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Showing 1 to 12 of 12 for “"wannier functions"”.
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On Exponentially Localized Wannier Functions in Non-Periodic Insulators
<p>Exponentially localized Wannier functions (ELWFs) are an orthogonal basis for the low energy states of a material consisting of functions which decay exponentially quickly in space. When a material is insulating and periodic, conditions which guarantee the existence of ELWFs in dimensions one, …
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Wannier Functions and Their Role in Improving Density Functional Approximations
… frontier energies. We show how these localized functions can be used in the localized orbital scaling correction to remedy many of the density functional approximation shortcomings related to delocalization error.</p>
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Modelling of Berry phase and Fermi-level topologies for emergent quantum phenomena prediction in selected solid state systems
… perturbations and offer routes to novel quantum functions. This thesis investigates three representative compounds - SrSi2, CoSi, and NbP - to reveal how external stimuli, namely tensile strain and electric fields, tune their electronic bands and topological traits. By combining first-principles …
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Electronic structure and quantum conductance of nanostructures
… calculations, in a basis of maximally-localized Wannier functions, that become explicit tight-binding orbitals. Once this optimal basis is determined, the Hamiltonian matrix becomes short-ranged, diagonally-dominant, and transferable - i.e. a large nanostructure can be constructed by assembling …
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Quantum simulation beyond periodicity: A theoretical study of the many-body and topological properties of quasiperiodic systems
… sites, corresponding to localised orbitals (Wannier functions), which are typically constructed using the periodicity of the system. These technique can therefore not apply to the context of non-periodic quantum systems in general, and optical quasicrystals in particular. First, we address …
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MULTI-BAND BOSE HUBBARD MODELS AND EFFECTIVE THREE-BODY INTERACTIONS
… repre- sentation for constructing real-valued Wannier functions localized in a unit cell for optical lattices. The developed numerical method is general and can be applied to a wide array of optical lattice geometries in one, two or three dimensions.
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Inelastic transport In molecular junctions from first principles
… calculations based on maximally localized Wannier functions and non-equilibrium Green's functions. Our approach is designed to determine inelastic transport properties such as differential conductances, inelastic tunneling spectroscopies and nonequilibrium vibrational populations. Our …
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Strongly Correlated 2D Electronic Systems: Interplay between Band Topology and Electron-electron Interaction
… obstruction to constructing symmetric, localized Wannier functions. We circumvented this lattice obstruction by either enlarging the low energy Hilbert space [6] or by constructing a momentum space model[7] for twisted bilayer graphene(TBLG) aligned with hexagonal boron nitride(hBN). We also …
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Electronic structure and quantum conductance of molecular and nano electronics
… function technique and maximally localized Wannier functions. The main focus of this thesis lies on clarifying the effect of chemical modifications on electron transport at the nanoscale, as well as on predicting and designing new type of molecular and nanoelectronic devices. In the first …
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THE THEORY OF COMBINATORY DIFFERENTIATION AND LOCALITY IN QUANTUM CHEMISTRY
… Chapter three is a reformulation of the Wannier localization problem with a more consistent Physical model and a more appropriate mathematical optimization framework. This reformulation has lead to a simpler theory that practically accelerates Wannier90 by about $100 \times$ on average …
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Examining Topological Insulators and Topological Semimetals Using First Principles Calculations
The importance and promise that topological materials hold has been recently underscored by the award of the Nobel Prize in Physics in 2016 ``for theoretical discoveries of topological phase transitions and topological phases of matter." This dissertation explores the novel qualities and useful …
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In Pursuit of Local Correlation for Reduced-Scaling Electronic Structure Methods in Molecules and Periodic Solids
… (BFGS) based Pipek-Mezey Wannier function (PMWF) solver [Clement, et al. 2021 }, Submitted to J. Chem. Theory Comput.]. Although orbital localization in the context of the linear combination of atomic orbitals (LCAO) representation of periodic crystalline solids is not new …