Broken relationship between superconducting pairing interaction and electronic dispersion kinks in LSCO

TL;DR

This study uses ARPES to investigate the relationship between electron-boson coupling and superconductivity in LSCO, revealing that kinks in electronic dispersion persist even when superconductivity vanishes, challenging conventional theories.

Contribution

It demonstrates that the electron-bosonic mode coupling indicated by dispersion kinks is not directly linked to superconductivity in LSCO, suggesting alternative pairing mechanisms.

Findings

Kinks remain strong in heavily overdoped LSCO even without superconductivity.

The persistence of kinks contradicts the conventional bosonic mode-mediated pairing theory.

Superconductivity may originate from broad electronic interactions or unconventional mechanisms.

Abstract

Electronic band dispersions in copper oxide superconductors have kinks around 70 meV that are typically attributed to coupling of electrons to a bosonic mode. We performed angle resolved photoemission spectroscopy (ARPES) experiments on overdoped cuprate high temperature superconductors to test the relationship between the superconducting transition temperature and electron-bosonic mode coupling. Remarkably, the kinks remain strong in the heavily overdoped region of the doping phase diagram of LSCO, even when the superconductivity completely disappears. This unexpected observation is incompatible with the conventional picture of superconductivity mediated by the sharp bosonic modes that are responsible for the kink. Therefore, the pairing likely originates from something else, such as from interactions with a very broad electronic spectrum or from an unconventional mechanism without pairing glue.