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Advances in Condensed Matter Physics
Volume 2010 (2010), Article ID 423725, 64 pages
http://dx.doi.org/10.1155/2010/423725
Review Article

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

1I. E. Tamm Theoretical Department, Lebedev Physical Institute, 119991 Moscow, Russia
2Institute for Theoretical Physics, Goethe University, 60438 Frankfurt am Main, Germany
3Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
4Theoretische Abteilung, Max-Planck-Institut für Festkörperphysik, 70569 Stuttgart, Germany

Received 20 July 2009; Revised 1 November 2009; Accepted 24 February 2010

Academic Editor: Carlo Di Castro

Copyright © 2010 E. G. Maksimov et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In this paper we discuss experimental evidence related to the structure and origin of the bosonic spectral function 𝛼 2 𝐹 ( 𝜔 ) in high-temperature superconducting (HTSC) cuprates at and near optimal doping. Global properties of 𝛼 2 𝐹 ( 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 < 𝜆 𝑒 𝑝 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.