An Isotopic Fingerprint of Electron-Phonon Coupling in High-Tc Cuprates

TL;DR

This study uses angle-resolved photoemission spectroscopy to identify how oxygen isotope substitution affects electron-phonon interactions in high-Tc cuprates, highlighting phonons' dominant role in the pairing mechanism.

Contribution

It provides direct experimental evidence of isotope effects on electron-boson coupling in cuprates, pinpointing specific phonon modes involved.

Findings

Oxygen isotope substitution causes a measurable shift in the electron-boson coupling kink.

The magnitude and direction of the kink shift match theoretical predictions based on phonon frequency changes.

Phonons are confirmed as the dominant bosonic mode influencing electron pairing in these materials.

Abstract

Angle-resolved photoemission spectroscopy with low-energy tunable photons along the nodal direction of oxygen isotope substituted Bi2Sr2CaCu2O8+delta reveals a distinct oxygen isotope shift near the electron-boson coupling "kink" in the electronic dispersion. The magnitude (a few meV) and direction of the kink shift are as expected due to the measured isotopic shift of phonon frequency, which are also in agreement with theoretical expectations. This demonstrates the participation of the phonons as dominant players, as well as pinpointing the most relevant of the phonon branches.