Addressing Electron Spins Embedded in Metallic Graphene Nanoribbons

Abstract

Spin-hosting graphene nanostructures are promising metal-free systems for elementary quantum spintronic devices. Conventionally, spins are protected from quenching by electronic band gaps, which also hinder electronic access to their quantum state. Here, we present a narrow graphene nanoribbon substitutionally doped with boron heteroatoms that combines a metallic character with the presence of localized spin 1/2 states in its interior. The ribbon was fabricated by onsurface synthesis on a Au(111) substrate. Transport measurements through ribbons suspended between the tip and the sample of a scanning tunneling microscope revealed their ballistic behavior, characteristic of metallic nanowires. Conductance spectra show fingerprints of localized spin states in the form of Kondo resonances and inelastic tunneling excitations. Density functional theory rationalizes the metallic character of the graphene nanoribbon due to the partial depopulation of the valence band induced by the boron atoms. The transferred charge builds localized magnetic moments around the boron atoms. The orthogonal symmetry of the spin-hosting state's and the valence band's wave functions protects them from mixing, maintaining the spin states localized. The combination of ballistic transport and spin localization into a single graphene nanoribbon offers the perspective of electronically addressing and controlling carbon spins in real device architectures.

On-Surface Synthesis of Graphene Nanoribbons with Atomically Precise Structural Heterogeneities and On-Site Characterizations

“…Quite a lot of results have been achieved since the development of on-surface synthesis, which can precisely control the substitutional site through rationally designing the precursor molecules. Up to now, various heteroatoms, such as boron (B), − nitrogen (N), − oxygen (O), , and sulfur (S) atoms, have been implanted in GNRs with different configurations.…”

Graph machine learning framework for depicting wavefunction on interface

“…The origin leaves room for discussion of new theories. The wavefunction symmetry mechanism [50], as a key factor, will affect the degree of spatial localization. Furthermore, for all samples, the curvature of energy band is highly correlated with the distribution state of wavefunction.…”

Low Coverage of Long Graphene Nanoribbons by On-surface Double Layer Polymerization on Au(111)

“…On-surface synthesized graphene nanoribbons (GNRs) are a class of low electronic gap conjugated organic oligomers having chemically tunable electronic properties for fabricating molecular materials [1][2][3][4] and also for measuring the current − voltage characteristics of a single isolated molecular wire for monomolecular electronics. [5][6][7] Among the family, the standard on-surface 7-carbon atoms wide armchair type GNR (7-aGNR) synthesis protocol is a two-step process with the initial formation of polyanthryl oligomers by the activation of an Ullmann coupling reaction followed by a cyclodehydrogenation along the polyanthryl backbone. 8,9 In solution, a Ullmann coupling reaction is assisted by metal catalysis.…”