Electron spin diffusion in monolayerMoS2

Abstract

Electron spin diffusion is investigated in monolayer ${\mathrm{MoS}}_{2}$ in the absence of external electric and magnetic fields. The electron-impurity scattering, which is shown to play a negligible role in spin relaxation in time domain in this material, has a marked effect on the in-plane spin diffusion due to the anisotropic spin precession frequency in the spatial domain. With the electron-impurity and intervalley electron-phonon scatterings separately included in the scattering term, we study the intra- and intervalley diffusion processes of the in-plane spins by analytically solving the kinetic spin Bloch equations. The intravalley process is found to be dominant in the in-plane spin diffusion, in contrast to the case of spin relaxation in time domain, where the intervalley process can be comparable to or even more important than the intravalley one. For the intravalley process, we find that the in-plane spin diffusion is suppressed with the increase of impurity density but effectively enhanced by increasing electron density in both the degenerate and nondegenerate limits. We also take into account the electron-electron Coulomb scattering in the intravalley process. Interestingly, we find that in the nondegenerate limit, the intravalley spin-diffusion length presents an opposite trend in the electron-density dependence compared to the one with only electron-impurity scattering.