A recent angle resolved photoelectron spectroscopy (ARPES) study by Douglas et al. \cite {dessau-comment} on oxygen isotope exchanged Bi_2Sr_2CaCu_2O8+δ superconductors reported an absence of isotope effect at optimal doping, questioning the previous work by us \cite {gweon-nature}. Here, we report a new result that sheds light on this puzzling discrepancy as well as the nature of the electron lattice interaction in the cuprates: the anomalous isotope effect at optimal doping \cite {gweon-nature}, re-confirmed here, vanishes on a mere 2 % overdoping of holes. This result implies a rapid change of the nature of the electron-lattice interaction near optimal doping. We also find that the data by Douglas et al. \cite {dessau-comment} are actually characteristic of significantly over-doped samples, not of optimally doped samples as they claimed.
@article{arxiv.0708.1027,
title = {Unusual oxygen isotope effects in cuprates -- importance of doping},
author = {G. -H. Gweon and T. Sasagawa and H. Takagi and D. -H. Lee and A. Lanzara},
journal= {arXiv preprint arXiv:0708.1027},
year = {2007}
}