Strong Electron-Phonon coupling in High Temperature Superconductors

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  • 13 February 2001
Abstract
The identification of phonon anomalies in the electronic tunneling spectra played a decisive role in our understanding of conventional superconductors [1]. Recently an abrupt change in the electronic quasiparticle dispersion near (50+15) meV binding energy has been observed in angle resolved photoemission spectroscopy (ARPES) from Bi2Sr2CaCu2O8 (Bi2212) [2-4]. This behavior indicates a many-body effect likely to be very important for the physical properties and pairing mechanism. While two groups have positively identified this effect [2,3], there is no consensus on the origin of the feature: with phonons, the magnetic resonance mode and energy gap as possible candidates. This paper reports new data revealing the following behavior of this effect: a) it has an energy scale of 50-80 meV and is ubiquitous in hole doped materials; b) the effect is seen well above the critical temperature (Tc); c) the coupling gets weaker with increasing doping; d) the momentum dependence of the effect is weak. These results rule out both the magnetic resonance mode and energy gap as possible explanations, leaving phonons as the only surviving candidate.

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