Current induced spin resonance in Si quantum wells

Full text: Spin-orbit interaction in Si quantum wells manifests itself in the appearance of the Bychkov-Rashba field which describes the additional spin splitting in terms of an effective magnetic field seen by moving electrons. The BR field shifts the electron spin resonance (ESR) of the two-dimensional electron gas when a dc current is applied. An ac current at the Larmor frequency is thus expected to cause spin transitions. We present evidence for this effect from an analysis of the angular dependence of the ESR amplitude and the lineshape which is of 'Dysonian' character. We present a model that explains the latter in terms of interference of the microwave electric field due to eddy currents and that induced by the precessing magnetization. We also show that the current induced Bychkov-Rashba field exceeds the microwave magnetic field in a cavity by a factor that is proportional to the electron mobility. For state of the art Si quantum wells this factor may amount to 1000 which (i) enhances the sensitivity accordingly, (ii) it increases the Rabi frequency which reduces the time required for spin rotations and (iii) it reduces the power needed for such operations by many orders of magnitude which may be relevant for spin-based quantum computers. (author)