Dissertations / Theses on the topic 'Vortex quantiques'
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Boulier, Thomas. "Controlled vortex lattices and non-classical light with microcavity polaritons." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066524.
Full textPolaritons are bosonic quasiparticles coming from the strong coupling between photons and excitons in a solid-state semiconductor microcavity. Due to their short lifetime and their strong nonlinear interactions, polaritons are an ideal system to study fundamental problems of out-of-equilibrium quantum hydrodynamics as well as more applied problematic in quantum optics, such as the implementation of ultrafast opto-electronic switches or the generation of non-classical states of light.In this thesis the two themes are treated. In the first part of my thesis I will depict several schemes by which we optically inject a controlled angular momentum in a polartion superfluid, in order to observe its nucleation into elementary vortices. The impact of the geometry, disorder, and polariton-polariton nonlinear interactions is studied. We show the conservation of angular momentum in the steady state regime despite the open, out-of-equilibrium nature of the system. In the linear regime, an interference pattern containing phase defects is visible. In the nonlinear(superfluid) regime, the interference disappear and the vortices nucleate as a consequence of the angular momentum conservation. Finally, constraining the geometry we were able to create in a controlled way a stable ring of elementary vortices of the same sign, opening the way to the study of vortex-vortex interactions in quantum fluids of light.A second aspect of polaritons is the quantum properties of their emitted light. In the second part of the manuscript I describe a novel source of continuous-variable squeezed light in pillar-shaped semiconductor microcavities in the strong coupling regime. Indeed, the generation of squeezedand entangled light fields is a crucial ingredient for the implementation of quantum information protocols. In this context, semiconductor materials offer a strong potential for the implementation of on-chip devices operating at the quantum level. Here, degenerate polariton four-wave mixing is obtained by exciting the pillar at normal incidence. We observe a bistable behavior and we demonstrate the generation of squeezing near the turning point of the bistability curve. The confined pillar geometry allows for a larger amount of squeezing than planar microcavities due to the discrete energy levels protected from excess noise. By analyzing the noise of the emitted light we obtain a measured intensity squeezing of 20,3%, inferred to be 35,8% after corrections for losses in the detection setup
Giuriato, Umberto. "Dynamique des particules actives dans les superfluides et leur interaction avec les vortex quantiques." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4062.
Full textSuperfluids are inviscid flows in which vorticity is supported on filaments with quantized circulation. Such objects, known as quantum vortices, exhibit a hydrodynamical behavior. Experimentally, the dynamics of superfluids has been studied by using particles, which nowadays have become the main tool for visualizing quantum vortices. In this Thesis, we study numerically and analytically the dynamics of active and finite-size particles in superfluids. The superfluid is modeled with the Gross–Pitaevskii equation, while the particles are implemented as moving repulsive potentials coupled with the macroscopic wave function describing the superfluid. Firstly, the model is used to investigate the interaction between particles and quantum vortices at very low temperatures. This part aims to give a theoretical background to the current experiments in which macroscopic particles are used to sample superfluid vortices and quantum turbulence. Specifically, we address the following problems: the capture of a particle by a quantum vortex, the reconnections of vortex filaments and the propagation of Kelvin waves in presence trapped particles and the dynamics of particles in decaying quantum turbulence. In the last part of the manuscript, finite temperature effects are studied in the Fourier-truncated Gross–Pitaevskii model. The goal is to characterize the dynamics of impurities immersed in a thermal bath and how their presence modifies the statistical properties of the fluid. In particular, the random motion of the impurities and the temperature dependence of the friction coefficient are studied. Finally, the clustering of impurities and its effect on the phase transitions of the condensate are investigated
Villerot, Sophie. "Structure microscopique et dynamique des vortex dans un superfluide dense." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00775920.
Full textPigeon, Simon. "Fluides Quantiques et Dispositifs à Polaritons." Phd thesis, Université Paris-Diderot - Paris VII, 2011. http://tel.archives-ouvertes.fr/tel-00597945.
Full textVictorin, Nicolas. "Gaz quantiques à plusieurs composantes sous champ de jauge." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY049.
Full textThe first observation of Bose-Einstein condensation (BEC) in dilute atomic vapors has been a breakthrough both fundamentally, verifying theoretical concept predicted by Bose and Einstein several decades ago, revealing the statistical property of quantum particles. Since then, a new field has emerged and experimentalists are able to study this artificial matter in a very clean and controllable way. Cold-atom systems allows us to explore a whole range of fundamental phenomena that are extremely difficult or impossible to study in real materials, such as Bloch oscillation, Mott-superfluid transition, topology of band structure, orbital magnetism just to name a few. These progresses allow the quantum simulation of a large class of Hamiltonians subjected to magnetic field. Indeed, condensed matter phenomena under strong magnetic fields are still intriguing and are at the center of modern research. For instance, topological states of matter are realized in quantum Hall systems. A ladder is the simplest geometry where one can get some insight on two-dimensional quantum systems subjected to a synthetic gauge field.The first part of this thesis is dedicated to the study of double ring ladder subjected to gauge fluxes.Through both numerical and analytical calculation we explore the phase diagram of the system revealing known phases such as Meissner, vortex and biased ladder phase and the effect of commensurability of the total flux. Thanks to Bogoliubov approximation we are able to derive the excitation spectrum of the system and the nature of the low energy modes in the different phases revealing supersolid features as well as Josephson oscillation between the rings. The regime of infinite interaction between the boson enabled us to use exact mapping into fermions using Jordan-Wigner transformation to characterize the properties of the ground state. We explore the intermediate regime of interactions. Thanks to mode expansion and re-fermionization approach of the bosonized Hamiltonian of the double ring under gauge flux, we show the peculiarities of finite size periodic boundary condition on the current in the double ring with a rotating barrier inducing gauge flux.Exciton-polaritons in semiconductor microcavities constitute an amazing playground to study quantum fluids of light where remarkable effects, similar to those observed in cold atoms experiments, arise. Even though this quantum fluid of light is assumed to be composed, almost, upon pure condensate, the non-equilibrium nature of the gas make the comparison with typical condensates in cold atom experiment rather non trivial.The second part of the thesis is devoted to the study of excitons-polariton in honeycomb lattice. One of the most interesting aspect of the honeycomb lattice problem is that its low-energy excitations are massless, chiral, Dirac particles. Exciton-polariton, which are composite particle of light, in this lattice get back the relativist character of light but in a context where condensation is possible. Features of bosons in honeycomb lattice including retarded Green’s functions, Brillouin-zone selection mechanism and link between geometry of the lattice. We show that decay mode are suppressed as a consequence of the symmetry of the lattice leading to the possibility to engineer polaritonic dark-state. Then we obtain the Bogoliubov excitation spectrum of exciton-polariton. The usual bistability curve is shown to be unstable above C point showing the break-down of mean-field theory because of possible highly non-classical state. Finally experiment and theory are compared
XAVIER, GUIMARAES MARIA EMILIA. "Contributions a l'etude des champs quantiques en espace-temps conique et des solutions de type vortex couplees a la gravitation." Paris 6, 1996. http://www.theses.fr/1996PA066436.
Full textDomenge, Jean-Christophe. "Brisures de symétrie dans les modèles de Heisenberg classiques et quantiques en deux dimensions." Paris 6, 2005. https://tel.archives-ouvertes.fr/tel-00010943.
Full textGarcía, Alfonso Ernesto. "Etude théorique de la dynamique de nanogouttes d'hélium superfluide : formation d'agrégats, solvatation d'ions, explosion coulombienne, et nucléation et détection de vortex quantiques." Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSES069.
Full textSeveral dynamical processes involving Helium-4 nanodroplets (HNDs) are studied theoretically, in relation with experiments. HNDs are clusters of several hundred to several hundred billions of 4He atoms which exhibit remarkable properties: very low temperature, ~0.4K, superfluid properties, ability to pickup any dopant, weak interaction with any atom or molecule. The studied processes reflect the two main interests in HNDs: characterizing superfluid properties in a finite-size system (quantum vortex nucleation and detection), and using HNDs as an ideal environment to study dopant spectroscopy and dynamics (clustering, ion solvation, and Coulomb explosion). Extensive simulations are conducted using 4He-Density Functional Theory (4He-DFT) and its time-dependent version (4He-TDDFT). This approach can successfully simulate the equilibrium and dynamics of droplets of several thousand of atoms and provide detailed insight into the structural dynamics of the entire system which is not accessible experimentally: visualization of solvation shells, nature of helium droplet excitations. Rare gas (Rg) cluster formation is studied inside HeN under realistic conditions where one Rg atom collides with a solvated n-atom cluster to form the (n+1)-atom cluster. The 4He-DFT simulation results are compared to those of approximate atomistic approaches. Although quantum and superfluidity effects are better described with 4He-TDDFT, several common features are demonstrated. The most stable gas phase configuration is usually not produced, but an isomer with fewer bonds instead, and/or more dilute structures because of the rigidity of the helium solvation shell around the Rg atoms. The sinking of alkali (Ak) cations in HNDs is simulated in parallel with experimental investigations in the group of Stapelfeldt (Aarhus), in complement to earlier studies on Na+ sinking. It aims at shedding some light on the primary steps of solvation, by suddenly ionizing the alkali atom sitting in a dimple at the droplet surface. The build up of the first solvation shell around the ions is shown to be progressive, pointing to a Poissonian mechanism in which each He atom binds independently to the ion. For the lighter alkalis, the solvation shell is incomplete at the end of the dynamics, suggesting a kinetic rather than thermodynamical control of its formation. Coulomb explosion simulations of Ak2 molecules initially sitting at the droplet surface and suddenly ionized are conducted in order to understand the effect of the HNDs on Ak2++ fragmentation dynamics. The corresponding experiment in Stapelfeldt's group in Aarhus aimed at measuring the proportion of triplet to singlet state in the formation of Ak2, and at imaging the vibrational wave function. Several parameters are examined in the simulations: droplet size, zero point motion of Ak2 vibration, and orientational distribution of Ak2 on the droplet surface. The results validate the experimental approach, and evidence an unexpected curvature of the ion trajectories which could be used to measure droplet sizes individually, something that has only been possible up to now for very large sizes (by X-ray diffraction). The nucleation of quantum vortices, a characteristic of helium superfluidity, has been revealed in very large droplets (VLD) and attributed to angular momentum created by friction of the liquid in the nozzle prior to expansion and cooling. Here droplet-droplet collisions are explored as an alternative mechanism. The results show the nucleation of quantum vortices at indentations of the merged droplet, a mechanism general for all droplet sizes. However, no signature has been found to detect vortices in smaller droplets so far. In this work, fluorescence absorption or excitation spectroscopy of alkali atoms is proposed: a vortex is shown to shift and broaden the alkali spectrum. The effect could be measurable above the first excited states
Hivet, Romain. "Solitons, demi-solitons et réseaux de vortex dans un fluide de polaritons." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00911207.
Full textChevy, Frédéric. "Dynamique d'un condensat de Bose-Einstein." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2001. http://tel.archives-ouvertes.fr/tel-00001305.
Full textCastin, Yvan. "Etudes théoriques des atomes froids : du refroidissement laser aux condensats de Bose-Einstein." Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00267316.
Full textAnankine, Romain. "Cohérence quantique et superfluidité d'un gaz d'excitons piégés." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066144/document.
Full textSemiconductor excitons are bosonic quasi-particles compound of an electron and a hole bound by Coulomb attraction. They can undergo Bose-Einstein condensation in a very original fashion: excitons are distributed among four "spin" states. The lowest energy states are "dark" because optically inactive while at a higher energy, two "bright" states are coupled to the photon field. Below sub-kelvin temperatures, condensation of excitons leads to a macroscopic population of the dark states, as demonstrated in M. Beian's thesis in 2015. This dark condensate is coherently coupled with a small fraction of bright excitons whose their weak photoluminescence emitted allows to probe signatures for quantum coherence. In this thesis, we show the contribution of bright excitons to the Bose-Einstein condensation. We study a 2D dilute gas of excitons confined in a electrostatic trap where we reveal, below a critical temperature of about 1 K, a quantum long-range order with an increased temporal coherence of the photoluminescence emitted by bright excitons. The appearance of quantised vortices, signalled by density defects and phase singularities in spatial interferences patterns, gives us the demonstration that 85% of the trapped excitons participate in the formation of a four-component superfluid where a macroscopic population of dark excitons is coherently coupled with a fraction of condensed bright excitons
Boughdad, Omar. "Fluides de lumière dans un milieu non-linéaire photoréfractif." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4014.
Full textThis thesis presents an experimental study of hydrodynamical phenomena of a laser propagating nonlinearly. For a medium presenting an intensity-dependent refractive index, and in the frame of the paraxial approximation, The intensity of the laser beam is equivalent to a density of a fluid, the propagation direction is seen as a time evolution of the fluid as well as the phase gradient of the laser beam defines a flow velocity and the nonlinear refractive index change allows defining a sound velocity of the fluid. Under this analogy, we call the propagating laser beam a fluid of light. In this thesis, we provide a study of the superfluidity concept of a fluid of light in a selfdefocusing regime of the nonlinearity. It is defined as the absence of diffraction when the fluid of light encounters an obstacle. The parameters which control the superfluid transition are: the flow velocity as well as the sound velocity. They are controlled respectively through the wave vector and the intensity of the laser beam. In the frame of this analogy, we also present in this thesis a study of vortex shedding regime as a result of the interaction between the fluid of light and the obstacle. Here, the obstacle is considered to be strong. When twice the flow velocity at the poles of the obstacle is larger than the sound velocity, pairs of vortex/anti-vortex are emitted demonstrating a hydrodynamical behaviour of the fluid of light. In order to underline the nonlinear refractive index change, we also report in this thesis a study of the photorefractive effect using the self-phase modulation effect
Nam-Duk, Suh. "L'étude des structures cohérentes dans l'espace des phases du plasma unidimensionnel électrostatique : aspect classique et quantique." Orléans, 1989. http://www.theses.fr/1989ORLE2056.
Full textElias, Ricardo. "Solitons magnétiques et transitions topologiques." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4712/document.
Full textIn this thesis we study the magnetic solitons and its topological transitions, both theoretically and numerically. In the first part, we find a particular configuration of what is denominated the Bloch Point, a three-dimensional solution of the Free Energy minimization with exchange, Landau and dipolar terms. Oscillations around the Bloch point are found and quantized in order to understand the role of quantum fluctuations over its stability.In the second part, we look at the evolution of a system coupling ferromagnetic textures with nontrivial topology, with itinerant electrons. The interaction between the magnetic texture and the electrons is understood by means of spin-torque phenomena. This physical system is modeled with the equation Landau-Lifshitz-Gilbert equation coupled with Schrödinger equation for quantum electrons. Topological transitions are observed and understood in a general framework that unifies older works done in a more classical context. Among the large amount of topological transitions observed, we can distinguish the different roles played by electrons depending on parameters. The orders of magnitude of time and space in the topological transition events show the importance of quantum effects as well as the fundamental role of discretization
Stock, Sabine. "Vortex quantifié dans un condensat de Bose-Einstein : activation thermique et nucléation dynamique." Paris 6, 2006. https://tel.archives-ouvertes.fr/tel-00012211.
Full textStock, Sabine. "Vortex quantifiés dans un condensat de Bose-Einstein: activation thermique et nucléation dynamique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2006. http://tel.archives-ouvertes.fr/tel-00012211.
Full textMessio, Laura. "Etats fondamentaux et excitations de systèmes magnétiques frustrés, du classique au quantique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00523976.
Full textBretin, Vincent. "Rotations d'un condensat de Bose-Einstein." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2004. http://tel.archives-ouvertes.fr/tel-00005961.
Full textd'expériences sur des condensats de Bose-Einstein en rotation. Du
fait de la cohérence d'un condensat, la rotation s'introduit
généralement sous la forme de singularités de phase appelées
vortex. L'isolation et l'observation d'une unique ligne de vortex
ont permis d'étudier sa dynamique dans un condensat allongé. La
forme d'équilibre de la ligne de vortex ainsi que son évolution
sur des échelles de temps longues ont été caractérisées. Par leur
effet sur l'amortissement des modes de surface, les modes de
vibration de la ligne ont été mis en évidence. La limite des
rotations rapides a également été étudiée. Pour des vitesses de
rotation intermédiaires, elle est caractérisée par un grand nombre
de vortex arrangés en réseaux d'Abrikosov. Pour des vitesses
encore plus grandes, différentes phases sont attendues selon la
forme du potentiel. Cette limite a été étudiée dans le cas d'un
potentiel hybride contenant un petit terme quartique. Les nuages
en rotation, que nous avons caractérisés par plusieurs méthodes,
se révèlent avoir un comportement original. Leur observation
constitue un premier pas vers celle de phases corrélées proches du
régime Hall quantique fractionnaire.
Rougerie, Nicolas. "La théorie de Gross-Pitaevskii pour un condensat de Bose-Einstein en rotation : vortex et transitions de phase." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00547404.
Full textBleu, Olivier. "Physics of quantum fluids in two-dimensional topological systems." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC044/document.
Full textThis thesis is dedicated to the description of both single-particle and bosonic quantum fluid Physics in topological systems. After introductory chapters on these subjects, I first discuss single-particle topological phenomena in honeycomb lattices. This allows to compare two theoretical models leading to quantum anomalous Hall effect for electrons and photons and to discuss the photonic quantum valley Hall effect at the interface between opposite staggered cavity lattices.In a second part, I present some phenomena which emerge due to the interplay of the linear topological effects with the presence of interacting bosonic quantum fluid described by mean-field Gross-Pitaevskii equation. First, I show that the spin-anisotropic interactions lead to density-driven topological transitions for elementary excitations of a condensate loaded in the polariton quantum anomalous Hall model (thermal equilibrium and out-of-equilibrium quasi-resonant excitation configurations). Then, I show that the vortex excitations of a scalar condensate in a quantum valley Hall system, contrary to linear wavepackets, can exhibit a robust chiral propagation along the interface, with direction given by their winding in real space, leading to an analog of quantum spin Hall effect for these non-linear excitations. Finally, coming back to linear geometrical effects, I will focus on the anomalous Hall effect exhibited by an accelerated wavepacket in a two-band system. In this context, I present a non-adiabatic correction to the known semiclassical equations of motion which can be expressed in terms of the quantum geometric tensor elements. We also propose a protocol to directly measure the tensor components in radiative photonic systems
Hernangomez, Perez Daniel. "Spin-orbit Coupling and Strong Interactions in the Quantum Hall Regime." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY087.
Full textThe quantum Hall effect, appearing in disordered two-dimensional electron gases under strong perpendicular magnetic fields and low temperatures, has been a subject of intense research during the last thirty years due to its very spectacular macroscopic quantum transport properties. In this thesis, we expand the theoretical horizon by analytically considering the effects of spin-orbit coupling and strong electron-electron interaction in these systems.In the first part of the manuscript, we examine the simultaneous effect of Rashba spin-orbit and Zeeman interaction in the integer quantum Hall regime. Under these conditions, we extend a coherent-state vortex Green's function formalism to take into account the coupling between orbital and spin degrees of freedom within the electronic drift states. As a first application of this framework, we analytically compute controlled microscopic nonperturbative quantum functionals, such as the energy spectrum and the local density of states, in arbitrary locally flat electrostatic potential landscapes, which are then analyzed in detail in different temperature regimes and compared to scanning tunnelling experimental data. As a second application, we thoroughly study local equilibrium charge and spin transport properties and derive analytical useful formulas which incorporate the mixed non-relativistic and relativistic character of Rashba-coupled electron gases.In the second part of this thesis, we deal with the problem of analytically incorporating strong electron-electron interactions in the fractional quantum Hall regime. To this purpose, we consider a generalized two-body problem where both disorder and correlations are combined and introduce a new vortex coherent-state representation of the two-body states that naturally include long-range correlations between the electrons. The novelty of this theory is that correlations are topologically built in through the non-Euclidean metric of the Hilbert space. Next, we show that this kind of vortex states form a basis of an enlarged Hilbert space and derive the equation of motion for the Green's function in this representation. Finally, we check the consistency of our approach for any Landau level of the pair and discuss the necessity of going beyond the semiclassical (infinite magnetic field) approximation to obtain energy gaps within each energy level
Champel, T. "Oscillations quantiques magnétiques dans les systèmes de basse dimensionnalité.Etude de la symétrie de l'état supraconducteur dans le composé UPt3." Phd thesis, 2003. http://tel.archives-ouvertes.fr/tel-00202830.
Full textDans une deuxième partie, nous étudions les propriétés de l'état mixte dans le supraconducteur non-conventionnel UPt3 pour un champ magnétique parallèle à l'axe hexagonal du cristal principalement dans le cadre des modèles théoriques d'un état supraconducteur à deux composantes couplé avec un champ briseur de symétrie. Nous examinons la structure du réseau de vortex dans la phase A de UPt3 à partir de considérations de symétrie et de l'approximation locale de London, et montrons que seul l'état supraconducteur de symétrie E2u peut rendre compte des observations expérimentales. Nous mettons également en évidence que la transition entre les phases mixtes A et B est plutôt un crossover qu'une transition de phase du second ordre à cause de la présence de termes de gradients de mélange dans l'expression de l'énergie libre de Ginzburg-Landau. Enfin, nous démontrons que la dépendance de la pente du second champ critique au niveau de la température critique en fonction du taux d'impuretés n'est pas sensible à la symétrie de l'état supraconducteur.