▼ The 2D scattering problem of an electron by a magnetized nanoparticle is solved in the Born approximation with account of the dipole - dipole interaction of the magnetic moments of electron and nanomagnet. The scattering amplitudes in this problem are the two-component spinors. They are obtained as functions of the electron spin orientation, the electron energy and show anisotropy in scattering angle. The initially polarized beam of electrons scattered by nanomagnet consists of electrons with no spin flipped and spin flipped. The majority of electrons with no spin flipped are scattered by small angles. This can be used as one method of controlling spin currents. 2D spin-dependent scattering of slow unpolarized beams of electrons by charged nanomagnets is analyzed in the Born approximation. The obtained scattering lengths are larger than those from the neutral nanomagnets approximately by one order. It is shown that for particular parameters of the system it is possible to polarize completely the scattered electrons in a narrow range of scattering angles. The most suitable system for realization of these effects is 2D Si electron gas with immersed nanomagnets. The 2D spin-dependent electron scattering by the linear chain of periodic nanomagnets with account of the diffraction effects was studied. This effect takes place in 2D electron gas with immersed nanomagnets. By tuning a distance between nanomagnets, it is possible to obtain diffraction maximum of the scattered electrons at scattering angle, which corresponds to complete spin polarization of electrons. The total diffraction scattering lengths are proportional to N2 (N is a number of nanomagnets). The proposed system can be an efficient separator of spin polarized currents. Advisors/Committee Members: Prof. V. N. Mal’nev (advisor).

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Cette thèse couvre l'auto-assemblage de particules dipolaires (magnétiques/électriques). Ces systèmes sont abondants en physique de la matière condensée (molécules et nanoparticules magnétiques, particules colloïdales magnétiques, bactérie magnétotactique, etc.). Sur un plan fondamental, ils représentent un défi important en raison de l'anisotropie et de la longue portée de l'interaction de paire. Le principal objectif de ce travail de recherche est de prédire les microstructures de ces systèmes en tenant compte de façon adéquate de l'interaction complexe dipôle-dipôle ainsi que des effets stériques et ceux dus à un éventuel confinement. Comprendre et revisiter les interactions de filaments dipolaires tels que des aiguilles et des chaînes faites de billes dipolaires est une première étape importante de cette thèse. En effet, les chaînes sont les constituants élémentaires de nombreux systèmes dipolaires, notamment sous l'effet d'un champ magnétique extérieur appliqué. Ensuite, l'agrégation colonnaire des chaînes dipolaires est examinée, ce qui conduit aussi naturellement à l'étude des cristaux dipolaires massifs où une nouvelle phase est découverte. Le cas plus générique des chaînes hélicoïdales est discuté en considérant les situations limites que sont les chaînes linéaires droites et en zigzag. L'association des chaînes dipolaires, dans le cas bidimensionnel, forme des rubans, puis une monocouche avec un réseau hexagonal. La réponse non triviale d'un tel réseau à un champ magnétique perpendiculaire imposé est aussi étudiée. Il est démontré qu'un réseau rhombique peut être induit de cette façon. Finalement, la sédimentation de particules paramagnétiques dans une monocouche inclinée en présence d'un champ magnétique est explorée via une étude mêlant expériences, théorie et simulations. L'ordre induit par gravité s'avère être une voie prometteuse pour l'élaboration contrôlée de réseaux bidimensionnels

This thesis covers the self-assembly of dipolar (magnetic/dielectric) particles. These systems are abundant in condensed matter physics (magnetic molecules and nanoparticles, magnetic colloidal particles, magnetotactic bacteria, etc). They also represent a fundamental challenge owing to the both long range and anisotropic nature of the pair interaction. The main objective of this research work is to predict the microstructures of these systems by properly handling the intricate dipole-dipole interaction combined with steric and possibly confinement effects. Understanding and revisiting the interaction of dipolar filaments such as needles or chains made up of dipolar beads is a first important achievement in this thesis. Indeed, the chains are the fundamental building blocks of many dipolar systems especially under applied external magnetic field. Then, the columnar aggregation of dipolar chains is investigated which naturally leads to the study of the bulk dipolar crystals. A new phase is discovered there. The more generic case of helical chains is discussed by considering limiting situations such as straight linear…

Advisors/Committee Members: Messina, René (thesis director), Bécu, Lydiane (thesis director).

▼  Among the physical methods available for studying protein structures, CD stands out as a property that is easy to measure yet remarkably difficult to predict theoretically. The basic principle underlying the CD of polypeptides and proteins is reasonably understood: the mixing of electronic transitions of monomer groups in the context of a chiral environment of helices gives rise to transitions that are both electronically and magnetically allowed. Despite knowledge on the fundamentals of CD, accurate theoretical prediction is still a major challenge. A better theoretical understanding of protein CD would facilitate a fuller interpretation of protein CD experiments. Extensive theoretical studies have been conducted with some success to predict the CD spectra of polypeptides and proteins. One of such theoretical studies has been with the dipole interaction model, pioneered by J. Applequist. In this model, atoms and chromophores are considered to be point dipole oscillators that interact through mutually induced dipole moments in the presences of an electric field. The dipole interaction model has been assembled into a package (DInaMo) and used to successfully predict the far-UV CD of peptides and proteins. The major limitation of the method has been the neglect of the n-π* transition, and having to deal with a number of parameters, since no single parameter at the moment succeeds with all the different classes of proteins. Herein, in an attempt to improve the far-UV protein CD prediction capability of DInaMo, a number of issues are addressed: (1) Will the predicted CD be improved if mean polarizability values are used? (2) Since excluding methyl hydrogens on the amino acid residues have been successful, what happens if methylene and methylidyne hydrogens are also excluded? (3) How will the predicted spectrum differ upon addition of the n-π* amide transition? To answer these questions, a cyclic peptide (cyclo-(Gly-Pro-Gyl-D-Ala-Pro)) rebuilt with idealized bond angles and lengths, and a set of α-helical proteins obtained from the Protein Data Bank are energy minimized to adjust bond lengths and bond angles. The energy-minimized structures are then used to generate CD spectra with DInaMo. Mean polarizability parameters for methyl, methylene and methylidyne groups are developed and implemented on the cyclic peptide and protein. In addition, the effects of excluding methyl, methylene, and methylidyne hydrogens are investigated. Lastly, the n-π* transition is included in the predictions of α-helical proteins and peptides CD. Calculations using new mean polarizability parameters remove the need for different π-π* transition parameters and improve the CD results in lower RMSDs and better spectra morphology. Excluding more hydrogens improve results with larger protein. In addition, the n-π* transition parameters yield normal modes in the correct region and sign for this transition. Advisors/Committee Members: Kathryn Thomasson.

▼ Discotic liquid crystals (DLCs) have gain importance in recent years as charge and energy transporting materials for potential applications as organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs) and organic field-effect transistors (OFETs) devices. As such, much keen interests have been concentrated on tuning the mesomorphic and electronic properties of the DLCs. In our previous research, dibenzo[a,c]phenazines (DBP) has been found to be a good ambipolar candidate. However, to date little studies have been undertaken to tune the molecular energy by modifying the structure of DBP to further extend their usefulness in device applications The objective of this study is to incorporate an electron-deficient benzo[1,2,5]thiadiazole (BT) fragments onto the Ï-conjugated system of DBP with the following aims: (i) desymmetrization of the DBP for tuning the mesomorphism, and (ii) tuning the absorption and electrochemical properties of the discogen. Herein, we report the synthesis a series of tetraalkoxydibenzo[a,c]-[1,2,5]thiadiazolo[3,4-h]phenazines (sDBTPs). In addition, the liquid crystal properties will be investigated systematically using POM, DSC and X-ray diffraction. The primary findings will enable further development of new discotic core for application in devices such as bulky junction solar cell based on ambipolar molecules. Advisors/Committee Members: Hsiu-Hui Chen (chair), Kwang-Ming Lee (chair), Jrjeng Ruan (chair), Chi Wi Ong (committee member).

▼ In den letzten Jahren erregten verdünnte Quantengase mit der anisotropen und langreichweitigen Dipol-Dipol Wechselwirkung viel Aufmerksamkeit. Zunächst wurden dipolare Effekte bei atomaren Bose-Einstein Kondensaten aus 52Cr, 87Rb und 7Li nachgewiesen. Ein weiterer Fortschritt wurde vor kurzem dadurch erzielt, dass fermionische 40K87Rb Moleküle mit einem Dipolmoment von etwa 0.5 Debye in die Nähe der Quantenentartung gebracht wurden. Dies gelang durch Einsatz von der sogenannten STIRAP-Methode (Stimulated Raman Adiabatic Passage), um solche Molekülen in den Rotations- und Vibrationsgrundzustand zu bringen. Wegen des hohen Dipolmomentes kann die Dipol- Dipol-Wechselwirkung zwischen heteronuklearen Molekülen bis zu 10.000 Mal stärker als in magnetischen Systemen sein. In dieser Arbeit werden die statischen und dynamischen Eigenschaften polarisierter dipolarer Quantengase am absoluten Temperaturnullpunkt theoretisch untersucht. Der erste Teil behandelt dipolare Bose-Einstein-Kondensate, während der zweite Teil dipolaren Fermi-Gasen in der nichtsuperfluiden Phase gewidmet ist. Bei dipolaren Kondensaten untersuchen wir sowohl das homogene als auch das in einer harmonischen Falle gefangene Bose-Gas im Rahmen der Bogoliubov-de Gennes Theorie. Dabei berechnen wir die Quantenkorrekturen der physikalisch interessierenden Größen, die über die Molekularfeldtheorie hinausgehen. Im homogenen Fall bestimmen wir die Bogoliubov-Amplituden und gewinnen aus diesen die Grundzustandsenergie des Kondensates jenseits der Molekularfeldtheorie, die durch die Wechselwirkung entstehende Entleerung des Kondensates, und die entsprechende Lee-Huang-Yang- Korrektur zur Zustandsgleichung. Danach erhalten wir aus dem korrigiertem chemischem Potenzial den Beliaev- Term der Schallgeschwindigkeit. Für das harmonisch gefangene Kondensat leiten wir das Bogoliubov- Anregungsspektrum im Rahmen der lokalen Dichte-Näherung analytisch her. Durch die Berechnung der Quantenkorrekturen zur Grundzustandsenergie bestimmen wir die Bewegungsgleichungen für die Thomas-Fermi-Radien des Kondensates. Aus den entsprechenden Gleichgewichtslösungen bestimmen wir dann die Thomas-Fermi- Radien jenseits der Molekularfeldtheorie. Außerdem diskutieren wir den Einfluß der Quantenfluktuationen auf das Stabilitätsdiagramm. Weil dynamische Eigenschaften ein wichtiges experimentelles Hilfsmittel darstellen, Quantensysteme zu charakterisieren, untersuchen wir auch die niederenergetischen Anregungen sowie die Flugzeit-Expansion. Dabei ergibt sich, dass die von der dipolaren Wechselwirkung erzeugten Quantenfluktuationen so stark vom Verhältnis der Fallenfrequenzen abhängen, dass sie in künftigen Experimenten beobachtbar sein müßten. Als nächstes behandeln wir die polarisierten dipolaren Fermi Gase in einer allgemeinen tri-axialen harmonischen Falle. Um die physikalischen Eigenschaften solcher Systemen zu untersuchen, leiten wir als erstes ein zeitabhängiges Hartree-Fock- Variationsverfahren her. Dabei beschränken wir uns auf das hydrodynamische Regime, bei dem häufige Stöße zu einem… Advisors/Committee Members: [email protected] (contact), m (gender), Priv.-Doz. Dr. Axel Pelster (firstReferee), Prof. Dr. Jürgen Bosse (furtherReferee).

▼ Dipole-dipole interactions, the strongest, longest-range interactions possible between two neutral atoms, cannot be better manifested anywhere else than in a Rydberg atomic system. Rydberg atoms, having high principal quantum numbers n>>1 and dipole moments that scale as n², provide a powerful tool to examine dipole-dipole interactions. Therefore, we have studied the production and production rates of strontium Rydberg atoms created using two-photon excitation and have explored their properties in two distinct experiments. In the first experiment, very-high-n (n~300) Rydberg atoms are produced in a tightly collimated atomic beam allowing spectroscopic studies of their energy levels and their Stark effects. Simulations using a two-active-electron model, developed by our theoretical collaborators, allow detailed analysis of the results and are in remarkable agreement with the experimental results. The high density of Rydberg atoms achieved ~ 5*10⁵ cm^(-3), in this experiment will allow studies of strongly interacting Rydberg-Rydberg systems. The second experiment, in which a cold strontium Rydberg gas is excited in a magneto-optic trap, features an imaging technique offering both spatial and temporal resolution. We use this technique to observe and study the evolution of an ultra-cold strontium Rydberg gas which reveals the importance of Rydberg-Rydberg interactions in the early stages of this evolution. Strongly interacting Rydberg gas provides an opportunity to realize a very strongly-correlated ultra-cold plasma. Advisors/Committee Members: Dunning, F. B. (advisor), Killian, Thomas C. (committee member), Natelson, Douglas (committee member).

▼ This thesis reports the use of both dc and ac electric fi eld induced resonant energy transfer, RET, between cold Rydberg atoms as a useful tool for enhancement of interatomic interactions. A general technique for laser frequency stabilization and its suitability for Rydberg atom excitation is also demonstrated. RET between cold Rydberg atoms was used to determine Rydberg atom energy levels. The ⁸⁵Rb atoms are laser cooled and trapped in a magneto-optical trap. For energy level determination experiment, atoms were optically excited to 32d₅/₂ Rydberg states. The two-atom process 32d₅/₂ + 32d₅/₂ → 34p₃/₂+30g is resonant at an electric fi eld of approximately 0.3 V/cm through dipole dipole interaction. The experimentally observed resonant fi eld, together with the Stark map calculation is used to make a determination of the ⁸⁵Rb ng-series quantum defect to be ⵒg(n = 30) = 0.00405(6). The ac Stark eff ect was also used to induce RET between cold Rydberg atoms. When a 28.5 GHz dressing field was set at speci fic fi eld strengths, the two-atom dipole-dipole process 43d₅/₂ + 43d₅/₂ → 45p₃/₂ + 41f was dramatically enhanced, due to induced degeneracy of the initial and final states. This method for enhancing interactions is complementary to dc electric- field-induced RET, but has more flexibility due to the possibility of varying the applied frequency. At a dressing field of 28.5 GHz all of the participating levels (43d₅/₂, 45p₃/₂ and 41f) show signi cant shifts and these give a complicated series of resonances. An oscillating electric fi eld at 1.356 GHz was also used to promote the above RET process where the atoms are initially excited to the 43d₅/₂ Rydberg states. The ac fi eld strength was scanned to collect RET spectra. Di fferent resonances were observed for diff erent magnetic sublevels involved in the process. Compared to the higher dressing field frequency of 28.5 GHz, the choice of dressing frequency of 1.356 GHz, which is slightly blue detuned from the 41f - 41g transition, and structure of the spectra may be understood, by analogy with the dc field case.

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A blue sky, a white cloud or a red sunset are explained by classical multiple scattering theory of light. However, these phenomena neglect interference occurrence. Once it is taken into account, interference in a disordered medium may actually put a halt to the propagation of light, an effect known as Anderson Localization. Until now, experimental reports of Anderson Localization of light in 3D systems have not been conclusive. Our goal is to understand what are the underlying obstacles, and look for new insights from a theoretical point of view. In this dissertation, the properties of a cloud of two-level atoms scattering light are investigated. The dipole-dipole interaction generates collective modes, some of them, being localized. We found that finite-size effects dominate the lifetime of the localized modes, specifically by the ratio of localization length to their distance to the system boundaries. Localized modes saturates at maximum of 20% even above phase transition. Studying the steady-state regime, the coupling between localized modes and light is weak. Both results agrees with the difficulty of experimental evidence of light localization and promote the link of experiments and theory.

Um céu azul, uma nuvem branca ou um por do sol vermelho são explicados pela teoria clássica de espalhamento múltiplo da luz. No entanto, esses fenômenos negligenciam a ocorrência de interferências. Uma vez levada em conta, a interferência em um meio desordenado pode interromper a propagação da luz, um efeito conhecido como Localização de Anderson. Até agora, relatos experimentais de Anderson Localização de luz em sistemas 3D não foram conclusivos. Nosso objetivo é entender quais são os obstáculos fundamentais, e buscar novos insights do ponto de vista teórico. Nesta dissertação, as propriedades de uma nuvem de átomos de dois níveis espalhando luz de é investigado. A interação dipolo-dipolo gera modos coletivos, alguns deles, sendo localizados. Descobrimos que os efeitos de tamanho finito dominam o tempo de vida dos modos localizados, especificamente pela razão entre o comprimento da localização e sua distância até os limites do sistema. Os modos localizados saturam no máximo 20%, mesmo acima da transição de fase. Estudando o regime de estado estacionário, o acoplamento entre modos localizados e luz é fraco. Ambos os resultados concordam com a dificuldade da evidência experimental da localização da luz e promovem a ligação entre experimentos e teoria.

Advisors/Committee Members: Romain Pierre Marcel Bachelard, Felipe Arruda de Araujo Pinheiro, José Antonio Roversi.

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Ce travail concerne la modélisation, à l’échelle moléculaire, de l’interaction entre des nanoparticules carbonées et le rayonnement électromagnétique. Le but est d’aider à la compréhension des propriétés optiques des particules de suie afin de mieux quantifier l’influence des suies sur l’atmosphère et le climat. L’étude de l’interaction rayonnement/particules de suie fraîche a été effectuée par la méthode PDI ; il a été montré que : i) le coefficient d’absorption massique (MAC) des particules de suie dépend de la répartition des atomes dans la particule et de leurs liaisons, en particulier entre 200 et 350 nm ; ii) le MAC diffère selon que le cœur de la particule carbonée est occupé ou non par des plans graphitiques ; iii) un modèle analytique n’est pas adapté pour calculer le MAC d’une nanoparticule carbonée présentant des défauts structuraux. De plus, des méthodes de chimie quantique ont été utilisées pour caractériser le vieillissement des suies. Les résultats montrent que : i) NO, Cl, et HCl sont physisorbées sur une surface carbonée parfaite alors que sur une surface défective, ces espèces sont chimisorbées et conduisent à une modification de la surface ; ii) la présence de Cl conduit à un piégeage fort des molécules d’eau supérieur à celui obtenu lorsqu’un site oxygéné est présent sur la surface carbonée, expliquant ainsi le caractère hydrophile des suies émises lors d’incendies dans des milieux industriels. Enfin, la méthode PDI a été appliquée au calcul de la polarisabilité de HAP afin d’interpréter des spectres d’absorption des grains carbonés du milieu interstellaire, en incluant des molécules pour lesquelles aucune donnée n’était actuellement disponible.

This work concerns the modeling, at the molecular level, of the interaction between carbonaceous particles of nanometric size and the electromagnetic radiation. The goal is to improve our understanding of the optical properties of soot particles, to better quantify the influence of soot on the atmosphere and on climate change. The study of the interaction between radiation and fresh soot particles was carried out using the point dipole interaction method; it has been shown that: i) the mass absorption coefficient (MAC) of these soot nanoparticles may significantly depend on their atomistic details, especially between 200 and 350 nm; ii) the MAC depends on whether the heart of the carbonaceous particle is occupied or not by graphite planes; iii) an analytical model is not suitable for calculating the MAC of carbonaceous nanoparticles having structural defects. In addition, quantum chemical methods have been used to characterize the ageing of soot. The results obtained are i) NO, Cl, and HCl are physisorbed on a perfect carbonaceous surface whereas on a defective surface, these species are chemisorbed and lead to a modification of the surface; ii) on a carbonaceous surface, the presence of adsorbed Cl atoms leads to a strong trapping of the surrounding water molecules. This may be related to the highly hydrophilic nature of soot emitted during fires in…

Advisors/Committee Members: Picaud, Sylvain (thesis director), Rubayo Soneira, Jesús (thesis director).

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L’objectif de cette thèse est l’étude des différents aspects de l’interaction à quelques corps entre des atomes de Rydberg froids. Cette thèse a été réalisée dans le cadre d’une cotutelle entre l’Université Paris-Saclay et l’Université de Pise en travaillant sur deux différents montages expérimentaux sur des atomes de Rydberg froids : respectivement sur le Cs au Laboratoire Aimé Cotton et sur le Rb au département de Physique de l’Université de Pise. Au Laboratoire Aimé Cotton nous avons démontré l’existence des nouvelles interactions à quelques corps dans un gas gelé d’atomes de Rydberg. Ces nouvelles résonances sont la généralisation des résonances de Förster bien connues dans le domaine des atomes de Rydberg. Ces résonances agissent sur les degrés de liberté interne des atomes de Rydberg et ont l’effet d’un transfert résonant d’énergie et de population comme dans le cas des FRET (Fluorescence Resonance Energy Transfer). Comme dans le cas de la résonance de Förster à deux corps, les résonances FRET à trois corps sont accordées à la résonance avec un champ électrique externe et peuvent être observées pour différents nombres quantique principaux. Les effets à trois corps sont observés en absence de tout effet à deux corps et sont qualifiés de Borroméens. La présence d’un champ externe peut générer d’autres résonances entre atomes de Rydberg qui sont interdites en absence de champ électrique. Ces résonances, qu’on peut qualifier des résonances quasi-interdites, sont dues à un couplage dipole-dipole de type Förster. Nous avons identifié toutes ces résonances liées au couplage entre les niveaux de multiplicité de n différents.Dans le montage expérimental à Pise on a étudié les effets mécaniques liés à la répulsion van der Waals entre atomes de Rydberg. Nous avons étudié l’expansion due à l’interaction van der Waals dans une chaîne 1D des atomes de Rydberg de Rb qui ont étés excités avec une excitation laser hors résonance. La comparaison entre les différents désaccords de l’excitation laser démontre le rôle central joué par l’interaction van der Waals.

The aim of this thesis is to investigate different aspects of few-body interactions in cold Rydberg atoms. It has been realized in a co-tutelle program between the University of Paris-Saclay and the University of Pisa working on two different experimental set ups: one at Laboratoire Aimé Cotton on cold Cs Rydberg atoms and a second at Physics Department of Pisa on cold Rb Rydberg atoms. In Laboratoire Aimé Cotton we demonstrated the existence of new few-body interactions we observed in a frozen Rydberg gas of Cs atoms. These new resonances are a generalization of already known two-body Förster resonances. They act on the internal degrees of freedom of the Rydberg atoms leading to a resonant energy transfer analogous to the one in FRET (Fluorescence Resonance Energy Transfer). In analogy with Förster resonance, three-body FRETs are tuned with an external electric field and can be observed for different principal quantum number. The three-body interaction appeared in the…

Advisors/Committee Members: Pillet, Pierre (thesis director), Fuso, Francesco (thesis director).

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Lorsque l’on place des atomes suffisamment proches les uns des autres, l’interaction dipôle-dipôle résonante entre les atomes modifie leurs propriétés. Les atomes se comportent alors de manière collective. Ces effets collectifs se produisent lorsque les distances interparticulaires sont de l’ordre de l/(2Pi), où l est la longueur d’onde de la transition atomique. La densité atomique est alors de l’ordre de 10¹⁴ at/cm³. Afin de créer des échantillons d’atomes froids présentant des densités aussi élevées, nous avons mis en place plusieurs méthodes de chargement de nos pinces optiques de taille micrométrique. L’une d’elles utilise un processus d’évaporation forcée qui amène les atomes proches de la dégénérescence quantique. En utilisant des nuages denses contenant quelques centaines d’atomes à des densités spatiales élevées, et en étudiant les modifications de la diffusion de la lumière qui en résultent, nous avons pu mettre en évidence des effets collectifs entre les atomes. Nous avons par ailleurs mesuré le retard de Wigner associé à la diffusion élastique de la lumière par un atome unique de rubidium. Nous avons mesuré un retard proche de la valeur théorique, c’est-à-dire deux fois la durée de vie de la transition atomique (52 ns).

When several atoms are placed close to each other, the resonant dipole-dipole interactionbetween atoms modifies the atomic properties and atoms behave collectively. These collective effects occur for interatomic distances on the order of l/(2Pi) where l is the wavelength of the atomic transition. The atomic density is then on the order of 10¹⁴ at/cm³. To create such cold atomic samples, we load optical tweezers with a microscopic size according to several loading schemes. One of them uses forced evaporative cooling and brings the atoms close to quantum degeneracy. We have used dense clouds containing a few hundred atoms with a high spatial density to demonstrate collective effects between the atoms. In particular, we have studied how these effects modify the scattering of light by the cloud. Besides, we have also measured for the first time the time-delay associated to the elastic scattering of light by a single rubidium atom, the so-called Wigner delay. We have shown that this delay is close to the theoretical prediction of twice the lifetime of the atomic transition (52 ns).

Advisors/Committee Members: Browaeys, Antoine (thesis director), Sortais, Yvan (thesis director).

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Des atomes individuels piégés dans des matrices de pinces optiques et excités vers des états de Rydberg forment une plateforme expérimentale prometteuse pour la simulation quantique de modèles de spins. Lors de cette thèse, nous avons d’abord résolu le problème du chargement aléatoire des pièges, seulement 50 % d’entre eux étant chargés avec un atome. Nous avons développé une technique pour préparer des matrices 2D, puis 3D, d’atomes de 87Rb en les déplaçant un par un avec une pince optique mobile contrôlée par ordinateur. Nous avons ensuite réalisé le modèle d’Ising en excitant de manière cohérente les atomes depuis leur état électronique fondamental vers un niveau de Rydberg. Après avoir trouvé un régime optimal où l’interaction dipolaire entre deux atomes de Rydberg se réduit à une énergie de van der Waals, nous avons tenté de préparer adiabatiquement l’état de Néel qui minimise l’énergie d’interaction. Nous avons montré que l’efficacité de préparation étaitlimitée par la décohérence induite par les lasers d’excitation. Nous avons ensuite utilisé un autre régime d’interaction, le couplage dipolaire résonant, pour étudier des modèles de spins de type XY, dont le modèle Su-Schrieffer-Heeger, connu pour sa phase fermionique topologique protégée par une symétrie chirale. Ici, nous avons remplacé les fermions par des particules effectives de type `boson de cœur dur’, ce qui modifie les propriétés de cette phase. Nous avons d’abord retrouvé les propriétés à une particule, comme l’existence d’états de bords à énergie nulle. Nous avons ensuite préparé l’état fondamental à N corps pour un remplissage moitié, et observé sa dégénérescence causée par les états de bords, même en présence d’une perturbation qui lèverait cette dégénérescence dans le cas fermionique. Nous avons expliqué ce résultat par l’existence d’une symétrie plus générale, qui protège la phase bosonique.

Single atoms trapped in arrays of optical tweezers and excited to Rydberg states are a promising experimental platform for the quantum simulation of spin models. In this thesis, we first solved a long-standing challenge to this approach caused by the random loading of the traps, with only 50% of them filled with single atoms. We have engineered a robust and easy-to-use method to assemble perfectly filled two-dimensional arrays of 87Rb atoms by moving them one by one with a moveable optical tweezers controlled by computer, a technique further enhanced to trap, image and assemble three-dimensional arrays. We then implemented the quantum Ising model by coherently coupling ground-state atoms to a Rydberg level. After finding experimental parameters where the dipole-dipole interaction takes the ideal form of a van der Waals shift, we performed adiabatic preparation of the Néel state. We showed that the coherence time of our excitation lasers limited the efficiency of this technique. We then used a different type of interaction, a resonant dipolar coupling, to implement XY spin models and notably the Su-Schrieffer-Heeger model, known for its fermionic…

Advisors/Committee Members: Lahaye, Thierry (thesis director).

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Des atomes individuels piégés dans des matrices de pinces optiques et excités vers des états de Rydberg forment une plateforme expérimentale performante pour la simulation quantique de problèmes à N corps, comme le confirment les récents progrès dans le domaine. Lors de cette thèse, nous avons d’abord montré la production de matrices de pinces optiques, toutes chargées par des atomes uniques dans leur état fondamental. Notre technique de piégeage a été étendue au cas des atomes de Rydberg. Ces derniers sont chassés des zones de haute intensité par la force pondéromotrice. Par conséquent, nous avons créé par holographie des zones sombres entourés de lumière, pour les confiner. Nous avons aussi étudié les corrélations entre spins dans le cas des Hamiltoniens d’Ising ou XY, en utilisant le régime d’interaction de van der Waals ou dipolaire résonnant. Lors de notre étude du modèle d’Ising, nous avons observé l’apparition de corrélations antiferromagnétiques au cours d’une variation temporelle de l’Hamiltonien, mettant en évidence une vitesse effective pour la propagation des corrélations, ainsi qu’un mécanisme caractéristique de croissance site-à-site. Pour le modèle XY, nous avons montré la préparation d’un nombre contrôlé d’excitations de spin, ainsi que la production de chaînes ferromagnétiques, ou d’un ensemble de chaînes ferromagnétiques anti-alignées deux à deux. Enfin, nous avons utilisé d’autres termes d’échange, présents dans l’interaction dipolaire, pour créer des amplitudes de saut complexe pour une particule effective. Cette utilisation a conduit à l’apparition d’un champ de jauge artificiel, dont l’effet a été mesuré sur un système minimal composé de trois atomes, et ouvre la voie à l’observation d’états de bords chiraux, caractéristiques des isolants topologiques.

Rydberg-based platforms, involving single atoms trapped in arrays of optical tweezers and excited to Rydberg states, have recently proven attractive to perform quantum simulation of many-body physics. In this thesis, we first demonstrated the generation of arrays of optical tweezers fully loaded by single ground-state atoms. The trapping technique was then extended for Rydberg atoms. The latest are repelled from high-intensity regions via the ponderomotive force, so we created holographically dark regions surrounded by light to confine them. We also studied spin-spin correlations in artificial Ising or XY magnets, engineered by using either the van der Waals or the resonant dipolar coupling between Rydberg atoms. In the Ising case, we observed the growth of antiferromagnetic correlations during a dynamical tuning of the Hamiltonian, revealing an effective velocity for the spreading of correlations, and a typical site to site build-up mechanism. In the XY case, we demonstrated the preparation of a controlled number of spin excitations, and the generation of 1D XY ferromagnets and a 2D stripy order phase (ferromagnetic chains anti-aligned with respect to each other). Finally, we used additional exchange terms of the dipole-dipole interaction to…

Advisors/Committee Members: Lahaye, Thierry (thesis director).

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Au cours des dernières années, les progrès technologiques dans le domaine de la nanophotonique ont permis le développement des nanostructures optiques. Ces dernières possèdent la particularité de modifier l'émission lumineuse de nanoémetteurs quantiques .Cependant, l’interaction lumière-matière est considérée comme étant véhiculée par le champ électrique. Les études se sont alors concentrées sur le contrôle et la modification des propriétés d'excitation et d'émission des transitions dipolaires électriques.Récemment, il a été décrit qu’il existe dans la nature des nanoémetteurs possédant des transitions magnétiques détectables : ces nanoémetteurs sont les ions lanthanides.Les nanostructures optiques développant des résonances magnétiques pourraient alors modifier l’émission et l’excitation de transitions dipolaires magnétiques, de la même manière que leurs homologues électriques.Dernièrement , il a été démontré théoriquement que certain type de nanostructure, peuvent renforcer le champ magnétique optique par deux ordres de grandeur et qu’une fois couplé à un dipôle magnétique, ils peuvent augmenter fortement la fluorescence des transitions magnétiques comme celle qui que se trouve dans les ions de lanthanide.Une étude publiée dans Physical review letters, a rapporté qu’il était aussi possible d’étudier l’excitation de transitions dipolaires magnétiques.L’objectif de ma thèse a donc été d’utiliser certaines nanostructures ayant des affinités particulières avec le champ magnétique afin d’étudier et de manipuler l’émission et l'absorbption de transitions dipolaires magnétiques.

During the last years, technological progresses in the field of nanophotonic have allowed the development of optical nanostructures to manipulate the emission of fluorescent nanoemitters . However, light-matter interactions are usually considered to be mediated by the optical electric field only, discarding the magnetic side of it. Indeed, most of the past studies have been only studying the modification of the excitation or emission properties of electric dipole transitions. Recently, it was demonstrated that magnetic dipole could also be found in lanthanide ions. It was also shown that by changing the magnetic local density of states near these ions, the emission fluorescent of the magnetic transitions could be enhanced or decreased with respect to their electric counterpart. In here, we demonstrate experimentally, in perfect agreement with numerical simulations, the manipulation of magnetic and electric dipolar transitions by means of plasmonic cavities. Using a near-field scanning optical microscope (NSOM), we bring in close proximity a nanoparticle doped with trivalent europium to plasmonic cavities of different sizes made of aluminum , allowing perfect control over the interactions between the emitter and the nanostructures. In this study, we show both an increase and decrease of electric and magnetic signal from the particle, and we also display the spatial distribution of both the electric and magnetic radiative local density of state…

Advisors/Committee Members: Aigouy, Lionel (thesis director), Mivelle, Mathieu (thesis director).

▼ The Indian Ocean Dipole (IOD) is an interannual mode of variability in the tropical Indian Ocean which has the potential to severely impact the surrounding countries. A prominent feature of the IOD is its positive skewness, where positive IOD events tend to be larger than negative events resulting in stronger impacts. Models from the Coupled Model Intercomparison Project phase 5 (CMIP5) show a threefold increase in the frequency of extreme events by 2100. However, the contribution of feedbacks associated with the IOD to this skewness and how they respond to increasing greenhouse gases are not well understood. The nonlinearity of four feedbacks (the Bjerknes feedback, sea surface temperature (SST)-cloud-radiation feedback, wind-evaporation-SST feedback, and nonlinear dynamic heating) was investigated and their responses to a warmer climate examined using CMIP5 models. A single model was first used to examine the nonlinearity of the four feedbacks, allowing the cause and effect of each feedback process to be determined. Following this, the analysis was applied to a multi-model ensemble to determine the cause of positive IOD skewness. The role of nonlinear dynamic heating in increasing the frequency of extreme events was then examined. This provides a better understanding of IOD dynamics and future behaviour. The positive Bjerknes feedback controls IOD skewness through the thermocline feedback. In a warmer climate, models show that the skewness of the IOD weakens and the asymmetry of the thermocline feedback displays a significant relationship with this reduced skewness. This decreased asymmetry occurs due to the mean state change of the tropical Indian Ocean where the Walker circulation exhibits weakening. The weaker mean westerly winds allow the climatological thermocline to shoal in the east, reducing the asymmetry of the thermocline feedback and thereby IOD skewness. The other feedbacks do not show as strong a relationship with IOD skewness. The negative SST-cloud-radiation feedback shows stronger damping of positive IODs and this is detrimental for IOD skewness. Under greenhouse warming there appears to be a shift amongst most models, with weaker damping of positive IODs and stronger damping of negative IODs. This is unfavourable for the reduction in skewness that occurs under increasing greenhouse gases. The positive wind-evaporation-SST feedback is not well simulated in coupled models. Therefore the relationship between IOD skewness and the wind-evaporation-SST feedback is uncertain and there does not appear to be a significant change in the asymmetry of this feedback in a warmer climate. Nonlinear dynamic heating involves advection of heat by oceanic currents, reinforcing positive IODs but damping negative IOD events. Amongst the models analysed, this process does not appear to contribute significantly to IOD skewness; however it does play an important role in the generation of extreme events and the projected increase. Nonlinear zonal and vertical advection during…

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Στή διατριβή αυτή αναπτύσσονται δύο θεωρίες τχού προσδιορίζουν τή βασική καί μερικές άπό τίς διεγερμένες καταστάσεις των διπολικών κρυστάλλων « Ή πρώτη άπό αυτές, πού αναφέρεται σάν "κλασσική" ασχολείται μέ τό πρόβλημα τής βασικής κατάστασης, όταν υπάρχει £να εξωτερικό ομογενές μαγνητικό πεδίο, καί αποτελεί επέκταση της θεωρίας τοο Niemeijer πού ασχολήθηκε μέ τό πρόβλημα της βασικής κατάστασης γωρίς τήν επίδραση εξωτερικού πεδίου. *Η θεωρία, ονομάσθηκε κλασσική, γιατί τελικά, σάν μεταβλητές στό πρόβλημα, χρησιμο- ποιοονται οι αναμενόμενες τιμές της ολικής στροφορμής, πού υπάρχει σέ κάθε κρυσταλλική θέση. *Η θεωρία αυτή όπως καί του Niemeijer, 7 βασίζεται στην προσέγγιση των Lutfinger καί Tisza , σχετικά μέ τήν περιοδικότητα τής αναμενόμενης τιμής, τών ολικών στροφορ- μών τοο κρυστάλλου. *Η δεύτερη θεωρία, είναι καθαρά κβαντική, καί επομένως γε~ νικώτερη τής πρώτης, άν καί βασίζεται στην ίδια προσέγγιση των Luttinger καί Tisza. Προβλέπει τή βασική καί μερικές άπό τίς διεγερμένες καταστάσεις τοϋ κρυστάλλου είτε υπάρχει, είΐτε όχι, εξωτερικό ομογενές μαγνητικό πεδίο, σέ οποιαδήποτε διεύθυνση. Ή διαφορά τών δύο θεωριών οφείλεται στην εκλογή διάφορε'!,! ?<ών κυματοσυναρτήσεων γ ua τή λύση του προβλήματος. Στην κλασσική, χρησιμοποιείται κυματοσυνάρτηση τής μορφής Hartree, δηλ, γινόμενο κυματοσυναρτήσεων μιας στροφορμής, ένώ στην κβαντική γενική κυματοσυνάρτηση πολλών στροφορμών. "Εφαρμογή τών δύο θεωριών γίνεται, μέ αξιοσημείωτα αποτελέσματα, στην περίπτωση του παραμαγυητι."ου άλατος CM,Η, ~

In this dessertation we develop two methods that determine the ground state and some of the excited states of dinolar crystals. The first method, refered, to as "classical", deals with the problem of t:ie ground state in the presence of an external 8 homogeneous magnetic field. This is an extension of Niemeijer's theory, which deals with the problem of the ground state in the absence of an external magnetic field. This method was named classical, because one finally uses as variables of the problem bhe expectation value s of the total angular momentum of the crystal sites„ This theory, as well as the one by Niemeijer, is 7 Dased on the Luthinger and Tisza approximation for the periodicity of the expectation value of the total angular momentum of bhe crystal. The second method is purely quantum mechanical and consequently more general than the first one, even though Lt is based on the same approximation of Luthinger and Tisza. Ct predicts the ground state and some of the excited states of ;he crystals with, or without, an external homogeneous magnetic field in any direction. The difference between the two theories is due to the choice of different wave functions for the solution of the problem. In this case of the theory, Hartree - type wave functions are used, i.e. a product of one particle wave functions 3f angular Momentum. In the case of the quantum Method no res- :rictions are imposed on the wave functions. The two methods are succesfully applied for the case of :he paramagnetic salt C.M.N.-

▼ In the first part of the thesis, we study the absorption coefficient of quantum dots doped in metallic photonic crystals under different circumferences. We study numerically the temporal evolution of the absorption coefficient profile where a probe field is applied to monitor the absorption process in two cases, when quantum dots are embedded lightly and densely. We also studied the effect of a changing plasma frequency on the absorption profile of quantum dots two possible field configurations. We show that the changes in plasma energy can take the system from the absorption region to the transparent and gain region. As the next part, we developed an analytical theory for the photonic band structure and density of states of two-dimensional rectangular metallic photonic crystals. We found that the location of the photonic band gap can be controlled by modifying the plasma energy of either metal. We showed that by changing the plasma energy one can control the spontaneous emission in the metallic photonic crystal. Finally, I studied hybrid systems (quantum dot - metallic nanoparticle). The main advantage of hybrid systems when compared with other nano-optical systems is the possibility for direct energy and quantum information transfer between nanoparticles. In this project, we investigate the control of thermal energy loss in metallic nanoparticles, an effect which could destroy the quality of transformed information if not properly controlled.

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Les atomes neutres sont des candidats prometteurs pour la réalisation et l’étude d’états intriqués à quelques dizaines de particules. Pour générer de tels états, une approche consiste à utiliser le mécanisme de blocage dipolaire résultant des fortes interactions dipôle-dipôle entre atomes de Rydberg.Suivant cette approche, cette thèse présente la conception et la caractérisation d’un dispositif expérimental permettant de manipuler des atomes de 87Rb individuels piégés dans des pinces op- tiques microscopiques, et à les exciter vers des états de Rydberg. Un environnement électrostatique stable et des électrodes de contrôle permettent une manipulation fine de ces états. Avec deux pinces optiques séparées de quelques microns, nous démontrons le blocage de Rydberg entre deux atomes, et nous observons leur excitation collective.Enfin, en opérant en régime de blocage partiel, nous développons une méthode permettant de mesurer l’interaction de van der Waals ∆E = C6 /R6 entre deux atomes séparés par une distance R contrôlée. Les coefficients C6 obtenus pour différents états de Rydberg sont en bon accord avec des calculs théoriques ab initio, et nous observons l’augmentation spectaculaire de l’interaction en fonction du nombre quantique principal n de l’état de Rydberg.

Neutral atoms are promising candidates for the realization of entangled states involving up to a few tens of particles. To generate such states, one approach consists in using the dipole blockade mechanism, which results from the strong dipole-dipole interactions between Rydberg atoms.Following this approach, this thesis describes the design and the characterization of an experimental apparatus allowing to manipulate single 87Rb atoms trapped in microscopic optical tweezers, and to excite them towards Rydberg states. A stable electrostatic environment and controlled electrodes enable the fine manipulation of these states. Using two optical tweezers separated by a few microns, we demonstrate the Rydberg blockade between two single atoms, and we observe their collective excitation.Finally, by operating in the partial blockade regime, we develop a method allowing to measure the van der Waals interaction ∆E = C6 /R6 between two atoms separated by a controlled distance R. The C6 coefficients obtained for various Rydberg states agree well with ab initio theoretical calculations, and we observe the dramatic increase of the interaction with the principal quantum number n of the Rydberg state.

Advisors/Committee Members: Browaeys, Antoine (thesis director).

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Les vapeurs atomiques confinées dans des cellules nanométriques constituent une plateforme intéressante pour la réalisation de senseurs atomiques. Dans cette thèse, nous étudions l’interaction entre la lumière et un ensemble d’atomes d’alcalins dans une telle cellule. Nous nous concentrons sur les phénomènes qui pourraient modifier la réponse optique du système et ainsi affecter la sensibilité du senseur. Premièrement, nous étudions la réponse non locale à la lumière induite par le mouvement des atomes dans la vapeur thermique. Quand la distance de relaxation des atomes excède la taille de la cellule, la réponse optique dépend de la taille du système. En transmission, nous avons montré que cela entraine une modification des propriétés de la vapeur avec une période égale à la longueur d’onde de la transition optique. Nous avons ensuite montré que lorsque la densité augmente, la réponse redevient locale. De plus, dans ce régime dense, l’interaction dipôle-dipôle résonnante engendre des déplacements de fréquences collectifs pour des ensembles sub-longueur d’onde. Nous avons démontré que ces shifts sont induits par la cavité formée par la cellule, clarifiant ainsi un débat de plus de 40 ans. Pour ce faire, nous avons développé un modèle pour extraire les effets de la densité déconvolués de ceux de la cavité. Proche des surfaces, la réponse optique des atomes est aussi impactée par l’interaction de van der Waals. Nous avons introduit une nouvelle méthode pour extraire avec précision la force de cette interaction. Nous avons également construit une nouvelle génération de nano-cellules super-polies en verre et enfin comparé les propriétés spectrales en transmission et spectroscopie hors d’axe.

Alkali vapors confined in nano-scale cells are promising tools for future integrated atom-based sensor. In this thesis, we investigate the interaction between light and an ensemble of atoms confined in a nano-geometry. We focus on the different processes that can modify the optical response of the atomic ensemble and possibly affect the sensitivity of a sensor based on that technology. First, we study the non-local response of atoms to a light excitation due the atomic motion in thermal vapors. When the distance over which the atoms relaxes is larger than the size of the cell, the optical response depends on the size of the system. We have observed that for transmission spectroscopy, this leads to a periodic modification of the optical response with a period equal to the wavelength of the optical transition. Subsequently we showed that when the density of atom increases, the atomic response becomes local again. In this dense regime, the resonant dipole-dipole interaction in a sub-wavelength geometry leads to collective frequency shifts of the spectral lines. We demonstrate that these shifts were induced by the cavity formed by the cell walls, hence clarifying a long-standing issue. We developed a model to extract the density shifts deconvolved from the cavity effects. Close to a surface, the optical response is also affected by the…

Advisors/Committee Members: Browaeys, Antoine (thesis director), Sortais, Yvan (thesis director), Adams, Charles (thesis director).

▼ Three-dimensional linear ray theory is used to investigate internal waves interacting with a Lamb-Chaplygin pancake vortex dipole. These interactions involve waves propagating in the same (co-propagating) and opposite (counter-propagating) horizontal directions as the dipole translation. Co-propagating internal waves in the vertical symmetry plane between the vortices of the dipole can approach critical levels where the wave energy is absorbed by the dipole or where the waves are overturned and possibly break. As wave breaking cannot be simulated with this linear model, changes in wave steepness are calculated to aid in estimating the onset of breaking. Counter-propagating internal waves in the vertical symmetry plane can experience horizontal and vertical reflections, including turning points similar to waves in two-dimensional steady shear. Wave capture is also a possible effect of either type of interaction, depending on initial wave properties and positioning relative to the vortex dipole. Away from the vertical symmetry plane, a spanwise converging (focusing) and diverging (defocusing) of wave energy is observed in co- and counter-propagating interactions as symmetric off-center rays interact with the dipole's individual vortices. Some off-center rays experience multiple horizontal refractions similar to wave trapping.

▼ In recent years, improved control of the motional and internal quantum states of ultracold neutral atoms and ions has opened intriguing possibilities for quantum simulation and quantum computation. Many-body effects have been explored with hundreds of thousands of quantum-degenerate neutral atoms and coherent light-matter interfaces have been built. Systems of single or a few trapped ions have been used to demonstrate universal quantum computing algorithms and to detect variations of fundamental constants in precision atomic clocks. Now in our experiment we investigate how the two systems can be advantageously combined. We immerse a single trapped Yb+ ion in a Bose-Einstein condensate of Rb atoms. Our hybrid setup consists of a linear RF-Paul trap which is overlapped with a magnetic trap and an optical dipole trap for the neutral atoms. A first synergetic effect is the sympathetic cooling of the trapped ions to very low temperatures through collisions with the ultracold neutral gas and thus without applying laser light to the ions. We observe the dynamics of this effect by measuring the mean ion energy after having an initially hot ion immersed into the condensate for various interaction times, while at the same time monitoring the effects of the collisions on the condensate. The observed ion cooling effect calls for further research into the possibility of using such hybrid systems for the continuous cooling of quantum computers. To this end a good understanding of the fundamental interaction processes between the ion and the neutrals is essential. We investigate the energy dependent elastic scattering properties by measuring neutral atom losses and temperature increase from an ultracold thermal cloud of Rb. By comparison with a Monte-Carlo simulation we gain a deeper understanding of how the different parameters affect the collisional effects. Additionally, we observe charge exchange reactions at the single particle level and measure the energy-independent reaction rate constants. The reaction products are identified by in-trap mass spectrometry, revealing the branching ratio between radiative and non-radiative charge exchange processes.

▼ Lipid-protein and protein-protein interactions are likely to play important roles in the function and regulation of charge-transporting membrane proteins. This thesis focuses on two different membrane proteins, the photosynthetic reaction centre (RC) from purple bacteria and the Na+,K+-ATPase. The influence of the lipid surroundings and cholesterol derivatives on the kinetics of electron transfer of the RC were investigated by reconstituting the protein in phosphatidylcholine vesicles containing cholesterol and derivatives known to modulate the membrane dipole potential. The experiments performed on the Na+,K+-ATPase were designed to contribute to a better understanding of the role that oligomeric protein-protein interactions have in the enzyme’s mechanism. Our results show that the cholesterol derivatives significantly modify the electron transfer kinetics within the RCs and their multiphasic behavior. These effects seem to be associated with the extent of the dipole potential change experienced by the RC within the phospholipid membrane. Indeed, the largest effects on the rates are observed when 6-ketocholestanol and cholesterol are present, consistent by with their previously demonstrated significant increase of the dipole potential. We interpret this data as indicating an increased free energy barrier for protons to enter the protein. The consequences of the increased dipole potential seem to be experienced across the entire protein, since the rates of the P+QA- charge recombination in the presence of AQ- acting as QA are also modified by the same effectors. Also interesting is the effect of the dipole potential on the two conformational states of the RCs (previously reported) as revealed by the biphasic decays of the electron transfer kinetics. In particular, we report for the first time a biphasicity of the P+QA- charge recombination in the WT RCs. This non exponential behaviour, absent in the phospholipid membrane or isolated RCs, is induced by the presence of the cholesterol derivatives, suggesting that the equilibration time between the two RC conformations is slowed down significantly by these molecules. According to this work, the dipole potential seems to be an important parameter that has to be taken into account for a fine understanding of the charge transfer function of the RCs. Reported literature values of the dissociation constant, Kd, of ATP with the E1 conformation of the Na+,K+-ATPase based on equilibrium titrations and kinetic methods disagree. Using isothermal titration calorimetry (ITC) and simulations of the expected equilibrium behaviour for different binding models, this thesis presents an explanation for this apparent discrepancy based on protein-protein interactions. Because of the importance of Mg2+ in ATP hydrolysis, kinetic studies of Mg2+ binding to the protein were also carried out. These studies showed that ATP alone is responsible for Mg2+ complexation, with no significant contribution from the enzyme environment.

▼ This dissertation studies electric polar molecular self-assemblies and artificial electric polar molecular rotors via low temperature ultrahigh vacuum scanning tunneling microscopy. The influence of molecular dipole interaction on two fluorinated sexiphenyl (2F-6P) isomers self-assembly processes is investigated. The slight modification on 6P induces a dipole moment in the molecule and results a completely different assembly structure. Analysis of cluster dipolar energy and atom specific interactions between molecules reveals that fluorinated 2F-6P self-assembly is under more influence of H-F interaction than the dipolar interaction for closer intermolecular distances.A comprehensive study of a double decker molecular rotor [phthalocyaninato-porphyrinato-europium] is conducted on different substrates. Single molecular rotor has its alkyl chains removed after adsorption on Au(111). With thermal energy provided from the substrate, the rotor spins at both ~ 80 K and ~ 5 K surface temperatures. Molecule rotations can be terminated mechanically using a blocker fragment and its rotation can be reinitiated after the removal of this blocker. Single molecular rotor survives rotation during lateral movement under tip manipulation.On Ag(111) surface, the molecular rotors self-assemble into parallelogram clusters. Alkyl chains of the stators are also intact leading to large inter-molecular distances. No cluster rotation is observed in experiments because the dipole interaction energy in a parallelogram network needs to be overcome. On Cu(111), the molecular rotors self-assemble into infinite hexagonal networks, which is the most compact assembly. STM tip provides electrical energy for rotor network to rotate through its electrical field. The dipolar interaction energy between rotors has a degenerate ground state for such rotors network, which makes a synchronized rotation of the network achievable. Synchronized rotation by means of STM lateral manipulation and imaging are observed in large flat areas. Detail analysis of the rotation process reveals that synchronized rotation of the rotors do not propagate into areas close to step edges, and consequently it creates the rotor domains. Advisors/Committee Members: Hla, Saw-Wai (Advisor).

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Capes

Enfocam-se evidencias de modelagem numérica e observacional da influência das anomalias de TSM dos Oceanos Pacífico Equatorial (El Niño e La Niña) e Atlântico Tropical (dipolo de TSM interhemisférico) que permeiam os modos de variabilidade climática global (MVCG) sobre o ciclo evolutivo de uma categoria de SCM, o complexo convectivo de mesoescala tropical (CCMT) comumente formado sobre a Região Nordeste do Brasil - NEB. A análise inclui dados de reanálises do conjunto ERA-interim do tipo full resolution com saída de 6 em 6 horas do European Center for Médium Range Wheather Forecasting (ECMWF), como condição de contorno e lateral para configurar um cenário numérico de mesoescala. Inclui também dados de precipitação diária e mensais dos postos pluviométricos para o período de 1957 a 1998 provenientes da rede de monitoramento da Agência Executiva de Gestão das Águas do Estado da Paraíba – AESA - PB. O modelo BRAMS foi ajustado para este propósito, em que se utilizou duas grades aninhadas com resolução espacial de 5 km. O ambiente de mesoescala simulado numericamente reproduziu, com eficiência, os estágios de desenvolvimento do ciclo evolutivo do CCMT; em que se investigou as principais características atmosféricas de superfície, da dinâmica na estrutura vertical e da termodinâmica do sistema. Ressaltou-se o papel do trabalho combinado entre a convergência de umidade em baixos níveis; como fonte de energia é favorável a formação de um corredor de umidade entre a superfície e 850 hPa, o núcleo de convergência de massa nas camadas intermediárias da troposfera associado ao centro de movimentos ascendentes, a instabilidade convectiva e o cisalhamento vertical do vento na gênese e na manutenção do sistema. Após submeter o cenário numérico de mesoescala em ambiente de MVCG, constatou-se: supressão dos movimentos ascendentes associados à queda do suprimento de umidade em baixos níveis resultando na quebra do corredor de umidade entre a superfície e 850 hPa, entre outras características atmosféricas, nas simulações com anomalias de TSM relacionadas a El Niño e dipolo positivo de TSM. Padrão contrário foi constatado nas simulações com anomalias de TSM relacionadas à La Niña e dipolo negativo de TSM. Sinais semelhantes foram encontrados nas análises dos dados observados de precipitação. A oscilação interanual da precipitação observada associada aos SCMs revela que em anos de El Niño e dipolo negativo de TSM os sistemas precipitantes em mesoescala são mais numerosos. Se subtraído os episódios fracos de El Niño se observa um resultado abaixo do número de…

Advisors/Committee Members: CAVALCANTI, Enilson Palmeira., BRITO, José Ivaldo Barbosa de., GOMES FILHO, Manoel Francisco., ARAVÉQUIA, José Antônio., NÓBREGA, Ranyére Silva..

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

As interações que ocorrem dentro de hemoproteínas são importantes para os sistemas biológicos e constituem termos de forte interesse para compreensão de sistemas vivos. Desta forma, é importante conhecer as interações vibracionais e eletrostáticas neste sistema. Neste trabalho foi feito um estudo sobre a interação entre o íon ferro(II) e o monóxido de carbono confinados em cavidades esféricas que mimetizam volumes de cavidades proteicas e um estudo do potencial de Morse confinado para o monóxido de carbono. Dessa forma, descrevemos como os autovalores de energia no estado fundamental para os potenciais da interação íon-dipolo e Morse se comportam no confinamento para um dos possíveis ligantes da mioglobina e da hemoglobina. Para o potencial de Morse desdobramos os cálculos para as seguintes moléculas diatômicas: nitrogênio, lítio e hidreto de sódio. Foi calculada, via Método Variacional, a energia para o sistema íon-dipolo confinado e potencial de Morse confinado. A função de onda teste sugerida foi inspirada na Mecânica Quântica Supersimétrica. Por fim, verificou-se como a energia de interação entre o íon e o dipolo se comporta com a mudança de permissividade do meio e como é o comportamento vibracional das moléculas de CO, N2, Li2 e NaH.

The interactions that occur within hemeproteins were important for biological systems and they were terms of strong interest for understanding living systems. ln this way, it is important to know the vibrational and electrostatic interactions in this system. ln this work a study is made on the interaction between iron ion and carbon monoxide confined in spherical cavities that mimic volumes of protein cavities and a study of the confined Morse potential for carbon monoxide. ln this way, we describe how the eigenvalues of energy in the ground state for the potentials of ion-dipole interaction and Morse behave in the confinement regime for one of the possible ligands of myoglobin and hemoglobin. For the Morse potential , we perform the calculations for the following diatomic molecules: nitrogen, lithium and sodium hydride. The energy for the confined ion-dipole system is calculated using the Variational Method. The suggested trial wavefunction is inspired by Supersymmetric Quantum Mechanics. Finally, it is verified how the energy of interaction between the ion and the dipole behaves in a change…

Advisors/Committee Members: Universidade Estadual Paulista (UNESP), Drigo Filho, Elso [UNESP].

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Le travail théorique présenté dans cette thèse concerne la formation de molécules ultra-froides bialcalines et le contrôle de leurs degrés de liberté externes et internes. Cette étude est motivée par les nombreuses expériences en cours visant à l'obtention d'un gaz quantique dégénéré de molécules dans leur état fondamental absolu. Le schéma de formation étudié repose sur le processus de transfert adiabatique stimulé (STIRAP) réalisé en présence d'un potentiel optique de piégeage (réseau optique) des atomes et des molécules.Nous avons déterminé les paramètres du réseau optique (intensité et fréquence du champ laser) qui permettent de piéger efficacement des dimères d'alcalins en évaluant la polarisabilité dynamique acquise par les molécules soumises à un champ externe. Ces calculs reposent en particulier sur la connaissance détaillée de la structure électronique des molécules. Nous avons identifié des plages de longueur d'ondes dites « magiques » où la polarisabilité est la même pour chaque niveau peuplé au cours du transfert adiabatique, permettant ainsi un transfert optimal. Ce formalisme nous a également permis d'obtenir les coefficients Van der Waals de l'interaction à longue portée nécessaires pour étudier les taux de collisions entre molécules.Nous avons réalisé une étude plus détaillée de la molécule RbCs. En étudiant précisément la probabilité de transition de la molécule vers un niveau excité, nous avons proposé un schéma STIRAP pour transférer des molécules de RbCs, initialement dans un niveau vibrationnel excité, vers leur état rovibrationnel fondamental.Ces travaux ont montré l'importance de la connaissance précise de la structure hyperfine de l'état électronique moléculaire excité pour réaliser un gaz dégénéré de molécules dans un état quantique bien défini. Un modèle asymptotique nous a permis d'obtenir une première estimation de la structure hyperfine des courbes d'énergies potentielles des premiers états moléculaires excités des molécules Cs2 et RbCs.

The theoretical work presented in this thesis is focused on the formation of ultracold bialcaline molecules and on the control of their external and internal degrees of freedom. This study is motivated by the increasing number of experiments aiming at obtaining a quantum degenerate gas of molecules in their absolute ground state. The formation scheme we worked on is based on the Stimulated Raman Adiabatic Passage (STIRAP) technique operated while molecules are trapped inside an optical lattice.We have determined the parameters of the optical lattice (intensity and wavelength of the laser) that allow for an efficient trapping of the alkali dimers by evaluating the dynamic polarizability of molecules in the presence of an external field. Such calculations require the accurate knowledge of the electronic structure of the molecules. We have identified the so-called ``magic'' wavelength for which all levels populated during the STIRAP sequence have the same polarizability, thus ensuring an optimal transfer. The same approach has also been used to compute…

Advisors/Committee Members: Dulieu, Olivier (thesis director).

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Cette thèse porte sur l’étude des interactions dipôle-dipôle entre des atomes de Rydberg froids formés au sein d'un jet supersonique, en particulier sur l'étude des transitions Landau-Zener autour d'une résonance de Förster dans des sytèmes de paires d'atomes de Rydberg. L'adiabaticité de la transition dépend de la distance entre les atomes de la paire et est contrôlée par l'application d'un champ électrique homogène dépendant du temps. L'étude des processus binaires, non collisionnels et dont l'efficacité est contrôlé par l'expérimentateur, permet de sonder l'environnement de chaque atome et constitue une mesure de la distribution de plus proches voisins. Nous en déduisons une méthode originale de mesure directe et précise de la densité d'un gaz de Rydberg. Cette méthode ne nécessite ni la connaissance du nombre d'atomes de Rydberg ni celle du volume du gaz. Après un passage adiabatique de paire, les atomes de Rydberg constituant cette paire se trouvent dans un état intriqué. Nous proposons une méthode pour prouver leur intrication, fondée sur la mesure de la fluctuation quantique au cours d'oscillations de Rabi entre des états de paire.

This thesis deals with the study of dipole-dipole interaction between Rydberg atoms, in particular of Landau-Zener transitions around a Förster resonance for Rydberg atoms pairs. The adiabaticity of the transition depends of the interatomic distance and is controlled by a time-dependant electric field. The adiabatic transition efficiency is the control knob to probe the nearest neighbour distribution. We infer a new and original method to measure the density of a gas very accurately by probing the nearest neighbour distibution in the gas, which depends parametrically on its density. Such adiabatic transitions should leave the pair of Rydberg atoms in an entangled state. We investigated how quantum fluctuations could reveal the atom entanglement, in two-atom Rabi oscillation measurements.

Advisors/Committee Members: Pillet, Pierre (thesis director).

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Le problème de la détection et de ladescription des nouveaux états quantiquesmacroscopiques, caractérisées par des propriétésexotiques et non-conventionnelles, estd’importance fondamentale dans la physiquemoderne. Ces états offrent des perspectivesfascinantes dans le domaine de traitementd’information, de simulations quantiques et derecherche des nouveaux types des matériaux.Dans ce travail de thèse nous développons unethéorie qui permet de décrire des phases non conventionnellesdans des systèmes des gazultra-froids dipolaires. Ces systèmes sontactivement étudiés expérimentalement enutilisant des atomes à grand-spins, desmolécules polaires et des excitations dipolairesdans des semi-conducteurs. Nous mettonsl'accent sur la révélation du rôle de l’interactiondipôle-dipôle à long porté.Nous considérons l’effet de rotonization dansun système de gaz des bosons dipolaires «tiltés»aux interactions faibles dans une couchehomogène. Nous prédisons l’effet derotonization pour un gaz de Bose faiblementcorrélé des excitons dipolaires dans une couchede semi-conducteur et nous calculons lediagramme de stabilité. Ensuite, nousconsidérons des superfluides d’onde-p desfermions identiques dans des réseaux 2D.Finalement, nous faisons une discussion sur unautre état superfluide intéressant des moléculespolaires fermioniques, qui devrait apparaitredans des systèmes bicouches.

The problem of revealing anddescribing novel macroscopic quantum statescharacter- ized by exotic and non-conventionalproperties is of fundamental importance formodern physics. Such states offer fascinatingprospects for potential applications in quantumin- formation processing, quantum simulation,and material research. In the present Thesis wedevelop a theory for describing nonconventionalphases of ultracold dipolar gases.The related systems of large-spin atoms, polarmolecules, and dipolar excitons in semiconductorsare actively studied in experiments.We put the main emphasis on revealing the roleof the long-range character of the dipole-dipoleinteraction.We consider the effect of rotonization for a 2Dweakly interacting gas of tilted dipolar bosonsin a homogeneous layer. We predict the effectof rotonization for a weakly correlated Bosegas of dipolar excitons in a semiconductorlayer and calculate the stability diagram. Wethen consider p-wave superfluids of identicalfermions in 2D lattices. Finally, we discussanother interesting novel superfluid offermionic polar molecules

Advisors/Committee Members: Shlyapnikov, Georgy V. (thesis director).

▼ Peptoids are peptidomimetic polymers, which have attracted much attention over the past two decades. They have similar building blocks to peptides, and the similarity makes the backbone of peptoids hydrophilic and biocompatible.1 Two types of peptoid polymers are under development. One is sequence-defined peptoids, which exhibit excellent bioactivities.2 Another one is polypeptoids. The good biocompatibility and highly tunable side chain substituents allow polypeptoids to be used broadly in future biomedical applications. Varying polymer architectures, including linear polymers, cyclic polymers, comb-like polymers, and dendrimers can provide distinctive properties to the polymers. Cyclic polymers employ a cyclic architecture and lack chain ends, so their diffusion behaviors, aggregation behaviors, thermal transition behaviors, and crystallization behaviors are very different from the linear analogs. Facile synthetic approaches are required to expand the application of cyclic polymers into a broader scope. In chapter 1, the history of polypeptoids, the synthesis of cyclic polymers, the development of functional polypeptoids, and the cutting-edge biomedical research of polypeptoids were reviewed. In chapter 2, we reported our most recent work of the polymerization reaction of cyclic polypeptoids using a bicyclic amidine initiator. The study was described from the aspects of molecular weight control, identification of the polymerization, kinetics of the polymerization, and polymer architecture. Zwitterionic ring-opening polymerization of N-substituted N-carboxyanhydrides (R-NCA) mediated by the bicyclic amidine has been developed and well-defined cyclic polypeptoids can be synthesized. Pursuit of varying polymer architectures never ends because unique properties can be possibly discovered with the latest developed architecture. Besides cyclic polymers, linear bottlebrush polymers also attracted much attention due to their distinctive features. In chapter 3, we took one step forward and synthesized the cyclic bottlebrush polypeptoids. We then conducted a systematic study on the characterization of the cyclic bottlebrush polypeptoids and on the solution aggregation behaviors of zwitterionic cyclic polypeptoids with and without long side chains. It was revealed that zwitterionic cyclic polypeptoids tend to form clusters due to dipole-dipole interaction in methanol and even the long side chains cannot prevent this process. Another important direction of polypeptoid research, the biomedical application, was assessed in chapter 4. Redox-responsive micelles based on amphiphilic diblock copolypeptoids were prepared, and the solution stability, the morphology in dry state, the redox-responsive behaviors, drug release in vitro, and cell viability and cell inhibition activity of the micelles were completely studied.