Zusammenfassung
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 (Ï€,
Ï€) 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 Bi 2 Sr 2 CaCu 2 O 8+δ phonons contribute ~10% and non-phononic
excitations ~90%.
Nutzer