Teses / dissertações sobre o tema "Polarisation du spin"
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Joly, Alexandre. "Optimisation du transfert du spin électronique à la polarisation d’un laser à semi-conducteur à émission par la surface". Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S084/document.
Texto completo da fonteOptimisation of the spin transport to the polarization of a vertical cavity semiconductor laser
Naylor, Adam David. "Measuring spin polarisation with point-contact Andreev reflection". Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534829.
Texto completo da fonteEustace, David Andrew. "Spin polarisation effects in electron energy loss spectroscopy". Thesis, University of Glasgow, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438978.
Texto completo da fonteTati, Bismaths Logane. "Étude du mouvement du spin d’électrons dans les puits quantiques dépendant du spin". Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/public/theses_doctorat/2008/TATI_BISMATHS_Logane_2008.pdf.
Texto completo da fonteIn the first part of my PhD I studied the spin-motion of spin-polarized electrons in the quantum well system Au/Co(001). The existence of a ferromagnetic interface and of quantum interferences leads to an oscillatory behaviour of the spin-motion angles. I also showed that these oscillations are well described by a Fabry-Perot interferometer model, and that the simulation of the experimental data allows the study of the spin-dependent reflection properties of the buried interface which are not directly accessible. In the second part, I performed a similar study of the system Fe/Ag(001). Two periods of oscillations were identified in this case: a long one due to quantum interference of electrons in the Fe films, and a short one with the period of one monolayer, which are attribute to the periodic variation of the morphology of the Fe film, alterning between filled and incompletely filled atomic layers
Kaladzhyan, Vardan. "Spin polarisation and topological properties of Yu-Shiba-Rusinov states". Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC215/document.
Texto completo da fonteIn this manuscript we first revisit the physics of Yu-Shiba-Rusinov subgap states, focusing on their spin polarisation. We start by showing theoretically that we can extract a considerable amount of information about the host superconductor, by analysing spin-polarised local density of states related to the presence of magnetic impurities. First, we demonstrate that the spin-orbit coupling in two-dimensional and one-dimensional systems, both superconducting and metallic, can be read-off directly and unambiguously via spin-resolved STM. We analyse the impurity-induced oscillations in the local density of states. In particular, we focus on the Fourier transform (FT) of the Friedel oscillations and we note that high-intensity FT features appear at a wave vector given by twice the inverse spin-orbit length. Second, in unconventional superconductors with both s-wave and p-wave pairing, by analysing the spin-resolved spectral structure of the Yu-Shiba-Rusinov states it is possible to determine the dominating pairing mechanism. Most strikingly, we demonstrate that a careful analysis of spin-polarised density of states allows not only to unambiguously characterise the degree of triplet pairing, but also to define the orientation of the triplet pairing vector, also known as the d-vector.Finally, we discuss two different ways of engineering and controlling topological phases with both scalar and magnetic impurities. We start with providing a microscopic theory of scalar impurity structures on chiral superconductors. We show that given a non-trivial chiral superconductor, the scalar impurities give rise to a complex hierarchy of distinct non-trivial phases with high Chern numbers. Second, we propose and study theoretically a new promising platform that we call 'dynamical Shiba chain', i.e. a chain of classical magnetic impurities in an s-wave superconductor with precessing spins. We have shown that it can be employed not only for engineering a topological superconducting phase, but most remarkably for controlling topological phase transitions by means of magnetisation texture dynamics.This manuscript is organised as follows. In the first part, the essential introductory information on superconductivity, Friedel oscillations and Yu-Shiba-Rusinov states is provided. The second part is dedicated to spin polarisation of Yu-Shiba-Rusinov states and the properties that could be extracted by means of spin-resolved STM measurements. In the last part, two setups proposed for topological phase engineering based on impurity-induced states are presented, followed by conclusions with a brief summary of the thesis achievements and further directions to pursue
Zarpellon, Juliana. "Estudo de multicamadas com anisotropia magnética perpendicular e sua aplicação em dispositivos emissores de luz polarizada em spin : Spin-LED e VCSEL". Paris 6, 2011. http://www.theses.fr/2011PA066064.
Texto completo da fonteNewbold, David Michael. "Inclusive hyperon polarisation studies at the CERN SPS hyperon beam". Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265386.
Texto completo da fonteTappero, Rémy. "Approche théorique des structures électroniques et magnétiques et des transitions de phases de systèmes à polarisation de spins (MnS et MnS2) : simulation des spectres de diffraction neutronique". Pau, 1999. http://www.theses.fr/1999PAUU3006.
Texto completo da fonteZagdoun, Alexandre. "Dynamic Nuclear Polarisation Surface Enhanced NMR Spectroscopy". Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2014. http://tel.archives-ouvertes.fr/tel-01065554.
Texto completo da fonteIacovita, Cristian. "Spin-dependent tunneling into single cobalt-phthalocyanine molecules". Strasbourg, 2009. http://www.theses.fr/2009STRA6058.
Texto completo da fonteThe thesis presents an experimental study of both the electronic and the spin-polarized properties of single cobalt-phthalocyanine (CoPc) molecules, which are potentially interesting for the emerging eld of molecular spintronics. The CoPc molecules were deposited on a nonmagnetic and a magnetic surface and individually studied at low temperature using a scanning tunneling microscope. Two fundamental aspects of molecular spintronics are addressed, namely the injection of electron spins into a single molecule and the magnetic coupling of the molecule with the underlying magnetic surface. To do so, spin-polarized scanning tunneling spectroscopy is employed to locally inject spin-polarized electron across the vacuum barrier into a single CoPc molecule. Using the spin-polarized Co terminated tip and Co nanoislands of opposite magnetization as magnetic electrodes, and the CoPc molecule as an active element, spin-polarized electronic features are identied over the center of the molecule. The Co nanoislands were grown on Cu(111) and thoroughly calibrated to eliminate electronic artifacts. The stationary spin states of CoPc arise from the d-orbitals of the cobalt ion and reect two molecular spin orientations. DFT calculations establish that CoPc couples ferromagnetically with the Co nanoislands through two exchange mechanisms (direct and superexchange), illustrating the important role played by the organic ligands in the spin-dependent transport properties. Comparative experimental studies are done on non-magnetic surfaces [Au(111) and Cu(111)], where the paramagnetic CoPc becomes non-magnetic upon adsorption, as DFT calculations predict
Iacovita, Cristian Bucher Jean-Pierre. "Spin-dependent tunneling into single cobalt-phthalocyanine molecules". Strasbourg : Université de Strasbourg, 2009. http://eprints-scd-ulp.u-strasbg.fr:8080/1162/01/IACOVITA_Cristian_2009.pdf.
Texto completo da fonteMonseu, Nicolas. "Etude de la polarisation dans un collisionneur eí/eñ. Détermination du champ invariant de spin grâce à l'intégrateur pas à pas Zgoubi". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY047.
Texto completo da fonteInvariant Spin Field (ISF), and its evolution, gives an acute insight in the polarization behaviour of a polarized accelerator, allows to estimate the equilibrium polarization of electron accelerators, an is also useful in the design and understanding of proton machines. The increased luminosity of colliders, the higher precision of the experiments, the inclusion of previously neglected effects, marks a necessary step forward in ISF precision. The present thesis proposes different methods to compute Invariant Spin Field, based on particle tracking, allowing a better precision in the orbital dynamic effect on the spin dynamic, as well as the inclusion of effects complicated to study and usually neglected, such as non linear dynamic effects, Beam-Beam effect, etc. The inclusion of these different effects has not been done, because elaboration of new methods is quite demanding. This is a candidate for future research. We implemented the Stroboscopic Averaging algorithm to compute ISF. The "simple" implementation leads to a non-managable computing time, but the "backward" implementation solves the problem by making the computation of the ISF dependent on only one orbital trajectory, thus allowing a parallelisation of the algorithm. It has been suggested that the spin tune could be computed through a spectral analysis. We implemented an algorithm for this purpose, allowing us to compute the spin tune form the spin-orbit trajectory. Following these ideas, we also proposed new methods based on a prior knowledge of the spin tune, to compute ISF. Combining the different methods leads to a better understandings of the spin dynamic, as each method provides a different point of view
Nguyen, Viet-Hung. "Transport électronique et effets de Spin dans les nanostructures de graphène". Paris 11, 2010. http://www.theses.fr/2010PA112153.
Texto completo da fonteWe study electronic transport and spin polarization effects in some typical graphene nanostructures. The study corves many transport phenomena such as microscopic pictures of charge states, tunneling processes, behaviors of conductance and electrical current, and spin polarization effects. To this aim, the non-equilibrium Green's function method within the effective models describing excited states around the K-points of large area graphene structures has been developed. The approach was then applied to clarify the general scenario of charge transport in these structures. In narrow armchair grapheme nanoribbons, the transport picture has been explored by using the atomistic tight binding description. The effects of energy bandgap engineering, edge roughness, and normal conducting contacts were investigated. Along with their transport properties, the spin polarization effects in ferromagnetic gate structures based on graphene have been also considered. The study shown many possibilities of controlling spin polarized current, e. G. , by the gate and the bias voltages. Possibilities of obtaining the current with high spin polarization were discussed. The calculation techniques developed were then self-consistently coupled to 2D Poisson equation to consider the device operation of large area graphene FETs. It is shown that though limited for digital applications, the device characteristics observed may be convenient for analogue circuits
Kerridge, Gregg Charles. "Magneto-optical investigations of two-dimensional electron systems in GaAs-Alâ†xGaâ†1â†-â†xAs single heterojunctions". Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286493.
Texto completo da fonteShonfield, Peter K. A. "Molybdenum and tungsten complexes for moleular electronics". Thesis, University of Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264635.
Texto completo da fonteDemory, Justin. "Initialisation de spin et rotation de polarisation dans une boîte quantique en microcavité". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS006/document.
Texto completo da fonteSingle photons are ideal candidates to carry quantum information and the major challenge that optical quatum computing must face is to engineer photon matter interaction. A promising way to do so is to implement an efficient spin-photon interface making use of the polarization rotation (so-called Faraday or Kerr rotation) induced by a single spin. Thanks to the polarization rotation, it is possible to transfer the spin state into a polarization state. However, observations of Kerr rotation induced by a single spin were reported only recently, with rotation angles in the few 10-3 degree range.Cavity-QED effects are used to demonstrate a giant exaltation of the spin-photon interaction. The device is a single semiconductor quantum dot spin inserted inside a micropillar, a geometry which currently constitutes the most efficient photonic interface between an external laser beam and a confined cavity mode. Further, quantum dots confine a spin state of charge carrier which can be initialized and optically measured.In this thesis, I realized an experimental setup used to initialize a spin state confined in the quantum dot and to analyze the polarization rotation induced by this spin state. I demonstrated that it was possible to initialize the spin state confined in quantum dot with a circularly polarized beam. Having a well-known spin state, I observed the polarization rotation of ± 6 ° induced by a single spin. This macroscopic polarization rotation is three orders of magnitude three orders of magnitude higher than the previous state of artIn parallel of this experimental work, I studied theoretically spin initialization and polarization rotation phenomenon in our systems. I developed analytical models to characterize and predict the resonant excitation and polarization rotation experiences. Thanks to this theoretical work, I determined realistic parameters for the device to realize an optimal spin-photon interface.This novel way of interfacing a flying qubit and a solid-state quantum memory opens the road for a wide range of applications for quantum information processing and long-distance quantum communication
Bernet, Colin. "Caractérisation des micromégas et mesure de la polarisation des gluons sur COMPASS". Paris 7, 2004. http://www.theses.fr/2004PA077205.
Texto completo da fonteBrunetti, Adalberto. "Battements de la polarisation de spin et structure fine du polariton en microcavités semiconductrices". Montpellier 2, 2007. http://www.theses.fr/2007MON20020.
Texto completo da fonteClowes, Robin T. "Sensitivity improvement in triple resonance NMR". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388663.
Texto completo da fonteRobinet, Florent. "Mesure de la polarisation des gluons dans le nucléon par la muo-production de mésons charmés à COMPASS". Paris 7, 2008. http://www.theses.fr/2008PA077138.
Texto completo da fonteThe 1/2 spin of the nucleon decomposes into three contributions : the quark and the gluon spin and their angular momenta. It is known that the fraction of the nucleon spin carried by the quarks is small. Nowadays, a series of measurements aims to determine the contribution of the gluon spin in order, perhaps, to recover the totality of the nucleon spin. This is one of the main goals of the COMPASS experiment at CERN where spin asymmetries are measured using a polarized nucleon beam on a polarized nucleon target. The photon-gluon fusion processes, sensitive to the gluon polarization, are selected by detecting D° in the final state. This method offers a very clean selection of the desired signal but is statistically limited. The work presented in this thesis is primarily focused on the development of an analysis method maximizing the statistics. In particular, the D° mesons reconstruction is submitted to a high combinatorial background. Parameterizing the probability for an event to be signal, the statistical error is significantly reduced. The momentum resolution, associated with the particule detection, is an important factor allowing to minimize the combinatorial background. This thesis presents the characteristics of drift chamber-type detectors contributing to the performances of the COMPASS spectrometer. Finally, the results, joined by the systematic errors study, are presented along with their implications on the contribution of the gluon spin to the nucleon spin
Siarry, Bruno. "Manipulation du spin et de la cohérence dans des boîtes quantiques d'InAs/GaAs par expériences pompe-sonde résonantes". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066579/document.
Texto completo da fonteThis work is a study of the dynamics and coherence of the spin in neutral and p-doped InAs/GaAs quantum dots (QDs) ensembles. The study is done thanks to pump-probe experiments, resonant with the fundamental transition. Firstly, the periodicity of the exciting laser is transferred to the precession of the hole spins in a transverse magnetic field, in the Modelocking frame. This techniques allows to overcome the strong inhomogeneities of the sample studied ( 105 QDs), and to observe a resynchronization of the spins at long delays. We can therefore estimate the coherence time of the hole spin to be 800 ns. Furthermore, similar experimental conditions allow us to observe dynamical nuclear polarization (DNP), and its important influence on the electron spin precession in a transverse field. The geometry of the DNP is characterized, and its long dynamic (500 ms) is measured. In a second part, the development of a heterodyne detection allows to improve greatly the sensitivity of the pump-probe setup, and hence to study small ensembles (300) of neutral QDs embedded in a cavity. We have characterized the fine structure of the electron-hole pair states in a longitudinal magnetic field, and demonstrated the manipulation of the phase of the quantum beats between these states by the magnetic field, when the excitation is done according to an axis that is not a symmetry axis of the system
Fiandrino, Annie. "Nouveaux bosons vectoriels au delà du modèle standard : effets de polarisation en production hadronique". Aix-Marseille 1, 1993. http://www.theses.fr/1993AIX11024.
Texto completo da fonteProcureur, Sébastien. "Détermination de la polarisation des gluons dans le nucléon par la production de hadrons à grande impulsion transverse à COMPASS". Paris 11, 2006. http://www.theses.fr/2006PA112117.
Texto completo da fonteThe main goal of the COMPASS experiment at CERN is the determination of the gluon polarisation in the nucleon, Delta G / G. For this, the helicity asymmetry of the photon gluon fusion process is measured, in the scattering of polarized muons on a polarised deuteron target. This process can be tagged by the production of hadrons with high transverse momentum (p_T), that allows to get a large statistics. On the other hand, a physical background remains and complicates Delta G / G extraction. This PhD thesis presents different studies performed to optimize the determination of Delta G / G in this channel. In particular, a study of the spectrometer alignment is presented, leading to an improvement of its resolution. Performances of the 12 Micromegas detectors have also been studied during 2004 run. Then, the asymmetries obtained in the analysis of 2002 to 2004 data are calculated, for various high p_T selection: 1 or 2 hadrons, low or high Q^2. An optimization of the selection, based on a neural network, has also been developped. ,and a detailed study of the experimental false asymmetry has been performed. Delta G / G extraction is then described, based on Monte Carlo simulations (using PYTHIA or LEPTO). For the first time, the asymmetry of so called resolved photon processes is estimated. An improvement on the reconstruction of nucleon momentum fraction carried by the gluon is also proposed, by reconstructing pseudo-jets. Finally, small values obtained for Delta G / G are discussed, within the framework of the nucleon spin decomposition
Gallo, Pascal. "Nanostructures III-V pour l'électronique de spin". Toulouse, INSA, 2006. http://eprint.insa-toulouse.fr/archive/00000156/.
Texto completo da fonteSelf-organised growth of quantum dots seems to be one of the best methods to obtain nanostructures able to confine carriers in the three directions of space. Growth is performed by molecular beam epitaxy; this technique provides high quality crystals, coherently with their environment. However, its major drawback is that it generates randomly sized structures, which is detrimental for device applications. A solution to this odd is to pattern the substrate in order to create regularly spaced nucleation sites for the quantum dots. The technique employed to do so is nanoimprint, which prevents from creating non radiative recombination centers in the substrate. This work shows state of the art results of luminescence from nanoimprinted regrown structures. Quantum dots are here applied to spintronics, which principle is to use the spin of the carriers as a support of quantum information. Three major obstacles have to be overcome in this field; first, polarized carriers have to be injected in the semiconductor; second, the polarized carriers have to be transported through the material; finally, the carriers may recombine, providing polarized photons. In this thesis, we design a device that allows characterizing all these parameters: the spinLED. Quantum dots allow a particularly good efficiency in the conversion of polarized carriers into polarized photons. As the spin relaxation times of the carriers are short, about 100ps, it was necessary to adapt the spinLED structure to make it compatible with hyperfrequency measurements
Andrieux, Vincent. "Polarisation of quarks and gluons inside the nucleon". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112244/document.
Texto completo da fonteThe work presented in this thesis is related to the study of the longitudinal spin structure of the nucleon. The aim is to determine the contribution to the spin 1/2 of the proton in terms of its constituents, quarks and gluons. The analysis is performed on the data taken with the COMPASS experiment, which benefits from a polarised muon beam at 200 GeV scattered off polarised protons from an ammonia target of 1.2 m long. The double longitudinal spin asymmetry of deep inelastic scattering cross-Section. The spin-Dependent structure function of the proton g₁p is derived from these measurements, which extend the kinematic world coverage to unexplored region so far (0,0036 < x< 0,57; 1,03 < Q² (GeV/c)² < 96 and 23 < W² (GeV/c)² < 320).The results obtained with a high statistical precision are included in a Next-To-Leading order QCD analysis of world g₁p, g₁d and g₁n (proton, deuteron and neutron) data to parametrise the polarised quark and gluon distributions. The g₁ world coverage of the x and Q² kinematic domain, which is a key point in the sensitivity to the gluon polarisation ΔG, turns out to be too limited for an accurate ΔG determination. Nevertheless, the QCD analysis allows to determine the quark spin contributions to the proton spin to 0.26<ΔΣ<0.33 at Q² = 3 (GeV/c)² in the MSbar scheme. The dominant uncertainty on ΔΣ is related to the choice of functional forms assumed in the fit. Finally, the Bjorken sum rule, which constitutes a fundamental test of QCD, is verified on the COMPASS data alone with a precision of 9%
Fegan, Stuart. "Polarisation observables from strangeness photoproduction on a frozen spin target with CLAS at Jefferson Lab". Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3158/.
Texto completo da fonteUtfeld, Claudia. "Probing the electron momentum density : The Fermi surface and spin polarisation of electronically complex materials". Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520209.
Texto completo da fonteBreeze, Ben G. "Electron paramagnetic resonance studies of point defects in diamond : quantification, spin polarisation and preferential orientation". Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/90151/.
Texto completo da fonteYsacco, Cedric. "Préparation et étude de nouveaux dinitroxydes comme agents de polarisation en polarisation dynamique nucléaire (PDN) en phase solide". Electronic Thesis or Diss., Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4819.
Texto completo da fontePreparation and study of new dinitroxydes as polarizing agents in dynamic nuclear polarization (DNP) in solid state. Nowadays, nuclear magnetic resonance (NMR) spectroscopy is one of the most important structure elucidation techniques in chemistry and biochemistry, NMR is also the underlying principle of magnetic resonance imaging (MRI). However, the use of NMR to investigate various materials or biological systems is still limited by its inherent low sensitivity. This arises from the relatively small size of the Zeeman interaction of the nuclear spins with an external magnetic field which leads to small Boltzmann polarizations (PI) and weak NMR signals. Dynamic Nuclear Polarization (DNP) is a prominent process to achieve a high non-equilibrium nuclear spin polarization by transferring to nuclear spins the higher electron spin polarization PS (PS/PI = 658 for 1H)) of unpaired electrons, belonging for example to stable free radicals. The past fifteen years has witnessed a renaissance in the use of DNP. This renewed interest is due to the outstanding work of the R. G. Griffin's group and the more recent work of the Ardenkjaer-Larsen's group. These authors have shown, among other, that with the use of trityl radicals or dinitroxides, PDN allowed to reach impressive signal enhancements for solid state and liquid NMR. The characteristics of the paramagnetic species used as polarizing agent play a pivotal role in the efficiency of a DNP process. In the course of our work we have performed the synthesis of five new dinitroxides, and through collaborations we tested their performance as polarizing agents for solid state PDN at 100 K, 9,4 T [263 GHz (RPE), 400 MHz (RMN)]
Rodríguez-Arias, Inés. "Collective behaviours in interacting spin systems". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS332/document.
Texto completo da fonteDynamic nuclear polarization (DNP) is one of the most promising techniques towards a new generation of Magnetic Resonance Imaging (MRI). The idea is to use the Nuclear Magnetic Resonance (NMR) in other nuclei rather than the traditional hydrogen, such as carbon. For the carbon signal to be detected, one needs to enhance its spin polarization. In thermal equilibrium — at low temperature and high magnetic field — electron spins are far more polarized than any system of nuclear spins, which is due to their smaller mass. With the DNP technique we bring the system out-of-equilibrium irradiating it with microwaves. This triggers polarization transfer from the electron spins to the nuclear ones. During my Ph.D, I have studied both analytically and numerically the competition between the dipolar interactions among electron spins (which can be tuned experimentally) and the disorder naturally present in the sample. I proposed two models to study DNP: a Heisenberg spin-chain and a system free-fermions in the Anderson model. Two different regimes were found : For strongly interacting electron spins, the out-of-equilibrium steady state displays an effective thermodynamic behavior characterised by a very low spin temperature. In the weakly interacting regime, it is not possible to define a spin temperature, and it is associated to a many-body localized phase (or an Anderson-localized phase). My research was focused on the properties of the two phases with respect to the performance of DNP, and I found it to be optimal at the transition between the two. This is a very important result that has been verified by recent experiments carried in École Normale Supérieure de Paris
Hilaire, Paul. "A cavity-based spin-photon interface". Thesis, Sorbonne Paris Cité, 2019. https://theses.md.univ-paris-diderot.fr/HILAIRE_Paul_va2.pdf.
Texto completo da fonteThe development of future quantum networks requires an efficient interface between stationary and flying qubits. A promising approach is a single spin of a charge confined in a quantum dot (QD) deterministically coupled to a micropillar cavity. Here we focus on the development of polarization-based photonic gates, whereby the polarization state of a single incoming photon is manipulated through its interaction with the spin state. In this framework, we first investigate the polarization rotation of coherent light interacting with QDcavity systems. We developed a polarization tomography technique allowing to analyze the polarization density matrix of the reflected photons in the Poincaré sphere. We show an excellent injection efficiency of photons into the cavity and a macroscopic rotation of polarization induced by a single neutral quantum dot. To realize efficient photonic gates, the quantum dot fundamental state should correspond to a charged quantum dot, where the confined charge has a spin degree of freedom that can be optically adressed. We thus demonstrate the deterministic assembly of such spin-photon interfaces, that can perform as state-ofthe-art single-photon sources. We then benefit from the macroscopic spin-dependent polarization rotation offered by such cavity-based spin-photon interfaces to demonstrate the macroscopic measurement back action induced on the spin by a single photon detection event. Such a phenomenon highlights the strong correlations between the spin state and the photon polarization. These results open the way toward the realization of entanglement between a spin and a photon emitted by an external source, which is a building block for the implementation of photon-photon gates
Wang, Weimin. "Structure électronique et magnétique des oxydes de métaux de transition : le cas de Fe3O4". Phd thesis, Université de Cergy Pontoise, 2012. http://tel.archives-ouvertes.fr/tel-00841671.
Texto completo da fontePanebianco, Stefano. "Mesure de la polarisation des gluons par l'asymétrie de spin dans la production de mésons charmés". Paris 11, 2005. http://www.theses.fr/2005PA112136.
Texto completo da fonteThe main aim of the compass experiment is the measurement of the gluon polarization in the nucleon, which can be accessed by the spin asymetry in the scattering of a polarized muon beam on a polarized nucleon target. The process sensitive to the gluon distribution is the photon-gluon fusion, which can be tagged by looking at the production of charmed mesons, however it is a rare process, dominated by a large background. The measurement of the efficiency and the space resolution of the three drift chamber stations of the spectrometer is a necessary step in understanding the performances of the reconstruction of particle trajectories. The hadron identification, which is fundamental in the reconstruction of charmed meson decay, is performed by a rich. A statistical treatement of signal and bakground, together with an upgrade project to replace the present front end electronics, have been developped in order to increase the identification performances. The second part of this work concerns the spin asymmetry measurement, which requires the application of selection criteria in order to minimize the noise over signal ratio, and the development of event-weighting methods to reduce the statistical error. Although the error bars are still large, this work presents a preliminary result, based on 2002-2004 statistics, leading to a gluon polarization compatible with zero. The comparison with nlo-qcd fits and with other direct measurements shows that this result is compatible with the existing measurements but, given the present accuracy, it does not allow to distinguish between different models
Ndilimabaka, Hervé Maurice. "Etude de l'oxyde magnétique semi-conducteur Fe2-xTixO3±δ : du contrôle de l'interaction d'échange à la polarisation de spin". Versailles-St Quentin en Yvelines, 2008. http://www.theses.fr/2008VERS0022.
Texto completo da fonteThis thesis is based upon the study of physical properties, in thin films (70 double-exchange type transition with an easy axis being out of plan and magnetoresistance phenomenon are observed around T~110K
Bensafa, Imad Khaled. "Mesure de l'asymétrie de spin de faisceau en diffusion Compton virtuelle polarisée sur le proton". Clermont-Ferrand 2, 2006. http://tel.archives-ouvertes.fr/docs/00/08/34/67/PDF/bensafa.pdf.
Texto completo da fonteSiarry, Bruno. "Manipulation du spin et de la cohérence dans des boîtes quantiques d'InAs/GaAs par expériences pompe-sonde résonantes". Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066579.
Texto completo da fonteThis work is a study of the dynamics and coherence of the spin in neutral and p-doped InAs/GaAs quantum dots (QDs) ensembles. The study is done thanks to pump-probe experiments, resonant with the fundamental transition. Firstly, the periodicity of the exciting laser is transferred to the precession of the hole spins in a transverse magnetic field, in the Modelocking frame. This techniques allows to overcome the strong inhomogeneities of the sample studied ( 105 QDs), and to observe a resynchronization of the spins at long delays. We can therefore estimate the coherence time of the hole spin to be 800 ns. Furthermore, similar experimental conditions allow us to observe dynamical nuclear polarization (DNP), and its important influence on the electron spin precession in a transverse field. The geometry of the DNP is characterized, and its long dynamic (500 ms) is measured. In a second part, the development of a heterodyne detection allows to improve greatly the sensitivity of the pump-probe setup, and hence to study small ensembles (300) of neutral QDs embedded in a cavity. We have characterized the fine structure of the electron-hole pair states in a longitudinal magnetic field, and demonstrated the manipulation of the phase of the quantum beats between these states by the magnetic field, when the excitation is done according to an axis that is not a symmetry axis of the system
Leymarie, Edouard. "Méthodes de variation de contraste par polarisation nucléaire en diffusion de neutrons aux petits angles : Observation de domaines de polarisation nucléaire par diffusion de neutrons". Phd thesis, Paris 11, 2002. https://tel.archives-ouvertes.fr/tel-00002103v2.
Texto completo da fonteIn this thesis we study the theoretical and experimental aspects of Contrast Variation by Nuclear Polarization (CVNP) applied to small-angle neutron scattering. The basics of neutron scattering theory is developed by highlighting the origin of the CVNP method : the strong spin dependence of thermal neutron scattering, especially on protons. We also present the principles of NMR with a special attention on the method of dynamic nuclear polarization by the solid effect which makes it possible to control the proton polarization and therefore the contrast for neutron scattering. We present a theoretical study of the CVNP method called static which supposes that the nuclear polarization is homogeneous in the sample and constant during the experiment. We show that it allows one to obtain partial structure functions of systems with multiple components, by carrying out several acquisitions with different polarizations on a single sample. For this purpose, we tested a simple device to stabilize the nuclear polarization. We describe finally a new application of the CVNP method called dynamic. In a solution of deuterated glycerol-water containing a small concentration of paramagnetic centres, we showed the existence of domains of polarized protons at the onset of dynamic polarization. This reinforces considerably the coherent scattering of paramagnetic centres. We describe the theoretical reasons explaining the appearance of these domains of polarization, as well as the various techniques used to observe them by neutron scattering
Marco-Rius, Irene. "Preserving hyperpolarised nuclear spin order to study cancer metabolism". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245345.
Texto completo da fonteHonda, S., H. Itoh, J. Inoue, H. Kurebayashi, T. Trypiniotis, C. H. W. Barnes, A. Hirohata e J. A. C. Bland. "Spin polarization control through resonant states in an Fe/GaAs Schottky barrier". American Physical Society, 2008. http://hdl.handle.net/2237/11246.
Texto completo da fonteMcAndrew, Michael Gabriel. "A measurement of the quark polarisation of the nucleon". Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366732.
Texto completo da fonteHamié, Ali. "Hétérostructures à base de l'oxyde ferrimagnétique rendu semiconducteur Fe2-xTixO3-δ : vers des effets de polarisation en spin". Versailles-St Quentin en Yvelines, 2011. http://www.theses.fr/2011VERS0028.
Texto completo da fonteThis work is a contribution to research about spintronics on artificial heterostructures based on Fe1. 5Ti0. 5O3-d and Fe3O4 on a compatible Si-Technology SrTiO3(001) substrate. The solid solution Ilmenite-Hematite (Fe2-xTixO3-δ, FTO for x=1. 5) is predicted to be a half-metal by certain ab-initio calculations. The FTO system has a rhomboedric structure with R(-3) (order) or R(-3)c (disorder) symmetry, depending on the atomic order of titanium along the c-direction. Until now, FTO thin films have been deposited on the isostructural Al2O3(0001) substrate. The previous study on FTO/ Al2O3(0001), done at GEMaC (Groupe d’Etudes de la Matière Condensée) have shown a strong influence of the oxygen pressure during the growth process on semi-conducting and magnetic properties. The magnetite (Fe3O4), well studied, is also predicted to have half-metallic behavior, leading for a full spin polarization (100%). With Curie temperatures much higher than 300K, these two iron oxides are very promising materials for spintronics room temperature applications. No work has been reported yet for the growth of FTO/STO thin film and seldom works on the growth of Fe3O4/STO. We perform epitaxy on STO(001) substrate of simple FTO and Fe3O4 thin films and heterostructures by Pulsed Laser Deposition (PLD) and studies them with advanced techniques such as XRD, RHEED and AFM and High-Resolution Transmission Electron Microscopy and EELS, and as SQUID and VSM magnetometries, (UV-visible-IR) spectrophotometer for the optical properties, and also transport measurements. FTO/STO(001) thin films remain with rhombohedral structure without induced distortion from the compressive strain of the substrate on the films. An atomic order of the Ti along the (c) axis has been found for the sample prepared under oxygen pressure PO2=2. 6×10-7 Torr and substrate temperature TS=730°C. A ferromagnetic behavior with a “state of the art” magnetization (1. 57 B/formula) for this composition x=0. 5 is found for this ordered sample. The magnetic properties of the thin films depend mostly on the order/disorder symmetry. An epitaxial "cube on cube" of single phase Fe3O4 is been obtained on STO(100). The films showed a high crystalline quality with magnetic properties close to the ones of the bulk. A high density of the anti-phase boundaries is found on these thin films by TEM. The control of the growth of the thin films of FTO and Fe3O4 separately deposited on STO(001) allowed us to elaborate a bilayer Fe3O4/FTO/STO(001). No “exchange bias” is found. The small thickness value of the FTO film and the low coercive field of R(-3)c FTO induce a simultaneous magnetic switching of the Fe3O4/FTO bilayer. The magnetic properties are similar to Fe3O4/STO(001) single film
Ysacco, Cedric. "Préparation et étude de nouveaux dinitroxydes comme agents de polarisation en polarisation dynamique nucléaire (PDN) en phase solide". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4819.
Texto completo da fontePreparation and study of new dinitroxydes as polarizing agents in dynamic nuclear polarization (DNP) in solid state. Nowadays, nuclear magnetic resonance (NMR) spectroscopy is one of the most important structure elucidation techniques in chemistry and biochemistry, NMR is also the underlying principle of magnetic resonance imaging (MRI). However, the use of NMR to investigate various materials or biological systems is still limited by its inherent low sensitivity. This arises from the relatively small size of the Zeeman interaction of the nuclear spins with an external magnetic field which leads to small Boltzmann polarizations (PI) and weak NMR signals. Dynamic Nuclear Polarization (DNP) is a prominent process to achieve a high non-equilibrium nuclear spin polarization by transferring to nuclear spins the higher electron spin polarization PS (PS/PI = 658 for 1H)) of unpaired electrons, belonging for example to stable free radicals. The past fifteen years has witnessed a renaissance in the use of DNP. This renewed interest is due to the outstanding work of the R. G. Griffin's group and the more recent work of the Ardenkjaer-Larsen's group. These authors have shown, among other, that with the use of trityl radicals or dinitroxides, PDN allowed to reach impressive signal enhancements for solid state and liquid NMR. The characteristics of the paramagnetic species used as polarizing agent play a pivotal role in the efficiency of a DNP process. In the course of our work we have performed the synthesis of five new dinitroxides, and through collaborations we tested their performance as polarizing agents for solid state PDN at 100 K, 9,4 T [263 GHz (RPE), 400 MHz (RMN)]
Renucci, Pierre. "Dynamique des polaritons de microcavité : cohérences optiques, cohérences de spin". Toulouse, INSA, 2001. http://www.theses.fr/2001ISAT0020.
Texto completo da fonteThis thesis is a contribution to the study, via ultrafast time-resolved optical spectroscopy, of optical and spin coherence phenomena involving polaritons in semiconductor microcavities. Coherent control of spin and population of polaritons is performed and we show that the scattering processes responsible for the loss of optical coherence are less efficient when the quasi-particule exhibits a strong photonic character. At low density, the analysis of spin coherences evidences a quenching of spin and alignment relaxation processes for negative detuning. At higher density, a strong non-linear mechanism is observed in the strong coupling regime. This effect is interpreted as stimulated parametric scattering, a coherent process which relies on a bosonic approach of interacting polaritons. Under transverse magnetic field, spin quantum beats are observed. Under resonant excitation, an electron-hole spin correlation is evidenced. To finish with, we show that the absolute value of the effective transverse electron Landé factor increases with the excitonic character of the quasi-particule
Chen, Liming. "Mesure de la corrélation de spin ttbar et de la polarisation du W dans les événements ttbar di-leptonique avec ATLAS". Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4132.
Texto completo da fonteThe Standard Model (SM) is a self-consistent theory that explains the elementary particles and interactions. To further confirm the SM theory, the Large Hadron Collider (LHC) was built at CERN to accurately validate the SM and search for the last SM particle, the Higgs boson. The multipurpose ATLAS detector is set up at one of the LHC interaction point. Nearly covering the whole solid angle, it detects particles over a wide range of energies with well-designed sub-detectors to record proton-proton (pp) collision up to a 14TeV center-of-mass energy and a luminosity of 1034 cm-2 s-1. A large number of ttbar events are produced and can be used for precise top quark property studies. Events that decay in exactly two opposite sign isolated leptons, at least two high transverse momentum jets and large missing energy are considered as di-leptonic t tbar signal events. To suppress the background, at least one of jets must be b-tagged. This channel has a lesser branching ratio with respect to other channels but its features allow to reject the QCD and W+jet backgrounds significantly.This thesis presents the differential measurement of ttbar spin correlation and W boson polarization using the 4.6 fb-1 7TeV pp collision data recorded in 2011. Both of the measurements apply Bayesian unfolding algorithm to extract the parton "true" spectrum from the "observed" one. The regularization is well studied in the different analyses. The combined unfolded spectrum of ttbar spin correlation agrees with the SM NLO prediction at differential level. The extracted W boson helicity combined results of F0, FL and FR fractions are also consistent with SM NLO values
Hélaine, Victor. "Mesure du moment dipolaire électrique du neutron : analyse simultanée de spin et analyse préliminaire de données". Caen, 2014. http://www.theses.fr/2014CAEN2059.
Texto completo da fonteIn the framework of the neutron Electric Dipole Moment (nEDM) experiment at the Paul Scherrer Institut (Switzerland), this thesis deals with the development of a new system of spin analysis. The goal here is to simultaneously detect the two spin components of ultra cold neutrons in order to increase the number of detected neutrons and therefore lower the nEDM statistical error. Such a system has been designed using GEANT4-UCN simulations, built at LPC Caen and then tested as part of the experiment. In parallel to this work, the 2013 nEDM data taken at PSI have been analysed. Finally, methods to recover magnetic observables of first interest to control nEDM systematic errors have been studied and possible improvements are proposed
Matozzo, Paola. "Helicene-porphyrin conjugates : exciton coupling and chiral-Induced spin selectivity". Electronic Thesis or Diss., Université de Rennes (2023-....), 2023. http://www.theses.fr/2023URENS108.
Texto completo da fonteDuring this thesis work, new helical molecular structures were prepared, their chiroptical responses, in particular the Exciton Coupling phenomenon, were studied and an intriguing property recently discovered, the Chiral-Induced Spin Selectivity, was investigated through different techniques. First, we illustrated two novel families of helicene-porphyrin conjugates, H6Pr1-3 and PrZnPhH6, prepared starting from one common helicenic core and porphyrin units. The first systems H6Pr1-3 were fully characterized and their photophysical and chiroptical properties were investigated experimentally and through theoretical calculations (thanks to our collaborators at University at Buffalo), unambiguously confirming the presence and effectiveness of EC chirality in helicenes through the very strong bisignate CD response in the Soret band along with slightly ECD-active Q-bands. Interestingly, these systems also revealed CPL activity which is still very rare in chiral porphyrins. This work was published in Chemical Communications. The second type of helicene-porphyrin conjugate displayed similar exciton chirality but with overall less intense chiroptical activities (both in ECD and in CPL). These results led us to further investigations on the Exciton Coupling of these systems: the role of the interchromophoric distance and of the conjugation were explored by changing the spacer between the chiral unit and the chromophores, as well as the metallic centers. A noteworthy enhancement was achieved with the family of molecules MPrH6: the 2,5-bis-ethynyl carbo[6]helicene is directly linked to the porphyrins avoiding the spacer, so that the interchromophoric distance was reduced. Therefore, the investigation of the properties was extended to the influence of the metal and several derivatives were prepared. Thanks to the promising results these derivatives were selected as preliminary candidates for CISS measurements through mc-AFM, in collaboration with Naaman’s group at Weizmann Institute of Science and spin polarization as high as 50% was obtained for the zinc complex. The last system MPrOMeH6, which includes a direct C-C bond between the chiral unit and the chromophore, was designed to optimize the distance between the metallic centers in the porphyrin core and to exploit the metal-metal interactions, specifically in magnetically-active centres like the V(IV)O derivative, that will be studied further through EPR spectroscopy. Overall, these results nicely illustrate how molecular engineering using functionalization with strongly polarizable units in close proximity enables the fine-tuning of the chiroptical signatures. This strategy also allows the access to CPL active porphyrin derivatives and opens up new opportunities for spintronics applications. In the last chapter we described the investigation of the spin filtering ability of helicene-based Self-Assembled Monolayer through the formation of a chemical bond with the surface: the helicenic unit was decorated with a redox moiety and a grafting unit, in order to obtain a proper orientation on the surface and to explore how the electron transfer reaction depends on the chirality through Spin Dependent Electrochemistry. More specifically, the bis-ethynyl hexahelicene has been functionalized with a conjugated ferrocene unit as redox probe on one side and i) a carboxylic acid (anchoring group for TiO2) for H6FeCOOH; ii) a thioacetate moiety (for Au surface) for H6FeSAc and ii) with a terminal alkyne (for Si-H surface). Promising preliminary results have been obtained for the H6FeCOOH and H6FeSAc derivatives but further characterizations are needed to explore the organization of the compounds on surface, the measurements are ongoing in collaboration with Naaman’s group. Thanks to the combination of the carbohelicene with chromophores and different grafting functions we are able to obtain promising materials with intriguing chiroptical properties and spin filtering ability
Faure-Vincent, Jérôme. "Transport tunnel polarisé en spin dans le système épitaxié Fe/MgO/Fe : interactions magnétiques et symétries électroniques". Vandoeuvre-les-Nancy, INPL, 2004. http://docnum.univ-lorraine.fr/public/INPL_T_2004_FAURE_VINCENT_J.pdf.
Texto completo da fonteMonocrystalline Fe(1 00)/MgO(1 00)/Fe(1 00) magnetic tunnel junctions (MT J), elaborated by Molecular Beam Epitaxy constitute ideal systems for validation of specific concepts related to the spin polarized transport in crystalline multilayers. The analysis of the band structure shows that the Fe(100) behaves as a half-metal with respect to the 01 electronic symmetry; this new concept of spin polarization/filtering in terms of symmetry being at the origin of huge magnetoresistive effects theoretically predicted in these systems. Our magnetotransport results validate the effects of electronic symmetry filtering. Moreover, they illustrate the influence of the electronic structure on tunnel transport, whose complex mechanisms go weil beyond the free- electron framework. The precise control of the bidimensional epitaxial growth of MgO allowed us the elaboration of extremely thin insulating barriers for which we provide a first experimental proof of magnetic coupling by spin polarized tunneling
Bataille, Alexandre. "Etude des propriétés physiques des films de Fe3O4 et de la polarisation en spin à l'interface Fe3O4/gamma-Al2O3". Paris 11, 2005. https://tel.archives-ouvertes.fr/tel-00085941.
Texto completo da fonteMagnetite Fe3O4 is a promising material for spintronics since band structure calculations predict it to be half-metallic, i. E. Fully spin-polarised at the Fermi level. One thus expects large magnetoresistance in magnetic tunnel junctions using Fe3O4 as electrode. We have grown 3 to 50 nm-thick Fe3O4 thin films onto γ-Al2O3 by molecular beam epitaxy. The films are single crystalline but comprise a large number of antiphase boundaries which are responsible for the magnetic anomalies of Fe3O4 thin films. We have qualitatively reproduced the magnetic behavior of our samples with a one-dimensionnal model, and compared the results with the characteristic size of the antiphase boundaries measured by a fractal analysis. We also studied the Verwey transitions of our thin films. The transition is not seen for thicknesses below 20 nm because of finite size effects and all samples show slow magnetization dynamics. We have also developed a growth method allowing us to deposit γ-Al2O3 epitaxially onto Fe3O4, and to control the stoichiometry at the interface. γ-Al2O3 thin films of thicknesses greater than 2 nm exhibit all the characteristics required for a tunnel barrier (electrical continuity, magnetic decoupling). We finally studied the spin polarization at the Fe3O4/γ-Al2O3 interface by too distinct methods. Direct measurements by spin resolved photoemission yields to -40 % for the spin polarization whereas the tunnel magnetoresistance is +3\% at room temperature for Fe3O4/ γ-Al2O3/Co
Berdot, Thibaut. "Mouvement du spin de l’électron dans les systèmes Fe/Ag(001) et MgO/Fe(001)". Strasbourg, 2011. https://publication-theses.unistra.fr/public/theses_doctorat/2011/BERDOT_Thibaut_2011.pdf.
Texto completo da fonteIn this work, we carried out spin-polarized electron reflection experiments. The infuence of the relaxation on the spin-dependant refleetion properties is shawn. First of ail, Fe/Ag(OOI) system has been studied. A precession angle of 180° has been obtained. This corresponds to the largest value that is possible to detect. We think that this effect can be explained by the relaxation of the lartice parameter during the growth. Ab initio calculations confirm this hypothesis. The second part of this work has been dedicated to the study of MgOlFe(OO1) system. A strong sensitivity of the spin motion angles ta the MgO thickness is shawn. According to Magneto-Optic Kerr effect experiments, this phenomenon cannot be explained by a modification of the Fe magnetization during the growth of MgO. However, other experimental studies demonstrate that MgO induces an out of-plane relaxation of the Fe surface layer. This relaxation could be of 10% for an MgO thickness of 0,35 ML and would induce strong changes of the electronic band structure. The qualitative agreement of our ab initia calculations with the ex peri- mental data suggests strongly that this effect is responsible for the variation of the spin motion angles and confirm that the MgOlFe(OO1) interface is important regarding the spin-dependant reflection properties
Pierre, Edgard. "Développement et optimisation d’un système de polarisation de neutrons ultra froids dans le cadre d’une nouvelle mesure du moment dipolaire électrique du neutron". Caen, 2012. http://www.theses.fr/2012CAEN2021.
Texto completo da fonteThe work presented in this thesis has been performed within the framework of an experiment located at the Paul Scherrer Institut (PSI) and dedicated to the measurement of the neutron electric dipole moment (nEDM). The expected sensitivity is 10^-27 e. Cm at the end of 2013. The experiment requires a polarized ultracold neutron (UCN) beam. A new polarizing system, a spin transport device and a spin reversal system have been developped for this purpose. Their study is detailed in this thesis. These systems are currently installed on the experiment. Thanks to magnetic field mappings done on the spectrometer, to magnetic field simulations using the Radia and Maentouch programs and also to Monte-Carlo simulations using the Geant4 software, the efficiency of the device has been calculated. The measured efficiency is 88. 5+/-0. 3%, which is slightly less than the expected value of 95%. Furthermore, this preliminary data taken in October 2011 allows the determination of some fundamental parameters of the experiment such as the filling, storage and longitudinal depolarization time constants of the spectrometer. These parameters are promising for the continuation of the experiment