2025-08-28 京都大学
わずかに酸素をドープした単層型銅酸化物La2CuO4+δで、ネール状態と超伝導状態の共存状態が見つかった。CuO2層上で広がりを持つ伝導キャリア（青丸）が作る超伝導状態と、Cuに局在する磁気モーメント（赤矢印）が作るネール状態は、本来は水と油のように相容れない状態である。対立する性質が融和した斬新な共存状態が、最古の銅酸化物で実現していたことが分かった。
＜関連情報＞
- https://www.kyoto-u.ac.jp/ja/research-news/2025-08-28
- https://www.kyoto-u.ac.jp/sites/default/files/2025-08/web_2508_Ishida-d9090dcc95941014b01eafef85f13d75.pdf
- https://www.nature.com/articles/s41598-025-11950-7
無限段単層銅酸化物La2CuO4+δにおけるネール状態から生じる超伝導性 Superconductivity emerging from the Néel state in infinite-stage single-layer cuprate La2CuO4+δ
Yoshihiko Ihara,Ramender Kumar,Kota Miyakoshi,Migaku Oda & Kenji Ishida
Scientific Reports Published:DOI:https://doi.org/10.1038/s41598-025-11950-7
Abstract
In copper oxides (cuprates) with single CuO2 layer such as La2-x Ba(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 Néel state in a single-layer cuprate LaCu2O4+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 Néel state that retains sizable magnetic moments and hosts only a small carrier density.
