Ab initio ultrafast spin dynamics in solds*

We present a first-principles real-time density-matrix approach [1] to simulate ultrafast spin-orbit-mediated dynamics in solids with arbitrary crystal symmetry. Through the complete theoretical descriptions of pump, probe and scattering processes including electron-phonon, electron-impurity and electron-electron scattering, our method can directly simulate the nonequilibrium ultrafast pump-probe measurements for coupled spin and electron dynamics and is applicable to any temperatures and doping levels. We use this method to simulate spin dynamics of GaAs and obtain excellent agreement with experiments. It is found that the relative contributions of different scattering mechanisms and phonon modes vary considerably between spin and carrier relaxation processes. Importantly, we point out that at low temperatures the electron-electron scattering becomes very important and causes the strong reduction of spin relaxation time under in-plane magnetic fields.
[1] J. Xu et. al., Nat. Commun. 11.1 (2020): 1-10.