Oxygen isotope effect on electron dynamics in Bi2Sr2CaCu2Oy: angle-resolved photoemission spectroscopy

In order to directly examine the impact of phonons in electronic structure, angle-resolved photoemission spectroscopy (ARPES) measurements have been performed on optimally doped Bi2Sr2CaCu2Oy (Tc ∼ 92 K) upon oxygen isotope substitution. The obtained ARPES data show clear and giant changes induced by 16O → 18O exchange, which are found to be strongly energy, momentum dependent and effective only at low temperatures (T < Tc). This direct observation of unconventional electron-phonon interactions should urge reconsideration of the role of phonons in high-Tc materials.