Physics Commons^™

A Study Of The Lithium Ionic Conductor Li5La3Ta2O12: From Synthesis Through Materials And Transport Characterization, Brian M. Ray

Theses and Dissertations--Physics and Astronomy

The ionic conductivity of the lithium ionic conductor, Li5La3Ta2O12, is studied in an attempt to better understand the intrinsic bulk ionic conductivity and extrinsic sample dependent contributions to the ionic conductivity, such as grain boundary effects and the electrode-electrolyte interface. To characterize the material, traditional AC impedance spectroscopy studies were performed as well novel in-situ nanoscale transport measurements. To perform the nanoscale measurements, higher quality samples were required and new synthesis techniques developed. The results of these new synthesis techniques was samples with higher densities, up to 96% of theoretical, and slightly higher room temperature ionic conductivity, 2x10^−5 S/cm. By …

The Dijet Cross Section Measurement In Proton-Proton Collisions At A Center Of Mass Energy Of 500 Gev At Star, Grant D. Webb

Theses and Dissertations--Physics and Astronomy

Polarized deep inelastic scattering experiments play a vital role in the exploration of the spin structure of the proton. The polarized proton-proton collider at RHIC provides direct access to the gluon spin distribution through longitudinal double spin asymmetry measurements of inclusive jets, pions, and dijets. This thesis presents the measurement of the dijet double differential cross-section in proton-proton collisions at center of mass energies of √s = 500 GeV. The data represent an integrated luminosity of 8.7 pb^-1 recorded by the STAR detector during the 2009 RHIC run. A comprehensive jet analysis was performed to determine the ideal …

Time Dependent Holography, Diptarka Das

Theses and Dissertations--Physics and Astronomy

One of the most important results emerging from string theory is the gauge gravity duality (AdS/CFT correspondence) which tells us that certain problems in particular gravitational backgrounds can be exactly mapped to a particular dual gauge theory a quantum theory very similar to the one explaining the interactions between fundamental subatomic particles. The chief merit of the duality is that a difficult problem in one theory can be mapped to a simpler and solvable problem in the other theory. The duality can be used both ways.

Most of the current theoretical framework is suited to study equilibrium systems, or …

A Systematic Transport And Thermodynamic Study Of Heavy Transition Metal Oxides With Hexagonal Structure, Kamal H. Butrouna

Theses and Dissertations--Physics and Astronomy

There is no apparent, dominant interaction in heavy transition metal oxides (TMO), especially in 5d-TMO, where all relevant interactions are of comparable energy scales, and therefore strongly compete. In particular, the spin-orbit interaction (SOI) strongly competes with the electron-lattice and on-site Coulomb interaction (U). Therefore, any tool that allows one to tune the relative strengths of SOI and U is expected to offer an opportunity for the discovery and study of novel materials. BaIrO₃ is a magnetic insulator driven by SOI whereas the isostructural BaRuO₃ is a paramagnetic metal. The contrasting ground states have been shown to result …

A Study Of Periodic And Aperiodic Ferromagnetic Antidot Lattices, Vinayak S. Bhat

Theses and Dissertations--Physics and Astronomy

This thesis reports our study of the effect of domain wall pinning by ferromagnetic (FM) metamaterials [1] in the form of periodic antidot lattices (ADL) on spin wave spectra in the reversible regime. This study was then extended to artificial quasicrystals in the form of Penrose P2 tilings (P2T). Our DC magnetization study of these metamaterials showed reproducible and temperature dependent knee anomalies in the hysteretic regime that are due to the isolated switching of the FM segments. Our dumbbell model analysis [2] of simulated magnetization maps indicates that FM switching in P2T is nonstochastic. We have also acquired …

Reference Compensation For Localized Surface-Plasmon Resonance Sensors, Neha Nehru

Theses and Dissertations--Electrical and Computer Engineering

Noble metal nanoparticles supporting localized surface plasmon resonances (LSPR) have been extensively investigated for label free detection of various biological and chemical interactions. When compared to other optical sensing techniques, LSPR sensors offer label-free detection of biomolecular interactions in localized sensing volume solutions. However, these sensors also suffer from a major disadvantage – LSPR sensors remain highly susceptible to interference because they respond to both solution refractive index change and non-specific binding as well as specific binding of the target analyte. These interactions can severely compromise the measurement of the target analyte in a complex unknown media and hence limit …

Modification Of Plasmonic Nano Structures' Absorption And Scattering Under Evanescent Wave Illumination Above Optical Waveguides Or With The Presence Of Different Material Nano Scale Atomic Force Microscope Tips, Gazi Mostafa Huda

Theses and Dissertations--Electrical and Computer Engineering

The interaction of an evanescent wave and plasmonic nanostructures are simulated in Finite Element Method. Specifically, the optical absorption cross section (C_abs) of a silver nanoparticle (AgNP) and a gold nanoparticle (AuNP) in the presence of metallic (gold) and dielectric (silicon) atomic force microscope (AFM) probes are numerically calculated in COMSOL. The system was illuminated by a transverse magnetic polarized, total internally reflected (TIR) waves or propagating surface plasmon (SP) wave. Both material nanoscale probes localize and enhance the field between the apex of the tip and the particle. Based on the absorption cross section equation the author …

Voltage Modulated Infrared Reflectance Study Of Soluble Organic Semiconductors In Thin Film Transistors, Emily Geraldine Bittle

Theses and Dissertations--Physics and Astronomy

Soluble organic semiconductors have attracted interest due to their potential in making flexible and cheap electronics. Though their use is being implemented in electronics today, the conduction mechanism is still under investigation. In order to study the charge transport, this study examines the position, voltage, and frequency dependence of charge induced changes in far infrared absorption in soluble organic semiconductors in thin-film transistor structures. Measurements are compared to a simple model of a one-dimensional conductor which gives insight into the charge distribution and timing in devices. Main results of the study are dynamic measurements of charge taken by varying the …

Investigation Of Spin-Independent Cp Violation In Neutron And Nuclear Radiative Β Decays, Daheng He

Theses and Dissertations--Physics and Astronomy

CP violation is an important condition to explain the preponderance of baryons in our universe, yet the available CP violation in the Standard Model (SM) via the so-called Cabibbo-Kobayashi-Maskawa mechanism seems to not provide enough CP violation. Thus searching for new sources of CP violation is one of the central tasks of modern physics. In this thesis, we focus on a new possible source of CP violation which generates triple-product correlations in momenta which can appear in neutron and nuclear radiative β decay. We show that at low energies such a CP violating correlation may arise from the exotic coupling …

Active Optimal Control Strategies For Increasing The Efficiency Of Photovoltaic Cells, Sharif Aljoaba

Theses and Dissertations--Electrical and Computer Engineering

Energy consumption has increased drastically during the last century. Currently, the worldwide energy consumption is about 17.4 TW and is predicted to reach 25 TW by 2035. Solar energy has emerged as one of the potential renewable energy sources. Since its first physical recognition in 1887 by Adams and Day till nowadays, research in solar energy is continuously developing. This has lead to many achievements and milestones that introduced it as one of the most reliable and sustainable energy sources. Recently, the International Energy Agency declared that solar energy is predicted to be one of the major electricity production energy …

A Systematic Study Of Transport, Magnetic And Thermal Properties Of Layered Iridates, Oleksandr B. Korneta

Theses and Dissertations--Physics and Astronomy

A unique feature of the 5d-iridates is that the spin-orbit interaction (SOI) and Coulomb interactions U are of comparable strength and therefore compete vigorously. The relative strength of these interactions stabilizes new exotic ground states that provide a fertile ground for studying new physics. SOI is proportional to Z^4 (Z is the atomic number), and it is now recognized that strong SOI can drive novel narrow-gap insulating states in heavy transition metal oxides such as iridates. Indeed, strong SOI necessarily introduces strong lattice degrees of freedom that become critical to new physics in the iridates. This dissertation thoroughly examines a …

The Development And Implementation Of Electromechanical Devices To Study The Physical Properties Of Sr2iro4 And Tas3, John A. Nichols

Theses and Dissertations--Physics and Astronomy

Transition metal oxides (TMO) have proven to exhibit novel properties such as high temperature superconductivity, magnetic ordering, charge and spin density waves, metal to insulator transitions and colossal magnetoresistance. Among these are a spin-orbit coupling (SOC) induced Mott insulator Sr₂IrO₄. The electric transport properties of this material remain finite even at cryogenic temperatures enabling its complex electronic structure to be investigated by a scanning tunneling microscope. At T = 77 K, we observed two features which represent the Mott gap with a value of 2D ~ 615 meV. Additionally an inelastic loss feature was observed inside …

Magnetic And Orbital Orders Coupled To Negative Thermal Expansion In Mott Insulators, Ca2ru1-Xmxo4 (M = 3d Transition Metal Ion), Tongfei Qi

Theses and Dissertations--Physics and Astronomy

Ca₂RuO₄ is a structurally-driven Mott insulator with a metal-insulator (MI) transition at T_MI = 357K, followed by a well-separated antiferromagnetic order at T_N = 110 K. Slightly substituting Ru with a 3d transition metal ion M effectively shifts T_MI and induces exotic magnetic behavior below T_N. Moreover, M doping for Ru produces negative thermal expansion in Ca₂Ru_1-xM_xO₄ (M = Cr, Mn, Fe or Cu); the lattice volume expands on cooling with a total volume expansion ratio reaching as high as 1%. The onset of the …

Magnetic Properties Of Nb/Ni Superconducting / Ferromagnetic Multilayers, Sergiy A. Kryukov

Theses and Dissertations--Physics and Astronomy

Magnetic properties of Nb/Ni superconducting (SC) / ferromagnetic (FM) multilayers exhibit interesting properties near and below SC transition. A complex Field (H) – Temperature (T) phase boundary is observed in perpendicular and parallel orientation of ML with respect to DC field. We address the critical need to develop methods to make reliable magnetic measurements on SC thin films and ML, in spite of their extreme shape anisotropy and the strong diamagnetic response of the SC state.

Abrupt, highly reproducible “switching” of the SC state magnetization near the normal-state FM coercive fields has been observed in Nb/Ni ML. The SC penetration …

Gauge-Gravity Duality And Its Applications To Cosmology And Fluid Dynamics, Jae-Hyuk Oh

University of Kentucky Doctoral Dissertations

This thesis is devoted to the study of two important applications of gauge-gravity duality: the cosmological singularity problem and conformal fluid dynamics. Gauge-gravity duality is a concrete dual relationship between a gauge theory (such as electromagnetism, the theories of weak and strong interactions), and a theory of strings which contains gravity. The most concrete application of this duality is the AdS/CFT correspondence, where the theory containing gravity lives in the bulk of an asymptotically anti-de-Sitter space-time, while the dual gauge theory is a deformation of a conformal field theory which lives on the boundary of anti-de-Sitter space-time(AdS).

Our first application …

Determining Interstellar Reddening: A New Approach Using Spectroscopy And Photometry, Syed A. Uddin

University of Kentucky Master's Theses

The mystery of Canis Major overdensity is addressed. We discuss concurrent methods and their limitations on the determination of interstellar reddening. We establish a new way to determine line of sight interstellear reddening by observing stellar spectral lines and UBV colors. We observe and analyze spectra of 22 stars in different open clusters. We find that Hydrogen Balmer line at 4861 angstrom can predict the stellar atmospheric parameters and intrinsic colors with reasonable accuracy. Comparing with observed colors we derive the reddening of the stars. We compare our results with standard database WEBDA and find that within 90% probability limit …

A Systematic Study Of Thermodynamic And Transport Properties Of Layered 4d And 5d Correlated Electron Systems, Shalinee Chikara

University of Kentucky Doctoral Dissertations

Correlated electron materials have been at the forefront of condensed matter research in the past couple of decades. Correlation in materials, especially, with open d and f electronic shells often lead to very exciting and intriguing phenomenon like high temperature superconductivity, Mott metal-insulator transition, colossal magnetoresistance (CMR). This thesis focuses on triple-layered Sr₄Ru₃O₁₀, Sr substituted double layered (Ca1-- xA_x)₃Ru₂O₇ (A = Ba, Sr) and 5d system Sr₂IrO₄ and Sr₃Ir₂O₇. Triple-layered Sr₄Ru₃O_{10 …}

Universal Binding And Recoil Corrections To Bound State G-Factors, Timothy James Semple Martin

University of Kentucky Doctoral Dissertations

The gyromagnetic ratio of bound particles is an active field of experimental and theoretical research. Early measurements of corrections to the bound g-factor came from experiments involving hydrogen-like ions. As the sensitivity of such experiments has increased, it has become possible to instead use them to measure the electron-ion mass ratio -- but only if the theoretical bound g-factor is known with sufficient precision for these systems. By constructing an effective nonrelativistic Lagrangian, we derive leading order binding and recoil corrections for systems comprised of particles with arbitrary spin.

Lagrangians for spin one-half and spin one-theories are developed, …

Physical Conditions In A Galactic Star Forming Region W22, Akshaya Rane

University of Kentucky Master's Theses

This document describes study of an active star forming region in our galaxy (the Milky Way) known as W22. Physical conditions in these regions can help us in understanding star formation processes in the universe and hence the structure and evolution of the universe. Zeeman effect measurements in 18 cm OH absorption line were carried out in order to estimate the line of sight magnetic field strength in the molecular cloud associated with this star forming region. Other physical parameters such as hydrogen column density, optical depth, critical magnetic field were also determined from these measurements. The region was mapped …

Magnetic Shielding Studies For The Neutron Electric Dipole Moment Experiment At The Spallation Neutron Source, Susan Kate Malkowski

Theses and Dissertations--Physics and Astronomy

The neutron Electric Dipole Moment Experiment at the Spallation Neutron Source requires an overall magnetic shielding factor of order 10⁵ to attenuate external background magnetic fields. At present, the shielding design includes an external (room-temperature) multi-layer μ-metal magnetic shield, a cryogenic (4 Kelvin) Pb superconducting shield, and a cryogenic (4 Kelvin) ferromagnetic shield composed of Metglas ribbon. This research determined how to construct a Metglas shield using minimal material that produced axial and transverse shielding factors of ~267 and ~1500. In addition, the μ-metal and Metglas shields were modeled using finite element analysis. The FEA model includes external coils …

Measurement Of Single-Target Spin Asymmetries In The Electroproduction Of Negative Pions In The Semi-Inclusive Deep Inelastic Reaction N↑(E,Éπ¯)X On A Transversely Polarized 3he Target, Chiranjib Dutta

University of Kentucky Doctoral Dissertations

The experiment E06010 measured the target single spin asymmetry (SSA) in the semiinclusive deep inelastic (SIDIS) n↑(e,éπ¯)X reaction with a transversely polarized ³He target as an effective neutron target. This is the very first independent measurement of the neutron SSA, following the measurements at HERMES and COMPASS on the proton and the deuteron. The experiment acquired data in Hall A at Jefferson Laboratory with a continuous electron beam of energy 5.9 GeV, probing the valence quark region, with x = 0.13→0.41, at Q² = 1.31→3.1 GeV². The two contributing mechanisms to the measured asymmetry, viz, the …

Inelastic Collisions In Cold Dipolar Gases, Catherine A. Newell

University of Kentucky Doctoral Dissertations

Inelastic collisions between dipolar molecules, assumed to be trapped in a static electric field at cold (> 10⁻³K) temperatures, are investigated and compared with elastic collisions. For molecules with a Λ-doublet energy-level structure, a dipole moment arises because of the existence of two nearly degenerate states of opposite parity, and the collision of two such dipoles can be solved entirely analytically in the energy range of interest. Cross sections and rate constants are found to satisfy simple, universal formulas. In contrast, for molecules in a Σ electronic ground state, the static electric field induces a dipole moment in …

Tunneling Spectroscopy Study Of Calcium Ruthenate, Anthony Bautista

University of Kentucky Doctoral Dissertations

The ruthenates are perhaps one of the most diverse group of materials known up to date. These compounds exhibit a wide array of behaviors ranging from the exotic pwave superconductivity in Sr₂RuO₄, to the itinerant ferromagnetism in SrRuO₃, and the Mott-insulating behavior in Ca₂RuO₄. One of the most intriguing compounds belonging to this group is Ca₃Ru₂O₇ which is known to undergo an antiferromagnetic ordering at 56K and an insulating transition at 48K. Most intriguing, however, is the behavior displayed by this compound in the presence …

Near-Field Radiative Transfer: Thermal Radiation, Thermophotovoltaic Power Generation And Optical Characterization, Mathieu Francoeur

University of Kentucky Doctoral Dissertations

This dissertation focuses on near-field radiative transfer, which can be defined as the discipline concerned with energy transfer via electromagnetic waves at sub-wavelength distances. Three specific subjects related to this discipline are investigated, namely nearfield thermal radiation, nanoscale-gap thermophotovoltaic (nano-TPV) power generation and optical characterization. An algorithm for the solution of near-field thermal radiation problems in one-dimensional layered media is developed, and several tests are performed showing the accuracy, consistency and versatility of the procedure. The possibility of tuning near-field radiative heat transfer via thin films supporting surface phononpolaritons (SPhPs) in the infrared is afterwards investigated via the computation of …

Persistent Currents And Quantum Critical Phenomena In Mesoscopic Physics, Oleksandr Zelyak

University of Kentucky Doctoral Dissertations

In this thesis, we study persistent currents and quantum critical phenomena in the systems of mesoscopic physics. As an introduction in Chapter 1 we familiarize the reader with the area of mesoscopic physics. We explain how mesoscopic systems are different from quantum systems of single atoms and molecules and bulk systems with an Avogadro number of elements. We also describe some important mesoscopic phenomena.

One of the mathematical tools that we extensively use in our studies is Random Matrix Theorty. This theory is not a part of standard physics courses and for educational purposes we provide the basics of Random …

Specific Heat Measurements On Strongly Correlated Electron Systems, Vijayalakshmi Varadarajan

University of Kentucky Doctoral Dissertations

Studies on strongly correlated electron systems over decades have allowed physicists to discover unusual properties such as spin density waves, ferromagnetic and antiferromagnetic states with unusual ordering of spins and orbitals, and Mott insulating states, to name a few.

In this thesis, the focus will be on the specific heat property of these materials exhibiting novel electronic ground states in the presence and absence of a field. The purpose of these measurements is to characterize the phase transitions into these states and the low energy excitations in these states. From measurements at the phase transitions, one can learn about the …

Study Of Qcd Critical Point Using Canonical Ensemble Method, Anyi Li

University of Kentucky Doctoral Dissertations

QCD at non-zero baryon density is expected to have a critical point where the finite temperature crossover at zero density turns into a first order phase transition. To identify this point, we use the canonical ensemble approach to scan the temperaturedensity plane through lattice QCD simulations with Wilson-type fermions. In order to scan a wide range of the phase diagram, we develop an algorithm, the ”winding number expansion method” (WNEM) to fix the numerical instability problem due to the discrete Fourier transform for calculating the projected determinant. For a given temperature, we measure the chemical potential as a function of …

Studies Of Low-Lying States In 94zr Excited With The Inelastic Neutron Scattering Reaction, Esmat Elhami

University of Kentucky Doctoral Dissertations

The aim of nuclear structure studies is to observe and describe the structures and associated symmetries in nuclei, which in turn help us in understanding the nature of nucleon-nucleon interactions in a nucleus as a many-body quantum system. The protons and neutrons as constituents of a nucleus and their interactions are responsible for nuclear properties. The evolution of nuclear structure as a function of valence nucleon number, i.e., the number of nucleons beyond a magic number, can be inferred from the experimental level scheme and transition rates. In particular, the studies of low-lying, low-spin excited states in stable nuclei provide …

A Systematic Study Of Thermodynamic And Transport Properties Of Layered CaN+1(Ru1-XCrX)NO3n+1, Vinobalan Durairaj

University of Kentucky Doctoral Dissertations

Orbital degrees of freedom play vital role in prompting novel phenomena in ruthenium based Ruddlesden-Popper compounds through coupling of orbits to spin and lattice. Physical properties are then particularly susceptible to small perturbations by external magnetic fields and/or slight structural changes. Current study pertains to the impact when a more-extended 4d Ruthenium ion is replaced by a less-extended 3d Chromium ion.

Perovskite CaRuO₃ (n=∞) is characterized by borderline magnetism and non- Fermi liquid behavior – common occurrences in quantum critical compounds. Remarkably, Cr substitution as low as x=0.05 abruptly drives CaRu_1−xCr_xO₃ from a paramagnetic …