A re-examination of the oxygen isotope effect in ARPES spectra of Bi2212

We have re-examined the oxygen isotope effect in high-temperature superconductors Bi2Sr2CaCu2O8+δ using high-precision angle-resolved photoemission spectroscopy with low-energy photons in order to elucidate the origin of the kink. The results taken with a much improved energy and momentum resolution showed the absence of the reported unusual oxygen isotope effect.