Condensed Matter Physics Commons^™

Ab Initio Studies Of Structure And Properties Of Group-Iv Monochalcogenide Monolayers, Shiva Prasad Poudel

Graduate Theses and Dissertations

The goal of this dissertation is to study the structure of ferroelectric group-IV monochalcogenide monolayers (MMLs) and their material properties. This work also established a new buckled honeycomb phase of these monolayers. Chapter 1 serves as an introduction where the motivation for these studies is established. In chapter 2, I used eight different exchange-correlation functionals (XC) to study the structure of these 2D ferroelectrics and found that their properties are independent of the choice of XC functionals. These findings reveal that the ground-state ferroelectric unit cell can be described by only five independent parameters, whereas their paraelectric (square or rectangular) …

Crystal Growth And Property Tuning Of Layered Magnetic Topological Semimetals, Krishna Pandey

Graduate Theses and Dissertations

The demand for energy-efficient devices has been growing rapidly due to the need for data-driven technologies and the global energy crisis. As device size approaches the atomic scale, the miniaturization of electronic devices may stop in the near future unless fundamentally new materials or device concepts are developed. The emergent topological materials with exotic properties show remarkable robustness against crystal lattice defects, which are promising for next-generation technology. These materials host exotic properties such as high mobility, large magnetoresistance, chiral anomaly, and surface Fermi arcs, etc. Among various topological materials, the ZrSiS-family materials exhibit two types of Dirac states, which …

Towards Highly Sensitive Capacitance Measurements Of A Quantum Anomalous Hall Phase In Van Der Waal Heterostructures, Kayla Cerminara

UNLV Theses, Dissertations, Professional Papers, and Capstones

One of the pioneering achievements in condensed matter physics of the 20th century is the observation of the quantum Hall e↵ect (QHE) in which the Hall resistance in a two-dimensional (2D) sample takes on quantized values in the presence of a strong perpendicular magnetic field. The precise quantization of the hall resistance to one part in a billion has provided a practical, worldwide resistance standard. A long-standing goal has been to realize a similar state of matter but without the need of a strong quantizing magnetic field. The quantum anomalous Hall e↵ect (QAHE) is such a state that is predicted …

Tuning Properties Of Topological Insulators: An Ab-Initio Approach, Karunya Shailesh Shirali

LSU Doctoral Dissertations

This thesis develops a first-principles based approach to explore the tuning of topological properties of the tetradymite topological insulators. We begin by setting up a framework to systematically obtain the bulk and surface properties of topological insulators, treating the structural and electronic properties on an equal footing. We determine a consistent method for including the van der Waals interactions, which are responsible for the weak coupling between sets of atomic layers in this family of layered materials, which is important in obtaining accurate structural properties. We obtain close agreement with experimental values for both the bulk and surface states.

To …

Synthesis And Characterization Of Chiral Magnetic Oxide: Mnmoteo6, Chase Hames, August Meads

Symposium of Student Scholars

The chiral materials lack mirror reflection symmetry in their crystal structures like right and left hands. Such materials often host unique non-collinear or topological magnetic textures such as magnetic skyrmions. If such magnetic textures are formed in insulating oxides with coupled electric and magnetic properties, then such magnetic structures can be controlled and manipulated using electric fields rather than electric current. With this motivation, we are synthesizing and characterizing chiral materials belonging to MMoTeO₆ (M=Mn, Co, Fe, Cu, Ni) family. I will discuss about the phase formation and solid-state synthesis of MnTeMoO₆ along with its structural, electrical and …

Modeling The Effects Of Surface Roughness On Electron Yield, Trace Taylor, Matthew Robertson, Jr Dennison

Conference Proceedings

Surface conditions—including surface morphology, composition, contamination, and oxidation—can significantly affect electron yields and consequently spacecraft charging. The effects of surface roughness on electron yield are modeled in this study by considering four aspects of electron yield calculations: (i) simple models of rough surface geometry, (ii) the angular distributions of electrons emitted from various points on these surfaces, (iii) the likelihood of these emitted electrons escaping the rough surface, and (iv) the relative fractions of smooth and rough surfaces. Three simple periodic one-dimensional surface profiles were considered—namely rectangular, triangular, and sawtooth features; each surface profile was characterized by an aspect ratio …

Laboratory Simulations Of Simultaneous Reduced Gravity And Ionizing Radiation Environments, Achal Duhoon, Jr Dennison

Conference Proceedings

A novel system has been developed to simulate the combined effects of reduced gravity and ionizing radiation present during spaceflight on biological and particulate samples. The miniature rotary cell culture system (mRCCS) was designed to synchronously rotate up to five independent vessels containing particulate samples suspended in fluid media, constructed using radiation tolerant, biocompatible, and vacuum compatible materials. Reduced gravity conditions were achieved when particles (e.g., 200 µm polystyrene microcarrier beads with or without adhered cell clusters) were suspended inside the vessels moving near terminal velocity in viscous fluid media with densities matched to the suspended …

Exploring Magneto-Excitons In Bulk And Mono-Layer Semiconductors Using Non-Linear Spectroscopy Techniques, Varun Mapara

USF Tampa Graduate Theses and Dissertations

The research in two-dimensional (2D) materials has evolved from ``traditional" quantum wells based on group III-V and II-VI semiconductors to atomically thin sheets of van der Waals materials such as 2D semiconducting Transition Metal Dichalcogenides (TMDs). These 2D materials remain a stimulating field that continues to introduce new challenges. From both a fundamental physics and technological perspective, magneto-optical spectroscopy has been an essential tool in this research field. TMDs, for example, pose the challenge of characterizing their spin-valley-resolved physics and deriving implications in quantum computation and information research. With the discovery of valley Zeeman effects, the spin-valley physics of TMDs …

Assessment Of Radiation Exposure Levels From Selected Scrap Metal Stores In Dar Es Salaam, Tanzania, Innocent J. Lugendo

Journal of Humanities and Social Sciences

This study analyses the radiation exposure rate emanating from scrap metal stores in Dar es Salaam, Tanzania, using the ion chamber based survey meter and a Gamma-Scout radiation detector. Two (2) scrap metal stores located at Manzese and Ubungo-External were selected for the investigation. The radiation exposure rates in μSv/hr at 20 randomly selected points in each store were determined using a survey meter. More readings were taken at points 100m away from each of the stores to establish the background radiation exposure. From the readings of the survey meter, 3 points with the highest radiation exposure rates from each …

Review Of Elastic Light Scattering From Single Aerosol Particles And Application In Bioaerosol Detection, Yong-Le Pan, Kevin B. Aptowicz, Jessica Arnold, Samuel Cheng, Aimable Kalume, Patricio Piedra, Chuji Wang, Joshua Santarpia, Gorden Videen

Physics & Engineering Faculty Publications

Elastic light scattering (ELS) from single micron-sized particles has been used as a fast, non-destructive diagnostic tool in life science, physics, chemistry, climatology, and astrophysics. Due to the large scattering cross-section, ELS can be used to find trace amounts of suspect particles such as bioaerosols among complex, diverse atmospheric aerosols, based on single-particle interrogation. In this article, we briefly summarized the main computational models and instrumentation developed for ELS, then reviewed how properties like particle size, refractive index, degree of symmetry, and surface roughness, in addition to packing density, shape of primary particles in an aggregate, and special helix structures …

Charge Transport And Spin Dynamics Of Color Centers In Diamond, Damon Daw

Dissertations, Theses, and Capstone Projects

Solid state defects in diamond are promising candidates for room temperature quantum information processors (1, 3, 5). Chief among these defects is the nitrogen vacancy center (‘NV center’ or ‘NV’). The NV has long coherence times (at 300K) and its state is easily initialized, manipulated and read out (5). However, the outstanding issue of entangling NV centers in a scalable fashion, at room temperature remains a challenge. This thesis presents experimental and theoretical work aimed at achieving this goal by developing the ‘flying qubit’ framework in (1). This method for remote entanglement utilizes a charge carrier (initialized into a definite …

Modeling Defect Mediated Color-Tunability In Leds With Eu-Doped Gan-Based Active Layers, Hayley J. Austin, Brandon Mitchell, Dolf Timmerman, Jun Tatebayashi, Shuhei Ichikawa, Yasufumi Fujiwara, Volkmar Dierolf

Physics & Engineering Faculty Publications

Color tunability from red to orange to yellow has been demonstrated in GaN-based LED devices with Eu-doped GaN layers as the active region. Under current injection, this is achieved by varying the current density and the pulse conditions. The underlying mechanism behind this color tunability is a redistribution of energy among the D-5(J) states of a Eu3+ ion. This energy shuffling is facilitated by a local defect that has been neglected in previous modeling work. Including this defect allows for a quantitative prediction of the relative time-averaged populations of the Eu3+ ion's D-5(0) and D-5(1) states. Extracting, from experimental results, …

Microwave-Assisted Synthesis Of Co-Doped Sno2/Rgo For Indoor Humidity Monitoring, Mohamed Morsy

Nanotechnology Research Centre

The evaluation of indoor humidity is challenging compared to other environmental parameters such as light intensity, temperature, sound and so forth. The proper selection of sensing materials and structural tuning will lead to high-performance humidity sensors. Herein, the SnO2/rGO and SnO2/rGO doped with Co nanocomposite were produced by microwave route. The obtained nanocomposite was characterized by XRD, SEM, EDAX, DTA, TGA, FTIR, Raman, and HRTEM. The successful incorporation of Co onto the rGO/SnO2 is affrmed by the XRD and supported with matching SEM and TEM outcomes where nanoscale particles exist. FTIR reveals the existence of the C– –C stretching band …

Quantum Capacitance Investigation Of Different Tas2 Polymorphs For Energy Storage Applications – First Principles Study, Mahmoud Elattar

Theses and Dissertations

Energy is an essential requirement, which has a growing demand due to the growth of population and the world transformation into electronic. More than 70% of energy resources are fossil-fuel based which has an environmental impact due to the CO₂ emissions. Energy hubs for Fossil-fuel to electric energy conversion, controlled CO₂ emissions processing units, and energy storage system are key factors for a smooth transition to green energy without lack of energy supplies, where electrical energy storage systems (ESS) are key enablers to achieve that. One of the effective components which determines the ESS efficiency is the electrode …

Investigating The Mechanical Performance Of Nano Additives Reinforced High-Performance Concrete, Mohamed Morsy

Nanotechnology Research Centre

It is known that nanomaterials have been broadly employed worldwide as reinforcements for the production of high-strength and high mechanical performance concrete-based structures. Hereinafter, high-performance concrete (HPC) modifed with three types of additives were synthesized: exfoliated nano clay (NC), nano-silica (NS), and hybrid particles [silica fume (SF) & limestone (LS)]. The compressive, splitting tensile and flexural strengths, were investigated at 28 days of hydration. The exfoliated NC was simply prepared via exfoliating the thermally activated ordinary clay with the aid of organic ammonium chloride. The results revealed that all types of the employed additives provided an augmentation in the mechanical …

Oxide Two-Dimensional Electron Gas With High Mobility At Room-Temperature, K. Eom, H. Paik, J. Seo, N. Campbell, Evgeny Y. Tsymbal, S. H. Oh, M. Rzchowski, D. G. Schlom, Chang-Beom Eom

Evgeny Tsymbal Publications

No abstract provided.

Ferroelectric Control Of Magnetic Skyrmions In Two-Dimensional Van Der Waals Heterostructures, K. Huang, Ding-Fu Shao, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

No abstract provided.

Tilted Spin Current Generated By The Collinear Antiferromagnet Ruo2, A. Bose, N. J. Schreiber, R. Jain, Ding-Fu Shao, H. P. Nair, J. Sun, X. S. Zhang, D. A. Muller, D. A. Muller, Evgeny Y. Tsymbal, D. G. Schlom, D. C. Ralph

Evgeny Tsymbal Publications

No abstract provided.

Toward Novel Optical Functionalities Through Intelligent Photonic Structure Design, Robert J. Williamson

College of Graduate Studies: Theses & Dissertations

Photonic Metamaterials is a branch of electromagnetism that has been of great interest in recent years. This is further enhanced by the introduction of micro- and nanofabrication methods capable of producing metamaterial structures with which it is possible to create specific optical phenomena. The study of iso-frequency k-surfaces is of importance when discussing optical interactions with media. Previous research found evidence of materials exhibiting k-surfaces of bi-hyperbolic nature, though they failed to find any further hyperboloid dispersions. In this thesis we describe the k-surface topologies and including tri- and tetra-hyperbolic as well as analyze the polariton-interactions that cause these hyperbolic …

A Modulated Structure Derived From The Xa-Type Mn2Rusn Heusler Compound, Xingzhong Li, Wen-Yong Zhang, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

A modulated structure derived from the inverse Heusler phase (the XA-type and the disordered variant L2₁B-type) has been observed in rapidly quenched Mn2RuSn ribbons. The powder X-ray diffraction pattern of the quenched ribbons can be indexed as an L2₁B-type structure. Electron diffraction patterns of the new structure mostly resemble those of the XA-type (and the disordered variant L2₁B-type) structure and additional reflections with denser spacing indicate a long periodicity. Orthogonal domains of the modulated structure were revealed by a selected-area electron diffraction pattern and the corresponding dark-field transmission electron microscopy images. The structure was …