Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Avec l’augmentation de la température, certains composés oxydes, transparents dans le proche infrarouge, deviennent progressivement opaques à l’approche de la fusion. Un tel comportement est inhabituel et impacte profondément leurs propriétés radiatives. Afin de comprendre ce phénomène, des mesures par spectroscopie d’émission infrarouge ont été effectuées depuis la température ambiante jusqu’à la fusion sur plusieurs oxydes cristallins (Mg2SiO4, LiAlO2, LiGaO2, ZnO, YAlO3, LaAlO3, LiNbO3, MgO). Ces données ont été complétées ponctuellement par des mesures de conductivité électriques, de RMN et de diffraction des rayons X en température. L’analyse des données expérimentales du facteur d’émission menée à l’aide d’un modèle de fonction diélectrique semi-quantique et incluant un terme de Drude étendu, a permis de caractériser finement la réponse de ces matériaux et de proposer une origine physique pour le mécanisme responsable de l’opacification. Le phénomène est thermiquement activé et peut être expliqué par la formation et la mobilité de polarons. Ce travail a également montré l’existence d’un lien étroit entre la microstructure des composés et les caractéristiques de l’opacification. / With increasing temperature, some oxide compounds that are transparent in the near infrared range become progressively opaque when approaching the liquid phase. Such a behavior is unusual and deeply impacts their thermal radiative properties. To understand this phenomenon, infrared emittance spectra were acquired from room temperature up to the liquid state on several crystalline oxides (Mg2SiO4, LiAlO2, LiGaO2, ZnO, YAlO3, LaAlO3, LiNbO3, MgO). These data have been selectively completed by electrical conductivity measurements, NMR and X-ray diffraction experiments versus temperature. The analysis of the experimental emittance data with a semi-quantum dielectric function model including an extended Drude term, allowed to characterize finely the material responses and to suggest a physical origin for the opacification mechanism. The phenomenon is thermally activated and can be explained by the formation and the mobility of polarons. This work also showed the existence of a close link between the material microstructure and the characteristics of the opacification.

Lo Loc Ping = 多體量子系統問題 / 盧樂平. / Thesis submitted in: October 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 168-171). / Text in English; abstracts in English and Chinese. / Lo Loc Ping = Duo ti liang zi xi tong wen ti / Lu Leping. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgment --- p.iii / Chapter I --- Computational Quantum Mechanics and Its Applications 電算量子力學及其應用 --- p.1 / Chapter 1 --- An Overview of Quantum Mechanics and Some Important Tools of Theory --- p.2 / Chapter 1.1 --- The Schrodinger Equation --- p.2 / Chapter 1.2 --- The Variational Method --- p.4 / Chapter 1.2.1 --- Rayleigh-Ritz Approach --- p.4 / Chapter 1.2.2 --- Linear Variation --- p.5 / Chapter 2 --- Theoretical Methodology of Electronic Structures: Ab Initio Molecular Orbital Theory --- p.7 / Chapter 2.1 --- The Molecular Hamiltonian --- p.7 / Chapter 2.2 --- Hartree Description and Linear Combination of Atomic Orbitals Expan- sion --- p.8 / Chapter 2.3 --- Slater Determinant and the Pauli Exclusion Principle --- p.9 / Chapter 2.4 --- The Expansion of E in Terms of Integrals over MOs --- p.11 / Chapter 2.5 --- Derivation of the Hartree´ؤFock Equations --- p.15 / Chapter 2.6 --- The Self-Consistent Field Calculation --- p.18 / Chapter 2.7 --- Koopmans' Theorem --- p.19 / Chapter 2.8 --- Orbital and the Total SCF Electronic Energy --- p.20 / Chapter 2.9 --- AO Basic Sets --- p.21 / Chapter 2.9.1 --- Slater-Type Orbitals --- p.21 / Chapter 2.9.2 --- Gaussian Functions --- p.22 / Chapter 2.10 --- The Hartree-Fock Limit --- p.23 / Chapter 2.11 --- Electron Correlation --- p.23 / Chapter 2.11.1 --- Weakness in the Single Determinant Model --- p.23 / Chapter 2.11.2 --- Configuration Interaction --- p.24 / Chapter 2.11.3 --- The Coupled-Cluster Method --- p.25 / Chapter 2.11.4 --- Density Functional Theory --- p.26 / Chapter 2.12 --- Frontier Orbitals --- p.31 / Chapter 3 --- Theoretical Investigation of the Interaction between Metal and Tris(8- hydroxyquinoline) aluminum in Organic Light Emitting Diodes --- p.32 / Chapter 3.1 --- Organic Light Emitting Diodes and Tris(8-hydro-xyquinoline) aluminum --- p.32 / Chapter 3.2 --- Computational Methodology --- p.33 / Chapter 3.3 --- Alq3 --- p.34 / Chapter 3.3.1 --- Molecular Structure --- p.34 / Chapter 3.3.2 --- Electronic Structure --- p.36 / Chapter 3.3.3 --- Transition and Relaxation Energies --- p.44 / Chapter 3.3.4 --- Interactions with Metals --- p.45 / Chapter 3.4 --- "Li-Alq3, Na-Alq3 and K-Alq3 Complexes" --- p.46 / Chapter 3.4.1 --- Molecular Structure --- p.46 / Chapter 3.4.2 --- Ground-State Electronic Structure --- p.55 / Chapter 3.4.3 --- Transition and Relaxation Energies --- p.67 / Chapter 3.5 --- "Be-Alq3, Mg´ؤAlq3 and Ca´ؤAlq3 Complexes" --- p.68 / Chapter 3.5.1 --- Molecular Structure --- p.68 / Chapter 3.5.2 --- Ground-State Electronic Structure --- p.76 / Chapter 3.5.3 --- Transition and Relaxation Energies --- p.87 / Chapter 3.6 --- "B-Alq3, Al-Alq3 and Ga-Alq3 Complexes" --- p.87 / Chapter 3.6.1 --- Molecular Structure --- p.87 / Chapter 3.6.2 --- Ground-State Electronic Structure --- p.95 / Chapter 3.6.3 --- Transition and Relaxation Energies --- p.106 / Chapter II --- Analytical Studies of Polarons and the Electron-Phonon Interaction 極子與電子一聲子相互作用的 解析研究 --- p.107 / Chapter 4 --- Optimal Coupled-Cluster Approximation of the Ground-State Energy of the E× (α1 + α1) Jahn-Teller System --- p.108 / Chapter 4.1 --- The Jahn-Teller Effect --- p.108 / Chapter 4.2 --- Approximation in the Coupled-Cluster Method and the Jahn-Teller Hamiltonian --- p.110 / Chapter 4.3 --- Variational Coupled-Cluster Approximation --- p.112 / Chapter 4.3.1 --- The Zeroth Level --- p.113 / Chapter 4.3.2 --- The First Level --- p.113 / Chapter 4.3.3 --- The Second and the Third Levels --- p.114 / Chapter 4.4 --- An 'Optimal' Hamiltonian --- p.115 / Chapter 4.5 --- Treatment for the k> 1 Case --- p.117 / Chapter 4.6 --- Energies and Other Physical Phenomena --- p.118 / Chapter 5 --- Small-to-Large Ground-State Polaron Crossover in One-Dimension Extended E×e Jahn-Teller System Using Variational Coupled-Cluster Approximation --- p.134 / Chapter 5.1 --- Polaron Formation --- p.134 / Chapter 5.2 --- Model Hamiltonian and the MLF Transformation --- p.135 / Chapter 5.3 --- Variatonal Coupled-Cluster Approximation --- p.137 / Chapter 5.3.1 --- Zeorth Level --- p.139 / Chapter 5.3.2 --- First Level --- p.139 / Chapter 5.3.3 --- Second Level --- p.142 / Chapter 5.4 --- Energies and Static Correlation Functions --- p.142 / Chapter 5.5 --- Approximate Form of the MLF Transformation for K = 0 --- p.153 / Chapter 5.5.1 --- Zeroth Level --- p.154 / Chapter 5.5.2 --- First Level --- p.155 / Chapter 5.5.3 --- Second Level --- p.156 / Chapter 5.5.4 --- Energies and Static Correlation Functions --- p.157 / Chapter 5.6 --- Synopsis --- p.167 / Bibliography --- p.171

Yeung Man Yi = 多體量子系統問題 / 楊曼儀. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves [247-249]). / Text in English; abstracts in English and Chinese. / Yeung Man Yi = Duo ti liang zi xi tong wen ti / Yang Manyi. / Abstract --- p.i / Acknowledgment --- p.iii / Chapter I --- Computational Quantum Mechanics and Its Applications / 電算量子力學及其應用 --- p.1 / Chapter 1 --- Theoretical Methodology of Electronic Structures: Ab Initio Molecular Orbital Theory --- p.2 / Chapter 1.1 --- Molecular Hamiltonian --- p.2 / Chapter 1.2 --- Hartree Products --- p.5 / Chapter 1.3 --- Slater Determinants and Pauli Exclusion Principle --- p.6 / Chapter 1.4 --- Expansion of Total Electronic Energy in terms of Integrals over MOs --- p.8 / Chapter 1.5 --- Derivation of the Hartree-Fock Equations --- p.11 / Chapter 1.6 --- Orbital Energies and the Koopmans' Theorem --- p.14 / Chapter 1.7 --- AO Basic Sets --- p.17 / Chapter 1.7.1 --- Slater-Type Orbitals --- p.18 / Chapter 1.7.2 --- Gaussian Functions --- p.18 / Chapter 1.8 --- Self-Consistent Field Calculation --- p.19 / Chapter 1.9 --- Hartree-Fock Limit --- p.20 / Chapter 1.10 --- Electron Correlation --- p.20 / Chapter 1.10.1 --- Configuration Interaction --- p.20 / Chapter 1.10.2 --- Density Functional Theory --- p.21 / Chapter 2 --- Theoretical Investigation of Organic Light Emitting Molecules --- p.29 / Chapter 2.1 --- Introduction --- p.29 / Chapter 2.2 --- Methodology --- p.31 / Chapter 2.2.1 --- Theoretical Methodology --- p.31 / Chapter 2.2.2 --- Computational Methodology --- p.35 / Chapter 2.3 --- ADN series --- p.35 / Chapter 2.3.1 --- Molecular Structure --- p.36 / Chapter 2.3.2 --- Electronic Structure --- p.49 / Chapter 2.3.3 --- Absorption and Emission Energy --- p.55 / Chapter 2.3.4 --- Reorganization Energy --- p.56 / Chapter 2.3.5 --- Mobility --- p.57 / Chapter 2.3.6 --- Summary on ADN series --- p.66 / Chapter 2.4 --- XOT series --- p.67 / Chapter 2.4.1 --- Molecular Structure --- p.68 / Chapter 2.4.2 --- Electronic Structure --- p.89 / Chapter 2.4.3 --- Absorption and Emission Energy --- p.96 / Chapter 2.4.4 --- Reorganization Energy and Mobility --- p.98 / Chapter 2.4.5 --- Summary on XOT series --- p.100 / Chapter 2.5 --- KPA series --- p.102 / Chapter 2.5.1 --- Molecular Structure --- p.102 / Chapter 2.5.2 --- Electronic Structure --- p.123 / Chapter 2.5.3 --- Absorption and Emission Energy --- p.131 / Chapter 2.5.4 --- Reorganization Energy and Mobility --- p.131 / Chapter 2.5.5 --- Summary on KPA series --- p.133 / Chapter 2.6 --- NPA series --- p.136 / Chapter 2.6.1 --- Molecular Structure --- p.136 / Chapter 2.6.2 --- Electronic Structure --- p.160 / Chapter 2.6.3 --- Absorption and Emission Energy --- p.166 / Chapter 2.6.4 --- Reorganization Energy and Mobility --- p.167 / Chapter 2.6.5 --- Summary on NPA series --- p.169 / Chapter II --- Analytical Studies of Polarons and the Electron-Phonon Interaction / 極子與電子一聲子相互作用的解析研究 --- p.172 / Chapter 3 --- Study on Holstein Model Using Variational Approximation --- p.173 / Chapter 3.1 --- Holstein Hamiltonian --- p.173 / Chapter 3.2 --- Variational Transformation --- p.175 / Chapter 3.2.1 --- Lang-Firsov Transformation --- p.175 / Chapter 3.2.2 --- Squeezing Transformation --- p.177 / Chapter 3.3 --- Energy and Static Correlation Functions --- p.179 / Chapter 4 --- Study on Holstein Model Using Coupled-Cluster Method --- p.193 / Chapter 4.1 --- Approximation in the Coupled-Cluster Method --- p.193 / Chapter 4.2 --- Approach 1 --- p.195 / Chapter 4.2.1 --- The Zeroth and the First Levels --- p.195 / Chapter 4.2.2 --- Energies and Static Correlation Functions --- p.196 / Chapter 4.3 --- Approach 2 --- p.206 / Chapter 4.3.1 --- The Zeroth and the First Levels --- p.206 / Chapter 4.3.2 --- Energies and Static Correlation Functions --- p.210 / Chapter 4.4 --- Approach 3 --- p.225 / Chapter 4.4.1 --- The Zeroth and the First Levels --- p.226 / Chapter 4.4.2 --- Energies and Static Correlation Functions --- p.228 / Chapter 4.5 --- Comparison with the Variational Method --- p.243

Orientador: José Antônio Souza. / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Física.

Orientador: Hermes Adolfo de Aquino / Banca: José Antônio Malmonge / Banca: Rinaldo Gregório Filho / Resumo: Os polímeros são muito conhecidos por serem materiais de fácil processamento, leveza, isolantes elétricos e até mesmo térmicos. Essas propriedades viabilizaram várias aplicações tecnológicas desde utensílios domésticos à indústria. No fim do século passado as pesquisas voltaram-se em busca de energias renováveis e novos materiais que associassem as vantagens dos polímeros com as propriedades elétricas dos metais. Com essas pesquisas surgiu uma nova classe de polímeros chamada de Polímeros Condutores Intrínsecos (PCIs) que dispõem de boas propriedades de condução elétrica inerente ao material. Esses PCIs podem ser sintetizados em forma de fibras ou filmes, sozinhos ou com vários outros polímeros para formar blendas com diferentes propriedades. O polipirrol (PPy) é um PCI que proporciona altas condutividades elétricas e boa estabilidade oxidativa, algo difícil de se conseguir com essa classe de polímeros. Esse trabalho teve como objetivo sintetizar amostras de PPy por dois métodos de síntese química: convencional (em solução aquosa) e microemulsão com dodecil sulfato de sódio (SDS - surfactante e dopante). No primeiro método foi variada a razão molar de monômero/oxidante e no segundo variou-se as razões molares de monômero/oxidante/dopante. Para o estudo dessas amostras foram realizadas análises estruturais, morfológicas, térmicas, ópticas e elétricas. De maneira geral, as amostras que apresentaram melhores características morfológicas, ópticas e de condutividade elétrica, foram as obtidas no processo químico em microemulsão, de tal maneira que, quanto maior a quantidade de SDS e menor a temperatura, menor foi o tamanho das partículas de PPy, maior a conjugação das cadeias e maior a dopagem com SDS. / Abstract: The polymers are known to be materials easy processed, slight, electrical insulators and even heat. These properties made possible many technological applications, from household items to the industry. At the end of last century the polls turned in search of renewable energy and new materials that combines the benefits of polymers with the electrical properties of metals. With these studies emerged a new class of polymers called Intrinsic Conducting Polymers (PICs) that have good electrical conduction properties inherent to the material. These PICs can be synthesized in the form of fibers or films, either alone or with various other polymers to form blends with different properties. The polypyrrole (PPy) is a PIC that provides high electrical conductivity and good oxidative stability, something difficult to achieve with this class of polymers. This study aimed to synthesize PPy samples by two methods of chemical synthesis: conventional (aqueous solution) and microemulsion SDS (dodecilsulfate of sodium - surfactant and dopant). In the first method was varied the molar ratio of monomer/oxidant and the second was varied molar ratios of monomer/oxidant/dopant. For the study of these samples were performed structural analyses, morphological, thermal, optical and electrical. In general, samples that showed better morphological characteristics, optical and electrical conductivity were obtained in the chemical process of microemulsion, such a way that the larger the amount of SDS and the lower the temperature, the smaller the particle size of PPy, the greater the conjugation of chains and the higher the doping with SDS. / Mestre

The polaron problem is studied, on an infinite lattice, using the continuous-time path-integral quantum Monte Carlo scheme The method is based on the Feynman technique to analytically integrate out the phonon degrees of freedom. The transformed problem is that of a single electron with retarded self-interaction in imaginary time. The Metropolis algorithm is used to sample an ensemble of electron trajectories with twisted (rather than periodic) boundary conditions in imaginary time, which allows dynamic properties of the system to by measured directly. The method is numerically "exact", in the sense that there are no systematic errors due to finite system size, trotter decomposition or finite temperature The implementation of the algorithm in continuous imaginary time dramatically increases computational efficiency compared with the traditional discrete imaginary time algorithms.

This thesis describes work on several research topics in which transport and spectroscopy are influenced by strong electron-nuclear or nuclear-nuclear interactions. First, I give a broad overview of the motivations and background for the main topics covered in this thesis. In the next section, I explore the applicability of perturbative quantum master equations to linear absorption and nonlinear two-dimensional and pump-probe spectroscopies. Next, I introduce a theory of charge transport in organic semiconductors that unifies two popular pictures: incoherent polaron hopping and transient localization due to dynamic disorder. In the next section, I investigate the impact of phonon anharmonicity on the charge transport dynamics of soft semiconductors. Finally, I present a new method of efficiently calculating anharmonic vibrational spectra from ab initio molecular potential energy surfaces.

No description available.

Atoms in optical lattices are promising candidates to implement quantum information processing. Their behaviour is well understood on a microscopic level, they exhibit excellent coherence properties, and they can be easily manipulated using external fields. In very deep optical lattices, each atom is restricted to a single lattice site and can be used as a qubit. If the lattice is shallow enough such that the atoms can move, their properties can be used to simulate certain condensed matter phenomena such as superconductivity. In this thesis, we show how technical problems of optical lattices such as restricted decoherence times, or fundamental shortcomings such as the lack of phonons or strong spin interactions, can be overcome by using current or near-future experimental techniques. We introduce a scheme that makes it possible to simulate model Hamiltonians known from high-temperature superconductivity. For this purpose, previous simulation schemes to realise the spin interaction terms are extended. We especially overcome the condition of a filling factor of exactly one, which otherwise would restrict the phase of the simulated system to a Mott-insulator. This scheme makes a large range of parameters accessible, which is difficult to cover with a condensed matter setup. We also investigate the properties of optical lattices submerged into a Bose-Einstein condensate (BEC). A weak-coupling expansion in the BEC-impurity interaction strength is used to derive a model that describes the lattice atoms in terms of polarons, i.e.~atoms dressed by Bogoliubov phonons. This is analogous to the description of electrons in solids, and we observe similar effects such as a crossover from coherent to incoherent transport for increasing temperatures. Moreover, the condensate mediates an attractive off-site interaction, which leads to macroscopic clusters at experimentally realistic parameters. Since the atoms in the lattice can also be used as a quantum register with the BEC mediating a two-qubit gate, we derive a quantum master equation to examine the coherence properties of the atomic qubits. We show that the system exhibits sub- and superdecoherence and that a fast implementation of the two-qubit gate competes with dephasing. Finally, we show how to realise the encoding of qubits in a decoherence-free subspace (DFS) using optical lattices. We develop methods for implementing robust gate operations on qubits encoded in a DFS exploiting collisional interactions between the atoms. We also give a detailed analysis of the performance and stability of the gate operations and show that a robust implementation of quantum repeaters can be achieved using our setup. We compare the robust repeater scheme to one that makes use of conventional qubits only, and show the conditions under which one outperforms the other.