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Foley, Simon Timothy. "Effects of electron-electron interactions on electronic transport in disordered systems". Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273932.
Pełny tekst źródłaSergueev, Nikolai. "Electron-phonon interactions in molecular electronic devices". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102171.
Pełny tekst źródłaIn our formalism, we calculate electronic Hamiltonian via density functional theory (DFT) within the nonequilibrium Green's functions (NEGF) which takes care of nonequilibrium transport conditions and open device boundaries for the devices. From the total energy of the device scattering region, we derive the dynamic matrix in analytical form within DFT-NEGF and it gives the vibrational spectrum of the relevant atoms. The vibrational spectrum together with the vibrational eigenvector gives the electron-phonon coupling strength at nonequilibrium for various scattering states. A self-consistent Born approximation (SCBA) allows one to determine the phonon self-energy, the electron Green's function, the electronic density matrix and the electronic Hamiltonian, all self-consistently within equal footing. The main technical development of this work is the DFT-NEGF-SCBA formalism and its associated codes.
A number of important physics issues are studied in this work. We start with a detailed analysis of transport properties of C60 molecular tunnel junction. We find that charge transport is mediated by resonances due to an alignment of the Fermi level of the electrodes and the lowest unoccupied C60 molecular orbital. We then make a first step toward the problem of analyzing phonon modes of the C60 by examining the rotational and the center-of-mass motions by calculating the total energy. We obtain the characteristic frequencies of the libration and the center-of-mass modes, the latter is quantitatively consistent with recent experimental measurements. Next, we developed a DFT-NEGF theory for the general purpose of calculating any vibrational modes in molecular tunnel junctions. We derive an analytical expression for dynamic matrix within the framework of DFT-NEGF. Diagonalizing the dynamic matrix we obtain the vibrational (phonon) spectrum of the device. Using this technique we calculate the vibrational spectrum of benzenedithiolate molecule in a tunnel junction and we investigate electron-phonon coupling under an applied bias voltage during current flow. We find that the electron-phonon coupling strength for this molecular device changes drastically as the bias voltage increases, due to dominant contributions from the center-of-mass vibrational modes of the molecule. Finally, we have investigated the reverse problem, namely the effect of molecular vibrations on the tunneling current. For this purpose we developed the DFT-NEGF-SCBA formalism, and an example is given illustrating the power of this formalism.
Sica, G. "Electron-electron and electron-phonon interactions in strongly correlated systems". Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12194.
Pełny tekst źródłaSica, Gerardo. "Electron-electron and electron-phonon interactions in strongly correlated systems". Doctoral thesis, Universita degli studi di Salerno, 2013. http://hdl.handle.net/10556/1418.
Pełny tekst źródłaIn this work we investigate some aspects of the physics of strongly correlated systems by taking into account both electron-electron and electron-phonon interactions as basic mechanisms for reproducing electronic correlations in real materials. The relevance of the electron-electron interactions is discussed in the first part of this thesis in the framework of a self-consistent theoretical approach, named Composite Operator Method (COM), which accounts for the relevant quasi-particle excitations in terms of a set of composite operators that appear as a result of the modification imposed by the interactions on the canonical electronic fields. We show that the COM allows the calculation of all the relevant Green’s and correlation functions in terms of a number of unknown internal parameters to be determined self-consistently. Therefore, depending on the balance between unknown parameters and self-consistent equations, exact and approximate solutions can be obtained. By way of example, we discuss the application of the COM to the extended t-U- J-h model in the atomic limit, and to the two-dimensional single-band Hubbard model. In the former case, we show that the COM provides the exact solution of the model in one dimension. We study the effects of electronic correlations as responsible for the formation of a plethora of different charge and/or spin orderings. We report the phase diagram of the model, as well as a detailed analysis of both zero and finite temperature single-particle and thermodynamic properties. As far as the single-band Hubbard model is concerned, we illustrate an approximated selfconsistent scheme based on the choice of a two-field basis. We report a detailed analysis of many unconventional features that arise in single-particle properties, thermodynamics and system’s response functions. We emphasize that the accuracy of the COM in describing the effects of electronic correlations strongly relies on the choice of the basis, paving the way for possible multi-pole extensions to the twofield theory. To this purpose, we also study a three-field approach to the single-band Hubbard model, showing a significant step forward in the agreements with numerical data with respect to the two-pole results. The role of the electron-phonon interaction in the physics of strongly correlated systems is discussed in the second part of this thesis. We show that in highly polarizable lattices the competition between unscreened Coulomb and Fröhlich interactions results in a short-range polaronic exchange term Jp that favours the formation of local and light pairs of bosonic nature, named bipolarons, which condense with a critical temperature well in excess of hundred kelvins. These findings, discussed in the framework of the so-called polaronic t-Jp model, are further investigated in the presence of a finite on-site potential ~U , coming from the competition between on-site Coulomb and Fröhlich interactions. We discuss the role of ~U as the driving parameter for a small-to-large bipolaron transition, providing a possible explanation of the BEC-BCS crossover in terms of the properties of the bipolaronic ground state. Finally, we show that a hard-core bipolarons gas, studied as a charged Bose-Fermi mixture, allows for the description of many non Fermi liquid behaviours, allowing also for a microscopic explanation of pseudogap features in terms of a thermal-induced recombination of polarons and bipolarons, without any assumption on preexisting order or broken symmetries. [edited by author]
XI n.s.
Ren, Yan-Ru. "Orbital spin-splitting factors for conduction electrons in lead". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25961.
Pełny tekst źródłaScience, Faculty of
Physics and Astronomy, Department of
Graduate
Chen, T. M. "Electron-electron interactions in GaAs quantum wires". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597526.
Pełny tekst źródłaPierre, Frédéric. "Interactions electron-electron dans les fils mesoscopiques". Paris 6, 2000. http://www.theses.fr/2000PA066375.
Pełny tekst źródłaPhinney, Isabelle Y. "Probing electron-electron and electron-phonon interactions in twisted bilayer graphene". Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127092.
Pełny tekst źródłaCataloged from the official PDF of thesis.
Includes bibliographical references (pages 81-86).
Two-dimensional systems, and, most recently, moire systems, have risen to the forefront of condensed matter physics with the advent of experimental techniques that allow for controlled stacking of van der Waals heterostructures [17, 54]. For example, it was recently discovered that when two pieces of atomically thin carbon (graphene) are twisted at 1.1° with respect to one another, they display a variety of effects, including superconducting behavior [10]. Experimental investigation of the behavior of small-angle twisted bilayer graphene (SA-TBG) as a function of twist angle is imperative to understanding the mechanisms that play into the many interesting, strongly-interacting phenomena that the moire system displays. In this thesis, I present three experiments which explore electron-electron and electron-phonon interactions in SA-TBG. I first consider SA-TBG as a host for a viscous electron fluid and look for the onset of fluid behavior via electron transport. Then I investigate the temperature dependence of resistivity in SA-TBG devices at a number of angles. The final experiment examines magnetophonons in three devices above the magic angle and compares the findings to theoretical results.
by Isabelle Y. Phinney.
S.B.
S.B. Massachusetts Institute of Technology, Department of Physics
Bassett, L. C. "Probing electron-electron interactions with a quantum antidot". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596454.
Pełny tekst źródłaUng, Kim-Chau. "Effects of electron-electron and electron-phonon interactions in narrow-band systems". Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186622.
Pełny tekst źródłaZoccante, Paolo. "Electron-electron renormalization of the electron-phonon coupling in many-valley systems : the case of ZrNCl". Paris 6, 2013. http://www.theses.fr/2013PA066760.
Pełny tekst źródłaLix ZrNCl est un supraconducteur lamellaire; sa température critique supraconductrice (TC ) augmente lorsque la quantité de dopant dans le matériau est réduite. Ce comportement est inattendu, car le système présente des bandes paraboliques centrées sur les points spéciaux à haute symétrie K et une structure électronique quasi-2D, avec une densité d’états presque constante. Lix ZrNCl peut être considéré comme la réalisation physique d’un gaz d’électrons avec deux vallées dégénérées. Dans la première partie de cette thèse, nous étudions les propriétés supraconductrices en fonction du dopage de Lix ZrNCl en utilisant la Théorie de la Fonctionnelle de la Densité (DFT). Les spectres vibrationnels du système montrent un fort couplage dans la région proche de Γ et K. Les températures critiques calculées sont en accord avec les données expérimentales à haut dopage, mais n’expliquent pas la hausse de TC à bas dopage. Dans la deuxième partie de la thèse, on établit une correspondance exacte entre l’Hamiltonien électron-phonon d’un système à plusieurs vallées et l’Hamiltonien d’un gaz d’électrons dans un champ magnétique. Des calculs Monte Carlo Quantique sont utilisés pour corriger les résultats obtenus avec la DFT. L’inclusion des effets à N-corps provoque une hausse de la température critique à bas dopage, due à la renormalisation de l’interaction électron-phonon. Cette augmentation dépend fortement de l’épaisseur de la couche électronique et des interactions avec les autres plans chargés. À cause de la nature fondamentale de ce mécanisme, nous nous attendons à trouver un comportement similaire sur une grande gamme de matériaux présentant une dégénérescence de vallées
Gardel, Emily Jeanette. "Microbe-electrode interactions: The chemico-physical environment and electron transfer". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11185.
Pełny tekst źródłaEngineering and Applied Sciences
Moreira, Leandro Malard. "Raman spectroscopy of graphene:: probing phonons, electrons and electron-phonon interactions". Universidade Federal de Minas Gerais, 2009. http://hdl.handle.net/1843/ESCZ-7ZFGDY.
Pełny tekst źródłaDesde a identificação de uma ou poucas camadas de grafeno em um substrato em 2004, trabalhos intensivos tem sido feitos para se caracterizar esse novo material. Em particular, a Espectroscopia Raman Ressonante tem sido muito importante para elucidar propriedades físicas e químicas em sistemas de grafeno. A Espectroscopia Raman Ressonante também tem se mostrado como uma ferramenta importante para se estudar fônons, elétrons e interações elétron-fônon em grafeno. Nesta tese, ao usarmos diferentes energias de laser de excitação, nós obtivemos propriedades importantes sobre as estruturas eletrônicas e vibracionais para uma e duas camadas de grafeno. Para uma monocamada de grafeno, nós determinamos a dispersão de fônons perto do ponto de Dirac para o modo óptico transversal no plano (iTO) e para o modo acústico longitudinal no plano (iLA). Comparamos nossos resultados experimentais como cálculos teóricos recentes para a dispersao de fônons nas proximidades do ponto K. Para a bicamada de grafeno, nós obtivemos os parâmetros de estrutura eletrônica do modelo de Slonczewski-Weiss-McClure. Nossos resultados mostram que a bicamada de grafeno possue uma forte assimetria elétron-buraco, que por sua vez é mais forte que no grafite. Em experimentos aplicando uma tensão de porta, variamos o nível de Fermi em uma bicamada de grafeno, o que levou uma quebra de simetria, deixando assim ambos os modos de vibração simétricos (S) e anti-simétricos (AS) ativos em Raman. A dependência da energia e do amortecimento desses modos de fônons com a energia de Fermi é explicada através do acoplamento elétron-buraco intra- ou inter- banca. Nossos resultados experimentais deram suporte às previsões teóricas para interações elétron-fónon em uma bicamada de grafeno.
Ozfidan, Asli Isil. "Electron-Electron Interactions in Optical Properties of Graphene Quantum Dots". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32857.
Pełny tekst źródłaSzulakowska, Ludmila. "Electron-electron Interactions and Optical Properties of Two-dimensional Nanocrystals". Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40983.
Pełny tekst źródłaSchultze, Martin. "Attosecond real time observation of ionization and electron-electron interactions". Diss., kostenfrei, 2008. http://edoc.ub.uni-muenchen.de/9509/.
Pełny tekst źródłaSchwab, Peter [Verfasser]. "Electron-Electron Interactions and Charge Transport in Mesoscopic Conductors / Peter Schwab". Augsburg : Universität Augsburg, 2007. http://d-nb.info/1077692536/34.
Pełny tekst źródłaGee, Philip James. "Studies of electron-electron interactions in a system of reduced dimensionality". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360300.
Pełny tekst źródłaKumar, Arvind Shankar Shankar. "Investigating Electron-Electron Interactions in 2D Semiconductor Systems through Quantum Transport". Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1624475904980951.
Pełny tekst źródłaPrada, Marta. "Electronic interactions in few electron quantum dot networks for memory storage applications". Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418761.
Pełny tekst źródłaGrumbling, Emily Rose. "Electronic Structure, Intermolecular Interactions and Electron Emission Dynamics via Anion Photoelectron Imaging". Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195933.
Pełny tekst źródłaKnoop, Steven. "Electron dynamics in ion-atom interactions". [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2006. http://irs.ub.rug.nl/ppn/292151632.
Pełny tekst źródłaMonckton, Rhiannon. "Low energy electron interactions with water". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/low-energy-electron-interactions-with-water(c807bd78-59e3-4570-be3c-34feafc01fdf).html.
Pełny tekst źródłaJura, Michael Pemberton. "Imaging electron flow, interference, and interactions in high-mobility two-dimensional electron gases /". May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Pełny tekst źródłaDe, Vega Esteban Sandra. "Plasmon-electron interactions in low dimensional materials". Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/668847.
Pełny tekst źródłaDesde el advenimiento de la tecnología moderna, muchos desarrollos científicos han venido de la mano con la miniaturización y la velocidad. Una prueba de esto es el éxito de la Ley de Moore que predijo que el número de transistores por procesador se doblaría cada dos años y que no habría sido posible si los transistores hubiesen mantenido su tamaño original. A finales de 2018 investigadores del MIT y de la Universidad de Colorado batieron un nuevo récord del transistor más pequeño hasta la fecha de solo 2.5 nm de tamaño. En lo que a 2019 se refiere, ya hay transistores de 5 nm disponibles en el mercado. Considerando estas dimensiones, es de vital importancia tanto entender como poder manipular los materiales en la nanoescala, donde se compartan de una manera totalmente diferente a cómo lo hacen macroscópicamente. Así pues, los investigadores han puesto especial empeño en explicar diversos fenómenos en la nanoescala, en diseñar nuevos nanodispositivos y en proponer o predecir nuevos mecanismos para lograr las nuevas generaciones de chips y circuitos integrados. De hecho, el ascenso de los materiales de baja dimensionalidad (grafeno, TMDs, hBN, P negro y otros), i.e., con planos atómicos están enlazados por fuerzas de van der Waals (2D) o cuyos átomos se ordenan en cadenas o tubos (1D), ha venido por la constante búsqueda de nuevos diseños más compactos y eficientes. En esta tesis, estudiamos las propiedades ópticas de algunos de estos materiales y cómo se modifican debido a la interacción con electrones que, dependiendo del caso concreto, son dopantes o inciden en haces de electrones altamente focalizados. Más en particular, empezamos con un análisis de plasmones, la oscilación colectiva de electrones acoplada a la luz, en nanotubos de carbono (CNTs) finitos altamente dopados. A continuación, exploramos cómo seleccionar el modo del plasmón adecuado usando haces de electrones además de cómo mejorar la interacción entre dos emisores cuánticos cuando el modo plasmónico principal hace de mediador. Predecimos un valor de 10^8 para el factor de Purcell que respalda el uso de CNTs como elementos plasmónicos activos de gran potencial en optoelectrónica y óptica cuántica. Continuamos con sistemas unidimesionales pero esta vez eligiendo cadenas atómicas para emular estructuras sólidas simples donde examinar la dinámica de los electrones cuando están guiados por campos fuertes. Más concretamente, abordamos las cuestiones aún pendientes sobre el papel que juegan las interacciones electrón-electrón y la elección apropiada de material para la generación más eficiente de armónicos altos, y comprobamos nuestras conclusiones en sistemas 1D más realistas: los nanotubos de carbono. Así pues, encontramos que la adición de una pequeña cantidad de carga puede producir excitación de plasmones intrabanda que concentran el campo incidente y fomentan la eficiencia de la generación de armónicos altos. Después, investigamos cómo emplear heteroestructuras 2D para desarrollar nuevas formas más compactas de generar plasmones sin tener que utilizar fuentes externas, por ello utilizamos electrones de efecto túnel. El dispositivo que planteamos es un sándwich de grafeno-hBN-grafeno que se activaría por medio de un electrón que salta de una lámina de grafeno a la otra por efecto túnel, en el proceso pierde energía y ésta se invierte en excitar plasmones. Predecimos una eficiencia de generación que puede alcanzar un plasmón por electrón que salta por efecto túnel y que se mantiene a pesar de las posibles distorsiones por rotación de las láminas o de los cambios en el dopado. Además, completamos este estudio analizando el caso para estructuras de grafeno-aislante-metal y comprobamos que son menos eficientes que sus homólogas de grafeno-hBN-grafeno. En resumen, estos resultados abren la puerta hacia la generación de armónicos más eficiente en nanosólidos y hacia la manipulación en la nanoescala sin elementos ópticos para futuros nanodispositivos optoelectrónicos.
Löfgren, Torbjörn. "Numerical modeling of electron beam-plasma interactions". Doctoral thesis, KTH, Alfvén Laboratory, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2878.
Pełny tekst źródłaMalton, S. P. "Laser interactions with high brightness electron beams". Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444964/.
Pełny tekst źródłaLeadley, David Romwald. "Electron-phonon interactions in low dimensional structures". Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:3e8fe3de-4c61-48ac-a475-050b76901a6f.
Pełny tekst źródłaMontgomery, M. J. "Ineleastic electron-phonon interactions in atomic wires". Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411758.
Pełny tekst źródłaMcKenna, Paul. "Electron and laser interactions with positive ions". Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326350.
Pełny tekst źródłaSiak, Selina Chin Yoke. "Localisation and interactions in disordered electron systems". Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292495.
Pełny tekst źródłaRosser, David M. "Effects of Strain, Electron-Electron Interactions, and Spin-Orbit Coupling in Honeycomb Layered Materials". Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10598952.
Pełny tekst źródłaElectronic transport and angle-resolved photoemission spectroscopy (ARPES) measurements were conducted on two different layered, honeycomb materials: graphene and sodium iridate (Na2IrO3). Graphene, the first two dimensional crystal observed in a laboratory, offers a system to explore novel quantum critical states theoretically predicted under the application of strain. Uniaxial strain was studied in suspended graphene using a microelectromechanical system (MEMS) via electronic transport. Strain was investigated as well by intercalation of C60 at the graphene-substrate (SiC) interface via ARPES. Sodium iridate is a relativistic Mott insulator proximate to the Kitaev model with unconventional electronic structure. An in-gap metallic feature was observed in ARPES measurements of Na2IrO3. Complementary evidence of a metallic conduction channel was observed in electronic transport measurements.
Burmistrov, Igor. "[Theta] renormalization, superuniversality, and electron-electron interactions in the theory of the quantum Hall effect". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2006. http://dare.uva.nl/document/23446.
Pełny tekst źródłaDash, Louise Karenza. "Electron-electron interactions and correlations in atomic scale wires : Luttinger liquids and their spectral signatures". Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269623.
Pełny tekst źródłaBruch, Anton [Verfasser]. "Operating machines at the nanoscale : Effects of electron-electron interactions and strong system-bath coupling on the working principles of electronic nanomachines / Anton Bruch". Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1150704586/34.
Pełny tekst źródłaHowrigan, Shaun. "Electron-photon interactions in quantum dots, coupled oscillators". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/MQ33388.pdf.
Pełny tekst źródłaKhan, Anuja. "Solution structure and interactions of electron transfer proteins". Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415724.
Pełny tekst źródłaHardikar, Rahul Padmakar. "Dynamic electron-phonon interactions in one-dimensional models". Diss., Mississippi State : Mississippi State University, 2007. http://library.msstate.edu/etd/show.asp?etd=etd-11092007-143010.
Pełny tekst źródłaHagelberg, Frank. "Electron Dynamics in Molecular Interactions: Principles and Applications". Digital Commons @ East Tennessee State University, 2014. http://amzn.com/1848164874.
Pełny tekst źródłahttps://dc.etsu.edu/etsu_books/1055/thumbnail.jpg
Caldwell, Joshua D. "Investigation of electron-nuclear spin interactions in two-dimensional electron systems via magnetoresistively detected magnetic resonance". [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008397.
Pełny tekst źródłaSpark, Stephen N. "Pulsed mm-wave electron cyclotron maser experiments". Thesis, University of Strathclyde, 1988. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21311.
Pełny tekst źródłaNapier, Stuart A. "Electron correlation and spin-dependent effects in the electron impact excitation of zinc atoms". University of Western Australia. School of Physics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0098.
Pełny tekst źródłaYang, Xiaodong. "Effects of Electron-Phonon Interaction in Metals". Diss., Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/83903.
Pełny tekst źródłaPh.D.
Phonons and electrons are two types of excitations which are responsible for many properties of condensed matter materials. The interaction between them plays an important role in condensed matter physics. In this thesis we present some theoretical investigations of the effects due to the interactions between phonons and electrons interactions. We show evidence that a structural martensitic transition is related to significant changes in the electronic structure, as revealed in thermodynamic measurements made in high magnetic fields. The effect of the magnetic field is considered unusual, as many influential investigations of martensitic transitions have emphasized that the structural transitions are primarily lattice dynamical and are driven by the entropy due to the phonons. We provide a theoretical frame-work which can be used to describe the effect of a magnetic field on the lattice dynamics in which the field dependence originates from the dielectric constant. The temperature-dependence of the phonon spectrum of alpha-uranium has recently been measured by Manley et al. using inelastic neutron scattering and x-ray scattering techniques. Although there is scant evidence of anharmonic interactions, the phonons were reported to show some softening of the optic modes at the zone boundary. The same group of authors later reported that an extra vibrational mode was observed to form at a temperature above 450 K. The existence of the proposed new mode is inconsistent with the usual theory of harmonic phonons, as applied to a structure composed of a monoclinic Bravais lattice with a two-atom basis. We investigate the effect that the f electron-phonon interaction has on the phonon spectrum and its role on the possible formation of a breathing mode of mixed electronic and phonon character. We examine the model by using Green’s function techniques to obtain the phonon spectral density. Some materials undergo phase transitions from a high temperature state with periodic translational invariance to a state in which the electronic charge density is modulated periodically. The wave vector of the modulation may be either commensurate or incommensurate with the reciprocal lattice vectors of the high temperature structure. In the case of an incommensurate charge density wave, the system supports phason excitation. For an incommensurate state, the new ground state has a lower symmetry than the high temperature state since the charge density does not have long-ranged periodic translational order. If the metal is ideal (with no impurities), a charge density wave should be able to slide throughout the crystal without resistance, resulting in current flow similar to that of a superconductor. The phason is an excitation of the charge density wave which is related to the collective motion of electrons. We estimate the phason density of states, and the phason contribution to the specific heat. Angle-resolved photoemission experiments have been performed on USb2, and very narrow quasiparticle peaks have been observed in a band which local spin-density approximation (LSDA) predicts to osculate the Fermi energy. The observed band is found to be depressed by 17 meV below the Fermi energy. The experimentally observed quasiparticle dispersion relation for this band exhibits a kink at an energy of about 23 meV below the Fermi energy. The kink is not found in LSDA calculations and, therefore, is attributable to a change in the quasiparticle mass renormalization by a factor of approximately 2. The existence of a kink in the quasiparticle dispersion relation of a band which does not cross the Fermi energy is unprecedented. The kink in the quasiparticle dispersion relation is attributed to the effect of the interband self-energy involving transitions from the osculating band into a band that does cross the Fermi energy.
Temple University--Theses
Stano, Peter. "Controlling electron quantum dot qubits by spin-orbit interactions". [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983802254.
Pełny tekst źródłaKiefer, Daniel. "Relativistic electron mirrors from high intensity laser nanofoil interactions". Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-153796.
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