Correlation-enhanced electron-phonon coupling: Applications of GW and screened hybrid functional to bismuthates, chloronitrides, and other high Tc superconductors

TL;DR

This paper introduces a methodology using GW and screened hybrid functional DFT to accurately evaluate electron-phonon coupling, explaining high Tc superconductivity in bismuthates and chloronitrides, and suggesting broader applications.

Contribution

It presents a new approach to accurately assess electron-phonon coupling beyond LDA, addressing longstanding high Tc superconductor puzzles and enabling design of new materials.

Findings

Corrected EPC explains high superconducting temperatures in bismuthates and chloronitrides.

Standard DFT underestimates EPC due to non-local correlation effects.

Methodology can be applied to other superconductors like cuprates and iron-based materials.

Abstract

We show that the electron-phonon coupling (EPC) in many materials can be significantly underestimated by the standard density functional theory (DFT) in the local density approximation (LDA) due to large non-local correlation effects. We present a simple yet efficient methodology to evaluate the realistic EPC going beyond LDA by using more advanced and accurate GW and screened hybrid functional DFT approaches. The corrections we propose explain the extraordinarily high superconducting temperatures that are observed in two distinct classes of compounds-the bismuthates and the transition metal chloronitrides, thus solving a thirty-year-old puzzle. Our work calls for the critically reevaluation of the EPC of certain phonon modes in many other materials such as cuprates and iron-based superconductors. The proposed methodology can be used to design new correlation-enhanced high temperature superconductors and other functional materials involving electron-phonon interaction.