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Direct Evidence of Two Gaps in Underdoped Bi2212

Description: This short paper summarizes the results we presented at the LEHTSC2007 conference. Recent doping and temperature dependence of angle-resolved photoemission data of underdoped superconducting cuprate Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (Bi2212) have revealed the presence of two energy scales exhibiting distinct behaviours. One, which dominates the antinodal region, increases with underdoping and does not show obvious temperature dependence across Tc. This is a behaviour known for more than a d… more
Date: March 6, 2008
Creator: Tanaka, K.; Lee, W. S.; Hussain, Zahid. & Shen, Z. X.
Partner: UNT Libraries Government Documents Department
open access

Final Report - Composite Fermion Approach to Strongly Interacting Quasi Two Dimensional Electron Gas Systems

Description: Work related to this project introduced the idea of an “effective monopole strength” Q* that acted as the effective angular momentum of the lowest shell of composite Fermions (CF). This allowed us to predict the angular momentum of the lowest band of energy states for any value of the applied magnetic field simply by determining N{sub QP} the number of quasielectrons (QE) or quasiholes (QH) in a partially filled CF shell and adding angular momenta of the N{sub QP} Fermions excitations. The … more
Date: November 30, 2009
Creator: Quinn, John
Partner: UNT Libraries Government Documents Department
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UPS Study of the Adsorption of Oxygen on Reduced SrTiO{Sub 3} Surfaces

Description: The adsorption of oxygen on a reduced SrTiO{sub 3} (111) surface occurs in two distinct phases. At low exposures (less than 1 L), the adsorption leads to the incorporation of O{sup =} ions into the vacant lattice oxygen sites. At higher exposures a second different oxygen species adsorbs.
Date: October 1, 1980
Creator: Ferrer, S. & Somorjai, G. A.
Partner: UNT Libraries Government Documents Department
open access

Fourier-Transform Analysis of Normal Photoelectron Diffraction Data for Surface-Structure Determination

Description: A direct method for surface-structure determination from normal emission photoelectron diffraction (NPD) data is presented. Fourier transforms of the calculated NPD intensities yield peaks at adsorbate-substrate normal interlayer distances. Applications are demonstrated using theoretical NPD curves for the Se/Ni system calculated by dynamical theory. These results show that interplanar spacings between the overlayer and as many as four substrate layers could be determined with an accuracy of be… more
Date: May 1, 1981
Creator: Hussain, Z.; Shirley, D. A.; Li, C. H. & Tong, S. Y.
Partner: UNT Libraries Government Documents Department
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NMR Study of Molecular Reforientation Under Fivefold Symmetry Solid Permethylferrocene

Description: The ring reorientation in permethylferrocene has been studied using high resolution solid state {sup 13}C NMR. The constraints which symmetry places upon the number and types of motional parameters which may be determined from the NMR spectrum are discussed. From comparison of the experimental lineshapes in the slow reorientation temperatures range with theoretical models for random rotations and symmetry related jumps, it is concluded that the reorientation occurs as jumps between symmetry rel… more
Date: August 1, 1980
Creator: Wemmer, D. E.; Ruben, D. J. & Pines, A.
Partner: UNT Libraries Government Documents Department
open access

INFLUENCE OF FILM STRUCTURE AND LIGHT ON CHARGE TRAPPING AND DISSIPATION DYNAMICS IN SPUN-CAST ORGANIC THIN-FILM TRANSISTORS MEASURED BY SCANNING KELVIN PROBE MICROSCOPY

Description: Herein, time-dependent scanning Kelvin probe microscopy of solution processed organic thin film transistors (OTFTs) reveals a correlation between film microstructure and OTFT device performance with the location of trapped charge within the device channel. The accumulation of the observed trapped charge is concurrent with the decrease in I{sub SD} during operation (V{sub G}=-40 V, V{sub SD}= -10 V). We discuss the charge trapping and dissipation dynamics as they relate to the film structure and… more
Date: May 3, 2012
Creator: Teague, L.; Moth, M. & Anthony, J.
Partner: UNT Libraries Government Documents Department
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Itinerant and localized magnetic moments in ferrimagnetic Mn{sub 2}CoGa thin films identified with x-ray magnetic linear dichroism: experiment and ab initio theory

Description: Epitaxial thin films of the half-metallic X{sub a}-compound Mn{sub 2}CoGa (Hg{sub 2}CuTi prototype) were prepared by dc magnetron co-sputtering with different heat treatments on MgO (001) substrates. High-quality #12;lms with a bulk magnetization of 1.95(5) {mu}{sub #22;}B per unit cell were obtained. The average Mn magnetic moment and the Co moment are parallel, in agreement with theory. The x-ray magnetic circular dichroism spectra agree with calculations based on density functional theory an… more
Date: August 8, 2011
Creator: Meinert, Markus; Schmalhorst, Jan-Michael; Klewe, Cristoph; Reiss, Gunter; Arenholz, Elke; Bohnert, Tim et al.
Partner: UNT Libraries Government Documents Department
open access

FeMn/Fe/Co/Cu(1,1,10) films studied using the magneto-optic Kerr effect and photoemission electron microscopy

Description: FeMn/Fe/Co/Cu(1,1,10) films were grown epitaxially and investigated using the magneto-optic Kerr effect and photoemission electron microscopy. We found that FeMn/Fe/Co/Cu(1,1,10) exhibits the same properties as FeMn/Co/Cu(1,1,10) for the ferromagnetic phase of the face centered cubic (fcc) Fe film but a different property for the non-ferromagnetic phase of the fcc Fe film. This result indicates that the characteristic property reported in the literature for FeMn/Co/Cu(001) comes from the FeMn s… more
Date: July 31, 2011
Creator: Meng, Y.; Li, J.; Tan, A.; Park, J.; Jin, E.; Son, H. et al.
Partner: UNT Libraries Government Documents Department
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Study of Liquid Crystal Conformation by Multiple Quantum NMR: n-Pentyl Cyanobiphenyl

Description: The multiple quantum NMR spectrum of 4-cyano-4'-n-pentyl-d{sub 11}-biphenyl in the nematic phase is presented. The sub-spectra of the higher quantum transitions are easier to interpret than the single quantum spectrum. A preliminary analysis of the biphenyl conformation indicates that the dihedral angle is 32° ± 1°.
Date: September 1, 1980
Creator: Sinton, S. & Pines, A.
Partner: UNT Libraries Government Documents Department
open access

Three-Sublattice Model for a Triangular Lattice Gas

Description: A three-sublattice Bragg-Williams model of a triangular lattice gas with repulsive nearest-neighbor interactions is presented. It is intended to represent intercalated Li{sup +} in Li{sub x}TiS{sub 2} . An order-disorder phase diagram and thermodynamic functions are computed. In particular the incremental capacity is calculated and compared with the experimental data of Thompson. It is found that (a) ordering results ln minima in the incremental capacity, (b) sharp maxirna (divergences) are cau… more
Date: March 1, 1980
Creator: Osorlo, R. & Falicov, L. M.
Partner: UNT Libraries Government Documents Department
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Bounds and self-consistent estimates for elastic constants of polycrystals of hcp solid He{sup 4}

Description: Recent advances in methods for computing both Hashin-Shtrikman bounds and related selfconsistent (or CPA) estimates of elastic constants for polycrystals composed of randomly oriented crystals can be applied successfully to hexagonal close packed solid He{sup 4}. In particular, since the shear modulus C{sub 44} of hexagonal close-packed solid He is known to undergo large temperature variations when 20 mK {<=}#20; T {<=}#20; 200 mK, bounds and estimates computed with this class of effectiv… more
Date: February 15, 2012
Creator: Berryman, J. G.
Partner: UNT Libraries Government Documents Department
open access

Characterization of a high-temperature superconducting conductor on round core cables in magnetic fields up to 20 T

Description: The next generation of high-field magnets that will operate at magnetic fields substantially above 20 T, or at temperatures substantially above 4.2 K, requires high-temperature superconductors (HTS). Conductor on round core (CORC) cables, in which RE-Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (RE = rare earth) (REBCO) coated conductors are wound in a helical fashion on a fl‚exible core, are a practical and versatile HTS cable option for low-inductance, high-field magnets. We performed the first tes… more
Date: February 13, 2013
Creator: van der Laan, Danko; Noyes, Patrick; Miller, George; Weijers, Hubertus & Willering, Gerard
Partner: UNT Libraries Government Documents Department
open access

Charge Imbalance

Description: The purpose of this article is to review the theory of charge imbalance, and to discuss its relevance to a number of experimental situations. We introduce the concepts of quasiparticle charge and charge imbalance, and discuss the generation and detection of charge imbalance by tunneling. We describe the relaxation of the injected charge imbalance by inelastic scattering processes, and show how the Boltzmann equation can be solved to obtain the steady state quasiparticle distribution and the cha… more
Date: September 1, 1980
Creator: Clarke, John
Partner: UNT Libraries Government Documents Department
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Nodal Quasiparticle Meltdown in Ultra-High Resolution Pump-Probe Angle-Resolved Photoemission

Description: High-T{sub c} cuprate superconductors are characterized by a strong momentum-dependent anisotropy between the low energy excitations along the Brillouin zone diagonal (nodal direction) and those along the Brillouin zone face (antinodal direction). Most obvious is the d-wave superconducting gap, with the largest magnitude found in the antinodal direction and no gap in the nodal direction. Additionally, while antin- odal quasiparticle excitations appear only below T{sub c}, superconductivity is t… more
Date: June 3, 2011
Creator: Graf, Jeff; Jozwiak, Chris; Smallwood, Chris L.; Eisaki, H.; Kaindl, Robert A.; Lee, Dung-Hai et al.
Partner: UNT Libraries Government Documents Department
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