Download or read book A Study of Optically Pumped Nuclear Magnetic Polarization on Gallium Arsenide written by Yunpu Li and published by . This book was released on 2012 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis aims to study the dynamic process of optically pumped nuclear spin polarization on Gallium Arsenide. First of all, the time-resolved optical Faraday rotation is applied to observe the electron spin dynamics in the presence of the nuclear magnetic field. And then the optically-pumped NMR is measured on different parameters, including the dependences of light helicity, irradiation intensity, photon energy, illumination time and temperature. We report a new phenomenology at low irradiation intensity. A nuclear polarization model combining hyperfine and quadrupolar relaxation is developed, with experimental data supported. By exploiting the two competing mechanism on various photon energies, illumination intensity and NMR pulse sequences, we use high field stray-field NMR imaging to realize all-optical creation of three-dimensional patterning of positive and negative nuclear polarization on the micron length scale. Finally, the effect of nuclear spin diffusion effect is investigated. We demonstrate in a remarkable way the unambiguous evidence of diffusion, which results in a great enhancement of quadrupolar relaxation in the nanometer scale.
Download or read book Development of Optically pumped and Optically detected Nuclear Magnetic Resonance in a Longitudinal Magnetic Field and Studies of GaAs Quantum Wells written by Erika Lynn Sesti and published by . This book was released on 2014 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optically-pumped nuclear magnetic resonance (OPNMR) and optically-detected nuclear magnetic resonance (ODNMR) are valuable techniques to examine the coupling of nuclei to electrons in two dimensional semiconductors. Both techniques probe the polarization of conduction band electrons that have been excited with circularly polarized light. The polarized electrons can both relax radiatively back to the valence band emitting a polarized photon or transfer their polarization to surrounding nuclei via the Fermi-contact hyperfine interaction. The coupling of the nuclei to the electron is monitored by photoluminescence polarization in ODNMR and the nuclear spin orientation is measured through radio frequency (rf) detection in OPNMR. This dissertation describes the construction of an apparatus that is capable of performing OPNMR and ODNMR simultaneously, which has not been done in any other lab to date. The combination of the two techniques provides the capability to observe both the electron and nuclear spin orientation under the same experimental conditions. GaAs quantum wells were used as a test material due to extensive prior studies by both OPNMR and ODNMR. These studies provided a good foundational launching point for the new studies presented. While GaAs quantum wells have been extensively studied in the past, unanticipated results were discovered that afforded us the capability to extract the exact positons of electronic transitions that agree with theoretical calculations. Preliminary ODNMR measurements of 71Ga and 75As are shown, along with the comparison of 69Ga ODNMR to 69Ga OPNMR profiles. The comparisons show unexpected behavior and more experiments are necessary to elucidate the origin.
Download or read book Optical Polarization of Nuclear Spins in Gallium Arsenide written by Anant Krishna Paravastu and published by . This book was released on 2004 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Strain and Quantum Confinement in Optically Pumped Nuclear Magnetic Resonance in GaAs written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A combined experimental-theoretical study of optically pumped NMR (OPNMR) has been performed in a GaAs/Al0.1Ga0.9As quantum well film with thermally induced biaxial strain. The photon energy dependence of the Ga-71 OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8-5.4 K. The data were compared to the nuclear spin polarization calculated from differential absorption to spin-up and spin-down states of the conduction band using a modified Pidgeon Brown model. Reasonable agreement between theory and experiment is obtained, facilitating assignment of features in the OPNMR energy dependence to specific interband transitions. Despite the approximations made in the quantum-mechanical model and the inexact correspondence between the experimental and calculated observables, the results provide insight into how effects of strain and quantum confinement are manifested in OPNMR signals.
Download or read book Model for Optically induced Nuclear Spin Polarization in GaAs written by Patrick Joseph Coles and published by . This book was released on 2008 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Time sequenced Optical Nuclear Magnetic Resonance of Gallium Arsenide written by Steven Keith Buratto and published by . This book was released on 1993 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Spin Alignment in Optically Pumped Semiconductors written by Matthew M. Willmering and published by . This book was released on 2017 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear magnetic resonance (NMR) has shown its ability to be a very informative analytical technique due to the ability to measure very small changes in the energy splittings due to the nuclei's local environment. However, this ability is hindered by the low sensitivity of the experiment. Many methods have been postulated and implemented to enhance the sensitivity of NMR experiments; one of which is optically pumped NMR (OPNMR). In this dissertation, the usefulness and potential applications of OPNMR are presented. First, a doubly resonant OPNMR probe was fabricated in order to complete more advanced NMR techniques while optically pumping the semiconductor sample. OPNMR was then shown to be very benecial and accurate for measuring light hole transitions in semiconductors, which are typically difficult to observe using traditional techniques. The optical pumping behavior of a sample (CdTe) has been debated, but was measured here in order to obtain the expected trends and behavior. Discussion of the potential uses of optically oriented isolated spins pairs is presented and the characterization of such spin pairs is implemented, which included the first experimental report of a postulated NMR sequence (a version of spin echo double resonance). An Al2O3/GaAs interface was studied by OPNMR in order to observe the properties for the first time and the measured polarization was much higher than previously reported. Lastly, molecular dynamic and density functional theory calculations were used collaboratively to provide an accurate model for amorphous alumina.
Download or read book Optical Pumping and Photoluminescence Detection of Spin polarized Electrons in Uniaxially Stressed Gallium Arsenide written by Paul Zorabedian and published by . This book was released on 1982 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics of Electron and Nuclear Spin Interaction in Laser Assisted Nuclear Magnetic Resonance Spectroscopy of Gallium Arsenide Nanostructures written by Wieland Alexander Worthoff and published by . This book was released on 2011 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1987 with total page 1124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Manipulating Quantum Coherence in Solid State Systems written by Michael E. Flatté and published by Springer Science & Business Media. This book was released on 2007-05-31 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book features the proceedings of the NATO Advanced Study Institute "Manipulating Quantum Coherence in Solid State Systems", held in Cluj-Napoca, Romania, August 2005, which presented a fundamental introduction to solid-state approaches to achieving quantum computation. This proceedings volume describes the properties of quantum coherence in semiconductor spin-based systems and the behavior of quantum coherence in superconducting systems.
Download or read book Nuclear Polarization in Solids by Optical Pumping written by William Burgess Grant and published by . This book was released on 1971 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Composite Fermions written by Jainendra K. Jain and published by Cambridge University Press. This book was released on 2007-03-29 with total page 561 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book was first published in 2007. When electrons are confined to two dimensions, cooled to near absolute zero temperature, and subjected to a strong magnetic field, they form an exotic new collective state of matter. Investigations into this began with the observations of integral and fractional quantum Hall effects, which are among the most important discoveries in condensed matter physics. The fractional quantum Hall effect and a stream of other unexpected findings are explained by a new class of particles: composite fermions. This textbook is a self-contained, pedagogical introduction to the physics and experimental manifestations of composite fermions. Ideal for graduate students and academic researchers, it contains numerous exercises to reinforce the concepts presented. The topics covered include the integral and fractional quantum Hall effects, the composite-fermion Fermi sea, various kinds of excitations, the role of spin, edge state transport, electron solid, bilayer physics, fractional braiding statistics and fractional local charge.
Download or read book Spin and Charge Ordering in the Quantum Hall Regime written by Benedikt Frieß and published by Springer. This book was released on 2016-06-24 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book presents a comprehensive yet concise introduction to the physics of two-dimensional electron systems in the quantum Hall regime, as well as an up-to-date overview of the current fields of research concerning the integer and fractional quantum Hall effect. The physics of two-dimensional electron systems at low temperatures and high magnetic fields are governed by the formation of discrete energy levels referred to as Landau levels. These narrow energy bands not only form the basis of the well-known quantum Hall effect but also promote strong interactions between the electrons, giving rise to some of the finest manifestations of many-body physics in solid state science. Examples include skyrmionic spin textures, ferromagnetic spin transitions, stripe and bubble phases, as well as fractional quantum Hall states with potential non-abelian exchange statistics. The thesis succeeds in profoundly deepening our understanding of these exotic states of matter, with a main focus on the density-modulated phases in the quantum Hall regime. These phases arise from the interplay of competing interactions and are characterized by a self-organized ordering of electrons in spatial patterns. Similar phases of matter are currently being studied in other material systems as well, most notably in high-temperature superconductors. The thesis stands out not only in terms of its contribution to improving readers’ grasp of physics, but also in the diversity and novelty of the measurement techniques employed, which take advantage of the interaction between the electrons and the surrounding crystal lattice.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 934 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Journal of Chemical Physics written by and published by . This book was released on 2003 with total page 1168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Magnetic Resonance in Gallium Arsenide written by Michael Francis Finch and published by . This book was released on 1987 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nuclear Magnetic Resonance (NMR) lineshapes of 69Ga in GaAs:In were studied for two different levels of indium dopant. The lineshapes were developed by fourier analysis of the spin echoes. First order quadrupole effects manifested themselves as wings in the lineshapes. As expected the wings were larger in the more heavily doped sample. The dependence of the second moment of the lineshapes on the orientation of the crystal in the field supports a continuous solid model of the strain, in which the strain attenuates as the cube of the distance from the impurity site. Because of noise levels the model can only be confirmed for distances greater than 10A from the impurity, and no determination of the strain on the first through eighth shells surrounding the impurity can be made. Keywords: Gallium Arsenide semiconductors, Semiconductors, Nuclear magnetic resonance spectroscopy, Spectroscopy.
