Unusual oxygen isotope effects in cuprates -- importance of doping

TL;DR

This study investigates oxygen isotope effects in cuprate superconductors, revealing that the anomalous isotope effect disappears with slight overdoping and clarifying discrepancies in previous ARPES studies, thus highlighting a rapid change in electron-lattice interactions near optimal doping.

Contribution

We demonstrate that the anomalous isotope effect vanishes with minimal overdoping and clarify the doping level of samples in previous studies, advancing understanding of electron-lattice interactions in cuprates.

Findings

Anomalous isotope effect disappears with 2% overdoping.

Previous ARPES data correspond to overdoped samples.

Rapid change in electron-lattice interaction near optimal doping.

Abstract

A recent angle resolved photoelectron spectroscopy (ARPES) study by Douglas et al. \cite {dessau-comment} on oxygen isotope exchanged Bi_2Sr_2CaCu_2O$_{8+\delta}$ 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.