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2019

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Full-Text Articles in Physics

Magnetic And Structural Transitions In Euag4as2 Studied Using 151eu Mössbauer Spectroscopy, D. H. Ryan, Sergey L. Bud’Ko, Chaowei Hu, N. Ni Dec 2019

Magnetic And Structural Transitions In Euag4as2 Studied Using 151eu Mössbauer Spectroscopy, D. H. Ryan, Sergey L. Bud’Ko, Chaowei Hu, N. Ni

Ames Laboratory Accepted Manuscripts

151Eu Mössbauer spectroscopy confirms that the europium in EuAg4As2 is fully divalent and that the spectrum at 5 K consists of a single, sharp magnetic pattern with a hyperfine field (Bhf) of 27.1(1) T and an isomer shift of −11.04(3) mm/s (relative to EuF3). The temperature dependence of the spectra shows that the ordering of the Eu moments proceeds via an incommensurate sine modulated structure starting at 15 K. The structure squares up below 9 K. A search for charge density or phonon softening signatures at the 120 K ...


Optimizing Measurement Strengths For Qubit Quasiprobabilities Behind Out-Of-Time-Ordered Correlators, Razieh Mohseninia, José Raúl González Alonso, Justin Dressel Dec 2019

Optimizing Measurement Strengths For Qubit Quasiprobabilities Behind Out-Of-Time-Ordered Correlators, Razieh Mohseninia, José Raúl González Alonso, Justin Dressel

Mathematics, Physics, and Computer Science Faculty Articles and Research

Out-of-time-ordered correlators (OTOCs) have been proposed as a tool to witness quantum information scrambling in many-body system dynamics. These correlators can be understood as averages over nonclassical multitime quasiprobability distributions (QPDs). These QPDs have more information and their nonclassical features witness quantum information scrambling in a more nuanced way. However, their high dimensionality and nonclassicality make QPDs challenging to measure experimentally. We focus on the topical case of a many-qubit system and show how to obtain such a QPD in the laboratory using circuits with three and four sequential measurements. Averaging distinct values over the same measured distribution reveals either ...


First-Principles Study Of High-Pressure Phase Stability And Superconductivity Of Bi4i4, Shiyu Deng, Xianqi Song, Quan Li, Yu Xie, Changfeng Chen, Yanming Ma Dec 2019

First-Principles Study Of High-Pressure Phase Stability And Superconductivity Of Bi4i4, Shiyu Deng, Xianqi Song, Quan Li, Yu Xie, Changfeng Chen, Yanming Ma

Physics & Astronomy Faculty Publications

Bismuth iodide Bi4I4 exhibits intricate crystal structures and topological insulating states that are highly susceptible to influence by environments, making its physical properties highly tunable by external conditions. In this work, we study the evolution of structural and electronic properties of Bi4I4 at high pressure using an advanced structure search method in conjunction with first-principles calculations. Our results indicate that the most stable ambient-pressure monoclinic α−Bi4I4 phase in C2/m symmetry transforms to a trigonal P31c structure (ɛ−Bi4I4) at 8.4 GPa, then to a tetragonal P4/mmm structure (ζ−Bi4I4) above 16.6 GPa. In contrast to ...


The First-Order Magnetoelastic Transition In Eu2in: A 151eu Mössbauer Study, D. H. Ryan, Durga Paudyal, Francois Guillou, Yaroslav Mudryk, Arjun K. Pathak, Vitalij K. Pecharsky Dec 2019

The First-Order Magnetoelastic Transition In Eu2in: A 151eu Mössbauer Study, D. H. Ryan, Durga Paudyal, Francois Guillou, Yaroslav Mudryk, Arjun K. Pathak, Vitalij K. Pecharsky

Ames Laboratory Accepted Manuscripts

Our 151Eu Mössbauer investigation of Eu2In and Eu2Sn shows that the europium in both materials is fully divalent. We confirm the distinct thermodynamic orders of the magnetic transitions and reveal a remarkable difference between the magnetic environments of the europium atoms in the two compounds. Possible structural and electronic origins for these differences are discussed using DFT calculations.


Magnetic Structure Of Nd In Ndfeaso Studied By X-Ray Resonant Magnetic Scattering, M. G. Kim, J.-W. Kim, J.-Q. Yan, Alan I. Goldman, Andreas Kreyssig Dec 2019

Magnetic Structure Of Nd In Ndfeaso Studied By X-Ray Resonant Magnetic Scattering, M. G. Kim, J.-W. Kim, J.-Q. Yan, Alan I. Goldman, Andreas Kreyssig

Ames Laboratory Accepted Manuscripts

The magnetic structure of Nd in NdFeAsO compound has been investigated by x-ray resonant magnetic scattering at the Nd L2 edge (E=6.725 keV) at 1.7≤T≤15 K. At T=1.7 K we find that the Nd moments are aligned along the crystallographic c direction with the (1, 0, 0) propagation vector, and are arranged antiferromagnetically along the a direction and ferromagnetically along the b and c directions. At 1.7


Exploratory Measurements Of Large Winds And Shears In The Lower Thermosphere And Their Variability Using An Enhanced Sodium Lidar, Tao Yuan Dec 2019

Exploratory Measurements Of Large Winds And Shears In The Lower Thermosphere And Their Variability Using An Enhanced Sodium Lidar, Tao Yuan

Funded Research Records

No abstract provided.


Is Contact Nucleation Caused By Pressure Perturbation?, Fan Yang, Will Cantrell, Alexander Kostinski, Raymond Shaw, Andrew M. Vogelmann Dec 2019

Is Contact Nucleation Caused By Pressure Perturbation?, Fan Yang, Will Cantrell, Alexander Kostinski, Raymond Shaw, Andrew M. Vogelmann

Michigan Tech Publications

The reason why ice nucleation is more efficient by contact nucleation than by immersion nucleation has been elusive for over half a century. Six proposed mechanisms are summarized in this study. Among them, the pressure perturbation hypothesis, which arose from recent experiments, can qualitatively explain nearly all existing results relevant to contact nucleation. To explore the plausibility of this hypothesis in a more quantitative fashion and to guide future investigations, this study assessed the magnitude of pressure perturbation needed to cause contact nucleation and the associated spatial scales. The pressure perturbations needed were estimated using measured contact nucleation efficiencies for ...


Magnetoelastoresistance In Wte2: Exploring Electronic Structure And Extremely Large Magnetoresistance Under Strain, Na Hyun Jo, Lin-Lin Wang, Peter P. Orth, Sergey L. Bud’Ko, Paul C. Canfield Dec 2019

Magnetoelastoresistance In Wte2: Exploring Electronic Structure And Extremely Large Magnetoresistance Under Strain, Na Hyun Jo, Lin-Lin Wang, Peter P. Orth, Sergey L. Bud’Ko, Paul C. Canfield

Physics and Astronomy Publications

Strain describes the deformation of a material as a result of applied stress. It has been widely employed to probe transport properties of materials, ranging from semiconductors to correlated materials. In order to understand, and eventually control, transport behavior under strain, it is important to quantify the effects of strain on the electronic bandstructure, carrier density, and mobility. Here, we demonstrate that much information can be obtained by exploring magnetoelastoresistance (MER), which refers to magnetic field-driven changes of the elastoresistance. We use this powerful approach to study the combined effect of strain and magnetic fields on the semimetallic transition metal ...


The Distribution Of Ultra-Diffuse And Ultra-Compact Galaxies In The Frontier Fields, Steven Janssens, Roberto Abraham, Jean Brodie, Duncan Forbes, Aaron Romanowsky Dec 2019

The Distribution Of Ultra-Diffuse And Ultra-Compact Galaxies In The Frontier Fields, Steven Janssens, Roberto Abraham, Jean Brodie, Duncan Forbes, Aaron Romanowsky

Faculty Publications

Large low-surface-brightness galaxies have recently been found to be abundant in nearby galaxy clusters. In this paper, we investigate these ultra-diffuse galaxies (UDGs) in the six Hubble Frontier Fields galaxy clusters: A2744, MACS J0416.1−2403, MACS J0717.5+3745, MACS J1149.5+2223, AS1063, and A370. These are the most massive (1–3 × 1015 M ⊙) and distant (0.308 < z < 0.545) systems in which this class of galaxy has yet been discovered. We estimate that the clusters host of the order of ~200–1400 UDGs inside the virial radius (R 200), consistent with the UDG abundance–halo-mass relation found in the local universe, and suggest that UDGs may be formed in clusters. Within each cluster, however, we find that UDGs are not evenly distributed. Instead their projected spatial distributions are lopsided, and they are deficient in the regions of highest mass density as traced by gravitational lensing. While the deficiency of UDGs in central regions is not surprising, the lopsidedness is puzzling. The UDGs, and their lopsided spatial distributions, may be associated with known substructures late in their infall into the clusters, meaning that we find evidence both for formation of UDGs in clusters and for UDGs falling into clusters. We also investigate the ultra-compact dwarfs (UCDs) residing in the clusters, and find that the spatial distributions of UDGs and UCDs appear anticorrelated. Around 15% of UDGs exhibit either compact nuclei or nearby point sources. Taken together, these observations provide additional evidence for a picture in which at least some UDGs are destroyed in dense cluster environments and leave behind a residue of UCDs.


Comparison Of Charge Storage Properties Of Prussian Blue Analogues Containing Cobalt And Copper, Amanda Rensmo, Jennifer R. Hampton Dec 2019

Comparison Of Charge Storage Properties Of Prussian Blue Analogues Containing Cobalt And Copper, Amanda Rensmo, Jennifer R. Hampton

Faculty Publications

Prussian blue analogues are of great interest as alternative battery materials because of their long life cycle and potential use of earth-abundant elements. In this work, thin film mixed-metal hexacyanoferrates (HCFs) based on NiCo and NiCu alloys were fabricated in an all electrochemical process. The structure and composition of the samples were characterized, along with the charge storage capacity and kinetics of the charge transfer reaction. For both NiCo-HCF and NiCu-HCF samples, the total charge capacity increased with the substitution of Ni with more Co or Cu, and the increase was larger for Cu samples than for Co samples. On ...


Growth And Characterization Of Organic Ferroelectric And Magnetic Thin Films, Xuanyuan Jiang Dec 2019

Growth And Characterization Of Organic Ferroelectric And Magnetic Thin Films, Xuanyuan Jiang

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

Compared to inorganic materials, organic materials are environmentally friendly, flexible, and often with low cost. Inspired by these advantages, organic materials-based electronics have been intensively studied for comparable or better functionalities to inorganic electronics.

This dissertation mainly focuses on the growth and characterizations of organic ferroelectrics and magnetic thin films. For organic ferroelectrics, we investigate the growth and ferroelectric measurements of thin film croconic acid (CA), a proton-transfer molecular ferroelectric (FE) material with a large spontaneous polarization and a small coercive field, as well as the origin of ferroelectricity in CA in terms of the photostriction effect, including the discovery ...


Model‐Based Properties Of The Dayside Open/Closed Boundary: Is There A Ut‐Dependent Variation?, David A. Smith, Jan J. Sojka Dec 2019

Model‐Based Properties Of The Dayside Open/Closed Boundary: Is There A Ut‐Dependent Variation?, David A. Smith, Jan J. Sojka

All Physics Faculty Publications

The open‐closed boundary (OCB) defines a region of significant transformation in Earth's protective magnetic shield. Principle among these changes is the transition of magnetic field lines from having two foot points, one in each hemisphere, to one foot point at Earth, the other mapping to the solar wind. Charged particles in the solar wind are able to follow these open field lines into Earth's upper atmosphere. The OCB also defines the polar cap boundary. Being able to identify and track the OCB allows study of several components of the geomagnetic system. Among them are the electrodynamics of ...


Anomalous Stranski-Krastanov Growth Of (111)-Oriented Quantum Dots With Tunable Wetting Layer Thickness, Christopher F. Schuck, Simon K. Roy, Trent Garrett, Paul J. Simmonds Dec 2019

Anomalous Stranski-Krastanov Growth Of (111)-Oriented Quantum Dots With Tunable Wetting Layer Thickness, Christopher F. Schuck, Simon K. Roy, Trent Garrett, Paul J. Simmonds

Materials Science and Engineering Faculty Publications and Presentations

Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In0.52Al0.48As(111)A surfaces lattice-matched to InP substrates. In this study, we show that the tensile-strained self-assembly process for these GaAs(111)A QDs unexpectedly deviates from the well-known Stranski-Krastanov (SK) growth mode. Traditionally, QDs formed via the SK growth mode form on top of a flat wetting layer (WL) whose thickness is fixed. The inability to tune WL thickness has inhibited researchers’ attempts to fully control QD-WL interactions in these hybrid 0D-2D quantum systems. In contrast, using microscopy, spectroscopy, and computational modeling, we ...


The Conundrum Of Relaxation Volumes In First-Principles Calculations Of Charged Defects In Uo₂, Anuj Goyal, Kiran Mathew, Richard G. Hennig, Aleksandr V. Chernatynskiy Dec 2019

The Conundrum Of Relaxation Volumes In First-Principles Calculations Of Charged Defects In Uo₂, Anuj Goyal, Kiran Mathew, Richard G. Hennig, Aleksandr V. Chernatynskiy

Physics Faculty Research & Creative Works

The defect relaxation volumes obtained from density-functional theory (DFT) calculations of charged vacancies and interstitials are much larger than their neutral counterparts, seemingly unphysically large. We focus on UO2 as our primary material of interest, but also consider Si and GaAs to reveal the generality of our results. In this work, we investigate the possible reasons for this and revisit the methods that address the calculation of charged defects in periodic DFT. We probe the dependence of the proposed energy corrections to charged defect formation energies on relaxation volumes and find that corrections such as potential alignment remain ambiguous with ...


Search For Gravitational Waves From Scorpius X-1 In The Second Advanced Ligo Observing Run With An Improved Hidden Markov Model, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Dec 2019

Search For Gravitational Waves From Scorpius X-1 In The Second Advanced Ligo Observing Run With An Improved Hidden Markov Model, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h0 ...


Decomposing The Hamiltonian Of Quantum Circuits Using Machine Learning, Jordan Burns, Yih Sung, Colby Wight Dec 2019

Decomposing The Hamiltonian Of Quantum Circuits Using Machine Learning, Jordan Burns, Yih Sung, Colby Wight

Physics Capstone Projects

Quantum computing is one of the most promising techniques for simulating physical systems that cannot be simulated on classical computers[1]. A significant drawback of this approach is the inherent difficulty in designing circuits that can represent these systems on quantum computers. Every quantum circuit is built out of small components called quantum gates. Each of these gates manipulate the quantum system in a specific way. When used in combination, a finite subset of these gates, the set of universal gates, can be used to construct any possible quantum circuit[2].


Lattice Thermal Conductivity Of Quartz At High Pressure And Temperature From The Boltzmann Transport Equation, Xue Xiong, Eugene J. Ragasa, Aleksandr V. Chernatynskiy, Dawei Tang, Simon R. Phillpot Dec 2019

Lattice Thermal Conductivity Of Quartz At High Pressure And Temperature From The Boltzmann Transport Equation, Xue Xiong, Eugene J. Ragasa, Aleksandr V. Chernatynskiy, Dawei Tang, Simon R. Phillpot

Physics Faculty Research & Creative Works

The thermal conductivities along the basal and hexagonal directions of α-quartz silica, the low-temperature form of crystalline SiO2, are predicted from the solution of the Boltzmann transport equation combined with the van Beest, Kramer, and van Santen potential for the temperature up to 900 K and the pressure as high as 4 GPa. The thermal conductivities at atmospheric pressure, which show a negative and nonlinear dependence on temperature, are in reasonable agreement with the experimental data. The influence of pressure on thermal conductivity is positive and linear. The pressure (P) and temperature (T) dependences of the thermal conductivity (λ ...


Local Orbital Degeneracy Lifting As A Precursor To An Orbital-Selective Peierls Transition, E. S. Bozin, W. G. Yin, R. J. Koch, M. Abeykoon, Yew San Hor, H. Zheng, H. C. Lei, C. Petrovic, J. F. Mitchell, S. J. L. Billinge Dec 2019

Local Orbital Degeneracy Lifting As A Precursor To An Orbital-Selective Peierls Transition, E. S. Bozin, W. G. Yin, R. J. Koch, M. Abeykoon, Yew San Hor, H. Zheng, H. C. Lei, C. Petrovic, J. F. Mitchell, S. J. L. Billinge

Physics Faculty Research & Creative Works

Fundamental electronic principles underlying all transition metal compounds are the symmetry and filling of the d-electron orbitals and the influence of this filling on structural configurations and responses. Here we use a sensitive local structural technique, x-ray atomic pair distribution function analysis, to reveal the presence of fluctuating local-structural distortions at high temperature in one such compound, CuIr2S4. We show that this hitherto overlooked fluctuating symmetry-lowering is electronic in origin and will modify the energy-level spectrum and electronic and magnetic properties. The explanation is a local, fluctuating, orbital-degeneracy-lifted state. The natural extension of our result would be ...


Measurement Of The Production Cross Section Of Four Top Quarks In Proton-Proton Collisions At 13 Tev, Caleb Fangmeier Dec 2019

Measurement Of The Production Cross Section Of Four Top Quarks In Proton-Proton Collisions At 13 Tev, Caleb Fangmeier

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

The field of particle physics involves not only searches for new particles and measurements of their interactions, but also the design and construction of advanced particle detectors. This thesis presents the measurement of the production cross section of four top quarks in proton-proton collisions at a center-of-mass energy of 13 TeV using 137 fb$^{-1}$ of integrated luminosity recorded by the CMS experiment at the LHC. This analysis considers events in the final state of a same-sign pair of leptons, notable for being a final state with relatively few Standard Model background events. A boosted decision tree is utilized to ...


The Astrophysics Of Nanohertz Gravitational Waves, S. Burke-Spolaor, S. R. Taylor, M. Charisi, T. Dolch, J. S. Hazboun, A. M. Holgado, L. Z. Kelley, T. J. W. Lazio, D. R. Madison, N. Mcmann, C. M. F. Mingarelli, A. Rasskazov, X. Siemens, J. J. Simon, Tristan L. Smith Dec 2019

The Astrophysics Of Nanohertz Gravitational Waves, S. Burke-Spolaor, S. R. Taylor, M. Charisi, T. Dolch, J. S. Hazboun, A. M. Holgado, L. Z. Kelley, T. J. W. Lazio, D. R. Madison, N. Mcmann, C. M. F. Mingarelli, A. Rasskazov, X. Siemens, J. J. Simon, Tristan L. Smith

Physics & Astronomy Faculty Works

Pulsar timing array (PTA) collaborations in North America, Australia, and Europe, have been exploiting the exquisite timing precision of millisecond pulsars over decades of observations to search for correlated timing deviations induced by gravitational waves (GWs). PTAs are sensitive to the frequency band ranging just below 1 nanohertz to a few tens of microhertz. The discovery space of this band is potentially rich with populations of inspiraling supermassive black hole binaries, decaying cosmic string networks, relic post-inflation GWs, and even non-GW imprints of axionic dark matter. This article aims to provide an understanding of the exciting open science questions in ...


An Application Of The Ising Model, Juliano A. Everett Dec 2019

An Application Of The Ising Model, Juliano A. Everett

Publications and Research

Understanding how the Ising model works,what it represents, and how it can be applied to neurology. Given that an Ising model is an Entropy model that could be representative of the firing of neurons, some assumptions of the system are made and then the process is simulated through Monte Carlo methods.


Parton Distribution Functions From Loffe Time Pseudo-Distributions, Bálint Joó, Joseph Karpie, Kostas Orginos, Anatoly V. Radyushkin, David Richards, Savvas Zafeiropoulos Dec 2019

Parton Distribution Functions From Loffe Time Pseudo-Distributions, Bálint Joó, Joseph Karpie, Kostas Orginos, Anatoly V. Radyushkin, David Richards, Savvas Zafeiropoulos

Physics Faculty Publications

In this paper, we present a detailed study of the unpolarized nucleon parton distribution function (PDF) employing the approach of parton pseudo-distribution functions. We perform a systematic analysis using three lattice ensembles at two volumes, with lattice spacings a = 0.127 fm and a = 0.094 fm, for a pion mass of roughly 400 MeV. With two lattice spacings and two volumes, both continuum limit and infinite volume extrapolation systematic errors of the PDF are considered. In addition to the x dependence of the PDF, we compute their first two moments and compare them with the pertinent phenomenological determinations.


Generalized Parton Distributions And Pseudodistributions, Anatoly V. Radyushkin Dec 2019

Generalized Parton Distributions And Pseudodistributions, Anatoly V. Radyushkin

Physics Faculty Publications

We derive one-loop matching relations for the Ioffe-time distributions (ITDs) related to the pion distribution amplitude (DA) and generalized parton distributions (GPDs). They are obtained from a universal expression for the one-loop correction in an operator form, and will be used in the ongoing lattice calculations of the pion DA and GPDs within the parton pseudodistributions approach.


Consistency Checks For Two-Body Finite-Volume Matrix Elements: Conserved Currents And Bound States, Raúl A. Briceño, Maxwell T. Hansen, Andrew W. Jackura Dec 2019

Consistency Checks For Two-Body Finite-Volume Matrix Elements: Conserved Currents And Bound States, Raúl A. Briceño, Maxwell T. Hansen, Andrew W. Jackura

Physics Faculty Publications

Recently, a framework has been developed to study form factors of two-hadron states probed by an external current. The method is based on relating finite-volume matrix elements, computed using numerical lattice QCD, to the corresponding infinite-volume observables. As the formalism is complicated, it is important to provide nontrivial checks on the final results and also to explore limiting cases in which more straightforward predictions may be extracted. In this work we provide examples on both fronts. First, we show that, in the case of a conserved vector current, the formalism ensures that the finite-volume matrix element of the conserved charge ...


Question 1: Electric Cars; Question 2: Chicken Poop, Larry Weinstein Dec 2019

Question 1: Electric Cars; Question 2: Chicken Poop, Larry Weinstein

Physics Faculty Publications

How much more electrical energy will the United States need to generate if everyone drives electric cars? How much chicken excrement is produced in the United States every year?. [Extracted from the article]


Solutions For Fermi Questions, December 2019: Question 1: Electric Cars; Question 2: Chicken Poop, Larry Weinstein Dec 2019

Solutions For Fermi Questions, December 2019: Question 1: Electric Cars; Question 2: Chicken Poop, Larry Weinstein

Physics Faculty Publications

How much more electrical energy will the United States need to generate if everyone drives electric cars? B I Answer: i b If we all switch from gasoline-fueled to electricity-fueled cars, then we will need to generate more electrical energy. Thus, if we replace all of our gasoline-fueled cars with electricity-fueled cars, we will need to generate about 30% more electrical energy. [Extracted from the article]


Beam Asymmetry Σ For The Photoproduction Of Η And Ή Mesons At Eγ = 8.8gev, S. Adhikari, A. Ali, M. J. Amaryan, A. Austregesilo, F. Barbosa, J. Barlow, A. Barnes, E. Barriga, R. Barsotti, T. D. Beattie, V. V. Berdnikov, T. Black, N. Wickramaarachchi, B. Zihlmann, The Gluex Collaboration Dec 2019

Beam Asymmetry Σ For The Photoproduction Of Η And Ή Mesons At Eγ = 8.8gev, S. Adhikari, A. Ali, M. J. Amaryan, A. Austregesilo, F. Barbosa, J. Barlow, A. Barnes, E. Barriga, R. Barsotti, T. D. Beattie, V. V. Berdnikov, T. Black, N. Wickramaarachchi, B. Zihlmann, The Gluex Collaboration

Physics Faculty Publications

We report on the measurement of the beam asymmetry Σ for the reactions →γp→pη and →γp→pη′ from the GlueX experiment using an 8.2–8.8-GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Laboratory. These measurements are made as a function of momentum transfer −t with significantly higher statistical precision than our earlier η measurements and are the first measurements of η′ in this energy range. We compare the results to theoretical predictions based on t-channel quasiparticle exchange. We also compare the ratio of Ση to Ση ...


Pion Valence Structure From Ioffe-Time Parton Pseudodistribution Functions, Bálint Joó, Joseph Karpie, Kostas Orinos, Anatoly V. Radyushkin, David G. Richards, Raza Sabbir Sufian, Savvas Zafeiropoulos Dec 2019

Pion Valence Structure From Ioffe-Time Parton Pseudodistribution Functions, Bálint Joó, Joseph Karpie, Kostas Orinos, Anatoly V. Radyushkin, David G. Richards, Raza Sabbir Sufian, Savvas Zafeiropoulos

Physics Faculty Publications

We present a calculation of the pion valence quark distribution extracted using the formalism of reduced Ioffe-time pseudodistributions or more commonly known as pseudo-PDFs. Our calculation is carried out on two different 2 + 1 flavor QCD ensembles using the isotropic-clover fermion action, with lattice dimensions 243 × 64 and 323 × 96 at the lattice spacing of a = 0.127 fm, and with the quark mass equivalent to a pion mass of mπ ≃ 415 MeV. We incorporate several combinations of smeared-point and smeared-smeared pion source-sink interpolation fields in obtaining the lattice QCD matrix elements using the summation method. After ...


Topological Magnetoelectric Effect As Probed By Nanoshell Plasmonic Modes, Railing Chang, Huai Yi Xie, Ya-Chih Wang, Hai-Pang Chiang, P.T. Leung Dec 2019

Topological Magnetoelectric Effect As Probed By Nanoshell Plasmonic Modes, Railing Chang, Huai Yi Xie, Ya-Chih Wang, Hai-Pang Chiang, P.T. Leung

Physics Faculty Publications and Presentations

Axion electrodynamics is applied to study the response of a plasmonic nanoshell with a core made of topological insulator (TI) materials. The electric polarizability of such a system is calculated in the long wavelength limit via the introduction of two scalar potentials satisfying the various appropriate boundary conditions. Our focus is on the topological magneto-electric effect (TME) as manifested in the coupled plasmonic resonances of the nanoshell. It is found that for a TI with broken time-reversal symmetry, such TME will lead to observable red-shifts in the coupled plasmonic modes, with more significant manifestation of such shifts for the bonding ...


Microstructure Evolution During Near-Tg Annealing And Its Effect On Shear Banding In Model Alloys, Meng-Hao Yang, Bei Cai, Yang Sun, Feng Zhang, Yi-Fan Wang, Cai-Zhuang Wang, Kai-Ming Ho Dec 2019

Microstructure Evolution During Near-Tg Annealing And Its Effect On Shear Banding In Model Alloys, Meng-Hao Yang, Bei Cai, Yang Sun, Feng Zhang, Yi-Fan Wang, Cai-Zhuang Wang, Kai-Ming Ho

Ames Laboratory Accepted Manuscripts

By performing extensive molecular dynamics simulations, we investigate the deformation behavior in Al90Sm10 and Cu64.5Zr35.5 alloys after elongated isothermal annealing in the vicinity of the glass-transition temperature (Tg). Different microstructural response to the annealing process was observed: Al90Sm10 maintains the glassy structure with improved energetic stability, enhanced short-range order (SRO), and a more pronounced spatial network that extends beyond the first atomic shell, while Cu64.5Zr35.5 forms nanocrystalline Laves Cu2Zr phases. Shear banding occurs in both annealed systems under shear loading. For Al90Sm10, the spatial network formed by the local clusters characterizing the SRO of the system ...