▎ 摘　　要

We present a microscopic theory of spin dynamics in weakly disordered graphene with uniform proximity-induced spin-orbit coupling (SOC). A time-dependent perturbative treatment is employed to derive the spin Bloch equations governing the spin dynamics at high electronic density for arbitrary ratio lambda(SOC)/eta, where eta is the disorder-induced quasiparticle broadening and lambda(SOC) is the largest spin-orbit energy scale. Rich scenarios are predicted, depending on a delicate competition between interface-induced Bychkov-Rashba and spin-valley interaction. In the motional narrowing regime of weak SOC (lambda(SOC )<< n), the anisotropy ratio of out-of-plane to in-plane spin lifetimes zeta= tau(perpendicular to)(s)/tau(parallel to)(s) agrees qualitatively with a toy model of spins in a fluctuating SOC field proposed recently by Cummings and co-workers Phys. Rev. Lett. 119, 206601 (2017). For well-resolved SOC (lambda(SOC) greater than or similar to eta), the spin dynamics is characterized by fast damped oscillations with spins relaxing on the timescale of a single scattering event. In this regime, qualitatively different formulas for zeta are obtained, which can be useful to model spin transport in ultraclean van der Waals heterostructures.