Spin Splitting of Dopant Edge States in Magnetic Zigzag Graphene Nanoribbons

TL;DR

This study demonstrates a method to stabilize and observe spin-polarized edge states in zigzag graphene nanoribbons by nitrogen doping, revealing giant spin splitting and magnetic order crucial for spintronic applications.

Contribution

The paper introduces a nitrogen-doping technique to passivate reactive edge states in ZGNRs, enabling direct observation of their magnetic properties through first-principles calculations and spectroscopy.

Findings

Giant spin splitting (~850 Tesla) observed in nitrogen-doped ZGNRs.

Passivation of reactive edge states enables direct experimental access.

Confirmation of ferromagnetic edge order in ZGNRs.

Abstract

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 featuring two parallel zigzag edges along the main axis of the ribbon, are predicted to 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 atomically-precise ZGNRs, their unique electronic structure has thus far been obscured from direct observations by the innate chemical reactivity of spin-ordered edge states. Here we present a general technique for passivating the chemically highly reactive spin-polarized edge states by introducing a superlattice of substitutional nitrogen-dopants along the edges of a ZGNR. First-principles GW calculations and scanning tunneling spectroscopy reveal a giant spin splitting of the low-lying nitrogen lone-pair flat bands by a large exchange field (~850 Tesla) induced by the spin-polarized ferromagnetically ordered edges 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.