Strong long-range electron-phonon interaction as possible driving force for charge ordering in cuprates

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity Theory

Background:

• Cuprate superconductors exhibit complex charge ordering (CO) phenomena.
• Understanding the interplay of electron-phonon interaction (EPI) and carrier density is crucial for explaining CO behavior.
• The coexistence of bipolarons and delocalized carriers is a key characteristic of these systems.

Purpose of the Study:

• To develop a theoretical model for charge ordering (CO) in systems with strong electron-phonon interaction (EPI) and high carrier density.
• To investigate the factors governing bipolaron size and the doping dependence of CO in cuprates.
• To elucidate the physical mechanisms behind the varied doping behavior of CO wave vectors in different cuprates.

Main Methods:

• Development of a generalized variation method to calculate bipolaron size (CO period) in the ground state.
• Analysis of doping dependences for CO period and CO decay temperature.
• Theoretical prediction of the ratio between CO wave vector and high-energy anomaly (HEA) wave vector in ARPES spectra.
• Calculation of resonant X-ray scattering cross-sections for CO.

Main Results:

• The model reproduces charge ordering (CO) phenomena observed in cuprate superconductors.
• Calculated doping dependences of CO period and CO decay temperature show quantitative agreement with experimental cuprate data.
• The predicted ratio of CO wave vector to HEA wave vector aligns with experimental observations in cuprates.
• Resonant X-ray scattering calculations match experimental results, including peak asymmetry.
• A spectral gap emerges for delocalized carriers due to scattering by autolocalized carriers, analogous to photonic crystals.

Conclusions:

• The generalized variation method effectively models charge ordering (CO) in cuprates, explaining diverse doping behaviors.
• The model provides a physical basis for observed CO characteristics and their relationship with electronic properties.
• The study offers insights into the complex electronic structure and emergent phenomena in correlated electron systems like cuprates.