Coupling of the B 1 g Phonon to the Antinodal Electronic States of B i 2 S r 2 C a 0.92 Y 0.08 C u 2 O 8 + δ

Angle-resolved photoemission spectroscopy on optimally doped ${\mathrm{B}\mathrm{i}}_{2}{\mathrm{S}\mathrm{r}}_{2}{\mathrm{C}\mathrm{a}}_{0.92}{\mathrm{Y}}_{0.08}{\mathrm{C}\mathrm{u}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ uncovers a coupling of the electronic bands to a 40 meV mode in an extended $k$-space region away from the nodal direction, leading to a new interpretation of the strong renormalization of the electronic structure seen in Bi2212. Phenomenological agreements with neutron and Raman experiments suggest that this mode is the ${B}_{1g}$ oxygen bond-buckling phonon. A theoretical calculation based on this assignment reproduces the electronic renormalization seen in the data.