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 40 for “"quantum critical point"”.
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Superconductivity in the proximity of a quantum critical point
… to absolute zero can result in a low temperature quantum fluid which deviates strongly from typical metallic behaviour; unconventional superconductivity can be induced by the strange metal region surrounding the zero-temperature phase transition. In this thesis we focus on three systems which …
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Competition and unification of Kondo coherence and magnetic ordering
The heavy fermion quantum critical point is one of the most puzzling problems in the field of highly correlated electrons. This is a quantum critical point separating a non-magnetic heavy fermi liquid metal from an antiferromagnetically ordered metal. The major problem facing us is the fact that, …
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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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Quantum critical matter: Casimir pairing, emergent orders and topological defects
In this thesis we address a few problems on critical phenomena in two- and three dimensional quantum materials. Specifically we consider high temperature superconductors, dimerized quantum magnets and frustrated magnets. First, motivated by the recent discovery of a magnetic quantum critical point …
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Quantum Tuning and Emergent Phases in Charge and Spin Ordered Materials
… any tuning in the proximity of a ferroelectric quantum critical point. This work presents the first high-precision dielectric measurements under hydrostatic pressure carried out on a quantum critical ferroelectric, leading to a full pressure-temperature phase diagram for SrTiO$_3$. The influence …
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Magnetic Penetration Depth Analysis of Unconventional Superconductors
… of antiferromagnetism and the presence of a quantum critical point on superconductivity. We also seek to characterize the superconductivity and compare to similar materials. Additionally we seek to study how superconductivity arises from novel methods such as charge density waves.
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Magnetic and Structural Instabilities in Cerium Diantimonides under Pressure
… 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 pressure. However, above 17 kbar CeSb₂ enters a strongly correlated high-pressure structure, in …
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Aspects of quantum criticality in itinerant electron ferromagnetic systems
… This thesis is mainly concerned with such quantum critical points and is an investigation into the various phenomena seen in the phase diagram of itinerant ferromagnetic systems. We apply a standard theory of itinerant quantum criticality to a quantum-critical end-point in a …
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Explorations in two dimensional strongly correlated quantum matter: from exactly solvable models to conformal bootstrap
… two projects that touch upon the role of quantum mechanics in classifying phases of matter and their transitions. In the first project, we set out to answer: is it possible to find a lattice model in the Ising universality class that realizes the Kramers Wannier symmetry in such a way that …
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Emergence of charge density wave domain walls above the superconducting dome in TiSe2
… pressure and established the existence of a quantum critical point (QCP) at $P_c = 5.1 +- 0.2 GPa, which is more than 1 GPa beyond the end of the SC region. Unexpectedly, at P = 3 GPa we observed a weakly first order, incommensurate CDW phase, suggesting the presence of a Lifshitz tricritical …
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Non-perturbative approaches to strongly correlated electron systems
… field theory is dual to a d+1 dimensional quantum gravitational theory. Problems in strongly coupled field theory then have an equivalent description using weakly interacting gravitational theory, allowing a non-perturbative analysis. Chapter 1 will serve as an introduction. We will review …
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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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High pressure studies of superconductivity and anomalous normal states in novel quantum materials
… parameters for accessing or tuning away from the quantum critical point but also to enter novel phases that cannot usually be found in any materials at ambient conditions. Sb (Chapter 4): High-pressure phase Sb-II exhibits a novel incommensurate host-guest structure, giving rise to exotic sliding …
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A study of holographic superconductors
The proposal that the physics of quantum critical phase transition in strongly coupled condensed matter systems can be described by a gravitational theory within the frame work of gauge/gravity correspondence is investigated more extensively for s-wave superconductors. We consider a gravitational …
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Superconductor-insulator transition induced by electrostatic charging in high temperature superconductors.
… function, which suggests the presence of a quantum critical point. However the scaling failed at the lowest temperatures indicating the possible presence of an additional phase between the superconducting and insulating regimes. In the presence of magnetic field, a cleaner …
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Pairing symmetry, competing orders, and quantum criticality in iron based superconductors via London penetration depth measurements
… reaches a maximum. This may arise from quantum fluctuations associated with a quantum critical point buried beneath the superconducting dome.
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The Death of Quasiparticles: Strongly Interacting Gapless Phases with Fermi Surfaces and Fractional Statistics
… a powerful organizing principle for many quantum phases of matter, ranging from conventional magnets and superconductors to exotic insulators with topological order. In this thesis, I describe my research in gapless quantum phases in which the framework of quasiparticles breaks down. The …
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Search, Discovery, Synthesis and Characterization of Itinerant Magnets Composed of Non-magnetic Constituents
… magnetism, non-Fermi liquid behavior, and quantum criticality. Surprisingly, while many systems exhibit both local and itinerant magnetism, only two are known to contain no local moment ions: Sc3In and ZrZn2. Doping experiments on Sc3In were used to investigate the effects of both magnetic …
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Frustrated Magnetism in Strongly Correlated Electron Systems
… induced as a result of magnetic frustration and quantum fluctuations. We show that emergent spin textures can arise close to a magnetic field-induced quantum critical point, when the single magnon excitations have several degenerate non-coplanar minima. In this case, quantum fluctuations can lift …
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Development of High-Pressure Calorimetry Techniques and Calorimetry Study of the Heavy-Fermion Superconductor CeSb2
… pressure pushes this magnetic transition to a quantum critical point (QCP) and the material becomes an unconventional superconductor. Applying the new calorimetry technique, we discover two magnetic transitions in this phase. We track these transitions as further pressure pushes them together …
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