Ballistic-electron coherent spin precession in a Rashba two-dimensional electron system

In a remarkable manifestation of the Rashba spin-orbit coupling effect, spin polarized carriers injected into a narrow two-dimensional electron system channel have ballistic trajectories and a weakly relativistic Fermi velocity. In the carrier rest frame, the intrinsic electric field in the quantum well transforms as an effective magnetic field, ${H}^*$, transverse to the trajectories. Electrons with initial spin momentum and polarization orientations along the channel precess because of ${H}^*$ with a wavelength $\ensuremath{\lambda}$. For long mean free paths $l$, spin detection probes at distances $L$ $l$ record conductance oscillations with wavelength $\ensuremath{\lambda}$. Two unique experiments that demonstrate these oscillations are discussed.