Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Publication Type
Articles 1 - 15 of 15
Full-Text Articles in Physical Sciences and Mathematics
Spatial Interferences Of Photodetachment Near A Repulsive Center, B. C. Yang, John B. Delos, M. L. Du
Spatial Interferences Of Photodetachment Near A Repulsive Center, B. C. Yang, John B. Delos, M. L. Du
Arts & Sciences Articles
We study the detached-electron flux distributions from the photodetachment of electrons from a negative ion near a repulsive center. Using a semiclassical approach, we calculate the electron flux on spherical detectors with various radii. The classically allowed angular range of the interference patterns on the spherical screen increases as the detached-electron energy is increased. In the classically allowed range, we find that there are always two trajectories going from the negative ion to the observation point on the screen, inducing quantum interference patterns. We have also extended the formulas into the tunneling region. The interference patterns also reflect the quantum …
Anisotropic Infrared Response Of Vanadium Dioxide Microcrystals, T. J. Huffman, Peng Xu, M. M. Qazilbash, Et Al.
Anisotropic Infrared Response Of Vanadium Dioxide Microcrystals, T. J. Huffman, Peng Xu, M. M. Qazilbash, Et Al.
Arts & Sciences Articles
Vanadium dioxide (VO2) undergoes a phase transition at a temperature of 340 K between an insulating monoclinic M-1 phase and a conducting rutile phase. Accurate measurements of possible anisotropy of the electronic properties and phonon features of VO2 in the insulating monoclinic M-1 and metallic rutile phases are a prerequisite for understanding the phase transition in this correlated system. Recently, it has become possible to grow single domain untwinned VO2 microcrystals, which makes it possible to investigate the true anisotropy of VO2. We performed polarized transmission infrared micro-spectroscopy on these untwinned microcrystals in the spectral range between 200 cm(-1) and …
Optical Characterization Of Magnetism In Magnetic/Nonmagnetic Heterostructures, Yichun Fan
Optical Characterization Of Magnetism In Magnetic/Nonmagnetic Heterostructures, Yichun Fan
Dissertations, Theses, and Masters Projects
This thesis focuses on the study of the static and dynamic magnetic interactions in ferromagnetic/nonmagnetic heterostructures using interface-specific and time-resolved optical techniques. The goal of this thesis is to elucidate the interface exchange coupling, magnetic anisotropy, and coherent spin dynamics in these advanced material systems, crucial to the realization of high performance spintronic devices.;First, a pronounced exchange bias (EB) phenomenon is observed in Fe/MgO (001) by magnetic second harmonic generation. The bulk magnetization does not, in marked contrast to typical systems where EB is manifested only in the net magnetization. The magnitude of the exchange bias varies with interface oxygen …
Intelligent Feature Selection Techniques For Pattern Classification Of Time-Domain Signals, Corey Alexander Miller
Intelligent Feature Selection Techniques For Pattern Classification Of Time-Domain Signals, Corey Alexander Miller
Dissertations, Theses, and Masters Projects
Time-domain signals form the basis of analysis for a variety of applications, including those involving variable conditions or physical changes that result in degraded signal quality. Typical approaches to signal analysis fail under these conditions, as these types of changes often lie outside the scope of the domain's basic analytic theory and are too complex for modeling. Sophisticated signal processing techniques are required as a result. In this work, we develop a robust signal analysis technique that is suitable for a wide variety of time-domain signal analysis applications. Statistical pattern classification routines are applied to problems of interest involving a …
Applications Of Holographic Dualities, Dylan Judd Albrecht
Applications Of Holographic Dualities, Dylan Judd Albrecht
Dissertations, Theses, and Masters Projects
We introduce and review some of the building blocks to what is known as the AdS/CFT correspondence. We then present, using the framework of the correspondence, two applications: one to QCD (Chapters 2 and 3) and one to superconductivity (Chapter 4). The work presented in these chapters was carried out by the author and collaborators during the author's graduate studies.
Low Energy Tests Of The Standard Model, Benjamin Carl Rislow
Low Energy Tests Of The Standard Model, Benjamin Carl Rislow
Dissertations, Theses, and Masters Projects
The Standard Model describes a wide range of fundamental interactions. Searches are ongoing for experimental results that differ from the Standard Model predictions. Such disagreements would both indicate that the Standard Model is incomplete and constrain the properties of New Physics scenarios. to probe the Standard Model over a wide kinematic range, low energy tests are necessary to complement experiments in the high energy regime. We perform calculations for experiments that are representative of two general types of low energy tests. The Qweak experiment at Jefferson Lab is a low energy measurement of the weak charge of the proton. Since …
A Search For A New Gauge Boson, Eric Lyle Jensen
A Search For A New Gauge Boson, Eric Lyle Jensen
Dissertations, Theses, and Masters Projects
In the Standard Model, gauge bosons mediate the strong, weak, and electromagnetic forces. New forces could have escaped detection only if their mediators are either heavier than O (TeV) or weakly coupled to charged matter. New vector bosons with small coupling a' arise naturally from a small kinetic mixing with the photon and have received considerable attention as an explanation of various dark matter related anomalies. Such particles could be produced in electron-nucleus fixed-target scattering and then decay to e+ e -- pairs. New light vector bosons and their associated forces are a common feature of Standard Model extensions, but …
Thermal Tuning Of Mid-Infrared Plasmonic Antenna Arrays Using A Phase Change Material, Mikhail A. Kats, Romain Blanchard, (...), M. M. Qazilbash, Et Al.
Thermal Tuning Of Mid-Infrared Plasmonic Antenna Arrays Using A Phase Change Material, Mikhail A. Kats, Romain Blanchard, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
We demonstrate that the resonances of infrared plasmonic antennas can be tuned or switched on/off by taking advantage of the thermally driven insulator-to-metal phase transition in vanadium dioxide (VO2). Y-shaped antennas were fabricated on a 180 nm film of VO2 deposited on a sapphire substrate, and their resonances were shown to depend on the temperature of the VO2 film in proximity of its phase transition, in good agreement with full-wave simulations. We achieved tunability of the resonance wavelength of approximately 10% (>1 μm at λ ∼ 10 μm).
Experimental Generation And Manipulation Of Quantum Squeezed Vacuum Via Polarization Self-Rotation In Rb Vapor, Travis Scott Horrom
Experimental Generation And Manipulation Of Quantum Squeezed Vacuum Via Polarization Self-Rotation In Rb Vapor, Travis Scott Horrom
Dissertations, Theses, and Masters Projects
Nonclassical states of light are of increasing interest due to their applications in the emerging field of quantum information processing and communication. Squeezed light is such a state of the electromagnetic field in which the quantum noise properties are altered compared with those of coherent light. Squeezed light and squeezed vacuum states are potentially useful for quantum information protocols as well as optical measurements, where sensitivities can be limited by quantum noise. We experimentally study a source of squeezed vacuum resulting from the interaction of near-resonant light with both cold and hot Rb atoms via the nonlinear polarization self-rotation effect …
Magnetic Order And Dimensional Crossover In Optical Lattices With Repulsive Interaction, Jie Xu
Magnetic Order And Dimensional Crossover In Optical Lattices With Repulsive Interaction, Jie Xu
Dissertations, Theses, and Masters Projects
One of the most interesting and challenging problems in physics is understanding strongly correlated many-body systems, where strong interactions can yield many remarkable phenomena such as superfluidity in 4He, high-temperature superconductivity, etc. In order to attack these problems, we often need to reduce the complexity of the systems to simple models in hopes of getting better insights into the properties of the systems. The Hubbard model, the focus of this dissertation, is one of the most famous examples of such model, which describes a tunneling of electrons between nearest neighbor sites of a lattice with on-site interactions. This simple model …
Multi-Meson Systems From Lattice Quantum Chromodynamics, Zhifeng Shi
Multi-Meson Systems From Lattice Quantum Chromodynamics, Zhifeng Shi
Dissertations, Theses, and Masters Projects
Systems of non-zero isospin chemical potential ( muI), where the chemical potential for up and down quarks is equal in magnitude but of opposite sign, do not suffer from the sign problem, and normal LQCD techniques can be successfully adapted to study such systems. From chiral perturbation theory (chiPT), in addition to the deconfined phase transition at high temperature at zero chemical potential, another phase transition from ordinary hadronic states to a Bose Einstein Condensate (BEC) state has been conjectured [1] at non-zero isospin chemical potential. Such a BEC phase is of phenomenological relevance in the interior of neutron stars.;In …
Advanced Topographic Characterization Of Variously Prepared Niobium Surfaces And Linkage To Rf Losses, Chen Xu
Dissertations, Theses, and Masters Projects
Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. The shallow penetration (∼ 40 nm) of the RF into superconducting niobium lends great importance to SRF cavity interior surface chemistry and topography. These in turn are strongly influenced by the chemical etching "surface clean-up" that follows fabrication.;The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD functions …
Model Sensitivity In Holographic Superconductors And Their Deconstructed Cousins, Joshua X. Erlich, Zhen Wang
Model Sensitivity In Holographic Superconductors And Their Deconstructed Cousins, Joshua X. Erlich, Zhen Wang
Arts & Sciences Articles
Holographic models of superconductors successfully reproduce certain experimental features of high-temperature superconductors, such as a large gap-to-Tc ratio compared to that of conventional superconductors. By deconstructing the extra dimension of these holographic models, similar phenomenology is described by a class of models defined in the natural dimension of the superconducting system. We analyze the sensitivity of certain observables in holographic and deconstructed holographic superconductors to details of the extra-dimensional spacetime. Our results support the notion that certain quantitative successes of simple models of this type are accidental. However, we also find a certain universal relationship between superconducting observables.
Excited State Calculations In Solids By Auxiliary-Field Quantum Monte Carlo, Fengjie Ma, Shiwei Zhang, Henry Krakauer
Excited State Calculations In Solids By Auxiliary-Field Quantum Monte Carlo, Fengjie Ma, Shiwei Zhang, Henry Krakauer
Arts & Sciences Articles
We present an approach for ab initio many-body calculations of excited states in solids. Using auxiliary-field quantum Monte Carlo, we introduce an orthogonalization constraint with virtual orbitals to prevent collapse of the stochastic Slater determinants in the imaginary-time propagation. Trial wave functions from density-functional calculations are used for the constraints. Detailed band structures can be calculated. Results for standard semiconductors are in good agreement with experiments; comparisons are also made with GW calculations and the connections and differences are discussed. For the challenging ZnO wurtzite structure, we obtain a fundamental band gap of 3.26(16) eV, consistent with experiments.
Studies Of Molecular Dynamics Of Fmoc-Alanine-D3 Through Solid State Deuteron Nuclear Magnetic Resonance, Jianhua Sun
Studies Of Molecular Dynamics Of Fmoc-Alanine-D3 Through Solid State Deuteron Nuclear Magnetic Resonance, Jianhua Sun
Dissertations, Theses, and Masters Projects
No abstract provided.