Physical Sciences and Mathematics Commons^™

Transient Transmission Oscillations In Doped And Undoped Lithium Niobate Induced By Near-Infrared Femtosecond Pulses, Bryan J. Crossman, Gregory J. Taft

Physics Faculty Publications

Transient transmission oscillations in X-cut and Z-cut congruent, iron-doped, and magnesium-doped lithium niobate samples were measured using 50 fs, 800 nm, 0.5 nJ pulses from a self-mode-locked Ti:sapphire laser in an optical pump–probe system. Several Raman-active oscillation modes excited by these pulses were observed as changes in the transmitted probe intensity versus time delay between the pump and probe pulses. The samples were rotated to determine how the incident polarization of the pump pulses affects the mode excitations. The observed Raman-active oscillations correspond to previously reported symmetry modes measured with traditional, continuous-wave, Raman spectroscopy using the same scattering …

Boundary Twists, Instabilities, And Creation Of Skyrmions And Antiskyrmions, Aldo Raeliarijaona, Rabindra Nepal, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We formulate and study the general boundary conditions dictating the magnetization profile in the vicinity of an interface between magnets with dissimilar properties. Boundary twists in the vicinity of an edge due to Dzyaloshinskii-Moriya interactions have been first discussed by Wilson et al. [Phys. Rev. B 88, 214420 (2013)] and by Rohart and Thiaville [Phys. Rev. B 88, 184422 (2013)]. We show that in general case the boundary conditions lead to the magnetization profile corresponding to the Néel, Bloch, or intermediate twist. We explore how such twists can be utilized for creation of skyrmions and antiskyrmions, e.g., in a view …

Properties Of Si Quantum Dots, Carolyn C. F Cadogan

Electronic Thesis and Dissertation Repository

The fundamental properties of matter in confined particles change dramatically due to quantum effects. In this work, we have explored the optical properties of silicon quantum dots (Si-QDs) embedded in Si₃N₄; and the role of crystallinity on the optical properties and formation of Si-QDs in Al₂O₃. This work examined the role of (1) annealing temperature and the composition of the film, (2) Al doping of the host Si₃N₄ film, (3) doping Si-QDs and (4) Al and P passivation of Si-QDs on the PL intensity of Si-QDs embedded in Si …

Computational Prediction, Characterization, And Methodology Development For Two-Dimensional Nanostructures: Phosphorene And Phosphide Binary Compounds., Congyan Zhang

Electronic Theses and Dissertations

In this thesis, a comprehensive computational simulation was carried out for predicting, characterizing, and applications of two-dimensional (2D) materials. The newly discovered GaP and InP layers were selected as an example to demonstrate how to explore new 2D materials using computational simulations. The performance of phosphorene as the anode material of Lithium-ion battery was discussed as the example of the application of 2D material. Furthermore, the semi-empirical Hamiltonian for phosphorous and lithium elements have been developed for our future work on the application of phosphorus and lithium-based systems. The novel 2D materials of GaP and InP binary compounds were found …

Strong Electron-Boson Coupling In The Iron-Based Superconductor Bafe1.9pt0.1as2 Revealed By Infrared Spectroscopy, Zhen Xing, Shanta Saha, J. Paglione, M. M. Qazilbash

Arts & Sciences Articles

Understanding the formation of Cooper pairs in iron-based superconductors is one of the most important topics in condensed matter physics. In conventional superconductors, the electron-phonon interaction leads to the formation of Cooper pairs. In conventional strong-coupling superconductors like lead (Pb), the features due to electron-phonon interaction are evident in the infrared absorption spectra. Here we investigate the infrared absorption spectra of the iron arsenide superconductor BaFe1.9Pt0.1As2. We find that this superconductor has fully gapped (nodeless) Fermi surfaces, and we observe the strong-coupling electron-boson interaction features in the infrared absorption spectra. Through modeling with the Eliashberg function based on Eliashberg theory, …

Directly Photoexcited Dirac And Weyl Fermions In Zrsis And Nbas, Christopher P. Weber, Leslie M. Schoop, Stuart S. P. Parkin, Robert C. Newby, Alex Nateprov, Bettina Lotsch, Bala Murali Krishna Mariserla, J. Matthew Kim, Keshav M. Dani, Hans A. Bechtel, Ernerst Arushanov, Mazhar Ali

Physics

We report ultrafast optical measurements of the Dirac line-node semimetal ZrSiS and the Weyl semimetal NbAs, using mid-infrared pump photons from 86 meV to 500 meV to directly excite Dirac and Weyl fermions within the linearly dispersing bands. In NbAs, the photoexcited Weyl fermions initially form a non-thermal distribution, signified by a brief spike in the differential reflectivity whose sign is controlled by the relative energy of the pump and probe photons. In ZrSiS, electron-electron scattering rapidly thermalizes the electrons, and the spike is not observed. Subsequently, hot carriers in both materials cool within a few picoseconds. This cooling, as …

Physical Electronic Properties Of Self-Assembled 2d And 3d Surface Mounted Metal-Organic Frameworks, Radwan Elzein

USF Tampa Graduate Theses and Dissertations

Metal-organic frameworks stand at the frontiers of molecular electronic research because they combine desirable physical properties of organic and inorganic components. They are crystalline porous solids constructed by inorganic nodes coordinated to organic ligands to form 1D, 2D, or 3D structures. They possess unique characteristics such as ultrahigh surface area crystal lattices up to 10000 m² g^-1, and tunable nanoporous sizes ranging from 0.2 to 50 nm. Their unprecedented structural diversity and flexibility beyond solid state materials can lead to unique properties such as tailorable electronic and ionic conductivity which can serve as interesting platforms for a …

The Effects Of Pressure And Magnetic Field On Phase Transitions And Related Physical Properties In Solid State Caloric Materials, Ahmad Ikhwan Us Saleheen

LSU Doctoral Dissertations

Solid-state caloric effects, such as the magnetocaloric (MCE) and barocaloric (BCE) effects, may be utilized in future cooling technologies that are more efficient and environment-friendly. Large caloric effects often occur near phase transitions, especially near coupled first-order magnetostructural transitions (MST), and are initiated by external parameters, such as magnetic field or hydrostatic pressure. In this dissertation, the effects of pressure, temperature, and magnetic field on the phase transitions in three material systems are studied in order to elucidate how the respective caloric effects are affected.

In the first study, the realization of a coupled MST in a MnNiSi-based system through …

Genetic Algorithm Design Of Photonic Crystals For Energy-Efficient Ultrafast Laser Transmitters, Troy A. Hutchins-Delgado

Shared Knowledge Conference

Photonic crystals allow light to be controlled and manipulated such that novel photonic devices can be created. We are interested in using photonic crystals to increase the energy efficiency of our semiconductor whistle-geometry ring lasers. A photonic crystal will enable us to reduce the ring size, while maintaining confinement, thereby reducing its operating power. Photonic crystals can also exhibit slow light that will increase the interaction with the material. This will increase the gain, and therefore, lower the threshold for lasing to occur. Designing a photonic crystal for a particular application can be a challenge due to its number of …

Two-Dimensional Layered Materials (Graphene-Mos2) Nanocatalysts For Hydrogen Production, Jacob Dobler, Taylor Robinson, Sanju Gupta 7455940

Posters-at-the-Capitol

Recent development of two-dimensional layered materials including graphene-family and related nanomaterials have arisen as potential game changer for energy, water and sensing applications. While graphene is a form of carbon arranged hexagonally within atomic thin sheet, MoS₂ is becoming a popular, efficient, and cost-effective catalyst for electrochemical energy devices, in contrast to expensive platinum and palladium catalysts. In this work, we electrochemically desulfurize few-layer molybdenum disulfide (MoS₂) and aerogels with reduced graphene oxide (rGO) prepared under hydrothermal conditions ((P< 20 bar, T< 200 ^oC), for improving hydrogen evolution reaction (HER) activity via point defects (S-vacancy). Moreover, the interactions between rGO …

Physical Properties Of Engineered Nanocomposites For Defense Applications, Alex Henson, Sanju Gupta

Posters-at-the-Capitol

Polymer nanocomposites are significant for modern and future technologies (aerospace, defense, water purification etc.) due to their tailored properties, lightweight and low cost. However, ‘forward’ engineered polymer (host matrix) composites with smaller size nanoparticles (guest) providing desired properties targeting specific applications remains a challenging task as they depend largely on nanoparticles size, shape and loading (volume fraction). This study develops polymer nanocomposites impregnated with ‘organic-inorganic’ silsesquioxane nanoparticles and graphene nanoribbons, and investigates microscopic structure and dynamics of interfacial layer to predict macroscale properties. The nanocomposites consist of poly(2-vinylpyridine) (P2VP) polymer (segment ~5nm) with spherical silsesquioxane nanoparticles (diameter ~2-5nm) and planar …

Rectifying Garbage-In Equals Garbage-Out Using A Secondary Electron Yield Materials Database, Phil Lundgreen, Jr Dennison

Presentations

No abstract provided.

An Introduction To Quantile-Quantile Plots For The Experimental Physicist, Allen Andersen, Jr Dennison

Journal Articles

No abstract provided.

Non-Abelian Quasiholes In Lattice Moore-Read States And Parent Hamiltonians, Sourav Manna, Julia Wildeboer, Germán Sierra, Anne E. B. Nielsen

Physics and Astronomy Faculty Publications

This work concerns Ising quasiholes in Moore-Read type lattice wave functions derived from conformal field theory. We commence with constructing Moore-Read type lattice states and then add quasiholes to them. By use of Metropolis Monte Carlo simulations, we analyze the features of the quasiholes, such as their size, shape, charge, and braiding properties. The braiding properties, which turn out to be the same as in the continuum Moore-Read state, demonstrate the topological attributes of the Moore-Read lattice states in a direct way. We also derive parent Hamiltonians for which the states with quasiholes included are ground states. One advantage of …

Quantum Phase Transitions In Disordered Boson Systems, Zhiyuan Yao

Doctoral Dissertations

In this dissertation, we study the superfluid-insulator quantum phase transition in disordered boson systems. Recently, there has been considerable controversy over the validity of the scaling relations of the superfluid--Bose-glass quantum phase transition in three dimensions. Results from experimental and numerical studies on disordered quantum magnets contradict the scaling relations and the associated conventional scaling hypothesis for the singular part of the free energy. We determine various critical exponents of the superfluid--Bose-glass quantum phase transition in three-dimensional disordered Bose-Hubbard model through extensive Monte Carlo simulations. Our numerical study shows the previous studies on disordered quantum magnets were performed outside the …

Geometry, Growth And Pattern Formation In Thin Elastic Structures, Salem Al-Mosleh

Doctoral Dissertations

Thin shells are abundant in nature and industry, from atomic to planetary scales. The mechanical behavior of a thin shell depends crucially on its geometry and embedding in 3 dimensions (3D). In fact, the behavior of extremely thin shells becomes scale independent and only depends on geometry. That is why the crumpling of graphene will have similarities to the crumpling of paper. In this thesis, we start by discussing the static behavior of thin shells, highlighting the role of asymptotic curves (curves with zero normal curvature) in determining the possible deformations and in controlling the folding patterns. In particular, we …

Copper-Nanoparticle Decorated Graphene Thin Films: Applications In Metal-Assisted Etching And Synthesis Of Next-Generation Graphene-Based Nanomaterials, Jaewoo Park

Electronic Thesis and Dissertation Repository

Since 2006, the experimental discovery of graphene, a single-layer of carbon atoms, has spurred tremendous efforts towards new graphene-based materials. In graphene research, there is a recent trend towards next-generation materials in which graphene layers are locally modified in a controlled fashion at the nanoscale and tailored for specific applications. Examples include nanoparticle-decorated graphene thin films with surface potential tailored for nanoelectronics or advanced catalysis, graphene nanoribbons, graphene quantum dots, and the scalable fabrication of tiny pores in graphene, which are suitable to applications requiring ultrathin molecular sieving membranes. This research is focused on the development of new applications of …

Dhital_Pnas.Pdf, Chetan Dhital

Chetan Dhital

No abstract provided.

Real-Time Video Processing Of Arcing Events To Determine Coincidence, Jr Dennison, Gregory Wilson, Jonh Mojica Decena, Brian Wood

Posters

No abstract provided.

Real-Time Video Processing Of Arcing Events To Determine Coincidence, Jr Dennison, Gregory Wilson, Jonh Mojica Decena, Brian Wood

Posters

A system has been developed and tested for real-time monitoring of environmentally-induced electrostatic discharge events to test spacecraft component and material survivability. Simultaneous detection by several parallel methods in coincidence, enhances event detection, minimizes false signals, and collects complementary information to determine arc location, intensity, and timing. This research focuses on four computer-interfaced video cameras which provide spatial and temporal detection of visual arcing from the surface of various elements. A real time processing solution was developed which can calculate integrated intensities, sensitively detect intensity threshold events, and store relevant video frames from these threshold events. Post processing of this …

Charging Effects Of High Voltage Probe Pulse On Pulsed Electroacoustic Measurements, Zachary Gibson, Jr Dennison, Erick W. Griffiths, Lee Pearson, Anthony Pearson

Presentations

No abstract provided.

Characterizing Vibrationally Induced Damage Of Carbon Nanotube Forests, Jordan Lee, Brian Wood, Ashlan Keeler, Jr Dennison, T. -C. Shen

Presentations

No abstract provided.

Detection And Classification Of High Energy Beta Radiation Induced Damage Of Raspberry Pi Zero Intended For Opal Cubesat, Jonh Mojica Decena, Ryan J. Martineau, Jr Dennison, Brian Wood, Michael J. Taylor

Presentations

No abstract provided.

Electron Yield Measurements Of Multilayer Conductive Materials, Gregory Wilson, Matthew Robertson, Jordan Lee, Jr Dennison

Presentations

No abstract provided.

Effects Of Radiation On The Electrostatic Discharge Of Polymers, Kip Quilter, Megan Loveland, Alexandra Hughlett, Jr Dennison

Posters

No abstract provided.

Characterization Of Electron Yield Suppression With Carbon Nanotube Forest Grown On Silicon Substrates, Brian Wood, Jordan Lee, Justin Christensen, Gregory Wilson, Jr Dennison, T. -C. Shen

Presentations

No abstract provided.

Simulating Microgravity And Space Radiation With A Rotary Cell Culture System (Rccs), Alexandra Nelson, Lori Caldwell, Eryn Hanson, Jr Dennison, Elizabeth Vargis

Presentations

No abstract provided.

Characterizing Vibrationally Induced Damage Of Carbon Nanotube Forests, Jordan Lee, Brian Wood, Ashlan Keeler, Jr Dennison, T. -C. Shen

Presentations

No abstract provided.

Detection And Classification Of High Energy Beta Radiation Induced Damage Of Raspberry Pi Zero Intended For Opal Cubesat, Jonh Mojica Decena, Jr Dennison, Brian Wood, Ryan J. Martineau, Michael Taylor

Presentations

No abstract provided.

Charging Effects Of High Voltage Probe Pulse On Pulsed Electroacoustic Measurements, Zachary Gibson, Jr Dennison, Lee Pearson, Erick Griffiths, Anthony Pearson

Presentations

No abstract provided.