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Ferroelectric-Driven Tunable Magnetism In Ultrathin Platinum Films, Qilong Sun, Farzad Mahfouzi, Julian P. Velev, Evgeny Y. Tsymbal, Nicholas Kioussis

Department of Physics and Astronomy: Faculty Publications

Electric control of magnetism in magnetoelectric (ME) multiferroics is expected to have a significant impact on a wide range of technological applications. Here, we predict the modulation of magnetism in ultrathin platinum films due to the ferroelectric polarization of the BaTiO₃ substrate, which along with biaxial strain changes the density of states at the Fermi energy. We demonstrate that both the magnitude and direction of the magnetization depend strongly on the polarization direction and/or strain. This leads to an unprecedented ME effect involving a giant change of magnetocrystalline anisotropy under polarization switching due to the large spin-orbit coupling of …

Herschel Gould Belt Survey Observations Of Dense Cores In The Cepheus Flare Clouds, James Di Francesco, Jared Keown, Cassandra Fallscheer, Philippe André, Bilal Ladjelate, Vera Könyves, Alexander Men'shchikov, Shaun Stephens-Whale, Quang Nguyen-Luong, Peter Martin, Sarah Sadavoy, Stefano Pezzuto, Eleonora Fiorellino, Milena Benedettini, Nicola Schneider, Sylvain Bontemps, Doris Arzoumanian, Pedro Palmeirim, Jason M. Kirk, Derek Ward-Thompson

All Faculty Scholarship for the College of the Sciences

We present Herschel SPIRE and PACS maps of the Cepheus Flare clouds L1157, L1172, L1228, L1241, and L1251, observed by the Herschel Gould Belt Survey of nearby star-forming molecular clouds. Through modified blackbody fits to the SPIRE and PACS data, we determine typical cloud column densities of (0.5–1.0) × 10²¹ cm⁻² and typical cloud temperatures of 14–15 K. Using the getsources identification algorithm, we extract 832 dense cores from the SPIRE and PACS data at 160–500 μm. From placement in a mass versus size diagram, we consider 303 to be candidate prestellar cores, and 178 of these …

Development And Applications Of Condensed Phase Cavity Ring-Down Spectroscopy For Studies Of Electrochemical And Interfacial., Shadi Ahmad Alnaanah

Electronic Theses and Dissertations

This dissertation reports the development of ultra-sensitive platforms based on the laser cavity ring-down spectroscopic (CRDS) technique to enable optical and spectroelectrochemical investigations in the condensed phase of matter at challenging scenarios. Firstly, an electrically-active solid/liquid interface for the evanescent-wave cavity ring-down spectroscopy (EW-CRDS) was developed to specroelectrochemically investigate redox events. By coating the interface of total internal reflection of the EW-CRDS platform with a high quality optically transparent and electrically conductive indium tin oxide thin film (ITO), we demonstrated that sufficiently long ring-down times can be achieved to allow for spectroelectrochemical investigations of redox species at solid/liquid interfaces at …

Investigation Of Clinoptilolite Zeolite As A Candidate System For Study By Positron Annihilation, Edward Perez

Physics Theses - Archive

This thesis reports on the characterization of a clinoptilolite zeolite (〖Na〗_3 [〖Al〗_3 〖Si〗_15 O_36 ]12H_2 O) using Energy-dispersive X-ray spectroscopy (EDX/EDS) for chemical analysis, low energy Secondary Electron (SE) analysis for three-dimensional imaging and topography, and Transmission Electron Microscopy (TEM) for two-dimensional imaging at the nanometer level. The goal of this work was to provide additional information that can aid in the interpretation of the data obtained using positron beam based spectroscopies. The measurements were performed using the Hitachi S-3000N Variable Pressure Scanning Electron Microscope (SEM) integrated with a NORAN 7 EDS/EBSD system, the Hitachi S-4800 II Field Emission Scanning …

Polarization-Selective Modulation Of Supercavity Resonances Originating From Bound States In The Continuum, Chan Kyaw, Riad Yahiaoui, Joshua A. Burrow, Viet Tran, Kyron Keelen, Wesley Sims, Eddie C. Red, Willie S. Rockward, Mikkel A. Thomas, Andrew M. Sarangan, Imad Agha, Thomas A. Searles

Electro-Optics and Photonics Faculty Publications

Bound states in the continuum (BICs) are widely studied for their ability to confine light, produce sharp resonances for sensing applications and serve as avenues for lasing action with topological characteristics. Primarily, the formation of BICs in periodic photonic band gap structures are driven by symmetry incompatibility; structural manipulation or variation of incidence angle from incoming light. In this work, we report two modalities for driving the formation of BICs in terahertz metasurfaces. At normal incidence, we experimentally confirm polarization driven symmetry-protected BICs by the variation of the linear polarization state of light. In addition, we demonstrate through strong coupling …

Spectroscopic Diagnostics For Supersonic Air Microwave Discharges, James E. Caplinger

Theses and Dissertations

Optical Emission Spectroscopy (OES) is an increasingly relevant technique in plasma diagnostics due to its inherent non-invasive nature and simple application relative to other popular techniques. In this work, common OES techniques are combined with novel methods, developed here, in an effort to provide comprehensive OES techniques for stationary and supersonic air microwave discharges. To this end, a detailed collisional-radiative model for strong atomic oxygen lines has been developed and used to identify the importance of often overlooked mechanisms including cascade emission and metastable excitation. Using these results, a combined argon actinometry technique was developed which makes use of the …

Spatial And Temporal Variability Of Carbonaceous Aerosol Absorption In The Po Valley, Stefania Gilardoni, Paola Massoli, Angela Marinoni, Claudio Mazzoleni, Andrew Freedman, Giovanni Lonati, Silvana De Iuliis, Vorne Gianelle

Michigan Tech Publications, Part 1

Knowledge gaps in the optical properties of carbonaceous aerosols account for a significant fraction of the uncertainty of aerosol-light interactions in climate models. Both black carbon (BC) and brown carbon (BrC) can display a range of optical properties in ambient aerosol due to different sources and chemical transformation pathways. This study investigates the optical absorption properties of BC and BrC at an urban and a rural site in the Po Valley (Italy), a known European pollution hot spot. We observed spatial and seasonal variability of aerosol absorption coefficients, with the highest values measured in winter at the urban site of …

Useable Coarse-Grained Models For Semiconducting Polymers And Thermosets, Michael Montgomery Henry

Boise State University Theses and Dissertations

This work aims to inform the formulation and processing of polymer mixtures through the use of models that have minimally sufficient complexity. Models with minimal complexity are easier to develop, understand, explain, and extend, all of which underpin model validation, verification, and reproducibility.

We develop simplified models for two different material systems, semiconducting polymers and thermosets. With the relatively low cost of predicting morphologies enabled by these models, we investigate structure-property-processing relationships in record system sizes and combinatorial parameter spaces. The insight from these models lays the foundation for improving the efficiency of organic solar cells and air travel.

The …

Vibration Overtone Hyperpolarizability Measured For H2 Using Electric Field Induced Second Harmonic Generation, Rachel Ellis

UNLV Theses, Dissertations, Professional Papers, and Capstones

The vibrational contribution to the second hyperpolarizability (γ) of gas phase H2 was measured using electric field induced second harmonic generation. Measurements were made for the pure vibrational 3-0 Q(J) overtone transitions (v=0,J → v’=3,J for J = 0,1,2,3). Measured intensities were found to be 4-14% larger than ab initio calculations. The first chapter of this thesis provides an introduction to nonlinear optics, second harmonic generation, and the tensor nature of hyperpolarizabilities. The second chapter provides theoretical expressions for γ and relevant static and Raman polarizabilities. The third chapter covers the experimental design and electric field induced second harmonic generation. …

Measurement Of Pion-Pion Final State Interactions In Η → Π +Π −Γ With Clas At Jefferson Lab, Torri C. Jeske

Physics Theses & Dissertations

Decays of pseudoscalar mesons proceed from the chiral anomaly, which arises from spontaneous chiral symmetry breaking. In the limit of massless quarks (chiral limit), the η → π +π −γ the decay width is determined solely by the box anomaly term in the Wess Zumino Witten Lagrangian. Since the physical quarks are not massless, the decay region of the η meson is far from the chiral limit and thus proper inclusion of the momentum dependence is essential to reproduce the measured decay width. Several theoretical frameworks have been proposed to describe these interactions. We report a new measurement of the …

Ultrafast Spin-Currents And Charge Conversion At 3d-5d Interfaces Probed By Time-Domain Terahertz Spectroscopy, T. H. Dang, J. Hawecker, E. Rongione, G. Baez Flores, D. Q. To, J. C. Rojas-Sanchez, H. Nong, J. Mangeney, J. Tignon, F. Godel, S. Collin, P. Seneor, M. Bibes, A. Fert, M. Anane, J. M. George, L. Vila, M. Cosset-Cheneau, D. Dolfi, R. Lebrun, P. Bortolotti, Kirill Belashchenko, S. Dhillon, H. Jaffrès

Kirill Belashchenko Publications

Spintronic structures are extensively investigated for their spin-orbit torque properties, required for magnetic commutation functionalities. Current progress in these materials is dependent on the interface engineering for the optimization of spin transmission. Here, we advance the analysis of ultrafast spin-charge conversion phenomena at ferromagnetic-Transition metal interfaces due to their inverse spin-Hall effect properties. In particular, the intrinsic inverse spin-Hall effect of Pt-based systems and extrinsic inverse spin-Hall effect of Au:W and Au:Ta in NiFe/Au:(W,Ta) bilayers are investigated. The spin-charge conversion is probed by complementary techniques-ultrafast THz time-domain spectroscopy in the dynamic regime for THz pulse emission and ferromagnetic resonance spin-pumping …

Hyperpolarized Carbon-13 Magnetic Resonance Measurements Of Tissue Perfusion And Metabolism, Keith Michel

Dissertations and Theses (Open Access)

Hyperpolarized Magnetic Resonance Imaging (HP MRI) is an emerging modality that enables non-invasive interrogation of cells and tissues with unprecedented biochemical detail. This technology provides rapid imaging measurements of the activity of a small quantity of molecules with a strongly polarized nuclear magnetic moment. This polarization is created in a polarizer separate from the imaging magnet, and decays continuously towards a non-detectable thermal equilibrium once the imaging agent is removed from the polarizer and administered by intravenous injection. Specialized imaging strategies are therefore needed to extract as much information as possible from the HP signal during its limited lifetime.

In …

Machine Learning Based Predictions Of Dissolved Oxygen In A Small Coastal Embayment, Manuel Valera, Ryan K. Walter, Barbara A. Bailey, Jose E. Castillo

Physics

Coastal dissolved oxygen (DO) concentrations have a profound impact on nearshore ecosystems and, in recent years, there has been an increased prevalance of low DO hypoxic events that negatively impact nearshore organisms. Even with advanced numerical models, accurate prediction of coastal DO variability is challenging and computationally expensive. Here, we apply machine learning techniques in order to reconstruct and predict nearshore DO concentrations in a small coastal embayment while using a comprehensive set of nearshore and offshore measurements and easily measured input (training) parameters. We show that both random forest regression (RFR) and support vector regression (SVR) models accurately reproduce …

Data Processing & Analysis For Atomic Force Microscopy (Afm), Molly Mcdonough, Polievkt Perov, Walter Johnson, Stevan Radojev

Undergraduate Theses and Capstone Projects

Scanning Probe Microscopy (SPM) has become a critical tool for characterization of materials in fields such as physics, material science, chemistry, and biology. Atomic Force Microscopy (AFM) is an increasingly useful technique because of its high resolution in three dimensions, the sample does not need to be conductive, and the technique does not need to take place in vacuum. AFM can image a wide variety of topographies and many different types of materials. AFM can deliver 3D topography information from the angstrom level to the micron scale with high resolution. One of the most important aspects of Atomic Force Microscopy …

Deeply Virtual Compton Scattering At Hall A, Jefferson Lab, Mohamed Nuhman Hashir Rashad

Physics Theses & Dissertations

The Standard Model of particle physics defines quarks and leptons as the basic building blocks of all matter. The interaction between them are mediated by force carrying gauge bosons. Quantum ChromoDynamics (QCD), the theory that explains the strong interaction is still not complete enough to derive the physical observables of a Quark-Gluon system from the fundamental degrees of freedom of it’s constituents. Experimentally observable single particle densities provide important insights into our understanding of the quark-gluon system and hence help fill in the gaps of QCD. Generalized Parton Distributions (GPDs) provide simultaneous information of both spacial and longitudinal momentum distributions …

Synthesis, X-Ray Absorption, And X-Ray Diffraction Spectroscopy Studies Of Uranium Based Heavy Fermion Systems, Vahe Mkrtchyan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Heavy fermion systems have attracted a great deal of interest since the discovery of the phenomenon in the 1970s. Over the past 35 years, the research in this field revealed a variety of unprecedented properties that the conventional theoretical framework considered conflicting or impossible. The subset of intermetallic compounds containing rare earth and actinide elements is of special interest, as these materials exhibit a range of exotic properties associated with 4f or 5f electrons. A thorough examination of the reports in the literature indicates a delicate interplay between the competing ground states, giving rise to anomalous properties including non-Fermi liquid …

The Importance Of Frontier Orbital Symmetry In The Adsorption Of Diiodobenzene On Mos2(0001), Prescott E. Evans, Zahra Hooshmand, Talat S. Rahman, Peter Dowben

Peter Dowben Publications

Evidence of a role of frontier orbital symmetry, in the adsorption process of diiodobenzene on MoS₂(0001), appears in the huge differences in the rate of adsorption between 1,3-diiodobenzene, 1,2-diiodobenzene and 1,4-diiodobenzene isomers on MoS₂. Experiments indicate that the rate of adsorption of 1,3-diiodobenzene on MoS2(0001) is much greater than that of the 1,2-diodobenzene and 1,4-diiodbenzene isomers. As the differences in calculated diiodobenzene isomer-MoS₂ system adsorption energies and electron affinities are negligible, frontier orbital symmetry appears to play a significant role in diiodobenzene adsorption on MoS₂(0001). The experimental and theory results, in combination, suggest …

Exploring Information For Quantum Machine Learning Models, Michael Telahun

Electronic Theses and Dissertations

Quantum computing performs calculations by using physical phenomena and quantum mechanics principles to solve problems. This form of computation theoretically has been shown to provide speed ups to some problems of modern-day processing. With much anticipation the utilization of quantum phenomena in the field of Machine Learning has become apparent. The work here develops models from two software frameworks: TensorFlow Quantum (TFQ) and PennyLane for machine learning purposes. Both developed models utilize an information encoding technique amplitude encoding for preparation of states in a quantum learning model. This thesis explores both the capacity for amplitude encoding to provide enriched state …

Predicting The Hydration Free Energy Of Small Alkanes And Alcohols From Custom, Electronic Structure-Based Force Fields, T. Ryan Rogers

Graduate Theses and Dissertations

Mathematical theories reveal the fundamental physics involved in experimentalphenomena. Computer models of such theories are routinely used to corroborate or explain experiments and predict properties of chemical systems. Therefore, an important effort in computational chemistry is the development of more accurate and efficient chemical models. Current-generation models are only beginning to approach experimental-quality predictions of hydration free energies (HFEs).Using computations of quantum mechanical (QM) forces and classical simulations based on these forces, I investigate models to predict several properties of solutes and solutions. This dissertation is a collection of projects exemplifying methods used to gain insight into chemical systems.

Simulations …

Optical Properties Of Ultrathin In(Ga)As/Gaas And In(Ga)N/Gan Quantum Wells, Yurii Maidaniuk

Graduate Theses and Dissertations

Recently, structures based on ultrathin quantum wells (QWs) began to play a critical role in modern devices, such as lasers, solar cells, infrared photodetectors, and light-emitting diodes. However, due to the lack of understanding of the formation mechanism of ultrathin QWs during the capping process, scientists and engineers cannot fully explore the potential of such structures. This study aims to investigate how structural parameters of ultrathin QWs affect their emission properties by conducting a systematic analysis of the optical properties of In(Ga)As/GaAs and In(Ga)N/GaN ultrathin QWs. Specifically, the analysis involved photoluminescence measurements combined with effective bandgap simulation, x-ray diffraction, and …

Monte Carlo Simulations Of Awkward Actions, David John Amdahl

Physics & Astronomy ETDs

Time derivatives of scalar fields occur quadratically in textbook actions. A simple Legendre transformation turns the Lagrangian into a Hamiltonian that is quadratic in the momentum. The partition function over the momentum is Gaussian. Mean values of operators are basically euclidian path integrals of their classical counterparts with positive weight functions. Monte Carlo simulations can estimate such mean values. This familiar framework falls apart when the time derivatives do not occur quadratically. The Legendre transformation becomes difficult or so intractable that the Hamiltonian can’t be determined. Even if the Hamiltonian is found, it usually is so complicated that the partition …

A Climatological Analysis Of The Monsoon Break Following The Summer Monsoon Onset Over Luzon Island, Philippines, Lyndon Mark P. Olaguera, Jun Matsumoto, Hisayuki Kubota, Esperanza O. Cayanan, Flaviana D. Hilario

Physics Faculty Publications

This study investigates the climatology of the monsoon break following the onset of the summer rainy season over Luzon Island (120–122.5°E, 13–22°N) in the Philippines from 1979–2017. The first post-onset monsoon break is remarkable in stations located over the north and central Luzon Island and occurs climatologically in early June. Composite analysis of the large-scale circulation features during the monsoon break period shows that this break is associated with the westward extension of the western North Pacific Subtropical High (WNPSH), which weakened the monsoon southwesterlies and induced enhanced low-level divergence over Luzon Island. The westward extension of the WNPSH may …

A Model For Massless Gravitons In Radiation And Matter Dominated Universes, Ioannis Haranas, Eli Cavan, Ioannis Gkigkitzis

Physics and Computer Science Faculty Publications

A massless model of the graviton is explored by considering the minimum amount of information they can carry. The total entropy of the universe is calculated and compared to estimates from Super Massive Black holes and massive models of the graviton. The running cosmological constant is calculated using the entropy relation previously computed and compared to its experimentally accepted value. Both results are quantified considering radiation and matter dominated universes.

The Vimentin Cytoskeleton: When Polymer Physics Meets Cell Biology, Alison E. Patteson, Robert J. Carroll, Daniel V. Iwamoto, Paul A. Janmey

Physics - All Scholarship

The proper functions of tissues depend on the ability of cells to withstand stress and maintain shape. Central to this process is the cytoskeleton, comprised of three polymeric networks: F-actin, microtubules, and intermediate filaments (IFs). IF proteins are among the most abundant cytoskeletal proteins in cells; yet they remain some of the least understood. Their structure and function deviate from those of their cytoskeletal partners, F-actin and microtubules. IF networks show a unique combination of extensibility, flexibility and toughness that confers mechanical resilience to the cell. Vimentin is an IF protein expressed in mesenchymal cells. This review highlights exciting new …

Band Structure Topology And Spin Transport In Magnon Systems, Bo Li

Department of Physics and Astronomy: Dissertations, Theses, and Student Research

As the spin excitation quanta in magnetic materials, the magnon is at the heart of the spintronics research because it plays a key role in magnetic dynamics, energy and spin transport, and even determining the ground state of magnetic systems. In this thesis, we will study the band-structure topology and transport properties of magnons in both collinear and noncollinear magnets. Inspired by the great success of topological insulators, exploring magnon topology can unveil the topological nature of bosonic particles and widen the zoo of topological materials. We propose a three-dimensional magnon topological insulator model protected by sublattice chiral symmetries, which …

Radial Basis Densities And The Density Functional-Based Atom-In-Molecule: Designing Charge-Transfer Potentials, Godwin Amo-Kwao

Nanoscience and Microsystems ETDs

Classical potentials that are capable of describing charge transfer and charge polarization in complex systems are of central importance for classical atomistic simulation of biomolecules and materials. Current potentials—regardless of the system—do not generalize well, and, with the exception of highly-specialized empirical potentials tuned for specific systems, cannot describe chemical bond formation and breaking. The charge-transfer embedded atom method (CT-EAM), a formal, DFT-based extension to the original EAM for metals, has been developed to address these issues by modeling charge distortion and charge transfer in interacting systems using pseudoatom building blocks instead of the electron densities of isolated atoms. CT-EAM …

Exploring Hidden Structure Of The Nearby Universe And The Limits And Capabilities Of Two Neutral Hydrogen Surveys, Monica Sanchez Barrantes

Physics & Astronomy ETDs

We can use the 21 cm neutral hydrogen (HI) emission line to detect galaxies in optically obscured regions, but it is also a faint line that is difficult to detect at higher redshifts. This work presents two HI surveys. The ALFAZOA Survey maps new and predicted large-scale structure across the Galactic plane, and finds a total of 217 completely new galaxies across both of the survey phases. The completeness limits for ALFAZOA Shallow and Deep are presented. Follow-up observations of confused galaxies in ALFAZOA using the VLA determine that confusion in this survey will not cause significant deviations for the …

Proximity-Induced Magnetization In Graphene: Towards Efficient Spin Gating, Mihovil Bosnar, Ivor Lončarić, P. Lazić, Kirill Belashchenko, Igor Žutić

Kirill Belashchenko Publications

Gate-tunable spin-dependent properties could be induced in graphene at room temperature through the magnetic proximity effect by placing it in contact with a metallic ferromagnet. Because strong chemical bonding with the metallic substrate makes gating ineffective, an intervening passivation layer is needed. Previously considered passivation layers result in a large shift of the Dirac point away from the Fermi level, so that unrealistically large gate fields are required to tune the spin polarization in graphene (Gr). We show that a monolayer of Au or Pt used as the passivation layer between Co and graphene brings the Dirac point closer to …

Maternal Social Status, Offspring 2d:4d Ratio And Postnatal Growth, In Macaca Mulatta (Rhesus Macaques), Juan Pablo Arroyo

USF Tampa Graduate Theses and Dissertations

Early life exposure to stressors can disrupt growth and development, resulting in long-term compromised function and increased risk for disease throughout the lifecourse. Maternal exposure to psychosocial stressors (i.e., stressors derived from social status, social inequalities, and social interactions) during pregnancy has been associated with reduced fetal growth, adverse birth outcomes, and increased morbidity for the offspring later in life. Maternal hormonal responses to stress, such as fluctuations in glucocorticoids (e.g., cortisol) and androgens (e.g., testosterone), can result in increased developmental instability, interfere with offspring growth in-utero, and may alter developmental processes of sexual dimorphism. Second digit to fourth digit …

Spontaneous Raman Scattering Enhancement With Microcavities And Multipass Resonators For Trace Gas Detection, Juan Sebastian Gomez Velez

USF Tampa Graduate Theses and Dissertations

The continual increase in production and use of chemicals in an ever-growing field of applications naturally brings forth the necessity to accurately and efficiently measure molecular composition. Spontaneous Raman scattering is a reliable technique which can optically identify molecules based on their intrinsic rotational-vibrational energy structure. The Raman emission from a substance can be spectrally analyzed to detect molecular species simultaneously and with isotopic sensitivity using a single laser source. However, even though the process is non-invasive and effective, the rate at which the emission occurs is notoriously low due to a weak scattering cross-section. Therefore, research into the development …