Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 22 for “"Berry phase"”.
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Stoner magnetism and Berry phase in quantum materials
… solids often exhibit carrier bands with Berry phase in 𝑘 space, resulting in carriers behaving like spinning objects and generating orbital magnetization in position space. This thesis explores the impact of orbital magnetization arising in this way on the correlated electron phases. The …
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Modelling of Berry phase and Fermi-level topologies for emergent quantum phenomena prediction in selected solid state systems
… we aim to uncover mechanisms behind quantum phase transitions (QPTs) and to establish design principles for materials with tailored quantum states. We perform density functional theory (DFT) calculations within the plane-wave pseudopotential framework using the Quantum ESPRESSO (QE) suite. …
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Non-Abelian Anyons in the Kitaev Honeycomb Model
The non-Abelian Berry phase is an essential feature of non-Abelian anyons for the realization of topological quantum computation. This thesis is primarily a study about the numerical calculation of the Berry phase of non-Abelian anyons in the Kitaev honeycomb lattice model. It is also a guide for …
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Black holes and Berry's phase : some aspects of geometry in physics
… first focus attention on the occurrence of the Berry phase in certain situations. This gives some insight into the geometry of quantum mechanics. Then we turn our attention to the analysis of quantum fields in black hole spacetimes. This brings us to the renormalisation of the stress- tensor via …
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Geometry and topological phase of matter
… field theories of isotropic-nematic quantum phase transitions of Quantum states. The low-energy theory of the nematic field has z=2 dynamics due to a Berry phase of the order parameter, which is related to the Hall viscosity in parity and time-reversal-symmetry (TRS) broken states. The vortex …
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Novel electronic behaviors in graphene nanostructures
… of graphene, such as high mobility, Berry phase, photoresponse mediated by hot carriers, and at the same time acquire new features due to nanoscale heterogenities. In this thesis, I explore the novel electronic behaviors which emerge in this fashion. I focus on two types of systems: …
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Two applications of Berry's phase in fermionic field theory
… configurations. In this thesis, two examples of Berry's geometrical phase in a fermionic sea are studied: the anomalous commutator in gauge field theory and the intrinsic orbital angular momentum in superftuid 3He-A. Chapter 1 is a brief introduction. Chapter 2 reviews Berry's Phase and several …
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Interacting non-Abelian anyons in an exactly solvable lattice model
… the degenerate ground state space is given by a Berry phase, which under suitable conditions coincides with the statistics. By considering a range of finite size systems, we find a physical regime where the Berry phase gives the predicted statistics of the anoyonic vortices with high fidelity. …
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Exceptional surfaces as topological obstructions in dynamical systems
… In particular, we develop a formulation of the Berry phase for classical dynamical systems and demonstrate its usage on a toy-model. Thereafter we discuss classical eigensystem degeneracy and analyse its topological properties as an exceptional surface (ES). Upon identifying the limitations of …
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Phase coherent transport phenomena in HgTe quantum well structures
… over the electronic spin. Therefore, spin and phase coherent transport are very important phenomena. This thesis describes experiments with mercury based quantum well structures. This narrow gap material provides a very good template to study spin related effects. It exhibits large Zeeman spin …
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Examining mean-field approximations and Bogoliubov-de Gennes (BdG) equations for topological quantum computing - some considerations on the conceptual basis of Majorana zero modes in p+ip superconductors
… role of particle number conservation in Berry phase of transporting a bound quasiparticle around a vortex in a s-wave superconductor. We then study the effect of particle number conservation and superconducting condensate on braiding MZM in vortices in chiral p-wave superconductors and …
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Electric multipole moments and higher-order topological phases in crystalline insulators and superconductors
… of energy bands in crystalline insulators have Berry phases associated with the positions of electronic charge is at the basis of our understanding of topological band theory. We show, by using the Berry phase formulation and generalizations of it, as well as by exact diagonalization of …
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A tight-binding analysis of the electronic properties of III-nitride semiconductors
… the tight-binding model in conjunction with the Berry phase theory of electronic polarisation to probe the atomistic origins of spontaneous polarisation and piezoelectricity as well as attempting to accurately calculate the values and coefficients associated with these phenomena. We first develop …
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Quantum oscillation studies in the unconventional superconductor YFe₂Ge₂ and in the Dirac semimetal candidates NbXSb (X = Ge/Si)
… have been compared to DFT calculations. The Berry phase has been estimated for the observed Fermi surface sheets in both materials, suggesting a topological nature in these materials.
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Soft Hair and Subregions in Quantum Gravity
… ambiguities in the traditional construction of phase spaces in field theory, and resolving these ambiguities is a step that must be taken before one can fully understand edge modes and soft hair. We provide two possible approaches to such a resolution. The first approach applies to theories …
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High Pressure Quantum Oscillation Study of BiTeI and Bi2Te3
… agreement with Hall effect measurements. The phase of the oscillations showed that both Fermi surfaces have a Berry phase of $\pi$ associated with them, consistent with theoretical predictions for a Rashba system. As pressure is applied, it was observed that the inner Fermi surface expands …
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Quantum oscillations in Dirac semimetals
… as they provide a tool to directly measure the Berry phase under certain conditions. The (double) Dirac semimetal NbTe₄ has shown the occurrence of multiple charge-density-wave (CDW) phases, and as a result a complex band structure at low temperatures. Density functional theory (DFT) …
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Quantum Algorithms and Complexity for Numerical Problems
… an adiabatic quantum algorithm based on the Berry phases for the counting problem. For the running time, it is not as good as the optimal algorithm in the quantum circuit model, but better than the classical random algorithm. Moreover, since the Berry phase is a purely geometric feature, the …
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Advanced light manipulation and waveguiding in plasmonic nanostructured optical fibers.
… the optical properties of the fibers, such as phase, polarization state, amplitude, mode profile are fixed and cannot be altered once after the fiber drawing fabrication. The advent of new fabrication technologies for optical nanostructures such as plasmonic and metasurfaces allows us to …
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