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1

Coherent, mechanical control of a single electronic spin.  

PubMed

We demonstrate coherent quantum control of a single spin driven by the motion of a mechanical resonator. The motion of a mechanical resonator is magnetically coupled to the electronic spin of a single nitrogen-vacancy center in diamond. Synchronization of spin-addressing protocols to the motion of the driven oscillator is used to fully exploit the coherence of this hybrid mechanical-spin system. We demonstrate applications of this coherent mechanical spin-control technique to nanoscale scanning magnetometry. PMID:22800099

Hong, Sungkun; Grinolds, Michael S; Maletinsky, Patrick; Walsworth, Ronald L; Lukin, Mikhail D; Yacoby, Amir

2012-07-18

2

Single spins in diamond: polarization, readout, and coherent control  

NASA Astrophysics Data System (ADS)

The Nitrogen-Vacancy (N-V) color center in diamond is well suited for studying electronic and nuclear spin phenomena, since its spin state can be both initialized and read out optically. Moreover, N-V center spins may allow for quantum information processing, as measurements have shown long room- temperature electron spin coherence times well into the microsecond regime. Here, we report on recent experimental progress towards coherent control and coupling of single spins in diamond. Using magneto-photoluminescence imaging and electron spin resonance (ESR) measurements at room temperature, we have investigated single N-V center spins that are coupled to electron spins of nearby nitrogen (N) defects. These N spins are optically inactive (`dark'), but can be detected via the N-V center, as the N-V and the N spins are coupled via the magnetic dipolar interaction. Some of the N-V centers are strongly coupled to only one single N spin, allowing the controlled polarization and readout of this single `dark' N spin. From time-resolved pump-probe measurements we find the relaxation time of the single N electron spin to be 75 microseconds at room temperature. More recently, we have demonstrated the coherent control of the N-V center spin using optical detection of pulsed ESR and spin echo techniques. Using these tools at different static magnetic fields, we have found that the main source of decoherence for the N-V center spins in our sample is the dipolar coupling to the surrounding bath of N spins. These results pave the way towards room-temperature coherent control of coupled spin states in diamond. R. Hanson, F. M. Mendoza, R. J. Epstein and D. D. Awschalom, Phys. Rev. Lett. 97, 087601 (2006). R. Hanson, O. Gywat and D.D. Awschalom, Phys. Rev. B 74, 161203(R) (2006).

Gywat, Oliver

2007-03-01

3

Coherence and control of single electron spins in quantum dots  

NASA Astrophysics Data System (ADS)

Following our earlier work on single-shot read-out and relaxation of a single spin in a quantum dot, we now demonstrate coherent control of a single spin (detection is done using a second spin in a neighbouring dot). First, we manipulate the spin using conventional magnetic resonance. Next, we show that we can also rotate the spin using electric fields instead of magnetic fields. In both cases, 90 rotations can be realized in about 50 ns or less. We use these control techniques to probe decoherence of an isolated electron spin. The spin dephases in about 30 ns, due to the hyperfine interaction with the uncontrolled nuclear spin bath in the host material of the dot. However, since the nuclear spin dynamics is very slow, this dephasing can be largely reversed using a spin-echo pulse. Echo decay times of about 0.5 us are obtained at 70 mT. In parallel, we have started work on quantum dots in graphene, which is expected to offer superior coherence times. As a first step, we have succeeded in opening a bandgap in bilayer graphene, necessary for electrostatic confinement of carriers. F.H.L. Koppens et al., Nature 446, 56 (2006). K.C. Nowack et al., Science Express, 1 Nov 2007. F.H.L. Koppens et al., arXiv:0711.0479. J.B. Oostinga, Nature Mat., in press.

Vandersypen, Lieven

2008-03-01

4

Electrical control of single hole spins in nanowire quantum dots.  

PubMed

The development of viable quantum computation devices will require the ability to preserve the coherence of quantum bits (qubits). Single electron spins in semiconductor quantum dots are a versatile platform for quantum information processing, but controlling decoherence remains a considerable challenge. Hole spins in III-V semiconductors have unique properties, such as a strong spin-orbit interaction and weak coupling to nuclear spins, and therefore, have the potential for enhanced spin control and longer coherence times. A weaker hyperfine interaction has previously been reported in self-assembled quantum dots using quantum optics techniques, but the development of hole-spin-based electronic devices in conventional III-V heterostructures has been limited by fabrication challenges. Here, we show that gate-tunable hole quantum dots can be formed in InSb nanowires and used to demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tunable between hole and electron quantum dots, which allows the hyperfine interaction strengths, g-factors and spin blockade anisotropies to be compared directly in the two regimes. PMID:23416794

Pribiag, V S; Nadj-Perge, S; Frolov, S M; van den Berg, J W G; van Weperen, I; Plissard, S R; Bakkers, E P A M; Kouwenhoven, L P

2013-02-17

5

Electrical control of single hole spins in nanowire quantum dots  

NASA Astrophysics Data System (ADS)

The development of viable quantum computation devices will require the ability to preserve the coherence of quantum bits (qubits). Single electron spins in semiconductor quantum dots are a versatile platform for quantum information processing, but controlling decoherence remains a considerable challenge. Hole spins in III-V semiconductors have unique properties, such as a strong spin-orbit interaction and weak coupling to nuclear spins, and therefore, have the potential for enhanced spin control and longer coherence times. A weaker hyperfine interaction has previously been reported in self-assembled quantum dots using quantum optics techniques, but the development of hole-spin-based electronic devices in conventional III-V heterostructures has been limited by fabrication challenges. Here, we show that gate-tunable hole quantum dots can be formed in InSb nanowires and used to demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tunable between hole and electron quantum dots, which allows the hyperfine interaction strengths, g-factors and spin blockade anisotropies to be compared directly in the two regimes.

Pribiag, V. S.; Nadj-Perge, S.; Frolov, S. M.; van den Berg, J. W. G.; van Weperen, I.; Plissard, S. R.; Bakkers, E. P. A. M.; Kouwenhoven, L. P.

2013-03-01

6

Coherent mechanical control of a single electronic spin  

NASA Astrophysics Data System (ADS)

Quantum control of spins via electrical, magnetic, and optical means has generated numerous applications in metrology and quantum information technology. In this talk we present an alternative control scheme that uses the mechanical motion of a resonator to coherently control spins. Specifically, by coupling the motion of a magnetically coated mechanical oscillator to a single nitrogen-vacancy (NV) defect in diamond, we demonstrate manipulations of both the amplitude and phase of the NV's electronic spin. Coherent control is achieved by synchronizing NV-addressing optical and microwave manipulations to the driven motion of the coupled mechanical oscillator, which additionally allows for a stroboscopic readout of the resonator's motion. We demonstrate applications of this mechanical spin control to sensitive nanoscale scanning magnetometry and discuss the potential for sensitive motion sensing of nanomechanical resonators.

Grinolds, Michael

2013-03-01

7

Readout and control of a single nuclear spin with a metastable electron spin ancilla.  

PubMed

Electron and nuclear spins associated with point defects in insulators are promising systems for solid-state quantum technology. The electron spin is usually used for readout and addressing, and nuclear spins are used as exquisite quantum bits and memory systems. With these systems, single-shot readout of single nuclear spins as well as entanglement, aided by the electron spin, have been shown. Although the electron spin in this example is essential for readout, it usually limits the nuclear spin coherence, leading to a quest for defects with spin-free ground states. Here, we isolate a hitherto unidentified defect in diamond and use it at room temperature to demonstrate optical spin polarization and readout with exceptionally high contrast (up to 45%), coherent manipulation of an individual excited triplet state spin, and coherent nuclear spin manipulation using the triplet electron spin as a metastable ancilla. We demonstrate nuclear magnetic resonance and Rabi oscillations of the uncoupled nuclear spin in the spin-free electronic ground state. Our study demonstrates that nuclei coupled to single metastable electron spins are useful quantum systems with long memory times, in spite of electronic relaxation processes. PMID:23793305

Lee, Sang-Yun; Widmann, Matthias; Rendler, Torsten; Doherty, Marcus W; Babinec, Thomas M; Yang, Sen; Eyer, Moritz; Siyushev, Petr; Hausmann, Birgit J M; Loncar, Marko; Bodrog, Zoltán; Gali, Adam; Manson, Neil B; Fedder, Helmut; Wrachtrup, Jörg

2013-06-23

8

Ultrafast Coherent Control of a Single Electron Spin in a Quantum Dot  

NASA Astrophysics Data System (ADS)

Practical quantum information processing schemes require fast single-qubit operations. For spin-based qubits, this involves performing arbitrary coherent rotations of the spin state on timescales much faster than the spin coherence time. While we recently demonstrated the ability to initialize and monitor the evolution of single spins in quantum dots (QDs)ootnotetextM. H. Mikkelsen, J. Berezovsky, N. G. Stoltz, L. A. Coldren, D. D. Awschalom, Nature Physics 3, 770 (2007); J. Berezovsky, M. H. Mikkelsen, O. Gywat, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 314, 1916 (2006)., here we present an all-optical scheme for ultrafast manipulation of these states through arbitrary angles. The GaAs QDs are embedded in a diode structure to allow controllable charging of the QDs and positioned within a vertical optical cavity to enhance the small single spin signal. By applying off-resonant optical pulses, we coherently rotate a single electron spin in a QD up to ? radians on picosecond timescales ootnotetextJ. Berezovsky, M. H. Mikkelsen, N. G. Stoltz, L. A. Coldren, D. D. Awschalom, Science 320, 349 (2008)..We directly observe this spin manipulation using time-resolved Kerr rotation spectroscopy at T=10K. Measurements of the spin rotation as a function of laser detuning and intensity confirm that the optical Stark effect is the operative mechanism and the results are well-described by a model including the electron-nuclear spin interaction. Using short tipping pulses, this technique enables one to perform a large number of operations within the coherence time. This ability to perform arbitrary single-qubit operations enables sequential all-optical initialization, ultrafast control and detection of a single electron spin for quantum information purposes.

Mikkelsen, Maiken H.

2009-03-01

9

Voltage control of electron-nuclear spin correlation time in a single quantum dot  

NASA Astrophysics Data System (ADS)

We demonstrate bias control of the efficiency of the hyperfine coupling between a single electron in an InAs quantum dot and the surrounding nuclear spins monitored through the positively charged exciton X+ emission. In applied longitudinal magnetic fields, we vary simultaneously the correlation time of the hyperfine interaction and the nuclear spin relaxation time and thereby the amplitude of the achieved dynamic nuclear polarization under optical pumping conditions. In applied transverse magnetic fields, a change in the applied bias allows a switch from the anomalous Hanle effect to the standard electron spin depolarization curves.

Nilsson, J.; Bouet, L.; Bennett, A. J.; Amand, T.; Stevenson, R. M.; Farrer, I.; Ritchie, D. A.; Kunz, S.; Marie, X.; Shields, A. J.; Urbaszek, B.

2013-08-01

10

Measurement and control of single spins in diamond above 600 K  

NASA Astrophysics Data System (ADS)

The nitrogen vacancy (NV) center in diamond stands out among spin qubit systems in large part because its spin can be controlled under ambient conditions whereas most other solid state qubits operate only at cryogenic temperatures. However, despite the intense interest in the NV center's room temperature properties for nanoscale sensing and quantum information applications, the ultimate thermal limits to its measurement and control have been largely unknown. We demonstrate that the NV center's spin can be optically addressed and coherently controlled at temperatures exceeding 600 K and show that its addressability is eventually limited by thermal quenching of the optical spin readout [1]. These measurements, in combination with computational studies, provide important information about the electronic states that facilitate the optical spin measurement and, moreover, suggest that the coherence of the NV center's spin states could be utilized for thermometry. We infer that single spins in diamond offer temperature sensitivities better than 100 mK/?Hz up to 600 K using conventional sensing techniques and show that advanced measurement schemes provide a pathway to reach 10 mK/?Hz sensitivities. Together with diamond's ideal thermal and mechanical properties, these results suggest that NV center thermometers could be applied in cellular thermometry and scanning thermal microscopy. [4pt] [1] D. M. Toyli*, D. J. Christle*, A. Alkauskas, B. B. Buckley, C. G. Van de Walle, and D. D. Awschalom, Phys. Rev. X 2, 031001 (2012).

Toyli, David M.

2013-03-01

11

Sensing single remote nuclear spins  

NASA Astrophysics Data System (ADS)

The detection of single nuclear spins would be useful for fields ranging from basic science to quantum information technology. However, although sensing based on diamond defects and other methods have shown high sensitivity, they have not been capable of detecting single nuclear spins, and defect-based techniques further require strong defect-spin coupling. Here, we present the detection and identification of single and remote 13C nuclear spins embedded in nuclear spin baths surrounding a single electron spin of a nitrogen-vacancy centre in diamond. We are able to amplify and detect the weak magnetic field noise (~10 nT) from a single nuclear spin located ~3 nm from the centre using dynamical decoupling control, and achieve a detectable hyperfine coupling strength as weak as ~300 Hz. We also confirm the quantum nature of the coupling, and measure the spin-defect distance and the vector components of the nuclear field. The technique marks a step towards imaging, detecting and controlling nuclear spins in single molecules.

Zhao, Nan; Honert, Jan; Schmid, Bernhard; Klas, Michael; Isoya, Junichi; Markham, Matthew; Twitchen, Daniel; Jelezko, Fedor; Liu, Ren-Bao; Fedder, Helmut; Wrachtrup, Jörg

2012-10-01

12

Optical control of spin coherence in singly charged (In,Ga)As/GaAs quantum dots.  

PubMed

Electron spin coherence has been generated optically in n-type modulation doped (In,Ga)As/GaAs quantum dots (QDs) which contain on average a single electron per dot. The coherence arises from resonant excitation of the QDs by circularly polarized laser pulses, creating a coherent superposition of an electron and a trion. Time dependent Faraday rotation is used to probe the spin precession of the optically oriented electrons about a transverse magnetic field. The coherence generation can be controlled by pulse intensity, being most efficient for (2n+1)pi pulses. PMID:16803342

Greilich, A; Oulton, R; Zhukov, E A; Yugova, I A; Yakovlev, D R; Bayer, M; Shabaev, A; Efros, Al L; Merkulov, I A; Stavarache, V; Reuter, D; Wieck, A

2006-06-07

13

Single spins in semiconductor quantum dot microcavities  

NASA Astrophysics Data System (ADS)

Semiconductor quantum dots can be utilized to capture single electron or hole spins and they have therewith promise for various applications in fields like spintronics, spin based quantum information processing and chiral photonics. We integrate quantum dots into semiconductor microcavities to enhance light-matter interaction for ultrafast optical manipulation and read-out. Single electron and single hole spins can be statistically or deterministically loaded into the quantum dots and coherently controlled. Within the about ?s-coherence times of the spins about 105 complete single qubit rotations can be performed with ultrafast optical pulses. By utilizing a ?-type energy level system of a single quantum-dot electron spin in a magnetic field and ultrafast non-linear frequency conversion, quantum-dot spin-photon entanglement is observed.

Höfling, Sven; De Greve, Kristiaan; McMahon, Peter L.; Press, David; Yu, Leo; Pelc, Jason S.; Natarajan, Chandra M.; Kim, Na Young; Ladd, Thaddeus; Abe, Eisuke; Maier, Sebastian; Bisping, Dirk; Langer, Fabian; Schneider, Christian; Kamp, Martin; Hadfield, Robert H.; Forchel, Alfred; Fejer, M. M.; Yamamoto, Yoshihisa

2013-09-01

14

Single-donor spin qubits in silicon  

NASA Astrophysics Data System (ADS)

The idea of using the spin of a single donor atom in silicon to encode quantum information goes back to the Kane proposal [1] in 1998. We have now resolved the technical challenges involved in the readout and control of the electron and nuclear spin of a single atom. The key breakthrough was the development of a device structure where the donor is tunnel-coupled to the island of an electrostatically-induced single-electron transistor [2]. This device allowed the single-shot readout of the electron spin with visibility > 90% and 3 ?s readout time [3]. More recently we have integrated the single-shot readout device with a broadband microwave transmission line to coherently control the electron and nuclear spins. The resonance frequency of the electron is found by monitoring the excess spin-up counts while sweeping the microwave frequency. At any time, one of two possible frequencies is found to be in resonance with the electron spin, depending on the state of the nuclear spin. Alternately probing the two frequencies yields the (quantum nondemolition) single-shot readout of the nucleus, with fidelity > 99.99%. Then we demonstrate the coherent control (Rabi oscillations) of both the electron and the nucleus, both detected in single-shot mode. The ?-pulse fidelity is ˜70% for the electron and ˜99% for the nucleus. Hahn echo and multi-pulse dynamical decoupling sequences allow us to explore the true coherence of the qubits, yielding T2e˜200 ?s for the electron, and T2n˜60 ms for the nucleus. These results are fully consistent with the bulk values for donors in a natural Si sample. Further improvements in qubit coherence can be expected by moving to isotopically pure ^28Si substrates.[4pt] [1] B. E. Kane, Nature 393, 133 (1998).[0pt] [2] A. Morello et al., Phys. Rev. B 80, 081307(R) (2009).[0pt] [3] A. Morello et al., Nature 467, 687 (2010).

Morello, Andrea

2012-02-01

15

Time resolved control of electron tunnelling times and single-shot spin readout in a quantum dot  

NASA Astrophysics Data System (ADS)

We are pursuing a capability to perform time resolved manipulations of single spins in quantum dot circuits involving more than two quantum dots. In this paper, we demonstrate full counting statistics as well as averaging techniques used to calibrate the tunnel barriers. We make use of this to implement the Delft protocol [1] for single shot single spin readout in a device designed to form a triple quantum dot potential. We are able to tune the tunnelling times over around three orders of magnitude. We obtain a spin relaxation time of 300?s at 10 T.

Gaudreau, L.; Kam, A.; Kycia, J. B.; Studenikin, S. A.; Granger, G.; Mason, J. D.; Zawadzki, P.; Sachrajda, A. S.

2010-02-01

16

Gate controlled spin pumping at a quantum spin Hall edge  

NASA Astrophysics Data System (ADS)

We propose a four-terminal device designed to manipulate by all electrical means the spin of a magnetic adatom positioned at the edge of a quantum spin Hall insulator. We show that an electrical gate, able to tune the interface resistance between a quantum spin Hall insulator and the source and drain electrodes, can switch the device between two regimes: one where the system exhibits spin pumping and the other where the adatom remains in its ground state. This demonstrates an all-electrical route to control single spins by exploiting helical edge states of topological materials.

Narayan, Awadhesh; Hurley, Aaron; Sanvito, Stefano

2013-09-01

17

Single-pulse terahertz coherent control of spin resonance in the canted antiferromagnet YFeO3, mediated by dielectric anisotropy  

NASA Astrophysics Data System (ADS)

We report on the coherent control of terahertz (THz) spin waves in a canted antiferromagnet yttrium orthoferrite, YFeO3, associated with a quasiferromagnetic (quasi-FM) spin resonance at a frequency of 0.3 THz, using a single-incident THz pulse. The spin resonance is excited impulsively by the magnetic field component of the THz pulse. The intrinsic dielectric anisotropy of YFeO3 in the THz range allows for coherent control of both the amplitude and the phase of the excited spin wave. The coherent control is based on simultaneous generation of two interfering phase-shifted spin waves whose amplitudes and relative phase, dictated by the dielectric anisotropy of the YFeO3 crystal, can be controlled by varying the polarization of the incident THz pulse with respect to the crystal axes. The spatially anisotropic decay of the THz-excited FM spin resonance in YFeO3, leading to an increasingly linear polarization of the THz oscillation at the spin resonance frequency, suggests a key role of magnon-phonon coupling in spin-wave energy dissipation.

Jin, Zuanming; Mics, Zoltán; Ma, Guohong; Cheng, Zhenxiang; Bonn, Mischa; Turchinovich, Dmitry

2013-03-01

18

Driven coherent oscillations of a single electron spin in a quantum dot  

Microsoft Academic Search

The ability to control the quantum state of a single electron spin in a quantum dot is at the heart of recent developments towards a scalable spin-based quantum computer. In combination with the recently demonstrated controlled exchange gate between two neighbouring spins, driven coherent single spin rotations would permit universal quantum operations. Here, we report the experimental realization of single

F. H. L. Koppens; C. Buizert; K. J. Tielrooij; I. T. Vink; K. C. Nowack; T. Meunier; L. P. Kouwenhoven; L. M. K. Vandersypen

2006-01-01

19

Nanoscale imaging magnetometry with single spins in diamond  

NASA Astrophysics Data System (ADS)

Single Nitrogen-Vacancy colour centers in diamond are gaining popularity because of its exceptional optical and spin properties. The single spin of the defect can be manipulated optically, providing a efficient way to entangle single electron spins and couple nuclear spins qubits in diamond.[1] Long spin coherence time of these single defects finds application as sensitive magnetic field probes. Using engineered diamond we can achieve ultrahigh sensitivity using which we will be able to detect a single external electron or nucelar spin.[2] Controlled creation of these color centers inside nanodiamonds offers diverse applications. By attaching these single spins to the tip of a scanning probe, we were able to perform sensitive scanning probe magnetometry at nanoscale.[3] Improving this device by using quantum grade diamond and synchronized NMR pulse sequences we would have the ability to perform nanoscale NMR/MRI of single molecules.[0pt] [1] Neumann, P. et al. Multipartite Entanglement Among Single Spins in Diamond. Science 320, 1326-1329 (2008).[0pt] [2] Maze, J. R. et al. Nanoscale magnetic sensing with an individual electronic spin in diamond. Nature 455, 644-647(2008).[0pt] [3] Balasubramanian, G. et al. Nanoscale imaging magnetometry with diamond spins under ambient conditions. Nature 455, 648-651(2008).

Balasubramanian, Gopalakrishnan; Tisler, Julia; Kolesov, Roman; Jelezko, Fedor; Wrachtrup, Joerg

2009-03-01

20

Driven coherent oscillations of a single electron spin in a quantum dot  

Microsoft Academic Search

The ability to control the quantum state of a single electron spin in a quantum dot is at the heart of recent developments towards a scalable spin-based quantum computer. In combination with the recently demonstrated controlled exchange gate between two neighbouring spins [1], driven coherent single spin rotations would permit universal quantum operations. In this talk, I will discuss the

Frank Koppens; Christo Buizert; Klaas-Jan Tielrooij; Ivo Vink; Katja Nowack; Tristan Meunier; Leo Kouwenhoven; Lieven Vandersypen

2007-01-01

21

Predictions for single spin asymmetries in and  

Microsoft Academic Search

.   Predictions for the single transverse spin asymmetry in semi-inclusive DIS processes are given; non-negligible values of may arise from spin effects in the fragmentation of a polarized quark into a final hadron with a transverse momentum with respect to the jet axis, the so-called Collins effect. The elementary single spin asymmetry of the fragmenting quark\\u000a has been fixed in

M. Anselmino; M. Boglione; J. Hansson; F. Murgia

2000-01-01

22

Magnetic resonance of a single molecular spin  

Microsoft Academic Search

Magnetic-resonance spectroscopy on single molecules represents the ultimate limit in sensitivity of electron spin resonance: the detection of a single molecular spin. This is achieved by combining single molecule spectroscopy and optically detected magnetic resonance. Experimental results on pentacene in p-terphenyl both in zero-field and in the presence of a weak magnetic field demonstrate that magnetic-resonance spectroscopy on single molecules

Jürgen Köhler

1999-01-01

23

Repetitive readout of a single electronic spin via quantum logic with nuclear spin ancillae.  

PubMed

Robust measurement of single quantum bits plays a key role in the realization of quantum computation and communication as well as in quantum metrology and sensing. We have implemented a method for the improved readout of single electronic spin qubits in solid-state systems. The method makes use of quantum logic operations on a system consisting of a single electronic spin and several proximal nuclear spin ancillae in order to repetitively readout the state of the electronic spin. Using coherent manipulation of a single nitrogen vacancy center in room-temperature diamond, full quantum control of an electronic-nuclear system consisting of up to three spins was achieved. We took advantage of a single nuclear-spin memory in order to obtain a 10-fold enhancement in the signal amplitude of the electronic spin readout. We also present a two-level, concatenated procedure to improve the readout by use of a pair of nuclear spin ancillae, an important step toward the realization of robust quantum information processors using electronic- and nuclear-spin qubits. Our technique can be used to improve the sensitivity and speed of spin-based nanoscale diamond magnetometers. PMID:19745117

Jiang, L; Hodges, J S; Maze, J R; Maurer, P; Taylor, J M; Cory, D G; Hemmer, P R; Walsworth, R L; Yacoby, A; Zibrov, A S; Lukin, M D

2009-09-10

24

Single-shot readout of an electron spin in silicon.  

PubMed

The size of silicon transistors used in microelectronic devices is shrinking to the level at which quantum effects become important. Although this presents a significant challenge for the further scaling of microprocessors, it provides the potential for radical innovations in the form of spin-based quantum computers and spintronic devices. An electron spin in silicon can represent a well-isolated quantum bit with long coherence times because of the weak spin-orbit coupling and the possibility of eliminating nuclear spins from the bulk crystal. However, the control of single electrons in silicon has proved challenging, and so far the observation and manipulation of a single spin has been impossible. Here we report the demonstration of single-shot, time-resolved readout of an electron spin in silicon. This has been performed in a device consisting of implanted phosphorus donors coupled to a metal-oxide-semiconductor single-electron transistor-compatible with current microelectronic technology. We observed a spin lifetime of ?6?seconds at a magnetic field of 1.5?tesla, and achieved a spin readout fidelity better than 90 per cent. High-fidelity single-shot spin readout in silicon opens the way to the development of a new generation of quantum computing and spintronic devices, built using the most important material in the semiconductor industry. PMID:20877281

Morello, Andrea; Pla, Jarryd J; Zwanenburg, Floris A; Chan, Kok W; Tan, Kuan Y; Huebl, Hans; Möttönen, Mikko; Nugroho, Christopher D; Yang, Changyi; van Donkelaar, Jessica A; Alves, Andrew D C; Jamieson, David N; Escott, Christopher C; Hollenberg, Lloyd C L; Clark, Robert G; Dzurak, Andrew S

2010-09-26

25

Detection and Control of Individual Nuclear Spins Using a Weakly Coupled Electron Spin  

SciTech Connect

We experimentally isolate, characterize, and coherently control up to six individual nuclear spins that are weakly coupled to an electron spin in diamond. Our method employs multipulse sequences on the electron spin that resonantly amplify the interaction with a selected nuclear spin and at the same time dynamically suppress decoherence caused by the rest of the spin bath. We are able to address nuclear spins with interaction strengths that are an order of magnitude smaller than the electron spin dephasing rate. Our results provide a route towards tomography with single-nuclear-spin sensitivity and greatly extend the number of available quantum bits for quantum information processing in diamond.

Taminiau, T.H.; Wagenaar, J.J.T.; van der Sar, T.; Jelezko, F.; Dobrovitski, Viatcheslav V.; Hanson, R.

2012-09-28

26

Nanoscale imaging magnetometry with single spins in diamond  

Microsoft Academic Search

Single Nitrogen-Vacancy colour centers in diamond are gaining popularity because of its exceptional optical and spin properties. The single spin of the defect can be manipulated optically, providing a efficient way to entangle single electron spins and couple nuclear spins qubits in diamond.[1] Long spin coherence time of these single defects finds application as sensitive magnetic field probes. Using engineered

Gopalakrishnan Balasubramanian; Julia Tisler; Roman Kolesov; Fedor Jelezko; Joerg Wrachtrup

2009-01-01

27

Single spins in self-assembled quantum dots.  

PubMed

Self-assembled quantum dots have excellent photonic properties. For instance, a single quantum dot is a high-brightness, narrow-linewidth source of single photons. Furthermore, the environment of a single quantum dot can be tailored relatively easily using semiconductor heterostructure and post-growth processing techniques, enabling electrical control of the quantum dot charge and control over the photonic modes with which the quantum dot interacts. A single electron or hole trapped inside a quantum dot has spintronics applications. Although the spin dephasing is rather rapid, a single spin can be manipulated using optical techniques on subnanosecond timescales. Optical experiments are also providing new insights into old issues, such as the central spin problem. This Review provides a snapshot of this active field, with some indications for the future. It covers the basic materials and optical properties of single quantum dots, techniques for initializing, manipulating and reading out single spin qubits, and the mechanisms that limit the electron-spin and hole-spin coherence. PMID:23695745

Warburton, Richard J

2013-06-01

28

Single spins in self-assembled quantum dots  

NASA Astrophysics Data System (ADS)

Self-assembled quantum dots have excellent photonic properties. For instance, a single quantum dot is a high-brightness, narrow-linewidth source of single photons. Furthermore, the environment of a single quantum dot can be tailored relatively easily using semiconductor heterostructure and post-growth processing techniques, enabling electrical control of the quantum dot charge and control over the photonic modes with which the quantum dot interacts. A single electron or hole trapped inside a quantum dot has spintronics applications. Although the spin dephasing is rather rapid, a single spin can be manipulated using optical techniques on subnanosecond timescales. Optical experiments are also providing new insights into old issues, such as the central spin problem. This Review provides a snapshot of this active field, with some indications for the future. It covers the basic materials and optical properties of single quantum dots, techniques for initializing, manipulating and reading out single spin qubits, and the mechanisms that limit the electron-spin and hole-spin coherence.

Warburton, Richard J.

2013-06-01

29

Magnetic resonance of a single molecular spin  

NASA Astrophysics Data System (ADS)

Magnetic-resonance spectroscopy on single molecules represents the ultimate limit in sensitivity of electron spin resonance: the detection of a single molecular spin. This is achieved by combining single molecule spectroscopy and optically detected magnetic resonance. Experimental results on pentacene in p-terphenyl both in zero-field and in the presence of a weak magnetic field demonstrate that magnetic-resonance spectroscopy on single molecules adds on to the specificity of single-molecule spectroscopy. It proved possible to identify single molecules which contain 13C nuclei in natural abundance and to observe the splitting of the electron spin resonance line resulting from the hyperfine intercation of a single molecular spin with a single 13C nuclear spin. From the Zeeman effect the orientation of the symmetry axes of individual molecules with respect to the direction of the external magnetic field is obtained. This allows to compare the orientation of individual molecules with their substitutional-site specific transition frequencies depending on the quality of the host crystal.

Köhler, Jürgen

1999-03-01

30

Single Spins in Diamond -- Novel Probes for Nanoscience  

Microsoft Academic Search

Nitrogen-Vacancy color centers in diamond are gaining popularity because of its exceptional optical and spin properties. The single spin of the defect can be manipulated optically, providing an efficient way to entangle single electron spins and couple nuclear spin qubits in diamond. Long spin coherence time of these single defects finds application as sensitive magnetic field probes. Using engineered diamond

Gopalakrishnan Balasubramanian; Julia Tisler; Fedor Jelezko; Joerg Wrachtrup

2010-01-01

31

Single spin asymmetries in electroproduction at CLAS  

SciTech Connect

We present measurements of spin asymmetries in semi-inclusive processes in hard scattering kinematics using a 5.7 GeV electron beam and the CEBAF Large Acceptance Spectrometer (CLAS) at JLab. Scattering of longitudinally polarized electrons of an unpolarized liquid-hydrogen and off a polarized NH{sub 3} targets was studied over a wide range of kinematics. Non-zero single-beam and single-target spin asymmetries have been observed in semi-inclusive pion production in hard-scattering kinematics (Q{sup 2} > 1.2 GeV{sup 2}, W{sup 4} > 4 GeV{sup 2}). Systematic studies of factorization of x and z dependences have been done for different spin-dependent and spin-independent observables. No significant x/z dependence has been observed within statistical uncertainties, which is consistent with factorization of hard scattering and fragmentation processes.

Harut Avakian; Latifa Elouadrhiri

2004-06-02

32

Coherence of single spins coupled to a nuclear spin bath of varying density  

NASA Astrophysics Data System (ADS)

The dynamics of single electron and nuclear spins in a diamond lattice with different C13 nuclear spin concentration is investigated. It is shown that coherent control of up to three individual nuclei in a dense nuclear spin cluster is feasible. The free-induction decays of nuclear spin Bell states and single nuclear coherences among C13 nuclear spins are compared and analyzed. Reduction in a free-induction-decay time T2? and a coherence time T2 upon increase in nuclear spin concentration has been found. For pure diamond, T2? as long as 30?s and T2 of up to 0.65 ms for the electron spin has been observed. The C13 concentration dependence of T2? is explained by Fermi contact and dipolar interactions with nuclei in the lattice. It has been found that T2 decreases approximately as 1/n , where n is C13 concentration, which corresponds to the reported theoretical line of T2 for an electron spin interacting with a nuclear spin bath.

Mizuochi, N.; Neumann, P.; Rempp, F.; Beck, J.; Jacques, V.; Siyushev, P.; Nakamura, K.; Twitchen, D. J.; Watanabe, H.; Yamasaki, S.; Jelezko, F.; Wrachtrup, J.

2009-07-01

33

Manipulating single electron spins and coherence in quantum dots  

NASA Astrophysics Data System (ADS)

The non-destructive detection of a single electron spin in a quantum dot (QD) is demonstrated using a time- averaged magneto-optical Kerr rotation measurementootnotetextJ. Berezovsky, M. H. Mikkelsen, O. Gywat, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 314, 1916 (2006).. This technique provides a means to directly probe the spin off- resonance, thus minimally disturbing the system. Furthermore, the ability to sequentially initialize, manipulate, and read out the state of a qubit, such as an electron spin in a quantum dot, is necessary for virtually any scheme for quantum information processing. In addition to the time-averaged measurements, we have extended the single dot KR technique into the time domain with pulsed pump and probe lasers, allowing the observation of the coherent evolution of an electron spin stateootnotetextM. H. Mikkelsen, J. Berezovsky, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Nature Physics 3, 770 (2007).. The dot is formed by interface fluctuations of a GaAs quantum well and embedded in a diode structure to allow controllable gating/charging of the QD. To enhance the small single spin signal, the QD is positioned within a vertical optical cavity. Observations of coherent single spin precession in an applied magnetic field allow a direct measurement of the electron g-factor and transverse spin lifetime. These measurements reveal information about the relevant spin decoherence mechanisms, while also providing a sensitive probe of the local nuclear spin environment. Finally, we have recently eveloped a scheme for high speed all-optical manipulation of the spin state that enables multiple operations within the coherence timeootnotetextJ. Berezovsky, M. H. Mikkelsen, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, accepted for publication (2008).. The results represent progress toward the control and coupling of single spins and photons for quantum information processingootnotetextS. Ghosh, W.H. Wang, F. M. Mendoza, R. C. Myers, X. Li, N. Samarth, A. C. Gossard, and D. D. Awschalom, Nature Materials, 5, 267 (2006). as well as quantum non-demolition measurements of a single spin.

Awschalom, David

2008-05-01

34

Excited-State Spectroscopy Using Single Spin Manipulation in Diamond  

NASA Astrophysics Data System (ADS)

We use single-spin resonant spectroscopy to study the spin structure in the orbital excited state of a diamond nitrogen-vacancy (N-V) center at room temperature. The data show that the excited-state spin levels have a zero-field splitting that is approximately half of the value of the ground state levels, a g factor similar to the ground state value, and a hyperfine splitting ˜20× larger than in the ground state. In addition, the width of the resonances reflects the electronic lifetime in the excited state. We also show that the spin level splitting can significantly differ between N-V centers, likely due to the effects of local strain, which provides a pathway to control over the spin Hamiltonian and may be useful for quantum-information processing.

Fuchs, G. D.; Dobrovitski, V. V.; Hanson, R.; Batra, A.; Weis, C. D.; Schenkel, T.; Awschalom, D. D.

2008-09-01

35

Spin-transfer torque on a single magnetic adatom  

NASA Astrophysics Data System (ADS)

We theoretically show how the spin orientation of a single magnetic adatom can be controlled by spin polarized electrons in a scanning tunnelling microscope configuration. The underlying physical mechanism is spin assisted inelastic tunnelling. Experiments with Mn adatoms deposited on a Cu2N surface have been reported for non-polarized currents [1-2]. We show that by changing the direction of the applied current, the orientation of the magnetic adatom can be completely reversed on a time scale that ranges from a few nanoseconds to microseconds, depending on bias and temperature. The changes in the adatom magnetization direction are, in turn, reflected in the tunnelling conductance. Therefore, this effect opens the possibility of writing/reading a single spin without the need of a local magnetic field.[4pt] [1] C.F. Hirjibehedin, C. P. Lutz, A. J. Heinrich, Science 312, 1021 (2006).[0pt] [2] C. Hirjibehedin et al., Science 317, 1199 (2007).

Delgado, Fernando; José Palacios, Juan; Fernández-Rossier, Joaquín

2010-03-01

36

A single-atom electron spin qubit in silicon.  

PubMed

A single atom is the prototypical quantum system, and a natural candidate for a quantum bit, or qubit--the elementary unit of a quantum computer. Atoms have been successfully used to store and process quantum information in electromagnetic traps, as well as in diamond through the use of the nitrogen-vacancy-centre point defect. Solid-state electrical devices possess great potential to scale up such demonstrations from few-qubit control to larger-scale quantum processors. Coherent control of spin qubits has been achieved in lithographically defined double quantum dots in both GaAs (refs 3-5) and Si (ref. 6). However, it is a formidable challenge to combine the electrical measurement capabilities of engineered nanostructures with the benefits inherent in atomic spin qubits. Here we demonstrate the coherent manipulation of an individual electron spin qubit bound to a phosphorus donor atom in natural silicon, measured electrically via single-shot read-out. We use electron spin resonance to drive Rabi oscillations, and a Hahn echo pulse sequence reveals a spin coherence time exceeding 200?µs. This time should be even longer in isotopically enriched (28)Si samples. Combined with a device architecture that is compatible with modern integrated circuit technology, the electron spin of a single phosphorus atom in silicon should be an excellent platform on which to build a scalable quantum computer. PMID:22992519

Pla, Jarryd J; Tan, Kuan Y; Dehollain, Juan P; Lim, Wee H; Morton, John J L; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

2012-09-19

37

Interface Controlled Tunneling Spin Polarization  

NASA Astrophysics Data System (ADS)

In recent years spin-dependent tunneling in magnetic tunnel junctions has aroused enormous interest and developed into a vigorous field of research. However, despite extensive efforts to elucidate the mechanisms of spin-dependent tunneling, a complete understanding of this phenomenon is still lacking. In this talk we will consider various factors controlling the spin polarization of the tunneling current and emphasize the decisive role of interface bonding. We will show that the tunneling spin polarization is primarily determined by the electronic and atomic structure of ferromagnet/insulator interfaces rather than bulk properties. Starting from a simple tight-binding model which demonstrates the importance of interface states that are controlled by the hybridization between the atoms at the interface, we will, then, consider spin-dependent tunneling from the oxidized Co surface through vacuum [1] and in Co/Al2O3/Co tunnel junctions [2], where the cobalt-oxygen bonding at the interfaces play a crucial role. Our results indicate that the common argument of the dominant s-electron tunneling which is often used to explain positive values of the spin polarization in alumina-based tunnel junctions might be qualitatively incorrect. Moreover, oxygen atoms adsorbed by cobalt at the Co/Al2O3 interface may be a prerequisite for the positive spin polarization. The importance of the interface bonding and structure in spin-dependent tunneling makes the quantitative description of transport characteristics much more complicated; however, it broadens dramatically the possibility to engineer magnetic tunnel junctions with properties desirable for device applications. [1] K.D. Belashchenko, E.Y. Tsymbal, M. van Schilfgaarde, D. Stewart, I.I. Oleynik, and S.S. Jaswal, Phys. Rev. B 69, 174408 (2004). [2] K.D. Belashchenko, E.Y. Tsymbal, I.I. Oleynik, and M. van Schilfgaarde, submitted paper.

Tsymbal, Evgeny Y.

2005-03-01

38

Optically detected spin coherence of single molecules  

NASA Astrophysics Data System (ADS)

Optically detected electron paramagnetic resonance of single molecules of pentacene in a p-terphenyl crystal at 1.8 K is presented. Transient nutation of a single electronic spin is demonstrated, showing a coherence damping within several microseconds. The fluorescence photons of a single molecule can be used as an internal timebase to trigger the application of microwave pulses. Because of this it is possible to enhance or switch off the optically detected magnetic resonance effect, depending on the delay between the triggering photon and the microwave pulse.

Wrachtrup, J.; von Borczyskowski, C.; Bernard, J.; Orrit, M.; Brown, R.

1993-11-01

39

Single-spin addressing in an atomic Mott insulator.  

PubMed

Ultracold atoms in optical lattices provide a versatile tool with which to investigate fundamental properties of quantum many-body systems. In particular, the high degree of control of experimental parameters has allowed the study of many interesting phenomena, such as quantum phase transitions and quantum spin dynamics. Here we demonstrate how such control can be implemented at the most fundamental level of a single spin at a specific site of an optical lattice. Using a tightly focused laser beam together with a microwave field, we were able to flip the spin of individual atoms in a Mott insulator with sub-diffraction-limited resolution, well below the lattice spacing. The Mott insulator provided us with a large two-dimensional array of perfectly arranged atoms, in which we created arbitrary spin patterns by sequentially addressing selected lattice sites after freezing out the atom distribution. We directly monitored the tunnelling quantum dynamics of single atoms in the lattice prepared along a single line, and observed that our addressing scheme leaves the atoms in the motional ground state. The results should enable studies of entropy transport and the quantum dynamics of spin impurities, the implementation of novel cooling schemes, and the engineering of quantum many-body phases and various quantum information processing applications. PMID:21412333

Weitenberg, Christof; Endres, Manuel; Sherson, Jacob F; Cheneau, Marc; Schauss, Peter; Fukuhara, Takeshi; Bloch, Immanuel; Kuhr, Stefan

2011-03-17

40

Collins Mechanism Contributions to Single Spin Asymmetry  

SciTech Connect

We present recent developments on the single transverse spin physics, in particular, the Collins mechanism contributions in various hadronic reactions, such as semi-inclusive hadron production in DIS process, azimuthal distribution of hadron in high energy jet in pp collisions. We will demonstrate that the transverse momentum dependent and collinear factorization approaches are consistent with each other in the description of the Collins effects in the semi-inclusive hadron production in DIS process.

Yuan Feng [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 and RIKEN/BNL Research Center, Building 510A, Brookhaven National Laboratory, Upton, NY 11973 (United States)

2009-12-17

41

Collins Mechanism Contributions to Single Spin Asymmetry  

SciTech Connect

We present recent developments on the single transverse spin physics,in particular, the Collins mechanism contributions in various hadronic reactions,such as semi-inclusive hadron production in DIS process, azimuthal distributionof hadron in high energy jet in pp collisions. We will demonstrate thatthe transverse momentum dependent and collinear factorization approaches areconsistentwith each other in the description of the Collins effects in the semi-inclusivehadron production in DIS process.

Yuan, Feng

2009-09-11

42

Quantum Non-demolition measurements of single spins in semiconductors  

NASA Astrophysics Data System (ADS)

For the development of large-scale quantum computers, electron spin-encoded qubits in solid-state are appealing because of their favorable decoherence time scales, high potential for scalability, and many handles for precision control. However, an additional requirement that is traditionally challenging in the solid-state is a capacity for high-fidelity qubit readout. We propose a scheme for measuring the state of a single donor electron spin using a field-effect transistor induced two-dimensional electron gas and electrically detected magnetic resonance techniques. The scheme is facilitated by hyperfine coupling to the donor nucleus. We analyze the potential sensitivity and outline experimental requirements. Our measurement provides a single-shot, projective, and effectively quantum non-demolition measurement of an electron spin-encoded qubit state.

Sarovar, Mohan; Young, Kevin; Schenkel, Thomas; Whaley, K. Birgitta

2008-03-01

43

Forward Transverse Single Spin Asymmetries at PHENIX  

NASA Astrophysics Data System (ADS)

Recent measurements of single transverse spin asymmetries in proton-proton collisions measured by the PHENIX experiment at RHIC are presented. The focus is on the single particle left-right asymmetry AN for ?0 at ?s = 200 GeV and ?s = 62.4 GeV and the measurement of di-hadron correlations at ?s = 200 GeV which are produced by the fragmentation of a transversely polarized quark via the Interference Fragmentation Function (IFF) H1< and thus provide a probe for the quark transversity distribution function.

Vossen, Anselm; PHENIX Collaboration

2011-09-01

44

Three-dimensional optical manipulation of a single electron spin.  

PubMed

Nitrogen vacancy (NV) centres in diamond are promising elemental blocks for quantum optics, spin-based quantum information processing and high-resolution sensing. However, fully exploiting the capabilities of these NV centres requires suitable strategies to accurately manipulate them. Here, we use optical tweezers as a tool to achieve deterministic trapping and three-dimensional spatial manipulation of individual nanodiamonds hosting a single NV spin. Remarkably, we find that the NV axis is nearly fixed inside the trap and can be controlled in situ by adjusting the polarization of the trapping light. By combining this unique spatial and angular control with coherent manipulation of the NV spin and fluorescence lifetime measurements near an integrated photonic system, we demonstrate individual optically trapped NV centres as a novel route for both three-dimensional vectorial magnetometry and sensing of the local density of optical states. PMID:23396312

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

2013-02-10

45

Three-dimensional optical manipulation of a single electron spin  

NASA Astrophysics Data System (ADS)

Nitrogen vacancy (NV) centres in diamond are promising elemental blocks for quantum optics, spin-based quantum information processing and high-resolution sensing. However, fully exploiting the capabilities of these NV centres requires suitable strategies to accurately manipulate them. Here, we use optical tweezers as a tool to achieve deterministic trapping and three-dimensional spatial manipulation of individual nanodiamonds hosting a single NV spin. Remarkably, we find that the NV axis is nearly fixed inside the trap and can be controlled in situ by adjusting the polarization of the trapping light. By combining this unique spatial and angular control with coherent manipulation of the NV spin and fluorescence lifetime measurements near an integrated photonic system, we demonstrate individual optically trapped NV centres as a novel route for both three-dimensional vectorial magnetometry and sensing of the local density of optical states.

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

2013-03-01

46

Universal Dynamical Decoupling of a Single Solid-State Spin from a Spin Bath  

NASA Astrophysics Data System (ADS)

Controlling the interaction of a single quantum system with its environment is a fundamental challenge in quantum science and technology. We strongly suppressed the coupling of a single spin in diamond with the surrounding spin bath by using double-axis dynamical decoupling. The coherence was preserved for arbitrary quantum states, as verified by quantum process tomography. The resulting coherence time enhancement followed a general scaling with the number of decoupling pulses. No limit was observed for the decoupling action up to 136 pulses, for which the coherence time was enhanced more than 25 times compared to that obtained with spin echo. These results uncover a new regime for experimental quantum science and allow us to overcome a major hurdle for implementing quantum information protocols.

de Lange, G.; Wang, Z. H.; Ristè, D.; Dobrovitski, V. V.; Hanson, R.

2010-10-01

47

Increasing the electron spin coherence time by coherent optical control of the nuclear spin fluctuations  

NASA Astrophysics Data System (ADS)

A single electron spin plays a central role for spin-based quantum information science and electronic devices. One crucial requirement for the future success is to have a long quantum coherence time. It has been demonstrated that in III-V materials, the electron spin coherence time deteriorates rapidly due to the hyperfine coupling with the nuclear environment. Here, we report the increase of the electron spin coherence time by optical controlled suppression of nuclear spin fluctuations through coherent dark-state spectroscopy. The experiment is performed in a single negatively charged InAs self assembled quantum dot (SAQD). The dynamic nuclear spin polarization manifests itself as a hysteresis in the probe absorption spectrum and in the spectral position of the dark state as a function of the frequency scanning direction of the probe field. We demonstrated that the nuclear field can be locked to the maximum trion excitation by observing a flat-top of the trion absorption lineshape, and the switching of the nuclei from unstable to stable configurations by fixing the laser frequencies and monitoring the coherent optical response as a function of time. The optically controlled locking of the nuclear field leads to an enhancement of the electron spin coherence time, which is measured through dark state spectroscopy. The suppression of the nuclear field fluctuations result from a hole spin assisted dynamic nuclear spin polarization feed-back process. We further demonstrated the electron spin coherence enhancement by a three-beam measurement, where two-pump beams lock the nuclear field and the third probe measures the coherence time through the dark state. The inferred spin coherence time is increased by nearly 3 orders of magnitude compared to its thermal value. Our work lays the groundwork for the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.

Xu, Xiaodong

2010-03-01

48

Ultrafast optical control of individual quantum dot spin qubits.  

PubMed

Single spins in semiconductor quantum dots form a promising platform for solid-state quantum information processing. The spin-up and spin-down states of a single electron or hole, trapped inside a quantum dot, can represent a single qubit with a reasonably long decoherence time. The spin qubit can be optically coupled to excited (charged exciton) states that are also trapped in the quantum dot, which provides a mechanism to quickly initialize, manipulate and measure the spin state with optical pulses, and to interface between a stationary matter qubit and a 'flying' photonic qubit for quantum communication and distributed quantum information processing. The interaction of the spin qubit with light may be enhanced by placing the quantum dot inside a monolithic microcavity. An entire system, consisting of a two-dimensional array of quantum dots and a planar microcavity, may plausibly be constructed by modern semiconductor nano-fabrication technology and could offer a path toward chip-sized scalable quantum repeaters and quantum computers.This article reviews the recent experimental developments in optical control of single quantum dot spins for quantum information processing. We highlight demonstrations of a complete set of all-optical single-qubit operations on a single quantum dot spin: initialization, an arbitrary SU(2) gate, and measurement. We review the decoherence and dephasing mechanisms due to hyperfine interaction with the nuclear-spin bath, and show how the single-qubit operations can be combined to perform spin echo sequences that extend the qubit decoherence from a few nanoseconds to several microseconds, more than 5 orders of magnitude longer than the single-qubit gate time. Two-qubit coupling is discussed, both within a single chip by means of exchange coupling of nearby spins and optically induced geometric phases, as well as over longer-distances. Long-distance spin-spin entanglement can be generated if each spin can emit a photon that is entangled with the spin, and these photons are then interfered. We review recent work demonstrating entanglement between a stationary spin qubit and a flying photonic qubit. These experiments utilize the polarization- and frequency-dependent spontaneous emission from the lowest charged exciton state to single spin Zeeman sublevels. PMID:24006335

Greve, Kristiaan De; Press, David; McMahon, Peter L; Yamamoto, Yoshihisa

2013-09-04

49

Ultrafast optical control of individual quantum dot spin qubits  

NASA Astrophysics Data System (ADS)

Single spins in semiconductor quantum dots form a promising platform for solid-state quantum information processing. The spin-up and spin-down states of a single electron or hole, trapped inside a quantum dot, can represent a single qubit with a reasonably long decoherence time. The spin qubit can be optically coupled to excited (charged exciton) states that are also trapped in the quantum dot, which provides a mechanism to quickly initialize, manipulate and measure the spin state with optical pulses, and to interface between a stationary matter qubit and a ‘flying’ photonic qubit for quantum communication and distributed quantum information processing. The interaction of the spin qubit with light may be enhanced by placing the quantum dot inside a monolithic microcavity. An entire system, consisting of a two-dimensional array of quantum dots and a planar microcavity, may plausibly be constructed by modern semiconductor nano-fabrication technology and could offer a path toward chip-sized scalable quantum repeaters and quantum computers. This article reviews the recent experimental developments in optical control of single quantum dot spins for quantum information processing. We highlight demonstrations of a complete set of all-optical single-qubit operations on a single quantum dot spin: initialization, an arbitrary SU(2) gate, and measurement. We review the decoherence and dephasing mechanisms due to hyperfine interaction with the nuclear-spin bath, and show how the single-qubit operations can be combined to perform spin echo sequences that extend the qubit decoherence from a few nanoseconds to several microseconds, more than 5 orders of magnitude longer than the single-qubit gate time. Two-qubit coupling is discussed, both within a single chip by means of exchange coupling of nearby spins and optically induced geometric phases, as well as over longer-distances. Long-distance spin–spin entanglement can be generated if each spin can emit a photon that is entangled with the spin, and these photons are then interfered. We review recent work demonstrating entanglement between a stationary spin qubit and a flying photonic qubit. These experiments utilize the polarization- and frequency-dependent spontaneous emission from the lowest charged exciton state to single spin Zeeman sublevels.

De Greve, Kristiaan; Press, David; McMahon, Peter L.; Yamamoto, Yoshihisa

2013-09-01

50

Switched control of electron nuclear spin systems  

SciTech Connect

We study control of electron-nuclear spin dynamics at magnetic field strengths where the Larmor frequency of the nucleus is comparable to the hyperfine coupling strength. The quantization axis for the nuclear spin differs from the static B{sub 0} field direction and depends on the state of the electron spin. The quantization axis can be switched by flipping the state of electron spin, allowing for universal control of nuclear spin states. We show that by performing a sequence of flips (each followed by a suitable delay), we can perform any desired rotation of the nuclear spin, which can also be conditioned on the state of the electron spin. These operations, combined with electron spin rotations, can be used to synthesize any unitary transformation of the coupled electron-nuclear spin system. We discuss how these methods can be used for design of experiments for transfer of polarization from the electron to the nuclear spins.

Khaneja, Navin [Division of Engineering and Applied Science, Harvard University, 33 Oxford Street, Cambridge, Massachusetts 02138 (United States)

2007-09-15

51

Visualization of spin dynamics in single nanosized magnetic elements.  

PubMed

The design of future spintronic devices requires a quantitative understanding of the microscopic linear and nonlinear spin relaxation processes governing the magnetization reversal in nanometer-scale ferromagnetic systems. Ferromagnetic resonance is the method of choice for a quantitative analysis of relaxation rates, magnetic anisotropy and susceptibility in a single experiment. The approach offers the possibility of coherent control and manipulation of nanoscaled structures by microwave irradiation. Here, we analyze the different excitation modes in a single nanometer-sized ferromagnetic stripe. Measurements are performed using a microresonator set-up which offers a sensitivity to quantitatively analyze the dynamic and static magnetic properties of single nanomagnets with volumes of (100 nm)(3). Uniform as well as non-uniform volume modes of the spin wave excitation spectrum are identified and found to be in excellent agreement with the results of micromagnetic simulations which allow the visualization of the spatial distribution of these modes in the nanostructures. PMID:21693797

Banholzer, A; Narkowicz, R; Hassel, C; Meckenstock, R; Stienen, S; Posth, O; Suter, D; Farle, M; Lindner, J

2011-06-21

52

QCD Resummation for Single Spin Asymmetries  

SciTech Connect

We study the transverse momentum dependent factorization for single spin asymmetries in Drell-Yan and semi-inclusive deep inelastic scattering processes at one-loop order. The next-to-leading order hard factors are calculated in the Ji-Ma-Yuan factorization scheme. We further derive the QCD resummation formalisms for these observables following the Collins-Soper-Sterman method. The results are expressed in terms of the collinear correlation functions from initial and/or final state hadrons coupled with the Sudakov form factor containing all order soft-gluon resummation effects. The scheme-independent coefficients are calculated up to one-loop order.

Kang Zhongbo [RIKEN/BNL Research Center, Building 510A, Brookhaven National Laboratory, Upton, New York 11973 (United States); Xiao Bowen [Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Yuan Feng [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); RIKEN/BNL Research Center, Building 510A, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2011-10-07

53

QCD Resummation for Single Spin Asymmetries  

SciTech Connect

We study the transverse momentum dependent factorization for single spin asymmetries in Drell-Yan and semi-inclusive deep inelastic scattering processes at one-loop order. The next-to-leading order hard factors are calculated in the Ji-Ma-Yuan factorization scheme. We further derive the QCD resummation formalisms for these observables following the Collins-Soper-Sterman method. The results are expressed in terms of the collinear correlation functions from initial and/or final state hadrons coupled with the Sudakov form factor containing all order soft-gluon resummation effects. The scheme-independent coefficients are calculated up to one-loop order.

Kang Z.; Xiao, Bo-Wen; Yuan, Feng

2011-10-05

54

Universal quantum computation using exchange interactions and measurements of single- and two-spin observables  

SciTech Connect

We show how to construct a universal set of quantum logic gates using control over exchange interactions and single- and two-spin measurements only. Single-spin unitary operations are teleported between neighboring spins instead of being executed directly, thus potentially eliminating a major difficulty in the construction of several of the most promising proposals for solid-state quantum computation, such as spin-coupled quantum dots, donor-atom nuclear spins in silicon, and electrons on helium. Contrary to previous proposals dealing with this difficulty, our scheme requires no encoding redundancy. We also discuss an application to superconducting phase qubits.

Wu, L.-A.; Lidar, Daniel A. [Chemical Physics Theory Group, Chemistry Department, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada)

2003-05-01

55

Pulsed Nuclear Pumping and Spin Diffusion in a Single Charged Quantum Dot  

NASA Astrophysics Data System (ADS)

We report the observation of a feedback process between the nuclear spins in a single charged quantum dot under coherently pulsed optical excitation and its trion transition. The optical pulse sequence intersperses resonant narrow-band pumping for spin initialization with off-resonant ultrafast pulses for coherent electron-spin rotation. A hysteretic sawtooth pattern in the free-induction decay of the single electron spin is observed; a mathematical model indicates a competition between optical nuclear pumping and nuclear spin-diffusion. This effect allows dynamic tuning of the electron Larmor frequency to a value determined by the pulse timing, potentially allowing more complex coherent control operations.

Ladd, Thaddeus D.; Press, David; de Greve, Kristiaan; McMahon, Peter L.; Friess, Benedikt; Schneider, Christian; Kamp, Martin; Höfling, Sven; Forchel, Alfred; Yamamoto, Yoshihisa

2010-09-01

56

Optical detection and manipulation of single electron spin coherence in a semiconductor quantum dot  

Microsoft Academic Search

We demonstrate the ability to sequentially initialize, manipulate, and readout the state of a single electron spin in a quantum dot using all-optical techniques. The GaAs quantum dots are embedded in a diode structure to allow controllable charging of the quantum dots and positioned within a vertical optical cavity to enhance the small single spin signal. First, we demonstrate the

Maiken Sophia Hogh Mikkelsen

2009-01-01

57

Symmetry and Controllability for Quantum Spin Networks  

NASA Astrophysics Data System (ADS)

Symmetry is found to be an important tool to study the controllability problems in quantum control. Based on quantum spin networks subject to control of a single node by a local potential (Z-control), we have considered the relation of symmetriy and subspace controllability. Focusing on the single excitation subspace it is shown that for single-node Z-controls external symmetries are characterized by eigenstates of the system Hamiltonian that have zero overlap with the control node, and there are no internal symmetries. For uniformly coupled XXZ chains a characterization of all possible symmetries is derived from Bethe ansatz. Moreover, for uniform Heisenberg and XX chains, basic number theory can be used to prove that the lack of symmetry is equivalent to subspace controllability. On the other hand, symmetries in the Hamiltonian can be classified into two types: the internal and the external symmetries. Based on the external symmetries, we can rigorously prove the subspace controllability in each of the invariant subspaces for both XXZ and XYZ chains, but not for XX or Ising chains. All these results are useful to design the appropriate control strategy when implementing QIP in real physical systems.

Wang, Xiaoting; Schirmer, Sophie; Burgarth, Daniel; Pemberton-Ross, Peter; Jacobs, Kurt

2013-03-01

58

Present Status and Future Prospects of Quantum Information Processing: With Special Focus on Optically Controlled Semiconductor Spins and Single-Photon Technologies  

NASA Astrophysics Data System (ADS)

The scheme of directly controlling electron spins trapped in semiconductor quantum dots or donor impurities as qubits using optical pulses has various advantages, such as the achievements of local excitation and fast operation, low power consumption, easy implementation of an interface with optical fiber communication networks, and the capability of transferring information to nuclear spins, which are expected to serve as quantum memories with a long coherence time. In this report, I introduce the present status of the research and development of this scheme and discuss its potential application to quantum information processing.

Yamamoto, Yoshihisa

2011-10-01

59

Theoretical Study of Interaction between Photons and Single Spins  

NASA Astrophysics Data System (ADS)

Spin is a promising candidate for new resources of information technology. The major applications of spin-based technology are quantum computation, quantum communication and high-sensitive magnetometry. Optical control and detection of spin coherence are important techniques for such applications. In quantum communication and distributed quantum computing, quantum networks consisting of local nodes which are connected by quantum channels are essential. They provide platforms for transmission of flying qubits from one node to another. Within physical implementation of such networks, local nodes consist of clusters of stationary qubits. A single photon can form the flying qubit. The quantum information carried by the flying qubits can be conducted between local nodes through waveguides. Therefore quantum interfacing is the key element for the scalability in the quantum network. In the first two chapters of the thesis, we focus on the strong coupling region of the quantum interfacing. Solid-state systems have the advantages of stability and integratability. In solid-state systems, one-dimensional waveguides serve as an outstanding medium for transporting photons. Waveguides provide suitable circumstance for the strong interaction between photons and atoms for the small interaction section. This strong coupling between the atom and waveguide allows the photons to be directionally emitted into one optical channel connecting different quantum nodes. First, we follow the control scheme of the interplay between a stationary qubit and a flying qubit at an interface, which is composed of a ?-type system coupled to a one-dimensional waveguide. It shows that the sending and receiving process can be independently controlled by changing the driving laser pulses. We extend a general control scheme of a spin-photon quantum interface. Our scheme removes the constraints of Markovian process and therefore can be applied to the atom-waveguide devices for quantum network applications. In the three-level system, the exact solution for the driving pulse shows Markovian approximation applies for relatively slow pulses, while non-Markovian dynamics is essential for rapid operation near the cut-off frequency of the waveguide. Secondly, we investigate the dynamic evolution of a single two-level system embedded in the one-dimensional waveguide. It is well known that if the transition frequency of the two-level system is below the cut-off frequency of the one-dimensional waveguide, the spontaneous emission decay will be totally inhibited. However, we find that even the transition frequency is set above the cut-off frequency, the decay is partly suppressed due to the existence of an exciton bound state. When the transition frequency is tuned to the edge of the cut-off frequency, the decay rate is remarkably enhanced. And the Rabi oscillation appears between the discrete bound state and a resonance with finite lifetime. The Non-Markovian spontaneous emission near the band edge reveals the strong coupling between the atom and the continuum. The trapped polariton makes the optical system behave like a cavity without mirror. And the individual quantum dot has shown to be potential to serve as the deterministic single-photon source. Another limit of spin-photon interaction is the weak interaction regime, which often occurs in optical detection of single spins. The interaction between a single spin and a probe device is extremely weak, making measurement difficult. The measurement thus is weak. But disturbance caused by the measurement is also weak. In the weak interaction region, correlations of sequential or continuous weak measurement reveal faithfully dynamics of a single spin. We study the weak measurement of a single spin by a continuouswave light, which is based on the weak Faraday rotation effect. (Abstract shortened by UMI.)

Chen, Ting

60

Theory of quantum control of spin-photon dynamics and spin decoherence in semiconductors  

NASA Astrophysics Data System (ADS)

Single electron spin in a semiconductor quantum dot (QD) and single photon wavepacket propagating in an optical waveguide are investigated as carriers of quantum bit (qubit) for information processing. Cavity quantum electrodynamics of the coupled system composed of charged QD, microcavity and waveguide provides a quantum interface for the interplay of stationary spin qubits and flying photon qubits via cavity assisted optical control. This interface forms the basis for a wide range of essential functions of a quantum network, including transferring, swapping, and entangling qubits at distributed quantum nodes as well as a deterministic source and an efficient detector of a single photon wavepacket with arbitrarily specified shape. The cavity assisted optical process also made possible ultrafast initialization and QND readout of the spin qubit in QD. In addition, the strong optical nonlinearity of dot-cavity-waveguide coupled system enables phase gate and entanglement operation for flying single photon qubits in waveguides. The coherence of the electron spin is the wellspring of these quantum applications being investigated. At low temperature and strong magnetic field, the dominant cause of electron spin decoherence is the coupling with the interacting lattice nuclear spins. We present a quantum solution to the coupled dynamics of the electron with the nuclear spin bath. The decoherence is treated in terms of quantum entanglement of the electron with the nuclear pair-flip excitations driven by the various nuclear interactions. A novel nuclear interaction, mediated by virtue spin-flips of the single electron, plays an important role in single spin free-induction decay (FID). The spin echo not only refocuses the dephasing by inhomogeneous broadening in ensemble dynamics but also eliminates the decoherence by electron-mediated nuclear interaction. Thus, the decoherence times for single spin FID and ensemble spin echo are significantly different. The quantum theory of decoherence also leads to a method of coherence recovery of the electron by disentanglement, realized through maneuvering the nuclear bath evolution by control of the electron spin-flip. The studies form the basis to outline the construction of a solid-state quantum network for scalable and distributed processing of quantum information.

Yao, Wang

61

Optical detection and manipulation of single electron spin coherence in a semiconductor quantum dot  

NASA Astrophysics Data System (ADS)

We demonstrate the ability to sequentially initialize, manipulate, and readout the state of a single electron spin in a quantum dot using all-optical techniques. The GaAs quantum dots are embedded in a diode structure to allow controllable charging of the quantum dots and positioned within a vertical optical cavity to enhance the small single spin signal. First, we demonstrate the detection of a single electron spin in a quantum dot using a time-averaged magnetooptical Kerr rotation measurement at T = 10 K. This technique provides a means to directly probe the spin off-resonance, thus minimally disturbing the system. Next, we have extended this technique into the time domain using pulsed pump and probe lasers, allowing for direct observation of the coherent evolution of a single electron spin-state. The coherent single spin precession in an applied magnetic field reveals the electron g-factor and a transverse spin lifetime of ˜ 10 ns. Additionally, the observed spin dynamics provide a sensitive probe of the local nuclear spin environment. Finally, by applying off-resonant optical pulses, we coherently rotate a single electron spin in a quantum dot up to pi radians on picosecond timescales. Measurements of the spin rotation as a function of laser detuning and intensity confirm that the optical Stark effect is the operative mechanism and the results are well-described by a model including the electron-nuclear spin interaction. Using short tipping pulses, this technique enables one to perform a large number of operations within the coherence time. As an alternative system for single spin control, few Mn-ion spins in a GaAs quantum well were measured using polarized photoluminescence. A new mechanism for optically addressing and controlling small numbers of magnetic ions in semiconductors is demonstrated without the need for magnetic fields or magnetic materials. The polarized Mn-spins precess in a transverse magnetic field enabling Hanle measurements of the spin lifetimes. The observed Mn-ion spin lifetimes reach promising timescales in the low doping limit, demonstrating that individual magnetic spins in a solid are useful systems for coherent manipulation of spin information.

Mikkelsen, Maiken Sophia Hogh

62

Quantum Spin Dynamics in Single-Molecule Magnets  

Microsoft Academic Search

This thesis contains a thorough investigation of the quantum spin dynamics in Mn12-ac and Mn6 Single-molecule magnets. In particular, we have investigated the interplay between quantum tunneling of magnetization and nuclear spin dynamics in Mn12-ac by ultra-low temperature NMR experiments. We discuss the effect of quantum tunneling on the nuclear spin-lattice relaxation, the nuclear spin diffusion, the thermalization of the

Andrea Morello

2004-01-01

63

Single-shot readout of multiple nuclear spin qubits in diamond under ambient conditions  

NASA Astrophysics Data System (ADS)

Nuclear spins are attractive candidates for solid-state quantum information storage and processing owing to their extremely long coherence time. However, since this appealing property results from a high level of isolation from the environment, it remains a challenging task to polarize, manipulate and readout with high fidelity individual nuclear spins. A promising approach to overcome this limitation consists in utilizing an ancillary single electronic spin to detect and control remote nuclear spins coupled by hyperfine interaction. In this talk, I will show how the electronic spin of a single Nitrogen-Vacancy (NV) defect in diamond can be used as a robust platform to observe the real-time evolution of surrounding single nuclear spins under ambient conditions. Using a diamond sample with a natural abundance of ^13C isotopes, we first demonstrate high fidelity initialization and single-shot readout of an individual ^13C nuclear spin. By including the intrinsic ^14N nuclear spin of the NV defect in the quantum register, we then report the simultaneous observation of quantum jumps linked to both nuclear spin species, providing an efficient initialization of the two qubits. These results open up new avenues for diamond-based quantum information processing (QIP) including active feedback in quantum error correction protocols and tests of quantum correlations with solid-state single spins at room temperature.

Jacques, Vincent

2013-03-01

64

Spin transport and tunable Gilbert damping in a single-molecule magnet junction  

NASA Astrophysics Data System (ADS)

We study time-dependent electronic and spin transport through an electronic level connected to two leads and coupled with a single-molecule magnet via exchange interaction. The molecular spin is treated as a classical variable and precesses around an external magnetic field. We derive expressions for charge and spin currents by means of the Keldysh nonequilibrium Green's functions technique in linear order with respect to the time-dependent magnetic field created by this precession. The coupling between the electronic spins and the magnetization dynamics of the molecule creates inelastic tunneling processes which contribute to the spin currents. The inelastic spin currents, in turn, generate a spin-transfer torque acting on the molecular spin. This back-action includes a contribution to the Gilbert damping and a modification of the precession frequency. The Gilbert damping coefficient can be controlled by the bias and gate voltages or via the external magnetic field and has a nonmonotonic dependence on the tunneling rates.

Filipovi?, Milena; Holmqvist, Cecilia; Haupt, Federica; Belzig, Wolfgang

2013-01-01

65

Spin-Atomic Vibration Interaction and Spin-Flip Hamiltonian of a Single Atomic Spin in a Crystal Field  

NASA Astrophysics Data System (ADS)

We derive the spin-atomic vibration interaction VSA and the spin-flip Hamiltonian VSF of a single atomic spin in a crystal field. We here apply the perturbation theory to a model with the spin-orbit interaction and the kinetic and potential energies of electrons. The model also takes into account the difference in vibration displacement between an effective nucleus and electrons, ?r. Examining the coefficients of VSA and VSF, we first show that VSA appears for ?r\

Kokado, Satoshi; Harigaya, Kikuo; Sakuma, Akimasa

2010-11-01

66

Magnetic-texture-controlled transverse spin injection  

NASA Astrophysics Data System (ADS)

We propose an effect whereby an electric current along the interface between a ferromagnetic and normal metal leads to injection of pure spin current into the normal metal, if the magnetization direction in the ferromagnet varies spatially along the direction of current. For the specific example of a ferromagnetic spin spiral, we compute the inverse spin Hall effect voltage this spin current gives rise to when injected into a Pt layer. Furthermore, we show that this pure spin current leads to modification of the parameters that govern spin transfer and current-driven domain-wall motion, which can be used to tune the latter in layered magnetic systems. This effect in principle enables in situ control over the location, magnitude, and polarization of spin-current injection in devices.

van der Bijl, E.; Troncoso, R. E.; Duine, R. A.

2013-08-01

67

Single Spins in Diamond -- Novel Probes for Nanoscience  

NASA Astrophysics Data System (ADS)

Nitrogen-Vacancy color centers in diamond are gaining popularity because of its exceptional optical and spin properties. The single spin of the defect can be manipulated optically, providing an efficient way to entangle single electron spins and couple nuclear spin qubits in diamond. Long spin coherence time of these single defects finds application as sensitive magnetic field probes. Using engineered diamond we achieve ultrahigh sensitivity, which offers us possibilities to detect single external electron or nuclear spin. Broad emission/excitation spectrum and point like nature of the NV defects are attractive features in using them as FRET fluorophore. Attaching the emitter to the tip of a scanning probe microscope we were able to construct a scanning FRET microscope and image single molecules under ambient conditions. By attaching these single spins sensors to the tip of a scanning probe, we were able to perform sensitive scanning probe magnetometry at nanoscale.[1] Improving this device by using quantum grade diamond and synchronized NMR pulse sequences we would have the ability to perform nanoscale NMR/MRI of a single molecules. The method has far reaching potential in solving structure of biomolecules under ambient conditions. [1] Balasubramanian, G. et al. Nanoscale imaging magnetometry with diamond spins under ambient conditions. Nature 455, 648-651(2008).

Balasubramanian, Gopalakrishnan; Tisler, Julia; Jelezko, Fedor; Wrachtrup, Joerg

2010-03-01

68

Single zone control systems  

SciTech Connect

The number of old single zone systems which are operating today is quite high, providing numerous opportunities for retrofit to improve both space conditions and energy consumption characteristics. This report will cover the fundamentals of system controls applied to the single zone unit.

Kapka, L.A.

1987-01-01

69

Experimental control of a nuclear spin quantum register in diamond with decoherence-protected gates  

NASA Astrophysics Data System (ADS)

Nuclear spins are one of the most promising candidates for long-lived quantum bits that store and process quantum information. Individual nuclear spins in diamond have been addressed using the nearby electron spin of a nitrogen vacancy center. However, the relatively fast decoherence of the electron spin limits coherent control to the nearest, strongly coupled, nuclear spins. Here, we employ decoherence-protected gates [1] to access individual spins embedded in a bath of nuclear spins that are weakly coupled to an electron spin [2]. We demonstrate the initialization, control and readout of the nuclear spins and discuss our recent progress in implementing two-qubit entangling operations between nuclear spins. These results greatly extend the number of available quantum bits in diamond and provide a way towards tomography with single nuclear spin sensitivity even in decohering environments. [1] T. van der Sar et al., Nature 484, 82 (2012). [2] T. H. Taminiau et al., Phys. Rev. Lett. 109, 137602 (2012).

Taminiau, Tim Hugo; van der Sar, Toeno; Dobrovitski, V. V.; Hanson, Ronald

2013-03-01

70

Ultrafast optical spin echo of a single electron spin in a quantum dot  

NASA Astrophysics Data System (ADS)

We report on the ultrafast optical implementation of a Hahn Echo sequence on a single electron spin in an InGaAs quantum dot. With this technique, we were able to overcome the shot-to-shot variations of the electron spin's magnetic environment in our multi-shot, time-averaged read-out scheme. We measured the electron spin coherence time T2, both as a function of applied magnetic field, and for different types of sample surface treatment. Measured T2-times of 3 ?s, together with our experiment all-optical single spin rotation times of 30 ps, would allow 10^5 single qubit gate operations. Furthermore, we observe pronounced non-linear, hysteretic effects in a 2-pulse Ramsey interference experiment, which we attribute to an electron-spin dependent polarization of the nuclear spins. .

de Greve, Kristiaan; Press, David; McMahon, Peter; Ladd, Thaddeus; Friess, Benedikt; Kamp, Martin; Schneider, Christian; Hoefling, Sven; Forchel, Alfred; Yamamoto, Yoshihisa

2010-03-01

71

Quantum Computing Through Control of Spin-Orbit Coupling  

NASA Astrophysics Data System (ADS)

We propose a scheme for performing universal quantum computation in a linear array of single electron quantum dots using spin-orbit coupling. Quantum gates are carried out by pulsing the exchange interaction between neighboring dots. While this interaction is dominated by the isotropic Heisenberg term S_1ot S_2, spin-orbit coupling introduces small anisotropic corrections. We show that control over these corrections, even if limited, is sufficient for universal quantum computation over qubits encoded into pairs of electron spins on neighboring dots. There is no need for additional control mechanisms. The simplicity of our scheme hinges on these corrections having rotational symmetry about a fixed axis in spin space, and we discuss the conditions for which this is the case. For example, we show that in a linear array of GaAs quantum dots lying in the [001] plane and aligned along the [110] direction, the symmetry axis is fixed along the [1\\overline 10] direction within the Hund-Mulliken approximation. Control of spin-orbit coupling either through pulse shaping, or direct control of the Dresselhaus and Rashba terms is also discussed. We find the number of voltage pulses required to carry out either single qubit rotations or CNOT gates scales as the inverse of the strength of spin-orbit coupling. Work supported by NSF NIRT Grant No. DMR-0103034.

Stepanenko, D.; Bonesteel, N. E.

2004-03-01

72

K-band single-chip electron spin resonance detector  

NASA Astrophysics Data System (ADS)

We report on the design, fabrication, and characterization of an integrated detector for electron spin resonance spectroscopy operating at 27 GHz. The microsystem, consisting of an LC-oscillator and a frequency division module, is integrated onto a single silicon chip using a conventional complementary metal-oxide-semiconductor technology. The achieved room temperature spin sensitivity is about 108 spins/G Hz1/2, with a sensitive volume of about (100 ?m)3. Operation at 77 K is also demonstrated.

Anders, Jens; Angerhofer, Alexander; Boero, Giovanni

2012-04-01

73

Ultrafast optical entanglement control between two quantum dot spins  

NASA Astrophysics Data System (ADS)

A single electron spin in an InAs quantum dot is very attractive as a qubit since this system is potentially scalable and allows complete quantum control on an ultrafast timescale using optical pulses. While great progress has been achieved with single spin qubits, it is essential for quantum information applications to move toward entangled multi-qubit systems. Two-qubit systems have been studied in electrostatically-defined quantum dots, but their optical functionality remains unexplored. Here we demonstrate ultrafast optical control of two interacting qubits consisting of two electron spins in separate InAs dots. We initialize the system into a spin singlet state using a cw laser. We then manipulate the entangled state of the two spins with single qubit gates (acting only on one spin) by using pulses faster than the exchange interaction. This allows us to generate all four Bell states. Two-qubit gates are obtained either by the natural exchange precession or by using a longer laser pulse that induces a phase shift in the precession. The two-qubit exchange rate (30 GHz) here gives SWAP gate times of 16 ps, the fastest of any candidate for quantum information processing.

Carter, Sam; Kim, Danny; Greilich, Alex; Bracker, Allan; Gammon, Daniel

2011-03-01

74

Paramagnetic resonance and detection of a single electron spin  

NASA Astrophysics Data System (ADS)

Two methods of detection of a single electron spin, namely, optical detection (1993) and tunnelling spectroscopy (1998) are described. Both methods are based on the spin chemistry laws. Physical principles and prospects of application of these methods are considered. The bibliography includes 34 references.

Buchachenko, Anatolii L.; Dalidchik, Fedor I.; Kovalevskii, Sergei A.; Shub, Boris R.

2001-07-01

75

OSP Quantum Mechanics: Single Measurments of Spin States Worksheet  

NSDL National Science Digital Library

This set of tutorial worksheets, based on the OSP Quantum Mechanics Simulations, help students explore the measurement of quantum spins. The tutorial starts with an introduction of the physics of spins, and then presents the results of a single measurement on pure, mixed, and superposition states.

Christian, Wolfgang; Belloni, Mario

2010-01-11

76

Radio-Frequency Magnetometry Using a Single Electron Spin  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a simple and robust protocol for the detection of weak radio-frequency magnetic fields using a single electron spin in diamond. Our method relies on spin locking, where the Rabi frequency of the spin is adjusted to match the MHz signal frequency. In a proof-of-principle experiment we detect a 7.5 MHz magnetic probe field of ˜40nT amplitude with <10kHz spectral resolution. Rotating-frame magnetometry may provide a direct and sensitive route to high-resolution spectroscopy of nanoscale nuclear spin signals.

Loretz, M.; Rosskopf, T.; Degen, C. L.

2013-01-01

77

Controllable entanglement sudden birth of Heisenberg spins  

NASA Astrophysics Data System (ADS)

We investigate the Entanglement Sudden Birth (ESB) of two Heisenberg spins A and B. The third controller, qutrit C is introduced, which only has the Dzyaloshinskii-Moriya (DM) spin-orbit interaction with qubit B. We find that the DM interaction is necessary to induce the Entanglement Sudden Birth of the system qubits A and B, and the initial states of the system qubits and the qurit C are also important to control its Entanglement Sudden Birth.

Zheng, Qiang; Zhi, Qi-Jun; Zhang, Xiao-Ping; Ren, Zhong-Zhou

2011-02-01

78

Collins Fragmentation and the Single Transverse Spin Asymmetry  

SciTech Connect

We study the Collins mechanism for the single transverse spin asymmetry in the collinear factorization approach. The correspondent twist-three fragmentation function is identified. We show that the Collins function calculated in this approach is universal.We further examine its contribution to the single transverse spin asymmetry of semi-inclusive hadron production in deep inelastic scattering and demonstrate that the transverse momentum dependent and twist-three collinear approaches are consistent in the intermediate transverse momentum region where both apply.

Yuan, Feng; Zhou, Jian

2009-03-26

79

Single-spin asymmetries: The Trento conventions  

SciTech Connect

During the workshop 'Transversity: New Developments in Nucleon Spin Structure' (ECT, Trento, Italy, 14-18 June 2004), a series of recommendations was put forward by the participants concerning definitions and notations for describing effects of intrinsic transverse-momentum of partons in semi-inclusive deep inelastic scattering.

Bacchetta, Alessandro; D'Alesio, Umberto; Diehl, Markus; Miller, C. Andy [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); INFN, Sezione di Cagliari and Dipartimento di Fisica, Universita di Cagliari, I-09042 Monserrato (Italy); Deutsches Elektronen-Synchroton DESY, D-22603 Hamburg (Germany); TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada)

2004-12-01

80

Quantum Entanglement and Spin Control in Silicon Nanocrystal  

PubMed Central

Selective coherence control and electrically mediated exchange coupling of single electron spin between triplet and singlet states using numerically derived optimal control of proton pulses is demonstrated. We obtained spatial confinement below size of the Bohr radius for proton spin chain FWHM. Precise manipulation of individual spins and polarization of electron spin states are analyzed via proton induced emission and controlled population of energy shells in pure 29Si nanocrystal. Entangled quantum states of channeled proton trajectories are mapped in transverse and angular phase space of 29Si axial channel alignment in order to avoid transversal excitations. Proton density and proton energy as impact parameter functions are characterized in single particle density matrix via discretization of diagonal and nearest off-diagonal elements. We combined high field and low densities (1 MeV/92 nm) to create inseparable quantum state by superimposing the hyperpolarizationed proton spin chain with electron spin of 29Si. Quantum discretization of density of states (DOS) was performed by the Monte Carlo simulation method using numerical solutions of proton equations of motion. Distribution of gaussian coherent states is obtained by continuous modulation of individual spin phase and amplitude. Obtained results allow precise engineering and faithful mapping of spin states. This would provide the effective quantum key distribution (QKD) and transmission of quantum information over remote distances between quantum memory centers for scalable quantum communication network. Furthermore, obtained results give insights in application of channeled protons subatomic microscopy as a complete versatile scanning-probe system capable of both quantum engineering of charged particle states and characterization of quantum states below diffraction limit linear and in-depth resolution. PACS numbers: 03.65.Ud, 03.67.Bg, 61.85.+p, 67.30.hj

Berec, Vesna

2012-01-01

81

Tools for Studying Electron and Spin Transport in Single Molecules  

NASA Astrophysics Data System (ADS)

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

Ralph, Daniel C.

2005-03-01

82

Electrical manipulation of spin states in a single electrostatically gated transition-metal complex.  

PubMed

We demonstrate an electrically controlled high-spin (S = 5/2) to low-spin (S = 1/2) transition in a three-terminal device incorporating a single Mn(2+) ion coordinated by two terpyridine ligands. By adjusting the gate-voltage we reduce the terpyridine moiety and thereby strengthen the ligand-field on the Mn-atom. Adding a single electron thus stabilizes the low-spin configuration and the corresponding sequential tunnelling current is suppressed by spin-blockade. From low-temperature inelastic cotunneling spectroscopy, we infer the magnetic excitation spectrum of the molecule and uncover also a strongly gate-dependent singlet-triplet splitting on the low-spin side. The measured bias-spectroscopy is shown to be consistent with an exact diagonalization of the Mn-complex, and an interpretation of the data is given in terms of a simplified effective model. PMID:20000819

Osorio, Edgar A; Moth-Poulsen, Kasper; van der Zant, Herre S J; Paaske, Jens; Hedegård, Per; Flensberg, Karsten; Bendix, Jesper; Bjørnholm, Thomas

2010-01-01

83

Room-temperature entanglement between single defect spins in diamond  

NASA Astrophysics Data System (ADS)

Entanglement is the central yet fleeting phenomenon of quantum physics. Once being considered a peculiar counter-intuitive property of quantum theory, it has developed into the most central element of quantum technology. Consequently, there have been a number of experimental demonstrations of entanglement between photons, atoms, ions and solid-state systems such as spins or quantum dots, superconducting circuits and macroscopic diamond. Here we experimentally demonstrate entanglement between two engineered single solid-state spin quantum bits (qubits) at ambient conditions. Photon emission of defect pairs reveals ground-state spin correlation. Entanglement (fidelity=0.67+/-0.04) is proved by quantum state tomography. Moreover, the lifetime of electron spin entanglement is extended to milliseconds by entanglement swapping to nuclear spins. The experiments mark an important step towards a scalable room-temperature quantum device being of potential use in quantum information processing as well as metrology.

Dolde, F.; Jakobi, I.; Naydenov, B.; Zhao, N.; Pezzagna, S.; Trautmann, C.; Meijer, J.; Neumann, P.; Jelezko, F.; Wrachtrup, J.

2013-03-01

84

Robust spin crossover and memristance across a single molecule.  

PubMed

A nanoscale molecular switch can be used to store information in a single molecule. Although the switching process can be detected electrically in the form of a change in the molecule's conductance, adding spin functionality to molecular switches is a key concept for realizing molecular spintronic devices. Here we show that iron-based spin-crossover molecules can be individually and reproducibly switched between a combined high-spin, high-conduction state and a low-spin, low-conduction state, provided the individual molecule is decoupled from a metallic substrate by a thin insulating layer. These results represent a step to achieving combined spin and conduction switching functionality on the level of individual molecules. PMID:22760637

Miyamachi, Toshio; Gruber, Manuel; Davesne, Vincent; Bowen, Martin; Boukari, Samy; Joly, Loïc; Scheurer, Fabrice; Rogez, Guillaume; Yamada, Toyo Kazu; Ohresser, Philippe; Beaurepaire, Eric; Wulfhekel, Wulf

2012-07-03

85

Spectral control of spin qubits in diamond photonic structures  

NASA Astrophysics Data System (ADS)

Integrated photonic networks based on cavity-coupled spin impurities offer a promising platform for scalable quantum computing. A key ingredient for this technology involves heralding entanglement by interfering indistinguishable photons emitted by pairs of identical spin qubits. The nitrogen-vacancy (NV) center in diamond is an attractive candidate for such a spin-photon interface, as it exhibits long-lived electronic spin coherence, rapid spin manipulation and readout, and the coexistence of both robust cycling and spin-altering Lambda-type transitions. We discuss current research in our lab to control the spectral properties of single NV centers by dynamic Stark tuning [1] and cavity Purcell enhancement [2]. In particular, we report progress on fabricating photonic structures in ultra-pure diamond, where NV centers are likely to have favorable optical properties. [4pt] [1] V. M. Acosta et al., Dynamic stabilization of the optical resonances of single nitrogen-vacancy centers in diamond, arXiv:1112.5490v1 [quant-ph]. [0pt] [2] A. Faraon et al., Coupling of nitrogen-vacancy centers to photonic crystal cavities in monocrystalline diamond, Submitted.

Acosta, Victor; Santori, Charles; Faraon, Andrei; Huang, Zhihong; Beausoleil, Raymond

2012-06-01

86

High Dynamic Range Magnetometry with a Single Spin in Diamond  

NASA Astrophysics Data System (ADS)

Detection of the weak magnetic fields associated with nanometer sized volumes of spins could allow for non-invasive, element-specific probing of a variety of important physical and biological systems. Averaging out random noise which is the commonly used standard measurement strategy (SM) in most nano-sensors, will at best lead to a field variance that is inversely proportional to the total averaging time. Further, there exists a trade-off between the field sensitivity and the dynamic range in the SM. In this work, we demonstrate an alternative approach for accurate magnetic sensing, using novel phase estimation algorithms (PEA), implemented on a single electronic spin associated with the nitrogen-vacancy (NV) defect center in diamond. The field variance in our approach scales down faster than the SM. The trade-off between the field sensitivity and the dynamic range no longer exists in this approach. Our results show an improvement of ˜6.25 dB in the field sensitivity compared to the SM, over a large field sensing range ( ˜±0.3 mT). Besides their direct impact on applications in demonstrated nanoscale magnetic sensing and imaging, this may also open the way for application of other quantum feedback and control techniques to magnetometry.

Nusran, N. M.; Ummal Momeen, M.; Gurudev Dutt, M. V.

2012-02-01

87

Manipulating single electron spins and coherence in quantum dots  

Microsoft Academic Search

The non-destructive detection of a single electron spin in a quantum dot (QD) is demonstrated using a time- averaged magneto-optical Kerr rotation measurement ootnotetextJ. Berezovsky, M. H. Mikkelsen, O. Gywat, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 314, 1916 (2006).. This technique provides a means to directly probe the spin off- resonance, thus minimally disturbing the

David Awschalom

2008-01-01

88

Quantum Zeno phenomenon on a single solid-state spin  

NASA Astrophysics Data System (ADS)

The quantum Zeno effect, i.e., the inhibition of coherent quantum dynamics by measurement operations, is one of the most intriguing predictions of quantum mechanics. Here we experimentally demonstrate the quantum Zeno effect by inhibiting the microwave-driven coherent spin dynamics between two ground-state spin levels of a single nitrogen vacancy center in diamond. Our experiments are supported by a detailed analysis of the population dynamics via a semiclassical model.

Wolters, Janik; Strauß, Max; Schoenfeld, Rolf Simon; Benson, Oliver

2013-08-01

89

Observation of spin flips with a single trapped proton.  

PubMed

Radio-frequency induced spin transitions of one individual proton are observed. The spin quantum jumps are detected via the continuous Stern-Gerlach effect, which is used in an experiment with a single proton stored in a cryogenic Penning trap. This is an important milestone towards a direct high-precision measurement of the magnetic moment of the proton and a new test of the matter-antimatter symmetry in the baryon sector. PMID:21770638

Ulmer, S; Rodegheri, C C; Blaum, K; Kracke, H; Mooser, A; Quint, W; Walz, J

2011-06-20

90

Observation of Spin Flips with a Single Trapped Proton  

SciTech Connect

Radio-frequency induced spin transitions of one individual proton are observed. The spin quantum jumps are detected via the continuous Stern-Gerlach effect, which is used in an experiment with a single proton stored in a cryogenic Penning trap. This is an important milestone towards a direct high-precision measurement of the magnetic moment of the proton and a new test of the matter-antimatter symmetry in the baryon sector.

Ulmer, S. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Ruprecht Karls-Universitaet Heidelberg, D-69047 Heidelberg (Germany); Rodegheri, C. C. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Blaum, K. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Ruprecht Karls-Universitaet Heidelberg, D-69047 Heidelberg (Germany); Kracke, H.; Mooser, A.; Walz, J. [Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Helmholtz Institut Mainz, D-55099 Mainz (Germany); Quint, W. [Ruprecht Karls-Universitaet Heidelberg, D-69047 Heidelberg (Germany); GSI--Helmholtzzentrum fuer Schwerionenforschung, D-64291 Darmstadt (Germany)

2011-06-24

91

Resonance control of solitons of spin waves  

NASA Astrophysics Data System (ADS)

It has been shown that the effect of scattering on a resonance can be used to control spin-wave solitons using pumping by an external circularly polarized periodic field with a special modulation of the frequency. The conditions imposed on the pumping parameters at which this control is most efficient have been found.

Batalov, S. V.; Shagalov, A. G.

2013-10-01

92

Fluorescence detection of single molecule magnetic resonance for pentacene in p-terphenyl. The hyperfine interaction of a single triplet spin with a single 13C nuclear spin  

NASA Astrophysics Data System (ADS)

We report the observation of the broadening of a magnetic-resonance transition between triplet sublevels of a single pentacene molecule owing to the interaction of the triplet electron spin with a single 13C nuclear spin. Analysis of this broadening allows the assignment of particular features in the fluorescence—excitation spectrum to pentacene molecules containing 13C isotopes in specific positions.

Köhler, J.; Brouwer, A. C. J.; Groenen, E. J. J.; Schmidt, J.

1994-09-01

93

Spin-transfer torque in a single ferromagnet  

NASA Astrophysics Data System (ADS)

A spin polarized current, with sufficiently high current density, is able to switch a magnet or induce magnetization precession. This is the consequence of the ¡°spin-transfer torque¡+/- that originates from spin angular momentum transfer between conduction electrons and the magnetization. Previously most theories and experiments explore F/N/F trilayer and F/N multilayer structures, where F denotes a ferromagnet and N denotes a nonmagnetic metal. These structures have been generally presumed indispensable, since non-collinear magnetizations between a polarizing layer and a free layer are required to generate spin torques, and the GMR effect is essential in detecting magnetization variations. In this work, spin-transfer torque effects in a single ferromagnetic layer are demonstrated, using current injection through a point-contact at 4.2 K. Firstly, differential resistance peaks, generally regarded as signatures of spin-wave excitations, are observed in a single ferromagnetic layer in high magnetic fields [1]. The current values corresponding to the peak positions linearly depend on the external field in the range of 2 to 9 Tesla. Secondly, hysteretic current-induced switching is observed in a single ferromagnet in low magnetic fields. Both experiments can be interpreted by a simple model based on heterogeneous current distribution and domain wall scattering. Systematic variations between low field and high field regions have been investigated and the implications will be discussed. [1] Y. Ji, C. L. Chien and M. D. Stiles, Phys. Rev. Lett. 90, 106601 (2003)

Ji, Yi

2004-03-01

94

Gaussian approximation and single-spin measurement in magnetic resonance force microscopy with spin noise  

SciTech Connect

A promising technique for measuring single electron spins is magnetic resonance force microscopy (MRFM), in which a microcantilever with a permanent magnetic tip is resonantly driven by a single oscillating spin. The most effective experimental technique is the oscillating cantilever-driven adiabatic reversals (OSCAR) protocol, in which the signal takes the form of a frequency shift. If the quality factor of the cantilever is high enough, this signal will be amplified over time to the point where it can be detected by optical or other techniques. An important requirement, however, is that this measurement process occurs on a time scale that is short compared to any noise which disturbs the orientation of the measured spin. We describe a model of spin noise for the MRFM system and show how this noise is transformed to become time dependent in going to the usual rotating frame. We simplify the description of the cantilever-spin system by approximating the cantilever wave function as a Gaussian wave packet and show that the resulting approximation closely matches the full quantum behavior. We then examine the problem of detecting the signal for a cantilever with thermal noise and spin with spin noise, deriving a condition for this to be a useful measurement.

Raghunathan, Shesha; Brun, Todd A. [Center for Quantum Information Science and Technology, Communication Sciences Institute, Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089 (United States); Goan, Hsi-Sheng [Department of Physics and Center for Theoretical Sciences, National Taiwan University, Taipei 10617, Taiwan (China); Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

2010-11-15

95

Gaussian approximation and single-spin measurement in magnetic resonance force microscopy with spin noise  

NASA Astrophysics Data System (ADS)

A promising technique for measuring single electron spins is magnetic resonance force microscopy (MRFM), in which a microcantilever with a permanent magnetic tip is resonantly driven by a single oscillating spin. The most effective experimental technique is the oscillating cantilever-driven adiabatic reversals (OSCAR) protocol, in which the signal takes the form of a frequency shift. If the quality factor of the cantilever is high enough, this signal will be amplified over time to the point where it can be detected by optical or other techniques. An important requirement, however, is that this measurement process occurs on a time scale that is short compared to any noise which disturbs the orientation of the measured spin. We describe a model of spin noise for the MRFM system and show how this noise is transformed to become time dependent in going to the usual rotating frame. We simplify the description of the cantilever-spin system by approximating the cantilever wave function as a Gaussian wave packet and show that the resulting approximation closely matches the full quantum behavior. We then examine the problem of detecting the signal for a cantilever with thermal noise and spin with spin noise, deriving a condition for this to be a useful measurement.

Raghunathan, Shesha; Brun, Todd A.; Goan, Hsi-Sheng

2010-11-01

96

Thermoelectrically Controlled Spin-Switch  

Microsoft Academic Search

The search for novel spintronic devices brings about new ways to control switching in magnetic thin-films. In this work we experimentally demonstrate a device based on thermoelectrically controlled exchange coupling. The read out signal from a giant magnetoresistance element is controlled by exchange coupling through a weakly ferromagnetic Ni-Cu alloy. This exchange coupling is shown to vary strongly with changes

S. Andersson; V. Korenivski

2010-01-01

97

Single shot NMR on single, dark nuclear spins  

Microsoft Academic Search

The electron and nuclear spins associated with the nitrogen-vacancy (NV)\\u000acenter in diamond are supposed to be building blocks for quantum computing\\u000adevices and nanometer scale magnetometry operating under ambient conditions.\\u000aFor every such building block precise knowledge of the involved quantum states\\u000ais crucial. Especially for solid state systems the corresponding hilbert space\\u000acan be large. Here, we experimentally

G. Waldherr; J. Beck; M. Steiner; P. Neumann; A. Gali; F. Jelezko; J. Wrachtrup

2010-01-01

98

Magnetic resonance of a single molecular spin  

NASA Astrophysics Data System (ADS)

THE introduction of optical detection methods for observing magnetic resonance transitions in metastable paramagnetic states1-4 has contributed enormously to our understanding of the properties of photoexcited molecules in condensed phases. In such experiments the luminescence intensity is recorded as a function of the frequency of an applied microwave field. At resonance with transitions between sublevels of a metastable paramagnetic state, the lifetime of the metastable state is altered and a consequent change in the luminescence intensity is observed. Here we report the observation of such optically detected magnetic resonance transitions for the triplet state of a single pentacene molecule embedded in a p-terphenyl host crystal. This result has been obtained by combining the conventional optical detection technique for observing magnetic resonance transitions1-4 with the new single-molecule optical detection methods developed recently5,6. This observation opens the way for magnetic resonance studies in condensed phases with single-molecule sensitivity.

Köhler, J.; Disselhorst, J. A. J. M.; Donckers, M. C. J. M.; Groenen, E. J. J.; Schmidt, J.; Moerner, W. E.

1993-05-01

99

Single-Spin Asymmetries and Transversity in QCD  

SciTech Connect

Initial- and final-state interactions from gluon exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, as well as nuclear shadowing and antishadowing-leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. The physics of such processes thus require the understanding of QCD at the amplitude level; in particular, the physics of spin requires an understanding of the phase structure of final-state and initial-state interactions, as well as the structure of the basic wavefunctions of hadrons themselves. I also discuss transversity in exclusive channels, including how one can use single-spin asymmetries to determine the relative phases of the timelike baryon form factors, as well as the anomalous physics of the normal-normal spin-spin correlation observed in large-angle proton-proton elastic scattering. As an illustration of the utility of light-front wavefunctions, the transversity distribution of a single electron is computed, as defined from its two-particle QED quantum fluctuations.

Brodsky, S.J.; /SLAC

2005-12-14

100

Quantum Interference Control of Ballistic Pure Spin Currents in Semiconductors.*  

NASA Astrophysics Data System (ADS)

One of the main obstacles to the development of spintronic devices is the difficulty in injecting and controlling spin currents in semiconductors, especially in the absence of charge currents. Our approach has been to exploit nonlinear optical processes and quantum interference effects to control electron properties in common semiconductors such as GaAs. We have typically employed 150 fs pulses at 1550 nm and 775 nm and used interference between single photon and two-photon absorption pathways to generate and control spin or electrical currents through the relative phase of the beams. Maximum electrical currents are generated when both beams are co-linearly polarized along the [111] direction (bond direction between Ga and As). However, with orthogonally, linearly polarized beams incident collinearly on any surface of GaAs it is possible to generate ballistic spin currents along the polarization direction of the 1550 nm beam [1]. These currents are generated in the absence of electrical currents. With other polarization combinations and crystal orientations it is possible to generate spin currents with or without electrical currents, and electrical currents with or without spin currents. In another configuration the 1550 and 775 nm pulses are incident non-collinearly on GaAs producing pure spin current gratings in bulk [100]-oriented GaAs; the relative phase between the beams and therefore the amplitude of the spin current is modulated periodically across the sample. Through the generation of various types of spin, electrical and spin/electrical current gratings we are able to observe the ballistic as well as diffusive transport characteristics of these currents. [1] M.J. Stevens, A.L. Smirl, R. Bhat, A. Najmaie, J.Sipe and H.M. van Driel, Quantum Inteference Control of Ballistic Pure Spin Currents in Semiconductors, Phys. Rev. Lett. 90, 136603-1(2003). * Work performed in collaboration with J. Sipe, R. Bhat and Y. Kerachian (University of Toronto) and A. Smirl, M. Stevens (University of Iowa) and funded by NSERC, Photonics Research Ontario and the DARPA Spintronics Program.

van Driel, Henry

2004-03-01

101

Matrix Formalism for Spin Dynamics Near a Single Depolarization Resonance  

SciTech Connect

A matrix formalism is developed to describe the spin dynamics in a synchrotron near a single depolarization resonance as the particle energy (and therefore its spin precession frequency) is varied in a prescribed pattern as a function of time such as during acceleration. This formalism is first applied to the case of crossing the resonance with a constant crossing speed and a finite total step size, and then applied also to other more involved cases when the single resonance is crossed repeatedly in a prescribed manner consisting of linear ramping segments or sudden jumps. How repeated crossings produce an interference behavior is discussed using the results obtained. For a polarized beam with finite energy spread, a spin echo experiment is suggested to explore this interference effect.

Chao, Alexander W.; /SLAC

2005-10-26

102

Control of magnetic fluctuations by spin current.  

PubMed

We use microfocus Brillouin light scattering spectroscopy to study the interaction of spin current with magnetic fluctuations in a Permalloy microdisk located on top of a Pt strip carrying an electric current. We show that the fluctuations can be efficiently suppressed or enhanced by different directions of the electric current. Additionally, we find that the effect of spin current on magnetic fluctuations is strongly influenced by nonlinear magnon-magnon interactions. The observed phenomena can be used for controllable reduction of thermal noise in spintronic nanodevices. PMID:21981525

Demidov, V E; Urazhdin, S; Edwards, E R J; Stiles, M D; McMichael, R D; Demokritov, S O

2011-09-02

103

Single-Atom Spin-Flip Spectroscopy  

NASA Astrophysics Data System (ADS)

The energy levels of a magnetic atom split in an applied magnetic field. We recently built an STM with a base temperature of 0.6K and a maximum magnetic field of 7T. These operating conditions allow the direct measurement of the Zeeman energy with inelastic tunneling spectroscopy [1]. We found that the Mn atoms have to be removed from the metal conduction electrons to suppress strong interactions such as the Kondo effect; we use Al2O3 grown on NiAl (110). The tell-tale sign of a vibrational mode in inelastic spectroscopy is the predictable frequency shift with mass. In spin-flip spectroscopy we can continuously tune the Zeeman energy with the applied magnetic field. We observe that the measured Zeeman energy is proportional to the magnetic field which yields a local measure of the 'g-value'. We find g- values in the vicinity of g=2, however the exact value depends on the local environment. When a Mn atom sits near the edge of the oxide film we observe strong coupling with the conduction electrons of the substrate resulting in a Kondo effect with Kondo temperatures of a few Kelvin. In contrast to previous STM work we do not observe the Kondo resonance as a Fano line shape. The logarithmic temperature dependence of the Kondo resonance as well as its splitting in magnetic field corroborates the interpretation as a Kondo effect. [1] A.J. Heinrich, J.A. Gupta, C.P. Lutz, D.M. Eigler, Science 306, 466 (2004).

Heinrich, Andreas

2005-03-01

104

Detection of a single electron spin  

Microsoft Academic Search

\\u000a The past decade has been characterised by the unpredicted blossoming of ultra high spectrally and spatially resolving microscopic\\u000a and spectroscopic techniques. Well known examples of these are scanning tunneling microscopy and high resolution laser spectroscopy.\\u000a The ultimate goal in resolution and sensitivity is the detection of single atoms or molecules. This has been achieved by both\\u000a techniques. Atomic resolution in

J. Wrachtrup; C. von Borczyskowski; M. Vogel; A. Gruber; J. Bernard; R. Brown; M. Orrit

105

Using nanoscale transistors to measure single donor spins in semiconductors  

NASA Astrophysics Data System (ADS)

We propose a technique for measuring the state of a single donor electron spin using a field-effect transistor induced two-dimensional electron gas and electrically detected magnetic resonance techniques. The scheme is facilitated by hyperfine coupling to the donor nucleus. We analyze the potential sensitivity and outline experimental requirements. Our measurement provides a single-shot, projective, and quantum non-demolition measurement of an electron-encoded qubit state.

Sarovar, M.; Young, K. C.; Schenkel, T.; Whaley, K. B.

2009-04-01

106

Landau-Zener-Stückelberg Interferometry of a Single Electronic Spin in a Noisy Environment  

NASA Astrophysics Data System (ADS)

We demonstrate quantum coherent control of single electronic spins in a nitron-vacancy center in diamond by exploiting and implementing the general concept of Landau-Zener-Stückelberg interferometry at room temperature. The interferometry manipulates an effective two-level system of electronic spins which are coupled to the nearby N14 nuclear spin in the nitron-vacancy center as well as the nuclear spin bath in the diamond. With a microwave field to control the energy gap between the two levels and an AC field as the time-dependent driving field in Landau-Zener-Stückelberg interferometry, the interference pattern can be generated and controlled by controlling a number of parameters in the fields, corresponding to coherent control of the state of the electronic spins. In particular, the interference pattern is observed oscillating as a function of the frequency of the microwave field. Decays in the visibility of the interference pattern are also observed and well explained by numerical simulation which takes into account the thermal fluctuations arising from the nuclear bath. Therefore, our work also demonstrates that Landau-Zener-Stückelberg interferometry can be used for probing decoherence processes of electronic spins.

Huang, Pu; Zhou, Jingwei; Fang, Fang; Kong, Xi; Xu, Xiangkun; Ju, Chenyong; Du, Jiangfeng

2011-08-01

107

Single-spin addressing in an atomic Mott insulator  

Microsoft Academic Search

Ultracold atoms in optical lattices provide a versatile tool with which to investigate fundamental properties of quantum many-body systems. In particular, the high degree of control of experimental parameters has allowed the study of many interesting phenomena, such as quantum phase transitions and quantum spin dynamics. Here we demonstrate how such control can be implemented at the most fundamental level

Christof Weitenberg; Manuel Endres; Jacob F. Sherson; Marc Cheneau; Peter Schauß; Takeshi Fukuhara; Immanuel Bloch; Stefan Kuhr

2011-01-01

108

Control of spin waves in a thin film ferromagnetic insulator through interfacial spin scattering.  

PubMed

Control of spin waves in a ferrite thin film via interfacial spin scattering was demonstrated. The experiments used a 4.6???m-thick yttrium iron garnet (YIG) film strip with a 20-nm thick Pt capping layer. A dc current pulse was applied to the Pt layer and produced a spin current across the Pt thickness. As the spin current scatters off the YIG surface, it can either amplify or attenuate spin-wave pulses that travel in the YIG strip, depending on the current or field configuration. The spin scattering also affects the saturation behavior of high-power spin waves. PMID:22107222

Wang, Zihui; Sun, Yiyan; Wu, Mingzhong; Tiberkevich, Vasil; Slavin, Andrei

2011-09-29

109

Electron spin lifetime of a single antimony donor in silicon  

NASA Astrophysics Data System (ADS)

We present measurements of the electron spin lifetime (T1) of a single Sb donor in Si. For a magnetic field (B) oriented along the [100] Si crystal direction and low temperature (T) such that kT<spin relaxation due to g-factor dependence on crystal strain. The magnitude of T1 is within a factor of two of theoretical estimates and is in close agreement with values obtained for bulk donor ensembles.

Tracy, L. A.; Lu, T. M.; Bishop, N. C.; Ten Eyck, G. A.; Pluym, T.; Wendt, J. R.; Lilly, M. P.; Carroll, M. S.

2013-09-01

110

Electron Spin Resonance on a Single Carbon Nanotube  

NASA Astrophysics Data System (ADS)

Little is known about the spin properties of carbon nanotubes (CNT) such as their spin-coherence time. We are in process of directly determining the electron spin coherence time of a single walled carbon nanotube by measuring the microwave reflection (S11) off a single CNT in a magnetic field at 0.3K. We expect to observe resonant microwave absorption at the Zeeman frequency, which is 27GHz/Tesla. The linewidth of these absorption peaks will provide a direct measurement of the spin-coherence time of the CNT electrons which is currently lacking in the research literature. Absorption peaks associated with the Coulomb energy, the quantum energy level separation, the energy mismatch between bands are also expected to be measured. A homodyne reflectometer has been constructed in our lab that can resolve S11 changes of 1 part in 10^5. We expect that our technique of measuring the microwave reflection off of a single nanostructure will be a power spectroscopic tool to investigate a wide variety of quantum excitations in nanostructures, an important prerequisite for powerful quantum information processing based on integrated nanosystems.

Rutherglen, Christopher; Burke, Peter

2005-03-01

111

Controllable effects of quantum fluctuations on spin free-induction decay at room temperature  

PubMed Central

Fluctuations of local fields cause decoherence of quantum objects. Usually at high temperatures, thermal noises are much stronger than quantum fluctuations unless the thermal effects are suppressed by certain techniques such as spin echo. Here we report the discovery of strong quantum-fluctuation effects of nuclear spin baths on free-induction decay of single electron spins in solids at room temperature. We find that the competition between the quantum and thermal fluctuations is controllable by an external magnetic field. These findings are based on Ramsey interference measurement of single nitrogen-vacancy center spins in diamond and numerical simulation of the decoherence, which are in excellent agreement.

Liu, Gang-Qin; Pan, Xin-Yu; Jiang, Zhan-Feng; Zhao, Nan; Liu, Ren-Bao

2012-01-01

112

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

NASA Astrophysics Data System (ADS)

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

Blundell, Stephen

2005-03-01

113

Coherent spin control by electromagnetic vacuum fluctuations  

SciTech Connect

In coherent control, electromagnetic vacuum fluctuations usually cause coherence loss through irreversible spontaneous emission. However, since the dissipation via emission is essentially due to correlation of the fluctuations, when emission ends in a superposition of multiple final states, correlation between different pathways may build up if the 'which way' information is not fully resolved (i.e., the emission spectrum is broader than the transition energy range). Such correlation can be exploited for spin-flip control in a {Lambda}-type three-level system, which manifests itself as an all-optical spin echo in nonlinear optics with two orders of optical fields saved as compared with stimulated Raman processes. This finding represents a class of optical nonlinearity induced by electromagnetic vacuum fluctuations.

Wang Jing [Department of Physics, Chinese University of Hong Kong, Shatin, N.T. (Hong Kong); Department of Physics, Tsinghua University, Beijing 100084 (China); Liu Renbao [Department of Physics, Chinese University of Hong Kong, Shatin, N.T. (Hong Kong); Zhu Bangfen [Department of Physics, Tsinghua University, Beijing 100084 (China); Institute of Advanced Study, Tsinghua University, Beijing 100084 (China); Sham, L. J. [Department of Physics, University of California-San Diego, La Jolla, California 92093-0319 (United States); Steel, D. G. [H. M. Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2011-05-15

114

Standing spin waves as a basis for the control of terahertz spin dynamics: time dependent density functional theory study.  

PubMed

We report on the linear response density functional study of the magnetization dynamics in Co(100) film driven by a nonuniform magnetic field. At resonant frequencies in the terahertz range, the magnetic field excites standing spin waves of the system and the induced magnetization penetrates the whole volume of the film. The pattern of magnetization precession is strongly influenced by the spin-flip excitations of single electrons which lead to the Landau damping of the spin-wave modes. Our results pave the way for the precise control of terahertz magnetization dynamics in itinerant magnets. PMID:20868192

Buczek, Pawe?; Ernst, Arthur; Sandratskii, Leonid M

2010-08-27

115

Coherent Population Trapping of Single Spins in Diamond under Optical Excitation  

NASA Astrophysics Data System (ADS)

Coherent population trapping is demonstrated in single nitrogen-vacancy centers in diamond under optical excitation. For sufficient excitation power, the fluorescence intensity drops almost to the background level when the laser modulation frequency matches the 2.88 GHz splitting of the ground states. The results are well described theoretically by a four-level model, allowing the relative transition strengths to be determined for individual centers. The results show that all-optical control of single spins is possible in diamond.

Santori, Charles; Tamarat, Philippe; Neumann, Philipp; Wrachtrup, Jörg; Fattal, David; Beausoleil, Raymond G.; Rabeau, James; Olivero, Paolo; Greentree, Andrew D.; Prawer, Steven; Jelezko, Fedor; Hemmer, Philip

2006-12-01

116

Coherently Controlling Spin Squeezing in Optomechanical System  

NASA Astrophysics Data System (ADS)

We investigate spin squeezing in optomechanical system. We first derive the mean spin direction, the optimally squeezed angle and then calculate the spin squeezing parameter, which is independent of the frequency of the cavity field. The lager coupling strength more rapidly generates spin squeezed state, but the corresponding spin squeezed state maintains shorter time interval.

Ouyang, Xiao-Fang

2013-10-01

117

Towards force detected single electron spin resonance at room temperature  

NASA Astrophysics Data System (ADS)

Electrically detected magnetic resonance (EDMR) spectroscopy has shown that electron tunneling at or within silicon dioxide layers is strongly dependent on spin-selection rules [1]. Also demonstrated is the detection of single electron tunneling events by electrostatic force with sub-nanometer spatial resolution [2,3]. Here we propose to combine force detected single electron tunneling microscopy with EDMR to demonstrate a new kind of single spin force microscope. This approach has much better sensitivity than magnetic force based single spin microscopes [4], since electrostatic forces are much larger than corresponding magnetic forces. In this method, a paramagnetic state in an oxidized AFM probe tip is brought within tunneling range of a paramagnetic state in an oxide surface [5]. Under appropriate energy conditions, one of the unpaired electrons can randomly tunnel between the two states causing a random telegraph signal (RTS) to appear on the AFM cantilever frequency. Simulations predict that if magnetic resonance conditions are achieved, a measurable change in the RTS signal is detectable at room temperature. The theory and a quantitative simulation of this atomic scale spin resonance measurement will be presented, along with experimentally observed random telegraph signals.[4pt] [1] D. R. McCamey, et al., Phys. Rev. B, 78, 045302 (2008). [2] L. J. Klein and C.C. Williams, Appl. Phys. Lett. 79, 1828 (2001). [3] E. Bussmann and D.J. Kim, and C.C. Williams, Appl. Phys. Lett. 85, 2538 (2004). [4] D. Rugar et al., Nature 430, 329 (2004). [5] J.P. Johnson, Ph.D. Thesis, Dept. of Physics, University of Utah (2010).

Williams, C. C.; Payne, A.; Ambal, K.; Boehme, C.

2013-03-01

118

Optimal spin-state transition in singly occupied quantum dots network  

NASA Astrophysics Data System (ADS)

We present a general model to study the spin-state transition in a network of singly occupied lateral quantum dots. The perturbative expansion of the extended Hubbard model is used to describe the dynamics of confined electrons as an effective spin Hamiltonian in the strong correlation regime. To optimize the transition, we apply the gradient ascent pulse engineering algorithm to control the exchange couplings constrained to the manifolds evaluated by Heitler-London approximation. The method is applicable to an arbitrary number of quantum dots in any arrangement. Results of the method applied to the case of triple quantum dot are presented for linear and triangular topologies.

Yaghouti, M.; Sharifi, M. J.; Kazemi, A.

2013-01-01

119

Curvature-induced spin-orbit coupling and spin relaxation in a chmically-clean single-layer graphene  

NASA Astrophysics Data System (ADS)

Based on the second-order perturbation theory, we show that curvature induced by corrugations or periodic ripples in single-layer graphenes generates two types of effective spin-orbit coupling. In addition to the spin-orbit coupling reported previously that couples with sublattice pseudospin and corresponds to the Rashba-type spin-orbit coupling, there is an additional spin-orbit coupling that does not couple with the pseudospin. The additional spin-orbit coupling depends on the direction of principal curvature, which is similar with the curvature-induced spin-orbit coupling of carbon nanotubes that depends on the chiral angle. However, the spin-orbit coupling of single-layer graphenes can not be obtained from the trivial extension of the spin-orbit coupling of carbon nanotubes owing to their distinct topological structure. Via the numerical calcualtion, we show that both types of the curvature-induced spin-orbit coupling make the same order of contribution to spin relaxation in chemically-clean single-layer graphene with nanoscale corrugation. The spin relaxation dependence on the corrugation roughness is also investigated.

Jeong, Jae-Seung; Shin, Jeongkyu; Lee, Hyun-Woo

2012-02-01

120

High-fidelity readout and control of a nuclear spin qubit in silicon.  

PubMed

Detection of nuclear spin precession is critical for a wide range of scientific techniques that have applications in diverse fields including analytical chemistry, materials science, medicine and biology. Fundamentally, it is possible because of the extreme isolation of nuclear spins from their environment. This isolation also makes single nuclear spins desirable for quantum-information processing, as shown by pioneering studies on nitrogen-vacancy centres in diamond. The nuclear spin of a (31)P donor in silicon is very promising as a quantum bit: bulk measurements indicate that it has excellent coherence times and silicon is the dominant material in the microelectronics industry. Here we demonstrate electrical detection and coherent manipulation of a single (31)P nuclear spin qubit with sufficiently high fidelities for fault-tolerant quantum computing. By integrating single-shot readout of the electron spin with on-chip electron spin resonance, we demonstrate quantum non-demolition and electrical single-shot readout of the nuclear spin with a readout fidelity higher than 99.8 percent-the highest so far reported for any solid-state qubit. The single nuclear spin is then operated as a qubit by applying coherent radio-frequency pulses. For an ionized (31)P donor, we find a nuclear spin coherence time of 60 milliseconds and a one-qubit gate control fidelity exceeding 98 percent. These results demonstrate that the dominant technology of modern electronics can be adapted to host a complete electrical measurement and control platform for nuclear-spin-based quantum-information processing. PMID:23598342

Pla, Jarryd J; Tan, Kuan Y; Dehollain, Juan P; Lim, Wee H; Morton, John J L; Zwanenburg, Floris A; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

2013-04-18

121

Injection, detection and gate voltage control of spins in the spin field effect transistor  

NASA Astrophysics Data System (ADS)

We demonstrate electrical spin injection and gate voltage control of spin precession in an InAs quantum well channel that has Permalloy injector and detector, and is covered by a gate oxide and a Au gate electrode. The electrical injection and detection of ballistic spin-polarized electrons are characterized using conventional lateral spin valve techniques. An external magnetic field is used to overcome the shape anisotropy of the magnetizations of injector and detector. We can then inject spins that have both spin orientation and velocity along the axis of the channel, and we observe an oscillatory channel conductance as a function of monotonically increasing gate voltage. This conductance oscillation is the hallmark of a spin field effect transistor. After presenting the basic results, we discuss issues associated with (1) the Hanle effect in a two-dimensional electron gas with high spin-orbit interaction and (2) the observation of a conductance oscillation in a multimode (two-dimensional) channel.

Chang, Joonyeon; Cheol Koo, Hyun; Eom, Jonghwa; Hee Han, Suk; Johnson, Mark

2011-05-01

122

Active control of vortex breakdown by a spinning wave generator  

Microsoft Academic Search

The results of an experimental study on an active control of the vortex breakdown are presented. Four different modes of spinning disturbances are imposed on the vortex breakdown by a spinning wave generator, which is a device to produce, at a specified frequency, a sinusoidal wave disturbance spinning in the circumferential direction. It is shown that the m = 0

M. Kikuchi; K. Hirano; T. Yuge; M. Kurosaka

1993-01-01

123

Curvature-induced spin-orbit coupling and spin relaxation in a chemically clean single-layer graphene  

NASA Astrophysics Data System (ADS)

The study of spin-related phenomena in materials requires knowledge of the precise form of effective spin-orbit coupling for conducting carriers in solid-state systems. We demonstrate theoretically that curvature induced by corrugations or periodic ripples in single-layer graphenes generates two types of effective spin-orbit couplings. In addition to the spin-orbit coupling reported previously that couples with sublattice pseudospin and corresponds to the Rashba-type spin-orbit coupling in a corrugated single-layer graphene, there is an additional spin-orbit coupling that does not couple with the pseudospin, which can not be obtained from the extension of the curvature-induced spin-orbit coupling of carbon nanotubes. Via numerical calculation we show that both types of the curvature-induced spin-orbit coupling make the same order of contribution to spin relaxation in chemically clean single-layer graphene with nanoscale corrugation. The spin-relaxation dependence on the corrugation roughness is also studied.

Jeong, Jae-Seung; Shin, Jeongkyu; Lee, Hyun-Woo

2011-11-01

124

Nuclear spin selective laser control of rotational and torsional dynamics.  

PubMed

We explore the possibility of controlling rotational-torsional dynamics of non-rigid molecules with strong, non-resonant laser pulses and demonstrate that transient, laser-induced torsional alignment depends on the nuclear spin of the molecule. Consequently, nuclear spin isomers can be manipulated selectively by a sequence of time-delayed laser pulses. We show that two pulses with different polarization directions can induce either overall rotation or internal torsion, depending on the nuclear spin. Nuclear spin selective control of the angular momentum distribution may open new ways to separate and explore nuclear spin isomers of polyatomic molecules. PMID:22380044

Floss, J; Grohmann, T; Leibscher, M; Seideman, T

2012-02-28

125

Mapping Spin Coherence of a Single Rare-Earth Ion in a Crystal onto a Single Photon Polarization State  

NASA Astrophysics Data System (ADS)

We report on optical detection of a single photostable Ce3+ ion in an yttrium aluminium garnet (YAG) crystal and on its magneto-optical properties at room temperature. The spin quantum state of the emitting level of a single cerium ion in YAG can be initialized by a circularly polarized laser pulse. Coherent precession of the electron spin is read out by observing temporal behavior of circularly polarized fluorescence of the ion. This implies direct mapping of the spin quantum state of Ce3+ ion onto the polarization state of the emitted photon and represents the quantum interface between a single spin and a single photon.

Kolesov, Roman; Xia, Kangwei; Reuter, Rolf; Jamali, Mohammad; Stöhr, Rainer; Inal, Tugrul; Siyushev, Petr; Wrachtrup, Jörg

2013-09-01

126

Mapping Spin Coherence of a Single Rare-Earth Ion in a Crystal onto a Single Photon Polarization State.  

PubMed

We report on optical detection of a single photostable Ce^{3+} ion in an yttrium aluminium garnet (YAG) crystal and on its magneto-optical properties at room temperature. The spin quantum state of the emitting level of a single cerium ion in YAG can be initialized by a circularly polarized laser pulse. Coherent precession of the electron spin is read out by observing temporal behavior of circularly polarized fluorescence of the ion. This implies direct mapping of the spin quantum state of Ce^{3+} ion onto the polarization state of the emitted photon and represents the quantum interface between a single spin and a single photon. PMID:24093236

Kolesov, Roman; Xia, Kangwei; Reuter, Rolf; Jamali, Mohammad; Stöhr, Rainer; Inal, Tugrul; Siyushev, Petr; Wrachtrup, Jörg

2013-09-20

127

Dynamics revealed by correlations of time-distributed weak measurements of a single spin  

NASA Astrophysics Data System (ADS)

We show that the correlations in stochastic outputs of time-distributed weak measurements can be used to study the dynamics of an individual quantum object, with a proof-of-principle setup based on small Faraday rotation caused by a single spin in a quantum dot. In particular, the third-order correlation can reveal the 'true' spin decoherence, which would otherwise be concealed by the inhomogeneous broadening effect in the second-order correlations. The viability of such approaches lies in the fact that (i) in weak measurement the state collapse that would disturb the system dynamics occurs at a very low probability and (ii) a shot of measurement projecting the quantum object to a known basis state serves as a starter or stopper of the evolution without pumping or coherently controlling the system as otherwise required in conventional spin echo.

Liu, R.-B.; Fung, S.-H.; Fung, H.-K.; Korotkov, A. N.; Sham, L. J.

2010-01-01

128

Optical control and detection of spin coherence in semiconductor nanostructures  

NASA Astrophysics Data System (ADS)

Understanding the coherent dynamics of electron spins in quantum dots (QDs) is important for potential applications in solid-state, spin-based electronics and quantum information processing. Here, results are presented focusing on optical initialization, manipulation, and readout of spin coherence in various semiconductor nanostructures. Layered semiconductor nanocrystals are fabricated containing a spherical "quantum shell" in which electrons and holes are confined. As in a planar quantum well, the quantized energy levels and g-factors are found to depend on the shell thickness. Taking this idea a step further, nanocrystals with a concentric, tunnel-coupled core and shell are investigated. Based on the energy and g-factor dependences in these structures, spins can be selectively initialized into, and read out from, states in the core and shell. In contrast to these two ensemble measurements, we next turn to measurements of single electron spins in single QDs. First, we demonstrate the detection of a single electron spin in a QD using a nondestructive, continuously averaged magneto-optical Kerr rotation (KR) measurement. This continuous single QD KR technique is then extended into the time domain using pulsed pump and probe lasers, allowing the observation of the coherent evolution of an electron spin state with nanosecond temporal resolution. By sweeping the delay between the pump and probe, the dynamics of the spin in the QD are mapped out in time, providing a direct measurement of the electron g-factor and spin lifetime. Finally, this time-resolved single spin measurement is used to observe ultrafast coherent manipulation of the spin in the QD using an off-resonant optical pulse. Via the optical Stark effect, this optical pulse coherently rotates the spin state through angles up to pi radians, on picosecond timescales.

Berezovsky, Jesse A.

129

Spin-coated polyethylene films probed by single molecules.  

PubMed

We have studied ultrathin spin-coated high-density polyethylene films by means of single-molecule spectroscopy and microscopy at 1.8 K. The films have been doped with 2.3,8.9-dibenzanthanthrene (DBATT) molecules, which function as local reporters of their immediate environment. The orientation distributions of single DBATT probe molecules in 100-200 nm thin films of high-density polyethylene differ markedly from those in low-density films. We have found a preferential orientation of dopant molecules along two well-defined, mutually perpendicular directions. These directions are preserved over at least a 2 mm distance. The strong orientation preference of the probe molecules requires the presence of abundant lateral crystal faces and is therefore not consistent with a spherulitic morphology. Instead, a "shish-kebab" crystal structure is invoked to explain our results. PMID:17064117

Wirtz, A C; Hofmann, C; Groenen, E J J

2006-11-01

130

Controlling Spin Squeezing in One-Axis Twisting with Decay  

NASA Astrophysics Data System (ADS)

We investigate how an appropriate choice of the external field allows one to control spin squeezing of a collective spin governed by one-axis twisting with decay. By adopting frozen-spin approximation, we succussed in obtaining analytical expressions of the optimally squeezing angle and the spin squeezing parameter. The squeezing parameter is a periodical function, the period depends on the decay rate and the strength of the linear interaction, while the degree of squeezing is only determined by the external field, the smaller external field induces the stronger spin squeezing.

Yi, Xiao-Jie; Huang, Guo-Qiang; Wang, Jian-Min

2013-10-01

131

Electronic measurement and control of spin transport in silicon  

NASA Astrophysics Data System (ADS)

The spin lifetime and diffusion length of electrons are transport parameters that define the scale of coherence in spintronic devices and circuits. As these parameters are many orders of magnitude larger in semiconductors than in metals, semiconductors could be the most suitable for spintronics. So far, spin transport has only been measured in direct-bandgap semiconductors or in combination with magnetic semiconductors, excluding a wide range of non-magnetic semiconductors with indirect bandgaps. Most notable in this group is silicon, Si, which (in addition to its market entrenchment in electronics) has long been predicted a superior semiconductor for spintronics with enhanced lifetime and transport length due to low spin-orbit scattering and lattice inversion symmetry. Despite this promise, a demonstration of coherent spin transport in Si has remained elusive, because most experiments focused on magnetoresistive devices; these methods fail because of a fundamental impedance mismatch between ferromagnetic metal and semiconductor, and measurements are obscured by other magnetoelectronic effects. Here we demonstrate conduction-band spin transport across 10?m undoped Si in a device that operates by spin-dependent ballistic hot-electron filtering through ferromagnetic thin films for both spin injection and spin detection. As it is not based on magnetoresistance, the hot-electron spin injection and spin detection avoids impedance mismatch issues and prevents interference from parasitic effects. The clean collector current shows independent magnetic and electrical control of spin precession, and thus confirms spin coherent drift in the conduction band of silicon.

Appelbaum, Ian; Huang, Biqin; Monsma, Douwe J.

2007-05-01

132

Time-optimal control of spin 1\\/2 particles in the presence of radiation damping and relaxation  

Microsoft Academic Search

We consider the time-optimal control of an ensemble of uncoupled spin 1\\/2 particles in the presence of relaxation and radiation damping effects, whose dynamics is governed by nonlinear equations generalizing the standard linear Bloch equations. For a single spin, the optimal control strategy can be fully characterized analytically. However, in order to take into account the inhomogeneity of the static

Y. Zhang; M. Lapert; D. Sugny; M. Braun; S. J. Glaser

2011-01-01

133

Single-Particle Coherence and Spin Squeezing in Four-Qubit Phase State  

NASA Astrophysics Data System (ADS)

We investigate single-particle coherence and spin squeezing in four-qubit phase state governed by an one-axis twisting Hamiltonian. In particular, we are interesting in the dependence of single-particle coherence and spin squeezing on the nonlinear interaction. It is shown that single-particle coherence and spin squeezing parameter only depend on the nonlinear interaction and they are periodic function of nonlinear interaction.

Liu, He-Sheng

2013-11-01

134

Optical Detection of Single-Electron Spin Resonance in a Quantum Dot  

Microsoft Academic Search

We demonstrate optically detected spin resonance of a single electron confined to a self-assembled quantum dot. The dot is rendered dark by resonant optical pumping of the spin with a laser. Contrast is restored by applying a radio frequency (rf) magnetic field at the spin resonance. The scheme is sensitive even to rf fields of just a few muT. In

Martin Kroner; Kathrina M. Weiss; Benjamin Biedermann; Stefan Seidl; Stephan Manus; Alexander W. Holleitner; Antonio Badolato; Pierre M. Petroff; Brian D. Gerardot; Richard J. Warburton; Khaled Karrai

2008-01-01

135

Global fitting of single spin asymmetry: An attempt  

NASA Astrophysics Data System (ADS)

We present an attempt of global analysis of semi-inclusive deep inelastic scattering ?p???'?X data on single spin asymmetries and data on left-right asymmetry AN in p?p??X in order to simultaneously extract information on the Sivers function and the twist-three quark-gluon Efremov-Teryaev-Qiu-Sterman function. We explore different possibilities such as the node of the Sivers function in x or k? in order to explain “sign mismatch” between these functions. We show that ?± semi-inclusive deep inelastic scattering data and ?0 STAR data can be well described in a combined fit based on both the transverse momentum dependent and collinear twist-three factorization formalisms; however, ?± BRAHMS data are not described in a satisfactory way. This leaves the question open of a solution to the “sign mismatch.” Possible explanations are then discussed.

Kang, Zhong-Bo; Prokudin, Alexei

2012-04-01

136

Distinguishing between nonorthogonal quantum states of a single nuclear spin.  

PubMed

An important task for quantum-information processing is optimal discrimination between two nonorthogonal quantum states, which until now has been realized only optically. Here, we present and compare experimental realizations of optimal quantum measurements for distinguishing between two nonorthogonal quantum states encoded in a single (14)N nuclear spin at a nitrogen-vacancy defect in diamond. Implemented measurement schemes are the minimum-error measurement (known as Helstrom measurement), unambiguous state discrimination using a standard projective measurement, and optimal unambiguous state discrimination [known as Ivanovic-Dieks-Peres (IDP) measurement], which utilizes a three-dimensional Hilbert space. This allows us to benchmark the IDP measurement against the standard projective measurements. Measurement efficiencies are found to be above 80% for all schemes and reach a value of 90% for the IDP measurement. PMID:23215260

Waldherr, Gerald; Dada, Adetunmise C; Neumann, Philipp; Jelezko, Fedor; Andersson, Erika; Wrachtrup, Jörg

2012-11-02

137

Global fitting of single spin asymmetry: an attempt  

SciTech Connect

We present an attempt of global analysis of Semi-Inclusive Deep Inelastic Scattering (SIDIS) $\\ell p^\\uparrow \\to \\ell' \\pi X$ data on single spin asymmetries and data on left-right asymmetry $A_N$ in $p^\\uparrow p \\to \\pi X$ in order to simultaneously extract information on Sivers function and twist-three quark-gluon Efremov-Teryaev-Qiu-Sterman (ETQS) function. We explore different possibilities such as node of Sivers function in $x$ or $k_\\perp$ in order to explain ``sign mismatch'' between these functions. We show that $\\pi^\\pm$ SIDIS data and $\\pi^0$ STAR data can be well described in a combined TMD and twist-3 fit, however $\\pi^\\pm$ BRAHMS data are not described in a satisfactory way. This leaves open a question to the solution of the ``sign mismatch''. Possible explanations are then discussed.

Alexey Prokudin,Zhong-Bo Kang

2012-04-01

138

Calculation of TMD Evolution for Transverse Single Spin Asymmetry Measurements  

SciTech Connect

In this letter, we show that it is necessary to include the full treatment of QCD evolution of Transverse Momentum Dependent parton densities to explain discrepancies between HERMES data and recent COMPASS data on a proton target for the Sivers transverse single spin asymmetry in Semi-Inclusive Deep Inelastic Scattering (SIDIS). Calculations based on existing fits to TMDs in SIDIS, and including evolution within the Collins-Soper-Sterman with properly defined TMD PDFs are shown to provide a good explanation for the discrepancy. The non-perturbative input needed for the implementation of evolution is taken from earlier analyses of unpolarized Drell-Yan (DY) scattering at high energy. Its success in describing the Sivers function in SIDIS data at much lower energies is strong evidence in support of the unifying aspect of the QCD TMD-factorization formalism.

Mert Aybat, Ted Rogers, Alexey Prokudin

2012-06-01

139

Decoherence of a single-ion qubit immersed in a spin-polarized atomic bath.  

PubMed

We report on the immersion of a spin qubit encoded in a single trapped ion into a spin-polarized neutral atom environment, which possesses both continuous (motional) and discrete (spin) degrees of freedom. The environment offers the possibility of a precise microscopic description, which allows us to understand dynamics and decoherence from first principles. We observe the spin dynamics of the qubit and measure the decoherence times (T(1) and T(2)), which are determined by the spin-exchange interaction as well as by an unexpectedly strong spin-nonconserving coupling mechanism. PMID:23679585

Ratschbacher, L; Sias, C; Carcagni, L; Silver, J M; Zipkes, C; Köhl, M

2013-04-19

140

Nondestructive optical measurements of a single electron spin in a quantum dot.  

PubMed

Kerr rotation measurements on a single electron spin confined in a charge-tunable semiconductor quantum dot demonstrate a means to directly probe the spin off-resonance, thus minimally disturbing the system. Energy-resolved magneto-optical spectra reveal information about the optically oriented spin polarization and the transverse spin lifetime of the electron as a function of the charging of the dot. These results represent progress toward the manipulation and coupling of single spins and photons for quantum information processing. PMID:17095655

Berezovsky, J; Mikkelsen, M H; Gywat, O; Stoltz, N G; Coldren, L A; Awschalom, D D

2006-11-09

141

Quantum interference of stored dual-channel spin-wave excitations in a single tripod system  

SciTech Connect

We present an experimental demonstration of dual-channel memory in a single tripod atomic system. The total readout signal exhibits either constructive or destructive interference when the dual-channel spin-wave excitations (SWEs) are retrieved by two reading beams with a controllable relative phase. When the two reading beams have opposite phases, the SWEs will remain in the medium, which can be retrieved later with two in-phase reading beams. Such a phase-sensitive storage and retrieval scheme can be used to measure and control the relative phase between the two SWEs in the memory medium, which may find applications in quantum-information processing.

Wang Hai; Li Shujing; Xu Zhongxiao; Zhao Xingbo; Zhang Lijun; Li Jiahua; Wu Yuelong; Xie Changde; Peng Kunchi [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China); Xiao Min [The State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China); Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

2011-04-15

142

Polarization Dependence of the Spin-Density-Wave Excitations in Single-Domain Chromium  

SciTech Connect

A polarised neutron scattering experiment has been performed on a single-Q, single domain sample of Cr in a magnetic field of 4 T in the transverse spin-density-wave phase. It is confirmed that the longitudinal fluctuations are enhanced for energy transfers E {lt} 8 meV similarly as in the longitudinal spin-density-wave phase. The spin wave modes with deltaS parallel and perpendicular to Q are isotropic within the E-range investigated.

Boeni, P. [Labor fuer Neutronenstreuung, Villigen PSI (Switzerland); Sternlieb, B.J.; Shirane, G. [Brookhaven National Lab., Upton, NY (United States); Roessli, B.; Werner, S.A. [Institut Laue Langevin, Grenoble Cedex (France); Lorenzo, J.E. [Laboratoire de Crystallographie, CNRS, Grenoble (France)

1997-12-31

143

All-optical control of a solid-state spin using coherent dark states.  

PubMed

The study of individual quantum systems in solids, for use as quantum bits (qubits) and probes of decoherence, requires protocols for their initialization, unitary manipulation, and readout. In many solid-state quantum systems, these operations rely on disparate techniques that can vary widely depending on the particular qubit structure. One such qubit, the nitrogen-vacancy (NV) center spin in diamond, can be initialized and read out through its special spin-selective intersystem crossing, while microwave electron spin resonance techniques provide unitary spin rotations. Instead, we demonstrate an alternative, fully optical approach to these control protocols in an NV center that does not rely on its intersystem crossing. By tuning an NV center to an excited-state spin anticrossing at cryogenic temperatures, we use coherent population trapping and stimulated Raman techniques to realize initialization, readout, and unitary manipulation of a single spin. Each of these techniques can be performed directly along any arbitrarily chosen quantum basis, removing the need for extra control steps to map the spin to and from a preferred basis. Combining these protocols, we perform measurements of the NV center's spin coherence, a demonstration of this full optical control. Consisting solely of optical pulses, these techniques enable control within a smaller footprint and within photonic networks. Likewise, this unified approach obviates the need for both electron spin resonance manipulation and spin addressability through the intersystem crossing. This method could therefore be applied to a wide range of potential solid-state qubits, including those which currently lack a means to be addressed. PMID:23610403

Yale, Christopher G; Buckley, Bob B; Christle, David J; Burkard, Guido; Heremans, F Joseph; Bassett, Lee C; Awschalom, David D

2013-04-22

144

Picosecond coherent optical manipulation of a single electron spin in a quantum dot.  

PubMed

Most schemes for quantum information processing require fast single-qubit operations. For spin-based qubits, this involves performing arbitrary coherent rotations of the spin state on time scales much faster than the spin coherence time. By applying off-resonant, picosecond-scale optical pulses, we demonstrated the coherent rotation of a single electron spin through arbitrary angles up to pi radians. We directly observed this spin manipulation using time-resolved Kerr rotation spectroscopy and found that the results are well described by a model that includes the electronnuclear spin interaction. Measurements of the spin rotation as a function of laser detuning and intensity confirmed that the optical Stark effect is the operative mechanism. PMID:18420929

Berezovsky, J; Mikkelsen, M H; Stoltz, N G; Coldren, L A; Awschalom, D D

2008-04-18

145

Control of domain wall motion by interference of spin wave  

NASA Astrophysics Data System (ADS)

We propose a method to control the motions of magnetic domain walls using the interference phenomenon of the spin wave. It is found that when the distances between two neighboring walls are integer multiples of half wavelengths of the spin wave, the transmission coefficients of the spin wave are local maxima. This interference effect provides a new method for controlling the spin-wave-induced domain-wall motion, not only the speed of the domain wall motion but also its moving direction. In addition, tuning the distance of walls, we can find the direct relationship between the domain-wall velocity and the transmission coefficient, a crucial parameter of the spin-wave-induced domain-wall motions.

Moon, Kyoung-Woong; Sun Chun, Byong; Kim, Wondong; Hwang, Chanyong

2013-09-01

146

Externally controlled spin state switching in metal-organic complexes.  

NASA Astrophysics Data System (ADS)

Recent transport experiments have demonstrated that a manipulation of the charge of individual molecules is feasible using electromigrated metal junctions [1] or electrochemical gates in conjunction with the STM [2]. Using elaborated density functional theory calculations, we will discuss a possibility to induce -- by means of charging or applied stress -- a switching between low and high spin states in certain metal-organic systems, [Fe(bpp)2]^2+ (bpp: bispyrazolyl pyridine) and [Mn(tpy)2]^2+ (tpy: terpyridine). Based upon a recent success of the single molecular conduction experiment through Ru(II) complex [3], we anticipate the transport properties of Fe(II) and Mn(II) complexes to be gate controlled via exploiting their spin degree of freedom. [1] E. A. Osorio et al., J. Phys.: Condens. Matter20, 374121 (2008); [2] F. Chen el al., Ann. Rev. Phys. Chem. 58, 535 (2007); Li et al., Nanotechnology 18, 044018 (2007). [3] M. Ruben, A. Landa, E. L"ortscher, H. Riel, M. Mayor, H. G"orls, H. Weber, A. Arnold, and F. Evers, Small (online), DOI: 10.1002/smll.200800390 (2008).

Bagrets, Alexei; Meded, Velimir; Ruben, Mario; Evers, Ferdinand

2009-03-01

147

Polytype control of spin qubits in silicon carbide  

NASA Astrophysics Data System (ADS)

The search for coherently addressable spin states in technologically important materials is a promising direction for solid-state quantum information science. Silicon carbide, a particularly suitable target, is not a single material but a collection of about 250 known polytypes, each with its own set of physical properties and technological applications. We show that in spite of these differences, the 4H-, 6H-, and 3C-SiC polytypes all exhibit optically addressable spins with long coherence times [1]. These results include room temperature spins in all three polytypes and suggest a new method for tuning quantum states using crystal polymorphism. Long spin coherence times allow us to use double electron-electron resonance to measure magnetic dipole interactions between spin ensembles in inequivalent lattice sites of the same crystal. Since such inequivalent spin have distinct optical and spin transition energies, these interactions could lead to dipole-coupled networks of separately addressable spins.[4pt] [1] A. Falk et al., submitted

Falk, A. L.; Buckley, B. B.; Calusine, G.; Koehl, W. F.; Politi, A.; Awschalom, D. D.; Dobrovitski, V. V.; Zorman, C. A.; Feng, P. X.-L.

2013-03-01

148

Large nuclear spin polarization in gate-defined quantum dots using a single-domain nanomagnet.  

PubMed

The electron-nuclei (hyperfine) interaction is central to spin qubits in solid state systems. It can be a severe decoherence source but also allows dynamic access to the nuclear spin states. We study a double quantum dot exposed to an on-chip single-domain nanomagnet and show that its inhomogeneous magnetic field crucially modifies the complex nuclear spin dynamics such that the Overhauser field tends to compensate external magnetic fields. This turns out to be beneficial for polarizing the nuclear spin ensemble. We reach a nuclear spin polarization of ?50%, unrivaled in lateral dots, and explain our manipulation technique using a comprehensive rate equation model. PMID:23679779

Petersen, Gunnar; Hoffmann, Eric A; Schuh, Dieter; Wegscheider, Werner; Giedke, Geza; Ludwig, Stefan

2013-04-26

149

Large Nuclear Spin Polarization in Gate-Defined Quantum Dots Using a Single-Domain Nanomagnet  

NASA Astrophysics Data System (ADS)

The electron-nuclei (hyperfine) interaction is central to spin qubits in solid state systems. It can be a severe decoherence source but also allows dynamic access to the nuclear spin states. We study a double quantum dot exposed to an on-chip single-domain nanomagnet and show that its inhomogeneous magnetic field crucially modifies the complex nuclear spin dynamics such that the Overhauser field tends to compensate external magnetic fields. This turns out to be beneficial for polarizing the nuclear spin ensemble. We reach a nuclear spin polarization of ?50%, unrivaled in lateral dots, and explain our manipulation technique using a comprehensive rate equation model.

Petersen, Gunnar; Hoffmann, Eric A.; Schuh, Dieter; Wegscheider, Werner; Giedke, Geza; Ludwig, Stefan

2013-04-01

150

Spin system trajectory analysis under optimal control pulses.  

PubMed

Several methods are proposed for the analysis, visualization and interpretation of high-dimensional spin system trajectories produced by quantum mechanical simulations. It is noted that expectation values of specific observables in large spin systems often feature fast, complicated and hard-to-interpret time dynamics and suggested that populations of carefully selected subspaces of states are much easier to analyze and interpret. As an illustration of the utility of the proposed methods, it is demonstrated that the apparent "noisy" appearance of many optimal control pulses in NMR and EPR spectroscopy is an illusion - the underlying spin dynamics is shown to be smooth, orderly and very tightly controlled. PMID:23541031

Kuprov, Ilya

2013-02-27

151

Control of exciton spin statistics through spin polarization in organic optoelectronic devices.  

PubMed

Spintronics based on organic semiconductor materials is attractive because of its rich fundamental physics and potential for device applications. Manipulating spins is obviously important for spintronics, and is usually achieved by using magnetic electrodes. Here we show a new approach where spin populations can be controlled primarily by energetics rather than kinetics. We find that exciton spin statistics can be substantially controlled by spin-polarizing carriers after injection using high magnetic fields and low temperatures, where the Zeeman energy is comparable with the thermal energy. By using this method, we demonstrate that singlet exciton formation can be suppressed by up to 53% in organic light-emitting diodes, and the dark conductance of organic photovoltaic devices can be increased by up to 45% due to enhanced formation of triplet charge-transfer states, leading to less recombination to the ground state. PMID:23149736

Wang, Jianpu; Chepelianskii, Alexei; Gao, Feng; Greenham, Neil C

2012-01-01

152

Resonant control of spin dynamics in ultracold quantum gases by microwave dressing  

SciTech Connect

We study experimentally interaction-driven spin oscillations in optical lattices in the presence of an off-resonant microwave field. We show that the energy shift induced by this microwave field can be used to control the spin oscillations by tuning the system either into resonance to achieve near-unity contrast or far away from resonance to suppress the oscillations. Finally, we propose a scheme based on this technique to create a flat sample with either singly or doubly occupied sites, starting from an inhomogeneous Mott insulator, where singly and doubly occupied sites coexist.

Gerbier, Fabrice; Widera, Artur; Foelling, Simon; Mandel, Olaf; Bloch, Immanuel [Institut fuer Physik, Johannes Gutenberg-Universitaet, 55099 Mainz (Germany)

2006-04-15

153

Spinoptical metamaterials: spin-controlled photonics based on symmetry violation  

NASA Astrophysics Data System (ADS)

Spinoptics provides a route to control light, whereby the photon helicity (spin angular momentum) degeneracy is removed due to a geometric gradient onto a metasurface. The alliance of spinoptics and metamaterials offers the dispersion engineering of a structured matter in a polarization helicity dependent manner. We show that polarization-controlled optical modes of metamaterials arise where the spatial inversion symmetry is violated. The emerged spin-split dispersion of spontaneous emission originates from the spin-orbit interaction of light, generating a selection rule based on symmetry restrictions in a spinoptical metamaterial. The inversion asymmetric metasurface is obtained via anisotropic optical antenna patterns. This type of metamaterial provides a route for spin-controlled nanophotonic applications based on the design of the metasurface symmetry properties.

Shitrit, Nir; Yulevich, Igor; Maguid, Elhanan; Ozeri, Dror; Veksler, Dekel; Kleiner, Vladimir; Hasman, Erez

2013-09-01

154

Single-quantum coherence filter for strongly coupled spin systems for localized (1)H NMR spectroscopy.  

PubMed

A pulse sequence for localized in vivo (1)H NMR spectroscopy is presented, which selectively filters single-quantum coherence built up by strongly coupled spin systems. Uncoupled and weakly coupled spin systems do not contribute to the signal output. Analytical calculations using a product operator description of the strongly coupled AB spin system as well as in vitro tests demonstrate that the proposed filter produces a signal output for a strongly coupled AB spin system, whereas the resonances of a weakly coupled AX spin system and of uncoupled spins are widely suppressed. As a potential application, the detection of the strongly coupled AA'BB' spin system of taurine at 1.5 T is discussed. PMID:10910692

Trabesinger, A H; Mueller, D C; Boesiger, P

2000-08-01

155

Study of thermally induced spin state transition in NdCoO3 single crystal  

NASA Astrophysics Data System (ADS)

We have carried out Magnetization, Raman spectroscopy and IR spectroscopy studies as a function of temperature to investigate the spin state transition in NdCoO3 single crystal. The crystal has been grown by Optical Float Zone technique and characterized by Synchrotron X-ray Diffraction. Our results indicate that the spin crossover from low spin state (LS) to intermediate spin state (IS) occurs continuously over a wide range of temperature above 200K. The wide temperature range of the spin crossover reflects possible electronic or magnetic in-homogeneity at the microscopic level, which is a common feature of some cobalt perovskites. The magnetization studies indicate a spin gap which is higher than that of LaCoO3 (180 K) and Raman spectroscopy studies reveal a Jahn Teller vibration mode characteristic of the intermediate spin state similar to that reported for LaCoO3 in literature.

Janaki, J.; Nithya, R.; Ganesamoorthy, S.; Sairam, T. N.; Ravindran, T. R.; Vinod, K.; Bharathi, A.

2013-02-01

156

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

NASA Astrophysics Data System (ADS)

The spin of an electron or hole in an InAs quantum dot is an attractive qubit because it combines the advantages of a semiconductor platform with the power of ultrafast optical coherent control techniques. In the last few years, basic quantum operations such as initialization, rotation, and readout have become possible using single spins, but now improvements in spin coherence and demonstrations of multi-qubit systems are needed. In this work, we combine advances in the design and growth of coupled quantum dots with optical coherent control techniques to demonstrate ultrafast manipulation and coherence improvements for one or two interacting electron [1] or hole [2] spins in a coupled pair of InAs dots. For each of these spin systems, we use a sequence of picosecond and nanosecond pulses to initialize, manipulate, and measure the coherent spin dynamics. These dynamics include precession about a magnetic field and also entangling dynamics from the exchange interaction for coupled spins. For a single electron spin, precession dephases after only a few nanoseconds due to the hyperfine interaction with nuclear spins. For hole spins, we measure a dephasing time an order of magnitude longer due to a weaker hyperfine interaction. Coupled electron and hole spins are essential for multi-qubit systems, and they can also be used to decrease sensitivity to the environment. In these systems, we typically measure the coherent dynamics of the singlet-triplet states (ms=0), which are much less sensitive to the nuclear environment. At present, dephasing is due to fluctuations in the electrical environment. With careful sample design, we can make these systems much less sensitive to electrical fluctuations, giving a powerful combination of long coherence times and ultrafast gates. Finally, we demonstrate that these spin qubits can be incorporated into a photonic crystal cavity and manipulated with optical pulses, a major step toward a quantum interface between photons and these spin qubits.[4pt] [1] D. Kim et al., Nature Phys. 7, 223 (2011).[0pt] [2] A. Greilich et al., Nature Photon. 5, 702 (2011).

Carter, Samuel

2013-03-01

157

Magnetic attitude control of near earth spinning satellites  

Microsoft Academic Search

Magnetic attitude control systems were employed in several satellite programs due to their salient features like simplicity in construction, absence of moving parts, less power and space requirements and less weight. A control law suitable for keeping the spin axis of the satellite perpendicular to the plane of a near circular orbit was derived, and a control scheme incorporating the

S. Rajaram; P. S. Goel

1977-01-01

158

Protein carbon-13 spin systems by a single two-dimensional nuclear magnetic resonance experiment  

Microsoft Academic Search

By applying a two-dimensional double-quantum carbon-13 nuclear magnetic resonance experiment to a protein uniformly enriched to 26% carbon-13, networks of directly bonded carbon atoms were identified by virtue of their one-bond spin-spin couplings and were classified by amino acid type according to their particular single- and double-quantum chemical shift patterns. Spin systems of 75 of the 98 amino acid residues

B. H. Oh; W. M. Westler; P. Darba; J. L. Markley

1988-01-01

159

Controlling the Gilbert damping using spin pumping and magnetic impurities  

NASA Astrophysics Data System (ADS)

The ability to control the magnetic damping parameter of thin magnetic films is an important issue when designing for example giant magnetoresistance (GMR) devices. A well-known way to influence the damping of the ferromagnetic (F) layer is by using the spin pumping effect in which a spin current is emitted into an adjacent normal (N) layer by bringing the F-layer into ferromagnetic resonance (FMR). As N layer, we used the well studied strongly spin sinking material Pt and the bad spin sink Cu, but also a Cu layer with Co impurities. We find that by adding a small amount of Co impurities, the Cu layer becomes as effective in damping as a Pt layer. In the latter case, the damping is caused by the strong spin orbit coupling. Using magnetic impurities, we rather make use of the inelastic spin scattering. This opens up new ways to control the damping of a ferromagnetic thin layer, for example in current-in-plane (CIP) GMR sensors, where the extra damping can suppress the spin transfer torque which becomes dominant with the further decrease of the size of the sensor.

Verhagen, Tim; Tinkey, Holly; van Ruitenbeek, Jan; Aarts, Jan

2013-03-01

160

Sensitive magnetic control of ensemble nuclear spin hyperpolarization in diamond.  

PubMed

Dynamic nuclear polarization, which transfers the spin polarization of electrons to nuclei, is routinely applied to enhance the sensitivity of nuclear magnetic resonance. This method is particularly useful when spin hyperpolarization can be produced and controlled optically or electrically. Here we show complete polarization of nuclei located near optically polarized nitrogen-vacancy centres in diamond. Close to the ground-state level anti-crossing condition of the nitrogen-vacancy electron spins, (13)C nuclei in the first shell are polarized in a pattern that depends sensitively upon the magnetic field. Based on the anisotropy of the hyperfine coupling and of the optical polarization mechanism, we predict and observe a reversal of the nuclear spin polarization with only a few millitesla change in the magnetic field. This method of magnetic control of high nuclear polarization at room temperature can be applied in sensitivity enhanced nuclear magnetic resonance of bulk nuclei, nuclear-based spintronics, and quantum computation in diamond. PMID:23736952

Wang, Hai-Jing; Shin, Chang S; Avalos, Claudia E; Seltzer, Scott J; Budker, Dmitry; Pines, Alexander; Bajaj, Vikram S

2013-01-01

161

Nonequilibrium spin-current detection with a single Kondo impurity  

NASA Astrophysics Data System (ADS)

We present a theoretical study based on the Anderson model of the transport properties of a Kondo impurity (atom or quantum dot) connected to ferromagnetic leads, which can sustain a nonequilibrium spin current. We analyze the case where the spin current is injected by an external source and when it is generated by the voltage bias. Due to the presence of ferromagnetic contacts, a static exchange field is produced that eventually destroys the Kondo correlations. We find that such a field can be compensated by an appropriated combination of the spin-dependent chemical potentials leading to the restoration of the Kondo resonance. In this respect, a Kondo impurity may be regarded as a very sensitive sensor for nonequilibrium spin phenomena.

Lim, Jong Soo; López, Rosa; Limot, Laurent; Simon, Pascal

2013-10-01

162

Nanoscale magnetic imaging of a single electron spin under ambient conditions  

NASA Astrophysics Data System (ADS)

The detection of ensembles of spins under ambient conditions has revolutionized the biological, chemical and physical sciences through magnetic resonance imaging and nuclear magnetic resonance. Pushing sensing capabilities to the individual-spin level would enable unprecedented applications such as single-molecule structural imaging; however, the weak magnetic fields from single spins are undetectable by conventional far-field resonance techniques. In recent years, there has been a considerable effort to develop nanoscale scanning magnetometers, which are able to measure fewer spins by bringing the sensor in close proximity to its target. The most sensitive of these magnetometers generally require low temperatures for operation, but the ability to measure under ambient conditions (standard temperature and pressure) is critical for many imaging applications, particularly in biological systems. Here we demonstrate detection and nanoscale imaging of the magnetic field from an initialized single electron spin under ambient conditions using a scanning nitrogen-vacancy magnetometer. Real-space, quantitative magnetic-field images are obtained by deterministically scanning our nitrogen-vacancy magnetometer 50nm above a target electron spin, while measuring the local magnetic field using dynamically decoupled magnetometry protocols. We discuss how this single-spin detection enables the study of a variety of room-temperature phenomena in condensed-matter physics with an unprecedented combination of spatial resolution and spin sensitivity.

Grinolds, M. S.; Hong, S.; Maletinsky, P.; Luan, L.; Lukin, M. D.; Walsworth, R. L.; Yacoby, A.

2013-04-01

163

Spin-Polarized Transport on Zigzag Graphene Nanoribbon with a Single Defect  

Microsoft Academic Search

We calculate the electric conductance of a graphene nanoribbon (GNR) with and without a point defect. In the case of a zigzag GNR, magnetic moments are formed near the zigzag edges, and the electric current on each edge is spin-polarized. By breaking the symmetry of the magnetic moments with a single defect, such as a nonmagnetic vacancy, a net spin-polarized

Hideki Kumazaki; Dai S. Hirashima

2009-01-01

164

Spin wave instability in single crystal Zn-Y hexagonal ferrite at 8.93 GHz  

Microsoft Academic Search

Resonance saturation (RS), subsidiary absorption (SA), and parallel pump (PP) spin wave instability threshold measurements have been made on single crystal easy plane disks of Mn substituted Zn-Y type hexagonal ferrite materials at 8.93 GHz and room temperature. For each configuration, ``butterfly curves'' of the spin wave instability threshold microwave field amplitude hcrit as a function of the static field

Richard G. Cox; Carl E. Patton; Michael A. Wittenauer; Pavel Kabos; Liang Chen

2001-01-01

165

Universal Phase Shift and Nonexponential Decay of Driven Single-Spin Oscillations  

Microsoft Academic Search

We study, both theoretically and experimentally, driven Rabi oscillations of a single electron spin coupled to a nuclear-spin bath. Because of the long correlation time of the bath, two unusual features are observed in the oscillations. The decay follows a power law, and the oscillations are shifted in phase by a universal value of ˜pi\\/4. These properties are well understood

F. H. L. Koppens; D. Klauser; W. A. Coish; K. C. Nowack; L. P. Kouwenhoven; D. Loss; L. M. K. Vandersypen

2007-01-01

166

Detection of spin polarized carrier in silicon nanowire with single crystal MnSi as magnetic contacts.  

PubMed

We report the formation of single crystal MnSi nanowires, MnSi/Si/MnSi nanowire heterostructures, to study the spin transport in silicon nanostructure. Scanning electron microscopy studies show that silicon nanowires can be converted into single crystal MnSi nanowires through controlled solid-state reaction. High-resolution transmission electron microscope studies show that MnSi/Si/MnSi heterostructures have clean, atomically sharp interfaces with an epitaxial relationship of Si[311]//MnSi[120] and Si(345)//MnSi(214). Magnetoresistance (MR) studies show that the single crystal MnSi nanowire exhibits metallic behavior with paramagnetic to ferromagnetic transition temperature of 29.7 K and a negative MR up to 1.8% at low temperature. Furthermore, using single crystal MnSi/p-Si/MnSi nanowire heterostructures, we have studied carrier tunneling via the Schottky barrier and spin polarized carrier transport in the silicon nanodevices. PMID:20499889

Lin, Yung-Chen; Chen, Yu; Shailos, Alexandros; Huang, Yu

2010-06-01

167

Spin-resolved measurements of single molecular magnets on graphene  

NASA Astrophysics Data System (ADS)

The use of magnetic molecules opens a gateway to a flexible design of novel spintronic devices to store, manipulate, and read spin information at the nanoscale. Crucial is the precise knowledge of molecular properties at the interface towards an electrode. Progress in this field relies on resolving and understanding the physics at the relevant interfaces. In particular the role of individual molecular constituents and the impact of the atomic environment on molecular properties determine device relevant parameters, such as conductance and spin polarization. Recently, the incorporation of a graphene sheet to electronically decouple molecules from a ferromagnetic surface has been addressed by surface averaging high-resolution electron energy loss spectroscopy. Here, we applied spin-polarized scanning tunneling microscopy to resolve the physics of the molecule-graphene-ferromagnet interface. The analysis focuses on different phthalocyanine molecules adsorbed on cobalt-intercalated graphene on Ir(111). The phthalocyanine constitutes of an organic macrocyclic ligand and can be functionalized with various metal ions in order to modify, e.g. the molecular spin state. We will discuss the spin-dependent transport from magnetic surfaces through such molecules. In particular, the spin polarization of molecular frontier orbitals is resolved with sub-molecular spatial resolution and the variations in the lifetimes of different orbitals are discussed.

Brede, Jens; Decker, Regis; Schwoebel, Joerg; Bazarnik, Maciej; Wiesendanger, Roland

2013-03-01

168

Optical control of a spin switch in the weak spin-orbit coupling limit  

SciTech Connect

A method to optically control a dark transition, for instance, the coupling between different spin states, is proposed. The control is achieved by manipulating the direction, amplitude, and duration of dynamic Stark shifts. Laser-driven spin switches can be prepared by conveniently generalizing different optical techniques, such as {pi}-pulse schemes and adiabatic passage schemes. The efficiency and robustness of the schemes is analyzed for both two-level and multilevel systems, implying quantum state selective wave packet transfer between states of different multiplicity.

Sola, Ignacio R.; Gonzalez-Vazquez, Jesus; Malinovsky, Vladimir S. [Departamento de Quimica Fisica I, Universidad Complutense, 28040 Madrid (Spain); MagiQ Technologies Inc., 171 Madison Avenue, Suite 1300, New York, New York 10016 (United States)

2006-10-15

169

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

NASA Astrophysics Data System (ADS)

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

de Greve, Kristiaan

2012-02-01

170

Spin valleytronics in silicene: Quantum spin Hall-quantum anomalous Hall insulators and single-valley semimetals  

NASA Astrophysics Data System (ADS)

Valley-based electronics, known as valleytronics, is one of the keys to breaking through to a new stage of electronics. The valley degree of freedom is ubiquitous in the honeycomb lattice system. The honeycomb lattice structure of silicon, called silicene, is a fascinating playground of valleytronics. We investigate topological phases of silicene by introducing different exchange fields on the A and B sites. There emerges a rich variety of topologically protected states, each of which has a characteristic spin-valley structure. The single Dirac-cone semimetal is such a state where one gap is closed while the other three gaps are open, evading the Nielsen-Ninomiya fermion-doubling problem. We have newly discovered a hybrid topological insulator named the quantum spin-quantum anomalous Hall insulator, where the quantum anomalous Hall effect occurs at one valley and the quantum spin Hall effect occurs at the other valley. Along its phase boundary, single-valley semimetals emerge, where only one of the two valleys is gapless with degenerated spins. These semimetals are also topologically protected because they appear in the interface of different topological insulators. Such a spin-valley-dependent physics will be observed by optical absorption or edge modes.

Ezawa, Motohiko

2013-04-01

171

Coherent control and detection of spin qubits in semiconductor with magnetic field engineering  

NASA Astrophysics Data System (ADS)

Electrical control and detection of the spin qubits in semiconductor quantum dots (QDs) are among the major rapidly progressing fields for possible implementation of scalable quantum information processing. Coherent control of one-[1-3] and two-[4,5] spin qubits by electrical means had been demonstrated with various approaches. We have used an engineered magnetic field structure realized with proximal micro-magnets to transduce the spin and charge degrees of freedom and to selectively address one of the two spins [3]. We have demonstrated an all-electrical two-qubit gate consisting of single-spin rotations and interdot spin exchange in double QDs. A partially entangled output state is obtained by the application of the two-qubit gate to an initial, uncorrelated state. Our calculations taking into account of the nuclear spin fluctuation show the degree of entanglement. Non-uniform magnetic field also enables spin selective photon-assisted tunneling in double QDs, which then constitutes non-demolition spin read-out system in combination with a near-by charge detector [6]. [4pt] In collaboration with R. Brunner, Inst. of Phys., Montanuniversitaet Leoben, 8700, Austria, M. Pioro-Ladrière, D'ep. de Phys., Universit'e de Sherbrooke, Sherbrooke, Qu'ebec, J1K-2R1, Canada, T. Kubo, Y. -S. Shin, T. Obata, and S. Tarucha, ICORP-JST and Dep. of Appl. Phys., Univ. of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.[4pt] [1] F. H. Koppens, et al., Nature 442, 766 (2006).[0pt] [2] K. C. Nowack, et al., Science 318, 1430 (2007).[0pt] [3] M. Pioro-Ladrière, et al., Nature Physics 4, 776 (2008).[0pt] [4] J. R. Petta, et al., Science 309, 2180 (2005).[0pt] [5] R. Brunner, et al., Phys. Rev. Lett. 107, 146801 (2011).[0pt] [6] Y. -S. Shin, et al., Phys. Rev. Lett. 104, 046802 (2010).

Tokura, Yasuhiro

2012-02-01

172

Theory of single nuclear spin detection in magnetic resonance force microscopy  

NASA Astrophysics Data System (ADS)

We develop a theory for the measurement of a nuclear spin state in a paramagnetic atom with Oscillating Cantilever-Driven Adiabatic Reversals (OSCAR) in Magnetic Resonance Force Microscopy (MRFM). In this theory, we use a semi-classical approach where the electron-nuclear spin system, with hyperfine interaction, is treated quantum mechanically and the motion of the ferromagnetic particle on the cantilever tip is treated classically. Our computations support the idea of the measurement of a nuclear spin state by detection of a single electron spin.

Chemudupati, Srinivasa; Tsifrinovich, Vladimir

2008-10-01

173

CALCULATIONS OF SINGLE-INCLUSIVE CROSS SECTIONS AND SPIN ASYMMETRIES IN PP SCATTERING.  

SciTech Connect

We present calculations of cross sections and spin asymmetries in single-inclusive reactions in, pp scattering. We discuss next-to-leading order predictions as well as all-order soft-gluon 'threshold' resummations.

VOGELSANG,W.

2004-10-10

174

Quantum control of a spin qubit coupled to a photonic crystal cavity  

NASA Astrophysics Data System (ADS)

A key ingredient for a quantum network is an interface between stationary quantum bits and photons, which act as flying qubits for interactions and communication. Photonic crystal architectures are promising platforms for enhancing the coupling of light to solid-state qubits. Quantum dots can be integrated into a photonic crystal, with optical transitions coupling to photons and spin states forming a long-lived quantum memory. Many researchers have now succeeded in coupling these emitters to photonic crystal cavities, but there have been no demonstrations of a functional spin qubit and quantum gates in this environment. Here, we have developed a coupled cavity-quantum dot system in which the dot is controllably charged with a single electron. We perform the initialization, rotation and measurement of a single electron spin qubit using laser pulses, and find that the cavity can significantly improve these processes.

Carter, Samuel G.; Sweeney, Timothy M.; Kim, Mijin; Kim, Chul Soo; Solenov, Dmitry; Economou, Sophia E.; Reinecke, Thomas L.; Yang, Lily; Bracker, Allan S.; Gammon, Daniel

2013-04-01

175

Magnetization dynamics in the presence of pure spin currents in magnetic single and double layers in spin ballistic and diffusive regimes.  

SciTech Connect

In this paper we study the spin transport by using the spin-pumping effect in epitaxial magnetic single and double layer film structures. For the magnetic single layer sample we show the spin-pumping-induced interface damping increases and saturates with the Au capping layer thickness. In addition magnetic double layer structures allowed us to investigate both the spin-pump and spin-sink effects. Coupling of pure spin currents to the magnetization via spin-sink effect is studied using time-resolved magneto-optical Kerr effect. These measurements were used to study the propagation of pure spin currents across a Au spacer layer between the two ferromagnets. The propagation of spin momentum density through the Au spacer layer was well described by spin-diffusion equation, which takes into account electron momentum and spin-flip scattering. The spin-diffusion theory was integrated into modified Landau-Lifshitz equations accounting in self-consistent manner for spin-pump/sink mechanism and spin momentum density propagation. Good agreement between theory and experimental data was found.

Mosendz, O.; Woltersdorf, G.; Kardasz, B.; Heinrich, B.; Back, C. H.; Materials Science Division; Univ. Regensburg; Simon Fraser Univ.

2009-01-01

176

Single-spin microscope with sub-nanoscale resolution based on optically detected magnetic resonance  

NASA Astrophysics Data System (ADS)

Recently we proposed a new approach which potentially has single spin sensitivity, sub-nanometer spatial resolution, and ability to operate at room temperature (J. Appl. Phys. 97, 014903 (2005); U.S. Patent No. 7,305,869, 2007). In our approach a nanoscale photoluminescent center exhibits optically detected magnetic resonance (ODMR) in the vicinity of magnetic moment in the sample related with unpaired individual electron or nuclear spins, or ensemble of spins. We consider as a sensor material that exhibit ODMR properties nitrogen-vacancy (N-V) centers in diamond. N-V centers in diamond has serious advantage having extraordinary chemical and photostability, very long spin lifetimes, and ability single-spin detection at room temperature. The variety of possible scanning schemes has been considered. The potential application to 3D imaging of biological structure has been analyzed.

Berman, Gennady P.; Chernobrod, Boris M.

2010-01-01

177

Spin-phonon coupling in single Mn-doped CdTe quantum dot  

NASA Astrophysics Data System (ADS)

The spin dynamics of a single Mn atom in a laser driven CdTe quantum dot is addressed theoretically. Recent experimental results [Gall , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.102.127402 102, 127402 (2009); Goryca , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.087401 103, 087401 (2009); Gall , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.81.245315 81, 245315 (2010)] show that it is possible to induce Mn spin polarization by means of circularly polarized optical pumping. Pumping is made possible by the faster Mn spin relaxation in the presence of the exciton. Here we discuss different Mn spin-relaxation mechanisms: first, Mn-phonon coupling, which is enhanced in the presence of the exciton; second, phonon induced hole spin relaxation combined with carrier-Mn spin-flip coupling and photon emission results in Mn spin relaxation. We model the Mn spin dynamics under the influence of a pumping laser that injects excitons into the dot, taking into account exciton-Mn exchange and phonon induced spin relaxation of both Mn and holes. Our simulations account for the optically induced Mn spin pumping.

Cao, C. L.; Besombes, L.; Fernández-Rossier, J.

2011-11-01

178

Controlled coupling of spin-resolved quantum Hall edge states  

NASA Astrophysics Data System (ADS)

Spin resolved edge states in quantum Hall systems at filling fraction ? = 2 posses large coherence [1] and relaxation [2] lengths. They are ideal candidates for the implementation of dual-rail quantum computation architectures [3] by encoding the qubit in the spin degree of freedom of the co-propagating spin resolved edge states. An important element for realization of such architectures is a coherent beam splitter that controllably mixes the two co-propagating spin-resolved edge channels to create any superposition of the two logic states. In this talk we demonstrate a new method to controllably couple spin resolved edge states and induce inter-edge charge transfer associated to spin-flip scattering events [4]. The process exploits the coupling of the electron spin with a spatially-dependent periodic in-plane magnetic field that is created by an array of Cobalt nano-magnets placed at the boundary of the GaAs/AlGaAs modulation doped heterostructure. The maximum charge/spin transfer of 28 ± 1 % is achieved at 250 mK by fine tuning the perpendicular magnetic field. These results are key steps towards the realization of a scalable quantum interferometric device currently under investigation in our group. [4pt] [1] Y. Ji et al. Nature 422 (2003) 415.[0pt] [2] G. Muller et al. Phy. Rev. B 45 (1992) 3932.[0pt] [3] V. Giovannetti et al., Phys. Rev. B 77 (2008) 155320.[0pt] [4] B. Karmakar et al., (accepted in PRL).

Karmakar, Biswajit

2012-02-01

179

Experimental Implementation of Assisted Quantum Adiabatic Passage in a Single Spin  

NASA Astrophysics Data System (ADS)

Quantum adiabatic passages can be greatly accelerated by a suitable control field, called a counter-diabatic field, which varies during the scan through resonance. Here, we implement this technique on the electron spin of a single nitrogen-vacancy center in diamond. We demonstrate two versions of this scheme. The first follows closely the procedure originally proposed by Demirplak and Rice [J. Phys. Chem. A 107, 9937 (2003)]. In the second scheme, we use a control field whose amplitude is constant but whose phase varies with time. This version, which we call the rapid-scan approach, allows an even faster passage through resonance and therefore makes it applicable also for systems with shorter decoherence times.

Zhang, Jingfu; Shim, Jeong Hyun; Niemeyer, Ingo; Taniguchi, T.; Teraji, T.; Abe, H.; Onoda, S.; Yamamoto, T.; Ohshima, T.; Isoya, J.; Suter, Dieter

2013-06-01

180

Anisotropy Energy, Spin-Atomic Vibration Interaction, and Spin-Flip Hamiltonian of a Single Atomic Spin in a Crystal Field  

NASA Astrophysics Data System (ADS)

We derive the anisotropy energy VA, the spin-atomic vibration interaction VSA, and the spin-flip Hamiltonian VSF of a single atomic spin system, "Fe^ 2+ (3d^6) in a crystal field of tetragonal symmetry" [1,2]. We here apply the perturbation theory to a model with the spin- orbit interaction and the kinetic and potential energies of electrons. The model also takes into account the difference in vibration displacement between an effective nucleus and electrons, ?r. We first find conditions to enhance a coefficient |D| of VA=-|D|SZ^2, where D is an anisotropy constant and SZ is the Z component of a spin operator. Second, we show that VSA appears for ?r0, while VSF is present independently of ?r. Also, the magnitudes of the coefficients of VSA can be larger than those of the conventional spin-phonon interaction depending on vibration frequency. [4pt] [1] S. Kokado et al., J. Phys. Soc. Jpn. 79, 114721 (2010).[0pt] [2] S. Kokado et al., phys. stat. solidi (c) 7, 2612 (2010).

Kokado, Satoshi; Harigaya, Kikuo; Sakuma, Akimasa

2011-03-01

181

Coherent Control of Spin Precession Motion with Impulsive Magnetic Fields of Half-Cycle Terahertz Radiation  

NASA Astrophysics Data System (ADS)

Coherent control of the precession motion of magnetizations in a single crystal YFeO3 with double half-cycle pulse terahertz waves was demonstrated. Quasiferromagnetic (0.299 THz) and quasiantiferromagnetic (0.527 THz) precession modes were selectively excited by choosing an appropriate interval of two pulses and were observed as free induction decay (FID) signals from the spin system. By observing the circularly polarized FID signals due to ferromagnetic resonance, we also succeeded in confirming directly the energy storage in the spin system and recovery from that to the electromagnetic radiation.

Yamaguchi, Keita; Nakajima, Makoto; Suemoto, Tohru

2010-12-01

182

Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization  

NASA Astrophysics Data System (ADS)

One fundamental requirement for quantum computation is to carry out universal manipulations of quantum bits at rates much faster than the qubit's rate of decoherence. Recently, fast gate operations have been demonstrated in logical spin qubits composed of two electron spins where the rapid exchange of the two electrons permits electrically controllable rotations around one axis of the qubit. However, universal control of the qubit requires arbitrary rotations around at least two axes. Here, we show that by subjecting each electron spin to a magnetic field of different magnitude, we achieve full quantum control of the two-electron logical spin qubit with nanosecond operation times. Using a single device, a magnetic-field gradient of several hundred millitesla is generated and sustained using dynamic nuclear polarization of the underlying Ga and As nuclei. Universal control of the two-electron qubit is then demonstrated using quantum state tomography. The presented technique provides the basis for single- and potentially multiple-qubit operations with gate times that approach the threshold required for quantum error correction.

Foletti, Sandra; Bluhm, Hendrik; Mahalu, Diana; Umansky, Vladimir; Yacoby, Amir

2009-12-01

183

Nanoscale broadband transmission lines for spin qubit control  

NASA Astrophysics Data System (ADS)

The intense interest in spin-based quantum information processing has caused an increasing overlap between the two traditionally distinct disciplines of magnetic resonance and nanotechnology. In this work we discuss rigorous design guidelines to integrate microwave circuits with charge-sensitive nanostructures, and describe how to simulate such structures accurately and efficiently. We present a new design for an on-chip, broadband, nanoscale microwave line that optimizes the magnetic field used to drive a spin-based quantum bit (or qubit) while minimizing the disturbance to a nearby charge sensor. This new structure was successfully employed in a single-spin qubit experiment, and shows that the simulations accurately predict the magnetic field values even at frequencies as high as 30 GHz.

Dehollain, J. P.; Pla, J. J.; Siew, E.; Tan, K. Y.; Dzurak, A. S.; Morello, A.

2013-01-01

184

Control of the spin geometric phase in semiconductor quantum rings  

PubMed Central

Since the formulation of the geometric phase by Berry, its relevance has been demonstrated in a large variety of physical systems. However, a geometric phase of the most fundamental spin-1/2 system, the electron spin, has not been observed directly and controlled independently from dynamical phases. Here we report experimental evidence on the manipulation of an electron spin through a purely geometric effect in an InGaAs-based quantum ring with Rashba spin-orbit coupling. By applying an in-plane magnetic field, a phase shift of the Aharonov–Casher interference pattern towards the small spin-orbit-coupling regions is observed. A perturbation theory for a one-dimensional Rashba ring under small in-plane fields reveals that the phase shift originates exclusively from the modulation of a pure geometric-phase component of the electron spin beyond the adiabatic limit, independently from dynamical phases. The phase shift is well reproduced by implementing two independent approaches, that is, perturbation theory and non-perturbative transport simulations.

Nagasawa, Fumiya; Frustaglia, Diego; Saarikoski, Henri; Richter, Klaus; Nitta, Junsaku

2013-01-01

185

Control of the spin geometric phase in semiconductor quantum rings.  

PubMed

Since the formulation of the geometric phase by Berry, its relevance has been demonstrated in a large variety of physical systems. However, a geometric phase of the most fundamental spin-1/2 system, the electron spin, has not been observed directly and controlled independently from dynamical phases. Here we report experimental evidence on the manipulation of an electron spin through a purely geometric effect in an InGaAs-based quantum ring with Rashba spin-orbit coupling. By applying an in-plane magnetic field, a phase shift of the Aharonov-Casher interference pattern towards the small spin-orbit-coupling regions is observed. A perturbation theory for a one-dimensional Rashba ring under small in-plane fields reveals that the phase shift originates exclusively from the modulation of a pure geometric-phase component of the electron spin beyond the adiabatic limit, independently from dynamical phases. The phase shift is well reproduced by implementing two independent approaches, that is, perturbation theory and non-perturbative transport simulations. PMID:24067870

Nagasawa, Fumiya; Frustaglia, Diego; Saarikoski, Henri; Richter, Klaus; Nitta, Junsaku

2013-09-26

186

Nuclear feedback in a single electron-charged quantum dot under pulsed optical control  

NASA Astrophysics Data System (ADS)

Electron spins in quantum dots under coherent control exhibit a number of novel feedback processes. Here, we present experimental and theoretical evidence of a feedback process between nuclear spins and a single electron spin in a single charged InAs quantum dot, controlled by the coherently modified probability of exciting a trion state. We present a mathematical model describing competition between optical nuclear pumping and nuclear spin-diffusion inside the quantum dot. The model correctly postdicts the observation of a hysteretic sawtooth pattern in the free-induction-decay of the single electron spin, hysteresis while scanning a narrow-band laser through the quantum dot's optical resonance frequency, and non-sinusoidal fringes in the spin echo. Both the coherent electron-spin rotations, implemented with off-resonant ultrafast laser pulses, and the resonant narrowband optical pumping for spin initialization interspersed between ultrafast pulses, play a role in the observed behavior. This effect allows dynamic tuning of the electron Larmor frequency to a value determined by the pulse timing, potentially allowing more complex coherent control operations.

Ladd, Thaddeus D.; Press, David; de Greve, Kristiaan; McMahon, Peter L.; Friess, Benedikt; Schneider, Christian; Kamp, Martin; Höfling, Sven; Forchel, Alfred; Yamamoto, Yoshihisa

2011-02-01

187

Model for the coherent optical manipulation of a single spin state in a charged quantum dot  

NASA Astrophysics Data System (ADS)

The optically driven coherent dynamics associated with the single-shot initialization and readout of a localized spin in a charged semiconductor quantum dot embedded in a realistic structure is theoretically studied using a new Maxwell-pseudospin model. Generalized pseudospin master equation is derived for description of the time evolution of spin coherences and spin populations in terms of the real state pseudospin (coherence) vector including dissipation in the system through spin-relaxation processes. The equation is solved in the time-domain self-consistently with the vector Maxwell equations for the optical wave propagation coupled to it via macroscopic medium polarization. Using the model, the long-lived electron spin coherence left behind a single resonant ultrashort optical excitation of the electron-trion transition in a charged quantum dot is simulated in the low- and high-intensity Rabi oscillation regime. Signatures of the polarized photoluminescence (PL) resulting from the numerical simulations, such as the appearance of a second echo pulse following the excitation and a characteristic nonmonotonic PL trace shape, specific for initial spin-up orientation, are discussed for realization of high-fidelity schemes for coherent readout of a single spin polarization state.

Slavcheva, G.

2008-03-01

188

3He spin filters for spherical neutron polarimetry at the hot neutrons single crystal diffractometer POLI-HEiDi  

NASA Astrophysics Data System (ADS)

3D vector polarisation analysis called also SNP (Spherical Neutron Polarimetry) is a powerful method for the detailed investigation of complex magnetic structures. The precise control of the incoming and scattered neutron polarisations is essential for this technique. Here we show an instrumental setup, that was recently implemented on the new single crystal diffractometer POLI-HEiDi at the FRM II for performing SNP experiments using two 3He spin filters for the production and for the analysis of the neutron polarisation. The design and optimisation procedure for the used spin filter cells are presented. Methods for in-situ measurements of the incoming polarisation as well as the particularities of the using two spin filters and corrections for the time dependent relaxation are discussed. Statistical precision of 1% has been achieved for the measurements of the polarisation matrix under the real experimental conditions using described cells and applying proposed correction method for the data.

Hutanu, V.; Meven, M.; Masalovich, S.; Heger, G.; Roth, G.

2011-06-01

189

Enhanced Spin Squeezing Through Quantum Control of Qudits  

NASA Astrophysics Data System (ADS)

Spin squeezed states have applications in metrology and quantum information processing. Most spin squeezing research to date has focused on ensembles of qubit spins. We explore squeezed state production in an ensemble of spin f>1/2 alkali atoms (qudits). Collective interactions are achieved through coherent quantum feedback of a laser probe, interacting with the ensemble through Faraday interaction. This process is enhanced with control of the atomic qudits, both before and after the collective interaction. Initial preparation increases the collective squeezing parameter through enhancement of resolvable quantum fluctuations, but comes at the price of increased decoherence. We find an optimal state preparation, achieving an increased squeezing parameter while remaining robust to decoherence. After the collective interaction, qudit control maps generated entanglement to different pseudo-spin subspaces where it is metrologically useful, e.g., the clock transition or the stretched state for magnetometry. These considerations highlight the unique capabilities of our platform: we can transfer correlations between subspaces to explore a wider variety of nonclassical states, with ultimate application in sensors or quantum information processors.

Norris, Leigh; Trail, Collin; Jessen, Poul; Deutsch, Ivan

2012-06-01

190

Imaging single spin probes embedded in a conductive diamagnetic layer.  

SciTech Connect

The detection of spin noise by means of scanning tunneling microscopy (STM) has recently been substantially improved by the work presented by Komeda and Manassen (Komeda, T.; Manassen, Y. Appl. Phys. Lett. 2008, 92, 212506). The application of this technique to molecular paramagnets requires the positioning and anchoring of paramagnetic molecules at surfaces. It also requires the possibility of tunneling high current densities into the STM-molecule-substrate tunneling junction. In this letter, we exploit the self-assembly of 1,10-phenantroline on the Au(111) surface to form a diamagnetic matrix that hosts individual molecules and dimers of diphenyl-2-picryl-hydrazyl (DPPH). STM measurements are used to characterize the molecular layer. Electron spin resonance (ESR) measurements elucidate the role of thermal annealing in the preservation of the paramagnetic nature of the DPPH molecules.

Messina, P.; Fradin, F. (Materials Science Division)

2009-01-01

191

Formal Analysis of a SpaceCraft Controller Using SPIN  

Microsoft Academic Search

This paper documents an application of the finite state model checker SPIN to formally analyze a multi-threaded plan execution module. The plan execution module is one component of NASA's New Millennium Remote Agent, an artificial intelligence based spacecraft control system ar- chitecture which launched in October of 1998 as part of the DEEP SPACE 1 mission. The bottom layer of

Klaus Havelund; Michael R. Lowry; John Penix

2001-01-01

192

Formal Analysis of a Space Craft Controller using SPIN  

Microsoft Academic Search

This paper documents an application of the finite state model checker SPIN to formally verify a multi-threaded plan execution programming language. The plan execu- tion language is one component of NASA's New Millennium Remote Agent, an artificial intelligence based spacecraft control system architecture that is scheduled to launch in October of 1998 as part of theDEEP SPACE 1 mission to

Klaus Havelund; Mike Lowryand; John Penix

1998-01-01

193

Determination of spin Hamiltonians from projected single reference configuration interaction calculations. I. Spin 1/2 systems  

NASA Astrophysics Data System (ADS)

The most reliable wave-function based treatments of magnetic systems usually start from a complete active space self-consistent field calculation of the magnetic electrons in the magnetic orbitals, followed by extensive and expensive configuration interaction (CI) calculations. This second step, which introduces crucial spin polarization and dynamic correlation effects, is necessary to reach reliable values of the magnetic coupling constants. The computational cost of these approaches increases exponentially with the number of unpaired electrons. The single-determinantal unrestricted density functional Kohn-Sham calculations are computationally much simpler, and may provide reasonable estimates of these quantities, but their results are strongly dependent on the chosen exchange-correlation potential. The present work, which may be seen as an ab initio transcription of the unrestricted density functional theory technique, returns to the perturbative definition of the Heisenberg Hamiltonian as an effective Hamiltonian, and proposes a direct estimate of its diagonal energies through single reference CI calculations. The differences between these diagonal terms actually determine the entire Heisenberg Hamiltonian. The reference determinants must be vectors of the model space and the components on the other vectors of the model space are cancelled along the iterative process. The method is successfully tested on a series of bicentric and multicentric spin 12 systems. The projected single reference difference dedicated CI treatment is both accurate and of moderate cost. It opens the way to parameter-free calculations of large spin assemblies.

Monari, A.; Maynau, D.; Malrieu, J.-P.

2010-07-01

194

Fluorescence thermometry enhanced by the quantum coherence of single spins in diamond.  

PubMed

We demonstrate fluorescence thermometry techniques with sensitivities approaching 10 mK · Hz(-1/2) based on the spin-dependent photoluminescence of nitrogen vacancy (NV) centers in diamond. These techniques use dynamical decoupling protocols to convert thermally induced shifts in the NV center's spin resonance frequencies into large changes in its fluorescence. By mitigating interactions with nearby nuclear spins and facilitating selective thermal measurements, these protocols enhance the spin coherence times accessible for thermometry by 45-fold, corresponding to a 7-fold improvement in the NV center's temperature sensitivity. Moreover, we demonstrate these techniques can be applied over a broad temperature range and in both finite and near-zero magnetic field environments. This versatility suggests that the quantum coherence of single spins could be practically leveraged for sensitive thermometry in a wide variety of biological and microscale systems. PMID:23650364

Toyli, David M; de las Casas, Charles F; Christle, David J; Dobrovitski, Viatcheslav V; Awschalom, David D

2013-05-06

195

Spin-polarized current of a transistor in single Mn12 molecular magnets.  

PubMed

Focusing on the framework of how to realize the molecular spintronics in a single molecular magnet, we present theoretical studies on the spin-polarized quantum transport behavior through a single Mn12 molecular magnet. Our theoretical results were obtained by carrying out density functional theoretical calculation within the Keldysh nonequilibrium Green function formalism. The ultimate goal of the molecular spintronics is to develop single molecule transistors which generate spin-polarized currents through the molecular magnet. We obtained the density of states, the transmission coefficients and the characteristic features of the current-voltage (I-V) on the spin-polarized transport properties of Mn12 by the theoretical calculation. These results show the possibility for the realization of molecular spintroinics using single molecular magnets. PMID:18047130

Park, Joonho; Yang, Heok; Park, K S; Lee, Eok-Kyun

2007-11-01

196

Testing the validity of the single-spin approximation in inspiral-merger-ringdown waveforms  

NASA Astrophysics Data System (ADS)

Gravitational-wave signals from black-hole binaries with nonprecessing spins are described by four parameters—each black hole’s mass and spin. It has been shown that the dominant spin effects can be modeled by a single spin parameter, leading to the development of several three-parameter waveform models. Previous studies indicate that these models should be adequate for gravitational-wave detection. In this paper we focus on the systematic biases that would result from using them to estimate binary parameters, and consider a one-parameter family of configurations at mass ratio 4 and for one choice of effective single spin. We find that for low-mass binaries within that family of configurations, where the observable waveform is dominated by the inspiral, the systematic bias in all physical parameters is smaller than the parameter uncertainty due to degeneracies between the mass ratio and the spins, at least up to signal-to-noise ratios (SNRs) of 50. For higher-mass binaries, where the merger and ringdown make a greater contribution to the observed signal, the bias in the mass ratio is comparable to its uncertainty at SNRs of only ˜30, and the bias in the measurement of the total spin is larger than the uncertainty defined by the 90% confidence region even at an SNR of only 10. Although this bias may be mitigated in future models by a better choice of single-effective-spin parameter, these results suggest that it may be possible to accurately measure both black-hole spins in intermediate-mass binaries.

Pürrer, Michael; Hannam, Mark; Ajith, P.; Husa, Sascha

2013-09-01

197

Coherent optical manipulation of a single spin state in a charged quantum dot: theory and modelling  

NASA Astrophysics Data System (ADS)

The optically-induced coherent spin dynamics in a charged quantum dot (QD) is studied theoretically using a new dynamical model for rigorous description of circularly polarized ultrashort optical pulse resonant interactions with the electron-trion system. Generalized pseudospin master equation is derived for description of the time evolution of spin coherences and spin populations in terms of the real state pseudospin (coherence) vector including dissipation in the system through spin relaxation processes. The equation is solved in the time domain self-consistently with the vector Maxwell equations for the optical wave propagation coupled to it via macroscopic medium polarization. Using the model the long-lived electron spin coherence left behind a single resonant ultrashort optical excitation of the electron-trion transition in a charged QD is simulated in the lowand high-intensity Rabi oscillations regime. Signatures of the polarized photoluminescence (PL) resulting from the numerical simulations, such as the appearance of a second echo pulse after the excitation and a characteristic PL trace shape, specific for initial spin-up orientation, are discussed for realization of high-fidelity schemes for coherent readout of a single spin polarization state.

Slavcheva, Gabriela M.

2007-10-01

198

Efficient organometallic spin filter between single-wall carbon nanotube or graphene electrodes.  

PubMed

We present a theoretical study of spin transport in a class of molecular systems consisting of an organometallic benzene-vanadium cluster placed in between graphene or single-wall carbon-nanotube-model contacts. Ab initio modeling is performed by combining spin density functional theory and nonequilibrium Green's function techniques. We consider weak and strong cluster-contact bonds. Depending on the bonding we find from 73% (strong bonds) up to 99% (weak bonds) spin polarization of the electron transmission, and enhanced polarization with increased cluster length. PMID:17677656

Koleini, Mohammad; Paulsson, Magnus; Brandbyge, Mads

2007-05-07

199

Spin-one Heisenberg antiferromagnetic chain with exchange and single-ion anisotropies  

NASA Astrophysics Data System (ADS)

Using density-matrix renormalization group calculations, ground-state properties of the spin-1 Heisenberg chain with exchange and single-ion anisotropies in an external field are studied. Our findings confirm and refine recent numerical and analytic results by Sengupta and Batista [Phys. Rev. Lett. 99, 217205 (2007)] on the same model. In particular, we present evidence for two types of biconical (or supersolid) and for two types of spin-flop (or superfluid) structures for chains of finite length. Basic features of the quantum phase diagram may be interpreted qualitatively in the framework of classical spin models.

Peters, D.; McCulloch, I. P.; Selke, W.

2009-04-01

200

Efficient Organometallic Spin Filter between Single-Wall Carbon Nanotube or Graphene Electrodes  

Microsoft Academic Search

We present a theoretical study of spin transport in a class of molecular systems consisting of an organometallic benzene-vanadium cluster placed in between graphene or single-wall carbon-nanotube-model contacts. Ab initio modeling is performed by combining spin density functional theory and nonequilibrium Green's function techniques. We consider weak and strong cluster-contact bonds. Depending on the bonding we find from 73% (strong

Mohammad Koleini; Magnus Paulsson; Mads Brandbyge

2007-01-01

201

Optimal control of stochastic magnetization dynamics by spin current  

NASA Astrophysics Data System (ADS)

Fluctuation-induced stochastic magnetization dynamics plays an important role in spintronics devices. Here we propose that it can be optimally controlled by spin currents to minimize or maximize the Freidlin-Wentzell action functional of the system hence to increase or decrease the probability of the large fluctuations. We apply this method to study the thermally activated magnetization switching problem and to demonstrate the merits of the optimal control strategy.

Wang, Yong; Zhang, Fu-Chun

2013-05-01

202

Time optimal control in spin systems  

Microsoft Academic Search

In this paper, we study the design of pulse sequences for nuclear magnetic resonance spectroscopy as a problem of time optimal control of the unitary propagator. Radio-frequency pulses are used in coherent spectroscopy to implement a unitary transfer between states. Pulse sequences that accomplish a desired transfer should be as short as possible in order to minimize the effects of

Navin Khaneja; Roger Brockett; Steffen J. Glaser

2001-01-01

203

Gate control of the electron spin-diffusion length in semiconductor quantum wells  

NASA Astrophysics Data System (ADS)

The spin diffusion length is a key parameter to describe the transport properties of spin polarized electrons in solids. Electrical spin injection in semiconductor structures, a major issue in spintronics, critically depends on this spin diffusion length. Gate control of the spin diffusion length could be of great importance for the operation of devices based on the electric field manipulation and transport of electron spin. Here we demonstrate that the spin diffusion length in a GaAs quantum well can be electrically controlled. Through the measurement of the spin diffusion coefficient by spin grating spectroscopy and of the spin relaxation time by time-resolved optical orientation experiments, we show that the diffusion length can be increased by more than 200% with an applied gate voltage of 5?V. These experiments allow at the same time the direct simultaneous measurements of both the Rashba and Dresselhaus spin-orbit splittings.

Wang, G.; Liu, B. L.; Balocchi, A.; Renucci, P.; Zhu, C. R.; Amand, T.; Fontaine, C.; Marie, X.

2013-09-01

204

Gate control of the electron spin-diffusion length in semiconductor quantum wells  

PubMed Central

The spin diffusion length is a key parameter to describe the transport properties of spin polarized electrons in solids. Electrical spin injection in semiconductor structures, a major issue in spintronics, critically depends on this spin diffusion length. Gate control of the spin diffusion length could be of great importance for the operation of devices based on the electric field manipulation and transport of electron spin. Here we demonstrate that the spin diffusion length in a GaAs quantum well can be electrically controlled. Through the measurement of the spin diffusion coefficient by spin grating spectroscopy and of the spin relaxation time by time-resolved optical orientation experiments, we show that the diffusion length can be increased by more than 200% with an applied gate voltage of 5?V. These experiments allow at the same time the direct simultaneous measurements of both the Rashba and Dresselhaus spin-orbit splittings.

Wang, G.; Liu, B. L.; Balocchi, A.; Renucci, P.; Zhu, C. R.; Amand, T.; Fontaine, C.; Marie, X.

2013-01-01

205

Gate control of the electron spin-diffusion length in semiconductor quantum wells.  

PubMed

The spin diffusion length is a key parameter to describe the transport properties of spin polarized electrons in solids. Electrical spin injection in semiconductor structures, a major issue in spintronics, critically depends on this spin diffusion length. Gate control of the spin diffusion length could be of great importance for the operation of devices based on the electric field manipulation and transport of electron spin. Here we demonstrate that the spin diffusion length in a GaAs quantum well can be electrically controlled. Through the measurement of the spin diffusion coefficient by spin grating spectroscopy and of the spin relaxation time by time-resolved optical orientation experiments, we show that the diffusion length can be increased by more than 200% with an applied gate voltage of 5?V. These experiments allow at the same time the direct simultaneous measurements of both the Rashba and Dresselhaus spin-orbit splittings. PMID:24052071

Wang, G; Liu, B L; Balocchi, A; Renucci, P; Zhu, C R; Amand, T; Fontaine, C; Marie, X

2013-09-20

206

Characteristics of silicon nanowire single electron transistor pairs as readout devices in impurity spin qubit structures  

NASA Astrophysics Data System (ADS)

Quantum computer schemes based on electron and nuclear spins of single dopant atoms in silicon are attractive candidates for large scale quantum information processing. Silicon based Single Electron Transistors (SET) promise to enable single spin readout through spin dependent charge measurements. We present results from our development of silicon SET structures that are designed as pairs for integration with two P atoms. Devices with undoped, 10 nm wide silicon wires are formed by electron beam lithography without size reduction by stress limited oxidation. Device characterization at 4.2 K shows charging energies of 5-10 meV and total capacitances of 10 aF. We will discuss Si-SET fabrication yields, critical performance criteria (offset charges, random telegraph signals), and the coupling of Si-SETs to radio frequency tank circuits in light of the very stringent requirements posed by qubit devices.

Park, Sang-Joon; Liddle, James Alexander; Schenkel, Thomas; Persaud, Arun; Nilsson, Joakim; Bokor, Jeffrey

2004-03-01

207

Shot noise and spin-orbit coherent control of entangled and spin-polarized electrons  

NASA Astrophysics Data System (ADS)

We extend our previous work on shot noise for entangled and spin polarized electrons in a beam-splitter geometry with spin-orbit (SO) interaction in one of the incoming leads (lead 1). In addition to accounting for both the Dresselhaus and the Rashba spin-orbit terms, we present general formulas for the shot noise of singlet and triplets states derived within the scattering approach. We determine the full scattering matrix of the system for the case of leads with two orbital channels coupled via weak SO interactions inducing channel anticrossings. We show that this interband coupling coherently transfers electrons between the channels and gives rise to an additional modulation angle—dependent on both the Rashba and Dresselhaus interaction strengths—which allows for further independent coherent control of the electrons traversing the incoming leads. We derive explicit shot noise formulas for a variety of correlated pairs (e.g., Bell states) and lead spin polarizations. Interestingly, the singlet and each of the triplets defined along the quantization axis perpendicular to lead 1 (with the local SO interaction) and in the plane of the beam splitter display distinctive shot noise for injection energies near the channel anticrossings; hence, one can tell apart all the triplets, in addition to the singlet, through noise measurements. We also find that spin-orbit induced backscattering within lead 1 reduces the visibility of the noise oscillations, due to the additional partition noise in this lead. Finally, we consider injection of two-particle wavepackets into leads with multiple discrete states and find that two-particle entanglement can still be observed via noise bunching and antibunching.

Egues, J. Carlos; Burkard, Guido; Saraga, D. S.; Schliemann, John; Loss, Daniel

2005-12-01

208

Strong tuning of Rashba spin-orbit interaction in single InAs nanowires.  

PubMed

A key concept in the emerging field of spintronics is the gate voltage or electric field control of spin precession via the effective magnetic field generated by the Rashba spin-orbit interaction. Here, we demonstrate the generation and tuning of electric field induced Rashba spin-orbit interaction in InAs nanowires where a strong electric field is created by either a double gate or a solid electrolyte surrounding gate. In particular, the electrolyte gating enables 6-fold tuning of Rashba coefficient and nearly 3 orders of magnitude tuning of spin relaxation time within only 1 V of gate bias. Such a dramatic tuning of spin-orbit interaction in nanowires may have implications in nanowire-based spintronic devices. PMID:22545669

Liang, Dong; Gao, Xuan P A

2012-05-04

209

Electron Spin Resonance in an Irradiated Single Crystal of Dimethylglyoxime  

Microsoft Academic Search

The paramagnetic resonance of gamma-irradiated single crystals of dimethylglyoxime has been measured at 23 kMc\\/sec and 9 kMc\\/sec for various orientations of the crystal in the magnetic field. The resonance pattern was found to have a triplet structure caused by coupling to a single N14 nucleus. Both the nuclear coupling and the spectroscopic splitting factor were found to be anisotropic

Ichiro Miyagawa; Walter Gordy

1959-01-01

210

Quantum control and measurement of spins in laser cooled gases  

NASA Astrophysics Data System (ADS)

Quantum information processing (QIP) requires three important ingredients: (i) preparing a desired initial quantum state, usually highly pure; (ii) controlling the dynamical evolution, usually via a desired unitary transformation; (iii) measuring the desired information encoded in the final quantum state. Many physical platforms are being developed for QIP, including trapped ions, semiconductor quantum dots, and atoms in optical lattices. In these cases, it is the spins of the system that encode the quantum information. Spins are natural carriers of quantum information given their long coherence times and our ability to control them with a variety of external electromagnetic fields. In addition, spins in laser-cooled atomic gases are an excellent testbed for exploring QIP protocols because of our ability to initially prepare highly pure states and employ the well-developed tools of quantum optics and coherent spectroscopy. In this talk I will give an overview of recent theory and experiment in the control and measurement of spins in laser-cooled atomic gases. We consider the hyperfine magnetic sublevels in the ground electronic states of ^133Cs, a 16-dimensional Hilbert space. We can explore all three ingredients described above: preparation of an arbitrary superposition state, evolution through an arbitrary unitary matrix, and readout through quantum state reconstruction of the full density matrix. We employ the tools of optimal quantum control and quantum estimation theory. The implementation involves atoms controlled by radio-frequency, microwave, a optical fields, and measured via polarization spectroscopy. The experiment is performed in the group of Prof. Poul S. Jessen, University of Arizona. This work was supported by the National Science Foundation.

Deutsch, Ivan

2012-10-01

211

Single mode approximation for sub-Ohmic spin-boson model: adiabatic limit and critical properties  

NASA Astrophysics Data System (ADS)

In this work, we study the quantum phase transition in the sub-Ohmic spin-boson model using a single-mode approximation. It combines the rotating wave transformation and the transformations used in the numerical renormalization group (NRG). Analytical results for the critical coupling strength ? c , the magnetic susceptibility ?( T), and the spin-spin correlation function C( ?) at finite temperatures are obtained and further confirmed by numerical results. We obtain the same ? c as the mean-field approximation. The critical exponents are classical: ? = 1/2, ? = 3, ? = 1, x = 1/2, y t ? = 1/2, in agreement with the spin-boson model in 0 < s < 1/2 regime. C( ?) has nontrivial behavior reflecting coherent oscillation with temperature dependent damping effects due to the environment. We point out that the original NRG has a problem with the crossover temperature T ?, and propose a chain Hamiltonian possibly suitable for implementing NRG without boson state truncation error.

Liu, Fei-Ran; Tong, Ning-Hua

2013-04-01

212

Influences of DMI on spin-polarized current through a single-molecule magnet  

NASA Astrophysics Data System (ADS)

We theoretically investigate the influences of the Dzyaloshinskii-Moriya interaction (DMI) on the spin-polarized transport through a single-molecular magnets, which is weakly coupled to ferromagnetic lead-L(pL) and nonmagnetic lead-R. The spin current is obtained by means of the rate-equation approach in the sequential-tunneling region. Due to the coherent superposition of the molecular state |1 induced by the DMI, we can observe the continuous pure spin current and negative differential conductance (NDC) under the full polarization pL=1 condition and polarization reversal of spin-current in the case of 0

Luo, Bo; Liu, Juan; Yao, Kai-Lun

2013-11-01

213

Electrostatic spin crossover in a molecular junction of a single-molecule magnet Fe{2}.  

PubMed

Spin crossover by means of an electric bias is investigated by spin-polarized density-functional theory calculations combined with the Keldysh nonequilibrium Green's technique in a molecular junction, where an individual single-molecule magnet Fe{2}(acpybutO)(O{2}CMe)(NCS){2} is sandwiched between two infinite Au(100) nanoelectrodes. Our study demonstrates that the spin crossover, based on the Stark effect, is achieved in this molecular junction under an electric bias but not in the isolated molecule under external electric fields. The main reason is that the polarizability of the molecular junction has an opposite sign to that of the isolated molecule, and thus from the Stark effect the condition for the spin crossover in the molecular junction is contrary to that in the isolated molecule. PMID:22304282

Hao, Hua; Zheng, XiaoHong; Song, LingLing; Wang, RuiNing; Zeng, Zhi

2012-01-05

214

Examining the effects of balloon control ring on ring spinning  

Microsoft Academic Search

The ring spinning process has been used to produce fine and high quality staple fibre yarns. The stability of the rotating\\u000a yarn loop (i.e. balloon) between the yarn-guide and the traveller-ring is crucial to the success and economics of this process.\\u000a Balloon control rings are used to contain the yarn-loop, by reducing the yarn tension and decreasing the balloon flutter

Zheng-Xue Tang; W. Barrie Fraser; Lijing Wang; Xungai Wang

2008-01-01

215

Measurable quantum geometric phase from a rotating single spin.  

PubMed

We demonstrate that the internal magnetic states of a single nitrogen-vacancy defect, within a rotating diamond crystal, acquire geometric phases. The geometric phase shift is manifest as a relative phase between components of a superposition of magnetic substates. We demonstrate that under reasonable experimental conditions a phase shift of up to four radians could be measured. Such a measurement of the accumulation of a geometric phase, due to macroscopic rotation, would be the first for a single atom-scale quantum system. PMID:23004241

Maclaurin, D; Doherty, M W; Hollenberg, L C L; Martin, A M

2012-06-12

216

Magnetic-field-induced quantum criticality in a spin- S planar ferromagnet with single-ion anisotropy  

NASA Astrophysics Data System (ADS)

The effects of single-ion anisotropy on quantum criticality in a d-dimensional spin- S planar ferromagnet is explored by means of the two-time Green's function method. We work at the Tyablikov decoupling level for exchange interactions and the Anderson-Callen decoupling level for single-ion anisotropy. In our analysis a longitudinal external magnetic field is used as the non-thermal control parameter and the phase diagram and the quantum critical properties are established for suitable values of the single-ion anisotropy parameter D. We find that the single-ion anisotropy has sensible effects on the structure of the phase diagram close to the quantum critical point. However, for values of the uniaxial crystal-field parameter below a positive threshold, the conventional magnetic-field-induced quantum critical scenario remains unchanged.

Mercaldo, M. T.; Rabuffo, I.; De Cesare, L.; Caramico D'Auria, A.

2013-08-01

217

Dynamical decoupling of a single-electron spin at room temperature  

NASA Astrophysics Data System (ADS)

Here we report the increase of the coherence time T2 of a single-electron spin at room temperature by using dynamical decoupling. We show that the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence can prolong the T2 of a single nitrogen-vacancy center in diamond up to 2.44 ms compared to the Hahn echo measurement where T2=400?s. Moreover, by performing spin-locking experiments we demonstrate that with CPMG the maximum possible T2 is reached. On the other hand, we do not observe a strong increase of the coherence time in nanodiamonds, possibly due to the short spin-lattice relaxation time T1=100?s (compared to T1=5.93 ms in bulk). An application for detecting low magnetic fields is demonstrated, where we show that the sensitivity using the CPMG method is improved by about a factor of 2 compared to the Hahn echo method.

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

2011-02-01

218

Ultrafast spin-motion entanglement and interferometry in single atomic qubits  

NASA Astrophysics Data System (ADS)

We report entanglement between the hyperfine spin state and motional dynamics of a single atom on a timescale of 15 ns. We extract single pulses from a picosecond mode-locked laser and split them into short pulse trains tailored to create the desired spectrum by tuning the relative delays and frequency shifts appropriately. The resulting interaction imparts a momentum transfer of 2k to each of the two spin states in opposite directions. We apply pairs of momentum kicks to create an interferometer and probe the collapse and revival of spin coherence as the motional wavepacket is split and recombined. This technique holds promise for applications such as interferometry [1] and scalable entangling gates [2,3]. [4pt] [1] J.F. Poyatos et al., PRA 54, 1532 (1996)[0pt] [2] J.J. Garcia-Ripoll et al., PRL 91, 157901 (2003)[0pt] [3] L.-M. Duan, PRL 93, 100502 (2004).

Senko, Crystal; Mizrahi, Jonathan; Campbell, Wesley C.; Johnson, Kale G.; Conover, Charles W. S.; Monroe, Christopher

2012-06-01

219

Spin incommensurability varies linearly with hole content in single-layer Bi2201 cuprate  

NASA Astrophysics Data System (ADS)

We have performed inelastic neutron scattering measurements on the single-layer cuprate Bi2+xSr2-xCuO6+y (Bi2201) with x=0.2, 0.3, 0.4 and 0.5, a doping range that spans the spin-glass (SG) to superconducting (SC) phase boundary [1]. The doping evolution of low energy spin fluctuations (11 meV) was found to be characterized by a change of incommensurate modulation wave vector from the tetragonal [110] to [100]/[010] directions, while maintaining a linear relation between the incommensurability and the hole concentration, ? p. In the SC regime, the spectral weight is strongly suppressed below ˜4 meV. Similarities and differences in the spin correlations between Bi2201 and the prototypical single-layer system La2-xSrxCuO4 will be discussed.[4pt] [1] M. Enoki et al., arXiv:1205.3301.

Tranquada, John; Enoki, M.; Fujita, M.; Nishizaki, T.; Yamada, K.; Iikubo, S.; Singh, D. K.; Chang, S.

2013-03-01

220

Phenomenology of single-spin effects in hadron production at high energies  

SciTech Connect

Within a phenomenological model, experimental data on the transverse single-spin asymmetry (A{sub N}) and polarization (P{sub N}) of hadrons are analyzed for 68 different inclusive reactions in hadron-hadron, hadron-nucleus, nucleus-nucleus, and lepton-nucleon interactions. A mechanism that is based on the interaction of the chromomagnetic moment of massive constituent quarks with the effective nonuniform chromomagnetic field of QCD strings formed after the initial color exchange is considered as the origin of single-spin effects. Quark-spin precession in the chromomagnetic field is taken into account. Dynamical masses and anomalous chromomagnetic moments are estimated for constituent u, d, s, c, and b quarks.

Abramov, V. V., E-mail: Victor.Abramov@ihep.r [Institute of High Energy Physics (Russian Federation)

2009-11-15

221

No single answer controls corrosion  

SciTech Connect

This article examines the variety of techniques used by utilities to control corrosion. The article includes field experiences on the use of methyl ethyl ketoxime as an alternative to the toxic hydrazine and experiences in monitoring for dissolved oxygen, levels of iron, copper, ammonia, cation conductivity and scavenger residuals. The methyl ethyl ketoxime was tested in a 2,400-psig, 1,000 F superheat steam generator and three bayonet-type boilers at 752 F.

Rumpf, R.R.; Gonzalez, W.J.

1993-01-01

222

Controllable effects of quantum fluctuations on spin free-induction decay at room temperature  

Microsoft Academic Search

Fluctuations of local fields cause decoherence of quantum objects. It is generally believed that at high temperatures, thermal noises are much stronger than quantum fluctuations unless the thermal effects are suppressed by certain techniques such as spin echo. Here we report the discovery of strong quantum-fluctuation effects of nuclear spin baths on free-induction decay of single electron spins in solids

Xin-Yu Pan; Gang-Qin Liu; Dong-Qi Liu; Zhan-Feng Jiang; Nan Zhao; Ren-Bao Liu

2011-01-01

223

Optical Control of One and Two Hole Spins in Interacting Quantum Dots.  

National Technical Information Service (NTIS)

A single hole spin in a semiconductor quantum dot has emerged as a quantum bit that is potentially superior to an electron spin. A key feature of holes is that they have a greatly reduced hyperfine interaction with nuclear spins, which is one of the bigge...

A. Greilich A. S. Bracker D. Gammon D. Kim S. G. Carter

2011-01-01

224

Ultrafast coherent control of Spin- and magnetization dynamics  

NASA Astrophysics Data System (ADS)

The manipulating of the electron spin is not only relevant for magnetic storage but may also lead to the development of novel electronic devices with new characteristics (so-called spintronics). Therefore, the investigations of the physical mechanisms underlying the manipulation of electron spin in ferromagnets, semiconductors and hybrid ferromagnet/semiconductor structures constitute at present an exciting area of research. Due to the fact that in antiferromagnets no angular momentum is associated with the order parameter, spin dynamics in these materials is intrinsically much faster than in ferromagnets, expanding the area of spin-dynamics even more ^[1]. Femto-second laser excitation opens the way to excite magnetic systems on a time scale much shorter than fundamental time scales such as spin-lattice relaxation or precession times. This has already lead to surprising and exciting results like changes in magnetization on a sub-picoscond time scale ^[2]. Fs laser pulses can also be used to generate short magnetic field pulses, that allow coherent control of the magnetization dynamics ^[3] . Recent progress in this area will be discussed, demonstrating in particular the use of time resolved magneto-optical methods to investigate the static and dynamic properties of magnetically ordered structures and the possibility of direct spin manipulation with optical fields^[4,5]. [1] A. V. Kimel, A. Kirilyuk, A. Tsvetkov, R. V. Pisarev, and Th. Rasing, Nature 429 850 (2004). [2] Spin Dynamics in Confined Magnetic Structures I-II, edited by B. Hillebrands and K. Ounadjela (Springer-Verlag, Berlin, 2002-2003). [3] Th. Gerrits, H. A. M. van den Berg, J. Hohlfeld, L. Bär, and Th. Rasing, Nature 418, 509 (2002). [4] A. Kimel, A. Kirilyuk, P.A. Usachev, R.V. Pisarev, A.M. Balbashov and Th. Rasing, Nature 435, 655 (2005) [5] F. Hansteen, A.V. Kimel, A. Kirilyuk and Th. Rasing, PRL 95, 047402-1 (2005). Acknowledgements This work was partially supported by the European IST network SPINOSA, the RTN network DYNAMICS, the Russian Foundation for Basic Research (RFBR), Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) as well as Stichting voor Fundamenteel Onderzoek der Materie (FOM).

Rasing, Theo

2006-03-01

225

Work distribution functions for hysteresis loops in a single-spin system  

Microsoft Academic Search

We compute the distribution of the work done in driving a single Ising spin with a time-dependent magnetic field. Using Glauber dynamics we perform Monte Carlo simulations to find the work distributions at different driving rates. We find that in general the work distributions are broad with a significant probability for processes with negative dissipated work. The special cases of

Rahul Marathe; Abhishek Dhar

2005-01-01

226

Ergodicity properties of energy conserving single spin flip dynamics in the XY model  

Microsoft Academic Search

A single spin flip stochastic energy conserving dynamics for the XY model is considered. We study the ergodicity properties of the dynamics. It is shown that phase space trajectories densely fill the geometrically connected parts of the energy surface. We also show that while the dynamics is discrete and the phase point jumps around, it cannot make transitions between closed

Abhishek Dhar

1998-01-01

227

Electron spin decoherence by interacting nuclear spins in quantum dot II: Coherent control  

NASA Astrophysics Data System (ADS)

Due to the hyperfine interaction, the nuclear spins in a quantum dot, driven by nuclear spin pair-wise flip-flops, evolve in different pathways in the Hilbert space for different electron spin states, resulting in the electron-nuclei entanglement and hence the electron spin decoherence. When the electron spin is flipped by a pulse, the nuclear spin states for different electron spin states swap their pathways, and could intersect in the Hilbert space, which disentangles the electron and the nuclei and hence restores the electron spin coherence. The coherence restoration by disentanglement and the conventional spin echo in ensemble dynamics are fundamentally different and generally occur at different time. Pulse sequences can be applied to force the disentanglement to coincide with the spin echo, making the coherence recovery observable in ensemble dynamics. This work was supported by NSF DMR-0403465, NSA/ARO, and DARPA/AFOSR.

Liu, Ren-Bao; Yao, Wang; Sham, Lu J.

2006-03-01

228

Spin-selective optical absorption of singly charged excitons in a quantum dot  

Microsoft Academic Search

We report high resolution laser absorption spectroscopy of a single InGaAs\\/GaAs self-assembled quantum dot embedded in a field-effect structure. We show experimentally that the interband optical absorption to the lower Zeeman branch of the singly charged exciton is strongly inhibited due to spin (Pauli) blockade of the optical transition. At high magnetic fields the optical absorption to the upper Zeeman

Alexander Högele; Martin Kroner; Stefan Seidl; Khaled Karrai; Mete Atatüre; Jan Dreiser; Atac Imamoglu; Richard J. Warburton; Antonio Badolato; Brian D. Gerardot; Pierre M. Petroff

2005-01-01

229

Spin-1 atoms in optical superlattices: Single-atom tunneling and entanglement  

SciTech Connect

We examine spinor Bose-Einstein condensates in optical superlattices theoretically using a Bose-Hubbard Hamiltonian that takes spin effects into account. Assuming that a small number of spin-1 bosons is loaded in an optical potential, we study single-particle tunneling that occurs when one lattice site is ramped up relative to a neighboring site. Spin-dependent effects modify the tunneling events in a qualitative and quantitative way. Depending on the asymmetry of the double well, different types of magnetic order occur, making the system of spin-1 bosons in an optical superlattice a model for mesoscopic magnetism. We use a double-well potential as a unit cell for a one-dimensional superlattice. Homogeneous and inhomogeneous magnetic fields are applied, and the effects of the linear and the quadratic Zeeman shifts are examined. We also investigate the bipartite entanglement between the sites and construct states of maximal entanglement. The entanglement in our system is due to both orbital and spin degrees of freedom. We calculate the contribution of orbital and spin entanglements and show that the sum of these two terms gives a lower bound for the total entanglement.

Wagner, Andreas; Bruder, Christoph; Demler, Eugene [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)

2011-12-15

230

Effect of Addition of Al to Single-Crystalline CoFe Electrodes on Nonlocal Spin Signals in Lateral Spin-Valve Devices  

NASA Astrophysics Data System (ADS)

Using single-crystalline spin injectors and detectors, we examine the effect of the addition of Al to CoFe electrodes on nonlocal spin signals in metallic lateral spin valves (LSVs). A molecular beam epitaxy technique enables us to obtain Heusler-alloy-like CoFeAl epitaxial layers with an ordered B2 structure. The LSVs with the CoFeAl electrodes show a remarkable enhancement of the nonlocal spin signals, six times larger than that of the LSV with the CoFe electrodes, at room temperature. The relatively low electrical resistivity of the CoFeAl electrodes means that the enhancement of the spin signals originates from an increase in the spin polarization due to the Al addition to CoFe.

Oki, Soichiro; Yamada, Shinya; Hashimoto, Naoki; Miyao, Masanobu; Kimura, Takashi; Hamaya, Kohei

2012-06-01

231

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

Microsoft Academic Search

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

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

2007-01-01

232

Tunable topological insulators with a single spin-polarized surface Dirac cone  

NASA Astrophysics Data System (ADS)

The topological insulator is a fundamentally new time-reversal-invariant topologically ordered phase of matter, which exhibits exotic quantum-Hall-like behavior even in the absence of an applied magnetic field. These materials are characterized by a spin-orbit coupling induced bulk energy gap and an odd number of spin-polarized Dirac cones localized on their surfaces. In this talk, I will review the first experimental realization of the topological insulator in Bi1-xSbx [1,2], and then report our recent experimental discovery and findings of a new generation of topological insulators with order-of-magnitude larger bulk band gaps and a single spin-helical surface Dirac cone [3,4]. I will also discuss a novel `effective gating' technique that can be used to optimize the insulating properties of the bulk, and to tune the Dirac carrier density on the surfaces of these new topological insulators [5]. These experiments pave the way for future transport based studies of topological insulator devices, and offer the potential for a graphene-like revolution to take place for topological insulators. [1] ``A topological Dirac insulator in a quantum spin Hall phase'', D. Hsieh et al., Nature 452, 970 (2008). [2] ``Observation of unconventional quantum spin textures in topological insulators'', D. Hsieh et al., Science 323, 919 (2009). [3] ``Observation of a large-gap topological-insulator class with a single Dirac cone on the surface'', Y. Xia et al., Nature Phys. 5, 398 (2009). [4] ``Observation of time-reversal-protected single-Dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3'', D. Hsieh et al., Phys. Rev. Lett., 103, 146401 (2009). [5] ``A tunable topological insulator in the spin helical Dirac transport regime'', D. Hsieh et al., Nature 460, 1101 (2009).

Hsieh, David

2010-03-01

233

Current fluctuations in noncollinear single-electron spin-valve transistors  

NASA Astrophysics Data System (ADS)

We present a theoretical framework to analyze fluctuations of electric current through a noncollinear single-electron spin-valve transistor in the limit of weak tunnel coupling. The system under consideration consists of two tunnel junctions that connect a small, nonmagnetic metallic island to two ferromagnetic leads with noncollinear magnetization. We study the current noise spectrum as a function of bias voltage, frequency, and the relative angle between the leads’ magnetization directions and find that both the zero- and the finite-frequency current noise are strongly affected by charging energy and spin accumulation in the island.

Lindebaum, Stephan; König, Jürgen

2012-09-01

234

UNIQUE DESCRIPTION FOR SINGLE TRANSVERSE SPIN ASYMMETRIES IN DIS AND HADRONIC COLLISIONS.  

SciTech Connect

We derive a unique formula for the single-transverse-spin asymmetry in semi-inclusive hadron production in deep inelastic scattering, valid for all transverse momentum region. Based on this, we further study the integrated asymmetry weighted with transverse-momentum. They can be evaluated in terms of the twist-three quark-gluon correlation functions, which are responsible for the single spin asymmetry in single inclusive hadron production in hadronic collisions. By using the fitted twist-three functions from the hadronic collision data, we find a consistent description for SSAs in deep inelastic scattering. This demonstrates that we have a unique picture for SSAs in these two processes, and shall provide important guidelines for future studies.

YUAN, F.

2006-12-18

235

Rashba control for the spin excitation of a fully spin-polarized vertical quantum dot  

NASA Astrophysics Data System (ADS)

Far-infrared radiation absorption of a quantum dot with few electrons in an orthogonal magnetic field could monitor the crossover to the fully spin-polarized state. A Rashba spin-orbit coupling can tune the energy and the spin density of the first excited state that has a spin texture carrying one extra unit of angular momentum. The spin-orbit coupling can squeeze a flipped spin density at the center of the dot and can increase the gap in the spectrum.

Lucignano, P.; Jouault, B.; Tagliacozzo, A.; Altshuler, B. L.

2005-03-01

236

Single vortex fluctuations in a superconducting chip as generating dephasing and spin flips in cold atom traps  

NASA Astrophysics Data System (ADS)

We study trapping of a cold atom by a single vortex line in an extreme type-II superconducting chip, allowing for pinning and friction. We evaluate the atom's spin flip rate and its dephasing due to the vortex fluctuations in equilibrium and find that they decay rapidly when the distance to the vortex exceeds the magnetic penetration length. We find that there are special spin orientations, depending on the spin location relative to the vortex, at which spin dephasing is considerably reduced while perpendicular directions have a reduced spin flip rate.

Fruchtman, Amir; Horovitz, Baruch

2012-09-01

237

Chip-Scale Nanofabrication of Single Spins and Spin Arrays in Diamond  

SciTech Connect

We demonstrate a technique to nanofabricate nitrogen vacancy (NV) centers in diamond based on broad-beam nitrogen implantation through apertures in electron beam lithography resist. This method enables high-throughput nanofabrication of single NV centers on sub-100-nm length scales. Secondary ion mass spectroscopy measurements facilitate depth profiling of the implanted nitrogen to provide three-dimensional characterization of the NV center spatial distribution. Measurements of NV center coherence with on-chip coplanar waveguides suggest a pathway for incorporating this scalable nanofabrication technique in future quantum applications.

Toyli, David M.; Weis, Christoph D.; Fuchs, D.; Schenkel, Thomas; Awschalom, David D.

2010-07-02

238

Random spin freezing in single crystalline Ce2CuSi3  

NASA Astrophysics Data System (ADS)

We present the results of ac and dc susceptibility, magnetization and magnetic relaxation measurements performed on single crystalline Ce2CuSi3, a hexagonal AlB2-type nonmagnetic atom disorder compound, with the magnetic field applied along two typical crystallographic directions, i.e. H?c-axis and H//c-axis. For both the directions, spin-glass state is confirmed to form at low temperature with almost the same spin freezing temperature Tf (~2.07K), initial frequency shift ?Tf (~0.015) and activation energy Ea/kB (~10.04 K) in zero dc field. Strong magnetic anisotropy is also found to be a significant feature of this compound. The experimental results and the dynamical analyses suggest that spin-glass behavior is intrinsic to the title compound.

Li, D. X.; Nimori, S.; Ohta, S.; Yamamura, Y.; Shikama, Y.

2012-12-01

239

Measurement of Single and Double Spin Asymmetries in Deep Inelastic Pion Electroproduction with a Longitudinally Polarized Target  

SciTech Connect

We report the first measurement of the transverse momentum dependence of double spin asymmetries in semi-inclusive production of pions in deep inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). A significant non-zero $\\sin2\\phi$ single spin asymmetry was also observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton. The azimuthal modulations of single spin asymmetries have been measured over a wide kinematic range.

Avakian, H; Bosted, P; Elouadrhiri, L; Adhikari, K P; Aghasyan, M; Amaryan, M; Anghinolfi, M; Baghdasaryan, H; Ball, J; Battaglieri, M; Bedlinskiy, I; Biselli, A S; Branford, D; Briscoe, W J; Brooks, W; Carman, D S; Casey, L; Cole, P L; Collins, P; Crabb, D; Crede, V; D& #x27; Angelo, A; Daniel, A; Dashyan, N; DeVita, R; DeSanctis, E; Deur, A; Dey, B; Dhamija, S; Dickson, R; Djalali, C; Dodge, G; Doughty, D; Dupre, R; El Alaoui, A; Eugenio, P; Fegan, S; Fersch, M; Guler, N; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Hassall, N; Heddle, D; Hicks, K; Holtrop, M; Ilieva, Y; Ireland, D G; Isupov, E L; Jawalkar, S S; Jo, H S; Joo, K; Keller, D; Khandaker, M; Khetarpal,; Kim, W; Klein, A; Klein, F J; Konczykowski, P; Kubarovsky, V; Kuhn, S E; Kuleshov, S V; Kuznetsov, V; Livingston, K; Lu, H Y; Markov, N; Mayer, M; McAndrew, J; McCracken, M E; McKInnon, B; Meyer, C A; Mineeva, T; Mirazita, M; Mokeev, V; Moreno, B; Moriya, K; Morrison, B; Moutarde, H; Munevar, E; Nadel-Turonski, P; Nasseripour, R; Niccolai, S; Niculescu, G; Niculescu, I; Niroula, M R; Osipenko, M; Ostrovidov, A I; Paremuzyan, R; Park, K; Park, S; Pasyuk, E; Anefalos Pereira, S; Perrin, Y; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Protopopescu; Raue, B A; Ricco, G; Ripani, M; Rosner, G; Rossi, P; Sabatie, F; Saini, M S; Salamanca, J; Salgado, C; Schumacher, R A; Seder, E; Seraydaryan, H; Sharabian, Y G; Sober, D I; Sokhan, D; Stapanyan, S S; Stepanyan, S; Stoler, P; Strauch, S; Suleiman, R; Taiuti, M; Tedeschi, D J; Tkachenko, S; Ungaro, M; Vernarsky, B; Vineyard, M F; Voutier, E; Watts, D P; Weinstein, L B; Weygand, D P; Wood, M H; Zhang, J; Zhao, B

2010-12-01

240

Interband optical injection and control of electron spin populations and ballistic spin currents in bulk semiconductors  

Microsoft Academic Search

This thesis theoretically studies interband optical injection of spin current, carrier spin, current, and carrier population by one-photon absorption, two-photon absorption, and the interference of one- and two-photon absorption (\\

Ravi Dinesh Rama Bhat

2006-01-01

241

Cotunneling signatures of spin-electric coupling in frustrated triangular single-molecule magnets  

NASA Astrophysics Data System (ADS)

The ground state (GS) of frustrated (antiferromagnetic) triangular single-molecule magnets is characterized by two total-spin S = 1/2 doublets with opposite chirality. According to a group theory analysis [M. Trif et al., Phys. Rev. Lett. 101, 217201 (2008)] an external electric field can efficiently couple these two chiral spin states, even when the spin-orbit interaction (SOI) is absent. The strength of this coupling, d, is determined by an off-diagonal matrix element of the dipole operator, which can be calculated by ab-initio methods [M. F. Islam et al., Phys. Rev. B 82, 155446 (2010)]. In this work we propose that Coulomb-blockade transport experiments in the cotunneling regime can provide a direct way to determine the spin-electric coupling strength. Indeed, an electric field generates a d-dependent splitting of the GS manifold, which can be detected in the inelastic cotunneling conductance. Our theoretical analysis is supported by master-equation calculations of quantum transport in the cotunneling regime. We employ a Hubbard-model approach to elucidate the relationship between the Hubbard parameters t and U, and the spin-electric coupling constant d. This allows us to predict the regime in which the coupling constant d can be extracted from experiment.

Nossa, Javier; Canali, Carlo

2013-03-01

242

Magnetic anisotropy and high-spin effects in single-molecule transistors  

NASA Astrophysics Data System (ADS)

Fabrication of single-molecule transistors where electron transport occurs through an individual molecule has become possible due to the recent progress in molecular electronics. Three-terminal configuration allows charging molecules and performing transport spectroscopy in multiple redox states. Single-molecule magnets combining large spin with uniaxial anisotropy are of special interest as appealing candidates for high density memory applications and quantum information processing. We study single-molecule magnets Fe4. Three-terminal junctions are fabricated using electromigration of gold nanowires followed by a self-breaking. High-spin Kondo effect and inelastic cotunneling excitations show up in transport measurements. Several excitations feature the energy close to the energy of zero-field splitting (ZFS) of a ground spin multiplet in bulk. This splitting is caused by the anisotropy and is a hallmark of single-molecule magnets. We observe nonlinear Zeeman effect due to a misalignment of an anisotropy axis and a magnetic field direction. The ZFS energy is increased in oxidized and reduced states of the molecule indicating enhancement of the anisotropy in these states.

Zyazin, Alexander; van den Berg, Johan; Osorio, Edgar; Konstantinidis, Nikos; Leijnse, Martin; May, Falk; Hofstetter, Walter; Danieli, Chiara; Cornia, Andrea; Wegewijs, Maarten; van der Zant, Herre

2011-03-01

243

Mechanical read out of a single electron spin in a carbon nanotube  

NASA Astrophysics Data System (ADS)

The spin of a single electron in a suspended carbon nanotube can be read out by using its coupling to the nano-mechanical motion of the nanotube. To show this, we consider a single electron confined within a quantum dot formed by the suspended carbon nanotube. The spin-orbit interaction induces a coupling between the spin and one of the bending modes of the suspended part of the nanotube [1]. We simulate the response of the system to the external driving with a Jaynes-Cummings model by solving the quantum master equation. Using parameters comparable to those used in recent experiments, we show how information of the spin state of the system can be acquired by measuring its mechanical motion [2]. The mechanical motion can be detected by observing the current through a nearby charge detector. [4pt] [1] A. Palyi, P.R. Struck, M. Rudner, K. Flensberg, G. Burkard, Phys. Rev. Lett. 108, 206811 (2012).[0pt] [2] H. Wang, P. R. Struck, G. Burkard, manuscript in preparation.

Burkard, Guido; Wang, Heng; Struck, Philipp

2013-03-01

244

Controlled exchange interaction for quantum logic operations with spin qubits in coupled quantum dots  

Microsoft Academic Search

A two-electron system confined in two coupled semiconductor quantum dots is investigated as a candidate for performing quantum logic operations with spin qubits. We study different processes of swapping the electron spins by a controlled switching on and off of the exchange interaction. The resulting spin swap corresponds to an elementary operation in quantum-information processing. We perform direct simulations of

S. Moskal; S. Bednarek; J. Adamowski

2007-01-01

245

Dynamics and thermalization of the nuclear spin bath in the single-molecule magnet Mn12-ac : Test for the theory of spin tunneling  

NASA Astrophysics Data System (ADS)

The description of the tunneling of a macroscopic variable in the presence of a bath of localized spins is a subject of great fundamental and practical interest, and is relevant for many solid-state qubit designs. Most of the attention is usually given to the dynamics of the “central spin” (i.e., the qubit), while little is known about the spin bath itself. Here, we present a detailed study of the dynamics of the nuclear spin bath in the Mn12-ac single-molecule magnet, probed by NMR experiments down to very low temperatures (T?20mK) . The results are critically analyzed in the framework of the Prokof’ev-Stamp theory of nuclear-spin-mediated quantum tunneling. We find that the longitudinal relaxation rate of the Mn55 nuclei in Mn12-ac becomes roughly T independent below T?0.8K and can be strongly suppressed with a longitudinal magnetic field. This is consistent with the nuclear relaxation being caused by quantum tunneling of the molecular spin, and we attribute the tunneling fluctuations to the minority of fast-relaxing molecules present in the sample. The transverse nuclear relaxation is also T independent for T<0.8K , and can be explained qualitatively and quantitatively by the dipolar coupling between like nuclei in neighboring molecules. This intercluster nuclear spin diffusion mechanism is an essential ingredient for the global relaxation of the nuclear spin bath. We also show that the isotopic substitution of H1 by H2 leads to a slower nuclear longitudinal relaxation, consistent with the decreased tunneling probability of the molecular spin. Finally, we demonstrate that even at the lowest temperatures—where only T -independent quantum tunneling fluctuations are present—the nuclear spins remain in thermal equilibrium with the lattice phonons, and we investigate the time scale for their thermal equilibration. After a review of the theory of macroscopic spin tunneling in the presence of a spin bath, we argue that most of our experimental results are consistent with that theory, but the thermalization of the nuclear spins is not. This calls for an extension of the spin-bath theory to include the effect of spin-phonon couplings in the nuclear-spin-mediated tunneling process.

Morello, Andrea; de Jongh, L. J.

2007-11-01

246

Coherent population trapping of an electron spin in a single negatively charged quantum dot  

Microsoft Academic Search

Coherent population trapping (CPT) refers to the steady-state trapping of population in a coherent superposition of two ground states that are coupled by coherent optical fields to an intermediate state in a three-level atomic system. Recently, CPT has been observed in an ensemble of donor-bound spins in GaAs (ref. 2) and in single nitrogen-vacancy centres in diamond by using a

Xiaodong Xu; Bo Sun; Paul R. Berman; Duncan G. Steel; Allan S. Bracker; Dan Gammon; L. J. Sham

2008-01-01

247

Morphologic Parameters of Normal Swallowing Events Using Single-Shot Fast Spin Echo Dynamic MRI  

Microsoft Academic Search

This study was designed to determine visible and measurable morphological parameters in normal swallowing using dynamic MRI with single-shot fast spin echo (SSFSE), as a preliminary study in view of noninvasive MRI swallowing evaluation in patients with dysphagia. Seven healthy volunteers aged 24–40 underwent dynamic MRI with SSFSE, with a 1.5-T unit, using a head and neck antenna. Patients repeated

Dana M. Hartl; Marcella Albiter; Frédéric Kolb; Bernard Luboinski; Robert Sigal

2003-01-01

248

Spin?freezing in superconducting La 2 CuO 4.03 single crystal  

Microsoft Academic Search

Electron spin?freezing at Tf=8 K has been detected in superconducting (Tc=12\\\\ K) single crystal La2CuO4+y (y\\\\simeq0.03) by ZF??SR. According to diffraction data, the crystal is in Bmab phase without any traces of structural phase\\u000a separation. TF??SR experiment has shown that no Abrikosov flux line lattice is formed below Tc. The data allow us to assume that the magnetic and superconducting

V. Yu. Pomjakushin; A. Amato; V. N. Duginov; F. N. Gygax; D. Herlach; A. N. Ponomarev; A. Schenck; A. A. Zakharov

1997-01-01

249

Wet-spinning of neat single-walled carbon nanotube fiber from 100+% sulfuric acid  

Microsoft Academic Search

Single-Walled Carbon Nanotubes (SWNT) have been found to have excellent solubility in super acids such as 100+% H2SO4, and chlorsulfonic acid. The solutions display liquid crystalline behavior at high concentrations in super acids. Traditional wet-spinning method has been applied to SWNTs to make fibers from SWNTs only with the assistance of 100+% H2SO 4 (neat SWNT fibers). Extensive conditions, including

Fan Hua

2008-01-01

250

Scale dependence of twist-three contributions to single spin asymmetries  

SciTech Connect

We reexamine the scale dependence of twist-three correlation functions relevant for the single transverse spin asymmetry in the framework of collinear factorization. Evolution equations are derived for both the flavor-nonsinglet and flavor-singlet distributions and arbitrary parton momenta. Our results do not agree with the recent calculations of the evolution in the limit of vanishing gluon momentum. Possible sources for this discrepancy are identified.

Braun, V. M.; Pirnay, B. [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040, Regensburg (Germany); Manashov, A. N. [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040, Regensburg (Germany); Department of Theoretical Physics, St. Petersburg State University, 199034, St. Petersburg (Russian Federation)

2009-12-01

251

Transient dynamics in magnetic force microscopy for a single-spin measurement  

SciTech Connect

We analyze a single-spin measurement using a transient process in magnetic force microscopy which could increase the maximum operating temperature by a factor of Q (the quality factor of the cantilever) in comparison with the static Stern-Gerlach effect. We obtain an exact solution of the master equation, which confirms this result. We also discuss the conditions required to create a macroscopic quantum superposition in the cantilever.

Berman, G.P. [Theoretical Division and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Borgonovi, F. [Dipartimento di Matematica e Fisica, Universita Cattolica, via Musei 41, 25121 Brescia (Italy); INFM, Unita di Brescia, 25121 Brescia, Italy and and INFN, Sezione di Pavia, 27100 Pavia (Italy); Lopez, G.V. [Departamento de Fisica de la Universidad de Guadalajara S.R. 500, 44420 Guadalajara, Jalisco (Mexico); Tsifrinovich, V.I. [IDS Department, Polytechnic University, Six Metrotech Center, Brooklyn, New York 11201 (United States)

2003-07-01

252

Electron spin resonance absorption spectrum of CO2- molecule-ions in single crystal calcite  

Microsoft Academic Search

An electron spin resonance absorption spectrum due to CO2- molecule-ions has been observed at 3 cm wavelength in single crystals of optical grade calcite. The spectrum exhibits orthorhombic symmetry with both the 12C and 13C isotopically substituted CO2- molecule-ions having the same g-tensor components given by gzz = 2·00161, gxx = 2·00320 and gyy = 1·99727, where z refers to

S. A. Marshall; A. R. Reinberg; R. A. Serway; J. A. Hodges

1964-01-01

253

Hadron structure and left-right asymmetry in inclusive production in single-spin hadron-hadron collisions  

SciTech Connect

Theoretical arguments and experimental facts are presented which show the following. Left-right asymmetries are expected to exist in a number of single-spin inclusive production processes. Measuring such asymmetries by using different types of projectile-target combinations, one can obtain useful information on the spin structure of hadrons in general, and determine the spin-dependent quark distribution functions in particular. Quantitative predictions for these asymmetries in various reactions are presented.

Boros, C.; Liang Zuo-tang; Meng Ta-chung [Institut fuer Theoretische Physik, Freie Universitaet Berlin, Arnimallee 14, 14195 Berlin (Germany)

1995-05-01

254

Optical pumping of a single electron spin bound to a fluorine donor in a ZnSe nanostructure.  

PubMed

Here we demonstrate optical pumping of a single electron within a semiconductor nanostructure comprised of a single fluorine donor located within a ZnSe/ZnMgSe quantum well. Experiments were performed to detect optical pumping behavior by observing single photons emitted from the nanostructure when the electron changes spin state. These results demonstrate initialization and read-out of the electron spin qubit and open the door for coherent optical manipulation of a spin by taking advantage of an unconventional nanostructure. PMID:23215051

Sleiter, Darin J; Sanaka, Kaoru; Kim, Y M; Lischka, Klaus; Pawlis, Alexander; Yamamoto, Yoshihisa

2012-12-24

255

Process Dependent Sivers Function and Implication for Single Spin Asymmetry in Inclusive Hadron Production  

SciTech Connect

We study the single transverse spin asymmetries in the single inclusive particle production within the framework of the generalized parton model (GPM). By carefully analyzing the initial- and final-state interactions, we include the process-dependence of the Sivers functions into the GPM formalism. The modified GPM formalism has a close connection with the collinear twist-3 approach. Within the new formalism, we make predictions for inclusive {pi}{sup 0} and direct photon productions at RHIC energies. We find the predictions are opposite to those in the conventional GPM approach.

Leonard Gamberg, Zhong-Bo Kang

2011-01-01

256

Process dependent Sivers function and implication for single spin asymmetry in inclusive hadron production  

SciTech Connect

We study the single transverse spin asymmetries in the single inclusive particle production within the framework of the generalized parton model (GPM). By carefully analyzing the initial- and final-state interactions, we include the process-dependence of the Sivers functions into the GPM formalism. The modified GPM formalism has a close connection with the collinear twist-3 approach. Within the new formalism, we make predictions for inclusive {pi}{sup 0} and direct photon productions at RHIC energies. We find the predictions are opposite to those in the conventional GPM approach.

Gamberg, L.; Kang, Z.

2010-12-01

257

Process dependent Sivers function and implications for single spin asymmetry in inclusive hadron production  

SciTech Connect

We study the single transverse spin asymmetries in the single inclusive particle production within the framework of the generalized parton model (GPM). By carefully analyzing the initial- and final-state interactions, we include the process-dependence of the Sivers functions into the GPM formalism. The modified GPM formalism has a close connection with the collinear twist-3 approach. Within the new formalism, we make predictions for inclusive $\\pi^0$ and direct photon productions at RHIC energies. We find the predictions are opposite to those in the conventional GPM approach.

Leonard Gamberg, Zhong-Bo Kang

2011-01-01

258

Sivers effect and the single spin asymmetry AN in p?p?hX processes  

NASA Astrophysics Data System (ADS)

The single spin asymmetry AN, for large PT single inclusive particle production in p?p collisions, is considered within a generalized parton model and a transverse momentum dependent factorization scheme. The focus is on the Sivers effect and the study of its potential contribution to AN, based on a careful analysis of the Sivers functions extracted from azimuthal asymmetries in semi-inclusive deep inelastic scattering processes. It is found that such Sivers functions could explain most features of the AN data, including some recent STAR results which show the persistence of a nonzero AN up to surprisingly large PT values.

Anselmino, M.; Boglione, M.; D'Alesio, U.; Melis, S.; Murgia, F.; Prokudin, A.

2013-09-01

259

TOPICAL REVIEW A review of the coherent optical control of the exciton and spin states of semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

The spin of a carrier trapped in a self-assembled quantum dot has the potential to be a robust optically active qubit that is compatible with existing III-V semiconductor device technology. A key requirement for building a quantum processor is the ability to dynamically prepare, control and detect single quantum states. Here, experimental progress in the coherent optical control of single semiconductor quantum dots over the past decade is reviewed, alongside an introductory discussion of the basic principles of coherent control.

Ramsay, A. J.

2010-10-01

260

Strong spin-phonon coupling between a single-molecule magnet and a carbon nanotube nanoelectromechanical system  

NASA Astrophysics Data System (ADS)

Magnetic relaxation processes were first discussed for a crystal of paramagnetic transition ions. It was suggested that mechanical vibrations of the crystal lattice (phonons) modulate the crystal electric field of the magnetic ion, thus inducing a `direct' relaxation between two different spin states. Direct relaxation has also been predicted for single-molecule magnets with a large spin and a high magnetic anisotropy and was first demonstrated in a Mn12 acetate crystal. The spin-lattice relaxation time for such a direct transition is limited by the phonon density of states at the spin resonance. In a three-dimensional system, such as a single-molecule magnet crystal, the phonon energy spectrum is continuous, but in a one-dimensional system, like a suspended carbon nanotube, the spectrum is discrete and can be engineered to an extremely low density of states. An individual single-molecule magnet, coupled to a suspended carbon nanotube, should therefore exhibit extremely long relaxation times and the system's reduced size should result in a strong spin-phonon coupling. Here, we provide the first experimental evidence for a strong spin-phonon coupling between a single molecule spin and a carbon nanotube resonator, ultimately enabling coherent spin manipulation and quantum entanglement.

Ganzhorn, Marc; Klyatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang

2013-03-01

261

Controlling a Nanowire Spin-Orbit Qubit via Electric-Dipole Spin Resonance  

NASA Astrophysics Data System (ADS)

A semiconductor nanowire quantum dot with strong spin-orbit coupling (SOC) can be used to achieve a spin-orbit qubit. In contrast to a spin qubit, the spin-orbit qubit can respond to an external ac electric field, an effect called electric-dipole spin resonance. Here we develop a theory that can apply in the strong SOC regime. We find that there is an optimal SOC strength ?opt=2/2, where the Rabi frequency induced by the ac electric field becomes maximal. Also, we show that both the level spacing and the Rabi frequency of the spin-orbit qubit have periodic responses to the direction of the external static magnetic field. These responses can be used to determine the SOC in the nanowire.

Li, Rui; You, J. Q.; Sun, C. P.; Nori, Franco

2013-08-01

262

Voltage-controlled Spin Wave Logic Device: Ring Interferometer  

Microsoft Academic Search

Spin wave logic circuitry transmits information by propagating spin waves along magnetically insulating wave guides. This is less power-consuming than ordinary circuits and is expected to work at THz frequency and room temperature. Logical operations are performed by modulating the interference of spin waves through a phase shifter. A great deal of effort has been devoted to the problem of

Tianyu Liu; Giovanni Vignale

2011-01-01

263

Control of spin-wave emission from spin-torque nano-oscillators by microwave pumping  

Microsoft Academic Search

We demonstrate that microwave pumping of a spin-torque nano-oscillator can lead to transfer of the spin-wave energy generated by the oscillator into a mode with frequency given by the difference between the pumping frequency and that of the auto-oscillation. The decay length of spin waves at the combination frequency is significantly increased, while the directionality of emission is preserved. The

Vladislav E. Demidov; Sergei Urazhdin; Vasyl Tiberkevich; Andrei Slavin; Sergej O. Demokritov

2011-01-01

264

Spin excitations in a single La2CuO4 layer.  

PubMed

Cuprates and other high-temperature superconductors consist of two-dimensional layers that are crucial to their properties. The dynamics of the quantum spins in these layers lie at the heart of the mystery of the cuprates. In bulk cuprates such as La(2)CuO(4), the presence of a weak coupling between the two-dimensional layers stabilizes a three-dimensional magnetic order up to high temperatures. In a truly two-dimensional system however, thermal spin fluctuations melt long-range order at any finite temperature. Here, we measure the spin response of isolated layers of La(2)CuO(4) that are only one-unit-cell-thick. We show that coherent magnetic excitations, magnons, known from the bulk order, persist even in a single layer of La(2)CuO(4), with no evidence for more complex correlations such as resonating valence bond correlations. These magnons are, therefore, well described by spin-wave theory (SWT). On the other hand, we also observe a high-energy magnetic continuum in the isotropic magnetic response that is not well described by two-magnon SWT, or indeed any existing theories. PMID:22941330

Dean, M P M; Springell, R S; Monney, C; Zhou, K J; Pereiro, J; Božovi?, I; Dalla Piazza, B; Rønnow, H M; Morenzoni, E; van den Brink, J; Schmitt, T; Hill, J P

2012-09-02

265

Single-parameter quantum charge and spin pumping in armchair graphene nanoribbons  

NASA Astrophysics Data System (ADS)

We investigate quantum charge and spin pumping in armchair graphene nanoribbons under a single ac gate voltage connected with nonmagnetic/ferromagnetic leads via the nonequilibrium Green's function method. In the case of nonmagnetic leads, where only part of the nanoribbon is subject to an ac gate voltage to break the left-right spatial symmetry, we discover that peaks of the charge pumping current appear at the Fermi energies around the sub-band edges in the ac-field-free region of the nanoribbon. In the case of ferromagnetic leads with the lead magnetizations being antiparallel to break the left-right symmetry, similar peaks appear in the spin pumping current when the Fermi energies are around the edges of the the majority-spin sub-bands in the ferromagnetic leads. All these peaks originate from the pronounced symmetry breaking in the transmissions with energies being around the corresponding sub-band edges. Moreover, we predict a pure spin current in the case of ferromagnetic leads with the whole graphene nanoribbon under an ac gate voltage. The ac-field-strength and ac-field-frequency dependencies of the pumping current are also investigated with the underlying physics revealed.

Zhou, Y.; Wu, M. W.

2012-08-01

266

Vibrational detection and control of spin in mixed-valence molecular transistors  

NASA Astrophysics Data System (ADS)

We investigate electron transport through a mixed-valence molecular complex in which an excess electron can tunnel between heterovalent transition metal ions, each having a fixed localized spin. We show that in this class of molecules the interplay of the spins and the vibrational breathing modes of the ionic ligand shells allows the total molecular spin to be detected as well as controlled by nonequilibrium transport. Due to a spin-dependent pseudo-Jahn-Teller effect electronic transitions with different spin values can be distinguished by their vibronic conductance side peaks, without using an external magnetic field. Conversely, we show that the spin state of the entire molecule can also be controlled via the nonequilibrium quantized molecular vibrations due to a vibration-induced spin blockade.

Reckermann, F.; Leijnse, M.; Wegewijs, M. R.

2009-02-01

267

High-dynamic-range magnetometry with a single electronic spin in diamond  

NASA Astrophysics Data System (ADS)

Magnetic sensors capable of detecting nanoscale volumes of spins allow for non-invasive, element-specific probing. The error in such measurements is usually reduced by increasing the measurement time, and noise averaging the signal. However, achieving the best precision requires restricting the maximum possible field strength to much less than the spectral linewidth of the sensor. Quantum entanglement and squeezing can then be used to improve precision (although they are difficult to implement in solid-state environments). When the field strength is comparable to or greater than the spectral linewidth, an undesirable trade-off between field strength and signal precision occurs. Here, we implement novel phase estimation algorithms on a single electronic spin associated with the nitrogen-vacancy defect centre in diamond to achieve an ~8.5-fold improvement in the ratio of the maximum field strength to precision, for field magnitudes that are large (~0.3 mT) compared to the spectral linewidth of the sensor (~4.5 µT). The field uncertainty in our approach scales as 1/T0.88, compared to 1/T0.5 in the standard measurement approach, where T is the measurement time. Quantum phase estimation algorithms have also recently been implemented using a single nuclear spin in a nitrogen-vacancy centre. Besides their direct impact on applications in magnetic sensing and imaging at the nanoscale, these results may prove useful in improving a variety of high-precision spectroscopy techniques.

Nusran, N. M.; Momeen, M. Ummal; Dutt, M. V. Gurudev

2012-02-01

268

High-dynamic-range magnetometry with a single electronic spin in diamond.  

PubMed

Magnetic sensors capable of detecting nanoscale volumes of spins allow for non-invasive, element-specific probing. The error in such measurements is usually reduced by increasing the measurement time, and noise averaging the signal. However, achieving the best precision requires restricting the maximum possible field strength to much less than the spectral linewidth of the sensor. Quantum entanglement and squeezing can then be used to improve precision (although they are difficult to implement in solid-state environments). When the field strength is comparable to or greater than the spectral linewidth, an undesirable trade-off between field strength and signal precision occurs. Here, we implement novel phase estimation algorithms on a single electronic spin associated with the nitrogen-vacancy defect centre in diamond to achieve an ?8.5-fold improvement in the ratio of the maximum field strength to precision, for field magnitudes that are large (?0.3 mT) compared to the spectral linewidth of the sensor (?4.5 µT). The field uncertainty in our approach scales as 1/T(0.88), compared to 1/T(0.5) in the standard measurement approach, where T is the measurement time. Quantum phase estimation algorithms have also recently been implemented using a single nuclear spin in a nitrogen-vacancy centre. Besides their direct impact on applications in magnetic sensing and imaging at the nanoscale, these results may prove useful in improving a variety of high-precision spectroscopy techniques. PMID:22179565

Nusran, N M; Momeen, M Ummal; Dutt, M V Gurudev

2011-12-18

269

Using heat to control the sample spinning speed in MAS NMR.  

PubMed

A new approach using temperature to control the spinning speed of a sample rotor in magic-angle spinning NMR is presented. Instead of an electro-mechanical valve that regulates the flow of drive gas to control the spinning speed in traditional MAS NMR systems, we use a small heater wire located directly in the stator. The sample spinning speed is controlled very accurately with a surprisingly low heating power of 1 W. Results on a benchtop unit demonstrate the capability of the system. PMID:21820341

Mihaliuk, Eugene; Gullion, Terry

2011-07-23

270

Critical Properties of Mixed Ising Spin System with Different Trimodal Transverse Fields in the Presence of Single-Ion Anisotropy  

Microsoft Academic Search

Within the framework of an effective field approximation, the effects of single-ion anisotropy and different trimodal transverse fields of two sublattices on the critical properties of the mixed spin-1\\/2 and spin-1 Ising system are investigated on the simple cubic lattice. A smaller single-ion anisotropy can magnify magnetic ordering phases and a larger one can depress magnetic ordering phase for T-?1\\/2

Chen Qiang; Yan Shi-Lei

2006-01-01

271

Temperature dependence of electron-spin relaxation in a single InAs quantum dot at zero applied magnetic field  

NASA Astrophysics Data System (ADS)

The temperature-dependent electron spin relaxation of positively charged excitons in a single InAs quantum dot was measured by time-resolved photoluminescence spectroscopy at zero applied magnetic fields. The experimental results show that the electron-spin relaxation is clearly divided into two different temperature regimes: (i) at T < 50 K, spin relaxation depends on the dynamical nuclear spin polarization and is approximately temperature-independent, as predicted by Merkulov et al. [Phys. Rev. B 65, 205309 (2002)] (ii) T > about 50 K, spin relaxation speeds up with increasing temperature. A model of a two longitudinal optical phonon scattering process coupled with hyperfine interaction is proposed to account for the accelerated electron spin relaxation at higher temperatures.

Dou, X. M.; Sun, B. Q.; Jiang, D. S.; Ni, H. Q.; Niu, Z. C.

2012-03-01

272

High-resolution spectroscopy of single NV defects coupled with nearby 13C nuclear spins in diamond  

NASA Astrophysics Data System (ADS)

We report a systematic study of the hyperfine interaction between the electron spin of a single nitrogen-vacancy (NV) defect in diamond and nearby 13C nuclear spins, by using pulsed electron-spin resonance spectroscopy. We isolate a set of discrete values of the hyperfine coupling strength ranging from 14 MHz to 400 kHz and corresponding to 13C nuclear spins placed at different lattice sites of the diamond matrix. For each lattice site, the hyperfine interaction is further investigated through nuclear-spin polarization measurements and by studying the magnetic field dependence of the hyperfine splitting. This work provides information that is relevant for the development of nuclear-spin-based quantum register in diamond.

Dréau, A.; Maze, J.-R.; Lesik, M.; Roch, J.-F.; Jacques, V.

2012-04-01

273

Phase Diagram of the mixed spin-2 and spin-5/2 Ising system with two different single-ion anisotropies  

NASA Astrophysics Data System (ADS)

In the last five decades the Ising model has been one of the most largely used to describe critical behavior of several systems in the nature. In particular, in the physics of the condensed matter it is important to describe critical behavior and other thermodynamics properties of a variety of physic systems (disordered system, spins glass, random field Ising model, etc.). Recently, several extensions have been made in the spin-1/2 Ising model to describe a wide variety of physic systems. For example, the models consisting of mixed spins of different magnitudes are interesting extensions, which are so-called mixed-spin Ising models. In this work we present a study of the effects of two single-ion anisotropies in the phase diagram and in the compensation temperatures of the mixed spin-2 and spin-5/2 Ising ferrimagnetic system. We employ the mean-field theory based on the Bogoliubov inequality for the Gibbs free energy, and the Landau expansion of the free energy in the order parameter to describe the phase diagrams. In the plane critical temperature versus single-ion anisotropie the phase diagram display behavior tricritical (second-order transition separated of the first-order transition lines by a tricritical point).

Cruz Filho, José.; Godoy, Mauricio; Arruda, Alberto

2012-02-01

274

Observation of transitions to spin-slip structures in single-crystal holmium  

SciTech Connect

We present the results of magnetization measurements on single-crystal holmium using a SQUID magnetometer in the temperature range from 4.2 to 140 K in magnetic fields from 0.01 to 3 T applied along the {ital b} axis. Our magnetization data shows the Neel temperature to be {ital T}{sub {ital N}}=132 K. In addition, we observe anomalies in the temperature dependence of the magnetization at 21, 42, and 98 K. These anomalies can be accounted for within the spin-slip model; Bohr {ital et} {ital al}. (Physica (Amsterdam) 140{ital A}, 349 (1986)) have pointed out the existences of ferrimagnetic structures spin slip and Cowley and Bates (J. Phys. C 21, 4113 (1988)) additional structures that breaks the hexagonal symmetry.

Ali, N.; Willis, F. (Department of Physics, Southern Illinois University, Carbondale, Illinois 62901-4401 (USA)); Steinitz, M.O.; Kahrizi, M. (Department of Physics, St. Francis Xavier University, Antigonish, Nova Scotia, Canada B2G1C0 (CA)); Tindall, D.A. (Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada B3H3J5 (CA))

1989-12-01

275

Gd-Based Single-Ion Magnets with Tunable Magnetic Anisotropy: Molecular Design of Spin Qubits  

NASA Astrophysics Data System (ADS)

We report ac susceptibility and continuous wave and pulsed EPR experiments performed on GdW10 and GdW30 polyoxometalate clusters, in which a Gd3+ ion is coordinated to different polyoxometalate moieties. Despite the isotropic character of gadolinium as a free ion, these molecules show slow magnetic relaxation at very low temperatures, characteristic of single molecule magnets. For T?200mK, the spin-lattice relaxation becomes dominated by pure quantum tunneling events, with rates that agree quantitatively with those predicted by the Prokof’ev and Stamp model [Phys. Rev. Lett. 80, 5794 (1998)PRLTAO0031-900710.1103/PhysRevLett.80.5794]. The sign of the magnetic anisotropy, the energy level splittings, and the tunneling rates strongly depend on the molecular structure. We argue that GdW30 molecules are also promising spin qubits with a coherence figure of merit QM?50.

Martínez-Pérez, M. J.; Cardona-Serra, S.; Schlegel, C.; Moro, F.; Alonso, P. J.; Prima-García, H.; Clemente-Juan, J. M.; Evangelisti, M.; Gaita-Ariño, A.; Sesé, J.; van Slageren, J.; Coronado, E.; Luis, F.

2012-06-01

276

Gd-based single-ion magnets with tunable magnetic anisotropy: molecular design of spin qubits.  

PubMed

We report ac susceptibility and continuous wave and pulsed EPR experiments performed on GdW10 and GdW30 polyoxometalate clusters, in which a Gd3+ ion is coordinated to different polyoxometalate moieties. Despite the isotropic character of gadolinium as a free ion, these molecules show slow magnetic relaxation at very low temperatures, characteristic of single molecule magnets. For T?200??mK, the spin-lattice relaxation becomes dominated by pure quantum tunneling events, with rates that agree quantitatively with those predicted by the Prokof'ev and Stamp model [Phys. Rev. Lett. 80, 5794 (1998)]. The sign of the magnetic anisotropy, the energy level splittings, and the tunneling rates strongly depend on the molecular structure. We argue that GdW30 molecules are also promising spin qubits with a coherence figure of merit Q(M)?50. PMID:23004325

Martínez-Pérez, M J; Cardona-Serra, S; Schlegel, C; Moro, F; Alonso, P J; Prima-García, H; Clemente-Juan, J M; Evangelisti, M; Gaita-Ariño, A; Sesé, J; van Slageren, J; Coronado, E; Luis, F

2012-06-15

277

19F nuclear spin relaxation and spin diffusion effects in the single-ion magnet LiYF4:Ho3+  

NASA Astrophysics Data System (ADS)

Temperature and magnetic field dependences of the 19F nuclear spin-lattice relaxation in a single crystal of LiYF4 doped with holmium are described by an approach based on a detailed consideration of the magnetic dipole-dipole interactions between nuclei and impurity paramagnetic ions and nuclear spin diffusion processes. The observed non-exponential long time recovery of the nuclear magnetization after saturation at intermediate temperatures is in agreement with predictions of the spin-diffusion theory in a case of the diffusion limited relaxation. At avoided level crossings in the spectrum of electron-nuclear states of Ho3 + ions, rates of nuclear spin-lattice relaxation increase due to quasi-resonant energy exchange between nuclei and paramagnetic ions in contrast to the predominant role played by electronic cross-relaxation processes in the low-frequency ac-susceptibility.

Malkin, B. Z.; Vanyunin, M. V.; Graf, M. J.; Lago, J.; Borsa, F.; Lascialfari, A.; Tkachuk, A. M.; Barbara, B.

2008-11-01

278

Polytype control of spin qubits in silicon carbide.  

PubMed

Crystal defects can confine isolated electronic spins and are promising candidates for solid-state quantum information. Alongside research focusing on nitrogen-vacancy centres in diamond, an alternative strategy seeks to identify new spin systems with an expanded set of technological capabilities, a materials-driven approach that could ultimately lead to 'designer' spins with tailored properties. Here we show that the 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states, including states in all three with room-temperature quantum coherence. The prevalence of this spin coherence shows that crystal polymorphism can be a degree of freedom for engineering spin qubits. Long spin coherence times allow us to use double electron-electron resonance to measure magnetic dipole interactions between spin ensembles in inequivalent lattice sites of the same crystal. Together with the distinct optical and spin transition energies of such inequivalent states, these interactions provide a route to dipole-coupled networks of separately addressable spins. PMID:23652007

Falk, Abram L; Buckley, Bob B; Calusine, Greg; Koehl, William F; Dobrovitski, Viatcheslav V; Politi, Alberto; Zorman, Christian A; Feng, Philip X-L; Awschalom, David D

2013-01-01

279

The low-temperature properties of the spin-one Heisenberg antiferromagnetic chain with the single-ion anisotropy  

NASA Astrophysics Data System (ADS)

The one-dimensional spin-one Heisenberg antiferromagnet with the single-ion anisotropy is explored on the basis of the modified spin-wave theory. The ground-state and low-temperature properties of the system are obtained within the self-consistent method. It is shown that the single-ion anisotropy suppresses the quantum and thermal spin fluctuations. The temperature dependence of the magnon internal energy and specific heat exhibits the power-law form in the low-temperature region. The power exponents are dependent on the anisotropy. Our results agree quite well with the quantum Monte Carlo estimates the exact results and some experimental data.

Chen, Yuan; Wu, You

2013-04-01

280

Magnetic and electrical properties of spin valve with single and double specular oxide layers  

SciTech Connect

Appropriate oxide capping on a spin valve significantly improved electrical and magnetic properties. The interlayer exchange coupling oscillated in the thickness range of a Cu spacer (between 20 and 30 Aa). The coupling was antiferromagnetic and it allowed us to reduce the Cu spacer down to 20 Aa without sacrificing the good properties of the spin valve. The improvement is due to enhanced specular reflection at the interface between the magnetic and the oxide layer and to less current shunting through the Cu spacer. In particular, the Cu in the capping acts as a filter controlling the diffusion of oxygen, which has led to the soft magnetic properties. Embedding an additional thin oxide layer into the pinned layer further improved the magnetoresistance response of the spin valve. Confinement of electrons between two oxides helps increase the occurrence of spin-dependent scattering. As a result, high giant magnetoresistance values resulted. The coupling oscillated from ferromagnetic to antiferromagnetic as a function of thickness of the Cu spacer. No significant bias in the coupling was observed and this lack of bias can be attributed to the smoothness of the interfaces. The oscillations were observable due to amplified Ruderman{endash}Kittel{endash}Kasuya{endash}Yoshida-like coupling by strong reflection at the interfaces of the oxides. {copyright} 2001 American Institute of Physics.

Hong, Jongill; Noma, Kenji; Kanai, Hitoshi; Kane, Junichi

2001-06-01

281

Single crystal diffraction analysis of the thermal spin conversion in [Fe(btr) {2}(NCS) {2}](H {2}O): evidence for spin-like domain formation  

NASA Astrophysics Data System (ADS)

The structural properties of the spin crossover compound [Fe(btr)2(NCS)2](H2O), where btr stands for 4,4’-bis-1,2,4-triazole, are investigated by single crystal X-ray diffraction at different temperatures in the thermal spin transition regime. The 104.0(5) K low spin (LS) crystal structure is compared to the room temperature high spin (HS) crystal structure. The C2/c space group is retained in the LS state with an abrupt anisotropic shortening of the b and c cell parameters and a lengthening of a at the transition temperature. The major structural modifications related to the spin transition are a shortening of the Fe-N bond lengths (? d_{Fe-NCS} = -0.175(4) Å, ? d_{Fe-N(btr)} = -0.213(3) Å) and a reorientation of the NCS groups with a more linear Fe-N-C-S geometry on going from HS to LS. Diffraction measurements have also been performed at 124 K on a trapped mixed spin state. The observed diffraction pattern shows the coexistence of two crystal lattices corresponding to ordered LS and HS species, which is a direct evidence of spin-like domain formation during the transition. The corresponding fraction of HS species (?_{HS}? 0.10) has been determined by structural refinement using several reference temperature measurements. To investigate dynamical aspects, X-ray data were collected versus time during the spin transition at constant temperature (T = 117.2(2) K). No evidence has been found for any putative presence of an intermediate structural state during the spin transition.

Pillet, S.; Hubsch, J.; Lecomte, C.

2004-04-01

282

Magnetoelectric effects and valley-controlled spin quantum gates in transition metal dichalcogenide bilayers.  

PubMed

In monolayer group-VI transition metal dichalcogenides, charge carriers have spin and valley degrees of freedom, both associated with magnetic moments. On the other hand, the layer degree of freedom in multilayers is associated with electrical polarization. Here we show that transition metal dichalcogenide bilayers offer an unprecedented platform to realize a strong coupling between the spin, valley and layer pseudospin of holes. Such coupling gives rise to the spin Hall effect and spin-dependent selection rule for optical transitions in inversion symmetric bilayer and leads to a variety of magnetoelectric effects permitting quantum manipulation of these electronic degrees of freedom. Oscillating electric and magnetic fields can both drive the hole spin resonance where the two fields have valley-dependent interference, making an interplay between the spin and valley as information carriers possible for potential valley-spintronic applications. We show how to realize quantum gates on the spin qubit controlled by the valley bit. PMID:23784147

Gong, Zhirui; Liu, Gui-Bin; Yu, Hongyi; Xiao, Di; Cui, Xiaodong; Xu, Xiaodong; Yao, Wang

2013-06-19

283

Magnetoelectric effects and valley-controlled spin quantum gates in transition metal dichalcogenide bilayers  

NASA Astrophysics Data System (ADS)

In monolayer group-VI transition metal dichalcogenides, charge carriers have spin and valley degrees of freedom, both associated with magnetic moments. On the other hand, the layer degree of freedom in multilayers is associated with electrical polarization. Here we show that transition metal dichalcogenide bilayers offer an unprecedented platform to realize a strong coupling between the spin, valley and layer pseudospin of holes. Such coupling gives rise to the spin Hall effect and spin-dependent selection rule for optical transitions in inversion symmetric bilayer and leads to a variety of magnetoelectric effects permitting quantum manipulation of these electronic degrees of freedom. Oscillating electric and magnetic fields can both drive the hole spin resonance where the two fields have valley-dependent interference, making an interplay between the spin and valley as information carriers possible for potential valley-spintronic applications. We show how to realize quantum gates on the spin qubit controlled by the valley bit.

Gong, Zhirui; Liu, Gui-Bin; Yu, Hongyi; Xiao, Di; Cui, Xiaodong; Xu, Xiaodong; Yao, Wang

2013-06-01

284

Spin-Orbit Splitting in Single-Layer MoS2 Revealed by Triply Resonant Raman Scattering  

NASA Astrophysics Data System (ADS)

Although new spintronic devices based on the giant spin-orbit splitting of single-layer MoS2 have been proposed, such splitting has not been studied effectively in experiments. This Letter reports the valence band spin-orbit splitting in single-layer MoS2 for the first time, probed by the triply resonant Raman scattering process. We found that upon 325 nm laser irradiation, the second order overtone and combination Raman modes of single-layer MoS2 are dramatically enhanced. Such resonant Raman enhancement arises from the electron-two-phonon triple resonance via the deformation potential and Fröhlich interaction. As a sensitive and precise probe for the spin-orbit splitting, the triply resonant Raman scattering will provide a new and independent route to study the spin characteristics of MoS2.

Sun, Linfeng; Yan, Jiaxu; Zhan, Da; Liu, Lei; Hu, Hailong; Li, Hong; Tay, Ben Kang; Kuo, Jer-Lai; Huang, Chung-Che; Hewak, Daniel W.; Lee, Pooi See; Shen, Ze Xiang

2013-09-01

285

Spin-Controlled Superconductivity and Tunable Triplet Correlations in Graphene Nanostructures  

NASA Astrophysics Data System (ADS)

We study graphene ferromagnet/superconductor/ferromagnet (F/S/F) nanostructures via a microscopic self-consistent Dirac Bogoliubov-de Gennes formalism. We show that as a result of proximity effects, experimentally accessible spin switching phenomena can occur as one tunes the Fermi level ?F of the F regions or varies the angle ? between exchange field orientations. Superconductivity can then be switched on and off by varying either ? or ?F (a spin-controlled superconducting graphene switch). The induced equal-spin triplet correlations in S can be controlled by tuning ?F, effectively making a graphene based two-dimensional spin-triplet valve.

Halterman, Klaus; Valls, Oriol T.; Alidoust, Mohammad

2013-07-01

286

Fast quantum state control of a single trapped neutral atom  

NASA Astrophysics Data System (ADS)

We demonstrate the initialization, readout, and high-speed manipulation of a qubit stored in a single Rb87 atom trapped in a submicrometer-sized optical tweezer. Single-qubit rotations are performed on a time scale below 100ns using two-photon Raman transitions. Using the spin-echo technique, we measure an irreversible dephasing time of 34ms . The readout of the single atom qubit is at the quantum projection noise limit when averaging up to 1000 individual events.

Jones, M. P. A.; Beugnon, J.; Gaëtan, A.; Zhang, J.; Messin, G.; Browaeys, A.; Grangier, P.

2007-04-01

287

Twist-3 predictions for single spin asymmetry for light-hadron productions at RHIC  

SciTech Connect

We present several predictions for the single spin asymmetry for the {pi}, K, and {eta}-meson productions at RHIC kinematics using the twist-3 quark-gluon correlation functions determined from our analysis of RHIC data. After discussing the P{sub T}-dependence of A{sub N}, we give predictions for A{sub N} for pions and kaons at {radical}(S) = 500 GeV and A{sub N} for the {eta}-meson at {radical}(S) = 200 GeV.

Kanazawa, Koichi [Graduate School of Science and Technology, Niigata University, Ikarashi, Niigata 950-2181 (Japan)

2011-12-14

288

Azimuthal and single spin asymmetry in deep-inelasticlepton-nucleon scattering  

SciTech Connect

The collinear expansion technique is generalized to thefactorization of unintegrated parton distributions and other higher twistparton correlations from the corresponding collinear hard parts thatinvolve multiple parton final state interaction. Such a generalizedfactorization provides a consistent approach to the calculation ofinclusive and semi-inclusive cross sections of deep-inelasticlepton-nucleon scattering. As an example, the azimuthal asymmetry iscalculated to the order of 1/Q in semi-inclusive deeply inelasticlepton-nucleon scattering with transversely polarized target. Anon-vanishing single-spin asymmetry in the "triggered inclusive process"is predicted to be 1/Q suppressed with a part of the coefficient relatedto a moment of the Sivers function.

Liang, Zuo-tang; Wang, Xin-Nian

2006-09-21

289

Evolution of twist-3 multiparton correlation functions relevant to single transverse-spin asymmetry  

SciTech Connect

We construct two sets of twist-3 correlation functions that are responsible for generating the novel single transverse-spin asymmetry in the QCD collinear factorization approach. We derive evolution equations for these universal three-parton correlation functions. We calculate evolution kernels relevant to the gluonic pole contributions to the asymmetry at the order of {alpha}{sub s}. We find that all evolution kernels are infrared safe as they should be and have a lot in common with the Dokshitzer-Gribov-Lipatov-Alterelli-Parisi evolution kernels of unpolarized parton distributions. By solving the evolution equations, we explicitly demonstrate the factorization scale dependence of these twist-3 correlation functions.

Kang Zhongbo; Qiu Jianwei [Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

2009-01-01

290

New analysis of the single transverse-spin asymmetry for hadron production at RHIC  

SciTech Connect

We analyze the single transverse-spin asymmetry (SSAs) for inclusive hadron production in the pp collision at RHIC based on the twist-3 mechanism in QCD. As an origin of SSAs, we take into account of all kinds of pole contributions associated with the twist-3 quark-gluon correlation functions in the polarized proton. By the inclusion of the soft-fermion-pole contribution in addition to the soft-gluon-pole contribution, we find SSAs observed at RHIC are better described for all kinds of mesons. P{sub T} dependence of the asymmetry and the comparison with the FNAL data are also presented.

Kanazawa, Koichi [Graduate School of Science and Technology, Niigata University, Ikarashi, Niigata 950-2181 (Japan); Koike, Yuji [Department of Physics, Niigata University, Ikarashi, Niigata 950-2181 (Japan)

2010-08-01

291

Single-photon-level optical storage in a solid-state spin-wave memory  

NASA Astrophysics Data System (ADS)

A long-lived quantum memory is a firm requirement for implementing a quantum repeater scheme. Recent progress in solid-state rare-earth-ion-doped systems justifies their status as very strong candidates for such systems. Nonetheless an optical memory based on spin-wave storage at the single-photon level has not been shown in such a system to date, which is crucial for achieving the long storage times required for quantum repeaters. In this paper we show that it is possible to execute a complete atomic frequency comb (AFC) scheme, including spin-wave storage, with weak coherent pulses of n¯=2.5±0.6 photons per pulse. We discuss in detail the experimental steps required to obtain this result and demonstrate the coherence of a stored time-bin pulse. We show a noise level of (7.1±2.3)×10?3 photons per mode during storage, and this relatively low noise level paves the way for future quantum optics experiments using spin waves in rare-earth-doped crystals.

Timoney, N.; Usmani, I.; Jobez, P.; Afzelius, M.; Gisin, N.

2013-08-01

292

Molecular Quantum Spintronics: Supramolecular Spin Valves Based on Single-Molecule Magnets and Carbon Nanotubes  

PubMed Central

We built new hybrid devices consisting of chemical vapor deposition (CVD) grown carbon nanotube (CNT) transistors, decorated with TbPc2 (Pc = phthalocyanine) rare-earth based single-molecule magnets (SMMs). The drafting was achieved by tailoring supramolecular ?-? interactions between CNTs and SMMs. The magnetoresistance hysteresis loop measurements revealed steep steps, which we can relate to the magnetization reversal of individual SMMs. Indeed, we established that the electronic transport properties of these devices depend strongly on the relative magnetization orientations of the grafted SMMs. The SMMs are playing the role of localized spin polarizer and analyzer on the CNT electronic conducting channel. As a result, we measured magneto-resistance ratios up to several hundred percent. We used this spin valve effect to confirm the strong uniaxial anisotropy and the superparamagnetic blocking temperature (TB ~ 1 K) of isolated TbPc2 SMMs. For the first time, the strength of exchange interaction between the different SMMs of the molecular spin valve geometry could be determined. Our results introduce a new design for operable molecular spintronic devices using the quantum effects of individual SMMs.

Urdampilleta, Matias; Nguyen, Ngoc-Viet; Cleuziou, Jean-Pierre; Klyatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang

2011-01-01

293

Maximized orbital and spin Kondo effects in a single-electron transistor  

NASA Astrophysics Data System (ADS)

We investigate the charge fluctuations of a single-electron box (metallic grain) coupled to a lead via a smaller quantum dot in the Kondo regime. The most interesting aspect of this problem resides in the interplay between spin Kondo physics stemming from the screening of the spin of the small dot and orbital Kondo physics emerging when charging states of the grain with (charge) Q=0 and Q=e are almost degenerate. Combining Wilson’s numerical renormalization-group method with perturbative scaling approaches we push forward our previous work [K. Le Hur and P. Simon, Phys. Rev. B 67, 201308R (2003)]. We emphasize that, for symmetric and slightly asymmetric barriers, the strong entanglement of charge and spin flip events in this setup inevitably results in a nontrivial stable SU(4) Kondo fixed point near the degeneracy points of the grain. By analogy with a small dot sandwiched between two leads, the ground state is Fermi-liquid-like, which considerably smears out the Coulomb staircase behavior and prevents the Matveev logarithmic singularity from arising. Most notably, the associated Kondo temperature TSU(4)K might be raised compared to that in conductance experiments through a small quantum dot (˜1 K), which makes the observation of our predictions a priori accessible. We discuss the robustness of the SU(4) correlated state against the inclusion of an external magnetic field, a deviation from the degeneracy points, particle-hole symmetry in the small dot, and asymmetric tunnel junctions and comment on the different crossovers.

Le Hur, Karyn; Simon, Pascal; Borda, László

2004-01-01

294

MFDs (Matrix Fraction Descriptions) of Spinning Satellite and Attitude Control Using Gyrotorquers.  

National Technical Information Service (NTIS)

The questions related to the matrix fraction descriptions (MFDs) and the minimal realizations of the transfer matrix of a spinning satellite system and control system design using output feedback are considered. The control torques are generated using gyr...

A. Iyer S. N. Singh T. A. Nartker

1989-01-01

295

Electric field control of spin rotation in bilayer graphene.  

PubMed

The manipulation of the electron spin degree of freedom is at the core of the spintronics paradigm, which offers the perspective of reduced power consumption, enabled by the decoupling of information processing from net charge transfer. Spintronics also offers the possibility of devising hybrid devices able to perform logic, communication, and storage operations. Graphene, with its potentially long spin-coherence length, is a promising material for spin-encoded information transport. However, the small spin-orbit interaction is also a limitation for the design of conventional devices based on the canonical Datta-Das spin field-effect transistors. An alternative solution can be found in magnetic doping of graphene or, as discussed in the present work, in exploiting the proximity effect between graphene and ferromagnetic oxides (FOs). Graphene in proximity to FO experiences an exchange proximity interaction, that acts as an effective Zeeman field for electrons in graphene, inducing a spin precession around the magnetization axis of the FO. Here we show that in an appropriately designed double-gate field-effect transistor, with a bilayer graphene channel and FO used as a gate dielectric, spin-precession of carriers can be turned ON and OFF with the application of a differential voltage to the gates. This feature is directly probed in the spin-resolved conductance of the bilayer. PMID:20929246

Michetti, Paolo; Recher, Patrik; Iannaccone, Giuseppe

2010-11-10

296

Controllable non-equilibrium spin injection of conduction electrons in magnetic quantum dots  

NASA Astrophysics Data System (ADS)

A non-equilibrium Green's function (NEGF) approach has been used to calculate the spin current and spin polarization of a two terminal mesoscopic system including a magnetic quantum dot. Numerical results show that spatial magnetization of the transport electrons can be controlled by the bias voltage in coherent regime. In this regime and for low magnetic fields bias voltage appears to be more effective than magnetic field for spin injection inside the dot.

Phirouznia, A.; Bourkheili, S. Hassanpour; Hesari, V. Zare

2012-04-01

297

Diabatic couplings for charge recombination via Boys localization and spin-flip configuration interaction singles  

NASA Astrophysics Data System (ADS)

We describe a straightforward technique for obtaining diabatic couplings applicable to charge transfer from or charge recombination to the electronic ground state. Our method is nearly black box, requiring minimal chemical intuition from the user, and merges two well-established approaches in electronic structure theory: first, smooth and balanced adiabatic states are generated using spin-flip-configuration interaction singles (SF-CIS) based on a triplet HF state; second, Boys localization is applied to rotate all adiabatic states into charge-localized diabatic states. The method is computationally inexpensive, scaling only with the cost of CIS, and does not require a choice of active space, which is usually required for such intrinsically multiconfigurational problems. Molecular LiF in vacuum and LiF solvated by a single water molecule are examined as model systems. We find nearly smooth diabatic potential energy surfaces and couplings and we find that the Condon approximation is obeyed approximately for this model problem.

Alguire, Ethan; Subotnik, Joseph E.

2011-07-01

298

Spin-wave storage using chirped control fields in atomic frequency comb-based quantum memory  

NASA Astrophysics Data System (ADS)

It has been shown that an inhomogeneously broadened optical transition shaped into an atomic frequency comb can store a large number of temporal modes of the electromagnetic field at the single-photon level without the need to increase the optical depth of the storage material. The readout of light modes is made efficient thanks to the rephasing of the optical-wavelength coherence similar to photon-echo-type techniques, and the reemission time is given by the comb structure. For on-demand readout and long storage times, two control fields are used to transfer the optical coherence back and forth into a spin wave. Here, we present a detailed analysis of the spin-wave storage based on chirped adiabatic control fields. In particular, we verify that chirped fields require significantly weaker intensities than ? pulses. The price to pay is a reduction of the multimode storage capacity that we quantify for realistic material parameters associated with solids doped with rare-earth-metal ions.

Miná?, Ji?í; Sangouard, Nicolas; Afzelius, Mikael; de Riedmatten, Hugues; Gisin, Nicolas

2010-10-01

299

T2-weighted breathold imaging of the liver: a quantitative and qualitative comparison of fast spin echo and half Fourier single shot fast spin echo imaging  

Microsoft Academic Search

The imaging characteristics of two EPI-hybrid breath-hold sequences, T2-weighted fast spin-echo [FSE, effective echo time\\u000a (TEeff) 138ms] and half Fourier single shot turbo spin-echo (HASTE, TEeff 60 ms), were compared in hepatic imaging.\\u000a \\u000a A total of 111 patients with suspected hepatic disease were studied at 1.5 Tesla using a body phase-array coil. The signal-to-noise\\u000a (S\\/N) and contrast-to-noise (C\\/N) ratios for

Thomas K. Helmberger; Julia Schröder; Nicolaus Holzknecht; Michaela Gregor; Andreas Heuck; Rainer Petsch; Maximilian F. Reiser

1999-01-01

300

Optical Control of Nuclear Spin Ensembles in Diamond  

NASA Astrophysics Data System (ADS)

We present new results on the hyperpolarization of ^13C nuclear spins in diamond through optically-oriented nitrogen vacancy (NV-) defects. Optical illumination of high NV- concentration diamonds at cryogenic temperatures and 9.4 Tesla results in a negative nuclear spin temperature with measured bulk-average polarization over 5%, although local polarization may be higher. The negative spin-temperature is attributed to a population inversion within the dipolar energy levels of the NV- spin ensemble. In our quantitative model, nuclei near defects equilibrate with the NV- dipolar energy reservoir and polarization is transported to the bulk material via spin diffusion. This model is tested by investigating a series of samples with varied defect density. We also investigate the nuclear hyperpolarization of NV- containing diamond nanocrystals. Such materials may be useful for surface transfer of polarization to target molecules for enhanced NMR sensitivity. Additionally, we investigate the dynamics and decoherence of the hyperpolarized nuclear spin ensemble and its interaction with electronic defect spins. Such phenomena are of fundamental interest to the use of diamond for quantum information applications.

King, Jonathan; Reimer, Jeffrey

2012-02-01

301

Controlling spin-wave propagation with Oersted fields  

NASA Astrophysics Data System (ADS)

The goal of magnon spintronics is to utilize the coherent propagation of spin waves for low-power data processing. Spin waves carry angular momentum and can transport spin information over distances much larger than the spin diffusion length of metals. However, in thin magnetic films the highly anisotropic dispersion relation leads to strong changes in the spin-wave energy for different angles between their propagation direction and the magnetization orientation. Consequently, spin waves only travel along a straight path if the magnetization direction is fixed by a global external magnetic field. We demonstrate that locally rotating magnetic fields generated via electric current pulses allow to vary the propagation direction of spin waves. Using spatially resolved Brillouin light scattering microscopy the propagation behavior was directly verified.footnotetextK. Vogt, H. Schultheiss, S. Jain, J.E. Pearson, A. Hoffmann, S.D. Bader, and B. Hillebrands, Appl. Phys. Lett. 101, 042410 (2012) We have modeled the current generated magnetic fields with a finite element code and calculated the magnetic response using micro magnetic simulations.

Vogt, K.; Hillebrands, B.; Schultheiss, H.; Pearson, J. E.; Fradin, F. Y.; Bader, S. D.; Hoffmann, A.

2013-03-01

302

Measurement of Single- and Double-Spin Asymmetries in Deep Inelastic Pion Electroproduction with a Longitudinally Polarized Target  

NASA Astrophysics Data System (ADS)

We report the first measurement of the transverse momentum dependence of double-spin asymmetries in semi-inclusive production of pions in deep-inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Jefferson Lab (JLab). Modulations of single spin asymmetries over the azimuthal angle between lepton scattering and hadron production planes ? have been measured over a wide kinematic range in Bjorken x and virtual photon squared four-momentum Q2. A significant nonzero sin?2? single spin asymmetry was observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton.

Avakian, H.; Bosted, P.; Burkert, V. D.; Elouadrhiri, L.; Adhikari, K. P.; Aghasyan, M.; Amaryan, M.; Anghinolfi, M.; Baghdasaryan, H.; Ball, J.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Branford, D.; Briscoe, W. J.; Brooks, W.; Carman, D. S.; Casey, L.; Cole, P. L.; Collins, P.; Crabb, D.; Crede, V.; D'Angelo, A.; Daniel, A.; Dashyan, N.; de Vita, R.; de Sanctis, E.; Deur, A.; Dey, B.; Dhamija, S.; Dickson, R.; Djalali, C.; Dodge, G.; Doughty, D.; Dupre, R.; El Alaoui, A.; Eugenio, P.; Fegan, S.; Fersch, R.; Forest, T. A.; Fradi, A.; Gabrielyan, M. Y.; Gavalian, G.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Gohn, W.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Hassall, N.; Heddle, D.; Hicks, K.; Holtrop, M.; Ilieva, Y.; Ireland, D. G.; Isupov, E. L.; Jawalkar, S. S.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Khetarpal, P.; Kim, W.; Klein, A.; Klein, F. J.; Konczykowski, P.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Kuznetsov, V.; Livingston, K.; Lu, H. Y.; Markov, N.; Mayer, M.; Martinez, D.; McAndrew, J.; McCracken, M. E.; McKinnon, B.; Meyer, C. A.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Moreno, B.; Moriya, K.; Morrison, B.; Moutarde, H.; Munevar, E.; Nadel-Turonski, P.; Nasseripour, R.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Niroula, M. R.; Osipenko, M.; Ostrovidov, A. I.; Paremuzyan, R.; Park, K.; Park, S.; Pasyuk, E.; Anefalos Pereira, S.; Perrin, Y.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Raue, B. A.; Ricco, G.; Ripani, M.; Rosner, G.; Rossi, P.; Sabatié, F.; Saini, M. S.; Salamanca, J.; Salgado, C.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Sober, D. I.; Sokhan, D.; Stepanyan, S. S.; Stepanyan, S.; Stoler, P.; Strauch, S.; Suleiman, R.; Taiuti, M.; Tedeschi, D. J.; Tkachenko, S.; Ungaro, M.; Vernarsky, B.; Vineyard, M. F.; Voutier, E.; Watts, D. P.; Weinstein, L. B.; Weygand, D. P.; Wood, M. H.; Zhang, J.; Zhao, B.; Zhao, Z. W.

2010-12-01

303

Measurement of Single- and Double-Spin Asymmetries in Deep Inelastic Pion Electroproduction with a Longitudinally Polarized Target  

SciTech Connect

We report the first measurement of the transverse momentum dependence of double-spin asymmetries in semi-inclusive production of pions in deep-inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Jefferson Lab (JLab). Modulations of single spin asymmetries over the azimuthal angle between lepton scattering and hadron production planes {phi} have been measured over a wide kinematic range in Bjorken x and virtual photon squared four-momentum Q{sup 2}. A significant nonzero sin2{phi} single spin asymmetry was observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton.

Avakian, H.; Bosted, P.; Burkert, V. D.; Elouadrhiri, L.; Brooks, W.; Carman, D. S.; Deur, A.; Guo, L.; Kubarovsky, V.; Nadel-Turonski, P.; Weygand, D. P. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Adhikari, K. P.; Amaryan, M.; Dodge, G.; Gavalian, G.; Guler, N.; Klein, A.; Kuhn, S. E.; Niroula, M. R.; Seraydaryan, H. [Old Dominion University, Norfolk, Virginia 23529 (United States)

2010-12-31

304

Ultrafast coherent electron spin control and correlated tunneling dynamics of two-dimensional electron gases  

NASA Astrophysics Data System (ADS)

Electron spins form a two-level quantum system in which the remarkable properties of quantum mechanics can be probed and utilized for many applications. By learning to manipulate these spins, it may be possible to construct a completely new form of technology based on the electron spin degree of freedom, known as spintronics. The most ambitious goal of spintronics is the development of quantum computing, in which electron spins are utilized as quantum bits, or qubits, with properties that are not possible with classical bits. Before these ideas can become reality, a system must be found in which spin lifetimes are long enough and in which spins can be completely controlled. Semiconductors are an excellent candidate for electron spin control since they can be integrated into on-chip devices and produced on a scalable level. The focus of this dissertation is on electron spin control in two different semiconductor systems, namely a two-dimensional electron gas in a modulation-doped quantum well and donor-bound electrons in bulk semiconductors. Both systems have been studied extensively for a variety of purposes. However, the ability to manipulate spins has been elusive. In this dissertation, the first experimentally successful demonstration of electron spin control in a two-dimensional electron gas is presented, in which ultrafast optical pulses induce spin rotations via the optical Stark effect. Donor-bound electron spin manipulation in bulk semiconductors is also investigated in this dissertation. Important information was obtained on the limiting factors that serve to prohibit spin control in this system. By taking these new factors into account, it is our hope that full electron spin control can eventually be accomplished in this system. Finally, through the course of investigating electron spin dynamics, a strange nonlinear optical behavior was observed in a bilayer system, which was determined to result from a coupling of optical interactions with tunneling rates between layers. The data suggest that there is a strong interplay between interlayer and intralayer correlations in this system. Investigations into the nature of this interaction were undertaken and are presented in the last part of this dissertation. This dissertation includes previously published and unpublished co-authored material.

Phelps, Carey E.

305

Suppression of Walker breakdown in magnetic domain wall propagation through structural control of spin wave emission  

NASA Astrophysics Data System (ADS)

The control of individual magnetic domain walls has potential for future spintronic memory and data processing applications. The speed and reliability of such devices are determined by the dynamic properties of the domain walls. Typically, spin precession limitations lead to Walker breakdown, limiting wall velocity resulting in low mobility. Here, we show the suppression of Walker breakdown by the careful design of small amplitude periodic nanowire structuring to match the periodicity of domain wall spin structure transformations. This opens up a channel for energy dissipation via spin wave emission, allowing a domain wall to maintain its spin structure during propagation.

Burn, David M.; Atkinson, Del

2013-06-01

306

Optimal control of a spinning double-pyramid Earth-pointing tethered formation  

Microsoft Academic Search

The dynamics and control of a tethered satellite formation for Earth-pointing observation missions is considered. For most practical applications in Earth orbit, a tether formation must be spinning in order to maintain tension in the tethers. It is possible to obtain periodic spinning solutions for a triangular formation whose initial conditions are close to the orbit normal. However, these solutions

Paul Williams

2009-01-01

307

Optical pumping of a single hole spin in a quantum dot  

Microsoft Academic Search

The spin of an electron is a natural two-level system for realizing a quantum bit in the solid state. For an electron trapped in a semiconductor quantum dot, strong quantum confinement highly suppresses the detrimental effect of phonon-related spin relaxation. However, this advantage is offset by the hyperfine interaction between the electron spin and the 104 to 106 spins of

Brian D. Gerardot; Daniel Brunner; Paul A. Dalgarno; Patrik Öhberg; Stefan Seidl; Martin Kroner; Khaled Karrai; Nick G. Stoltz; Pierre M. Petroff; Richard J. Warburton

2008-01-01

308

Electrically driven single-electron spin resonance in a slanting Zeeman field  

Microsoft Academic Search

The rapid rise of spintronics and quantum information science has led to a strong interest in developing the ability to coherently manipulate electron spins. Electron spin resonance is a powerful technique for manipulating spins that is commonly achieved by applying an oscillating magnetic field. However, the technique has proven very challenging when addressing individual spins. In contrast, by mixing the

M. Pioro-Ladrière; T. Obata; Y. Tokura; Y.-S. Shin; T. Kubo; K. Yoshida; T. Taniyama; S. Tarucha

2008-01-01

309

A scanning superconducting quantum interference device with single electron spin sensitivity.  

PubMed

Superconducting quantum interference devices (SQUIDs) can be used to detect weak magnetic fields and have traditionally been the most sensitive magnetometers available. However, because of their relatively large effective size (on the order of 1 µm), the devices have so far been unable to achieve the level of sensitivity required to detect the field generated by the spin magnetic moment (?B) of a single electron. Here we show that nanoscale SQUIDs with diameters as small as 46 nm can be fabricated on the apex of a sharp tip. The nano-SQUIDs have an extremely low flux noise of 50 n?0 Hz(-1/2) and a spin sensitivity of down to 0.38 ?B Hz(-1/2), which is almost two orders of magnitude better than previous devices. They can also operate over a wide range of magnetic fields, providing a sensitivity of 0.6 ?B Hz(-1/2) at 1 T. The unique geometry of our nano-SQUIDs makes them well suited to scanning probe microscopy, and we use the devices to image vortices in a type II superconductor, spaced 120 nm apart, and to record magnetic fields due to alternating currents down to 50 nT. PMID:23995454

Vasyukov, Denis; Anahory, Yonathan; Embon, Lior; Halbertal, Dorri; Cuppens, Jo; Neeman, Lior; Finkler, Amit; Segev, Yehonathan; Myasoedov, Yuri; Rappaport, Michael L; Huber, Martin E; Zeldov, Eli

2013-09-01

310

Symmetric rotating-wave approximation for the generalized single-mode spin-boson system  

SciTech Connect

The single-mode spin-boson model exhibits behavior not included in the rotating-wave approximation (RWA) in the ultra and deep-strong coupling regimes, where counter-rotating contributions become important. We introduce a symmetric rotating-wave approximation that treats rotating and counter-rotating terms equally, preserves the invariances of the Hamiltonian with respect to its parameters, and reproduces several qualitative features of the spin-boson spectrum not present in the original rotating-wave approximation both off-resonance and at deep-strong coupling. The symmetric rotating-wave approximation allows for the treatment of certain ultra- and deep-strong coupling regimes with similar accuracy and mathematical simplicity as does the RWA in the weak-coupling regime. Additionally, we symmetrize the generalized form of the rotating-wave approximation to obtain the same qualitative correspondence with the addition of improved quantitative agreement with the exact numerical results. The method is readily extended to higher accuracy if needed. Finally, we introduce the two-photon parity operator for the two-photon Rabi Hamiltonian and obtain its generalized symmetric rotating-wave approximation. The existence of this operator reveals a parity symmetry similar to that in the Rabi Hamiltonian as well as another symmetry that is unique to the two-photon case, providing insight into the mathematical structure of the two-photon spectrum, significantly simplifying the numerics, and revealing some interesting dynamical properties.

Albert, Victor V.; Scholes, Gregory D.; Brumer, Paul [Department of Chemistry and Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, M5S 3H6 (Canada)

2011-10-15

311

Zeeman-type spin splitting controlled by an electric field  

NASA Astrophysics Data System (ADS)

Transition-metal dichalcogenides such as WSe2 and MoS2 have electronic band structures that are ideal for hosting many exotic spin-orbit phenomena. Here we investigate the possibility to generate and modulate a giant Zeeman-type spin polarization in WSe2 under an external electric field. By tuning the perpendicular electric field applied to the WSe2 channel with an electric-double-layer transistor, we observe a systematic crossover from weak localization to weak anti-localization in magnetotransport. Our optical reflection measurements also reveal an electrically tunable exciton splitting. Using first-principles calculations, we propose that these are probably due to the emergence of a merely out-of-plane and momentum-independent spin splitting at and in the vicinity of the vertices of the WSe2 Brillouin zone under electric field. The non-magnetic approach for creating such an intriguing spin splitting keeps the system time-reversally invariant, thereby suggesting a new method for manipulating the spin degrees of freedom of electrons.

Yuan, Hongtao; Bahramy, Mohammad Saeed; Morimoto, Kazuhiro; Wu, Sanfeng; Nomura, Kentaro; Yang, Bohm-Jung; Shimotani, Hidekazu; Suzuki, Ryuji; Toh, Minglin; Kloc, Christian; Xu, Xiaodong; Arita, Ryotaro; Nagaosa, Naoto; Iwasa, Yoshihiro

2013-09-01

312

Contribution of twist-3 multigluon correlation functions to single spin asymmetry in semi-inclusive deep inelastic scattering  

SciTech Connect

As a possible source of the single transverse-spin asymmetry, we study the contribution from purely gluonic correlation represented by the twist-3 ''three-gluon correlation'' functions in the transversely polarized nucleon. We first define a complete set of the relevant three-gluon correlation functions, and then derive its contribution to the twist-3 single-spin-dependent cross section for the D-meson production in semi-inclusive deep inelastic scattering, which is relevant to determine the three-gluon correlations. Our cross-section formula differs from the corresponding result in the literature, and the origin of the discrepancy is clarified.

Beppu, Hiroo; Yoshida, Shinsuke [Graduate School of Science and Technology, Niigata University, Ikarashi, Niigata 950-2181 (Japan); Koike, Yuji [Department of Physics, Niigata University, Ikarashi, Niigata 950-2181 (Japan); Tanaka, Kazuhiro [Department of Physics, Juntendo University, Inzai, Chiba 270-1695 (Japan)

2010-09-01

313

Processing, spinning, and fabrication of continuous fibers of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes (SWNTs) show great promise for use in a wide range of applications. One of the most promising avenues for attaining these applications is the dispersion of SWNTs at high concentrations in superacids and processing into macroscopic articles such as fibers or films. Fibers spun from SWNT/superacid dispersions indicate that the morphology of the starting SWNT material influences the final morphology of the as-spun fiber. Here, we describe a method (termed disentanglement) of dispersing SWNTs in superacids and treating them using a high-shear, rotor/stator homogenizer, followed by coagulation to recover the solid SWNT material for use in fiber spinning. Several lines of experimental evidence (rheology and optical microscopy of the SWNTs in solution, scanning electron microscopy (SEM) of the coagulated material, and SEM of fibers spun from the coagulated material) show that this disentanglement treatment radically improves the degree of alignment in the SWNTs' morphology, which in turn improves the dispersibility and processability. Raman microscopy and thermogravimetric analysis (TGA) before and after homogenization show that the treatment does not damage the SWNTs. Although this technique is particularly important as a pre-processing step for fiber spinning of neat SWNT fibers, it is also useful for neat SWNT films, SWNT/polymer composites, and surfactant- or polymer-stabilized SWNT dispersions. Macroscopic neat SWNT fibers were successfully produced and characterized. Studies on coagulated fiber morphology suggest that slow acid removal is crucial to minimizing voids. Better SWNT coalescence and alignment were obtained by using appropriate coagulant and dope concentration. SWNTs were disentangled and dissolved at high concentrations (8 - 10 wt%) in 102% sulfuric acid. Fibers were subsequently extruded by dry-jet wet spinning into ice water and polyvinyl alcohol (PVA) / ice water. Drawing the fiber continuously while spinning further aligned the SWNTs within the fiber. The use of PVA (< 1%) in the coagulant slowed acid removal allowing better SWNT coalescence without damaging the SWNT electrical properties. The resulting combination of pre-processing and fiber drawing shows a threefold improvement in fiber tensile strength.

Booker, Richard Delane

314

Hill’s determinant approach to single-mode spin-boson model  

NASA Astrophysics Data System (ADS)

An efficient and stable numerical scheme based on Hill’s determinant is proposed for computing the whole spectrum of the single-mode spin-boson model. Its shown that for the low-lying levels a simple version of Hill’s determinant method works well, while for high levels a normalization of the determinant is necessary and this normalization results in an entire function whose zeros correspond to the energy levels. It is very convenient to use this entire function to compute all the energy levels numerically. Some high levels of the model are computed and compared with Irish’s general rotating-wave approximation. A scaling law in the large photon number limit is numerically tested and several statistical properties of the spectrum are investigated.

Wang, Qing-Wei; Liu, Yu-Liang

2013-11-01

315

Helicity asymmetry E measurement for single ?0 photoproduction with a frozen spin target  

NASA Astrophysics Data System (ADS)

The helicity asymmetry for single neutral pion photoproduction was measured using the CLAS detector in Hall B at the Thomas Jefferson National Accelerator Facility. This measurement used longitudinally polarized protons and circularly polarized photons with photon energis between 0.35 GeV to 2.4 GeV. The target was a frozen-spin butanol (C4H9OH) target, polarized at about 85%. The helicity asymmetry E for the ?p-->p?0 was measured with missing-mass technique at the high statistics of about 12×106 events. The experimental results are compared to three available theoretical predictions, SAID, MAID, and EBAC. The preliminary results are in good agreement with the model calculations at low E? energy bins. However, a significant deviation is observed at high energy bins. Therefore, the new data will help to constrain the parameters of the theoretical models.

Iwamoto, Hideko; CLAS Collaboration

2012-04-01

316

Spin mixing conductance at a well-controlled platinum/yttrium iron garnet interface  

NASA Astrophysics Data System (ADS)

A platinum (Pt)/yttrium iron garnet (YIG) bilayer system with a well-controlled interface has been developed; spin mixing conductance at the Pt/YIG interface has been studied. A clear interface with good crystal perfection is experimentally demonstrated to be one of the important factors for an ultimate spin mixing conductance. The spin mixing conductance is obtained to be 1.3 × 1018 m-2 at the well-controlled Pt/YIG interface, which is close to a theoretical prediction.

Qiu, Z.; Ando, K.; Uchida, K.; Kajiwara, Y.; Takahashi, R.; Nakayama, H.; An, T.; Fujikawa, Y.; Saitoh, E.

2013-08-01

317

Spin crossover in a single Fe(phen)2(NCS)2 molecule adsorbed onto metallic substrates: An ab initio calculation  

NASA Astrophysics Data System (ADS)

The spin crossover from high-spin (HS) to low-spin (LS) magnetic state of a single Fe(phen)2(NCS)2 molecule adsorbed onto a metallic substrate is shown to be possible by means of density functional theory. The calculation also shows that a monolayer of nitrogen on Cu(001) reduces drastically the molecule-surface adsorption energy and chemical bonding, making the molecule switchable between its two magnetic states by means of an external stimuli, as observed experimentally. To show that the spin transition is not strongly affected by the type of exchange and correlation potential, both the generalized-gradient approximation (GGA) and the so-called GGA+U method have been used including weak van der Waals interactions. The calculated scanning tunneling microscopy (STM) images of the HS and LS states within the Hamann-Tersoff approximation explain correctly the experimental data.

Gueddida, S.; Alouani, M.

2013-04-01

318

Optimal control of the inversion of two spins in Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We investigate the optimal control of the inversion of two spin 1/2 particles in Nuclear Magnetic Resonance. The two spins, which differ by their resonance offset, are controlled by the same radio frequency magnetic field. Using the Pontryagin Maximum Principle, we compute the optimal control sequence which allows to reach the target state in a given time, while minimizing the energy of the magnetic field. A comparison with the time-optimal solution for bounded control amplitude realizing the same control in the same time is made. An experimental illustration is done using techniques of Nuclear Magnetic Resonance.

Assémat, E.; Attar, L.; Penouilh, M.-J.; Picquet, M.; Tabard, A.; Zhang, Y.; Glaser, S. J.; Sugny, D.

2012-09-01

319

Controlled exchange interaction for quantum logic operations with spin qubits in coupled quantum dots  

SciTech Connect

A two-electron system confined in two coupled semiconductor quantum dots is investigated as a candidate for performing quantum logic operations with spin qubits. We study different processes of swapping the electron spins by a controlled switching on and off of the exchange interaction. The resulting spin swap corresponds to an elementary operation in quantum-information processing. We perform direct simulations of the time evolution of the two-electron system. Our results show that, in order to obtain the full interchange of spins, the exchange interaction should change smoothly in time. The presence of jumps and spikes in the time characteristics of the confinement potential leads to a considerable increase of the spin-swap time. We propose several mechanisms to modify the exchange interaction by changing the confinement potential profile and discuss their advantages and disadvantages.

Moskal, S.; Bednarek, S.; Adamowski, J. [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Cracow (Poland)

2007-09-15

320

Spintronic single-qubit gate based on a quantum ring with spin-orbit interaction  

Microsoft Academic Search

In a quantum ring connected with two external leads the spin properties of an\\u000aincoming electron are modified by the spin-orbit interaction resulting in a\\u000atransformation of the qubit state carried by the spin. The ring acts as a one\\u000aqubit spintronic quantum gate whose properties can be varied by tuning the\\u000aRashba parameter of the spin-orbit interaction, by changing

Péter Földi; Balázs Molnár; Mihaly G. Benedict; F. M. Peeters

2005-01-01

321

Voltage-controlled spin transport through a pair of Buckminster fullerene molecules encapsulating cobalt atoms  

NASA Astrophysics Data System (ADS)

Carbon-based nanostructures such as fullerenes, carbon nanotubes, and graphene, are promising candidates for spintronic applications because of their weak spin-orbit coupling and hyperfine interaction which lead to long spin coherence lengths. In particular, a fullerene C60 molecule is an interesting carbon nanostructure which can be used as a molecular bridge in magnetic tunnel junctions due to its remarkable structural stability and electronic properties which make the molecule convenient for easier spin injection in magnetic nanojunctions. Here, we show that using cobalt atoms encapsulated in a pair of Buckminster fullerene molecules sandwiched between gold electrodes, density of states spin polarizations as large as 95% are found by varying the gate and/or bias voltage, due to the spin-splitting of Co 3d orbitals. The current-voltage characteristics and strong (up to 100%) spin polarization of the current indicate that the device can be utilized for highly efficient spin injection into nonmagnetic conductors. These results open the way to voltage-controlled spin filters and magnetic sensors using molecular magnetic junctions.

Saffarzadeh, Alireza; Kirczenow, George

2013-03-01

322

Evidence Of An Incommensurate Spin-Density Wave Instability In Single Crystal Bafe2as Detected By 75as NMR  

SciTech Connect

We report a {sup 75}As NMR study of BaFe{sub 2}As{sub 2} in both single crystal and polycrystal forms. The temperature dependence of the {sup 75}As NMR spectra shows magnetic broadening associated with a spin-density-wave instability at 85 K for the single crystal and at 138 K for the polycrystal material. The nuclear spin-lattice relaxation rate T{sub 1}{sup -1} exhibits a sharp maximum at the transition and is independent of field orientation in the single crystal. Our study suggests that there is no significant difference in the physics of single crystal and polycrystal BaFe{sub 2}As{sub 2} even though some properties differ qualitatively.

Baek, Seung H [Los Alamos National Laboratory; Klimczuk, Tomasz W [Los Alamos National Laboratory; Ronning, Filip [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Curro, Nicholas J [UC-DAVIS

2008-01-01

323

Next-to-Leading Order Calculation of the Single Transverse Spin Asymmetry in the Drell-Yan Process  

SciTech Connect

We calculate the next-to-leading order perturbative QCD corrections to the transverse momentum weighted single transverse spin asymmetry in Drell-Yan lepton pair production in hadronic collisions. We identify the splitting function relevant for the scale evolution of the twist-three quark-gluon correlation function. We comment on the consequences of our results for phenomenology.

Vogelsang, Werner; Yuan, Feng

2009-03-30

324

Electron spin resonance of phosphorescent fluorine-substituted aromatics. I. 1-Fluoronaphthalene and 2-fluoronaphthalene in durene single crystals  

Microsoft Academic Search

The lowest excited triplet state of the three compounds naphthalene, 1-fluoronaphthalene and 2-fluoronaphthalene, has been investigated by electron spin resonance spectroscopy. The phosphorescent molecules were oriented and diluted in durene single crystals. Zero field energies, principal values of the g tensors and hyperfine coupling constants for hydrogen and fluorine nuclei in the three canonical orientations are reported. A detailed comparative

J. Mispelter; J.-Ph. Grivet; J.-M. Lhoste

1971-01-01

325

Predictions for single spin asymmetries in lepton + p(transv. polarized) -> pion + X and gamma^* + p(transv. polarized) -> pion + X  

Microsoft Academic Search

Predictions for the single transverse spin asymmetry A_N in semi-inclusive\\u000aDIS processes are given; non negligible values of A_N may arise from spin\\u000aeffects in the fragmentation of a polarized quark into a final hadron with a\\u000atransverse momentum k_T with respect to the jet axis, the so-called Collins\\u000aeffect. The elementary single spin asymmetry of the fragmenting quark has

M. Anselmino; M. Boglione; J. Hansson; F. Murgia

1999-01-01

326

Controlling spin ordering in frustrated magnets via thin film heteroepitaxy  

NASA Astrophysics Data System (ADS)

Competing exchange interactions can give rise to varying degrees of frustration that manifest itself in noncollinear magnetic moment ordering or canonical geometric frustration in magnets with large ground-state degeneracies. Relieving this frustration has the potential to stabilize ground states inaccessible in the bulk. We demonstrate that heteroepitaxial lattice distortions can modify the strength of exchange interactions in thin films of the frustrated ferrimagnet, CuCr2O4. The reduction of magnetic frustration in CuCr2O4 through lattice distortions results in greater collinear spin ordering in CuCr2O4 thin films and an enhanced magnetization. We identify heteroepitaxial lattice distortions as a method to tune spin functionality and potentially lift ground-state degeneracies more broadly in frustrated magnets.

Iwata-Harms, Jodi M.; Wong, Franklin J.; Alaan, Urusa S.; Kirby, B. J.; Borchers, Julie A.; Toney, Michael F.; Nelson-Cheeseman, Brittany B.; Liberati, Marco; Arenholz, Elke; Suzuki, Yuri

2012-06-01

327

FEM Optimization of Spin Forming Using a Fuzzy Control Algorithm  

Microsoft Academic Search

Finite element (FE) simulation of the manufacturing of a conical nosing such as a pressure vessel from circular tubes, using the spin forming method, was performed on the commercially available software package, ANSYS\\/LS-DYNA3D. The finite element method (FEM) provides a powerful tool for evaluating the potential to form the pressure vessel with proposed modifications to the process. The use of

S. Yoshihara; P. Ray; B. J. MacDonald; H. Koyama; M. Kawahara

2004-01-01

328

Electric control of spin-dependent Goos-Hänchen shift in a magnetically modulated semiconductor nanostructure  

NASA Astrophysics Data System (ADS)

We theoretically investigate how to manipulate spin-dependent Goos-Hänchen (GH) shifts by an applied bias in a realistic magnetic-barrier nanostructure, which is experimentally created by depositing a ferromagnetic stripe with perpendicular magnetization on the top of heterostructure. GH shifts of transmitted electron beams are calculated numerically with the help of the stationary phase method. It is shown that both magnitude and sign of spin polarization in GH shifts are closely relative to the applied bias, which can give rise to a bias-controllable spin beam splitter.

Kong, Yong-Hong; Fu, Xi; Chen, Sai-Yan; Li, Ai-Hua; Liang, Xiao-Lin

2013-11-01

329

Magneto-optical control of atomic spin mixing in dipolar spinor Bose-Einstein condensates  

SciTech Connect

We study the role in an external photoassociation light field in the spin mixing dynamics of a spin-one Bose condensate with long-range magnetic dipole-dipole interaction. The mean-field energy functional of the system is found to be formally identical to that of two coupled nonrigid pendulums, manifesting either constructive or destructive interferences. The interplay between photoassociation and the magnetic dipole-dipole interaction provides a novel route to the magneto-optical quantum control of atomic spin mixing in dipolar spinor condensates.

Jing, H.; Jiang, Y. [Department of Physics, Henan Normal University, Xinxiang 453007 (China); Meystre, P. [B2 Institute and Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)

2009-12-15

330

Efficient and accurate local single reference correlation methods for high-spin open-shell molecules using pair natural orbitals  

NASA Astrophysics Data System (ADS)

A production level implementation of the high-spin open-shell (spin unrestricted) single reference coupled pair, quadratic configuration interaction and coupled cluster methods with up to doubly excited determinants in the framework of the local pair natural orbital (LPNO) concept is reported. This work is an extension of the closed-shell LPNO methods developed earlier [F. Neese, F. Wennmohs, and A. Hansen, J. Chem. Phys. 130, 114108 (2009); F. Neese, A. Hansen, and D. G. Liakos, J. Chem. Phys. 131, 064103 (2009)]. The internal space is spanned by localized orbitals, while the external space for each electron pair is represented by a truncated PNO expansion. The laborious integral transformation associated with the large number of PNOs becomes feasible through the extensive use of density fitting (resolution of the identity (RI)) techniques. Technical complications arising for the open-shell case and the use of quasi-restricted orbitals for the construction of the reference determinant are discussed in detail. As in the closed-shell case, only three cutoff parameters control the average number of PNOs per electron pair, the size of the significant pair list, and the number of contributing auxiliary basis functions per PNO. The chosen threshold default values ensure robustness and the results of the parent canonical methods are reproduced to high accuracy. Comprehensive numerical tests on absolute and relative energies as well as timings consistently show that the outstanding performance of the LPNO methods carries over to the open-shell case with minor modifications. Finally, hyperfine couplings calculated with the variational LPNO-CEPA/1 method, for which a well-defined expectation value type density exists, indicate the great potential of the LPNO approach for the efficient calculation of molecular properties.

Hansen, Andreas; Liakos, Dimitrios G.; Neese, Frank

2011-12-01

331

Multiferroic M-Type Hexaferrites with a Room-Temperature Conical State and Magnetically Controllable Spin Helicity  

NASA Astrophysics Data System (ADS)

Magnetic and magnetoelectric (ME) properties have been studied for single crystals of Sc-doped M-type barium hexaferrites. Magnetization (M) and neutron diffraction measurements revealed that by tuning Sc concentration a longitudinal conical state is stabilized up to above room temperatures. ME measurements have shown that a transverse magnetic field (H) can induce electric polarization (P) at lower temperatures and that the spin helicity is nonvolatile and endurable up to near the conical magnetic transition temperature. It was also revealed that the response (reversal or retention) of the P vector upon the reversal of M varies with temperature. In turn, this feature allows us to control the relation between the spin helicity and the M vectors with H and temperature.

Tokunaga, Y.; Kaneko, Y.; Okuyama, D.; Ishiwata, S.; Arima, T.; Wakimoto, S.; Kakurai, K.; Taguchi, Y.; Tokura, Y.

2010-12-01

332

Multiferroic M-type hexaferrites with a room-temperature conical state and magnetically controllable spin helicity.  

PubMed

Magnetic and magnetoelectric (ME) properties have been studied for single crystals of Sc-doped M-type barium hexaferrites. Magnetization (M) and neutron diffraction measurements revealed that by tuning Sc concentration a longitudinal conical state is stabilized up to above room temperatures. ME measurements have shown that a transverse magnetic field (H) can induce electric polarization (P) at lower temperatures and that the spin helicity is nonvolatile and endurable up to near the conical magnetic transition temperature. It was also revealed that the response (reversal or retention) of the P vector upon the reversal of M varies with temperature. In turn, this feature allows us to control the relation between the spin helicity and the M vectors with H and temperature. PMID:21231619

Tokunaga, Y; Kaneko, Y; Okuyama, D; Ishiwata, S; Arima, T; Wakimoto, S; Kakurai, K; Taguchi, Y; Tokura, Y

2010-12-13

333

Coherent Control of the Route of an Ultrafast Magnetic Phase Transition via Low-Amplitude Spin Precession  

NASA Astrophysics Data System (ADS)

Time-resolved magneto-optical imaging of laser-excited rare-earth orthoferrite (SmPr)FeO3 demonstrates that a single 60 fs circularly polarized laser pulse is capable of creating a magnetic domain on a picosecond time scale with a magnetization direction determined by the helicity of light. Depending on the light intensity and sample temperature, pulses of the same helicity can create domains with opposite magnetizations. We argue that this phenomenon relies on a twofold effect of light which (i) instantaneously excites coherent low-amplitude spin precession and (ii) triggers a spin reorientation phase transition. The former dynamically breaks the equivalence between two otherwise degenerate states with opposite magnetizations in the high-temperature phase and thus controls the route of the phase transition.

de Jong, J. A.; Razdolski, I.; Kalashnikova, A. M.; Pisarev, R. V.; Balbashov, A. M.; Kirilyuk, A.; Rasing, Th.; Kimel, A. V.

2012-04-01

334

Organic polyanionic high-spin molecular clusters: topological-symmetry controlled models for organic ferromagnetic metals.  

PubMed

Trianionic spin-quartet and tetraanionic spin-quintet molecular clusters derived from m-dibenzoylbenzene in solution were identified by CW-ESR/pulse-ESR based two-dimensional electron spin transient nutation spectroscopy, and their spin and clustering structures in the ground state were determined in terms of a D-tensor based phenomenological approach and DFT calculations. The molecular structures obtained semiempirically are supported by DFT-based quantum chemical calculations. The DFT calculations have been tested for a sodium ion bridged fluorenone-based cluster, [fluorenone(-)? {Na(+)(dme)(2)}](2), whose crystal structure was reported in the literature [H. Bock, H.-F. Herrmann, D. Fenske and H. Goesmann, Angew. Chem., Int. Ed. Engl., 1988, 27, 1067], reproducing the experimentally determined moelcular structure of the dimer cluster. It is suggested that both the quartet and quintet clusters in the 2-MTHF glass and solution form the cross-typed structures with the two m-dibenzoylbenzene moieties in cis-configuration. A dianionic spin-triplet m-dibenzoylbenzene derivative was detected for the first time and its charge and spin densities were studied by the quantum chemical calculations. The high-spin states of the open-shell entities under study were confirmed by X-band pulse-ESR based electron spin nutation spectroscopy in organic frozen glasses. The D values and other spin Hamiltonian parameters of all the polyanionic high-spin species were determined by the hybrid eigenfield spectral simulation for fine-structure ESR spectra. m-Dibenzoylbenzene provides pseudo-degenerate ?-LUMOs arising from its topological symmetry of the ?-electron network and its dianion in the triplet ground state is a prototypical model for topologically-controlled genuinely organic ferromagnetic metals. PMID:21103561

Nakazawa, Shigeaki; Sato, Kazunobu; Shiomi, Daisuke; Yano, Masafumi; Kinoshita, Takamasa; Franco, Maria Luisa T M B; Lazana, Maria Celina R L R; Shohoji, Maria Candida B L; Itoh, Koichi; Takui, Takeji

2010-11-22

335

Controlling the quantum state of a single photon emitted from a single polariton  

SciTech Connect

We investigate in detail the optimal conditions for a high fidelity transfer from a single-polariton state to a single-photon state and subsequent homodyne detection of the single photon. We assume that, using various possible techniques, the single polariton has initially been stored as a spin-wave grating in a cloud of cold atoms inside a low-finesse cavity. This state is then transferred to a single-photon optical pulse using an auxiliary beam. We optimize the retrieval efficiency and determine the mode of the local oscillator that maximizes the homodyne efficiency of such a photon. We find that both efficiencies can have values close to one in a large region of experimental parameters.

Stanojevic, Jovica; Parigi, Valentina; Bimbard, Erwan; Tualle-Brouri, Rosa; Ourjoumtsev, Alexei; Grangier, Philippe [Laboratoire Charles Fabry, Institut d'Optique, CNRS, Universite Paris-Sud, Campus Polytechnique, RD 128, FR-91127 Palaiseau cedex (France)

2011-11-15

336

Magnetic field controlled reversal of ferroelectric polarization in conical spin ordered multiferroics: Monte Carlo simulation  

Microsoft Academic Search

To understand the fascinating multiferroicity observed in CoCr2O4, Monte Carlo simulation is performed on a three-dimensional spinel lattice with classical Heisenberg spins. The conical spin order is confirmed to be the origin of the peculiar magnetoelectric behavior with coexisting magnetization and ferroelectric polarization. Furthermore, the simultaneous reversals of magnetization and polarization controlled by the external magnetic field are reproduced, consisting

Xiaoyan Yao; Veng Cheong Lo; Jun-Ming Liu

2009-01-01

337

A Spin-Polarized Current Direction Controller Based on a Nonuniform Rashba Quantum Wire  

NASA Astrophysics Data System (ADS)

A spin-polarized current direction controller scheme is proposed based on a nonuniform Rashba quantum wire. It is shown that |PLRz| = |PRLz|, whereas their signs are opposite, and the effect of this phenomenon is due to the two broken symmetries and the unbroken C2-rotation symmetry of the investigated system. In addition, the spin-polarized current is nonzero even with a strong disorder strength, which demonstrates that this structure may be utilized for potential applications.

Xu, Zhong-Hui; Xiao, Wen; Chen, Yu-Guang

2013-05-01

338

Large anisotropy of the spin-orbit interaction in a single InAs self-assembled quantum dot.  

PubMed

The anisotropy of the spin-orbit interaction (SOI) is studied for a single uncapped InAs self-assembled quantum dot holding just a few electrons. The SOI energy is evaluated from anticrossing or SOI-induced hybridization between the ground and excited states with opposite spins. The magnetic angular dependence of the SOI energy falls on an absolute cosine function for azimuthal rotation, and a cosinelike function for tilting rotation. Furthermore, the SOI energy is quenched for a specific magnetic field vector. The angular dependence of SOI is found to compare well with calculation of Rashba SOI in a two-dimensional harmonic potential. PMID:20867321

Takahashi, S; Deacon, R S; Yoshida, K; Oiwa, A; Shibata, K; Hirakawa, K; Tokura, Y; Tarucha, S

2010-06-14

339

Control of spin-up and slewing of the WISP Shuttle-antennae system  

NASA Astrophysics Data System (ADS)

This paper deals with the dynamics and control of planar spin-up and slewing of the Space Shuttle carrying two 150 m long, flexible antenna booms. A recently developed technique of robust vibration suppression is used with the spin-up and slewing maneuvers. Open loop control of spin-up is achieved with very little residual vibration. Slewing through 90 degrees is completed in less than sixteen minutes by combining input shaping for vibration reduction with closed loop PID control. Robustness of the control to frequency errors is demonstrated. Results are based on an order-n dynamical formulation for a discretized model that permits a study of large deflection of the booms.

Banerjee, Arun K.

1991-08-01

340

General positivity bounds for spin observables in single particle inclusive production  

SciTech Connect

Positivity constraints, derived initially assuming parity conservation, for the inclusive reaction of the type A(spin1/2)+B(spin1/2){yields}C+X, where the spins of both initial spin-1/2 particles can be in any possible directions and no polarization is observed in the final state, are generalized to the case of parity violation. By means of a systematic method, we obtain nontrivial bounds involving all the spin observables of the reaction and we discuss some relevant physics processes. Particularly, we discover a nontrivial positivity constraint for the processes pp{yields}W{sup {+-}}/Z{sup 0}+X or pp{yields}{ell}{sup {+-}}+X where {ell}{sup {+-}} decayed from W{sup {+-}}/Z{sup 0}, which could be checked at the ongoing longitudinal spin program at Relativistic Heavy Ion Collider.

Kang, Z.B.; Soffer, J.

2011-06-08

341

Single spin states in a defect center resolved by optical spectroscopy  

NASA Astrophysics Data System (ADS)

Individual paramagnetic defect centers in diamond nanocrystals have been investigated by low-temperature high-resolution optical spectroscopy. Narrow fluorescence excitation spectral lines have been found, indicating transitions between individual spin sublevels. Spectral diffusion is explained by cross relaxation among spin sublevels and by the presence of excited electrons in the conduction band of diamond. The relaxation times are in the millisecond range. The system may be useful for quantum information processing with individual electron spins.

Jelezko, F.; Popa, I.; Gruber, A.; Tietz, C.; Wrachtrup, J.; Nizovtsev, A.; Kilin, S.

2002-09-01

342

Manipulation of a single electron spin in a quantum dot without magnetic field  

NASA Astrophysics Data System (ADS)

In this paper, we propose the construction of a nanodevice performing the spin rotations of an electron confined in an electrostatic quantum dot without the use of a magnetic field. Sinusoidally varying voltage applied in different phases to four gates causes the electron to move along a two-dimensional closed path. The spin-orbit interaction that is present in the structure induces spin rotations. For a properly adjusted AC signal duration, the logical NOT operation or the Hadamard quantum gate can be performed on the electron spin. We perform a simulation of the nanodevice's time evolution.

Bednarek, S.; Paw?owski, J.; Skubis, A.

2012-05-01

343

Longitudinal and spin-valley Hall optical conductivity in single layer MoS2  

NASA Astrophysics Data System (ADS)

A monolayer of MoS2 has a noncentrosymmetric crystal structure, with spin-polarized bands. It is a two-valley semiconductor with the direct gap falling in the visible range of the electromagnetic spectrum. Its optical properties are of particular interest in relation to valleytronics and possible device applications. We study the longitudinal and the transverse Hall dynamical conductivity which is decomposed into charge, spin, and valley contributions. The circular polarized light associated with each of the two valleys separately is considered and results are filtered according to spin polarization. Temperature can greatly change the spin admixture seen in the frequency window where they are not closely in balance.

Li, Zhou; Carbotte, J. P.

2012-11-01

344

Modified Pulsed-continuous arterial spin labeling for labeling of a single artery  

PubMed Central

Imaging the contribution of different arterial vessels to the blood supply of the brain can potentially guide the treatment of vascular disease and other disorders. Previously available only with catheter angiography, vessel selective labeling of arteries has now been demonstrated with pulsed and continuous arterial spin labeling (ASL) methods. Pulsed continuous labeling, which permits continuous labeling on standard scanner RF hardware, has been used to encode the contribution of different vessels to the blood supply of the brain. Vessel encoding requires a longer scan, a more complex reconstruction algorithm, and may be more sensitive to fluctuations in flow, however. Here a method is presented for single artery selective labeling in which a disc around the targeted vessel is labeled. Based on pulsed-continuous labeling, this method is achieved by rotating the directions of added in-plane gradients. Numerical simulations of the simplest strategy show good efficiency but poor suppression of labeling at large distances from the target vessel. Amplitude modulation of the rotating in-plane gradients results in better suppression of distant vessels. In-vivo results demonstrate highly selective labeling of individual vessels and a rapid falloff of the labeling with distance from the center of the labeling disc, in agreement with the simulations.

Dai, Weiying; Robson, Philip M.; Shankaranarayanan, Ajit; Alsop, David C.

2012-01-01

345

Single spin asymmetries in lp{yields}hX processes: A test of factorization  

SciTech Connect

Predictions for the transverse single spin asymmetry (SSA), A{sub N}, are given for the inclusive processes lp{sup {up_arrow}{yields}h}X and lp{sup {up_arrow}{yields}j}et+X, which could be measured in operating or future experiments. These estimates are based on the Sivers distributions and the Collins fragmentation functions which fit the azimuthal asymmetries measured in semi-inclusive deep inelastic scattering (SIDIS) processes (lp{sup {up_arrow}{yields}l'}hX). The factorization in terms of transverse momentum dependent distribution and fragmentation functions (TMD factorization)--which supplies the theoretical framework in which SIDIS azimuthal asymmetries are analyzed--is assumed to hold also for the lp{yields}hX inclusive process at large P{sub T}. A measurement of A{sub N} would then provide a direct test of the validity of the TMD factorization in this case and would have important consequences for the study and understanding of SSAs in pp{sup {up_arrow}{yields}h}X processes.

Anselmino, M.; Boglione, M.; Prokudin, A. [Dipartimento di Fisica Teorica, Universita di Torino, Via P. Giuria 1, I-10125 Torino (Italy); INFN, Sezione di Torino, Via P. Giuria 1, I-10125 Torino (Italy); D'Alesio, U. [Dipartimento di Fisica, Universita di Cagliari, I-09042 Monserrato (Italy); INFN, Sezione di Cagliari, C.P. 170, I-09042 Monserrato (Italy); Melis, S. [Dipartimento di Scienze e Tecnologie Avanzate, Universita del Piemonte Orientale, Viale T. Michel 11, I-15121 Alessandria (Italy); INFN, Sezione di Torino, Via P. Giuria 1, I-10125 Torino (Italy); Murgia, F. [INFN, Sezione di Cagliari, C.P. 170, I-09042 Monserrato (Italy)

2010-02-01

346

Wet-spinning of neat single-walled carbon nanotube fiber from 100+% sulfuric acid  

NASA Astrophysics Data System (ADS)

Single-Walled Carbon Nanotubes (SWNT) have been found to have excellent solubility in super acids such as 100+% H2SO4, and chlorsulfonic acid. The solutions display liquid crystalline behavior at high concentrations in super acids. Traditional wet-spinning method has been applied to SWNTs to make fibers from SWNTs only with the assistance of 100+% H2SO 4 (neat SWNT fibers). Extensive conditions, including concentrations, coagulation, and operation temperature, have been explored with Daca mixer and other custom-designed apparatuses (SBM and Refined Mixer). Fibers' properties have been tremendously improved through the research. Different characterizations have been done and all of them confirmed the neat SWNT fibers have the best alignment to-date among any macroscopic neat SWNT articles, as well as electrical conductivities. Meanwhile, neat SWNT fibers were used for X-ray diffraction study. For the first time, direct evidence has been provided to support the strong intercalation between SWNTs and super acids. Interestingly, for the first time, it has been reported that liquid sulfuric acid forms shell structure while exposed to SWNTs.

Hua, Fan

347

Optical Pumping and Electron Spin Resonance of Single 87Rb Atoms on Helium Nanodroplets  

NASA Astrophysics Data System (ADS)

Our recent development of electron spin resonance (ESR) spectroscopy on superfluid helium nanodroplets (HeN) provides a sensitive tool to investigate interactions between a surface located alkali-metal atom and an ESR silent species inside the droplet. Highest sensitivity is expected for alkali-metal atoms with large hyperfine coupling. We present hyperfine resolved ESR spectra of single 87Rb (hyperfine constant a_HFS = 3417 MHz) atoms isolated on HeN. In accordance with our previous work on 85Rb (AHFS= 1012 MHz) we find a droplet size dependent increase of AHFS between 400 and 450 ppm, due to the electronic perturbation by the helium environment. The process of optical pumping and of optical detection on HeN is investigated in detail in order to optimize the ESR signal. A simple model for optical pumping on HeN is presented, which agrees well with the experimental results. M. Koch, G. Auböck, C. Callegari, and W.E. Ernst, Phys. Rev. Lett. 103, 035302 (2009) A. Volk, J. Poms, M. Koch, and W.E. Ernst, J. Phys. Chem. A, in press

Koch, Markus; Poms, Johannes; Volk, Alexander; Ernst, Wolfgang E.

2011-06-01

348

The importance of strain on spin-spin coupling in Pr5/8Ca3/8MnO3 single crystal film  

SciTech Connect

The influence of anisotropic strains on coupling spins is systematically investigated in pulsed laser deposited single crystal Pr5/8Ca3/8MnO3 film. The substrate was chosen to introduce tensile and compressive strain onto the film. Various experiments, i.e., zero field cooled/field cooled (ZFC/FC) magnetization measurement, hysteresis loops, and exchange bias field detection, have revealed distinct difference along two perpendicular in-plane axes which represent tensile and compressive strain orientation, respectively. We found that the observed phenomenon can be explained by the external strain effect.

Fu, Xinwen [Shanghai University, Shanghai, Peoples R China; Gao, Yuze [Max-Planck-Institute for Solid State Research, Stuttgart, Germany; Wu, Zhiwei [Shanghai University, Shanghai, Peoples R China; Zhang, Jincang [Shanghai University, Shanghai, Peoples R China; Li, Qing [ORNL; Cao, Guixin [ORNL

2012-01-01

349

Stable Supervisory-Adaptive Controller for Spinning Satellite using Only Magnetorquers  

Microsoft Academic Search

In this paper, an adaptive controller for spinning satellites has been designed to achieve high attitude accuracy. In the cases which magnetorquers are used as actuators, the generated torque is perpendicular to the Earth's magnetic field, so a satellite is not completely controllable. In addition, the maximum value of achievable torque is limited due to capacity of magnetorquers. Hence, implementation

H. Bolandi; B. G. Vaghei

2009-01-01

350

Spin-polarized current-induced magnetization reversal in single nanowires  

NASA Astrophysics Data System (ADS)

Using electrochemical deposition, 6 ?m long Ni nanowires, with typical diameters of the order of 80 nm, are grown in ion-track etched membranes. Electric contacts are established during the growth, allowing resistance measurements of a single magnetic wire. Whatever the angle of the applied magnetic field with the wire, the full loops of magnetoresistance of a nickel nanowire can be described quantitatively on the basis of anisotropic magnetoresistance of a uniform magnet, and exhibit a jump of the magnetization at the so-called switching field. Hybrid wires made half with nickel and half with a Co/Cu multilayer were also produced. The multilayer could be grown using either a single bath technique or a multiple bath setup, with the result of a different magnetic anisotropy in the Co layers. When the multilayer is made of an optimal number of layers, the two parts of the hybrid wire act as two resistances in series, having no magnetic interaction onto each other. In contrast, the action of a current pulse on the nickel magnetization is to provoke a switch, when injected before the unstable state of the hysteresis cycle has been reached. But the amount of applied field discrepancy where the current still has an effect is given by a measured value ?Hmax, which appears to be substantially dependent on the presence or not of a multilayer close enough to the nickel wire and on the orientation of the magnetization in the multilayer. The role of the multilayer’s presence or state evidences the role of spin polarization in the current-induced switches of nickel. This is confirmed by measurements of the amplitude of ?Hmax in homogeneous nickel wires that exclude spurious effects such as the induced oersted-field, heating, or a combination of the two to account for all the current-induced switches.

Kelly, Derek; Wegrowe, Jean-Eric; Truong, Trong-Kha; Hoffer, Xavier; Ansermet, Jean-Philippe

2003-10-01

351

Gate-controlled persistent spin helix state in (In,Ga)As quantum wells  

NASA Astrophysics Data System (ADS)

In layered semiconductors with spin-orbit interaction (SOI) a persistent spin helix (PSH) state with suppressed spin relaxation is expected if the strengths of the Rashba and Dresselhaus SOI terms, ? and ?, are equal. Here we demonstrate gate control and detection of the PSH in two-dimensional electron systems with strong SOI including terms cubic in momentum. We consider strain-free InGaAs/InAlAs quantum wells and first determine a ratio ?/??1 for nongated structures by measuring the spin-galvanic and circular photogalvanic effects. Upon gate tuning the Rashba SOI strength in a complementary magnetotransport experiment, we monitor the complete crossover from weak antilocalization via weak localization to weak antilocalization, where the emergence of weak localization reflects a PSH-type state. A corresponding numerical analysis reveals that such a PSH-type state indeed prevails even in presence of strong cubic SOI, however no longer at ?=?.

Kohda, M.; Lechner, V.; Kunihashi, Y.; Dollinger, T.; Olbrich, P.; Schönhuber, C.; Caspers, I.; Bel'kov, V. V.; Golub, L. E.; Weiss, D.; Richter, K.; Nitta, J.; Ganichev, S. D.

2012-08-01

352

Calculations of two-color interband optical injection and control of carrier population, spin, current, and spin current in bulk semiconductors  

Microsoft Academic Search

Quantum interference between one- and two-photon absorption pathways allows coherent control of interband transitions in unbiased bulk semiconductors; carrier population, carrier spin polarization, photocurrent injection, and spin current injection can all be controlled. We calculate injection spectra for these effects using a 14x14 k.p Hamiltonian including remote band effects for five bulk semiconductors of zinc-blende symmetry: InSb, GaSb, InP, GaAs,

R. D. R. Bhat; J. E. Sipe

2006-01-01

353

Spin-flip time dependent density functional theory applied to excited states with single, double, or mixed electron excitation character  

NASA Astrophysics Data System (ADS)

We analyze the ability of spin-flip time dependent density functional theory (TD-DFT) to uniformly describe excited states of single, double, and mixed excitation character in closed-shell molecular systems, using the polyene oligomers as a primary test case. The results of comparison between conventional and spin-flip TD-DFT and with correlated ab initio methods indicate that spin-flip TD-DFT provides a more consistent description of the ordering and relative positions of the excited states than conventional TD-DFT provided a suitable exchange-correlation functional is used in the calculations. It is found that spin-flip TD-DFT provides a physically appealing picture of excitation processes which involve one or two electrons, as it captures their most important features and facilitates a more uniform description of excited states with different character. This makes spin-flip TD-DFT a promising approach for general modeling of excited states and spectra of medium and large size molecules, which exhibit low-lying excited states with strong double excitation character.

Rinkevicius, Zilvinas; Vahtras, Olav; A?Gren, Hans

2010-09-01

354

Opposing spin-canting mechanism in single-crystal LuV O3 and YV O3  

NASA Astrophysics Data System (ADS)

A canted-spin ferromagnetic moment M parallel to the orthorhombic ( Pbnm ) a axis of a YV O3 single crystal changes sign from the direction of a measuring field H?1 kOe on warming from 5 K across a first-order orbital-spin reordering temperature TCG ; the magnetization changes sign again on warming across T* in the interval TCG < T* < TN , where TN is the antiferromagnetic Néel temperature. Although the magnitude of M and its sign changes are the same for a sample cooled in a measuring field (FC) and zero-applied field (ZFC) to 5 K , the M (T) curves differ for warming after FC and ZFC to just above TCG ; but the sign reversal of M occurs at the same T* with the same measuring field H . These unusual features are argued to be the result of two coupled spin-canting mechanisms that oppose one another, an antisymmetric exchange operating on a c -axis spin component, and a 90° site anisotropy in the a-b plane operating on a b -axis component of the spin. The relative strength of the antisymmetric exchange increases with decreasing V-O-V bond angle to give a T* close to a TOO ? TN in LaV O3 and no T* above TCG in LuV O3 .

Yan, J.-Q.; Zhou, J.-S.; Goodenough, J. B.

2005-09-01

355

Spin probe ESR studies of dynamics of single walled carbon nanotubes  

Microsoft Academic Search

The highly sensitive technique of spin-probe Electron Spin Resonance (ESR) has been used to study dynamics of carbon nanotubes. The ESR signals were recorded for the nitroxide free radical TEMPO in carbon nanotubes from 5 to 300K. The onset of the fast dynamics of the probe molecule was indicated by appearance of a narrow triplet at 230K. The ESR measurements

A. K. Dhami; Shrivalli Bhat; Ajay Sharma; S. V. Bhat

2008-01-01

356

Detection of single micron-sized magnetic bead and magnetic nanoparticles using spin valve sensors for biological applications  

NASA Astrophysics Data System (ADS)

We have fabricated a series of highly sensitive spin valve sensors on a micron scale that successfully detected the presence of a single superparamagnetic bead (Dynabeads M-280, 2.8 ?m in diameter), and thus showed suitability for identifying biomolecules labeled by such magnetic beads. By polarizing the magnetic microbead on a spin valve sensor with a dc magnetic field and modulating its magnetization with an orthogonal ac magnetic field, we observed a magnetoresistance (MR) signal reduction caused by the magnetic dipole field from the bead that partially cancelled the applied fields to the spin valve. A lock-in technique was used to measure a voltage signal due to the MR reduction. A signal of 1.2 mV rms or 5.2 m? of resistance reduction was obtained from a 3 ?m wide sensor and a signal of 3.8 mV rms or 11.9 m? from a 2.5 ?m wide sensor. Micromagnetic simulations were also performed for the spin valve sensors with a single bead and gave results consistent with experiments. Further experiments and simulations suggested that these sensors or their variations can detect 1-10 Co nanoparticles with a diameter of ~11 nm, and are suitable for DNA fragment detection.

Li, Guanxiong; Joshi, Vikram; White, Robert L.; Wang, Shan X.; Kemp, Jennifer T.; Webb, Chris; Davis, Ronald W.; Sun, Shouheng

2003-05-01

357

Single Electron Spin Resonance in a Si-MOS Double Quantum Dot  

NASA Astrophysics Data System (ADS)

Pauli spin blockade is used as a means to detect the flip of spins in a silicon metal-oxide-semiconductor (MOS) based double quantum dot. Microwave driven electron spin resonance (ESR) signals, with a linewidth as narrow as 1.5 G, has been observed only in a narrow range of magnetic fields. ESR spectroscopy in the magnetic field - microwave frequency plane shows an unexpected level anti-crossing, with an energy gap of about 50 MHz. The spectral line gives an estimation of the lower bound for inhomogeneous phase decoherence time T2^* of about a couple of hundred ns for individual spins in the nano-structured system with a Si/SiO2 interface. We explain the anti-crossing gap as due to spin-orbit mixing with higher states, which is also responsible for the narrow-window visibility of the ESR signal in Si based double quantum dots.

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

2013-03-01

358

Optimal Congestion Control in Single Destination Networks  

Microsoft Academic Search

We present an algorithm for optimal routing in communication networks, resulting in minimum time and minimum total delay clearing of congested traffic towards a single destination. The algorithm is suitable for on-line implementation and can also be applied in the presence of time constant external arrival rates. In the case where several optimal solutions exist, the solution given is of

G. I. STASSINOPOULOS; PANAGIOTIS KONSTANTOPOULOS

1985-01-01

359

Effects of the single-ion anisotropy and dimerization on 1D spin-1 antiferromagnetic Heisenberg chain  

NASA Astrophysics Data System (ADS)

One-dimensional quantum spin-1 antiferromagnetic Heisenberg chain (AFHC) with exchange anisotropy Jz, dimerization /? and single-ion anisotropy D?n(Snz)2 was investigated on the basis of the continuum representation of the model Hamiltonian. Analytical results for the excitation spectrum, phase order and the phase fluctuation /? were derived in a self-consistent-harmonic-field approach. We studied the effects of the single-ion anisotropy and dimerization on two gaps by taking the different momentum cutoff ?i in two scalar field spaces Hi (/i=1,2). The occurrences of richer phase transitions were understood in the viewpoints of the phase fluctuation and the /z polar spin fluctuation. And the Gaussian critical line was given as Jz-D-??1?=0.

Jiang, Qing; Chen, Xin Yi

2001-12-01

360

Transverse single spin asymmetry in e+p??e+J/?+X and transverse momentum dependent evolution of the Sivers function  

NASA Astrophysics Data System (ADS)

We extend our analysis of transverse single spin asymmetry in electroproduction of J/? to include the effect of the scale evolution of the transverse momentum dependent (TMD) parton distribution functions and gluon Sivers function. We estimate single spin asymmetry for JLab, HERMES, COMPASS, and eRHIC energies using the color evaporation model of charmonium production, using an analytically obtained approximate solution of TMD evolution equations discussed in the literature. We find that there is a reduction in the asymmetry compared with our predictions for the earlier case considered by us, wherein the Q2 dependence came only from DGLAP evolution of the unpolarized gluon densities and a different parametrization of the TMD Sivers function was used.

Godbole, Rohini M.; Misra, Anuradha; Mukherjee, Asmita; Rawoot, Vaibhav S.

2013-07-01

361

Magnetic Attitude Control of Near Earth Spinning Satellites.  

National Technical Information Service (NTIS)

Magnetic attitude control systems were employed in several satellite programs due to their salient features like simplicity in construction, absence of moving parts, less power and space requirements and less weight. A control law suitable for keeping the...

S. Rajaram P. S. Goel

1977-01-01

362

Electrical Control of the high spin system Mn2+ in ZnO  

NASA Astrophysics Data System (ADS)

We examine the high spin impurity Mn^2+ in single crystal ZnO (S=5/2, I=5/2), and report a strong linear coupling (K = 52.3 rad/V/m) of the manganese electrical and magnetic moments that preserves quantum coherence. We combine pulsed EPR and electric field techniques to manipulate the Mn states and study electron spin lifetimes, finding T2e and T1e times of 0.8ms and 100ms at 2K in the natural material. We investigate the `forbidden' transitions that become allowed in the low symmetry environment and use these to manipulate the nuclear spin state on a sub-microsecond timescale that is inaccessible via ENDOR and RF techniques. Finally, we explore the existence of subspaces that are robust against strain-induced decoherence and the application of this material as an entanglement-based field sensor.

George, Richard; Morton, John; Ardavan, Arzhang; Edwards, James

2011-03-01

363

Nuclear magnetic resonance linewidth and spin diffusion in {sup 29}Si isotopically controlled silicon  

SciTech Connect

A nuclear magnetic resonance (NMR) study was performed with n-type silicon single crystals containing {sup 29}Si isotope abundance f ranges from 1.2% to 99.2%. The nuclear spin diffusion coefficient D has been determined from the linewidth of significantly enhanced {sup 29}Si NMR signals utilizing a developed dynamic nuclear polarization (DNP) method. The {sup 29}Si NMR linewidth depends linearly on f, at least when f<10%, and approaches {proportional_to}f{sup 1/2} dependence when f>50%. The estimated {sup 29}Si nuclear spin diffusion time T{sub sd} between phosphorus atoms used for DNP is more than ten times shorter than the nuclear polarization time T{sub 1}{sup p} of {sup 29}Si nuclei around phosphorus. Therefore, the regime of 'rapid spin diffusion' is realized in the DNP experiments.

Hayashi, Hiroshi; Itoh, Kohei M.; Vlasenko, Leonid S. [Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); A. F. Ioffe Physico-Technical Institute, 194021 Saint Petersburg (Russian Federation)

2008-10-15

364

Forward Neutral-Pion Transverse Single-Spin Asymmetries in p plus p Collisions at s=200 GeV  

Microsoft Academic Search

We report precision measurements of the Feynman x (x{sub F}) dependence, and first measurements of the transverse momentum (p{sub T}) dependence, of transverse single-spin asymmetries for the production of ° mesons from polarized proton collisions at (s)=200 GeV. The x{sub F} dependence of the results is in fair agreement with perturbative QCD model calculations that identify orbital motion of quarks

B. I. Abelev; M. M. Aggarwal; Z. Ahammed; B. D. Anderson; D. Arkhipkin; G. S. Averichev; Y. Bai; J. Balewski; O. Barannikova; L. S. Barnby; J. Baudot; S. Baumgart; D. R. Beavis; R. Bellwied; F. Benedosso; R. R. Betts; S. Bhardwaj; A. Bhasin; A. K. Bhati; H. Bichsel; J. Bielcik; J. Bielcikova; L. C. Bland; S. L. Blyth; M. Bombara; B. E. Bonner; M. Botje; J. Bouchet; E. Braidot; A. V. Brandin; S. Bueltmann; T. P. Burton; M. Bystersky; X. Z. Cai; H. Caines; M. C. D. Sanchez; J. Callner; O. Catu; D. Cebra; M. C. Cervantes; Z. Chajecki; P. Chaloupka; S. Chattopadhyay; H. F. Chen; J. H. Chen; J. Cheng; M. Cherney; A. Chikanian; K. E. Choi; W. Christie; S. U. Chung; R. F. Clarke; M. J. M. Codrington; J. P. Coffin; T. M. Cormier; M. R. Cosentino; J. G. Cramer; H. J. Crawford; D. Das; S. Dash; M. Daugherity; M. M. de Moura; T. G. Dedovich; M. DePhillips; A. A. Derevschikov; R. D. de Souza; L. Didenko; T. Dietel; P. Djawotho; S. M. Dogra; X. Dong; J. L. Drachenberg; J. E. Draper; F. Du; J. C. Dunlop; M. R. D. Mazumdar; W. R. Edwards; L. G. Efimov; E. Elhalhuli; V. Emelianov; J. Engelage; G. Eppley; B. Erazmus; M. Estienne; L. Eun; P. Fachini; R. Fatemi; J. Fedorisin; A. Feng; P. Filip; E. Finch; V. Fine; Y. Fisyak; J. Fu; C. A. Gagliardi; L. Gaillard; M. S. Ganti; E. Garcia-Solis; V. Ghazikhanian; P. Ghosh; Y. N. Gorbunov; A. Gordon; H. Gos; O. Grebenyuk; D. Grosnick; B. Grube; S. M. Guertin; Ksff Guimaraes; A. Gupta; N. Gupta; W. Guryn; B. Haag; T. J. Hallman; A. Hamed; J. W. Harris; W. He; M. Heinz; T. W. Henry; S. Heppelmann; B. Hippolyte; A. Hirsch; E. Hjort; A. M. Hoffman; G. W. Hoffmann; D. J. Hofman; R. S. Hollis; M. J. Horner; H. Z. Huang; E. W. Hughes; T. J. Humanic; G. Igo; A. Iordanova; P. Jacobs; W. W. Jacobs; P. Jakl; F. Jin; P. G. Jones; E. G. Judd; S. Kabana; K. Kajimoto; K. Kang; J. Kapitan; M. Kaplan; D. Keane; A. Kechechyan; D. Kettler; V. Y. Khodyrev; J. Kiryluk; A. Kisiel; S. R. Klein; A. G. Knospe; A. Kocoloski; D. D. Koetke; T. Kollegger; M. Kopytine; L. Kotchenda; V. Kouchpil; K. L. Kowalik; P. Kravtsov; V. I. Kravtsov; K. Krueger; C. Kuhn; A. Kumar; P. Kurnadi; M. A. C. Lamont; J. M. Landgraf; J. Langdon; S. Lange; S. LaPointe; F. Laue; J. Lauret; A. Lebedev; R. Lednicky; C. H. Lee; M. J. LeVine; C. Li; Q. Li; Y. Li; G. Lin; X. Lin; S. J. Lindenbaum; M. A. Lisa; F. Liu; H. Liu; J. Liu; L. Liu; T. Ljubicic; W. J. Llope; R. S. Longacre; W. A. Love; Y. Lu; T. Ludlam; D. Lynn; G. L. Ma; J. G. Ma; Y. G. Ma; D. P. Mahapatra; R. Majka; L. K. Mangotra; R. Manweiler; S. Margetis; C. Markert; H. S. Matis; Y. A. Matulenko; T. S. McShane; A. Meschanin; J. Millane; C. Miller; M. L. Miller; N. G. Minaev; S. Mioduszewski; A. Mischke; J. Mitchell; B. Mohanty; D. A. Morozov; M. G. Munhoz; B. K. Nandi; C. Nattrass; T. K. Nayak; J. M. Nelson; C. Nepali; P. K. Netrakanti; M. J. Ng; L. V. Nogach; S. B. Nurushev; G. Odyniec; A. Ogawa; H. Okada; V. Okorokov; D. Olson; M. Pachr; S. K. Pal; Y. Panebratsev; A. I. Pavlinov; T. Pawlak; T. Peitzmann; V. Perevoztchikov; C. Perkins; W. Peryt; S. C. Phatak; M. Planinic; J. Pluta; N. Poljak; N. Porile; A. M. Poskanzer; M. Potekhin; Bvks Potukuchi; D. Prindle; C. Pruneau; N. K. Pruthi; J. Putschke; I. A. Qattan; G. Rakness; R. Raniwala; S. Raniwala; R. L. Ray; D. Relyea; A. Ridiger; H. G. Ritter; J. B. Roberts; O. V. Rogachevskiy; J. L. Romero; A. Rose; C. Roy; L. Ruan; M. J. Russcher; V. Rykov; R. Sahoo; I. Sakrejda; T. Sakuma; S. Salur; J. Sandweiss; M. Sarsour; J. Schambach; R. P. Scharenberg; N. Schmitz; J. Seger; I. Selyuzhenkov; P. Seyboth; A. Shabetai; E. Shahaliev; M. Shao; M. Sharma; X. H. Shi; E. P. Sichtermann; F. Simon; R. N. Singaraju; M. J. Skoby; N. Smirnov; R. Snellings; P. Sorensen; J. Sowinski; J. Speltz; H. M. Spinka; B. Srivastava; A. Stadnik; T. D. S. Stanislaus; D. Staszak; R. Stock; M. Strikhanov; B. Stringfellow; A. A. P. Suaide; M. C. Suarez; N. L. Subba; M. Sumbera; X. M. Sun; Z. Sun; B. Surrow; T. J. M. Symons; A. S. de Toledo; J. Takahashi; A. H. Tang; Z. Tang; T. Tarnowsky; J. Tatarowicz; D. Thein; J. H. Thomas; J. Tian; A. R. Timmins; S. Timoshenko; M. Tokarev; T. A. Trainor; V. N. Tram; A. L. Trattner; S. Trentalange; R. E. Tribble; O. D. Tsai; J. Ulery; T. Ullrich; D. G. Underwood; G. Van Buren; N. van der Kolk; M. van Leeuwen; A. M. Vander Molen; R. Varma; G. M. S. Vasconcelos; I. M. Vasilevski; A. N. Vasiliev; R. Vernet; F. Videbaek; S. E. Vigdor; Y. P. Viyogi; S. Vokal; S. A. Voloshin; M. Wada; W. T. Waggoner; F. Wang; G. Wang; J. S. Wang; Q. Wang; X. Wang; Y. Wang; J. C. Webb; G. D. Westfall; C. J. Whitten; H. Wieman; S. W. Wissink; R. Witt; J. Wu; Y. Wu; N. Xu; Q. H. Xu; Z. Xu; P. Yepes; I. K. Yoo; Q. Yue; N. Zachariou; M. Zawisza; W. Zhan; H. Zhang; S. Zhang; W. M. Zhang; Y. Zhang; Z. P. Zhang; Y. Zhao; C. Zhong; J. Zhou; R. Zoulkarneev; Y. Zoulkarneeva; J. X. Zuo

2008-01-01

365

EPR study of Mn in ferroelastic BiVO4 single crystal: Monoclinic spin hamiltonian parameters and their temperature dependence  

Microsoft Academic Search

Zero-field splitting (ZFS) parameters of Mn in a BiVO4 single crystal obtained with a Q-band EPR spectrometer at room temperature are analyzed with the monoclinic spin Hamiltonian and compared with those of Baran et al. The ZFS Bk shows that the site symmetry of Mn (or Bi) center in the ferroelastic BiVO4 crystal is monoclinic. The temperature dependence of Mn

Tae Ho Yeom; Czeslaw Rudowicz; Sung Ho Choh

1994-01-01

366

A new device for coating single particles under controlled conditions  

Microsoft Academic Search

A new device for coating a single levitated particle in a controllable environment is designed and tested. This enables fluidized bed processing to be simulated experimentally on a single-particle level. The device consists of a coating chamber, which contains a capillary tube for levitating the particle, a micro-dispenser for producing discrete drops of controlled size and velocity and a device

Daniel Ström; Stina Karlsson; Staffan Folestad; Ingela Niklasson Björn; Thomas Laurell; Johan Nilsson; Anders Rasmuson

2005-01-01

367

An electrostatic gate for mechanically controlled single-molecule junctions  

NASA Astrophysics Data System (ADS)

We present a fabrication scheme for a tunable single-molecule transistor that allows for controlling the electrode separation and provides an electrostatic gate. The experimental approach is based on the mechanically controlled break junction technique but integrates an additional bottom gate electrode and an uninterrupted high-? gate dielectric. The device performance is demonstrated for a single-molecule junction showing Coulomb blockade characteristics.

Ballmann, Stefan; Weber, Heiko B.

2012-12-01

368

Controlling and Detecting Spin Correlations of Ultracold Atoms in Optical Lattices  

NASA Astrophysics Data System (ADS)

We report on the controlled creation of a valence bond state of delocalized effective-spin singlet and triplet dimers by means of a bichromatic optical superlattice. We demonstrate a coherent coupling between the singlet and triplet states and show how the superlattice can be employed to measure the singlet-fraction employing a spin-blockade effect. Our method provides a reliable way to detect and control nearest-neighbor spin correlations in many-body systems of ultracold atoms. Being able to measure these correlations is an important ingredient in studying quantum magnetism in optical lattices. We furthermore employ a SWAP operation between atoms which are part of different triplets, thus effectively increasing their bond-length. Such a SWAP operation provides an important step towards the massively parallel creation of a multiparticle entangled state in the lattice.

Trotzky, Stefan; Chen, Yu-Ao; Schnorrberger, Ute; Cheinet, Patrick; Bloch, Immanuel

2010-12-01

369

Computerized rapid high resolution quantitative analysis of plasma lipoproteins based upon single vertical spin centrifugation.  

PubMed

A method has been developed for rapidly quantitating the cholesterol concentration of normal and certain variant lipoproteins in a large number of patients (over 240 in one week). The method employs a microcomputer interfaced to the vertical autoprofiler (VAP) described earlier (Chung et al. 1981. J. Lipid Res. 22: 1003-1014). Software developed to accomplish rapid on-line analysis of the VAP signal uses peak shapes and positions derived from prior VAP analysis of isolated authentic lipoproteins HDL, LDL, and VLDL to quantitate these species in a VAP profile. Variant lipoproteins VHDL (a species with density greater than that of HDL(3)), MDL (a species, most likely Lp(a), with density intermediate between that of HDL and LDL), and IDL are subsequently quantitated by a method combining difference calculations with curve shapes. The procedure has been validated qualitatively by negative stain electron microscopy, gradient gel electrophoresis, strip electrophoresis, chemical analysis of the lipids, radioimmunoassay of the apolipoproteins, and measurement of the density of the peak centers. It has been validated quantitatively by comparison with Lipid Research Clinic methodology for HDL-, LDL-, and VLDL-cholesterol, and for MDL- and IDL-cholesterol by comparison of the amounts of MDL or IDL predicted to be present by the method with that known to be present following standard addition to whole plasma. These validations show that the method is a rapid and accurate technique of lipoprotein analysis suitable for the routine screening of patients for abnormal amounts of normal or variant lipoproteins, as well as for use as a research tool for quantitation of changes in cholesterol content of six or seven different plasma lipoprotein fractions.-Cone, J. T., J. P. Segrest, B. H. Chung, J. B. Ragland, S. M. Sabesin, and A. Glasscock. Computerized rapid high resolution quantitative analysis of plasma lipoproteins based upon single vertical spin centrifugation. PMID:7130860

Cone, J T; Segrest, J P; Chung, B H; Ragland, J B; Sabesin, S M; Glasscock, A

1982-08-01

370

Quantum Hall charge sensor for single-donor nuclear spin detection in silicon  

NASA Astrophysics Data System (ADS)

We propose a novel optical and electrical hybrid scheme for the measurement of nuclear spin qubits in silicon. By combining the environmental insensitivity of the integer quantum Hall effect with the optically distinguishable hyperfine states of phosphorus impurities in silicon, our system can offer both nuclear spin measurement and robustness against environmental defects. 31P donor spins in isotopically purified 28Si are often discussed as very promising quantum memory qubits due to their extremely long decoherence times, and our proposed device offers an effective implementation for such a quantum memory system.

Sleiter, D.; Y Kim, N.; Nozawa, K.; Ladd, T. D.; Thewalt, M. L. W.; Yamamoto, Y.

2010-09-01

371

Optical pumping of the electronic and nuclear spin of single charge-tunable quantum dots.  

PubMed

We present a comprehensive examination of optical pumping of spins in individual GaAs quantum dots as we change the net charge from positive to neutral to negative with a charge-tunable heterostructure. Negative photoluminescence polarization memory is enhanced by optical pumping of ground state electron spins, which we prove with the first measurements of the Hanle effect on an individual quantum dot. We use the Overhauser effect in a high longitudinal magnetic field to demonstrate efficient optical pumping of nuclear spins for all three charge states of the quantum dot. PMID:15783594

Bracker, A S; Stinaff, E A; Gammon, D; Ware, M E; Tischler, J G; Shabaev, A; Efros, Al L; Park, D; Gershoni, D; Korenev, V L; Merkulov, I A

2005-02-02

372

Nonlinear Feedback Control of a Spinning Two-Spacecraft Coulomb Virtual Structure  

Microsoft Academic Search

This paper studies a spinning two-spacecraft Coulomb virtual structure control scenario in an orbital environment. Only Coulomb forces are utilized to control the two-spacecraft formation shape while flying in a geostationary orbit. After deriving the separation distance equation of motion which determines the two-vehicle formation shape, a feed-forward nominal control charge is developed by assuming a purely two-spacecraft configuration. An

Shuquan Wang; Hanspeter Schaub

2011-01-01

373

Controlling single cluster dynamics at the nanoscale  

NASA Astrophysics Data System (ADS)

Gold nanoclusters deposited on highly oriented pyrolitic graphite are selectively detached and moved as a function of their size using the atomic force microscope. Control is obtained working in amplitude modulation and by tuning the interaction strength between oscillating tip and clusters. We show that fundamental controlling parameter is the energy dissipation that can be adjusted varying the tip amplitude oscillation and monitoring the phase shift signal. We characterize the energy detachment threshold of nanoclusters with sizes of 24 and 42 nm of diameter, then we precisely induce and control the movement of clusters with diameter below 40 nm within a mixed deposition.

Paolicelli, G.; Rovatti, M.; Vanossi, A.; Valeri, S.

2009-10-01

374

A New Control Strategy of Single-Stage Flyback Inverter  

Microsoft Academic Search

This paper presents a new control strategy for a single-stage flyback inverter, which consists of two flyback converters. The two converters alternately work in the proposed control scheme, which eliminate about 30% additional freewheeling power compared with a conventional differential control scheme. The control scheme is analyzed in detail. The 100-VA prototype with improved efficiency verifies the analysis.

Fanghua Zhang; Chunying Gong

2009-01-01

375

Electric-field-induced spin flop in BiFeO3 single crystals at room temperature.  

PubMed

Bismuth ferrite, BiFeO3, is the only known room-temperature magnetic ferroelectric material. We demonstrate here, using neutron scattering measurements in high quality single crystals, that the antiferromagnetic and ferroelectric order parameters are intimately coupled. Initially in a single ferroelectric state, our crystals have a canted antiferromagnetic structure describing a unique cycloid. Under electrical poling, polarization reorientation induces a spin flop. We argue here that the coupling between the two orders may be stronger in the bulk than in thin films where the cycloid is absent. PMID:18643458

Lebeugle, D; Colson, D; Forget, A; Viret, M; Bataille, A M; Gukasov, A

2008-06-02

376

Manifestation of spin selection rules on the quantum tunneling of magnetization in a single-molecule magnet.  

PubMed

We present low temperature magnetometry measurements on a new Mn3 single-molecule magnet in which the quantum tunneling of magnetization (QTM) displays clear evidence for quantum mechanical selection rules. A QTM resonance appearing only at high temperatures demonstrates tunneling between excited states with spin projections differing by a multiple of three. This is dictated by the C3 molecular symmetry, which forbids pure tunneling from the lowest metastable state. Transverse field resonances are understood by correctly orienting the Jahn-Teller axes of the individual manganese ions and including transverse dipolar fields. These factors are likely to be important for QTM in all single-molecule magnets. PMID:19659173

Henderson, J J; Koo, C; Feng, P L; del Barco, E; Hill, S; Tupitsyn, I S; Stamp, P C E; Hendrickson, D N

2009-07-02

377

Stochastic theory of optically detected single-spin coherent phenomena: Evidence for non-Markovian dephasing of pentacene in p-terphenyl  

Microsoft Academic Search

The optically detected coherent response of a single chromophore molecule in an organic host matrix to a microwave radiation resonant to a transition between triplet spin substates is analyzed using a model in which N independent random telegraph processes produce fluctuations of the spin transition frequency. Measurements of (i) Hahn echoes, (ii) power-broadened line shapes, (iii) transient nutation, and (iv)

S. Ya. Kilin; A. P. Nizovtsev; P. R. Berman; J. Wrachtrup; C. Von Borczyskowski

1997-01-01

378

Electron and nuclear spin interactions in the optical spectra of single GaAs quantum dots.  

PubMed

Fine and hyperfine splittings arising from electron, hole, and nuclear spin interactions in the magneto-optical spectra of individual localized excitons are studied. We explain the magnetic field dependence of the energy splitting through competition between Zeeman, exchange, and hyperfine interactions. An unexpectedly small hyperfine contribution to the splitting close to zero applied field is described well by the interplay between fluctuations of the hyperfine field experienced by the nuclear spin and nuclear dipole/dipole interactions. PMID:11384450

Gammon, D; Efros, A L; Kennedy, T A; Rosen, M; Katzer, D S; Park, D; Brown, S W; Korenev, V L; Merkulov, I A

2001-05-28

379

Technology spin-off from space power automation to terrestrial electrical power distribution control and operation  

Microsoft Academic Search

Areas which hold potential for technology spin-off from space power automation into terrestrial electrical power distribution control and automation are investigated. Areas touched upon include load management, loss reduction, trend analysis, energy storage, and fault diagnosis and analysis with expert systems. A brief overview of terrestrial electric power technology and automation in terrestrial distribution is provided. Power handling capabilities, hardware,

C. T. Callis; R. P. Broadwater; A. Chandrasekaran

1987-01-01

380

Spin coupling and relaxation inside molecule-metal contacts.  

PubMed

Advances in molecular electronics depend on the ability to control the charge and spin of single molecules at the interface with a metal. Here we show that bonding of metal-organic complexes to a metallic substrate induces the formation of coupled metal-ligand spin states, increasing the spin degeneracy of the molecules and opening multiple spin relaxation channels. Scanning tunnelling spectroscopy reveals the sign and magnitude of intramolecular exchange coupling as well as the orbital character of the spin-polarized molecular states. We observe coexisting Kondo, spin, and vibrational inelastic channels in a single molecule, which lead to pronounced intramolecular variations of the conductance and spin dynamics. The spin degeneracy of the molecules can be controlled by artificially fabricating molecular clusters of different size and shape. By comparing data for vibronic and spin-exchange excitations, we provide a positive test of the universal scaling properties of inelastic Kondo processes having different physical origin. PMID:21971505

Mugarza, Aitor; Krull, Cornelius; Robles, Roberto; Stepanow, Sebastian; Ceballos, Gustavo; Gambardella, Pietro

2011-10-04

381

Temperature-controllable spin-polarized current and spin polarization in a Rashba three-terminal double-quantum-dot device  

NASA Astrophysics Data System (ADS)

We propose a Rashba three-terminal double-quantum-dot device to generate a spin-polarized current and manipulate the electron spin in each quantum dot by utilizing the temperature gradient instead of the electric bias voltage. This device possesses a nonresonant tunneling channel and two resonant tunneling channels. The Keldysh nonequilibrium Green's function techniques are employed to determinate the spin-polarized current flowing from the electrodes and the spin accumulation in each quantum dot. We find that their signs and magnitudes are well controllable by the gate voltage or the temperature gradient. This result is attributed to the change in the slope of the transmission probability at the Fermi levels in the low-temperature region. Importantly, an obviously pure spin current can be injected into or extracted from one of the three electrodes by properly choosing the temperature gradient and the gate voltages. Therefore, the device can be used as an ideal thermal generator to produce a pure spin current and manipulate the electron spin in the quantum dot.

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

2013-05-01

382

Single and Double Spin Asymmetry Measurements in Semi-Inclusive and Inclusive DIS on Polarized He-3  

SciTech Connect

Jefferson Lab experiment E06-010 measured the target-single spin (SSA) and double spin asymmetries (DSA) in semi-inclusive deep inelastic pion electroproduction on a transversely polarized He-3 target. The measured asymmetry (A_UT) is sensitive to the nucleon transversity and Sivers distribution functions, whereas the measured A_LT asymmetry is related to the transverse momentum dependent PDF g_1T. The kinematics were chosen to be in the valence quark region with x ~ 0.16-0.35 and Q^2 ~ 1.4-2.7 GeV^2. The Collins moment, which is sensitive to transversity, the Sivers and A_LT moments, which are sensitive to the orbital motion of the quarks, were extracted using the azimuthal angular dependence of the measured asymmetries. These data, when combined with the data from other experiments on transversely polarized proton and deuteron targets, will help in extracting the nucleon transverse momentum dependent distribution functions via a global analysis. These semi-inclusive results will be presented and discussed along with the preliminary results for the inclusive single spin asymmetries.

Sulkosky, Vincent A. [MIT; Allada, Kalyan C. [JLAB

2012-06-01

383

Optical manipulation and electrical control of valley pseudo-spins in atomically thin semiconductors  

NASA Astrophysics Data System (ADS)

Electronic valleys are energy extrema of Bloch bands in momentum space. In analogy to electrons with spin degrees of freedom, valley indices can be considered as pseudo-spins for new modes of electronic and photonic device operation. In this paper, we will review our experimental progress on the investigation of these pseudo-spins using atomically thin semiconductors (MoS2, MoSe2 etc.), which are either monolayer or bilayer group VI transition metal dichalcogenides. We will show that these new 2D semiconductors not only behave as remarkable excitonic systems, but also provide an ideal platform for realizing the optical manipulation and electrical control of valley degrees of freedom.

Wu, Sanfeng; Ross, Jason S.; Huang, Chunming; Ghimire, Nirmal J.; Yan, Jiaqiang; Mandrus, David G.; Xiao, Di; Yao, Wang; Cobden, David H.; Xu, Xiaodong

2013-09-01

384

Constrained active space unrestricted mean-field methods for controlling spin-contamination.  

PubMed

We have recently proposed a novel approach for obtaining high-spin restricted open-shell Hartree-Fock wave functions by imposing constraints on the unrestricted Hartree-Fock (UHF) method [T. Tsuchimochi and G. E. Scuseria, J. Chem. Phys. 133, 141102 (2010)]. We here extend these ideas to the case where the constraints are released in an active space but imposed elsewhere. If the active space is properly chosen, our constrained UHF (CUHF) method greatly benefits from a controlled broken-symmetry effect while avoiding the massive spin contamination of traditional UHF. We also revisit and apply Lo?wdin's projection operator to CUHF and obtain multireference wave functions with moderate computational cost. We report singlet-triplet energy splittings showing that our constrained scheme outperforms fully unrestricted methods. This constrained approach can be readily used in spin density functional theory with similar favorable effects. PMID:21322655

Tsuchimochi, Takashi; Scuseria, Gustavo E

2011-02-14

385

Electric Control of Spin Chirality in Multiferroic Ni3V2O8  

NASA Astrophysics Data System (ADS)

We discuss electric control of spin chirality in the magnetically frustrated multiferroic Ni3V2O8 through polarized magnetic neutron diffraction. Cooling to the cycloidal magneto-electric phase in an electric field E causes the incommensurate Bragg reflections to become neutron spin polarizing, the sense of neutron polarization reversing with E. Comprehensive polarized neutron diffraction measurements establish the chiral nature of the long range ordered spin configuration and its response to E. Concomitant evolution of chiral and ferroelectric domains is observed by comparing polarized neutron diffraction data to pyroelectric current measurements and hysteresis under different poling conditions [1]. [1] I. Cabrera, M. Kenzelmann, G. Lawes, Y. Chen, W. C. Chen, R. Erwin, T. R. Gentile, J. Leao, J. W. Lynn, N. Rogado, R. J. Cava, and C. Broholm, (unpublished), 2008.

Cabrera, Ivelisse; Kenzelmann, Michel; Lawes, Gavin; Zaharko, Oksana; Broholm, Collin

2009-03-01

386

Spin control by application of electric current and voltage in FeCo-MgO junctions.  

PubMed

Efficient control and detection of spins are the most important tasks in spintronics. The current and voltage applied to a magnetic tunnel junction may exert a torque on the magnetic thin layer in the junction and cause its reversal or continuous precession. The discovery of the giant tunnelling magnetoresistance effect in ferromagnetic tunnelling junctions using an MgO barrier enabled us to obtain a large signal output from the magnetization reversal and precession. Also, the interplay of large spin configuration-electric conduction coupling provides highly nonlinear effects like the spin-torque diode effect. The negative resistance effect and amplification using it are predicted. A new discovery about a voltage-induced magnetic anisotropy change in Fe ultrathin films is also discussed. PMID:21859728

Suzuki, Yoshishige; Kubota, Hitoshi; Tulapurkar, Ashwin; Nozaki, Takayuki

2011-09-28

387

Control of Ferromagnetic Relaxation in Magnetic Thin Films through Thermally Induced Interfacial Spin Transfer  

NASA Astrophysics Data System (ADS)

Relaxation control in magnetic thin films via thermally induced interfacial spin transfers was demonstrated for the first time. The experiments used a trilayered structure that consisted of an yttrium iron garnet (YIG) thin film grown on a gadolinium gallium garnet substrate and capped with a nanometer-thick Pt layer. As a temperature gradient is applied across the thickness of the structure, there exists a spin angular momentum transfer across the YIG/Pt interface. This spin transfer results in a torque on YIG magnetic moments. The torque can either speed up or slow down the relaxation in the YIG film, depending on the sign of the temperature gradient with respect to the trilayered structure.

Lu, Lei; Sun, Yiyan; Jantz, Michael; Wu, Mingzhong

2012-06-01

388

Control of ferromagnetic relaxation in magnetic thin films through thermally induced interfacial spin transfer.  

PubMed

Relaxation control in magnetic thin films via thermally induced interfacial spin transfers was demonstrated for the first time. The experiments used a trilayered structure that consisted of an yttrium iron garnet (YIG) thin film grown on a gadolinium gallium garnet substrate and capped with a nanometer-thick Pt layer. As a temperature gradient is applied across the thickness of the structure, there exists a spin angular momentum transfer across the YIG/Pt interface. This spin transfer results in a torque on YIG magnetic moments. The torque can either speed up or slow down the relaxation in the YIG film, depending on the sign of the temperature gradient with respect to the trilayered structure. PMID:23004648

Lu, Lei; Sun, Yiyan; Jantz, Michael; Wu, Mingzhong

2012-06-19

389

A Neurofuzzy Controller for a Single Link Flexible Manipulator  

Microsoft Academic Search

This paper presents an adaptive neurofuzzy controller for tip position tracking control of a single link flexible manipulator.\\u000a The controller has a self- organizing fuzzy neural structure in which fuzzy rules are generated during the control process\\u000a using an online learning algorithm. In order to demonstrate the superior performance of the proposed controller, the results\\u000a are compared with those obtained

Samaneh Sarraf; Ali Fallah; T. Seyedena

2007-01-01

390

Enhanced conversion of triple to single-quantum coherence in the triple-quantum MAS NMR spectrosocopy of spin-5\\/2 nuclei  

Microsoft Academic Search

A new type of fast amplitude modulated pulse scheme is presented here that yields a significant sensitivity enhancement in the triple-quantum magic angle spinning NMR spectrum of a spin-5\\/2 nucleus. Enhancement is achieved by fast phase alternation of the triple to single-quantum conversion pulse, which transfers triple to single-quantum coherence in a direct, non-adiabatic manner. The success of this pulse

Amir Goldbourt; P. K. Madhu; Shimon Vega

2000-01-01

391

Controlling the relaxation of propagating spin waves in yttrium iron garnet/Pt bilayers with thermal gradients  

NASA Astrophysics Data System (ADS)

The spin currents generated by thermal gradients through the spin Seebeck effect (SSE) are usually detected by the voltage generated in a normal metal by means of the inverse spin Hall effect. Here, we present a detailed account of an experimental investigation of the action of spin currents due to SSE on the relaxation rate of spin waves. Propagating spin-wave packets with a frequency in the range of 1-2 GHz are launched in film strips of single-crystal yttrium iron garnet, Y3Fe5O12 (YIG) while a thermal gradient is applied across the thickness in the so-called longitudinal SSE configuration. No change in damping is observed in bare YIG films. However, if the YIG film is covered with an ultrathin platinum layer, we observe a striking change in the amplitude of the detected spin-wave pulses. Depending on the sign of the gradient, the spin-wave relaxation rate can be increased or decreased, leading in the latter case to an apparent amplification. The change in the relaxation rate is attributed to the action of a spin current generated in the YIG film by the SSE while the role of the Pt layer is to supply or absorb the flow of spins.

Cunha, R. O.; Padrón-Hernández, E.; Azevedo, A.; Rezende, S. M.

2013-05-01

392

Local control of single atom magnetocrystalline anisotropy.  

PubMed

Individual Fe atoms on a Cu_{2}N/Cu(100) surface exhibit strong magnetic anisotropy due to the crystal field. We show that we can controllably enhance or reduce this anisotropy by adjusting the relative position of a second nearby Fe atom, with atomic precision, in a low-temperature scanning tunneling microscope. Local inelastic electron tunneling spectroscopy, combined with a qualitative first-principles model, reveal that the change in uniaxial anisotropy is driven by local strain due to the presence of the second Fe atom. PMID:24093296

Bryant, B; Spinelli, A; Wagenaar, J J T; Gerrits, M; Otte, A F

2013-09-17

393

Local Control of Single Atom Magnetocrystalline Anisotropy  

NASA Astrophysics Data System (ADS)

Individual Fe atoms on a Cu2N/Cu(100) surface exhibit strong magnetic anisotropy due to the crystal field. We show that we can controllably enhance or reduce this anisotropy by adjusting the relative position of a second nearby Fe atom, with atomic precision, in a low-temperature scanning tunneling microscope. Local inelastic electron tunneling spectroscopy, combined with a qualitative first-principles model, reveal that the change in uniaxial anisotropy is driven by local strain due to the presence of the second Fe atom.

Bryant, B.; Spinelli, A.; Wagenaar, J. J. T.; Gerrits, M.; Otte, A. F.

2013-09-01

394

Refining the spin Hamiltonian in the spin-1/2 kagome lattice antiferromagnet ZnCu3(OH)6Cl2 using single crystals.  

PubMed

We report thermodynamic measurements of the S=1/2 kagome lattice antiferromagnet ZnCu3(OH)6Cl2, a promising candidate system with a spin-liquid ground state. Using single crystal samples, the magnetic susceptibility both perpendicular and parallel to the kagome plane has been measured. A small, temperature-dependent anisotropy has been observed, where ?(z)/?(p)>1 at high temperatures and ?(z)/?(p)<1 at low temperatures. Fits of the high-temperature data to a Curie-Weiss model also reveal an anisotropy. By comparing with theoretical calculations, the presence of a small easy-axis exchange anisotropy can be deduced as the primary perturbation to the dominant Heisenberg nearest neighbor interaction. These results have great bearing on the interpretation of theoretical calculations based on the kagome Heisenberg antiferromagnet model to the experiments on ZnCu3(OH)6Cl2. PMID:22587279

Han, Tianheng; Chu, Shaoyan; Lee, Young S

2012-04-10

395

The magnetic coupling between Sm3+ and the canted spin in an antiferromagnetic SmFeO3 single crystal  

SciTech Connect

The perovskite SmFeO3 exhibits type-G AF ordering at TN 670 K and an easy axis rotation transition at TSR 480 K. Owing to the peculiar site anisotropy of rare-earth Sm3+, the moment on Sm3+ is oriented antiparallel to the canted spin from the Fe3+ sublattice along the a axis at T < TSR. Development of the magnetic moment on Sm3+ as temperature decreases makes it possible to balance the two magnetic moments at Tcomp. Application of a moderate external magnetic field along the a axis can trigger an abrupt reversal of the moment on Sm3+ and the canted spin relative to the external field at a temperature around Tcomp. We report here a study of the field-induced magnetic-moment reversal in a single crystal SmFeO3 by measuring the magnetization and specific heat with the external field along different crystallographic axes.

Cheng, J G [University of Texas, Austin; Zhou, J.-S. [University of Texas, Austin; Mandrus, D. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Goodenough, J [University of Texas, Austin; Marshall, L [University of Texas, Austin; Yan, Jiaqiang [ORNL

2012-01-01

396

Hole spin relaxation in Ge–Si core–shell nanowire qubits  

Microsoft Academic Search

Controlling decoherence is the biggest challenge in efforts to develop quantum information hardware. Single electron spins in gallium arsenide are a leading candidate among implementations of solid-state quantum bits, but their strong coupling to nuclear spins produces high decoherence rates. Group IV semiconductors, on the other hand, have relatively low nuclear spin densities, making them an attractive platform for spin

Yongjie Hu; Ferdinand Kuemmeth; Charles M. Lieber; Charles M. Marcus

2011-01-01

397

Spin-component scaled coupled-clusters singles and doubles optimized towards calculation of noncovalent interactions.  

PubMed

The same- and opposite-spin scaling parameters for the SCS-CCSD method were reparametrized on the basis of benchmark CCSD(T)/CBS set interaction energies from the S22 set. New parameters were close to the original ones but swap between the different spin components, being 1.11 for the opposite- and 1.28 for the same-spin component. The RMSD, and especially, the largest error for the S22 were significantly reduced in comparison with the original parametrization. These statistical factors were only slightly worse when the S22x5 test set, containing not only the equilibrium but also the non-equilibrium geometries, was used. This new method, named the SCS(MI)-CCSD ("MI" stands for "Molecular Interactions") can thus be recommended for highly accurate calculations of interaction energies of various noncovalent interaction types, for which the CCSD(T)/CBS calculations are impractical. PMID:20623085

Pitonák, Michal; Rezác, Jan; Hobza, Pavel

2010-07-12

398

Longitudinal and spin/valley Hall optical conductivity in single layer MoS2  

NASA Astrophysics Data System (ADS)

A monolayer of MoS2 has a non-centrosymmetric crystal structure, with spin polarized bands. It is a two valley semiconductor with direct gap falling in the visible range of the electromagnetic spectrum. Its optical properties are of particular interest in relation to valleytronic and possible device applications. Circular polarized light associated with each of the two valleys separately is considered and results are filtered according to spin polarization. Temperature can greatly change the spin mixture seen in the frequency window where they are not closely in balance.[4pt] [1] Zhou Li and J. P. Carbotte, submitted to Phys. Rev. B.[0pt] [2] D. Xiao et.al, Phys. Rev. Lett. 108,196802 (2012).

Li, Zhou; Carbotte, Jules

2013-03-01

399

On the spin and parity of a single-produced resonance at the LHC  

NASA Astrophysics Data System (ADS)

Both LHC experiments, ATLAS and CMS, observed a new narrow resonance near 125 GeV.We demonstrate that the spin, parity, and, more generally, the tensor structure of the boson couplings of this resonance can be obtained by studying mass and angular distributions of events where the resonance decays to pairs of gauge bosons, ZZ, WW and ?? To account for all spin correlations we calculate kinematic distributions analytically and develop a Monte Carlo generator. We also discuss how to use angular and mass distributions of the resonance decay products for optimal background rejection and for distinguishing different signal hypotheses. By the end of the 8 TeV run of the LHC, it might be possible to separate extreme hypotheses of the spin and parity of the new resonance with a confidence level of 99% or better for a wide range of models.

Bolognesi, Sara; Gao, Yanyan; Gritsan, Andrei V.; Melnikov, Kirill; Schulze, Markus; Tran, Nhan V.; Whitbeck, Andrew

2013-05-01

400

Spin valve effect and magnetoresistivity in single crystalline Ca3Ru2O7.  

PubMed

The laminar perovskite Ca3Ru2O7 naturally forms ferromagnetic double layers of alternating moment directions, as in the spin-valve superlattices. The mechanism of the huge magnetoresistive effect in the material has been controversial due to a lack of clear understanding of various magnetic phases and phase transitions. In this neutron diffraction study in a magnetic field, we identify four different magnetic phases in Ca3Ru2O7 and determine all first-order and second-order phase transitions between them. The spin-valve mechanism then readily explains the dominant magnetoresistive effect in Ca3Ru2O7. PMID:18643623

Bao, Wei; Mao, Z Q; Qu, Z; Lynn, J W

2008-06-17

401

Single Rigid Body Representation, Control and Stability for Robotic Applications  

Microsoft Academic Search

In this paper, a novel formulation of the dynamics, control and stability of a single rigid body is presented. Effects of gravity, and visco-elastic coupling to an inertial frame of reference at a single point of contact are included. This formulation is very convenient, and analytically tractable for animation and computer simulation of human, animal, robotic and humanoid movements, for

Hooshang Hemami; Behzad Dariush

2000-01-01

402

Optimal control of coupled spin dynamics in the presence of relaxation  

NASA Astrophysics Data System (ADS)

In this thesis, we study methods for optimal manipulation of coupled spin dynamics in the presence of relaxation. We use these methods to compute analytical upper bounds for the efficiency of coherence and polarization transfer between coupled nuclear spins in multidimensional nuclear magnetic resonance (NMR) experiments, under the presence of relaxation. We derive relaxation optimized pulse sequences which achieve or approach these bounds and maximize the sensitivity of the experiments. The two systems examined in detail in this thesis, arising in the context of protein NMR spectroscopy, are a coupled heteronuclear spin pair and an Ising spin chain. New schemes for coherence and polarization transfer are found, which yield substantial gains in transfer efficiency, compared to the traditionally used pulse sequences. From the standpoint of mathematical control theory, the problems arising in connection with optimal manipulation of dissipative quantum dynamics, motivate the study of a class of dissipative bilinear control systems and the computation of their reachable sets. For these systems we show that the optimal solution, corresponding to the maximization of transfer efficiency, and the reachable set can be found by solving a semidefinite program.

Stefanatos, Dionisis

403

Adaptive Control of Single-Input, Single-Output Linear Systems.  

National Technical Information Service (NTIS)

A procedure is presented for designing an adaptive control for a single-input, single-out-put process admitting an essentially unknown but fixed linear model, so that the resulting closed-loop system is stable with zero steady-state tracking error between...

A. Feuer A. S. Morse

1977-01-01

404

Control of Spin-Triplet Josephson Junctions with Perpendicular Anisotropy  

NASA Astrophysics Data System (ADS)

We present recent work on S/F'/F/F''/S Josephson Junctions with the magnetic multilayer Ni/[Co/Ni]n as the central F layer [1]. This multilayer possesses strong intrinsic perpendicular (out-of-plane) anisotropy at Co and Ni thicknesses of a few monolayers. If a hard ferromagnet is used for F', and a softer ferromagnet is used for F'', both with magnetizations in plane, the direction of the F'' layer's magnetization is predicted to control the state of the junction [2]. We are fabricating such junctions with the goal of controllably switching the junction between the 0 and ? states. By integrating these junctions in a SQUID device, a measurement of the 0and ? state of the junction can be performed. We will report on our progress.[1] E.C. Gingrich, P. Quarterman, Y. Wang, R. Loloee, W.P. Pratt, and N.O. Birge, arXiv:1208.3118v1.[2] A.F. Volkov, F.S. Bergeret, and K.B. Efetov, Phys. Rev. Lett. 90, 117006 (2003).

Gingrich, Eric; Diesch, Simon; Pratt, William; Birge, Norman

2013-03-01

405

Adaptive control of single-input, single-output linear systems  

Microsoft Academic Search

A procedure is presented for designing parameter-adaptive control for a single-input, single-output process admitting an essentially unknown but fixed linear model, so that the resulting closed-loop system is globally stable with zero steady-state tracking error between the output of the process and the output of a prespecified linear reference model. The adaptive controller is a differentiator-free dynamical system forced only

A. Feuer; A. Morse

1978-01-01

406

Spin-Dependent Light-Harvesting in Colloidal Nanocrystals by Controlling Electronic Trap States with Optically Detected Magnetic Resonance  

NASA Astrophysics Data System (ADS)

Colloidal synthesis of semiconductor nanocrystals offers high levels of control over both particle size and geometry, leading to the development of novel optoelectronic device architectures (e.g. CdSe/CdS tetrapods). Unfortunately, realization of such devices is forestalled due to the ubiquitous existence of energetic ``trap'' states which compete with quantum-confined band-edge excitonic states and drive down device efficiencies. Although the existence of such states is readily confirmed via observation of single particle photoluminescence blinking and delayed photoluminescence decay dynamics, little detail is actually known as to the characteristics of these trap states due to difficulties in directly accessing them experimentally. We use pulsed optically detected magnetic resonance spectroscopy in order to begin to probe the chemical and electronic nature of these long-lived states, shedding light on their relation to band-edge states. Ultimately, it is found that spin coherence extends up to T2=328±22 ns at 3.5 K, allowing for the coherent control of light harvesting in heterostructured nano-tetrapods which permits remote readout of spin information.

van Schooten, K. J.; Huang, J.; Talapin, D. V.; Boehme, C.; Lupton, J. M.

2013-03-01

407

Control topology options for single-phase UPS inverters  

Microsoft Academic Search

Four control topologies for single-phase uninterruptible power system (UPS) inverters are presented and compared, with the common objective of providing a dynamically stiff, low total harmonic distortion (THD), sinusoidal output voltage. Full-state feedback, full-state command controllers are shown, utilizing both filter inductor current and filter capacitor current feedback to augment output voltage control. All controllers presented include output voltage decoupling

Michael J. Ryan; William E. Brumsickle; Robert D. Lorenz

1997-01-01

408

Multifunction Single-Package Antenna System for Spin-Stabilized Near-Synchronous Satellite.  

National Technical Information Service (NTIS)

An antenna system is described for a spin-stabilized satellite with its axis normal to the orbital plane. Three antennas in a compact lightweight package comprise the antenna system: a switched-beam X-band transmitting antenna, an omnidirectional X-band r...

J. B. Rankin M. E. Devane M. L. Rosenthal

1969-01-01

409

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

Microsoft Academic Search

NMR microimaging may be used to observe the effect of molecular diffusion in the vicinity of a thin wire subjected to current pulses. By this means the pulsed gradient spin echo technique can utilize very large pulsed magnetic field gradients, on the order of 100 T m-1. The quadratic dependence of gradient amplitude on distance from the wire leads to

Paul T. Callaghan; Janez Stepisnik

1995-01-01

410

Spin-phonon coupling in the single-layer extended t-J model  

NASA Astrophysics Data System (ADS)

We consider the implications of spin-phonon coupling within the slave-boson, mean-field treatment of the extended t-J model of a high-temperature superconductor. In materials such as YBaCuO, where the CuO2 plane is buckled, this interaction is linear in O displacement along the c axis, and the coupling constant is found to be large. We calculate the spin effects on phonon dynamics, finding at and below the spin singlet formation temperature changes in frequency shift and linewidth broadening for certain, key phonon modes which correspond well with experiment near the optimal doping level. Furthermore, the theory predicts that phonon anomalies in underdoped compounds should show evidence of spin-gap phenomena with the same characteristic temperature as that found in NMR studies; this is exactly as observed in YBaCuO systems, suggesting a possible unified understanding of the anomalies in magnetic and lattice properties. Finally, such a coupling affords the possibility of a small isotope effect, and our estimate is in good agreement with recent site-selective O-substitution experiments.

Normand, B.; Kohno, H.; Fukuyama, H.

1996-01-01

411

Advanced Undergraduate-Laboratory Experiment on Electron Spin Resonance in Single-Crystal Ruby  

ERIC Educational Resources Information Center

An electron-spin-resonance experiment which has been successfully performed in an advanced undergraduate physics laboratory is described. A discussion of that part of the theory of magnetic resonance necessary for the understanding of the experiment is also provided in this article. (DT)

Collins, Lee A.; And Others

1974-01-01

412

Landau-Zener tunneling of a single Tb3+ magnetic moment allowing the electronic read-out of a nuclear spin  

NASA Astrophysics Data System (ADS)

A multiterminal device based on a carbon nanotube quantum dot was used at very low temperature to probe a single electronic and nuclear spin embedded in a bis-(phthalocyaninato) terbium (III) complex (TbPc2). A spin-valve signature with large conductance jumps was found when two molecules were strongly coupled to the nanotube. The application of a transverse field separated the magnetic signal of both molecules and enabled single-shot read-out of the terbium nuclear spin. The Landau-Zener (LZ) quantum tunneling probability was studied as a function of field sweep rate, establishing a good agreement with the LZ equation and yielding the tunnel splitting ?. It was found that ? increased linearly as a function of the transverse field. These studies are an essential prerequisite for the coherent manipulation of a single nuclear spin in TbPc2.

Urdampilleta, M.; Klyatskaya, S.; Ruben, M.; Wernsdorfer, W.

2013-05-01

413

Attitude determination, control and navigation of a spinning satellite  

NASA Astrophysics Data System (ADS)

This study examines the concepts of autonomous spacecraft navigation, attitude determination and control. Navigation in orbit requires a minimum of two independent horizon to celestial body measurements that are correlated with time to establish a position in orbit over the earth. Sensor systems applicable for navigation are combinations of one sun sensor, star sensor, horizon sensor and clock, or star sensor, horizon sensor and clock. The clock is necessary to correlate inertial position with the earth's rotation. Star sensor measurements have distinct advantages over use of a sun sensor. A star sensor provides a higher rate of usable data than a sun sensor because there are more celestial objects for it to detect. Star and horizon sensor data combinations allow independent and concurrent navigation and attitude determination.

Rodden, J. J.

414

Microscopy beyond the diffraction limit using actively controlled single molecules.  

PubMed

In this short review, the general principles are described for obtaining microscopic images with resolution beyond the optical diffraction limit with single molecules. Although it has been known for several decades that single-molecule emitters can blink or turn on and off, in recent work the addition of on/off control of molecular emission to maintain concentrations at very low levels in each imaging frame combined with sequential imaging of sparse subsets has enabled the reconstruction of images with resolution far below the optical diffraction limit. Single-molecule active control microscopy provides a powerful window into information about nanoscale structures that was previously unavailable. PMID:22582796

Moerner, W E

2012-04-12

415

Microscopy beyond the diffraction limit using actively controlled single molecules  

PubMed Central

Summary In this short review, the general principles are described for obtaining microscopic images with resolution beyond the optical diffraction limit with single molecules. Although it has been known for several decades that single-molecule emitters can blink or turn on and off, in recent work the addition of on/off control of molecular emission to maintain concentrations at very low levels in each imaging frame combined with sequential imaging of sparse subsets has enabled the reconstruction of images with resolution far below the optical diffraction limit. Single-molecule active control microscopy provides a powerful window into information about nanoscale structures that was previously unavailable.

MOERNER, W.E.

2013-01-01

416

The role of spin in the kinetic control of recombination in organic photovoltaics.  

PubMed

In biological complexes, cascade structures promote the spatial separation of photogenerated electrons and holes, preventing their recombination. In contrast, the photogenerated excitons in organic photovoltaic cells are dissociated at a single donor-acceptor heterojunction formed within a de-mixed blend of the donor and acceptor semiconductors. The nanoscale morphology and high charge densities give a high rate of electron-hole encounters, which should in principle result in the formation of spin-triplet excitons, as in organic light-emitting diodes. Although organic photovoltaic cells would have poor quantum efficiencies if every encounter led to recombination, state-of-the-art examples nevertheless demonstrate near-unity quantum efficiency. Here we show that this suppression of recombination arises through the interplay between spin, energetics and delocalization of electronic excitations in organic semiconductors. We use time-resolved spectroscopy to study a series of model high-efficiency polymer-fullerene systems in which the lowest-energy molecular triplet exciton (T1) for the polymer is lower in energy than the intermolecular charge transfer state. We observe the formation of T1 states following bimolecular recombination, indicating that encounters of spin-uncorrelated electrons and holes generate charge transfer states with both spin-singlet ((1)CT) and spin-triplet ((3)CT) characters. We show that the formation of triplet excitons can be the main loss mechanism in organic photovoltaic cells. But we also find that, even when energetically favoured, the relaxation of (3)CT states to T1 states can be strongly suppressed by wavefunction delocalization, allowing for the dissociation of (3)CT states back to free charges, thereby reducing recombination and enhancing device performance. Our results point towards new design rules both for photoconversion systems, enabling the suppression of electron-hole recombination, and for organic light-emitting diodes, avoiding the formation of triplet excitons and enhancing fluorescence efficiency. PMID:23925118

Rao, Akshay; Chow, Philip C Y; Gélinas, Simon; Schlenker, Cody W; Li, Chang-Zhi; Yip, Hin-Lap; Jen, Alex K-Y; Ginger, David S; Friend, Richard H

2013-08-07

417

The spatial dependence of spin and charge correlations in a one-dimensional, single impurity, Anderson model  

SciTech Connect

Summarized are the results of a series of quantum Monte Carlo calculations of the spatial dependence of spin and charge correlations in a one-dimensional, single impurity, symmetric Anderson model. We corroborated several features of the model of Gubernatis, Hirsch, and Scalapino, and because we achieved lower temperatures, we were able to identify several additional unusual features in the behavior of the correlations as functions of U and ..beta... We also showed the existence of a charge compensation sum role and found a power law decay of the correlations at low temperatures.

Gubernatis, J.E.

1986-01-01

418

A Four-Quadrant Thrust Controller for Marine Propellers with Loss Estimation and Anti-Spin: Theory and Experiments  

Microsoft Academic Search

Abstract—In this paper a nonlinear thrust controller for fixed pitch marine propellers with torque loss estimation and an anti- spin strategy is presented. The controller, designed to operate in the four-quadrant plane composed by the shaft speed and the vessel speed, is a combination of a thrust controller developed for calm\\/moderate sea states and an anti-spin strategy to reduce power

Luca Pivano; Tor Arne Johansen; Øyvind N. Smogeli

419

Giant tunnel electroresistance and electrical control of spin polarization with ferroelectric tunnel barriers  

NASA Astrophysics Data System (ADS)

At room temperature, we use piezoresponse force microscopy to show robust ferroelectricity in BaTiO3 ultrathin films, and conductive-tip atomic force microscopy to demonstrate the resistive readout of the polarization state via its influence on the tunnel current [1]. This giant electroresistance nondestructive readout paves the way for ferroelectric memories with simplified architectures, higher densities and faster operation. Additionally, ferroelectric tunnel junctions with ferromagnetic electrodes were engineered to demonstrate local, large and non-volatile control of carrier spin polarization by switching ferroelectric polarization [2]. Our results represent a giant interfacial type of magnetoelectric coupling and suggest a new low-power approach for spin-based information control. [4pt] [1] V. Garcia et al., Nature 460, 81 (2009) [0pt] [2] V. Garcia et al., Science 327, 1106 (2010)

Garcia, Vincent

2011-03-01

420

Quantum Control of the Hyperfine Spin of a Cs Atom Ensemble  

SciTech Connect

We demonstrate quantum control of a large spin angular momentum associated with the F=3 hyperfine ground state of {sup 133}Cs. Time-dependent magnetic fields and a static tensor light shift are used to implement near-optimal controls and map a fiducial state to a broad range of target states, with yields in the range 0.8-0.9. Squeezed states are produced also by an adiabatic scheme that is more robust against errors. Universal control facilitates the encoding and manipulation of qubits and qudits in atomic ground states and may lead to the improvement of some precision measurements.

Chaudhury, Souma; Herr, Tobias; Jessen, Poul S. [College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); Merkel, Seth; Silberfarb, Andrew; Deutsch, Ivan H. [Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

2007-10-19

421

Shot noise and s-o coherent control of entangled and spin polarized electrons.  

NASA Astrophysics Data System (ADS)

We extend our previous work on shot noise for entangled and spin polarized electrons in a beam-splitter geometry with spin-orbit (s-o) interaction in the incoming leads. Besides accounting for both the Dresselhaus and the Rashba spin-orbit terms, we present general formulas for the shot noise of singlet and triplets states derived within the scattering approach. We determine the full scattering matrix of the system for the case of leads with two orbital channels coupled via a weak s-o interaction inducing channel anti-crossings. We show that this interband coupling gives rise to an additional modulation angle which allows for further coherent control of the electrons. We also derive explicit shot noise formulas for a variety of correlated pairs (e.g., Bell states) and lead spin polarizations. Interestingly, the singlet and textiteach of the triplets defined along the quantization axis perpendicular to lead 1 and in the plane of the beam splitter display distinctive shot noise for injection energies near the channel anti-crossings -- one can tell apart all the triplets through noise measurements. Finally, we find that backscattering within lead 1 reduces the visibility of the noise oscillations. This work was supported by NCCR Nanoscale Science, EU-Spintronics, CNPq, Swiss NSF, DARPA, ARO, and ONR (to appear in PRB).

Egues, J. Carlos; Burkard, Guido; Saraga, Daniel; Schliemann, John; Loss, Daniel

2006-03-01

422

Control of methyl methacrylate radical polymerization via Enhanced Spin Capturing Polymerization (ESCP)  

Microsoft Academic Search

The nitrone mediated polymerization of methyl methacrylate (MMA) via the enhanced (termination) spin capturing polymerization (ESCP) process is made possible via the addition of small amounts of styrene (between 5 and 10 vol.%) to the reaction mixture. Efficient control over the molecular weight between 7000 and 57,000 g mol?1 (at 60 °C) yields macromolecules that feature a mid-chain alkoxyamine functionality and are rich

Lin Zang; Edgar H. H. Wong; Christopher Barner-Kowollik; Thomas Junkers

2010-01-01

423

Dramatic reduction of read disturb through pulse width control in spin torque random access memory  

NASA Astrophysics Data System (ADS)

Magnetizations dynamic effect in low current read disturb region is studied both experimentally and theoretically. Dramatic read error rate reduction through read pulse width control is theoretically predicted and experimentally observed. The strong dependence of read error rate upon pulse width contrasts conventional energy barrier approach and can only be obtained considering detailed magnetization dynamics at long time thermal magnetization reversal region. Our study provides a design possibility for ultra-fast low current spin torque random access memory.

Wang, Zihui; Wang, Xiaobin; Gan, Huadong; Jung, Dongha; Satoh, Kimihiro; Lin, Tsann; Zhou, Yuchen; Zhang, Jing; Huai, Yiming; Chang, Yao-Jen; Wu, Te-ho

2013-09-01

424

Probing Spin Orbit Interaction in Single Layer Graphene via Electronic Transport  

NASA Astrophysics Data System (ADS)

An important effect on the dynamics of spins in materials is the spin orbit interaction (SOI), which may reflect or arise from intrinsic symmetries in the lattice structure, or via broken symmetries (Rashba interaction) in the system. Resonant scatterers, limiting electron mobility in graphene, are realized by impurities such as hydrogen atoms, molecules, clusters of impurities, vacancies, or metallic islands deposited on (or grown under) the surface of graphene. Resonant scatterers can also generate or enhance the Rashba SOI in graphene samples. We have developed analytical spinor solutions of the Dirac equation that include spin dependent observables, and use these to examine the role of SOI on scattering cross sections.By making use of the ratio of the total to transport cross section in the system at low energy, we predict a strong enhancement in the scattering isotropy in the presence of the intrinsic SOI. Similarly, we see fundamental changes in resonant scatterers in the presence of the Rashba SOI, which also lead to enhanced isotropy. We will discuss how these results have implications on the better characterization of impurities in graphene samples, and how typical experimental results can provide quantitative estimates of the SOI present in the system.

Ulloa, Sergio; Asmar, Mahmoud

2013-03-01