Enhanced Electron-Phonon Coupling for Charge-Density-Wave Formation in La_{1.8-x}Eu_{0.2}Sr_{x}CuO_{4+δ}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Charge density wave (CDW) correlations are common in copper-oxide superconductors.
• The role of electron-phonon coupling (EPC) in cuprate CDWs remains a significant debate in condensed matter physics.

Purpose of the Study:

• To investigate the interplay between charge order and EPC in stripe-ordered cuprates.
• To determine how doping and temperature affect this relationship.
• To elucidate the feedback mechanism between CDW and EPC.

Main Methods:

• Utilized Cu L_{3} edge resonant inelastic x-ray scattering.
• Studied CDW and Cu-O bond-stretching phonons in La_{1.8-x}Eu_{0.2}Sr_{x}CuO_{4+δ}.
• Analyzed EPC by varying incident photon energy relative to the absorption resonance.

Main Results:

• Found enhanced EPC in a specific momentum region around the CDW ordering vector.
• Quantified the EPC matrix element at the CDW ordering vector as M≃0.36 eV, decreasing to M≃0.30 eV at higher temperatures without CDW.
• Observed a clear correlation between CDW presence and EPC strength.

Conclusions:

• The CDW state enhances the electron-phonon coupling.
• This enhancement creates a feedback mechanism that further stabilizes the CDW.
• Suggests a crucial role for EPC in the formation and stability of CDWs in cuprate superconductors.