  Angle-resolved photoemission spectroscopy (ARPES) on optimally doped
Bi2Sr2Ca0.92Y0.08Cu2O(8+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 B1g oxygen bond-buckling phonon. A
theoretical calculation based on this assignment reproduces the electronic
renormalization seen in the data.
