Substrate Effects on Spin Relaxation in Two-Dimensional Dirac Materials with Strong Spin-Orbit Coupling

Abstract

Understanding substrate effects on spin dynamics and relaxation in two-dimensional (2D) materials is of key importance for spintronics and quantum information applications. However, the key factors that determine the substrate effect on spin relaxation, in particular for materials with strong spin-orbit coupling, have not been well understood. Here we performed first-principles real-time density-matrix dynamics simulations with spin-orbit coupling (SOC) and quantum descriptions of electron-phonon and electron-impurity scattering for the spin lifetimes of supported/free-standing germanene, a prototypical strong SOC 2D Dirac material. We show that the effects of different substrates on spin lifetime can surprisingly differ by two orders of magnitude. We find that such huge difference seems to be mostly caused by substrate-induced modifications of spin-flip scattering matrix elements, in sharp contrast to the substrate effects on weak SOC materials like graphene.