Bosonic Spectral Function and the Electron-Phonon Interaction in HTSC Cuprates

摘要

In this paper we discuss experimental evidence related to thestructure and origin of the bosonic spectral functionα2F(ω)in high-temperature superconducting (HTSC) cuprates atand near optimal doping. Global properties ofα2F(ω), such as number and positions of peaks, are extractedby combining optics, neutron scattering, ARPES and tunnellingmeasurements. These methods give evidence for strongelectron-phonon interaction (EPI) with1<λep≲3.5in cuprates near optimal doping. We clarify how theseresults are in favor of the modified Migdal-Eliashberg (ME) theoryfor HTSC cuprates near optimal doping. In Section 2 we discusstheoretical ingredients—such as strong EPI, strongcorrelations—which are necessary to explain the mechanism ofd-wave pairing in optimally doped cuprates. These comprise the MEtheory for EPI in strongly correlated systems which give rise tothe forward scattering peak. The latter is supported by thelong-range part of EPI due to the weakly screened Madelunginteraction in the ionic-metallic structure of layered HTSCcuprates. In this approach EPI is responsible for the strength ofpairing while the residual Coulomb interaction and spinfluctuations trigger the d-wave pairing.