Condensed Matter Physics Commons^™

Emission Spectroscopy Of Ingaas Quantum Dots Via High-Resolution Fabry-Perot Interferometer, Raju Bhai Kc

Graduate Theses, Dissertations, and Problem Reports

Single photons emitted from self-assembled quantum dots have been widely studied to use as a promising qubit for quantum information processing. Therefore, it is critical to fully understand the emission spectra from the quantum dot's excitation if we want to use a single photon as a quantum bit. It is almost impossible to produce rotationally symmetric quantum dots due to various growth conditions and restrictions. So the real quantum dots do not have a perfectly symmetric structure. A broken rotational symmetry causes an asymmetric exchange interaction between electron and hole, leading to a fine structure splitting between two excited states. …

Study Of Electronic And Magnetic Properties Of Bilayer Graphene Nanoflakes And Bimetallic Chalcogenides Using First-Principles Density Functional Theory And Machine Learning, Dharmendra Pant

Dissertations, Master's Theses and Master's Reports

Graphene, a one-atom-thick material, has been a wonder material since its discovery because of its superlative electronic, mechanical, and optical properties. When a layer of graphene is rotated over another layer, it exhibits many intriguing behaviors, ranging from superconductivity to the anomalous Hall effect to ferromagnetism at a magic angle of 1°, and hence the twisted bilayer graphene has been the subject of intense research in recent years. The surge in interest in this moiré structure can be attributed to the emergence of electronic flat minibands near the magic angle. Here, we studied the electronic and magnetic properties of twisted …

Discovering And Understanding High Performance Materials Using Density Functional Theory: Quantum Mechanical Simulations And The Consequences Of Symmetry, Olivia M. Pavlic

Graduate Theses, Dissertations, and Problem Reports

There are two primary ways that atomic level modeling data is used: materials prediction and understanding materials properties. This dissertation work encom- passes two studies, each of which explore one application. Both studies rely on the highly successful density functional theory (DFT) formalism but differ in that two different implementations of DFT are used on two different high performance materials. The first study on bulk magnesium (Mg) metal alloys explores materials prediction and relies on VASP, a commercially maintained plane-wave DFT code which has been used extensively to successfully study a wide range of materials. [1] The approach used in …

Exploring Mottness And Electronic Order In Strongly Correlated Vanadate Thin Films, Nathan Bairen

UNF Graduate Theses and Dissertations

Mott insulators provide a window into some of the most intensely investigated phenomena in physics. Recent discoveries—including the emergence of high-temperature superconductivity in doped Mott insulators not from the cuprate family of superconductors—have inspired investigation into systems with strong electron-electron interactions. One of these systems is La_1-xSr_xVO₃, in which one end-member, LaVO₃, is a Mott insulator and the other, SrVO_3, is a strongly correlated metal.

Herein, we detail two studies regarding this system. In our oxidation study, we optimized the growth parameters for LaVO_3, finding that the ultra-high vacuum technique …

Development Of High Kinetic Inductance Superconducting Nanowire Devices On High Permittivity Strontium Titanate Substrates, Jamie Timmons

UNF Graduate Theses and Dissertations

This thesis involves the fabrication and characterization of devices made from two different superconducting materials: yttrium barium copper oxide (YBCO), a high-TC complex oxide, and niobium nitride (NbN), a low-TC transition metal nitride. Both types of devices are fabricated on strontium titanate substrates, which provides a good lattice match to YBCO and also an extremely large permittivity at low temperature. We demonstrate that wet etching of YBCO thin films via bromine can be a viable microfrabriation technique for the material. Using approximately 35 nm thick epitaxially grown YBCO on an STO substrate, we were able to fabricate YBCO “microwires” with …

Aspects Of Topology In Moiré Graphene, Ahmed Khalifa

Theses and Dissertations--Physics and Astronomy

Moiré materials, such as twisted bilayer graphene, have provided a rich platform for fundamental physics and potential technological applications. Superconductivity,
correlated insulators, and Chern insulators are examples of phenomena that have been found experimentally in moiré systems. The interplay of strong electron-electron interactions and topology lies at the heart of the mechanism driving these phenomena. In this work, we study the topological aspects of moiré graphene materials, such as the valley Chern and Chern insulating phases. To study the topological response of these phases, we construct models to describe the edge states which are the telltale signs of nontrivial topology. …

Growth And Characterization Of Sm3hfbi5, Patrick Lambdin

MSU Graduate Theses

First found experimentally in 2015, topological Weyl materials are desirable compounds that have garnered much interest due to their ability to conduct electricity via their surface states even though the bulk material is a semimetal. Such a candidate, Sm3HfBi5, was discovered with a flux crystal growth method, following an extensive amount of reaction syntheses. This thesis reports on the discovery, growth, structural characterization via x-ray diffraction, and magnetization measurements on Sm3HfBi5.

Diffuse Scattering And 3d-∆Pdf Analyses: Order-Disorder Phase Transitions In (Sr1−Xcax)3rh4sn13 And Nano2, Puspa Upreti

Graduate Research Theses & Dissertations

Classification of structural phase transitions as being of the displacive or order-disorder types is usually done based on spectroscopic measurements performed above the transition. Transitions of the displacive type typically occur when soft phonon modes condense upon approaching the phase transition, whereas those of the order-disorder type are characterized by structures in which the atoms are located randomly above the phase transition at T* at the minima of a multiwell potential. In the ordered state, i.e., when T

We have performed single crystal x-ray scattering experiments and three-dimensional pair distribution functions (3D-∆PDF) analyses to understand the nature of phase transitions …

Investigation Of Role Of Tungsten Ions On Structural And Optical Properties Of Sodium Borosilicate Germanate Glass For Optoelectronic Applications, Mohamed Mundher, Mohammed A. Farag, Ayman A. Bendary, Mohamed Y. Hassaan, Abu Bakr El-Bediwi

Al-Azhar Bulletin of Science

In the current work, the role of tungsten ions on the structural and optical properties of sodium borosilicate germinate glass with the composition [70 Na 2B4O7e15 SiO2e(15-x) (Ge2O3) e x (WO3) while, x ¼ 0,2,4, 6, 8 mol %] were studied. Fast quenching method were used to prepare the glass samples. Experimental and empirical density results confirm the amorphous nature of the prepared samples. Fourier transform infrared, FTIR, results showed N4 decreases as WO3 increases. These results suggest that the decreasing in non-bridging oxygen (NBO), back conversion BO4 to BO3, occur by the increase of WO3. Optical band gap show …

Investigations Into The Electronic And Magnetic Properties Of (Crps4)N Layers, Alexandria R. Alcantara

UNF Graduate Theses and Dissertations

2D magnetic semiconductors have become of interest due to their magneto-optical effects in lower dimensionality. More specifically, CrPS4 has gained renewed attention due to its A-type AFM order and air stability prompting analysis and stability studies in its layered forms for use in scalable technology such as spintronic and optoelectronic devices. In this study, we benchmark our approach using the SCAN meta-GGA functional used without U-parameterization on bulk CrPS4 to demonstrate the accuracy of our methodology to use as tools to go beyond current CrPS4 theoretical studies. We examine the 2D electronic nature and optical spectrum for use in experimental …

Surface Reconstruction In Iron Garnets, Sushree Dash

Dissertations, Master's Theses and Master's Reports

This dissertation presents the results of a study investigating the physical mechanisms underlying an unexpectedly large increase in magneto-optic efficiency observed in iron garnet. Such materials are technologically important for telecommunications due to their nonreciprocal optical action. In the past, our group had found evidence of an enhanced Faraday rotation in bismuth-substituted iron garnet films less than 50 nm thick. Subsequent investigation revealed that this enhancement could be traced to surface effects. This is significant because understanding these phenomena could be used to formulate engineering solutions for device miniaturization. In this dissertation, we present the result of a research project …

A Method For Single-Particle Magnetic Particle Spectroscopy With A Nanofabricated Coplanar Stripline, Jacob Martin

Theses and Dissertations

Drawing from magnetic particle imaging principles, magnetic particle spectroscopy (MPS) serves as a valuable tool employing superparamagnetic iron-oxide nanoparticles (SPIONs) in diverse applications ranging from medical imaging to biosensing and the comprehensive study of magnetic particles’ characteristics. MPS leverages the nonlinear response exhibited by SPIONs when a external magnetic field is applied, enabling a highly sensitive method for examining biological systems and more. However, conventional MPS setups demand a high particle concentration of approximately 10^15 particles per liter to generate a detectable response. The first objective of this work is to simulate the dynamics of a system with the ability …

Long-Range And Chaotic Active Mixing Of Swimming Microbes In A Vortex Chain Flow, Nghia Le

Honors Theses

We present experiments studying the motion and active mixing of swimming mi- crobes in laminar, vortex-dominated fluid flows. We are testing a theory that predicts the existence of swimming invariant manifolds (SwIMs) - invisible, one-way barriers blocking the paths of self-propelled tracers in the flow in one direction. We also pro- pose that the SwIMs together can form chute structures in three-dimensional phase space that facilitate cross-vortex transport of the microbes. We also observe evidence of how these structures promote long-range transport at different non-dimensional velocities (microbe’s velocity relative to flow velocity). Long-range transport is quan- tified by measuring the …

Structural And Magneto Conductivity Studies Of Nio/Smba2cu3o7-Δ Superconducting Composite, Hadi Basma, Sajida Rmeid, Ramadan Awad, Mohammed Said

BAU Journal - Science and Technology

In this work, we investigate the effect of NiO nanoparticles' addition on the structure, superconductivity, and magneto conductivity for the SmBa₂Cu₃O_7-δ phase. Composite nano/superconductor of (NiO)_x/SmBa₂Cu₃O_7-δ (0.00≤x≤0.12 wt.%) were prepared by conventional solid-state reaction technique and characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The orthorhombic structure was maintained whereas the lattice parameters showed unsystematic variations with the NiO nanoparticles addition. The superconducting transition temperature T_c, determined from electrical resistivity measurements, showed an enhancement with x up to 0.04wt.% followed by a reduction …

Perspectives On Determinism In Quantum Mechanics: Born, Bohm, And The “Quantal Newtonian” Laws, Viraht Sahni

Publications and Research

Quantum mechanics has a deterministic Schrödinger equation for the wave function. The Göttingen–Copenhagen statistical interpretation is based on the Born Rule that interprets the wave function as a “probability amplitude.” A precept of this interpretation is the lack of determinism in quantum mechanics. The Bohm interpretation is that the wave function is a source of a field experienced by the electrons, thereby attributing determinism to quantum theory. In this paper, we present a new perspective on such determinism. The ideas are based on the equations of motion or “Quantal Newtonian” Laws obeyed by each electron. These Laws, derived from …

Highly Efficient Photocatalysts For Methylene Blue Degradation Based On A Platform Of Deposited Go-Zno Nanoparticles On Polyurethane Foam, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Pyseg: A Python Package For 2d Material Flake Localization, Segmentation, And Thickness Prediction, Diana B. Horangic

Student Research Projects

Thin materials are of interest for their extraordinary physical, mechanical, thermal, electrical, and optical properties. Monolayers and bilayers of 2D materials can be manufactured through a variety of exfoliation methods. To determine layer thickness, Raman spectroscopy or other methods like Rayleigh scattering are used. These methods are, however, slow, and they require equipment beyond an optical microscope. A Python package that automates flake identification processes was built, with access solely to RGB data from an optical microscope assumed. My package, pyseg, localizes flakes on a substrate and then makes a rough estimate of their thickness from first principles. It can …

Spacecraft Charging Test Considerations For Composite Materials, Allen Andersen, Wousik Kim, J. R. Dennison, Brian Wood, Todd A. Schneider, Jason Vaughn, Kenneth H. Wright Jr., Nelson W. Green, Eric Suh, Joel Schwartz, Abdul-Majeed Azad

Journal Articles

Composite materials present a growing challenge for spacecraft charging assessments. We review some recent lessons learned for charging tests of composite materials using both parallel-plate and electron beam test geometries. We also discuss examples of materials that exhibit significant variations between samples, despite them all having the same trade name.

Towards The Electronic Response Of Carbon-Based Van Der Waals Heterostructures In A Diamond Anvil Cell, George Thomas Foskaris

UNLV Theses, Dissertations, Professional Papers, and Capstones

The nanoscale regime of materials has been at the forefront of research and interest in condensed matter physics for many years. In a merger of the fields of two-dimensional (2D) materials and high pressure physics, we present an investigation of the electronic response of carbon-based, van der Waals (vdW) heterostructures in a diamond anvil cell (DAC). Combining these fields presents us with the ability to study the characteristics of such systems both optically, and through electrical transport. Properties such as conductance, band structure, and layer number are considered. The samples in this study are assembled using exfoliation and stacking techniques …

Characterization Of Losses In Superconducting Radio-Frequency Cavities By Combined Temperature And Magnetic Field Mapping, Ishwari Prasad Parajuli

Physics Theses & Dissertations

Superconducting radio-frequency (SRF) cavities are one of the fundamental building blocks of modern particle accelerators. To achieve the highest quality factors (10¹⁰-10¹¹), SRF cavities are operated at liquid helium temperatures. Magnetic flux trapped on the surface of SRF cavities during cool-down below the critical temperature is one of the leading sources of residual RF losses. Instruments capable of detecting the distribution of trapped flux on the cavity surface are in high demand in order to better understand its relation to the cavity material, surface treatments and environmental conditions. We have designed, developed, and commissioned two novel …