Localized quantum spin reversal by spin injection in a spin quantum dot: A model calculation

We theoretically study the reversal of localized quantum spin induced by spin injection in a spin quantum dot, where the dot has a localized quantum spin and it is connected to the left and the right electrodes. We consider a situation in which up spins are sequentially injected from the left electrode into the dot, and an exchange interaction acts between the injected spins and the localized spin. When the right electrode interface has energy levels of conduction electrons with only down spin, we obtain the reversal time of localized spin and the time dependence of the expectation value of localized spin, using a simple approach based on the time dependent Schrodinger equation. It is also shown that a system with the nonmagnetic right electrode interface exhibits the spin reversal or nonreversal depending on the exchange interaction. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.