Key pairing interaction in layered doped ionic insulators

TL;DR

This paper demonstrates that the Fröhlich electron-phonon interaction with high-frequency optical phonons is the primary pairing mechanism in layered doped ionic superconductors, challenging the view that EPI is weak or irrelevant.

Contribution

It provides a semi-analytical, self-consistent evaluation of EPI strength and electron-electron interactions in high-Tc superconductors using a continuum RPA approach.

Findings

EPI is the key pairing interaction in layered doped ionic insulators.

EPI remains significant across doping levels, including overdoped regimes.

The study goes beyond traditional BCS-Migdal-Eliashberg theory in underdoped superconductors.

Abstract

A controversial issue on whether the electron-phonon interaction (EPI) is crucial for high-temperature superconductivity or it is weak and inessential has remained one of the most challenging problems of contemporary condensed matter physics. We employ a continuum RPA approximation for the dielectric response function allowing for a selfconsistent semi-analytical evaluation of the EPI strength, electron-electron attractions, and the carrier mass renormalisation in layered high-temperature superconductors. We show that the Fr\"{o}hlich EPI with high-frequency optical phonons in doped ionic lattices is the key pairing interaction, which is beyond the BCS-Migdal-Eliashberg approximation in underdoped superconductors, and it remains a significant player in overdoped compounds.