Phonon dispersion and electron-phonon interaction for YBa_2Cu_3O_7 from first-principles calculations

TL;DR

This study uses first-principles calculations to analyze phonon behavior and electron-phonon interactions in YBa_2Cu_3O_7, finding weak coupling and suggesting phonons are not key to its high-temperature superconductivity.

Contribution

It provides detailed phonon dispersion and electron-phonon coupling calculations for YBa_2Cu_3O_7, challenging previous assumptions about their role in high-T_c superconductivity.

Findings

Phonon dispersion matches experimental data.

Electron-phonon coupling lambda=0.27, lower than earlier estimates.

Conventional electron-phonon interaction likely not responsible for high-T_c in this material.

Abstract

We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the high-T_c superconductor YBa_2Cu_3O_7 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. The calculated phonon dispersion curves are in excellent agreement with Raman, infrared and neutron data. Calculation of the Eliashberg function alpha^2F leads to a small electron-phonon coupling lambda=0.27 in disagreement with earlier approximate treatments. Our calculations strongly support the view that conventional electron-phonon coupling is not an important contribution to superconductivity in high-T_c materials.