Characteristics of oxygen isotope substitutions in the quasiparticle spectrum of Bi2Sr2CaCu2O8+E. Schachinger1, J. P. Carbotte2, 3 and T. Timusk2, 3
1 Institute of Theoretical and Computational Physics, Graz University of Technology - A-8010 Graz, Austria, EU
2 Department of Physics and Astronomy, McMaster University - Hamilton, Ontario N1G 2W1, Canada
3 The Canadian Institute for Advanced Research - Toronto, Ontario M5G 1Z8, Canada
received 30 April 2009; accepted in final form 9 June 2009; published June 2009
published online 30 June 2009
There is an ongoing debate about the nature of the bosonic excitations responsible for the quasiparticle self-energy in high-temperature superconductors —are they phonons or spin fluctuations? We present a careful analysis of the bosonic excitations as revealed by the “kink” feature at 70 meV in angle-resolved photoemission data using Eliashberg theory for a d-wave superconductor. Starting from the assumption that nodal quasiparticles are not coupled to the magnetic resonance, the sharp structure at 70 meV can be assigned to phonons. We find that not only can we account for the shifts of the kink energy seen on oxygen isotope substitution but also get a quantitative estimate of the fraction of the area under the electron-boson spectral density which is due to phonons. We conclude that for optimally doped Bi2Sr2CaCu2O8+ phonons contribute ~ 10% and non-phononic excitations ~ 90%.
74.20.Mn - Nonconventional mechanisms (spin fluctuations, polarons and bipolarons, resonating valence bond model, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.).
74.25.Kc - Phonons.
74.72.Hs - Bi-based cuprates.
© EPLA 2009