g-Factor Tuning and Manipulation of Spins by an Electric Current

We investigate the Zeeman splitting of two-dimensional electrons in an asymmetric silicon quantum well, by electron-spin-resonance (ESR) experiments. Applying a small dc current we observe a shift in the resonance field due to the additional current-induced Bychkov-Rashba (BR) type of spin-orbit (SO) field. This finding demonstrates SO coupling in the most straightforward way: in the presence of a transverse electric field the drift velocity of the carriers imposes an effective SO magnetic field. This effect allows selective tuning of the g-factor by an applied dc current. In addition, we show that an ac current may be used to induce spin resonance very efficiently.