Abstract
Using the local density approximation and a realistic phonon spectrum
we determine the momentum and frequency dependence of α2F(k,ω) in
YBa2Cu3O7 for the bonding, antibonding, and chain band. The resulting
self-energy Σ is rather small near the Fermi surface. For instance,
for the antibonding band the maximum of ReΣ as a function of frequency
is about 7 meV at the nodal point in the normal state and the ratio
of bare and renormalized Fermi velocities is 1.18. These values are
a factor of 3–5 too small compared to the experiment showing that
only a small part of Σ can be attributed to phonons. Furthermore,
the frequency dependence of the renormalization factor Z(k,ω) is
smooth and has no anomalies at the observed kink frequencies which
means that phonons cannot produce well-pronounced kinks in stoichiometric
YBa2Cu3O7, at least, within the local density approximation.
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