Superconductivity suppression and bilayer decoupling in Pr-substituted YBa₂Cu₃O_7-δ

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Superconductivity suppression in Yttrium Barium Copper Oxide (YBCO) by Praseodymium (Pr) substitution is a long-standing mystery.
• Pr is unique among rare-earth elements for its dramatic impact on YBCO's superconducting properties despite being isovalent to Yttrium.

Purpose of the Study:

• To elucidate the mechanism by which Pr substitution modifies the low-energy electronic structure of YBCO.
• To investigate the role of Pr 4f electrons and their hybridization with YBCO electronic states.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) to probe the electronic structure.
• Density Functional Theory (DFT)+[Formula: see text] calculations to model electronic behavior.

Main Results:

• No evidence of f-electron hybridization or additional f-state Fermi surface sheets was found, contradicting prevailing models.
• Strong electron doping was observed, primarily on the antibonding Fermi surface.
• Significant modifications to Cu-derived states, including CuO2 bilayer decoupling and enhanced CuO chain hopping, were identified.

Conclusions:

• The findings challenge the Fehrenbacher-Rice (FR) and Liechtenstein-Mazin (LM) models for superconductivity suppression in Pr-YBCO.
• Indirect electron-release pathways, beyond simple 4f state ionization, are implied.
• Pr-substituted YBCO presents a platform for studying correlation-driven phenomena in coupled 1D-2D systems.