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Injection and detection of spin in a semiconductor by tunneling via interface states

Injection and detection of spin accumulation in a semiconductor having localized states at the interface is evaluated. Spin transport from a ferromagnetic contact by sequential, two-step tunneling via interface states is treated not in itself, but in parallel with direct tunneling. The spin accumulation induced in the semiconductor channel is not suppressed, as previously argued, but genuinely enhanced by the additional spin current via interface states. Spin detection with a ferromagnetic contact yields a weighted average of the spin accumulation in the channel and in the localized states. In the regime where the spin accumulation in the localized states is much larger than that in the channel, the detected spin signal is insensitive to the spin accumulation in the localized states and the ferromagnet probes the spin accumulation in the semiconductor channel.