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 Title
 Stability of BoseEinstein Condensates in a Random Potential.
 Creator

Pawlak, Kelly, Department of Physics
 Abstract/Description

In 1924 Bose and Einstein predicted that certain types of atomic gases, when cooled down to almost 0K, tend to condense (while remaining a gas) and form a "super atom" that behaves like a single wave rather than an assembly of particles. This phenomenon, known as BoseEinstein condensation (BEC), is counterintuitive as gases usually solidify at very low temperatures. Over the years, many scientists have failed trying to directly observe this phenomenon in laboratory experiments until 1995....
Show moreIn 1924 Bose and Einstein predicted that certain types of atomic gases, when cooled down to almost 0K, tend to condense (while remaining a gas) and form a "super atom" that behaves like a single wave rather than an assembly of particles. This phenomenon, known as BoseEinstein condensation (BEC), is counterintuitive as gases usually solidify at very low temperatures. Over the years, many scientists have failed trying to directly observe this phenomenon in laboratory experiments until 1995. Using a new experimental technique called laser cooling, two groups led by Wolfgang Ketterle and Eric Cornell (MIT) and Carl Wieman (CU) finally observed the formation of BECs and were awarded the physics Nobel Prize in 2001. BECs are now a very active topic in theoretical and experimental physics, having potential use in dozens of applications. Theoretically, the dynamics of the condensate are accurately modeled by the Gross—Pitaevskii equation (GPE). The analysis of the GPE is formidable due to its nonlinearity and therefore numerical simulations are necessary to survey basic BEC dynamics. As a result, there are many open questions regarding the behavior of BEC's and their dynamics. My research looks to answer the question of stability of the condensate. Given a certain experimental configuration, will the condensate remain stable so that data can be collected? Certain kinds of experimental variations are accurately modeled by a low frequency random potential (i.e. "noise"). By including this noise into mathematical workups of common experimental configurations, we can theoretically test the stability of the condensate. We use a 1D mathematical model with the assumption that the gas is dilute and noninteracting sans infrequent elastic collisions between the particles. The results are nontrivial, and show that the condensate favors periodicity.
Show less  Date Issued
 2013
 Identifier
 FSU_migr_undergradresearch0007
 Format
 Citation
 Title
 Magnetocaloric Effect in CeCoIn5 Utilizing a Miniature Cell for High Magnetic Fields and Low Temperatures.
 Creator

Bernheisel, Ashley, Department of Physics
 Abstract/Description

We studied the relationship between superconductivity and magnetism in the heavy fermion CeCoIn5 using a miniature cell in a top loading dilution refrigerator with a 16 T magnet (XCF – Xtreme Conditions Fridge). The construction and measurement techniques for a miniature cell are discussed. We were able to observe a first order superconducting phase transition with an upper critical field Hc2 at roughly 0.2 K. It changed position and shape with angle and magnetic field sweep rate because of...
Show moreWe studied the relationship between superconductivity and magnetism in the heavy fermion CeCoIn5 using a miniature cell in a top loading dilution refrigerator with a 16 T magnet (XCF – Xtreme Conditions Fridge). The construction and measurement techniques for a miniature cell are discussed. We were able to observe a first order superconducting phase transition with an upper critical field Hc2 at roughly 0.2 K. It changed position and shape with angle and magnetic field sweep rate because of CeCoIn5's anisotropic crystal structure and small heat exchanges through the wires used in the calorimeter.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0293
 Format
 Thesis
 Title
 Photomechanical Responses in Polymerized Azobenzene and Application to Heliostats.
 Creator

Roberts, Dennice, Department of Physics
 Abstract/Description

The search for viable forms of alternative energy has been a topic of recent research, and harvesting of solar energy has already been realized in various forms. Certain compounds have been shown to have visible physical responses when hit with light, transforming optical energy into motion. This project aims to better characterize properties of azobenzene, one such polymeric photomechanical actuator by considering it under various conditions of incident LED light. While much previous...
Show moreThe search for viable forms of alternative energy has been a topic of recent research, and harvesting of solar energy has already been realized in various forms. Certain compounds have been shown to have visible physical responses when hit with light, transforming optical energy into motion. This project aims to better characterize properties of azobenzene, one such polymeric photomechanical actuator by considering it under various conditions of incident LED light. While much previous research has been done on azobenzene polymerized in a polyacrylate, this project holds its focus on an azobenzenedoped polyimide compound. It also attempts to understand the role this smart material may play in solar heliostats. The movement of these apparati is usually controlled by electromagnetic motors, but could instead be moved using azobenzene as a photonpowered motor that does work on the polymer network.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0367
 Format
 Thesis
 Title
 The SelfDual Nonlinear Schrödinger Equation: Properties and Dynamics.
 Creator

Pawlak, Kelly, Department of Physics
 Abstract/Description

We introduce a new nonlinear equation, the SelfDual Nonlinear Schrödinger Equation (SDNLS) which resembles the GrossPitaevskii Equation [6] [4]. Unique to the SDNLS is its invariance under the Fourier transform — a form of duality which is reflected in systems such as the quantum harmonic oscillator. In this paper we explore various properties of the equation, starting with two proposed derivations based on known physics. We have managed to find a set of analytic timeindependent solutions...
Show moreWe introduce a new nonlinear equation, the SelfDual Nonlinear Schrödinger Equation (SDNLS) which resembles the GrossPitaevskii Equation [6] [4]. Unique to the SDNLS is its invariance under the Fourier transform — a form of duality which is reflected in systems such as the quantum harmonic oscillator. In this paper we explore various properties of the equation, starting with two proposed derivations based on known physics. We have managed to find a set of analytic timeindependent solutions as well as a set of dynamical ones, which are presented in the paper. In addition to these we explore numerical solutions and comment on the qualitative behavior of these solutions in different parameter regimes. Finally, we make remarks regarding the future study of this equation. This thesis reflects a portion of a manuscript soon to be submitted to Physical Review A, entitled "SelfDual Nonlocal Nonlinear Schrödinger Equation" in the upcoming months.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0335
 Format
 Thesis
 Title
 Meson Spectroscopy: γp>Λ^0 K^+ π^+ π^ Simulated Photoproduction of Strange Mesons.
 Creator

Norris, John, Department of Physics
 Abstract/Description

The goal of this project was to simulate a small scale experiment in meson spectroscopy involving the photoproduction of strange mesons according to: . The decay channels selected for study consisted of the final state topologies: and where the brackets denote a particle is allowed to go undetected. The theory behind the process predicts that when the 9 GeV photon is incident on the target proton (quark content udu), there is a resulting pair production and exchange of a strange quark and...
Show moreThe goal of this project was to simulate a small scale experiment in meson spectroscopy involving the photoproduction of strange mesons according to: . The decay channels selected for study consisted of the final state topologies: and where the brackets denote a particle is allowed to go undetected. The theory behind the process predicts that when the 9 GeV photon is incident on the target proton (quark content udu), there is a resulting pair production and exchange of a strange quark and antiquark. This interaction results in the formation of a recoil baryon (uds), and an (unobserved) excited Kaon system ( us(bar) ). These systems then decay and the products of these decays are used to study the physics of the interaction. In order to accomplish this task, a Monte Carlo simulation program was employed to generate phase space events corresponding to the end state topologies produced via the subsequent decays of these two systems. The resulting 1,003,648 simulated events consisting solely of particle 4vectors which were then processed by a number of different software utilities to further simulate the effects of propagation through and interaction with the virtual detector array; as well as to introduce additional background events which are an inevitable consequence of any real experimental setup. The resultant fully processed events were then reconstructed and processed by an analysis software program, employing a unique analysis plugin written specifically for this project, currently under development for use in the GlueX experiment being conducted at Jefferson Labs in Virginia. The acceptances that resulted from the above procedures were found to initially be 7.25% for the 5 particle state and 26.93% for the missing state, which is consistent with current estimates. However the subsequent kinematic fitting reduced these values to 1.27% and 4.59%, respectively, indicating there is still an issue in this part of the software. Once the acceptances had been generated, the phase spaces of both reactions were fully mapped out by means of invariant mass spectra.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0421
 Format
 Thesis
 Title
 Semiconductor NanostructureBased Field Effect Transistors for Biosensing Applications.
 Creator

Hazel, Anthony, Department of Physics
 Abstract/Description

Semiconductor nanostructures have shown great potential for detecting and measuring chemical and biological interactions. The advantage of the electrically based schemes is realtime, labelfree detection, which had been absent from methods which involved chemical and/or optical markers such as fluorescent labels. The most common technique is the utilization of single nanowirebased fieldeffect transistors (FETs), where the nanowire acts as the semiconducting channel. As biomolecules...
Show moreSemiconductor nanostructures have shown great potential for detecting and measuring chemical and biological interactions. The advantage of the electrically based schemes is realtime, labelfree detection, which had been absent from methods which involved chemical and/or optical markers such as fluorescent labels. The most common technique is the utilization of single nanowirebased fieldeffect transistors (FETs), where the nanowire acts as the semiconducting channel. As biomolecules interact with nanowire via chemisorption, the charge of the biomolecule supplies a local electric field that will affect the current through the wire. This project will focus on the use of tin dioxide (SnO2) nanobeltbased FETs and testing the viability of an extended gate design. The extended gate – a gold contact pad functionalized with a 16mercaptohexadecanoic acid (MHA) selfassemble monolayer (SAM) – will be functionalized instead of the nanobelt, which will be isolated via an oxide dielectric layer. Since MHA has an isoelectric point of 4.3, pH tests will determine if an appreciable signal can be obtained with the extended gate design.
Show less  Date Issued
 2012
 Identifier
 FSU_migr_uhm0115
 Format
 Thesis
 Title
 W Boson Production Charge Asymmetry in the Electron Channel.
 Creator

Huff, Ashley, Department of Physics
 Abstract/Description

We present a measurement of the W boson production charge asymmetry in protonantiproton collisions in the electron channel through W> enu decays using data collected with the DØ detector. The collision of an up quark with an antidown quark can produce a W+ boson while the collision of an antiup quark and a down quark can produce a W boson. These particles decay rapidly but we are able to measure their asymmetry by studying the resulting final state electrons and neutrinos. These results...
Show moreWe present a measurement of the W boson production charge asymmetry in protonantiproton collisions in the electron channel through W> enu decays using data collected with the DØ detector. The collision of an up quark with an antidown quark can produce a W+ boson while the collision of an antiup quark and a down quark can produce a W boson. These particles decay rapidly but we are able to measure their asymmetry by studying the resulting final state electrons and neutrinos. These results will be used to further constrain fits to parton distribution functions (PDFs) and improve the accuracy of future predictions for new physics.
Show less  Date Issued
 2013
 Identifier
 FSU_migr_uhm0176
 Format
 Thesis
 Title
 Studies in Developing a Particle Flow Algorithm for the New CMS Forward Calorimetry Upgrade.
 Creator

Black, Hampton, Department of Physics
 Abstract/Description

This thesis covers comparison studies for the Shashlik calorimeter, one of three possible electromagnetic calorimeter (ECAL) upgrades for the CMS detector at CERN. Currently, the lead tungstate crystals are doing very well; however, when the LHC will increase the total integrated luminosity, the crystals in the forward endcap will eventually become severely damaged from radiation, which is why scientists are investigating possible replacements. The methods used involved developing a Particle...
Show moreThis thesis covers comparison studies for the Shashlik calorimeter, one of three possible electromagnetic calorimeter (ECAL) upgrades for the CMS detector at CERN. Currently, the lead tungstate crystals are doing very well; however, when the LHC will increase the total integrated luminosity, the crystals in the forward endcap will eventually become severely damaged from radiation, which is why scientists are investigating possible replacements. The methods used involved developing a Particle Flow algorithm, in hopes of getting better results and increased accuracy when the number of interactions per proton bunch crossing (instantaneous luminosity) increases from 30 to 140. The Particle Flow algorithm could give improvement on the resolution in the high intensity environment compared to simpler algorithms. The Particle Flow algorithm being tested is still under development. Comparisons between three different clustering algorithms for the simplest case of electrons are presented. Initial studies of pions are also shown. The resolution for electrons is found to be around 68% for energies greater than 200 GeV.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0396
 Format
 Thesis
 Title
 Effective RMatrix Parameters of the WoodsSaxon Potential.
 Creator

Abrahamsen, Dylan, Department of Physics
 Abstract/Description

The phenomenological Rmatrix approach is one of the most practical tools for the study of multichannel resonant scattering data. This approach, however, has been subject to criticism for the relatively unconstrained phenomenological parameters. In this study the objective is to observe the connection between effective square well radius, the limiting case of the Rmatrix channel radius, and the parameters of the actual potential model. In this work the effective channel radius is determined...
Show moreThe phenomenological Rmatrix approach is one of the most practical tools for the study of multichannel resonant scattering data. This approach, however, has been subject to criticism for the relatively unconstrained phenomenological parameters. In this study the objective is to observe the connection between effective square well radius, the limiting case of the Rmatrix channel radius, and the parameters of the actual potential model. In this work the effective channel radius is determined by comparing the scattering observables of the WoodsSaxon potential and the square well.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0289
 Format
 Thesis
 Title
 Network Theoretical Approaches to Partitioning of Red Power Grids.
 Creator

Israels, Brett, Department of Physics
 Abstract/Description

Power grids are innately susceptible to electrical faults. Here we present divisive and agglomerative networktheoretical approaches to achieve intentional intelligent islanding of a power grid in order to limit cascading power failures in case a fault occurs. A power grid is modeled here as a network consisting of nodes and edges. The various methods we use are designed to partition a power grid network into smaller communities of noes with local generating capacity (islands). Here we...
Show morePower grids are innately susceptible to electrical faults. Here we present divisive and agglomerative networktheoretical approaches to achieve intentional intelligent islanding of a power grid in order to limit cascading power failures in case a fault occurs. A power grid is modeled here as a network consisting of nodes and edges. The various methods we use are designed to partition a power grid network into smaller communities of noes with local generating capacity (islands). Here we discuss results of using spectral matrix methods along with Monte Carlo methods to analyze and partition an illustrative example network, as well as the Floridian power grid, and the power distribution system for a conceptual allelectric naval vessel. We also contrast the effects of approximating the generating capacity of generators according to their degrees versus using their actual generating capacities. Finally, we propose an implementation strategy as well as possible directions for future study.
Show less  Date Issued
 2012
 Identifier
 FSU_migr_uhm0110
 Format
 Thesis
 Title
 The Search for Large Extra Dimensions via Single Photon plus Missing Energy Final States.
 Creator

Gomez, Alicia, Department of Physics
 Abstract/Description

There is a hierarchy problem present in the standard model of particle physics; the force of gravity is many magnitudes weaker than the other fundamental forces. The ADD model (ArkaniHamad, Dimopoulos, Dvali) proposes a solution to this hierarchy problem though the introduction of large extra spatial dimensions. Using 7.3 fb1 of data from the D0 detector at Fermi National Accelerator Laboratory, we analyze protonantiproton collisions at a center of mass energy of 1.96 TeV which result in...
Show moreThere is a hierarchy problem present in the standard model of particle physics; the force of gravity is many magnitudes weaker than the other fundamental forces. The ADD model (ArkaniHamad, Dimopoulos, Dvali) proposes a solution to this hierarchy problem though the introduction of large extra spatial dimensions. Using 7.3 fb1 of data from the D0 detector at Fermi National Accelerator Laboratory, we analyze protonantiproton collisions at a center of mass energy of 1.96 TeV which result in one photon plus missing transverse energy, where this missing transverse energy is associated with a graviton traveling into another dimension. We set limits on the value of the fundamental Planck scale MD from 1026 GeV to 868 GeV for two to eight extra spatial dimensions. This is a work in progress, and has not been approved by the D0 collaboration.
Show less  Date Issued
 2013
 Identifier
 FSU_migr_uhm0233
 Format
 Thesis
 Title
 High Pressure Fermiology of Uranium238: Sample Preparation Effects on Crystal Quality.
 Creator

Bernstein, Michael, Department of Physics
 Abstract/Description

The purpose of this thesis is to present the results of how the preparation of a sample of Uranium238 changes its crystal quality. First this thesis will explain the process of etching Uranium and what this does to a crystal batch. This thesis will then explore the process of "cutting" Uranium with an Electric Discharge Machine (EDM) and how this negatively affects the crystal. It will then delve into the effects of Jacksonpolishing and how it improves crystal quality. The largest portion...
Show moreThe purpose of this thesis is to present the results of how the preparation of a sample of Uranium238 changes its crystal quality. First this thesis will explain the process of etching Uranium and what this does to a crystal batch. This thesis will then explore the process of "cutting" Uranium with an Electric Discharge Machine (EDM) and how this negatively affects the crystal. It will then delve into the effects of Jacksonpolishing and how it improves crystal quality. The largest portion of this thesis will concentrate on the annealing of a crystal. It will explain what annealing is and why it too improves crystal quality. It will present the process used and data found concerning the melting point found for this particular batch of Uranium. It will then explore a range of temperatures and durations of anneals that either do or do not produce an improvement in crystal quality. It will also argue that certain shapes of crystals are affected differently by annealing than others. It will then provide a recommended path heading forward.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0295
 Format
 Thesis
 Title
 Domain Coarsening in the Hyperbolic Plane.
 Creator

Raffield, Jesse, Department of Physics
 Abstract/Description

Since the simplest case was solved exactly by Onsager in 1944, the twodimensional Ising model has become one of the most studied models in statistical physics. Despite its simplicity, it has found applications in research ranging from condensed matter physics to biology. Our research focused on an interesting variant of this model that lives within an area of negative Gaussian curvature instead of traditional Euclidean space. Specifically, a series of MonteCarlo simulations were conducted...
Show moreSince the simplest case was solved exactly by Onsager in 1944, the twodimensional Ising model has become one of the most studied models in statistical physics. Despite its simplicity, it has found applications in research ranging from condensed matter physics to biology. Our research focused on an interesting variant of this model that lives within an area of negative Gaussian curvature instead of traditional Euclidean space. Specifically, a series of MonteCarlo simulations were conducted to analyze how domains within the model coarsen as a function of time. In the Euclidean model, the feature size goes as t1/3<\sup>, which is close to our results on two of the Euclidean lattices, but for our model on a hyperbolic lattice the characteristic growth exponent was found to be much lower, approximately 0.13.
Show less  Date Issued
 2013
 Identifier
 FSU_migr_uhm0199
 Format
 Thesis
 Title
 Study of the e/pi ratio for the shashlik detector via simulated proton collision events.
 Creator

Jones, Spencer, Department of Physics
 Abstract/Description

The intention of this research project was to calculate the e/π ratio for the proposed Shashlik Detector for the Compact Muon Solenoid Experiment by simulating proton collision events in a virtual detector. The e/π ratio is the ratio of the Shashlik's ability to measure the energy of electromagnetic to hadronic particles. An upgrade is required for the electromagnetic calorimeter due to radiation damage of the current detector. The Shashlik Detector is a potential replacement for the current...
Show moreThe intention of this research project was to calculate the e/π ratio for the proposed Shashlik Detector for the Compact Muon Solenoid Experiment by simulating proton collision events in a virtual detector. The e/π ratio is the ratio of the Shashlik's ability to measure the energy of electromagnetic to hadronic particles. An upgrade is required for the electromagnetic calorimeter due to radiation damage of the current detector. The Shashlik Detector is a potential replacement for the current PbWO4 electromagnetic calorimeter and is designed with a layered pattern of scintillating material and absorber. I have analyzed this ratio for various absorber and scintillator thicknesses to determine the best ratio of materials to use.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0397
 Format
 Thesis
 Title
 Lagrange Meshes in Nuclear Physics.
 Creator

Hynds, Taylor, Department of Physics
 Abstract/Description

We examine different methods of solving the Schroedinger equation for two and threebody systems. We begin by constructing variational wave functions as expansions in a basis of orthogonal polynomials. This method has been found to give accurate results, given a sufficiently large basis. However, computationally this can become very cumbersome. We therefore employ the Lagrangemesh method, which leads to a simple calculation of both potential and kinetic matrix elements that is both...
Show moreWe examine different methods of solving the Schroedinger equation for two and threebody systems. We begin by constructing variational wave functions as expansions in a basis of orthogonal polynomials. This method has been found to give accurate results, given a sufficiently large basis. However, computationally this can become very cumbersome. We therefore employ the Lagrangemesh method, which leads to a simple calculation of both potential and kinetic matrix elements that is both computationally efficient and results in little to no loss in accuracy. This method has been applied to several problems with well known analytical solutions, and has given excellent results. We demonstrate the efficacy of this method in analyzing nuclear systems.
Show less  Date Issued
 2013
 Identifier
 FSU_migr_uhm0177
 Format
 Thesis
 Title
 Onchip Cavities for Magnetic Resonance Studies.
 Creator

Serniak, Kyle, Department of Physics
 Abstract/Description

The control of dynamics of spins in solidstate materials has direct implications at both fundamental and applied levels. Research topics, in particular quantum computing, rely heavily on both complex control techniques and long spin coherence times to achieve intricate and robust information control. A natural way of driving spin orientation is by using electromagnetic fields (photons) and it can be done either as a classical rotation or by entanglement with the field itself. We are focusing...
Show moreThe control of dynamics of spins in solidstate materials has direct implications at both fundamental and applied levels. Research topics, in particular quantum computing, rely heavily on both complex control techniques and long spin coherence times to achieve intricate and robust information control. A natural way of driving spin orientation is by using electromagnetic fields (photons) and it can be done either as a classical rotation or by entanglement with the field itself. We are focusing on implementing such techniques in solidstate systems containing diluted, highly coherent spins. The goal of this project is to design and implement an innovative setup for electron spin resonance spectroscopy (ESR) using onchip coplanar waveguide resonant cavities. Onchip cavity designs, such as microstrips, have been attracting interest as of late due to their high sensitivities and low noise baselines, which makes them particularly well suited for studying small, dilute spin samples. [3, 4] Through simulations we aim to optimize coupling gap parameters and maximize the quality factor of the cavity resonances in a nearly ideal system. Cavities were fabricated by photolithography and electron beam evaporation techniques at NHMFL, and their transmission properties were studied at 4.2 K and 15 mK. Future studies will include the fabrication of silver, aluminum, and niobium cavities of varying thickness and testing of cavity eï¬ectiveness in an ESR setup utilizing a dilution refrigerator.
Show less  Date Issued
 2013
 Identifier
 FSU_migr_uhm0183
 Format
 Thesis
 Title
 The Three Body Coulomb Problem: An Examination of Bound States and Stability as a Function of Individual Masses.
 Creator

Kondyukov, Grigoriy, Department of Physics
 Abstract/Description

In this work we study quantum nonrelativistic threebody systems interacting via Coulomb potential. The solution in this undertaking utilizes and expansion of wave functions using products of Laguerre polynomial, followed by variational adjustment of coordinate scaling parameters. The method used in this study was originally developed by C.L. Pekeris and its advantage stems from recursion relations available for Laguerre polynomial. We developed an implementation of modular C++ code for...
Show moreIn this work we study quantum nonrelativistic threebody systems interacting via Coulomb potential. The solution in this undertaking utilizes and expansion of wave functions using products of Laguerre polynomial, followed by variational adjustment of coordinate scaling parameters. The method used in this study was originally developed by C.L. Pekeris and its advantage stems from recursion relations available for Laguerre polynomial. We developed an implementation of modular C++ code for solving the threebody problem numerically with high precision, improving upon previous works. The stability of threebody systems as well as excitation energies of excited states and ionization energy in the parameter space of charges and masses is investigated.
Show less  Date Issued
 2015
 Identifier
 FSU_migr_uhm0502
 Format
 Thesis
 Title
 Feasibility of Using the James Webb Space Telescope for Infrared Observations of Type Ia Supernovae at Latetime.
 Creator

Alvarez, Pradiip, Department of Physics
 Abstract/Description

Despite the triumph of Type Ia Supernovae measuring cosmological distances, many of the details of the origin and evolution of SNe Ia remain unknown or highly controversial. There is still much debate about the specifics of the earliest phases of the thermonuclear explosion and the properties of the progenitor system. A better understanding of the distribution of radioactive burning products in SNe Ia via the analysis of the emission profile of [FeII] lines (in particular the strong 1.644 μm...
Show moreDespite the triumph of Type Ia Supernovae measuring cosmological distances, many of the details of the origin and evolution of SNe Ia remain unknown or highly controversial. There is still much debate about the specifics of the earliest phases of the thermonuclear explosion and the properties of the progenitor system. A better understanding of the distribution of radioactive burning products in SNe Ia via the analysis of the emission profile of [FeII] lines (in particular the strong 1.644 μm feature) could provide a clearer picture of these longstanding questions. Currently, we are pushing ground telescopes to the limit in order to observe only a few very nearby SNe Ia in the nearinfrared at latetime. The James Webb Space Telescope (JWST) will open a new window to the universe, allowing us to study infrared light from the cosmos with an unprecedented level of detail. Based on the current study, using the JWST Nearinfrared Spectrograph Exposure Time Calculator, we estimate that about 50 SNe Ia between epochs of 300400 days could be analyzed in a 3year study, generating as many as 105 spectra. Such a large scale study would allow making more definitive conclusions about unanswered questions such as the nature and distribution of dark energy in the universe and the large scale properties of the cosmos.
Show less  Date Issued
 2012
 Identifier
 FSU_migr_uhm0116
 Format
 Thesis
 Title
 Landau quantization and spinmomentum locking in topological Kondo insulators.
 Creator

Schlottmann, P.
 Abstract/Description

SmB6 has been predicted to be a strong topological Kondo insulator and experimentally it has been confirmed that at low temperatures the electrical conductivity only takes place at the surfaces of the crystal. Quantum oscillations and ARPES measurements revealed several Dirac cones on the (001) and (101) surfaces of the crystal. We considered three types of surface Dirac cones with an additional parabolic dispersion and studied their Landau quantization and the expectation value of the spin...
Show moreSmB6 has been predicted to be a strong topological Kondo insulator and experimentally it has been confirmed that at low temperatures the electrical conductivity only takes place at the surfaces of the crystal. Quantum oscillations and ARPES measurements revealed several Dirac cones on the (001) and (101) surfaces of the crystal. We considered three types of surface Dirac cones with an additional parabolic dispersion and studied their Landau quantization and the expectation value of the spin of the electrons. The Landau quantization is quite similar in all three cases and would give rise to very similar de Haasvan Alphen oscillations. The spinmomentum locking, on the other hand, differs dramatically. Without the additional parabolic dispersion the spins are locked in the plane of the surface. The parabolic dispersion, however, produces a gradual canting of the spins out of the surface plane. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Show less  Date Issued
 201605
 Identifier
 FSU_libsubv1_wos_000377962500116, 10.1063/1.4942795
 Format
 Citation
 Title
 Commensurate and incommensurate spindensity waves in heavy electron systems.
 Creator

Schlottmann, P.
 Abstract/Description

The nesting of the Fermi surfaces of an electron and a hole pocket separated by a nesting vector Q and the interaction between electrons gives rise to itinerant antiferromagnetism. The order can gradually be suppressed by mismatching the nesting and a quantum critical point (QCP) is obtained as the Neel temperature tends to zero. The transfer of pairs of electrons between the pockets can lead to a superconducting dome above the QCP (if Q is commensurate with the lattice, i.e. equal to G/2)....
Show moreThe nesting of the Fermi surfaces of an electron and a hole pocket separated by a nesting vector Q and the interaction between electrons gives rise to itinerant antiferromagnetism. The order can gradually be suppressed by mismatching the nesting and a quantum critical point (QCP) is obtained as the Neel temperature tends to zero. The transfer of pairs of electrons between the pockets can lead to a superconducting dome above the QCP (if Q is commensurate with the lattice, i.e. equal to G/2). If the vector Q is not commensurate with the lattice there are eight possible phases: commensurate and incommensurate spin and charge density waves and four superconductivity phases, two of them with modulated order parameter of the FFLO type. The renormalization group equations are studied and numerically integrated. A reentrant SDW phase (either commensurate or incommensurate) is obtained as a function of the mismatch of the Fermi surfaces and the magnitude of vertical bar Q  G/2 vertical bar. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Show less  Date Issued
 201605
 Identifier
 FSU_libsubv1_wos_000377962500103, 10.1063/1.4942549
 Format
 Citation
 Title
 Charge density waves and superconductivity in alphauranium.
 Creator

VanGennep, Derrick, Department of Physics
 Abstract/Description

We have measured the electrical resistivity and magnetoresistance of several αuranium single crystals under pressure. The residual resistivity ratios (RRRs) of these samples ranged from 158 to 265 and the pressure dependence is discussed. Superconductivity was observed at temperatures varying from approximately 20 mK at ambient pressure to 3 K at 16 kBar and critical fields were observed up to 0.5 T at 16 kBar. Sharp features were seen at each of the three charge density wave (CDW)...
Show moreWe have measured the electrical resistivity and magnetoresistance of several αuranium single crystals under pressure. The residual resistivity ratios (RRRs) of these samples ranged from 158 to 265 and the pressure dependence is discussed. Superconductivity was observed at temperatures varying from approximately 20 mK at ambient pressure to 3 K at 16 kBar and critical fields were observed up to 0.5 T at 16 kBar. Sharp features were seen at each of the three charge density wave (CDW) transitions starting near 40 K. The magnetic field and pressure dependences of the CDWs as well as superconductivity are presented and discussed.
Show less  Date Issued
 2012
 Identifier
 FSU_migr_uhm0132
 Format
 Thesis
 Title
 Magnetic Field Angles in Collapsing Molecular Clouds.
 Creator

Brooker, Ezra S., Department of Physics
 Abstract/Description

Star formation holds many answers to how the universe has evolved and how we came into existence. A big question in star formation theory centers around the role of magnetic fields and how strong they must be in the cloud to coincide with the observed star formation rate. However, measuring the magnetic fields in molecular clouds can be difficult due to the clouds being cold and optically thick in the optical band. Turbulence increases the difficulty by creating chaotic conditions within the...
Show moreStar formation holds many answers to how the universe has evolved and how we came into existence. A big question in star formation theory centers around the role of magnetic fields and how strong they must be in the cloud to coincide with the observed star formation rate. However, measuring the magnetic fields in molecular clouds can be difficult due to the clouds being cold and optically thick in the optical band. Turbulence increases the difficulty by creating chaotic conditions within the clouds. One method of determining determining these characteristics is by simulating collapsing molecular gas clouds using the principles of selfgravitation, magnetic fields, and turbulence, the main components of star formation. Data analysis of Enzo simulation data was done to help determine what the relative strength and angular orientation of magnetic fields around prestellar cores were relative to the global cloud. For our trans and superAlfvénic simulations, the preliminary results indicate that magnetic field orientations of prestellar cores are positively correlated with the mean magnetic field direction of the molecular cloud. This is similar to trends found in both observations and a subAlfvénic simulation.
Show less  Date Issued
 2015
 Identifier
 FSU_migr_uhm0539
 Format
 Thesis
 Title
 Physics of Compact Stars.
 Creator

Magilligan, Aaron K., Department of Physics
 Abstract/Description

Compact stars are an exciting and active area of research. This thesis covers two types of compact stellar objects: the white dwarf star and the neutron star. These stars do not rely on nuclear reactions to generate hydrostatic equilibrium; they are supported by the quantum degeneracy of their components (electrons and neutrons, respectively). Simple models are used to examine the inner structure of white dwarf stars. However, the study of neutron stars requires a model that can account for...
Show moreCompact stars are an exciting and active area of research. This thesis covers two types of compact stellar objects: the white dwarf star and the neutron star. These stars do not rely on nuclear reactions to generate hydrostatic equilibrium; they are supported by the quantum degeneracy of their components (electrons and neutrons, respectively). Simple models are used to examine the inner structure of white dwarf stars. However, the study of neutron stars requires a model that can account for their extreme density. The TolmanOppenheimerVolkoff (TOV) equation incorporates corrections from General Relativity to capture an accurate view of the structure of these much more dense objects.
Show less  Date Issued
 2015
 Identifier
 FSU_migr_uhm0460
 Format
 Thesis
 Title
 Microwave Properties of XRay Selected AGN.
 Creator

Rasmussen, Kaitlin C., Department of Physics
 Abstract/Description

When studying the Cosmic Microwave Background in detail, one needs to take into account extragalactic contamination sources such as Active Galactic Nuclei (AGN): distant galaxies whose high radiation output act as pollutants to sky surveys. The Cosmic Microwave Background isn't the only thing that these sources effect, either — surveys of extragalactic material, such as those of intergalactic gas, at any wavelength must account for AGN output. In this thesis we want to investigate whether...
Show moreWhen studying the Cosmic Microwave Background in detail, one needs to take into account extragalactic contamination sources such as Active Galactic Nuclei (AGN): distant galaxies whose high radiation output act as pollutants to sky surveys. The Cosmic Microwave Background isn't the only thing that these sources effect, either — surveys of extragalactic material, such as those of intergalactic gas, at any wavelength must account for AGN output. In this thesis we want to investigate whether there is a relationship between Xray and microwave contamination. Do the bright Xray sources we account for in CMB cosmology have an effect on studies of the intergalactic medium in the microwave? We found that while an increase in Xray flux does correspond to an increase in microwave flux, this is due to the fact that a loud source tends to produce more radiation across the entire spectrum. No particular correlation between Xray and microwave flux was discovered. As a result, bright Xray sources do not need to be accounted for in microwave surveys of intergalactic gas.
Show less  Date Issued
 2015
 Identifier
 FSU_migr_uhm0508
 Format
 Thesis
 Title
 Optimization of Local Annealing Processes in GaAs/AlGaAs Heterostructures for Spintronic Applications.
 Creator

Byrne, April M., Department of Physics
 Abstract/Description

This thesis presents work on optimizing a local annealing process for creating Ohmic contacts to a 2D electron gas (2DEG) within a GaAs/AlGaAs heterostructure. The optimization of this process will allow for fabrication of Hall devices to be used in the study of magnetic properties in quantum dots. To confirm good Ohmic contacts had been made to the 2DEG, data including IV characteristics was collected to show a linear relationship between current and voltage. Also, in order to preserve the...
Show moreThis thesis presents work on optimizing a local annealing process for creating Ohmic contacts to a 2D electron gas (2DEG) within a GaAs/AlGaAs heterostructure. The optimization of this process will allow for fabrication of Hall devices to be used in the study of magnetic properties in quantum dots. To confirm good Ohmic contacts had been made to the 2DEG, data including IV characteristics was collected to show a linear relationship between current and voltage. Also, in order to preserve the sample and its magnetic properties, temperature was measured near the contact to confirm that the contacts were heated to about 415°C with the quantum dots at a temperature between 200°C and 250°C.
Show less  Date Issued
 2015
 Identifier
 FSU_migr_uhm0517
 Format
 Thesis
 Title
 How Turbulence Enables Corecollapse Supernova Explosions.
 Creator

Mabanta, Quintin A., Murphy, Jeremiah W.
 Abstract/Description

An important result in corecollapse supernova (CCSN) theory is that spherically symmetric, onedimensional simulations routinely fail to explode, yet multidimensional simulations often explode. Numerical investigations suggest that turbulence eases the condition for explosion, but how it does it is not fully understood. We develop a turbulence model for neutrinodriven convection, and show that this turbulence model reduces the condition for explosions by about 30%, in concordance with...
Show moreAn important result in corecollapse supernova (CCSN) theory is that spherically symmetric, onedimensional simulations routinely fail to explode, yet multidimensional simulations often explode. Numerical investigations suggest that turbulence eases the condition for explosion, but how it does it is not fully understood. We develop a turbulence model for neutrinodriven convection, and show that this turbulence model reduces the condition for explosions by about 30%, in concordance with multidimensional simulations. In addition, we identify which turbulent terms enable explosions. Contrary to prior suggestions, turbulent ram pressure is not the dominant factor in reducing the condition for explosion. Instead, there are many contributing factors, with ram pressure being only one of them, but the dominant factor is turbulent dissipation (TD). Primarily, TD provides extra heating, adding significant thermal pressure and reducing the condition for explosion. The source of this TD power is turbulent kinetic energy, which ultimately derives its energy from the higher potential of an unstable convective profile. Investigating a turbulence model in conjunction with an explosion condition enables insight that is difficult to glean from merely analyzing complex multidimensional simulations. An explosion condition presents a clear diagnostic to explain why stars explode, and the turbulence model allows us to explore how turbulence enables explosion. Although we find that TD is a significant contributor to successful supernova explosions, it is important to note that this work is to some extent qualitative. Therefore, we suggest ways to further verify and validate our predictions with multidimensional simulations.
Show less  Date Issued
 20180320
 Identifier
 FSU_libsubv1_wos_000428455800008, 10.3847/15384357/aaaec7
 Format
 Citation
 Title
 SNe Ia AND THEIR ENVIRONMENT: THEORY AND APPLICATIONS TO SN 2014J.
 Creator

Dragulin, Paul, Hoeflich, Peter
 Abstract/Description

We present theoretical semianalytic models for the interaction of stellar winds with the interstellar medium (ISM) or prior mass loss implemented in our code SPICE, assuming spherical symmetry and powerlaw ambient density profiles and using the Pitheorem. This allows us to test a wide variety of configurations, their functional dependencies, and to find classes of solutions for given observations. Here, we study Type Ia Supernova (SN Ia) surroundings of single and double degenerate systems...
Show moreWe present theoretical semianalytic models for the interaction of stellar winds with the interstellar medium (ISM) or prior mass loss implemented in our code SPICE, assuming spherical symmetry and powerlaw ambient density profiles and using the Pitheorem. This allows us to test a wide variety of configurations, their functional dependencies, and to find classes of solutions for given observations. Here, we study Type Ia Supernova (SN Ia) surroundings of single and double degenerate systems, and their observational signatures. Winds may originate from the progenitor prior to the white dwarf (WD) stage, the WD, a donor star, or an accretion disk (AD). For MCh explosions, the AD wind dominates and produces a lowdensity void several light years across, surrounded by a dense shell. The bubble explains the lack of observed interaction in late time SN light curves for, at least, several years. The shell produces narrow ISM lines Doppler shifted by 10100 km s(1), and equivalent widths of approximate to 100 m angstrom and approximate to 1 m angstrom in cases of ambient environments with constant density and produced by prior mass loss, respectively. For SN2014J, both mergers and MCh mass explosions have been suggested based on radio and narrow lines. As a consistent and most likely solution, we find an AD wind running into an environment produced by the red giant wind of the progenitor during the preWD stage, and a short delay, 0.0131.4 Myr, between the WD formation and the explosion. Our framework may be applied more generally to stellar winds and star formation feedback in large scale galactic evolution simulations.
Show less  Date Issued
 20160210
 Identifier
 FSU_libsubv1_wos_000370370800026, 10.3847/0004637X/818/1/26
 Format
 Citation
 Title
 Soft Collinear Effective Theory For Gravity.
 Creator

Okui, Takemichi, Yunesi, Arash
 Abstract/Description

We present how to construct a soft collinear effective theory (SCET) for gravity at the leading and nexttoleading powers from the ground up. The soft graviton theorem and decoupling of collinear gravitons at the leading power are manifest from the outset in the effective symmetries of the theory. At the nexttoleading power, certain simple structures of amplitudes, which are completely obscure in Feynman diagrams of the full theory, are also revealed, which greatly simplifies calculations....
Show moreWe present how to construct a soft collinear effective theory (SCET) for gravity at the leading and nexttoleading powers from the ground up. The soft graviton theorem and decoupling of collinear gravitons at the leading power are manifest from the outset in the effective symmetries of the theory. At the nexttoleading power, certain simple structures of amplitudes, which are completely obscure in Feynman diagrams of the full theory, are also revealed, which greatly simplifies calculations. The effective Lagrangian is highly constrained by effectivelymultiple copies of diffeomorphism invariance that are inevitably present in gravity SCET due to mode separation, an essential ingredient of any SCET. Further explorations of effective theories of gravity with mode separation may shed light on Lagrangianlevel understandings of some of the surprising properties of gravitational scattering amplitudes. A gravity SCET with an appropriate inclusion of Glauber modes may serve as a powerful tool for studying gravitational scattering in the Regge limit.
Show less  Date Issued
 20180312
 Identifier
 FSU_libsubv1_wos_000427114700012, 10.1103/PhysRevD.97.066011
 Format
 Citation
 Title
 Validating Neuralnetwork Refinements Of Nuclear Mass Models.
 Creator

Utama, R., Piekarewicz, J.
 Abstract/Description

Background: Nuclear astrophysics centers on the role of nuclear physics in the cosmos. In particular, nuclear masses at the limits of stability are critical in the development of stellar structure and the origin of the elements. Purpose: We aim to test and validate the predictions of recently refined nuclear mass models against the newly published AME2016 compilation. Methods: The basic paradigm underlining the recently refined nuclear mass models is based on existing stateoftheart models...
Show moreBackground: Nuclear astrophysics centers on the role of nuclear physics in the cosmos. In particular, nuclear masses at the limits of stability are critical in the development of stellar structure and the origin of the elements. Purpose: We aim to test and validate the predictions of recently refined nuclear mass models against the newly published AME2016 compilation. Methods: The basic paradigm underlining the recently refined nuclear mass models is based on existing stateoftheart models that are subsequently refined through the training of an artificial neural network. Bayesian inference is used to determine the parameters of the neural network so that statistical uncertainties are provided for all model predictions. Results: We observe a significant improvement in the Bayesian neural network (BNN) predictions relative to the corresponding "bare" models when compared to the nearly 50 new masses reported in the AME2016 compilation. Further, AME2016 estimates for the handful of impactful isotopes in the determination of rprocess abundances are found to be in fairly good agreement with our theoretical predictions. Indeed, the BNNimproved DufloZuker model predicts a rootmeansquare deviation relative to experiment of sigma(rms) similar or equal to 400 keV. Conclusions: Given the excellent performance of the BNN refinement in confronting the recently published AME2016 compilation, we are confident of its critical role in our quest for mass models of the highest quality. Moreover, as uncertainty quantification is at the core of the BNN approach, the improved mass models are in a unique position to identify those nuclei that will have the strongest impact in resolving some of the outstanding questions in nuclear astrophysics.
Show less  Date Issued
 20180116
 Identifier
 FSU_libsubv1_wos_000423123400001, 10.1103/PhysRevC.97.014306
 Format
 Citation
 Title
 Delta(c) Semileptonic Decays In A Quark Model.
 Creator

Hussain, Md Mozammel, Roberts, Winston
 Abstract/Description

Hadronic form factors for semileptonic decay of the Lambda(c) are calculated in a nonrelativistic quark model. The full quark model wave functions are employed to numerically calculate the form factors to all relevant orders in ( 1/m(c), 1/m(s)). The form factors obtained satisfy relationships expected from the heavy quark effective theory ( HQET). The differential decay rates and branching fractions are calculated for transitions to the ground state and a number of excited states of Lambda...
Show moreHadronic form factors for semileptonic decay of the Lambda(c) are calculated in a nonrelativistic quark model. The full quark model wave functions are employed to numerically calculate the form factors to all relevant orders in ( 1/m(c), 1/m(s)). The form factors obtained satisfy relationships expected from the heavy quark effective theory ( HQET). The differential decay rates and branching fractions are calculated for transitions to the ground state and a number of excited states of Lambda The branching fraction of the semileptonic decay width to the total width of Lambda(c) has been calculated and compared with other theoretical estimates and experimental results. The branching fractions for Lambda(c) >Lambda*iota(+)nu(iota)>Sigma pi iota(+)nu(iota) and Lambda(c) > Lambda*iota(+)nu(iota) > NK iota(+)nu(iota) are also calculated. Apart from decays to the ground state Lambda(1115), it is found that decays through the Lambda(1405) provide a significant portion of the branching fraction Lambda(c) > Xs iota nu(iota). A new estimate for f = B(Lambda(+)(c) > Lambda iota(+) nu(iota))/B(Lambda(+)(c) > Chi(+)(s) nu(iota)) is obtained.
Show less  Date Issued
 20170313
 Identifier
 FSU_libsubv1_wos_000396030900002, 10.1103/PhysRevD.95.053005
 Format
 Citation
 Title
 A Brief History Of The Introduction Of Generalized Ensembles To Markov Chain Monte Carlo Simulations.
 Creator

Berg, Bernd A.
 Abstract/Description

The most efficient weights for Markov chain Monte Carlo calculations of physical observables are not necessarily those of the canonical ensemble. Generalized ensembles, which do not exist in nature but can be simulated on computers, lead often to a much faster convergence. In particular, they have been used for simulations of first order phase transitions and for simulations of complex systems in which conflicting constraints lead to a rugged free energy landscape. Starting off with the...
Show moreThe most efficient weights for Markov chain Monte Carlo calculations of physical observables are not necessarily those of the canonical ensemble. Generalized ensembles, which do not exist in nature but can be simulated on computers, lead often to a much faster convergence. In particular, they have been used for simulations of first order phase transitions and for simulations of complex systems in which conflicting constraints lead to a rugged free energy landscape. Starting off with the Metropolis algorithm and Hastings' extension, I present a minireview which focuses on the explosive use of generalized ensembles in the early 1990s. Illustrations are given, which range from spin models to peptides.
Show less  Date Issued
 201704
 Identifier
 FSU_libsubv1_wos_000399440100003, 10.1140/epjst/e2016602362
 Format
 Citation
 Title
 Student Reasoning of Conservation of Mechanical Energy in a Gravitational Field Without Other WorkProducing Forces.
 Creator

Smith, Cody R
 Abstract/Description

This thesis aimed to provide insight into the process students go through in their effort to understand conservation of mechanical energy in an undergraduate studio physics classroom. The data collected includes a transcript of the conversations a group had while working through a lab that asked students to plot potential and kinetic energies versus time of a bouncing kick ball over the course of 3 bounces, the lab reports of 3 groups from said lab, and all of those group members' Force...
Show moreThis thesis aimed to provide insight into the process students go through in their effort to understand conservation of mechanical energy in an undergraduate studio physics classroom. The data collected includes a transcript of the conversations a group had while working through a lab that asked students to plot potential and kinetic energies versus time of a bouncing kick ball over the course of 3 bounces, the lab reports of 3 groups from said lab, and all of those group members' Force Concept Inventory and Energy and Momentum Concept Survey pre and posttests. The transcript proved most useful in pointing out common starting points in student reasoning, showing what ideas students begin a lab with before they make sense of it all by the end. The most confounding issues that students seemed to have came when a second dimension of motion was added to scenarios (i.e. thinking about a ball rolling down a ramp instead of just bouncing straight up and down). Unfortunately there was not enough evidence for me to make claim about why this second dimension is more of a problem for students, only that this remained an issue for them from the beginning to the end of the semester.
Show less  Date Issued
 20180802
 Identifier
 FSU_libsubv1_scholarship_submission_1533244807_a4691678
 Format
 Thesis
 Title
 Macroscopically Constrained Wanglandau Method For Systems With Multiple Order Parameters And Its Application To Drawing Complex Phase Diagrams.
 Creator

Chan, C. H., Brown, G., Rikvold, P. A.
 Abstract/Description

A generalized approach to WangLandau simulations, macroscopically constrained WangLandau, is proposed to simulate the density of states of a system with multiple macroscopic order parameters. The method breaks a multidimensional randomwalk process in phase space into many separate, onedimensional randomwalk processes in welldefined subspaces. Each of these random walks is constrained to a different set of values of the macroscopic order parameters. When the multivariable density of...
Show moreA generalized approach to WangLandau simulations, macroscopically constrained WangLandau, is proposed to simulate the density of states of a system with multiple macroscopic order parameters. The method breaks a multidimensional randomwalk process in phase space into many separate, onedimensional randomwalk processes in welldefined subspaces. Each of these random walks is constrained to a different set of values of the macroscopic order parameters. When the multivariable density of states is obtained for one set of values of fieldlike model parameters, the density of states for any other values of these parameters can be obtained by a simple transformation of the total system energy. All thermodynamic quantities of the system can then be rapidly calculated at any point in the phase diagram. We demonstrate how to use the multivariable density of states to draw the phase diagram, as well as orderparameter probability distributions at specific phase points, for a model spincrossover material: an antiferromagnetic Ising model with ferromagnetic longrange interactions. The fieldlike parameters in this model are an effective magnetic field and the strength of the longrange interaction.
Show less  Date Issued
 20170508
 Identifier
 FSU_libsubv1_wos_000401233400009, 10.1103/PhysRevE.95.053302
 Format
 Citation
 Title
 Nuclear Charge Radii.
 Creator

Utama, R., Chen, WeiChia, Piekarewicz, J.
 Abstract/Description

The distribution of electric charge in atomic nuclei is fundamental to our understanding of the complex nuclear dynamics and a quintessential observable to validate nuclear structure models.. The aim of this study is to explore a novel approach that combines sophisticated models of nuclear structure with Bayesian neural networks (BNN) to generate predictions for the charge radii of thousands of nuclei throughout the nuclear chart. A class of relativistic energy density functionals is used to...
Show moreThe distribution of electric charge in atomic nuclei is fundamental to our understanding of the complex nuclear dynamics and a quintessential observable to validate nuclear structure models.. The aim of this study is to explore a novel approach that combines sophisticated models of nuclear structure with Bayesian neural networks (BNN) to generate predictions for the charge radii of thousands of nuclei throughout the nuclear chart. A class of relativistic energy density functionals is used to provide robust predictions for nuclear charge radii. In turn, these predictions are refined through Bayesian learning for a neural network that is trained using residuals between theoretical predictions and the experimental data. Although predictions obtained with density functional theory provide a fairly good description of experiment, our results show significant improvement (better than 40%) after BNN refinement. Moreover, these improved results for nuclear charge radii are supplemented with theoretical error bars. We have successfully demonstrated the ability of the BNN approach to significantly increase the accuracy of nuclear models in the predictions of nuclear charge radii. However, as many before us, we failed to uncover the underlying physics behind the intriguing behavior of charge radii along the calcium isotopic chain.
Show less  Date Issued
 201611
 Identifier
 FSU_libsubv1_wos_000386497800002, 10.1088/09543899/43/11/114002
 Format
 Citation
 Title
 Nuclear mass predictions for the crustal composition of neutron stars: A Bayesian neural network approach.
 Creator

Utama, R., Piekarewicz, J., Prosper, H. B.
 Abstract/Description

Background: Besides their intrinsic nuclearstructure value, nuclear mass models are essential for astrophysical applications, such as rprocess nucleosynthesis and neutronstar structure. Purpose: To overcome the intrinsic limitations of existing "stateoftheart" mass models through a refinement based on a Bayesian neural network (BNN) formalism. Methods: A novel BNN approach is implemented with the goal of optimizing mass residuals between theory and experiment. Results: A significant...
Show moreBackground: Besides their intrinsic nuclearstructure value, nuclear mass models are essential for astrophysical applications, such as rprocess nucleosynthesis and neutronstar structure. Purpose: To overcome the intrinsic limitations of existing "stateoftheart" mass models through a refinement based on a Bayesian neural network (BNN) formalism. Methods: A novel BNN approach is implemented with the goal of optimizing mass residuals between theory and experiment. Results: A significant improvement (of about 40%) in the mass predictions of existing models is obtained after BNN refinement. Moreover, these improved results are now accompanied by proper statistical errors. Finally, by constructing a "world average" of these predictions, a mass model is obtained that is used to predict the composition of the outer crust of a neutron star. Conclusions: The power of the Bayesian neural network method has been successfully demonstrated by a systematic improvement in the accuracy of the predictions of nuclear masses. Extension to other nuclear observables is a natural next step that is currently under investigation.
Show less  Date Issued
 20160120
 Identifier
 FSU_libsubv1_wos_000368514400002, 10.1103/PhysRevC.93.014311
 Format
 Citation
 Title
 Radiative Decay Of Neutronunbound Intruder States In O19.
 Creator

Dungan, R., Tabor, S. L., Tripathi, Vandana, Volya, A., Kravvaris, K., Abromeit, B., Caussyn, D. D., Morrow, S., Parker, J. J., Tai, P.L., VonMoss, J. M.
 Abstract/Description

The Be9(C14, alpha gamma) reaction at ELab = 30 and 35 MeV was used to study excited states of O19. The Florida State University (FSU) gamma detector array was used to detect gamma radiation in coincidence with charged particles detected and identified with a silicon Delta EE particle telescope. gamma decays have been observed for the first time from six states ranging from 368 to 2147 keV above the neutron separation energy (Sn = 3962 keV) in O19. The gammadecaying states are...
Show moreThe Be9(C14, alpha gamma) reaction at ELab = 30 and 35 MeV was used to study excited states of O19. The Florida State University (FSU) gamma detector array was used to detect gamma radiation in coincidence with charged particles detected and identified with a silicon Delta EE particle telescope. gamma decays have been observed for the first time from six states ranging from 368 to 2147 keV above the neutron separation energy (Sn = 3962 keV) in O19. The gammadecaying states are interspersed among states previously observed to decay by neutron emission. The ability of electromagnetic decay to compete successfully with neutron decay is explained in terms of neutron angular momentum barriers and small spectroscopic factors implying higher spin and complex structure for these intruder states. These results illustrate the need for complementary experimental approaches to best illuminate the complete nuclear structure.
Show less  Date Issued
 20160222
 Identifier
 FSU_libsubv1_wos_000370798600001, 10.1103/PhysRevC.93.021302
 Format
 Citation
 Title
 Nonmonotonic Dnalengthdependent Mobility In Pluronic Gels.
 Creator

You, Seungyong, Wei, Ling, Shanbhag, Sachin, Van Winkle, David H.
 Abstract/Description

Twodimensional electrophoresis was used to analyze the mobility of DNA fragments in micellar gels of pluronic F127 (EO100PO70EO100) and pluronic P123 (EO20PO70EO20). The 203500 base pair DNA fragments were separated by size first in agarose gels, and then in pluronic gels at room temperature. In agarose gels, the DNA mobility decreases monotonically with increasing DNA length. In pluronic gels, however, the mobility varies nonmonotonically according to fragment lengths that are strongly...
Show moreTwodimensional electrophoresis was used to analyze the mobility of DNA fragments in micellar gels of pluronic F127 (EO100PO70EO100) and pluronic P123 (EO20PO70EO20). The 203500 base pair DNA fragments were separated by size first in agarose gels, and then in pluronic gels at room temperature. In agarose gels, the DNA mobility decreases monotonically with increasing DNA length. In pluronic gels, however, the mobility varies nonmonotonically according to fragment lengths that are strongly correlated with the diameter of the spherical micelles. Brownian dynamics (BD) simulations with shortranged intraDNA hydrodynamic interactions were performed to numerically calculate the lengthdependent mobility in pluronic lattices. The rising and falling trends, as well as the oscillations of mobility, were captured by the coarsegrained BD simulations. Molecular dynamics simulations in pluronic F127, with explicitly modeled micelle coronas, justified that the hydrodynamic interactions mediated by the complex fluid of hydrated poly(ethylene oxide) are a possible reason for the initial rise of mobility with DNA length.
Show less  Date Issued
 20170407
 Identifier
 FSU_libsubv1_wos_000399393400005, 10.1103/PhysRevE.95.042602
 Format
 Citation
 Title
 Subcoulomb He3 Transfer And Its Use To Extract Threeparticle Asymptotic Normalization Coefficients.
 Creator

Avila, M. L., Baby, L. T., Belarge, J., Keeley, N., Kemper, K. W., Koshchiy, E., Kuchera, A. N., Rogachev, G. V., Rusek, K., SantiagoGonzalez, D.
 Abstract/Description

Data for the C13(Li6, t)O16 reaction, obtained in inverse kinematics at a C13 incident energy of 7.72 MeV, are presented. A distorted wave Born approximation (DWBA) analysis was used to extract spectroscopic factors and asymptotic normalization coefficients (ANCs) for the overlaps, subject to the assumption of a fixed overlap. The variation of the extracted spectroscopic factors and ANCs as a function of various inputs to the DWBA calculations was explored. The extracted ANCs were found...
Show moreData for the C13(Li6, t)O16 reaction, obtained in inverse kinematics at a C13 incident energy of 7.72 MeV, are presented. A distorted wave Born approximation (DWBA) analysis was used to extract spectroscopic factors and asymptotic normalization coefficients (ANCs) for the < O16 vertical bar C13 + He3 > overlaps, subject to the assumption of a fixed < Li6 vertical bar He3 + H3 > overlap. The variation of the extracted spectroscopic factors and ANCs as a function of various inputs to the DWBA calculations was explored. The extracted ANCs were found to vary as a cubic function of the radius of the potential well binding the transferred He3 to the C13 core while the spectroscopic factors varied as a quartic function of the radius. The ANC values could be determined to within a factor of two for this system.
Show less  Date Issued
 20180122
 Identifier
 FSU_libsubv1_wos_000423230200004, 10.1103/PhysRevC.97.014313
 Format
 Citation
 Title
 Orbital twochannel Kondo effect in epitaxial ferromagnetic L1(0)MnAl films.
 Creator

Zhu, L. J., Nie, S. H., Xiong, P., Schlottmann, P., Zhao, J. H.
 Abstract/Description

The orbital twochannel Kondo effect displaying exotic nonFermi liquid behaviour arises in the intricate scenario of two conduction electrons compensating a pseudospin1/2 impurity of twolevel system. Despite extensive efforts for several decades, no material system has been clearly identified to exhibit all three transport regimes characteristic of the twochannel Kondo effect in the same sample, leaving the interpretation of the experimental results a subject of debate. Here we present a...
Show moreThe orbital twochannel Kondo effect displaying exotic nonFermi liquid behaviour arises in the intricate scenario of two conduction electrons compensating a pseudospin1/2 impurity of twolevel system. Despite extensive efforts for several decades, no material system has been clearly identified to exhibit all three transport regimes characteristic of the twochannel Kondo effect in the same sample, leaving the interpretation of the experimental results a subject of debate. Here we present a transport study suggestive of a robust orbital twochannel Kondo effect in epitaxial ferromagnetic L1(0)MnAl films, as evidenced by a magnetic fieldindependent resistivity upturn with a clear transition from logarithmic to squareroot temperature dependence and deviation from it in three distinct temperature regimes. Our results also provide an experimental indication of the presence of twochannel Kondo physics in a ferromagnet, pointing to considerable robustness of the orbital twochannel Kondo effect even in the presence of spin polarization of the conduction electrons.
Show less  Date Issued
 201602
 Identifier
 FSU_libsubv1_wos_000371042300002, 10.1038/ncomms10817
 Format
 Citation
 Title
 Acoustic wave absorption as a probe of dynamical geometrical response of fractional quantum Hall liquids.
 Creator

Yang, Kun
 Abstract/Description

We show that an acoustic crystalline wave gives rise to an effect similar to that of a gravitational wave to an electron gas. Applying this idea to a twodimensional electron gas in the fractional quantum Hall regime, this allows for experimental study of its intraLandau level dynamical response in the longwavelength limit. To study such response we generalize Haldane's geometrical description of fractional quantum Hall states to situations where the external metric is time dependent. We...
Show moreWe show that an acoustic crystalline wave gives rise to an effect similar to that of a gravitational wave to an electron gas. Applying this idea to a twodimensional electron gas in the fractional quantum Hall regime, this allows for experimental study of its intraLandau level dynamical response in the longwavelength limit. To study such response we generalize Haldane's geometrical description of fractional quantum Hall states to situations where the external metric is time dependent. We show that such timedependent metric (generated by acoustic wave) couples to collective modes of the system, including a quadrapolar mode at long wavelength, and magnetoroton at finite wavelength. Energies of these modes can be revealed in spectroscopic measurements, controlled by straininduced Fermi velocity anisotropy. We argue that such geometrical probe provides a potentially highly useful alternative probe of quantum Hall liquids, in addition to the usual electromagnetic response.
Show less  Date Issued
 20160415
 Identifier
 FSU_libsubv1_wos_000374297500001, 10.1103/PhysRevB.93.161302
 Format
 Citation
 Title
 Difference In Proton Radii Of Mirror Nuclei As A Possible Surrogate For The Neutron Skin.
 Creator

Yang, Junjie, Piekarewicz, J.
 Abstract/Description

It has recently been suggested that differences in the charge radii of mirror nuclei are proportional to the neutronskin thickness of neutronrich nuclei and to the slope of the symmetry energy L [Brown, Phys. Rev. Lett. 102, 122502 (2009)]. The determination of the neutron skin has important implications for nuclear physics and astrophysics. Although the use of electroweak probes provides a largely modelindependent determination of the neutron skin, the experimental challenges are enormous...
Show moreIt has recently been suggested that differences in the charge radii of mirror nuclei are proportional to the neutronskin thickness of neutronrich nuclei and to the slope of the symmetry energy L [Brown, Phys. Rev. Lett. 102, 122502 (2009)]. The determination of the neutron skin has important implications for nuclear physics and astrophysics. Although the use of electroweak probes provides a largely modelindependent determination of the neutron skin, the experimental challenges are enormous. Thus, the possibility that differences in the charge radii of mirror nuclei may be used as a surrogate for the neutron skin is a welcome alternative. To test the validity of this assumption we perform calculations based on a set of relativistic energy density functionals that span a wide region of values of L. Our results confirm that the difference in charge radii between various neutrondeficient nickel isotopes and their corresponding mirror nuclei is indeed strongly correlated to both the neutronskin thickness and L. Moreover, given that various neutronstar properties are also sensitive to L, a datatodata relation emerges between the difference in charge radii of mirror nuclei and the radius of lowmass neutron stars.
Show less  Date Issued
 20180122
 Identifier
 FSU_libsubv1_wos_000423230200005, 10.1103/PhysRevC.97.014314
 Format
 Citation
 Title
 Simple derivation of the FongWandzura pulse sequence.
 Creator

Zeuch, Daniel, Bonesteel, N. E.
 Abstract/Description

We give an analytic construction of a class of twoqubit gate pulse sequences that act on five of the six spin1/2 particles used to encode a pair of exchangeonly threespin qubits. Within this class, the problem of gate construction reduces to that of finding a smaller sequence that acts on four spins and is subject to a simple constraint. The optimal sequence satisfying this constraint yields a twoqubit gate sequence equivalent to that found numerically by Fong and Wandzura. Our...
Show moreWe give an analytic construction of a class of twoqubit gate pulse sequences that act on five of the six spin1/2 particles used to encode a pair of exchangeonly threespin qubits. Within this class, the problem of gate construction reduces to that of finding a smaller sequence that acts on four spins and is subject to a simple constraint. The optimal sequence satisfying this constraint yields a twoqubit gate sequence equivalent to that found numerically by Fong and Wandzura. Our construction is sufficiently simple that it can be carried out entirely with pen, paper, and knowledge of a few basic facts about quantum spin.
Show less  Date Issued
 20160125
 Identifier
 FSU_libsubv1_wos_000368983200001, 10.1103/PhysRevA.93.010303
 Format
 Citation
 Title
 Spin correlations and topological entanglement entropy in a nonAbelian spinone spin liquid.
 Creator

Wildeboer, Julia, Bonesteel, N. E.
 Abstract/Description

We analyze the properties of a nonAbelian spinone chiral spin liquid state proposed by Greiter and Thomale [Phys. Rev. Lett. 102, 207203 (2009)] using Monte Carlo. In this state the bosonic nu = 1 MooreRead Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a threedimensional space of these states corresponding to the topological degeneracy of the bosonic MooreRead state on the...
Show moreWe analyze the properties of a nonAbelian spinone chiral spin liquid state proposed by Greiter and Thomale [Phys. Rev. Lett. 102, 207203 (2009)] using Monte Carlo. In this state the bosonic nu = 1 MooreRead Pfaffian wave function is used to describe a gas of bosonic spin flips on a square lattice with one flux quantum per plaquette. For toroidal geometries there is a threedimensional space of these states corresponding to the topological degeneracy of the bosonic MooreRead state on the torus. We show that spin correlations for different states in this space become indistinguishable for large system size. We also calculate the Renyi entanglement entropy for different system partitions to extract the topological entanglement entropy and provide evidence that the topological order of the lattice spinliquid state is the same as that of the continuum MooreRead state from which it is constructed.
Show less  Date Issued
 20160718
 Identifier
 FSU_libsubv1_wos_000380104300008, 10.1103/PhysRevB.94.045125
 Format
 Citation
 Title
 Structure And Ferromagnetic Instability Of The Oxygendeficient Srtio3 Surface.
 Creator

Ghosh, Soham S., Manousakis, Efstratios
 Abstract/Description

SrTiO3 (STO) is the substrate of choice to grow oxide thin films and oxide heterojunctions, which can form quasitwodimensional electronic phases that exhibit a wealth of phenomena, and thus a workhorse in the emerging field of metaloxide electronics. Hence, it is of great importance to know the exact character of the STO surface itself under various oxygen environments. Using density functional theory within the spin generalized gradient approximation we have investigated the structural,...
Show moreSrTiO3 (STO) is the substrate of choice to grow oxide thin films and oxide heterojunctions, which can form quasitwodimensional electronic phases that exhibit a wealth of phenomena, and thus a workhorse in the emerging field of metaloxide electronics. Hence, it is of great importance to know the exact character of the STO surface itself under various oxygen environments. Using density functional theory within the spin generalized gradient approximation we have investigated the structural, electronic, and magnetic properties of the oxygendeficient STO surface. We find that the surface oxygen vacancies order in periodic arrays giving rise to surface magnetic moments and a quasitwodimensional electron gas in the occupied Ti 3d orbitals. The surface confinement, the oxygenvacancy ordering, and the octahedra distortions give rise to spinpolarized t(2g) dispersive subbands; their energy split near the Brillouin zone center acts as an effective Zeeman term, which, when we turn on a Rashba interaction, produces bands with momentumspin correlations similar to those recently discovered on oxygendeficient STO surface.
Show less  Date Issued
 20160824
 Identifier
 FSU_libsubv1_wos_000381890100001, 10.1103/PhysRevB.94.085141
 Format
 Citation
 Title
 Strong correlations generically protect dwave superconductivity against disorder.
 Creator

Tang, Shao, Dobrosavljevic, V., Miranda, E.
 Abstract/Description

We address the question of why strongly correlated dwave superconductors, such as the cuprates, prove to be surprisingly robust against the introduction of nonmagnetic impurities. We show that, very generally, both the pairbreaking and the normal state transport scattering rates are significantly suppressed by strong correlations effects arising in the proximity to a Mott insulating state. We also show that the correlationrenormalized scattering amplitude is generically enhanced in the...
Show moreWe address the question of why strongly correlated dwave superconductors, such as the cuprates, prove to be surprisingly robust against the introduction of nonmagnetic impurities. We show that, very generally, both the pairbreaking and the normal state transport scattering rates are significantly suppressed by strong correlations effects arising in the proximity to a Mott insulating state. We also show that the correlationrenormalized scattering amplitude is generically enhanced in the forward direction, an effect which was previously often ascribed to the specific scattering by charged impurities outside the copperoxide planes.
Show less  Date Issued
 20160505
 Identifier
 FSU_libsubv1_wos_000375534600001, 10.1103/PhysRevB.93.195109
 Format
 Citation
 Title
 Power Of Two.
 Creator

Piekarewicz, J., Linero, A. R., Giuliani, P., Chicken, E.
 Abstract/Description

Background: Besides its intrinsic value as a fundamental nuclearstructure observable, the weakcharge density of Pb208a quantity that is closely related to its neutron distributionis of fundamental importance in constraining the equation of state of neutronrich matter. Purpose: To assess the impact that a second electroweak measurement of the weakcharge form factor of Pb208 may have on the determination of its overall weakcharge density. Methods: Using the two putative experimental...
Show moreBackground: Besides its intrinsic value as a fundamental nuclearstructure observable, the weakcharge density of Pb208a quantity that is closely related to its neutron distributionis of fundamental importance in constraining the equation of state of neutronrich matter. Purpose: To assess the impact that a second electroweak measurement of the weakcharge form factor of Pb208 may have on the determination of its overall weakcharge density. Methods: Using the two putative experimental values of the form factor, together with a simple implementation of Bayes' theorem, we calibrate a theoretically soundyet surprisingly little knownsymmetrized Fermi function, that is characterized by a density and form factor that are both known exactly in closed form. Results: Using the charge form factor of Pb208 as a proxy for its weakcharge form factor, we demonstrate that using only two experimental points to calibrate the symmetrized Fermi function is sufficient to accurately reproduce the experimental charge form factor over a significant range of momentum transfers. Conclusions: It is demonstrated that a second measurement of the weakcharge form factor of Pb208 supplemented by a robust theoretical input in the form of the symmetrized Fermi function would place significant constraints on the neutron distribution of Pb208. In turn, such constraints will become vital in the interpretation of hadronic experiments that will probe the neutronrich skin of exotic nuclei at future radioactive beam facilities.
Show less  Date Issued
 20160915
 Identifier
 FSU_libsubv1_wos_000383149400001, 10.1103/PhysRevC.94.034316
 Format
 Citation
 Title
 Systematically Generated Twoqubit Anyon Braids.
 Creator

Carnahan, Caitlin, Zeuch, Daniel, Bonesteel, N. E.
 Abstract/Description

Fibonacci anyons are nonAbelian particles for which braiding is universal for quantum computation. Reichardt has shown how to systematically generate nontrivial braids for three Fibonacci anyons which yield unitary operations with offdiagonal matrix elements that can be made arbitrarily small in a particular natural basis through a simple and efficient iterative procedure. This procedure does not require brute force search, the SolovayKitaev method, or any other numerical technique, but...
Show moreFibonacci anyons are nonAbelian particles for which braiding is universal for quantum computation. Reichardt has shown how to systematically generate nontrivial braids for three Fibonacci anyons which yield unitary operations with offdiagonal matrix elements that can be made arbitrarily small in a particular natural basis through a simple and efficient iterative procedure. This procedure does not require brute force search, the SolovayKitaev method, or any other numerical technique, but the phases of the resulting diagonal matrix elements cannot be directly controlled. We show that despite this lack of control the resulting braids can be used to systematically construct entangling gates for two qubits encoded by Fibonacci anyons.
Show less  Date Issued
 20160520
 Identifier
 FSU_libsubv1_wos_000376243800001, 10.1103/PhysRevA.93.052328
 Format
 Citation
 Title
 The Transmembrane Domain Mediates Tetramerization of Amino3hydroxy5methyl4isoxazolepropionic Acid (AMPA) Receptors.
 Creator

Gan, Quan, Dai, Jian, Zhou, HuanXiang, Wollmuth, Lonnie P.
 Abstract/Description

AMPA receptors (AMPARs) mediate fast excitatory neurotransmission in the central nervous system. Functional AMPARs are tetrameric complexes with a highly modular structure, consisting of four evolutionarily distinct structural domains: an aminoterminal domain (ATD), a ligandbinding domain (LBD), a channelforming transmembrane domain (TMD), and a carboxylterminal domain (CTD). Here we show that the isolated TMD of the GluA1 AMPAR is fully capable of tetramerization. Additionally, removal...
Show moreAMPA receptors (AMPARs) mediate fast excitatory neurotransmission in the central nervous system. Functional AMPARs are tetrameric complexes with a highly modular structure, consisting of four evolutionarily distinct structural domains: an aminoterminal domain (ATD), a ligandbinding domain (LBD), a channelforming transmembrane domain (TMD), and a carboxylterminal domain (CTD). Here we show that the isolated TMD of the GluA1 AMPAR is fully capable of tetramerization. Additionally, removal of the extracellular domains from the receptor did not affect membrane topology or surface delivery. Furthermore, whereas the ATD and CTD contribute positively to tetramerization, the LBD presents a barrier to the process by reducing the stability of the receptor complex. These experiments pinpoint the TMD as the tetramerization domain for AMPARs, with other domains playing modulatory roles. They also raise intriguing questions about the evolution of iGluRs as well as the mechanisms regulating the biogenesis of AMPAR complexes.
Show less  Date Issued
 20160318
 Identifier
 FSU_libsubv1_wos_000372894200044, 10.1074/jbc.M115.686246
 Format
 Citation
 Title
 Effective twodimensional thickness for the BerezinskiiKosterlitzThoulesslike transition in a highly underdoped La2xSrxCuO4.
 Creator

Baity, P. G., Shi, Xiaoyan, Shi, Zhenzhong, Benfatto, L., Popovic, Dragana
 Abstract/Description

The nature of the superconducting transition in highly underdoped thick films of La2xSrxCuO4 (x = 0.07 and 0.08) has been investigated using the inplane transport measurements. The contribution of superconducting fluctuations to the conductivity in zero magnetic field, or paraconductivity, was determined from the magnetoresistance measured in fields applied perpendicular to the CuO2 planes. Both the temperature dependence of the paraconductivity above the transition and the nonlinear...
Show moreThe nature of the superconducting transition in highly underdoped thick films of La2xSrxCuO4 (x = 0.07 and 0.08) has been investigated using the inplane transport measurements. The contribution of superconducting fluctuations to the conductivity in zero magnetic field, or paraconductivity, was determined from the magnetoresistance measured in fields applied perpendicular to the CuO2 planes. Both the temperature dependence of the paraconductivity above the transition and the nonlinear currentvoltage (I  V) characteristics measured across it exhibit the main signatures of the BerezinskiiKosterlitzThouless (BKT) transition. The quantitative comparison of the superfluid stiffness, extracted from the I  V data, with the renormalizationgroup results for the BKT theory, reveals a large value of the vortexcore energy. This finding is confirmed by the analysis of the paraconductivity obtained using different methods. The results strongly suggest that the characteristic energy scale controlling the BKT behavior in this layered system corresponds to the superfluid stiffness of a few layers.
Show less  Date Issued
 20160125
 Identifier
 FSU_libsubv1_wos_000369218500009, 10.1103/PhysRevB.93.024519
 Format
 Citation