Impact of Electron-Impurity Scattering on the Spin Relaxation Time in Graphene: A First-Principles Study

The effect of electron-impurity scattering on momentum and spin relaxation times in graphene is studied by means of relativistic ab initio calculations. Assuming carbon and silicon adatoms as natural impurities in graphene, we are able to simulate fast spin relaxation observed experimentally. We investigate the dependence of the relaxation times on the impurity position and demonstrate that C or Si adatoms act as real-space spin hot spots inducing spin-flip rates about 5 orders of magnitude larger than those of in-plane impurities. This fact confirms the hypothesis that the adatom-induced spin-orbit coupling leads to fast spin relaxation in graphene.

Figure 1

Determined from fist-principles out-of-plane distances for C and Si adatoms with corresponding energetics. Inset: Charge distribution for C adatom on top of the bridge position in graphene.

Figure 2

Upper panel: Spin and momentum relaxation time, $T_1$ and $\tau$, caused by C and Si adatoms (for spins in the out-of-plane direction). The lines are to guide the eyes. Lower panel: Local density of states of the adatoms and C host atom (the latter one is multiplied by the factor of 200). The energy is counted with respect to the Dirac point.