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ESC FY2002 Annual Report: Synchrotron-Radiation-Based Photoelectron Spectroscopy at the Advanced Light Source

Description: Despite recent intensive experimental effort, the electronic structure of Pu, particularly {delta}-Pu, remains ill defined. An evaluation of our previous synchrotron-radiation-based investigation of {alpha}-Pu and {delta}-Pu has lead to a new paradigm for the interpretation of photoemission spectra of U, Np, {alpha}-Pu, {delta}-Pu and Am. This approach is founded upon a model in which spin and spin-orbit splittings are included in the picture of the 5f states and upon the observation of chiral/… more
Date: October 4, 2002
Creator: Tobin, J G; Chung, B W; Schulze, R K & Shuh, D K
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Universal versus Material-Dependent Two-Gap Behaviors in the High-Tc Cuprates: Angle-Resolved Photoemission Study of La_2-xSr_xCuO_4

Description: We have investigated the doping and temperature dependences of the pseudogap/superconducting gap in the single-layer cuprate La{sub 2-x}Sr{sub x}CuO{sub 4} by angle-resolved photoemission spectroscopy. The results clearly exhibit two distinct energy and temperature scales, namely, the gap around ({pi}, 0) of magnitude {Delta}{asterisk} and the gap around the node characterized by the d-wave order parameter {delta}{sub 0}, like the double-layer cuprate Bi2212. In comparison with Bi2212 having hi… more
Date: June 4, 2010
Creator: Yoshida, T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Energy Gaps in the Failed High-Tc Superconductor La_1.875Ba_0.125CuO_4

Description: A central issue on high-T{sub c} superconductivity is the nature of the normal-state gap (pseudogap) in the underdoped regime and its relationship with superconductivity. Despite persistent efforts, theoretical ideas for the pseudogap evolve around fluctuating superconductivity, competing order and spectral weight suppression due to many-body effects. Recently, while some experiments in the superconducting state indicate a distinction between the superconducting gap and pseudogap, others in the… more
Date: May 4, 2010
Creator: He, R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Bogoliubov Angle, Particle-Hole Mixture and Angular Resolved Photoemission Spectroscopy in Superconductors

Description: Superconducting excitations - Bogoliubov quasiparticles - are the quantum mechanical mixture of negatively charged electron (-e) and positively charged hole (+e). We propose a new observable for Angular Resolved Photoemission Spectroscopy (ARPES) studies that is the manifestation of the particle-hole entanglement of the superconducting quasiparticles. We call this observable a Bogoliubov angle. This angle measures the relative weight of particle and hole amplitude in the superconducting (Bogoli… more
Date: May 4, 2010
Creator: Balatsky, A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Surface and bulk contribution to Cu(111) quantum efficiency

Description: The quantum efficiency (QE) of Cu(111) is measured for different impinging light angles with photon energies just above the work function. We observe that the vectorial photoelectric effect, an enhancement of the QE due to illumination with light with an electric vector perpendicular to the sample surface, is stronger in the more surface sensitive regime. This can be explained by a contribution to photoemission due to the variation in the electromagnetic potential at the surface. The contributi… more
Date: November 4, 2008
Creator: Pedersoli, Emanuele; Greaves, Corin Michael Ricardo; Wan, Weishi; Coleman-Smith, Christopher; Padmore, Howard A.; Pagliara, Stefania et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Chemical states and electronic structure of a HfO(-2) / Ge(001) interface

Description: We report the chemical bonding structure and valence band alignment at the HfO{sub 2}/Ge (001) interface by systematically probing various core level spectra as well as valence band spectra using soft x-rays at the Stanford Synchrotron Radiation Laboratory. We investigated the chemical bonding changes as a function of depth through the dielectric stack by taking a series of synchrotron photoemission spectra as we etched through the HfO{sub 2} film using a dilute HF-solution. We found that a ver… more
Date: May 4, 2005
Creator: Seo, Kang-ill; McIntyre, Paul C.; /Stanford U., Materials Sci. Dept.; Sun, Shiyu; Lee, Dong-Ick; Pianetta, Piero et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Quantum Efficiency and Topography of Heated and Plasma-Cleaned Copper Photocathode Surfaces

Description: We present measurements of photoemission quantum efficiency (QE) for copper photocathodes heated and cleaned by low energy argon and hydrogen ion plasma. The QE and surface roughness parameters were measured before and after processing and surface chemical composition was tracked in-situ with x-ray photoelectron spectroscopy (XPS). Thermal annealing at 230 C was sufficient to improve the QE by 3-4 orders of magnitude, depending on the initial QE. Exposure to residual gas slowly reduced the QE b… more
Date: August 4, 2005
Creator: Palmer, Dennis T.; Kirby, R. E. & King, F. K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Electronic structure of the iron-based superconductor LaOFeP

Description: The recent discovery of superconductivity in the iron oxypnictide family of compounds1?9 has generated intense interest. The layeredcrystal structure with transition-metal ions in planar square-lattice form and the discovery of spin-density-wave order near 130 K seem to hint at a strong similarity with the copper oxide superconductors. An important current issue is the nature ofthe ground state of the parent compounds. Two distinct classes of theories, distinguished by the underlying band struc… more
Date: September 4, 2008
Creator: Lu, D. H.; Yi, M.; Mo, S. K.; Erickson, A. S.; Analytis, J.; Chu, J. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The Anomalous Currents In The Front Foils of the JET Lost Alpha Diagnostic KA-2

Description: We have examined the observed currents in the front foils of the JET Faraday cup lost alpha particle diagnostic KA-2. In particular, we have sought to understand the currents during Ohmic plasmas for which the ion flux at the detectors was initially assumed to be negligible. We have considered two sources of this current: plasma ions #2; both deuterium and impurity#3; in the vicinity of the detector #2; including charge exchange neutrals#3; and photoemission from scattered UV radiation. Based u… more
Date: May 4, 2011
Creator: F.E. Cecil, V. Kiptily, A. Salmi, A. Horton, K. Fullard, A. Murari, D. Darrow, K. Hill and JET-EFDA Contributors
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Effects of Out-of-Plane Disorder on the Nodal Quasiparticle and Superconducting Gap in Single-Layer Bi_2Sr_1.6Ln_0.4CuO_6 delta (Ln = La, Nd, Gd)

Description: How out-of-plane disorder affects the electronic structure has been investigated for the single-layer cuprates Bi{sub 2}Sr{sub 1.6}Ln{sub 0.4}CuO{sub 6+{delta}} (Ln = La, Nd, Gd) by angle-resolved photoemission spectroscopy. We have observed that, with increasing disorder, while the Fermi surface shape and band dispersions are not affected, the quasi-particle width increases, the anti-nodal gap is enhanced and the superconducting gap in the nodal region is depressed. The results indicate that t… more
Date: January 4, 2011
Creator: Hashimoto, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Fermi Surface and Van Hove Singularities in the Itinerant Metamagnet Sr(3)Ru(2)O(7)

Description: The low-energy electronic structure of the itinerant metamagnet Sr{sub 3}Ru{sub 2}O{sub 7} is investigated by angle resolved photoemission and density functional calculations. We find well-defined quasiparticle bands with resolution limited line widths and Fermi velocities up to an order of magnitude lower than in single layer Sr{sub 2}RuO{sub 4}. The complete topography, the cyclotron masses and the orbital character of the Fermi surface are determined, in agreement with bulk sensitive de Haas… more
Date: January 4, 2011
Creator: Tamai, A.; Allan, M. P.; Mercure, J. F.; Meevasana, W.; Dunkel, R.; Lu, D. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Photocathode Optimization for a Dynamic Transmission Electron Microscope: Final Report

Description: The Dynamic Transmission Electron Microscope (DTEM) team at Harvey Mudd College has been sponsored by LLNL to design and build a test setup for optimizing the performance of the DTEM's electron source. Unlike a traditional TEM, the DTEM achieves much faster exposure times by using photoemission from a photocathode to produce electrons for imaging. The DTEM team's work is motivated by the need to improve the coherence and current density of the electron cloud produced by the electron gun in orde… more
Date: August 4, 2011
Creator: Ellis, Perry; Flom, Zeke; Heinselman, Karen; Nguyen, Tim; Tung, Spencer; Haskell, Richard et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Construction of the Magnetic Phase Diagram of FeMn/Ni/Cu(001) Using Photoemission Electron Microscopy

Description: Single crystalline FeMn/Ni bilayer was epitaxially grown on Cu(001) substrate and investigated by photoemission electron microscopy (PEEM). The FeMn and Ni films were grown into two cross wedges to facilitate an independent control of the FeMn (0-20 ML) and Ni (0-20 ML) film thicknesses. The Ni magnetic phases were determined by Ni domain images as a function of the Ni thickness (d{sub Ni}) and the FeMn thickness (d{sub FeMn}). The result shows that as the Ni thickness increases, the Ni film un… more
Date: January 4, 2011
Creator: Wu, J.; Scholl, A.; Arenholz, E.; Hwang, C. & Qiu, Z. Q.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Absence of X-point band overlap in divalent hexaborides and variability of the surface chemical potential

Description: Angle-resolved photoemission measurements of divalent hexaborides reveals a >1 eV X-point gap between the valence and conduction bands, in contradiction to the band overlap assumed in several models of their novel ferromagnetism. While the global ARPES band structure and gap size observed are consistent with the results of bulk-sensitive soft x-ray absorption and emission boron K-edge spectroscopy, the surface-sensitive photoemission measurements also show a variation with cation, surface an… more
Date: November 4, 2001
Creator: Denlinger, Jonathan D.; Gweon, Gey-Hong; Mo, Sung-Kwan; Allen, James W.; Sarrao, John L.; Bianchi, Adrian D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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