Synchrotron-radiation photoemission and energy loss studies of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> and EuBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub>

The authors studied the electric structure of two high-temperature superconductors, with particular emphasis on photoemission resonance effects and on collective excitation phenomena. The photoemission resonances simplified the identification of valence spectral features. In particular, they provided evidence for Cu satellite features, whose analysis is of crucial importance in the identification of the valence state of Cu. From the energy loss spectra, they derived the plasmon energies and the energies of quasi-optical transitions in an energy range up to 110 eV. These data were interpreted in terms of the initial states derived from photoemission and of possible empty states immediately above the Fermi level. The study included a careful search for changes in the photoemission and energy loss spectra during the phase transition of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub>. Based on previous data on the charge-density-wave-like phase transition in TiSe<sub>2</sub>, the results set an upper limit for the width of the superconductivity gap, and are relevant to proposed superconductivity mechanisms such as incipient charge-density-wave and/or excitonic pairing

Wisconsin Univ., Madison, WI, USA
high temperature superconductivity
electric structure
photoemission resonance effects
collective excitation phenomena
valence spectral features
Cu satellite features
valence state
energy loss spectra
plasmon energies
quasi-optical transitions
initial states
empty states
Fermi level
phase transition
superconductivity gap
incipient charge-density-wave
excitonic pairing

 Record created 2006-10-03, last modified 2018-03-18

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