Anomalous magnetism in hydrogenated graphene

Abstract

We revisit the problem of local moment formation in graphene due to chemisorption of individual atomic hydrogen or other analogous sp${}^3$ covalent functionalizations. We describe graphene with the single orbital Hubbard model, so that the H chemisorption is equivalent to a vacancy in the honeycomb lattice. In order to circumvent artefacts related to periodic unit cells, we use either huge simulation cells of up to $8\times 10^5$ sites, or an embedding scheme that allows the modelling of a single vacancy in an otherwise pristine infinite honeycomb lattice. We find three results that stress the anomalous nature of the magnetic moment ($m$) in this system. First, in the non-interacting ($U=0$), zero temperature ($T=0$) case, the $m(B)$ is a continuous smooth curve with divergent susceptibility, different from the step-wise constant function found for a single unpaired spins in a gapped system. Second, for $U=0$ and $T>0$, the linear susceptibility follows a power law $\propto T^{-\alpha }$ with an exponent of $\alpha =0.77$ different from conventional Curie's law. For $U>0$, in the mean field approximation, the integrated moment is smaller than $m=1{\mu }_B$, in contrast with results using periodic unit cells. These three results highlight that the magnetic response of the local moment induced by sp${}^3$ functionalizations in graphene is different both from that of local moments in gaped systems, for which the magnetic moment is quantized and follows a Curie law, and from Pauli paramagnetism in conductors, for which a linear susceptibility can be defined at $T=0$.

References in corpus (19)

• Control of graphene's properties by reversible hydrogenation
• Graphane: a two-dimensional hydrocarbon
• Graphene Spintronics
• Magnetism in Graphene Induced by Single-Atom Defects
• Emergence of magnetism in graphene materials and nanostructures
• The Kernel Polynomial Method
• Hydrogen on graphene: Electronic structure, total energy, structural distortions, and magnetism from first-principles calculations
• Magnetism in graphene nano-islands
• Atomic-scale control of graphene magnetism using hydrogen atoms
• Disorder Induced Localized States in Graphene
• Vacancy induced magnetism in graphene and graphene ribbons
• Modeling disorder in graphene
• Spin Transport in Hydrogenated Graphene
• Orbital selective and tunable Kondo effect of magnetic adatoms on graphene: Correlated electronic structure calculations
• Enhancement of spin relaxation time in hydrogenated graphene spin valve devices
• Interactions and magnetic moments near vacancies and resonant impurities in graphene
• Patched Green's function techniques for two dimensional systems: Electronic behaviour of bubbles and perforations in graphene
• Unconventional Yu-Shiba-Rusinov states in hydrogenated graphene
• In-gap impurity states as the hallmark of the Quantum Spin Hall phase

Cited by in corpus (9)

• Impurity-induced triple point fermions in twisted bilayer graphene
• Theory of intermolecular exchange in coupled spin-1/2 nanographenes
• Electrical spin manipulation in graphene nanostructures
• Defect-induced magnetism and Yu-Shiba-Rusinov states in twisted bilayer graphene
• Probing local moments in nanographenes with electron tunneling spectroscopy
• Impurity-induced resonant spinon zero modes in Dirac quantum spin-liquids
• Hydrogen adatoms on graphene: the role of hybridization and lattice distortion
• Kondo effect due to a hydrogen impurity in graphene: a multichannel Kondo problem with diverging hybridization
• Emergent quantum matter in graphene nanoribbons