Open-shell nanographenes exhibit unconventional π-magnetism arising from topological frustration or strong electron–electron interaction. However, conventional design approaches are typically limited to a single magnetic origin, which can restrict the number of correlated spins or the type of magnetic ordering in open-shell nanographenes. Here we present a design strategy that combines topological frustration and electron–electron interactions to fabricate a large fully fused ‘butterfly’-shaped tetraradical nanographene on Au(111). We employ bond-resolved scanning tunnelling microscopy and spin-excitation spectroscopy to resolve the molecular backbone and reveal the strongly correlated open-shell character, respectively. This nanographene contains four unpaired electrons with both ferromagnetic and anti-ferromagnetic interactions, harbouring a many-body singlet ground state and strong multi-spin entanglement, which is well described by many-body calculations. Furthermore, we study the magnetic properties and spin states in the nanographene using a nickelocene magnetic probe. The ability to imprint and characterize many-body strongly correlated spins in polyradical nanographenes paves the way for future advancements in quantum information technologies.

开壳纳米石墨烯表现出由拓扑挫败或强电子-电子相互作用产生的非常规π磁性。然而，传统的设计方法通常仅限于单个磁源，这可能限制开壳纳米石墨烯中相关自旋的数量或磁排序的类型。在这里，我们提出了一种设计策略，结合拓扑挫败和电子-电子相互作用，在 Au(111) 上制造大型完全熔融的“蝴蝶”形四基纳米石墨烯。我们采用键分辨扫描隧道显微镜和自旋激发光谱来分别解析分子主链并揭示强相关的开壳特征。这种纳米石墨烯包含四个不成对的电子，具有铁磁和反铁磁相互作用，具有多体单重态基态和强多自旋纠缠，这可以通过多体计算得到很好的描述。此外，我们使用二茂镍磁性探针研究了纳米石墨烯的磁性和自旋态。在多自由基纳米石墨烯中印记和表征多体强相关自旋的能力为量子信息技术的未来进步铺平了道路。