Asymmetric Spin Relaxation Dynamics of Electrons and Holes in CsPbI₃: An Ab Initio Quantum Dynamics Study

Lead halide perovskites are promising for spintronics due to their strong spin-orbit coupling (SOC). Experiments show asymmetric, temperature-dependent spin relaxation in γ-CsPbI₃, with electrons relaxing faster than holes via the Elliott-Yafet carrier-phonon mechanism. Ab initio non-adiabatic molecular dynamics with SOC and half-electron correction reproduce this asymmetry. The difference arises from band-edge orbital character: the conduction band minimum (CBM) is Pb-p-dominated and spin-mixed under SOC, while the valence band maximum remains spin-pure due to s-type Pb and I p orbitals. Spin mixing in the CBM leads to a smaller spin mismatch and stronger non-adiabatic couplings, accelerating electron spin relaxation. Lower temperatures extend spin lifetimes by reducing carrier-phonon interactions. In contrast, elevated temperatures enhance lattice disorder and spin state mixing, increasing wave function overlap and non-adiabatic couplings, thereby speeding up spin relaxation. This work offers atomistic insight into asymmetric and temperature-dependent spin dynamics, influencing spintronic device design through thermal and structural control.