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Physics

Superconductor

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Impact Of F-D Kondo Cloud On Superconductivity Of Nickelates, Byungkyun Kang, Hyunsoo Kim, Qiang Zhu, Chul Hong Park Mar 2023

Impact Of F-D Kondo Cloud On Superconductivity Of Nickelates, Byungkyun Kang, Hyunsoo Kim, Qiang Zhu, Chul Hong Park

Physics Faculty Research & Creative Works

The Discovery of Superconducting Nickelates Reignited Hope for Elucidating the High-Tc Superconductivity Mechanism in Isostructural Cuprates. While the Superconducting Gap Opens Up on a Single Band of the Quasi-2D Fermi Surface in the Cuprates, the Nickelates Are Known to Have a 3D Nature of an Electronic Structure with a Multi-Band. This Raises a Serious Question About the Role of the 2D Nature for the High-Tc Superconductivity. Here, Employing GW + Dynamical Mean Field Theory (DMFT), We Report the Kondo Effect Driven by the Strong Correlation of Nd-4f and Ni-3d Electrons Emerging at Low Temperature. the Kondo Effect Modifies …

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Magnetic Charge Ordering Of Pinwheel Artificial Spin Ice In In-Plane External Magnetic Fields And Its Application For Tunable Vortex Pinning, Timothy Draher Jan 2022

Magnetic Charge Ordering Of Pinwheel Artificial Spin Ice In In-Plane External Magnetic Fields And Its Application For Tunable Vortex Pinning, Timothy Draher

Graduate Research Theses & Dissertations

Pinwheel artificial spin ice (ASI) systems fabricated using permalloy nanobars offer tunable control of superconducting vortices in an ASI-superconductor hybrid. Vortex pinningis achieved by tuning the ordering of the ASI’s magnetic charge distribution via an external field to create an optimal potential energy landscape to which superconducting vortex motion can be impeded or pinned. Magnetic charge ordering in a pinwheel ASI is visualized using MuMax3 micromagnetic simulations to aid in characterizing the correlation of charge ordering amongst the spin ice system with the application of the external field. Vortex pinning is characterized in a sample of pinwheel spin ice patterned …

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Collected Papers (On Physics, Artificial Intelligence, Health Issues, Decision Making, Economics, Statistics), Volume Xi, Florentin Smarandache Jan 2022

Collected Papers (On Physics, Artificial Intelligence, Health Issues, Decision Making, Economics, Statistics), Volume Xi, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

This eleventh volume of Collected Papers includes 90 papers comprising 988 pages on Physics, Artificial Intelligence, Health Issues, Decision Making, Economics, Statistics, written between 2001-2022 by the author alone or in collaboration with 84 co-authors from 19 countries.

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Magnetic Field Penetration Technique To Study Field Shielding Of Multilayered Superconductors, Iresha Harshani Senevirathne, Alex Gurevich, Jean R. Delayen, A-M Valente-Feliciano Jan 2022

Magnetic Field Penetration Technique To Study Field Shielding Of Multilayered Superconductors, Iresha Harshani Senevirathne, Alex Gurevich, Jean R. Delayen, A-M Valente-Feliciano

Physics Faculty Publications

The SIS structure which consists of alternative thin layers of superconductors and insulators on a bulk niobium has been proposed to shield niobium cavity surface from high magnetic field and hence increase the accelerating gradient. The study of the behavior of multilayer superconductors in an external magnetic field is essential to optimize their SRF performance. In this work we report the development of a simple and efficient technique to measure penetration of magnetic field into bulk, thin film and multilayer superconductors. Experimental setup contains a small superconducting solenoid which can produce a parallel surface magnetic field up to 0.5 T …

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Non-Local Spin Valve Interferometer: Experimental Observation Of Superconducting Spin Current And Spin Aharonov-Bohm Effect, Ning Lu Apr 2019

Non-Local Spin Valve Interferometer: Experimental Observation Of Superconducting Spin Current And Spin Aharonov-Bohm Effect, Ning Lu

Theses and Dissertations

An electron interferometer was designed and fabricated via a normal metal (supercon- ductor)/insulator/ferromagnet non-local lateral spin valve with a ring-shaped normal metal/insulator spacer, and spin current interference was observed. At 4.2 K, a very high spin signal of 200 mΩ was found in a device with 2 µm injector-detector dis- tance and magnetic field swept parallel to the plane. With a perpendicular magnetic field sweep, a Hanle effect measurement showed both spin precession and h/e oscil- lation. Because of the non-adiabatic nature of the precessing spins at low fields as they traverse the normal metal ring, this is an …

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Crystal Growth And Manipulation Of Intercalated Chalcogenides As Superconductors And Topological Insulators, Nathaniel Smith Aug 2018

Crystal Growth And Manipulation Of Intercalated Chalcogenides As Superconductors And Topological Insulators, Nathaniel Smith

Theses and Dissertations

Superconductors are unusual quantum materials which offer no resistance to electric current. The fascinating physics of this phenomenon is complemented by wide-ranging technical applications from power transmission to magnetic levitation. Commercially successful superconductors are found in powerful magnets in medical imaging, particle accelerators, and next-generation quantum computing. In my effort to uncover the mysteries and fundamental mechanisms of superconductivity, I use an array of techniques to synthesize and study single crystals of unconventional superconductors including the iron telluride and bismuth selenide family of superconductors. My study of atomic valence and crystal structure in iron telluride has uncovered previously unknown chemical …

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Numerical Studies Of Iron Based Superconductors Using Spin-Fermion Models, Christopher Brian Bishop Dec 2017

Numerical Studies Of Iron Based Superconductors Using Spin-Fermion Models, Christopher Brian Bishop

Doctoral Dissertations

The iron pnictide and iron chalchogenide superconductors are studied numerically using classical Monte Carlo techniques to reproduce experimental data and make predictions about the nature of the relevant interactions. The focus will be using Spin-Fermion models in a classical approximation to explore the phase diagram and calculate important physical properties of these materials over a wide range of temperatures.

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Computational Exploration Of Vortex Nucleation In Type Ii Superconductors Using A Finite Element Method In Ginzburg-Landau Theory, Alden Roy Pack Dec 2017

Computational Exploration Of Vortex Nucleation In Type Ii Superconductors Using A Finite Element Method In Ginzburg-Landau Theory, Alden Roy Pack

Theses and Dissertations

Using a finite element method, we numerically solve the time-dependent Ginzburg-Landau equations of superconductivity to explore vortex nucleation in type II superconductors. We consider a cylindrical geometry and simulate the transition from a superconducting state to a mixed state. Using saddle-node bifurcation theory we evaluate the superheating field for a cylinder. We explore how surface roughness and thermal fluctuations influence vortex nucleation. This allows us to simulate material inhomogeneities that may lead to instabilities in superconducting resonant frequency cavities used in particle accelerators.

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Computational Exploration Of Vortex Nucleation In Type Ii Superconductors Using A Finite Element Method In Ginzburg-Landau Theory, Alden Roy Pack Dec 2017

Computational Exploration Of Vortex Nucleation In Type Ii Superconductors Using A Finite Element Method In Ginzburg-Landau Theory, Alden Roy Pack

Theses and Dissertations

Using a finite element method, we numerically solve the time-dependent Ginzburg-Landau equations of superconductivity to explore vortex nucleation in type II superconductors. We consider a cylindrical geometry and simulate the transition from a superconducting state to a mixed state. Using saddle-node bifurcation theory we evaluate the superheating field for a cylinder. We explore how surface roughness and thermal fluctuations influence vortex nucleation. This allows us to simulate material inhomogeneities that may lead to instabilities in superconducting resonant frequency cavities used in particle accelerators.

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Temperature Dependence Of Dynamical Spin Injection In A Superconducting Niobium Thin Film, Tyler S. Townsend Jan 2017

Temperature Dependence Of Dynamical Spin Injection In A Superconducting Niobium Thin Film, Tyler S. Townsend

Honors Undergraduate Theses

Spintronics is a research field that focuses on the manipulation of the quantum mechanical spin of charge carriers in solid state materials for future technological applications. Creating large spin currents with large relaxation times is sought after in the field of spintronics which may be aided by combining spintronics with superconductivity. This thesis provides a phenomological study of the effective change in ferromagnetic resonance linewidth, by dynamical spin injection into a permalloy-copper-niobium tri-layer in the superconducting state. The ferromagetic resonance linewidth was measured from 2-14 K. It was observed that there was a change in the behavior of the resonance …

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High Powered Pulsed Terahertz Light Generation From Superconducting Antenna Arrays, Nicholas C. Padgett Jan 2016

High Powered Pulsed Terahertz Light Generation From Superconducting Antenna Arrays, Nicholas C. Padgett

Browse all Theses and Dissertations

Terahertz radiation is invaluable for use in spectroscopy and imaging work due to its nondestructive nature. It has become a key focus for those wishing to develop sensors capable of detecting weapons and narcotics unobtrusively and at a distance as well as characterizing materials and identifying defects. An ultrafast pulsed (femtoseconds) laser incident on a superconducting ring has been predicted to cause the emission of terahertz (THz) radiation. It is theorized that the radiation is a result of the supercurrent being modulated by the breaking and recombining of Cooper pairs on the order of picoseconds, where the time scale determines …

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From JEff=1/2 Insulator To P-Wave Superconductor In Single-Crystal Sr2Ir1−XRuXO4 (0≤X≤1), Shujuan Yuan, Saicharan Aswartham, Jsaminka Terzic, H. Zheng, H. D. Zhao, P. Schlottmann, Gang Cao Dec 2015

From JEff=1/2 Insulator To P-Wave Superconductor In Single-Crystal Sr2Ir1−XRuXO4 (0≤X≤1), Shujuan Yuan, Saicharan Aswartham, Jsaminka Terzic, H. Zheng, H. D. Zhao, P. Schlottmann, Gang Cao

Physics and Astronomy Faculty Publications

Sr2IrO4 is a magnetic insulator assisted by strong spin-orbit coupling (SOC) whereas Sr2RuO4 is a p-wave superconductor. The contrasting ground states have been shown to result from the critical role of the strong SOC in the iridate. Our investigation of structural, transport, and magnetic properties reveals that substituting 4dRu4+(4d4) ions for 5dIr4+(5d5) ions in Sr2IrO4 directly adds holes to the t2g bands, reduces the SOC, and thus rebalances the competing energies in single-crystal Sr …

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Terahertz Radiation From High-Temperature Superconducting Bscco Mesas Of Various Geometries, Daniel P. Cerkoney Dec 2015

Terahertz Radiation From High-Temperature Superconducting Bscco Mesas Of Various Geometries, Daniel P. Cerkoney

HIM 1990-2015

The purpose of this thesis is to examine the radiation from high-temperature superconducting mesas of Bi2Sr2CaCu2O8+ (BSCCO). This is motivated by the need for coherent sources of continuous wave terahertz (THz) emission capable of radiating practically in the THz frequency band. As BSCCO has been shown to be tunable from 0.5–2.4 THz (i.e., through the entire socalled terahertz gap centered about 1 THz), and has a higher peak operating temperature near 1 THz than most alternative sources, it is a good candidate for imaging and spectroscopy device applications [1]. When a static DC voltage is applied to a BSCCO mesa, …

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Equations Of State In A Strongly Interacting Relativistic System, Jason Paul Keith Jan 2014

Equations Of State In A Strongly Interacting Relativistic System, Jason Paul Keith

Open Access Theses & Dissertations

It has long been understood that the ground state of a superdense quark system, a Fermi liquid of weakly interacting quarks, is unstable with respect to the formation of diquark condensates. This nonperturbative phenomenon is essentially equivalent to the Cooper in-stability of conventional BCS superconductivity. As the quark pairs have nonzero color charge, this kind of superconductivity breaks the SU(3) color gauge symmetry, thus the phe-nomenon is called color superconductivity. However, not much is known about the behavior of quark systems at moderate densities between the formation of baryons and asymptotic freedom. Strong theoretical and experimental evidence suggests that there …

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Electrochemistry And Staging In La2cuo4+D, P Blakeslee, R J. Birgeneau, F C. Chou, Rebecca J. Christianson, M A. Kastner, Y S. Lee, B O. Wells Jul 2011

Electrochemistry And Staging In La2cuo4+D, P Blakeslee, R J. Birgeneau, F C. Chou, Rebecca J. Christianson, M A. Kastner, Y S. Lee, B O. Wells

Rebecca J. Christianson

Measurements are reported of the time dependence of the current during electrochemical oxidation and reduction at a fixed voltage of single crystals and ceramic samples of La2CuO4+d. Staging peaks in neutron measurements of the single crystals together with the electrochemical measurements and magnetization measurements confirm that stage n=6 corresponds to d=0.055 +/- 0.05, the high-d side of the oxygen-rich–oxygen-poor miscibility gap. Furthermore, stage n=4 occurs at a value of d consistent with d{n^-1. For ceramic samples it is shown that two different superconducting compounds are formed depending on the oxidation voltage used.

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Josephson Scanning Tunneling Microscopy: A Local And Direct Probe Of The Superconducting Order Parameter, Richard P. Barber Jr., Hikari Kimura, Shuhei Ono, Yoichi Ando, Robert C. Dynes Oct 2009

Josephson Scanning Tunneling Microscopy: A Local And Direct Probe Of The Superconducting Order Parameter, Richard P. Barber Jr., Hikari Kimura, Shuhei Ono, Yoichi Ando, Robert C. Dynes

Physics

Direct measurements of the superconducting superfluid on the surface of vacuum-cleaved Bi2Sr2CaCu2O8+ BSCCO samples are reported. These measurements are accomplished via Josephson tunneling into the sample using a scanning tunneling microscope STM equipped with a superconducting tip. The spatial resolution of the STM of lateral distances less than the superconducting coherence length allows it to reveal local inhomogeneities in the pair wave function of the BSCCO. Instrument performance is demonstrated first with Josephson measurements of Pb films followed by the layered superconductor NbSe2. The relevant measurement parameter, the Josephson ICRN product, is discussed within the context of both BCS superconductors …

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Intergranular Phases In Cyclically Annealed Yba2cu3o7-X And Their Implications For Critical Current Densities, Andrew Peter Clarke Dec 2008

Intergranular Phases In Cyclically Annealed Yba2cu3o7-X And Their Implications For Critical Current Densities, Andrew Peter Clarke

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

We report changes in the intergranular material and grain morphology of YBa2Cu3O7-x during cyclic anneals between 780 and 980 ºC in oxygen at atmospheric pressure. Two endothermic reactions were detected: (a) the eutectic reaction of YBa2Cu3O7-x with CuO and BaCuO2 at 900 ºC (enthalpy ∆Ha) and (b) the peritectic reaction of YBa2Cu3O7-x with CuO at 950 ºC (∆Hb). During the first anneal, only reaction (b) is detected, and although it should only occur if there is an excess of CuO, …

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Scanning Josephson Tunneling Microscopy Of Single Crystal Bi2Sr2Cacu2O8+Δ With A Conventional Superconducting Tip, Richard P. Barber Jr., Hikari Kimura, Shuhei Ono, Yoichi Ando, Robert C. Dynes Jul 2008

Scanning Josephson Tunneling Microscopy Of Single Crystal Bi2Sr2Cacu2O8+Δ With A Conventional Superconducting Tip, Richard P. Barber Jr., Hikari Kimura, Shuhei Ono, Yoichi Ando, Robert C. Dynes

Physics

We have performed both Josephson and quasiparticle tunneling in vacuum tunnel junctions formed between a conventional superconducting scanning tunneling microscope tip and overdoped Bi2Sr2CaCu2O8+δ single crystals. A Josephson current is observed with a peak centered at a small finite voltage due to the thermal-fluctuation-dominated superconducting phase dynamics. Josephson measurements at different surface locations yield local values for the Josephson IcRn product. Corresponding energy gap measurements were also performed and a surprising inverse correlation was observed between the local IcRn product and the local energy gap.

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Negative Magnetoresistance, Negative Electroresistance, And Metallic Behavior On The Insulating Side Of The Two-Dimensional Superconductor-Insulator Transition In Granular Pb Films, Richard P. Barber Jr., Shih-Ying Hsu, James M. Valles Jr., Robert C. Dynes, Rolfe Eldridge Glover Iii Apr 2006

Negative Magnetoresistance, Negative Electroresistance, And Metallic Behavior On The Insulating Side Of The Two-Dimensional Superconductor-Insulator Transition In Granular Pb Films, Richard P. Barber Jr., Shih-Ying Hsu, James M. Valles Jr., Robert C. Dynes, Rolfe Eldridge Glover Iii

Physics

Granular Pb thin films on the insulating side of the two-dimensional superconductor-insulator transition are observed to exhibit a large negative magnetoresistance and electroresistance change in resistance with electric field at low temperatures. At high measurement voltages and low temperatures, the film resistances become temperature independent creating a "metallic" state. These phenomena are explained as manifestations of transport due to intergranular quasiparticle tunneling. This explanation might also provide insights into the similar behavior observed in other superconductors.

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Electronic Structure Properties And Bcs Superconductivity In Ss-Pyrochlore Oxides: KoSS₂O₆, Rolando Saniz, Julia E. Medvedeva, Lin Hui Ye, Tatsuya Shishidou, Arthur J. Freeman Sep 2004

Electronic Structure Properties And Bcs Superconductivity In Ss-Pyrochlore Oxides: KoSS₂O₆, Rolando Saniz, Julia E. Medvedeva, Lin Hui Ye, Tatsuya Shishidou, Arthur J. Freeman

Physics Faculty Research & Creative Works

We report a first-principles density-functional calculation of the electronic structure and properties of the recently discovered superconducting β-pyrochlore oxide KOs2O6. We find that the electronic structure near the Fermi energy EF is dominated by strongly hybridized Os 5d and O 2p states. A van Hove singularity very close to Ef leads to a relatively large density of states at EF, and the Fermi surface exhibits strong nesting along several directions. These features could provide the scattering processes leading to the observed anomalous temperature dependence of the resistivity and to the rather large …

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Resistive Transitions In Quench-Condensed Bi Films Near A Normal-Metal Ground Plane, Richard P. Barber Jr., Ben Kain Oct 2003

Resistive Transitions In Quench-Condensed Bi Films Near A Normal-Metal Ground Plane, Richard P. Barber Jr., Ben Kain

Physics

We report observations of the zero-field resistive transitions of superconducting quench-condensed Bi0.97Tl0.03 films both near electrically isolated normal-metal ground planes and on clean fire-polished glass. Transition temperatures, obtained by fitting the data with the two-dimensional Aslamazov-Larkin theory of fluctuation conductance, were found to be significantly enhanced for films deposited over ground planes versus those deposited onto insulating substrates. Conductivity enhancement due to superconducting fluctuations was found to be much less than expected for the thinnest samples. This suppression was coincident with broadened superconductor transitions that are consistent with nonuniform sample thickness. Sufficiently thick films showed reasonable agreement with both the …

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Tuning The Transition Temperature Of Superconducting Ag/Pb Films Via The Proximity Effect, Richard P. Barber Jr., Ben Kain, S. R. Khan Nov 2002

Tuning The Transition Temperature Of Superconducting Ag/Pb Films Via The Proximity Effect, Richard P. Barber Jr., Ben Kain, S. R. Khan

Physics

We report measurements of the transition temperature (TC) of superconducting films composed of various combinations of Ag and Pb layers. For samples with good electrical contact between the layers, the measured TC values show reasonable agreement with the Cooper model of the proximity effect. In poorly coupled samples, the normal layers appear to cause little if any suppression of the TC. We present a simple predictive expression for TC as a function of Ag content.

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Crossover From Phase Fluctuation To Amplitude-Dominated Superconductivity: A Model System, Richard P. Barber Jr., L. Merchant, J. Ostrick, Robert C. Dynes Mar 2001

Crossover From Phase Fluctuation To Amplitude-Dominated Superconductivity: A Model System, Richard P. Barber Jr., L. Merchant, J. Ostrick, Robert C. Dynes

Physics

We have experimentally studied a model system that demonstrates the crossover from a superconductor that is dominated by phase fluctuations, to one in which the amplitude of the order parameter is the controlling influence on Tc. This model system is comprised of two-dimensional granular Pb with an overlayer of Ag. The system displays many aspects of the phase diagram of the concentration dependence of Tc in the high-Tc superconductors, and this crossover has been applied to explain the phase diagram in that case. We point out the similarities and differences between the model system presented in this paper and the …

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Superconductor-Insulator Transition In Granular Pb Films Near A Superconducting Ground Plane, Richard P. Barber Jr., S. R. Khan, Eric Morre Pedersen, Ben Kain, A. J. Jordan Mar 2000

Superconductor-Insulator Transition In Granular Pb Films Near A Superconducting Ground Plane, Richard P. Barber Jr., S. R. Khan, Eric Morre Pedersen, Ben Kain, A. J. Jordan

Physics

We report observations of the zero-field superconductor-insulator transition in granular quench-condensed Pb for samples within 10-15 nm of relatively thick superconducting ground planes. Resistance vs temperature measurements of sufficiently thick Pb samples exhibit broadened superconductor transitions consistent with previous results on clean dielectric substrates. The lack of any measurable influence by the superconducting planes on the Pb film resistance is discussed within the context of zero-field vortex-antivortex unbinding explanations for the transition broadening.

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Tunneling Into Granular Pb Films In The Superconducting And Insulating Regimes, Richard P. Barber Jr., L. Merchant, Porta Arthur La, Robert C. Dynes Feb 1994

Tunneling Into Granular Pb Films In The Superconducting And Insulating Regimes, Richard P. Barber Jr., L. Merchant, Porta Arthur La, Robert C. Dynes

Physics

Tunneling measurements have been performed on both sides of the insulator-superconductor transition in quench-condensed granular Pb films. The results indicate that the Pb film consists of fully superconducting grains with essentially bulk values for the superconducting energy gap and transition temperature, even when the film exhibits insulating behavior in transport measurements. The density of states inferred from measurements in perpendicular magnetic field are consistent with magnetic spin-flip broadening.

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Low-Field Magnetoresistance In Granular Pb Films Near The Insulator-Superconductor Transition, Richard P. Barber Jr., Robert C. Dynes Oct 1993

Low-Field Magnetoresistance In Granular Pb Films Near The Insulator-Superconductor Transition, Richard P. Barber Jr., Robert C. Dynes

Physics

We have studied the insulator-superconductor transition in quench-condensed granular Pb films from 0.1 to 10 K. Resistance measurements were made in zero magnetic field and low noise conditions. Magnetoresistance measurements were also performed for low magnetic fields (less than 100 G). The magnetoresistance results on the superconducting side of the transition suggest that we are directly probing the finite length scales associated with the range of phase coherence in these granular materials.

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Hyper-Resistivity To Global-Superconductivity Transition By Annealing In Quench-Condensed Pb Films, Richard P. Barber Jr., Rolfe Eldridge Glover Iii Oct 1990

Hyper-Resistivity To Global-Superconductivity Transition By Annealing In Quench-Condensed Pb Films, Richard P. Barber Jr., Rolfe Eldridge Glover Iii

Physics

The rapid rise in resistance occurring in barely conducting quench-condensed Pb films cooled through temperatures characteristic of the bulk superconducting transition is found to be strongly current dependent, the resistance increasing rapidly with decreasing current and temperature. Annealing the same film at temperatures below 40 K changes the behavior to that of a conventional superconductor with resistance that drops as the film current and temperature decrease. Experimental evidence suggests this results from a transition from quasiparticle-dominated to Josephson-dominated tunneling.

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