| Self Assembled Semiconductor Quantum Dots for Spin Based All Optical and Electronic Quantum Computing |
17-Apr-2008 |
27 pages |
| Authors:
Hadis Morkoc; Supriyo Bandyopadhyay; Alison Baski; Shiv Khanna; VIRGINIA COMMONWEALTH UNIV RICHMOND
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 | This project involved the study of self-assembled quantum dots as hosts for spin based qubits. Both semiconductor quantum dots, nanowires, and organic quantum dots were studied and the spin relaxation times were measured. The organic Alq3 appears to have very long longitudinal spin relaxation time of nearly 1 second at a temperature of 100 K, and a nearly temperature independent transverse relaxation time > 3 nsec in the range 2-300 ... |
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| Optical Detection of Nuclear Spin States |
31 JAN 2007 |
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| Authors:
David Cory; Chandrasekhar Ramanathan; Timothy Havel; MASSACHUSETTS INST OF TECH CAMBRIDGE
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 | The goal of this project was to improve our control over nuclear spins in the solid state, and to extend this control to coupled electron-nuclear spins. Our key results are summarized below. 1. We extended the control techniques developed in liquid state NMR quantum information processing to the control of a three-qubit solid state NMR quantum information processor. 2. To explore multi-body spin dynamics and their sensitivity to decoherence, we ... |
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| Scalable Spin-Qubit Circuits with Quantum Dots |
31 DEC 2006 |
13 pages |
| Authors:
D. G. Austing; L. Kouwenhoven; D. Loss; C. M. Marcus; S. Tarucha; R. M. Westervelt; J. P. Leburton; B. Altshuler; ILLINOIS UNIV AT URBANA-CHAMAPIGN
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| Double and triple coupled quantum dots have been fabricated by planar and vertical technology to contain just a few electrons in each dot. Electron imaging by scanning probe microscopy with the capability of wavefunction mapping in quantum dots has been demonstrated. Gate voltage and magnetic field control of charge and spin states, as well as exchange coupling between electron spins and between electron and nuclear spins have been achieved. Coherent ... |
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| Interface Sensitive Study of Spin Injection, Transport and Relaxation in Ferromagnet-Semiconductor Quantum Well Systems for Spin Applications |
29 NOV 2006 |
5 pages |
| Authors:
Jinbo Qi; Ying Xu; Norman Tolk; VANDERBILT UNIV NASHVILLE TN
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| In this report, we present our observation of optically excited nonequilibrium spin dynamics in (Ga,Mn)As at room temperature. Our observation demonstrates two different regimes: 1) an initial ultrafast oscillatory behavior during the subpicosecond and picosecond time scale after photo-excitation, which we find to be related to photo-induced carrier (electrons and holes) spins; 2) a slow demagnetization over hundreds of picoseconds, which, we believe, results from not only strong-coupled hole-Mn spins ... |
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| Spin Interactions and Spin Dynamics in Electronic Nanostructures |
31 AUG 2006 |
28 pages |
| Authors:
Robert A. Buhrman; CORNELL UNIV ITHACA NY
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| This multidisciplinary research project was concerned with the development, understanding and application of powerful techniques for the manipulation and study of spin systems, the fabrication and study of interacting spin assemblies, and the study, characterization and application of spin transfer effects and of nanomagnet dynamics excited by spin polarized currents. Major accomplishments achieved during this project include the development and application of new tools and innovative techniques for the manipulation ... |
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| Optically Controlled Quantum Dot Spins for Scaleable Quantum Computing |
17 JAN 2006 |
8 pages |
| Authors:
Duncan G. Steel; MICHIGAN UNIV ANN ARBOR DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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| This program conducted experimental research aimed at developing an optically driven quantum dot quantum computer. The work was done in collaboration with D. Gammon at the Naval Research Laboratory and L. J. Sham at UCSD. D. Gammon had responsibility for growing & characterizing the material, L. J. Sham is responsible for theoretical support & concept development. The group at Michigan along with this QuaCGR student are responsible for experimental demonstration ... |
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| Determination of Chromium Valence Over the Range Cr(0)-Cr(VI) by Electron Energy Loss Spectroscopy |
2006 |
14 pages |
| Authors:
Tyrone L. Daulton; Brenda J. Little; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS MARINE GEOSCIENCES DIV
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| Chromium is a redox active 3d transition metal with a wide range of valences (-2 to + 6) that control the geochemistry and toxicity of the element. Therefore, techniques that measure Cr valence are important bio/geochemical tools. Until now, all established methods to determine Cr valence were bulk techniques with many specific to a single, or at best, only a few oxidation state(s). We report an electron energy loss spectroscopy ... |
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| Artificial `Spin Ice' in a Geometrically Frustrated Lattice of Nanoscale Ferromagnetic Islands |
2006 |
6 pages |
| Authors:
Peter Schiffer; R. F. Wang; C. Nisoli; R. S. Freitas; J. Li; W. McConville; B. J. Cooley; M. S. Lund; N. Samarth; C. Leighton; PENNSYLVANIA STATE UNIV UNIVERSITY PARK OFFICE OF SPONSORED PROGRAMS
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| Frustration, defined as a competition between interactions such that not all of them can be satisfied, is important in systems ranging from neural networks to structural glasses. Geometrical frustration, which arises from the topology of a well-ordered structure rather than from disorder, has recently become a topic of considerable interest. In particular, geometrical frustration among spins in magnetic materials can lead to exotic lowtemperature states, including spin ice, in which ... |
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| Optically Controlled Quantum Dot Spins for Scaleable Quantum Computing |
DEC 2005 |
10 pages |
| Authors:
Duncan G. Steel; MICHIGAN UNIV ANN ARBOR
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| The objective of this program has been to work towards development of spin based quantum dots for optically driven quantum information processing. Using a combination of ultrahigh resolution laser spectroscopy to study the physics of the dots and ultrafast laser technology to coherently control the spins, we made several advances. Our main achievements include working with a model system based on the exciton optical Bloch vector where we demonstrated the ... |
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| Novel Techniques for Quantum State Manipulation in Mesoscopic Systems |
05 OCT 2005 |
16 pages |
| Authors:
Mikhail Lukin; HARVARD UNIV CAMBRIDGE MA
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| The most recent results achieved: We showed that electron spin flips are dominated by nuclear interactions and are slowed by several orders of magnitude when a magnetic field of a few millitesla is applied. We demonstrated coherent control of a quantum two-level system based on two-electron spin states in a double quantum dot allowing state preparation, coherent manipulation, and projective read-out. We showed how realistic charge manipulation and measurement techniques, ... |
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| Reaction Kinetics of PO2Cl(-), PO2Cl2(-), POCl2(-), and POCl3(-) with O2 and O3 from 163 to 400 K |
28 SEP 2004 |
7 pages |
| Authors:
Abel I. Fernandez; Anthony J. Midey; Thomas M. Miller; A. A. Viggiano; AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
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| Rate constants and product branching ratios for the gas-phase reactions of O2 and O3 with the anions (a) PO2Cl-, (b)POCl3(-) (c) POCl2(-), and (d) PO2Cl2(-) were measured in a selected ion flow tube. The kinetics were measured at temperatures of 163-400 K and a He pressure of 0.4 Torr. Only PO2Cl(-) reacts with O2 to a measureable extent, having k(163-400 K) = 1.1 x 10(exp -8)(T/K)(exp -1.0)cu cm/molecule/s, while O3 ... |
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| Trends in Nanotechnology Conference (TNT 2003) Held in Salamanca, Spain, 15-19 Sep 2003. Posters Abstracts |
SEP 2003 |
555 pages |
| Authors:
Uzi Landman; GEORGIA INST OF TECH ATLANTA SCHOOL OFPHYSICS
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| In response to the growing awareness of the importance of nanotechnology, "Trends in Nanotechnology" (TNT) has become key meeting in the nanotechnology field since it brings fresh ideas on organization, first level speakers, and an environment suitable to keep discussions, ideas exchange and enhance scientific and personal relations among participants. TNT2003 was held in large part due to the overwhelming success of earlier Nanotechnology Conferences, TNT2000, TNT2001 and TNT2002. The ... |
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| Large Scale Type II Quantum Computing in NV-Diamond Using PBG-Based Cavities |
16 JUN 2003 |
3 pages |
| Authors:
Sharhriar; NORTHWESTERN UNIV EVANSTON IL
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| Experimentally, our key accomplishment to date has been the demonstration of alignment of spins (i.e., the individual qubits) in NV-Diamond. Essentially, this represents our ability to initialize all the qubits into their individual (i.e., uncoupled) true ground states, as well as the ability to perform single qubit operations on a collective scale. Furthermore, we have derived the explicit quantum circuits and algorithms necessary for performing the multi-qubit operations, necessary for ... |
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| Symposium P: Novel Aspects of Spintronic Materials and Devices |
09 JUN 2003 |
20 pages |
| Authors:
Laurens W. Molenkamp; Hiro Munekata; Christopher J. Palmstrom; Igor Zutic; MATERIALS RESEARCH SOCIETY WARRENDALE PA
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| Symposium P, Novel Aspects of Spintronic Materials and Devices, provided an overview of challenges and recent progress in controlling the spin degrees of freedom in solid-state systems. It is instructive to think of a spintronics scheme as consisting of three different stages: generation of spin polarization, spin manipulation, and spin detection. Spin polarization can be defined as the ratio of the sum and the difference of spin-resolved components (spin-up and ... |
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| Quantum Computing in Solid State, and Coherent Behavior of Open Quantum Systems |
JAN 2003 |
49 pages |
| Authors:
Vladimir Privman; CLARKSON UNIV POTSDAM NY CENTER FOR ADVANCED MATERIALS PROCESSING
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| We have developed and investigated models of realization of quantum computing in solid-state semiconductor heterostructures, and explored decoherence properties of relevance in evaluation of quantum-computing systems. Quantum bits (qubits) are nuclear or outer bound electron spins in donor atoms embedded in the zero-spin host material, which could be an isotope of Si. In order to accomplish control of each qubit and also have controlled qubit-qubit interactions, we consider exchange of ... |
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| Role of Spin Momentum Current in Magnetic Non-Local Damping of Ultrathin Film Structures |
2003 |
9 pages |
| Authors:
G. Woltersdorf; R. Urban; B. Heinrich; SIMON FRASER UNIV BURNABY (BRITISH COLUMBIA)
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| Non-local clamping was investigated by Ferromagnetic Resonance (FMR) using ultrathin magnetic single and double layer structures prepared by Molecular Beam Epitaxy (MBE). The double layer structures show magnetic damping which is caused by spin transport across a normal metal spacer (N). In double layer structures a thin Fe layer, F1, was separated from a thick Fe layer, F2, by a Au(001) sparer. The interface magnetic anisotropies separated the FMR fields ... |
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| Physics Utilizing Spin-Polarized Gases |
08 AUG 2002 |
5 pages |
| Authors:
William Happer; PRINCETON UNIV NJ DEPT OF PHYSICS
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| We have completed a thorough study of masing action of hyperpolarized He-3 gas in inhomogeneous magnetic fields. The self interaction of the He-3 magnetization has a large effect on the maser gain. We have developed a simple new magnetic resonance method for investigating the interactions of Xe-129 spins with protons in polymers. We have shown that there are novel magnetic resonance transitions in alkali-metal vapors that have vanishing spin-exchange broadening ... |
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| Potential Energy Surfaces and Dynamics of High Energy Materials |
04 FEB 2002 |
15 pages |
| Authors:
Mark S. Gordon; IOWA STATE UNIV AMES DEPT OF CHEMISTRY
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| On the theoretical side, a new highly scalable code for frozen core second order perturbation theory gradients for closed shell molecules has been developed. The development of analogous codes for molecules with unpaired electrons is in progress. A working unrestricted second order perturbation theory code is now in GAMESS, and work on a scalable version of this code will begin shortly. The derivation for the spin-restricted open shell second order ... |
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| Quantum Information Processing |
02 DEC 2001 |
6 pages |
| Authors:
David P. DiVincenzo; Charles H. Bennett; IBM THOMAS J WATSON RESEARCH CENTER YORKTOWN HEIGHTS NY
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| We have made progress on many fronts on the understanding and characterization of entanglement. Various new forms of bound (i.e. undistillable) entanglement have been introduced, as part of our work on unextendable product states. Cases of "superactivation" of bound entanglement, in which two different bound entangled states, when joined, produce distillable entanglement, have been established for fourparty states and have been conjectured for bipartite states. These results show that the ... |
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| NATO ASI at Windsor on 13-26 August Programme |
26 AUG 2001 |
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| Authors:
NATO ADVANCED STUDY INST BRUSSELS (BELGIUM)
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| Nanostructures: Physics and Technology International Symposium (9th), St. Petersburg, Russia, June 18-22, 2001 Proceedings |
22 JUN 2001 |
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| Authors:
Zh. Alferov; L. Esaki; RUSSIAN ACADEMY OF SCIENCES SAINT PETERSBURG IOFFE PHYSICAL- TECHNICAL INST
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| Polarized Electron Photoemission Studies of Spin Relaxation in Thin GaAs Epitaxial Films |
JUN 2001 |
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| Authors:
Yuri A. Mamaev; Yuri P. Yashin; Arsen V. Subashiev; Anton N. Ambrajei; Alexander V. Rochansky; SAINT PETERSBURG STATE TECHNICAL UNIV (RUSSIA) LABORATORY OF SPIN-POLARIZED ELECTRON SPECTROSCOPY
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| The results of systematic study of polarized electron emission from unstrained GaAs thin epitaxial layers with varying thickness are presented. Excitation spectra of the polarized photoemission reflect the optical spin orientation of the electrons produced by the circularly polarized light excitation and spin relaxation kinetics. The interpretation of the spectra and their temperature dependencies shows the importance of valence band wrapping and correlation between the spin and the momentum of ... |
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| Spin-Orbit Interaction in AlGaAs/GaAs P-Type Quantum Wells - A Possible Explanation of the "Metal-Insulator" Transition Observed in Two-Dimensional Hole Systems |
JUN 2001 |
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| Authors:
L. S. Golub; S. Pedersen; RUSSIAN ACADEMY OF SCIENCES SAINT PETERSBURG IOFFE PHYSICAL-TECHNICAL INST
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| We have performed a calculation of the temperature dependence of the weak-localization correction to resistance in a AlGaAs/GaAs p-type quantum well. In such systems where the spin orbit coupling by far dominates the energy dispersion, we find that the spin relaxation time becomes comparable with the estimated value of the phase coherence time at sufficiently low temperatures and low hole densities. We wish to suggest this crossover between these different ... |
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| Spin-Orbit Interaction of Electrons on Curved Surface |
JUN 2001 |
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| Authors:
M. V. Entin; L. I. Magarill; RUSSIAN ACADEMY OF SCIENCES NOVOSIBIRSKINST OF SEMICONDUCTOR PHYSICS
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| Spin-orbit (SO) interaction of electrons confined near the curved semiconductor surface is studied. The curvature of surface determines the new mechanism of SO interaction which complements the known mechanisms occurring in planar systems. The specific cases of nanosphere and nanotube are considered. |
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| Injection of Spin-Polarized Carriers from a ZnMnSe/CdSe Semimagnetic Superlattice into a Non-Magnetic ZnCdSe Quantum Well |
JUN 2001 |
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| Authors:
Ya. V. Terent'ev; A. A. Toropov; S. V. Sorokin; A. V. Lebedev; S. V. Ivanov; RUSSIAN ACADEMY OF SCIENCES SAINT PETERSBURG IOFFE PHYSICAL-TECHNICAL INST
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| We report on magneto-optical studies of spin injection from a ZnMnSe/CdSe semimag- netic short-period superlattice (SL) to a non-magnetic ZnCdSe quantum well (QW). The carriers are photo-generated in the semimagnetic SL spin polarized via the effect of giant Zeeman splitting and then injected into the non-magnetic QW through a tunneling mechanism. Near 25% injection efficiency has been demonstrated at the magnetic field of 0.8 T and low temperature (1.8 K). ... |
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| Spin Dynamics of Excitons in GaAs/AlGaAs Superlattices in a Magnetic Field |
JUN 2001 |
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| Authors:
Yu. K. Dolgikh; S. A. Eliseev; I. Ya. Gerlovin; V. V. Ovsyankin; Yu. P. Efimov; SAINT PETERSBURG STATE UNIV (RUSSIA) INST OF PHYSICS
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| Kinetics of resonance luminescence of GaAs/ AlGaAs-superlattices in circular and linear polarizations is studied in a magnetic field of up to 5 T. Quantum beats of the luminescence are detected and their nature is identified. The energy and phase relaxation rates of excitons spins are determined from the experimental data. |
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| Spin Quantum Beats in InP Quantum Dots in a Magnetic Field |
JUN 2001 |
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| Authors:
I. A. Yugova; V. G. Davydov; I. Ya. Gerlovin; I. V. Ignatiev; I. E. Kozin; SAINT PETERSBURG STATE UNIV (RUSSIA) INST OF PHYSICS
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| In this paper, we studied quantum beats observed in kinetics of photoluminescence of a single layer of InP self-assembled quantum dots in a magnetic field. The reason for the quantum beats is shown to be Zeeman splitting of the exciton radiative level. Studies of behavior of the quantum beats versus the magnetic field magnitude and orientation and versus polarization of the exciting and detected light have allowed us to identify ... |
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| Spin Coherence in Semiconductor Nanostructures |
JUN 2001 |
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| Authors:
X. Marie; A. Jbeli; M. Paillard; T. Amand; J. M. Gerard; INSTITUT NATIONAL DES SCIENCES APPLIQUEES DE TOULOUSE (FRANCE) LAB DE MATIERECONDENSEE
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| We have studied the spin dynamics in self-organized InAs/ GaAs quantum dots (QD) by time-resolved photoluminescence performed under strictly resonant excitation. We demonstrate that the carrier spins in these nanostructures are totally frozen on the exciton lifetime scale. |
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| Spin Quantum Beats of Hot Trion in Quantum Dots |
JUN 2001 |
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| Authors:
I. E. Kozin; V. G. Davydov; I. V. Ignatiev; A. Kavokin; K. Kavokin; SAINT PETERSBURG STATE UNIV (RUSSIA) INST OF PHYSICS
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| Spins of resident holes in charged quantum dots (QD's) act as local magnets inducing Zeeman splitting of excitons trapped into dots. This has been evidenced by observation of quantum beats in linearly polarized time-resolved photoluminescence of a biased array of self-assembled InP QD's. A theory is developed that considers the exchange interaction within the positively charged exciton (trion) states formed in the QD. |
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| Spin Sensitive Bleaching of Absorption in P-Type GaAs/AlGaAs QWs |
JUN 2001 |
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| Authors:
S. D. Ganichev; S. N. Danilov; V. V. Bel'kov; E. L. Ivchenko; L. E. Vorobjev; REGENSBURG UNIV (GERMANY) INSTITUT FUREXPERIMENTELLE UND ANGEWANDTE PHYSIK
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| Ferromagnetic and Structural Properties of Mn-Implanted p-GaN |
APR 2001 |
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| Authors:
N. Theodoropoulou; A. F. Hebard; M. E. Overberg; C. R. Abernathy; S. J. Pearton; FLORIDA UNIV GAINESVILLE
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| High doses (10(exp 15) - 5 x 10(exp 16)/sq cm) of Mn(+) ions were implanted into p-GaN at ^ 350 deg C and annealed at 700 - 1000 deg C. At the high end of this dose range, platelet structures of Ga(x)Mn(1-x)N were formed. The presence of these regions correlated with ferromagnetic behavior in the samples up to ^ 250 K. At low doses, the implantation led to a buried ... |
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| A Landau-Ginzburg Description of Sb Overlayers |
APR 2001 |
6 pages |
| Authors:
R. Skomski; T. Komesu; H. K. Jeong; C. N. Borca; P. A. Dowben; NEBRASKA UNIV LINCOLN DEPT OF PHYSICS AND ASTRONOMY
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| The spin polarization of Sb overlayers on the semi-Heusler alloy NiMnSb is investigated in terms of the Landau-Ginzburg approach. The half-metallic semi-Heusler alloy NiMnSb acts as a ferromagnetic perturbation and induces a spin polarization in the semimetallic Sb overlayer. Using a Gaussian approximation, the propagation of the spin perturbation in the overlayer is calculated. The results are compared with spin-polarized inverse photoemission spectroscopy (SPIPES) results and with recent spin-dependent envelope-function ... |
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| First-Principles Theory of Transition Metal Impurities in Silicon Carbide |
14 DEC 2000 |
4 pages |
| Authors:
Walter R. Lambrecht; CASE WESTERN RESERVE UNIV CLEVELAND OHDEPT OF PHYSICS
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| A theoretical study of the electronic structure of selected transition metal impurities in silicon carbide is carried out using a first- principles approach. Polytype dependence, site preference and charge and spin states are investigated. |
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| Anharmonic Interactions Between Novel Surfaces and Adsorbates |
11 AUG 2000 |
3 pages |
| Authors:
Amy Y. Liu; GEORGETOWN UNIV WASHINGTON DC DEPT OF PHYSICS
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| Work was completed on three technical projects: the development of a scheme for optimizing Gaussian basis sets for use in density-functional calculations, a systematic investigation of the need to include non-linear core corrections in pseudopotential calculations, and a study of the adsorption of hydrazoic acid on aluminum surfaces. |
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| Spin-Dependent Electron Behaviour in Quantum Point Contacts and Dots |
23 JUN 2000 |
4 pages |
| Authors:
A. M. Bychkov; I. I. Yakymenko; K. F. Berggren; LINKOEPING UNIV (SWEDEN)
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| We investigate theoretically the effect of spontaneous electron spin polarization in quantum point contacts and quantum dots. Self-consistent calculation process has been developed in the framework of Kohn-Sham LSDA scheme. The existence of the detected spin-polarized states in the low-density regime can be used to explain an anomalous 0.7-structure in the conductance of quantum point contacts. The properties of the potential device based on such an effect are briefly discussed. ... |
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| Spontaneous Spin Polarization in a Quantum Wire |
23 JUN 2000 |
3 pages |
| Authors:
V. V'yurkov; A. Vetrov; RUSSIAN ACADEMY OF SCIENCES MOSCOW INST OF PHYSICS AND TECHNOLOGY
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| An existence of predominant symmetrical spin configuration (spin polarized phase) and "diluted" density of states under the Fermi level in the quantum wire is considered. The reduction of quantum wire conductance is in agreement with recent experimental data. |
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| Electron Spin Relaxation in Zinc-Blende Heterostructures |
23 JUN 2000 |
3 pages |
| Authors:
N. S. Averkiev; L. E. Golub; M. Willander; RUSSIAN ACADEMY OF SCIENCES SAINT PETERSBURG IOFFE PHYSICAL-TECHNICAL INST
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| Spin relaxation in-plane anisotropy is predicted for heterostructures based on zinc-blende semiconductors. It is shown that it manifests itself especially brightly if the two spin relaxation mechanisms (Dyakonov-Perel and Rashba) are comparable in efficiency. It is demonstrated that for the quantum well grown along the 001 direction, the main axes of spin relaxation rate tensor are 110 and 110. |
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| Potential Energy Surfaces and Dynamics for High Energy Species |
14 MAR 2000 |
13 pages |
| Authors:
Mark S. Gordon; IOWA STATE UNIV AMES
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| The stability of the asymmetric dimer of NO (a-N2-02: 3) with respect to spin forbidden radiationless decay has been investigated. The spin-allowed decay channel a N2O2(1A')-> N2O(X1 +) +O(1D) is endoergic. However, the spin forbidden spin decay channel a-N2O2(1A)- > N2O9X1 +) + O(EP) is exoergic. Large- scale multi-reference CI wave functions, approximately 300,000 - 1,400,000 configuration state functions, based on double zeta plus polarization and triple ... |
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| Optical Studies of the Influence of Microscopic Structure on the Optoelectronic Properties of 6.1 Angstrom-Lattice Constant III-V Superlattices |
FEB 2000 |
17 pages |
| Authors:
Thomas C. Hasenberg; Michael E. Flatte'; Thomas F. Boggess; IOWA UNIV IOWA CITY DEPT OF PHYSICS AND ASTRONOMY
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| The influence of the microscopic structure (particularly at material interfaces) on the optoelectronic properties of 6.1 Angstrom-lattice constant III-V superlattices is presented. Included are discussions of four research areas: 1) Theoretical studies of binary antimonide superlattices, 2) MBE growth of these superlattices. 3) Structural characterization using X-ray diffraction. and 4) continuous-wave and ultrafast optical characterization. The theoretical effort included spin lifetime calculations for bulk ... |
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| A New Virial-Theorem-Based Semi-Ab-Initio Method for Atomistic Simulations |
SEP 1999 |
32 pages |
| Authors:
Genrich L. Krasko; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| A new semi-ab-initio method for atomistic simulations based on the virial theorem has been suggested. The method is completely within the realm of the density-functional theory and uses the so-called "reduced" electron spin- density functional (SDF). The crucial component of the method is the ansatz expressing (for both one-component and two-component systems) the electron density at point r as a superposition of "atomic" densities due ... |
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| Electronic Properties and Many-Body Effects in Quantum Dots |
18 JUN 1999 |
6 pages |
| Authors:
Satyadev Nagaraja; Jean-Pierre Leburton; ILLINOIS UNIV AT URBANA-CAMPAIGN BECKMAN INST FOR ADVANCED SCIENCES AND TECHNOLOGY
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| We investigate the shell structure and electron electron interaction in planar quantum dots within the density functional theory. We observe that the Coulomb repulsion does not alter the shell structure when the dot is symmetric in the two dimensional (2D) plane. If the dot is asymmetric, no pre-determined shell structure emerges except when Coulomb repulsion leads to accidental Coulomb degeneracies. Our investigations on double-quantum dots reveal double electron charging for ... |
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| Mesoscopic Superconductors in Proximity to Nanomagnets |
18 JUN 1999 |
4 pages |
| Authors:
V. T. Petrashov; I. A. Sosnin; I. Cox; A. Parsons; C. Troadec; LONDON UNIV (UNITED KINGDOM)
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| We report a study of electron transport through mesoscopic superconducting (aluminum) wires with ferromagnetic (nickel) and superconducting electrodes in the temperature range of 0.28-1.5 K in magnetic fields up to 5 T. We observe spectacular changes in the differential voltage-current characteristics, dV/dI vs I. when the measuring current is injected from the ferromagnetic electrodes: the dV/dII curves become non-symmetric with respect to the current direction and show the regions with ... |
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| Magnetic Field-Induced Type-I Type-II Transition in (ZuMu)Se/(ZaBe)Se Spin Superlattices |
18 JUN 1999 |
4 pages |
| Authors:
B. Koenig; U. Zehnder; D. R. Yakovlev; W. Ossau; T. Gerhard; RUSSIAN ACADEMY OF SCIENCES SAINT PETERSBURG IOFFE PHYSICAL-TECHNICAL INST
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| We have performed a magnetooptical study on spin superlattice structures fabricated on the basis of (ZnMn)Se/(ZnBe)Se. The band alignment of a Zn(0.91)Mn(0.09)Se/ Zn(0.972)Be(0.028)Se superlattice was found to undergo a type-I to type-Il transition for one of the exciton spin component. This spin superlattice formation manifests itself in an asymmetric Zeeman splitting of a spatially direct exciton resulting from a spin dependent change of the exciton binding energy. A pronounced broadening ... |
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| Damping of Manganese Spin Precession in the Presence of Free Carriers in CdMnTe Quantum Wells |
18 JUN 1999 |
4 pages |
| Authors:
C. Camilleri; D. Scalbert; J. Allegre; M. Dyakonov; M. Nawrocki; WARSAW UNIV POLAND INST OF EXPERIMENTAL PHYSICS
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| The transverse relaxation time T2 of the Mn spins has been measured by time resolved photo induced Kerr rotation in n-type and p-type CdMnTe quantum wells with a magnetic field applied parallel to the quantum well plane. The dependencies of T2 on the magnetic field and on the carrier density indicate the influence of carriers on T2. A model, akin to dielectric relaxation, is proposed to explain qualitatively these results. ... |
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| Raman Excited Spin Coherences for Turbulence Imaging |
APR 1999 |
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| Authors:
Selim Shahriar; Shaoul Ezekiel; MASSACHUSETTS INST OF TECH CAMBRIDGE
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| The objective of this project was to explore the feasibility of using Raman excited spin coherence for turbulence imaging. We experimentally demonstrated that it is possible to use degenerate four-wave mixing (DFWM) in Na vapor to correct intracavity high-speed turbulence aberrations. The use of sodium vapor as a phase conjugate mirror (PCM) provides gains greater than unity and an ideal response time of about 16 nsec, even with cw laser ... |
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| Method of Controlling a Super Conductor. |
16 FEB 1999 |
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| Authors:
Michael Osofsky; Robert J. Soulen Jr.; Raymond Auyeung; James S. Horwitz; Doug B. Chrisey; DEPARTMENT OF THE NAVY WASHINGTON DC
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| The order parameter of a superconductor is reduced by Injecting spin-polarized carriers into the superconductor. The reduction in the order parameter is used to modulate the critical current of the superconductor In a typical embodiment a current is caused to flow through a superconductor. Spin polarized electrons are then injected into the path of the current in the superconductor by biasing a magnetic metal with respect to a terminal of ... |
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| Laser Spin-Exchange Polarized He-3 and Xe-129 for Diagnostics of Gas- Permeable Media with Nuclear Magnetic Resonance Imaging |
FEB 1999 |
14 pages |
| Authors:
William Happer; PRINCETON UNIV NJ
|
| Major advances in the physics and technology for the production and utilization of laser-polarized He-3 and Xe-129 have resulted from this DARPA- sponsored research. A high-capacity polarizer and accumulator for Xe-129 has been developed and has been successfully transferred to the commercial sector. We have developed a powerful new method for imaging the three-dimensional distribution of the electronic spin polarization of the alkalimetal vapors used for spin-exchange optical pumping of ... |
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| Developing Rare-Earth-Doped Semiconductor Light Sources |
15 JUL 1998 |
3 pages |
| Authors:
Hyatt M. Gibbs; ARIZONA UNIV TUCSON
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| Studies were performed on the precession of spin polarized electrons in a magnetic field of up to l2T. Even at densities high enough to provide gain and to see lasing, sufficient spin polarization remains for the lasing emission to alternate back and forth between right and left circular polarization as the spins precess. Thus, the vertical-cavity surface-emitting laser emission is locked to the spin precession ... |
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| Anomalous Magnetoresistance in Multy-Level 2D Systems |
JUN 1998 |
2 pages |
| Authors:
N. S. Averkiev; L. E. Golub; G. E. Pikus; RUSSIAN ACADEMY OF SCIENCES SAINT PETERSBURG IOFFE PHYSICAL-TECHNICAL INST
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| A weak localization is a quantum interference of waves propagating through the closed trajectory in the opposite directions. This interference may be destroyed by different wave phase breaking processes: magnetic field, inelastic processes, spin relaxation etc. These mechanisms give additive contributions in the total interference breaking rate. One can show that the role of the intersubband transitions leads to the averaging of the pammeters which defines the weak localization. The ... |
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| Ab Initio Study on Spin Polarization of III-V Compound Tips |
JUN 1998 |
2 pages |
| Authors:
Makoto Sawamura; Tomohide Maruyama; Koichi Mukasa; HOKKAIDO UNIV SAPPORO (JAPAN)
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Reports by Keyword(s)
SPIN STATES
