Teses / dissertações sobre o tema "Topological effects"
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Battenfeld, Ingo. "Topological domain theory". Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2214.
Texto completo da fonteCalvanese, Strinati Marcello. "Topological effects in one-dimensional quantum systems". Doctoral thesis, Scuola Normale Superiore, 2018. http://hdl.handle.net/11384/85903.
Texto completo da fonteSingla, Swati. "Topological Effects on Properties of Multicomponent Polymer Systems". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5067.
Texto completo da fonteAsker, Andreas. "Axion Electrodynamics and Measurable Effects in Topological Insulators". Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-67519.
Texto completo da fonteSbierski, Björn [Verfasser]. "On disorder effects in topological insulators and semimetals / Björn Sbierski". Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1102197114/34.
Texto completo da fonteZhang, Yi 1979. "Computer simulation and topological modeling of radiation effects in zircon". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/41587.
Texto completo da fonteIncludes bibliographical references.
The purpose of this study is to understand on atomic level the structural response of zircon (ZrSiO4) to irradiation using molecular dynamics (MD) computer simulations, and to develop topological models that can describe these structural changes. Topological signatures, encoded using the concepts of primitive-rings and local clusters, were developed and used to differentiate crystalline and non-crystalline atoms in various zircon structures. Since primitive-rings and local clusters are general concepts applicable to all materials, and the algorithms to systematically identify them are well-established, topological signatures based on them are easy to implement and the method of topological signatures is applicable to all structures. The method of topological signatures is better than the Wigner-Seitz cell method, which depends on the original crystalline reference grid that is unusable in heavily damaged structures or regions; it is also better than those methods based only on local structures limited to first coordination shell, since one can decide whether or not to include ring contents of large rings into the topological signatures, effectively controlling the range of the topological signatures. The early-stage evolution of non-crystalline disorder and the subsequent recrystallization in zircon collision cascade simulations were successfully modeled by using the topological signatures to identify non-crystalline atoms. Simply using the number of displaced atoms was unable to correctly show the initial peak of structural damage followed by the subsequent annealing stage. Using the topological signatures, amorphization within a single collision cascade was observed in zircon.
(cont.) In the radiation-induced amorphous zircon simulated in this study, the method of topological signatures was able to differentiate the amorphous region in the center of the simulation box and the crystalline region surrounding it. A few isolated remnant crystalline islands were identified in the amorphous region. About 5% of atoms in melted and melt-quenched structures were identified as crystalline atoms. Different amorphous zircon structures were found to be topologically different. Upon amorphization of zircon, the average ring size and the number of atoms in local cluster were found to increase. Larger average ring sizes were found in more pervasively amorphized structures. The radiation-induced amorphous structure was the least pervasively amorphized one, followed by the melt-quenched. The liquid-state amorphous structure was most pervasively amorphized and had the largest average ring size. Phase-separation of zircon into SiO2- and ZrO2-rich local regions was observed when zircon was amorphized in simulations, either thermally or by radiation. It was found in simulations using constant pressure ensembles that the zircon structure underwent abnormally huge volume swelling when it amorphized, which was attributed to the ion charges used in the potential model. Although the ion charges used in the originally chosen potential model were overall balanced, they were not balanced with regard to the phase decomposition products, and thus resulted in strong Coulombic repulsive force within locally SiO2- and ZrO2-rich regions when phase separation occurred. After the ion charges were re-balanced (and other potential parameters refitted), the volume expansion was found to be under control. The charge imbalance of SiO2 units was also found to produce unrealistically large fraction of 3-coordinated Si and shorter Si-O bond length.
(cont.) The issue of charge-balance with regard to phase decomposition products applies to all complex ceramics that decompose into separate phases upon amorphization. Threshold displacement energies in zircon were systematically determined. Many special directions, such as those directed toward neighboring atoms or open spaces surrounding the PKA, were considered. Cascade detail was extensively examined, including PKA trajectory, cascade extent, time scale, thermal spike, recoil density, distribution of PKA energy among sub-lattices and number of displaced atoms. The crystallographic features of the zircon structure were found to have profound implications for collision cascades. It was found that energetic PKAs were always deflected into the open channel along the z direction. Their displacements along the longitudinal x direction were never greater than about 4 nm in our simulations. The estimation of the cascade extent assuming homogeneous media thus greatly over-predicts the PKA displacement along the longitudinal direction. The effects of PKA mass on collision cascade were studied by comparing the cascades caused by Zr and U PKAs. The U atoms were simply "super-mass" Zr atoms in this study: U-Zr, U-Si and U-O interactions were the same as Zr-Zr, Zr-Si and Zr-O interactions, respectively. It was found that heavier PKAs produced longer cascades, more structural damage, and higher temperature in thermal spike. U also traveled further along the longitudinal x direction because it was less prone to change of velocity direction. The depleted regions in the core of the cascades surrounded by a densified shell, which were found in simulations by Trachenko et al., were not found in our study. After extensive tests of recently published zircon potentials, it was found that three out of the five tested potentials yielded poor elastic constants and appear to be unfit for serious simulations. Published simulation results using these potentials should accordingly be viewed cautiously.
by Yi Zhang.
Ph.D.
Nalitov, Anton. "Spin dynamics ande topological effects in physics of indirect excitons and microcavity polaritons". Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22569/document.
Texto completo da fonteThe present thesis manuscript is devoted to new phenomena in physics of light-matter quasiparticles in heterostructures, related to spin and topology. It is divided into four parts. Chapter 1 gives a necessary background, introducing basic properties of microcavity polaritons and indirect excitons in coupled quantum wells. Chapter 2 is focused on spin dynamics and topological defects formation in indirect exciton many-body systems. The last 2 chapters are related to microcavity-based structures. Chapter 3 is devoted to polariton spin dynamics in optical parametric oscillators. Finally, Chapter 4 studies pillar microcavity lattices and introduces the polariton topological insulator
Palin, Victor. "Heusler compounds for spin-orbitronics : exploration of topological effects and magnetic anisotropy engineering". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0031.
Texto completo da fonteOver the last decades, the needs in storage capacity as shot up with computing development. The energy crisis that we are going through in the 21th century requires to develop new fundamental materials for data storage. It was with this purpose that physicist develop new ways to store information in order to reduce device’s scale, energy consumption and manufacturing cost while memories’ size and information’s speed has shot up. The research conducted in this thesis make use of two different ways to improve data storage:- The first one is by using emerging materials in science, called topological insulator, that host peculiar spin texture predicted to generate very high spin-to-charge interconversion. This non-trivial state of matter can be complex to stabilize and image. This is the goal of the first part of this thesis where topological insulators coming from the half-Heusler family are engineered by molecular beam epitaxy. Structural characterization are carried out by X-ray and electronic diffraction along with scanning tunneling microscopy and transmission electron microscopy that confirm an epitaxial growth in the desired structure predicted to host a non-trivial topology. Angle resolved photoemission spectroscopy is performed and reveals the presence of linear states around the Γ point of the Brillouin zone. Nonetheless, the complex Fermi surfaces imaged do not allow to draw clear conclusions on the non-trivial nature of both alloys. Transport measurements were performed to test the potential interconversion efficiency of our compounds and spin Seebeck experiments revealed a spin-to-charge conversion two to three times higher in our TIs compared to a Pt control sample.- The second way chosen to improve conventional magnetic memories is by playing with magnetic anisotropy. Here again, Heusler family offers a vast variety of compounds allowing to fulfill this goal. The Mn3Z family compounds has attracted a lot of attention owing to their tetragonalized unit cell that allows to stabilize perpendicular magnetic anisotropy (PMA) even in a thin film geometry. In this thesis, we investigate Mn(100-x)Ga(x) and Mn(100-x)Ge(x) alloys and manage to stabilize them in their D0(22) structure that offers PMA. A peculiar zoom is then done on Mn3Ge-based stacks composed of a second Heusler alloy with remarkable properties, the Co2MnZ’ family (Z' = Si, Ge). Co2MnZ’ compounds have a half-metallic behavior making them very suitable for spin transfer torque related applications due to their low magnetic damping and full spin polarization at the Fermi level. Here we develop Mn3Ge/Co2MnZ' heterostructures (bilayers and superlattices) and manage to grow both compounds in the desired structures. The overall system is perpendicularly magnetized (thanks to Mn3Ge), terminated with a half-metal magnet (thanks to Co2MnZ') and the thicknesses used for both layers allow to tune the magnetic properties and obtained 100% of remanence
Song, Kenan. "Theoretical study of disorder and proximity effects in three-dimensional models of topological insulators". Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/663940.
Texto completo da fonteEste doctorado. El proyecto cubre las investigaciones sobre aislantes topológicos (TI) de la familia Bi2Se3 con diferentes defectos y el estudio de efectos de proximidad de TI en la heteroestructura de grafeno con TI. La primera parte de este proyecto se centra principalmente en el efecto del desorden en las propiedades electrónicas de TI con espesor ultrafino (<3 nm). Se ha encontrado que la falta de coincidencia de rotación entre capas quíntuples de TI puede aumentar el “gap” de volumen de los TI pero preservar la textura de espín tipo Rashba en el estado de la superficie; mientras que la hidrogenación en una superficie de TI puede ayudar a reducir el efecto túnel cuántico y cerrar el “gap” de los estados de superficie en el punto Γ con la textura de espín tipo Rashba para la película TI ultrafina. Además, este esquema también puede crear otro punto Dirac (DP) en el punto M con textura de espín tipo Dresselhaus. La segunda parte del proyecto investiga los efectos de proximidad de TI dentro de la heteroestructura de grafeno/TI y el DP en el grafeno se pliega desde el punto K / K' a Γ punto en la zona Brillouin, debido al plegamiento de la banda, encontrando que la alineación entre el sustrato de TI y el grafeno desempeña un papel clave en la formación de la estructura de la banda y la textura de espín del grafeno. La configuración de apilamiento “hollow” podría inducir la distorsión de unión de Kekulé a la capa de grafeno, dando como resultado el agrandamiento del “gap” (3.2 meV) y el Rashba SOC, lo que da como resultado la precesión de espín cercana al Γ punto. Además, esta textura atípica de Rashba espín hace que la componente de espín fuera del plano disminuya gradualmente a medida que el punto k se aleja del punto Γ, lo que lleva a la anisotropía de giro en la capa de grafeno. Por otro lado, la configuración de apilamiento “bridge” o “top” podría traer la evidente división de la banda en dirección lateral, que podría ser el origen del efecto Edelstein en la capa de grafeno; sin embargo, no hay una anisotropía de espín evidente en dicha configuración. Todas las primeras dos partes se han llevado a cabo a través del cálculo de la teoría funcional de la densidad (DFT) y se ha construido un modelo de unión ajustada (TB) para los resultados de DFT con el fin de proporcionar una explicación analítica de la estructura de la banda y la textura del spin de grafeno en el dispositivo de heteroestructura. La última parte de este doctorado. La actividad de investigación se centra en estudiar el efecto de impurezas magnéticas y no magnéticas con un esquema de dopaje aleatorio sobre las propiedades electrónicas de los TI. El cálculo numérico basado en el modelo 3D Fu-Kane-Mele TB mostró que el dopaje no magnético en la superficie de TI solo podía inducir el potencial in situ en la superficie DP y elevarlo hacia arriba, preservando la textura estándar de espín tipo Rashba; mientras, el dopaje magnético podría romper la simetría de inversión de tiempo y abrir el “gap” de superficie con la anisotropía de espín también, lo que significa que la componente de espín fuera del plano en la superficie TI dopada magnéticamente disminuye gradualmente a medida que el punto k se aleja del Γ punto. Los trabajos de investigación en este proyecto podrían proporcionar una guía para la lista de experimentos sobre las propiedades electrónicas de TI con diferentes tipos de defectos e impurezas (magnéticos y no magnéticos); particularmente, el estudio de los efectos de proximidad en los TI podrían explicar el fenómeno fundamental básico observado en dicho dispositivo para el estudio de la dinámica de espín en el laboratorio.
This PhD. project covers the researches on the Bi2Se3-family topological insulators (TIs) with different defects and the study of the proximity effects of TI in the heterostructure of graphene with TI. The first part of this project mainly focuses on the effect of disorder on the electronic properties of TI with ultrathin thickness (< 3 nm). It was found that rotation mismatch between quintuple of TI can enlarge the bulk gap of TI but preserve the Rashba type spin texture on the surface state; while, the hydrogenation on one TI surface can help reduce the quantum tunneling effect and close the surface gap at Γ point with Rashba type spin texture for ultrathin TI film. Furthermore, this scheme can also create another Dirac point (DP) at M point with Dresselhaus type spin texture. The second part of the project investigates in the proximity effects of TI within the heterostructure of graphene/TI and the DP on graphene is folded from K/K' point to Γ point in Brillouin zone, due to the band folding, and it was found that the alignment between TI substrate and graphene played the key role in forming the band structure and the spin texture of graphene. Hollow configuration could induce the Kekulé bonding distortion to graphene layer, mainly resulting in the enlarged gap (3.2 meV), and the Rashba SOC, resulting in the spin precession close to the Γ point. Furthermore, this atypcial Rashba spin texture has the out-of-plane spin component decrease gradually as the k point moves away from the Γ point, leading to the spin anisotropy on graphene layer. While, the bridge or the top configuration could bring the evident band splitting in lateral direction, which could be the origin of the Edelstein effect in graphene layer; however, there is no evident spin anisotropy in such configuration. All the first two parts were carried out through density functional theory (DFT) calculation and a tight binding (TB) model was built up and fitted to the DFT results in order to provide an analytical explanation for the band structure and the spin texture of graphene in the heterostructure device. The last part of this PhD. research work was to study the effect of both non-magnetic and magnetic impurities with random doping scheme on the electronic properties of TI. Numerical calculation based on 3D Fu-Kane-Mele TB model showed that non-magnetic doping on TI surface could only induce the onsite potential on the surface state and lift the DP upwards, preserving the standard Rashba type spin texture; while, the magnetic doping could break the time reversal symmetry and open up the surface gap with the spin anisotropy as well, which means the out-of-plane spin component on magnetically doped TI surface decreases gradually as the k point moves away from the Γ point. Research works in this project could provide a guideline to the experimentlist on the electronic properties of TI with different kinds of defects and impurities (magnetic and non-magnetic ones); particularly, the study of the proximity effect of TI could explain the basic fundamental phenomenon observed in such device for spin dynamics study in the laboratory.
Ruhl, Lindsey C. "Micro-Topological Effects on Redox-Sensitive Nutrient Availability of Manganese, Iron, Sulfur, and Phosphorus". ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/342.
Texto completo da fonteSchmirander, Thorben [Verfasser]. "Spin-Orbit Coupling Effects and Magnetism of the Topological Edge States of Graphene / Thorben Schmirander". Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2021. http://nbn-resolving.de/urn:nbn:de:gbv:18-ediss-95527.
Texto completo da fonteSchlitz, Richard [Verfasser], Sebastian T. B. [Gutachter] Goennenwein e Felix [Gutachter] Casanova. "Topological Transport Effects and Pure Spin Currents in Nanostructures / Richard Schlitz ; Gutachter: Sebastian T. B. Goennenwein, Felix Casanova". Dresden : Technische Universität Dresden, 2020. http://d-nb.info/1227201397/34.
Texto completo da fonteWatzman, Sarah June. "Thermal Energy Conversion Utilizing Magnetization Dynamics and Two-Carrier Effects". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523621461827864.
Texto completo da fonteRavindren, Sriram. "New insights into the Glass Structure and Melt Dynamics of Ge-As-Se Alloys: Topological Phases, Eutectic Effects, Slow Homogenization of Melts and Nanoscale Phase Separation Effects". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427798415.
Texto completo da fonteKönig, Elio Johannes [Verfasser], e A. D. [Akademischer Betreuer] Mirlin. "Interaction and disorder effects in topological insulators = Wechselwirkungs- und Unordnungseffekte in topologischen Isolatoren [[Elektronische Ressource]] / Elio Johannes König. Betreuer: A. D. Mirlin". Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1068263393/34.
Texto completo da fonteHunt, Rebecca Ann. "Determining Topological Effects of Heterocyclic Diamidines with AT Rich DNA: A Study Using Gel Electrophoresis, Mass Spectrometry, and the Polymerase Chain Reaction". Digital Archive @ GSU, 2010. http://digitalarchive.gsu.edu/chemistry_theses/31.
Texto completo da fonteYang, Shuo-Ying [Verfasser], Stuart S. P. [Gutachter] Parkin, Ingrid [Gutachter] Mertig e Vitto Zheng [Gutachter] Han. "In search of extraordinary Hall effects in topological semimetals / Shuo-Ying Yang ; Gutachter: Stuart S. P. Parkin, Ingrid Mertig, Vitto Zheng Han". Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2020. http://d-nb.info/1222513757/34.
Texto completo da fonteRoychowdhury, Krishanu [Verfasser], Roderich [Akademischer Betreuer] Moessner, Matthias [Akademischer Betreuer] Vojta e Kirill [Akademischer Betreuer] Shtengel. "Aspects of many-body systems on a kagome lattice : strong correlation effects and topological order / Krishanu Roychowdhury. Betreuer: Roderich Moessner. Gutachter: Matthias Vojta ; Kirill Shtengel". Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://d-nb.info/1088185495/34.
Texto completo da fonteRepellin, Cécile. "Numerical study of fractional topological insulators". Thesis, Paris, Ecole normale supérieure, 2015. http://www.theses.fr/2015ENSU0028/document.
Texto completo da fonteTopological insulators are band insulators which are fundamentally different from atomic insulators. Only a non-local quantity called topological invariant can distinguish these two phases. The quantum Hall effect is the first example of a topological insulator, but the same phase can arise in the absence of a magnetic field, and is called a Chern insulator. In the presence of strong interactions, topological insulators may host exotic excitations called anyons. The fractional quantum Hall effect is the only experimentally realized example of such phase. In this manuscript, we study the conditions of emergence of different types of fractional topological insulators, using numerical simulations. We first look at the fractional quantum Hall effect on the torus. We introduce a new projective construction of exotic quantum Hall states that complements the existing construction. We study the low energy excitations on the torus of two of the most emblematic quantum Hall states, the Laughlin and Moore-Read states. We propose and validate model wave functions to describe them. We apply this knowledge to characterize the excitations of the Laughlin state in Chern insulators. We show the stability of other fractional quantum Hall states in Chern insulators, the composite fermion, Halperin and NASS states. We explore the physics of fractional phases with no equivalent in a quantum Hall system, using two different strategies: first by choosing a model with a higher value of the topological invariant, second by adding time-reversal symmetry, which changes the nature of the topological invariant
Silva, Júlio Eloísio Brandão da. "Efeitos geométricos, inerciais e topológicos na condutividade Hall". Universidade Federal da Paraíba, 2017. http://tede.biblioteca.ufpb.br:8080/handle/tede/9491.
Texto completo da fonteMade available in DSpace on 2017-09-11T14:24:18Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2910617 bytes, checksum: 78d320ecf6eab76dd1627257ec1aa34d (MD5) Previous issue date: 2017-03-16
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Electromagnetic fields acting on particles have been extensively studied in different areas of physics. In quantum mechanics for example, effects such as Aharonov-Bohm, Landau levels and Hall conductivity, have always motivated new papers including analogous inertial models. Inertial effects play an important role in classical mechanics, but have been largely ignored in quantum mechanics. However, the analogy between inertial forces on mass particles and electromagnetic forces on charged particles is not new. Another factor that may influence the classical and quantum behavior of particles is geometry. An element related to geometry that has been extensively studied in several areas is the topological defect. Topological defects represent an interface between areas such as cosmology, gravitation, and condensed matter. Such defects in condensed matter can be developed through the classical theory of elasticity. However, due to the interdisciplinarity of this theme, approaches from gravitation can also describe them. Based on this analogy, the medium formed by a topological defect is characterized by a metric tensor. From this approach, several problems can be discussed by analyzing the influence of the topological defect in the solution of the problem. In this work, it will be discussed how magnetic field, rotation and topological defects, especially the disclination, influence in the Landau Levels and the Hall conductivity for a noninteracting planar two-dimensional electron gas. First we will discuss the influence of each of these elements and then the influence of all of them simultaneously.
A atuação de campos eletromagnéticos em partículas têm sido extensivamente estudada em diferentes áreas da física. Em mecânica quântica por exemplo, efeitos como Aharonov-Bohm, níveis de Landau e condutividade Hall, têm sempre motivado novos trabalhos inclusive para modelos análogos inerciais. Os efeitos inerciais desempenham um papel importante na mecânica clássica, mas tem sido largamente ignorados em mecânica quântica. No entanto, a analogia entre forças inerciais sobre partículas de massa e forças eletromagnéticas sobre partículas carregadas não é nova. Um outro fator que pode influenciar no comportamento clássico e quântico de partículas é a geometria. Um elemento relacionado a geometria e que tem sido bastante estudado em diversas áreas, é o defeito topológico. Os defeitos topológicos representam uma interface entre áreas como cosmologia, gravitação e matéria condensada. Tais defeitos em matéria condensada podem ser desenvolvidos através da teoria clássica da elasticidade. Contudo, devido a interdisciplinaridade desse tema, abordagens provenientes da gravitação podem também descrevê-los. Com base nessa analogia, caracteriza-se o meio formado por um defeito topológico mediante um tensor métrico. A partir dessa abordagem, diversos problemas podem ser discutidos analisando a influência do defeito topológico na solução do problema. Nesse trabalho, será discutido como campo magnético, rotação e defeitos topológicos, em especial a desclinação, influenciam os níveis de Landau e a condutividade Hall para um gás de elétrons bidimensional planar não interagente. Primeiramente discutiremos a influência de cada um desses elementos e em seguida a influência de todos simultaneamente. Será mostrado como a rotação quebra a degenerescência dos níveis de Landau aumentando consequentemente a condutividade Hall. Será mostrado também que acoplamento dos três elementos gera uma região para campos magnéticos fracos com sem estados ligados. Com um outro ponto de partida mostraremos também que a rotação pode ser utilizada para sintonizar a condutividade Hall.
Vistoli, Lorenzo. "Topological and electronic properties of electron-doped manganite thin films". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS113.
Texto completo da fonteOxide thin films feature a wide range of physical phenomena and rich phase diagrams tunable by strain and interface engineering. CaMnO3, in particular, is extremely sensitive to both doping and strain and, when grown with compressive strain, transitions from an insulating and antiferromagnetic state to a metallic and weakly ferromagnetic state at only 2% Ce doping.We used a combination of angle-resolved photoemission spectroscopy, magnetotransport, and density functional theory to study the electronic properties of this material. We observed the existence of two separate charge carriers, light electrons and heavy polarons, whose physical nature differs because of drastically different couplings to phonons. We ascribe these differences to a different relative band filling due to correlations, which enhance greatly the coupling to phonons of the heavy polarons band. Magnetotransport experiments reveal that the polaron band dominates transport despite its lower mobility.Compressive strain also gives rise to a strong magnetic anisotropy which stabilizes magnetic bubbles that accompany a topological Hall effect. This suggests that these bubbles have topological character, i.e. are skyrmion bubbles. The topological Hall effect diverges as the manganite approaches the metal-insulator transition at low dopings. We used a recently developed theory in order to interpret this behavior, and we conclude that correlations may come into play, enhancing the effective mass of the carriers, and in turn the topological Hall effect.As this manganite is highly sensitive to changes in doping and carrier density, we grew BiFeO3/(Ca,Ce)MnO3 ferroelectric field-effect transistors. Upon switching the ferroelectric polarization of the BiFeO3 top layer, we could not observe any sizable changes in the properties of the underlying manganite layers. We used transmission electron microscopy to study the properties of these bilayers with an atomic resolution, and we observed that polarization pinning at the BiFeO3/(Ca,Ce)MnO3 impedes a complete switch of the polarization and so reduces the operational capabilities of these devices. Nevertheless, we could detect modifications of the electronic properties of the manganite induced by polarization reversal at the atomic scale
Amaouch, Mohamed. "Applications des approches topologiques ELF et QTAIM dans un contexte quasirelativiste à 2 composantes". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066496/document.
Texto completo da fonteThis thesis deals with the aplication of topological approaches of the chemical bonding by means of analysing properties of density-based functions like Electron Localization Function (ELF) and the Quantum Theory of Atoms in Molecumes (QTAIM) to systems involving heavy elements such as 6p elements or actinides . It is divided into two main parts: (i) the evaluation of the spin-orbit coupling (SOC) effects on the electronic structure by means of combination of the QTAIM and ELF topological analyses in the field of quasirelativistic quantum calculations, and (ii) the rationalization of structural distorsions on molecules containing heavy atoms, and the role of the SOC on these distorsions. We were able to emphasize different situations for which SOC has strong, moderate or tiny influence on the chemical bonding, depending on the chemical environnement on which the heavy element is involved. In the second part of this thesis we tested our approach consisting of ELF/QTAIM interbasin repulsion energy analysis in connection with the molecular geometry of the system, in the spirit of the VSEPR and LCP models
Farrell, Aaron. "Topological superconductivity without proximity effect". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119741.
Texto completo da fonteRécemment, une région d'intérêt en la recherché de la matière condensée est le recherche pour les "Majorana Fermions". Les physiciens sont fascinés avec cette particule pour des raisons fondamentales et pratiques. Fondamentalement, une particule se comporte comme un Majorana Fermion n'a jamais été trouvée avant. Pratiquement, un Majorana Fermion pourrait être utilisé pour la construction d'un ordinateur quantique. Dans les dernières années, les chercheurs ont commencé à chercher pour des Majorana Fermions dans les supraconducteurs. En particulier, les supraconducteurs topologiques sont crus de supportes les Majorana Fermions dans leur vortex cores et de ce fait des nombreux dispositifs supraconducteurs topologiques ont été proposées. Les propositions récemment sont basées sur les hétérostructures de trois ou deux couches. Dans ces hétérostructures, les bandes d'un semiconducteur avec le couplage de spin-orbit sont séparées par le champ Zeeman d'une couche ferromagnétique (ou un champ appliqué). Après cette, supraconductivité topologique est établie dans la couche de semiconductrice en raison de la proximité d'une couche de supraconducteur ordinaire. Dans cette thèse nous proposons une simplification des dispositifs décrits ci-dessus; nous suggérons un moyen d'enlever la couche de supraconductivité. Nous commençons par proposer un Hamiltonian du cette système et procède à développer des nombreuses méthodes pour analyser cette Hamiltonian avec l'objectif ultime de classifier la topologie de ce système.
Thomas, Candice. "Strained HgTe/CdTe topological insulators, toward spintronic applications". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY090/document.
Texto completo da fonteWith graphene-like transport properties governed by massless Dirac fermions and a topological protection preventing from backscattering phenomena, topological insulators, characterized by an insulating bulk and conducting surfaces, are of main interest to build low power consumption electronic building-blocks of primary importance for future electronics.Indeed, the absence of disorder, the generation of dissipation-less spin-polarized current or even the possibility to generate pure spin current without magnetic materials are some of the promises of these new materials.The objective of this PhD thesis has been to experimentally demonstrate the eligibility of HgTe three dimensional topological insulator system for applications and especially for spintronics.To do so, strong efforts have been dedicated to the improvement of the growth process by molecular beam epitaxy.Chemical composition, strain, defect density and sharpness of the HgTe interfaces have been identified as the major parameters of study and improvement to ensure HgTe inverted band structure, bulk gap opening and to emphasize the resulting topological surface state electronic properties. Verification of the topological nature of this system has then been performed using low temperature magneto-transport measurements of Hall bars designed with various HgTe thicknesses. It is worth noting that the high desorption rate of Hg has made the nanofabrication process more complex and required the development of a low temperature process adapted to this constraint. While the thicker samples have evidenced very complex transport signatures that need to be further investigated and understood, the thickness reduction has led to the suppression of any additional contributions, such as bulk or even side surfaces, and the demonstration of quantum Hall effect with vanishing resistance. Consequently, we have managed to demonstrate direct evidences of Dirac fermions by temperature dependent analysis of the quantum Hall effect. The next step has been to use the topological properties and especially the locking predicted between momentum and spin to test the HgTe potential for spintronics. Spin pumping experiments have demonstrated the power of these topological structures for spin injection and detection. Moreover, the implementation of HgTe into simple p-n junction has also been investigated to realize a first spin-based logic element
Nakagawa, Masaya. "Kondo Effect and Topological Phenomena in Ultracold Atoms". 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225388.
Texto completo da fonteTemaismithi, Jesada. "Aspects of the topological Kondo effect". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:58e3ab62-9ade-47c3-aea2-3cde43e28726.
Texto completo da fonteVeyrat, Louis. "Quantum Transport Study in 3D Topological Insulators Nanostructures". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-210217.
Texto completo da fonteAndrews, Bartholomew. "Stability of topological states and crystalline solids". Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288876.
Texto completo da fontevan, Caspel Moos. "The topological Casimir effect on a torus". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44948.
Texto completo da fonteO'Neill, Christopher David. "Topological properties of SnTe and Fe3Sn2". Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20391.
Texto completo da fonteSticlet, Doru. "Edge states in Chern Insulators and Majorana fermions in topological superconductors". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112318/document.
Texto completo da fonteThis thesis follows two threads in the field of topological insulators and superconductors. The first part of the thesis is devoted to the study of two-dimensional quantum anomalous Hall insulators on a lattice, in the absence of an external magnetic flux, but induced by an inhomogeneous flux in the unit cell. The system possesses several gapped phases characterized by a topological invariant, the Chern number, that is related to the conductance carried by the edge states. Here we show that two-band models admit an arbitrary large number of Chern phases or, equivalently, an arbitrary number of edge states, by adding hopping between distant neighbor sites. This result is based on a formula proving that the Chern number of a band depends on certain properties of a finite set of points in the Brillouin zone, i.e. the Dirac points for the gapless system. These ideas are made more concrete in the study of a modified Haldane model, and also by creating an artificial model with five Chern phases, whose edge states are determined in detail. The second part of the thesis focuses on one-dimensional topological superconductors with exotic zero-energy edge states: the Majorana bound states. Here we investigate the presence of Majorana fermions in spin-orbit coupled semiconducting wire in proximity to an s-wave superconductor. We show that the spin-polarization of the electronic degrees of freedom in the Majorana wave function depends on the relative weight of Dresselhaus and Rashba spin-orbit couplings. We also investigate Majorana fermions in linear superconductor-normal and long superconductor-normal-superconductor (SNS) junctions where they appear as extended states in the normal junction. Furthermore, ring geometries can be mapped to an SNS junction, and, we have shown that under the action of superconducting phases gradients, extended Majorana fermions can form again inside the normal wire. Finally a two-band model with multiple Majorana fermions is treated and we show that Josephson junctions built from this model maintain the 4π periodicity for the fractional Josephson effect, one of Majorana fermions signatures
Dos, Santos Luiz Henrique Bravo. "Topological Properties of Interacting Fermionic Systems". Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10195.
Texto completo da fontePhysics
McIver, James W. "Nonlinear optical and optoelectronic studies of topological insulator surfaces". Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13064980.
Texto completo da fontePhysics
Noel, Paul. "Dynamical spin injection and spin to charge current conversion in oxide-based Rashba interfaces and topological insulators". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY062.
Texto completo da fonteUsing a ferromagnetic layer has been the first method to obtain and detect spin currents, allowing to modify the magnetization state of an adjacent layer using spin transfer torque. However, in recent years, an alternative way to manipulate spin currents has been proposed. An emerging field of spintronics, called spin-orbitronics, exploits the interplay between charge and spin currents enabled by the spin-orbit coupling (SOC) in non-magnetic systems. An efficient current conversion can be obtained through the Spin Hall Effect in heavy metals such as Platinum or Tantalum. The conversion can also be obtained by exploiting the Edelstein Effect in Rashba interfaces and topological insulators.The spin to charge conversion by means of Inverse Edelstein Effect and inverse Spin Hall Effect can be studied by the spin pumping by ferromagnetic resonance technique. This manuscript present these two conversion mechanisms as well as the technique that was used to measure them, which is based on an electrical detection of the ferromagnetic resonance. Results on the spin to charge current conversion obtained in metals, oxide-based Rashba interfaces and topological insulators will be presented. Among these systems we have demonstrated the possibility to tune the conversion efficiency by using a gate voltage in a two-dimensional electron gas at the surface of an oxide SrTiO3. Moreover it is possible to tune this effect, a remanent way, thanks to the ferroelectricity obtained in SrTiO3 at cryogenic temperatures.Other studied systems such as topological insulators HgTe and Sb2Te3 also have promising properties for an efficient spin to charge current conversion at room temperature. In particular we showed than in HgTe by using a thin HgCdTe protective layer, it is possible to obtain a spin to charge current conversion efficiency one order of magnitude larger than in Pt.These results suggest that stwo dimensional electron gases at oxide interfaces and topological insulators have a strong potential for the efficient detection of spin currents for possible beyond CMOS applications
Souza, Jean Carlo 1993. "Estudos de ressonância de spin eletrônico (RSE) em isolantes topológicos dopados com terras-rara". [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/326704.
Texto completo da fonteDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: A ideia de topologia na Física da Matéria da Condensada, apesar de ter surgido com o efeito Hall quântico inteiro, só voltou a ser explorada recentemente na busca de novas fases da matéria depois do surgimento dos Isolantes Topológicos (ITs) 2D. Após a previsão teórica, e a descoberta experimental, foi proposto que esta nova fase poderia ser generalizada para sistemas 3D, em que o volume do material seria isolante com estados metálicos de superfície que possuiriam canais de spin polarizados. Apesar de diversos experimentos e o surgimento de outras fases topológicas da matéria subsequentes, ainda há dúvidas sobre a natureza dos ITs 3D. Os efeitos topológicos mais claros ainda não foram observados de forma inequívoca e reprodutível experimentalmente e ainda seria de extrema valia encontrar técnicas experimentais que possam complementar os mais discutidos experimentos de ARPES. Nesta dissertação foram estudadas duas famílias distintas de materiais propostas como possíveis ITs 3D: os binários Bi2Se3 e Sb2Te3 e o half-Heusler YPdBi. Utilizando a técnica de auto-fluxo e a fusão estequiométrica, os sistemas foram sintetizados dopados com os terras-rara Gd3+, Nd3+ e Er3+ para realizar estudos de ressonância de spin eletrônico (RSE) e do papel dos efeitos de campo cristalino (CEF) - no caso do half-Heusler. Para o ternário YPdBi foram feitos dois estudos. Na família dos half-Heuslers, a ordem topológica surge da relação entre o acoplamento spin-órbita e a hibridização, que está ligada com a mudança do parâmetro de rede, então os efeitos de CEF poderiam estar refletindo a transição entre a trivialidade e a não-trivialidade. A partir das medidas de susceptibilidade magnética em função da temperatura das amostras dopadas com Nd3+ e Er3+ combinadas com os estudos de RSE, foi possível extrair os parâmetros de campo cristalino (CFP) de quarta e sexta ordem. Comparando esses dados com resultados anteriores para o material, supostamente, não-trivial YPtBi, observou-se uma mudança sistemática no sinal dos CFP. Resultados prévios para as amostras de YPtBi dopadas com Nd3+ mostram uma evolução não usual para uma forma de linha difusiva com a potência de micro-onda. Neste trabalho também foi realizado um estudo da forma de linha em função da potência. Apenas a ressonância do Nd3+ para os monocristais de 10% de Nd em YPdBi mostrou uma forma de linha difusiva que evolui com a potência da micro-onda. No caso dos binários Bi2Se3 e Sb2Te3, o objetivo era otimizar a rampa de tratamento térmico para obter monocristais melhores que poderiam permitir a observação de um espectro totalmente resolvido do Gd3+. Após mudanças no crescimento dos monocristais, o espectro totalmente resolvido foi obtido para as amostras de Bi2Se3. No caso do Sb2Te3 apenas uma linha central com a estrutura fina colapsada foi observada. Acompanhando o deslocamento g e a evolução da largura de linha dH da RSE do Gd3+ com a temperatura, o comportamento negativo do deslocamento g para toda a faixa de temperatura indica que elétrons do tipo p são os grandes responsáveis pela formação da superfície de Fermi residual destes sistemas. Um aumento no coeficiente angular de dH em função da temperatura, a taxa Korringa b, foi observado em baixas temperaturas, logo diferentes concentrações de Gd3+ foram utilizadas para estudar este comportamento. Novamente observou-se um comportamento anômalo em baixas temperaturas, o que poderia estar relacionado com a evolução dos CFP com a temperatura. Todos esses resultados foram discutidos levando-se em conta a possibilidade de existência de topologia não-trivial na estrutura eletrônica desses materiais, com foco particular na relação da interação spin-órbita e os efeitos de campo cristalino com a manifestação da topologia não trivial nesses sistemas
Abstract: The idea of topological systems in Condensed Matter Physics, although already explored in the Quantum Hall Effect, has recently become a topic of intense scientific investigation. In particular, great efforts have been dedicated to the search for new quantum phases since the proposal of the Topological Insulators (TIs) in 2D. After the theoretical prediction and the experimental discovery of the TIs in the 2D case, the existence of the Quantum Hall Spin Effect in 3D, 3D TIs, was proposed, where an insulator bulk and metallic surface states with spin polarized channels could be experimentally realized. Although many experiments have been performed, and some groups claimed the direct observation of such new topological phases, there is still a lot of controversy about the nature of the 3D TIs and about the actual microscopic origin of the metallic states on the surface of the studied materials. Other signatures of the topological phases have not been unambiguously and repeatedly measured yet and there is an obvious lack of a supplementary lab technique to be compared to the most used technique to probe these states, which is ARPES. In this work we have studied two different classes of 3D TIs: the binaries Bi2Se3 and Sb2Te3 and the half-Heusler YPdBi. We have been able to grow single crystals of these materials pure and rare-earth doped with Gd3+, Nd3+ and Er3+ using the self-flux technique and the stoichiometric melting. The aim was to use these crystals to study Electron Spin Resonance (ESR) as a potential probe to investigate the existence of the metallic surface states and to explore the possible of the crystalline electrical field (CEF) effects on the formation of the non-trivial electronic structure of these materials. Regarding the YPdBi, our ESR and magnetization studies have revealed that, in the half-Heusler family, the topological order emerges from the interplay between spin-orbit coupling and the hybridization, which is connected with the changes on the lattice parameter. Thus, the CEF effects could reflect the transition from trivial to nontrivial topology. From the magnetic susceptibility data as a function of temperature from the Nd3+ and Er3+ doped samples combined with the ESR studies, it was possible to extract the fourth and sixth order crystal field parameters (CFP). Comparing our data with the previous results from YPtBi, which is a putative non-trivial material, a systematic change in the sign of the CFP was observed. Previous results with the YPtBi Nd-doped samples show an unusual evolution of the Nd3+ ESR line to a diusive-like line shape as a function of the microwave power. In this work we have performed a similar study of the Nd3+ ESR line shape as a function of the microwave power. Only for the single crystal of 10% Nd in YPdBi resonance shows a diffusive-like line shape that evolves with the microwave power. In the case of the binaries Bi2Se3 e Sb2Te3, the aim of this work was to optimize the heat treatment used in previous works of our group to obtain better single crystals that could allow the observation of the full resolved spectra from Gd3+. After many changes in the single crystal growth method, we were able to observe fully resolved Gd3+ ESR spectra in the Bi2Se3 samples. Regarding the Sb2Te3 single crystals, only a single Gd3+ Dysonian ESR line was observed. Following the Gd3+ ESR dg and dH as a function of temperature, the observed negative behavior of dg, in the whole temperature range studied, indicates that p-type electrons are the main source for the formation of the small the Fermi surface of these materials. An increase of the angular coefficient of dH as a function of temperature, the Korringa rate b, at low temperatures was observed and different concentrations of Gd3+ were required to investigate this anomaly. Again this anomalous behavior at low temperatures was observed for the all Gd-doped samples, which could be related to an evolution of CFP with temperature. We discuss our results taking into account the existence of non-trivial topological states in our samples and the role of spin-orbit and CEF effects might have in the formation of such states
Mestrado
Física
Mestre em Física
132653/2015-0
CNPQ
CAPES
FAPESP
Munoz, De Las Heras Alberto. "Non-Hermitian and Topological Features of Photonic Systems". Doctoral thesis, Università degli studi di Trento, 2022. https://hdl.handle.net/11572/331092.
Texto completo da fonteRonetti, Flavio. "Charge and heat transport in topological systems". Electronic Thesis or Diss., Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0541.
Texto completo da fonteIn this thesis, I address the intriguing and appealing topic of charge and heat transport in quantum Hall systems, which are among the most famous example of topological phases of matter, in presence of external time-dependent voltages. Quantum Hall effect occurs in two-dimensional electron systems in the limit of strong perpendicular magnetic fields. The hallmark of quantum Hall systems is the emergence of one-dimensional metallic edge states on the boundary. Along these edge states particles propagate with a definite direction. The coherence length ensured by topological protection guarantees to access wave-like nature of electrons. This properties inspired a new field of research, known as electron quantum optic. Single-electron source can be realized by applying to a quantum Hall system a periodic train of Lorentzian-shaped pulses.Plateaus of the Hall resistance appear also at fractional values of the resistance quantum. The physical explanation of fractional quantum Hall effect cannot neglect the correlation between electrons and this phase of matter is inherently strongly-correlated. By considering the application of a periodic train of Lorentzian pulses to a quantum Hall system, I investigate the charge density of a state composed by many levitons in the fractional quantum Hall regime, thus finding that it is re-arranged into a regular pattern of peaks and valleys, reminiscent of Wigner crystallization in strongly-interacting electronic systems. Then, I analyze heat transport properties of levitons in quantum Hall systems, which represent a new point of view on electron quantum optics, extending and generalizing the results obtained in the charge domain
Ronetti, Flavio. "Charge and heat transport in topological systems". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0541/document.
Texto completo da fonteIn this thesis, I address the intriguing and appealing topic of charge and heat transport in quantum Hall systems, which are among the most famous example of topological phases of matter, in presence of external time-dependent voltages. Quantum Hall effect occurs in two-dimensional electron systems in the limit of strong perpendicular magnetic fields. The hallmark of quantum Hall systems is the emergence of one-dimensional metallic edge states on the boundary. Along these edge states particles propagate with a definite direction. The coherence length ensured by topological protection guarantees to access wave-like nature of electrons. This properties inspired a new field of research, known as electron quantum optic. Single-electron source can be realized by applying to a quantum Hall system a periodic train of Lorentzian-shaped pulses.Plateaus of the Hall resistance appear also at fractional values of the resistance quantum. The physical explanation of fractional quantum Hall effect cannot neglect the correlation between electrons and this phase of matter is inherently strongly-correlated. By considering the application of a periodic train of Lorentzian pulses to a quantum Hall system, I investigate the charge density of a state composed by many levitons in the fractional quantum Hall regime, thus finding that it is re-arranged into a regular pattern of peaks and valleys, reminiscent of Wigner crystallization in strongly-interacting electronic systems. Then, I analyze heat transport properties of levitons in quantum Hall systems, which represent a new point of view on electron quantum optics, extending and generalizing the results obtained in the charge domain
Latief, Andy Octavian. "Tunnelling density of states studies of the topological Kondo effect". Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8475/.
Texto completo da fonteHerviou, Loïc. "Topological Phases and Majorana Fermions". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX036/document.
Texto completo da fonteIn this thesis, we study theoretically different aspects of topological systems. These models present resilient properties due to a non-trivial topology of their band structures, and in particular exotic edge excitations such as Majorana fermions.Entanglement entropy and entanglement spectrum have been fundamental to the study of these systems and of gapless systems in general, but are difficult to measure experimentally. Bipartite charge fluctuations were proposed as a weak measurement of this entanglement, in particular for one-dimensional gapless phases. We extend previous results on standard Luttinger Liquids to generic families of one- and two-dimensional non-interacting topological systems. Through exact computations, we show that their critical points are characterized by universal coefficients that reveal the topological aspect of the transitions. In two dimensions, the Dirac cones give quantized contributions to the fluctuations and various correlation functions. These contributions depend on their winding numbers, allowing for a precise determination of the topological structure of the gapless points. A volume law is also present and linked to the Quantum Fisher information, with characteristic non-analyticities at the phase transitions.In a second time, we include interactions and show that some of these signatures are preserved in topological superconductors even in their presence. Through analytical (bosonization, renormalization group) and numerical (exact diagonalization and DMRG) methods, we study the phase diagram of two Coulomb-coupled topological superconducting wires. We are interested in their behavior when the interactions are strong enough to break the topological protection: the interplay between unconventional superconductivity and interactions leads to exotic phases. We show the appearance of phases spontaneously breaking the time-reversal symmetry, with non-trivial orbital currents, and of an unusual gapless phase that is the extension of two critical interacting Majorana modes.Finally, we are interested in electronic transport mediated by Majorana fermions. We study a floating superconducting island carrying several such impurities. This device is thought to be a potential building block for a quantum computer. The Majorana fermions affect the statistics of the charge carriers, which leads to very resilient fractionalized transport. We extend previous studies to the charge degenerate case, where the total number of fermions in the island is not fixed, and map it to the well-known Multi-Channel Kondo model at large interaction. We reinterpret this standard model in terms of a particle moving in a highly dimensional, dissipative lattice
Kayali, Mohammad Amin. "Spontaneous vortex phase and pinning in ferromagnetic-superconducting systems". Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/409.
Texto completo da fonteStefanini, Martino. "Anioni: particelle identiche e topologia in meccanica quantistica". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/12052/.
Texto completo da fonteBleu, Olivier. "Physics of quantum fluids in two-dimensional topological systems". Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC044/document.
Texto completo da fonteThis thesis is dedicated to the description of both single-particle and bosonic quantum fluid Physics in topological systems. After introductory chapters on these subjects, I first discuss single-particle topological phenomena in honeycomb lattices. This allows to compare two theoretical models leading to quantum anomalous Hall effect for electrons and photons and to discuss the photonic quantum valley Hall effect at the interface between opposite staggered cavity lattices.In a second part, I present some phenomena which emerge due to the interplay of the linear topological effects with the presence of interacting bosonic quantum fluid described by mean-field Gross-Pitaevskii equation. First, I show that the spin-anisotropic interactions lead to density-driven topological transitions for elementary excitations of a condensate loaded in the polariton quantum anomalous Hall model (thermal equilibrium and out-of-equilibrium quasi-resonant excitation configurations). Then, I show that the vortex excitations of a scalar condensate in a quantum valley Hall system, contrary to linear wavepackets, can exhibit a robust chiral propagation along the interface, with direction given by their winding in real space, leading to an analog of quantum spin Hall effect for these non-linear excitations. Finally, coming back to linear geometrical effects, I will focus on the anomalous Hall effect exhibited by an accelerated wavepacket in a two-band system. In this context, I present a non-adiabatic correction to the known semiclassical equations of motion which can be expressed in terms of the quantum geometric tensor elements. We also propose a protocol to directly measure the tensor components in radiative photonic systems
Chantler, Michael J. "The effect of variation in illuminant direction on texture classification". Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1264.
Texto completo da fonteSTERNATIVO, PIETRO. "Electronic Transport in Tunnel Junctions of Quantum Spin Hall Effect Topological Insulators". Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2591780.
Texto completo da fonteWang, Hangtian. "Interfacial Engineering of the Magnetism in 2D Magnets, Topological Insulators, and Their Heterostructures". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0206.
Texto completo da fonteWith the critical node of integrated circuits (IC) entering the 1 nm stage, traditional three-dimensional materials cannot maintain their original physical properties, and thus cannot meet the needs of IC manufacturing processes. Meanwhile, the shrinking line width also introduces an inevitable increase in static power consumption. Therefore, researching new materials and new technologies to break through the "Size Wall" and "Power Wall" has become a crucial direction in the IC industry. As a new member of the two-dimensional (2D) material family, the 2D magnets can maintain its long-range magnetic order at the atomic scale with its physical properties easily controlled by external stimuli, which provides an ideal platform for the high-density and low-power spintronic devices. However, due to the dimensional effect, 2D magnetism cannot exist at high temperatures. Although several methods can enhance the Curie temperature (Tc) of 2D magnets (such as doping, ion intercalation, or laser pumping), they are far from easy-controllability and high-efficiency. More importantly, the widely-used preparation method via mechanical exfoliation abandons the merit of 2D interfacial effect, which was proved to be an important approach to efficient 2D magnetic manipulation. Therefore, studying the interfacial effect in epitaxial 2D magnets is regarded as a key field to achieving large-scale, high-Tc, easy-controlling, and stable 2D ferromagnetic order. Topological insulator (TI) is another 2D material with strong spin-orbital coupling. The topology-protected surface states provided TI with numerous fascinates spin-related effects, such as spin-momentum locking, spin exchange effect, etc., which makes this material a potential candidate to fabricate effective spintronic devices. In addition, the TI can be integrated with 2D magnets to form a 2D heterostructure, in which not only the magnetism can be enhanced via the interfacial effect, but also the spin-related properties of the heterostructure can be manipulated due to the advantages of these two materials
Macaluso, Elia. "Probing Quasihole and Edge Excitations of Atomic and Photonic Fractional Quantum Hall Systems". Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/250215.
Texto completo da fonteMacaluso, Elia. "Probing Quasihole and Edge Excitations of Atomic and Photonic Fractional Quantum Hall Systems". Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/250215.
Texto completo da fonteLang, Kening. "Topological Effect on Self-assembly Behavior of Precisely Synthesized AmBn type Giant Molecules". University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1490651233006441.
Texto completo da fonteEriksson, Hjalmar. "From the quantum Hall effect to topological insulators : A theoretical overview of recent fundamental developments in condensed matter physics". Thesis, Uppsala University, Theoretical Physics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-126860.
Texto completo da fonteIn this overview I describe the simplest models for the quantum Hall and quantum spin Hall effects, and give some general indications as to the description of topological insulators. As a background to the theoretical models I will first trace the development leading up to the description of topological insulators . Then I will present Laughlin's original model for the quantum Hall effect and briefly discuss its limitations. After that I will describe the Kane and Mele model for the quantum spin Hall effect in graphene and discuss its relation to a general quantum spin Hall system. I will conclude by giving a conceptual description of topological insulators and mention some potential applications of such states.