Physics Commons^™

Physical Properties Of Unconventional Superconductors, Valentina Anatolyevna Kuznetsova

Doctoral Dissertations

In the following development, we attempt to obtain basic physical properties of majority of unconventional superconductors through a Bardeen-Cooper-Schrieffer-type weak-coupling approach. The method we adopted in our study is model-independent. The weak-coupling approach depends only on the symmetry of the coupling, not on its origin. It is known that a general analysis of physical properties of unconventional superconductors is possible, but has not been done yet. The goal of our work is to develop and test such analysis, using available experimental data.

Since paramagnetic limiting for spin-singlet superconductors can be suppressed in superconductors with broken inversion symmetry of crystal lattice, …

Characterization Of The Temperature Dependence Of Optical Components In A Cryo-Vacuum Chamber Used For Space Sensor Testing, Jesse M. Labello

Masters Theses

The space sensor cryo-vacuum chambers at Arnold Air Force Base are world class sensor characterization and calibration facilities. The chambers provide a simulated deep space background and accurate infrared projections. Several large optical systems are used within the chambers to accomplish this. Calibration of the chambers requires the use of a database of the measured optical properties of these components to simulate the output. However, as the information in the database is room temperature information and the chambers run near 20K, some discrepancies exist between the actual output and the model output. The purpose of this work is to translate …

Impact Of The Equation Of State In Core-Collapse Supernovae, Mark Lewis Baird

Masters Theses

One of the key ingredients to the core collapse supernova mechanism is the physics of matter at or near nuclear density. Included in simulations as part of the Equation of State (EoS), nuclear repulsion experienced at high densities is responsible for the bounce shock, which initially causes the outer envelope of the supernova to expand, as well as determining the structure of the newly formed proto-neutron star. Recent years have seen renewed interest in this fundamental piece of supernova physics, resulting in several promising candidate EoS parameterizations. We will present the impact of several of their variations in the nuclear …

Design Construction And Use Of A Thermomechanical Detwinning Apparatus: Detwinning Of Orthorhombic Nb2bacu2o3, Chad J. Bircher

Masters Theses

In this thesis I will describe a device designed and built for thermo- mechanically detwinning crystals. Twinning is a process in which a crys- talline structrure with two different axes of nearly equal length alternate directions throughout the material, effectively generating a single bulk material with two or more distinct internal crystals. This structure defect can lead to many other effects in the crystal, and it is useful to elimi- nate twinning in many materials in order to determine which properties are fundamental properties of the crystal, and which properties are ar- tifacts of the structural imperfections. The apparatus described …

Transport Critical Currents In Ybacuo-Based Coated Conductors: Angular, Magnetic Field, And Temperature Dependencies, Samuel M. Travaglini

Masters Theses

High-temperature superconductivity has been a focus of much study over the past 20 years, particularly within the cuprate class of superconductors. The effectiveness of these cuprate superconductors is limited by factors including the formation of vortices within the superconductor, orientation within external magnetic fields, the strength of these magnetic fields, temperature, and whether any doping agents have been used. Any of these factors individually can affect the transport critical current levels. In this research, YBaCuO and NdBaCuO-based coated conductors were studied in a liquid-nitrogen-cooled environment at either 77 K or 65 K. Field levels were varied between 0 T and …

Static And Dynamic Magnetism In The Electron-Doped High-Temperature Superconductor Pr0.88Lace0.12Cuo4-Δ And In The F-Electron, Non-Fermi Liquid Alloy Sc1-XUXPd3, Stephen Dennis Wilson

Doctoral Dissertations

Here we present detailed studies of the spin dynamics within the electron-doped high temperature superconductor Pr_.88LaCe_.12CuO_4-δ (PLCCO) and within the non-Fermi liquid metal Sc_1-xU_xPd₃ (ScUPd). Comprehensive neutron scattering experiments were carried out mapping the evolution of magnetism within these systems as they are tuned across their respective phase diagrams. The novel features of the magnetic spectra within these systems are correlated with known anomalies in their quasiparticle behaviors driven through either the appearance of a superconducting phase in PLCCO or the emergence of a non-Fermi liquid phase in ScUPd.

For …

Structure And Transport Properties Of Epitaxial Oxide Thin Films: From Synthesis To Characterization, Junsoo Shin

Doctoral Dissertations

Epitaxial thin films and heterostructures based on perovskite oxides have attracted significant attention in physics since perovskites exhibit an enormous range of electrical, magnetic, and optical properties, making them exciting systems for studies of the fundamental physical mechanisms of interactions between electron, lattice, and spin degrees of freedom. This dissertation has been focused on ferroelectricity in lowdimensional ferroelectric materials using ultra-thin ferroelectric epitaxial films (BaTiO₃) with a metallic electrode (SrRuO₃) by studying polarized ordering of the crystal structure and electronic transport through the films. High quality and highly oxidized epitaxial films are a prerequisite for the …

Analysis Of A Gluonic Penguin Decay With The Babar Detector, Gerald Conrad Ragghianti Jr.

Masters Theses

This thesis presents a branching fraction analysis of the neutral B meson decay channel B → ϕK⁰_s where the K⁰_s decays to π⁰π⁰. The decay is dominated by gluonic penguin transitions, which have been very important for the main program of BABAR: the search for physics beyond the Standard Model. The decay channel has been established and is included in the CP analysis, which is sensitive to new physics. The data set consists of 227 million BB̅ pairs recorded by the BABAR detector at the Stanford Linear Accelerator Center. Sophisticated analysis techniques …

Surface Plasmon Enhanced Heating Of Gold Nanoparticles: A Plasmonic Optical Switch, Philip Gareth Evans

Doctoral Dissertations

Recent work by Lereu et al. (Appl. Phys. Lett. Vol. 86, 154101, 2005) demonstrates a method of all-optical transfer of modulation signals using surface plasmon excitation on thin gold films. Localized heating of the film, resulting from surface plasmon decay, alter the optical properties of the device. A similar optical modulation method is now presented using gold nanoparticles. Computational models are used to generate realistic values of the thermo-optical response of gold and the thermal dynamics of a hot nanoparticle-substrate device. Differential pump-probe reflectivity measurements were perferomed and demonstrate modulation frequencies of upto 10kHz, an improvement of two orders of …

Density Functional Theory And Phase Shifts, Anthony G. Wald

Masters Theses

This thesis describes how phase shifts of the nucleon-nucleon system may be utilized to determine the nuclear Density Functional (DF). The nucleonnucleon interaction, hereafter denoted by N-N interaction, is input to quantum many-body calculations. However, this approach complicates the determination of physical quantities such as the calculation of spectroscopic information and of energy levels. A major advantage in employing the approach via Density Functional Theory (DFT) to this system is that the N-N problem can be considered to be a non-interacting, single-particle system.

In order to use DFT one must know the density functional, and this is typically the most …