Triggering and probing of phase-coherent spin packets by time-resolved spin transport across an Fe/GaAs Schottky barrier

Time-resolved electrical spin transport is used to generate and probe spin currents in GaAs electrically. We use high bandwidth current pulses to inject phase-coherent spin packets from Fe into n-GaAs. By means of time-resolved Faraday rotation we demonstrate that spins are injected with a clearly defined phase by the observation of multiple Larmor precession cycles. We furthermore show that spin precession of optically created spin packets in n-GaAs can be probed electrically by spin-polarized photo-current pulses. The injection and detection experiments are not direct reciprocals of each other. In particular, we find that interfacial spin accumulation generated by the photocurrent pulse plays a critical role in time-resolved electrical spin detection.