The mechanism behind superconductivity suppression induced by Pr substitutions in YBa2Cu3O7−δ (YBCO) has been a mystery since its discovery: in spite of being isovalent to Y3+ with a small magnetic moment, it is the only rare-earth element that has a dramatic impact on YBCO's superconducting properties. Using angle-resolved photoemission spectroscopy (ARPES) and DFT+U calculations, we uncover how Pr substitution modifies the low-energy electronic structure of YBCO. Contrary to the prevailing Fehrenbacher-Rice (FR) and Liechtenstein-Mazin (LM) models, the low energy electronic structure contains no signature of any f-electron hybridization or new states. Yet, strong electron doping is observed primarily on the antibonding Fermi surface. Meanwhile, we reveal major electronic structure modifications to Cu-derived states with increasing Pr substitution: a pronounced CuO2 bilayer decoupling and an enhanced CuO chain hopping, implying indirect electron-release pathways beyond simple 4f state ionization. Our results challenge the long-standing FR/LM mechanism and establish Pr substituted YBCO as a potential platform for exploring correlation-driven phenomena in coupled 1D-2D systems.
@article{arxiv.2510.15078,
title = {Superconductivity suppression and bilayer decoupling in Pr substituted YBa$_2$Cu$_3$O$_{7-\delta}$},
author = {Jinming Yang and Zheting Jin and Siqi Wang and Camilla Moir and Mingyu Xu and Brandon Gunn and Xian Du and Zhibo Kang and Keke Feng and Makoto Hashimoto and Donghui Lu and Jessica McChesney and Martin Sundermann and Hlynur Gretarsson and Shize Yang and Wei-Wei Xie and Alex Frano and Sohrab Ismail-Beigi and M. Brian Maple and Yu He},
journal= {arXiv preprint arXiv:2510.15078},
year = {2025}
}