Magnetic Field Dependence of Spin-Phonon Relaxation and Dephasing from First Principles

Spintronic devices require materials with long spin lifetimes, diffusion lengths and strong spin-orbit coupling (SOC). Strong SOC usually leads to significant k-dependent deviations of the electron g-factor from its free electron value, which in the presence of magnetic fields, leads to strong dephasing in the spin dynamics. We demonstrate real-time first-principles calculations of T₁, T₂, and T₂* lifetimes using a density-matrix dynamics approach. T₂, which represents the spin coherence time, is calculated by simulating a real-time Hahn spin-echo measurement in order to separate the effects of spin dephasing from the overall relaxation time. We predict the magnetic field dependence of each of these spin relaxation lifetimes for crystalline materials with varying complexity and SOC strength, ranging from Si to perovskite CsPbBr₃. We show the transition from relaxation-dominated dynamics with T₂ ~ T₂* at low magnetic fields to dephasing-dominated dynamics T₂ » T₂* at high magnetic fields, even for intrinsic spin-phonon relaxation due to g-factor fluctuations.