Spin relaxation in fluorinated single and bilayer graphene

Susanne Wellnhofer, Adam Stabile, Denis Kochan, Martin Gmitra, Ya Wen Chuang, Jun Zhu, Jaroslav Fabian

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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 hundred 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.

Original languageEnglish (US)
Article number035421
JournalPhysical Review B
Volume100
Issue number3
DOIs
StatePublished - Jul 16 2019

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Wellnhofer, S., Stabile, A., Kochan, D., Gmitra, M., Chuang, Y. W., Zhu, J., & Fabian, J. (2019). Spin relaxation in fluorinated single and bilayer graphene. Physical Review B, 100(3), [035421]. https://doi.org/10.1103/PhysRevB.100.035421