Tunneling study of the electron–phonon interaction in Bi2Sr2CaCu2O8

Abstract Spectral function of the electron–phonon (e–ph) interaction α 2 F ( ω ) of slightly overdoped Bi 2 Sr 2 CaCu 2 O 8 is composed of many peaks which correspond to those of the phonon density of states F ( ω ), and there is no other peak. This clearly indicates a phonon mechanism of high- T c superconductivity. The ratio of integral intensity of corresponding peaks in α 2 F ( ω ) and F ( ω ) varies from 0.5 to 2.5 meV as an average per mode, and there is no particularly large peak. Thus, the numerosity of phonon modes favors for a strong interaction. However, for explaining a large relative gap 2 Δ (0)/ k B T c for underdoped cuprates a simple e–ph interaction is insufficient, and we proposed a phonon model supplemented by a magnetic pair-break interaction. Various properties of cuprates are discussed based on this model.