Energy-dependent evolution of electron spin polarization in bulk intrinsic GaAs

Abstract

Time-resolved circularly polarized pump-probe spectroscopy is used to study the electron spin coherence dynamics in intrinsic GaAs at 9.6K. It is found that the oscillation amplitude of absorption quantum beats reflecting electron spin coherence varies nonmonotonically with photon energy increaing. A circularly dichromatic pump-probe model is developed with both spin-polarized-dependent band filling and band-gap renormalization effects taken into account. The model shows that the oscillation amplitude of quantum beats is dependent on the initial degree of electron spin polarization, spin-detectable sensitivity and band-filling factor whose product results in the non-monotonic variation of the quantum-beat amplitude and agrees very well with our experimental results. The degree of electron-spin polarization involved in energy-split two-level system is defined for the first time. It is found that a degree of electron spin polarization of up to 100% can be photocreated at higher excess-energy levels.