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 43 for “"Quantum Phase Transition"”.
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MATRIX FIELD THEORY: APPLICATIONS TO SUPERCONDUCTIVITY
… s-wave and d-wave superconductors and the quantum phase transitions associated with them. The thesis can be divided into three parts. The first part includes chapters 1 to 3. In chapter one a general physical introduction is given. In chapters two and three the theory is developed and used …
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An Exploration of Quantum Critical Phenomena in One-Dimensional Lattice Systems: Geometric Frustration & Quantum Fluctuations
… of critical phenomena within one-dimensional quantum lattice spin systems. People are exposed to classical critical phenomena everyday in the form of phase transitions, such as from water to ice. Surrounding quantum phase transitions, there is a number of exciting phenomena still to be …
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Disorder at first-order classical and quantum phase transitions
… the effects of quenched disorder on classical, quantum and nonequilibrium phase transitions. After a short introduction which covers the basic concepts of phase transitions, finite-size scaling and random disorder, the dissertation focuses on four separate but related projects. First, we …
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Studies on the effect of noise in boundary quantum phase transitions
<p>Boundary quantum phase transitions are abrupt ground state transitions triggered by the change of the boundary conditions at single or multiple (but finite) points.</p><p>When boundary effects dominate, understanding boundary quantum phase transitions requires a deeper knowledge of strongly …
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Quantum Critical Ferroelectricity and Emergent Phenomena in KTaO3 and SrTiO3
This thesis explores the quantum phase diagrams of KTaO3 and SrTiO3, both quantum paraelectrics near to a ferroelectric quantum critical point, including study of material properties which may be influenced by proximity to a ferroelectric quantum phase transition. A quantum critical phase …
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Quantum phase transitions in disordered magnets
… study the effects of quenched weak disorder on quantum phase transitions in disordered magnets. The presence of disorder in the system can lead to a variety of exotic phenomena, e.g., the smearing of transitions or quantum Griffiths singularities. Phase transitions are smeared if individual …
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Phase transitions in quasiperiodic and driven optical lattices
… are a versatile tool for precisely-controlled quantum simulation of a range of condensed matter phenomena. This thesis describes work to apply this tool in two areas: the simulation of quasicrystalline materials with a novel lattice geometry, and the use of Floquet driving to engineer …
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Electrical transport and superconductivity in doped quantum critical ferroelectrics
… transport and superconductivity in doped quantum critical ferroelectrics) presents the results of research into the electrical transport and superconductivity found in the neighbourhood of quantum phase transitions in carrier-doped ferroelectrics and paraelectrics. The materials of …
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Magnetic and Structural Instabilities in Cerium Diantimonides under Pressure
… pressure is commonly employed to discover new phases, by continuously tuning a magnetic state, in the limit of low-temperatures, through a quantum phase transition. CeSb₂ hosts a number of distinct magnetic phases below 16 K, which initially remain relatively static under the application of …
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Field theoretical methods for strongly correlated electron systems
… as a powerful computational tool to study quantum many-body systems. They have been applied successfully to the study of various systems of strongly correlated electrons in condensed matter physics, particularly to problems where a non-perturbative treatment is required. In the first part …
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Ultracold quantum gases in three-dimensional optical lattice potentials
… a standing wave laser light field. In this novel quantum system we have been able to both realize a quantum phase transition from a superfluid to a Mott insulator, and to observe the collapse and revival of a macroscopic matter wave field. Quantum phase transitions are driven by quantum …
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Electron Transport through Carbon Nanotube Quantum Dots in A Dissipative Environment
… is essential in understanding funda- mental quantum-mechanical concepts, such as quantum measurement and quantum entanglement. It is thought that a dissipative environment may be responsible for certain types of quantum (i.e. zero-temperature) phase transitions. We observe such a quantum …
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Zigzag Phase Transition in Quantum Wires and Localization in the Inhomogeneous One-Dimensional Electron Gas
… one-dimensional (1D) electron gas: the transition from one-dimensional to higher dimensional behavior, and the role of inhomogeneity. The interplay between interactions, reduced dimensionality, and inhomogeneity drives a rich variety of phenomena in mesoscopic physics. In 1D, …
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Physics of ultracold spin mixtures in low and stable magnetic field environment
… level, enabling the observation of the quantum phase transition in a ferromagetic atomic mixture, the investigation of its static properties and the study of dynamical properties such as the local decay of the metastable state into the true ground state, resulting in the probabilistic …
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Coherent micromanipulation of 1-D BEC in designed potentials
The manipulation of quantum degenerate gases has seen a flourishing of results in the last years. One of the most used tools to create and address a Bose-Einstein condensate (BEC) is the atomchip: A lithographycally patterned surface on which gold conductors are used to generate magnetic fields. To …
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Strongly Correlated Electronic Matter: Phases and their Transport
… It can broadly be divided into two categories: phases of matter and their transport. My research into phases of matter has been concerned with the low energy properties of interacting electrons at fractional filling of an underlying lattice. I, along with collaborators, have shown that it is …
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Effective action approach to quantum phase transitions in bosonic lattices
… a new, field-theoretic method for describing the quantum phase transition between Mott insulating and superfluid states observed in bosonic optical lattices. I begin by adding to the Hamiltonian of interest a symmetry breaking source term. Using time-dependent perturbation theory, I then expand …
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Non-perturbative approaches to strongly correlated electron systems
… superconductivity and the metal-insulator transitions. Having a proper understanding of strongly correlated electron systems requires a non-perturbative analysis because Fermi liquid theory inevitably breaks down due to the strong correlation. In this thesis, we will study two …
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Two-dimensional superconducting states near zero temperature quantum phase transitions
… decades. In two dimensions, only two electronic phases are predicted to exist at zero temperature – superconducting and insulating. Contrary to this theoretical expectation, previous transport measurements on 2-dimensional (2D) thin films have found evidence for metallic resistivity down to …
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Quantum phase transitions in the presence of disorder and dissipation
<p>"A quantum phase transition is a phase transition at absolute zero occurring under variations in an external non-thermal parameter such as magnetic field or pressure. Quantum phase transitions are one among the important topics currently investigated in condensed matter physics. They are …
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