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Bulk band gaps in divalent hexaborides: A soft x-ray emission study

Description: Boron K-edge soft x-ray emission and absorption are used to address the fundamental question of whether divalent hexaborides are intrinsic semimetals or defect-doped bandgap insulators. These bulk sensitive measurements, complementary and consistent with surface-sensitive angle-resolved photoemission experiments, confirm the existence of a bulk band gap and the location of the chemical potential at the bottom of the conduction band.
Date: October 3, 2001
Creator: Denlinger, Jonathan D.; Gweon, Gey-Hong; Allen, James W.; Bianchi, Andrea D. & Fisk, Zachary
Partner: UNT Libraries Government Documents Department

Temperature dependent 5f-states in URu2Si2

Description: A dramatic temperature dependent enhancement of U 5f spectral weight at EF is observed in angle-resolved photoemission measurements of URu{sub 2}Si{sub 2} at the center of an X-point hole-pocket. Comparison of this temperature dependent behavior for excitation both at and below the U 5d->5f resonant threshold is presented.
Date: November 1, 2001
Creator: Denlinger, Jonathan D.; Gweon, Gey-Hong; Allen, James W. & Sarrao, John L.
Partner: UNT Libraries Government Documents Department

Probing the band structure of LaTe2 using angle resolved photoemission spectroscopy

Description: With the current interest in the rare-earth tellurides ashigh temperature charge density wave materials, a greater understandingof the physics of these systems is needed, particularly in the case ofthe ditellurides. We report a detailed study of the band structure ofLaTe_2 in the charge density wave state using high-resolution angleresolved photoemission spectroscopy (ARPES). From thiswork we hope toprovide insights into the successes and weaknesses of past theoreticalstudy as well as helping to clear up prior ambiguities by providing anexperimental basis for future work inthe tellurides.
Date: November 1, 2006
Creator: Garcia, Daniel R.; Zhou, Shuyun Y.; Gweon, Gey-Hong; Jung, M.H.; Kwon, Y.S. & Lanzara, Alessandra
Partner: UNT Libraries Government Documents Department

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 and time of the position of the surface chemical potential in the band structure.
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.
Partner: UNT Libraries Government Documents Department

Possibility of minimal surface contributions to low photon energy angle-resolved photoemission of CeRu{sub 2}Si{sub 2}

Description: Surface-related effects in angle-resolved valence spectra of CeRu{sub 2}Si{sub 2} at the Ce 4d {yields} 5f resonance threshold for different cleaved surfaces are presented and compared to angle-integrated valence spectra and to bulk-sensitive Ce 3d-edge valence spectra. Evidence that Ce 4d-edge photoemission spectroscopy on ideal cleaved surfaces is dominated by bulk Ce 4f states is presented.
Date: November 1, 2001
Creator: Denlinger, Jonathan D.; Gweon, Gey-Hong; Allen, James W. & Sarrao, John L.
Partner: UNT Libraries Government Documents Department

Bulk band gaps in divalent hexaborides

Description: Complementary angle-resolved photoemission and bulk-sensitive k-resolved resonant inelastic x-ray scattering of divalent hexaborides reveal 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. This semiconducting gap implies that carriers detected in transport measurements arise from defects, and the measured location of the bulk Fermi level at the bottom of the conduction band implicates boron vacancies as the origin of the excess electrons. The measured band structure and X-point gap in CaB6 additionally provide a stringent test case for proper inclusion of many-body effects in quasi-particle band calculations.
Date: August 1, 2002
Creator: Denlinger, Jonathan; Clack, Jules A.; Allen, James W.; Gweon, Gey-Hong; Poirier, Derek M.; Olson, Cliff G. et al.
Partner: UNT Libraries Government Documents Department