Electron-Phonon Coupling in High-Temperature Cuprate Superconductors Determined from Electron Relaxation Rates

TL;DR

This study uses ultrafast optical spectroscopy to measure electron relaxation times in cuprate superconductors, revealing significant electron-phonon interactions that may influence high-temperature superconductivity.

Contribution

It provides direct experimental estimates of electron-phonon coupling strength in cuprates using femtosecond spectroscopy, highlighting its potential role in pairing mechanisms.

Findings

Measured electron-phonon coupling constants in two cuprates.

Identified electron-phonon interaction as the primary relaxation process.

Suggests electron-phonon interaction may be fundamental to superconductivity.

Abstract

We determined electronic relaxation times via pump-probe optical spectroscopy using sub-15 fs pulses for the normal state of two different cuprate superconductors.We show that the primary relaxation process is the electron-phonon interaction and extract a measure of its strength, the second moment of the Eliashberg function\lambda<\omega^{2}>=800\pm200 meV^{2} for La_{1.85}Sr_{0.15}CuO_{4} and \lambda<\omega^{2}>=400\pm100 meV^{2} for YBa_{2}Cu_{3}O_{6.5}. These values suggest a possible fundamental role of the electron-phonon interaction in the superconducting pairing mechanism.