Physics Commons^™

Quantitative, Photocurrent Multidimensional Coherent Spectroscopy, Adam Halaoui

Electronic Theses and Dissertations

Multidimensional coherent spectroscopy (MDCS) is a quickly growing field that has a lot of advantages over more conventional forms of spectroscopy. These advantages all come from the fact that MDCS allows us to get time resolved correlated emission and absorption spectra using very precisely chosen interactions between the density matrix and the excitation laser. MDCS spectra gives the researcher a lot of information that can be extracted purely through qualitative analysis. This is possible because state couplings are entirely separated on the spectra, and once we know how to read the data, we can see how carriers transport in the …

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 …

Building A Quantum Engineering Undergraduate Program, Abraham Asfaw, Alexandre Blais, Kenneth R. Brown, Jonathan Candelaria, Christopher Cantwell, Lincoln D. Carr, Joshua Combes, Dripto M. Debroy, John M. Donohue, Sophia E. Economou, Emily Edwards, Michael F. J. Fox, Steven M. Girvin, Alan Ho, Hilary M. Hurst, Zubin Jacob, Blake R. Johnson, Ezekiel Johnston-Halperin, Robert Joynt, Eliot Kapit, Judith Klein-Seetharaman, Martin Laforest, H. J. Lewandowski, Theresa W. Lynn, Corey Rae H. Mcrae, Celia Merzbacher, Spyridon Michalakis, Prineha Narang, William D. Oliver, Jens Palsberg, David P. Pappas, Michael G. Raymer, David J. Reilly, Mark Saffman, Thomas A. Searles, Jeffrey H. Shapiro, Chandralekha Singh

Faculty Research, Scholarly, and Creative Activity

Contribution: A roadmap is provided for building a quantum engineering education program to satisfy U.S. national and international workforce needs.

Background: The rapidly growing quantum information science and engineering (QISE) industry will require both quantum-aware and quantum-proficient engineers at the bachelor's level.

Research Question: What is the best way to provide a flexible framework that can be tailored for the full academic ecosystem?

Methodology: A workshop of 480 QISE researchers from across academia, government, industry, and national laboratories was convened to draw on best practices; representative authors developed this roadmap.

Findings: 1) For quantum-aware engineers, …

Compressible Hydrodynamics Of Few Body Optical Vortices, Jasmine M. Andersen

Electronic Theses and Dissertations

The ubiquity of vortices nearly rivals that of the innumerable fluids and spaces in which they live. Not only do they exist in systems such as superfluids, superconductors, optical fields, or cold atomic gases, for example, but they also exist in our atmospheres, oceans, and even in our veins. This makes understanding and accurately predicting the dynamics of vortices in various systems a relevant and meaningful endeavor.

From a typical hydrodynamic perspective, vortices move within a given fluid because of the background fluid density and phase gradients at the vortex location. However, we find that these gradients alone are insufficient …

Modeling Disorder In Proteins Yields Insights Into The Evolution Of Stability And Function, Jonathan Huihui

Electronic Theses and Dissertations

The central dogma of molecular biology dictates that a DNA sequence codes for an RNA sequence, which in turn codes for a sequence of amino acids that comprises a protein. Proteins are responsible with performing myriad functions within living organisms and most proteins require a folded structure in order to perform their function. The protein's structure is the direct link from sequence to function. This is known as the sequence - structure - function paradigm. However, this does not mean that the unfolded state is unimportant. In order to properly model the stability of the folded state, one needs to …

Feedback Induced Magnetic Phases In Binary Bose-Einstein Condensates, Hilary M. Hurst, Shangjie Guo, I. B. Spielman

Faculty Research, Scholarly, and Creative Activity

Weak measurement in tandem with real-time feedback control is a new route toward engineering novel non-equilibrium quantum matter. Here we develop a theoretical toolbox for quantum feedback control of multicomponent Bose-Einstein condensates (BECs) using backaction-limited weak measurements in conjunction with spatially resolved feedback. Feedback in the form of a single-particle potential can introduce effective interactions that enter into the stochastic equation governing system dynamics. The effective interactions are tunable and can be made analogous to Feshbach resonances -- spin-independent and spin-dependent -- but without changing atomic scattering parameters. Feedback cooling prevents runaway heating due to measurement backaction and we present …

Non-Hermitian Topology Of One-Dimensional Spin-Torque Oscillator Arrays, Benedetta Flebus, Rembert A. Duine, Hilary M. Hurst

Faculty Research, Scholarly, and Creative Activity

Magnetic systems have been extensively studied both from a fundamental physics perspective and as building blocks for a variety of applications. Their topological properties, in particular those of excitations, remain relatively unexplored due to their inherently dissipative nature. The recent introduction of non-Hermitian topological classifications opens up new opportunities for engineering topological phases in dissipative systems. Here, we propose a magnonic realization of a non-Hermitian topological system. A crucial ingredient of our proposal is the injection of spin current into the magnetic system, which alters and can even change the sign of terms describing dissipation. We show that the magnetic …

Quantum Control With Spinor Bose-Einstein Condensates, Hilary M. Hurst

Faculty Research, Scholarly, and Creative Activity

Understanding and controlling many-body quantum systems in noisy environments is paramount to developing robust quantum technologies. An external environment can be thought of as a measurement reservoir which extracts information about the quantum system. Cold atoms are well suited to examine system-environment interaction via weak (i.e. minimally destructive) measurement techniques, wherein the measurement probe acts as the environment and also provides a noisy record of system dynamics. The measurement record can then be used in a feedback scheme, opening the door to real time control of quantum gases. In this talk I discuss our theoretical proposal to use weak measurement …

Electron-Induced Massive Dynamics Of Magnetic Domain Walls, Hilary M. Hurst, Victor Galitski, Tero T. Heikkilä

Faculty Research, Scholarly, and Creative Activity

We study the dynamics of domain walls (DWs) in a metallic, ferromagnetic nanowire. We develop a Keldysh collective coordinate technique to describe the effect of conduction electrons on rigid magnetic structures. The effective Lagrangian and Langevin equations of motion for a DW are derived. The DW dynamics is described by two collective degrees of freedom: position and tilt-angle. The coupled Langevin equations therefore involve two correlated noise sources, leading to a generalized fluctuation-dissipation theorem (FDT). The DW response kernel due to electrons contains two parts: one related to dissipation via FDT, and another `inertial' part. We prove that the latter …

Examining Artifacts Of The Watershed Segmentation, Emily Jo Armitage

Electronic Theses and Dissertations

The watershed segmentation is an algorithm used to systematically track cell intercalary behaviors during germ band extension of the Drosophila embryo. Neighboring cells share a contracting vertical interface, called a T1, which continues contracting to a single point, a T2, and extending in the horizontal direction to create what is called a T3 interface (Fig. 1). Additionally, higher order vertices called rosettes occur when five or more cells meet at a common vertex. Simulated T2 events demonstrate that cell angle and not noise level in the image contributes to the incorrect detection of artifactual T1s in more acute angled cells …

Quantification Of Dynamic Epithelial Sheet Architecture In Botryllus Schlosseri Using 2-D & 3-D Image Analysis, Roopa Madhu

Electronic Theses and Dissertations

Epithelial tubules form critical structures in various body tissues; how- ever, since they are difficult to access experimentally, their architecture and dynamics are not well understood. Here we examine the dynamic remodeling of epithelial tubes in vivo using a novel and uniquely accessible model system: the extracorporeal vasculature of Botryllus schlosseri (sea squirt). In Botryllus, massive retraction of blood vessels can be triggered without loss of barrier function, through (i) disrupting collagen crosslinking in the basement membrane using β-aminopropionitrile (BAPN); or (ii) disrupting the integrin pathway through inhibition of focal adhesion kinase (FAK). We performed stereographic projections of 3-dimensional …

Gas Adsorption In Carbon Nanohorns: Equilibrium And Kinetics, Justin Matthew Petucci

Electronic Theses and Dissertations

A study of gas adsorption has been carried out with the focus of better understanding the relationships between the individual properties of the adsorbent/adsorbate (e.g. material structure, interactions, gas size and shape, etc.) and the overall adsorptive properties of the combined system (e.g. capacity, binding strength, equilibration time, etc.) as a function of thermodynamical variables. This is useful from the perspective of a comprehensive and fundamental understanding as well as for practical applications. The equilibrium regime of adsorption on carbon nanostructure materials (nanohorns, nanotubes, and graphite) is investigated using molecular statics (MS) and grand canonical monte carlo (GCMC) methods for …

2d Confinement Of Thermal Gradients In Metallic Non-Local Spin Valves, Rachel K. Bennet

Electronic Theses and Dissertations

Non-local spin valves (NLSVs) are a valuable tool in the growing field of spintronics due to their unique ability to separate charge current from pure spin current. Their potential applications as read heads for hard-disk drives, as well as use as logic gates and other spin sensors, makes detailed understanding of their behavior under a wide range of operating conditions very important.

In this dissertation, I present results of extreme thermal engineering of the supporting substrate of NLSVs, which has a dramatic impact on the background signal of the device as well as contributions from thermal spin effects such as …

Transport Signatures Of Dirac States In Topological Insulator - Ferromagnet Heterostructures, Hilary M. Hurst

Faculty Research, Scholarly, and Creative Activity

No abstract provided.

Measurement-Induced Dynamics And Stabilization Of Spinor-Condensate Domain Walls, Hilary M. Hurst, I. B. Spielman

Faculty Research, Scholarly, and Creative Activity

Weakly measuring many-body systems and allowing for feedback in real-time can simultaneously create and measure new phenomena in strongly correlated quantum systems. We study the dynamics of a continuously measured two-component Bose-Einstein condensate (BEC) potentially containing a domain wall, and focus on the trade-off between usable information obtained from measurement and quantum backaction. Each weakly measured system yields a measurement record from which we extract real-time dynamics of the domain wall. We show that quantum backaction due to measurement causes two primary effects: domain wall diffusion and overall heating. The system dynamics and signal-to-noise ratio depend on the choice of …

Induced Quantum Dot Probe For Material Characterization, Yun-Pil Shim, Rusko Ruskov, Hilary M. Hurst, Charles Tahan

Faculty Research, Scholarly, and Creative Activity

We propose a non-destructive means of characterizing a semiconductor wafer via measuring parameters of an induced quantum dot on the material system of interest with a separate probe chip that can also house the measurement circuitry. We show that a single wire can create the dot, determine if an electron is present, and be used to measure critical device parameters. Adding more wires enables more complicated (potentially multi-dot) systems and measurements. As one application for this concept we consider silicon metal-oxide-semiconductor and silicon/silicon-germanium quantum dot qubits relevant to quantum computing and show how to measure low-lying excited states (so-called "valley" …

Status Of The Los Alamos Room Temperature Neutorn Electric Dipole Moment Search, Robert W. Pattie Jr.

ETSU Faculty Works

A discovery of the neutron's permanent electric dipole moment larger than the standard model prediction of d_n ≈ 10^-31 e·cm would signal a new source of CP-violation and help explain the matter-antimatter asymmetry in the universe. Tightening the limits on d_n constrain extensions to the standard model in a complementary fashion to the atomic and electron EDM searches. The recent upgrade of the Los Alamos ultracold neutron source makes it possible for a new room temperature search with the statistical reach to improve upon current limits by a factor of 10 or more. During the 2018 LANSCE …

Multidimensional Spectroscopy Of Mixed-Cation Perovskite Thin Films, Geoffrey Michael Diederich

Electronic Theses and Dissertations

Metal halide perovskite (MHP) thin films are currently undergoing an intense re- search thrust due to the excellent performance of MHP based photovoltaic (PV) devices, which have the potential to revolutionize the worlds energy production via a unique combination of low-cost fabrication and high power conversion efficiency (PCE). However, the vast majority of research is currently aimed at incremental improvements in device PCE, resulting in a body of work without the foundational understanding of the charge-carrier dynamics of the system upon photoexcitation.

This thesis begins with the development of a phase-modulated multidimensional coherent spectroscopy (PM-MDCS) experiment. PM-MDCS is an ultrafast …

Quantitative Aspects Of Interface Remodeling During Germband Extension, Timothy E. Vanderleest

Electronic Theses and Dissertations

Oriented cell intercalation is an essential developmental process that shapes tissue morphologies through the directional insertion of cells between their neighbors. Intercalary behaviors in the early Drosophila embryo occur through a remodeling of cell topologies, with cells contracting shared AP interfaces to a single point, followed by newly juxtaposed DV cells constructing horizontally-oriented interfaces between them. Previous research has focused on properties of cell-cell interfaces, and led to a model in which actomyosin networks mediate higher line tensions at AP interfaces to direct contraction. However, the contribution of tricellular vertices to tissue elongation remains unclear. This study shows that cell …

Nanoscale Thermal Transport In Thermally Isolated Nanostructures, Brian G. Green

Electronic Theses and Dissertations

Experiments with nanoscale structures, designed to measure some of their thermal and optical properties, are the subjects of this dissertation. We studied the transport of thermal energy in systems of nanoparticles, and used the method of transient thermoreflectance to monitor those dynamics, and assess whether thermal transport features special to nanoscale systems emerged. This same method was also used to study the thermal transport of a single system of layered membranes. Optical properties were investigated using computational simulations of a nanoparticle system, using the method of finite-difference time-domain simulation.

In nanoparticle studies, there are two features of interest special to …

Coupling Of Light's Orbital Angular Momentum To A Quantum Dot Ensemble, Alaa A. Bahamran

Electronic Theses and Dissertations

We theoretically and experimentally investigate the transfer of orbital angular momentum from light to an ensemble of semiconductor-based nanostructures composed of lead sulfide quantum dots. Using an ensemble of quantum dots offers a higher cross-section and more absorption of twisted light fields compared to experimentally challenging single-nanostructure measurements. However, each quantum dot (except for on-center) sees a displaced light beam parallel to its own axis of symmetry. The transition matrix elements for the light-matter interaction are calculated by expressing the displaced light beam in terms of the appropriate light field centered on the nanoparticles. The resulting transition rate induced by …

Monte Carlo Of Trapped Ultracold Neutrons In The Ucnτ Trap, Nathan Callahan, Chen-Yu Liu, Fransisco Gonzalez, Evan Adamek, James D. Bowman, Leah J. Broussard, S. M. Clayton, S. Currie, C. Cude-Woods, E. B. Dees, X. Ding, E. M. Egnel, D. Fellers, W. Fox, Peter Geltenbort, Kevin P. Hickerson, M. A. Hoffbauer, A. T. Holley, A. Komives, S. W.T. Macdonald, Marc Makela, C. L. Morris, J. D. Ortiz, Robert W. Pattie Jr., J. Ramsey, D. J. Salvat, A. Saunders, Susan J. Seestrom, E. I. Sharapov, Sky L. Sjue, Z. Tang, J. Vanderwerp, B. Vogelaar, P. L. Walstrom, Z. Wang, H. Weaver, W. Wei, J. Wexler, A. R. Young, B. A. Zeck

ETSU Faculty Works

In the UCNτ experiment, ultracold neutrons (UCN) are confined by magnetic fields and the Earth’s gravitational field. Field-trapping mitigates the problem of UCN loss on material surfaces, which caused the largest correction in prior neutron experiments using material bottles. However, the neutron dynamics in field traps differ qualitatively from those in material bottles. In the latter case, neutrons bounce off material surfaces with significant diffusivity and the population quickly reaches a static spatial distribution with a density gradient induced by the gravitational potential. In contrast, the field-confined UCN—whose dynamics can be described by Hamiltonian mechanics—do not exhibit the stochastic behaviors …

Developing A Femtosecond Stimulated Raman Spectroscopy Experiment For Solid State Materials, Daniel Hammerland

Electronic Theses and Dissertations

Femtosecond Stimulated Raman Spectroscopy (FSRS) is a ultrafast spectroscopy technique first implemented by chemists to understand isomerization and other ultrafast molecular morphology changes by resolving vibrational dynamics[1, 2, 3]. FSRS has an unparalleled temporal and spectral resolution [4, 1, 5, 6] that arises as a result of a clever combination of picosecond and femtosecond pulses. However, despite this capability, FSRS has yet to be applied to modern materials in condensed matter physics. This thesis explores the design and implementation of FSRS to study two-dimensional materials in order to measure their quantum confined vibrational dynamics on utlrafast time scales.

Heat, Charge And Spin Transport Of Thin Film Nanostructures, Devin John Wesenberg

Electronic Theses and Dissertations

Understanding of fundamental physics of transport properties in thin film nanostructures is crucial for application in spintronic, spin caloritronics and thermoelectric applications. Much of the difficulty in the understanding stems from the measurement itself. In this dissertation I present our thermal isolation platform that is primarily used for detection of thermally induced effects in a wide variety of materials. We can accurately and precisely produce in-plane thermal gradients in these membranes, allowing for thin film measurements on 2-D structures. First, we look at thermoelectric enhancements of doped semiconducting single-walled carbon nanotube thin films. We use the Wiedemann-Franz law to calculate …

Learning From Disorder And Noise In Physical Biology, Taylor Emil Firman

Electronic Theses and Dissertations

Stochasticity, disorder, and noise play crucial roles in the functioning of many biological systems over many different length scales. On the molecular scale, most proteins are envisioned as pristinely folded structures, but intrinsically disordered proteins (IDPs) have no such folded state and still serve distinct purposes within the cell. At the scale of gene regulation, realistic in vivo conditions produce stochastic fluctuations in gene expression that can lead to advantageous bet-hedging strategies, but can be difficult to characterize using a deterministic framework. Even at the organismal scale, germband extension (GBE) in Drosophila melanogaster embryos systematically elongates the epithelial tissue using …

Highly Directional Receiver And Source Antennas Using Photonic Band Gap Crystals, Rana Biswas, Gary L. Tuttle, Ekmel Ozbay, Burak Temelkuran, Mihail Sigalas, Kai-Ming Ho

Gary Tuttle

A directional antenna made with photonic band gap structures has been presented. The directional antenna is formed with two photonic band gap structures oriented back to back and separated from each other by a distance to form a resonant cavity between the photonic band gap structures. An antenna element is placed in the resonant cavity. The resonant frequency of the cavity is tuned by adjusting the distance between the photonic band gap structures. The resonant cavity can be asymmetrical or symmetrical.

Kinetic Theory Of Dark Solitons With Tunable Friction, Hilary M. Hurst, Dimitry K. Efimkin, I. B. Spielman, Victor Galitski

Faculty Research, Scholarly, and Creative Activity

We study controllable friction in a system consisting of a dark soliton in a one-dimensional Bose-Einstein condensate coupled to a non-interacting Fermi gas. The fermions act as impurity atoms, not part of the original condensate, that scatter off of the soliton. We study semi-classical dynamics of the dark soliton, a particle-like object with negative mass, and calculate its friction coefficient. Surprisingly, it depends periodically on the ratio of interspecies (impurity-condensate) to intraspecies (condensate-condensate) interaction strengths. By tuning this ratio, one can access a regime where the friction coefficient vanishes. We develop a general theory of stochastic dynamics for negative mass …

Brownian Motion Of Solitons In A Bose-Einstein Condensate, Lauren M. Aycock, Hilary M. Hurst, Dimitry K. Efimkin, Dina Genkina, Hsin-I Lu, Victor M. Galitski, I. B. Spielman

Faculty Research, Scholarly, and Creative Activity

We observed and controlled the Brownian motion of solitons. We launched solitonic excitations in highly elongated ⁸⁷ Rb Bose-Einstein condensates (BECs) and showed that a dilute background of impurity atoms in a different internal state dramatically affects the soliton. With no impurities and in one-dimension (1D), these solitons would have an infinite lifetime, a consequence of integrability. In our experiment, the added impurities scatter off the much larger soliton, contributing to its Brownian motion and decreasing its lifetime. We describe the soliton's diffusive behavior using a quasi-1D scattering theory of impurity atoms interacting with a soliton, giving diffusion coefficients consistent …

Real-Space Mean-Field Theory Of A Spin-1 Bose Gas In Synthetic Dimensions, Hilary M. Hurst, Justin H. Wilson, J. H. Pixley, I. B. Spielman, Stefan S. Natu

Faculty Research, Scholarly, and Creative Activity

The internal degrees of freedom provided by ultracold atoms give a route for realizing higher dimensional physics in systems with limited spatial dimensions. Non-spatial degrees of freedom in these systems are dubbed "synthetic dimensions". This connection is useful from an experimental standpoint but complicated by the fact that interactions alter the condensate ground state. Here we use the Gross-Pitaevskii equation to study ground state properties of a spin-1 Bose gas under the combined influence of an optical lattice, spin-orbit coupling, and interactions at the mean field level. The associated phases depend on the sign of the spin-dependent interaction parameter and …

"Blinded By The Lines: Mid-Ir Spectra Of Mira Variables Taken With Spitzer", Dana Baylis-Aguirre, Michelle J. Creech-Eakman, Donald G. Luttermoser, Tina Gueth

ETSU Faculty Works

We present preliminary analysis of mid-infrared spectra of M-type and C-type Mira variables. Due to the brightness of this sample, it is straightforward to monitor changes with phase in the infrared spectral features of these regular pulsators. We have spectra of 25 Mira variables, taken with phase, using the Spitzer Infrared Spectrograph (IRS) high-resolution module. Each star has multiple spectra obtained over a one-year period from 2008-09. This is a rich, unique data set due to multiple observations of each star and the high signal-to-noise ratio from quick exposure times to prevent saturation of the IRS instrument. This paper focuses …