WorldWideScience

Sample records for edge spin accumulation

  1. Edge spin accumulation in semiconductor two-dimensional hole gases

    Czech Academy of Sciences Publication Activity Database

    Nomura, K.; Wunderlich, J.; Sinova, J.; Kaestner, B.; MacDonald, A. H.; Jungwirth, Tomáš

    2005-01-01

    Roč. 72, č. 24 (2005), 245330/1-245330/5 ISSN 1098-0121 R&D Projects: GA MŠk(CS) LC510 Institutional research plan: CEZ:AV0Z10100521 Keywords : spin Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.185, year: 2005

  2. Bulk and edge spin transport in topological magnon insulators

    Science.gov (United States)

    Rückriegel, Andreas; Brataas, Arne; Duine, Rembert A.

    2018-02-01

    We investigate the spin transport properties of a topological magnon insulator, a magnetic insulator characterized by topologically nontrivial bulk magnon bands and protected magnon edge modes located in the bulk band gaps. Employing the Landau-Lifshitz-Gilbert phenomenology, we calculate the spin current driven through a normal metal |topological magnon insulator |normal metal heterostructure by a spin accumulation imbalance between the metals, with and without random lattice defects. We show that bulk and edge transport are characterized by different length scales. This results in a characteristic system size where the magnon transport crosses over from being bulk dominated for small systems to edge dominated for larger systems. These findings are generic and relevant for topological transport in systems of nonconserved bosons.

  3. Long coherence times for edge spins

    Science.gov (United States)

    Kemp, Jack; Yao, Norman Y.; Laumann, Christopher R.; Fendley, Paul

    2017-06-01

    We show that in certain one-dimensional spin chains with open boundary conditions, the edge spins retain memory of their initial state for very long times, even at infinite temperature. The long coherence times do not require disorder, only an ordered phase. In the integrable Ising and XYZ chains, the presence of a strong zero mode means the coherence time is infinite. When Ising is perturbed by interactions breaking the integrability, the coherence time remains exponentially long in the perturbing couplings. We show that this is a consequence of an edge ‘almost’ strong zero mode that almost commutes with the Hamiltonian. We compute this operator explicitly, allowing us to estimate accurately the plateau value of edge spin autocorrelator.

  4. Dynamical spin accumulation in large-spin magnetic molecules

    Science.gov (United States)

    Płomińska, Anna; Weymann, Ireneusz; Misiorny, Maciej

    2018-01-01

    The frequency-dependent transport through a nanodevice containing a large-spin magnetic molecule is studied theoretically in the Kondo regime. Specifically, the effect of magnetic anisotropy on dynamical spin accumulation is of primary interest. Such accumulation arises due to finite components of frequency-dependent conductance that are off diagonal in spin. Here, employing the Kubo formalism and the numerical renormalization group method, we demonstrate that the dynamical transport properties strongly depend on the relative orientation of spin moments in electrodes of the device, as well as on intrinsic parameters of the molecule. In particular, the effect of dynamical spin accumulation is found to be greatly affected by the type of magnetic anisotropy exhibited by the molecule, and it develops for frequencies corresponding to the Kondo temperature. For the parallel magnetic configuration of the device, the presence of dynamical spin accumulation is conditioned by the interplay of ferromagnetic-lead-induced exchange field and the Kondo correlations.

  5. Spin injection and spin accumulation in all-metal mesoscopic spin valves

    NARCIS (Netherlands)

    Jedema, FJ; Nijboer, MS; Filip, AT; van Wees, BJ

    2003-01-01

    We study the electrical injection and detection of spin accumulation in lateral ferromagnetic-metal-nonmagnetic-metal-ferromagnetic-metal (F/N/F) spin valve devices with transparent interfaces. Different ferromagnetic metals, Permalloy (Py), cobalt (Co), and nickel (Ni), are used as electrical spin

  6. Information processing in patterned magnetic nanostructures with edge spin waves.

    Science.gov (United States)

    Lara, Antonio; Robledo Moreno, Javier; Guslienko, Konstantin Y; Aliev, Farkhad G

    2017-07-17

    Low dissipation data processing with spins is one of the promising directions for future information and communication technologies. Despite a significant progress, the available magnonic devices are not broadband yet and have restricted capabilities to redirect spin waves. Here we propose a breakthrough approach to spin wave manipulation in patterned magnetic nanostructures with unmatched characteristics, which exploits a spin wave analogue to edge waves propagating along a water-wall boundary. Using theory, micromagnetic simulations and experiment we investigate spin waves propagating along the edges in magnetic structures, under an in-plane DC magnetic field inclined with respect to the edge. The proposed edge spin waves overcome important challenges faced by previous technologies such as the manipulation of the spin wave propagation direction, and they substantially improve the capability of transmitting information at frequencies exceeding 10 GHz. The concept of the edge spin waves allows to design a broad of logic devices such as splitters, interferometers, or edge spin wave transistors with unprecedented characteristics and a potentially strong impact on information technologies.

  7. Bulk and edge spin transport in topological magnon insulators

    NARCIS (Netherlands)

    Rückriegel, A.; Brataas, A.; Duine, R.A.

    2018-01-01

    We investigate the spin transport properties of a topological magnon insulator, a magnetic insulator characterized by topologically nontrivial bulk magnon bands and protected magnon edge modes located in the bulk band gaps. Employing the Landau-Lifshitz-Gilbert phenomenology, we calculate the spin

  8. An edge index for the quantum spin-Hall effect

    International Nuclear Information System (INIS)

    Prodan, Emil

    2009-01-01

    Quantum spin-Hall systems are topological insulators displaying dissipationless spin currents flowing at the edges of the samples. In contradistinction to the quantum Hall systems where the charge conductance of the edge modes is quantized, the spin conductance is not and it remained an open problem to find the observable whose edge current is quantized. In this paper, we define a particular observable and the edge current corresponding to this observable. We show that this current is quantized and that the quantization is given by the index of a certain Fredholm operator. This provides a new topological invariant that is shown to take the generic values 0 and 2, in line with the Z 2 topological classification of time-reversal invariant systems. The result gives an effective tool for the investigation of the edge structure in quantum spin-Hall systems. Based on a reasonable assumption, we also show that the edge conducting channels are not destroyed by a random edge. (fast track communication)

  9. Spin heat accumulation induced by tunneling from a ferromagnet.

    Science.gov (United States)

    Vera-Marun, I J; van Wees, B J; Jansen, R

    2014-02-07

    An electric current from a ferromagnet into a nonmagnetic material can induce a spin-dependent electron temperature. Here, it is shown that this spin heat accumulation, when created by tunneling from a ferromagnet, produces a non-negligible voltage signal that is comparable to that due to the coexisting electrical spin accumulation and can give a different Hanle spin precession signature. The effect is governed by the spin polarization of the Peltier coefficient of the tunnel contact, its Seebeck coefficient, and the spin heat resistance of the nonmagnetic material, which is related to the electrical spin resistance by a spin-Wiedemann-Franz law. Moreover, spin heat injection is subject to a heat conductivity mismatch that is overcome if the tunnel interface has a sufficiently large resistance.

  10. Pure spin current induced by adiabatic quantum pumping in zigzag-edged graphene nanoribbons

    International Nuclear Information System (INIS)

    Souma, Satofumi; Ogawa, Matsuto

    2014-01-01

    We show theoretically that pure spin current can be generated in zigzag edged graphene nanoribbons through the adiabatic pumping by edge selective pumping potentials. The origin of such pure spin current is the spin splitting of the edge localized states, which are oppositely spin polarized at opposite edges. In the proposed device, each edge of the ribbon is covered by two independent time-periodic local gate potentials with a definite phase difference, inducing the edge spin polarized current. When the pumping phase difference is opposite in sign between two edges, the total charge currents is zero and the pure edge spin current is generated

  11. Origin of spin-polarization in edge boron doped zigzag graphene nanoribbon: a potential spin filter.

    Science.gov (United States)

    Chakrabarty, Soubhik; Wasey, A H M Abdul; Thapa, Ranjit; Das, Gour Prasad

    2018-06-04

    To realize the graphene based spintronic device the prime challenge is to control the electronic structure of edges. In this work we find the origin of spin filtering property in edge boron doped zigzag graphene nanoribbon (ZGNRs) and provide a guide to prepare the graphene based next generation spin filter based device. Here we unveil the role of orbital (p-electron) to tune the electronic, magnetic and transport properties of the edge B doped ZGNRs. When all the edge carbon atoms at one of the edges of ZGNRs are replaced by B (100% edge B-doping), the system undergoes semiconductor to metal transition. The role of passivation of the edge with single/double atomic hydrogen on the electronic properties and its relation with the p electron is correlated in-depth. 50% edge B-doped ZGNRs (50% of the edge C atoms at one of the edges are replaced by B) also shows half-metallicity when the doped edge is left unpassivated. The half-metallic systems show 100% spin-filtering efficiency for a wide range of bias voltages. Zero bias transmission function of the other configurations shows asymmetric behavior for the up and down spin channels, thereby indicating their possible application potential in nano-spintronics. © 2018 IOP Publishing Ltd.

  12. Tunneling between edge states in a quantum spin Hall system.

    Science.gov (United States)

    Ström, Anders; Johannesson, Henrik

    2009-03-06

    We analyze a quantum spin Hall device with a point contact connecting two of its edges. The contact supports a net spin tunneling current that can be probed experimentally via a two-terminal resistance measurement. We find that the low-bias tunneling current and the differential conductance exhibit scaling with voltage and temperature that depend nonlinearly on the strength of the electron-electron interaction.

  13. Spin-accumulation effect in magnetic nano-bridge

    International Nuclear Information System (INIS)

    Khvalkovskii, A.V.; Zvezdin, A.A.; Zvezdin, K.A.; Pullini, D.; Perlo, P.

    2004-01-01

    Large values of magnetoresistance experimentally observed in magnetic nano-contacts and nano-wires are explained in terms of spin accumulation. The investigation of the spin-accumulation effect in magnetic nano-contacts (Phys. Rev. Lett. 82 (1999) 2923) and nano-bridges (JETP Lett. 75 (10) (2002) 613), which are considered to be very promising for various spintronic applications, is presented. The two-dimensional spin-diffusion problem in a magnetic nano-bridge is solved. Dependences of the specific resistance of the domain wall and of the distribution of non-equilibrium spin density on the nano-bridge geometry and the material parameters are obtained

  14. Spin Accumulation of Spinor Atoms in Optical Lattices

    International Nuclear Information System (INIS)

    Li Hong; Jiang Zhanfeng

    2007-01-01

    We obtain an effective spin correlation Hamiltonian describing the interaction of light with a two-level atom, then we investigate the classical trajectory of the two-level atom system by numerical integration of the Heisenberg equation of motion. Our results show that the spin accumulation is a very popular phenomenon as long as the spin character cannot be ignored in the Hamiltonian. We propose experimental protocol to observe this new phenomenon in further experiments.

  15. Spin Heat Accumulation Induced by Tunneling from a Ferromagnet

    NARCIS (Netherlands)

    Vera-Marun, I.J.; Wees, B.J. van; Jansen, R.

    2014-01-01

    An electric current from a ferromagnet into a nonmagnetic material can induce a spin-dependent electron temperature. Here, it is shown that this spin heat accumulation, when created by tunneling from a ferromagnet, produces a non-negligible voltage signal that is comparable to that due to the

  16. Induced Superconductivity in the Quantum Spin Hall Edge

    Science.gov (United States)

    Ren, Hechen; Hart, Sean; Wagner, Timo; Leubner, Philipp; Muehlbauer, Mathias; Bruene, Christoph; Buhmann, Hartmut; Molenkamp, Laurens; Yacoby, Amir

    2014-03-01

    Two-dimensional topological insulators have a gapped bulk and helical edge states, making it a quantum spin Hall insulator. Combining such edge states with superconductivity can be an excellent platform for observing and manipulating localized Majorana fermions. In the context of condensed matter, these are emergent electronic states that obey non-Abelian statistics and hence support fault-tolerant quantum computing. To realize such theoretical constructions, an essential step is to show these edge channels are capable of carrying coherent supercurrent. In our experiment, we fabricate Josephson junctions with HgTe/HgCdTe quantum wells, a two-dimensional material that becomes a quantum spin Hall insulator when the quantum well is thicker than 6.3 nm and the bulk density is depleted. In this regime, we observe supercurrents whose densities are confined to the edges of the junctions, with edge widths ranging from 180 nm to 408 nm. To verify the topological nature of these edges, we measure identical junctions with HgTe/HgCdTe quantum wells thinner than 6.3 nm and observe only uniform supercurrent density across the junctions. This research is supported by Microsoft Corporation Project Q, the NSF DMR-1206016, the DOE SCGF Program, the German Research Foundation, and EU ERC-AG program.

  17. Large spin Seebeck effects in zigzag-edge silicene nanoribbons

    International Nuclear Information System (INIS)

    Yang, Xi-Feng; Liu, Yu-Shen; Feng, Jin-Fu; Wang, Xue-Feng

    2014-01-01

    Using the first-principles methods, we investigate the thermospin properties of a two-probe model based on zigzag-edge silicene nanoribbons (ZSiNRs). Compared with the odd-width ZSiNRs, the spin Seebeck coefficient of the even-width ZSiNRs is obviously enhanced at room temperature. This fact is attributed to a nearly perfect symmetry of the linear conductance gap with the different spin index with respect to the Fermi level induced by the different parity of the wave functions. More interestingly, the corresponding charge Seebeck coefficient is near zero. Therefore, when a thermal bias is presented in the even-width ZSiNRs, a nearly pure spin current is achieved. Meanwhile, the spin polarization of the current approaches infinite

  18. Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

    Science.gov (United States)

    Mani, Arjun; Benjamin, Colin

    2016-04-13

    On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin-orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible--the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case.

  19. Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

    International Nuclear Information System (INIS)

    Mani, Arjun; Benjamin, Colin

    2016-01-01

    On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin–orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible—the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case. (paper)

  20. Large spin accumulation due to spin-charge coupling across a break-junction

    Science.gov (United States)

    Chen, Shuhan; Zou, Han; Chui, Siu-Tat; Ji, Yi

    2013-03-01

    We investigate large spin signals in break-junction nonlocal spin valves (NLSV). The break-junction is a nanometer-sized vacuum tunneling gap between the spin detector and the nonmagnetic channel, formed by electro-static discharge. The spin signals can be either inverted or non-inverted and the magnitudes are much larger than those of standard NLSV. Spin signals with high percentage values (10% - 0%) have been observed. When the frequency of the a.c. modulation is varied, the absolute magnitudes of signals remain the same although the percentage values change. These observations affirm the nonlocal nature of the measurements and rule out local magnetoresistive effects. Owing to the spin-charge coupling across the break-junction, the spin accumulation in a ferromagnet splits into two terms. One term decays on the charge screening length (0.1 nm) and the other decays on the spin diffusion length (10 nm nm). The magnitude of the former is proportional to the resistance of the junction. Therefore a highly resistive break-junction leads to a large spin accumulation and thereby a large spin signal. The signs of the spin signal are determined by the relationship between spin-dependent conductivities, diffusion constants, and density of states of the ferromagnet. This work was supported by US DOE grant No. DE-FG02-07ER46374.

  1. Rigorous decoupling between edge states in frustrated spin chains and ladders

    Science.gov (United States)

    Chepiga, Natalia; Mila, Frédéric

    2018-05-01

    We investigate the occurrence of exact zero modes in one-dimensional quantum magnets of finite length that possess edge states. Building on conclusions first reached in the context of the spin-1/2 X Y chain in a field and then for the spin-1 J1-J2 Heisenberg model, we show that the development of incommensurate correlations in the bulk invariably leads to oscillations in the sign of the coupling between edge states, and hence to exact zero energy modes at the crossing points where the coupling between the edge states rigorously vanishes. This is true regardless of the origin of the frustration (e.g., next-nearest-neighbor coupling or biquadratic coupling for the spin-1 chain), of the value of the bulk spin (we report on spin-1/2, spin-1, and spin-2 examples), and of the value of the edge-state emergent spin (spin-1/2 or spin-1).

  2. Magnetic proximity control of spin currents and giant spin accumulation in graphene

    Science.gov (United States)

    Singh, Simranjeet

    Two dimensional (2D) materials provide a unique platform to explore the full potential of magnetic proximity driven phenomena. We will present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to the ferromagnetic-insulator (FMI) magnetization in graphene/FMI heterostructures. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. We also discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the non-local spin signals in graphene, which is due to spin relaxation by thermally-induced transverse fluctuations of the FMI magnetization. Additionally, it has been a challenge to grow a smooth, robust and pin-hole free tunnel barriers on graphene, which can withstand large current densities for efficient electrical spin injection. We have experimentally demonstrated giant spin accumulation in graphene lateral spin valves employing SrO tunnel barriers. Nonlocal spin signals, as large as 2 mV, are observed in graphene lateral spin valves at room temperature. This high spin accumulations observed using SrO tunnel barriers puts graphene on the roadmap for exploring the possibility of achieving a non-local magnetization switching due to the spin torque from electrically injected spins. Financial support from ONR (No. N00014-14-1-0350), NSF (No. DMR-1310661), and C-SPIN, one of the six SRC STARnet Centers, sponsored by MARCO and DARPA.

  3. Edge-defect induced spin-dependent Seebeck effect and spin figure of merit in graphene nanoribbons.

    Science.gov (United States)

    Liu, Qing-Bo; Wu, Dan-Dan; Fu, Hua-Hua

    2017-10-11

    By using the first-principle calculations combined with the non-equilibrium Green's function approach, we have studied spin caloritronic properties of graphene nanoribbons (GNRs) with different edge defects. The theoretical results show that the edge-defected GNRs with sawtooth shapes can exhibit spin-dependent currents with opposite flowing directions by applying temperature gradients, indicating the occurrence of the spin-dependent Seebeck effect (SDSE). The edge defects bring about two opposite effects on the thermal spin currents: the enhancement of the symmetry of thermal spin-dependent currents, which contributes to the realization of pure thermal spin currents, and the decreasing of the spin thermoelectric conversion efficiency of the devices. It is fortunate that applying a gate voltage is an efficient route to optimize these two opposite spin thermoelectric properties towards realistic device applications. Moreover, due to the existence of spin-splitting band gaps, the edge-defected GNRs can be designed as spin-dependent Seebeck diodes and rectifiers, indicating that the edge-defected GNRs are potential candidates for room-temperature spin caloritronic devices.

  4. Spin accumulation in disordered topological insulator ultrathin films

    Science.gov (United States)

    Siu, Zhuo Bin; Ho, Cong Son; Tan, Seng Ghee; Jalil, Mansoor B. A.

    2017-08-01

    Topological insulator (TI) ultrathin films differ from the more commonly studied semi-infinite bulk TIs in that the former possess both top and bottom surfaces where the surface states localized at different surfaces can couple to one another across the finite thickness of the film. In the presence of an in-plane magnetization, the TI thin films display two distinct phases depending on which of the inter-surface coupling or the magnetization is stronger. In this work, we consider a Bi2Se3 TI thin film system with an in-plane magnetization and numerically calculate the resulting spin accumulation on both surfaces of the film due to an in-plane electric field to linear order. We describe a numerical scheme for performing the Kubo formula calculation in which we include impurity scattering and vertex corrections. We find that the sums of the spin accumulation over the two surfaces in the in-plane direction perpendicular to the magnetization and in the out of plane direction are antisymmetric in Fermi energy around the charge neutrality point and are non-vanishing only when the symmetry between the top and bottom TI surfaces is broken. The impurity scattering, in general, diminishes the magnitude of the spin accumulation.

  5. Spin injection, accumulation, and precession in a mesoscopic nonmagnetic metal island

    NARCIS (Netherlands)

    Zaffalon, M; van Wees, BJ

    We experimentally study spin accumulation in an aluminum island with all dimensions smaller than the spin-relaxation length, so that the spin imbalance throughout the island is uniform. Electrical injection and detection of the spin accumulation are carried out in a four-terminal geometry by means

  6. Aging effect of spin accumulation in non-local spin valves

    International Nuclear Information System (INIS)

    Zhao, Bing; Zhang, Ziyu; Chen, Xiaobing; Zhang, Xiaohan; Pan, Jiahui; Ma, Jiajun; Li, Juan; Wang, Zhicheng; Wang, Le; Xu, Xiaoguang; Jiang, Yong

    2017-01-01

    Highlights: • First time to reveal the whole temporal evolution life of spintronics devices. • The gradual oxidation of the junctions’ areas and that of the channel are confirmed to be the predominant factors to determine the temporal evolution. • Physically, the temporal evolution can be evaluated by theories of S. Takahashi and A. Fert. • This study may offer some useful advice for the design and protection of future industrial spintronics devices. - Abstract: A temporal evolution of spin accumulation of Co/MgO/Ag spin valves have been studied by using the nonlocal spin detection technique over almost a 3-month period in the ambient environment after the fabrication of the devices. Three different stages of the spin accumulation are first observed due to aging effect. The aging effect comes from two contributions–the gradual oxidation of the Ag/MgO and MgO/Co interfaces at the junctions’ areas which arises from the annealing process and the oxidation of the side surfaces of the Ag channels. The theories of S. Takahashi and A. Fert are introduced to evaluate the different evolution stages of spin accumulation.

  7. Aging effect of spin accumulation in non-local spin valves

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Bing; Zhang, Ziyu; Chen, Xiaobing; Zhang, Xiaohan; Pan, Jiahui; Ma, Jiajun; Li, Juan; Wang, Zhicheng [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Wang, Le, E-mail: wangle@ruc.edu.cn [Department of Physics, Renmin University of China, Beijing 100872 (China); Xu, Xiaoguang, E-mail: xgxu@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Jiang, Yong [State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2017-06-15

    Highlights: • First time to reveal the whole temporal evolution life of spintronics devices. • The gradual oxidation of the junctions’ areas and that of the channel are confirmed to be the predominant factors to determine the temporal evolution. • Physically, the temporal evolution can be evaluated by theories of S. Takahashi and A. Fert. • This study may offer some useful advice for the design and protection of future industrial spintronics devices. - Abstract: A temporal evolution of spin accumulation of Co/MgO/Ag spin valves have been studied by using the nonlocal spin detection technique over almost a 3-month period in the ambient environment after the fabrication of the devices. Three different stages of the spin accumulation are first observed due to aging effect. The aging effect comes from two contributions–the gradual oxidation of the Ag/MgO and MgO/Co interfaces at the junctions’ areas which arises from the annealing process and the oxidation of the side surfaces of the Ag channels. The theories of S. Takahashi and A. Fert are introduced to evaluate the different evolution stages of spin accumulation.

  8. Infinite coherence time of edge spins in finite-length chains

    Science.gov (United States)

    Maceira, Ivo A.; Mila, Frédéric

    2018-02-01

    Motivated by the recent observation that exponentially long coherence times can be achieved for edge spins in models with strong zero modes, we study the impact of level crossings in finite-length spin chains on the dynamics of the edge spins. Focusing on the X Y spin-1 /2 chain with a transverse or longitudinal magnetic field, two models relevant to understanding recent experimental results on cobalt adatoms, we show that the edge spins can remain coherent for an infinite time even for a finite-length chain if the magnetic field is tuned to a value at which there is a level crossing. Furthermore, we show that the edge spins remain coherent for any initial state for the integrable case of a transverse field because all states have level crossings at the same value of the field, while the coherence time is increasingly large for lower temperatures in the case of a longitudinal field, which is nonintegrable.

  9. Enhanced spin accumulation in Fe3O4 based spin injection devices below the Verwey transition

    Science.gov (United States)

    Bhat, Shwetha G.; Kumar, P. S. Anil

    2016-12-01

    Spin injection into GaAs and Si (both n and p-type) semiconductors using Fe3O4 is achieved with and without a tunnel barrier (MgO) via three-terminal electrical Hanle measurement. Interestingly, the magnitude of spin accumulation voltage (ΔV) in semiconductor is found to be associated with a drastic increment in ΔV in Fe3O4 based devices for temperature metal-to-insulator transition of Fe3O4 at T V. Observations from our elaborate investigations show that spin polarization of Fe3O4 has an explicit influence on the enhanced spin injection. It is argued that the theoretical prediction of half-metallicity of Fe3O4 above and below T V has to be reinvestigated.

  10. Magnetoresistance in Hybrid Pt/CoFe2O4 Bilayers Controlled by Competing Spin Accumulation and Interfacial Chemical Reconstruction.

    Science.gov (United States)

    Vasili, Hari Babu; Gamino, Matheus; Gàzquez, Jaume; Sánchez, Florencio; Valvidares, Manuel; Gargiani, Pierluigi; Pellegrin, Eric; Fontcuberta, Josep

    2018-04-11

    Pure spin currents have potential for use in energy-friendly spintronics. They can be generated by a flow of charge along a nonmagnetic metal with large spin-orbit coupling. This produces a spin accumulation at the surfaces, controllable by the magnetization of an adjacent ferromagnetic layer. Paramagnetic metals typically used are close to ferromagnetic instability and thus magnetic proximity effects can contribute to the observed angular-dependent magnetoresistance (ADMR). As interface phenomena govern the spin conductance across the metal/ferromagnetic-insulator heterostructures, unraveling these distinct contributions is pivotal for a full understanding of spin current conductance. Here, we report X-ray absorption and magnetic circular dichroism (XMCD) at Pt M and (Co, Fe) L absorption edges and atomically resolved energy electron loss spectroscopy (EELS) data of Pt/CoFe 2 O 4 bilayers, where CoFe 2 O 4 layers have been capped by Pt grown at different temperatures. It was found that the ADMR differs dramatically, dominated either by spin Hall magnetoresistance (SMR) associated with the spin Hall effect or by anisotropic magnetoresistance. The XMCD and EELS data indicate that the Pt layer grown at room temperature does not display any magnetic moment, whereas when grown at a higher temperature, it becomes magnetic due to interfacial Pt-(Co, Fe) alloying. These results enable differentiation of spin accumulation from interfacial chemical reconstructions and tailoring of the angular-dependent magnetoresistance.

  11. Circularly polarized near-field optical mapping of spin-resolved quantum Hall chiral edge states.

    Science.gov (United States)

    Mamyouda, Syuhei; Ito, Hironori; Shibata, Yusuke; Kashiwaya, Satoshi; Yamaguchi, Masumi; Akazaki, Tatsushi; Tamura, Hiroyuki; Ootuka, Youiti; Nomura, Shintaro

    2015-04-08

    We have successfully developed a circularly polarized near-field scanning optical microscope (NSOM) that enables us to irradiate circularly polarized light with spatial resolution below the diffraction limit. As a demonstration, we perform real-space mapping of the quantum Hall chiral edge states near the edge of a Hall-bar structure by injecting spin polarized electrons optically at low temperature. The obtained real-space mappings show that spin-polarized electrons are injected optically to the two-dimensional electron layer. Our general method to locally inject spins using a circularly polarized NSOM should be broadly applicable to characterize a variety of nanomaterials and nanostructures.

  12. Self-similar spectral structures and edge-locking hierarchy in open-boundary spin chains

    International Nuclear Information System (INIS)

    Haque, Masudul

    2010-01-01

    For an anisotropic Heisenberg (XXZ) spin chain, we show that an open boundary induces a series of approximately self-similar features at different energy scales, high up in the eigenvalue spectrum. We present a nonequilibrium phenomenon related to this fractal structure, involving states in which a connected block near the edge is polarized oppositely to the rest of the chain. We show that such oppositely polarized blocks can be 'locked' to the edge of the spin chain and that there is a hierarchy of edge-locking effects at various orders of the anisotropy. The phenomenon enables dramatic control of quantum-state transmission and magnetization control.

  13. Edge physics of the quantum spin Hall insulator from a quantum dot excited by optical absorption.

    Science.gov (United States)

    Vasseur, Romain; Moore, Joel E

    2014-04-11

    The gapless edge modes of the quantum spin Hall insulator form a helical liquid in which the direction of motion along the edge is determined by the spin orientation of the electrons. In order to probe the Luttinger liquid physics of these edge states and their interaction with a magnetic (Kondo) impurity, we consider a setup where the helical liquid is tunnel coupled to a semiconductor quantum dot that is excited by optical absorption, thereby inducing an effective quantum quench of the tunneling. At low energy, the absorption spectrum is dominated by a power-law singularity. The corresponding exponent is directly related to the interaction strength (Luttinger parameter) and can be computed exactly using boundary conformal field theory thanks to the unique nature of the quantum spin Hall edge.

  14. Induced spin-accumulation and spin-polarization in a quantum-dot ring by using magnetic quantum dots and Rashba spin-orbit effect

    International Nuclear Information System (INIS)

    Eslami, L.; Faizabadi, E.

    2014-01-01

    The effect of magnetic contacts on spin-dependent electron transport and spin-accumulation in a quantum ring, which is threaded by a magnetic flux, is studied. The quantum ring is made up of four quantum dots, where two of them possess magnetic structure and other ones are subjected to the Rashba spin-orbit coupling. The magnetic quantum dots, referred to as magnetic quantum contacts, are connected to two external leads. Two different configurations of magnetic moments of the quantum contacts are considered; the parallel and the anti-parallel ones. When the magnetic moments are parallel, the degeneracy between the transmission coefficients of spin-up and spin-down electrons is lifted and the system can be adjusted to operate as a spin-filter. In addition, the accumulation of spin-up and spin-down electrons in non-magnetic quantum dots are different in the case of parallel magnetic moments. When the intra-dot Coulomb interaction is taken into account, we find that the electron interactions participate in separation between the accumulations of electrons with different spin directions in non-magnetic quantum dots. Furthermore, the spin-accumulation in non-magnetic quantum dots can be tuned in the both parallel and anti-parallel magnetic moments by adjusting the Rashba spin-orbit strength and the magnetic flux. Thus, the quantum ring with magnetic quantum contacts could be utilized to create tunable local magnetic moments which can be used in designing optimized nanodevices.

  15. 100% spin accumulation in non-half-metallic ferromagnet-semiconductor junctions

    International Nuclear Information System (INIS)

    Petukhov, A G; Niggemann, J; Smelyanskiy, V N; Osipov, V V

    2007-01-01

    We show that the spin polarization of electron density in non-magnetic degenerate semiconductors can achieve 100%. The effect of 100% spin accumulation does not require a half-metallic ferromagnetic contact and can be realized in ferromagnet-semiconductor FM-n + -n junctions even at moderate spin selectivity of the FM-n + contact when the electrons with spin 'up' are extracted from n semiconductor through the heavily doped n + layer into the ferromagnet and the electrons with spin 'down' are accumulated near the n + -n interface. We derived a general equation relating spin polarization of the current to that of the electron density in non-magnetic semiconductors. We found that the effect of complete spin polarization is achieved near the n + -n interface when the concentration of the spin 'up' electrons tends to zero in this region while the diffusion current of these electrons remains finite

  16. Probing spin-polarized edge state superconductivity by Andreev reflection in in-plane magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Reinthaler, Rolf W.; Tkachov, Grigory; Hankiewicz, Ewelina M. [Faculty of Physics and Astrophysics, University of Wuerzburg, Wuerzburg (Germany)

    2015-07-01

    Finding signatures of unconventional superconductivity in Quantum Spin Hall systems is one of the challenges of solid state physics. Here we induce superconductivity in a 3D topological insulator thin film to cause the formation of helical edge states, which are protected against backscattering even in finite magnetic fields. Above a critical in-plane magnetic field, which is much smaller than the critical field of typical superconductors, the quasi-particle gap closes, giving rise to energy-dependent spin polarization. In this regime the spin-polarized edge state superconductivity can be detected by Andreev reflection. We propose measurement setups to experimentally observe the spin-dependent excess current and dI/dV characteristics.

  17. Penetration depth and nonlocal manipulation of quantum spin hall edge states in chiral honeycomb nanoribbons.

    Science.gov (United States)

    Xu, Yong; Uddin, Salah; Wang, Jun; Wu, Jiansheng; Liu, Jun-Feng

    2017-08-08

    We have studied numerically the penetration depth of quantum spin hall edge states in chiral honeycomb nanoribbons based on the Green's function method. The changing of edge orientation from armchair to zigzag direction decreases the penetration depth drastically. The penetration depth is used to estimate the gap opened for the finite-size effect. Beside this, we also proposed a nonlocal transistor based on the zigzag-like chiral ribbons in which the current is carried at one edge and the manipulation is by the edge magnetization at the other edge. The difficulty that the edge magnetization is unstable in the presence of a ballistic current can be removed by this nonlocal manipulation.

  18. Dynamic detection of spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance (Conference Presentation)

    Science.gov (United States)

    Crowell, Paul A.; Liu, Changjiang; Patel, Sahil; Peterson, Tim; Geppert, Chad C.; Christie, Kevin; Stecklein, Gordon; Palmstrøm, Chris J.

    2016-10-01

    A distinguishing feature of spin accumulation in ferromagnet-semiconductor devices is its precession in a magnetic field. This is the basis for detection techniques such as the Hanle effect, but these approaches become ineffective as the spin lifetime in the semiconductor decreases. For this reason, no electrical Hanle measurement has been demonstrated in GaAs at room temperature. We show here that by forcing the magnetization in the ferromagnet to precess at resonance instead of relying only on the Larmor precession of the spin accumulation in the semiconductor, an electrically generated spin accumulation can be detected up to 300 K. The injection bias and temperature dependence of the measured spin signal agree with those obtained using traditional methods. We further show that this new approach enables a measurement of short spin lifetimes (C. Liu, S. J. Patel, T. A. Peterson, C. C. Geppert, K. D. Christie, C. J. Palmstrøm, and P. A. Crowell, "Dynamic detection of electron spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance," Nature Communications 7, 10296 (2016). http://dx.doi.org/10.1038/ncomms10296

  19. Renormalized second post-Newtonian spin contributions to the accumulated orbital phase for LISA sources

    International Nuclear Information System (INIS)

    Gergely, Laszlo Arpad; Mikoczi, Balazs

    2009-01-01

    We give here a new third post-Newtonian (3PN) spin-spin contribution (in the PN parameter ε) to the accumulated orbital phase of a compact binary, arising from the spin-orbit precessional motion of the spins. In the equal mass case, this contribution vanishes, but Laser Interferometer Space Antenna (LISA) sources of merging supermassive binary black holes have typically a mass ratio of 1:10. For such nonequal masses, this 3PN correction is periodic in time, with a period approximately ε -1 times larger than the period of gravitational waves. We derive a renormalized and simpler expression of the spin-spin coefficient at 2PN, as an average over the time scale of this period of the combined 2PN and 3PN contribution. We also find that for LISA sources the quadrupole-monopole contribution to the phase dominates over the spin-spin contribution, while the self-spin contribution is negligible even for the dominant spin. Finally, we define a renormalized total spin coefficient σ to be employed in the search for gravitational waves emitted by LISA sources.

  20. Effects of nuclear spins on the transport properties of the edge of two-dimensional topological insulators

    Science.gov (United States)

    Hsu, Chen-Hsuan; Stano, Peter; Klinovaja, Jelena; Loss, Daniel

    2018-03-01

    The electrons in the edge channels of two-dimensional topological insulators can be described as a helical Tomonaga-Luttinger liquid. They couple to nuclear spins embedded in the host materials through the hyperfine interaction, and are therefore subject to elastic spin-flip backscattering on the nuclear spins. We investigate the nuclear-spin-induced edge resistance due to such backscattering by performing a renormalization-group analysis. Remarkably, the effect of this backscattering mechanism is stronger in a helical edge than in nonhelical channels, which are believed to be present in the trivial regime of InAs/GaSb quantum wells. In a system with sufficiently long edges, the disordered nuclear spins lead to an edge resistance which grows exponentially upon lowering the temperature. On the other hand, electrons from the edge states mediate an anisotropic Ruderman-Kittel-Kasuya-Yosida nuclear spin-spin interaction, which induces a spiral nuclear spin order below the transition temperature. We discuss the features of the spiral order, as well as its experimental signatures. In the ordered phase, we identify two backscattering mechanisms, due to charge impurities and magnons. The backscattering on charge impurities is allowed by the internally generated magnetic field, and leads to an Anderson-type localization of the edge states. The magnon-mediated backscattering results in a power-law resistance, which is suppressed at zero temperature. Overall, we find that in a sufficiently long edge the nuclear spins, whether ordered or not, suppress the edge conductance to zero as the temperature approaches zero.

  1. Electric-field induced spin accumulation in the Landau level states of topological insulator thin films

    Science.gov (United States)

    Siu, Zhuo Bin; Chowdhury, Debashree; Basu, Banasri; Jalil, Mansoor B. A.

    2017-08-01

    A topological insulator (TI) thin film differs from the more typically studied thick TI system in that the former has both a top and a bottom surface where the states localized at both surfaces can couple to one other across the finite thickness. An out-of-plane magnetic field leads to the formation of discrete Landau level states in the system, whereas an in-plane magnetization breaks the angular momentum symmetry of the system. In this work, we study the spin accumulation induced by the application of an in-plane electric field to the TI thin film system where the Landau level states and inter-surface coupling are simultaneously present. We show, via Kubo formula calculations, that the in-plane spin accumulation perpendicular to the magnetization due to the electric field vanishes for a TI thin film with symmetric top and bottom surfaces. A finite in-plane spin accumulation perpendicular to both the electric field and magnetization emerges upon applying either a differential magnetization coupling or a potential difference between the two film surfaces. This spin accumulation results from the breaking of the antisymmetry of the spin accumulation around the k-space equal-energy contours.

  2. Spin transport properties of partially edge-hydrogenated MoS2 nanoribbon heterostructure

    International Nuclear Information System (INIS)

    Peng, Li; Yao, Kailun; Zhu, Sicong; Ni, Yun; Zu, Fengxia; Wang, Shuling; Guo, Bin; Tian, Yong

    2014-01-01

    We report ab initio calculations of electronic transport properties of heterostructure based on MoS 2 nanoribbons. The heterostructure consists of edge hydrogen-passivated and non-passivated zigzag MoS 2 nanoribbons (ZMoS 2 NR-H/ZMoS 2 NR). Our calculations show that the heterostructure has half-metallic behavior which is independent of the nanoribbon width. The opening of spin channels of the heterostructure depends on the matching of particular electronic orbitals in the Mo-dominated edges of ZMoS 2 NR-H and ZMoS 2 NR. Perfect spin filter effect appears at small bias voltages, and large negative differential resistance and rectifying effects are also observed in the heterostructure.

  3. Edge-spin-derived magnetism in few-layer MoS2 nanomeshes

    Directory of Open Access Journals (Sweden)

    G. Kondo

    2017-12-01

    Full Text Available Magnetism arising from edge spins is highly interesting, particularly in 2D atomically thin materials in which the influence of edges becomes more significant. Among such materials, molybdenum disulfide (MoS2; one of the transition metal dichalcogenide (TMD family is attracting significant attention. The causes for magnetism observed in the TMD family, including in MoS2, have been discussed by considering various aspects, such as pure zigzag atomic-structure edges, grain boundaries, and vacancies. Here, we report the observation of ferromagnetism (FM in few-layer MoS2 nanomeshes (NMs; honeycomb-like array of hexagonal nanopores with low-contamination and low-defect pore edges, which have been created by a specific non-lithographic method. We confirm robust FM arising from pore edges in oxygen(O-terminated MoS2-NMs at room temperature, while it disappears in hydrogen(H-terminated samples. The observed high-sensitivity of FM to NM structures and critical annealing temperatures suggest a possibility that the Mo-atom dangling bond in pore edge is a dominant factor for the FM.

  4. Single-shot readout of accumulation mode Si/SiGe spin qubits using RF reflectometry

    Science.gov (United States)

    Volk, Christian; Martins, Frederico; Malinowski, Filip; Marcus, Charles M.; Kuemmeth, Ferdinand

    Spin qubits based on gate-defined quantum dots are promising systems for realizing quantum computation. Due to their low concentration of nuclear-spin-carrying isotopes, Si/SiGe heterostructures are of particular interest. While high fidelities have been reported for single-qubit and two-qubit gate operations, qubit initialization and measurement times are relatively slow. In order to develop fast read-out techniques compatible with the operation of spin qubits, we characterize double and triple quantum dots confined in undoped Si/Si0.7Ge0.3 heterostructures using accumulation and depletion gates and a nearby RF charge sensor dot. We implement a RF reflectometry technique that allows single-shot charge read-out at integration times on the order of a few μs. We show our recent advancement towards implementing spin qubits in these structures, including spin-selective single-shot read-out.

  5. The phase accumulation and antenna near field of microscopic propagating spin wave devices

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Crosby S.; Kostylev, Mikhail, E-mail: mikhail.kostylev@uwa.edu.au; Ivanov, Eugene [School of Physics M013, The University of Western Australia, Crawley, WA 6009 (Australia); Ding, Junjia; Adeyeye, Adekunle O. [Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore (Singapore)

    2014-01-20

    We studied phase accumulation by the highly non-reciprocal magnetostatic surface spin waves in thin Permalloy microstripes excited and received by microscopic coplanar antennae. We find that the experimentally measured characteristic length of the near field of the antenna is smaller than the total width of the coplanar. This is confirmed by our numerical simulations. Consequently, the distance over which the spin wave accumulates its phase while travelling between the input and output antennae coincides with the distance between the antennae symmetry axes with good accuracy.

  6. The phase accumulation and antenna near field of microscopic propagating spin wave devices

    International Nuclear Information System (INIS)

    Chang, Crosby S.; Kostylev, Mikhail; Ivanov, Eugene; Ding, Junjia; Adeyeye, Adekunle O.

    2014-01-01

    We studied phase accumulation by the highly non-reciprocal magnetostatic surface spin waves in thin Permalloy microstripes excited and received by microscopic coplanar antennae. We find that the experimentally measured characteristic length of the near field of the antenna is smaller than the total width of the coplanar. This is confirmed by our numerical simulations. Consequently, the distance over which the spin wave accumulates its phase while travelling between the input and output antennae coincides with the distance between the antennae symmetry axes with good accuracy

  7. Charge and spin transport in edge channels of a ν=0 quantum Hall system on the surface of topological insulators.

    Science.gov (United States)

    Morimoto, Takahiro; Furusaki, Akira; Nagaosa, Naoto

    2015-04-10

    Three-dimensional topological insulators of finite thickness can show the quantum Hall effect (QHE) at the filling factor ν=0 under an external magnetic field if there is a finite potential difference between the top and bottom surfaces. We calculate energy spectra of surface Weyl fermions in the ν=0 QHE and find that gapped edge states with helical spin structure are formed from Weyl fermions on the side surfaces under certain conditions. These edge channels account for the nonlocal charge transport in the ν=0 QHE which is observed in a recent experiment on (Bi_{1-x}Sb_{x})_{2}Te_{3} films. The edge channels also support spin transport due to the spin-momentum locking. We propose an experimental setup to observe various spintronics functions such as spin transport and spin conversion.

  8. Generalized partition function zeros of 1D spin models and their critical behavior at edge singularities

    International Nuclear Information System (INIS)

    Dalmazi, D; Sa, F L

    2010-01-01

    Here we study the partition function zeros of the one-dimensional Blume-Emery-Griffiths model close to their edge singularities. The model contains four couplings (H, J, Δ, K) including the magnetic field H and the Ising coupling J. We assume that only one of the three couplings (J, Δ, K) is complex and the magnetic field is real. The generalized zeros z i tend to form continuous curves on the complex z-plane in the thermodynamic limit. The linear density at the edges z E diverges usually with ρ(z) ∼ |z - z E | σ and σ = -1/2. However, as in the case of complex magnetic fields (Yang-Lee edge singularity), if we have a triple degeneracy of the transfer matrix eigenvalues a new critical behavior with σ = -2/3 can appear as we prove here explicitly for the cases where either Δ or K is complex. Our proof applies for a general three-state spin model with short-range interactions. The Fisher zeros (complex J) are more involved; in practice, we have not been able to find an explicit example with σ = -2/3 as far as the other couplings (H, Δ, K) are kept as real numbers. Our results are supported by numerical computations of zeros. We show that it is absolutely necessary to have a non-vanishing magnetic field for a new critical behavior. The appearance of σ = -2/3 at the edge closest to the positive real axis indicates its possible relevance for tricritical phenomena in higher-dimensional spin models.

  9. Symmetry-Dependent Spin Transport Properties and Spin-Filter Effects in Zigzag-Edged Germanene Nanoribbons

    Directory of Open Access Journals (Sweden)

    Can Cao

    2015-01-01

    Full Text Available We performed the first-principles calculations to investigate the spin-dependent electronic transport properties of zigzag-edged germanium nanoribbons (ZGeNRs. We choose of ZGeNRs with odd and even widths of 5 and 6, and the symmetry-dependent transport properties have been found, although the σ mirror plane is absent in ZGeNRs. Furthermore, even-N and odd-N ZGeNRs have very different current-voltage relationships. We find that the even 6-ZGeNR shows a dual spin-filter effect in antiparallel (AP magnetism configuration, but the odd 5-ZGeNR behaves as conventional conductors with linear current-voltage dependence. It is found that when the two electrodes are in parallel configuration, the 6-ZGeNR system is in a low resistance state, while it can switch to a much higher resistance state when the electrodes are in AP configuration, and the magnetoresistance of 270% can be observed.

  10. Edge states and conformal boundary conditions in super spin chains and super sigma models

    International Nuclear Information System (INIS)

    Bondesan, Roberto; Jacobsen, Jesper L.; Saleur, Hubert

    2011-01-01

    The sigma models on projective superspaces CP N+M-1|N with topological angle θ=πmod2π flow to non-unitary, logarithmic conformal field theories in the low-energy limit. In this paper, we determine the exact spectrum of these theories for all open boundary conditions preserving the full global symmetry of the model, generalizing recent work on the particular case M=0 [C. Candu et al., JHEP 1002 (2010) 015]. In the sigma model setting, these boundary conditions are associated with complex line bundles, and are labelled by an integer, related with the exact value of θ. Our approach relies on a spin chain regularization, where the boundary conditions now correspond to the introduction of additional edge states. The exact values of the exponents then follow from a lengthy algebraic analysis, a reformulation of the spin chain in terms of crossing and non-crossing loops (represented as a certain subalgebra of the Brauer algebra), and earlier results on the so-called one- and two-boundary Temperley-Lieb algebras (also known as blob algebras). A remarkable result is that the exponents, in general, turn out to be irrational. The case M=1 has direct applications to the spin quantum Hall effect, which will be discussed in a sequel.

  11. Edge states and conformal boundary conditions in super spin chains and super sigma models

    Energy Technology Data Exchange (ETDEWEB)

    Bondesan, Roberto, E-mail: roberto.bondesan@cea.f [LPTENS, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris (France); Institute de Physique Theorique, CEA Saclay, F-91191 Gif-sur-Yvette (France); Jacobsen, Jesper L. [LPTENS, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris (France); Universite Pierre et Marie Curie, 4 place Jussieu, 75252 Paris (France); Saleur, Hubert [Institute de Physique Theorique, CEA Saclay, F-91191 Gif-sur-Yvette (France); Physics Department, USC, Los Angeles, CA 90089-0484 (United States)

    2011-08-11

    The sigma models on projective superspaces CP{sup N+M-1{vert_bar}N} with topological angle {theta}={pi}mod2{pi} flow to non-unitary, logarithmic conformal field theories in the low-energy limit. In this paper, we determine the exact spectrum of these theories for all open boundary conditions preserving the full global symmetry of the model, generalizing recent work on the particular case M=0 [C. Candu et al., JHEP 1002 (2010) 015]. In the sigma model setting, these boundary conditions are associated with complex line bundles, and are labelled by an integer, related with the exact value of {theta}. Our approach relies on a spin chain regularization, where the boundary conditions now correspond to the introduction of additional edge states. The exact values of the exponents then follow from a lengthy algebraic analysis, a reformulation of the spin chain in terms of crossing and non-crossing loops (represented as a certain subalgebra of the Brauer algebra), and earlier results on the so-called one- and two-boundary Temperley-Lieb algebras (also known as blob algebras). A remarkable result is that the exponents, in general, turn out to be irrational. The case M=1 has direct applications to the spin quantum Hall effect, which will be discussed in a sequel.

  12. Exploratory study of the effects of wing-leading-edge modifications on the stall/spin behavior of a light general aviation airplane

    Science.gov (United States)

    1979-01-01

    Configurations with full-span and segmented leading-edge flaps and full-span and segmented leading-edge droop were tested. Studies were conducted with wind-tunnel models, with an outdoor radio-controlled model, and with a full-scale airplane. Results show that wing-leading-edge modifications can produce large effects on stall/spin characteristics, particularly on spin resistance. One outboard wing-leading-edge modification tested significantly improved lateral stability at stall, spin resistance, and developed spin characteristics.

  13. Non-Dirac Chern insulators with large band gaps and spin-polarized edge states.

    Science.gov (United States)

    Xue, Y; Zhang, J Y; Zhao, B; Wei, X Y; Yang, Z Q

    2018-05-10

    Based on first-principles calculations and k·p models, we demonstrate that PbC/MnSe heterostructures are a non-Dirac type of Chern insulator with very large band gaps (244 meV) and exotically half-metallic edge states, providing the possibilities of realizing very robust, completely spin polarized, and dissipationless spintronic devices from the heterostructures. The achieved extraordinarily large nontrivial band gap can be ascribed to the contribution of the non-Dirac type electrons (composed of px and py) and the very strong atomic spin-orbit coupling (SOC) interaction of the heavy Pb element in the system. Surprisingly, the band structures are found to be sensitive to the different exchange and correlation functionals adopted in the first-principles calculations. Chern insulators with various mechanisms are acquired from them. These discoveries show that the predicted nontrivial topology in PbC/MnSe heterostructures is robust and can be observed in experiments at high temperatures. The system has great potential to have attractive applications in future spintronics.

  14. Electron spin polarization induced by spin Hall effect in semiconductors with a linear in the momentum spin-orbit splitting of conduction band

    OpenAIRE

    Korenev, V. L.

    2005-01-01

    It is shown that spin Hall effect creates uniform spin polarization of electrons in semiconductor with a linear in the momentum spin splitting of conduction band. In turn, the profile of the non-uniform spin polarization accumulated at the edge of the sample oscillates in space even in the absence of an external magnetic field.

  15. Maximum magnitude in bias-dependent spin accumulation signals of CoFe/MgO/Si on insulator devices

    International Nuclear Information System (INIS)

    Ishikawa, M.; Sugiyama, H.; Inokuchi, T.; Tanamoto, T.; Saito, Y.; Hamaya, K.; Tezuka, N.

    2013-01-01

    We study in detail how the bias voltage (V bias ) and interface resistance (RA) depend on the magnitude of spin accumulation signals (|ΔV| or |ΔV|/I, where I is current) as detected by three-terminal Hanle measurements in CoFe/MgO/Si on insulator (SOI) devices with various MgO layer thicknesses and SOI carrier densities. We find the apparent maximum magnitude of spin polarization as a function of V bias and the correlation between the magnitude of spin accumulation signals and the shape of differential conductance (dI/dV) curves within the framework of the standard spin diffusion model. All of the experimental results can be explained by taking into account the density of states (DOS) in CoFe under the influence of the applied V bias and the quality of MgO tunnel barrier. These results indicate that it is important to consider the DOS of the ferromagnetic materials under the influence of an applied V bias and the quality of tunnel barrier when observing large spin accumulation signals in Si

  16. Electronic Structure from Iron L-edge Spectroscopy : An Example of Spin Transition Evidenced by Soft X-ray Absorption Spectroscopy

    NARCIS (Netherlands)

    Cartier dit Moulin, Ch.; Flank, A.M.; Rudolf, P.; Chen, C.T.

    1993-01-01

    Soft X-ray Absorption Spectroscopy at the transition metal L2,3 edges provides information about the 3d unoccupied states by dipole allowed transitions. We have recorded iron L2,3 edges in order to follow the reversible thermal spin interconversion (S=2 S=0) of the Fe(II)(o-phenantroline)2(NCS)2.

  17. Influence of MHD effects and edge conditions on ITER helium ash accumulation and sustained ignition

    International Nuclear Information System (INIS)

    Redi, M.H.; Cohen, S.A.

    1990-06-01

    Dilution of reacting species by build-up of helium ash and its effect on ignition in the ITER tokamak have been studies in a series of simulations with the one-dimensional BALDUR transport code. Thermal diffusivities, obtained from ITER scaling laws and with radial variations observed in JET, gave τ E ∼ 2--4 sec. Refueling of deuterium and tritium maintained constant electron density, while carbon recycling was 100% and the helium ash recycling was varied from 1.0 to 0.5. Including MHD effects, specifically sawteeth and beta limits, we find that ignition can be sustained for 200 seconds with R helium = 0.95. These simulations, the only non-zero-dimensional, time-dependent simulations thus far made for ITER plasmas, emphasize that edge plasma conditions, MHD behavior, and helium particle transport are critical synergistic issues for sustained ignition. 27 refs., 2 figs., 1 tab

  18. Effects of V-shaped edge defect and H-saturation on spin-dependent electronic transport of zigzag MoS2 nanoribbons

    International Nuclear Information System (INIS)

    Li, Xin-Mei; Long, Meng-Qiu; Cui, Li-Ling; Xiao, Jin; Zhang, Xiao-Jiao; Zhang, Dan; Xu, Hui

    2014-01-01

    Based on nonequilibrium Green's function in combination with density functional theory calculations, the spin-dependent electronic transport properties of one-dimensional zigzag molybdenum disulfide (MoS 2 ) nanoribbons with V-shaped defect and H-saturation on the edges have been studied. Our results show that the spin-polarized transport properties can be found in all the considered zigzag MoS 2 nanoribbons systems. The edge defects, especially the V-shaped defect on the Mo edge, and H-saturation on the edges can suppress the electronic transport of the systems. Also, the spin-filtering and negative differential resistance behaviors can be observed obviously. The mechanisms are proposed for these phenomena. - Highlights: • The spin-dependent electronic transport of zigzag MoS 2 nanoribbons. • The effects of V-shaped edge defect and H-saturation. • The effects of spin-filter and negative differential resistance can be observed

  19. Topological quantum phase transitions and edge states in spin-orbital coupled Fermi gases.

    Science.gov (United States)

    Zhou, Tao; Gao, Yi; Wang, Z D

    2014-06-11

    We study superconducting states in the presence of spin-orbital coupling and Zeeman field. It is found that a phase transition from a Fulde-Ferrell-Larkin-Ovchinnikov state to the topological superconducting state occurs upon increasing the spin-orbital coupling. The nature of this topological phase transition and its critical property are investigated numerically. Physical properties of the topological superconducting phase are also explored. Moreover, the local density of states is calculated, through which the topological feature may be tested experimentally.

  20. Regular and irregular dynamics of spin-polarized wavepackets in a mesoscopic quantum dot at the edge of topological insulator

    Energy Technology Data Exchange (ETDEWEB)

    Khomitsky, D. V., E-mail: khomitsky@phys.unn.ru; Chubanov, A. A.; Konakov, A. A. [Lobachevsky National Research State University of Nizhny Novgorod, Department of Physics (Russian Federation)

    2016-12-15

    The dynamics of Dirac–Weyl spin-polarized wavepackets driven by a periodic electric field is considered for the electrons in a mesoscopic quantum dot formed at the edge of the two-dimensional HgTe/CdTe topological insulator with Dirac–Weyl massless energy spectra, where the motion of carriers is less sensitive to disorder and impurity potentials. It is observed that the interplay of strongly coupled spin and charge degrees of freedom creates the regimes of irregular dynamics in both coordinate and spin channels. The border between the regular and irregular regimes determined by the strength and frequency of the driving field is found analytically within the quasiclassical approach by means of the Ince–Strutt diagram for the Mathieu equation, and is supported by full quantum-mechanical simulations of the driven dynamics. The investigation of quasienergy spectrum by Floquet approach reveals the presence of non-Poissonian level statistics, which indicates the possibility of chaotic quantum dynamics and corresponds to the areas of parameters for irregular regimes within the quasiclassical approach. We find that the influence of weak disorder leads to partial suppression of the dynamical chaos. Our findings are of interest both for progress in the fundamental field of quantum chaotic dynamics and for further experimental and technological applications of spindependent phenomena in nanostructures based on topological insulators.

  1. The effect of spin-orbit coupling in band structure and edge states of bilayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Sahdan, Muhammad Fauzi; Darma, Yudi, E-mail: yudi@fi.itb.ac.id [Department of Physics, InstitutTeknologi Bandung, Jalan Ganesa 10, Bandung 40132 (Indonesia)

    2015-04-16

    Topological insulators are predicted to be useful ranging from spintronics to quantum computation. Graphene was first predicted to be the precursor of topological insulator by Kane-Mele. They developed a Hamiltonian model to describe the gap opening in graphene. In this work, we investigate the band structure of bilayer grapheme and also its edge states by using this model with analytical approach. The results of our calculation show that the gap opening occurs at K and K’ point in bilayer graphene.In addition, a pair of gapless edge modes occurs both in the zigzag and arm-chair configurations are no longer exist. There are gap created at the edge even though thery are very small.

  2. Nuclear Spin relaxation mediated by Fermi-edge electrons in n-type GaAs

    Science.gov (United States)

    Kotur, M.; Dzhioev, R. I.; Kavokin, K. V.; Korenev, V. L.; Namozov, B. R.; Pak, P. E.; Kusrayev, Yu. G.

    2014-03-01

    A method based on the optical orientation technique was developed to measure the nuclear-spin lattice relaxation time T 1 in semiconductors. It was applied to bulk n-type GaAs, where T 1 was measured after switching off the optical excitation in magnetic fields from 400 to 1200 G at low (< 30 K) temperatures. The spin-lattice relaxation of nuclei in the studied sample with n D = 9 × 1016 cm-3 was found to be determined by hyperfine scattering of itinerant electrons (Korringa mechanism) which predicts invariability of T 1 with the change in magnetic field and linear dependence of the relaxation rate on temperature. This result extends the experimentally verified applicability of the Korringa relaxation law in degenerate semiconductors, previously studied in strong magnetic fields (several Tesla), to the moderate field range.

  3. Magnon Accumulation by Clocked Laser Excitation as Source of Long-Range Spin Waves in Transparent Magnetic Films

    Directory of Open Access Journals (Sweden)

    M. Jäckl

    2017-04-01

    Full Text Available Optical tools are promising for spin-wave generation because of the possibilities of ultrafast manipulation and local excitation. However, a single laser pulse can inject spin waves (SWs only with a broad frequency spectrum, resulting in short propagation distances and low wave amplitudes. Here, we excite a magnetic garnet film by a train of fs-laser pulses with a 1-GHz repetition rate so that the pulse separation is shorter than the decay time of magnetic modes, which allows us to achieve a collective impact on the magnetization and establish a quasistationary source of spin waves, namely, a coherent accumulation of magnons (“magnon cloud”. This approach has several appealing features: (i The magnon source is tunable, (ii the SW amplitude can be significantly enhanced, (iii the SW spectrum is quite narrow, providing long-distance propagation, (iv the periodic pumping results in an almost constant-in-time SW amplitude for the distances larger than 20  μm away from the source, and (v the SW emission shows pronounced directionality. These results expand the capabilities of ultrafast coherent optical control of magnetization and pave the way for applications in data processing, including the quantum regime. The quasistationary magnon accumulation might also be of interest for applications in magnon Bose-Einstein condensates.

  4. Realization of tunable spin-dependent splitting in intrinsic photonic spin Hall effect

    Energy Technology Data Exchange (ETDEWEB)

    Ling, Xiaohui [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Laboratory for spin photonics, College of Physics and Microelectronic Science, Hunan University, Changsha 410082 (China); Department of Physics and Electronic Information Science, Hengyang Normal University, Hengyang 421002 (China); Yi, Xunong [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Zhou, Xinxing; Liu, Yachao; Shu, Weixing; Wen, Shuangchun [Laboratory for spin photonics, College of Physics and Microelectronic Science, Hunan University, Changsha 410082 (China); Luo, Hailu, E-mail: hailuluo@hnu.edu.cn [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Laboratory for spin photonics, College of Physics and Microelectronic Science, Hunan University, Changsha 410082 (China)

    2014-10-13

    We report the realization of tunable spin-dependent splitting in intrinsic photonic spin Hall effect. By breaking the rotational symmetry of a cylindrical vector beam, the intrinsic vortex phases that the two spin components of the vector beam carries, which is similar to the geometric Pancharatnam-Berry phase, are no longer continuous in the azimuthal direction, and leads to observation of spin accumulation at the opposite edge of the beam. Due to the inherent nature of the phase and independency of light-matter interaction, the observed photonic spin Hall effect is intrinsic. Modulating the topological charge of the vector beam, the spin-dependent splitting can be enhanced and the direction of spin accumulation is switchable. Our findings may provide a possible route for generation and manipulation of spin-polarized photons, and enables spin-based photonics applications.

  5. Tunable hybridization of Majorana bound states at the quantum spin Hall edge

    Science.gov (United States)

    Keidel, Felix; Burset, Pablo; Trauzettel, Björn

    2018-02-01

    Confinement at the helical edge of a topological insulator is possible in the presence of proximity-induced magnetic (F) or superconducting (S) order. The interplay of both phenomena leads to the formation of localized Majorana bound states (MBS) or likewise (under certain resonance conditions) the formation of ordinary Andreev bound states (ABS). We investigate the properties of bound states in junctions composed of alternating regions of F or S barriers. Interestingly, the direction of magnetization in F regions and the relative superconducting phase between S regions can be exploited to hybridize MBS or ABS at will. We show that the local properties of MBS translate into a particular nonlocal superconducting pairing amplitude. Remarkably, the symmetry of the pairing amplitude contains information about the nature of the bound state that it stems from. Hence this symmetry can in principle be used to distinguish MBS from ABS, owing to the strong connection between local density of states and nonlocal pairing in our setup.

  6. Direct observation of the edge spin structure and chain length dependence of a finite haldane chain by high field ESR measurements

    International Nuclear Information System (INIS)

    Yoshida, Makoto; Ohta, Hitoshi; Ito, Toshimitsu; Ajiro, Yoshitami

    2006-01-01

    We have performed high field and multi-frequency ESR measurements of finite length S=1 antiferromagnetic chains in Y 2 BaNi 0.96 Mg 0.04 O 5 . Owing to the high spectral resolution by high fields and high frequencies, observed ESR signals can be separated into the contributions of the finite chains with various chain lengths. Our results clearly show that the edge spins actually interact with each other through the quantum spin chain and the interaction depends on the chain length N. (author)

  7. A combined DFT and restricted open-shell configuration interaction method including spin-orbit coupling: Application to transition metal L-edge X-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roemelt, Michael; Maganas, Dimitrios; Neese, Frank [Max-Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Muelheim an der Ruhr (Germany); DeBeer, Serena [Max-Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Muelheim an der Ruhr (Germany); Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853 (United States)

    2013-05-28

    A novel restricted-open-shell configuration interaction with singles (ROCIS) approach for the calculation of transition metal L-edge X-ray absorption spectra is introduced. In this method, one first calculates the ground state and a number of excited states of the non-relativistic Hamiltonian. By construction, the total spin is a good quantum number in each of these states. For a ground state with total spin S excited states with spin S Prime = S, S - 1, and S + 1 are constructed. Using Wigner-Eckart algebra, all magnetic sublevels with M{sub S}= S, Horizontal-Ellipsis , -S for each multiplet of spin S are obtained. The spin-orbit operator is represented by a mean-field approximation to the full Breit-Pauli spin-orbit operator and is diagonalized over this N-particle basis. This is equivalent to a quasi-degenerate treatment of the spin-orbit interaction to all orders. Importantly, the excitation space spans all of the molecular multiplets that arise from the atomic Russell-Saunders terms. Hence, the method represents a rigorous first-principles approach to the complicated low-symmetry molecular multiplet problem met in L-edge X-ray absorption spectroscopy. In order to gain computational efficiency, as well as additional accuracy, the excitation space is restricted to single excitations and the configuration interaction matrix is slightly parameterized in order to account for dynamic correlation effects in an average way. To this end, it is advantageous to employ Kohn-Sham rather than Hartree-Fock orbitals thus defining the density functional theory/ROCIS method. However, the method can also be used in an entirely non-empirical fashion. Only three global empirical parameters are introduced and have been determined here for future application of the method to any system containing any transition metal. The three parameters were carefully calibrated using the L-edge X-ray absorption spectroscopy spectra of a test set of coordination complexes containing first row

  8. K-edge x-ray dichroism investigation of Fe1−xCoxSi: Experimental evidence for spin polarization crossover

    International Nuclear Information System (INIS)

    Hearne, G.R.; Diguet, G.; Baudelet, F.; Itié, J.-P.; Manyala, N.

    2015-01-01

    Both Fe and Co K-edge x-ray magnetic circular dichroism (XMCD) have been employed as element-specific probes of the magnetic moments in the composition series of the disordered ferromagnet Fe 1−x Co x Si (for x=0.2, 0.3, 0.4, 0.5). A definitive single peaked XMCD profile occurs for all compositions at both Fe and Co K-edges. The Fe 4p orbital moment, deduced from the integral of the XMCD signal, has a steep dependence on x at low doping levels and evolves to a different (weaker) dependence at x≥0.3, similar to the behavior of the magnetization in the Co composition range studied here. It is systematically higher, by at least a factor of two, than the corresponding Co orbital moment for most of the composition series. Fine structure beyond the K-edge absorption (limited range EXAFS) suggests that the local order (atomic environment) is very similar across the series, from the perspective of both the Fe and Co absorbing atom. The variation in the XMCD integral across the Co composition range has two regimes, that which occurs below x=0.3 and then evolves to different behavior at higher doping levels. This is more conspicuously present in the Fe contribution. This is rationalized as the evolution from a half-metallic ferromagnet at low Co doping to that of a strong ferromagnet at x>0.3 and as such, spin polarization crossover occurs. The Fermi level is tuned from the majority spin band for x<0.3 where a strongly polarized majority spin electron gas prevails, to a regime where minority spin carriers dominate at higher doping. The evolution of the Fe-derived spin polarized (3d) bands, indirectly probed here via the 4p states, is the primary determinant of the doping dependence of the magnetism in this alloy series. - Highlights: • Element-specific probing of the electronic structure of the Fe 1−x Co x Si series. • XMCD at the level of 10 −4 at the K-edge in such low-moment systems. • Element-specific probing of magnetic contributions from both Fe and Co

  9. Edge-state-dependent tunneling of dipole-exchange spin waves in submicrometer magnetic strips with an air gap.

    Science.gov (United States)

    Xing, X J; Zhang, D; Li, S W

    2012-12-14

    We have investigated the tunneling of dipole-exchange spin waves across an air gap in submicrometer-sized permalloy magnetic strips by means of micromagnetic simulations. The magnetizations beside the gap could form three distinct end-domain states with various strengths of dipolar coupling. Spin-wave tunneling through the gap at individual end-domain states is studied. It is found that the tunneling behavior is strongly dependent on these domain states. Nonmonotonic decay of transmission of spin waves with the increase of the gap width is observed. The underlying mechanism for these behaviors is proposed. The tunneling characteristics of the dipole-exchange spin waves differ essentially from those of the magnetostatic ones reported previously.

  10. Predicting Near Edge X-ray Absorption Spectra with the Spin-Free Exact-Two-Component Hamiltonian and Orthogonality Constrained Density Functional Theory.

    Science.gov (United States)

    Verma, Prakash; Derricotte, Wallace D; Evangelista, Francesco A

    2016-01-12

    Orthogonality constrained density functional theory (OCDFT) provides near-edge X-ray absorption (NEXAS) spectra of first-row elements within one electronvolt from experimental values. However, with increasing atomic number, scalar relativistic effects become the dominant source of error in a nonrelativistic OCDFT treatment of core-valence excitations. In this work we report a novel implementation of the spin-free exact-two-component (X2C) one-electron treatment of scalar relativistic effects and its combination with a recently developed OCDFT approach to compute a manifold of core-valence excited states. The inclusion of scalar relativistic effects in OCDFT reduces the mean absolute error of second-row elements core-valence excitations from 10.3 to 2.3 eV. For all the excitations considered, the results from X2C calculations are also found to be in excellent agreement with those from low-order spin-free Douglas-Kroll-Hess relativistic Hamiltonians. The X2C-OCDFT NEXAS spectra of three organotitanium complexes (TiCl4, TiCpCl3, TiCp2Cl2) are in very good agreement with unshifted experimental results and show a maximum absolute error of 5-6 eV. In addition, a decomposition of the total transition dipole moment into partial atomic contributions is proposed and applied to analyze the nature of the Ti pre-edge transitions in the three organotitanium complexes.

  11. Investigation of a Spin Transition in a LaCoO3 Single Crystal by the Method of X-Ray Magnetic Circular Dichroism at the Cobalt K- and L 2,3-Edges

    Science.gov (United States)

    Sikolenko, V. V.; Troyanchuk, I. O.; Karpinsky, D. V.; Rogalev, A.; Wilhelm, F.; Rosenberg, R.; Prabhakaran, D.; Efimova, E. A.; Efimov, V. V.; Tiutiunnikov, S. I.; Bobrikov, I. A.

    2018-02-01

    Spin transitions of cobalt ions in LaCoO3 single crystals have been studied by the method of X-ray magnetic circular dichroism (XMCD) at the K- and L 2,3-edges of Co3+ ions. The orbital momentum of cobalt ions obtained for the K-edge at the 3 d level in the region of the spin transition in the temperature range from 25 to 120 K increases by a factor of approximately 1.6, whereas the slope of the magnetization curve value in the same temperature range and magnetic field increases by a factor of more than 10. XMCD experiments at the cobalt L 2,3-edges demonstrate gradual growth of the ratio of the orbital momentum to the spin one L/ S from 0.48 to 0.53 in the temperature range from 60 K to 120 K.

  12. Study of apical oxygen atoms in a spin-ladder cuprate compound by X-ray absorption spectroscopy near the Cu K edge

    Energy Technology Data Exchange (ETDEWEB)

    Hatterer, C.J.; Eustache, B.; Collin, L.; Beuran, C.F.; Partiot, C.; Germain, P.; Xu, X.Z.; Lagues, M. [CNRS, Paris (France). Surfaces et Supraconducteurs; Michalowicz, A. [Laboratoire de Physique des Milieux Desordonnes, Universite Paris XII Val-de-Marne, 61 avenue du general de Gaulle, 94010, Creteil Cedex (France)]|[LURE, Universite Paris Sud, 91405, Orsay Cedex (France); Moscovici, J. [Laboratoire de Physique des Milieux Desordonnes, Universite Paris XII Val-de-Marne, 61 avenue du general de Gaulle, 94010, Creteil Cedex (France); Deville Cavellin, C. [CNRS, Paris (France). Surfaces et Supraconducteurs]|[Laboratoire d`Electronique, Universite Paris XII Val-de-Marne, 61 av. du general de Gaulle, 94010, Creteil Cedex (France); Traverse, A. [LURE, Universite Paris Sud, 91405, Orsay Cedex (France)

    1997-04-01

    The structure of high-T{sub c} superconducting cuprate compounds is based on CuO{sub 2} planes alternating with blocks that behave as charge reservoirs. The apical oxygen atoms which belong to these reservoirs are suspected to play a role in the mechanism of superconductivity. It thus seems necessary to measure the amount of apical oxygen atoms in various compounds, as a function of the superconducting properties. Polarisation dependent X-ray absorption spectroscopy (XAS) measurements were performed near the Cu K-edge on three types of phases. We collected information about the neighbourhood of the copper atom in the cuprate planes and in the direction perpendicular to these planes. Two of these phases have well known structures: Bi2212 in which copper atoms are on a pyramidal site and infinite layer phase, a square planar cuprate without apical oxygen. We used the obtained results as reference data to study a new copper-rich phase related to the spin-ladder series. (orig.)

  13. Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer.

    Science.gov (United States)

    Frank, Patrick; Szilagyi, Robert K; Gramlich, Volker; Hsu, Hua-Fen; Hedman, Britt; Hodgson, Keith O

    2017-02-06

    Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M II (itao)(SO 4 )(H 2 O) 0,1 ] (M = Co, Ni, Cu) and [Cu(Me 6 tren)(SO 4 )] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal-sulfur bond, while the XAS preedge of [Zn(itao)(SO 4 )] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO 4 )] but not of [Cu(Me 6 tren)(SO 4 )] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Preedge transitions also appear in the sulfur K-edge XAS of crystalline [M II (SO 4 )(H 2 O)] (M = Fe, Co, Ni, and Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground-state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-down (β) spin orbitals of the sulfate ligand, inducing negative spin density at the sulfate sulfur. Ground-state DFT calculations show that sulfur 3p character then mixes into metal 4s and 4p valence orbitals and various combinations of ligand antibonding orbitals, producing measurable sulfur XAS transitions. TDDFT calculations confirm the presence of XAS preedge features 0.5-2 eV below the rising sulfur K-edge energy. The 2472.1 eV feature arises when orbitals at lower energy than the frontier occupied orbitals with S 3p character mix with the copper(II) electron hole. Transmission of spin polarization and thus of radical character through several bonds between the sulfur and electron hole provides a new mechanism for the counterintuitive appearance of preedge transitions in the XAS spectra of transition-metal oxoanion ligands in the absence of any direct metal-absorber bond. The 2472.1 eV transition is evidence for further radicalization from copper(II), which

  14. Low-temperature conductivity of weakly interacting quantum spin Hall edges in strained-layer InAs/GaInSb

    Science.gov (United States)

    Li, Tingxin; Wang, Pengjie; Sullivan, Gerard; Lin, Xi; Du, Rui-Rui

    2017-12-01

    We report low-temperature transport measurements in strained InAs /G a0.68I n0.32Sb quantum wells, which supports time-reversal symmetry-protected helical edge states. The temperature and bias voltage dependence of the helical edge conductance for devices of various sizes are consistent with the theoretical expectation of a weakly interacting helical edge state. Moreover, we found that the magnetoresistance of the helical edge states is related to the edge interaction effect and the disorder strength.

  15. Spin accumulation in Si channels using CoFe/MgO/Si and CoFe/AlOx/Si tunnel contacts with high quality tunnel barriers prepared by radical-oxygen annealing

    International Nuclear Information System (INIS)

    Akushichi, T.; Shuto, Y.; Sugahara, S.; Takamura, Y.

    2015-01-01

    We investigate spin injection into Si channels using three-terminal spin-accumulation (3T-SA) devices with high-quality CoFe/MgO/n-Si and CoFe/AlO x /n-Si tunnel spin-injectors whose tunnel barriers are formed by radical oxidation of Mg and Al thin films deposited on Si(100) substrates and successive annealing under radical-oxygen exposure. When the MgO and AlO x barriers are not treated by the radical-oxygen annealing, the Hanle-effect signals obtained from the 3T-SA devices are closely fitted by a single Lorentz function representing a signal due to trap spins. On the other hand, when the tunnel barriers are annealed under radical-oxygen exposure, the Hanle-effect signals can be accurately fitted by the superposition of a Lorentz function and a non-Lorentz function representing a signal due to accumulated spins in the Si channel. These results suggest that the quality improvement of tunnel barriers treated by radical-oxygen annealing is highly effective for spin-injection into Si channels

  16. Mesoscopic spin Hall effect in semiconductor nanostructures

    Science.gov (United States)

    Zarbo, Liviu

    The spin Hall effect (SHE) is a name given to a collection of diverse phenomena which share two principal features: (i) longitudinal electric current flowing through a paramagnetic semiconductor or metallic sample leads to transverse spin current and spin accumulation of opposite sign at opposing lateral edges; (ii) SHE does not require externally applied magnetic field or magnetic ordering in the equilibrium state of the sample, instead it relies on the presence of spin-orbit (SO) couplings within the sample. This thesis elaborates on a new type of phenomenon within the SHE family, predicted in our recent studies [Phys. Rev. B 72, 075361 (2005); Phys. Rev. Lett. 95, 046601 (2005); Phys. Rev. B 72, 075335 (2005); Phys. Rev. B 73 , 075303 (2006); and Europhys. Lett. 77, 47004 (2007)], where pure spin current flows through the transverse electrodes attached to a clean finitesize two-dimensional electron gas (2DEG) due to unpolarized charge current injected through its longitudinal leads. If transverse leads are removed, the effect manifests as nonequilibrium spin Hall accumulation at the lateral edges of 2DEG wires. The SO coupling driving this SHE effect is of the Rashba type, which arises due to structural inversion asymmetry of semiconductor heterostructure hosting the 2DEG. We term the effect "mesoscopic" because the spin Hall currents and accumulations reach optimal value in samples of the size of the spin precession length---the distance over which the spin of an electron precesses by an angle pi. In strongly SO-coupled structures this scale is of the order of ˜100 nm, and, therefore, mesoscopic in the sense of being much larger than the characteristic microscopic scales (such as the Fermi wavelength, screening length, or the mean free path in disordered systems), but still much smaller than the macroscopic ones. Although the first theoretical proposal for SHE, driven by asymmetry in SO-dependent scattering of spin-up and spin-down electrons off impurities

  17. Edge instabilities of topological superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Johannes S. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Assaad, Fakher F. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Schnyder, Andreas P. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2016-07-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground state degeneracy and a diverging density of states. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry broken phases, which lift the ground-state degeneracy. Here, we employ Monte Carlo simulations combined with mean-field considerations to examine the instabilities of the flat-band edge states of d{sub xy}-wave superconductors. We find that attractive interactions induce a complex s-wave pairing instability together with a density wave instability. Repulsive interactions, on the other hand, lead to ferromagnetism mixed with spin-triplet pairing at the edge. We discuss the implications of our findings for experiments on cuprate high-temperature superconductors.

  18. Edge Matters

    DEFF Research Database (Denmark)

    Earon, Ofri

    2013-01-01

    of this container is to separate inside from outside and to protect and provide privacy, psychological as well as physical (Venturi, 1966). But, if dwelling phenomenon takes place both inside and outside the private house – why is the urban house an enclosed box? What is the differentiation between inside...... and outside the contemporary urban house? And what is the interplay between them? The research argues for re-thinking the edge zone between inside and outside the urban house. Therefore, although, residential buildings in the city are the objects of study, the focal point here is the edge zone along...... the building. The research explores and develops the architectural characteristics of correlations between the resident, the singular unit, the building and the given location at the edge zone. It approaches the edge zone of the urban house as a platform for dynamic interactions between these behaviours...

  19. Operator spin foam models

    International Nuclear Information System (INIS)

    Bahr, Benjamin; Hellmann, Frank; Kaminski, Wojciech; Kisielowski, Marcin; Lewandowski, Jerzy

    2011-01-01

    The goal of this paper is to introduce a systematic approach to spin foams. We define operator spin foams, that is foams labelled by group representations and operators, as our main tool. A set of moves we define in the set of the operator spin foams (among other operations) allows us to split the faces and the edges of the foams. We assign to each operator spin foam a contracted operator, by using the contractions at the vertices and suitably adjusted face amplitudes. The emergence of the face amplitudes is the consequence of assuming the invariance of the contracted operator with respect to the moves. Next, we define spin foam models and consider the class of models assumed to be symmetric with respect to the moves we have introduced, and assuming their partition functions (state sums) are defined by the contracted operators. Briefly speaking, those operator spin foam models are invariant with respect to the cellular decomposition, and are sensitive only to the topology and colouring of the foam. Imposing an extra symmetry leads to a family we call natural operator spin foam models. This symmetry, combined with assumed invariance with respect to the edge splitting move, determines a complete characterization of a general natural model. It can be obtained by applying arbitrary (quantum) constraints on an arbitrary BF spin foam model. In particular, imposing suitable constraints on a spin(4) BF spin foam model is exactly the way we tend to view 4D quantum gravity, starting with the BC model and continuing with the Engle-Pereira-Rovelli-Livine (EPRL) or Freidel-Krasnov (FK) models. That makes our framework directly applicable to those models. Specifically, our operator spin foam framework can be translated into the language of spin foams and partition functions. Among our natural spin foam models there are the BF spin foam model, the BC model, and a model corresponding to the EPRL intertwiners. Our operator spin foam framework can also be used for more general spin

  20. Quadratic dependence of the spin-induced Hall voltage on longitudinal electric field

    International Nuclear Information System (INIS)

    Miah, M. Idrish

    2008-01-01

    The effect of optically induced spins in semiconductors in the low electric field is investigated. Here we report an experiment which investigates the effect of a longitudinal electric field (E) on the spin-polarized carriers generated by a circularly polarized light in semiconductors. Our experiment observes the effect as a spin-induced anomalous Hall voltage (V AH ) resulting from spin-carrier electrons accumulating at the transverse edges of the sample. Unlike the ordinary Hall effect, a quadratic dependence of V AH on E is observed, which agrees with the results of the recent theoretical investigations. It is also found that V AH depends on the doping density. The results are discussed

  1. Quadratic dependence of the spin-induced Hall voltage on longitudinal electric field

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish [Nanoscale Science and Technology 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 4331 (Bangladesh)], E-mail: m.miah@griffith.edu.au

    2008-10-15

    The effect of optically induced spins in semiconductors in the low electric field is investigated. Here we report an experiment which investigates the effect of a longitudinal electric field (E) on the spin-polarized carriers generated by a circularly polarized light in semiconductors. Our experiment observes the effect as a spin-induced anomalous Hall voltage (V{sub AH}) resulting from spin-carrier electrons accumulating at the transverse edges of the sample. Unlike the ordinary Hall effect, a quadratic dependence of V{sub AH} on E is observed, which agrees with the results of the recent theoretical investigations. It is also found that V{sub AH} depends on the doping density. The results are discussed.

  2. Spin current and spin transfer torque in ferromagnet/superconductor spin valves

    Science.gov (United States)

    Moen, Evan; Valls, Oriol T.

    2018-05-01

    Using fully self-consistent methods, we study spin transport in fabricable spin valve systems consisting of two magnetic layers, a superconducting layer, and a spacer normal layer between the ferromagnets. Our methods ensure that the proper relations between spin current gradients and spin transfer torques are satisfied. We present results as a function of geometrical parameters, interfacial barrier values, misalignment angle between the ferromagnets, and bias voltage. Our main results are for the spin current and spin accumulation as functions of position within the spin valve structure. We see precession of the spin current about the exchange fields within the ferromagnets, and penetration of the spin current into the superconductor for biases greater than the critical bias, defined in the text. The spin accumulation exhibits oscillating behavior in the normal metal, with a strong dependence on the physical parameters both as to the structure and formation of the peaks. We also study the bias dependence of the spatially averaged spin transfer torque and spin accumulation. We examine the critical-bias effect of these quantities, and their dependence on the physical parameters. Our results are predictive of the outcome of future experiments, as they take into account imperfect interfaces and a realistic geometry.

  3. Noise in tunneling spin current across coupled quantum spin chains

    Science.gov (United States)

    Aftergood, Joshua; Takei, So

    2018-01-01

    We theoretically study the spin current and its dc noise generated between two spin-1 /2 spin chains weakly coupled at a single site in the presence of an over-population of spin excitations and a temperature elevation in one subsystem relative to the other, and we compare the corresponding transport quantities across two weakly coupled magnetic insulators hosting magnons. In the spin chain scenario, we find that applying a temperature bias exclusively leads to a vanishing spin current and a concomitant divergence in the spin Fano factor, defined as the spin current noise-to-signal ratio. This divergence is shown to have an exact analogy to the physics of electron scattering between fractional quantum Hall edge states and not to arise in the magnon scenario. We also reveal a suppression in the spin current noise that exclusively arises in the spin chain scenario due to the fermion nature of the spin-1/2 operators. We discuss how the spin Fano factor may be extracted experimentally via the inverse spin Hall effect used extensively in spintronics.

  4. Spin Hall effects

    Science.gov (United States)

    Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

    2015-10-01

    Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

  5. Spinning geometry = Twisted geometry

    International Nuclear Information System (INIS)

    Freidel, Laurent; Ziprick, Jonathan

    2014-01-01

    It is well known that the SU(2)-gauge invariant phase space of loop gravity can be represented in terms of twisted geometries. These are piecewise-linear-flat geometries obtained by gluing together polyhedra, but the resulting geometries are not continuous across the faces. Here we show that this phase space can also be represented by continuous, piecewise-flat three-geometries called spinning geometries. These are composed of metric-flat three-cells glued together consistently. The geometry of each cell and the manner in which they are glued is compatible with the choice of fluxes and holonomies. We first remark that the fluxes provide each edge with an angular momentum. By studying the piecewise-flat geometries which minimize edge lengths, we show that these angular momenta can be literally interpreted as the spin of the edges: the geometries of all edges are necessarily helices. We also show that the compatibility of the gluing maps with the holonomy data results in the same conclusion. This shows that a spinning geometry represents a way to glue together the three-cells of a twisted geometry to form a continuous geometry which represents a point in the loop gravity phase space. (paper)

  6. Edge Detection,

    Science.gov (United States)

    1985-09-01

    PROJECT. T ASK0 Artificial Inteligence Laboratory AREA It WORK UNIT NUMBERS V 545 Technology Square ( Cambridge, HA 02139 I I* CONTOOL1LIN@4OFFICE NAME...ARD-A1t62 62 EDGE DETECTION(U) NASSACNUSETTS INST OF TECH CAMBRIDGE 1/1 ARTIFICIAL INTELLIGENCE LAB E C HILDRETH SEP 85 AI-M-8 N99SI4-8S-C-6595...used to carry out this analysis. cce~iO a N) ’.~" D LI’BL. P p ------------ Sj. t i MASSACHUSETTS INSTITUTE OF TECHNOLOGY i ARTIFICIAL INTELLIGENCE

  7. Protected Pseudohelical Edge States in Z2-Trivial Proximitized Graphene

    Science.gov (United States)

    Frank, Tobias; Högl, Petra; Gmitra, Martin; Kochan, Denis; Fabian, Jaroslav

    2018-04-01

    We investigate topological properties of models that describe graphene on realistic substrates which induce proximity spin-orbit coupling in graphene. A Z2 phase diagram is calculated for the parameter space of (generally different) intrinsic spin-orbit coupling on the two graphene sublattices, in the presence of Rashba coupling. The most fascinating case is that of staggered intrinsic spin-orbit coupling which, despite being topologically trivial, Z2=0 , does exhibit edge states protected by time-reversal symmetry for zigzag ribbons as wide as micrometers. We call these states pseudohelical as their helicity is locked to the sublattice. The spin character and robustness of the pseudohelical modes is best exhibited on a finite flake, which shows that the edge states have zero g factor, carry a pure spin current in the cross section of the flake, and exhibit spin-flip reflectionless tunneling at the armchair edges.

  8. 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

  9. Edge rotational magnons in magnonic crystals

    International Nuclear Information System (INIS)

    Lisenkov, Ivan; Kalyabin, Dmitry; Nikitov, Sergey

    2013-01-01

    It is predicted that in 2D magnonic crystals the edge rotational magnons of forward volume magnetostatic spin waves can exist. Under certain conditions, locally bounded magnons may appear within the crystal consisting of the ferromagnetic matrix and periodically inserted magnetic/non-magnetic inclusions. It is also shown that interplay of different resonances in 2D magnonic crystal may provide conditions for spin wave modes existence with negative group velocity

  10. 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.

  11. Living edge

    DEFF Research Database (Denmark)

    Earon, Ofri

    2014-01-01

    was originally introduced to enhance indoor qualities including light and view. Throughout the paper, it is argued that these ecological motives have grown to architectural and urban dimensions. The paper analyzes the characteristics and potentials of these dimensions and their interconnections. The paper...... on the ground level, but there is a lack of recognition in the significance of communicative characters as well at the higher part of the edge. The city’s planning approach is “Consider urban life before urban space. Consider urban space before buildings” This urban strategy neglects the possible architectural...... contribution to the street atmosphere and its effect on urban life. Bay balcony has been a common architectural element in Copenhagen’s residential buildings, since the end of the twenties. It is a domestic border with an architectural thickness combining window, door, windowsill and balcony. The bay balcony...

  12. Spin injection into GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Endres, Bernhard

    2013-11-01

    In this work spin injection into GaAs from Fe and (Ga,Mn)As was investigated. For the realization of any spintronic device the detailed knowledge about the spin lifetime, the spatial distribution of spin-polarized carriers and the influence of electric fields is essential. In the present work all these aspects have been analyzed by optical measurements of the polar magneto-optic Kerr effect (pMOKE) at the cleaved edge of the samples. Besides the attempt to observe spin pumping and thermal spin injection into n-GaAs the spin solar cell effect is demonstrated, a novel mechanism for the optical generation of spins in semiconductors with potential for future spintronic applications. Also important for spin-based devices as transistors is the presented realization of electrical spin injection into a two-dimensional electron gas.

  13. Geometrical spin symmetry and spin

    International Nuclear Information System (INIS)

    Pestov, I. B.

    2011-01-01

    Unification of General Theory of Relativity and Quantum Mechanics leads to General Quantum Mechanics which includes into itself spindynamics as a theory of spin phenomena. The key concepts of spindynamics are geometrical spin symmetry and the spin field (space of defining representation of spin symmetry). The essence of spin is the bipolar structure of geometrical spin symmetry induced by the gravitational potential. The bipolar structure provides a natural derivation of the equations of spindynamics. Spindynamics involves all phenomena connected with spin and provides new understanding of the strong interaction.

  14. Graphene nanoFlakes with large spin.

    Science.gov (United States)

    Wang, Wei L; Meng, Sheng; Kaxiras, Efthimios

    2008-01-01

    We investigate, using benzenoid graph theory and first-principles calculations, the magnetic properties of arbitrarily shaped finite graphene fragments to which we refer as graphene nanoflakes (GNFs). We demonstrate that the spin of a GNF depends on its shape due to topological frustration of the pi-bonds. For example, a zigzag-edged triangular GNF has a nonzero net spin, resembling an artificial ferrimagnetic atom, with the spin value scaling with its linear size. In general, the principle of topological frustration can be used to introduce large net spin and interesting spin distributions in graphene. These results suggest an avenue to nanoscale spintronics through the sculpting of graphene fragments.

  15. Magnetism of zigzag edge phosphorene nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zhili, E-mail: zlzhu@zzu.edu.cn, E-mail: jiayu@zzu.edu.cn; Li, Chong; Yu, Weiyang; Chang, Dahu; Sun, Qiang; Jia, Yu, E-mail: zlzhu@zzu.edu.cn, E-mail: jiayu@zzu.edu.cn [International Joint Research Laboratory for Quantum Functional Materials of Henan, and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001 (China)

    2014-09-15

    We have investigated, by means of ab initio calculations, the electronic and magnetic structures of zigzag edge phosphorene nanoribbons (ZPNRs) with various widths. The stable magnetic state was found in pristine ZPNRs by allowing the systems to be spin-polarized. The ground state of pristine ZPNRs prefers ferromagnetic order in the same edge but antiferromagnetic order between two opposite edges. The magnetism arises from the dangling bond states as well as edge localized π-orbital states. The presence of a dangling bond is crucial to the formation of the magnetism of ZPNRs. The hydrogenated ZPNRs get nonmagnetic semiconductors with a direct band gap. While, the O-saturated ZPNRs show magnetic ground states due to the weak P-O bond in the ribbon plane between the p{sub z}-orbitals of the edge O and P atoms.

  16. Quantum spin transport in semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Christoph

    2012-05-15

    In this work, we study and quantitatively predict the quantum spin Hall effect, the spin-orbit interaction induced intrinsic spin-Hall effect, spin-orbit induced magnetizations, and spin-polarized electric currents in nanostructured two-dimensional electron or hole gases with and without the presence of magnetic fields. We propose concrete device geometries for the generation, detection, and manipulation of spin polarization and spin-polarized currents. To this end a novel multi-band quantum transport theory, that we termed the multi-scattering Buettiker probe model, is developed. The method treats quantum interference and coherence in open quantum devices on the same footing as incoherent scattering and incorporates inhomogeneous magnetic fields in a gauge-invariant and nonperturbative manner. The spin-orbit interaction parameters that control effects such as band energy spin splittings, g-factors, and spin relaxations are calculated microscopically in terms of an atomistic relativistic tight-binding model. We calculate the transverse electron focusing in external magnetic and electric fields. We have performed detailed studies of the intrinsic spin-Hall effect and its inverse effect in various material systems and geometries. We find a geometry dependent threshold value for the spin-orbit interaction for the inverse intrinsic spin-Hall effect that cannot be met by n-type GaAs structures. We propose geometries that spin polarize electric current in zero magnetic field and analyze the out-of-plane spin polarization by all electrical means. We predict unexpectedly large spin-orbit induced spin-polarization effects in zero magnetic fields that are caused by resonant enhancements of the spin-orbit interaction in specially band engineered and geometrically designed p-type nanostructures. We propose a concrete realization of a spin transistor in HgTe quantum wells, that employs the helical edge channel in the quantum spin Hall effect.

  17. Quantum spin transport in semiconductor nanostructures

    International Nuclear Information System (INIS)

    Schindler, Christoph

    2012-01-01

    In this work, we study and quantitatively predict the quantum spin Hall effect, the spin-orbit interaction induced intrinsic spin-Hall effect, spin-orbit induced magnetizations, and spin-polarized electric currents in nanostructured two-dimensional electron or hole gases with and without the presence of magnetic fields. We propose concrete device geometries for the generation, detection, and manipulation of spin polarization and spin-polarized currents. To this end a novel multi-band quantum transport theory, that we termed the multi-scattering Buettiker probe model, is developed. The method treats quantum interference and coherence in open quantum devices on the same footing as incoherent scattering and incorporates inhomogeneous magnetic fields in a gauge-invariant and nonperturbative manner. The spin-orbit interaction parameters that control effects such as band energy spin splittings, g-factors, and spin relaxations are calculated microscopically in terms of an atomistic relativistic tight-binding model. We calculate the transverse electron focusing in external magnetic and electric fields. We have performed detailed studies of the intrinsic spin-Hall effect and its inverse effect in various material systems and geometries. We find a geometry dependent threshold value for the spin-orbit interaction for the inverse intrinsic spin-Hall effect that cannot be met by n-type GaAs structures. We propose geometries that spin polarize electric current in zero magnetic field and analyze the out-of-plane spin polarization by all electrical means. We predict unexpectedly large spin-orbit induced spin-polarization effects in zero magnetic fields that are caused by resonant enhancements of the spin-orbit interaction in specially band engineered and geometrically designed p-type nanostructures. We propose a concrete realization of a spin transistor in HgTe quantum wells, that employs the helical edge channel in the quantum spin Hall effect.

  18. X-ray imaging of spin currents and magnetisation dynamics at the nanoscale

    International Nuclear Information System (INIS)

    Bonetti, Stefano

    2017-01-01

    Understanding how spins move in time and space is the aim of both fundamental and applied research in modern magnetism. Over the past three decades, research in this field has led to technological advances that have had a major impact on our society, while improving the understanding of the fundamentals of spin physics. However, important questions still remain unanswered, because it is experimentally challenging to directly observe spins and their motion with a combined high spatial and temporal resolution. In this article, we present an overview of the recent advances in x-ray microscopy that allow researchers to directly watch spins move in time and space at the microscopically relevant scales. We discuss scanning x-ray transmission microscopy (STXM) at resonant soft x-ray edges, which is available at most modern synchrotron light sources. This technique measures magnetic contrast through the x-ray magnetic circular dichroism (XMCD) effect at the resonant absorption edges, while focusing the x-ray radiation at the nanometre scale, and using the intrinsic pulsed structure of synchrotron-generated x-rays to create time-resolved images of magnetism at the nanoscale. In particular, we discuss how the presence of spin currents can be detected by imaging spin accumulation, and how the magnetisation dynamics in thin ferromagnetic films can be directly imaged. We discuss how a direct look at the phenomena allows for a deeper understanding of the the physics at play, that is not accessible to other, more indirect techniques. Finally, we present an overview of the exciting opportunities that lie ahead to further understand the fundamentals of novel spin physics, opportunities offered by the appearance of diffraction limited storage rings and free electron lasers. (topical review)

  19. Quantum nature of edge magnetism in graphene.

    Science.gov (United States)

    Golor, Michael; Wessel, Stefan; Schmidt, Manuel J

    2014-01-31

    It is argued that the subtle crossover from decoherence-dominated classical magnetism to fluctuation-dominated quantum magnetism is experimentally accessible in graphene nanoribbons. We show that the width of a nanoribbon determines whether the edge magnetism is on the classical side, on the quantum side, or in between. In the classical regime, decoherence is dominant and leads to static spin polarizations at the ribbon edges, which are well described by mean-field theories. The quantum Zeno effect is identified as the basic mechanism which is responsible for the spin polarization and thereby enables the application of graphene in spintronics. On the quantum side, however, the spin polarization is destroyed by dynamical processes. The great tunability of graphene magnetism thus offers a viable route for the study of the quantum-classical crossover.

  20. Electron transport in edge-disordered graphene nanoribbons

    DEFF Research Database (Denmark)

    Saloriutta, Karri; Hancock, Y.; Karkkainen, Asta

    2011-01-01

    Ab initio methods are used to study the spin-resolved transport properties of graphene nanoribbons (GNRs) that have both chemical and structural edge disorder. Oxygen edge adsorbates on ideal and protruded ribbons are chosen as representative examples, with the protrusions forming the smallest...

  1. Spin-forming Project Report

    Energy Technology Data Exchange (ETDEWEB)

    Switzner, Nathan; Henry, Dick

    2009-03-20

    In a second development order, spin-forming equipment was again evaluated using the test shape, a hemispherical shell. In this second development order, pure vanadium and alloy titanium (Ti-6Al-4V) were spin-formed, as well as additional copper and 21-6-9 stainless. In the first development order the following materials had been spin-formed: copper (alloy C11000 ETP), 6061 aluminum, 304L stainless steel, 21-6-9 stainless steel, and tantalum-2.5% tungsten. Significant challenges included properly adjusting the rotations-per-minute (RPM), cracking at un-beveled edges and laser marks, redressing of notches, surface cracking, non-uniform temperature evolution in the titanium, and cracking of the tailstock. Lessons learned were that 300 RPM worked better than 600 RPM for most materials (at the feed rate of 800 mm/min); beveling the edges to lower the stress reduces edge cracking; notches, laser marks, or edge defects in the preform doom the process to cracking and failure; coolant is required for vanadium spin-forming; increasing the number of passes to nine or more eliminates surface cracking for vanadium; titanium develops a hot zone in front of the rollers; and the tailstock should be redesigned to eliminate the cylindrical stress concentrator in the center.

  2. Role of edges in the electronic and magnetic structures of nanographene

    International Nuclear Information System (INIS)

    Enoki, Toshiaki

    2012-01-01

    In graphene edges or nanographene, the presence of edges strongly affects the electronic structure depending on their edge shape (zigzag and armchair edges) as observed with the electron wave interference and the creation of non-bonding π-electron state (edge state). We investigate the edge-inherent electronic features and the magnetic properties of edge-sate spins in nanographene/graphene edges. Graphene nanostructures are fabricated by heat-induced conversion/fabrication of nanodiamond particles/graphite step edges; single-layer nanographene islands (mean size 10 nm) and armchair-edged nanographene ribbons (width 8 nm). Scanning tunneling microscopy (STM)/scanning tunneling spectroscopy observations demonstrate that edge states are created in zigzag edges in spite of the absence of such states in armchair edges. In addition, zigzag edges tend to be short and defective, whereas armchair edges are long and continuous in general. These findings suggest that a zigzag edge has lower aromatic stability than an armchair edge, consistent with Clar's aromatic sextet rule. The manner in which electron wave scattering takes place is different between zigzag and armchair edges. In the vicinity of an armchair edge, a honeycomb superlattice is observed in STM images together with a fine structure of threefold symmetry, in spite of the (√3×√3 )R30 o superlattice at a zigzag edge. The honeycomb lattice is a consequence of the intervalley K-K' transition that accompanies the electron wave interference taking place at the armchair edge. The Raman G-band is also affected by the interference, showing polarization angle dependence specifically at armchair edges. The magnetism of a three-dimensional disordered network of nanographene sheets is understood on the basis of the ferrimagnetic structure of the edge-state spins in individual constituent nanographene sheets. The strengthening of the inter-nanographene-sheet magnetic interaction brings about a spin glass state.

  3. H-mode edge rotation in W7-AS

    International Nuclear Information System (INIS)

    Hirsch, M.; Baldzuhn, J.; Ehmler, H.; Grigull, P.; Maassberg, H.; McCormick, K.; Wagner, F.; Wobig, H.

    2005-01-01

    In W7-AS three regimes of improved confinement exist which base on negative radial electric fields at the plasma edge resulting there from ion-root conditions of the ambipolar radial fluxes. Experimental control besides the magnetic configuration is given via the edge density profile i.e. the recycling and fuelling conditions. However, the ordering element seems to be the radial electric field profile (respectively its shear) and its interplay with the gradients of ion temperature and density. At low to medium densities the so called optimum confinement regime occurs with maximum density gradients located well inside the plasma boundary and large negative values of E r extending deep in the bulk plasma. For a large inner fraction of the bulk the ion temperature can be sufficiently high that ion transport conditions already can be explained by neoclassics. This regime delivers maximum values of T i , τ e and n τ e T i . Density gradients located right inside the plasma boundary result in the classical H-mode phenomena reminiscent to other toroidal devices with the capability of an edge layer with nearly complete suppression of turbulence either quasi stationary (in a quiescent H-mode) or intermittently (in between ELMs). At even higher densities and highly collisional plasmas with the maximum of ∇n shifted to or even out of the plasma boundary the High Density H-mode (HDH) opens access to steady state conditions with no measurable impurity accumulation. These improved confinement regimes are accessed and left via significant transitions of the transport properties albeit these transitions occur on rather different timescales. A comprehensive picture of improved edge confinement regimes in W7-AS is drawn based on the assumption that a weak edge bounded transport barrier resulting from the ion root conditions (thus E r <0) is the ground state of the (turbulent) edge plasma and already behaves as a barrier for anomalous transport. On top of that the classical H

  4. Positivity of spin foam amplitudes

    International Nuclear Information System (INIS)

    Baez, John C; Christensen, J Daniel

    2002-01-01

    The amplitude for a spin foam in the Barrett-Crane model of Riemannian quantum gravity is given as a product over its vertices, edges and faces, with one factor of the Riemannian 10j symbols appearing for each vertex, and simpler factors for the edges and faces. We prove that these amplitudes are always nonnegative for closed spin foams. As a corollary, all open spin foams going between a fixed pair of spin networks have real amplitudes of the same sign. This means one can use the Metropolis algorithm to compute expectation values of observables in the Riemannian Barrett-Crane model, as in statistical mechanics, even though this theory is based on a real-time (e iS ) rather than imaginary-time e -S path integral. Our proof uses the fact that when the Riemannian 10j symbols are nonzero, their sign is positive or negative depending on whether the sum of the ten spins is an integer or half-integer. For the product of 10j symbols appearing in the amplitude for a closed spin foam, these signs cancel. We conclude with some numerical evidence suggesting that the Lorentzian 10j symbols are always nonnegative, which would imply similar results for the Lorentzian Barrett-Crane model

  5. Unconventional quantized edge transport in the presence of inter-edge coupling in intercalated graphene

    OpenAIRE

    Li, Yuanchang

    2016-01-01

    It is generally believed that the inter-edge coupling destroys the quantum spin Hall (QSH) effect along with the gap opening at the Dirac points. Using first-principles calculations, we find that the quantized edge transport persists in the presence of inter-edge coupling in Ta intercalated epitaxial graphene on SiC(0001), being a QSH insulator with the non-trivial gap of 81 meV. In this case, the band is characterized by two perfect Dirac cones with different Fermi velocities, yet only one m...

  6. 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.

  7. Spin doctoring

    OpenAIRE

    Vozková, Markéta

    2011-01-01

    1 ABSTRACT The aim of this text is to provide an analysis of the phenomenon of spin doctoring in the Euro-Atlantic area. Spin doctors are educated people in the fields of semiotics, cultural studies, public relations, political communication and especially familiar with the infrastructure and the functioning of the media industry. Critical reflection of manipulative communication techniques puts spin phenomenon in historical perspective and traces its practical use in today's social communica...

  8. Theory of the spin Peltier effect

    Science.gov (United States)

    Ohnuma, Y.; Matsuo, M.; Maekawa, S.

    2017-10-01

    A microscopic theory of the spin Peltier effect in a bilayer structure comprising a paramagnetic metal (PM) and a ferromagnetic insulator (FI) based on the nonequilibrium Green's function method is presented. Spin current and heat current driven by temperature gradient and spin accumulation are formulated as functions of spin susceptibilities in the PM and the FI, and are summarized by Onsager's reciprocal relations. By using the current formulas, we estimate heat generation and absorption at the interface driven by the heat-current injection mediated by spins from PM into FI.

  9. A white beam neutron spin splitter

    International Nuclear Information System (INIS)

    Krist, T.; Klose, F.; Felcher, G.P.

    1997-01-01

    The polarization of a narrow, highly collimated polychromatic neutron beam is tested by a neutron spin splitter that permits the simultaneous measurement of both spin states. The device consists of a Si-Co 0.11 Fe 0.89 supermirror, which totally reflects one spin state up to a momentum transfer q=0.04 angstrom -1 , whilst transmits neutrons of the opposite spin state. The supermirror is sandwitched between two thick silicon wafers and is magnetically saturated by a magnetic field of 400 Oe parallel to its surface. The neutron beam enters through the edge of one of the two silicon wavers, its spin components are split by the supermirror and exit from the opposite edges of the two silicon wafers and are recorded at different channels of a position-sensitive detector. The device is shown to have excellent efficiency over a broad range of wavelengths

  10. A white beam neutron spin splitter

    Energy Technology Data Exchange (ETDEWEB)

    Krist, T. [Hahn Meitner Institute, Berlin (Germany); Klose, F.; Felcher, G.P. [Argonne National Lab., IL (United States)

    1997-07-23

    The polarization of a narrow, highly collimated polychromatic neutron beam is tested by a neutron spin splitter that permits the simultaneous measurement of both spin states. The device consists of a Si-Co{sub 0.11} Fe{sub 0.89} supermirror, which totally reflects one spin state up to a momentum transfer q=0.04 {angstrom}{sup -1}, whilst transmits neutrons of the opposite spin state. The supermirror is sandwitched between two thick silicon wafers and is magnetically saturated by a magnetic field of 400 Oe parallel to its surface. The neutron beam enters through the edge of one of the two silicon wavers, its spin components are split by the supermirror and exit from the opposite edges of the two silicon wafers and are recorded at different channels of a position-sensitive detector. The device is shown to have excellent efficiency over a broad range of wavelengths.

  11. Spin thermoelectric effects in organic single-molecule devices

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H.L.; Wang, M.X.; Qian, C.; Hong, X.K.; Zhang, D.B.; Liu, Y.S.; Yang, X.F., E-mail: xfyang@cslg.edu.cn

    2017-05-25

    Highlights: • A stronger spin thermoelectric performance in a polyacetylene device is observed. • For the antiferromagnetic (AFM) ordering, a transport gap is opened. Thus the thermoelectric effects are largely enhanced. - Abstract: The spin thermoelectric performance of a polyacetylene chain bridging two zigzag graphene nanoribbons (ZGNRs) is investigated based on first principles method. Two different edge spin arrangements in ZGNRs are considered. For ferromagnetic (FM) ordering, transmission eigenstates with different spin indices distributed below and above Fermi level are observed, leading directly to a strong spin thermoelectric effect in a wide temperature range. With the edge spins arranged in the antiferromagnetic (AFM) ordering, an obvious transport gap appears in the system, which greatly enhances the thermoelectric effects. The presence of a small spin splitting also induces a spin thermoelectric effect greater than the charge thermoelectric effect in certain temperature range. In general, the single-molecule junction exhibits the potential to be used for the design of perfect thermospin devices.

  12. Spin diffusion and torques in disordered antiferromagnets

    KAUST Repository

    Manchon, Aurelien

    2017-02-01

    We have developed a drift-diffusion equation of spin transport in collinear bipartite metallic antiferromagnets. Starting from a model tight-binding Hamiltonian, we obtain the quantum kinetic equation within Keldysh formalism and expand it to the lowest order in spatial gradient using Wigner expansion method. In the diffusive limit, these equations track the spatio-temporal evolution of the spin accumulations and spin currents on each sublattice of the antiferromagnet. We use these equations to address the nature of the spin transfer torque in (i) a spin-valve composed of a ferromagnet and an antiferromagnet, (ii) a metallic bilayer consisting of an antiferromagnet adjacent to a heavy metal possessing spin Hall effect, and in (iii) a single antiferromagnet possessing spin Hall effect. We show that the latter can experience a self-torque thanks to the non-vanishing spin Hall effect in the antiferromagnet.

  13. Spin diffusion and torques in disordered antiferromagnets

    KAUST Repository

    Manchon, Aurelien

    2017-01-01

    We have developed a drift-diffusion equation of spin transport in collinear bipartite metallic antiferromagnets. Starting from a model tight-binding Hamiltonian, we obtain the quantum kinetic equation within Keldysh formalism and expand it to the lowest order in spatial gradient using Wigner expansion method. In the diffusive limit, these equations track the spatio-temporal evolution of the spin accumulations and spin currents on each sublattice of the antiferromagnet. We use these equations to address the nature of the spin transfer torque in (i) a spin-valve composed of a ferromagnet and an antiferromagnet, (ii) a metallic bilayer consisting of an antiferromagnet adjacent to a heavy metal possessing spin Hall effect, and in (iii) a single antiferromagnet possessing spin Hall effect. We show that the latter can experience a self-torque thanks to the non-vanishing spin Hall effect in the antiferromagnet.

  14. Spin currents in a normal two-dimensional electron gas in contact with a spin-orbit interaction region

    International Nuclear Information System (INIS)

    Sukhanov, Aleksei A; Sablikov, Vladimir A; Tkach, Yurii Ya

    2009-01-01

    Spin effects in a normal two-dimensional (2D) electron gas in lateral contact with a 2D region with spin-orbit interaction are studied. The peculiarity of this system is the presence of spin-dependent scattering of electrons from the interface. This results in an equilibrium edge spin current and nontrivial spin responses to a particle current. We investigate the spatial distribution of the spin currents and spin density under non-equilibrium conditions caused by a ballistic electron current flowing normal or parallel to the interface. The parallel electron current is found to generate a spin density near the interface and to change the edge spin current. The perpendicular electron current changes the edge spin current proportionally to the electron current and produces a bulk spin current penetrating deep into the normal region. This spin current has two components, one of which is directed normal to the interface and polarized parallel to it, and the second is parallel to the interface and is polarized in the plane perpendicular to the contact line. Both spin currents have a high degree of polarization (∼40-60%).

  15. Magnetization and spin-polarized conductance of asymmetrically hydrogenated graphene nanoribbons: significance of sigma bands

    International Nuclear Information System (INIS)

    Honda, Syuta; Inuzuka, Kouhei; Inoshita, Takeshi; Ota, Norio; Sano, Nobuyuki

    2014-01-01

    The magnetization and spin transport of asymmetric zigzag-edge graphene nanoribbons, terminated by hydrogen on one edge while unterminated on the other edge, were investigated by a combination of first-principles calculations and a tight-binding approach. At the unterminated edge, a spin-polarized σ edge state of minority spin appears near the Fermi level and contributes to spin transport. This state enters the band gap for ribbon widths of less than 15 chains, dominating the spin-polarized current. This indicates the importance of the σ edge states in the design of spintronic devices using graphene nanoribbons. We also examined the case where the ‘unterminated’ edge is partially terminated by hydrogen. (paper)

  16. Spin 1990

    International Nuclear Information System (INIS)

    Anton, Gisela

    1990-01-01

    The idea of the intrinsic angular momentum, or 'spin', of a particle has played an essential part in fundamental physics for more than 60 years, and its continuing importance was underlined at the 9th International Symposium on High Energy Spin Physics, held in September in Bonn.

  17. Spin 1990

    Energy Technology Data Exchange (ETDEWEB)

    Anton, Gisela

    1990-12-15

    The idea of the intrinsic angular momentum, or 'spin', of a particle has played an essential part in fundamental physics for more than 60 years, and its continuing importance was underlined at the 9th International Symposium on High Energy Spin Physics, held in September in Bonn.

  18. Spin tomography

    Energy Technology Data Exchange (ETDEWEB)

    D' Ariano, G M [Quantum Optics and Information Group, INFM Udr Pavia, Dipartimento di Fisica ' Alessandro Volta' and INFM, Via Bassi 6, 27100 Pavia (Italy); Maccone, L [Quantum Optics and Information Group, INFM Udr Pavia, Dipartimento di Fisica ' Alessandro Volta' and INFM, Via Bassi 6, 27100 Pavia (Italy); Paini, M [Quantum Optics and Information Group, INFM Udr Pavia, Dipartimento di Fisica ' Alessandro Volta' and INFM, Via Bassi 6, 27100 Pavia (Italy)

    2003-02-01

    We propose a tomographic reconstruction scheme for spin states. The experimental set-up, which is a modification of the Stern-Gerlach scheme, can be easily performed with currently available technology. The method is generalized to multiparticle states, analysing the spin-1/2 case for indistinguishable particles. Some Monte Carlo numerical simulations are given to illustrate the technique.

  19. Spin tomography

    International Nuclear Information System (INIS)

    D'Ariano, G M; Maccone, L; Paini, M

    2003-01-01

    We propose a tomographic reconstruction scheme for spin states. The experimental set-up, which is a modification of the Stern-Gerlach scheme, can be easily performed with currently available technology. The method is generalized to multiparticle states, analysing the spin-1/2 case for indistinguishable particles. Some Monte Carlo numerical simulations are given to illustrate the technique

  20. Spin glasses

    CERN Document Server

    Bovier, Anton

    2007-01-01

    Spin glass theory is going through a stunning period of progress while finding exciting new applications in areas beyond theoretical physics, in particular in combinatorics and computer science. This collection of state-of-the-art review papers written by leading experts in the field covers the topic from a wide variety of angles. The topics covered are mean field spin glasses, including a pedagogical account of Talagrand's proof of the Parisi solution, short range spin glasses, emphasizing the open problem of the relevance of the mean-field theory for lattice models, and the dynamics of spin glasses, in particular the problem of ageing in mean field models. The book will serve as a concise introduction to the state of the art of spin glass theory, usefull to both graduate students and young researchers, as well as to anyone curious to know what is going on in this exciting area of mathematical physics.

  1. Spin symposium

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1989-01-15

    The recent 8th International Symposium on High Energy Spin Physics at the University of Minnesota in Minneapolis, Minnesota, opened with a bang when L. Pondrom (Wisconsin), donning a hard hat borrowed from construction workers, ventured that 'spin, the notorious inessential complication of hadronic physics, is finally telling us what real QCD (quantum chromodynamics, the field theory of quarks and gluons) looks like.' He was referring to an animated discussion on the meaning of the recent spin oriented (polarized) scattering results from the European Muon Collaboration (EMC) at CERN and reported at the Symposium by R. Garnet (Liverpool) and P. Schuler (Yale) which show that the proton spin is not simply a reflection of the spins of its constituent quarks.

  2. Edge states in quantum Hall effect in graphene

    International Nuclear Information System (INIS)

    Gusynin, V.P.; Miransky, V.A.; Sharapov, S.G.; Shovkovy, I.A.

    2008-01-01

    We review recent results concerning the spectrum of edge states in the quantum Hall effect in graphene. In particular, special attention is paid to the derivation of the conditions under which gapless edge states exist in the spectrum of graphene with 'zigzag' and 'armchair' edges. It is found that in the case of a half-plane or a ribbon with zigzag edges, there are gapless edge states only when a spin gap dominates over a Dirac mass gap. In the case of a half-plane with an armchair edge, the existence of the gapless edge states depends on the specific type of Dirac mass gaps. The implications of these results for the dynamics in the quantum Hall effect in graphene are discussed

  3. Edge morphology evolution of graphene domains during chemical vapor deposition cooling revealed through hydrogen etching.

    Science.gov (United States)

    Zhang, Haoran; Zhang, Yanhui; Zhang, Yaqian; Chen, Zhiying; Sui, Yanping; Ge, Xiaoming; Yu, Guanghui; Jin, Zhi; Liu, Xinyu

    2016-02-21

    During cooling, considerable changes such as wrinkle formation and edge passivation occur in graphene synthesized on the Cu substrate. Wrinkle formation is caused by the difference in the thermal expansion coefficients of graphene and its substrate. This work emphasizes the cooling-induced edge passivation. The graphene-edge passivation can limit the regrowth of graphene at the domain edge. Our work shows that silicon-containing particles tend to accumulate at the graphene edge, and the formation of these particles is related to cooling. Furthermore, a clear curvature can be observed at the graphene edge on the Cu substrate, indicating the sinking of the graphene edge into the Cu substrate. Both the sinking of the graphene edge and the accumulation of silicon-containing particles are responsible for edge passivation. In addition, two kinds of graphene edge morphologies are observed after etching, which were explained by different etching mechanisms that illustrate the changes of the graphene edge during cooling.

  4. Ground state analysis of magnetic nanographene molecules with modified edge

    International Nuclear Information System (INIS)

    Gorjizadeh, Narjes; Ota, Norio; Kawazoe, Yoshiyuki

    2013-01-01

    Highlights: ► Graphene molecules can become ferromagnetic by edge modifications. ► Dihydrogenation of one zigzag edge of rectangular flakes make them ferromagnetic. ► Triangular flakes become high-spin state by dehydrogenization of one zigzag edge. - Abstract: We study spin states of edge modified nanographene molecules with rectangular and triangular shapes by first principle calculations using density functional theory (DFT) and Hartree–Fock (HF) methods with Møller–Plesset (MP) correlation energy correction at different levels. Anthracene (C 14 H 10 ) and phenalenyl (C 13 H 9 ), which contain three benzene rings combined in two different ways, can be considered as fragments of a graphene sheet. Carbon-based ferromagnetic materials are of great interest both in fundamental science and technological potential in organic spintronics devices. We show that non-magnetic rectangular molecules such as C 14 H 10 can become ferromagnetic with high-spin state as the ground state by dihydrogenization of one of the zigzag edges, while triangular molecules such as C 13 H 9 become ferromagnetic with high-spin state by dehydrogenization of one of the zigzag edges

  5. Stability of edge states and edge magnetism in graphene nanoribbons

    OpenAIRE

    Kunstmann, Jens; Özdoğan, Cem; Quandt, Alexander; Fehske, Holger

    2010-01-01

    We critically discuss the stability of edge states and edge magnetism in zigzag edge graphene nanoribbons (ZGNRs). We point out that magnetic edge states might not exist in real systems, and show that there are at least three very natural mechanisms - edge reconstruction, edge passivation, and edge closure - which dramatically reduce the effect of edge states in ZGNRs or even totally eliminate them. Even if systems with magnetic edge states could be made, the intrinsic magnetism would not be ...

  6. Spin Physics at COMPASS

    International Nuclear Information System (INIS)

    Schill, Christian

    2012-01-01

    The COMPASS experiment is a fixed target experiment at the CERN SPS using muon and hadron beams for the investigation of the spin structure of the nucleon and hadron spectroscopy. The main objective of the muon physics program is the study of the spin of the nucleon in terms of its constituents, quarks and gluons. COMPASS has accumulated data during 6 years scattering polarized muons off longitudinally or transversely polarized deuteron ( 6 LiD) or proton (NH 3 ) targets. Results for the gluon polarization are obtained from longitudinal double spin cross section asymmetries using two different channels, open charm production and high transverse momentum hadron pairs, both proceeding through the photon-gluon fusion process. Also, the longitudinal spin structure functions of the proton and the deuteron were measured in parallel as well as the helicity distributions for the three lightest quark flavours. With a transversely polarized target, results were obtained with proton and deuteron targets for the Collins and Sivers asymmetries for charged hadrons as well as for identified kaons and pions. The Collins asymmetry is sensitive to the transverse spin structure of the nucleon, while the Sivers asymmetry reflects correlations between the quark transverse momentum and the nucleon spin. Recently, a new proposal for the COMPASS II experiment was accepted by the CERN SPS which includes two new topics: Exclusive reactions like DVCS and DVMP using the muon beam and a hydrogen target to study generalized parton distributions and Drell-Yan measurements using a pion beam and a polarized NH 3 target to study transverse momentum dependent distributions.

  7. Spin systems

    CERN Document Server

    Caspers, W J

    1989-01-01

    This book is about spin systems as models for magnetic materials, especially antiferromagnetic lattices. Spin-systems are well-defined models, for which, in special cases, exact properties may be derived. These special cases are for the greater part, one- dimensional and restricted in their applicability, but they may give insight into general properties that also exist in higher dimension. This work pays special attention to qualitative differences between spin lattices of different dimensions. It also replaces the traditional picture of an (ordered) antiferromagnetic state of a Heisenberg sy

  8. Nanoindentation near the edge

    Science.gov (United States)

    J.E. Jakes; C.R. Frihart; J.F. Beecher; R.J. Moon; P.J. Resto; Z.H. Melgarejo; O.M. Saurez; H. Baumgart; A.A. Elmustafa; D.S. Stone

    2009-01-01

    Whenever a nanoindent is placed near an edge, such as the free edge of the specimen or heterophase interface intersecting the surface, the elastic discontinuity associated with the edge produces artifacts in the load-depth data. Unless properly handled in the data analysis, the artifacts can produce spurious results that obscure any real trends in properties as...

  9. Spin-independent transparency of pure spin current at normal/ferromagnetic metal interface

    Science.gov (United States)

    Hao, Runrun; Zhong, Hai; Kang, Yun; Tian, Yufei; Yan, Shishen; Liu, Guolei; Han, Guangbing; Yu, Shuyun; Mei, Liangmo; Kang, Shishou

    2018-03-01

    The spin transparency at the normal/ferromagnetic metal (NM/FM) interface was studied in Pt/YIG/Cu/FM multilayers. The spin current generated by the spin Hall effect (SHE) in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect (ISHE) in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents ({{\\boldsymbol{σ }}}sc}), the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electrochemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 (Py) than that of Ni is obtained from the nonlocal voltage measurements. Project supported by the National Basic Research Program of China (Grant No. 2015CB921502), the National Natural Science Foundation of China (Grant Nos. 11474184 and 11627805), the 111 Project, China (Grant No. B13029), and the Fundamental Research Funds of Shandong University, China.

  10. 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...

  11. Spin Conference

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    The 5th International Symposium on High Energy Spin Physics met in September at Brookhaven. The symposium has evolved to include a number of diverse specialities: theory, including parity violations and proposed quantum chromodynamics (QCD) tests with polarized beams; experiment, including the large spin effects discovered in high transverse momentum elastic scattering and hyperon production, dibaryons, and magnetic moments; acceleration and storage of polarized protons and electrons; and development of polarized sources and targets

  12. Parity Anomaly and Spin Transmutation in Quantum Spin Hall Josephson Junctions.

    Science.gov (United States)

    Peng, Yang; Vinkler-Aviv, Yuval; Brouwer, Piet W; Glazman, Leonid I; von Oppen, Felix

    2016-12-23

    We study the Josephson effect in a quantum spin Hall system coupled to a localized magnetic impurity. As a consequence of the fermion parity anomaly, the spin of the combined system of impurity and spin-Hall edge alternates between half-integer and integer values when the superconducting phase difference across the junction advances by 2π. This leads to characteristic differences in the splittings of the spin multiplets by exchange coupling and single-ion anisotropy at phase differences, for which time-reversal symmetry is preserved. We discuss the resulting 8π-periodic (or Z_{4}) fractional Josephson effect in the context of recent experiments.

  13. Floquet edge states in germanene nanoribbons

    KAUST Repository

    Tahir, Muhammad

    2016-08-23

    We theoretically demonstrate versatile electronic properties of germanene monolayers under circularly, linearly, and elliptically polarized light. We show for the high frequency regime that the edge states can be controlled by tuning the amplitude of the light and by applying a static electric field. For circularly polarized light the band gap in one valley is reduced and in the other enhanced, enabling single valley edge states. For linearly polarized light spin-split states are found for both valleys, being connected by time reversal symmetry. The effects of elliptically polarized light are similar to those of circularly polarized light. The transport properties of zigzag nanoribbons in the presence of disorder confirm a nontrivial nature of the edge states under circularly and elliptically polarized light.

  14. Topological helical edge states in water waves over a topographical bottom

    KAUST Repository

    Wu, Shi qiao

    2017-11-27

    We present the discovery of topologically protected helical edge states in water wave systems, which are realized in water wave propagating over a topographical bottom whose height is modulated periodically in a two-dimensional triangular pattern. We develop an effective Hamiltonian to characterize the dispersion relation and use spin Chern numbers to classify the topology. Through full wave simulations we unambiguously demonstrate the robustness of the helical edge states which are immune to defects and disorders so that the backscattering loss is significantly reduced. A spin splitter is designed for water wave systems, where helical edge states with different spin orientations are spatially separated with each other, and potential applications are discussed.

  15. Topological helical edge states in water waves over a topographical bottom

    KAUST Repository

    Wu, Shi qiao; Wu, Ying; Mei, Jun

    2017-01-01

    We present the discovery of topologically protected helical edge states in water wave systems, which are realized in water wave propagating over a topographical bottom whose height is modulated periodically in a two-dimensional triangular pattern. We develop an effective Hamiltonian to characterize the dispersion relation and use spin Chern numbers to classify the topology. Through full wave simulations we unambiguously demonstrate the robustness of the helical edge states which are immune to defects and disorders so that the backscattering loss is significantly reduced. A spin splitter is designed for water wave systems, where helical edge states with different spin orientations are spatially separated with each other, and potential applications are discussed.

  16. Thermoelectric effects and spin injection into superconductors with exchange field

    Energy Technology Data Exchange (ETDEWEB)

    Heikkilae, Tero [Dept. Phys., Univ. Jyvaeskylae (Finland); Silaev, Mihail [O.V. Lounasmaa Lab, Aalto Univ. (Finland); Dept. Theor. Physics, KTH, Stockholm (Sweden); Virtanen, Pauli [O.V. Lounasmaa Lab, Aalto Univ. (Finland); Giazotto, Francesco [NEST CNR-INFM and SNS Pisa (Italy); Ozaeta, Asier; Bergeret, Sebastian [CFM-CSIC and DIPC, San Sebastian (Spain)

    2015-07-01

    When a thin superconducting film is exposed to a longitudinal magnetic field or is in proximity to a ferromagnet, an exchange field separating the spin bands emerges in it. For low enough exchange fields superconductivity survives, but its response to external driving is strongly modified. In my talk I will show how at linear response such systems exhibit very strong thermoelectric response with an almost ideal efficiency. For strong driving, this effect creates a spin accumulation that can only relax via thermalization, and therefore at low temperatures has a very long range. Therefore our work explains recent observations of the long-range spin accumulation in spin-split superconductors. When injecting spin from injectors with non-collinear magnetization compared to the exchange field, the spins start to rotate around the latter. I will describe how superconductivity modifies this spin Hanle effect so that the resulting nonlocal magnetoresistance depends on the details of spin relaxation, therefore allowing for probing them.

  17. Effect of quantum tunneling on spin Hall magnetoresistance.

    Science.gov (United States)

    Ok, Seulgi; Chen, Wei; Sigrist, Manfred; Manske, Dirk

    2017-02-22

    We present a formalism that simultaneously incorporates the effect of quantum tunneling and spin diffusion on the spin Hall magnetoresistance observed in normal metal/ferromagnetic insulator bilayers (such as Pt/Y 3 Fe 5 O 12 ) and normal metal/ferromagnetic metal bilayers (such as Pt/Co), in which the angle of magnetization influences the magnetoresistance of the normal metal. In the normal metal side the spin diffusion is known to affect the landscape of the spin accumulation caused by spin Hall effect and subsequently the magnetoresistance, while on the ferromagnet side the quantum tunneling effect is detrimental to the interface spin current which also affects the spin accumulation. The influence of generic material properties such as spin diffusion length, layer thickness, interface coupling, and insulating gap can be quantified in a unified manner, and experiments that reveal the quantum feature of the magnetoresistance are suggested.

  18. An edge pedestal model

    International Nuclear Information System (INIS)

    Stacev, W.M.

    2001-01-01

    A new model for calculation of the gradient scale lengths in the edge pedestal region and of the edge transport barrier width in H-mode tokamak plasmas will be described. Model problem calculations which demonstrate the promise of this model for predicting experimental pedestal properties will be discussed. The density and Prague gradient scale lengths (L) in the edge are calculated from the particle and ion and electron energy radial transport equations, making use of (presumed) known particle and energy fluxes flowing across the edge transport barrier from the core into the SOL and of edge transport coefficients. The average values of the particle and heat fluxes in the edge transport barrier are calculated in terms of the fluxes crossing into the SOL and the atomic physics reaction rates (ionisation, charge-exchange, elastic scattering, impurity radiation) in the edge by integrating the respective transport equations from the pedestal to the separatrix. An important implication of this model is that the pedestal gradient scale lengths depend not just on local pedestal platers properties but also on particle and energy fluxes from the core plasma and on recycling neutral fluxes that penetrate into the plasma edge, both of which in turn depend on the pedestal properties. The MHD edge pressure gradient constraint α≤ α C is used to determine the pressure width of the edge transport barrier, Δ TB = Δ TB (α c ). Three different models for the MHD edge pressure gradient constraint have been investigated: (1) nominal ideal ballooning mode theory, (2) ballooning mode theory taking into account the edge geometry and shear to access He second stability region; and pedestal β-limit theory when the ballooning modes are stabilised by diamagnetic effects. A series of calculations have been made for a DIII-D model problem. The calculated gradient scale lengths and edge transport barrier widths are of the magnitude of values observed experimentally, and certain trends

  19. Next generation spin torque memories

    CERN Document Server

    Kaushik, Brajesh Kumar; Kulkarni, Anant Aravind; Prajapati, Sanjay

    2017-01-01

    This book offers detailed insights into spin transfer torque (STT) based devices, circuits and memories. Starting with the basic concepts and device physics, it then addresses advanced STT applications and discusses the outlook for this cutting-edge technology. It also describes the architectures, performance parameters, fabrication, and the prospects of STT based devices. Further, moving from the device to the system perspective it presents a non-volatile computing architecture composed of STT based magneto-resistive and all-spin logic devices and demonstrates that efficient STT based magneto-resistive and all-spin logic devices can turn the dream of instant on/off non-volatile computing into reality.

  20. Spin modes

    International Nuclear Information System (INIS)

    Gaarde, C.

    1985-01-01

    An analysis of spectra of (p,n) reactions showed that they were very selective in exciting spin modes. Charge exchange reactions at intermediate energies give important new understanding of the M1-type of excitations and of the spin structure of continuum p spectra in general. In this paper, the author discusses three charge exchange reactions: (p,n); ( 3 H,t); and (d,2p) at several targets. Low-lying states and the Δ region are discussed separately. Finally, the charge exchange reaction with heavy ion beams is briefly discussed. (G.J.P./Auth.)

  1. Entanglement in 3D Kitaev spin liquids

    Science.gov (United States)

    Matern, S.; Hermanns, M.

    2018-06-01

    Quantum spin liquids are highly fascinating quantum liquids in which the spin degrees of freedom fractionalize. An interesting class of spin liquids are the exactly solvable, three-dimensional Kitaev spin liquids. Their fractionalized excitations are Majonara fermions, which may exhibit a variety of topological band structures—ranging from topologically protected Weyl semi-metals over nodal semi-metals to systems with Majorana Fermi surfaces. We study the entanglement spectrum of such Kitaev spin liquids and verify that it is closely related to the topologically protected edge spectrum. Moreover, we find that in some cases the entanglement spectrum contains even more information about the topological features than the surface spectrum, and thus provides a simple and reliable tool to probe the topology of a system.

  2. Out-of-equilibrium spin transport in mesoscopic superconductors.

    Science.gov (United States)

    Quay, C H L; Aprili, M

    2018-08-06

    The excitations in conventional superconductors, Bogoliubov quasi-particles, are spin-[Formula: see text] fermions but their charge is energy-dependent and, in fact, zero at the gap edge. Therefore, in superconductors (unlike normal metals) spin and charge degrees of freedom may be separated. In this article, we review spin injection into conventional superconductors and focus on recent experiments on mesoscopic superconductors. We show how quasi-particle spin transport and out-of-equilibrium spin-dependent superconductivity can be triggered using the Zeeman splitting of the quasi-particle density of states in thin-film superconductors with small spin-mixing scattering. Finally, we address the spin dynamics and the feedback of quasi-particle spin imbalances on the amplitude of the superconducting energy gap.This article is part of the theme issue 'Andreev bound states'. © 2018 The Author(s).

  3. Spinning worlds

    NARCIS (Netherlands)

    Schwarz, H.

    2017-01-01

    The thesis "Spinning Worlds" is about the characterisation of two types of gas-giant exoplanets: Hot Jupiters, with orbital periods of fewer than five days, and young, wide-orbit gas giants, with orbital periods as long as thousands of years. The thesis is based on near-infrared observations of 1

  4. Spin transport at high temperatures in epitaxial Heusler alloy/n-GaAs lateral spin valves

    Science.gov (United States)

    Peterson, Timothy A.; Christie, Kevin D.; Patel, Sahil J.; Crowell, Paul A.; Palmstrøm, Chris J.

    2015-03-01

    We report on electrical injection and detection of spin accumulation in ferromagnet/ n-GaAs lateral spin-valve devices, observed up to and above room temperature. The ferromagnet in these measurements is the Heusler alloy Co2FeSi, and the semiconductor channel is GaAs doped at 3 ×1016 cm-3. The spin signal is enhanced by operating the detection contact under forward bias. The enhancement originates from drift effects at low-temperatures and an increase of the detection efficiency at all temperatures. The detector bias dependence of the observed spin-valve signal is interpreted by taking into account the quantum well (QW) which forms in the degenerately doped region immediately behind the Schottky tunnel barrier. In particular, we believe the QW is responsible for the minority spin accumulation (majority spin current) under large forward bias. The spin diffusion length and lifetime are determined by measuring the separation dependence of the non-local spin valve signal in a family of devices patterned by electron beam lithography. A spin diffusion length of 700 nm and lifetime of 46 picoseconds are found at a temperature of 295 K. This work was supported by the NSF under DMR-1104951, the NSF MRSEC program and C-SPIN, a SRC STARNET center sponsored by MARCO and DARPA.

  5. String fields, higher spins and number theory

    CERN Document Server

    Polyakov, Dimitri

    2018-01-01

    The book aims to analyze and explore deep and profound relations between string field theory, higher spin gauge theories and holography the disciplines that have been on the cutting edge of theoretical high energy physics and other fields. These intriguing relations and connections involve some profound ideas in number theory, which appear to be part of a unifying language to describe these connections.

  6. Magnetism of Nanographene-Based Microporous Carbon and Its Applications: Interplay of Edge Geometry and Chemistry Details in the Edge State

    Science.gov (United States)

    Enoki, Toshiaki; Kiguchi, Manabu

    2018-03-01

    This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. Nanographenes have important edge geometry dependence in their electronic structures. In armchair edges, electron wave interference works to contribute to energetic stability. Meanwhile, zigzag edges possess an edge-localized and spin-polarized nonbonding edge state, which causes electronic, magnetic, and chemical activities. In addition to the geometry dependence, the electronic structures are seriously affected by edge chemistry details. The edge chemistry dependence together with edge geometries on the electronic structures are discussed with samples of randomly networked nanographenes (microporous activated carbon fibers) in pristine state and under high-temperature annealing. In the pristine sample with the edges oxidized in ambient atmospheric conditions, the edge state, which is otherwise unstable, can be stabilized because of the charge transfer from nanographene to terminating oxygen. Nanographene, whose edges consist of a combination of magnetic zigzag edges and nonmagnetic armchair edges, is found to be ferrimagnetic with a nonzero net magnetic moment created under the interplay between a strong intrazigzag-edge ferromagnetic interaction and intermediate-strength interzigzag-edge antiferromagnetic-ferromagnetic interaction. At heat-treatment temperatures just below the fusion start (approximately 1500 K), the edge-terminating structure is changed from oxygen-containing groups to hydrogen in the nanographene network. Additionally, hydrogen-terminated zigzag edges, which are present as the majority and chemically unstable, play a triggering role in fusion above 1500 K. The fusion start brings about an insulator-to-metal transition at TI -M˜1500 K . Local fusions taking place percolatively between nanographenes work to expand the π -bond network, eventually resulting in the development of antiferromagnetic short-range order toward spin glass in the

  7. Spin echo dynamics under an applied drift field in graphene nanoribbon superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakar, Sanjay, E-mail: sprabhakar@wlu.ca [M 2NeT Laboratory, Wilfrid Laurier University, 75 University Avenue West, Waterloo, Ontario N2L 3C5 (Canada); Melnik, Roderick [M 2NeT Laboratory, Wilfrid Laurier University, 75 University Avenue West, Waterloo, Ontario N2L 3C5 (Canada); Gregorio Millan Institute, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Bonilla, Luis L. [Gregorio Millan Institute, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Raynolds, James E. [Drinker Biddle and Reath LLP, Washington, DC 20005 (United States)

    2013-12-02

    We investigate the evolution of spin dynamics in graphene nanoribbon superlattices (GNSLs) with armchair and zigzag edges in the presence of a drift field. We determine the exact evolution operator and show that it exhibits spin echo phenomena due to rapid oscillations of the quantum states along the ribbon. The evolution of the spin polarization is accompanied by strong beating patterns. We also provide detailed analysis of the band structure of GNSLs with armchair and zigzag edges.

  8. Spin echo dynamics under an applied drift field in graphene nanoribbon superlattices

    International Nuclear Information System (INIS)

    Prabhakar, Sanjay; Melnik, Roderick; Bonilla, Luis L.; Raynolds, James E.

    2013-01-01

    We investigate the evolution of spin dynamics in graphene nanoribbon superlattices (GNSLs) with armchair and zigzag edges in the presence of a drift field. We determine the exact evolution operator and show that it exhibits spin echo phenomena due to rapid oscillations of the quantum states along the ribbon. The evolution of the spin polarization is accompanied by strong beating patterns. We also provide detailed analysis of the band structure of GNSLs with armchair and zigzag edges

  9. Current-based detection of nonlocal spin transport in graphene for spin-based logic applications

    Science.gov (United States)

    Wen, Hua; Zhu, Tiancong; Luo, Yunqiu Kelly; Amamou, Walid; Kawakami, Roland K.

    2014-05-01

    Graphene has been proposed for novel spintronic devices due to its robust and efficient spin transport properties at room temperature. Some of the most promising proposals require current-based readout for integration purposes, but the current-based detection of spin accumulation has not yet been developed. In this work, we demonstrate current-based detection of spin transport in graphene using a modified nonlocal geometry. By adding a variable shunt resistor in parallel to the nonlocal voltmeter, we are able to systematically cross over from the conventional voltage-based detection to current-based detection. As the shunt resistor is reduced, the output current from the spin accumulation increases as the shunt resistance drops below a characteristic value R*. We analyze this behavior using a one-dimensional drift-diffusion model, which accounts well for the observed behavior. These results provide the experimental and theoretical foundation for current-based detection of nonlocal spin transport.

  10. Edge effects in composites

    International Nuclear Information System (INIS)

    Guz, A.N.; Kokhanenko, Yu.V.

    1995-01-01

    In the present article we survey papers on edge effects investigated by the rigorous approach. We interpret edge effects as stressed states created in a composite as a result of zones in which the stresses exhibit a rapidly changing behavior in comparison with the slow variation of the stresses outside such zones. Here the range of the edge effect is defined as the distance from the point of its inception to the boundary of the edge zone in a given direction. The transition of the stresses to the slowly varying state is determined within prescribed error limits. The size and configuration of the edge zone depends on the tolerated error. Clearly, the main difficulty associated with the rigorous approach is finding solutions of the elasticity problems. The finite-difference approach is suggested for the approximate solution of these problems. In light of the comparative time consumption of the finite-difference approach, it is best directed at certain classes of problems rather than at particular individual problems. Not too many papers on the investigation of edge effects by the rigorous approach have been published to date. Below, following in their footsteps, we formulate edge effect problems in composites, determine classes of problems, and investigate edge effects in composite materials and structural elements using them in Cartesian (planar and three-dimensional problems) and cylindrical (axisymmetric problems) coordinate frames. We note that the division of approaches to the study of edge effects into qualitative (nonrigorous) and quantitative (rigorous) reflects the authors own point of view. Of course, other schemes of classification of the approaches to the investigation of the regions of rapidly varying states in composites are possible

  11. Edge colouring by total labellings

    DEFF Research Database (Denmark)

    Brandt, Stephan; Rautenbach, D.; Stiebitz, M.

    2010-01-01

    We introduce the concept of an edge-colouring total k-labelling. This is a labelling of the vertices and the edges of a graph G with labels 1, 2, ..., k such that the weights of the edges define a proper edge colouring of G. Here the weight of an edge is the sum of its label and the labels of its...

  12. Adobe Edge Quickstart Guide

    CERN Document Server

    Labrecque, Joseph

    2012-01-01

    Adobe Edge Quickstart Guide is a practical guide on creating engaging content for the Web with Adobe's newest HTML5 tool. By taking a chapter-by-chapter look at each major aspect of Adobe Edge, the book lets you digest the available features in small, easily understandable chunks, allowing you to start using Adobe Edge for your web design needs immediately. If you are interested in creating engaging motion and interactive compositions using web standards with professional tooling, then this book is for you. Those with a background in Flash Professional wanting to get started quickly with Adobe

  13. Spin Coherence in Semiconductor Nanostructures

    National Research Council Canada - National Science Library

    Flatte, Michael E

    2006-01-01

    ... dots, tuning of spin coherence times for electron spin, tuning of dipolar magnetic fields for nuclear spin, spontaneous spin polarization generation and new designs for spin-based teleportation and spin transistors...

  14. Adobe Edge Preview 3

    CERN Document Server

    Grover, Chris

    2011-01-01

    Want to use an Adobe tool to design animated web graphics that work on iPhone and iPad? You've come to the right book. Adobe Edge Preview 3: The Missing Manual shows you how to build HTML5 graphics using simple visual tools. No programming experience? No problem. Adobe Edge writes the underlying code for you. With this eBook, you'll be designing great-looking web elements in no time. Get to know the workspace. Learn how Adobe Edge Preview 3 performs its magic.Create and import graphics. Make drawings with Edge's tools, or use art you designed in other programs.Work with text. Build menus, lab

  15. Pavement edge treatment.

    Science.gov (United States)

    2013-01-01

    Four projects were built over two construction seasons using special devices attached to the paving machine that produces a 30 slope on the outside pavement edge instead of the near vertical drop-off common with conventional paving equipment. This ...

  16. Edge Simulation Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Krasheninnikov, Sergei I. [Univ. of California, San Diego, CA (United States); Angus, Justin [Univ. of California, San Diego, CA (United States); Lee, Wonjae [Univ. of California, San Diego, CA (United States)

    2018-01-05

    The goal of the Edge Simulation Laboratory (ESL) multi-institutional project is to advance scientific understanding of the edge plasma region of magnetic fusion devices via a coordinated effort utilizing modern computing resources, advanced algorithms, and ongoing theoretical development. The UCSD team was involved in the development of the COGENT code for kinetic studies across a magnetic separatrix. This work included a kinetic treatment of electrons and multiple ion species (impurities) and accurate collision operators.

  17. Spin diffusion in bulk GaN measured with MnAs spin injector

    KAUST Repository

    Jahangir, Shafat; Dogan, Fatih; Kum, Hyun; Manchon, Aurelien; Bhattacharya, Pallab

    2012-01-01

    Spin injection and precession in bulk wurtzite n-GaN with different doping densities are demonstrated with a ferromagnetic MnAs contact using the three-terminal Hanle measurement technique. Theoretical analysis using minimum fitting parameters indicates that the spin accumulation is primarily in the n-GaN channel rather than at the ferromagnet (FM)/semiconductor (SC) interface states. Spin relaxation in GaN is interpreted in terms of the D’yakonov-Perel mechanism, yielding a maximum spin lifetime of 44 ps and a spin diffusion length of 175 nm at room temperature. Our results indicate that epitaxial ferromagnetic MnAs is a suitable high-temperature spin injector for GaN.

  18. Spin injection and detection in lateral spin valves with hybrid interfaces

    Science.gov (United States)

    Wang, Le; Liu, Wenyu; Ying, Hao; Chen, Luchen; Lu, Zhanjie; Han, Shuo; Chen, Shanshan; Zhao, Bing; Xu, Xiaoguang; Jiang, Yong

    2018-06-01

    Spin injection and detection in lateral spin valves with hybrid interfaces comprising a Co/Ag transparent contact and a Co/MgO/Ag junction (III) are investigated at room temperature in comparison with pure Co/Ag transparent contacts (I) and Co/MgO/Ag junctions (II). The measured spin-accumulation signals of a type III device are five times higher than those for type I. The extracted spin diffusion length in Ag is 180 nm for all three types of devices. The enhancement of the spin signal of the hybrid structure is mainly attributed to the increase of the interfacial spin polarization from the Co/MgO/Ag junction.

  19. Spin diffusion in bulk GaN measured with MnAs spin injector

    KAUST Repository

    Jahangir, Shafat

    2012-07-16

    Spin injection and precession in bulk wurtzite n-GaN with different doping densities are demonstrated with a ferromagnetic MnAs contact using the three-terminal Hanle measurement technique. Theoretical analysis using minimum fitting parameters indicates that the spin accumulation is primarily in the n-GaN channel rather than at the ferromagnet (FM)/semiconductor (SC) interface states. Spin relaxation in GaN is interpreted in terms of the D’yakonov-Perel mechanism, yielding a maximum spin lifetime of 44 ps and a spin diffusion length of 175 nm at room temperature. Our results indicate that epitaxial ferromagnetic MnAs is a suitable high-temperature spin injector for GaN.

  20. Relaxation of electron–hole spins in strained graphene nanoribbons

    International Nuclear Information System (INIS)

    Prabhakar, Sanjay; Melnik, Roderick

    2015-01-01

    We investigate the influence of magnetic field originating from the electromechanical effect on the spin-flip behaviors caused by electromagnetic field radiation in the strained graphene nanoribbons (GNRs). We show that the spin splitting energy difference (≈10 meV) due to pseudospin is much larger than the spin-orbit coupling effect (Balakrishnan et al 2013 Nat. Phys. 9 284) that might provide an evidence of broken symmetry of degeneracy. The induced spin splitting energy due to ripple waves can be further enhanced with increasing values of applied tensile edge stress for potential applications in straintronic devices. In particular, we show that the enhancement in the magnitude of the ripple waves due to externally applied tensile edge stress extends the tuning of spin-flip behaviors to larger widths of GNRs. (paper)

  1. Extrinsic spin Nernst effect from first principles.

    Science.gov (United States)

    Tauber, Katarina; Gradhand, Martin; Fedorov, Dmitry V; Mertig, Ingrid

    2012-07-13

    We present an ab initio description of the thermal transport phenomenon called the spin Nernst effect. It refers to generation of a spin accumulation or a pure spin current transverse to an applied temperature gradient. This is similar to the intensively studied spin Hall effect described by intrinsic and extrinsic mechanisms due to an applied electric field. Analogously, several contributions are present for the spin Nernst effect. Here we investigate the extrinsic skew scattering mechanism which is dominant in the limit of dilute alloys. Our calculations are based on a fully relativistic Korringa-Kohn-Rostoker method and a solution of the linearized Boltzmann equation. As a first application, we consider a Cu host with Au, Ti, and Bi impurities.

  2. Antiresonance induced spin-polarized current generation

    Science.gov (United States)

    Yin, Sun; Min, Wen-Jing; Gao, Kun; Xie, Shi-Jie; Liu, De-Sheng

    2011-12-01

    According to the one-dimensional antiresonance effect (Wang X R, Wang Y and Sun Z Z 2003 Phys. Rev. B 65 193402), we propose a possible spin-polarized current generation device. Our proposed model consists of one chain and an impurity coupling to the chain. The energy level of the impurity can be occupied by an electron with a specific spin, and the electron with such a spin is blocked because of the antiresonance effect. Based on this phenomenon our model can generate the spin-polarized current flowing through the chain due to different polarization rates. On the other hand, the device can also be used to measure the generated spin accumulation. Our model is feasible with today's technology.

  3. The Edge supersonic transport

    Science.gov (United States)

    Agosta, Roxana; Bilbija, Dushan; Deutsch, Marc; Gallant, David; Rose, Don; Shreve, Gene; Smario, David; Suffredini, Brian

    1992-01-01

    As intercontinental business and tourism volumes continue their rapid expansion, the need to reduce travel times becomes increasingly acute. The Edge Supersonic Transport Aircraft is designed to meet this demand by the year 2015. With a maximum range of 5750 nm, a payload of 294 passengers and a cruising speed of M = 2.4, The Edge will cut current international flight durations in half, while maintaining competitive first class, business class, and economy class comfort levels. Moreover, this transport will render a minimal impact upon the environment, and will meet all Federal Aviation Administration Part 36, Stage III noise requirements. The cornerstone of The Edge's superior flight performance is its aerodynamically efficient, dual-configuration design incorporating variable-geometry wingtips. This arrangement combines the benefits of a high aspect ratio wing at takeoff and low cruising speeds with the high performance of an arrow-wing in supersonic cruise. And while the structural weight concerns relating to swinging wingtips are substantial, The Edge looks to ever-advancing material technologies to further increase its viability. Heeding well the lessons of the past, The Edge design holds economic feasibility as its primary focus. Therefore, in addition to its inherently superior aerodynamic performance, The Edge uses a lightweight, largely windowless configuration, relying on a synthetic vision system for outside viewing by both pilot and passengers. Additionally, a fly-by-light flight control system is incorporated to address aircraft supersonic cruise instability. The Edge will be produced at an estimated volume of 400 aircraft and will be offered to airlines in 2015 at $167 million per transport (1992 dollars).

  4. Properties on the edge: graphene edge energies, edge stresses, edge warping, and the Wulff shape of graphene flakes

    International Nuclear Information System (INIS)

    Branicio, Paulo S; Jhon, Mark H; Gan, Chee Kwan; Srolovitz, David J

    2011-01-01

    It has been shown that the broken bonds of an unreconstructed graphene edge generate compressive edge stresses leading to edge warping. Here, we investigate edge energies and edge stresses of graphene nanoribbons with arbitrary orientations from armchair to zigzag, considering both flat and warped edge shapes in the presence and absence of hydrogen. We use the second generation reactive empirical bond order potential to calculate the edge energies and stresses for clean and hydrogenated edges. Using these energies, we perform a Wulff construction to determine the equilibrium shapes of flat graphene flakes as a function of hydrogen chemical potential. While edge stresses for clean, flat edges are compressive, they become tensile if allowed to warp. Conversely, we find that edge energies change little (∼1%) with edge warping. Hydrogenation of the edges virtually eliminates both the edge energy and edge stresses. For warped edges an approximately linear relationship is found between amplitudes and wavelengths. The equilibrium shape of a graphene flake is determined by the value of the hydrogen chemical potential. For very small (and large) values of it the flakes have a nearly hexagonal (dodecagon) shape with zigzag oriented edges, while for intermediate values graphene flakes are found with complex shapes

  5. Analysis of multi-step transitions in spin crossover nanochains

    Energy Technology Data Exchange (ETDEWEB)

    Chiruta, Daniel [GEMaC, Université de Versailles Saint-Quentin-en-Yvelines, CNRS-UVSQ (UMR 8635), 78035 Versailles Cedex (France); LISV, Université de Versailles Saint-Quentin-en-Yvelines, 78140 Velizy (France); Faculty of Electrical Engineering and Computer Science, Stefan cel Mare University, Suceava 720229 (Romania); Linares, Jorge, E-mail: jorge.linares@uvsq.fr [GEMaC, Université de Versailles Saint-Quentin-en-Yvelines, CNRS-UVSQ (UMR 8635), 78035 Versailles Cedex (France); Garcia, Yann, E-mail: yann.garcia@uclouvain.be [Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Molecules, Solids and Reactivity (IMCN/MOST), Place Louis Pasteur, 1, 1348 Louvain-la-Neuve (Belgium); Dimian, Mihai [Faculty of Electrical Engineering and Computer Science, Stefan cel Mare University, Suceava 720229 (Romania); Dahoo, Pierre Richard [LATMOS, Université de Versailles-Saint-Quentin-en-Yvelines, CNRS-UPMC-UVSQ (UMR 8190), 78280 Guyancourt (France)

    2014-02-01

    The temperature driven phase transition occurring in spin crossover nanochains has been studied by an Ising-like model considering both short-range and long-range interactions. Various types of spin crossover profiles have been described in this framework, including a novel three-step transition identified in a nanosystem with eight molecules, which is modeled for the first time. A special interest has been also given to stepwise transitions accompanied by two hysteresis loops. The edge and size effects on spin crossover behavior have been investigated in order to get a deeper insight of the underlying mechanisms involved in these unusual spin transitions.

  6. Spin glasses

    International Nuclear Information System (INIS)

    Mookerjee, Abhijit

    1976-01-01

    ''Spin glasses'', are entire class of magnetic alloys of moderate dilution, in which the magnetic atoms are far enough apart to be unlike the pure metal, but close enough so that the indirect exchange energy between them (mediated by the s-d interaction between local moments and conduction electrons) dominates all other energies. Characteristic critical phenomena displayed such as freezing of spin orientation at 'Tsub(c)' and spreading of magnetic ordering, are pointed out. Anomalous behaviour, associated with these critical phenomena, as reflected in : (i) Moessbauer spectroscopy giving hyperfine splitting at Tsub(c), (ii) maxima in susceptibility and remanent magnetism, (iii) thermopower maxima and change in slope, (iv) Characteristic cusp in susceptibility and its removal by very small magnetic fields, and (v) conductivity-resistivity measurements, are discussed. Theoretical developments aimed at explaining these phenomena, in particular, the ideas from percolation and localisation theories, and the approach based on the gellations of polymers, are discussed. Finally, a new approach based on renormalisation group in disordered systems is also briefly mentioned. (K.B.)

  7. Theory of edge radiation

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, G.; Kocharyan, V.; Saldin, E.; Schneidmiller, E.; Yurkov, M.

    2008-08-15

    We formulate a complete theory of Edge Radiation based on a novel method relying on Fourier Optics techniques. Similar types of radiation like Transition UndulatorRadiation are addressed in the framework of the same formalism. Special attention is payed in discussing the validity of approximations upon which the theory is built. Our study makes consistent use of both similarity techniques and comparisons with numerical results from simulation. We discuss both near and far zone. Physical understanding of many asymptotes is discussed. Based on the solution of the field equation with a tensor Green's function technique, we also discuss an analytical model to describe the presence of a vacuum chamber. In particular, explicit calculations for a circular vacuum chamber are reported. Finally, we consider the use of Edge Radiation as a tool for electron beam diagnostics. We discuss Coherent Edge Radiation, Extraction of Edge Radiation by a mirror, and other issues becoming important at high electron energy and long radiation wavelength. Based on this work we also study the impact of Edge Radiation on XFEL setups and we discuss recent results. (orig.)

  8. Heat and spin interconversion

    International Nuclear Information System (INIS)

    Ohnuma, Yuichi; Matsuo, Mamoru; Maekawa, Sadamichi; Saitoh, Eeiji

    2017-01-01

    Spin Seebeck and spin Peltier effects, which are mutual conversion phenomena of heat and spin, are discussed on the basis of the microscopic theory. First, the spin Seebeck effect, which is the spin-current generation due to heat current, is discussed. The recent progress in research on the spin Seebeck effect are introduced. We explain the origin of the observed sign changes of the spin Seebeck effect in compensated ferromagnets. Next, the spin Peltier effect, which is the heat-current generation due to spin current, is discussed. Finally, we show that the spin Seebeck and spin Peltier effects are summarized by Onsager's reciprocal relation and derive Kelvin's relation for the spin and heat transports. (author)

  9. Entangled spins and ghost-spins

    Directory of Open Access Journals (Sweden)

    Dileep P. Jatkar

    2017-09-01

    Full Text Available We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in [20] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves, the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.

  10. Spin transport in nanowires

    OpenAIRE

    Pramanik, S.; bandyopadhyay, S.; Cahay, M.

    2003-01-01

    We study high-field spin transport of electrons in a quasi one-dimensional channel of a $GaAs$ gate controlled spin interferometer (SPINFET) using a semiclassical formalism (spin density matrix evolution coupled with Boltzmann transport equation). Spin dephasing (or depolarization) is predominantly caused by D'yakonov-Perel' relaxation associated with momentum dependent spin orbit coupling effects that arise due to bulk inversion asymmetry (Dresselhaus spin orbit coupling) and structural inve...

  11. Spin-Tunnel Investigation of a 1/20-Scale Model of the Northrop F-5E Airplane

    Science.gov (United States)

    Scher, Stanley H.; White, William L.

    1977-01-01

    An investigation has been conducted in the Langley spin tunnel to determine the spin and recovery characteristics of a 1/20-scale model of the Northrop F-5E airplane. The investigation included erect and inverted spins, a range of center-of- gravity locations and moments of inertia, symmetric and asymmetric store loadings, and a determination of the parachute size required for emergency spin recovery. The effects of increased elevator trailing-edge-up deflections, of leading-edge and trailing-edge flap deflections, and of simulating the geometry of large external stores were also determined.

  12. High Speed Edge Detection

    Science.gov (United States)

    Prokop, Norman F (Inventor)

    2016-01-01

    Analog circuits for detecting edges in pixel arrays are disclosed. A comparator may be configured to receive an all pass signal and a low pass signal for a pixel intensity in an array of pixels. A latch may be configured to receive a counter signal and a latching signal from the comparator. The comparator may be configured to send the latching signal to the latch when the all pass signal is below the low pass signal minus an offset. The latch may be configured to hold a last negative edge location when the latching signal is received from the comparator.

  13. Strong coupling between a permalloy ferromagnetic contact and helical edge channel in a narrow HgTe quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Kononov, A.; Egorov, S. V. [Russian Academy Sciences, Institute of Solid State Physics (Russian Federation); Kvon, Z. D.; Mikhailov, N. N.; Dvoretsky, S. A. [Institute of Semiconductor Physics (Russian Federation); Deviatov, E. V., E-mail: dev@issp.ac.ru [Russian Academy Sciences, Institute of Solid State Physics (Russian Federation)

    2016-11-15

    We experimentally investigate spin-polarized electron transport between a permalloy ferromagnet and the edge of a two-dimensional electron system with band inversion, realized in a narrow, 8 nm wide, HgTe quantum well. In zero magnetic field, we observe strong asymmetry of the edge potential distribution with respect to the ferromagnetic ground lead. This result indicates that the helical edge channel, specific for the structures with band inversion even at the conductive bulk, is strongly coupled to the ferromagnetic side contact, possibly due to the effects of proximity magnetization. This allows selective and spin-sensitive contacting of helical edge states.

  14. Spin splitting generated in a Y-shaped semiconductor nanostructure with a quantum point contact

    International Nuclear Information System (INIS)

    Wójcik, P.; Adamowski, J.; Wołoszyn, M.; Spisak, B. J.

    2015-01-01

    We have studied the spin splitting of the current in the Y-shaped semiconductor nanostructure with a quantum point contact (QPC) in a perpendicular magnetic field. Our calculations show that the appropriate tuning of the QPC potential and the external magnetic field leads to an almost perfect separation of the spin-polarized currents: electrons with opposite spins flow out through different output branches. The spin splitting results from the joint effect of the QPC, the spin Zeeman splitting, and the electron transport through the edge states formed in the nanowire at the sufficiently high magnetic field. The Y-shaped nanostructure can be used to split the unpolarized current into two spin currents with opposite spins as well as to detect the flow of the spin current. We have found that the separation of the spin currents is only slightly affected by the Rashba spin-orbit coupling. The spin-splitter device is an analogue of the optical device—the birefractive crystal that splits the unpolarized light into two beams with perpendicular polarizations. In the magnetic-field range, in which the current is carried through the edges states, the spin splitting is robust against the spin-independent scattering. This feature opens up a possibility of the application of the Y-shaped nanostructure as a non-ballistic spin-splitter device in spintronics

  15. Spin splitting generated in a Y-shaped semiconductor nanostructure with a quantum point contact

    Science.gov (United States)

    Wójcik, P.; Adamowski, J.; Wołoszyn, M.; Spisak, B. J.

    2015-07-01

    We have studied the spin splitting of the current in the Y-shaped semiconductor nanostructure with a quantum point contact (QPC) in a perpendicular magnetic field. Our calculations show that the appropriate tuning of the QPC potential and the external magnetic field leads to an almost perfect separation of the spin-polarized currents: electrons with opposite spins flow out through different output branches. The spin splitting results from the joint effect of the QPC, the spin Zeeman splitting, and the electron transport through the edge states formed in the nanowire at the sufficiently high magnetic field. The Y-shaped nanostructure can be used to split the unpolarized current into two spin currents with opposite spins as well as to detect the flow of the spin current. We have found that the separation of the spin currents is only slightly affected by the Rashba spin-orbit coupling. The spin-splitter device is an analogue of the optical device—the birefractive crystal that splits the unpolarized light into two beams with perpendicular polarizations. In the magnetic-field range, in which the current is carried through the edges states, the spin splitting is robust against the spin-independent scattering. This feature opens up a possibility of the application of the Y-shaped nanostructure as a non-ballistic spin-splitter device in spintronics.

  16. The Influence of Stellar Spin on Ignition of Thermonuclear Runaways

    DEFF Research Database (Denmark)

    Galloway, Duncan K.; In't Zand, Jean J. M.; Chenevez, Jérôme

    2018-01-01

    timescales of hours to days. We measured the burst rate as a function of accretion rate, from seven neutron stars with known spin rates, using a burst sample accumulated over several decades. At the highest accretion rates, the burst rate is lower for faster spinning stars. The observations imply that fast...

  17. Topological Magnonics: A Paradigm for Spin-Wave Manipulation and Device Design

    Science.gov (United States)

    Wang, X. S.; Zhang, H. W.; Wang, X. R.

    2018-02-01

    Conventional magnonic devices use magnetostatic waves whose properties are sensitive to device geometry and the details of magnetization structure, so the design and the scalability of the device or circuitry are difficult. We propose topological magnonics, in which topological exchange spin waves are used as information carriers, that do not suffer from conventional problems of magnonic devices with additional nice features of nanoscale wavelength and high frequency. We show that a perpendicularly magnetized ferromagnet on a honeycomb lattice is generically a topological magnetic material in the sense that topologically protected chiral edge spin waves exist in the band gap as long as a spin-orbit-induced nearest-neighbor pseudodipolar interaction (and/or a next-nearest-neighbor Dzyaloshinskii-Moriya interaction) is present. The edge spin waves propagate unidirectionally along sample edges and domain walls regardless of the system geometry and defects. As a proof of concept, spin-wave diodes, spin-wave beam splitters, and spin-wave interferometers are designed by using sample edges and domain walls to manipulate the propagation of topologically protected chiral spin waves. Since magnetic domain walls can be controlled by magnetic fields or electric current or fields, one can essentially draw, erase, and redraw different spin-wave devices and circuitry on the same magnetic plate so that the proposed devices are reconfigurable and tunable. The topological magnonics opens up an alternative direction towards a robust, reconfigurable and scalable spin-wave circuitry.

  18. The Inner Urban Edge

    Science.gov (United States)

    Ferebee, Ann; Carpenter, Edward K.

    1974-01-01

    In this article, renewal of the inner urban edge is discussed. Norfolk (Virginia) is attempting to blur the difference between old and new neighbor hoods through zoning and architectural controls. Cincinnati (Ohio) is developing an environmentally sound hillside design. Reading (Pennsylvania) is utilizing old railyards for greenbelts of hiking and…

  19. Swords with Blunt Edges

    Science.gov (United States)

    Popham, W. James

    2004-01-01

    Many U.S. educators now wonder whether they're teachers or targets. This mentality stems from the specter of their school being sanctioned for failing the state accountability tests mandated under No Child Left Behind (NCLB). According to this author, most of those tests are like blunt-edged swords: They function badly in two directions. While…

  20. Spin-orbit torque in two-dimensional antiferromagnetic topological insulators

    KAUST Repository

    Ghosh, Sumit; Manchon, Aurelien

    2017-01-01

    We investigate spin transport in two-dimensional ferromagnetic (FTI) and antiferromagnetic (AFTI) topological insulators. In the presence of an in-plane magnetization AFTI supports zero energy modes, which enables topologically protected edge conduction at low energy. We address the nature of current-driven spin torque in these structures and study the impact of spin-independent disorder. Interestingly, upon strong disorder the spin torque develops an antidamping component (i.e., even upon magnetization reversal) along the edges, which could enable current-driven manipulation of the antiferromagnetic order parameter. This antidamping torque decreases when increasing the system size and when the system enters the trivial insulator regime.

  1. Spin-orbit torque in two-dimensional antiferromagnetic topological insulators

    KAUST Repository

    Ghosh, Sumit

    2017-01-24

    We investigate spin transport in two-dimensional ferromagnetic (FTI) and antiferromagnetic (AFTI) topological insulators. In the presence of an in-plane magnetization AFTI supports zero energy modes, which enables topologically protected edge conduction at low energy. We address the nature of current-driven spin torque in these structures and study the impact of spin-independent disorder. Interestingly, upon strong disorder the spin torque develops an antidamping component (i.e., even upon magnetization reversal) along the edges, which could enable current-driven manipulation of the antiferromagnetic order parameter. This antidamping torque decreases when increasing the system size and when the system enters the trivial insulator regime.

  2. Magnetic Nanostructures Spin Dynamics and Spin Transport

    CERN Document Server

    Farle, Michael

    2013-01-01

    Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.

  3. Nonreciprocity of edge modes in 1D magnonic crystal

    International Nuclear Information System (INIS)

    Lisenkov, I.; Kalyabin, D.; Osokin, S.; Klos, J.W.; Krawczyk, M.; Nikitov, S.

    2015-01-01

    Spin waves propagation in 1D magnonic crystals is investigated theoretically. Mathematical model based on plane wave expansion method is applied to different types of magnonic crystals, namely bi-component magnonic crystal with symmetric/asymmetric boundaries and ferromagnetic film with periodically corrugated top surface. It is shown that edge modes in magnonic crystals may exhibit nonreciprocal behaviour at much lower frequencies than in homogeneous films. - Highlights: • Magnetostatic surface spin waves in 1D magnonic crystals were studied theoretically. • Mathematical model is based on plane wave method. • Mathematical model was applied to different types of magnonic crystals. • Stop band formation and nonreciprocity were obtained

  4. Structural, electronic and magnetic properties of transition-metal embedded zigzag-edged graphene nanoribbons

    International Nuclear Information System (INIS)

    Yu Guodong; Lü Xiaoling; Jiang Liwei; Gao Wenzhu; Zheng Yisong

    2013-01-01

    By means of ab initio calculations within density-functional theory, the structural, electronic and magnetic properties of a zigzag-edged graphene nanoribbon (ZGNR) with 3d transition-metal atoms (TMAs) (Sc–Zn) embedded in the periodically distributed single vacancies are systematically studied. Different from the pristine ZGNR, all of these composite structures show the subband structures with nontrivial spin polarizations, regardless of the type and the embedding position of the TMA. Embedding one kind of these atoms (V, Cr, Ni, Cu or Zn) near one ribbon edge can cause a notable edge distortion. Except for the cases of Sc, Fe and Co doping, other kinds of TMAs embedded near an edge of the ribbon can suppress the inherent magnetism of the zigzag edge. By further analysis, we find that two effects are responsible for the suppression of edge magnetism. One is the variation of the occupied spin-polarized subbands due to the hybridization of the edge state of the ZGNR and 3d atomic states of the dopant. The other is the delocalization of the edge state caused by the exotic TMA. The unilateral magnetism of these TMA-embedded ZGNRs can be utilized to realize the spin-polarized electronic transport, which is the key electronic property in the context of spintronics applications of carbon-based materials. (paper)

  5. Enhancement of spin polarization induced by Coulomb on-site repulsion between localized pz electrons in graphene embedded with line defects.

    Science.gov (United States)

    Ren, Ji-Chang; Wang, Zhigang; Zhang, Rui-Qin; Ding, Zejun; Van Hove, Michel A

    2015-11-11

    It is well known that the effect of Coulomb on-site repulsion can significantly alter the physical properties of the systems that contain localized d and/or f electrons. However, little attention has been paid to the Coulomb on-site repulsion between localized p electrons. In this study, we demonstrated that Coulomb on-site repulsion between localized pz electrons also plays an important role in graphene embedded with line defects. It is shown that the magnetism of the system largely depends on the choice of the effective Coulomb on-site parameter Ueff. Ueff at the edges of the defect enhances the exchange splitting, which increases the magnetic moment and stabilizes a ferromagnetic state of the system. In contrast, Ueff at the center of the defect weakens the spin polarization of the system. The behavior of the magnetism is explained with the Stoner criterion and the charge accumulation at the edges of the defect. Based on the linear response approach, we estimate reasonable values of Ueff to be 2.55 eV (2.3 eV) at the center (edges) of the defects. More importantly, using a DFT+U+J method, we find that exchange interactions between localized p electrons also play an important role in the spin polarization of the system. These results imply that Coulomb on-site repulsion is necessary to describe the strong interaction between localized pz electrons of carbon related materials.

  6. Realizing stable fully spin polarized transport in SiC nanoribbons with dopant

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Xixi; Wang, Xianlong; Zheng, Xiaohong, E-mail: xhzheng@theory.issp.ac.cn; Zeng, Zhi [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Hao, Hua [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2016-06-06

    Intrinsic half-metallicity recently reported in zigzag edged SiC nanoribbons is basically undetectable due to negligible energy difference between the antiferromagnetic (AFM) and ferromagnetic (FM) configurations. In this Letter, by density functional theory calculations, we demonstrate a scheme of N doping at the carbon edge to selectively close the edge state channel at this edge and achieve 100% spin filtering, no matter whether it is in an AFM state or FM state. This turns SiC nanoribbon into a promising material for obtaining stable and completely spin polarized transport and may find application in spintronic devices.

  7. 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 ...

  8. Physics and application of persistent spin helix state in semiconductor heterostructures

    Science.gov (United States)

    Kohda, Makoto; Salis, Gian

    2017-07-01

    In order to utilize the spin degree of freedom in semiconductors, control of spin states and transfer of the spin information are fundamental requirements for future spintronic devices and quantum computing. Spin orbit (SO) interaction generates an effective magnetic field for moving electrons and enables spin generation, spin manipulation and spin detection without using external magnetic field and magnetic materials. However, spin relaxation also takes place due to a momentum dependent SO-induced effective magnetic field. As a result, SO interaction is considered to be a double-edged sword facilitating spin control but preventing spin transport over long distances. The persistent spin helix (PSH) state solves this problem since uniaxial alignment of the SO field with SU(2) symmetry enables the suppression of spin relaxation while spin precession can still be controlled. Consequently, understanding the PSH becomes an important step towards future spintronic technologies for classical and quantum applications. Here, we review recent progress of PSH in semiconductor heterostructures and its device application. Fundamental physics of SO interaction and the conditions of a PSH state in semiconductor heterostructures are discussed. We introduce experimental techniques to observe a PSH and explain both optical and electrical measurements for detecting a long spin relaxation time and the formation of a helical spin texture. After emphasizing the bulk Dresselhaus SO coefficient γ, the application of PSH states for spin transistors and logic circuits are discussed.

  9. ICRF edge modeling

    International Nuclear Information System (INIS)

    1991-01-01

    This report describes the technical progress for the DOE sponsored grant, ''ICRF Edge Modeling.'' An emphasis is placed on the progress since the Technical Progress Report (January 10, 1990) was submitted to the Department of Energy. The design of ICRF antennas for C-Mod and TFTR was investigated during this period. In addition, quasilinear models for electron heating were refined and applied to the design of ICRF antennas. The relevant professional activities sponsored by this grant are given. 4 refs., 11 figs

  10. ICRF edge modeling studies

    Energy Technology Data Exchange (ETDEWEB)

    Lehrman, I.S. (Grumman Corp. Research Center, Princeton, NJ (USA)); Colestock, P.L. (Princeton Univ., NJ (USA). Plasma Physics Lab.)

    1990-04-01

    Theoretical models have been developed, and are currently being refined, to explain the edge plasma-antenna interaction that occurs during ICRF heating. The periodic structure of a Faraday shielded antenna is found to result in strong ponderomotive force in the vicinity of the antenna. A fluid model, which incorporates the ponderomotive force, shows an increase in transport to the Faraday shield. A kinetic model shows that the strong antenna near fields act to increase the energy of deuterons which strike the shield, thereby increasing the sputtering of shield material. Estimates of edge impurity harmonic heating show no significant heating for either in or out-of-phase antenna operation. Additionally, a particle model for electrons near the shield shows that heating results from the parallel electric field associated with the fast wave. A quasilinear model for edge electron heating is presented and compared to the particle calculations. The models' predictions are shown to be consistent with measurements of enhanced transport. (orig.).

  11. Spin-polarized spin excitation spectroscopy

    International Nuclear Information System (INIS)

    Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J

    2010-01-01

    We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu 2 N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.

  12. Spin-polarized transport properties of Fe atomic chain adsorbed on zigzag graphene nanoribbons

    International Nuclear Information System (INIS)

    Zhang, Z L; Chen, Y P; Xie, Y E; Zhang, M; Zhong, J X

    2011-01-01

    The spin-polarized transport properties of Fe atomic chain adsorbed on zigzag graphene nanoribbons (ZGNRs) are investigated using the density-functional theory in combination with the nonequilibrium Green's function method. We find that the Fe chain has drastic effects on spin-polarized transport properties of ZGNRs compared with a single Fe atom adsorbed on the ZGNRs. When the Fe chain is adsorbed on the centre of the ZGNR, the original semiconductor transforms into metal, showing a very wide range of spin-polarized transport. Particularly, the spin polarization around the Fermi level is up to 100%. This is because the adsorbed Fe chain not only induces many localized states but also has effects on the edge states of ZGNR, which can effectively modulate the spin-polarized transports. The spin polarization of ZGNRs is sensitive to the adsorption site of the Fe chain. When the Fe chain is adsorbed on the edge of ZGNR, the spin degeneracy of conductance is completely broken. The spin polarization is found to be more pronounced because the edge state of one edge is destroyed by the additional Fe chain. These results have direct implications for the control of the spin-dependent conductance in ZGNRs with the adsorption of Fe chains.

  13. Magnon Spin Nernst Effect in Antiferromagnets

    Science.gov (United States)

    Zyuzin, Vladimir A.; Kovalev, Alexey A.

    2016-11-01

    We predict that a temperature gradient can induce a magnon-mediated spin Hall response in an antiferromagnet with nontrivial magnon Berry curvature. We develop a linear response theory which gives a general condition for a Hall current to be well defined, even when the thermal Hall response is forbidden by symmetry. We apply our theory to a honeycomb lattice antiferromagnet and discuss a role of magnon edge states in a finite geometry.

  14. Magnon Spin Nernst Effect in Antiferromagnets.

    Science.gov (United States)

    Zyuzin, Vladimir A; Kovalev, Alexey A

    2016-11-18

    We predict that a temperature gradient can induce a magnon-mediated spin Hall response in an antiferromagnet with nontrivial magnon Berry curvature. We develop a linear response theory which gives a general condition for a Hall current to be well defined, even when the thermal Hall response is forbidden by symmetry. We apply our theory to a honeycomb lattice antiferromagnet and discuss a role of magnon edge states in a finite geometry.

  15. Magnon edge states in the hardcore- Bose-Hubbard model.

    Science.gov (United States)

    Owerre, S A

    2016-11-02

    Quantum Monte Carlo (QMC) simulation has uncovered nonzero Berry curvature and bosonic edge states in the hardcore-Bose-Hubbard model on the gapped honeycomb lattice. The competition between the chemical potential and staggered onsite potential leads to an interesting quantum phase diagram comprising the superfluid phase, Mott insulator, and charge density wave insulator. In this paper, we present a semiclassical perspective of this system by mapping to a spin-1/2 quantum XY model. We give an explicit analytical origin of the quantum phase diagram, the Berry curvatures, and the edge states using semiclassical approximations. We find very good agreement between the semiclassical analyses and the QMC results. Our results show that the topological properties of the hardcore-Bose-Hubbard model are the same as those of magnon in the corresponding quantum spin system. Our results are applicable to systems of ultracold bosonic atoms trapped in honeycomb optical lattices.

  16. Smoothness in Binomial Edge Ideals

    Directory of Open Access Journals (Sweden)

    Hamid Damadi

    2016-06-01

    Full Text Available In this paper we study some geometric properties of the algebraic set associated to the binomial edge ideal of a graph. We study the singularity and smoothness of the algebraic set associated to the binomial edge ideal of a graph. Some of these algebraic sets are irreducible and some of them are reducible. If every irreducible component of the algebraic set is smooth we call the graph an edge smooth graph, otherwise it is called an edge singular graph. We show that complete graphs are edge smooth and introduce two conditions such that the graph G is edge singular if and only if it satisfies these conditions. Then, it is shown that cycles and most of trees are edge singular. In addition, it is proved that complete bipartite graphs are edge smooth.

  17. Spin Glass Models of Syntax and Language Evolution

    OpenAIRE

    Siva, Karthik; Tao, Jim; Marcolli, Matilde

    2015-01-01

    Using the SSWL database of syntactic parameters of world languages, and the MIT Media Lab data on language interactions, we construct a spin glass model of language evolution. We treat binary syntactic parameters as spin states, with languages as vertices of a graph, and assigned interaction energies along the edges. We study a rough model of syntax evolution, under the assumption that a strong interaction energy tends to cause parameters to align, as in the case of ferromagnetic materials. W...

  18. Advanced accumulator for PWR

    International Nuclear Information System (INIS)

    Ichimura, Taiki; Chikahata, Hideyuki

    1997-01-01

    Advanced accumulators have been incorporated into the APWR design in order to simplify the safety system configuration and to improve reliability. The advanced accumulators refill the reactor vessel with a large discharge flow rate in a large LOCA, then switch to a small flow rate to continue safety injection for core reflooding. The functions of the conventional accumulator and the low head safety injection pump are integrated into this advanced accumulator. Injection performance tests simulating LOCA conditions and visualization tests for new designs have been carried out. This paper describes the APWR ECCS configuration, the advanced accumulator design and some of the injection performance and visualization test results. It was verified that the flow resistance of the advanced accumulator is independent of the model scale. The similarity law and performance data of the advanced accumulator for applying APWR was established. (author)

  19. Spin nematics next to spin singlets

    Science.gov (United States)

    Yokoyama, Yuto; Hotta, Chisa

    2018-05-01

    We provide a route to generate nematic order in a spin-1/2 system. Unlike the well-known magnon-binding mechanism, our spin nematics requires neither the frustration effect nor spin polarization in a high field or in the vicinity of a ferromagnet, but instead appears next to the spin singlet phase. We start from a state consisting of a quantum spin-1/2 singlet dimer placed on each site of a triangular lattice, and show that interdimer ring exchange interactions efficiently dope the SU(2) triplets that itinerate and interact, easily driving a stable singlet state to either Bose-Einstein condensates or a triplet crystal, some hosting a spin nematic order. A variety of roles the ring exchange serves includes the generation of a bilinear-biquadratic interaction between nearby triplets, which is responsible for the emergent nematic order separated from the singlet phase by a first-order transition.

  20. Role of helical edge modes in the chiral quantum anomalous Hall state.

    Science.gov (United States)

    Mani, Arjun; Benjamin, Colin

    2018-01-22

    Although indications are that a single chiral quantum anomalous Hall(QAH) edge mode might have been experimentally detected. There have been very many recent experiments which conjecture that a chiral QAH edge mode always materializes along with a pair of quasi-helical quantum spin Hall (QSH) edge modes. In this work we deal with a substantial 'What If?' question- in case the QSH edge modes, from which these QAH edge modes evolve, are not topologically-protected then the QAH edge modes wont be topologically-protected too and thus unfit for use in any applications. Further, as a corollary one can also ask if the topological-protection of QSH edge modes does not carry over during the evolution process to QAH edge modes then again our 'What if?' scenario becomes apparent. The 'how' of the resolution of this 'What if?' conundrum is the main objective of our work. We show in similar set-ups affected by disorder and inelastic scattering, transport via trivial QAH edge mode leads to quantization of Hall resistance and not that via topological QAH edge modes. This perhaps begs a substantial reinterpretation of those experiments which purported to find signatures of chiral(topological) QAH edge modes albeit in conjunction with quasi helical QSH edge modes.

  1. Tunable electronic properties of partially edge-hydrogenated armchair boron-nitrogen-carbon nanoribbons.

    Science.gov (United States)

    Alaal, Naresh; Medhekar, Nikhil; Shukla, Alok

    2018-04-18

    We employ a first-principles calculations based density-functional-theory (DFT) approach to study the electronic properties of partially and fully edge-hydrogenated armchair boron-nitrogen-carbon (BNC) nanoribbons (ABNCNRs), with widths between 0.85 nm to 2.3 nm. Due to the partial passivation of edges, the electrons, which do not participate in the bonding, form new energy states located near the Fermi-level. Because of these additional bands, some ABNCNRs exhibit metallic behavior, which is quite uncommon in armchair nanoribbons. Our calculations reveal that metallic behavior is observed for the following passivation patterns: (i) when the B atom from one edge and the N atom from another edge are unpassivated. (ii) when the N atoms from both the edges are unpassivated. (iii) when the C atom from one edge and the N atom from another edge are unpassivated. Furthermore, spin-polarization is also observed for certain passivation schemes, which is also quite uncommon for armchair nanoribbons. Thus, our results suggest that the ABNCNRs exhibit a wide range of electronic and magnetic properties in that the fully edge-hydrogenated ABNCNRs are direct band gap semiconductors, while the partially edge-hydrogenated ones are either semiconducting, or metallic, while simultaneously exhibiting spin polarization, based on the nature of passivation. We also find that the ribbons with larger widths are more stable as compared to the narrower ones.

  2. Ash accumulation effects using bench marked 0-D model

    International Nuclear Information System (INIS)

    Hu, S.C.; Guo, J.P.; Miley, G.H.

    1990-01-01

    Ash accumulation is a key issue relative to our ability to achieve D- 3 He ARIES III burn conditions. 1-1/2-d transport simulations using the BALDUR code have been used to examine the correlation between the global ash particle confinement time and the edge exhaust (or recycling) efficiency. This provides a way to benchmark the widely used 0-D model. The burn conditions for an ARIES-III plasma with various ash edge recycling coefficients are examined

  3. Spin-Mechatronics

    Science.gov (United States)

    Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi

    2017-01-01

    We investigate the interconversion phenomena between spin and mechanical angular momentum in moving objects. In particular, the recent results on spin manipulation and spin-current generation by mechanical motion are examined. In accelerating systems, spin-dependent gauge fields emerge, which enable the conversion from mechanical angular momentum into spins. Such a spin-mechanical effect is predicted by quantum theory in a non-inertial frame. Experiments which confirm the effect, i.e., the resonance frequency shift in nuclear magnetic resonance, the stray field measurement of rotating metals, and electric voltage generation in liquid metals, are discussed.

  4. Competing edge networks

    Science.gov (United States)

    Parsons, Mark; Grindrod, Peter

    2012-06-01

    We introduce a model for a pair of nonlinear evolving networks, defined over a common set of vertices, subject to edgewise competition. Each network may grow new edges spontaneously or through triad closure. Both networks inhibit the other's growth and encourage the other's demise. These nonlinear stochastic competition equations yield to a mean field analysis resulting in a nonlinear deterministic system. There may be multiple equilibria; and bifurcations of different types are shown to occur within a reduced parameter space. This situation models competitive communication networks such as BlackBerry Messenger displacing SMS; or instant messaging displacing emails.

  5. Degenerate band edge laser

    Science.gov (United States)

    Veysi, Mehdi; Othman, Mohamed A. K.; Figotin, Alexander; Capolino, Filippo

    2018-05-01

    We propose a class of lasers based on a fourth-order exceptional point of degeneracy (EPD) referred to as the degenerate band edge (DBE). EPDs have been found in parity-time-symmetric photonic structures that require loss and/or gain; here we show that the DBE is a different kind of EPD since it occurs in periodic structures that are lossless and gainless. Because of this property, a small level of gain is sufficient to induce single-frequency lasing based on a synchronous operation of four degenerate Floquet-Bloch eigenwaves. This lasing scheme constitutes a light-matter interaction mechanism that leads also to a unique scaling law of the laser threshold with the inverse of the fifth power of the laser-cavity length. The DBE laser has the lowest lasing threshold in comparison to a regular band edge laser and to a conventional laser in cavities with the same loaded quality (Q ) factor and length. In particular, even without mirror reflectors the DBE laser exhibits a lasing threshold which is an order of magnitude lower than that of a uniform cavity laser of the same length and with very high mirror reflectivity. Importantly, this novel DBE lasing regime enforces mode selectivity and coherent single-frequency operation even for pumping rates well beyond the lasing threshold, in contrast to the multifrequency nature of conventional uniform cavity lasers.

  6. High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes.

    Science.gov (United States)

    Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

    2014-08-21

    We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 10(4). When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 10(6).

  7. Spin-polarized scanning-tunneling probe for helical Luttinger liquids.

    Science.gov (United States)

    Das, Sourin; Rao, Sumathi

    2011-06-10

    We propose a three-terminal spin-polarized STM setup for probing the helical nature of the Luttinger liquid edge state that appears in the quantum spin Hall system. We show that the three-terminal tunneling conductance depends on the angle (θ) between the magnetization direction of the tip and the local orientation of the electron spin on the edge while the two terminal conductance is independent of this angle. We demonstrate that chiral injection of an electron into the helical Luttinger liquid (when θ is zero or π) is associated with fractionalization of the spin of the injected electron in addition to the fractionalization of its charge. We also point out a spin current amplification effect induced by the spin fractionalization.

  8. Manipulating the voltage dependence of tunneling spin torques

    KAUST Repository

    Manchon, Aurelien

    2012-10-01

    Voltage-driven spin transfer torques in magnetic tunnel junctions provide an outstanding tool to design advanced spin-based devices for memory and reprogrammable logic applications. The non-linear voltage dependence of the torque has a direct impact on current-driven magnetization dynamics and on devices performances. After a brief overview of the progress made to date in the theoretical description of the spin torque in tunnel junctions, I present different ways to alter and control the bias dependence of both components of the spin torque. Engineering the junction (barrier and electrodes) structural asymmetries or controlling the spin accumulation profile in the free layer offer promising tools to design effcient spin devices.

  9. Spin in hadron physics

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    The following topics were ealt with: Hadron physics with proton and deuteron probes, physics projects with Georgian participation, spin physics with antiprotons and leptons, spin filtering experiments, ISTC projects, technical issues for FAIR. (HSI)

  10. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H B [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  11. The Extreme Spin of the Black Hole Cygnus X-1

    Science.gov (United States)

    Gou, Lijun; McClintock, Jeffrey E.; Reid, Mark J.; Orosz, Jerome A.; Steiner, James F.; Narayan, Ramesh; Xiang, Jingen; Remillard, Ronald A.; Arnaud, Keith A.; Davis, Shane W.

    2011-01-01

    Remarkably, an astronomical black hole is completely described by the two numbers that specify its mass and its spin. Knowledge of spin is crucial for understanding how, for example, black holes produce relativistic jets. Recently, it has become possible to measure the spins of black holes by focusing on the very inner region of an accreting disk of hot gas orbiting the black hole. According to General Relativity (GR), this disk is truncated at an inner radius 1 that depends only on the mass and spin of the black hole. We measure the radius of the inner edge of this disk by fitting its continuum X-ray spectrum to a fully relativistic model. Using our measurement of this radius, we deduce that the spin of Cygnus X-1 exceeds 97% of the maximum value allowed by GR.

  12. Robustness of edge states in topological quantum dots against global electric field

    Science.gov (United States)

    Qu, Jin-Xian; Zhang, Shu-Hui; Liu, Ding-Yang; Wang, Ping; Yang, Wen

    2017-07-01

    The topological insulator has attracted increasing attention as a new state of quantum matter featured by the symmetry-protected edge states. Although the qualitative robustness of the edge states against local perturbations has been well established, it is not clear how these topological edge states respond quantitatively to a global perturbation. Here, we study the response of topological edge states in a HgTe quantum dot to an external in-plane electric field—a paradigmatic global perturbation in solid-state environments. We find that the stability of the topological edge state could be larger than that of the ground bulk state by several orders of magnitudes. This robustness may be verified by standard transport measurements in the Coulomb blockage regime. Our work may pave the way towards utilizing these topological edge states as stable memory devices for charge and/or spin information and stable emitter of single terahertz photons or entangled terahertz photon pairs for quantum communication.

  13. A Beautiful Spin

    International Nuclear Information System (INIS)

    Ji Xiangdong

    2003-01-01

    Spin is a beautiful concept that plays an ever important role in modern physics. In this talk, I start with a discussion of the origin of spin, and then turn to three themes in which spin has been crucial in subatomic physics: a lab to explore physics beyond the standard model, a tool to measure physical observables that are hard to obtain otherwise, a probe to unravel nonperturbative QCD. I conclude with some remarks on a world without spin

  14. Performance Comparisons of Improved Regular Repeat Accumulate (RA and Irregular Repeat Accumulate (IRA Turbo Decoding

    Directory of Open Access Journals (Sweden)

    Ahmed Abdulkadhim Hamad

    2017-08-01

    Full Text Available In this paper, different techniques are used to improve the turbo decoding of regular repeat accumulate (RA and irregular repeat accumulate (IRA codes. The adaptive scaling of a-posteriori information produced by Soft-output Viterbi decoder (SOVA is proposed. The encoded pilots are another scheme that applied for short length RA codes. This work also suggests a simple and a fast method to generate a random interleaver having a free 4 cycle Tanner graph. Progressive edge growth algorithm (PEG is also studied and simulated to create the Tanner graphs which have a great girth.

  15. Detection of fractional solitons in quantum spin Hall systems

    Science.gov (United States)

    Fleckenstein, C.; Traverso Ziani, N.; Trauzettel, B.

    2018-03-01

    We propose two experimental setups that allow for the implementation and the detection of fractional solitons of the Goldstone-Wilczek type. The first setup is based on two magnetic barriers at the edge of a quantum spin Hall system for generating the fractional soliton. If then a quantum point contact is created with the other edge, the linear conductance shows evidence of the fractional soliton. The second setup consists of a single magnetic barrier covering both edges and implementing a long quantum point contact. In this case, the fractional soliton can unambiguously be detected as a dip in the conductance without the need to control the magnetization of the barrier.

  16. Generating spin squeezing states and Greenberger-Horne-Zeilinger entanglement using a hybrid phonon-spin ensemble in diamond

    Science.gov (United States)

    Xia, Keyu; Twamley, Jason

    2016-11-01

    Quantum squeezing and entanglement of spins can be used to improve the sensitivity in quantum metrology. Here we propose a scheme to create collective coupling of an ensemble of spins to a mechanical vibrational mode actuated by an external magnetic field. We find an evolution time where the mechanical motion decouples from the spins, and the accumulated geometric phase yields a squeezing of 5.9 dB for 20 spins. We also show the creation of a Greenberger-Horne-Zeilinger spin state for 20 spins with a fidelity of ˜0.62 at cryogenic temperature. The numerical simulations show that the geometric-phase-based scheme is mostly immune to thermal mechanical noise.

  17. Spin at Lausanne

    International Nuclear Information System (INIS)

    Anon.

    1980-01-01

    From 25 September to 1 October, some 150 spin enthusiasts gathered in Lausanne for the 1980 International Symposium on High Energy Physics with Polarized Beams and Polarized Targets. The programme was densely packed, covering physics interests with spin as well as the accelerator and target techniques which make spin physics possible

  18. Spin-Caloritronic Batteries

    DEFF Research Database (Denmark)

    Yu, Xiao-Qin; Zhu, Zhen-Gang; Su, Gang

    2017-01-01

    The thermoelectric performance of a topological energy converter is analyzed. The H-shaped device is based on a combination of transverse topological effects involving the spin: the inverse spin Hall effect and the spin Nernst effect. The device can convert a temperature drop in one arm into an e...

  19. Spinning Eggs and Ballerinas

    Science.gov (United States)

    Cross, Rod

    2013-01-01

    Measurements are presented on the rise of a spinning egg. It was found that the spin, the angular momentum and the kinetic energy all decrease as the egg rises, unlike the case of a ballerina who can increase her spin and kinetic energy by reducing her moment of inertia. The observed effects can be explained, in part, in terms of rolling friction…

  20. Selective Population of Edge States in a 2D Topological Band System.

    Science.gov (United States)

    Galilo, Bogdan; Lee, Derek K K; Barnett, Ryan

    2015-12-11

    We consider a system of interacting spin-one atoms in a hexagonal lattice under the presence of a synthetic gauge field. Quenching the quadratic Zeeman field is shown to lead to a dynamical instability of the edge modes. This, in turn, leads to a spin current along the boundary of the system which grows exponentially fast in time following the quench. Tuning the magnitude of the quench can be used to selectively populate edge modes of different momenta. Implications of the intrinsic symmetries of the Hamiltonian on the dynamics are discussed. The results hold for atoms with both antiferromagnetic and ferromagnetic interactions.

  1. Microbial accumulation of uranium

    International Nuclear Information System (INIS)

    Zhang Wei; Dong Faqin; Dai Qunwei

    2005-01-01

    The mechanism of microbial accumulation of uranium and the effects of some factors (including pH, initial uranium concentration, pretreatment of bacteria, and so on) on microbial accumulation of uranium are discussed briefly. The research direction and application prospect are presented. (authors)

  2. Disorder effects on helical edge transport in graphene under a strong tilted magnetic field

    Science.gov (United States)

    Huang, Chunli; Cazalilla, Miguel A.

    2015-10-01

    In a recent experiment, Young et al. [Nature (London) 505, 528 (2014), 10.1038/nature12800] observed a metal to insulator transition as well as transport through helical edge states in monolayer graphene under a strong, tilted magnetic field. Under such conditions, the bulk is a magnetic insulator which can exhibit metallic conduction through helical edges. It was found that the two-terminal conductance of the helical channels deviates from the expected quantized value (=e2/h per edge, at zero temperature). Motivated by this observation, we study the effect of disorder on the conduction through the edge channels. We show that, unlike for helical edges of topological insulators in semiconducting quantum wells, a disorder Rashba spin-orbit coupling does not lead to backscattering, at least to leading order. Instead, we find that the lack of perfect antialignment of the electron spins in the helical channels to be the most likely cause for backscattering arising from scalar (i.e., spin-independent) impurities. The intrinsic spin-orbit coupling and other time-reversal symmetry-breaking and/or sublattice parity-breaking potentials also lead to (subleading) corrections to the channel conductance.

  3. Cheating on the edge.

    Directory of Open Access Journals (Sweden)

    Lee Alan Dugatkin

    2008-07-01

    Full Text Available We present the results of an individual agent-based model of antibiotic resistance in bacteria. Our model examines antibiotic resistance when two strategies exist: "producers"--who secrete a substance that breaks down antibiotics--and nonproducers ("cheats" who do not secrete, or carry the machinery associated with secretion. The model allows for populations of up to 10,000, in which bacteria are affected by their nearest neighbors, and we assume cheaters die when there are no producers in their neighborhood. Each of 10,000 slots on our grid (a torus could be occupied by a producer or a nonproducer, or could (temporarily be unoccupied. The most surprising and dramatic result we uncovered is that when producers and nonproducers coexist at equilibrium, nonproducers are almost always found on the edges of clusters of producers.

  4. Challenges in edge modeling

    International Nuclear Information System (INIS)

    Schneider, R.

    2007-01-01

    Fluid models like B2, UEDGE or EDGE2D are the working horses for scrape-off layer physics, both for design and experimental support. The concept of a numerical tokamak, aiming at a predictive code for ITER, triggers the need to re-assess the available tools and their necessary extensions. These additional physics issues will be summarized from a personal point-of-view. Depending on the specific problem, several complexity levels of scrape-off layer models will be needed. Therefore, a hierarchy of tools is necessary, which will be discussed. Furthermore, the experience existing in other scientific fields with multi-scale problems and modeling should be used. Here, the coupling of different length and time scales are in particular of interest for fusion problems. (author)

  5. Edge remap for solids

    Energy Technology Data Exchange (ETDEWEB)

    Kamm, James R.; Love, Edward; Robinson, Allen C; Young, Joseph G.; Ridzal, Denis

    2013-12-01

    We review the edge element formulation for describing the kinematics of hyperelastic solids. This approach is used to frame the problem of remapping the inverse deformation gradient for Arbitrary Lagrangian-Eulerian (ALE) simulations of solid dynamics. For hyperelastic materials, the stress state is completely determined by the deformation gradient, so remapping this quantity effectively updates the stress state of the material. A method, inspired by the constrained transport remap in electromagnetics, is reviewed, according to which the zero-curl constraint on the inverse deformation gradient is implicitly satisfied. Open issues related to the accuracy of this approach are identified. An optimization-based approach is implemented to enforce positivity of the determinant of the deformation gradient. The efficacy of this approach is illustrated with numerical examples.

  6. Playing on the edge

    DEFF Research Database (Denmark)

    Cermak-Sassenrath, Daniel

    2018-01-01

    and specific ways. For instance, gambling for money, party and drinking games, professional play and show sports, art installations, violent and military propaganda computer games, pervasive/mobile gaming, live-action role playing, festivals, performances, and games such as Ghosting and Planking. It is argued......Everything gets more interesting, challenging, or intense the closer it gets to the edge, and so does play. How edgy can play become and still be play? Based on Huizinga’s notion of play, this chapter discusses how a wide range of playful activities pushes the boundaries of play in different...... that in concert with a number of characteristics that mark an activity as play, play is essentially a subjective perspective and individual decision of the player. Huizinga calls this attitude the play spirit, which informs a player’s actions and is in turn sustained by them. Edgy digital or mobile games do...

  7. Competing edge networks

    International Nuclear Information System (INIS)

    Parsons, Mark; Grindrod, Peter

    2012-01-01

    We introduce a model for a pair of nonlinear evolving networks, defined over a common set of vertices, subject to edgewise competition. Each network may grow new edges spontaneously or through triad closure. Both networks inhibit the other's growth and encourage the other's demise. These nonlinear stochastic competition equations yield to a mean field analysis resulting in a nonlinear deterministic system. There may be multiple equilibria; and bifurcations of different types are shown to occur within a reduced parameter space. This situation models competitive communication networks such as BlackBerry Messenger displacing SMS; or instant messaging displacing emails. -- Highlights: ► A model for edgewise-competing evolving network pairs is introduced. ► Defined competition equations yield to a mean field analysis. ► Multiple equilibrium states and different bifurcation types can occur. ► The system is sensitive to sparse initial conditions and near unstable equilibriums.

  8. Spin-Driven Emergent Antiferromagnetism and Metal-Insulator Transition in Nanoscale p-Si

    Science.gov (United States)

    Lou, Paul C.; Kumar, Sandeep

    2018-04-01

    The entanglement of the charge, spin and orbital degrees of freedom can give rise to emergent behavior especially in thin films, surfaces and interfaces. Often, materials that exhibit those properties require large spin orbit coupling. We hypothesize that the emergent behavior can also occur due to spin, electron and phonon interactions in widely studied simple materials such as Si. That is, large intrinsic spin-orbit coupling is not an essential requirement for emergent behavior. The central hypothesis is that when one of the specimen dimensions is of the same order (or smaller) as the spin diffusion length, then non-equilibrium spin accumulation due to spin injection or spin-Hall effect (SHE) will lead to emergent phase transformations in the non-ferromagnetic semiconductors. In this experimental work, we report spin mediated emergent antiferromagnetism and metal insulator transition in a Pd (1 nm)/Ni81Fe19 (25 nm)/MgO (1 nm)/p-Si (~400 nm) thin film specimen. The spin-Hall effect in p-Si, observed through Rashba spin-orbit coupling mediated spin-Hall magnetoresistance behavior, is proposed to cause the spin accumulation and resulting emergent behavior. The phase transition is discovered from the diverging behavior in longitudinal third harmonic voltage, which is related to the thermal conductivity and heat capacity.

  9. Separately contacted edge states: A new spectroscopic tool for the investigation of the quantum Hall effect

    OpenAIRE

    Wuertz, A.; Wildfeuer, R.; Lorke, A.; Deviatov, E. V.; Dolgopolov, V. T.

    2001-01-01

    Using an innovative combination of a quasi-Corbino sample geometry and the cross-gate technique, we have developed a method that enables us to separately contact single edge channels in the quantum Hall regime and investigate equilibration among them. Performing 4-point resistance measurements, we directly obtain information on the energetic and geometric structure of the edge region and the equilibration-length for current transport across the Landau- as well as the spin-gap. Based on an alm...

  10. Charge and Spin Transport in Spin-orbit Coupled and Topological Systems

    KAUST Repository

    Ndiaye, Papa Birame

    2017-10-31

    thermally driven. Chapters 5 and 6 carry throughout tight-binding studies on the topological charge-spin transport in two-dimensional lattices with ferromagnetic skyrmions and 3Q magnetic structure. We use the Landauer-Buttiker formalism and evaluate the robustness of the topological signals. For the 3Q state, a spin-polarized quantum anomalous Hall state with chiral edge modes, unaffected by deformation and disorder, is reachable in zero net magnetization. We finish with concluding remarks and perspectives.

  11. Spin physics in semiconductors

    CERN Document Server

    2017-01-01

    This book offers an extensive introduction to the extremely rich and intriguing field of spin-related phenomena in semiconductors. In this second edition, all chapters have been updated to include the latest experimental and theoretical research. Furthermore, it covers the entire field: bulk semiconductors, two-dimensional semiconductor structures, quantum dots, optical and electric effects, spin-related effects, electron-nuclei spin interactions, Spin Hall effect, spin torques, etc. Thanks to its self-contained style, the book is ideally suited for graduate students and researchers new to the field.

  12. Inverse spin Hall effect by spin injection

    Science.gov (United States)

    Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.

    2007-09-01

    Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.

  13. Cutting Edge Localisation in an Edge Profile Milling Head

    NARCIS (Netherlands)

    Fernandez Robles, Laura; Azzopardi, George; Alegre, Enrique; Petkov, Nicolai

    2015-01-01

    Wear evaluation of cutting tools is a key issue for prolonging their lifetime and ensuring high quality of products. In this paper, we present a method for the effective localisation of cutting edges of inserts in digital images of an edge profile milling head. We introduce a new image data set of

  14. The impact of structural relaxation on spin polarization and magnetization reversal of individual nano structures studied by spin-polarized scanning tunneling microscopy.

    Science.gov (United States)

    Sander, Dirk; Phark, Soo-Hyon; Corbetta, Marco; Fischer, Jeison A; Oka, Hirofumi; Kirschner, Jürgen

    2014-10-01

    The application of low temperature spin-polarized scanning tunneling microscopy and spectroscopy in magnetic fields for the quantitative characterization of spin polarization, magnetization reversal and magnetic anisotropy of individual nano structures is reviewed. We find that structural relaxation, spin polarization and magnetic anisotropy vary on the nm scale near the border of a bilayer Co island on Cu(1 1 1). This relaxation is lifted by perimetric decoration with Fe. We discuss the role of spatial variations of the spin-dependent electronic properties within and at the edge of a single nano structure for its magnetic properties.

  15. Bulk electron spin polarization generated by the spin Hall current

    OpenAIRE

    Korenev, V. L.

    2005-01-01

    It is shown that the spin Hall current generates a non-equilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known equilibrium polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

  16. Bulk electron spin polarization generated by the spin Hall current

    Science.gov (United States)

    Korenev, V. L.

    2006-07-01

    It is shown that the spin Hall current generates a nonequilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known “equilibrium” polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

  17. Nonneutralized charge effects on tokamak edge magnetohydrodynamic stability

    International Nuclear Information System (INIS)

    Zheng, Linjin; Horton, W.; Miura, H.; Shi, T.H.; Wang, H.Q.

    2016-01-01

    Owing to the large ion orbits, excessive electrons can accumulate at tokamak edge. We find that the nonneutralized electrons at tokamak edge can contribute an electric compressive stress in the direction parallel to magnetic field by their mutual repulsive force. By extending the Chew–Goldburger–Low theory (Chew et al., 1956 [13]), it is shown that this newly recognized compressive stress can significantly change the plasma average magnetic well, so that a stabilization of magnetohydrodynamic modes in the pedestal can result. This linear stability regime helps to explain why in certain parameter regimes the tokamak high confinement can be rather quiet as observed experimentally.

  18. Topographic and spectroscopic characterization of electronic edge states in CVD grown graphene nanoribbons.

    Science.gov (United States)

    Pan, Minghu; Girão, E Costa; Jia, Xiaoting; Bhaviripudi, Sreekar; Li, Qing; Kong, Jing; Meunier, V; Dresselhaus, Mildred S

    2012-04-11

    We used scanning tunneling microscopy and spectroscopy (STM/S) techniques to analyze the relationships between the edge shapes and the electronic structures in as-grown chemical vapor deposition (CVD) graphene nanoribbons (GNRs). A rich variety of single-layered graphene nanoribbons exhibiting a width of several to 100 nm and up to 1 μm long were studied. High-resolution STM images highlight highly crystalline nanoribbon structures with well-defined and clean edges. Theoretical calculations indicate clear spin-split edge states induced by electron-electron Coulomb repulsion. The edge defects can significantly modify these edge states, and different edge structures for both sides of a single ribbon produce asymmetric electronic edge states, which reflect the more realistic features of CVD grown GNRs. Three structural models are proposed and analyzed to explain the observations. By comparing the models with an atomic resolution image at the edge, a pristine (2,1) structure was ruled out in favor of a reconstructed edge structure composed of 5-7 member rings, showing a better match with experimental results, and thereby suggesting the possibility of a defective morphology at the edge of CVD grown nanoribbons. © 2012 American Chemical Society

  19. Electron Spin Optical Orientation in Charged Quantum Dots

    Science.gov (United States)

    Shabaev, A.; Gershoni, D.; Korenev, V. L.

    2005-03-01

    We present a theory of nonresonant optical orientation of electron spins localized in quantum dots. This theory explains the negative circularly polarized photoluminescence of singlet trions localized in quantum dots previously observed in experiments where trion polarization changed to negative with time and where the degree of the negative polarization increased with intensity of pumping light. We have shown that this effect can be explained by the accumulation of dark excitons that occurs due to the spin blocking of the singlet trion formation - the major mechanism of dark exciton recombination. The accumulation of dark excitons results from a lack of electrons with a spin matching the exciton polarization. The electron spin lifetime is shortened by a transverse magnetic field or a temperature increase. This takes the block off the dark exciton recombination and restores the positive degree of trion polarization. The presented theory gives good agreement with experimental data.

  20. Muon spin relaxation in random spin systems

    International Nuclear Information System (INIS)

    Toshimitsu Yamazaki

    1981-01-01

    The longitudinal relaxation function Gsub(z)(t) of the positive muon can reflect dynamical characters of local field in a unique way even when the correlation time is longer than the Larmor period of local field. This method has been applied to studies of spin dynamics in spin glass systems, revealing sharp but continuous temperature dependence of the correlation time. Its principle and applications are reviewed. (author)

  1. Characterization of topological phases of dimerized Kitaev chain via edge correlation functions

    Science.gov (United States)

    Wang, Yucheng; Miao, Jian-Jian; Jin, Hui-Ke; Chen, Shu

    2017-11-01

    We study analytically topological properties of a noninteracting modified dimerized Kitaev chain and an exactly solvable interacting dimerized Kitaev chain under open boundary conditions by analyzing two introduced edge correlation functions. The interacting dimerized Kitaev chain at the symmetry point Δ =t and the chemical potential μ =0 can be exactly solved by applying two Jordan-Wigner transformations and a spin rotation, which permits us to calculate the edge correlation functions analytically. We demonstrate that the two edge correlation functions can be used to characterize the trivial, Su-Schrieffer-Heeger-like topological and topological superconductor phases of both the noninteracting and interacting systems and give their phase diagrams.

  2. Intrinsic spin polarized electronic structure of CrO2 epitaxial film revealed by bulk-sensitive spin-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

    Fujiwara, Hirokazu; Sunagawa, Masanori; Kittaka, Tomoko; Terashima, Kensei; Wakita, Takanori; Muraoka, Yuji; Yokoya, Takayoshi

    2015-01-01

    We have performed bulk-sensitive spin-resolved photoemission spectroscopy in order to clarify the intrinsic spin-resolved electronic states of half-metallic ferromagnet CrO 2 . We used CrO 2 epitaxial films on TiO 2 (100), which shows a peak at 1 eV with a clear Fermi edge, consistent with the bulk-sensitive PES spectrum for CrO 2 . In spin-resolved spectra at 40 K, while the Fermi edge was observed in the spin up (majority spin) state, no states at the Fermi level (E F ) with an energy gap of 0.5 eV below E F were observed in the spin down (minority spin) state. At 300 K, the gap in the spin down state closes. These results are consistent with resistivity measurements and magnetic hysteresis curves of the fabricated CrO 2 film, constituting spectroscopic evidence for the half-metallicity of CrO 2 at low temperature and reducing the spin polarization at room temperature. We also discuss the electron correlation effects of Cr 3d

  3. Demonstration of a robust magnonic spin wave interferometer.

    Science.gov (United States)

    Kanazawa, Naoki; Goto, Taichi; Sekiguchi, Koji; Granovsky, Alexander B; Ross, Caroline A; Takagi, Hiroyuki; Nakamura, Yuichi; Inoue, Mitsuteru

    2016-07-22

    Magnonics is an emerging field dealing with ultralow power consumption logic circuits, in which the flow of spin waves, rather than electric charges, transmits and processes information. Waves, including spin waves, excel at encoding information via their phase using interference. This enables a number of inputs to be processed in one device, which offers the promise of multi-input multi-output logic gates. To realize such an integrated device, it is essential to demonstrate spin wave interferometers using spatially isotropic spin waves with high operational stability. However, spin wave reflection at the waveguide edge has previously limited the stability of interfering waves, precluding the use of isotropic spin waves, i.e., forward volume waves. Here, a spin wave absorber is demonstrated comprising a yttrium iron garnet waveguide partially covered by gold. This device is shown experimentally to be a robust spin wave interferometer using the forward volume mode, with a large ON/OFF isolation value of 13.7 dB even in magnetic fields over 30 Oe.

  4. The susceptibilities in the spin-S Ising model

    International Nuclear Information System (INIS)

    Ainane, A.; Saber, M.

    1995-08-01

    The susceptibilities of the spin-S Ising model are evaluated using the effective field theory introduced by Tucker et al. for studying general spin-S Ising model. The susceptibilities are studied for all spin values from S = 1/2 to S = 5/2. (author). 12 refs, 4 figs

  5. Bulk magnon spin current theory for the longitudinal spin Seebeck effect

    Energy Technology Data Exchange (ETDEWEB)

    Rezende, S.M., E-mail: rezende@df.ufpe.br [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, Pernambuco (Brazil); Rodríguez-Suárez, R.L. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, Pernambuco (Brazil); Facultad de Física, Pontificia Universidad Católica de Chile, Casilla, 306 Santiago (Chile); Cunha, R.O.; López Ortiz, J.C.; Azevedo, A. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, Pernambuco (Brazil)

    2016-02-15

    The longitudinal spin Seebeck effect (LSSE) consists in the generation of a spin current parallel to a temperature gradient applied across the thickness of a bilayer made of a ferromagnetic insulator (FMI), such as yttrium iron garnet (YIG), and a metallic layer (ML) with strong spin orbit coupling, such as platinum. The LSSE is usually detected by a DC voltage generated along the ML due to the conversion of the spin current into a charge current perpendicular to the static magnetic field by means of the inverse spin Hall effect. Here we present a model for the LSSE that relies on the bulk magnon spin current created by the temperature gradient across the thickness of the FMI. We show that the spin current pumped into the metallic layer by the magnon accumulation in the FMI provides continuity of the spin current at the FMI/ML interface and is essential for the existence of the LSSE. The results of the theory are in good agreement with experimental LSSE data in YIG/Pt bilayers on the variation of the DC voltage with the sample temperature, with the FMI layer thickness and with the intensity of high magnetic fields. - Highlights: • We present a theory for the longitudinal spin Seebeck effect based on bulk magnons. • The model explains quantitatively the measured voltage in YIG/Pt created by the LSSE. • The model explains quantitatively the temperature dependence of LSSE measured in YIG/Pt. • The model agrees qualitatively with the measured dependence of LSSE with YIG thickness. • The model agrees qualitatively with the measured dependence of LSSE on magnetic field.

  6. Neutron spin quantum precession using multilayer spin splitters and a phase-spin echo interferometer

    International Nuclear Information System (INIS)

    Ebisawa, Toru; Tasaki, Seiji; Kawai, Takeshi; Hino, Masahiro; Akiyoshi, Tsunekazu; Achiwa, Norio; Otake, Yoshie; Funahashi, Haruhiko.

    1996-01-01

    Neutron spin quantum precession by multilayer spin splitter has been demonstrated using a new spin interferometer. The multilayer spin splitter consists of a magnetic multilayer mirror on top, followed by a gap layer and a non magnetic multilayer mirror which are evaporated on a silicon substrate. Using the multilayer spin splitter, a polarized neutron wave in a magnetic field perpendicular to the polarization is split into two spin eigenstates with a phase shift in the direction of the magnetic field. The spin quantum precession is equal to the phase shift, which depends on the effective thickness of the gap layer. The demonstration experiments verify the multilayer spin splitter as a neutron spin precession device as well as the coherent superposition principle of the two spin eigenstates. We have developed a new phase-spin echo interferometer using the multilayer spin splitters. We present successful performance tests of the multilayer spin splitter and the phase-spin echo interferometer. (author)

  7. Higher spin gauge theories

    CERN Document Server

    Henneaux, Marc; Vasiliev, Mikhail A

    2017-01-01

    Symmetries play a fundamental role in physics. Non-Abelian gauge symmetries are the symmetries behind theories for massless spin-1 particles, while the reparametrization symmetry is behind Einstein's gravity theory for massless spin-2 particles. In supersymmetric theories these particles can be connected also to massless fermionic particles. Does Nature stop at spin-2 or can there also be massless higher spin theories. In the past strong indications have been given that such theories do not exist. However, in recent times ways to evade those constraints have been found and higher spin gauge theories have been constructed. With the advent of the AdS/CFT duality correspondence even stronger indications have been given that higher spin gauge theories play an important role in fundamental physics. All these issues were discussed at an international workshop in Singapore in November 2015 where the leading scientists in the field participated. This volume presents an up-to-date, detailed overview of the theories i...

  8. The Nuclear Spin Nanomagnet

    OpenAIRE

    Korenev, V. L.

    2007-01-01

    Linearly polarized light tuned slightly below the optical transition of the negatively charged exciton (trion) in a single quantum dot causes the spontaneous nuclear spin polarization (self-polarization) at a level close to 100%. The effective magnetic field of spin-polarized nuclei brings the optical transition energy into resonance with photon energy. The resonantly enhanced Overhauser effect sustains the stability of the nuclear self-polarization even in the absence of spin polarization of...

  9. Conductance and spin polarization for a quantum wire with the competition of Rashba and Dresselhaus spin-orbit coupling

    International Nuclear Information System (INIS)

    Fu Xi; Chen Zeshun; Zhong Feng; Zhou Guanghui

    2010-01-01

    We investigate theoretically the spin transport of a quantum wire (QW) with weak Rashba and Dresselhaus spin-orbit coupling (SOC) nonadiabatically connected to two normal leads. Using scattering matrix method and Landauer-Buettiker formula within effective free-electron approximation, we have calculated spin-dependent conductances G ↑ and G ↓ , total conductance G and spin polarization P z for a hard-wall potential confined QW. It is demonstrated that, the SOCs induce the splitting of G ↑ and G ↓ and form spin polarization P z . Moreover, the conductances present quantized plateaus, the plateaus and P z show oscillation structures near the subband edges. Furthermore, with the increase of QW width a strong spin polarization (P z ∼1) gradually becomes weak, which can be used to realize a spin filter. When the two SOCs coexist, the total conductance presents an isotropy transport due to the Rashba and Dresselhaus Hamiltonians being fixed, and the alteration of two SOCs strength ratio changes the sign of spin polarization. This may provide a way of realizing the expression of unit information by tuning gate voltage.

  10. All-electric spin modulator based on a two-dimensional topological insulator

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Xianbo; Ai, Guoping [School of Computer Science, Jiangxi University of Traditional Chinese Medicine, Nanchang 330004 (China); Liu, Ying; Yang, Shengyuan A., E-mail: shengyuan-yang@sutd.edu.sg [Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore 487372 (Singapore); Liu, Zhengfang [School of Science, East China Jiaotong University, Nanchang 330013 (China); Zhou, Guanghui, E-mail: ghzhou@hunnu.edu.cn [Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education), and Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha 410081 (China)

    2016-01-18

    We propose and investigate a spin modulator device consisting of two ferromagnetic leads connected by a two-dimensional topological insulator as the channel material. It exploits the unique features of the topological spin-helical edge states, such that the injected carriers with a non-collinear spin-polarization direction would travel through both edges and show interference effect. The conductance of the device can be controlled in a simple and all-electric manner by a side-gate voltage, which effectively rotates the spin-polarization of the carrier. At low voltages, the rotation angle is linear in the gate voltage, and the device can function as a good spin-polarization rotator by replacing the drain electrode with a non-magnetic material.

  11. Generation and detection of spin polarization in parallel coupled double quantum dots connected to four terminals

    International Nuclear Information System (INIS)

    An, Xing-Tao; Mu, Hui-Ying; Li, Yu-Xian; Liu, Jian-Jun

    2011-01-01

    A four-terminal parallel double quantum dots (QDs) device is proposed to generate and detect the spin polarization in QDs. It is found that the spin accumulation in QDs and the spin-polarized currents in the upper and down leads can be generated when a bias voltage is applied between the left and right leads. It is more interesting that the spin polarization in the QDs can be detected using the upper and down leads. Moreover, the direction and magnitude of the spin polarization in the QDs, and in the upper and down leads can be tuned by the energy levels of QDs and the bias. -- Highlights: → The spin polarization in the quantum dots can be generated and controlled. → The spin polarization in quantum dots can be detected by the nonferromagnetic leads. → The system our studied is a discrete level spin Hall system.

  12. Possibility of Cooper-pair formation controlled by multi-terminal spin injection

    Science.gov (United States)

    Ohnishi, K.; Sakamoto, M.; Ishitaki, M.; Kimura, T.

    2018-03-01

    A multi-terminal lateral spin valve consisting of three ferromagnetic nanopillars on a Cu/Nb bilayer has been fabricated. We investigated the influence of the spin injection on the superconducting properties at the Cu/Nb interface. The non-local spin valve signal exhibits a clear spin insulation signature due to the superconducting gap of the Nb. The magnitude of the spin signal is found to show the probe configuration dependence. From the careful analysis of the bias current dependence, we found the suppression of the superconductivity due to the exchange interaction between the Cooper pair and accumulated spin plays an important role in the multi-terminal spin injections. We also discuss about the possibility of the Cooper-pair formation due to the spin injection from the two injectors with the anti-parallel alignment.

  13. Understanding and tuning the quantum-confinement effect and edge magnetism in zigzag graphene nanoribbon.

    Science.gov (United States)

    Huang, Liang Feng; Zhang, Guo Ren; Zheng, Xiao Hong; Gong, Peng Lai; Cao, Teng Fei; Zeng, Zhi

    2013-02-06

    The electronic structure of zigzag graphene nanoribbon (ZGNR) is studied using density functional theory. The mechanisms underlying the quantum-confinement effect and edge magnetism in ZGNR are systematically investigated by combining the simulated results and some useful analytic models. The quantum-confinement effect and the inter-edge superexchange interaction can be tuned by varying the ribbon width, and the spin polarization and direct exchange splitting of the edge states can be tuned by varying their electronic occupations. The two edges of ZGNR can be equally or unequally tuned by charge doping or Li adsorption, respectively. The Li adatom has a site-selective adsorption on ZGNR, and it is a nondestructive and memorable approach to effectively modify the edge states in ZGNR. These systematic understanding and effective tuning of ZGNR electronics presented in this work are helpful for further investigation and application of ZGNR and other magnetic graphene systems.

  14. A controllable spin prism

    International Nuclear Information System (INIS)

    Hakioglu, T

    2009-01-01

    Based on Khodas et al (2004 Phys. Rev. Lett. 92 086602), we propose a device acting like a controllable prism for an incident spin. The device is a large quantum well where Rashba and Dresselhaus spin-orbit interactions are present and controlled by the plunger gate potential, the electric field and the barrier height. A totally destructive interference can be manipulated externally between the Rashba and Dresselhaus couplings. The spin-dependent transmission/reflection amplitudes are calculated as the control parameters are changed. The device operates as a spin prism/converter/filter in different regimes and may stimulate research in promising directions in spintronics in analogy with linear optics.

  15. Electrical Detection of Spin-to-Charge Conversion in a Topological Insulator Bi2Te3

    Science.gov (United States)

    Li, Connie H.; van't Erve, Olaf M. J.; Li, Yaoyi; Li, Lian; Jonker, Berry T.

    Spin-momentum locking in topological insulators (TIs) dictates that an unpolarized charge current creates a net spin polarization. We recently demonstrated the first electrical detection of this spontaneous polarization in a transport geometry, using a ferromagnetic (FM) / tunnel barrier contact, where the projection of the TI surface state spin on the magnetization of detector is measured as a voltage [1]. Alternatively, if spins are injected into the TI surface state system, it is distinctively associated with a unique carrier momentum, and hence should generated a charge accumulation, similar to that of inverse spin Hall effect. Here we experimentally demonstrate both effects in the same device fabricated in Bi2Te3: the electrical detection of the spin accumulation generated by an unpolarized current flowing through the surface states, and that of the charge accumulation generated by spins injected into the surface states system. This reverse measurement is an independent confirmation of spin-momentum locking in the TI surface states, and offers additional avenue for spin manipulation. It further demonstrates the robustness and versatility of electrical access to the TI surface state spin system, an important step towards its utilization in TI-based spintronics devices. C.H. Li et al., Nat. Nanotech. 9, 218 (2014). Supported by NRL core funds and Nanoscience Institute.

  16. Topologically Massive Higher Spin Gravity

    NARCIS (Netherlands)

    Bagchi, A.; Lal, S.; Saha, A.; Sahoo, B.

    2011-01-01

    We look at the generalisation of topologically massive gravity (TMG) to higher spins, specifically spin-3. We find a special "chiral" point for the spin-three, analogous to the spin-two example, which actually coincides with the usual spin-two chiral point. But in contrast to usual TMG, there is the

  17. Nonlinear neoclassical transport in toroidal edge plasmas

    International Nuclear Information System (INIS)

    Fueloep, T.; Helander, P.

    2001-01-01

    In conventional neoclassical theory, the density and temperature gradients are not allowed to be as steep as frequently observed in the tokamak edge. In this paper the theory of neoclassical transport in a collisional, impure plasma is extended to allow for steeper profiles than normally assumed. The dynamics of highly charged impurity ions then becomes nonlinear, which affects the transport of all species. As earlier found in the banana regime, when the bulk plasma gradients are large the impurity ions undergo a poloidal redistribution, which reduces their parallel friction with the bulk ions and suppresses the neoclassical ion particle flux. The neoclassical confinement is thus improved in regions with large radial gradients. When the plasma is collisional and the gradients are large, the impurities accumulate on the inboard side of the torus

  18. The edge of space time

    International Nuclear Information System (INIS)

    Hawking, S.

    1993-01-01

    What happened at the beginning of the expansion of the universe. Did space time have an edge at the Big Bang. The answer is that, if the boundary conditions of the universe are that it has no boundary, time ceases to be well-defined in the very early universe as the direction ''north'' ceases to be well defined at the North Pole of the Earth. The quantity that we measure as time has a beginning but that does not mean spacetime has an edge, just as the surface of the Earth does not have an edge at the North Pole. 8 figs

  19. Spin-orbit and spin-lattice coupling

    International Nuclear Information System (INIS)

    Bauer, Gerrit E.W.; Ziman, Timothy; Mori, Michiyasu

    2014-01-01

    We pursued theoretical research on the coupling of electron spins in the condensed matter to the lattice as mediated by the spin-orbit interaction with special focus on the spin and anomalous Hall effects. (author)

  20. Finite size effects on the helical edge states on the Lieb lattice

    International Nuclear Information System (INIS)

    Chen Rui; Zhou Bin

    2016-01-01

    For a two-dimensional Lieb lattice, that is, a line-centered square lattice, the inclusion of the intrinsic spin–orbit (ISO) coupling opens a topologically nontrivial gap, and gives rise to the quantum spin Hall (QSH) effect characterized by two pairs of gapless helical edge states within the bulk gap. Generally, due to the finite size effect in QSH systems, the edge states on the two sides of a strip of finite width can couple together to open a gap in the spectrum. In this paper, we investigate the finite size effect of helical edge states on the Lieb lattice with ISO coupling under three different kinds of boundary conditions, i.e., the straight, bearded and asymmetry edges. The spectrum and wave function of edge modes are derived analytically for a tight-binding model on the Lieb lattice. For a strip Lieb lattice with two straight edges, the ISO coupling induces the Dirac-like bulk states to localize at the edges to become the helical edge states with the same Dirac-like spectrum. Moreover, it is found that in the case with two straight edges the gapless Dirac-like spectrum remains unchanged with decreasing the width of the strip Lieb lattice, and no gap is opened in the edge band. It is concluded that the finite size effect of QSH states is absent in the case with the straight edges. However, in the other two cases with the bearded and asymmetry edges, the energy gap induced by the finite size effect is still opened with decreasing the width of the strip. It is also proposed that the edge band dispersion can be controlled by applying an on-site potential energy on the outermost atoms. (paper)

  1. Reduction of airfoil trailing edge noise by trailing edge blowing

    International Nuclear Information System (INIS)

    Gerhard, T; Carolus, T; Erbslöh, S

    2014-01-01

    The paper deals with airfoil trailing edge noise and its reduction by trailing edge blowing. A Somers S834 airfoil section which originally was designed for small wind turbines is investigated. To mimic realistic Reynolds numbers the boundary layer is tripped on pressure and suction side. The chordwise position of the blowing slot is varied. The acoustic sources, i.e. the unsteady flow quantities in the turbulent boundary layer in the vicinity of the trailing edge, are quantified for the airfoil without and with trailing edge blowing by means of a large eddy simulation and complementary measurements. Eventually the far field airfoil noise is measured by a two-microphone filtering and correlation and a 40 microphone array technique. Both, LES-prediction and measurements showed that a suitable blowing jet on the airfoil suction side is able to reduce significantly the turbulence intensity and the induced surface pressure fluctuations in the trailing edge region. As a consequence, trailing edge noise associated with a spectral hump around 500 Hz could be reduced by 3 dB. For that a jet velocity of 50% of the free field velocity was sufficient. The most favourable slot position was at 90% chord length

  2. The effects of Rashba spin-orbit coupling on spin-polarized transport in hexagonal graphene nano-rings and flakes

    Science.gov (United States)

    Laghaei, M.; Heidari Semiromi, E.

    2018-03-01

    Quantum transport properties and spin polarization in hexagonal graphene nanostructures with zigzag edges and different sizes were investigated in the presence of Rashba spin-orbit interaction (RSOI). The nanostructure was considered as a channel to which two semi-infinite armchair graphene nanoribbons were coupled as input and output leads. Spin transmission and spin polarization in x, y, and z directions were calculated through applying Landauer-Buttiker formalism with tight binding model and the Green's function to the system. In these quantum structures it is shown that changing the size of system, induce and control the spin polarized currents. In short, these graphene systems are typical candidates for electrical spintronic devices as spin filtering.

  3. Spin Current Noise of the Spin Seebeck Effect and Spin Pumping

    Science.gov (United States)

    Matsuo, M.; Ohnuma, Y.; Kato, T.; Maekawa, S.

    2018-01-01

    We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal-metal-(NM-)ferromagnet(FM) bilayer system. Starting with a simple ferromagnet-insulator-(FI-)NM interface model with both spin-conserving and non-spin-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for a yttrium-iron-garnet-platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the non-spin-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.

  4. Plastids and Carotenoid Accumulation.

    Science.gov (United States)

    Li, Li; Yuan, Hui; Zeng, Yunliu; Xu, Qiang

    Plastids are ubiquitously present in plants and are the organelles for carotenoid biosynthesis and storage. Based on their morphology and function, plastids are classified into various types, i.e. proplastids, etioplasts, chloroplasts, amyloplasts, and chromoplasts. All plastids, except proplastids, can synthesize carotenoids. However, plastid types have a profound effect on carotenoid accumulation and stability. In this chapter, we discuss carotenoid biosynthesis and regulation in various plastids with a focus on carotenoids in chromoplasts. Plastid transition related to carotenoid biosynthesis and the different capacity of various plastids to sequester carotenoids and the associated effect on carotenoid stability are described in light of carotenoid accumulation in plants.

  5. Half metallicity in bare BC{sub 2}N nanoribbons with zigzag edges

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hong, E-mail: lihong@ncut.edu.cn [College of Mechanical and Material Engineering, North China University of Technology, Beijing 100144 (China); Xiao, Xiang; Tie, Jun [College of Mechanical and Material Engineering, North China University of Technology, Beijing 100144 (China); Lu, Jing [State Key Laboratory of Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China)

    2017-06-09

    We study the electronic and magnetic properties of bare zigzag BC{sub 2}N nanoribbons (ZBC{sub 2}NNRs) by using first principles calculations. The ZBC{sub 2}NNRs which we studied are assigned to four edge types, and we carefully examine the size effect and edge magnetic coupling orders. We find that the N edge and the C edge adjacent to N atoms have a ferromagnetic coupling, while the B edge and the C edge adjacent to B atoms have an anti-ferromagnetic coupling. These novel properties arise from the unsaturated edge with specific edge determined magnetic moment distribution. All the investigated ribbons exhibit magnetic ground states with room-temperature accessible half-metallic character, irrespective of the ribbon width. Our results suggest that ZBC{sub 2}NNRs can have potential applications in spintronics. - Highlights: • DFT study on bare zigzag BC{sub 2}N nanoribbons (ZBC{sub 2}NNRs). • All the studied bare ZBC{sub 2}NNRs are half-metals at room temperature. • The half-metal characters come from specific spin couplings on the edge atoms. • We predict bare ZBC{sub 2}NNRs as practical candidate for spintronics.

  6. Thermally induced spin-dependent current based on Zigzag Germanene Nanoribbons

    Science.gov (United States)

    Majidi, Danial; Faez, Rahim

    2017-02-01

    In this paper, using first principle calculation and non-equilibrium Green's function, the thermally induced spin current in Hydrogen terminated Zigzag-edge Germanene Nanoribbon (ZGeNR-H) is investigated. In this model, because of the difference between the source and the drain temperature of ZGeNR device, the spin up and spin down currents flow in the opposite direction with two different threshold temperatures (Tth). Hence, a pure spin polarized current which belongs to spin down is obtained. It is shown that, for temperatures above the threshold temperature spin down current increases with the increasing temperature up to 75 K and then decreases. But spin up current rises steadily and in the high temperature we can obtain polarized spin up current. In addition, we show an acceptable spin current around the room temperature for ZGeNR. The transmission peaks in ZGeNR which are closer to the Fermi level rather than Zigzag Graphene Nanoribbon (ZGNRS) which causes ZGeNR to have spin current at higher temperatures. Finally, it is indicated that by tuning the back gate voltage, the spin current can be completely modulated and polarized. Simulation results verify the Zigzag Germanene Nanoribbon as a promising candidate for spin caloritronics devices, which can be applied in future low power consumption technology.

  7. Gas lensing in a heated spinning pipe

    CSIR Research Space (South Africa)

    Mafusire, C

    2006-07-01

    Full Text Available ; and (II) the aberrations introduced to the laser are a function of the distance from the edge of the pipe, as well as the speed of the pipe spin- ning. This is because of the turbulence near the pipe wall. The speed of the pipe will be used...- merically. This work forms the basis for an extended study of the dynamics of beam propa- gation through turbulent systems, and in particular, the following aspects will be explored in future work: (I) Using the recent advances in lasers beam propagation...

  8. Low Temperature Electrical Spin Injection from Highly Spin Polarized Co₂CrAl Heusler Alloy into p-Si.

    Science.gov (United States)

    Kar, Uddipta; Panda, J; Nath, T K

    2018-06-01

    The low temperature spin accumulation in p-Si using Co2CrAl/SiO2 tunnel junction has been investigated in detail. The heterojunction has been fabricated using electron beam evaporation (EBE) technique. The 3-terminal contacts in Hanle geometry has been made for spin transport measurements. The electrical transport properties have been investigated at different isothermal conditions in the temperature range of 10-300 K. The current-voltage characteristics of the junction shows excellent rectifying magnetic diode like behaviour in lower temperature range (below 200 K). At higher temperature, the junction shows nonlinear behaviour without rectifying characteristics. We have observed spin accumulation signal in p-Si semiconductor using SiO2/Co2CrAl tunnel junction in the low temperature regime (30-100 K). Hence the highly spin polarized Full Heusler alloys compounds, like Co2CrAl etc., are very attractive and can act as efficient tunnel device for spin injection in the area of spintronics devices in near future. The estimated spin life time is τ = 54 pS and spin diffusion length inside p-Si is LSD = 289 nm at 30 K for this heterostructure.

  9. Spin-Hall effect and emergent antiferromagnetic phase transition in n-Si

    Science.gov (United States)

    Lou, Paul C.; Kumar, Sandeep

    2018-04-01

    Spin current experiences minimal dephasing and scattering in Si due to small spin-orbit coupling and spin-lattice interactions is the primary source of spin relaxation. We hypothesize that if the specimen dimension is of the same order as the spin diffusion length then spin polarization will lead to non-equilibrium spin accumulation and emergent phase transition. In n-Si, spin diffusion length has been reported up to 6 μm. The spin accumulation in Si will modify the thermal transport behavior of Si, which can be detected with thermal characterization. In this study, we report observation of spin-Hall effect and emergent antiferromagnetic phase transition behavior using magneto-electro-thermal transport characterization. The freestanding Pd (1 nm)/Ni80Fe20 (75 nm)/MgO (1 nm)/n-Si (2 μm) thin film specimen exhibits a magnetic field dependent thermal transport and spin-Hall magnetoresistance behavior attributed to Rashba effect. An emergent phase transition is discovered using self-heating 3ω method, which shows a diverging behavior at 270 K as a function of temperature similar to a second order phase transition. We propose that spin-Hall effect leads to the spin accumulation and resulting emergent antiferromagnetic phase transition. We propose that the length scale for Rashba effect can be equal to the spin diffusion length and two-dimensional electron gas is not essential for it. The emergent antiferromagnetic phase transition is attributed to the site inversion asymmetry in diamond cubic Si lattice.

  10. Effect of spin rotation coupling on spin transport

    International Nuclear Information System (INIS)

    Chowdhury, Debashree; Basu, B.

    2013-01-01

    We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k → ⋅p → perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k → ⋅p → framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied

  11. Effect of spin rotation coupling on spin transport

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, Debashree, E-mail: debashreephys@gmail.com; Basu, B., E-mail: sribbasu@gmail.com

    2013-12-15

    We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k{sup →}⋅p{sup →} perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k{sup →}⋅p{sup →} framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied.

  12. Spin temperature concept verified by optical magnetometry of nuclear spins

    Science.gov (United States)

    Vladimirova, M.; Cronenberger, S.; Scalbert, D.; Ryzhov, I. I.; Zapasskii, V. S.; Kozlov, G. G.; Lemaître, A.; Kavokin, K. V.

    2018-01-01

    We develop a method of nonperturbative optical control over adiabatic remagnetization of the nuclear spin system and apply it to verify the spin temperature concept in GaAs microcavities. The nuclear spin system is shown to exactly follow the predictions of the spin temperature theory, despite the quadrupole interaction that was earlier reported to disrupt nuclear spin thermalization. These findings open a way for the deep cooling of nuclear spins in semiconductor structures, with the prospect of realizing nuclear spin-ordered states for high-fidelity spin-photon interfaces.

  13. Diffraction at a Straight Edge

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 5. Diffraction at a Straight Edge: A Gem from Sommerfeld's Work in Classical Physics. Rajaram Nityananda. General Article Volume 20 Issue 5 May 2015 pp 389-400 ...

  14. DAVs: Red Edge and Outbursts

    Science.gov (United States)

    Luan, Jing

    2018-04-01

    As established by ground based surveys, white dwarfs with hydrogen atmospheres pulsate as they cool across the temperature range, 12500Kred edge is a two-decade old puzzle. Recently, Kepler discovered a number of cool DAVs exhibiting sporadic outbursts separated by days, each lasting several hours, and releasing \\sim 10^{33}-10^{34} {erg}. We provide quantitative explanations for both the red edge and the outbursts. The minimal frequency for overstable modes rises abruptly near the red edge. Although high frequency overstable modes exist below the red edge, their photometric amplitudes are generally too small to be detected by ground based observations. Nevertheless, these overstable parent modes can manifest themselves through nonlinear mode couplings to damped daughter modes which generate limit cycles giving rise to photometric outbursts.

  15. Edge Fracture in Complex Fluids.

    Science.gov (United States)

    Hemingway, Ewan J; Kusumaatmaja, Halim; Fielding, Suzanne M

    2017-07-14

    We study theoretically the edge fracture instability in sheared complex fluids, by means of linear stability analysis and direct nonlinear simulations. We derive an exact analytical expression for the onset of edge fracture in terms of the shear-rate derivative of the fluid's second normal stress difference, the shear-rate derivative of the shear stress, the jump in shear stress across the interface between the fluid and the outside medium (usually air), the surface tension of that interface, and the rheometer gap size. We provide a full mechanistic understanding of the edge fracture instability, carefully validated against our simulations. These findings, which are robust with respect to choice of rheological constitutive model, also suggest a possible route to mitigating edge fracture, potentially allowing experimentalists to achieve and accurately measure flows stronger than hitherto possible.

  16. Spin labels. Applications in biology

    International Nuclear Information System (INIS)

    Frangopol, T.P.; Frangopol, M.; Ionescu, S.M.; Pop, I.V.; Benga, G.

    1980-11-01

    The main applications of spin labels in the study of biomembranes, enzymes, nucleic acids, in pharmacology, spin immunoassay are reviewed along with the fundamentals of the spin label method. 137 references. (author)

  17. Spin Switching via Quantum Dot Spin Valves

    Science.gov (United States)

    Gergs, N. M.; Bender, S. A.; Duine, R. A.; Schuricht, D.

    2018-01-01

    We develop a theory for spin transport and magnetization dynamics in a quantum dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot. Our theory is able to take into account effects of strong correlations. We demonstrate that, as a result of these strong correlations, the dot gate voltage enables control over the current-induced torques on the magnets and, in particular, enables voltage-controlled magnetic switching. The electrical resistance of the structure can be used to read out the magnetic state. Our model may be realized by a number of experimental systems, including magnetic scanning-tunneling microscope tips and artificial quantum dot systems.

  18. Spin Hall magnetoresistance in Ta/CoFe2O4 nanostructures

    Science.gov (United States)

    Hui, Ya-Juan; Cheng, Wei-Ming; Zhang, Zhao-Bing; Ji, Hong-Kai; Cheng, Xiao-Min; You, Long; Miao, Xiang-Shui

    2016-07-01

    Spin Hall magnetoresistance (SMR) has been investigated in Ta/CoFe2O4 nanostructures grown on different substrates. Spin currents in CoFe2O4 films are electrically detected in adjacent Ta layers owing to inverse spin Hall effects. The sign of the magnetic-field-dependent resistivity signal shows different polarities along different axes, showing different spin-dependent electron transports. A cosinelike curve of the angular dependence signal with opposite polarity is observed in two orthogonal magnetization planes, whereas a basic line is observed in another plane, revealing the spin accumulation phenomenon. The roughness of the CoFe2O4 surface tuned by substrate strains is responsible for the extent of spin accumulations and the strength of the SMR signal in the nanostructures.

  19. Gap states and edge properties of rectangular graphene quantum dot in staggered potential

    Science.gov (United States)

    Jeong, Y. H.; Eric Yang, S.-R.

    2017-09-01

    We investigate edge properties of a gapful rectangular graphene quantum dot in a staggered potential. In such a system gap states with discrete and closely spaced energy levels exist that are spatially located on the left or right zigzag edge. We find that, although the bulk states outside the energy gap are nearly unaffected, spin degeneracy of each gap state is lifted by the staggered potential. We have computed the occupation numbers of spin-up and -down gap states at various values of the strength of the staggered potential. The electronic and magnetic properties of the zigzag edges depend sensitively on these numbers. We discuss the possibility of applying this system as a single electron spintronic device.

  20. Physics lab in spin

    CERN Multimedia

    Hawkes, N

    1999-01-01

    RAL is fostering commerical exploitation of its research and facilities in two main ways : spin-out companies exploit work done at the lab, spin-in companies work on site taking advantage of the facilities and the expertise available (1/2 page).

  1. Summary: Symmetries and spin

    International Nuclear Information System (INIS)

    Haxton, W.C.

    1988-01-01

    I discuss a number of the themes of the Symmetries and Spin session of the 8th International Symposium on High Energy Spin Physics: parity nonconservation, CP/T nonconservation, and tests of charge symmetry and charge independence. 28 refs., 1 fig

  2. Spin, mass, and symmetry

    International Nuclear Information System (INIS)

    Peskin, M.E.

    1994-01-01

    When the strong interactions were a mystery, spin seemed to be just a complication on top of an already puzzling set of phenomena. But now that particle physicists have understood the strong, weak, and electromagnetic interactions, to be gauge theories, with matter built of quarks and leptons, it is recognized that the special properties of spin 1/2 and spin 1 particles have taken central role in the understanding of Nature. The lectures in this summer school will be devoted to the use of spin in unravelling detailed questions about the fundamental interactions. Thus, why not begin by posing a deeper question: Why is there spin? More precisely, why do the basic pointlike constituents of Nature carry intrinsic nonzero quanta of angular momentum? Though the authos has found no definite answer to this question, the pursuit of an answer has led through a wonderful tangle of speculations on the deep structure of Nature. Is spin constructed or is it fundamental? Is it the requirement of symmetry? In the furthest flights taken, it seems that space-time itself is too restrictive a notion, and that this must be generalized in order to gain a full appreciation of spin. In any case, there is no doubt that spin must play a central role in unlocking the mysteries of fundamental physics

  3. Classical spins in superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, H [Tokyo Univ.; Maki, K

    1968-08-01

    It is shown that there exists a localized excited state in the energy gap in a superconductor with a classical spin. At finite concentration localized excited states around classical spins form an impurity band. The process of growth of the impurity band and its effects on observable quantities are investigated.

  4. Spin, mass, and symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Peskin, M.E. [Stanford Univ., CA (United States)

    1994-12-01

    When the strong interactions were a mystery, spin seemed to be just a complication on top of an already puzzling set of phenomena. But now that particle physicists have understood the strong, weak, and electromagnetic interactions, to be gauge theories, with matter built of quarks and leptons, it is recognized that the special properties of spin 1/2 and spin 1 particles have taken central role in the understanding of Nature. The lectures in this summer school will be devoted to the use of spin in unravelling detailed questions about the fundamental interactions. Thus, why not begin by posing a deeper question: Why is there spin? More precisely, why do the basic pointlike constituents of Nature carry intrinsic nonzero quanta of angular momentum? Though the authos has found no definite answer to this question, the pursuit of an answer has led through a wonderful tangle of speculations on the deep structure of Nature. Is spin constructed or is it fundamental? Is it the requirement of symmetry? In the furthest flights taken, it seems that space-time itself is too restrictive a notion, and that this must be generalized in order to gain a full appreciation of spin. In any case, there is no doubt that spin must play a central role in unlocking the mysteries of fundamental physics.

  5. More spinoff from spin

    International Nuclear Information System (INIS)

    Masaike, Akira

    1993-01-01

    Despite playing a major role in today's Standard Model, spin - the intrinsic angular momentum carried by particles - is sometimes dismissed as an inessential complication. However several major spin questions with important implications for the Standard Model remain unanswered, and recent results and new technological developments made the 10th International Symposium on High Energy Spin Physics, held in Nagoya, Japan, in November, highly topical. The symposium covered a wide range of physics, reflecting the diversity of spin effects, however four main themes were - the spin content of the nucleon, tests of symmetries and physics beyond standard models, intermediate energy physics, and spin technologies. Opening the meeting, T. Kinoshita reviewed the status of measurements of the anomalous magnetic moment (g-2) of the electron and the muon. The forthcoming experiment at Brookhaven (September 1991, page 23) will probe beyond the energy ranges open to existing electronpositron colliders. For example muon substructure will be opened up to 5 TeV and Ws to 2 TeV. R.L. Jaffe classified quark-parton distributions in terms of their spin dependence, pointing out their leftright attributes, and emphasized the importance of measuring transverse spin distributions through lepton pair production

  6. Accumulation by Conservation

    NARCIS (Netherlands)

    Büscher, Bram; Fletcher, Robert

    2015-01-01

    Following the financial crisis and its aftermath, it is clear that the inherent contradictions of capitalist accumulation have become even more intense and plunged the global economy into unprecedented turmoil and urgency. Governments, business leaders and other elite agents are frantically

  7. Accumulation by Conservation

    NARCIS (Netherlands)

    Büscher, Bram; Fletcher, Robert

    2014-01-01

    Following the financial crisis and its aftermath, it is clear that the inherent contradictions of capitalist accumulation have become even more intense and plunged the global economy into unprecedented turmoil and urgency. Governments, business leaders and other elite agents are frantically

  8. Creation / accumulation city

    NARCIS (Netherlands)

    Doevendans, C.H.; Schram, A.L.

    2005-01-01

    A distinction between basic archetypes of urban form was made by Bruno Fortier: the accumulation city as opposed to the creation city. These archetypes derive from archaeology - being based on the Roman and the Egyptian city - but are interpreted as morphological paradigms, as a set of assumptions

  9. Edge of polar cap patches

    Science.gov (United States)

    Hosokawa, K.; Taguchi, S.; Ogawa, Y.

    2016-04-01

    On the night of 4 December 2013, a sequence of polar cap patches was captured by an all-sky airglow imager (ASI) in Longyearbyen, Norway (78.1°N, 15.5°E). The 630.0 nm airglow images from the ASI of 4 second exposure time, oversampled the emission of natural lifetime (with quenching) of at least ˜30 sec, introduce no observational blurring effects. By using such high-quality ASI images, we succeeded in visualizing an asymmetry in the gradients between the leading/trailing edges of the patches in a 2-D fashion. The gradient in the leading edge was found to be 2-3 times steeper than that in the trailing edge. We also identified fingerlike structures, appearing only along the trailing edge of the patches, whose horizontal scale size ranged from 55 to 210 km. These fingers are considered to be manifestations of plasma structuring through the gradient-drift instability (GDI), which is known to occur only along the trailing edge of patches. That is, the current 2-D observations visualized, for the first time, how GDI stirs the patch plasma and such a mixing process makes the trailing edge more gradual. This result strongly implies a close connection between the GDI-driven plasma stirring and the asymmetry in the large-scale shape of patches and then suggests that the fingerlike structures can be used as markers to estimate the fine-scale structure in the plasma flow within patches.

  10. Spin-Wave Diode

    Directory of Open Access Journals (Sweden)

    Jin Lan (兰金

    2015-12-01

    Full Text Available A diode, a device allowing unidirectional signal transmission, is a fundamental element of logic structures, and it lies at the heart of modern information systems. The spin wave or magnon, representing a collective quasiparticle excitation of the magnetic order in magnetic materials, is a promising candidate for an information carrier for the next-generation energy-saving technologies. Here, we propose a scalable and reprogrammable pure spin-wave logic hardware architecture using domain walls and surface anisotropy stripes as waveguides on a single magnetic wafer. We demonstrate theoretically the design principle of the simplest logic component, a spin-wave diode, utilizing the chiral bound states in a magnetic domain wall with a Dzyaloshinskii-Moriya interaction, and confirm its performance through micromagnetic simulations. Our findings open a new vista for realizing different types of pure spin-wave logic components and finally achieving an energy-efficient and hardware-reprogrammable spin-wave computer.

  11. Spin physics at BNL

    International Nuclear Information System (INIS)

    Lowenstein, D.I.

    1985-01-01

    Spin Physics at the Alternating Gradient Synchrotron (AGS) of Brookhaven National Laboratory is the most recent of new capabilities being explored at this facility. During the summer of 1984 the AGS accelerated beams of polarized protons to 16.5 GeV/c at 40% polarization to two experiments (E782, E785). These experiments; single spin asymmetry in inclusive polarized pp interactions; and spin-spin effects in polarized pp elastic scattering, operated at the highest polarized proton energy ever achieved by any accelerator in the world. These experiments are reviewed after the complementary spin physics program with unpolarized protons, and the future possibilities with a booster injector for the AGS and the secondary benefits of a Relativisitic Heavy Ion Collider (RHIC), are placed within the context of the present physics program

  12. Superconductivity and spin fluctuations

    International Nuclear Information System (INIS)

    Scalapino, D.J.

    1999-01-01

    The organizers of the Memorial Session for Herman Rietschel asked that the author review some of the history of the interplay of superconductivity and spin fluctuations. Initially, Berk and Schrieffer showed how paramagnon spin fluctuations could suppress superconductivity in nearly-ferromagnetic materials. Following this, Rietschel and various co-workers wrote a number of papers in which they investigated the role of spin fluctuations in reducing the Tc of various electron-phonon superconductors. Paramagnon spin fluctuations are also believed to provide the p-wave pairing mechanism responsible for the superfluid phases of 3 He. More recently, antiferromagnetic spin fluctuations have been proposed as the mechanism for d-wave pairing in the heavy-fermion superconductors and in some organic materials as well as possibly the high-Tc cuprates. Here the author will review some of this early history and discuss some of the things he has learned more recently from numerical simulations

  13. Spin Hall and spin swapping torques in diffusive ferromagnets

    KAUST Repository

    Pauyac, C. O.

    2017-12-08

    A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precessional effects displays a complex spatial dependence that can be exploited to generate torques and nucleate/propagate domain walls in centrosymmetric geometries without use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.

  14. Spin Hall and spin swapping torques in diffusive ferromagnets

    KAUST Repository

    Pauyac, C. O.; Chshiev, M.; Manchon, Aurelien; Nikolaev, S. A.

    2017-01-01

    A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precessional effects displays a complex spatial dependence that can be exploited to generate torques and nucleate/propagate domain walls in centrosymmetric geometries without use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.

  15. Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry.

    Science.gov (United States)

    Murani, Anil; Kasumov, Alik; Sengupta, Shamashis; Kasumov, Yu A; Volkov, V T; Khodos, I I; Brisset, F; Delagrange, Raphaëlle; Chepelianskii, Alexei; Deblock, Richard; Bouchiat, Hélène; Guéron, Sophie

    2017-07-05

    The protection against backscattering provided by topology is a striking property. In two-dimensional insulators, a consequence of this topological protection is the ballistic nature of the one-dimensional helical edge states. One demonstration of ballisticity is the quantized Hall conductance. Here we provide another demonstration of ballistic transport, in the way the edge states carry a supercurrent. The system we have investigated is a micrometre-long monocrystalline bismuth nanowire with topological surfaces, that we connect to two superconducting electrodes. We have measured the relation between the Josephson current flowing through the nanowire and the superconducting phase difference at its ends, the current-phase relation. The sharp sawtooth-shaped phase-modulated current-phase relation we find demonstrates that transport occurs selectively along two ballistic edges of the nanowire. In addition, we show that a magnetic field induces 0-π transitions and ϕ 0 -junction behaviour, providing a way to manipulate the phase of the supercurrent-carrying edge states and generate spin supercurrents.

  16. Topological phases in superconductor-noncollinear magnet interfaces with strong spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Menke, H.; Schnyder, A.P. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Toews, A. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Quantum Matter Institute, University of British Columbia, Vancouver, BC (Canada)

    2016-07-01

    Majorana fermions are predicted to emerge at interfaces between conventional s-wave superconductors and non-collinear magnets. In these heterostructures, the spin moments of the non-collinear magnet induce a low-energy band of Shiba bound states in the superconductor. Depending on the type of order of the magnet, the band structure of these bound states can be topologically nontrivial. Thus far, research has focused on systems where the influence of spin-orbit coupling can be neglected. Here, we explore the interplay between non-collinear (or non-coplanar) spin textures and Rashba-type spin-orbit interaction. This situation is realized, for example, in heterostructures between helical magnets and heavy elemental superconductors, such as Pb. Using a unitary transformation in spin space, we show that the effects of Rashba-type spin-orbit coupling are equivalent to the effects of the non-collinear spin texture of the helical magnet. We explore the topological phase diagram as a function of spin-orbit coupling, spin texture, and chemical potential, and find many interesting topological phases, such as p{sub x}-, (p{sub x} + p{sub y})-, and (p{sub x} + i p{sub y})-wave states. Conditions for the formation and the nature of Majorana edge channels are examined. Furthermore, we study the topological edge currents of these phases.

  17. Resonant spin Hall effect in two dimensional electron gas

    Science.gov (United States)

    Shen, Shun-Qing

    2005-03-01

    Remarkable phenomena have been observed in 2DEG over last two decades, most notably, the discovery of integer and fractional quantum Hall effect. The study of spin transport provides a good opportunity to explore spin physics in two-dimensional electron gas (2DEG) with spin-orbit coupling and other interaction. It is already known that the spin-orbit coupling leads to a zero-field spin splitting, and competes with the Zeeman spin splitting if the system is subjected to a magnetic field perpendicular to the plane of 2DEG. The result can be detected as beating of the Shubnikov-de Haas oscillation. Very recently the speaker and his collaborators studied transport properties of a two-dimensional electron system with Rashba spin-orbit coupling in a perpendicular magnetic field. The spin-orbit coupling competes with the Zeeman splitting to generate additional degeneracies between different Landau levels at certain magnetic fields. It is predicted theoretically that this degeneracy, if occurring at the Fermi level, gives rise to a resonant spin Hall conductance, whose height is divergent as 1/T and whose weight is divergent as -lnT at low temperatures. The charge Hall conductance changes by 2e^2/h instead of e^2/h as the magnetic field changes through the resonant point. The speaker will address the resonance condition, symmetries in the spin-orbit coupling, the singularity of magnetic susceptibility, nonlinear electric field effect, the edge effect and the disorder effect due to impurities. This work was supported by the Research Grants Council of Hong Kong under Grant No.: HKU 7088/01P. *S. Q. Shen, M. Ma, X. C. Xie, and F. C. Zhang, Phys. Rev. Lett. 92, 256603 (2004) *S. Q. Shen, Y. J. Bao, M. Ma, X. C. Xie, and F. C. Zhang, cond-mat/0410169

  18. Exchange magnetic field torques in YIG/Pt bilayers observed by the spin-Hall magnetoresistance

    NARCIS (Netherlands)

    Vlietstra, N.; Shan, J.; Castel, V.; Ben Youssef, J.; Bauer, G. E. W.; van Wees, B. J.

    2013-01-01

    The effective field torque of an yttrium-iron-garnet (YIG) film on the spin accumulation in an attached platinum (Pt) film is measured by the spin-Hall magnetoresistance (SMR). As a result, the magnetization direction of a ferromagnetic insulating layer can be measured electrically. Experimental

  19. Tests of spinning turbine fragment impact on casing models

    International Nuclear Information System (INIS)

    Wilbeck, J.S.

    1984-01-01

    Ten 1/11-scale model turbine missile impact tests were conducted at a Naval spin chamber test facility to assess turbine missile effects in nuclear plant design. The objective of the tests was to determine the effects of missile spin, blade crush, and target edge conditions on the impact of turbine disk fragments on the steel casing. The results were intended for use in making realistic estimates for the initial conditions of fragments that might escape the casing in the event of a disk burst in a nuclear plant. The burst of a modified gas turbine rotor in a high-speed spin chamber provided three missiles with the proper rotational and translational velocities of actual steam turbine fragments. Tests of bladed, spinning missiles were compared with previous tests of unbladed, nonspinning missiles. The total residual energy of the spinning missiles, as observed from high-speed photographs of disk burst, was the same as that of the nonspinning missiles launched in a piercing orientation. Tests with bladed missiles showed that for equal burst speeds, the residual energy of bladed missiles is less than that of unbladed missiles. Impacts of missiles near the edge of targets resulted in residual missile velocities greater than for central impact. (orig.)

  20. Changes in habitat use at rainforest edges through succession: A case study of understory birds in the Brazilian Amazon

    Science.gov (United States)

    Luke L. Powell; Gustavo Zurita; Jared D.  Wolfe; Erik I.  Johnson; Philip C  Stouffer

    2015-01-01

    Primary tropical rain forests are being rapidly perforated with new edges via roads, logging, and pastures, and vast areas of secondary forest accumulate following abandonment of agricultural lands. To determine how insectivorous Amazonian understory birds respond to edges between primary rain forest and three age classes of secondary forest, we radio-tracked two...

  1. Resonant Tunneling Spin Pump

    Science.gov (United States)

    Ting, David Z.

    2007-01-01

    The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

  2. Nuclear spins in nanostructures

    International Nuclear Information System (INIS)

    Coish, W.A.; Baugh, J.

    2009-01-01

    We review recent theoretical and experimental advances toward understanding the effects of nuclear spins in confined nanostructures. These systems, which include quantum dots, defect centers, and molecular magnets, are particularly interesting for their importance in quantum information processing devices, which aim to coherently manipulate single electron spins with high precision. On one hand, interactions between confined electron spins and a nuclear-spin environment provide a decoherence source for the electron, and on the other, a strong effective magnetic field that can be used to execute local coherent rotations. A great deal of effort has been directed toward understanding the details of the relevant decoherence processes and to find new methods to manipulate the coupled electron-nuclear system. A sequence of spectacular new results have provided understanding of spin-bath decoherence, nuclear spin diffusion, and preparation of the nuclear state through dynamic polarization and more general manipulation of the nuclear-spin density matrix through ''state narrowing.'' These results demonstrate the richness of this physical system and promise many new mysteries for the future. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  3. Design lithium storage materials by lithium adatoms adsorption at the edges of zigzag silicene nanoribbon: A first principle study

    Science.gov (United States)

    Guo, Gang; Mao, Yuliang; Zhong, Jianxin; Yuan, Jianmei; Zhao, Hongquan

    2017-06-01

    First-principles spin-polarized calculations are performed to design lithium storage materials using the active edges of zigzag silicene nanoribbon (ZSiNR). We predict that edge-adsorption of Li adatoms on zigzag silicene nanoribbon is preferred in energy to form new type lithium storage materials. Significant charge transfer from Li adatoms to Si atoms at the edges of ZSiNR is found, indicating the main ionic interactions. It is found that the band structures of ZSiNR with Li adsorptions are sensitive with the variation of sites of adatoms at the two edges. Ferro-magnetic to antiferro-magnetic change is found in ZSiNR with symmetrical adsorption of Li adatoms at its two edges. Other unsymmetrical Li adsorptions at the edges of ZSiNR prefer to stay in ferro-magnetic state as that in narrow pristine ZSiNR.

  4. Selenium accumulation by plants

    Science.gov (United States)

    White, Philip J.

    2016-01-01

    Background Selenium (Se) is an essential mineral element for animals and humans, which they acquire largely from plants. The Se concentration in edible plants is determined by the Se phytoavailability in soils. Selenium is not an essential element for plants, but excessive Se can be toxic. Thus, soil Se phytoavailability determines the ecology of plants. Most plants cannot grow on seleniferous soils. Most plants that grow on seleniferous soils accumulate 100 mg Se kg–1 dry matter. These plants are considered to be Se accumulators. Some species can even accumulate Se concentrations of 1000–15 000 mg Se kg–1 dry matter and are called Se hyperaccumulators. Scope This article provides an overview of Se uptake, translocation and metabolism in plants and highlights the possible genetic basis of differences in these between and within plant species. The review focuses initially on adaptations allowing plants to tolerate large Se concentrations in their tissues and the evolutionary origin of species that hyperaccumulate Se. It then describes the variation in tissue Se concentrations between and within angiosperm species and identifies genes encoding enzymes limiting the rates of incorporation of Se into organic compounds and chromosomal loci that might enable the development of crops with greater Se concentrations in their edible portions. Finally, it discusses transgenic approaches enabling plants to tolerate greater Se concentrations in the rhizosphere and in their tissues. Conclusions The trait of Se hyperaccumulation has evolved several times in separate angiosperm clades. The ability to tolerate large tissue Se concentrations is primarily related to the ability to divert Se away from the accumulation of selenocysteine and selenomethionine, which might be incorporated into non-functional proteins, through the synthesis of less toxic Se metabilites. There is potential to breed or select crops with greater Se concentrations in their edible tissues, which

  5. Accumulation of satellites

    International Nuclear Information System (INIS)

    Safronov, V.S.; Ruskol, E.L.

    1977-01-01

    Formation and evolution of circumplanetary satellite swarms are investigated. Characteristic times of various processes are estimated. The characteristic time for the accumulation of the bodies in the swarm was several orders of magnitude shorter than that of the planet, i.e. than the time of the replenishment of the material by the swarm (10 8 yr). The model of the accumulation of the swarm is constructed taking into account the increase of its mass due to trapping of heliocentrically moving particles and its decrease due to outfall of the inner part of the swarm onto the growing planet. The accumulation of circumplanetary bodies is also considered. The main features of the evolution of the swarm essentially depend on the size distribution of bodies in the swarm and in the zone of the planet and also on the degree of the concentration of the swarm mass toward the planet. If the sum of the exponents of the inverse power laws of these distributions is less than 7, the model of the transparent swarm developed in this paper should be preferred. When this sum is greater than 7, the model of opaque swarm suggested by A. Harris and W.M. Kaula is better. There is predominant trapping of small particles into the swarm due to their more frequent collisions. Optical thickness of the protoplanetary cloud in radial direction is estimated. It is shown that at the final stage of the planetary accumulation, the cloud was semitransparent in the region of terrestrial planets and volatile substances evaporated at collisions could be swept out from the outer parts of the satellite swarm by the solar wind

  6. Antiproton Accumulator (AA)

    CERN Multimedia

    Photographic Service

    1980-01-01

    The AA in its final stage of construction, before it disappeared from view under concrete shielding. Antiprotons were first injected, stochastically cooled and accumulated in July 1980. From 1981 on, the AA provided antiprotons for collisions with protons, first in the ISR, then in the SPS Collider. From 1983 on, it also sent antiprotons, via the PS, to the Low-Energy Antiproton Ring (LEAR). The AA was dismantled in 1997 and shipped to Japan.

  7. Spin drift and spin diffusion currents in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Idrish Miah, M [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)], E-mail: m.miah@griffith.edu.au

    2008-09-15

    On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  8. Spin drift and spin diffusion currents in semiconductors

    Directory of Open Access Journals (Sweden)

    M Idrish Miah

    2008-01-01

    Full Text Available On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  9. Spin drift and spin diffusion currents in semiconductors

    International Nuclear Information System (INIS)

    Idrish Miah, M

    2008-01-01

    On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

  10. Quantifying Spin Hall Angles from Spin Pumping : Experiments and Theory

    NARCIS (Netherlands)

    Mosendz, O.; Pearson, J.E.; Fradin, F.Y.; Bauer, G.E.W.; Bader, S.D.; Hoffmann, A.

    2010-01-01

    Spin Hall effects intermix spin and charge currents even in nonmagnetic materials and, therefore, ultimately may allow the use of spin transport without the need for ferromagnets. We show how spin Hall effects can be quantified by integrating Ni80Fe20|normal metal (N) bilayers into a coplanar

  11. Compound nucleus effects in spin-spin cross sections

    International Nuclear Information System (INIS)

    Thompson, W.J.

    1976-01-01

    By comparison with recent data, it is shown that spin-spin cross sections for low-energy neutrons may be dominated by a simple compound-elastic level-density effect, independent of spin-spin terms in the nucleon-nucleus optical-model potential. (Auth.)

  12. Protected Edge Modes without Symmetry

    Directory of Open Access Journals (Sweden)

    Michael Levin

    2013-05-01

    Full Text Available We discuss the question of when a gapped two-dimensional electron system without any symmetry has a protected gapless edge mode. While it is well known that systems with a nonzero thermal Hall conductance, K_{H}≠0, support such modes, here we show that robust modes can also occur when K_{H}=0—if the system has quasiparticles with fractional statistics. We show that some types of fractional statistics are compatible with a gapped edge, while others are fundamentally incompatible. More generally, we give a criterion for when an electron system with Abelian statistics and K_{H}=0 can support a gapped edge: We show that a gapped edge is possible if and only if there exists a subset of quasiparticle types M such that (1 all the quasiparticles in M have trivial mutual statistics, and (2 every quasiparticle that is not in M has nontrivial mutual statistics with at least one quasiparticle in M. We derive this criterion using three different approaches: a microscopic analysis of the edge, a general argument based on braiding statistics, and finally a conformal field theory approach that uses constraints from modular invariance. We also discuss the analogous result for two-dimensional boson systems.

  13. Frustrated spin systems

    CERN Document Server

    2013-01-01

    This book covers all principal aspects of currently investigated frustrated systems, from exactly solved frustrated models to real experimental frustrated systems, going through renormalization group treatment, Monte Carlo investigation of frustrated classical Ising and vector spin models, low-dimensional systems, spin ice and quantum spin glass. The reader can - within a single book - obtain a global view of the current research development in the field of frustrated systems.This new edition is updated with recent theoretical, numerical and experimental developments in the field of frustrated

  14. SPINning parallel systems software

    International Nuclear Information System (INIS)

    Matlin, O.S.; Lusk, E.; McCune, W.

    2002-01-01

    We describe our experiences in using Spin to verify parts of the Multi Purpose Daemon (MPD) parallel process management system. MPD is a distributed collection of processes connected by Unix network sockets. MPD is dynamic processes and connections among them are created and destroyed as MPD is initialized, runs user processes, recovers from faults, and terminates. This dynamic nature is easily expressible in the Spin/Promela framework but poses performance and scalability challenges. We present here the results of expressing some of the parallel algorithms of MPD and executing both simulation and verification runs with Spin

  15. Spins in chemistry

    CERN Document Server

    McWeeny, Roy

    2004-01-01

    Originally delivered as a series of lectures, this volume systematically traces the evolution of the ""spin"" concept from its role in quantum mechanics to its assimilation into the field of chemistry. Author Roy McWeeny presents an in-depth illustration of the deductive methods of quantum theory and their application to spins in chemistry, following the path from the earliest concepts to the sophisticated physical methods employed in the investigation of molecular structure and properties. Starting with the origin and development of the spin concept, the text advances to an examination of sp

  16. NUCLEON SPIN: Enigma confirmed

    International Nuclear Information System (INIS)

    Anon.

    1994-01-01

    In 1987 the European Muon Collaboration (EMC - June 1988, page 9) reported results from a polarized muon-proton scattering experiment at CERN which puzzled the particle and nuclear physics communities. Contrary to the prediction of the naive quark model, the EMC found that little of the proton spin seemed to be carried by the spins of the quarks. An extensive experimental programme was therefore immediately proposed at CERN, SLAC (Stanford) and DESY (Hamburg) to measure the spin structure function of the neutron and to repeat the proton measurement with improved accuracy

  17. Spin-polarized SEM

    International Nuclear Information System (INIS)

    Konoto, Makoto

    2007-01-01

    Development of highly effective evaluation technology of magnetic structures on a nanometric scale is a key to understanding spintronics and related phenomena. A high-resolution spin-polarized scanning electron microscope (spin SEM) developed recently is quite suitable for probing such nanostructures because of the capability of analyzing local magnetization vectors in three dimensions. Utilizing the spin SEM, a layered antiferromagnetic structure with the 1nm-alternation of bilayer-sheet magnetization has been successfully resolved. The real-space imaging with full analysis of the temperature-dependent magnetization vectors will be demonstrated. (author)

  18. High spin structure functions

    International Nuclear Information System (INIS)

    Khan, H.

    1990-01-01

    This thesis explores deep inelastic scattering of a lepton beam from a polarized nuclear target with spin J=1. After reviewing the formation for spin-1/2, the structure functions for a spin-1 target are defined in terms of the helicity amplitudes for forward compton scattering. A version of the convolution model, which incorporates relativistic and binding energy corrections is used to calculate the structure functions of a neutron target. A simple parameterization of these structure functions is given in terms of a few neutron wave function parameters and the free nucleon structure functions. This allows for an easy comparison of structure functions calculated using different neutron models. (author)

  19. Spin Hall effect transistor

    Czech Academy of Sciences Publication Activity Database

    Wunderlich, Joerg; Park, B.G.; Irvine, A.C.; Zarbo, Liviu; Rozkotová, E.; Němec, P.; Novák, Vít; Sinova, Jairo; Jungwirth, Tomáš

    2010-01-01

    Roč. 330, č. 6012 (2010), s. 1801-1804 ISSN 0036-8075 R&D Projects: GA AV ČR KAN400100652; GA MŠk LC510 EU Projects: European Commission(XE) 215368 - SemiSpinNet Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100521 Keywords : spin Hall effect * spintronics * spin transistor Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 31.364, year: 2010

  20. Spinning of refractory metals

    International Nuclear Information System (INIS)

    Chang Wenkua; Zheng Han

    1989-01-01

    The effects of spinning process parameters including max. pass percentage reduction, spinning temperature, feed rate, lubricant and annealing technology on the quality of shaped components are summarized and discussed in the present paper. The above mentioned parameters are adopted in the process of spinning of barrel-shaped and specially shaped components of refractory metals and their alloys W, Mo, Nb, Zr, TZM molybdenum alloy, C-103, C-752 niobium alloy etc. The cause of leading to usual defects of spun products of refractory metals such as lamellar as 'scaling', crack, swelling, wrinkle, etc. have been analysed and the ways to eliminate the defects have been put forward. 8 figs., 5 tabs. (Author)

  1. Superconductivity switch from spin-singlet to -triplet pairing in a topological superconducting junction

    Science.gov (United States)

    Tao, Ze; Chen, F. J.; Zhou, L. Y.; Li, Bin; Tao, Y. C.; Wang, J.

    2018-06-01

    The interedge coupling is the cardinal characteristic of the narrow quantum spin Hall (QSH) insulator, and thus could bring about exotic transport phenomena. Herein, we present a theoretical investigation of the spin-resolved Andreev reflection (AR) in a QSH insulator strip touching on two neighbouring ferromagnetic insulators and one s-wave superconductor. It is demonstrated that, due to the interplay of the interedge coupling and ferromagnetic configuration, there could be not only usual local ARs leading to the spin-singlet pairing with the incident electron and Andreev-reflected hole from different spin subbands, but also novel local ARs giving rise to the spin-triplet pairing from the same spin subband. However, only the latter exists in the absence of the interedge coupling, and therefore the two pairings in turn testify the helical spin texture of the edge states. By proper tuning of the band structures of the ferromagnetic layers, under the resonance bias voltage, the usual and novel local ARs of can be all exhibited, resulting in fully spin-polarized pure spin-singlet superconductivity and pure spin-triplet superconductivity, respectively, which suggests a superconductivity switch from spin-singlet to -triplet pairing by electrical control. The results can be experimentally confirmed by the tunneling conductance and the noise power.

  2. Spin transfer torque with spin diffusion in magnetic tunnel junctions

    KAUST Repository

    Manchon, Aurelien

    2012-08-09

    Spin transport in magnetic tunnel junctions in the presence of spin diffusion is considered theoretically. Combining ballistic tunneling across the barrier and diffusive transport in the electrodes, we solve the spin dynamics equation in the metallic layers. We show that spin diffusion mixes the transverse spin current components and dramatically modifies the bias dependence of the effective spin transfer torque. This leads to a significant linear bias dependence of the out-of-plane torque, as well as a nonconventional thickness dependence of both spin torque components.

  3. Electron spin and nuclear spin manipulation in semiconductor nanosystems

    International Nuclear Information System (INIS)

    Hirayama, Yoshiro; Yusa, Go; Sasaki, Satoshi

    2006-01-01

    Manipulations of electron spin and nuclear spin have been studied in AlGaAs/GaAs semiconductor nanosystems. Non-local manipulation of electron spins has been realized by using the correlation effect between localized and mobile electron spins in a quantum dot- quantum wire coupled system. Interaction between electron and nuclear spins was exploited to achieve a coherent control of nuclear spins in a semiconductor point contact device. Using this device, we have demonstrated a fully coherent manipulation of any two states among the four spin levels of Ga and As nuclei. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Selenium accumulation by plants.

    Science.gov (United States)

    White, Philip J

    2016-02-01

    Selenium (Se) is an essential mineral element for animals and humans, which they acquire largely from plants. The Se concentration in edible plants is determined by the Se phytoavailability in soils. Selenium is not an essential element for plants, but excessive Se can be toxic. Thus, soil Se phytoavailability determines the ecology of plants. Most plants cannot grow on seleniferous soils. Most plants that grow on seleniferous soils accumulate plant species have evolved tolerance to Se, and commonly accumulate tissue Se concentrations >100 mg Se kg(-1) dry matter. These plants are considered to be Se accumulators. Some species can even accumulate Se concentrations of 1000-15 000 mg Se kg(-1 )dry matter and are called Se hyperaccumulators. This article provides an overview of Se uptake, translocation and metabolism in plants and highlights the possible genetic basis of differences in these between and within plant species. The review focuses initially on adaptations allowing plants to tolerate large Se concentrations in their tissues and the evolutionary origin of species that hyperaccumulate Se. It then describes the variation in tissue Se concentrations between and within angiosperm species and identifies genes encoding enzymes limiting the rates of incorporation of Se into organic compounds and chromosomal loci that might enable the development of crops with greater Se concentrations in their edible portions. Finally, it discusses transgenic approaches enabling plants to tolerate greater Se concentrations in the rhizosphere and in their tissues. The trait of Se hyperaccumulation has evolved several times in separate angiosperm clades. The ability to tolerate large tissue Se concentrations is primarily related to the ability to divert Se away from the accumulation of selenocysteine and selenomethionine, which might be incorporated into non-functional proteins, through the synthesis of less toxic Se metabilites. There is potential to breed or select crops

  5. Competition of edge effects on the electronic properties and excitonic effects in short graphene nanoribbons

    International Nuclear Information System (INIS)

    Lu, Yan; Wei, Sheng; Jin, Jing; Wang, Li; Lu, Wengang

    2016-01-01

    We explore the electronic properties and exciton effects in short graphene nanoribbons (SGNRs), which have two armchair edges and two zigzag edges. Our results show that both of these two types of edges have profound effects on the electronic properties and exciton effects. Both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) states are alternatively changed between the bulk and the edge states as the lengths of the zigzag edges increase, due to the competition between the states of the two types of edges. The energy gaps, as a function of the lengths of the armchair edges, will then induce two kinds of trends. Furthermore, two kinds of exciton energies and exciton binding energies are found, which can be understood through the two kinds of HOMO and LUMO states in SGNRs. In addition, we find that the three triplet exciton states are not totally energy degenerate in SGNRs due to the spin-polarized states on the zigzag edges. (paper)

  6. Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures

    KAUST Repository

    Ortiz Pauyac, Christian; Wang, Xuhui; Chshiev, Mairbek; Manchon, Aurelien

    2013-01-01

    In a ferromagnetic heterostructure, the interplay between Rashba spin-orbit coupling and exchange splitting gives rise to a current-driven spin torque. In a realistic device setup, we investigate the Rashba spin torque in the diffusive regime and report two major findings: (i) a nonvanishing torque exists at the edges of the device even when the magnetization and effective Rashba field are aligned; (ii) anisotropic spin relaxation rates driven by the Rashba spin-orbit coupling assign the spin torque a general expression T = T y (θ) m × (y × m) + T y (θ) y × m + T z (θ) m × (z × m) + T z (θ) z × m, where the coefficients T, y, z depend on the magnetization direction. Our results agree with recent experiments. © 2013 AIP Publishing LLC.

  7. Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures

    KAUST Repository

    Ortiz Pauyac, Christian

    2013-06-26

    In a ferromagnetic heterostructure, the interplay between Rashba spin-orbit coupling and exchange splitting gives rise to a current-driven spin torque. In a realistic device setup, we investigate the Rashba spin torque in the diffusive regime and report two major findings: (i) a nonvanishing torque exists at the edges of the device even when the magnetization and effective Rashba field are aligned; (ii) anisotropic spin relaxation rates driven by the Rashba spin-orbit coupling assign the spin torque a general expression T = T y (θ) m × (y × m) + T y (θ) y × m + T z (θ) m × (z × m) + T z (θ) z × m, where the coefficients T, y, z depend on the magnetization direction. Our results agree with recent experiments. © 2013 AIP Publishing LLC.

  8. Spin-filtering and giant magnetoresistance effects in polyacetylene-based molecular devices

    Science.gov (United States)

    Chen, Tong; Yan, Shenlang; Xu, Liang; Liu, Desheng; Li, Quan; Wang, Lingling; Long, Mengqiu

    2017-07-01

    Using the non-equilibrium Green's function formalism in combination with density functional theory, we performed ab initio calculations of spin-dependent electron transport in molecular devices consisting of a polyacetylene (CnHn+1) chain vertically attached to a carbon chain sandwiched between two semi-infinite zigzag-edged graphene nanoribbon electrodes. Spin-charge transport in the device could be modulated to different magnetic configurations by an external magnetic field. The results showed that single spin conduction could be obtained. Specifically, the proposed CnHn+1 devices exhibited several interesting effects, including (dual) spin filtering, spin negative differential resistance, odd-even oscillation, and magnetoresistance (MR). Marked spin polarization with a filtering efficiency of up to 100% over a large bias range was found, and the highest MR ratio for the CnHn+1 junctions reached 4.6 × 104. In addition, the physical mechanisms for these phenomena were also revealed.

  9. All-graphene edge contacts

    DEFF Research Database (Denmark)

    Jacobsen, Kåre Wedel; Falkenberg, Jesper Toft; Papior, Nick Rübner

    2016-01-01

    Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures as a func......Using ab-initio methods we investigate the possibility of three-terminalgraphene "T-junction" devices and show that these all-graphene edge contactsare energetically feasible when the 1D interface itself is free from foreignatoms. We examine the energetics of various junction structures...... to be in therange of 1-10 kΩμm which is comparable to the best contact resistance reportedfor edge-contacted graphene-metal contacts. We conclude that conductingall-carbon T-junctions should be feasible....

  10. When measured spin polarization is not spin polarization

    International Nuclear Information System (INIS)

    Dowben, P A; Wu Ning; Binek, Christian

    2011-01-01

    Spin polarization is an unusually ambiguous scientific idiom and, as such, is rarely well defined. A given experimental methodology may allow one to quantify a spin polarization but only in its particular context. As one might expect, these ambiguities sometimes give rise to inappropriate interpretations when comparing the spin polarizations determined through different methods. The spin polarization of CrO 2 and Cr 2 O 3 illustrate some of the complications which hinders comparisons of spin polarization values. (viewpoint)

  11. Improving color constancy by photometric edge weighting

    NARCIS (Netherlands)

    Gijsenij, A.; Gevers, T.; van de Weijer, J.

    2012-01-01

    Edge-based color constancy methods make use of image derivatives to estimate the illuminant. However, different edge types exist in real-world images, such as material, shadow, and highlight edges. These different edge types may have a distinctive influence on the performance of the illuminant

  12. Spin-4 extended conformal algebras

    International Nuclear Information System (INIS)

    Kakas, A.C.

    1988-01-01

    We construct spin-4 extended conformal algebras using the second hamiltonian structure of the KdV hierarchy. In the presence of a U(1) current a family of spin-4 algebras exists but the additional requirement that the spin-1 and spin-4 currents commute fixes the algebra uniquely. (orig.)

  13. Anisotropic spin relaxation in graphene

    NARCIS (Netherlands)

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

    2008-01-01

    Spin relaxation in graphene is investigated in electrical graphene spin valve devices in the nonlocal geometry. Ferromagnetic electrodes with in-plane magnetizations inject spins parallel to the graphene layer. They are subject to Hanle spin precession under a magnetic field B applied perpendicular

  14. Spin squeezing and quantum correlations

    Indian Academy of Sciences (India)

    2 states. A coherent spin-s state. (CSS) θ φ can then be thought of as having no quantum correlations as the constituent. 2s elementary spins point in the same direction ˆn(θ φ) which is the mean spin direction. 2. State classification and squeezing. In order to discuss squeezing, we begin with the squeezing condition itself.

  15. Geometry of spin coherent states

    Science.gov (United States)

    Chryssomalakos, C.; Guzmán-González, E.; Serrano-Ensástiga, E.

    2018-04-01

    Spin states of maximal projection along some direction in space are called (spin) coherent, and are, in many respects, the ‘most classical’ available. For any spin s, the spin coherent states form a 2-sphere in the projective Hilbert space \

  16. Evidence for Topological Edge States in a Large Energy Gap near the Step Edges on the Surface of ZrTe_{5}

    Directory of Open Access Journals (Sweden)

    R. Wu

    2016-05-01

    Full Text Available Two-dimensional topological insulators with a large bulk band gap are promising for experimental studies of quantum spin Hall effect and for spintronic device applications. Despite considerable theoretical efforts in predicting large-gap two-dimensional topological insulator candidates, none of them have been experimentally demonstrated to have a full gap, which is crucial for quantum spin Hall effect. Here, by combining scanning tunneling microscopy/spectroscopy and angle-resolved photoemission spectroscopy, we reveal that ZrTe_{5} crystal hosts a large full gap of ∼100  meV on the surface and a nearly constant density of states within the entire gap at the monolayer step edge. These features are well reproduced by our first-principles calculations, which point to the topologically nontrivial nature of the edge states.

  17. Terwilliger and spin physics

    International Nuclear Information System (INIS)

    O'FAllon, J.R.

    1991-01-01

    The history of spin physics experiments is presented, with emphasis of Kent Terwilliger's involvement. Development of polarized beams and targets at the ZGS and AGS is recalled. P-P elastic scattering experiments are reviewed

  18. Transverse spin effects

    International Nuclear Information System (INIS)

    Ratcliffe, P.G.

    1993-01-01

    A discussion is presented of the role that transverse spin physics can play in providing information on the bound state dynamics in hadronic physics. Care is taken to distinguish between single- and double-spin measurements, each being discussed separately. In the case of single-spin effects it is stressed that as yet no satisfactory explanation has been provided within the framework if perturbative QCD which in fact generally predicts negligible effects. In order to clarify the situation experimental data at yet higher p T are necessary and semi-leptonic data could shed some light on the underlying scattering mechanisms. As regards double-spin correlations, the theoretical picture (although clouded by some ill-informed, often erroneous statements and even recent papers) is rather well understood and what is dearly missing is the experimental study of, for example, g 2 in deep-inelastic scattering. (author). 31 refs

  19. Spin polarized deuterium

    International Nuclear Information System (INIS)

    Glyde, H.R.; Hernadi, S.I.

    1986-01-01

    Several ground state properties of (electron) spin-polarized deuterium (D) such as the energy, single quasiparticle energies and lifetimes, Landau parameters and sound velocities are evaluated. The calculations begin with the Kolos-Wolneiwicz potential and use the Galitskii-FeynmanHartree-Fock (GFHF) approximation. The deuteron nucleas has spin I = 1, and spin states I/sub z/ = 1,0,-1. We explore D 1 , D 2 and D 3 in which, respectively, one spin state only is populated, two states are equally populated, and three states are equally populated. We find the GFHF describes D 1 well, but D 2 and D 3 less well. The Landau parameters, F/sub L/, are small compared to liquid 3 He and very small for doubly polarized D 1 (i.e. the F/sub L/ decrease with nuclear polarization)

  20. The knife-edge chamber

    International Nuclear Information System (INIS)

    Barasch, E.F.; Bowcock, T.J.V.; Drew, M.M.; Elliott, S.M.; Lee, B.; McIntyre, P.M.; Pang, Y.; Popovic, M.; Smith, D.D.

    1990-01-01

    In this paper the design for a new technology for particle track detectors is described. Using standard IC fabrication techniques, a pattern of microscopic knife edges and field-shaping electrodes can be fabricated on a silicon substrate. The knife-edge chamber uniquely offers attractive performance for the track chambers required for SSC detectors, for which no present technology is yet satisfactory. Its features include: excellent radiation hardness (10 Mrad), excellent spatial resolution (∼20 μm), short drift time (20 ns), and large pulse height (1 mV)

  1. Microscopic studies of nonlocal spin dynamics and spin transport (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris, E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-05-07

    Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

  2. Microscopic studies of nonlocal spin dynamics and spin transport (invited)

    Science.gov (United States)

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

    2015-05-01

    Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

  3. Microscopic studies of nonlocal spin dynamics and spin transport (invited)

    International Nuclear Information System (INIS)

    Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

    2015-01-01

    Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems

  4. Exertional Rhabdomyolysis after Spinning

    OpenAIRE

    Jeong, Youjin; Kweon, Hyuk-Jung; Oh, Eun-Jung; Ahn, Ah-Leum; Choi, Jae-Kyung; Cho, Dong-Yung

    2016-01-01

    Any strenuous muscular exercise may trigger rhabdomyolysis. We report an episode of clinically manifested exertional rhabdomyolysis due to stationary cycling, commonly known as spinning. Reports of spinning-related rhabdomyolysis are rare in the English literature, and the current case appears to be the first such case reported in South Korea. A previously healthy 21-year-old Asian woman presented with severe thigh pain and reddish-brown urinary discoloration 24?48 hours after attending a spi...

  5. Higher Spins & Strings

    CERN Multimedia

    CERN. Geneva

    2014-01-01

    The conjectured relation between higher spin theories on anti de-Sitter (AdS) spaces and weakly coupled conformal field theories is reviewed. I shall then outline the evidence in favour of a concrete duality of this kind, relating a specific higher spin theory on AdS3 to a family of 2d minimal model CFTs. Finally, I shall explain how this relation fits into the framework of the familiar stringy AdS/CFT correspondence.

  6. 1D ferromagnetic edge contacts to 2D graphene/h-BN heterostructures

    Science.gov (United States)

    Karpiak, Bogdan; Dankert, André; Cummings, Aron W.; Power, Stephen R.; Roche, Stephan; Dash, Saroj P.

    2018-03-01

    We report the fabrication of one-dimensional (1D) ferromagnetic edge contacts to two-dimensional (2D) graphene/h-BN heterostructures. While aiming to study spin injection/detection with 1D edge contacts, a spurious magnetoresistance signal was observed, which is found to originate from the local Hall effect in graphene due to fringe fields from ferromagnetic edge contacts and in the presence of charge current spreading in the nonlocal measurement configuration. Such behavior has been confirmed by the absence of a Hanle signal and gate-dependent magnetoresistance measurements that reveal a change in sign of the signal for the electron- and hole-doped regimes, which is in contrast to the expected behavior of the spin signal. Calculations show that the contact-induced fringe fields are typically on the order of hundreds of mT, but can be reduced below 100 mT with careful optimization of the contact geometry. There may be an additional contribution from magnetoresistance effects due to tunneling anisotropy in the contacts, which needs further investigation. These studies are useful for optimization of spin injection and detection in 2D material heterostructures through 1D edge contacts.

  7. Entangled spin chain

    Science.gov (United States)

    Salberger, Olof; Korepin, Vladimir

    We introduce a new model of interacting spin 1/2. It describes interactions of three nearest neighbors. The Hamiltonian can be expressed in terms of Fredkin gates. The Fredkin gate (also known as the controlled swap gate) is a computational circuit suitable for reversible computing. Our construction generalizes the model presented by Peter Shor and Ramis Movassagh to half-integer spins. Our model can be solved by means of Catalan combinatorics in the form of random walks on the upper half plane of a square lattice (Dyck walks). Each Dyck path can be mapped on a wave function of spins. The ground state is an equally weighted superposition of Dyck walks (instead of Motzkin walks). We can also express it as a matrix product state. We further construct a model of interacting spins 3/2 and greater half-integer spins. The models with higher spins require coloring of Dyck walks. We construct a SU(k) symmetric model (where k is the number of colors). The leading term of the entanglement entropy is then proportional to the square root of the length of the lattice (like in the Shor-Movassagh model). The gap closes as a high power of the length of the lattice [5, 11].

  8. Topological Phases in Graphene Nanoribbons: Junction States, Spin Centers, and Quantum Spin Chains

    Science.gov (United States)

    Cao, Ting; Zhao, Fangzhou; Louie, Steven G.

    2017-08-01

    We show that semiconducting graphene nanoribbons (GNRs) of different width, edge, and end termination (synthesizable from molecular precursors with atomic precision) belong to different electronic topological classes. The topological phase of GNRs is protected by spatial symmetries and dictated by the terminating unit cell. We have derived explicit formulas for their topological invariants and shown that localized junction states developed between two GNRs of distinct topology may be tuned by lateral junction geometry. The topology of a GNR can be further modified by dopants, such as a periodic array of boron atoms. In a superlattice consisting of segments of doped and pristine GNRs, the junction states are stable spin centers, forming a Heisenberg antiferromagnetic spin 1 /2 chain with tunable exchange interaction. The discoveries here not only are of scientific interest for studies of quasi-one-dimensional systems, but also open a new path for design principles of future GNR-based devices through their topological characters.

  9. Proximity effect in semiconductor films with spin-splitting and spin-orbit interaction

    Energy Technology Data Exchange (ETDEWEB)

    Michelsen, Jens; Grein, Roland [Institut fuer Theoretische Festkoerperphysik, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany)

    2012-07-01

    Superconducting heterostructures with spin-active materials have emerged as promising platforms for engineering topological superconductors featuring Majorana bound states at surfaces, edges and vortices. Here we present a method for evaluating, from a microscopic model, the band structure of a semiconductor film of finite thickness deposited on top of a conventional superconductor. Analytical expressions for the proximity induced gap openings are presented in terms of microscopic parameters and the proximity effect in presence of spin-orbit and exchange splitting is visualized in terms of Andreev reflection processes. An expression for the topological invariant, associated with the existence of Majorana bound states, is shown to depend only on parameters of the semiconductor film. The finite thickness of the film leads to resonant states in the film giving rise to a complex band structure with the topological phase alternating between trivial and non-trivial as the parameters are tuned of the film are tuned.

  10. High-resolution Al L2,3-edge x-ray absorption near edge structure spectra of Al-containing crystals and glasses: coordination number and bonding information from edge components

    International Nuclear Information System (INIS)

    Weigel, C; Calas, G; Cormier, L; Galoisy, L; Henderson, G S

    2008-01-01

    High-resolution Al L 2,3 -edge x-ray absorption near edge structure (XANES) spectra have been measured in selected materials containing aluminium in 4-, 5- and 6-coordination. A shift of 1.5 eV is observed between the onset of [4] Al and [6] Al L 2,3 -edge XANES, in agreement with the magnitude of the shift observed at the Al K-edge. The differences in the position and shape of low-energy components of Al L 2,3 -edge XANES spectra provide a unique fingerprint of the geometry of the Al site and of the nature of Al-O chemical bond. The high resolution allows the calculation of electronic parameters such as the spin-orbit coupling and exchange energy using intermediate coupling theory. The electron-hole exchange energy decreases in tetrahedral as compared to octahedral symmetry, in relation with the increased screening of the core hole in the former. Al L 2,3 -edge XANES spectra confirm a major structural difference between glassy and crystalline NaAlSi 2 O 6 , with Al in 4- and 6-coordination, respectively, Al coordination remaining unchanged in NaAl 1-x Fe x Si 2 O 6 glasses, as Fe is substituted for Al

  11. Theory of spin Hall effect

    OpenAIRE

    Chudnovsky, Eugene M.

    2007-01-01

    An extension of Drude model is proposed that accounts for spin and spin-orbit interaction of charge carriers. Spin currents appear due to combined action of the external electric field, crystal field and scattering of charge carriers. The expression for spin Hall conductivity is derived for metals and semiconductors that is independent of the scattering mechanism. In cubic metals, spin Hall conductivity $\\sigma_s$ and charge conductivity $\\sigma_c$ are related through $\\sigma_s = [2 \\pi \\hbar...

  12. Spin valley and giant quantum spin Hall gap of hydrofluorinated bismuth nanosheet.

    Science.gov (United States)

    Gao, Heng; Wu, Wei; Hu, Tao; Stroppa, Alessandro; Wang, Xinran; Wang, Baigeng; Miao, Feng; Ren, Wei

    2018-05-09

    Spin-valley and electronic band topological properties have been extensively explored in quantum material science, yet their coexistence has rarely been realized in stoichiometric two-dimensional (2D) materials. We theoretically predict the quantum spin Hall effect (QSHE) in the hydrofluorinated bismuth (Bi 2 HF) nanosheet where the hydrogen (H) and fluorine (F) atoms are functionalized on opposite sides of bismuth (Bi) atomic monolayer. Such Bi 2 HF nanosheet is found to be a 2D topological insulator with a giant band gap of 0.97 eV which might host room temperature QSHE. The atomistic structure of Bi 2 HF nanosheet is noncentrosymmetric and the spontaneous polarization arises from the hydrofluorinated morphology. The phonon spectrum and ab initio molecular dynamic (AIMD) calculations reveal that the proposed Bi 2 HF nanosheet is dynamically and thermally stable. The inversion symmetry breaking together with spin-orbit coupling (SOC) leads to the coupling between spin and valley in Bi 2 HF nanosheet. The emerging valley-dependent properties and the interplay between intrinsic dipole and SOC are investigated using first-principles calculations combined with an effective Hamiltonian model. The topological invariant of the Bi 2 HF nanosheet is confirmed by using Wilson loop method and the calculated helical metallic edge states are shown to host QSHE. The Bi 2 HF nanosheet is therefore a promising platform to realize room temperature QSHE and valley spintronics.

  13. Nonlocal effects on dynamic damage accumulation in brittle solids

    Energy Technology Data Exchange (ETDEWEB)

    Chen, E.P.

    1995-12-01

    This paper presents a nonlocal analysis of the dynamic damage accumulation processes in brittle solids. A nonlocal formulation of a microcrack based continuum damage model is developed and implemented into a transient dynamic finite element computer code. The code is then applied to the study of the damage accumulation process in a concrete plate with a central hole and subjected to the action of a step tensile pulse applied at opposite edges of the plate. Several finite element discretizations are used to examine the mesh size effect. Comparisons between calculated results based on local and nonlocal formulations are made and nonlocal effects are discussed.

  14. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-04-15

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

  16. Systematic construction of spin liquids on the square lattice from tensor networks with SU(2) symmetry

    Science.gov (United States)

    Mambrini, Matthieu; Orús, Román; Poilblanc, Didier

    2016-11-01

    We elaborate a simple classification scheme of all rank-5 SU(2) spin rotational symmetric tensors according to (i) the onsite physical spin S , (ii) the local Hilbert space V⊗4 of the four virtual (composite) spins attached to each site, and (iii) the irreducible representations of the C4 v 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 ≤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 (D -1 )-dimensional manifold of spin liquids (potentially) preserving lattice symmetries and defined in terms of 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 symmetries (lattice nematics) or (ii) time-reversal symmetry (chiral spin liquids) or (iii) SU(2) spin rotation symmetry down to U(1 ) (spin nematics or Néel antiferromagnets) can also be constructed. We apply this framework to search for new topological chiral spin liquids characterized by well-defined chiral edge modes, as revealed by their entanglement spectrum. In particular, we show how the symmetrization of a double-layer PEPS leads to a chiral topological state with a gapless edge described by a SU (2) 2 Wess-Zumino-Witten model.

  17. Electrical control of a confined electron spin in a silicene quantum dot

    Science.gov (United States)

    Szafran, Bartłomiej; Mreńca-Kolasińska, Alina; Rzeszotarski, Bartłomiej; Żebrowski, Dariusz

    2018-04-01

    We study spin control for an electron confined in a flake of silicene. We find that the lowest-energy conduction-band levels are split by the diagonal intrinsic spin-orbit coupling into Kramers doublets with a definite projection of the spin on the orbital magnetic moment. We study the spin control by AC electric fields using the nondiagonal Rashba component of the spin-orbit interactions with the time-dependent atomistic tight-binding approach. The Rashba interactions in AC electric fields produce Rabi spin-flip times of the order of a nanosecond. These times can be reduced to tens of picoseconds provided that the vertical electric field is tuned to an avoided crossing opened by the Rashba spin-orbit interaction. We demonstrate that the speedup of the spin transitions is possible due to the intervalley coupling induced by the armchair edge of the flake. The study is confronted with the results for circular quantum dots decoupled from the edge with well defined angular momentum and valley index.

  18. Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching

    Directory of Open Access Journals (Sweden)

    Nikky Pathak

    2017-03-01

    Full Text Available The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP and Dual-Phase (DP steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition or drilled and then reamed (reamed edge condition. The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures.

  19. Damage Evolution in Complex-Phase and Dual-Phase Steels during Edge Stretching.

    Science.gov (United States)

    Pathak, Nikky; Butcher, Cliff; Worswick, Michael James; Bellhouse, Erika; Gao, Jeff

    2017-03-27

    The role of microstructural damage in controlling the edge stretchability of Complex-Phase (CP) and Dual-Phase (DP) steels was evaluated using hole tension experiments. The experiments considered a tensile specimen with a hole at the center of specimen that is either sheared (sheared edge condition) or drilled and then reamed (reamed edge condition). The damage mechanism and accumulation in the CP and DP steels were systematically characterized by interrupting the hole tension tests at different strain levels using scanning electron microscope (SEM) analysis and optical microscopy. Martensite cracking and decohesion of ferrite-martensite interfaces are the dominant nucleation mechanisms in the DP780. The primary source of void nucleation in the CP800 is nucleation at TiN particles, with secondary void formation at martensite/bainite interfaces near the failure strain. The rate of damage evolution is considerably higher for the sheared edge in contrast with the reamed edge since the shearing process alters the microstructure in the shear affected zone (SAZ) by introducing work-hardening and initial damage behind the sheared edge. The CP microstructures were shown to be less prone to shear-induced damage than the DP materials resulting in much higher sheared edge formability. Microstructural damage in the CP and DP steels was characterized to understand the interaction between microstructure, damage evolution and edge formability during edge stretching. An analytical model for void evolution and coalescence was developed and applied to predict the damage rate in these rather diverse microstructures.

  20. At the edge of intonation

    DEFF Research Database (Denmark)

    Niebuhr, Oliver

    2012-01-01

    The paper is concerned with the 'edge of intonation' in a twofold sense. It focuses on utterance-final F0 movements and crosses the traditional segment-prosody divide by investigating the interplay of F0 and voiceless fricatives in speech production. An experiment was performed for German with four...

  1. Capillary Sharp Inner Edge Manufacturing

    Czech Academy of Sciences Publication Activity Database

    Hošek, Jan; Studenovský, K.; Najdek, D.

    2009-01-01

    Roč. 19, č. 35 (2009), s. 19-25 ISSN 1584-5982. [MECAHITECH 09 /1./. Bukurešť, 08.10.2009-09.10.2009] R&D Projects: GA AV ČR IAA200760905 Institutional research plan: CEZ:AV0Z20760514 Keywords : capillary * edge * manufacturing Subject RIV: JR - Other Machinery

  2. Spin-current emission governed by nonlinear spin dynamics.

    Science.gov (United States)

    Tashiro, Takaharu; Matsuura, Saki; Nomura, Akiyo; Watanabe, Shun; Kang, Keehoon; Sirringhaus, Henning; Ando, Kazuya

    2015-10-16

    Coupling between conduction electrons and localized magnetization is responsible for a variety of phenomena in spintronic devices. This coupling enables to generate spin currents from dynamical magnetization. Due to the nonlinearity of magnetization dynamics, the spin-current emission through the dynamical spin-exchange coupling offers a route for nonlinear generation of spin currents. Here, we demonstrate spin-current emission governed by nonlinear magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current emission from the magnetic insulator is probed by the inverse spin Hall effect, which demonstrates nontrivial temperature and excitation power dependences of the voltage generation. The experimental results reveal that nonlinear magnetization dynamics and enhanced spin-current emission due to magnon scatterings are triggered by decreasing temperature. This result illustrates the crucial role of the nonlinear magnon interactions in the spin-current emission driven by dynamical magnetization, or nonequilibrium magnons, from magnetic insulators.

  3. Development of edge effects around experimental ecosystem hotspots is affected by edge density and matrix type

    Science.gov (United States)

    Ecological edge effects are sensitive to landscape context. In particular, edge effects can be altered by matrix type and by the presence of other nearby edges. We experimentally altered patch configurations in an African savanna to determine how edge density and matrix type influence edge effect de...

  4. Spin Torques in Systems with Spin Filtering and Spin Orbit Interaction

    KAUST Repository

    Ortiz Pauyac, Christian

    2016-06-19

    In the present thesis we introduce the reader to the field of spintronics and explore new phenomena, such as spin transfer torques, spin filtering, and three types of spin-orbit torques, Rashba, spin Hall, and spin swapping, which have emerged very recently and are promising candidates for a new generation of memory devices in computer technology. A general overview of these phenomena is presented in Chap. 1. In Chap. 2 we study spin transfer torques in tunnel junctions in the presence of spin filtering. In Chap. 3 we discuss the Rashba torque in ferromagnetic films, and in Chap. 4 we study spin Hall effect and spin swapping in ferromagnetic films, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives are summarized in Chap. 5.

  5. A cluster-bethe-lattice approach to spin-waves in dilute ferromagnets

    International Nuclear Information System (INIS)

    Salzberg, J.B.; Silva, C.E.T.G. da; Falicov, L.M.

    1975-01-01

    The spin-wave spectra of a dilute ferromagnet within the cluster-bethe-lattice approximation is studied. Short range order effects for the alloy are included. A study of finite size clusters connected at their edges to Bethe lattices of the same coordination number allows one to determine:(i) the stability condition for the magnetic system; (ii) the continuum spin-wave local density of states and (iii) the existence of localized states below and above the continuum states

  6. Matrix-assisted relaxation in Fe(phen)2(NCS)2 spin-crossover microparticles, experimental and theoretical investigations

    International Nuclear Information System (INIS)

    Enachescu, Cristian; Stancu, Alexandru; Tanasa, Radu; Tissot, Antoine; Laisney, Jérôme; Boillot, Marie-Laure

    2016-01-01

    In this study, we present the influence of the embedding matrix on the relaxation of Fe(phen) 2 (NCS) 2 (phen = 1,10-phenanthroline) spin-transition microparticles as revealed by experiments and provide an explanation within the framework of an elastic model based on a Monte-Carlo method. Experiments show that the shape of the high-spin → low-spin relaxation curves is drastically changed when the particles are dispersed in glycerol. This effect was considered in the model by means of interactions between the microparticles and the matrix. A faster start of the relaxation for microparticles embedded in glycerol is due to an initial positive local pressure acting on the edge spin-crossover molecules from the matrix side. This local pressure diminishes and eventually becomes negative during relaxation, as an effect of the decrease of the volume of spin-crossover microparticles from high-spin to low-spin.

  7. Blue shift of the plasma edge of a ferromagnetic semimetal

    International Nuclear Information System (INIS)

    Wachter, P.; Bommeli, F.; Degiorgi, L.; Burlet, P.; Bourdarot, F.

    1998-01-01

    Full text: In general rare earth pnictides are semimetals and antiferromagnets. Only some nitrides are quoted as ferri or ferromagnetic. However, it has been shown when prepared stoichiometrically and in single crystalline form the free carrier concentration is only in the percent per cation range, thus they are typical low carrier systems. Under these conditions the nitrides are all canted antiferromagnets and metamagnets, i.e. they show Abstract only. The full magnetic moment only with an applied magnetic field. However, when prepared as single crystals but with excess of the rare earths they become spontaneously ferromagnets due to the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in addition to the superexchange mechanisms. On such ferromagnetic compositions of TbN and GdN and also in EuB 6 a new magneto-optic effect has been discovered, a spontaneous blue shift of the plasma edge upon magnetic order. The plasma edge is measured with optical reflectivity and it depends on the free carrier concentration. In other words the free carrier concentration increases upon ferromagnetic order. This effect can be understood with the spontaneous exchange splitting of mainly the 5d conduction band, lowering the bottom of the spin up 5d band, thus increasing the indirect overlap with the valence p band of the anions and thus enhancing the carrier concentration. This blue shift of the plasma edge follows a spin correlation function. An external magnetic field applied near TC enhances the blue shift since the magnetization is not yet saturated. For T→0 a magnetic field has no effect since the magnetization is spontaneously saturated

  8. Optical spin generation/detection and spin transport lifetimes

    International Nuclear Information System (INIS)

    Miah, M. Idrish

    2011-01-01

    We generate electron spins in semiconductors by optical pumping. The detection of them is also performed by optical technique using time-resolved pump-probe photoluminescence polarization measurements in the presence of an external magnetic field perpendicular to the generated spin. The spin polarization in dependences of the pulse length, pump-probe delay and external magnetic field is studied. From the dependence of spin-polarization on the delay of the probe, the electronic spin transport lifetimes and the spin relaxation frequencies as a function of the strength of the magnetic field are estimated. The results are discussed based on hyperfine effects for interacting electrons.

  9. Optical spin generation/detection and spin transport lifetimes

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)

    2011-02-25

    We generate electron spins in semiconductors by optical pumping. The detection of them is also performed by optical technique using time-resolved pump-probe photoluminescence polarization measurements in the presence of an external magnetic field perpendicular to the generated spin. The spin polarization in dependences of the pulse length, pump-probe delay and external magnetic field is studied. From the dependence of spin-polarization on the delay of the probe, the electronic spin transport lifetimes and the spin relaxation frequencies as a function of the strength of the magnetic field are estimated. The results are discussed based on hyperfine effects for interacting electrons.

  10. Magnetocaloric effect in quantum spin-s chains

    Directory of Open Access Journals (Sweden)

    A. Honecker

    2009-01-01

    Full Text Available We compute the entropy of antiferromagnetic quantum spin-s chains in an external magnetic field using exact diagonalization and Quantum Monte Carlo simulations. The magnetocaloric effect, i. e., temperature variations during adiabatic field changes, can be derived from the isentropes. First, we focus on the example of the spin-s=1 chain and show that one can cool by closing the Haldane gap with a magnetic field. We then move to quantum spin-s chains and demonstrate linear scaling with s close to the saturation field. In passing, we propose a new method to compute many low-lying excited states using the Lanczos recursion.

  11. Rotational Invariance of the 2d Spin - Spin Correlation Function

    Science.gov (United States)

    Pinson, Haru

    2012-09-01

    At the critical temperature in the 2d Ising model on the square lattice, we establish the rotational invariance of the spin-spin correlation function using the asymptotics of the spin-spin correlation function along special directions (McCoy and Wu in the two dimensional Ising model. Harvard University Press, Cambridge, 1973) and the finite difference Hirota equation for which the spin-spin correlation function is shown to satisfy (Perk in Phys Lett A 79:3-5, 1980; Perk in Proceedings of III international symposium on selected topics in statistical mechanics, Dubna, August 22-26, 1984, JINR, vol II, pp 138-151, 1985).

  12. Simulation of multi-steps thermal transition in 2D spin-crossover nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Jureschi, Catalin-Maricel [LISV, Université de Versailles Saint-Quentin-en-Yvelines, 78140 Velizy (France); Faculty of Electrical Engineering and Computer Science and MANSiD, Stefan cel Mare University, Suceava 720229 (Romania); Pottier, Benjamin-Louis [Departement de Sciences Physiques, Université de Versailles Saint-Quentin-en-Yvelines, 78035 Versailles Cedex (France); Linares, Jorge, E-mail: jorge.linares@uvsq.fr [GEMaC, Université de Versailles Saint-Quentin-en-Yvelines, CNRS-UVSQ (UMR 8635), 78035 Versailles Cedex (France); Richard Dahoo, Pierre [LATMOS, Université de Versailles-Saint-Quentin-en-Yvelines, Sorbonne Universités, CNRS-UMR 8190, F-78280 Guyancourt (France); Alayli, Yasser [LISV, Université de Versailles Saint-Quentin-en-Yvelines, 78140 Velizy (France); Rotaru, Aurelian [Faculty of Electrical Engineering and Computer Science and MANSiD, Stefan cel Mare University, Suceava 720229 (Romania)

    2016-04-01

    We have used an Ising like model to study the thermal behavior of a 2D spin crossover (SCO) system embedded in a matrix. The interaction parameter between edge SCO molecules and its local environment was included in the standard Ising like model as an additional term. The influence of the system's size and the ratio between the number of edge molecules and the other molecules were also discussed.

  13. Edge-injective and edge-surjective vertex labellings

    DEFF Research Database (Denmark)

    Brandt, Stephan; Rautenbach, D.; Regen, F.

    2010-01-01

    For a graph G = (V, E) we consider vertex-k-labellings f : V → {1,2, ,k} for which the induced edge weighting w : E → {2, 3,., 2k} with w(uv) = f(u) + f(v) is injective or surjective or both. We study the relation between these labellings and the number theoretic notions of an additive basis and ...

  14. Modulation of electronic and magnetic properties in InSe nanoribbons: edge effect

    Science.gov (United States)

    Wu, Meng; Shi, Jun-jie; Zhang, Min; Ding, Yi-min; Wang, Hui; Cen, Yu-lang; Guo, Wen-hui; Pan, Shu-hang; Zhu, Yao-hui

    2018-05-01

    Quite recently, the two-dimensional (2D) InSe nanosheet has become a hot material with great promise for advanced functional nano-devices. In this work, for the first time, we perform first-principles calculations on the structural, electronic, magnetic and transport properties of 1D InSe nanoribbons with/without hydrogen or halogen saturation. We find that armchair ribbons, with various edges and distortions, are all nonmagnetic semiconductors, with a direct bandgap of 1.3 (1.4) eV for bare (H-saturated) ribbons, and have the same high electron mobility of about 103 cm2V‑1s‑1 as the 2D InSe nanosheet. Zigzag InSe nanoribbons exhibit metallic behavior and diverse intrinsic ferromagnetic properties, with the magnetic moment of 0.5–0.7 μ B per unit cell, especially for their single-edge spin polarization. The edge spin orientation, mainly dominated by the unpaired electrons of the edge atoms, depends sensitively on the edge chirality. Hydrogen or halogen saturation can effectively recover the structural distortion, and modulate the electronic and magnetic properties. The binding energy calculations show that the stability of InSe nanoribbons is analogous to that of graphene and better than in 2D InSe nanosheets. These InSe nanoribbons, with novel electronic and magnetic properties, are thus very promising for use in electronic, spintronic and magnetoresistive nano-devices.

  15. Edge magnetism impact on electrical conductance and thermoelectric properties of graphenelike nanoribbons

    Science.gov (United States)

    Krompiewski, Stefan; Cuniberti, Gianaurelio

    2017-10-01

    Edge states in narrow quasi-two-dimensional nanostructures determine, to a large extent, their electric, thermoelectric, and magnetic properties. Nonmagnetic edge states may quite often lead to topological-insulator-type behavior. However, another scenario develops when the zigzag edges are magnetic and the time reversal symmetry is broken. In this work we report on the electronic band structure modifications, electrical conductance, and thermoelectric properties of narrow zigzag nanoribbons with spontaneously magnetized edges. Theoretical studies based on the Kane-Mele-Hubbard tight-binding model show that for silicene, germanene, and stanene both the Seebeck coefficient and the thermoelectric power factor are strongly enhanced for energies close to the charge neutrality point. A perpendicular gate voltage lifts the spin degeneracy of energy bands in the ground state with antiparallel magnetized zigzag edges and makes the electrical conductance significantly spin polarized. Simultaneously the gate voltage worsens the thermoelectric performance. Estimated room-temperature figures of merit for the aforementioned nanoribbons can exceed a value of 3 if phonon thermal conductances are adequately reduced.

  16. Efficient Spin Injection into Semiconductor

    International Nuclear Information System (INIS)

    Nahid, M.A.I.

    2010-06-01

    Spintronic research has made tremendous progress nowadays for making future devices obtain extra advantages of low power, and faster and higher scalability compared to present electronic devices. A spintronic device is based on the transport of an electron's spin instead of charge. Efficient spin injection is one of the very important requirements for future spintronic devices. However, the effective spin injection is an exceedingly difficult task. In this paper, the importance of spin injection, basics of spin current and the essential requirements of spin injection are illustrated. The experimental technique of electrical spin injection into semiconductor is also discussed based on the experimental experience. The electrical spin injection can easily be implemented for spin injection into any semiconductor. (author)

  17. Quantum phase transitions in effective spin-ladder models for graphene zigzag nanoribbons

    Science.gov (United States)

    Koop, Cornelie; Wessel, Stefan

    2017-10-01

    We examine the magnetic correlations in quantum spin models that were derived recently as effective low-energy theories for electronic correlation effects on the edge states of graphene nanoribbons. For this purpose, we employ quantum Monte Carlo simulations to access the large-distance properties, accounting for quantum fluctuations beyond mean-field-theory approaches to edge magnetism. For certain chiral nanoribbons, antiferromagnetic interedge couplings were previously found to induce a gapped quantum disordered ground state of the effective spin model. We find that the extended nature of the intraedge couplings in the effective spin model for zigzag nanoribbons leads to a quantum phase transition at a large, finite value of the interedge coupling. This quantum critical point separates the quantum disordered region from a gapless phase of stable edge magnetism at weak intraedge coupling, which includes the ground states of spin-ladder models for wide zigzag nanoribbons. To study the quantum critical behavior, the effective spin model can be related to a model of two antiferromagnetically coupled Haldane-Shastry spin-half chains with long-ranged ferromagnetic intrachain couplings. The results for the critical exponents are compared also to several recent renormalization-group calculations for related long-ranged interacting quantum systems.

  18. Electric field numerical simulation of disc type electrostatic spinning spinneret

    Science.gov (United States)

    Wei, L.; Deng, ZL; Qin, XH; Liang, ZY

    2018-01-01

    Electrospinning is a new type of free-end spinning built on electric field. Different from traditional single needle spinneret, in this study, a new disc type free surface spinneret is used to produce multiple jets, this will greatly improve production efficiency of nanofiber. The electric-field distribution of spinneret is the crux of the formation and trajectory of jets. In order to probe the electric field intensity of the disc type spinneret, computational software of Ansoft Maxwell 12 is adopted for a precise and intuitive analysis. The results showed that the whole round cambered surface of the spinning solution at edge of each layer of the spinneret with the maximum curvature has the highest electric field intensity, and through the simulation of the electric field distribution of different spinneret parameters such as layer, the height and radius of the spinneret. Influences of various parameters on the electrostatic spinning are obtained.

  19. Generalized Multi-Edge Analysis for K-Edge Densitometry

    International Nuclear Information System (INIS)

    Collins, M.

    1998-01-01

    In K-edge densitometry (KED), a continuous-energy x-ray beam is transmitted through a liquid sample. The actinide content of the sample can be measured through analysis of the transmitted portion of the x-ray beam. Traditional methods for KED analysis allow the simultaneous calculation of, at most, two actinide concentrations. A generalized multi-edge KED analytical method is presented, allowing up to six actinide concentrations to be calculated simultaneously. Applications of this method for hybrid KED/x-ray fluorescence (HKED) systems are discussed. Current HKED systems require the operator to know the approximate actinide content of each sample, and manually select the proper analysis mode. The new multi-edge KED technique allows rapid identification of the major actinide components in a sample, independent of actinide content. The proper HKED analysis mode can be selected automatically, without requiring sample content information from the user. Automatic HKED analysis would be especially useful in an analytical laboratory setting, where samples with truly unknown characteristics are encountered. Because this technique requires no hardware modifications, several facilities that use HKED may eventually benefit from this approach

  20. The Antiproton Accumulator (AA)

    CERN Multimedia

    1980-01-01

    Section 06 - 08*) of the AA where the dispersion (and hence the horizontal beam size) is large. One can distinguish (left to right): A vacuum-tank, two bending magnets (BST06 and BST07 in blue) with a quadrupole (QDN07, in red) in between, another vacuum-tank, a wide quadrupole (QFW08) and a further tank . The tanks are covered with heating tape for bake-out. The tank left of BST06 contained the stack core pickup for stochastic cooling (see 7906193, 7906190, 8005051), the two other tanks served mainly as vacuum chambers in the region where the beam was large. Peter Zettwoch works on BST06. *) see: H. Koziol, Antiproton Accumulator Parameter List, PS/AA/Note 84-2 (1984)

  1. Solids Accumulation Scouting Studies

    Energy Technology Data Exchange (ETDEWEB)

    Duignan, M. R.; Steeper, T. J.; Steimke, J. L.

    2012-09-26

    The objective of Solids Accumulation activities was to perform scaled testing to understand the behavior of remaining solids in a Double Shell Tank (DST), specifically AW-105, at Hanford during multiple fill, mix, and transfer operations. It is important to know if fissionable materials can concentrate when waste is transferred from staging tanks prior to feeding waste treatment plants. Specifically, there is a concern that large, dense particles containing plutonium could accumulate in poorly mixed regions of a blend tank heel for tanks that employ mixing jet pumps. At the request of the DOE Hanford Tank Operations Contractor, Washington River Protection Solutions, the Engineering Development Laboratory of the Savannah River National Laboratory performed a scouting study in a 1/22-scale model of a waste staging tank to investigate this concern and to develop measurement techniques that could be applied in a more extensive study at a larger scale. Simulated waste tank solids: Gibbsite, Zirconia, Sand, and Stainless Steel, with stainless steel particles representing the heavier particles, e.g., plutonium, and supernatant were charged to the test tank and rotating liquid jets were used to mix most of the solids while the simulant was pumped out. Subsequently, the volume and shape of the mounds of residual solids and the spatial concentration profiles for the surrogate for heavier particles were measured. Several techniques were developed and equipment designed to accomplish the measurements needed and they included: 1. Magnetic particle separator to remove simulant stainless steel solids. A device was designed and built to capture these solids, which represent the heavier solids during a waste transfer from a staging tank. 2. Photographic equipment to determine the volume of the solids mounds. The mounds were photographed as they were exposed at different tank waste levels to develop a composite of topographical areas. 3. Laser rangefinders to determine the volume of

  2. Edge-entanglement spectrum correspondence in a nonchiral topological phase and Kramers-Wannier duality

    Science.gov (United States)

    Ho, Wen Wei; Cincio, Lukasz; Moradi, Heidar; Gaiotto, Davide; Vidal, Guifre

    2015-03-01

    In a system with chiral topological order, there is a remarkable correspondence between the edge and entanglement spectra: the low-energy spectrum of the system in the presence of a physical edge coincides with the lowest part of the entanglement spectrum (ES) across a virtual cut of the system into two parts, up to rescaling and shifting. This correspondence is believed to be due to the existence of protected gapless edge modes. In this paper, we explore whether the edge-entanglement spectrum correspondence extends to nonchiral topological phases, where there are no protected gapless edge modes. Specifically, we consider the Wen-plaquette model, which is equivalent to the Kitaev toric code model and has Z2 topological order (quantum double of Z2) . The unperturbed Wen-plaquette model displays an exact correspondence: both the edge and entanglement spectra within each topological sector a (a =1 ,⋯,4 ) are flat and equally degenerate. Here, we show, through a detailed microscopic calculation, that in the presence of generic local perturbations: (i) the effective degrees of freedom for both the physical edge and the entanglement cut consist of a (spin-1 /2 ) spin chain, with effective Hamiltonians Hedgea and Henta, respectively, both of which have a Z2 symmetry enforced by the bulk topological order; (ii) there is in general no match between the low-energy spectra of Hedgea and Henta, that is, there is no edge-ES correspondence. However, if supplement the Z2 topological order with a global symmetry (translational invariance along the edge/entanglement cut), i.e., by considering the Wen-plaquette model as a symmetry-enriched topological phase (SET), then there is a finite domain in Hamiltonian space in which both Hedgea and Henta realize the critical Ising model, whose low-energy effective theory is the c =1 /2 Ising CFT. This is achieved because the presence of the global symmetry implies that the effective degrees of freedom of both the edge and entanglement

  3. Overview of spin physics

    International Nuclear Information System (INIS)

    Yokosawa, A.

    1992-01-01

    Spin physics activities at medium and high energies became significantly active when polarized targets and polarized beams became accessible for hadron-hadron scattering experiments. My overview of spin physics will be inclined to the study of strong interaction using facilities at Argonne ZGS, Brookhaven AGS (including RHIC), CERN, Fermilab, LAMPF, an SATURNE. In 1960 accelerator physicists had already been convinced that the ZGS could be unique in accelerating a polarized beam; polarized beams were being accelerated through linear accelerators elsewhere at that time. However, there was much concern about going ahead with the construction of a polarized beam because (i) the source intensity was not high enough to accelerate in the accelerator, (ii) the use of the accelerator would be limited to only polarized-beam physics, that is, proton-proton interaction, and (iii) p-p elastic scattering was not the most popular topic in high-energy physics. In fact, within spin physics, π-nucleon physics looked attractive, since the determination of spin and parity of possible πp resonances attracted much attention. To proceed we needed more data beside total cross sections and elastic differential cross sections; measurements of polarization and other parameters were urgently needed. Polarization measurements had traditionally been performed by analyzing the spin of recoil protons. The drawbacks of this technique are: (i) it involves double scattering, resulting in poor accuracy of the data, and (ii) a carbon analyzer can only be used for a limited region of energy

  4. Modeling of ITER edge plasma in the presence of resonant magnetic perturbations

    Energy Technology Data Exchange (ETDEWEB)

    Rozhansky, V.; Kaveeva, E.; Veselova, I.; Voskoboynikov, S. [Peter the Great St. Petersburg Polytechnic University, St. Petersburg (Russian Federation); Coster, D. [Max-Planck Institut fur Plasmaphysik, EURATOM Association, Garching (Germany)

    2016-08-15

    The modeling of the ITER edge is performed with the use of the code B2SOLPS5.2 in the presence of the electron conductivity caused by RMPs as well as for the reference case with the same input parameters but without RMPs. The radial electric field close to the neoclassical one is obtained without RMPs. Even the modest level of RMPs changes the direction of the electric field and causes the toroidal spin-up of the edge plasma. At the same time the pump-out effect is small. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Engineering spin-wave channels in submicrometer magnonic waveguides

    Directory of Open Access Journals (Sweden)

    XiangJun Xing

    2013-03-01

    Full Text Available Based on micromagnetic simulations and model calculations, we demonstrate that degenerate well and barrier magnon modes can exist concurrently in a single magnetic waveguide magnetized perpendicularly to the long axis in a broad frequency band, corresponding to copropagating edge and centre spin waves, respectively. The dispersion relations of these magnon modes clearly show that the edge and centre modes possess much different wave characteristics. By tailoring the antenna size, the edge mode can be selectively activated. If the antenna is sufficiently narrow, both the edge and centre modes are excited with considerable efficiency and propagate along the waveguide. By roughening the lateral boundary of the waveguide, the characteristics of the relevant channel can be easily engineered. Moreover, the coupling of the edge and centre modes can be conveniently controlled by scaling the width of the waveguide. For a wide waveguide with a narrow antenna, the edge and centre modes travel relatively independently in spatially-separate channels, whereas for a narrow strip, these modes strongly superpose in space. These discoveries might find potential applications in emerging magnonic devices.

  6. General topological features and instanton vacuum in quantum Hall and spin liquids

    International Nuclear Information System (INIS)

    Pruisken, A.M.M.; Shankar, R.; Surendran, Naveen

    2005-01-01

    We introduce the concept of superuniversality in quantum Hall liquids and spin liquids. This concept has emerged from previous studies of the quantum Hall effect and states that all the fundamental features of the quantum Hall effect are generically displayed as general topological features of the θ parameter in nonlinear σ models in two dimensions. To establish superuniversality in spin liquids we revisit the mapping by Haldane who argued that the antiferromagnetic Heisenberg spin-s chain in 1+1 space-time dimensions is effectively described by the O(3) nonlinear σ model with a θ term. By combining the path integral representation for the dimerized spin s=1/2 chain with renormalization-group decimation techniques we generalize the Haldane approach to include a more complicated theory, the fermionic rotor chain, involving four different renormalization-group parameters. We show how the renormalization-group calculation technique can be used to build a bridge between the fermionic rotor chain and the O(3) nonlinear σ model with the θ term. As an integral and fundamental aspect of the mapping we establish the topological significance of the dangling spin at the edge of the chain. The edge spin in spin liquids is in all respects identical to the massless chiral edge excitations in quantum Hall liquids. We consider various different geometries of the spin chain such as open and closed chains, chains with an even and odd number of sides. We show that for each of the different geometries the θ term has a distinctly different physical meaning. We compare each case with a topologically equivalent quantum Hall liquid

  7. Spin Structures in Magnetic Nanoparticles

    DEFF Research Database (Denmark)

    Mørup, Steen; Brok, Erik; Frandsen, Cathrine

    2013-01-01

    Spin structures in nanoparticles of ferrimagnetic materials may deviate locally in a nontrivial way from ideal collinear spin structures. For instance, magnetic frustration due to the reduced numbers of magnetic neighbors at the particle surface or around defects in the interior can lead to spin...... canting and hence a reduced magnetization. Moreover, relaxation between almost degenerate canted spin states can lead to anomalous temperature dependences of the magnetization at low temperatures. In ensembles of nanoparticles, interparticle exchange interactions can also result in spin reorientation....... Here, we give a short review of anomalous spin structures in nanoparticles....

  8. SPIN-selling

    CERN Document Server

    Rackham, Neil

    1995-01-01

    True or false? In selling high-value products or services: "closing" increases your chance of success; it is essential to describe the benefits of your product or service to the customer; objection handling is an important skill; and open questions are more effective than closed questions. All false, says Neil Rackham. He and his team studied more than 35,000 sales calls made by 10,000 sales people in 23 countries over 12 years. Their findings revealed that many of the methods developed for selling low-value goods just don't work for major sales. Rackham went on to introduce his SPIN-selling method, where SPIN describes the whole selling process - Situation questions, Problem questions, Implication questions, Need-payoff questions. SPIN-selling provides you with a set of simple and practical techniques which have been tried in many of today's leading companies with dramatic improvements to their sales performance.

  9. Perspectives on spin glasses

    CERN Document Server

    Contucci, Pierluigi

    2013-01-01

    Presenting and developing the theory of spin glasses as a prototype for complex systems, this book is a rigorous and up-to-date introduction to their properties. The book combines a mathematical description with a physical insight of spin glass models. Topics covered include the physical origins of those models and their treatment with replica theory; mathematical properties like correlation inequalities and their use in the thermodynamic limit theory; main exact solutions of the mean field models and their probabilistic structures; and the theory of the structural properties of the spin glass phase such as stochastic stability and the overlap identities. Finally, a detailed account is given of the recent numerical simulation results and properties, including overlap equivalence, ultrametricity and decay of correlations. The book is ideal for mathematical physicists and probabilists working in disordered systems.

  10. Exertional Rhabdomyolysis after Spinning.

    Science.gov (United States)

    Jeong, Youjin; Kweon, Hyuk-Jung; Oh, Eun-Jung; Ahn, Ah-Leum; Choi, Jae-Kyung; Cho, Dong-Yung

    2016-11-01

    Any strenuous muscular exercise may trigger rhabdomyolysis. We report an episode of clinically manifested exertional rhabdomyolysis due to stationary cycling, commonly known as spinning. Reports of spinning-related rhabdomyolysis are rare in the English literature, and the current case appears to be the first such case reported in South Korea. A previously healthy 21-year-old Asian woman presented with severe thigh pain and reddish-brown urinary discoloration 24-48 hours after attending a spinning class at a local gymnasium. Paired with key laboratory findings, her symptoms were suggestive of rhabdomyolysis. She required hospital admission to sustain renal function through fluid resuscitation therapy and fluid balance monitoring. Because exertional rhabdomyolysis may occur in any unfit but otherwise healthy individual who indulges in stationary cycling, the potential health risks of this activity must be considered.

  11. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden

    1975-01-01

    The selection rules for the linear couplings between magnons and phonons propagating in the c direction of a simple basal-plane hcp ferromagnet are determined by general symmetry considerations. The acoustic-optical magnon-phonon interactions observed in the heavy-rare-earth metals have been...... explained by Liu as originating from the mixing of the spin states of the conduction electrons due to the spin-orbit coupling. We find that this coupling mechanism introduces interactions which violate the selection rules for a simple ferromagnet. The interactions between the magnons and phonons propagating...... in the c direction of Tb have been studied experimentally by means of inelastic neutron scattering. The magnons are coupled to both the acoustic- and optical-transverse phonons. By studying the behavior of the acoustic-optical coupling, we conclude that it is a spin-mixed-induced coupling as proposed...

  12. Edge imaging in intense beams

    Directory of Open Access Journals (Sweden)

    S. Bernal

    2002-06-01

    Full Text Available The appearance of rings of charge observed near the edge of beams from high-perveance guns is described with a simple ray tracing technique inspired by the particle-core model. We illustrate the technique, which has no analog in light optics, with examples from experiments employing solenoid focusing of an electron beam. The rings of charge result from the combined effects of external focusing and space-charge forces acting on paraxial fringe particles with relatively large initial transverse velocities. The model is independent of the physical mechanisms responsible for the fringe particles. Furthermore, the focal length for edge imaging in a uniform focusing channel is derived using a linearized trajectory equation for the motion of fringe particles. Counterintuitively, the focal length decreases as the beam current increases.

  13. Nonreference Medical Image Edge Map Measure

    Directory of Open Access Journals (Sweden)

    Karen Panetta

    2014-01-01

    Full Text Available Edge detection is a key step in medical image processing. It is widely used to extract features, perform segmentation, and further assist in diagnosis. A poor quality edge map can result in false alarms and misses in cancer detection algorithms. Therefore, it is necessary to have a reliable edge measure to assist in selecting the optimal edge map. Existing reference based edge measures require a ground truth edge map to evaluate the similarity between the generated edge map and the ground truth. However, the ground truth images are not available for medical images. Therefore, a nonreference edge measure is ideal for medical image processing applications. In this paper, a nonreference reconstruction based edge map evaluation (NREM is proposed. The theoretical basis is that a good edge map keeps the structure and details of the original image thus would yield a good reconstructed image. The NREM is based on comparing the similarity between the reconstructed image with the original image using this concept. The edge measure is used for selecting the optimal edge detection algorithm and optimal parameters for the algorithm. Experimental results show that the quantitative evaluations given by the edge measure have good correlations with human visual analysis.

  14. Gyrosheath near the tokamak edge

    International Nuclear Information System (INIS)

    Hazeltine, R.D.; Xiao, H.; Valanju, P.M.

    1993-03-01

    A new model for the structure of the radial electric field profile in the edge during the H-mode is proposed. Charge separation caused by the difference between electron and ion gyromotion, or more importantly in a tokamak, the banana motion (halo effect) can self-consistently produce an electric dipole moment that causes the sheared radial electric field. The calculated results based on the model are consistent with D-III D and TEXTOR experimental results

  15. Control of electron spin decoherence in nuclear spin baths

    Science.gov (United States)

    Liu, Ren-Bao

    2011-03-01

    Nuclear spin baths are a main mechanism of decoherence of spin qubits in solid-state systems, such as quantum dots and nitrogen-vacancy (NV) centers of diamond. The decoherence results from entanglement between the electron and nuclear spins, established by quantum evolution of the bath conditioned on the electron spin state. When the electron spin is flipped, the conditional bath evolution is manipulated. Such manipulation of bath through control of the electron spin not only leads to preservation of the center spin coherence but also demonstrates quantum nature of the bath. In an NV center system, the electron spin effectively interacts with hundreds of 13 C nuclear spins. Under repeated flip control (dynamical decoupling), the electron spin coherence can be preserved for a long time (> 1 ms) . Thereforesomecharacteristicoscillations , duetocouplingtoabonded 13 C nuclear spin pair (a dimer), are imprinted on the electron spin coherence profile, which are very sensitive to the position and orientation of the dimer. With such finger-print oscillations, a dimer can be uniquely identified. Thus, we propose magnetometry with single-nucleus sensitivity and atomic resolution, using NV center spin coherence to identify single molecules. Through the center spin coherence, we could also explore the many-body physics in an interacting spin bath. The information of elementary excitations and many-body correlations can be extracted from the center spin coherence under many-pulse dynamical decoupling control. Another application of the preserved spin coherence is identifying quantumness of a spin bath through the back-action of the electron spin to the bath. We show that the multiple transition of an NV center in a nuclear spin bath can have longer coherence time than the single transition does, when the classical noises due to inhomogeneous broadening is removed by spin echo. This counter-intuitive result unambiguously demonstrates the quantumness of the nuclear spin bath

  16. Spin Physics at RHIC

    International Nuclear Information System (INIS)

    Bland, L.C.

    2003-01-01

    The physics goals that will be addressed by colliding polarized protons at the Relativistic Heavy Ion Collider (RHIC) are described. The RHIC spin program provides a new generation of experiments that will unfold the quark, anti-quark and gluon contributions to the proton's spin. In addition to these longer term goals, this paper describes what was learned from the first polarized proton collisions at √(s)=200 GeV. These collisions took place in a five-week run during the second year of RHIC operation

  17. CONFERENCE: Muon spin rotation

    Energy Technology Data Exchange (ETDEWEB)

    Karlsson, Erik

    1986-11-15

    An international physics conference centred on muons without a word about leptons, weak interactions, EMC effects, exotic decay modes or any other standard high energy physics jargon. Could such a thing even have been imagined ten years ago? Yet about 120 physicists and chemists from 16 nations gathered at the end of June in Uppsala (Sweden) for their fourth meeting on Muon Spin Rotation, Relaxation and Resonance, without worrying about the muon as an elementary particle. This reflects how the experimental techniques based on the muon spin interactions have reached maturity and are widely recognized by condensed matter physicists and specialized chemists as useful tools.

  18. Spin Waves in Terbium

    DEFF Research Database (Denmark)

    Jensen, J.; Houmann, Jens Christian Gylden; Bjerrum Møller, Hans

    1975-01-01

    with the symmetry, we deduce the dispersion relation for the spin waves in a basal-plane ferromagnet. This phenomenological spin-wave theory accounts for the observed behavior of the magnon energies in Tb. The two q⃗-dependent Bogoliubov components of the magnon energies are derived from the experimental results......, which are corrected for the effect of the direct coupling between the magnons and the phonons, and for the field dependence of the relative magnetization at finite temperatures. A large q⃗-dependent difference between the two energy components is observed, showing that the anisotropy of the two...

  19. Spin puzzle in nucleon

    International Nuclear Information System (INIS)

    Ramachandran, R.

    1994-09-01

    The object of this brief review is to reconcile different points of view on how the spin of proton is made up from its constituents. On the basis of naive quark model with flavour symmetry such as isospin or SU(3) one finds a static description. On the contrary the local SU(3) colour symmetry gives a dynamical view. Both these views are contrasted and the role of U(1) axial anomaly and the ambiguity for the measurable spin content is discussed. (author). 16 refs, 1 fig

  20. Dynamics of magnetization in ferromagnet with spin-transfer torque

    Science.gov (United States)

    Li, Zai-Dong; He, Peng-Bin; Liu, Wu-Ming

    2014-11-01

    We review our recent works on dynamics of magnetization in ferromagnet with spin-transfer torque. Driven by constant spin-polarized current, the spin-transfer torque counteracts both the precession driven by the effective field and the Gilbert damping term different from the common understanding. When the spin current exceeds the critical value, the conjunctive action of Gilbert damping and spin-transfer torque leads naturally the novel screw-pitch effect characterized by the temporal oscillation of domain wall velocity and width. Driven by space- and time-dependent spin-polarized current and magnetic field, we expatiate the formation of domain wall velocity in ferromagnetic nanowire. We discuss the properties of dynamic magnetic soliton in uniaxial anisotropic ferromagnetic nanowire driven by spin-transfer torque, and analyze the modulation instability and dark soliton on the spin wave background, which shows the characteristic breather behavior of the soliton as it propagates along the ferromagnetic nanowire. With stronger breather character, we get the novel magnetic rogue wave and clarify its formation mechanism. The generation of magnetic rogue wave mainly arises from the accumulation of energy and magnons toward to its central part. We also observe that the spin-polarized current can control the exchange rate of magnons between the envelope soliton and the background, and the critical current condition is obtained analytically. At last, we have theoretically investigated the current-excited and frequency-adjusted ferromagnetic resonance in magnetic trilayers. A particular case of the perpendicular analyzer reveals that the ferromagnetic resonance curves, including the resonant location and the resonant linewidth, can be adjusted by changing the pinned magnetization direction and the direct current. Under the control of the current and external magnetic field, several magnetic states, such as quasi-parallel and quasi-antiparallel stable states, out

  1. Spin transfer torque with spin diffusion in magnetic tunnel junctions

    KAUST Repository

    Manchon, Aurelien; Matsumoto, R.; Jaffres, H.; Grollier, J.

    2012-01-01

    in the metallic layers. We show that spin diffusion mixes the transverse spin current components and dramatically modifies the bias dependence of the effective spin transfer torque. This leads to a significant linear bias dependence of the out-of-plane torque

  2. Knife-edge seal for vacuum bagging

    Science.gov (United States)

    Rauschl, J. A.

    1980-01-01

    Cam actuated clamps pinch bagging material between long knife edge (mounted to clamps) and high temperature rubber cushion bonded to baseplate. No adhesive, tape, or sealing groove is needed to seal edge of bagging sheet against base plate.

  3. Environmental Dataset Gateway (EDG) REST Interface

    Data.gov (United States)

    U.S. Environmental Protection Agency — Use the Environmental Dataset Gateway (EDG) to find and access EPA's environmental resources. Many options are available for easily reusing EDG content in other...

  4. Organizing on the Edge: Appreciation and Critique

    National Research Council Canada - National Science Library

    Scott, W. R

    2006-01-01

    .... Hayes, "Power to the Edge: Command, Control in the Information Age" (2003). The author places the "edge" perspective in the broader context of organizational studies, noting both its strengths and limitations...

  5. Edge effect on weevils and spiders

    Directory of Open Access Journals (Sweden)

    R. Horváth

    2002-05-01

    Full Text Available The edge effect on weevils and spiders was tested along oak forest – meadow transects using sweep-net samples at the Síkfökút Project in Hungary. For spiders the species richness was significantly higher in the forest edge than either in the meadow or the forest interior. For weevils the species richness of the forest edge was higher than that of the meadow, but the difference was not statistically significant whereas the species richness of the forest interior was significantly lower than that of the forest edge and the meadow. The composition of the spider assemblage of the edge was more similar to the forest, while the composition of weevils in the edge was more similar to the meadow. Our results based on two invertebrate groups operating on different trophic levels suggest that there is a significant edge effect for the studied taxa resulting in higher species richness in the edge.

  6. Observation of impurity accumulation and concurrent impurity influx in PBX

    International Nuclear Information System (INIS)

    Sesnic, S.S.; Fonck, R.J.; Ida, K.; Couture, P.; Kaita, R.; Kaye, S.; Kugel, H.; LeBlanc, B.; Okabayashi, M.; Paul, S.; Powell, E.T.; Reusch, M.; Takahashi, H.; Gammel, G.; Morris, W.

    1987-01-01

    Impurity studies in L- and H-mode discharges in PBX have shown that both types of discharges can evolve into either an impurity accumulative or nonaccumulative case. In a typical accumulative discharge, Z eff peaks in the center to values of about 5. The central metallic densities can be high, n met /n e ≅ 0.01, resulting in central radiated power densities in excess of 1 W/cm 3 , consistent with bolometric estimates. The radial profiles of metals obtained independently from the line radiation in the soft X-ray and the VUV regions are very peaked. Concurrent with the peaking, an increase in the impurity influx coming from the edge of the plasma is observed. At the beginning of the accumulation phase the inward particle flux for titanium has values of 6x10 10 and 10x10 10 particles/cm 2 s at minor radii of 6 and 17 cm. At the end of the accumulation phase, this particle flux is strongly increased to values of 3x10 12 and 1x10 12 particles/cm 2 s. This increased flux is mainly due to influx from the edge of the plasma and to a lesser extent due to increased convective transport. Using the measured particle flux, an estimate of the diffusion coefficient D and the convective velocity v is obtained. (orig.)

  7. The Antiproton Accumulator (AA)

    CERN Multimedia

    1980-01-01

    A section of the AA where the dispersion (and hence the horizontal beam size) is large. One can distinguish (left to right): A large vacuum-tank, a quadrupole (QDN09*), a bending magnet (BST08), another vacuum-tank, a wide quadrupole (QFW08) and (in the background) a further bending magnet (BST08). The tanks are covered with heating tape for bake-out. The tank left of QDN09 contained the kickers for stochastic pre-cooling (see 790621, 8002234, 8002637X), the other one served mainly as vacuum chamber in the region where the beam was large. Peter Zettwoch works on QFW08. * see: H. Koziol, Antiproton Accumulator Parameter List, PS/AA/Note 84-2 (1984) See under 7911303, 7911597X, 8004261 and 8202324. For photos of the AA in different phases of completion (between 1979 and 1982) see: 7911303, 7911597X, 8004261, 8004608X, 8005563X, 8005565X, 8006716X, 8006722X, 8010939X, 8010941X, 8202324, 8202658X, 8203628X .

  8. Dynamic spin polarization by orientation-dependent separation in a ferromagnet-semiconductor hybrid

    Science.gov (United States)

    Korenev, V. L.; Akimov, I. A.; Zaitsev, S. V.; Sapega, V. F.; Langer, L.; Yakovlev, D. R.; Danilov, Yu. A.; Bayer, M.

    2012-07-01

    Integration of magnetism into semiconductor electronics would facilitate an all-in-one-chip computer. Ferromagnet/bulk semiconductor hybrids have been, so far, mainly considered as key devices to read out the ferromagnetism by means of spin injection. Here we demonstrate that a Mn-based ferromagnetic layer acts as an orientation-dependent separator for carrier spins confined in a semiconductor quantum well that is set apart from the ferromagnet by a barrier only a few nanometers thick. By this spin-separation effect, a non-equilibrium electron-spin polarization is accumulated in the quantum well due to spin-dependent electron transfer to the ferromagnet. The significant advance of this hybrid design is that the excellent optical properties of the quantum well are maintained. This opens up the possibility of optical readout of the ferromagnet's magnetization and control of the non-equilibrium spin polarization in non-magnetic quantum wells.

  9. Transverse Spin Physics: Recent Developments

    International Nuclear Information System (INIS)

    Yuan, Feng

    2008-01-01

    Transverse-spin physics has been very active and rapidly developing in the last few years. In this talk, I will briefly summarize recent theoretical developments, focusing on the associated QCD dynamics in transverse spin physics

  10. A stochastic picture of spin

    International Nuclear Information System (INIS)

    Faris, W.G.

    1981-01-01

    Dankel has shown how to incorporate spin into stochastic mechanics. The resulting non-local hidden variable theory gives an appealing picture of spin correlation experiments in which Bell's inequality is violated. (orig.)

  11. Batteries and accumulators in France

    International Nuclear Information System (INIS)

    2012-12-01

    The present report gives an overview of the batteries and accumulators market in France in 2011 based on the data reported through ADEME's Register of Batteries and accumulators. In 2001, the French Environmental Agency, known as ADEME, implemented a follow-up of the batteries and accumulators market, creating the Observatory of batteries and accumulators (B and A). In 2010, ADEME created the National Register of producers of Batteries and Accumulators in the context of the implementation of the order issued on November 18, 2009. This is one of the four enforcement orders for the decree 2009-1139 issued on September 22, 2009, concerning batteries and accumulators put on the market and the disposal of waste batteries and accumulators, and which transposes the EU-Directive 2006/66/CE into French law. This Register follows the former Observatory for batteries and accumulators. This Register aims to record the producers on French territory and to collect the B and A producers and recycling companies' annual reporting: the regulation indeed requires that all B and A producers and recycling companies report annually on the Register the quantities of batteries and accumulators they put on the market, collect and treat. Based on this data analysis, ADEME issues an annual report allowing both the follow-up of the batteries and accumulators market in France and communication regarding the achievement of the collection and recovery objectives set by EU regulation. This booklet presents the situation in France in 2011

  12. Muonium spin exchange in spin-polarized media: Spin-flip and -nonflip collisions

    International Nuclear Information System (INIS)

    Senba, M.

    1994-01-01

    The transverse relaxation of the muon spin in muonium due to electron spin exchange with a polarized spin-1/2 medium is investigated. Stochastic calculations, which assume that spin exchange is a Poisson process, are carried out for the case where the electron spin polarization of the medium is on the same axis as the applied field. Two precession signals of muonium observed in intermediate fields (B>30 G) are shown to have different relaxation rates which depend on the polarization of the medium. Furthermore, the precession frequencies are shifted by an amount which depends on the spin-nonflip rate. From the two relaxation rates and the frequency shift in intermediate fields, one can determine (i) the encounter rate of muonium and the paramagnetic species, (ii) the polarization of the medium, and most importantly (iii) the quantum-mechanical phase shift (and its sign) associated with the potential energy difference between electron singlet and triplet encounters. Effects of spin-nonflip collisions on spin dynamics are discussed for non-Poisson as well as Poisson processes. In unpolarized media, the time evolution of the muon spin in muonium is not influenced by spin-nonflip collisions, if the collision process is Poissonian. This seemingly obvious statement is not true anymore in non-Poissonian processes, i.e., it is necessary to specify both spin-flip and spin-nonflip rates to fully characterize spin dynamics

  13. Design lithium storage materials by lithium adatoms adsorption at the edges of zigzag silicene nanoribbon: A first principle study

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Gang [Hunan Key Laboratory for Micro–Nano Energy Materials and Devices, School of Physics and Optoelectronic Engineering, Xiangtan University, Hunan, 411105 (China); Mao, Yuliang, E-mail: ylmao@xtu.edu.cn [Hunan Key Laboratory for Micro–Nano Energy Materials and Devices, School of Physics and Optoelectronic Engineering, Xiangtan University, Hunan, 411105 (China); Zhong, Jianxin [Hunan Key Laboratory for Micro–Nano Energy Materials and Devices, School of Physics and Optoelectronic Engineering, Xiangtan University, Hunan, 411105 (China); Yuan, Jianmei [Hunan Key Laboratory for Computation and Simulation in Science and Engineering, School of Mathematics and Computational Science, Xiangtan University, Hunan, 411105 (China); Zhao, Hongquan, E-mail: hqzhao@cigit.ac.cn [Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, 401120 (China)

    2017-06-01

    Highlights: • Edge-adsorption of Li adatoms on zigzag silicene nanoribbon is preferred in energy to form new type lithium storage materials. • Significant charge transfer from Li adatoms to Si atoms is found, indicating the main ionic interactions. • The band structures of zigzag silicene nanoribbon are sensitive with the variation of sites of Li adatoms at the two edges. • The local magnetic moments at the two edges of zigzag silicene nanoribbon are suppressed by the adsorptions of Li adatoms. - Abstract: First-principles spin-polarized calculations are performed to design lithium storage materials using the active edges of zigzag silicene nanoribbon (ZSiNR). We predict that edge-adsorption of Li adatoms on zigzag silicene nanoribbon is preferred in energy to form new type lithium storage materials. Significant charge transfer from Li adatoms to Si atoms at the edges of ZSiNR is found, indicating the main ionic interactions. It is found that the band structures of ZSiNR with Li adsorptions are sensitive with the variation of sites of adatoms at the two edges. Ferro-magnetic to antiferro-magnetic change is found in ZSiNR with symmetrical adsorption of Li adatoms at its two edges. Other unsymmetrical Li adsorptions at the edges of ZSiNR prefer to stay in ferro-magnetic state as that in narrow pristine ZSiNR.

  14. Design lithium storage materials by lithium adatoms adsorption at the edges of zigzag silicene nanoribbon: A first principle study

    International Nuclear Information System (INIS)

    Guo, Gang; Mao, Yuliang; Zhong, Jianxin; Yuan, Jianmei; Zhao, Hongquan

    2017-01-01

    Highlights: • Edge-adsorption of Li adatoms on zigzag silicene nanoribbon is preferred in energy to form new type lithium storage materials. • Significant charge transfer from Li adatoms to Si atoms is found, indicating the main ionic interactions. • The band structures of zigzag silicene nanoribbon are sensitive with the variation of sites of Li adatoms at the two edges. • The local magnetic moments at the two edges of zigzag silicene nanoribbon are suppressed by the adsorptions of Li adatoms. - Abstract: First-principles spin-polarized calculations are performed to design lithium storage materials using the active edges of zigzag silicene nanoribbon (ZSiNR). We predict that edge-adsorption of Li adatoms on zigzag silicene nanoribbon is preferred in energy to form new type lithium storage materials. Significant charge transfer from Li adatoms to Si atoms at the edges of ZSiNR is found, indicating the main ionic interactions. It is found that the band structures of ZSiNR with Li adsorptions are sensitive with the variation of sites of adatoms at the two edges. Ferro-magnetic to antiferro-magnetic change is found in ZSiNR with symmetrical adsorption of Li adatoms at its two edges. Other unsymmetrical Li adsorptions at the edges of ZSiNR prefer to stay in ferro-magnetic state as that in narrow pristine ZSiNR.

  15. CFAR Edge Detector for Polarimetric SAR Images

    DEFF Research Database (Denmark)

    Schou, Jesper; Skriver, Henning; Nielsen, Allan Aasbjerg

    2003-01-01

    Finding the edges between different regions in an image is one of the fundamental steps of image analysis, and several edge detectors suitable for the special statistics of synthetic aperture radar (SAR) intensity images have previously been developed. In this paper, a new edge detector for polar...

  16. Energetics of highly kinked step edges

    NARCIS (Netherlands)

    Zandvliet, Henricus J.W.

    2010-01-01

    We have determined the step edge free energy, the step edge stiffness and dimensionless inverse step edge stiffness of the highly kinked < 010> oriented step on a (001) surface of a simple square lattice within the framework of a solid-on-solid model. We have found an exact expression for the step

  17. Acyclicity in edge-colored graphs

    DEFF Research Database (Denmark)

    Gutin, Gregory; Jones, Mark; Sheng, Bin

    2017-01-01

    A walk W in edge-colored graphs is called properly colored (PC) if every pair of consecutive edges in W is of different color. We introduce and study five types of PC acyclicity in edge-colored graphs such that graphs of PC acyclicity of type i is a proper superset of graphs of acyclicity of type...

  18. Antiferromagnetic spin-orbitronics

    KAUST Repository

    Manchon, Aurelien; Saidaoui, Hamed Ben Mohamed; Ghosh, Sumit

    2015-01-01

    Antiferromagnets have long remained an intriguing and exotic state of matter, whose application has been restricted to enabling interfacial exchange bias in metallic and tunneling spin-valves [1]. Their role in the expanding field of applied spintronics has been mostly passive and the in-depth investigation of their basic properties mostly considered from a fundamental perspective.

  19. Antiferromagnetic spin-orbitronics

    KAUST Repository

    Manchon, Aurelien

    2015-05-01

    Antiferromagnets have long remained an intriguing and exotic state of matter, whose application has been restricted to enabling interfacial exchange bias in metallic and tunneling spin-valves [1]. Their role in the expanding field of applied spintronics has been mostly passive and the in-depth investigation of their basic properties mostly considered from a fundamental perspective.

  20. Brookhaven: Spin result underlined

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1990-09-15

    A recent experiment looking at violent proton-proton elastic scattering confirms, with high precision, earlier data which puzzled many theorists. Most pictures of strong interactions based on perturbative quark-gluon field theory (Quantum Chromodynamics, QCD) suggested that spin effects should disappear with energy and as the collisions become more violent.

  1. Nuclear Spin Relaxation

    Indian Academy of Sciences (India)

    IAS Admin

    ments have shown that in some cases the nuclear spin systems may be held in special configurations called .... these methods have been commercialized, and used for clinical trials, in which hyperpolarized NMR is used to .... symmetric under exchange, meaning that exchanging the two nuclei leaves the state unchanged.

  2. Nuclear spin-off

    International Nuclear Information System (INIS)

    1981-11-01

    This booklet gives examples of 'nuclear spin off', from research programmes carried out for the UKAEA, under the following headings; non destructive testing; tribology; environmental protection; flow measurement; material sciences; mechanical engineering; marine services; biochemical technology; electronic instrumentation. (U.K.)

  3. Spin and isospin modes

    International Nuclear Information System (INIS)

    Suzuki, T.; Sagawa, H.

    2000-01-01

    Complete text of publication follows. Spin and isospin modes in nuclei are investigated. We discuss some of the following topics. 1. Spin-dipole excitations in 12 C and 16 O are studied (1). Effects of tensor and spin-orbit interactions on the distribution of the strengths are investigated, and neutral current neutrino scattering cross sections in 16 O are obtained for heavy-flavor neutrinos from the supernovae. 2. Gamow-Teller (GT) and spin-dipole (SD) modes in 208 Bi are investigated. Quenching and fragmentation of the GT strength are discussed (2). SD excitations and electric dipole (E1) transitions between the GT and SD states are studied (3). Calculated E1 strengths are compared with the sum rule values obtained within the 1p-1h and 1p-1h + 2p-2h configuration spaces. 3. Coulomb displacement energy (CDE) of the IAS of 14 Be is calculated, and the effects of the halo on the CDE and the configuration of the halo state are investigated. 4. Spreading width of IAS and isospin dependence of the width are investigated (4). Our formula for the width explains very well the observed isospin dependence (5). (author)

  4. Spin-polarized photoemission

    International Nuclear Information System (INIS)

    Johnson, Peter D.

    1997-01-01

    Spin-polarized photoemission has developed into a versatile tool for the study of surface and thin film magnetism. In this review, we examine the methodology of the technique and its application to a number of different problems, including both valence band and core level studies. After a detailed review of spin-polarization measurement techniques and the related experimental requirements we consider in detail studies of the bulk properties both above and below the Curie temperature. This section also includes a discussion of observations relating to unique metastable phases obtained via epitaxial growth. The application of the technique to the study of surfaces, both clean and adsorbate covered, is reviewed. The report then examines, in detail, studies of the spin-polarized electronic structure of thin films and the related interfacial magnetism. Finally, observations of spin-polarized quantum well states in non-magnetic thin films are discussed with particular reference to their mediation of the oscillatory exchange coupling in related magnetic multilayers. (author)

  5. Spin physics at ELSA

    International Nuclear Information System (INIS)

    Althoff, K.H.

    1989-01-01

    In 1987 the new Bonn stretcher accelerator ELSA came into operation. In this paper a short description of the accelerator and the three experimental facilities PHOENICS, ELAN and SAPHIR is given. The determination of spin observables is one of the main subjects of the experimental program. Some experiments are discussed in more detail

  6. Spin physics in semiconductors

    CERN Document Server

    Dyakonov, Mikhail I

    2008-01-01

    This book describes beautiful optical and transport phenomena related to the electron and nuclear spins in semiconductors with emphasis on a clear presentation of the physics involved. Recent results on quantum wells and quantum dots are reviewed. The book is intended for students and researchers in the fields of semiconductor physics and nanoelectronics.

  7. Brookhaven: Spin result underlined

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    A recent experiment looking at violent proton-proton elastic scattering confirms, with high precision, earlier data which puzzled many theorists. Most pictures of strong interactions based on perturbative quark-gluon field theory (Quantum Chromodynamics, QCD) suggested that spin effects should disappear with energy and as the collisions become more violent

  8. Spin polarizability of hyperons

    Indian Academy of Sciences (India)

    K B VIJAYA KUMAR. Department of Physics, Mangalore University, Mangalagangothri 574 199, India. E-mail: kbvijayakumar@yahoo.com. DOI: 10.1007/s12043-014-0869-4; ePublication: 4 November 2014. Abstract. We review the recent progress of the theoretical understanding of spin polarizabilities of the hyperon in the ...

  9. The invariance of spin

    International Nuclear Information System (INIS)

    Bramson, B.D.

    1978-01-01

    An isolated system in general relativity makes a transition between stationary states. It is shown that the spin vectors of the system, long before and long after the emission of radiation, are supertranslation invariant and, hence, independent of the choice of Minkowski observation space. (author)

  10. Spin Injection in Indium Arsenide

    Directory of Open Access Journals (Sweden)

    Mark eJohnson

    2015-08-01

    Full Text Available In a two dimensional electron system (2DES, coherent spin precession of a ballistic spin polarized current, controlled by the Rashba spin orbit interaction, is a remarkable phenomenon that’s been observed only recently. Datta and Das predicted this precession would manifest as an oscillation in the source-drain conductance of the channel in a spin-injected field effect transistor (Spin FET. The indium arsenide single quantum well materials system has proven to be ideal for experimental confirmation. The 2DES carriers have high mobility, low sheet resistance, and high spin orbit interaction. Techniques for electrical injection and detection of spin polarized carriers were developed over the last two decades. Adapting the proposed Spin FET to the Johnson-Silsbee nonlocal geometry was a key to the first experimental demonstration of gate voltage controlled coherent spin precession. More recently, a new technique measured the oscillation as a function of channel length. This article gives an overview of the experimental phenomenology of the spin injection technique. We then review details of the application of the technique to InAs single quantum well (SQW devices. The effective magnetic field associated with Rashba spin-orbit coupling is described, and a heuristic model of coherent spin precession is presented. The two successful empirical demonstrations of the Datta Das conductance oscillation are then described and discussed.

  11. An overview of spin physics

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1991-07-01

    Spin physics is playing an increasingly important role in high energy experiments and theory. This review looks at selected topics in high energy spin physics that were discussed at the 9th International Symposium on High Energy Spin Physics at Bonn in September 1990

  12. Mechanical generation of spin current

    Directory of Open Access Journals (Sweden)

    Mamoru eMatsuo

    2015-07-01

    Full Text Available We focus the recent results on spin-current generation from mechanical motion such as rigid rotation and elastic deformations. Spin transport theory in accelerating frames is constructed by using the low energy expansion of the generally covariant Dirac equation. Related issues on spin-manipulation by mechanical rotation are also discussed.

  13. Spin Transport in Semiconductor heterostructures

    International Nuclear Information System (INIS)

    Marinescu, Domnita Catalina

    2011-01-01

    The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.

  14. Spinning Them Off: Entrepreneuring Practices in Corporate Spin-Offs

    Directory of Open Access Journals (Sweden)

    Katja Maria Hydle

    2016-01-01

    Full Text Available This paper focuses on the practices between parent and child firms in corporate spinoffs. We uncover the enacted aspects of knowledge, called knowing, through theories from seven cases of incumbent-backed spin-offs and find that the management of the parent firms are highly involved in the spin-offs. The practices associated with spinning off are solving problems, involving multidisciplinary expertise and entrepreneuring management at the parent firm. We contribute to the spin-off literature by discussing the knowledge required for successfully spinning off child firms and to practice theory by empirically uncovering the practical understanding involved in the origin and perpetuation of an organization.

  15. Brillouin-Mandelstam spectroscopy of standing spin waves in a ferrite waveguide

    Science.gov (United States)

    Balinskiy, Michael; Kargar, Fariborz; Chiang, Howard; Balandin, Alexander A.; Khitun, Alexander G.

    2018-05-01

    This article reports results of experimental investigation of the spin wave interference over large distances in the Y3Fe2(FeO4)3 waveguide using Brillouin-Mandelstam spectroscopy. Two coherent spin waves are excited by the micro-antennas fabricated at the edges of the waveguide. The amplitudes of the input spin waves are adjusted to provide approximately the same intensity in the central region of the waveguide. The relative phase between the excited spin waves is controlled by the phase shifter. The change of the local intensity distribution in the standing spin wave is monitored using Brillouin-Mandelstam light scattering spectroscopy. Experimental data demonstrate the oscillation of the scattered light intensity depending on the relative phase of the interfering spin waves. The oscillations of the intensity, tunable via the relative phase shift, are observed as far as 7.5 mm away from the spin-wave generating antennas at room temperature. The obtained results are important for developing techniques for remote control of spin currents, with potential applications in spin-based memory and logic devices.

  16. Edge and coupled core/edge transport modelling in tokamaks

    International Nuclear Information System (INIS)

    Lodestro, L.L.; Casper, T.A.; Cohen, R.H.

    1999-01-01

    Recent advances in the theory and modelling of tokamak edge, scrape-off-layer (SOL) and divertor plasmas are described. The effects of the poloidal E x B drift on inner/outer divertor-plate asymmetries within a 1D analysis are shown to be in good agreement with experimental trends; above a critical v ExB , the model predicts transitions to supersonic flow at the inboard midplane. 2D simulations show the importance of E x B flow in the private-flux region and of ∇ B-drifts. A theory of rough plasma-facing surfaces is given, predicting modifications to the SOL plasma. The parametric dependence of detached-plasma states in slab geometry has been explored; with sufficient pumping, the location of the ionization front can be controlled; otherwise only fronts near the plate or the X-point are stable. Studies with a more accurate Monte-Carlo neutrals model and a detailed non-LTE radiation-transport code indicate various effects are important for quantitative modelling. Detailed simulations of the DIII-D core and edge are presented; impurity and plasma flow are discussed and shown to be well modelled with UEDGE. (author)

  17. Edge and coupled core-edge transport modelling in tokamaks

    International Nuclear Information System (INIS)

    Lodestro, L.L.; Casper, T.A.; Cohen, R.H.

    2001-01-01

    Recent advances in the theory and modelling of tokamak edge, scrape-off-layer (SOL) and divertor plasmas are described. The effects of the poloidal ExB drift on inner/outer divertor-plate asymmetries within a 1D analysis are shown to be in good agreement with experimental trends; above a critical v ExB, the model predicts transitions to supersonic SOL flow at the inboard midplane. 2D simulations show the importance of ExB flow in the private-flux region and of ∇ B-drifts. A theory of rough plasma-facing surfaces is given, predicting modifications to the SOL plasma. The parametric dependence of detached-plasma states in slab geometry has been explored; with sufficient pumping, the location of the ionization front can be controlled; otherwise only fronts near the plate or the X-point are stable. Studies with a more accurate Monte-Carlo neutrals model and a detailed non-LTE radiation-transport code indicate various effects are important for quantitative modelling. Detailed simulations of the DIII-D core and edge are presented; impurity and plasma flow are discussed and shown to be well modelled with UEDGE. (author)

  18. Spin-orbit induced electronic spin separation in semiconductor nanostructures.

    Science.gov (United States)

    Kohda, Makoto; Nakamura, Shuji; Nishihara, Yoshitaka; Kobayashi, Kensuke; Ono, Teruo; Ohe, Jun-ichiro; Tokura, Yasuhiro; Mineno, Taiki; Nitta, Junsaku

    2012-01-01

    The demonstration of quantized spin splitting by Stern and Gerlach is one of the most important experiments in modern physics. Their discovery was the precursor of recent developments in spin-based technologies. Although electrical spin separation of charged particles is fundamental in spintronics, in non-uniform magnetic fields it has been difficult to separate the spin states of charged particles due to the Lorentz force, as well as to the insufficient and uncontrollable field gradients. Here we demonstrate electronic spin separation in a semiconductor nanostructure. To avoid the Lorentz force, which is inevitably induced when an external magnetic field is applied, we utilized the effective non-uniform magnetic field which originates from the Rashba spin-orbit interaction in an InGaAs-based heterostructure. Using a Stern-Gerlach-inspired mechanism, together with a quantum point contact, we obtained field gradients of 10(8) T m(-1) resulting in a highly polarized spin current.

  19. Spin Relaxation and Manipulation in Spin-orbit Qubits

    Science.gov (United States)

    Borhani, Massoud; Hu, Xuedong

    2012-02-01

    We derive a generalized form of the Electric Dipole Spin Resonance (EDSR) Hamiltonian in the presence of the spin-orbit interaction for single spins in an elliptic quantum dot (QD) subject to an arbitrary (in both direction and magnitude) applied magnetic field. We predict a nonlinear behavior of the Rabi frequency as a function of the magnetic field for sufficiently large Zeeman energies, and present a microscopic expression for the anisotropic electron g-tensor. Similarly, an EDSR Hamiltonian is devised for two spins confined in a double quantum dot (DQD). Finally, we calculate two-electron-spin relaxation rates due to phonon emission, for both in-plane and perpendicular magnetic fields. Our results have immediate applications to current EDSR experiments on nanowire QDs, g-factor optimization of confined carriers, and spin decay measurements in DQD spin-orbit qubits.

  20. Excitation of coherent propagating spin waves by pure spin currents.

    Science.gov (United States)

    Demidov, Vladislav E; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O

    2016-01-28

    Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics.

  1. Large spin Hall magnetoresistance and its correlation to the spin-orbit torque in W/CoFeB/MgO structures

    Science.gov (United States)

    Cho, Soonha; Baek, Seung-heon Chris; Lee, Kyeong-Dong; Jo, Younghun; Park, Byong-Guk

    2015-01-01

    The phenomena based on spin-orbit interaction in heavy metal/ferromagnet/oxide structures have been investigated extensively due to their applicability to the manipulation of the magnetization direction via the in-plane current. This implies the existence of an inverse effect, in which the conductivity in such structures should depend on the magnetization orientation. In this work, we report a systematic study of the magnetoresistance (MR) of W/CoFeB/MgO structures and its correlation with the current-induced torque to the magnetization. We observe that the MR is independent of the angle between the magnetization and current direction but is determined by the relative magnetization orientation with respect to the spin direction accumulated by the spin Hall effect, for which the symmetry is identical to that of so-called the spin Hall magnetoresistance. The MR of ~1% in W/CoFeB/MgO samples is considerably larger than those in other structures of Ta/CoFeB/MgO or Pt/Co/AlOx, which indicates a larger spin Hall angle of W. Moreover, the similar W thickness dependence of the MR and the current-induced magnetization switching efficiency demonstrates that MR in a non-magnet/ferromagnet structure can be utilized to understand other closely correlated spin-orbit coupling effects such as the inverse spin Hall effect or the spin-orbit spin transfer torques. PMID:26423608

  2. Finding a Hadamard matrix by simulated annealing of spin vectors

    Science.gov (United States)

    Bayu Suksmono, Andriyan

    2017-05-01

    Reformulation of a combinatorial problem into optimization of a statistical-mechanics system enables finding a better solution using heuristics derived from a physical process, such as by the simulated annealing (SA). In this paper, we present a Hadamard matrix (H-matrix) searching method based on the SA on an Ising model. By equivalence, an H-matrix can be converted into a seminormalized Hadamard (SH) matrix, whose first column is unit vector and the rest ones are vectors with equal number of -1 and +1 called SH-vectors. We define SH spin vectors as representation of the SH vectors, which play a similar role as the spins on Ising model. The topology of the lattice is generalized into a graph, whose edges represent orthogonality relationship among the SH spin vectors. Starting from a randomly generated quasi H-matrix Q, which is a matrix similar to the SH-matrix without imposing orthogonality, we perform the SA. The transitions of Q are conducted by random exchange of {+, -} spin-pair within the SH-spin vectors that follow the Metropolis update rule. Upon transition toward zeroth energy, the Q-matrix is evolved following a Markov chain toward an orthogonal matrix, at which the H-matrix is said to be found. We demonstrate the capability of the proposed method to find some low-order H-matrices, including the ones that cannot trivially be constructed by the Sylvester method.

  3. Spin foam models of matter coupled to gravity

    International Nuclear Information System (INIS)

    Mikovic, A

    2002-01-01

    We construct a class of spin foam models describing matter coupled to gravity, such that the gravitational sector is described by the unitary irreducible representations of the appropriate symmetry group, while the matter sector is described by the finite-dimensional irreducible representations of that group. The corresponding spin foam amplitudes in the four-dimensional gravity case are expressed in terms of the spin network amplitudes for pentagrams with additional external and internal matter edges. We also give a quantum field theory formulation of the model, where the matter degrees of freedom are described by spin network fields carrying the indices from the appropriate group representation. In the non-topological Lorentzian gravity case, we argue that the matter representations should be appropriate SO(3) or SO(2) representations contained in a given Lorentz matter representation, depending on whether one wants to describe a massive or a massless matter field. The corresponding spin network amplitudes are given as multiple integrals of propagators which are matrix spherical functions

  4. Image Edge Tracking via Ant Colony Optimization

    Science.gov (United States)

    Li, Ruowei; Wu, Hongkun; Liu, Shilong; Rahman, M. A.; Liu, Sanchi; Kwok, Ngai Ming

    2018-04-01

    A good edge plot should use continuous thin lines to describe the complete contour of the captured object. However, the detection of weak edges is a challenging task because of the associated low pixel intensities. Ant Colony Optimization (ACO) has been employed by many researchers to address this problem. The algorithm is a meta-heuristic method developed by mimicking the natural behaviour of ants. It uses iterative searches to find the optimal solution that cannot be found via traditional optimization approaches. In this work, ACO is employed to track and repair broken edges obtained via conventional Sobel edge detector to produced a result with more connected edges.

  5. K-edge densitometer (KED)

    Energy Technology Data Exchange (ETDEWEB)

    Sprinkle, J.K.; Hansen, W.J.

    1993-02-11

    In 1979, a K-edge densitometer (KED) was installed by the Safeguards Assay group from Los Alamos National Laboratory in the PNC reprocessing plant at Tokai-mura, Japan. It uses an active nondestructive assay technique, KED, to measure the plutonium concentration of the product solution. The measurement uncertainty of an assay depends on the count time chosen, but can be 0.5% or better. The computer hardware and software were upgraded in 1992. This manual describes the operation of the instrument, with an emphasis on the user interface to the software.

  6. Instant Adobe Edge Inspect starter

    CERN Document Server

    Khan, Joseph

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. This easy-to-understand Starter guide will get you up to speed with Adobe Edge Inspect quickly and with little effort.This book is for frontend web developers and designers who are developing and testing web applications targeted for mobile browsers. It's assumed that you have a basic understanding of creating web applications using HTML, CSS, and JavaScript, as well as being familiar with running web pages from local HTTP servers. Readers are a

  7. Andreev spectrum with high spin-orbit interactions: Revealing spin splitting and topologically protected crossings

    Science.gov (United States)

    Murani, A.; Chepelianskii, A.; Guéron, S.; Bouchiat, H.

    2017-10-01

    In order to point out experimentally accessible signatures of spin-orbit interaction, we investigate numerically the Andreev spectrum of a multichannel mesoscopic quantum wire (N) with high spin-orbit interaction coupled to superconducting electrodes (S), contrasting topological and nontopological behaviors. In the nontopological case (square lattice with Rashba interactions), we find that the Kramers degeneracy of Andreev levels is lifted by a phase difference between the S reservoirs except at multiples of π , when the normal quantum wires can host several conduction channels. The level crossings at these points invariant by time-reversal symmetry are not lifted by disorder. Whereas the dc Josephson current is insensitive to these level crossings, the high-frequency admittance (susceptibility) at finite temperature reveals these level crossings and the lifting of their degeneracy at π by a small Zeeman field. We have also investigated the hexagonal lattice with intrinsic spin-orbit interaction in the range of parameters where it is a two-dimensional topological insulator with one-dimensional helical edges protected against disorder. Nontopological superconducting contacts can induce topological superconductivity in this system characterized by zero-energy level crossing of Andreev levels. Both Josephson current and finite-frequency admittance carry then very specific signatures at low temperature of this disorder-protected Andreev level crossing at π and zero energy.

  8. Asymmetrical edges induced strong current-polarization in embedded graphene nanoribbons

    Science.gov (United States)

    Li, Kuanhong; Zhang, Xiang-Hua

    2018-05-01

    We investigate the electronic structures and transport properties of the embedded zigzag graphene nanoribbon (E-ZGNR) in hexagonal boron nitride trenches, which are achievable in recent experiments. Our first principles results show that the E-ZGNR has a significant enhanced conductivity relative to common ZGNRs due to the existence of asymmetrical edge structures. Moreover, only one spin-orientation electrons possess a widely opened band gap at the magnetic ground state with anti-ferromagnetic configuration, resulting in a full current-polarization at low bias region. Our findings indicate that the state-of-the-art embedding technology is quite useful for tuning the electronic structure of ZGNR and building possible spin injection and spin filter devices in spintronics.

  9. Electrical spin injection and detection in silicon nanowires with axial doping gradient.

    Science.gov (United States)

    Kountouriotis, Konstantinos; Barreda, Jorge L; Keiper, Timothy David; Zhang, Mei; Xiong, Peng

    2018-06-13

    The interest in spin transport in nanoscopic semiconductor channels is driven by both the inevitable miniaturization of spintronics devices toward nanoscale and the rich spin-dependent physics the quantum confinement engenders. For such studies, the all-important issue of the ferromagnet/semiconductor (FM/SC) interface becomes even more critical at nanoscale. Here we elucidate the effects of the FM/SC interface on electrical spin injection and detection at nanoscale dimensions, utilizing a unique type of Si nanowires (NWs) with an inherent axial doping gradient. Two-terminal and nonlocal four-terminal lateral spin-valve measurements were performed using different combinations from a series of FM contacts positioned along the same NW. The data are analyzed with a general model of spin accumulation in a normal channel under electrical spin injection from a FM, which reveals a distinct correlation of decreasing spin-valve signal with increasing injector junction resistance. The observation is attributed to the diminishing contribution of the d-electrons in the FM to the injected current spin polarization with increasing Schottky barrier width. The results demonstrate that there is a window of interface parameters for optimal spin injection efficiency and current spin polarization, which provides important design guidelines for nano-spintronic devices with quasi-1D semiconductor channels.

  10. Theory of in-plane current induced spin torque in metal/ferromagnet bilayers

    Science.gov (United States)

    Sakanashi, Kohei; Sigrist, Manfred; Chen, Wei

    2018-05-01

    Using a semiclassical approach that simultaneously incorporates the spin Hall effect (SHE), spin diffusion, quantum well states, and interface spin–orbit coupling (SOC), we address the interplay of these mechanisms as the origin of the spin–orbit torque (SOT) induced by in-plane currents, as observed in the normal metal/ferromagnetic metal bilayer thin films. Focusing on the bilayers with a ferromagnet much thinner than its spin diffusion length, such as Pt/Co with  ∼10 nm thickness, our approach addresses simultaneously the two contributions to the SOT, namely the spin-transfer torque (SHE-STT) due to SHE-induced spin injection, and the inverse spin Galvanic effect spin–orbit torque (ISGE-SOT) due to SOC-induced spin accumulation. The SOC produces an effective magnetic field at the interface, hence it modifies the angular momentum conservation expected for the SHE-STT. The SHE-induced spin voltage and the interface spin current are mutually dependent and, hence, are solved in a self-consistent manner. The result suggests that the SHE-STT and ISGE-SOT are of the same order of magnitude, and the spin transport mediated by the quantum well states may be an important mechanism for the experimentally observed rapid variation of the SOT with respect to the thickness of the ferromagnet.

  11. Prediction of giant intrinsic spin-Hall effect in strained p-GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Christoph; Kubis, Tillmann; Vogl, Peter [Walter Schottky Institut, Technische Universitaet Muenchen, Garching (Germany)

    2009-07-01

    We present a systematic study of the intrinsic spin-Hall effect and its inverse effect in various two dimensional nanostructures using the non-equilibrium Green's function technique. We include elastic impurity scattering as well as inelastic acoustical phonon scattering. The parameters for the Dresselhaus and Rashba spin-orbit coupling are obtained from an atomistic tight binding calculation. We predict exceptionally large spin polarization effects in specially band engineered and geometrically designed nanostructures. In strained p-GasAs, we find a k-linear spin splitting that is enhanced by a factor of 50 compared to the unstrained case. We propose a T shaped three-terminal device that acts as a spin polarizer without external magnetic field. Optimizing the geometry with respect to the spin-precession length results in a spin accumulation at the drain contacts of up to 25%. We also study the inverse intrinsic spin-Hall effect. In a four-terminal ''H'' shaped structure it can be used to measure the direct spin-Hall effect by simply applying a gate voltage. For such a measurement, we predict a threshold value for the spin-orbit coupling strength that cannot be met by simple n-GaAs systems.

  12. Spin current evolution in the separated spin-up and spin-down quantum hydrodynamics

    International Nuclear Information System (INIS)

    Trukhanova, Mariya Iv.

    2015-01-01

    We have developed a method of quantum hydrodynamics (QHD) that describes particles with spin-up and with spin-down in separate. We have derived the equation of the spin current evolution as a part of the set of the quantum hydrodynamics equations that treat particles with different projection of spin on the preferable direction as two different species. We have studied orthogonal propagation of waves in the external magnetic field and determined the contribution of quantum corrections due to the Bohm potential and to magnetization energy of particles with different projections of spin in the spin-current wave dispersion. We have analyzed the limits of weak and strong magnetic fields. - Highlights: • We derive the spin current equation for particles with different projection of spin. • We predict the contribution of Bohm potential to the dynamics of spin current. • We derive the spin-current wave in the system of spin-polarized particles. • We study the propagation of spin-acoustic wave in magnetized dielectrics.

  13. Spin Torques in Systems with Spin Filtering and Spin Orbit Interaction

    KAUST Repository

    Ortiz Pauyac, Christian

    2016-01-01

    filtering. In Chap. 3 we discuss the Rashba torque in ferromagnetic films, and in Chap. 4 we study spin Hall effect and spin swapping in ferromagnetic films, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives

  14. Large Deviations for the Annealed Ising Model on Inhomogeneous Random Graphs: Spins and Degrees

    Science.gov (United States)

    Dommers, Sander; Giardinà, Cristian; Giberti, Claudio; Hofstad, Remco van der

    2018-04-01

    We prove a large deviations principle for the total spin and the number of edges under the annealed Ising measure on generalized random graphs. We also give detailed results on how the annealing over the Ising model changes the degrees of the vertices in the graph and show how it gives rise to interesting correlated random graphs.

  15. Magnetic dichroism and spin structure of antiferromagnetic NiO(001) films

    NARCIS (Netherlands)

    Altieri, S; Finazzi, M; Hsieh, HH; Lin, HJ; Chen, CT; Hibma, T; Valeri, S; Sawatzky, GA

    2003-01-01

    We find that Ni L-2 edge x-ray magnetic linear dichroism is fully reversed for NiO(001) films on materials with reversed lattice mismatch. We relate this phenomenon to a preferential stabilization of magnetic S domains with main spin component either in or out of the plane, via dipolar interactions.

  16. Photon-gated spin transistor

    OpenAIRE

    Li, Fan; Song, Cheng; Cui, Bin; Peng, Jingjing; Gu, Youdi; Wang, Guangyue; Pan, Feng

    2017-01-01

    Spin-polarized field-effect transistor (spin-FET), where a dielectric layer is generally employed for the electrical gating as the traditional FET, stands out as a seminal spintronic device under the miniaturization trend of electronics. It would be fundamentally transformative if optical gating was used for spin-FET. We report a new type of spin-polarized field-effect transistor (spin-FET) with optical gating, which is fabricated by partial exposure of the (La,Sr)MnO3 channel to light-emitti...

  17. Coherent and correlated spin transport in nanoscale superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Morten, Jan Petter

    2008-03-15

    Motivated by the desire for better understanding of nano electronic systems, we theoretically study the conductance and noise characteristics of current flow between superconductors, ferromagnets, and normal-metals. Such nano structures can reveal information about superconductor proximity effects, spin-relaxation processes, and spintronic effects with potential applications for different areas of mesoscopic physics. We employ the quasiclassical theory of superconductivity in the Keldysh formalism, and calculate the nonequilibrium transport of spin and charge using various approaches like the circuit theory of quantum transport and full counting statistics. For two of the studied structures, we have been able to compare our theory to experimental data and obtain good agreement. Transport and relaxation of spin polarized current in superconductors is governed by energy-dependent transport coefficients and spin-flip rates which are determined by quantum interference effects. We calculate the resulting temperature-dependent spin flow in ferromagnet-superconductor devices. Experimental data for spin accumulation and spin relaxation in a superconducting nano wire is in agreement with the theory, and allows for a spin-flip spectroscopy that determines the dominant mechanism for spin-flip relaxation in the studied samples. A ferromagnet precessing under resonance conditions can give rise to pure spin current injection into superconductors. We find that the absorbed spin current is measurable as a temperature dependent Gilbert damping, which we calculate and compare to experimental data. Crossed Andreev reflection denotes superconducting pairing of electrons flowing from different normal-metal or ferromagnet terminals into a superconductor. We calculate the nonlocal currents resulting from this process in competition with direct electron transport between the normal-metal terminals. We take dephasing into account, and study the nonlocal current when the types of contact in

  18. How Forest Inhomogeneities Affect the Edge Flow

    DEFF Research Database (Denmark)

    Boudreault, Louis-Étienne; Dupont, Sylvain; Bechmann, Andreas

    2016-01-01

    Most of our knowledge on forest-edge flows comes from numerical and wind-tunnel experiments where canopies are horizontally homogeneous. To investigate the impact of tree-scale heterogeneities (>1 m) on the edge-flow dynamics, the flow in an inhomogeneous forest edge on Falster island in Denmark...... is investigated using large-eddy simulation. The three-dimensional forest structure is prescribed in the model using high resolution helicopter-based lidar scans. After evaluating the simulation against wind measurements upwind and downwind of the forest leading edge, the flow dynamics are compared between...... the scanned forest and an equivalent homogeneous forest. The simulations reveal that forest inhomogeneities facilitate flow penetration into the canopy from the edge, inducing important dispersive fluxes in the edge region as a consequence of the flow spatial variability. Further downstream from the edge...

  19. Energetics of edge oxidization of graphene nanoribbons

    Science.gov (United States)

    Yasuma, Airi; Yamanaka, Ayaka; Okada, Susumu

    2018-06-01

    On the basis of the density functional theory, we studied the geometries and energetics of O atoms adsorbed on graphene edges for simulating the initial stage of the edge oxidization of graphene. Our calculations showed that oxygen atoms are preferentially adsorbed onto the graphene edges with the zigzag portion, resulting in a large adsorption energy of about 5 eV. On the other hand, the edges with armchair shape are rarely oxidized, or the oxidization causes substantial structural reconstructions, because of the stable covalent bond at the armchair edge with the triple bond nature. Furthermore, the energetics sensitively depends on the edge angles owing to the inhomogeneity of the charge density at the edge atomic sites.

  20. Quantized edge modes in atomic-scale point contacts in graphene

    Science.gov (United States)

    Kinikar, Amogh; Phanindra Sai, T.; Bhattacharyya, Semonti; Agarwala, Adhip; Biswas, Tathagata; Sarker, Sanjoy K.; Krishnamurthy, H. R.; Jain, Manish; Shenoy, Vijay B.; Ghosh, Arindam

    2017-07-01

    The zigzag edges of single- or few-layer graphene are perfect one-dimensional conductors owing to a set of gapless states that are topologically protected against backscattering. Direct experimental evidence of these states has been limited so far to their local thermodynamic and magnetic properties, determined by the competing effects of edge topology and electron-electron interaction. However, experimental signatures of edge-bound electrical conduction have remained elusive, primarily due to the lack of graphitic nanostructures with low structural and/or chemical edge disorder. Here, we report the experimental detection of edge-mode electrical transport in suspended atomic-scale constrictions of single and multilayer graphene created during nanomechanical exfoliation of highly oriented pyrolytic graphite. The edge-mode transport leads to the observed quantization of conductance close to multiples of G0 = 2e2/h. At the same time, conductance plateaux at G0/2 and a split zero-bias anomaly in non-equilibrium transport suggest conduction via spin-polarized states in the presence of an electron-electron interaction.

  1. Current-induced magnetic switching of a single molecule magnet on a spin valve

    International Nuclear Information System (INIS)

    Zhang, Xiao; Wang, Zheng-Chuan; Zheng, Qing-Rong; Zhu, Zheng-Gang; Su, Gang

    2015-01-01

    The current-induced magnetic switching of a single-molecule magnet (SMM) attached on the central region of a spin valve is explored, and the condition for the switching current is derived. Electrons flowing through the spin valve will interact with the SMM via the s–d exchange interaction, producing the spin accumulation that satisfies the spin diffusion equation. We further describe the spin motion of the SMM by a Heisenberg-like equation. Based on the linear stability analysis, we obtain the critical current from two coupled equations. The results of the critical current versus the external magnetic field indicate that one can manipulate the magnetic state of the SMM by an external magnetic field. - Highlights: • We theoretically study the current-induced magnetic switching of the SMM. • We describe the spin motion of the SMM by a Heisenberg-like equation. • We describe the spin accumulation by the spin diffusion equation. • We obtain the critical current by the linear stability analysis. • Our approach can be easily extended to other SMMs

  2. Current-induced magnetic switching of a single molecule magnet on a spin valve

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiao [Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, School of Physics, University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Zheng-Chuan, E-mail: wangzc@ucas.ac.cn [Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, School of Physics, University of Chinese Academy of Sciences, Beijing 100049 (China); Zheng, Qing-Rong [Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, School of Physics, University of Chinese Academy of Sciences, Beijing 100049 (China); Zhu, Zheng-Gang [Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, School of Physics, University of Chinese Academy of Sciences, Beijing 100049 (China); School of Electronics, Electric and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049 (China); Su, Gang, E-mail: gsu@ucas.ac.cn [Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, School of Physics, University of Chinese Academy of Sciences, Beijing 100049 (China)

    2015-04-17

    The current-induced magnetic switching of a single-molecule magnet (SMM) attached on the central region of a spin valve is explored, and the condition for the switching current is derived. Electrons flowing through the spin valve will interact with the SMM via the s–d exchange interaction, producing the spin accumulation that satisfies the spin diffusion equation. We further describe the spin motion of the SMM by a Heisenberg-like equation. Based on the linear stability analysis, we obtain the critical current from two coupled equations. The results of the critical current versus the external magnetic field indicate that one can manipulate the magnetic state of the SMM by an external magnetic field. - Highlights: • We theoretically study the current-induced magnetic switching of the SMM. • We describe the spin motion of the SMM by a Heisenberg-like equation. • We describe the spin accumulation by the spin diffusion equation. • We obtain the critical current by the linear stability analysis. • Our approach can be easily extended to other SMMs.

  3. Haptic Edge Detection Through Shear

    Science.gov (United States)

    Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

    2016-03-01

    Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals.

  4. Efficient spin transport through polyaniline

    Science.gov (United States)

    Mendes, J. B. S.; Alves Santos, O.; Gomes, J. P.; Assis, H. S.; Felix, J. F.; Rodríguez-Suárez, R. L.; Rezende, S. M.; Azevedo, A.

    2017-01-01

    By using the spin pumping process, we show that it is possible to transport a pure spin current across layers of conducting polyaniline (PANI) with several hundred nanometers sandwiched between a film of the ferrimagnetic insulator yttrium iron garnet (YIG) and a thin layer of platinum. The spin current generated by microwave-driven ferromagnetic resonance of the YIG film, injected through the YIG/PANI interface, crosses the whole PANI layer and then is injected into the Pt layer. By means of the inverse spin Hall effect in the Pt, the spin current is converted into charge current and electrically detected as a dc voltage. We measured a spin diffusion length in PANI of 590 ± 40 nm, which is very large compared with normal metals, demonstrating that PANI can be used as an efficient spin current conductor and poor charge current conductor, opening the path towards spintronics applications based in this very attractive material.

  5. Bladder-type hydropneumatic accumulators

    International Nuclear Information System (INIS)

    Anigas, F.

    1985-01-01

    Hydropneumatic pressure accumulators allow liquids to be stored under pressure, their operating principle being based on the inherent compressibility of elements in a liquid and gaseous state. A wide range of fluids can be covered by means of the appropriate choice of the material for the body and bladder. Their main applications are: energy accumulation, safety reserve, suspension. (author)

  6. Spin Funneling for Enhanced Spin Injection into Ferromagnets

    Science.gov (United States)

    Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

    2016-07-01

    It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory.

  7. Shot noise of spin current and spin transfer torque

    Science.gov (United States)

    Yu, Yunjin; Zhan, Hongxin; Wan, Langhui; Wang, Bin; Wei, Yadong; Sun, Qingfeng; Wang, Jian

    2013-04-01

    We report the theoretical investigation of the shot noise of the spin current (Sσ) and the spin transfer torque (Sτ) for non-collinear spin polarized transport in a spin-valve device which consists of a normal scattering region connected by two ferromagnetic electrodes (MNM system). Our theory was developed using the non-equilibrium Green’s function method, and general nonlinear Sσ - V and Sτ - V relations were derived as a function of the angle θ between the magnetizations of two leads. We have applied our theory to a quantum dot system with a resonant level coupled with two ferromagnetic electrodes. It was found that, for the MNM system, the auto-correlation of the spin current is enough to characterize the fluctuation of the spin current. For a system with three ferromagnetic layers, however, both auto-correlation and cross-correlation of the spin current are needed to characterize the noise of the spin current. For a quantum dot with a resonant level, the derivative of spin torque with respect to bias voltage is proportional to sinθ when the system is far away from resonance. When the system is near resonance, the spin transfer torque becomes a non-sinusoidal function of θ. The derivative of the noise of the spin transfer torque with respect to the bias voltage Nτ behaves differently when the system is near or far away from resonance. Specifically, the differential shot noise of the spin transfer torque Nτ is a concave function of θ near resonance while it becomes a convex function of θ far away from resonance. For certain bias voltages, the period Nτ(θ) becomes π instead of 2π. For small θ, it was found that the differential shot noise of the spin transfer torque is very sensitive to the bias voltage and the other system parameters.

  8. Shot noise of spin current and spin transfer torque

    International Nuclear Information System (INIS)

    Yu Yunjin; Zhan Hongxin; Wan Langhui; Wang Bin; Wei Yadong; Sun Qingfeng; Wang Jian

    2013-01-01

    We report the theoretical investigation of the shot noise of the spin current (S σ ) and the spin transfer torque (S τ ) for non-collinear spin polarized transport in a spin-valve device which consists of a normal scattering region connected by two ferromagnetic electrodes (MNM system). Our theory was developed using the non-equilibrium Green’s function method, and general nonlinear S σ − V and S τ − V relations were derived as a function of the angle θ between the magnetizations of two leads. We have applied our theory to a quantum dot system with a resonant level coupled with two ferromagnetic electrodes. It was found that, for the MNM system, the auto-correlation of the spin current is enough to characterize the fluctuation of the spin current. For a system with three ferromagnetic layers, however, both auto-correlation and cross-correlation of the spin current are needed to characterize the noise of the spin current. For a quantum dot with a resonant level, the derivative of spin torque with respect to bias voltage is proportional to sinθ when the system is far away from resonance. When the system is near resonance, the spin transfer torque becomes a non-sinusoidal function of θ. The derivative of the noise of the spin transfer torque with respect to the bias voltage N τ behaves differently when the system is near or far away from resonance. Specifically, the differential shot noise of the spin transfer torque N τ is a concave function of θ near resonance while it becomes a convex function of θ far away from resonance. For certain bias voltages, the period N τ (θ) becomes π instead of 2π. For small θ, it was found that the differential shot noise of the spin transfer torque is very sensitive to the bias voltage and the other system parameters. (paper)

  9. Spin-polarized charge transport in HgTe/CdTe quantum well topological insulator under a ferromagnetic metal strip

    Science.gov (United States)

    Wu, Zhenhua; Luo, Kun; Yu, Jiahan; Wu, Xiaobo; Lin, Liangzhong

    2018-02-01

    Electron tunneling through a single magnetic barrier in a HgTe topological insulator has been theoretically investigated. We find that the perpendicular magnetic field would not lead to spin-flip of the edge states due to the conservation of the angular moment. By tuning the magnetic field and the Fermi energy, the edge channels can be transited from switch-on states to switch-off states and the current from unpolarized states can be filtered to fully spin polarized states. These features offer us an efficient way to control charge/spin transport in a HgTe/CdTe quantum well, and pave a way to construct the nanoelectronic devices utilizing the topological edge states.

  10. Nucleon spin structure functions

    International Nuclear Information System (INIS)

    Close, F.E.

    1989-01-01

    There has been recent excitement arising from the claim by the EMC collaboration that none of the proton's spin is carried by quarks. There are many textbooks, including those written by some members of this audience which assert that the proton's spin is carried by quarks. I will review the history of deep inelastic scattering of polarized leptons from polarized protons, culminating in this most recent dramatic claim. I will show that, for the last decade, data have appeared consistent with predictions of the quark model and highlight what the new and potentially exciting data are. I will conclude with suggestions for the future, and discuss the polarization dependence of inclusive hadron production. 35 refs

  11. Art of spin decomposition

    International Nuclear Information System (INIS)

    Chen Xiangsong; Sun Weimin; Wang Fan; Goldman, T.

    2011-01-01

    We analyze the problem of spin decomposition for an interacting system from a natural perspective of constructing angular-momentum eigenstates. We split, from the total angular-momentum operator, a proper part which can be separately conserved for a stationary state. This part commutes with the total Hamiltonian and thus specifies the quantum angular momentum. We first show how this can be done in a gauge-dependent way, by seeking a specific gauge in which part of the total angular-momentum operator vanishes identically. We then construct a gauge-invariant operator with the desired property. Our analysis clarifies what is the most pertinent choice among the various proposals for decomposing the nucleon spin. A similar analysis is performed for extracting a proper part from the total Hamiltonian to construct energy eigenstates.

  12. Spin and Madelung fluid

    International Nuclear Information System (INIS)

    Salesi, G.

    1995-07-01

    Starting from the Pauli current the decomposition of the non-relativistic local velocity has been obtained in two parts (in the ordinary tensorial language): one parallel and the other orthogonal to the impulse. The former is recognized to be the classical part, that is, the center-of-mass (CM) velocity, and the latter the quantum one, that is, the velocity of the motion in the CM frame (namely, the internal spin motion or Zitterbewegung). Inserting this complete, composite expression of the velocity into the kinetic energy term of the classical non-relativistic (i.e. Newtonian) Lagrangian, the author straightforwardly get the appearance of the so called quantum potential associates as it is known, to the Madelung fluid. In such a way, the quantum mechanical behaviour of particles appears to be strictly correlated to the existence of spin and Zitterbewegung

  13. Pangaea, She No Spin

    Science.gov (United States)

    McDowell, M.

    2002-12-01

    Looking at lopsided Pangaea, shown imaginatively on many illustrated proposals, I wondered what would happen if the configuration were put in high relief on a globe and spun on axis. Then I wondered if the present configuration of land masses would itself balance as a spinning top. So I got two Replogle globes, two boxes of colored modeling clay sticks, and two fat knitting needles, to fit through the capped holes at the poles of the globes. The clay sticks I cut up into 3 mm. (1/8") slices, using a different color for each continent, and applied to the first globe, assuming the extreme exaggeration above the geoid, no matter how crude, would tell the story. Inserting one needle through the globe and securing it, I balanced the globe on the point of the needle and twirled it like a top. Result: Wobbly! Top end of needle gyrated unevenly, and here it was supposed to make a smooth precessional cone. Oh boy. For the second globe, I used a Scotese "free stuff" interpretation of Pangaea, which I had to augment considerably using USGS, DuToit, Irving and other references, fitting it on the globe and applying identical clay color slices to what I judged generally accepted land surfaces. Result: the thing would hardly stand up, let alone spin. Conclusion: Although a refinement of application on the "today" globe might eliminate nutation, creating a smoother spin, there is no way any refinement of Pangaea on the same size globe can come close. While the concept of a supercontinent may be viable, I theorize that it had to have evolved on a far smaller globe, where land mass could balance, and the "breakup" would not have caused us to wildly gyrate on our axis. Because Pangaea, she no spin.

  14. Nuclear spin off

    International Nuclear Information System (INIS)

    1984-01-01

    The focus for nuclear energy research in the UK has been mainly the generation of electricity. However, nuclear technology is also applied in many areas other than energy production. Nuclear Spin Off shows how technology has been transferred to industry, agriculture, medicine and other areas, creating considerable material benefit. Nuclear research has produced revolutionary new materials and measuring and detection techniques. This film shows a wide range of uses. (author)

  15. Spinning out a star.

    Science.gov (United States)

    Lord, Michael D; Mandel, Stanley W; Wager, Jeffrey D

    2002-06-01

    Spinouts rarely take off; most, in fact, fall into one or more of four traps that doom them from the start. Some companies spin out ventures that are too close to the core of their businesses, in effect selling off their crown jewels. Sometimes, a parent company uses the spinout primarily to pawn off debt or expenses or to quickly raise external capital for itself. Other times, a company may try to spin out an area of its business that lacks one or more of the critical legs of a successful company--a coherent business model, say, or a solid financial base. And in many cases, parent companies can't bring themselves to sever their ownership ties and give up control of their spinouts. R.J. Reynolds, the tobacco giant, managed to avoid these traps when it successfully spun out a most unlikely venture, the pharmaceutical company Targacept. As the story illustrates, the problem with spinouts is similar to the problem of rich children. Their parents have the wherewithal to spoil them or shelter them or cling to them, but what they need is tough love and discipline--much the same discipline that characterizes successful start-ups. R.J. Reynolds recognized that it didn't know that much about the pharmaceutical business and couldn't merely try to spin out a small clone of itself. It had to treat the venture as if it were essentially starting from scratch, with a passionate entrepreneurial leader, a solid business plan, help from outside partners in the industry, and ultimately substantial venture backing. That these lessons are less obvious to executives contemplating spinning out ventures closer to their core businesses may be why so many spinouts fail.

  16. Characterization of heterogeneous nickel sites in CO dehydrogenase from Clostridium thermoaceticum by nickel L-edge x-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ralston, C.Y. [Univ. of California, Davis, CA (United States); Kumar, M.; Ragsdale, S.W. [Univ. of Nebraska, Lincoln, NE (United States)] [and others

    1997-04-01

    L-edge x-ray absorption spectroscopy (XAS) is a useful spectroscopic technique for determining the electronic state of transition metals. For first row transition metals, the L-edge represents a transition from 2p core levels to 3d valence levels. Coulomb and exchange interactions between the core hole and 3d valence electrons make the L-edge sensitive to the number and configuration of 3d electrons, hence to the metal spin state and oxidation state. The authors have used L-edge XAS to characterize the Ni sites in the carbon monoxide dehydrogenase (CODH) enzyme from Clostridium thermoaceticum. This CODH catalyzes both CO oxidation and acetyl-CoA synthesis at two Ni and Fe containing centers, C and A, respectively. Since the enzyme exhibits complex EPR signals that never integrate to one spin per Ni, there is evidence for heterogeneity in the types of Ni present. The Ni L-edge protein spectra were recorded at ALS beamline 9.3.2. The photon energy resolutions used for protein samples and for Ni model compound spectra were 350 and 270 meV respectively. During data collection the sample chamber was maintained at less than 5{times}10{sup {minus}9} Torr using a helium cryopump. Model compound spectra were measured using total electron yield detection, while protein spectra were recorded using fluorescence detection with a windowless 13-element germanium detector, and were calibrated using the total electron yield spectrum of NiF{sub 2} or NiO. Each protein spectrum presented represents the sum of approximately 40 15-minute scans. The authors have found that by using L-edge XAS they are able to distinguish between different spin and oxidation states of Ni compounds. They have used this result to characterize the Ni containing CODH protein in various states. The L-edge spectra are consistent with other results showing that when CODH is reacted with CO, the metal centers undergo reduction.

  17. RHIC spin physics

    International Nuclear Information System (INIS)

    Bunce, G.

    1994-01-01

    The physics potential of colliding beams of protons, polarized either longitudinally or transversely, at RHIC is remarkable. A luminosity of L = 2 x 10 32 cm -2 with 70% polarized beams will be available with up to 250 GeV energy in each beam. The proposal to collide polarized protons in RHIC was submitted in August 1992 and approved in October 1993. We have funding for R ampersand D on Siberian Snakes, so that RHIC will be able to accelerate polarized protons early in its program. The expected date of the first heavy ion collisions is 1999. The spin physics program includes measurement of gluon and sea quark polarization in the longitudinally polarized proton, measurement and then application of parity violation in W and Z production, measurement of hard scattering parton-parton asymmetries, and quark polarization or transversity in transversely polarized protons. Single spin asymmetries allow sensitive searches for parity violation (longitudinal polarization), and correlations between quark spin and gluons (transverse). Probes include direct photons (to P T = 20 GeV/c), jets (to P T > 50 GeV/c), Drell-Yan pairs to M ell ell = 9 GeV, W ± , Z. This program is described in our Particle World paper. Here we will emphasize the new information included in our Update, given to the Brookhaven PAC this September

  18. Nuclear spin circular dichroism

    International Nuclear Information System (INIS)

    Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

    2014-01-01

    Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra

  19. Rotary spin echoes

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, I. [Commissariat a l' energie atomique et aux energies alternatives - CEA, Centre d' Etudes Nucleaires de Saclay, BP2, Gif-sur-Yvette (France)

    1959-07-01

    Torrey has observed the free precession of nuclear spins around an r-f field H{sub 1}, fixed in a frame rotating at the Larmor frequency ω{sub 0} = γH{sub 0} around a large d-c magnetic field H{sub 0}. He showed that for an H{sub 1}, much larger than inhomogeneity of H{sub 0}, the latter has a negligible effect on the decay of the spin magnetization which is mainly due to the inhomogeneity of H{sub 1}. We report here on a method of overcoming the inhomogeneity of H{sub 1}, by production of echoes in the rotating frame ('rotary echoes'). These echoes are obtained by a 180 deg. phase shift at t = τ on the r-f field so that H{sub 1}, is suddenly reversed, producing a re-focussing of the magnetization vectors at the time t = 2 τ. The rotary echoes so obtained are very similar to the usual spin-echoes with, however some specific features that make them particularly suitable for the measurement of long relaxation times. Reprint of a paper published in Physical Review Letters, vol. 2, no. 7, Apr 1959, p. 301-302.

  20. Rotary spin echoes

    International Nuclear Information System (INIS)

    Solomon, I.

    1959-01-01

    Torrey has observed the free precession of nuclear spins around an r-f field H 1 , fixed in a frame rotating at the Larmor frequency ω 0 = γH 0 around a large d-c magnetic field H 0 . He showed that for an H 1 , much larger than inhomogeneity of H 0 , the latter has a negligible effect on the decay of the spin magnetization which is mainly due to the inhomogeneity of H 1 . We report here on a method of overcoming the inhomogeneity of H 1 , by production of echoes in the rotating frame ('rotary echoes'). These echoes are obtained by a 180 deg. phase shift at t = τ on the r-f field so that H 1 , is suddenly reversed, producing a re-focussing of the magnetization vectors at the time t = 2 τ. The rotary echoes so obtained are very similar to the usual spin-echoes with, however some specific features that make them particularly suitable for the measurement of long relaxation times. Reprint of a paper published in Physical Review Letters, vol. 2, no. 7, Apr 1959, p. 301-302

  1. RHIC spin physics

    International Nuclear Information System (INIS)

    Bunce, G.

    1993-01-01

    The physics potential of colliding beams of protons, polarized either longitudinally or transversely, at RHIC is remarkable. A luminosity of L = 2 x 10 32 cm -2 sec -1 with 70% polarized beams will be available with up to 250 GeV energy in each beam. The proposal to collide polarized protons in RHIC was submitted in August 1992 and approved in October 1993, just after this workshop. The collaboration has been encouraged to complete R ampersand D on Siberian Snakes, so that RHIC will be able to accelerate polarized protons early in its program. The expected date of the first heavy ion collisions is 1999. The spin physics program includes measurement of gluon and sea quark polarization in the longitudinally polarized proton, measurement and then application of parity violation in W and Z production, measurement of hard scattering parton-parton asymmetries, and quark polarization or transversity in transversely polarized protons. Single spin asymmetries allow sensitive searches for parity violation (longitudinal polarization), and correlations between quark spin and gluons (transverse). Probes include direct photons (to p T = 20 GeV/c), jets (to p T > 50 GeV/c), Drell-Yan pairs (to m ll = 9 GeV), W +/- , Z. Here, the collaboration emphasizes the new information included in the Update, given to the Brookhaven PAC this September

  2. Quasiparticle Breakdown in a Quantum Spin Liquid

    International Nuclear Information System (INIS)

    Stone, Matthew B.; Zalinznyak, I.; Hong, T.; Broholm, C.L.; Reich, D.H.

    2006-01-01

    Much of modern condensed matter physics is understood in terms of elementary excitations, or quasiparticles -- fundamental quanta of energy and momentum. Various strongly interacting atomic systems are successfully treated as a collection of quasiparticles with weak or no interactions. However, there are interesting limitations to this description: in some systems the very existence of quasiparticles cannot be taken for granted. Like unstable elementary particles, quasiparticles cannot survive beyond a threshold where certain decay channels become allowed by conservation laws; their spectrum terminates at this threshold. Such quasiparticle breakdown was first predicted for an exotic state of matter -- super-fluid 4 He at temperatures close to absolute zero, a quantum Bose liquid where zero-point atomic motion precludes crystallization. Here we show, using neutron scattering, that quasiparticle breakdown can also occur in a quantum magnet and, by implication, in other systems with Bose quasiparticles. We have measured spin excitations in a two-dimensional quantum magnet, piperazinium hexachlorodicuprate (PHCC), in which spin-1/2 copper ions form a non-magnetic quantum spin liquid, and find remarkable similarities with excitations in superfluid 4 He. We observe a threshold momentum beyond which the quasiparticle peak merges with the two-quasiparticle continuum. It then acquires a finite energy width and becomes indistinguishable from a leading-edge singularity, so that excited states are no longer quasiparticles but occupy a wide band of energy. Our findings have important ramifications for understanding excitations with gapped spectra in many condensed matter systems, ranging from band insulators to high-transition-temperature superconductors.

  3. The electron-nuclear spin system in (In,Ga)As quantum dots

    International Nuclear Information System (INIS)

    Auer, Thomas

    2008-01-01

    polarised by optically oriented electrons also in the studied sample, so that it is even a task to keep the nuclear spins randomly oriented. An important finding was to confirm that the nuclear spins can be significantly polarised also at zero external field. I showed that the polarised nuclear spin system can have a supporting effect on the electron spin polarisation or - when the direction of the nuclear field gains a large transverse component - may depolarise the resident electron spin further than the unpolarized nuclear fluctuation field. I demonstrated that the direction of the Overhauser field may indeed be directed by very small external fields. By determining the internal fields acting on the nuclear spins, the Knight field and the nuclear dipole-dipole field, it could be estimated that the nuclear spin system can in principle be polarised to a degree close to unity. The accumulation dynamics of the electron spins polarised via the effect of negative circular polarisation was found to occur on a timescale of hundred nanoseconds. The nuclear spin system becomes polarised by optical orientation within tens of milliseconds. Finally, I observed spin memory times in the system persisting over up to 0.5 s after the excitation had been switched off. This extremely long spin lifetimes were explained in terms of a coupled electron-nuclear spin state, the nuclear spin polaron. (orig.)

  4. Predicted solar cell edge radiation effects

    International Nuclear Information System (INIS)

    Gates, M.T.

    1993-01-01

    The Advanced Solar Cell Orbital Test (ASCOT) will test six types of solar cells in a high energy proton environment. During the design of the experiment a question was raised about the effects of proton radiation incident on the edge of the solar cells and whether edge radiation shielding was required. Historical geosynchronous data indicated that edge radiation damage is not detectable over the normal end of life solar cell degradation; however because the ASCOT radiation environment has a much higher and more energetic fluence of protons, considerably more edge damage is expected. A computer analysis of the problem was made by modeling the expected radiation damage at the cell edge and using a network model of small interconnected solar cells to predict degradation in the cell's electrical output. The model indicated that the deepest penetration of edge radiation was at the top of the cell near the junction where the protons have access to the cell through the low density cell/cover adhesive layer. The network model indicated that the cells could tolerate high fluences at their edge as long as there was high electrical resistance between the edge radiated region and the contact system on top of the cell. The predicted edge radiation related loss was less than 2% of maximum power for GaAs/Ge solar cells. As a result, no edge radiation protection was used for ASCOT

  5. The effect of spin-orbit coupling in band structure of few-layer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Sahdan, Muhammad Fauzi, E-mail: sahdan89@yahoo.co.id; Darma, Yudi, E-mail: sahdan89@yahoo.co.id [Department of Physics, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung 40132 (Indonesia)

    2014-03-24

    Topological insulators are electronic materials that have a bulk band gap like an ordinary insulator but have protected conducting states on their edge or surface. This can be happened due to spin-orbit coupling and time-reversal symmetry. Moreover, the edge current flows through their edge or surface depends on its spin orientation and also it is robust against non-magnetic impurities. Therefore, topological insulators are predicted to be useful ranging from spintronics to quantum computation. Graphene was first predicted to be the precursor of topological insulator by Kane-Mele. They developed a Hamiltonian model to describe the gap opening in graphene. In this work, we investigate the band structure of few-layer graphene by using this model with analytical approach. The results of our calculations show that the gap opening occurs at K and K’ point, not only in single layer, but also in bilayer and trilayer graphene.

  6. Nuclear spin noise in the central spin model

    Science.gov (United States)

    Fröhling, Nina; Anders, Frithjof B.; Glazov, Mikhail

    2018-05-01

    We study theoretically the fluctuations of the nuclear spins in quantum dots employing the central spin model which accounts for the hyperfine interaction of the nuclei with the electron spin. These fluctuations are calculated both with an analytical approach using homogeneous hyperfine couplings (box model) and with a numerical simulation using a distribution of hyperfine coupling constants. The approaches are in good agreement. The box model serves as a benchmark with low computational cost that explains the basic features of the nuclear spin noise well. We also demonstrate that the nuclear spin noise spectra comprise a two-peak structure centered at the nuclear Zeeman frequency in high magnetic fields with the shape of the spectrum controlled by the distribution of the hyperfine constants. This allows for direct access to this distribution function through nuclear spin noise spectroscopy.

  7. Entanglement entropy in random quantum spin-S chains

    International Nuclear Information System (INIS)

    Saguia, A.; Boechat, B.; Continentino, M. A.; Sarandy, M. S.

    2007-01-01

    We discuss the scaling of entanglement entropy in the random singlet phase (RSP) of disordered quantum magnetic chains of general spin S. Through an analysis of the general structure of the RSP, we show that the entanglement entropy scales logarithmically with the size of a block, and we provide a closed expression for this scaling. This result is applicable for arbitrary quantum spin chains in the RSP, being dependent only on the magnitude S of the spin. Remarkably, the logarithmic scaling holds for the disordered chain even if the pure chain with no disorder does not exhibit conformal invariance, as is the case for Heisenberg integer-spin chains. Our conclusions are supported by explicit evaluations of the entanglement entropy for random spin-1 and spin-3/2 chains using an asymptotically exact real-space renormalization group approach

  8. Spinning particle approach to higher spin field theory

    International Nuclear Information System (INIS)

    Corradini, Olindo

    2011-01-01

    We shortly review on the connection between higher-spin gauge field theories and supersymmetric spinning particle models. In such approach the higher spin equations of motion are linked to the first-class constraint algebra associated with the quantization of particle models. Here we consider a class of spinning particle models characterized by local O(N)-extended supersymmetry since these models are known to provide an alternative approach to the geometric formulation of higher spin field theory. We describe the canonical quantization of the models in curved target space and discuss the obstructions that appear in presence of an arbitrarily curved background. We then point out the special role that conformally flat spaces appear to have in such models and present a derivation of the higher-spin curvatures for maximally symmetric spaces.

  9. Spin current through quantum-dot spin valves

    International Nuclear Information System (INIS)

    Wang, J; Xing, D Y

    2006-01-01

    We report a theoretical study of the influence of the Coulomb interaction on the equilibrium spin current in a quantum-dot spin valve, in which the quantum dot described by the Anderson impurity model is coupled to two ferromagnetic leads with noncollinear magnetizations. In the Kondo regime, electrons transmit through the quantum dot via higher-order virtual processes, in which the spin of either lead electrons or a localized electron on the quantum dot may reverse. It is found that the magnitude of the spin current decreases with increasing Coulomb interactions due to spin flip effects on the dot. However, the spatial direction of the spin current remains unchanged; it is determined only by the exchange coupling between two noncollinear magnetizations

  10. Graphene spin diode: Strain-modulated spin rectification

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yunhua; Wang, B., E-mail: stslyl@mail.sysu.edu.cn, E-mail: wangbiao@mail.sysu.edu.cn [Sino-French Institute of Nuclear Engineering and Technology, School of Physics and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275 (China); Liu, Yulan, E-mail: stslyl@mail.sysu.edu.cn, E-mail: wangbiao@mail.sysu.edu.cn [School of Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

    2014-08-04

    Strain effects on spin transport in a ferromagnetic/strained/normal graphene junction are explored theoretically. It is shown that the spin-resolved Fermi energy range can be controlled by the armchair direction strain because the strain-induced pseudomagnetic field suppresses the current. The spin rectification effect for the bias reversal occurs because of a combination of ferromagnetic exchange splitting and the broken spatial symmetry of the junction. In addition, the spin rectification performance can be tuned remarkably by manipulation of the strains. In view of this strain-modulated spin rectification effect, we propose that the graphene-based ferromagnetic/strained/normal junction can be used as a tunable spin diode.

  11. Spin Transfer Torque in Graphene

    Science.gov (United States)

    Lin, Chia-Ching; Chen, Zhihong

    2014-03-01

    Graphene is an idea channel material for spin transport due to its long spin diffusion length. To develop graphene based spin logic, it is important to demonstrate spin transfer torque in graphene. Here, we report the experimental measurement of spin transfer torque in graphene nonlocal spin valve devices. Assisted by a small external in-plane magnetic field, the magnetization reversal of the receiving magnet is induced by pure spin diffusion currents from the injector magnet. The magnetization switching is reversible between parallel and antiparallel configurations by controlling the polarity of the applied charged currents. Current induced heating and Oersted field from the nonlocal charge flow have also been excluded in this study. Next, we further enhance the spin angular momentum absorption at the interface of the receiving magnet and graphene channel by removing the tunneling barrier in the receiving magnet. The device with a tunneling barrier only at the injector magnet shows a comparable nonlocal spin valve signal but lower electrical noise. Moreover, in the same preset condition, the critical charge current density for spin torque in the single tunneling barrier device shows a substantial reduction if compared to the double tunneling barrier device.

  12. Spin dynamics in electron synchrotrons

    International Nuclear Information System (INIS)

    Schmidt, Jan Felix

    2017-01-01

    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.

  13. Ethical decisions at the edge.

    Science.gov (United States)

    Gillett, Grant

    2008-05-01

    Medicine grows incrementally in its ability to treat patients and at the growing edge it poses problems about the appropriateness of treatments that are different from those where good practice conforms to widely agreed standards. The growth of access to medical knowledge and the diversity of contemporary theoretical and clinical medicine have spawned deep divisions in the profession and divergent opinions about what constitutes reasonable care. That hallmark of acceptable practice is also under pressures from the threat of litigation, a highly commercialised contemporary medical environment, patient demands based on medical journalism and the internet and the exponential growth of bio-medical technology. Patient empowerment can result in complaints arising in new and complex areas and expert opinion can often differ markedly depending on where on the medical spectrum the experts are aligned. This column lays out some broad-brush principles to assess the adequacy of medical advice in such a climate.

  14. Imaging edges of nanostructured graphene

    DEFF Research Database (Denmark)

    Kling, Jens; Cagliani, Alberto; Booth, T. J.

    Graphene, as the forefather of 2D-materials, attracts much attention due to its extraordinary properties like transparency, flexibility and outstanding high conductivity, together with a thickness of only one atom. However, graphene also possesses no band gap, which makes it unsuitable for many...... electronic applications like transistors. It has been shown theoretically that by nanostructuring pristine graphene, e.g. with regular holes, the electronic properties can be tuned and a band gap introduced. The size, distance and edge termination of these “defects” influence the adaptability....... Such nanostructuring can be done experimentally, but especially characterization at atomic level is a huge challenge. High-resolution TEM (HRTEM) is used to characterize the atomic structure of graphene. We optimized the imaging conditions used for the FEI Titan ETEM. To reduce the knock-on damage of the carbon atoms...

  15. Spin waves and spin instabilities in quantum plasmas

    OpenAIRE

    Andreev, P. A.; Kuz'menkov, L. S.

    2014-01-01

    We describe main ideas of method of many-particle quantum hydrodynamics allows to derive equations for description of quantum plasma evolution. We also present definitions of collective quantum variables suitable for quantum plasmas. We show that evolution of magnetic moments (spins) in quantum plasmas leads to several new branches of wave dispersion: spin-electromagnetic plasma waves and self-consistent spin waves. Propagation of neutron beams through quantum plasmas is also considered. Inst...

  16. Field-controlled spin current in frustrated spin chains

    Directory of Open Access Journals (Sweden)

    A.K. Kolezhuk

    2009-01-01

    Full Text Available We study states with spontaneous spin current, emerging in frustrated antiferromagnetic spin-S chains subject to a strong external magnetic field. As a numerical tool, we use a non-Abelian symmetry realization of the density matrix renormalization group. The field dependence of the order parameter and the critical exponents are presented for zigzag chains with S=1/2, 1, 3/2, and 2.

  17. Hardy's argument and successive spin-s measurements

    International Nuclear Information System (INIS)

    Ahanj, Ali

    2010-01-01

    We consider a hidden-variable theoretic description of successive measurements of noncommuting spin observables on an input spin-s state. In this scenario, the hidden-variable theory leads to a Hardy-type argument that quantum predictions violate it. We show that the maximum probability of success of Hardy's argument in quantum theory is ((1/2)) 4s , which is more than in the spatial case.

  18. Amplitude-dependent topological edge states in nonlinear phononic lattices

    Science.gov (United States)

    Pal, Raj Kumar; Vila, Javier; Leamy, Michael; Ruzzene, Massimo

    2018-03-01

    This work investigates the effect of nonlinearities on topologically protected edge states in one- and two-dimensional phononic lattices. We first show that localized modes arise at the interface between two spring-mass chains that are inverted copies of each other. Explicit expressions derived for the frequencies of the localized modes guide the study of the effect of cubic nonlinearities on the resonant characteristics of the interface, which are shown to be described by a Duffing-like equation. Nonlinearities produce amplitude-dependent frequency shifts, which in the case of a softening nonlinearity cause the localized mode to migrate to the bulk spectrum. The case of a hexagonal lattice implementing a phononic analog of a crystal exhibiting the quantum spin Hall effect is also investigated in the presence of weakly nonlinear cubic springs. An asymptotic analysis provides estimates of the amplitude dependence of the localized modes, while numerical simulations illustrate how the lattice response transitions from bulk-to-edge mode-dominated by varying the excitation amplitude. In contrast with the interface mode of the first example studies, this occurs both for hardening and softening springs. The results of this study provide a theoretical framework for the investigation of nonlinear effects that induce and control topologically protected wave modes through nonlinear interactions and amplitude tuning.

  19. Model predictive control of trailing edge flaps on a wind turbine blade

    Energy Technology Data Exchange (ETDEWEB)

    Castaignet, D.B.

    2011-11-15

    Trailing edge flaps on wind turbine blades have been investigated for several years. Aero-servoelastic simulations carried out with different simulation tools, trailing edge flaps configurations and controller designs proved that trailing edge flaps are a suitable solution for reducing some of the wind turbine fatigue and extreme loads. This potential was confirmed with wind tunnel tests made on blade sections with trailing edge flaps and on a scaled two-bladed wind turbine in a wind tunnel. The work presented in this thesis includes a full-scale test run on a Vestas V27 wind turbine equipped with three trailing edge flaps on one blade, located on DTU's Risoe Campus in Roskilde, Denmark. This thesis is divided into three parts: the controller design, results from simulations, and results from the experiments. The trailing edge flaps controller designed for this project is based on a frequency-weighted model predictive control, tuned in order to target only the flapwise blade root loads at the frequencies contributing the most to blade root fatigue damage (the 1P, 2P and 3P frequencies), and to avoid unnecessary wear and tear of the actuators at high frequencies. A disturbance model consisting in periodic disturbances at the rotor speed harmonic frequencies and a quasi-steady input disturbance is aggregated to an analytical model of a spinning blade with trailing edge flaps. Simulations on a multi-megawatt wind turbine show the potential of the trailing edge flaps to reduce the flapwise blade root fatigue loads by 23%, but also the main shaft and the tower fatigue loads by up to 32%. Extreme loads during normal production also benefit from the trailing edge flaps. At last, the same controller was run on the Vestas V27 wind turbine located at the Risoe Campus of the Technical University of Denmark, in Roskilde, Denmark. One blade of the turbine was equipped with three independent trailing edge flaps. In spite of the failure of several sensors and actuators, the

  20. Magnetohydrodynamic stability of tokamak edge plasmas

    International Nuclear Information System (INIS)

    Connor, J.W.; Hastie, R.J.; Wilson, H.R.; Miller, R.L.

    1998-01-01

    A new formalism for analyzing the magnetohydrodynamic stability of a limiter tokamak edge plasma is developed. Two radially localized, high toroidal mode number n instabilities are studied in detail: a peeling mode and an edge ballooning mode. The peeling mode, driven by edge current density and stabilized by edge pressure gradient, has features which are consistent with several properties of tokamak behavior in the high confinement open-quotes Hclose quotes-mode of operation, and edge localized modes (or ELMs) in particular. The edge ballooning mode, driven by the pressure gradient, is identified; this penetrates ∼n 1/3 rational surfaces into the plasma (rather than ∼n 1/2 , expected from conventional ballooning mode theory). Furthermore, there exists a coupling between these two modes and this coupling provides a picture of the ELM cycle