Department of Chemistry, University of California, Berkeley, CA, USA.
Department of Physics, University of California, Berkeley, CA, USA.
Nature. 2021 Dec;600(7890):647-652. doi: 10.1038/s41586-021-04201-y. Epub 2021 Dec 22.
Spin-ordered electronic states in hydrogen-terminated zigzag nanographene give rise to magnetic quantum phenomena that have sparked renewed interest in carbon-based spintronics. Zigzag graphene nanoribbons (ZGNRs)-quasi one-dimensional semiconducting strips of graphene bounded by parallel zigzag edges-host intrinsic electronic edge states that are ferromagnetically ordered along the edges of the ribbon and antiferromagnetically coupled across its width. Despite recent advances in the bottom-up synthesis of GNRs featuring symmetry protected topological phases and even metallic zero mode bands, the unique magnetic edge structure of ZGNRs has long been obscured from direct observation by a strong hybridization of the zigzag edge states with the surface states of the underlying support. Here, we present a general technique to thermodynamically stabilize and electronically decouple the highly reactive spin-polarized edge states by introducing a superlattice of substitutional N-atom dopants along the edges of a ZGNR. First-principles GW calculations and scanning tunnelling spectroscopy reveal a giant spin splitting of low-lying nitrogen lone-pair flat bands by an exchange field (~850 tesla) induced by the ferromagnetically ordered edge states of ZGNRs. Our findings directly corroborate the nature of the predicted emergent magnetic order in ZGNRs and provide a robust platform for their exploration and functional integration into nanoscale sensing and logic devices.
氢终止的锯齿形纳米石墨烯中的自旋有序电子态导致了磁量子现象，这重新激发了人们对基于碳的自旋电子学的兴趣。锯齿形石墨烯纳米带（ZGNRs）-由平行锯齿边缘限定的石墨烯的准一维半导体条带-具有固有电子边缘态，这些边缘态沿条带的边缘呈铁磁有序，而在其宽度上呈反铁磁耦合。尽管在自下而上合成具有对称保护拓扑相甚至金属零模带的 GNRs 方面取得了最近的进展，但 ZGNRs 的独特磁性边缘结构长期以来一直受到其强杂化的阻碍，这种杂化是由锯齿边缘态与下面的支撑表面态之间的强杂化。在这里，我们提出了一种通用技术，通过在 ZGNR 的边缘引入取代 N 原子掺杂的超晶格，来热力学稳定和电子解耦高反应性的自旋极化边缘态。第一性原理 GW 计算和扫描隧道光谱揭示了由 ZGNR 的铁磁有序边缘态引起的交换场（~850 特斯拉）对低能氮孤对平面带的巨大自旋分裂。我们的发现直接证实了 ZGNRs 中预测的新兴磁序的性质，并为它们的探索和功能集成到纳米尺度传感和逻辑器件中提供了一个稳健的平台。
