Superconductivity-induced self-energy evolution of the nodal electron of optimally doped Bi2 Sr2 Ca0.92 Y0.08 Cu2 O8+δ

The temperature dependent evolution of the renormalization effect in optimally doped Bi2 Sr2 Ca0.92 Y0.08 Cu2 O8+δ along the nodal direction has been studied via angle-resolved photoemission spectroscopy. Fine structure is observed in the real part of the self-energy (Re Σ), including a subkink and maximum, suggesting that electrons couple to a spectrum of bosonic modes, instead of just one mode. Upon cooling through the superconducting phase transition, the fine structures of the extracted Re Σ exhibit a two-processes evolution demonstrating an interplay between kink renormalization and superconductivity. We show that this two-process evolution can be qualitatively explained by a simple Holstein model in which a spectrum of bosonic modes is considered.