transport properties of the thin films of these materials. In this study, the structural, magnetic, and electron-transport properties of a SGS material CoFeCrAl in the thin film geometry have been investigated. CoFeCrAl films were grown on atomically flat SiO2 substrates using magnetron sputtering. The Curie temperature was measured to be 550 K very close to the value reported for bulk CoFeCrAl. Electron-transport measurements on the oriented films revealed a negative temperature coefficient of resistivity, small anomalous Hall conductivity and linear field dependence of magnetoresistance, which are transport signatures of SGS. The effect of elemental compositions and structural ordering on the SGS properties of the CoFeCrAl films will be discussed. Research supported by NSF (Y. J.), DoE (B. B., D. J. S), ARO (T. A. G., S. R. V.), SDSU (P. K.), and NRI (Facilities).

  12. Perturbative harmonic modulation of longitudinal electron-spin magnetization for short T1 determination

    Science.gov (United States)

    Suzuki, Takayuki

    2015-10-01

    Longitudinally detected T1 measurement scheme (LOD-T1) is studied in detail. In contrast to the original work on LOD-T1 , using high power microwave pulses, this work deals with general and practically frequent cases in which perfect inversion of the electron-spin magnetization is not feasible due to the effect of relaxation during microwave pulses. Theoretical studies, numerical simulations, and experiments reveal a pair of separate contributions of the dynamics of the longitudinal magnetization to the LOD signal, namely, the periodic modulation and the relaxation contributions. The latter alone which is of interest can be extracted to give relaxation curves. In addition, it is shown that T1 information can be obtained even when the available microwave power is so low that the electron magnetization can only be perturbatively modulated, at the cost of reduced sensitivity. To overcome this, a modified pulse sequence is proposed. In this new method, the pulse excitations are repeated during half a period of the resonance of the longitudinal detection circuit. The method is called the perturbative harmonic modulation method for longitudinally detected T1 measurement (HM-LOD-T1). HM-LOD-T1 experiments are demonstrated in 2,2-diphenyl-1-picrylhydrazyl (DPPH).

  13. Perturbative harmonic modulation of longitudinal electron-spin magnetization for short T(1) determination.

    Science.gov (United States)

    Suzuki, Takayuki

    2015-10-01

    Longitudinally detected T1 measurement scheme (LOD-T1) is studied in detail. In contrast to the original work on LOD-T1, using high power microwave pulses, this work deals with general and practically frequent cases in which perfect inversion of the electron-spin magnetization is not feasible due to the effect of relaxation during microwave pulses. Theoretical studies, numerical simulations, and experiments reveal a pair of separate contributions of the dynamics of the longitudinal magnetization to the LOD signal, namely, the periodic modulation and the relaxation contributions. The latter alone which is of interest can be extracted to give relaxation curves. In addition, it is shown that T1 information can be obtained even when the available microwave power is so low that the electron magnetization can only be perturbatively modulated, at the cost of reduced sensitivity. To overcome this, a modified pulse sequence is proposed. In this new method, the pulse excitations are repeated during half a period of the resonance of the longitudinal detection circuit. The method is called the perturbative harmonic modulation method for longitudinally detected T1 measurement (HM-LOD-T1). HM-LOD-T1 experiments are demonstrated in 2,2-diphenyl-1-picrylhydrazyl (DPPH). Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Ionic Association and Electron Spin Relaxation Rates in Aquo Gadolinium(III) Complexes

    Science.gov (United States)

    Sur, Sandip K.; Bryant, Robert G.

    1996-05-01

    The electron paramagnetic resonance linewidth of aquo gadolinium(III) ion changes with the counter-ion identity and concentration in aqueous solutions. The EPR linewidth of 2 mMgadolinium(III) chloride increases from 49.2 to 89.0 mT when carbonate ion is added and decreases to 17.3 mT when nitrite ion is added. These observations suggest association reactions between aquo gadolinium(III) ion and anions that change the electron spin relaxation rates of the aquo ion. The concentration dependence of the gadolinium(III) EPR linewidth is consistent with binding constants for nitrite and nitrate ion with the aquo gadolinium(III) ion of 37 ± 6 and 2.3 ± 0.3 L mol-1respectively. The decreases in the EPR linewidth factors with these association reactions are difficult to understand unless the anion reactions increase the symmetry of the metal center. Although first-coordination reactions may not be ruled out, the decrease in EPR linewidth is more consistent with an outer-sphere association reaction that also reduces the coordination number of the metal center from 9 to 8.

  15. Electron spin resonance spectroscopy of high purity crystals at millikelvin temperatures

    Science.gov (United States)

    Farr, Warrick G.; Creedon, Daniel L.; Goryachev, Maxim; Benmessai, Karim; Tobar, Michael E.

    2013-12-01

    Progress in the emerging field of engineered quantum systems requires the development of devices that can act as quantum memories. The realisation of such devices by doping solid state cavities with paramagnetic ions imposes a trade-off between ion concentration and cavity coherence time. Here, we investigate an alternative approach involving interactions between photons and naturally occurring impurity ions in ultra-pure crystalline microwave cavities exhibiting exceptionally high quality factors. We implement a hybrid Whispering Gallery/Electron Spin Resonance method to perform rigorous spectroscopy of an undoped single-crystal sapphire resonator over the frequency range 8{19 GHz, and at external applied DC magnetic fields up to 0.9 T. Measurements of a high purity sapphire cooled close to 100 mK reveal the presence of Fe3+, Cr3+, and V2+ impurities. A host of electron transitions are measured and identified, including the two-photon classically forbidden quadrupole transition (Δms = 2) for Fe3+, as well as hyperfine transitions of V2+.

  16. Quaternary dating by electron spin resonance (ESR applied to human tooth enamel

    Directory of Open Access Journals (Sweden)

    Carvajal Eduar

    2011-12-01

    Full Text Available This paper presents the results obtained from using electron paramagnetic resonance (EPR to analyse tooth enamel found at the Aguazuque archaeological site (Cundinamarca, Colombia, located on the savannah near Bogota at 4° 37' North and 74°17' West. It was presumed that the tooth enamel came from a collective burial consisting of 23 people, involving men, women and children. The tooth enamel was irradiated with gamma rays and the resulting free radicals were measured using an electron spin resonance (ESR X-band spectrometer to obtain a signal intensity compared to absorbed doses curve. Fitting this curve allowed the mean archaeological dose accumulated in the enamel during the period that it was buried to be estimated, giving a 2.10 ± 0.14 Gyvalue. ROSY software was used for estimating age, giving a mean 3,256 ± 190y before present (BP age. These results highlight EPR's potential when using the quaternary ancient ruins dating technique in Colombia and its use with other kinds of samples like stalagmites, calcite, mollusc shells and reefs.

  17. Formation of radicals in coal pyrolysis examined by electron spin resonance

    Science.gov (United States)

    Chang, Tong; Guo, Qiang; Hao, Haigang; Wu, Baoshan; Yang, Yong

    2017-09-01

    Electron spin resonance (ESR) spectroscopy is used to study materials with unpaired electrons, such as organic radicals and metal complexes. This method can also be used to follow radical reactions during pyrolysis of carbonaceous materials. However, the temperature dependence of ESR measurement should be considered. To enable reasonable comparisons, results measured at different temperatures must be converted. In this study, we investigated the behavior of free radicals in the process of coal pyrolysis using in situ and ex situ ESR. The ESR data were collected at both pyrolysis and room temperatures, and apparent differences were analyzed. The differences were diminished when our data were converted to the same measurement temperature level based on the Boltzmann distribution law. Furthermore, we investigated the effects of process conditions on the behavior of free radicals in the solid phase of coal. We found that temperature is the most important factor determining the formation and behavior of free radicals in the solid phase, followed by the residence time. Relatively active radicals were quenched by hydrogen-donor solvents to some degree, while stable radicals remained.

  18. Formation of radicals in coal pyrolysis examined by electron spin resonance

    Directory of Open Access Journals (Sweden)

    Tong Chang

    2017-09-01

    Full Text Available Electron spin resonance (ESR spectroscopy is used to study materials with unpaired electrons, such as organic radicals and metal complexes. This method can also be used to follow radical reactions during pyrolysis of carbonaceous materials. However, the temperature dependence of ESR measurement should be considered. To enable reasonable comparisons, results measured at different temperatures must be converted. In this study, we investigated the behavior of free radicals in the process of coal pyrolysis using in situ and ex situ ESR. The ESR data were collected at both pyrolysis and room temperatures, and apparent differences were analyzed. The differences were diminished when our data were converted to the same measurement temperature level based on the Boltzmann distribution law. Furthermore, we investigated the effects of process conditions on the behavior of free radicals in the solid phase of coal. We found that temperature is the most important factor determining the formation and behavior of free radicals in the solid phase, followed by the residence time. Relatively active radicals were quenched by hydrogen-donor solvents to some degree, while stable radicals remained.

  19. Quantum angular momentum, projective geometry and the networks of seven and ten spins: Fano, Desargues and alternative incidence configurations

    Science.gov (United States)

    Santos, Robenilson F.; Arruda, Manuela S.; Bitencourt, Ana Carla P.; Ragni, Mirco; Prudente, Frederico V.; Coletti, Cecilia; Marzuoli, Annalisa; Aquilanti, Vincenzo

    2017-07-01

    The basic ingredients of the quantum theory of orbital and spin angular momentum (vector coefficients, 3nj symbols) encounter continuing relevance in wide areas beyond the traditional ones (molecular, atomic and nuclear spectroscopies and dynamics). This paper offers insight on the connection at the most elementary of levels with the diagrammatic approaches to projective geometry. In particular here we exhibit how the Fano, Desargues and related incidence configurations emerge in the Racah and in the Biedenharn-Elliott identities, corresponding respectively to the hexagonal and pentagonal relationships that provide the basis for the construction of 3nj symbols and of spin networks. It is shown that the treatment, although mostly confined to the quadrangulation of the real projective plane, permits however the introduction of networks involving seven and ten spins, and preludes to developments towards computational and asymptotic approaches for quantum and semi-classical applications to spectroscopy and dynamics.

  20. Automotive mechatronics automotive networking, driving stability systems, electronics

    CERN Document Server

    2015-01-01

    As the complexity of automotive vehicles increases this book presents operational and practical issues of automotive mechatronics. It is a comprehensive introduction to controlled automotive systems and provides detailed information of sensors for travel, angle, engine speed, vehicle speed, acceleration, pressure, temperature, flow, gas concentration etc. The measurement principles of the different sensor groups are explained and examples to show the measurement principles applied in different types. Contents Basics of mechatronics.- Architecture.- Electronic control unit.- Software development.- Basic principles of networking.- Automotive networking.- Bus systems.- Automotive sensors.- Sensor measuring principles.- Sensor types.- Electric actuators.- Electrohydraulic actuators.- Electronic transmission control.- Electronic transmission control unit.- Modules for transmission control.- Antilock braking system.- Traction control system.- Electronic stability program.- Automatic brake functions.- Hydraulic modu...

  1. Electron spin resonance microscopic imaging of oxygen concentration in cancer spheroids

    Science.gov (United States)

    Hashem, Mada; Weiler-Sagie, Michal; Kuppusamy, Periannan; Neufeld, Gera; Neeman, Michal; Blank, Aharon

    2015-07-01

    Oxygen (O2) plays a central role in most living organisms. The concentration of O2 is important in physiology and pathology. Despite the importance of accurate knowledge of the O2 levels, there is very limited capability to measure with high spatial resolution its distribution in millimeter-scale live biological samples. Many of the current oximetric methods, such as oxygen microelectrodes and fluorescence lifetime imaging, are compromised by O2 consumption, sample destruction, invasiveness, and difficulty to calibrate. Here, we present a new method, based on the use of the pulsed electron spin resonance (ESR) microimaging technique to obtain a 3D mapping of oxygen concentration in millimeter-scale biological samples. ESR imaging requires the incorporation of a suitable stable and inert paramagnetic spin probe into the desirable object. In this work, we use microcrystals of a paramagnetic spin probe in a new crystallographic packing form (denoted tg-LiNc-BuO). These paramagnetic species interact with paramagnetic oxygen molecules, causing a spectral line broadening that is linearly proportional to the oxygen concentration. Typical ESR results include 4D spatial-spectral images that give an indication about the oxygen concentration in different regions of the sample. This new oximetry microimaging method addresses all the problems mentioned above. It is noninvasive, sensitive to physiological oxygen levels, and easy to calibrate. Furthermore, in principle, it can be used for repetitive measurements without causing cell damage. The tissue model used in this research is spheroids of Human Colorectal carcinoma cell line (HCT-116) with a typical diameter of ∼600 μm. Most studies of the microenvironmental O2 conditions inside such viable spheroids carried out in the past used microelectrodes, which require an invasive puncturing of the spheroid and are also not applicable to 3D O2 imaging. High resolution 3D oxygen maps could make it possible to evaluate the

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

    Directory of Open Access Journals (Sweden)

    Schudt Christian

    2005-07-01

    Full Text Available Abstract Background The sources and measurement of reactive oxygen species (ROS in intact organs are largely unresolved. This may be related to methodological problems associated with the techniques currently employed for ROS detection. Electron spin resonance (ESR with spin trapping is a specific method for ROS detection, and may address some these technical problems. Methods We have established a protocol for the measurement of intravascular ROS release from isolated buffer-perfused and ventilated rabbit and mouse lungs, combining lung perfusion with the spin probe l-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine (CPH and ESR spectroscopy. We then employed this technique to characterize hypoxia-dependent ROS release, with specific attention paid to NADPH oxidase-dependent superoxide formation as a possible vasoconstrictor pathway. Results While perfusing lungs with CPH over a range of inspired oxygen concentrations (1–21 %, the rate of CP• formation exhibited an oxygen-dependence, with a minimum at 2.5 % O2. Addition of superoxide dismutase (SOD to the buffer fluid illustrated that a minor proportion of this intravascular ROS leak was attributable to superoxide. Stimulation of the lungs by injection of phorbol-12-myristate-13-acetate (PMA into the pulmonary artery caused a rapid increase in CP• formation, concomitant with pulmonary vasoconstriction. Both the PMA-induced CPH oxidation and the vasoconstrictor response were largely suppressed by SOD. When the PMA challenge was performed at different oxygen concentrations, maximum superoxide liberation and pulmonary vasoconstriction occurred at 5 % O2. Using a NADPH oxidase inhibitor and NADPH-oxidase deficient mice, we illustrated that the PMA-induced superoxide release was attributable to the stimulation of NADPH oxidases. Conclusion The perfusion of isolated lungs with CPH is suitable for detection of intravascular ROS release by ESR spectroscopy. We employed this technique to

  3. Mechanically Reinforced Skin-Electronics with Networked Nanocomposite Elastomer.

    Science.gov (United States)

    Han, Seungyong; Kim, Min Ku; Wang, Bo; Wie, Dae Seung; Wang, Shuodao; Lee, Chi Hwan

    2016-12-01

    Mechanically reinforced skin-electronics are presented by exploiting networked nanocomposite elastomers where high quality metal nanowires serve as conducting paths. Theoretical and experimental studies show that the established skin-electronics exhibit superior mechanical enhancements against crack and delamination phenomena. Device applications include a class of biomedical devices that offers the ability of thermotherapeutic stimulation and electrophysiological monitoring, all via the skin. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Topological Electronic Structures and Spintronics Applications for Silicene and Other Spin-Orbit Thin Films

    Science.gov (United States)

    Lin, Hsin

    2014-03-01

    While spin-orbit coupling plays a critical role in generating topologically insulating phases, it also provides a novel route for realizing spin-split states in nonmagnetic materials without the need for exchange coupling. Two-dimensional thin films with significant spin-orbit coupling strength enable potential applications for spintronics devices because the spin-splitting energy can be controlled by an external field (gating). Moreover, spin-orbit coupling can induce nontrivial topological phases, i.e. quantum spin Hall phases, which could harbor back-scattering-free spin-polarized current at the edge. Recently, we have shown via first-principles calculations that field-gated silicene possesses two gapped Dirac cones exhibiting nearly 100% spin-polarization, situated at the corners of the Brillouin zone. Band gaps as well as the band topology can be tuned with an external electric field perpendicular to the plane, which breaks the inversion symmetry of the system due to the presence of buckling in the honeycomb structure. Using this fact, we propose a design for a silicene-based spin-filter that would enable the spin-polarization of an output current to be switched electrically, without the need to switch external magnetic fields. Our quantum transport calculations indicate that the proposed designs will be highly efficient (nearly 100% spin polarization) and robust against weak disorder and edge imperfections. We also propose a Y-shaped spin/valley separator that produces spin-polarized current at two output terminals with opposite spins. Ge, Sn, and Pb counterparts of silicene are shown to have similar properties, but their larger spin-orbit coupling results in larger energy differences between the spin-split states making these materials better suited for room temperature applications. Other spin-orbit thin films will be discussed. Our investigations demonstrate that spin-orbit thin films present great potential for manipulating spin/valley degrees of freedom

  5. Spin-polarized electronic band structures of the Fe{sub 4}N-Co{sub 4}N system

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Yasuhiko, E-mail: yas-takahashi@aist.go.jp [National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, Higashi 1-1-1 Tsukuba, Ibaraki 305-8565 (Japan); Imai, Yoji; Kumagai, Toshiya [National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, Higashi 1-1-1 Tsukuba, Ibaraki 305-8565 (Japan)

    2011-12-15

    We have calculated spin-polarized electronic band structures of cubic antiperovskite metal nitrides (Fe{sub 4}N, Fe{sub 3}CoN, FeCo{sub 3}N and Co{sub 4}N) by the full-potential method with mixed basis augmented plane wave plus local orbitals. It was shown that FeCo{sub 3}N has an energy gap of 0.2 eV at the Fermi level in the up-spin band and hence its half-metallic behavior is expected. - Highlights: > Calculated spin-polarized electronic band structures of cubic antiperovskite metal nitrides. > All calculations were by the full-potential method. > Obtained densities of states and spin-polarized electronic energy bands of Fe{sub 4}N, Fe{sub 3}CoN, FeCo{sub 3}N, and Co{sub 4}N. > FeCo{sub 3}N has an energy gap of 0.2 eV at the Fermi level and hence half-metallic behavior.

  6. Two-band electronic metal and neighboring spin Bose-metal on a zigzag strip with longer-ranged repulsion

    Science.gov (United States)

    Lai, Hsin-Hua; Motrunich, Olexei I.

    2010-01-01

    We consider an electronic model for realizing the spin Bose-metal (SBM) phase on a two-leg triangular strip—a spin liquid phase found by Sheng [Phys. Rev. B 79, 205112 (2009)] in a spin-1/2 model with ring exchanges. The SBM can be viewed as a “C1S2” Mott insulator of electrons where the overall charge transporting mode is gapped out. We start from a two-band “C2S2” metal and consider extended repulsion motivated by recent ab initio derivation of electronic model for κ-ET spin liquid material [K. Nakamura , J. Phys. Soc. Jpn. 78, 083710 (2009)]. Using weak coupling renormalization group analysis, we find that the extended interactions allow much wider C2S2 metallic phase than in the Hubbard model with on-site repulsion only. An eight-fermion umklapp term plays a crucial role in producing a Mott insulator but cannot be treated in weak coupling. We use bosonization to extend the analysis to intermediate coupling and study phases obtained out of the C2S2 metal upon increasing overall repulsion strength, finding that the SBM phase is a natural outcome for extended interactions.

  7. Spin structure of Rashba-split electronic states of Bi overlayers on Cu(1 1 1)

    Energy Technology Data Exchange (ETDEWEB)

    Jakobs, S., E-mail: jakobs@physik.uni-kl.de [Department of Physics and Research Center OPTIMAS, TU Kaiserslautern, Kaiserslautern (Germany); Graduate School Materials Science in Mainz, Erwin Schrödinger Straße 46, 67663 Kaiserslautern (Germany); Ruffing, A.; Jungkenn, D.; Cinchetti, M.; Mathias, S.; Aeschlimann, M. [Department of Physics and Research Center OPTIMAS, TU Kaiserslautern, Kaiserslautern (Germany)

    2015-05-15

    Highlights: • The spin texture of the QW system 1 ML Bi/Cu(1 1 1) is investigated with SR-2PPE. • We confirm the Rashba-like behavior of the unoccupied spin-split states. • Large out-of-plane spin components are induced by in-plane potential gradients. - Abstract: We investigate the unoccupied Rashba-type spin-orbit split band structure of the commensurate and incommensurate Bi monolayer on Cu(1 1 1) with spin- and angle-resolved two-photon-photoemission spectroscopy. Because of the unique geometrical structure of these Bi monolayers on Cu(1 1 1), it can be expected that both in-plane and out-of-plane potential gradients play an important role for the Rashba-type spin-structure in these systems. Our spin-resolved data of spin-split states in Bi/Cu(1 1 1) confirm the expected Rashba behavior of the in-plane spin-components that is caused by the out-of-plane potential gradient. But in addition, we indeed find out-of-plane spin components with different magnitudes in both monolayer Bi/Cu(1 1 1) systems, which we therefore attribute to the structurally induced in-plane potential gradients.

  8. Simulation of electron spin resonance spectroscopy in diverse environments: An integrated approach

    Science.gov (United States)

    Zerbetto, Mirco; Polimeno, Antonino; Barone, Vincenzo

    2009-12-01

    We discuss in this work a new software tool, named E-SpiReS (Electron Spin Resonance Simulations), aimed at the interpretation of dynamical properties of molecules in fluids from electron spin resonance (ESR) measurements. The code implements an integrated computational approach (ICA) for the calculation of relevant molecular properties that are needed in order to obtain spectral lines. The protocol encompasses information from atomistic level (quantum mechanical) to coarse grained level (hydrodynamical), and evaluates ESR spectra for rigid or flexible single or multi-labeled paramagnetic molecules in isotropic and ordered phases, based on a numerical solution of a stochastic Liouville equation. E-SpiReS automatically interfaces all the computational methodologies scheduled in the ICA in a way completely transparent for the user, who controls the whole calculation flow via a graphical interface. Parallelized algorithms are employed in order to allow running on calculation clusters, and a web applet Java has been developed with which it is possible to work from any operating system, avoiding the problems of recompilation. E-SpiReS has been used in the study of a number of different systems and two relevant cases are reported to underline the promising applicability of the ICA to complex systems and the importance of similar software tools in handling a laborious protocol. Program summaryProgram title: E-SpiReS Catalogue identifier: AEEM_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEM_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL v2.0 No. of lines in distributed program, including test data, etc.: 311 761 No. of bytes in distributed program, including test data, etc.: 10 039 531 Distribution format: tar.gz Programming language: C (core programs) and Java (graphical interface) Computer: PC and Macintosh Operating system: Unix and Windows Has the code been vectorized or

  9. Chiral Spin-Density Wave, Spin-Charge-Chern Liquid, and d+id Superconductivity in 1/4-Doped Correlated Electronic Systems on the Honeycomb Lattice

    Directory of Open Access Journals (Sweden)

    Shenghan Jiang

    2014-09-01

    Full Text Available Recently, two interesting candidate quantum phases—the chiral spin-density wave state featuring anomalous quantum Hall effect and the d+id superconductor—were proposed for the Hubbard model on the honeycomb lattice at 1/4 doping. Using a combination of exact diagonalization, density matrix renormalization group, the variational Monte Carlo method, and quantum field theories, we study the quantum phase diagrams of both the Hubbard model and the t-J model on the honeycomb lattice at 1/4 doping. The main advantage of our approach is the use of symmetry quantum numbers of ground-state wave functions on finite-size systems (up to 32 sites to sharply distinguish different quantum phases. Our results show that for 1≲U/t<40 in the Hubbard model and for 0.1spin-density wave state or a spin-charge-Chern liquid, but not a d+id superconductor. However, in the t-J model, upon increasing J, the system goes through a first-order phase transition at J/t=0.80(2 into the d+id superconductor. Here, the spin-charge-Chern liquid state is a new type of topologically ordered quantum phase with Abelian anyons and fractionalized excitations. Experimental signatures of these quantum phases, such as tunneling conductance, are calculated. These results are discussed in the context of 1/4-doped graphene systems and other correlated electronic materials on the honeycomb lattice.

  10. The use of electronic communication (social network) by open and ...

    African Journals Online (AJOL)

    social network) by open and distance learners, henceforth referred to as ODL in the work. The case of National Open University of Nigeria, Benin study centre. The study is to explore the electronic device mostly used by open and distance ...

  11. Influence of spin-orbit interaction within the insulating barrier on the electron transport in magnetic tunnel junctions

    Science.gov (United States)

    Vedyayev, A.; Ryzhanova, N.; Strelkov, N.; Titova, M.; Chshiev, M.; Rodmacq, B.; Auffret, S.; Cuchet, L.; Nistor, L.; Dieny, B.

    2017-02-01

    We present a theory of the anisotropy of tunneling magnetoresistance (ATMR) phenomenon in magnetic tunnel junctions (MTJs) attributed to Rashba spin-orbit interaction in the insulating barrier. ATMR represents the difference of tunnel magnetoresistance (TMR) amplitude measured with in-plane and out-of-plane magnetic configurations. It is demonstrated that within the spin-polarized free-electron model the change of conductance associated with the ATMR is exactly twice the change of conductance measured at full saturation (i.e., in parallel configuration of magnetizations) between in-plane and out-of-plane configuration, i.e., the tunneling anisotropic magnetoresistance (TAMR). Both ATMR and TAMR are closely related to the TMR amplitude and spin-orbit constant. The predicted ATMR phenomenon is confirmed experimentally, showing a few percent value in the case of the widely studied CoFeB/MgO/CoFeB based MTJ.

  12. Evidence of weak ferromagnetism in doped plasticized polyaniline (PANI-DDoESSA)0.5 from electron spin resonance measurements.

    Science.gov (United States)

    Santana, V T; Nascimento, O R; Djurado, D; Travers, J P; Pron, A; Walmsley, L

    2013-03-20

    X-band electron spin resonance (ESR) measurements have been performed on a conducting free-standing film of polyaniline plasticized and protonated with di-n-dodecyl ester of sulfosuccinic acid (DDoESSA). The magnetic field was applied parallel and perpendicular to the plane of the film. At around 75 K a transition is observed from Pauli susceptibility to a localized state in which the spin 1/2 polarons behave as spin 1/2 dimers. A rough estimation of the intradimer and interdimer exchange constants is obtained. Below 5 K, ESR data reveal a weak ferromagnetism with the Dzyaloshinskii-Moriya vector mainly oriented in the plane of the film. The existence of a relatively well-defined n-fold axis along the chain direction in the crystalline regions confers a symmetry compatible with such analysis.

  13. Spin current

    CERN Document Server

    Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

    2017-01-01

    Since the discovery of the giant magnetoresistance effect in magnetic multilayers in 1988, a new branch of physics and technology, called spin-electronics or spintronics, has emerged, where the flow of electrical charge as well as the flow of electron spin, the so-called “spin current,” are manipulated and controlled together. The physics of magnetism and the application of spin current have progressed in tandem with the nanofabrication technology of magnets and the engineering of interfaces and thin films. This book aims to provide an introduction and guide to the new physics and applications of spin current, with an emphasis on the interaction between spin and charge currents in magnetic nanostructures.

  14. Percolation on shopping and cashback electronic commerce networks

    Science.gov (United States)

    Fu, Tao; Chen, Yini; Qin, Zhen; Guo, Liping

    2013-06-01

    Many realistic networks live in the form of multiple networks, including interacting networks and interdependent networks. Here we study percolation properties of a special kind of interacting networks, namely Shopping and Cashback Electronic Commerce Networks (SCECNs). We investigate two actual SCECNs to extract their structural properties, and develop a mathematical framework based on generating functions for analyzing directed interacting networks. Then we derive the necessary and sufficient condition for the absence of the system-wide giant in- and out- component, and propose arithmetic to calculate the corresponding structural measures in the sub-critical and supercritical regimes. We apply our mathematical framework and arithmetic to those two actual SCECNs to observe its accuracy, and give some explanations on the discrepancies. We show those structural measures based on our mathematical framework and arithmetic are useful to appraise the status of SCECNs. We also find that the supercritical regime of the whole network is maintained mainly by hyperlinks between different kinds of websites, while those hyperlinks between the same kinds of websites can only enlarge the sizes of in-components and out-components.

  15. Rich eight-branch spectrum of the oblique propagating longitudinal waves in partially spin-polarized electron-positron-ion plasmas.

    Science.gov (United States)

    Andreev, Pavel A; Iqbal, Z

    2016-03-01

    We consider the separate spin evolution of electrons and positrons in electron-positron and electron-positron-ion plasmas. We consider the oblique propagating longitudinal waves in these systems. Working in a regime of high-density n(0) ∼ 10(27) cm(-3) and high-magnetic-field B(0)=10(10) G, we report the presence of the spin-electron acoustic waves and their dispersion dependencies. In electron-positron plasmas, similarly to the electron-ion plasmas, we find one spin-electron acoustic wave (SEAW) at the propagation parallel or perpendicular to the external field and two spin-electron acoustic waves at the oblique propagation. At the parallel or perpendicular propagation of the longitudinal waves in electron-positron-ion plasmas, we find four branches: the Langmuir wave, the positron-acoustic wave, and a pair of waves having spin nature, they are the SEAW and the wave discovered in this paper, called the spin-electron-positron acoustic wave (SEPAW). At the oblique propagation we find eight longitudinal waves: the Langmuir wave, the Trivelpiece--Gould wave, a pair of positron-acoustic waves, a pair of SEAWs, and a pair of SEPAWs. Thus, for the first time, we report the existence of the second positron-acoustic wave existing at the oblique propagation and the existence of SEPAWs.

  16. Gauge field theory approach to spin transport in a 2D electron gas

    Directory of Open Access Journals (Sweden)

    B. Berche

    2009-01-01

    Full Text Available We discuss the Pauli Hamiltonian including the spin-orbit interaction within an U(1×SU(2 gauge theory interpretation, where the gauge symmetry appears to be broken. This interpretation offers new insight into the problem of spin currents in the condensed matter environment, and can be extended to Rashba and Dresselhaus spin-orbit interactions. We present a few outcomes of the present formulation: i it automatically leads to zero spin conductivity, in contrast to predictions of Gauge symmetric treatments, ii a topological quantization condition leading to voltage quantization follows, and iii spin interferometers can be conceived in which, starting from an arbitrary incoming unpolarized spinor, it is always possible to construct a perfect spin filtering condition.

  17. Magnetic resonance force microscopy of paramagnetic electron spins at millikelvin temperatures.

    Science.gov (United States)

    Vinante, A; Wijts, G; Usenko, O; Schinkelshoek, L; Oosterkamp, T H

    2011-12-06

    Magnetic resonance force microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here we demonstrate MRFM operation at temperatures as low as 30 mK, thanks to a recently developed superconducting quantum interference device (SQUID)-based cantilever detection technique, which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centres on a silicon surface down to millikelvin temperatures. Fluctuations of such defects are supposedly linked to 1/f magnetic noise and decoherence in SQUIDs, as well as in several superconducting and single spin qubits. We find evidence that spin diffusion has a key role in the low-temperature spin dynamics.

  18. Ultrafast electron spin dynamics in ZnO and Zn1-xCoxO sol-gel thin films

    Directory of Open Access Journals (Sweden)

    Leitenstorfer A.

    2013-03-01

    Full Text Available We probe the electron spin dynamics in ZnO and Zn1-xCoxO sol-gel films with time-resolved Faraday rotation spectroscopy. Dephasing times T2* on the order of nanoseconds are observed at room temperature due to charge-separated states. In ZnCoO the effective electron Landé g factor rises with increasing Co2+ concentration, providing the mean-field electron-Co2+ exchange energy N0α = +0.25 ± 0.02 eV.

  19. A Study of the Spin Structure on the Neutron in Deep Inelastic Scattering of Polarized Electrons on Polarized Neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Spengos, M

    2004-01-06

    The internal spin structure of the neutron, was studied in deep inelastic scattering of longitudinally polarized electrons from a polarized {sup 3}He target in the End Station A of the Stanford Linear Accelerator Center (SLAC). The spin asymmetry of the neutron was measured at energies between 19 and 26 GeV in the range 0.03 {le} x {le} 0.06 at an average Q{sup 2} of 2 (GeV/c){sup 2}. The results are in agreement with a new measurement of the asymmetry by SMC within their six times larger uncertainties. The spin dependent structure function g{sub 1}(x) for the neutron was determined from the asymmetry measurement and, its integral over x is found to be {integral}g{sub 1}{sup n}(x)dx = -0.038 {+-} 0.009. This result is 2.7 standard deviations from the Ellis-Jaffe Sum Rule and combined with the EMC results from the proton in very good agreement with the Bjorken Sum Rule. In the Quark Parton Model (QPM), in conjunction with the weak coupling constants F and D, from baryon decay, the result implies that the quarks contribute approximately 32% of the nucleon helicity. Finally, different ways of evolving the data, based on various theoretical models, is attempted and future aspects for spin physics, with emphasis at spin physics at SLAC, are discussed.

  20. Electronic collaboration in dermatology resident training through social networking.

    Science.gov (United States)

    Meeks, Natalie M; McGuire, April L; Carroll, Bryan T

    2017-04-01

    The use of online educational resources and professional social networking sites is increasing. The field of dermatology is currently under-utilizing online social networking as a means of professional collaboration and sharing of training materials. In this study, we sought to assess the current structure of and satisfaction with dermatology resident education and gauge interest for a professional social networking site for educational collaboration. Two surveys-one for residents and one for faculty-were electronically distributed via the American Society for Dermatologic Surgery and Association of Professors of Dermatology (APD) listserves. The surveys confirmed that there is interest among dermatology residents and faculty in a dermatology professional networking site with the goal to enhance educational collaboration.

  1. Investigation of radiosterilization of Benzydamine Hydrochloride by electron spin resonance spectroscopy

    Science.gov (United States)

    Çolak, Şeyda

    2016-10-01

    The use of ionizing radiation for sterilization of pharmaceuticals is an attractive and growing technology. In the present work, the spectroscopic and kinetic features of the radicals induced in gamma irradiated solid Benzydamine Hydrochloride (BH) sample is investigated in the dose range of 3-34 kGy at different temperatures using Electron Spin Resonance (ESR) spectroscopy. Gamma irradiated BH indicated eight resonance peaks centered at g=2.0029 originating from two different radical species. Decay activation energy of the radical mostly responsible from central intense resonance line was calculated to be 25.6±1.5 kJ/mol by using the signal intensity decay data derived from annealing studies performed at high temperatures. A linear function of the applied dose was found to describe best the experimental dose-response data. However, the discrimination of irradiated BH from unirradiated one was possible even 3 months after storage at normal conditions. Basing on these findings it was concluded that BH and BH containing drugs could be safely sterilized by gamma radiation and that ESR spectroscopy could be successfully used as a potential technique for monitoring their radiosterilizations.

  2. An electron spin resonance probe method for the understanding of petroleum asphaltene macrostructure

    Energy Technology Data Exchange (ETDEWEB)

    Wong, G.K.; Yen, T.F. [Department of Civil and Environmental Engineering, University of Southern California, 3620 South Vermont Avenue 224A, 90089-2531 Los Angeles, CA (United States)

    2000-10-01

    Molecularly, petroleum asphaltenes are induced dipoles, which agglomerate into nanometer-sized colloids of different aggregation states. The electron spin resonance (ESR) vanadyl probe method is used to investigate the asphaltene macrostructures under different temperatures and microwave powers. Oxovanadium complexes native to an asphaltene isolated from Boscan crude oil, Venezuela, function as tracers to examine the behavior of micelle agglomerates when subjected to a microwave field. Both mobile and bounded oxovanadium compounds in colloidal asphaltene solution are in a state of equilibrium. It is noted that a greater amount of mobile vanadyl complexes can be stabilized in a dispersing medium (single-aromatic ring solvent series) with a higher-valued Hansen hydrogen bonding solubility parameter. We found that conversion of ESR vanadyl hyperfine lines occurs from anisotropic to isotropic as the temperature of a 4% Boscan asphaltene solution in o-xylene increased from 25C to 100C. Free tumbling of total vanadyl complexes in organic solvent signifies dissociation of micelles at packing imperfections prior to their release from aromatic hosts. Coupling of petroleum asphaltenes with microwave power can overcome charge transfer and charge balance interactions within micelle agglomerates. The relative content of mobile to bounded vanadyl complexes in 4% Boscan asphaltene solution of o-xylene was found to increase with microwave power at 45C. Microwave energy will enable effective dispersion of colloidal asphaltene in heavy oil refining and upgrading.

  3. A study of the processes related to coagulation of asphaltenes by electronic spin resonance

    Energy Technology Data Exchange (ETDEWEB)

    Tagirzyanov, M.I.; Yakubov, M.R.; Romanov, G.V. [A.E. Arbuzov Inst. of Organic and Physical Chemistry, Russian Academy of Sciences (Russian Federation)

    2004-07-01

    This study examined the coagulation of asphaltenes in crude oil from the Volga-Ural region in Russia. In particular, it examined the contents of vanadyl complexes and free radicals in crude oils and asphaltenes by electron spin resonance. Asphaltenes fall into two major structural categories based on vanadium content. The interactions between vanadyl complexes and free radicals of the asphaltenes liquid phase were modelled in order to determine if they can form diamagnetic associations. Asphaltenes with low vanadium content (less than 0.1 per cent by weight), have large polyaromatic fragments in the molecules. Therefore, more than half of the free radicals recombine when the asphaltene are separated from the crude oil. Vanadium rich asphaltenes (greater than 0.3 per cent by weight) have polyaromatic fragments in the inner part of the structure. It was concluded that interaction between vanadyl complexes and asphaltene fragments containing free radicals do not result in the formation of diamagnetic associations. 23 refs., 3 tabs., 3 figs.

  4. Antioxidant activity in hepatopancreas of the shrimp (Pleoticus muelleri) by electron paramagnetic spin resonance spectrometry.

    Science.gov (United States)

    Díaz, Ana C; Fernández Gimenez, Analía V; Mendiara, Sara N; Fenucci, Jorge L

    2004-05-19

    Free radical scavenging properties of hepatopancreas extracts of Pleoticus muelleri were evaluated by electron paramagnetic spin resonance spectrometry methods (EPR) against the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The present study was carried out to characterize different physiological stages of the shrimp under environmental and nutritional stress, evaluating the effect on growth, survival, and functional morphology of the hepatopancreas. Feeding trials were carried out on juveniles (1 g initial weight) held in aquaria. Each diet, with different concentrations of vitamins A and E, was tested in triplicate groups during 25 days. The control groups were fed with fresh squid mantle and with a vitamin-free diet. For all of the diets, the extracts exhibited strong DPPH radical scavenging activity, suggesting that the tissue is a powerful natural antioxidant. Individuals fed with different concentrations of vitamin E showed the strongest effect on the DPPH radicals, reducing the DPPH radicals to 50%, after an incubation period of 3 min. In contrast, the extracts of control animals, fed with squid mantle, had the weakest antioxidant activity (4%). These data indicated that the presence of vitamin E in the diet can provide immediate protection against free radicals.

  5. Electron spin resonance. Part two: a diagnostic method in the environmental sciences.

    Science.gov (United States)

    Rhodes, Christopher J

    2011-01-01

    A review is presented of some of the ways in which electron spin resonance (ESR) spectroscopy may be useful to investigate systems of relevance to the environmental sciences. Specifically considered are: quantititave ESR, photocatalysis for pollution control; sorption and mobility of molecules in zeolites; free radicals produced by mechanical action and by shock waves from explosives; measurement of peroxyl radicals and nitrate radicals in air; determination of particulate matter polyaromatic hydrocarbons (PAH), soot and black carbon in air; estimation of nitrate and nitrite in vegetables and fruit; lipid-peroxidation by solid particles (silica, asbestos, coal dust); ESR of soils and other biogenic substances: formation of soil organic matter carbon capture and sequestration (CCS) and no-till farming; detection of reactive oxygen species in the photosynthetic apparatus of higher plants under light stress; molecular mobility and intracellular glasses in seeds and pollen; molecular mobility in dry cotton; characterisation of the surface of carbon black used for chromatography; ESR dating for archaeology and determining seawater levels; measurement of the quality of tea-leaves by ESR; green-catalysts and catalytic media; studies of petroleum (crude oil); fuels; methane hydrate; fuel cells; photovoltaics; source rocks; kerogen; carbonaceous chondrites to find an ESR-based marker for extraterrestrial origin; samples from the Moon taken on the Apollo 11 and Apollo 12 missions to understand space-weathering; ESR studies of organic matter in regard to oil and gas formation in the North Sea; solvation by ionic liquids as green solvents, ESR in food and nutraceutical research.

  6. Magnetic phase transitions in ferrite nanoparticles characterized by electron spin resonance

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Arias, Yesica, E-mail: yeika01@hotmail.com; Vázquez-Victorio, Gabriela; Ortega-Zempoalteca, Raul; Acevedo-Salas, Ulises; Valenzuela, Raul [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Ammar, Souad [Laboratoires ITODYS, Université de Paris-Diderot, PRES Sorbonne Paris Cité, CNRS-UMR 7086, 75205 Paris Cedex (France)

    2015-05-07

    Ferrite magnetic nanoparticles in the composition Zn{sub 0.7}Ni{sub 0.3}Fe{sub 2}O{sub 4} were synthesized by the polyol method, with an average size of 8 nm. Electron spin resonance (ESR) measurements were carried out at a frequency of 9.45 GHz in the 100–500 K temperature range. Obtained results exhibited a characteristic ESR signal in terms of resonance field, H{sub res}, linewidth, ΔH, and peak ratio, R, for each magnetic phase. At low temperatures, the ferrimagnetic phase showed low H{sub res}, broad ΔH, and asymmetric R. At high temperatures, these parameters exhibited opposite values: high H{sub res}, small ΔH, and R ∼ 1. For intermediate temperatures, a different phase was observed, which was identified as a superparamagnetic phase by means of zero-field cooling-field cooling and hysteresis loops measurements. The observed differences were explained in terms of the internal fields and especially due to the cubic anisotropy in the ordered phase.

  7. Electron spin resonance characterization of radical components in irradiated black pepper skin and core

    Energy Technology Data Exchange (ETDEWEB)

    Yamaoki, Rumi, E-mail: yamaoki@gly.oups.ac.jp [Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094 (Japan); Kimura, Shojiro [Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094 (Japan); Ohta, Masatoshi [Faculty of Engineering, Niigata University, 8050 Igarashi 2-no-cho, Nishi-ku, Niigata 950-2181 (Japan)

    2011-11-15

    Characteristics of free radical components of irradiated black pepper fruit (skin) and the pepper seed (core) were analyzed using electron spin resonance. A weak signal near g=2.005 was observed in black pepper before irradiation. Complex spectra near g=2.005 with three lines (the skin) or seven lines (the core) were observed in irradiated black pepper (both end line width; ca. 6.8 mT). The spectral intensities decreased considerably at 30 days after irradiation, and continued to decrease steadily thereafter. The spectra simulated on the basis of the content and the stability of radical components derived from plant constituents, including fiber, starch, polyphenol, mono- and disaccharide, were in good agreement with the observed spectra. Analysis showed that the signal intensities derived from fiber in the skin for an absorbed dose were higher, and the rates of decrease were lower, than that in the core. In particular, the cellulose radical component in the skin was highly stable. - Highlights: > We identified the radical components in irradiated black pepper skin and core. > The ESR spectra near g=2.005 with 3-7 lines were emerged after irradiation. > Spectra simulated basing on the content and the stability of radical from the plant constituents. > Cellulose radical component in black pepper skin was highly stable. > Single signal near g=2.005 was the most stable in black pepper core.

  8. Identification of irradiated wheat by germination test, DNA comet assay and electron spin resonance

    Science.gov (United States)

    Barros, Adilson C.; Freund, Maria Teresa L.; Villavicencio, Ana Lúcia C. H.; Delincée, Henry; Arthur, Valter

    2002-03-01

    In several countries, there has been an increase in the use of radiation for food processing thus improving the quality and sanitary conditions, inhibiting pathogenic microorganisms, delaying the natural aging process and so extending product lifetime. The need to develop analytical methods to detect these irradiated products is also increasing. The goal of this research was to identify wheat irradiated using different radiation doses. Seeds were irradiated with a gamma 60Co source (Gammacell 220 GC) in the Centro de Energia Nuclear na Agricultura and the Instituto de Pesquisas Energéticas e Nucleares. Dose rate used were 1.6 and 5.8kGy/h. Applied doses were 0.0, 0.10, 0.25, 0.50, 0.75, 1.0, and 2.0kGy. After irradiation, seeds were analysed over a 6 month period. Three different detection methods were employed to determine how irradiation had modified the samples. Screening methods consisted of a germination test measuring the inhibition of shooting and rooting and analysis of DNA fragmentation. The method of electron spin resonance spectroscopy allowed a better dosimetric evaluation. These techniques make the identification of irradiated wheat with different doses possible.

  9. Direct Nanoscale Sensing of the Internal Electric Field in Operating Semiconductor Devices Using Single Electron Spins.

    Science.gov (United States)

    Iwasaki, Takayuki; Naruki, Wataru; Tahara, Kosuke; Makino, Toshiharu; Kato, Hiromitsu; Ogura, Masahiko; Takeuchi, Daisuke; Yamasaki, Satoshi; Hatano, Mutsuko

    2017-02-28

    The electric field inside semiconductor devices is a key physical parameter that determines the properties of the devices. However, techniques based on scanning probe microscopy are limited to sensing at the surface only. Here, we demonstrate the direct sensing of the internal electric field in diamond power devices using single nitrogen-vacancy (NV) centers. The NV center embedded inside the device acts as a nanoscale electric field sensor. We fabricated vertical diamond p-i-n diodes containing the single NV centers. By performing optically detected magnetic resonance measurements under reverse-biased conditions with an applied voltage of up to 150 V, we found a large splitting in the magnetic resonance frequencies. This indicated that the NV center senses the transverse electric field in the space-charge region formed in the i-layer. The experimentally obtained electric field values are in good agreement with those calculated by a device simulator. Furthermore, we demonstrate the sensing of the electric field in different directions by utilizing NV centers with different N-V axes. This direct and quantitative sensing method using an electron spin in a wide-band-gap material provides a way to monitor the electric field in operating semiconductor devices.

  10. Identification of. gamma. -irradiated spices by electron spin resonance (ESR) spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Uchiyama, Sadao; Kawamura, Yoko; Saito, Yukio (National Inst. of Hygienic Sciences, Tokyo (Japan))

    1990-12-01

    The electron spin resonance (ESR) spectrometry spectra of white (WP), black (BP) and red (Capsicum annuum L. var. frutescerns L., RP) peppers each had a principal signal with a g-value of 2.0043, and the intensities of the principal signals were increased not only by {gamma}-irradiation but also by heating. Irradiated RP also showed a minor signal -30G from the principal one, and the intensity of the minor signal increased linearly with increasing dose from 10 to 50 kGy. Since the minor signal was observed in RP irradiated at 10 kGy and stored for one year, but did not appear either after heating or after exposure to this signal is unique to {gamma}-irradiated RP and should therefore be useful for the identification of {gamma}-irradiated spices of Capsicum genus, such as paprika and chili pepper. The computer simulation of the ESR spectra suggested that the minor signal should be assigned to methyl radical and the principal signal mainly to a combination of phenoxyl and peroxyl radicals. Such minor signals were found in {gamma}-irradiated allspice and cinnamon among 10 kinds of other spices. (author).

  11. Pre-Town Meeting on spin physics at an Electron-Ion Collider

    Energy Technology Data Exchange (ETDEWEB)

    Aschenauer, Elke-Caroline; Bland, Leslie; Huang, Jin; Tarasov, Andrey [Brookhaven National Laboratory, Physics Department, Upton, NY (United States); Balitsky, Ian; Radyushkin, Anatoly [Old Dominion University, Physics Department, Norfolk, VA (United States); Jefferson Lab, Newport News, VA (United States); Brodsky, Stanley J. [Stanford University, SLAC National Accelerator Laboratory, Stanford, CA (United States); Burkardt, Matthias [New Mexico State University, Department of Physics, Las Cruces, NM (United States); Burkert, Volker; Chen, Jian-Ping; Kubarovsky, Valery; Melnitchouk, Wally; Qiu, Jian-Wei; Richards, David [Jefferson Lab, Newport News, VA (United States); Deshpande, Abhay [Brookhaven National Laboratory, RIKEN BNL Research Center, Upton, NY (United States); Stony Brook University, SUNY, Department of Physics and Astronomy, Stony Brook, NY (United States); Diehl, Markus [Deutsches Elektronen-Synchroton DESY, Hamburg (Germany); Gamberg, Leonard [Penn State University-Berks, Division of Science, Reading, PA (United States); Grosse Perdekamp, Matthias [University of Illinois at Urbana-Champaign, Urbana, IL (United States); Hyde, Charles [Old Dominion University, Physics Department, Norfolk, VA (United States); Ji, Xiangdong [Shanghai Jiao Tong University, INPAC, Department of Physics, and Shanghai Key Lab for Particle Physics and Cosmology, Shanghai (China); Peking University, Center for High-Energy Physics, Beijing (China); University of Maryland, Maryland Center for Fundamental Physics, College Park, MD (United States); Jiang, Xiaodong; Liu, Ming [Los Alamos National Laboratory, Los Alamos, NM (United States); Kang, Zhong-Bo [University of California, Department of Physics and Astronomy, Los Angeles, CA (United States); University of California, Mani L. Bhaumik Institute for Theoretical Physics, Los Angeles, CA (United States); Lajoie, John [Iowa State University, Ames, IA (United States); Liu, Keh-Fei [University of Kentucky, Dept. of Physics and Astronomy Center for Computational Sciences, Lexington, KY (United States); Liuti, Simonetta [University of Virginia, Department of Physics, Charlottesville, VA (United States); Mulders, Piet [VU University Amsterdam, Nikhef and Department of Physics and Astronomy, Amsterdam (Netherlands); Prokudin, Alexei [Jefferson Lab, Newport News, VA (United States); Penn State University-Berks, Division of Science, Reading, PA (United States); Sichtermann, Ernst; Yuan, Feng [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Stratmann, Marco; Vogelsang, Werner [Tuebingen University, Institute for Theoretical Physics, Tuebingen (Germany)

    2017-04-15

    A polarized ep/eA collider (Electron-Ion Collider, or EIC), with polarized proton and light-ion beams and unpolarized heavy-ion beams with a variable center-of-mass energy √(s) ∝ 20 to ∝ 100 GeV (upgradable to ∝ 150 GeV) and a luminosity up to ∝ 10{sup 34} cm{sup -2}s{sup -1}, would be uniquely suited to address several outstanding questions of Quantum Chromodynamics, and thereby lead to new qualitative and quantitative information on the microscopic structure of hadrons and nuclei. During this meeting at Jefferson Lab we addressed recent theoretical and experimental developments in the spin and the three-dimensional structure of the nucleon (sea quark and gluon spatial distributions, orbital motion, polarization, and their correlations). This mini-review contains a short update on progress in these areas since the EIC White paper (A. Accardi et al., Eur. Phys. J. A 52, 268 (2016)). (orig.)

  12. Electron spin resonance and thermoluminescence in powder form of clear fused quartz: effects of grinding

    CERN Document Server

    Ranjbar, A H; Randle, K

    1999-01-01

    Clear fused quartz (CFQ) tubes were powdered either manually by using a mortar and pestle (for coarse production) or mechanically, using a micronising mill (for fine production). A high and multisignal electron spin resonance (ESR) background was found in the fine powder even after annealing it at 900 deg. C for 20 min. In the case of the coarse powder, the signal (ESR background) varied inversely with particle size and was quite high for particle sizes lower than 38 mu m. In a subsidiary experiment, using fine SiO sub 2 powder (99.8% pure, with the particle size of approx 0.007 mu m), manufactured by using flame hydrolysis, only a weak background signal was found. The sup 6 sup 0 Co gamma-ray irradiated powders (approx 22 Gy) were subjected to ESR analysis or thermoluminescence (TL) readout. The ESR intensity of the coarse powder varied directly with particle size. Thus, the intensity for a particle size of 20-38 mu m was very low and almost the same as the unirradiated intensity. In TL readout the results w...

  13. Measurement of electron spin-lattice relaxation times in radical doped butanol samples at 1 K using the NEDOR method

    Energy Technology Data Exchange (ETDEWEB)

    Hess, C., E-mail: hess@ep1.rub.de [Ruhr-Universitaet Bochum, Experimentalphysik I, Universitaetsstr. 150, 44801 Bochum (Germany); Herick, J.; Berlin, A.; Meyer, W.; Reicherz, G. [Ruhr-Universitaet Bochum, Experimentalphysik I, Universitaetsstr. 150, 44801 Bochum (Germany)

    2012-12-01

    The electron spin-lattice relaxation time (T{sub 1e}) 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 T{sub 1e} 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 T{sub 1e} has been investigated. For radical concentrations as used in DNP (several 10{sup 19} spins/cm{sup 3}) the relaxation rate (T{sub 1e}{sup -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 {sup 6}LiD. These samples exhibited a linewidth behavior similar to that of the cylindrically shaped butanol samples.

  14. Effect of disorder on the magnetic and electronic structure of a prospective spin-gapless semiconductor MnCrVAl

    Directory of Open Access Journals (Sweden)

    P. Kharel

    2017-05-01

    Full Text Available Recent discovery of a new class of materials, spin-gapless semiconductors (SGS, has attracted considerable attention in the last few years, primarily due to potential applications in the emerging field of spin-based electronics (spintronics. Here, we investigate structural, electronic, and magnetic properties of one potential SGS compound, MnCrVAl, using various experimental and theoretical techniques. Our calculations show that this material exhibits ≈ 0.5 eV band gap for the majority-spin states, while for the minority-spin it is nearly gapless. The calculated magnetic moment for the completely ordered structure is 2.9 μB/f.u., which is different from our experimentally measured value of almost zero. This discrepancy is explained by the structural disorder. In particular, A2 type disorder, where Mn or Cr atoms exchange their positions with Al atoms, results in induced antiferromagnetic exchange coupling, which, at a certain level of disorder, effectively reduces the total magnetic moment to zero. This is consistent with our x-ray diffraction measurements which indicate the presence of A2 disorder in all of our samples. In addition, we also show that B2 disorder does not result in antiferromagnetic exchange coupling and therefore does not significantly reduce the total magnetic moment.

  15. METAL OXIDE DOPED ANTIBACTERIAL POLYMERIC COATED TEXTILE MATERIALS AND ASSESSEMENT OF ANTIBACTERIAL ACTIVITY WITH ELECTRON SPIN RESONANCE

    Directory of Open Access Journals (Sweden)

    GEDIK Gorkem

    2017-05-01

    Full Text Available Antibacterial activity of a food conveyor belt is an essential property in some cases. However, every antibacterial chemical is not suitable to contact with food materials. Many metal oxides are suitable option for this purpose. The aim of this study was to investigate antibacterial properties of zinc oxide doped PVC polymer coated with electron spin resonance technique. Therefore, optimum zinc oxide containing PVC paste was prepared and applied to textile surface. Coating construction was designed as double layered, first layer did not contain antibacterial agent, thin second layer contained zinc oxide at 10-35% concentration. Oxygen radicals released from zinc oxide containing polymeric coated surface were spin trapped with DMPO (dimethylpyrroline-N-oxide spin trap and measured with Electron Spin Resonance (ESR. Besides conveyor belt samples, oxygen radical release from zinc oxide surface was measured with ESR under UV light and dark conditions. Oxygen radical release was determined even at dark conditions. Antibacterial properties were tested with ISO 22196 standard using Listeria innocua species. Measured antibacterial properties were related with ESR results. Higher concentration of zinc oxide resulted in higher antibacterial efficiency. DCFH-DA flourometric assay was carried out to determine oxidative stress insidebacteria. It is tought that, this technique will lead to decrease on the labour and time needed for conventional antibacterial tests.

  16. A solid state paramagnetic maser device driven by electron spin injection

    NARCIS (Netherlands)

    Watts, S. M.; van Wees, B. J.

    2006-01-01

    In response to an external, microwave-frequency magnetic field, a paramagnetic medium will absorb energy from the field that drives the magnetization dynamics. Here we describe a new process by which an external spin-injection source, when combined with the microwave field spin pumping, can drive

  17. Ultrafast electron, lattice and spin dynamics on rare earth metal surfaces. Investigated with linear and nonlinear optical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Radu, I.E.

    2006-03-15

    This thesis presents the femtosecond laser-induced electron, lattice and spin dynamics on two representative rare-earth systems: The ferromagnetic gadolinium Gd(0001) and the paramagnetic yttrium Y(0001) metals. The employed investigation tools are the time-resolved linear reflectivity and second-harmonic generation, which provide complementary information about the bulk and surface/interface dynamics, respectively. The femtosecond laser excitation of the exchange-split surface state of Gd(0001) triggers simultaneously the coherent vibrational dynamics of the lattice and spin subsystems in the surface region at a frequency of 3 THz. The coherent optical phonon corresponds to the vibration of the topmost atomic layer against the underlying bulk along the normal direction to the surface. The coupling mechanism between phonons and magnons is attributed to the modulation of the exchange interaction J between neighbour atoms due to the coherent lattice vibration. This leads to an oscillatory motion of the magnetic moments having the same frequency as the lattice vibration. Thus these results reveal a new type of phonon-magnon coupling mediated by the modulation of the exchange interaction and not by the conventional spin-orbit interaction. Moreover, we show that coherent spin dynamics in the THz frequency domain is achievable, which is at least one order of magnitude faster than previously reported. The laser-induced (de)magnetization dynamics of the ferromagnetic Gd(0001) thin films have been studied. Upon photo-excitation, the nonlinear magneto-optics measurements performed in this work show a sudden drop in the spin polarization of the surface state by more than 50% in a <100 fs time interval. Under comparable experimental conditions, the time-resolved photoemission studies reveal a constant exchange splitting of the surface state. The ultrafast decrease of spin polarization can be explained by the quasi-elastic spin-flip scattering of the hot electrons among spin

  18. Crossover between the Hikami and spin-resolved band limits of weak anti-localization in two-dimensional electron gases

    Science.gov (United States)

    Araki, Yasufumi; Khalsa, Guru; MacDonald, Allan H.

    2014-03-01

    We investigate the quantum interference corrections to transport which lead to weak localization (WL) or weak anti-localization (WAL) for the case of spin-independent disorder scattering in two-dimensional electron gases with spin-orbit interactions of arbitrary strength. We formulate our theory in terms of microscopic linear response including multiple scattering by the disorder potential to derive the current-current response function when Rashba (or Dresselhaus) spin-orbit coupling is included in the electronic band structure. We analyze the crossover from the weak spin-orbit coupling limit in which spin-splitting of the bands is not resolved, to the strong spin-orbit coupling limit of clearly spin-split bands. In the weak and strong spin-orbit coupling limits we generally recover the well-known WL and WAL behavior first predicted by Hikami, Larkin and Nagaoka, although the degeneracy of spin triplet channels is lifted leading to a more complex crossover between the traditional WL and WAL limits. Our results can be summarized by a phase diagram in spin-orbit coupling strength and temperature (or the coherence length from inelastic scattering), with several regions separated by different crossover lines. Y. A. is supported by JSPS Postdoctoral Fellowship for Research Abroad (No.25-56).

  19. Perpendicular hot electron spin-valve effect in a new magnetic field sensor: The spin-valve transistor

    NARCIS (Netherlands)

    Monsma, D.J.; Lodder, J.C.; Popma, T.J.A.; Dieny, B.

    1995-01-01

    A new magnetic field sensor is presented, based on perpendicular hot electron transport in a giant magnetoresistance (Co/Cu)4 multilayer, which serves as a base region of an n-silicon metal-base transistor structure. A 215% change in collector current is found in 500 Oe (77 K), with typical

  20. Charge and spin control of ultrafast electron and hole dynamics in single CdSe/ZnSe quantum dots

    Science.gov (United States)

    Hinz, C.; Gumbsheimer, P.; Traum, C.; Holtkemper, M.; Bauer, B.; Haase, J.; Mahapatra, S.; Frey, A.; Brunner, K.; Reiter, D. E.; Kuhn, T.; Seletskiy, D. V.; Leitenstorfer, A.

    2018-01-01

    We study the dynamics of photoexcited electrons and holes in single negatively charged CdSe/ZnSe quantum dots with two-color femtosecond pump-probe spectroscopy. An initial characterization of the energy level structure is performed at low temperatures and magnetic fields of up to 5 T. Emission and absorption resonances are assigned to specific transitions between few-fermion states by a theoretical model based on a configuration interaction approach. To analyze the dynamics of individual charge carriers, we initialize the quantum system into excited trion states with defined energy and spin. Subsequently, the time-dependent occupation of the trion ground state is monitored by spectrally resolved differential transmission measurements. We observe subpicosecond dynamics for a hole excited to the D shell. The energy dependence of this D -to-S shell intraband transition is investigated in quantum dots of varying size. Excitation of an electron-hole pair in the respective p shells leads to the formation of singlet and triplet spin configurations. Relaxation of the p -shell singlet is observed to occur on a time scale of a few picoseconds. Pumping of p -shell triplet transitions opens up two pathways with distinctly different scattering times. These processes are shown to be governed by the mixing of singlet and triplet states due to exchange interactions enabling simultaneous electron and hole spin flips. To isolate the relaxation channels, we align the spin of the residual electron by a magnetic field and employ laser pulses of defined helicity. This step provides ultrafast preparation of a fully inverted trion ground state of the quantum dot with near unity probability, enabling deterministic addition of a single photon to the probe pulse. Therefore our experiments represent a significant step towards using single quantum emitters with well-controled inversion to manipulate the photon statistics of ultrafast light pulses.

  1. Evidence for Fast Electron Transfer between the High-Spin Haems in Cytochrome bd-I from Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Sergey A Siletsky

    Full Text Available Cytochrome bd-I is one of the three proton motive force-generating quinol oxidases in the O2-dependent respiratory chain of Escherichia coli. It contains one low-spin haem (b558 and the two high-spin haems (b595 and d as the redox-active cofactors. In order to examine the flash-induced intraprotein reverse electron transfer (the so-called ''electron backflow'', CO was photolyzed from the ferrous haem d in one-electron reduced (b5583+b5953+d2+-CO cytochrome bd-I, and the fully reduced (b5582+b5952+d2+-CO oxidase as a control. In contrast to the fully reduced cytochrome bd-I, the transient spectrum of one-electron reduced oxidase at a delay time of 1.5 μs is clearly different from that at a delay time of 200 ns. The difference between the two spectra can be modeled as the electron transfer from haem d to haem b595 in 3-4% of the cytochrome bd-I population. Thus, the interhaem electron backflow reaction induced by photodissociation of CO from haem d in one-electron reduced cytochrome bd-I comprises two kinetically different phases: the previously unnoticed fast electron transfer from haem d to haem b595 within 0.2-1.5 μs and the slower well-defined electron equilibration with τ ~16 μs. The major new finding of this work is the lack of electron transfer at 200 ns.

  2. π-electron S = ½ quantum spin-liquid state in an ionic polyaromatic hydrocarbon.

    Science.gov (United States)

    Takabayashi, Yasuhiro; Menelaou, Melita; Tamura, Hiroyuki; Takemori, Nayuta; Koretsune, Takashi; Štefančič, Aleš; Klupp, Gyöngyi; Buurma, A Johan C; Nomura, Yusuke; Arita, Ryotaro; Arčon, Denis; Rosseinsky, Matthew J; Prassides, Kosmas

    2017-07-01

    Molecular solids with cooperative electronic properties based purely on π electrons from carbon atoms offer a fertile ground in the search for exotic states of matter, including unconventional superconductivity and quantum magnetism. The field was ignited by reports of high-temperature superconductivity in materials obtained by the reaction of alkali metals with polyaromatic hydrocarbons, such as phenanthrene and picene, but the composition and structure of any compound in this family remained unknown. Here we isolate the binary caesium salts of phenanthrene, Cs(C14H10) and Cs2(C14H10), to show that they are multiorbital strongly correlated Mott insulators. Whereas Cs2(C14H10) is diamagnetic because of orbital polarization, Cs(C14H10) is a Heisenberg antiferromagnet with a gapped spin-liquid state that emerges from the coupled highly frustrated Δ-chain magnetic topology of the alternating-exchange spiral tubes of S = ½ (C14H10)•- radical anions. The absence of long-range magnetic order down to 1.8 K (T/J ≈ 0.02; J is the dominant exchange constant) renders the compound an excellent candidate for a spin-½ quantum-spin liquid (QSL) that arises purely from carbon π electrons.

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

    Science.gov (United States)

    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.

  4. π-electron S = ½ quantum spin-liquid state in an ionic polyaromatic hydrocarbon

    Science.gov (United States)

    Takabayashi, Yasuhiro; Menelaou, Melita; Tamura, Hiroyuki; Takemori, Nayuta; Koretsune, Takashi; Štefančič, Aleš; Klupp, Gyöngyi; Buurma, A. Johan C.; Nomura, Yusuke; Arita, Ryotaro; Arčon, Denis; Rosseinsky, Matthew J.; Prassides, Kosmas

    2017-07-01

    Molecular solids with cooperative electronic properties based purely on π electrons from carbon atoms offer a fertile ground in the search for exotic states of matter, including unconventional superconductivity and quantum magnetism. The field was ignited by reports of high-temperature superconductivity in materials obtained by the reaction of alkali metals with polyaromatic hydrocarbons, such as phenanthrene and picene, but the composition and structure of any compound in this family remained unknown. Here we isolate the binary caesium salts of phenanthrene, Cs(C14H10) and Cs2(C14H10), to show that they are multiorbital strongly correlated Mott insulators. Whereas Cs2(C14H10) is diamagnetic because of orbital polarization, Cs(C14H10) is a Heisenberg antiferromagnet with a gapped spin-liquid state that emerges from the coupled highly frustrated Δ-chain magnetic topology of the alternating-exchange spiral tubes of S = ½ (C14H10)•- radical anions. The absence of long-range magnetic order down to 1.8 K (T/J ≈ 0.02 J is the dominant exchange constant) renders the compound an excellent candidate for a spin-½ quantum-spin liquid (QSL) that arises purely from carbon π electrons.

  5. Electronic periscope for underground networks; Periscopio electronico para redes subterraneas

    Energy Technology Data Exchange (ETDEWEB)

    Araujo Filho, Edival Demetrio de [Companhia Energetica de Brasilia, DF (Brazil)]. E-mail: demetrio@ceb.com.br

    2000-07-01

    This paper aims at the perfection of the operational procedures adopted by the technician of Project and Underground Work Management of the Brasilia Energetic Company, Brazil, during the survey of the system duct bank characteristics (Organized formation of electro duct) . The execution of projects, reviews and budgets depend upon the verification of duct availability in the analysed network. The introduction of the device named Electronic Periscope proposed in this work aims at the efficiency of the field surveys.

  6. Traffic Rules in Electronic Financial Transactions (EFT Networks

    Directory of Open Access Journals (Sweden)

    Vedran Batoš

    2002-01-01

    Full Text Available This paper presents the traffic rules in the EFT (ElectronicFinancial Transactions networks, based on the implementationof the solution called Gold-Net developed and implementedby Euronet Worldwide Inc. Following the traffic rulesin EFT networks, out of its worldwide experience, Gold-Netevolved a comprehensive and expandable EFT network solutiondesigned to meet an institution's needs today and in the future.It is an ITM (Integrated Transaction Management solution,modular and expandable, and consists of a comprehensiveEFT software modules with ATM and POS driving capabilities.The combination of ATM management and the onlineconnection form the intercept processing control module. Asthe marketplace grows, this solution ensures that an ente1prisemay position itself for future growth and expanded service offerings.

  7. Molecular Imaging by Optically Detected Electron Spin Resonance of Nitrogen-Vacancies in Nanodiamonds

    Science.gov (United States)

    Hegyi, Alex; Yablonovitch, Eli

    2013-03-01

    Molecular imaging refers to a class of noninvasive biomedical imaging techniques with the sensitivity and specificity to image biochemical variations in-vivo. An ideal molecular imaging technique visualizes a biochemical target according to a range of criteria, including high spatial and temporal resolution, high contrast relative to non-targeted tissues, depth-independent penetration into tissue, lack of harm to the organism under study, and low cost. Because no existing molecular imaging modality is ideal for all purposes, new imaging approaches are needed. Here we demonstrate a novel molecular imaging approach, called nanodiamond imaging, that uses nanodiamonds containing nitrogen-vacancy (NV) color centers as an imaging agent, and image nanodiamond targets in pieces of chicken breast. Nanodiamonds can be tagged with biologically active molecules so they bind to specific receptors; their distribution can then be quantified in-vivo via optically-detected magnetic resonance of the NVs. In effect, we are demonstrating Optically-Detected Functional-Electron-Spin-Resonance-Imaging, OD-f-ESRI. By combining optical detection with magnetic resonance, nanodiamond imaging achieves high sensitivity and high spatial resolution. It is absent of the complications of ionizing radiation, and the cost should be similar to all-optical imaging. Because nanodiamond imaging is limited by the depth of optical penetration into tissue to depths of a few cm, nanodiamond imaging should open up new avenues of investigation for applications where high depth penetration is not required, such as in small-animal imaging, tumor margin imaging, sentinel lymph node mapping, and perhaps mammography.

  8. Role of linear and cubic terms for drift-induced Dresselhaus spin-orbit splitting in a two-dimensional electron gas

    Science.gov (United States)

    Studer, M.; Walser, M. P.; Baer, S.; Rusterholz, H.; Schön, S.; Schuh, D.; Wegscheider, W.; Ensslin, K.; Salis, G.

    2010-12-01

    The Dresselhaus spin-orbit interaction (SOI) of a series of two-dimensional electron gases hosted in GaAs/AlGaAs and InGaAs/GaAs (001) quantum wells (QWs) is measured by monitoring the precession frequency of the spins as a function of an in-plane electric field. The measured spin-orbit-induced spin splitting is linear in the drift velocity, even in the regime where the cubic Dresselhaus SOI is important. We relate the measured splitting to the Dresselhaus coupling parameter γ , the QW confinement, the Fermi wave number kF , and strain effects. From this, γ is determined quantitatively, including its sign.

  9. First-principles study of the honeycomb-lattice iridates Na2IrO3 in the presence of strong spin-orbit interaction and electron correlations.

    Science.gov (United States)

    Yamaji, Youhei; Nomura, Yusuke; Kurita, Moyuru; Arita, Ryotaro; Imada, Masatoshi

    2014-09-05

    An effective low-energy Hamiltonian of itinerant electrons for iridium oxide Na2IrO3 is derived by an ab initio downfolding scheme. The model is then reduced to an effective spin model on a honeycomb lattice by the strong coupling expansion. Here we show that the ab initio model contains spin-spin anisotropic exchange terms in addition to the extensively studied Kitaev and Heisenberg exchange interactions, and allows us to describe the experimentally observed zigzag magnetic order, interpreted as the state stabilized by the antiferromagnetic coupling of the ferromagnetic chains. We clarify possible routes to realize quantum spin liquids from existing Na2IrO3.

  10. A correction to the Immirzi parameter of SU(2 spin networks

    Directory of Open Access Journals (Sweden)

    M. Sadiq

    2015-02-01

    Full Text Available The elegant predictions of loop quantum gravity are obscured by the free Immirzi parameter (γ. Dreyer (2003, considering the asymptotic quasinormal modes spectrum of a black hole, proposed that γ may be fixed by letting the j=1 transitions of spin networks as the dominant processes contributing to the black hole area, as opposed to the expected j=1/2 transitions. This suggested that the gauge group of the theory might be SO(3 rather than SU(2. Corichi (2003, maintaining SU(2 as the underlying gauge group, and invoking the principle of local fermion-number conservation, reported the same value of γ for j=1 processes as obtained by Dreyer. In this note, preserving the SU(2 structure of the theory, and considering j=1 transitions as the dominant processes, we point out that the value of γ is in fact twice the value reported by these authors. We arrive at this result by assuming the asymptotic quasinormal modes themselves as dynamical systems obeying SU(2 symmetry.

  11. Ferromagnetic resonance characterization of nano-FePt by electron spin resonance

    CSIR Research Space (South Africa)

    Nkosi, SS

    2013-01-01

    Full Text Available . We attribute the high field absorption to ferromagnetic resonance (FMR). Upon increasing iron content in FePt system, no detectable spin waves modes were identified already at room temperature. This signifies a homogeneous distribution...

  12. Electrons, holes, and spin in Nd2-xCexCuO4-delta

    NARCIS (Netherlands)

    Tjernberg, O; Tjeng, LH; Ghiringhelli, G; Nugroho, AA; Menovsky, AA; Brookes, NB

    2003-01-01

    The spin nature of the states at the top of the valence band in Nd2CuO4 and Nd1.85Ce0.15CuO4-delta has been investigated with spin polarized resonant photoemission. A clear Zhang-Rice singlet state is observed at the top of the valence band in the undoped compound showing that the parent compound of

  13. Electronic transport through EuO spin-filter tunnel junctions

    KAUST Repository

    Jutong, Nuttachai

    2012-11-12

    Epitaxial spin-filter tunnel junctions based on the ferromagnetic semiconductor europium monoxide (EuO) are investigated by means of density functional theory. In particular, we focus on the spin transport properties of Cu(100)/EuO(100)/Cu(100) junctions. The dependence of the transmission coefficient and the current-voltage curves on the interface spacing and EuO thickness is explained in terms of the EuO density of states and the complex band structure. Furthermore, we also discuss the relation between the spin transport properties and the Cu-EuO interface geometry. The level alignment of the junction is sensitively affected by the interface spacing, since this determines the charge transfer between EuO and the Cu electrodes. Our calculations indicate that EuO epitaxially grown on Cu can act as a perfect spin filter, with a spin polarization of the current close to 100%, and with both the Eu-5d conduction-band and the Eu-4f valence-band states contributing to the coherent transport. For epitaxial EuO on Cu, a symmetry filtering is observed, with the Δ1 states dominating the transmission. This leads to a transport gap larger than the fundamental EuO band gap. Importantly, the high spin polarization of the current is preserved up to large bias voltages.

  14. Magnetization plateau as a result of the uniform and gradual electron doping in a coupled spin-electron double-tetrahedral chain

    Science.gov (United States)

    Gálisová, Lucia

    2017-11-01

    The double-tetrahedral chain in a longitudinal magnetic field, whose nodal lattice sites occupied by the localized Ising spins regularly alternate with triangular plaquettes with the dynamics described by the Hubbard model, is rigorously investigated. It is demonstrated that the uniform change of electron concentration controlled by the chemical potential in a combination with the competition between model parameters and the external magnetic field leads to the formation of one chiral and seven nonchiral phases at the absolute zero temperature. Rational plateaux at one-third and one-half of the saturation magnetization can also be identified in the low-temperature magnetization curves. On the other hand, the gradual electron doping results in 11 different ground-state regions that distinguish from each other by the evolution of the electron distribution during this process. Several doping-dependent magnetization plateaux are observed in the magnetization process as a result of the continuous change of electron content in the model.

  15. Studi Spektroskopi Electron Spin Resonance (Esr Lapisan Tipis Amorf Silikon Karbon (A-Sic:H Hasil Deposisi Metode Dc Sputtering

    Directory of Open Access Journals (Sweden)

    Rosari Saleh

    2002-04-01

    Full Text Available The dangling bond defect density in sputtered amorphous silicon carbon alloys have been studied by electron spin resonance (ESR. The results show that the spin density decreased slightly with increasing methane fl ow rate (CH4. The infl uence of carbon and hydrogen incorporation on g-value revealed that for CH4 fl ow rate up to 8 sccm, the ESR signal is dominated by defects characteristic of a-Si:H fi lms and for CH4 fl ow rate higher than 8 sccm the g-value decreased towards those usually found in a-C:H fi lms. Infrared (IR results suggest that as CH4 fl ow rate increases more carbon and hydrogen is incorporated into the fi lms to form Si-H, Si-C and C-H bonds. A direct relation between the IR results and the defect density and g-value is observed.

  16. Ultrafast Relaxation Dynamics of Photoexcited Heme Model Compounds: Observation of Multiple Electronic Spin States and Vibrational Cooling.

    Science.gov (United States)

    Govind, Chinju; Karunakaran, Venugopal

    2017-04-13

    Hemin is a unique model compound of heme proteins carrying out variable biological functions. Here, the excited state relaxation dynamics of heme model compounds in the ferric form are systematically investigated by changing the axial ligand (Cl/Br), the peripheral substituent (vinyl/ethyl-meso), and the solvent (methanol/DMSO) using femtosecond pump-probe spectroscopy upon excitation at 380 nm. The relaxation time constants of these model compounds are obtained by global analysis. Excited state deactivation pathway of the model compounds comprising the decay of the porphyrin excited state (S*) to ligand to metal charge transfer state (LMCT, τ 1 ), back electron transfer from metal to ligand (MLCT, τ 2 ), and relaxation to the ground state through different electronic spin states of iron (τ 3 and τ 4 ) are proposed along with the vibrational cooling processes. This is based on the excited state absorption spectral evolution, similarities between the transient absorption spectra of the ferric form and steady state absorption spectra of the low-spin ferrous form, and the data analysis. The observation of an increase of all the relaxation time constants in DMSO compared to the methanol reflects the stabilization of intermediate states involved in the electronic relaxation. The transient absorption spectra of met-myoglobin are also measured for comparison. Thus, the transient absorption spectra of these model compounds reveal the involvement of multiple iron spin states in the electronic relaxation dynamics, which could be an alternative pathway to the ground state beside the vibrational cooling processes and associated with the inherent features of the heme b type.

  17. Triangular CdS nanostructure: effect of Mn doping on photoluminescence, electron spin resonance, and magneto-optical properties

    Science.gov (United States)

    Jadhav, Punam A.; Panmand, Rajendra P.; Patil, Deepak R.; Fouad, H.; Gosavi, Suresh W.; Kale, Bharat B.

    2017-06-01

    In this paper, we report synthesis and study of magneto-optic Faraday effect for dilute magnetic semiconductor nanostructure. The colloidal CdS nanocrystals were prepared via hot injection method and successfully doped with Mn2+ cations. The synthesized nanoparticles were characterized by using UV-Vis spectroscopy, X-ray diffraction, photoluminescence spectroscopy, transmission electron microscopy, and electron spin resonance spectroscopy. Systematic studies on effect of Mn2+ doping on photoluminescence, electron spin resonance, and magneto-optical properties are carried out. UV-Vis spectral analysis confirms blue shift in bandgap of CdS nanoparticles due to quantum confinement effect. The X-ray diffraction study confirms hexagonal wurtzite phase formation of CdS nanoparticles without any impurity phases. TEM analysis confirms uniform particle size, having particle size distribution around 5 nm. As-synthesized undoped CdS shows triangular-shaped nanocrystals with hexagonal structure; however, triangular shape of CdS nanoparticles is not conserved after Mn2+ doping. The photoluminescence characteristic spectra of Mn2+-doped CdS nanocrystals showed emission band at 660 nm and its intensity was found to increase with increasing Mn2+ concentration. Electron spin resonance signal, with six-line hyperfine structure splitting, confirmed doping of Mn2+ ions in CdS lattice. Magneto-optic measurements showed linear variation of Faraday rotation with respect to applied magnetic field, indicating paramagnetic behavior of Mn-doped CdS. The highest Verdet constant 24.81 deg/T cm was observed for 2% Mn-doped CdS nanocrystals, which further decreases with increasing Mn2+ concentration.

  18. Magnetic pseudo-fields in a rotating electron-nuclear spin system

    Science.gov (United States)

    Wood, A. A.; Lilette, E.; Fein, Y. Y.; Perunicic, V. S.; Hollenberg, L. C. L.; Scholten, R. E.; Martin, A. M.

    2017-11-01

    Analogous to the precession of a Foucault pendulum observed on the rotating Earth, a precessing spin observed in a rotating frame of reference appears frequency-shifted. This can be understood as arising from a magnetic pseudo-field in the rotating frame that nevertheless has physically significant consequences, such as the Barnett effect. To detect these pseudo-fields, a rotating-frame sensor is required. Here we use quantum sensors, nitrogen-vacancy (NV) centres, in a rapidly rotating diamond to detect pseudo-fields in the rotating frame. Whereas conventional magnetic fields induce precession at a rate proportional to the gyromagnetic ratio, rotation shifts the precession of all spins equally, and thus primarily affect 13C nuclear spins in the sample. We are thus able to explore these effects via quantum sensing in a rapidly rotating frame, and define a new approach to quantum control using rotationally induced nuclear spin-selective magnetic fields. This work provides an integral step towards realizing precision rotation sensing and quantum spin gyroscopes.

  19. Electron percolation in realistic models of carbon nanotube networks

    Science.gov (United States)

    Simoneau, Louis-Philippe; Villeneuve, Jérémie; Rochefort, Alain

    2015-09-01

    The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.

  20. Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve

    Directory of Open Access Journals (Sweden)

    Ma Jing-Min

    2011-01-01

    Full Text Available Abstract Spin-dependent transport through a quantum-dot (QD ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively. PACS numbers:

  1. Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru [Faculty of Physics, Lomonosov Moscow State University, Moscow (Russian Federation)

    2015-06-15

    We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.

  2. Spin transverse force on spin current in an electric field.

    Science.gov (United States)

    Shen, Shun-Qing

    2005-10-28

    As a relativistic quantum mechanical effect, it is shown that the electron field exerts a transverse force on an electron spin 1/2 only if the electron is moving. The spin force, analogue to the Lorentz for an electron charge in a magnetic field, is perpendicular to the electric field and the spin current whose spin polarization is projected along the electric field. This spin-dependent force can be used to understand the Zitterbewegung of the electron wave packet with spin-orbit coupling and is relevant to the generation of the charge Hall effect driven by the spin current in semiconductors.

  3. Electron spin resonance investigaton of semiconductor materials for application in thin-film silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Lihong

    2012-07-01

    In the present work, hydrogenated silicon and its alloys silicon carbide and silicon oxide have been investigated using electron spin resonance (ESR). The microstructure of these materials ranges from highly crystalline to amorphous. The correlation between the paramagnetic defects, microstructure, optical and electrical properties has been discussed. Correspondingly, these properties were characterized by the spin density (N{sub S}), g-value and the lineshape of ESR spectra, Infrared (I{sup IR}{sub C}) and/or Raman crystallinity (I{sup RS}{sub C}) as well as optical absorption and electrical dark conductivity ({sigma}{sub D}). 1. As the light absorber, Si layers essentially should have low defect density and good stability against light exposure. The spin density (N{sub S}) measured by ESR is often used as a measure for the paramagnetic defect density (N{sub D}) in the material. However, ESR sample preparation procedures can potentially cause discrepancy between N{sub S} and N{sub D}. Using Mo-foil, Al-foil and ZnO:Al-covered glass as sacrificial substrates, {mu}c-Si:H and a-Si:H films were deposited by plasma-enhanced chemical vapor deposition (PECVD), and ESR powder samples have been prepared with corresponding procedures. Possible preparation-related metastability and instability effects have been investigated in terms of substrate dependence, HCl-etching and atmosphere exposure. A sequence of 'preparation - annealing - air-exposure - annealing' has been designed to investigate the metastability and instability effects. N{sub S} after post-preparation air exposure is higher than in the annealed states, especially for the highly crystalline {mu}c-Si:H material the discrepancy reached one order of magnitude. Low temperature ESR measurements at 40 K indicated that atmospheric exposure leads to a redistribution of the defect states which in turn influence the evaluated N{sub S}. In annealed conditions the samples tend to have lower N{sub S} presumably due

  4. THE USE OF ELECTRONIC SOCIAL NETWORKS IN SOCIAL AND EDUCATIONAL WORK WITH PUPILS

    OpenAIRE

    Natalia V. Oleksiuk; Lesya V. Lebedenko

    2015-01-01

    Electronic social networks are powerful means of communication for million registered users, because some social groups are gaining considerable popularity among pupils of secondary schools. The author believes that the use of electronic social networks is actual not just for training purposes, but also to implement the social and educational work in the school environment. In publication there have been reviewed electronic social networks, including business networks, comparison of their pro...

  5. An electron spin polarization study of the interaction of photoexcited triplet molecules with mono- and polynitroxyl stable free radicals

    Energy Technology Data Exchange (ETDEWEB)

    Turro, N.J.; Khudyakov, I.V.; Bossmann, S.H. (Columbia Univ., New York, NY (United States)); Dwyer, D.W. (State Univ. of New York, Brockport (United States))

    1993-02-11

    Time-resolved electron spin resonance (TR ESR) has been used to investigate the chemically induced dynamic electron polarization (CIDEP) generated by the interaction of stable free radicals with the triplet states of benzophenone, benzil, and 2-acetylnaphthalene. The stable radicals were mono-, di-, tri-, and tetranitroxyl free radicals possessing the 2,2,6,6-tetramethylpiperidine-N-oxyl moiety. All of the stable radical systems investigated were found to be emissively polarized by interaction with the triplet states, and the phase of polarization was independent of the sign of zero-field splitting (D) of the interacting triple molecule. Possible and likely mechanisms of polarization transfer (creation) resulting from the interaction of photoexcited triplet molecules with nitroxyls in the strong electron exchange are discussed. The emissive CIDEP of nitroxyls observed in the interactions with triplet benzil, which has D > 0, provides strong support for the operation of the radical-triplet pair mechanism. Within the time scale of TR ESR experiments ([approximately]10[sup [minus]7]--10[sup [minus]6] s) no significant variation in the shape of the CIDEP spectra of the nitroxyls was observed, either in viscous media or in micelles. It is concluded that intramolecular spin exchange (or conformational change) of polynitroyls occurs much faster than the time resolution of the experiment. 24 refs., 6 figs., 1 tab.

  6. Strong evidence for d-electron spin transport at room temperature at a LaAlO3/SrTiO3 interface

    Science.gov (United States)

    Ohshima, Ryo; Ando, Yuichiro; Matsuzaki, Kosuke; Susaki, Tomofumi; Weiler, Mathias; Klingler, Stefan; Huebl, Hans; Shikoh, Eiji; Shinjo, Teruya; Goennenwein, Sebastian T. B.; Shiraishi, Masashi

    2017-06-01

    A d-orbital electron has an anisotropic electron orbital and is a source of magnetism. The realization of a two-dimensional electron gas (2DEG) embedded at a LaAlO3/SrTiO3 interface surprised researchers in materials and physical sciences because the 2DEG consists of 3d-electrons of Ti with extraordinarily large carrier mobility, even in the insulating oxide heterostructure. To date, a wide variety of physical phenomena, such as ferromagnetism and the quantum Hall effect, have been discovered in this 2DEG system, demonstrating the ability of d-electron 2DEG systems to provide a material platform for the study of interesting physics. However, because of both ferromagnetism and the Rashba field, long-range spin transport and the exploitation of spintronics functions have been believed difficult to implement in d-electron 2DEG systems. Here, we report the experimental demonstration of room-temperature spin transport in a d-electron-based 2DEG at a LaAlO3/SrTiO3 interface, where the spin relaxation length is about 300 nm. Our finding, which counters the conventional understandings of d-electron 2DEGs, highlights the spin-functionality of conductive oxide systems and opens the field of d-electron spintronics.

  7. The spin-ladder and spin-chain system (La,Y,Sr,Ca){sub 14}Cu{sub 24}O{sub 41}: Electronic phases, charge and spin dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Vuletic, T. [Institut za fiziku, P.O. Box 304, HR-10001 Zagreb (Croatia); Korin-Hamzic, B. [Institut za fiziku, P.O. Box 304, HR-10001 Zagreb (Croatia); Ivek, T. [Institut za fiziku, P.O. Box 304, HR-10001 Zagreb (Croatia); Tomic, S. [Institut za fiziku, P.O. Box 304, HR-10001 Zagreb (Croatia)]. E-mail: stomic@ifs.hr; Gorshunov, B. [Physikalisches Institut, Universitaet Stuttgart, D-70550 Stuttgart (Germany); Dressel, M. [Physikalisches Institut, Universitaet Stuttgart, D-70550 Stuttgart (Germany)]. E-mail: dressel@pi1.physik.uni-stuttgart.de; Akimitsu, J. [Department of Physics, Aoyama-Gakuin University, Kanagawa (Japan)

    2006-05-15

    The quasi-one-dimensional cuprates (La,Y,Sr,Ca){sub 14}Cu{sub 24}O{sub 41}, consisting of spin-chains and spin-ladders, have attracted much attention, mainly because they represent the first superconducting copper oxide with a non-square lattice. Theoretically, in isolated hole-doped two-leg ladders, superconductivity is tightly associated with the spin gap, although in competition with a charge-density wave (CDW). Indeed, both the gapped spin-liquid and CDW states have been established in the doped spin-ladders of Sr{sub 14-x}Ca{sub x}Cu{sub 24}O{sub 41}, however the relevance of these objects to electronic properties and superconductivity is still subject of intensive discussion. In this treatise, an appreciable set of experimental data is reviewed, which has been acquired in recent years, indicating a variety of magnetic and charge arrangements found in the chains and ladders of underdoped (La,Y){sub y}(S,Ca){sub 14-y}Cu{sub 24}O{sub 41} and fully doped Sr{sub 14-x}Ca{sub x}Cu{sub 24}O{sub 41}. Based on these data, phase diagrams are constructed for the chains of underdoped systems (as a function of La, Y-substitution), as well as for the chains and ladders of the fully doped ones (as a function of Ca-substitution). We try to reconcile contradictory results concerning the charge dynamics in the ladders, like the hole redistribution between ladders and chains, collective modes and pseudogap, field-dependent transport and the temperature scales and doping levels at which the two-dimensional CDW develops in the ladder planes. The remaining open issues are clearly extracted. In the discussion the experimental results are contrasted with theoretical predictions, which allows us to conclude with two important remarks concerning the nature of the competing CDW and superconducting ground states. A density wave in ladders, characterized by a sinusoidal charge modulation, belongs to the class of broken symmetry patterns, which is theoretically predicted for strongly

  8. Real-time In Situ Electron Spin Resonance Measurements on Fungal Spores of Penicillium digitatum during Exposure of Oxygen Plasmas

    CERN Document Server

    Ishikawa, Kenji; Tanaka, Hiromasa; Tamiya, Kazuhiro; Hashizume, Hiroshi; Ohta, Takayuki; Ito, Masafumi; Iseki, Sachiko; Takeda, Keigo; Kondo, Hiroki; Sekine, Makoto; Hori, Masaru

    2012-01-01

    We report the kinetic analysis of free radicals on fungal spores of Penicillium digitatum interacted with atomic oxygen generated plasma electric discharge using real time in situ electron spin resonance (ESR) measurements. We have obtained information that the ESR signal from the spores was observed and preliminarily assignable to semiquinone radical with a g-value of around 2.004 and a line width of approximately 5G. The decay of the signal is possibly linked to the inactivation of the fungal spore. The real-time in situ ESR has proven to be a useful method to elucidate plasma-induced surface reactions on biological specimens.

  9. Electron spin resonance investigation of Mn^{2+} ions and their dynamics in manganese doped SrTiO_3

    OpenAIRE

    Laguta, V. V.; Kondakova, I. V.; Bykov, I. P.; Glinchuk, M. D.; Vilarinho, P M; Tkach, A; L. Jastrabik

    2007-01-01

    Using electron spin resonance, lattice position and dynamic properties of Mn2+ ions were studied in 0.5 and 2 % manganese doped SrTiO3 ceramics prepared by conventional mixed oxide method. The measurements showed that Mn2+ ions substitute preferably up to 97 % for Sr if the ceramics is prepared with a deficit of Sr ions. Motional narrowing of the Mn2+ ESR spectrum was observed when temperature increases from 120 K to 240-250 K that was explained as a manifestation of off-center position of th...

  10. Multi-frequency force-detected electron spin resonance in the millimeter-wave region up to 150 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Ohmichi, E., E-mail: ohmichi@harbor.kobe-u.ac.jp; Tokuda, Y.; Tabuse, R.; Tsubokura, D.; Okamoto, T. [Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan); Ohta, H. [Molecular Photoscience Research Center, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe 657-8501 (Japan)

    2016-07-15

    In this article, a novel technique is developed for multi-frequency force-detected electron spin resonance (ESR) in the millimeter-wave region. We constructed a compact ESR probehead, in which the cantilever bending is sensitively detected by a fiber-optic Fabry-Perot interferometer. With this setup, ESR absorption of diphenyl-picrylhydrazyl radical (<1 μg) was clearly observed at multiple frequencies of up to 150 GHz. We also observed the hyperfine splitting of low-concentration Mn{sup 2+} impurities(∼0.2%) in MgO.

  11. ELECTRONIC-STRUCTURE AND SPIN-STATE TRANSITION OF LACOO3

    NARCIS (Netherlands)

    ABBATE, M; FUGGLE, JC; FUJIMORI, A; TJENG, LH; CHEN, CT; POTZE, R; SAWATZKY, GA; EISAKI, H; UCHIDA, S

    1993-01-01

    We present soft-x-ray absorption spectra (XAS) of LaCoO3 taken at different temperatures (80-630 K). The shape of the multiplets in the Co 2p XAS spectra conveys information on the symmetry and spin of the ground state. The 0 Is XAS spectra are related to unoccupied metal bands through covalent

  12. Strong electron-hole symmetric Rashba spin-orbit coupling in graphene/monolayer transition metal dichalcogenide heterostructures

    Science.gov (United States)

    Yang, Bowen; Lohmann, Mark; Barroso, David; Liao, Ingrid; Lin, Zhisheng; Liu, Yawen; Bartels, Ludwig; Watanabe, Kenji; Taniguchi, Takashi; Shi, Jing

    2017-07-01

    Despite its extremely weak intrinsic spin-orbit coupling (SOC), graphene has been shown to acquire considerable SOC by proximity coupling with exfoliated transition metal dichalcogenides (TMDs). Here we demonstrate strong induced Rashba SOC in graphene that is proximity coupled to a monolayer TMD film, Mo S2 or WS e2 , grown by chemical-vapor deposition with drastically different Fermi level positions. Graphene/TMD heterostructures are fabricated with a pickup-transfer technique utilizing hexagonal boron nitride, which serves as a flat template to promote intimate contact and therefore a strong interfacial interaction between TMD and graphene as evidenced by quenching of the TMD photoluminescence. We observe strong induced graphene SOC that manifests itself in a pronounced weak-antilocalization (WAL) effect in the graphene magnetoconductance. The spin-relaxation rate extracted from the WAL analysis varies linearly with the momentum scattering time and is independent of the carrier type. This indicates a dominantly Dyakonov-Perel spin-relaxation mechanism caused by the induced Rashba SOC. Our analysis yields a Rashba SOC energy of ˜1.5 meV in graphene/WS e2 and ˜0.9 meV in graphene/Mo S2 . The nearly electron-hole symmetric nature of the induced Rashba SOC provides a clue to possible underlying SOC mechanisms.

  13. Electronic properties of precious-metal coated W tips in STM: Role of spin-orbit coupling

    Science.gov (United States)

    Yamashita, T.; Akiyama, T.; Nakamura, K.; Ito, T.; Rhim, S. H.; Freeman, A. J.

    2013-03-01

    Scanning tunneling microscopy (STM) has proved a versatile tool invigorating many physics at an atomic scale, where chemical identity and shape of the probe tip greatly affect resolution and sensitivity. There have been many efforts to functionalize STM tips: coating W tips with organic molecules and 3d transition metals, which facilitate the selective imaging with enhanced tunneling current. In this work, we model W(110) tips coated by precious metals such as Au, Ag, and Pt, in which large spin-orbit coupling significantly influences the electronic structure of the STM probe. Furthermore, we argue that this spin-orbit coupling can be used as a spin detecting STM probe without additional bias switching. The stability of the W(110) apex atom for each metal coating is also discussed. Supported at N. U. by the DOE (DE-FG02-05ER45372), and at Mie U. by the Young Researcher Overseas Visits Program for Vitalizing Brain Circulation (R2214) from the Japan Society for the Promotion of Science.

  14. Magnetic Field Effects in a Correlated Electron System with Spin-State Degree of Freedom — Implications for an Excitonic Insulator —

    Science.gov (United States)

    Tatsuno, Taro; Mizoguchi, Eriko; Nasu, Joji; Naka, Makoto; Ishihara, Sumio

    2016-08-01

    Magnetic field (H) effects on a correlated electron system with a spin-state degree of freedom are examined. The effective Hamiltonian derived from the two-orbital Hubbard model is analyzed by the mean-field approximation. Applying a magnetic field to the low-spin (LS) phase induces an excitonic insulating phase as well as a spin-state ordered phase where the LS and high-spin (HS) states are ordered alternately. When H is applied to the HS phase, a reentrant transition for the HS phase appears. A rich variety of the phase diagrams is attributed to the spin-state degree of freedom and their combinations in the wave function as well as in the real-space configuration. The present results provide a possible interpretation for the recent experimental observation of LaCoO3 under a strong magnetic field.

  15. Electron spin dynamics of Ce3 + ions in YAG crystals studied by pulse-EPR and pump-probe Faraday rotation

    Science.gov (United States)

    Azamat, D. V.; Belykh, V. V.; Yakovlev, D. R.; Fobbe, F.; Feng, D. H.; Evers, E.; Jastrabik, L.; Dejneka, A.; Bayer, M.

    2017-08-01

    The spin relaxation dynamics of Ce3 + ions in heavily cerium-doped YAG crystals is studied using pulse-electron paramagnetic resonance and time-resolved pump-probe Faraday rotation. Both techniques address the 4 f ground state, while pump-probe Faraday rotation also provides access to the excited 5 d state. We measure a millisecond spin-lattice relaxation time T1, a microsecond spin coherence time T2, and a ˜10 ns inhomogeneous spin dephasing time T2* for the Ce3 + ground state at low temperatures. The spin-lattice relaxation of Ce3 + ions is due to modified Raman processes involving the optical phonon mode at ˜125 cm-1 . The relaxation at higher temperature goes through a first excited level of the 5/2 2F term at about ℏ ω ≈228 cm-1 . Effects provided by the hyperfine interaction of the Ce3 + with the 27Al nuclei are observed.

  16. Ground-state phase diagram, fermionic entanglement and kinetically-induced frustration in a hybrid ladder with localized spins and mobile electrons

    Science.gov (United States)

    Carvalho, R. C. P.; Pereira, M. S. S.; de Oliveira, I. N.; Strečka, J.; Lyra, M. L.

    2017-09-01

    We introduce an exactly solvable hybrid spin-ladder model containing localized nodal Ising spins and interstitial mobile electrons, which are allowed to perform a quantum-mechanical hopping between the ladder’s legs. The quantum-mechanical hopping process induces an antiferromagnetic coupling between the ladder’s legs that competes with a direct exchange coupling of the nodal spins. The model is exactly mapped onto the Ising spin ladder with temperature-dependent two- and four-spin interactions, which is subsequently solved using the transfer-matrix technique. We report the ground-state phase diagram and compute the fermionic concurrence to characterize the quantum entanglement between the pair of interstitial mobile electrons. We further provide a detailed analysis of the local spin ordering including the pair and four-spin correlation functions around an elementary plaquette, as well as, the local ordering diagrams. It is shown that a complex sequence of distinct local orderings and frustrated correlations takes place when the model parameters drive the investigated system close to a zero-temperature triple coexistence point.

  17. Implementation of Dynamically Corrected Gates on a Single Electron Spin in Diamond

    Science.gov (United States)

    Rong, Xing; Geng, Jianpei; Wang, Zixiang; Zhang, Qi; Ju, Chenyong; Shi, Fazhan; Duan, Chang-Kui; Du, Jiangfeng

    2014-02-01

    Precise control of an open quantum system is critical to quantum information processing but is challenging due to inevitable interactions between the quantum system and the environment. We demonstrated experimentally a type of dynamically corrected gates using only bounded-strength pulses on the nitrogen-vacancy centers in diamond. The infidelity of quantum gates caused by a nuclear-spin bath is reduced from being the second order to the sixth order of the noise-to-control-field ratio, which offers greater efficiency in reducing infidelity. The quantum gates have been protected to the limit essentially set by the spin-lattice relaxation time T1. Our work marks an important step towards fault-tolerant quantum computation in realistic systems.

  18. Anomalies of the electronic structure and physical properties of rare-earth cobaltites near spin crossover

    Science.gov (United States)

    Dudnikov, V. A.; Orlov, Yu. S.; Kazak, N. V.; Platunov, M. S.; Ovchinnikov, S. G.

    2016-10-01

    The features of the characteristics of LnCoO3 cobaltites, where Ln is a rare-earth element, are discussed. Both experiment and theory demonstrate that their essentials are related to the low-spin ground state of cobalt ions. The thermally induced occupation of the excited high-spin state gives rise to peaks in the magnetic susceptibility, specific heat, and thermal expansion, as well as to a smooth insulator-metal transition. The analysis is based both on the data from the current literature concerning LaCoO3 and in many aspects on our own studies of GdCoO3 and La1- x Gd x CoO3 solid solutions.

  19. Encoding neural and synaptic functionalities in electron spin: A pathway to efficient neuromorphic computing

    Science.gov (United States)

    Sengupta, Abhronil; Roy, Kaushik

    2017-12-01

    Present day computers expend orders of magnitude more computational resources to perform various cognitive and perception related tasks that humans routinely perform every day. This has recently resulted in a seismic shift in the field of computation where research efforts are being directed to develop a neurocomputer that attempts to mimic the human brain by nanoelectronic components and thereby harness its efficiency in recognition problems. Bridging the gap between neuroscience and nanoelectronics, this paper attempts to provide a review of the recent developments in the field of spintronic device based neuromorphic computing. Description of various spin-transfer torque mechanisms that can be potentially utilized for realizing device structures mimicking neural and synaptic functionalities is provided. A cross-layer perspective extending from the device to the circuit and system level is presented to envision the design of an All-Spin neuromorphic processor enabled with on-chip learning functionalities. Device-circuit-algorithm co-simulation framework calibrated to experimental results suggest that such All-Spin neuromorphic systems can potentially achieve almost two orders of magnitude energy improvement in comparison to state-of-the-art CMOS implementations.

  20. Second-order Dirac equation of graphene electrons in an electromagnetic field and their novel spin

    OpenAIRE

    Luo, Ji

    2013-01-01

    The second-order Dirac equation (DE) and its velocity operator of graphene electrons in an electromagnetic field are obtained according to tight-binding k.p method. With extra terms included, they demonstrate the motion of graphene electrons more completely through a more complete Ehrenfest theorem and present finer properties of graphene electrons. Eigen-energy given by the second-order DE for field-free graphene indicates that extra terms may affect the trembling motion of graphene electron...

  1. Systematic construction of spin liquids on the square lattice from tensor networks with SU(2) symmetry

    CERN Document Server

    Mambrini, Matthieu; Poilblanc, Didier

    2016-01-01

    We elaborate a simple classification scheme of all rank-5 SU(2)-spin rotational symmetric tensors according to i) the on-site physical spin-$S$, (ii) the local Hilbert space $V^{\\otimes 4}$ of the four virtual (composite) spins attached to each site and (iii) the irreducible representations of the $C_{4v}$ point group of the square lattice. We apply our scheme to draw a complete list of all SU(2)-symmetric translationally and rotationally-invariant Projected Entangled Pair States (PEPS) with bond dimension $D\\leqslant 6$. All known SU(2)-symmetric PEPS on the square lattice are recovered and simple generalizations are provided in some cases. More generally, to each of our symmetry class can be associated a $({\\cal D}-1)$-dimensional manifold of spin liquids (potentially) preserving lattice symmetries and defined in terms of ${\\cal D}$ independent tensors of a given bond dimension $D$. In addition, generic (low-dimensional) families of PEPS explicitly breaking either (i) particular point-group lattice symmetri...

  2. Manipulation of spin transfer torque using light

    Science.gov (United States)

    Rontani, Massimo; Vendelbjerg, Karsten; Sham, Lu

    We show that the spin transfer torque induced by a spin-polarized current on a nanomagnet as the current flows through a semiconductor-nanomagnet-semiconductor junction is externally controlled by shining the junction off-resonantly with a strong laser beam. The excitonic coherence driven by the laser dresses the virtual electron-hole pairs coupling conduction and valence bands and inducing an evanescent state in the proximity of the nanomagnet. The Fano-like quantum interference between this localized state and the continuum spectrum is different in the two spin channels and hence it dramatically alters the spin transport, leading to the coherent control of the spin transfer torque. This work is supported by EU-FP7 Marie Curie Initial Training Network INDEX.

  3. High-Frequency and -Field Electron Paramagnetic Resonance of High-Spin Manganese(III) in Porphyrinic Complexes.

    Science.gov (United States)

    Krzystek, J.; Telser, Joshua; Pardi, Luca A.; Goldberg, David P.; Hoffman, Brian M.; Brunel, Louis-Claude

    1999-12-27

    High-field and -frequency electron paramagnetic resonance (HFEPR) spectroscopy has been used to study two complexes of high-spin manganese(III), d(4), S = 2. The complexes studied were (tetraphenylporphyrinato)manganese(III) chloride and (phthalocyanato)manganese(III) chloride. Our previous HFEPR study (Goldberg, D. P.; Telser, J.; Krzystek, J.; Montalban, A. G.; Brunel, L.-C.; Barrett, A. G. M.; Hoffman, B. M. J. Am. Chem. Soc. 1997, 119, 8722-8723) included results on the porphyrin complex; however, we were unable to obtain true powder pattern HFEPR spectra, as the crystallites oriented in the intense external magnetic field. In this work we are now able to immobilize the powder, either in an n-eicosane mull or KBr pellet and obtain true powder pattern spectra. These spectra have been fully analyzed using spectral simulation software, and a complete set of spin Hamiltonian parameters has been determined for each complex. Both complexes are rigorously axial systems, with relatively low magnitude zero-field splitting: D approximately -2.3 cm(-)(1) and g values quite close to 2.00. Prior to this work, no experimental nor theoretical data exist for the metal-based electronic energy levels in Mn(III) complexes of porphyrinic ligands. This lack of information is in contrast to other transition metal complexes and is likely due to the dominance of ligand-based transitions in the absorption spectra of Mn(III) complexes of this type. We have therefore made use of theoretical values for the electronic energy levels of (phthalocyanato)copper(II), which electronically resembles these Mn(III) complexes. This analogy works surprisingly well in terms of the agreement between the calculated and experimentally determined EPR parameters. These results show a significant mixing of the triplet (S = 1) excited state with the quintet (S = 2) ground state in Mn(III) complexes with porphyrinic ligands. This is in agreement with the experimental observation of lower spin ground states in

  4. Electron tomography reveals unbranched networks of actin filaments in lamellipodia.

    Science.gov (United States)

    Urban, Edit; Jacob, Sonja; Nemethova, Maria; Resch, Guenter P; Small, J Victor

    2010-05-01

    Eukaryotic cells can initiate movement using the forces exerted by polymerizing actin filaments to extend lamellipodial and filopodial protrusions. In the current model, actin filaments in lamellipodia are organized in a branched, dendritic network. We applied electron tomography to vitreously frozen 'live' cells, fixed cells and cytoskeletons, embedded in vitreous ice or in deep-negative stain. In lamellipodia from four cell types, including rapidly migrating fish keratocytes, we found that actin filaments are almost exclusively unbranched. The vast majority of apparent filament junctions proved to be overlapping filaments, rather than branched end-to-side junctions. Analysis of the tomograms revealed that actin filaments terminate at the membrane interface within a zone several hundred nanometres wide at the lamellipodium front, and yielded the first direct measurements of filament densities. Actin filament pairs were also identified as lamellipodium components and bundle precursors. These data provide a new structural basis for understanding actin-driven protrusion during cell migration.

  5. Manganese oxide microswitch for electronic memory based on neural networks

    Science.gov (United States)

    Ramesham, R.; Daud, T.; Moopenn, A.; Thakoor, A. P.; Khanna, S. K.

    1989-01-01

    A solid-state, resistance tailorable, programmable-once, binary, nonvolatile memory switch based on manganese oxide thin films is reported. MnO(x) exhibits irreversible memory switching from conducting (on) to insulating (off) state, with the off and on resistance ratio of greater than 10,000. The switching mechanism is current-triggered chemical transformation of a conductive MnO(2-Delta) to an insulating Mn2O3 state. The energy required for switching is of the order of 4-20 nJ/sq micron. The low switching energy, stability of the on and off states, and tailorability of the on state resistance make these microswitches well suited as programmable binary synapses in electronic associative memories based on neural network models.

  6. Engineering the Eigenstates of Coupled Spin-1/2 Atoms on a Surface.

    Science.gov (United States)

    Yang, Kai; Bae, Yujeong; Paul, William; Natterer, Fabian D; Willke, Philip; Lado, Jose L; Ferrón, Alejandro; Choi, Taeyoung; Fernández-Rossier, Joaquín; Heinrich, Andreas J; Lutz, Christopher P

    2017-12-01

    Quantum spin networks having engineered geometries and interactions are eagerly pursued for quantum simulation and access to emergent quantum phenomena such as spin liquids. Spin-1/2 centers are particularly desirable, because they readily manifest coherent quantum fluctuations. Here we introduce a controllable spin-1/2 architecture consisting of titanium atoms on a magnesium oxide surface. We tailor the spin interactions by atomic-precision positioning using a scanning tunneling microscope (STM) and subsequently perform electron spin resonance on individual atoms to drive transitions into and out of quantum eigenstates of the coupled-spin system. Interactions between the atoms are mapped over a range of distances extending from highly anisotropic dipole coupling to strong exchange coupling. The local magnetic field of the magnetic STM tip serves to precisely tune the superposition states of a pair of spins. The precise control of the spin-spin interactions and ability to probe the states of the coupled-spin network by addressing individual spins will enable the exploration of quantum many-body systems based on networks of spin-1/2 atoms on surfaces.

  7. Engineering the Eigenstates of Coupled Spin-1 /2 Atoms on a Surface

    Science.gov (United States)

    Yang, Kai; Bae, Yujeong; Paul, William; Natterer, Fabian D.; Willke, Philip; Lado, Jose L.; Ferrón, Alejandro; Choi, Taeyoung; Fernández-Rossier, Joaquín; Heinrich, Andreas J.; Lutz, Christopher P.

    2017-12-01

    Quantum spin networks having engineered geometries and interactions are eagerly pursued for quantum simulation and access to emergent quantum phenomena such as spin liquids. Spin-1 /2 centers are particularly desirable, because they readily manifest coherent quantum fluctuations. Here we introduce a controllable spin-1 /2 architecture consisting of titanium atoms on a magnesium oxide surface. We tailor the spin interactions by atomic-precision positioning using a scanning tunneling microscope (STM) and subsequently perform electron spin resonance on individual atoms to drive transitions into and out of quantum eigenstates of the coupled-spin system. Interactions between the atoms are mapped over a range of distances extending from highly anisotropic dipole coupling to strong exchange coupling. The local magnetic field of the magnetic STM tip serves to precisely tune the superposition states of a pair of spins. The precise control of the spin-spin interactions and ability to probe the states of the coupled-spin network by addressing individual spins will enable the exploration of quantum many-body systems based on networks of spin-1 /2 atoms on surfaces.

  8. Optical response of two-dimensional few-electron concentric double quantum rings: A local-spin-density-functional theory study

    Science.gov (United States)

    Malet, F.; Pi, M.; Barranco, M.; Lipparini, E.; Serra, Ll.

    2006-11-01

    We have investigated the dipole charge- and spin-density response of few-electron two-dimensional concentric nanorings as a function of the intensity of a perpendicularly applied magnetic field. We show that the dipole response displays signatures associated with the localization of electron states in the inner and outer ring favored by the perpendicularly applied magnetic field. Electron localization produces a more fragmented spectrum due to the appearance of additional edge excitations in the inner and outer ring.

  9. A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup

    Energy Technology Data Exchange (ETDEWEB)

    Waidyawansa, Dinayadura Buddhini [Ohio Univ., Athens, OH (United States)

    2013-08-01

    The beam normal single spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable of the imaginary part of the two-photon exchange process. Moreover, it is a potential source of false asymmetry in parity violating electron scattering experiments. The Q{sub weak} experiment uses parity violating electron scattering to make a direct measurement of the weak charge of the proton. The targeted 4% measurement of the weak charge of the proton probes for parity violating new physics beyond the Standard Model. The beam normal single spin asymmetry at Q{sub weak} kinematics is at least three orders of magnitude larger than 5 ppb precision of the parity violating asymmetry. To better understand this parity conserving background, the Q{sub weak} Collaboration has performed elastic scattering measurements with fully transversely polarized electron beam on the proton and aluminum. This dissertation presents the analysis of the 3% measurement (1.3% statistical and 2.6% systematic) of beam normal single spin asymmetry in electronproton scattering at a Q2 of 0.025 (GeV/c)2. It is the most precise existing measurement of beam normal single spin asymmetry available at the time. A measurement of this precision helps to improve the theoretical models on beam normal single spin asymmetry and thereby our understanding of the doubly virtual Compton scattering process.

  10. The zero-moment half metal: How could it change spin electronics?

    Directory of Open Access Journals (Sweden)

    Davide Betto

    2016-05-01

    Full Text Available The Heusler compound Mn2RuxGa (MRG may well be the first compensated half metal. Here, the structural, magnetic and transport properties of thin films of MRG are discussed. There is evidence of half-metallicity up to x = 0.7, and compensation of the two Mn sublattice moments is observed at specific compositions and temperatures, leading to a zero-moment half metal. There are potential benefits for using such films with perpendicular anisotropy for spin-torque magnetic tunnel junctions and oscillators, such as low critical current, high tunnel magnetoresistance ratio, insensitivity to external fields and resonance frequency in the THz range.

  11. The zero-moment half metal: How could it change spin electronics?

    Energy Technology Data Exchange (ETDEWEB)

    Betto, Davide; Rode, Karsten, E-mail: rodek@tcd.ie; Thiyagarajah, Naganivetha; Lau, Yong-Chang; Borisov, Kiril; Atcheson, Gwenael; Stamenov, Plamen; Coey, J. M. D. [CRANN, AMBER and School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Žic, Mario; Archer, Thomas [CRANN, and School of Physics, Trinity College Dublin, Dublin 2 (Ireland)

    2016-05-15

    The Heusler compound Mn{sub 2}Ru{sub x}Ga (MRG) may well be the first compensated half metal. Here, the structural, magnetic and transport properties of thin films of MRG are discussed. There is evidence of half-metallicity up to x = 0.7, and compensation of the two Mn sublattice moments is observed at specific compositions and temperatures, leading to a zero-moment half metal. There are potential benefits for using such films with perpendicular anisotropy for spin-torque magnetic tunnel junctions and oscillators, such as low critical current, high tunnel magnetoresistance ratio, insensitivity to external fields and resonance frequency in the THz range.

  12. Superconductivity, spin and charge order, and quantum criticality in correlated electron materials

    Directory of Open Access Journals (Sweden)

    Chu J.-H.

    2012-03-01

    Full Text Available We describe recent experiments performed in our laboratory that address spin or charge ordered phases in novel rare earth and actinide based materials and phenomena that emerge when these ordered phases are suppressed toward 0 K by varying an external control parameter such as chemical composition, pressure, or magnetic field. Specific examples discussed include magnetic order, heavy fermion behavior, and unconventional quantum criticality in noncentrosymmetric M2T12P7 compounds (M = rare earth, actinide; T = Co, Fe and the interplay of superconductivity and charge density waves in rare earth tritelluride compounds RTe3 (R = Gd, Tb, Dy.

  13. Multifrequency electron spin-echo envelope modulation studies of nitrogen ligation to the manganese cluster of photosystem II.

    Science.gov (United States)

    Yeagle, Gregory J; Gilchrist, M Lane; Walker, Lee M; Debus, Richard J; Britt, R David

    2008-03-27

    The CalEPR Center at UC-Davis (http://brittepr.ucdavis.edu) is equipped with five research grade electron paramagnetic resonance (EPR) instruments operating at various excitation frequencies between 8 and 130GHz. Of particular note for this RSC meeting are two pulsed EPR spectrometers working at the intermediate microwave frequencies of 31 and 35GHz. Previous lower frequency electron spin-echo envelope modulation (ESEEM) studies indicated that histidine nitrogen is electronically coupled to the Mn cluster in the S2 state of photosystem II (PSII). However, the amplitude and resolution of the spectra were relatively poor at these low frequencies, precluding any in-depth analysis of the electronic structure properties of this closely associated nitrogen nucleus. With the intermediate frequency instruments, we are much closer to the 'exact cancellation' limit, which optimizes ESEEM spectra for hyperfine-coupled nuclei such as 14N and 15N. Herein, we report the results from ESEEM studies of both 14N- and 15N-labelled PSII at these two frequencies. Spectral simulations were constrained by both isotope datasets at both frequencies, with a focus on high-resolution spectral examination of the histidine ligation to the Mn cluster in the S2 state.

  14. The Electronic Medical Records and Genomics (eMERGE) Network: past, present, and future

    National Research Council Canada - National Science Library

    Gottesman, Omri; Kuivaniemi, Helena; Tromp, Gerard; Faucett, W Andrew; Li, Rongling; Manolio, Teri A; Sanderson, Saskia C; Kannry, Joseph; Zinberg, Randi; Basford, Melissa A; Brilliant, Murray; Carey, David J; Chisholm, Rex L; Chute, Christopher G; Connolly, John J; Crosslin, David; Denny, Joshua C; Gallego, Carlos J; Haines, Jonathan L; Hakonarson, Hakon; Harley, John; Jarvik, Gail P; Kohane, Isaac; Kullo, Iftikhar J; Larson, Eric B; McCarty, Catherine; Ritchie, Marylyn D; Roden, Dan M; Smith, Maureen E; Böttinger, Erwin P; Williams, Marc S

    2013-01-01

    The Electronic Medical Records and Genomics Network is a National Human Genome Research Institute-funded consortium engaged in the development of methods and best practices for using the electronic...

  15. K-shell Analysis Reveals Distinct Functional Parts in an Electron Transfer Network and Its Implications for Extracellular Electron Transfer

    Directory of Open Access Journals (Sweden)

    Dewu eDing

    2016-04-01

    Full Text Available Shewanella oneidensis MR-1 is capable of extracellular electron transfer (EET and hence has attracted considerable attention. The EET pathways mainly consist of c-type cytochromes, along with some other proteins involved in electron transfer processes. By whole genome study and protein interactions inquisition, we constructed a large-scale electron transfer network containing 2276 interactions among 454 electron transfer related proteins in S. oneidensis MR-1. Using the k-shell decomposition method, we identified and analyzed distinct parts of the electron transfer network. We found that there was a negative correlation between the ks (k-shell values and the average DR_100 (disordered regions per 100 amino acids in every shell, which suggested that disordered regions of proteins played an important role during the formation and extension of the electron transfer network. Furthermore, proteins in the top three shells of the network are mainly located in the cytoplasm and inner membrane; these proteins can be responsible for transfer of electrons into the quinone pool in a wide variety of environmental conditions. In most of the other shells, proteins are broadly located throughout the five cellular compartments (cytoplasm, inner membrane, periplasm, outer membrane and extracellular, which ensures the important EET ability of S. oneidensis MR-1. Specifically, the fourth shell was responsible for EET and the c-type cytochromes in the remaining shells of the electron transfer network were involved in aiding EET. Taken together, these results show that there are distinct functional parts in the electron transfer network of S. oneidensis MR-1, and the EET processes could achieve high efficiency through cooperation through such an electron transfer network.

  16. Frequency dependence of electron spin-lattice relaxation for semiquinones in alcohol solutions.

    Science.gov (United States)

    Elajaili, Hanan B; Biller, Joshua R; Eaton, Sandra S; Eaton, Gareth R

    2014-10-01

    The spin-lattice relaxation rates at 293 K for three anionic semiquinones (2,5-di-t-butyl-1,4-benzosemiquinone, 2,6-di-t-butyl-1,4-benzosemiquinone, and 2,3,5,6-tetramethoxy-1,4-benzosemiquinone) were studied at up to 8 frequencies between 250 MHz and 34 GHz in ethanol or methanol solution containing high concentrations of OH(-). The relaxation rates are about a factor of 2 faster at lower frequencies than at 9 or 34 GHz. However, in perdeuterated alcohols the relaxation rates exhibit little frequency dependence, which demonstrates that the dominant frequency-dependent contribution to relaxation is modulation of dipolar interactions with solvent nuclei. The relaxation rates were modeled as the sum of two frequency-independent contributions (spin rotation and a local mode) and two frequency-dependent contributions (modulation of dipolar interaction with solvent nuclei and a much smaller contribution from modulation of g anisotropy). The correlation time for modulation of the interaction with solvent nuclei is longer than the tumbling correlation time of the semiquinone and is consistent with hydrogen bonding of the alcohol to the oxygen atoms of the semiquinones. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. The Iso-electronic Series $Ca_{2-x}Sr_{x}RuO_{4}$: Structural Distortion, Effective Dimensionality, Spin Fluctuations and Quantum Criticality

    OpenAIRE

    Acharya, Swagata; Dey, Dibyendu; Maitra, T.; Taraphder, A.

    2016-01-01

    The iso-electronic $d^{4}$ compounds of the $4d$ series show rich phase diagrams due to competing spin, charge and orbital degrees of freedom in presence of strong correlations and structural distortions. One such iso-electronic series, $Ca_{2-x}Sr_{x}RuO_{4}$, is studied within the GGA (and spin-orbit coupled GGA) plus DMFT formalism using the hybridization expansion of continuous time Quantum Monte Carlo solver. While the local dynamical correlations make $Sr_{2}RuO_{4}$ a Hund's metal, the...

  18. Development of a LabVIEW-based surface with innovative controls for the control system of the spin-polarized electron test source Photo-CATCH

    Energy Technology Data Exchange (ETDEWEB)

    Roesch, Heidi Ayse; Enders, Joachim; Espig, Martin; Fritzsche, Yuliya; Wagner, Markus [TU Darmstadt, Institut fuer Kernphysik (Germany)

    2016-07-01

    Operations of the spin-polarized electron source of the S-DALINAC will be supported by a photo-cathode activation, test and cleaning system, Photo-CATCH. Besides cathode-performance studies, this teststand produces spin-polarized electron bunches from a GaAs photo-cathode that are then transported, manipulated, and characterized by devices in a low-energy beam line. To set and monitor the various components of the beamline, a control system was developed, based on the EPICS framework. As interfaces, LabVIEW was used in combination with a gamepad as a controlling device.

  19. Model for the high-temperature oxygen-ordering thermodynamics in YBa2Cu3O6+x - inclusion of electron spin and charge degrees of freedom

    DEFF Research Database (Denmark)

    Schleger, P.; Hardy, W.N.; Casalta, H.

    1994-01-01

    A lattice-gas model for the high temperature oxygen-ordering thermodynamics in YBa2Cu3O6+x is presented, which assumes constant effective pair interactions between oxygen atoms and includes in a simple fashion the effect of the electron spin and charge degrees of freedom. This is done using...... a commonly utilized picture relating the creation of mobile electron holes and unpaired spins to the insertion of oxygen into the basal plane. The model is solved using the nearest-neighbor square approximation of the cluster-variation method. In addition, preliminary Monte Carlo results using next...

  20. Spin distribution and electronic structure of the ferromagnetic half-metal [Mn(bipy)(N{sub 3}){sub 2}]: Ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.L. [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)]. E-mail: liyanli128@163.com; Yao, K.L. [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China) and International Center of Materials Physics, Chinese Academy of Science, Shenyang 110015 (China) and CCAST (World Lab), P.O. Box 8730, Beijing 10080 (China)]. E-mail: klyao@hust.edu.cn; Liu, Z.L. [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2007-05-31

    Ab initio calculations have been performed to study the electronic structure and the alternating ferromagnetic-antiferromagnetic interactions of the manganese(II)-azido one-dimensional compound: [Mn(bipy)(N{sub 3}){sub 2}] (bipy=2,2'-bipyridine). The density of states, the total energy and the spin magnetic moment were calculated. The calculations predict that the compound [Mn(bipy)(N{sub 3}){sub 2}] is a ferromagnetic half-metal and the spin magnetic moment is 4.000{mu} {sub B} per molecule. At the same time, it has a metallic antiferromagnetic metastable state. Based on the spin distribution obtained from ab initio calculations, we found that the spin populations are strongly positive on the Mn{sup 2+} ions. For the end-on (EO) azido groups, the magnetic moments are mainly distributed on the two terminal N1 and N3 atoms, weakly positive on the central N2 atoms. While for the end-to-end (EE) azido groups, the magnetic moments of the terminal N6 atoms are larger and that of the other terminal N4 atoms are smaller. The analysis of the spin populations shows that the ferromagnetic coupling through the azido groups is resulted from a spin delocalization mechanism together with the spin polarization effect. The results of our calculation are in good agreement with the experiment.