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Studies Of Geometrical Profiling In Fabricated Tapered Optical Fbers Using Whispering Gallery Modes Spectroscopy, Vishnu Kavungal, Gerald Farrell, Qiang Wu, Arun Kumar Mallik, Yuliya Semenova 2018 Dublin Institute of Technology

Studies Of Geometrical Profiling In Fabricated Tapered Optical Fbers Using Whispering Gallery Modes Spectroscopy, Vishnu Kavungal, Gerald Farrell, Qiang Wu, Arun Kumar Mallik, Yuliya Semenova

Articles

This paper experimentally demonstrates a method for geometrical profiling of asymmetries in fabricated thin microfiber tapers with waist diameters ranging from ∼10 to ∼50µm with submicron accuracy. The method is based on the analysis of whispering gallery mode resonances excited in cylindrical fiber resonators as a result of evanescent coupling of light propagating through the fiber taper. The submicron accuracy of the proposed method has been verified by SEM studies. The method can be applied as a quality control tool in fabrication of microfiber based devices and sensors or for fine-tuning of microfiber fabrication set-ups.


Investigation Of Novel Electrolytes For Use In Lithium-Ion Batteries And Direct Methanol Fuel Cells, Kartik Pilar 2018 The Graduate Center, City University of New York

Investigation Of Novel Electrolytes For Use In Lithium-Ion Batteries And Direct Methanol Fuel Cells, Kartik Pilar

All Dissertations, Theses, and Capstone Projects

Energy storage and conversion plays a critical role in the efficient use of available energy and is crucial for the utilization of renewable energy sources. To achieve maximum efficiency of renewable energy sources, improvements to energy storage materials must be developed. In this work, novel electrolytes for secondary batteries and fuel cells have been studied using nuclear magnetic resonance and high pressure x-ray scattering techniques to form a better understanding of dynamic and structural properties of these materials. Ionic liquids have been studied due to their potential as a safer alternative to organic solvent-based electrolytes in lithium-ion batteries and composite ...


Ionic Depletion At The Crystalline Gibbs Layer Of Peg-Capped Gold Nanoparticle Brushes At Aqueous Surfaces, Wenjie Wang, Honghu Zhang, Surya Mallapragada, Alex Travesset, David Vaknin 2018 Ames Laboratory

Ionic Depletion At The Crystalline Gibbs Layer Of Peg-Capped Gold Nanoparticle Brushes At Aqueous Surfaces, Wenjie Wang, Honghu Zhang, Surya Mallapragada, Alex Travesset, David Vaknin

Surya K. Mallapragada

In situ surface-sensitive x-ray diffraction and grazing incidence x-ray fluorescence spectroscopy (GIXFS) methods are combined to determine the ionic distributions across the liquid/vapor interfaces of thiolated-polyethylene-glycol–capped gold nanoparticle (PEG-AuNP) solutions. Induced by the addition of salts (i.e., Cs2SO4) to PEG-AuNPs solutions, two-dimensional hexagonal lattices of PEG-AuNPs form spontaneously at the aqueous surfaces, as is demonstrated by x-ray reflectivity and grazing incidence small-angle x-ray scattering. By taking advantage of element specificity with the GIXFS method, we find that the cation Cs+ concentration at the crystalline film is significantly reduced in parts of the PEG-AuNP film compared with that ...


Nonequilibrium Polarization Dynamics In Antiferroelectrics, M. M. Vopson, Xiaoli Tan 2018 University of Portsmouth

Nonequilibrium Polarization Dynamics In Antiferroelectrics, M. M. Vopson, Xiaoli Tan

Xiaoli Tan

A nonequilibrium statistical domain nucleation model of polarization dynamics in less understood antiferroelectric systems is introduced. Predictions of the model have been successfully tested experimentally using an antiferroelectric Pb0.99Nb0.02[( Zr0.57Sn0.43) Ti-0.94(0.06)] O-0.98(3) polycrystalline ceramic. We determined the activation energy of the domain nucleation process for this particular antiferroelectric sample to be W-b = 1.07 eV and the critical volume of the polar nucleus V * = 98 x 10(-27)m(3), which corresponds to a linear length scale of 2.86 nm.


Superelasticity And Cryogenic Linear Shape Memory Effects Of Cafe2as2, John T. Sypek, Hang Yu, Keith J. Dusoe, Gil Drachuck, Hetal Patel, Amanda M. Giroux, Alan I. Goldman, Andreas Kreyssig, Paul C. Canfield, Serguei L. Bud’ko, Christopher R. Weinberger, Seok-Woo Lee 2018 University of Connecticut

Superelasticity And Cryogenic Linear Shape Memory Effects Of Cafe2as2, John T. Sypek, Hang Yu, Keith J. Dusoe, Gil Drachuck, Hetal Patel, Amanda M. Giroux, Alan I. Goldman, Andreas Kreyssig, Paul C. Canfield, Serguei L. Bud’Ko, Christopher R. Weinberger, Seok-Woo Lee

Paul C. Canfield

Shape memory materials have the ability to recover their original shape after a significant amount of deformation when they are subjected to certain stimuli, for instance, heat or magnetic fields. However, their performance is often limited by the energetics and geometry of the martensitic-austenitic phase transformation. Here, we report a unique shape memory behavior in CaFe2As2, which exhibits superelasticity with over 13% recoverable strain, over 3 GPa yield strength, repeatable stress–strain response even at the micrometer scale, and cryogenic linear shape memory effects near 50 K. These properties are acheived through a reversible uni-axial phase transformation mechanism, the tetragonal ...


Vortex Creep At Very Low Temperatures In Single Crystals Of The Extreme Type-Ii Superconductor Rh9in4s4, Edwin Herrera, José Benito-Llorens, Udhara S. Kaluarachchi, Serguei Bud'ko, Paul C. Canfield, Isabel Guillamón, Hermann Suderow 2018 Universidad Autónoma de Madrid

Vortex Creep At Very Low Temperatures In Single Crystals Of The Extreme Type-Ii Superconductor Rh9in4s4, Edwin Herrera, José Benito-Llorens, Udhara S. Kaluarachchi, Serguei Bud'ko, Paul C. Canfield, Isabel Guillamón, Hermann Suderow

Paul C. Canfield

We image vortex creep at very low temperatures using scanning tunneling microscopy in the superconductor Rh9In4S4 (Tc=2.25K). We measure the superconducting gap of Rh9In4S4, finding Δ≈0.33meV, and image a hexagonal vortex lattice up to close to Hc2, observing slow vortex creep at temperatures as low as 150 mK. We estimate thermal and quantum barriers for vortex motion and show that thermal fluctuations likely cause vortex creep, in spite of being at temperatures T/Tc


Pressure Induced Half-Collapsed-Tetragonal Phase In Cakfe4as4, Udhara Kaluarachchi, Valentin Taufour, Aashish Sapkota, Vladislav Borisov, Tai Kong, W. R. Meier, Karunakar Kothapalli, Benjamin G. Ueland, Andreas Kreyssig, Roser Valenti, Robert J. McQueeney, Alan I. Goldman, Sergey L. Bud'ko, Paul C. Canfield 2018 Iowa State University and Ames Laboratory

Pressure Induced Half-Collapsed-Tetragonal Phase In Cakfe4as4, Udhara Kaluarachchi, Valentin Taufour, Aashish Sapkota, Vladislav Borisov, Tai Kong, W. R. Meier, Karunakar Kothapalli, Benjamin G. Ueland, Andreas Kreyssig, Roser Valenti, Robert J. Mcqueeney, Alan I. Goldman, Sergey L. Bud'ko, Paul C. Canfield

Paul C. Canfield

We report the temperature-pressure phase diagram of CaKFe4As4 established using high-pressure electrical resistivity, magnetization, and high-energy x-ray diffraction measurements up to 6 GPa. With increasing pressure, both resistivity and magnetization data show that the bulk superconducting transition of CaKFe4As4 is suppressed and then disappears at p≳4 GPa. High-pressure x-ray data clearly indicate a phase transition to a collapsed tetragonal phase in CaKFe4As4 under pressure that coincides with the abrupt loss of bulk superconductivity near 4 GPa. The x-ray data, combined with resistivity data, indicate that the collapsed tetragonal transition line is essentially independent of pressure, occurring at 4.0 ...


Nmr Study Of The New Magnetic Superconductor Cak ( Fe 0.951 Ni 0.049 ) 4 As 4 : Microscopic Coexistence Of The Hedgehog Spin-Vortex Crystal And Superconductivity, Qing-Ping Ding, William R. Meier, A. E. Böhmer, S. L. Bud’ko, Paul C. Canfield, Yuji Furukawa 2018 Iowa State University and Ames Laboratory

Nmr Study Of The New Magnetic Superconductor Cak ( Fe 0.951 Ni 0.049 ) 4 As 4 : Microscopic Coexistence Of The Hedgehog Spin-Vortex Crystal And Superconductivity, Qing-Ping Ding, William R. Meier, A. E. Böhmer, S. L. Bud’Ko, Paul C. Canfield, Yuji Furukawa

Paul C. Canfield

The coexistence of a new-type antiferromagnetic (AFM) state, the so-called hedgehog spin-vortex crystal (SVC), and superconductivity (SC) is evidenced by an 75 As nuclear magnetic resonance study on single-crystalline CaK ( Fe 0.951 Ni 0.049 ) 4 As 4 . The hedgehog SVC order is clearly demonstrated by the direct observation of internal magnetic induction along the c axis at the As1 site (close to K) and a zero net internal magnetic induction at the As2 site (close to Ca) below an AFM ordering temperature T N ∼ 52 K. The nuclear spin-lattice relaxation rate 1 / T 1 shows a distinct decrease ...


Dirac Node Arcs In Ptsn4, Yun Wu, Lin-Lin Wang, Eundeok Mun, Duane D. Johnson, Daixiang Mou, Lunan Huang, Youngbin Lee, Serguei L. Bud’ko, Paul C. Canfield, Adam Kaminski 2018 Iowa State University and Ames Laboratory

Dirac Node Arcs In Ptsn4, Yun Wu, Lin-Lin Wang, Eundeok Mun, Duane D. Johnson, Daixiang Mou, Lunan Huang, Youngbin Lee, Serguei L. Bud’Ko, Paul C. Canfield, Adam Kaminski

Paul C. Canfield

In topological quantum materials1–3 the conduction and valence bands are connected at points or along lines in the momentum space. A number of studies have demonstrated that several materials are indeed Dirac/Weyl semimetals4–8 . However, there is still no experimental confirmation of materials with line nodes, in which the Dirac nodes form closed loops in the momentum space2,3 . Here we report the discovery of a novel topological structure—Dirac node arcs—in the ultrahigh magnetoresistive material PtSn4 using laser-based angle-resolved photoemission spectroscopy data and density functional theory calculations. Unlike the closed loops of line nodes, the Dirac ...


Extremely Large Magnetoresistance And Kohler's Rule In Pdsn4 : A Complete Study Of Thermodynamic, Transport, And Band-Structure Properties, Na Hyan Jo, Yun Wu, Lin-Lin Wang, Peter Orth, Savannah S. Downing, Soham Manni, Dixiang Mou, Duane D. Johnson, Adam Kaminski, Sergey L. Bud’ko, Paul C. Canfield 2018 Iowa State University and Ames Laboratory

Extremely Large Magnetoresistance And Kohler's Rule In Pdsn4 : A Complete Study Of Thermodynamic, Transport, And Band-Structure Properties, Na Hyan Jo, Yun Wu, Lin-Lin Wang, Peter Orth, Savannah S. Downing, Soham Manni, Dixiang Mou, Duane D. Johnson, Adam Kaminski, Sergey L. Bud’Ko, Paul C. Canfield

Paul C. Canfield

The recently discovered material PtSn4 is known to exhibit extremely large magnetoresistance (XMR) that also manifests Dirac arc nodes on the surface. PdSn4 is isostructural to PtSn4 with the same electron count. We report on the physical properties of high-quality single crystals of PdSn4 including specific heat, temperature- and magnetic-field-dependent resistivity and magnetization, and electronic band-structure properties obtained from angle-resolved photoemission spectroscopy (ARPES). We observe that PdSn4 has physical properties that are qualitatively similar to those of PtSn4, but find also pronounced differences. Importantly, the Dirac arc node surface state of PtSn4 is gapped out for PdSn4. By comparing these ...


Nmr Evidence For Static Local Nematicity And Its Cooperative Interplay With Low-Energy Magnetic Fluctuations In Fese Under Pressure, Paul W. Wiecki, A. E. Böhmer, Serguei L. Bud’ko, Paul C. Canfield, Yuji Furukawa 2018 Iowa State University and Ames Laboratory

Nmr Evidence For Static Local Nematicity And Its Cooperative Interplay With Low-Energy Magnetic Fluctuations In Fese Under Pressure, Paul W. Wiecki, A. E. Böhmer, Serguei L. Bud’Ko, Paul C. Canfield, Yuji Furukawa

Paul C. Canfield

We present 77Se -NMR measurements on single-crystalline FeSe under pressures up to 2 GPa. Based on the observation of the splitting and broadening of the NMR spectrum due to structural twin domains, we discovered that static, local nematic ordering exists well above the bulk nematic ordering temperature, T s . The static, local nematic order and the low-energy stripe-type antiferromagnetic spin fluctuations, as revealed by NMR spin-lattice relaxation rate measurements, are both insensitive to pressure application. These NMR results provide clear evidence for the microscopic cooperation between magnetism and local nematicity in FeSe.


Zno Nanoparticles Modulate The Ionic Transport And Voltage Regulation Of Lysenin Nanochannels, Sheenah L. Bryant, Josh E. Eixenberger, Steven Rossland, Holly Apsley, Connor Hoffman, Nisha Shrestha, Michael McHugh, Alex Punnoose, Daniel Fologea 2018 Boise State University

Zno Nanoparticles Modulate The Ionic Transport And Voltage Regulation Of Lysenin Nanochannels, Sheenah L. Bryant, Josh E. Eixenberger, Steven Rossland, Holly Apsley, Connor Hoffman, Nisha Shrestha, Michael Mchugh, Alex Punnoose, Daniel Fologea

Daniel Fologea

Background: The insufficient understanding of unintended biological impacts from nanomaterials (NMs) represents a serious impediment to their use for scientific, technological, and medical applications. While previous studies have focused on understanding nanotoxicity effects mostly resulting from cellular internalization, recent work indicates that NMs may interfere with transmembrane transport mechanisms, hence enabling contributions to nanotoxicity by affecting key biological activities dependent on transmembrane transport. In this line of inquiry, we investigated the effects of charged nanoparticles (NPs) on the transport properties of lysenin, a pore-forming toxin that shares fundamental features with ion channels such as regulation and high transport rate. Results ...


Simulation Of Charge Transport In Multi-Island Tunneling Devices: Application To Disordered One-Dimensional Systems At Low And High Biases, Madhusudan A. Savaikar, Douglas R. Banyai, Paul Bergstrom, John A. Jaszczak 2018 Michigan Technological University

Simulation Of Charge Transport In Multi-Island Tunneling Devices: Application To Disordered One-Dimensional Systems At Low And High Biases, Madhusudan A. Savaikar, Douglas R. Banyai, Paul Bergstrom, John A. Jaszczak

John Jaszczak

Although devices have been fabricated displaying interesting single-electron transport characteristics, there has been limited progress in the development of tools that can simulate such devices based on their physical geometry over a range of bias conditions up to a few volts per junction. In this work, we present the development of a multi-island transport simulator, MITS, a simulator of tunneling transport in multi-island devices that takes into account geometrical and material parameters, and can span low and high source-drain biases. First, the capabilities of MITS are demonstrated by modeling experimentaldevices described in the literature, and showing that the simulated device ...


Roughening And Preroughening Of Diamond-Cubic {111} Surfaces, Donald L. Woodraska, John A. Jaszczak 2018 Michigan Technological University

Roughening And Preroughening Of Diamond-Cubic {111} Surfaces, Donald L. Woodraska, John A. Jaszczak

John Jaszczak

A solid-on-solid model for {111} surfaces of diamond-cubic materials that correctly takes into account the diamond-cubic crystal structure has been developed for Monte Carlo simulation. In addition to a roughening transition at temperature TR, a distinct preroughening transition at TPR≈0.43TR is indicated by divergences in the surface specific heat and order-parameter susceptibility. Preroughening appears to arise naturally in our nearest-neighbor bond model from the entropic freedom available in the nontrivial crystal structure. Preroughening is shown to dramatically lower the nucleation barrier for growth and etching at low driving forces.


Mechanism For Spatial Organization In Quantum Dot Self-Assembly, Da Gao, Adam Kaczynski, John A. Jaszczak 2018 Michigan Technological University

Mechanism For Spatial Organization In Quantum Dot Self-Assembly, Da Gao, Adam Kaczynski, John A. Jaszczak

John Jaszczak

Inspired by experimental observations of spatially ordered growth hillocks on the (001) surfaces of natural graphite crystals, a mechanism for spatial organization in quantum dotself-assembly is proposed. The regular arrangement of steps from a screw dislocation-generated growth spiral provides the overall template for such ordering. An ordered array of quantum dots may be formed or nucleated from impurities driven to the step corners by diffusion and by their interactions with the spiral’s steps and kinks. Kinetic Monte Carlo simulation of a solid-on-solid model supports the feasibility of such a mechanism.


Giant Intrinsic Carrier Mobilities In Graphene And Its Bilayer, S. V. Morozov, K. S. Novoselov, M. I. Katsnelson, F. Schedin, D. C. Elias, John A. Jaszczak, A. K. Geim 2018 University of Manchester

Giant Intrinsic Carrier Mobilities In Graphene And Its Bilayer, S. V. Morozov, K. S. Novoselov, M. I. Katsnelson, F. Schedin, D. C. Elias, John A. Jaszczak, A. K. Geim

John Jaszczak

We have studied temperature dependences of electron transport in graphene and its bilayer and found extremely low electron-phonon scattering rates that set the fundamental limit on possible charge carrier mobilities at room temperature. Our measurements show that mobilities higher than 200,000 cm2/V s are achievable, if extrinsic disorder is eliminated. A sharp (threshold-like) increase in resistivity observed above ∼200K is unexpected but can qualitatively be understood within a model of a rippled graphene sheet in which scattering occurs on intraripple flexural phonons.


Physics 3710 – Problem Set #2, David Peak 2018 Utah State University

Physics 3710 – Problem Set #2, David Peak

Problems

Physics 3710 – Problem Set #2 Newtonian relativity

Problems 1-4 refer to: Sound travels at about 330 m/s in still air. Observer O is at rest with respect to still air, observer O′ travels with constant velocity +50 m/s in the common x, x′ direction. Event A is the emission of a sound pulse from a stationary source at the origin of O; it occurs at xA = 0 at tA = 0. Event B is the reflection of the pulse at xB = +100 m. Event C is the detection of the reflected pulse at xC = 0 ...


Physics 3710 – Problem Set #3, David Peak 2018 Utah State University

Physics 3710 – Problem Set #3, David Peak

Problems

Physics 3710 – Problem Set #3 Relativistic kinematics, I


Physics 3710 – Problem Set #4, David Peak 2018 Utah State University

Physics 3710 – Problem Set #4, David Peak

Problems

Physics 3710 – Problem Set #4 Relativistic kinematics, II


Physics 3710 – Problem Set #5, David Peak 2018 Utah State University

Physics 3710 – Problem Set #5, David Peak

Problems

Physics 3710 – Problem Set #5 Relativistic dynamics, I

Problems 1-5 refer to: One mass, m1 = 1 (in some units), collides head-on with a second mass, m2 = 2 , and sticks to it, forming a composite body of mass M . There are no external forces. Observer O records m1 as initially moving with dimensionless velocity, u1 = +0.9 in the x - direction, while m2 is recorded to be at rest. Do not make unwarranted assumptions about M , please; that’s the point of this set of problems.


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