Spin splitting of dopant edge state in magnetic zigzag graphene nanoribbons

• Published in: Nature (London) 2021-12, Vol.600 (7890), p.647-652
• Main Authors: Blackwell, Raymond E., Zhao, Fangzhou, Brooks, Erin, Zhu, Junmian, Piskun, Ilya, Wang, Shenkai, Delgado, Aidan, Lee, Yea-Lee, Louie, Steven G., Fischer, Felix R.
• Format: Article
• Language: English
• Subjects: 119/118; 142/136; 639/638/298/920; 639/638/542/968; 639/766/119/997; 639/925/918/1052; Adsorption; Analysis; Antiferromagnetism; Carbon; Chemical properties; Dopants; Electron spin; Electron states; electronic properties and devices; Ferromagnetism; First principles; Functional integration; Geometry; Graphene; Humanities and Social Sciences; Hybridization; Hydrogen; magnetic materials; Magnetic properties; magnetic properties and materials; MATERIALS SCIENCE; Microscopy; multidisciplinary; Nanoribbons; Nanotechnology; Nitrogen; Particle spin; scanning probe microscopy; Science; Science (multidisciplinary); Spectroscopy; Spectrum analysis; Splitting; Structure; Superlattices; Topography
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-021-04201-y

Spin-ordered electronic states in hydrogen-terminated zigzag nanographene give rise to magnetic quantum phenomena 1 , 2 that have sparked renewed interest in carbon-based spintronics 3 , 4 . 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 1 , 2 , 5 . Despite recent advances in the bottom-up synthesis of GNRs featuring symmetry protected topological phases 6 – 8 and even metallic zero mode bands 9 , 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 10 – 15 . 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 15 – 21 . Decoupling spin-polarized edge states using substitutional N-atom dopants along the edges of a zigzag graphene nanoribbon (ZGNR) reveals giant spin splitting of a N-dopant edge state, and supports the predicted emergent magnetic order in ZGNRs.