Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 25: Superconductivity: Cuprate High-Temperature Superconductors 1
TT 25.8: Talk
Wednesday, March 25, 2009, 11:30–11:45, HSZ 304
Momentum dependence of the electron-phonon coupling, phonon-induced pairing interaction, and self-energy effects in YBa2Cu3O7 within the local density approximation — •Dirk Manske1, Rolf Heid2, Roland Zeyher1, and Klaus-Peter Bohnen2 — 1Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany — 2Forschungszentrum Karlsruhe, Germany
Using the local density approximation (LDA) and a realistic phonon spectrum we calculate the momentum and frequency dependence of the electron-phonon coupling in YBa2Cu3O7 and determine its consequences for the phonon-induced pairing interaction and for the electronic self-energy in the normal state.
The phonon-induced interaction has a pronounced peak for large momentum transfers and the interband contributions between bonding and antibonding band are of the same magnitude as the intraband ones. The dimensionless coupling constant in the d-wave channel λd, relevant for superconductivity, is only 0.022, i.e., even about ten times smaller than the small value of the s-wave channel.
For electronic states at the Fermi energy, the maximum in the real part of the phonon-induced self-energy at low frequencies is about a factor 5 too small compared to the experiment, resulting in a very small and smooth change in the slope of the electronic dispersion [1].
These findings suggest that phonons are not the important low-energy excitations, and cannot produce well-pronounced kinks in YBa2Cu3O7, at least, within LDA.
[1] R. Heid, K.-P. Bohnen, R. Zeyher, D. Manske, PRL 100, 137001 (2008).