Electron-phonon interaction alone does not explain the photoemission kink in cuprate superconductors

TL;DR

This study uses advanced first-principles calculations to show that electron-phonon interactions cannot account for the photoemission kink observed in cuprate superconductors, challenging phonon-based explanations of high-temperature superconductivity.

Contribution

The paper provides the first comprehensive ab initio analysis demonstrating that phonons are insufficient to explain the ARPES kink in LSCO, ruling out electron-phonon interactions as the primary cause.

Findings

Electron-phonon coupling effects are nearly an order of magnitude too small.

Phonons cannot explain the observed photoemission kink in LSCO.

Results challenge phonon-based theories of high-temperature superconductivity.

Abstract

Despite over two decades of intense research efforts, the origin of high-temperature superconductivity in the copper oxides remains elusive. Angle-resolved photoemission experiments (ARPES) revealed a kink in the dispersion relations (energy vs. wavevector) of electronic states in the cuprates at binding energies of 50-80 meV, and raised the hope that this anomaly could be key to understanding high-temperature superconductivity. The kink is often interpreted in terms of interactions between the electrons and a bosonic field. While there is no consensus on the nature of the bosons or even whether a boson model is appropriate, phonons and spin fluctuations have alternatively been proposed as possible candidates. Here we report state-of-the-art first-principles calculations of the role of phonons and the electron-phonon interaction in the photoemission spectra of La2-xSrxCuO4 (LSCO). Our study demonstrates that the phonon-induced renormalization of the electron energies and the Fermi velocity is almost one order of magnitude smaller than the effect observed in photoemission experiments. Hence, the present finding rules out electron-phonon interaction in bulk LSCO as the possible origin of the measured kink. This result should bear on several proposed theories of high temperature superconductivity in addition to theories concerning the origin of kinks in cuprate photoemission data.