Physics Commons^™

Combined Risk Based Inspection And Fault Tree Analysis For Repetitive 3-Phase Line Piping Leakage At West Java Offshore Topside Facility, Dona Yuliati, Akhmad Herman Yuwono, Datu Rizal Asral, Donanta Dhaneswara

Journal of Materials Exploration and Findings

Hydrocarbon releases might result in serious consequences in various aspects. In addition to the contribution to environmental pollution, repetitive leakages need high repair costs. This study aim is to minimize potential repetitive leakage for other typical 3-phase piping systems. We conducted the risk assessment by adopting Risk Based Inspection (RBI) API 581 to identify risk level, calculating piping lifetime, recommended inspection plan and mitigations. The most relevant root causes can be obtained through quantitative Fault Tree Analysis (FTA). Observation and investigation was taken from eight 3-phase piping systems that experienced repetitive leakages. It has been found that the risk level …

Nitrogen Gas Quenching Pressure Effect On Bs S155 Alloy Steel In Vacuum Furnace, Agus Mulyadi Hasanudin, Eddy Sumarno Siradj

Journal of Materials Exploration and Findings

The production of metal and alloy products requires the use of heat treatment, when during the heat treatment process, quenching is a crucial step. The quenching medium can be anything from water, a salt bath, oil, air and gas. In a vacuum furnace, pressurized gas, most frequently nitrogen (N₂) gas, serves as one of the quenching mediums. One of the drawbacks of the quenching process is the distortion and dimensional change of the parts. This paper aims to investigate the influence of nitrogen gas quenching pressure on the distortion and dimensional change of aerospace actuator gear planet parts …

Modeling Lithographic Quantum Dots And Donors For Quantum Computation And Simulation, Mitchell Ian Brickson

Physics & Astronomy ETDs

Our first focus is on few-hole quantum dots in germanium. We use discontinous Galerkin methods to discretize and solve the equations of a highly detailed k·p model that describes these systems, enabling a better understanding of experimental magnetospectroscopy results. We confirm the expected anisotropy of single-hole g-factors and describe mechanisms by which different orbital states have different g-factors. Building on this, we show that the g-factors in Ge holes are suciently sensitive to details of the device electrostatics that magnetospectroscopy data can be used to make a prediction of the underlying confinement potential. The second focus is on designing quantum …

Atomic-Level Mechanisms Of Fast Relaxation In Metallic Glasses, Leo W. Zella

Doctoral Dissertations

Glasses are ubiquitous in daily life and have unique properties which are a consequence of the underlying disordered structure. By understanding the fundamental processes that govern these properties, we can modify glasses for desired applications. Key to understanding the structure-dynamics relationship in glasses is the variety of relaxation processes that exist below the glass transition temperature. Though these relaxations are well characterized with macroscopic experimental techniques, the microscopic nature of these relaxations is difficult to elucidate with experimental tools due to the requirements of timescale and spatial resolution. There remain many questions regarding the microscopic nature of relaxation in glass …

Enhanced Luminescence Efficiency In Eu-Doped Gan Superlattice Structures Revealed By Terahertz Emission Spectroscopy, Fumikazu Murakami, Atsushi Takeo, Brandon Mitchell, Volkmar Dierolf, Yasufumi Fujiwara, Masayoshi Tonouchi

Physics & Engineering Faculty Publications

Eu-doped Gallium nitride (GaN) is a promising candidate for GaN-based red light-emitting diodes, which are needed for future micro-display technologies. Introducing a superlattice structure comprised of alternating undoped and Eu-doped GaN layers has been observed to lead to an order-of-magnitude increase in output power; however, the underlying mechanism remains unknown. Here, we explore the optical and electrical properties of these superlattice structures utilizing terahertz emission spectroscopy. We find that ~0.1% Eu doping reduces the bandgap of GaN by ~40 meV and increases the index of refraction by ~20%, which would result in potential barriers and carrier confinement within a superlattice …

Experiments With Monopoles, Rings And Knots In Spinor Bose-Einstein Condensates, Alina A. Blinova

Doctoral Dissertations

Topological excitations are ubiquitous in nature, their charge being a naturally-quantized, conserved quantity that can exhibit particle-like behavior. Spinor Bose-Einstein condensates (BECs) are an exceptionally versatile system for the study and exploration of topological excitations. Between the spin-1 and spin-2 ⁸⁷Rb condensates there are seven possible broken-symmetry magnetic phases, with each one hosting unique opportunities for topological defects. We have created and observed several novel topological excitations in a spinor ⁸⁷Rb BEC. In this dissertation I present and discuss three principal experimental findings: (1) The discovery of an Alice ring, or a half-quantum vortex ring, emerging from a …

Breakdown Of The Drift-Diffusion Model For Transverse Spin Transport In A Disordered Pt Film, Kirill D. Belashchenko, Giovanni G. Baez Flores, Wuzhang Fang, Alexey Kovalev, Mark Van Schilfgaarde, Paul M. Haney, Mark D. Stiles

Department of Physics and Astronomy: Faculty Publications

Spin-accumulation and spin-current profiles are calculated for a disordered Pt film subjected to an in-plane electric current within the nonequilibrium Green's function approach. In the bulklike region of the sample, this approach captures the intrinsic spin Hall effect found in other calculations. Near the surfaces, the results reveal qualitative differences with the results of the widely used spin-diffusion model, even when the boundary conditions are modified to try to account for them. One difference is that the effective spin-diffusion length for transverse spin transport is significantly different from its longitudinal counterpart and is instead similar to the mean-free path. This …

Majorana Bound States In A D-Wave Superconductor Planar Josephson Junction, Hamed Vakili, Moaz Ali, Mohamed Elekhtiar, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We study phase-controlled planar Josephson junctions comprising a two-dimensional electron gas with strong spin-orbit coupling and d-wave superconductors, which have an advantage of a high critical temperature. We show that a region between the two superconductors can be tuned into a topological state by the in-plane Zeeman field, and can host Majorana bound states. The phase diagram as a function of the Zeeman field, chemical potential, and the phase difference between superconductors exhibits the appearance of Majorana bound states for a wide range of parameters. We further investigate the behavior of the topological gap and its dependence on the …

Biosynthesis Of Mgo Nanoparticles And Their Impact On The Properties Of The Pva/Gelatin Nanocomposites For Smart Food Packaging Applications, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Enhancement Of Er Luminescence From Bridge-Type Photonic Crystal Nanocavities With Er, O-Co-Doped Gaas, Zhidong Fang, Jun Tatebayashi, Ryohei Homi, Masayuki Ogawa, Hirotake Kajii, Masahiko Kondow, Kyoko Kitamura, Brandon Mitchell, Shuhei Ichikawa, Yasufumi Fujiwara

Physics & Engineering Faculty Publications

A bridge-type photonic crystal (PhC) nanocavity based on Er,O-codoped GaAs is employed to realize enhancement of Er luminescence. By adjusting the structural design and measurement temperature, the cavity mode's wavelength can be coupled to Er luminescence. The peak emission intensity from an Er-2O defect center was enhanced 7.3 times at 40 nW pump power and 77 K. The experimental Q-factor is estimated to be over 1.2 x 104, and the luminescence intensity shows superlinearity with excitation power, suggesting Er luminescence amplification. This result would pave the way towards the realization of highly efficient single-photon emitters based on rare-earth elements.

On The Origins Of Life — Modelling The Initial Stages Of Complex Coacervate Droplet Formation, Yixuan Wu

Western Libraries Undergraduate Research Awards (WLURAs)

Coacervate droplets are considered a plausible model for protocells due to their spontaneous formation and ability to compartmentalize macromolecules such as nucleic acid and peptides. Although experimental studies have observed and synthesized coacervates under different laboratory conditions, little is known about their structure. Here we present atomistic molecular dynamic simulations of the interactions between water and oppositely charged proteins that cluster together in a salt-dependent process. Observing such liquid-liquid phase separation on an atomic level would serve as a model for the initial stages of complex coacervate formation. Molecular Dynamics was used to compute diagnostics of the structure at different …

Ferroelectric Hafnia Surface In Action, Xia Hong

Nebraska Center for Materials and Nanoscience: Faculty Publications

Piezoresponse microscopy and spectroscopy reveal the inextricable role of surface electrochemistry in stabilizing and controlling ferroelectricity in doped hafnia.

Doped hafnia (HfO₂), a relatively new member of the ferroelectric family, has challenged in many ways our conventional perception of ferroelectric oxides. It possesses extremely localized electric dipoles that are independently switchable,¹ making it immune to finite size effects — the loss of long-range dipole order in ferroic materials due to size scaling. While polycrystalline grains and microstructures can yield lower polarization and poorer cycling behavior in canonical ferroelectrics such as Pb(Zr,Ti)O₃ and BaTiO₃, in …

Dynamics Of Spin And Charge Of Color Centers In Diamond Under Cryogenic Conditions, Richard G. Monge

Dissertations, Theses, and Capstone Projects

Individual quantum systems in semiconductors are currently the most sought-after platform for applications in quantum science. Most notably, the nitrogen-vacancy (NV) center in diamond features a defect deep within the electronic bandgap, making it amenable for precise manipulation to help pave the way to perform fundamental quantum physics experimentation. The NV center also offers long coherence times and versatile spin-dependent fluorescent properties, making it an ideal candidate for a nanoscale magnetometer. Furthermore, multi-color excitation offers deterministic charge state manipulation. While ambient operation has been key to their appeal, bringing NVs to cryogenic conditions opens new opportunities for alternate forms of …

Nonlinear Processes In Room Temperature Exciton-Polaritons, Prathmesh Deshmukh

Dissertations, Theses, and Capstone Projects

Strong light-matter coupling in solid state systems is an intriguing process that allows one to exploit the advantages of both light and matter. In this context, microcavities have become essential platforms for studying the strong coupling regime, where hybrid light-matter states known as exciton-polaritons form, leading to enhanced light matter interaction, modified material properties, and novel quantum phenomena. In this thesis, we explore the phenomenology of exciton-polaritons in strained TMD microcavities, 2D perovskites, fluorescent proteins and organic dyes encompassing thermalization, polariton lasing, and the observation of nonlinear effects.

Transition metal dichalcogenides (TMDs) have emerged as a remarkable class of two- …

The Role Of Nuclear Quantum Effects In Supercooled Water And Amorphous Ice, Ali H. Eltareb

Dissertations, Theses, and Capstone Projects

Water is one of the most important substances on Earth and plays a fundamental role in numerous scientific and engineering applications. Interestingly, water behaves much differently than other liquids. For example, water shows an anomalous density maximum at 277 K, the solid phase (ice) is less denser than the liquid, and its thermodynamic response functions, such as the specific heat C_P and isothermal compressibility κ_T, also increase anomalously upon cooling. In the glassy state, water can exist in two different forms, low-density and high-density amorphous ice (LDA and HDA). While water has been scrutinized for many centuries, …

A Simple Method For Determining Shallow Charge Distributions In Dielectrics Via Pulsed Electroacoustic Measurements, Zachary Gibson, J. R. Dennison

Journal Articles

The understanding of charge dynamics in dielectric materials is paramount in mitigating electrostatic discharge events for spacecraft. The most critical spacecraft charging events are found to result from incident electrons in the energy range of 10 keV to 50 keV. The charge embedded in dielectric materials in this energy range are deposited a distance into the material on the order of a few to tens of microns. One way to measure and understand the deposited charge is via pulsed electroacoustic measurements (PEA). However, the typical PEA spatial resolution of ~ 10 μm is not sufficient to resolve or discern charge …

Topological Hall Effect In Particulate Magnetic Nanostructure, Ahsan Ullah

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

Conduction electrons change their spin direction due to the exchange interaction with the lattice spins. Ideally, the spins of the conduction electrons follow the atomic spin adiabatically, so that spins like S1, S2, and S3 can be interpreted as time-ordered sequences t1 < t2 < t3. Such spin sequences yield a quantum-mechanical phase factor in the wave function,  →ei, where  is known as the Berry phase. The corresponding spin rotation translates into a Berry curvature and an emergent magnetic field and subsequently, Hall-effect contribution known as the topological Hall-effect. This dissertation explores topological Hall-effect in particulate magnets, where noncollinear spins are stabilized by competition between different magnetic interactions. The topologically non-trivial spin textures in these nanostructures are flower states, curling states, vortex, and magnetic bubbles, which give rise to topological Hall-effect and have finite spin chirality and Skyrmion number Q. Topological Hall-effect is investigated in noninteracting nanoparticles, exchanges coupled centrosymmetric nanoparticles, exchanges coupled non-centrosymmetric nanoparticles which possess Dzyaloshinskii-Moriya interaction (DMI), and exchanged coupled Hard and soft magnetic films. Micromagnetic modeling, simulations, analytical calculations, and experimental methods are used to determine topological Hall-effect. In very small noninteracting nanoparticles, the reverse magnetic fields enhance Q due to the flower state until the reversal occurs, whereas, for particles with a radius greater than coherence radius, the Q jumps to a larger value at the nucleation field representing the curling state. The comparisons of magnetization patterns between experimental and computed magnetic force microscopy (MFM) measurements show the presence of spin chirality. Magnetic and Hall-effect measurements identify topological Hall-effect in the exchange-coupled Co and CoSi-nanoparticle films. The origin of the topological Hall-effect namely, the chiral domains with domain-wall chirality quantified by an integer skyrmion number in Co and chiral spins with partial skyrmion number in CoSi. These spin structures are different from the Skyrmions due to DMI in B-20 crystals and multilayered thin films with Cnv symmetry. In these films THE caused by cooperative magnetization reversal in the exchange-coupled Co-nanoparticles and peripheral chiral spin textures in CoSi-nanoparticles.

Advisor: Xiaoshan Xu

Chirality, Symmetry-Breaking, And Chemical Substitution In Multiferroics, Kiman Park

Doctoral Dissertations

Multiferroic materials attract significant attention due to their potential utility in a broad range of device applications. The inclusion of heavy metal centers in these materials enhances their magnetoelectric properties, yielding fascinating physical phenomena such as the Dzyaloshinskii–Moriya interaction, nonreciprocal directional dichroism, enhancement of spin-phonon coupling, and spin-orbit-entangled ground states. This dissertation provides a comprehensive survey of magnetoelectric multiferroics containing heavy metal centers and explores spectroscopic techniques under extreme conditions. A microscopic examination of phase transitions, symmetry-breaking, and structure-property relationships enhances the fundamental understanding of coupling mechanisms.

In A2Mo3O8 (A = Fe, Zn, Ni, and Mn), we use optical spectroscopy …

Synthesis, Characterization, And Simulation Of Two-Dimensional Materials, Lawrence Hudy

Theses and Dissertations

ABSTRACT

SYNTHESIS, CHARACTERIZATION, AND SIMULATION OF TWO-DIMENSIONAL MATERIALS

by

Lawrence Hudy

The University of Wisconsin-Milwaukee, 2023Under the Supervision of Professor Michael Weinert

This dissertation focuses on my journey through many aspects of surface science leading to the first principles investigation of transition metal dichalcogenides studying the impact of defects, twist, and decreasing interlayer separation to probe their effect on the electronic properties of these materials. My journey started out learning many aspects of material science such as methods for material synthesis and characterization but later ended on simulation of material properties using density functional theory. In the first experiments, we …

Nonlinear Charge And Spin Currents In Non-Centrosymmetric Electron Systems, Aniruddha Pan

All Dissertations

In this thesis, we discuss the existence of spin and charge currents in systems with broken spin inversion symmetry proportional to the magnitude square of the driving electric and thermal fields. This outcome is predicated on symmetry considerations in the momentum space, whereby the product between the current operator and the out-of-equilibrium distribution function has to be even.

First, we derive the second-order correction to the particle distribution function $\delta f^{(2)}$ in a semi-classical approximation, considering the local change in the equilibrium distribution function caused by external fields. Our approach departs significantly from the previous theory where $\delta f^{(2)}$ is …

Super-Resolution Microscopy With Color Centers In Diamond, Forrest A. Hubert

Optical Science and Engineering ETDs

This dissertation explores the development and application of diamond color centers, specifically the silicon-vacancy (SiV) and nitrogen-vacancy (NV) centers, in super-resolution microscopy and magnetic imaging techniques. It demonstrates the potential of SiV centers as photostable fluorophores in stimulated emission depletion (STED) microscopy, with a resolution of approximately 90 nm. The research also presents a method for nanoscale magnetic microscopy using NV centers by combining charge state depletion (CSD) microscopy with optically detected magnetic resonance (ODMR) to image magnetic fields produced by 30 nm iron-oxide nanoparticles. The individual magnetic feature width reaches ~100 nm while resolving magnetic field patterns from nanoparticles …

Two-Dimensional Crystal Phases Of Graphene Monoxide & Interaction Of Lithium With Graphene Monoxide, Danylo Radevych

Theses and Dissertations

This work explores the possible existence, properties, and potential applications of different polytypes of graphene monoxide (GmO) - two-dimensional crystalline monolayers composed of equal numbers of O and C atoms. In addition to previously experimentally discovered and theoretically modeled α phase, prediction and discovery of the second phase - β-GmO - is reported along with evaluation of six other possible phases. Structural parameters, electronic and mechanical properties of all the phases, including α-GmO, are determined using density functional calculations and compared. It is suggested that multiple phases of GmO can co-exist in the same composite, and developing a synthesis process …

Construction Of Zinc Oxide And Magnesium Oxide Heterostructures By Atomic Layer Deposition, Netra Sharma

Theses and Dissertations

Zinc oxide (ZnO) has gained wide technological interest due to its direct bandgap of ~3.37 eV and high exciton binding energy of ~60 meV and has exhibited promise for numerous electronics and opto-electronics applications. ZnO can also be alloyed with materials like magnesium oxide (MgO) to tailor the bandgap. Such heterostructures (Zn, Mg)O can be used in optoelectronic devices like quantum well lasers, photodetectors, etc.In this work, we studied the physical properties of zinc oxide (ZnO), magnesium oxide (MgO) and the heterostructures of zinc and magnesium oxide (Zn,Mg)O grown by atomic layer deposition (ALD) using a homemade viscous flow type …

Exploring Skyrmions Dynamics And Structure Using Neutron Scattering, W-L-Namila Chandula Liyanage

Doctoral Dissertations

Magnetic skyrmions are topologically protected chiral spin textures with great potential for next-generation consumer technologies. These magnetic structures can be described as spins continuously wrapping into a closed coplanar loop, featuring a core and fencing perimeter with opposite out-of-plane orientations. While conventional depictions of magnetic skyrmions use a two-dimensional projection, recent research underscores the importance of their three-dimensional structure in determining their topology and stability. Magnetic skyrmions typically emerge just below the curie temperature of a magnetic material, creating what is known as a skyrmion pocket. In most materials the stability pocket is at low temperatures and finite fields, however …

Growth And Emergent Functionalities Of Oxide Thin Films Utilizing Interface Engineering, Detian Yang

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

Complex oxide interfaces have offered intriguing novel emergent phenomena and multiple functionalities through interfacial reconstructions of spin, orbital, charge, and lattice degrees of freedom. Interface engineering via manipulating interfacial interaction, defects and multiple interfacial quantum charges and orders constitutes the essential method and technique to achieve desired functionalities in oxide heterostructures. In this thesis, shown are two examples of utilizing interfacial reconstruction and interfacial strain engineering to achieve intrinsic exchange bias and realize epitaxial growth of mixed-valence hexagonal manganite thin films, respectively.

Firstly, we demonstrated intrinsic exchange bias induced by interfacial reconstruction in Ni_xCo_yFe_3-x-yO …

Intercalation And High-Pressure Investigations Of Black Arsenic Phosphorus: Unraveling Material Transformations., Dinushika Vithanage

Electronic Theses and Dissertations

Black arsenic phosphorus (b-As_yP_1-y) alloys have emerged as intriguing materials within the realm of two-dimensional (2D) materials, following the discovery of black phosphorus (BP). These alloys possess capability to overcome major limitations of BP and exhibit potential for tunability and enhancement of properties making them promising materials for a wide range of applications, including lithium-ion batteries. Inspired by the intriguing findings obtained for BP, this research focuses on understanding the structural modifications that can be achieved in b-As_yP_1-y alloys through the application of intercalation and high pressure. The initial phase of our investigation …

Functionalized Go Nanoplatelets With Folic Acid As A Novel Material For Boosting Humidity Sensing Of Chitosan/Pva Nanocomposites For Active Food Packaging, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Enhanced Acousto-Optic Properties Of Silicon Carbide Based Layered Structure, Namrata Dewan Soni

Al-Bahir Journal for Engineering and Pure Sciences

This study investigates the feasibility of using silicon carbide-based layered surface acoustic wave (SAW) devices in acousto-optic applications. The acousto-optic properties of the temperature-stable layered structure TeO3/SiC/128oY-X LiNbO3 are investigated through theoretical analysis. This analysis includes the evaluation of key parameters such as the overlap integral, figure of merit, and diffraction efficiency. The SAW propagation characteristics and field profiles required for these calculations are obtained using SAW software. Results show that the layered structure has high diffraction efficiency of nearly 96% and a promising value for the acousto-optic figure of merit, indicating potential use in low driving power acousto-optic devices. …

Thermal, Magnetic, And Electrical Properties Of Thin Films And Nanostructures: From Magnetic Insulators To Organic Thermoelectrics, Michael J. M. Roos

Electronic Theses and Dissertations

Modern fabrication and growth techniques allow for the development of increasingly smaller and more complex solid state structures, the characterization of which require highly specialized measurement platforms. In this dissertation I present the development of techniques and instrumentation used in magnetic, thermal, and electrical property measurements of thin films and nanostructures. The understanding of trapped-flux induced artifacts in SQUID magnetometry of large paramagnetic substrates allows for the resolution of increasingly small moments. Using these methods, the antiferromagnetic coupling of the interface between a Y₃Fe₅O₁₂ film and Gd₃Ga₅O₁₂substrate is quantitatively …

The Study Of Excitons In 2d Novel Materials And Their Van Der Waals Heterostructures In The Magnetic Field, Anastasia Spiridonova

Dissertations, Theses, and Capstone Projects

This research focuses on the direct and indirect excitons in Rydberg states in monolayers, bilayers, and van der Waals heterostructures composed of 2D semiconductors in the presence of the external magnetic field. In our work, we report binding energies of direct and indirect excitons in Rydberg states, the energy contribution from the magnetic field to the binding energies of magnetoexcitons, and diamagnetic coefficients (DMCs) of magnetoexcitons.

We study isotropic materials: transition metal dichalcogenides, TMDCs (WSe₂, WS₂, MoSe₂, MoS₂), and Xenes (silicene, germanene, stanene), and anisotropic materials: phosphorene and transition metal trichalcogenides, TMTCs …