Tesis sobre el tema "Moteurs à effet hall"
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Joncquières, Valentin. "Modélisation et simulation numérique des moteurs à effet Hall". Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0035/document.
Texto completoThe space propulsion has been a political issue in the midst of the Cold War and remains nowadays a strategic and industrial issue. The chemical propulsion on rocket engines is limited by its ejection velocity and its lifetime. Electric propulsion and more particularly Hall effect thrusters appear then as the most powerful and used technology for space satellite operation. The physic inside a thruster is complex because of the electromagnetic fields and important collision processes. Therefore, all specificities of the engine operation are not perfectly understood. After hundreds of hours of tests, thruster walls are curiously eroded and electromagnetic instabilities are developping within the ionization chamber. The measured electron mobility is in contradiction with the analytical models and raises issues on the plasma behavior inside the discharg chamber. As a result, the AVIP code was developed to provide a massively parallel and unstructured 3D code to Safran Aircraft Engines modeling unsteady plasma inside the thruster. Lagrangian and Eulerian methods are used and integrated in the solver and my work has focused on the development of a fluid model which is faster and therefore better suited to industrial conception. The model is based on a set of equations for neutrals, ions and electrons without drift-diffusion hypothesis, combined with a Poisson equation to describe the electric potential. A rigorous expression of collision terms and a precise description of the boundary conditions for sheaths have been established. This model has been implemented numerically in an unstructured formalism and optimized to obtain good performances on new computing architectures. The model and the numerical implementation allow us to perform a real Hall effect thruster simulation. Overall operating properties such as the acceleration of the ions or the location of the ionization zone are captured. Finally, a second application has successfully reproduced azimuthal instabilities in the Hall thruster with the fluid model and justified the role of these instabilities in the anomalous electron transport and in theerosion of the walls
Guichaoua, Lise. "Nouveaux matériaux de confinement de plasma pour les moteurs à Effet Hall". Limoges, 2013. http://www.theses.fr/2013LIMO4056.
Texto completoFonblanc, Diane. "Nouvelles céramiques de confinement de plasmas à base de BN issues de précurseurs organométalliques : application aux moteurs à effet Hall". Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0076.
Texto completoThe main objective is here to develop a new generation of ceramic materials used for plasma confinement in Hall-effect thrusters using the PDCs (polymer-derived ceramics) route. A state of the art of the different confinement materials and a review of the previous work done on this topic allowed to determine the key parameters of such materials and to move towards the use of preceramic polymers as precursors of the materials envisaged. After having detailed the various protocols used to chemically modify a commercial polymer with boron, to shape the compounds obtained and then to convert the polymers into ceramics bypyrolysis, Si-B-(C)-N dense ceramic pieces have been produced with various boron content. A complete study from the chemical structure of the polymers to the properties of the resulting ceramics allowed selecting the optimal formulation of the polymer as a ceramic precursor. c-BN/Si-B-(C)-N composites were then prepared by filler addition, then shaped and characterized before a scale-up to prepare engine-size ceramic rings. The last part consists of an opening on the use of the PDCs route for the realization of dense Si-Al-(C)-N pieces of controlled composition, with a study of the impact of aluminum on the polymers andceramics properties
Doulazmi, Mustapha. "Etude expérimentale comparative de différentes méthodes de mesure et d'acquisition d'amplitude angulaire : application en rééducation des handicapés moteurs". Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPL097N.
Texto completoVaudolon, Julien. "Electric field determination and magnetic topology optimization in Hall thrusters". Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2026/document.
Texto completoElectric propulsion is facing new challenges. Recently, the launch of "all-electric" satellites has marked the debut of a new era. Going all-electric now appears as an interesting alternative to conventional systems for telecom operators. A laser spectroscopy technique was used during this research to investigate the ion velocity distribution dynamics. The different methods for determining the electric field in Hall thrusters were exposed. Two unstable ion regimes were identified and examined. Measurement uncertainties using electrostatic probes were assessed. Planar probed have been designed and tested. A thorough investigation of the influence of the magnetic field parameters on the performance of Hall thrusters was performed. The wall-less Hall thruster design was presented, and preliminary experiments have revealed its interest for the electric propulsion community
Tiberj, Antoine. "Matériau SOI pour capteur à effet Hall". Montpellier 2, 2003. http://www.theses.fr/2003MON20012.
Texto completoCoche, Philippe. "Modélisation cinétique d’un propulseur à effet Hall". Toulouse 3, 2013. http://thesesups.ups-tlse.fr/1995/.
Texto completoHall effect thrusters are used for station-keeping of satellites in geostationary orbit. The originality of this kind of thruster is the use of a magnetic field which traps the electrons and creates a high electric field region. In this region, the ions are accelerated and extracted from the plasma to provide a thrust. Electron transport across the magnetic field lines is a major issue in predicting the thruster performance. Several transport mechanisms as collision phenomena and plasma turbulence have been identified to play a role but their exact contribution is still not clear. Based on two numerical particle models ("Particle-In-Cell"), composed of an explicit and implicit trajectory-tracking schemes, this work thesis aims at analyzing the proceeding of a discharge in order to isolate the transport mechanisms of electrons. It also aims at providing a better understanding of the plasma turbulence on the discharge behavior. We emphasize the strong unstationnary character of the discharge. We also study a particular transport mechanism, governed by turbulence and volumic collisions, using a particle-test numerical model
Couturaud, Olivier. "Effets tunnels dans des nano-capteurs de Hall". Montpellier 2, 2008. http://www.theses.fr/2008MON20122.
Texto completoAs part of this thesis, we studied a family of Hall effect sensors , composed of submicrometers Hall cross and microgradiometers made from optimized quantum wells. The first one left this thesis is dedicated to manufacture and to characterization of sensors. They will study everything of manners the resistance of contacts and the depletion length restricting the functioning of sensors In second part, we study the tunnel effect of electrons between the edges of the sample. In the presence of a quantizing magnetic field, at the transition between two quantized Hall plateaus, a succession of sharp peaks is detected in the Hall signal RH and in the longitudinal resistance RL. The peaks appearing on the high-í side of the RL transition appear to be different from the peaks appearing on the low-í side. They mainly differ by their temperature dependence. On the high-í side of the RL transition, the temperature evolution of the peaks is typical for resonant tunneling through a single state in one of the antidots that are progressively formed when the initially occupied LL is emptied. On the low í of the transition, by contrast, the temperature dependence is different. This may be related to the asymmetry of the density of states
Papic, Zlatko. "Effet Hall quantique fractionnaire dans des systèmes multicomposantes". Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00624760.
Texto completoPerez, Luna Jaime. "Modélisation et diagnostics d'un propulseur à effet Hall". Toulouse 3, 2008. http://www.theses.fr/2008TOU30155.
Texto completoOne of the greatest challenges in space exploration is to develop spacecrafts capable of covering great distances with little fuel. Electric thrusters, among which is the Hall effect thruster, are capable of this thanks to their high exhaust velocity. During my PhD, I have tried to understand the physics involved in these thrusters, by means of numerical models and accurate diagnostics. My hosting group has been working on hybrid modeling of these thrusters for about ten years. However, the electron fluid description in such models is still a challenge. One of the problems of the fluid model is the difficulty of solving the fluid equations in 2D. This first problem has been overcome by using a new algorithm. This algorithm makes it now easier to study thrusters with complex magnetic fields. The second problem concerns electron transport which is not well understood. A deep study of a fully particle model in the axial and azimuthal directions has shown that an azimuthal electric field wave, present in the thruster, enhances the electron transport. Also, I have developed a new method to extract the electric field and ionization term profiles from laser spectroscopy measurements. The comparison between these results and those obtained with our hybrid model shows the limit of the electron transport description used until now. This comparison has also shown a possible path to follow in order to correctly describe the electron transport in hybrid models for Hall effect thrusters
Djerbi, Ridha. "Effet Hall anormal du composé à fermions lourds CeRu2Si2 sous pression : résistivité, effet Hall et magnétorésistance de ses alliages avec le lanthane". Grenoble 1, 1989. http://www.theses.fr/1989GRE10016.
Texto completoDominguez, Didier. "Application de l'effet Hall quantique en métrologie conservation de l'ohm et détermination de la constante de structure fine /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376046031.
Texto completoLaveder, Dimitri. "Dynamique tridimensionnelle d'ondes d'Alfvén en magnétohydrodynamique avec effet Hall". Nice, 2001. http://www.theses.fr/2001NICE5627.
Texto completoAlfvén waves propagating in plasma along an ambient magnetic field are studied in the framework of the magnetohydrodynamics including the Hall Effect (Hall-MHD), which extends the usual MHD to scales comparable to the ion inertial length and to frequencies close to the ion-cyclotron resonance. The validity of Hall-MHD, along with the properties of these waves which in this frequency domain become dispersive, that are exact solutions of the Hall-MHD equations, are subject to various instabilities, giving rise to strong nonlinear phenomena. After discussing the one-dimensional case, attention is paid to three-dimensional configurations. The transverse instability and the collapse of a small-amplitude Alfvén wave resulting in the formation of intense magnetic filaments, predicted by the Nonlinear Schrödinger model and then shown to also occur within the full Hall-MHD system. This “filamentation” phenomenon is nevertheless modified by the presence of quasi-transverse instabilities that inhibits the field amplification and favor the generation of strong density gradients. When the Alfvén wave generates a quasi-incompressible flow at large longitudinal scales that, after averaging on the scale of the wave, is described by the « reduced-MHD » model. Increasing the dispersion, this quasi-two-dimensional flow is replaced by a fully three-dimensional turbulence
Hassaïne, Mokhtar. "Théories de Chern-Simons et l'effet Hall quantique". Tours, 2000. http://www.theses.fr/2000TOUR4037.
Texto completoTherme, Pierre. "Effet des apprentissages moteurs sur les conduites de l'enfant psychotique". Aix-Marseille 2, 1989. http://www.theses.fr/1989AIX22041.
Texto completoDelgard, Adrien. "Inductances cinétiques et capacités quantiques en régime d'effet Hall dans les conducteurs de Hall". Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS063/document.
Texto completoIn a two dimensional electron gas, low energy transport in presence of a magnetic field occurs in chiral 1D channels located on the edges of the sample. In the Buttiker’s description of a.c. quantum transport, the “emittance” determines the amplitude of the imaginary part of the admittance, whose sign and physical meaning are determined by the topology: in the case of an Hall bar the emittance is an inductance, while it is a capacitance in the case of a corbino sample.Emittance is related to the density of states and to the drift velocity of carriers. So quantum capacitances and inductances give access to the velocity of the charge carriers through the transit time/dwell time of charges in the quantum circuit.We performed systematic studies on samples with different topologies : Hall bars and Corbino disks. Our samples have no gate, which makes us able to observe the inner properties of the quantum states. We have measured the ac admittance of quantum Hall samples using standard electrical techniques in the [0.1-100] kHz frequency range, at low temperature under high magnetic field.We measured kinetic inductances of Hall bars with three contacts and showed the perfect inductive nature of edge states. We measured quantum capacitances of Corbino disks as well. In both topologies we observed the close relation between the emittance and the density of states. We show also the proportionality between the emittance and the length of the circuit. We obtain the transit time of electrons through the device, and finally the drift velocity on edge states.At high temperature we still observe an inductive behavior of Hall bars, induced by increase of energy relaxation time with magnetic field
Papic, Zlatko. "Fractional quantum hall effect in multicomponent systems". Paris 11, 2010. http://www.theses.fr/2010PA112121.
Texto completoWe study a number of fractional quantum Hall systems, such as quantum Hall bilayers, wide quantum wells or graphene, where underlying multicomponent degrees of freedom lead to the novel physical phenomena. In the quantum Hall bilayer at the filling factor ν=1 we study mixed composite boson-composite fermion trial wave functions in order to describe the disordering of the exciton superfluid as the bilayer distance is increased. We propose wave functions to describe the states of the bilayer for intermediate distances and examine their properties. At the bilayer total filling ν=1/2 and ν=2/5 we study the quantum phase transition between the multicomponent Halperin states and the polarized, Abelian and non-Abelian, phases as the tunneling term is varied. We use a combination of exact diagonalization and the effective BCS model to study the transitions. Furthermore we introduce a realistic model of the wide quantum well which is used to examine even-denominator quantum Hall states at ν=1/2 and ν=1/4 in the lowest Landau level. Finally, we explore some possibilities for the fractional quantum Hall effect in graphene based on the multicomponent picture of spin and valley degrees of freedom
Vermot-Gaud, Jacques Néel Louis. "Etude d'une application de l'effet Hall à la réalisation d'éléments de circuits logiques". S.l. : Université Grenoble 1, 2008. http://tel.archives-ouvertes.fr/tel-00277341.
Texto completoBrun-Picard, Jérémy. "Une nouvelle génération d'étalons quantiques fondée sur l'effet Hall quantique". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS549/document.
Texto completoThe future International System of Units, based on fundamental constants, will allow to take full advantage of the quantum standards of resistance, current and voltage that are linked to the planck constant and the elementary charge only.In this thesis, we have developed and studied a resistance standard based on the quantum Hall effect in graphene obtained by chemical vapor deposition (propane/hydrogen) on silicon carbide substrate. For the first time we were able to show that a graphene resistance standard could operate at more practical experimental conditions than its counterpart in GaAs/AlGaAs, ie at higher temperatures (T⋍10 K), weaker magnetics fields (B ⋍ 3,5 T) and larger measurement currents (I⋍500 μA). From an understanding and improvement perspective, we have analyzed the fabrication process of the Hall bar and its reproducibility, tested a method to modify the electronic density, and investigated the quantum Hall effect dissipation mechanisms.In a second part, we have demonstrated that it was possible torealize a programmable and versatile quantum current source from the elementary charge, by combining the two quantum standards of voltage and resistance in a quantum circuit integrating a cryogenic current comparator. Currents were generated in the range from 1 μA to 5 mA, with a relative uncertainty never achieved before of 10⁻⁸. We have also showed that this current standard, realizing the new definition of the ampere, could be used to calibrate an ammeter
Regnault, Nicolas. "Solutions exactes de la gravité réduite : effet Hall quantique de spin". Phd thesis, Université Paris Sud - Paris XI, 2002. http://tel.archives-ouvertes.fr/tel-00001360.
Texto completoThiébaut, Nicolas. "Effet Hall quantique fractionnaire dans la bicouche et le puits large". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112050/document.
Texto completoDue to technological advances in the manufacture of semiconductors enable, in it possible since the early 80s to create devices in which electrons are strongly confined in a plane, thus effectively realizing a two-dimensional electron system. The application of a strong perpendicular magnetic field to this system led to the observation of the integer quantum Hall effect (QHE) in 1980 and fractional QHE in 1982. Under a strong magnetic field the energy spectrum of the two-dimensional electrons is quantified in Landau levels that are macroscopically degenerate, and the behavior of the system is governed by the filling factor of Landau levels. The integer QHE appears around magnetic field values which correspond to an integer filling of the Landau levels, while the fractional equivalent is obtained around certain fractions of the filling factor ν (ν = 1/3, 2/5, 5 / 2, ...). Although for integers values of ν is the individual behavior of electrons dictates the behavior of the system, the fractional filling factors the electronic correlations dominate. Because of those strong correlations, the underlying fractional QHE motivates an important experimental and theoretical research effort since its discovery. Indeed, in the fractional regime the strong correlations induce novel properties such as the existence fractionally-charged quasiparticles, but they also make the theoretical description of the system laborious. In 1983 Robert Laughlin proposed a variational wave function model for the description of the QHE observed at fractional filling ν = 1/3. He discussed the validity of this trial wave function in a comprehensive numerical study of interactions between electrons. The success of this method made it a paradigm, and many test wave functions have been proposed since then for the explanation of quantum Hall effects observed with other fillings factors. In particular, the wave function of Moore and Read is relevant for the description of the QHE observed at half-filling the second Landau level. This suggests the existence of non-Abelian quasiparticles with potential applications in topologically-protected quantum computing. QHE has also been observed at half filling the lowest Landau level, but the nature of the underlying quantum state is still debated; it is observed that in bilayer systems and wells wide. The large wells, which are the focus of this thesis, refer to systems in which the thickness of the two-dimensional electron system cannot be trivially neglected and usually corresponds to a thickness of about 100 nm. Due to the confinement potential felt by the electrons, their energy levels in the direction of confinement are quantized in sub-bands. In a narrow well only the lowest subband is populated and the corresponding degree of freedom is thus frozen, but in a wide well the excited sub-bands are relevant. Under these conditions fractional QHE at half-filling can also result from the stabilization of a two-state components that also populates the excited sub-band. The corresponding trial state, proposed by Bertrand Halperin in 1983, competes with the state of Moore and Read. In addition to these two states, a metal composite fermion state is a relevant trial state as well as an electronic Wigner crystal, the latter behaving as an insulator. The competition between these states is refered by a variational Monte-Carlo study combined with exact diagonalization calculations. The nature of the state that is stabilized depends on the nature of the confinement potential. In this PhD thesis three confinement potentials are studied: the bilayer, the wide well, and the wide well in the presence of an external bias
Bocquillon, Erwann. "Electron quantum optics in quantum Hall edge channels". Paris 6, 2012. http://www.theses.fr/2012PA066692.
Texto completoThis thesis is devoted to the implementation of quantum optics experiments in a ballistic quantum conductor, with single charge resolution. A mesoscopic capacitor produces on-demand single-electron excitations in the outermost edge channel of quantum Hall effect. We measure current fluctuations after partitioning of excitations on an electronic beamsplitter, in analogy with the Hanbury-Brown & Twiss experiment, so as to unveil neutral excitations (electron/holes pairs) that can accompany the emission of the charge. Thermal excitations in the Fermi sea are then responsible for two-particle interferences that yield information on the energy distribution of the generated quasiparticles. Using two independent and synchronized sources, we generate two indistinguishable quasiparticles that interfere on a beamsplitter as in the Hong-Ou-Mandel experiment. The visibility of this phenomenon could be limited by decoherence of the wavepackets due to interactions with the environment and especially with other co-propagating edge channels. By measuring the capacitive coupling between two co-propagating edge channels, we characterize the effects of Coulomb interaction on propagation and highlight a neutral mode of propagation. These experiments constitute the first implementations of electron quantum optics experiments with single charges. They pave the way to more complex experiments such as the tomography of a mono-electronic wavepacket
Taillefumier, Mathieu. "Quelques mécanismes non conventionnels de l'effet Hall anormal". Phd thesis, Université Joseph Fourier (Grenoble), 2006. http://tel.archives-ouvertes.fr/tel-00012052.
Texto completopremières parties sont axées sur l'étude de quelques mécanismes
intrinsèques de l'effet Hall anormal. Nous montrons notamment que la
diffusion des porteurs de charge par des impuretés ou des défauts
donne une contribution intrinsèque non négligeable à l'effet Hall
anormal. Nous proposons ensuite une expérience, basée sur un réseau de
nanocylindres magnétiques, placé au dessus d'un gaz d'électrons
bidimensionnel, dans laquelle les contributions intrinsèques de
l'effet Hall anormal sont clairement identifiables et contrôlables.
Enfin, nous abordons le problème du mécanisme de chiralité de spin
proposé pour expliquer l'effet Hall dans le composé pyrochlore
Nd$_2$Mo$_2$O$_7$. En utilisant un modèle de gaz sur réseau ainsi
qu'une configuration magnétique non colinéaire (chirale), nous
montrons que la conductivité transverse a une dépendance complexe par
rapport à la chiralité de spin.
La dernière partie de ce manuscrit est dédiée à l'étude de quelques
propriétés des gaz d'électrons soumis à un champ magnétique
inhomogène. Après un bref rappel sur la dynamique d'électron en
présence d'un gradient de champ magnétique constant, nous abordons le
problème d'un champ magnétique périodique spatialement. En calculant
quelques états de Bloch aux points de haute symétrie, nous montrons qu'il
existe des états pour lesquels les électrons sont localisés au
voisinage des lignes de champ nul. Le calcul des courants de
probabilité montre que ces états sont porteurs de courants permanents
dont l'origine est liée aux inhomogénéités du champ magnétique au
voisinages des lignes de champ nul.
Moukila, Henri Serge. "Contribution à la caractérisation des semi-conducteurs par une méthode hyperfréquence". Toulouse, INPT, 1986. http://www.theses.fr/1986INPT020H.
Texto completoBAZZALI, DANIEL. "Calculs d'energies dans le premier niveau de landau". Cergy-Pontoise, 1999. http://www.theses.fr/1999CERG0075.
Texto completoRalko, Arnaud. "Particules identiques bidimensionnelles fortement corrélées : nouveaux aspects". Paris 11, 2003. http://www.theses.fr/2003PA112128.
Texto completoThe aim of this thesis is to establish and to analyse a natural mechanism which allows a bi-dimensionnal system of identical charged particles, for example in the fractional quantum Hall effect picture, to have an anyonic behaviour (intermediate statistics between the bosonic and the fermionic cases). The two particles problem with quadratic perpendicular confinements (magnetic and/or harmonic) is exactly solved with the help of the bi-confluent Heun functions. Our states display anyonic features, induced by the competition between confinement forces and Coulomb repulsion. A complete analysis exhibits divergent radial distribution of probability, Klauder phenomenon or anyonic trajectories. Depending of the type of the confinement, these particles have special behaviours in the ground state energy : anyonicity yields successive transitions of states which give discontinuities in the magnetization (as it can be seen in numerical studies of the litterature). For three particles, in the Taut's scheme, we find solutions with same characteristics of the two particles-states. An ad hoc generalization for N particles is given : these generalized states have always anyonic behaviour and contain the Laughlin's quantum Hall states in their structure. In the Random Phase Approximation, we verify that the system is equivalent to a free-like anyons one (Jain's ansatz). Finally, the case of one charged particle on a sphere of radius R, under a constant radial magnetic field and interacting with a central charge placed at the north pole is treated. We obtain exact solutions in terms of Heun functions as well as the energy spectrum. The different regimes are studied and in the R → ∞ limit, one recovers the local planar solutions
Vanhaverbeke, Antoine. "Corrélations entre hétéogénéités magnétiques et transport électrique dans des nanostructures". Paris 11, 2005. https://tel.archives-ouvertes.fr/tel-00121862.
Texto completoRossi, Alberto. "Développement d'outils d'optimisation dédiés aux circuits magnétiques des propulseurs à effet Hall". Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19234/1/ROSSI_Alberto_public.pdf.
Texto completoRIGAL, LAURENT. "Effet hall quantique : excitation de texture de spin et diagramme de phase". Toulouse, INSA, 1999. http://www.theses.fr/1999ISAT0030.
Texto completoKnothe, Angelika Hildegard. "Quantum Hall Ferromagnetism in Multicomponent Systems". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS595/document.
Texto completoThe present thesis deals with two-dimensional quantum Hall systems in which the electrons may be endowed with multiple discrete degrees of freedom. Quantum Hall ferromagnetism provides a framework to treat these electronic degrees of freedom as effective spins and isospins of the electrons. Different orderings of the electronic spins and isospins then characterise different possible phases of the system. Using this analogy, various aspects of the two-dimensional systems in the quantum Hall regime are explored theoretically by studying the corresponding spin and isospin structure. The work consists of three parts in which different two-dimensional materials are investigated in the quantum Hall regime. In any of the three projects presented within this thesis, Hartree Fock theory is employed to study the multicomponent spin and isospin system at the mean field level. All our considerations are stimulated directly by experimental results. We draw our main motivation from the key idea that purely theoretical investigations of abstract models may us allow to obtain deeper insights into the physical processes and mechanisms that determine the properties of the materials. This, in turn, we hope to allow conclusions about the experiments by providing possible explanations of the phenomena observed, as well as prospects for future investigations
Guignard, Jérémie. "Etude de l'effet Hall quantique dans le graphène exfolié en vue d'une application en métrologie quantique". Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00664374.
Texto completoLian, Yunlong. "Skyrmions in quantum Hall systems". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS308/document.
Texto completoThis thesis studies skyrmions in the SU(4) quantum Hall ferromagnet. Skyrmions are localized textures in ferromagnetic systems. The graphene monolayer in a strong magnetic field can be viewed as a ferromagnet with electron spin and Dirac-valley pseudospin – Landau levels with different spin and valley are close in energy and form well-separated groups. Within one group, the Coulomb interaction has a manifest SU(4)-invariant form. The model of skyrmions used in this thesis is a classical, static field theory obtained from the variational principle. The model has phenomenological parameters, which depend on substrates and other experimental settings. Based on symmetry analysis, I propose the ansatz for skyrmions at quarter-filling and halffilling of the N = 0 Landau level in graphene monolayer. Energy minimization of single skyrmions is then performed to determine the parameters in the skyrmion ansatz, resulting in different types of spin-valley skyrmions at both filling factors. Large skyrmions are identified in certain ranges of the phenomenological parameters, where the ferromagnetic background of the skyrmion undergoes a phase transition. Single-mode spin-valley waves are also analyzed to characterize the SU(4) quantum Hall ferromagnet. A particular example shows instability of the ferromagnetic ground state
Nguyen, Thanh Nam. "Fabrication et études des propriétés magnétiques et de transport de films de GdCo, de multicouches à base de GdCo et de multicouches Fe/Cr". Université Joseph Fourier (Grenoble), 2007. http://www.theses.fr/2007GRE10236.
Texto completoCharlebois, Serge. "Étude expérimentale des excitations topologiques de l'effet Hall quantique à [nu] = 1 dans les hétérostructures semiconductrices à double puits quantique". Sherbrooke : Université de Sherbrooke, 2002.
Buscar texto completoFavre, Jacques. "Etude des défauts d'irradiation par mesure in situ de l'effet Hall dans les semi-conducteurs à faible largeur de bande interdite /". Saclay : Commissariat à l'énergie atomique, 1991. http://catalogue.bnf.fr/ark:/12148/cb354155298.
Texto completoChaput, Laurent Pecheur Pierre. "Calcul des propriétés de transport de matériaux thermoélectriques". Vandoeuvre-les-Nancy : INPL, 2006. http://www.scd.inpl-nancy.fr/theses/2006_CHAPUT_L.pdf.
Texto completoMadon, Benjamin. "Etude des effets magneto-transverses dans les matériaux ferromagnétiques : effets Righi-Leduc planaire et anomal et géométrie Corbino". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX029/document.
Texto completoAbstract: During this PhD we studied different electric, thermal and thermoelectric properties. For instance, we characterized the anomalous and planar Righi-Leduc effects which are the thermal equivalent of the anomalous and planar Hall effects. These effect have to be taken into account when interpreting spin Seebeck measurements.We used the technics that we developped during this study to look at the Nernst effect in InSb. We developped, a carrier mobility distribution model to explain its non-linearity at fields around 1T.We built a ferromagnetic resonance experiment in order to study the impact of thermal and thermoelectric properties in spin pumping effect.Lastly, we studied electric transport in the Corbino geometry. Corbino geometry is the one of a disc where there are no free boundaries where electric charges can accumulate. This causes the apparition of an orthoradial Hall current which consequence is the increase of resistance of the disc. We showed an increase of resistance in the Corbino geometry in CoGd and CoTb originating from anomalous Hall effect. Despite the anomalous Hall effect does not dissipate, it produces an orthoradial current which dissipates. We also found in permalloy that this increase of resistance is counterbalanced by a decrease of resistance due to the anisotropic magnetoresistance.The similarity between anomalous Hall effect and spin Hall effect which share a common microscopic origin implies that we expect in platinum the apparition of an orthoradial spin current without possibility for the charges to accumulateition. This current should dissipate just the way it does for the anomalous Hall effect.The study of this spin current will be the topic of a futur study
Trifu, Alexandru Vladimir. "Mesures de couples de spin orbite dans des héterostructures métal lourde/ferromagnet à base de Pt, avec anisotropie magnétique planaire". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY044/document.
Texto completoMoore’s law is based on empirical observation and states that every two years approximately, the number of transistors in dense integrated circuits doubles. This trend has held up well in the past several decades (1970s and onwards). However, the continuous miniaturisation of transistors brings about a significant increase in leakage current, which increases the stand-by power consumption. This energy loss has become a major problem in microelectronics during the last several years, making the development of new technologies more difficult. One of the solutions that can address this issue is to place non-volatile memory elements inside the chip, that retain the configuration of the transistor during power-off and allow to restore it at power-on. Magnetic Random Access Memories (MRAM) are considered by the ITRS as a credible candidate for the potential replacement for SRAM and DRAM beyond the 20 nm technological node. Though the basic requirements for reading and writing a single memory element are fulfilled, the present approach based on Spin Transfer Torque (STT) suffers from an innate lack of flexibility. The electric current drives the magnetization switching of a free ferromagnetic layer by transferring angular momentum from an adjacent ferromagnet. Therefore, STT-based memory elements are two terminal devices in which the “pillar” shape defines both the “read” and the “write” current paths. Independent optimisation of the reading and writing parameters is therefore difficult, while the large writing current density injected through the tunnel barrier causes its accelerated ageing, particularly for fast switching. Consequently, the integration of MRAM into semiconductor technology poses significant difficulties.Recent demonstrations of magnetization switching induced by in-plane current injection in heavy metal (HM)/ferromagnet (FM) heterostructures have drawn increasing attention to spin-torques based on orbital-to-spin momentum transfer induced by Spin Hall and interfacial effects (SOTs). Unlike STT-MRAM, the in-plane current injection geometry of SOT-MRAM allows for a three-terminal device which decouples the “read” and “write” mechanisms, allowing the independent tuning of reading and writing parameters. However, an essential first step in order to control and optimise the SOTs for any kind of application, is to better understand their origin. The origin of the SOTs remains one of the most important unanswered questions to date. While some experimental studies suggest a SHE (Spin Hall Effect)-only model for the SOTs, others point towards a combined contribution of the bulk (SHE) and interface (Rashba Effect and Interfacial SHE). At the same time, many studies start with a SHE only hypothesis and do not consider interfacial effects. Furthermore, there are not so many systematic studies on the effects of interfaces. This thesis tries to fill in this gap, by providing a systematic study on the effects of interfaces on the SOTs, in Pt-based NM/FM/HM multilayers with in-plane magnetic anisotropy. For this purpose, this thesis explores three different, but related avenues. First, we changed the interface/bulk effect ratio by modifying the Pt thickness and following the evolution of the SOTs. Second, we explored different HM/FM/NM combinations, in order to study different interfaces. And third, we changed the properties of the interfaces by changing the crystallographic structure of the interface and by oxidation. The measurement technique and associated data analysis method, as well as the theoretical considerations needed for the interpretation of the results are also detailed in this manuscript
Wahl, Claire. "Décohérence et intéractions dans les dispositifs d' optique quantique électronique". Electronic Thesis or Diss., Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4033.
Texto completoWe consider an electronic analog of the Hong-Ou-Mandel (HOM) interferometer, where two single electrons travel along opposite chiral edge states and collide at a Quantum Point Contact. Studying the current noise, we show that because of interactions between co-propagating edge states, the degree of indistinguishability between the two electron wavepackets is dramatically reduced, leading to reduced contrast for the HOM signal. This decoherence phenomenon strongly depends on the energy resolution of the packets. Insofar as interactions cause charge fractionalization, we show that charge and neutral modes interfere with each other, leading to satellite dips or peaks in the current noise. Our calculations explain recent experimental results where an electronic HOM signal with reduced contrast was observed
GOERBIG, Mark Oliver. "Etude theorique des phases de densite inhomogene dans les systemes a effet Hall quantique". Phd thesis, Université Paris Sud - Paris XI, 2004. http://tel.archives-ouvertes.fr/tel-00007072.
Texto completoGoerbig, Mark Oliver. "Etude théorique des phases de densité inhomogène dans les systèmes à effet Hall quantique". Paris 11, 2004. http://www.theses.fr/2004PA112109.
Texto completoThe issue of this thesis is the study of the different electron-solid and quantum-liquid phases, which are found in two-dimensional electron systems under a perpendicular magnetic field. The formation of these phases is due to the strong Coulomb repulsion between the electrons of a partially filled Landau level. The energy calculations of the thesis allow one to understand recent experimental investigations, which have revealed a non-monotonic behaviour of the transverse (Hall) resistance. This effect is due to multiple first-order transitions between the competing phases. The derivation of a model of interacting composite fermions - the quasiparticles responsible for the fractional quantum Hall effect - furthermore allows for the study of new phases, which occur at high magnetic fields. Most saliently, a recently observed fractional quantum Hall effect at unusual values of the field has been identified as the manifestation of a second generation of composite fermions
Albarède, Luc. "Etudes expérimentales d'un propulseur à effet Hall : comportement stationnaire et dynamique du flux d'électrons". Orléans, 2004. http://www.theses.fr/2004ORLE2070.
Texto completoCavalier, Jordan. "Modèles cinétiques et caractérisation expérimentale des fluctuations électrostatiques dans un propulseur à effet Hall". Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0130/document.
Texto completoThe study of turbulent phenomena that grow at the exit plane of the Hall thruster is required to modelize the anomalous transport (in contrast to the diffusion transport) of electrons across the magnetic field lines. The dispersion relations of two instabilities that can be responsible for this transport have been mesured at millimetric scales by mean of the collective light scattering diagnostic. The aim of the thesis is to describe them theoretically as well as experimentally, improving the understanding of the Hall thruster transport. In the thesis, an instability that propagates principally azimuthally is caracterized as the ExB electron drift instability and an analytical model that describes the experimental frequency is derived and validated. In addition, the manuscript presents an original method to unfold the signal of the collective scattering diagnostic from the instrumental function of this mode. Once corrected, the experimental dispersion relations can be adjusted by the frequency given by the analytical model, allowing to measure experimentally and in an original way the electron temperature and density in the energetic ion jet of the Hall thruster plasma. The second instability that is mainly propagating in the axial direction is caracterized as the two-stream instability between the simply and doubly charged ions of the plasma
Oudini, Noureddine. "Modélisation d'une source d'ions à effet Hall pour des applications de traitement de surface". Phd thesis, Université Paul Sabatier - Toulouse III, 2011. http://tel.archives-ouvertes.fr/tel-00641383.
Texto completoOudini, Noureddine. "Modélisation d'une source d'ions à effet Hall pour des applications de traitement de surface". Phd thesis, Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1368/.
Texto completoIn End-Hall Ion Source (EHIS) an ion beam is extracted from a magnetized plasma without extracting grids. The EHIS sources are mainly used in surface processing technology. In these sources, the plasma is generated by applying an external voltage between the electrodes in order to create a DC discharge. The presence of a magnetic field parallel to a conical anode reduces the electron mobility across the magnetic field lines. As a consequence, an electric field forms in the anode region of the plasma in order to insure electron transport towards the anode. Ions are generated inside the EHIS by electron impact ionization of the injected argon atoms, are extracted from the source by the electric field formed along the anode, and form an ion beam which is used in different surface processing applications. The End-Hall Ion Sources have been optimized empirically and the physics of these sources is far from being clearly understood. In order to improve our understanding of the EHIS operation, we have developed an axisymmetric self-consistent model based on a particle description of argon atoms and ions, and on a fluid model of electron transport. Electrons are supposed to be in Boltzmann equilibrium along the magnetic field lines and plasma quasi-neutrality is assumed. The electric field is therefore obtained from a current continuity equation and not from Poisson equation. The model has been able reproduce most of the features of the source and has helped clarifying a number of questions related to the physics of EHIS
Fuchey, Eric. "Electroproduction de pions neutres dans le Hall A au Jefferson Laboratory". Clermont-Ferrand 2, 2010. http://www.theses.fr/2010CLF22037.
Texto completoDesrat, Wilfried. "Résonance magnétique nucléaire détectée résistivement sur des hétérostructutres GaAs/GaAlAs en régime Hall quantique". Toulouse, INSA, 2002. http://www.theses.fr/2002ISAT0006.
Texto completoChepelianskii, Alexei. "Non equilibrium transport and chirality in mesoscopic physics". Paris 11, 2010. http://www.theses.fr/2010PA112324.
Texto completoDuring my thesis I investigated the signatures of chiraIity in the electrical transport of mesoscopic systems. This led me to study the magnetic field symmetry of nonlinear transport. I showed that even for two terminal devices, nonlinear transport has rich magnetic field symmetry properties, with possible completely antisymmetric behavior. However the symmetry properties are not determined by chirality alone. For this reason I proposed photo-magnetism as a more selective probe for chirality and started a new experiment to detect this effect in quantum dots using a Hall magnetometer. This research exhibited subtle dynamical effects of transport in ballistic Hall bars under irradiation and inspired later research on zero resistance states. I also looked for signatures of chirality in the transport properties of single chiral molecules. This led me to realize technically challenging experiments on transport through DNA, showing that conduction in DNA could be enhanced by connecting the molecules to a disconnected array of nanoparticles. Finally I developed a contact-Iess experiment to probe photo-transport in nanowires under visible illumination. This experiment can also probe chirality by detecting photo-transport under circularly-polarized Iight
Ouffoue, Cyrius. "Système intégré dédié à des applications de mesure de courant sans contact à gamme dynamique variable en milieu industriel". Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/OUFFOUE_Cyrius_2010_ED269.pdf.
Texto completoThis thesis work has been carried out during a collaborative project between SOCOMEC and InESS laboratory. The goal was to develop a CMOS integrated system for huge dynamic range current measurement. The current dynamic range goes from a few tens of amps to tens of thousands amps. The main objective of such a system is to replace the bulky current sensor like current transformers and Rogowski torus in many industrial applications. By integrating this current measurement system in CMOS technology, we can add many features like amplification, gain control and analog to digital converters. In this work, we proposed a new current sensor based on a Hall effects sensors network. This current sensor has been tested and validated
Kammerer, Jean-Baptiste. "Capteurs intégrés pour la mesure à haute résolution de champs magnétiques". Université Louis Pasteur (Strasbourg) (1971-2008), 2004. http://www.theses.fr/2004STR13064.
Texto completoIntegrated technologies allow to develop magnetic measurement systems on chip. Since they can be integrated using any standard manufacturing process, Hall effect sensors are particularly attractive for low cost magnetometers design. Thus, the first part of this thesis is focused on the improvement of this type of sensors using electronic circuits. We demonstrate that the association of a specific circuit and a Hall effect sensor of a particular shape allows to reach any absolute sensitivity. We also propose a new method for canceling the piezo-resistance effect which is responsible for a parasitic cross-sensitivity. The developed Hall effect sensors are particularly useful for low voltage technologies and for measurement systems subjected to vibrations. Thanks to the rise of nanotechnologies, thin film ferromagnetic based devices and more particularly magnetic tunnel junctions should be part of the standard components of microelectronics industry very soon. Thus, in the second part of this thesis, we studied the potentialities of this new device and we propose a new measurement technique based on the fluxgate principle generalized to two dimensions and applied to the magnetic tunnel junction. The realized magnetometer allows to measure simultaneously and in a very localized way, two components of a magnetic field with a very high sensitivity. All the realized systems tends to benefit from a sensitive element using specific electronic circuits