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Full-Text Articles in Physics
Quantum Critical Behavior Of A Three-Dimensional Superfluid-Mott Glass Transition, Jack Crewse, Cameron Lerch, Thomas Vojta
Quantum Critical Behavior Of A Three-Dimensional Superfluid-Mott Glass Transition, Jack Crewse, Cameron Lerch, Thomas Vojta
Physics Faculty Research & Creative Works
The superfluid to insulator quantum phase transition of a three-dimensional particle-hole symmetric system of disordered bosons is studied. To this end, a site-diluted quantum rotor Hamiltonian is mapped onto a classical (3+1)-dimensional XY model with columnar disorder and analyzed by means of large-scale Monte Carlo simulations. The superfluid-Mott insulator transition of the clean, undiluted system is in the four-dimensional XY universality class and shows mean-field critical behavior with logarithmic corrections. The clean correlation length exponent ν=1/2 violates the Harris criterion, indicating that disorder must be a relevant perturbation. For nonzero dilutions below the lattice percolation threshold of pc=0.688392, …
Electrical Control Of Structural And Physical Properties Via Strong Spin-Orbit Interactions In Sr2Iro4, Gang Cao, Jasminka Terzic, H. D. Zhao, H. Zheng, Lance E. De Long, Peter S. Riseborough
Electrical Control Of Structural And Physical Properties Via Strong Spin-Orbit Interactions In Sr2Iro4, Gang Cao, Jasminka Terzic, H. D. Zhao, H. Zheng, Lance E. De Long, Peter S. Riseborough
Physics and Astronomy Faculty Publications
Electrical control of structural and physical properties is a long-sought, but elusive goal of contemporary science and technology. We demonstrate that a combination of strong spin-orbit interactions (SOI) and a canted antiferromagnetic Mott state is sufficient to attain that goal. The antiferromagnetic insulator Sr2IrO4 provides a model system in which strong SOI lock canted Ir magnetic moments to IrO6 octahedra, causing them to rigidly rotate together. A novel coupling between an applied electrical current and the canting angle reduces the Néel temperature and drives a large, nonlinear lattice expansion that closely tracks the magnetization, increases the …
Epitaxial Thin Films Of Dirac Semimetal Antiperovskite Cu3Pdn, C. X. Quintela, N. Campbell, D. F. Shao, J. Irwin, D. T. Harris, L. Lie, T. J. Anderson, N. Reiser, X. Q. Pan, Evgeny Y. Tsymbal, M. S. Rzchowski, C B. Eom
Epitaxial Thin Films Of Dirac Semimetal Antiperovskite Cu3Pdn, C. X. Quintela, N. Campbell, D. F. Shao, J. Irwin, D. T. Harris, L. Lie, T. J. Anderson, N. Reiser, X. Q. Pan, Evgeny Y. Tsymbal, M. S. Rzchowski, C B. Eom
Evgeny Tsymbal Publications
The growth and study of materials showing novel topological states of matter is one of the frontiers in condensed matter physics. Among this class of materials, the nitride antiperovskite Cu3PdN has been proposed as a new three-dimensional Dirac semimetal. However, the experimental realization of Cu3PdN and the consequent study of its electronic properties have been hindered due to the difficulty of synthesizing this material. In this study, we report fabrication and both structural and transport characterization of epitaxial Cu3PdN thin films grown on (001)-oriented SrTiO3 substrates by reactive magnetron sputtering and post-annealed in …
Complex Band Structure Of Topologically Protected Edge States, Xiaoqian Dang, John D. Burton, Alan Kalitsov, Julian P. Velev, Evgeny Y. Tsymbal
Complex Band Structure Of Topologically Protected Edge States, Xiaoqian Dang, John D. Burton, Alan Kalitsov, Julian P. Velev, Evgeny Y. Tsymbal
Evgeny Tsymbal Publications
One of the great successes of modern condensed matter physics is the discovery of topological insulators (TIs). A thorough investigation of their properties could bring such materials from fundamental research to potential applications. Here, we report on theoretical investigations of the complex band structure (CBS) of two-dimensional (2D) TIs. We utilize the tight-binding form of the Bernevig, Hughes, and Zhang model as a prototype for a generic 2D TI. Based on this model, we outline the conditions that the CBS must satisfy in order to guarantee the presence of topologically protected edge states. Furthermore, we use the Green’s function technique …
Insulator-Insulator Contact Charging As A Function Of Pressure, Michael Hogue
Insulator-Insulator Contact Charging As A Function Of Pressure, Michael Hogue
Electronic Theses and Dissertations
Metal - metal and to an extent metal - insulator contact or triboelectric charging are well known phenomena with good theoretical understanding of the charge exchange mechanism. However, insulator insulator charging is not as well understood. Theoretical and experimental research has been performed that shows that the surface charge on an insulator after triboelectric charging with another insulator is rapidly dissipated with lowered atmospheric pressure. This pressure discharge is consistent with surface ions being evaporated off the surface once their vapor pressure falls below the saturation vapor pressure. A two-phase equilibrium model based on an ideal gas of singly …
Measuring Charge Storage Decay Time And Resistivity Of Spacecraft Insulators, Jerilyn Brunson, John R. Dennison
Measuring Charge Storage Decay Time And Resistivity Of Spacecraft Insulators, Jerilyn Brunson, John R. Dennison
All Physics Faculty Publications
An informal discussion of how accurate measurements of resistivity and increasing understanding of the behavior of insulating materials used on spacecraft is fundamental to advancing the design and utility of the spacecraft. Build up of charge can vary between different areas of the spacecraft, with excess charge accumulating and leading to functional anomalies or component failure. The most important parameter in determining how charge will decay through an insulator is the resistivity of the material. Current industry standards for measuring resistivity have been shown to be inconsistent with actual phenomena, and new methods of measuring resistivity must be developed and …
Evolution Of The Electron Yield Curves Of Insulators As A Function Ofimpinging Electron Fluence And Energy, Alec Sim, John R. Dennison, Clint Thomson
Evolution Of The Electron Yield Curves Of Insulators As A Function Ofimpinging Electron Fluence And Energy, Alec Sim, John R. Dennison, Clint Thomson
All Physics Faculty Publications
Electron emission and concomitant charge accumulation near the surface of insulators is central to understanding spacecraft charging. We present a study of changes in electron emission yields as a result of internal charge build up due to electron dose. Evolution of total, backscattered and secondary yield results over a broad range of incident energies are presented for two representative insulators, KaptonTM and Al2O3. Reliable yield curves for un-charged insulators are measured and quantifiable changes in yields are observed due to fluences. We find excellent agreement with a phenomenological argument based on insulator charging predicted by …
Measurement Of Charge Storage Decay Time And Resistivity Of Spacecraft Insulators, Prasanna V. Swaminathan
Measurement Of Charge Storage Decay Time And Resistivity Of Spacecraft Insulators, Prasanna V. Swaminathan
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Insulators used in the construction of spacecraft are irradiated with high-energy electrons in the space environment and this sometimes causes the insulators to charge to very high voltages. Such charged insulators can generate spontaneous electric partial-discharge pulses of the order of mA to tens of A. These pulses sometimes last enough time to destroy the expensive micro-circuitry present in the spacecraft. In evaluating the threat to the spacecraft due to these discharges, calculation of the resistivity becomes a critical parameter since it determines how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate. So far, …
Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraftcharging, A. R. Fredrickson, John R. Dennison
Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraftcharging, A. R. Fredrickson, John R. Dennison
All Physics Faculty Publications
Novel methods have been developed to measure conductivity and charge storage in thin film insulating spacecraft materials subjected to space radiations. For a variety of such samples, conductivity values differ by up to 104 from values based on ASTM standards. Conductivity and charge storage properties are found to be functions of prior radiation history. A highly-charged insulator emits electrons for hours (Malter Effect) after the irradiation beam is turned off. Visible light can be used to induce emission from previously charged samples with shallow traps.
Charge Storage, Conductivity And Charge Profiles Of Insulators As Related To Spacecraft Charging, John R. Dennison, A. R. Frederickson, Prasanna Swaminathan
Charge Storage, Conductivity And Charge Profiles Of Insulators As Related To Spacecraft Charging, John R. Dennison, A. R. Frederickson, Prasanna Swaminathan
All Physics Faculty Publications
Dissipation of charges built up near the surface of insulators due to space environment interaction is central to understanding spacecraft charging. Conductivity of insulating materials is key to determine how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate. To understand these processes requires knowledge of how charge is deposited within the insulator, the mechanisms for charge trapping and charge transport within the insulator, and how the profile of trapped charge affects the transport and emission of charges from insulators. One must consider generation of mobile electrons and holes, their trapping, thermal detrapping, mobility and …
Comparison Of Classical And Charge Storage Methods For Determining Conductivity Of Thin Film Insulators, Prasanna Swaminathan, A. R. Frederickson, John R. Dennison, Alec Sim, J. Brunson, Eric Crapo
Comparison Of Classical And Charge Storage Methods For Determining Conductivity Of Thin Film Insulators, Prasanna Swaminathan, A. R. Frederickson, John R. Dennison, Alec Sim, J. Brunson, Eric Crapo
All Physics Faculty Publications
Conductivity of insulating materials is a key parameter to determine how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate. Classical ASTM and IEC methods to measure thin film insulator conductivity apply a constant voltage to two electrodes around the sample and measure the resulting current for tens of minutes. However, conductivity is more appropriately measured for spacecraft charging applications as the "decay" of charge deposited on the surface of an insulator. Charge decay methods expose one side of the insulator in vacuum to sequences of charged particles, light, and plasma, with a metal electrode …
Instrumentation For Studies Of Electron Emission And Charging From Insulators, C. D. Thomson, V. V. Zavyalov, John R. Dennison
Instrumentation For Studies Of Electron Emission And Charging From Insulators, C. D. Thomson, V. V. Zavyalov, John R. Dennison
All Physics Faculty Publications
Making measurements of electron emission properties of insulators is difficult since insulators can charge either negatively or positively under charge particle bombardment. In addition, high incident energies or high fluences can result in modification of a material’s conductivity, bulk and surface charge profile, structural makeup through bond breaking and defect creation, and emission properties. We discuss here some of the charging difficulties associated with making insulator-yield measurements and review the methods used in previous studies of electron emission from insulators. We present work undertaken by our group to make consistent and accurate measurements of the electron/ion yield properties for numerous …