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Electron–Phonon Coupling Deduced from Phonon Line Shapes
Author(s) -
Bock A.,
Ostertun S.,
Subke K.O.
Publication year - 1999
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199909)215:1<495::aid-pssb495>3.0.co;2-x
Subject(s) - phonon , condensed matter physics , coupling (piping) , fano factor , physics , line (geometry) , raman spectroscopy , electron , surface phonon , superconductivity , atomic physics , materials science , quantum mechanics , optics , geometry , mathematics , shot noise , detector , metallurgy
We investigate the Fano‐type line shape of the Ba mode of Y 1— x Ca x Ba 2 Cu 3 O 6+ y films observed in Raman spectra with A 1g symmetry. The line shape is described with an extended Fano formula that allows us to obtain the bare phonon parameters and the self‐energy effects based on a phenomenological description of the real and imaginary part of the low‐energy electronic response. It turns out that the phonon intensity originates almost entirely from a coupling to this electronic response with negligible contributions from interband (high‐energy) electronic excitations. In the normal state we obtain a measure of the electron–phonon coupling via the mass‐enhancement factor λ. We find λ‐ = 6.8 ± 0.5% around optimum doping and only weak changes of the self‐energy in the superconducting state. With increased disorder at the Ba site we find a decreased intensity of the Ba mode which we can relate to a decreased electron–phonon coupling.