Condensed Matter Physics Commons^™

Magnetic Phases Of Large-Spin Ultracold Bosons: Quantum Dimer Models And Spin Liquid Phases, Todd C. Rutkowski

Graduate Dissertations and Theses

This thesis investigates the plausibility of producing a quantum spin liquid (QSL) with ultracold bosonic atoms optically confined to the Mott insulating state. QSLs have received a great deal of attention for being an antiferromagnetic groundstate with many exotic properties, including the absence of local order, long-range entanglement, and fractionalized excitations. However, the identification and characterization of these phases in solid state systems remains a great challenge. Here we outline an alternate route to uncovering the QSL phase, which from the nature of spin angular momentum for ultracold atoms encounters many properties unique to these systems along the way. This …

Tests Of Radiation Damage Threshold Of Raspberry Pi Zerio In Leo Environment For Opal Cubesat Project, Jonh Mojica Decena, Jr Dennison, Brian Wood, Ryan J. Martineau, Michael J. Taylor

Posters

No abstract provided.

Unconventional Pairing Symmetry Of Interacting Dirac Fermions On A Π -Flux Lattice, Huaiming Guo, Ehsan Khatami, Yao Wang, Thomas Devereaux, Rajiv Singh, Richard Scalettar

Faculty Publications

The pairing symmetry of interacting Dirac fermions on the π-flux lattice is studied with the determinant quantum Monte Carlo and numerical linked-cluster expansion methods. The s∗- (i.e., extended s-) and d-wave pairing symmetries, which are distinct in the conventional square lattice, are degenerate under the Landau gauge. We demonstrate that the dominant pairing channel at strong interactions is an unconventional ds∗-wave phase consisting of alternating stripes of s∗- and d-wave phases. A complementary mean-field analysis shows that while the s∗- and d-wave symmetries individually have nodes in the energy spectrum, the ds∗ channel is fully gapped. The results represent a …

Analysis Of Electron Yield Properties Of Low-Density Polyethylene, Jr Dennison, Jordan Lee

Posters

At extremely high altitudes, spacecraft are submitted to solar radiation of varying charged-particle fluxes. This radiation can induce charging of the spacecraft itself, creating unwanted and disastrous effects on electrical components from electrostatic breakdown or arc-induced damage of structural or optical components. To prevent these effects, space-like environment tests are performed on materials to understand how they interact with the space plasma environment.

Radiation Damage Threshold Of Satellite Cots Components: Raspberry Pi Zero For Opal Cubesat, Jonh Mojica Decena, Brian Wood, Ryan J. Martineau, Jr Dennison, Michael Tayor

Posters

The use of inexpensive microprocessors or commercial of the shelf (COTS) components is one of the most common cost-saving methods in the constructions of CubeSats. Design of electronics that can maintain full functionality over the duration of the mission requires careful determination of the space radiation environment and total ionizing dose (TID) delivered to the components. Larger, more expensive or longer mission satellites tend to use more expensive components than the ones used in CubeSat to assure reliability. Radiation survivability of a Raspberry Pi Zero was studied with the USU Space Survivability Test Chamber using 0.2 to 2.5 MeV beta …

The Effects Of Beta Transition On Dielectric Breakdown In Ldpe, Tyler Kippen, Allen Andersen, Jr Dennison

Presentations

No abstract provided.

Effects Of Acoustic Coupling Layer Electrical Conducitivity On Pulsed Electroacoustic Measurements, Zachary Gibson, Jr Dennison, Lee Pearson, Erick Griffiths, Anthony Pearson

Posters

No abstract provided.

Radiation Damage Threshold Of Satellite Cots Components: Raspberry Pi Zero For Opal Cubesat, Jonh Mojica Decena, Brian Wood, Ryan J. Martineau, Michael Tayor, Jr Dennison

Posters

No abstract provided.

Analysis Of Electron Yield Properties Of Low-Density Polyethylene, Jordan Lee, Jr Dennison

Posters

No abstract provided.

Resonant Tunneling Across A Ferroelectric Domain Wall, M. Li, L. L. Tao, J. P. Velev, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Motivated by recent experimental observations, we explore electron transport properties of a ferroelectric tunnel junction (FTJ) with an embedded head-to-head ferroelectric domain wall, using first-principles density-functional theory calculations. We consider a FTJ with La_0.5Sr_0.5MnO₃ electrodes separated by a BaTiO₃ barrier layer and show that an in-plane charged domain wall in the ferroelectric BaTiO₃ can be induced by polar interfaces. The resulting V-shaped electrostatic potential profile across the BaTiO₃ layer creates a quantum well and leads to the formation of a two-dimensional electron gas, which stabilizes the domain wall. The confined electronic states …

Quasiprobability Behind The Out-Of-Time-Ordered Correlator, Nicole Yunger Halpern, Brian Swingle, Justin Dressel

Mathematics, Physics, and Computer Science Faculty Articles and Research

Two topics, evolving rapidly in separate fields, were combined recently: the out-of-time-ordered correlator (OTOC) signals quantum-information scrambling in many-body systems. The Kirkwood-Dirac (KD) quasiprobability represents operators in quantum optics. The OTOC was shown to equal a moment of a summed quasiprobability [Yunger Halpern, Phys. Rev. A 95, 012120 (2017)]. That quasiprobability, we argue, is an extension of the KD distribution. We explore the quasiprobability's structure from experimental, numerical, and theoretical perspectives. First, we simplify and analyze Yunger Halpern's weak-measurement and interference protocols for measuring the OTOC and its quasiprobability. We decrease, exponentially in system size, the number of trials …

Characterizing The Effects Of Radiation On Muscle Cells, Lori Caldwell, Charles Harding, Eryn Hanson, Jr Dennison, Elizabeth Vargis

Presentations

No abstract provided.

Coarse-Grained Modeling Studies Of Polymeric And Granular Systems, Hong Trung Nguyen

USF Tampa Graduate Theses and Dissertations

This Dissertation is devoted to computational study of the solidification, dynamics and mechanics of model semiflexible polymers with variable chain flexibility as well as a computational investigation of the clogging phenomena observed in granular materials.

Chain stiffness is an intrinsic factor that governs single-chain flexibility. It plays a critical role in the physics of polymeric materials. In this work, we employ a coarse-grained polymer model in which chain stiffness can be tuned by a single parameter (bending stiffness kb) that yields chain shape ranging from coil-like to rod-like in the flexible and very stiff limit respectively. In chapter 2, we …

Dielectric Properties Of Thin Cr2o3 Films Grown On Elemental And Oxide Metallic Substrates, Ather Mahmood, Mike Street, Will Echtenkamp, Chun Pui Kwan, Jonathan P. Bird, Christian Binek

Christian Binek Publications

In an attempt to optimize leakage characteristics of α-Cr₂O₃ thin films, its dielectric properties were investigated at local and macroscopic scale. The films were grown on Pd(111), Pt(111), and V₂O₃ (0001), supported on Al₂O₃ substrate. The local conductivity was measured by conductive atomic force microscopy mapping of Cr₂O₃ surfaces, which revealed the nature of defects that formed conducting paths with the bottom Pd or Pt layer. A strong correlation was found between these electrical defects and the grain boundaries revealed in the corresponding topographic scans. In comparison, …

Predicting The Ground-State Structure Of Sodium Boride, Xin-Ling He, Xiao Dong, Quansheng Wu, Zhisheng Zhao, Qiang Zhu, Artem R. Oganov, Yongjun Tian, Dongli Yu, Xiang-Feng Zhou, Hui-Tian Wang

Physics & Astronomy Faculty Research

Binary borides has been a subject of extensive research. However, the exact compositions and crystal structures of sodium borides remained controversial. Here, using the ab initio variable-composition evolutionary algorithm, a new stable Na2B30 with I212121 symmetry (I212121-Na2B30) is found, which is -7.38meV/atom lower in energy than the Imma-Na2B30 structure reported by experimentalists. Interestingly, the Imma-Na2B30 structure is predicted to be a topological nodal line semimetal, which may result in superior electronic transport. In contrast, I212121-Na2B30 is an ultrahard semiconductor with an unprecedented open-framework structure, whose interstitial helical boron sublattice enhances its hardness and energetic stability.

Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher Carr

Dissertations

Recent efforts have demonstrated confinement in porous scaffolds at the nanoscale can alter the hydrogen sorption properties of metal hydrides, though not to an extent feasible for use in onboard hydrogen storage applications, proposing the need for a method allowing further modifications. The work presented here explores how the functionalization of nanoporous carbon scaffold surfaces with heteroatoms can modify the hydrogen sorption properties of confined metal hydrides in relation to non-functionalized scaffolds (FS). Investigations of nanoconfined LiBH₄and NaAlH₄indicate functionalizing the carbon scaffold surface with nitrogen can shift the activation energy of hydrogen desorption in excess of …

Polarization-Controlled Modulation Doping Of A Ferroelectric From First Principles, Xiaohui Liu, Evgeny Y. Tsymbal, Karin M. Rabe

Evgeny Tsymbal Publications

In a ferroelectric field effect transistor (FeFET), it is generally assumed that the ferroelectric gate plays a purely electrostatic role. Recently it has been shown that in some cases, which could be called “active FeFETs,” electronic states in the ferroelectric contribute to the device conductance as the result of a modulation doping effect in which carriers are transferred from the channel into the ferroelectric layers near the interface. Here we report first-principles calculations and model analysis to elucidate the various aspects of this mechanism and to provide guidance in materials choices and interface termination for optimizing the on-off ratio, using …

Dissipation Effects In Schrödinger And Quantal Density Functional Theories Of Electrons In An Electromagnetic Field, Xiao-Yin Pan, Viraht Sahni

Publications and Research

Dissipative effects arise in an electronic system when it interacts with a time-dependent environment. Here, the Schrödinger theory of electrons in an electromagnetic field including dissipative effects is described from a new perspective. Dissipation is accounted for via the effective Hamiltonian approach in which the electron mass is time-dependent. The perspective is that of the individual electron: the corresponding equation of motion for the electron or time-dependent differential virial theorem—the ‘Quantal Newtonian’ second law—is derived. According to the law, each electron experiences an external field comprised of a binding electric field, the Lorentz field, and the electromagnetic field. In addition, …

Nv Center Detection Of Electric Fields And Low-Intensity Light, Nicholas Harmon, Michael Flatte

Faculty Works

Nitrogen vacancy (NV) center spins in diamond are attractive candidates for quantum information processing and sensitive, nanoscale magnetometers due to their long spin coherence times under ambient conditions [1]. The ground state of the NV spin is also sensitive to electric fields [2]. We present a theory of quantum detection using positive operator valued measurements (POVMs) wherein the presence of an electric field is determined by spin-dependent fluorescence of an NV center. The predicted sensitivity to small electric fields can also be used for photon detection. Photons incident upon a chromophore near the diamond interface may induce a charge polarization …

Effects Of Acoustic Coupling Layer Electrical Conductivity On Pulsed Electroacoustic Measurements, Zachary Gibson, Jr Dennison, Lee Pearson, Erick Griffiths, Anthony Pearson

Posters

The spatial resolution of Pulsed Electroacoustic (PEA) measurements can be limited by the acoustic thickness of the coupling material coupling the sample to the detector assembly. Our investigations studied the effect of adhesive material and thickness to optimize the quality of the PEA signal.

Nanostructural Origin Of Semiconductivity And Large Magnetoresistance In Epitaxial Nico2O4/Al2O3 Thin Films, Congmian Zhen, Xiaozhe Zhang, Wengang Wei, Wenzhe Guo, Ankit Pant, Xiaoshan Xu, Jian Shen, Li Ma, Denglu Hou

Xiaoshan Xu Papers

Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo₂O₄, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo₂O₄ films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo₂O₄ epitaxial films grown on MgAl₂O₄ (1 1 1) and on Al₂O₃ (0 0 1) substrates. Although the optimal growth conditions are similar for the …

Coexistence Of Ferromagnetism And Unconventional Spin-Glass Freezing In The Site-Disordered Kagome Ferrite Srsn2Fe4O11, L. Shlyk, S. Strobel, Barry Farmer, Lance E. De Long, R. Niewa

Physics and Astronomy Faculty Publications

Single-crystal x-ray diffraction refinements indicate SrSn₂Fe₄O₁₁ crystallizes in the hexagonal R-type ferrite structure with noncentrosymmetric space group P6₃mc and lattice parameters a = 5.9541(2)Å, c = 13.5761(5)Å, Z = 2 (R(F) = 0.034). Octahedrally coordinated 2a [M(1) and M(1a)] and 6c sites [M(2)] have random, mixed occupation by Sn and Fe; whereas the tetrahedrally coordinated 2b sites [Fe(3) and Fe(3a)] are exclusively occupied by Fe, whose displacement from the ideal position with trigonal-bipyramidal coordination causes the loss of inversion symmetry. …

Electronic And Optical Properties Of La-Doped Sr3Ir2O7 Epitaxial Thin Films, Maryam Souri, Jsaminka Terzic, J. M. Johnson, John G. Connell, John H. Gruenewald, J. Thompson, Joseph W. Brill, J. Hwang, Gang Cao, Sung S. Ambrose Seo

Physics and Astronomy Faculty Publications

We have investigated structural, transport, and optical properties of tensile strained (Sr_1−xLa_x)₃Ir₂O₇ (x = 0, 0.025, 0.05) epitaxial thin films. While high-T_c superconductivity is predicted theoretically in the system, we have observed that all of the samples remain insulating with finite optical gap energies and Mott variable-range hopping characteristics in transport. Cross-sectional scanning transmission electron microscopy indicates that structural defects such as stacking faults appear in this system. The insulating behavior of the La-doped Sr₃Ir₂O₇ thin films is presumably due to disorder-induced …

Effects Of Structural And Electronic Disorder In Topological Insulator Sb2te3 Thin Films, Inna Korzhovska

Dissertations, Theses, and Capstone Projects

Topological quantum matter is a unique and potentially transformative protectorate against disorder-induced backscattering. The ultimate disorder limits to the topological state, however, are still not known - understanding these limits is critical to potential applications in the fields of spintronics and information processing. In topological insulators spin-orbit interaction and time-reversal-symmetry invariance guarantees - at least up to a certain disorder strength - that charge transport through 2D gapless Dirac surface states is robust against backscattering by non-magnetic disorder. Strong disorder may destroy topological protection and gap out Dirac surface states, although recent theories predict that under severe electronic disorder a …

Time-Evolved Constant Voltage Conductivity Measurements Of Common Spaceborne Polymeric Materials, Brian Wood, David King, Jr Dennison

Presentations

No abstract provided.

Mutual Influence Between Macrospin Reversal Order And Spin-Wave Dynamics In Isolated Artificial Spin-Ice Vertices, F. Montoncello, L. Giovannini, Wonbae Bang, J. B. Ketterson, M. B. Jungfleisch, A. Hoffmann, Barry W. Farmer, Lance E. De Long

Physics and Astronomy Faculty Publications

We theoretically and experimentally investigate magnetization reversal and associated spin-wave dynamics of isolated threefold vertices that constitute a Kagome lattice. The three permalloy macrospins making up the vertex have an elliptical cross section and a uniform thickness. We study the dc magnetization curve and the frequency versus field curves (dispersions) of those spin-wave modes that produce the largest response. We also investigate each macrospin reversal from a dynamic perspective, by performing micromagnetic simulations of the reversal processes, and revealing their relationships to the soft-mode profile calculated at the equilibrium state immediately before reversal. The theoretical results are compared with the …

Sensor Design For In-Flight Testing Of Small-Satellite Thruster, Alex Souvall

Senior Theses and Projects

No abstract provided.

Structure And Magnetism Of Mn5ge3 Nanoparticles, Onur Tosun, Mohammed Salehi-Fashami, Balamurugan Balasubramanian, Ralph Skomski, David J. Sellmyer, George C. Hadjipanayis

Nebraska Center for Materials and Nanoscience: Faculty Publications

In this work, we investigated the magnetic and structural properties of isolated Mn₅Ge₃ nanoparticles prepared by the cluster-beam deposition technique. Particles with sizes between 7.2 and 12.6 nm were produced by varying the argon pressure and power in the cluster gun. X-ray diffraction (XRD)and selected area diffraction (SAD) measurements show that the nanoparticles crystallize in the hexagonal Mn₅Si₃-type crystal structure, which is also the structure of bulk Mn₅Ge₃. The temperature dependence of the magnetization shows that the as-made particles are ferromagnetic at room temperature and have slightly different Curie …

Structural, Magnetic, And Electron-Transport Properties Of Epitaxial Mn2Ptsn Films, Y. Jin, Shah R. Valloppilly, Parashu Kharel, Jace Waybright, Pavel V. Lukashev, Xingzhong Li, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The growth of new magnetic materials on suitable insulating substrates is an important part of the development of spin-electronics devices for memory or information processing. Epitaxial thin films of Mn₂PtSn were grown on a MgO [001] substrate by magnetron co-sputtering of the constituents. Structural, magnetic, and electron-transport properties were investigated. The epitaxial Mn₂PtSn film has an inverse tetragonal structure with the c-axis aligned in the plane of the MgO substrate. The lattice constants determined using XRD and TEM analysis are c=6.124Å and a=b=4.505Å. The orientation of Mn₂PtSn c-axis which …

Multi-Walled Carbon Nanotube-Coated Spiral Coils For Loss Reduction In Wireless Power Transfer Systems, Kamran Keramatnejad, Dawei Li, Hossein Rabiee Golgir, Loic Constantin, Xi Huang, Qiming Zou, Jean-Francois Silvain, Stephen Ducharme, Yongfeng Lu

Stephen Ducharme Publications

Realization of high efficiency and long transmission range in high-frequency wireless power transfer (WPT) systems has always been hindered by the increased resistance due to the eddy current loss occurring in the inductive coils. In this study, multi-walled carbon nanotube-coated copper (MWCNT-Cu) coils are successfully introduced to address this limitation by implementing the frequency-inert MWCNT channels along with using their high-surface areas to realize the electromagnetic shielding of the Cu substrate through multiple reflection mechanisms. At a frequency of 15 MHz, the resistance of the individual MWCNT-Cu coil was reduced to less than 40% of its original value for primitive …