Spin relaxation in fluorinated single and bilayer graphene

Abstract

We present a joint experiment-theory study on the role of fluorine adatoms in spin and momentum scattering of charge carriers in dilute fluorinated graphene and bilayer graphene. The experimental spin-flip and momentum scattering rates and their dependence on the density of fluorine and carrier doping are obtained through weak localization and conductivity measurements, respectively, and suggest the role of fluorine as resonant magnetic impurities. For the estimated fluorine concentration of a few 100 ppm, the observed spin lifetimes are in the range of 1-10\,ps. Theoretically, we established tight-binding electronic structures of fluorinated graphene and bilayer graphene by fitting to density functional supercell calculations and performed a comprehensive analysis of the spin-flip and momentum scattering rates within the same devices, aiming to develop a consistent description of both scattering channels. We find that resonant scattering in graphene is very sensitive to the precise position of the resonance level, as well as to the magnitude of the exchange coupling between itinerant carriers and localized spins. The experimental data point to the presence of weak spin-flip scatterers that, at the same time, relax the electron momentum strongly, nearly preserving the electron-hole symmetry. Such scatterers would exhibit resonance energies much closer to the neutrality point than what density functional theory predicts in the dilute limit. The inclusion of a magnetic moment on fluorine adatoms allowed us to qualitatively capture the carrier density dependence of the experimental rates but predicts a greater (weaker) spin (momentum) relaxation rate than the measurements. We discuss possible scenarios that may be responsible for the discrepancies. Our systematic study exposes the complexities involved in accurately capturing the behavior of adatoms on graphene.

11 pages, 13 figures

References in corpus (26)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Graphane: a two-dimensional hydrocarbon
• Fluorographene: Two Dimensional Counterpart of Teflon
• Localization and delocalization errors in density functional theory and implications for band-gap prediction
• Carrier transport in 2D graphene layers
• A self-consistent theory for graphene transport
• Emergence of magnetism in graphene materials and nanostructures
• Intrinsic and Rashba Spin-orbit Interactions in Graphene Sheets
• Atomic-scale control of graphene magnetism using hydrogen atoms
• Quantum Anomalous Hall Effect in Graphene from Rashba and Exchange Effects
• Defect scattering in graphene
• Electronic transport in graphene: A semi-classical approach including midgap states
• Weak localisation in graphene flakes
• Magnetic Moment Formation in Graphene Detected by Scattering of Pure Spin Currents
• On resonant scatterers as a factor limiting carrier mobility in graphene
• Adsorbate-limited conductivity of graphene
• Single particle relaxation time versus transport scattering time in a 2D graphene layer
• Unified description of the dc conductivity of monolayer and bilayer graphene at finite densities based on resonant scatterers
• Colossal negative magnetoresistance in dilute fluorinated graphene
• The Effect of Cluster Formation on Graphene Mobility
• Evidence for spin-flip scattering and local moments in dilute fluorinated graphene
• Spin-orbit coupling in fluorinated graphene
• Inducing Kondo Screening of Vacancy Magnetic Moments in Graphene with Gating and Local Curvature
• Ab initio spin-flip conductance of hydrogenated graphene nanoribbons: Spin-orbit interaction and scattering with local impurity spins
• Copper adatoms on graphene: theory of orbital and spin-orbital effects
• Effective Mass in Bilayer Graphene at Low Carrier Densities: the Role of Potential Disorder and Electron-Electron Interaction