摘要：In this paper we discuss experimental evidence related to the
structure and origin of the bosonic spectral function 𝛼2𝐹(𝜔) in high-temperature superconducting (HTSC) cuprates at
and near optimal doping. Global properties of 𝛼2𝐹(𝜔), such as number and positions of peaks, are extracted
by combining optics, neutron scattering, ARPES and tunnelling
measurements. These methods give evidence for strong
electron-phonon interaction (EPI) with 1<𝜆𝑒𝑝≲3.5 in cuprates near optimal doping. We clarify how these
results are in favor of the modified Migdal-Eliashberg (ME) theory
for HTSC cuprates near optimal doping. In Section 2 we discuss
theoretical ingredients—such as strong EPI, strong
correlations—which are necessary to explain the mechanism of
d-wave pairing in optimally doped cuprates. These comprise the ME
theory for EPI in strongly correlated systems which give rise to
the forward scattering peak. The latter is supported by the
long-range part of EPI due to the weakly screened Madelung
interaction in the ionic-metallic structure of layered HTSC
cuprates. In this approach EPI is responsible for the strength of
pairing while the residual Coulomb interaction and spin
fluctuations trigger the d-wave pairing.
