Condensed Matter Physics Commons^™

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.

Tunneling Time And Faraday/Kerr Effects In Pt-Symmetric Systems, Peng Guo, Vladimir Gasparian, Antonio Antonio Perez-Garrido, Ester Jodar Ferrandez

Research & Publications

We review the generalization of tunneling time and anomalous behaviour of Fara- day and Kerr rotation angles in parity and time (PT )-symmetric systems. Similarities of two phenomena are discussed, both exhibit a phase transition-like anomalous behaviour in a certain range of model parameters. Anomalous behaviour of tunneling time and Faraday/Kerr angles in PT -symmetric systems is caused by the motion of poles of scattering amplitudes in the en- ergy/frequency complex plane.

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 …

Optimizing Mn-Al Permanent Magnet Performance Through Control Of The Phase Transformation, Ternary Element Addition, And Advanced Processing, Thomas R. Keller

Dartmouth College Ph.D Dissertations

The growing need for electrical power in machines and vehicles brings with it a growing need for critical materials. The current high-performance permanent magnets (PMs) based on rare-earth (RE) elements Nd and Sm cannot escape the problem of raw material cost, geographic scarcity in the earth’s crust, and lack of circular global supply chains. This poses a problem of industrial ecology: can PMs be made from inexpensive, more abundant materials while still meeting sufficient performance criteria? PMs based on the magnetic τ phase of Mn-Al offer a possible alternative to REPMs. However, years of innovation have not yet achieved real-world …

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 …

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, …

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- …

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

Modifying The Composition Of A High Temperature Superconductor, Drue Lubanski

Electronic Theses and Dissertations

The purpose of this research was to recreate a known superconductor, YBa₂Cu₃O_x, and modify it in an attempt to raise its transition temperature. A superconductor is any material that excludes magnetic flux from its interior when at a temperature below its transition temperature. A “high temperature” superconductor refers to material that shows superconductivity at or above the temperature of liquid nitrogen temperatures (77.15K).

Here we were successful in reproducing the original YBa₂Cu₃O_x and measuring its critical temperature; However, our efforts at raising the transition temperature have, as of yet, …

Strong Ultrafast Demagnetization Due To The Intraband Transitions, G. P. Zhang, Mitsuko Murakami

Symposium Projects

Demagnetization in ferromagnetic transition metals driven by a femtosecond laser pulse is a fundamental problem in solid state physics, and its understanding is essential to the development of spintronic devices. Ab initio calculation of time-dependent magnetic moment in the velocity gauge so far has not been successful in reproducing the large amount of demagnetization observed in experiments. In this work, we propose a method to incorporate intraband transitions within the velocity gauge through a convective derivative in the crystal momentum space. Our results for transition-element bulk crystals (bcc Fe, hcp Co and fcc Ni) based on the time-dependent quantum Liouville …

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 …

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 …

Insights Into The Structural And Electronic Properties Of 2d Polar Sic/Gec Heterostructures And Asxp1−X Alloys., Kazi Jannatul Tasnim

Electronic Theses and Dissertations

Due to the unique structural and electronic properties along with the practical applications in current and near future, investigations about the group-IV graphene-like two-dimensional (2D) sheets have been accelerated. Among them, 2D SiC and GeC sheets are polar materials with in-plane charge transfer from Si (Ge) to C atoms. An interesting question is how the electrostatic force, triggered by such in-plane charge transfer, plays a role in stabilizing the vertical heterostructures formed by 2D SiC and GeC sheets beyond vdW interaction. To answer this question, we have systematically investigated, in my PhD research projects, the effects of the electrostatic interaction …

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 …

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 …

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

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. …

Phase Transitions And Magnetocaloric Effects In Metastable Phases Of Intermetallic Compounds, Tej Bahadur Poudel Chhetri

LSU Doctoral Dissertations

The interplay between spin and lattice degrees of freedom in magnetic materials often results in interesting magnetoresponsive effects. The magnetocaloric effect is one such magnetothermal phenomenon that may be utilized in energy-efficient magnetic cooling systems. This effect becomes more prominent near a coupling of magnetic and structural transitions, i.e., magnetostructural transitions (MSTs). This dissertation investigates phase transitions (magnetic and structural) in metastable phases of MnNiGe- and MnCoGe-based compounds generated through high-pressure synthesis/annealing and thermal quenching techniques and assesses their magnetocaloric effects.

First, the effects of doping, hydrostatic pressure, and thermal quenching on phase transitions and related magnetocaloric effects in Mn …

Dynamical Polymer Chain Heterogeneities And Their Impacts On The Glass Transition, William Forrest Drayer

USF Tampa Graduate Theses and Dissertations

The utilization of polymeric materials has endured since prehistory, at first unknowinglyin the form of natural biopolymers such as wood and leather, culminating and continuing through the development of the plastics industry in the early twentieth century. Polymers, along with other materials including silicate glasses, readily exhibit the glass transition upon quenching: a continuous but rapid change from viscous (liquid) to elastic (solid) behavior. The physics surrounding the glass transition have been studied for over a century; while considerable progress has been made, there remains no universally accepted predictive theory of the glass transition. Modern development of glassy materials consists …

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 …

Design And Implementation Of Montmorillonite Clay-Based Catalyst For Carbon Nanotube Synthesizing, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Synthesis And Functional Properties Of La2fecro6 Based Nanostructures, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Effective Nanomembranes From Chitosan/Pva Blend Decorated Graphene Oxide With Gum Rosin And Silver Nanoparticles For Removal Of Heavy Metals And Microbes From Water Resources, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Effective Non-Hermiticity And Topology In Markovian Quadratic Bosonic Dynamics, Vincent Paul Flynn

Dartmouth College Ph.D Dissertations

Recently, there has been an explosion of interest in re-imagining many-body quantum phenomena beyond equilibrium. One such effort has extended the symmetry-protected topological (SPT) phase classification of non-interacting fermions to driven and dissipative settings, uncovering novel topological phenomena that are not known to exist in equilibrium which may have wide-ranging applications in quantum science. Similar physics in non-interacting bosonic systems has remained elusive. Even at equilibrium, an "effective non-Hermiticity" intrinsic to bosonic Hamiltonians poses theoretical challenges. While this non-Hermiticity has been acknowledged, its implications have not been explored in-depth. Beyond this dynamical peculiarity, major roadblocks have arisen in the search …

Oxidation Resistance Of An Atomically Flat Cu(111) Surface: A First-Principles Study, Bipin Lamichhane

Theses and Dissertations

The first-principles calculation based on density functional theory (DFT) was used to study the oxidation resistance of atomically flat and atomic-step edges of Cu(111), diffusion of Cu atoms in different surfaces of alumina and interface properties of alumina and Cu(111), and magnetic properties of Mn-substituted strontium hexaferrite. The dissociation of oxygen molecules is the primary reason for the corrosion of metals, which deteriorates their application. Cu(111) flat surface, mono-atomic, and multi-atomic step edges were used to study oxygen diffusion. Penetration of oxygen on a Cu(111) flat surface requires high energy, indicating oxidation resistance. Our DFT result of oxygen diffusion into …

Origin And Structure Of The First Sharp Diffraction Peak Of Amorphous Solids, Devilal Dahal

Dissertations

Several explanations have been reported in the literature about the origin of extended-range oscillations (EROs) in the atomic pair-correlation function of amorphous materials. Although the radial ordering beyond the short-range order of about 5 Å has been extensively studied in amorphous materials, the exact nature of the radial ordering beyond a nanometer is still not resolved. This dissertation address this problem and explains the nature of the EROs by using high-quality models of amorphous silicon (a-Si) obtained from Monte Carlo and Molecular Dynamics simulations. The extended-range ordering in a-Si is examined through radial oscillations on the length …

Domain Wall Saddle Point Morphology In Ferroelectric Triglycine Sulfate, C. J. Mccluskey, A. Kumar, Alexei Gruverman, I. Luk’Yanchuk, J. M. Gregg

Alexei Gruverman Publications

Ferroelectric domain walls, across which there is a divergence in polarization, usually have enhanced electrical conductivity relative to bulk. However, in lead germanate, head-to-head and tail-to-tail walls are electrically insulating. Recent studies have shown that this is because, when oppositely oriented domains meet, polar divergence is obviated by a combination of domain bifurcation and suspected local dipolar rotation. To explore the uniqueness, or otherwise, of this microstructure, we have used tomographic piezoresponse force microscopy to map three-dimensional domain morphologies in another uniaxial ferroelectric system: triglycine sulfate. This mapping reveals an abundance of domain wall saddle points, which are characteristic of …

Fabrication Of Black Phosphorus Terahertz Photoconductive Antennas, Nathan Tanner Sawyers

Physics Undergraduate Honors Theses

Terahertz (THz) photoconductive antennas (PCAs) using 40nm thin-film flakes of black phosphorus (BP) and hexagonal boron nitride (hBN) have been shown computationally to be capable of THz emission comparable to those based on GaAs [2]. In this paper, I briefly describe the scientific and practical interest in THz emissions and explain what warrants research into black phosphorus as a photoconductive semiconductor in THz devices. Furthermore, I outline the basic principle of how these antennas work and mention alternative designs produced by other researchers in the past. Finally, I summarize the fabrication process of these antennas, as well as the measurements …