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1

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

2

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

3

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

4

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

5

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

6

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

7

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

8

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

9

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

10

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

11

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

12

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

13

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

14

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

15

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

16

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

17

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

18

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

19

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

20

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

21

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

22

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

23

Nuclear-spin noise  

Microsoft Academic Search

The spectral density of the Nyquist noise current in a tuned circuit coupled to a sample of nuclear spins has been measured at He4 temperatures with a dc SQUID used as a rf amplifier. When the sample is in thermal equilibrium, a dip is observed in the spectral density at the Larmor frequency. For zero spin polarization, on the other

Tycho Sleator; Erwin L. Hahn; Claude Hilbert; John Clarke

1985-01-01

24

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

25

Nuclear spin driven quantum tunneling of magnetization in a new lanthanide single-molecule magnet: bis(phthalocyaninato)holmium anion.  

PubMed

The first measurements of magnetization hysteresis loops on a diluted single crystal of [(Pc)2Ho]-.TBA+ (Pc = phthalocyaninato, TBA = tetrabutylammonium) in the subkelvin temperature range are reported. Characteristic staircase-like structure was observed, indicating the occurrence of the quantum tunneling of magnetization (QTM), which is a characteristic feature of SMMs. The quantum process in the new lanthanide SMMs is due to resonant quantum tunneling between entangled states of the electronic and nuclear spin systems, which is an essentially different mechanism from those of the known transition-metal-cluster SMMs. Evidence of the two-body quantum process was also observed for the first time in lanthanide complex systems. PMID:15771471

Ishikawa, Naoto; Sugita, Miki; Wernsdorfer, Wolfgang

2005-03-23

26

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

27

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

28

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

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

Nuclear Spin-Lattice Relaxation in Magnetic Insulators.  

National Technical Information Service (NTIS)

First-order nuclear spin-lattice relaxation arises in magnetic insulators when a nuclear spin directly interacts with one or more spin waves via the hyperfine interaction. The direct process, in which a single magnon is emitted, is not ordinarily allowed ...

D. Beeman P. Pincus

1968-01-01

31

Liquid-state nuclear spin comagnetometers.  

PubMed

We discuss nuclear spin comagnetometers based on ultralow-field nuclear magnetic resonance in mixtures of miscible solvents, each rich in a different nuclear spin. In one version thereof, Larmor precession of protons and 19F nuclei in a mixture of thermally polarized pentane and hexafluorobenzene is monitored via a sensitive alkali-vapor magnetometer. We realize transverse relaxation times in excess of 20 s and suppression of magnetic field fluctuations by a factor of 3400. We estimate it should be possible to achieve single-shot sensitivity of about 5×10(-9)??Hz, or about 5×10(-11)??Hz in ?1 day of integration. In a second version, spin precession of protons and 129Xe nuclei in a mixture of pentane and hyperpolarized liquid xenon is monitored using superconducting quantum interference devices. Application to spin-gravity experiments, electric dipole moment experiments, and sensitive gyroscopes is discussed. PMID:23004267

Ledbetter, M P; Pustelny, S; Budker, D; Romalis, M V; Blanchard, J W; Pines, A

2012-06-15

32

Nuclear magnetic resonance in [N(CH3)4]2CoCl4 single crystals: transferred hyperfine interaction and spin-lattice relaxation rate  

NASA Astrophysics Data System (ADS)

The molecular susceptibility and paramagnetic shift of [N(CH3)4]2CoCl4 single crystals were measured, and from these experimental results we obtained the transferred hyperfine interaction, Hhf, due to the transfer of spin density from Co2+ ions to [N(CH3)4]+ ions. The transferred hyperfine interaction can be expressed as a linear equation, with Hhf increasing with increasing temperature. The remarkable change in Hhf near Tc5 (=192 K) corresponds to a phase transition. The proton spin-lattice relaxation times of [N(CH3)4]2CoCl4 single crystals were also investigated, and it was found that the relaxation process can be described by a single exponential function. The variation of the relaxation time with temperature undergoes a remarkable change near Tc5, confirming the presence of a phase transition at that temperature. From the above results, we conclude that the increase in Hhf with increasing temperature is large enough to allow the transfer of spin density between Co2+ ions and the nuclear spins of the nonmagnetic [N(CH3)4]+ ions in the lattice, and thus the increase in the relaxation time with temperature is attributed to an increase in the transferred hyperfine field.

Lim, Ae Ran

2005-06-01

33

Nuclear spin noise imaging  

PubMed Central

NMR images were obtained from the proton spin noise signals of a water-containing phantom, which was placed in the highly tuned, low-noise resonant circuit of a cryogenically cooled NMR probe in the presence of systematically varied magnetic field gradients. The spatially resolved proton spin density was obtained from the raw signal by a modified projection–reconstruction protocol. Although spin noise imaging is inherently less sensitive than conventional magnetic resonance imaging, it affords an entirely noninvasive visualization of the interior of opaque objects or subjects. Thus, tomography becomes possible even when neither x-ray nor radio frequency radiation can be applied for technical or safety reasons.

Muller, Norbert; Jerschow, Alexej

2006-01-01

34

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

35

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

36

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

37

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

38

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

39

Communication: Long-lived states of nuclear spins in solids.  

PubMed

We report an observation of extremely long-lived spin states in systems of dipolar-coupled nuclear spins in solids. The "suspended echo" experiment uses a simple stimulated echo pulse sequence and creates non-equilibrium states which live many orders of magnitude longer than the characteristic time of spin-spin dynamics T2. Large amounts of information can be encoded in such long-lived states and subsequently retrieved by an application of a single "reading" pulse. PMID:24028094

Turanov, A; Khitrin, A K

2013-09-01

40

Electron spin decoherence by interacting nuclear spins in quantum dot I: Quantum theory  

NASA Astrophysics Data System (ADS)

We present a quantum theory to the electron spin decoherence by a nuclear pair-correlation method for the electron-nuclear spin dynamics under a strong magnetic field and low temperature. The theory incorporates the electron nuclear hyperfine interaction, the intrinsic nuclear interactions, and the nuclear coupling mediated by the hyperfine interaction with the electron in question. Results for both single electron spin free-induction decay (FID) and ensemble electron spin echo will be discussed. Single spin FID is affected by both the intrinsic and the hyperfine-mediated nuclear interactions, with the dominance determined by the dot size and external field. The spin echo eliminates the hyperfine-mediated decoherence but only reduces the decoherence by the intrinsic nuclear interactions. Thus, the decoherence times for FID and spin echo are significantly different. Electron spin decoherence is explained in terms of the quantum entanglement with the pair-flip excitations in the nuclear spin environment. This work was supported by NSF DMR- 0403465, NSA/ARO, and DARPA/AFOSR.

Yao, Wang; Liu, R.-B.; Sham, Lu J.

2006-03-01

41

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

42

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

43

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

44

Ultrafast entangling gates between nuclear spins using photoexcited triplet states  

NASA Astrophysics Data System (ADS)

The representation of information within the spins of electrons and nuclei has been a powerful method in the ongoing development of quantum computers. Although nuclear spins are advantageous as quantum bits (qubits) because of their long coherence lifetimes (exceeding seconds), they exhibit very slow spin interactions and have weak thermal polarization. A coupled electron spin can be used to polarize the nuclear spin and create fast single-qubit gates, however, the permanent presence of electron spins is a source of nuclear decoherence. Here we show how a transient electron spin, arising from the optically excited triplet state of C60, can be used to hyperpolarize, manipulate and measure two nearby nuclear spins. Implementing a scheme that uses the spinor nature of the electron, we performed an entangling gate in hundreds of nanoseconds: five orders of magnitude faster than the liquid-state J coupling. This approach can be widely applied to systems comprising an electron spin coupled to multiple nuclear spins, such as nitrogen-vacancy centres in diamond, while the successful use of a transient electron spin motivates the design of new molecules able to exploit photoexcited triplet states.

Filidou, Vasileia; Simmons, Stephanie; Karlen, Steven D.; Giustino, Feliciano; Anderson, Harry L.; Morton, John J. L.

2012-08-01

45

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

46

Quantum computing with nuclear spins in semiconductors  

NASA Astrophysics Data System (ADS)

The successful implementation of a scalable, fault-tolerant quantum computer would introduce a type of information processing more powerful than any available today. Reciprocally, the discovery of a fundamental obstacle to such a system would be an important advance in the foundations of quantum theory. No such fundamental obstacles are currently known, but neither has any architecture been shown to be experimentally scalable. Many technologies have been considered for finding such an architecture; in this work I focus on nuclear spins in semiconductors. Semiconductors provide promising optical means for polarizing and measuring small nuclear spin ensembles, which are tasks that pose critical challenges to quantum computers based on nuclear magnetic resonance (NMR). At the same time, semiconductor nuclei are sufficiently coherent quantum oscillators to allow complex information processing using resonant radio-frequency pulse sequences. In particular, the isotopically clean and magnetically quiet environment of pure, high quality, bulk single-crystal silicon provides a nuclear environment allowing what may be the longest absolute coherence time of any solid-state qubit currently under consideration. I have experimentally tested this claim using high-power NMR pulse sequences to eliminate inhomogeneous dephasing and dipolar evolution among an ensemble of 29Si nuclei in isotopically modified silicon crystals. Intrinsic decoherence processes are only observed in polycrystalline silicon, where 1/f charging noise processes are likely to blame. In high-quality single crystal samples, nuclear coherence persists for over 25 seconds, a timescale limited only by pulse sequence imperfections. I will discuss an architecture that takes advantage of this clean nuclear environment, but I will also address its scalability limitations due to silicon's poor optical characteristics. These limitations will suggest new experiments employing nuclear spins in optically controlled semiconductor quantum dots, which may hold more promise for future scalable quantum computer architectures.

Ladd, Thaddeus D.

47

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

48

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

49

Spectrum of an electron spin coupled to an unpolarized bath of nuclear spins.  

PubMed

The main source of decoherence for an electron spin confined to a quantum dot is the hyperfine interaction with nuclear spins. To analyze this process theoretically we diagonalize the central spin Hamiltonian in the high magnetic B-field limit. Then we project the eigenstates onto an unpolarized state of the nuclear bath and find that the resulting density of states has Gaussian tails. The level spacing of the nuclear sublevels is exponentially small in the middle of each of the two electron Zeeman levels but increases superexponentially away from the center. This suggests to select states from the wings of the distribution when the system is projected on a single eigenstate by a measurement to reduce the noise of the nuclear spin bath. This theory is valid when the external magnetic field is larger than a typical Overhauser field at high nuclear spin temperature. PMID:21469823

Tsyplyatyev, Oleksandr; Loss, Daniel

2011-03-08

50

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

51

Nuclear Spin of Phosphorus Donors in Silicon: Spin Relaxation Times and Environmental Decoupling  

NASA Astrophysics Data System (ADS)

All shallow donors in silicon (and their various isotopes) have non-zero nuclear spins and thus, both the electron and nuclear spins of neutral donors have been proposed for coding, manipulating and storing quantum information. We have recently demonstrated that the spin of electrons bound to donors have extremely long coherence times of at least T2e= 60ms at liquid helium temperatures which permits 10^6 single-qubit operations before the electron spin decoheres [1]. Here we extend this work and demonstrate that spin states of both the electron and nucleus of a ^31P donor can be accurately controlled using resonant microwave and RF pulses in pulsed electron nuclear double resonance (ENDOR) experiments. We measure the spin relaxation times of the ^31P nuclear spin and observe long longitudinal relaxation times T1n= 70s at 6K, limited by hyperfine interaction with the electron spin residing on the donor. We implement a recently proposed bang-bang strategy which decouples the nuclear spin from a decohering environment, through repeated manipulation of the coupled electron spin [2]. This highlights the potential benefits of physical ‘qubit’ systems beyond the simple 2-level structure. [1] A. M. Tyryshkin et al. PRB, 68, 193207 (2003); [2] J. J. L. Morton et al. Nature Physics in press (2005)

Tyryshkin, Alexei; Lyon, Stephen; Morton, John; Ardavan, Arzhang

2006-03-01

52

Electron and Nuclear Spin Dynamics in Antiferromagnetic Molecular Rings  

SciTech Connect

We study theoretically the spin dynamics of antiferromagnetic molecular rings, such as the ferric wheel Fe{sub 10} . For a single nuclear or impurity spin coupled to one of the electron spins of the ring, we calculate nuclear and electronic spin correlation functions and show that nuclear magnetic resonance (NMR) and electron spin resonance (ESR) techniques can be used to detect coherent tunneling of the Neel vector in these rings. The location of the NMR/ESR resonances gives the tunnel splitting and its linewidth an upper bound on the decoherence rate of the electron spin dynamics. We illustrate the experimental feasibility of our proposal with estimates for Fe{sub 10} molecules.

Meier, Florian; Loss, Daniel

2001-06-04

53

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

54

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

55

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

56

Dressed qubits in nuclear spin baths  

SciTech Connect

We present a method to encode a dressed qubit into the product state of an electron spin localized in a quantum dot and its surrounding nuclear spins via a dressing transformation. In this scheme, the hyperfine coupling and a portion of a nuclear dipole-dipole interaction become logic gates, while they are the sources of decoherence in electron-spin qubit proposals. We discuss errors and corrections for the dressed qubits. Interestingly, the effective Hamiltonian of nuclear spins is equivalent to a pairing Hamiltonian, which provides the microscopic mechanism to protect dressed qubits against decoherence.

Wu Lianao [Department of Theoretical Physics and History of Science, Basque Country University (EHU/UPV), Post Office Box 644, ES-48080 Bilbao (Spain) and IKERBASQUE, Basque Foundation for Science, ES-48011 Bilbao (Spain)

2010-04-15

57

Isobaric Spin in Nuclear Physics.  

National Technical Information Service (NTIS)

A review is given of the state of isobaric spin studies in low energy physics. Topics include: isobaric spin quantum numbers; charge independance; isobaric spin impurities; selection rules for extranuclear reactions (beta decay, radiative transitions), di...

D. Robson

1966-01-01

58

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

59

Nuclear-spin noise and spontaneous emission  

Microsoft Academic Search

The spontaneous emission from nuclear spins has been observed at liquid-4He temperatures. The spins, 35Cl nuclei, are placed in the inductor of a tuned LCR circuit coupled to a dc superconducting quantum interference device used as a radio-frequency amplifier. When the spins are saturated and have zero polarization, the emission is observed at the nuclear quadrupole Larmor frequency as a

Tycho Sleator; Claude Hilbert; John Clarke

1987-01-01

60

Nuclear rotation at low spin  

NASA Astrophysics Data System (ADS)

Two subjects related to nuclear rotation at low angular momentum are discussed. One is the ?-soft ``rotation'' in a microscopic calculation of the IBM-2, where it will be shown that we can reproduce ?-soft collective levels in a microscopic IBM-2 using a standard effective nucleon-nucleon Hamiltonian. The other is about the rotation of the axially-symmetric rotor. It is shown that, in and near the ground state, the proton and neutron deformed ellipsoids are rotating in the opposite directions, whereas they rotate about almost the same axis in states of higher spins. This holds, quite similarly, for angular-momentum-projected Nilsson wave functions and for wave functions in the Interacting Boson Model.

Takaharu, Otsuka; Mizusaki, T.; Honma, M.

1994-03-01

61

Nuclear Spin Driven Quantum Tunneling of Magnetization in a New Lanthanide Single-Molecule Magnet: Bis(phthalocyaninato)holmium anion  

Microsoft Academic Search

The first measurements of magnetization hysteresis loops on diluted single crystal of [(Pc)2Ho]-TBA+ (Pc: phthalocyaninato, TBA: tetrabutylammonium) in the subkelvin temperature range are reported. Characteristic staircase-like structure was observed, indicating the occurrence of the quantum tunneling of magnetization (QTM), which is a characteristic feature of SMMs. The quantum process in the new lanthanide SMMs is due to resonant quantum tunneling

Naoto Ishikawa; Miki Sugita; Wolfgang Wernsdorfer

2005-01-01

62

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

63

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

64

Polarization of nuclear spins by a cold nanoscale resonator  

SciTech Connect

A cold nanoscale resonator coupled to a system of nuclear spins can induce spin relaxation. In the low-temperature limit where spin-lattice interactions are ''frozen out,'' spontaneous emission by nuclear spins into a resonant mechanical mode can become the dominant mechanism for cooling the spins to thermal equilibrium with their environment. We provide a theoretical framework for the study of resonator-induced cooling of nuclear spins in this low-temperature regime. Relaxation equations are derived from first principles, in the limit where energy donated by the spins to the resonator is quickly dissipated into the cold bath that damps it. A physical interpretation of the processes contributing to spin polarization is given. For a system of spins that have identical couplings to the resonator, the interaction Hamiltonian conserves spin angular momentum, and the resonator cannot relax the spins to thermal equilibrium unless this symmetry is broken by the spin Hamiltonian. The mechanism by which such a spin system becomes ''trapped'' away from thermal equilibrium can be visualized using a semiclassical model, which shows how an indirect spin-spin interaction arises from the coupling of multiple spins to one resonator. The internal spin Hamiltonian can affect the polarization process in two ways: (1) By modifying the structure of the spin-spin correlations in the energy eigenstates, and (2) by splitting the degeneracy within a manifold of energy eigenstates, so that zero-frequency off-diagonal terms in the density matrix are converted to oscillating coherences. Shifting the frequencies of these coherences sufficiently far from zero suppresses the development of resonator-induced correlations within the manifold during polarization from a totally disordered state. Modification of the spin-spin correlations by means of either mechanism affects the strength of the fluctuating spin dipole that drives the resonator. In the case where product states can be chosen as energy eigenstates, spontaneous emission from eigenstate populations into the resonant mode can be interpreted as independent emission by individual spins, and the spins relax exponentially to thermal equilibrium if the development of resonator-induced correlations is suppressed. When the spin Hamiltonian includes a significant contribution from the homonuclear dipolar coupling, the energy eigenstates entail a correlation specific to the coupling network. Simulations of dipole-dipole coupled systems of up to five spins suggest that these systems contain weakly emitting eigenstates that can trap a fraction of the population for time periods >>100/R{sub 0}, where R{sub 0} is the rate constant for resonator-enhanced spontaneous emission by a single spin 1/2. Much of the polarization, however, relaxes with rates comparable to R{sub 0}. A distribution of characteristic high-field chemical shifts tends to increase the relaxation rates of weakly emitting states, enabling transitions to states that can quickly relax to thermal equilibrium. The theoretical framework presented in this paper is illustrated with discussions of spin polarization in the contexts of force-detected nuclear-magnetic-resonance spectroscopy and magnetic-resonance force microscopy.

Butler, Mark C.; Weitekamp, Daniel P. [A. A. Noyes Laboratory of Chemical Physics, California Institute of Technology, MC 127-72, Pasadena, California 91125 (United States)

2011-12-15

65

Conversion of Nuclear Spin Isomers of Ethylene  

NASA Astrophysics Data System (ADS)

A theoretical model of the nuclear spin isomer conversion in C2H4 induced by the intramolecular spin-spin interaction between hydrogen nuclei has been developed. In the ground electronic state, C2H4 has four nuclear spin isomers in contrast to two isomers in the molecules studied so far in this field of research. At the gas pressure of 1 Torr, the rate of conversion between isomers with the nuclear spin symmetries B1u and B2u was found to be 5.2 - 10-4 s-1, which coincides within experimental uncertainties with the rate recently measured by Sun et al. ( Science 2005, 310, 1938 ). It was determined that at low gas pressures the conversion is induced mainly by the mixing of only one pair of rotational states. The calculated pressure dependence of the conversion rate predicts that conversion slows down with increasing pressure at pressures higher than 300 Torr.

Chapovsky, P. L.; Zhivonitko, V. V.; Koptyug, I. V.

2013-10-01

66

Spins in silicon MOSFETs: electron spin relaxation and hyperpolarization of nuclear spins  

NASA Astrophysics Data System (ADS)

The spin degree of freedom of both mobile and localized electrons in silicon have extraordinary long spin relaxation times, making silicon an attractive candidate for spintronics applications and quantum information processing. In this talk, we will discuss recent results in measuring the conduction electron spin relaxation and coherence times in silicon MOS systems using electrically detected magnetic resonance. We will also discuss an all-electrical donor nuclear spin polarization method in silicon by exploiting the tunable interaction of donor bound electrons with conduction electrons, demonstrating that donor nuclear spins can be initialized through local gate control of electrical currents without the need for optical excitation.

Lo, C. C.; Weis, C. D.; van Tol, J.; Bokor, J.; Schenkel, T.; Morton, J. J. L.

2013-09-01

67

Nuclear spin conversion in diatomic molecules  

NASA Astrophysics Data System (ADS)

A mechanism of the internal interaction in dimers that mixes different nuclear spin modifications has been proposed. It has been shown that the intramolecular current associated with transitions between electronic terms of different parities can generate different magnetic fields on nuclei, leading to transitions between spin modifications and to the corresponding changes in rotational states. In the framework of the known quantum relaxation process, this interaction initiates irreversible conversion of nuclear spin modifications. The estimated conversion rate for nitrogen at atmospheric pressure is quite high (10-3-10-5 s-1).

Il'ichev, L. V.; Shalagin, A. M.

2013-07-01

68

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

69

Snowballs of radioactive ions — nuclear spin polarization of core ions  

Microsoft Academic Search

Short-lived ions12B (beta-radioactive, T1\\/2=20.3 ms) sustaining nuclear spin polarization were introduced into superfluid helium at 1.7 K. It was found that the12B ions were transported as charged entities under a static electric field and that the nuclear polarization was maintained throughout the lifetime of12B nuclei. Polarization of12B was determined through beta-NMR method. “Snowball”, a singly charged microcluster of helium atoms

N. Takahashi; T. Shimoda; Y. Fujita; T. Itahashi; H. Miyatake

1995-01-01

70

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

71

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

72

Nuclear spin detection and optical pumping in semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

Quantum memory devices and scalable quantum computers are important objectives of current research efforts. Quantum computers promise to solve certain problems which are intractable on classical computers and may provide insight into unanswered questions in computational theory. Quantum memory would provide coherent storage of a 'qubit' and could be used in conjunction with a quantum computer or in a quantum communication system. Both systems require a way of preparing qubits in a known state, a mechanism for measuring their states and addressing capability. Nuclear spins within a solid-state system have been proposed as one means for realizing a quantum computer. The preparation of nuclear spins in a known state and qubit readout remain a formidable challenge. Quantum dots provide a means of polarizing and measuring nuclear spins. We have observed the energy level shifts due to the nuclear spins in InAs quantum dots and we have measured the timescale for nuclear polarization to develop. Quantum dots are nano-scale regions of a small band-gap semiconductor embedded in a larger band-gap semiconductor which can trap a single electron-hole pair or exciton. The energy levels for the exciton are quantized and are affected by many parameters including hyperfine interactions with the nuclei from the lattice. There are between 104 and 105 nuclei within the dot and it is possible through optical pumping to align the nuclear spins in one direction. We can also use the interaction of the nuclear spins with the exciton to determine the average nuclear spin direction. Future work in this area may ultimately lead to useful applications for nuclear spins in the area of quantum information processing devices. In this thesis I will present results demonstrating nuclear polarization in InAs quantum dots. In addition, I will present background material and experimental details with the basic goal that a reader of this thesis could reproduce the results we have obtained. There is also a theoretical discussion in which I present a model for the nuclear polarization process and compare the predicted timescales to the measured results. I will also discuss work I carried out using sculpted ferromagnets with the goal of creating large magnetic field gradients. Such devices could be used in conjunction with quantum clots in order to do atomic plane imaging as discussed in Chapter 9. Chapter 4 provides a background to the discussion regarding magnetic field gradient calculations.

Goldman, Jonathan R.

73

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

74

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

75

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

76

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

77

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

78

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

79

Nuclear spin relaxation and intermolecular interactions  

Microsoft Academic Search

In order to specify what kind of information about intermolecular interactio~ls can be obtained by nuclear spin relaxation, we consider a suitable microscopic representation of a liquid. For reasons which will become clear below, this article is entirely confined to the treatment of the liquid phase. The molecular or microscopic picture of a liquid may be considered to be a

H G Hertz; A Kratochwill; H Weingärtner

1985-01-01

80

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

81

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

82

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

83

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

84

Nuclear spin conversion in H2O  

NASA Astrophysics Data System (ADS)

Nuclear spin conversion (NSC) in water molecules has often been investigated in the gas or solid phase. It has not been observed in the former yet because of the difficulty in producing an efficient disequilibrium of the spin isomer populations. Another, again failed, attempt at such an experiment is presented based on the supposed spin-selective adsorption ability of nanoporous materials. To explain the reason for so many failures, the NSC rate has been calculated in the framework of the quantum relaxation model, using the best available values of the energy levels of the vibrational ground state, the intramolecular magnetic interactions, and the collisional relaxation rates. The characteristic time of NSC in the gas phase is of the order of 1 s at ambient temperature. As NSC is observed in low-temperature matrices, the quantum relaxation model can be adapted to estimate the rate in such environments. Finally, some recent experimental results devoted to astrophysical problems are discussed.

Cacciani, P.; Cosléou, J.; Khelkhal, M.

2012-01-01

85

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

86

Spin excitations in quantum Hall systems and their effect on nuclear spin relaxation and photoluminescence  

NASA Astrophysics Data System (ADS)

Two problems with respect to spin excitations in quantum Hall systems are studied by means of exact numerical diagonalization. The first one is related to the formation of reversed-spin quasielectrons (QER) in a two-dimensional electron gas (2DEG). The single-particle properties of QER's as well as the pseudopotentials of their interaction with one another and with Laughlin quasielectrons (QE's) and quasiholes (QH's) are calculated. Based on the short-range character of the QER-QE R and QER-QE repulsion, the partially unpolarized incompressible states at the filling factors nu = 411 and nu = 513 are postulated within Haldane's hierarchy scheme. To describe photoluminescence, the family of bound h(QER)n states of a valence hole h and n QE R's are predicted in analogy to the found earlier fractionally charged excitons hQEn. The binding energy and optical selection rules for both families are compared. The h QER is found radiative in contrast to the dark hQE, and the h(QER)2 is found nonradiative in contrast to the bright hQE2. The second problem involves the numerical study of the relaxation rates of nuclear spins coupled through the hyperfine interaction to a 2DEG at magnetic fields corresponding to both fractional and integral Landau level fillings nu. The spectral functions tau-1(E) describing the response of the 2DEG to the reversal of an embedded localized spin are calculated. In a (locally) incompressible nu = 1 or ? state, the finite Coulomb energy of short spin waves, together with the small nuclear Zeeman energy, prevent nuclear spin relaxation even in the limit of vanishing electron Zeeman energy (EZ). However, we find that the nuclear spins can couple to the internal excitations of mobile finite-size skyrmions that appear in the 2DEG at sufficiently low E Z and at nu slightly different from 1 or ?. The experimentally observed dependence of nuclear spin relaxation rate on E Z and nu is explained in terms of the occurrence of skyrmions and anti-skyrmions of various topological charge.

Szlufarska, Izabela Anna

87

Nuclear-spin polarimeter using photoelectron signals  

NASA Astrophysics Data System (ADS)

It is widely believed that the hyperfine states must be resolved in one way or the other to measure the degree of nuclear-spin polarization of atoms and ions. We theoretically show that the angle-resolved photoelectron signals produced by resonant multiphoton ionization by short and hence broadband two-color laser pulses, which cover all fine-structure and hyperfine manifold of the ground and resonant excited states, can serve as a new type of nuclear-spin polarimeter. Because of the use of time-delayed short laser pulses the proposed method has very high (subnanosecond) time resolution, and does not suffer from the Doppler broadening. Specific results are presented for the two-photon resonant three-photon ionization of hydrogen atoms using 205- and 410-nm laser pulses with picosecond to femtosecond pulse durations. The proposed scheme is immediately applicable to other unstable elements such as 11Be+, 27Mg+, and 35Ca+, etc.

Deng, Li; Iwasaki, Masahiko; Nakajima, Takashi

2013-07-01

88

Copper Site Nuclear Spin Relaxation Anomaly and the Knight Shift  

Microsoft Academic Search

In the low doping limit, a high Tc cuprate preserves a two band structure. O2p electrons are itinerant, Cu3d electrons are localized. Therefore the two component model is suitable to describe nuclear spin relaxation at copper sites. In addition to the Korringa process, the hyperfine interaction between nuclear spins and local electron spins is considered, which gives rise to the

Wei Guo; Likun Wang; Rushan Han

2007-01-01

89

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

90

Detection and manipulation of nuclear spin states in fermionic strontium  

NASA Astrophysics Data System (ADS)

Fermionic 87Sr has a nuclear spin of I=9/2, higher than any other element with a similar electronic structure. This large nuclear spin has many applications in quantum simulation and computation, for which preparation and detection of the spin state are requirements. For an ultracold 87Sr cloud, we show two complementary methods to characterize the spin-state mixture: optical Stern-Gerlach state separation and state-selective absorption imaging. We use these methods to optimize the preparation of a variety of spin-state mixtures by optical pumping and to measure an upper bound of the 87Sr spin-relaxation rate.

Stellmer, Simon; Grimm, Rudolf; Schreck, Florian

2011-10-01

91

Detection and manipulation of nuclear spin states in fermionic strontium  

SciTech Connect

Fermionic {sup 87}Sr has a nuclear spin of I=9/2, higher than any other element with a similar electronic structure. This large nuclear spin has many applications in quantum simulation and computation, for which preparation and detection of the spin state are requirements. For an ultracold {sup 87}Sr cloud, we show two complementary methods to characterize the spin-state mixture: optical Stern-Gerlach state separation and state-selective absorption imaging. We use these methods to optimize the preparation of a variety of spin-state mixtures by optical pumping and to measure an upper bound of the {sup 87}Sr spin-relaxation rate.

Stellmer, Simon; Grimm, Rudolf [Institut fuer Quantenoptik und Quanteninformation (IQOQI), Oesterreichische Akademie der Wissenschaften, A-6020 Innsbruck (Austria); Institut fuer Experimentalphysik und Zentrum fuer Quantenphysik, Universitaet Innsbruck, A-6020 Innsbruck (Austria); Schreck, Florian [Institut fuer Quantenoptik und Quanteninformation (IQOQI), Oesterreichische Akademie der Wissenschaften, A-6020 Innsbruck (Austria)

2011-10-15

92

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

PubMed

Electron spins are strong candidates with which to implement spintronics because they are both mobile and able to be manipulated. The relatively short lifetimes of electron spins, however, present a problem for the long-term storage of spin information. We demonstrated an ensemble nuclear spin memory in phosphorous-doped silicon, which can be read out electrically and has a lifetime exceeding 100 seconds. The electronic spin information can be mapped onto and stored in the nuclear spin of the phosphorus donors, and the nuclear spins can then be repetitively read out electrically for time periods that exceed the electron spin lifetime. We discuss how this memory can be used in conjunction with other silicon spintronic devices. PMID:21164011

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

2010-12-17

93

Nuclear spin polarized H and D by means of spin-exchange optical pumping  

NASA Astrophysics Data System (ADS)

Optically pumped spin-exchange sources for polarized hydrogen and deuterium atoms have been demonstrated to yield high atomic flow and high electron spin polarization. For maximum nuclear polarization the source has to be operated in spin temperature equilibrium, which has already been demonstrated for hydrogen. In spin temperature equilibrium the nuclear spin polarization PI equals the electron spin polarization PS for hydrogen and is even larger than PS for deuterium. We discuss the general properties of spin temperature equilibrium for a sample of deuterium atoms. One result are the equations PI=4PS/(3+PS2) and Pzz=PS.PI, where Pzz is the nuclear tensor polarization. Furthermore we demonstrate that the deuterium atoms from our source are in spin temperature equilibrium within the experimental accuracy.

Stenger, Jörn; Grosshauser, Carsten; Kilian, Wolfgang; Nagengast, Wolfgang; Ranzenberger, Bernd; Rith, Klaus; Schmidt, Frank

1998-01-01

94

Harnessing nuclear spin polarization fluctuations in a semiconductor nanowire  

NASA Astrophysics Data System (ADS)

Soon after the first measurements of nuclear magnetic resonance in a condensed-matter system, Bloch predicted the presence of statistical fluctuations proportional to in the polarization of an ensemble of N spins. Such spin noise has recently emerged as a critical ingredient for nanometre-scale magnetic resonance imaging. This prominence is a consequence of present magnetic resonance imaging resolutions having reached less than (100nm)3, a size scale at which statistical spin fluctuations begin to dominate the polarization dynamics. Here, we demonstrate a technique that creates spin order in nanometre-scale ensembles of nuclear spins by harnessing these fluctuations to produce polarizations both larger and narrower than the thermal distribution. This method may provide a route to enhancing the weak magnetic signals produced by nanometre-scale volumes of nuclear spins or a way of initializing the nuclear hyperfine field of electron-spin qubits in the solid state.

Peddibhotla, P.; Xue, F.; Hauge, H. I. T.; Assali, S.; Bakkers, E. P. A. M.; Poggio, M.

2013-10-01

95

Nuclear spin selective alignment of ethylene and analogues.  

PubMed

We investigate the alignment of ethylene and of some of its analogues via short, non-resonant laser pulses and show that it depends crucially on the nuclear spin of the molecules. We calculate the time-dependent alignment factors of the four nuclear spin isomers of ethylene and analyze them by comparison with the symmetric top molecule allene. Moreover, we explore how the nuclear spin selective alignment depends on the asymmetry of the molecules and on the intensity of the laser pulse. As an application, we discuss how nuclear spin selective alignment could be applied in order to separate different isotopomers of ethylene. PMID:21639449

Grohmann, Thomas; Leibscher, Monika

2011-05-28

96

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

97

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

98

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

99

Nuclear quadrupole resonance single-pulse echoes.  

PubMed

We report the first detection of a spin echo after excitation of a powder sample by a single pulse at the resonance frequency during nuclear quadrupole resonance (NQR). These echoes can occur in samples that have an inhomogeneously broadened line, in this case due to the distribution of electric field gradients. The echoes are easily detectable when the Rabi frequency approaches the linewidth and the average effective tipping angle is close to 270 degrees. When limited by a weak radio-frequency field, the single-pulse echo can be used to increase the signal to noise ratio over conventional techniques. These effects can be used to optimize the NQR detection of contraband containing quadrupole nuclei and they are demonstrated with glycine hemihydrochloride and hexhydro-1,3,5-trinitro-1,3,5-triazine (RDX). PMID:18571445

Prescott, David W; Miller, Joel B; Tourigny, Chris; Sauer, Karen L

2008-05-29

100

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

101

Nuclear Spin Relaxation in Ellipsoids Undergoing Rotational Brownian Motion  

Microsoft Academic Search

The nuclear spin relaxation times T1 and T2 have been calculated for two identical nuclei of spin I = ½ fixed in an ellipsoid undergoing rotational Brownian motion. The ellipsoid is subject to small random changes in orientation in which the rotation probabilities about its three major axes are different. This anisotropic motion yields five nuclear correlation times; isotropic motion

D. E. Woessner

1962-01-01

102

Coulomb “Blockade” of Nuclear Spin Relaxation in Quantum Dots  

Microsoft Academic Search

We study the mechanism of nuclear spin relaxation in quantum dots due to the\\u000aelectron exchange with 2D gas. We show that the nuclear spin relaxation rate is\\u000adramatically affected by the Coulomb blockade and can be controlled by gate\\u000avoltage. In the case of strong spin-orbit coupling the relaxation rate is\\u000amaximal in the Coulomb blockade valleys whereas for

Y. B. Lyanda-Geller; I. L. Aleiner; B. L. Altshuler

2002-01-01

103

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

104

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

105

Nonsecular resonances for the coupling between nuclear spins in solids  

NASA Astrophysics Data System (ADS)

Spin-spin relaxation in solid-state nuclear-magnetic resonance in strong magnetic fields is normally described only with the help of the secular part of the full spin-spin interaction Hamiltonian. This approximation is associated with the averaging of the spin-spin interaction over the fast motion of spins under the combined action of the static and the radio-frequency (rf) fields. Here, we report a set of conditions (nonsecular resonances) when the averaging over the above fast motion preserves some of the nonsecular terms entering the full interaction Hamiltonian. These conditions relate the value of the static magnetic field with the frequency and the amplitude of the rf field. When the above conditions are satisfied, the effective spin-spin interaction Hamiltonian has an unconventional form with tunable parameters. This tunable Hamiltonian offers interesting possibilities to manipulate nuclear spins in solids and can shed new light on the fundamental properties of the nuclear-spin-spin relaxation phenomenon.

Kropf, Chahan M.; Fine, Boris V.

2012-09-01

106

Intrinsic spin fluctuations reveal the dynamical response function of holes coupled to nuclear spin baths in (In,Ga)As quantum dots.  

PubMed

The problem of how single central spins interact with a nuclear spin bath is essential for understanding decoherence and relaxation in many quantum systems, yet is highly nontrivial owing to the many-body couplings involved. Different models yield widely varying time scales and dynamical responses (exponential, power-law, gaussian, etc.). Here we detect the small random fluctuations of central spins in thermal equilibrium [holes in singly charged (In,Ga)As quantum dots] to reveal the time scales and functional form of bath-induced spin relaxation. This spin noise indicates long (400 ns) spin correlation times at a zero magnetic field that increase to ?5???s as dominant hole-nuclear relaxation channels are suppressed with small (100 G) applied fields. Concomitantly, the noise line shape evolves from Lorentzian to power law, indicating a crossover from exponential to slow [?1/log(t)] dynamics. PMID:22681099

Li, Yan; Sinitsyn, N; Smith, D L; Reuter, D; Wieck, A D; Yakovlev, D R; Bayer, M; Crooker, S A

2012-05-03

107

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

108

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

109

Proposals of nuclear spin quantum memory in group-IV elemental and II-VI semiconductors  

NASA Astrophysics Data System (ADS)

Schemes for the nuclear spin quantum memory are proposed based on a system composed of two electrons or one electron coupled to a single nuclear spin in isotopically purified group-IV elemental and II-VI compound semiconductors. The qubit consists of the singlet state and one of the triplet states of two electrons or simply of an electron spin. These systems are free from the decoherence due to the nuclear dipole-dipole interaction and are advantageous for the long memory time. In the case of two electrons, the protocol for the quantum state transfer between the electron-spin qubit and the nuclear spin qubit is based on the magnetic or electric field tuning of the singlet-triplet state crossing and on the hyperfine coupling supplemented with a well-defined scheme to initialize the nuclear spin. In the case of a single-electron qubit, the quantum state transfer is driven by the hyperfine interaction itself without the need of the nuclear spin initialization. Many practical systems are considered, e.g., two electrons loaded on a Si or ZnSe quantum dot, a single-electron charged state in a Si quantum dot doped with a P atom, a single-electron charged S28i quantum dot doped with an isotope atom of S29i , and a localized electron system of Si:P and ZnSe:F in the bulk crystal. General aspects of these systems are investigated and a comparison of merits and demerits is made between the two-electron qubit and the single-electron qubit.

Çak?r, Özgür; Takagahara, Toshihide

2009-10-01

110

Spin Modes in Nuclei and Nuclear Forces  

SciTech Connect

Spin modes in stable and unstable exotic nuclei are studied and important roles of tensor and three-body forces on nuclear structure are discussed. New shell model Hamiltonians, which have proper tensor components, are shown to explain shell evolutions toward drip-lines and spin properties of both stable and exotic nuclei, for example, Gamow-Teller transitions in {sup 12}C and {sup 14}C and an anomalous M1 transition in {sup 17}C. The importance and the necessity of the repulsive monopole corrections in isospin T = 1 channel to the microscopic two-body interactions are pointed out. The corrections are shown to lead to the proper shell evolutions in neutron-rich isotopes. The three-body force, in particular the Fujita-Miyazawa force induced by {Delta} excitations, is pointed out to be responsible for the repulsive corrections among the valence neutrons. The important roles of the three-body force on the energies and transitions in exotic oxygen and calcium isotopes are demonstrated.

Suzuki, Toshio [Department of Physics and Graduate School of Integrated Basic Sciences, College of Humanities and Sciences, Nihon University, Sakurajosui 3-25-40, Setagaya-ku, Tokyo 156-8550 (Japan) and Center for Nuclear Study, University of Tokyo, Hirosawa, Wako-shi, Saitama, 351-0198 (Japan); Otsuka, Takaharu [Department of Physics and Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2011-05-06

111

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

112

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

113

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

114

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

115

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

116

Nuclear spin-induced Cotton-Mouton effect in molecules  

NASA Astrophysics Data System (ADS)

In nuclear magneto-optic spectroscopy, effects of nuclear magnetization are detected in light passing through a sample containing spin-polarized nuclei. An optical analogue of nuclear magnetic resonance (NMR) chemical shift has been predicted and observed in the nuclear spin optical rotation of linearly polarized light propagating parallel to the nuclear magnetization. A recently proposed magneto-optic analogue of the NMR spin-spin coupling, the nuclear spin-induced Cotton-Mouton (NSCM) effect entails an ellipticity induced to linearly polarized light when passing through a medium with the nuclear spins polarized in a direction perpendicular to the light beam. Here we present a first-principles electronic structure formulation of NSCM in terms of response theory as well as ab initio and density-functional theory calculations for small molecules. The roles of basis set (we use completeness-optimized sets), electron correlation, and relativistic effects are discussed. It is found that the explicitly temperature-dependent contribution to NSCM, arising from the partial orientation of the molecules due to the nuclear magnetization, typically dominates the effect. This part of NSCM is proportional to the tensor product of molecular polarizability and the NMR direct dipolar coupling tensor. Hence, NSCM provides a means of investigating the dipolar coupling and, thus, molecular structure in a formally isotropic medium. Overall ellipticities of the order of magnitude of 10-8...10-7 rad/(M cm) are predicted for fully polarized nuclei. These should be detectable with modern instrumentation in the Voigt setup.

Fu, Li-juan; Vaara, Juha

2013-05-01

117

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

118

Anomalous Quasielastic Electron Scattering from Single H2, D2, and HD Molecules at Large Momentum Transfer: Indications of Nuclear Spin Effects  

NASA Astrophysics Data System (ADS)

Quasielectron electron scattering from gaseous H2, D2, a 50?50 mixture of H2 and D2, and HD is investigated with 2.25 keV impact energy and a momentum transfer ?q of 19.7 a.u. The energy transfer is less than the dissociation energy. The spectral positions of the H and D recoil peaks agree with Rutherford scattering theory. Surprisingly, in the spectrum of the 50?50 H2-D2 mixture, the integrated intensity of the H peak is 31%±4% lower (as compared to that of D) than predicted by Rutherford scattering, despite equal screening of nuclear charges by the electrons. In contrast, the ratio of scattering intensities from H and D in HD agrees with the predictions of Rutherford scattering. Comparison is made with neutron Compton scattering results from the same systems, but at higher energy transfers causing bond breaking. Possible theoretical explanations are outlined.

Cooper, G.; Hitchcock, A. P.; Chatzidimitriou-Dreismann, C. A.

2008-02-01

119

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

120

Electrical detection of coherent nuclear spin oscillations in phosphorus-doped silicon using pulsed ENDOR.  

PubMed

We demonstrate the electrical detection of pulsed X-band electron nuclear double resonance (ENDOR) in phosphorus-doped silicon at 5 K. A pulse sequence analogous to Davies ENDOR in conventional electron spin resonance is used to measure the nuclear spin transition frequencies of the (31)P nuclear spins, where the (31)P electron spins are detected electrically via spin-dependent transitions through Si/SiO(2) interface states, thus not relying on a polarization of the electron spin system. In addition, the electrical detection of coherent nuclear spin oscillations is shown, demonstrating the feasibility to electrically read out the spin states of possible nuclear spin qubits. PMID:21635127

Hoehne, Felix; Dreher, Lukas; Huebl, Hans; Stutzmann, Martin; Brandt, Martin S

2011-05-03

121

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

122

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

123

Nuclear Spin-Lattice Relaxation in Dilute Paramagnetic Sapphire  

Microsoft Academic Search

The exchange of energy between nuclear spin system and lattice has been theoretically and experimentally studied for circumstances in which the nuclear Zeeman energy levels are not necessarily equally spaced. Starting from the master rate equations for the nuclear energy level populations, expressions are found for the population difference of an adjacent pair of energy levels as a function of

W. W. Simmons; W. J. O'Sullivan; W. A. Robinson

1962-01-01

124

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

125

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

126

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

127

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

128

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

129

Cooling Nuclear Spins in Diamond via Dark State Spectroscopy  

NASA Astrophysics Data System (ADS)

Optical cooling methods in atomic physics, developed over the last half century, enable reaching temperatures as low as a few nK. Some of these methods can be applied for cooling spin ensembles in solid state systems. We describe a method for cooling the nuclear spins of^ 13C impurities in diamond, via optical manipulation of the electronic spin associated with an NV^- center. We present the physical mechanism which leads to optical pumping of the nuclear spin ensemble into particular nuclear states. The method relies on optically driving three electronic levels in the ? configuration, and on using the formation of dark states under the conditions of Coherent Population Trapping, (CPT). The dynamics of the nuclear ensemble during this cooling process can be described analytically by using statistical tools, including anomalous random walk models and Levy flights. I survey the theoretical results of the model and discuss some predictions for experimental signatures of Levy flights in this system.

Pick, Adi; Gullans, Michael; Togan, Emre; Chu, Yiwen; Yelin, Susanne; Lukin, Mikhail

2012-02-01

130

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

131

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

132

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

133

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

134

All-Electrical Nuclear Spin Polarization of Donors in Silicon  

NASA Astrophysics Data System (ADS)

We demonstrate an all-electrical donor nuclear spin polarization method in silicon by exploiting the tunable interaction of donor bound electrons with a two-dimensional electron gas, and achieve over two orders of magnitude nuclear hyperpolarization at T=5K and B=12T with an in-plane magnetic field. We also show an intricate dependence of nuclear polarization effects on the orientation of the magnetic field, and both hyperpolarization and antipolarization can be controllably achieved in the quantum Hall regime. Our results demonstrate that donor nuclear spin qubits can be initialized through local gate control of electrical currents without the need for optical excitation, enabling the implementation of nuclear spin qubit initialization in dense multiqubit arrays.

Lo, C. C.; Weis, C. D.; van Tol, J.; Bokor, J.; Schenkel, T.

2013-02-01

135

All-electrical nuclear spin polarization of donors in silicon.  

PubMed

We demonstrate an all-electrical donor nuclear spin polarization method in silicon by exploiting the tunable interaction of donor bound electrons with a two-dimensional electron gas, and achieve over two orders of magnitude nuclear hyperpolarization at T=5 K and B=12 T with an in-plane magnetic field. We also show an intricate dependence of nuclear polarization effects on the orientation of the magnetic field, and both hyperpolarization and antipolarization can be controllably achieved in the quantum Hall regime. Our results demonstrate that donor nuclear spin qubits can be initialized through local gate control of electrical currents without the need for optical excitation, enabling the implementation of nuclear spin qubit initialization in dense multiqubit arrays. PMID:23414045

Lo, C C; Weis, C D; van Tol, J; Bokor, J; Schenkel, T

2013-01-31

136

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

137

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

138

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

139

Nuclear transport of single molecules  

PubMed Central

The mechanism by which macromolecules are selectively translocated through the nuclear pore complex (NPC) is still essentially unresolved. Single molecule methods can provide unique information on topographic properties and kinetic processes of asynchronous supramolecular assemblies with excellent spatial and time resolution. Here, single-molecule far-field fluorescence microscopy was applied to the NPC of permeabilized cells. The nucleoporin Nup358 could be localized at a distance of 70 nm from POM121-GFP along the NPC axis. Binding sites of NTF2, the transport receptor of RanGDP, were observed in cytoplasmic filaments and central framework, but not nucleoplasmic filaments of the NPC. The dwell times of NTF2 and transportin 1 at their NPC binding sites were 5.8 ± 0.2 and 7.1 ± 0.2 ms, respectively. Notably, the dwell times of these receptors were reduced upon binding to a specific transport substrate, suggesting that translocation is accelerated for loaded receptor molecules. Together with the known transport rates, our data suggest that nucleocytoplasmic transport occurs via multiple parallel pathways within single NPCs.

Kubitscheck, Ulrich; Grunwald, David; Hoekstra, Andreas; Rohleder, Daniel; Kues, Thorsten; Siebrasse, Jan Peter; Peters, Reiner

2005-01-01

140

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

141

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

142

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

143

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

144

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

145

International conference on spin observables of nuclear probes: Summary talk  

SciTech Connect

A selected summary of the presentation and discussions at the 4th Telluride Conference is presented. The summary deals mainly with the effects of nuclear spin and isospin on the interaction between nucleons and their consequences in nuclear structure. 11 figs.

Garvey, G.T.

1988-01-01

146

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

147

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

148

Nuclear Moments of Inertia at High Spin.  

National Technical Information Service (NTIS)

The competition between collective motion and alignment at high spin can be evaluated by measuring two complementary dynamic moments of inertia. The first, I band, measured in gamma - gamma correlation experiments, relates to the collective properties of ...

M. A. Deleplanque

1982-01-01

149

Staggered-spin contribution to nuclear spin-lattice relaxation in two-leg antiferromagnetic spin-12 ladders  

NASA Astrophysics Data System (ADS)

We study the nuclear spin-lattice relaxation rate 1/T1 in the two-leg antiferromagnetic spin-1/2 Heisenberg ladder. More specifically, we consider the contribution to 1/T1 from the processes with momentum transfer (?,?). In the limit of weak coupling between the two chains, this contribution is of activation type with gap 2? at low temperatures (? is the spin gap), but crosses over to a slowly decaying temperature dependence at the crossover temperature T~?. This crossover possibly explains the recent high-temperature NMR results on ladder-containing cuprates by Imai et al.

Ivanov, D. A.; Lee, Patrick A.

1999-02-01

150

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

151

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

152

The Nuclear Cusp Condition in Spin-Polarized Thomas - Theory.  

NASA Astrophysics Data System (ADS)

Thomas-Fermi theory, which was introduced in the 1920s, was developed into rigorous mathematics in the 1970s by Lieb, Simon, Benilan, Brezis, and others. Later, Goldstein and Rieder extended rigorous Thomas-Fermi theory to a spin polarized context, to include the nuclear cusp condition, and to the case where a magnetic field is present. But they did not investigate incorporating the nuclear cusp condition into the spin polarized context. The purpose of my thesis is to do precisely that. I proved the existence and uniqueness of the problem of minimizing the energy functional by solving a non-linear elliptic partial differential equation on { bf R}^3 which arose from the Euler -Lagrange equation. A topological argument then related the Lagrange multipliers to the numbers of spin up and spin down electrons.

Lung, Chien-An.

153

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

154

Electrical injection of spin-polarized electrons and electrical detection of dynamic nuclear polarization using a Heusler alloy spin source  

NASA Astrophysics Data System (ADS)

We demonstrated electrical spin injection from a half-metallic Heusler alloy Co2MnSi electrode into a GaAs channel through observation of a spin-valve signal and a Hanle signal in the four-terminal nonlocal geometry. Furthermore, we electrically detected a nuclear field acting on electron spins, which was produced by the dynamic nuclear polarization, through observation of transient oblique Hanle signals. Samples with a Co2MnSi spin source exhibited higher spin-injection efficiency and a larger nuclear field compared to samples with a Co50Fe50 spin source, suggesting that the spin polarization of Co2MnSi is higher. This higher polarization is promising for realizing future spintronic devices and for understanding spin interactions as well as spin-dependent transport properties in a semiconductor channel.

Akiho, Takafumi; Shan, Jinhai; Liu, Hong-xi; Matsuda, Ken-ichi; Yamamoto, Masafumi; Uemura, Tetsuya

2013-06-01

155

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

156

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

157

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

158

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

159

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

160

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

161

Optimization of 1H spin density for dynamic nuclear polarization using photo-excited triplet electron spins  

Microsoft Academic Search

In dynamic nuclear polarization (DNP) using photo-excited triplet electron spins, known as Microwave-Induced Optical Nuclear Polarization (MIONP), the attainable 1H polarization is determined by the ratio of the buildup rate and the spin–lattice relaxation rate, in turn depend on the 1H spin density. It is shown that the final 1H polarization can be enhanced by diluting the 1H spins with

Akinori Kagawa; Yu Murokawa; Kazuyuki Takeda; Masahiro Kitagawa

2009-01-01

162

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

163

Dynamic nuclear polarization of single nitrogen isoelectronic centers in GaAs  

NASA Astrophysics Data System (ADS)

Due to their very long coherence time, nuclear spins of atomic systems represent good candidates for spin-based qubits in semiconductors. In this work, the dynamic nuclear polarization of isoelectronic centers formed from two nitrogen impurities in GaAs is investigated as a function of the external magnetic field and the polarization ellipticity of the exciting light. The nuclear spins of a single center are probed by the Overhauser shift of the neutral exciton and negatively charged exciton bound states. A nuclear magnetic field of 25 mT is measured at low external magnetic field and it decreases with this external field, indicating an efficiency loss in the exciton-nucleus spin-flip process. A peculiar Overhauser shift, scaling as the square of the ellipticity, is found for the exciton. A strong hysteretic behavior is also observed for both the neutral and charged excitons. These effects are believed to originate from the complex dynamic of the hyperfine interaction between the different excitonic spin states and nuclei. Our results show that dynamic nuclear polarization, much studied in quantum dots, is scalable to a single atomic-sized system. These results represent a first step towards the optical control of single nuclear spins in semiconductors.

Ethier-Majcher, Gabriel; St-Jean, Philippe; Francoeur, Sebastien

2013-03-01

164

Cross polarization from spins I=12 to spins S=1 in nuclear magnetic resonance with magic angle sample spinning.  

PubMed

Spin locking of the nuclear magnetization of a spin with S=1 such as deuterium in the presence of a radio-frequency field under magic angle spinning (MAS) is described in terms of adiabatic modulations of the energy levels. In a brief initial period, part of the initial density operator nutates about the Hamiltonian and is dephased. The remaining spin-locked state undergoes persistent oscillatory transfer processes between various coherences with a periodicity given by the rotation of the sample. While all crystallites in the powder undergo such periodic transfer processes, the phases of the oscillations depend on the angle gamma of the crystallites. The angle gamma is the azimuthal angle defining the orientation of the unique axis of the quadrupolar interaction tensor in a rotor-fixed frame. The theory is extended to describe cross-polarization between spins S=1 and I=12 under MAS. There are four distinct Hartmann-Hahn matching conditions that correspond to four zero-quantum matching conditions, all of which are shifted and broadened compared to their spin S=12 counterparts. These matching conditions are further split into a family of sideband conditions separated by the spinning frequency. The theory allows the calculation of both shifts and broadening factors of the matching conditions, as verified by simulations and experiments. PMID:16729818

Gopalakrishnan, Karthik; Bodenhausen, Geoffrey

2006-05-21

165

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

166

Relaxation of the electron spin in a quantum dot due to interaction with nuclear spin bath  

NASA Astrophysics Data System (ADS)

Understanding the dynamics of electron spins in semiconducting nanostructures is important for novel applications in spintronics and in quantum information processing. An electron spin in a quantum dot is strongly affected by its interaction with the environmental degrees of freedom, in particular, with the nuclear spins. In this work we study the longitudinal relaxation of the electron spin component S^z by the nuclear spin bath for different applied fields and initial polarizations of the bath. We numerically simulate the motion of the compound system (the electron spin plus the bath) by explicitly solving the corresponding time-dependent Schrödinger equation using the method described in [1]. Typically, S^z exhibits a pronounced oscillation with subsequent saturation; at high fields, several such oscillations are observed. We compare our numerical results with the earlier analytical predictions [2], and discuss the agreements and differences. [1] V. V. Dobrovitski and H. A. De Raedt, Phys. Rev. E 67, 056702 (2003)[2] A. V. Khaetskii, D. Loss, and L. Glazman, Phys. Rev. Lett. 88, 186802 (2002); I. A. Merkulov, E. L. Efros, and M. Rosen, Phys. Rev. B 65, 205309 (2002).

Al-Hassanieh, Khaled; Dobrovitski, V. V.; Dagotto, E.; Harmon, B. N.

2005-03-01

167

Generating entanglement and squeezed states of nuclear spins in quantum dots.  

PubMed

We present a scheme for achieving coherent spin squeezing of nuclear spin states in semiconductor quantum dots. The nuclear polarization dependence of the electron spin resonance generates a unitary evolution that drives nuclear spins into a collective entangled state. The polarization dependence of the resonance generates an area-preserving, twisting dynamics that squeezes and stretches the nuclear spin Wigner distribution without the need for nuclear spin flips. Our estimates of squeezing times indicate that the entanglement threshold can be reached in current experiments. PMID:22181759

Rudner, M S; Vandersypen, L M K; Vuleti?, V; Levitov, L S

2011-11-08

168

Hole - Nuclear Spin Interaction in Semiconductor Quantum Dots  

NASA Astrophysics Data System (ADS)

Spins of localized electrons in semiconductor quantum dots (QDs) are attractive for future spintronic and quantum information devices since they are not subject to the classical spin relaxation mechanisms known for free carriers [1]. It is now well established that the main spin dephasing mechanism in QDs is due to the coupling of conduction electron spin with the randomly fluctuating nuclear spins (Fermi contact term) [2-5]. For a valence electron (or hole), this coupling is expected to be much weaker because of the p-symmetry of the valence band states and no experimental evidence of such a hole-nuclear spin interaction has been reported so far [6]. We have measured the carrier spin dynamics in p-doped InAs/GaAs quantum dots by pump probe and time-resolved photoluminescence experiments. We demonstrate that the hole spin dynamics in these QDs is governed by the interaction with randomly fluctuating nuclear spins [7]. Our calculations based on dipole-dipole coupling between the hole and the quantum dot nuclei lead to a hole spin dephasing time for an ensemble of dots of 15 ns in close agreement with experiments.[4pt] In collaboration with B. Eble, C. Testelin, F. Bernardot, and M. Chamarro, Institut des Nanosciences de Paris, Universit'e P. et M. Curie, CNRS, Paris, F-75015 France; A. Balocchi, T. Amand, and B. Urbaszek, Universit'e de Toulouse ; LPCNO, INSA-CNRS-UPS, 135 av. de Rangueil, 31077 Toulouse Cedex 4, France; and A. Lemaître, Laboratoire de Photonique et de Nanostructures, CNRS, Route de Nozay, F-91460, Marcoussis, France. [4pt] [1] Spin Physics in Semiconductors, edited by M. D'Yakonov (Springer, Berlin, 2008) [0pt] [2] I. Merkulov et al, Phys. Rev. B 65, 205309 (2002) [0pt] [3] P.-F. Braun, X. Marie et al, PRL 94, 116601 (2005) [0pt] [4] A. C. Johnson et al , Nature 435, 925 (2005) [0pt] [5] A. Greilich et al, Science 313, 341(2006) [0pt] [6] S. Laurent et al, Phys. Rev. Lett. 94, 147401 (2005) [0pt] [7] B. Eble et al, Phys. Rev. Lett. 102, 146601 (2009)

Marie, Xavier

2010-03-01

169

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

170

Nuclear Spin Gyroscope Based on an Atomic Comagnetometer  

SciTech Connect

We describe a nuclear spin gyroscope based on an alkali-metal-noble-gas comagnetometer. Optically pumped alkali-metal vapor is used to polarize the noble-gas atoms and detect their gyroscopic precession. Spin precession due to magnetic fields as well as their gradients and transients can be cancelled in this arrangement. The sensitivity is enhanced by using a high-density alkali-metal vapor in a spin-exchange relaxation free regime. With a K-{sup 3}He comagnetometer we demonstrate rotation sensitivity of 5x10{sup -7} rad s{sup -1} Hz{sup -1/2}, equivalent to a magnetic field sensitivity of 2.5 fT/Hz{sup 1/2}. The rotation signal can be increased by a factor of 10 using {sup 21}Ne with a smaller magnetic moment. The comagnetometer is also a promising tool in searches for anomalous spin couplings beyond the standard model.

Kornack, T.W.; Ghosh, R.K.; Romalis, M.V. [Department of Physics, Princeton University, Princeton, New Jersey 08550 (United States)

2005-12-02

171

Dependence of nuclear spin singlet lifetimes on RF spin-locking power  

NASA Astrophysics Data System (ADS)

We measure the lifetime of long-lived nuclear spin singlet states as a function of the strength of the RF spin-locking field and present a simple theoretical model that agrees well with our measurements, including the low-RF-power regime. We also measure the lifetime of a long-lived coherence between singlet and triplet states that does not require a spin-locking field for preservation. Our results indicate that for many molecules, singlet states can be created using weak RF spin-locking fields: more than two orders of magnitude lower RF power than in previous studies. Our findings suggest that for many endogenous biomolecules, singlets and related states with enhanced lifetimes might be achievable in vivo with safe levels of RF power.

DeVience, Stephen J.; Walsworth, Ronald L.; Rosen, Matthew S.

2012-05-01

172

Dependence of nuclear spin singlet lifetimes on RF spin-locking power.  

PubMed

We measure the lifetime of long-lived nuclear spin singlet states as a function of the strength of the RF spin-locking field and present a simple theoretical model that agrees well with our measurements, including the low-RF-power regime. We also measure the lifetime of a long-lived coherence between singlet and triplet states that does not require a spin-locking field for preservation. Our results indicate that for many molecules, singlet states can be created using weak RF spin-locking fields: more than two orders of magnitude lower RF power than in previous studies. Our findings suggest that for many endogenous biomolecules, singlets and related states with enhanced lifetimes might be achievable in vivo with safe levels of RF power. PMID:22578548

DeVience, Stephen J; Walsworth, Ronald L; Rosen, Matthew S

2012-03-28

173

Creating nuclear spin entanglement using an optical degree of freedom  

SciTech Connect

Molecular nanostructures are promising building blocks for future quantum technologies, provided methods of harnessing their multiple degrees of freedom can be identified and implemented. Due to low decoherence rates, nuclear spins are considered ideal candidates for storing quantum information, while optical excitations can give rise to fast and controllable interactions for information processing. A recent paper [M. Schaffry et al., Phys. Rev. Lett. 104, 200501 (2010)] proposed a method for entangling two nuclear spins through their mutual coupling to a transient optically excited electron spin. Building on the same idea, we present here an extended and much more detailed theoretical framework, showing that this method is in fact applicable to a much wider class of molecular structures than previously discussed in the original proposal.

Schaffry, Marcus [Department of Materials, Oxford University, Oxford OX1 3PH (United Kingdom); Lovett, Brendon W. [Department of Materials, Oxford University, Oxford OX1 3PH (United Kingdom); SUPA, Department of Physics, Heriot Watt University, Edinburgh EH14 4AS (United Kingdom); Gauger, Erik M. [Department of Materials, Oxford University, Oxford OX1 3PH (United Kingdom); Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore)

2011-09-15

174

A silicon-based nuclear spin quantum computer  

Microsoft Academic Search

Quantum computers promise to exceed the computational efficiency of ordinary classical machines because quantum algorithms allow the execution of certain tasks in fewer steps. But practical implementation of these machines poses a formidable challenge. Here I present a scheme for implementing a quantum-mechanical computer. Information is encoded onto the nuclear spins of donor atoms in doped silicon electronic devices. Logical

B. E. Kane

1998-01-01

175

Nuclear tetrahedral configurations at spin zero  

SciTech Connect

The possibility of the existence of stable tetrahedral deformations at spin zero is investigated using the Skyrme-HFBCS approach and the generator coordinate method (GCM). The study is limited to nuclei in which the tetrahedral mode has been predicted to be favored on the basis of non-self-consistent models. Our results indicate that a clear identification of tetrahedral deformations is unlikely because they are strongly mixed with the axial octupole mode. However, the excitation energies related to the tetrahedral mode are systematically lower than those of the axial octupole mode in all the nuclei included in this study.

Zberecki, Krzysztof; Magierski, Piotr [Faculty of Physics, Warsaw University of Technology, ul. Koszykowa 75, PL-00-662 Warsaw (Poland); Heenen, Paul-Henri [Service de Physique Nucleaire Theorique, U.L.B-C.P. 229, B-1050 Brussels (Belgium)

2009-01-15

176

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

177

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

178

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

179

Preparation of nonequilibrium nuclear spin states in double quantum dots  

NASA Astrophysics Data System (ADS)

We theoretically study the dynamic polarization of lattice nuclear spins in GaAs double quantum dots containing two electrons. In our prior work [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.226807 104, 226807 (2010)], we identified three regimes of long-term dynamics, including the buildup of a large difference in the Overhauser fields across the dots, the saturation of the nuclear polarization process associated with the formation of so-called dark states, and the elimination of the difference field. In particular, when the dots are different sizes, we found that the Overhauser field becomes larger in the smaller dot. Here we present a detailed theoretical analysis of these problems, including a model of the polarization dynamics and the development of a numerical method to efficiently simulate semiclassical-central-spin problems. When nuclear spin noise is included, the results agree with our prior work indicating that large difference fields and dark states are stable configurations, while the elimination of the difference field is unstable; however, in the absence of noise, we find all three steady states are achieved depending on parameters. These results are in good agreement with dynamic nuclear polarization experiments in double quantum dots.

Gullans, M.; Krich, J. J.; Taylor, J. M.; Halperin, B. I.; Lukin, M. D.

2013-07-01

180

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

181

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

182

Selective polarization of nuclear spins in a wire-like quantum Hall system  

SciTech Connect

Nuclear spins are polarized selectively in a mesoscopic wire-like quantum Hall system by using the fractional quantum Hall system at Landau level filling factor nu = 2/3. The nuclear spin polarized region is limited by setting the filling factor in the wire to 2/3, while leaving the filling factor in the bulk away from 2/3. The longitudinal relaxation rate of selectively polarized nuclear spins probes electron spin properties in the wire.

Kobayashi, Takashi; Sasaki, Satoshi [NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198 (Japan); Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Kumada, Norio; Ota, Takeshi [NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198 (Japan); Hirayama, Yoshiro [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); ERATO-JST Nuclear Spin Electronics Project, 468-15 Aramaki Aza-Aoba, Aoba-ku, Sendai 980-0845 (Japan)

2010-01-04

183

Nuclear spin response studies in inelastic polarized proton scattering  

SciTech Connect

Spin-flip probabilities S/sub nn/ have been measured for inelastic proton scattering at incident proton energies around 300 MeV from a number of nuclei. At low excitation energies S/sub nn/ is below the free value. For excitation energies above about 30 MeV for momentum transfers between about 0.35 fm/sup /minus/1/ and 0.65 fm/sup / minus/1/ S/sub nn/ exceeds free values significantly. These results suggest that the relative ..delta..S = 1(..delta..S = 0 + ..delta..S = 1) nuclear spin response approaches about 90% in the region of the enhancement. Comparison of the data with slab response calculations are presented. Decomposition of the measured cross sections into sigma(..delta..S = 0) and sigma(..delta..S = 1) permit extraction of nonspin-flip and spin-flip dipole and quadrupole strengths. 29 refs., 11 figs.

Jones, K.W.

1988-01-01

184

Room-temperature high-speed nuclear-spin quantum memory in diamond  

NASA Astrophysics Data System (ADS)

Quantum memories provide intermediate storage of quantum information until it is needed for the next step of a quantum algorithm or a quantum communication process. Relevant figures of merit are therefore the fidelity with which the information can be written and retrieved, the storage time, and also the speed of the read-write process. Here, we present experimental data on a quantum memory consisting of a single 13C nuclear spin that is strongly coupled to the electron spin of a nitrogen-vacancy (NV) center in diamond. The strong hyperfine interaction of the nearest-neighbor carbon results in transfer times of 300 ns between the register qubit and the memory qubit, with an overall fidelity of 88% for the write-storage-read cycle. The observed storage times of 3.3 ms appear to be limited by the T1 relaxation of the electron spin. We discuss a possible scheme that may extend the storage time beyond this limit.

Shim, J. H.; Niemeyer, I.; Zhang, J.; Suter, D.

2013-01-01

185

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

186

Spin Density Matrices for Nuclear Density Functionals with Parity Violation  

NASA Astrophysics Data System (ADS)

Within the context of the radial density functional [1], we apply the spin density matrix (SDM) used in atomic and molecular physics [2] to nuclear physics. The vector part of the SDM defines a ``hedgehog'' situation, which exists only if nuclear states contain some amount of parity violation. Thus, looking for the vector profile of the SDM could be used as a test for parity violation in nuclei. The difference between the scalar profile and the vector profile of the SDM will be illustrated by a toy model. [4pt] [1] B. G. Giraud, Phys. Rev. C 78, 014307 (2008).[0pt] [2] A. Goerling, Phys. Rev. A 47, 2783 (1993).

Barrett, Bruce; Giraud, Bertrand

2010-11-01

187

Fast Nuclear Spin Hyperpolarization of Phosphorus in Silicon  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a method for obtaining nuclear spin hyperpolarization, that is, polarization significantly in excess of that expected at thermal equilibrium. By exploiting a nonequilibrium Overhauser process, driven by white light irradiation, we obtain more than 68% negative nuclear polarization of phosphorus donors in silicon. This polarization is reached with a time constant of ˜150sec, at a temperature of 1.37 K and a magnetic field of 8.5 T. The ability to obtain such large polarizations is discussed with regards to its significance for quantum information processing and magnetic resonance imaging.

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

2009-01-01

188

Nuclear Magnetic Resonance Relaxation Studies of 51V in BiVO4 Single Crystal  

Microsoft Academic Search

Temperature dependences of the nuclear spin-lattice relaxation time of 51V in BiVO4 single crystals, undoped and doped with 1 mol% of Eu2O3, respectively, were measured in the temperature range of 140-400 K. The spin-lattice relaxation times, T1s, of both samples were divided into the long and short components. For the doped crystal, the long component of the relaxation time is

I. G. Kim; T. H. Yeom; D. Y. Jeong; A. R. Lim; S. H. Choh; K. S. Hong

2002-01-01

189

Charge order and low frequency spin dynamics in lanthanum cuprates revealed by Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We report detailed 17O, 139La, and 63,65Cu Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered La1.875Ba0.125CuO4 single crystal and in oriented powder samples of La1.8- x Eu0.2Sr x CuO4. We observe a partial wipeout of the 17O NMR intensity and a simultaneous drop of the 17O electric field gradient (EFG) at low temperatures where the spin stripe order sets in. In contrast, the 63,65Cu intensity is completely wiped out at the same temperature. The drop of the 17O quadrupole frequency is compatible with a charge stripe order. The 17O spin lattice relaxation rate shows a peak similar to that of the 139La, which is of magnetic origin. This peak is doping dependent and is maximal at x ? 1/8.

Grafe, H.-J.; Curro, N. J.; Young, B. L.; Vyalikh, A.; Vavilova, J.; Gu, G. D.; Hücker, M.; Büchner, B.

2010-10-01

190

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

191

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

192

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

193

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

194

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

195

Dephasing time of GaAs electron-spin qubits coupled to a nuclear bath exceeding 200?s  

NASA Astrophysics Data System (ADS)

Qubits, the quantum mechanical bits required for quantum computing, must retain their quantum states for times long enough to allow the information contained in them to be processed. In many types of electron-spin qubits, the primary source of information loss is decoherence due to the interaction with nuclear spins of the host lattice. For electrons in gate-defined GaAs quantum dots, spin-echo measurements have revealed coherence times of about 1?s at magnetic fields below 100mT (refs 1, 2). Here, we show that coherence in such devices can survive much longer, and provide a detailed understanding of the measured nuclear-spin-induced decoherence. At fields above a few hundred millitesla, the coherence time measured using a single-pulse spin echo is 30?s. At lower fields, the echo first collapses, but then revives at times determined by the relative Larmor precession of different nuclear species. This behaviour was recently predicted, and can, as we show, be quantitatively accounted for by a semiclassical model for the dynamics of electron and nuclear spins. Using a multiple-pulse Carr-Purcell-Meiboom-Gillecho sequence, the decoherence time can be extended to more than 200?s, an improvement by two orders of magnitude compared with previous measurements.

Bluhm, Hendrik; Foletti, Sandra; Neder, Izhar; Rudner, Mark; Mahalu, Diana; Umansky, Vladimir; Yacoby, Amir

2011-02-01

196

Spectroscopic Measurement of LEAD-204 Isotope Shift and LEAD-205 Nuclear Spin.  

NASA Astrophysics Data System (ADS)

The isotope shift of ('204)Pb and the nuclear spin of 1.4 x 10('7)-y ('205)Pb was determined from a high -resolution optical measurement of the 6p('2) ('3)P(,o) -6p7s('3)P(,1)('o) 283.3-nm resonance line. The value of the shift, relative to ('208)Pb is -140.2(8) x 10('-3)cm(' -1), the negative sign indicating a shift to lower wave numbers. The precision is 3-4 times greater than that of previous measurements. The spin of ('205)Pb l = 5/2 was obtained from the measurement of the relative intensities of its three hyperfine components. This method of absorption spectroscopy determination of ground state nuclear spin is applicable to any stable or longlived isotope. High resolution optical absorption spectra were obtained with a 25.4cm diffraction grating in a 9.1m focal length Czerny-Turner spectrometer. A signal-averaging scanning technique was used to record the spectra. Increased precision in the isotope shift measurement was attained by using separated isotope samples of ('204)Pb and ('207)Pb. A controlled amount of the later was incorporated in the absorption cell to provide internal calibration by its 6p7s ('3)P(,1)('o) hfs separation. Absorption spectra were recorded for several optical thicknesses of the absorber. A single spin value of increased precision was derived from the entire set of combined data.

Schonberger, Peter

197

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

198

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

199

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

200

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

201

Solid effect in magic angle spinning dynamic nuclear polarization  

PubMed Central

For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\omega _0 ^{ - 2}\\end{equation*} \\end{document}?0?2 field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ? = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements to address the unfavorable field dependence of the solid effect.

Corzilius, Bjorn; Smith, Albert A.; Griffin, Robert G.

2012-01-01

202

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

203

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

204

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

205

Nuclear spin relaxation/resonance of 8Li in Al  

NASA Astrophysics Data System (ADS)

A low energy beam of spin polarized 8Li has been used to study the behaviour of isolated 8Li implanted into a 150 nm thick film of Al on an MgO substrate. The spin relaxation rate 1/T1 and ?-NMR lineshape were measured as a function of temperature in a large magnetic field of 4.1 T. The resonances from different sites are unresolved due to the large nuclear dipolar interaction with the host 27Al magnetic dipole moments. Nevertheless the temperature variation of the site averaged 1/T1 and Knight shift show evidence for a transition between the octahedral O and substitutional S sites at about 150 K, as observed in other fcc metals.

Wang, D.; Salman, Z.; Chow, K. H.; Fan, I.; Hossain, M. D.; Keeler, T. A.; Kiefl, R. F.; Levy, C. D. P.; Mansour, A. I.; Morris, G. D.; Pearson, M. R.; Parolin, T. J.; Saadaoui, H.; Smadella, M.; Song, Q.; Macfarlane, W. A.

2009-04-01

206

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

207

Nuclear Hydrogen for Peak Electricity Production and Spinning Reserve  

SciTech Connect

Nuclear energy can be used to produce hydrogen. The key strategic question is this: ''What are the early markets for nuclear hydrogen?'' The answer determines (1) whether there are incentives to implement nuclear hydrogen technology today or whether the development of such a technology could be delayed by decades until a hydrogen economy has evolved, (2) the industrial partners required to develop such a technology, and (3) the technological requirements for the hydrogen production system (rate of production, steady-state or variable production, hydrogen purity, etc.). Understanding ''early'' markets for any new product is difficult because the customer may not even recognize that the product could exist. This study is an initial examination of how nuclear hydrogen could be used in two interconnected early markets: the production of electricity for peak and intermediate electrical loads and spinning reserve for the electrical grid. The study is intended to provide an initial description that can then be used to consult with potential customers (utilities, the Electric Power Research Institute, etc.) to better determine the potential real-world viability of this early market for nuclear hydrogen and provide the starting point for a more definitive assessment of the concept. If this set of applications is economically viable, it offers several unique advantages: (1) the market is approximately equivalent in size to the existing nuclear electric enterprise in the United States, (2) the entire market is within the utility industry and does not require development of an external market for hydrogen or a significant hydrogen infrastructure beyond the utility site, (3) the technology and scale match those of nuclear hydrogen production, (4) the market exists today, and (5) the market is sufficient in size to justify development of nuclear hydrogen production techniques independent of the development of any other market for hydrogen. These characteristics make it an ideal early market for nuclear hydrogen.

Forsberg, C.W.

2005-01-20

208

Investigation of a new model of dipolar-coupled nuclear spin relaxation and applications of dynamic nuclear polarization  

NASA Astrophysics Data System (ADS)

This work presents the results of various investigations using various techniques of hyperpolarizing the nuclei of atoms. Hyperpolarization implies magnetic order in excess of the thermal order obtained naturally as described by Curie's law. The main portion of this work presents the results of a detailed experimental exploration of predictions arising from a new model of transverse nuclear spin relaxation in quantum systems, based on possible manifestations of microscopic chaos in quantum systems. Experiments have been carried out on a number of hyperpolarized xenon samples, each differing in its relative percentage of xenon isotopes in order to vary the homonuclear and heteronuclear dipole couplings in the spin system. The experiments were performed under a variety of conditions in an attempt to observe the behaviors predicted by the model. Additionally, much more extensive measurements were made on a number of samples of solid CaF2 in both single crystal and powder forms. These samples, although thermally polarized, were observed with superior signal to noise ratios than even the hyperpolarized xenon solids, allowing for more precise measurements for comparison to the theory. This work thus contains the first experimental evidence for the majority of the model's predictions. Additionally, this work contains the first precise measurements of the frequency-shift enhancement parameters for 129Xe and krypton in the presence of spin-polarized Rb. The determination of these important numbers will be useful to many groups who utilize spin-exchange optical pumping in their labs. This work built on the prior knowledge of a precise number for the frequency-shift enhancement parameter of 3He in Rb vapor. Finally, I detail work using NMR to detect nuclear-spin polarization enhancement in silicon phosphorus by a novel, photo-induced hyperpolarization technique developed by the Boehme research group at the University of Utah. Significant nuclear polarization enhancements were observed by the Boehme group due to electron-photon interactions in semiconductor soilds; these enhancements were observed by their effects on the ambient electrons and measured with electron spin resonance techniques. The work described here details experiments to observe the enhanced nuclear polarization by directly measuring the intensity increase in an NMR measurement. I will conclude this dissertation with a brief appendix giving a summary of one additional project involving the use of high pressure fluorinated gas NMR to measure the internal topology and characteristics of energy-rich oil shales.

Sorte, Eric G.

209

Solid-State Nuclear Spin-Flip Maser Pumped by Dynamic Nuclear Polarization  

Microsoft Academic Search

We report the observation of a coherent, maser-type rf radiation of the 27Al nuclear-spin system in Al2O3: Cr3+ pumped by dynamic nuclear polarization to negative temperature. A theoretical description is presented for the sharp, superradiant bursts which follow the fast tuning of a resonant LC circuit to a selected NMR line of 27Al. Experimental results are discussed which demonstrate the

P. Bösiger; E. Brun; D. Meier

1977-01-01

210

Nuclear Spins of Neutron-deficient Lanthanum and Cerium Isotopes  

Microsoft Academic Search

Nuclear spins of some neutron-deficient lanthanum and cerium isotopes have been measured by the atomic-beam magnetic resonance method. The results are: 131La (59 min) I=3\\/2, 132La (4.5 h) I=2, 132mLa (25 min) I=6, 133La (4.0 h) I=5\\/2, 135La (19.4 h) I=5\\/2, 136La (10 min) I=1, 130Ce (25 min) I=0, 132Ce (4.2 h) I=0, 133Ce (5.4 h) I=9\\/2, 133mCe (97 min)

S. Ingelman; C. Ekstroem; M. Olsmats; B. Wannberg

1973-01-01

211

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

212

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

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

213

Nuclear Spin Orientation Dependence of Magnetoconductance: A New Method for Measuring the Spin of Charged Excitations in the QHE  

SciTech Connect

A new method for measuring the spin of the electrically charged ground state excitations m the Q$j~j quantum Hall effect ia proposed and demonstmted for the tirst time in GaAs/AIGaAs nndtiquantum wells. The method is &sed on the nuclear spin orientation dependence of" the 2D dc conductivity y in the quantum Hall regime due to the nuclear hyperfine interaction. As a demonstration of this method the spin of the electrically charged excitations of the ground state is determined at filling factor v = 1.

Bowers, C.R.; Reno, J.L.; Simmons, J.A.; Vitkalov, S.A.

1998-12-01

214

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

215

Quadrupolar spectra of nuclear spins in strained InxGa1-xAs quantum dots  

NASA Astrophysics Data System (ADS)

Self-assembled quantum dots (QDs) are born out of lattice mismatched ingredients where strain plays an indispensable role. Through the electric quadrupolar coupling, strain affects the magnetic environment as seen by the nuclear spins. To guide prospective single-QD nuclear magnetic resonance (NMR), as well as dynamic nuclear spin polarization experiments, an atomistic insight to the strain and quadrupolar field distributions is presented. A number of implications of the structural and compositional profile of the QD have been identified. A high aspect ratio of the QD geometry enhances the quadrupolar interaction. The inclined interfaces introduce biaxiality and the tilting of the major quadrupolar principal axis away from the growth axis; the alloy mixing of gallium into the QD enhances both of these features while reducing the quadrupolar energy. Regarding the NMR spectra, both Faraday and Voigt geometries are investigated, unraveling in the first place the extend of inhomogeneous broadening and the appearance of the normally forbidden transitions. Moreover, it is shown that from the main extend of the NMR spectra the alloy mole fraction of a single QD can be inferred. By means of the element-resolved NMR intensities it is found that In nuclei has a factor of 5 dominance over those of As. In the presence of an external magnetic field, the borderlines between the quadrupolar and Zeeman regimes are extracted as 1.5 T for In and 1.1 T for As nuclei. At these values the nuclear spin depolarization rates of the respective nuclei get maximized due to the noncollinear secular hyperfine interaction with a resident electron in the QD.

Bulutay, Ceyhun

2012-03-01

216

Optimization of 1H spin density for dynamic nuclear polarization using photo-excited triplet electron spins  

NASA Astrophysics Data System (ADS)

In dynamic nuclear polarization (DNP) using photo-excited triplet electron spins, known as Microwave-Induced Optical Nuclear Polarization (MIONP), the attainable 1H polarization is determined by the ratio of the buildup rate and the spin-lattice relaxation rate, in turn depend on the 1H spin density. It is shown that the final 1H polarization can be enhanced by diluting the 1H spins with partial deuteration. The DNP experiments are demonstrated in 0.05 mol% pentacene-doped p-terphenyl for various 1H abundances. It is also shown that the 1H spin diffusion coefficient can be determined by examining the initial buildup rate of 1H polarization for various repetition rates of the DNP sequence.

Kagawa, Akinori; Murokawa, Yu; Takeda, Kazuyuki; Kitagawa, Masahiro

2009-03-01

217

Optimization of 1H spin density for dynamic nuclear polarization using photo-excited triplet electron spins.  

PubMed

In dynamic nuclear polarization (DNP) using photo-excited triplet electron spins, known as Microwave-Induced Optical Nuclear Polarization (MIONP), the attainable (1)H polarization is determined by the ratio of the buildup rate and the spin-lattice relaxation rate, in turn depend on the (1)H spin density. It is shown that the final (1)H polarization can be enhanced by diluting the (1)H spins with partial deuteration. The DNP experiments are demonstrated in 0.05 mol% pentacene-doped p-terphenyl for various (1)H abundances. It is also shown that the (1)H spin diffusion coefficient can be determined by examining the initial buildup rate of (1)H polarization for various repetition rates of the DNP sequence. PMID:19091611

Kagawa, Akinori; Murokawa, Yu; Takeda, Kazuyuki; Kitagawa, Masahiro

2008-11-27

218

Single and Multi-Nucleon Transfer Reactions for Nuclear Moment Studies Toward Radioactive-Ion Beams  

Microsoft Academic Search

This study is a part of an experimental program to measure nuclear moments in transfer reactions. It aims to probe for a first time the nuclear -spin orientation in multi-nucleon transfer. Fist experiments were performed to measure the quadrupole moment of an isomeric state in 66Cu (Ipi = 6-, Ex = 1154 keV, T1\\/2 = 595(20) ns) in single nucleon

R. L. Lozeva; D. L. Balabanski; G. P. Georgiev; G. Audi; A. Blazhev; S. Cabaret; J.-M. Daugas; T. Faul; M. Ferraton; E. Fiori; C. Gaulard; K. Hauschilda; F. Ibrahim; J. Jolie; A. Lopez-Martens; P. Morel; K. Moschner; L. Risegari; O. Roig; S. Szilner; D. Verney; D. T. Yordanov; K.-O. Zell

2010-01-01

219

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

220

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

221

Effects of barrier-induced nuclear spin magnetization inhomogeneities on diffusion-attenuated MR signal.  

PubMed

The spatial distribution of the transverse nuclear spin magnetization, appearing in a single compartment with impermeable boundaries in a Stejskal-Tanner gradient pulse MR experiment, is analyzed in detail. At short diffusion times the presence of diffusion-restrictive barriers (membranes) reduces effective diffusivity near the membranes and leads to an inhomogeneous spin magnetization distribution (the edge-enhancement effect). In this case, the signal reveals a quasi-two-compartment behavior and can be empirically modeled remarkably well by a biexponential function. The current results provide a framework for interpreting experimental MR data on various phenomena, including water diffusion in giant axons, metabolite diffusion in the brain, and hyperpolarized gas diffusion in lung airways. PMID:14523959

Sukstanskii, A L; Ackerman, J J H; Yablonskiy, D A

2003-10-01

222

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

223

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

224

Nuclear Spin-Dependent Parity Violation in Diatomic Molecules  

NASA Astrophysics Data System (ADS)

Nuclear spin-dependent parity violation (NSD-PV) effects arise from exchange of the Z^0 boson (parametrized by the electroweak coupling constants C2P,N) between electrons and the nucleus, and from the interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The latter scales with the nucleon number A of the nucleus as A^3/2, while the Z^0 coupling is independent of A; the former will be the dominant source of NSD-PV in nuclei with A greater than 20. NSD-PV effects can be dramatically amplified in diatomic molecules by bringing two levels of opposite parity close to degeneracy in a strong magnetic field. This opens the prospect for measurements across a broad range of nuclei. As a precursor to the measurement of the nuclear anapole moment of ^137Ba, we have experimentally observed and characterized opposite-parity level crossings in ^138BaF. These are found to be in excellent agreement with parameter-free predictions and indicate that the sensitivity necessary for NSD-PV measurements should be within reach.

Ammon, Jeffrey; Cahn, Sidney; Kirilov, Emil; Demille, David; Kozlov, Mikhail; Paolino, Richard

2012-06-01

225

A co-magnetometer-based nuclear spin gyroscope  

NASA Astrophysics Data System (ADS)

We describe a new atomic gyroscope based on an alkali metal--noble gas co-magnetometer. Unlike atomic and laser gyroscopes based on the Sagnac effect, nuclear spin gyroscopes do not require a large enclosed area and can be made quite compact. A high density alkali-metal magnetometer operating in a spin-exchange relaxation free (SERF) regime is used to polarize the noble gas atoms and detect their gyroscopic precession. In this arrangement it is also possible to cancel the response to the magnetic fields as well as their gradients and transients between the two atomic species, giving a clean signal proportional to the rotation. Using a K--^3He co-magnetometer we demonstrated rotation sensitivity of 2 x10-7 rad/sec/Hz^1/2. The rotation signal can be increased by an order of magnitude using Ne-21 atoms which have a smaller magnetic moment, while the fundamental limit on the gyroscope sensitivity is about 10-10 rad/sec/ Hz^1/2 for a 10 cm^3 measurement cell. We will also present data on the long-term stability of the gyroscope obtained during a search for Lorentz violation using the K--^3He co-magnetometer.

Kornack, Thomas

2005-05-01

226

Stable three-axis nuclear-spin gyroscope in diamond  

NASA Astrophysics Data System (ADS)

Gyroscopes find wide applications in everyday life from navigation and inertial sensing to rotation sensors in hand-held devices and automobiles. Current devices, based on either atomic or solid-state systems, impose a choice between long-time stability and high sensitivity in a miniaturized system. Here, we introduce a quantum sensor that overcomes these limitations by providing a sensitive and stable three-axis gyroscope in the solid state. We achieve high sensitivity by exploiting the long coherence time of the 14N nuclear spin associated with the nitrogen-vacancy center in diamond, combined with the efficient polarization and measurement of its electronic spin. Although the gyroscope is based on a simple Ramsey interferometry scheme, we use coherent control of the quantum sensor to improve its coherence time and robustness against long-time drifts. Such a sensor can achieve a sensitivity of ?˜0.5(mdegs-1)/Hzmm3 while offering enhanced stability in a small footprint. In addition, we exploit the four axes of delocalization of the nitrogen-vacancy center to measure not only the rate of rotation, but also its direction, thus obtaining a compact three-axis gyroscope.

Ajoy, Ashok; Cappellaro, Paola

2012-12-01

227

Single cell elemental analysis using nuclear microscopy  

NASA Astrophysics Data System (ADS)

The use of Particle Induced X-ray Emission (PIXE), Rutherford Backscattering Spectrometry (RBS) and Scanning Transmission Ion Microscopy (STIM) to provide quantitative elemental analysis of single cells is an area which has high potential, particularly when the trace elements such as Ca, Fe, Zn and Cu can be monitored. We describe the methodology of sample preparation for two cell types, the procedures of cell imaging using STIM, and the quantitative elemental analysis of single cells using RBS and PIXE. Recent work on single cells at the Nuclear Microscopy Research Centre, National University of Singapore has centred around two research areas: (a) Apoptosis (programmed cell death), which has been recently implicated in a wide range of pathological conditions such as cancer, Parkinson's disease etc, and (b) Malaria (infection of red blood cells by the malaria parasite). Firstly we present results on the elemental analysis of human Chang liver cells (ATTCC CCL 13) where vanadium ions were used to trigger apoptosis, and demonstrate that nuclear microscopy has the capability of monitoring vanadium loading within individual cells. Secondly we present the results of elemental changes taking place in individual mouse red blood cells which have been infected with the malaria parasite and treated with the anti-malaria drug Qinghaosu (QHS).

Ren, M. Q.; Thong, P. S. P.; Kara, U.; Watt, F.

1999-04-01

228

Critical divergence of 55Mn nuclear spin relaxation rate in MnSi revealed by muon-núclear-spin double relaxation  

Microsoft Academic Search

The very short 55Mn nuclear spin relaxation time (0.5mus⪷TMn1⪷30mus) in the critical temperature region of MnSi was measured for the first time through zero-field mu+ spin relaxation, which reflects the nuclear spin dynamics. The observed temperature dependence of 1\\/TMn1 shows a clear divergent behaviour similar to that of the mu+ spin relaxation 1\\/Tmu1.

T. Matsuzaki; K. Nishiyama; K. Nagamine; T. Yamazaki; M. Senba; J. M. Bailey; J. H. Brewer

1987-01-01

229

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

230

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

231

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

232

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

233

Improved single particle potential for transport model simulations of nuclear reactions induced by rare isotope beams  

SciTech Connect

Taking into account more accurately the isospin dependence of nucleon-nucleon interactions in the in-medium many-body force term of the Gogny effective interaction, new expressions for the single-nucleon potential and the symmetry energy are derived. Effects of both the spin (isospin) and the density dependence of nuclear effective interactions on the symmetry potential and the symmetry energy are examined. It is shown that they both play a crucial role in determining the symmetry potential and the symmetry energy at suprasaturation densities. The improved single-nucleon potential will be useful for more accurate simulation of nuclear reactions induced by rare-isotope beams within transport models.

Xu Chang [Department of Physics and Astronomy, Texas A and M University-Commerce, Commerce, Texas 75429-3011 (United States); Department of Physics, Nanjing University, Nanjing 210008 (China); Li Baoan [Department of Physics and Astronomy, Texas A and M University-Commerce, Commerce, Texas 75429-3011 (United States)

2010-04-15

234

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

235

Nuclear Spin-Lattice Relaxation in Ferromagnetic Insulators at Low Temperatures  

Microsoft Academic Search

A theoretical study of the nuclear spin-lattice relaxation in cubic ferromagnetic insulators at ultralow temperatures is presented. Calculations are performed for nuclei which belong to the magnetic atoms, considering only the direct processes. Three mechanisms are considered: the relaxation to mixed magnon-phonon modes, indirect nuclear-spin interaction modulated by lattice vibrations, and nuclear quadrupole energy modulated by lattice vibrations. The first

Akio Honma

1966-01-01

236

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

237

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

238

Frequency-stepped acquisition in nuclear magnetic resonance spectroscopy under magic angle spinning  

NASA Astrophysics Data System (ADS)

The nuclear magnetic resonance of paramagnetic solids is usually characterized by the presence of large chemical shifts and shift anisotropies due to hyperfine interactions. Frequently the resulting spectra cover a frequency range of several megahertz, which is greater than the bandwidth of commercially available radio-frequency (RF) probes, making it impossible to acquire the whole spectrum in a single experiment. In these cases it common to record a series of spectra, in which the probe is tuned to a different frequency for each, and then sum the results to give the ``true'' spectrum. While this method is very widely used on static samples, the application of frequency stepping under magic-angle spinning (MAS) is less common, owing to the increased complexity of the spin dynamics when describing the interplay of the RF irradiation with the mechanical rotation of the shift tensor. In this paper, we present a theoretical description, based on the jolting frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983)], for describing the spin dynamics of a powder sample under MAS when subjected to a selective pulse of low RF-field amplitude. The formalism is used to describe the frequency stepping method under MAS, and under what circumstances the true spectrum is reproduced. We also present an experimental validation of the methodology under ultra-fast MAS with the paramagnetic materials LiMnPO4 and TbCsDPA.

Pell, Andrew J.; Clément, Raphaële J.; Grey, Clare P.; Emsley, Lyndon; Pintacuda, Guido

2013-03-01

239

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

240

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

241

Effects of Nuclear Spin Polarization on Reaction Dynamics in Photosynthetic Bacterial Reaction Centers  

PubMed Central

Singlet-triplet mixing in the initial radical-pair state, P[unk]I[unk], of photosynthetic bacterial reaction centers is due to the hyperfine mechanism at low magnetic fields and both the hyperfine and ?g mechanisms at high magnetic fields (>1 kG). Since the hyperfine field felt by the electron spins in P[unk]I[unk] is dependent upon the nuclear spin state in each radical, the relative probabilities of charge recombination to the triplet state of the primary electron donor, 3PI, or the ground state, PI, will depend on the nuclear spin configuration. As a result these recombination products will have non-equilibrium distributions of nuclear spin states (nuclear spin polarization). This polarization will persist until the 3PI state decays. In addition, due to unequal nuclear spin relaxation rates in the diamagnetic PI and paramagnetic 3PI states, net polarization of the nuclear spins can result, especially in experiments that involve recycling of the system through the radical-pair state. This net polarization can persist for very long times, especially at low temperatures. Nuclear spin polarization can have consequences on any subsequent process that involves re-formation of the radical-pair state. Numerical calculations of the nuclear polarization caused by both of these mechanics are presented, including the effect of such polarization on subsequent yields of 3PI, 3PI decay rates, the decay rate of the radical pair, and saturation behavior. The effect of this polarization under certain circumstances can be very dramatic and can explain previously noted discrepancies between experiments and theories that do not include nuclear spin polarization effects. Our analysis suggests new classes of experiments and indicates the need to reinterpret some past experimental results.

Goldstein, Richard A.; Boxer, Steven G.

1987-01-01

242

Electrically generated nuclear spin polarization in In.04Ga.96As  

NASA Astrophysics Data System (ADS)

The promises of lower power consumption and simple interfacing to magnetic storage has driven interest in the development of spintronics, in which devices could take advantage of electron spin as a means to store, move, and process data. Due to its long lifetime in moderate fields, nuclear polarization could serve as intermediate timescale data storage in both classical spintronic and quantum computation schemes. Here, we investigate the role of nuclear spins in materials with electrically driven spin polarization. The electron spin polarization generated by electrical current in a non-magnetic semiconductor is transferred via dynamic nuclear polarization to the nuclei. The resulting nuclear field is interrogated using Larmor magnetometry. We measure nuclear field as a function of current, applied magnetic field, and temperature. Polarization decay dynamics and the role of nuclei in devices are also discussed.

Trowbridge, Christopher; Norman, Benjamin; Kato, Yuichiro K.; Awschalom, David; Sih, Vanessa

2013-03-01

243

Effects of Substituent Groups on Spin-Spin Coupling in Nuclear Magnetic Resonance.  

National Technical Information Service (NTIS)

The initial phases of this investigation were motivated by the observation that certain spin-spin coupling constants are directly additive whereas others are pairwise additive with respect to the substituent groups. During the study it has been found that...

E. R. Malinowski

1966-01-01

244

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

245

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

246

Accessing long-lived nuclear singlet states between chemically equivalent spins without breaking symmetry  

PubMed Central

Long-lived nuclear spin states could greatly enhance the applicability of hyperpolarized nuclear magnetic resonance. Using singlet states between inequivalent spin pairs has been shown to extend the signal lifetime by more than an order of magnitude compared to the spin lattice relaxation time (T1), but they have to be prevented from evolving into other states. In the most interesting case the singlet is between chemically equivalent spins, as it can then be inherently an eigenstate. However this presents major challenges in the conversion from bulk magnetization to singlet. In the only case demonstrated so far, a reversible chemical reaction to break symmetry was required. Here we present a pulse sequence technique that interconverts between singlet spin order and bulk magnetization without breaking the symmetry of the spin system. This technique is independent of field strength and is applicable to a broad range of molecules.

Feng, Yesu; Davis, Ryan M.; Warren, Warren S.

2013-01-01

247

Electrical current and coupled electron-nuclear spin dynamics in double quantum dots  

NASA Astrophysics Data System (ADS)

We examine electronic transport in a spin-blockaded double quantum dot. We show that by tuning the strength of the spin-orbit interaction the current flowing through the double dot exhibits a dip at zero magnetic field or a peak at a magnetic field for which the two-electron energy levels anticross. This behavior is due to the dependence of the singlet-triplet mixing on the field and spin-orbit amplitude. We derive approximate expressions for the current as a function of the amplitudes of the states involved in the transport. We also consider an alternative model that takes into account a finite number of nuclear spins and study the resulting coupled dynamics between electron and nuclear spins. We show that if the spin ensemble is in a thermal state there are regular oscillations in the transient current followed by quasichaotic revivals akin to those seen in a thermal Jaynes-Cummings model.

Giavaras, G.; Lambert, Neill; Nori, Franco

2013-03-01

248

Line Broadening in the Electron Resonance Spectra of Spin Probes Dissolved in Anisotropic Media: The Effect of Nuclear Spin Quantization  

Microsoft Academic Search

The line broadening in the electron resonance spectra of monoradicals dissolved in anisotropic media, such as liquid crystals, provides a valuable probe of both the orientational order and the molecular dynamics. However, the fast-motion relaxation theory employed to extract this information from the linewidths assumes that the nuclear spin is quantized along the direction of the magnetic field. This approximation

G. R. Luckhurst; C. Zannoni

1977-01-01

249

Coherent storage of photoexcited triplet states using 29Si nuclear spins in silicon.  

PubMed

Pulsed electron paramagnetic resonance spectroscopy of the photoexcited, metastable triplet state of the oxygen-vacancy center in silicon reveals that the lifetime of the m(s)=±1 sublevels differs significantly from that of the m(s)=0 state. We exploit this significant difference in decay rates to the ground singlet state to achieve nearly ~100% electron-spin polarization within the triplet. We further demonstrate the transfer of a coherent state of the triplet electron spin to, and from, a hyperfine-coupled, nearest-neighbor (29)Si nuclear spin. We measure the coherence time of the (29)Si nuclear spin employed in this operation and find it to be unaffected by the presence of the triplet electron spin and equal to the bulk value measured by nuclear magnetic resonance. PMID:22463668

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

2012-02-27

250

New host-lattices for hyperfine optical hole burning: Materials of low nuclear spin moment  

Microsoft Academic Search

Optical hole burning (OHB) on lanthanides in inorganic host-lattices provides a promising method for optical storage application. To gain a high memory capacity, materials of low nuclear spin moments are of interest because of line broadening due to spin flip-flop processes in spin rich host-lattices. In this work, it is shown that only a small number of elements may be

A. Caprez; P. Meyer; P. Mikhail; J. Hulliger

1997-01-01

251

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

252

Dynamical nuclear spin polarization induced by electronic current through double quantum dots  

NASA Astrophysics Data System (ADS)

We analyse electron-spin relaxation in electronic transport through coherently coupled double quantum dots (DQDs) in the spin blockade regime. In particular, we focus on hyperfine (HF) interaction as the spin-relaxation mechanism. We pay special attention to the effect of the dynamical nuclear spin polarization induced by the electronic current on the nuclear environment. We discuss the behaviour of the electronic current and the induced nuclear spin polarization versus an external magnetic field for different HF coupling intensities and interdot tunnelling strengths. We take into account, for each magnetic field, all HF-mediated spin-relaxation processes coming from different opposite spin level approaches. We find that the current as a function of the external magnetic field shows a peak or a dip and that the transition from a current dip to a current peak behaviour is obtained by decreasing the HF coupling or by increasing the interdot tunnelling strength. We give a physical picture in terms of the interplay between the electrons tunnelling out of the DQD and the spin-flip processes due to the nuclear environment.

López-Monís, Carlos; Iñarrea, Jesús; Platero, Gloria

2011-05-01

253

Theory of nuclear spin interactions in ferromagnetic insulators. I. The thermodynamic properties  

Microsoft Academic Search

A field theoretical perturbation method is employed to investigate the low temperature thermodynamic properties of a ferromagnetic insulator in which there is a Heisenberg exchange interaction between neighbouring electronic spins and an additional hyperfine coupling between the nuclear and electronic spins. The calculations make use of the diagrammatic formalism of Vaks et al (1968), and the contributions are classified by

M. G. Cottam; M. J. Jones

1973-01-01

254

Theory of nuclear spin interactions in ferromagnetic insulators. II. The excitation spectrum  

Microsoft Academic Search

For pt. I see ibid., vol. 6, 1007 (1973). The method of the preceding paper is used to investigate the excitation spectrum of a Heisenberg ferromagnet in which there is a hyperfine coupling between the nuclear and electronic spins. This formalism employs a perturbation expansion in terms of the parameters 1\\/z, where z is the number of spins interacting with

M. G. Cottam; M. J. Jones

1973-01-01

255

Optimized basis sets for the calculation of indirect nuclear spin-spin coupling constants involving the atoms B, Al, Si, P, and Cl  

NASA Astrophysics Data System (ADS)

The aug-cc-pVTZ-J series of basis sets for indirect nuclear spin-spin coupling constants has been extended to the atoms B, Al, Si, P, and Cl. The basis sets were obtained according to the scheme previously described by Provasi et al. [J. Chem. Phys. 115, 1324 (2001)]. First, the completely uncontracted correlation consistent aug-cc-pVTZ basis sets were extended with four tight s and three tight d functions. Second, the s and p basis functions were contracted with the molecular orbital coefficients of self-consistent-field calculations performed with the uncontracted basis sets on the simplest hydrides of each atom. As a first illustration, we have calculated the one-bond indirect spin-spin coupling constants in BH4-, BF, AlH, AlF, SiH4, SiF4, PH3, PF3, H2S, SF6, HCl, and ClF at the level of density functional theory using the Becke three parameter Lee-Yang-Parr and the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes.

Provasi, Patricio F.; Sauer, Stephan P. A.

2010-08-01

256

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

257

Infrared Spectroscopy of Chloromethyl Radical in Solid Parahydrogen and Its Nuclear Spin Conversion  

NASA Astrophysics Data System (ADS)

We present high-resolution infrared absorption spectra of chloromethyl radical produced by in situ UV photolysis of chloroiodomethane isolated in solid parahydrogen. The radicals were stable over a few days in solid parahydrogen kept at 3.6 K. Analysis of the rotation-vibration spectra revealed that the radical exhibited quantized one-dimensional rotational motion about the C-Cl bond, while the ortho and para nuclear spin species were still clearly distinguishable in the spectra. Temporal change of the spectra indicated that the nuclear spin conversion between the ortho and para nuclear spin species of the radical in solid parahydrogen occurred in a time scale of a few hours at 3.6 K. It was also found that the nuclear spin conversion became significantly slower in a higher concentration of chloroiodomethane.

Miyamoto, Yuki; Tsubouchi, Masaaki; Momose, Takamasa

2013-10-01

258

Infrared Spectroscopy of Chloromethyl Radical in Solid Parahydrogen and its Nuclear Spin Conversion.  

PubMed

We present high-resolution infrared absorption spectra of chloromethyl radical produced by {\\it in situ} UV photolysis of chloroiodomethane isolated in solid parahydrogen. The radicals were stable over a few days in solid parahydrogen kept at 3.6 K. Analysis of the rotation-vibration spectra revealed that the radical exhibited quantized one-dimensional rotational motion about the C-Cl bond, while the {\\it ortho} and {\\it para} nuclear spin species were still clearly distinguishable in the spectra. Temporal change of the spectra indicated that the nuclear spin conversion between the {\\it ortho} and {\\it para} nuclear spin species of the radical in solid parahydrogen occurred in a time scale of a few hours at 3.6 K. It was also found that the nuclear spin conversion became significantly slower in a higher concentration of chloroiodomethane. PMID:23506119

Miyamoto, Yuki; Tsubouchi, Masaaki; Momose, Takamasa

2013-03-18

259

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

260

Nuclear spin selection rules in chemical reactions by angular momentum algebra  

NASA Astrophysics Data System (ADS)

The detailed selection rules for reactive collisions reported by Quack using molecular symmetry group are derived by using angular momentum algebra. Instead of the representations of the permutation inversion group for both nuclear spin and rovibronic coordinate wavefunctions, those of the rotation group for nuclear spin wavefunction only are used. The method allows more straightforward derivation of Quack’s results and further extension of the calculation for separating elementary reactions and application to higher proton systems.

Oka, Takeshi

2004-12-01

261

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

262

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

263

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

264

Description of 158Er at Ultrahigh Spin in Nuclear Density Functional Theory  

SciTech Connect

Rotational bands in 158Er at ultrahigh spin have been studied in the framework of relativistic and nonrelativistic nuclear density-functional theories. Consistent results are obtained across the theoretical models used but some puzzles remain when confronted with experiment. Namely, the many-body configurations which provide good description of experimental transition quadrupole moments and dynamic moments of inertia require substantial increase of the spins of observed bands as compared with experimental estimates, which are still subject to large uncertainties. If, however, the theoretical spin assignments turned out to be correct, experimental band 1 in 158Er would be the highest spin structure ever observed.

Afanasjev, A. V. [Mississippi State University/JIHIR, ORNL; Shi, Yue [Peking University; Nazarewicz, Witold [UTK/ORNL/University of Warsaw

2012-01-01

265

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

266

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

267

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

268

Dynamical magnetic and nuclear polarization in complex spin systems: semi-magnetic II–VI quantum dots  

NASA Astrophysics Data System (ADS)

Dynamical magnetic and nuclear polarization in complex spin systems is discussed on the example of transfer of spin from exciton to the central spin of magnetic impurity in a quantum dot in the presence of a finite number of nuclear spins. The exciton is described in terms of electron and heavy-hole spins interacting via exchange interaction with magnetic impurity, via hyperfine interaction with a finite number of nuclear spins and via dipole interaction with photons. The time evolution of the exciton, magnetic impurity and nuclear spins is calculated exactly between quantum jumps corresponding to exciton radiative recombination. The collapse of the wavefunction and the refilling of the quantum dot with a new spin-polarized exciton is shown to lead to the build up of magnetization of the magnetic impurity as well as nuclear spin polarization. The competition between electron spin transfer to magnetic impurity and to nuclear spins simultaneous with the creation of dark excitons is elucidated. The technique presented here opens up the possibility of studying optically induced dynamical magnetic and nuclear polarization in complex spin systems.

Abolfath, Ramin M.; Trojnar, Anna; Roostaei, Bahman; Brabec, Thomas; Hawrylak, Pawel

2013-06-01

269

14N Pulsed nuclear quadrupole resonance. 2. Effect of a single radio-frequency pulse in the general case  

Microsoft Academic Search

A novel theory, based on density operator calculations, is provided for assessing the nuclear quadrupole resonance behaviour of a spin 1 (14N) subjected to a single radio-frequency pulse. It is for a powder sample in zero magnetic field for an electric field gradient tensor without symmetry. A complete set of equations is obtained for the quantities of interest. It is

Daniel Canet; Lionel Merlat; Benoit Cordier; Denis Grandclaude; Alain Retournard; Maude Ferrari

2006-01-01

270

Spin-mediated consciousness theory: possible roles of neural membrane nuclear spin ensembles and paramagnetic oxygen  

Microsoft Academic Search

A novel theory of consciousness is proposed in this paper. We postulate that consciousness is intrinsically connected to quantum spin since the latter is the origin of quantum effects in both Bohm and Hestenes quantum formulism and a fundamental quantum process associated with the structure of space-time. That is, spin is the “mind-pixel”. The unity of mind is achieved by

Huping Hu; Maoxin Wu

2004-01-01

271

Electron spin coherence and electron nuclear double resonance of Bi donors in natural Si  

NASA Astrophysics Data System (ADS)

We have shown that the electron spin coherence times of Si:Bi donors in natural silicon are limited by the same mechanism of spectral diffusion as seen in Si:P, though the smaller Bohr radius of the Bi donor leads to ˜30% longer T2 times (up to 0.8 ms). We have mapped out the 36 ENDOR transitions observable at X-band arising from the I=9/2 nuclear spin of ^209Bi, going up to 1.3 GHz. We also demonstrate the transfer of electron spin coherence to and from the ^209Bi nuclear spin with a fidelity of ˜63%. Using pulsed ESR at W-band (100 GHz), we observe optically-induced dynamic nuclear polarisation, consistent with the mechanism of exciton capture proposed in by T. Sekiguchi et al.. Finally, we explore the zero-field splitting of 7.5 GHz in this system, within the context of coupling to superconducting resonators.

Morton, John; Simmons, Stephanie; George, Richard; Witzel, Wayne; Riemann, H.; Abrosimov, Nikolai; Notzel, N.; Thewalt, Mike

2011-03-01

272

Gauge invariance of the nuclear spin/electron orbit interaction and NMR spectral parameters.  

PubMed

A gauge transformation of the vector potential A(m(I)), associated to the magnetic dipole m(I) of nucleus I in a molecule, has been studied. The conditions for gauge invariance of nuclear magnetic shielding, nuclear spin/electron orbit contribution to spin-spin coupling between two nuclei, I and J, and electronic current density induced by m(I), have been expressed via quantum mechanical sum rules that are identically satisfied for exact and optimal variational wavefunctions. It is shown that separate diamagnetic and paramagnetic contributions to the properties transform into one another in the gauge transformation, whereas their sum is invariant. Therefore, only total response properties have a physical meaning. In particular, the disjoint diamagnetic and paramagnetic components of nuclear spin/electron orbit contributions to coupling constants are not uniquely defined. The diamagnetic contribution to the nuclear spin-spin coupling tensor, evaluated as an expectation value in the Ramsey theory, can alternatively be expressed as a sum-over-states formula, by rewriting the second-order Hamiltonian in commutator form à la Geertsen, as previously reported by Sauer. Other sum-over-states formulae are obtained via a gauge transformation, by a procedure formally allowing for a continuous translation of the origin of the m(I)-induced current density, analogous to those previously proposed for magnetizabilities and nuclear magnetic shielding. PMID:22920104

Lazzeretti, Paolo

2012-08-21

273

Small tip angle NMR as a probe of electron-mediated nuclear spin-spin couplings in YBa2Cu3O7  

NASA Astrophysics Data System (ADS)

We develop the theory and application of small tip angle NMR techniques that can be used to measure couplings between nuclear spins and multiple neighboring spins. We employ the techniques to measure indirect (electron-mediated) nuclear spin-spin couplings between neighboring 63,65Cu and 17O nuclear spins in the high-temperature superconductor YBa2Cu3O7. Predictions for the values of these couplings can be obtained from the existing phenomenological models of electronic spin susceptibility ?(q,?) and hyperfine couplings that have been used in attempts to understand the wide body of YBa2Cu3O7 NMR data gathered to date. We find that the measured couplings are incompatible with these models.

Pennington, C. H.; Yu, S.; Gorny, K. R.; Buoni, M. J.; Hults, W. L.; Smith, J. L.

2001-02-01

274

Nonconservation of the spin projection on the nuclear symmetry axis in neutron resonances, and Coriolis mixing  

SciTech Connect

It is shown that the effect of the Coriolis mixing in deformed nuclei grows as the nuclear level density increases and at sufficiently high excitation energies E/sub 0/ (E/sub 0/spin projection on the nuclear symmetry axis.

Kadmenskii, S.G.; Markushev, V.P.; Furman, V.I.

1982-02-01

275

Dynamic nuclear spin polarization in the resonant laser excitation of an InGaAs quantum dot.  

PubMed

Resonant optical excitation of lowest-energy excitonic transitions in self-assembled quantum dots leads to nuclear spin polarization that is qualitatively different from the well-known optical orientation phenomena. By carrying out a comprehensive set of experiments, we demonstrate that nuclear spin polarization manifests itself in quantum dots subjected to finite external magnetic field as locking of the higher energy Zeeman transition to the driving laser field, as well as the avoidance of the resonance condition for the lower energy Zeeman branch. We interpret our findings on the basis of dynamic nuclear spin polarization originating from noncollinear hyperfine interaction and find excellent agreement between experiment and theory. Our results provide evidence for the significance of noncollinear hyperfine processes not only for nuclear spin diffusion and decay, but also for buildup dynamics of nuclear spin polarization in a coupled electron-nuclear spin system. PMID:23003088

Högele, A; Kroner, M; Latta, C; Claassen, M; Carusotto, I; Bulutay, C; Imamoglu, A

2012-05-09

276

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

277

Quenching of Nuclear Spin Diffusion in Strained GaAs-AlGaAs Multiple Quantum Wells  

NASA Astrophysics Data System (ADS)

NMR Knight shift and spin lattice relaxation measurements have recently provided new insight into the formation of charged spin texture excitations (i.e. Skyrmions) in the context of the quantum Hall effect in GaAs/AlGaAs quantum wells. Although the observable nuclei in these NMR experiments ( ^69Ga, ^71Ga and ^75As) all posses a nuclear quadrupole moment, no quadrupole splitting is observed due to the cubic symmetry of the lattice. We demonstrate that uniform and controlled strain can be useful to identify optically pumped NMR signal contributions from different layers in the sample and to determine the nuclear spin polarization. A uniform biaxial strain in the plane of wells can be induced by epoxy bonding of the GaAs/AlGaAs multilayer structure to a Si (100) support. The result is a quadrupole splitting of 55 kHz at 1.5-4.2 K. Differences in the spin lattice relaxation of the central versus satellite transitions of the ^71Ga signal are attributed to quenching of spin diffusion at the GaAs/AlGaAs boundary. Spin diffusion into the barrier regions influences the apparent nuclear spin lattice relaxation time in the wells, an effect we have modelled with the relaxation-diffusion equation. These calculations may be beneficial in NMR studies of the QHE.

Vitkalov, Sergey A.; Bowers, C. Russell; Reno, John L.; Simmons, Jerry A.

1998-03-01

278

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

279

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

280

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

281

Diamond nitrogen-vacancy center as a probe of random fluctuations in a nuclear spin ensemble  

NASA Astrophysics Data System (ADS)

New schemes that exploit the unique properties of nitrogen-vacancy (NV) centers in diamond are presently being explored as a platform for high-resolution magnetic sensing. Here we focus on the ability of a NV center to monitor an adjacent mesoscopic nuclear spin bath. For this purpose, we conduct comparative experiments where the NV spin evolves under the influence of surrounding 13C nuclei or, alternatively, in the presence of asynchronous alternating current fields engineered to emulate bath fluctuations. Our study reveals substantial differences that underscore the limitations of the semi-classical picture when interpreting and predicting the outcome of experiments designed to probe small nuclear spin ensembles. In particular, our study elucidates the NV center response to bath fluctuations under common pulse sequences, and explores a detection protocol designed to probe time correlations of the nuclear spin bath dynamics. Further, we show that the presence of macroscopic nuclear spin order is key to the emergence of semi-classical spin magnetometry.

Laraoui, Abdelghani; Hodges, Jonathan S.; Ryan, Colm A.; Meriles, Carlos A.

2011-09-01

282

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

283

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

PubMed

A key to ultralong electron spin memory in quantum dots (QDs) at zero magnetic field is the polarization of the nuclei, such that the electron spin is stabilized along the average nuclear magnetic field. We demonstrate that spin-polarized electrons in n-doped (In,Ga)As/GaAs QDs align the nuclear field via the hyperfine interaction. A feedback onto the electrons occurs, leading to stabilization of their polarization due to formation of a nuclear spin polaron [I. A. Merkulov, Phys. Solid State 40, 930 (1998)]. Spin depolarization of both systems is consequently greatly reduced, and spin memory of the coupled electron-nuclear spin system is retained over 0.3 sec at temperature of 2 K. PMID:17358564

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

2007-03-07

284

Subsecond Spin Relaxation Times in Quantum Dots at Zero Applied Magnetic Field Due to a Strong Electron-Nuclear Interaction  

NASA Astrophysics Data System (ADS)

A key to ultralong electron spin memory in quantum dots (QDs) at zero magnetic field is the polarization of the nuclei, such that the electron spin is stabilized along the average nuclear magnetic field. We demonstrate that spin-polarized electrons in n-doped (In,Ga)As/GaAs QDs align the nuclear field via the hyperfine interaction. A feedback onto the electrons occurs, leading to stabilization of their polarization due to formation of a nuclear spin polaron [I. A. Merkulov, Phys. Solid State 40, 930 (1998).PSOSED1063-783410.1134/1.1130450]. Spin depolarization of both systems is consequently greatly reduced, and spin memory of the coupled electron-nuclear spin system is retained over 0.3 sec at temperature of 2 K.

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

2007-03-01

285

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

286

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

287

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

288

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

289

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

290

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

291

Nuclear spin structure in dark matter search: The zero momentum transfer limit  

Microsoft Academic Search

We review the calculation of spin-dependent matrix elements relevant to\\u000ascattering of weakly interacting massive particles on nuclei. A comprehensive\\u000alist, to our knowledge, of the proton and neutron total spin expectation values\\u000a($<{\\\\bf S}_{p}>$ and $<{\\\\bf S}_{n}>$) calculated within different nuclear\\u000amodels is presented. These values allow a conclusion about the event rate\\u000aexpected in direct dark matter search

V. A. Bednyakov; F. Simkovic

2004-01-01

292

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

293

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

294

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

295

Electronic structure and indirect spin-spin interactions in bournonite (CuPbSbS3) according to antimony nuclear quadrupole resonance  

NASA Astrophysics Data System (ADS)

A complex sulfide CuPbSbS3 (bournonite) has been studied by the nuclear quadrupole resonance on 121,123Sb. The temperature dependences of the spectroscopic and relaxation parameters in the temperature range of 10-295 K have been obtained. The crystallochemical features of the environment of the two non-equivalent Sb positions in the unit cell have been revealed from the nuclear quadrupole resonance spectra. The existence of the lattice vibrations with the frequency ? = 110 cm-1 has been demonstrated on the basis of the temperature dependence of the nuclear quadrupole resonance frequencies. Slow beats have been observed on the decay curve of the spin echo signal. Experimental data have been analyzed in order to reveal the existence of the indirect spin-spin interactions involving Sb atoms. The indirect spin-spin coupling constant has been estimated as J = 2.5 ± 0.5 kHz.

Orlova, A. Yu.; Gainov, R. R.; Dooglav, A. V.; Pen'kov, I. N.

2013-06-01

296

Theoretical aspects of dynamic nuclear polarization in the solid state--spin temperature and thermal mixing.  

PubMed

Dynamic nuclear polarization is a method which allows for a dramatic increase of the NMR signals due to polarization transfer between electrons and their neighboring nuclei, via microwave irradiation. These experiments have become popular in recent years due to the ability to create hyper-polarized chemically and biologically relevant molecules, in frozen glass forming mixtures containing free radicals. Three mechanisms have been proposed for the polarization transfer between electrons and their surrounding nuclei in such non-conducting samples: the solid effect and cross effect mechanisms, which are based on quantum mechanics and relaxation on small spin systems, and thermal mixing, which originates from the thermodynamic macroscopic notion of spin temperature. We have recently introduced a spin model, which is based on the density matrix formalism and includes relaxation, and applied it to study the solid effect and cross effect mechanisms on small spin systems. In this publication we use the same model to describe the thermal mixing mechanism, and the creation of spin temperature. This is obtained without relying on the spin temperature formalism. Simulations of small model systems are used on systems with homogeneously and inhomogeneously broadened EPR lines. For the case of a homogeneously broadened line we show that the nuclear enhancement results from the thermal mixing and solid effect mechanisms, and that spin temperatures are created in the system. In the inhomogeneous case the enhancements are attributed to the solid effect and cross effect mechanisms, but not thermal mixing. PMID:23160533

Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon

2012-11-16

297

About long-lived nuclear spin states involved in para-hydrogenated molecules.  

PubMed

This study deals with a spin system constituted of three nonequivalent protons, two of them originating from para-hydrogen (p-H(2)) after a hydrogenation reaction carried out in the earth magnetic field. It is shown that three singlet states are created provided indirect (J) couplings exist between the three spins, implying hyperpolarization transfer toward the third spin. Upon insertion of the sample in the NMR (Nuclear Magnetic Resonance) high field magnet, the following events occur: (i) the longitudinal two-spin orders which are parts of the singlet states survive; (ii) the other two terms (of these singlet states) tend to be destroyed by magnetic field gradients but at the same time are partly converted into differences of longitudinal polarizations. Nuclear spin relaxation is studied by appropriate NMR measurements when evolution takes place in the high field magnet or in the earth field. In the former case, relaxation is classical although complicated by numerous relaxation rates associated with both longitudinal two-spin orders and longitudinal polarizations. In the latter case, an equilibration between the singlet states first occur, their disappearance being thereafter driven by relaxation rates which remain very small because of the absence of any dipolar contribution. Thus, even in the case of a three-spin system, long-lived states exist; this unexpected property could be very useful for many applications. PMID:17263430

Canet, Daniel; Bouguet-Bonnet, Sabine; Aroulanda, Christie; Reineri, Francesca

2007-02-01

298

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

299

Nuclear-Spin Selection Rules in the Chemistry of Interstellar Nitrogen Hydrides  

NASA Astrophysics Data System (ADS)

Nitrogen hydrides are at the root of the nitrogen chemistry in interstellar space. The detailed modeling of their gas phase formation, however, requires the knowledge of nuclear-spin branching ratios for chemical reactions involving multiprotonated species. We investigate in this work the nuclear-spin selection rules in both exothermic and near thermoneutral ion-molecule reactions involved in the synthesis of ammonia, assuming full scrambling of protons in the reaction complexes. The formalism of Oka [ J. Mol. Spectrosc. 2004, 228, 635 ] is employed for highly exothermic ion-molecule and dissociative recombination reactions. For thermoneutral reactions, a simple state-to-state statistical approach is suggested, which is in qualitative agreement with both quantum scattering and microcanonical statistical calculations. This model is applied to the seven atom reaction NH4+ + H2, of possible importance in the nuclear-spin thermalization of ammonia.

Rist, Claire; Faure, Alexandre; Hily-Blant, Pierre; Le Gal, Romane

2013-10-01

300

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

301

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

302

Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: The importance of level crossings  

PubMed Central

We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T1e is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants.

Thurber, Kent R.; Tycko, Robert

2012-01-01

303

Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: the importance of level crossings.  

PubMed

We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T(1e) is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251

Thurber, Kent R; Tycko, Robert

2012-08-28

304

Vector Model Of Electron Spin Echo Envelope Modulation Due To Nuclear Hyperfine And Zeeman Interactions  

SciTech Connect

The transverse electron spin magnetization of a paramagnetic center with effective spin S=? interacting with nonquadrupolar nuclei may be presented as a function of pairs of nuclei magnetization vectors which process around the effective magnetic field directions. Each vector of the pair starts its precession perpendicular to both effective fields. The FID signal is proportional to the scalar product of the vectors for nuclear spin I=?. The ESE signal can be described using two pairs of magnetization vectors. The ESE shape is not equal to two back-to-back FID signals except in the absence of ESE envelope modulation. A recursion relation is obtained which allows calculation of ESE signals for larger nuclear spins in the absence of NQI. This relation can be used to calculate the time course of the ESE signal for arbitrary nuclear spin as a function of the nuclear magnetization vectors. Although this formalism allows quantitative calculation of modulation from nuclei, it also provides a qualitative means of visualizing the modulation based on simple magnetization vectors.

Maryasov, Alexander G. (OFFICE OF FELLOWSHIP PROG); Bowman, Michael K. (BATTELLE (PACIFIC NW LAB)); Tsvetkov, Yuri D. (OFFICE OF FELLOWSHIP PROG)

2002-12-01

305

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

306

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

307

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

308

Nuclear-Spin-Independent Short-Range Three-Body Physics in Ultracold Atoms  

SciTech Connect

We investigate three-body recombination loss across a Feshbach resonance in a gas of ultracold {sup 7}Li atoms prepared in the absolute ground state and perform a comparison with previously reported results of a different nuclear-spin state [N. Gross et al., Phys. Rev. Lett. 103, 163202 (2009)]. We extend the previously reported universality in three-body recombination loss across a Feshbach resonance to the absolute ground state. We show that the positions and widths of recombination minima and Efimov resonances are identical for both states which indicates that the short-range physics is nuclear-spin independent.

Gross, Noam; Shotan, Zav; Khaykovich, Lev [Department of Physics, Bar-Ilan University, Ramat-Gan, 52900 (Israel); Kokkelmans, Servaas [Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven (Netherlands)

2010-09-03

309

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

310

Electronic population effect in halogen nuclear spin - lattice relaxation in praseodymium trihalide compounds  

Microsoft Academic Search

Nuclear quadrupole resonance determinations of the spin - lattice relaxation rates of the 0953-8984\\/8\\/42\\/018\\/img7, 0953-8984\\/8\\/42\\/018\\/img8 and 0953-8984\\/8\\/42\\/018\\/img9 nuclei in the praseodymium trihalide crystals 0953-8984\\/8\\/42\\/018\\/img10 and 0953-8984\\/8\\/42\\/018\\/img11 are reported. Data are presented in the temperature range 7 - 297 K. They are shown to be dominated by magnetic dipole interactions between the halogen nuclear spins and the 0953-8984\\/8\\/42\\/018\\/img12 paramagnetic ions. The

Sunyu Su; Pablo Prado; Robin L. Armstrong; Mariano Zuriaga

1996-01-01

311

Studies of nuclear rotational bands with the spin spectrometer  

Microsoft Academic Search

In the last few years increasingly sophisticated gamma-ray spectrometer arrays have been built at a number of laboratories around the world. These instruments, coupled with versatile heavy-ion accelerators, are capable of probing the detailed behaviour of atomic nuclei under extreme conditions of angular momentum and temperature. Characteristics of one such detector array, the Spin Spectrometer at Oak Ridge National Laboratory,

L. L. Riedinger; M. P. Carpenter; L. H. Courtney; V. P. Janzen

1987-01-01

312

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

313

Robust few-electron quantum dot devices in nuclear spin engineered Si/SiGe  

NASA Astrophysics Data System (ADS)

Spins in gate-defined quantum dots are currently discussed as one of the most promising scalable qubit architecture. Since the identification of the hyperfine interaction as a dominant spin qubit decoherence mechanism, Si/SiGe heterostructures have been receiving steadily increasing attention for realizing devices almost free of nuclear spin carrying isotopes. Building Si/SiGe heterostructures from material enriched in nuclear spin-free isotopes brings new perspectives of reaching a regime of further improved decoherence times compared to Si/SiGe of natural isotope composition. In such isotopically engineered heterostructures, the decoherence is predicted to no longer be governed by the hyperfine interaction with the nuclear spin bath, but solely by dipolar interactions. In the first part of my presentation I will review the development of two-dimensional electron systems in 28Si for spin qubit applications in my group and discuss few electron double quantum dot devices based on these heterostructures. Being able to avoid hyperfine-induced decoherence then brings a second major limitation for the realization of robust spin qubits into focus. Indeed, the manipulation of such qubits relies on Coulomb interactions, enabling electronic noise to cause decoherence. Charge traps in the heterostructure may contribute to decoherence through a fluctuation of charges or through dipolar interactions of the spin degree of freedom of the trap and the qubit. In the second part of my talk I will present our recent study of charge noise in modulation-doped Si/SiGe heterostructures and discuss device and heterostructure designs which efficiently suppress charge noise.

Bougeard, Dominique

2013-03-01

314

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

315

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

316

Realization of quantum non-demolition measurement of nuclear spin 1\\/2 of cold ytterbium atom  

Microsoft Academic Search

We have demonstrated a quantum non-demolition (QND) measurement with a collective spin of cold ytterbium atoms (171Yb) via Faraday rotation interaction, and have observed 1.8-1.5+2.4 dB spin squeezing. Since 171Yb atoms have only a nuclear spin of one-half in the ground state, the system constitutes the simplest spin ensemble and is thus robust against decoherence. Furthermore, we have considered the

T. Takano; R. Namiki; Y. Takahashi

2009-01-01

317

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

318

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

319

A study of the transferred hyperfine field and spin lattice relaxation time of [N(CH3)]CuCl4 single crystals  

NASA Astrophysics Data System (ADS)

The molecular susceptibility and paramagnetic shift of [N(CH3)]CuCl4 single crystals were measured, and from these experimental results we obtained the transferred hyperfine interaction, Hhf, due to the spin transfer from Cu ions to [N(CH3)] ions. We conclude that the decrease in Hhf with increasing temperature is not sufficient to allow the spin transfer between Cu ions and the nuclear spins of the nonmagnetic [N(CH3)] ions in the lattice. In addition, the proton spin lattice relaxation time, T1, of [N(CH3)]CuCl4 single crystals was determined as a function of temperature; the variation in T1 with temperature exhibited discontinuities near 263 and 200 K, confirming previous reports of phase transitions at these temperatures. Comparison of the T1 and Hhf results revealed that T1 decreases with increasing Hhf, which is the opposite of the trend reported for [N(CH3)]CoCl4. This difference may be due to differences in the electronic structures of Co and Cu ions: Cu has one s electron outside closed d shells whereas Co has unpaired d electrons, which screen the nuclear charge from the motion of the outer electrons.

Lim, Ae Ran; Lim, Kye-Young

2007-04-01

320

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

321

Magnetic property of a single crystal of spin-1/2 triple-chain magnet Cu3(OH)4SO4  

NASA Astrophysics Data System (ADS)

The spin-1/2 triple-chain magnet Cu3(OH)4SO4 (mineral name: antlerite) is a candidate `idlespin' system. In order to study the phase transitions in this compound in detail, we have performed specific-heat measurements under magnetic fields up to 10 T and in the temperature range down to 1.9 K and proton nuclear magnetic resonance (1H-NMR) experiments with single crystals. We found at least three successive phase transitions at zero field around 5 K which strongly depend on the value and the direction of the applied field. Another transition around 3 K was also found. 1H-NMR spectra in a low-temperature and low-field ordered phase indicated an antiferromagnetic commensurate spin structure with at least four sublattices, which is discussed in connection with the idle-spin state. Phase diagrams show a richness of magnetic phases for this compound.

Fujii, Yutaka; Ishikawa, Yuya; Kikuchi, Hikomitsu; Narumi, Yasuo; Nojiri, Hiroyuki; Hara, Shigeo; Sato, Hirohiko

2013-06-01

322

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

323

Nuclear Magnetic Resonance Relaxation Studies of 51V in BiVO4 Single Crystal  

NASA Astrophysics Data System (ADS)

Temperature dependences of the nuclear spin-lattice relaxation time of 51V in BiVO4 single crystals, undoped and doped with 1 mol% of Eu2O3, respectively, were measured in the temperature range of 140-400 K. The spin-lattice relaxation times, T1s, of both samples were divided into the long and short components. For the doped crystal, the long component of the relaxation time is much shorter than those of the undoped crystal since the paramagnetic relaxation through Eu3+ ions was dominant. From data of the undoped BiVO4, it is found that the slow motion leads to the phase transition starting at 260 K, and its thermal activation energy is 0.033 eV. That is, we observed the thermally activated motion in ferroelastic which precedes the paraelastic phase transition.

Kim, I. G.; Yeom, T. H.; Jeong, D. Y.; Lim, A. R.; Choh, S. H.; Hong, K. S.

2002-10-01

324

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

325

Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe  

NASA Astrophysics Data System (ADS)

We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B1S) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4 mm diameter sapphire rotor containing the sample. The predicted average B1S field is 13 ?T/W1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is ?SB1S = 0.84 MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (?) vs. ?1S/(2?) for a sample of 13C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment.

Nanni, Emilio A.; Barnes, Alexander B.; Matsuki, Yoh; Woskov, Paul P.; Corzilius, Björn; Griffin, Robert G.; Temkin, Richard J.

2011-05-01

326

NMR Investigation of Optical Polarization of Nuclear Spins in GaAs  

NASA Astrophysics Data System (ADS)

Light-induced nuclear spin alignments have been measured in GaAs as a function of photon energy, irradiation time, and sample temperature using NMR spectroscopy at 9.4 Tesla and 10 to 50 K. Significant optical enhancements were observed at a range of photon energies, starting just below the band gap and persisting through 100 meV above the gap. Irradiation above the band gap resulted in thermally activated NMR signal enhancements while sub band gap irradiation did not. Short and long irradiation time dependencies revealed insights into the nature of cross relaxation between electronic nuclear spins, contradicting mechanisms based on either localized electron-nuclear contact at defect sites or cross relaxation between nuclei and free electrons. We propose that the presence of a mobile or delocalized enabling electronic species characterized by a long electron-nuclear correlation time, such as an exciton, is necessary in any mechanism which explains the data.

Paravastu, Anant; Hayes, Sophia; Schwickert, Birgit; Reimer, Jeffrey; Dinh, Long; Balooch, Mehdi

2003-03-01

327

The nuclear spin-isospin response to quasifree nucleon scattering  

SciTech Connect

The Neutron-Time-of-Flight (NTOF) facility at LAMPF has been used to measure complete sets of polarization-transfer coefficients for quasifree ({ital {rvec p}},{ital {rvec n}}) scattering from {sup 2}H, {sup 12}C, and {sup 40}Ca at 494 MeV and scattering angles of 12.5{degree}, 18{degree}, and 27{degree} ({ital q}=1.2, 1.7, 2.5 fm{sup {minus}1}). These measurements yield separated transverse ({sigma}{times}{bold q}) and longitudinal ({sigma}{center_dot}q) isovector spin responses. Comparison of the separated responses to calculations and to electron-scattering responses reveals a strong enhancement in the spin transverse channel. This excess transverse strength masks the effect of pionic correlations in the response ratio.

Taddeucci, T.N. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1995-07-15

328

Korringa-Like Nuclear Spin-Lattice Relaxation in a 2DES at ?= 1/2  

NASA Astrophysics Data System (ADS)

Via a resistively-detected NMR technique, the nuclear spin lattice relaxation time T1 of ^71Ga at low temperatures has been measured in a GaAs/AlGaAs heterostructure containing two weakly-coupled 2D electron systems (2DES), each at Landau level filling ?= 1/2. Incomplete electronic spin polarization, which has been reported previously [1,2] for low density 2DESs at ?= 1/2, should facilitate hyperfine- coupled nuclear spin relaxation owing to the presence of both electron spin states at the Fermi level. Within composite fermion theory, a Korringa law temperature dependence: T1T = constant, is expected for temperatures T<1 K. Our measurements made at temperatures in the range 35 mK nuclear spin relaxation mechanisms in this system.[1] I. V. Kukushkin, K. v. Klitzing, and K. Eberl. Phys. Rev. Lett. 82, 3665 (1999); A. E. Dementyev, et al., Phys. Rev. Lett. 83, 5074 (1999); S. Melinte, et al., Phys. Rev. Lett. 84, 354 (2000).[2] I.B. Spielman, L.A. Tracy, J.P. Eisenstein, L.N. Pfeiffer, K.W. West, condmat/0410092.This work was supported by the DOE, NSF, and NDSEG.

Tracy, L. A.; Pfeiffer, L. N.

2005-03-01

329

Nuclear enhancement of the spin Hall angle in n-InxGa1-xAs  

NASA Astrophysics Data System (ADS)

We present measurements of the inverse spin Hall effect in vertical Fe/InxGa1-xAs heterostructures as identified via a Hanle effect in the local Hall voltage. The spin Hall angle is greatly enhanced in the presence of polarized nuclei, achieving typical values of ?˜5x10-2. Phenomenological modeling of the observed line-shapes shows that the nuclear polarization acts as a linear prefactor to the standard spin Hall conductivity. This enhancement far exceeds expectations based on the energy splitting of the electron or nuclear spin systems. Our samples are doped just above the Mott transition (n˜3nc) where metallic impurity band conduction is dominant. A strong coupling between localized moments and delocalized states is evidenced by the temperature dependence and sensitivity to disorder at higher In concentrations. This leads us to interpret our results using an Anderson-like model of polarized impurities whereby both dynamic nuclear polarization and resonant skew scattering arise as a result of a spin polarized doubly occupied (D^-) impurity band.

Geppert, Chad; Christie, Kevin; Chan, Mun; Hu, Qi; Palmstrøm, Chris; Crowell, Paul

2012-02-01

330

Phase transitions in dissipative quantum transport and mesoscopic nuclear spin pumping  

NASA Astrophysics Data System (ADS)

Topological phase transitions can occur in the dissipative dynamics of a quantum system when the ratio of matrix elements for competing transport channels is varied. Here we establish a relation between such behavior in a class of non-Hermitian quantum walk problems [M. S. Rudner and L. S. Levitov, Phys. Rev. Lett. 102, 065703 (2009)10.1103/PhysRevLett.102.065703] and nuclear spin pumping in double quantum dots, which is mediated by the decay of a spin-blockaded electron triplet state in the presence of spin-orbit and hyperfine interactions. The transition occurs when the strength of spin-orbit coupling exceeds the strength of the net hyperfine coupling and results in the complete suppression of nuclear spin pumping. Below the transition point, nuclear pumping is accompanied by a strong reduction in current due to the presence of nondecaying “dark states” in this regime. Due to its topological character, the transition is expected to be robust against dephasing of the electronic degrees of freedom.

Rudner, M. S.; Levitov, L. S.

2010-10-01

331

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

332

Anomalous nuclear spin relaxation of adsorbed helium-3  

Microsoft Academic Search

Within the framework of a general theory of two-dimensional NMR we are able to elucidate certain anomalous features of spin relaxation in adsorbed and porous systems. We explain the linear dependence of relaxation time on applied magnetic field, and this is demonstrated to be related to the relative insensitivity ofT1to temperature. We also show thatT1remains field dependent on the “fast”

Brian P. Cowan

1983-01-01

333

Description of Nuclear Reactions of Particles with Spin  

NASA Astrophysics Data System (ADS)

As for nuclear reactions of spinless particles (this is the only case and the simplest one normally treated in lectures and textbooks) scattering amplitudes between entrance and exit states are a useful tool for the description of two-particle nuclear reactions.

Schieck, Hans Paetz Gen.

334

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

335

Photochemically Induced Dynamic Nuclear Polarization (Photo-CIDNP) Magic-Angle Spinning NMR  

Microsoft Academic Search

Photochemically induced dynamic nuclear polarization (photo-CIDNP) is non-Boltzmann nuclear magnetization which can be observed\\u000a by NMR spectroscopy as enhanced absorptive (positive) or emissive (negative) signals. In solids, photo-CIDNP has been observed\\u000a since its discovery in 1994 in various photosynthetic reaction centers (RCs) by magic angle spinning (MAS) solid-state NMR.\\u000a The photo-CIDNP effect in solids can be explained by a combination

Eugenio Daviso; Gunnar Jeschke; Jörg Matysik

336

Muon spin relaxation and hyperfine-enhanced Pr141 nuclear spin dynamics in Pr(Os,Ru)4Sb12 and (Pr,La)Os4Sb12  

NASA Astrophysics Data System (ADS)

Zero- and longitudinal-field muon spin relaxation experiments have been carried out in the alloy series Pr(Os1-xRux)4Sb12 and Pr1-yLayOs4Sb12 to elucidate the anomalous dynamic muon spin relaxation observed in these materials. The damping rate ? associated with this relaxation varies with temperature, applied magnetic field, and dopant concentrations x and y in a manner consistent with the “hyperfine enhancement” of Pr141 nuclear spins first discussed by Bleaney [Physica (Utrecht) 69, 317 (1973)]. This mechanism arises from Van Vleck-like admixture of magnetic Pr3+ crystalline-electric-field-split excited states into the nonmagnetic singlet ground state by the nuclear hyperfine coupling, thereby increasing the strengths of spin-spin interactions between Pr141 and muon spins and within the Pr141 spin system. We find qualitative agreement with this scenario and conclude that electronic spin fluctuations are not directly involved in the dynamic muon spin relaxation.

Shu, Lei; Maclaughlin, D. E.; Aoki, Y.; Tunashima, Y.; Yonezawa, Y.; Sanada, S.; Kikuchi, D.; Sato, H.; Heffner, R. H.; Higemoto, W.; Ohishi, K.; Ito, T. U.; Bernal, O. O.; Hillier, A. D.; Kadono, R.; Koda, A.; Ishida, K.; Sugawara, H.; Frederick, N. A.; Yuhasz, W. M.; Sayles, T. A.; Yanagisawa, T.; Maple, M. B.

2007-07-01

337

Using spin fluctuations to reveal long hole spin lifetimes and hole-nuclear coupling in (In,Ga)As quantum dots  

NASA Astrophysics Data System (ADS)

``Spin noise spectroscopy'' is a recently-developed technique for passively measuring the spin dynamics of electrons and holes via their intrinsic random spin fluctuations. In accord with the fluctuation-dissipation theorem, the frequency spectra of this spin noise alone reveals spin dephasing times and Land'e g-factors. Using these methods we measure hole spins confined in self-assembled (In,Ga)As/GaAs quantum dots (QDs). Owing to their p-type wavefunctions, holes experience much less hyperfine interaction with lattice nuclei as compared with confined electrons, leading in principle to long spin decoherence times which are favorable for potential qubit applications. We observe very long hole spin correlation times (˜400 ns) in zero magnetic field, ultimately limited by dephasing from hole-nuclear hyperfine interactions. Suppressing this dephasing with small longitudinal fields (< 100 G) directly reveals the hyperfine coupling strength, and unveils intrinsic hole spin relaxation times up to ˜5 ?s. Importantly, the lineshape of the noise evolves from a Lorentzian to a power-law as the hole-nuclear dephasing is suppressed.

Li, Yan; Crooker, S. A.; Reuter, D.; Wieck, A. D.; Yakovlev, D. R.; Bayer, M.

2012-02-01

338

Nuclear spin temperatures of hydrogen and water molecules on amorphous solid water  

NASA Astrophysics Data System (ADS)

To clarify the meaning of the nuclear spin temperatures of H2 and H2O molecules associated with various astronomical targets, it is important to understand the mechanisms that could alter these temperatures; i.e., the molecules' ortho/para nuclear-spin ratio (OPR). We have performed a series of experiments to investigate how the OPRs of H2 and H2O behave on the surface of amorphous solid water (ASW), which is analogous to cosmic ice dust. The OPR of H2 initially shows a high temperature limit of 3 upon its formation through H-H recombination at ~10 K and gradually decreases toward lower temperatures on the surface. The spin temperatures of H2O molecules that are thermally desorbed from various types of ASW at ~10 K always return the high-temperature limit.

Watanabe, Naoki; Hama, Tetsuya; Kouchi, Akira

2013-06-01

339

Nuclear Spin Measurements in Some Nuclides of the Alkali Elements Rubidium and Francium.  

National Technical Information Service (NTIS)

The nuclear spins of several nuclides of the alkali elements rubidium and francium have been measured using atomic-beam magnetic resonance techniques. The following results have been obtained: exp 77 Rb I = 3/2, exp 78 Rb I = 0 sup(78m)Rb I = 4, exp 79 Rb...

C. Ekstroem S. Ingleman G. Wannberg M. Skarestad

1977-01-01

340

Angular dependence of nuclear spin echo decay in thin-film yttrium iron garnet  

Microsoft Academic Search

The angular dependence of the nuclear spin echo decay of 57Fe in monocrystalline thin-film Y3Fe5O12 was measured. The experimental results for the octahedral Fe3+ a-ions were explained by the orientation fluctuations of the electron magnetization about the local symmetry axis.

G. N. Abelyashev; S. N. Polulyah; V. N. Berzhanskij; N. A. Sergeev

1995-01-01

341

Nuclear spin dependence of the reaction of H3+ with H2. I. Kinetics and modeling  

NASA Astrophysics Data System (ADS)

The chemical reaction H3+ + H2 --> H2 + H3+ is the simplest bimolecular reaction involving a polyatomic, yet is complex enough that exact quantum mechanical calculations to adequately model its dynamics are still unfeasible. In particular, the branching fractions for the ``identity,'' ``proton hop,'' and ``hydrogen exchange'' reaction pathways are unknown, and to date, experimental measurements of this process have been limited. In this work, the nuclear-spin-dependent steady-state kinetics of the H3+ + H2 reaction is examined in detail, and employed to generate models of the ortho:para ratio of H3+ formed in plasmas of varying ortho:para H2 ratios. One model is based entirely on nuclear spin statistics, and is appropriate for temperatures high enough to populate a large number of H3+ rotational states. Efforts are made to include the influence of three-body collisions in this model by deriving nuclear spin product branching fractions for the H5+ + H2 reaction. Another model, based on rate coefficients calculated using a microcanonical statistical approach, is appropriate for lower-temperature plasmas in which energetic considerations begin to compete with the nuclear spin branching fractions. These models serve as a theoretical framework for interpreting the results of laboratory studies on the reaction of H3+ with H2.

Crabtree, Kyle N.; Tom, Brian A.; McCall, Benjamin J.

2011-05-01

342

Nuclear spin-lattice relaxation of 195Pt between 10 mK and 1 K  

Microsoft Academic Search

The nuclear spin-lattice relaxation time tau1 of 195Pt has been measured between 10 mK and 1 K in a magnetic field of 0.045 T. The data agree with Korringa's relation kappa = tau1T with kappa = 29.6 msK.

M. I. Aalto; H. K. Collan; R. G. Gylling; K. O. Nores

1972-01-01

343

A spin polarizer for radioactive nuclear beams by taking advantage of polarized electron transfer reactions  

Microsoft Academic Search

A versatile spin polarizer for radioactive nuclear beams is proposed for spectroscopic studies of exotic nuclei far from stability. The polarizer takes advantage of the polarized electron transfer process, as in the optically pumped polarized proton ion sources. The feasibility of the polarizer has been experimentally investigated at the test stand. Successful results are reported.

T. Shimoda; S. Shimizu; E. Doumoto; M. Yagi; M. Asai; M. Nakamura; Y. Hirayama; K. Horie; T. Shigematsu; H. Izumi; N. Takahashi

2002-01-01

344

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

345

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

346

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

347

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

348

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

349

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

350

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

351

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

352

Reanalysis of nuclear spin matrix elements for dark matter spin-dependent scattering  

NASA Astrophysics Data System (ADS)

We show how to include in the existing calculations for nuclei other than Xe129 and Xe131 the corrections to the isovector coupling arising in chiral effective field theory recently found in Menendez et al. [Phys. Rev. D 86, 103511 (2012)PRVDAQ1550-7998]. The dominant, momentum-independent, two-body current effect can be taken into account by formally redefining the static spin matrix elements ?Sp,n?. By further using the normalized form factor at q?0 built with the one-body level structure functions, we show that the weakly interacting massive particles (WIMP)-nucleus cross section and the upper limits on the WIMP-nucleon cross sections coincide with the ones derived by using the exact functions at the two-body level. We explicitly show it in the case of XENON100 limits on the WIMP-neutron cross section, and we recalculate the limits on the WIMP-proton spin-dependent cross section set by COUPP. We also give practical formulas to obtain ?Sp,n? given the structure functions in the various formalisms and notations existing in the literature. We argue that the standard treatment of the spin-dependent cross section in terms of three independent isospin functions, S00(q), S11(q), and S01(q), is redundant in the sense that the interference function S01(q) is the double product |S01(q)|=2S00(q)S11(q) even when including the new effective field theory corrections.

Cannoni, M.

2013-04-01

353

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

354

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

355

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

356

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

357

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

358

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

359

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

360

Rabi and Larmor nuclear quadrupole double resonance of spin-1 nuclei  

NASA Astrophysics Data System (ADS)

We demonstrate the creation of two novel double-resonance conditions between spin-1 and spin-1/2 nuclei in a crystalline solid. Using a magnetic field oscillating at the spin-1/2 Larmor frequency, the nuclear quadrupole resonance (NQR) frequency is matched to the Rabi or Rabi plus Larmor frequency, as opposed to the Larmor frequency as is conventionally done. We derive expressions for the cross-polarization rate for all three conditions in terms of the relevant secular dipolar Hamiltonian, and demonstrate with these expressions how to measure the strength of the heterogenous dipolar coupling using only low magnetic fields. In addition, the combination of different resonance conditions permits the measurement of the spin-1/2 angular momentum vector using spin-1 NQR, opening up an alternate modality for the monitoring of low-field nuclear magnetic resonance. We use ammonium nitrate to explore these resonance conditions, and furthermore use the oscillating field to increase the signal-to-noise ratio per time by a factor of 3.5 for NQR detection of this substance.

Prescott, D. W.; Malone, M. W.; Douglass, S. P.; Sauer, K. L.

2012-12-01

361

Paramagnetic Resonance Absorption in Uranium (III) Chloride and the Nuclear Spin, Magnetic Dipole Moment, and Electric Quadrupole Moment of Uranium233  

Microsoft Academic Search

Paramagnetic resonance absorption in single crystals of U233Cl3 diluted with LaCl3 has been investigated. The values of the parameters in the appropriate Hamiltonian are given. The values of the nuclear spin, magnetic dipole moment, and electric quadrupole moment obtained from these studies are discussed. The ratios of the mo ments of U235 and U233, which can be obtained with much

Paul B. Dorain; Clyde A. Hutchison; Eugene Wong

1957-01-01

362

Nuclear orientation of radon isotopes by spin-exchange optical pumping  

SciTech Connect

This paper reports the first demonstration of nuclear orientation of radon atoms. The method employed was spin exchange with potassium atoms polarized by optical pumping. The radon isotopes were produced at the ISOLDE isotope separator of CERN. The nuclear alignment of /sup 209/Rn and /sup 223/Rn has been measured by observation of ..gamma..-ray anisotropies and the magnetic dipole moment for /sup 209/Rn has been measured by the nuclear-magnetic-resonance method to be chemically bond..mu..chemically bond = 0.838 81(39)..mu../sub N/.

Kitano, M.; Calaprice, F.P.; Pitt, M.L.; Clayhold, J.; Happer, W.; Kadar-Kallen, M.; Musolf, M.; Ulm, G.; Wendt, K.; Chupp, T.

1988-05-23

363

Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair.  

PubMed

In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water (1)H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft-tissue contrast in clinical magnetic resonance imaging. PMID:24116610

Chang, Zhiwei; Halle, Bertil

2013-10-14

364

Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair  

NASA Astrophysics Data System (ADS)

In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water 1H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft-tissue contrast in clinical magnetic resonance imaging.

Chang, Zhiwei; Halle, Bertil

2013-10-01

365

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

366

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

367

High-Spin Isomeric States in Nuclear Reactions Induced by He Isotopes  

NASA Astrophysics Data System (ADS)

The high-spin states production in nuclear reactions is reviewed. The analysis of various experiments, our estimates and calculations reveal that in different compound nucleus energy regions maximal relative yield of high-spin states can be realized by different projectiles: at low energies -- by neutrons, in ˜ 20 -- 50 MeV region -- by ?-particles, at higher energies -- by heavy ions. It was predicted [1] that there are energy ranges in which neutron-rich radioactive ions (^6,8He, for example) are favorable. ?m/?g (the ratio between the yields of high-spin Jm and low-spin Jg metastable states of a nucleus in one and the same reaction) e.g. the isomeric cross-section ratio is a very good indicator of high-spin states production capability of a nuclear reaction. These experiments demonstrate that maximal values of isomeric cross-section ratios (up to 30) are obtained in ?-particle induced reactions. Experiment with ^6He beam [2] confirms the predictions of the work [1] concerning the prospects of neutron-rich radioactive-ion beams in high-spin states population. The results of calculations of the isomeric cross section ratios using the code EMPIRE-II-18 approach to statistical theory of nuclear reactions demonstrate rather good agreement with the experimental data. Due to that these prediction power of these calculation is confirmed. The results of widespread calculations of the isomeric cross-section ratios of the reactions with ^6,8He are presented. [1] T.V.Chvilskaya et al., AIP-Conference Proceedings ENAM-98 1998. V. 455. P. 482. [2] P.A.DeYoung et al., Phys.Rev.C. 2000. V. 62. P.047601.

Chuvilskaya, Tatjana; Shirokova, Alla

2010-11-01

368

Growth of semiconductor nanostructures by MBE for the study of electron and nuclear spin enhancement and other physical phenomena  

NASA Astrophysics Data System (ADS)

Molecular beam epitaxy (MBE) is an extremely versatile thin film technique, which can produce single-crystal layers with atomic dimensional controls and thus permit the preparation of novel structures and devices tailored to meet specific needs. Spin relaxation time ts is one of the key features in spin-related phenomena and thus of great importance for spintronics. In this work, we prepare high quality samples, mainly of CdTe epilayers, by MBE, characterize their spin relaxation dynamics, and discuss the results theoretically. First, with the goal of understanding the mechanisms of electron relaxation dynamics and nuclear spin enhancement, we focus on the growth and characterization of CdTe epilayers. By changing the shutter sequences and inserting ZnSe buffer layer, we have reproducibly grown (111) and (100) CdTe epilayers of high crystalline qualities by MBE, despite the large lattice mismatch between CdTe and GaAs substrate. Then we investigate ts for the (111) and (100) CdTe epilayers. It is found that for the (111) CdTe, spin relaxation rate t-1s is significantly enhanced and shows no temperature dependence through 130K to 300K, while t-1s for the (100) CdTe is strongly affected by the temperature. It is also found that t-1s is dependent on material quality for both (111) and (100) CdTe. We theoretically discuss the effect of strain and defect on spin relaxation time of CdTe. It is the first experimental observation of the effect of strain on t-1s in a II-VI semiconductor material. Second, the growth and characterization of ZnTe/ZnSe related type II quantum structures, or quantum dots (QDs), are also presented in this work. The PL of Zn-Se-Te related type II quantum structures show blue shifts with higher intensities of exciting laser, an indication of type II QDs. Besides being an attractive method to p-type dope wide bandgap materials, the resulting material may be a promising structure for spin enhancement properties. Third, we present the study of the enhancement of nuclear spin polarization through pumping laser. We find strong enhancement both in bulk CdTe as well as in CdTe epilayers, independent of the helicity of the laser, which is on the contrary to the prior reports by others. Compared with GaAs crystal, we ascribe this independence to the surface spin-dependent recombination. GaAs/AlAs and GaAs/GaAlAs multiple coupled double quantum wells (QWs), and CdTe/CdMgTe QW have also been grown and explored. The measurements show good quality of the material and are consistent with the designed structures. Last, we summary the work and propose the future directions. Samples are in-situ monitored by reflection high energy electron diffraction (RHEED). Post growth characterization techniques, such as time resolved Kerr rotation (TRKR), X-ray diffraction (XRD), photoluminescence (PL), and optical pumping nuclear magnetic resonance (OPNMR), are introduced and applied to the samples.

Zhang, Qiang

369

Natural reference for nuclear high-spin states  

SciTech Connect

We suggest two new representations of the data on rotational nuclei. The first is reference-free and the second arises from a natural reference related to the variable moment of inertia model parameters of the ground-state band of the system. As such, neither representation contains any free parameters. By defining a 'configuration spin' we show how a new ground-state band reference can be applied. Its use allows a complete description of the changes associated with the first, and higher, band crossings. We apply these new representations to discuss the nature of the first band crossing along even-even isotopic chains in the erbium and osmium isotopes and to odd-even nuclei in the vicinity of {sup 158}Er.

Rowley, Neil; Ollier, James; Simpson, John [UMR 8608, Universite de Paris Sud/IN2P3, Division de Physique Theorique, Institut de Physique Nucleaire, F-91406 Orsay Cedex (France); STFC Daresbury Laboratory, Daresbury, Warrington WA44AD (United Kingdom)

2009-08-15

370

Relativistic impulse approximation, nuclear currents, and the spin-difference function  

NASA Astrophysics Data System (ADS)

Traditional nonrelativistic impulse-approximation treatments of p-nucleus scattering using a local nucleon-nucleon t matrix neglect nuclear currents which are intrinsic to relativistic approaches also employing a local t matrix. Inclusion of these current terms is essen- tial to understanding the spin-difference function (Dqk+Dkq) +i(P-Ay), as shown by comparison with 12C(p,p')12C*(12.71 MeV, 1+, T=0) spin-difference data at 150 MeV.

Sparrow, D. A.; Piekarewicz, J.; Rost, E.; Shepard, J. R.; McNeil, J. A.; Carey, T. A.; McClelland, J. B.

1985-05-01

371

Magnetic equivalence of terminal nuclei in the azide anion broken by nuclear spin relaxation  

NASA Astrophysics Data System (ADS)

NMR spectra of water solution of sodium azide selectively 15N labelled in the central position were studied using an iterative least-squares method. In agreement with predictions based on Bloch-Wangsness-Redfield nuclear spin relaxation theory, it is demonstrated that quadrupolar relaxation of the magnetically equivalent terminal 14N (spin-1) nuclei in the azide anion renders the J coupling between these nuclei an observable quantity. In isotropic fluids, this seems to be the first experimental evidence of relaxation-broken magnetic equivalence symmetry.

Bernatowicz, P.; Szyma?ski, S.

372

Cell Potassium by K39 Spin Echo Nuclear Magnetic Resonance.  

National Technical Information Service (NTIS)

Pulsed nuclear magnetic resonance (NMR) measurements of K39 in solutions and bacteria were made, by the use of a super-conducting magnet with a field of 50,300 gauss, which provides the necessary increase in sensitivity. Transverse relaxation time (T2) of...

F. W. Cope R. Damadian

1970-01-01

373

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

374

Magnetic-field cycling triplet-DNP/NMR system for true quantum computation with hyperpolarized nuclear spins  

NASA Astrophysics Data System (ADS)

Toward NMR quantum computing with hyperpolarization beyond the entanglement threshold, a system has been developed enabling dynamic nuclear polarization (DNP) using photo-excited triplet electron spins with X-band microwave apparatus, followed by solid-state NMR experiments using the polarized nuclear spin system. In order to perform the triplet-DNP and NMR experiments in different magnetic fields, the triplet-DNP system and the NMR system are made to be spatially separated, between which the sample can be shuttled. It is shown that the system developed in this work fulfils the requirements for solid-state NMR quantum computing with hyperpolarized nuclear spin systems.

Kagawa, A.; Negoro, M.; Takeda, K.; Kitagawa, M.

2009-04-01

375

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

376

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

377

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

378

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

379

Isovector spin observables in nuclear charge reactions at LAMPF  

SciTech Connect

LAMPF has undertaken a major development program to upgrade facilities for nuclear charge-exchange studies at intermediate energies. The major components of this upgrade are a medium-resolution spectrometer and neutron time-of-flight system for good resolution (delta E < 1 MeV) charge-exchange perograms in (n,p) and (p,n) respectively. Major emphasis is placed on polarization phenomena using polarized beams and analyzing the polarization of the outgoing particle.

McClelland, J.B.

1988-01-01

380

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

381

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

SciTech Connect

Invention of scanning tunneling microscope (STM) and atomic force microscope (AFM) initiated a new era of material science and technology characterized by 2-D imaging with atomic resolution and manipulation of individual atoms. However, for further progress in material science, and in particular in structural biology, 3-D imaging with sub-nanometer resolution is very desirable. Currently the most promising technique for 3-D imaging is magnetic resonance force microscopy (MRFM), which senses individual electron spins [1,2] with nanoscale resolution and can detect collective magnetization of about 100 nuclear spins [3]. The highest sensitivity demonstrated by MRFM is based on a time modulation technique called the oscillating cantilever-driven adiabatic reversals (OSCAAR) which requires a long phase relaxation time T 2 of measured spins, which usually corresponds to rather low temperature. For example, a temperature of 300 mK was used in the case of 3D imaging of the tobacco mosaic virus [3]. This limitation is incompatible with the room-temperature operation needed for the study of biological systems under physiological conditions.

Berman, Gennady P [Los Alamos National Laboratory; Chernobrod, Boris [Los Alamos National Laboratory

2009-01-01

382

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

SciTech Connect

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

Kozlov, G. G. [St. Petersburg State University, Institute of Physics (Russian Federation)], E-mail: gkozlov@photonics.phys.spbu.ru

2007-10-15

383

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

384

Electron-nuclear spin coupling in nano-scale devices: self-sustaining resistance oscillations and controlled multiple quantum coherences  

NASA Astrophysics Data System (ADS)

Author: G Yusa, K. Muraki, K. Takashina (NTT BRL), K. Hashimoto (SORST-JST), and Y. Hirayama (NTT BRL and SORST-JST). We studied electron-nuclear spin coupled systems implemented in microscopic fractional quantum Hall devices and found that in a constant voltage measurement, the longitudinal resistance of such devices oscillates self-sustainingly with a period of about 200 sec. Such behavior suggests that the average nuclear spin polarization self-sustainingly oscillates between randomized and polarized states. When the resistance is measured in constant current mode, on the other hand, nuclear spins are polarized and reach a steady state in about 200 sec. Using the polarized state as an initial state, quantum mechanical superpositional states between four nuclear spin states (multiple quantum coherence) are controlled by pulsed radio frequency radiation resonant with nuclear spin transitions (nuclear magnetic resonance, NMR). Any arbitrary multiple quantum coherent state can be detected as change in the longitudinal resistance. Our findings represent a big step closer to practical all-electrical solid state nuclear spin quantum computing and quantum memory devices.

Yusa, Go

2005-03-01

385

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

386

Fluctuation-Induced Heat Release from Temperature-Quenched Nuclear Spins near a Quantum Critical Point  

NASA Astrophysics Data System (ADS)

The quasi-two-dimensional quantum antiferromagnet Cr(diethylenetriamine)(O2)2.H2O [1] has a magnetic-field-tuned quantum critical point (QCP) at 12.3 T, where a highly polarized antiferromagnetic phase turns into a field-induced ferromagnetic phase. We report a novel relaxation phenomenon near this QCP: quantum-fluctuation-driven annealing of hydrogen nuclear spins frozen in a non-equilibrium high-energy state by temperature quenching. This relaxation phenomenon, with readily detectable heat release from the nuclear spins as they are annealed, reveals the extent of a quantum critical region around the QCP and provides a unique avenue to investigate the dynamics of the divergent quantum fluctuations that underlie quantum criticality. [1] C. M. Ramsey et al., Chem. Mater. 15, 92 (2003).

Kim, Y. H.; Kaur, N.; Atkins, B. M.; Dalal, N. S.; Takano, Y.

2010-03-01

387

Enhancement of the skyrmionic excitations due to the suppression of Zeeman energy by optical orientation of nuclear spins  

Microsoft Academic Search

An effective experimental method for compensation of Zeeman energy of two-dimensional (2D) electrons based on optical pumping of nuclear spins is proposed and used to enhance skyrmionic excitations under conditions of integer and fractional quantum Hall effect. We demonstrate that photoexcitation by circularly polarized light can result in a strong spin orientation of nuclei along (or against) the direction of

I. V. Kukushkin; K. V. Klitzing; K. Eberl

1999-01-01

388

A convenient way of measuring nuclear spin-lattice relaxation times based on the null method  

Microsoft Academic Search

Describes a method for measuring the nuclear spin-lattice relaxation time T1 by the free precession technique, which offers certain practical advantages, particularly in the measurement of relative values of T1. The method is a simple modification of the original signal-growth technique of Carr and Purcell. Instead of measuring the time constant for the signal growth or the time required for

S. K. Ghosh; E. Tettamanti; A. Panatta

1980-01-01

389

The Low-Temperature Nuclear Spin Equilibrium of H_3^+ in Collisions with H_2  

NASA Astrophysics Data System (ADS)

Observations of H_3^+ in diffuse molecular clouds have revealed that the ratio of its ortho and para nuclear spin modifications are not in thermodynamic equilibrium with the environment. This discrepancy could be explained if the reaction H_3^+ + H_2 to H_2 + H_3^+, which interconverts the nuclear spin modifications of H_3^+, has a nonthermal outcome at low temperatures, possibly arising from nuclear spin selection rules on systems of identical fermions. While the nuclear spin dependence of this reaction has previously been investigated experimentally, the prior measurements were limited to temperatures above ˜130 K, well above the 50-70 K typical of diffuse molecular clouds. To investigate whether the outcome of the H_3^+ + H_2 reaction is nonthermal, H_3^+ ions were allowed to interact with H_2 in the temperature-controlled environment of a 22-pole radiofrequency ion trap, and the relative abundances of ortho- and para-H_3^+ at steady state were measured using action spectroscopy. By carefully controlling the ortho:para ratio of the H_2 samples in conjunction with the ion trap temperature, the outcome of the reaction was observed to be close to thermodynamic equilibrium over the temperature range of 45-100 K. Thus, the nonequilibrium ortho:para ratio of H_3^+ observed in diffuse molecular clouds does not arise from a nonthermal outcome of the H_3^+ + H_2 reaction at low temperature. This implies that the origin of the discrepancy lies in the respective formation and destruction mechanisms of H_3^+.

Grussie, Florian; Berg, Max H.; Wolf, Andreas; Kreckel, Holger; Crabtree, Kyle N.; McCall, Benjamin J.; Gartner, Sabrina; Schlemmer, Stephan

2013-06-01

390

Body-fixed relativistic molecular Hamiltonian and its application to nuclear spin-rotation tensor  

NASA Astrophysics Data System (ADS)

A relativistic molecular Hamiltonian that describes electrons fully relativistically and nuclei quasi-relativistically is proposed and transformed from the laboratory to the body-fixed frame of reference. As a first application of the resulting body-fixed relativistic molecular Hamiltonian, the long anticipated relativistic theory of nuclear spin-rotation (NSR) tensor is formulated rigorously. A ``relativistic mapping'' between experimental NSR and NMR is further proposed, which is of great value in establishing high-precision absolute NMR shielding scales.

Xiao, Yunlong; Liu, Wenjian

2013-04-01

391

Spin, Hyperfine Structure, and Nuclear Magnetic Dipole Moment of O15  

Microsoft Academic Search

The nuclear spin and hfs splitting of O15(tau12=124 ) in the 3P2 atomic ground state have been determined by the atomic beam magnetic resonance method. O15 was produced in the reaction N14(d, n)O15 by allowing a 5-MeV deuteron beam from the Columbia Van de Graaff accelerator to impinge upon a gaseous N2 target. The radioactive gas flowed continuously from the

E. D. Commins; H. R. Feldman

1963-01-01

392

Nuclear Ground State Spins of the Francium Isotopes 208-213, 220-222Fr  

Microsoft Academic Search

The nuclear ground state spins of some francium isotopes have been measured using on-line atomic-beam magnetic resonance techniques. The following results have been obtained: 208Fr I = 7, 209Fr I = 9\\/2, 210Fr I = 6, 211Fr I = 9\\/2, 212Fr I = 5, 213Fr I = 9\\/2, 220Fr I = 1, 221Fr I = 5\\/2 and 222Fr I =

C. Ekström; S. Ingelman; G. Wannberg; M. Skarestad

1978-01-01

393

Nuclear-spin relaxation of ²º?Pb in ferroelectric powders  

SciTech Connect

The ²º?Pb nuclear system (nuclear spin I = 1/2; magnetic Moment ? ?0.58 ?N; isotopic abundance ? 22%) in ferroelectric solids has been proposed for a search for a Schiff moment associated with simultaneous violation of parity (P) and time-reversal invariance (T) in fundamental interactions [1] (see also a discussion of the sensitivity of such search in Ref. [2]). The idea is that, due to the Schiff moment, a ferroelectric sample would acquire a P,T-odd magnetic polarization along the direction of its electric polarization. In conclusion, we have presented the first experimental study of relaxation properties of ²º?Pb in PT and PZT below room temperature. We find that above T? 50 K, longitudinal relaxation rate follows the T² dependence characteristic of the two-phonon Raman process. On the other hand, as the temperature is decreased below T? 50 K, the longitudinal relaxation rates drop slower than ?T2 (as opposed to ?T7 expected for the Raman process), and the relaxation is probably due to a direct process associated with paramagnetic impurities and nuclear-spin diffusion. While the longitudinal relaxation times T? vary between several seconds and over an hour in the temperature range between 290 and 10 K, the transverse relaxation time T? is found to be ?1.5 ms for all temperatures and all powder samples studied. D: we never discuss the origin of T? relaxation. Maybe we should. 1.5 ms is only a bit shorter from what would be expected from nuclear spin-spin interactions. Any comments? At some point Sasha asked Oleg to calculate T? exactly for PT and PZT, but I forgot what was the result. If such calculation exists, it would be great to compare with the expt. result. The obtained results provide an important input in the design of the experiments to search for P,T-violating effects in solid ferroelectrics

Bouchard, Louis S.; Sushkov, Alexander O.; Budker, Dmitry; Ford, Joe; Lipton, Andrew S.

2008-02-05

394

Nuclear Spin-Lattice Relaxation in CaF2 Crystals via Paramagnetic Centers  

Microsoft Academic Search

The results of nuclear spin-lattice relaxation-time measurements in the laboratory reference frame (T1) and the rotating reference frame (T1r), made on F19 nuclei in CaF2 crystals doped either with Eu3+, Ce3+, or Mn2+ paramagnetic centers, are reported. From 0.25 to 0.36 of the Debye temperature, values of the correlation time tauc are found from T1r minima for Mn2+ ions. Over

D. Tse; I. J. Lowe

1968-01-01

395

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

396

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

397

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

398

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

399

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

400

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

401

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

402

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

403

The Statistical Model in Nuclear Fission-Excitation Energy and Spin Population in Fragments  

NASA Astrophysics Data System (ADS)

We apply the statistical model of nuclear physics to the fission process, in particular to calculate excitation energy and spin distributions in fission products. We give the functions for these distributions, and by applying a Monte Carlo procedure we construct the distribution functions for the fragment kinetic energies. The temperature parameter which is needed for the distribution functions is calculated from an empirical law which relates nuclear temperature to the Q-value of the reaction. Results of the calculations are compared with experimental data, and excellent agreement is observed in all cases.

Faust, Herbert

2011-10-01

404

Ultra long spin coherence time for Fe3+ in ZnO: A new spin qubit  

NASA Astrophysics Data System (ADS)

We show by means of two pulse electron spin echo experiments on Fe3+ transition metal ions in natural ZnO that their spins S = \\frac{5}{2} have a spin coherence time limited at T=6 K first by instantaneous diffusion (?150 ?s), then by nuclear spectral diffusion (?450 ?s) and ultimately by spin-lattice processes (?1.4 ms). We predict a spin coherence time in the millisecond range for such a spin qubit in isotopically and chemically purified ZnO. The spin state of a single Fe3+ spin qubit could be readout by optical methods and it could be coherently manipulated using pulsed electron spin resonance (ESR) methods. A free carrier electrically gated between two nearby Fe3+ ions could efficiently couple two Fe3+ spin qubits. All those elements suggest the high potential of the Fe3+ spin qubits in ZnO for the implementation of a scalable ESR quantum computer.

Tribollet, J.; Behrends, J.; Lips, K.

2008-10-01

405

Nuclear-magnetic-resonance interaction mechanism in Rb2CoCl4 single crystals with the electric magnetic type  

NASA Astrophysics Data System (ADS)

The 87Rb spin-lattice relaxation time of Rb2CoCl4 single crystals grown using the slow evaporation method was measured using nuclear magnetic resonance. The recovery trace for the central line of 87Rb with dominant magnetic relaxation cannot be represented with a single exponential function, but can be represented with a linear combination of two exponential functions. The change in the 87Rb spin-lattice relaxation rate near Tc1 corresponds to the ferroelectric to incommensurate phase transition. There is a weak anomalous contribution to T1, and this seems to be the only detectable influence of a structural phase transition. The temperature dependence of T1 -1 near Ti is more or less continuous and is not affected by the normal-incommensurate phase transition. For T>Ti, the spin-lattice relaxation rate is governed by molecular motion as described by the Bloembergen-Purcell-Pound theory. This behavior is different to that found for Rb in Rb2ZnCl4. The phase-transition temperatures of the Rb2CoCl4 and Rb2ZnCl4 single crystals are quite similar, but their phase-transition mechanisms are different. The nuclear-magnetic-resonance (NMR) interaction mechanism in Rb2ZnCl4 is well known to be of the electric quadrupolar type whereas in Rb2CoCl4 it is of magnetic origin. Therefore a completely different NMR behavior is obtained in the two crystals.

Lim, Ae Ran; Hong, Kwan Soo

2005-08-01

406

Transverse nuclear spin relaxation in phosphatidylcholine bilayers containing gramicidin.  

PubMed

Deuterium nuclear magnetic resonance has been used to study transverse relaxation in samples of 1,2-dimyristoyl-sn-glycero-3-phosphocholine, perdeuterated and specifically deuterated at the alpha position of the chains, containing the polypeptide gramicidin at concentrations of 0, 1, and 4 mol%. For 4 mol% gramicidin, the bilayer is thought to undergo a continuous phase change rather than a phase transition proceeding via two phase coexistence. Information is obtained regarding lipid dynamics in the continuous phase change region of the phase diagram. In the presence of gramicidin, the transverse relaxation time measured by the quadrupole echo technique, T2e, passes through a minimum in the gel phase. The gramicidin concentration dependence of T2e suggests that the polypeptide reduces the temperature sensitivity of the correlation time responsible for the minimum. The polypeptide also increases the sensitivity of the first spectral moment, M1, to the quadrupole echo pulse separation. This behavior is attributed to a polypeptide-induced enhancement of the spread in T2e along the acyl chains. Quadrupole Carr-Purcell-Meiboom-Gill experiments are used to separate contributions to the observed behavior from fast and slow motions. PMID:1691657

Morrow, M R

1990-04-13

407

Realization of quantum non-demolition measurement of nuclear spin 1/2 of cold ytterbium atom  

NASA Astrophysics Data System (ADS)

We have demonstrated a quantum non-demolition (QND) measurement with a collective spin of cold ytterbium atoms (171Yb) via Faraday rotation interaction, and have observed 1.8-1.5+2.4 dB spin squeezing. Since 171Yb atoms have only a nuclear spin of one-half in the ground state, the system constitutes the simplest spin ensemble and is thus robust against decoherence. Furthermore, we have considered the atomic quantum swapping gate as a quantum information device using multiple Faraday rotation interactions, and have found that we can realize the quantum-domain performance for a realistic experimental condition.

Takano, T.; Namiki, R.; Takahashi, Y.

2009-04-01

408

Nuclear spin dependence of hydrogenic plasmas in the laboratory and the diffuse interstellar medium  

NASA Astrophysics Data System (ADS)

Observations of diffuse molecular clouds have shown that the excitation temperature T(H_3^+) derived from the (J,K) = (1,0) (ortho) and (1,1) (para) rotational levels of H_3^+ does not necessarily agree with the kinetic temperature (T01) inferred from UV measurements of H_2. In four of the five diffuse molecular cloud sight lines for which both H_3^+ and H_2 observations are available, T(H_3^+) is lower than T01 by 30 K. The reaction H_3^+ + H_2 ? H_2 + H_3^+ is expected to thermalize the H_3^+ nuclear spin distribution, but the interplay of nuclear spin selection rules and energetic restrictions at the low temperatures of the diffuse interstellar medium may prevent full thermalization at steady state. Alternatively, the nonthermal distribution could arise if H_3^+ does not experience a sufficient number of thermalizing collisions with H_2 during its lifetime. We have studied the nuclear spin dependence of the reaction of H_3^+ with H_2 in the laboratory by measuring the ortho:para ratio of H_3^+ formed in plasmas of varying ortho:para H_2 ratios. This study was performed in a hollow cathode cell which enabled the first measurements of this reaction at low temperature (130 K). From these measurements, we derived the ratio of the ``proton hop'' and ``hydrogen exchange'' rate coefficients as a function of temperature. The ratio, ?, was found to decrease with temperature, already reaching the statistical limit of 0.5 at a temperature of 130 K. Knowledge of ? enables modeling of the ortho:para ratio of H_3^+ in diffuse molecular clouds. We have modeled the nuclear spin dependence of the formation, thermalization, and destruction processes of H_3^+, and found that the nonthermal distribution is not caused by nuclear spin selection rules or energetic restrictions in the H_3^+ + H_2 reaction. Rather, it is likely caused by incomplete thermalization prior to H_3^+ destruction via electron dissociative recombination.

Crabtree, K. N.; Indriolo, N.; Kreckel, H.; Kauffman, C. A.; Tom, B. A.; Becka, E.; McGuire, B. A.; McCall, B. J.

2011-05-01

409

Nuclear Spin Dependence of Hydrogenic Plasmas in the Laboratory and the Diffuse Interstellar Medium  

NASA Astrophysics Data System (ADS)

Observations of diffuse molecular clouds have shown that the excitation temperature T(H3+) derived from the (J,K) = (1,0) (ortho) and (1,1) (para) rotational levels of H3+ does not necessarily agree with the kinetic temperature (T01) inferred from UV measurements of H2. In four of the five diffuse molecular cloud sight lines for which both H3+ and H2 observations are available, T(H3+) is lower than T01 by 30 K. The reaction H3+ + H2 ? H2 + H3+ is expected to thermalize the H3+ nuclear spin distribution, but the interplay of nuclear spin selection rules and energetic restrictions at the low temperatures of the diffuse interstellar medium may prevent full thermalization at steady state. Alternatively, the nonthermal distribution could arise if H3+ does not experience a sufficient number of thermalizing collisions with H2 during its lifetime. We have studied the nuclear spin dependence of the reaction of H3+ with H2 in the laboratory by measuring the ortho:para ratio of H3+ formed in plasmas of varying ortho:para H2 ratios. This study was performed in a hollow cathode cell which enabled the first measurements of this reaction at low temperature (130 K). From these measurements, we derived the ratio of the "proton hop" and "hydrogen exchange" rate coefficients as a function of temperature. The ratio, ?, was found to decrease with temperature, already reaching the statistical limit of 0.5 at a temperature of 130 K. Knowledge of ? enables modeling of the ortho:para ratio of H3+ in diffuse molecular clouds. We have modeled the nuclear spin dependence of the formation, thermalization, and destruction processes of H3+, and found that the nonthermal distribution is not caused by nuclear spin selection rules or energetic restrictions in the H3+ + H2 reaction. Rather, it is likely caused by incomplete thermalization prior to H3+ destruction via electron dissociative recombination.

Crabtree, Kyle N.; Indriolo, Nick; Kreckel, Holger; Kauffman, Carrie A.; Tom, Brian A.; Beçka, Eftalda; McGuire, Brett A.; McCall, Benjamin J.

2011-10-01

410

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

411

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

412

Prospects of Optical Single Atom Detection in Noble Gas Solids for Measurements of Rare Nuclear Reactions  

NASA Astrophysics Data System (ADS)

Optical detection of single atoms captured in solid noble gas matrices provides an alternative technique to study rare nuclear reactions relevant to nuclear astrophysics. I will describe the prospects of applying this approach for cross section measurements of the ^22Ne,,),25Mg reaction, which is the crucial neutron source for the weak s process inside of massive stars. Noble gas solids are a promising medium for the capture, detection, and manipulation of atoms and nuclear spins. They provide stable and chemically inert confinement for a wide variety of guest species. Because noble gas solids are transparent at optical wavelengths, the guest atoms can be probed using lasers. We have observed that ytterbium in solid neon exhibits intersystem crossing (ISC) which results in a strong green fluorescence (546 nm) under excitation with blue light (389 nm). Several groups have observed ISC in many other guest-host pairs, notably magnesium in krypton. Because of the large wavelength separation of the excitation light and fluorescence light, optical detection of individual embedded guest atoms is feasible. This work is supported by DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

Singh, Jaideep; Bailey, Kevin G.; Lu, Zheng-Tian; Mueller, Peter; O'Connor, Thomas P.; Xu, Chen-Yu; Tang, Xiaodong

2013-04-01

413

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

414

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

415

Optical pumping and hyperpolarized spin relaxation  

NASA Astrophysics Data System (ADS)

Optical pumping is to use light photons to polarize the atomic electron spins first and then the nuclear spins of noble gases get polarized through the spin exchange between atomic electron spins and nuclear spins. Using optical pumping nuclear spins of noble gases such as 3He and 129Xe can be polarized to 50% or higher, hundred thousand times higher than the proton polarization in conventional MRI. It has been found in this theoretical work that the conventional spin relaxation equations are not valid for the hyperpolarized spins. We find that hyperpolarization and spin coupling result in the multipole spin orders. These multipole spin orders cross-relax each other. New longitudinal relaxation equations for the dipole-dipole coupled hyperpolarized spins at room temperature have been derived. These new equations predict that the longitudinal magnetization relaxation of hyperpolarized spins is, in general, bi-exponential decay instead of single exponential decay. The potential applications of the findings in quantifying the paramagnetic source in lung and other tissue and in modeling hyperpolarized spin relaxation in bio-compatible media are pointed out as well.

Wu, Xizeng

2003-12-01

416

Modeling of proton spin relaxation in muscle tissue using nuclear magnetic resonance spin grouping and exchange analysis  

Microsoft Academic Search

NMR spin relaxation experiments performed on healthy mouse muscle tissue at 40 MHz and 293 K are reported. The spin-lattice relaxation experiments were performed using different combinations of selective and nonselective radio frequency pulses. Relaxation experiments in the rotating frame at H⁠= 10, 5 and 1 G are also reported. The experimental results were analyzed using the spin-grouping method,

W. T. Sobol; I. G. Cameron; W. R. Inch; M. M. Pintar

1986-01-01

417

The role of spin-orbit potential in nuclear prolate-shape dominance  

NASA Astrophysics Data System (ADS)

It is confirmed, in terms of the Woods-Saxon-Strutinsky method, that the spin-orbit potential plays a decisive role in the predominance of prolate deformation, which has been a long standing problem in nuclear physics. It is originated from the combined effects of the spin-orbit coupling and the diffused surface of the potential, in agreement with the previous work based on a more schematic Nilsson-Strutinsky method. The degree of prolate-shape dominance exhibits an oscillatory behavior with respect to the strength of spin-orbit potential and, the prolate-shape dominance is realized at the proper strength of the spin-orbit potential together with the standard surface diffuseness; this oscillatory behavior disappears in case of small diffuseness corresponding to ellipsoidal cavity. The calculated energy differences between oblate and prolate minima in this Letter are consistent with those of our extensive self-consistent calculations of the Hartree-Fock + BCS method with the Skyrme interaction.

Takahara, Satoshi; Onishi, Naoki; Shimizu, Yoshifumi R.; Tajima, Naoki

2011-08-01

418

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

419

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

420

Ignition conditions for inertial confinement fusion targets with a nuclear spin-polarized DT fuel  

NASA Astrophysics Data System (ADS)

The nuclear fusion cross-section is modified when the spins of the interacting nuclei are polarized. In the case of deuterium-tritium it has been theoretically predicted that the nuclear fusion cross-section could be increased by a factor ? = 1.5 if all the nuclei were polarized. In inertial confinement fusion this would result in a modification of the required ignition conditions. Using numerical simulations it is found that the required hot-spot temperature and areal density can both be reduced by about 15% for a fully polarized nuclear fuel. Moreover, numerical simulations of a directly driven capsule show that the required laser power and energy to achieve a high gain scale as ?-0.6 and ?-0.4 respectively, while the maximum achievable energy gain scales as ?0.9.

Temporal, M.; Brandon, V.; Canaud, B.; Didelez, J. P.; Fedosejevs, R.; Ramis, R.

2012-10-01