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Manipulation Of Spin Crossover Phenomenon In An Fe(Ii) Molecular Complex And Application To Molecular Spintronics, Guanhua Hao

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

Molecules with a large local magnetic moment have attracted considerable attention for application in spintronic devices. One candidate of a suitable device goes to the spin crossover molecule, where these 3d transition metal compounds are able to exhibit a robust spin state transition between distinct states. By proper design, the spintronic devices fabricated via spin crossover molecular thin films could achieve novel functionality while retaining flexibility and other traits based on its “organic” nature.

Controlling the spin state transition is a key factor of these possibilities. This thesis work investigates the manipulation of the spin state transition in [Fe{H …

Structural, Vibrational And Transport Properties Of Novel Complex Systems., Bhupendra Man Shing Karki

Electronic Theses and Dissertations

Electron correlation effects in quantum materials are very strong. It is critical to investigate the structure of quantum materials to better understand and manipulate their physical properties. Quantum effects are prominent at the atomic microscopic length scale, which can not be examined by average long range structural measurements using traditional diffraction methods. Instead, pair distribution function (PDF) analysis, a local structure probe, can effectively unveil the mystery of local structure, which is more sensitive to local behavior than bulk average features. The first section of my dissertation will concentrate on the local structural study of the Iron oxy-chalcogenides, {\cSSe}, which …

Intercalation And High Pressure Studies Of Black Phosphorous - Pathways To Novel Materials And Physics., Manthila Chathurange Rajapakse

Electronic Theses and Dissertations

Discovery of graphene in 2004 initiated a new trend of materials known as two-dimensional (2D) materials which have exciting surface properties and anisotropies than their bulk counterparts. Phosphorene, which is the layered version of black phosphorous (BP) is one of the top 2D materials in terms of research interests and applications of the present day. Moving a step further, our interest is to understand the possibilities for structural modifications of phosphorene, by means of stimuli such as intercalation and high-pressure. It has been predicted by theoretical studies that these stimuli may lead to the formation of new structures and phases …

Microscopic Object Classification Through Passive Motion Observations With Holographic Microscopy, Christian Lindensmith, Jay Nadeau, Manuel Bedrossian, Louis Sumrall, J. Kent Wallace, Eugene Serabyn

Physics Faculty Publications and Presentations

Digital holographic microscopy provides the ability to observe throughout a volume that is large compared to its resolution element without the need to refocus through the volume. This capability enables simultaneous observations of large numbers of small objects within such a volume. We have constructed a microscope that can observe a volume 0.4 x 0.4 x 1.0 μm with submicrometer resolution for observation of microorganisms and minerals in liquid environments in earth and on potential planetary missions. Because environmental samples are likely to contain mixtures of inorganics and microorganisms that are of comparable sizes near the resolution limit of the …

Structural Microheterogeneity In Ionic Liquid/Solvent Mixtures Influenced By Solvent Polarity And Ion Concentration, Babatunde Falola

Open Access Theses & Dissertations

Room temperature ionic liquid (RTIL) and organic solvent mixtures, in supercapacitors, have desirable properties in comparison to conventional electrolytes. We studied the nanostructural properties of mixtures of the RTIL: 1-butyl-3-methylimidazolium bis (trifluoromethyl sulfonyl) imide (abbreviated to BMIM+[TSI]-), with organic solvents: acetonitrile, dichloromethane, benzene, toluene, and tetrahydrofuran. The mass percentage at which macroscopic phase separation is visible in each RTIL and solvent mixture was determined by slowly increasing the solvent concentration. Small-angle x-ray scattering (SAXS) measurements, at RTIL mass percentage lower than the phase separation concentrations, were carried out to determine whether nanoheterogeneity is presently leading up to macroscopic phase separation. …

Sawtooth-Based Chromate Multiferroic - Insight Into Structure And Magnetism, Hector Cein Mandujano

Open Access Theses & Dissertations

The coexistence of two order parameters is a particular occurrence in bulk single-phase materials. Such materials possessing (anti)ferromagnetism, ferroelectricity, and ferroelasticity are known as multiferroics. In this work we revisit BeCr2O4, which is one of the oldest material to be studied in this context. Cr3+ occupies octahedral 4a site and Be2+ occupies tetrahedral 4c site in this compound, forming a close packing structure with a 90° and 138° Cr-O-Cr bonds allowing magnetic superexchange interactions. In the present work, BeCr2O4 powder was prepared using solid-state reaction method and the crystal structure was studied in detail using laboratory and synchrotron X-ray diffraction. …

Vortex-Oriented Ferroelectric Domains In Snte/Pbte Monolayer Lateral Heterostructures, Kai Chang, John W. D. Villanova, Jing-Rong Ji, Souvik Das, Felix Kuster, Salvador Barraza-Lopez, Paolo Sessi, Stuart S. P. Parkin

Physics Faculty Publications and Presentations

Heterostructures formed from interfaces between materials with complementary properties often display unconventional physics. Of especial interest are heterostructures formed with ferroelectric materials. These are mostly formed by combining thin layers in vertical stacks. Here the first in situ molecular beam epitaxial growth and scanning tunneling microscopy characterization of atomically sharp lateral heterostructures between a ferroelectric SnTe monolayer and a paraelectric PbTe monolayer are reported. The bias voltage dependence of the apparent heights of SnTe and PbTe monolayers, which are closely related to the type-II band alignment of the heterostructure, is investigated. Remarkably, it is discovered that the ferroelectric domains in …

Beam Formation And Vernier Steering Off Of A Rough Surface, Eric K. Nagamine, Kenneth W. Burgi, Samuel D. Butler

Faculty Publications

Wavefront shaping can refocus light after it reflects from an optically rough surface. One proposed use case of this effect is in indirect imaging; if any rough surface could be turned into an illumination source, objects out of the direct line of sight could be illuminated. In this paper, we demonstrate the superior performance of a genetic algorithm compared to other iterative feedback-based wavefront shaping algorithms in achieving reflective inverse diffusion for a focal plane system. Next, the ability to control the pointing direction of the refocused beam with high precision over a narrow angular range is demonstrated, though the …

Calculation And Optimization Of Correlation Function In Distillation Method Of Lattice Quantum Chromodynamcis, Ren-Qiang Zhang, Xiang-Yu Jiang, Jiongchi Yu, Chong Zeng, Ming Gong, Shun Xu

Research Collection School Of Computing and Information Systems

Lattice quantum chromodynamics (lattice QCD) is a theory based on quantum chromodynamics, which is widely used in strong interaction related calculations. As a research method that can give accurate and reliable theoretical results, with the improvement of computer ability, Lattice QCD is playing an increasingly important role in recent years. Distillation method is an important numerical method to calculate hadron correlation function in lattice QCD, and can improve the signal-to-noise ratio of calculated physical quantities. Distillation is a method to approximately compute full propagator via replace the laplacian operator with it's outerproduct of laplace eigenvectors. In this way, the construction …

Nanoscale Assembly Of Dectin-1 And Its Glucan Ligand In Immunocyte Membranes And Pathogen Cell Walls, Akram Etemadi Amin

Physics & Astronomy ETDs

Candida spp. pathogens continue to be a significant health care burden with high mortality and exceeding enormous healthcare costs. Candida infection range varies from dermatological infection to more severe bloodstream infection in debilitated patients. Due to this, research dedicated to understanding biophysical interactions between Candida species and the host’s immune cells is essential. The C-type lectin’s (CtLs) are known to bind to Candida cell walls and play a crucial role in downstream immune signaling. It is known that β-glucans, the highly immunogenic polysaccharide in Candida’s cell wall, are mostly masked underneath a layer of mannosylated proteins. The amount of …

Macroscopic Superposition States In Isolated Quantum Systems, Roman V. Buniy, Stephen D. H. Hsu

Mathematics, Physics, and Computer Science Faculty Articles and Research

For any choice of initial state and weak assumptions about the Hamiltonian, large isolated quantum systems undergoing Schrödinger evolution spend most of their time in macroscopic superposition states. The result follows from von Neumann’s 1929 Quantum Ergodic Theorem. As a specific example, we consider a box containing a solid ball and some gas molecules. Regardless of the initial state, the system will evolve into a quantum superposition of states with the ball in macroscopically different positions. Thus, despite their seeming fragility, macroscopic superposition states are ubiquitous consequences of quantum evolution. We discuss the connection to many worlds quantum mechanics.

Electronic, Magnetic, And Structural Properties Of Comnvsb, Adam Ramker, Pavel Lukashev Ph.D.

Summer Undergraduate Research Program (SURP) Symposium

Background

• Spin degree of freedom in electronic devices.
• Ideal candidate – room temperature half-metal.
• Heusler compounds attractive because of high Curie temperature
• Various mechanisms altering degree of spin polarization – mechanical strain, structural disorder, temperature, termination surface/interface, etc.
• CoMnVSb: nearly a spin gapless semiconductor.

Sustainable And Biodegradable Nanocellulose Composite Materials, Jacob Scheel, Tim Kidd Ph.D.

Summer Undergraduate Research Program (SURP) Symposium

Nanocellulose is made from a mixture of cellulose powder, and a variety of different materials and liquids. Unfortunately the cost to produce nanocellulose isn’t ideal, thanks to shrinkage. The goal of my research this year was to try to make nanocellulose more cost effective, by reduce shrinkage.

Chemical Substitution Induced Half-Metallicity In Crmnsb0.5si0.5, Lukas Stuelke, Pavel Lukashev Ph.D.

Summer Undergraduate Research Program (SURP) Symposium

Background

⮚Research on magnetic materials for potential applications in spin-based electronics: one of the most active fields in academia and industry. ⮚High degree of spin polarization – wanted in spintronics. ⮚Spintronics – an emerging technology utilizing a spin degree of freedom. ⮚Various mechanisms alter degree of spin polarization – mechanical strain, structural disorder, temperature, termination surface/interface, etc. ⮚Magnetic materials that conduct electrons of only one spin are called half-metals, and have a great potential in spintronics.

Seasonal Variation Of Multiple-Muon Cosmic Ray Air Showers Observed In The Nova Detector Detector On The Surface, M. A. Acero, P. Adamson, L. Aliaga, N. Anfimov, A. Antoshkin, E. Arrieta-Diaz, L. Asquith, A. Aurisano, A. Back, C. Backhouse, M. Baird, N. Balashov, P. Baldi, B. A. Bambah, S. Bashar, K. Bays, R. Bernstein, V. Bhatnagar, B. Bhuyan, J. Bian, Roberto Petti, Et. Al.

Faculty Publications

We report the rate of cosmic ray air showers with multiplicities exceeding 15 muon tracks recorded in the NOvA Far Detector between May 2016 and May 2018. The detector is located on the surface under an overburden of 3.6 meters water equivalent. We observe a seasonal dependence in the rate of multiple-muon showers, which varies in magnitude with multiplicity and zenith angle. During this period, the effective atmospheric temperature and surface pressure ranged between 210 K and 230 K and 940 mbar and 990 mbar, respectively; the shower rates are anticorrelated with the variation in the effective temperature. The variations …

X Radiation Dose Monitoring For Adolescent And Adult Patients In Selected Health Care Environment Related Places, Kevin Riandi

Journal of Environmental Science and Sustainable Development

A study on patient absorption dose according to age group was carried out. The amount of absorbed A study on patient absorption dose according to age group was carried out. The amount of absorbed dose of X-ray radiation affect the body cells. Health care hospitals such as clinics, environments that use ionizing radiation. Based on the procedure for using ionizing radiation for medical purposes, the Indonesian Nuclear Energy Supervisory Agency recommends monitoring radiation doses for health workers on health service environment. Likewise with the patient, because the patient is directly exposed to the ionizing radiation. Some researh explained that the …

Detecting Optical Transients Using Artificial Neural Networks And Reference Images From Different Surveys, Katarzyna Wardęga, Adam Zadrozny, Martin Beroiz, Richard S. Camuccio, Mario C. Diaz

Physics & Astronomy Faculty Publications

We present a technique to detect optical transients based on an artificial neural networks method. We describe the architecture of two networks capable of comparing images of the same part of the sky taken by different telescopes. One image corresponds to the epoch in which a potential transient could exist; the other is a reference image of an earlier epoch. We use data obtained by the Dr. Cristina V. Torres Memorial Astronomical Observatory and archival reference images from the Sloan Digital Sky Survey. We trained a convolutional neural network and a dense layer network on simulated source samples and then …

Absolute Triple Differential Cross Sections For Low-Energy Electron Impact Ionization Of Biochemically Relevant Systems: Water, Tetrahydrofuran, And Hydrated Tetrahydrofuran, Jiaqi Zhou, Esam Ali, Maomao Gong, Shaokui Jia, Yutian Li, Yingying Wang, Zhen Zhang, Xiaorui Xue, Dmitry V. Fursa, Igor Bray, Xiangjun Chen, Don H. Madison, Alexander Dorn, Xueguang Ren

Physics Faculty Research & Creative Works

An experimental procedure is reported, which provides the absolute triple differential cross sections (ATDCSs) for electron-impact ionization of large (bio)molecules. This type of measurements represents the most stringent tests for new or existing theoretical models. We will use this procedure to test the accuracy of the best currently available theoretical models for the problems of electron-impact (65 eV) ionization of the molecules water (H₂O), tetrahydrofuran (C₄H₈O), and their hydrogen-bonded dimer H₂O · C₄H₈O. The cross sections were calculated using the molecular three-body distorted-wave (M3DW) model, the multicenter three-distorted-wave …

Search For Anisotropic Gravitational-Wave Backgrounds Using Data From Advanced Ligo And Advanced Virgo's First Three Observing Runs, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Karla E. Ramirez, W. H. Wang

Physics & Astronomy Faculty Publications

We report results from searches for anisotropic stochastic gravitational-wave backgrounds using data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. For the first time, we include Virgo data in our analysis and run our search with a new efficient pipeline called PyStoch on data folded over one sidereal day. We use gravitational-wave radiometry (broadband and narrow band) to produce sky maps of stochastic gravitational-wave backgrounds and to search for gravitational waves from point sources. A spherical harmonic decomposition method is employed to look for gravitationalwave emission from spatially-extended sources. Neither technique found evidence of …

Protein And Polysaccharide-Based Electroactive And Conductive Materials For Biomedical Applications, Xiao Hu, Samuel Ricci, Sebastian Naranjo Naranjo, Zachary Hill, Peter Gawason

College of Science & Mathematics Departmental Research

Electrically responsive biomaterials are an important and emerging technology in the fields of biomedical and material sciences. A great deal of research explores the integral role of electrical conduction in normal and diseased cell biology, and material scientists are focusing an even greater amount of attention on natural and hybrid materials as sources of biomaterials which can mimic the properties of cells. This review establishes a summary of those efforts for the latter group, detailing the current materials, theories, methods, and applications of electrically conductive biomaterials fabricated from protein polymers and polysaccharides. These materials can be used to improve human …

Atomic Photoionization By Multiple Temporal Pairs Of Slits, Jean Marcel Ngoko Djiokap

Department of Physics and Astronomy: Faculty Publications

We study interactions between multiple temporal pairs of slits in coherent control of photoionization of S-state atoms using a pulse train of N + 1 pairs evenly delayed in time by τ , in which the two pulses in a pair with a delay τ₀ are counter-rotating circularly polarized. For interacting two double-slit experiments, while Ramsey interference between two identical Archimedean spirals yields pairs of principal spirals, interference of two spirals with opposite handedness does not lead to spirals, but instead to crocodile-eye-like patterns with nictares. For more than two interacting experiments, the resulting patterns turn out just to …

Computational Studies Of Carbon Nanocluster Solidification, Chathuri C. Silva

Dissertations

A subset of micron-size meteoritic carbon particles formed in red giant atmospheres show a core-rim structure, likely condensed from a vapor phase into super-cooled carbon droplets that nucleated graphene sheets (~40Å) on randomly oriented 5-atom loops during solidification, followed by coating with a graphite rim. Similar particles form during slow cooling of carbon vapor in the lab.

Here we investigate the nucleation and growth of carbon rings and graphene sheets using density functional theory (DFT). Our objectives: (1). explore different computational techniques in DFT-VASP for various carbon structures and compare the results with literature, (2). investigate the nucleation and growth …

Advancement In Infrared Optics Through The Exploration Of Solution Derived Arsenic Selenide (As2se3) Thin Films, Annabella Orsini

Physics and Astronomy Summer Fellows

There are great opportunities for advancement in the realm of infrared (IR) optics through the use of chalcogenide glasses (ChGs). The development of IR optics using ChGs is important for applications in search and rescue operations, firefighting efforts, medical imaging, and satellites. Instead of creating bulky, expensive, single crystal IR glasses, ChGs can be deposited as thin films by solution derived (SD) spin or dip coating. Our research takes a multidisciplinary approach to investigate ChGs thin films using physics, chemistry, optics, and materials science.

Upper Limits On The Isotropic Gravitational-Wave Background From Advanced Ligo And Advanced Virgo's Third Observing Run, R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Karla E. Ramirez, W. H. Wang

Physics & Astronomy Faculty Publications

We report results of a search for an isotropic gravitational-wave background (GWB) using data from Advanced LIGO’s and Advanced Virgo’s third observing run (O3) combined with upper limits from the earlier O1 and O2 runs. Unlike in previous observing runs in the advanced detector era, we include Virgo in the search for the GWB. The results of the search are consistent with uncorrelated noise, and therefore we place upper limits on the strength of the GWB. We find that the dimensionless energy density ΩGW≤5.8×10−9 at the 95% credible level for a flat (frequency-independent) GWB, using a prior which is uniform …

54fe(D,P)55fe Single Neutron Transfer Presentation, Matthew Quirin, Raymond Saunders

Physics and Astronomy Presentations

During our summer research at the John D Fox Laboratory, we used the 9 MV Tandem van de Graaff accelerator and the Super Enge Split-Pole Spectrograph to make measurements of the neutron transfer reaction 54Fe(d,p) 55Fe to observe and explore excited states of 55Fe and shell structure beyond the magic number N=28. We have created momentum spectra and angular distribution plots of the protons from the reaction which will be analyzed to determine the angular momentum values of states and single-neutron energies in 55Fe in an effort to better understand nuclear structure.

54fe(D,P)55fe Single Neutron Transfer, Matthew Quirin, Raymond Saunders

Physics and Astronomy Summer Fellows

During our summer research at the John D Fox Laboratory, we used the 9 MV Tandem van de Graaff accelerator and the Super Enge Split-Pole Spectrograph to make measurements of the neutron transfer reaction 54Fe(d,p) 55Fe to observe and explore excited states of 55Fe and shell structure beyond the magic number N=28. We have created momentum spectra and angular distribution plots of the protons from the reaction which will be analyzed to determine the angular momentum values of states and single-neutron energies in 55Fe in an effort to better understand nuclear structure.

Bridging The 12-6-4 Model And The Fluctuating Charge Model, Pengfei Li

Chemistry: Faculty Publications and Other Works

Metal ions play important roles in various biological systems. Molecular dynamics (MD) using classical force field has become a popular research tool to study biological systems at the atomic level. However, meaningful MD simulations require reliable models and parameters. Previously we showed that the 12-6 Lennard-Jones nonbonded model for ions could not reproduce the experimental hydration free energy (HFE) and ion-oxygen distance (IOD) values simultaneously when ion has a charge of +2 or higher. We discussed that this deficiency arises from the overlook of the ion-induced dipole interaction in the 12-6 model, and this term is proportional to 1/r …

Study Of The Effects Of Cavity Mode Spacing On Mode-Hopping In Iii–V/Si Hybrid Photonic Crystal Lasers, Praveen K.J. Singaravelu, Sharon M. Butler, Robert N. Sheehan, Alexandros A. Liles, Stephen P. Hegarty, Liam O'Faolain

Cappa Publications

We present a design methodology for hybrid lasers to realise mode-hop free operation by controlling the cavity mode spacing. In this study, a compact hybrid photonic crystal laser (H-PhCL) was employed which allowed a reduction of the Fabry–Perot length of the laser cavity and eliminated the need for an active mode stabilisation mechanism in order to realise mode-hop free operation. The H-PhCL was formed by butt-coupling a reflective semiconductor optical amplifier (RSOA) with a two-dimensional silicon (Si) photonic crystal (PhC) cavity. Continuous stable single frequency operation with >40 dB side-mode suppression ratio (SMSR) of the laser was achieved for gain …

Lagrangian And Eulerian Accelerations In Turbulent Stratified Shear Flows, Frank G. Jacobitz, Kai Schneider

School of Engineering: Faculty Scholarship

The Lagrangian and Eulerian acceleration properties of fluid particles in homogeneous turbulence with uniform shear and uniform stable stratification are studied using direct numerical simulations. The Richardson number is varied from Ri=0, corresponding to unstratified shear flow, to Ri=1, corresponding to strongly stratified shear flow. The probability density functions (pdfs) of both Lagrangian and Eulerian accelerations have a stretched-exponential shape and they show a strong and similar influence on the Richardson number. The extreme values of the Eulerian acceleration are stronger than those observed for the Lagrangian acceleration. Geometrical statistics explain that the magnitude of the Eulerian acceleration is larger …

Experimental Observation Of Topological Z2 Excitonpolaritons In Transition Metal Dichalcogenide Monolayers, Mengyao Li, Ivan Sinev, Fedor Benimetskiy, Tatyana Ivanova, Ekaterina Khestanova, Svetlana Kiriushechkina, Anton Vakulenko, Sriram Guddala, Maurice Skolnick, Vinod M. Menon, Dmitry Krizhanovskii, Andrea Alù, Anton Samusev, Alexander B. Khanikaev

Publications and Research

The rise of quantum science and technologies motivates photonics research to seek new platforms with strong light-matter interactions to facilitate quantum behaviors at moderate light intensities. Topological polaritons (TPs) offer an ideal platform in this context, with unique properties stemming from resilient topological states of light strongly coupled with matter. Here we explore polaritonic metasurfaces based on 2D transition metal dichalcogenides (TMDs) as a promising platform for topological polaritonics. We show that the strong coupling between topological photonic modes of the metasurface and excitons in TMDs yields a topological polaritonic Z₂ phase. We experimentally confirm the emergence of one-way …