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 24 for “"exact diagonalization"”.
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Exact Diagonalization Studies of Strongly Correlated Systems
In this dissertation, we use exact diagonalization to study a few strongly correlated systems, ranging from the Fermi-Hubbard model to the fractional quantum Hall effect (FQHE). The discussion starts with an overview of strongly correlated systems and what is meant by strongly correlated. Then, we …
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Exact diagonalization study of strongly correlated topological quantum states
… from strong interaction. This thesis uses the exact diagonalization method to investigate quantum lattice models with strong interaction. Our research topics revolve around quantum phase transitions between novel phases. The goal is to find the best schemes for realizing these novel phases in …
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Hyperfine structure and hyperfine transitions of helium-3
… tests the theory of hyperfine structure. An exact diagonalization provides a comprehensive interpretation of the results across the complete range of hyperfine coupling strengths of 3He. The theoretical investigation shows that suppression of the hyperfine transitions is caused mainly by …
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Electric multipole moments and higher-order topological phases in crystalline insulators and superconductors
… and generalizations of it, as well as by exact diagonalization of tight-binding models, that crystalline insulators can generate charge and polarization patterns compatible with the notion of quadrupole and octupole electric moments. In the presence of certain symmetries, these moments are …
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Bogoliubov Excitations of Inhomogeneous Bose-Einstein Condensates
… of the Gross-Pitaevskii equation and by an exact diagonalization of the disordered Bogoliubov problem. In the second part, Bloch oscillations of Bose-Einstein condensates in presence of time-dependent interactions are considered. In general, the interaction leads to dephasing and destroys …
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Tunable Exchange Interaction in Coupled Quantum Dots
… for VMC with s-p orbital trial wavefunction and exact diagonalization (ED) method in the exchange energies. For N = 2 electrons in triple quantum dot (TQD), we observe a discontinuity in the J-derivative with detuning voltage ( dJdVT ) in triangular TQDs at B = 0 T as crossing of the eigenenergy …
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Electronic properties of doped Mott insulators and high temperature superconductors
… single hole in the tt't"J model in terms of the exact diagonalization and the self-consistent Born approximation methods. We show spins dress the doped hole in two distinct ways, namely with a staggered moment and a liquid spin configurations. The resulting two-band picture captures the momentum …
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Cluster Dynamical Mean-Field Theory: Applications to High-Tc Cuprates and to Quantum Chemistry
… and cluster versions, followed by the Exact Diagonalization impurity solver for the solution of the quantum impurity model. Maximum Entropy analytic continuation method is also discussed, which is useful to obtain the physically relevant response functions. Then we apply dynamical …
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Stability of Topological States and Crystalline Solids
… Chern insulators. We investigate, using exact diagonalization, fractional Chern insulators in higher Chern bands of the Harper-Hofstadter model, and examine the robustness of their many-body energy gap in the effective continuum limit. We report evidence of stable states in this regime; …
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On numerical methods in quantum spin systems
… present a numerical study on the embedding of an exactly solvable point in a phase diagram of an extended Heisenberg model on a kagome lattice. Chapter 6 studies a quantum Heisenberg model on the stuffed honeycomb lattice. Phase transitions in quantum many body systems manifest themselves as a …
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Aspects of critical spin 1 chains and 2 dimensional symmetry protected topological phases of matter
… can be verified in numerical calculations using exact diagonalization (ED) and the density matrix renormalization group (DMRG) algorithm. In particular, the bosonization method gives a formula for the evolution of four Tomonaga-Luttinger liquid (TLL) parameters as a function of the lattice …
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Accurate Treatments of Electronic Correlation: Phase Transitions in an Idealized 1D Ferroelectric and Modelling Experimental Quantum Dots
… for methods such as Conguration Interaction and “exact diagonalization"", and it’s perfect parallelism allows one to speed up computation with little effort on large parallel computers. Our work has focused on two systems. The first is a 1D ionic Hubbard model with a complex phase diagram that we …
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The Many Phases of the Surface Code: Coherent Errors and Many-Body Localisation
… and trivial MBL and how it can be combined with exact diagonalization to obtain an approximate phase diagram.
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Numerical methods for cold atom systems
… non-perturbative numerical methods ranging from exact diagonalization to quantum Monte Carlo techniques. Emphasis is given to the effect of interactions. A major goal of this work is to compare theoretical predictions with available experimental results. We begin by introducing the effective …
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Spectral properties of strongly correlated electron systems
… are accurately taken into account via the exact diagonalization of finite clusters. Long-range order is described by variational optimization of a ficticious symmetry-breaking field. In comparison with related cluster methods, our approach is more flexible and, for a given cluster size, …
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The Gutzwiller variational method for strongly correlated systems
… to be so in the present case. Compared with the exact diagonalization results, we show that the Gutzwiller method indeed offers a better solution than the slave-boson approach. As the second problem, we have studied the ground-state properties of paramagnetic LaMnO3 under hydrostatic pressure at …
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Many-body localization and tensor networks
… MBL systems. Chapter 4 studies an efficient full diagonalization method using Wegner unitary gates. Chapter 5 studies the distribution of the entanglement entropy in the MBL-ergodic transition region. Chapter 6 studies the the influence of pseudo-spin SU (2) symmetry on the MBL phase. Chapter 7 is …
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Studies of and methods for electronic properties of large chemical systems
… states of a Hamiltonian matrix ensemble without exact diagonalization. We develop an error analysis for this method, and show that it is accurate to the eighth moment of the density of states. Finally, we apply the method to various extensions of the Anderson model, to good result. Third, we …
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Electronic struture and quantum transport in systems of quantum dots exposed to magnetic fields
… via a configuration interaction approach, i.e., exact diagonalization of the two-body Hamiltonian matrix. Additionally, we introduce a stable numerical method for the evaluation of matrix elements containing integrals due to electron-electron (e-e) interactions. In this respect we have employed a …
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Chern-Simons theory of magnetization plateaus on the kagome lattice
… present some numerical results based on some exact diagonalization studies. Here, we specifically focus on the 2/3-magnetization plateau which we previously argued should be a chiral spin liquid with a spin hall conductance of 1/2 . Such a topological state has a non-trivial ground state …
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