0105659

1. Theory of Optical Orientation in n-type SemiconductorsW. O. Putikka, Ohio State University (DMR-0105659)Robert Joynt, University of Wisconsin (DMR-0081039)preprint, cond-mat/0309155 • Optical orientation experiments in n-type semiconductors have uncovered a parameter regime where spins have long lifetimes, of order 100 ns in GaAs • Our model for these systems uses two strongly interacting spin states: localized donor states and itinerant conduction band states, with the spin lifetime determined by the relative occupation of each type of state (as determined by thermodynamics) and the different response of the spin relaxation of each type of state to external parameters • Conduction band spins relax by scattering through the D’yakonov-Perel’ mechanism • Localized spins relax through interactions with phonons (when in an external magnetic field) and through anisotropic spin-spin interactions (Dzyaloshinskii-Moriya interactions) Comparison of theory to data (solid symbols) from Awschalom and Kikkawa, PRL 80, 4313 (1998). The solid lines are the theoretical total relaxation rate, while the dashed line is the component due to spin-phonon relaxation, the dashed-dotted lines are the components due to anisotropic interactions between donor spins and the dotted line is the component from the D’yakonov-Perel’ relaxation of conduction band spins.