In copper oxides (cuprates) with single CuO2 layer such as La2−xBa(Sr)xCuO4, antiferromagnetism coexists with superconductivity at small doping levels x, where chemical disorders are significant. Here, we report that superconductivity occurs in a uniform and fully ordered Neˊel state in a single-layer cuprate La2CuO4+δ with a small amount of excess oxygen (δ=0.015) as demonstrated by the 139La nuclear quadrupole resonance measurement. A uniform oxygen distribution in the crystal is crucial for achieving microscopic phase coexistence and overcoming the miscibility gap associated with the staging instability; self-organized periodic oxygen arrangement driven by mobile oxygen atoms. This finding prompts the reconsideration of superconductivity in cuprates, highlighting that it can emerge in a robust Neˊel state that retains sizable magnetic moments and hosts only a small carrier density.
@article{arxiv.2507.20138,
title = {Superconductivity emerging from the N${\'e}$el state in ${\it infinite}$-${\it stage}$ single-layer cuprate La$_2$CuO$_{4+\delta}$},
author = {Yoshihiko Ihara and Ramender Kumar and Kota Miyakoshi and Migaku Oda and Kenji Ishida},
journal= {arXiv preprint arXiv:2507.20138},
year = {2025}
}