Transport and recombination through weakly coupled localized spin pairs in semiconductors during coherent spin excitation

Semianalytical predictions for the transients of spin-dependent transport and recombination rates through localized states in semiconductors during coherent electron-spin excitation are made for the case of weakly spin-coupled charge-carrier ensembles. The results show that the on-resonant Rabi frequency of electrically or optically detected spin oscillation doubles abruptly as the strength of the resonant microwave field γB1 exceeds the Larmor frequency separation within the pair of charge-carrier states between which the transport or recombination transition takes place. For the case of a Larmor frequency separation of the order of γB1 and arbitrary excitation frequencies, the charge carrier-pairs exhibit four different nutation frequencies. From the calculations, a simple set of equations for the prediction of these frequencies is derived.