Abstract:

Intrinsic spin-orbit coupling in graphene is relatively weak, some tens of micro eVs. On one hand, this is good, as the projected intrinsic spin relaxation is also slow, on the order of microseconds. On the other hand, a greater value for the spin-orbit interaction is desired for spin manipulation and spin-orbit induced phenomena, such as the spin Hall effect. In this talk I will review the basics of the spin-orbit physics in graphene and show how to effectively increase the value of the spin-orbit interaction (to meVs) by adding adatoms. Specifically, our first-principles calculations show that hydrogen induces local spin-orbit coupling of about 1 meV, while fluorine up to 30 meV. For each adatom I will present a minimal realistic hopping model explaining the first-principles results. Such models are useful for investigating model spin relaxation, spin and charge transport in functionalized graphene.
Moreover, I will also present phenomenological theory, based on first-principles calculations, of the exchange splitting and spin relaxation in graphene with hydrogen adatoms or vacancies. I will show that resonant scattering and the exchange interaction with the paramagnetic impurities at the adatom site or vacancy can explain the experimentally observed short spin relaxation times, providing a competitive mechanism to that based on spin-orbit coupling.
 
 
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