Intrinsic spin-orbit coupling in graphene is relatively weak, some tens of micro eVs [1-3]. On one hand, this is nice, 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 (quantum) spin Hall effect. In this talk I will review basics of the spin-orbit physics in graphene and show how to effectively increase the value of the spin-orbit interaction by adding adatoms [3]. Examples will be hydrogen, fluorine, and copper adatoms. I will present our first-principles results as well as phenomenological model Hamiltonians which should be useful to study model spin transport and spin relaxation. I will also discuss the spin relaxation problem in graphene: experiments get the spin relaxation times of 100 ps, orders of magnitude below what is theoretically expected [4]. The cause appears to be extrinsic, due to impurities. I will argue that the mechanism is resonant scattering by a small concentration of magnetic moments (wherever they come from) [5].
[1] M. Gmitra, S. Konschuh, C. Ertler, C. Ambrosch-Draxl, and J. Fabian, Phys. Rev. B 80, 235431 (2009).
[2] S. Konschuh, M. Gmitra, and J. Fabian, Phys. Rev. B 82, 245412 (2010).
[3] M. Gmitra, D. Kochan, and J. Fabian, Phys. Rev. Lett. 110, 246602 (2013).
[4] W. Han, R. Kawakami, M. Gmitra, and J. Fabian, Nature Nanotechnology 9, 794 (2014)
[5] D. Kochan, M. Gmitra, and J. Fabian, Phys. Rev. Lett. 112, 116602 (2014).
