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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Theoretical Description of Electronic Transitions in Large Molecular Systems in the Optical and X-Ray Regions

List, Nanna Holmgaard January 2015 (has links)
The size and conformational complexity of proteins and other large systems represent major challenges for today's methods of quantum chemistry.This thesis is centered around the development of new computational tools to gain molecular-level insight into electronic transitions in such systems. To meet this challenge, we focus on the polarizable embedding (PE) model, which takes advantage of the fact that many electronic transitions are localized to a smaller part of the entire system.This motivates a partitioning of the large system into two regions that are treated at different levels of theory:The smaller part directly involved in the electronic process is described using accurate quantum-chemical methods, while the effects of the rest of the system, the environment, are incorporated into the Hamiltonian of the quantum region in an effective manner. This thesis presents extensions of the PE model with theaim of expanding its range of applicability to describe electronic transitions in large molecular systemsin the optical and X-ray regions. The developments cover both improvements with regardto the quantum region as well as the embedding potential representing the environment.Regarding the former, a damped linear response formulation has been implemented to allow for calculations of absorption spectra of large molecular systems acrossthe entire frequency range. A special feature of this development is its abilityto address core excitations that are otherwise not easily accessible.Another important development presented in this thesis is the coupling of the PE model to a multi-configuration self-consistent-field description of the quantum region and its further combination with response theory. In essence, this extends the PE model to the study of electronic transitions in large systems that are prone to static correlation --- a situation that is frequently encountered in biological systems. In addition to the direct environmental effects on the electronic structure of the quantum region, another important component of the description of electronic transitions in large molecular systems is an accurate account of the indirect effects of the environment, i.e., the geometrical distortions in the quantum region imposed by the environment. In thisthesis we have taken the first step toward the inclusion of geometry distortions in the PE frameworkby formulating and implementing molecular gradients for the quantum region. To identify critical points related to the environment description, we perform a theoretical analysis of the PE model starting from a full quantum-mechanicaltreatment of a composite system. Based on this, we present strategies for an accurate yet efficient construction of the embedding potentialcovering both the calculation of ground state and transition properties. The accurate representation of the environment makes it possible to reduce the size of the quantum region without compromising the overall accuracy of the final results. This further enables use of highly accurate quantum-chemical methods despite their unfavorable scaling with the size of the system. Finally, some examples of applications will be presented to demonstrate how the PE model may be applied as a tool to gain insight into and rationalize the factors influencing electronic transitions in large molecular systems of increasing complexity. / <p>The dissertation was awarded the best PhD thesis prize 2016 by the Danish Academy of Natural Sciences.</p><p></p><p>QC 20170209</p>
42

Quantum Measurement and Feedback Control of highly nonclassical Photonic States / Mesure et Feedback quantique pour états Photonique fortement non classique

Lolli, Jared 10 November 2017 (has links)
Ces dernières années, les progrès réalisés dans le contrôle de l'interaction lumière-matière au niveau quantique ont conduit à de nombreuses avancées en optique quantique, en particulier dans l'étude de phénomènes quantiques fondamentaux, dans la conception de systèmes quantiques artificiels et dans les applications en information quantique. Il a notamment été possible d'augmenter considérablement l'intensité de l'interaction lumière-matière et de contrôler le couplage de systèmes quantiques à leur environnement, afin d'obtenir des états non conventionnels et fortement non classiques. Cependant, pour exploiter ces états quantiques en vue d'applications technologiques, il est crucial de pouvoir mesurer et contrôler ces systèmes avec précision. Dans ce contexte, ce travail de thèse est consacré à l'étude de nouveaux protocoles pour la mesure et le contrôle de systèmes quantiques dans lesquels des fortes interactions et des symétries particuliers conduisent à la génération d'états fortement non classiques. Nous nous intéressons dans un premier temps au régime de couplage ultra-fort de l'électrodynamique quantique en cavité (et de circuit). Plus précisément, l'état de fondamental n'est plus le vide standard, car il devient énergiquement favorable qu'il contienne des photons.Dans ce régime on peut même obtenir des chat de Schrödinger comme état fondamental.En revanche, pour assurer la conservation de l'énergie, les photons contenus dans ce vide exotique sont liés à la cavité et ne peuvent pas s'échapper dans l'environnement. Cela signifie qu'ils ne peuvent être mesurés par simple photodétection. Nous proposons dans ce travail un protocole spécialement conçu pour surmonter cette difficulté. Nous montrons qu'il est possible de déduire les propriétés photoniques de l'état fondamental à partir du déplacement de Lamb d'un système à deux niveaux auxiliaire.Les résonateurs optiques à paires de photons constituent une autre classe de systèmes dans lesquels la symétrie de parité conduit à des états quantiques non conventionnels. Grâce à "l'ingénierie de réservoir", il est aujourd'hui possible de contrôler l'interaction d'un système avec son environnement, de façon à le stabiliser dans des états quantiques particulièrement intéressants. En particulier, quand un résonateur (une cavité optique) est couplé à l'environnement par échange de paires de photons, il est possible de créer de chats de Schrödinger optiques dans la dynamique transitoire du système. Les corrélations quantiques de ces états sont par contre rapidement perdues en raison de la présence inévitable de dissipation à un photon. Protéger le système contre cette perturbation est le but du protocole de feedback basé sur la parité que nous présentons dans cette thèse / In recent years, the field of quantum optics has thrived thanks to the possibility of controlling light-matter interaction at the quantum level.This is relevant for the study of fundamental quantum phenomena, the generation of artificial quantum systems, and for quantum information applications.In particular, it has been possible to considerably increase the intensity of light-matter interaction and to shape the coupling of quantum systems to the environment, so to realise unconventional and highly nonclassical states.However, in order to exploit these quantum states for technological applications, the question of how to measure and control these systems is crucial.Our work is focused on proposing and exploring new protocols for the measurement and the control of quantum systems, in which strong interactions and peculiar symmetries lead to the generation of highly nonclassical states.The first situation that we consider is the ultrastrong coupling regime in cavity (circuit) quantum electrodynamics.In this regime, it becomes energetically favourable to have photons and atomic excitations in the ground state, that is no more represented by the standard vacuum.In particular, in case of parity symmetry, the ground state is given by a light-matter Schrödinger cat state.However, according to energy conservation, the photons contained in these exotic vacua are bound to the cavity, and cannot be emitted into the environment.This means that we can not explore and control them by simple photodetection.In our work we propose a protocol that is especially designed to overcome this issue.We show that we can infer the photonic properties of the ground state from the Lamb shift of an ancillary two-level system.Another class of systems in which the fundamental parity symmetry leads to very unconventional quantum states is given by two-photon driven-dissipative resonators.Thanks to the reservoir engineering, it is today possible to shape the interaction with the environment to stabilize the system in particularly interesting quantum states.When a resonator (an optical cavity) exchanges with the environment by pairs of photons, it has been possible to observe the presence of optical Schrödinger cat states in the transient dynamics of the system.However, the quantum correlations of these states quickly decays due to the unavoidable presence of one-photon dissipation.Protecting the system against this perturbation is the goal of the parity triggered feedback protocol that we present in this thesis
43

Microscopias de varredura por sondas aplicadas ao estudo de amostras biológicas, vítreas e cerâmicas / Scanning probe microscopy applied to the study of biological samples, glass and ceramics

Souza, Samuel Teixeira de 07 November 2014 (has links)
In this work, scanning multiprobes microscopes were used to study the physical properties of biological, vitreous and ceramics samples. In particular, we have used three different scanning probe microscopy techniques to the study the samples. At first, an atomic force microscope was used to evaluate the mechanical properties of macrophages due to cell adhesion to an extracellular matrix and to study the changes in DNA molecules conformation treated with thymol and adsorbed onto a mica surface modified by poly-L-lysine. The results of these studies show that the cytoskeleton-mediated cell-matrix interactions directly affect biomechanical events in cells by modifying physical properties of the cytoskeleton and that the modification of mica surface using poly-L-Lysine provides a strong and firm bond with DNA. This strong fixation of DNA, allows the study of DNA conformational change on mica when interacting with tymol. The atomic force microscope was also used in studies of laser induced thermal expansion in commercial phosphate glasses. The ability of this technique to detect nanoscale surface deformations and the good agreement between theoretical and experimental results show the potential of this technique to study the amplitude and the dynamic of thermal effects in solid materials. In another study, conductive atomic force microscopy was used to analyze electrical properties of barium titanate semiconductor ceramic and their correlation with specific topographic features of the sample. Finally, using the scanning near-field optical microscopy, we studied interactions between cells and gold nanoparticles, without the need of fluorescent labeling on the nanoparticles, with high spatial resolution. During the presentation of these studies the challenges and necessary instrumentation for their realization was discussed. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho, microscópios de varredura multi-sondas foram utilizados para o estudo de propriedades físicas de amostras biológicas, vítreas e cerâmicas. Em especial, usamos três diferentes técnicas de microscopia de varredura por sonda no estudo destas amostras. Primeiramente, um microscópio de força atômica foi usado para avaliar os efeitos na mecânica da membrana de macrófagos, verificando a interferência da adesão celular por uma matriz extracelular. Em seguida, estudamos as mudanças de conformação de moléculas de DNA tratadas com Timol e adsorvidas sobre uma superfície de uma mica modificada por poli-L-lisina. Os resultados destes estudos implicam que as interações célula-MEC mediada pelo citoesqueleto afetam diretamente os eventos biomecânicos das membranas, modificando as propriedades físicas do citoesqueleto celular, e que a modificação da superfície da mica utilizando poli-L-Lisina proporciona uma ligação forte e firme com o DNA. Esta forte fixação do DNA, permitiu o estudo da mudança conformacional do DNA na mica quando interagindo com o timol. O microscópio de força atômica também foi usado para realizar de estudos da expansão térmica em vidros fosfatos comerciais, induzida por um laser. A capacidade desta técnica de detectar deformações superficiais em nano-escala e a boa concordância dos resultados teóricos e experimentais mostra o potencial desta técnica para o estudo da amplitude e dinâmica de efeitos térmicos em materiais sólidos. Num outro estudo, a microscopia força atômica condutora foi usada para a análise de propriedades elétricas de cerâmicas de titanato de bário semicondutor e suas correlações com características topográficas específicas da amostra. Por fim, estudamos interações entre células e nanopartículas de ouro, com o uso da microscopia de varredura em campo próximo, sem a necessidade de marcação fluorescente nas nanopartículas e com alta resolução espacial. Durante a apresentação de cada um destes estudos foi discutido os desafios e parte da instrumentação necessárias para a realização dos mesmos.
44

Étude de l'effet laser dans les structures à plasmon Tamm / Study of lasing in Tamm plasmon structure

Lheureux, Guillaume 11 December 2015 (has links)
Ce travail de thèse porte sur l'étude expérimentale de structures à plasmons Tamm actives, composées d'une couche d'argent déposée sur un miroir de Bragg semiconduc­ teur AlGaAs/GaAs contenant des puits quantiques InGaAs. Après une description des modes Tamm et de leurs propriétés planaires, nous nous sommes intéressés plus parti­ culièrement aux structures à plasmons Tamm confinés par un micro-disque de métal. Des mesures de photoluminescence ont permis de mettre en évidence un effet laser dans ces structures. Une étude approfondie a montré une évolution du seuil laser en fonction du diamètre du disque, résultant d'un compromis entre confinement et pertes. Dans un second temps, nous avons étudié la réponse optique de structures à plasmon Tamm asy­ métriques, où le plasmon Tamm est confiné par des micro-rectangles. Cette asymétrie lève la dégénérescence en énergie qui existe entre les deux modes linéairement polarisés de la structure. Ceci, associé à un fort désaccord spectral entre l'émission des puits et le plasmon Tamm, permet d'obtenir une émission laser linéairement polarisée . Enfin, nous présentons l'étude d'une structure à plasmon Tamm comportant un réseau permettant le couplage du plasmon Tamm au plasmon de surface de l'interface air/argent. Grâce à des mesures tirant parti de l'aspect propagatif des modes, nous avons mis en évidence un battement entre plasmon Tamm et plasmon de surface / This thesis focuses on the experimental study of actives Tamm plasmons structures, consisting in a layer of silver deposited on a AlGaAs/GaAs semiconductor Bragg mir­ ror which con.tains InGaAs quantum wells. After describing Tamm planar modes and their properties, we focused particularly on structures where Tamm plasmons are la­ terally confined by a metallic micro-disk. Photoluminescence measurements have been carried out in order to demonstrate lasing in these structures. A comprehensive study has shown a change in the lasing threshold with the diameter of the disk, resulting from a compromise between the confinement and the lasses. Secondly, we studied the optical response of asymmetric Tamm plasmon structures, where the Tamm plasmon is confined by micro-rectangles. This asymmetry lifts the degeneracy of energy between the two linearly polarized modes of the structure. Combined with a strong spectral de­ tuning between the quantum wells emission and the Tamm plasmon, this allows linearly polarized laser emission to set-up. Finally, we present the study of a Tamm plasmon structure comprising a gratting to couple the Tamm plasmon to the surface plasmon at the silver/air interface. Thanks to propagation measurements, we have highlighted the beating between Tamm plasmon and surface plasmon modes
45

Electronic strong coupling of molecular materials in the liquid phase / Couplage fort des transitions électronique de matériaux moléculaires en phase liquide

Bahsoun, Hadi 14 September 2017 (has links)
Cette thèse contribue à la compréhension fondamentale du phénomène de couplage fort de la lumière avec des molécules organiques en mettant en œuvre de nouveaux systèmes et de nouvelles techniques, afin d'étudier les modifications de propriétés de molécules couplées à des résonances photoniques. Nous présentons des techniques de nanofabrication avancées pour la création de grands réseaux de trous sur des métaux et de cavités de Fabry-Pérot (FP) nanofluidiques. Ces systèmes sont ensuite utilisés pour étudier, sous régime de couplage fort, les modifications des propriétés de surface et de volume de molécules organiques en phase solide et liquide. En particulier les transitions électroniques de molécules du colorant cyanine en solution liquide ont été couplées à des modes photoniques résonants de cavités FP nanofluidiques spécialement conçues. Leur couplage fort a conduit à une amélioration du rendement quantique d'émission, mettant en évidence la nature radiative des états polaritoniques. / This thesis contributes to the fundamental understanding of the phenomenon of strong coupling of light with organic molecules by implementing new systems and techniques in order to investigate property modifications of molecules coupled with photonic resonances. State-of-the-art nanofabrication techniques for the formation of large hole-array gratings in metals and nanofluidic Fabry-Perot (FP) cavities are presented. These systems were then invested to study, under strong coupling, surface and bulk properties modifications of organic molecules in the solid and liquid phase. In particular, electronic transitions of cyanine dye molecules in liquid solutions were coupled to resonant photonic modes of specially designed nanofluidic FP cavities. Their strong coupling has led to an enhancement of the emission quantum yield, highlighting the radiative nature of the associated polaritonic states.
46

Nanoscale Photonics / From single molecule nanofluidics to light-matter interaction in nanostructures

Ghosh, Siddharth 15 August 2016 (has links)
No description available.
47

The two-dimensional Bose Gas in box potentials / Le Gaz de Bose à deux dimensions dans des potentiels en boîtes

Corman, Laura 02 June 2016 (has links)
Les gaz quantiques atomiques constituent un outil de choix pour étudier la physique à N corps grâce à leurs nombreux paramètres de contrôle. Ils offrent la possibilité d’explorer la physique en basse dimension, modifiée par rapport au cas à trois dimensions (3D) à cause du rôle accru des fluctuations. Dans ce travail, nous étudions le gaz de Bose à deux dimensions (2D) avec un confine-ment original dans le plan atomique, uniforme et de motif arbitraire. Ces gaz2D et uniformes, développés sur un montage existant, ont été installés sur un nouveau montage grâce à des potentiels optiques polyvalents.Nous présentons une série d’expériences exploitant cette géométrie flexible.D’abord, nous étudions le comportement statique et dynamique d’un gaz uni-forme lors de la transition d’un état 3D normal vers un état 2D superfluide.Nous observons l’établissement de la cohérence de phase dans un gaz à l’équilibre puis nous montrons l’apparition après une trempe de défauts topologiques dont le nombre est comparé à la prédiction de Kibble-Zurek. Ensuite, nous étudions grâce au nouveau montage les effets collectifs dans l’interaction lumière-matière, où les propriétés de résonance d’un nuage d’atomes dense sont fortement modifiées par rapport à celles d’un atome unique. Enfin, nous proposons deux protocoles pour le nouveau montage. Le premier permet d’évaporer de manière uniforme un gaz 2D grâce au réseau incliné du confinement à 2D. Le second propose de produire des supercourants de manière déterministe dans des pièges en anneaux, soit par condensation dans un champ de jauge, soit en réalisant une pompe à vortex topologique. / Degenerate atomic gases are a versatile tool to study many-body physics. They offer the possibility to explore low-dimension physics, which strongly differs from the three dimensional (3D) case due to the enhanced role of fluctuations. In this work, we study degenerate 2D Bose gases whose original in-plane confinement is uniform and of arbitrary shape. These 2D uniform traps, which we first developed on an existing set-up, were subsequently implemented on a newset-up using versatile optical potentials. We present a series of experiments that take advantage of this flexible geometry. First, we study the static and dynamic behaviours of a uniform gas at the transition between a 3D normal and a 2D superfluid state. We observe the establishement of extended phase coherence, followed, as the gas is quench cooled, by the apparition of topological defects whose scaling is compared to the Kibble-Zurek prediction. Second, we present the first results of the new set-up : we investigate collective effects in light-matter interactions, where the resonance properties of a dense ensemble of atoms are strongly modified with respect to the single atom ones. Last, we develop two experimental proposals for the new set-up. The first one studies how a 2D gas can be uniformly evaporated using the tilted lattice providing the 2D confinement. In the second one, we propose to produce su-percurrents in a deterministic way in ring-shaped traps either by condensing inan artificial gauge field or by implementing a topological vortex pump.
48

Study of Light-Matter Interaction at the Nanoscale with Quantum Dots in Photonic and Plasmonic Metamaterials

Indukuri, S R K Chaitanya January 2016 (has links) (PDF)
Optical properties of nanoscopic materials have been intensively pursued over last couple of decades due to their tunable optical properties. Recent interests in this field have been mainly focused on the preparation of ordered arrays of nano materials and study of their optical properties. These interests have been motivated by the applications of such systems for nano photonic devices. Theoretical predictions from such systems reveal complex absorption and emission properties, different from individual ones mainly because of energy transfer between them. These properties can be controlled further by preparing hybrid arrays of nanostructures, including nano crystals of different types. Hybrid arrays with semiconductor quantum dots and metallic nanoparticles are an example of such system. Optical properties of such a system can be tuned by controlling the interaction between excitons and plasmons. This thesis presents the experimental studies on optical properties of polymer capped nanoparticles, quantum dot arrays and hybrid arrays with semi conducting quantum dot and metal nanoparticles. A brief summary of the experimental methods and results have been highlighted below. In this thesis, we study the controlling decay dynamics of CdSe quantum dots by 2D photonic-plasmonic and metamaterial templates. In Chapter 1 we provide a detailed background on the theoretical methods of Light-Matter interaction at nano scale. We also have given the detailed information on both weak and strong coupling region in the light-matter interaction. This chapter includes the discussion controlling light-matter interaction with both photonic crystals and plasmonic materials with some appropriate examples from the literature. In this chapter we have also explained the relevance of our work in this area and organization of the chapters and there importance has given. In chapter 2 we provide details about various experimental methods used in this thesis. A brief introduction is given on the materials used, their synthesis and the preparation of different type of self assembled plasmonic-photonic templates. This chapter starts with an explanation of the materials used along with the justification; moves on to the preparation of different 2D wire metamaterial. The characterization techniques for these different types of templates like spectroscopic ellipsometer, atomic force spectroscopy, scanning electron microscopy and transmission electron microscopy are discussed. We also discussed optical spectroscopic techniques like confocal optical microscopy and near field optical microscopy techniques. The first two chapters form the basis of all the experiments discussed in the forth coming chapters. In chapter 3 Finite difference time domain (FDTD) simulations were performed on two different plasmonic sub wavelength photonic templates embedded with CdSe quantum dots. Tunable loading of these templates with plasmonic nano antenna allowed control of the emission from the embedded quantum dots. We discuss how large loading of nano antenna can effectively control the optical density of states for the quantum dots leading to enhancement of their radiative decay rates as observed in experiments. On the other hand, at low level of loading, while FDTD fails to capture the observed enhancement of decay rates in experiment, an alternative mechanism is suggested to exist in such cases. Thus, subtle interplay of multiple mechanisms engineered by appropriate placement and loading of plasmonic nano antenna in such templates is demonstrated as an effective method to control optical density of states and hence spontaneous emission of embedded quantum dots. In Chapter 4 we report results of controlled tuning of the local density of states (LDOS) in versatile, flexible and hierarchical self assembled plasmonic templates. Using 5 nm diameter gold (Au) spherical nano antenna within a polymer template randomly dispersed with quantum dots, we show how the photo-luminescence intensity and lifetime anisotropy of these dots can be significantly enhanced through LDOS tuning. Finite difference time domain simulations corroborate the experimental observations and extend the regime of enhancement to a wider range of geometric and spectral parameters bringing out the versatility of these functional plasmonic templates. It is also demonstrated how the templates act as plasmonic resonators for effectively engineer giant enhancement of the scattering efficiency of these nano antenna embedded in the templates. Our work provides an alternative method to achieve spontaneous emission intensity and anisotropy enhancement with true nanoscale plasmon resonators. In chapter 5 we reported enhancement optical properties of quantum dot monolayers on top of the functional, flexible and hierarchical self-assembled plasmonic template using extremely small gold (Au) nanoparticles of diameter 5 nm. We reported how the LODS changes with different polarizations for CdSe quantum dot present on top of the template. We observed the enhanced radiative LDOS from the nano antenna filled pores indicating plasmonic enhanced emission from these templates. The difference in spectral and spatial profile of LDOS and Pur-cells with polarization of quantum dot emission results in the anisotropic emission in these templates. In chapter 6 we reported the emergence of strong coupling between quantum emitters and 2D hyperbolic metamaterials (HMM). We studied both spectral dependence and effect of filling fraction of the HMM on strong interaction. We also show the controlling of the transition from weak coupling region to strong coupling region by changing the distance between QD monolayer and HMM. By using FDTD simulation we are able to calculate both spectral function S(!) and coupling efficiency. In chapter 7 as a conclusion we concluded the work done in this thesis. We also indicated the future directions in this field and possible application.
49

Basis sets for light-matter interaction: from static coherent states to moving Gaussians

Eidi, Mohammad Reza 06 October 2022 (has links)
This thesis develops a computationally efficient way of employing Gaussian wave packets to study laser-induced electron dynamics in atomic and molecular systems by directly solving the time-dependent Schrödinger equation (TDSE). First, we investigate charge migration (treating the nuclei classically), high-order harmonic generation (HHG), and single-isolated attosecond pulse generation in the Hydrogen molecular ion subjected to intense laser fields in a different range of frequencies with a basis of static coherent states (SCS). Then, seeking for a smarter way of constructing and guiding a minimal set of time-dependent basis functions, we introduce a fast and accurate approach for optimizing s-type Gaussian type orbitals (GTOs) and apply it to calculate electronic states of different 1D and 3D time-independent systems. Finally, we apply our optimization approach to time-dependent problems. With our approach we obtain excellent agreement with the exact results for HHG spectra of the 1D Hydrogen atom and molecular ion exposed to intense laser fields, which is not possible even with a much larger basis of static s-type GTOs. / Diese Arbeit sucht nach einem computereffizienten Ansatz für die Verwendung von Gaußschen Wellenpaketen zur Untersuchung der Quantenelektronendynamik in atomaren und molekularen laserinduzierten Systemen durch direkte Lösung der zeitabhängigen Schrödingergleichung (TDSE). Beginnend mit statischen kohärenten Zuständen (SCS) untersuchen wir die Ladungsmigration (wobei wir die Kerne klassisch behandeln), die Erzeugung von Oberwellen höherer Ordnung (HHG) und die Erzeugung von isolierten Attosekundenimpulsen im 3D-Wasserstoffmolekül-Ion \ih, das intensiven Laserfeldern in einem unterschiedlichen Frequenzbereich ausgesetzt ist. Auf der Suche nach einer intelligenteren Methode zur Konstruktion und Führung eines minimalen Satzes von Basisfunktionen stellen wir einen schnellen und genauen Ansatz zur Optimierung von Gauß-Orbitalen (GTOs) vom s-Typ vor und wenden ihn erfolgreich zur Berechnung gewünschter elektronischer Zustände verschiedener 1D- und 3D-Quantensysteme an. Letztendlich erweitern wir unseren Optimierungsansatz auf zeitabhängige Szenarien. Wir demonstrieren, wie diese Methode eine ausgezeichnete Übereinstimmung mit den exakten Ergebnissen in den HHG-Spektren des 1D-Wasserstoffatoms und des 1D-\ih, die intensiven Laserfeldern ausgesetzt sind, erzielt, wo die nicht optimierten s-Typ GTOs nicht übereinstimmen, selbst nach den ersten paar Harmonien im Plateaubereich.
50

Bose-Einstein Condensates in Synthetic Gauge Fields and Spaces: Quantum Transport, Dynamics, and Topological States

Chuan-Hsun Li (7046690) 14 August 2019 (has links)
<p>Bose-Einstein condensates (BECs) in light-induced synthetic gauge fields and spaces can provide a highly-tunable platform for quantum simulations. Chapter 1 presents a short introduction to the concepts of BECs and our BEC machine. Chapter 2 introduces some basic ideas of how to use light-matter interactions to create synthetic gauge fields and spaces for neutral atoms. Three main research topics of the thesis are summarized below.</p> <p>Chapter 3: Recently, using bosonic quasiparticles (including their condensates) as spin carriers in spintronics has become promising for coherent spin transport over macroscopic distances. However, understanding the effects of spin-orbit (SO) coupling and many-body interactions on such a spin transport is barely explored. We study the effects of synthetic SO coupling (which can be turned on and off, not allowed in usual materials) and atomic interactions on the spin transport in an atomic BEC.</p> <p>Chapter 4: Interplay between matter and fields in physical spaces with nontrivial geometries can lead to phenomena unattainable in planar spaces. However, realizing such spaces is often impeded by experimental challenges. We synthesize real and curved synthetic dimensions into a Hall cylinder for a BEC, which develops symmetry-protected topological states absent in the planar counterpart. Our work opens the door to engineering synthetic gauge fields in spaces with a wide range of geometries and observing novel phenomena inherent to such spaces.</p> <p>Chapter 5: Rotational properties of a BEC are important to study its superfluidity. Recent studies have found that SO coupling can change a BEC's rotational and superfluid properties, but this topic is barely explored experimentally. We study rotational dynamics of a SO-coupled BEC in an effective rotating frame induced by a synthetic magnetic field. Our work may allow for studying how SO coupling modify a BEC's rotational and superfluid properties.</p> <p>Chapter 6 presents some possible future directions.</p>

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